EPA/600/R-00/063

June 2000

Arsenic Removal from Drinking Water

by Coagulation/Filtration

and Lime Softening Plants

by

Keith A. Fields

Abraham Chen

Lili Wang

Battelle

Columbus, OH 43201-2693

Contract No. 68-C7-0008

Work Assignment 2-09

for

Work Assignment Manager

Thomas J. Sorg

Water Supply and Water Resources Division

National Risk Management Research Laboratory

Cincinnati, OH 45268

National Risk Management Research Laboratory

Office of Research and Development

U.S. Environmental Protection Agency

Cincinnati, OH 45268

Printed on Recycled Paper
ii

Disclaimer

The information in this document has been funded by the United States Environmental Protection Agency (EPA) under Work Assignment (WA) 2-09 of Contract No. 

68-C7-0008 to Battelle. It has been subjected to the Agency’s peer and administrative reviews and has been approved for publication as an EPA document. Mention of 

trade names or commercial products does not constitute an endorsement or recommendation for use.
iii

Foreword

The United States Environmental Protection Agency is charged by Congress with

protecting the Nation’s land, air, and water resources. Under a mandate of national 

environmental laws, the Agency strives to formulate and implement action leading to 

a compatible balance between human activities and the ability of natural systems to 

support and nurture life. To meet this mandate, EPA’s research program is providing 

data and technical support for solving environmental problems today and building a 

science knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect our health, and prevent or reduce environmental risks in 

the future.

The National Risk Management Research Laboratory is the Agency’s center for investigation of technological and management approaches for reducing risks from threats 

to human health and the environment. The focus of the Laboratory’s research program is on methods for prevention and control of pollution to air, land, water, and subsurface resources: protection of water quality in public water systems; remediation of 

contaminated sites and ground water; and prevention and control of indoor air. The 

goal of this research effort is to evaluate the performance on a full-scale level of five 

processes, including coagulation/filtration, lime softening, iron oxidation/filtration, ion 

exchange, and activated alumina, to consistently remove arsenic over a sustained 

period of time (1 year).

This publication has been produced as part of the Laboratory’s strategic long-term 

research plan. It is published and made available by EPA’s Office of Research and 

Development to assist the user community and to link researchers with their clients.

E. Timothy Oppelt, Director

National Risk Management Research Laboratory
iv

Abstract

This report documents treatment plant information as well as results of sampling and 

analysis at two coagulation/filtration plants (referred to in this document as Plants A 

and B) and one lime softening plant (referred to as Plant C). The objective of sampling and analysis was to evaluate the effectiveness of the water treatment plants to 

consistently remove arsenic (As) from source water. Additionally, data were collected 

in this study to evaluate the characteristics of the residuals produced by the treatment 

processes.

The study was divided into three phases: source water sampling, preliminary sampling, and long-term evaluation. The first phase, source water sampling, was conducted to evaluate source water characteristics at each plant. The second phase,

preliminary sampling, consisted of a four-week sampling period to refine procedures 

prior to implementing the long-term evaluation phase. The third phase, long-term 

evaluation, consisted of weekly sample collection and analysis for approximately

1 year. Sludge samples also were collected at each facility during a single sampling 

event from settling lagoons/ponds during a two-month period. Samples of recycle

supernatant water (Plant A) and supernatant discharge water (Plants B and C) were 

collected monthly beginning in November 1998 and continuing until June 1999.

Long-term evaluation of Plants A and B demonstrated that conventional coagulation/filtration can consistently achieve low levels of arsenic in the treated water (i.e., 

less than 5 μg/L). The total arsenic concentrations at Plant A were reduced by an

average of 52%, which represents a decrease of average arsenic concentrations

from 7.5 μg/L in the source water to 3.5 μg/L in the finished water. Average total arsenic removal efficiency at Plant B was 79%, with an average source water concentration of 19.1 μg/L and an average finished water concentration of 4.0 μg/L. Adsorption 

and coprecipitation of As(V) with iron and aluminum flocs are believed to have been 

the primary arsenic removal mechanisms at these plants.

The lime softening facility, Plant C, was not able to consistently reduce arsenic to low 

levels in treated water. The average total arsenic concentration in Plant C source

water was 32.0 μg/L, and the lime softening plant reduced the average total arsenic 

concentration to 16.6 μg/L in the finished water, which equals a 45% removal efficiency. As(III) was the primary species of soluble arsenic in the raw water and was 

almost completely oxidized to As(V) as a result of two chlorination steps that occurred 

prior to softening and prior to filtration. The primary mechanism of arsenic removal 

was likely adsorption and coprecipitation of As(V) with iron that was present in the

source water. Plant C operated at a pH of 9.6, a level at which arsenic removal by 

coprecipitation with calcium carbonate is reported to be less than 10% (Sorg and

Logsdon, 1978; McNeill and Edwards, 1997b).

None of the sludge samples collected at Plants A, B, and C qualified as a hazardous 

waste based on Toxicity Characteristic Leaching Procedure (TCLP) testing for metals.

Therefore, nonhazardous waste landfills should be able to accept the sludge generated by these treatment processes.
v

Contents

Foreword .................................................................................................................iii

Abstract ...................................................................................................................iv

Appendices..............................................................................................................vi

Figures ................................................................................................................... vii

Tables.................................................................................................................... viii

Acronyms and Abbreviations.....................................................................................x

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

1.1 Background............................................................................................... 1

1.1.1 General Chemistry of Arsenic .......................................................... 1

1.1.2 Determination of Arsenic Species .................................................... 3

1.1.3 Treatment Technologies for Arsenic Removal.................................. 3

1.1.3.1 Coagulation/Filtration......................................................... 3

1.1.3.2 Lime Softening .................................................................. 4

1.1.4 Data Gaps....................................................................................... 5

1.2 Objectives ................................................................................................. 5

1.3 Report Organization .................................................................................. 5

2.0 Conclusions ...................................................................................................... 6

3.0 Materials and Methods ...................................................................................... 7

3.1 General Project Approach.......................................................................... 7

3.2 Preparation of Sampling Kits and Sample Coolers ..................................... 8

3.2.1 Preparation of Arsenic Speciation Kits ............................................. 8

3.2.2 Preparation of Recycle Backwash Water/Supernatant 

Discharge Sampling Kits .................................................................. 9

3.2.3 Preparation of Sample Coolers........................................................ 9

3.3 Sampling Procedures .............................................................................. 10

3.3.1 General Approach and Sampling Schedules.................................. 10

3.3.2 Arsenic Field Speciation Procedure............................................... 10

3.3.3 Recycle Supernatant Water/Supernatant Discharge Sampling 

Procedure...................................................................................... 13

3.3.4 Sampling Procedure for Other Water Quality Parameters .............. 13

3.4 Analytical Procedures.............................................................................. 13

4.0 Results and Discussion................................................................................... 17

4.1 Plant Selection ........................................................................................ 17

4.2 Plant A .................................................................................................... 17

4.2.1 Plant A Description........................................................................ 18
vi

4.2.2 Initial Source Water Sampling........................................................ 18

4.2.3 Preliminary Sampling..................................................................... 19

4.2.4 Long-Term Sampling..................................................................... 22

4.2.4.1 Arsenic ............................................................................ 22

4.2.4.2 Other Water Quality Parameters...................................... 24

4.2.4.3 Recycle Supernatant Water............................................. 26

4.2.4.4 Sludge............................................................................. 27

4.3 Plant B .................................................................................................... 28

4.3.1 Plant B Description........................................................................ 29

4.3.2 Initial Source Water Sampling........................................................ 29

4.3.3 Preliminary Sampling..................................................................... 30

4.3.4 Long-Term Sampling..................................................................... 33

4.3.4.1 Arsenic ............................................................................ 33

4.3.4.2 Other Water Quality Parameters...................................... 35

4.3.4.3 Supernatant Discharge Water.......................................... 38

4.3.4.4 Sludge............................................................................. 38

4.4 Plant C.................................................................................................... 39

4.4.1 Plant C Description........................................................................ 39

4.4.2 Initial Source Water Sampling........................................................ 40

4.4.3 Preliminary Sampling..................................................................... 41

4.4.4 Long-Term Sampling..................................................................... 44

4.4.4.1 Arsenic ............................................................................ 44

4.4.4.2 Other Water Quality Parameters...................................... 46

4.4.4.3 Supernatant Discharge Water.......................................... 49

4.4.4.4 Sludge............................................................................. 49

5.0 Quality Assurance/Quality Control................................................................... 51

5.1 Quality Assurance Objectives .................................................................. 51

5.2 Overall Assessment of Data Quality......................................................... 51

5.2.1 Total Arsenic, Aluminum, Iron, and Manganese............................. 51

5.2.2 Water Quality Parameters ............................................................. 52

5.2.3 TCLP Metals in Sludge.................................................................. 52

6.0 References...................................................................................................... 53

Appendices

Appendix A. Complete Analytical Results from Long-Term Sampling at 

Plant A ........................................................................................... 55

Appendix B. Complete Analytical Results from Long-Term Sampling at 

Plant B ........................................................................................... 69

Appendix C. Complete Analytical Results from Long-Term Sampling at 

Plant C ........................................................................................... 83
vii

Figures

Page

Figure 1-1. Solubility Diagrams for As(III) and As(V)............................................. 2

Figure 3-1. Example of Sample Bottle Label....................................................... 10

Figure 3-2. Photographs of a Typical Sample Cooler (with Three Sample 

Compartments) and a Color-Coded Instruction Sheet....................... 11

Figure 3-3. Instruction Sheet for Arsenic Field Speciation................................... 14

Figure 3-4. Instruction Sheet for Recycle Supernatant Water/Supernatant 

Discharge Sampling......................................................................... 15

Figure 4-1. Schematic Diagram of Plant A Treatment Process............................ 18

Figure 4-2. Process Flow Diagram and Sampling Locations at Plant A............... 20

Figure 4-3. Total Arsenic Analytical Results During Long-Term Sampling at 

Plant A............................................................................................. 24

Figure 4-4. Arsenic Form and Species Analytical Results During Long-Term 

Sampling at Plant A.......................................................................... 25

Figure 4-5. Inlet Turbidity, pH, TOC, and Alkalinity Analytical Results at 

Plant A............................................................................................. 27

Figure 4-6. Schematic Diagram, Plant B............................................................. 29

Figure 4-7. Process Flow Diagrams and Sampling Locations at Plant B ............. 31

Figure 4-8. Total Arsenic Analytical Results During Long-Term Sampling at 

Plant B............................................................................................. 35

Figure 4-9. Arsenic Form and Species Analytical Results During Long-Term 

Sampling at Plant B.......................................................................... 36

Figure 4-10. Inlet Turbidity, pH, TOC, and Alkalinity Analytical Results at 

Plant B............................................................................................. 38

Figure 4-11. Schematic Diagram, Plant C............................................................. 40

Figure 4-12. Process Flow Diagram and Sampling Locations at Plant C............... 42

Figure 4-13. Total Arsenic Analytical Results during Long-Term Sampling at 

Plant C............................................................................................. 46

Figure 4-14. Arsenic Form and Species Analytical Results During Long-Term 

Sampling at Plant C ......................................................................... 47

Figure 4-15. Inlet Turbidity, pH, Hardness, and Alkalinity Analytical Results at 

Plant C............................................................................................. 49
viii

Tables

Page

Table 3-1. Sample Containers and Preservation Methods ................................... 9

Table 3-2. Summary of Sampling Activities at Plants A, B, and C...................... 12

Table 3-3. Summary of Sampling Schedule for Plants A and B.......................... 12

Table 3-4. Summary of Sampling Schedule for Plant C..................................... 13

Table 3-5. Summary of Analytical Methods for Arsenic Treatment Study ........... 16

Table 4-1. Initial List of Treatment Facilities Identified for the Study................... 17

Table 4-2. Source Water Analytical Results at Plant A (February 3, 1998)......... 19

Table 4-3. Analytical Results from Preliminary Sampling at Plant A 

(April 9, 1998 through April 30, 1998)............................................... 21

Table 4-4. Summary of Arsenic Analytical Results at Plant A (June 1998–

June 1999)....................................................................................... 23

Table 4-5. Summary of Water Quality Parameter Analytical Results at Plant A 

(June 1998–June 1999) ................................................................... 26

Table 4-6. Summary of Analytical Results from Recycle Backwash Water 

Samples at Plant A (November 11, 1998–June 16, 1999)................. 27

Table 4-7. Previous Analytical Results of Sludge Sampling at Plant A (1996–

1997)............................................................................................... 28

Table 4-8. Analytical Results of Sludge Sampling at Plant A 

(December 2, 1998) ......................................................................... 28

Table 4-9. Source Water Analytical Results at Plant B (February 5, 1998)......... 30

Table 4-10. Analytical Results from Preliminary Sampling at Plant B (April 23, 

1998 through May 14, 1998) ............................................................ 32

Table 4-11. Summary of Arsenic Analytical Results at Plant B (June 1998–

June 1999)....................................................................................... 34

Table 4-12. Summary of Water Quality Parameter Analytical Results at Plant B 

(June 1998–June 1999) ................................................................... 37

Table 4-13. Summary of Analytical Results from Supernatant Discharge Water 

Samples at Plant B (November 12, 1998–June 17, 1999)................. 39

Table 4-14. Analytical Results of Sludge Sampling at Plant B 

(December 15, 1998) ....................................................................... 39

Table 4-15. Arsenic Concentrations in Ground Water Wells at Plant C (1992)..... 40

Table 4-16. Source Water Sampling Analytical Results at Plant C 

(February 27, 1998) ......................................................................... 41

Table 4-17. Analytical Results from Preliminary Sampling at Plant C (April 27, 

1998 through May 18, 1998) ............................................................ 43

Table 4-18. Summary of Arsenic Analytical Results at Plant C (June 1998–

June 1999)....................................................................................... 45
ix

Table 4-19. Summary of Water Quality Parameter Analytical Results at Plant C 

(June 1998–June 1999) ................................................................... 48

Table 4-20. Summary of Analytical Results from Supernatant Discharge Water 

Samples at Plant C (November 9, 1998–June 14, 1999)................... 50

Table 4-21. Analytical Results of Sludge Sampling at Plant C 

(November 16, 1998) ....................................................................... 50
x

Acronyms and Abbreviations

AF after-filtration sampling location

AWWA American Water Works Association

DI distilled

EDR electrodialysis reversal

EPA United States Environmental Protection Agency

GFAAS graphite-furnace atomic-absorption spectrophotometer

GI gastrointestinal

gpm gallons per minute

HDPE high-density polyethylene

ICP-MS inductively coupled plasma-mass spectrometry

ID identification

IN inlet sampling location

MCL maximum contaminant level

MDL method detection limit

mgd million gallons per day

MS matrix spike

MSD matrix spike duplicate

ND not detected

NOM natural organic matter

NTU nephelometric turbidity units

PAC powdered activated carbon

PAX-18 liquid polyaluminum chloride

PF before filtration (prefiltration) sampling location

POC point of contact

QA quality assurance

QAPP Quality Assurance Project Plan

QA/QC Quality Assurance/Quality Control

RPD relative percent difference

SDWA Safe Drinking Water Act

STLC soluble threshold limit concentration

TCLP Toxicity Characteristic Leaching Procedure

TDS total dissolved solids
xi

TOC total organic carbon

TSS total suspended solids

WA work assignment

WAM work assignment manager

%R percent recovery
xii

Acknowledgments

Sincere appreciation is extended to the three water treatment facilities that participated in this study. The staff from each facility contributed greatly to this project by 

collecting samples every week for more than 12 months. The success of this study 

depended on the personnel of these plants, and all performed exceptionally well.

Their work on this project was uncompensated, making their superb efforts even

more remarkable. Personnel from all plants are thanked for their hard work and

dedication throughout the duration of this project.
1

1. Introduction

This project consisted, in part, of a field study to collect 

samples from various locations throughout the treatment 

processes at two coagulation/filtration plants and one

lime softening plant. These samples were analyzed and 

used to evaluate the effectiveness of conventional coagulation/filtration and lime softening processes to consistently reduce arsenic (As) in source water to low levels.

This project also includes the collection of process residual samples that were used to determine the quantity 

and chemical characteristics of the residuals produced 

by these treatment processes. This report describes the 

design and operation of the three treatment plants and

presents the results of the analyses of the water samples 

collected from the plants during one year of operation.

1.1 Background

The Safe Drinking Water Act (SDWA) of 1994 mandates 

that the United States Environmental Protection Agency 

(EPA) identify and regulate drinking water contaminants 

that may have an adverse human health effect and that 

are known or anticipated to occur in public water supply 

systems. Arsenic is a naturally occurring contaminant

that has known adverse human health effects. Excessive 

amounts of arsenic can cause acute gastrointestinal (GI) 

and cardiac damage. Chronic doses can cause vascular 

disorders such as blackfoot disease (Chen, S.L., et al.,

1994), and epidemiological studies have linked arsenic 

to skin and lung cancer (Tate and Arnold, 1990). In

1975, under the SDWA, EPA established a maximum 

contaminant level (MCL) for arsenic at 0.05 mg/L. Since 

that time, revision of the MCL has been considered a

number of times, but no change has been made. The

SDWA was amended in 1996 and these amendments 

required that the EPA develop an arsenic research strategy and publish a proposal to revise the arsenic MCL by 

January 2000.

A draft arsenic research plan was prepared by the EPA 

in December 1996 and was finalized in February 1998

based upon a technical review by the EPA’s Board of

Scientific Counselors (EPA, 1998). The plan identifies

the research needed by the EPA to support a proposed 

revision of the arsenic MCL. The plan also identifies a

number of treatment methods available for arsenic removal and recognizes the need to determine the capability of these technologies to reduce arsenic to a level

significantly lower than the current MCL. This study was 

conducted as part of the EPA’s arsenic research strategy to determine the ability of conventional water treatment processes to consistently remove arsenic from

drinking water.

1.1.1 General Chemistry of Arsenic

Arsenic is a common, naturally occurring drinking water 

contaminant that originates from arsenic-containing rocks

and soil and is transported to natural waters through erosion and dissolution. Arsenic occurs in natural waters in 

both organic and inorganic forms. However, inorganic

arsenic is predominant in natural waters and is the most 

likely form of arsenic to exist at concentrations that cause

regulatory concern (Edwards et al., 1998).

The valence and species of inorganic arsenic are dependent on the oxidation-reduction conditions and the

pH of the water. As a general rule of thumb, the reduced, 

trivalent form [As(III)] normally is found in ground water

(assuming anaerobic conditions) and the oxidized, pentavalent form [As(V)] in surface water (assuming aerobic 

conditions), although this does not always hold true for

ground water, where both forms have been found together in the same water source. Arsenate exists in four 

forms in aqueous solution based on pH: H3AsO4, 

H2AsO4

−

, HAsO4

2−

, and AsO4

3−

. Similarly, arsenite exists 

in five forms: H4AsO3

+

, H3AsO3, H2AsO3

−

, HAsO3

2−

, and

AsO3

3−

. As shown in Figure 1-1, which contains solubility 

diagrams for As(III) and As(V), ionic forms of arsenate

dominate at pH >3, while arsenite is neutral at pH <9

and ionic at pH >9. Conventional treatment technologies 

used for arsenic removal, such as coagulation/filtration 

and lime softening, rely on adsorption and coprecipitation of arsenic to metal hydroxides. Therefore, the valence and species of soluble arsenic are very significant 

in evaluating arsenic removal.
2

Figure 1-1. Solubility Diagrams for As(III) and As(V)
3

Although soluble arsenic species typically make up the

majority of the total arsenic concentration in natural

waters, some research indicates that particulate arsenic 

can exist at significant concentrations. Studies by Chen 

et al. (1994) and Hemond (1995) measured particulate

arsenic at levels of 17 and 50% of the total arsenic concentration, respectively, in the subject source waters.

Therefore, determination of the particulate arsenic concentration is important because it can provide insight into 

the arsenic removal mechanisms that occur during treatment.

1.1.2 Determination of Arsenic Species

Although total arsenic can be effectively preserved in

field samples, presently no method exists to consistently 

preserve inorganic arsenic species in field samples. Preservation of total arsenic is accomplished by acidifying 

the sample to pH < 2 in the field. However, a high level 

of ambiguity exists when acids such as nitric acid (HNO3) 

or hydrochloric acid (HCl) are used to preserve inorganic 

species of arsenic. Interconversion of As(III) and As(V)

in samples preserved with 0.05 N HCl have been reported to occur within one day (Andreae, 1977). Another 

laboratory study conducted by Eaton et al. (1997) examined preservation of arsenic using humic acid, ascorbic

acid, and HCl; the study concluded that no effective

methods exist for preserving As(III) and As(V) in water

samples. Some researchers have used freezing of samples as a means of preserving the inorganic species of 

arsenic. However, freezing is neither a cost-effective nor 

a practical method for field sampling.

In response to the lack of techniques available for adequately preserving arsenic species, field speciation protocols have been developed by Ficklin (1982), Clifford et 

al. (1983), and Edwards et al. (1998). In each of these

studies, an anion exchange resin column is used for field 

speciation of arsenic. Ficklin (1982) used a strong anion 

exchange resin (Dowex 1 × 8, 100-200 mesh, acetate

form) in a 10 cm × 7 mm glass column to separate

As(III) from As(V) in water samples that had been filtered 

through a 0.45-μm membrane filter and acidified with 1% 

HCl. The resin was supplied in chloride form and was

converted to the acetate form. However, in the protocol 

by Clifford et al. (1983), a chloride-form strong base anion

resin (ASB-2, 30-60 mesh) was used to separate As(III) 

from As(V). In this method, the sample was not filtered 

or preserved with acid. Both Ficklin and Clifford used a

graphite-furnace atomic-absorption spectrophotometer 

(GFAAS) to determine the arsenic concentration.

More recently, Edwards et al. (1998) made the following 

modifications to Ficklin’s method: (1) substituted 50- to

100-mesh resin for the 100- to 200-mesh resin to allow 

faster sample flow; (2) used 12-cm × 15-mm polypropylene columns to improve safety and speed of sample 

treatment; (3) Used 0.05% H2SO4 instead of 1% HCl to 

acidify samples prior to resin treatment. Edwards et

al.’s use of H2SO4 helped to prevent potential problems

associated with overacidification of the sample, and also 

helped to prevent Cl−

 from interfering with the inductively 

coupled plasma/mass spectrometry (ICP-MS) analysis. 

The reported recoveries of As(III) and As(V) ranged from 

80 to 120% by Ficklin (1982), 95 to 117% by Clifford et 

al. (1983), and 100 to 105% by Edwards et al. (1998).

For this study, the decision was made to utilize a field

speciation technique similar to that used by Edwards et 

al. (1998).

1.1.3 Treatment Technologies for 

Arsenic Removal

Several common treatment technologies are used for removal of inorganic contaminants, including arsenic, from 

drinking water supplies. Large-scale treatment facilities 

often use conventional coagulation with alum or iron

salts followed by sedimentation and filtration to remove

arsenic. Lime softening is another common, conventional treatment process that can potentially remove 

arsenic from source waters. Smaller-scale systems and 

point-of-entry systems often use anion exchange resins

or activated alumina. Other arsenic removal technologies 

include manganese greensand, reverse osmosis, electrodialysis reversal (EDR), nanofiltration, and adsorption on 

activated carbon. This report focuses on the two conventional treatment processes commonly used for arsenic

removal at large-scale operations: coagulation/filtration 

and lime softening. Two additional reports will be developed that focus on (1) iron removal plants and (2) anion 

exchange and activated alumina plants.

1.1.3.1 Coagulation/Filtration

Conventional coagulation/filtration is a common water

treatment methodology used to remove suspended and 

dissolved solids from source water. The coagulation process promotes aggregation of the suspended solids to

form flocs, which then can be removed through sedimentation and/or filtration. Coagulation is typically described 

as a process consisting of three steps: coagulant formation, particle destabilization, and interparticle collisions. 

The first two steps, coagulant formation and particle destabilization, occur during rapid mixing, and the third

step occurs during flocculation. Alum and iron (III) salts,

such as ferric chloride, are the most common coagulants 

used for drinking water treatment (Amirtharajah and

O’Melia, 1990).

Coagulation using alum and iron (III) salts can be used

to remove dissolved inorganic drinking water contaminants, such as arsenic. Removal mechanisms for dis-
4

solved inorganics consist of two primary mechanisms:

adsorption and occlusion (Benefield and Morgan, 1990). 

During the adsorption process, the dissolved contaminant attaches to the surface of a particle or precipitate.

Occlusion occurs when the dissolved contaminant is

adsorbed to a particle and then entrapped as the particle 

continues to agglomerate. Several factors affect the coagulation process, including coagulant dosage, pH, turbidity, natural organic mater (NOM), anions and cations 

in solution, zeta potential, and temperature (Amirtharajah 

and O’Melia, 1990).

Numerous bench- and pilot-scale studies and some

short-term full-scale evaluations have been performed to 

evaluate arsenic removal using conventional coagulation/filtration using alum and iron (III) salts. Most of these 

studies have focused on removal of As(V) rather than

As(III) because better As(V) removal can be achieved

under comparable conditions, and As(III) can easily be

converted to As(V) using a strong oxidant such as chlorine (Hering et al., 1996; Sorg, 1993). Ferric and alum

coagulation are equally effective on a molar basis

(Edwards, 1994). However, on a weight basis (e.g., mg/L 

of ferric chloride vs. mg/L of alum), coagulation with iron 

(III) salts achieves better removal than coagulation with 

aluminum salts (Sorg and Logsdon, 1978; Sorg, 1993;

Chen, R.C., et al., 1994; Scott et al., 1995). These results 

are observed primarily because iron hydroxide is less

soluble than aluminum hydroxide over a wider pH range 

(Benefield and Morgan, 1990). McNeill and Edwards

(1997a) observed that aluminum flocs with sorbed arsenic could pass through filters and that arsenic removal

increased when capture of aluminum flocs increased.

Other research indicates that As(V) removal is not pH

dependent between pH 5.5 to 8.5 when iron coagulants 

are used, although As(V) removal efficiency decreases

above pH 7 using alum (Sorg, 1993).

Previous studies also indicate that arsenic removal is

directly correlated with coagulant dosage (i.e., more coagulant increases arsenic removal) (Sorg and Logsdon,

1978; Sorg, 1993; Hering et al., 1996; Gulledge and

O’Conner, 1973). Also, arsenic removal efficiency appears to be independent of initial arsenic concentration 

at levels of interest to drinking water treatment (Hering et 

al., 1996; Chen, R.C., et al., 1994; Edwards, 1994). Although no correlation between turbidity removal and arsenic removal has been established, turbidity removal is a 

prerequisite for arsenic removal (Chen, R.C., et al.,

1994).

1.1.3.2 Lime Softening

Lime softening commonly is used to reduce hardness in 

source waters. Hardness is due primarily to the presence of calcium and magnesium ions. The lime provides 

hydroxide ions that increase pH, which results in calcium 

and magnesium removal due to the formation of CaCO3

and Mg(OH)2 precipitates. Also, lime softening has been 

used for removal of heavy metals, radionuclides, dissolved organics, and viruses (Benefield and Morgan,

1990) through adsorption and occlusion with calcium

carbonate and magnesium hydroxide. The typical lime

softening treatment process train includes rapid mixing

of the lime, flocculation of solids, and sedimentation.

These three processes are often combined into a single 

unit referred to as a solids-contact softener (Benefield

and Morgan, 1990). Filtration usually follows these three 

processes. Lime and lime-soda typically are used for

softening, and selection is dependent on the type of

hardness. Lime alone is used for source waters that

contain little or no noncarbonate hardness, while high

noncarbonate hardness may require both lime and lime

soda. Caustic soda is sometimes used instead of lime

and lime-soda to decrease sludge production (increases 

dissolved solids, but produces less sludge).

Only a few studies have been conducted to evaluate 

arsenic removal during lime softening. Bench-scale and 

pilot-scale studies by Sorg and Logsdon (1978) indicate 

that arsenic removal during lime softening is pH

dependent. Removal of As(III) and As(V) are low at pH

less than 10; however, As(V) removal approaches 100% 

and As(III) removal approaches 75% at pH greater than 

10.5. As part of a survey of full-scale water treatment

plants by McNeill and Edwards (1995), lime softening 

plants were able to achieve up to 90% arsenate removal 

if pH was high enough to precipitate magnesium hydroxide (i.e., near pH 11). When only CaCO3

 precipitated,

As(V) removal was between 0 and 10%; however, when 

CaCO3 and Mg(OH)2 were precipitated, As(V) removals

were between 60 and 95% (McNeill and Edwards,

1995). Coprecipitation of As(V) with Mg(OH)2 appears to 

be the primary arsenic removal mechanism for As(V)

during lime softening. 

McNeill and Edwards published results from bench-scale 

experiments designed to evaluate the basic mechanisms 

of arsenic removal during lime softening (McNeill and

Edwards, 1997b). Consistent with previous findings, 

greater than 90% arsenate removal was observed at

above pH 11 where Mg(OH)2 was precipitated (McNeill 

and Edwards, 1997b). Also, it was determined that trace 

amounts of orthophosphate and the presence of carbonate could limit arsenate removal by Mg(OH)2

. If manganese was present in the source water, some As(V) removal could be achieved through sorption with Mn(OH)2

, 

although Mn3(AsO4)2 precipitate formation was not determined to be a major mechanism (McNeill and Edwards, 

1997b). Other findings from the same study indicated

that arsenate removal percentages were relatively constant for arsenic concentrations between 5 to 75 μg/L. 

Also, addition of iron before softening could increase
5

arsenic removal; however, competition between arsenic 

and carbonate for sorption sites on the iron hydroxide 

reduced the removal efficiency to levels below those

normally achieved with a conventional coagulation/filtration process using iron (III) salts (McNeill and Edwards, 

1997b).

1.1.4 Data Gaps

The removal of arsenic from drinking water by conventional coagulation/filtration has been extensively studied 

at the laboratory and pilot-scale level. To a lesser degree, arsenic removal by lime softening has been studied at the laboratory and pilot-scale level. Although some 

short-term full-scale evaluations have been performed 

for both treatment processes, little data exist on the

capability of these processes in full-scale applications to 

reduce arsenic on a sustained basis. Thus, a need exists 

to determine the effectiveness of coagulation/filtration 

and lime softening to produce drinking water low in arsenic on a long-term basis, under varying operational and 

seasonal conditions.

Another data gap that exists concerning conventional 

drinking water treatment processes is the production and 

disposal of residuals. Currently, little or no data exist on 

the amounts and the chemical composition of residuals

generated by the arsenic removal processes and the

methods that are environmentally acceptable for their

disposal. Therefore, information needs to be collected on 

the quality and the chemical characteristics of the wastes

produced by the coagulation/filtration and lime softening 

plants.

1.2 Objectives

One objective of this project was to evaluate the effectiveness of conventional coagulation/filtration and lime

softening to consistently reduce arsenic concentrations in 

source water to low levels. This report presents the results of weekly monitoring for approximately one year at 

two coagulation/filtration plants and one lime softening

plant.

