EPA/600/R-00/086

August 2000

Arsenic Removal from 

Drinking Water by 

Iron Removal Plants

by

Keith Fields

Abraham Chen

Lili Wang

Battelle

Columbus, OH 43201-2693

Contract No. 68-C7-0008

Work Assignment 3-09

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 iron removal plants (referred to as Plants A and B). 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 chemical

characteristics of residuals produced by the treatment processes.

The study was divided into three phases: source water sampling, preliminary sampling, and longterm evaluation. The first phase, source water sampling, was conducted to evaluate source water 

characteristics at each plant. The second phase, preliminary sampling, was initiated at Plant A in 

April 1998 and at Plant B in May 1998. This phase consisted of a four-week sampling period to 

refine procedures for subsequent events during the third phase. The third phase, long-term 

evaluation, consisted of weekly sample collection and analysis beginning in June 1998 and

continuing through June 1999 at Plant A and through December 1998 at Plant B. Plant personnel 

conducted all sampling during the long-term evaluation phase and Battelle coordinated sampling 

logistics. Sludge samples also were collected at Plant A during a single sampling event from an 

outdoor settling pond in November 1998. Samples of supernatant discharge (Plant A) and recycle 

supernatant (Plant B) were collected monthly beginning in November 1998 and continuing until

June 1999 at Plant A and until January 1999 at Plant B.

Results from the long-term evaluation phase were varied regarding the ability of the iron removal 

process to consistently achieve low-level arsenic concentrations (e.g., <5 μg/L in the finished 

water). The total arsenic concentrations at Plant A were reduced by an average of 87%, which

represents a decrease in average arsenic concentration from 20.3 μg/L to 3.0 μg/L. Adsorption

and coprecipitation with iron hydroxide precipitates are believed to be the primary arsenic removal 

mechanisms. The total arsenic concentrations at Plant B were reduced by an average of 74%,

which represents a decrease in average arsenic concentration from 48.5 μg/L to 11.9 μg/L. At

Plant B, it appeared that only the particulate arsenic in the source water was removed. This particulate arsenic was most likely associated with the oxidized iron particles present in the source 

water (i.e., arsenic sorbed onto iron particles). The primary difference in arsenic removal efficiency 

at Plants A and B is believed to be the amount of iron in the source water. Source water at Plant A 

averaged 2,284 μg/L of iron, while Plant B averaged 1,137 μg/L. Increasing the iron in the source 

water at Plant B using a coagulant, such as ferric chloride, would likely enable Plant B to consistently achieve lower levels of arsenic.

None of the sludge samples collected at Plant A qualified as a hazardous waste based on the

Toxicity Characteristic Leaching Procedure (TCLP) test for metals. Therefore, nonhazardous waste

landfills should be able to accept the sludge generated by this treatment facility. Stricter hazardous waste classification regulations in some states, such as California, on total arsenic concentrations in solid waste also were met at Plant A. Sludge samples were not collected at Plant B; 

however, analytical results were provided from a 1994 sludge sampling event.
v

Contents

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

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

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

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

Acronyms and Abbreviations....................................................................................ix

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

1.1.4 Data Gaps ....................................................................................... 4

1.2 Objectives ................................................................................................. 4

1.3 Report Organization .................................................................................. 4

2.0 Conclusions ...................................................................................................... 5

3.0 Materials and Methods ...................................................................................... 6

3.1 General Project Approach.......................................................................... 6

3.2 Preparation of Sampling Kits and Sample Coolers ..................................... 7

3.2.1 Preparation of Arsenic Speciation Kits.............................................. 7

3.2.2 Preparation of Recycle Backwash Water/Supernatant 

Discharge Sampling Kits .................................................................. 8

3.2.3 Preparation of Sample Coolers ........................................................ 8

3.3 Sampling Procedures ................................................................................ 9

3.3.1 General Approach and Sampling Schedules .................................... 9

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

3.3.3 Recycle Supernatant/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................................................................................... 16

4.1 Plant Selection ........................................................................................ 16

4.2 Plant A .................................................................................................... 16

4.2.1 Plant A Description ........................................................................ 17

4.2.2 Initial Source Water Sampling........................................................ 17

4.2.3 Preliminary Sampling..................................................................... 17

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 Supernatant Discharge.................................................... 24

4.2.4.4 Sludge............................................................................. 26
vi

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

4.3.1 Plant B Description ........................................................................ 28

4.3.2 Initial Source Water Sampling........................................................ 28

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...................................... 34

4.3.4.3 Recycle Supernatant ....................................................... 37

4.3.4.4 Sludge............................................................................. 37

5.0 Quality Assurance/Quality Control................................................................... 39

5.1 Quality Assurance Objectives .................................................................. 39

5.2 Overall Assessment of Data Quality......................................................... 39

5.2.1 Total Arsenic, Aluminum, Iron, and Manganese.............................. 39

5.2.2 Water Quality Parameters .............................................................. 40

5.2.3 TCLP Metals in Sludge .................................................................. 40

6.0 References...................................................................................................... 41

Appendices

Appendix A: Complete Analytical Results from Long-Term Sampling at Plant A..... 43

Appendix B: Complete Analytical Results from Long-Term Sampling at Plant B..... 57
vii

Figures

Page

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

Figure 3-1. Example of Sample Bottle Label......................................................... 9

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................................... 12

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

Sampling.......................................................................................... 14

Figure 4-1. Schematic Diagram, Plant A............................................................. 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............................................................................................. 23

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

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

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

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

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

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

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

Plant B............................................................................................. 34

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

Sampling at Plant B.......................................................................... 35

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

Plant B............................................................................................. 37
viii

Tables

Page

Table 3-1. Sample Containers and Preservation Methods ................................... 8

Table 3-2. Summary of Sampling Activities at Plants A and B ........................... 10

Table 3-3. Summary of Sampling Schedule for Plants A and B.......................... 10

Table 3-4. Summary of Analytical Methods for Arsenic Treatment Study ........... 15

Table 4-1. Initial List of Treatment Facilities Identified for the Study................... 16

Table 4-2. Source Water Analytical Results at Plant A (February 10, 1998)....... 19

Table 4-3. Analytical Results from Preliminary Sampling at Plant A (April 22 to 

May 13, 1998).................................................................................. 21

Table 4-4. Summary of Arsenic Analytical Results at Plant A ............................ 22

Table 4-5. Summary of Water Quality Parameter Analytical Results at Plant A.. 26

Table 4-6. Summary of Analytical Results from Supernatant Discharge 

Samples at Plant A........................................................................... 27

Table 4-7. Analytical Results of Sludge Sampling at Plant A.............................. 28

Table 4-8. Source Water Analytical Results at Plant B (February 4, 1998)......... 30

Table 4-9. Analytical Results from Preliminary Sampling at Plant B (May 7 

through May 28, 1998)..................................................................... 32

Table 4-10. Summary of Arsenic Analytical Results at Plant B ............................ 33

Table 4-11. Summary of Water Quality Parameter Analytical Results at Plant B.. 36

Table 4-12. Summary of Analytical Results from Recycle Supernatant Samples 

at Plant B......................................................................................... 38
ix

Acronyms and Abbreviations

AF after filtration

As arsenic

AS after softening

ASTM American Society for Testing and Materials

AWWA American Water Works Association

AWWARF American Water Works Association Research Foundation

cfs cubic feet per second

DI distilled

EDR electrodialysis reversal

EPA United States Environmental Protection Agency

GFAAS graphite-furnace atomic-absorption spectrophotometer

GI gastrointestinal

gpm gallons per minute

GW ground water

HCl hydrochloric acid

HDPE high-density polyethylene

ICP-MS inductively coupled plasma/mass spectrometry

ID identification

IN inlet

KMnO4 potassium permanganate

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

NS not sampled

NTU nephelometric turbidity units

PF prefiltration

POC point of contact

ppm parts per million

psi pounds per square inch
x

QA quality assurance

QAPP Quality Assurance Project Plan

QA/QC Quality Assurance/Quality Control

RPD relative percent difference

SDWA Safe Drinking Water Act

SW surface water

TCLP Toxicity Characteristic Leaching Procedure

TDS total dissolved solids

TOC total organic carbon

TSS total suspended solids

WA work assignment

WAM work assignment manager

%R percent recovery
xi

Acknowledgments

Sincere appreciation is extended to the two 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 at Plant A and more than 6 months at Plant B. Their work on this project 

was uncompensated, making their superb efforts even more remarkable. Personnel from both

plants are thanked for their hard work and dedication throughout the duration of this project.
1

1.0 Introduction

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

drinking water samples from various locations throughout the treatment processes at two iron removal plants. 

These samples were analyzed and used to evaluate the 

effectiveness of conventional iron removal 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 the treatment processes. This report describes 

the design and operation of the two treatment plants and 

presents the analytical results of the water samples collected during the study.

1.1 Background

The Safe Drinking Water Act (SDWA) of 1974 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 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 remove arsenic to a level significantly lower than the current MCL. This study was conducted as part of an EPA Work Assignment (WA) 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 from [As(III)] normally is found in ground water 

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

aerobic conditions), although this rule 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, and arsenite is neutral at pH <9 

and ionic at pH >9. Conventional treatment technologies 

used for arsenic removal, such as iron removal, 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.

Although soluble arsenic species typically make up the

majority of the total arsenic concentration in natural

waters, some research indicates that arsenic can exist as 

particulate at significant concentrations. Studies by Cheng
2

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

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

arsenic at levels of 17 and 50% of the total arsenic concentration, respectively, in 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 method exists 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 costeffective 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 50-100 

mesh resin for the 100-200 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 the 

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 filtration to remove arsenic. Chemical precipitation is another common, conventional treatment process 

used for water softening as well as iron and manganese 

removal 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 iron removal, a conventional treatment process used for arsenic removal at large-scale 

operations. Two additional reports have been developed

for (1) coagulation/filtration and lime softening plants and 

(2) anion exchange and activated alumina plants.

Chemical precipitation/filtration commonly is used for removal of iron from source waters. This process, referred 

to in this document as iron removal, involves two major 

steps: (1) oxidation of reduced iron, Fe(II), to the relatively insoluble Fe(III) in order to form precipitates; and

(2) filtration of the water to remove the precipitated iron 

hydroxides. The most common oxidants used to precipitate soluble iron are air, chlorine, and potassium permanganate.

Iron removal can be used to remove arsenic from drinking water. Two primary removal mechanisms exist: adsorption and coprecipitation (Benefield and Morgan,

1990). During the adsorption process, dissolved arsenic 

attaches to the surface of a particle or precipitate. And

during the coprecipitation process, dissolved arsenic is

adsorbed to a particle and entrapped as the particle continues to agglomerate. The following major steps occur

when using iron removal for arsenic treatment: (1) the soluble iron and any As(III) are oxidized; (2) As(V) attaches 

to the iron hydroxides through adsorption and/or coprecipitation; and (3) the particle/precipitate subsequently is filtered from the water.
4

Several bench- and pilot-scale studies and some shortterm full-scale evaluations have been conducted to evaluate arsenic removal during iron hydroxide precipitation. 

Most of the 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

be easily converted to As(V) using a strong oxidant such 

as chlorine (Hering et al., 1996; Sorg, 1993). McNeill and 

Edwards (1995) conducted a survey of full-scale treatment facilities and observed that arsenic removal efficiencies of 80 to 95 percent were obtained at facilities 

with greater than 1.5 mg/L Fe(II) in the source water.

However, arsenic removal efficiency may be reduced in 

the presence of orthophosphate, natural organic matter

(NOM), and silicate due to competition for sorptive sites 

on iron hydroxide precipitates (Edwards, 1994; Meng et 

al., 2000).

Previous studies also indicate that arsenic removal during iron hydroxide precipitation is directly correlated with 

the initial, or inlet, iron concentration (i.e., arsenic removal efficiency increases with increasing iron concentrations) (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; Cheng et al., 1994; 

Edwards, 1994). Other research indicates that As(V)

removal is not pH-dependent between pH 5.5 and 8.5 for 

iron hydroxide precipitation (Sorg and Logsdon, 1978;

Sorg, 1993; Hering et al., 1996).

1.1.4 Data Gaps

The removal of arsenic from drinking water by adsorption and coprecipitation with metal hydroxides has been 

extensively studied at the laboratory and pilot-scale level.

Although some short-term full-scale evaluations have

been performed for iron removal, little data exist on the

capability of (natural) iron removal in full-scale applications to reduce arsenic on a sustained basis. Thus, a

need exists to determine the effectiveness of the iron

removal process to produce drinking water with low levels of arsenic on a long-term basis, under varying operational and seasonal conditions.

Another data gap is the generation and disposal of residuals from conventional drinking water treatment processes. Currently, little or no data exist on the amounts and 

the chemical composition of residuals generated by the

arsenic removal processes and the environmental impacts 

of their disposal. Therefore, information needs to be collected on the quantity and the chemical characteristics of 

the wastes produced by iron removal plants.

1.2 Objectives

One objective of this study was to evaluate the effectiveness of conventional iron removal to consistently reduce 

arsenic concentrations in source water to low levels.

This report presents the results of weekly monitoring for 

approximately one year and 6 months at Plants A and B, 

respectively.

Another objective of this study was to examine the residuals produced during treatment at iron removal plants.

Information was collected on the 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 iron

removal plants. 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 and B present the complete set of analytical data collected at Plants A and B,

respectively, during long-term sampling.
5

2.0 Conclusions

The U.S. EPA has begun the process of revising the

arsenic MCL. It is anticipated that the revised limit will be 

significantly lower than the current 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 study were to 

document arsenic removal at two iron removal plants, 

and to assess potential impacts of 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 sampling (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 four-week sampling period to refine the

sampling approach before implementing the long-term 

sampling 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 collection and analysis of water samples at both 

water treatment plants. The long-term evaluation also

included sludge sampling (November 1998 at Plant A

only), supernatant discharge sampling (November 1998

through June 1999 at Plant A), and recycle supernatant 

sampling (November 1998 through January 1999 at

Plant B). During the long-term sampling, plant personnel 

conducted sampling and Battelle coordinated sampling 

logistics.

The primary focus of this study was the long-term performance of the two iron removal plants. Total arsenic

concentrations at Plant A were reduced from an average 

of 20.3 μg/L to 3.0 μg/L. Total arsenic concentrations at 

Plant B were reduced from an average of 48.5 μg/L to

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

iron hydroxides precipitates are believed to be the primary arsenic removal mechanism at Plant A. Plant A

oxidized As(III) in the source water to As(V) using chlorination. At Plant B, it appeared that only the particulate 

arsenic in the source water was removed. Particulate 

arsenic most likely represents the arsenic sorbed to oxidized iron particles. The primary difference in arsenic

removal between Plants A and B is believed to be the

amount of iron in the source water. Source water at

Plant A averaged 2,284 μg/L of iron, while Plant B averaged 1,137 μg/L. Therefore, increasing the available iron 

at Plant B by using a coagulant such as ferric chloride 

would likely enable Plant B to consistently achieve lower 

levels of arsenic.

