The Pennsylvania State University

The Graduate School

College of Engineering

MEMBRANE FILTRATION AND POLYMER COAGULATION FOR WATER

REUSE IN LAUNDRY WASTEWATER TREATMENT FROM BENCH-SCALE

TO FULL-SCALE OPERATION

A Thesis in

Environmental Engineering

by

Xia Shang

copy 2012 Xia Shang

Submitted in Fulfillment

of the Requirements

for the Degree of

Master of Science

May 2012

II

The thesis of Xia Shang was reviewed and approved by the following

Brian A Dempsey

Professor of Environmental Engineering

Thesis Adviser

Rachel A Brennan

Associate Professor of Environmental Engineering

Fred S Cannon

Professor of Environmental Engineering

Peggy A Johnson

Professor of Civil Engineering

Head of the Department of Civil and Environmental Engineering

Signatures are on file in the Graduate School

III

ABSTRACT

Membrane filtration has been widely employed for treating potable water and wastewater

This thesis dealt with the use of microfiltration (MF) for treatment and reuse of laundry

wastewater The most important issues with respect to laundry water reuse are treated

water quality membrane fouling and cost and energy consumption Only the first two of

these issues were addressed in this thesis This thesis was focused on developing

methods to improve performance of the Armyrsquos full-scale Shower Water Reuse System

(SWRS) specifically for treating and reusing laundry wastewater The SWRS uses

pretreatment with pre- filtration (15 microm steel mesh) MF (02 microm PVDF) reverse osmosis

(RO) and Granular activated carbon (GAC) Based on the information from the Army

and their contractors the major problem in using the SWRS for laundry wastewater was

fouling of the MF Therefore the objectives were to investigate the effects of coagulants

for improving MF performance and for removal of contaminants

Coagulation has been used prior to MF for decreasing membrane fouling enhancing

MF flux and improving removal of contaminants There are problems in employing

conventional coagulants (eg alum and ferric chloride) for treating laundry wastewater due

to the difficulties in achieving effective coagulation at high pH high total suspended solids

(TSS) and high chemical oxygen demand (COD) In particular the very high doses of

inorganic coagulants that are required for these water quality conditions result in voluminous

sludge production which is inappropriate prior to membrane treatment As a result cationic

polyelectrolytes were investigated

The effects of different cationic polymers on laundry wastewater treatment were first

investigated using batch coagulationprecipitation with sedimentation (without membrane

filtration) evaluating Zeta Potential (ZP) changes and removal of COD TSS turbidity and

total phosphorus (TP) Subsequently the influence of cationic polymers on MF performance

was studied by measuring specific resistance and cake compressibility Based on these initial

experiments a commercial poly-quaternary amine containing epichlorohydrin

dimethylamine (Epi-DMA) was selected as the best polymer based on successful

neutralization of contaminant charge and low specific resistance on polyvinylidine

fluoride (PVDF) MF over a broad range of pH and coagulant dose The initial

experiments also demonstrated that Epi-DMA was effective for removal of contaminants

IV

after sedimentation eg 63 of COD 77 of TSS 96 of turbidity and 26 of TP

were removed

Subsequent bench-scale experiments focused on evaluating the effects of Epi-DMA

on reducing membrane fouling and increasing critical flux defined as the maximum flux

for which trans-membrane pressure (TMP) increased linearly with permeate flux Epi-

DMA coagulation significantly increased the critical flux from 50 L m-2h-1 for the raw

sample to 510 L m-2h-1 for the charge neutralization (CN) condition Epi-DMA additions

also substantially decreased resistance to filtration over a broad range of coagulant doses

including doses less than 50 of that required for CN

The effects of Epi-DMA on MF of laundry wastewater were further investigated by

conducting multi-cycle tests with backwashing every 15 min These bench-scale

experiments were run at 50 L m-2h-1 which is a typical membrane flux used in full-scale

MF operations The multi-cycle experiments demonstrated that increases in the trans-

membrane pressure (TMP) that occurred during each cycle were nearly eliminated by the

backwash for under-dosing (UD) and CN conditions but that TMP increases during over-

dosing (OD) coagulation conditions were not eliminated during backwash

Finally the use of Epi-DMA was tested on the full-scale SWRS which was set up

outside the Penn State laundry facility The setup included two 3000 gal bladders

Laundry wastewater was pumped from the laundry facility into the bladders and Epi-

DMA was introduced into the bladders prior to the pre-treatment The effects on the

down-stream membrane units were investigated The tests were performed over a range

of Epi-DMA doses including no coagulant UD CN and OD The tests demonstrated

that negligible fouling of the MF occurred but serious fouling was observed in the RO

unit Formation of inorganic precipitates was suspected as the main reason for RO failure

The full-scale MF without coagulant did not foul as much as the bench-scale MF

experiments had indicated This could have been due to more rigorous backwashing with

the SWRS or due to retention of partially coagulated solids in the bladders despite inter-

experiment flushing with tap water Issues regarding MF and RO behavior in the full-

scale SWRS are currently under investigation and some conclusions are reported in this

thesis

V

TABLE OF CONTENTS

LIST OF FIGURES X

LIST OF TABLES XIV

ACKNOWLEDGEMENTS XVI

DEDICATION XVII

ABBREVIATIONS XVIII

CHAPTER 1 INTRODUCTION 1

11 Project background 1

12 Objectives 4

13 Organization of the thesis 5

CHAPTER 2 MATERIALS AND METHODS 7

21 Laundry wastewater description 7

22 Zeta potential (COD TSS Turbidity TP) 8

221 Zeta Sizer Nano series 8

222 Zeta Compact 9

22 DI water 9

23 pH and conductivity 9

24 Total suspended solids 9

25 COD and Total phosphorus 9

26 Turbidity 10

27 SEM 10

28 TEM 10

29 Particle size distribution and particle images 10

210 Polymeric coagulants 11

VI

211 Membranes 13

2111 Membrane characteristics 13

2112 Preparation of membrane 13

2113 Hydraulic cleaning of membranes 14

2114 Flux recovery 14

212 Batch tests for zeta potential titration 14

213 Jar tests 15

214 Specific resistance and cake compressibility 15

215 Critical flux determination 18

2151 Sample pretreatment 18

2152 Microfiltration process 19

216 Multi-cycle filtration test 20

2161 Sample preparation 20

2162 Microfiltration process 20

217 Dead end microfiltration test 22

CHAPTER 3 IMPACT OF POLYMERS ON COAGULATION OF LAUNDRY

WASTEWATER 23

31 Batch tests 24

32 Jar tests 26

33 Specific resistance to filtration and cake compressibility 29

34 Summary 33

CHAPTER 4 IN-LINE COAGULATION AND MF CRITICAL FLUX AND

LONG-TERM MF OPERATION 34

41 Jar tests identifying dosing regimes 35

42 Critical Fluxes for the dosing regimes 36

43 Multi-cycle constant flux MF experiments 39

VII

44 Multi-cycle microfiltration tests at 50 L m-2h-1 for simulating the full-

scale operation 44

45 Contaminant removals in bench scale MF experiments 46

45 Summary 47

CHAPTER 5 FULL-SCALE EXPERIMENTS ON THE SHOWER WASTEWATER

REUSE SYSTEM 48

51 SWRS description 50

511 System overview 50

512 Microfiltration characteristics 53

513 RO filter 53

514 Chemical injection system 53

515 Air system 54

516 GAC filter and UV light 54

517 Microfiltration operating without high pressure pump set-up and

backwashing strategy 54

52 SWRS setup and dosing strategy at Penn State Laundry Building 54

53 SWRS operation at various microfiltration permeate flux with clean

water 56

54 Results of long-term SWRS operation 57

55 Water quality changes 60

56 SWRS operation problems 61

561 Pre-filter fouling 61

562 RO scaling 61

563 Other problems 62

57 Hypotheses regarding differences between bench-scale experiments and

full-scale tests 62

VIII

571 Water quality 62

572 Pre-filter sequence 62

573 Cross-flow and backwash 62

574 Coagulated lint particle in the settlement 63

58 Additional multi-cycle bench-scale microfiltration tests on Penn State

laundry wastewater 63

59 SWRS RO Membrane cleaning procedure and SEMEDS analysis 65

591 RO fouling during operation 65

592 RO membrane autopsy and sample preparation 65

593 SEM images 65

594 EDS analysis 66

595 TEM images 72

596 RO cleaning and cleaning solutions 74

597 Cleaning solution analysis 75

510 Summary 76

CHAPTER 6 CONCLUSIONS 77

61 Polymer selection for laundry wastewater treatment 77

62 Bench scale MF experiments 77

63 Full-scale tests and RO scaling 79

CHAPTER 7 RECOMMENDATIONS 80

REFERENCES 81

Appendix A Material and Water Quality changes in Bench Scale Experiments 86

Appendix B Example of Data Processing for Critical Flux Determination Experiment

100

Appendix C Example of Data Processing for a Multi-cycle Membrane Filtration

Experiment 104

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

II

The thesis of Xia Shang was reviewed and approved by the following

Brian A Dempsey

Professor of Environmental Engineering

Thesis Adviser

Rachel A Brennan

Associate Professor of Environmental Engineering

Fred S Cannon

Professor of Environmental Engineering

Peggy A Johnson

Professor of Civil Engineering

Head of the Department of Civil and Environmental Engineering

Signatures are on file in the Graduate School

III

ABSTRACT

Membrane filtration has been widely employed for treating potable water and wastewater

This thesis dealt with the use of microfiltration (MF) for treatment and reuse of laundry

wastewater The most important issues with respect to laundry water reuse are treated

water quality membrane fouling and cost and energy consumption Only the first two of

these issues were addressed in this thesis This thesis was focused on developing

methods to improve performance of the Armyrsquos full-scale Shower Water Reuse System

(SWRS) specifically for treating and reusing laundry wastewater The SWRS uses

pretreatment with pre- filtration (15 microm steel mesh) MF (02 microm PVDF) reverse osmosis

(RO) and Granular activated carbon (GAC) Based on the information from the Army

and their contractors the major problem in using the SWRS for laundry wastewater was

fouling of the MF Therefore the objectives were to investigate the effects of coagulants

for improving MF performance and for removal of contaminants

Coagulation has been used prior to MF for decreasing membrane fouling enhancing

MF flux and improving removal of contaminants There are problems in employing

conventional coagulants (eg alum and ferric chloride) for treating laundry wastewater due

to the difficulties in achieving effective coagulation at high pH high total suspended solids

(TSS) and high chemical oxygen demand (COD) In particular the very high doses of

inorganic coagulants that are required for these water quality conditions result in voluminous

sludge production which is inappropriate prior to membrane treatment As a result cationic

polyelectrolytes were investigated

The effects of different cationic polymers on laundry wastewater treatment were first

investigated using batch coagulationprecipitation with sedimentation (without membrane

filtration) evaluating Zeta Potential (ZP) changes and removal of COD TSS turbidity and

total phosphorus (TP) Subsequently the influence of cationic polymers on MF performance

was studied by measuring specific resistance and cake compressibility Based on these initial

experiments a commercial poly-quaternary amine containing epichlorohydrin

dimethylamine (Epi-DMA) was selected as the best polymer based on successful

neutralization of contaminant charge and low specific resistance on polyvinylidine

fluoride (PVDF) MF over a broad range of pH and coagulant dose The initial

experiments also demonstrated that Epi-DMA was effective for removal of contaminants

IV

after sedimentation eg 63 of COD 77 of TSS 96 of turbidity and 26 of TP

were removed

Subsequent bench-scale experiments focused on evaluating the effects of Epi-DMA

on reducing membrane fouling and increasing critical flux defined as the maximum flux

for which trans-membrane pressure (TMP) increased linearly with permeate flux Epi-