Another objective of this study was to examine the residuals produced during treatment at conventional coagulation/filtration and lime softening plants. Information was

collected on the quality and chemical characteristics of

the wastes produced by these drinking water treatment 

processes.

1.3 Report Organization

Section 1.0 provides background information for the field

study and project objectives. Section 2.0 of this report presents the conclusions from the study of the two conventional coagulation/filtration plants and the lime softening 

plant. Section 3.0 describes the materials and methods 

used to conduct this study. Section 4.0 discusses the

results of the study and Section 5.0 provides specific

information on quality assurance/quality control (QA/QC) 

procedures. Section 6.0 is a list of references cited in the 

text. Appendices A, B, and C present the complete set of 

analytical data collected at Plants A and B (the two coagulation/filtration plants), and C (the lime softening plant),

respectively, during long-term sampling.
6

2. Conclusions

The U.S. EPA currently is in the process of revising the 

arsenic MCL, and it is anticipated that the revised standard will be significantly lower than the existing MCL of

0.05 mg/L. Therefore, there is a need to determine the

ability of existing treatment processes to consistently remove arsenic to low levels. The primary objectives of

this project were to document arsenic removal at two

conventional coagulation/filtration plants and one lime

softening plant, and to characterize the residuals (sludge 

and supernatant water) at these treatment plants.

The study was divided into three major phases: source

water sampling (February 1998), preliminary sampling

(April and May 1998), and long-term evaluation (June

1998 through June 1999). For the first phase, Battelle

staff traveled to each facility to conduct source water

sampling, which provided information on source water

characteristics. The second phase, preliminary sampling, 

consisted of a 4-week sampling period to refine the sampling approach before implementing the long-term evaluation phase. Battelle staff again traveled to each facility 

to coordinate the first sampling event and train plant personnel in sampling procedures for subsequent events.

The third phase, long-term evaluation, consisted of weekly

sample collection and analysis at each of the water treatment plants, sludge sampling (November and December 

1998), and recycle supernatant water (Plant A) and supernatant discharge (Plants B and C) sampling (November 

1998 through June 1999). During the long-term evaluation phase, plant personnel conducted sampling and

Battelle staff coordinated sampling logistics.

The primary focus of this study was the long-term performance of two coagulation/filtration plants and one

lime softening plant. The two coagulation/filtration plants 

demonstrated the ability to consistently achieve low

levels of arsenic in the treated water (i.e., less than

5 μg/L). Adsorption and coprecipitation of As(V) with

metal hydroxides, such as iron hydroxide and alum hydroxide, are believed to be the primary arsenic removal 

mechanisms in coagulation/filtration plants. As(III) removal during coagulation/filtration was not observed

during this study because both plants had surface water 

source where the soluble arsenic was primarily arsenate. 

Interestingly, Plant B conducted a 6-week test wherein

the coagulant was changed from alum to liquid polyaluminum chloride (i.e., PAX-18). During this test, arsenic removal was negatively impacted. Average removal

efficiency using alum was 84% compared to 43% using 

PAX-18. The difference in removal efficiencies may be

the result of the difference in pH achieved with each

coagulant.

The lime softening plant (Plant C) evaluated for this

project was not able to consistently reduce arsenic to

low levels in the treated water. The plant did not operate 

at a significantly high pH to precipitate magnesium hydroxide, and the arsenic removal by coprecipitation with 

calcium carbonate is low (<10%) (Sorg and Logsdon,

1978; McNeill and Edwards, 1997b). However, arsenic

removal efficiency at Plant C was approximately 45%. It 

is believed that the primary mechanism of arsenic removal is coprecipitation of As(V) with iron that is present 

in the source water. Prior research indicates that arsenic 

removal by iron oxides during lime softening can be

hindered by competition for sorption sites with carbonate 

(McNeill and Edwards, 1997b). Also, little research exists on the coprecipitation of arsenic and iron hydroxide 

at pH values greater than 8.

The secondary focus of this study was on residual production and the chemical characteristics of the residuals. 

None of the sludge sampled during this study qualified 

as a hazardous waste based on the Toxicity Characteristic Leaching Procedure (TCLP) tests for metals.

Therefore, the sludge generated by these treatment processes should be accepted by nonhazardous waste

landfills. However, stricter requirements in California regarding hazardous waste classification were not met by 

Plant A based on total arsenic concentrations. Supernatant water from sludge lagoons was either discharged 

to surface water bodies under state permits (Plants B 

and C) or recycled back to the inlet (Plant A). The recycle supernatant did not appear to contain high concentrations of arsenic. The ecological risks associated with 

discharging these waters were not assessed.
7

3. Materials and Methods

This section discusses the materials and methods used 

for performing the source water, preliminary, and longterm sampling and data collection at two coagulation/filtration plants and one lime softening plant. Section 3.1

describes the general project approach. Section 3.2

describes the preparation of arsenic speciation kits and

sample coolers. Section 3.3 provides detailed sampling

procedures. Section 3.4 discusses pertinent analytical

procedures.

3.1 General Project Approach

Several consecutive tasks were performed to accomplish 

the project objectives described in Section 1.2. These

tasks involved the following activities:

• Select treatment plants and conduct an initial site 

visit to collect source water samples at each 

selected plant

• Prepare a preliminary sampling and data 

collection plan for each plant

• Finalize the sampling and data collection plan 

after completion of four weekly preliminary 

sampling events at each plant 

• Implement the final sampling and data collection 

plan with weekly sampling events at each plant for 

one full year.

For initial plant selection, a list of potential treatment 

plant candidates was compiled. Plant operators or other 

key personnel were contacted via telephone to obtain/

confirm information and solicit interest in participating in 

the project. Each facility was evaluated, in order of

importance, on source water arsenic concentrations,

source water type, available manpower to conduct the

year-long study, availability of historical arsenic data,

and plant size. Battelle recommended the selection of

two coagulation/filtration plants (designated as Plants A

and B) and one lime softening plant (designated as

Plant C) for initial site visits and source water sampling. 

These recommendations were later approved by the

EPA Work Assignment Manager (WAM). The information collected during the site visits, including the concentration and speciation of arsenic in each source water,

was tabulated and used as the basis for the final plant

selection.

Following the final plant selection (Plants A, B, and C

again were selected), a preliminary sampling and data

collection plan was prepared for each plant to document 

the plant’s operation and performance for arsenic removal and the critical parameters that would impact the 

removal. Each preliminary plan also described the data

collection effort to characterize the residuals produced 

by the treatment process. The approved preliminary 

plans were implemented at Plants A, B, and C during a 

4-week trial period. A Battelle staff member revisited the 

plants during the first week of the trial period to observe 

plant operations, perform sampling, conduct training of

plant support personnel, and establish/coordinate all required logistics (such as receiving/shipping of sample

coolers, chain-of-custody coordination, communication 

methods, and emergency/contingency plans). The remaining three sampling events during the preliminary 

sampling were performed by a designated point of contact (POC) or an alternate at each plant. The experience 

gained during the trial period was used to finalize the

long-term sampling and data collection plans.

All water and residual samples were collected and

analyzed in accordance with the Category III Quality 

Assurance Project Plan (QAPP) prepared by Battelle

(1998) for this project. Water samples were collected

weekly at Plants A, B, and C at three locations: (1) the 

inlet to the treatment plants (IN); (2) before the filtration 

process (PF); and (3) after the filtration process/at the

plant outlet (AF). During the preliminary and long-term 

sampling phases, field arsenic speciation was conducted 

once every four weeks. Starting from November 1998,

samples of recycle supernatant water (from the settling 

pond at Plant A) or supernatant discharge water (from

lagoons at Plants B and C) were collected once every

four weeks from each plant. Three sludge samples also 
8

were collected from either the settling pond or lagoons

during one sampling event at each of the three plants.

All sample containers and arsenic speciation kits were

prepared by Battelle and sent in coolers on a weekly

basis to each plant via Federal Express. The coolers

were returned to Battelle immediately after the sample

collection had been completed. Analyses of arsenic, aluminum, iron, and manganese in water were conducted 

by Battelle’s ICP-MS laboratory. Wilson Environmental 

Laboratories in Westerville, OH, was subcontracted to

perform all other chemical analyses. Battelle coordinated 

all sampling logistics.

3.2 Preparation of Sampling Kits and 

Sample Coolers

All arsenic speciation kits, recycle supernatant water/

supernatant discharge sampling kits, and sample coolers 

were prepared at Battelle. The following sections describe the relevant preparation procedures.

3.2.1 Preparation of Arsenic 

Speciation Kits

The arsenic field speciation method used an anion

exchange resin column to separate the soluble arsenic

species, As(V) and As(III). A 250-mL bottle (identified as 

bottle A) was used to contain an unfiltered sample,

which was analyzed to determine the total arsenic concentration (both soluble and particulate). The soluble

portion of the sample was obtained by passing the unfiltered sample through a 0.45-μm screw-on disc filter to

remove any particulate arsenic and collect the filtrate in 

a 125-mL bottle (identified as bottle B). Bottle B contained 0.05% (volume/volume) ultra-pure sulfuric acid to 

acidify the sample to about pH 2. At this pH, As(III) was 

completely protonated as H3AsO3, and As(V) was present in both ionic (i.e., H2AsO4

−

) and protonated forms

(i.e., H3AsO4) (see Figure 1-1). A portion of the acidified 

sample in bottle B was run through the resin column.

The resin retains the As(V) and allowed As(III) (i.e.,

H3AsO3) to pass through the column. (Note that the resin 

will retain only H2AsO4

−

 and that H3AsO4, when passing 

though the column, will be ionized to H2AsO4

−

 due to

elevated pH values in the column caused by the buffer

capacity of acetate exchanged from the resin.) The elute 

of the column was collected in another 125-mL bottle

(identified as bottle C). Samples in bottles A, B, and C

were analyzed for total arsenic using ICP-MS. As(III)

concentration was the total arsenic concentration of the 

resin-treated sample in bottle C. As(V) concentration 

was calculated by subtracting As(III) from the total soluble arsenic concentration of the sample in bottle B.

Arsenic speciation kits were prepared in batch at Battelle 

based on a method modified from Edwards et al. (1998). 

Each arsenic speciation kit contained the following:

• Two anion exchange resin columns

• Primary and duplicate A, B, and C bottles

• One 400-mL disposable beaker

• Two 60-mL disposable syringes

• Several 0.45-μm syringe-adapted disc filters.

Each speciation kit was packed in a plastic zip-lock bag 

along with latex gloves and a step-by-step speciation 

sampling instruction sheet. All chemicals used for preparing the kits were of analytical grade or higher. The

arsenic speciation kits were prepared according to the

following procedures:

• Resin Preparation. Before packing into columns, 

the anion exchange resin (Dowex 1-X8, 50-100 

mesh) was converted from the chloride form (as 

supplied by Supelco) to the acetate form according to the method used by Edwards et al. (1998).

First, 1 kg of the resin was placed in a 3-L beaker. 

One liter of 1N sodium hydroxide (NaOH) then 

was added to the resin, stirred for an hour using 

an overhead stirrer, and drained. This NaOH rinse 

was repeated sequentially three times. The 

NaOH-treated resin was then rinsed with two 1-L 

batches of reagent grade water, followed by three 

acetic acid rinses. Each acetic acid rinse 

consisted of adding 1 L of 1N reagent grade 

acetic acid to the resin, stirring for 5 minutes, and 

draining the spent acid. The acetic acid-treated 

resin was subsequently rinsed with 3-L batches of 

reagent-grade water. The resin slurry was stored 

in a 2-L bottle and kept moist until use.

• Anion Exchange Column Preparation. The 

resin columns used were 12 cm × 15 mm in size 

and made of polypropylene (Bio-Rad Laboratories, CA). Each column was slurry packed with 

about 20 g (drained weight) of the prepared resin, 

yielding a resin depth of approximately 10.5 cm. 

The column was sealed with two plastic caps (one 

each on top and bottom) to prevent contamination 

and retain moisture prior to use.

• Sample Bottles. VWRbrandTM TraceCleanTM highdensity polyethylene (HDPE) sample bottles (250 

and 125 mL) were used to prepare bottles A, B, 

and C. Bottles A and C were spiked with 500 and 

250 μL of concentrated ultra-pure nitric acid 

(HNO3), respectively; and bottle B was spiked with 

1.25 mL of 5% (volume/volume) ultra-pure sulfuric 

acid (H2SO4). H2SO4 was used to acidify the 

sample in bottle B because chloride (Cl−

) in HCl 

could interfere with the ICP-MS arsenic detection 
9

and HNO3 (an oxidizing agent) could damage the 

resin or form nitric acid-arsenic redox couples 

(Edwards et al., 1998).

• Beaker, Syringes, and Filters. One 400-mL 

disposable plastic beaker was used to collect a 

water sample. Samples were filtered using 60-mL 

disposable plastic syringes with 0.45-μm screw-on 

disc filters. All disposable beakers, syringes, and 

filters were rinsed with distilled (DI) water and airdried before being packed into the sampling kits.

3.2.2 Preparation of Recycle Backwash 

Water/Supernatant Discharge 

Sampling Kits

The recycle backwash water/supernatant discharge samples were collected for pH, hardness (Plant C only), total 

and soluble As, Al, Fe, and Mn measurements. Each

sampling kit contained the following items:

• Primary and duplicate A and B bottles (both 

preserved with HNO3) to contain unfiltered and 

filtered samples for total and soluble As, Al, Fe, 

and Mn analyses

• One 400-mL disposable beaker

• Two 60-mL disposable syringes

• Several 0.45-μm screw-on disc filters

• Bottles provided by Wilson Environmental 

Laboratories used for pH and hardness (Plant C 

only) analyses.

The sampling kit was prepared in a similar way as the

arsenic speciation kit except that bottle B was preserved 

with HNO3 instead of H2SO4. The sampling kit was

packed in a plastic zip-lock bag along with latex gloves

and a step-by-step sampling instruction sheet.

3.2.3 Preparation of Sample Coolers

Sample containers for analysis of all water quality parameters except for total As, Al, Fe, and Mn were provided 

by Wilson Environmental Laboratories. These containers 

were new, rinsed with DI water, allowed to air dry, and

contained appropriate preservatives before being delivered to Battelle. These bottles were labeled with the letter D, E, F, or G, designating the specific analysis to be 

performed. Table 3-1 lists the sample container size and 

type (for water and sludge samples), sample preservation used, analysis to be performed, and holding time. All 

sample containers were labeled prior to shipment.

Table 3-1. Sample Containers and Preservation Methods

Container Size Container Type Preservation Method Analyte Hold Time

Arsenic Speciation Samples

250 mL (A) certified clean HDPE bottles 4°C, HNO3 for pH <2 Total As, Al, Fe, Mn 6 months

125 mL (B) certified clean HDPE bottles 4°C, 0.05 % H2SO4 Dissolved As, Al, Fe, Mn 6 months

125 mL (C) certified clean HDPE bottles 4°C, HNO3

 for pH <2 Dissolved As, Al, Fe, Mn 6 months

Recycle Backwash Water/Supernatant Discharge Samples

pH immediate 250 mL (D) plastic 4°C TSS 7 days

250 mL (A) certified clean HDPE bottles 4°C, HNO3

 for pH <2 Total As, Al, Fe, Mn 6 months

250 mL (B) certified clean HDPE bottles 4°C, HNO3

 for pH <2 Dissolved As, Al, Fe, Mn 6 months

Water Quality Parameter Samples

Alkalinity 14 days 250 mL (D) plastic 4°C pH immediate

Turbidity 48 hours

250 mL (D) plastic 4°C Sulfate 28 days

Fluoride 28 days

250 mL (E) plastic 4°C, HNO3

 for pH<2 Hardness 6 months

250 mL (F) plastic 4°C, H2

 SO4 for pH <2 NO3

−

/NO2

− 28 days

500 mL (G) glass 4°C, H2SO4

 for pH<2 TOC 14 days

Sludge Samples

8 oz (SL1) glass jar 4°C Total As, Al, Fe, Mn 6 months

4 oz (SL2) glass jar 4°C Water content, pH,

TCLP metals 14 days

4 oz (SL2) glass jar 4°C Water content, pH,

TCLP metals 14 days

TOC = total organic carbon.

TSS = total suspended solids.
10

Figure 3-1 presents an example sample bottle label. The 

sample identification (ID) consisted of five parts, including a two-letter code for a water treatment plant, the

sampling date (mm/dd/yy), a two-letter code for a specific sampling location (e.g., IN for inlet water, PF for

before the filtration process, and AF for after the filtration 

process or at the plant outlet), a one-letter code designating the analyses to be performed (see Table 3-1), 

and a code indicating whether the sample is a primary

sample or a field duplicate sample. A field duplicate was 

identified by adding a “dup” to the label and a primary

sample used no additional coding.

Figure 3-1. Example of Sample Bottle Label

After the sample bottles were labeled, they were placed 

in coolers subdivided into three compartments, each corresponding to a specific sampling location at each plant. 

Color coding was used to identify sampling locations and 

all associated sample bottles. For example, red, blue,

and yellow were used to designate sample locations for 

raw water at the plant inlet, before the filtration process, 

and after the filtration process (or at the plant outlet),

respectively. Other sampling and shipping-related materials, including latex gloves, chain-of-custody forms, prepaid Federal Express air bills, sampling instructions, ice 

packs, and bubble wrap, also were packed into coolers. 

Arsenic speciation kits or recycle supernatant water/discharge sampling kits were included in the cooler when the 

arsenic speciation or recycle supernatant water/discharge 

samples were collected. After preparation, sample coolers 

were sent to all plants every Thursday via Federal Express for the following week’s sampling activity. Figure 3-2 

shows photographs of a sample cooler with three sample compartments and a color-coded instruction sheet

placed under the lid of the cooler.

3.3 Sampling Procedures

3.3.1 General Approach and Sampling 

Schedules

One or two Battelle staff members traveled to each plant 

to collect source water samples, meet plant operators, 

solicit interest in participating in this year-long sampling 

program, and obtain plant design and operating information and historical water quality data. After the plant

selection, one Battelle staff member returned to each

plant to collect samples at selected sampling locations 

and train the plant operator or a designated POC to perform sampling and field arsenic speciation. The remaining three preliminary sampling events and long-term 

sampling events then were conducted by the trained

plant personnel. Residuals sampling, including a single

sludge sampling event and the monthly collection of recycle supernatant water or supernatant samples from

either a settling pond or lagoon also were collected by the 

designated plant employees with detailed instructions 

provided by Battelle over the telephone. Table 3-2 summarizes the sampling activities at Plants A, B, and C.

During the preliminary and long-term sampling, the sample collection was conducted on a 4-week cycle, with

each week having unique sampling requirements. Tables 3-3 (Plants A and B) and 3-4 (Plant C) summarize 

the schedules for the initial source water, the preliminary, the long-term, and the sludge sampling.

After receipt of the weekly sample coolers, plant personnel began sampling activities at the selected locations on 

the scheduled dates. Upon completion, all sample bottles were sealed with tape and placed in the same coolers for return shipment to Battelle by Federal Express.

Upon receipt of the samples, the designated Battelle

sample custodian immediately examined and compared 

the conditions of all sample bottles with those indicated

in the chain-of-custody forms. Samples then were distributed to Battelle’s ICP-MS laboratory and Wilson Environmental Laboratories for chemical analyses.

Throughout the duration of the study, Battelle staff maintained frequent telephone contact with each plant to

ensure that all sampling activities were carried out as

planned. For example, after scheduled arrival of sample 

coolers, one Battelle staff member would call to confirm 

the receipt of the coolers, answer any questions, discuss 

irregular plant operations and unusual observations, and 

propose/suggest corrective actions. When available, results of the chemical analyses also were discussed over 

the telephone and data sheets were sent quarterly to the 

plants for review. Further, plant operational and water

quality data (such as plant flowrate, chlorine addition

rate, ferric chloride or alum dosage [Plants A and B],

lime dosage [Plant C], pH, hardness [Plant C], and turbidity) were sent along with sample coolers or transmitted via facsimile to Battelle for information/evaluation.

3.3.2 Arsenic Field Speciation Procedure

The procedures for performing field arsenic speciation 

are shown in Figure 3-3 and are described as follows

(“steps” refer to Figure 3-3):

AC-02/15/98-PF-B-DUP

Date: 02/15/98 Time: 11am

Collector’s Name: Sample Collector

Location: Any City WTP

Sample ID: AC-02/15/98-PF-B-DUP

Send to: Battelle

Analysis Required: Total As, Al, Fe, and Mn 

Preservative: 0.05% sulfuric acid
11

Figure 3-2. Photographs of a Typical Sample Cooler (with Three Sample Compartments) and a ColorCoded Instruction Sheet

• Bottle A: A 400-mL disposable plastic beaker was 

rinsed thoroughly with the water to be sampled. 

The beaker then was used to collect a water 

sample and to fill bottle A with an aliquot of that 

sample (step 3). If necessary, additional sample 

water was added to the beaker after bottle A was 

filled to complete arsenic speciation sampling.

• Bottle B: A 60-mL disposable plastic syringe was 

rinsed thoroughly with the water in the plastic 

beaker by completely filling and emptying the 

syringe (step 4). After attaching a 0.45-μm disc 

filter and wasting about 10 drops of the filtrate, the 

syringe was used to filter the water sample from 

the beaker and fill bottle B. Bottle B then was 

tightly capped and vigorously shaken for about 

15 seconds to allow thorough mixing of the filtered 

water and sulfuric acid (step 5).
12

Table 3-2. Summary of Sampling Activities at Plants A, B, and C

Sampling Activities

Sampling 

Frequency Plant A Plant B Plant C

Initial source water sampling Once 02/03/98 02/05/98 02/27/98

Preliminary sampling Weekly 04/09/98 through 04/30/98 04/23/98 through 05/14/98 04/27/98 through 05/18/98

Long-term sampling Weekly (a) 06/24/98 through 06/16/99 06/25/98 through 06/17/99 06/22/98 through 06/14/99

Sludge sampling Once 12/02/98 12/15/98 11/16/98

Recycle water sampling Weekly 11/11/98 through 06/16/99 11/12/98 through 06/17/99 11/09/98 through 06/14/99

(a) Except for the weeks of 11/23/98, 12/21/98, and 12/28/98.

Table 3-3. Summary of Sampling Schedule for Plants A and B

Water Sampling

Initial Source 

Water Sampling Preliminary Sampling Cycle Long-Term Sampling Cycle Sludge 

Sampling

Analyte (Once) Week 1 Week 2 Week 3 Week 4 Week 1 Week 2 Week 3 Week 4 (Once)

As (total) W

(a) W(a) W W W W(a) W W, R(a) W

As (total soluble) W

(a) W(a) W(a) R(a)

As (particulate) W

(a) W(a) W(a) R(a)

As(III) W

(a) W(a) W(a)

As(V) W

(a) W(a) W(a)

Al (total) W

(a) W(a) W W W W(a) W W, R(a) W

Fe (total) W

(a) W(a) W W W W(a) W W, R(a) W

Mn (total) W

(a) W(a) W W W W(a) W W, R(a) W

Al (dissolved) W

(a) W, R(a)

Fe (dissolved) W

(a) W, R(a)

Mn (dissolved) W

(a) W, R(a)

Alkalinity W

(a) W W(a) W W W W(a) W W

Sulfate W

(a) W W(a) W W W W(a) W W

NO3-NO2 (N) W

(a) W W(a) W W W W(a) W W

TOC W

(a) W W(a) W W W W(a) W W

Turbidity W

(a) W W(a) W W W W(a) W W

pH W

(a) W W(a) W W W W(a) W, R(a) W

Hardness W

(a)

Ca Hardness W

(a)

Mg Hardness W

(a)

TCLP Metals S

Percent Moisture S

pH S

As (total) S

Fe (total) S

(a) = Duplicate samples collected and analyzed.

W = Water samples collected from the inlet, prefiltration, and after filtration locations.

R = Recycle supernatant water sample collected at Plant A; Supernatant discharge water sample collected at Plant B.

S = Sludge sample; three sludge samples were collected at each of Plants A and B.

Empty cells indicate no samples taken.

• Bottle C: The protective caps on the top and 

bottom of a resin column were removed and 

approximately 40 mL of the water in bottle B was 

wasted through the column. This initial 40 mL was 

used to displace the water in the resin column and 

to ensure attainability of a representative sample 

from the column. The resin column then was positioned over bottle C, and the water from bottle B 

was passed through the column until approximately 20 mL of the resin-treated sample had 

been collected in bottle C (step 6).

• The procedure as described under the above 

three bullets was repeated to obtain duplicate 

bottles A, B, and C.

• Upon completion, the individual performing the 

speciation signed on a chain-of-custody form 

(step 7). All sample bottles (for arsenic speciation 

and other water quality parameters), along with 

the signed chain-of-custody form, were placed in 

the original cooler with ice packs and shipped via 

Federal Express to Battelle (step 8).
13

Table 3-4. Summary of Sampling Schedule for Plant C

Water Sampling

Initial Source 

Water Sampling Preliminary Sampling Cycle Long-Term Sampling Cycle Sludge Sampling

Analyte (Once) Week 1 Week 2 Week 3 Week 4 Week 1 Week 2 Week 3 Week 4 (Once)

As (total) W

(a) W(a) W W W W(a) W W, R(a) W

As (total soluble) W

(a) W(a) W(a) R(a)

As (particulate) W

(a) W(a) W(a) R(a)

As(III) W

(a) W(a) W(a)

As(V) W

(a) W(a) W(a)

Al (total) W

(a) W(a) W W W W(a) W W, R(a) W

Fe (total) W

(a) W(a) W W W W(a) W W, R(a) W

Mn (total) W

(a) W(a) W W W W(a) W W, R(a) W

Al (dissolved) W

(a) W, R(a)

Fe (dissolved) W

(a) W, R(a)

Mn (dissolved) W

(a) W, R(a)

Alkalinity W

(a) W W(a) W W W W(a) W W

Sulfate W

(a) W W(a) W W W W(a) W W

NO3-NO2 (N) W

(a) W W(a) W W W W(a) W W

TOC W

(a)

Turbidity W

(a) W W(a) W W W W(a) W W

pH W

(a) W W(a) W W W W(a) W, R(a) W

Hardness W

(a) W W(a) W W W W(a) W, R(a) W

Ca Hardness W

(a) W W(a) W W W W(a) W, R(a) W

Mg Hardness W

(a) W W(a) W W W W(a) W, R(a) W

TCLP Metals S

Percent Moisture S

pH S

As (total) S

Fe (total) S

(a) = Duplicate samples collected and analyzed.

W = Water samples collected from the inlet, prefiltration, and after filtration locations.

R = Supernatant discharge water sample.

S = Sludge samples; three collected at Plant C.

Empty cells indicate no samples taken.

3.3.3 Recycle Supernatant 

Water/Supernatant Discharge 

Sampling Procedure

Figure 3-4 shows an instruction sheet for performing recycle backwash water and supernatant discharge sampling. Because both total and dissolved As, Al, Fe, and 

Mn were analyzed, the procedure for recycle supernatant water/supernatant discharge sampling was similar to 

that for arsenic speciation, except that the steps for collecting samples in bottle C were omitted.

3.3.4 Sampling Procedure for Other 

Water Quality Parameters

All other water quality parameters identified in Tables 3-3 

and 3-4, were analyzed using samples either in bottles A, 

B, and C or in bottles provided by Wilson Environmental 

Laboratories (i.e., bottles D, E, F, and G). All bottles D, 

E, F, and G were filled directly from sample taps and

preserved according to the respective analytical methods. 

These sample bottles along with bottles A, B, and C

were placed in the original coolers with ice packs and

shipped via Federal Express to Battelle.

3.4 Analytical Procedures

The analytical procedures used for this project were

described in Section 4.0 of the QAPP prepared by

Battelle (1998). Table 3-5 presents a summary of all

analytical methods used. All of the methods used are

standard EPA methods. Analyses of As, Al, Fe, and Mn 

in water samples were accomplished by ICP-MS using

EPA Method 200.8. ICP-MS was chosen as the method 

for As, Al, Fe, and Mn analyses because it had a low

method detection limit (MDL) and was a relatively lowcost method (about $35/sample). ICP-MS analyses were 

conducted on a Perkin Elmer Sciex Model 6000 equipped

with a crossflow pneumatic nebulizer and an automatic 

sampler. Yttrium (88.9Y) was added to all samples as an 

internal standard to correct for instrument drift. Because 

arsenic is monoisotopic, all measurements were made at 

a mass/ charge ratio of 75. To eliminate an appreciable
14

Figure 3-3. Instruction Sheet for Arsenic Field Speciation
15

Figure 3-4. Instruction Sheet for Recycle Supernatant Water/Supernatant Discharge Sampling
16

Table 3-5. Summary of Analytical Methods for Arsenic Treatment Study

Sample Matrix Analyte Method Analytical Laboratory

As (total) EPA 200.8 Battelle ICP/MS 

Total Al EPA 200.8 Battelle ICP/MS 

Total Fe EPA 200.8 Battelle ICP/MS 

Total Mn EPA 200.8 Battelle ICP/MS 

Alkalinity EPA 310.1 Wilson Environmental

pH EPA 150.1 Wilson Environmental

Turbidity EPA 180.1 Wilson Environmental

Hardness EPA 215.1/242.1 Wilson Environmental

SO4

2− EPA 375.4 Wilson Environmental

TOC EPA 415.1 Wilson Environmental

Aqueous (including samples collected at the 

plant inlet, before the filtration process, after the 

filtration process, and supernatant water from 

sludge settling ponds/lagoons that was recycled 

or discharged)

NO3

−

/NO2

− EPA 353.2 Wilson Environmental

Water content ASTM D 2216 Wilson Environmental

pH SW-846 9045 Wilson Environmental

TCLP metals SW-846 1311 Wilson Environmental

Total As SW-846 3051, 6020 Wilson Environmental

Sludge 

Total Fe SW-846 3051, 6020 Wilson Environmental

interference from a chloride molecular species (40Ar35Cl), 

all ion current data at m/e 75 were corrected using

chloride measurements in all samples, and the MDL was 

0.1 μg/L As. All the unfiltered water samples (i.e., in bottle A) were digested using EPA Method 200.8 prior to

analysis. Filtered water samples (i.e., in bottles B and C) 

were analyzed directly without digestion. Wilson Environmental Laboratories in Westerville, OH, was subcontracted to perform all other chemical analyses. QA/QC of 

all methods followed the guidelines provided in the QAPP

(Battelle, 1998) and the data quality in terms of precision, accuracy, MDL, and completeness is discussed in 

Section 5.0 of this report.
17

4. Results and Discussion

This section presents the results of the treatment plant

selection process, which resulted in the selection of two 

coagulation/filtration plants, referred to as Plants A and

B, and one lime softening plant, referred to as Plant C. In 

addition, results from water and residuals sampling and

analysis at Plants A, B, and C are summarized and discussed. Complete analytical results from long-term water 

sampling at Plants A, B, and C are presented in Appendices A, B, and C, respectively.

