Conceptual Design of Alternatives for the Use of Free ......• Ozone as an intermediate oxidant after enhanced coagulation and clarification ... Plate Settler Feed Pumps Three, each

COPYRIGHT

Conceptual Design the Use of Free Chlorine in the

Poughkeepsie’s Water Treatment

Poughkeepsie Joint Water

COPYRIGHT 2012 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

F ina l

Conceptual Design of Alternatives for the Use of Free Chlorine in the

Distribution System Poughkeepsie’s Water Treatment

Poughkeepsie Joint Water Project

F ina l Repor t

of Alternatives for the Use of Free Chlorine in the

Distribution System for Poughkeepsie’s Water Treatment

Facility

Prepared for

Project Board

March 2012

Contents

Section Page

PJWB DBP CONCEPT DESIGN DRAFT REPORT 043012_FINAL III COPYRIGHT 2012 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

1 Introduction ...................................................................................................................................... 1-1

1.1 Project Background.......................................................................................................................... 1-1

1.2 Bench-Scale Testing Results ............................................................................................................ 1-1

2 Existing Conditions ............................................................................................................................ 2-1

2.1 Raw Water Quality ........................................................................................................................... 2-1

2.2 WTP Overview ................................................................................................................................. 2-2

2.2.1 Liquid Treatment Processes ............................................................................................... 2-2

2.3 Residuals Treatment Processes ....................................................................................................... 2-3

3 Alternatives for Disinfection By-Product Control ................................................................................ 3-1

3.1 Introduction ..................................................................................................................................... 3-1

3.1.1 Alternative 1 Chlorine Dioxide with Enhanced Coagulation Design ................................... 3-1

3.1.2 Alternative 2 Enhanced Coagulation with Intermediate Ozone Design ............................. 3-4

3.1.3 Alternative 3 MIEX Design .................................................................................................. 3-7

4 Residuals Impacts from DBP Control Alternatives ............................................................................... 4-1

4.1 Solids Generation............................................................................................................................. 4-1

4.2 Impact of Increased Solids Generation ............................................................................................ 4-1

4.3 MIEX Residuals ................................................................................................................................. 4-2

5 Cost Evaluation of Alternatives .......................................................................................................... 5-1

5.1 Introduction/Assumptions ............................................................................................................... 5-1

5.2 Capital Costs .................................................................................................................................... 5-2

5.3 Operating and Maintenance Costs .................................................................................................. 5-2

6 Recommendations and Implementation Plan ..................................................................................... 6-1

6.1 Assessment of Compliance Reliability ............................................................................................. 6-1

6.2 Phased Implementation .................................................................................................................. 6-2

6.3 Recommendations ........................................................................................................................... 6-4

Tables

2-1 Raw Water Quality

2-2 Residuals System Design

3-1 Alternative 1 – Basis of Design

3-2 Alternative 2A/2B Basis of Design

3-3 Alternative 3A/3B MIEX Basis of Design Table

4-1 Projected Solids

4-2 Thickener Capacity/Loading

4-3 Centrifuge Capacity/Loading

5-1 Capital Cost Markups Used for Estimates

5-2 Operation and Maintenance Cost Assumptions

5-3 Capital Costs

5-4 Operating and Net Present Cost

6-1 Phased Approach Costs

CONTENTS, CONTINUED

IV PJWB DBP CONCEPT DESIGN DRAFT REPORT 043012_FINAL COPYRIGHT 2012 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

Figures

2-1 Frequency plots for flow and turbidity

2-2 Frequency plots for flow and turbidity

2-3 PWTF Process Flow Diagram

3-1 Purate Process Schematic

3-2 Alternative 1 – Basis of Design

3-3 Alternative 2A/2B Site Plan

3-4 Alternative 3A/3B MIEX Site Plan

6-1 Total Trihalomethane (TTHM) Formation Estimate

6-2 Haloacetic Acid (HAA5) Formation Estimate

6-3 Flowchart of Phased Implementation Approach

PJWB DBP CONCEPT DESIGN DRAFT REPORT 043012_FINAL 1-1 COPYRIGHT 2012 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

SECTION 1

Introduction

%.% Project Background The Poughkeepsie Joint Water Project Board (PJWPB) supplies water to the City of Poughkeepsie, the Town of

Poughkeepsie, and the Village of Wappingers Falls. From 2004 through 2009, chloramines were utilized as the

disinfectant to maintain chlorine residual in the distribution system and to minimize disinfectant byproduct

formation. Due to unintended consequences and water quality issues in the distribution system with chloramines,

the PJWPB decided to return to free chlorine for the distribution system disinfectant in 2009. With the return to

free chlorine disinfection, reduction of chlorinated DBPs must to be addressed at the WTP by the reduction of

precursors, such as total organic carbon (TOC), for the PJWPB to be in compliance with the upcoming Stage 2

DBPR in October 2013. Sampling for the Stage 2 DBPR at the required sites in the distribution system must begin

in October 2012. For each of the alternatives developed, use of ultraviolet light will be maintained for primary

disinfection at the WTP.

