membrane filtration basics 101 - va awwa operations/2014 va... · 2016. 11. 22. · membrane...

Membrane Filtration

Basics 101 Paul J. Delphos, Black & Veatch 757-456-5380, ext 12

VA AWWA Plant Operations Committee Operators Conference Virginia Beach, VA

May 19-21, 2014

Presentation Overview

Market Assessment

Membrane Theory

Example Applications

What’s The Big Deal??

1st Significant MF/UF System in North America in 1993 (Saratoga, CA – 3.6 mgd)

Over 250 plants now on-line

Historically, small facilities (i.e. < 1 mgd) for small clients

Trend is to fewer, but larger facilities

Minneapolis – 70 and 90 mgd

Singapore – 72 mgd

Lancaster – 24 mgd, expandable to 36 mgd

Desalination Is Growing As Well

SWRO

BWRO

EDR

BWRO

SWRO EDR BWNF

250

20 15 71

110

92 44 110

BWNF

Number of Installations Capacity (mgd)

Other Perspectives

Membrane System Sales To Reach $9 Billion by 2008 (Mcllvaine Company, 2006)

$6.8 Billion in 2005 (33% Top End Growth)

Includes Desalination and Low-Pressure Membranes

Microfiltration from $1.9 to $2.5 Billion

Only 2.5% of US Drinking Water is Treated with MF/UF Membranes

Expected to Reach $10 Billion by 2010

Nearly All New Revenues Are

From New Projects

What Are Membranes?

Cartridge/Pressure

Submerged/Vacuum

Membrane Theory Overview

Colloids

Bacteria

Pollens Yeasts

Organic macromolecules

Organic compounds

Viruses Dissolved

salts

Reverse osmosis

Nanofiltration

Microfiltration

Sand filter

1 0.1 0.01 0.001 0.0001 10 100 um

hair visible

to

naked

eye

Giardia Smallest

microorganisms

Polio

virus

Ultrafiltration

How Do Membranes Work?

Membranes can remove anything that

is larger than its pores.

Giardia

Cryptosporidium

• Membranes fail incrementally – one fiber at a time.

• Statistically, individual fiber breaks are insignificant

to the overall microbial water quality.

Membrane Failure Mode

Bubble point

Air pressure

Sonic wave

Bio-challenge

Turbidity

Particle

monitoring

Direct

Measures

Indirect

Measures

The accepted standard is moving towards

continuous (safety interlock) turbidimeters.

Detection limit 0.001 NTU.

On-Line Integrity Testing

Some Key (and New) Terms

NEW

Flux

Flux Decline

Specific Flux/Permeability

Reverse Filtration

Membrane Integrity

Log Removal

Recovery

Transmembrane Pressure

OLD

Overflow Rate

Declining Rate

????

Backwash

Filter Breakthrough

Filtered Turbidity

Backwash Volume

Filter Head Loss

Piloting Overview

Number of Systems?

Regulatory Acceptance

Verified Membrane Applicability

Basis of Design

Operator Experience

Data Evaluation

City of Lancaster MF Pilot

0

10

20

30

40

50

60

Nov Jan Mar Apr Jun

gfd

p

si

0

2

4

6

8

10

12

ZW 500-C, Sp Permeability @ 20°C ZW 500-C, Instantaneous Flux ZW 500-C, Average TMP

Flux

Recovery/Waste Disposal

Cold Water TMP Issues

Daily Cleans vs. Monthly Cleans

Turbidity

TOC/UV254

Particle Counts – log removal

MIT’s

Membrane Fouling

Causes

Biological

Organic/Colloidal/

Particle

Chemical Scaling

Membrane Compression

Synthetic Polymers

Mitigation Measures

Chlorination

Cross-Flow

Backwash

Chemical Cleaning

Additives/Coagulants

Pretreatment

Membrane Fouling Directly Impacts Costs

Fouling is the limiting factor in most membrane system designs

By removing organics, or natural organic matter (NOM), membranes become much more effective

Coagulation removes NOM by:

