Solid Waste EPA-542-R-02-004

and Emergency Response September 2002

(5102G) www.epa.gov/tio

clu-in.org/arsenic

Arsenic Treatment Technologies for Soil, Waste, and Water
i

TABLE OF CONTENTS

Section Page

LIST OF ACRONYMS AND ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

NOTICE AND DISCLAIMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

PART I OVERVIEW AND FINDINGS

1.0 EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 1

2.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 1

2.1 Who Needs to Know about Arsenic Treatment Technologies? . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 1

2.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 1

2.3 How Often Does Arsenic Occur in Drinking Water? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 1

2.4 How Often Does Arsenic Occur at Hazardous Waste Sites? . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 2

2.5 What Are the Structure and Contents of the Report? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 4

2.6 What Technologies and Media Are Addressed in This Report? . . . . . . . . . . . . . . . . . . . . . . . . 2 - 4

2.7 How Is Technology Scale Defined? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 4

2.8 How Are Treatment Trains Addressed? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 5

2.9 What Are the Sources of Information for This Report? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 5

2.10 What Other Types of Literature Were Searched and Referenced for This Report? . . . . . . . . . . 2 - 5

2.11 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 6

3.0 COMPARISON OF ARSENIC TREATMENT TECHNOLOGIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 1

3.1 What Technologies Are Used to Treat Arsenic? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 1

3.2 What Technologies Are Used Most Often to Treat Arsenic? . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 1

3.3 What Factors Affect Technology Selection for Drinking Water Treatment? . . . . . . . . . . . . . . 3 - 3

3.4 How Effective Are Arsenic Treatment Technologies? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3

3.5 What Are Special Considerations for Retrofitting Existing Water Treatment Systems? . . . . . . 3 - 4

3.6 How Do I Screen Arsenic Treatment Technologies? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 4

3.7 What Does Arsenic Treatment Cost? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 6

3.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 6

PART II ARSENIC TREATMENT TECHNOLOGY SUMMARIES

PART IIA ARSENIC TREATMENT TECHNOLOGIES APPLICABLE TO SOIL AND WASTE

4.0 SOLIDIFICATION AND STABILIZATION TREATMENT FOR ARSENIC . . . . . . . . . . . . . . . . . . . 4 - 1

5.0 VITRIFICATION FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 1

6.0 SOIL WASHING/ACID EXTRACTION FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 1

7.0 PYROMETALLURGICAL RECOVERY FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 1

8.0 IN SITU SOIL FLUSHING FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 1

PART IIB ARSENIC TREATMENT TECHNOLOGIES APPLICABLE TO WATER

9.0 PRECIPITATION/COPRECIPITATION FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 1

10.0 MEMBRANE FILTRATION FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 1

11.0 ADSORPTION TREATMENT FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 1
ii

12.0 ION EXCHANGE FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 1

13.0 PERMEABLE REACTIVE BARRIERS FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 1

PART IIC ARSENIC TREATMENT TECHNOLOGIES APPLICABLE TO SOIL, WASTE, AND

WATER

14.0 ELECTROKINETIC TREATMENT OF ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 1

15.0 PHYTOREMEDIATION TREATMENT OF ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 - 1

16.0 BIOLOGICAL TREATMENT FOR ARSENIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 - 1

APPENDICES

APPENDIX A ñ LITERATURE SEARCH RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

APPENDIX B ñ SUPERFUND SITES WITH ARSENIC AS A CONSTITUENT OF CONCERN . . . . . . . . . . . B-1

LIST OF TABLES

Table Page

1.1 Arsenic Treatment Technology Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 3

1.2 Summary of Key Data and Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 4

2.1 Number of Superfund Sites with Arsenic as a Contaminant of Concern by Media . . . . . . . . . . . . . . . . . 2 - 2

2.2 Number of Superfund Sites with Arsenic as a Contaminant of Concern by Site Type . . . . . . . . . . . . . . 2 - 4

3.1 Applicability of Arsenic Treatment Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 9

3.2 Arsenic Treatment Technologies Screening Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 10

3.3 Available Arsenic Treatment Cost Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 15

3.4 Summary of Cost Data for Treatment of Arsenic in Drinking Water . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 17

4.1 Solidification/Stabilization Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 6

4.2 Long-Term Solidification/Stabilization Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . 4 - 12

5.1 Vitrification Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 5

6.1 Soil Washing/Acid Extraction Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . 6 - 4

7.1 Pyrometallurgical Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 4

8.1 In Situ Soil Flushing Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 4

9.1 Precipitation/Coprecipitation Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7

10.1 Membrane Filtration Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 5

11.1 Adsorption Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 6

12.1 Ion Exchange Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 5

13.1 Permeable Reactive Barrier Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 6

14.1 Electrokinetics Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 5

15.1 Phytoremediation Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 - 5

16.1 Biological Treatment Performance Data for Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 - 4

LIST OF FIGURES

Figure Page

2.1 Top Twelve Contaminants of Concern at Superfund Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3

2.2 Number of Applications of Arsenic Treatment Technologies at Superfund Sites . . . . . . . . . . . . . . . . . . 2 - 4

3.1 Number of Identified Applications of Arsenic Treatment Technologies for Soil and Waste . . . . . . . . . . 3 - 2

3.2 Number of Identified Applications of Arsenic Treatment Technologies for Water . . . . . . . . . . . . . . . . . 3 - 2
LIST OF FIGURES (continued)

iii

Figure Page

3.3 Number of Identified Applications of Arsenic Treatment Technologies for Soil, Waste, and Water . . . 3 - 3

4.1 Binders and Reagents Used for Solidification/Stabilization of Arsenic for 21 Identified Superfund

Remedial Action Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 1

4.2 Scale of Identified Solidification/Stabilization Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . 4 - 2

5.1 Scale of Identified Vitrification Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 2

6.1 Scale of Identified Soil Washing/Acid Extraction Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . 6 - 1

7.1 Scale of Identified Pyrometallurgical Recovery Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . 7 - 1

8.1 Scale of Identified In Situ Soil Flushing Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . . . . . 8 - 1

9.1 Scale of Identified Precipitaition/Coprecipitation Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . 9 - 2

10.1 Scale of Identified Membrane Filtration Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . . . . 10 - 1

11.1 Scale of Identified Adsorption Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 2

12.1 Scale of Identified Ion Exchange Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 2

13.1 Scale of Identified Permeable Reactive barrier Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . 13 - 3

14.1 Scale of Identified Electrokinetics Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 3

15.1 Scale of Identified Phytoremediation Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . 15 - 2

16.1 Scale of Identified Biological Treatment Projects for Arsenic Treatment . . . . . . . . . . . . . . . . . . . . . . . 16 - 2
iv

LIST OF ACRONYMS AND ABBREVIATIONS

AA Activated alumina

AC Activated carbon

ASR Annual Status Report

As(III) Trivalent arsenic, common inorganic form

in water is arsenite, H3AsO3

As(V) Pentavalent arsenic, common inorganic

form in water is arsenate, H2AsO4

-

BDAT best demonstrated available technology

BTEX Benzene, toluene, ethylbenzene, and

xylene

CCA Chromated copper arsenate

CERCLA Comprehensive Environmental Response,

Compensation, and Liability Act

CERCLIS 3 CERCLA Information System

CLU-IN EPA’s CLeanUp INformation system

CWS Community Water System

cy Cubic yard

DDT Dichloro-diphenyl-trichloroethane

DI Deionized

DOC Dissolved organic carbon

DoD Department of Defense

DOE Department of Energy

EDTA Ethylenediaminetetraacetic acid

EPA U.S. Environmental Protection Agency

EPT Extraction Procedure Toxicity Test

FRTR Federal Remediation Technologies

Roundtable

ft feet

GJO DOE’s Grand Junction Office

gpd gallons per day

gpm gallons per minute

HTMR High temperature metals recovery

MCL Maximum Contaminant Level

(enforceable drinking water standard)

MF Microfiltration

MHO Metallurgie-Hoboken-Overpelt

mgd million gallons per day

mg/kg milligrams per kilogram

mg/L milligrams per Liter

NF Nanofiltration

NPL National Priorities List

OCLC Online Computer Library Center

ORD EPA Office of Research and Development

OU Operable Unit

PAH Polycyclic aromatic hydrocarbons

PCB Polychlorinated biphenyls

POTW Publicly owned treatment works

PRB Permeable reactive barrier

RCRA Resource Conservation and Recovery Act

Redox Reduction/oxidation

RO Reverse osmosis

ROD Record of Decision

SDWA Safe Drinking Water Act

SMZ surfactant modified zeolite

SNAP Superfund NPL Assessment Program

S/S Solidification/Stabilization

SVOC Semivolatile organic compounds

TCLP Toxicity Characteristic Leaching

Procedure

TNT 2,3,6-trinitrotoluene

TWA Total Waste Analysis

UF Ultrafiltration

VOC Volatile organic compounds

WET Waste Extraction Test

ZVI Zero valent iron
v

FOREWORD

The purpose of this report is to provide a synopsis of the availability, performance, and cost of 13 arsenic treatment

technologies for soil, water, and waste. Its intended audience includes hazardous waste site managers; generators

and treaters of arsenic-contaminated waste and wastewater; owners and operators of drinking water treatment plants;

regulators; and the interested public. 

There is a growing need for cost-effective arsenic treatment. The presence of arsenic in the environment can pose a

risk to human health. Historical and current industrial use of arsenic has resulted in soil and groundwater

contamination that may require remediation. Some industrial wastes and wastewaters currently being produced

require treatment to remove or immobilize arsenic. In addition, arsenic must be removed from some sources of

drinking water before they can be used. 

Recently the EPA reduced the maximum contaminant level (MCL) for arsenic in drinking water from 0.050 mg/L to 

0.010 mg/L, effective in 2006. Current and future drinking water and groundwater treatment systems will require

better-performing technologies to achieve this lower level. EPA recently prepared an issue paper, Proven

Alternatives for Aboveground Treatment of Arsenic in Groundwater, that describes four technologies

(precipitation/coprecipitation, adsorption, ion exchange, and membrane filtration) for removing arsenic from water. 

The paper also discusses special considerations for retrofitting systems to meet the lower arsenic drinking water

standard. This information is incorporated in this report, as well as details on emerging approaches, such as

phytoremediation and electrokinetics, for addressing arsenic in groundwater.

This report is intended to be used as a screening tool for arsenic treatment technologies. It provides descriptions of

the theory, design, and operation of the technologies; information on commercial availability and use; performance

and cost data, where available; and a discussion of factors affecting effectiveness and cost. As a technology

overview document, the information can serve as a starting point for identifying options for arsenic treatment. The

feasibility of particular technologies will depend heavily on site-specific factors, and final treatment and remedy

decisions will require further analysis, expertise, and possibly treatability studies. 
vi

NOTICE AND DISCLAIMER

Preparation of this report has been funded by the U.S. Environmental Protection Agency (EPA) Technology

Innovation Office (TIO) under Contract Numbers 68-W-99-003 and 68-W-02-034. Information in this report is

derived from numerous sources (including personal communications with experts in the field), some of which have

been peer-reviewed. This study has undergone EPA and external review by subject-matter experts. Mention of

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

A PDF version of Arsenic Treatment Technologies for Soil, Waste, and Water, is available for viewing or

downloading from the Hazardous Waste Cleanup Information (CLU-IN) system web site at http://clu-in.org/arsenic. 

A limited number of printed copies are available free of charge, and may be ordered via the web site, by mail or by

facsimile from:

U.S. EPA/National Service Center for Environmental Publications (NSCEP)

P.O. Box 42419

Cincinnati, OH 45242-2419

Telephone: (513) 489-8190 or (800) 490-9198

Fax: (513) 489-8695

ACKNOWLEDGMENTS

Special acknowledgment is given to the federal and state staff and other remediation professionals for providing

information for this document. Their cooperation and willingness to share their expertise on arsenic treatment

technologies encourages their application at other sites. Contributors to the report included: U.S. EPA Office of

Groundwater and Drinking Water; U.S. EPA National Risk Management Research Laboratory; U.S. EPA Office of

Emergency and Remedial Response; U.S. EPA Office of Solid Waste; U.S. EPA Region I; U.S. EPA Region III;

David Ellis and Hilton Frey of Dupont; Richard M. Markey and James C. Redwine of Southern Company; James D.

Navratil of Clemson University; Robert G. Robbins of the Aquamin Science Consortium International; Cindy

Schreier of Prima Environmental; David Smythe of the University of Waterloo; Enid J. "Jeri" Sullivan of the Los

Alamos National Laboratory; and G. B. Wickramanayake of the Battelle Memorial Institute. 
PART I

OVERVIEW AND FINDINGS
1 - 1

1.0 EXECUTIVE SUMMARY

This report contains information on the current state of

the treatment of soil, waste, and water containing

arsenic, a contaminant that can be difficult to treat and

may cause a variety of adverse health effects in humans. 

This information can help managers at sites with

arsenic-contaminated media, generators of arseniccontaminated waste and wastewater, and owners and

operators of drinking water treatment plants to:

• Identify proven and effective arsenic treatment

technologies

• Screen those technologies based on effectiveness,

treatment goals, application-specific characteristics,

and cost

• Apply experience from sites with similar treatment

challenges

• Find more detailed arsenic treatment information 

Arsenic is in many industrial raw materials, products,

and wastes, and is a contaminant of concern in soil and

groundwater at many remediation sites. Because

arsenic readily changes valence state and reacts to form

species with varying toxicity and mobility, effective

treatment of arsenic can be difficult. Treatment can

result in residuals that, under some environmental

conditions, become more toxic and mobile. In addition,

the recent reduction in the maximum contaminant level

(MCL) for arsenic in drinking water from 0.050 to

0.010 mg/L will impact technology selection and

application for drinking water treatment, and could

result in lower treatment goals for remediation of

arsenic-contaminated sites. A lower treatment goal may

affect the selection, design, and operation of arsenic

treatment systems. 

This report identifies 13 technologies to treat arsenic in

soil, waste, and water. Table 1.1 provides brief

descriptions of these technologies. Part II of this report

contains more detailed information about each

technology.

Table 1.2 summarizes the technology applications and

performance identified for this report. The table

provides information on the number of projects that met

certain current or revised regulatory standards,

including the RCRA regulatory threshold for the

toxicity characteristic of 5.0 mg/L leachable arsenic, the

former MCL of 0.050 mg/L arsenic, and the revised

MCL of 0.010 mg/L. The table presents information for

solid-phase media (soil and waste) and aqueous media

(water, including groundwater, surface water, drinking

water, and wastewater). The technologies used to treat

one type of media typically show similar applicability

and effectiveness when applied to a similar media. For

example, technologies used to treat arsenic in soil have

about the same applicability and effectiveness, and are

used with similar frequency, to treat solid industrial

wastes. Similarly, technologies used to treat one type

of water (e.g., groundwater) typically show similar

applicability, effectiveness, and frequency of use when

treating another type of water (e.g., surface water). 

Soil and Waste Treatment Technologies

In general, soil and waste are treated by immobilizing

the arsenic using solidification/stabilization (S/S). This

technology is usually capable of reducing the

leachability of arsenic to below 5.0 mg/L (as measured

by the toxicity characteristic leaching procedure

[TCLP]), which is a common treatment goal for soil and

waste. S/S is generally the least expensive technology

for treatment of arsenic-contaminated soil and waste. 

Pyrometallurgical processes are applicable to some soil

and waste from metals mining and smelting industries. 

However, the information gathered for this report did

not indicate any current users of these technologies for

arsenic in the U. S. Other soil and waste treatment

technologies, including vitrification, soil washing/acid

extraction, and soil flushing, have had only limited

application to the treatment of arsenic. Although these

technologies may be capable of effectively treating

arsenic, data on performance are limited. In addition,

these technologies tend to be more expensive than S/S.

Water Treatment Technologies

Based on the information gathered for this report, 

precipitation/coprecipitation is frequently used to treat

arsenic-contaminated water, and is capable of treating a

wide range of influent concentrations to the revised

MCL for arsenic. The effectiveness of this technology

is less likely to be reduced by characteristics and

contaminants other than arsenic, compared to other

water treatment technologies. It is also capable of

treating water characteristics or contaminants other than

arsenic, such as hardness or heavy metals. Systems

using this technology generally require skilled

operators; therefore, precipitation/coprecipitation is

more cost effective at a large scale where labor costs

can be spread over a larger amount of treated water

produced.

The effectiveness of adsorption and ion exchange for

arsenic treatment is more likely than precipitation/

coprecipitation to be affected by characteristics and

contaminants other than arsenic. However, these

technologies are capable of treating arsenic to the

revised MCL. Small capacity systems using these

technologies tend to have lower operating and

maintenance costs, and require less operator expertise. 

Adsorption and ion exchange tend to be used more

often when arsenic is the only contaminant to be

treated, for relatively smaller systems, and as a

polishing technology for the effluent from larger

systems. Membrane filtration is used less frequently
1 - 2

because it tends to have higher costs and produce a

larger volume of residuals than other arsenic treatment

technologies.

Innovative Technologies

Innovative technologies, such as permeable reactive

barriers, biological treatment, phytoremediation, and

electrokinetic treatment, are also being used to treat

arsenic-contaminated soil, waste, and water. The

references identified for this report contain information

about only a few applications of these technologies at

full scale. However, they may be used to treat arsenic

more frequently in the future. Additional treatment data

are needed to determine their applicability and

effectiveness.

Permeable reactive barriers are used to treat

groundwater in situ. This technology tends to have

lower operation and maintenance costs than ex situ

(pump and treat) technologies, and typically requires a

treatment time of many years. This report identified

three full-scale applications of this technology, but

treatment data were available for only one application. 

In that application, a permeable reactive barrier is

treating arsenic to below the revised MCL.

Biological treatment for arsenic is used primarily to

treat water above-ground in processes that use

microorganisms to enhance precipitation/

coprecipitation. Bioleaching of arsenic from soil has

also been tested on a bench scale. This technology may

require pretreatment or addition of nutrients and other

treatment agents to encourage the growth of key

microorganisms.

Phytoremediation is an in situ technology intended to be

applicable to soil, waste, and water. This technology

tends to have low capital, operating, and maintenance

costs relative to other arsenic treatment technologies

because it relies on the activity and growth of plants. 

However, the effectiveness of this technology may be

reduced by a variety of factors, such as the weather, soil

and groundwater contaminants and characteristics, the

presence of weeds or pests, and other factors. The

references identified for this report contained

information on one full-scale application of this

technology to arsenic treatment.

Electrokinetic treatment is an in situ technology

intended to be applicable to soil, waste and water. This

technology is most applicable to fine-grained soils, such

as clays. The references identified for this report

contained information on one full-scale application of

this technology to arsenic treatment.
1 - 3

Table 1.1

Arsenic Treatment Technology Descriptions

Technology Description

Technologies for Soil and Waste Treatment

Solidification/

Stabilization

Physically binds or encloses contaminants within a stabilized mass and chemically reduces the

hazard potential of a waste by converting the contaminants into less soluble, mobile, or toxic

forms.

Vitrification High temperature treatment that reduces the mobility of metals by incorporating them into a

chemically durable, leach resistant, vitreous mass. The process also may cause contaminants

to volatilize, thereby reducing their concentration in the soil and waste.

Soil Washing/

Acid Extraction

An ex situ technology that takes advantage of the behavior of some contaminants to

preferentially adsorb onto the fines fraction of soil. The soil is suspended in a wash solution

and the fines are separated from the suspension, thereby reducing the contaminant

concentration in the remaining soil.

Pyrometallurgical

Recovery

Uses heat to convert a contaminated waste feed into a product with a high concentration of the

contaminant that can be reused or sold.

In Situ Soil

Flushing

Extracts organic and inorganic contaminants from soil by using water, a solution of chemicals

in water, or an organic extractant, without excavating the contaminated material itself. The

solution is injected into or sprayed onto the area of contamination, causing the contaminants

to become mobilized by dissolution or emulsification. After passing through the

contamination zone, the contaminant-bearing flushing solution is collected and pumped to the

surface for treatment, discharge, or reinjection.

Technologies for Water Treatment

Precipitation/

Coprecipitation

Uses chemicals to transform dissolved contaminants into an insoluble solid or form another

insoluble solid onto which dissolved contaminants are adsorbed. The solid is then removed

from the liquid phase by clarification or filtration.

Membrane

Filtration

Separates contaminants from water by passing it through a semi-permeable barrier or

membrane. The membrane allows some constituents to pass, while blocking others. 

Adsorption Concentrates solutes at the surface of a sorbent, thereby reducing their concentration in the

bulk liquid phase. The adsorption media is usually packed into a column. As contaminated

water is passed through the column, contaminants are adsorbed.

Ion Exchange Exchanges ions held electrostatically on the surface of a solid with ions of similar charge in a

solution. The ion exchange media is usually packed into a column. As contaminated water is

passed through the column, contaminants are removed.

Permeable

Reactive Barriers

Walls containing reactive media that are installed across the path of a contaminated

groundwater plume to intercept the plume. The barrier allows water to pass through while the

media remove the contaminants by precipitation, degradation, adsorption, or ion exchange.

Technologies for Soil, Waste, and Water Treatment

Electrokinetic

Treatment

Based on the theory that a low-density current applied to soil will mobilize contaminants in

the form of charged species. A current passed between electrodes inserted into the subsurface

is intended to cause water, ions, and particulates to move through the soil. Contaminants

arriving at the electrodes can be removed by means of electroplating or electrodeposition,

precipitation or coprecipitation, adsorption, complexing with ion exchange resins, or by

pumping of water (or other fluid) near the electrode.

Phytoremediation Involves the use of plants to degrade, extract, contain, or immobilize contaminants in soil,

sediment, and groundwater.

Biological

Treatment

Involves the use of microorganisms that act directly on contaminant species or create ambient

conditions that cause the contaminant to leach from soil or precipitate/coprecipitate from

water.
1 - 4

Table 1.2

Summary of Key Data and Findings

Technology

Media Treated

Number of Applications Identifieda

(Number with Performance Data) Soil and Waste Water

Soiland

Waste Water

Bench

Scale

Pilot

Scale

Full

Scale Total

Number of

Applications

Achieving <5.0

mg/L Leachable

Arsenic

Number of

Applications

Achieving <0.050

mg/L Arsenic

Number of

Applications

Achieving

<0.010 mg/L

Arsenic

Solidification/Stabilization g - NC 10 (10) 34 (32) 44 (42) 37 - -

Vitrification g - NC 10 (5) 6 (2) 16 (7) 7 - -Soil Washing/Acid Extraction g - 2 (0) 3 (0) 4 (0) 9 (0) - - -Pyrometallurgical Recovery g - 0 0 4 (2) 4 (2) 2 - -In Situ Soil Flushing g - 0 2 (0) 2 (0) 4 (0) - - -Precipitation/Coprecipitation - g NC 24 (22) 45 (30) 68 (51) - 36 19

Membrane Filtration - g 6 (0) 25 (2) 2 (2) 33 (4) - 4 2

Adsorption - g NC 7 (4) 14 (8) 21 (12) - 12 7

Ion Exchange - g NC 0 7 (4) 7 (4) - 3 2Permeable Reactive Barriers - g 5 (4) 2 (1) 3 (1) 10 (6) - 6 4

Electrokinetics g g 3 (0) 3 (1) 1 (0) 7 (1) - 1 0Phytoremediation g g 4 (0) 2 (0) 1 (0) 7 (0) - - -Biological Treatment g g 1 3 (2) 1 (0) 5 (2) - 1 0

a Applications were identified through a search of available technical literature (See Sections 2.9 and 2.10). The number of applications include only those

identified during the preparation of this report, and are not comprehensive. Limited information on treatment of industrial wastes and wastewaters wasidentified, therefore the table may not be representative of these types of applications.

NC = Data not collected ! = Not applicable

Source: Adapted from data in Sections 4.0 to 16.0 of this report
2 - 1

2.0 INTRODUCTION

2.1 Who Needs to Know about Arsenic Treatment

Technologies?

This report was prepared to provide information on the

current state of arsenic treatment for soil, waste, and

water. The report may be used to:

• Identify proven and effective arsenic treatment

technologies

• Screen those technologies based on effectiveness,

treatment goals, application-specific characteristics,

and cost

• Apply experience from sites with similar treatment

challenges

• Find more detailed arsenic treatment information 

The report may be used by remediation site managers,

hazardous waste generators (for example, wood treaters,

herbicide manufacturers, mine and landfill operators),

drinking water treatment plant designers and operators,

and the general public to help screen arsenic treatment

options.

Arsenic is a common inorganic element found widely in

the environment. It is in many industrial products,

wastes, and wastewaters, and is a contaminant of

concern at many remediation sites. Arseniccontaminated soil, waste, and water must be treated by

removing the arsenic or immobilizing it. Because

arsenic readily changes valence states and reacts to

form species with varying toxicity and mobility,

effective, long-term treatment of arsenic can be

difficult. In some disposal environments arsenic has

leached from arsenic-bearing wastes at high

concentrations (Ref. 2.11).

Recently, the EPA reduced the maximum contaminant

level (MCL) for arsenic in drinking water from 0.050

mg/L to 0.010 mg/L, effective in 2006 (Ref. 2.9). 

Drinking water suppliers may need to add new

treatment processes or retrofit existing treatment

systems to meet the revised MCL. In addition, it may

affect Superfund remediation sites and other sites that

base cleanup goals on the arsenic drinking water MCL. 

This report provides information needed to help meet

the challenges of arsenic treatment.

2.2 Background

Where Does Arsenic Come From?

Arsenic occurs naturally in rocks, soil, water, air,

plants, and animals. Natural activities such as volcanic

action, erosion of rocks, and forest fires, can release

arsenic into the environment. Industrial products

containing arsenic include wood preservatives, paints,

dyes, pharmaceuticals, herbicides, and semiconductors. The man-made sources of arsenic in the

environment include mining and smelting operations;

agricultural applications; burning of fossil fuels and

wastes; pulp and paper production; cement

manufacturing; and former agricultural uses of arsenic 

(Ref. 2.1). 

What Are the Health Effects of Arsenic?

Many studies document the adverse health effects in

humans exposed to inorganic arsenic compounds. A

discussion of those effects is available in the following

documents:

• National Primary Drinking Water Regulations;

Arsenic and Clarifications to Compliance and New

Source Contaminants Monitoring (66 FR 6976 /

January 22, 2001) (Ref. 2.1)

• The Agency for Toxic Substances and Disease

Registry (ATSDR) ToxFAQsTM for Arsenic (Ref.

2.13). 

How Does Arsenic Chemistry Affect Treatment?

Arsenic is a metalloid or inorganic semiconductor that

can form inorganic and organic compounds. It occurs

with valence states of -3, 0, +3 (arsenite), and +5

(arsenate). However, the valence states of -3 and 0

occur only rarely in nature. This discussion of arsenic

chemistry focuses on inorganic species of As(III) and

As(V). Inorganic compounds of arsenic include

hydrides (e.g., arsine), halides, oxides, acids, and

sulfides (Ref. 2.4). 

The toxicity and mobility of arsenic varies with its

valence state and chemical form. Arsenite and arsenate

are the dominant species in surface water and sea water,

and organic arsenic species can be found in natural gas

and shale oil (Ref. 2.12). Different chemical

compounds containing arsenic exhibit varying degrees

of toxicity and solubility.

Arsenic readily changes its valence state and chemical

form in the environment. Some conditions that may

affect arsenic valence and speciation include (Ref. 2.7):

• pH - in the pH range of 4 to 10, As(V) species

are negatively charged in water, and the

predominant As(III) species is neutral in

charge

• redox potential

• the presence of complexing ions, such as ions

of sulfur, iron, and calcium

• microbial activity

Adsorption-desorption reactions can also affect the

mobility of arsenic in the environment. Clays,
2 - 2

carbonaceous materials, and oxides of iron, aluminum,

and manganese are soil components that may participate

in adsorptive reactions with arsenic (Ref. 2.7).

The unstable nature of arsenic species may make it

difficult to treat or result in treated wastes whose

toxicity and mobility can change under some

environmental conditions. Therefore, the successful

treatment and long-term disposal of arsenic requires an

understanding of arsenic chemistry and the disposal

environment.

2.3 How Often Does Arsenic Occur in Drinking

Water?

Arsenic is a fairly common environmental contaminant.

Both groundwater (e.g., aquifers) and surface water

(e.g., lakes and rivers) sources of drinking water can

contain arsenic. The levels of arsenic are typically

higher in groundwater sources. Arsenic levels in

groundwater tend to vary geographically. In the U.S.,

Western states (AK, AZ, CA, ID, NV, OR, UT, and

WA) tend to have the highest concentrations (>0.010

mg/L), while states in the North Central (MT, ND, SD,

WY), Midwest Central (IL, IN, IA, MI, MN, OH, and

WI), and New England (CT, MA, ME, NH, NJ, NY, RI,

and VT) regions tend to have low to moderate

concentrations (0.002 to 0.010 mg/L). However, some

portions of these areas may have no detected arsenic in

drinking water. Other regions of the U.S. may have

isolated areas of high concentration. EPA estimates that

4,000 drinking water treatment systems may require

additional treatment technologies, a retrofit of existing

treatment technologies, or other measures to achieve the

revised MCL for arsenic. An estimated 5.4% of

community water systems (CWSs) using groundwater

as a drinking water source and 0.7% of CWSs using

surface water have average arsenic levels above 0.010

mg/L. (Ref. 2.1)

2.4 How Often Does Arsenic Occur at Hazardous

Waste Sites?

Hazardous waste sites fall under several clean-up

programs, such as Superfund, Resource Conservation

and Recovery Act (RCRA) corrective actions, and state

cleanup programs. This section contains information

on the occurrence and treatment of arsenic at National

Priorities List (NPL) sites, known as Superfund sites.

Information on arsenic occurrence and treatment at

Superfund sites was complied from the CERCLIS 3

database (Ref. 2.3), the Superfund NPL Assessment

Program (SNAP) database, and the database supporting

the document "Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition)" (Ref.

2.8). The information sources identified for this report

did not contain information on arsenic occurrence and

treatment at RCRA corrective action and state cleanup

program sites.

Table 2.1 lists the number of Superfund sites with

arsenic as a contaminant of concern by media. 

Groundwater and soil were the most common media

contaminated with arsenic at 380 and 372 sites,

respectively. The number of sites in Table 2.1 exceeds

the number of total sites with arsenic contamination 

(568) because each site may have more than one type of

media contaminated with arsenic.

Table 2.1

Number of Superfund Sites with Arsenic as a

Contaminant of Concern by Media

Media Type Number of Sites

Groundwater 380

Soil 372

Sediment 154

Surface Water 86

Debris 77

Sludge 45

Solid Waste 30

Leachate 24

Other 21

Liquid Waste 12

Air 8

Residuals 1

Source: Ref. 2.3

Arsenic occurs frequently at NPL sites. Figure 2.1

shows the most common contaminants of concern

present at Superfund sites for which a Record of

Decision (ROD) has been signed, through FY 1999, the

most recent year for which such information is

available. Arsenic is the second most common

contaminant of concern (after lead), occurring at 568

sites (47% of all sites on the NPL with RODs). 
2 - 3

Lead

Arsenic

Benzene

Chromium

Toluene

Cadmium

Zinc

Xylenes

Vinyl chloride

Nickel

1,1,1-TCA

Trichloroethylene

357 352

375 373 384 382

425

457

518

591

568

529

0

100

200

300

400

500

600

700

Number of Sites

Lead

Arsenic

Benzene

Chromium

Toluene

Cadmium

Zinc

Xylenes

Vinyl chloride

Nickel

1,1,1-TCA

Trichloroethylene

357 352

375 373 384 382

425

457

518

591

568

529

0

100

200

300

400

500

600

700

Number of Sites

Figure 2.1

Top Twelve Contaminants of Concern at Superfund Sites

Source: Ref. 2.3

Table 2.2 lists the number of Superfund sites with

arsenic as a contaminant of concern by site type. The

most common site types were landfills and other

disposal facilities, chemicals and allied products, and

lumber and wood products. Some sites may have more

than one site type.

Figure 2.2 shows the use of treatment technologies to

address arsenic at Superfund sites. These projects may

be planned, ongoing, or completed. Solidification/

stabilization was the most common treatment

technology for soil and waste, used in 45 projects to

treat arsenic. The most common treatment technology

for water was precipitation/coprecipitation, which is

known to have been used in nine projects. 

More detail on these applications is provided in the

technology-specific sections (Sections 4.0 through

16.0). Information in Figure 2.2 on the treatment of

contaminant sources (i.e., contaminated soil, sludge,

sediment, or other environmental media excluding

groundwater) and in situ groundwater treatment is

based on a detailed review of RODs and contacts with

RPMs. A similar information source for pump and treat

technologies (precipitation/coprecipitation, membrane

filtration, adsorption, ion exchange) for groundwater

containing arsenic at Superfund Sites was not available. 
2 - 4

1

0

0

4

2

5

0

9

2

1

2

1

45

Phytoremediation

Electrokinetics

Biological Treatment

Permeable Reactive Barriers

Ion Exchange

Adsorption

Membrane Filtration

Precipitation/Coprecipitation

In Situ Soil Flushing

Pyrometallurgical Recovery

Soil Washing/Acid Extraction

Vitrification

Solidification/Stabilization

Treatment Technology

1

0

0

4

2

5

0

9

2

1

2

1

45

1

0

0

4

2

5

0

9

2

1

2

1

45

Phytoremediation

Electrokinetics

Biological Treatment

Permeable Reactive Barriers

Ion Exchange

Adsorption

Membrane Filtration

Precipitation/Coprecipitation

In Situ Soil Flushing

Pyrometallurgical Recovery

Soil Washing/Acid Extraction

Vitrification

Solidification/Stabilization

Phytoremediation

Electrokinetics

Biological Treatment

Permeable Reactive Barriers

Ion Exchange

Adsorption

Membrane Filtration

Precipitation/Coprecipitation

In Situ Soil Flushing

Pyrometallurgical Recovery

Soil Washing/Acid Extraction

Vitrification

Solidification/Stabilization

Treatment Technology

Table 2.2

Number of Superfund Sites with Arsenic as a

Contaminant of Concern by Site Type

Site Type

Number of

Sitesb

Landfills and Other Disposal 209

Chemicals and Allied Products 42

Lumber and Wood Products 33

Groundwater Plume Site 26

Metal Fabrication and Finishing 20

Batteries and Scrap Metal 18

Military and Other Ordnance 18

Transportation Equipment 15

Primary Metals Processing 14

Chemicals and Chemical Waste 12

Ordnance Production 12

Electrical Equipment 11

Radioactive Products 9

Product Storage and Distribution 8

Waste Oil and Used Oil 8

Metals 6

Drums and Tanks 6

Transportation 5

Research and Development 5

Othera 104

Sources: Ref. 2.3, 2.15

a Includes site types with fewer than 5 sites, sites

whose site types were identified as “other”or

“multiple”, and unspecified industrial waste

facilities.

b Some sites have more than one site type.

Figure 2.2

Number of Applications of Arsenic Treatment

Technologies at Superfund Sitesa

a Information on the application of groundwater

pump and treat technologies, including

precipitation/coprecipitation, membrane filtration,

adsorption, and ion exchange, is based on available

data and is not comprehensive.

2.5 What Are the Structure and Contents of the

Report?

Part I of this report, the Overview and Findings,

contains an Executive Summary, an Introduction, and a

Comparison of Arsenic Treatment Technologies. This

Introduction describes the purpose of the report,

presents background information, and summarizes the

methodology used to gather and analyze data. The

"Comparison of Technologies" Section (3.0) analyzes

and compares the data gathered. 

Part II of this report contains 13 sections, each

summarizing the available information for an arsenic

treatment technology. Each summary includes a brief

description of the technology, information about how it

is used to treat arsenic, its status and scale, and

available cost and performance data, including the

amount and type of soil, waste, and water treated and a

summary of the results of analyses of untreated soil,

waste, and water and treatment residuals for total and

leachable arsenic concentrations. The technology

summaries are organized as follows: the technologies

typically used to treat soil and waste appear first, in the

order of their frequency of full-scale applications,

followed by those typically used for water in the same

order, and then by those used to treat soil, waste, and

water.
2 - 5

2.6 What Technologies and Media Are Addressed in

the Report?

This report provides information on the 13 technologies

listed in Table 1.1. These technologies have been used

at full scale for the treatment of arsenic in soil, waste,

and water. For the purposes of this report, the term

“soil” includes soil, debris, sludge, sediments, and other

solid-phase environmental media. Waste includes nonhazardous and hazardous solid waste generated by

industry. Water includes groundwater, drinking water,

non-hazardous and hazardous industrial wastewater,

surface water, mine drainage, and leachate. 

2.7 How Is Technology Scale Defined?

This report includes available information on bench-,

pilot- and full-scale applications for the 13

technologies. Full-scale projects include those used

commercially to treat industrial wastes and those used

to remediate an entire area of contamination. Pilotscale projects are usually conducted in the field to test

the effectiveness of the technology on a specific soil,

waste, and water or to obtain information for scaling a

treatment system up to full scale. Bench-scale projects

are conducted on a small scale, usually in a laboratory

to evaluate the technology’s ability to treat soil, waste,

and water. These often occur during the early phases of

technology development. 