4.1 Plant Selection

The plant selection process consisted of identifying potential treatment facilities, contacting these facilities via

telephone, and conducting initial site visits during which

source water samples were collected and analyzed. Initially, a list was prepared consisting of six potential coagulation/filtration treatment facilities and two lime softening facilities. These potential candidate facilities were

contacted to discuss the study and determine details of 

plant operation. Each facility was evaluated and assigned an overall plant rating based, in order of importance, on source water arsenic concentrations, source

water type, available manpower to conduct the year-long 

study, availability of historical arsenic data, and plant

size. Selection was based primarily on source water arsenic concentrations, and preference was given to facilities with arsenic concentrations greater than 20 μg/L. 

Another major consideration was the availability of manpower, because the year-long study would require significant resources. Also, it was desirable to have historical 

arsenic analytical data, fairly large facilities (i.e., >20,000 

people served), and to have a mix of plants using ground 

water and/or surface water sources.

From the eight initial plants, three plants (two coagulation/filtration and one lime softening) were selected for

site visits and source water sampling (Plants A, B, and C 

in Table 4-1). The same plants that were selected for the 

initial site visits also were selected for the subsequent

phases of the study. Results from source water sampling 

at each of the three facilities are presented in the sections that follow.

4.2 Plant A

Water and residual samples were collected and analyzed 

at Plant A, a coagulation/filtration plant, during three

phases of the study. The first phase consisted of source 

water sampling used to help determine if the plant should

be considered for additional phases. Source water sampling at Plant A was performed in February 1998. Following source water sampling, the second phase of the 

study was initiated. This second phase consisted of

weekly water sampling for a 4-week period in April 1998 

and was designed to determine if the sampling locations 

and proposed water quality analyses were appropriate 

for the third phase, long-term evaluation. The third phase 

was initiated in June 1998 and continued through June

1999. This long-term evaluation consisted of weekly sampling and analysis of process water at three locations 

throughout the treatment process. Also, arsenic speciation sampling was conducted every fourth week. The

third phase of the study also included residual sample

Table 4-1. Initial List of Treatment Facilities Identified for the Study

Plant ID Process

Source Water Arsenic 

Concentration, July 1994 

(μg/L)

Source Water Arsenic 

Concentration, March 1995 

(μg/L)

Population 

Served Historical Data

Source 

Water Type

A C/F NS 66.9 2,500,000 Yes SW

B C/F NS 33.2 65,000 Yes SW

C LS 33.2 52.5 35,000 Yes GW

C/F = coagulation/filtration. GW = ground water. NS = not sampled.

LS = lime softening. SW = surface water.
18

collection and analysis. Recycle supernatant water samples from the settling pond were collected monthly beginning in November 1998, and three sludge samples were 

collected during a single sampling event from a dewatered sludge pond.

4.2.1 Plant A Description

Plant A began operation in December 1986 and can

treat up to 600 million gallons of water per day (mgd).

However, based on discussions with plant personnel, the 

average plant flowrate is approximately 420 mgd. This

plant uses ozonation, coupled with coagulation/filtration

for water treatment. Figure 4-1 is a schematic diagram of 

the treatment process at Plant A.

During treatment, the influent water is split into four treatment trains immediately prior to ozonation and the trains 

are recombined prior to distribution. At the design flowrate, the treatment process takes approximately 40 minutes. Typically, it takes approximately 1 hour for raw

water to be processed. The treatment process consists

of the following major elements:

• Screening. The raw water is passed through a 

screen with a 2-inch mesh to remove debris.

• Ozonation. Ceramic diffusers are used to feed 

1.5 mg/L of ozone at the influent of the unit. There 

is approximately a 5-minute contact time. Ozonation is used for disinfection and microflocculation 

to improve filtration and control taste and odor. 

The plant produces approximately 13,000 lb/day 

of ozone with six generators.

• Rapid Mixing. 1 to 2 mg/L of ferric chloride and 

1 to 5 mg/L of cationic polymer are mixed with the 

water.

• Flocculation. Flocculation occurs in three basins 

placed in series with approximately 8.5 minutes of 

contact time.

• Filtration. Filtration is accomplished with a highrate filter (13.5 gpm/ft2

). The filter media is anthracite coal (1.5 mm effective size) and a thin layer of 

pea gravel. Typically, backwashing occurs every 6 

to 40 hours (average 20 hours) and the backwash 

water is sent to settling ponds. Supernatant water 

is fed into the water treatment plant influent. Backwashing accounts for approximately 2% of plant 

flow.

• Chlorination. Chlorine is added during the treatment process for disinfection. The treatment plant 

chlorinates in order to maintain approximately 

2 mg/L of residual chlorine.

4.2.2 Initial Source Water Sampling

Source water for Plant A is supplied primarily via an

aqueduct system that carries ground water and surface 

water runoff from the Sierra Nevada Mountains. This

water is collected and stored in a series of eight reservoirs. The aqueduct is enclosed for 200 miles between

the last of the eight reservoirs and the water treatment 

plant. Due in part to the high arsenic concentrations in

the source water, a water treatment facility was constructed in 1995 at the inlet of the last reservoir. This

plant doses 3 to 7 mg/L of ferric chloride and a cationic

Figure 4-1. Schematic Diagram of Plant A Treatment Process
19

polymer into the reservoir, which is used as a large

settling basin. The reservoir is relatively effective at removing arsenic. The long-term average arsenic concentration in the source water prior to entering the reservoir 

is approximately 25 μg/L and the reservoir effluent has

an average arsenic concentration of 8 to 10 μg/L. The

reservoir treatment plant is not considered part of Plant A 

and is not included in the sampling phases of this study.

An initial site visit to Plant A was conducted February 3, 

1998, during which time source water samples were collected. The total arsenic concentration during the initial

sampling event was 10.4 μg/L. Particulate arsenic accounted for 2.4 μg/L of the total arsenic concentration,

and soluble arsenic, primarily arsenate, accounted for

the remaining 8.0 μg/L of the total arsenic. The particulate arsenic is probably attached to the iron, which was

detected at a concentration of 170 μg/L. The As(V) concentration was 7.9 μg/L and the As(III) concentration

was 0.1 μg/L, which is consistent with what would be

expected for a surface water source. Table 4-2 presents 

the analytical results from the source water sampling.

Although the total arsenic in the source water at this plant 

was below the desired concentration of 20 μg/L, it was

selected for incorporation into the preliminary sampling

and long-term evaluation phases. Selection of Plant A was 

based on the very large size and the availability of resources at the facility to conduct the long-term sampling.

4.2.3 Preliminary Sampling

During the preliminary sampling phase of this study,

water samples were collected at three locations within

the treatment plant: IN, PF, and AF. The IN samples 

were collected from a tap located after initial screening

and after the supernatant from the sludge settling lagoons 

had been recycled. The PF and AF samples were collected from sample taps located on treatment train two of 

the four parallel trains at Plant A. The PF sampling tap

was located after flocculation and just prior to filtration.

The AF sampling tap was located after filtration and prior 

to final chlorine addition and distribution. Figure 4-2 is a 

process flowchart for Plant A that shows sampling locations within the treatment process and the associated

sample analyses performed at each location.

Alkalinity, turbidity, pH, total aluminum, total iron, total

manganese, TOC, and total arsenic analyses were performed on samples collected each of the four weeks at

each of the three sampling locations. Arsenic speciation 

was conducted once during the preliminary study on

samples collected from each sampling location. Soluble, 

and particulate were determined as part of the arsenic

speciation, as well as the species (arsenite and arsenate) making up the soluble fraction of the total arsenic. 

Table 4-3 presents the results of the 4-week preliminary 

sampling period.

Results from the preliminary sampling events indicated 

that inlet total arsenic concentrations ranged from approximately 12 to 17 μg/L. As found during the initial

source water sampling, the total arsenic in the source

water was primarily As(V) and contained only minor concentrations of As(III) and particulate arsenic. As would

be expected, the species of arsenic did not vary during

the treatment process. The average total arsenic removal by Plant A was approximately 48% during preliminary

Table 4-2. Source Water Analytical Results at Plant A (February 3, 1998)

Parameter Unit

Primary

Sample

Duplicate

Sample

Average 

Concentration

Alkalinity mg/L(a) 98 95 97

Sulfate mg/L 44 44 44

Turbidity NTU 0.67 0.68 0.68

pH — 8.1 8.1 8.1

Hardness mg/L(a) 104 93.5 98.8

Ca Hardness mg/L(a) 74 65 70

Mg Hardness mg/L(a) 29 29 29

Total Al μg/L <400 <400 <400

Total Fe μg/L 160 180 170

Total Mn μg/L <20 <20 <20

NO3−NO2

 (N) mg/L(b) 0.12 0.13 0.13

TOC mg/L 1 2 1.5

As (total) μg/L 11.1 9.6 10.4

As (total soluble) μg/L 7.3 8.6 8.0

As (particulate) μg/L 3.8 1.0 2.4

As(III) μg/L ND 0.2 0.1

As(V) μg/L 7.3 8.4 7.9

(a) As CaCO3.

(b) Combined NO3−N and NO2−N.

ND = not detected.

NTU = nephelometric turbidity units.
20

INFLUENT

RECYCLE

BACKWASH WATER

SCREENING

1

OZONATION

RAPID MIXING

BASIN #1

FLOCCULATION

2

FILTRATION

3

DISTRIBUTION

SYSTEM

WEEKLY

MONTHLY

As (total), As (III), As (V)

Plant A

Coagulation/Filtration

Design Flow: 600 mgd

LEGEND

DA: Cl2

FILTRATION

FeCl3

Cationic Polymer

FeCl3

Disinfectant Addition

Point

Unit Process

Chemical Added to

Unit Process

SETTLING PONDS

RAPID MIXING

BASIN #2

DA: Cl2

DA: Cl2

SS Sludge Sampling 

Location

1 Water Sampling 

Location

Backwash Water

As (total), Alkalinity, pH,

TOC, Turbidity, Total Al,

Total Fe, Total Mn

As (total), As (III), As (V)

As (total), Alkalinity, pH,

TOC, Turbidity, Total Al,

Total Fe, Total Mn

As (total), As (III), As (V)

As (total), Alkalinity, pH,

TOC, Turbidity, Total Al,

Total Fe, Total Mn

SS

As (total), water content,

 pH, TCLP metals

NOTE:

Four treatment trains operate in

parallel at this plant. These trains

split immediately before ozonation

and recombine prior to distribution. 

Sample locations 2 and 3 are located in

Treatment Train 2.

Treatment Train 1 2 3 4

A 4s (dissolved and total),

pH

SLUDGE SENT TO HAZARDOUS

WASTE LANDFILL

Figure 4-2. Process Flow Diagram and Sampling Locations at Plant A
21

Table 4-3. Analytical Results from Preliminary Sampling at Plant A (April 9, 1998 through April 30, 1998)

Sampling Date/Location

4/9/98(a) 4/16/98 4/23/98 4/30/98

Parameter Units IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(b) 113

111

108

108

107

107 112 110 110 116 115 115 124 119 116

Turbidity NTU 1.6

1.6

2.1

2.1

0.1

0.1 2.5 7.1 0.2 1.4 1.9 <0.1 1.1 7.5 <0.1

pH —

8.1

8.1

7.8

7.8

7.7

7.7 8.4 8.2 8.0 7.9 7.9 7.8 8.3 8.1 8.0

Total Al μg/L <400

<400

<400

<400

<400

<400 <400 <400 <400 <400 <400 <400 <400 <400 <400

Total Fe μg/L 280

300

780

720

60

60 460 1,040 40 250 940 100 170 1,190 50

Total Mn μg/L 30

30

40

40

<20

<20 70 70 50 50 70 50 <20 60 <20

TOC mg/L 2

3

3

3

2

2

2 3 2 3 3 2 2 3 2

As (total) μg/L 13.6

12.1

8.6

8.5

6.1

6.1 14.5 16.2 7.3 14.2 15.6 7.2 16.6 19.3 9.5

As (total soluble) μg/L 12.0

12.0

7.8

7.8

6.4

6.5 NA NA NA NA NA NA NA NA NA

As (particulate) μg/L 1.6

0.1

0.8

0.7

ND

ND NA NA NA NA NA NA NA NA NA

As (III) μg/L 0.2

0.3

0.2

0.2

0.1

0.2 NA NA NA NA NA NA NA NA NA

As (V) μg/L 11.8

11.7

7.6

7.6

6.3

6.3 NA NA NA NA NA NA NA NA NA

(a) Duplicate samples were taken on 4/9/98.

(b) As CaCO3

.

IN = inlet; PF = prefiltration; AF = after filtration.

NA = not applicable.

ND = not detected.
22

sampling, reducing the finished water total arsenic concentration to 6.1 to 9.5 μg/L. Plant A does not have a

sedimentation step following flocculation; therefore, the

majority of the arsenic removal occurred during filtration. 

The As(V) attaches to iron flocs and is then removed

during filtration, which is why the PF sampling location

consistently has higher total arsenic concentrations.

McNeill and Edwards (1997a) developed the following

simplified model for predicting arsenic removal at iron

and alum coagulation facilities based on raw water Fe

and Al concentrations:

(1 K [Fe Al]mM)

K [Fe Al]mM Arsenic Sorbed(%) 100

+ × +

× +

= × (1)

where K = 78 mM−1

This model was based on data collected at over 14 fullscale facilities, and was able to accurately predict arsenic removal within ±13% (90th percentile confidence

interval). Applying this model to the preliminary results

from Plant A, the predicted removal ranged between 51 

and 62% compared to actual removals ranging from 43

to 52%. During the first sampling event, the actual and

predicted arsenic removal percentages were very close

(51% predicted and 52% actual). However, a 19% difference in arsenic removal was observed during the last

sampling event in which the calculated removal was 62% 

and the actual removal was 43%. Estimated arsenic

removal percentages for the other two sampling events

were within ±13% of the actual removal observed. Therefore, the simplified model appeared to approximate the

arsenic removal at Plant A fairly well.

Other water quality parameters were analyzed to support 

understanding of the mechanisms of arsenic removal.

TOC and pH concentrations were relatively constant

throughout the treatment process during the preliminary 

sampling phase. Also, the pH was approximately 8.0 and 

in the range where no effect on arsenic removal efficiency using iron (III) salts has been observed in previous 

studies (Sorg and Logsdon, 1978; Sorg, 1993; Hering et 

al., 1996).

A slight decrease in alkalinity was observed after the

addition of the ferric chloride coagulant (i.e., at the PF

sampling location). This decrease in alkalinity is a result 

of a chemical reaction with ferric chloride:

2FeCl3 + 3Ca(HCO3)2 → 2Fe(OH)3↓

+ 3CaCl2 + 6CO2

(2)

Total aluminum concentrations were below detection 

limits at all three locations during each sampling event

and were not considered to play a role in arsenic removal; however, the detection limits were relatively high 

(400 μg/L). Total manganese concentrations ranged from

<20 to 70 μg/L in the inlet and <20 to 50 μg/L in the

outlet. The total iron concentrations averaged 293 μg/L 

at the inlet, 980 μg/L at the prefiltration sampling location, and 63 μg/L at the after-filtration sampling location. 

The increase at the prefiltration location is due to the

addition of FeCl3 as a coagulant. The iron then is removed in the filters. It appears that the primary arsenic

removal mechanism at Plant A is adsorption and coprecipitation of As(V) with the iron flocs.

Based on the results of the preliminary sampling effort,

only minor changes were made to the approach for the 

long-term evaluation. Sampling locations and primary

analytes remained unchanged. However, aluminum, iron, 

and manganese analysis was modified to achieve lower 

detection limits by using ICP-MS. Also, it was determined that part of the sample in bottle B from the arsenic 

speciation kits would be used to determine dissolved 

aluminum, iron, and manganese concentrations.

4.2.4 Long-Term Sampling

Long-term sampling and analysis consisted of 49 weeks 

of sampling with 12 arsenic speciation sampling events. 

During the long-term sampling phase of this study, water 

samples were collected at the same three locations that 

were used during the preliminary sampling phase: IN,

PF, and AF. Alkalinity, turbidity, pH, total aluminum, total 

iron, total manganese, TOC, and total arsenic analysis

was performed on samples collected each week. Arsenic 

speciation sampling was conducted 12 times during the 

long-term sampling phase on samples collected from

each sampling location. Dissolved aluminum, iron, and

manganese concentrations at each sampling location

were determined monthly using a sample from bottle B

of the arsenic speciation kits. Additionally, residual sampling was performed during this phase and consisted of 

collection and analysis of recycle supernatant water and 

sludge from the settling pond. The following subsections 

summarize the analytical results for arsenic, other water 

quality parameters, and residuals. Figure 4-2 is a process flow diagram for Plant A that indicates sampling 

locations during the long-term evaluation and the analyses performed on samples from each location.

4.2.4.1 Arsenic

Table 4-4 provides a summary of the arsenic analytical 

results collected at the three treatment process locations 

at Plant A. Total arsenic concentrations at the inlet

ranged from 2.6 μg/L to 12.1 μg/L with an average concentration of 7.5 μg/L. These concentrations are slightly 

lower than what was observed during the initial source

water and preliminary sampling phases of this study.
23

Table 4-4. Summary of Arsenic Analytical Results at Plant A (June 1998–June 1999)

Parameter Sample Location Units

Number of 

Samples

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

As (total) Inlet μg/L 49 2.6 12.1 7.5 2.1

Prefiltration μg/L 49 2.0 23.4 8.7 3.9

After filtration μg/L 48 0.8 6.0 3.5 1.1

As (total Inlet μg/L 12 5.1 10.9 7.7 1.7

soluble) Prefiltration μg/L 12 2.7 6.0 4.3 1.1

After filtration μg/L 12 2.0 4.8 3.5 0.9

As Inlet μg/L 12 <0.1 1.9 0.5 0.6

(particulate) Prefiltration μg/L 12 1.7 7.8 4.3 1.8

After filtration μg/L 12 <0.1 0.5 0.2 0.2

As(III) Inlet μg/L 12 0.3 2.0 0.7 0.5

Prefiltration μg/L 12 <0.1 2.1 0.6 0.6

After filtration μg/L 12 <0.1 1.9 0.6 0.5

As(V) Inlet μg/L 12 4.8 10.2 6.9 1.7

Prefiltration μg/L 12 2.2 5.4 3.6 0.9

After filtration μg/L 12 1.6 4.3 3.0 0.7

One-half of the detection limit was used for nondetect samples for calculations.

Primary and duplicate samples were averaged for calculations.

These results are due to a general trend of slightly higher arsenic concentrations that occur seasonally during 

the months of February through July. Total arsenic concentrations at the PF sampling location ranged from 2.0 

to 23.4 μg/L, with an average of 8.7 μg/L. Therefore, in

general, no reduction of arsenic was observed between 

the inlet and prefiltration sampling locations. In fact, the 

data indicated that a slight increase in total arsenic concentration occurred due to the formation of iron flocs which 

sorbed the arsenate. The flocs accumulated just prior to

the filtration step where the PF samples were collected.

Samples collected at the after-filtration location contained total arsenic concentrations ranging from 0.8 μg/L 

to 6.0 μg/L with an average concentration of 3.5 μg/L.

The average removal percentage of total arsenic between the inlet and after-filtration sampling locations was 

53%. The average arsenic removal predicted by the

McNeill and Edwards (1997a) sorption model was 43%, 

which is within the 90th percentile confidence interval of 

the model. However, individual sampling events showed 

differences in actual and predicted arsenic removals as

high as 63% and the average difference was approximately 20%, which is outside of the 90th percentile confidence interval for the model. The discrepancies between 

the actual and predicted values may be due to temperature and competition for sorption sites by natural organic 

matter (McNeill and Edwards, 1997a). Also, the low

arsenic concentration in the source water (average

7.5 μg/L) likely contributed to the discrepancy between

the predicted and actual removal efficiencies. However,

it appears that the difference is not a result of iron floc

passing through the filter because the particulate arsenic 

and total iron concentrations at the outlet are very low.

Figure 4-3 is a graph showing the total arsenic concentration recorded at each sampling location throughout

the study, as well as removal percentages calculated for 

each sampling event.

Particulate arsenic concentrations averaged 0.5 μg/L at

the inlet, 4.3 μg/L at the prefiltration sampling location,

and 0.2 μg/L at the after-filtration sampling location. The 

increase of particulate arsenic at the prefiltration sampling location is due to sorption and coprecipitation of

arsenic on/with the iron flocs formed. This observation is 

supported by the decrease of particulate arsenic in the

after-filtration sampling location.

As(III) and As(V) make up the soluble portion of the total 

arsenic concentration. Throughout the duration of the

study and at each sampling location, As(V) made up the 

majority of the soluble arsenic. As(III) concentrations 

averaged 0.7 μg/L at the inlet, 0.6 μg/L at the prefiltration 

location, and 0.6 μg/L at the after-filtration location, indicating that As(III) was not removed by the treatment process. Although the As(III) concentrations were low, no

apparent conversion to As(V) was observed after ozonation. Average As(V) concentrations were 6.9 μg/L at the 

inlet, 3.6 μg/L at the prefiltration location, and 3.0 μg/L at 

the after-filtration location. The As(V) concentration decreased at the prefiltration location due to coprecipitation/adsorption of the arsenic with iron flocs. This result 

correlates with the increase in particulate arsenic at this 

same location. The arsenic that was not removed with

the coagulant passes through the system. Figure 4-4 

provides charts showing the fractions of the total arsenic 

concentration made up by particulate arsenic, As(III),

and As(V) throughout the long-term evaluation.

The Plant A water treatment system was able to consistently remove arsenic to low levels (i.e., average

treated water total arsenic concentration is 3.5 μg/L).
24

0

5

10

15

20

25

6/4/98 7/24/98 9/12/98 11/1/98 12/21/98 2/9/99 3/31/99 5/20/99 7/9/99

Date

Arsenic Concentration (μg/L)

-10%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Percent Arsenic Removal

Inlet

Prefiltration

After Filtration

%Removal

Figure 4-3. Total Arsenic Analytical Results During Long-Term Sampling at Plant A

The primary arsenic removal mechanism appears to be

coprecipitation/adsorption with iron flocs followed by filtration. The simplified sorption model developed by McNeill 

and Edwards (1997a) appears to approximate the arsenic removal process at Plant A reasonably well, although 

discrepancies were noted.

4.2.4.2 Other Water Quality Parameters

In addition to arsenic analysis, other water quality parameters were analyzed to provide insight into the chemical 

processes occurring at the treatment facility. Table 4-5 

summarizes the analytical results for several water quality parameters obtained during the long-term sampling at 

Plant A.

Alkalinity concentrations ranged from 45 mg/L to 112 mg/L

(as CaCO3) in the inlet with an average of 89 mg/L. The 

analytical data indicated seasonal variations in alkalinity 

concentrations, with a dip occurring during July and

August. This dip correlated with the snow melt in the

Sierra Nevada mountains, which resulted in a higher

percentage of the source water coming from lower-alkalinity melted snow. However, these data did not appear

to correlate with arsenic analytical results or removal efficiencies at Plant A. Figure 4-5 plots the inlet alkalinity,

turbidity, pH, and TOC concentrations throughout the

duration of the study.

During long-term sampling, turbidity concentrations averaged 1.2 NTU at the inlet, 1.8 NTU at the prefiltration 

location, and <0.1 NTU at the after-filtration location. As 

seen in Figure 4-5, spikes in the inlet turbidity concentrations were observed during the study and are most likely 

due to precipitation events that increase suspended solids in the source water. The ferric chloride dosages are 

adjusted to account for the varying turbidity concentrations. The data show that Plant A effectively removes turbidity from the source water, although no correlation was 

observed regarding arsenic removal efficiency.

The average pH was 8.0 at the inlet, 7.9 just prior to

filtration, and 7.8 in the finished water. These pH values 

are in the range (pH 5.5 to 8.5) where arsenic removal

efficiency by iron oxides is not affected (Sorg, 1993). On 

March 24, 1999, a pH of 5.2 was reported; however, this 

figure is considered to be an outlier because plant operational data did not indicate any change in pH. TOC concentrations also were relatively constant, with averages of 

2.4 mg/L, 2.7 mg/L, and 2.4 mg/L, at the inlet, prefiltration, 

and after-filtration sampling locations, respectively. TOC 

does not appear to impact arsenic removal efficiency.

Total iron concentrations at the inlet sampling location 

ranged from <30 to 767 μg/L and averaged 146 μg/L. At

the prefiltration sampling location, total iron concentrations 

ranged from <30 to 2,646 μg/L and averaged 642 μg/L.
25

Inlet

Prefiltration

After Filtration

0

2

4

6

8

10

12

14

7/15/98

8/5/989/2/98

9/30/98

10/28/98

12/2/981/13/992/11/993/10/99

4/7/995/5/996/2/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

0

2

4

6

8

10

12

14

7/15/98

8/5/989/2/98

9/30/98

10/28/98

12/2/981/13/992/11/993/10/99

4/7/995/5/996/2/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

0

2

4

6

8

10

12

14

7/15/98

8/5/989/2/98

9/30/98

10/28/98

12/2/981/13/992/11/993/10/99

4/7/995/5/996/2/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

Figure 4-4. Arsenic Form and Species Analytical Results During Long-Term Sampling at Plant A
26

Table 4-5. Summary of Water Quality Parameter Analytical Results at Plant A (June 1998–June 1999)

Parameter Sample Location Units

Number of 

Samples

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

Alkalinity Inlet mg/L 48 45 112 89 20.7

Prefiltration mg/L 48 43 111 88 20.6

After filtration mg/L 48 42 109 87 20.5

Turbidity Inlet NTU 48 0.3 5.5 1.2 1.0

Prefiltration NTU 48 0.4 18.5 1.8 2.7

After filtration NTU 48 <0.1 0.2 <0.1 0.04

pH Inlet — 48 5.2 8.3 8.0 0.4

Prefiltration — 48 7.5 8.1 7.9 0.1

After filtration — 48 7.4 8.0 7.8 0.2

TOC Inlet mg/L 47 1.5 4.8 2.4 0.6

Prefiltration mg/L 48 <1.0 12.0 2.7 1.5

After filtration mg/L 48 1.5 7.4 2.4 0.9

Total Al Inlet μg/L 49 <11 717 68 104.2

Prefiltration μg/L 49 18.2 246 64 48.8

After filtration μg/L 49 <11 39 12 7.6

Total Fe Inlet μg/L 49 <30 767 146 175.1

Prefiltration μg/L 49 <30 2,646 642 474.5

After filtration μg/L 49 <30 63.8 <30 14.7

Total Mn Inlet μg/L 49 4.4 112 20.9 20.0

Prefiltration μg/L 49 8.9 85.5 27.1 17.0

After filtration μg/L 49 <0.5 45.4 4.7 7.2

Dissolved Al Inlet μg/L 12 <11 22.6 <11 4.9

Prefiltration μg/L 12 <11 <11 <11 NA

After filtration μg/L 12 <11 18 <11 3.7

Dissolved Fe Inlet μg/L 12 <30 45.7 <30 8.9

Prefiltration μg/L 12 <30 <30 <30 NA

After filtration μg/L 12 <30 <30 <30 NA

Dissolved Mn Inlet μg/L 12 1.1 10.8 3.1 2.6

Prefiltration μg/L 12 1.4 69.7 8.7 19.2

After filtration μg/L 12 <0.5 5.8 2.3 2.3

One-half of the detection limit was used for nondetect samples for calculations.

Primary and duplicate samples were averaged for calculations.

The total iron concentration increased at the prefiltration 

location due to the addition of FeCl3 as a coagulant. The 

average total iron concentration at the after-filtration 

sampling location was <30 μg/L. Also, average dissolved 

iron concentrations were below the detection limit at the 

inlet, prefiltration, and after-filtration sampling locations. 

As stated previously, iron is the key factor in arsenic

removal at Plant A. It is believed that the majority of the 

arsenic removal is through adsorption and coprecipitation of As(V) with iron hydroxides.

Total aluminum concentrations averaged 68 μg/L at the

inlet, 64 μg/L at the prefiltration location, and 12 μg/L at 

the after-filtration location. The average dissolved aluminum concentration at all three locations was less than

the detection limit. It did not appear that coprecipitation 

with aluminum hydroxide was a significant factor in the

removal of arsenic at Plant A, because minor concentrations were present and almost all of the aluminum was in 

the particulate form at the inlet.

Total manganese concentrations averaged 20.9 μg/L, 

27.1 μg/L, and 4.7 μg/L, at the inlet, prefiltration, and afterfiltration sampling locations, respectively. Average dissolved manganese concentrations were 3.1 μg/L at the

inlet, 8.7 μg/L at the prefiltration location, and 2.3 μg/L at 

the after-filtration location.

4.2.4.3 Recycle Supernatant Water

Approximately 2% of the total flow at Plant A is used for 

backwashing filters. The filter backwash water then is

sent to a sludge settling pond and the supernatant is

recycled. The supernatant water is added continuously 

to the source water and processed at the facility. Supernatant samples were collected from a sample tap in the 

piping that transports the water from the sludge settling 

pond to the source water inlet. Results of supernatant

sampling are summarized in Table 4-6.

The soluble arsenic concentrations are approximately 

equal to those measured in the source water; however,

the particulate arsenic is approximately 3.0 μg/L higher

on average. This result would be expected because the 

backwash water contains some unsettled iron solids, which

most likely contain sorbed arsenic. The low dissolved iron 

concentrations observed during the study support this

assumption. Based on these results, it does not appear
27

0

1

2

3

4

5

6

7

8

9

6/4/98 7/24/98 9/12/98 11/1/98 12/21/98 2/9/99 3/31/99 5/20/99 7/9/99

Date

Measurement (Turbidity, pH, TOC)

0

20

40

60

80

100

120

Measurement (Alkalinity)

Turbidity (NTU)

pH (units)

TOC (mg/L)

Alkalinity (mg/L as CaCO3)

Figure 4-5. Inlet Turbidity, pH, TOC, and Alkalinity Analytical Results at Plant A

that the recycle backwash water would impact the treatment process either positively or negatively.

4.2.4.4 Sludge

Sludge is generated at Plant A from backwashing the

anthracite coal/pea gravel filters. Typically, backwashing 

occurs every 6 to 40 hours (average 20 hours) and the 

backwash water is sent to settling ponds. Supernatant

water from the settling ponds is recycled into plant influent. 

Approximately 2% of plant flow is used for backwashing.

Approximately once per year, or as required, the settling 

ponds are drained and the sludge is removed. Approximately 18,000 tons of sludge are removed per year. The 

sludge is considered California hazardous waste due to 

elevated concentrations of arsenic and copper based on 

exceedances of regulatory levels for the soluble threshold limit concentration (STLC). Total arsenic and TCLP

results have not exceeded regulatory levels for classification as California hazardous waste. Table 4-7 contains analytical results from sludge sampling conducted 

during three sampling events at Plant A in October 1996, 

March 1997, and May 1997.