The secondary focus of this study was on the chemical 

characteristics of the residuals generated during the treatment processes. None of the sludge samples collected at 

Plant A qualified as a hazardous waste based on Toxicity Characteristic Leaching Procedure (TCLP) tests for 

metals. Therefore, sludge generated by this plant should 

be accepted by nonhazardous waste landfills. Sludge

samples were not collected at Plant B; however, the plant 

did provide analytical results from a 1994 sampling event. 

TCLP tests were not performed on this sample, although 

the total arsenic concentration exceeded stricter requirements in California regarding hazardous waste classification. Supernatant water from the settling pond at Plant A 

was discharged to the sanitary sewer, whereas backwash 

water at Plant B was allowed to settle in a concrete vat 

then combined with the source water. The recycle supernatant at Plant B did not appear to adversely impact treatment plant operations.
6

3.0 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 iron removal

plants. 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 study 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 

up to one 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 on the following 

criteria: 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 iron

removal plants (designated as Plants A and B) 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 and B 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 both plants over a four-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-ofcustody 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 

from four sampling locations at Plant A: (1) the inlet to

the treatment plant (IN); (2) before the filtration process 

(prefiltration [PF]); (3) after the filtration process (AF);

and (4) after a final zeolite resin softening process (AS). 

Also, water samples were collected weekly from three

sampling locations at Plant B: (1) the inlet to the treatment 

plant (IN); (2) before the filtration process (PF); (3) and

after the filtration process at the plant outlet (AF). During 

the preliminary and long-term sampling phases, field arsenic speciation sampling was conducted once every four 

weeks. Starting from November 1998, samples of supernatant discharge (from a settling pond at Plant A) or recycle supernatant (from a concrete vat at Plant B) were

collected once every four weeks from each plant. Finally,
7

three sludge samples were collected from the settling

pond at Plant A during one sampling event.

All sample containers and arsenic speciation kits were

prepared 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 using

an ICP-MS method. 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/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 collecting 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 retained 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 eluate from 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 made up the total arsenic concentration of the resin-treated sample in bottle C. The 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:

• One anion exchange resin column

• 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 for 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 reagentgrade 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, respectively, of concentrated ultra-pure 

HNO3; 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 Cl– in HCl could interfere with the ICP-MS 

arsenic detection and HNO3 (an oxidizing agent) 
8

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, 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 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

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

250 mL (D) plastic 4°C pH immediate

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

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.
9

(for water and sludge samples), sample preservation used,

analysis to be performed, and holding time. All sample 

containers were labeled prior to shipment.

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. 

When arsenic speciation or recycle supernatant/supernatant discharge samples were to be collected, arsenic 

speciation kits or recycle supernatant/supernatant discharge sampling kits also were included in the cooler.

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

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 (Plant 

A only) and the monthly collection of recycle supernatant 

or supernatant discharge, 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 both plants.

During the preliminary and long-term sampling, sample

collection was conducted on a four-week cycle, with each

week having unique sampling requirements. Table 3-3 

summarizes the schedules for the initial source water,

the preliminary, the long-term, and the sludge sampling

at both plants.

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 

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 on 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, and turbidity) were sent along with sample coolers 

or transmitted via facsimile to Battelle for information/ 

evaluation. 

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

Date: 02/15/98 Time: 11 a.m.

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
10

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

Sampling Activities

Sampling 

Frequency Plant A Plant B

Initial source water sampling Once 02/10/98 02/4/98

Preliminary sampling Weekly 4/22/98 through 5/13/98 5/7/98 through 5/28/98

Long-term sampling Weekly(a) 6/24/98 through 06/16/99 6/11/98 through 12/8/98

Sludge sampling Once 11/18/98 NS

Recycle water sampling Weekly 11/11/98 through 06/16/99 11/10/98 through 1/15/99

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

NS = Not sampled.

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* W* W W W W* W W, R* W

As (total soluble) W* W* W* R*

As (particulate) W* W* W* R*

As (III) W* W* W*

As (V) W* W* W*

Al (total) W* W* W* W W, R* W

Fe (total) W* W* W W W W* W W, R* W

Mn (total) W* W* W W W W* W W, R* W

Al (dissolved) W* R*

Fe (dissolved) W* R*

Mn (dissolved) W* R*

Alkalinity W* W* W W W W W* W W

Sulfate W*

NO3-NO2 (N) W*

TOC W*

Turbidity W* W* W

pH W* W* W W W W W* W, R* W

Hardness W* W* W

Ca Hardness W* W* W

Mg Hardness W* W* W

TCLP Metals S

Percent Moisture S

pH S

As (total) S

Fe (total) S

Mn (total) S

* = Duplicate samples collected and analyzed.

W = Water samples collected from the inlet, prefiltration, and after-filtration locations (Plants A and B) and from after-softening location (Plant A 

only).

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

S = Sludge samples collected at Plant A.

Empty cells indicate no samples taken.

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):

• 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
11

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

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).

• 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.
12

Figure 3-3. Instruction Sheet for Arsenic Field Speciation
13

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).

3.3.3 Recycle Supernatant/Supernatant 

Discharge Sampling Procedure

Figure 3-4 shows an instruction sheet for performing recycle supernatant and supernatant discharge sampling. 

Because both total and dissolved As, Al, Fe, and Mn

were analyzed, the procedure for recycle supernatant/ 

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 Table 3-3, 

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 3-4 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 low-cost 

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

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.

It should be noted that turbidity tests were not run on site. 

Relatively high levels of reduced iron in raw water samples may have oxidized during transportation of samples 

to the analytical laboratory, resulting in elevated turbidity 

readings. The turbidity might have been much lower if

readings had been taken on site.
14

Figure 3-4. Instruction Sheet for Recycle Supernatant/Supernatant Discharge Sampling
15

Table 3-4. 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

ASTM = American Society for Testing and Materials.
16

4.0 Results and Discussion

This section presents the results of the treatment plant

selection process, which resulted in the selection of two 

iron removal plants, referred to as Plants A and B. In

addition, results from water and residuals sampling and

analysis at each plant are summarized and discussed. 

Complete analytical results from long-term water sampling at Plants A and B are presented in Appendices A 

and B, 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 eight potential iron 

removal treatment facilities. These 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 on the following criteria: source water arsenic concentrations, source water 

type, availability of manpower to conduct study, availability of historical 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 

long-term 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 a 

mix of plants using ground water and/or surface water

sources.

From the eight initial plants, two iron removal plants 

were selected for site visits and source water sampling

(see 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 sampling at

both facilities during each phase of the study are presented in the sections that follow.

4.2 Plant A

Water and residual samples were collected and analyzed 

at Plant A during three phases of the study. The first

phase consisted of source water sampling, which was

used to help determine if the plant should be considered 

for further evaluation. 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 four-week period in April and May 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 four locations throughout the treatment process. Also, arsenic speciation sampling was conducted every fourth week. The third phase 

of the study also included residual sample collection and 

analysis. Supernatant discharge samples from the settling pond were collected monthly beginning in November 

1998, and three sludge samples were collected during a 

single sampling event from the settling pond.

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

Plant 

ID Process

Source Water Arsenic 

Concentration, March 1995(a)

(μg/L)

Source Water Arsenic 

Concentration, September 1997(a)

(μg/L)

Population

Served

Historical 

Data

Source Water 

Type

A Iron removal 30.2 Not sampled 15,000 Yes Ground water

B Iron removal Not sampled 65 Up to 20,000 Yes Surface water

(a) Results provided by treatment facility.
17

4.2.1 Plant A Description

Plant A is one of three plants that provides water to a

city with a population of approximately 15,000 (approximately 6,000 connections). Plant A was built in 1970 and 

treats ground water using an iron removal process followed by zeolite softening. The plant is capable of treating 1.6 million gallons per day (mgd). A schematic diagram 

of the Plant A treatment process is shown in Figure 4-1.

The treatment process consists of the following major

elements:

• Aeration. Aeration is used to oxidize iron and 

manganese as well as remove H2S, NH3, SO2, and 

CH4.

• Chlorination. Approximately 5 mg/L total chlorine 

(1.5-2 mg/L free chlorine) is added to oxidize 

remaining iron and manganese and to disinfect 

filters and softeners.

• Sedimentation. Sedimentation occurs in a baffled 

basin with approximately 20 minutes retention 

time. After sedimentation, potassium permanganate (KMnO4

) is added to remove manganese, 

taste, and odor as well as to continuously regenerate the manganese greensand in the filter.

• Filtration. The filtering media consists of 

manganese greensand (top) and graded gravel 

(bottom). A water backwash occurs every 20 hours 

and an air backwash occurs every 72 hours.

• Softening. Approximately two thirds of the filtered 

water is sent through a zeolite resin softener (ion

exchange) to reduce hardness. Regeneration 

occurs every 175,000 gal processed with 27% 

solution of NaCl. The regeneration takes approximately 1 hour and consists of a 12-minute backwash, 20-minute brine rinse, and a slow/fast rinse 

cycle.

• Postchlorination. Approximately 5 to 6 mg/L of 

total chlorine (<1 mg/L free chlorine) is added for 

distribution residual. Also, 0.9 to 1.2 mg/L of 

fluoride (H2SiF6) is added. No ammonia is added 

because the water contains NH3 and about 0.8 to 

1.0 mg/L of residual chloramines is maintained in 

the finished water.

• Backwash. Backwash water and regenerant 

waste is sent to an outdoor settling pond and 

supernatant is discharged to the sanitary sewer. 

Sludge is sent to wastewater plant drying beds and 

then to local farm fields. No arsenic sampling on 

sludge had been conducted prior to this study.

4.2.2 Initial Source Water Sampling

Plant A obtains source water from three ground water

wells (Wells 5, 6, and 7). Each well is approximately

275 ft deep. An initial site visit to Plant A was conducted 

February 10, 1998 during which time source water samples were collected from the intake, which represents a 

combined sample from ground water Wells 5, 6, and 7.

The total arsenic concentration during the initial sampling event was 23.5 μg/L. Particulate arsenic accounted 

for 1.7 μg/L of the total arsenic concentration, and soluble arsenic accounted for the remaining 21.8 μg/L. Field 

arsenic speciation sampling indicated that the soluble

arsenic consisted of 20.1 μg/L of As(III) and 1.7 μg/L of 

As(V), which was consistent with what would be expected for a ground water source. Also, as would be

expected at an iron removal plant, the total iron concentration was relatively high, 2,700 μg/L. Table 4-2 presents 

the complete analytical results from the initial source

water sampling event.

Due primarily to the relatively high source water arsenic 

concentrations and the availability of plant personnel to

perform preliminary and long-term sampling, Plant A was 

selected for incorporation into the preliminary and longterm evaluation phases of this project.

4.2.3 Preliminary Sampling

During the preliminary sampling phase of this study,

water samples were collected at four locations within the 

treatment plant: inlet (IN), before filtration (PF), after filtration (AF), and after softening (AS). The IN samples 

were collected from a tap located prior to treatment and 

represents combined water from Wells 5, 6, and 7. The 

PF samples were collected after the water had undergone aeration, chlorination, and sedimentation.

After filtration and prior to zeolite softening, the AF samples were collected. Finally, the AS samples were collected after softening and prior to final chlorination and

H2SiF6 addition. 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, pH, total iron, total manganese, and total arsenic analyses were performed on samples collected at 

each of the four sampling locations each week. Turbidity, 

hardness, and arsenic speciation analyses were conducted once during the preliminary study on samples

collected at each sampling location. Soluble and particulate arsenic were determined as part of the arsenic
18

Figure 4-1. Schematic Diagram, Plant A
19

Table 4-2. Source Water Analytical Results at Plant A (February 10, 1998)

Parameter Unit

Primary

Sample

Duplicate

Sample Average

Alkalinity mg/L(a) 413 412 412.5

Sulfate mg/L <1 <1 <1

Turbidity NTU 25 24 24.5

pH 7.6 7.6 7.6

Hardness mg/L(a) 270 270 270

Ca Hardness mg/L(a) 140 137 138.5

Mg Hardness mg/L(a) 130 133 131.5

Total Al μg/L 400 400 400

Total Fe μg/L 2,640 2,760 2,700

Total Mn μg/L <20 <20 <20

NO3−NO2

(N)(b) mg/L <0.02 <0.02 <0.02

TOC mg/L 6 7 6.5

As (total) μg/L 23.5 23.4 23.5

As (total soluble) μg/L 21.9 21.6 21.8

As (particulate) μg/L 1.6 1.8 1.7

As (III) μg/L 19.7 20.5 20.1

As (V) μg/L 2.2 1.1 1.7

(a) As CaCO3.

(b) Combined NO3−N and NO2−N.

ND = not detected.

TOC = total organic carbon.

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

concentration. Table 4-3 presents the results from the

four-week preliminary sampling period.

Results from the preliminary sampling events indicated 

that inlet total arsenic concentrations ranged from approximately 23.7 to 18.6 μg/L. Consistent with the initial 

source water sampling, the source water contained 

primarily As(III) and minor concentrations of As(V) and

particulate arsenic. As would be expected following chlorination and sedimentation, As(III) had been almost completely oxidized to As(V) at the PF sampling location. It 

appeared that, after the As(III) had been oxidized to

As(V), it coprecipitated with the oxidized iron. Therefore, 

at the PF sampling location, arsenic was present primarily as particulate. The majority of the arsenic removal 

occurred during filtration. No significant removal occurred

during sedimentation or softening.

The average total arsenic removal by Plant A was approximately 91% during the preliminary sampling, reducing the 

finished water total arsenic concentration to between 3.4 

and 0.6 μg/L. McNeill and Edwards (1997) developed the

following simplified model for predicting arsenic removal 

during metal hydroxide precipitation based on raw water 

Fe and Al concentrations:

[ ]

(1 K [Fe Al]mM)

K Fe Al mM ArsenicSorbed(%) 100

+ × +

× +

= × (1)

where K = 78 mM−1

.

This model was based on data collected at more than 14 

full-scale 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 from 77% to 

79% compared to actual removal rate ranging from 84% 

to 97%. The maximum difference between the actual

and predicted arsenic removal efficiencies was 10%. It

should be noted that the calculation did not incorporate 

aluminum concentrations because they were not obtained during the preliminary sampling phase. Nevertheless, the simplified model appeared to approximate the

arsenic removal at Plant A fairly well, and was used to

evaluate long-term system performance.