Charge Neutralization

Adsorption To Precipitates

With membranes, coagulation is geared to TOC removal

The “cake layer” on pressure systems improves TOC removal

Membrane Fouling

0

2

4

6

8

10

12

14

16

0 50 100 150 200 250 300

Time

Pre

ssu

re -

psi

Membrane

Fouling

Backwash

Irreversable

Fouling

Backwash &

Chemical Cleaning

Membrane Fouling Example

Before and After Backwashing

0

2

4

6

8

10

12

14

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18

20

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22-

Jul

24-

Jul

26-

Jul

28-

Jul

30-

Jul

1-

Aug

3-

Aug

5-

Aug

7-

Aug

9-

Aug

11-

Aug

13-

Aug

15-

Aug

17-

Aug

19-

Aug

21-

Aug

Date

TM

P (

ps

i)

Before BP VacuumAfter BP Vacuum

(1) Vacuum increase due to flux increase corresponding

to re-adjusted permeate flow.

(2) Rain event - organics/color raw water spike, alum

dosage not increased to compensate.

(3) High vacuum alarm --> tank dumped, re-started with

higher alum dosage.

(4) Caustic dosing interrupted.

(5) High vacuum alarm --> clean

(6) Clean - vacuum recovers to 4"Hg.

(7) Ferric dosing interrupted? (Floc tank pH = 6.8).

(8) High vaccum alarm --> system off for 6.5 hours and

then re-started.

(1) (2) (3) (5)(4) (6) (7) (8)

SEM Images of Fouling Layer (UF Membrane, CA, 100k MWCO)

Clean Membrane

Growth of NOM Fouling Layer Over Time

Effect of Backwashing on Fouling Layer

HIOP Cake Layer with Sorbed NOM

Effect of Backwashing on Cake Layer

Clean Membrane, CA 100k MWCO

Dead-End Filtration – 30 Minutes

Dead-End Filtration – 1 Hour

NOM Layer Before Backwash

NOM Layer After Backwash

Coagulant Aid (HIOPS) + NOM Before BW

Coagulant Aid + NOM After BW

Turbidity/pathogen/TOC removal on raw water

Replace conventional filters following flocculation/sedimentation

Treatment of conventional filter backwash water

Pretreatment ahead of RO or NF membrane system

Fe/Mn removal following oxidation

Arsenic Removal

Pathogen removal following conventional treatment

Potential Applications For Low Pressure

Membranes

Typical Pressure MF/UF System

Air System B/W Water

Cl2

Raw

Water

Source

Supply

Pump

Particle

Strainer

CIP System

Membrane

Modules Backwash Waste/

Concentrate

To

Disposal

Finished

Water

Storage

Finished

Water

Pumping

Permeate

Submerged - Enhanced Coagulation

Air

Permeate Pump

Feed Water

Bleed/Concentrate

Flocculation Chamber

Coagulant

Flash Mixer

High solids concentration in tank

Filtered Water

5 to 50 psi

Filtered Water

Filtered Water

Solids and

Liquids Under

Pressure

Pressure vs. Submerged

Pressure vs. Submerged

Pressure

Advantages

Skid-mounted

Easy to install

Great for small systems

Easy competition

High Fluxes

Disadvantages

Larger systems

Fouling/energy

Low Dosages of Coagulant

Backwashing

Submerged

Advantages

Use of existing tanks

Larger systems

Low energy

Great for poor raw water

Low fouling

Backwash recovery

Disadvantages

Modifications can be expensive

Low flux rates

Concentrate with fiber breakage

Filtered Water

5 to 50 psi

Filtered Water

Filtered Water

Solids and

Liquids Under

Pressure

Outside-In vs. Inside-Out

Outside-In vs. Inside-Out

Outside-In

Advantages

Submerged option

Larger active area

Higher solids

Lower Pressure

Dead-end flow

Disadvantages

Lower comparative flux

Irreversible fouling?