During the long-term evaluation phase, sludge samples

were collected on December 2, 1998, from three locations 

within a dewatered sludge pond. These sludge samples 

were analyzed for pH, percent moisture, total arsenic, and 

total iron. Also, a TCLP test was performed on each

sample to determine the quantities of leachable arsenic,

Table 4-6. Summary of Analytical Results from Recycle Backwash Water Samples at Plant A 

(November 11, 1998–June 16, 1999)

Parameter Units

Number of 

Sample Events

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

As (total) μg/L 8 3.7 19.7 10.2 5.1

As (soluble) μg/L 8 3.8 10.9 7.1 2.6

As (particulate) μg/L 8 <0.1 11.7 3.2 4.1

pH — 7 7.6 7.9 7.8 0.1

Total Al μg/L 8 <11 113 47 44

Total Fe μg/L 8 174 1367 535 420

Total Mn μg/L 8 52.8 572 169 174

Dissolved Al μg/L 8 <11 <11 <11 NA

Dissolved Fe μg/L 8 <30 127 37.9 39.3

Dissolved Mn μg/L 8 33.2 235 78.3 67.0
28

Table 4-7. Previous Analytical Results of Sludge Sampling at Plant A (1996–1997)

Analyte Description October 1996 March 1997 May 1997

Total Arsenic Number of samples 10 10 10

Minimum concentration (mg/kg) 110 73 110

Maximum concentration (mg/kg) 740 370 210

80% UCL concentration (mg/kg) 418 265 180

Regulatory level (mg/kg) 500 500 500

Arsenic-STLC Number of samples 10 10 10

Minimum concentration (mg/L) 4.1 5 9.5

Maximum concentration (mg/L) 37 21 15

80% UCL concentration (mg/L) 22 15 13

Regulatory level (mg/L) 5 5 5

Arsenic-TCLP Number of samples 10 10 10

Minimum concentration (mg/L) <0.2 <0.2 <0.2

Maximum concentration (mg/L) <0.2 0.3 0.3

80% UCL concentration (mg/L) NA NA NA

Regulatory level (mg/L) 5 5 5

UCL = upper confidence level.

barium, cadmium, chromium, lead, mercury,selenium, and 

silver. The sample collected from location 2 did not have 

the same appearance as the samples from locations 1

and 3. It was reported to look more like soil than dried

sludge. This difference in appearance probably accounts 

for the differences in measured arsenic and iron concentrations between the location 2 sample and the samples 

from locations 1 and 3. Assuming that the samples collected from locations 1 and 3 are more representative of 

the sludge produced by Plant A, total arsenic concentrations were 806 and 880 mg/kg dry, respectively, and 

total iron concentrations were 83,200 and 95,000 mg/kg 

dry, respectively. These total arsenic concentrations exceed the regulatory levels for total arsenic in California,

which would classify this sludge as hazardous waste.

Arsenic was detected in one sample leachate at a concentration of 0.106 mg/L, which was well below the regulatory limit of 5 mg/L. Table 4-8 presents the results of

sludge analysis at each of the three sampling locations.

4.3 Plant B

Water and residual samples were collected and analyzed 

at Plant B, a coagulation/filtration plant, during three

phases of the study: source water sampling, preliminary 

sampling, and long-term evaluation. Source water sampling at Plant B was performed in February 1998. Preliminary sampling consisted of weekly water sampling for 

a 4-week period in April/May 1998 and was designed to 

determine if the sampling locations and proposed water 

quality analysis were appropriate for the third phase, longterm evaluation. The third phase was initiated in June

1998 and continued through June 1999. Arsenic speciation sampling was conducted every fourth week. The third 

phase of this study also included residual sample collection and analysis. Supernatant water samples from the

settling tank were collected monthly beginning in November 1998, and three sludge samples were collected during 

a single sampling event from a dewatered sludge lagoon.

Table 4-8. Analytical Results of Sludge Sampling at Plant A (December 2, 1998)

Parameter Unit DL Location 1 Location 2 Location 3

As-TCLP mg/L 0.05 0.106 <0.05 <0.05

Ba-TCLP mg/L 1.0 1.1 1.1 <1.0

Cd-TCLP mg/L 0.020 <0.020 <0.020 <0.020

Cr-TCLP mg/L 0.030 <0.030 <0.030 <0.030

Pb-TCLP mg/L 0.50 <0.50 <0.50 <0.50

Hg-TCLP mg/L 0.0002 <0.0002 <0.0002 <0.0002

Se-TCLP mg/L 0.05 <0.050 <0.050 <0.050

Ag-TCLP mg/L 0.020 <0.020 <0.020 <0.020

TCLP extraction NA NA Complete Complete Complete

pH — — 7.0 8.1 7.2

Percent moisture % 0.1 31.6 14.6 38.6

Total As mg/kg, dry 2.0 806 9.0(a) 880

Total Fe mg/kg, dry 1,370 83,200 17,600 95,000

(a) Confirmed by sample re-analysis. The sample looked like soil instead of dry sludge.

DL = Detection limit.
29

4.3.1 Plant B Description

Plant B is used to treat surface water for a population of 

approximately 65,000. The plant processes 6 to 8 mgd

during the winter months and 30 to 35 mgd during the

summer. The design flowrate is 62.5 mgd. The plant utilizes coagulation, sedimentation, and filtration for water

treatment. Figure 4-6 is a schematic diagram of the treatment process used at Plant B.

The treatment process at Plant B consists of the following major elements:

• Screening. Screening is required to remove 

debris from the raw water at the river intake.

• Pre-Chlorination. Approximately 3 to 4 mg/L of 

chlorine is added to the raw water for disinfection 

and to provide residual chlorine for the distribution 

system.

• Rapid Mixing. Depending on influent turbidity, 

25 to 30 mg/L of alum is added to the water. Also, 

0.75 mg/L Cat Floc-TL polymer is used when 

water temperature is less than 10°C, typically 

October through April. Jar testing conducted by 

the treatment plant was used to develop relationships for estimating alum dosage based on 

influent turbidity.

• Flocculation. Flocculation of alum hydroxide and 

various contaminants, including arsenic, occurs

during this treatment process. During late 

summer, powdered activated carbon (PAC) may 

be added for taste and odor control.

• Sedimentation. Sedimentation of flocs occurs in 

primary and secondary clarifiers.

• Filtration. Additional solids removal is accomplished through filtration. Filtering is accomplished 

with a dual media consisting of anthracite and 

sand. Backwashing occurs approximately every 

50 hours.

• Clearwell Storage. Ammonia is added prior to 

clearwell storage to form monochloramine. No 

posttreatment chlorination is performed.

• Backwash. Backwashing occurs approximately 

every 50 hours. The sludge eventually is sent to a 

landfill and the supernatant water from the sludge 

lagoon is discharged to the Missouri River under a 

state permit.

4.3.2 Initial Source Water Sampling

Plant B influent water is supplied from the Missouri 

River. Based on discussions with plant personnel, the

turbidity ranges from 2 to 3 NTU in the winter and between 10 and 100 NTU during the spring and summer

due to snow melt and rain. The primary source of arsenic in the source water is believed to come from the

Yellowstone Basin that drains into the Madison River,

the largest tributary of the Missouri River. Historically,

Figure 4-6. Schematic Diagram, Plant B
30

arsenic concentrations in the source water have ranged 

from 16 to 25 μg/L.

An initial site visit to Plant B was conducted on February 

5, 1998, during which time source water samples were

collected. During this sampling event, samples were collected and analyzed for arsenic (total, particulate, soluble, 

As[III], As[V]) and various other water quality parameters 

that may affect arsenic removal. Table 4-9 presents the 

analytical results from the source water sampling. The

total arsenic concentration in the source water averaged 

21.2 μg/L. Particulate arsenic averaged 1.4 μg/L of the

total, and all of the soluble arsenic was As(V). The inlet 

iron concentration averaged 2,790 μg/L, which was relatively high and did not correlate well with the total iron

data collected during the preliminary sampling and longterm evaluation phases. Aluminum concentrations were

less than the detection limit, and manganese concentrations were 30 μg/L.

Alkalinity concentrations averaged 122 mg/L (as CaCO3) 

and total hardness concentrations averaged 281.5 mg/L 

(as CaCO3). Therefore, the source water would be classified as hard. Based on discussions with plant personnel, turbidity concentrations are typically in the range of 

2 to 3 NTU in the winter. Consistent with this information, 

turbidity concentrations were relatively low during the

source water sampling event conducted in February, averaging 1.1 NTU. The pH averaged 8.2, which is relatively 

high for effective arsenic removal using alum (Sorg and 

Logsdon, 1978; Sorg, 1993).

4.3.3 Preliminary Sampling

Water samples collected during the preliminary sampling 

phase of this study were taken at three locations within

the treatment plant: (1) the IN; (2) PF; and (3) AF. The 

IN and PF sampling locations were open channels transporting the raw and partially treated water to the various 

treatment processes in the plant. Therefore, a scoop

was used to take grab samples at IN and PF sampling

locations. The IN sample was collected from a channel

immediately following initial screening. The PF sample

was collected from the channel located after rapid mixing, flocculation and sedimentation. A sink facet located 

in the plant was used as the AF sampling location and

represents the finished water entering the distribution

system. Figure 4-7 is a process flow diagram for Plant B 

that shows sampling locations used during the preliminary sampling, as well as the analyses performed on

samples collected from each location.

Alkalinity, turbidity, pH, total aluminum, total iron, total

manganese, TOC, and total arsenic analysis was performed on all water samples collected at Plant B. Arsenic speciation sampling was conducted at each sampling 

location once during the preliminary study. Arsenic form 

(soluble and particulate) and species (arsenate and

arsenite) were determined as part of the arsenic speciation. Table 4-10 presents the results of the 4-week preliminary sampling period.

Results from the preliminary sampling events indicated

that inlet total arsenic concentrations ranged from approximately 20.9 to 23.3 μg/L. The total arsenic in the

source water was primarily As(V) and contained only minor concentrations of As(III) and particulate arsenic. As

would be expected, the species of arsenic did not vary

significantly during the treatment process. The average 

total arsenic removal by Plant B was approximately 86% 

during preliminary sampling. In general, the majority of the

arsenic removal occurred during sedimentation (average

Table 4-9. Source Water Analytical Results at Plant B (February 5, 1998)

Parameter Units

Primary

Sample

Duplicate

Sample

Average 

Concentration

Alkalinity mg/L(a) 122 122 122

Sulfate mg/L 38 37 37.5

Turbidity NTU 1.08 1.11 1.095

pH — 8.2 8.2 8.2

Hardness mg/L(a) 286 277 281.5

Ca Hardness mg/L(a) 147 140 143.5

Mg Hardness mg/L(a) 138 138 138

Total Al μg/L <400 <400 <400

Total Fe μg/L 2,780 2,800 2,790

Total Mn μg/L 30 30 30

NO3−NO2

 (N) mg/L(b) 0.23 0.22 0.22

TOC mg/L 3 3 3

As (total) μg/L 22.5 20.0 21.2

As (total soluble) μg/L 20.3 19.3 19.8

As (particulate) μg/L 2.2 0.7 1.4

As(III) μg/L <0.1 <0.1 <0.1

As(V) μg/L 20.3 19.3 19.8

(a) As CaCO3.

(b) Combined NO3−N and NO2−N.
31

INFLUENT

SCREENING

1

RAPID MIXING

BASIN

FLOCCULATION

SECONDARY

CLARIFIER (2)

2

FILTRATION

3

DISTRIBUTION

SYSTEM

MONTHLY WEEKLY

As (total), Alkalinity, pH,

TOC, Turbidity, Total Al,

Total Fe, Total Mn

As (total), As (III), As (V)

Plant B

Coagulation/Filtration

Design Flow: 62.5 mgd

DA: Cl2

LEGEND

SS

DA: Cl2

FILTRATION

Al2(SO4)

3

Sludge Sampling

Location

Disinfectant Addition

Point

Unit Process

Chemical Added to

Unit Process

Cat Floc-TL Polymer

NH3

PRIMARY

CLARIFIER (5)

1 Water Sampling

Location

SETTLING

TANK

Backwash Water

SUPERNATANT WATER

DISCHARGED TO

MISSOURI RIVER

SS

As (total), Water Content,

pH, TCLP metals

As (total), Alkalinity, pH,

TOC, Turbidity, Total Al,

Total Fe, Total Mn

As (total), As (III), As (V)

As (total), Alkalinity, pH,

TOC, Turbidity, Total Al,

Total Fe, Total Mn

As (total), As (III), As (V)

4

As (dissolved and total),

pH

SETTLING

LAGOON

SLUDGE SENT TO

LANDFILL

Al2(SO4)

3

Figure 4-7. Process Flow Diagram and Sampling Locations at Plant B
3

2

Table 4-10. Analytical Results from Preliminary Sampling at Plant B (April 23, 1998 through May 14, 1998)

Sampling Date and Location

4/23/98(a) 4/30/98 5/7/98 5/14/98

Parameter Units IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(b) 134

136

114

114

114

114 132 111 110 132 113 112 127 107 107

Turbidity NTU 4

4

0.8

0.8

<0.1

<0.1 6.3 <0.1 <0.1 7 1.0 <0.1 5.1 0.7 <0.1

pH —

8.5

8.5

7.4

7.4

7.4

7.4 8.7 7.5 7.5 8.7 7.4 7.3 8.5 7.5 7.4

Total Al μg/L 500

<400

500

500

<400

<400 500 600 <400 680 590 <400 450 530 <400

Total Fe μg/L 500

420

40

50

40

50 440 40 <30 540 40 <30 400 50 <30

Total Mn μg/L 70

90

40

50

40

50 60 <20 <20 40 <20 <20 50 40 30

TOC mg/L 3

3

3

3

3

3

3 3 3 3 3 3 3 3 3

As (total) μg/L 23.3

23.0

6.1

5.7

3.4

3.3 23.3 6.9 4.1 21.2 5.5 2.7 20.9 4.2 2.4

As (total 

soluble) μg/L 24.226.3

4.2

4.1

4.4

4.6

NA NA NA NA NA NA NA NA NA

As (particulate) μg/L ND

ND

1.9

1. 7

ND

ND

NA NA NA NA NA NA NA NA NA

As(III) μg/L 0.8

0.7

0.3

0.4

0.3

0.4

NA NA NA NA NA NA NA NA NA

As(V) μg/L 23.4

25.6

3.9

3.6

4.1

4.2

NA NA NA NA NA NA NA NA NA

(a) Duplicate samples were taken on 4/23/98.

(b) As CaCO3

.

NA = not applicable.

ND = not detected.
33

75%). Additional arsenic removal occurred during filtration to achieve the 86% average removal, leaving only

2.4 to 4.2 μg/L in the finished water.

Very good correlation with the sorption model proposed 

by McNeill and Edwards (1997a) was observed. Predicted arsenic removal ranged between 89 and 91%,

while actual removals ranged between 82 and 89%. The 

largest deviation between the predicted and actual arsenic removal was 10%, which is within the 90th percentile 

confidence interval of the model. Therefore, this simplified sorption model appeared to approximate the system 

performance and was used in evaluating long-term data.

Other water quality parameters were analyzed to support 

understanding of the mechanisms of arsenic removal.

TOC concentrations were relatively constant (i.e., 3 mg/L)

throughout the treatment process, indicating no significant TOC removal by the plant. Similar to Plant A, the

lack of TOC removal does not appear to impact arsenic 

removal.

During alum coagulation, the alum reacts with natural

alkalinity to form aluminum hydroxide:

Al2(SO4)·14.3H2O + Ca(HCO3) → 2Al(OH)3

+ 3CaSO4 + 14.3H2O +6CO2

(3)

Therefore, alkalinity concentrations and pH values decreased between the inlet and prefiltration sampling 

locations. Average alkalinity concentrations decreased

from 132 to 111 mg/L (as CaCO3) and average pH values decreased from 8.6 to 7.5. The alkalinity and pH then

remained constant between the prefiltration and afterfiltration sampling locations. Turbidity concentrations averaged 5.6 NTU during the preliminary sampling phase.

These turbidity values are almost 6 times higher than the 

values observed during the preliminary sampling event;

however, this would be expected due to snow melt and 

precipitation during the spring months.

Total aluminum concentrations ranged between <400

and 680 μg/L in the inlet and between 500 and 600 μg/L 

in the prefiltration location. Total aluminum was less than 

detection during all four sampling events at the afterfiltration sampling location. An increase in aluminum

concentration due to the addition of alum is not observed 

at the prefiltration sampling location because it is located 

after sedimentation. However, based on plant alum dosage data, the calculated aluminum concentration available for coagulation ranged between 2.5 and 4.1 mg/L. 

Total manganese concentrations ranged from 40 to

90 μg/L in the inlet and <20 to 50 μg/L in the prefiltration 

and after-filtration locations. The total iron concentrations 

averaged 460 μg/L at the inlet, 44 μg/L at the prefiltration 

sampling location, and <30 μg/L at the after-filtration 

sampling location. The inlet iron concentrations were significantly lower than the concentration obtained during

the source water sampling event and consistent with the 

concentrations observed during the long-term evaluation phase. It appears that arsenic removal is primarily

achieved through adsorption and coprecipitation of As(V) 

with the aluminum flocs formed from the alum coagulant 

and the iron in the source water.

Based on the results of the preliminary sampling effort,

only minor changes were made to the approach for the

long-term evaluation. As with Plant A, sampling locations 

and primary analytes remained unchanged; however, 

aluminum, iron, and manganese analyses were modified 

to ICP-MS. Also, part of the sample in bottle B from the 

arsenic speciation kits was used to determine dissolved 

aluminum, iron, and manganese concentrations.

4.3.4 Long-Term Sampling

Long-term sampling and analysis consisted of 49 weeks 

of water sampling at the same three locations used during the preliminary sampling phase. All weekly samples 

were analyzed for alkalinity, turbidity, pH, total aluminum, total iron, total manganese, TOC, and total arsenic. 

Arsenic speciation sampling was conducted at each sampling location 12 times during the long-term sampling 

phase on samples collected from each sampling location 

and included determination of dissolved aluminum, iron, 

and manganese concentrations. Supernatant discharge

water and sludge sampling and analysis also was performed during this phase. The following subsections summarize the arsenic, other water quality parameters, and 

residuals analytical results.

4.3.4.1 Arsenic

Table 4-11 provides a summary of the arsenic analytical 

results collected at the three sampling locations. Total

arsenic concentrations at the inlet ranged from 15 to 

23.9 μg/L with an average concentration of 19.1 μg/L. 

These arsenic concentrations correspond well with the

historical data collected by the plant where total arsenic 

concentrations have ranged from 16 to 25 μg/L. Total

arsenic concentrations at the prefiltration location ranged 

from 3.0 to 15.5 μg/L with an average of 6.4 μg/L. Therefore, an average arsenic removal rate of 66% occurred

prior to filtration in the sedimentation basins. Samples

collected after-filtration location contained total arsenic

concentrations ranging from 1.5 to 11.8 μg/L with an

average concentration of 4.0 μg/L. The average removal 

percentage of total arsenic (comparing raw water and

finished water concentrations) was 79%. These removal 

percentages were calculated based on an average of all 

total arsenic data collected during the long-term evaluation, including the 6-week period when a polyaluminum
34

Table 4-11. Summary of Arsenic Analytical Results at Plant B (June 1998–June 1999)

Parameter Sample Location Units

Number of 

Samples

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

As (total) Inlet μg/L 49 15 23.9 19.1 2.4

Prefiltration μg/L 49 3.0 15.5 6.4 2.7

After filtration μg/L 49 1.5 11.8 4.0 2.7

As Inlet μg/L 12 18.3 23.0 20.3 1.3

(total soluble) Prefiltration μg/L 12 2.1 12.1 4.3 3.1

After filtration μg/L 12 2.2 12.5 4.6 3.2

As Inlet μg/L 12 <0.1 0.6 0.2 0.2

(particulate) Prefiltration μg/L 12 0.6 4.5 2.6 1.2

After filtration μg/L 12 <0.1 0.3 <0.1 0.1

As(III) Inlet μg/L 12 0.1 1.2 0.6 0.3

Prefiltration μg/L 12 <0.1 1.2 0.4 0.3

After filtration μg/L 12 <0.1 0.8 0.4 0.2

As(V) Inlet μg/L 12 17.9 21.8 19.7 1.2

Prefiltration μg/L 12 1.8 11.8 3.9 3.2

After filtration μg/L 12 1.9 12.1 4.2 3.3

One-half of the detection limit was used for nondetect samples for calculations.

Primary and duplicate samples were averaged for calculation.

chloride coagulant was used instead of alum. The removal efficiencies observed during the long-term evaluation correspond well with the removal percentages observed during the preliminary sampling phase (75% and 

86% arsenic removal achieved at the PF and AF sampling locations, respectively). Figure 4-8 is a graph

showing the total arsenic concentration recorded at each 

sampling location throughout the study.

Particulate arsenic concentrations averaged 0.2 μg/L at

the inlet, 2.6 μg/L at the prefiltration sampling location,

and <0.1 μg/L at the after-filtration sampling location. The 

increase of particulate arsenic at the prefiltration sampling location was attributed to the sorption and coprecipitation of the arsenic and the aluminum flocs. The decrease of particulate arsenic in the after-filtration sampling location supports this observation. The low levels of 

particulate arsenic at the after-filtration location indicated 

that the system effectively removes arsenic sorbed to

metal flocs.

As(III) and As(V) make up the soluble portion of the total 

arsenic concentration. Throughout the duration of the

study and at each sampling location, As(V) made up the 

majority of the soluble arsenic, averaging 97, 90, and

91% at the IN, PF, and AF sampling locations, respectively. As(III) concentrations averaged 0.6 μg/L at the

inlet, 0.4 μg/L at the prefiltration location, and 0.4 μg/L at 

the after-filtration location. The treatment process removed approximately 33% of the inlet As(III). This removal was probably due to conversion of As(III) to As(V) 

during chlorination, followed by sorption/occlusion with

alum flocs, sedimentation, and filtration. Average As(V)

concentrations were 19.7 μg/L at the inlet, 3.9 μg/L at

the prefiltration location, and 4.2 μg/L at the after-filtration 

location. The As(V) concentration decreased at the prefiltration location due to adsorption and coprecipitation of

the arsenic with the aluminum flocs in the sedimentation 

basins. This result correlated with the increase in particulate arsenic at this same location. Figure 4-9 shows 

the fractions of the total arsenic concentration made up 

of particulate arsenic, As(III), and As(V).

As seen in Figure 4-9, a significant decrease in arsenic 

removal efficiency was observed beginning October 29,

1998, and continuing through December 10, 1998. This 

decrease in removal efficiency corresponded to an operational change at the plant. During this period, Plant B 

was testing an alternative coagulant to alum called PAX18, which is a liquid polyaluminum chloride coagulant

that is supposed to reduce the amount of sludge produced. During the six sampling events that occurred 

while this alternative coagulant was used, total arsenic

concentrations averaged 18.8 μg/L at the inlet, 12.9 μg/L 

at the prefiltration location, and 10.8 μg/L at the afterfiltration location. In comparison, results from total arsenic concentrations measured during the 43 sampling

events when alum was used as the coagulant averaged 

19.1 μg/L at the inlet, 5.5 μg/L at the prefiltration location, and 3.0 μg/L at the after-filtration location. These

results correspond to arsenic removal efficiency of 43% 

when the PAX-18 coagulant was being used and 84%

when the alum coagulant was used.

Removal efficiency using alum correlated very well to the 

simple sorption model (McNeill and Edwards, 1997a). In 

fact, the maximum deviation between the calculated and 

actual removal was 12%, which is within the 90th percentile confidence interval of the model. Based on the

correlation, it is believed that arsenic removal is achieved

through adsorption on and coprecipitation with the aluminum flocs. The iron concentrations in the source water,
35

0

5

10

15

20

25

30

6/4/98 7/24/98 9/12/98 11/1/98 12/21/98 2/9/99 3/31/99 5/20/99 7/9/99

Date

Arsenic Concentration (μg/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Percent Arsenic Removal

Inlet

Prefiltration

After Filtration

% Removal

Figure 4-8. Total Arsenic Analytical Results During Long-Term Sampling at Plant B

which were figured into the sorption model, also may

contribute to arsenic removal because the particulate 

arsenic at the inlet is most likely attached to the iron.

Removal efficiency using the PAX-18 did not correlate

well to the sorption model. Actual arsenic removal was

28 to 42% less than removal predicted by the model. 

Based on the arsenate results at the outlet, it appeared 

that significantly less As(V) attached to the aluminum

flocs produced by the PAX-18 than the alum. Research 

indicates that arsenate removal efficiency decreases

above pH 7 using alum (Sorg and Logsdon, 1978; Sorg, 

1993). During operation with PAX-18, the average pH of 

the finished water increased from 7.4 to 7.8. This

increase may explain the difference in removal efficiency. Additional research is needed to identify the mechanisms affecting removal of arsenic using polyaluminum 

chloride. However, this study indicated that removal efficiency using PAX-18 was significantly less than alum.

The Plant B water treatment system was able to consistently remove arsenic to low levels when alum is used 

as the coagulant (i.e., average treated water total arsenic concentration was 3.0 μg/L when alum was used as 

the coagulant). The primary arsenic removal mechanism 

was adsorption and coprecipitation with the alum coagulant followed by sedimentation and filtration. Based on

the literature, increased arsenic removal could possibly

be achieved by lowering pH to 7 or below and by increasing coagulant dosage.

4.3.4.2 Other Water Quality Parameters

Other water quality parameters also were analyzed to

provide information regarding the ability of the treatment 

plant to remove arsenic. Table 4-12 summarizes the

analytical results for several water quality parameters

obtained during long-term sampling.

Alkalinity concentrations ranged from 119 to 146 mg/L

(as CaCO3) in the inlet with an average of 131 mg/L. Figure 4-10 shows that alkalinity in the source water fluctuated slightly seasonally with the lowest concentrations 

in the late summer and the highest concentrations in the 

spring. Concentrations decreased between the inlet and 

prefiltration sampling location and remained relatively

constant between the prefiltration and after-filtration locations. These data do not appear to correlate with arsenic 

analytical results or removal efficiencies.

During long-term sampling, turbidity concentrations averaged 3.4 NTU at the inlet, 0.8 NTU at the prefiltration 

location, and <0.1 NTU at the after-filtration location. Inlet turbidity concentrations ranged from 11.8 to 1.0 NTU 

and varied seasonally (see Figure 4-10). The highest turbidities were observed in the late spring, corresponding
36

0

5

10

15

20

25

7/16/98

8/6/989/3/98

10/1/98

10/29/98

12/3/981/14/992/11/993/11/99

4/8/995/6/996/3/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

0

5

1 0

1 5

2 0

2 5

7/16/98

8/6/989/3/98

10/1/98

10/29/98

12/3/981/14/992/11/993/11/99

4/8/995/6/996/3/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

0

5

1 0

1 5

2 0

2 5

7/16/98

8/6/989/3/98

10/1/98

10/29/98

12/3/981/14/992/11/993/11/99

4/8/995/6/996/3/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

Inlet

Prefiltration

After Filtration

Figure 4-9. Arsenic Form and Species Analytical Results During Long-Term Sampling at Plant B
37

Table 4-12. Summary of Water Quality Parameter Analytical Results at Plant B (June 1998–June 1999)

Parameter Sample Location Units

Number of 

Samples

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

Alkalinity Inlet mg/L 49 119 146 131 7.8

Prefiltration mg/L 49 96 132 114 10.2

After filtration mg/L 49 96 126 113 9.4

Turbidity Inlet NTU 49 1 11.8 3.4 2.3

Prefiltration NTU 49 0.3 1.2 0.8 0.2

After filtration NTU 49 <0.1 0.3 <0.1 0.04

pH Inlet — 49 7.9 8.6 8.4 0.1

Prefiltration — 49 7.2 8.1 7.5 0.2

After filtration — 49 7.2 8 7.4 0.2

TOC Inlet mg/L 49 2.8 9.8 3.7 1.0

Prefiltration mg/L 49 2.3 8.6 3.1 0.9

After filtration mg/L 49 1.7 8.7 3.1 0.9

Total Al Inlet μg/L 49 43.4 501 173 129.7

Prefiltration μg/L 49 67.6 809 493 145.3

After filtration μg/L 49 28.1 98 56 18.2

Total Fe Inlet μg/L 49 32.2 507 164 129.3

Prefiltration μg/L 49 <30 75.6 <30 14.1

After filtration μg/L 49 <30 57.4 <30 6.4

Total Mn Inlet μg/L 49 11.0 39.0 19.6 7.1

Prefiltration μg/L 49 0.6 18.2 9.3 3.7

After filtration μg/L 49 <0.5 5.8 0.7 0.8

Dissolved Al Inlet μg/L 12 <11 <11 <11 NA

Prefiltration μg/L 12 41.7 120 73 22.4

After filtration μg/L 12 25.7 77 43 17.1

Dissolved Fe Inlet μg/L 12 <30 <30 <30 NA

Prefiltration μg/L 12 <30 <30 <30 NA

After filtration μg/L 12 <30 <30 <30 NA

Dissolved Mn Inlet μg/L 12 1.8 7.5 4.0 1.9

Prefiltration μg/L 12 1.3 9.7 5.5 2.7

After filtration μg/L 12 <0.5 <0.5 <0.5 NA

One-half of the detection limit was used for nondetect samples for calculations.

Primary and duplicate samples were averaged for calculations.

to snow melt and spring rains, while the lowest values 

were observed in the winter. Coagulant dosages were

determined by the source water turbidity concentration 

and ranged from 29.0 to 44.7 lb/day (2.6 to 4.1 mg/L) 

when alum was used and 14.0 to 16.7 lb/day (1.3 to

1.5 mg/L) when PAX-18 was used. The data show that

Plant B effectively removed turbidity from the source

water; however, no correlation between turbidity removal 

and arsenic removal was observed. Turbidity removal

was still very good (i.e., typically <0.1 NTU) when the

plant was using PAX-18, although PAX-18 was used

during the winter when turbidities were lowest.

The average pH was 8.4 at the inlet, 7.5 before filtration, 

and 7.4 after filtration. As seen in Figure 4-10, inlet pH 

was constant throughout the duration of the study. As

stated previously, the pH increase, noted at the beforeand after-filtration sampling locations, during usage of

the PAX-18 may have adversely affected the arsenic 

removal efficiency. TOC concentrations were relatively

constant (see Figure 4-10), with averages of 3.7 mg/L,

3.1 mg/L, and 3.1 mg/L at the inlet, prefiltration, and

after-filtration sampling locations, respectively. A spike in 

the TOC concentration was observed on May 20, 1999, 

although the cause is not known. Eliminating this data

point would reduce the average TOC concentrations to

3.5, 3.0, and 3.0 mg/L at the IN, PF, and AF sampling

locations, respectively. The decrease in TOC between

the inlet and prefiltration sampling location is most likely 

due to the coagulation process followed by sedimentation. The decrease corresponded to an average 14%

TOC removal.

