chloramine replacement alternative evaluation...based on this timeframe, the board of public works...

CHLORAMINE REPLACEMENT ALTERNATIVE EVALUATION

DRAFT

B&V PROJECT NO. 196301

B&V FILE NO. 42.2000

PREPARED FOR

Hannibal Board of Public Works

22 DECEMBER 2017

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City of Hannibal | CHLORAMINE REPLACEMENT ALTERNATIVE EVALUATION

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Table of Contents

Executive Summary .............................................................................................................................................. 1

1.0 Introduction .............................................................................................................................................. 1

1.1 Project Overview ....................................................................................................................................... 1

1.2 Background ................................................................................................................................................. 1

1.3 Report Methodology ................................................................................................................................ 2

1.4 List of Abbreviations and Acronymns .............................................................................................. 3

2.0 Existing Facility and Operating Conditions.................................................................................... 5

2.1 Water Demands ......................................................................................................................................... 5

2.2 Raw Water Quality ................................................................................................................................... 6

2.2.1 Raw Water TOC ....................................................................................................................... 6

2.3 Finished Water Quality ........................................................................................................................... 8

2.3.1 Finished Water TOC .............................................................................................................. 8

2.4 Existing Treatment Process Description ...................................................................................... 10

2.5 Water Age .................................................................................................................................................. 11

3.0 Treatment Objectives with Free Chlorine Disinfection ........................................................... 15

3.1 Target DBP Levels at DBPR Monitoring Locations .................................................................. 15

3.2 Target Effluent TOC ............................................................................................................................... 15

4.0 Treatment Alternatives for Reducing DBP Formation ............................................................ 19

4.1 Granular Activated Carbon ................................................................................................................ 19

4.1.1 GAC Adsorption ................................................................................................................... 19

4.1.2 GAC Design Criteria ............................................................................................................ 20

4.1.3 Carbon Reactivation ........................................................................................................... 20

4.1.4 GAC Filter-Adsorbers......................................................................................................... 20

4.1.5 Post-Filter GAC Contactors ............................................................................................. 21

4.1.6 GAC Testing ........................................................................................................................... 22

4.1.7 GAC Size and Media Life Estimate ................................................................................ 25

4.2 Reverse Osmosis .................................................................................................................................... 27

4.3 Enhanced Coagulation ......................................................................................................................... 27

4.4 Ozone .......................................................................................................................................................... 29

4.5 Aeration ..................................................................................................................................................... 30

4.6 Combination of Process Optimizations ......................................................................................... 32

5.0 Facility Requirements for Viable Alternatives ........................................................................... 35

5.1 Alternative 1: Post-Filter GAC Adsorption .................................................................................. 35

5.1.1 Site Location .......................................................................................................................... 35

5.1.2 Transfer Pumping Modifications .................................................................................. 36

5.1.3 GAC System – Pressure Vessels ..................................................................................... 36

5.2 Alternative 2: Reverse Osmosis ....................................................................................................... 38

5.2.1 Site Location .......................................................................................................................... 39


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5.2.2 Pretreatment Facility Requirements .......................................................................... 40

5.2.3 RO System Facility Requirements ................................................................................ 40

5.2.4 Post-Treatment Requirements ...................................................................................... 41

5.2.5 Brine Discharge Considerations ................................................................................... 42

5.3 Alternative 3: Preozone with Enhanced Coagulation and Aeration ................................. 42

5.3.1 Site Location .......................................................................................................................... 42

5.3.2 Ozone Facility Requirements ......................................................................................... 43

5.3.3 Enhanced Coagulation Facility Requirements ........................................................ 43

5.3.4 Aeration Facility Requirements .................................................................................... 43

6.0 Cost Development ................................................................................................................................. 45

6.1 Cost Criteria .............................................................................................................................................. 45

6.2 Capital Costs ............................................................................................................................................. 46

6.3 Present Worth Costs ............................................................................................................................. 47

6.4 Comparision of Alternatives .............................................................................................................. 49

7.0 RECOMMENDATIONS ........................................................................................................................... 50

Appendix A. Bench-Scale Testing Results ................................................................................................. 1

1.0 GAC Adsorption Testing ........................................................................................................................ 1

1.1 Rapid Small-Scale Column Testing .................................................................................................... 1

1.2 GAC Filter Pilot Testing .......................................................................................................................... 3

2.0 Enhanced Coagulation Testing ........................................................................................................... 6

2.1 Current Coagulant (DFLOC 3610) ...................................................................................................... 6

2.2 High Aluminum PACL (DFLOC 3606) ............................................................................................... 8

3.0 Ozone Testing ........................................................................................................................................... 9

3.1 PreOzone ...................................................................................................................................................... 9

3.2 Intermediate Ozone .............................................................................................................................. 11

4.0 Combination of Process Alternatives Testing ............................................................................. 12

LIST OF TABLES

Table ES-1 Present Worth Costs ......................................................................................................................................... 1

Table 2-1 Design Water Demand ....................................................................................................................................... 5

Table 2-2 Raw Water Quality ............................................................................................................................................. 6

Table 2-3 Finished Water Quality ...................................................................................................................................... 8

Table 3-1. Hannibal WTP Treatment Objectives for Disinfection Byproducts ............................................ 15

Table 3-2 Additional TOC Removal ................................................................................................................................ 18

Table 4-1 Estimated Blended Effluent TOC from GAC System ........................................................................... 26

Table 4-2. Matrix of Enhanced Coagulation Alternatives Evaluated ................................................................ 28

Table 4-3. Removal of TTHMs in Aerated Samples from On-Site Pilot Testing ........................................... 30

Table 5-1 GAC System Design Criteria – Pressure Vessels ................................................................................... 38

Table 5-2. MF/UF System Design Parameters ........................................................................................................... 40

Table 5-3. Cartridge Filter Design Parameters .......................................................................................................... 41


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Table 5-4 RO System Design Parameters .................................................................................................................... 41

Table 6-1 Operational Costs .............................................................................................................................................. 45

Table 6-2 Summary of Capital Costs .............................................................................................................................. 47

Table 6-3 Present Worth Costs for DBP Compliance Alternatives.................................................................... 48

Table 6-4 Summary of Advantages and Disadvantages for Each Alternative .............................................. 49

LIST OF FIGURES

Figure 2-1 Historical TOC Data at Hannibal WTP ....................................................................................................... 7

Figure 2-2 Raw Water TOC Concentrations 2005 - 2017 ....................................................................................... 7

Figure 2-3 Historical Finished Water TOC Data at Hannibal WTP ....................................................................... 9

Figure 2-4. Raw and Finished Water TOC Concentrations ................................................................................... 10

Figure 2-5. Hannibal WTP Process Flow Diagram ................................................................................................... 11

Figure 2-6 Average Water Age without Ralls County ............................................................................................ 12

Figure 2-7 Maximum Water Age without Ralls County ......................................................................................... 13

Figure 3-1 Formation of TTHMs vs Time at Various TOC Concentrations .................................................. 16

Figure 3-2 Formation of HAA5s vs Time at Various TOC Concentrations ..................................................... 17

Figure 4-1 Activated Carbon .................................................................................................................................... 19

Figure 4-2. GAC Pilot Columns ......................................................................................................................................... 22

Figure 4-3 TOC Removal at Average Flow through One Train (Post Filter GAC)........................................ 23

Figure 4-4 DBP Formation from GAC Pilot Plant ...................................................................................................... 24

Figure 4-5. DOC Reduction for Enhanced Coagulation Alternatives, where percent reduction is relative to baseline conditions (40 mg/L DFLOC 3610 and 20 mg/L PAC) ................................................................................................................................................. 29

Figure 4-6 In-line Aeration (Medora) .......................................................................................................................... 31

Figure 4-7. Reduction in DOC for Combinations of Various Process Alternatives. Percentages are relative to baseline DOC of 3.2 mg/L which represents current plant operations. .................................................................................................................... 33

Figure 4-8. Reduction in TTHM formation for Combinations of Various Process Alternatives. Percentages are relative to baseline TTHMs of 155.7 µg/L which represents TTHM formation under current plant operations. .............................. 34

Figure 5-1. Alternative 1 Process Schematic - Post-Filter GAC Adsorption .................................................. 35

Figure 5-2. Alternative 1 GAC Site Layout ................................................................................................................... 35

Figure 5-3. Alternative 1 GAC Conceptual Layout .................................................................................................... 35

Figure 5-4. Alternative 2 Process Schematic – Reverse Osmosis ...................................................................... 35

Figure 5-5. Alternative 2 RO Site Layout ..................................................................................................................... 37

Figure 5-6. Alternative 2 RO Conceptual Layout ................................................................................................... 7

Figure 5-7. Alternative 3 Process Schematic – Preozone, Enhanced Coagulation, Aeration ............... 8

Figure 5-8. Alternative 3 Site Layout .......................................................................................................................... 8

... 3

... 3

... 3


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Figure A-1. TOC Breakthrough Curve for Accelerated Column Test using Filtrasorb400 (F400) and 15-min EBCT (Calgon 2017) ........................................................................................ 2

Figure A-2. TOC Breakthrough Curve for Rapid-Scale Simulated Column Test using Filtrasorb400 (F400) and UltraCarb 1240AW with 7.5-min EBCT (October 2017) .............................................................................................................................................................. 3

Figure A-3 Column 1 Pilot Results at 6.0 minutes EBCT (12 inches of GAC in Filters) .............................. 4

Figure 1-4 Column 2 Pilot Results at 14 minutes EBCT (28 inches of GAC in Filters) ................................ 5


BLACK & VEATCH | Page 1

Executive Summary The City of Hannibal, Missouri passed an ordinance requiring that the application of chloramines

(specifically the use of ammonia) at the City’s surface water treatment plant be discontinued by

March 31, 2020. Chloramine disinfection was implemented at the Hannibal Water Treatment Plant

(HWTP) in September 2015 to meet the Environmental Protection Agency’s Stage 2 Disinfection

Byproduct Rule (State 2 DBPR). This study evaluates treatment alternatives and distribution

system modifications that can be implemented to maintain regulatory compliance in the absence of

chloramine disinfection. As a goal, treatment objectives will target 80 percent of the maximum

contaminant level (MCL) for regulated disinfection byproducts (DBPs).

The proposed treatment alternatives focus on the reduction of total organic carbon (TOC), which acts as a DBP precursor. It is estimated than an additional 35 to 53 percent reduction of TOC would be required to meet the treatment objectives. Bench-scale and pilot testing was conducted to evaluate the effectiveness of treatment alternatives to reduce the amount of organic carbon and reduce the formation of regulated disinfection byproducts (total trihalomethanes (TTHMs) and five regulated haloacetic acids (HAA5s)). Treatment alternatives considered under bench-scale testing included enhanced coagulation, ozone, adsorption, aeration, and reverse osmosis. These alternatives were selected as potential viable treatment methods from the results of the July 2017 report titled Chloramine Replacement Alternative Evaluation Initial Findings Report.

Of the treatment alternatives available for removing organic precursors and reducing DBPs, the

following have been identified as the most effective and viable options for the HWTP.

Alternative 1. Post-Filter Granular Activated Carbon (GAC) Adsorption

Alternative 2. Reverse Osmosis

Alternative 3. Preozone with Enhanced Coagulation and Aeration

Table ES-1 summarizes the capital, operational, and present worth costs for each of the

alternatives. The capital cost reflects the cost of infrastructure required for the plant’s rated

capacity of 7.5 million gallons per day (MGD) and the O&M cost reflects the cost of operating the

plant at an average flow rate of 2.9 MGD. The present worth cost evaluates the value of each

alternative in today’s dollars over a 25 year operating period.

Table ES-1. Present Worth Costs for DBP Compliance Alternatives

ALTERNATIVE 1 ALTERNATIVE 2 ALTERNATIVE 3

Description Granular Activated

Carbon Reverse Osmosis

Ozone + Aeration +

Enhanced Coagulation

Project Total w/ Owner’s Contingency $14,346,000 $22,197,000 $13,204,000

Annual O&M Costs $691,000 $391,000 $377,000

Present Worth Costs (25 years) $27,837,000 $29,831,000 $20,564,000

While all of the alternatives present viable solutions for meeting DBP compliance, there are

drawbacks associated with each alternative – such as cost of implementation, annual operational

expenses, schedule for implementation and ability to comply with referendum timeline, and

limitations in the amount of data available to build confidence in the treatment solution.



1.0 Introduction

1.1 PROJECT OVERVIEW

The City of Hannibal Missouri is evaluating treatment alternatives that will allow chloramines

(specifically the use of ammonia) to be discontinued as part of its water treatment process and

continue to meet federal drinking water regulations. Chloramine disinfection was implemented at

the Hannibal’s Water Treatment Plant (HWTP) in September 2015 to meet the Environmental

Protection Agency’s Stage 2 Disinfection Byproduct Rule (State 2 DBPR). This rule requires that

four specific locations within the distribution system achieve local running annual average

maximum containment levels (MCL) below 80 µg/L for total trihalomethanes (TTHMs) and 60 µg/L

for five regulated haloacetic acids (HAA5s).

This study evaluates various options for replacing the chloramine disinfection system with

alternative systems that can achieve regulatory compliance.

1.2 BACKGROUND

On April 4, 2017, voters in Hannibal passed Proposition 1, requiring the removal of ammonia from

the City’s drinking water supply within 90 days of adoption (which occurred on May 16, 2017).

This established a timeframe for discontinuing the use of ammonia by August 15, 2017.

Based on this timeframe, the Board of Public Works (BPW) retained Black & Veatch to conduct an

initial evaluation of the current treatment process to determine if any feasible treatment

modifications could be implemented within the 90-day timeframe to comply with the referendum

while also maintaining compliance with the facility’s regulatory requirements. The findings of this

evaluation are included in the July 2017 report titled Chloramine Replacement Alternative

Evaluation Initial Findings Report. The potential solutions evaluated were selected based on the

results of the plant assessment, review of historical data, industry standards, and recommendations

from previous reports, including the Granular Activated Carbon System Preliminary Engineering

Report, dated February 22, 2017, prepared by Jacobs. This study outlined a number of potential

alternatives for consideration and served as an initial screening evaluation to identify which

treatment alternatives would have the most impact. Treatment alternatives that appeared to be the

most viable underwent additional bench-scale and pilot testing needed to validate the effectiveness

of the alternatives and to develop capital and operating costs.