DMA coagulation significantly increased the critical flux from 50 L m-2h-1 for the raw

sample to 510 L m-2h-1 for the charge neutralization (CN) condition Epi-DMA additions

also substantially decreased resistance to filtration over a broad range of coagulant doses

including doses less than 50 of that required for CN

The effects of Epi-DMA on MF of laundry wastewater were further investigated by

conducting multi-cycle tests with backwashing every 15 min These bench-scale

experiments were run at 50 L m-2h-1 which is a typical membrane flux used in full-scale

MF operations The multi-cycle experiments demonstrated that increases in the trans-

membrane pressure (TMP) that occurred during each cycle were nearly eliminated by the

backwash for under-dosing (UD) and CN conditions but that TMP increases during over-

dosing (OD) coagulation conditions were not eliminated during backwash

Finally the use of Epi-DMA was tested on the full-scale SWRS which was set up

outside the Penn State laundry facility The setup included two 3000 gal bladders

Laundry wastewater was pumped from the laundry facility into the bladders and Epi-

DMA was introduced into the bladders prior to the pre-treatment The effects on the

down-stream membrane units were investigated The tests were performed over a range

of Epi-DMA doses including no coagulant UD CN and OD The tests demonstrated

that negligible fouling of the MF occurred but serious fouling was observed in the RO

unit Formation of inorganic precipitates was suspected as the main reason for RO failure

The full-scale MF without coagulant did not foul as much as the bench-scale MF

experiments had indicated This could have been due to more rigorous backwashing with

the SWRS or due to retention of partially coagulated solids in the bladders despite inter-

experiment flushing with tap water Issues regarding MF and RO behavior in the full-

scale SWRS are currently under investigation and some conclusions are reported in this

thesis

V

TABLE OF CONTENTS

LIST OF FIGURES X

LIST OF TABLES XIV

ACKNOWLEDGEMENTS XVI

DEDICATION XVII

ABBREVIATIONS XVIII

CHAPTER 1 INTRODUCTION 1

11 Project background 1

12 Objectives 4

13 Organization of the thesis 5

CHAPTER 2 MATERIALS AND METHODS 7

21 Laundry wastewater description 7

22 Zeta potential (COD TSS Turbidity TP) 8

221 Zeta Sizer Nano series 8

222 Zeta Compact 9

22 DI water 9

23 pH and conductivity 9

24 Total suspended solids 9

25 COD and Total phosphorus 9

26 Turbidity 10

27 SEM 10

28 TEM 10

29 Particle size distribution and particle images 10

210 Polymeric coagulants 11

VI

211 Membranes 13

2111 Membrane characteristics 13

2112 Preparation of membrane 13

2113 Hydraulic cleaning of membranes 14

2114 Flux recovery 14

212 Batch tests for zeta potential titration 14

213 Jar tests 15

214 Specific resistance and cake compressibility 15

215 Critical flux determination 18

2151 Sample pretreatment 18

2152 Microfiltration process 19

216 Multi-cycle filtration test 20

2161 Sample preparation 20

2162 Microfiltration process 20

217 Dead end microfiltration test 22

CHAPTER 3 IMPACT OF POLYMERS ON COAGULATION OF LAUNDRY

WASTEWATER 23

31 Batch tests 24

32 Jar tests 26

33 Specific resistance to filtration and cake compressibility 29

34 Summary 33

CHAPTER 4 IN-LINE COAGULATION AND MF CRITICAL FLUX AND

LONG-TERM MF OPERATION 34

41 Jar tests identifying dosing regimes 35

42 Critical Fluxes for the dosing regimes 36

43 Multi-cycle constant flux MF experiments 39

VII

44 Multi-cycle microfiltration tests at 50 L m-2h-1 for simulating the full-

scale operation 44

45 Contaminant removals in bench scale MF experiments 46

45 Summary 47

CHAPTER 5 FULL-SCALE EXPERIMENTS ON THE SHOWER WASTEWATER

REUSE SYSTEM 48

51 SWRS description 50

511 System overview 50

512 Microfiltration characteristics 53

513 RO filter 53

514 Chemical injection system 53

515 Air system 54

516 GAC filter and UV light 54

517 Microfiltration operating without high pressure pump set-up and

backwashing strategy 54

52 SWRS setup and dosing strategy at Penn State Laundry Building 54

53 SWRS operation at various microfiltration permeate flux with clean

water 56

54 Results of long-term SWRS operation 57

55 Water quality changes 60

56 SWRS operation problems 61

561 Pre-filter fouling 61

562 RO scaling 61

563 Other problems 62

57 Hypotheses regarding differences between bench-scale experiments and

full-scale tests 62

VIII

571 Water quality 62

572 Pre-filter sequence 62

573 Cross-flow and backwash 62

574 Coagulated lint particle in the settlement 63

58 Additional multi-cycle bench-scale microfiltration tests on Penn State

laundry wastewater 63

59 SWRS RO Membrane cleaning procedure and SEMEDS analysis 65

591 RO fouling during operation 65

592 RO membrane autopsy and sample preparation 65

593 SEM images 65

594 EDS analysis 66

595 TEM images 72

596 RO cleaning and cleaning solutions 74

597 Cleaning solution analysis 75

510 Summary 76

CHAPTER 6 CONCLUSIONS 77

61 Polymer selection for laundry wastewater treatment 77

62 Bench scale MF experiments 77

63 Full-scale tests and RO scaling 79

CHAPTER 7 RECOMMENDATIONS 80

REFERENCES 81

Appendix A Material and Water Quality changes in Bench Scale Experiments 86

Appendix B Example of Data Processing for Critical Flux Determination Experiment

100

Appendix C Example of Data Processing for a Multi-cycle Membrane Filtration

Experiment 104

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

III

ABSTRACT

Membrane filtration has been widely employed for treating potable water and wastewater

This thesis dealt with the use of microfiltration (MF) for treatment and reuse of laundry

wastewater The most important issues with respect to laundry water reuse are treated

water quality membrane fouling and cost and energy consumption Only the first two of

these issues were addressed in this thesis This thesis was focused on developing

methods to improve performance of the Armyrsquos full-scale Shower Water Reuse System

(SWRS) specifically for treating and reusing laundry wastewater The SWRS uses

pretreatment with pre- filtration (15 microm steel mesh) MF (02 microm PVDF) reverse osmosis

(RO) and Granular activated carbon (GAC) Based on the information from the Army

and their contractors the major problem in using the SWRS for laundry wastewater was

fouling of the MF Therefore the objectives were to investigate the effects of coagulants

for improving MF performance and for removal of contaminants

Coagulation has been used prior to MF for decreasing membrane fouling enhancing

MF flux and improving removal of contaminants There are problems in employing

conventional coagulants (eg alum and ferric chloride) for treating laundry wastewater due

to the difficulties in achieving effective coagulation at high pH high total suspended solids

(TSS) and high chemical oxygen demand (COD) In particular the very high doses of

inorganic coagulants that are required for these water quality conditions result in voluminous

sludge production which is inappropriate prior to membrane treatment As a result cationic

polyelectrolytes were investigated

The effects of different cationic polymers on laundry wastewater treatment were first

investigated using batch coagulationprecipitation with sedimentation (without membrane

filtration) evaluating Zeta Potential (ZP) changes and removal of COD TSS turbidity and

total phosphorus (TP) Subsequently the influence of cationic polymers on MF performance

was studied by measuring specific resistance and cake compressibility Based on these initial

experiments a commercial poly-quaternary amine containing epichlorohydrin

dimethylamine (Epi-DMA) was selected as the best polymer based on successful

neutralization of contaminant charge and low specific resistance on polyvinylidine

fluoride (PVDF) MF over a broad range of pH and coagulant dose The initial

experiments also demonstrated that Epi-DMA was effective for removal of contaminants

IV

after sedimentation eg 63 of COD 77 of TSS 96 of turbidity and 26 of TP

were removed

Subsequent bench-scale experiments focused on evaluating the effects of Epi-DMA

on reducing membrane fouling and increasing critical flux defined as the maximum flux

for which trans-membrane pressure (TMP) increased linearly with permeate flux Epi-

DMA coagulation significantly increased the critical flux from 50 L m-2h-1 for the raw

sample to 510 L m-2h-1 for the charge neutralization (CN) condition Epi-DMA additions

also substantially decreased resistance to filtration over a broad range of coagulant doses

including doses less than 50 of that required for CN

The effects of Epi-DMA on MF of laundry wastewater were further investigated by

conducting multi-cycle tests with backwashing every 15 min These bench-scale

experiments were run at 50 L m-2h-1 which is a typical membrane flux used in full-scale

MF operations The multi-cycle experiments demonstrated that increases in the trans-

membrane pressure (TMP) that occurred during each cycle were nearly eliminated by the

backwash for under-dosing (UD) and CN conditions but that TMP increases during over-

dosing (OD) coagulation conditions were not eliminated during backwash

Finally the use of Epi-DMA was tested on the full-scale SWRS which was set up

outside the Penn State laundry facility The setup included two 3000 gal bladders

Laundry wastewater was pumped from the laundry facility into the bladders and Epi-

DMA was introduced into the bladders prior to the pre-treatment The effects on the

down-stream membrane units were investigated The tests were performed over a range

of Epi-DMA doses including no coagulant UD CN and OD The tests demonstrated

that negligible fouling of the MF occurred but serious fouling was observed in the RO

unit Formation of inorganic precipitates was suspected as the main reason for RO failure

The full-scale MF without coagulant did not foul as much as the bench-scale MF

experiments had indicated This could have been due to more rigorous backwashing with

the SWRS or due to retention of partially coagulated solids in the bladders despite inter-

experiment flushing with tap water Issues regarding MF and RO behavior in the full-

scale SWRS are currently under investigation and some conclusions are reported in this