Other water quality parameters were analyzed to support 

understanding of mechanisms of arsenic removal. During preliminary sampling, pH was relatively constant, at 

approximately 7.7 throughout the treatment process. This 

pH is in the range where no effect on arsenic removal

efficiency using iron hydroxide precipitation has been observed in previous studies (Sorg and Logsdon, 1978;

Sorg, 1993; Hering et al., 1996).

Oxidation of Fe(II) by chlorine may be described by the 

following chemical reaction:

2Fe2+ + Cl2 + 6H2O ⇔ 2Fe(OH)3

(s) + 2Cl− + 6H+(2)

The slight decrease in alkalinity observed after oxidation of 

the iron (i.e., at the PF sampling location) is a result of stoichiometry of iron oxidation in which protons are produced 

and alkalinity is destroyed (Benefield and Morgan, 1990).
20

INFLUENT

1

AERATION

SEDIMENTATION

2

FILTRATION

(GREENSAND)

3

DISTRIBUTION

SYSTEM

MONTHLY WEEKLY

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

Hardness, Dissolved Al, Fe, and Mn

Plant A

Iron Removal

Design Flow: 1.6 mgd

LEGEND

DA: Cl2

FILTRATION

KMnO4

Disinfectant Addition

Point

Unit Process

Chemical Added to

Unit Process

DA: Cl2

ZEOLITE

SOFTENING

4

As (total), Alkalinity, pH,

Total Al, Fe, and Mn

H2SiF6

KMnO4

SS

Sludge Sampling

Location

1

Water Sampling

Location

SETTLING

POND

Backwash Water

SUPERNATANT WATER

AND WASTEWATER

DISCHARGED TO

SS

As (total), Percent moisture, pH,

TCLP metals, Total Al, Fe, and Mn

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

Turbidity, Hardness,

Total Al, Fe, and Mn

As (total), Alkalinity, pH,

Total Al, Fe, and Mn

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

Turbidity, Hardness,

Total Al, Fe, and Mn

As (total), Alkalinity, pH,

Total Al, Fe, and Mn

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

Turbidity, Hardness,

Total Al, Fe, Mn

As (total), Alkalinity, pH,

Total Al, Fe, and Mn

As (dissolved and total), pH,

Al, Fe, and Mn (dissolved and total) 5

Approx. 2/3 of Flow Treated

Using Zeolite Softening

DA: Cl2

SLUDGE SENT TO DRYING BEDS,

THEN TO LOCAL FARM FIELDS

Regenerant Waste

SANITARY SEWER

(Yearly Basis)

Sludge

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 22–May 13, 1998)

Sampling Date 4/22/98(a) 4/29/98 5/6/98 5/13/98

Sampling Location

Parameter Unit IN PF AF AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(b) 411

410

387

385

382

381

387

387 409 385 381 387 407 391 387 389 413 375 382 374

Turbidity(c) NTU 24

22

5.1

5.2

0.3

0.2

0.2

0.1

pH —

7.6

7.6

7.6 

7.6 

7.7 

7.7

7.6

7.6 7.7 7.6 7.6 7.6 7.7 7.7 7.7 7.7 7.7 7.6 7.5 7.5

Hardness mg/L(b) 306

302

297

306

292

296

13.1

7.9

Ca Hardness mg/L(b) 150

150

150

160

145

147

10.7

5.6

Mg Hardness mg/L(b) 157

152

147

146

147

148

2.5

2.3

Total Fe μg/L 2,650

2,620

2,540

2,530

50

50

<30

160 2,520 2,570 50 30 2,540 2,380 70 50 2,390 2,290 120 <30

Total Mn μg/L 60

50

50

70

60

60

30

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

As (total) μg/L 21.4

21.6

20.0

18.8

3.1

2.4

3.3

3.5 23.7 22.1 3.2 2.7 18.6 20.3 2.1 1.3 20.2 21.3 2.0 0.6

As (total soluble) μg/L 24.5

24.7

4.1

4.1

2.8

2.8

3.6

3.6

As (particulate) μg/L ND

ND

15.9

14.7

0.3

ND

ND

ND

As (III) μg/L 19.6

22

0.2

0.1

0.1

0.2

0.1

0.2

As (V) μg/L 4.9

2.7

3.9

4.0

2.7

2.6

3.5

3.4

(a) Duplicate samples were taken on 4/22/98.

(b) As CaCO3.

(c) Inlet turbidity concentrations may be elevated due to oxidation of iron occurring after sample collection and prior to laboratory analysis.

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

ND = not detected.

NTU = nephelometric turbidity units.
22

The source water at Plant A would be classified as hard 

to very hard and the zeolite softening process effectively 

reduced hardness from approximately 304 mg/L (as

CaCO3) to 11 mg/L (as CaCO3). As stated previously, 

approximately two-thirds of the water processed at Plant 

A is treated using zeolite softening. Turbidity also was

effectively removed at Plant A with concentrations decreasing from approximately 23 NTU to 5.2 NTU following aeration, chlorination, and sedimentation. Relatively 

high turbidity concentrations at the inlet may be a result 

of iron oxidation after the sample was collected and prior 

to analysis. After filtration the turbidity decreased to approximately 0.3 NTU. Total manganese concentrations 

were relatively constant throughout the treatment process 

with concentrations ranging between 60 and <20 μg/L.

Total iron concentrations ranged from 2,390 to 2,635 μg/L 

in the source water and <30 to 50 μg/L in the finished

water. Total iron concentrations were relatively constant 

between the plant inlet and prior to filtration, with significant iron removal occurring as a result of filtration. It

appears that the primary arsenic removal mechanism at 

Plant A is adsorption and coprecipitation of As(V) with

the iron hydroxide precipitates.

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, except for the addition of 

aluminum. The 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

determined 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 four locations that

were used during the preliminary sampling phase. Alkalinity, pH, total arsenic, total aluminum, total iron, and

total manganese analyses were performed on sampled 

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 

supernatant discharge 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 at each 

location.

4.2.4.1 Arsenic

Table 4-4 provides a summary of the arsenic analytical

results collected at the four treatment process locations. 

Total arsenic concentrations at the inlet ranged from

12.5 μg/L to 42.5 μg/L, with an average concentration of 

20.7 μg/L. These concentrations were basically consistent with what had been observed during the preliminary 

phases of the study. Total arsenic concentrations at the

Table 4-4. Summary of Arsenic Analytical Results at Plant A (June 24, 1998–June 16, 1999)

Parameter Sample Location Units

Number of 

Samples

Minimum 

Concentration

Maximum 

Concentration

Average 

Concentration

Standard 

Deviation

As (total) Inlet μg/L 49 12.5 42.5 20.7 3.8

Prefiltration μg/L 49 3.8 23.8 19.3 4.0

After filtration μg/L 49 1.0 8.0 3.1 1.1

After softening μg/L 49 0.8 10.1 2.8 0.1

As (total soluble) Inlet μg/L 12 15.1 25.4 20.3 3.7

Prefiltration μg/L 12 3.1 10 5.3 2.3

After filtration μg/L 12 2.3 4.1 3.0 0.5

After softening μg/L 12 1.7 10.2 4.0 2.5

As (particulate) Inlet μg/L 12 <0.1 4.9 1.8 2.1

Prefiltration μg/L 12 10 17.9 14.3 2.4

After filtration μg/L 12 <0.1 5.1 0.8 1.5

After softening μg/L 12 <0.1 <0.1 <0.1 NA

As (III) Inlet μg/L 12 10.8 21.3 16.0 3.7

Prefiltration μg/L 12 0.1 4.8 0.9 1.3

After filtration μg/L 12 0.1 0.8 0.4 0.2

After softening μg/L 12 <0.1 0.8 0.5 0.3

As (V) Inlet μg/L 12 1.1 10.8 4.3 2.4

Prefiltration μg/L 12 2.7 5.4 4.0 0.8

After filtration μg/L 12 2.0 3.6 2.5 0.5

After softening μg/L 12 1.2 10.2 3.1 2.6
23

PF sampling location ranged from 3.8 μg/L to 23.8 μg/L, 

with an average of 19.3 μg/L. It should be noted that only 

three sampling events produced approximately 3 to 6 μg/L 

of arsenic at the PF location. Therefore, only minor arsenic removal occurred during the sedimentation process. 

Samples collected after filtration contained total arsenic 

concentrations ranging from 1.0 μg/L to 8.0 μg/L, with an 

average of 3.1 μg/L; and total arsenic concentrations averaged 2.8 μg/L in samples collected after the zeolite softening process. The data indicate that the majority of the 

arsenic removal occurred in the filters.

The average removal percentage of total arsenic between 

the IN and AF sampling locations was 85% and between 

the IN and AS locations was 87%. These data indicate

that the vast majority of the arsenic was removed during 

filtration and that the softening process did little to improve 

removal efficiency. The average arsenic removal predicted by McNeill and Edwards (1997) sorption model was 

76%, which is within the 90th percentile confidence interval of the model. Figure 4-3 is a graph showing the total 

arsenic concentration recorded at each sampling location 

throughout the study, as well as the removal percentage 

calculated for each sampling event. As shown in this figure, total arsenic concentrations at the IN and AF sampling locations remain relatively constant throughout the

study with no seasonal effects noted. The three dips in

the arsenic concentrations at the PF sampling location 

may have been a result of reduced process flow occurring 

during the winter months, resulting in longer retention

times in the sedimentation basins.

Particulate arsenic concentrations averaged 1.8 μg/L at 

the inlet, 14.3 μg/L before filtration, 0.8 μg/L after filtration, and <0.1 after softening. The increase in particulate 

arsenic at the PF sampling location was due to sorption 

and coprecipitation of arsenic on/with iron hydroxide precipitates. This observation was supported by the decrease of particulate arsenic in the AF sampling location.

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

arsenic concentration. The average As(III) and As(V) concentrations in the source water were 16.0 and 4.3 μg/L, 

respectively. The As(III) was oxidized to As(V) by chlorination prior to the PF sampling location and the As(V) 

was sorbed to and coprecipitated with the iron hydroxide. 

Therefore, the majority of the total arsenic in the water

prior to filtration was in particulate form (i.e., attached to 

the iron). Average As(III) concentrations remained low

and relatively constant following oxidation and the average As(V) concentrations decreased slightly from 4.3 μg/L 

in the source water to 3.1 μg/L after softening.

0

5

10

15

20

25

30

35

40

45

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

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Inlet

Prefiltration

After Filtration

After Softening

% Removal

Figure 4-3. Total Arsenic Analytical Results During Long-Term Sampling at Plant A
24

Figure 4-4 shows As(III), As(V), and particulate arsenic 

concentrations measured during the long-term evaluation.

Plant A water treatment system was able to consistently 

remove arsenic to low levels (i.e., average treated water 

total arsenic concentration was 2.8 μg/L). The primary

arsenic removal mechanism appears to be coprecipitation with iron hydroxide precipitates followed by filtration. The simplified sorption model developed by McNeill 

and Edwards (1997) appears to approximate the arsenic 

removal process at Plant A reasonably well, although the 

model consistently underestimated the removal by approximately 11%.

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 were relatively constant ranging 

between 347 mg/L and 415 mg/L (as CaCO3) in the

source water, with an average of 413 mg/L. As observed 

during the preliminary sampling, a slight decrease in

average alkalinity to 398 mg/L was observed after oxidation of the iron due to the stoichiometry of iron oxidation process. Turbidity concentrations ranged from 13.8

NTU to 26 NTU, with an average of 19 NTU. Increased 

turbidity concentrations may have resulted from oxidation 

of iron occurring after the sample was collected and prior 

to analysis at the laboratory. The bulk of the turbidity was 

removed during sedimentation, reducing concentrations 

to an average of 5.1 NTU. The system effectively removed turbidity with an average finished water concentration of 0.1 NTU. Figure 4-5 plots inlet alkalinity, pH,

and hardness concentrations observed throughout the

duration of the study.

The pH was constant, averaging 7.6 or 7.7 at each sampling location within the treatment process. This pH is in 

the range (pH 5.5 to 8.5) where arsenic removal 

efficiency by iron oxides is not affected (Sorg and

Longsdon, 1978; Sorg, 1993; Hering et al., 1996). Total 

hardness concentrations ranged from 286 mg/L to

432 mg/L (as CaCO3) in the plant source water, with an 

average of 316 mg/L. These concentrations were relatively constant with the exception of the sample collected 

on September 30, 1998. Similar to alkalinity, a slight

decrease in hardness was observed following oxidation of 

iron, resulting in an average hardness concentration of

291 mg/L. As would be expected, considerable removal 

of hardness was observed following zeolite softening,

reducing total hardness to an average of 5.2 mg/L (as

CaCO3).

Total iron concentrations at the inlet sampling location

ranged from 762 μg/L to 3,289 μg/L and averaged 2,284 

μg/L. At the PF sampling location, total iron concentrations ranged from 267 μg/L to 3,026 μg/L and averaged 

2,241 μg/L. Therefore, the total iron concentrations were 

relatively constant between the source and just prior to

the filters. However, dissolved iron analytical results

show that approximately half of the iron entering the

plant was in the reduced form. The average dissolved 

iron concentration in source water was 953 μg/L. After 

aeration and chlorination, practically all iron was oxidized 

with concentrations of <30 μg/L at all other sampling 

locations throughout the study. The filtration process 

removed most of the iron, reducing average total iron

concentrations to 71.5 μg/L. The zeolite softener filtered 

additional iron particles and the average total iron concentration after the softening process was <30 μg/L. 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 17.9 μg/L at

the inlet and <11 μg/L at the other three sampling locations. Concentrations of dissolved aluminum averaged 

20.4 μg/L in the source water and <11 μg/L at the other 

three sampling locations. It did not appear that coprecipitation with aluminum hydroxide was a significant 

factor in the removal of arsenic, because only minor concentrations were present.

Total and dissolved manganese concentrations were relatively low. Total manganese concentrations averaged 

22.2 μg/L in the source water, 42.4 μg/L prior to filtration, 

22.7 μg/L after filtration, and 5.1 μg/L after softening.

The increase in manganese prior to filtration is most

likely due to the addition of KMnO4 for the greensand filters. Average dissolved manganese concentrations were 

21.0 μg/L in the source water, 17.5 μg/L prior to filtration, 

9.0 μg/L after filtration, and 2.5 μg/L after softening.