As part of the initial study, the team conducted meetings with the Missouri Department of Natural

Resources (MDNR) to determine the required testing and approval process for implementing any

changes to the current treatment process. Ultimately, it was determined that there were no

immediate measures that could be implemented within 90 days that would assure that regulatory

compliance could be maintained. As such, the City Council reevaluated the timeline in conjunction

with other pertinent information presented by BPW and revised the ordinance with a new

compliance date (for removal of chloramines) of March 31, 2020.



This preliminary design report expands upon the initial screening evaluation conducted in the

previous reports to:

• Refine the treatment requirements for leading alternatives

• Develop opinions of probable costs and life cycle cost estimates for each alternative

• Recommend with the BPW input the most appropriate treatment approach to achieve

compliance with the ordinance while meeting the facility’s regulatory requirements.

Based on the requirements of the revised ordinance, the recommendation from this report must be

submitted to MDNR by March 31, 2018.

1.3 REPORT METHODOLOGY

Black & Veatch’s Initial Findings Study (July 2017) provided an initial review of the City’s potential

source water alternatives, treatment alternatives, and distribution system modifications to be

considered in lieu of chloramine treatment. The report included:

• Evaluation of alternative coagulants, oxidants and treatment processes to reduce

dissolved organic carbon (DOC) and disinfection byproduct (DBP) formation.

• Analysis of required free chlorine contact times to achieve disinfection compliance.

• Evaluation of alternative water supplies from nearby aquifers and surface waters.

• Analysis of distribution system modeling to reduce water age in the system.

The results of this initial evaluation provided a basis for recommendations on viable alternatives to

be investigated further. Following the initial evaluation, additional bench-scale and pilot testing

was conducted to identify viable treatment solutions to control DBP formation without the use of

chloramines. As a result, treatment objectives, facility design requirements, and detailed opinion of

probable cost estimates were developed for the following alternatives:

• Alternative 1 – Post-filter Granular Activated Carbon (GAC) contactors

• Alternative 2 – Reverse osmosis membranes

• Alternative 3 - Ozone addition for raw water; in combination with enhanced coagulation

treatment, and distribution system aeration

It should be noted that the use of chloramine as a secondary disinfectant is an approved method by

the United States Environmental Protection Agency (USEPA) for controlling disinfection

byproducts. Additionally, many regional utilities similar in size utilize chloramines in treatment.

As a result, there is limited performance data for full-scale systems (particularly using the same raw

water source) that are using methods other than chloramines to meet disinfection byproduct

regulations. The evaluation presented in this report is based on preliminary engineering

evaluations and extrapolation of results from bench and pilot-scale testing. Because there is a

limited data associated with installations in Missouri where ozone, reverse osmosis, aeration, or

GAC are being used for DBP control, there is some inherent risk that additional treatment measures

may require further pilot testing to adequately confirm regulatory compliance. As such, schedule

and cost data provided are subject to revision as further information becomes available and

assessed against regulatory compliance.



1.4 LIST OF ABBREVIATIONS AND ACRONYMNS

AACE – Association for the Advancement of Cost Engineering

ACT – accelerated column test

BPW – Board of Public Works

CT – contact time

DBP – disinfection byproduct

DBPR – Disinfectant and Disinfection Byproduct Rule

DNR – Department of Natural Resources

DOC – dissolved organic carbon

EBCT – Empty Bed Contact Time

GAC – granular activated carbon

gpm – gallons per minute

HAA5 - five regulated haloacetic acids

HWTP – Hannibal Water Treatment Plant

MCL – maximum containment levels

MDNR – Missouri Department of Natural Resources

MF/UF – microfiltration/ultrafiltration

MG – million gallon(s)

mg/L – milligrams per liter

MGD – million gallons per day

nm – nanometers

NOM – natural organic matter

NPDES – National Pollutant Discharge Elimination System

PAC – powered activated carbon

PACl – polyaluminum chloride

RO – reverse osmosis

RSSCT – rapid small-scale column test

SCADA –supervisory control and data acquisition

SDI – silt density index

SDS – simulated distribution system

Stage 1 DBPR – Stage 1 Disinfectants and Disinfection Byproduct Rule

Stage 2 DBPR – Stage 2 Disinfectants and Disinfection Byproduct Rule



SU – standard units

TDS – total dissolved solids

TOC – total organic carbon

THM- trihalomethanes

TTHM – total trihalomethanes

µg/L – micrograms per liter

USEPA – United States Environmental Protection Agency

UV – ultraviolet

UVA – ultraviolet absorbance

WTP – water treatment plant



2.0 Existing Facility and Operating Conditions

2.1 WATER DEMANDS

Estimated future water demands were determined to establish average treatment plant flow rates

for the 25 year project life. The average water demand will be used to determine annual operating

costs for the alternatives being evaluated.

When estimating future water use, evaluation of the system’s historical water use, population

projections, major water users, and national trends are considered. In 2013, the City of Hannibal

conducted a water demand study (Water System Facility Plan, Horner and Shifrin). The study

estimated the 2032 average day demand of approximately 3.3 million gallons per day (MGD),

showing very little change in annual water usage.

Included in this quantity is wholesale water supplied to Public Water Supply District No. 1 of Ralls

County. This wholesale district is in the process of building its own water supply and treatment

system and intends to no longer use the Hannibal supply as a wholesale water source. In 2016, the

average water supplied to Ralls County was about 0.40 MGD. It is anticipated by the time this

project is implemented Ralls County will no longer be served by Hannibal. Therefore, water supply

to Ralls County will no longer be considered as part of the overall system requirements.

Based on the available information, the design average water demand will be 3.3 MGD minus the

0.4 MGD from Ralls County that is no longer being served. Therefore, the design average flow rate

for this evaluation is 2.9 MGD.

The water treatment plant currently has a rated capacity of 7.5 MGD. MDNR requires that any new

treatment processes be designed to effectively treat the rated capacity of the treatment plant. The

BPW could elect to de-rate the capacity of the treatment plant. However, de-rating the treatment

plant capacity would require flow restriction devices be implemented at the plant, and could

negatively impact fire protection, growth, and system resiliency. Therefore, for the basis of this

study it is recommended that each of the proposed treatment alternatives be designed for the

plant’s rated treatment capacity of 7.5 MGD.

Table 2-1 summarizes the design flows considered in this evaluation.

Table 2-1 Design Water Demand

PARAMETER MINIMUM AVERAGE MAXIMUM

Design Plant flow, mgd 1.5 2.9 7.5

1. Average flow does not include Ralls County



2.2 RAW WATER QUALITY

The Mississippi River is the source of supply to the treatment plant. The raw water quality from the

Mississippi River can vary throughout the year which impacts the overall treatment process. Any

new improvements will need to be robust enough to handle changing raw water conditions.

Table 2-2 summarizes general historical raw water data from January 2011 through November

2016.

Table 2-2 Raw Water Quality

PARAMETER UNIT AVERAGE MAXIMUM MINIMUM 90TH PERCENTILE

Turbidity NTU 21.2 407.3 1.9 50.0

Temperature Degrees F (C) 54.3 (12.4) 96.4 (35.7) 1.0 (-17.2) 78.1 (25.6)

pH SU 8.02 8.95 7.29 8.31

TOC mg/L 5.1 11.1 1.9 6.3

Alkalinity mg/L CaCO3 172 220 90 200

Hardness mg/L CaCO3 233 246 214 243

1. Data from the GAC System Preliminary Report, Jacobs 2016

2.2.1 Raw Water TOC

Total organic carbon (TOC) present in the raw water supply reacts with chlorine to form DBPs in

the distribution system. The current treatment process removes a portion of TOC present in the

raw water. Additional removal will be required to meet DBP regulations once chloramines are no

longer used as a treatment component.

To establish a benchmark for plant performance, the historical raw water TOC was evaluated.

Figure 2-1 shows the TOC concentrations of the raw water to the Hannibal WTP since 2005. The

figure displays variations throughout the year. The variations could be impacted by river flow,

agricultural activity, and upstream vegetation. A statistical analysis was performed and the results

provided in Figure 2-2. The average raw water TOC was 5.1 mg/L and 95th percentile was 6.7

mg/L.



Figure 2-1 Historical TOC Data at Hannibal WTP

Figure 2-2 Raw Water TOC Concentrations 2005 - 2017



2.3 FINISHED WATER QUALITY

Finished water quality for the water treatment plant from January 2011 to November 2016 is

summarized in Table 2-3 below.

Table 2-3 Finished Water Quality

PARAMETER UNIT AVERAGE MAXIMUM MINIMUM

90TH

PERCENTILE

pH SU 7.8 8.6 6.3 8.0

Alkalinity mg/L 163 216 86 190

Hardness mg/L 229 238 214 238

TOC mg/L 2.7 5.6 0.6 3.5

1. Data from the GAC System Preliminary Report, Jacobs 2016

2.3.1 Finished Water TOC

Historical finished water TOC was evaluated to establish a baseline TOC removal across the

treatment process. Finished water TOC will be correlated to DBP formation in Section 3 to establish

the additional treatment requirements necessary to comply with regulations once chloramines are

no longer used.

Figure 2-3 illustrates the historical finished water TOC concentrations from January 2005 to

October 2017. Over this timeframe, finished water produced at the plant had an average TOC of 2.7

mg/L with a 95th percentile TOC of 3.7 mg/L. The percent TOC removal across the treatment plant

(i.e. from raw water to finished water) averaged 47 percent.



Figure 2-3 Historical Finished Water TOC Data at Hannibal WTP

Since 2015, the plant has implemented a number of process changes that have resulted in improved

TOC removal. Therefore, the historical finished water TOC since 2005 may not reflect the current

treatment capabilities in regards to TOC removal. Plant staff has been collecting daily raw and

finished water TOC values since January 2017. The daily concentrations are shown in Figure 2-4

below.



Figure 2-4. Raw and Finished Water TOC Concentrations

Review of the 2017 data shows the average finished water TOC is 2.3 mg/L versus the historical

average concentration of 2.7 mg/L. The 95th percentile value for 2017 is 3.4 mg/L versus 3.7 mg/L

from the historical information. The average raw water TOC concentration for this period was 5.5

mg/L, resulting in a 58 percent TOC removal was achieved through the plant (11 percent greater

than the historical average).

2.4 EXISTING TREATMENT PROCESS DESCRIPTION

Raw water is supplied to the treatment plant from the Mississippi River via an intake structure

located north of downtown Hannibal. The raw water is treated with permanganate to address taste

and odor causing compounds and periodically with an algaecide for algae control. Following

chemical addition, the raw water enters a 3.5 million gallon (MG) pre-sedimentation basin.

Powdered activated carbon (PAC) and polyaluminum chloride (PACl) coagulant are added in rapid

mix chambers upstream of the primary flocculation and settling basin. Clarified water is then

delivered to a secondary rapid mix, flocculation and sedimentation basin, where lime can be added

for pH adjustment (if required). Additionally, operators have the ability to feed copper sulfate to

the secondary basin as needed for algae control.

Sodium hypochlorite and fluoride are added in a splitter structure prior to the filter feed basins,

which have a total volume of 0.7 MG. The City has the capability to feed filter-aid polymer at this

location; however, filter-aid polymer is not being fed at this time. From the filter feed basins,

pretreated water is conveyed through four multi-media filters consisting of anthracite and sand



with a base gravel layer on top of clay tile underdrains. Under current operations, the target

residual free chlorine across the filters is 0.2 mg/L. Filter effluent is pumped through ultraviolet

(UV) disinfection reactors to an onsite 2.5 MG finished water reservoir. Prior to the reservoir,

chlorine is added to boost the chlorine residual and ammonia is added to form chloramines.

Finished water from the reservoir is then conveyed either by gravity to the low pressure zone of the

system, or through high service pumps to the high pressure zone of the distribution system.

The process flow diagram for the Hannibal WTP is presented in Figure 2-5.

Figure 2-5. Hannibal WTP Process Flow Diagram

2.5 WATER AGE

Removal of chloramines will require the system to convert back to a free chlorine residual

throughout the distribution system. The long hydraulic retention time within BPW’s distribution

system will result in continued formation of DBPs as the water progresses through the system.

Distribution system modeling was performed to estimate approximate water age at various

locations within the system. The model was calibrated under late fall conditions under several

operating conditions that reflect current operational system constraints.

Water age was then modeled to determine the impact of removing Ralls County, a wholesale water

consumer. Water age was evaluated under average water age conditions and maximum water age.

Figure 2-6 and Figure 2-7 illustrate the approximate water age in various pipes throughout the

distribution system for both scenarios.



Figure 2-6 Average Water Age without Ralls County



Figure 2-7 Maximum Water Age without Ralls County

The modeling reveals that a large area of the distribution system has water age less than 1-2 days,

even under worst case water age conditions. However, as expected, as the water moves away from

the plant, specifically west and southeast, water age significantly increases. Three of the four DBP

sample locations are located in high water age locations. The model shows predicted water age of

about 7 days at these locations. Therefore, unless distribution modifications are incorporated, such



as flush hydrants or removal of storage, the treatment plant improvements need to provide

adequate DBP precursor removal to account for at least 7 days of distribution residence time.



3.0 Treatment Objectives with Free Chlorine Disinfection The Hannibal WTP will need to modify their treatment objectives in order to comply with current

regulations once free chlorine is applied in lieu of chloramines. According to the Minimum Design

Standards for Missouri Community Water Systems (MDNR 2013), Hannibal BPW should maintain a

minimum disinfectant residual of 1.0 mg/L leaving the plant and 0.5 mg/L at remote points in the

distribution system. To maintain disinfectant residuals above the minimum 0.5 mg/L, the Hannibal

WTP will target a chlorine residual of approximately 1.0 mg/l at remote locations in the

distribution system. Free chlorine will result in higher DBP formation, and thus require the

implementation of water treatment plant process modifications to reduce DBP precursors and/or

oxidant demand to comply with regulatory standards.