thesis

V

TABLE OF CONTENTS

LIST OF FIGURES X

LIST OF TABLES XIV

ACKNOWLEDGEMENTS XVI

DEDICATION XVII

ABBREVIATIONS XVIII

CHAPTER 1 INTRODUCTION 1

11 Project background 1

12 Objectives 4

13 Organization of the thesis 5

CHAPTER 2 MATERIALS AND METHODS 7

21 Laundry wastewater description 7

22 Zeta potential (COD TSS Turbidity TP) 8

221 Zeta Sizer Nano series 8

222 Zeta Compact 9

22 DI water 9

23 pH and conductivity 9

24 Total suspended solids 9

25 COD and Total phosphorus 9

26 Turbidity 10

27 SEM 10

28 TEM 10

29 Particle size distribution and particle images 10

210 Polymeric coagulants 11

VI

211 Membranes 13

2111 Membrane characteristics 13

2112 Preparation of membrane 13

2113 Hydraulic cleaning of membranes 14

2114 Flux recovery 14

212 Batch tests for zeta potential titration 14

213 Jar tests 15

214 Specific resistance and cake compressibility 15

215 Critical flux determination 18

2151 Sample pretreatment 18

2152 Microfiltration process 19

216 Multi-cycle filtration test 20

2161 Sample preparation 20

2162 Microfiltration process 20

217 Dead end microfiltration test 22

CHAPTER 3 IMPACT OF POLYMERS ON COAGULATION OF LAUNDRY

WASTEWATER 23

31 Batch tests 24

32 Jar tests 26

33 Specific resistance to filtration and cake compressibility 29

34 Summary 33

CHAPTER 4 IN-LINE COAGULATION AND MF CRITICAL FLUX AND

LONG-TERM MF OPERATION 34

41 Jar tests identifying dosing regimes 35

42 Critical Fluxes for the dosing regimes 36

43 Multi-cycle constant flux MF experiments 39

VII

44 Multi-cycle microfiltration tests at 50 L m-2h-1 for simulating the full-

scale operation 44

45 Contaminant removals in bench scale MF experiments 46

45 Summary 47

CHAPTER 5 FULL-SCALE EXPERIMENTS ON THE SHOWER WASTEWATER

REUSE SYSTEM 48

51 SWRS description 50

511 System overview 50

512 Microfiltration characteristics 53

513 RO filter 53

514 Chemical injection system 53

515 Air system 54

516 GAC filter and UV light 54

517 Microfiltration operating without high pressure pump set-up and

backwashing strategy 54

52 SWRS setup and dosing strategy at Penn State Laundry Building 54

53 SWRS operation at various microfiltration permeate flux with clean

water 56

54 Results of long-term SWRS operation 57

55 Water quality changes 60

56 SWRS operation problems 61

561 Pre-filter fouling 61

562 RO scaling 61

563 Other problems 62

57 Hypotheses regarding differences between bench-scale experiments and

full-scale tests 62

VIII

571 Water quality 62

572 Pre-filter sequence 62

573 Cross-flow and backwash 62

574 Coagulated lint particle in the settlement 63

58 Additional multi-cycle bench-scale microfiltration tests on Penn State

laundry wastewater 63

59 SWRS RO Membrane cleaning procedure and SEMEDS analysis 65

591 RO fouling during operation 65

592 RO membrane autopsy and sample preparation 65

593 SEM images 65

594 EDS analysis 66

595 TEM images 72

596 RO cleaning and cleaning solutions 74

597 Cleaning solution analysis 75

510 Summary 76

CHAPTER 6 CONCLUSIONS 77

61 Polymer selection for laundry wastewater treatment 77

62 Bench scale MF experiments 77

63 Full-scale tests and RO scaling 79

CHAPTER 7 RECOMMENDATIONS 80

REFERENCES 81

Appendix A Material and Water Quality changes in Bench Scale Experiments 86

Appendix B Example of Data Processing for Critical Flux Determination Experiment

100

Appendix C Example of Data Processing for a Multi-cycle Membrane Filtration

Experiment 104

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

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20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

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0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

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40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

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0

20

Zeta

po

ten

tial

(mV

)

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0

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60

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100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

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po

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tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

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40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

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0

20

Ze

ta p

ote

nti

al

(mV

)

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0

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100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

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20

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po

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tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

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100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

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po

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tial

(mV

)

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0

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0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

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nti

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(mV

)

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0

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0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

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ta p

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nti

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(mV

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0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

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po

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tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

IV

after sedimentation eg 63 of COD 77 of TSS 96 of turbidity and 26 of TP

were removed

Subsequent bench-scale experiments focused on evaluating the effects of Epi-DMA

on reducing membrane fouling and increasing critical flux defined as the maximum flux

for which trans-membrane pressure (TMP) increased linearly with permeate flux Epi-

DMA coagulation significantly increased the critical flux from 50 L m-2h-1 for the raw

sample to 510 L m-2h-1 for the charge neutralization (CN) condition Epi-DMA additions

also substantially decreased resistance to filtration over a broad range of coagulant doses

including doses less than 50 of that required for CN

The effects of Epi-DMA on MF of laundry wastewater were further investigated by

conducting multi-cycle tests with backwashing every 15 min These bench-scale

experiments were run at 50 L m-2h-1 which is a typical membrane flux used in full-scale

MF operations The multi-cycle experiments demonstrated that increases in the trans-

membrane pressure (TMP) that occurred during each cycle were nearly eliminated by the

backwash for under-dosing (UD) and CN conditions but that TMP increases during over-

dosing (OD) coagulation conditions were not eliminated during backwash

Finally the use of Epi-DMA was tested on the full-scale SWRS which was set up

outside the Penn State laundry facility The setup included two 3000 gal bladders

Laundry wastewater was pumped from the laundry facility into the bladders and Epi-

DMA was introduced into the bladders prior to the pre-treatment The effects on the

down-stream membrane units were investigated The tests were performed over a range

of Epi-DMA doses including no coagulant UD CN and OD The tests demonstrated

that negligible fouling of the MF occurred but serious fouling was observed in the RO

unit Formation of inorganic precipitates was suspected as the main reason for RO failure

The full-scale MF without coagulant did not foul as much as the bench-scale MF

experiments had indicated This could have been due to more rigorous backwashing with

the SWRS or due to retention of partially coagulated solids in the bladders despite inter-

experiment flushing with tap water Issues regarding MF and RO behavior in the full-

scale SWRS are currently under investigation and some conclusions are reported in this