The purpose of this report is to identify the estimated size, design criteria, budgetary capital, and additional

operating costs for alternatives for treatment process upgrades, on a conceptual level to enable comparison of

alternatives. The PJWPB can use this report to make an informed decision on the treatment processes to install to

continue to maintain free chlorine disinfection while meeting the upcoming Stage 2 DBPR.

%.' Bench-Scale Testing Results Bench scale testing in the summer 2010 (September) and spring of 2011 (May) was completed to assess multiple

treatment improvement options, including:

- Enhanced Coagulation with Ferric Chloride, Alum, and Polyaluminum chloride

- Oxidation using chlorine dioxide and ozone

- Organics removal using magnetic ion exchange (MIEX)

These processes were tested alone or in conjunction with one another to assess DBP formation potential at

various detention times.

The processes identified that could allow the PJWPB to meet the Stage 1 and Stage 2 DBP regulations in the future

with free chlorine as the distribution disinfectant include:

• Chlorine dioxide as a pre-oxidant with enhanced coagulation

• Ozone as an intermediate oxidant after enhanced coagulation and clarification

• MIEX applied to the raw water ahead of the current treatment units without changing coagulation.

These treatment processes are the basis of this conceptual design evaluation in the sections below. Details of the

bench scale evaluation and results can be found in the reports titled “Treatment Alternatives for Reducing

Disinfection Byproducts, Dec 2010 and September 2011”.


SECTION 2

Existing Conditions

'.% Raw Water Quality

Raw water values from 2006 to 2010 were used to develop a raw water profile to be used for this design. For

plant flow, turbidity, pH, alkalinity, and DOC, histograms with cumulative frequency plots were developed. These

graphs were used to determine the sensitivity of the data and to help select the proper maximum and design

conditions. Figures 2-1 and 2-2 demonstrate the frequency plots for flow and turbidity.

0.00%

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FIGURE 2-1 Frequency Plot For Influent Flow

FIGURE 2-2 Frequency Plot For Influent Turbidity

EXISTING CONDITIONS

2-2 PJWB DBP CONCEPT DESIGN DRAFT REPORT 043012_FINAL COPYRIGHT 2012 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

Table 2-1 presents a summary of the raw water quality used in this investigation. This water quality data set was

used to establish values for chemical doses and residuals quantities in the conceptual design discussed later in this

report.

TABLE 2-1

Raw Water Quality

April 2006 to October 2010

# of Data

points Average

10th

Percentile

90th

Percentile

95th

Percentile

99th

Percentile

Standard

Deviation

Raw Water (MGD) 699 9.3 7.5 11.0 11.3 12.6 1.44

Turbidity NTU 549 49.4 13.2 96.3 120.0 217.8 41.5

Temp C 518 14.9 2.2 25.5 26.2 27.2 8.6

pH: 551 7.65 7.45 7.85 7.91 8.03 0.18

Alkalinity (mg/L): 537 63.6 51.2 74.6 76.9 79.0 9.1

Calcium (mg/L): 528 26.5 21.2 32.6 35.4 41.8 4.9

Hardness (mg/L): 527 81.1 65.6 97.9 101.0 112.4 12.8

UV 254: 542 0.13 0.10 0.17 0.18 0.23 0.05

TOC (mg/L): 517 4.18 3.02 5.57 6.35 8.21 1.44

DOC (mg/L): 513 3.77 2.90 4.80 5.32 6.09 0.87

Fe (mg/L) 49 0.07 0.01 0.10 0.18 0.66 0.13

Mn (mg/L) 33 0.01 0.003 0.011 0.012 0.014 0.003

Bromide (ug/L) 228 6.8 N/A N/A 19.4 N/A N/A

Note: Percentile denotes the value at which X% of valves are below that number.

Based on the analysis presented above, the minimum flow was considered as the 10th percentile flow, and the

peak was assumed as 99th percentile flow. This number is below the rated plant flow of 19.3 MGD. For

development of chemical doses and solids generated, the 90th percentile turbidity and Dissolved Organic Carbon

were used along with the following flows:

• Minimum flow of 5.5 mgd

• Average flow of 9.3 mgd

• Peak flow of 12.6 mgd

• Maximum flow of 19.3 mgd

'.' WTP Overview

The Poughkeepsie Water Treatment Facility (PWTF) is a conventional WTP that was last upgraded in 2001 to meet

new regulations and water quality goals. A description of the liquid unit processes and solids unit processes are

detailed below. Figure 2-3 shows the overall PWTF process flow diagram.

'.'.% Liquid Treatment Processes

In the liquid treatment process, raw water is pumped from the Hudson River. At the intake, potassium

permanganate is added for manganese oxidation. At the rapid mix tank, seasonal carbon is added. Also at the

rapid mix tank, polyaluminum chloride and a flocculation/ sedimentation polymer are added. Following Rapid mix,

flow is directed to three (3) solids contact clarifiers. Effluent from the contact clarifiers flows into rectangular

sedimentation basins for additional settling time.

EXISTING CONDITIONS


Chlorine is added to the settled water upstream of the filters. There are six (6) filters, dual media sand/anthracite

design. Individual filter effluent is disinfected utilizing ultraviolet (UV) disinfection. The individual filter effluent is

combined into a single pipe and flows to a clearwell to backwash supply water, and to the equalization chamber

for pumping via high lift pumps to the distribution system. Prior to pumping, phosphoric acid, fluoride, and pH

adjustment (caustic) is added.