This section establishes the target treatment goals and in-plant treatment objectives for finished

water quality within these constraints in order to establish the minimum requirements for viable

treatment alternatives in lieu of chloramines.

3.1 TARGET DBP LEVELS AT DBPR MONITORING LOCATIONS

The treatment objective for TTHMs and HAA5s has been established as eighty percent of the

maximum contaminant levels permitted, as indicated in Table 3-1 (essentially providing a 20%

factor of safety to the design criteria). Regulatory compliance requires that each of four monitoring

locations maintain an annual running average less than the MCL. Since it is an average of four

values taken over the four seasons, summer values may be greater than the MCL and winter

conditions lower, which meets compliance so long as the average result is less than the MCL.

Table 3-1. Hannibal WTP Treatment Objectives for Disinfection Byproducts

PARAMETER TREATMENT OBJECTIVE

(80% OF MCL) MCL

Total Trihalomethanes (TTHMs) 64 µg/L 80 µg/L

Five Regulated Haloacetic Acids (HAA5s) 48 µg/L 60 µg/L

3.2 TARGET EFFLUENT TOC

In order to reduce DBP formation to the target levels specified above, a target effluent TOC should

be established as a means for managing DBP precursors at the Hannibal WTP. In general, reducing

the concentration of TOC or DBP precursors at the point of chlorination reduces the formation of

disinfection byproducts in the distribution system. In some cases however, when alternative

oxidants are applied, DBP formation can be reduced without necessarily reducing the concentration

of TOC.

The target effluent TOC (without chloramines) is based partially on historical data collected prior to

the implementation of chloramine disinfection in 2015 and bench-scale testing conducted as part

of this study. Bench-scale testing included adjusting the TOC concentration of filtered effluent with

GAC to achieve TOC concentrations of 1.0, 1.5, 2.0 and 2.9 mg/L. The samples were then

chlorinated and held for 3 to 10 days to establish DBP concentrations at various TOC



concentrations and water age. This hold period is referred to as simulated distribution system

(SDS) testing and requires that the samples are held in individual amber bottles, headspace free, at

room temperature, and in the dark. Results of this testing for TTHM production is shown in Figure

3-1. Similarly, results from HAA5 testing is shown in Figure 3-2.

Figure 3-1 Formation of TTHMs vs Time at Various TOC Concentrations



Figure 3-2 Formation of HAA5s vs Time at Various TOC Concentrations

As discussed in Section 2, the water age in the distribution system at several of the DBP compliance

points is estimated to be about 7 days. Reviewing the test results show that finished water TOC of

about 1.75 mg/L at 7 days (about half way between the 1.5 mg/l and 2.0 mg/l curves) is required to

meet the target TTHM goal of 64 ppb. The testing showed that TOC concentrations below 2.0 mg/L

would meet the HAA5 target goal of 48 ppb.

Reducing the water age to 5 days lowers the TTHM concentration by about 8 ppb. Therefore, there

would be some treatment advantages to install flushing hydrants and eliminating storage in the

system to reduce water age. However, the overall impact to performance and treatment would be

minimal, and you would most likely not see the benefit from an operational cost standpoint on

treatment. In addition, reducing storage in the system impacts fire protection and reliability of the

system. Therefore, these measures are not recommended at this time.

Based on this information, the additional TOC removal required to meet DBP limits is listed in Table

3-2. This analysis ignores the fraction of TOC removed by the unit process as the yield of DBPs is

not purely a function of the TOC. The relationship was developed based on an adsorption

technology (PAC/GAC) and therefore is representative of the effluent TOC levels expected to be

required by adsorption technologies. Other technologies that utilize pre-oxidation or coagulation

may have slightly different outcomes. The 95th percentile was used as the basis of worst case,

maximum treatment conditions.



Table 3-2 Additional TOC Removal

PARAMETER AVERAGE 95TH PERCENTILE

Historical Finished Water TOC, mg/L 2.7 mg/L 3.7 mg/L

Target Finished Water TOC, mg/L 1.75 mg/L 1.75 mg/L

Additional TOC Removal Required, % 35% 53%

The target effluent TOC has been verified through bench-scale testing and distribution system

analysis and should enable compliance with MCLs for regulated DBPs after transitioning from

chloramines to free chlorine. The target of 1.75 mg/L TOC is based on average flow conditions.

The target effluent TOC does not necessarily apply to treatment solutions involving alternative

oxidation processes, such as ozone. Since alternative oxidation processes do not directly remove

organic precursors and instead convert the organic compounds into those less prone to form DBPs,

their performance cannot be measured solely on TOC removal. Therefore, alternative oxidation

processes should be evaluated on their ability to meet target DBP levels in the distribution system.



4.0 Treatment Alternatives for Reducing DBP Formation This section describes the potential treatment alternatives available for reducing the concentration

of disinfection byproducts after the Hannibal WTP transitions to free chlorine. The following

treatment alternatives are discussed in subsequent sections.

• Removal of organic precursors and pre-formed DBPs through GAC adsorption.

• Removal of organic precursors through enhanced coagulation, powdered activated carbon,

reverse osmosis and ion exchange resins.

• Reduction of chlorine demand through the use of alternative oxidants upstream of chlorine

disinfection.

• Removal of THMs at the plant and in the distribution system through aeration.

4.1 GRANULAR ACTIVATED CARBON

GAC is a well-known adsorbent for organics and has been widely applied in water treatment. GAC

typically has a relatively high adsorptive affinity for taste and odor-causing compounds and DOC,

including pre-formed DBPs. A reduction in DOC equates to a decrease in DBP precursors as

described in Section 3.

4.1.1 GAC Adsorption

Activated carbon is typically produced from coal through activation, which converts the carbon into

a highly porous, graphite-based media. As shown in Figure 4-1, organic contaminants diffuse

through the pores of the carbon matrix until enough adsorption bonds are formed to effectively

bind the compound. As organics are adsorbed onto the carbon media, adsorption sites are

consumed until the media is exhausted of its adsorption capacity at which point it must be replaced.

Figure 4-1 Activated Carbon

The rate and capacity of the carbon for adsorption depends on a number of factors, including

adsorbent composition, particle size, pore size and the structure and size of the organic molecules

targeted for removal. Bench-scale and pilot testing is usually conducted to determine these



adsorption characteristics and to evaluate the effectiveness of the treatment option for a specific

water source.

There are two options for integrating GAC adsorption at the Hannibal WTP.

• Option 1: Conversion of existing granular media filters to GAC filter adsorbers (i.e. GAC filter cap). This would involve removing a portion of the anthracite/sand media and replacing with GAC.

• Option 2: Installation of post-filter GAC contactors. Each of these approaches, and their applicability with respect to compliance with DBP treatment

objectives at the Hannibal WTP are discussed below. It should be noted that both of these

approaches would require modifications to current disinfection practices to minimize or eliminate

the presence of free chlorine in the water entering the GAC absorbers/contactors.

4.1.2 GAC Design Criteria

In USEPA’s definition of best available technology for DBP control, the empty bed contact time

(EBCT) is identified as the parameter with the greatest impact on performance for DBP control for

GAC system designs. EBCT is equal to the volume of carbon media in the filter or contactor divided

by the volumetric rate of flow through the filter or contactor, expressed in minutes. In general, GAC

adsorption efficiency for a particular contaminant increases with increasing EBCT.

MDNR has limited experience in approving post filter GAC system as they are not widely used in the

state. Based on the MDNR Minimum Design Standards for Missouri Community Water System, a

GAC system can be implemented after a pilot or full-scale test is conducted. MDNR requires a

minimum EBCT of 10 minutes at design capacity (7.5 MGD). Further, the minimum 10 minutes

should be met with at least one unit out of service. For any GAC system pilot testing should be

completed prior to preparation of plans to develop breakthrough curves; to determine usage rates;

to determine the optimum carbon; to confirm the optimum grain size of carbon; and to determine if

10 minute contact time is adequate.

4.1.3 Carbon Reactivation

Carbon can be supplied as new material or regenerated from previously used GAC media. For

drinking water applications used GAC material must come from the same treatment process and

must follow a rigorous reactivation process to ensure contamination does not occur. The material

must be collected at the plant and shipped to a certified regeneration facility.

As such, there are limits to the savings realized for using reactivated GAC media. In general, using

reactivated GAC has been shown to reduce GAC costs by approximately 20 percent as compared to

using virgin GAC. However, potential cost savings are dependent on the size of the water treatment

facility (and amount of GAC being regenerated) and the distance of the water treatment plant from

the regeneration facility. The closest NSF-certified regeneration facility to the Hannibal WTP is in

Ohio.

4.1.4 GAC Filter-Adsorbers.

In addition to providing the capability to remove natural organic matter (NOM) and synthetic

organics by adsorption, GAC is also an excellent filter medium for removal of turbidity and



suspended particles. Filter-adsorbers or GAC filter caps make use of this dual functionality by

replacing a portion of the anthracite/sand media in the filter bed with a layer of granular activated

carbon.

Two options were considered for retrofitting the existing filters with GAC. Option 1 includes

removal of the existing 12 inches of anthracite and replacement with GAC. Option 2 includes

demolition of the existing underdrains and installation of new low profile (either stainless steel or

IMS caps) that don’t require support gravel to increase the GAC media depth to 28 inches.

For Option 1, at the design average capacity of 2.9 MGD and peak capacity of 7.5 MGD, assuming one

filter is off-line for backwashing, the EBCTs would be 6.0 minutes at average flow and 2.3 minutes

at peak flow. For option 2 the EBCT increases to 14.0 minutes at average flow and 5.4 minutes at

peak flow. Neither of these scenarios meet the minimum MDNR required contact time of 10

minutes.

4.1.5 Post-Filter GAC Contactors

Most utilities that elect to use GAC adsorption to meet the Stage 2 DBPR requirements construct

post-filtration GAC contactors in order to achieve EBCTs sufficient to provide efficient removal of

DBP precursor compounds while maintaining reasonable GAC replacement intervals.

Post-filter GAC can either be installed in steel pressure vessels or concrete structures. Typically,

larger facilities will use concrete as it allows for larger individual contactors. For facilities sized

similar to Hannibal steel vessels are typically used.

GAC contactors, if implemented, would likely be designed to treat the entire filter effluent instead of

a side-stream approach. Through a side-stream approach, the capital cost would be lower, but the

GAC media would likely have to be replaced frequently in order to maintain the target TOC

concentration in the treated water. The side-stream approach would rely on the GAC contactors to

maintain a low, constant TOC concentration, resulting in replacement of the media as soon as

breakthrough is seen. However, a facility designed for the full flow could still implement side-

stream treatment when the media is newer and/or when lower filter effluent TOC concentrations

are present. By allowing the ability to both use side-stream and full flow treatment it will lengthen

the GAC media life.

In any arrangement where GAC contactors are used, it is recommended that a parallel, lead-lag

concept be used to treat the entire flow. For example, three parallel GAC trains could be used

where one train has new GAC media, the second train is about 50 percent spent, and the third train

is about 90 percent spent. The effluent from the three trains would be blended together to achieve

the final TOC target in the treated water. In general, the more contactors that are used the longer

each vessel can remain in treatment before being exhausted, resulting in lower overall media

replacement costs (for example, if six vessels are used and the target TOC removal is 35 percent,

Vessel 1 could be operated until it removed only 10 percent, Vessel 2 – 20%, Vessel 3- 30%, and so

forth, resulting in blended average of 35 percent. If only 3 vessels are used to achieve the same

target removal the oldest vessel would have to be replaced sooner, when it was removing 25

percent of TOC (Vessel 1 -25%, Vessel 2 – 35%, Vessel 3 – 45%)).



4.1.6 GAC Testing

Bench-scale testing and pilot testing was conducted to evaluate the efficacy of GAC adsorption

installed both in the existing filters and downstream of the existing filters. Testing included:

• Post-filter Accelerated Column Testing (ACT), conducted by Calgon Carbon

• Post-filter Rapid Small Scale Column Test (RSSCT), conducted by Evoqua Inc

• Pre-Filter and post-filter on-site pilot testing

Accelerated and rapid small-scale column testing (ACT and RSSCT) were initially conducted to

determine whether GAC would be a viable treatment alternative. These tests are typically

conducted to evaluate GAC performance and establish breakthrough curves used to estimate life

cycle costs without waiting for results in real time. Because accelerated column tests are conducted

using grab samples, it is not always well-suited for predicting performance in surface water

treatment plants where the influent TOC concentration varies seasonally. These tests are also

typically performed when schedule does not allow for pilot testing, which can take 3 months to 2

years depending on the time it takes for breakthrough to occur. In the case of Hannibal the

implementation schedule was extended with the revised ordinance date, which allowed for on-site

pilot testing to be conducted. Therefore, this analysis will use the pilot results as the basis of the life

cycle costs. The results of the initial RSSCT and ACT are provided in Appendix A. The results of

the RSSCT and ACT showed that GAC adsorption is effective at reducing DBP precursors.

4.1.6.1 On-site Pilot Testing

On-site pilot testing was conducted to develop a better understanding of GAC performance under

varying water quality conditions representative of actual plant operations. Pilot testing was

valuable for refining the TOC breakthrough curve and estimating life cycle costs of GAC treatment.

Pilot testing began on August 22, 2017 and is continuing to operate. Data through November 18,

2017 is included in this evaluation.

In total, four GAC columns were tested:

• Column 1 replicated 12 inches of GAC media depth in the

existing filters with an EBCT of 3.1 minutes.

• Column 2 replicated 28 inches of GAC media depth in the

existing filters with an EBCT of 7.1 minutes.

• Column 3 replicated GAC contactor downstream of the

filters with 7.5 min EBCT

• Column 4 replicated GAC contactor downstream of the

filters with a 15 min EBCT (fed from Column 3 effluent).

GAC Filter Cap Pilot Testing (Columns 1 & 2)

Pilot testing was conducted to simulate installation of GAC

media as a filter cap on the existing filters. Results of pilot

testing indicate that TOC breakthrough occurred within 10 Figure 4-2. GAC Pilot Columns



simulated days for Column 1 and 63 simulated days for Column 2. Due to the frequency of

replacement and associated O&M, this alternative is not a sustainable solution for reducing TOC and

controlling DBP formation. Full results from the pilot testing are provided in Appendix A.