4.2.4.3 Supernatant Discharge

Backwash water is generated from backwashing the

filtration units every 24 hours and from backwashing the 

zeolite resin softeners after every 275,000 gallons processed. All backwash water and regenerant waste at

Plant A is sent to an outdoor settling pond and supernatant from the pond is discharged continuously to the

sanitary sewer. Supernatant discharge samples were

collected at the outfall of the settling pond into the sanitary sewer. Results of the supernatant discharge sampling are summarized in Table 4-6.
25

Inlet

Prefiltration

After Softening

0

5

10

15

20

25

30

07/15/199808/05/199809/02/199809/30/199810/28/199812/02/199801/13/199902/10/199903/10/199904/07/199905/05/199906/02/1999

Concentration ( μg/L)

As (V)

As (III)

As (particulate)

0

5

10

15

20

25

30

07/15/199808/05/199809/02/199809/30/199810/28/199812/02/199801/13/199902/10/199903/10/199904/07/199905/05/199906/02/1999

Concentration ( μg/L)

As (V)

As (III)

As (particulate)

0

5

10

15

20

25

30

07/15/199808/05/199809/02/199809/30/199810/28/199812/02/199801/13/199902/10/199903/10/199904/07/199905/05/199906/02/1999

Concentration ( μg/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 24, 1998–June 16, 1999)

Parameter

Sample 

Location Units

Number of 

Samples Minimum Maximum Average

Standard 

Deviation

Alkalinity Inlet mg/L 49 347 415 413 12.9

Prefiltration mg/L 49 380 415 398 6.2

After filtration mg/L 49 378 409 393 6.6

After softening mg/L 49 377 414 394 6.7

Turbidity(a) Inlet NTU 12 13.8 26 19 3.4

Prefiltration NTU 12 3.0 7.2 5.1 0.9

After filtration NTU 12 0.1 2.3 0.5 0.6

After softening NTU 12 0.05 0.3 0.1 0.08

pH Inlet – 49 7.5 7.8 7.6 0.05

Prefiltration – 49 7.6 8.0 7.7 0.09

After filtration – 49 7.5 8.0 7.6 0.09

After softening – 49 7.5 8.1 7.7 0.14

Total Hardness Inlet mg/L 11 286 432 316 41.3

Prefiltration mg/L 12 270 308 291 11.9

After filtration mg/L 12 165 317 280 38.9

After softening mg/L 12 3.0 11.4 5.2 2.5

Total Al Inlet μg/L 49 <11 324 17.9 45.4

Prefiltration μg/L 49 <11 35.9 <11 6.5

After filtration μg/L 49 <11 22.8 <11 5.4

After softening μg/L 49 <11 34.4 <11 6.6

Total Fe Inlet μg/L 49 762 3,289 2,284 424

Prefiltration μg/L 49 267 3,026 2,241 565

After filtration μg/L 49 <30 440 71.5 96.4

After softening μg/L 49 <30 128 <30 22.3

Total Mn Inlet μg/L 49 14.5 57.3 22.2 7.1

Prefiltration μg/L 49 14.9 694 42.4 103

After filtration μg/L 49 4.8 95.8 22.7 16.2

After softening μg/L 49 1.2 24.3 5.1 5.6

Dissolved Al Inlet μg/L 12 <11 121 20.4 33.3

Prefiltration μg/L 12 <11 24.1 <11 7.5

After filtration μg/L 12 <11 51.8 <11 13.6

After softening μg/L 12 <11 68.6 <11 18.2

Dissolved Fe Inlet μg/L 12 <30 1,943 953 720

Prefiltration μg/L 12 <30 <30 <30 NA

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

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

Dissolved Mn Inlet μg/L 12 17.4 24.1 21.0 2.2

Prefiltration μg/L 12 13.9 21.6 17.5 2.3

After filtration μg/L 12 2.9 17.6 9.0 4.1

After softening μg/L 12 1.2 5.0 2.5 1.4

(a) Inlet turbidity concentrations may be elevated due to oxidation of iron occurring after sample collection and prior to laboratory analysis.

The total arsenic concentrations in the supernatant discharge ranged from 9.4 μg/L to 167.0 μg/L, with an average of 72.4 μg/L. Approximately 40% of the total arsenic 

concentration was soluble and 60% was particulate. As 

expected, the average iron concentration in the supernatant water was relatively high at 5,780 μg/L. Practically 

all of the iron is in the oxidized form. The particulate

arsenic is most likely sorbed to unsettled iron solids.

4.2.4.4 Sludge

Sludge is generated from cleaning sedimentation basins 

and from backwashing the greensand filters and zeolite

resin softeners. The sedimentation basins are cleaned

out once per year, and the wastewater and sludge are

sent directly to the sanitary sewer. A water backwash is 

performed on the greensand filters every 24 hours and

an air backwash is performed every 72 hours. Regeneration of the zeolite softeners occurs after every 275,000 

gallons processed, and involves using a 27% solution of 

NaCl. The regeneration takes about 1 hour to complete, 

and consists of a 12-minute backwash, a 20-minute brine

rinse, and slow/fast rinse cycle.

The backwash water and regenerant waste are sent to

an outdoor settling pond. Historically, the retention pond
27

5

10

15

20

25

30

35

40

45

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

0

50

100

150

200

250

300

350

400

450

500

pH (units)

Hardness (mg/L as CaCO3)

Alkalinity (mg/L as CaCO3)

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

was drained and the sludge removed once per year.

Sludge then was transferred to the municipal wastewater 

treatment plant and placed on the wastewater plant

drying beds. After drying, the sludge would be placed on 

local farm fields.

During the long-term evaluation phase of this project, 

sludge samples were collected from three locations 

within the sludge settling pond at Plant A. These sludge 

samples were analyzed for pH, percent moisture, total

arsenic, total aluminum, total manganese, and total iron. 

Also, a TCLP test was performed on each sample to

determine the quantities of leachable arsenic, barium,

cadmium, chromium, lead, mercury, selenium, and silver. Total arsenic concentrations ranged from 255 mg/kg 

to 392 mg/kg, and total iron ranged from 78,600 mg/kg

to 93,000 mg/kg. Arsenic was detected at less than

0.05 mg/L in the TCLP extraction procedure. Also, concentrations were below the more stringent regulatory 

levels in California for total arsenic. Table 4-7 presents

the results of sludge analysis at each of the three sampling locations.

Table 4-6. Summary of Analytical Results from Supernatant Discharge Samples at Plant A 

(November 11, 1998–June 16, 1999)

Parameter Units

Number of Sample 

Events Minimum Maximum Average Stardard Deviation

As (total) μg/L 8 9.4 167.0 72.4 59.4

As (soluble) μg/L 8 3.3 138.0 28.7 46.3

As (particulate) μg/L 8 5.2 111.5 43.6 34.9

pH – 8 4.6 7.9 7.2 1.1

Total Al μg/L 8 <11 20.0 12.2 5.0

Total Fe μg/L 8 1,048 14,470 5,780 4,527

Total Mn μg/L 8 101.5 1746 974 666

Dissolved Al μg/L 8 <11 <11 <11 NA

Dissolved Fe μg/L 8 <30 92.0 <30 27.1

Dissolved Mn μg/L 8 16.5 1020 186.3 342
28

Table 4-7. Analytical Results of Sludge Sampling at Plant A (November 18, 1998)

Parameter Unit *D.L. Location 1 Location 2 Location 3

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

Ba-TCLP mg/L 1.0 19.4 18.2 5.1

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

Cr-TCLP mg/L 0.030 <0.030 0.040 <0.030

Pb-TCLP mg/L 0.20 <0.20 <0.20 <0.20

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 <0.02 <0.02 <0.02

Percent moisture % 0.1 40.5 46.9 46.1

TCLP extraction – complete complete complete

pH – 7.6 7.6 7.5

Total As mg/kg, dry 255(a) 392 372

Total Al mg/kg, dry 7,300 5,000 4,580

Total Fe mg/kg, dry 78,600(a) 89,070 93,000

Total Mn mg/kg, dry NA 1,490 1,950

* Detection limit

(a) Re-analyzed by Wilson Environmental Laboratories.

4.3 Plant B

Source water sampling at Plant B was performed in February 1998. Preliminary sampling consisted of weekly 

water sampling for a four-week period in May 1998.

Long-term sampling was initiated in June 1998 and continued through December 1998. Arsenic speciation sampling was conducted every fourth week. The third phase 

of this study also included collection and analysis of recycle supernatant during two sampling events in November 

1998 and January 1999. No sludge samples were collected at Plant B.

4.3.1 Plant B Description

Plant B began operation in the spring of 1993 and provides a portion of the treated water for approximately 

6,000 residents and up to 20,000 tourists. The plant

utilizes an iron removal process for water treatment and 

can process 1.4 mgd. The plant typically operates from

June through November. Figure 4-6 is a schematic diagram of the treatment process at Plant A.

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

• Intake. The plant intake consists of water from a 

mining tunnel and recycle supernatant from 

backwashing activities.

• Chlorination. Approximately 3 mg/L 

(37-40 lb/day) of chlorine is added for iron 

and manganese oxidation.

• Reaction Vessels. There are two reaction vessels 

in series and sulfur dioxide (3-4 lb/day) is added 

after the first reaction vessel based on manufacturers recommendation to reduce polysulfide in the 

filter media. These reaction vessels are designed 

to handle 4,000 gallons per minute (gpm).

• Filtration Vessel. The filtration vessel contains 

five layers of filtering media, including anthracite 

coal. The filtering rate is 10 gpm/ft2, and the vessel 

is backwashed every 8 hours or at 10 pounds per 

square inch (psi) pressure differential.

• Blending. Treated water is blended with nontreated water from another mining tunnel and one 

spring in the finished water wet well. No posttreatment chlorination is performed because the 

residual chlorine is 1 to 2 mg/L.

• Backwash. Backwash water is sent to a concrete 

vat where the solids are settled out and the supernatant water is recycled after about 90 minutes of 

settling. This water is sent back to the intake where 

it is blended with the raw water from the mining 

tunnel. The solids settle to the bottom of the 

concrete vat and are then sent to a sludge holding 

tank. This sludge is processed through a filter 

press and then sent to a municipal landfill.

4.3.2 Initial Source Water Sampling

Source water at Plant B comes from surface water runoff 

transported via a mining tunnel. Following treatment, this 

source water is blended with several other sources,

including another mining tunnel, one spring, and three

deep wells. These other sources do not require treatment. 

The blended water is chlorinated and distributed. Based 

on discussions with plant personnel, the water treated at 

Plant B has a turbidity of approximately 4-14 NTU and is 

supplied at a flowrate of approximately 7.5 cubic feet per 

second (cfs). Historically, arsenic concentrations in the

source water have ranged from 40 to 80 μg/L.
2

9

Figure 4-6. Schematic Diagram, Plant B
30

An initial site visit to Plant B was conducted on February 

4, 1998, and source water samples were collected at that 

time. During this sampling event, samples were collected 

and analyzed for arsenic (total, particulate, soluble,

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

may affect arsenic removal. Table 4-8 presents the analytical results from the source water sampling. The total 

arsenic concentrations in the source water averaged

48.6 μg/L. Particulate arsenic averaged at 35.7 μg/L and 

the soluble arsenic was mostly As(V), measured at

10.8 μg/L. The average As(III) concentration measured during the initial source water sampling event was 2.1 μg/L. 

Also, the inlet iron concentration averaged 890 μg/L, the 

aluminum concentration was less than the detection limit, 

and the average manganese concentration was 50 μg/L.

Alkalinity concentrations averaged 135 mg/L (as CaCO3) 

and total hardness concentrations averaged 522.5 mg/L. 

Therefore, the source water was considered very hard.

Turbidity averaged 4.0 NTU and the sulfate concentration averaged 420 mg/L. The pH averaged 7.7, which is 

in the range where no effect on arsenic removal efficiency using iron hydroxide precipitation has been observed 

in previous studies (Sorg and Logsdon, 1978; Sorg, 1993;

Hering et al., 1996).

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: the inlet to the plant (IN), before the 

filtration process (PF), and after the filtration process

(AF). Sample taps were used to collect samples at each 

location. The IN samples were collected at the influent of 

the system after the source water was combined with the 

recycle supernatant from the concrete vat. The PF

samples were collected after addition of chlorine and

processing of water through the two reaction vessels. AF 

samples were collected immediately following filtration

and represent finished water. Figure 4-7 is a process

flow diagram for Plant B that shows sampling locations

used during the preliminary and long-term sampling, as 

well as the analyses performed on samples collected

from each location.

Alkalinity, pH, total iron, total manganese, and total

arsenic analysis were performed on all water samples

collected at Plant B. Turbidity and hardness analysis and 

arsenic speciation sampling were 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 4-9 presents the results of the fourweek preliminary sampling period.

Results from the preliminary sampling events indicated 

that inlet total arsenic concentrations ranged from 34.1 to 

45.7 μg/L. The total arsenic in the source water was primarily particulate and the soluble fraction of the total

arsenic was primarily As(V). The As(III) concentrations

measured during the preliminary sampling period was

relatively low, averaging only 2.6 μg/L. As expected, the 

species of arsenic did not vary significantly during the

treatment process. The average total arsenic removed 

was approximately 64% during preliminary sampling,

leaving an average of 15.0 μg/L of total arsenic in the finished water. Arsenic speciation sampling during the first 

week of the sampling period indicated that soluble arsenic was not removed and that only the arsenic entering

the treatment plant as particulate was removed. Because

Table 4-8. Source Water Analytical Results at Plant B (February 4, 1998)

Parameter Unit Primary Sample Duplicate Sample Average Concentration

Alkalinity mg/L(a) 134 136 135

Sulfate mg/L 420 420 420

Turbidity NTU 4 4.1 4.0

pH – 7.7 7.7 7.7

Hardness mg/L(a) 537 508 522

Ca Hardness mg/L(a) 402 370 386

Mg Hardness mg/L(a) 135 138 136

Total Al μg/L <400 <400 <400

Total Fe μg/L 910 870 890

Total Mn μg/L 60 40 50

NO3–NO2

 (N) mg/L(b) 0.11 0.11 0.11

TOC mg/L 1 1 1

As (total) μg/L 49.7 47.6 48.6

As (total soluble) μg/L 13.0 12.8 12.9

As (particulate) μg/L 36.7 34.8 35.7

As (III) μg/L 2.0 2.3 2.1

As (V) μg/L 11.0 10.5 10.8

(a) As CaCO3.