'.1 Residuals Treatment Processes

The Alum Sludge Treatment Facility (ASTF) provides for dewatering and disposal of solids generated at the water

treatment facility. The treatment process is depicted in Figure 2-3 and includes:

- Waste Backwash Equalization

- Waste Backwash Treatment with Plate Settlers

- Gravity Thickening for Settled Solids

- Thickened Sludge Storage Tank

- Centrifuges for Dewatering

Dewatered solids are taken off-site for landfill disposal. Supernate from the waste backwash treatment system is

recycled to the head of the plant upstream of rapid mix. Other liquid flow streams, such as the gravity thickener

supernate, and the centrate from dewatering, are directed back to the waste backwash equalization tank. Table

2-2 lists the design basis for each of the processes.

TABLE 2-2 Residuals System Design

Unit Process Design Criteria Notes

Backwash Equalization Tank 270,000 gallons

Clarifier Sludge Pumps Three, each at 350 gpm capacity

Plate Settler Feed Pumps Three, each at 200 gpm

Plate Settlers (waste backwash treatment) Two inclined plate settlers; 400 gpd/sf

loading rate each

Settled Sludge Pumps from BW Treatment Two @ 80 gpm each

Sludge Thickener One, 2500 lbs/day dry solids 1995 design memo

Sludge Thickener Underflow Pumps Two @ 80 gpm capacity each

Thickened Sludge Storage Tank 84,000 gallons

Centrifuge Feed Pumps Two @ 20 gpm each

Centrifuge Two, 5,000 lb/day at 3.5% inlet solids Units over 20 years old, backdrives replaced

in 2001. 1995 design memo information.

EXISTING CONDITIONS


FIGURE 2-3 PWTF Process Flow Diagram


SECTION 3

Alternatives for Disinfection By-Product Control

1.% Introduction Several alternatives were developed as a part of this study, based upon the results of previous bench-scale

testing. The design parameters developed for these alternatives will be discussed in this section. The alternatives

include:

• Alternative 1- Chlorine Dioxide: Preoxidation with chlorine dioxide; enhanced coagulation with alum and

sulfuric acid

• Alternative 2A – Ozone Enhanced Coagulation: with alum and sulfuric acid; intermediate ozone

• Alternative 2B – Ozone Enhanced Coagulation: with alum and CO2; intermediate ozone

• Alternative 3A – MIEX with Alum: pretreatment with alum coagulation; MIEX at 600 Bed Volumes

• Alternative 3B – MIEX with Alum: pretreatment with reduced alum coagulant dose, MIEX at 1000 Bed

Volumes

For each of the alternatives above, conceptual level footprint requirements were developed. These footprints all

included re-use of existing facilities/areas to maximize plant space when applicable. Location sketches were

developed for each alternative and the points of interconnection for new processes were identified.

1.%.% Alternative % Chlorine Dioxide with Enhanced Coagulation Alternative 1 includes enhanced coagulation with alum followed by organics oxidation by chlorine dioxide gas. In

order to optimize organics removal, the pH needs to be depressed. In Alternative 1, sulfuric acid will be used to

depress pH. Since sulfuric acid is also a component in the on-site generation of chlorine dioxide, carbon dioxide

gas was not evaluated for pH depression.

Currently, the plant has approximately 15,200 gallons of coagulant storage. In order to have thirty days of

storage at average flow 9.3 MGD and average alum coagulant dose of 60 mg/L, 25,800 gallons of storage are

required for Alternative 1. Since this exceeds the current coagulant storage, new storage facilities will need to be

constructed. Additionally, new chemical metering pumps and a day tank

are required.

Chlorine dioxide is generated using sulfuric acid and Purate®. Purate® is a

blended chemical consisting of approximately 40% Sodium Chlorate and

approximately 7.5% Hydrogen Peroxide. When Purate® and sulfuric acid

are combined, salt, chlorine dioxide, oxygen and water are produced. The

chlorine dioxide system will consist of 300 gallon Purate® storage totes, a

sulfuric acid storage tank, and a chlorine dioxide generator, an educator,

and a booster pump. The educator and booster pump will allow for the

chlorine dioxide gas to be dosed into a liquid stream.

The Purate® storage area and the chlorine dioxide generation system will

be installed in the existing chemical building. Since the existing

coagulation tanks will be replaced with a new alum storage system and the existing fluosilicic tank is no longer in

use- the existing PACL and Fluosilicic Acid area will be converted into Purate® storage and chlorine dioxide

generation area.

Sulfuric acid will be required for pH adjustment and for chlorine dioxide generation. One tank will be provided for

acid storage. This tank will be sized for average dose and flow required for pH adjustment and for the chlorine

dioxide generation. The doses required were determined using a WaterPro model based on raw water conditions.