The report focuses on full- and pilot-scale data. Benchscale data are presented only when less than 5 full-scale

applications of a technology were identified. For the

technologies with at least 5 identified full-scale

applications (solidification/stabilization, vitrification,

precipitation/coprecipitation, adsorption, and ion

exchange), the report does not include bench-scale data. 

2.8 How Are Treatment Trains Addressed?

Treatment trains consist of two or more technologies

used together, either integrated into a single process or

operated as a series of treatments in sequence. The

technologies in a train may treat the same contaminant. 

The information gathered for this report included many

projects that used treatment trains. A common

treatment train used for arsenic in water includes an

oxidation step to change arsenic from As(III) to its less

soluble As(V) state, followed by precipitation/

coprecipitation and filtration to remove the precipitate. 

Some trains are employed when one technology alone is

not capable of treating all of the contaminants. For

example, at the Baird and McGuire Superfund Site

(Table 9.1), an above-ground system consisting of air

stripping, metals precipitation, and activated carbon

adsorption was used to treat groundwater contaminated

with volatile organic compounds (VOCs), arsenic, and

semivolatile organic compounds (SVOCs). In this

treatment train the air stripping was intended to treat

VOCs, the precipitation, arsenic, and the activated

carbon adsorption, SVOCs and any remaining VOCs.

In many cases, the available information does not

specify the technologies within the train that are

intended to treat arsenic. Influent and effluent

concentrations, where available, often were provided

for the entire train, and not the individual components. 

In such cases, engineering judgement was used to

identify the technology that treated arsenic. For

example, at the Greenwood Chemical Superfund site

(Table 9.1), a treatment train consisting of metals

precipitation, filtration, UV oxidation and carbon

adsorption was used to treat groundwater contaminated

with arsenic, VOCs, halogenated VOCs, and SVOCs. 

The precipitation and filtration were assumed to remove

arsenic, and the UV oxidation and carbon adsorption

were assumed to have only a negligible effect on the

arsenic concentration.

Where a train included more than one potential arsenic

treatment technology, all arsenic treatment technologies

were assumed to contribute to arsenic treatment, unless

available information indicated otherwise. For

example, at the Higgins Farm Superfund site, arseniccontaminated groundwater was treated with

precipitation and ion exchange (Tables 9.1 and 12.1). 

Information about this treatment is presented in both the

precipitation/coprecipitation (Section 9.0) and ion

exchange (Section 12.0) sections. 

Activated carbon adsorption is most commonly used to

treat organic contaminants. This technology is

generally ineffective on As(III) (Ref. 2.14). Where

treatment trains included activated carbon adsorption

and another arsenic treatment technology, it was

assumed that activated carbon adsorption did not

contribute to the arsenic treatment, unless the available

information indicated otherwise.

2.9 What Are the Sources of Information for This

Report?

This report is based on an electronic literature search

and information gathered from readily-available data

sources, including:

• Documents and databases prepared by EPA,

DOD, and DOE

• Technical literature

• Information supplied by vendors of treatment

technologies

• Internet sites

• Information from technology experts
2 - 6

Most of the information sources used for this report

contained information about treatments of

environmental media and drinking water. Only limited

information was identified about the treatment of 

industrial waste and wastewater containing arsenic. 

This does not necessarily indicate that treatment

industrial wastes and wastewater containing arsenic

occurs less frequently, because data on industrial

treatments may be published less frequently.

The authors and reviewers of this report identified these

information sources based on their experience with

arsenic treatment. In addition, a draft version of this

report was presented at the U.S. EPA Workshop on

Managing Arsenic Risks to the Environment, which

was held in Denver, Colorado in May of 2001. 

Information gathered from this workshop and sources

identified by workshop attendees were also reviewed

and incorporated where appropriate. Proceedings for

this workshop may be available from EPA in 2002.

2.10 What Other Types of Literature Were

Searched and Referenced for This Report?

To identify recent and relevant documents containing

information on the application of arsenic treatment

technologies in addition to the sources listed in Section

2.9, a literature search was conducted using the

Dialog® and Online Computer Library Center (OCLC)

services. The search was limited to articles published

between January 1, 1998 and May 30, 2001 in order to

ensure that the information gathered was current. The

search identified documents that included in their title

the words "arsenic," "treatment," and one of a list of

key words intended to encompass the types of soil,

waste, and water containing arsenic that might be

subject to treatment. Those key words were:

- Waste - Water

- Sludge - Mine

- Mining - Debris

- Groundwater - Soil

- Hazardous - Toxic

- Sediment - Slag

The Dialog® search identified 463 references, and the

OCLC search found 45 references. Appendix A lists

the title, author, and publication source for each of the

508 references identified through the literature search. 

The search results were reviewed to identify the

references (in English) that provided information on the

treatment of waste that contains arsenic using one of the

technologies listed in Table 1.1. Using this

methodology, a total of 44 documents identified

through the literature search were obtained and

reviewed in detail to gather information for this report. 

These documents are identified in Appendix A with an

asterisk (*). 

2.11 References

2.1 U.S. EPA. National Primary Drinking Water

Regulations; Arsenic and Clarifications to

Compliance and New Source Contaminants

Monitoring; Proposed Rule. Federal Register, Vol

65, Number 121, p. 38888. June 22, 2000. 

http://www.epa.gov/safewater/ars/arsenic.pdf.

2.2 U.S. Occupational Safety and Health

Administration. Occupational Safety and Health

Guidelines for Arsenic, Organic Compounds (as

As). November, 2001.

http://www.osha-slc.gov/SLTC/healthguidelines/

arsenic/recognition.html.

2.3 U.S. EPA Office of Emergency and Remedial

Response. Comprehensive Environmental

Response Compensation and Liability Information

System database (CERCLIS 3). October 2001.

2.4 Kirk-Othmer. "Arsenic and Arsenic Alloys." The

Kirk-Othemer Encyclopedia of Chemical

Technology, Volume 3. John Wiley and Sons,

New York. 1992.

2.5 Kirk-Othmer. "Arsenic Compounds" The KirkOthemer Encyclopedia of Chemical Technology,

Volume 3. John Wiley and Sons, New York. 

1992.

2.6 EPA. Treatment Technology Performance and

Cost Data for Remediation of Wood Preserving

Sites. Office of Research and Development.

EPA-625-R-97-009. October 1997.

http://epa.gov/ncepihom.

2.7 Vance, David B. "Arsenic - Chemical Behavior

and Treatment”. October, 2001.

http://2the4.net/arsenicart.htm.

2.8 EPA. Treatment Technologies for Site Cleanup: 

Annual Status Report (Tenth Edition). Office of

Solid Waste and Emergency Response. EPA-542-

R-01-004. February 2001. http://clu-in.org.

2.9 U.S. EPA. National Primary Drinking Water

Regulations; Arsenic and Clarifications to

Compliance and New Source Contaminants

Monitoring; Final Rule. Federal Register,

Volume 66, Number 14, p. 6975-7066. January

22, 2001. 

http://www.epa.gov/sbrefa/documents/pnl14f.pdf
2 - 7

2.10 U.S. EPA Office of Water. Fact Sheet: EPA to

Implement 10ppb Standard for Arsenic in

Drinking Water. EPA 815-F-01-010. October,

2001. http://www.epa.gov/safewater/ars/

ars-oct-factsheet.html.

2.11 Federal Register. Land Disposal Restrictions:

Advanced Notice of Proposed Rulemaking. 

Volume 65, Number 118. June 19, 2000. pp.

37944 - 37946.

http://www.epa.gov/fedrgstr/EPA-WASTE/2000/

June/Day-19/f15392.htm

2.12 National Research Council. Arsenic in Drinking

Water. Washington, D.C. National Academy

Press. 1999. 

http://www.nap.edu/catalog/6444.html

2.13 The Agency for Toxic Substances and Disease

Registry (ATSDR): ToxFAQsTM for Arsenic (12).

July, 2001. 

http://www.atsdr.cdc.gov/tfacts2.html.

2.14 U.S. EPA. Cost Analyses for Selected

Groundwater Cleanup Projects: Pump and Treat

Systems and Permeable Reactive Barriers, EPA542-R-00-013, February 2001. http://clu-in.org

2.15 U.S. EPA Office of Emergency and Remedial

Response. Superfund NPL Assessment Program 

(SNAP) database. April 11, 2002.
3 - 1

Arsenic Treatment Technologies

Soil and Waste Treatment Technologies

• Solidification/

Stabilization

• Vitrification

• Soil Washing/Acid

Extraction

• Pyrometallurgical

Recovery

• In Situ Soil Flushing

Water Treatment Technologies

• Precipitation/

Coprecipitation

• Membrane Filtration

• Adsorption

• Ion Exchange

• Permeable Reactive

Barriers

Soil, Waste, and Water Treatment Technologies

• Electrokinetics

• Phytoremediation

• Biological Treatment

3.0 COMPARISON OF ARSENIC TREATMENT

TECHNOLOGIES

3.1 What Technologies Are Used to Treat Arsenic?

This report identifies 13 technologies applicable to

arsenic-contaminated soil, waste, and water. 

Technologies are considered applicable if they have

been used at full scale to treat arsenic. 

Table 3.1 summarizes their applicability to arseniccontaminated media. The media treated by these

technologies can be grouped into two general

categories: soil and waste; and water.

Technologies applicable to one type of soil and waste

are typically applicable to other types. For example,

solidification/stabilization has been used to effectively

treat industrial waste, soil, sludge, and sediment. 

Similarly, technologies applicable to one type of water

are generally applicable to other types. For example,

precipitation/coprecipitation has been used to

effectively treat industrial wastewaters, groundwater,

and drinking water. 

3.2 What Technologies Are Used Most Often to

Treat Arsenic?

This section provides information on the number of

treatment projects identified for each technology and

estimates of the relative frequency of their application. 

Figures 3.1 to 3.3 show the number of treatment

projects identified for each technology. Figure 3.1

shows the number for technologies applicable to soil

and waste based on available data. The most frequently

used technology for soil and waste containing arsenic is

solidification/stabilization. The available data show

that this technology can effectively meet regulatory

cleanup levels, is commercially available to treat both

soil and waste, is usually less expensive, and generates

a residual that typically does not require further

treatment prior to disposal.

Other arsenic treatment technologies for soil and waste

are typically used for specific applications. 

Vitrification may be used when a combination of

contaminants are present that cannot be effectively

treated using solidification/stabilization. It has also

been used when the vitrification residual could be sold

as a commercial product. However, vitrification

typically requires large amounts of energy, can be more

expensive than S/S, and may generate off-gasses

containing arsenic. 

Soil washing/acid extraction is used to treat soil

primarily. However, it is not applicable to all types of

soil or to waste. Pyrometallurgical treatment has been

used primarily to recycle arsenic from industrial wastes

containing high concentrations of arsenic from metals

refining and smelting operations. These technologies

may not be applicable to soil and waste containing low

concentrations of arsenic. In situ soil flushing treats

soil in place, eliminating the need to excavate soil. 

However, no performance data were identified for the

limited number of full-scale applications of this

technology to arsenic.

Figure 3.2 shows the number of treatment projects

identified for technologies applicable to water. For

water containing arsenic, the most frequently used

technology is precipitation/coprecipitation. Based on

the information gathered for this report, precipitation/

coprecipitation is frequently used to treat arseniccontaminated water, and is capable of treating a wide

range of influent concentrations to the revised MCL for

arsenic. The effectiveness of this technology is less

likely to be reduced by characteristics and contaminants

other than arsenic, compared to other water treatment

technologies. It is also capable of treating water

characteristics or contaminants other than arsenic, such

as hardness or heavy metals. Systems using this

technology generally require skilled operators;

therefore, precipitation/ coprecipitation is more cost

effective at a large scale where labor costs can be

spread over a larger amount of treated water produced.

The effectiveness of adsorption and ion exchange for

arsenic treatment is more likely than precipitation/

coprecipitation to be affected by characteristics and

contaminants other than arsenic. However, these

technologies are capable of treating arsenic to the 
3 - 2

Number of Applications

Stabilization* Acid Extraction Recovery Flushing

Solidification/ Vitrification* Soil Washing/ Pyrometallurgical In Situ Soil 

58

6 4 4 2

19

10

3

0 2 2 0 0

0

10

20

30

40

50

60

70

Full

Pilot

Bench

Number of Applications

Stabilization* Acid Extraction Recovery Flushing

Solidification/ Vitrification* Soil Washing/ Pyrometallurgical In Situ Soil 

58

6 4 4 2

19

10

3

0 2 2 0 0

0

10

20

30

40

50

60

70

Full

Pilot

Bench

45

2

15

7

3

24 25

8

0 2

6 5

0

5

10

15

20

25

30

35

40

45

50

Precipitation/

Coprecipitation*

Membrane 

Filtration

Adsorption* Ion Exchange* Permeable Reactive 

Barriers

Number of Applications

Full

Pilot

Bench

0

45

2

15

7

3

24 25

8

0 2

6 5

0

5

10

15

20

25

30

35

40

45

50

Precipitation/

Coprecipitation*

Membrane 

Filtration

Adsorption* Ion Exchange* Permeable Reactive 

Barriers

Number of Applications

Full

Pilot

Bench

0

Figure 3.1

Number of Identified Applications of Arsenic Treatment Technologies for Soil and Waste 

* Bench-scale data not collected for this technology.

Figure 3.2

Number of Identified Applications of Arsenic Treatment Technologies for Water 

* Bench-scale data not collected for this technology.
3 - 3

111

3

2

3 3

4

1

0

1

2

3

4

5

Electrokinetics Phytoremediation Biological 

Treatment

Number of Applications

Full

Pilot

Bench

111

3

2

3 3

4

1

0

1

2

3

4

5

Electrokinetics Phytoremediation Biological 

Treatment

Number of Applications

Full

Pilot

Bench

Figure 3.3

Number of Identified Applications of Arsenic Treatment Technologies for Soil, Waste, and Water 

revised MCL. Small capacity systems using these

technologies tend to have lower operating and

maintenance costs, and require less operator expertise. 

Adsorption and ion exchange tend to be used more

often when arsenic is the only contaminant to be

treated, for relatively smaller systems, and as a

polishing technology for the effluent from larger

systems. Membrane filtration is used less frequently

because it tends to have higher costs and produce a

larger volume of residuals than other arsenic treatment

technologies.

Permeable reactive barriers are used to treat

groundwater in situ. This technology tends to have

lower operation and maintenance costs than ex situ

(pump and treat) technologies, and typically requires a

treatment time of many years. This report identified

three full-scale applications of this technology, but

treatment data were available for only one application. 

In that application, a permeable reactive barrier is

treating arsenic to below the revised MCL.

Figure 3.3 shows the number of treatment projects

identified for technologies applicable to soil, waste, and

water. Three arsenic treatment technologies are

generally applicable to soil, waste, and water:

electrokinetics, phytoremediation, and biological

treatment. These technologies have been applied in

only a limited number of applications.

Electrokinetic treatment is an in situ technology

intended to be applicable to soil, waste and water. This

technology is most applicable to fine-grained soils, such

as clays. The references identified for this report

contained information on one full-scale application of

this technology to arsenic treatment.

Phytoremediation is an in situ technology intended to be

applicable to soil, waste, and water. This technology

tends to have low capital, operating, and maintenance

costs relative to other arsenic treatment technologies

because it relies on the activity and growth of plants. 

However, this technology tends to be less robust. The

references identified for this report contained

information on one full-scale application of this

technology to arsenic treatment.

Biological treatment for arsenic is used primarily to

treat water above-ground in processes that use

microorganisms to enhance precipitation/

coprecipitation. Bioleaching of arsenic from soil has

also been tested on a bench scale. This technology may

require pretreatment or addition of nutrients and other

treatment agents to encourage the growth of key

microorganisms.

3.3 What Factors Affect Technology Selection for

Drinking Water Treatment?

For the treatment of drinking water, technology

selection depends on several of factors, such as existing

systems, the need to treat for other contaminants, and

the size of the treatment system. Although the data

collected for this report indicate that

precipitation/coprecipitation is the technology most

commonly used to remove arsenic from drinking water,

in the future other technologies may become more
3 - 4

Leaching Procedure Descriptions

Toxicity Characteristic Leaching Procedure

(TCLP): The TCLP is used in identifying RCRA

hazardous wastes that exhibit the characteristic of

toxicity. In this procedure, liquids are separated

from the solid phase of the waste, and the solid

phase is then reduced in particle size until it is

capable of passing through a 9.5 mm sieve. The

solids are then extracted for 18 hours with a solution

of acetic acid equal to 20 times the weight of the

solid phase. The pH of the extraction fluid is a

function of the alkalinity of the waste. Following

extraction, the liquid extract is separated from the

solid phase by filtration. If compatible, the initial

liquid phase of the waste is added to the liquid

extract and analyzed, otherwise they are analyzed

separately. The RCRA TCLP regulatory threshold

for arsenic is 5.0 mg/L in the extraction fluid (Ref.

3.22).

Extraction Procedure Toxicity Test (EPT): This

procedure is similar to the TCLP test, with the

following differences:

• The extraction period is 24 hours

• The extraction fluid is a pH 5 solution of acetic

acid.

The EPT was replaced by the TCLP test in March,

1990 for purposes of hazardous waste identification,

and is therefore no longer widely used (Ref. 3.23)

Waste Extraction Test (WET): The WET is used

in identifying hazardous wastes in California. This

procedure is similar to the TCLP, with the following

differences

• The solid phase is reduced in particle size until it

is capable of passing through a 2 mm sieve., 

• The waste is extracted for 48 hours 

• The extraction fluid is a pH 5 solution of sodium

citrate equal to 10 times the weight of the solid

phase. The WET regulatory threshold for arsenic

is 5.0 mg/L (Ref. 3.24).

common as drinking water treatment facilities modify

their operations to meet the revised arsenic MCL.

Precipitation/coprecipitation is often used to remove

contaminants other than arsenic from drinking water,

such as hardness or suspended solids. However, the

precipitation/coprecipitation processes applied to

drinking water usually also remove arsenic, or can be

easily modified to do so. Where precipitation/

coprecipitation processes are already in place, or are

needed to remove other contaminants, these processes

are commonly used to remove arsenic. Where

precipitation/coprecipitation is not needed to treat

drinking water for other contaminants, treaters may be

more likely to choose another technology, such as

adsorption, ion exchange, or reverse osmosis. 

In addition, the size of a drinking water treatment

system may affect the choice of technology. 

Precipitation/coprecipitation processes tend to be more

complex, requiring more unit operations and greater

operational expertise and monitoring, while adsorption

and ion exchange units are usually less complex and

require less operator expertise and monitoring. 

Therefore, operators of smaller drinking water treatment

systems are more likely to select adsorption or ion

exchange to treat arsenic instead of precipitation/

coprecipitation. 

3.4 How Effective Are Arsenic Treatment

Technologies?

Applications are considered to have performance data

when analytical data for arsenic are available both

before and after treatment. For the technologies

applicable to soil and waste, Table 1.2 (presented in the

Executive Summary) includes performance data only

for those projects with leachable arsenic concentration

data for the treated soil and waste, and either leachable

or total arsenic concentrations for the untreated soil and

waste. Performance data were compared to the RCRA

TCLP regulatory threshold of 5.0 mg/L (Ref. 3.1). For

this table, projects that measured leachability with other

procedures, such as the EPT and the WET, were also

compared directly to this level. The tables in the

technology-specific sections (Sections 4.0 to 16.0)

identify the leaching procedures used to measure

performance. The text box to the right describes the

leaching procedures most frequently identified in the

information sources used for this report.

For the technologies applicable to water, the

performance was compared to the former MCL of 0.050

mg/L, and the revised MCL of 0.010 mg/L (Ref. 3.2). 

Information was available on relatively few projects

that have treated arsenic to below 0.010 mg/L. 

However, this does not necessarily indicate that these

treatment technologies cannot achieve 0.010 mg/L

arsenic. In many cases, the treatment goal in the

projects was greater than 0.010 mg/L, and in most cases

was the previous arsenic MCL of 0.050 mg/L. In such

cases, the treatment technology may be capable of

meeting 0.010 mg/L arsenic with modifications to the

treatment technology design or operating parameters.

3.5 What Are Special Considerations for

Retrofitting Existing Water Treatment

Systems?

On January 22, 2001, EPA published a revised MCL for

arsenic in drinking water that would require public
3 - 5

water suppliers to maintain arsenic concentrations at or

below 0.010 mg/L by 2006 (Ref. 2.9). Some 4,000

drinking water treatment systems may require

additional treatment technologies, a retrofit of existing

treatment technologies, or other measures to achieve

this level (Ref. 2.10). In addition, this revised MCL

may affect Superfund remediation sites and other sites

that base cleanup goals on the arsenic drinking water

MCL. A lower goal could affect the selection, design,

and operation of treatment systems.

Site-specific conditions will determine the type of

changes needed to meet the revised MCL. Some

arsenic treatment systems may be retrofitted, while

other may require new arsenic treatment systems to be

designed. In addition, treatment to lower arsenic

concentrations could require the use of multiple

technologies in sequence. For example, a site with an

existing metals precipitation/coprecipitation system

may need to add another technology such as ion

exchange to achieve a lower treatment goal. 

In some cases, a lower treatment goal might be met by

changing the operating parameters of existing systems. 

For example, changing the type or amount of treatment

chemicals used, replacing spent treatment media more

frequently, or changing treatment system flow rates can

reduce arsenic concentrations in the treatment system

effluent. However, such changes may increase

operating costs from use of additional treatment

chemicals or media, use of more expensive treatment

chemicals or media, and from disposal of increased

volumes of treatment residuals.

Examples of technology-specific modifications that can

help reduce effluent concentrations of arsenic include:

Precipitation/Coprecipitation

• Use of additional treatment chemicals

• Use of different treatment chemicals

• Addition of another technology to the treatment

train, such as membrane filtration

Adsorption

• Addition of an adsorption media bed

• Use of a different adsorption media

• More frequent replacement or regeneration of

adsorption media

• Decrease in the flow rate of water treated

• Addition of another treatment technology to the

treatment train, such as membrane filtration

Ion Exchange

• Addition of an ion exchange bed

• Use of a different ion exchange resin

• More frequent regeneration or replacement of ion

exchange media

• Decrease in the flow rate of water treated

• Addition of another technology to the treatment

train, such as membrane filtration

Membrane Filtration

• Increase in the volume of reject generated per

volume of water treated

• Use of membranes with a smaller molecular

weight cutoff

• Decrease in the flow rate of water treated

• Addition of another treatment technology to the

treatment train, such as ion exchange

3.6 How Do I Screen Arsenic Treatment

Technologies?

Table 3.2 at the end of this section is a screening matrix

for arsenic treatment technologies. It can assist

decision makers in evaluating candidate treatment

technologies by providing information on relative

availability, cost, and other factors for each technology. 

The matrix is based on the Federal Remediation

Technologies Roundtable Technology (FRTR)

Treatment Technologies Screening Matrix (Ref. 3.3),

but has been tailored to treatment technologies for

arsenic in soil, waste, and water. Table 3.2 differs from

the FRTR matrix by:

• Limiting the scope of the table to the technologies

discussed in this report.

• Changing the information based on the narrow

scope of this report. For example, the FRTR

screening matrix lists the overall cost of

adsorption as “worse” (triangle symbol) in

comparison to other treatment technologies for

water. However, when applied to arsenic

treatment, the costs of the technologies discussed

in this report may vary based on scale, water

characteristics, and other factors. Therefore,

adsorption costs are not necessarily higher than

the costs of other technologies discussed in this

report, and this technology’s overall cost is rated

as “average” (circle symbol) in Table 3.2.

• Adding information about characteristics that can

affect technology performance or cost.

Table 3.2 includes the following information:

• Development Status - The scale at which the

technology has been applied. “F” indicates that

the technology has been applied to a site at full

scale. All of the technologies have been applied

at full scale.

• Treatment Trains - “Y” indicates that the

technology is typically used in combination with

other technologies, such as pretreatment or
3 - 6

treatment of residuals (excluding off gas). “N”

indicates that the technology is typically used

independently. 

• Residuals Produced - The residuals typically

produced that may require additional

management. “S” indicates production of a solid

residual, “L”, a liquid residual, and “V” a vapor

residual. All of the technologies generate a solid

residual, with the exceptions of soil flushing and

membrane filtration, which generate only liquid

residuals. Vitrification and pyrometallurgical

recovery produce a vapor residual. 

• O&M or Capital Intensive -This indicates the

main cost-intensive parts of the system. “O&M”

indicates that the operation and maintenance costs

tend to be high in comparison to other

technologies. “Cap” indicates that capital costs

tend to be high in comparison to other

technologies. “N” indicates neither operation and

maintenance nor capital costs are intensive. 

• Availability - The relative number of vendors that

can design, construct, or maintain the technology. 

A square indicates more than four vendors; a

circle, two to three vendors; and a triangle, fewer

than two vendors. All of the technologies have

more than four vendors with the exception of

pyrometallurgical recycling, bioremediation,

electrokinetics, and phytoremediation, which have

less than two. 

• System Reliability/Maintainability - The expected

reliability/maintainability of the technology. A

square indicates high reliability and low

maintenance; a circle, average reliability and

maintenance; and a triangle, low reliability and

high maintenance. Biological treatment,

electrokinetics, and phytoremediation are rated

low because of the limited number of applications

for those technologies, and indications that some

applications were not effective. 

• Overall Cost - Design, construction, and O&M

costs of the core process that defines each

technology, plus the treatment of residuals. A

square indicates lower overall cost; a circle,

average overall cost; and a triangle, higher overall

cost. Solidification/stabilization is rated a low

cost technology because it typically uses standard

equipment and relatively low cost chemicals and

additives. Phytoremediation is low cost because

of the low capital expense to purchase and plant

phytoremediating species and the low cost to

maintain the plants. 

• Characteristics That May Require Pretreatment

or Affect Performance or Cost - The types of

contaminants or other substances that generally

may interfere with arsenic treatment for each

technology. A “T” indicates that the presence of

the characteristic may interfere with technology

effectiveness or result in increased costs. 

Although these contaminants can usually be

removed before arsenic treatment through

pretreatment with another technology, the addition

of a pretreatment technology may increase overall

treatment costs and generate additional residuals

requiring disposal. “Other characteristics” are

technology-specific elements which affect

technology performance, cost, or both. These

characteristics are described in Sections 4.0

through 16.0.

 

The selection of a treatment technology for a particular

site will depend on many site-specific factors; thus the

matrix is not intended to be used as the sole basis for

treatment decisions.

More detailed information on selection and design of

arsenic treatment systems for small drinking water

systems is available in the document “Arsenic

Treatment Technology Design Manual for Small

Systems “ (Ref. 3.25).

3.7 What Does Arsenic Treatment Cost?

A limited amount of cost data on arsenic treatment was

identified for this report. Table 3.3 summarizes this

information. In many cases, the cost information was

incomplete. For example, some data were for operating

and maintenance (O&M) costs only, and did not specify

the associated capital costs. In other cases, a cost per

unit of soil, waste, and water treated was provided, but

total costs were not. For some technologies, no arsenicspecific cost data were identified.

The cost data were taken from a variety of sources,

including EPA, DoD, other government sources, and

information from technology vendors. The quality of

these data varied, with some sources providing detailed

information about the items included in the costs, while

other sources gave little detail about their basis. In

most cases, the particular year for the costs were not

provided. The costs in Table 3.3 are the costs reported

in the identified references, and are not adjusted for

inflation. Because of the variation in type of

information and quality, this report does not provide a

summary or interpretation of the costs in Table 3.3. 

In general, Table 3.3 only includes costs specifically for

treatment of arsenic. Because arsenic treatment is very

waste- and site-specific, general technology cost

estimates are unlikely to accurately predict arsenic
3 - 7

treatment costs. However, general technology cost

estimates were included for three technologies:

solidification/stabilization, pyrometallurgical recovery,

and phytoremediation.

One of the solidification/stabilization costs listed in

Table 3.3 is a general cost for treatment of metals, and

is not arsenic-specific. This cost was included because

solidification/stabilization processes for arsenic are

similar to those for treatment of metals. The only cost

for pyrometallurgical recovery listed in Table 3.3 is a

general cost for the treatment of volatile metals and is

not arsenic-specific. This cost was included because

arsenic is expected to behave in a manner similar to

other volatile metals when treated using

pryometallurgical recovery processes. For

phytoremediation, costs for applications to metals and

radionuclides are included due to the lack of data on

arsenic.

The EPA document "Technologies and Costs for

Removal of Arsenic From Drinking Water" (Ref. 3.4)

contains more information on the cost to reduce the

concentration of arsenic in drinking water from the

former MCL of 0.050 mg/L to below the revised MCL

of 0.010 mg/L. The document includes capital and

O&M cost curves for a variety of processes, including:

ï Retrofitting of existing precipitation/

coprecipitation processes to improve arsenic

removal (enhanced coagulation/filtration and

enhanced lime softening)

ï Precipitation/coprecipitation followed by

membrane filtration (coagulation-assisted

microfiltration)

ï Ion exchange (anion exchange) with varying

levels of sulfate in the influent

ï Two types of adsorption (activated alumina at

varying influent pH and greensand filtration)

ï Oxidation pretreatment technologies (chlorination

and potassium permanganate)

ï Treatment and disposal costs of treatment

residuals (including mechanical and

non-mechanical sludge dewatering)

ï Point-of-use systems using adsorption (activated

alumina) and membrane filtration (reverse

osmosis) 

The EPA cost curves are based on computer cost

models for drinking water treatment systems. Costs for

full-scale reverse osmosis, a common type of membrane

filtration, were not included because it generally is

more expensive and generates larger volumes of

treatment residuals than other arsenic treatment

technologies (Ref. 3.4). Although the cost information

is only for the removal of arsenic from drinking water,

many of the same treatment technologies can be used

for the treatment of other waters and may have similar

costs.

Table 3.4 presents estimated capital and annual O&M

costs for four treatment technologies based on cost

curves presented in ìTechnologies and Costs for

Removal of Arsenic From Drinking Waterî:

1. Precipitation/coprecipitation followed by

membrane filtration (coagulation-assisted

microfiltration)

2. Adsorption (greensand filtration)

3. Adsorption (activated alumina with pH of 7 to 8 in

the influent)

4. Ion exchange (anion exchange with <20 mg/L

sulfate in the influent)

The table presents the estimated costs for three

treatment system sizes: 0.01, 0.1, and 1 million gallons

per day (mgd). The costs presented in Table 3.4 are for

specific technologies listed in the table, and do not

include costs for oxidation pretreatment or management

of treatment residuals. Detailed descriptions of the

assumptions used to generate the arsenic treatment

technology cost curves are available (Ref. 3.4).

3.8 References

3.1 Code of Federal Regulations, Title 40, Part

261.24.

http://lula.law.cornell.edu/cfr/

3.2 U.S. EPA Office of Water. Fact Sheet: EPA To

Implement 10ppb Standard for Arsenic in

Drinking Water. EPA 815-F-01-010. October,

2001. http://

www.epa.gov/safewater/ars/ars-oct-factsheet.html

3.3 Federal Remediation Technologies Reference

Guide and Screening Manual, Version 4.0. 

Federal Remediation Technologies Roundtable. 

September 5, 2001.

http://www.frtr.gov/matrix2/top_page.html. 

3.4 U.S. EPA. Office of Water. Technologies and

Costs for Removal of Arsenic From Drinking

Water. EPA-R-00-028. December 2000. 

http://www.epa.gov/safewater/ars/

treatments_and_costs.pdf

3.5 U.S. EPA Office of Research and Development. 

Engineering Bulletin, Technology Alternatives for

the Remediation of Soils Contaminated with

Arsenic, Cadmium, Chromium, Mercury, and

Lead. Cincinnati, OH. March 1997. 

http://www.epa.gov/ncepi/Catalog/

EPA540S97500.html

3.6 Redwine, J.C. Successful In Situ Remediation

Case Histories: Soil Flushing And

Solidification/Stabilization With Portland Cement

And Chemical Additives. Southern Company

Services, Inc. Presented at the Air and Waste
3 - 8

Management Association’s 93rd Annual

Conference and Exhibition, Salt Lake City, June

2000.

3.7 Miller JP. In-Situ Solidification/Stabilization of

Arsenic Contaminated Soils. Electric Power

Research Institute. Report TR-106700. Palo

Alto, CA. November 1996. 

3.8 Federal Remediation Technologies Roundtable

(FRTR). In Situ Vitrification at the Parsons

Chemical/ETM Enterprises Superfund Site Grand

Ledge, Michigan. April 17, 2001

http://www.frtr.gov/costperf.htm

3.9 U.S. EPA. Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition). 

Office of Solid Waste and Emergency Response.

EPA-542-R-01-004. February 2001.

http://clu-in.org/asr.

3.10 U.S. EPA. Contaminants and Remedial Options

at Selected Metal-Contaminated Sites. Office of

Research and Development. EPA-540-R-95-512.

July 1995.

3.11 U.S. EPA. Database for EPA REACH IT

(REmediation And CHaracterization Innovative

Technologies). March 2001. 

http://www.epareachit.org.

3.12 U.S. EPA. Treatment Technology Performance

and Cost Data for Remediation of Wood

Preserving Sites. Office of Research and

Development. EPA-625-R-97-009. October

1997. 

http://www.epa.gov/ncepi/Catalog/

EPA625R97009.html

3.13 E-mail attachment sent from Doug Sutton of

Geotrans, Inc. to Linda Fiedler, U.S. EPA. April

20, 2001. 

3.14 E-mail attachment sent from Anni Loughlin of

U.S. EPA Region I to Linda Fiedler, U.S. EPA. 

August 21, 2001.

3.15 Miller JP, Hartsfield TH, Corey AC, Markey RM. 

In Situ Environmental Remediation of an

Energized Substation. EPRI. Palo Alto, CA.

Report No. 1005169. 2001.

3.16 Twidwell, L.G., et al. Technologies and Potential

Technologies for Removing Arsenic from Process

and Mine Wastewater. Presented at

"REWAS'99." San Sebastian, Spain. September

1999. http://www.mtech.edu/metallurgy/arsenic/

REWASAS%20for%20proceedings99%20in

%20word.pdf

3.17 U.S. EPA. Arsenic Removal from Drinking

Water by Ion Exchange and Activated Alumina

Plants. EPA-600-R-00-088. Office of Research

and Development. October 2000.

3.18 DOE. Permeable Reactive Treatment (PeRT)

Wall for Rads and Metals. Office of

Environmental Management, Office of Science

and Technology. DOE/EM-0557. September,

2000. http://apps.apps.em.doe.gov/ost/pubs/

itsrs/itsr2155.pdf

3.19 Applied Biosciences. June 28, 2001.

http://www.bioprocess.com 

3.20 Center for Bioremediation at Weber State

University. Arsenic Treatment Technologies. 

August 27, 200. http://www.weber.edu/

Bioremediation/arsenic.htm. .

3.21 Electric Power Research Institute. Electrokinetic

Removal of Arsenic from Contaminated Soil: 

Experimental Evaluation. July 2000. 

http://www.epri.com/

OrderableitemDesc.asp?product_id.

3.22 U.S. EPA. SW-846 On-Line. Test Methods for

Evaluating Solid Wastes. Physical/Chemical

Methods. Method 1311 Toxicity Characteristic

Leaching Procedure. July 1992.

http://www.epa.gov/epaoswer/hazwaste/test/pdfs/

1311.pdf. 

3.23 U.S. EPA. SW-846 On-Line. Test Methods for

Evaluating Solid Wastes. Physical/Chemical

Methods. Method 1310A Extraction Procedure

(EP) Toxicity Test Method and Structural

Integrity Test. July 1992.

http://www.epa.gov/epaoswer/hazwaste/test/pdfs/

1310a.pdf. 

3.24 California Code of Regulations. Title 22 Section

66261.126, Appendix II. Waste Extraction Test

(WET) Procedures. August, 2002. 

http://ccr.oal.ca.gov/

3.25 U.S. EPA. Arsenic Treatment Technology Design

Manual for Small Systems (100% Draft for Peer

Review). June 2002. http://www.epa.gov/

safewater/smallsys/

arsenicdesignmanualpeerreviewdraft.pdf

3.26 Cunningham, S. D. The Phytoremediation of Soils

Contaminated with Organic Pollutants: Problems

and Promise. International Phytoremediation

Conference. May 8-10, Arlington, VA. 1996.

3.27 Salt, D. E., M. et al. Phytoremedia-tion: A Novel

Strategy for the Removal of Toxic Metals from

the Environment Using Plants. Biotechnol.

13:468-474. 1995.

3.28 Dushenkov, S., D. et al.. Removal of Uranium

from Water Using Terrestrial Plants. Environ, Sci.

Technol. 31(12):3468-3474. 1997. 

3.29 Cunningham, S. D., and W. R. Berti, and J. W.

Huang. Phytoremediation of Contaminated Soils.

Trends Biotechnol. 13:393-397. 1995.
3 - 9

Table 3.1. 