Total aluminum concentrations averaged 173 μg/L at the 

inlet, 493 μg/L before filtration, and 56 μg/L after filtration. 

The average dissolved aluminum concentrations were

<11 μg/L at the inlet, 73 μg/L at the prefiltration location, 

and 43 μg/L at the after-filtration location. The increase

in total and dissolved aluminum at the prefiltration sampling location was due to the use of alum as the coagulant. Based on plant data, alum dosages ranged from

29 to 44.7 lb/day during the study, corresponding to aluminum concentrations ranging from 2,600 to 4,100 μg/L. 

The PAX-18 dosages ranged from 14 to 16.7 mg/L, 

corresponding to aluminum concentrations of 1,300 to

1,500 μg/L. These relatively high aluminum concentrations
38

0

2

4

6

8

10

12

14

6/4/98 7/24/98 9/12/98 11/1/98 12/21/98 2/9/99 3/31/99 5/20/99 7/9/99

Date

Measurement (Turbidity, pH, TOC)

0

20

40

60

80

100

120

140

160

Measurement (Alkalinity)

Turbidity (NTU)

pH (units)

TOC (mg/L)

Alkalinity (mg/L as CaCO3)

Figure 4-10. Inlet Turbidity, pH, TOC, and Alkalinity Analytical Results at Plant B

were not observed at the prefiltration location because it 

was located after the sedimentation basin.

Total manganese concentrations averaged 19.6 μg/L, 

9.3 μg/L, and 0.7 μg/L, at the inlet, prefiltration, and afterfiltration sampling locations, respectively. Average dissolved manganese concentrations were 4.0 μg/L at the

inlet, 5.5 μg/L at the prefiltration location, and <0.5 μg/L 

at the after-filtration location. These relatively minor manganese concentrations probably did not have a significant impact on arsenic removal efficiency.

Total iron concentrations at the inlet sampling location 

ranged from 32.2 μg/L to 507 μg/L and averaged 164 μg/L. 

At the prefiltration sampling location, total iron concentrations ranged from <30 to 75.6 μg/L and averaged 

<30 μg/L. The average total iron concentration at the

after-filtration sampling location was <30 μg/L. Also, average dissolved iron concentrations were below the detection limit at the inlet, prefiltration, and after-filtration sampling locations. These data indicate that iron probably was 

not a major factor in As(V) removal during treatment operations. However, arsenic may have been attached to the 

iron particles in the raw water, showing up as particulate 

arsenic, which were subsequently removed.

4.3.4.3 Supernatant Discharge Water

The filter backwash water at Plant B is sent to a sludge 

settling pond and the supernatant is discharged to the

adjacent river under a state permit. Supernatant discharge water samples were collected from a manhole

located in the piping that transports the water from the

sludge settling lagoon to the river. Total arsenic concentrations ranged from 4.6 to 56.1 μg/L and averaged

14.0 μg/L, approximately half of which was soluble and

half particulate. Total aluminum concentrations ranged

from 359 to 7,500 μg/L and total iron concentrations 

ranged from <30 to 191.5 μg/L. Results of supernatant 

discharge sampling are summarized in Table 4-13.

4.3.4.4 Sludge

Sludge is generated at Plant B from sedimentation in

primary and secondary clarifiers and from backwashing 

filters. For most of the year, wastewater and sludge from 

the clarifiers is sent directly to a sludge lagoon. However, the wastewater and sludge are sent directly to the 

sanitary sewer for 3 to 4 months in the winter due to

freezing conditions in the lagoon.

Backwashing occurs approximately every 50 hours. Backwash water is sent to a sludge settling tank. Sludge is

transferred from the settling tank and combined with the 

wastewater and sludge from the clarifiers prior to discharge into the sludge lagoon. Approximately once per

year, the sludge lagoon is dewatered using an underdrain 

system and the dewatered sludge is sent to a landfill. 

The volume of sludge sent to the landfill has not been

recorded, nor has metals analysis been performed.
39

Table 4-13. Summary of Analytical Results from Supernatant Discharge Water Samples at Plant B 

(November 12, 1998–June 17, 1999)

Parameter Units

Number of

Sampling Events

Minimum

Concentration

Maximum

Concentration

Average

Concentration

Standard

Deviation

As (total) μg/L 8 4.6 56.1 14.0 17.6

As (soluble) μg/L 8 2.5 19.2 6.7 5.8

As (particulate) μg/L 8 0.2 44.9 7.3 15.2

pH 8 7.5 8.0 7.8 0.2

Total Al μg/L 8 359 7,500 1,610 2,457

Total Fe μg/L 8 <30 191.5 49.3 60.7

Total Mn μg/L 8 7.1 160.5 32.5 52.1

Dissolved Al μg/L 8 46.4 2,216.0 327.7 763.2

Dissolved Fe μg/L 8 <30 62.7 <30 16.9

Dissolved Mn μg/L 8 <0.5 22.5 4.0 7.6

Sludge samples were collected on December 15, 1998

from three locations from within a dewatered sludge 

lagoon. These sludge samples were analyzed for pH,

percent moisture, total arsenic, and total iron. Also, a

TCLP test was performed on each sample to determine 

the quantity of leachable arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver. Total arsenic concentrations ranged from 293 to 493 mg/kg dry,

and total iron concentrations ranged from 14,600 to

15,800 mg/kg dry. Arsenic was detected in leachate from

all three samples at concentrations as high as 0.160 mg/L; 

however these concentrations were well below the regulatory limit of 5 mg/L. Table 4-14 presents the results of

sludge analysis at each of the three sampling locations.

4.4 Plant C

Water and residual samples were collected and analyzed

at Plant C, a lime softening plant, during three phases of 

the study: initial source water sampling (February 1998), 

preliminary sampling (April and May 1998) and long-term 

evaluation (June 1998 to June 1999). Arsenic speciation 

sampling was conducted during the initial source water

sampling, once during preliminary sampling, and every

fourth week during the long-term evaluation. The third

phase also included residual sample collection and analysis. Supernatant discharge water samples were collected 

monthly beginning in November 1998, and three sludge 

samples were collected during a single sampling event

from a dewatered sludge lagoon.

4.4.1 Plant C Description

Plant C serves a population of approximately 35,000

(more than 14,000 taps). The plant processes approximately 6.1 mgd and the design flowrate is 10 mgd. The 

plant treats ground water using a lime softening process 

followed by sand filtration. Figure 4-11 is a schematic

diagram of the treatment process used at Plant C.

The treatment process at Plant C consists of the following major elements:

• Intake. Raw ground water from multiple wells (up 

to 4) is combined in a common header.

• Aeration. Aeration is used to oxidize iron.

Table 4-14. Analytical Results of Sludge Sampling at Plant B (December 15, 1998)

Parameter Units DL Location 1 Location 2 Location 3

As-TCLP mg/L 0.05 0.058 0.160 0.114

Ba-TCLP mg/L 1.0 1.3 1.2 1.2

Cd-TCLP mg/L 0.020 <0.020 <0.020 <0.020

Cr-TCLP mg/L 0.030 <0.030 <0.030 <0.030

Pb-TCLP mg/L 0.20 <0.500 <0.500 <0.500

Hg-TCLP mg/L 0.0002 <0.0002 <0.0002 <0.0002

Se-TCLP mg/L 0.05 <0.050 <0.050 <0.050

Ag-TCLP mg/L 0.020 <0.020 <0.020 <0.020

TCLP extraction NA NA Complete Complete Complete

pH — — 7.0 6.9 6.9

Percent moisture % 0.1 74.9 82.3 78.2

As (total) mg/kg, dry 61 353 493 293

Fe (total) mg/kg, dry 379 14,600 14,800 15,800
40

Figure 4-11. Schematic Diagram, Plant C

• Clarification. Immediately after aeration, lime is 

added to the water in the middle section of each 

of four precipitators (solids-contact softeners) at a 

rate of 245 mg/L (dry lime stored on site in silos). 

In each of the precipitators, lime and water are 

mixed using a paddle-wheel mixer. The retention 

time in the precipitators is approximately 60 minutes. Sludge is collected from the bottom of the 

precipitators, sent to a slurry tank, and then 

placed in a sludge lagoon. Sludge from the lagoon 

is used on local farm fields.

• Chlorination. Chlorine is added into each clarifier collection trough at a rate of approximately 

100 to 200 lbs/day (correlating to approximately 

15 mg/L).

• Filtration. Filtering media consists of 10 inches 

of graded gravel and 2 feet of sand. There are 

15 separate filtering units that are backwashed 

approximately every 80 hours. Backwashing 

includes a surface scour.

• Clearwell Storage. Treated water is chlorinated 

prior to clearwell storage. The final chlorine concentration in finished water is approximately 

6 mg/L (<0.5 mg/L free chlorine).

• Backwash. Backwashing occurs every 80 hours 

and the backwash water is combined with sludge 

from the clarifiers, sent to a slurry tank, and then 

on to a sludge lagoon. Sludge from the lagoon is 

used on local farm fields. Approximately 

230,000 gal/day of water goes to lagoons.

4.4.2 Initial Source Water Sampling

The influent water is supplied from four deep (approximately 300 ft) ground water wells. Typically, only three

wells are used due to problems with the fourth well regarding, among other things, high arsenic concentrations. 

Based on plant records, the ground water hardness is

approximately 350 to 400 mg/L (as CaCO3) and iron concentrations are approximately 2 to 2.5 mg/L. Also, the

raw water contains 70 to 100 mg/L of CO2. Based on

samples collected and analyzed by the plant, arsenic 

concentrations observed in the source water wells range 

from <0.01 to 89 μg/L. Arsenic concentrations in samples 

collected near Plant C on November 25, 1992, from each 

of the ground water wells are presented in Table 4-15.

Table 4-15. Arsenic Concentrations in Ground Water 

Wells at Plant C (1992)

Well

Number

Arsenic Concentration

(μg/L)

6 89

7 75

8 38

9 <0.01

On February 27, 1998, an initial site visit to Plant C was 

conducted and water samples were collected. The ground

water supplying Plant C is hard (averaging 336.5 mg/L as 

CaCO3), with an average calcium hardness of 214.5 mg/L

as CaCO3 and an average magnesium hardness of

121.5 mg/L as CaCO3. Plant C also had relatively high

turbidity, averaging 20.5 NTU during the source water

sampling event. Consistent with plant records, the iron

concentration was relatively high, averaging 2,370 μg/L. 

As would be expected for a ground water source, the

majority of the soluble arsenic existed as arsenite (83% 

of the soluble arsenic). As(V) was detected during the

source water sampling at an average concentration of

2.0 μg/L. Particulate arsenic was not detected in the
41

source water samples. Table 4-16 presents the analytical 

results from the source water sampling.

The average arsenic concentration detected during the

source water sampling event was 9.4 μg/L. This concentration is lower than the minimum required for inclusion

into the preliminary and long-term phases of the study.

However, the historical data indicated that the source

water concentrations were much higher (see Table 4-15).

Therefore, the plant was included in the preliminary and 

long-term sampling phases of this study. It was determined during the preliminary sampling phase of the study

that the sampling tap used during the initial source water 

sampling was not located properly (this issue is discussed in detail in Section 4.4.3).

4.4.3 Preliminary Sampling

Water samples were collected at three locations (i.e., IN, 

PF, and AF) during the preliminary sampling phase of

this study. Sampling taps were available at the IN and

AF sampling locations; however, a scoop was used to

collect samples at the PF location. The inlet sampling

location represents a combined sample from the four

ground water wells and was located in the manifold piping 

where the water from the wells is combined. The PF samples were taken from the channel surrounding precipitator 

(i.e., solids-contact softener) No. 3 that transports the

softened water to the filtration vessels. Therefore, PF

sampling location represents water that has been aerated 

and processed through the solids-contact softener. The 

AF sampling tap was located after the filtration units

and represents water that enters the distribution system.

Figure 4-12 is a process flow diagram for Plant C that

shows each of the sampling locations.

Consistent with Plants A and B, preliminary sampling at 

Plant C consisted of weekly sample collection and analysis of various parameters (alkalinity, turbidity, pH, hardness, total iron, total manganese, and total arsenic

analysis). Arsenic speciation sampling, which included

determination of soluble and particulate arsenic, was conducted once during the preliminary study on samples collected from each sampling location. Table 4-17 presents 

the results of the 4-week preliminary sampling period.

Results from the preliminary sampling events indicated

that inlet total arsenic concentrations varied widely, ranging from approximately 2.4 to 83.4 μg/L. The influent 

samples collected on April 27 and May 11, 1998, contained relatively low concentrations of arsenic (i.e., 3.5

and 2.4 mg/L, respectively), when compared to concentrations in prefiltration and postfiltration samples. Reanalysis of samples confirmed the concentrations of the 

influent samples. Similarly, the inlet concentrations observed during the source water sampling event were relatively low. Subsequent discussion with plant personnel 

determined that the cause of the problem was the sample tap location. The sampling location was situated in

the manifold piping downstream of wells 6 and 9 and

upstream of wells 7 and 8. Review of the well operation 

log indicated that well 6 (producing the highest As concentration among the four wells) was not in operation

during sampling on April 27 and May 11, 1999; however, 

well 6 was running on May 4 and May 18. As a result of 

this finding, a new sampling location downstream of all

Table 4-16. Source Water Sampling Analytical Results at Plant C (February 27, 1998)

Parameter Units Primary Sample Duplicate Sample Average Concentration

Alkalinity mg/L(a) 400 397 398.5

Sulfate mg/L 7 7 7

Turbidity NTU 20 21 20.5

pH — 7.2 7.2 7.2

Hardness mg/L(a) 341 332 336.5

Ca Hardness mg/L(a) 217 212 214.5

Mg Hardness mg/L(a) 124 119 121.5

Total Al μg/L <400 <400 <400

Total Fe μg/L 2,410 2,330 2,370

Total Mn μg/L 200 210 205

NO3–NO2

 (N) mg/L(b) <0.02 <0.02 <0.02

TOC mg/L 3 3 3

As (total) μg/L 9.4 9.4 9.4

As (total soluble) μg/L 12.0 12.0 12.0

As (particulate) μg/L ND ND ND

As(III) μg/L 10.2 9.7 9.9

As(V) μg/L 1.8 2.3 2.0

(a) As CaCO3.

(b) Combined NO3–N and NO2–N.
42

INFLUENT

1

AERATION

PRECIPITATORS

(4 Units in Parallel)

2

FILTRATION

3

DISTRIBUTION

SYSTEM

MONTHLY

As (total), Alkalinity, pH,

Hardness, Turbidity,

Total Fe, Total Mn

As (total), As (III), As (V)

Plant C

Lime Softening

Design Flow: 10 mgd

DA: Cl2

LEGEND

1

DA: Cl2

FILTRATION

Lime

Lime

Sampling Location

Disinfectant Addition

Point

Unit Process

Chemical Added to

Unit Process

WEEKLY

SS Sludge Sampling 

Location

SETTLING

LAGOON

Backwash Water

SS

As (total), Water Content,

 pH, TCLP metals

As (total), Alkalinity, pH,

Hardness, Turbidity,

Total Fe, Total Mn

As (total), As (III), As (V)

As (total), Alkalinity, pH,

Hardness, Turbidity,

Total Fe, Total Mn As (total), As (III), As (V)

NOTE:

Prefiltration water samples were

collected from Precipitator 3.

DA: Cl2

SUPERNATANT WATER

DISCHARGED TO BAYU TECHE

As (dissolved and total), pH

4

SLURRY

TANK

SLUDGE USED ON LOCAL

FARM FIELDS

Figure 4-12. Process Flow Diagram and Sampling Locations at Plant C
4

3

Table 4-17. Analytical Results from Preliminary Sampling at Plant C (April 27, 1998 through May 18, 1998)

Sampling Date and Location

4/27/98(a) 5/4/98 5/11/98 5/18/98

Parameter Units IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(b) 395

384

180

180

191

189 378 190 208 403 239 201 366 217 202

Turbidity NTU 21

22

4.5

4.5

0.1

0.1 9.5 1.1 1.4 18.7 8.1 0.2 34 4.2 0.1

pH —

7.2

7.2

9.1

9.2

8.5

8.4 7.3 9.1 8.5 7.3 8.6 8.6 7.2 8.8 8.8

Hardness mg/L(b) 317

317

154

123

152

156 313 181 166 332 190 160 255 145 133

Ca Hardness mg/L(b) 195

195

46.9

33.2

42.4

46.4 195 61.9 48.9 210 75.9 48.4 165 51.4 42.7

Mg Hardness mg/L(b) 122

122

107

89.4

109

110 118 119 117 122 114 112 90.6 93.5 90.6

Total Fe μg/L 2,100

2,090

590

590

90

100 3,440 640 <30 2,030 500 <30 3,840 440 40

Total Mn μg/L 230

210

40

50

40

40 160 50 <20 160 <20 <20 130 <20 <20

As (total) μg/L 3.5

3.7

31.4

36.6

24.4

28.8 43.6 35.5 18.8 2.4 43.3 22.6 83.4 51.0 41.6

As (total soluble) μg/L 5.1

4.7

34.6

38.3

28.9

33.1 NA NA NA NA NA NA NA NA NA

As (particulate) μg/L ND

ND

ND

ND

ND

ND NA NA NA NA NA NA NA NA NA

As (III) μg/L 3.9

4.1

2.3

<0.1

1.5

1.8 NA NA NA NA NA NA NA NA NA

As (V) μg/L ND

0.6

32.3

38.6

27.4

31.3 NA NA NA NA NA NA NA NA NA

(a) Duplicate samples were taken on 4/27/98.

(b) As CaCO3

.
44

wells (i.e., wells 6, 7, 8, and 9) was used for the long-term 

sampling phase of the study. This new sample tap was 

located just prior to aeration, the first treatment process

implemented at Plant C.

The inappropriate sampling location used during the preliminary sampling events complicates evaluation of

arsenic removal efficiency. However, some observations 

regarding the arsenic can be made. For example, the

soluble arsenic in the raw water entering the treatment

plant was approximately 94% As(III). This level would be 

expected for a ground water source. It appeared that the 

majority of the As(III) was oxidized to As(V) prior to

filtration using two chlorine treatment steps. The average 

As(V) concentration observed at the sampling location 

situated after softening and chlorine addition made up

approximately 97% of the soluble arsenic. The soluble

arsenic in the finished water consisted of approximately 

95% As(V). Particulate arsenic was not detected in any 

of the samples collected during the preliminary sampling.

Total arsenic concentrations in the finished water ranged 

between 18.8 μg/L and 41.6 μg/L and averaged 27.4 μg/L.

Although arsenic removal efficiency could not be determined because of the raw water sampling location, the

data indicate that Plant C was not able to reduce arsenic 

concentrations to low levels. Prior research indicates 

that As(V) removal approaches 100% and As(III) removal approaches 75% at pH 11 (Sorg and Logsdon, 1978); 

however, arsenic removal efficiency decreases rapidly

below pH 11. McNeill and Edwards (1997b) showed that 

the primary arsenic removal mechanism during lime softening is adsorption and coprecipitation of As(III) and As(V) 

with magnesium hydroxide, which is precipitated near

pH 11. Therefore, it appeared that pH limited arsenic 

removal at Plant C, where the average pH after lime

softening was 8.9. This conclusion was further supported 

by the limited removal of magnesium hardness. The average magnesium hardness concentrations decreased from

113 mg/L in the raw water to only 107 mg/L in finished

water.

Total hardness concentrations averaged 304 mg/L,

164 mg/L, and 153 mg/L (as CaCO3) in the IN, PF, and 

AF sampling locations, respectively. The plant did soften 

the raw water significantly; however, Plant C removed

primarily calcium hardness, which was reduced an average of 76% during preliminary sampling. As stated in the 

previous paragraph, magnesium hardness was not effectively removed by Plant C, averaging only 5% removal. Alkalinity decreased after softening and then

remained constant between the softening and after filtration. This decrease was expected due to the chemical 

reactions that occur during the lime softening process 

(for carbonate hardness only):

CO2 + Ca(OH)2 = CaCO3↓ + H2O (4)

Ca(HCO3)2 + Ca(OH)2 = 2CaCO3↓ + 2H2O (5)

Mg(HCO3)2 + Ca(OH)2 = CaCO3↓ + MgCO3

 + 2H2O (6)

MgCO3 + Ca(OH)2 = Mg(OH)2↓ + CaCO3↓ (7)

Similarly, pH increased between the inlet and prefiltration sampling locations due to the addition of lime; however, this pH is significantly less than the optimal pH for 

arsenic removal (i.e., pH 11). 

Total manganese concentrations ranged from 130 to 

230 μg/L in the inlet, <20 to 50 μg/L before filtration, and 

<20 to 40 μg/L after filtration. The total iron concentrations averaged 2,851 μg/L at the inlet, 543 μg/L at the 

prefiltration sampling location, and 41 μg/L at the afterfiltration sampling location. The iron in the raw water is

most likely in the reduced state since the soluble arsenic 

was primarily As(III) in the raw water. As observed in

Plant A, arsenic removal by iron oxides can be significant. Therefore, the concentration of iron in the raw water 

was important and research indicates that this iron can

positively impact arsenic removal efficiency (McNeill and 

Edwards, 1997b).

Similar to Plants A and B, the preliminary sampling effort 

at Plant C resulted in only minor changes to the longterm sampling approach. Dissolved aluminum, iron, and 

manganese concentrations would be determined every

fourth week using leftover samples from the arsenic speciation kits. In addition, aluminum was added to the list

of analytes and the inlet sampling location was changed 

to be downstream of all ground water well inflows.

4.4.4 Long-Term Sampling

Weekly long-term sampling and analysis was performed 

for 49 weeks to determine concentrations of alkalinity,

turbidity, pH, hardness, total aluminum, total iron, total

manganese, and total arsenic. Long-term sampling also 

included 12 arsenic speciation sampling events that were

used to determinate arsenic form and species as well as 

dissolved metals (iron, manganese, and aluminum) at

each sampling location. The same three sampling locations that were used during the preliminary sampling phase

also were used during long-term sampling. Additionally, 

residual sampling was performed during this phase and 

consisted of collection and analysis of supernatant discharge water and sludge. Figure 4-12 shows the sampling locations during the long-term evaluation phase.

4.4.4.1 Arsenic

Table 4-18 provides a summary of the arsenic analytical 

results collected at the three treatment process locations. 

Total arsenic concentrations at the inlet ranged from 15.9
45

Table 4-18. Summary of Arsenic Analytical Results at Plant C (June 1998–June 1999)

Parameter Sample Location Units

Number of 

Samples

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

As (total) Inlet μg/L 49 15.9 84.9 32.0 10.5

Prefiltration μg/L 49 7.7 32.6 23.2 5.6

After filtration μg/L 49 6.3 33.1 16.6 4.2

As (total soluble) Inlet μg/L 12 21.9 40.8 33.8 6.0

Prefiltration μg/L 12 17.3 31.0 24.2 4.6

After filtration μg/L 12 13.9 22.5 17.1 2.4

As (particulate) Inlet μg/L 12 <0.1 7.3 1.2 2.2

Prefiltration μg/L 12 <0.1 4.0 1.0 1.5

After filtration μg/L 12 <0.1 1.1 0.3 0.4

As(III) Inlet μg/L 12 22 37.2 30.0 4.9

Prefiltration μg/L 12 <0.1 17.8 1.9 5.0

After filtration μg/L 12 <0.1 1.5 0.4 0.4

As(V) Inlet μg/L 12 <0.1 10.2 3.9 2.9

Prefiltration μg/L 12 12.6 29.9 22.3 4.9

After filtration μg/L 12 13.7 22.1 16.7 2.4

One-half of the detection limit was used for nondetect samples for calculations.

Primary and duplicate samples were averaged for calculations.

to 84.9 μg/L with an average concentration of 32.0 μg/L. 

Total arsenic concentrations at the prefiltration location

(i.e., after softening and before filtration) ranged from

7.7 to 32.6 μg/L with an average of 23.2 μg/L. Samples 

collected after filtration contained total arsenic concentrations ranging from 6.3 to 33.1 μg/L with an average

concentration of 16.6 μg/L. The total arsenic analytical

results were relatively constant, with the exception of a

peak in the raw water arsenic concentration that occurred

on April 26, 1999. The cause of this peak is not known; 

however, it is likely due to the ground water wells operating during this sampling event (i.e., wells 6 and 7, which 

have much higher arsenic concentration, may have been 

contributing more to the influent flow). The average removal percentage of total arsenic between the inlet and 

prefiltration sampling locations was 28%. The average 

removal percentage of total arsenic between the inlet

and after-filtration sampling locations was 48%. Total

arsenic removal efficiency also was relatively constant

during the long-term evaluation with the exception of

March 22, 1999, when arsenic removal was a minus 53%.

The explanation for this data point is not known but may 

be a result of well operation schedule, resulting in lower 

than normal inlet arsenic concentrations. Figure 4-13 is a 

graph showing the total arsenic concentration recorded

at each sampling location throughout the study, as well as 

removal percentages calculated for each sampling event.

Particulate arsenic concentrations averaged 1.2 μg/L at

the inlet, 1.0 μg/L at the prefiltration sampling location,

and 0.3 μg/L at the after-filtration sampling location. This 

indicates that approximately 75% of the particulate arsenic is removed by the system, primarily during filtration. 

As(III) concentrations averaged 30.0 μg/L at the inlet,

1.9 μg/L at the prefiltration location, and 0.4 μg/L at the 

after-filtration location. Substantial conversion of As(III)

to As(V) occurred between the inlet and finished water

due to the two chlorination steps. As(V) concentrations 

were 3.9 μg/L at the inlet, 22.3 μg/L at the prefiltration 

location, and 16.7 μg/L at the after-filtration location. The 

data were relatively consistent regarding As(III) and As(V)

concentrations at each sampling location. One deviation 

occurred on August 3, 1998, where the As(III) concentration after the precipitators and before the filters was

17.8 μg/L and the As(V) concentration was 12.6 μg/L. 

The cause of this deviation is not known.

These data showed that the inlet water at Plant C contained primarily the reduced species of arsenic (i.e.,

As[III]) with only minor concentrations of As(V) and particulate arsenic. The As(III) was converted to As(V) during the aeration and chlorination step prior to clarification 

(softening) and the chlorination step prior to filtration. 

The arsenic in the finished water consists almost entirely 

of As(V). Figure 4-14 shows the fractions of the total

arsenic concentration made up of particulate arsenic,

As(III), and As(V).

Based on studies by Sorg and Logsdon (1978), arsenic 

removals should be low at Plant C due to the relatively

low pH (average pH is 8.8 after lime softening) achieved 

during the softening process. Documented arsenic removal efficiencies when only calcium carbonate is precipitated are between 0 and 10% (McNeill and Edwards, 

1995). However, the average arsenic removal at Plant C 

was 48%. This removal most likely is associated with the 

iron in the source water. Total iron concentrations in the 

source water averaged 2,303 μg/L, practically all of

which was in reduced state. It is believed that adsorption 

and coprecipitation with the iron is the primary factor in

arsenic removal at this plant. Based on the simple sorption model by McNeill and Edwards (1997a), estimated
46

0

10

20

30

40

50

60

70

80

90

6/4/98 7/24/98 9/12/98 11/1/98 12/21/98 2/9/99 3/31/99 5/20/99 7/9/99

Date

Arsenic Concentration ( g/L)

-60%

-40%

-20%

0%

20%

40%

60%

80%

100%

Percent Arsenic Removed

Inlet

Prefiltration

After Filtration

%Removal

Figure 4-13. Total Arsenic Analytical Results During Long-Term Sampling at Plant C

arsenic removals should average approximately 75%

(approximately 30% higher than observed). However, in 

another study by McNeill and Edwards (1997b), it was

reported that carbonate can interfere with arsenic removal by iron hydroxide due to competition for sorption

sites. Additionally, the available research provides little

information on arsenic removal by coprecipitation with

iron hydroxide at pH values greater than 8.5. Therefore, 

arsenic removal through adsorption and coprecipitation

with iron hydroxide appeared to be limited by the lime

softening process.

The Plant C water treatment system was not able to

consistently remove arsenic to low levels (i.e., average 

total arsenic concentration in treated water was 16.6 μg/L).

The literature indicates that removal efficiency would

increase if the pH was increased. The primary arsenic

removal mechanism is coprecipitation with the iron in the 

source water followed by sedimentation and filtration.

4.4.4.2 Other Water Quality Parameters

As with Plants A and B, sampling and analysis of other 

water quality parameters were performed to provide

insight into the arsenic removal efficiency at the plant.

Table 4-19 summarizes the analytical results for several 

water quality parameters obtained during long-term sampling.

Inlet alkalinity concentrations were relatively constant, 

ranging from 300 to 411 mg/L (as CaCO3) with an average of 399 mg/L (see Figure 4-15). The alkalinity concentration decreased between the inlet and prefiltration 

sampling location and remained relatively constant between the prefiltration and after-filtration locations. This

reduction in alkalinity was associated with hardness

removal during the softening process.

During long-term sampling, turbidity concentrations

averaged 26.3 NTU at the inlet, 9.8 NTU at the prefiltration location, and 1.3 NTU at the after-filtration location. 

The inlet turbidity concentrations were relatively high,

ranging from 16.1 to 33 NTU, and are plotted on Figure 4-15. The data show that Plant B achieves an average turbidity removal efficiency of approximately 95%.

The average pH was 7.2 at the inlet, 8.8 at the prefiltration sampling location, and 8.6 at the after-filtration location. Inlet pH was relatively constant (see Figure 4-15). 

The pH increased at the prefiltration location due to the
47

Inlet

Prefiltration

After Filtration

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

7/13/98

8/3/98

8/31/989/28/98

10/26/9811/30/98

1/11/99

2/8/993/8/994/5/995/3/996/1/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

7/13/98

8/3/98

8/31/989/28/98

10/26/9811/30/98

1/11/99

2/8/993/8/994/5/995/3/996/1/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

7/13/98

8/3/98

8/31/989/28/98

10/26/9811/30/98

1/11/99

2/8/993/8/994/5/995/3/996/1/99

Concentration ( μ g/L)

As (V)

As (III)

As (particulate)

Figure 4-14. Arsenic Form and Species Analytical Results During Long-Term Sampling at Plant C
48

Table 4-19. Summary of Water Quality Parameter Analytical Results at Plant C (June 1998–June 1999)

Parameter Sample Location Units

Number of 

Samples

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

Alkalinity Inlet mg/L 49 300 411 399 15.4

Prefiltration mg/L 49 125 382 214 40.9

After filtration mg/L 49 146 321 198 30.4

Turbidity Inlet NTU 49 16.1 33 26.3 4.2

Prefiltration NTU 49 0.7 25.5 9.8 5.9

After filtration NTU 49 <0.1 25 1.3 3.61

pH Inlet — 49 7.1 7.4 7.2 0.1

Prefiltration — 49 7.9 10.1 8.8 0.5

After filtration — 49 7.8 9.3 8.6 0.3

Total Hardness Inlet mg/L 49 267 353 318 17.6

Prefiltration mg/L 49 85 304 179 37.3

After filtration mg/L 49 110 290 163 29.1

Total Al Inlet μg/L 49 <11 63 12 13.3

Prefiltration μg/L 49 13.4 87 43 16.1

After filtration μg/L 49 <11 99 20 15.9

Total Fe Inlet μg/L 49 92 3768 2389 556.7

Prefiltration μg/L 49 81 766 397 181.8

After filtration μg/L 49 <30 1110 76 165.2

Total Mn Inlet μg/L 49 75.9 204 140 27.5

Prefiltration μg/L 49 3.6 48.9 12.6 8.2

After filtration μg/L 49 1.0 54.7 4.8 8.0

Dissolved Al Inlet μg/L 12 <11 <11 <11 NA

Prefiltration μg/L 12 <11 36 18 10.6

After filtration μg/L 12 <11 12 <11 2.0

Dissolved Fe Inlet μg/L 12 1512 2966 2303 363

Prefiltration μg/L 12 <30 <30 <30 NA

After filtration μg/L 12 <30 <30 <30 NA

Dissolved Mn Inlet μg/L 12 106 189 146 28.7

Prefiltration μg/L 12 <0.5 7.8 2.6 2.1

After filtration μg/L 12 0.7 4.6 1.9 1.2

One-half of the detection limit was used for nondetect samples for calculations.