thesis

V

TABLE OF CONTENTS

LIST OF FIGURES X

LIST OF TABLES XIV

ACKNOWLEDGEMENTS XVI

DEDICATION XVII

ABBREVIATIONS XVIII

CHAPTER 1 INTRODUCTION 1

11 Project background 1

12 Objectives 4

13 Organization of the thesis 5

CHAPTER 2 MATERIALS AND METHODS 7

21 Laundry wastewater description 7

22 Zeta potential (COD TSS Turbidity TP) 8

221 Zeta Sizer Nano series 8

222 Zeta Compact 9

22 DI water 9

23 pH and conductivity 9

24 Total suspended solids 9

25 COD and Total phosphorus 9

26 Turbidity 10

27 SEM 10

28 TEM 10

29 Particle size distribution and particle images 10

210 Polymeric coagulants 11

VI

211 Membranes 13

2111 Membrane characteristics 13

2112 Preparation of membrane 13

2113 Hydraulic cleaning of membranes 14

2114 Flux recovery 14

212 Batch tests for zeta potential titration 14

213 Jar tests 15

214 Specific resistance and cake compressibility 15

215 Critical flux determination 18

2151 Sample pretreatment 18

2152 Microfiltration process 19

216 Multi-cycle filtration test 20

2161 Sample preparation 20

2162 Microfiltration process 20

217 Dead end microfiltration test 22

CHAPTER 3 IMPACT OF POLYMERS ON COAGULATION OF LAUNDRY

WASTEWATER 23

31 Batch tests 24

32 Jar tests 26

33 Specific resistance to filtration and cake compressibility 29

34 Summary 33

CHAPTER 4 IN-LINE COAGULATION AND MF CRITICAL FLUX AND

LONG-TERM MF OPERATION 34

41 Jar tests identifying dosing regimes 35

42 Critical Fluxes for the dosing regimes 36

43 Multi-cycle constant flux MF experiments 39

VII

44 Multi-cycle microfiltration tests at 50 L m-2h-1 for simulating the full-

scale operation 44

45 Contaminant removals in bench scale MF experiments 46

45 Summary 47

CHAPTER 5 FULL-SCALE EXPERIMENTS ON THE SHOWER WASTEWATER

REUSE SYSTEM 48

51 SWRS description 50

511 System overview 50

512 Microfiltration characteristics 53

513 RO filter 53

514 Chemical injection system 53

515 Air system 54

516 GAC filter and UV light 54

517 Microfiltration operating without high pressure pump set-up and

backwashing strategy 54

52 SWRS setup and dosing strategy at Penn State Laundry Building 54

53 SWRS operation at various microfiltration permeate flux with clean

water 56

54 Results of long-term SWRS operation 57

55 Water quality changes 60

56 SWRS operation problems 61

561 Pre-filter fouling 61

562 RO scaling 61

563 Other problems 62

57 Hypotheses regarding differences between bench-scale experiments and

full-scale tests 62

VIII

571 Water quality 62

572 Pre-filter sequence 62

573 Cross-flow and backwash 62

574 Coagulated lint particle in the settlement 63

58 Additional multi-cycle bench-scale microfiltration tests on Penn State

laundry wastewater 63

59 SWRS RO Membrane cleaning procedure and SEMEDS analysis 65

591 RO fouling during operation 65

592 RO membrane autopsy and sample preparation 65

593 SEM images 65

594 EDS analysis 66

595 TEM images 72

596 RO cleaning and cleaning solutions 74

597 Cleaning solution analysis 75

510 Summary 76

CHAPTER 6 CONCLUSIONS 77

61 Polymer selection for laundry wastewater treatment 77

62 Bench scale MF experiments 77

63 Full-scale tests and RO scaling 79

CHAPTER 7 RECOMMENDATIONS 80

REFERENCES 81

Appendix A Material and Water Quality changes in Bench Scale Experiments 86

Appendix B Example of Data Processing for Critical Flux Determination Experiment

100

Appendix C Example of Data Processing for a Multi-cycle Membrane Filtration

Experiment 104

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

V

TABLE OF CONTENTS

LIST OF FIGURES X

LIST OF TABLES XIV

ACKNOWLEDGEMENTS XVI

DEDICATION XVII

ABBREVIATIONS XVIII

CHAPTER 1 INTRODUCTION 1

11 Project background 1

12 Objectives 4

13 Organization of the thesis 5

CHAPTER 2 MATERIALS AND METHODS 7

21 Laundry wastewater description 7

22 Zeta potential (COD TSS Turbidity TP) 8

221 Zeta Sizer Nano series 8

222 Zeta Compact 9

22 DI water 9

23 pH and conductivity 9

24 Total suspended solids 9

25 COD and Total phosphorus 9

26 Turbidity 10

27 SEM 10

28 TEM 10

29 Particle size distribution and particle images 10

210 Polymeric coagulants 11

VI

211 Membranes 13

2111 Membrane characteristics 13

2112 Preparation of membrane 13

2113 Hydraulic cleaning of membranes 14

2114 Flux recovery 14

212 Batch tests for zeta potential titration 14

213 Jar tests 15

214 Specific resistance and cake compressibility 15

215 Critical flux determination 18

2151 Sample pretreatment 18

2152 Microfiltration process 19

216 Multi-cycle filtration test 20

2161 Sample preparation 20

2162 Microfiltration process 20

217 Dead end microfiltration test 22

CHAPTER 3 IMPACT OF POLYMERS ON COAGULATION OF LAUNDRY

WASTEWATER 23

31 Batch tests 24

32 Jar tests 26

33 Specific resistance to filtration and cake compressibility 29

34 Summary 33

CHAPTER 4 IN-LINE COAGULATION AND MF CRITICAL FLUX AND

LONG-TERM MF OPERATION 34

41 Jar tests identifying dosing regimes 35

42 Critical Fluxes for the dosing regimes 36

43 Multi-cycle constant flux MF experiments 39

VII

44 Multi-cycle microfiltration tests at 50 L m-2h-1 for simulating the full-

scale operation 44

45 Contaminant removals in bench scale MF experiments 46

45 Summary 47

CHAPTER 5 FULL-SCALE EXPERIMENTS ON THE SHOWER WASTEWATER

REUSE SYSTEM 48

51 SWRS description 50

511 System overview 50

512 Microfiltration characteristics 53

513 RO filter 53

514 Chemical injection system 53

515 Air system 54

516 GAC filter and UV light 54

517 Microfiltration operating without high pressure pump set-up and

backwashing strategy 54

52 SWRS setup and dosing strategy at Penn State Laundry Building 54

53 SWRS operation at various microfiltration permeate flux with clean

water 56

54 Results of long-term SWRS operation 57

55 Water quality changes 60

56 SWRS operation problems 61

561 Pre-filter fouling 61

562 RO scaling 61

563 Other problems 62

57 Hypotheses regarding differences between bench-scale experiments and

full-scale tests 62

VIII

571 Water quality 62

572 Pre-filter sequence 62

573 Cross-flow and backwash 62

574 Coagulated lint particle in the settlement 63

58 Additional multi-cycle bench-scale microfiltration tests on Penn State

laundry wastewater 63

59 SWRS RO Membrane cleaning procedure and SEMEDS analysis 65

591 RO fouling during operation 65

592 RO membrane autopsy and sample preparation 65

593 SEM images 65

594 EDS analysis 66

595 TEM images 72

596 RO cleaning and cleaning solutions 74

597 Cleaning solution analysis 75

510 Summary 76

CHAPTER 6 CONCLUSIONS 77

61 Polymer selection for laundry wastewater treatment 77

62 Bench scale MF experiments 77

63 Full-scale tests and RO scaling 79

CHAPTER 7 RECOMMENDATIONS 80

REFERENCES 81

Appendix A Material and Water Quality changes in Bench Scale Experiments 86

Appendix B Example of Data Processing for Critical Flux Determination Experiment

100

Appendix C Example of Data Processing for a Multi-cycle Membrane Filtration

Experiment 104

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

VI

211 Membranes 13

2111 Membrane characteristics 13

2112 Preparation of membrane 13

2113 Hydraulic cleaning of membranes 14

2114 Flux recovery 14

212 Batch tests for zeta potential titration 14

213 Jar tests 15

214 Specific resistance and cake compressibility 15

215 Critical flux determination 18

2151 Sample pretreatment 18

2152 Microfiltration process 19

216 Multi-cycle filtration test 20

2161 Sample preparation 20

2162 Microfiltration process 20

217 Dead end microfiltration test 22

CHAPTER 3 IMPACT OF POLYMERS ON COAGULATION OF LAUNDRY

WASTEWATER 23

31 Batch tests 24

32 Jar tests 26

33 Specific resistance to filtration and cake compressibility 29

34 Summary 33

CHAPTER 4 IN-LINE COAGULATION AND MF CRITICAL FLUX AND

LONG-TERM MF OPERATION 34

41 Jar tests identifying dosing regimes 35

42 Critical Fluxes for the dosing regimes 36

43 Multi-cycle constant flux MF experiments 39

VII

44 Multi-cycle microfiltration tests at 50 L m-2h-1 for simulating the full-

scale operation 44

45 Contaminant removals in bench scale MF experiments 46

45 Summary 47

CHAPTER 5 FULL-SCALE EXPERIMENTS ON THE SHOWER WASTEWATER

REUSE SYSTEM 48

51 SWRS description 50

511 System overview 50

512 Microfiltration characteristics 53

513 RO filter 53

514 Chemical injection system 53

515 Air system 54

516 GAC filter and UV light 54

517 Microfiltration operating without high pressure pump set-up and

backwashing strategy 54

52 SWRS setup and dosing strategy at Penn State Laundry Building 54

53 SWRS operation at various microfiltration permeate flux with clean

water 56

54 Results of long-term SWRS operation 57

55 Water quality changes 60

56 SWRS operation problems 61

561 Pre-filter fouling 61

562 RO scaling 61

563 Other problems 62

57 Hypotheses regarding differences between bench-scale experiments and

full-scale tests 62

VIII

571 Water quality 62

572 Pre-filter sequence 62

573 Cross-flow and backwash 62

574 Coagulated lint particle in the settlement 63

58 Additional multi-cycle bench-scale microfiltration tests on Penn State

laundry wastewater 63

59 SWRS RO Membrane cleaning procedure and SEMEDS analysis 65

591 RO fouling during operation 65

592 RO membrane autopsy and sample preparation 65

593 SEM images 65

594 EDS analysis 66

595 TEM images 72

596 RO cleaning and cleaning solutions 74

597 Cleaning solution analysis 75

510 Summary 76

CHAPTER 6 CONCLUSIONS 77

61 Polymer selection for laundry wastewater treatment 77

62 Bench scale MF experiments 77

63 Full-scale tests and RO scaling 79

CHAPTER 7 RECOMMENDATIONS 80

REFERENCES 81

Appendix A Material and Water Quality changes in Bench Scale Experiments 86

Appendix B Example of Data Processing for Critical Flux Determination Experiment

100

Appendix C Example of Data Processing for a Multi-cycle Membrane Filtration

Experiment 104

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

VII

44 Multi-cycle microfiltration tests at 50 L m-2h-1 for simulating the full-

scale operation 44

45 Contaminant removals in bench scale MF experiments 46

45 Summary 47

CHAPTER 5 FULL-SCALE EXPERIMENTS ON THE SHOWER WASTEWATER

REUSE SYSTEM 48

51 SWRS description 50

511 System overview 50

512 Microfiltration characteristics 53

513 RO filter 53

514 Chemical injection system 53

515 Air system 54

516 GAC filter and UV light 54

517 Microfiltration operating without high pressure pump set-up and

backwashing strategy 54

52 SWRS setup and dosing strategy at Penn State Laundry Building 54

53 SWRS operation at various microfiltration permeate flux with clean

water 56

54 Results of long-term SWRS operation 57

55 Water quality changes 60

56 SWRS operation problems 61

561 Pre-filter fouling 61

562 RO scaling 61

563 Other problems 62

57 Hypotheses regarding differences between bench-scale experiments and

full-scale tests 62

VIII

571 Water quality 62

572 Pre-filter sequence 62

573 Cross-flow and backwash 62

574 Coagulated lint particle in the settlement 63

58 Additional multi-cycle bench-scale microfiltration tests on Penn State

laundry wastewater 63

59 SWRS RO Membrane cleaning procedure and SEMEDS analysis 65

591 RO fouling during operation 65

592 RO membrane autopsy and sample preparation 65

593 SEM images 65

594 EDS analysis 66

595 TEM images 72

596 RO cleaning and cleaning solutions 74

597 Cleaning solution analysis 75

510 Summary 76

CHAPTER 6 CONCLUSIONS 77

61 Polymer selection for laundry wastewater treatment 77

62 Bench scale MF experiments 77

63 Full-scale tests and RO scaling 79

CHAPTER 7 RECOMMENDATIONS 80

REFERENCES 81

Appendix A Material and Water Quality changes in Bench Scale Experiments 86

Appendix B Example of Data Processing for Critical Flux Determination Experiment

100

Appendix C Example of Data Processing for a Multi-cycle Membrane Filtration

Experiment 104

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

VIII

571 Water quality 62

572 Pre-filter sequence 62

573 Cross-flow and backwash 62

574 Coagulated lint particle in the settlement 63

58 Additional multi-cycle bench-scale microfiltration tests on Penn State

laundry wastewater 63

59 SWRS RO Membrane cleaning procedure and SEMEDS analysis 65

591 RO fouling during operation 65

592 RO membrane autopsy and sample preparation 65

593 SEM images 65

594 EDS analysis 66

595 TEM images 72

596 RO cleaning and cleaning solutions 74

597 Cleaning solution analysis 75

510 Summary 76

CHAPTER 6 CONCLUSIONS 77

61 Polymer selection for laundry wastewater treatment 77

62 Bench scale MF experiments 77

63 Full-scale tests and RO scaling 79

CHAPTER 7 RECOMMENDATIONS 80

REFERENCES 81

Appendix A Material and Water Quality changes in Bench Scale Experiments 86

Appendix B Example of Data Processing for Critical Flux Determination Experiment

100

Appendix C Example of Data Processing for a Multi-cycle Membrane Filtration

Experiment 104

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

IX

Appendix D Images of SWRS Components and Hose Connection 110

Appendix E Water Quality During SWRS Operation 112

Appendix F SWRS Backwash Strategy without Starting the High Pressure Pump 116

Appendix G RO Fouling Report 117

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

X

LIST OF FIGURES

Figure 21 Schematic diagram of critical flux determination setup 20

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane

filtration test (By Dr Hyunchul Kim) 21

Figure 23 Schematic diagram of dead-end microfiltration experimental setup 22

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH

108 25

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different

pH conditions (pH 72 on the left side) and (pH 11 on the right side)

using five polymers 28

Figure 33 Specific resistance to filtration and cake compressibility (shown as slope)

during the membrane (022 microm PVDF) filtration of raw and coagulated

lint wastewaters (22ordmC) Two different coagulation regimes for each

polymer were employed ie charge-neutralizing (ZP between plusmn5 mV

and highest turbidity removal) and underdosing (more negative ZP

value and relatively poorer contaminant removal) conditions 32

Figure 41 Coagulation-sedimentation of laundry waste water (40ordmC) using

NALCOLYTE 8105 as the coagulant at pH 11 35

Figure 42 Dead-end microfiltration of laundry wastewater for critical flux

determination after various pre-treatment by coagulation with

NALCOLYTE 8105 at pH 11 and constant temperature of 40 ˚C

Permeate flux was constant for 10 min and increased stepwise 38

Figure 43 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for charge

neutralization condition at pH 11 and constant temperature of 40 ˚C 40

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment

XI

Figure 44 Transmembrane pressure to permeate volume in the PVDF microfiltration

(022microm) for ten cycles at various constant permeate flux of polymer

pre-treated laundry lint wastewater with NALCOLYTE 8105 for

overdosing condition at pH 11 and constant temperature of 40 ˚C 41

Figure 45 Transmembrane pressure to permeate volume in the PVDF

microfiltration (022microm) for ten cycles at various constant permeate

flux of polymer pre-treated laundry lint wastewater with NALCOLYTE

8105 for underdosing condition at pH 11 and constant temperature of

40 ˚C 42

Figure 46 Transmembrane to permeate volume in the PVDF microfiltration

(022microm) for multi-cycles at various constant permeate flux for raw

laundry wastewater at pH 11 and constant temperature of 40 ˚C 43

Figure 47 Transmembrane pressure to time in the PVDF microfiltration (022microm)

for ten cycles at 50 L m-2h-1 of polymer pre-treated laundry lint

wastewater with NALCOLYTE 8105 for zero-dosing underdosing

charge neutralization and overdosing conditions at pH 11and constant

temperature of 40 ˚C 44

Figure 48 Contaminant removal () for different treatment methods (pre-filtration

MF and the suspension collected after coagulation and precipitation)

and different dosing conditions on Cintas laundry wastewater 46

Figure 51 SWRS setup outside of the Laundry Building in the Pennsylvania State

University 50

Figure 52 SWRS flowchart under standard operation 52

Figure 53 SWRS front site overview and the main treating components 52

Figure 54 SWRS set-up at Penn State Laundry Building 55

Figure 55 Hose connection a sequential way used in Penn State Laundry

wastewater treatment by SWRS The SWRS unit is on treatment with

wastewater in Bladder 2 which has been coagulated before and

bladder 1 is filling with laundry wastewater at the same time 56

XII

Figure 56 Transmembrane pressure to flow rate for microfiltration of SWRS

operation using tap water 57

Figure 57 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1120 gpm using tap water 58

Figure 58 Transmembrane pressure to time for microfiltration of SWRS at a

constant permeate flow rate of 1055 gpm using tap water 58

Figure 59 Transmembrane pressure to flow rate for microfiltration of SWRS using

laundry wastewater when the flow rate declined due to the fouling on

the mesh filter 59

Figure 510 Contaminants residual and water quality changes during SWRS

operation 60

Figure 511 Multi-cycle test on Penn State laundry water with pre-filtration by 10