The maximum dose is to be used for conditions where alkalinity and pH in the raw water are high. The average

dose is to be used when raw water pH and alkalinity are average. The sulfuric acid dose will depress the pH to 6.2

FIGURE 3-1 Purate Process Schematic

ALTERNATIVES FOR DISINFECTION BY-PRODUCT CONTROL


for optimal organics removal with alum. During time of low raw water pH and alkalinity, no sulfuric acid is

required; the pH reduction due to alum addition alone will drop the pH to 6.2. The new sulfuric acid tank will

replace the existing ammonia storage tank in the chemical storage area.

Table 3-1 summarizes the design criteria for Alternative 1. Figure 3-2 shows the proposed site plan for this

alternative.

TABLE 3-1

Alternative 1- Chlorine Dioxide with Enhanced Coagulation - Basis of Design

Parameter Value

Plant Flow (min/ avg/ max) 5.50 MGD/ 9.3 MGD/ 19.3 MGD

Alum Dose (avg/ max) 60 mg/L/ 100 mg/L

Bulk Alum Storage Required 25,800 gallons

Bulk Alum Tank Number and Size 3 Tanks. 10’ Diameter, 18’ Height

Alum Day Tanks 1 Tank. 7’ Diameter, 14’ Height

Chlorine Dioxide System Purate® based system, 10 lb/hr maximum capacity

Sulfuric Acid for CLO2 Design Feed Rate 2.50 gph

Purate® Feed Design Rate 2.41 gph

pH Control Sulfuric Acid Dose (min/ avg/ max) 0 mg/L / 6.5 mg/L /15 mg/L

Number of Sulfuric Acid Feed Pumps 2 (1 duty and 1 standby)

Bulk Sulfuric Acid Provided 3,000 gallons (sized for one bulk delivery plus 10%)

Bulk Sulfuric Acid Tank Number and Size 1 Tank. 9’ Diameter, 8’ Height

Sulfuric Acid Day Tanks 1 Tank. 3’ Diameter, 6’ Height



FIGURE 3-2 Alternative 1-Chlorine Dioxide with Enhanced Coaguation Site Plan



1.%.' Alternative ' Enhanced Coagulation with Intermediate Ozone

Alternative 2 includes enhanced coagulation with alum followed by ozonation for organics removal. As in

Alternative 1, the pH will need to be depressed for organics removal. Two different sub-alternatives were

evaluated for pH depression:

• Alt 2A – Ozone Enhanced Coagulation: with alum and sulfuric acid; intermediate ozone

• Alt 2B – Ozone Enhanced Coagulation: with alum and CO2; intermediate ozone

Alternative 2A will utilize the same coagulation and sulfuric acid system as described above for Alternative 1. In

Alternative 2B, carbon dioxide is used for pH adjustment. Carbon dioxide consumes less alkalinity than sulfuric

acid. At times of high raw water alkalinity and pH, conditioning with sulfuric acid will result in a settled water

alkalinity 36 mg/L. With carbon dioxide, settled water alkalinity would be 49 mg/L.

In Alternative 2 A/B, clarified water will be ozonated. By adding ozone to the water, the organic material in the

water will be oxidized. The new ozone system will require ozone generation, liquid ozone storage, ozone

destruction, and an ozone contact basin.

The organics will be oxidized into assimilable organic carbon (AOC). AOC can be easily removed by biologically

activated filters (BAF). If AOC is not removed, it will lead to biological instability in the distribution system. BAF is

achieved by removing the pre-chlorine feed to the filters. Once the chlorine feed is removed, naturally occurring

biologic growth will develop and the organisms will consume the AOC.

Table 3-2 summarizes the design criteria for Alternative 2A/2B. Figure 3-3 shows the proposed site plan for this

alternative.

TABLE 3-2

Alternative 2A/2B- Enhanced Coagulation with Intermediate Ozone - Basis of Design

Parameter Value

Plant Flow (min/ avg/ max) 5.50 MGD/ 9.3 MGD/ 19.3 MGD

Alum Dose (avg/ max) 60 mg/L/ 100 mg/L

Bulk Alum Storage Required 25,800 gallons

Bulk Alum Tank Number and Size 3 Tanks. 10’ Diameter, 18’ Height

Alum Day Tanks 1 Tank. 7’ Diameter, 14’ Height

Applied Ozone Dose (avg/max) 1.0 mg/L/1.5 mg/L

Ozone Generator 240 lbs/day capacity, 1 duty, 1 standby

Ozone Contact Time 10 minutes

LOX Tank Vertical Tank, 9’ tall, 8’ diameter

LOX Vaporizers 1 duty, 1 standby. 24 sf footprint

Ozone Destructors 1 duty, 1 standby

Alternative 2A

pH Control Sulfuric Acid Dose (min/ avg/ max) 0 mg/L / 6.5 mg/L / 15 mg/L

Bulk Sulfuric Acid Provided 3,000 gallons (sized for one bulk delivery plus 10%)

Bulk Sulfuric Acid Tank Number and Size 1 Tank. 9’ Diameter, 8’ Height

Sulfuric Acid Day Tanks 1 Tank. 3’ Diameter, 6’ Height



TABLE 3-2

Alternative 2A/2B- Enhanced Coagulation with Intermediate Ozone - Basis of Design