Primary and duplicate samples were averaged for calculations.

lime softening process. A similar trend was observed

with total hardness concentrations; however, the hardness concentrations were relatively high at the inlet

(average 318 mg/L as CaCO3) and decreased after the

lime softening process to an average concentration of

179 mg/L at the prefiltration location and 163 at the afterfiltration location. It is important to note that the hardness 

reduction consisted primarily of calcium hardness reduction; magnesium hardness was relatively constant 

throughout the treatment process. This result is not surprising considering that optimal magnesium hydroxide 

formation is achieved at pH 11. Precipitation of magnesium hydroxide is associated strongly with arsenic removal, because the arsenate adsorbs and coprecipitates 

with the Mg(OH)2 (McNeill and Edwards, 1997b).

Total aluminum concentrations averaged 12 μg/L at the

inlet, 43 μg/L at the prefiltration location, and 20 μg/L at 

the after-filtration location. The slight increase in aluminum at the prefiltration sampling location is probably due 

to trace amounts of aluminum in the lime. Manufacturers 

data indicated the lime contains 0.45% Al2O3. The average dissolved aluminum concentrations were <11 μg/L at 

the inlet, 18 μg/L at the prefiltration location, and <11 μg/L

at the after-filtration location. Because of the low concentrations, aluminum is not considered a significant factor 

in arsenic removal.

Total manganese concentrations averaged 140 μg/L, 

12.6 μg/L, and 4.8 μg/L, at the inlet, prefiltration, and afterfiltration sampling locations, respectively. Average dissolved manganese concentrations were 146 μg/L at the 

inlet, 2.6 μg/L at the prefiltration location, and 1.9 μg/L at 

the after-filtration location. However, due to the relatively 

low concentrations of manganese compared to iron, it is 

not believed that the manganese is a significant factor in 

arsenic removal at Plant C.

Total iron concentrations at the inlet sampling location 

ranged from 92 to 3,768 μg/L and averaged 2,389 μg/L. 

At the prefiltration sampling location, total iron concentrations ranged from 81 to 766 μg/L and averaged 397 μg/L.

The average total iron concentration at the after-filtration 

sampling location was 76 μg/L. Also, average dissolved
49

6

11

16

21

26

31

36

41

46

6/4/98 7/24/98 9/12/98 11/1/98 12/21/98 2/9/99 3/31/99 5/20/99 7/9/99

Date

Measurement (Turbidity, pH)

0

50

100

150

200

250

300

350

400

450

Measurement (Hardness, Alkalinity)

Turbidity (NTU)

pH (units)

Hardness (mg/L as CaCO3)

Alkalinity (mg/L as CaCO3)

Figure 4-15. Inlet Turbidity, pH, Hardness, and Alkalinity Analytical Results at Plant C

iron concentrations were 2,303 μg/L at the inlet and

<30 μg/L at both the prefiltration and after-filtration locations. The data indicated that the iron in the source water 

was in the reduced state and was completely oxidized

during the aeration and chlorination steps. The average 

concentration of total iron at the inlet was reduced 97% 

by the treatment process. It is believed that the primary 

arsenic removal mechanism was adsorption and coprecipitation of As(V) with the iron.

4.4.4.3 Supernatant Discharge Water

The filter backwash water at Plant C is sent to a slurry

tank and then to a sludge settling lagoon. The supernatant of the sludge lagoon is discharged to an adjacent 

creek under a state permit. The plant is required to monitor the supernatant discharge for pH weekly and total

dissolved solids (TDS) monthly as part of its discharge permit. Supernatant discharge water samples were collected 

at the outfall of the sludge lagoon where it discharges to 

the creek. 

Results of supernatant discharge water sampling are

summarized in Table 4-20. Total arsenic concentrations 

averaged 20.8 μg/L, consisting of an average of 21.2 μg/L

of soluble arsenic and 0.7 μg/L of particulate arsenic.

The pH was elevated due to the lime softening process. 

As would be expected based on the concentrations in

the source water, total iron concentrations in the supernatant water were relatively high and total aluminum and 

manganese concentrations were relatively low.

4.4.4.4 Sludge

Sludge is generated from the lime softening precipitators 

and from backwashing the sand filters. Sludge is collected from the bottom of the four precipitators and sent 

to a slurry tank. Filter backwashing occurs approximately 

every 80 hours and the backwash water is combined

with sludge from the precipitators in a slurry tank and

then sent to a sludge lagoon. Approximately 230,000

gal/day of water goes to the lagoon. Approximately once 

every 2 years, or as required, the lagoon is dewatered 

using an underdrain system and the sludge is removed

(approximately 14,500 yd3 of sludge was removed in the 

spring of 1998). Sludge from the lagoon is used on local 

farm fields.

Sludge samples were collected on November 16, 1998

from three locations from within a dewatered sludge

lagoon at Plant C. These sludge samples were analyzed 

for pH, percent moisture, total arsenic, total aluminum,
50

Table 4-20. Summary of Analytical Results from Supernatant Discharge Water Samples at Plant C 

(November 9, 1998–June 14, 1999)

Parameter Units

Number of 

Sample 

Events

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

As (total) μg/L 8 14.7 27.2 20.8 4.3

As (soluble) μg/L 8 14.9 27.2 21.2 4.0

As (particulate) μg/L 8 <0.1 4.3 0.7 1.5

pH — 8 9.0 9.7 9.3 0.3

Total Al μg/L 8 35 98 60 24

Total Fe μg/L 8 223 1,545 716 505

Total Mn μg/L 8 7.2 35.2 19.3 10.1

Dissolved Al μg/L 8 <11 24.3 <11 7.2

Dissolved Fe μg/L 8 <30 44.3 <30 10.9

Dissolved Mn μg/L 8 1.3 25.5 7.4 7.9

total iron, total manganese, and TCLP metals (arsenic,

barium, cadmium, chromium, lead, mercury, selenium, 

and silver). Total arsenic concentrations ranged from

17.0 to 35.3 mg/kg dry, and total iron concentrations 

ranged from 3,190 to 7,920 mg/kg dry. Arsenic was not 

detected in leachate from any of the three samples; however, minor concentrations of barium, cadmium, chromium, lead, and silver were detected. Consistent with

Plants A and B, none of the sludge analytical results

from Plant C indicate exceedances of regulatory levels.

Table 4-21 presents the results of sludge analysis at

each of the three sampling locations.

Table 4-21. Analytical Results of Sludge Sampling at Plant C (November 16, 1998)

Parameter Unit DL Location 1 Location 2 Location 3

As-TCLP mg/L 0.05 <0.05 <0.05 <0.05

Ba-TCLP mg/L 1.0 3.3 2.6 3.9

Cd-TCLP mg/L 0.020 0.03 0.03 0.03

Cr-TCLP mg/L 0.030 0.06 0.06 0.05

Pb-TCLP mg/L 0.20 0.25 0.27 0.25

Hg-TCLP mg/L 0.0002 <0.0002 <0.0002 <0.0002

Se-TCLP mg/L 0.05 <0.05 <0.05 <0.05

Ag-TCLP mg/L 0.020 0.04 0.03 0.03

TCLP extraction NA NA Complete Complete Complete

pH — — 9.7 10.3 9.5

Percent moisture % 0.1 51.7 51.2 51.4

Total As μg/g, dry 0.1(a) 17.0 35.3 28.2

Total Al μg/g, dry 11(a) 1,370 841 919

Total Fe μg/g, dry 30(a) 3,190 7,920 6,510

Total Mn μg/g, dry 0.5(a) 230 261 281

(a) Detection limit is in units of μg/L for digestate.
51

5. Quality Assurance/Quality Control

5.1 Quality Assurance Objectives

The precision, accuracy, MDL, and completeness for

each of the analytical measurements required for this

study have been established in the QAPP (Battelle,

1998) and are listed in Table 1 of the QA/QC Summary 

Report, which is being prepared under separate cover.

These terms serve as indicators of data quality and were 

calculated in accordance with the formulas provided in

the QAPP. The precision, accuracy, and MDL of each of 

the measurements performed during the present study

are presented in the summary report. These quality

assurance (QA) data are organized according to the

date of sample receipt or sample analysis and are not

site-specific. Therefore, the QA/QC section of this report 

shares the same QA data with other water treatment 

plants that have been included in the study.

5.2 Overall Assessment of Data Quality

Quantitative QA objectives listed in the QA/QC Summary 

Report include precision as relative percent difference 

(RPD),accuracy as percent recovery (%R), MDL, and completeness. The precision, accuracy, and MDL or reporting 

limit of each of the measurements performed during the 

present study are presented. Total arsenic, aluminum, 

iron, and manganese analyses on water samples were

conducted in Battelle’s ICP-MS laboratory. The QA data 

associated with these metal analyses also are presented. Other water quality parameters, including alkalinity, 

pH, turbidity, hardness, nitrate-nitrite, sulfate, fluoride, 

TDS, and TSS, were analyzed by Wilson Environmental

Laboratories and their QA data were summarized. QA

data for TOC analysis performed by CT&E Environmental Laboratory are presented. The TCLP metal analysis 

on sludge samples also was conducted by Wilson Environmental Laboratories and its associated QA data

are summarized. Overall, the QA objectives of precision, 

accuracy, MDL, and completeness were achieved by all 

laboratories. Therefore, all the valid data were used to

evaluate the effectiveness of the treatment processes

and support conclusions.

5.2.1 Total Arsenic, Aluminum, Iron, 

and Manganese

At the early phase of the study, total arsenic analysis

was performed by Battelle’s ICP-MS laboratory, and total 

aluminum, iron, and manganese were analyzed by Wilson

Environmental Laboratories. Starting from June 1998, all 

four metals were analyzed by Battelle ICP-MS laboratory. Therefore, QA data for only the total arsenic analysis before June 16, 1998, and QA data for all four metals 

afterwards are presented.

The laboratory duplicate and matrix spike (MS) analyses 

were performed every 10 samples instead of 20 samples 

as required by the QAPP. All the samples were analyzed 

for four metals although metals other than arsenic may

not be required for every sample. Therefore, Battelle’s 

ICP-MS laboratory performed more QA/QC analyses

than what were specified in the QAPP. This fact should 

be considered when QC data are evaluated. 

Greater than 99% of the precision results for all metals

met the QA objective of ±25% (with only two iron outliers: 27% on August 8, 1998, and 74% on December

22, 1998; three arsenic outliers: 27% on August 18,

1998, 182% on October 1, 1998, and 27% on July 30,

1999; and four aluminum outliers: 26% and 33% on

August 18, 1998, 48% on December 15, 1998, and 48% 

on January 25, 1999). The majority of the accuracy data 

associated with MS analysis on August 31, 1998,

exceeded the QA limits of 75 to 125%. It is suspected

that MS analyses were not performed correctly on that

day. After this problem had been identified, Battelle’s

WAL, laboratory QA officer, and Battelle’s task leaders

met to discuss the cause of the deviation. Corrective

actions were taken including reanalyzing samples and

adjusting the amount of spike added to samples (i.e., the 

iron spike was increased from 50 to 100, 200, 225, or

even as high as 2,000 μg/L due to the fact that most of 

samples contain much more than 50 μg/L of iron). As

indicated in the QA/QC Summary Report, the MS data

quality was significantly improved since November 3,
52

1998. Excluding the data on August 31, 1998, only five

As data were outside the acceptable range for accuracy. 

However, 15 Al, 26 Fe, and 14 Mn accuracy data did not 

meet the QA objective. With exceptions of one 23% and 

one 38% of accuracy, the Al accuracy data range from 

65 to 125%. The Mn accuracy data range from 67 to

106%, with exception of one 37%. The Fe accuracy data 

range from 55 to 142%, with exceptions of one 14%, one 

23%, and one 38%.

All laboratory control samples showed %R within the

acceptable QA limit of 75 to 125% except for six outliers 

for total Fe with %R ranging from 73 to 143%. Al was not 

spiked to laboratory control samples until November 3,

1998, after corrective actions were taken. The MDL of

Fe is the same as target MDL; however, MDLs of other 

three metals were far below the target levels as specified 

in the QAPP.

5.2.2 Water Quality Parameters

Water quality parameters include alkalinity, pH, turbidity, 

hardness (Ca and Mg), nitrate-nitrite, sulfate, fluoride, 

TDS, TSS and TOC. As shown in Table 3 of the QA/QC 

Summary Report, all the precision data were within the

acceptable QA limit of ±25% except for two Mn analysis 

with a 29% RPD (April 10 and 17, 1998) and three

nitrate-nitrite analyses with 40% RPD (August 6, 1998,

January 13, 1999, and February 11, 1999). The high

RPDs of these analyses might have been caused by the 

low measured concentrations in the samples that were

close to the detection limits for Mn and nitrate-nitrite. The 

accuracy data indicate that only one Al (70% on March 

2, 1998), two Mn (66% and 64% on May 12, 1998), and 

one Mg (126% on August 7, 1998) %R slightly exceeded 

the QA objectives of 75 to 125%. Although the matrix

spike duplicate (MSD) analysis was not required by the

QAPP, the accuracy and the precision data relating to

MSD also were presented. The MS/MSD analyses are not

applicable to pH and turbidity measurements, though.

The laboratory did not perform MS/MSD analyses on Ca 

and Mg hardness analyses till October 15, 1998 upon

Battelle’s request. All laboratory control samples showed 

%R within the acceptable QA limit of 75 to 125%. Reporting limits were below the required levels for all the

analytes except for sulfate. The reporting limit of sulfate 

was 5 mg/L, exceeding the required MDL of 3.66 mg/L. 

All precision, accuracy, and %R values for the TOC analysis were within acceptable QA limits with the exception 

of one accuracy value that was slightly below the 75 to

125% range at 72% (February 21, 1999).

5.2.3 TCLP Metals in Sludge

The TCLP metals analyzed in the sludge samples

included As, Se, Hg, Ba, Cd, Cr, Pb, and Ag. The precision data were within QA limits of ±25%. The accuracy 

of MSs and percent recovery of laboratory control samples were all within QA limits of 75 to 125%, except for 

one slightly elevated RPD for TCLP Se MS/MSD at 26% 

(November 17, 1998).
53

6. References

Amirtharajah, A., and C.R. O’Melia. 1990. “Coagulation 

Processes: Destabilization, Mixing, and Flocculation.”

In American Water Works Association (Eds.), Water 

Quality and Treatment: A Handbook of Community

Water Supplies. New York: McGraw-Hill.

Andreae, M. 1977. “Determination of Arsenic Species in 

Natural Waters.” Anal. Chem., 49: 820-823.

Battelle. 1998. Quality Assurance Project Plan for Evaluation of Treatment Technology for the Removal of

Arsenic from Drinking Water. Prepared for EPA.

Benefield, L.D., and J.S. Morgan. 1990. “Chemical Precipitation.” Water Quality and Treatment.

Chen, S.L., S.R. Dzeng, M. Yang, K. Chiu, G. Shieh, and 

C.M. Wai. 1994. “Arsenic Species in Groundwaters of 

the Blackfoot Disease Area, Taiwan.” Environmental 

Science and Technology: 877-881.

Chen, R.C., S. Liang, H.C. Wang, and M.D. Beuhler.

1994. “Enhanced Coagulation for Arsenic Removal.” 

J. AWWA (September): 79-90.

Clifford, D., L. Ceber, and S. Chow. 1983. “Arsenic(III)/Arsenic(V) Separation by Chloride-Form IonExchange Resins.” Proceedings of the XI AWWA

WQTC.

Eaton, A.D., H.C. Wang, and J. Northington. 1997.

“Analytical Chemistry of Arsenic in Drinking Water.”

AWWARF Project 914.

Edwards, M. 1994. “Chemistry of Arsenic Removal

during Coagulation and Fe-Mn Oxidation.” J. AWWA 

(September): 64-78.

Edwards, M., S. Patel, L. McNeill, H. Chen, M. Frey, 

A.D. Eaton, R.C. Antweiler, and H.E. Taylor. 1998.

“Considerations in As Analysis and Speciation.” 

J. AWWA (March): 103-113.

EPA, see U.S. Environmental Protection Agency.

Ficklin, W.H. 1982. “Separation of Arsenic (III) and Arsenic (V) in Groundwaters by Ion Exchange.” Talanta, 

30(5): 371-373.

Gulledge, J.H., and J.T. O’Conner. 1973. “Removal of

Arsenic (V) from Water by Adorption on Aluminum and 

Ferric Hydroxides. J. AWWA (August): 548-552.

Hemond, H.F. 1995. “Movement and Distribution of

Arsenic in the Aberjona Watershed.” Environmental 

Health Perspectives.

Hering, J.G., P.Y. Chen, J.A. Wilkie, M. Elimelech, and

S. Lung. 1996. “Arsenic Removal by Ferric Chloride.”

J. AWWA. (April): 155-167.

McNeill, L.S., and M. Edwards. 1995. “Soluble Arsenic

Removal at Water Treatment Plants.” J. AWWA. 

(April): 105-113.

McNeill, L.S. and M. Edwards. 1997a. “Predicting As

Removal During Metal Hydroxide Precipitation.” 

J. AWWA. (January): 75-86.

McNeill, L.S. and M. Edwards. 1997b. “Arsenic Removal 

During Precipitative Softening.” Journal of Environmental Engineering (May): 453-460.

Scott, K.N., J.F. Green, H.D. Do, and S.J. McLean.

1995. “Arsenic Removal by Coagulation.” J. AWWA 

(April): 114-126.

Sorg, T.J. 1993. “Removal of Arsenic From Drinking 

Water by Conventional Treatment Methods.” Proceedings of the 1993 AWWA WQTC.

Sorg, T.J., and G.S. Logsdon. 1978. “Treatment Technology to Meet the Interim Primary Drinking Water

Regulations for Inorganics: Part 2.” J. AWWA (July).
54

Tate, C.H., and K.F. Arnold. 1990. “Health and Aesthetic 

Aspects of Water Quality.” In American Water Works 

Association (Eds.), Water Quality and Treatment: A

Handbook of Community Water Supplies. New York:

McGraw-Hill.

U.S. Environmental Protection Agency. 1998. Research 

Plan for Arsenic in Drinking Water. EPA/600/4-98/042. 

Office of Research and Development, Washington, DC.

February.
55

APPENDIX A

Complete Analytical Results from Long-Term Sampling at Plant A
5

6

Table A-1. Analytical Results from Long Term Sampling, Plant A (June 24 to July 15, 1998)

Sampling Date 6/24/98 7/1/98 7/8/98 7/15/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 82 78 77 71 67 67 63 60 60 56 54 52

Turbidity NTU 1.0 1.1 0.2 0.7 1.0 0.1 0.5 1.1 <0.1 1.8 2.4 <0.1

pH 8.2 8.0 7.9 8.0 7.9 7.7 7.9 7.8 7.7 8.1 7.9 7.7

TOC mg/L 2.2 <1.0 2.1 2.0 2.0 2.0 2.1 2.2 2.2 2.5 2.6 2.2

As (total) μg/L 12.1 9.3 3.9 7.0 8.1 3.1 7.0 8.0 3.1 7.1

7.2

6.5

5.5

2.3

2.9

As (total soluble) μg/L 6.8

6.8

3.1

3.1

2.2

2.2

As (particulate) μg/L 0.3

0.4

3.4

2.4

0.1

0.7

As (III) μg/L 0.4

0.3

0.1

0.1

<0.1

<0.1

As (V) μg/L 6.4

6.5

3.0

3.0

2.2

2.2

Total Al μg/L 115 55.4 21.5 27.0 49.2 <11 35.6 53.9 14.7 58.0

51.5

45.6

58.1

13.5

17.0

Total Fe μg/L 444 457 <30 108 <30 <30 73.7 464 <30 146

137

362

341

<30

<30

Total Mn μg/L 32.6 16.9 <0.5 7.5 14.4 <0.5 8.9 18.1 <0.5 22.4

20.9

19.1

21.1

<0.5

<0.5

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 1.9

1.5

3.0

3.0

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
5

7

Table A-2. Analytical Results from Long Term Sampling, Plant A (July 22 to August 12, 1998)

Sampling Date 7/22/98 7/29/98 8/5/98 8/12/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 51

52

49

49

50

50 47 44 44 45 44 42 4546

42

43

42

42

Turbidity NTU 6.1

5.0

0.6

0.6

<0.1

<0.1 0.6 1.5 <0.1 0.8 0.9 <0.1 0.4

0.4

1.2

1.1

<0.1

<0.1

pH 7.9

7.9

7.6

7.6

7.5

7.5 8.0 7.8 7.7 7.8 7.8 7.7 7.7

7.7

7.5

7.5

7.4

7.4

TOC mg/L 1.8

1.8

1.7

1.8

1.9

1.7 1.5 1.6 1.7 1.8 1.9 3.0 1.71.8

1.7

1.8

1.9

1.6

As (total) μg/L 10.5 7.6 2.3 5.6 10.0 2.1 4.8

6.5

5.9

6.2

2.3

2.2 4.8 4.7 0.8

As (total soluble) μg/L 5.9

5.6

2.7

2.7

2.1

2.0

As (particulate) μg/L <0.1

<0.1

3.1

3.5

0.2

0.2

As (III) μg/L 0.5

0.5

0.2

0.2

0.4

0.4

As (V) μg/L 5.4

5.1

2.5

2.5

1.7

1.6

Total Al μg/L 269 62.1 17.6 33.3 79.9 21.1 26.6

23.2

48.2

70.2

<11

12.1 48.2 35.6 21.7

Total Fe μg/L 646 450 <30 83.5 780 60.5 94.7

136

526

539

<30

<30 90.4 433 <30

Total Mn μg/L 112 23.9 <0.5 9.9 58.2 0.5 9.6

13.9

22.6

22.9

<0.5

<0.5 12.5 25.9 <0.5

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 45.7

<30

<30

<30

<30

<30

Dissolved Mn μg/L 1.8

1.6

4.9

4.7

0.8

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
5

8

Table A-3. Analytical Results from Long Term Sampling, Plant A (August 19 to September 9, 1998)

Sampling Date 8/19/98 8/26/98 9/2/98 9/9/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 51 47 48 63 61 61 66 62 62 75

74

75

75

76

75

Turbidity NTU 0.6 1.2 <0.1 0.6 0.8 <0.1 2.1 0.5 <0.1 0.6

0.7

0.4

0.5

<0.1

<0.1

pH 7.9 7.6 7.5 8.0 7.8 7.7 7.8 7.8 7.7 8.0

8.0

7.9

7.9

7.9

7.9

TOC mg/L 1.7 1.6 1.5 1.9 2.0 1.9 1.9 1.9 2.0 2.1

2.2

2.2

2.1

2.0

2.0

As (total) μg/L 5.9 5.4 1.3 6.6 7.1 3.2 6.9

5.0

6.7

5.9

2.7

2.7 7.2 7.0 4.0

As (total soluble) μg/L 6.7

6.8

3.8

4.0

3.4

3.2

As (particulate) μg/L 0.2

<0.1

2.9

1.9

<0.1

<0.1

As (III) μg/L 0.3

0.3

<0.1

<0.1

<0.1

<0.1

As (V) μg/L 6.4

6.5

3.8

4.0

3.4

3.2

Total Al μg/L 36.4 57 26.8 46.9 32.4 39.2 44.7

32.8

22.9

27.9

13.3

12.1 34.8 18.2 <11

Total Fe μg/L 77.5 486 <30 63.0 354 52.3 144

84.8

306

264

<30

<30 31.4 240 <30

Total Mn μg/L 16.4 26.3 45.4 14.7 22.8 0.5 47.2

32.6

18.2

16.5

<0.5

<0.5 9.5 14.6 10.7

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.2

2.2

2.9

2.6

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
5

9

Table A-4. Analytical Results from Long Term Sampling, Plant A (September 16 to October 7, 1998 )

Sampling Date 9/16/98 9/23/98 9/30/98 10/7/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 74 73 73 74 74 74 81 78 79 88

87

83

84

82

82

Turbidity NTU 1.1 0.4 <0.1 1.4 0.7 0.2 0.6 0.8 <0.1 1.2

1.2

1.1

1.1

<0.1

<0.1

pH 7.9 7.8 7.8 7.9 7.8 7.7 7.9 7.6 7.6 8.2

8.2

8.0

7.9

7.9

7.8

TOC mg/L 2.7 2.6 2.3 2.3 2.4 2.3 2.6 2.4 2.3 2.4

2.4

2.6

2.5

2.5

2.6

As (total) μg/L 8.1 7.9 4.6 8.9 9.9 4.2 8.2

9.2

4.3(b)

8.6

4.4

4.2 7.8 7.7 4.2

As (total soluble) μg/L 8.1

8.0

4.8

4.9

3.8

3.7

As (particulate) μg/L 0.1

1.2

<0.1

3.7

0.6

0.5

As (III) μg/L 0.7

0.8

0.4

0.4

0.4

0.4

As (V) μg/L 7.4

7.2

4.4

4.5

3.4

3.3

Total Al μg/L 30.5 36.6 <11 31.4 34.4 22.2 36.5

34.2

83.0

51.6

13.7

19.2 60.8 63.4 12.6

Total Fe μg/L 48.5 303 <30 85.6 419 41.5 57.5

59.4

461

382

<30

<30 81.8 374 31.0

Total Mn μg/L 12.6 20.0 9.1 18.0 36.4 1.5 15.4

15.3

31.8

24.5

0.5

0.6 15.1 22.2 0.6

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.6

2.6

3.0

2.9

<0.5

<0.5

(a) As CaCO3.

(b) Confirmed by sample re-analysis.

IN = inlet; PF = prefiltration; AF = after filtration.
6

0

Table A-5. Analytical Results from Long Term Sampling, Plant A (October 14 to November 4, 1998)

Sampling Date 10/14/98 10/21/98 10/28/98 11/4/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 86 85 81 92 91 89 58 95 95 96

96

92

91

92

91

Turbidity NTU 0.7 1.1 <0.1 0.6 0.7 <0.1 0.6 0.9 <0.1 0.7

0.7

1.0

1.0

<0.1

<0.1

pH 7.9 7.7 7.6 8.0 7.8 7.7 8.1 7.8 7.7 8.0

8.1

7.7

7.7

7.7

7.7

TOC mg/L 2.9 3.1 2.9 2.5 2.6 2.3 2.8 2.9 2.5 2.1

2.3

(b)

2.3

1.9

2.0

As (total) μg/L 5.0 2.0 4.2 7.8 8.0 6.0 7.4

7.5

13.9

9.2

4.7

4.4 7.8 9.1 4.9

As (total soluble) μg/L 8.2

7.7

5.3

5.1

4.5

4.5

As (particulate) μg/L <0.1

<0.1

8.6

4.1

0.2

<0.1

As (III) μg/L 2.0

2.1

2.0

2.2

1.9

2.0

As (V) μg/L 6.2

5.6

3.3

2.9

2.6

2.5

Total Al μg/L <11 25.3 14.5 24.7 28.2 15.2 27.8

36.8

176

75

<11

<11 40.1 95.4 15.9

Total Fe μg/L <30 67.8 <30 48.1 384 <30 38.6

38.9

1,160

1,565

<30

<30 88.2 597 <30

Total Mn μg/L 14.2 20.1 <0.5 11.4 14.2 <0.5 12.7

11.7

80.3

44.9

0.6

0.6 12.0 31.9 <0.5

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 4.5

4.7

5.4

5.7

0.7

<0.5

(a) As CaCO3.

(b) Sample container broken in laboratory.

IN = inlet; PF = prefiltration; AF = after filtration.
61

Table A-6. Analytical Results from Long Term Sampling, Plant A (November 11 to December 9, 1998)

Sampling Date 11/11/98 11/18/98 11/25/98(b) 12/2/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 98 95 95 99 94 95 99 97 94

Turbidity NTU 0.4 0.7 <0.1 1.2 1.5 0.2 0.9 1.0 <0.1

pH 8.0 7.8 7.7 7.9 7.8 7.7 8.0 7.8 7.7

TOC mg/L 2.3 2.4 2.1 2.0 2.0 2.0 2.3 2.2 2.1

As (total) μg/L 7.9 7.8 4.2 7.1 7.3 3.7 7.2

7.3

7.1

7.7

3.4

3.3

As (total soluble) μg/L 7.0

6.9

4.5

4.6

3.6

3.6

As (particulate) μg/L 0.2

0.4

2.6

3.1

<0.1

<0.1

As (III) μg/L 1.1

1.2

0.9

0.9

0.7

0.9

As (V) μg/L 5.9

5.7

3.6

3.7

2.9

2.7

Total Al μg/L 59.2 62.1 11.3 71.0 73.9 14.2 47.2

43.0

45.0

70.0

29.4

18.5

Total Fe μg/L 112 459 <30 156 416 <30 150

145

483

460

39.7

88.0

Total Mn μg/L 20.0 23.1 0.6 19.2 19.0 <0.5 14.5

14.3

17.7

18.4

1.3

1.1

Dissolved Al μg/L <11

<11

<11

<11

<11

18.4

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 3.4

3.7

3.4

3.6

1.0

1.1

(a) As CaCO3.

(b) No sampling due to Thanksgiving holiday.

IN = inlet; PF = prefiltration; AF = after filtration.
6

2

Table A-7. Analytical Results from Long Term Sampling, Plant A (December 9 to 30, 1998)

Sampling Date 12/9/98 12/16/98 12/23/98(b) 12/30/98(b)

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 98

97

94

95

94

94 98 95 96

Turbidity NTU 0.6

0.6

0.8

0.8

<0.1

<0.1 0.7 0.9 <0.1

pH 8.0

8.0

7.8

7.8

7.7

7.7 8.1 7.8 7.7

TOC mg/L 2.3

-

2.2

2.2

1.9

2.1 2.3 2.5 2.1

As (total) μg/L 7.2 7.4 3.3 7.0 6.9 2.9

As (total soluble) μg/L

As (particulate) μg/L

As (III) μg/L

As (V) μg/L

Total Al μg/L 40.5 36.4 11.2 37.0 24.7 <11

Total Fe μg/L 60.9 373 <30 46.8 374 <30

Total Mn μg/L 11.2 14.9 1.0 8.8 12.4 <0.5

Dissolved Al μg/L

Dissolved Fe μg/L

Dissolved Mn μg/L

(a) As CaCO3.