Applicability of Arsenic Treatment Technologies

Technology Soila Wasteb

Water

Groundwater

and Surface

Waterc Drinking Water Wastewaterd

Solidification/Stabilization g gVitrification g gSoil Washing/Acid Extraction gPyrometallurgical Treatment g gIn Situ Soil Flushing gPrecipitation/Coprecipitation gg gMembrane Filtration g gAdsorption g gIon Exchange g gPermeable Reactive Barriers gElectrokinetics g ggPhytoremediation g gBiological Treatment g g

g = Indicates treatment has been conducted at full scale.

a Soil includes soil, debris, sludge, sediments, and other solid phase environmental media.b Waste includes non-hazardous and hazardous solid waste generated by industry.c Groundwater and surface water also includes mine drainage.d Wastewater includes nonhazardous and hazardous industrial wastewater and leachate.
3 - 10

Table 3.2 

Arsenic Treatment Technologies Screening Matrix

Rating Codes 

 - Better;  - Average;  - Worse;Y - Yes; N - No.F - Full; P - Pilot.S - Solid; L - Liquid; V - Vapor.Cap - Capital; N - Neither; O&M - Operation &Maintenance.T - May require pretreatment or affect cost and

performance.

Development Status

Treatment Train

(excludes off-gas treatment)

Residuals Produced

O&M or Capital Intensive

Availability

System Reliability/Maintainability

Overall Cost

Characteristics That May Require

Pretreatment or Affect Performance or Cost

High Arsenic Concentration

Arsenic Chemical Form

pHOther Characteristics

Technology

Solidification/Stabilization F N S Cap T T • Redox potential

• Presence of organics• Fine particulate• Type of binder &

reagent

• Pretreatment

Vitrification F N S, V Cap

&O&M

• Presence of

halogenated organiccompounds

• Presence of volatile

metals

• Particle size• Lack of glass

forming materials

• Moisture content• Organic content• Volume of

contaminated soiland waste

• Characteristics of

treated waste
Table 3.2 

Arsenic Treatment Technologies Screening Matrix (continued)

Rating Codes  - Better;  - Average;  - Worse;Y - Yes; N - No.F - Full; P - Pilot.S - Solid; L - Liquid; V - Vapor.Cap - Capital; N - Neither; O&M - Operation &Maintenance.T - May require pretreatment or affect cost and

performance.

Development Status

Treatment Train

(excludes off-gas treatment)

Residuals Produced

O&M or Capital Intensive

Availability

System Reliability/Maintainability

Overall Cost

Characteristics That May Require

Pretreatment or Affect Performance or Cost

High Arsenic Concentration

Arsenic Chemical Form

pHOther Characteristics

3 - 11

Soil Washing/Acid Extraction F Y S, L Cap

&O&M

T • Soil homogeneity

• Multiple

contaminants

• Moisture content• Temperature• Soil particle size

distribution

Pyrometallurgical Recycling F N S, L,

V

Cap&O&M

• Particle size• Moisture content• Thermal conductivity• Presence of

impurities

Soil Flushing F Y L O&M T T • Number of

contaminants treated

• Soil characteristics• Precipitation• Temperature• Reuse of flushing

solution

• Contaminant

recovery
Table 3.2 

Arsenic Treatment Technologies Screening Matrix (continued)

Rating Codes  - Better;  - Average;  - Worse;Y - Yes; N - No.F - Full; P - Pilot.S - Solid; L - Liquid; V - Vapor.Cap - Capital; N - Neither; O&M - Operation &Maintenance.T - May require pretreatment or affect cost and

performance.

Development Status

Treatment Train

(excludes off-gas treatment)

Residuals Produced

O&M or Capital Intensive

Availability

System Reliability/Maintainability

Overall Cost

Characteristics That May Require

Pretreatment or Affect Performance or Cost

High Arsenic Concentration

Arsenic Chemical Form

pHOther Characteristics

3 - 12

Precipitation/Coprecipitation F Y S Cap

&O&M

a

T T • Presence of other

compounds

• Type of chemical

addition

• Chemical dosage• Treatment goal• Sludge disposal

Membrane Filtration F Y L Cap

&O&M

TTT • Suspended solids,

high molecularweight, dissolvedsolids, organiccompounds andcolloids

• Temperature• Type of membrane

filtration

• Initial waste stream• Rejected waste

stream
Table 3.2 

Arsenic Treatment Technologies Screening Matrix (continued)

Rating Codes  - Better;  - Average;  - Worse;Y - Yes; N - No.F - Full; P - Pilot.S - Solid; L - Liquid; V - Vapor.Cap - Capital; N - Neither; O&M - Operation &Maintenance.T - May require pretreatment or affect cost and

performance.

Development Status

Treatment Train

(excludes off-gas treatment)

Residuals Produced

O&M or Capital Intensive

Availability

System Reliability/Maintainability

Overall Cost

Characteristics That May Require

Pretreatment or Affect Performance or Cost

High Arsenic Concentration

Arsenic Chemical Form

pHOther Characteristics

3 - 13

Adsorption F Y S, L Cap

&O&M

a

TTT • Flow rate

• pH• Fouling• Contamination

concentration

• Spent media

Ion Exchange F Y S, L Cap

&O&M

a

TTT • Presence of

competing ions

• Presence of organics• Presence of trivalent

ion

• Project scale• Bed regeneration• Sulfate

Permeable Reactive Barriers F N S Cap T • Fractured rock

• Deep aquifers &

contaminant plumes

• High aquifer

hydraulicconductivity

• Stratigraphy• Barrier plugging• PRB depth
Table 3.2 

Arsenic Treatment Technologies Screening Matrix (continued)

Rating Codes  - Better;  - Average;  - Worse;Y - Yes; N - No.F - Full; P - Pilot.S - Solid; L - Liquid; V - Vapor.Cap - Capital; N - Neither; O&M - Operation &Maintenance.T - May require pretreatment or affect cost and

performance.

Development Status

Treatment Train

(excludes off-gas treatment)

Residuals Produced

O&M or Capital Intensive

Availability

System Reliability/Maintainability

Overall Cost

Characteristics That May Require

Pretreatment or Affect Performance or Cost

High Arsenic Concentration

Arsenic Chemical Form

pHOther Characteristics

3 - 14

Biological Treatment F Y S, L Cap

&O&M

TTT • Iron concentration

• Contaminant

concentration

• Available nutrients• Temperature• Pretreatment

requirements

Electrokinetics F Y S, L O&M TTT • Salinity & cation

exchange capacity

• Soil moisture• Polarity & magnitude

of ionic charge

• Soil type• Contaminant

extraction system

Phytoremediation F N L, S N TTT • Contaminant depth

• Climatic or seasonal

conditions

Source: Adapted from the Federal Remediation Technologies Roundtable Technology Screening Matrix. http://www.frtr.gov. September 2001. (Ref. 3.3)

a. Relative costs for precipitation/coprecipitation, adsorption, and ion exchange are sensitive to treatment system capacity, untreated water characteristics, and

other factors.
Table 3.3

Available Arsenic Treatment Cost Data

3 - 15

 Site

Amount

Treated

 Capital

Cost

 Annual 

O & M

Cost Unit Cost Total Cost Cost Explanation Source

 Solidification/Stabilization

- - - - $60 - $290 per

ton

- ï Cost is for S/S of metals and is not

arsenic-specific

ï Cost year not specified

3.5

Electrical Substation in Florida 3,300 cubic

yards

- - $85 per cubic

yard

- ï Excludes Disposal Costs

ï Costs in 1995 Dollars

3.6, 3.7

 Vitrification

Parsons Chemical Superfund Site 3,000 cubic

yards

$350,000

-

$550,000

- $375 - $425

per ton

- ï Capital cost includes pilot testing,

mobilization, and demobilization

ï Unit cots are for operation of

vitrification equipment only

ï Cost year nor specified

3.8

 Soil Washing/Acid Extraction

King of Prussia Superfund Site 12,800 cubic

yards

- - $400 per ton - ï Cost year not specified 3.9,

3.10

- - - - $100 - $300

per ton

- ï Cost year not specified 3.10

- - - - $65 per ton - ï Cost year not specified 3.11- 400 cubic

yards

- - $80 per ton - ï Cost year not specified 3.11

- 38,000 tons - - $203 per ton $7.7 million ï Cost year not specified 3.12

 Pyrometallurgical Recovery

- - - - $208 to $458

per ton

_ ï Cost is not arsenic-specific

ï Costs in 1991 dollars

3.10

 In Situ Soil Flushing - No cost data identified Precipitation/Coprecipitation

Vineland Chemical Company 1,400 gpm - $4 million - - ï Cost year not specified 3.13

Winthrop Landfill 65 gpm $2

million

$250,000 - - ï Cost year not specified 3.14

Energized Substation in Florida 44 million

gallons

- - $0.0006 per

gallon

- ï Cost year not specified 3.15

 Membrane Filtration - No cost data identified
Table 3.3

Available Arsenic Treatment Cost Data (Continued)

 Site

Amount

Treated

 Capital

Cost

 Annual 

O & M

Cost Unit Cost Total Cost Cost Explanation Source

3 - 16

 Adsorption

- - - - $0.003 - $0.76

per 1,000

gallons

- ï Cost year not specified 3.16

 Ion Exchange

- - $9,000 - - - ï Cost year not specified 3.17

 Permeable Reactive Barrier

Monticello Mill Tailings - $1.2

million

- - - ï Cost year not specified 3.18

 Electrokinetics

Pederok Plant, Kwint, Loppersum,

Netherlands

325 cubic

yards

- - $70 per ton - ï Cost year not specified 3.11

Blackwater River State Forest, FL - - - $883 per ton - ï Cost year not specified 3.21

 Phytoremediation

- 12 acres - - - $200,000 ï 1998 dollars

ï Cost is for phytoextraction of lead from

soil

3.26

- 1 acre, 20

inches deep

- - - $60,000 -

$100,000

ï Cost year not specifiedï Cost is for phytoextraction from soilï Contaminant was not specified

3.27

- - - - $2 - $6 per

1,000 gallons

- ï Cost is for ex situ treatment of water

containing radionuclides

ï Cost year not specified

3.28

- - - - $0.02 - $.76

per cubic yard

- ï Cost year not specified

ï Cost is for phytostabilization of metals,

and is not arsenic-specific

3.29

 Biological Treatment

- - - - $0.50 per

1,000 gallons

- ï Cost year not specified 3.19

- - - - $2 per 1,000

gallons

- ï Cost year not specified 3.20

- = Data nor provided gpm - gallons per minute
3 - 17

Table 3.4

Summary of Costa Data for Treatment of Arsenic in Drinking Water

Technology

Design Flow Rate

0.01 mgd 0.1 mgd 1 mgd

Capital Cost ($) Annual O&M

Cost ($)

Capital Cost ($) Annual O&M

Cost ($)

Capital Cost ($) Annual O&M

Cost ($)

Precipitation/Coprecipitation(coagulation-assistedmicrofiltration)

142,000 22,200 463,000 35,000 2,010,000 64,300

Adsorption (greensand filtration) 12,400 7,980 85,300 13,300 588,000 66,300Adsorption (activated alumina,influent pH 7 - 8)

15,400 6,010 52,200 23,000 430,000 201,000

Ion exchange (anion exchange,influent <20 mg/L sulfate)

23,000 5,770 54,000 12,100 350,000 52,200

Source: Derived from Ref. 3.4a. Costs are rounded to three significant figures and are in September 1998 dollars. Costs do not include pretreatment or management of treatment residuals. 

Costs for enhanced coagulation/filtration and enhanced lime softening are not presented because the costs curves for these technologies are for modification of

existing drinking water treatment systems only (Ref. 3.4), and are not comparable to other costs presented in this table, which are for new treatment systems.

mgd = million gallons per day O&M = operating and maintenance mg/L = milligrams per liter < = less than
II

ARSENIC TREATMENT TECHNOLOGY SUMMARIES
IIA

ARSENIC TREATMENT TECHNOLOGIES

APPLICABLE TO SOIL AND WASTE
4-1

Summary

Solidification and stabilization (S/S) is an

established treatment technology often used to

reduce the mobility of arsenic in soil and waste. The

most frequently used binders for S/S of arsenic are

pozzolanic materials such as cement and lime. S/S

can generally produce a stabilized product that

meets the regulatory threshold of 5 mg/L leachable

arsenic as measured by the TCLP. However,

leachability tests may not always be accurate

indicators of arsenic leachability for some wastes

under certain disposal conditions.

Dry

Reagents

Dry

Reagents

Pug Mill

Mixer

Pug Mill

Mixer

Waste

Material

Waste

Material

Liquid

Reagents

Liquid

Reagents

Water

(If Required)

Water

(If Required)

Stabilized Waste

Dry

Reagents

Dry

Reagents

Pug Mill

Mixer

Pug Mill

Mixer

Waste

Material

Waste

Material

Liquid

Reagents

Liquid

Reagents

Water

(If Required)

Water

(If Required)

Stabilized Waste

Model of a Solidification/Stabilization System

13

3 3

2 2

0

5

10

15

Cement Phosphate pH

Adjustment

Agents

Lime Sulfur

13

3 3

2 2

0

5

10

15

Cement Phosphate pH

Adjustment

Agents

Lime Sulfur

Technology Description: S/S reduces the mobility

of hazardous substances and contaminants in the

environment through both physical and chemical

means. It physically binds or encloses contaminants

within a stabilized mass and chemically reduces the

hazard potential of a waste by converting the

contaminants into less soluble, mobile, or toxic

forms. 

Media Treated:

• Soil

• Sludge

• Other solids

• Industrial waste

Binders and Reagents used in S/S of Arsenic:

• Cement

• Fly Ash

• Lime

• Phosphate

• pH adjustment agents

• Sulfur

4.0 SOLIDIFICATION AND

STABILIZATION TREATMENT FOR

ARSENIC

Technology Description and Principles

The stabilization process involves mixing a soil or

waste with binders such as Portland cement, lime, fly

ash, cement kiln dust, or polymers to create a slurry,

paste, or other semi-liquid state, which is allowed time

to cure into a solid form. When free liquids are present

the S/S process may involve a pretreatment step

(solidification) in which the waste is encapsulated or

absorbed, forming a solid material. Pozzolanic binders

such as cement and fly ash are used most frequently for

the S/S of arsenic. No site-specific information is

currently available on the use of organic binders to

immobilize arsenic.

The process also may include the addition of pH

adjustment agents, phosphates, or sulfur reagents to

reduce the setting or curing time, increase the

compressive strength, or reduce the leachability of

contaminants (Ref. 4.8). Information gathered for this

report included 45 Superfund remedial action projects

treating soil or waste containing arsenic using S/S. 

Figure 4.1 shows the frequency of use of binders and

reagents in 21 of those S/S treatments. The figure

includes some projects where no performance data were

available but information was available on the types of

binders and reagents used. Some projects used more

than one binder or reagent. Data were not available for

all 46 projects.

Figure 4.1

Binders and Reagents Used for

Solidification/Stabilization of Arsenic for 21

Identified Superfund Remedial Action Projects
4-2

19

58

0 20 40 60

Pilot

Full

Factors Affecting S/S Performance

• Valence state - The specific arsenic compound

or valence state of arsenic may affect the

leachability of the treated material because

these factors affect the solubility of arsenic.

• pH and redox potential - The pH and redox

potential of the waste and waste disposal

environment may affect the leachability of the

treated material because these factors affect the

solubility of arsenic and may cause arsenic to

react to form more soluble compounds or reach

a more soluble valence state.

• Presence of organics - The presence of volatile

or semivolatile organic compounds, oil and

grease, phenols, or other organic contaminants

may reduce the unconfined compressive

strength or durability of the S/S product, or

weaken the bonds between the waste particles

and the binder.

• Waste characteristics - The presence of

halides, cyanide, sulfate, calcium, or soluble

salts of manganese, tin, zinc, copper, or lead

may reduce the unconfined compressive

strength or durability of the S/S product, or

weaken the bonds between the waste particles

and the binder.

• Fine particulate - The presence of fine

particulate matter coats the waste particles and

weakens the bond between the waste and the

binder.

• Mixing - Thorough mixing is necessary to

ensure waste particles are coated with the

binder.

S/S often involves the use of additives or pretreatment

to convert arsenic and arsenic compounds into more

stable and less soluble forms, including pH adjustment

agents, ferric sulfate, persulfates, and other proprietary

reagents (Ref. 4.3, 4.8). Prior to S/S, the soil or waste

may be pretreated with chemical oxidation to render the

arsenic less soluble by converting it to its As(V) state

(Ref. 4.3). Pretreatment with incineration to convert

arsenic into ferric arsenate has also been studied, but

limited data are available on this process (Ref. 4.3).

This technology has also been used to immobilize

arsenic in soil in situ by injecting solutions of chemical

precipitants, pH adjustment agents, and chemical

oxidants. In this report, such applications are referred

to as in situ S/S. In one full-scale treatment, a solution

of ferrous iron, limestone, and potassium permanganate

was injected (Ref. 4.8). In another full-scale treatment,

a solution of unspecified pH adjustment agents and

phosphates was injected (Ref. 4.10).

Media and Contaminants Treated

S/S is used frequently to immobilize metals and

inorganics in soil and waste. It has been used to

immobilize arsenic in environmental media such as soil

and industrial wastes such as sludges and mine tailings.

Type, Number, and Scale of Identified Projects

Treating Soil and Wastes Containing Arsenic

S/S of soil and waste containing arsenic is

commercially available at full scale. Data sources used

for this report included information about 58 full-scale

and 19 pilot-scale applications of S/S to treat arsenic. 

This included 45 projects at 41 Superfund sites (Ref.

4.8). Figure 4.2 shows the number of applications at

both full and pilot scale. 

Figure 4.2

Scale of Identified Solidification/Stabilization

Projects for Arsenic Treatment

Summary of Performance Data

Table 4.1 provides performance data for 10 pilot-scale

treatability studies and 34 full-scale remediation

projects. Due to the large number of projects, Table 4.1

lists only those for which leachable arsenic

concentrations are available for the treated soil or

waste, with the exception of projects involving only in

situ stabilization. In situ projects without information

on the leachability of arsenic in the stabilized mass are

included in the table because this type of application is

more innovative and information is available for only a

few applications.

The performance of S/S treatment is usually measured

by leach testing a sample of the stabilized mass. For

most land-disposed arsenic-bearing hazardous wastes

that fall under RCRA (including both listed and
4-3

Case Study: Long-Term Stability of S/S of

Arsenic

 EPA obtained leachate data from landfills accepting

wastes treated using solidification/stabilization

operated by Waste Management, Inc., Envirosafe,

and Reynolds Metals. The Waste Management, Inc.

landfills received predominantly hazardous wastes

from a variety of sources, the Envirosafe landfill 

received primarily waste bearing RCRA waste code

K061 (emission control dust and sludge from the

primary production of steel in electric furnaces) and

the Reynolds Metals facility was a monofill

accepting waste bearing RCRA waste code K088

(spent potliners from primary aluminum reduction). 

Analysis of the leachate from 80 landfill cells

showed 9 cells, or 11%, had dissolved arsenic

concentrations higher than the TCLP level of 5.0

mg/L. The maximum dissolved arsenic

concentration observed in landfill leachate was 120

mg/L. Analysis of the leachate from 152 landfill

cells showed 29 cells, or 19%, had total arsenic

concentrations in excess of the TCLP level of 5.0

mg/L. The maximum total arsenic concentration

observed in landfill leachate was 1,610 mg/L (Ref.

4.12).

Another study reported the long-term stability of S/S

technologies treating wastes from three landfills

contaminated with heavy metals, including arsenic

(Ref. 4.16). S/S was performed at each site using

cement and a variety of chemical additives. TCLP

testing showed arsenic concentrations ranging from

zero to 0.017 mg/L after a 28-day cure time. Six

years later, TCLP testing showed leachable arsenic

concentrations that were slightly higher than those

for a 28-day cure time (0.005 - 0.022 mg/L), but the

levels remained below 0.5 mg/L. However, the

stabilized waste was stored above ground, and

therefore may not be representative of waste

disposed in a landfill (see Projects 12, 13, and 16 in

Table 4.1 and Table 4.2).

characteristic wastes), the treatment standard is less

than 5.0 mg/L arsenic in the extract generated by the

toxicity characteristic leaching procedure (TCLP). The

standard for spent potliners from primary aluminum

smelting (K088) is 26.1 mg/kg total arsenic (Ref. 4.10). 

For listed hazardous wastes, the waste must be disposed

in a Subtitle C land disposal unit after treatment to meet

the standard for arsenic and any other applicable

standards, unless it is specifically delisted. For

hazardous wastes exhibiting the characteristic for

arsenic, the waste may be disposed in a Subtitle D

landfill after being treated to remove the characteristic

and to meet all other applicable standards.

Of the 23 soil projects identified for this report, 22

achieved a leachable arsenic concentration of less than 

5.0 mg/L in the stabilized material. Of the 19 industrial

waste projects, 17 achieved a leachable arsenic

concentration of less than 5.0 mg/L in the stabilized

material. Leachability data are not available for the

projects that involve only in situ stabilization.

Four projects (Projects 25, 26, 27, and 41, Table 4.1)

included pretreatment to oxidize As(III) to As(V). In

these projects, the leachability of arsenic in industrial

wastes was reduced to less than 0.50 mg/L. The

compound treated in Projects 24, 25, and 26 was

identified as arsenous trisulfide. All three treatment

processes involved pretreating a waste containing 5,000

to 40,000 mg/kg arsenous trisulfide with chemical

oxidation (Ref. 4.1). The specific arsenic compound in

another S/S treatment (Project 41) was identified as

As2O3. This treatment process included pretreatment by

chemical oxidation to form ferric arsenate sludge

followed by S/S with lime (Ref. 4.3). 

Limited data are available about the long-term stability

of soil and waste containing arsenic treated using S/S. 

Projects 12, 13, and 16 were part of one study that

tested the leachability of arsenic six years after S/S was

performed (see Case Study: Long-Term Stability of S/S

or Arsenic).

The case study on Whitmoyer Laboratories Superfund

Site discusses in greater detail the treatment of arsenic

using S/S. This information is summarized in Table

4.1, Project 20.

Applicability, Advantages, and Potential Limitations

The mobility of arsenic depends upon its valence state,

the reduction-oxidation potential of the waste disposal

environment, and the specific arsenic compound

contained in the waste (Ref. 4.1). This mobility is

usually measured by testing the leachability of arsenic

under acidic conditions. In some disposal environments

the leachability of arsenic may be different than that

predicted by an acidic leach test, particularly when the

specific form of arsenic in the waste shows increased

solubility at higher pH and the waste disposal

environment has a high pH. Analytical data for

leachate from monofills containing wastes bearing

RCRA waste code K088 (spent aluminum potliners)

indicate that arsenic may leach from wastes at levels
4-4

Case Study: Whitmoyer Laboratories 

Superfund Site

 The Whitmoyer Laboratories Superfund Site was a

former veterinary feed additives and pharmaceuticals

manufacturing facility. It is located on

approximately 22 acres of land in Jackson Township,

Lebanon County, Pennsylvania. Production began at

the site in 1934. In the mid-1950's the facility began

using arsenic in the production of feed additives. 

Soils on most of the area covered by the facility are

contaminated with organic arsenic.

Off-site stabilization began in mid-1999 and was

completed by the spring of 2000. A total of 400 tons

of soil were stabilized using a mixture of 10% water,

10% ferric sulfate, and 5% Portland cement. The

concentration of leachabile arsenic in the treated soil

was below 5.0 mg/L, as measured by the TCLP. 

Information on the pretreatment arsenic leachability

was not available.

Factors Affecting S/S Costs

• Type of binder and reagent - The use of

proprietary binders or reagents may be more

expensive than the use of non-proprietary

binders (Ref. 4.16). 

• Pretreatment - The need to pretreat soil and

waste prior to S/S may increase management

costs (Ref. 4.18).

• Factors affecting S/S performance - Items in

the “Factors Affecting S/S Performance” box

will also affect costs.

higher than those predicted by the TCLP (see Case

Study: Long-term Stability of S/S of Arsenic).

Some S/S processes involve pretreatment of the waste

to render arsenic less soluble prior to stabilization (Ref.

4.1, 4.3). Such processes may render the waste less

mobile under a variety of disposal conditions (See

Projects 25, 26, 27,and 41 in Table 4.1), but also may

result in significantly higher waste management costs

for the additional treatment steps.

In situ S/S processes may reduce the mobility of arsenic

by changing it to less soluble forms, but do not remove

the arsenic. Ensuring thorough mixing of the binder

and the waste can also be challenging for in situ S/S

processes, particularly when the subsurface contains

large particle size soil and debris or subsurface

obstructions. The long-term effectiveness of this type

of treatment may be impacted if soil conditions cause

the stabilized arsenic to change to more soluble and

therefore more mobile forms.

Summary of Cost Data

The reported costs of treatment of soil containing

metals using S/S range from $60 to $290 per ton (Ref.

4.5, cost year not identified). Limited site-specific cost

data are currently available for S/S treatment of arsenic. 

At two sites, (Projects 21 and 22), total project costs, in

1995 dollars, were about $85 per cubic yard, excluding

disposal costs (Ref. 4.21).

References

4.1. U.S. EPA. Arsenic & Mercury - Workshop on

Removal, Recovery, Treatment, and Disposal.

Office of Research and Development. EPA-600-

R-92-105. August 1992.

http://epa.gov/ncepihom.

4.2. U.S. EPA. Contaminants and Remedial Options

at Selected Metal-Contaminated Sites. Office of

Research and Development. EPA-540-R-95-

512. July 1995. http://epa.gov/ncepihom.

4.3. U.S. EPA. Final Best Demonstrated Available

Technology (BDAT) Background Document for

K031, K084, K101, K102, Characteristic Arsenic

Wastes (D004), Characteristic Selenium Wastes

(D010), and P and U Wastes Containing Arsenic

and Selenium Listing Constituents. Office of

Solid Waste. May 1990.

4.4. U.S. EPA National Risk Management Research

Laboratory. Treatability Database. March 2001.

4.5. U.S. EPA Office of Research and Development. 

Engineering Bulletin, Technology Alternatives

for the Remediation of Soils Contaminated with

Arsenic, Cadmium, Chromium, Mercury, and

Lead. Cincinnati, OH. March 1997. 

http://www.epa.gov/ncepi/Catalog/

EPA540S97500.html

4.6. TIO. Database for EPA REACH IT

(Remediation And Characterization Innovative

Technologies). March 2001. 

http://www.epareachit.org.

4.7. U.S. EPA. Solidification/Stabilization Use at

Superfund Sites. Office of Solid Waste and

Emergency Response. EPA 542-R-00-010.

September 2000. http://clu-in.org. 

4.8. U.S. EPA. Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition). 

Office of Solid Waste and Emergency Response. 

EPA-542-R-01-004. February 2001. http://cluin.org.
4-5

4.9. U.S. EPA. Treatment Technology Performance

and Cost Data for Remediation of Wood

Preserving Sites. Office of Research and

Development. EPA-625-R-97-009. October

1997. http://epa.gov/ncepihom.

4.10. Code of Federal Regulations, Part 40, Section

268. http://lula.law.cornell.edu/cfr/

cfr.php?title=40&type=part&value=268

4.11. Personal communication with Jim Sook,

Chemical Waste Management, Inc. March 2001.

4.12. Federal Register. Land Disposal Restrictions: 

Advanced Notice of Proposed Rulemaking. 

Volume 65, Number 118. June 19, 2000. pp.

37944 - 37946. 

http://www.epa.gov/fedrgstr/EPA-WASTE/

2000/June/Day-19/f15392.htm

4.13. U.S. EPA. Biennial Reporting System. Draft

Analysis. 1997.

4.14. Fuessle, R.W. and M.A. Taylor. Stabilization of

Arsenic- and Barium-Rich Glass Manufacturing

Waste. Journal of Environmental Engineering,

March 2000. pp. 272 - 278. 

http://www.pubs.asce.org/journals/ee.html

4.15. Wickramanayake, Godage, Wendy Condit, and

Kim Cizerle. Treatment Options for Arsenic

Wastes. Presented at the U.S. EPA Workshop on

Managing Arsenic Risks to the Environment: 

Characterization of Waste, Chemistry, and

Treatment and Disposal. Denver, CO. May 1 -

3, 2001.

4.16. Klich, Ingrid. Permanence of Metals

Containment in Solidified and Stabilized Wastes. 

A Dissertation submitted to the Office of

Graduate Studies of Texas A&M University in

partial fulfillment of the requirements for the

degree of Doctor of Philosophy. December

1997.

4.17. Klean Earth Environmental Company. Spring

Hill Mine Study. August 2001.

http://www.keeco.com/spring.htm. 

4.18. Markey, R. Comparison and Economic Analysis

of Arsenic Remediation Methods Used in Soil

and Groundwater. M.S. Thesis. FAMU-FSU

College of Engineering. 2000. 

4.19. Bates, Edward, Endalkachew Sable-Demessie,

and Douglas W. Grosse. Solidification/

Stabilization for Remediation of Wood

Preserving Sites: Treatment for Dioxins, PCP,

Creosote, and Metals. Remediation. John Wiley

& Sons, Inc. Summer 2000. pp. 51 - 65. 

http://www.wiley.com/cda/product/

0,,REM,00.html 

4.20. Palfy, P., E. Vircikova, and L. Molnar. 

Processing of Arsenic Waste by Precipitation and

Solidification. Waste Management. Volume 19. 

1999. pp. 55 - 59. 

http://sdnp.delhi.nic.in/node/jnu/database/

biogeoch/bioch99.html

4.21 Redwine JC. Successful In Situ Remediation

Case Histories: Soil Flushing And

Solidification/Stabilization With Portland

Cement And Chemical Additives. Southern

Company Services, Inc. Presented at the Air and

Waste Management Association’s 93rd Annual

Conference and Exhibition, Salt Lake City, June

2000.

4.22 Miller JP. In-Situ Solidification/Stabilization of

Arsenic Contaminated Soils. Electric Power

Research Institute. Report TR-106700. Palo

Alto, CA. November 1996. 

4.23 E-mail from Bhupi Khona, U.S. EPA Region 3 to

Sankalpa Nagaraja, Tetra Tech EM, Inc.,

regarding S/S of Arsenic at the Whitmoyer

Laboratories Superfund site. May 3, 2002.
Table 4.1

Solidification/Stabilization Treatment Performance Data for Arsenic

4-6

Project

Number

Industry and Site

Type Waste or Media Scalea

Site Name, Location,

and Project

Completion Dateb

Initial Arsenic

Concentration

(mg/kg) or

Leachability

(mg/L) (Test

method)

Final Arsenic

Concentration

(mg/kg) or

Leachability (mg/L)

(Test method)

Binder or

Stabilization Process Source

Environmental Media

1 Disposal Pit 20,000 cy sludge

and soil

Full Pab Oil Superfund

Site, LA

August 1998

7.5 - 25.1 mg/kg <0.1 mg/L (TCLP) Cement, organophilic

clay, other unspecified

organic, ferric sulfate,

other unspecified

inorganic, and sulfur

4.8

2 Fire/Crash Training

Area;

Federal Facility

3,000 cy sludge

and soil

Full Jacksonville Naval

Air Station Superfund

Site, FL

October 1995

NDc - 61 mg/kg <5 mg/L (TCLP) Cement, lime, other

unspecified inorganic,

and kiln dust 

4.8

3 Metal Ore Mining and

Smelting

500,000 cy soil Full Anaconda Co.

Smelter Superfund

Site, MT

January 1994

50 - 100 mg/L

(EPT)

<2 mg/L (TCLP) Unspecified inorganic 4.8

4 Munitions

Manufacturing/

Storage

1,000 cy soil Full Fernald

Environmental

Management Project

Superfund Site, OH

September 1999

 3 - 18 mg/kg <5mg/L (TCLP) Cement and

other unspecified

inorganic

4.8

5 -- Soil Full -- 0.18 mg/L (EPT) 0.028 mg/L (EPT) Cement 4.46 -- Soil Full -- 0.19 mg/L (TCLP) 0.017 mg/L (TCLP) Cement 4.47 -- Soil Full -- 0.0086 mg/L

(EPT)

0.0049 mg/L (EPT) Proprietary binder 4.4

8 -- Soil Full -- 0.0091 mg/L

(TCLP)

<0.002 mg/L (TCLP) Proprietary binder 4.4

9 -- Soil Full -- 0.017 mg/L

(TCLP)

0.0035 mg/L (TCLP) Proprietary binder 4.4
Table 4.1

Solidification/Stabilization Treatment Performance Data for Arsenic (continued)

Project

Number

Industry and Site

Type Waste or Media Scalea

Site Name, Location,

and Project

Completion Dateb

Initial Arsenic

Concentration

(mg/kg) or

Leachability

(mg/L) (Test

method)

Final Arsenic

Concentration

(mg/kg) or

Leachability (mg/L)

(Test method)

Binder or

Stabilization Process Source

4-7

10 -- Soil Full -- 2,430 mg/kg 0.11 - 0.26 mg/L

(TCLP)

fly ash, cement, and

proprietary reagent

4.3

11 -- Soil Full -- 0.10 mg/L (TCLP) 0.04 mg/L (TCLP) -- 4.112 Oil Processing &

Reclamation

Filter cake and

oily sludge

Full Imperial Oil Co -

Champion Chemical

Co Superfund Site,

NJ

40 mg/kg NDc,d (TCLP) Cement and proprietary

additives

4.16

13 Oil Processing &

Reclamation

Soil Full Imperial Oil Co -

Champion Chemical

Co Superfund Site,

NJ

92 mg/kg 0.017d mg/L (TCLP) Cement and proprietary

additives

4.16

14 Pesticides Soil Full -- 0.60 mg/L (EPT)

28.0 mg/L (WET)

0.27 mg/L (EPT)

6.5 mg/L (WET)

-- 4.1

15 Pharmaceutical 3,800 tons sludge

and soil

Full -- 260,000 mg/kg

4,310 - 4,390 mg/L

(TCLP)

1.24 - 3.44 mg/L

(TCLP)

Potassium persulfate,

ferric sulfate, and

cement

4.15

16 Transformer and

Metal Salvage

Soil Full Portable Equipment

Salvage Co, OR

42 mg/kg 0.004d mg/L (TCLP) Proprietary binder 4.16

17 Wood Preserving 14,800 cy soil Full Macgillis And

Gibbs/Bell Lumber

And Pole Superfund

Site, MN

February 1998

1 - 672 mg/kg 55 mg/L (TCLP) Cement 4.8
Table 4.1

Solidification/Stabilization Treatment Performance Data for Arsenic (continued)

Project

Number

Industry and Site

Type Waste or Media Scalea

Site Name, Location,

and Project

Completion Dateb

Initial Arsenic

Concentration

(mg/kg) or

Leachability

(mg/L) (Test

method)

Final Arsenic

Concentration

(mg/kg) or

Leachability (mg/L)

(Test method)

Binder or

Stabilization Process Source

4-8

18 Wood Preserving Soil Full -- 91 - 128 mg/kg 0.015 - 0.29 mg/L Reduction of

hexavalent chromium

followed by

stabilization with

cement and lime

4.16

19 Wood Preserving 13,000 cy soil Full Palmetto Wood

Preserving Superfund

Site, SC

1989

6,200 mg/kg 0.02 mg/L (TCLP) Cement and a pH

adjustment agent

4.8

20 Veterinary feed

additives and

pharmaceutical

manufacturing

400 tons Full Whitmoyer

Laboratories

Superfund Site

-- < 5 mg/L (TCLP) Water, ferric sulfate,

and Portland cement

4.23

21 Electrical substation 1,000 cy soil Pilot Florida

1995

<0.5 -2,000 mg/kg

1.42 - 3.7 mg/L

(TCLP)

ND - 0.11 (TCLP) Cement and ferrous

sulfate

4.21,

4.22

22 Electrical substation 3,300 cy soil Pilot Florida

1995

<0.5 - 1,900 mg/kg

0.15 - 3.5 mg/L

(TCLP)

0.22 - 0.38 (TCLP) Cement and ferrous

sulfate

4.21,

4.22

23 Wood Preserving Soil Pilot Selma Pressure

Treating Superfund

Site, Selma, CA

1998

10 mg/L (TCLP) < 0.1 mg/L (TCLP) Proprietary binder 4.19
Table 4.1

Solidification/Stabilization Treatment Performance Data for Arsenic (continued)

Project

Number

Industry and Site

Type Waste or Media Scalea

Site Name, Location,

and Project

Completion Dateb

Initial Arsenic

Concentration

(mg/kg) or

Leachability

(mg/L) (Test

method)

Final Arsenic

Concentration

(mg/kg) or

Leachability (mg/L)

(Test method)

Binder or

Stabilization Process Source

4-9

Industrial Wastes

24 Food-grade H3PO4

manufacture from

phosphate rock

-- Full -- 70.0 mg/L (TCLP) 1.58 mg/L (TCLP) -- 4.1

25 Food-grade H3PO4

manufacture from

phosphate rock

Arsenous

trisulfide

Full -- 5,000 - 40,000

mg/kg

0.43 mg/L (TCLP) Oxidation with NaOH

and NaOCl followed

by stabilization with

bed ash

4.1

26 Food-grade H3PO4

manufacture from

phosphate rock

Arsenous

trisulfide

Full -- 5,000 - 40,000

mg/kg

<0.14 mg/L (TCLP) Oxidation with

hydrated lime and

NaOCl followed by

stabilization with bed

ash

4.1

27 Food-grade H3PO4

manufacture from

phosphate rock

Arsenous

trisulfide

Full -- 5,000 - 40,000

mg/kg

<0.10 mg/L (TCLP) Pretreatment with

cement and CaOCl2

followed by

stabilization with lime

and cement

4.1

28 -- Dry waste Full -- 0.005 mg/L

(TCLP)

<0.002 mg/L (TCLP) Cement and other

unspecified additives

4.4

29 -- Dry waste Full -- 0.01 mg/L (EPT) 0.0023 mg/L (TCLP) Cement and other

unspecified additives

4.4

30 -- Sludge Full -- 0.011 mg/L (EPT) 0.002 mg/L (EPT) Cement and other

unspecified additives

4.4

31 -- Sludge Full -- 0.014 mg/L

(TCLP)

<0.002 mg/L (TCLP) Cement and other

unspecified additives

4.4
Table 4.1

Solidification/Stabilization Treatment Performance Data for Arsenic (continued)

Project

Number

Industry and Site

Type Waste or Media Scalea

Site Name, Location,

and Project

Completion Dateb

Initial Arsenic

Concentration

(mg/kg) or

Leachability

(mg/L) (Test

method)

Final Arsenic

Concentration

(mg/kg) or

Leachability (mg/L)

(Test method)

Binder or

Stabilization Process Source

4-10

32 Pesticide Pesticide sludge Full -- 52.0 mg/L (WET)

19.0 mg/L (EPT)

5.20 mg/L (WET)

0.14 mg/L (EPT)

-- 4.1

33 Waste disposal Hazardous waste

landfill leachate

Full -- 4.20 mg/L (TCLP) 0.016 mg/L (TCLP) -- 4.1

34 Waste treatment Hazardous waste

incinerator ash

Full -- 0.07 mg/L (TCLP) 0.019 mg/L (TCLP) -- 4.1

35 Waste treatment Hazardous waste

incinerator pond

sludge

Full -- 0.30 mg/L (TCLP)

0.30 mg/L (EPT)

<0.01 mg/L (TCLP)

<0.01 mg/L (EPT)

-- 4.1

36 Glass Manufacturing D004/D005

Waste

Pilot -- 296 mg/L (TCLP) 66.3 mg/L (TCLP) Cement and fly ash 4.14

37 Glass Manufacturing D004/D005

Waste

Pilot -- 6 mg/L (TCLP) <1 mg/L (TCLP) Cement and fly ash and

ferrous sulfate

4.14

38 Glass Manufacturing D004/D005

Waste

Pilot -- 18 mg/L (TCLP) <1 mg/L (TCLP) Cement and fly ash and

ferric sulfate

4.14

39 Mining Mine Tailings Pilot Spring Hill Mine,

Montana

6,000 mg/kg NDc (TCLP) Silica

Microencapsulation

4.17

40 -- D004, spent

catalyst

Pilot -- 280,000 mg/kg 0.79 mg/L (TCLP)

1.25 mg/L (alkaline

leaching test at pH

9.5)

Chemical oxidation of

waste to form ferric

arsenate sludge,

followed by

stabilization with lime

4.3

41 -- P012, As O2 3 Pilot -- 750,000 mg/kg <0.05 - 0.59 mg/L

(TCLP)

0.34 - 0.79 mg/L

(alkaline leaching test

at pH 9.5)

Chemical oxidation of

waste to form ferric

arsenate sludge,

followed by

stabilization with lime

4.3
Table 4.1

Solidification/Stabilization Treatment Performance Data for Arsenic (continued)

Project

Number

Industry and Site

Type Waste or Media Scalea

Site Name, Location,

and Project

Completion Dateb

Initial Arsenic

Concentration

(mg/kg) or

Leachability

(mg/L) (Test

method)

Final Arsenic

Concentration

(mg/kg) or

Leachability (mg/L)

(Test method)

Binder or

Stabilization Process Source

4-11

42 -- Sludge Pilot -- 6,430 mg/L 0.823 mg/L (TCLP) Embedding calcium

and ferric

arsenates/arsenites in a

cement matrix

4.20

In Situ Stabilization Only

43 Agricultural

application of

pesticides

Soil, 5,000 cubic

yards

Full Wisconsin DNROrchard Soil NDc - 50 mg/L (type of analysis

not reported)

NDc - 1 mg/L (type of

analysis not reported)

In situ treatment of

contaminated soil by

injecting pH

adjustment agents and

phosphates

4.6

44 Wood preserving

wastes, soil, 50,000

cubic yards

Soil, 50,000

cubic yards

Full Silver Bow

Creek/Butte Area

Superfund Site, MT

1998

-- -- In situ treatment of

contaminated soil by

injecting a solution of

ferrous iron, limestone,

and potassium

permanganate

4.8

a Excludes all bench-scale projects. Also excludes full- and pilot-scale projects where data on the leachability of stabilized wastes are not available.b Project completion dates provided for Superfund remedial action projects only.c Detection limit not provided.d Analyzed after 28 days. See Table 1.2 for long-term TCLP data.EPT = Extraction procedure toxicity test.-- = Not available TCLP = Toxicity characteristic leaching procedure TWA = Total waste analysisWET = Waste extraction test OU = Operable Unit cy = Cubic yardmg/kg = Milligrams per kilogram mg/L = Milligrams per liter
4-12

Table 4.2

Long-Term Solidification/Stabilization Treatment Performance Data for Arsenic

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

(Total Waste

Analysis)

Final Arsenic

Concentration of

Leachability

(28 day cure time)

Long-Term Leachable Arsenic

Concentration

 (6 year cure time) Binder or

Stabilization

Process Archived Field

1 Oil Processing &

Reclamation

Filter cake

and oily

sludge

Full Imperial Oil Co. -

Champion

Chemical Co.