(b) Combined NO3–N and NO2–N.
31

INFLUENT

RECLAIMED

SUPERNATANT WATER

1

REACTION

VESSEL #1

REACTION

VESSEL #2

2

FILTRATION

VESSEL

3

DISTRIBUTION

SYSTEM

MONTHLY

WEEKLY

As (total), Alkalinity, pH,

Total Al, Fe, and Mn

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

Turbidity, Hardness,

Dissolved Al, Fe, and Mn

Plant B

Iron Removal

Design Flow: 1.4 mgd

DA: Cl2

LEGEND

1

DA: Cl 2

FILTRATION

SO2*

 SO2

Sampling Location

Disinfectant Addition

Point

Unit Process

Chemical Added to

Unit Process

SLUDGE HOLDING

TANK

Backwash

Water

As (total), Alkalinity, pH,

Total Al, Fe, and Mn

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

Turbidity, Hardness,

Dissolved Al, Fe, and Mn

As (total), Alkalinity, pH,

Total Al, Fe, and Mn

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

Turbidity, Hardness,

Dissolved Al, Fe, and Mn

* SO2 recommended by manufacturer to reduce

 polysulfide formation on the filter media.

4

Dissolved and total As,

Al, Fe, and Mn; pH

CONCRETE VAT

SLUDGE PROCESSED THROUGH A

FILTER PRESS AND SENT TO A

MUNICIPAL LANDFILL

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

2

Table 4-9. Analytical Results from Preliminary Sampling at Plant B (May 7 through May 28, 1998)

Sampling Date 5/7/98(a) 5/14/98 5/21/98 5/28/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(b) 149

146

142

142

143

142 144 141 144 156 147 148 151 147 144

Turbidity NTU 3.6

3.4

3.6

3.4

<0.1

<0.1

pH –

7.9

7.9

7.6

7.6

7.7

7.7 8.1 7.9 7.8 7.9 7.7 7.7 8.0 7.8 7.8

Hardness mg/L(b) 431

530

469

486

498

456

Ca Hardness mg/L(b) 290

392

332

350

360

317

Mg Hardness mg/L(b) 141

138

137

136

138

139

Total Fe μg/L 520

560

550

620

50

<30 690 870 80 840 780 70 1,230 1,300 110

Total Mn μg/L 40

40

50

50

<20

<20 60 50 <20 70 40 <20 50 40 <20

As (total) μg/L 28.9

39.4

34.5

38.4

13.9

13.7 45.5 48.9 13.6 41.2 41.4 15.2 45.7 50.9 17.5

As (total soluble) μg/L 14.8

15.1

14.5

14.1

14.9

14.6

As (particulate) μg/L 14.1

24.3

20.0

24.3

<0.1

<0.1

As (III) μg/L 1.2

4.0

2.8

2.7

2.3

2.6

As (V) μg/L 13.6

11.1

11.7

11.4

12.6

12.0

(a) Duplicate samples were taken on 5/7/98.

(b) As CaCO3

.

IN = inlet; PF = prefiltration; AF = after filtration.
33

of this, the simplified sorption model proposed by McNeill 

and Edwards (1997) does not apply to the arsenic

removal results at this plant.

Other water quality parameters also were analyzed to

support understanding of mechanisms of arsenic removal. Similar to Plant A, alkalinity concentrations and

pH decreased slightly between the IN and PF sampling 

locations, due to the stoichiometry of iron oxidation in

which hydrogen ions are produced and alkalinity is

destroyed (Benefield and Morgan, 1990). As would be

expected, alkalinity and pH remained constant between 

the PF and AF sampling locations. Source water turbidity 

concentrations averaged 3.5 NTU, which was consistent 

with plant data and data obtained during the initial

source water sampling. Unlike Plant A, increased turbidity due to oxidation of iron after sample collection and 

prior to analysis was not an issue at Plant B because the 

iron entered the facility in oxidized form. Plant B effectively removed turbidity with finished water concentrations averaging <0.1 NTU. Also, as observed during

the source water sampling event, the source water is

very hard. No removal of hardness by the treatment process was observed during the preliminary sampling.

Total manganese concentrations were relatively low,

averaging 55 μg/L in the source water, 45 μg/L prior to

filtration, and <20 after filtration. Total iron concentrations averaged 825 μg/L in the source water, 884 μg/L

prior to filtration, and 75 μg/L after filtration. The inlet iron 

concentrations were consistent with those observed during the initial source water sampling event. It appeared 

that arsenic removal was primarily achieved through

filtration of iron particles to which arsenic was sorbed

prior to treatment at Plant B.

Only minor changes were made to the approach for the 

long-term evaluation as a result of the preliminary sampling effort. As with Plant A, sampling locations and

primary analytes remained unchanged, except for the

addition of aluminum. Iron and manganese analysis 

were 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 determined dissolved aluminum, iron, and manganese 

concentrations.

4.3.4 Long-Term Sampling

Long-term sampling and analysis consisted of 26 weeks 

of water sampling at the three locations used during the 

preliminary sampling phase. All weekly samples were

analyzed for total arsenic, alkalinity, pH, total aluminum, 

total iron, and total manganese. Turbidity, hardness, dissolved aluminum, dissolved iron, and dissolved manganese analysis, as well as arsenic speciation sampling 

were conducted at each sampling location a total of

seven times during the long-term sampling phase. Arsenic speciation sampling included the determination of

soluble arsenic, particulate arsenic, As(V), and As(III)

concentrations. Recycle supernatant discharge analysis 

was performed twice during this phase. Sludge samples 

were not collected at Plant B during this study; however, 

results from sludge sampling conducted in 1994 are discussed in Subsection 4.3.4.4. The following subsections 

summarize the arsenic, water quality parameter, and

residual analytical results.

4.3.4.1 Arsenic

Table 4-10 provides a summary of the arsenic analytical 

results collected at the three sampling locations at Plant 

B. Total arsenic concentrations at the inlet location 

ranged from 33.3 to 97.9 μg/L, with an average concentration of 48.5 μg/L. Total arsenic concentrations at

the prefiltration location ranged from 6.7 to 81.1 μg/L

Table 4-10. Summary of Arsenic Analytical Results at Plant B (June 11, 1998–December 8, 1998)

Parameter

Sample 

Location Units

Number of 

Samples Minimum Maximum Average

Standard 

Deviation

As (total) Inlet μg/L 26 33.3 97.9 48.5 16.3

Prefiltration μg/L 26 6.7 81.1 41.8 16.6

After filtration μg/L 26 5.3 19.7 11.9 3.3

As (total soluble) Inlet μg/L 7 4.9 15.7 11.9 3.7

Prefiltration μg/L 7 0.8 14.4 10.8 4.7

After filtration μg/L 7 5.3 20.1 11.4 4.4

As (particulate) Inlet μg/L 7 20.9 70.0 38.9 18.3

Prefiltration μg/L 7 17.9 65.8 40.1 18.0

After filtration μg/L 7 <0.1 3.1 1.3 1.4

As (III) Inlet μg/L 7 0.1 2.2 1.4 0.82

Prefiltration μg/L 7 0.2 0.8 0.5 0.21

After filtration μg/L 7 0.1 0.8 0.3 0.28

As (V) Inlet μg/L 7 3.1 15.0 10.5 3.9

Prefiltration μg/L 7 0.4 14.0 10.2 4.7

After filtration μg/L 7 5.1 19.8 11.1 4.4
34

with an average of 41.8 μg/L. Therefore, very little arsenic was removed prior to filtration. Samples collected at 

the AF location contained total arsenic concentrations 

ranging from 5.3 to 19.7 μg/L, with an average of 11.9

μg/L. The average removal efficiency of total arsenic

(comparing raw water to finished water concentrations) 

was 74%. Figure 4-8 is a graph showing the arsenic concentrations recorded at each sampling location throughout the study.

Particulate arsenic concentrations averaged 38.9 μg/L at 

the inlet, 40.1 μg/L prior to filtration, and 1.3 μg/L after

filtration. These results indicate that very little adsorption 

and coprecipitation of soluble arsenic occurs during the

treatment process. Instead, the arsenic most likely is

attached to the oxidized iron particles prior to entering 

the facility.

This observation is supported by the As(III) and As(V)

analytical results. As(III) and As(V) make up the soluble 

fraction of the total arsenic concentration. As(III) concentrations in the source water ranged from 0.1 to 2.2 μg/L, 

with an average of 1.4 μg/L. Some of the As(III) was

converted to As(V) during chlorination, resulting in average As(III) concentrations at the prefiltration and afterfiltration sampling locations of 0.5 μg/L and 0.3 μg/L,

respectively. As(V) concentrations averaged 10.5 μg/L at 

the inlet, 10.2 μg/L prior to filtration, and 11.1 μg/L in the 

finished water. It is interesting that very little soluble arsenic was removed at Plant B. This observation is most 

likely a result of the lack of reduced iron in the source

water. Approximately 90% of the iron entering the facility 

is in the oxidized form, to which arsenic has already

sorbed. Figure 4-9 provides charts showing the fractions 

of the total arsenic concentration made up by particulate 

arsenic and soluble arsenic [As(III) and As(V)].

The Plant B water treatment system only removed arsenic that entered the facility in particulate form. This arsenic was most likely already sorbed to the oxidized iron

entering the facility. Also, with an average finished water 

total arsenic concentration of 11.9 μg/L, Plant B was not 

able to consistently remove arsenic from source water to 

low levels. However, arsenic removal would most likely

be enhanced if a coagulant such as ferric chloride was

included in the treatment process.

4.3.4.2 Other Water Quality Parameters

Table 4-11 summarizes the analytical results for several 

water quality parameters obtained during long-term sampling. Similar to that observed during the preliminary 

study, alkalinity concentrations were relatively constant

throughout long-term sampling as well as throughout the

0

20

40

60

80

100

120

5/25/98 6/24/98 7/24/98 8/23/98 9/22/98 10/22/98 11/21/98 12/21/98

Date

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
35

Inlet

Prefiltration

After Filtration

0

10

20

30

40

50

60

70

80

90

06/11/199807/14/199808/06/199809/01/199809/30/199810/27/199812/01/1998

Concentration ( μg/L)

As (V)

As (III)

As (particulate)

0

10

20

30

40

50

60

70

80

90

06/11/199807/14/199808/06/199809/01/199809/30/199810/27/199812/01/1998

Concentration ( μg/L)

As (V)

As (III)

As (particulate)

0

10

20

30

40

50

60

70

80

90

06/11/199807/14/199808/06/199809/01/199809/30/199810/27/199812/01/1998

Concentration ( μg/L)

As (V)

As (III)

As (particulate)

Figure 4-9. Arsenic Form and Species Analytical Results During Long-Term Sampling at Plant B
36

Table 4-11. Summary of Water Quality Parameter Analytical Results at Plant B (June 11, 1998–December 8, 1998)

Parameter

Sample 

Location Units

Number of 

Samples Minimum Maximum Average

Standard 

Deviation

Alkalinity Inlet mg/L 26 137 145 140 2.2

Prefiltration mg/L 26 133 143 137 2.6

After filtration mg/L 26 132 142 137 2.6

Turbidity Inlet NTU 7 4.6 13.3 8.8 3.5

Prefiltration NTU 7 4.0 13.1 8.0 3.6

After filtration NTU 7 0.2 0.8 0.4 0.22

pH Inlet – 26 7.5 8.6 7.9 0.20

Prefiltration – 26 7.2 7.9 7.7 0.14

After filtration – 26 7.5 7.8 7.7 0.08

Total Hardness Inlet mg/L 7 377 494 443 42.9

Prefiltration mg/L 7 329 473 421 52.4

After filtration mg/L 7 359 482 420 46.6

Total Al Inlet μg/L 26 <11 46.9 22.0 10.7

Prefiltration μg/L 26 <11 47.8 22.1 11.1

After filtration μg/L 26 <11 36.8 13.9 8.0

Total Fe Inlet μg/L 26 599 2,753 1,137 598

Prefiltration μg/L 26 116 2,167 1,001 509

After filtration μg/L 26 <30 306 66.7 60.8

Total Mn Inlet μg/L 26 29.9 135 61.6 27.0

Prefiltration μg/L 26 13.8 151 50.3 27.3

After filtration μg/L 26 <0.5 9.1 1.9 2.1

Dissolved Al Inlet μg/L 7 <11 <11 <11 NA

Prefiltration μg/L 7 <11 <11 <11 NA

After filtration μg/L 7 <11 <11 <11 NA

Dissolved Fe Inlet μg/L 7 <30 655 107 242

Prefiltration μg/L 7 <30 44.4 <30 11.1

After filtration μg/L 7 <30 31.5 <30 6.2

Dissolved Mn Inlet μg/L 7 25 41.1 31.9 4.9

Prefiltration μg/L 7 9.4 30.2 25.1 7.1

After filtration μg/L 7 <0.5 0.9 <0.5 0.30

treatment process, with only a slight decrease in concentration between samples collected at the inlet and prefiltration sampling locations. Figure 4-10 shows source

water alkalinity, turbidity, pH, and hardness concentrations throughout the long-term sampling phase. Average 

alkalinity concentrations at the inlet, prefiltration, and afterfiltration sampling locations were 140 mg/L, 137 mg/L,

and 137 mg/L (as CaCO3), respectively. Because the iron

entered the facility already oxidized, there was very little 

alkalinity reduction following chlorination.

During the long-term sampling, turbidity concentrations 

averaged 8.8 NTU at the inlet, 8.0 NTU at the PF location, and 0.4 NTU in the finished water, which are consistent with plant data. As shown in Figure 4-10, source 

water turbidity concentrations fluctuated significantly. 

These fluctuations would be expected for a surface water

source and are probably a result of precipitation events 

and/or snowmelt. The plant was effective at removing

turbidity. Hardness was not significantly removed by the 

treatment process. Average hardness concentrations in

samples collected at the plant inlet, before filtration, and 

after filtration were measured at 443 mg/L, 421 mg/L,

and 420 mg/L, respectively. As shown in Figure 4-10, 

source water hardness appears to increase throughout

the study, although the reason for this is not clear.

Values for pH were relatively constant throughout the

duration of the study and throughout the treatment process. Average pH was 7.9 in the source water, 7.7 prior 

to filtration, and 7.7 after filtration.

Total aluminum concentrations at the IN and PF sampling locations averaged approximately 22.0 μg/L and

decreased in the AF samples to 13.9 μg/L. The majority 

of the aluminum detected in water samples from the inlet 

sampling location was particulate form. The dissolved 

aluminum concentration was <11 μg/L throughout the

study at each sampling location. Due to the relatively low 

total aluminum concentrations, aluminum is not believed 

to have a significant effect on arsenic removal.