Alternative 2B

pH Control Carbon Dioxide Dose (min/ avg/ max) 0 mg/L / 8.0 mg/L / 30 mg/L

Feed System Gaseous into sidestream flow to feed location

Storage Size 14 Tons, horizontal tank

Feed Rate Maximum 200 lbs/hr



FIGURE 3-3 Alternative 2A/2B – Enhanced Coagulation with Intermediate Ozone - Site Plan



1.%.1 Alternative 1 MIEX

Alternative 3 include MIEX ion-exchange resin for organics removal followed by alum coagulation for turbidity

removal. The MIEX process is a magnetic ion exchange resign specially formulated for organics removal. Prior to

coagulation, the raw water will enter a basin where it will be mixed with the MIEX resin. The resin will remove the

organics and be separated from the main process flow. Once separated, the resin will be regenerated using a salt

solution. The regenerated resin will then be recalculated back to the main process stream.

The waste stream for the MIEX process is the organics laden brine stream that results from the regeneration of

the resin. The removal of organics will be based on the duration of time the resin has with the raw water with

varies inversely with Bed Volumes, or BV. The lower the BV’s the higher organics removal and the higher quantity

of brine produced. A small amount of resin will be carried over into the flocculation and clarification process, and

this resin will need to be replaced over time.

Since the organics will be removed prior to coagulation, flocculation, and clarification, the coagulation system can

be designed for turbidity removal. Thus, downward pH adjustment and higher coagulant doses for enhanced

coagulation are not required with Alternative 3. Lower coagulant doses can be used, resulting in fewer residuals

being created. Also, no new coagulant facilities will be required and the current PACL tanks and pumps can be

reused.

If MIEX is selected, then piloting of the process is required to determine precise organics removal projections and

operating conditions. The basis of design used for costing purposes is presented below.

Two sub-alternatives were evaluated:

• Alt 3A – MIEX with Alum: pretreatment with alum coagulation; MIEX at 600 Bed Volumes

• Alt 3B – MIEX with Alum: pretreatment with reduced alum coagulant dose, MIEX at 1000 Bed Volumes

Table 3-3 summarizes the design criteria for Alternative 3A/3B. Figure 3-4 shows the proposed site plan for this

alternative.

TABLE 3-3

Alternative 3A/3B - MIEX Basis of Design Table

Parameter Value

Plant Flow (min/avg/ max) 5.50 MGD/ 9.3 MGD/ 19.3 MGD

Average Alum Dose

Alternative 3A 40 mg/L

Alternative 3B 25 mg/L

Bed volumes of Resin Service in Contactor

Alternative 3A 1000 BV

Alternative 3B 600 BV

Number and Size of MIEX Contactors Two at 31ft x 31ft

Upflow Clarifier Rate 8 gpm/sf

High Rate Contractor Resin Concentration 200 mg/L

Loss of Resin 2 gallons per MG treated

Resin Contact Time 6 minutes

Tank Facility Footprint (includes salt storage) 35 ft x 65 ft

Resin Recirculation Tank Volume 4 tanks at 2,380 Gallons



TABLE 3-3

Alternative 3A/3B - MIEX Basis of Design Table

Parameter Value

Virgin Resin Tank Volume 1 tank at 560 Gallons

Salt Saturator Volume 1 tank at 11,650 Gallons

Brine Tank Volume 1 tank at 5,000 Gallons



FIGURE 3-4 Alternative 3A/3B - MIEX Site Plan


SECTION 4

Residuals Impacts from DBP Control Alternatives

Each of the DBP control options presented in Section 3 will have an impact on the type of residuals produced, the

amount of residuals produced, and thereby affect the capacity of the residuals systems (Section 2) and may

require capital or operating improvements to address limitations. The sections below discuss the details of these

additional impacts.

5.% Solids Generation

Existing plant production data, raw water quality information, and plant records were used to examine the

existing solids treatment facilities and their current capacity with PACL as the coagulant. Future solids generation

utilized this same plant data but used the coagulant doses during bench testing to achieve the DBP reduction

results. Table 4-1 is the resultant average and peak dry solids generated per day under various alternatives. For

most alternatives more solids will need to be treated and handled than under current conditions.

TABLE 4-1 Projected Solids

Alternative Average Coagulant Dose

(mg/L)

Average Solids (dry lbs/day) Peak Solids (dry lbs/day)

Chlorine Dioxide with Alum EC 60 6785 17,032

Intermediate Ozone with Alum EC 60 6785 17,032

MIEX at 1000 BV, 40 ppm Alum 40 6103 15,414

MIEX at 600 BV, 25 ppm alum 25 5591 14,720

2010 PACL Coagulation 55.7 5443 15,387

2011 PACL Coagulation 65 6099 15,246

PACL with Ozone 100 6832 15,813

2010 PACL Coagulation 55.7 5443 15,387

5.' Impact of Increased Solids Generation

The existing plate settler system is not affected by the increase in solids generation from coagulation.

Under current and most future conditions, the existing gravity thickener is adequate for handling the projected

solids generated (Table 4-2). Currently the plant views the thickener as one of the potential bottlenecks in the

residuals handling system. The projected loading rates compared to typical design parameters are within

acceptable ranges. To run at higher solids or hydraulic loading rates than currently practiced, more optimization

and polymer usage may be required.