Superfund Site,

NJ

40 mg/kg NDb (TCLP) 0.009 mg/L

(TCLP)

0.005 mg/L

(TCLP)

Cement and

proprietary

additives

2 Oil Processing &

Reclamation

Soil Full Imperial Oil Co. -

Champion

Chemical Co.

Superfund Site,

NJ

92 mg/kg 0.017 mg/L (TCLP) 0.021 mg/L

(TCLP)

0.022 mg/L

(TCLP)

Cement and

proprietary

additives

3 Transformer and

Metal Salvage

Soil Full Portable

Equipment

Salvage Co., OR

42 mg/kg 0.004 mg/L (TCLP) -- 0.005 mg/L

(TCLP)

Proprietary

binder

Source: 4.16a Excludes all bench-scale projects. Also excludes full- and pilot-scale projects where data on the leachability of stabilized wastes are not available.b Detection limit not provided.-- = Not available.ND = Not detected.TCLP = Toxicity characteristic leaching procedure.
5-1

Summary

Vitrification has been applied in a limited number of

projects to treat arsenic-contaminated soil and waste. 

For soil treatment, the process can be applied either

in situ or ex situ. This technology typically requires

large amounts of energy to achieve vitrification

temperatures, and therefore can be expensive to

operate. Off-gases may require further treatment to

remove hazardous constituents.

Technology Description: Vitrification is a high

temperature treatment aimed at reducing the

mobility of metals by incorporating them into a

chemically durable, leach resistant, vitreous mass

(Ref. 5.6). This process also may cause

contaminants to volatilize or undergo thermal

destruction, thereby reducing their concentration in

the soil or waste.

Media Treated

• Soil

• Waste

Energy Sources Used for Vitrification:

• Fossil fuels

• Direct joule heat

Energy Delivery Mechanisms Used for

Vitrification:

• Arcs

• Plasma torches

• Microwaves

• Electrodes (in situ)

In Situ Application Depth:

• Maximum demonstrated depth is 20 feet

• Depths greater than 20 feet may require

innovative techniques

Off-Gas

Collection 

Hood

Electrodes

Off-Gas

to Treatment

Melt 

Zone

Off-Gas

Collection 

Hood

Electrodes

Off-Gas

to Treatment

Melt 

Zone

5.0 VITRIFICATION FOR ARSENIC Model of an In Situ Vitrification System

Technology Description and Principles

During the vitrification treatment process, the metals

are surrounded by a glass matrix and become

chemically bonded inside the matrix. For example,

arsenates can be converted into silicoarsenates during

vitrification (Ref. 5.4). 

Ex situ processes provide heat to a melter through a

variety of sources, including combustion of fossil fuels,

and input of electric energy by direct joule heating. The

heat may be delivered via arcs, plasma torches, and

microwaves. In situ vitrification uses resistance heating

by passing an electric current through soil by means of

an array of electrodes (Ref. 5.6). In situ vitrification

can treat up to 1,000 tons of soil in a single melt.

Vitrification occurs at temperatures from 2,000 to

3,6000

F (Ref. 5.1, 5.4). These high temperatures may

cause arsenic to volatilize and contaminate the off-gas

of the vitrification unit. Vitrification units typically

employ treatment of the off-gas using air pollution

control devices such as baghouses (Ref. 5.5).

Pretreatment of the waste to be vitrified may reduce the

contamination of off-gasses with arsenic. For example,

in one application (Project 15), prior to vitrification of

flue dust containing arsenic trioxide (As2O3), a mixture

of the flue dust and lime was roasted at 400 0

C to

convert the more volatile arsenic trioxide to less volatile

calcium arsenate (Ca3(AsO4)2) (Ref. 5.5). Solid

residues from off-gas treatment may be recycled into

the feed to the vitrification unit (Ref. 5.6).

The maximum treatment depth for in situ vitrification

has been demonstrated to be about 20 feet (Ref. 5.6). 

Table 5.1 describes specific vitrification processes used

to treat soil and wastes containing arsenic. 

Media and Contaminants Treated

Vitrification has been applied to soil and wastes

contaminated with arsenic, metals, radionuclides, and

organics. This method is a RCRA best demonstrated

available technology (BDAT) for various arseniccontaining hazardous wastes, including K031, K084,

K101, K102, D004, and arsenic-containing P and U

wastes (Ref. 5.5, 5.6).
5-2

6

10

0 5 10

Pilot

Full

Case Study: Parsons Chemical Superfund Site

Vitrification

 The Parsons Chemical Superfund Site in Grand

Ledge, Michigan was an agricultural chemical

manufacturing facility. Full-scale in situ

vitrification was implemented to treat 3,000 cubic

yards of arsenic-contaminated soil. Initial arsenic

concentrations ranged from 8.4 to 10.1 mg/kg. Eight

separate melts were performed at the site, which

reduced arsenic concentrations to 0.717 to 5.49

mg/kg . The concentration of leachable arsenic in

the treated soils ranged from <0.004 to 0.0305

mg/L, as measured by the TCLP. The off-gas

emissions had arsenic concentrations of <0.000269

mg/m3

, <0.59 mg/hr (see Table 5.1, Project 6).

Type, Number, and Scale of Identified Projects

Treating Soil and Wastes Containing Arsenic

Vitrification of arsenic-contaminated soil and waste has

been conducted at both pilot and full scale. The sources

for this report contained information on ex situ

vitrification of arsenic-contaminated soil at pilot scale

at three sites and at full scale at one site. Information

was also identified for two in situ applications for

arsenic treatment at full scale. In addition, 7 pilot-scale

and 3 full-scale applications to industrial waste were

identified. Figure 5.1 shows the number of applications

identified at each scale. 

Figure 5.1

Scale of Identified Vitrification Projects for Arsenic

Treatment

Summary of Performance Data

Table 5.1 lists the vitrification performance data

identified in the sources used for this report. For ex situ

vitrification of soil, total arsenic concentrations prior to

treatment ranged from 8.7 to 540 mg/kg (Projects 2 and

4). Data on the leachability of arsenic from the vitrified

product were available only for Project 4, for which the

leachable arsenic concentration was reported as 0.9

mg/L. For in situ vitrification of soil, total arsenic

concentrations prior to treatment ranged from 10.1 to

4,400 mg/kg (Projects 6 and 5, respectively). The

leachability of arsenic in the stabilized soil and waste

ranged from <0.004 to 0.91 mg/L (Projects 5 and 6).

For treatment of industrial wastes, the total arsenic

concentrations prior to treatment ranged from 27 to

25,000 mg/kg (Projects 7 and 16) and leachable

concentrations in the vitrified waste ranged from 0.007

mg/L to 2.5 mg/L (Projects 15 and 16). For some of the

projects listed in Table 5.1, the waste treated was

identified as a spent potliner from primary aluminum

reduction (RCRA waste code K088) but the

concentration of arsenic in the waste was not identified. 

Some K088 wastes contain relatively low

concentrations of arsenic, and these projects may

involve treatment of such wastes.

The case study in this section discusses in greater detail

the in situ vitrification of arsenic-contaminated soil at

the Parsons Chemical Superfund Site. This information

is summarized in Table 5.1, Project 6.

Applicability, Advantages, and Potential Limitations

Arsenic concentrations present in soil or waste may

limit the performance of the vitrification treatment

process. For example, if the arsenic concentration in

the feed exceeds its solubility in glass, the technology’s

effectiveness may be limited (Ref. 5.6). Metals retained

in the melt must be dissolved to minimize the formation

of crystalline phases that can decrease leach resistance

of the vitrified product. The approximate solubility of

arsenic in silicate glass ranges from 1 - 3% by weight

(Ref. 5.7). 

The presence of chlorides, fluorides, sulfides, and

sulfates may interfere with the process, resulting in

higher mobility of arsenic in the vitrified product. 

Feeding additional slag-forming materials such as sand

to the process may compensate for the presence of

chlorides, fluorides, sulfides, and sulfates (Ref. 5.4). 

Chlorides, such as those found in chlorinated solvents,

in excess of 0.5 weight percent in the waste will

typically fume off and enter the off-gas. Chlorides in

the off-gas may result in the accumulation of salts of

alkali, alkaline earth, and heavy metals in the solid

residues collected by off-gas treatment. If the residue is

returned to the process for treatment, separation of the

chloride salts from the residue may be necessary. When

excess chlorides are present, dioxins and furans may

also form and enter the off-gas treatment system (Ref.

5.6). The presence of these constituents may also lead

to the formation of volatile metal species or corrosive

acids in the off-gas (Ref. 5.7).
5-3

Factors Affecting Vitrification Performance

• Presence of halogenated organic compounds - 

The combustion of halogenated organic

compounds may result in incomplete combustion

and the deposition of chlorides, which can result

in higher mobility of arsenic in the vitrified

product (Ref. 5.4).

• Presence of volatile metals - The presence of

volatile metals, such as mercury and cadmium,

and other volatile inorganics, such as arsenic,

may require treatment of the off-gas to reduce air

emissions of hazardous constituents (Ref. 5.6).

• Particle size - Some vitrification units require

that the particle size of the feed be controlled. 

For wastes containing refractory compounds that

melt above the unit's nominal processing

temperature, such as quartz and alumina, size

reduction may be required to achieve acceptable

throughputs and a homogeneous melt. Hightemperature processes, such as arcing and

plasma processes may not require size reduction

of the feed (Ref. 5.6).

• Lack of glass-forming materials - If

insufficient glass-forming materials (SiO2 >30%

by weight) and combined alkali (Na + K > 1.4%

by weight) are present in the waste the vitrified

product may be less durable. The addition of frit

or flux additives may compensate for the lack of

glass-forming and alkali materials (Ref. 5.6).

• Subsurface air pockets - For in situ

vitrification, subsurface air pockets, such as

those that may be associated with buried drums,

can cause bubbling and splattering of molten

material, resulting in a safety hazard (Ref. 5.10).

• Metals content - For in situ vitrification, a

metals content greater than 15% by weight may

result in pooling of molten metals at the bottom

of the melt, resulting in electrical short-circuiting

(Ref. 5.10). 

• Organic content - For in situ vitrification, an

organic content of greater than 10% by weight

may cause excessive heating of the melt,

resulting in damage to the treatment equipment

(Ref. 5.10). High organics concentrations may

also cause large volumes of off-gas as the

organics volatilize and combust, and may

overwhelm air emissions control systems. 

Factors Affecting Vitrification Costs

• Moisture content - Greater than 5% moisture

in the waste may result in greater mobility of

arsenic in the final treated matrix. These

wastes may require drying prior to vitrification

(Ref. 5.4). Wastes containing greater than 25%

moisture content may require excessive fuel

consumption or dewatering before treatment

(Ref. 5.6).

• Characteristics of treated waste - Depending

upon the qualities of the vitrified waste, the

treated soil and waste may be able to be reused

or sold.

• Factors affecting vitrification performance -

Items in the “Factors Affecting Vitrification

Performance” box will also affect costs.

During vitrification, combustion of the organic content

of the waste liberates heat, which will raise the

temperature of the waste, thus reducing the external

energy requirements. Therefore, this process may be

advantageous to wastes containing a combination of

arsenic and organic contaminants or for the treatment of

organo-arsenic compounds. However, high

concentrations of organics and moisture may result in

high volumes of off-gas as organics volatilize and

combust and water turns to steam. This can overwhelm

emissions control systems. 

Vitrification can also increase the density of treated

material, thereby reducing its volume. In some cases,

the vitrified product can be reused or sold. Vitrified

wastes containing arsenic have been reused as industrial

glass (Ref. 5.5). Metals retained in the melt that do not

dissolve in the glass phase can form crystalline phases

upon cooling that can decrease the leach resistance of

the vitrified product.

Excavation of soil is not required for in situ

vitrification. This technology has been demonstrated to

a depth of 20 feet. Contamination present at greater

depths may require innovative application techniques. 

In situ vitrification may be impeded by the presence of

subsurface air pockets, high metals concentrations, and

high organics concentrations (Ref. 5.10). 

Summary of Cost Data

Cost information for ex situ vitrification of soil and

wastes containing arsenic was not found in the

references identified for this report. The cost for in situ

vitrification of 3,000 cubic yards of soil containing

arsenic, mercury, lead, DDT, dieldrin and chlordane at

the Parsons Chemical Superfund site are presented

below (Ref. 5.8, cost year not provided):

• Treatability/pilot testing $50,000 - $150,000

• Mobilization $150,000 - $200,000

• Vitrification operation $375 - $425/ ton

• Demobilization $150,000 - $200,000
5-4

References

5.1. TIO. Database for EPA REACH IT (Remediation

And Characterization Innovative Technologies).

March 2001. http://www.epareachit.org.

5.2. U.S. EPA. Arsenic & Mercury - Workshop on

Removal, Recovery, Treatment, and Disposal.

Office of Research and Development. EPA-600-

R-92-105. August 1992.

5.3. U.S. EPA. BDAT Background Document for

Spent Potliners from Primary Aluminum

Reduction - K088. Office of Solid Waste. 

February 1996. 

http://yosemite1.epa.gov/EE/epa/ria.nsf/

ca2fb654a3ebbce28525648f007b8c26/22bebe132

177e059852567e8006919c3?OpenDocument

5.4. U.S. EPA. Best Demonstrated Available

Technology (BDAT) Background Document for

Wood Preserving Wastes: F032, F034, and F035;

Final. April 1996. 

http://www.epa.gov/epaoswer/hazwaste/ldr/

wood/bdat_bd.pdf

5.5. U.S. EPA. Final Best Demonstrated Available

Technology (BDAT) Background Document for

K031, K084, K101, K102, Characteristic Arsenic

Wastes (D004), Characteristic Selenium Wastes

(D010), and P and U Wastes Containing Arsenic

and Selenium Listing Constituents. Office of

Solid Waste. May 1990.

5.6. U.S. EPA Office of Research and Development. 

Engineering Bulletin, Technology Alternatives for

the Remediation of Soils Contaminated with

Arsenic, Cadmium, Chromium, Mercury, and

Lead. Cincinnati, OH. March 1997. 

http://www.epa.gov/ncepi/Catalog/

EPA540S97500.html

5.7. U.S. EPA. Contaminants and Remedial Options at

Selected Metal-Contaminated Sites. Office of

Research and Development. EPA-540-R-95-512.

July 1995. 

http://www.epa.gov/ncepi/Catalog/

EPA540R95512.html 

5.8. Federal Remediation Technologies Roundtable

(FRTR). In Situ Vitrification at the Parsons

Chemical/ETM Enterprises Superfund Site Grand

Ledge, Michigan.

http://www.frtr.gov/costperf.htm.

5.9. FRTR. In Situ Vitrification, U.S. Department of

Energy, Hanford Site, Richland, Washington; Oak

Ridge National Laboratory WAG 7; and Various

Commercial Sites. 

http://www.frtr.gov/costperf.htm.

5.10 U.S. EPA. SITE Technology Capsule, Geosafe

Corporation In Situ Vitrification Technology. 

Office of Research and Development. EPA

540/R-94/520a. November 1994. 

http://www.epa.gov/ORD/SITE/reports/

540_r-94_520a.pdf.
Table 5.1

Vitrification Treatment Performance Data for Arsenic

5-5

Project

Number

Industry or Site

Type

 Media or

Waste Scalea

Site Name or

Location

Initial Arsenic

Concentration

Vitrified Product and

Final Arsenic

Concentration

Vitrification Process

Description Source

Environmental Media

1 Metal Ore Mining

and Smelting

River and

harbor sludge

Pilot Ecotechneik

B.V., Utrecht,

Netherlands

117 mg/kg

(TWA)

Artificial gravel Rotary kiln vitrification at

1,150°C

5.1

2 Industrial Landfill Mixture of

solids, soil,

and sludge

Pilot MatanzaRiachuelo

River,

Monditech,

S.A., Buenos

Aires, Argentina

8.7 - 12 mg/kg

(TWA)

Artificial gravel, 0.01

mg/L (TCLP)

Seizing, grinding, and

milling pretreatment

followed by vitrification in

a rotary kiln at 1,000°C

5.1

3 -- Soil, 400 tons Full Chatham

Dockyard, St.

Mary’s Island,

VERT, Kent,

England

-- Glass fait Wastes are mixed with

sand and limestone and fed

to a furnace containing a

pool of molten glass

maintained at 1550°C. 

Glass is removed from

bottom of pool and water

cooled to produce fait.

5.1

4 -- Soil Pilot University of

Pittsburgh

Applied

Research

Center,

Harmarville, PA

540 mg/kg

(TWA)

Glass cullet 0.9 mg/L

(TCLP)

Vortec Corporation

Advanced Combustion

Melting System, counterrotating vortex combustor

followed by cyclone melter

and water quench

5.2

5 RCRA waste code

K031 and other

pesticide wastes

-- Full -- 4,400 mg/kg

(TWA)

0.91 mg/L (TCLP) In situ vitrification at 1200

degrees C with unspecified

air pollution control

equipment

5.5
Table 5.1

Vitrification Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

 Media or

Waste Scalea

Site Name or

Location

Initial Arsenic

Concentration

Vitrified Product and

Final Arsenic

Concentration

Vitrification Process

Description Source

5-6

6 Agricultural

chemicals

manufacturing

Soil, 3,000

cubic yards

Full Parsons

Chemical

Superfund Site,

MI

8.4 - 10.1 mg/kg

(TWA)

0.717 - 5.49 mg/kg

(TWA)

<0.004 - 0.0305 mg/L

(TCLP)

In situ vitrification, eight

separate melts. Stack gas

emissions of arsenic

<0.000269 milligrams per

cubic meter, <0.59

milligrams per hour.

5.8

Industrial Waste

7 Incinerator air

pollution control

scrubber wastewater

Incinerator

ash

Pilot University of

Pittsburgh

Applied

Research

Center,

Harmarville, PA

27 mg/kg (TWA) Glass cullet 0.05 mg/L

(TCLP)

Vortec Corporation

Advanced Combustion

Melting System, counterrotating vortex combustor

followed by cyclone melter

and water quench

5.2

8 Residues from

incineration of

municipal solid waste

Fly ash Pilot University of

Pittsburgh

Applied

Research

Center,

Harmarville, PA

981 mg/kg

(TWA)

Glass cullet <0.05 mg/L

(TCLP)

Vortec Corporation

Advanced Combustion

Melting System, counterrotating vortex combustor

followed by cyclone melter

and water quench

5.2

9 -- Hazardous

baghouse dust

Pilot University of

Pittsburgh

Applied

Research

Center,

Harmarville, PA

-- Glass cullet <0.02 mg/L

(TCLP)

Vortec Corporation

Advanced Combustion

Melting System, counterrotating vortex combustor

followed by cyclone melter

and water quench

5.2

10 Primary aluminum

reduction, RCRA

hazardous waste code

K088

Spent

potliners,

30,000 tons

per year

Full Barnard

Environmental,

Richland, WA

-- Molten glass Terra-Vit process,

resistance heating using

electrodes submerged in the

molten mass, molten glass

effluent is formed into

products

5.3
Table 5.1

Vitrification Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

 Media or

Waste Scalea

Site Name or

Location

Initial Arsenic

Concentration

Vitrified Product and

Final Arsenic

Concentration

Vitrification Process

Description Source

5-7

11 Primary aluminum

reduction, RCRA

hazardous waste code

K088

Spent

potliners, 200

- 300

kilograms per

hour

Pilot Elkem

Technology,

Norway

-- Slag Slagging process with

addition of iron ore and

quartz

5.3

12 Primary aluminum

reduction, RCRA

hazardous waste code

K088, and electric arc

furnace dust, RCRA

hazardous waste code

K066

Spent

potliners

Pilot Enviroscience,

Inc., Vancouver,

Washington 

-- Slag wool Extractive metallurgical

process conducted in a

shaft furnace to produce

zinc, calcium, and lead

oxides in the baghouse

dust, pig iron, and mineral

wool

5.3

13 Primary aluminum

reduction, RCRA

hazardous waste code

K088

Spent

potliners

Pilot Ormet

Corporation

-- Industrial glass Spent potliners and glassforming ingredients are

vitrified in an in-flight

suspension combustor

followed by a cyclone

separation and melting

chamber

5.3

14 Primary aluminum

reduction, RCRA

hazardous waste code

K088

Spent

potliners

Full Reynolds

Metals

-- Kiln residue has been

delisted, disposed at nonhazardous landfill

Spent potliners, limestone,

and brown sand are blended

and fed to a rotary kiln

vitrification unit

5.3
Table 5.1

Vitrification Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

 Media or

Waste Scalea

Site Name or

Location

Initial Arsenic

Concentration

Vitrified Product and

Final Arsenic

Concentration

Vitrification Process

Description Source

5-8

15 -- Flue dust Full -- -- 3,000 - 235,000 mg/kg

(TWA)

0.007 - 1.8 mg/L (TCLP)

Roasting at 400 degrees C

to convert arsenic trioxide

to calcium arsenate

followed by vitrification in

an iron silicate slag at

1,290 degrees C

5.5

16 Phosphoric acid

production, RCRA

hazardous waste code

D004

Sludge

containing

arsenic sulfide

Pilot Rhone-Poulenc 20,000 - 25,000

mg/kg (TWA)

<0.5 - 0.5 mg/L (EPT)

<0.5 - 2.5 mg/L (TCLP)

-- 5.5

a Excluding bench-scale treatments -- = Not available WET = Waste extraction testC = Celsius TCLP = Toxicity characteristic leaching procedureEPT = Extraction procedure toxicity test TWA = Total waste analysis
6-1

Scrubbing

Unit

Treatment 

Plant

Clean Soil

Contaminated 

Soil

Clean 

Water

Residual Soil

Reused Water

Wash

Water

Water and

Detergent

Scrubbing

Unit

Treatment 

Plant

Clean Soil

Contaminated 

Soil

Clean 

Water

Residual Soil

Reused Water

Wash

Water

Water and

Detergent

Model of Soil Washing System

3

2

4

01234

Bench

Pilot

Full

3

2

4

01234

Bench

Pilot

Full

Summary

Soil washing/acid extraction (soil washing) has been

used to treat arsenic-contaminated soil in a limited

number of applications. The process is limited to

soils in which contaminants are preferentially

adsorbed onto the fines fraction. The separated

fines must be further treated to remove or

immobilize arsenic.

Technology Description: Soil washing is an ex

situ technology that takes advantage of the behavior

of some contaminants to preferentially adsorb onto

the fines fraction. The soil is suspended in a wash

solution and the fines are separated from the

suspension, thereby reducing the contaminant

concentration in the remaining soil. 

Media Treated:

ï Soil (ex situ)

6.0 SOIL WASHING/ACID EXTRACTION

FOR ARSENIC

Technology Description and Principles

Soil washing uses particle size separation to reduce soil

contaminant concentrations. This process is based on

the concept that most contaminants tend to bind to the

finer soil particles (clay, silt) rather than the larger

particles (sand, gravel). Because the finer particles are

attached to larger particles through physical processes

(compaction and adhesion), physical methods can be

used to separate the relatively clean larger particles

from the finer particles, thus concentrating the

contamination bound to the finer particles for further

treatment (Ref. 6.7). 

In this process, soil is first screened to remove

oversized particles, and then homogenized. The soil is

then mixed with a wash solution consisting of water or

water enhanced with chemical additives such as

leaching agents, surfactants, acids, or chelating agents

to help remove organics and heavy metals. The

particles are separated by size (cyclone and/or gravity

separation depending on the type of contaminants in the

soil and particle size), concentrating the contaminants

with the fines. Because the soil washing process

removes and concentrates the contaminants but does not

destroy them, the resulting concentrated fines or sludge

usually require further treatment. The coarser-grained

soil is generally relatively ìcleanî, requiring no 

additional treatment. Wash water from the process is

treated and either reused in the process, or disposed

(Ref. 6.7). Commonly used methods for treating the

wastewater include ion exchange and solvent

extraction. 

Media and Contaminants Treated

Soil washing is suitable for use on soils contaminated

with SVOCs, fuels, heavy metals, pesticides, and some

VOCs, and works best on homogenous, relatively

simple contaminant mixtures (Ref. 6.1, 6.4, 6.7). Soil

washing has been used to treat soils contaminated with

arsenic.

Type, Number, and Scale of Identified Projects

Treating Soil and Wastes Containing Arsenic

Nine projects were identified where soil washing was

performed to treat arsenic. Of these, four were

performed at full scale, including two at Superfund

sites. Three projects were conducted at pilot scale, and

two at bench scale (Ref. 6.4). Figure 6.1 shows the

number of arsenic soil washing projects at bench, pilot,

and full scale. 

Figure 6.1

Scale of Identified Soil Washing/Acid Extraction

Projects for Arsenic Treatment
6-2

Factors Affecting Soil Washing Performance

• Soil homogeneity - Soils that vary widely and

frequently in characteristics such as soil type,

contaminant type and concentration, and where

blending for homogeneity is not feasible, may

not be suitable for soil washing (Ref. 6.1). 

• Multiple contaminants - Complex,

heterogeneous contaminant compositions can

make it difficult to formulate a simple washing

solution, requiring the use of multiple,

sequential washing processes to remove

contaminants (Ref. 6.1).

• Moisture content - The moisture content of the

soil may render its handling more difficult. 

Moisture content may be controlled by covering

the excavation, storage, and treatment areas to

reduce the amount of moisture in the soil (Ref.

6.1).

• Temperature - Cold weather can cause the

washing solution to freeze and can affect

leaching rates (Ref. 6.1).

Factors Affecting Soil Washing Costs

• Soil particle size distribution - Soils with a

high proportion of fines may require disposal

of a larger amount of treatment residual.

• Residuals management - Residuals from soil

washing, including spent washing solution and

removed fines, may require additional

treatment prior to disposal.

• Factors affecting soil washing performance -

Items in the “Factors Affecting Soil Washing

Performance” box will also affect costs.

Case Study: King of Prussia Superfund Site

 The King of Prussia Superfund Site in Winslow

Township, New Jersey is a former waste processing

and recycling facility. Soils were contaminated with

arsenic, berylllium, cadmium, chromium, copper,

lead, mercury, nickel, selenium, silver, and zinc

from the improper disposal of wastes (Project 1). 

Approximately 12,800 cubic yards of arseniccontaminated soil, sludge, and sediment was treated

using soil washing in 1993. The treatment reduced

arsenic concentrations from 1 mg/kg to 0.31 mg/kg,

a reduction of 69%.

Summary of Performance Data

Table 6.1. lists the available performance data. For soil

and waste, this report focuses on performance data

expressed as the leachability of arsenic in the treated

material. However, arsenic leachability data are not

available for any of the projects in Table 6.1. The case

study in this section discusses in greater detail the soil

washing to treat arsenic at the King of Prussia

Superfund Site. This information is summarized in

Table 6.1, Project 1.

Applicability, Advantages, and Potential Limitations

The principal advantage of soil washing is that it can be

used to reduce the volume of material requiring further

treatment (Ref. 6.3). However, this technology is

generally limited to soils with a range of particle size

distributions, and contaminants that preferentially

adsorb onto the fines fraction.

Summary of Cost Data

Table 6.1. shows the reported costs for soil washing to

treat arsenic. The unit costs range from $30 to $400 per

ton of material treated (costs not adjusted to a consistent

cost year). For one project treating 19,200 tons of soil,

sludge, and sediment (Table 6.1, Project 1), the total

reported treatment costs, including off-site disposal of

treatment residuals, was $7.7 million, or $400/ton (Ref.

6.6, 6.8, cost year not provided).

References

6.1. U.S. EPA. Engineering Bulletin. Technology

Alternatives for the Remediation of Soils

Contaminated with Arsenic, Cadmium,

Chromium, Mercury, and Lead. Office of

Emergency and Remedial Response. 540-S-97-

500. March 1997. 

http://www.epa.gov/ncepi/Catalog/

EPA540S97500.html

6.2. U.S. EPA. A Citizen’s Guide to Soil Washing.

Office of Solid Waste and Emergency Response. 

EPA 542-F-96-002. April 1996. 

http://www.epa.gov/tio/download/remed/

soilwash.pdf.

6.3. U.S. EPA. Treatment Technology Performance

and Cost Data for Remediation of Wood

Preserving Sites. Office of Research and

Development. EPA-625-R-97-009. October

1997. 

http://www.epa.gov/ncepi/Catalog/

EPA625R97009.html

6.4. U.S. EPA. Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition). 
6-3

Office of Solid Waste and Emergency Response.

EPA-542-R-01-004. February 2001. 

http://clu-in.org/asr.

6.5. U.S. EPA. Database for EPA REACH IT

(REmediation And CHaracterization Innovative

Technologies). March 2001. 

http://www.epareachit.org.

6.6. U.S. EPA. Contaminants and Remedial Options

at Selected Metal-Contaminated Sites. Office of

Research and Development. EPA-540-R-95-512.

July 1995.

6.7. Federal Remediation Technologies Roundtable: 

Remediation Technologies Screening Matrix and

Reference Guide Version 3.0. November 2000.

http://www.frtr.gov/matrix2/top_page.html.

6.8. Federal Remediation Technologies Roundtable

(FRTR). Soil Washing at the King of Prussia

Technical Corporation Superfund Site. 

http://www.frtr.gov/costperf.htm. 
6-4

Table 6.1

Arsenic Soil Washing Treatment Cost and Performance Data for Arsenic

Project

Number

Industry or Site

Type

Waste or

Media Scale

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Soil Washing Agent or

Process

Cost

($/ton)a Source

1 Waste treatment,

recycling, and

disposal

Soil

 (12,800 cy)

Full King of Prussia

Superfund Site,

Winslow Township,

NJ

1 mg/kg (TWA) 0.31 mg/kg

(TWA)

Screening, separation, and

froth flotation

$400 6.4, 6.8

2 Pesticide

manufacturing

Soil

(180,000 cy)

Full Vineland Chemical

Company Superfund

Site, Operable Unit 01

Vineland, NJ

-- -- -- -- 6.4

3 Inorganic

chemical

manufacturing,

wood preserving

Soil 

(5000 cy)

Full Ter Apel, Moerdijk,

Netherlands

15 - 455 mg/kg

(TWA)

20 mg/kg (TWA) -- -- 6.5

4 -- Soil Full -- 250 mg/kg

(TWA)

20 mg/kg (TWA) -- $100 -

$300

6.6

5 Herbicide

manufacturing,

explosives

manufacturing

Soil (130 cy) Pilot -- 97 - 227 mg/kg

(TWA)

6.6 - 142 mg/kg

(TWA)

-- $65 6.5

6 Munitions

Manufacturing

Soil,

sediments,

and other

solids

 (400 cy)

Pilot -- 2 - 129 mg/kg

(TWA)

0.61 - 3.1

(mg/kg)

-- $80 6.5

7 Munitions

Manufacturing

Soil Pilot -- -- -- -- -- 6.5

8 Pesticide

manufacturing

Soil Bench Camp Pendleton

Marine Corps Base

Superfund Site, CA

4.5 mg/kg

(TWA)

3 mg/kg (TWA) -- -- 6.5

9 Wood preserving Sediment Bench Thunder Bay,

Ontario, Canada

9.1 mg/kg

(TWA)

0.015 mg/kg

(TWA)

-- -- 6.3

a Cost year not provided.mg/kg = milligrams per kilogram -- = Not available TWA = Total waste analysis cy = Cubic yards
7-1

Summary

Information gathered for this report indicate that

pyrometallurgical processes have been implemented

to recover arsenic from soil and wastes in four fullscale applications. These technologies may have

only limited application because of their cost ($208

- $458 per ton in 1991 dollars) and because the cost

of importing arsenic is generally lower than

reclaiming it using pyrometallurgical processes

(Ref. 7.6). The average cost of imported arsenic

metal in 1999 was $0.45 per pound (Ref. 7.6, in

1999 dollars). In order to make recovery

economically feasible, the concentration of metals in

the waste should be over 10,000 mg/kg (Ref. 7.2).

Technology Description: Pyrometallurgical

recovery processes use heat to convert an arseniccontaminated waste feed into a product with a high

arsenic concentration that can be reused or sold. 