Inside-Out

Advantages

Great with clean water

Cross-flow operation minimizes irreversible fouling

Disadvantages

Recirculation required

Higher flux requirements

High fouling potential

Increased energy

MF/UF Modes of Operation

Conventional (Dead-End)

Feed

membrane filter

Cross-flow

Fe

ed

me

mb

ran

e f

ilte

r

Principal Suppliers of Low Pressure Drinking

Water Membrane Systems

Membrane System Suppliers

Pall Corporation (MF/UF)

GE - Zenon Environmental, Inc. (MF/UF)

Evoqua Water Technologies

(Siemens - US Filter/Memcor (MF) )

Wigen, Inc. (UF)

H2O Installations

WesTech

Kruger

Membrane Module Suppliers

GE (UF

Evoqua (MF)

Dow (UF)

Toray (UF)

Hydronautics, Inc. (UF)

Asahi (MF)

Primary Elements of Low-Pressure Membrane

System

Feed water/vacuum pumps

Ancillary pumps

Automatic screens

Skids with PLC-based controls

Clean-in-place (CIP)

SCADA system/PLC network

Air delivery system

Waste holding tank/pumps

Neutralization tank/pumps

Roanoke, VA – Crystal Spring

Spring has been used for drinking water since 1880s

In summer of 2000, VDH determine spring was GWUI as coliform counts increased

Virginia Membrane Plants - Memcor - 14

Koch - 1

VDH “Approved” Other Membrane Manufacturers

Competitive Bid Between Memcor and Pall

Crystal Spring WTP - Design Conditions

5 mgd firm (one rack out of service)

99.5% recovery (backwash recovery)

No pretreatment (chlorine was recommended by Pall)

30 day cleaning cycle

60 minute backwash frequency

10-year membrane warranty

Performance testing for successful bidder

Crystal Spring WTP - Bid Summary

Cost Component

US Filter - Memcor

Pall

Capital $1,600,317 $1,960,000

O&M (20-yr PW)

$436,625 $303,176

Membrane Repl. (20-yr PW)

$357,822 $429,130

Total 20-yr PW $2,394,764 $2,692,306

Performance Testing Operating Results

Flux: 34.8 gfd @ 15oC

TMP: 1 psi increase per 15 to 18 days

Average TMP: 10.5 psi

Backwashing: 150 sec/90 minutes

97% Recovery

CIP Interval of Over 90 days

Crystal Spring WTP – Performance Testing

Criteria

Flux: 34.6 gfd

Recovery: 95% w/o backwash recovery 99.5% w/ backwash recovery

Backwash: 150 sec/60 min

CIP Interval: 30 days

Chemical Consumption Limits

Power Consumption Limits

100 – day Duration

Performance Testing Water Quality Results

Turbidity

Raw: 0.06 NTU to 0.14 NTU

Permeate: 0.02 NTU (lower limit of turbidimeter)

Particle Counts

Raw: 25 to 75 >2 um/mL

Permeate: 2 to 8 >2 um/mL

1 to 1.5 log removal

Pilot Turbidity Spike Data

9.8

9.9

10

10.1

10.2

10.3

10.4

10.5

10.6

14:15 14:40 15:11 15:39 15:44 16:12 16:23 16:40 16:46

Time

TM

P (

ps

i)

0

5

10

15

20

25

30

35

Fe

ed

Tu

rbid

ity

(N

TU

)

TMP

Turbidity``

Permeate <0.023 NTU

Crystal Spring WTP

Spring, Pumps and Screens

Installed Membrane System

Installed Membrane System

CIP System

Membrane System Piping

Operating Data - Flow

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Dece

mber

Janu

ary

Febuar

y

Mar

chApri

l

May

June

July

August

Month

Flo

w (

mg

d)

Operating Data - Flux

20

22

24

26

28

30

32

34

Dec

ember

Januar

y

Febuar

y

Mar

chApri

lM

ay

June

July

August

Month

Flu

x (

gfd

)

Operating Data - Recovery

90%91%92%93%94%95%96%97%98%99%

100%

Dec

embe

r

Janu

ary

Febu

ary

Mar

chApr

il

May

June

July

Aug

ust

Month

Reco

very

(%

)