(b) No sampling due to Christmas holiday.

IN = inlet; PF = prefiltration; AF = after filtration.
6

3

Table A-8. Analytical Results from Long Term Sampling, Plant A (January 6 to 27, 1999)

Sampling Date 01/06/99 01/13/99 01/20/99 01/27/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 103 100 99 103 96 99 103

103

100

101

101

102 103 105 103

Turbidity NTU 0.3 1.2 <0.1 0.3 0.8 <0.1 0.3

0.4

1.7

1.6

<0.1

<0.1 0.4 3.0 <0.1

pH 7.9 7.8 7.8 8.0 7.8 7.8 8.1

8.1

8.0

8.0

8.0

8.0 8.2 8.0 8.0

TOC mg/L 2.4 3.9 1.9 2.2 2.3 1.9 2.5

2.4

2.7

2.8

2.7

2.5 2.0 2.5 2.2

As (total) μg/L 6.8 14.5 3.5 8.6

8.2

9.9

9.7

3.8

3.6 7.5 10.8 4.8 5.4 7.0 3.0

As (total soluble) μg/L 8.8

9.6

3.0

2.9

4.0

4.0

As (particulate) μg/L <0.1

<0.1

6.9

5.8

<0.1

<0.1

As (III) μg/L 0.7

0.7

0.8

0.7

0.7

0.7

As (V) μg/L 8.1

8.9

2.2

2.2

3.3

3.3

Total Al μg/L 20.3 50.5 <11 30.7

29.3

22.2

31.3

<11

<11 41.5 94.7 <11 14.8 33.7 <11

Total Fe μg/L 19.7 1,276 62.6 47.0

41.7

811

806

<30

<30 56.6 925 <30 60.8 920 33.9

Total Mn μg/L 4.4 40.5 14.7 6.8

6.6

10.2

9.5

<0.5

<0.5 6.0 22.1 4.8 8.0 19.0 3.6

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.6

4.2

3.5

3.8

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
6

4

Table A-9. Analytical Results from Long Term Sampling, Plant A (Feb 3 to 24, 1999)

Sampling Date 02/03/99 02/11/99 02/17/99 02/24/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 103 100 99 102 102 101 104

104

105

104

102

103 100 99 100

Turbidity NTU 0.7 1.3 <0.1 2.4 1.3 <0.1 1.1

1.0

1.3

1.3

<0.1

<0.1 2.8 1.2 <0.1

pH 8.3 8.0 8.0 8.2 8.0 8.0 8.2

8.2

8.0

8.0

7.9

8.0 8.2 8.0 8.0

TOC mg/L 2.4 2.6 2.1 2.5 2.7 2.3 2.6

2.7

2.7

3.0

2.0

2.3 3.3 3.0 2.8

As (total) μg/L 2.6 7.8 2.7 7.4

6.8

7.0

9.0

2.7

2.7 6.0 6.0 2.5 4.1 3.9 1.8

As (total soluble) μg/L 5.0

5.3

3.6

3.9

2.8

2.7

As (particulate) μg/L 2.4

1.5

3.4

5.1

<0.1

<0.1

As (III) μg/L 0.3

0.3

0.8

1.1

0.2

0.2

As (V) μg/L 4.7

5.0

2.8

2.8

2.6

2.5

Total Al μg/L 717 32.9 23.8 143

129

42.4

62.6

<11

<11 29.7 32.3 <11 33.0 38.3 <11

Total Fe μg/L 767 1,050 55.7 543

472

652

950

<30

<30 118 753 <30 104 642 48.8

Total Mn μg/L 54.5 23.3 4.9 45.6

37.6

81.3

89.7

5.6

5.9 26.6 33.7 14.9 11.9 15.7 9.6

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 1.9

2.1

63.6

75.8

5.8

5.8

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
6

5

Table A-10. Analytical Results from Long Term Sampling, Plant A (Mar 3 to Mar 24, 1999)

Sampling Date 03/03/99 03/10/99 03/17/99 03/24/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 105 103 103 109 110 109 104

104

101

102

102

102 104 103 103

Turbidity NTU 0.9 1.3 <0.1 0.5 0.7 <0.1 1.4

1.4

1.7

1.7

<0.1

<0.1 1.2 1.7 <0.1

pH 8.2 8.0 8.0 8.3 8.1 8.0 8.2

8.2

8.0

8.0

8.0

8.0 8.2 8.0 8.0

TOC mg/L (b) 3.2 2.8 2.6 2.5 2.2 2.9

3.1

3.1

2.6

2.6

2.4 2.5 2.4 2.2

As (total) μg/L 4.5 4.6 2.1 6.6

6.5

6.0

6.1

3.3

3.4 8.4 8.0 4.4 11.3 13.9 5.3

As (total soluble) μg/L 6.3

6.4

4.3

4.4

3.6

3.6

As (particulate) μg/L 0.3

0.1

1.7

1.7

<0.1

<0.1

As (III) μg/L 0.6

0.6

0.5

0.6

0.5

0.5

As (V) μg/L 5.7

5.8

3.8

3.8

3.1

3.1

Total Al μg/L 30.5 34.3 <11 21.0

19.5

17.1

19.5

<11

<11 59.3 56.7 12.0 46.1 55.6 <11

Total Fe μg/L 70.9 542 <30 <30

<30

444

459

<30

<30 116 512 36.4 96.8 628 <30

Total Mn μg/L 9.8 13.8 7.3 5.6

5.5

8.8

9.1

4.5

4.6 24.5 26.0 15.8 15.3 22.3 6.8

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.9

1.6

2.4

2.7

5.2

5.0

(a) As CaCO3.

(b) Sample container broken in laboratory.

IN = inlet; PF = prefiltration; AF = after filtration.
6

6

Table A-11. Analytical Results from Long Term Sampling, Plant A (Mar 31 to Apr 21, 1999)

Sampling Date 03/31/99 04/07/99 04/14/99 04/21/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 106 105 102 107 106 105 108

108

106

106

106

106 105 104 105

Turbidity NTU 0.9 1.4 0.2 2.4 2.7 <0.1 2.3

2.2

2.4

2.4

<0.1

<0.1 2.9 1.0 <0.1

pH 8.1 7.9 7.9 8.1 7.9 7.9 8.1

8.2

8.0

8.0

7.9

8.0 8.1 8.0 7.9

TOC mg/L 2.0 2.5 2.3 2.5 2.6 1.9 2.4

2.3

2.8

2.9

2.5

2.2 2.8 3.2 3.0

As (total) μg/L 11.0 10.7 4.5 10.8

10.8

10.6

10.9

4.5

4.6 10.5 8.5 4.3 7.6 6.8 (b)

As (total soluble) μg/L 11.0

10.9

6.1

5.6

4.8

4.8

As (particulate) μg/L <0.1

<0.1

4.5

5.4

<0.1

<0.1

As (III) μg/L 0.7

0.7

0.4

0.4

0.5

0.5

As (V) μg/L 10.3

10.2

5.7

5.2

4.3

4.3

Total Al μg/L 29.8 37.4 <11 88.5

96.9

104

98.7

<11

<11 62.5 59.4 <11 120 37.2 <11

Total Fe μg/L 59.9 534 <30 129

157

638

655

<30

<30 100 496 <30 209 552 <30

Total Mn μg/L 11.0 15.9 6.3 18.6

20.0

24.2

25.8

5.5

5.6 20.0 20.0 5.8 37.5 14.9 6.2

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.0

1.6

1.2

1.6

5.3

5.3

(a) As CaCO3.

(b) Sample container contaminated.

IN = inlet; PF = prefiltration; AF = after filtration.
6

7

Table A-12. Analytical Results from Long Term Sampling, Plant A (Apr 28 to May 19, 1999)

Sampling Date 04/28/99 05/05/99 05/12/99 05/19/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 107 106 105 112 110 109 111

109

109

109

108

108 112 111 109

Turbidity NTU 1.6 1.7 <0.1 2.7 6.2 <0.1 1.2

1.2

2.1

2.4

<0.1

<0.1 1.1 18.5 0.1

pH 8.2 8.0 7.9 8.2 8.0 8.0 8.2

8.2

8.0

8.0

8.0

8.0 8.2 8.0 8.0

TOC mg/L 2.9 2.6 2.3 4.8 4.4 7.4 2.8

2.5

3.0

3.3

2.3

2.6 4.3 12.0 5.4

As (total) μg/L 6.8 6.2 3.1 9.6

9.5

13.1

13.0

4.6

4.6 11.1 9.3 4.3 8.8 23.4 4.4

As (total soluble) μg/L 9.0

9.1

5.2

5.2

4.6

4.5

As (particulate) μg/L 0.5

0.4

7.9

7.8

<0.1

<0.1

As (III) μg/L 0.6

0.6

0.6

0.5

1.0

1.0

As (V) μg/L 8.4

8.5

4.6

4.7

3.6

3.5

Total Al μg/L 100 67.7 17.9 122

105

231

227

<11

<11 76.5 35.7 17.3 32.8 246 <11

Total Fe μg/L 103 601 23.2 241

216

1,316

1,330

<30

<30 752 102.5 <30 75.7 2,646 <30

Total Mn μg/L 17.8 15.5 6.4 24.7

24.1

62.0

63.0

5.6

5.6 74.3 12.8 3.9 12.1 72.2 4.7

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 1.2

1.1

3.0

2.9

4.8

4.8

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
6

8

Table A-13. Analytical Results from Long Term Sampling, Plant A (May 26 to June 16, 1999)

Sampling Date 05/26/99 06/02/99 06/09/99 06/16/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 107 105 104 101 100 100 97

97

96

96

96

95

Turbidity NTU 0.8 3.8 <0.1 2.7 1.7 <0.1 1.9

1.9

1.6

1.5

<0.1

<0.1

pH 8.2 8.0 8.0 8.2 8.0 7.9 8.2

8.2

7.9

7.9

7.8

7.9

TOC mg/L 2.4 2.5 2.0 2.6 2.6 2.2 2.0

2.5

2.4

2.5

2.2

2.1

As (total) μg/L 9.0 16.7 4.2 11.4

10.0

9.5

8.9

3.5

3.5 7.4 10.3 2.8 8.5 16.6 3.3

As (total soluble) μg/L 9.4

9.5

4.3

4.2

3.6

3.5

As (particulate) μg/L 2.0

0.6

5.2

4.7

0.1

<0.1

As (III) μg/L 0.8

0.9

0.4

0.3

0.4

0.4

As (V) μg/L 8.6

8.6

4.0

3.9

3.1

3.1

Total Al μg/L 39.8 193 9.0 111

115

54.1

48.9

19.7

11.5 79.0 100 <11 17.8 134 18.3

Total Fe μg/L 84.4 1,812 <30 254

257

605

552

<30

<30 144 870 <30 42.0 1,664 <30

Total Mn μg/L 10.0 51.5 3.7 85.8

53.0

28.7

28.3

3.8

3.4 24.7 33.7 3.9 8.8 52.7 5.2

Dissolved Al μg/L 22.6

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 1.4

1.1

2.3

2.5

3.4

3.2

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
69

APPENDIX B

Complete Analytical Results from Long-Term Sampling at Plant B
7

0

Table B-1. Analytical Results from Long Term Sampling, Plant B (June 25 to July 16, 1998)

Sampling Date 6/25/98 6/30/98 7/9/98 7/16/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 132 108 106 126 105 104 125 100 101 120 96 96

Turbidity NTU 11.8 0.9 0.3 9.5 0.6 <0.1 7.2 0.8 <0.1 8.7 0.8 <0.1

pH 8.4 7.4 7.3 8.3 7.3 7.2 8.2 7.3 7.3 8.6 7.3 7.3

TOC mg/L 3.2 2.6 2.6 3.2 2.6 2.6 3.9 3.6 4.4 3.9 3.2 3.2

As (total) μg/L 15.8 3.6 1.7 16.6 3.0 1.8 15.0 3.6 2.0 18.7

17.7

4.6

4.4

2.7

2.6

As (total soluble) μg/L 19.4

19.3

2.6

2.6

2.9

2.9

As (particulate) μg/L <0.1

<0.1

2.0

1.8

<0.1

<0.1

As (III) μg/L 1.2

1.1

0.6

0.9

0.6

1.0

As (V) μg/L 18.2

18.2

2.0

1.7

2.3

1.9

Total Al μg/L 493 353 41.1 441 266 49.1 325 345 60.1 488

466

528

529

63.7

65.8

Total Fe μg/L 507 <30 <30 456 <30 <30 345 <30 <30 471

474

<30

<30

<30

<30

Total Mn μg/L 36.6 8.3 0.5 36.4 6.9 <0.5 27.5 7.6 <0.5 31.4

32.1

8.9

8.9

0.6

<0.5

Dissolved Al μg/L 1.5

1.2

57.7

58.3

38.4

36.6

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.7

2.8

5.3

5.3

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
71

Table B-2. Analytical Results from Long Term Sampling, Plant B (July 23 to August 13, 1998)

Sampling Date 7/23/98 7/30/98 8/6/98 8/13/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 147

146

122

123

100

100 122 96.0 97.0 123 99.0 100 121120

100

99

98.0

98.0

Turbidity NTU 6.8

7.1

1.0

1.0

<0.1

<0.1 6.0 0.8 <0.1 3.6 1.2 <0.1 3.53.3

1.1

1.1

<0.1

<0.1

pH 8.1

8.1

7.5

7.4

7.4

7.4 8.6 7.4 7.3 8.4 7.5 7.4 8.5

8.5

7.3

7.3

7.3

7.3

TOC mg/L 3.6

3.8

2.9

2.8

2.9

3.0 3.5 2.9 3.0 3.3 3.0 1.7 3.5

3.3

2.8

2.9

2.8

2.7

As (total) μg/L 18.2 6.0 3.3 15.8 4.8 3.1 17.9

16.1

5.7

5.2

4.1

3.7 17.3 5.2 2.7

As (total soluble) μg/L 18.0

18.6

2.8

2.8

3.8

3.7

As (particulate) μg/L <0.1

<0.1

2.9

2.4

0.3

<0.1

As (III) μg/L 0.4

0.4

0.3

0.2

0.2

0.2

As (V) μg/L 17.6

18.2

2.6

2.5

3.6

3.5

Total Al μg/L 501 598 77.5 141 521 81.2 114

109

602

519

63.9

61.1 241 695 81.6

Total Fe μg/L 498 33.2 <30 164 <30 <30 128

126

<30

<30

<30

<30 245 41.1 <30

Total Mn μg/L 39.0 8.2 <0.5 21.3 13.6 0.9 14.4

13.4

14.5

12.6

0.7

0.8 18.4 15.7 0.8

Dissolved Al μg/L <11

<11

69.2

70.1

49.2

50.0

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.7

2.8

8.8

8.8

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
7

2

Table B-3. Analytical Results from Long Term Sampling, Plant B (August 20 to September 10, 1998)

Sampling Date 8/20/98 8/27/98 9/3/98 9/10/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 122 101 103 120 102 102 120 98.0 102 119

119

100

99.0

100

99.0

Turbidity NTU 3.6 0.9 <0.1 4.4 0.7 <0.1 4.6 1.0 <0.1 4.4

4.3

0.5

0.5

<0.1

<0.1

pH 8.6 7.6 7.5 8.4 7.3 7.3 8.4 7.3 7.3 8.3

8.3

7.3

7.3

7.3

7.3

TOC mg/L 3.7 3.1 2.9 3.7 3.2 3.0 3.7 3.2 3.1 4.1

4.0

3.0

2.9

3.5

3.2

As (total) μg/L 15.8 5.6 2.7 19.1 5.9 3.7 16.0

16.3

5.5

4.6

3.1

3.5 16.3 4.1 3.1

As (total soluble) μg/L 19.3

19.5

2.8

2.7

3.8

3.6

As (particulate) μg/L <0.1

<0.1

2.7

1.9

<0.1

<0.1

As (III) μg/L 0.1

0.2

<0.1

<0.1

<0.1

<0.1

As (V) μg/L 19.2

19.3

2.8

2.7

3.8

3.6

Total Al μg/L 307 67.6 62.9 84.8 466 71.0 78.1

75.1

588

510

58.8

69.1 76.5 309 56.3

Total Fe μg/L 282 30.4 <30 76.2 <30 <30 84.2

77.4

<30

<30

<30

<30 84.6 <30 <30

Total Mn μg/L 18.1 14.0 0.7 15.5 10.3 0.8 16.1

15.6

12.7

10.9

0.5

0.5 14.7 7.4 <0.5

Dissolved Al μg/L <11

<11

76.7

77.1

47.9

47.2

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 4.8

4.7

9.8

9.7

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
7

3

Table B-4. Analytical Results from Long Term Sampling, Plant B (September 17 to October 8, 1998)

Sampling Date 9/17/98 9/24/98 10/1/98 10/8/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 119 98.0 100 122 97.0 99.0 120 105 101 123

124

105

105

105

103

Turbidity NTU 4.4 0.7 <0.1 2.9 0.4 <0.1 2.0 1.2 <0.1 2.1

2.3

.8

.8

<.1

<.1

pH 8.3 7.3 7.3 8.3 7.3 7.3 8.3 7.4 7.3 8.4

8.4

7.4

7.4

7.4

7.4

TOC mg/L 3.9 3.3 3.7 3.9 3.0 3.1 3.9 3.3 3.2 3.8

3.9

4.3

3.3

3.2

3.2

As (total) μg/L 18.2 5.3 4.0 18.5 5.0 3.9 19.3

19.0

7.8

7.9

3.3

3.4 18.2 7.5 3.4

As (total soluble) μg/L 19.2

19.4

3.4

3.3

3.3

3.3

As (particulate) μg/L 0.1

<0.1

4.4

4.6

<0.1

<0.1

As (III) μg/L 0.6

0.6

0.5

0.5

0.5

0.5

As (V) μg/L 18.6

18.8

2.9

2.8

2.8

2.8

Total Al μg/L 74.7 406 64.0 77.0 382 71.7 84.7

88.3

644

637

56.0

57.6 147 809 60.3

Total Fe μg/L 77.6 <30 <30 78.8 <30 <30 75.7

78.4

<30

<30

<30

<30 121 <30 <30

Total Mn μg/L 17.0 10.9 0.5 14.0 10.7 0.7 13.8

13.8

17.9

17.8

0.7

0.8 15.3 12.1 0.5

Dissolved Al μg/L <11

<11

64.3

66.8

43.6

39.2

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 3.3

3.4

9.1

9.1

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
7

4

Table B-5. Analytical Results from Long Term Sampling, Plant B (October 15 to November 5, 1998)

Sampling Date 10/15/98 10/22/98 10/29/98(b) 11/5/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 124 110 108 124 104 104 122 116 116 124

126

119

118

119

119

Turbidity NTU 2.8 0.7 <0.1 1.7 0.6 <0.1 1.4 0.6 <0.1 1.2

1.2

0.6

0.6

<0.1

<0.1

pH 8.3 7.4 7.4 8.3 7.4 7.3 8.4 7.8 7.7 8.2

8.2

8.2

8.0

8.0

8.0

TOC mg/L 3.7 3.7 3.8 3.7 3.0 3.1 3.7 3.3 3.4 3.4

3.5

3.0

3.0

3.1

3.2

As (total) μg/L 18.7 6.5 3.9 17.9 5.0 2.8 19.8

19.7

12.3

12.4

9.8

10.2 20.8 15.5 11.8

As (total soluble) μg/L 19.4

19.2

9.5

9.5

10.1

10.1

As (particulate) μg/L 0.4

0.5

2.8

2.9

<0.1

<0.1

As (III) μg/L 0.4

0.4

0.3

0.3

0.3

0.3

As (V) μg/L 19.0

18.8

9.2

9.2

9.8

9.8

Total Al μg/L 160 578 54.1 443 580 46.2 62.5

72.2

494

497

79.3

84.6 109 563 98.4

Total Fe μg/L 107 <30 <30 90.4 70.0 <30 67.7

73.7

<30

<30

<30

<30 78.7 <30 <30

Total Mn μg/L 18.5 8.3 0.5 11.5 15.0 0.6 20.7

21.0

8.5

8.7

0.8

0.8 21.9 8.7 0.9

Dissolved Al μg/L <11

<11

123

118

75.6

78.2

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 4.3

4.4

1.7

1.0

<0.5

<0.5

(a) As CaCO3.

(b) The plant started using polyaluminum chloride (PAX-18) instead of alum since 10/27/98.

IN = inlet; PF = prefiltration; AF = after filtration.
7

5

Table B-6. Analytical Results from Long Term Sampling, Plant B (November 12 to December 3, 1998)

Sampling Date 11/12/98 11/19/98 11/26/98(b) 12/3/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 126 121 120 129 123 122 132 127 125

Turbidity NTU 1.0 0.6 <0.1 1.2 0.7 <0.1 1.5 0.8 0.2

pH 8.2 7.8 7.8 7.9 7.8 7.7 8.1 7.8 7.8

TOC mg/L 3.1 3.0 3.0 3.0 3.0 3.0 3.5 2.9 2.9

As (total) μg/L 18.6 10.6 10.5 17.4 12.3 10.2 17.0

17.2

12.9

12.6

11.0

10.9

As (total soluble) μg/L 20.1

19.3

12.3

12.0

12.3

12.7

As (particulate) μg/L <0.1

<0.1

0.6

0.6

<0.1

<0.1

As (III) μg/L 0.4

0.4

0.4

0.3

0.4

0.4

As (V) μg/L 19.7

18.9

11.9

11.7

11.9

12.3

Total Al μg/L 75.7 89.3 87.9 59.6 474 90.4 152

101

458

423

96.4

96.3

Total Fe μg/L 55.0 <30 <30 32.2 <30 <30 164

126

54.4

45.0

82.1

32.7

Total Mn μg/L 15.1 0.6 0.5 13.1 4.6 <0.5 15.5

14.9

6.4

6.1

0.9

0.7

Dissolved Al μg/L <11

<11

105

106

76.2

74.9

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 4.3

4.2

2.1

2.1

<0.5

<0.5

(a) As CaCO3.

(b) No sampling due to Thanksgiving holiday.

IN = inlet; PF = prefiltration; AF = after filtration.
7

6

Table B-7. Analytical Results from Long Term Sampling, Plant B (December 10 to 31, 1999)

Sampling Date 12/10/98 12/17/98(b) 12/24/98(c) 12/31/98©

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 134

135

126

127

126

126 134 120 119

Turbidity NTU 1.9

1.9

0.6

0.7

<0.1

<0.1 2.0 0.5 <0.1

pH 8.3

8.3

7.8

7.8

7.8

7.8 8.3 7.4 7.4

TOC mg/L 3.2

4.3

3.2

3.1

2.9

3.2 3.2 2.9 2.8

As (total) μg/L 19.2 13.8 11.2 17.7 4.7 2.5

As (total soluble) μg/L

As (particulate) μg/L

As (III) μg/L

As (V) μg/L

Total Al μg/L 128 473 87.5 137 509 42.3

Total Fe μg/L 52.9 <30 <30 48.5 <30 <30

Total Mn μg/L 15.9 4.7 0.6 16.0 6.6 <0.5

Dissolved Al μg/L

Dissolved Fe μg/L

Dissolved Mn μg/L

(a) As CaCO3.

(b) The plant stopped using polyaluminum chloride (PAX-18) since 12/15/98 a<0.1 uses alum instead.

(c) No sampling due to Christmas holiday.

IN = inlet; PF = prefiltration; AF = after filtration.
7

7

Table B-8. Analytical Results from Long Term Sampling, Plant B (January 7 to 28, 1999)

Sampling Date 01/07/99 01/14/99 01/21/99 01/28/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 131 117 118 131 117 114 134

131

117

118

117

117 137 132 119

Turbidity NTU 1.1 0.8 <0.1 1.6 0.8 <0.1 2.7

2.8

1.1

1.0

<0.1

<0.1 1.3 0.8 <0.1

pH 8.1 7.4 7.3 8.3 7.4 7.4 8.3

8.3

7.4

7.4

7.4

7.4 8.3 7.4 7.4

TOC mg/L 3.5 2.8 2.8 3.2 2.7 2.8 3.9

3.6

3.0

3.4

3.0

3.0 2.9 2.4 2.4

As (total) μg/L 15.3 4.8 2.3 21.0

20.1

6.2

5.8

1.9

1.8 16.5 5.5 1.6 18.0 5.3 1.6

As (total soluble) μg/L 21.0

21.0

2.3

2.3

2.3

2.3

As (particulate) μg/L <0.1

<0.1

3.9

3.5

<0.1

<0.1

As (III) μg/L 0.4

0.4

0.2

0.2

0.4

0.4

As (V) μg/L 20.6

20.6

2.1

2.1

1.9

1.9

Total Al μg/L 43.4 481 35.0 70.6

47.2

700

681

49.2

48.0 133 629 43.1 66.5 660 40.9

Total Fe μg/L 82.3 43.9 <30 <30

46.7

82.7

68.5

<30

<30 142 <30 <30 79.8 32.5 <30

Total Mn μg/L 13.8 8.0 <0.5 13.5

13.4

5.2

5.3

1.0

1.1 13.7 4.9 0.6 13.4 18.2 0.7

Dissolved Al μg/L <11

<11

72.7

72.0

40.8

41.6

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.0

1.6

3.8

3.7

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
7

8

Table B-9. Analytical Results from Long Term Sampling, Plant B (Feb 4 to Feb 25, 1999)

Sampling Date 02/04/99 02/11/99 02/18/99 02/25/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 136 121 117 136 118 119 134

135

118

118

118

110 134 120 118

Turbidity NTU 3.4 1.1 <0.1 1.8 0.9 <0.1 2.8

2.8

1.0

1.0

<0.1

<0.1 2.6 0.7 <0.1

pH 8.3 7.5 7.4 8.3 7.5 7.5 8.4

8.4

7.5

7.5

7.5

7.5 8.4 7.5 7.4

TOC mg/L 3.1 2.7 2.5 3.2 2.4 2.5 3.0

3.3

2.6

2.7

2.5

2.6 3.5 3.4 3.7

As (total) μg/L 19.4 5.2 1.7 18.9

18.4

6.5

6.3

2.0

2.0 15.0 4.7 1.5 19.2 5.7 2.6

As (total soluble) μg/L 20.1

20.9

2.2

2.1

2.2

2.2

As (particulate) μg/L <0.1

<0.1

4.3

4.2

<0.1

<0.1

As (III) μg/L 0.3

0.3

0.2

0.2

0.3

0.3

As (V) μg/L 19.8

20.6

2.0

1.9

1.9

1.9

Total Al μg/L 141 591 41.4 99.1

95.4

597

606

43.8

37.5 88.3 506 28.9 104 470 44.1

Total Fe μg/L 180 <30 <30 120

112

32.2

<30

<30

<30 96.9 <30 <30 152 30.9 <30

Total Mn μg/L 14.5 10.9 <0.5 11.0

11.0

7.9

7.4

<0.5

<0.5 11.7 6.5 0.6 16.1 13.8 <0.5

Dissolved Al μg/L <11

<11

66.3

67.1

30.6

29.9

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 2.1

1.9

5.0

5.1

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
7

9

Table B-10. Analytical Results from Long Term Sampling, Plant B (Mar 4 to Mar 25, 1999)

Sampling Date 03/04/99 03/11/99 03/18/99 03/25/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 131 119 122 138 122 122 136

137

123

122

123

123 138 123 123

Turbidity NTU 1.7 0.8 <0.1 1.5 0.8 <0.1 3.1

3.0

0.9

0.9

<0.1

<0.1 4.5 1.1 <0.1

pH 8.4 7.4 7.5 8.4 7.5 7.5 8.4

8.4

7.5

7.5

7.5

7.5 8.5 7.5 7.5

TOC mg/L 4.7 2.8 2.8 3.0 2.6 2.5 3.0

3.4

2.8

2.7

2.8

2.8 3.2 2.8 3.2

As (total) μg/L 20.8 6.6 3.1 21.5

20.6

7.4

7.4

3.2

3.2 20.2 6.6 3.3 21.4 8.6 3.9

As (total soluble) μg/L 20.9

20.8

3.6

3.8

3.6

3.7

As (particulate) μg/L 0.6

<0.1

3.8

3.6

<0.1

<0.1

As (III) μg/L 0.7

0.6

0.5

0.5

0.6

0.6

As (V) μg/L 20.2

20.2

3.1

3.3

3.0

3.1

Total Al μg/L 107 478 48.5 110

91.4

599

593

44.9

39.6 101 614 55.4 314 710 60.5

Total Fe μg/L 137 <30 <30 83.2

79.1

<30

<30

<30

<30 118 <30 <30 326 <30 <30

Total Mn μg/L 16.5 7.8 0.5 15.8

14.7

8.6

8.9

<0.5

<0.5 20.9 12.1 5.8 32.5 17.0 1.9

Dissolved Al μg/L <11

<11

59.3

57.8

29.9

33.8

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 3.2

3.2

5.9

5.9

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
8

0

Table B-11. Analytical Results from Long Term Sampling, Plant B (Apr 1 to Apr 22, 1999)

Sampling Date 04/01/99 04/08/99 04/15/99 04/22/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 141 124 125 142 127 125

142

144

126

125

123

123 142 124 121

Turbidity NTU 2.9 0.8 <0.1 3.5 0.6 <0.1 1.4

1.4

0.6

0.6

<0.1

<0.1 2.0 0.6 <0.1

pH 8.5 7.5 7.5 8.4 7.5 7.5 8.4

8.4

7.5

7.4

7.4

7.4 8.3 7.4 7.4

TOC mg/L 3.2 3.4 3.1 3.6 2.9 2.6 3.3

3.3

2.9

2.9

3.0

3.1 3.6 3.1 2.6

As (total) μg/L 21.3 6.2 3.9 22.4

22.0

6.5

6.2

4.7

4.6 21.8 6.2 4.1 22.8 5.9 3.8

As (total soluble) μg/L 21.8

21.7

4.5

4.1

4.5

4.5

As (particulate) μg/L 0.6

0.3

2.0

2.1

0.2

0.1

As (III) μg/L 0.6

0.5

0.4

0.4

0.4

0.4

As (V) μg/L 21.2

21.2

4.1

3.7

4.1

4.1

Total Al μg/L 159 493 42.4 171

137

431

420

47.6

45.3 87.0 400 39.9 153 499 47.9

Total Fe μg/L 150 33.8 <30 158

113

<30

<30

<30

<30 74.2 <30 <30 105 <30 <30

Total Mn μg/L 20.3 9.3 <0.5 24.5

23.4

10.9

10.5

0.7

0.7 23.0 8.0 0.7 23.5 10.3 0.5

Dissolved Al μg/L <11

<11

110

73.7

29.0

29.5

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 7.4

7.6

7.5

7.1

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
81

Table B-12. Analytical Results from Long Term Sampling, Plant B (Apr 29 to May 20, 1999)