RESIDUALS IMPACTS FROM DBP CONTROL ALTERNATIVES


TABLE 4-2

Thickener Capacity/Loading

Dry Solids (lbs/day)

Thickening (solids loading -

lbs/day/sqft)

Thickening (Hydraulic Loading -

gpm/sqft)

Design Capacity 2,500 1.6 -

Typical Design Values - 5 to 10 0.5 - 1.0

Solids Production (w/PACl) in 2010 5,443 3.4 0.28

Peak Day in 2010 13,375 8.4 0.64

Peak Week in 2010 11,971 7.5 0.38

Average Day at 19.3 MGD 12,252 7.7 0.58

Peak Day In Future (max) 17,000 10.7 0.80 (estimated)

For the centrifuges, the system appears to be undersized based on current and future solids generation as shown

in Table 4-3. The values shown in red are above the solids loading rate for a single unit. The original design of the

system was for a single centrifuge to be run during average conditions, and two only during peak conditions, and

only for one or two shifts per day. Recent operational experience at the PWTF demonstrated that the centrifuges

are undersized when both units had to be run on all three shifts to process the solids being generated in the plant.

Additionally, these units are over 30 years old and have reached the end of their useful life.

TABLE 4-3

Centrifuge Capacity/Loading

Dry

Solids

(lbs/day)

Throughput (lbs/hr)

based on 1 shift 7 days

week, single centrifuge

Throughput (lbs/hr) based on

two shifts, 7 days/week, single

centrifuge

Throughput (lbs/hr) based on

three shifts, 7 days/week, single

centrifuge

Current Design Capacity 5,000 625

Solids Production

(w/PACl) in 2010 5,443 778 363 247

Peak Day in 2010 13,375 1,911 892 608

Peak Week in 2010 11,971 1,710 798 544

Average Day at 19.3

MGD 16,136 2,305 1,076 733

5.1 MIEX Residuals

The MIEX process utilizes an ion exchange process inside of a mixed reactor. Periodically after a certain amount

of usage, or bed volumes, the media needs to be regenerated to renew its exchange capacity. Typically, sodium

chloride (brine) is utilized as the regenerant. The waste brine contains TDS, organic compounds, and other

contaminants adsorbed by the media. Alternately, sodium bicarbonate can be utilized to reduce the chloride

loading in the waste stream.

The brine residuals require disposal, this is typically accomplished directly via sewer to a publically owned

treatment works (POTW). Other options include additional brine treatment on-site for volume minimization, and

then either to the POTW or trucked for disposal.

RESIDUALS IMPACTS FROM DBP CONTROL ALTERNATIVES


For the PWTF to send to the sewer would require equalization and a small lift station to direct flow to the sewer

on the Marist University campus. Additionally, approval would be required from the City of Poughkeepsie’s

WWTP. Preliminary discussions with the City have indicated they would be hesitant to accept that flow.

To complete volume reduction would entail installing new equipment that would cost $500,000 to $1,000,000 in

capital costs. Additionally, some new solids would be added to the existing plant residuals, at approximately 20 to

40 lbs per million gallons of water produced. This concept was not pursued further in this study.

The estimated volumes of brine waste:

- 600 Bed Volumes – 3225 gallons/day

- 1000 Bed Volumes – 5100 gallons/day


Section 5

Cost Evaluation of Alternatives

7.% Introduction/Assumptions

The CH2M HILL Parametric Cost Estimating System (CPES) was used for estimating the costs of the various

alternatives. CPES is a proprietary conceptual design and cost estimating tool that generates quick, accurate, and

detailed cost estimates at the conceptual stage of a water treatment project

CPES construction and life cycle (O&M) cost models were developed for each of the alternatives and sub-

alternatives presented in Section 3 of this report. The cost estimates were prepared using a variety of cost data

including vender quotation, unit cost line items, and parametric estimating tools. The cost estimates are

considered to be consistent with Class 4 estimates as defined by the Estimate Classification system of the

American Association of the Advancement of Cost Engineering International (AACE International), formerly known

as the American Association of Cost Engineers (AACE). The estimates were developed without detailed

engineering data and are considered approximate. Class 4 estimates are normally expected to be accurate within

minus 30 percent to plus 50 percent. This range implies that there is a high probability that the final project cost

will fall within the range.

A contingency has been included in these cost estimates as a provision for unforeseeable, additional costs within

the general bounds of the project scope; particularly where experience has shown that unforeseeable costs are

likely to occur. The contingency is used as a means to reduce the risk of possible cost overruns.

Table 5-1 lists the markups applied within the capital cost model. Table 5-2 lists the assumptions for operating

costs used in the cost development.