Post-Filter GAC Pilot Testing (Columns 3 & 4)

Pilot testing was conducted to replicate installation of GAC in post-filter contactors. The pilot was

set up in a lead-lag configuration with each pilot column sized for 7.5 minutes of EBCT. Therefore,

the combined EBCT through the entire system was 15 minutes. (Columns 3 and 4)

TOC removal data for both pilot columns are shown in Figure 4-5 below.

Figure 4-3 TOC Removal at Average Flow through One Train (Post Filter GAC)

As described in Section 3.2, the target maximum effluent TOC concentration is 1.75 mg/L. Based on

the column 4 effluent TOC values, GAC breakthrough occurred after 52 days if the GAC system was

sized for 15 minutes at average flow of 2.9 MGD. At the plant design flow of 7.5 MGD the EBCT

would be only 5.8 minutes. Under this condition the EBCT at peak flow would not meet the

minimum required contact time by MDNR, and breakthrough would occur much sooner.

If the GAC system was sized for 15 minutes of EBCT at peak flow of 7.5 MGD, GAC treatment

breakthrough would be expected after around 140 days based on average flow of 2.9 MGD. Since

the TOC breakthrough curve was established using a single GAC contactor to treat the filter effluent,



it does not take into account operational advantages of running multiple vessels in a lead-lag

configuration to achieve a blended effluent TOC that meets the treatment objective. Under a lead-

lag configuration, operators can utilize a staggered GAC replacement plan. With six units, media

from a single GAC contactor would be replaced every 50 days, and based on this rotation the full

volume of GAC would be replaced every 300 days. Additional discussion on GAC media life and life

cycle cost analysis is provided in Section 4.1.7.

Pilot DBP Formation Testing

After the pilot had been in operation for two months, samples from the GAC pilot Column 4 effluent

were collected for evaluation of DBP formation potential. GAC effluent samples were dosed with

free chlorine and stored in amber bottles for 5 days prior to lab analysis of TTHM and HAA5s.

Figure 4-4 summarizes the effluent TOC and DBP formation results of the GAC pilot at 15 minutes

EBCT.

Figure 4-4 DBP Formation from GAC Pilot Plant

There were some inconsistencies in the TTHM formation from the SDS testing which is likely the

result of calibration issues with fine-tuning the applied chlorine dose required to meet the target

chlorine residual. In particular the 2nd, 4th and 5th data points appear to have inconsistent results for

TTHM formation. For example, the data first shows exceedance of the target MCL for TTHMs at

about 43 days. However, the chlorine residual after the 5 day hold in that sample was 1.76 mg/L



which exceeds the target chlorine residual of 0.5 to 1.0 mg/L. Therefore, the high chlorine residual

impacted the formation for this sample.

The TTHM formation at 57 and 64 simulated days of operation are relatively low compared with

the TTHM results for comparable TOC and SDS holds shown in Figure 3-1. These results do not

follow the general trend of increasing TTHM formation with increasing TOC and appear to be the

result of dosing or measurement error.

The blue dashed line illustrates a general trend line to reflect the anticipated TTHM vs time from

the pilot. The data shows that at approximately 58 days with 15 minutes of EBCT the target MCL

would be exceeded. This is slightly longer than the estimated TOC breakthrough of 52 days shown

in Figure 4-3. Because the data represents 5 day SDS and not 7 day, an additional 10 µg/L TTHM

formation is estimated to occur. Therefore, the results suggest that GAC performance at

approximately 50 days resulted in conditions that formed TTHMs greater than the target goal of 64

ug/L. This outcome is nominally consistent with the TOC breakthrough appearing to be observed at

52 days (7.5 mgd) or 140 days (2.9 mgd).

4.1.7 GAC Size and Media Life Estimate

To minimize life cycle costs, an analysis was conducted to identify the optimal GAC configuration

with respect to capital cost (number of GAC units) and operational costs (GAC media replacement).

While installing fewer GAC vessels would reduce capital costs, it requires more frequent media

replacement, increasing the annual operating costs. The annual operating costs are primarily driven

by the GAC media replacement. Thus, an analysis was conducted to determine the optimal number

of GAC units and estimated media replacement rate, based on the goal of maintaining a target TOC

of 1.75 mg/L in the blended effluent.

GAC performance data from pilot testing was used to determine the required GAC replacement

frequency. Since individual contactors will undergo media replacement on a staggered schedule, the

analysis takes into account effluent TOC concentrations at different media ages. The evaluation

considers that GAC equipment would be sized for the maximum flow of 7.5 mgd, but that the system

is operated at the average flow of 2.9 mgd.

The results show that with six GAC trains, a unit replacement rate of 50 days would be required to

maintain effluent TOC of 1.75 mg/L or lower. The unit replacement rate considers that one out of

every six contactor trains will receive new GAC media every 50 days, resulting in full GAC media

replacement every 300 days. The analysis considers that each train has two GAC vessels operated in

series, sized for 625,000 gal/d with a total EBCT of 15 minutes at peak flow (7.5 minutes EBCT per

vessel).

If the GAC system were designed to achieve 15 minutes of EBCT under average flow conditions, this

would result in a fewer number of GAC vessels and roughly half the GAC media volume. Under this

operating scenario, the loading rate on each GAC vessel would increase resulting in the need for

more frequent media replacement in order to achieve the same blended effluent TOC concentration.

If the system were designed for average flow conditions, one out of every three GAC contactors

would require media replacement every 30 days, resulting in full GAC media replacement every 90

days. Table 4-1 illustrates the estimated percent TOC removal for each train based on these two

conditions.



Table 4-1 Estimated Blended Effluent TOC from GAC System

PARAMETER 7.5 MGD FACILITY

WITH 15 MIN EBCT

2.9 MGD FACILITY

WITH 15 MIN EBCT

Number of Trains 6 3

Days Between GAC Replacement per Train 50 30

Estimated TOC with Staggered Replacement

Train 1 TOC, mg/L 0.90 1.35



Train 4 TOC, mg/L 2.00



Blended Effluent TOC, mg/L 1.75 1.75

A target blended effluent of 1.75 mg/L TOC was used as the basis for estimating lifecycle costs. Both

alternatives are based on expected operational performance at average flow rate of 2.9 MGD.

Table 4-2 provides a summary of estimated GAC life cycle costs based on the six train configuration

installed for a maximum treatment capacity of 7.5 MGD and operated at an average flow of 2.9 mgd,

and the three train configuration for 2.9 MGD.

Table 4-2 GAC Life Cycle Costs

PARAMETER 7.5 MGD AT 15 MIN 2.9 MGD AT 15 MIN

Design Flow Rate at 15 min EBCT, mgd 7.5 2.9

Number of GAC Contactor Trains 6 3

Number of GAC Vessels per Train (operated in series) 2 2

Days Between GAC Replacement per Train 50 30

Total GAC Installed with System, lbs 315,000 125,000

Estimated Complete Media Replacements per year 1.2 4.1

Total Media Replaced per Year 385,000 497,000

Total Yearly GAC Media Costs, $ $620,000 $795,000

1. Annual media replacement cost is based on average flow rate of 2.9 MGD and GAC unit cost of $1.6 per

lb.

Although installing fewer units would reduce the initial capital costs, it would result in higher O&M

costs due to increased frequency of GAC media replacement. Impacts on overall life cycle costs are



further discussed in Section 6.0. From a regulatory perspective, MDNR Minimum Design Standards

for Missouri Community Water Systems requires at least 10 minutes of EBCT at the plant rated flow

(7.5 MGD) for GAC systems being used for control of DBP precursors and DBP formation. If the

system were sized for the average capacity of 2.9 MGD rather than the rated capacity of 7.5 MGD,

the GAC system may not be able to reliably achieve the blended effluent TOC concentration of 1.75

mg/L under higher flow rates. Thus, it is recommended that the GAC system be designed for six

trains with at least 10 minutes EBCT at the plant rated capacity of 7.5 MGD. The actual amount of

media in each vessel is somewhat dependent on vessel manufacturers, which typically have vessels

incrementally increasing by 10,000 lbs. Further discussion on optimal sizing is included in Section

5.

4.2 REVERSE OSMOSIS

Reverse osmosis (RO) is a highly effective method for removing organic precursor compounds that

form regulated disinfection by-products in the presence of free chlorine residual. Reverse osmosis

has additional benefits of removing other constituents of concern, including total dissolved solids

(TDS), hardness, and taste- and odor-causing compounds. While RO provides significant water

quality benefits, there are several drawbacks to using RO membranes which often inhibits the

implementation of RO technologies strictly for DBP control. Drawbacks associated with applying RO

include the generation of a concentrated brine stream which creates challenges with disposal

options, the need for additional pretreatment and chemical dosing, increased operational

complexity, and increased energy consumption and operational costs.

RO is a process that applies a semi-permeable membrane to remove dissolved inorganic and

organic substances from water. Membrane recovery is limited by the concentration of certain

sparingly soluble cations (barium, calcium, and silica) and anions (sulfate and bicarbonate) in the

concentrate and their solubility products or metal complexes. Typical RO recoveries for surface

water treatment plants range from 80 to 90 percent. In other words, 80 to 90 percent of the feed

water passes through the RO membrane and is collected as permeate, while the remaining 10 to 20

percent exits the system as waste concentrate.

RO membranes typically remove 95 percent to 99 percent of TDS and dissolved organic

compounds. In order to meet the treatment objectives for TTHMs and HAA5s, only a portion of the

plant flow would need to be treated by reverse osmosis. As part of the initial screenings evaluation,

bench-scale testing was conducted to simulate RO applied to 25 percent and 50 percent of the total

plant flow. Based on known rejection rates and results of bench-scale testing, it is recommended

that the RO system be sized to treat 50 percent of the plant flow to achieve the target TOC and DBP

levels.

From a regulatory perspective, MDNR may require pilot testing prior to full-scale implementation.

Potential impacts of brine discharge on the Hannibal WTP’s NPDES permit are discussed in Section

5.2.

4.3 ENHANCED COAGULATION

Another method for controlling the formation of TTHMs and HAA5s is to reduce the concentration

of organic compounds prior to the addition of free chlorine. Currently, the coagulation process at

the Hannibal WTP is optimized to yield low settled water turbidity to maintain acceptable filter



operations and performance. While that provides some degree of TOC removal, additional TOC can

be removed from the source water through enhanced coagulation or through the use of alternative

coagulants. Since the degree of TOC removal varies by coagulant type and dosage, bench-scale

testing was conducted to determine whether the use of alternative coagulants or enhanced

coagulation processes could improve the TOC removal efficiency.

The coagulation process at the Hannibal WTP currently uses a polyaluminum chloride (PACl)

coagulant and achieves about 35-45 percent removal of DOC. In order to meet the treatment

objective, which is 80 percent of the MCL for TTHMs and HAA5s, an additional 35 to 53 percent

removal of TOC would be required.

Table 4- provides a matrix of the coagulation alternatives that were evaluated through bench-scale

testing. Specific details regarding the actual chemical dosages, pH conditions, and testing results are

available in 7.0Appendix A. Note that all results from bench-scale testing are indicated in terms of

DOC, since settled water samples were filtered through a 0.45 µm filter. TOC consists mostly of

dissolved organic compounds, and as such DOC makes up approximately 90 to 99 percent of TOC.

Since bench-scale testing was conducted using raw water samples collected in May, July and

October 2017, bench-scale testing results provide a good representation of coagulation

performance under seasonal raw water quality conditions that demonstrate both typical and

challenging TOC conditions.

Table 4-3. Matrix of Enhanced Coagulation Alternatives Evaluated

COAGULANT

COAGULANT DOSING SCHEME

Average Dose1

1.5x Coagulant

Dose1

2x Coagulant

Dose1

Average Dose +

pH Adjustment

Current PACL (DFLOC-3610) X X X X

High-aluminum PACL (DFLOC-3606) X X X X

Ferric Sulfate X X X X

1 Dosing of alternative coagulants was conducted on a metal equivalent basis.

Figure 4-5 summarizes the percent reduction in DOC observed from bench-scale testing of

enhanced coagulation alternatives. Based on these results, approximately 20% removal of DOC can

be achieved by doubling the plant’s current coagulant dose. The relative reduction in DOC that can

be achieved with the high aluminum PACl (DFLOC 3606) is fairly marginal and does not justify

changing coagulants when similar level of performance can be achieved from the plant’s current

coagulant.



Figure 4-5. DOC Reduction for Enhanced Coagulation Alternatives, where percent reduction is relative

to baseline conditions (40 mg/L DFLOC 3610 and 20 mg/L PAC)

Approximately 20 percent reduction in TTHM formation is achieved by doubling the plant’s current

coagulant dose. An additional 7 percent reduction in TTHM formation can be achieved by changing

to the high aluminum PACl with a dose of 64.7 mg/L (metal equivalent to doubling the dose of the

plant’s current coagulant). The plant has operated with double the coagulant dose in the past and

experienced operational issues due to plugging of the filters. If enhanced coagulation is considered

for DBP control, impacts on solids loading must be carefully evaluated to minimize impacts to filter

operations.

Since enhanced coagulation by itself cannot reduce DOC to the required levels, a more robust

treatment solution involving pre-ozonation followed by enhanced coagulation was evaluated

through bench-scale testing. This combination of process optimizations is described in Section 4.6.

4.4 OZONE

Ozone is a powerful oxidant, which oxidizes organic and inorganic compounds through two

pathways: (1) direct oxidation-reduction reactions with compounds present in the water and (2)

spontaneous auto decomposition to form hydroxyl radical followed by oxidation of organic

compounds. The organic and inorganic compounds present in the water exert an ozone demand



that must be satisfied before a residual ozone concentration is established. The rate of ozone

decomposition depends on several factors including alkalinity, temperature, and the composition

and concentration of NOM.