Total manganese concentrations averaged 61.6 μg/L,

50.3 μg/L, and 1.9 μg/L in samples collected at the inlet, 

prefiltration, and after-filtration sampling locations, respectively. Average dissolved manganese concentrations were 

31.9 μg/L in the source water, 25.1 μg/L before filtration, 

and <0.5 μg/L after filtration. Previous studies have not 

correlated manganese removal to arsenic removal; therefore, manganese is not believed to have a significant 

impact on arsenic removal efficiency.
37

0

2

4

6

8

10

12

14

16

18

20

5/25/98 6/24/98 7/24/98 8/23/98 9/22/98 10/22/98 11/21/98 12/21/98

Date

0

100

200

300

400

500

600

Turbidity (NTU)

pH (units)

Hardness (mg/L as CaCO3)

Alkalinity (mg/L as CaCO3)

Figure 4-10. Inlet Turbidity, pH, Hardness, and Alkalinity Analytical Results at Plant B

Total iron concentrations in samples collected at the IN

sampling location ranged from 599 to 2,753 μg/L, with an 

average of 1,137 μg/L. At the PF sampling location, total 

iron concentrations ranged from 116 to 2,167 μg/L, with 

an average of 1,001 μg/L. The average iron concentration in samples collected after filtration was 66.7 μg/L. 

Also, dissolved iron concentrations were relatively low in 

the source water, averaging 107 μg/L. All dissolved iron 

was oxidized during chlorination prior to filtration, resulting in average dissolved iron concentrations of <30 μg/L 

in samples collected at the prefiltration and after-filtration 

sampling locations. As stated previously, it is believed that 

arsenic removal at Plant B is achieved primarily through 

filtration of arsenic sorbed to iron particles formed prior to 

entering the facility.

4.3.4.3 Recycle Supernatant

The filtered backwash water is sent to a concrete vat,

where it is given time to settle. The supernatant water

then is recycled to the inlet of the plant and mixed with

the source water from the mining tunnel. On November 

10, 1998 and January 15, 1999, supernatant samples 

were collected to determine the concentrations of arsenic, aluminum, iron, and manganese recycled to the system. The November 10 test results show that essentially 

all of the arsenic (142 μg/L average) in the recycle

supernatant water was in particulate form. In contrast,

the arsenic results from January 15, 1999 were significantly lower (7.8 μg/L). This lower level most likely is

because the plant did not operate in January 1999, thereby giving the backwash water in the concrete vat more

time to settle. During typical operations, as observed in 

November 1998, the supernatant from the concrete vat 

is recycled every 90 minutes. The results for aluminum, 

iron, and manganese were significantly less on January 

15, 1999 than on November 10, 1998, which is consistent with the results observed for arsenic. The recycled

backwash water sample analytical results are shown in

Table 4-12.

4.3.4.4 Sludge

Sludge is generated at Plant B from filter backwashing. 

Sludge that settles in the concrete vat is transferred to a 

sludge holding tank. Approximately once a year, sludge is 

removed from the sludge holding tank, processed through 

a filter press, and sent to a municipal landfill. Based on 

discussions with plant personnel, approximately 2 to 3 yd3

of dewatered sludge is sent to a nonhazardous landfill

every year. Sludge samples were not collected at Plant B 

as part of this study; however, the plant provided results 

from a sludge sampling event conducted in January 1994. 

A primary compound detected in the sludge was Fe2O3, 

which comprised 30.4% by weight. Arsenic was detected 

at 6,700 mg/kg in the sludge sample.
38

Table 4-12. Summary of Analytical Results from Recycle Supernatant Samples at Plant B

Parameter Unit 11/10/98 01/15/99

pH –

7.8

7.8

8.1

8.1

As (total) μg/L 146

138

7.8

7.8

As (total soluble) μg/L 5.3

4.8

7.7

7.8

As (particulate) μg/L 141

133

<0.1

<0.1

Total Al μg/L 58.2

51.5

<11

<11

Total Fe μg/L 3,850

3,710

75.2

67.4

Total Mn μg/L 326

267

1.6

1.7

Dissolved Al μg/L 30.4

31.1

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

Dissolved Mn μg/L 1.0

1.0

<0.5

<0.5
39

5.0 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 Quality Assurance/ 

Quality Control (QA/QC) Summary Report (Battelle,

2000), which was 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 in the QA/QC 

Summary Report. 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 in the

QA/QC Summary Report. Other water quality parameters including alkalinity, pH, turbidity, hardness, nitratenitrite, sulfate, fluoride, total dissolved solids (TDS), and 

TSS were analyzed by Wilson Environmental Laboratories and their QA data are summarized in the QA/QC 

Summary Report. QA data for TOC analysis performed

by CT&E Environmental Laboratory are presented in the 

QA/QC Summary Report. 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 

Al, Fe, and Mn 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 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 Fe outliers: 

27% on August 8, 1998 and 74% on December 22,

1998; three As outliers: 27% on August 18, 1998, 182% 

on October 1, 1998, and 27% on July 30, 1999; and four 

Al 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 matrix 

spike (MS) analysis on August 31, 1998 exceeded the QA 

limits of 75 to 125%. It is suspected that matrix spike

analyses were not performed correctly on that day. After 

this problem had been identified, Battelle’s Work Assignment Leader, laboratory QA officer, and Battelle’s task

leaders met to discuss the cause of the deviation. Corrective actions were taken including re-analyzing samples 

and adjusting the amount of spike added to samples (i.e., 
40

the Fe spike was increased from 50 to 100, 200, 225, or 

even as high as 2,000 μg/L because most of samples

contain much more than 50 μg/L of Fe). As indicated in 

the QA/QC Summary Report (Battelle, 2000), the matrix 

spike data quality was significantly improved since

November 3, 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 analyses 

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 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 until October 15, 1998 at 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 limits 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

matrix spikes 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).
41

6.0 References

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.

Battelle. 2000. Quality Assurance/Quality Control (QA/

QC) Summary Report for Evaluation of Treatment 

Technologies for the Removal of Arsenic from Drinking 

Water. Under preparation.

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.

Cheng, 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 Ion-Exchange 

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. 1997. “Predicting As

Removal During Metal Hydroxide Precipitation.” J. 

AWWA. (January): 75-86.

Meng, X., S. Bang, and G.P. Korfiatis. 2000. “Effects of 

Silicate, Sulfate, and Carbonate on Arsenic Removal

by Ferric Chloride.” Water Resources, 34(4): 1255-

1261.

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).

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.
42

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.
43

APPENDIX A

Complete Analytical Results from Long-Term Sampling at Plant A
4

4

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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 418 389 388 392 418 399 394 394 419 403 396 391 413 399 386 390

Turbidity NTU 26.0 4.9 0.8 <0.1

pH 7.7 7.7 7.6 7.7 7.7 7.7 7.7 7.7 7.6 7.7 7.6 7.6 7.6 7.8 7.7 7.7

Total Hardness mg/L(a) 332 301 298 3.0

Ca Hardness mg/L(a) 180 152 155 2.0

Mg Hardness mg/L(a) 152 149 143 2.0

As (total) μg/L 21.0 23.3 2.7 3.4 18.8 18.8 5.6 2.5 18.1 19.3 2.3 1.9 20.6

20.9

20.6

19.6

4.8

4.8

2.7

2.6

As (total soluble) μg/L 25.6

25.1

5.3

5.3

2.9

3.1

3.3

3.1

As (particulate) μg/L <0.1

<0.1

15.3

14.3

2.0

1.8

<0.1

<0.1

As (III) μg/L 18.1

20.7

0.3

0.3

0.2

0.2

0.3

0.3

As (V) μg/L 7.5

4.4

5.1

5.0

2.7

2.9

3.0

2.9

Total Al μg/L 14.9 <11 <11 11.9 <11 <11 <11 11.6 14.3 <11 <11 16.9 17.0

18.2

12.0

<11

19.4

15.5

<11

11.8

Total Fe μg/L 2,015 2,178 <30 <30 1,958 2,005 440 <30 1,789 1,889 <30 128 1,918

1,939

1,897

1,824

309

300

<30

<30

Total Mn μg/L 19.7 17.2 21.4 2.7 19.1 17.5 47.1 2.0 18.8 19.4 31.7 2.8 19.4

19.4

19.0

18.2

48.6

44.4

2.7

2.7

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 1,901

1,612

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 18.4

18.7

15.4

14.9

13.4

13.8

1.9

2.0

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
4

5

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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 410

415

390

394

397

392

394

392 406 395 383 391 406 380 387 388 410411

393

392

388

389

386

387

Turbidity NTU 21 5.3 0.2 <0.1

pH 7.6

7.6

7.6

7.6

7.6

7.6

7.6

7.6 7.8 7.7 7.7 7.7 7.5 7.8 7.6 7.6 7.77.7

7.7

7.7

7.7

7.7

7.6

7.6

Total Hardness mg/L(a) 305 282 279 4.9

Ca Hardness mg/L(a) 147 127 127 2.9

Mg Hardness mg/L(a) 158 155 151 1.9

As (total) μg/L 19.6 20.5 3.0 2.8 20.5 18.7 3.1 2.0 19.0

12.3

20.3

18.6

2.9

2.9

2.0

2.1 19.5 15.6 3.0 0.8

As (total soluble) μg/L 24.7

23.6

4.6

4.3

2.8

2.7

3.1

3.3

As (particulate) μg/L <0.1

<0.1

15.7

14.3

0.1

0.2

<0.1

<0.1

As (III) μg/L 21.8

20.9

0.7

0.6

0.7

0.7

0.5

0.6

As (V) μg/L 2.9

2.7

3.9

3.7

2.0

2.0

1.5

1.5

Total Al μg/L 11.5 19.0 17.8 <11 12.6 <11 14.8 11.7 13.2

52.5

22.0

21.8

12.2

15.9

16.2

16.1 29.6 17.7 22.8 24.0

Total Fe μg/L 1,419 1,778 <30 <30 2,070 1,927 56.4 <30 2,394

1,798

2,572

2,200

37.1

34.8

<30

<30 2,392 3,026 191 <30

Total Mn μg/L 17.5 15.8 13.8 1.9 17.5 18.2 12.8 1.4 19.1

17.9

19.1

17.9

21.1

19.4

2.9

2.9 20.1 280(b) 36.0 2.2

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 2,052

1,835

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 18.2

17.6

14.9

15.2

17.2

18.1

1.8

1.7

(a) As CaCO3.

(b) Confirmed by sample re-analysis.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
4

6

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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a)413 393 390 384 416 394 383 392 415 395 386 395 414

414

400

401

396

397

393

393

Turbidity NTU 19.7 5.3 0.2 0.2

pH 7.6 7.6 7.6 7.5 7.6 7.6 7.6 7.7 7.6 7.7 7.6 7.9 7.7

7.7

7.8

7.8

7.8

7.8

7.9

7.9

Total Hardness mg/L(a) 288 270 274 4.0

Ca Hardness mg/L(a) 137 125 125 2.9

Mg Hardness mg/L(a) 150 145 149 1.5

As (total) μg/L 20.3 20.1 1.9 0.9 18.2 15.6 2.3 1.7 18.9

18.3

19.5

18.4

2.3

2.0

1.5

1.5 21.1 20.0 3.1 1.9

As (total soluble) μg/L 23.0

22.2

4.4

4.5

2.3

2.4

1.8

1.7

As (particulate) μg/L <0.1

<0.1

15.1

13.9

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 7.5

16.1

0.1

<0.1

0.1

0.1

0.1

<0.1

As (V) μg/L 15.5

6.1

4.3

4.5

2.2

2.4

1.7

1.7

Total Al μg/L 25.9 18.0 17.5 23.7 40.2 35.9 17.8 34.4 <11

32.6

<11

11.3

11.0

11.5

<11

<11 <11 16.0 14.3 13.7

Total Fe μg/L 2,343 2,499 <30 <30 3,289 2,972 <30 <30 1,983

1,936

2,000

1,943

31.1

<30

<30

<30 2,076 1,893 77.1 30.0

Total Mn μg/L 19.7 18.3 19.0 1.8 25.6 24.6 16.0 2.8 15.8

15.2

15.2

14.7

9.4

8.8

1.3

1.3 17.4 16.8 12.0 3.3

Dissolved Al μg/L 64.9

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 2,150

1,635

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 21.3

19.6

15.5

15.9

9.4

9.7

1.7

1.3

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
4

7

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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 417 402 398 397 413 403 401 400 411 404 395 401 415 395 391 398

Turbidity NTU 17.2 4.6 0.2 <0.1

pH 7.6 7.6 7.7 7.8 7.7 7.8 7.8 8.0 7.6 7.8 7.7 7.8 7.6 7.8 7.7 7.9

Total Hardness mg/L(a) 432 295 303 6.5

Ca Hardness mg/L(a) 295 145 150 3.9

Mg Hardness mg/L(a) 138 150 153 2.6

As (total) μg/L 22.0 22.0 3.0 2.0 23.4 22.6 3.5 6.9 25.5

24.1

13.4(b)

22.7

3.9

3.3

5.9

6.0 20.3 19.5 2.9 3.0

As (total soluble) μg/L 25.4

25.4

6.0

6.0

3.5

3.5

6.7

6.7

As (particulate) μg/L 0.1

<0.1

7.4

12.7

0.4

<0.1

<0.1

<0.1

As (III) μg/L 20.1

20.5

0.6

0.6

0.6

0.6

0.8

0.7

As (V) μg/L 5.3

4.9

5.4

5.4

2.9

2.9

5.9

6.0

Total Al μg/L 11.6 17.6 16.0 15.5 21.8 12.9 16.6 25.4 18.3

12.2

20.5

20.1

15.5

19.2

13.1

15.4 <11 <11 14.1 <11

Total Fe μg/L 2,325 2,287 <30 <30 2,387 2,175 45.0 57.5 2,176

2,227

2,040

2,165

31.3

38.9

<30

<30 2,185 2,028 <30 <30

Total Mn μg/L 17.5 16.3 10.9 1.5 20.0 19.5 29.7 15.8 19.1

19.2

15.9

16.5

10.3

10.4

1.9

2.2 18.3 17.9 13.6 1.7

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 1,544

1,300

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 17.3

17.6

13.8

14.0

8.4

8.3

1.7

1.6

(a) As CaCO3.