TABLE 5-1 Capital Cost Markups Used for Estimates

Item Value

Overhead 10%

Profit 5%

Mobilization/Bond/Insurance 5%

Contingency 30%

Local Adjustment Factor to Poughkeepsie NY 114

Escalation to Midpoint of Construction 1.10

In addition to the global markups provided above, the additional project costs were included in the capital cost

summary:

• Pilot Testing (estimated based on whether testing would be required or not, and expected effort to

complete)

• Engineering Design and SDC at 15% of construction costs

• Startup at 2% of total construction costs

COST EVALUATION OF ALTERNATIVES


TABLE 5-2 Operation and Maintenance Cost Assumptions

Net Present Cost (NPC) Calculation Inputs

Annual Discount Rate (i) 3%

Number of Years (n) 20 years

Power Costs

Power Cost $0.062/kWhr

Facility Electrical 2 Watts/square foot of building area

Chemical Costs

Alum $390/ton

PACL $304/ton

Sulfuric Acid $271/ton

Carbon Dioxide $640/ton

Purate $1,900/ton

Liquid Oxygen (LOX) $125.67/ton

Salt $140/ton

MIEX Resin $60.57/ton

Residuals Disposal Costs

Solids Disposal $72/dry ton

Brine Disposal (via tanker truck) $0.1495/gallon

Brine Disposal (via sewer) $0.35/1000 gallons

Repair, Maintenance, and Contingency 20% of subtotal of O&M costs

7.' Capital Costs Table 5-3 presents a breakdown of capital costs by each alternative by treatment systems required in that

alternative.

7.1 Operating and Maintenance Costs

The O&M costs were based on annual average flow rate of 9.3 mgd. Consumption is based on average flow

condition. The O&M costs presented are the additional O&M costs above the current facility O&M costs that

would occur with the installation of the new processes, chemical addition, and residuals production.

In evaluating MIEX (Alternatives 3A/3B) it became apparent that direct discharge of brine waste to the sewer may

be difficult. Therefore, within the O&M component we have calculated the expected cost for hauling of liquid

residuals to a nearby wastewater plant that would accept the brine from tanker trucks. This cost, inclusive of

transportation and disposal, was $0.165/gallon based upon current liquid hauling costs paid at the PWTF. If sewer

disposal was permissible, then a lower disposal cost could be realized, shown as alternative 3C in Table 5-4.



TABLE 5-3

Estimated Capital Costs of Alternatives

Individual Unit process Alternative 1A Alternative 2A Alternative 2B Alternative 3A Alternative 3B

Alum Storage and Feed $ 1,480,000 $ 1,480,000 $ 1,480,000 $ 100,000 $ 100,000

Chlorine Dioxide System $ 350,000 - - - -

New Sulfuric Acid System $ 190,000 $ 190,000 - - -

Carbon Dioxide System - - $ 530,000 - -

Ozone System and Contactor - $ 9,860,000 $ 9,860,000 - -

MIEX System - - - $ 17,320,000 $ 17,320,000

Pipelines $ 190,000 $ 380,000 $ 380,000 $ 1,712,599 $ 1,712,599

Centrifuges $ 1,810,000 $ 1,810,000 $ 1,810,000 $ 1,810,000 $ 1,810,000

Overall Construction Cost $ 4,020,000 $ 13,720,000 $ 14,060,000 $ 20,938,880 $ 20,938,880

Other Project Costs

Pilot Testing $ 300,000 $ 300,000 $ 500,000 $ 500,000

Engineering Design and SDCs (15%) $ 603,000 $ 2,058,000 $ 2,109,000 $ 3,140,832 $ 3,140,832

Startup (2%) $ 80,400 $ 274,400 $ 281,200 $ 418,778 $ 418,778

Total Project Cost $ 4,703,400 $ 16,352,400 $ 16,750,200 $ 24,998,490 $ 24,998,490



TABLE 5-4

Operating and Net Present Cost of Alternatives

Alt Description Project Costs Additional O&M

Costs

NPC O&M Costs Total NPC Costs

1 Chlorine Dioxide with EC $4,704,000 $331,000 $4,924,000 $9,627,00

2A Ozone with EC with Sulfuric Acid $16,352,000 $222,000 $3,303,000 $19,655,000

2B Ozone with EC with CO2 $16,750,000 $279,000 $4,151,000 $20,901,000

3A MIEX – 1000 BV, truck disposal $24,999,000 $664,000 $9,879,000 $34,877,000

3B MIEX – 600 BV, truck disposal $24,999,000 $709,000 $10,548,000 $35,546,000

3C MIEX – 600 BV, sewer disposal $24,999,000 $376,000 $5,594,000 $30,592,000


SECTION 6

Recommendations and Implementation Plan

9.% Assessment of Compliance Reliability

Based on the information presented section 5, it would appear that chlorine dioxide with enhanced coagulation

would be the least expensive way to achieve DBP compliance. However, the results received during bench-scale

testing show there is some potential risk of not being able to achieve DBP compliance with this alternative. Figure

6-1 is the Total Trihalomethane (TTHM) formation from previous bench testing and Figure 6-2 is the Haloacetic

Acid (HAA5) formation. Each treatment process tested is shown for formation at 5, 7 and 10 days detention time.

From the figures below, we can see that chlorine dioxide with enhanced coagulation is up near the safety factor

(80% of the maximum contaminant level) for TTHMs and in the safety factor, approaching the actual MCL for

HAA5s. This safety factor is present to acknowledge the bench tests are just one snapshot in time, and there is

some experimental error associated with laboratory analysis of DBPs. This does not mean that chlorine dioxide

with enhanced coagulation could NOT meet DBP requirements, but that there is more risk associated with this

option than would be with Alternative 2, ozone with enhanced coagulation. Therefore if the PJWPB wanted to

ensure compliance for Stage 2 DBPR, the option that would need to be implemented in Alternative 2.