When ozone is applied as a preoxidant it can reduce disinfection byproduct formation by two

primary methods: (1) enhancing the removal of DBP precursors during the coagulation process and

(2) oxidizing organic and inorganic compounds to reduce the total oxidant demand in primary

disinfection. Ozone has additional benefits of removing taste and odor causing compounds and

oxidizing iron, manganese, and other reduced inorganic compounds.

The ozone demand for the raw water supply to the Hannibal WTP is established though bench-

scale testing. A ratio between the ozone demand and raw water TOC is used as a basis for

estimating the required ozone dose. Based on preliminary bench-scale testing, an ozone demand-

to-TOC ratio of 0.5 mg/L has been established. Since this parameter is critical to the overall

facility requirements, should ozone be selected moving forward, additional bench-scale testing is

recommended to further refine the required ozone dose.

Ozone was tested as a preoxidant upstream of the coagulation process and as an intermediate

oxidant upstream of the filter. Preozone was more effective for reducing TTHM formation with

reduction rates of 24 to 30 percent, depending on influent TOC conditions and applied ozone

dose. Full bench-scale testing parameters and results are provided in Appendix A.

At the dosages required for preozonation, bromate formation in bench-scale samples was

consistently less than 3 µg/L. Given that the MCL for bromate is 10 µg/L, bromate formation

does not appear to be an issue.

4.5 AERATION

This alternative considers the volatilization of pre-formed TTHMs by means of spray aerators

located in the 2.5 MG finished water tank and in pipelines within the distribution system. Aeration

techniques are only effective for removing volatile THMs, primarily chloroform, and are ineffective

for removing HAA5s. Since the concentration of THMs in the distribution system is driving the

treatment objectives, aeration, combined with another treatment alternative, could be a viable

option for the Hannibal WTP.

On-site pilot testing was conducted to evaluate aeration performance in the plant’s high service

pump station discharge. For the on-site aeration testing, a nozzle was used to aerate chloraminated

finished water collected from a hydrant in the high service pipeline. Table 4-2 summarizes the

percent removal of TTHMs in the aerated finished water samples.

Table 4-2. Removal of TTHMs in Aerated Samples from On-Site Pilot Testing

SAMPLE

PERCENT REMOVAL

TTHM, %

Aerated Sample 1 31%





The results of the on-site pilot testing are consistent with published data, which finds that

approximately 30 to 50 percent removal of TTHMs is feasible using in-tank and in-line aeration

systems. Removal efficiency is dependent on several factors including the flow rate, air-to-water

ratio, the water temperature and the concentration of TTHMs. Performance guarantees for TTHM

removal rates available from aeration equipment suppliers are expected to range between 20 to 35

percent.

MDNR has indicated that the installation of aeration may impact the plant’s ability to receive

disinfection credits in the plant reservoir due to reduction in contact time. Thus to minimize

impacts to contact time, it is recommended that surface aerators be installed in the last two

channels of the 2.5 MG reservoir, rather than in the main tank section of the reservoir. Initial

discussion with MDNR has indicated this is potentially a viable solution. However, further analysis

by MDNR during the pre-design stage would be required to assure separating the tank aeration

zones would be acceptable. Should in-tank aeration be selected as one of the alternatives moving

forward, a new CT evaluation would be required to confirm disinfection credits can be met with the

installed aeration equipment.

In addition to the aeration equipment installed at the plant, in-line aeration equipment is

recommended to reduce TTHM levels at remote locations in the distribution system. In-line

aeration is relatively new. These systems pull water out of a pipeline and use the water to spray

into a vessel to release TTHMs before pumping back into the system.

Figure 4-6 In-line Aeration (Medora)

It is anticipated two of these systems would be required. One system would be installed off the

Paris Gravel Booster Station discharge that serves the west high pressure zone, while the other

system would be installed off the Southside Booster station. It is anticipated a 30 percent reduction

in TTHM could be achieved using these systems.



Additional distribution system in-tank mixing and aeration are also viable to reduce overall

distribution system TTHMs.

MDNR review and acceptance for the plant aeration and inline aeration concepts would be

required.

4.6 COMBINATION OF PROCESS OPTIMIZATIONS

With exception to post-filter GAC adsorption and RO, none of the other individual process

alternatives (enhanced coagulation, increased PAC dosing, ozonation or aeration) are capable of

reducing TOC and DBP formation to the required levels. While each alternative showed incremental

improvements to TOC or DBP formation, no individual treatment alternative was robust enough to

meet the treatment objectives. Thus, additional bench-scale testing was conducted to evaluate

whether a combination of process optimizations would sufficiently reduce DBP formation. The

following describes the findings from bench-scale testing, which compared preozone with

enhanced coagulation and preozone with increased PAC dosing.

As discussed previously, results from bench-scale testing showed that up to 30 percent reduction in

DBP formation could be achieved through the application of ozone upstream of the

presedimentation basin. Similarly, results from bench-scale testing showed that up to 20 percent

reduction in TOC and nearly 20 percent reduction in DBP formation could be achieved with

enhanced coagulation.

With this combined treatment approach in mind, additional bench-scale testing was conducted to

evaluate treatment performance with preozone followed by enhanced coagulation. Since the

addition of ozone does not reduce TOC, the viability of these treatment alternatives is based on

their ability to meet the treatment objectives for DBP formation only.

The scenarios evaluated for combining ozone with enhanced coagulation included:

• Baseline (40 mg/L coagulant, 20 mg/L PAC)

• Ozone (0.5xTOC) + Baseline

• Ozone + 1.5x baseline coagulant dose

• Ozone + 2x baseline coagulant dose

• Ozone + 1.5x baseline PAC dose

• Ozone + 2x baseline PAC dose

• Ozone + 2x baseline coagulant dose + 2x baseline PAC dose

Based on the cumulative ozone demand testing, an ozone-to-TOC ratio of 0.5 has been established

for the raw water. Based on raw water TOC of 5.9 mg/L, an ozone dose of 3 mg/L was used for all

treatment scenarios. Figure 4-7 summarizes the DOC removal rates for the combination of process

improvements described above. The percent removal is relative to the baseline condition, which

reflects current plant operations at the plant (average coagulant dose of 40 mg/L and average PAC

dose of 20 mg/L). Under bench-scale testing for baseline conditions, the settled water DOC was

measured as 3.2 mg/L. This testing showed that, when combined with a preozone dose of 3 mg/L,

adjusting the coagulant dose was more effective at removing DOC than adjusting the PAC dose. The



preferred alternative based on DOC removal would be pre-ozone with double the coagulant dose,

which was capable of reducing the DOC concentration by about 22 percent.

Figure 4-7. Reduction in DOC for Combinations of Various Process Alternatives. Percentages are

relative to baseline DOC of 3.2 mg/L which represents current plant operations.

As previously mentioned, DOC reduction does not directly correlate to reduction in TTHM

formation when alternative oxidation processes are applied. Therefore, DBP testing for each

condition was conducted. Figure 4-8 summarizes the percent reduction in TTHM formation with

respect to the baseline conditions.

Results from this evaluation show an anticipated reduction in TTHM formation of about 45 percent

when pre-ozone is used in conjunction with double the coagulant dose. Increasing the PAC dose

beyond 50 percent of the average dose had little impact on DOC removal and TTHM reduction.

Although doubling the coagulant dose and PAC dose results in the highest reduction of TTHMs, this

alternative is only marginally better than the alternative that doesn’t require increased PAC dosing.

Thus, preozone combined with doubling of the plant’s current coagulant dose is considered most

effective for reducing TOC and DBP formation.



Figure 4-8. Reduction in TTHM formation for Combinations of Various Process Alternatives.

Percentages are relative to baseline TTHMs of 155.7 µg/L which represents TTHM

formation under current plant operations.

Since neither treatment combination was capable of reducing TTHMs to the target levels, aeration must be considered to provide an additional barrier for TTHM removal under more challenging water quality conditions. Aeration is expected to provide at least 20 percent removal of pre-formed TTHMs. Based on the results for preozone with enhanced coagulation and incorporating the effects of aeration, TTHMs in the range of 55 to 68 µg/L could be expected.

Because bench-scale testing of each alternative was conducted over individual grab samples between May and October 2017, there are very few discrete data points from which to draw conclusions about the potential performance and reliability of this alternative under varying source water quality conditions. Additional bench-scale testing is recommended to confirm that this combination of process improvements would sufficiently reduce TTHM formation to meet the treatment objectives on a consistent basis. As mentioned in Section 4.4, it is also recommended that regular ozone bench-scale testing be conducted to develop ozone decay/demand curves and refine the required ozone dose.



5.0 Facility Requirements for Viable Alternatives Of the treatment alternatives available for removing organic precursors and reducing DBPs, the

following have been determined to be the most effective and viable options for the Hannibal WTP.

Alternative 1. Post-Filter GAC Adsorption

Alternative 2. Reverse Osmosis

Alternative 3. Preozone with Enhanced Coagulation and Aeration

The subsequent sections provide additional detail on the facility requirements for the proposed

treatment alternatives. All of the proposed treatment alternatives are designed for average plant

capacity of 2.9 MGD and peak plant capacity of 7.5 MGD.

5.1 ALTERNATIVE 1: POST-FILTER GAC ADSORPTION

Based on the results of bench-scale and pilot testing, post-filter GAC vessels are a viable treatment alternative for achieving the target TOC and DBP formation with free chlorine. The new GAC system would be installed downstream of the existing transfer pumps, prior to UV disinfection and the finished water reservoir, as shown in Figure 5-1.

Figure 5-1. Alternative 1 Process Schematic - Post-Filter GAC Adsorption

5.1.1 Site Location

The site location for the new GAC facility would be southwest of the filter building in available area near the new generator and UV facility. This location would have to be filled as it slopes downward from the plant. Alternative locations also considered included an area north of the filter building on park property, and another area that is within the footprint of the abandoned storage reservoir. However, both of these locations appear to pose more challenges from piping and access standpoint. Therefore, these locations are not considered at this time but could be re-evaluated during detailed design to re-assess their feasibility. Refer to Figure 5.2 for location of the proposed GAC facility.



5.1.2 Transfer Pumping Modifications

Currently two (2) 100 horsepower (hp) transfer pumps located in the basement of the filter room pump the filtered water from the transfer well through the UV facility and to the finished water storage reservoir. These pumps are designed specifically to raise the water to the level in the reservoir, which is approximately 50 feet in total lift. Installation of the GAC system downstream of these pumps will require additional pressure to push through the GAC vessels and associated piping. Vessel manufacturers recommend about 30 psi (70 feet) of pressure on the inlet to the vessel to account for pressure loss through the GAC and ensure proper operation, resulting in a need for larger (i.e. higher head) transfer pumps.

Replacement of the existing transfer pumps with larger transfer pumps at the same location may not be feasible. The new pumps would weigh substantially more and exceed the capacity of overhead gantry crane. In addition, the pumps are currently located on an elevated slab constructed in the early 1900’s. The slab most likely will not be able to handle the additional weight and vibration of the larger pumps. Overall space and power availability also make replacing these pumps difficult. Therefore, new transfer pumping is required. There are a number of potential approaches to this, as outlined below.

One transfer pumping alternative would be to concrete core through the north wall of the transfer well and divert the flow to a new transfer well and pump station. The pump station would be located just north of the new GAC Building. The pipeline and transfer well would have to be about 25 feet below grade to maintain the same hydraulic elevations as the existing transfer well.

Another alternative would be to leave the existing transfer pumps where they are and divert the flow to new booster pumps that would raise the pressure adequate to push through the GAC system. Typically, inline pumping where flow goes directly from one pump to another is challenging and not recommended. It can be difficult to maintain set pressures and flow rates, even with variable frequency drives. Therefore, an equalization tank located prior to the new GAC feed pumps is recommended for this alternative.

For the basis of this evaluation, the equalization tank and booster pumps will be used given that coring the sidewall of the transfer well poses risks to the structural stability of the existing transfer well. In addition, the plant can only be off-line for a few hours to make the connection. The anticipated cost for this alternative would most likely be more than the booster pumping alternative.

The size of the equalization tank is approximately 120,000 gallons to equal one hour of storage at average flow conditions. This tank can also supply the backwash to the GAC system.

5.1.3 GAC System – Pressure Vessels

Based on the testing the GAC system will be sized for at least 15 minutes of EBCT at peak flow. This

will provide assurance that the target removals can be achieved at peak flow conditions, but also

provides greater reliability and flexibility to manage GAC material.

For the current plant capacity of 7.5 mgd, post-filter GAC contactors would be done using modular

rubber-lined steel GAC vessels. GAC vessels are typically designed to hold at least a full 20,000 lb

bulk GAC delivery, and can be larger, typically in 10,000 lb increments, to optimize delivery. In

order to achieve an EBCT of 15 minutes at a maximum flow rate of 7.5 MGD, approximately twelve



GAC steel contactors (each 12 feet in diameter) would be required. A minimum of 26,000 lbs would

be required for each vessel. Therefore, 30,000 lb vessels would be required under this condition.

Two GAC configurations were considered. One alternative includes larger vessels that run in

parallel, each sized for at least 15 minutes of EBCT at peak flow. The other alternative is installing

multiple treatment trains with each train consisting of two vessels interconnected in series. The

total EBCT of each train would be 15 minutes at peak flow.

The advantage of the larger vessels in parallel is primarily construction costs as it requires less

vessels, valves, and piping. However, it provides less functionality and flexibility during treatment

to target a specific effluent TOC concentration. Therefore, more frequent carbon replacements are

required for this alternative.

The two vessels in series combination provide additional flexibility for treatment as it allows the

first vessel to be exhausted prior to impacting the second vessel. By sampling between the two

vessels a lead/lag approach can be used by utilizing the higher performing vessel first. This

typically extends the life of the GAC and reduces the risk of breakthrough. Therefore, for the basis

of this design concept, a series approach (with two vessels) will be used. An estimate of overall GAC

media life based on this configuration is included Section 4.1.

Regular backwashing of the GAC contactors is not anticipated due to typically very low turbidity of

filtered water. Any small amount of accumulated solids would be removed during routine

replacement of spent GAC from the lead GAC contactor. Occasional backwashing of the lead

contactor could be performed between media replacement if needed, without dramatically

reducing the efficiency of GAC usage in the lead-lag configuration.