Media Treated

• Soil

• Industrial wastes

Types of Pyrometallurgical Processes

• High temperature metals recovery

• Slag cleaning process

0

4

01234

Pilot

Full

7.0 PYROMETALLURGICAL RECOVERY

FOR ARSENIC

Technology Description and Principles

A variety of processes reportedly have been used to

recover arsenic from soil and waste containing arsenic. 

High temperature metals recovery (HTMR) involves

heating a waste feed to cause metals to volatilize or

“fume”. The airborne metals are then removed with the

off-gas and recovered, while the residual solid materials

are disposed. Other pyrometallurgical technologies

typically involve modifications at metal refining

facilities to recover arsenic from process residuals. 

The Metallurgie-Hoboken-Overpelt (MHO) slag

cleaning process involves blast smelting with the

addition of coke as a reducing agent of primary and

secondary materials from lead, copper, and iron

smelting operations (Ref. 7.9).

Media and Contaminants Treated

This technology has recovered heavy metals, such as

arsenic and lead, from soil, sludge, and industrial

wastes (Ref. 7.8). The references used for this report

contained information on applications of HTMR to

recover arsenic from contaminated soil (Ref. 7.3) and

secondary lead smelter soda slag (Ref. 7.8). In

addition, one metals refining process that was modified

to recover arsenic (Ref. 7.9) was identified. The

recycling and reuse of arsenic from consumer endproduct scrap is not typically done (Ref. 7.6).

Type, Number, and Scale of Identified Projects

Treating Soil and Wastes Containing Arsenic

This report identified application of pyrometallurgical

recovery of arsenic at full scale at four facilities (Ref.

7.3, 7.8, 7.9). No pilot-scale projects for arsenic were

found. 

Figure 7.1

Scale of Identified Pyrometallurgical Projects for

Arsenic Treatment

Summary of Performance Data

Table 7.1 presents the available performance data.

Because this technology typically generates a product

that is reused instead of disposed, the performance of

these processes is typically measured by the percent

removal of arsenic from the waste, the concentration of

arsenic in the recovered product, and the concentration

of impurities in the recovered product. Other soil and

waste treatment processes are usually evaluated by

leach testing the treated materials. 

Both of the soil projects identified have feed and treated

material arsenic concentrations. One project had an
7-2

Case Study: National Smelting and Refining

Company Superfund Site, Atlanta, Georgia

Secondary lead smelter slag from the National

Smelting and Refining Company Superfund Site in

Atlanta, Georgia was processed using high

temperature metals recovery at a full-scale facility. 

The initial waste feed had an arsenic concentration

range of 428 to 1,040 mg/kg. The effluent slag

concentration ranged from 92.1 to 1,340 mg/kg of

arsenic, but met project goals for arsenic leachability

(<5 mg/L TCLP). The oxide from the baghouse

fumes had an arsenic concentration of 1,010 to 1,170

mg/kg; however, the arsenic was not recovered (Ref.

7.8) (see Project 3, Table 7.1).

Factors Affecting Pyrometallurgical Recovery

Performance

• Particle size - Larger particles do not allow

heat transfer between the gas and solid phases

during HTMR. Smaller particles may increase

the particulate in the off-gas.

• Moisture content - A high water content

generally reduces the efficiency of HTMR

because it increases energy requirements.

• Thermal conductivity - Higher thermal

conductivity of the waste results in better heat

transfer into the waste matrix during HTMR

(Ref. 7.2).

• Presence of impurities - Impurities, such as

other heavy metals, may need to be removed,

which increases the complexity of the treatment

process.

Factors Affecting Pyrometallurgical Recovery

Costs

• Factors affecting pyrometallurgical recovery

performance - Items in the “Factors Affecting

Pyrometallurgical Recovey Performance” box

will also affect costs.

arsenic feed concentration of 86 mg/kg and a treated

arsenic concentration of 6.9 mg/kg (Project 1). The

other project had an leachable arsenic concentration in

the feed of 0.040 mg/L and 0.019 mg/L in the treated

material (Project 2).

Both of the industrial waste projects identified have

feed and residual arsenic data, and one has posttreatment leachability data. The feed concentrations

ranged from 428 to 2,100 mg/kg (Projects 3 and 4). 

The residual arsenic concentrations ranged from 92.1 to

1,340 mg/kg, with less than 5 mg/L leachability (Project

3).

The case study in this section discusses in greater detail

an HTMR application at the National Smelting and

Refining Company Superfund Site. This information is

summarized in Table 7.1, Project 3.

Applicability, Advantages, and Potential Limitations

Although recovering arsenic from soil and wastes is

feasible, it has not been done in the U.S. on a large

scale because it is generally less expensive to import

arsenic than to obtain it through reclamation processes

(Ref. 7.5-7). The cost of importing arsenic in 1999 was

approximately $0.45 per pound (Ref. 7.6, in 1999

dollars). In order to make recovery economically

feasible, the concentration of metals in the waste should

be over 10,000 mg/kg (Ref. 7.2). In some cases, the

presence of other metals in the waste, such as copper,

may provide sufficient economic incentive to recover

copper and arsenic together for the manufacture of

arsenical wood preservatives (Ref. 7.1). However,

concern over the toxicity of arsenical wood

preservatives is leading to its phase-out (Ref. 7.10).

At present, arsenic is not being recovered domestically

from arsenical residues and dusts at nonferrous

smelters, although some of these materials are

processed for the recovery of other materials (Ref. 7.6).

This technology may produce treatment residuals such

as slag, flue dust, and baghouse dust. Although some

residuals may be treated using the same process that

generated them, the residuals may require additional

treatment or disposal.

Summary of Cost Data

The estimated cost of treatment using HTMR ranges

from $208 to $458 per ton (in 1991 dollars). However,

these costs are not specific to treatment of arsenic (Ref.

7.2). No cost data for pyrometallurgical recovery for

arsenic was found.
7-3

References

7.1 U.S. EPA. Arsenic & Mercury - Workshop on

Removal, Recovery, Treatment, and Disposal.

Office of Research and Development. EPA-600-

R-92-105. August 1992. 

7.2 U.S. EPA. Contaminants and Remedial Options

at Selected Metal-Contaminated Sites. Office of

Research and Development. EPA-540-R-95-512. 

July 1995. http://www.epa.gov/ncepi/Catalog/

EPA540R95512.html

7.3 U.S. EPA National Risk Management Research

Laboratory. Treatability Database. March 2001.

7.4 Code of Federal Regulations, Part 40, Section

268. http://lula.law.cornell.edu/cfr/

cfr.php?title=40&type=part&value=268

7.5 U.S. EPA. Final Best Demonstrated Available

Technology (BDAT) Background Document for

K031, K084, K101, K102, Characteristic Arsenic

Wastes (D004), Characteristic Selenium Wastes

(D010), and P and U Wastes Containing Arsenic

and Selenium Listing Constituents. Office of

Solid Waste. May 1990.

7.6 U.S. Geological Survey. Mineral Commodity

Summaries. February 2000.

http://minerals.usgs.gov/minerals/pubs/

commodity/soda_ash/610300.pdf

7.7 U.S. EPA. Engineering Bulletin. Technology

Alternatives for the Remediation of Soils

Contaminated with Arsenic, Cadmium,

Chromium, Mercury, and Lead. Office of

Emergency and Remedial Response. March 1997. 

http://www.epa.gov/ncepi/Catalog/

EPA540S97500.html

7.8 U.S. EPA. Superfund Innovative Technology

Evaluation Program. Technology Profiles Tenth

Edition. Volume 1 Demonstration Program.

Office of Research and Development. EPA-540-

R-99-500a. February 1999. 

http://www.epa.gov/ncepi/Catalog/

EPA540R99500A.html

7.9 U.S. EPA. Profiles of Metal Recovery

Technologies for Mineral Processing and Other

Metal-Bearing Hazardous Wastes. December

1994.

7.10 U.S. EPA. Manufacturers to Use New Wood

Preservatives, Replacing Most Residential Uses of

CCA. February 12, 2002. 

http://www.epa.gov/pesticides/citizens/

cca_transition.htm
7-4

Table 7.1

Arsenic Pyrometallurgical Recovery Performance Data for Arsenic

Project

Number

Industry

or Site

Type

Media or

Waste

Reclaimed Scale

Site Name or

Location

Reclamation

Process Feed

Arsenic

Concentration

Reclamation Process

Residual Arsenic

Concentration

Recovered Arsenic

Concentration

Reclamation

Process Used Source

Environmental Media

1 -- Soil (amount not

available)

Full -- 86 mg/kg (TWA) 6.9 mg/kg (TWA) -- HTMR 7.3

2 -- Soil (amount not

available)

Full -- 0.040 mg/L (TCLP) 0.019 mg/L (TCLP) -- HTMR 7.3

Industrial Wastes

3 -- Secondary lead

smelter soda

slag (72 tons)

Full National

Smelting and

Refining

Company

Superfund

Site, Atlanta,

GA

428 - 1,040 mg/kg

(TWA)

Slag, 92.1 - 1,340

mg/kg (TWA)

Slag, <5 mg/L (TCLP)

Arsenic trioxide,

1,010 - 1,170 mg/kg

(TWA)

HTMR 7.8

4 -- Primary and

secondary

materials

(additional

description of

materials not

available)

Full Hoboken,

Belgium

2,100 mg/kg

(TWA)

Slag, 100 mg/kg

(TWA)

zinc flue dust, 1,000

mg/kg (TWA)

Lead-copper-iron

alloy, 52,000 mg/kg

(TWA)

lead bullion, 3,900

mg/kg (TWA)

Arsenic trioxide

(concentration not

available)

MHO 7.9

TCLP = Toxicity Characteristic Leaching Procedure. TWA = Total Waste Analysis.-- = Not available HTMR = High Temperature Metals Recovery.MHO = Metallurgie-Hoboken-Overpelt process.
8-1

Contaminated Soil

WellWell

Surfactant, Cosolvent, 

or Water Mixture

Ground Surface

Contaminated Soil

WellWell

Surfactant, Cosolvent, 

or Water Mixture

Ground Surface

Model of an In Situ Flushing System

2

2

0123

Pilot

Full

Summary

Data gathered for this report show that in situ soil

flushing has been used to treat arsenic-contaminated

soils in a limited number of applications. Two

projects have been identified that are currently

operating at full scale, but performance results are

not yet available.

Technology Description: In situ soil flushing is a

technology that extracts organic and inorganic

contaminants from soil by using water, a solution of

chemicals in water, or an organic extractant, without

excavating the contaminated material itself. The

solution is injected into or sprayed onto the area of

contamination, causing the contaminants to become

mobilized by dissolution or emulsification. After

passing through the contamination zone, the

contaminant-bearing flushing solution is collected

by downgradient wells or trenches and pumped to

the surface for removal, treatment, discharge, or

reinjection (Ref. 8.1).

Media Treated:

• Soil (in situ)

8.0 IN SITU SOIL FLUSHING FOR ARSENIC

Technology Description and Principles

In situ soil flushing techniques may employ water or a

mixture of water and additives as the flushing solution. 

Additives may include acids (sulfuric, hydrochloric,

nitric, phosphoric, or carbonic acid), bases (for

example, sodium hydroxide), chelating or complexing

agents (such as EDTA), reducing agents, or surfactant

to aid in the desorption and dissolution of the target

contaminants (Ref. 8.1).

Subsurface containment barriers or other hydraulic

controls have sometimes been used in conjunction with

soil flushing to help control the flow of flushing fluids

and assist in the capture of the contaminated fluid. 

Impermeable membranes have also been used in some

cases to limit infiltration of groundwater, which could

cause dilution of flushing solutions and loss of

hydraulic control (Ref. 8.1). 

Media and Contaminants Treated

Soil flushing has been used to treat soils in situ

contaminated with organic, inorganic, and metal

contaminants (Ref. 8.1), including arsenic.

Type, Number, and Scale of Identified Projects

Treating Soil Containing Arsenic

The references identified for this report contained

information on two full-scale in situ soil flushing

projects for the treatment of arsenic at two Superfund

sites (Ref. 8.4), and two at pilot scale at two other sites

(Ref. 8.6, 8.7). At one of the Superfund sites, 150,000

cubic yards of soil are being treated, while at the other

19,000 cubic yards of soil are being treated. Figure 8.1

shows the number of projects identified at pilot and full

scale. 

Figure 8.1

Scale of Identified In Situ Soil Flushing Projects for

Arsenic Treatment

Summary of Performance Data

Arsenic treatment is ongoing at two Superfund sites

using in situ soil flushing, and has been completed at

two other sites (Ref. 8.3, 8.4, 8.6, 8.7). Performance

data for the Superfund site projects are not yet available
8-2

Case Study: Vineland Chemical Company

Superfund Site

The Vineland Chemical Company Superfund Site in

Vineland, New Jersey is a former manufacturing

facility for herbicides containing arsenic. Soils

were contaminated with arsenic from the improper

storage and disposal of herbicide by-product salts 

(RCRA waste code K031). Approximately 150,000

cubic yards of soil were treated. Pretreatment

arsenic concentrations were as high as 650 mg/kg. 

The soil was flushed with groundwater from the

site, which was extracted, treated to remove arsenic,

and reinjected into the contaminated soil. Because

the species of arsenic contaminating the soil is

highly soluble in water, the addition of surfactants

and cosolvents was not necessary. No data are

currently available on the treatment performance

(Ref. 8.3, 8.4, 8.8) (see Project 1, Table 8.1). The

remedy at this site was changed to soil washing in

order to reduce treatment cost and the time needed

to remediate the site. 

Factors Affecting Soil Flushing Performance

• Number of contaminants treated - The

technology works best when a single

contaminant is targeted. Identifying a flushing

fluid that can effectively remove multiple

contaminants may be difficult (Ref. 8.1). 

• Soil characteristics - Some soil characteristics

may effect the performance of soil flushing. 

For example, an acidic flushing solution may

have reduced effectiveness in an alkaline soil

(Ref. 8.1).

• Precipitation - Soil flushing may cause arsenic

or other chemicals in the soil to precipitate and

obstruct the soil pore structure and inhibit flow

through the soil (Ref. 8.1).

• Temperature - Low temperatures may cause

the flushing solution to freeze, particularly

when shallow infiltration galleries and aboveground sprays are used to apply the flushing

solution (8.1).

Factors Affecting Soil Flushing Costs

• Reuse of flushing solution - The ability to

reuse the flushing solution may reduce the cost

by reducing the amount of flushing solution

required (Ref. 8.1).

• Contaminant recovery - Recovery of

contaminants from the flushing solution and the

reuse or sale of recovered contaminants may be

possible in some cases (Ref. 8.3, 8.4).

• Factors affecting soil flushing performance -

Items in the “Factors Affecting Soil Flushing

Performance” box will also affect costs.

as the projects are ongoing. Performance data are also

not available for the other two projects. See Table 8.1

for information on these projects. The case study in this

section discusses in greater detail a soil flushing

application at the Vineland Chemical Company

Superfund Site. This information is summarized in

Table 8.1, Project 3.

Applicability, Advantages, and Potential Limitations

The equipment used for in situ soil flushing is relatively

easy to construct and operate, and the process does not

involve excavation or disposal of the soil, thereby

avoiding the expense and hazards associated with these

activities (Ref. 8.1). Spent flushing solutions may

require treatment to remove contaminants prior to reuse

or disposal. Treatment of flushing fluid results in

process sludges and residual solids, such as spent

carbon and spent ion exchange resin, which may require

treatment before disposal. In some cases, the spent

flushing solution may be discharged to a publiclyowned treatment works (POTW), or reused in the

flushing process. Residual flushing additives in the soil

may be a concern and should be evaluated on a sitespecific basis (Ref. 8.1). In addition, soil flushing may

cause contaminants to mobilize and spread to

uncontaminated areas of soil or groundwater.

Summary of Cost Data

No data are currently available on the cost of soil

flushing systems used to treat arsenic.

References

8.1. U.S. EPA. Engineering Bulletin. Technology

Alternatives for the Remediation of Soils

Contaminated with Arsenic, Cadmium,

Chromium, Mercury, and Lead. Office of

Emergency and Remedial Response. EPA 540-S97-500. March 1997. 

http://www.epa.gov/ncepi/Catalog/

EPA540S97500.html
8-3

8.2. U.S. EPA. Contaminants and Remedial Options

at Selected Metal-Contaminated Sites. Office of

Research and Development. EPA-540-R-95-512

July 1995. 

http://www.epa.gov/ncepi/Catalog/

EPA540R95512.html

8.3. U.S. EPA. Database for EPA REACH IT

(REmediation And CHaracterization Innovative

Technologies). March 2001. 

http://www.epareachit.org.

8.4. U.S. EPA. Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition). 

Office of Solid Waste and Emergency Response. 

EPA-542-R-01-004. February 2001. 

http://www.epa.gov/ncepi/Catalog/

EPA542R01004.html

8.5. U.S. EPA. Recent Developments for In Situ

Treatment of Metals Contaminated Soil. EPA

March 1997. http://clu-in.org

8.6 Redwine JC. Innovative Technologies for

Remediation of Arsenic in Soil and Groundwater. 

Southern Company Services, Inc. Presented at the

Air and Waste Management Association’s 93rd

Annual Conference and Exhibition, Salt Lake

City, June 2000.

8.7 Miller JP, Hartsfield TH, Corey AC, Markey RM. 

In Situ Environmental Remediation of an

Energized Substation. EPRI. Palo Alto, CA.

Report No. 1005169. 2001.

8.8 U.S. EPA. Vineland Chemical Company, Inc.

Fact Sheet. April 2002. 

http://www.epa.gov/region02/

superfund/npl/0200209c.pdf
8-4

Table 8.1

Arsenic In Situ Soil Flushing Performance Data for Arsenic

Project

Number

Industry or

Site Type

Waste or

Media Scale

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Soil Flushing Agent or

Process Source

1 Pesticide

manufacturing

Soil

(150,000 cy)

Full Vineland Chemical

Company Superfund

Site, Operable Unit 01

Vineland, NJ

20 - 650 mg/kg

(TWA)

-- Flushing with groundwater

followed by extraction,

treatment, and reuse to flush

soil. Project was changed to

soil washing prior to

completion.

8.3, 8.4,

8.8

2 Primary

aluminum

production

Soil 

(19,000 cy)

Full Ormet Superfund Site,

Hannibal, OH

-- 0.027 mg/L Flushing with water followed

by extraction, treatment, and

discharge to surface water

under an NPDES permit. 

Project completion is

expected in 2007.

8.3, 8.4

3 Power

substation

Soil Pilot Ft. Walton Beach, FL -- -- Flushing with 0.01 M

phosphoric acid.

8.7

4 Power

substation

Soil Pilot Florida -- -- Treatment train consisting of

flushing with citric acid

followed by iron

coprecipitation and ceramic

membrane filtration.

8.6

mg/kg = milligrams per kilogram mg/L = milligrams per liter-- = Not available TWA = Total waste analysis
IIB

ARSENIC TREATMENT TECHNOLOGIES

APPLICABLE TO WATER
9 - 1

Oxidation/ 

Reduction 

(Pretreatment 

Process)

Groundwater

Solids to 

Disposal

Sludge 

Dewatering

Filtrate

Sludge Sludge 

Thickening

Thickener 

Overflow

pH Adjustment and Flocculation

Reagent Addition

Reagent Polymer

Effluent

Clarification

Oxidation/ 

Reduction 

(Pretreatment 

Process)

Groundwater

Solids to 

Disposal

Sludge 

Dewatering

Filtrate

Sludge Sludge 

Thickening

Thickener 

Overflow

pH Adjustment and Flocculation

Reagent Addition

Reagent Polymer

Effluent

Clarification

Model of a Precipitation/Coprecipitation System

Summary

Precipitation/coprecipitation has been the most

frequently used method to treat arseniccontaminated water, including groundwater, surface

water, leachate, mine drainage, drinking water, and

wastewater in numerous pilot- and full-scale

applications. Based on the information collected to

prepare this report, this technology typically can

reduce arsenic concentrations to less than 0.050

mg/L and in some cases has reduced arsenic

concentrations to below 0.010 mg/L. 

Technology Description: Precipitation uses

chemicals to transform dissolved contaminants into

an insoluble solid. In coprecipitation, the target

contaminant may be dissolved or in a colloidal or

suspended form. Dissolved contaminants do not

precipitate, but are adsorbed onto another species

that is precipitated. Colloidal or suspended

contaminants become enmeshed with other

precipitated species, or are removed through

processes such as coagulation and flocculation.

Many processes to remove arsenic from water

involve a combination of precipitation and

coprecipitation. The precipitated/coprecipitated

solid is then removed from the liquid phase by

clarification or filtration. Arsenic precipitation/

coprecipitation can use combinations of the

chemicals and methods listed below.

Media Treated:

• Drinking water

• Groundwater

• Wastewater

• Surface water

• Leachate

• Mine drainage

Chemicals and Methods Used for Arsenic

Precipitation/Coprecipitation:

• Ferric salts, (e.g.,

ferric chloride), ferric

sulfate, ferric

hydroxide

• Ammonium sulfate

• Alum (aluminum

hydroxide)

• pH adjustment

• Lime softening,

limestone, calcium

hydroxide

• Manganese sulfate

• Copper sulfate

• Sulfide

9.0 PRECIPITATION/COPRECIPITATION

FOR ARSENIC

Technology Description and Principles

For this report, technologies were considered

precipitation/coprecipitation if they involved the 

following steps:

• Mixing of treatment chemicals into the water

• Formation of a solid matrix through precipitation,

coprecipitation, or a combination of these

processes, and

• Separation of the solid matrix from the water

Technologies that remove arsenic by passing it through

a fixed bed of media, where the arsenic may be

removed through adsorption, precipitation/

coprecipitation, or a combination of these processes, are

discussed in the adsorption treatment section (Section

11.0).

Precipitation/coprecipitation usually involves pH

adjustment and addition of a chemical precipitant or

coagulant; it can also include addition of a chemical

oxidant (Ref. 9.1). Oxidation of arsenic to its less

soluble As(V) state can increase the effectiveness of
9 - 2

Precipitation/Coprecipitation Chemistry

The chemistry of precipitation/coprecipitation is

often complex, and depends upon a variety of

factors, including the speciation of arsenic, the

chemical precipitants used and their concentrations,

the pH of the water, and the presence of other

chemicals in the water to be treated. As a result, the

particular mechanism that results in the removal of

arsenic through precipitation/coprecipitation

treatment is process-specific, and in some cases is

not completely understood. For example, the

removal mechanism in the treatment of As(V) with

Fe(III) has been debated in the technical literature

(Ref. 9.33). 

It is beyond the scope of this report to provide all

possible chemical reactions and mechanisms for

precipitation/coprecipitation processes that are used

to remove arsenic. More detailed information on the

chemistry involved in specific processes can be

found in the references listed at the end of this

section.

45

24

0 10 20 30 40 50

Pilot

Full

precipitation/coprecipitation processes, and can be done

as a separate pretreatment step or as part of the

precipitation process. Some pretreatment processes that

oxidize As(III) to As(V) include ozonation, photo

oxidation, or the addition of oxidizing chemicals such

as potassium permanganate, sodium hypochlorite, or

hydrogen peroxide (Ref. 9.8, 9.16, 9.22, 9.25, 9.29). 

Clarification or filtration are commonly used to remove

the solid precipitate. 

Media and Contaminants Treated

Precipitation/coprecipitation is frequently used to treat

water contaminated with metals (Ref. 9.1). The

references identified for this report contained

information on its application to industrial wastewater,

groundwater, surface water, leachate, and mine

drainage. 

Type, Number, and Scale of Identified Projects

Treating Water Containing Arsenic

Precipitation/coprecipitation processes for arsenic in

drinking water, groundwater, and industrial wastewater

are commercially available. The data gathered in

support of this report include information on its fullscale application at 16 sites. Information on full-scale

treatment of drinking water is available for eight

facilities and of industrial wastewater for 21 facilities. 

Information on 24 pilot-scale applications was also

identified. Figure 9.1 shows the number of pilot- and

full-scale precipitation/coprecipitation projects in the

sources researched. 

Figure 9.1

Scale of Identified Precipitation/Coprecipitation

Projects for Arsenic Treatment

Summary of Performance Data

Table 9.1 presents the available performance data for

pilot- and full-scale precipitation/coprecipitation

treatment. It contains information on 69 applications,

including 20 groundwater, surface water, and mine

drainage, 15 drinking water, and 34 industrial

wastewater projects. The information that appears in

the "Precipitating Agent or Process" column of Table

9.1, including the chemicals used, the descriptions of

the processes, and whether it involved precipitation or

coprecipitation, is based on the cited references. This

information was not independently checked for

accuracy or technical feasability. For example, in some

cases, the reference used may apply the term

"precipitation" to a process that is actually

coprecipitation.

The effectiveness of this technology can be evaluated

by comparing influent and effluent contaminant

concentrations. All of the 12 environmental media

projects for which both influent and effluent arsenic

concentration data were available had influent

concentrations greater than 0.050 mg/L. The treatments

achieved effluent concentrations of less than 0.050

mg/L in eight of the projects and less than 0.010 mg/L

in four of the projects. Information on the leachability

of arsenic from the precipitates and sludges was

available for three projects. For all of these projects, the

concentration of leachable arsenic as measured by the

toxicity characteristic leaching procedure (TCLP) (the

RCRA regulatory threshold for identifying a waste that

is hazardous because it exhibits the characteristic of

toxicity for arsenic) was below 5.0 mg/L.
9 - 3

Factors Affecting Precipitation/Coprecipitation

Performance

• Valence state of arsenic - The presence of the

more soluble trivalent state of arsenic may

reduce the removal efficiency. The solubility of

arsenic depends upon its valence state, pH, the

specific arsenic compound, and the presence of

other chemicals with which arsenic might react

(Ref. 9.12). Oxidation to As(V) could improve

arsenic removal through precipitation/

coprecipitation (Ref. 9.7).

• pH - In general, arsenic removal will be

maximized at the pH at which the precipitated

species is least soluble. The optimal pH range

for precipitation/coprecipitation depends upon

the waste treated and the specific treatment

process (Ref. 9.7).

• Presence of other compounds - The presence

of other metals or contaminants may impact the

effectiveness of precipitation/coprecipitation. 

For example, sulfate could decrease arsenic

removal in processes using ferric chloride as a

coagulant, while the presence of calcium or iron

may increase the removal of arsenic in these

processes (Ref. 9.7).

Case Study: Winthrop Landfill Site

The Winthrop Landfill Site, located in Winthrop,

Maine, is a former dump site that accepted

municipal and industrial wastes (See Table 9.1,

Project 1). Groundwater at the site was

contaminated with arsenic and chlorinated and

nonchlorinated VOCs. A pump-and-treat system for

the groundwater has been in operation at the site

since 1995. Organic compounds have been

remediated to below action levels, and the pumpand-treat system is currently being operated for the

removal of arsenic alone. The treatment train

consists of equalization/pH adjustment to pH 3,

chemical oxidation with hydrogen peroxide,

precipitation/coprecipitation via pH adjustment to

PH 7, flocculation/clarification, and sand bed

filtration. It treats 65 gallons per minute of

groundwater containing average arsenic

concentrations of 0.3 mg/L to below 0.005 mg/L. 

Through May, 2001, 359 pounds of arsenic had

been removed from groundwater at the Winthrop

Landfill Site using this above ground treatment

system. Capital costs for the system were about $2

million, and O&M costs are approximately

$250,000 per year (Ref. 9.29, cost year not

provided).

Of the 12 drinking water projects having both influent

and effluent arsenic concentration data, eight had

influent concentrations greater than 0.050 mg/L. The

treatments achieved effluent concentrations of less than

0.050 mg/L in all eight of these projects, and less than

0.010 mg/L in two projects. Information on the

leachability of arsenic from the precipitates and sludges

was available for six projects. For these projects the

leachable concentration of arsenic was below 5.0 mg/L.

All of the 28 wastewater projects having both influent

and effluent arsenic concentration data had influent

concentrations greater than 0.050 mg/L. The treatments

achieved effluent concentrations of less than 0.050

mg/L in 16 of these projects, and less than 0.010 mg/L

in 11 projects. Information on the leachability of

arsenic from the precipitates and sludges was available

for four projects. Only one of these projects had a

leachable concentration of arsenic below 5.0 mg/L.

Projects that did not reduce effluent arsenic

concentrations to below 0.050 or 0.010 mg/L do not

necessarily indicate that precipitation/coprecipitation

cannot achieve these levels. The treatment goal for

some applications could have been above these

concentrations, and the technology may have been

designed and operated to meet a higher concentration. 

Information on treatment goals was not collected for

this report. 

Some projects in Table 9.1 include treatment trains, the

most common being precipitation/coprecipitation 

followed by activated carbon adsorption or membrane

filtration. In those cases, the performance data listed

are for the entire treatment train, not just the

precipitation/coprecipitation step.

The case study in this section discusses in greater detail

the removal of arsenic from groundwater using an

aboveground treatment system at the Winthrop Landfill

Superfund site. This information is summarized in

Table 9.1, Project 1.

Applicability, Advantages, and Potential Limitations

Precipitation/coprecipitation is an active ex situ

treatment technology designed to function with routine

chemical addition and sludge removal. It usually

generates a sludge residual, which typically requires

treatment such as dewatering and subsequent disposal. 

Some sludge from the precipitation/coprecipitation of

arsenic can be a hazardous waste and require additional

treatment such as solidification/stabilization prior to

disposal. In the presence of other metals or
9 - 4

Factors Affecting Precipitation/Coprecipitation

Costs

• Type of chemical addition - The chemical

added will affect costs. For example, calcium

hypochlorite, is a less expensive oxidant than

potassium permanganate (Ref. 9.16).

• Chemical dosage - The cost generally

increases with increased chemical addition. 

Larger amounts of chemicals added usually

results in a larger amount of sludge requiring

additional treatment or disposal (Ref. 9.7,

9.12).

• Treatment goal - Application could require

additional treatment to meet stringent cleanup

goals and/or effluent and disposal standards

(Ref. 9.7)

• Sludge disposal - Sludge produced from the

precipitation/coprecipitation process could be

considered a hazardous waste and require

additional treatment before disposal, or disposal

as hazardous waste (Ref. 9.7).

• Factors affecting

precipitation/coprecipitation performance -

Items in the “Factors Affecting

Precipitation/Coprecipitation Performance” box

will also affect costs.

contaminants, arsenic precipitation/coprecipitation

processes may also cause other compounds to

precipitate, which can render the resulting sludge

hazardous (Ref. 9.7). The effluent may also require

further treatment, such as pH adjustment, prior to

discharge or reuse.

More detailed information on selection and design of

arsenic treatment systems for small drinking water

systems is available in the document “Arsenic

Treatment Technology Design Manual for Small

Systems “ (Ref. 9.36).

Summary of Cost Data

Limited cost data are currently available for

precipitation/coprecipitation treatment of arsenic. At

the Winthrop Landfill Site (Project 1), groundwater

containing arsenic, 1,1-dichloroethane, and vinyl

chloride is being pumped and treated above ground

through a treatment train that includes precipitation. 

The total capital cost of this treatment system was $2

million ($1.8 million for construction and $0.2 million

for design). O&M costs were about $350,000 per year

for the first few years and are now approximately

$250,000 per year. The treatment system has a capacity

of 65 gpm. However, these costs are for the entire

treatment train (Ref. 9.29, cost year not provided). At

the power substation in Fort Walton, Florida, (Table

9.1, Project 4), the reported O&M cost was $0.006 per

gallon (for the entire treatment train, Ref 9.32, cost year

not provided). Capital cost information was not

provided.

A low-cost, point-of-use precipitation/coprecipitation

treatment designed for use in developing nations with

arsenic-contaminated drinking water was pilot-tested in

four areas of Bangladesh (Project 31). This simple

treatment process consists of a two-bucket system that

uses potassium permanganate and alum to precipitate

arsenic, followed by sedimentation and filtration. The

equipment cost of the project was approximately $6,

and treatment of 40 liters of water daily would require a

monthly chemical cost of $0.20 (Ref. 9.22, cost year not

provided). 

The document "Technologies and Costs for Removal of

Arsenic From Drinking Water" (Ref. 9.7) contains more

information on the cost of systems to treat arsenic in

drinking water to below the revised MCL of 0.010

mg/L. The document includes capital and O&M cost

curves for three precipitation/coprecipitation processes:

• Enhanced coagulation/filtration

• Enhanced lime softening

• Coagulation assisted microfiltration

These cost curves are based on computer cost models

for drinking water treatment systems. Table 3.4 in

Section 3 of this document contains cost estimates

based on these curves for coagulation assisted

microfiltration. The cost information available for

enhanced coagulation/ filtration and enhanced lime

softening are for retrofitting existing

precipitation/coprecipitation systems at 

drinking water treatment plants to meet the revised

MCL. Therefore, the cost information could not be

used to estimate the cost of a new precipitation/

coprecipitation treatment system. 

References

9.1 Federal Remediation Technologies Reference

Guide and Screening Manual, Version 3.0. 

Federal Remediation Technologies Roundtable

http://www.frtr.gov./matrix2/top_page.html

9.2 Twidwell, L.G., et al. Technologies and

Potential Technologies for Removing Arsenic

from Process and Mine Wastewater. Presented

at "REWAS '99." San Sebastian, Spain. 

September 1999.

http://www.mtech.edu/metallurgy/arsenic/

REWASAS%20for%20proceedings99%20in%2

0word.pdf
9 - 5

9.3 U.S. EPA. Final Best Demonstrated Available

Technology (BDAT) Background Document for

K031, K084, K101, K102, Characteristic Arsenic

Wastes (D004), Characteristic Selenium Wastes

(D010), and P and U Wastes Containing Arsenic

and Selenium Listing Constituents. Office of

Solid Waste. May 1990.

9.4 U.S. EPA. Best Demonstrated Available

Technology (BDAT) Background Document for

Wood Preserving Wastes: F032, F034, and

F035; Final. April, 1996. http://www.epa.gov/

epaoswer/hazwaste/ldr/wood/bdat_bd.pdf

9.5 U.S. EPA. Pump and Treat of Contaminated

Groundwater at the Baird and McGuire

Superfund Site, Holbrook, Massachusetts.

Federal Remediation Technologies Roundtable. 

September, 1998. 

http://www.frtr.gov/costperf.html. 

9.6 U.S. EPA. Development Document for Effluent

Limitations Guidelines and Standards for the

Centralized Waste Treatment Industry. 

December, 2000.

http://www.epa.gov/ost/guide/cwt/final/

devtdoc.html

9.7 U.S. EPA. Technologies and Costs for Removal

of Arsenic From Drinking Water. EPA-R-00-

028. Office of Water. December, 2000.

http://www.epa.gov/safewater/ars/

treatments_and_costs.pdf

9.8 U.S. EPA. Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition).

Office of Solid Waste and Emergency Response.

EPA-542-R-01-004. February 2001.

http://www.epa.gov/ncepi/Catalog/

EPA542R01004.html

9.9 U.S. EPA National Risk Management Research

Laboratory. Treatability Database.

9.10 U.S. EPA Technology Innovation Office. 

Database for EPA REACH IT (REmediation

And CHaracterization Innovative Technologies).

http://www.epareachit.org. March, 2001.

9.11 Electric Power Research Institute. Innovative

Technologies for Remediation of Arsenic in Soil

Groundwater: Soil Flushing, In-Situ Fixation,

Iron Coprecipitation, and Ceramic Membrane

Filtration. http://www.epri.com. 1996.

9.12 U.S. EPA Office of Research and Development. 

Contaminants and Remedial Options at Selected

Metal-Contaminated Sites. EPA/540/R-95/512. 

July, 1995. http://search.epa.gov/s97is.vts

9.13 U.S. EPA Office of Solid Waste and Emergency

Response. 1997 Biennial Reporting System

Database.

9.14 U.S. EPA. Groundwater Remedies Selected at

Superfund Sites. EPA 542-R-01-022. January,

2002. http://clu-in.org

9.15 U.S. EPA. Groundwater Pump and Treat

Systems: Summary of Selected Cost and

Performance Information at Superfund-financed

Sites. EPA-542-R-01-021b. EPA OSWER. 

December 2001. http://clu-in.org

9.16 MSE Technology Applications, Inc. Arsenic

Oxidation Demonstration Project - Final Report. 

January 1998. http://www.arsenic.org/

PDF%20Files/Mwtp-84.pdf

9.17 Vendor information provided by MSE

Technology Applications, Inc. 

9.18 HYDRO-Solutions and Purification. June 28,

2001. http://www.mosquitonet.com/~hydro

9.19 DPHE-Danida Arsenic Mitigation Pilot Project. 

June 28, 2001. 

http://phys4.harvard.edu/~wilson/

2bucket.html. 

9.20 Environmental Research Institute. Arsenic

Remediation Technology - AsRT. June 28,

2001. http://www.eng2.uconn.edu/~nikos/

asrt-brochure.html 

9.21 A Simple Household Device to Remove Arsenic

from Groundwater Hence Making it Suitable for

Drinking and Cooking. June 28, 2001

http://phys4.harvard.edu/~wilson/

asfilter1. html 

9.22 Appropriate Remediation Techniques for

Arsenic-Contaminated Wells in Bangladesh.