μm mesh filter after coagulation 64

Figure 512 SEM images of the fouled RO membrane without Au sputtering a) 03 k

x b) 10 kx 67

Figure 513 SEM images of the fouled RO membrane without Au sputtering c) 583

kx d) 845 kx 68

Figure 514 SEM images of the fouled RO membrane without Au sputtering a) 311

kx d) 612 kx 69

Figure 515 SEM images of the fouled RO membrane with Au sputtering a) 442 kx

b) 938 kx 70

Figure 516 SEM images of the fouled RO membrane where there may have been

less fouling a) 574 kx d) 1157 kx The membrane was pre-treated by

Au sputtering 71

Figure 517 TEM images of the cross-section of the fouled RO membrane 73

Figure D1 SWRS components a) diverter box b) RO GAC filter UV light and

chemical injection pump controller c) MF d) RO vessels 110

XIII

Figure D2 Laundry water inlet connections a) sump and sump pump b) outlet of

the sump pump from Laundry Building c) hose connection to two 3K

bladders d) 3K bladders and SWRS unit 111

XIV

LIST OF TABLES

Table 21 General characteristics of the laundry wastewater in this study 7

Table 22 The characteristics of polymers provided by manufacturers 12

Table 23 Membrane properties used in this study 13

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11

for the five polymers used in the jar tests 29

Table 51 RO cleaning solution and cleaning procedures for sample being shipped 74

Table 52 Concentration of the inorganic elements left in the cleaning solution after

the fouled RO membrane was cleaned 75

Table A1 General characteristics of membranes (Stephenson et al 2000) 86

Table A2 Cintas laundry wastewater quality changes by MF with different pre-

treatments 86

Table A3 Polymers from Cintas Company 87

Table A4 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Penn State Laundry Wastewater 88

Table A5 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 Plus in treating Penn State Laundry Wastewater 89

Table A6 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 90

Table A7 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 91

Table A8 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 92

Table A9 Data obtained from the coagulationprecipitation experiment by

ULTIMER 1460 in treating Cintas Laundry Wastewater 93

XV

Table A10 Data obtained from the coagulationprecipitation experiment by CORE

SHELL 71301 in treating Cintas Laundry Wastewater 94

Table A11 Data obtained from the coagulationprecipitation experiment by CAT-

FLOC 8108 PLUS in treating Cintas Laundry Wastewater 95

Table A12 Data obtained from the coagulationprecipitation experiment by

NACOLYTE 8105 in treating Cintas Laundry Wastewater 96

Table A13 Data obtained from the coagulationprecipitation experiment by NACO

2490 in treating Cintas Laundry Wastewater 97

Table A14 Data obtained from the coagulationprecipitation experiment by

NALCOLYTE 8105 in treating Cintas Laundry Wastewater 99

Table B1 Data processing for critical flux determination experiment 101

Table C2 Data processing for multi-cycle membrane experiments 105

Table E1 Water quality changes by coagulation MF RO and finished water 112

Table E2 Water quality changes by MF in SWRS operation (1) 113

Table E3 Water quality changes by MF in SWRS operation (2) 114

Table E4 Water quality changes by MF in SWRS operation (3) 115

Table F1 SWRS data of all treatment units with tap water (normal operation) during

the first 10 min operation with laundry water and after 30 min

operation with laundry water (RO scaling) 117

Table F2 SWRS data on the tap water after RO scaling 118

XVI

ACKNOWLEDGEMENTS

I am deeply indebted to my advisor Prof Brian A Dempsey who gave me the

opportunity to pursue higher learning and provided the continual support time advice

and guidance throughout this project and study at Penn State

I would like to thank Dr Hyunchul Kim who led me to the area of science and research

hand by hand for his generous support and guidance

I would also like to thank the committee member Prof Rachel A Brennan for her

suggestions from one of the best courses I have ever taken and Prof Fred S Cannon for

his valuable hints and the time on reviewing this thesis

The following peopleorganizations are also acknowledged and thanked for performing

specific analyses and supports Harry Su for providing the Energy-dispersive X-ray

spectroscopy (EDS) tests Bangzhi Liu (Material Research Institute) for coaching in the

use of the Field Emission Scanning Electron Microscope (FESEM) Missy Hazen for

supports in the use of Transmission electron microscopy (TEM) Henry Gong for

conducting the analysis of Inductively Coupled Plasma (ICP) and Albert Matyasovsky

for his encouragement and support

My family members and friends are deeply thanked for their encouragement and

continual support throughout my study

XVII

DEDICATION

This thesis is dedicated to my mother Qingping Ma for her support encouragement

and constant love that sustained me throughout my life

XVIII

ABBREVIATIONS

BOD Biological oxygen demand

CN Charge neutralization

Coag Coagulation

COD Chemical oxygen demand

DI De-ionized

EC Electrocoagulation

EDS Energy dispersive spectroscopy

Epi-DMA Epichlorohydrin dimethylamine

ETS Expeditionary tricon system

FESEM Field emission scanning electron microscope

GPM Gallon per minute

ICP Inductively coupled plasma

LMH L m-2h-1

MF Micro-filtration

MFI Micro-flow imaging

MW Molecular weight

NOM natural organic matter

OD Over-dosing

PA Polyamide

PACl Polyaluminum chloride

PDADMAC Poly-diallyldimethylammonium chloride

PP Polypropylene

XIX

PPM Part per million

PSD Particle size distribution

PVA Polyvinyl alcohol derivative

PVDF Polyvinylidene fluoride

RO Reverse osmosis

Sed Sedimentation

SEM Scanning electron microscope

SWRS Shower wastewater reuse system

TMP Trans-membrane pressure

TP Total phosphorus

TSS Total suspended solids

TEM Transmission electron microscopy

UD Under-dosing

UF Ultrafiltration

VFD Variable frequency drive

ZP Zeta potential

1

CHAPTER 1 INTRODUCTION

11 Project background

The increasing demand for usable water has focused attention on alternative sources

of water as well as water recycling and water re-use concepts Grey water which

contains water captured from sinks baths showers and laundries has traditionally been

considered a potential water source for re-use In industrialized countries approximately

150 liters of water are consumed per person per day and 60-70 of this water becomes

grey water (SHOMERA 2008)

Water is regarded as the second biggest logistic issue for military bases second only

to fuel Therefore conservation and reuse of grey water are important This is especially

true for military forward operating bases (FOBs) in Iraq and Afghanistan where water

supplies are limited and most bases do not have access to large water treatment facilities

Therefore an effective efficient reliable and flexible system for water recyclingreuse

system is particularly necessary to be investigated

Generally laundry effluents contain high levels of total suspended solids (TSS)

chemical oxygen demand (COD) total phosphorus (TP) and biological oxygen demand

(BOD) The pH of laundry waste water varies over a broad range from neutral to pH125

depending on what kind of detergent and other chemicals were used in the laundering

process (Sostrar-Turk et al2005) The most widely used methods for treatment of

laundry waste water are coagulation flotation precipitation adsorption and chemical

oxidation or a combination of these (Janpoor et al 2011) However the traditional

methods are insufficient for a small scale shower and laundry waste water treatment at

FOBs due to the inconstant water quality the need for simultaneous removal of TSS

surfactants and TP and especially the requirement for a small footprint and flexible

treatment unit that can be easily equipped and shipped

Besides conventional laundry wastewater treatment new technologies such as

membranes and electrocoagulation (EC) have been studied in recent years for the

2

treatment of laundry wastewater EC methods for laundry waste water treatment were

studied by several researchers ( Janpoor et al 2011 Can et al 2003 and Wang et al

2009) using aluminum plates Compared to conventional coagulants EC with aluminum

plates yielded better contaminant removal under some conditions However the product

water quality still failed to meet the minimum water quality guidelines for water re-use

In addition the effect of EC highly depends on the operating conditions so that the

application of EC will be challenging for laundries that have variable water quality and

high pH

In recent years membrane filtration has become widely used in wastewater

reclamation and recycling The study of potential water reuse by membrane filtration and

combined technologies has been conducted in areas of municipal wastewater effluent

(Wintgens et al 2005) municipal secondary effluents (Acero et al 2010) textile

effluents (Marcucci et al 2001) textile dyehouse wastewater (Soacutejka-Ledakowicz et al

1999) rural wastewater (Hyun et al 2009) and industrial wastewater (Sanchez et al

2010) Membrane filtration is an increasingly important technique for removal of

particulate suspensions in areas such as biotechnology water and wastewater treatment

and several industrial manufacturing processes For laundry wastewaters membrane

processes may have several advantages compared to conventional treatment including

better effluent quality reduced environmental impact of sludge reduced footprint

enhanced flexibility and increased tolerance of variable water quality (Baker 2004)

The main practical problems of membrane filtration are the reduction of permeate

flux with time or increase of transmembrane pressure (TMP) for constant permeate flux

caused by membrane fouling ie the accumulation of feed components in the pores and

on the membrane surface Membrane fouling involves specific interactions between the

membrane and adsorbed solutes and other solutes in the feed stream Fouling is

characterized by a time dependent decline in flux that can be irreversible in some cases

Thus fouling directly influences lifecycle costs for membrane treatment systems

Guilbaud et al (2010) used a direct nanofiltration (NF) process to treat grey waters

from washing machines in ships The results showed the tubular polyamide

3

nanofiltration membrane produced a quality of permeate that permitted recycling of 80

of the grey water when the NF was operated at 35 bar and 25 degC Pre-treatment was

needed to reduce the energy consumption and the cost Lee et al (2000) applied a pre-

treatment with the conventional coagulants polyaluminum chloride (PACl) and ferric

chloride (FeCl3) to test the flux enhancement in ultrafiltration (UF) and MF They

showed that the permeate flux was greatly enhanced by adding aluminum and ferric salts

whereas for the MF the flux decreased

Coagulation is a well-known traditional treatment with a long history in potable water

treatment industry The usage of coagulation as the pre-treatment step before other

technologies is also widely applied in all kinds of water treatment areas For most

wastewater the contaminants in the raw wastewater are negatively charged Similar

particles with negative surface charges repel each other and tend to remain stable without

adding a coagulant Al3+ and Fe3+ coagulant salts such as alum or ferric chloride can be

added resulting in destabilization and aggregation of particles in the waste water

Various organic polymers can also be added in order to coagulate including cationic

polymers that can also assist in neutralizing the negative charge on the contaminant

particles Charge neutralization (CN) means that just enough positively charged

coagulant has been added to neutralize the negatively charged contaminants Other

coagulation mechanisms may also be important including sweep floc and bridging For

MF treatment it is important to minimize the total mass and volume of added coagulant in

order to prevent excessive buildup of materials on the membrane CN by cationic

polymers has been used in potable water treatment in order to minimize production of

sludge

Most of the research dealing with laundry wastewater reuse by the combination of

coagulation and membrane filtration has been carried out in a lab or on a small pilot scale

(Hoinkis et al 2007) and no work has been reported on the use of cationic organic

polymers for the enhancement of MF and RO performance for laundry wastewater

4

12 Objectives

The objectives of this study were to investigate the application of coagulation plus

membrane filtration for the treatment of laundry wastewater for re-use Tests included

scales ranging from bench-scale lab experiments to full-scale operation In preliminary

studies it was discovered that very high doses of the conventional metallic coagulants