Typically, the full vessel volume is filled with media. Therefore, installing 12- 30,000 lb vessels

would actual result in longer EBCT than 15 minutes, approximately 17 minutes at peak flow.

Reducing the vessel size to 20,000 lbs could be considered. For 12- 20,000 lbs vessels the EBCT at

peak flow is about 11.4 minutes. This still meets the minimum MDNR requirement of 10 minutes of

EBCT, and would be effective for meeting treatment goals but would require more frequent media

replacement. For the basis of this evaluation, the 12- 30,000 lb vessels will be used. However, an

evaluation to determine possible capital cost savings of reducing the size of the vessels versus long

term operational costs and system resiliency should be conducted during detailed design if this

alternative is selected.

The backwash water will be supplied by the existing backwash tank using a dedicated backwash

pump. A second connection to the GAC feed pumps will also be provided if the pump is out of

service. Backwash wastewater will be disposed of to the existing backwash drain to the river. A

revised NPDES permit will be required to adjust the flow quantities and water characteristics in the

existing discharge.

The GAC equipment and booster pumps will be housed in a single story building matching the

architecture of the plant. A 24 inch influent and effluent header will be installed down the center of

the building that will supply each vessel through an 8 inch influent/effluent pipe. A dedicated 8

inch backwash supply and 12 backwash drain pipe header will also be routed down the center of

the building.



The interior of the GAC vessel has a conical shape to facilitate unloading of spent GAC media, which

is then hauled away. Replacement GAC is then fed into the steel vessel as a slurry using a plant

water supply. Replacement GAC is typically delivered in bulk trailers or hopper trailers, which are

operated by GAC supplier staff and fitted with the equipment required for loading a GAC vessel.

Table 5-1 summarizes the design parameters for the GAC system.

Table 5-1 GAC System Design Criteria – Pressure Vessels

FACILITY COMPONENT VALUE

Number of GAC Trains 6

Treatment Capacity per Train 1.25 MGD

GAC Contactor

Units per Train 2

Diameter (each) 12 ft

Surface Loading Rate

Average 3.0 gpm/sq ft

Maximum 7.7 gpm/sq ft

Media depth per Contactor 92 inches

Min GAC Media per Contactor (29.5lb/cu-ft) 26,000 lbs

Contactor Size, each 30,000 lbs

EBCT, Total per Train

Average 38 minutes

Maximum 15 minutes

Shell Height 108 inches

Approximate Overall Height 20 ft

Backwash System

Backwash Rate (maximum) 15 gpm/sq ft

Flow Rate 1700 gpm

5.2 ALTERNATIVE 2: REVERSE OSMOSIS

Reverse osmosis would be another viable alternative for DBP reduction. RO systems typically

reject 95-99 percent of the dissolved organic compounds that can form DBPs in the presence of free

chlorine residual. Given that the filter effluent TOC at the Hannibal WTP averages 2.7 mg/L with

95th percentile of 3.7 mg/L, the RO system would need to be sized to treat about 50% of the total

finished water flow in order to meet the target TOC of 1.75 mg/L.

The RO system would be installed downstream of the gravity filters and would require additional

pretreatment and chemical systems to minimize fouling of the RO membranes. Additionally, post-



treatment chemical addition may be required to stabilize the finished water and avoid corrosive

conditions in the distribution system. Figure 5- shows the systems and location for the proposed RO

system.

Figure 5-4. Alternative 2 Process Schematic - RO System

5.2.1 Site Location

The site location for the new RO facility would be southwest of the filter building in available area

near the new generator and UV facility, similar to the GAC Facility. Refer to Figure 5.5 for location

of the proposed RO facility. An equalization tank similar to the GAC system would be recommended

prior to the membrane feed pumps to facilitate operational control.



5.2.3 Pretreatment Facility Requirements

A pretreatment system consisting of membrane filtration is recommended upstream of the RO

system to improve the quality of the RO feed water. Microfiltration (MF) and ultrafiltration (UF)

membrane filters remove colloidal particles from water by straining it through a porous membrane.

Both processes are capable of reliably producing filtrate with exceptionally low turbidity and low

Silt Density Index (SDI), often below 0.05 NTU and 3, respectively. Maintaining a low SDI value is

important for RO operations. Refer to Figure 5-6 for Facility Layout.

Design parameters for the proposed MF/UF pretreatment system are summarized in Table 5-2. The

size of the MF/UF system will depend on RO recovery, which may range between 80 percent and 90

percent. For estimating the MF/UF system design requirements, an RO recovery of 85 percent is

assumed.

Table 5-2. MF/UF System Design Parameters

PARAMETER VALUE

Net Filtrate Total Flow Rate, mgd 4.41

Number of units 3 duty, 1 standby

MF/UF Recovery, % 97%

Design Flux, gfd 60

Maintenance Wash Chemical Sodium hypochlorite

Maintenance Wash Frequency 48 hours

CIP Cleaning Regiment Sodium hydroxide, Citric

Acid,

Sodium Hypochlorite

CIP Cleaning Frequency 30 days

5.2.4 RO System Facility Requirements

Filtrate from the MF/UF system will be conveyed to a new RO Feed Tank. Low pressure RO feed

pumps will transport water from the feed tank, through cartridge filters that protect the membrane

from accidental small particles, to the suction side of the feed pump on each RO unit. Three RO

trains configured in parallel are included in this evaluation. RO feed water will be dosed with

sodium metabisulfite to remove any residual free chlorine, which would damage the RO membrane.

Additionally, the RO feed water will be dosed with anti-scalant and sulfuric acid to prevent scaling

of the RO membranes. New chemical storage and feed systems will be required for sodium

metabisulfite, sulfuric acid and anti-scalant, as well as for chemicals periodically used for cleaning

of the RO units.



Table 5-3. Cartridge Filter Design Parameters

PARAMETER VALUE

Number of Cartridge Filter Units 3 duty

Cartridge Filter minimum pore size 5 µm

Cartridge Filter loading rate 3 gpm/10” equivalent

Expected replacement rate 4-6 months

The RO permeate will be blended with effluent from the existing gravity filters. While the average

water demand is 2.9 mgd, the Hannibal WTP is designed for a maximum treatment capacity of 7.5

mgd. Since the plant will rarely operate at maximum capacity, the RO system is designed without

redundancy.

Table 5-4 RO System Design Parameters

PARAMETER VALUE

Total Permeate Flow 3.75 mgd

Number of units 3 duty

Unit Permeate Flow 1.25 mgd

Estimated RO Recovery, % 85%

Design Flux, gfd 12

CIP Cleaning Chemical Citric Acid, Sodium

Hydroxide

CIP Cleaning Frequency 3-4 months

5.2.5 Post-Treatment Requirements

While RO provides the benefit of reducing the concentration of total dissolved solids in the finished

water, the RO permeate will have a pH of about 5.5 with hardness and alkalinity values of less than

10 mg/L as CaCO3. To minimize concerns about distribution system water quality and potential for

corrosion, the RO permeate must be stabilized. Post-treatment chemicals, such as sodium

hydroxide or sodium bicarbonate, may be applied directly to the RO permeate prior to blending

with filter effluent or on the blended finished water.

Additional water quality data and analysis would be required to refine post-treatment chemical

dosing to yield a finished water with corrosion index values that are compatible with historic values

in the existing distribution system. Bench-scale testing may also be required by MDNR to confirm

the level of corrosion control treatment needed to minimize potential changes to distribution

system water quality.



5.2.6 Brine Discharge Considerations

Based on initial mass balance calculations, the RO concentrate flow would be 0.56 mgd at maximum

plant capacity and 0.22 mgd at average plant capacity. Assuming 95 percent concentrate and 85

percent recovery, the concentration factor in the RO concentrate stream would be a factor of 6.4,

meaning that the concentration of dissolved compounds in the RO concentrate would be 6.4 times

the concentration in the RO feed.

Based on preliminary discussions with MDNR, it may be feasible to blend the RO concentrate with

the existing plant residuals and discharge to the Mississippi River. However, a new degradation

study would be required to confirm that the RO concentrate could be discharged to the Mississippi

River. The degradation study would consider mixing conditions at the current discharge location to

evaluate brine dispersion and determine whether there would be any aquatic species adversely

affected. Included with this alternative is a RO concentrate equalization basin to allow the potential

blending of backwash and concentrate flow prior to discharging to the river.

5.3 ALTERNATIVE 3: PREOZONE WITH ENHANCED COAGULATION AND

AERATION

The final alternative involves a multi-treatment approach for meeting the treatment objectives for

DBP formation, consisting of pre-ozonation, enhanced coagulation, and aeration in the finished

water storage reservoir and distribution system. Figure 5-7 shows the process components

impacted by this alternative.

Figure 5-7. Alternative 3 Process Schematic - Preozone with Enhanced Coagulation and Aeration

5.3.1 Site Location

A new ozone generation facility would be constructed east of the presedimentation basin, near the

2.5 MG finished water reservoir. The ozone solution would be dosed into the existing raw water

piping, using the existing head structure as an ozone contact basin. Coagulant would continue to be

dosed at the Primary Flocculation & Settling Basin using existing chemical storage and feed

equipment. New aeration equipment would be installed in the existing finished water storage tank



and in-line aeration equipment would be installed on the Paris Gravel Booster Station discharge

and on the Southside Booster Station discharge.

5.3.2 Ozone Facility Requirements

The proposed ozone system is designed for a transferred dose of 3.4 mg/L. The transferred dose is

based on an ozone-to-TOC ratio of 0.5 and 95th percentile value for raw water TOC of 6.7 mg/L.

Since side-stream injection systems typically have a transfer efficiency of 95 percent, the ozone

generation equipment will be designed for an applied dose of 3.6 mg/L. The system is designed for

sufficient capacity under peak design flow conditions with one major unit out of service. The major

system components include:

• Two ozone generators capable of producing 240 pounds per day (1 duty + 1 standby)

• Two closed looped cooling water systems (1 duty + 1 standby)

• Two Pressure Swing Adsorption (PSA) oxygen generation systems (1 duty + 1 standby)

• Three ozone injection skids (2 duty + 1 standby)

• Two ozone destruct units (1 duty + 1 standby)

• Two air compressors (1 duty + 1 standby)

The ozone solution would be fed into the raw water pipelines upstream of the influent head

structure through a side-stream injection. Sufficient contact time for ozone treatment can be

achieved in the existing structure; however, the structure would be retrofitted to include a concrete

weir wall and gas capture to deliver off-gas to the ozone destruct units. Figure 5-8 shows the

systems and location for the proposed ozone system.

5.3.3 Enhanced Coagulation Facility Requirements

Enhanced coagulation can effectively reduce TOC concentration by up to 20 percent using elevated

dosages of the plant’s current PACl coagulant (DFLOC-3610). The current chemical storage and feed

system has adequate capacity to meet the additional dosing requirements. While there are no

capital costs associated with increasing the coagulant dose, operational expenses will increase due

to increased chemical usage.

5.3.4 Aeration Facility Requirements

As mentioned, spray aeration equipment would be installed in the 2.5 MG finished water reservoir

located at the plant. MDNR does not permit aeration to occur within the same volume of water

used to achieve disinfection credits. Therefore, sufficient contact time must be provided in the

portions of the reservoir upstream of where the aeration equipment would be installed. With a free

chlorine residual of 2 mg/L, the plant would need approximately 22 minutes of contact time prior

to aeration in order to achieve the required CT. This is equivalent to 230,000 gallons of storage at

7.5 mgd flow rate. Therefore, there is sufficient volume in the existing reservoir to achieve the

necessary contact time in the first half of the reservoir, enabling the installation of aeration

equipment.

The aeration equipment would consist of four 15 horsepower (hp) floating aeration units and one

ventilation system. While this system is expected to remove approximately 20 percent of the

TTHMs in the finished water, DBPs will continue to form in the distribution system. Thus, in-line



aeration systems are also recommended to be installed at two other locations in the distribution

system. One in-line aerator would be installed in the discharge piping of the Paris Gravel Booster

Station, and the other in the discharge of the South Side Booster Pump Station. These in-line

aeration systems would reduce TTHMs by another 20 percent in the Paris Gravel and South Side

pressure zones.

The aeration tank and pump would be housed in a pre-fabricated building located near the existing

pump stations. The building footprint is estimated to be 15 ft by 30 ft.



6.0 Cost Development

6.1 COST CRITERIA

Estimates of capital costs were developed from unit and lump sum prices for the various

components for each facility. Equipment pricing was based primarily on equipment and material

quotes from vendors and manufacturers. Building infrastructure costs were based on 2017 building

cost data and information from similar projects recently constructed in the region. Cost

adjustments were made based on recent project experiences and in-house historical data.

Additional quantities for general requirements (permitting, contingencies) were combined to

obtain a total opinion of probable construction cost for the alternative. The primary purpose of the

costing included for each alternative in this study is to provide a budgetary estimate for each

alternative to facilitate with the selection of the preferred alternative among other non-economic

factors.

Generally, for this type of project an AACE (Association for the Advancement of Cost Engineering)

Class 4 estimate is used. Class 4 estimates are generally prepared based on limited information and

subsequently have fairly wide accuracy ranges. They are typically used for project screening,

determination of feasibility, concept evaluation, confirmation of economic and/or technical

feasibility, and preliminary budget approval. Typically, engineering is from 1% to 15% complete.

Typical accuracy ranges for Class 4 estimates are -15% to -30% on the low side, and +20% to +50%

on the high side, depending on the technological complexity of the project, appropriate reference

information, and the inclusion of an appropriate contingency determination. In unusual

circumstances, the actual cost of implementation may exceed the ranges specified.

Contingencies are defined as unknown or unforeseen costs. The level of detail available at the

planning/conceptual phase of the project does not provide sufficient definition to fully capture all

the costs associated with the project. As the project is developed and design details are refined,

contingency can be reduced. For this study, a contingency value of 25 percent was selected to

correspond with the level of project definition and potential for cost variability.