June 28, 2001. http://phys4.harvard.edu/

~wilson/murcott.html

9.23 Redox Treatment of Groundwater to Remove

Trace Arsenic at Point-of-Entry Water Treatment

Systems. June 28, 2001

http://phys4.harvard.edu/~wilson/Redox/

Desc.html 

9.24 U.S. EPA Office of Water. Arsenic in Drinking

Water. August 3, 2001. http://www.dainichiconsul.co.jp/english/arsenic/treat1.htm. 

9.25 U.S. EPA Office of Research and Development. 

Arsenic Removal from Drinking Water by

Coagulation/Filtration and Lime Softening

Plants. EPA/600/R-00/063. June, 2000.

http://www.epa.gov/ncepi/Catalog/

EPA600R00063.html

9.26 U.S. EPA and NSF International. ETV Joint

Verification Statement for Chemical

Coagulant/Filtration System Used in Packaged

Drinking Water Treatment Systems. March,

2001. 

9.27 FAMU-FSU College of Engineering. Arsenic

Remediation. August 21, 2001.

http://www.eng.fsu.edu/departments/civil/

research/arsenicremedia/index.htm 

9.28 U.S. EPA. Contaminants and Remedial Options

at Selected Metal-Contaminated Sites. Office of

Research and Development. EPA-540-R-95-

512. July 1995.
9 - 6

9.29 E-mail attachment sent from Anni Loughlin of

U.S. EPA Region I to Linda Fiedler, U.S. EPA. 

August 21, 2001.

9.30 U.S. EPA. Arsenic & Mercury - Workshop on

Removal, Recovery, Treatment, and Disposal. 

Office of Research and Development. EPA-600-

R-92-105. August 1992.

9.31 U.S. EPA. Profiles of Metal Recovery

Technologies for Mineral Processing and Other

Metal-Bearing Hazardous Wastes. December

1994.

9.32 Miller JP, Hartsfield TH, Corey AC, Markey

RM. In Situ Environmental Remediation of an

Energized Substation. EPRI. Palo Alto, CA.

Report No. 1005169. 2001.

9.33 Robins, Robert G. Some Chemical Aspects

Relating To Arsenic Remedial Technologies. 

Proceedings of the U.S. EPA Workshop on

Managing Arsenic Risks to the Environment. 

Denver, Colorado. May 1-3, 2001.

9.34 E-mail from Bhupi Khona, U.S. EPA Region 3 to

Sankalpa Nagaraja, Tetra Tech EM, Inc.,

regarding Groundwater Pump-and-Treat of

Arsenic at the Whitmoyer Laboratories

Superfund site. May 3, 2002.

9.35 Hydroglobe LLC. Removal of Arsenic from

Bangladesh Well Water by the Stevens

Technology for Arsenic Removal (S.T.A.R.). 

Hoboken, NJ. http://www.hydroglobe.net.

9.36 U.S. EPA. Arsenic Treatment Technology

Design Manual for Small Systems (100% Draft

for Peer Review). June 2002. 

http://www.epa.gov/ safewater/smallsys/

arsenicdesignmanualpeerreviewdraft.pdf
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic

9 - 7

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

Environmental Media- Coagulation/Filtration

1 Landfill Groundwater Full Winthrop

Landfill

Superfund Site,

Winthrop, ME

0.300 mg/L <0.005 mg/L -- Treatment train

consisting of pH

adjustment,

oxidation,

flocculation/

clarification, air

stripping, and sandbed filtration

9.29

2 Metal ore mining

and smelting

Surface water,

8,500,000

gallons

Full Tex-Tin 

Superfund Site,

OU 1, TX

-- -- -- Precipitation by pH

adjustment followed

by filtration

9.8

Environmental Media - Iron Coprecipitation

3 Herbicide

application 

Groundwater Full -- 0.005 - 3.8 mg/L <0.005 - 0.05

mg/L

<5 mg/L

(TCLP)

Iron coprecipitation

followed by 

membrane filtration

9.27

4 Power substation Groundwater,

44 million

gallons

Full Ft. Walton

Beach, FL

0.2-1.0 mg/L <0.005 mg/L -- Iron coprecipitation

followed by ceramic

membrane filtration

9.32

5 Chemical mixing Groundwater,

43,000 gpd

Full Baird and

McGuire

Superfund Site,

Holbrook, MA

-- -- -- Treatment train

consisting of air

stripping,

precipitation (ferric

chloride, lime slurry,

phosphoric and

sulfuric acids, and

ammonium sulfate),

filtration, and carbon

adsorption.

9.5, 9.15
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 8

6 Wood preserving

wastes

Groundwater Full Silver Bow

Creek/Butte

Area Superfund

Site - Rocker

Timber Framing

And Treatment

Plant OU, MT

-- -- -- In situ treatment of

contaminated

groundwater by

injecting a solution

of ferrous iron,

limestone, and

potassium

permanganate

9.8

7 Metal ore mining

and smelting

activities

Collection

pond water

Pilot Ryan Lode

Mine, AK

4.6 mg/L 0.027 mg/L -- Enhanced iron coprecipitation

followed by filtration

9.18

8 Herbicide

application

Groundwater Pilot -- 1 mg/L (TWA) <0.005 mg/L

(TWA)

-- Iron coprecipitation

followed by ceramic

membrane filtration

9.11

9 Metal ore mining Acid mine

water 

Pilot Susie

Mine/Valley

Forge site,

Rimini, MT

12.2 - 16.5 mg/L 0.017 - 0.053

mg/L

8,830-13,300

mg/kg

0.0051-0.0076

mg/L (TCLP)

Photo-oxidation of

arsenic followed by

iron coprecipitation

 9.16

10 Metals

processing

Leachate from

nickel roaster

flue dust

disposal area

Pilot Susie

Mine/Valley

Forge site,

Rimini, MT

423 - 439 mg/L <0.32 mg/L 102,000 mg/kg

0.547-0.658

mg/L (TCLP)

Photo-oxidation of

arsenic followed by

iron coprecipitation

9.16

Environmental Media - Other or Unspecified Precipitation Process

11 -- "Superfund

wastewater"

Full -- 0.1 - 1 mg/L 0.022 mg/L -- Chemical

precipitation

9.9

12 -- Groundwater Full -- 100 mg/L < 0.2 mg/L -- Precipitation 9.1713 -- "Superfund

wastewater"

Full -- 0.1 - 1 mg/L 0.110 mg/L -- Chemical

precipitation

9.9
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 9

14 -- Groundwater Full -- 100 mg/L <0.010 mg/L -- Reductive

Precipitation

(additional

information not

available)

9.17

15 Chemical

manufacturing

wastes,

groundwater

Groundwater Full Peterson/Puritan

Inc. Superfund

Site - OU 1,

PAC Area, RI

-- -- -- In-situ treatment of

arsenic-contaminated

groundwater by

injecting oxygenated

water

9.8

16 Chemical

manufacturing

Groundwater,

65,000 gpd

Full Greenwood

Chemical

Superfund Site,

Greenwood, VA

-- -- -- Treatment train

consisting of metals

precipitation,

filtration, UV

oxidation and carbon

adsorption

9.15

17 Waste disposal Groundwater,

43,000 gpd

Full Higgins Farm

Superfund Site,

Franklin

Township, NJ

-- -- -- Treatment train

consisting of air

stripping, metals

precipitation,

filtration, and ion

exchange 

9.15

18 Wood preserving Groundwater,

3,000 gpd

Full Saunders Supply

Company

Superfund Site,

Chuckatuck, VA

-- -- -- Treatment train

consisting of metals

precipitation,

filtration, and carbon

adsorption.

9.15

19 Herbicide

manufacturing

RCRA waste

code K031,

1 mgd

Full Vineland

Chemical

Company

Superfund Site,

Vineland, NJ

-- -- -- Metals precipitation

followed by filtration

9.15
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 10

20 Veterinary feed

additives and

pharmaceuticals

manufacturing

Groundwater,

50-100 gpm

Full Whitmoyer

Laboratories

Superfund Site

100 mg/L 0.025 mg/L -- Neutralization and

flocculation by

increasing pH to 9

9.34

Drinking Water - Iron Coprecipitation

21 -- Drinking water,

1.6 mgd

Full -- 0.0203 mg/L

(TWA)

0.0030 mg/L

(TWA)

<5 mg/L (WET) Ferric

coprecipitation

followed by zeolite

softening

9.7

22 -- Drinking water,

1.4 mgd

Full -- 0.0485 mg/L

(TWA)

0.0113 mg/L

(TWA)

<5 mg/L (WET) Ferric

coprecipitation

9.7

23 -- Drinking water Full McGrath Road

Baptist Church,

AK

0.370 mg/L <0.005 mg/L -- Enhanced iron co -

precipitation

followed by filtration

9.18

24 -- Drinking water,

600 mgd

Full -- 0.0026 - 0.0121

mg/L

0.0008 - 0.006

mg/L

806-880 mg/kg

<0.05-0.106

mg/L (TCLP)

Ozonation followed

by coagulation with

iron- and aluminumbased additives and

filtration

9.25

25 -- Drinking water,

62.5 mgd

Full -- 0.015 - 0.0239

mg/L

0.0015 - 0.0118

mg/L

293-493 mg/kg

0.058-0.114

mg/L (TCLP)

Coagulation with

iron and aluminum

based additives,

sedimentation, and

filtration

9.25

26 -- Drinking water Full -- Plant A: 0.02

mg/L

Plant B: 0.049

mg/L

Plant A: 0.003

mg/L

Plant B: 0.012

mg/L

-- Adsorption and

coprecipitation with

iron hydroxide

precipitates

9.10

27 -- Drinking water Pilot -- -- <0.002 mg/L 

Arsenic (V)

-- Iron coagulation

with direct filtration

9.24
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 11

28 – Drinking water,

5.3 gallons

Pilot Bhariab &

Sreenagar

Thana,

Bangladesh

0.28 - 0.59 mg/L <0.03 - 0.05 mg/L 1194 mg/kg Iron co -

precipitation

followed by filtration

9.35

Drinking Water - Lime Softening

29 -- Drinking water Full 5 facilities, 

identification

unknown

-- <0.003 mg/L

(TWA)

<5 mg/L

(TCLP)

Lime softening at 

pH >10.2

9.7

30 -- Drinking water, 

10 mgd

Full -- 0.0159 - 0.0849

mg/L

0.0063 - 0.0331

mg/L

17.0-35.3 mg/kg

<0.05 mg/L

(TCLP)

Oxidation followed

by lime softening

and filtration

9.25

Drinking Water - Point-of-Use Systems

31 -- Drinking water Pilot Harian Village

Rajshaji District

Bangladesh

0.092 - 0.120

mg/L

0.023 - 0.036

mg/L

-- Naturally-occurring

iron at 9 mg/L

facilitates

precipitation,

followed by

sedimentation,

filtration and

acidification

9.22

32 -- Drinking water Pilot West Bengal,

India

0.300 mg/L 0.030 mg/L -- Precipitation with

sodium hypochlorite

and alum, followed

by mixing,

flocculation,

sedimentation, and

up-flow filtration

9.22

33 -- Drinking water, 

40 liters per

day

Pilot Noakhali,

Bangladesh

0.12 - 0.46 mg/L <0.05 mg/L -- Coagulation with

potassium

permanganate andalum, followed bysedimentation and

filtration

9.19
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 12

34 -- Drinking water, 

 1.0-1.1 gpm

Pilot Spiro Tunnel

Water Filtration

Plant, Park City,

UT

0.0609 - 0.146

mg/L

0.0012 - 0.0345

mg/L

-- Precipitation with

ferric chloride and

sodium hypochlorite,

followed by filtration

9.26

35 -- Drinking water, 

20 liters per

day

Pilot West Bengal,

India

-- -- -- Precipitation by

ferric salt, oxidizing

agent, and activated

charcoal, followed

by sedimentation and

filtration

9.21

Wastewaters - Lime Softening

36 Veterinary

pharmaceuticals

K084,

wastewater

Full Charles City,

Iowa

399 - 1,670 mg/L

(TWA)

Calcium arsenate,

60.5 - 500 mg/L

(TWA)

45,200 mg/kg

(TWA) 2,200

mg/L (TCLP)

Calcium hydroxide 9.3

37 -- Wastewater Full -- 4.2 mg/L (TWA) 0.51 mg/L (TWA) -- Lime precipitation

followed by

sedimentation

9.4

38 -- Wastewater Full -- 4.2 mg/L (TWA) 0.34 mg/L (TWA) -- Lime precipitation

followed by

sedimentation and

filtration

9.4

39 -- Wastewater Full BP Minerals

America

-- -- Calcium

arsenate and

calcium arsenite,

1,900 - 6,900

mg/kg (TWA)

0.2 - 74.5 mg/L

(EP Tox)

Lime 9.3
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 13

Wastewaters - Metal Sulfates

40 Veterinary

pharmaceuticals

K084,

wastewater

Full Charles City,

Iowa

125 - 302 mg/L

(TWA)

Manganese

arsenate, 6.02 -

22.4 mg/L (TWA)

47,400 mg/kg

(TWA) 984

mg/L (TCLP)

Manganese sulfate 9.3

41 Metals

processing

Spent leachate

from the

recovery of Cu,

Ag, and Sb

from ores

(amount not

available)

Full Equity Silver

Mine, Houston,

British

Columbia,

Canada

-- -- 95 to 98%

recovery of

arsenic

Acid addition, 

chemical

precipitation with

copper sulfate, and

filtration

9.30

42 Metals

processing

Leachate from

filter cake from

purification of

zinc sulfate

electrowinning

solution

(amount not

available)

Full Texasgulf

Canada,

Timmons,

Ontario, Canada

-- -- 98% recovery of

arsenic

Acid addition, 

chemical

precipitation with

copper sulfate, and

filtration

9.30

Wastewaters - Iron Coprecipitation

43 -- Wastewater

from wet

scrubbing of

incinerator vent

gas (D004,

P011)

Full American

NuKem

69.6 - 83.7 mg/L

(TWA)

<0.02 - 0.6 mg/L

(TWA)

-- Chemical oxidation

followed by

precipitation with

ferric salts

9.3

44 Veterinary

pharmaceuticals

K084,

wastewater

Full Charles City,

Iowa

15 - 107 mg/L

(TWA)

Ferric arsenate, 

0.163 - 0.580

mg/L (TWA)

9,760 mg/kg

(TWA) 

0.508 mg/L

(TCLP)

Ferric sulfate 9.3
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 14

Wastewaters - Other or Unspecified Precipitation Process

45 -- Wastewater Full -- <0.1 - 3.0 mg/L

(TWA)

0.18 mg/L 

(average, TWA)

-- Chemical reduction

followed by

precipitation,

sedimentation, and

filtration

9.4

46 Centralized waste

treatment

industry

Wastewater Full -- 57 mg/L (TWA) 0.181 mg/L

(TWA)

-- Primary precipitation

with solids-liquid

separation

9.6

47 Centralized waste

treatment

industry

Wastewater Full -- 57 mg/L (TWA) 0.246 mg/L

(TWA)

-- Primary precipitation

with solids-liquid

separation followed

by secondary

precipitation with

solids-liquid

separation

9.6

48 Centralized waste

treatment

industry

Wastewater Full -- 57 mg/L (TWA) 0.084 mg/L

(TWA)

-- Primary precipitation

with solids-liquid

separation followed

by secondary

precipitation with

solids-liquid

separation and

multimedia filtration

9.6

49 Centralized waste

treatment

industry

Wastewater Full -- 57 mg/L (TWA) 0.011 mg/L

(TWA)

-- Selective metals

precipitation, solidsliquid separation,

secondary

precipitation, solidsliquid separation,

tertiary precipitation,

and solid-liquid

separation

9.6
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 15

50 Chemical and

allied products

Wastewater Full -- 0b. - 0.1 mg/L

(TWA)

0.0063 mg/L

(TWA)

-- Chemically assisted

clarification 

9.9

51 -- Domestic

wastewater

Full -- 0b. - 0.1 mg/L

(TWA)

0.0015 mg/L

(TWA)

-- Chemical

precipitation

9.9

52 Transportation

equipment

industry

Wastewater Full -- 0.1 - 1 mg/L

(TWA)

<0.002 mg/L

(TWA)

-- Chemical

precipitation and

filtration

9.9

53 Chemicals and

allied products

Wastewater Full -- 0.1 - 1 mg/L

(TWA)

0.028 mg/L

(TWA)

-- Chemically assisted

clarification

9.9

54 WR Metals

Industries

(WRMI) arsenic

leaching process

Metals

processing

Leachate from

arsenical fluedusts from nonferrous

smelters

(amount not

available)

Full WR Metals

Industries

(location not

available)

110,000 - 550,000

mg/kg (TWA)

-- -- Chemical

precipitation and

filtration

9.31

55 Metals

processing

Spent leachate

from the

recovery of Ag

from ores

(amount not

available)

Full Sheritt Gordon

Mines, LTD.,

Fort

Saskatchewan,

Alberta, Canada

-- -- -- Chemical

precipitation and

filtration

9.30

56 MetallurgieHobokenOverpelt (MHO)

solvent extraction

process

Metals

processing

Spent

electrolyte

from Cu

refining

(amount not

available)

Full Olen, Belgium -- -- 99.96%

recovery of

arsenic

Chemical

precipitation and

filtration 

9.31

57 Electric, gas, and

sanitary

Wastewater Pilot -- 0b. - 0.1 mg/L

(TWA)

0.0028 mg/L

(TWA)

-- Chemically assisted

clarification

9.9

58 Primary metals Wastewater Pilot -- 0b. - 0.1 mg/L

(TWA)

<0.0015 mg/L

(TWA)

-- Chemical

precipitation

9.9
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 16

59 -- Wastewater

bearing

unspecified

RCRA listed

waste code

Pilot -- 0b. - 0.1 mg/L

(TWA)

0.001 mg/L

(TWA)

-- Chemical

precipitation,

activated carbon

adsorption, and

filtration

9.9

60 -- Domestic

wastewater

Pilot -- 0b. - 0.1 mg/L

(TWA)

0.001 mg/L

(TWA)

-- Chemical

precipitation

9.9

61 -- Wastewater

bearing

unspecified

RCRA listed

waste code

Pilot -- 0.1 - 1 mg/L

(TWA)

0.012 mg/L

(TWA)

-- Chemical

precipitation,

activated carbon

adsorption, and

filtration

9.9

62 -- Wastewater

bearing

unspecified

RCRA listed

waste code

Pilot -- 0.1 - 1 mg/L

(TWA)

0.012 mg/L

(TWA)

-- Chemical

precipitation,

activated carbon

adsorption, and

filtration

9.9

63 -- Wastewater

bearing

unspecified

RCRA listed

waste code

Pilot -- 0.1 - 1 mg/L

(TWA)

0.006 mg/L

(TWA)

-- Chemical

precipitation,

activated carbon

adsorption, and

filtration

9.9

64 Landfill Hazardous

leachate, F039

Pilot -- 0.1 - 1 mg/L

(TWA)

0.008 mg/L

(TWA)

-- Chemical

precipitation,

activated carbon

adsorption, and

filtration

9.9

65 -- Wastewater

bearing

unspecified

RCRA listed

waste code

Pilot -- 0.1 - 1 mg/L

(TWA)

0.014 mg/L

(TWA)

-- Chemical

precipitation,

activated carbon

adsorption, and

filtration

9.9
Table 9.1

Arsenic Precipitation/Coprecipitation Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scalea

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration

Precipitating Agent

or Processc. Source

9 - 17

66 Municipal

landfill

Leachate Pilot -- 1 - 10 mg/L

(TWA)

8 mg/L (TWA) -- Chemical

precipitation,

activated carbon

adsorption, and

filtration

9.9

67 Metals

processing

Scrubber water

from lead

smelter

Pilot -- 3,300 mg/L 0.007 mg/L -- Mineral-like

precipitation

(additional

information not

available)

9.17

68 Metals

processing

Thickener

overflow from

lead smelter

Pilot -- 5.8 mg/L 0.003 mg/L -- Mineral-like

precipitation

(additional

information not

available)

9.17

69 -- Industrial

wastewater

Pilot -- 5.8 mg/kg < 0.5 mg/kg -- -- 9.17

a Excluding bench-scale treatments.b Detection limit not provided.c The information that appears in the "Precipitating Agent or Process" column, including the chemicals used, the descriptions of the precipitation/

coprecipitation processes, and whether the process involved precipitation or coprecipitation, were prepared based on the information reported in the cited

references. This information was not independently checked for accuracy or technical feasability. In some cases the term "precipitation" may be applied to a

process that is actually coprecipitation.

EPT = Extraction procedure toxicity testmg/L = milligrams per literRCRA = Resource Conservation and Recovery ActWET = Waste extraction test

mg/kg = milligrams per kilogram-- = Not availableTWA = Total waste analysisgpd = gallons per day

mgd = million gallons per dayTCLP = Toxicity characteristic leachingprocedure
10-1

Summary

 Membrane filtration can remove a wide range of

contaminants from water. Based on the information

collected to prepare this report, this technology

typically can reduce arsenic concentrations to less

than 0.050 mg/L and in some cases has reduced

arsenic concentrations to below 0.010 mg/L. 

However, its effectiveness is sensitive to a variety of

untreated water contaminants and characteristics. It

also produces a larger volume of residuals and tends

to be more expensive than other arsenic treatment

technologies. Therefore, it is used less frequently

than precipitation/coprecipitation, adsorption, and 

ion exchange. It is most commonly used to treat

groundwater and drinking water, or as a polishing

step for precipitation processes. Only two full-scale

projects using membrane filtration to treat arsenic

were identified in the sources researched for this

report. 

Technology Description: Membrane filtration

separates contaminants from water by passing it

through a semi-permeable barrier or membrane. 

The membrane allows some constituents to pass

through, while blocking others (Ref. 10.2, 10.3). 

Media Treated:

• Drinking water

• Groundwater

• Surface water

• Industrial wastewater

Types of Membrane Processes:

• Microfiltration

• Ultrafiltration

• Nanofiltration 

• Reverse osmosis

Contaminated 

Water

Membranes

Recycle Reject

Effluent

Contaminated 

Water

Membranes

Recycle Reject

Effluent

Model of a Membrane Filtration System

10.0 MEMBRANE FILTRATION FOR

ARSENIC

Technology Description and Principles

There are four types of membrane processes:

microfiltration (MF), ultrafiltration (UF), nanofiltration

(NF), and reverse osmosis (RO). All four of these

processes are pressure-driven and are categorized by the

size of the particles that can pass through the

membranes or by the molecular weight cut off (i.e.,

pore size) of the membrane (Ref. 10.2). The force

required to drive fluid across the membrane depends on

the pore size; NF and RO require a relatively high

pressure (50 to 150 pounds per square inch [psi]), while

MF and UF require lower pressure (5 to 100 psi ) (Ref.

10.4). The low pressure processes primarily remove

contaminants through physical sieving, and the high

pressure processes through chemical diffusion across

the permeable membrane (Ref. 10.4). 

Because arsenic species dissolved in water tend to have

relatively low molecular weights, only NF and RO

membrane processes are likely to effectively treat

dissolved arsenic (Ref. 10.4). MF has been used with

precipitation/coprecipitation to remove solids

containing arsenic. The sources used for this report did

not contain any information on the use of UF to remove

arsenic; therefore, UF is not discussed in this

technology summary. MF generates two treatment

residuals from the influent waste stream: a treated

effluent (permeate) and a rejected waste stream of

concentrated contaminants (reject).

RO is a high pressure process that primarily removes

smaller ions typically associated with total dissolved

solids. The molecular weight cut off for RO

membranes ranges from 1 to 20,000, which is a

significantly lower cut off than for NF membranes. The

molecular weight cut off for NF membranes ranges

from approximately 150 to 20,000. NF is a highpressure process that primarily removes larger divalent

ions associated with hardness (for example, calcium

[Ca], and magnesium [Mg] but not monovalent salts

(for example, sodium [Na] and chlorine [Cl]). NF is

slightly less efficient than RO in removing dissolved

arsenic from water (Ref. 10.4).
10-2

6

25

2

0 5 10 15 20 25

Bench

Pilot

Full

6

25

2

0 5 10 15 20 25

Bench

Pilot

Full

Factors Affecting Membrane Filtration

Performance

• Suspended solids, high molecular weight,

dissolved solids, organic compounds, and

colloids - The presence of these constituents in

the feed stream may cause membrane fouling.

• Oxidation state of arsenic - Prior oxidation of

the influent stream to convert As(III) to As(V)

will increase arsenic removal; As(V) is

generally larger and is captured by the

membrane more effectively than As(III).

• pH - pH may affect the adsorption of arsenic on

the membrane by creating an electrostatic

charge on the membrane surface.

• Temperature - Low influent stream

temperatures decreases membrane flux. 

Increasing system pressure or increasing the

membrane surface area may compensate for low

influent stream temperature.

MF is a low-pressure process that primarily removes

particles with a molecular weight above 50,000 or a

particle size greater than 0.050 micrometers. The pore

size of MF membranes is too large to effectively

remove dissolved arsenic species, but MF can remove

particulates containing arsenic and solids produced by

precipitation/coprecipitation (Ref. 10.4).

Media and Contaminants Treated

Drinking water, surface water, groundwater, and 

industrial wastewater can be treated with this 

technology. Membrane filtration can treat dissolved 

salts and other dissolved materials (Ref. 10.12).

Type, Number, and Scale of Identified Projects

Treating Water Containing Arsenic

The data gathered for this report identified one fullscale RO and one full-scale MF treatment of arsenic in

groundwater and surface water (Figure 10.1). The MF

application is a treatment train consisting of

precipitation/coprecipitation followed by MF to remove

solids. In addition, 16 pilot-scale and three bench-scale

applications of RO and eight pilot-scale and three

bench-scale applications of NF have been identified. 

One pilot-scale application of MF to remove solids

from precipitation/coprecipitation of arsenic has also

been identified. 

Figure 10.1

Scale of Identified Membrane Filtration Projects for

Arsenic Treatment

Summary of Performance Data

Table 10.1 presents the performance data found for this

technology. Performance results for membrane

filtration are typically reported as percent removal, (i.e.,

the percentage of arsenic, by mass, in the influent that is

removed or rejected from the influent wastewater

stream). A higher percentage indicates greater removal

of arsenic, and therefore, more effective treatment. 

Although many of the projects listed in Table 10.1 may

have reduced arsenic concentrations to below 0.05

mg/L or 0.01 mg/L, data on the concentration of arsenic

in the effluent and reject streams were not available for

most projects.

For two RO projects, the arsenic concentration in the

reject stream was available, allowing the concentration

in permeate to be calculated. For both projects, the

concentration of arsenic prior to treatment was greater

than 0.050 mg/L, and was reduced to less than 0.010

mg/L in the treated water.

For two projects involving removal of solids from

precipitation/coprecipitation treatment of arsenic with

MF, the arsenic concentration in the permeate was

available. The concentration prior to precipitation/

coprecipitation treatment was greater than 0.050 mg/L

for one project, and ranged from 0.005 to 3.8 mg/L for

the other. For both projects, the concentration in the

treated water was less than 0.005 mg/L.

The case study at the end of this section further

discusses the use of membrane filtration to remove

arsenic from groundwater used as a drinking water

source. Information for this site is summarized in Table

10.1, Project 31.
10-3

Case Study: Park City Spiro Tunnel Water

Filtration Plant

The Park City Spiro Tunnel Water Filtration Plant in

Park City, Utah treats groundwater from waterbearing fissures that collect in a tunnel of an

abandoned silver mine to generate drinking water. 

A pilot-scale RO unit treated contaminated water at

a flow rate of 0.77 gallons per minute (gpm) from

the Spiro tunnel for 34 days. The total and

dissolved arsenic in the feedwater averaged 0.065

and 0.042 mg/L, respectively. The total and

dissolved arsenic concentrations in the permeate

averaged <0.0005 and <0.0008 mg/L, respectively. 

The RO process reduced As (V) from 0.035 to

0.0005 mg/L and As (III) from 0.007 to 0.0005

mg/L. The membrane achieved 99% total As

removal and 98% As (V) removal (Ref. 10.12) (see

Project 31, Table 10.1). 

Factors Affecting Membrane Filtration Costs

• Type of membrane filtration - The type of

membrane selected may affect the cost of the

treatment (Ref. 10.1, 10.2).

• Initial waste stream - Certain waste streams

may require pretreatment, which would

increase costs (Ref. 10.4).

• Rejected waste stream - Based on

concentrations of the removed contaminant,

further treatment may be required prior to 

disposal or discharge (Ref. 10.4).

• Factors affecting membrane filtration

performance - Items in the “Factors Affecting

Membrane Filtration Performance” box will

also affect costs.

Applicability, Advantages, and Potential 

Limitations

Membrane technologies are capable of removing a wide

range of dissolved contaminants and suspended solids

from water (Ref. 10.12). RO and NF technologies

require no chemical addition to ensure adequate

separation. This type of treatment may be run in either

batch or continuous mode. This technology’s 

effectiveness is sensitive to a variety of contaminants

and characteristics in the untreated water. Suspended

solids, organics, colloids, and other contaminants can

cause membrane fouling. Therefore, it is typically

applied to groundwater and drinking water, which are

less likely to contain fouling contaminants. It is also

applied to remove solids from precipitation processes

and as a polishing step for other water treatment

technologies when lower concentrations must be

achieved. 

More detailed information on selection and design of

arsenic treatment systems for small drinking water

systems is available in the document “Arsenic

Treatment Technology Design Manual for Small

Systems “ (Ref. 10.15). 

Summary of Cost Data

The research conducted in support of this report did not

document any cost data for specific membrane filtration

projects to treat of arsenic. The document

"Technologies and Costs for Removal of Arsenic From

Drinking Water" (Ref. 10.4) contains additional

information on the cost of point-of-use reverse osmosis

systems to treat arsenic in drinking water to levels

below the revised MCL of 0.010 mg/L. The document

includes capital and O&M cost curves for this

technology. These cost curves are based on computer

cost models for drinking water treatment systems.

References

10.1 U.S. EPA Office of Research and Development. 

Arsenic & Mercury - Workshop on Removal,

Recovery, Treatment, and Disposal. EPA-600-

R-92-105. August 1992.

10.2 U.S. EPA Office of Research and Development. 

Regulations on the Disposal of Arsenic

Residuals from Drinking Water Treatment

Plants. Office of Research and Development. 

EPA-600-R-00-025. May 2000.

http://www.epa.gov/ORD/WebPubs/

residuals/index.htm

10.3 U.S. EPA Office of Solid Waste. BDAT

Background Document for Spent Potliners from

Primary Aluminum Reduction - K088. EPA

530-R-96-015. February 1996.

http://www.epa.gov/ncepi/Catalog/

EPA530R96015.html

10.4 U.S. EPA Office of Water. Technologies and

Cost for Removal of Arsenic from Drinking

Water. EPA 815-R-00-028. December 2000.

http://www.epa.gov/safewater/ars/

treatments_and_costs.pdf 

10.5 U.S. EPA National Risk Management Research

Laboratory. Treatability Database. March 2001.
10-4

10.6 U.S. Technology Innovation Office. Database

for EPA REACH IT (REmediation And

CHaracterization Innovative Technologies). 

http://www.epareachit.org. March 2001.

 10.7 U.S. EPA Office of Research and Development. 

Contaminants and Remedial Options at Selected

Metal-Contaminated Sites. EPA/540/R-95/512. 

July, 1995. http://search.epa.gov/s97is.vts

10.8 Federal Remediation Technologies Reference

Guide and Screening Manual, Version 4.0. 

Federal Remediation Technologies Roundtable. 

September 5, 2001.

http://www.frtr.gov/matrix2/top_page.html. 

10.9 U.S. EPA Office of Water. Arsenic in Drinking

Water Rule Economic Analysis. EPA 815-R-00-

026. December 2000.

http://www.epa.gov/safewater/ars/

econ_analysis.pdf

10.10 Code of Federal Regulations, Part 40, Section

268. Land Disposal Restrictions.

http://lula.law.cornell.edu/cfr/

cfr.php?title=40&type=part&value=268

10.11 Code of Federal Regulations, Part 400. Effluent

Limitations Guidelines.

http://www.epa.gov/docs/epacfr40/chapt-I.info/

subch-N.htm

10.12 Environmental Technology Verification Program

(ETV). Reverse Osmosis Membrane Filtration

Used In Packaged Drinking Water Treatment

Systems. http://www.membranes.com. March

2001.

10.13 Electric Power Research Institute. Innovative

Technologies for Remediation of Arsenic in Soil

Groundwater: Soil Flushing, In-Situ Fixation,

Iron Coprecipitation, and Ceramic Membrane

Filtration. http://www.epri.com. April 2000.

10.14 FAMU-FSU College of Engineering. Arsenic

Remediation.

http://www.eng.fsu.edu/departments/civil/

research/arsenicremedia/index.htm August 21,

2001.

10.15 U.S. EPA. Arsenic Treatment Technology

Design Manual for Small Systems (100% Draft

for Peer Review). June 2002. 

http://www.epa.gov/ safewater/smallsys/

arsenicdesignmanualpeerreviewdraft.pdf
Table 10.1

Membrane Filtration Treatment Performance Data for Arsenic

10-5

Project

Number Media or Waste Scale

Site Name or

Location

Initial Arsenic

Concentration

Percent Arsenic Removala or

Final Arsenic Concentration

Membrane or

Treatment Process Source

Nanofiltration

1 Groundwater Pilot Tarrytown, NY 0.038 - 0.154 mg/L 95% -- 10.42 Groundwater Pilot Tarrytown, NY 0.038 - 0.154 mg/L 95% -- 10.43 Groundwater with low

DOC (1mg/L) 

Pilot -- -- 60% Single element,

negatively charged

membrane

10.4

4 Groundwater with high

DOC (11mg/L) 

Pilot -- -- 80% Single element,

negatively charged

membrane

10.4

5 Groundwater with high

DOC (11mg/L) 

Pilot -- -- 75% initial, 

3-16% final

Single element,

negatively charged

membrane

10.4

6 Arsenic spiked surface

water

Pilot -- -- Arsenic (III) 20%

Arsenic (V) > 95%

Single element

membrane

10.4

7 Arsenic spiked surface

water

Pilot -- -- Arsenic (III) 30%

Arsenic (V) > 95%

Single element

membrane

10.4

8 Arsenic spiked surface

water

Pilot -- -- Arsenic (III) 52%

Arsenic (V) > 95%

Single element

membrane

10.4

9 Arsenic spiked DI water Bench -- -- Arsenic (III) 12%

Arsenic (V) 85%

Single element,

negatively charged

membrane

10.4

10 Arsenic spiked lake

water

Bench -- -- Arsenic (V) 89% Single element,

negatively charged

membrane

10.4

11 Arsenic spiked DI water Bench -- -- Arsenic (V) 90% Flat sheet, negatively

charged membrane

10.4
Table 10.1

Membrane Filtration Treatment Performance Data for Arsenic (continued)

Project

Number Media or Waste Scale

Site Name or

Location

Initial Arsenic

Concentration

Percent Arsenic Removala or

Final Arsenic Concentration

Membrane or

Treatment Process Source

10-6

Reverse Osmosis

12 Surface water

contaminated with wood

preserving wastes

Full -- 24.4 mg/L Arsenic removal, 99%

reject stream, 57.7 mg/L

treated effluent stream, 0.0394

mg/L

Treatment train

consisting of RO

followed by ion

exchange. Performance

data are for RO treatment

only.

10.1

13 Groundwater Pilot Charlotte Harbor, FL -- Arsenic (III) 46-84%

Arsenic (V) 96-99%

-- 10.4

14 Groundwater Pilot Cincinnati, OH -- Arsenic (III) 73% -- 10.415 Groundwater Pilot Eugene, OR -- 50% -- 10.416 Groundwater Pilot Fairbanks, AL -- 50% -- 10.417 Groundwater Pilot Hudson, NH -- 40% -- 10.418 Groundwater with low

DOC

Pilot -- -- > 80% Single element,

negatively charged

membrane

10.4

19 Groundwater with high

DOC

Pilot -- -- > 90% Single element,

negatively charged

membrane

10.4

20 Arsenic spiked surface

water

Pilot -- -- Arsenic (III) 60%

Arsenic (V) > 95%

Single element

membrane

10.4

21 Arsenic spiked surface

water

Pilot -- -- Arsenic (III) 68%

Arsenic (V) > 95%

Single element

membrane

10.4

22 Arsenic spiked surface

water

Pilot -- -- Arsenic (III) 75%

Arsenic (V) > 95%

Single element

membrane

10.4

23 Arsenic spiked surface

water

Pilot -- -- Arsenic (III) 85%

Arsenic (V) > 95%

Single element

membrane

10.4

24 Groundwater Pilot San Ysidro, NM -- 91% -- 10.425 Groundwater Pilot San Ysidro, NM -- 99% Hollow fiber, polyamide

membrane

10.4

26 Groundwater Pilot San Ysidro, NM -- 93-99% Hollow fiber, cellulose

acetate membrane

10.4
Table 10.1

Membrane Filtration Treatment Performance Data for Arsenic (continued)

Project

Number Media or Waste Scale

Site Name or

Location

Initial Arsenic

Concentration

Percent Arsenic Removala or

Final Arsenic Concentration

Membrane or

Treatment Process Source

10-7

27 Groundwater Pilot Tarrytown, NY -- 86% -- 10.428 Arsenic spiked lake

water

Bench -- -- Arsenic (III) 5%

Arsenic (V) 96%

-- 10.4

29 Arsenic spiked DI water Bench -- -- Arsenic (III) 5%

Arsenic (V) 96%

-- 10.4

30 Arsenic spiked DI water Bench -- -- Arsenic (V) 88% -- 10.431 Drinking water Pilot Park City Spiro

Tunnel Water

Filtration Plant, Park

City, Utah

0.065 mg/L 0.0005 mg/L -- 10.12

Microfiltration

32 Groundwater Full -- 0.005 - 3.8 mg/L <0.005 - 0.05 mg/L Iron coprecipitation

followed by membrane

filtration

10.14

33 Groundwater Pilot -- 0.2 - 1.0 mg/L <0.005 mg/L Iron coprecipitation

followed by ceramic

membrane filtration

10.13

a Percent arsenic rejection is 1 minus the mass of arsenic in the treated water divided by the mass of arsenic in the influent times 100 

[(1-(mass of arsenic influent/mass of arsenic effluent))*100].