Sampling Date 04/29/99 05/6/99 05/13/99 05/20/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a)140 122 120 140 121 119 137

140

121

120

118

118 139 122 119

Turbidity NTU 3.3 0.6 <0.1 2.7 0.6 <0.1 1.2

1.2

0.3

0.3

<0.1

<0.1 2.4 0.9 <0.1

pH 8.4 7.4 7.4 8.4 7.4 7.4 8.6

8.6

7.4

7.4

7.4

7.4 8.6 7.4 7.4

TOC mg/L 2.8 2.3 2.3 4.6 3.2 3.1 3.5

3.2

3.0

3.0

2.6

3.2 9.8 8.6 8.7

As (total) μg/L 20.9 6.1 4.1 22.7

22.1

6.0

6.0

3.8

3.8 23.9 5.7 3.4 23.5 7.0 3.9

As (total soluble) μg/L 23.1

23.0

3.7

3.7

3.8

3.8

As (particulate) μg/L <0.1

<0.1

2.3

2.3

<0.1

<0.1

As (III) μg/L 1.2

1.3

1.3

1.2

0.8

0.9

As (V) μg/L 21.9

21.7

2.4

2.5

3.0

2.9

Total Al μg/L 167 370 38.7 88.9

75.9

464

462

34.9

34.0 100 406 36.3 136 603 52.5

Total Fe μg/L 162 <30 <30 109

87.9

<30

<30

<30

<30 102 <30 <30 135 <30 <30

Total Mn μg/L 23.2 8.1 1.1 14.7

14.6

5.9

5.9

0.5

0.5 20.5 5.6 0.5 18.3 6.2 <0.5

Dissolved Al μg/L <11

<11

53.7

52.0

30.8

32.9

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 3.7

3.8

3.5

3.5

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
8

2

Table B-13. Analytical Results from Long Term Sampling, Plant B (May 27 to June 17, 1999)

Sampling Date 05/27/99 06/03/99 06/10/99 06/17/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 136 116 116 134 112 112 138

137

115

116

115

114 136 111 111

Turbidity NTU 3.6 1.1 <0.1 3.8 0.6 <0.1 5.5

5.7

0.5

0.5

<0.1

<0.1 6.6 0.7 <0.1

pH 8.5 7.3 7.3 8.3 7.3 7.3 8.4

8.4

7.3

7.3

7.2

7.2 8.4 7.2 7.2

TOC mg/L 3.3 2.7 3.2 3.6 2.8 2.9 3.0

4.7

2.5

2.8

2.6

2.7 3.6 3.2 3.2

As (total) μg/L 21.1 6.2 3.8 20.8

20.4

3.7

3.7

2.8

2.7 21.7 3.8 2.4 23.1 4.2 2.5

As (total soluble) μg/L 21.5

20.7

2.7

2.7

2.7

2.7

As (particulate) μg/L <0.1

<0.1

1.0

1.0

0.1

<0.1

As (III) μg/L 0.8

0.7

0.4

0.4

0.3

0.3

As (V) μg/L 20.8

20.0

2.3

2.3

2.4

2.3

Total Al μg/L 180 658 58.8 205

167

296

291

28.4

27.8 409 362 37.2 366 442 43.7

Total Fe μg/L 167 35.7 30.8 185

175

37.3

32.8

<30

<30 379 <30 17.9 437 18.8 <30

Total Mn μg/L 20.5 7.0 0.5 20.8

20.3

13.0

6.9

<0.5

<0.5 25.7 5.6 <0.5 36.0 8.9 <0.5

Dissolved Al μg/L <11

<11

41.4

42.1

26.2

25.2

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 7.5

7.4

4.5

5.1

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
83

APPENDIX C

Complete Analytical Results from Long-Term Sampling at Plant C
8

4

Table C-1. Analytical Results from Long Term Sampling, Plant C (June 22 to July 13, 1998)

Sampling Date 6/22/98 6/29/98 7/6/98 7/13/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 388 232 199 394 239 175 400 382 193 392 136 183

Turbidity NTU 23.2 6.3 1.6 16.1 7.6 0.6 29.0 18.3 0.8 16.3 3.3 0.4

pH 7.4 8.7 8.8 7.3 8.7 9.0 7.2 8.1 8.8 7.2 10.1 9.0

Total Hardness mg/L(a) 320 158 189 296 244 143 293 304 148 296 89.1 136

Ca Hardness mg/L(a) 200 56.0 72.0 180 132 45.0 177 180 51.0 180 27.7 42.9

Mg Hardness mg/L(a) 120 102 118 117 112 98.0 115 124 96.8 116 61.4 93.1

As (total) μg/L 42.5 27.8 21.7 26.7 23.9 19.8 34.0 22.9 17.6 25.7

27.9

16.8

16.6

17.2

17.0

As (total soluble) μg/L 35.5

35.4

17.4

17.3

18.8

19.2

As (particulate) μg/L <0.1

<0.1

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 29.1

30.3

<0.1

<0.1

<0.1

<0.1

As (V) μg/L 6.4

5.1

17.3

17.3

18.8

19.2

Total Al μg/L <11 28.5 17.0 <11 41.8 13.4 11.5 46.2 17.2 43.6

37.4

24.9

25.0

12.4

<11

Total Fe μg/L 2,217 258 64.9 1,155 401 <30 1,828 742 <30 1,571

1,796

81.4

81.4

<30

<30

Total Mn μg/L 117 7.1 4.4 103 12.8 3.7 101 48.9 2.9 114

129

3.7

3.5

2.0

2.1

Dissolved Al μg/L <11

<11

11.3

<11

<11

<11

Dissolved Fe μg/L 1,506

1,518

<30

<30

<30

<30

Dissolved Mn μg/L 108

105

<0.5

<0.5

1.4

1.4

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
8

5

Table C-2. Analytical Results from Long Term Sampling, Plant C (July 20 to August 10, 1998)

Sampling Date 7/20/98 7/28/98 8/3/98 8/10/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 392

394

224

222

147

146 397 229 194 393 204 168 400399

247

246

184

182

Turbidity NTU 31.0

30.0

5.1

4.9

0.3

0.3 18.8 5.8 0.6 29.0 3.1 0.5 31.031.0

26.0

25.0

0.2

0.2

pH 7.3

7.2

8.6

8.6

9.2

9.2 7.2 8.5 8.6 7.4 9.0 9.0 7.37.3

8.7

8.7

8.8

8.8

Total Hardness mg/L(a) 321

298

176

181

112

108 350 206 174 320 169 138 314

305

215

221

149

147

Ca Hardness mg/L(a) 202

185

62.7

66.9

31.7

31.0 217 82.4 56.4 195 54.2 36.2 192

187

103

107

47.2

45.7

Mg Hardness mg/L(a) 119

113

113

114

79.9

77.4 133 124 117.4 125 115 102 122

117

112

115

102

101

As (total) μg/L 37.1 28.5 19.3 38.6 29.2 20.8 33.6

37.3

29.0

28.7

20.9

20.6 35.7 28.1 19.4

As (total soluble) μg/L 41.0

39.8

30.3

30.7

22.4

22.7

As (particulate) μg/L <0.1

<0.1

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 32.5

34.1

17.9

17.8

0.4

0.4

As (V) μg/L 8.5

5.7

12.4

12.9

22.0

22.3

Total Al μg/L 38.3 31.4 12.9 11.2 40.2 15.4 <11

23.4

43.0

38.9

22.6

16.0 <11 47.6 16.1

Total Fe μg/L 1,879 205 <30 2,066 359 <30 1,934

2,092

322

337

34.6

31.6 2,173 704 <30

Total Mn μg/L 106 4.6 1.0 104 7.7 3.2 98.7

105

7.1

7.1

1.8

1.7 101 18.4 3.3

Dissolved Al μg/L <11

<11

14.7

15.3

<11

<11

Dissolved Fe μg/L 2,382

2,157

<30

<30

<30

<30

Dissolved Mn μg/L 126

120

1.4

1.4

0.9

0.9

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
8

6

Table C-3. Analytical Results from Long Term Sampling, Plant C (August 17 to September 8, 1998)

Sampling Date 8/17/98 8/25/98 8/31/98 9/8/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 394 181 177 400 235 195 398 225 189 403

399

189

188

184

183

Turbidity NTU 33.0 25.0 0.2 31 8.4 0.2 32.0 11.3 1.9 30.0

28.0

5.7

5.8

0.3

0.2

pH 7.2 9.6 8.8 7.3 8.4 8.4 7.2 8.7 8.5 7.2

7.2

9.0

9.0

8.4

8.4

Total Hardness mg/L(a) 317 175 151 324 202 158 322 194 157 341

328

157

155

155

165

Ca Hardness mg/L(a) 192 73.7 43.9 197 82.2 43.7 200 85.4 50.9 212

202

44.9

44.4

43.4

53.4

Mg Hardness mg/L(a) 124 101 108 126 119 114 123 109 106 129

126

112

110

111

112

As (total) μg/L 33.2 24.2 18.3 19.4 28.2 17.3 31.5

31.9

25.5

25.6

18.7

18.7 28.7 21.9 15.9

As (total soluble) μg/L 35.9

37.5

24.5

26.2

18.7

17.8

As (particulate) μg/L <0.1

<0.1

1.0

<0.1

<0.1

0.9

As (III) μg/L 26.1

26.7

1.0

1.0

0.7

0.7

As (V) μg/L 9.8

10.8

23.5

25.2

18.0

17.1

Total Al μg/L 11.7 50.4 13.8 22.1 57.5 23.0 15.5

12.7

48.0

46.5

35.9

29.8 <11 32.6 17.8

Total Fe μg/L 2,597 587 <30 91.5 458 235 2,279

2,310

661

644

253

255 1,989 269 <30

Total Mn μg/L 129 15.8 1.8 121 11.5 2.3 117

118

16.1

15.0

6.6

6.7 108 5.1 1.5

Dissolved Al μg/L <11

<11

22.7

22.7

<11

<11

Dissolved Fe μg/L 2,224

2,239

<30

<30

<30

<30

Dissolved Mn μg/L 122

120

5.0

5.0

2.0

1.9

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
8

7

Table C-4. Analytical Results from Long Term Sampling, Plant C (September 14 to October 5, 1998)

Sampling Date 9/14/98 9/21/98 9/28/98 10/5/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 410 197 214 404 252 209 397 216 212 403

404

201

199

197

197

Turbidity NTU 27 11.1 0.2 26.0 4.2 0.6 28.0 18.0 0.5 27.0

26.0

9.7

10.0

1.2

1.2

pH 7.1 8.8 8.3 7.2 8.0 8.1 7.3 9.0 8.4 7.3

7.3

9.1

9.2

8.5

8.5

Total Hardness mg/L 290 178 173 311 214 176 267 183 183 316

317

163

152

164

164

Ca Hardness mg/L 170 69.2 61.7 190 95.6 66.4 167 73.4 68.4 195

195

52.7

44.7

54.4

53.4

Mg Hardness mg/L 120 109 112 122 119 110 99.2 110 115 122

122

110

107

110

111

As (total) μg/L 16.2 20.2 13.1 28.9 21.6 14.0 35.0

36.8

28.8

28.8

17.5

17.9 28.0 20.6 14.9

As (total soluble) μg/L 36.0

35.7

26.8

26.8

16.3

16.9

As (particulate) μg/L <0.1

1.1

2.0

2.0

1.2

1.0

As (III) μg/L 34.0

33.7

0.7

0.7

0.7

0.7

As (V) μg/L 2.0

2.0

26.1

26.1

15.6

16.2

Total Al μg/L <11 50.0 22.2 <11 27.7 31.8 <11

<11

44.9

41.9

15.9

21.0 <11 28.7 18.7

Total Fe μg/L 1,498 473 <30 2,229 206 161 2,218

2,331

313

312

34.2

35.4 1,967 273 58.1

Total Mn μg/L 75.9 10.6 2.7 114 11.9 7.1 111

116

12.2

12.2

3.1

3.1 109 6.2 3.6

Dissolved Al μg/L <11

<11

16.4

16.4

<11

<11

Dissolved Fe μg/L 2,003

1,780

<30

<30

<30

<30

Dissolved Mn μg/L 106

107

0.9

0.9

1.6

1.6

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = outlet.
8

8

Table C-5. Analytical Results from Long Term Sampling, Plant C (October 12 to November 2, 1998)

Sampling Date 10/12/98 10/19/98 10/26/98 11/2/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 405 274 173 401 184 212 404 211 251 397

398

228

229

202

203

Turbidity NTU 18.3 5.7 1.1 25.0 7.1 0.8 26.0 6.1 0.4 22.0

24.0

6.8

6.5

0.1

0.1

pH 7.1 8.2 8.8 7.2 9.0 8.4 7.2 8.6 8.1 7.2

7.2

8.2

8.2

8.5

8.5

Total Hardness mg/L(a) 325 225 149 328 140 174 327 169 216 321

325

186

186

163

170

Ca Hardness mg/L(a) 205 83.9 45.2 205 40.0 66.7 205 52.9 100 202

202

66.7

67.4

50.2

59.2

Mg Hardness mg/L(a) 120 141 103 124 101 108 122 117 116 119

123

119

118

113

111

As (total) μg/L 26.4 17.6 13.1 26.0 21.4 12.3 29.0

28.5

22.1

21.4

12.8

12.3 31.6 23.3 18.2

As (total soluble) μg/L 33.1

32.7

24.6

26.0

15.2

15.0

As (particulate) μg/L <0.1

<0.1

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 28.4(b)

28.9(b)

0.4

0.2

<0.1

<0.1

As (V) μg/L 4.7

3.8

24.2

25.8

15.2

15.0

Total Al μg/L <11 17.2 20.3 16.0 28.5 14.0 <11

<11

40.2

46.1

15.1

14.2 <11 33.1 <11

Total Fe μg/L 2,785 145 56.3 3,768 295 <30 2,386

2,373

285

301

96.5

40.0 2,385 159 <30

Total Mn μg/L 145 7.3 2.7 204 6.5 1.9 154

154

6.5

6.4

5.9

5.7 147 7.0 2.1

Dissolved Al μg/L <11

<11

23.0

23.1

<11

<11

Dissolved Fe μg/L 2,316

2,115

<30

<30

<30

<30

Dissolved Mn μg/L 148

145

1.8

1.8

4.7

4.6

(a) As CaCO3.

(b) Rerun data.

IN = inlet; PF = prefiltration; AF = after filtration.
8

9

Table C-6. Analytical Results from Long Term Sampling, Plant C (November 9 to November 30, 1998)

Sampling Date 11/9/98 11/16/98 11/23/98(b) 11/30/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 403 267 194 403 125 181 399 201 153

Turbidity NTU 28 1.5 <0.1 24 11.3 0.2 25 2.8 0.3

pH 7.1 8.0 8.4 7.2 10.1 8.9 7.2 8.6 8.9

Total Hardness mg/L(a) 336 226 170 346 85 150 330 161 129

Ca Hardness mg/L(a) 212 99.6 55.4 225 35.7 46.7 207 42.9 32.7

Mg Hardness mg/L(a) 124 126 115 122 49.4 103 123 118 96.4

As (total) μg/L 34.5 26.0 16.9 32.3 14.2 14.7 31.4

30.5

23.4

24.0

15.6

15.7

As (total soluble) μg/L 33.7

33.4

25.6

25.9

17.9

17.6

As (particulate) μg/L <0.1

<0.1

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 29.7

30.8

0.3

0.2

0.2

0.2

As (V) μg/L 4.0

2.6

25.3

25.7

17.7

17.4

Total Al μg/L <11 42.7 12.9 <11 35.6 17.8 <11

19.6

16.4

18.7

19.1

21.8

Total Fe μg/L 2,680 159 35.3 2,704 119 <30 2,600

2,585

270

268

61.5

56.3

Total Mn μg/L 164 12.1 2.4 146 5.0 1.0 150

149

4.8

4.9

1.6

1.6

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L

2,495

2,458

<30

<30

<30

<30

Dissolved Mn μg/L 147

147

1.9

1.9

0.9

0.8

(a) As CaCO3.

(b) No sampling due to the Thanksgiving Holiday

IN = inlet; PF = prefiltration; AF = after filtration.
9

0

Table C-7. Analytical Results from Long Term Sampling, Plant C (December 7, 1998 to December 28 ,1998)

Sampling Date 12/7/98 12/14/98 12/21/98(b) 12/28/98(b)

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 396

398

173

174

205

204 408 143 188

Turbidity NTU 27

26

9.2

9.1

0.3

0.4 18.6 20 1.2

pH 7.3

7.2

9.7

9.7

8.3

8.3 7.2 10.1 8.8

Total Hardness mg/L(a) 320

314

133

133

168

167 335 147 157

Ca Hardness mg/L(a) 200

195

44.9

44.7

58.9

58.9 212 77.2 44.4

Mg Hardness mg/L(a) 121

119

88.5

88.1

109

108 123 69.6 113

As (total) μg/L 32.7 22.6 17.3 32.4 16.5 16.0

As (total soluble) μg/L

As (particulate) μg/L

As (III) μg/L

As (V) μg/L

Total Al μg/L <11 41.1 12.6 <11 29.4 11.1

Total Fe μg/L 2,756 376 <30 2,774 220 <30

Total Mn μg/L 159 10.9 2.9 177 4.8 1.1

Dissolved Al μg/L

Dissolved Fe μg/L

Dissolved Mn μg/L

(a) As CaCO3.

(b) No sampling due to Christmas Holiday.

IN = inlet; PF = prefiltration; AF = after filtration.
91

Table C-8. Analytical Results from Long Term Sampling, Plant C (January 4 to January 25, 1999)

Sampling Date 01/04/99 01/11/99 01/18/99 01/25/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 391 195 217 407 228 195 400

399

231

229

187

187 402 236 192

Turbidity NTU 21 0.7 0.7 29 11.6 0.3 22

22

16.8

16.3

0.9

0.9 29 5.6 0.7

pH 7.1 9.0 8.5 7.2 8.5 8.4 7.2

7.2

8.7

8.7

8.5

8.5 7.2 8.8 8.8

Total Hardness mg/L(a) 318 166 180 352 190 159 342

321

188

186

154

155 303 170 149

Ca Hardness mg/L(a) 200 61.4 66.7 232 78.4 52.2 215

197

76.9

75.7

42.4

41.7 185 57.2 38.7

Mg Hardness mg/L(a) 119 105 113 120 111 107 127

124

111

111

112

113 118 113 110

As (total) μg/L 41.1 32.6 18.9 33.5

33.0

21.0

21.0

13.5

13.9 15.9 12.9 9.2 30.3 25.5 17.6

As (total soluble) μg/L 29.7

30.0

22.1

22.7

15.2

15.5

As (particulate) μg/L 3.8

3.1

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 26.9

27.1

0.3

0.3

0.3

0.2

As (V) μg/L 2.9

2.7

21.8

22.4

14.9

15.2

Total Al μg/L <11 58.1 20.0 <11

<11

55.6

52.5

19.6

19.1 <11 71.9 13.4 <11 29.9 11.6

Total Fe μg/L 2,920 613 211 2,596

2,601

490

480

<30

<30 2,134 617 53.0 2,322 403 50.6

Total Mn μg/L 156 13.3 6.6 132

134

9.5

9.2

3.9

3.8 118 14.8 2.4 128 7.4 1.7

Dissolved Al μg/L <11

<11

32.1

33.1

<11

<11

Dissolved Fe μg/L 2,426

2,415

<30

<30

<30

<30

Dissolved Mn μg/L 181

180

2.7

2.8

1.8

4.0

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
9

2

Table C-9. Analytical Results from Long Term Sampling, Plant C (February 1, 1999 to February 22, 1999)

Sampling Date 02/01/99 02/08/99 02/15/99 02/22/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 411 181 193 399 196 210 399

398

222

223

212

212 405 237 193

Turbidity NTU 23 6.5 0.6 24 3.3 0.7 25

25

8.1

8.4

1.0

1.0 24 9.3 0.5

pH 7.2 9.2 8.7 7.2 8.6 8.3 7.2

7.2

8.8

8.8

8.4

8.4 7.3 8.6 8.4

Total Hardness mg/L(a) 353 160 157 338 157 174 323

337

187

188

184

181 317 183 153

Ca Hardness mg/L(a) 225 55.2 46.4 207 44.9 58.2 207

217

75.7

76.2

69.2

66.9 197 75.9 42.9

Mg Hardness mg/L(a) 128 105 111 123 112 116 115

120

111

112

115

115 119 108 110

As (total) μg/L 19.1 14.6 11.7 20.9

20.4

16.3

17.2

12.1

12.4 33.4 26.2 17.0 20.4 17.0 11.2

As (total soluble) μg/L 26.0

23.4

18.0

17.6

14.0

13.9

As (particulate) μg/L <0.1

<0.1

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 21.9

22.8

0.1

0.2

0.3

0.2

As (V) μg/L 4.1

0.6

17.9

17.4

13.7

13.7

Total Al μg/L <11 67.7 98.8 40.7

85.5

138

36.7

17.3

17.3 <11 34.8 17.3 <11 61.0 11.9

Total Fe μg/L 2,029 399 49.9 2,269

2,183

269

286

35.2

35.2 2,865 472 31.6 2,476 621 34.0

Total Mn μg/L 136 8.9 1.9 185

181

6.0

6.5

4.0

3.9 166 13.9 4.0 178 16.0 2.6

Dissolved Al μg/L <11

<11

16.2

16.1

<11

<11

Dissolved Fe μg/L 2,175

2,095

<30

<30

<30

<30

Dissolved Mn μg/L 185

193

0.9

1.0

3.2

3.1

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
9

3

Table C-10. Analytical Results from Long Term Sampling, Plant C (Mar 1, 1999 to Mar 22, 1999)

Sampling Date 03/01/99 03/08/99 03/15/99 03/22/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 405 157 185 408 253 211 394

396

192

191

321

322 405 218 200

Turbidity NTU 23 7.2 0.1 25 18.1 0.4 31

30

6.4

7.9

24

26 27 5.8 0.3

pH 7.2 9.3 8.7 7.2 8.5 8.7 7.2

7.2

9.1

9.1

7.9

7.9 7.2 8.6 8.4

Total Hardness mg/L(a) 328 142 143 325 225 183 331

321

155

154

291

290 326 178 187

Ca Hardness mg/L(a) 207 59.2 44.2 200 105 71.9 210

202

49.9

49.2

165

165 205 63.2 67.4

Mg Hardness mg/L(a) 121 82.4 98.8 125 120 111 121

119

105

105

126

125 122 115 120

As (total) μg/L 21.9 13.5 13.7 23.9

24.5

17.1

16.9

11.6

12.0 36.3 28.4 17.3 21.7 17.4 33.1

As (total soluble) μg/L 22.1

21.7

18.3

18.9

14.4

14.4

As (particulate) μg/L 1.8

2.8

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 21.5

22.5

0.5

0.5

0.5

0.4

As (V) μg/L 0.6

<0.1

17.8

18.4

13.9

14.0

Total Al μg/L <11 41.6 17.7 <11

<11

60.5

62.6

15.0

17.0 <11 44.8 84.8 <11 51.0 21.7

Total Fe μg/L 2,536 346 <30 2,464

2,641

617

600

<30

<30 2,901 401 1,110 2,501 378 <30

Total Mn μg/L 169 13.8 2.4 151

162

26.1

25.1

4.2

4.3 148 21.4 54.7 166 9.7 6.7

Dissolved Al μg/L <11

<11

35.9

35.9

12.6

12.2

Dissolved Fe μg/L 2,534

2,523

<30

<30

<30

<30

Dissolved Mn μg/L 162

163

7.8

7.9

1.9

2.0

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
9

4

Table C-11. Analytical Results from Long Term Sampling, Plant C (Mar 29, 1999 to Apr 19, 1999)

Sampling Date 03/29/99 04/05/99 04/12/99 04/19/99

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 396 227 308 401 238 166 405

402

182

182

183

184 402 232 238

Turbidity NTU 30 5.3 1.0 29 8.3 0.4 30

30

3.7

3.6

5.8

5.7 31 9.2 1.4

pH 7.2 8.6 7.8 7.3 8.5 9.3 7.2

7.2

9.3

9.3

8.8

8.8 7.2 8.6 8.8

Total Hardness mg/L(a) 300 165 242 340 222 125 303

296

132

133

144

145 305 181 179

Ca Hardness mg/L(a) 185 55.7 122 215 109 37.2 187

182

37.5

36.2

47.9

48.2 187 70.2 69.7

Mg Hardness mg/L(a) 115 109 119 125 113 87.7 116

114

94.7

96.8

96.4

96.8 118 111 110

As (total) μg/L 36.5 27.2 12.1 40.1

39.2

31.4

30.8

18.8

18.2 34.8 26.7 21.5 36.3 26.8 21.7

As (total soluble) μg/L 40.6

40.2

30.5

31.5

18.7

18.7

As (particulate) μg/L <0.1

<0.1

0.9

<0.1

0.1

<0.1

As (III) μg/L 37.4

37.0

1.1

1.1

0.3

0.3

As (V) μg/L 3.2

3.2

29.4

30.4

18.4

18.4

Total Al μg/L <11 40.5 17.9 <11

<11

52.4

47.6

12.8

13.9 5.1 23.6 21.0 12.3 51.9 18.0

Total Fe μg/L 2,571 273 63.6 2,518

2,488

451

454

<30

<30 3,073 323 156 2,954 411 55.8

Total Mn μg/L 147 6.2 22.8 140

139

11.1

11.0

1.4

1.4 177 7.2 8.7 168 12.8 6.6

Dissolved Al μg/L <11

<11

23.5

34.1

<11

<11

Dissolved Fe μg/L 2,611

2,437

<30

<30

<30

<30

Dissolved Mn μg/L 152

151

4.2

4.2

0.7

0.7

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration.
9

5

Table C-12. Analytical Results from Long Term Sampling, Plant C (Apr 26, 1999 to May 17, 1999)

Sampling Date 04/26/99 05/03/99 05/10/99 05/17/99

Sampling Location

Parameter Unit IN PF AF IN AR PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 410 210 193 404 403 223 194 293

307

225

226

212

213 409 188 190

Turbidity NTU 30.0 13.9 1.6 27.0 11.0 10.6 0.4 26

27

17.2

17.1

0.7

0.7 32 16.4 0.6

pH 7.2 9.0 8.7 7.2 7.6 8.9 9.2 7.2

7.1

8.7

8.7

8.6

8.6 7.2 9.3 9.0

Total Hardness mg/L(a) 310 212 167 316 303 171 148 298

299

203

198

181

185 309 161 139

Ca Hardness mg/L(a) 195 109 63.9 197 187 59.7 41.9 180

182

93.6

91.4

67.4

71.4 200 66.7 43.9

Mg Hardness mg/L(a) 115 104 103 119 116 111 106 118

117

109

107

114

113 109 94.3 94.7

As (total) μg/L 84.9 25.8 16.0 40.4

39.4

43.5

36.7

30.2

32.4

17.2

16.8 35.1 23.9 13.7 40.9 30.2 22.4

As (total soluble) μg/L 31.2

33.8

33.3

33.6

27.4

27.2

17.3

17.7

As (particulate) μg/L 9.2

5.5

10.2

3.1

2.8

5.2

<0.1

<0.1

As (III) μg/L 33.9

33.8

28.5

29.7

0.9

1.1

1.7

1.3

As (V) μg/L <0.1

<0.1

4.7

3.8

26.5

26.1

15.7

16.5

Total Al μg/L 20.8 52.1 15.0 <11

<11

<11

<11

25.5

30.6

11.4

<11 32.1 77.8 16.7 <11 57.6 13.5

Total Fe μg/L 2,435 663 <30 2,396

2,318

2,945

3,684

443

410

<30

<30 2,931 766 40.4 2,546 624 <30

Total Mn μg/L 135 18.6 3.2 134

134

139

141

9.6

9.9

2.2

1.4 156 23.7 4.1 143 17.3 3.6

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 2,485

2,456

891

1,017

<30

<30

<30

<30

Dissolved Mn μg/L 136

134

134

132

2.1

2.1

0.9

1.1

(a) As CaCO3.

IN = inlet; AR = after-aeration; PF = prefiltration; AF = after filtration.
9

6

Table C-13. Analytical Results from Long Term Sampling, Plant C (May 24, 1999 to Jun 14, 1999)

Sampling Date 05/24/99 06/01/99 06/07/99 06/14/99

Sampling Location

Parameter Unit IN PF AF IN AR PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 406 248 189 402 399 178 192 400

404

169

168

180

181 411 242 184

Turbidity NTU 27.0 18.2 0.5 31.0 8.3 10.2 0.6 31.0

31.0

14.2

14.0

5.1

5.0 23.0 13.1 0.4

pH 7.1 8.6 8.7 7.2 7.7 7.9 8.9 7.2

7.2

9.8

9.8

9.0

8.9 7.2 8.5 8.9

Total Hardness mg/L(a) 300 187 146 303 296 172 153 327

305

145

139

137

138 327 220 151

Ca Hardness mg/L(a) 187 73.7 45.7 190 185 83.9 54.2 220

197

68.4

64.2

53.9

56.9 207 110 51.2

Mg Hardness mg/L(a) 112 113 100 113 112 88.5 98.4 108

108

77.0

74.5

83.2

81.1 120 110 100

As (total) μg/L 35.1 27.4 18.5 38.4

39.1

36.3

35.8

26.6

26.6

16.3

16.6 39.0 24.5 20.0 16.5 7.7 6.3

As (total soluble) μg/L 40.8

40.7

36.1

36.9

22.9

22.8

17.2

16.0

As (particulate) μg/L <0.1

<0.1

0.2

<0.1

3.7

3.7

<0.1

0.6

As (III) μg/L 34.3

36.1

28.7

30.7

0.4

0.3

0.3

0.4

As (V) μg/L 6.4

4.5

7.4

6.3

22.5

22.5

16.8

15.7

Total Al μg/L <11 36.8 13.0 <11

<11

<11

22.4

19.0

17.7

11.3

<11 48.8 43.6 26.8 <11 66.2 14.9

Total Fe μg/L 2,872 220 <30 2,892

2,914

2,784

2,967

687

701

33.7

32.3 2,746 558 297 2,341 544 97.0

Total Mn μg/L 178 12.7 1.7 173

174

177

173

21.6

22.2

2.5

2.5

142 17.7 9.1 147 34.0 1.3

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 2,964

2,969

462

788

<30

<30

<30

<30

Dissolved Mn μg/L 180

183

179

183

2.2

2.2

1.7

1.6

(a) As CaCO3.

IN = inlet; AR = after-aeration; PF = prefiltration; AF = after filtration.