Annual operations and maintenance (O&M) costs were also developed to evaluate the life cycle cost

of each alternative. Table 6-1 summarizes the unit costs used to develop the annual O&M costs.

Table 6-1 Operational Costs

LIFE CYCLE COST FACTORS – UNIT COST ASSUMPTIONS

ITEM UNIT VALUE

Flow rate, average MGD 2.9

Cost of Electricity $/kW-hr 0.0799

General Maintenance % Equip 2%

Cost of Poly-aluminum chloride $/lb 0.35

Cost of Powered Activated Carbon $/lb 1.00

Cost of Granular Activated Carbon (new) $/lb 1.60



Twelve percent of the construction cost was added to all components of the water treatment facility

as an allowance for mobilization(s), contractor bonds, insurance, supervision, temporary facilities,

temporary utilities, equipment rental, and miscellaneous for the water treatment plant

construction.

The construction and operational costs were annualized over a 25 year period with an effective

interest rate of 2 percent (4% interest rate minus 2% inflation) to develop a present worth cost.

Costs for engineering, BPW administration, and inspection of 18 percent of the construction total

were added to develop a total project cost. Bond costs, costs per customer, and impact on rates are

not included in this evaluation.

Construction and operational costs are highly variable. The current bidding environment, material

and chemical costs, bond costs, and water quality can impact the overall costs. Once an alternative

is selected further refinement of that concept should be conducted to establish a project budget. If

specific budgets must be established from this report additional Owner contingencies should be

considered, depending upon the amount of impact/risk if unforeseen items impact overall costs.

Therefore, an additional Owner’s contingency of 10 percent was included in the evaluation.

6.2 CAPITAL COSTS

Table 6-2 summarizes the capital costs for the following alternatives:

Alternative 1 - Post-Filter GAC Adsorption sized for 15 minutes at 7.5 MGD

Alternative 2 - Reverse Osmosis sized for 50% of plant flow

Alternative 3 - Pre-ozone, enhanced coagulation, and aeration



Table 6-2 Summary of Capital Costs

ALTERNATIVE ALTERNATIVE 1 ALTERNATIVE 2 ALTERNATIVE 3

Description Granular Activated

Carbon

Reverse

Osmosis

Ozone + Aeration +

Enhanced Coagulation

Sitework $799,000 $780,000 $298,000

Site Electrical $253,000 $814,000 $408,000

Equalization Basin $0 $391,000 $0

Storage Tank $404,000 $376,000 $0

GAC Facility $8,413,000 $0 $0

Ozone Building $0 $0 $5,933,000

RO Facility $0 $12,908,000 $0

Inline Aeration (2 Facilities) $0 $0 $1,340,000

Tank Aeration $0 $0 $893,000

Head Structure Modifications $0 $0 $211,000

Subtotal $9,869,000 $15,269,000 $9,083,000

General Requirements (12%) $1,184,000 $1,832,000 $1,090,000

Total Construction Costs $11,053,000 $17,101,000 $10,173,000

Professional Services (12%) $1,326,000 $2,052,000 $1,221,000

Construction Oversight (6%) $663,000 $1,026,000 $610,000

Protect Total $13,042,000 $20,179,000 $12,004,000

Owner's Contingency (10%) $1,304,000 $2,018,000 $1,200,000

Project Total w/ Owner’s

Contingency $14,346,000 $22,197,000 $13,204,000

6.3 PRESENT WORTH COSTS

Operational costs incurred for each alternative were developed to determine the overall present

worth costs. Annual operational costs include chemical, power, labor, and equipment replacement

for 25 years of operation. Factors used are described in Section 6.1. Refer to Table 6-3 for summary

of present worth costs. Annual O&M costs are based on an average capacity of 2.9 MGD.

Operational costs for GAC are based on the breakthrough curve established from the pilot data, as

detailed in Section 4.1.7. The O&M costs for the RO alternative are based on estimates for energy

consumption, chemical use and process consumables for 1.45 MGD permeate production (50

percent flow at average capacity). O&M costs for the third alternative are based on ozone and

coagulant dosages established through bench-scale testing, as well as estimated energy

consumption for ozone generation and blower operation for aeration. As noted in Section 6.2, the

O&M costs have been derived based on the level of detail available at the planning/conceptual



phase. There is a potential for variation in operational costs due to variability in unit costs, energy

consumption, media replacement frequency, or chemical use, which could impact the overall life

cycle cost.

Table 6-3 Present Worth Costs for DBP Compliance Alternatives

ALTERNATIVE 1 ALTERNATIVE 2 ALTERNATIVE 3

Description Granular

Activated

Carbon

Reverse Osmosis

Ozone + Aeration +

Enhanced

Coagulation

Project Total w/ Owner’s Contingency $14,346,000 $22,197,000 $13,204,000

Annual O&M Costs $691,000 $391,000 $377,000

Present Worth Costs $27,837,000 $29,831,000 $20,564,000

As discussed in Section 4.1.7, the GAC alternative includes construction costs for a 7.5 MGD facility

sized for 15 minutes of contact time at peak flow. If the facility size was reduced to provide 15

minutes of contact time at average flow (2.9 MGD), the project total with Owner’s contingency

would be about $13,000,000. However, since there would be fewer vessels to stagger replacement,

and less total volume of GAC installed, the replacement frequency would increase. Therefore, the

overall net present value for installing fewer vessels is about $29,000,000, higher than the total

present worth costs for the full 7.5 MGD capacity. Furthermore, the fewer vessels would not be as

robust to handle higher flow rates and changing water quality, and would not meet MDNR

requirements for 10 minutes of EBCT at peak flow. Therefore, it would impact the performance and

reliability of the system and is not recommended.

The present worth cost of the GAC system is primarily driven by the cost and frequency of GAC

replacement, represented in the O&M costs. The O&M costs used to develop the present worth cost

for the GAC alternative is based on the use of virgin GAC for media replacement. Reactivated

carbon can potentially be utilized to reduce the annual O&M costs. This could result in up to 20

percent reduction in annual O&M costs. However, actual cost savings vary based on GAC usage rates

and distance from reactivation facility and must be verified with GAC suppliers. The GAC O&M

costs are based on the results of the one pilot system. Additional testing, piloting, and full scale

operation could result in different O&M costs.

Historically, the unit price of GAC has followed the Producer Price Index (PPI). However, the unit

price has experienced some fluctuations caused by regulatory changes and other global market

conditions. Typically, long-term contracts are negotiated with GAC suppliers to secure a fixed price

for GAC media over the duration of the contract.

For reverse osmosis, O&M costs are primarily driven by energy consumption from the RO process.

However, present worth costs are largely driven by the capital cost associated with installation of

RO equipment and MF/UF pretreatment equipment.



For the third alternative, O&M costs are largely driven by energy consumption from the ozone

generation process and by chemical use from enhanced coagulation. The initial capital cost of this

alternative is relatively low, as it requires fewer modifications to existing infrastructure.

6.4 COMPARISION OF ALTERNATIVES

Each alternative presents a set of benefits and drawbacks associated with cost of implementation,

ease of operation, and amount of data available to confirm treatment performance. While some

alternatives provide a very high level of confidence in treatment performance and are relatively

simple to operate/implement, those benefits must be weighed against the cost of implementation to

select the alternative that provides the most long-term value for the City. Other considerations

must be made regarding potential challenges with regulatory compliance, operator safety, and

reliability associated for each alternative. Table 6-4 summarizes a comparison between the

alternatives.

Table 6-4 Summary of Advantages and Disadvantages for Each Alternative

ALTERNATIVE ADVANTAGES DISADVANTAGES

Granular Activated Carbon • High level of confidence to meet DBP requirements.

• Able to treat wide range of water quality.

• Minimal impact on NPDES permit.

• Does not require additional chemicals.

• Relatively simple to operate.

• Highest operational costs.

• Additional transfer pumping.

• Requires close monitoring to assure correct effluent blend for target TOC removal.

• Frequent media replacements.

Reverse Osmosis • High level of confidence to meet DBP requirements.

• Relatively low operational costs (only treating partial flow).

• Considered advanced treatment that is able to adapt to changing regulations and future contaminants.

• Highest capital costs.

• Additional transfer pumping.

• Complex system which requires high operator oversight.

• Dispersion modeling needed for RO concentrate discharge approval to river.

• RO membranes can experience more fouling in surface water plants from organics.

Ozone + Enhanced

Coagulation Aeration

• Lowest initial capital cost.

• Lowest operational costs.

• Easiest to implement within existing infrastructure.

• Does not require additional transfer pumping.

• 6-12 months of additional testing is recommended to ensure feasibility under varying source water quality.

• Multi-treatment approach with several variables affecting performance

• Requires close monitoring to ensure TOC/DBP goals are met.

• Doubling coagulant dose may impact filter operations.



7.0 Recommendations Each alternative presents its own unique set of advantages and disadvantages with respect to

economic and non-economic factors. While one alternative may have a relatively low initial capital

investment, it may cost more annually to operate the system, resulting in an overall higher life cycle

cost. Schedule of implementation is also a major consideration, considering that the use of ammonia

for chloramination must be discontinued by March 31, 2020. Additionally, some alternatives may

require additional bench-scale testing to gain regulatory approval or to improve confidence that the

treatment alternative can consistently meet the performance objectives. Ultimately, HBPW will

need to make a decision on which alternative to implement to most effectively manage their risk

with respect to cost of implementation, schedule requirements to comply with ordinance timeline,

and confidence in the amount of data collected that the solution will consistently meet regulatory

requirements.

From a life cycle cost perspective, Alternative 3, which involves pre-ozone with enhanced

coagulation and aeration, would be the preferred treatment approach. However, managing DBP

formation with this approach would be relatively complicated as it involves a multi-treatment

approach with several variables that dictate performance and overall compliance with the

treatment objectives. Given that there are only a few, discrete data points collected from bench-

scale testing, this alternative has a much lower confidence factor than the other two alternatives, in

terms of ensuring compliance can be met on a consistent basis. If this alternative were to be

considered for future implementation, at a minimum, 6-12 months of monthly testing would be

recommended to evaluate and confirm treatment performance under varying seasonal water

quality conditions.

Alternative 1 (GAC) and Alternative 2 (RO) provide the highest level of confidence that the installed

system can effectively remove TOC to the required level to consistently comply with the DBP

treatment objectives. However, Alternatives 1 and 2 would result in significant life cycle costs over

the 25-year operating period considered in this evaluation. While the GAC system requires a lower

initial capital investment than the RO system, the operational expenses associated with GAC media

replacement result in life cycle cost similar to the RO system. The GAC media replacement rate was

estimated based on available pilot data. The actual rate of replacement during full-scale operations

may vary depending on filter effluent (GAC influent) TOC conditions and media performance.

Additional pilot testing would help refine the operational costs, but are not anticipated to impact

capital costs. Given the potential variability in operational expenses and the ability that has to

impact the overall life cycle cost, GAC would be the preferred alternative strictly from a cost

perspective as it has a substantially lower capital cost than RO. Additionally, an RO system would be

more complex to operate and maintain, and has potential for cost to escalate should concentrate

disposal not be permitted through the existing outfall.

HBPW will need to evaluate the tradeoffs and potential risks associated with implementing a more

costly solution (GAC or RO) that have a higher level of confidence in meeting treatment goals versus

implementing the lowest cost (preozone with enhanced coagulation and aeration) which would

require additional testing to confirm the treatment performance and effectiveness of the

alternative.

BLACK & VEATCH | Appendix A A1

Appendix A. Bench-Scale Testing Results

1.0 GAC Adsorption Testing

1.1 RAPID SMALL-SCALE COLUMN TESTING

Rapid small scale column testing was conducted using filter effluent collected from the Hannibal

WTP in June and again in November 2017. The testing assessed TOC removal and DBP formation

potential for filter effluent treated through a GAC column. The rapid small-scale GAC column is

designed to simulate 365 days of operation for alternative column configurations and GAC media.

In this way, the data can be used to establish an adsorption breakthrough curve that would

simulate breakthrough expected in a full scale system.

The results of the testing conducted by Calgon are presented in Figure A-1. The results indicate

that TOC breakthrough occurred after 150 simulated days in a post-filter GAC contactor

configuration with EBCT of 13 minutes in the June test, and approximately 100 simulated days in

the November test. Breakthrough is defined as the time at which the effluent TOC concentration

exceeds the target treatment objectives of 1.75 mg/L. The June test was conducted when the GAC

feed/filter effluent TOC was 2.25 mg/L, which is substantially lower than the design filter effluent

TOC of 2.75 mg/L. Thus, the breakthrough curve demonstrated in the June to some degree may

overestimate GAC performance and expected GAC media life. The November test was conducted

with the GAC feed/filter effluent TOC of 3.2 mg/L, which is above the average TOC concentration of

2.7 mg/L. The two tests show the variability of TOC in the feed water and how it impacts GAC

performance.


Figure A-1. TOC Breakthrough Curve for Accelerated Column Test using Filtrasorb400 (F400) and 15-

min EBCT (Calgon 2017)

A second rapid column test was conducted by Evoqua in October 2017. The objective of this test

was to draw a comparison of GAC performance for TOC removal using alternative GAC media. The

materials used were the Filtrasorb 400, which was used in the first rapid test and in the pilot, and

UltraCarb 1240AW.

Figure A-2 displays the results from the test. The data showed the Filtrasorb 400 performed

slightly better than the UltraCarb 1240. However, they are close enough that a lifecycle cost

analysis would need to be performed to select which media would provide the best value.

The curve developed from this test indicates that TOC breakthrough of 1.75 mg/L would occur in

the GAC media after 9,000 bed volumes, or 47 simulated days of operation at 7.5 minutes EBCT.

Although it is not a direct 1:1 ratio, adjusting the data set to 15 minutes of EBCT results in 94 days

to breakthrough.

The source water TOC for this sample was 3.1 mg/L, which is higher than the average expected TOC

of 2.7 mg/L.