DI = DeionizedDOC = Dissolved organic carbon-- = Not availableNF = NanofiltrationRO = Reverse Osmosis
11 - 1

Contaminated Water

Sorbent

Effluent

Model of an Adsorption System

Summary

Adsorption has been used to treat groundwater and

drinking water containing arsenic. Based on the

information collected for this report, this technology

typically can reduce arsenic concentrations to less

than 0.050 mg/L and in some cases has reduced

arsenic concentrations to below 0.010 mg/L. Its

effectiveness is sensitive to a variety of untreated

water contaminants and characteristics. It is used

less frequently than precipitation/coprecipitation,

and is most commonly used to treat groundwater and

drinking water, or as a polishing step for other water

treatment processes.

Technology Description: In adsorption, solutes

(contaminants) concentrate at the surface of a

sorbent, thereby reducing their concentration in the

bulk liquid phase. The adsorption media is usually

packed into a column. As contaminated water is

passed through the column, contaminants are

adsorbed. When adsorption sites become filled, the

column must be regenerated or disposed of and

replaced with new media. 

Media Treated:

• Groundwater

• Drinking water

Types of Sorbent Used in Adsorption to Treat

Arsenic:

• Activated alumina (AA)

• Activated carbon (AC)

• Copper-zinc granules

• Granular ferric hydroxide, ferric hydroxidecoated newspaper pulp, iron oxide coated sand,

iron filings mixed with sand

• Greensand filtration (KMnO4 coated glauconite)

• Proprietary media

• Surfactant-modified zeolite

11.0 ADSORPTION TREATMENT FOR 

ARSENIC

Technology Description and Principles

This section discusses arsenic removal processes that

use a fixed bed of media through which water is passed. 

Some of the processes described in this section rely on a

combination of adsorption, precipitation/

coprecipitation, ion exchange, and filtration. However,

the primary removal mechanism in each process is

adsorption. For example, greensand is made from

glauconite, a green, iron-rich, clay-like mineral that

usually occurs as small pellets mixed with other sand

particles. The glauconite-containing sand is treated

with potassium permanganate (KMnO4), forming a

layer of manganese oxides on the sand. As water

passes through a greensand filtration bed, the KMnO4

oxidizes As(III) to As(V), and As(V) adsorbs onto the

greensand surface. In addition, arsenic is removed by

ion exchange, displacing species from the manganese

oxide (presumably hydroxide ion [OH-

] and water

[H2O]). When the KMnO4 is exhausted, the greensand

media must be regenerated or replaced. Greensand

media is regenerated with a solution of excess KMnO4. 

Greensand filtration is also known as

oxidation/filtration (Ref. 11.3).

Activated alumina (AA) is the sorbent most commonly

used to remove arsenic from drinking water (Ref. 11.1),

and has also been used for groundwater (Ref. 11.4). 

The reported adsorption capacity of AA ranges from

0.003 to 0.112 grams of arsenic per gram of AA (Ref.

11.4). It is available in different mesh sizes and its

particle size affects contaminant removal efficiency. 

Up to 23,400 bed volumes of wastewater can be treated

before AA requires regeneration or disposal and

replacement with new media (Ref. 11.3). Regeneration

is a four-step process:

• Backwashing 

• Regeneration

• Neutralization

• Rinsing
11 - 2

8

15

0 5 10 15

Pilot

Full

The regeneration process desorbs the arsenic. The

regeneration fluid most commonly used for AA

treatment systems is a solution of sodium hydroxide. 

The most commonly used neutralization fluid is a

solution of sulfuric acid. The regeneration and

neutralization steps for AA adsorption systems might

produce a sludge because the alumina can be dissolved

by the strong acids and bases used in these processes,

forming an aluminum hydroxide precipitate in the spent

regeneration and neutralization fluids. This sludge

typically contains a high concentration of arsenic (Ref.

11.1).

Activated carbon (AC) is an organic sorbent that is

commonly used to remove organic and metal

contaminants from drinking water, groundwater, and

wastewater (Ref. 11.4). AC media are normally

regenerated using thermal techniques to desorb and

volatilize contaminants (Ref. 11.6). However,

regeneration of AC media used for the removal of

arsenic from water might not be feasible (Ref. 11.4). 

The arsenic might not volatilize at the temperatures

typically used in AC regeneration. In addition, off-gas

containing arsenic from the regeneration process may

be difficult or expensive to manage. 

The reported adsorption capacity of AC is 0.020 grams

of As(V) per gram of AC. As(III) is not effectively

removed by AC. AC impregnated with metals such as

copper and ferrous iron has a higher reported adsorption

capacity for arsenic. The reported adsorption capacity

for As(III) is 0.048 grams per gram of copperimpregnated carbon and for As(V) is 0.2 grams per

gram of ferrous iron-impregnated carbon (Ref. 11.4).

Iron-based adsorption media include granular ferric

hydroxide, ferric hydroxide-coated newspaper pulp,

ferric oxide, iron oxide-coated sand, sulfur-modified

iron, and iron filings mixed with sand. These media

have been used primarily to remove arsenic from

drinking water. Processes that use these media

typically remove arsenic using adsorption in

combination with oxidation, precipitation/

coprecipitation, ion exchange, or filtration. For

example, iron oxide-coated sand uses adsorption and

ion exchange with surface hydroxides to selectively

remove arsenic from water. The media requires

periodic regeneration or disposal and replacement with

new media. The regeneration process is similar to that

used for AA, and consists of rinsing the media with a

regenerating solution containing excess sodium

hydroxide, flushing with water, and neutralizing with a

strong acid, such as sulfuric acid (Ref. 11.3).

The sources used for this report contained information

on the use of surfactant-modified zeolite (SMZ) at

bench scale, but no pilot- or full-scale applications were

identified. SMZ is prepared by treating zeolite with a

solution of surfactant, such as

hexadecyltrimethylammonium bromide (HDTMA-Br). 

This process forms a stable coating on the zeolite

surface. The reported adsorption capacity of SMZ is

0.0055 grams of As(V) per gram of SMZ at 250

C. SMZ

must be periodically regenerated with surfactant

solution or disposed and replaced with new SMZ (Ref.

11.17).

Media and Contaminants Treated

Adsorption is frequently used to remove organic

contaminants and metals from industrial wastewater. It

has been used to remove arsenic from groundwater and

drinking water. 

Type, Number, and Scale of Identified Projects

Treating Water Containing Arsenic

Adsorption technologies to treat arsenic-contaminated

water in water are commercially available. Information

was found on 23 applications of adsorption (Figure

11.1), including 7 full- and 5 pilot-scale projects fro

groundwater and surface water and 8 full- and 3 pilotscale projects for drinking water. 

Figure 11.1

Scale of Identified Adsorption Projects for Arsenic

Treatment

Summary of Performance Data

Adsorption treatment effectiveness can be evaluated by

comparing influent and effluent contaminant

concentrations. Table 11.1 presents the available

performance data for this technology. Two of the four

groundwater and surface water projects having both

influent and effluent arsenic concentration data had

influent concentrations greater than 0.050 mg/L. 

Effluent concentrations of 0.050 mg/L or less were
11 - 3

Factors Affecting Adsorption Performance

• Fouling - The presence of suspended solids,

organics, solids, silica, or mica, can cause

fouling of adsorption media (Ref. 11.1, 11.4).

• Arsenic oxidation state - Adsorption is more

effective in removing As(V) than As(III) (Ref.

11.12).

• Flow rate - Increasing the rate of flow through

the adsorption unit can decrease the adsorption

of contaminants (Ref. 11.1).

• Wastewater pH - The optimal pH to maximize

adsorption of arsenic by activated alumina is

acidic (pH 6). Therefore, pretreatment and

post-treatment of the water could be required

(Ref. 11.4).

achieved in both of the projects. In the other two

groundwater and surface water projects the influent

arsenic concentration was between 0.010 mg/L and

0.050 mg/L, and the effluent concentration was less

than 0.010 mg/L.

Of the ten drinking water projects (eight full and two

pilot scale) having both influent and effluent arsenic

concentration data, eight had influent concentrations

greater than 0.050 mg/L. Effluent concentrations of 

less than 0.050 mg/L were achieved in seven of these

projects. For two drinking water projects the influent

arsenic concentration was between 0.010 mg/L and

0.050 mg/L, and the effluent concentration was less

than 0.010 mg/L.

Projects that did not reduce arsenic concentrations to

below 0.050 or 0.010 mg/L do not necessarily indicate

that adsorption cannot achieve these levels. The

treatment goal for some applications may have been

above these levels and the technology may have been

designed and operated to meet a higher arsenic

concentration. Information on treatment goals was not

collected for this report. 

Two pilot-scale studies were performed to compare the

effectiveness AA adsorption on As(III) and As(V)

(Projects 3 and 4 in Table 11.1). For As(III), 300 bed

volumes were treated before arsenic concentrations in

the effluent exceeded 0.050 mg/L, whereas 23,400 bed

volumes were treated for As(V) before reaching the

same concentration in the effluent. The results of these

studies indicate that the adsorption capacity of AA is

much greater for As(V).

The case study at the end of this section discusses in

greater detail the use of AA to remove arsenic from

drinking water. Information for this project is

summarized in Table 11.1, Project 13.

Applicability, Advantages, and Potential Limitations

For AA adsorption media, the spent regenerating

solution might contain a high concentration of arsenic

and other sorbed contaminants, and can be corrosive

(Ref. 11.3). Spent AA is produced when the AA can no

longer be regenerated (Ref. 11.3). The spent AA may

require treatment prior to disposal (Ref. 11.4). Because

regeneration of AA requires the use of strong acids and

bases, some of the AA media becomes dissolved during

the regeneration process. This can reduce the

adsorptive capacity of the AA and cause the AA

packing to become "cemented."

Regeneration of AC media involves the use of thermal

energy, which could release volatile arsenic

compounds. Use of air pollution control equipment

may be necessary to remove arsenic from the off-gas

produced (Ref. 11.6).

Competition for adsorption sites could reduce the

effectiveness of adsorption because other constituents

may be preferentially adsorbed, resulting in a need for

more frequent bed regeneration or replacement. The

presence of sulfate, chloride, and organic compounds

has reportedly reduced the adsorption capacity of AA

for arsenic (Ref. 11.3). The order for adsorption

preference for AA is provided below, with the

constituents with the greatest adsorption preference

appearing at the top left (Ref. 11.3):

OH-

 > H2AsO4

-

 > Si(OH)3O- > F- > HSeO3

-

 > SO4

2-

> H3AsO3

This technology’s effectiveness is also sensitive to a

variety of contaminants and characteristics in the

untreated water, and suspended solids, organics, silica,

or mica can cause fouling. Therefore, it is typically

applied to groundwater and drinking water, which are

less likely to contain fouling contaminants. It may also

be used as a polishing step for other water treatment

technologies. 

More detailed information on selection and design of

arsenic treatment systems for small drinking water

systems is available in the document “Arsenic

Treatment Technology Design Manual for Small

Systems “ (Ref. 11.20).

Summary of Cost Data

One source reported that the cost of removing arsenic

from drinking water using AA ranged from $0.003 to
11 - 4

Factors Affecting Adsorption Costs

• Contaminant concentration - Very high

concentrations of competing contaminants may

require frequent replacement or regeneration of

adsorbent (Ref. 11.2). The capacity of the

adsorption media increases with increasing

contaminant concentration (Ref. 11.1, 11.4). 

High arsenic concentrations can exhaust the

adsorption media quickly, resulting in the need

for frequent regeneration or replacement.

• Spent media - Spent media that can no longer

be regenerated might require treatment or

disposal (Ref. 11.4).

• Factors affecting adsorption performance -

Items in the “Factors Affecting Adsorption

Performance” box will also affect costs.

Case Study: Treatment of Drinking Water by an

Activated Alumina Plant

A drinking water treatment plant using AA (see

Table 11.1, Project 13) installed in February 1996

has an average flow rate of 3,000 gallons per day. 

The arsenic treatment system consists of two

parallel treatment trains, with two AA columns in

series in each train. For each of the trains, the AA

media in one column is exhausted and replaced

every 1 to 1.5 years after treating approximately

5,260 bed volumes.

Water samples for a long-term evaluation were

collected weekly for a year. Pretreatment arsenic

concentrations at the inlet ranged from 0.053 to

0.087 mg/L with an average of 0.063 mg/L. The

untreated water contained primarily As(V) with only

minor concentrations of As(III) and particulate

arsenic. During the entire study, the arsenic

concentration in the treated drinking water was

below 0.003 mg/L. Spent AA from the system had

leachable arsenic concentrations of less than 0.05

mg/L, as measured by the TCLP, and therefore,

could be disposed of as nonhazardous waste.

$0.76 per 1,000 gallons (Ref. 11.4, cost year not

provided). The document "Technologies and Costs for

Removal of Arsenic From Drinking Water" (Ref. 11.3)

contains detailed information on the cost of adsorption

systems to treat arsenic in drinking water to below the

revised MCL of 0.010 mg/L. The document includes

capital and operating and maintenance (O&M) cost

curves for four adsorption processes: 

• AA (at various influent pH levels)

• Granular ferric hydroxide

• Greensand filtration (KMNO4 coated sand)

• AA point-of-use systems

These cost curves are based on computer cost models

for drinking water systems. The curves show the costs

for adsorption treatment systems with different design

flow rates. The document also contains information on

the disposal cost of residuals from adsorption. Many of

the technologies used to treat drinking water are

applicable to treatment of other types of water, and may

have similar costs. Table 3.4 in Section 3 of this

document contains cost estimates based on these curves

for AA and greensand filtration. 

References

11.1 U.S. EPA. Regulations on the Disposal of

Arsenic Residuals from Drinking Water

Treatment Plants. Office of Research and

Development. EPA/600/R-00/025. May 2000.

http://www.epa.gov/ORD/WebPubs/residuals/

index.htm

11.2 Federal Remediation Technologies Reference

Guide and Screening Manual, Version 3.0. 

Federal Remediation Technologies Roundtable. 

March 30, 2001. http://www.frtr.gov/matrix2/

top_page.html. 

11.3 U.S. EPA. Technologies and Costs for Removal

of Arsenic From Drinking Water. EPA 815-R00-028. Office of Water. December 2000.

http://www.epa.gov/safewater/ars/

treatments_and_costs.pdf

11.4 Twidwell, L.G., et al. Technologies and

Potential Technologies for Removing Arsenic

from Process and Mine Wastewater. Presented

at "REWAS'99." San Sebastian, Spain. 

September 1999.

http://www.mtech.edu/metallurgy/arsenic/

REWASAS%20for%20proceedings99%20in%2

0word.pdf

11.5 U.S. EPA. Pump and Treat of Contaminated

Groundwater at the Mid-South Wood Products

Superfund Site, Mena, Arkansas. Federal

Remediation Technologies Roundtable. 

September 1998. 

http://www.frtr.gov/costperf.html. 

11.6 U.S. EPA. Final Best Demonstrated Available

Technology (BDAT) Background Document for

K031, K084, K101, K102, Characteristic Arsenic

Wastes (D004), Characteristic Selenium Wastes

(D010), and P and U Wastes Containing Arsenic

and Selenium Listing Constituents. Office of

Solid Waste. May 1990.
11 - 5

11.7 U.S. EPA. Groundwater Pump and Treat

Systems: Summary of Selected Cost and

Performance Information at Superfund-financed

Sites. EPA-542-R-01-021b. EPA OSWER. 

December 2001. http://clu-in.org

11.8 Murcott S. Appropriate Remediation

Technologies for Arsenic-Contaminated Wells in

Bangladesh. Massachusetts Institute of

Technology. February 1999.

http://web.mit.edu/civenv/html/people/faculty/

murcott.html

11.9 Haq N. Low-cost method developed to treat

arsenic water. West Bengal and Bangladesh

Arsenic Crisis Information Center. June 2001.

http://bicn.com/acic/resources/infobank/nfb/

2001-06-11-nv4n593.htm 

11.10 U.S. EPA. Arsenic Removal from Drinking

Water by Iron Removal Plants. EPA 600-R-00-

086. Office of Research and Development.

August 2000. 

http://www.epa.gov/ORD/WebPubs/iron/

index.html

11.11 Harbauer GmbH & Co. KG. Germany. Online

address: http://www.harbauer-berlin.de/arsenic. 

11.12 U.S. EPA. Arsenic Removal from Drinking

Water by Ion Exchange and Activated Alumina

Plants. EPA 600-R-00-088. Office of Research

and Development. October 2000.

http://www.epa.gov/ncepi/Catalog/

EPA600R00088.html

11.13 Environmental Research Institute. Arsenic

Remediation Technology - AsRT. June 28,

2001. http://www.eng2.uconn.edu/~nikos/asrtbrochure.html. 

11.14 Redox Treatment of Groundwater to Remove

Trace Arsenic at Point-of-Entry Water Treatment

Systems. June 28, 2001. 

http://phys4.harvard.edu/~wilson/Redox/

Desc.html. 

11.15 U.S. EPA. Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition). 

Office of Solid Waste and Emergency Response. 

EPA-542-R-01-004. February 2001. 

http://clu-in.org/asr

11.16 Electric Power Research Institute. Innovative

Technologies for Remediation of Arsenic in Soil

Groundwater: Soil Flushing, In-Situ Fixation,

Iron Coprecipitation, and Ceramic Membrane

Filtration. April 2000. http://www.epri.com

11.17 Sullivan, E. J., Bowman, R S., and Leieic, I.A. 

Sorption of Arsenate from Soil-Washing

Leachate by Surfactant-Modified Zeolite. 

Prepublication draft. January, 2002. 

bowman@nmt.edu

11.18 E-mail attachment from Cindy Schreier, Prima

Environmental to Sankalpa Nagaraja, Tetra Tech

EM Inc. June 18, 2002.

11.19 Severn Trent Services. UK. 

http://www.capitalcontrols.co.uk/

11.20 U.S. EPA. Arsenic Treatment Technology

Design Manual for Small Systems (100% Draft

for Peer Review). June 2002. 

http://www.epa.gov/ safewater/smallsys/

arsenicdesignmanualpeerreviewdraft.pdf
Table 11.1

Adsorption Treatment Performance Data for Arsenic

11 - 6

Project

Number

Industry or Site

Type Waste or Media Scalea

Site Name or

Location

Initial Arsenic 

Concentration

Final Arsenic 

Concentration

Adsorption Process

Descriptionb Source

Environmental Media - Activated Alumina

1 -- Groundwater Full -- -- <0.05 mg/L Activated alumina. 

Flow rate: 300

liters/hour.

11.9

2 -- Groundwater Pilot -- -- <0.05 mg/L Activated alumina

adsorption at pH 5

11.4

3 -- Solution

containing

trivalent arsenic

Pilot -- Trivalent

arsenic, 0.1

mg/L

Trivalent arsenic, 0.05

mg/L

Activated alumina

adsorption at pH 6.0 of

solution containing

trivalent arsenic. 300

bed volumes treated

before effluent exceeded

0.05 mg/L arsenic.

11.3

4 -- Solution

containing

pentavalent

arsenic

Pilot -- Pentavalent

arsenic, 0.1

mg/L

Pentavalent arsenic,

0.05 mg/L

Activated alumina

adsorbent at pH 6.0 of

solution containing

pentavalent arsenic. 

23,400 bed volumes

treated before effluent

exceeded 0.05 mg/L

arsenic.

11.3
Table 11.1

Adsorption Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type Waste or Media Scalea

Site Name or

Location

Initial Arsenic 

Concentration

Final Arsenic 

Concentration

Adsorption Process

Descriptionb Source

11 - 7

Environmental Media - Activated Carbon

5 Wood preserving Groundwater Full Mid-South Wood

Product Superfund

Site, Mena, AS

0.018 mg/L <0.005 mg/L (29 of 35

monitoring wells)

Treatment train

consisting of oil/water

separation, filtration,

and carbon adsorption. 

Performance data are for

the entire treatment

train.

11.5

6 Wood Preserving Groundwater,

27,000 gpd

Full North Cavalcade

Street Superfund Site

Houston, TX

-- -- Treatment train

consisting of filtration

followed by carbon

adsorption

11.7

7 Wood Preserving Groundwater,

3,000 gpd

Full Saunders Supply

Company Superfund

Site, Chuckatuck,

VA

-- -- Treatment train

consisting of metals

precipitation, filtration,

and carbon adsorption

11.7

8 Wood Preserving Groundwater,

4,000 gpd

Full McCormick and

Baxter Creosoting

Co. Superfund Site, 

Portland, OR

-- -- Treatment train

consisting of filtration,

ion exchange, and

carbon adsorption

11.7

9 Chemical mixing

and batching

Groundwater,

43,000 gpd

Full Baird and McGuire

Superfund Site, 

Holbrook, MA

-- -- Treatment train

consisting of air

stripping, metals

precipitation, filtration,

and carbon adsorption

11.7

10 Chemical

Manufacturing

Groundwater,

65,000 gpd

Full Greenwood

Chemical Superfund

Site, Greenwood,

VA

-- -- Treatment train

consisting of metals

precipitation, filtration,

UV oxidation and

carbon adsorption

11.7
Table 11.1

Adsorption Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type Waste or Media Scalea

Site Name or

Location

Initial Arsenic 

Concentration

Final Arsenic 

Concentration

Adsorption Process

Descriptionb Source

11 - 8

Environmental Media - Iron-Based Media

11 Landfill Groundwater Pilot -- -- 0.027 mg/L Treatment train

consisting of

precipitation from barite

addition followed by an

iron filings and sand

media filter. 

Performance data are for

the entire treatment

train.

11.8,

11.13

12 -- Groundwater,

3,600gpd

Pilot CA 0.018 mg/L <0.002 mg/L Fixed-bed adsorber with

sulfur-modified iron

adsorbent; 13,300 bed

volumes put through

unit

11.18

Drinking Water - Activated Alumina

13 -- Drinking water Full -- 0.063 mg/L <0.003 mg/L Two activated alumina

columns in series, media

replaced in one column

every 1.5 years

11.3

14 -- Drinking water Full -- 0.034 - 0.087

mg/L

<0.05 mg/L Activated alumina 11.12

15 -- Drinking water Full Project Earth

Industries, Inc.

0.34 mg/L 0.01 - 0.025 mg/L Activated alumina 11.8

16 -- Drinking water Full -- 0.049 mg/L <0.003 mg/L Two activated alumina

columns in series, media

replaced in column tank

every 1.5 years

11.3

17 -- Drinking water,

14,000 gpd

Full Bow, NH 0.057 - 0.062

mg/L

0.050 mg/L Activated alumina 11.3

Drinking Water - Iron-Based Media

18 -- Drinking water Full Harbauer GmbH &

Co., Berlin,

Germany

0.3 mg/L <0.01 mg/L Granular ferric

hydroxide

11.11
Table 11.1

Adsorption Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type Waste or Media Scalea

Site Name or

Location

Initial Arsenic 

Concentration

Final Arsenic 

Concentration

Adsorption Process

Descriptionb Source

11 - 9

19 -- Drinking Water Pilot -- 0.1 - 0.18 mg/L <0.01 mg/L Fixed bed adsorber with

ferric hydroxide-coated

newspaper pulp; 20,000

bed volumes treated

before effluent exceeded

0.01 mg/L arsenic

11.15

20 -- Drinking water Pilot -- 0.180 mg/L 0.010 mg/L Granular ferric

hydroxide

11.16

21 -- Drinking water Full -- 0.02mg/L 0.003 mg/L Fixed bed adsorber with

ferric oxide granules

11.19

Drinking Water - Other or Unknown Media

22 -- Drinking water Full -- 5 mg/L 0.01 mg/L Copper-zinc granules 11.1423 -- Drinking water Pilot ADI International -- -- Adsorption in

pressurized vessel

containing proprietary

media at pH 5.5 to 8.0

11.1

a Excluding bench-scale treatments.b Some processes employ a combination of adsorption, ion exchange, oxidation, precipitation/coprecipitation, or filtration to remove arsenic from water.

AA = activated aluminaEPT = Extraction procedure toxicity testmg/L = milligrams per literRCRA = Resource Conservation and RecoveryActgpd = gallons per day mgd = million gallons per day 

TCLP = Toxicity characteristic leachingprocedure mg/kg = milligrams per kilogram

-- = Not available TWA = Total waste analysisWET = Waste extraction test
12-1

Summary

Ion exchange has been used to treat groundwater

and drinking water containing arsenic. Based on the

information collected to prepare this report, this

technology typically can reduce arsenic

concentrations to less than 0.050 mg/L and in some

cases has reduced arsenic concentrations to below

0.010 mg/L. Its effectiveness is sensitive to a

variety of untreated water contaminants and

characteristics. It is used less frequently than

precipitation/coprecipitation, and is most commonly

used to treat groundwater and drinking water, or as a

polishing step for other water treatment processes.

Technology Description: Ion exchange is a

physical/chemical process in which ions held

electrostatically on the surface of a solid are

exchanged for ions of similar charge in a solution. 

It removes ions from the aqueous phase by the

exchange of cations or anions between the

contaminants and the exchange medium (Ref. 12.1,

12.4, 12.8).

Media Treated:

• Groundwater

• Surface water

• Drinking water

Exchange Media Used in Ion Exchange to Treat

Arsenic:

• Strong base anion exchange resins

Contaminated Water

Ion Exchange Resin

Effluent

12.0 ION EXCHANGE TREATMENT FOR Model of an Ion Exchange System

ARSENIC

Technology Description and Principles

The medium used for ion exchange is typically a resin

made from synthetic organic materials, inorganic

materials, or natural polymeric materials that contain

ionic functional groups to which exchangeable ions are

attached (Ref. 12.3). Four types of ion exchange media

have been used (Ref. 12.1):

• Strong acid

• Weak acid

• Strong base

• Weak base

Strong and weak acid resins exchange cations while

strong and weak base resins exchange anions. Because

dissolved arsenic is usually in an anionic form, and

weak base resins tend to be effective over a smaller pH

range, strong base resins are typically used for arsenic

treatment (Ref. 12.1).

Resins may also be categorized by the ion that is

exchanged with the one in solution. For example,

resins that exchange a chloride ion are referred to as

chloride-form resins. Another way of categorizing

resins is by the type of ion in solution that the resin

preferentially exchanges. For example, resins that

preferentially exchange sulfate ions are referred to as

sulfate-selective. Both sulfate-selective and nitrateselective resins have been used for arsenic removal

(Ref. 12.1).

The resin is usually packed into a column, and as

contaminated water is passed through the column,

contaminant ions are exchanged for other ions such as

chloride or hydroxide in the resin (Ref. 12.4). Ion

exchange is often preceded by treatments such as

filtration and oil-water separation to remove organics,

suspended solids, and other contaminants that can foul

the resins and reduce their effectiveness.

Ion exchange resins must be periodically regenerated to

remove the adsorbed contaminants and replenish the

exchanged ions (Ref. 12.4). Regeneration of a resin

occurs in three steps: 

• Backwashing

• Regeneration with a solution of ions 

• Final rinsing to remove the regenerating solution

The regeneration process results in a backwash

solution, a waste regenerating solution, and a waste

rinse water. The volume of spent regeneration solution

ranges from 1.5 to 10 percent of the treated water

volume depending on the feed water quality and type of

ion exchange unit (Ref. 12.4). The number of ion

exchange bed volumes that can be treated before
12-2

Factors Affecting Ion Exchange Performance

• Valence state - As(III) is generally not

removed by ion exchange (Ref. 12.4).

• Presence of competing ions - Competition for

the exchange ion can reduce the effectiveness

of ion exchange if ions in the resin are replaced

by ions other than arsenic, resulting in a need

for more frequent bed regeneration (Ref. 12.1,

12.9).

• Fouling - The presence of organics, suspended

solids, calcium, or iron, can cause fouling of

ion exchange resins (Ref. 12.4).

• Presence of trivalent iron - The presence of

Fe (III) could cause arsenic to form complexes

with the iron that are not removed by ion

exchange (Ref. 12.1).

• pH - For chloride-form, strong-base resins, a

pH in the range of 6.5 to 9 is optimal. Outside

of this range, arsenic removal effectiveness

decreases quickly (Ref. 12.1).

0

7

01234567

Pilot

Full

regeneration is needed can range from 300 to 60,000

(Ref. 12.1). The regenerating solution may be used up

to 25 times before treatment or disposal is required. 

The final rinsing step usually requires only a few bed

volumes of water (Ref. 12.4).

Ion exchange can be operated using multiple beds in

series to reduce the need for bed regeneration; beds first

in the series will require regeneration first, and fresh

beds can be added at the end of the series. Multiple

beds can also allow for continuous operation because

some of the beds can be regenerated while others

continue to treat water. Ion exchange beds are typically

operated as a fixed bed, in which the water to be treated

is passed over an immobile ion exchange resin. One

variation on this approach is to operate the bed in a nonfixed, countercurrent fashion in which water is applied

in one direction, usually downward, while spent ion

exchange resin is removed from the top of the bed. 

Regenerated resin is added to the bottom of the bed. 

This method may reduce the frequency of resin

regeneration (Ref. 12.4).

Media and Contaminants Treated

Anion exchange resins are used to remove soluble

forms of arsenic from wastewater, groundwater, and

drinking water (Ref. 12.1, 12.4). Ion exchange

treatment is generally not applicable to soil and waste. 

It is commonly used in drinking water treatment for

softening, removal of calcium, magnesium, and other

cations in exchange for sodium, as well as removing

nitrate, arsenate, chromate, and selenate (Ref. 12.9).

Type, Number, and Scale of Identified Projects

Treating Water Containing Arsenic

Ion exchange of arsenic and groundwater, surface

water, and drinking water is commercially available. 

Information is available on seven full-scale applications

(Figure 12.1), including three applications to

groundwater and surface water, and four applications to

drinking water. No pilot-scale applications or

applications to industrial wastewater were found in the

sources researched.

Summary of Performance Data

Table 12.1 presents the performance data found for this

technology. Ion exchange treatment effectiveness can

be evaluated by comparing influent and effluent

contaminant concentrations. The single surface water

project with both influent and effluent arsenic

concentration data had an influent concentrations of

0.0394 mg/L, and an effluent concentration of 0.0229

mg/L. Of the three drinking water projects with both

Figure 12.1

Scale of Identified Ion Exchange Projects for

Arsenic Treatment

influent and effluent concentration data, all had influent

concentrations greater than 0.010 mg/L. Effluent

concentrations of less than 0.010 mg/L were

consistently achieved in only one of these projects.

Projects that did not reduce arsenic concentrations to

below 0.050 or 0.010 mg/L do not necessarily indicate

that ion exchange cannot achieve these levels. The

treatment goal for some applications could have been

above these levels and the technology may have been

designed and operated to meet a higher arsenic

concentration. Information on treatment goals was not

collected for this report. 
12-3

Factors Affecting Ion Exchange Costs

• Bed regeneration - Regenerating ion

exchange beds reduces the amount of waste for

disposal and the cost of operation (Ref. 12.1).

• Sulfate - Sulfate (SO4) can compete with

arsenic for ion exchange sites, thus reducing

the exchange capacity of the ion exchange

media for arsenic. This can result in a need for

more frequent media regeneration or

replacement, and associated higher costs (Ref.

12.1).

• Factors affecting ion exchange performance

- Items in the “Factors Affecting Ion Exchange

Performance” box will also affect costs.

Case Study: National Risk Management

Research Laboratory Study

A study by EPA ORD’s National Risk Management

Research Laboratory tested an ion exchange system

at a drinking water treatment plant. Weekly

sampling for one year showed that the plant

achieved an average of 97 percent arsenic removal. 

The resin columns were frequently regenerated

(every 6 days). Influent arsenic concentrations

ranged from 0.045 to 0.065 mg/L and effluent

concentrations ranged from 0.0008 to 0.0045 mg/L

(Ref. 12.9) (see Project 1, Table 12.1).

The case study at the end of this section further

discusses the use of ion exchange to remove arsenic

from drinking water. Information for this project is

summarized in Table 12.1, Project 1.

Applicability, Advantages, and Potential Limitations

For ion exchange systems using chloride-form resins,

the treated water could contain increased levels of

chloride ions and as a result be corrosive. Chlorides

can also increase the redox potential of iron, thus

increasing the potential for water discoloration if the

iron is oxidized. The ion exchange process can also

lower the pH of treated waters (Ref. 12.4).

For ion exchange resins used to remove arsenic from

water, the spent regenerating solution might contain a

high concentration of arsenic and other sorbed

contaminants, and could be corrosive. Spent resin is

produced when the resin can no longer be regenerated.

The spent resin may require treatment prior to reuse or

disposal (Ref. 12.8).

The order for exchange for most strong-base resins is

provided below, with the constituents with the greatest

adsorption preference appearing at the top left (Ref.

12.4).

HCrO4

-

 > CrO4

2- > ClO4-

 > SeO4

2- > SO42- > NO3-

 > Br-

> (HPO4

2-, HAsO42-, SeO32-, CO32-) > CN-

 > NO2

-

 > Cl->

(H2PO4

-

, H2AsO4

-

, HCO3

-

) > OH- > CH3COO- > FThe effectiveness of ion exchange is also sensitive to a

variety of contaminants and characteristics in the

untreated water, and organics, suspended solids,

calcium, or iron can cause fouling. Therefore, it is

typically applied to groundwater and drinking water,

which are less likely to contain fouling contaminants. It

may also be used as a polishing step for other water

treatment technologies. 

More detailed information on selection and design of

arsenic treatment systems for small drinking water

systems is available in the document “Arsenic

Treatment Technology Design Manual for Small

Systems “ (Ref. 12.10).

Summary of Cost Data

One project reported a capital cost for an ion exchange

system of $6,886 with an additional $2,000 installation

fee (Ref. 12.9, cost year not provided). The capacity of

the system and O&M costs were not reported. Cost

data for other projects using ion exchange were not

found.

The document "Technologies and Costs for Removal of

Arsenic From Drinking Water" (Ref. 12.1) contains

additional information on the cost of ion exchange

systems to treat arsenic in drinking water to levels

below the revised MCL of 0.010 mg/L. The document

includes capital and O&M cost curves for ion exchange

at various influent sulfate (SO4) concentrations. These

cost curves are based on computer cost models for

drinking water treatment systems. 

The curves estimate the costs for ion exchange

treatment systems with different design flow rates. The

document also contains information on the disposal cost

for residuals from ion exchange. Table 3.4 in Section 3

of this document contains cost estimates based on these

curves for ion exchange. Many of the technologies

used to treat drinking water are applicable to treatment

of other types of water, and may have similar costs.
12-4

References

12.1 U.S. EPA. Technologies and Costs for

Removal of Arsenic From Drinking Water. 

EPA-R-00-028. Office of Water. December,

2000. http://www.epa.gov/safewater/ars/

treatments_and_costs.pdf

12.2 U.S. EPA. Arsenic & Mercury - Workshop on

Removal, Recovery, Treatment, and Disposal.

Office of Research and Development. EPA600-R-92-105. August 1992. 

http://www.epa.gov/ncepihom

12.3 Federal Remediation Technologies Reference

Guide and Screening Manual, Version 3.0. 

Federal Remediation Technologies Roundtable

(FRTR). 

http://www.frtr.gov/matrix2/top_page.html. 

12.4 U.S. EPA. Regulations on the Disposal of

Arsenic Residuals from Drinking Water

Treatment Plants. EPA-600-R-00-025. Office

of Research and Development. May 2000. 

http://www.epa.gov/ncepihom

12.5 Tidwell, L.G., et al. Technologies and Potential

Technologies for Removing Arsenic from

Process and Mine Wastewater. Presented at

"REWAS'99." San Sebastian, Spain. 

September 1999. 

http://www.mtech.edu/metallurgy/arsenic/

REWASAS%20for%20proceedings99%20in%2

0word.pdf

12.6 U.S. EPA. Final Best Demonstrated Available

Technology (BDAT) Background Document for

K031, K084, K101, K102, Characteristic

Arsenic Wastes (D004), Characteristic

Selenium Wastes (D010), and P and U Wastes

Containing Arsenic and Selenium Listing

Constituents. Office of Solid Waste. May

1990.

12.7 U.S. EPA. Groundwater Pump and Treat

Systems: Summary of Selected Cost and

Performance Information at Superfund-financed

Sites. EPA-542-R-01-021b. EPA OSWER. 