Operating Data - Turbidity

00.20.40.60.8

11.21.41.61.8

2

Dece

mber

Janu

ary

Febuar

y

Mar

chApri

l

May

June

July

August

Month

Tu

rbid

ity

Operating Data - TMP

0

5

10

15

20

25

30

Febuar

y

Mar

chApri

l

May

June

July

August

Month

TM

P (

psi)

Filter 1

Filter 2

Filter 3

Filter 4

Filter 5

Other 1st Year Results

CIP Interval: 1 per 6 months

Zero Fiber Breaks (over 10 million fibers)

Manpower Reqt’s: < 2 h/d, 5 d/wk

“The Plant Runs Itself” – Greg Belcher, City of Roanoke

Chesapeake, Virginia

7.5 MGD Submerged Membrane Plant

Dedicated in April 2006

Raw Water TOC – 4 to 6 mg/L

Raw Water Turbidity 25 to 50 NTU

Coagulant Feed – 20 to 25 mg/L

Coagulant pH – 5.5 to 6.0

Chesapeake TOC Data

Sample May 8 May 22 May 30 Jun 7

Raw 4.10 4.22 4.50 4.29

Permeate 1.36 1.77 1.88 1.82

% Reduction 67% 60% 58% 58%

Alum Dose (mg/L)

25 20 20 20

pH 5.46 5.87 5.90 5.85

Raw Water Strainers

Pretreatment Tanks

Membrane Tanks

Multiple Membrane Trains with Crane

Lancaster Pennsylvania

24 and 12 MGD WTPs

Regulatory Drivers

LT2 ESTWR (Crypto Removal)

Stage 2 D/DBP Rule

Future Rules

Conventional Facilities

Zenon 500 Upgrade

Direct vs. Clarified Feed

Lancaster, PA

24 and 12 mgd Membrane Facilities

Two of the Largest on the East Coast

Includes State-of-the-Art Thickening Process

Include Two-Stage Membrane Treatment with UV Disinfection

Over $70 million

Great client reference

Lancaster, PA - Pilot Operation

Raw

Pre-screened River Water

Alum Feed

Acid

15 minute floc

99.7% recovery

PACl later

Clarified

Post-clarification

Daily Cleans vs. Monthly Cleans

95% Recovery

EC Jar Tests

Data Evaluation - Permeate

Parameter Raw MF/UF Clarified

MF/UF

EC

Alum Dose 50 mg/L 30 mg/L 70 mg/L

Turbidity <0.03 NTU <0.03 NTU <0.3 NTU

Particle Cts

(#/mL)

<10 <10 NA

TOC Removal 35-50% 15-25% 35-50%

DBP’s 1 3 2

Lancaster – Other Findings

Raw will work on flashy river water

Need to pay attention closely during flashy events

Daily cleans – Helped when working

Heated daily cleans/backwashes helped short-term

High fluxes can be unstable

Lancaster – Other Findings (cont.)

Clarification process is not necessarily an additional barrier or a reduction of risk

Constructability and retrofit costs can be very difficult to quantify

Cold water (<3oC) was difficult

PACl worked best in cold water

Raw water membrane costs (capital and operating) – 30 to 40% above clarified

Swansea Water District, MA

First Desalination Project on East Coast for HDR

1.5 mgd Desalination plus 1 mgd Fe/Mn Groundwater Membrane Plant

Upon completion, will be the 2nd surface water desalination facility north of Florida

Pall/Toray

Summary

Membranes are here and will become a more technology in the future.

Membranes are a great particle removal mechanism

Significant fractions of organics are not normally removed with MF/UF, but when coupled with a coagulant, removals are equal to or better than conventional facilities

Membranes will work on all waters, cost is just the major factor – so, pick the correct system!!!!!!

For more information, contact:

Paul J. Delphos

DelphosP@bv.com

757-456-5380, ext 12

Membrane Filtration

Basics 101