(eg alum and ferric chloride) were required due to the high pH of laundry water and the

generally high coagulant demand in laundry water High doses of conventional

coagulants resulted in membrane fouling during lab tests and it was anticipated that filed

application of metallic coagulants would result in severe logistic problems associated

with large volumes of chemicals and with disposal of sludge Consequently various

cationic polymers were investigated The effects of each polymer on contaminant

removal and on reducing membrane fouling were compared Furthermore the study was

also to provide a better understanding about the problems faced in full scale operation

and the fouling of RO which occurred during operation Since coagulation is usually

applied as the pre-treatment for membrane filtration this study can be also regarded as

guidance in coagulant selection and processing optimizing in all kinds of water treatment

facilities equipped with a membrane filtration section

The steps designed to achieve this aim were to

1 Broadly evaluate the zeta potential profiles in coagulation

2 Determine the removal rate of the contaminants in coagulationsedimentation

3 Investigate the membrane performance via specific resistance and compressibility

tests

4 Evaluate the performance at different pH and coagulant dosages

5 Determine the dosing regimes for the final selected polymer

6 Determine the critical flux of MF under each dosing regime

7 Compare the membrane performance in long-term operation of multi-cycles with

hydraulic cleaning for different dosing and flux conditions

5

8 Conduct full scale operation based on the optimized polymer dosage

9 Diagnose the effects of coagulant dosing during full scale operation

10 Develop hypotheses about successes and failures during full-scale operation and test

the hypotheses in the lab and

11 Investigate the physical and chemical characteristics of the RO fouling that was

observed during full-scale operations

13 Organization of the thesis

This thesis addresses several aspects of the polymer coagulation process in laundry

wastewater treatment and PVDF membrane performance in this hybrid filtration process

Laundry wastewater for these studies was obtained from a local commercial laundry

(CINTAS Inc) and from the Penn State laundry facility

The experimental materials and methods are contained in Chapter 2 The

experimental results are presented in the following three chapters

Chapter 3 is primarily related to the polymer selection and screening process In this

chapter 9 polymers supplied by the Nalco Company (Naperville Illinois United States)

were investigated in batch tests to evaluate the coagulation performance of laundry

wastewater Zeta potential (ZP) was measured as a function of coagulant dose The

selection criteria were low required coagulant dose and broad range of doses producing

ZP in the range -10 to +10 mV Based on the batch test results five polymers were

selected for further investigation of contaminant removal and membrane performance

Jar tests (20 min of mixing followed by 60 min of settling) were performed to evaluate

the polymer effects on ZP TSS COD TP turbidity and pH At the same time a dead-

end filtration system with PVDF membranes was used to measure specific resistance to

filtration and coefficient of cake compressibility After comparing the performances of

these five cationic polymers NALCOLYTE 8105 (a polymerized epichlorohydrin

dimethylamine Epi-DMA) was selected for further study as was effective over a broad

coagulant dose and at high pH Some of the work reported in this chapter especially

6

specific resistance to filtration and cake compressibility tests were done by Dr Kim and

that is acknowledged in the chapter

In Chapter 4 membrane filtration test results are reported that allowed identification

of critical flux values as a function of coagulant dose Especially three dosing regimes

(under-dosing charge neutralization and over-dosing) were studied using NALCOLYTE

8105 Subsequently multi-cycle constant permeate flux experiments were run in order to

investigate longer term effects of NALCOLYTE 8105 on operation and fouling of PVDF

MF membranes

Chapter 5 includes reports regarding the use of NALCOLYTE 8105 as a pre-

treatment to the membrane processes in the full-scale SWRS which was located adjacent

to the Penn State laundry facility In this part of the study it was discovered that RO

fouling was a serious problem That and other issues associated with full-scale

implementation of the treatment strategy are currently under further investigation

The conclusions and recommendations drawn from this work are in Chapter 6 and 7

respectively

7

CHAPTER 2 MATERIALS AND METHODS

21 Laundry wastewater description

Laundry wastewater samples were randomly collected from two locations One was

from a discharge pipe of a local industrial laundry ndash Cintas which is a private company

categorized under Uniform Rental Service in State College PA And the other one was

obtained from a sump inside of the Laundry Building of Penn State The sample was

collected during the laundry process Temperature and pH of raw water sample were

measured on site and the sample was stored at 4 ˚C prior to use Table 21 shows the

general characteristics of raw wastewater sample collected for this study

Table 21 General characteristics of the laundry wastewater in this study

Parameter Cintas Laundry (N=3)

Penn State Laundry Building (N=3)

pH 122plusmn05 1056plusmn02

Temperature (ordmC) 41plusmn10 38

ZP (mV) -61plusmn70 -296plusmn33

Conductivity (μS cm-1

) 1240plusmn267 2020

Turbidity (NTU) 735plusmn130 110plusmn56

COD (mg L-1) 1196plusmn72 414plusmn105

TP (mg PO43-L) 704plusmn8 729plusmn29

TP (mg TPL) 23plusmn4 235plusmn96

TSS (mg L-1

) 319plusmn90 168plusmn96

The temperature and turbidity of raw sample from Penn State Laundry Building were

measured once

8

22 Zeta potential (COD TSS Turbidity TP)

Zeta potential is the measurement of the net charge of the particles by determining the

electrophoretic mobility The development of a net charge at the particle surface affects

the distribution of ions in the surrounding interfacial areas resulting in an electrical

double layer around each particle The inner region which is called Stern layer contains

opposite charged ions that are strongly bound to the particle and move with it The ions

in the outer diffuse region are less firmly attached and any ions beyond the boundary

between the two layers do not travel with the particle The boundary is called the surface

of hydrodynamic shear or slipping plane and the zeta potential indicates the potential that

exists at this boundary (Malvern Instrument 2003)

The technique measures the displacement of particles when subjected to an electrical

field in a polar medium The two technologies listed below were applied to measure the

zeta potential in this study

221 Zeta Sizer Nano series

Zeta Sizer (ZEN 3600 Malvern Instrument) was applied in most of the ZP

measurements including raw water batch tests jar tests and the determination of

coagulation regimes The electrophoresis experiment on the sample is obtained by

measuring the velocity of the particles using laser Doppler velocimetry The ZP can be

obtained by application of the Henry equation (Eq 1) Four measurements were taken

and the results were averaged

UE= [ ]( ) Eq (1)

Where = Zeta potential

ＵＥ

= Electrophoretic mobility

= Dielectric constant

= Viscosity

f = Henryrsquos function

9

222 Zeta Compact

The Zeta Compact supplied by CAD Instrumentation was used for the precise

measurement such as determining the ZP of the MF filtrate Three measurements were

taken and the results are averaged

22 DI water

The high purity DI water used in dilution and membrane filtration tests was generated

by Milli-Q (Millipore Gradient A10) The DOC and resistivity of this water were less

than 005 mg L-1and 182 MΩcm-1 respectively The DI water for all the other purposes

was obtained in the lab using a research-grade water system

23 pH and conductivity

The pH and conductivity were measured by a Hach Sension 156 pHconductivity

meter The instrument was calibrated with Hach pH and conductivity standards every

month

24 Total suspended solids

A glass fiber filter (01 microm Whatman GF) was used in TSS measurement The

weight of the original filter was measured by a digital balance before 30 ml of water

sample was filtered After the filter was completely dried in the drying oven overnight at

60 degC the weight was measured again The difference between the two measurements

was the TSS of the 30 ml sample

25 COD and Total phosphorus

The COD and TP were measured according to the standard methods in the Standard

Methods for Water and Wastewater Measurement (21st edition)

10

26 Turbidity

Turbidity was measured using a Hach 2100P turbidimeter which was calibrated using

Hach turbidity standards before use Samples were measured twice and the results were

averaged

27 SEM

The physical nature of the membrane surface and the foulant layer was examined by

field emission scanning electron microscope (FESEM) (Leo 1530) Samples were

completely dried before tests In order to increase the resolution of scanning electron

microscope (SEM) images some samples were pretreated by Au sputtering due to the

low electric conductivity of the membrane polymer Images were obtained under 05-10

kV at a magnification range of 300-12000x The SEM test was conducted with the

assistance of Dr Bangzhi Liu

28 TEM

The structure of RO membrane was viewed in the cross-sectional images which were

obtained by transmission electron microscopy (JEOL JEM 1200 EXII)

The samples were completely dried placed in the cryoultramicrotome at -120degC and

cut into 70 nm sections before Transmission electron microscopy (TEM) test These

sections were placed on 400 mesh copper grids and viewed in the microscope The TEM

was conducted with the assistance of Missy Hazen

29 Particle size distribution and particle images

The Micro-Flow Imaging (MFI) DPA4200 (Brightwell technologies Inc Canada)

was used to determine the particle size distribution (PSD) and to collect particle images

The procedures are listed below

11

1 Prior to each sample run particle-free fluid (DI water) was flushed through the

system to provide a clean baseline and to optimize the illumination

2 The samples and controls were allowed to stand for 10 min at atmospheric

pressure and room temperature in order to assist in removing any air bubbles

which might have formed after sample preparation Then the samples and

controls were gently inverted and swirled taking care not to introduce air bubbles

3 1ml of each sample and control was gently drawn up into the pipette tip (100-

1000microL sterile aerosol pipet tip VWR) and placed in the inlet port Stirring was

set to the lowest setting

4 Data for the first 02 ml was discarded in order to purge any fluid that had been

left in the fluid path

5 During the run successive frames were displayed in screen This provided visual

feedback on the nature of the particle population as well as visual confirmation of

the data obtained

6 For each test PSD particle images circularity and mean intensity were collected

7 After each test the system was flushed with DI water soaked in 2 detergent

solution overnight flushed with DI water and preserved with 5-6 mL of DI water

remaining in the syringe barrel to wet and protect the system

210 Polymeric coagulants

Polymers are water soluble long-chain organic molecules which are widely used as

coagulants coagulant aids or flocculants in water treatment industry The properties of

polymers are affected by specific functional groups within the small chemical unit which

makes up the polymer with a molecular weight (MW) ranging from 50000 to over

10000000 (Mangravite Intertech 2002) The positive or negative charge exhibited by

the polymer the formation of H-bonds and hydrophobic interactions or charge transfer

interactions are also determined by the functional groups and result in various

performances in coagulationflocculation process

12

The majority of the reported cationic polymers are covered by quaternary ammonium

containing structures (Jaeger et al 2010) Epichlorohydrin dimethylamine (Epi-DMA)

and poly (diallyldimethylammonium chloride) (PDADMAC) have been applied in water

treatment since late 1980s (Dentel 1991) and proven to be the best selected coagulants

for treating laundry discharges to enhance the downstream MF performance in this

Four packages of commercial polymers (Appendix A Table A3) were purchased

from Nalco Company and nine of them were independently introduced in the coagulation

process All polymers were diluted to 1 (vv) with DI water before use and the dosage

of the polymers in this study was expressed as part per million (PPM) micro-liter of

undiluted polymer per liter of solution The characteristics of polymers used in this study

are shown in Table 22

Table 22 The characteristics of polymers provided by manufacturers

Polymer Ionicity Charge density Molecular weight Composition Form

Ultimer 1460

Ultimer 7752

Core shell 71301

Core shell 71303

Core shell 71305

Cat-Floc 8102 Plus

Cat-Floc 8108 Plus

NALCOLYTE

8105

Nalco 2490

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Cationic

Amphoteric

50-80

50-80

50-80

20-50

1-30

Unknown

Prime

Prime

Prime

High

Very high

(gt20MM)

Very high

Very high

Low (lt50 K)

Medium (1-3

MM)

Low (lt50 K)

AcAmDADMAC

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

AcAmDMAEAMCQ

PolyDADMAC

PolyDADMAC

EpiDMA

AADMAEAMCQ

Liquid

Emulsion

Prime

Prime

Prime

Liquid

Prime

Prime

Prime

AcAm = acrylamide DADMAC = diallyldimethyl-ammonium chloride DMAEAMCQ = dimethylaminoethylacrylate

methyl chloride salt polyDADMAC = polydiallyldimethyl-ammonium chloride EpiDMA = epichlorohydrin and

dimethylamine (asymp polyquaternary amines) AA = acrylic acid

13

211 Membranes

2111 Membrane characteristics

Flat mesh-filters were obtained by cutting a 10 microm polypropylene (PP) bag filter