(b) Confirmed by sample re-analysis.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
4

8

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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 375 408 403 402 410 411 408 405 412 413 401 414 415

415

416

415

409

409

411

411

Turbidity NTU 16.4 7.2 0.1 0.3

pH 7.7 7.9 7.8 8.1 7.7 8.0 7.8 8.0 7.6 7.9 7.8 8.1 7.6

7.6

7.9

7.9

8.0

8.0

7.8

8.0

Total Hardness mg/L(a) 301 301 294 11.4

Ca Hardness mg/L(a) 152 152 147 6.0

Mg Hardness mg/L(a) 149 149 147 5.4

As (total) μg/L 21.3 18.4 3.8 3.1 20.5 20.3 4.0 6.0 20.8

21.2

21.1

21.4

4.1

3.9

10.1

10.1 22.5 20.7 4.6 3.9

As (total soluble) μg/L 19.2

18.6

9.7

10.1

4.1

4.1

10.2

10.3

As (particulate) μg/L 1.6

2.6

11.4

11.3

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 17.1

16.5

5.1

4.6

0.7

0.3

<0.1

<0.1

As (V) μg/L 2.1

2.1

4.6

5.5

3.4

3.8

10.2

10.3

Total Al μg/L <11 12.5 <11 21.4 13.0 11.8 <11 <11 <11

<11

<11

<11

<11

<11

<11

<11 <11 11.8 <11 11.8

Total Fe μg/L 2,800 2,495 <30 <30 2,826 2,715 43.1 <30 2,312

2,406

2,252

2,325

<30

<30

41.2

49.0 2,388 2,233 <30 <30

Total Mn μg/L 19.9 18.1 12.7 2.0 22.5 22.5 11.9 2.5 21.6

22.3

20.2

20.5

6.7

6.3

7.6

7.8 24.0 24.9 18.4 13.9

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 930

650

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 21.6

21.9

18.6

18.6

5.1

5.2

4.2

4.1

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
4

9

Table A-6. Analytical Results from Long Term Sampling, Plant A (November 11 to December 2, 1998)

Sampling Date 11/11/98 11/18/98 11/25/98(b) 12/02/98

Sampling Location

Parameter Unit IN PF AF AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 420 396 392 388 415 401 386 377 412 397 391 393

Turbidity NTU 15.8 4.8 0.3 0.1

pH 7.6 7.6 7.5 7.6 7.6 7.6 7.5 7.6 7.6 7.7 7.6 7.7

Total Hardness mg/L(a) 297 298 165 3.0

Ca Hardness mg/L(a) 152 150 150 1.5

Mg Hardness mg/L(a) 145 148 15 1.4

As (total) μg/L 23.0 23.8 2.6 2.1 20.0 6.5 2.3 1.9 19.9

20.3

17.1

19.1

3.3

3.3

2.0

1.9

As (total soluble) μg/L 15.6

15.9

3.4

3.6

2.5

2.6

2.5

2.5

As (particulate) μg/L 4.3

4.4

13.7

15.5

0.8

0.7

<0.1

<0.1

As (III) μg/L 10.6

11.1

0.3

0.3

0.3

0.3

0.2

0.2

As (V) μg/L 5.0

4.8

3.1

3.3

2.2

2.3

2.3

2.3

Total Al μg/L 17.0 <11 <11 14.6 <11 12.4 17.6 12.8 13.4

11.2

15.3

15.3

16.9

<11

13.1

13.6

Total Fe μg/L 2,642 2,573 <30 <30 2,322 401 <30 <30 2,383

2,302

2,337

2,331

144

142

<30

<30

Total Mn μg/L 22.9 22.2 10.8 1.8 35.4 694 11.5 1.4 23.4

22.8

21.9

21.7

10.8

10.3

1.2

1.1

Dissolved Al μg/L 11.3

31.8

12.1

31.0

<11

<11

<11

<11

Dissolved Fe μg/L 31.1

39.1

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 25.0

23.3

18.6

18.2

6.3

6.3

1.2

1.3

(a) As CaCO3.

(b) No sampling due to Thanksgiving holiday.

(c) Confirmed by sample re-analysis.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
5

0

Table A-7. Analytical Results from Long Term Sampling, Plant A (December 16 to 30, 1998)

Sampling Date 12/09/98 12/16/98 12/23/98(b) 12/30/98(b)

Sampling Location

Parameter Unit IN PF AF AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 416

415

393

394

388

387

385

386 418 396 392 394

Turbidity NTU

pH 7.6

7.6

7.7

7.7

7.6

7.7

7.7

7.7 7.7 7.7 7.7 7.7

Total Hardness mg/L(a)

Ca Hardness mg/L(a)

Mg Hardness mg/L(a)

As (total) μg/L 24.4 22.5 2.7 1.8 20.8 18.9 2.9 2.7

As (total soluble) μg/L

As (particulate) μg/L

As (III) μg/L

As (V) μg/L

Total Al μg/L 12.6 <11 <11 <11 <11 <11 16.6 <11

Total Fe μg/L 2,441 2,475 <30 <30 2365 2588 98.1 65.2

Total Mn μg/L 21.7 21.3 11.0 2.1 25.4 26.1 12.2 1.4

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; AS = after softening.
51

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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 416 401 394 395 413 396 397 396 413

414

393

394

396

395

391

390 398 398 378 388

Turbidity NTU 13.8 3.0 0.1 <0.1

pH 7.6 7.7 7.6 7.6 7.6 7.7 7.7 7.9 7.6

7.6

7.7

7.7

7.6

7.6

7.6

7.7 7.6 7.7 7.6 7.6

Total Hardness mg/L(a) 281 281 8.0

Ca Hardness mg/L(a) 145 147 3.6

Mg Hardness mg/L(a)136 134 4.0

As (total) μg/L 19.4 20.6 2.4 2.1 20.7

19.3

20.9

21.2

2.9

3.0

1.6

1.7 20.1 22.5 2.5 1.6 18.9 6.0 1.0 1.0

As (total soluble) μg/L 15.4

14.8

3.2

3.0

3.3

3.4

2.2

2.2

As (particulate) μg/L 5.3

4.5

17.7

18.2

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 11.3

12.1

0.4

0.4

0.2

0.2

0.6

0.6

As (V) μg/L 4.1

2.7

2.8

2.6

3.1

3.2

1.6

1.6

Total Al μg/L <11 <11 16.6 <11 <11

<11

<11

<11

<11

<11

<11

<11 11.1 <11 <11 <11 <11 <11 <11 <11

Total Fe μg/L 2,365 2,588 98.1 65.2 2,205

2,029

2,283

2,394

<30

<30

<30

116 2,245 2,506 41.7 <30 1,124 369 <30 9.1

Total Mn μg/L 25.5 26.1 12.2 1.4 19.0

14.5

18.5

19.0

4.6

5.0

1.6

2.2 14.5 15.3 6.1 2.0 16.4 121 <30 9.3

Dissolved Al μg/L 122

121

29.7

18.5

17.9

20.9

67.5

69.7

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 20.4

20.2

18.0

16.9

7.7

5.6

1.9

1.4

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
5

2

Table A-9. Analytical Results from Long Term Sampling, Plant A (Feb 3, to Feb 24, 1999)

Sampling Date 02/03/99 02/10/99 02/17/99 02/24/99

Sampling Location

Parameter Unit IN PF AF AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 419 398 391 391 413 394 389 395 414

415

391

390

393

394

390

391 409 391 387 389

Turbidity NTU 17.7 4.8 0.6 <0.1

pH 7.6 7.7 7.7 7.7 7.6 7.7 7.6 7.6 7.6

7.6

7.6

7.6

7.6

7.6

7.6

7.6 7.6 7.6 7.6 7.6

Total Hardness mg/L(a) 327 308 317 5.0

Ca Hardness mg/L(a) 177 160 167 3.0

Mg Hardness mg/L(a) 150 148 150 1.9

As (total) μg/L 19.5 21.0 3.3 2.7 19.7

20.0

20.7

19.9

3.6

3.8

2.2

2.2 18.7 21.0 4.2 2.9 12.5 3.8 2.3 3.1

As (total soluble) μg/L 16.2

15.8

3.2

3.4

3.1

3.2

3.0

3.2

As (particulate) μg/L 3.5

4.2

17.5

16.5

0.5

0.6

<0.1

<0.1

As (III) μg/L 11.6

11.8

0.3

0.3

0.4

0.4

0.6

0.6

As (V) μg/L 4.6

4.0

2.9

3.1

2.7

2.8

2.4

2.6

Total Al μg/L <11 <11 <11 <11 <11

<11

<11

<11

<11

<11

<11

<11 <11 <11 <11 <11 14.4 <11 13.3 <11

Total Fe μg/L 2,295 2,318 177 <30 2,249

2,301

2,430

2,341

211

212

<30

<30 2,485 2,637 260 35.1 762 267 36.4 37.5

Total Mn μg/L 19.6 19.3 24.3 24.3 21.8

22.3

25.3

24.6

39.6

38.4

1.4

1.5 20.6 19.0 19.0 2.1 22.8 16.5 18.8 2.2

Dissolved Al μg/L 20.9

19.3

25.4

15.7

25.9

77.7

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 23.0

22.8

21.3

21.9

7.5

7.9

1.3

1.3

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
5

3

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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 413 396 393 391 419 392 392 391 424

422

391

393

389

388

389

389 407 393 388 393

Turbidity NTU 22.0 5.1 2.3 0.1

pH 7.7 7.7 7.7 7.7 7.6 7.7 7.6 7.7 7.6

7.6

7.7

7.7

7.6

7.6

7.6

7.6 7.6 7.7 7.6 7.7

Total Hardness mg/L(a) 311 303 308 6.0

Ca Hardness mg/L(a) 160 155 157 3.0

Mg Hardness mg/L(a) 151 149 151 2.6

As (total) μg/L 20.3 23.2 5.1 3.6 21.1

22.6

19.0

18.8

8.1

7.9

3.4

3.4 22.1 20.7 2.3 2.7 21.5 20.0 2.3 3.3

As (total soluble) μg/L 16.9

17.0

4.5

4.7

2.9

2.9

4.0

4.1

As (particulate) μg/L 4.2

5.6

14.5

14.1

5.2

5.0

<0.1

<0.1

As (III) μg/L 15.6

16.0

0.8

0.7

0.6

0.5

0.8

0.8

As (V) μg/L 1.3

1.0

3.7

4.0

2.3

2.4

3.2

3.3

Total Al μg/L <11 <11 <11 12.9 <11

<11

<11

13.8

<11

<11

12.5

<11 12.9 13.5 <11 <11 14.7 <11 <11 <11

Total Fe μg/L 2,543 2,778 370 <30 2,493

2,476

2,349

2,304

797

766

<30

<30 2,585 2,492 39.3 <30 2,115 2,266 <30 <30

Total Mn μg/L 22.7 23.1 35.2 4.1 21.7

21.6

27.9

27.6

98.2

93.5

9.6

9.7 46.7 20.5 34.2 21.9 22.9 22.7 24.8 2.6

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 473

476

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 22.7

22.8

19.0

20.0

3.0

2.9

5.1

5.0

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
5

4

Table A-11. Analytical Results from Long Term Sampling, Plant A (March 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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 420 403 403 403 417 403 402 396 427

416

404

402

391

392

402

402 421 398 396 399

Turbidity NTU 16.7 5.0 0.7 0.1

pH 7.6 7.7 7.6 7.6 7.7 7.7 7.6 7.7 7.7

7.7

7.7

7.7

7.6

7.7

7.8

7.8 7.6 7.6 7.6 7.6

Total Hardness mg/L(a) 293 282 278 3.0

Ca Hardness mg/L(a) 147 140 137 1.5

Mg Hardness mg/L(a) 146 142 141 1.4

As (total) μg/L 20.6 20.1 2.3 1.6 21.9

21.7

19.8

19.6

2.4

2.5

2.1

2.2 19.6 19.9 2.4 4.9 21.5 20.9 3.0 2.1

As (total soluble) μg/L 20.9

20.5

4.5

4.5

2.6

2.4

2.2

2.3

As (particulate) μg/L 1.0

1.2

15.3

15.1

<0.1

0.1

<0.1

<0.1

As (III) μg/L 18.3

16.0

0.5

0.3

0.4

0.4

0.7

0.6

As (V) μg/L 2.6

4.5

4.0

4.2

2.2

2.0

1.5

1.7

Total Al μg/L <11 <11 <11 <11 <11

<11

<11

<11

<11

17.8

<11

<11 <11 <11 <11 <11 <11 <11 <11 <11

Total Fe μg/L 2,310 2,337 39.3 59.3 2,329

2,335

2,357

2,359

<30

<30

<30

<30 2,644 2,689 <30 <30 2,436 2,422 58.7 <30

Total Mn μg/L 21.0 20.2 43.3 2.9 20.8

21.0

22.3

22.5

64.8

66.5

3.6

3.6 22.6 22.7 24.7 9.6 22.6 22.9 15.5 2.4

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 1,000

1,000

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 23.6

23.1

18.8

18.7

6.8

6.7

2.5

2.8

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; AS = after softening.
5

5

Table A-12. Analytical Results from Long Term Sampling, Plant A (April 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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 423 397 395 401 419 398 396 396 349

347

396

394

363

393

396

395 421 400 397 397

Turbidity NTU 17.6 5.3 0.2 <0.1

pH 7.6 7.6 7.6 7.7 7.6 7.7 7.6 7.7 7.6

7.6

7.7

7.7

7.6

7.6

7.7

7.7 7.6 7.6 7.6 7.6

Total Hardness mg/L(a) 286 279 275 3.0

Ca Hardness mg/L(a) 142 137 135 1.2

Mg Hardness mg/L(a) 144 141 140 1.6

As (total) μg/L 20.1 21.4 2.9 4.9 21.0

22.9

21.4

20.7

3.2

3.1

2.0

2.0 20.0 21.0 2.6 1.8 19.5 19.6 2.6 1.0

As (total soluble) μg/L 21.0

21.8

15.0

5.1

2.9

3.1

2.0

2.0

As (particulate) μg/L <0.1

1.1

6.4

15.6

0.3

<0.1

<0.1

<0.1

As (III) μg/L 18.2

17.2

1.4

0.8

0.8

*

0.8

0.8

As (V) μg/L 3.5

4.6

3.6

4.3

2.1

*

1.2

1.3

Total Al μg/L 11.7 <11 <11 11.1

<11

<11

-

<11

25.9

<11

<11

15.2

<11 324 <11 <11 <11 18.7 <11 <11 <11

Total Fe μg/L 2,647 2,711 <30 <30 2,463

2,437

2,449

2,487

<30

<30

<30

<30 2,986 2,687 58.3 44.8 2,166 2,141 <30 <30

Total Mn μg/L 23.5 20.8 24.7 9.8 23.4

22.8

20.7

21.8

20.6

20.4

2.3

2.4 57.3 22.7 25.7 5.3 22.9 21.2 20.4 17.4

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 827

825

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 21.1

21.3

20.1

19.9

10.6

10.5

2.1

2.1

(a) As CaCO3.