Figure A-2. TOC Breakthrough Curve for Rapid-Scale Simulated Column Test using Filtrasorb400 (F400)

and UltraCarb 1240AW with 7.5-min EBCT (October 2017)

1.2 GAC FILTER PILOT TESTING

Pilot testing was conducted to replicate installation of GAC within the existing filters to determine

effectiveness for TOC removal. Pilot filter column 1 replicated GAC media depth of 12 inches with

an EBCT of 3.1 minutes. Filter column 2 replicated 28 inches of media with an EBCT of 7.1 minutes.

The EBCT used in the pilot were somewhat restricted based on the flow instrumentation associated

with the pilot unit. However, although the EBCT don’t align directly with design times, a correlation

can be made to adjust the performance of the pilot to align with the design condition.

Figures A-3 and A-4 show the pilot performance for both conditions at average flow rates through

the filters.


Figure A-3 Column 1 Pilot Results at 6.0 minutes EBCT (12 inches of GAC in Filters)


Figure 1-4 Column 2 Pilot Results at 14 minutes EBCT (28 inches of GAC in Filters)

The results from pilot column 1 show no additional TOC removal after about 12 days of operation.

Column 1 also never achieved the target TOC concentration of 1.75 mg/L. Column 2 shows TOC

removal up to about 63 days in operation. At around 63 days the pilot showed no additional TOC

removal occurs. The average TOC removal between 25 and 55 days is about 38 percent. This level

of removal would be close to sufficient to achieve DBP compliance, but would have to be monitored

closely to assure compliance. However, at 63 days, no additional TOC removal would be achieved.

To replace GAC media the annual costs would be extremely high, estimated at around $1.5 million

per year. In addition, removal and replacement of the GAC media at these short intervals would

significantly increase demands on plant staff and equipment availability.

While these EBCTs would be sufficient to provide effective control of tastes and odors, they are not

feasible for reducing TOC and DBPs. Based on these considerations and results of the pilot, the use

of GAC in the existing filters for compliance with DBP requirements is not recommended.


2.0 Enhanced Coagulation Testing An initial evaluation was performed to identify the optimal coagulant type and dosage to be applied

for control of DBP precursors. All coagulants were tested on an equivalent metal ion concentration

with polymer, and each coagulant was tested with and without pH adjustment. From the initial

screening evaluation, it was determined that the plant’s current coagulant (DFLOC 3610) and the

high aluminum PACL (DFLOC 3606) were the most viable options for increasing DOC removal.

2.1 CURRENT COAGULANT (DFLOC 3610)

Table A-1 summarizes the results from bench-scale testing conducted with the plant’s current

polyaluminum chloride (PACl) coagulant – DFLOC 3610. The purpose of testing was to evaluate

efficacy of enhanced coagulation under different treatment scenarios, which included increased

coagulant dosing and pH adjustment.

As demonstrated in Table A-1, doubling the dose of the plant’s current coagulant resulted in the

highest percent reduction in DOC and was most effective for reducing DBP precursors.

Table A-1. Coagulation Testing Results – Plant Current Coagulant DFLOC 3610 (May 2017)

CHEMICAL

JAR 1

(BASELINE) JAR 2 JAR 3 JAR 4 JAR 5 JAR 6

Jar Testing Results

Source Water Raw Water

Source Water DOC, mg/L 4.57

DFLOC 3610 Dose, mg/L 40 60 80 40 40 60

Polymer Dose, mg/L 1.6 2.4 3.2 1.6 1.6 2.4

Sulfuric Acid Dose, mg/L - - - 2.25 7.30 2.25

pH 8.04 7.94 7.84 7.99 7.79 7.80

Turbidity, NTU 1.85 1.67 1.08 2.60 2.15 2.04

UVA, cm-1

0.077 0.076 0.058 0.090 0.085 0.077

Percent Reduction UVA

relative to Baseline

- 1% 12% -17% -10% 0%

Settled Water DOC, mg/L 3.05 3.03 2.54 3.19 3.01 3.00

Percent Reduction DOC

relative to Baseline, %

- 1% 17% -5% 1% 2%

SDS Testing Results

Chlorine Dose Applied,

mg/L 2.1

- - - - -


CHEMICAL

JAR 1

(BASELINE) JAR 2 JAR 3 JAR 4 JAR 5 JAR 6

Chlorine Residual after 5-

day hold, mg/L 0.01

- - - - -

TTHM after 5-day hold, µg/L 84.1 - - - - -

HAA5 after 5-day hold, µg/L 23.4 - - - - -

Additional bench-scale testing was conducted in July 2017 to reevaluate the optimal coagulant type and dose under more challenging raw water quality conditions. Table A-2 summarizes the results of this evaluation, which again show that doubling the dose was most effective for reducing the concentration of DOC prior to chlorine disinfection.

Table A-2. Coagulation Testing Results – Current Coagulant DFLOC-3610 (July 2017)

PARAMETER JAR 1

(BASELINE) JAR 2 JAR 3 JAR 4

Jar Testing Results



Coagulant Dosage, mg/L 40 60 80 40

Polymer Dosage, mg/L 1.6 2.4 3.2 1.6

PAC Dosage, mg/L 20 20 20 20

Acid Dosage, mg/L - - - 34

pH 8.04 7.98 7.95 6.98

Turbidity, NTU 0.85 1.75 0.93 1.78

UVA, cm-1

0.060 0.049 0.042 0.051

Percent Reduction UVA relative to

Baseline 0% 18% 30% 15%

Settled Water DOC, mg/L 2.83 2.53 2.25 2.64

Percent Reduction DOC relative to

Baseline 0% 11% 20% 7%

SDS Testing Results

Chlorine Dose Applied, mg/L 4.0 Not tested 4.0 Not tested

Chlorine Residual after 5-day hold, mg/L 0.66 - 1.13 -

TTHM after 5-day hold, µg/L 122.8 - 101 -

HAA5 after 5-day hold, µg/L 58.1 - 41.8 -


2.2 HIGH ALUMINUM PACL (DFLOC 3606)

The results from retesting the high aluminum content coagulant (DFLOC 3606) are summarized in Table A-3 below. Percent reduction of UVA and DOC are calculated using the measured values from Jar 1 (plant’s current coagulant at average dose) as the baseline.

Table A-3. Coagulation Jar Testing Results - DFLOC 3606 (May 2017)

CHEMICAL JAR 1 JAR 2 JAR 3 JAR 4 JAR 5 JAR 6

Jar Testing Results



DFLOC 3606 Dose, mg/L 32.4 48.6 64.7 32.4 32.4 48.6

Polymer Dose, mg/L 1.5 1.9 2.6 1.5 1.5 1.9

Sulfuric Acid Dose, mg/L - - - 6.5 20 8.5

pH 7.96 7.99 7.99 7.95 7.60 7.61

Turbidity, NTU 4.12 3.51 3.12 3.52 4.64 3.72

UVA, cm-1

0.102 0.096 0.079 0.098 0.105 0.090

Percent Reduction UVA

relative to Baseline -32% -25% -3% -27% -36% -17%

Settled Water DOC, mg/L 2.72 2.54 2.47 2.80 2.67 2.54

Percent Reduction DOC

relative to Baseline, % 11% 17% 19% 8% 12% 17%

SDS Testing Results

Chlorine Dose Applied,

mg/L Not tested Not tested Not tested Not tested Not tested Not tested

Chlorine Residual after 5-

day hold, mg/L

- - - - - -

TTHM after 5-day hold, µg/L - - - - - -

HAA5 after 5-day hold, µg/L - - - - - -

Table A-4. Coagulation Jar Testing Results - DFLOC 3606 (July 2017)

CHEMICAL JAR 1 JAR 2 JAR 3 JAR 4

Jar Testing Results

DFLOC 3606 Dose, mg/L 32.4 48.6 64.7 32.4


CHEMICAL JAR 1 JAR 2 JAR 3 JAR 4

Polymer Dose, mg/L 1.3 1.9 2.6 1.3

Sulfuric Acid Dose, mg/L - - - 24.7

pH 8.05 8.06 8.03 7.10

Turbidity, NTU 2.50 2.90 3.60 5.00

UVA, cm-1

0.057 0.045 0.038 0.048

Percent Reduction UVA, % 5% 25% 37% 20%

DOC, mg/L 3.00 2.39 2.14 2.55

Percent Reduction DOC, % -6% 16% 24% 10%

SDS Testing Results



TTHM after 5-day hold, µg/L 131.5 - 89.5 -


3.0 Ozone Testing During the initial screening evaluation, alternative oxidants were evaluated to determine whether

they would be viable methods for oxidizing organic precursors and reducing chlorine demand to

control DBP formation. Of the alternative oxidants evaluated, ozone applied as a preoxidant

upstream of the presedimentation basin was deemed most effective.

3.1 PREOZONE

Table A-5 summarizes the bench-scale testing results for the preozone evaluation conducted during

the initial screening evaluation.

Table A-5. Preozone Bench-Scale Testing Results (May 2017)

PARAMETER BASELINE JAR 1 JAR 2 JAR 3

Jar Testing Results



Ozone Dose, mg/L - 1.5 2.5 3.5

Coagulant (DFLOC 3610) Dose, mg/L 40 40 40 40




pH 8.04 7.02 6.72 6.42

Turbidity, NTU 1.85 2.93 1.94 2.55

UVA, cm-1

0.077 0.072 0.057 0.064


Baseline - 35% 50% 58%



Baseline - 20% 26% 23%

SDS Testing Results



TTHM after 5-day hold, µg/L 84.1 - 36.2 -


Table A-6. Preozone Bench-Scale Testing Results (July 2017)


Jar Testing Results



Ozone Dosage, mg/L - 1.5 3.0 4.5



PAC Dose, mg/L 20 20 20 20

pH 8.04 8.20 7.98 7.98

Turbidity, NTU 0.85 0.97 0.89 1.15

UVA, cm-1

0.060 0.039 0.030 0.025

Percent Reduction UVA, % relative to

Baseline

- 35% 50% 58%



Baseline

- -12% -3% -4%

SDS Testing Results



Chlorine Dose Applied, mg/L 4.0 3.5 3.5 Not tested

Chlorine Residual after 5-day hold, mg/L 0.66 0.49 0.70 -

TTHM after 5-day hold, µg/L 122.8 86.1 87.6 -

HAA5 after 5-day hold, µg/L 58.1 35.8 31.7 -

3.2 INTERMEDIATE OZONE

Table A-7 summarizes the bench-scale testing results from the evaluation of ozone as an

intermediate oxidant. At comparable dosages, intermediate ozone was less effective for reducing

TTHM formation compared with preozone.

Table A-7. Intermediate Ozone Bench-Scale Testing Results (July 2017)


Jar Testing Results

Source Water Raw Water (Settled prior to ozonation)


Coagulant (DFLOC 3610) Dose, mg/L 40 40 40 40


Intermediate Ozone Dose, mg/L - 1.5 2.5 3.5

pH 8.04 7.98 8.01 7.80

Turbidity, NTU 0.85 0.80 1.50 0.70

UVA, cm-1

0.060 0.040 0.029 0.020


Baseline - 33% 52% 67%



Baseline - -11% -6% -2%

SDS Testing Results

Chlorine Dose Applied, mg/L 4.0 3.5 4.0 Not tested

Chlorine Residual after 5-day hold, mg/L 0.66 0.51 0.66 -

TTHM after 5-day hold, µg/L 122.8 116.6 99.1 -

HAA5 after 5-day hold, µg/L 58.1 38.6 37.7 -


4.0 Combination of Process Alternatives Testing Since ozone alone was not capable of reducing the DBP formation to acceptable levels, ozone was tested in combination with alternative treatment solutions, including enhanced coagulation and increased PAC dosing. As determined from previous testing, the optimal ozone dose is based on the ratio of 0.5 times the TOC concentration in the raw water.

Simulated distribution system (SDS) testing was conducted using free chlorine to target a 0.5 mg/L residual over a 5-day hold period. The results for TTHMs and HAA5s from testing preozone with enhanced coagulation and increased PAC dosing are summarized in the table below.

While the alternative that considered preozone with double the coagulant dose and double the PAC dose resulted in the lowest concentration of TTHMs, it has marginal performance benefits, reducing DBPs by only 5% compared with the better than the alternative that considered preozone with double the coagulant dose. Of the process alternatives evaluated, preozone with double the current coagulant dose was most effective for reducing DBPs.

Table A-8. Preozone with Enhanced Coagulation Testing Results (October 2017)

PARAMETER

BASELINE JAR 1

(3 mg/L O3)

JAR 2

(OZONE + 1.5x

COAG)

JAR 3

(OZONE + 2x

COAG)

Jar Testing Results






PAC Dose, mg/L 20 20 20 20

pH 8.02 7.79 7.76 7.55

Turbidity, NTU 1.37 1.33 1.20 1.65

UVA, cm-1

0.072 0.039 0.032 0.028


Baseline - 46% 56% 61%



Baseline 0% 2% 10% 22%

SDS Testing Results

Chlorine Dose Applied, mg/L 5.3 4.5 4.5 4.0

Chlorine Residual after 5-day hold, mg/L 0.51 0.47 0.68 0.44

TTHM after 5-day hold, µg/L 155.7 117.9 106 85.1

HAA5 after 5-day hold, µg/L 62.5 36.6 31.1 25.4


Table A-9. Preozone with Increased PAC Dosing Testing Results (October 2017)

PARAMETER

BASELINE

JAR 4

(OZONE +

1.5x PAC)

JAR 5

(OZONE + 2x

PAC)

JAR 6

(OZONE + 2x

COAG + 2x PAC)

Jar Testing Results






PAC Dose, mg/L 20 30 40 40

pH 8.02 7.65 7.67 7.43

Turbidity, NTU 1.37 2.20 0.94 1.03

UVA, cm-1

0.072 0.034 0.031 0.020


Baseline - 53% 57% 72%



Baseline 0% 13% 12% 25%

SDS Testing Results

Chlorine Dose Applied, mg/L 5.3 4.0 4.0 3.5

Chlorine Residual after 5-day hold, mg/L 0.51 0.40 0.46 0.55

TTHM after 5-day hold, µg/L 155.7 97.9 100.1 80.7

HAA5 after 5-day hold, µg/L 62.5 30.8 29.3 24.3

chloramine replacement alternative evaluation...based on this timeframe, the board of public works...

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