(Serfilco) into pieces for sample pre-filtration

A general characteristic of membranes concluded by Stephenson et al (2000) are

listed in Appendix A (Table A1) Hydrophobic symmetric Polyvinylidene fluoride

(PVDF) MF membrane (022 μm Millipore) was selected in this study PVDF is a

highly non-reactive and pure thermoplastic and the membrane has an excellent durability

chemical and temperature tolerance and biological resistance The general

characteristics are listed in Table 23

Table 23 Membrane properties used in this study

Manufacturer Millipore

Material Polyvinylidene fluoride (PVDF)

Type Flat sheet

pore size 022 μm

Effective filtration area (cm2) 113

Pure water permeability (at 20 degC 10 Psi)

(lm2 h) 2020a

Intrinsic membrane resistance Rm 119 times 1011 mminus1

Phobicity Hydrophobic

Protein Binding Capacity as Insulin (microgcm2) 262 a The pure water permeability was obtained with DI water using constant pressure

membrane filtration experiment described in Section 217

2112 Preparation of membrane

New membranes were soaked for 10 min in methyl alcohol to increase the

hydrophility then flushed and soaked overnight in DI water prior to filtration tests The

membrane pure water permeability was measured with Milli-Q water in the constant

pressure filtration test at 10 psi for 10 min

14

2113 Hydraulic cleaning of membranes

Hydraulic cleaning of the fouled membranes involves surface flushing and backwash

using Milli-Q The surface flushing was performed manually and the backwash was

conducted by 20 seconds filtration of pure water by a pressurized vessel (Model 720340

Advantec MFS Inc CA) at 10 psi regulated by nitrogen gas after flipping the membrane

upside down in the membrane module

2114 Flux recovery

After hydraulic cleaning pure water permeability was measured with Milli-Q water

by conducting a constant pressure MF test (Section 217) for 10 min to determine the

irreversible fouling indicated by flux recovery rate JWJ0 (JW the pure water flux after

hydraulic cleaning J0 the initial pure water flux of the membrane without fouling)

212 Batch tests for zeta potential titration

Laundry wastewater (1 L) was filtered with 10 μm PP mesh filters transferred to a

12 L glass beaker the pH was adjusted to desired conditions (pH 7 for neutralized

condition pH 11 for the other measurements) using diluted HCl and NaOH solutions and

a given volume of each polymer (started with a small dosage) was added into the beaker

with agitation corresponding to approximately 200 s-1 of velocity gradient (G-value) by a

magnetic stirrer (cylindrical 25mm x 8mm) Polymer was step dosed after each 7-min

agitation and 15 mL sample was collected at the end of every stirring stage to

measurement the ZP changes of the coagulated sample until the ZP showed positive

values The variation in pH and conductivity of the sample solution was also monitored

during ZP titration tests Nine commercial polymers were investigated under each pH

condition and five of them were selected for further experiments

15

213 Jar tests

A series of jar test runs were performed to compare the coagulants effect on the

removal of contaminants in terms of turbidity TSS COD and TP by

coagulationsedimentation Laundry wastewater was pre-filtered with 10 μm

polypropylene (PP-10) mesh filter and the pH of the filtrate was adjusted to desired

conditions using diluted HCl and NaOH solutions prior to jar test After the pretreatment

25 L water sample was equally transferred into five 600 mL glass beakers before the

addition of targeted polymer at the same time The mixing (220 s-1 as G-value) was

introduced by the Phipps amp Bird stirrer with conventional blades (Model 7790-400) for

20 min immediately after polymers were added and the suspended particles were then

allowed to settle for 1 hour At the end of the agitation 20 L of the mixture was collected

from each of the beakers and the ZP was measured using Zeta Sizer (ZEN 3600 Malvern

Instrument) Supernatant was collected at about 1 cm beneath the water surface to

determine the residual turbidity TSS COD pH and TP after settling

In some experiments the 600 mL glass beaker which contained laundry waste water

was individually located in a 24 L water bath beaker during jar tests to maintain the

temperature of suspension in the range of 40plusmn20 degC by replacing the water in the 24 L

beaker continuously In the other experiments the temperature of laundry waste water

was equivalent to the room temperature (asymp22 ordmC)

214 Specific resistance and cake compressibility

Specific resistance to filtration identifies the increase in hydraulic resistance as a

function of the incrementally increasing mass of filter cake This measurement has been

used by numerous investigators (Tiller 1990 Farizoglu et al 2006 Kim et al 2006) to

determine the effects of coagulant addition on filter performance or to identify

filterability of untreated or treated wastewater samples Experiments were conducted by

measuring permeate volume versus time with a constant TMP applied Additional tests

can be performed using a range of TMP conditions Data were manipulated as described

in the following equations The author of this thesis assisted in these measurements but

Dr Hyunchul Kim was in charge of these measurements

16

tV = [(μαC)(2A2ΔP)]V+(μRm)(AΔP) Eq (2)

α = ([slope]times2A2ΔP)(μC) Eq (3)

α = αoΔP n Eq (4)

where tV is the filtration time per the cumulative permeate volume (sec m-3) μ

the fluid viscosity calibrated by temperature (kg m-1 s-1) C the particle concentration of

sample suspension (kg m-3) A the effective membrane surface area (m2) ΔP the trans-

membrane pressure (TMP Pa) Rm the intrinsic membrane resistance (m-1) α the specific

resistance (m kg-1) and n is compressibility

The slope can be obtained by plotting the data as tV versus V and α is measured

from the slope assuming that other physical parameters are known from Eq (3)

Compressibility is then estimated from the slope in logarithmic plots between α and ΔP

from Eq (4) Specific resistance (α) values obtained in the equations typically represent

an average value of the compressed cake since most of the compress ion of cake occurs in

the first few minutes of operation (Lee et al 2005) Moreover the pressure drop ΔPm by

filter itself is not deducted from total pressure drop (ΔP) caused by both cake and filter

To overcome these limitations in use of the classic equation an alternate method

was used in this study for highly compressible cakes In both dead-end and cross-flow

operation the permeate flux (J) is given by

J = ΔP[(Rm+Rc)μ] Eq (5)

where the total pressure drop (ΔP) is attributed to both the filter (ΔPm) and the

cake (ΔPc) Rc is the cake resistance (m-1) which is related to the cake load (m) and the

specific cake resistance (αc) by

Rc = mtimesαc Eq (6)

where m equals to the cake mass (CV kg) divided by effective filtration area (A

m-2) In dead-end operation m and Rc grow with filtration time which results in

decrease of permeate flux at constant ΔP or increase of ΔP at constant flux In dead-end

17

filtration the cake resistance tends to dominate so that the filtration cycle depends on the

specific resistance of cake formed onto the surface of filter (Lee et al 2005) The

cumulative permeate volume (V measurable in real time) and particle concentration

retained onto filter (C representable as difference in total suspended solid concentration

between feed and permeate samples) can be used Therefore equations (5) and (6) can

be expressed in terms of Rc and αc respectively as follows

Rc = ΔP(μJ) ndash Rm Eq (7)

αc = A(CV) times [ΔP(μJ) ndash Rm] Eq (8)

These equations were used to determine time-varying specific cake resistance in

this study Intrinsic filter resistance (Rm) was measured using particle-free solution (eg

deionized water) to determine specific cake resistance using Eq (8) Cake resistance (Rc)

is to be zero for particle- free solution and Rm can be obtained by examining the trans-

filter pressure (ΔPm) as a function of permeate pure-water flux (J) In general Rm has

been obtained by determining the total pressure drop (ΔP) at the initial water flux (Jo) on

the assumption that cake resistance (Rc) is to be zero when filtration begins and no cake is

deposited on the filter surface (Lee et al 2005 Farizoglu and Keskinler 2006)

The pressure drop across cake (ΔPc) can be also calculated by subtracting the

pressure drop caused by the intrinsic filter resistance (Rm) from total pressure drop (ie

ΔPc = ΔP ndash ΔPm) thus Eq (4) can be modified as follows

αc = αoΔPcn Eq (9)

where αo is an empirical constant that represents specific cake resistance in the

absence of applied pressure Cake compressibility (n) can be obtained by examining the

specific cake resistance (αc m kg-1) as a function of trans-cake pressure (ΔPc Pa) and it

varies between zero for an incompressible layer to greater than a value of one for very

highly compressible layer

Determination of specific cake resistance and cake compressibility consists of two

steps ie (step-I) formation of cake layer by passing a given volume of sample solution

18

includes particles or flocs through a filter or membrane under low trans-cake pressure and

(step-II) compression of cake mass by step-wisely elevating feed pressure The filtration

experiment is conceptually divided into two groups but no suspension occurs in the

filtration of the sample solution between step-I and step-II Using the derived equations

and continuous filtration method it is possible to not only present the variation in

hydraulic resistance from cake itself as a function of trans-cake pressure but also

calibrate resistance to filtration due to additional accumulation o f particles or flocs while

the cake is being compressed by filtering the sample solution

215 Critical flux determination

2151 Sample pretreatment

Critical flux determination tests were conducted with dead-end microfiltration system

as reported (Choi and Dempsey 2004) after sample pretreatment which includes pH and

temperature adjustment and sample pre-filtration by 10 microm PP filter Then targeted dose

of diluted polymer was added into 2 L pretreated wastewater sample which was located

in a 25 L-volume beaker prior to mixing The polymer dosage was determined from the

previous results in jar tests Mixing for coagulation was provided by a laboratory stirrer

(RW20 digital IKA) at 240 rpm for 10 min and by a magnetic stirrer (oval 32mm x

16mm) at minimum rate to prevent the sample from settling during the filtration process

A water bath was applied in some tests to keep the temperature of sample at

40plusmn20 degC by continuously replacing the water left in the water bath with fresh warm tap

water

19

2152 Microfiltration process

A schematic diagram of the experimental setup is shown in Figure 21 After

pretreatment the coagulated laundry discharges were connected to the membrane module

(47 mm In-Line Polycarbonate Filter Holder Pall Corporation) driven by a peristaltic

pump (6~600 rpm Cole-Parmer Instrument Co) which operated at a constant flow rate

of 00147 gpm by a solid state speed controller (Master Flex Cole-Parmer Instrument

Co) The feed pressure was controlled to remain around 10 psi by adjusting a pressure

control valve at the retentate line from where one part of water was diverted back to the

feed tank The critical flux was achieved by stepwise increasing the permeate flux which

was controlled by another peristaltic pump until prominent membrane fouling occurred

in terms of TMP rise in this case The permeate flux was set at a small value at the first

stage and remained constant for 10 min then increased slightly (varied form 25 L m-2 h-1

to 100 L m-2 h-1 depending on membrane performance and water quality) to the next 10

min stage TMP was recorded every seconds by two pressure meters (VWR Traceable

pressure gauge) at the feed and permeate lines and the permeate flux was obtained with

equation 10 by continuously recording the permeate volume using a digital electronic

balance (Ohaus Navigator balance accuracy plusmn 01g) The TMP and permeate flux were

averaged in each stage

J = ∆V(A∆t) Eq (10)

Where J = permeate flux (L m-2 h-1)

∆V = volume of permeate (L)

A = effective filtration area of membrane (m-2)

∆t = time (h)