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

*Sample not received from field.
5

6

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 AS IN PF AF AS IN PF AF AS IN PF AF AS

Alkalinity mg/L(a) 441 400 395 396 422 399 391 399 425

424

400

403

397

399

398

394 412 394 389 383

Turbidity NTU 22 5.8 0.3 0.1

pH 7.6 7.7 7.6 7.6 7.6 7.7 7.6 7.7 7.6

7.6

7.6

7.5

7.6

7.6

7.6

7.6 7.6 7.7 7.6 7.6

Total Hardness mg/L(a) 299 295 292 5.1

Ca Hardness mg/L(a) 152 155 152 2.8

Mg Hardness mg/L(a) 147 140 139 2.3

As (total) μg/L 42.5 21.7 2.8 1.3 21.6

20.9

20.4

20.3

2.5

2.4

3.0

2.8 16.7 20.8 2.3 2.2 19.8 19.8 2.5 2.6

As (total soluble) μg/L 21.5

21.7

4.4

4.9

2.5

2.5

3.4

3.4

As (particulate) μg/L 0.1

<0.1

16.0

15.4

<0.1

<0.1

<0.1

<0.1

As (III) μg/L 17.7

18.5

0.7

0.6

0.4

0.4

0.5

0.4

As (V) μg/L 3.8

3.2

3.7

4.3

2.1

2.0

2.9

2.9

Total Al μg/L <11 18.6 <11 <11 <11

<11

<11

<11

<11

<11

<11

<11 <11 <11 <11 <11 11.5 13.3 12.4 <11

Total Fe μg/L 2,863 2,719 51.1 <30 1,953

1,858

2,073

2,073

56.9

56.8

30.3

<30 2,435 2,379 30.4 49.9 2,418 2,464 82.1 19.1

Total Mn μg/L 17.7 62.7 25.7 15.6 21.3

20.3

19.3

20.3

22.4

21.9

8.3

7.2 21.4 21.7 19.9 4.5 21.2 22.7 20.8 5.6

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 1,237

1,291

<30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 21.6

22.5

16.3

15.9

12.5

13.5

4.9

5.0

(a) As CaCO3.

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

*Sample not received from field.
57

APPENDIX B

Complete Analytical Results from Long-Term Sampling at Plant B
5

8

Table B-1. Analytical Results from Long Term Sampling, Plant B (June 11 to July 30, 1998)

Sampling Date 6/11/98 6/16/98 6/23/98 6/30/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 137 137 135 144

145

142

140

140

141 140 140 141 143 142 140

Turbidity NTU 11.4 11.1 0.8

pH 8.0 7.8 7.7 7.9

7.9

7.7

7.7

7.7

7.7 8.0 7.8 7.8 7.9 7.7 7.7

Total Hardness mg/L(a) 377 386 392

Ca Hardness mg/L(a) 262 267 277

Mg Hardness mg/L(a) 115 119 115

As (total) μg/L 63.8

72.4

63.7

65.7

13.4

13.4

50.2

49.9

46.4

55.1

12.2

12.3 76.8 47.4 12.6 37.9 34.3 9.8

As (total soluble) μg/L 11.9

11.4

11.1

11.5

11.8

11.6

As (particulate) μg/L 51.9

61.0

52.6

54.2

1.6

1.8

As (III) μg/L 1.9

1.8

0.6

2.0

0.7

0.6

As (V) μg/L 10.0

9.6

10.5

9.5

11.1

11.0

Total Al μg/L 36.1

53.6

40.8

50.1

11.2

<11

26.9

35.4

30.2

29.1

<11

<11 46.9 28.5 <11 34.9 28.6 16.8

Total Fe μg/L 1,625

1,937

1,639

1,720

137

140

1,672

1,698

1,616

1,858

57.7

87.5 2,753 1,514 83.4 1,410 1,140 57.3

Total Mn μg/L 54.9

66.4

42.9

47.3

1.2

1.2

71.7

72.4

62.2

72.0

0.8

2.7 101 81.0 0.8 81.7 51.6 0.6

Dissolved Al μg/L 1.3

2.8

1.9

1.1

0.6

0.6

Dissolved Fe μg/L <30

<30

<30

<30

<30

33.1

Dissolved Mn μg/L 32.0

32.2

30.3

30.1

<0.5

0.7

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; ND = not detected.
5

9

Table B-2. Analytical Results from Long Term Sampling, Plant B (July 7 to July 28, 1998)

Sampling Date 7/7/98 7/14/98 7/21/98 7/28/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 143 143 140 144 139 136 146

144

142

139

142

141 141 137 135

Turbidity NTU 13.3 13.1 0.3

pH 7.9 7.2 7.7 8.1 7.9 7.8 8.0

8.0

7.8

7.7

7.7

7.7 8.1 7.8 7.8

Total Hardness mg/L(a) 418 329 359

Ca Hardness mg/L(a) 304 232 260

Mg Hardness mg/L(a) 114 96.8 99.7

As (total) μg/L 33.4 29.1 8.7 32.9

33.7

34.3

33.3

9.7

9.7 38.5 37.7 12.3 39.8 39.9 9.1

As (total soluble) μg/L 10.2

9.8

9.6

9.9

9.7

9.7

As (particulate) μg/L 22.7

23.9

24.7

23.4

<0.1

<0.1

As (III) μg/L 0.9

0.8

0.3

0.3

0.1

0.2

As (V) μg/L 9.3

9.0

9.3

9.6

9.6

9.4

Total Al μg/L 23.1 34.6 12.3 23.6

27.4

29.5

22.9

19.5

15.9 37.5 20.2 12.7 20.1 29.4 11.8

Total Fe μg/L 832 752 30.5 820

796

801

747

<30

32.0 761 705 32.2 779 775 110

Total Mn μg/L 55.4 40.3 <0.5 39.3

38.2

36.4

35.6

<0.5

0.5 43.8 37.4 0.8 42.5 35.3 2.0

Dissolved Al μg/L 1.3

1.4

1.1

1.4

0.9

0.9

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 32.6

32.3

27.1

27.1

<0.5

<0.5

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; ND = not detected.
6

0

Table B-3. Analytical Results from Long Term Sampling, Plant B (August 6 to August 25, 1998)

Sampling Date 8/6/98 8/11/98 8/18/98 8/25/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 141 138 137 140

140

137

137

137

137 139 135 136 141 138 137

Turbidity NTU 5.9 4.7 0.2

pH 7.9 7.7 7.7 8.1

8.1

7.8

7.7

7.7

7.7 7.9 7.8 7.8 7.9 7.8 7.7

Total Hardness mg/L(a) 414 405 397

Ca Hardness mg/L(a) 285 277 272

Mg Hardness mg/L(a) 129 128 125

As (total) μg/L 40.1

37.6

36.5

39.1

12.2

12.2 35.5 14.5 13.8 41.7 42.0 11.4 41.1 39.7 12.5

As (total soluble) μg/L 12.2

12.6

11.8

11.9

10.9

11.2

As (particulate) μg/L 27.9

25.0

24.7

27.2

1.3

1.0

As (III) μg/L 2.2

2.3

0.5

0.5

0.4

0.4

As (V) μg/L 10.0

10.3

11.3

11.4

10. 5

10.8

Total Al μg/L 17.1

13.6

12.3

14.6

<11

<11 <11 <11 <11 24.9 23.2 12.8 17.8 47.8 30.8

Total Fe μg/L 845

769

730

738

53.2

76.9 722 302 53.9 833 848 37.2 843 823 31.0

Total Mn μg/L 41.5

38.2

31.0

31.3

0.5

0.7 32.8 13.8 1.4 44.1 40.1 0.9 43.0 34.4 0.8

Dissolved Al μg/L 1.6

2.1

1.4

7.5

1.3

1.7

Dissolved Fe μg/L 10.8

<30

<30

<30

<30

<30

Dissolved Mn μg/L 32.3

32.2

28.9

29.0

0.1

0.1

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; ND = not detected.
61

Table B-4. Analytical Results from Long Term Sampling, Plant B (September 1 to September 22, 1998)

Sampling Date 9/1/98 9/9/98 9/15/98 9/22/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 137 135 137 140

140

137

137

137

137 141 137 139 142 136 136

Turbidity NTU 4.6 4.0 0.2

pH 7.8 7.7 7.6 7.8

7.8

7.7

7.7

7.7

7.7 8.0 7.7 7.8 7.8 7.7 7.7

Total Hardness mg/L(a) 442 428 429

Ca Hardness mg/L(a) 312 300 300

Mg Hardness mg/L(a) 130 129 129

As (total) μg/L 34.5

34.4

29.3

32.9

11.4

11.2 97.9 69.2 16.0 52.2 50.9 18.3 48.2 50.3 14.4

As (total soluble) μg/L 13.4

13.6

13.2

13.1

12.3

11.9

As (particulate) μg/L 21.1

20.8

16.1

19.8

<0.1

<0.1

As (III) μg/L 0.1

0.1

0.2

0.2

0.1

0.1

As (V) μg/L 13.3

13.5

13.0

12.9

12.2

11.8

Total Al μg/L 13.8

16.6

11.9

15.7

<11

12.5 26.4 23.7 18.6 16.3 19.2 15.2 31.4 22.0 36.8

Total Fe μg/L 614

644

593

650

35.5

35.0 2,004 1,345 94.0 1,009 989 74.9 2,152 2,167 306

Total Mn μg/L 29.2

30.7

25.7

27.3

<0.5

0.6 67.3 33.2 0.6 99.0 39.1 9.1 51.3 54.8 7.0

Dissolved Al μg/L 1.6

4.0

2.0

1.6

1.7

5.7

Dissolved Fe μg/L ND

ND

ND

ND

ND

ND

Dissolved Mn μg/L 28.4

28.2

27.0

26.5

0.1

0.2

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; ND = not detected.
6

2

Table B-5. Analytical Results from Long Term Sampling, Plant B (September 30 to October 21, 1998)

Sampling Date 9/30/98 10/6/98 10/13/98 10/21/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 141 135 137 139

139

133

135

134

133 138 136 135 139 135 133

Turbidity NTU 11.8 10.9 0.3

pH 7.8 7.7 7.7 7.7

7.7

7.5

7.5

7.5

7.5 7.9 7.7 7.8 7.8 7.6 7.6

Total Hardness mg/L(a) 474 468 398

Ca Hardness mg/L(a) 337 332 287

Mg Hardness mg/L(a) 137 136 111

As (total) μg/L 79.2

92.3

80.0

82.2

14.6

12.1 41.2 41.6 10.2 38.1 8.3 5.3 42.1 38.2 5.3

As (total soluble) μg/L 15.8

15.7

14.3

14.3

10.3

10.2

As (particulate) μg/L 63.4

76.6

65.7

65.9

4.3

1.9

As (III) μg/L 0.7

0.7

0.8

0.7

0.8

0.8

As (V) μg/L 15.1

15.0

13.5

13.6

9.5

9.4

Total Al μg/L 23.4

21.5

25.6

32.9

19.6

14.4 17.1 11.0 15.9 11.5 2.9 <11 20.1 17.3 11.9

Total Fe μg/L 1,689

1,666

1,763

1,768

40.5

43.2 599 591 <30 612 116 <30 726 925 98.5

Total Mn μg/L 110

93.2

77.1

100

3.9

4.0 36.0 30.8 0.6 49.2 60.9 4.6 43.3 37.5 2.6

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L <30

<30

<30

<30

<30

<30

Dissolved Mn μg/L 25

25

25.8

25.6

0.2

0.2

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; ND = not detected.
6

3

Table B-6. Analytical Results from Long Term Sampling, Plant B (October 27 TO November 17, 1998)

Sampling Date 10/27/98 11/03/98 11/10/98 11/17/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 138 135 134 138

138

133

133

132

133 138 137 136 141 138 142

Turbidity NTU 9.4 5.7 0.5

pH 7.8 7.6 7.6 7.7

7.7

7.6

7.6

7.6

7.6 8.6 7.7 7.7 7.6 7.5 7.7

Total Hardness mg/L(a) 484 461 480

Ca Hardness mg/L(a) 345 327 345

Mg Hardness mg/L(a) 139 134 135

As (total) μg/L 40.8

40.5

42.2

41.7

8.6

8.3 51.3 49.5 11.2 48.7 49.6 12.5 46.1 50.6 13.0

As (total soluble) μg/L 4.7

5.1

0.9

0.8

5.4

5.2

As (particulate) μg/L 36.1

35.4

41.3

40.9

3.2

3.1

As (III) μg/L 1.7

1.8

0.5

0.4

0.2

0.1

As (V) μg/L 3.0

3.3

0.4

0.4

5.2

5.1

Total Al μg/L 19.7

15.8

22.3

15.2

15.5

<11 12.5 <11 12.9 14.2 31.2 16.8 12.5 13.6 <11

Total Fe μg/L 2,185

1,945

1,858

1,851

140

131 685 670 <30 686 679 <30 1,021 1,130 61.4

Total Mn μg/L 52.0

55.6

43.1

42.5

3.4

3.2 64.0 51.2 1.4 55.9 56.0 0.8 107 83.2 1.3

Dissolved Al μg/L <11

<11

<11

<11

<11

<11

Dissolved Fe μg/L 633

678

<30

58.9

<30

<30

Dissolved Mn μg/L 40.8

41.4

9.3

9.6

0.4

1.4

(a) As CaCO3.

IN = inlet; PF = prefiltration; AF = after filtration; ND = not detected.
6

4

Table B-7. Analytical Results from Long Term Sampling, Plant B (November 24, to December 8, 1998)

Sampling Date 11/24/98(b) 12/01/98 12/08/98 12/15/98

Sampling Location

Parameter Unit IN PF AF IN PF AF IN PF AF IN PF AF

Alkalinity mg/L(a) 142 135 139 140

139

134

136

138

136 139 137 139

Turbidity NTU 5.2 6.7 0.2

pH 7.5 7.5 7.8 7.8

7.8

7.7

7.7

7.8

7.8 7.6 7.4 7.6

Total Hardness mg/L(a) 494 473 482

Ca Hardness mg/L(a) 352 337 340

Mg Hardness mg/L(a) 142 136 143

As (total) μg/L 55.2

54.1

67.7

66.4

19.9

19.5 46.1 46.3 13.3

As (total soluble) μg/L 15.5

14.8

14.6

14.3

20.2

20.1

As (particulate) μg/L 39.7

39.3

53.1

52.1

<0.1

<0.1

As (III) μg/L 2.3

2.2

0.4

0.4

0.4

0.3

As (V) μg/L 13.2

12.6

14.2

13.9

19.8

19.8

Total Al μg/L 23.4

20.9

18.1

22.1

30.4

25.2 <11 13.3 <11

Total Fe μg/L 1,039

1,023

1,445

1,428

75.4

72.2 648 616 <30

Total Mn μg/L 138

133

153

149

1.6

1.6 52.9 39.2 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 32.9

32.0

28.4

27.1

0.5

0.6

(a) As CaCO3.

(b) No sampling due to Thanksgiving holiday.

IN = inlet; PF = prefiltration; AF = after filtration; ND = not detected.