FIGURE 6-1 Total Trihalomethane (TTHM) Formation Estimates

RECOMMENDATIONS AND IMPLEMENTATION PLAN


FIGURE 6-2 Haloacetic Acid (HAA5) Formation Estimates

9.' Phased Implementation

Understanding that the PJWPB may have limited capital to spend initially on this project, we have developed a

path forward for the PJWPB that will allow for continued reduction of DBP concentrations while assessing the

performance of different options. This approach will allow the PJWPB to judiciously utilize the capital dollars

available and not “waste” capital dollars on solutions that will not work the WTF and distribution systems towards

compliance with Stage 2 DBPR. The major steps of this approach include:

1) Implement Residuals Improvements to remove this bottleneck from the existing system and prepare for

enhanced coagulation

2) Implement enhanced coagulation first and evaluate system data for one full year. Implementing

enhanced coagulation is required for either Alternative 1 or 2 so this is work that would need to be

completed regardless of the final chose direction.

3) Develop a combined hydraulic model of the PJWPB distribution system to evaluate water age and

methods to reduce water age. Reductions in water age may reduce DBP formation at end points of the

system.

4) After initial results, make decision on whether to implement chlorine dioxide or intermediate ozone. This

approach has risk that the system will not be in compliance with Stage 2 DBPR by October 2013 and

therefore would require a 2-year extension from New York State Department of Health (NYSDOH) for

capital improvements.

The approach is demonstrated in a flow chart in Figure 6-3. Table 6-1 is a breakdown of the anticipated costs to

implement this phased approach.



FIGURE 6-3 Flowchart of Phased Implementation Approach



TABLE 6-1

Phased Approach Estimated Costs ($M)

Cost Item pH adjustment Chlorine Dioxide Ozone MIEX

H2SO4 CO2 H2SO4 CO2 H2SO4 CO2

Centrifuges $ 1.81 $ 1.81 $ 1.81 $ 1.81 $ 1.81 $ 1.81 $ 1.81

pH adjustment $ 0.19 $ 0.53 $ 0.19 $ 0.53 $ 0.19 $ 0.53

Chemical Feed

Modifications $ 0.10 $ 0.10 $ 0.10

Chlorine Dioxide $ 0.35 $ 0.35

New Alum Facility $ 1.48 $ 1.48 $ 1.48 $ 1.48

MIEX $ 17.32

Ozone $ 9.86 $ 9.86

Pipelines $ 0.19 $ 0.19 $ 0.38 $ 0.38 $ 1.71

Construction Total $ 0.10 $ 2.44 $ 4.02 $ 4.36 $ 13.72 $ 14.06 $ 20.94

Pilot Testing $ 0.30 $ 0.30 $ 0.50

Engineering, SDCs

(15%) $ 0.32 $ 0.37 $ 0.60 $ 0.65 $ 2.06 $ 2.11 $ 3.14

Startup ( 2%) $ 0.04 $ 0.05 $ 0.08 $ 0.09 $ 0.27 $ 0.28 $ 0.42

Project Total $ 2.46 $ 2.85 $ 4.70 $ 5.10 $ 16.35 $ 16.75 $ 25.00

Costs shown in Millions

9.1 Recommendations

The following conclusions and recommendations can be drawn from this report:

1) Pursuit of MIEX as an option for DBP compliance is more expensive on both a capital and life cycle cost

basis than those of chlorine dioxide and ozone. MIEX should only be considered further if there is a need

for a higher quality water for industrial users (i.e. IBM)

2) Ozone with enhanced coagulation is the least expensive option that will reliability allow PJWPB to achieve

compliance with the Stage 2 DBPR using free chlorine as the distribution disinfectant.

3) Replacing existing centrifuges is critical for immediate operations and for the ability to implement

enhanced coagulation

4) A phased approach to manage the capital expenditures of the PJWPB can be applied. It requires the

following immediate steps:

a. Develop implementation plan to address NYSDOH concerns over elevated DBPs in the distribution

b. Develop final plan for implementing enhanced coagulation (in conjunction with centrifuge

replacement)

c. Develop distribution system model to refine water age estimates and identify areas in the system

where water age could be improved, or localized treatment could be considered



d. Obtain temporary 30-day chemical storage waiver from NYSDOH to use existing PACL tanks to

implement enhanced coagulation testing

e. Start sampling as soon as possible after enhanced coagulation is implemented to see what effects

it has in the system on DBP formation. Gather as much data as possible before October 2012

when compliance sampling for Stage 2 DBPR begins

f. Evaluate data and utilize decision flowchart to determine next steps to take to meet Stage 2 DBPR

if enhanced coagulation alone with distribution system improvements does not reliably meet the

regulations.

Documents

Conceptual Design of Alternatives for the Use of Free ......• Ozone as an intermediate oxidant after enhanced coagulation and clarification ... Plate Settler Feed Pumps Three, each