The experiment was stopped after the TMP of 15 psi was reached An example of the

data processing for the critical flux determination is shown in Appendix B

20

Figure 21 Schematic diagram of critical flux determination setup

216 Multi-cycle filtration test

2161 Sample preparation

Laundry wastewater samples in the multi-cycle MF tests were pretreated using the

same procedures as described in section 2161 However some tests that were operating

at high permeate flux required another 2 L feed water to fill the feed tank when the water

level was running low

2162 Microfiltration process

A schematic diagram of the multi-cycle microfiltration experimental setup is shown

in Figure 22 8-10 cycles of MF tests were applied for each multi-cycle experiment to

investigate the performance of 022 microm flat sheet PVDF micro-filter in the longer term

coagulationMF process After coagulation the sample was immediately connected to

the system and feed at 00147 gpm for 10 min with no permeate flux after both of the

pressure gauges reached and stabilized around 10 psi for system calibration Each cycle

21

contained a filtration (15 min) process followed by hydraulic cleaning which included

surface flush and backwash (Section 2111) Permeate flux was controlled by a

peristaltic pump and was maintained constantly for membrane filtration During filtration

the pressure in both of the pressure gauges should stay in a reasonable range

(approximately 8~12 psi) and not exceed the limit (20 psi) by adjusting the pressure

control valve in the retentate line The MF experiment was stopped when the TMP was

higher than 20 psi The data was recorded the same way as described in section 2152

An example of the data processing is shown in Appendix C

Figure 22 Experimental set-up for a hybrid coagulationcross-flow membrane filtration

test (By Dr Hyunchul Kim)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

1 Feed tank

2 Feed pump

3 Dampener

4 Membrane module

5 Pressure control valve

6 Digital pressure gauge

7 Permeate pump

8 Digital balance

9 Pressure vessel for backwash

10 Nitrogen gas cylinder

11 Precision pressure regulator

Discharge

DIWDIW

1 2 3 4

56

6

7 8

9 10

11

Polymer

(1 Nalcolyte 8105)

22

217 Dead end microfiltration test

A schematic diagram of the dead-end MF experimental setup is shown in Figure 23

The membrane module was connected to the pressurized vessel (Model 720340

Advantec MFS Inc CA) and operated at a targeted feed pressure regulated by nitrogen

gas The pure water flux experiments were conducted with DI water at a constant

pressure of 10 psi A magnetic stirrer (oval 32mm x 16mm) was applied in coagulated

water sample at a minimum rate to prevent the sample from settling during filtration tests

The permeate flux was determined using a digital electronic balance (Ohaus Navigator

balance accuracy plusmn 01g) and calculated by equation 10 (section 2152) All

experiments were conducted at room temperature (asymp22 degC)

Figure 23 Schematic diagram of dead-end microfiltration experimental setup

23

CHAPTER 3 IMPACT OF POLYMERS ON

COAGULATION OF LAUNDRY WASTEWATER

The aim of this chapter was to provide an insight to the coagulation process of

laundry wastewater and to select the best polymers and the optimum polymer dosing for

coagulation Trends of zeta potential and removal of contaminants (COD turbidity TP

and TSS) by sedimentation were investigated for several cationic polymers at different

pH conditions In addition the specific resistances to filtration and the coefficients of

cake compressibility were investigated

Dr Hyunchul Kim was primarily responsible for the specific resistance and cake

compressibility work that is described in section 33 Those data are included in this

chapter because I was involved in these experiments (and will be a co-author on the

manuscript) and because those data are important for providing a comprehensive logic

about the process that was used to identify the best polymer and the optimized

operational conditions for treatment of laundry wastewater

24

31 Batch tests

Batch titration tests (Section 212) were conducted to identify the ability of different

polymers to neutralize the anionic charge on the particulate and dissolved materials in

laundry wastewater The ZP of raw laundry waste water was highly negative In the

coagulation process cationic polymer was added to reduce the particle negative surface

charge destabilize the suspension create agglomeration and form highly porous loosely

bonded aggregate (floc) (Kim et al 2001) Previous research shows the performance of

precipitation and membrane filtration is favored when the zeta potential after coagulation

is in the range of -10mV to +3mV (Sharp et al 2006) The surface charge on the solid

particle also depends on the pH in the solution (Stumm 1992) As the pH increases the

surface charge becomes increasing negative Therefore the goal in this part of the

experimental work was to find coagulants for which the required dose was low and that

would be effective over a broad range of doses Therefore we wanted to find polymers

that could bring ZP to gt-10 mV with a low coagulant dose and maintain ZP within the

range -10 to +3 mV over a broad range of coagulant doses

Since laundry wastewater usually is alkaline the ZP was determined as a function of

coagulant dose at both high and neutralized pH conditions Nine cationic polymers were

selected from four categories (packages) of commercial polymeric coagulant (Table A3

in Appendix A) in this test The selections were made based on recommendations by

technical personnel and from the polymer manufacturer

25

Figure 31 Effect of polymer dose on zeta potential at (top) pH 72 and (bottom) pH 108

Results from the batch tests are shown in Figure 31 In general ZP increased rapidly

with the lowest coagulant doses and the ZP stabilized near 0 mV for some of the

coagulants More chemical dosage was needed for high pH than for the pH neutralized

condition and some polymers (ULTIMER 1460 CORE SHELL 71303) failed to fully

neutralize the wastewater with moderate coagulant doses The failure to completely

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Zeta

po

ten

tial (m

V)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 72plusmn01

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800

Polymer dose (microL L-1

)

Ze

ta p

ote

nti

al

(mV

)

ULTIMER 1460

ULTIMER 7752

CORE SHELL 71301

CORE SHELL 71303

CORE SHELL 71305

CAT-FLOC 8102 PLUS

CAT-FLOC 8108 PLUS

NALCOLYTE 8105

NALCO 2490

pH 108plusmn03

26

neutralize could indicate that the cationic functional groups of some of the polymers were

weakly basic and that the cationic charge on the polymer might be lower at pH 108

In addition to the ability to neutralize negative charge on the contaminants the

following aspects should be taken into account in polymer selection

1 It should be easy to prepare diluted solutions

2 The concentrated and diluted solutions should be stable over a range of

temperatures and easy to apply in the desired dosage

3 The best polymer should result in low absolute ZP values over a broad range

of coagulant doses

4 Application of the polymer should result in reduced concentrations of

contaminants after sedimentation or membrane filtration

5 The polymer should be effective at low doses compared to conventional

coagulants

6 The coagulant should be relatively inexpensive

7 Application should result in reduced fouling and in improved long-term

operation in MF

8 The polymer should be effective for both neutral and high pH conditions

Ultimer 1460 Core shell 71301 Cat-Floc 8108 NALCOLYTE 8105 and Nalco

2490 seemed to satisfied many of the selection criteria (further evaluation of some of

these criteria is reported later in this thesis) and were selected for further testing

32 Jar tests

Zeta potential and contaminant removal profiles for the five selected coagulants were

obtained from coagulation-precipitation experiments Results from these batch tests are

shown in Figure 32 Generally the highest contaminant removals occurred at the CN

27

condition but removals were good for coagulant doses close to the CN dose Most of the

polymers achieved 90 removal of turbidity and TSS and 60 removal of COD after

precipitation at both pH conditions However jar test results showed that coagulation-

sedimentation of laundry wastewater with cationic polymers resulted in poor P removal

(less than 30 ) Similar results were also found by some other researchers Trejo-

Gaytan et al (2006) suggested that the poor P removal might be due to a lack of a

subsequent low-intensity mixing flocculation phase It should be noted that use of

cationic polymers in potable water treatment also often results in poor removal of anionic

contaminants especially natural organic matter (NOM)

The results showed that 160 microLL dosage of Ultimer 1460L was sufficient to achieve

a high removal of contaminants (90 of turbidity 78 of TSS 60 of COD) (Figure

32 a) The contaminant removals declined to approximately 40 of turbidity 12 of

TSS and 47 of COD when the dosage of Ultimer 1460 was increased to 291 microLL

which was an OD condition for which the ZP was +8mv ie the particles were re-

stabilized due to too charge reversal Similar results were found for the other polymers

The data regarding water quality changes as a function of coagulant doses are provided in

Table A4-13

28

Figure 32 Coagulation-sedimentation of lint wastewaters (22ordmC) with two different pH

conditions (pH 72 on the left side) and (pH 11 on the right side) using five polymers

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Nalcolyte 8105 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Ultimer 1460 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Core shell 71301 dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

20

40

60

80

100

0 100 200 300 400 500

Cat-Floc 8108 plus dose (microL L-1

)

Res

idu

al

()

-80

-60

-40

-20

0

20

Ze

ta p

ote

nti

al

(mV

)

Turbidity TSS TCOD T-P Zeta potential

0

30

60

90

120

150

0 100 200 300 400 500

Nalco 2490 dose (microL L-1

)

Resid

ual (

)

-80

-60

-40

-20

0

20

Zeta

po

ten

tial

(mV

)

Turbidity TSS TCOD T-P Zeta potential

a)

b)

c)

d)

i)

j)

e)

f)

g)

h)

29

To further investigate the impacts of cationic polymeric coagulants on the

downstream MF membranes and to optimize the chemical usage for membrane filtration

the coagulant doses needed to achieve CN (dose to raise ZP around 0 mv) and lowest

effective UD (dose to raise ZP to -10 mV) based on the jar test results are shown in Table

31 Maximum contaminant removals were achieved at CN conditions In most cases the

polymer dosage for lowest effective UD was around half of the dosage of CN while still

yielding acceptable performance in contaminant removal

Table 31 Coagulant doses required for charge neutralization and lowest effective

underdosing (zeta potential raised to around -10 mV) at pH 7 and pH 11 for the five

polymers used in the jar tests

pH pH 7 pH 11

Dosing Condition CN (μLL) UD (μLL) CN (μLL) UD (μLL)

Ultimer 1460 196 60 234 79

Core shell 71301 119 60 119 60

Cat-Floc 8108 plus 291 138 291 99

NALCOLYTE 8105 157 40 157 79

Nalco 2490 157 40 157 79

33 Specific resistance to filtration and cake compressibility

The feasibility of using the five selected cationic polymeric coagulants for pre-

treatment prior to MF in laundry wastewater treatment was also evaluated in terms of

specific resistance to filtration and cake compressibility CN and minimum effective UD

dosage conditions for each polymeric coagulant at different pH values were described in

section 32

At pH 7 with cationic polymers addition a lower specific resistance to MF compared

to the raw sample was found for all the five tested polymers at CN condition (Figure 33

30

a) while specific resistance increased for the water after pre-filtration by PP-10 mesh

filter NALCOLYTE 8105 (Epi-DMA) showed the lowest specific resistance among the

five polymers for CN condition at both pH 7 and pH 11(Figure 33 a b) Interestingly

Cat-Floc 8108 plus (PDADMAC) resulted in a nearly horizontal line (slope=01) in the

plot of specific resistance vs applied pressure (Figure 33 a) which means the cake

compression (represented by the slope) on the membrane was negligible as feed pressure

increased At pH 11 NALCOLYTE 8105 and Cat-Floc 8108 plus also showed a

prominent effect in decreasing specific resistance at CN condition because of their

function group were both quaternary amine

Cat-Floc 8108 plus and Ultimer 1460 were the only two polymers that decreased the

specific resistance for the UD condition at pH 7 (Figure 33 c) With Core Shell 71301

(high MW long-chain polymer) dosed in the pretreatment an increase of specific

resistance was found in Figure 33 (b) (c) and (d) which might due to the formation of

long-chain highly adhesive floc with both hydrophilic and hydrophobic functional

groups that could easily adsorb to the PVDF membrane

A substantial decrease in specific resistance was achieved only by NALCOLYTE

8105 for UN condition at pH 11 (Figure 33 d) which was a promising result since

minimum dosage and high pH was the ideal condition for application Combined with its

favorable effect listed about at pH 7 NALCOLYTE 8105 was selected as the best

polymer for further treatment