December 2001. http://clu-in.org

12.8 Murcott, S. Appropriate Remediation

Technologies for Arsenic-Contaminated Wells

in Bangladesh. Massachusetts Institute of

Technology. February 1999.

http://web.mit.edu/civenv/html/people/faculty/

murcott.html

12.9 U.S. EPA. Arsenic Removal from Drinking

Water by Ion Exchange and Activated Alumina

Plants. EPA-600-R-00-088. Office of Research

and Development. October 2000. 

http://www.epa.gov/ORD/WebPubs/exchange/E

PA600R00088.pdf

12.10 U.S. EPA. Arsenic Treatment Technology

Design Manual for Small Systems (100% Draft

for Peer Review). June 2002. 

http://www.epa.gov/safewater/smallsys/

arsenicdesignmanualpeerreviewdraft.pdf
Table 12.1

Ion Exchange Treatment Performance Data for Arsenic

12-5

Project

Number

Industry or Site

Type

Waste or

Media Scale

Site Name or

Location

Ion Exchange

Media or Process

Untreated

Arsenic

Concentration

Treated Arsenic

Concentration

Ion Exchange Media

Regeneration

Information Source

Drinking Water

1 -- Drinking

Water

Full -- Treatment train

consisting of

potassium

permanganate

greensand oxidizing

filter followed by a

mixed bed ion

exchange system

0.040 - 0.065

mg/La

<0.003 mg/La Bed regenerated every

6 days

12.1

2 -- Drinking

Water

Full -- Treatment train

consisting of a solid

oxidizing media

filter followed by an

anion exchange

system

0.019 - 0.055

mg/La

<0.005 - 0.080

mg/La

-- 12.1

3 -- Drinking

Water

Full -- Strongly basic gel

ion exchange resin in

chloride form

0.045 - 0.065

mg/L

0.0008 - 0.0045

mg/L

Resin regenerated

every four weeks

12.9

4 -- Drinking

Water

Full -- Chloride-form

strong-base resin

anion-exchange

process

-- 0.002 mg/L Spent NaCl brine

reused to regenerate

exhausted ionexchange bed

12.8

Environmental Media

5 Wood Preserving,

spill of chromated

copper arsenate

Surface water Full Vancouver,

Canada (site

name

unknown)

Anion and cation

resins

0.0394 mg/L 0.0229 mg/L -- 12.2

6 Waste disposal Groundwater,

43,000 gpd

Full Higgins Farm

Superfund

Site, Franklin

Township, NJ

Treatment train

consisting of air

stripping, metals

precipitation,

filtration, and ion

exchange

-- -- -- 12.7
Table 12.1

Ion Exchange Treatment Performance Data for Arsenic (continued)

Project

Number

Industry or Site

Type

Waste or

Media Scale

Site Name or

Location

Ion Exchange

Media or Process

Untreated

Arsenic

Concentration

Treated Arsenic

Concentration

Ion Exchange Media

Regeneration

Information Source

12-6

7 Wood preserving Groundwater,

4,000 gpd

Full McCormick

and Baxter

Creosoting

Co. Superfund

Site, Portland,

OR

Treatment train

consisting of

filtration, ion

exchange, and

carbon adsorption

-- -- -- 12.7

a Data are for entire treatment train, including unit operations that are not ion exchange.-- = Not available.TWA = Total waste analysis.gpd = gallons per daymg/L = milligrams per liter.
13-1

Plume

Porous Treatment Media

Direction of 

Groundwater Flow

Lower Confining Layer

(Aquitard)

Cap

Treatment

Wall

Decreased Contaminant 

Concentration

Plume

Porous Treatment Media

Direction of 

Groundwater Flow

Lower Confining Layer

(Aquitard)

Cap

Treatment

Wall

Decreased Contaminant 

Concentration

Model of a Permeable Reactive Barrier System

Technology Description: Permeable reactive

barriers (PRBs) are walls containing reactive media

that are installed across the path of a contaminated

groundwater plume to intercept the plume. The

barrier allows water to pass through while the media

remove the contaminants by precipitation,

degradation, adsorption, or ion exchange.

Media Treated:

• Groundwater (in situ)

Chemicals and Reactive Media Used in PRBs to

Treat Arsenic:

• Zero valent iron (ZVI)

• Limestone

• Basic oxygen furnace slag

• Surfactant modified zeolite

• Ion exchange resin

Installation Depth:

• Up to 30 feet deep using established techniques

• Innovative techniques required for depths

greater than 30 feet

Summary

Permeable reactive barriers (PRBs) are being used

to treat arsenic in groundwater at full scale at only a

few sites. Although many candidate materials for

the reactive portion of the barrier have been tested at

bench scale, only zero valent iron and limestone

have been used at full scale. The installation

techniques for PRBs are established for depths less

than 30 feet, and require innovative installation

techniques for deeper installations.

13.0 PERMEABLE REACTIVE BARRIERS

FOR ARSENIC

Technology Description and Principles

PRBs are applicable to the treatment of both organic

and inorganic contaminants. The former usually are

broken down into carbon dioxide and water, while the

latter are converted to species that are less toxic or less

mobile. The most frequent applications of PRBs is the

in situ treatment of groundwater contaminated with

chlorinated solvents. A number of different treatment

media have been used, the most common being zerovalent iron (ZVI). Other media include hydrated lime,

slag from steelmaking processes that use a basic oxygen

furnace, calcium oxides, chelators (ligands selected for

their specificity for a given metal), iron oxides,

sorbents, substitution agents (e.g., ion exchange resins)

and microbes (Ref. 13.6, 13.8, 13. 18). The cost of the

reactive media will impact the overall cost of PRB

remedies. The information sources used for this report

included information about PRB applications using

ZVI, basic oxygen furnace slag, limestone, surfactant

modified zeolite, and ion exchange resin to treat

arsenic.
13-2

For the PRB projects identified for this report, ZVI was

the most commonly used reactive media. As

groundwater reacts with ZVI, pH increases, Eh

decreases, and the concentration of dissolved hydrogen

increases. These basic chemical changes promote a

variety of processes that impact contaminant

concentrations. Increases in pH favor the precipitation

of carbonates of calcium and iron as well as insoluble

metal hydroxides. Decreases in Eh drive reduction of

metals and metalloids with multiple oxidation states. 

Finally, an increase in the partial pressure of hydrogen

in subsurface systems supports the activity of various

chemotrophic organisms that use hydrogen as an energy

source, especially sulfate-reducing bacteria and

iron-reducing bacteria (Ref. 13.15).

Arsenate [As (V)] ions bind tightly to the iron filings,

causing the ZVI to be oxidized to ferrous iron,

aerobically or anaerobically in the presence of water, as

shown by the following reactions:

(anaerobic) Fe0

 + 2H2O < Fe+2 + H2 + 2OH-

(aerobic) 2Fe0 + 2H2O + O2 < 2Fe+2 + 4OHThe process results in a positively charged iron surface

that sorbs the arsenate species by electrostatic

interactions (Ref. 13.5, 13.17).

In systems where dissolved sulfate is reduced to sulfide

by sulfate-reducing bacteria, arsenic may be removed

by the precipitation of insoluble arsenic sulfide (As2S3)

or co-precipitated with iron sulfides (FeS) (Ref. 13.15).

PRBs can be constructed by excavating a trench of the

appropriate width and backfilling it with a reactive

medium. Commercial PRBs are built in two basic

configurations: the funnel-and-gate and the continuous

wall. The funnel-and-gate uses impermeable walls, for

example, sheet pilings or slurry walls, as a “funnel” to

direct the contaminant plume to a “gate(s)” containing

the reactive media, while the continuous wall transects

the flow path of the plume with reactive media (Ref.

13.6).

Most PRBs installed to date have had depths of 50 feet

(ft) or less. Those having depths of 30 ft or less can be

installed with a continuous trencher, while depths

between 30 and 70 ft require a more innovative

installation method, such as biopolymers. Installation

of PRBs at depths greater than 70 ft is more challenging

(Ref. 13.13).

Media and Contaminants Treated

This technology can treat both organic and inorganic

contaminants. Organic contaminants are broken down

into less toxic elements and compounds, such as carbon

dioxide and water. Inorganic contaminants are

converted to species that are less toxic or less mobile. 

Inorganic contaminants that can be treated by PRBs

include, but are not limited to, chromium (Cr), nickel

(Ni), lead (Pb), uranium (U), technetium (Tc), iron (Fe),

manganese (Mn), selenium (Se), cobalt (Co), copper

(Cu), cadmium (Cd), zinc (Zn), arsenic (As), nitrate 

(NO3

-

), sulfate (SO4

2-), and phosphate (PO43-). The

characteristics that these elements have in common is

that they can undergo redox reactions and can form

solid precipitates with common groundwater

constituents, such as carbonate (CO3

2- ), sulfide (S2- ),

and hydroxide (OH- ). Some common sources of these

contaminants are mine tailings, septic systems, and

battery recycling/disposal facilities (Ref. 13.5, 13.6,

13.14).

PRBs are designed to treat groundwater in situ. This

technology is not applicable to other contaminated

media such as soil, debris, or industrial wastes.

Type, Number, and Scale of Identified Projects

Treating Water Containing Arsenic

PRBs are commercially available and are being used

to treat groundwater containing arsenic at a full scale at

two Superfund sites, the Monticello Mill Tailings and

Tonolli Corporation sites, although arsenic is not the

primary target contaminant for treatment by the

technology at either site (Ref. 13.1). At a third

Superfund site, the Asarco East Helena site, this

technology has been tested at a bench scale, and

implementation at a full scale to treat arsenic is

currently planned (Ref. 13.15). In 1999, a pilot-scale

treatment was conducted at Bodo Canyon Disposal Cell

Mill Tailings Site, Durango, Colorado, to remediate

groundwater contaminated with arsenic (Ref. 13.12). 

In addition, PRBs have been used in two bench-scale

treatability studies by the U.S. Department of Energy’s

Grand Junction Office (GJO) to evaluate their

application to the Monticello Mill Tailings site and a

former uranium ore processing site (Ref. 13.3). Figure

13.1 shows the number of applications found at each

scale.

Additional bench-scale studies of the treatment of

arsenic using PRBs that contain various reactive media

are listed below (Ref. 13.8, 13.11). These studies were

not conducted to evaluate the application of PRBs to

specific sites. The organizations conducting the studies

are listed in parentheses. However, no performance

data are available for the studies, and therefore, they are

not included in Figure 13.1 above, or in Table 13.1.
13-3

2

3

5

012345

Bench

Pilot

Full

Factors Affecting PRB Performance

ï Fractured rock - The presence of fractured

rock in contact with the PRB may allow

groundwater to flow around, rather than

through, the PRB (Ref. 13.6).

ï Deep aquifers and contaminant plumes -

PRBs may be difficult to install for deep

aquifers and contaminant plumes (>70 ft deep)

(Ref. 13.13).

ï High aquifer hydraulic conductivity - The

hydraulic conductivity of the barrier must be

greater than that of the aquifer to prevent

preferential flow around the barrier (Ref.

13.13).

ï Stratigraphy - Site stratigraphy may affect

PRB installation. For example, clay layers

might be "smeared" during installation,

reducing hydraulic conductivity near the PRB

(Ref. 13.6).

ï Barrier plugging - Permeability and reactivity

of the barrier may be reduced by precipitation

products and microbial growth (Ref. 13.6).

Other Bench-Scale Studies Using Adsorption or Ion

Exchange Barriers

ï Activated alumina (Dupont)

ï Bauxite (Dupont)

ï Ferric oxides and oxyhydroxides (Dupont,

University of Waterloo), 

ï Peat, humate, lignite, coal (Dupont)

ï Surfactant-modified zeolite (New Mexico Institute 

of Mining and Technology)

Other Bench-Scale Studies Using Precipitation Barriers

ï Ferrous hydroxide, ferrous carbonate, ferrous

sulfide (Dupont)

ï Limestone (Dupont)

ï Zero-Valent Metals (DOE GJO)

Figure 13.1

Scale of Identified Permeable Reactive Barrier

Projects for Arsenic Treatment

Summary of Performance Data

Table 1 provides performance data for full-scale PRB

treatment of groundwater contaminated with arsenic at

three sites, two pilot-scale treatability study and five

bench-scale treatability studies. PRB performance

typically is measured by taking groundwater samples at

points upgradient and downgradient of the wall and

measuring the concentration of contaminants of concern

at each point. Data on the Monticello site show a

reduction in arsenic concentration from a range of 0.010

to 0.013 mg/L before installation of the PRB to <0.002

mg/L after the installation of a PRB. One pilot-scale

study showed a reduction in arsenic concentrations

from 0.4 mg/L to 0.02 mg/L. Four bench-scale

treatability studies also show a reduction in arsenic

concentrations.

Applicability, Advantages, and Potential Limitations

PRBs are a passive treatment technology, designed to

function for a long time with little or no energy input. 

They produce less waste than active remediation (for

example, extraction systems like pump and treat), as the

contaminants are immobilized or altered in the

subsurface (Ref. 13.14). PRBs can treat groundwater

with multiple contaminants and can be effective over a

range of concentrations. PRBs require no aboveground

equipment, except monitoring devices, allowing return

of the property to economic use during remediation

(Ref. 13.5, 13.14). PRBs are best applied to shallow,

unconfined aquifer systems in unconsolidated deposits,

as long as the reactive material is more conductive than

the aquifer. (Ref. 13.13).

PRBs rely on the natural movement of groundwater;

therefore, aquifers with low hydraulic conductivity can

require relatively long periods of time to be remediated. 

In addition, PRBs do not remediate the entire plume,

but only the portion of the plume that has passed

through the PRB. Because cleanup of groundwater

contaminated with arsenic has been conducted at only

two Superfund sites and these barriers have been

recently installed (Tonolli in 1998 and Monticello in

1999), the long-term effectiveness of PRBs for arsenic

treatment has not been demonstrated (Ref. 13.13).
13-4

Case Study: Monticello Mill Tailings Site

Permeable Reactive Barrier

The Monticello Mill Tailings in Southeastern Utah

is a former uranium/vanadium processing mill and

mill tailings impoundment (disposal pit). In January

1998, the U.S. Department of Energy completed an

interim investigation to determine the nature and

extent of contamination in the surface water and

groundwater in operable unit 3 of the site. Arsenic

was one among several contaminants in the

groundwater, and was found at concentrations

ranging from 0.010 to 0.013 mg/L. A PRB

containing ZVI was constructed in June 1999 to

treat heavy metal and metalloid contaminants in the

groundwater. Five rounds of groundwater sampling

occurred between June 1999 and April 2000, and

was expected to continue on a quarterly basis until

July 2001. The average concentration of arsenic

entering the PRB, as measured from September to

November 1999 was 0.010 mg/L, and the effluent

concentration, measured in April 2000, was less

than 0.0002 mg/L (Ref. 13.1, 13.2, 13.14) (see

Project 2, Table 13.1).

Factors Affecting PRB Costs

ï PRB depth - PRBs at depths greater than 30

feet may be more expensive to install, requiring

special excavation equipment and construction

materials (Ref. 13.13).

ï Reactive media - Reactive media vary in cost,

therefore the reactive media selected can affect

PRB cost.

ï Factors affecting PRB performance - Items in

the ìFactors Affecting PRB Performanceî box

will also affect costs.

Summary of Cost Data

EPA compared the costs of pump-and-treat systems at

32 sites to the costs of PRBs at 16 sites. Although the

sites selected were not a statistically representative

sample of groundwater remediation projects, the capital

costs for PRBs were generally lower than those for

pump and treat systems (Ref. 13.13). However, at the

Monticello site, estimates showed that capital costs for

a PRB were greater than those for a pump-and-treat

system, but lower operations and maintenance costs

would result in a lower life-cycle cost to achieve similar

cleanup goals. For the PRB at the Monticello site, total

capital cost was $1,196,000, comprised of $1,052,000

for construction and $144,000 for the reactive PRB

media. Construction costs are assumed to include

actual construction costs and not design activities or

treatability studies (Ref. 13.14, cost year not provided). 

Cost data for the other projects described in the section

are not available.

References

13.1 U.S. EPA. Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition). 

Office of Solid Waste and Emergency Response. 

EPA-542-R-01-004. February 2001. http://cluin.org

13.2 Personal communication with Paul Mushovic,

RPM, Monticello Mill Tailings - OU3 Superfund

site. April 20, 2001.

13.3 U.S. Department of Energy, Grand Junction

Office (DOE-GJO). Permeable Reactive

Barriers: Treatability Studies. March 2000.

http://www.doegjpo.com/. 

13.4 Federal Remediation Technologies Roundtable:

Remediation Technologies Screening Matrix and

Reference Guide Version 3.0. 

http://www.frtr.gov/matrix2/top_page.html.

13.5 Ott N. Permeable Reactive Barriers for

Inorganics. National Network of Environmental

Management Studies (NNEMS) Fellow. July

2000. http://www.clu-in.org.

13.6 U.S. EPA. Permeable Reactive Barrier

Technologies for Contaminant Remediation.

Office of Research and Development. EPA-600-

R-98-125. September 1998.

http://www.epa.gov/ncepi/Catalog/

EPA600R98125.html

13.7 U.S. EPA Technology Innovation Office and

Office of Research and Development. 

Remediation Technologies Development Forum

(RTDF). Permeable Reactive Barrier Installation

Profiles. January 2000.

http://www.rtdf.org/public/permbarr/prbsumms/. 

13.8 DOE - GJO. Research and Application of

Permeable Reactive Barriers. K0002000. April

1998. 

http://www.gwrtac.org/pdf/permeab2.pdf

13.9 Baker MJ, Blowes DW, Ptacek CJ. Phosphorous

Adsorption and Precipitation in a Permeable

Reactive Wall: Applications for Wastewater

Disposal Systems. International Containment

Technology Conference and Exhibition,

February 9-12, 1997. St. Petersburg, Florida.
13-5

13.10 McRae CW, Blowes DW, Ptacek CJ. 

Laboratory-scale investigation of remediation of

As and Se using iron oxides. Sixth Symposium

and Exhibition on Groundwater and Soil

Remediation, March 18-21, 1997. Montreal,

Quebec, Canada.

13.11 U.S. EPA. In Situ Remediation Technology

Status Report: Treatment Walls. Office of Solid

Waste and Emergency Response. EPA 542-K94-004. April 1995. http://www.clu-in.org.

13.12 U.S. EPA. Innovative Remediation

Technologies: Field Scale Demonstration

Projects in North America, 2nd Edition. Office of

Solid Waste and Emergency Response. EPA542-B-00-004. June 2000. http://clu-in.org.

13.13 U.S. EPA. Cost Analyses for Selected

Groundwater Cleanup Projects: Pump and Treat

Systems and Permeable Reactive Barriers. 

Office of Solid Waste and Emergency Response. 

EPA-542-R-00-013. February 2001. http://cluin.org.

13.14 DOE. Permeable Reactive Treatment (PeRT)

Wall for Rads and Metals. Office of

Environmental Management, Office of Science

and Technology. DOE/EM-0557. September

2000. http://apps.em.doe.gov/ost/pubs/itsrs/

itsr2155.pdf

13.15 Attachment to an E-mail from Rick Wilkin, U.S.

EPA Region 8 to Linda Fiedler, U.S. EPA

Technology Innovation Office. July 27, 2001.

13.16 Lindberg J, Sterneland J, Johansson PO,

Gustafsson JP. Spodic material for in situ

treatment of arsenic in ground water. Ground

Water Monitoring and Remediation. 17, 125-3-. 

December 1997.

http://www.ce.kth.se/aom/amov/people/gustafjp/

abs11.htm

13.17 Su, C.; Puls, R. W. Arsenate and arsenite

removal by zerovalent iron: kinetics, redox

transformation, and implications for in situ

groundwater remediation. Environmental

Science and Technology. Volume 35. pp. 1487-

1492. 2001.

3.18 Smyth DJ, Blowes DW, Ptacek, CJ (Department

of Earth Sciences, University of Waterloo). 

Steel Production Wastes for Use in Permeable

Reactive Barriers (PRBs). Third International

Conference on Remediation of Chlorinated and

Recalcitrant Compounds. May 20-23, 2000. 

Monterey, CA.

13.19 Personal Communication from David Smyth,

University of Waterloo to Sankalpa Nagaraja,

Tetra Tech, EM Inc. August 13, 2002.
13-6

Table 13.1

Permeable Reactive Barrier Arsenic Treatment Performance Data for Arsenic

Project

Number Scale Site Name and Location

Initial Arsenic

Concentration (mg/L)

Final Arsenic

Concentration (mg/L)

Barrier Type and

Media Project Duration Source

1 Full Tonolli Corporation Superfund

Site, Nesquehoning, PA

0.313 Not available Trench, limestone August 1998 -

present

13.1, 13.7

2 Full Monticello Mill Tailings - OU3,

Monticello, UT

0.010 - 0.013 <0.0002 Funnel and gate, ZVI June 1999 -

present

13.1, 13.2,

13.14

3 Full Industrial Site, Chicago, IL -- -- Trench, basic oxygen

furnace slag

June 2002 -

present

13.19

4 Pilot Industrial Site, Northwestern

Ontario, Canada

0.4 mg/L 0.02 mg/L Trench, mixture of

ZVI, surfactant

modified zeolite, and

ion exchange resin

-- 13.19

5 Pilot Bodo Canyon Disposal Cell

Mill Tailings Site, Durango, CO

-- -- ZVI -- 13.12

6 Bench Former Uranium Ore Processing

Site, Tuba City, AZ

0.52 0.010 ZVI -- 13.3

7 Bench Monticello Mill Tailings,

Monticello, UT

0.024 0.001-0.008 ZVI -- 13.3

8 Bench Asarco East Helena Plant, East

Helena, MT

11 Not available ZVI -- 13.15

9 Bench -- 1-3 mg/L <0.02 mg/L -- -- 13.16

10 Bench – 4 mg/L <0.003 mg/L Basic oxygen furnace

slag

– 13.18

ZVI = Zero valent ironmg/L = Milligrams per liter-- = Not available
IIC

ARSENIC TREATMENT TECHNOLOGIES

APPLICABLE TO SOIL, WASTE, AND WATER
14-1

Process Control System

Extraction/

Exchange

Processing Processing

AC / DC

Converter

-Cathode

Cathodic

Process

Fluid Acid Front

and/or Anodic

Process Fluid

Anode+

Processed 

Media

OH -

F - Cl -

CN -

PO3-

4

NO -

3

Ca2+

Pb2+

Pb2+

Zn2+

Cr2+

H3O+

Extraction/

Exchange

Ca2+

Process Control System

Extraction/

Exchange

Processing Processing

AC / DC

Converter

-Cathode

Cathodic

Process

Fluid Acid Front

and/or Anodic

Process Fluid

Anode+

Processed 

Media

OH -

F - Cl -

CN -

PO3-

4

NO -

3

Ca2+

Pb2+

Pb2+

Zn2+

Cr2+

H3O+

Extraction/

Exchange

Ca2+

Model of an Electrokinetic Treatment System

Summary

 Electrokinetic treatment is an emerging remediation

technology designed to remove heavy metal

contaminants from soil and groundwater. The

technology is most applicable to soil with small

particle sizes, such as clay. However, its

effectiveness may be limited by a variety of

contaminants and soil and water characteristics. 

Information sources researched for this report

identified a limited number of applications of the

technology to arsenic. 

Technology Description: Electrokinetic

remediation is based on the theory that a lowdensity current will mobilize contaminants in the

form of charged species. A current passed between

electrodes is intended to cause water, ions, and

particulates to move through the soil, waste, and

water (Ref. 14.8). Contaminants arriving at the

electrodes can be removed by means of

electroplating or electrodeposition, precipitation or

coprecipitation, adsorption, complexing with ion

exchange resins, or by pumping of water (or other

fluid) near the electrode (Ref. 14.10). 

Media Treated:

• Soil

• Groundwater

• Industrial wastes

Chemicals Used in Electrokinetic Process to

Treat Arsenic:

• Sulfuric Acid

• Phosphoric Acid

• Oxalic Acid

14.0 ELECTROKINETIC TREATMENT OF

ARSENIC

Technology Description and Principles

In situ electrokinetic treatment of arsenic uses the

natural conductivity of the soil (created by pore water

and dissolved salts) to affect movement of water, ions,

and particulates through the soil (Ref. 14.8). Water

and/or chemical solutions can also be added to enhance

the recovery of metals by electrokinetics. Positively-
14-2

Factors Affecting Electrokinetic Treatment

Performance

• Contaminant properties - The applicability of

electrokinetics to soil and water containing

arsenic depends on the solubility of the

particular arsenic species. Electrokinetic

treatment is applicable to acid-soluble polar

compounds, but not to insoluble metals (Ref.

14.6).

• Salinity and cation exchange capacity - The

technology is most efficient when these

parameters are low (Ref. 14.14). Chemical

reduction of chloride ions at the anode by the

electrokinetic process may also produce

chlorine gas (Ref. 14.6).

• Soil moisture - Electrokinetic treatment

requires adequate soil moisture; therefore

addition of a conducting pore fluid may be

required (Ref. 14.7). Electrokinetic treatment is

most applicable to saturated soils (Ref. 14.9). 

However, adding fluid to allow treatment of

soils without sufficient moisture may flush

contaminants out of the targeted treatment area.

• Polarity and magnitude of the ionic charge -

These factors affect the direction and rate of

contaminant movement (Ref. 14.11).

• Soil type - Electrokinetic treatment is most

applicable to homogenous soils (Ref. 14.9). 

Fine-grained soils are more amenable to

electrokinetic treatment due to their large

surface area, which provides numerous sites for

reactions necessary for electrokinetic processes

(Ref. 14.13).

• pH - The pH can affect process

electrochemistry and cause precipitation of

contaminants or other species, reducing soil

permeability and inhibiting recovery. The

deposition of precipitation solids may be

prevented by flushing the cathode with water or

a dilute acid (Ref. 14.14).

charged metal or metalloid cations, such as As (V) and

As (III) migrate to the negatively-charged electrode

(cathode), while metal or metalloid anions migrate to

the positively charged electrode (anode) (Ref. 14.9). 

Extraction may occur at the electrodes or in an external

fluid cycling/extraction system (Ref. 14.11). 

Alternately, the metals can be stabilized in situ by

injecting stabilizing agents that react with and

immobilize the contaminants (Ref. 14.12). Arsenic has

been removed from soils treated by electrokinetics

using an external fluid cycling/extraction system (Ref.

14.2, 14.18).

This technology can also be applied ex situ to

groundwater by passing the water between electrodes. 

The current causes arsenic to migrate toward the

electrodes, and also alters the pH and oxidationreduction potential of the water, causing arsenic to

precipitate/coprecipitate. The solids are then removed

from the water using clarification and filtration (Ref.

14.21).

Media and Contaminants Treated

Electrokinetic treatment is an in situ treatment process

that has had limited use to treat soil, groundwater, and

industrial wastes containing arsenic. It has also been

used to treat other heavy metals such as zinc, cadmium,

mercury, chromium, and copper (Ref. 14.1, 14.4,

14.20).

Electrokinetic treatment may be capable of removing

contaminants from both saturated and unsaturated soil

zones, and may be able to perform without the addition

of chemical or biological agents to the site. This

technology also may be applicable to low-permeability

soils, such as clay (Ref. 14.1, 14.4, 14.9).

Type, Number, and Scale of Identified Projects

Treating Soil, Waste, and Water Containing Arsenic

The sources identified for this report contained

information on one full-scale, three pilot-scale, and

three bench-scale applications of electrokinetic

remediation to arsenic. Figure 14.1 shows the number

of applications identified at each scale. 

Summary of Performance Data 

Table 14.1 provides a performance summary of

electrokinetic treatment of arsenic. One full-scale

application reduced arsenic concentrations in soil from

greater than 250 mg/kg to less than 30 mg/kg. One ex

situ pilot-scale application reduced arsenic in

groundwater from 0.6 mg/L to 0.013 mg/L. The case

study at the end of this section further discusses this

project, and information in Table 14.1, Project 3

summarizes the available information about it.

Applicability, Advantages, and Potential Limitations

Electrokinetics is an emerging technology with

relatively few applications for arsenic treatment. It is

an in situ treatment technology, and therefore does not

require excavation of contaminated soil or pumping of

contaminated groundwater. Its effectiveness may be

limited by a variety of soil and contaminant

characteristics, as discussed in the box opposite. In
14-3

3

1

3

01234

Bench

Pilot

Full

Case Study: The Overpelt Project

A pilot-scale test of electrokinetic remediation of

arsenic in groundwater was conducted in Belgium

in 1997. This ex situ application involved pumping

groundwater contaminated with zinc, arsenic, and

cadmium and treating it in an electrokinetic

remediation system with a capacity of 6,600 gpm. 

The treatment system precipitated the

contaminants, and the precipitated solids were

removed using clarification and filtration. The

electrokinetic treatment system did not use

additives or chemicals. The treatment reduced

arsenic concentrations in groundwater from 0.6

mg/L to 0.013 mg/L. The reported costs of the

treatment were $0.004 per gallon for total cost, and

$0.002 per gallon for O&M. (Ref. 14.21) (see

Project 3, Table 14.1).

Factors Affecting Electrokinetic Treatment Costs

• Contaminant extraction system - Some

electrokinetic systems remove the contaminant

from the subsurface using an extraction fluid. 

In such systems, the extraction fluid may

require further treatment, which can increase

the cost (Ref. 14.4).

• Factors affecting electrokinetic treatment

performance - Items in the “Factors Affecting

Electrokinetic Treatment Performance” box

will also affect costs.

addition, its treatment depth is limited by the depth to

which the electrodes can be placed.

Figure 14.1

Scale of Electrokinetic Projects for Arsenic

Treatment

Summary of Cost Data

Estimated costs of in situ electrokinetic treatment of

soils containing arsenic range from $50 - $270 per cy

(Ref. 14.2, 14.4, cost year not provided). The reported

costs for one pilot-scale, ex situ treatment of

groundwater of the treatment were $0.004 per gallon for

total cost, and $0.002 per gallon for O&M. (Ref. 14.21)

(see Project 3, Table 14.1).

References

14.1 U.S. EPA. In Situ Remediation Technology:

Electrokinetics. Office of Solid Waste and

Emergency Response, Technology Innovation

Office. EPA-542-K-94-007. April 1995. 

http://clu-in.org

14.2 U.S. EPA. Database for EPA REACH IT

(REmediation And CHaracterization Innovative

Technologies). March 2001. 

http://www.epareachit.org.

14.3 U.S. EPA. Electrokinetics at an Active Power

Substation. Federal Remediation Technologies

Roundtable. March 2000.

http://www.frtr.gov/costperf.html. 

14.4 Electric Power Research Institute. Electrokinetic

Removal of Arsenic from Contaminated Soil: 

Experimental Evaluation. July 2000. 

http://www.epri.com/

OrderableitemDesc.asp?product_id. 

14.5 Ground-Water Remediation Technologies

Analysis Center. Technology Overview Report: 

Electrokinetics. July 1997.

http://www.gwrtac.org/pdf/elctro_o.pdf.

14.6 U.S. EPA. Contaminants and Remedial Options

at Selected Metal-Contaminated Sites. Office of

Research and Development. EPA-540-R-95-

512. July 1995.

http://www.epa.gov/ncepi/Catalog/

EPA540R95512.html

14.7 U.S. EPA. Recent Developments for In Situ

Treatment of Metals Contaminated Soils. 

Technology Innovation Office. Washington,

DC. March 5, 1997.

http://clu-in.org/download/remed/ metals2.pdf

14.8 Will, F. "Removing Toxic Substances from Soil

Using Electrochemistry," Chemistry and

Industry, p. 376-379. 1995. 
14-4

14.9 Evanko, C.R., and D.A. Dzomback. 

Remediation of Metals-Contaminated Soils and

Groundwater. Prepared for the Ground-Water

Remediation Technologies Analysis Center,

Technology Evaluation Report TE-97-01.

October 1997.

http://www.gwrtac.org/pdf/metals.pdf

14.10 Lindgren, E.R., et al. "Electrokinetic

Remediation of Contaminated Soils: An Update,"

Waste Management 92, Tucson, Arizona. 1992. 

14.11 Earthvision. "Electrokinetic Remediation,"

http://www.earthvision.net/filecomponent/

1727.html, as of October 1999.

14.12 LaChuisa, L. E-mail attachment from Laurie

LaChuisa, Electrokinetics, Inc., to Kate Mikulka,

Science Applications International Corporation,

Process description. August 1999. 

14.13 Acar, Y. B. and R. J. Gale. "Electrokinetic

Remediation: Basics and Technology Status,"

Journal of Hazardous Materials, 40: p. 117-137. 

1995. 

14.14 Van Cauwenberghe, L. Electrokinetics,

prepared for the Ground-Water Remediation

Technologies Analysis Center, GWRTAC O

Series Technology Overview Report TO-97-03. 

July 1997. 

http://www.gwrtac.org/pdf/elctro_o.pdf

14.15 LaChuisa, L. E-mail from Laurie LaChuisa,

Electrokinetics, Inc., to Kate Mikulka, Science

Applications International Corporation, Case

study for electrokinetic extraction/stabilization of

arsenic. August 1999. 

14.16 LaChuisa, L. E-mail from Laurie LaChuisa,

Electrokinetics, Inc., to Deborah R. Raja,

Science Applications International Corporation,

Responses to questions on Case Study. October

13, 1999. 

14.17 LaChuisa, L. Telephone contact between Laurie

LaChuisa, Electrokinetics, Inc., and Deborah R.

Raja, Science Applications International

Corporation, Responses to questions on Case

Study. October 11, 1999.

14.18 AAA Geokinetics - Electrokinetic Remediation.

April 24, 2001.

http://www.geokinetics.com/giiek.htm

14.19 Fabian, G.L., U.S. Army Environmental Center,

and Dr. R.M. Bricka, Waterways Experiment

Station. "Electrokinetic Remediation at NAWS

Point Mugu," paper presented at the

U.S./German Data Exchange Meeting.

September 1999.

14.20 Florida State University – College of

Engineering. August 2001. 

http://www.eng.fsu.edu/departments/civil/

research/arsenicremedia/index.htm

14.21 Pensaert, S. The Treatment of Aquifers

Contaminated with Arsenic, Zinc and Cadmium

by the Bipolar Electrolysis Technique: The

Overpelt Project. 1998. 

14.22 Ribeiro, AB, Mateus EP, Ottosen LM, BechNielsen G. Electrodialytic Removal of Cu, Cr,

and As from Chromated Copper ArsenateTreated Timber Waste. Environmental Science

& Technology. Vol. 34, No. 5. 2000.

http://www.vista.gov.vn/nganhangdulieu/tapchi/c

lv1899/2000/v34s5.htm

14.23 Redwine, J.C. Innovative Technologies for

Remediation of Arsenic in Soil and

Groundwater. Southern Co. Services, Inc. 

August 2001.

14.24 Markey, R. Comparison and Economic Analysis

of Arsenic Remediation Methods Used in Soil

and Groundwater. M.S. Thesis. FAMU-FSU

College of Engineering. 2000. 
14-5

Table 14.1

Electrokinetic Treatment Performance Data for Arsenic

Project

Number

Industry or

 Site Type

Waste or

Media, Volume Scale

Site Name and

Location

Initial Arsenic

Concentration

Final Arsenic Concentration

or Treatment Results

Electrokinetic Process

 Description Source

1 Wood Preserving Soil, 325 cubic

yards

Full Pederok Plant

Kwint,

Loppersum,

 Netherlands

> 250 mg/kg < 30 mg/kg Contaminant removed

by recirculation of

 electrolyte through

casing around electrodes

14.2,

14.18

2 Herbicide

application

Soil, 690 cubic

yards

Pilot -- 450 mg/kg -- -- 14.12,

14.15,14.16,

14.17

3 Metals refining

and smelting

Groundwater Pilot Belgium 0.6 mg/L 0.013 mg/L Bipolar electrolysis,

without use of

additional chemicals. 

Ex situ, pump and treat

application

14.21

4 Herbicide

application

Soil &

Groundwater

Pilot Florida ND - 1,400

mg/kg

<0.005 - 0.7

mg/L

-- Bipolar electrolysis,

without use of

additional chemicals

14.24

5 Cattle vat

(pesticide)

Soil Bench Blackwater River

State Forest, FL

113 mg/kg 4.7% of arsenic migrated to

anode, 1.6% to cathode

Addition of sulfuric acid

to enhance

electrokinetic process

14.4

6 Cattle vat

(pesticide)

Soil Bench Blackwater River

State Forest, FL

113 mg/kg 25% of arsenic migrated to

anode, none to cathode

Addition of phosphoric

acid to enhance

electrokinetic process

14.4

7 Wood Preserving Sawdust from

CCA-treated

 pole

Bench Leiria, Portugal 811- 871 mg/kg 27-99% removal efficiency Electrodialytic removal,

enhanced by addition of

oxalic acid

14.22

-- = Not availableCCA = Chromated copper arsenatemg/L = Milligrams per litermg/kg = Milligrams per kilogram
15-1

Technology Description: Phytoremediation is

designed to use plants to degrade, extract, contain,

or immobilize contaminants in soil, sediment, or

groundwater (Ref. 15.6). Typically, trees with deep

roots are applied to groundwater and other plants are

used for shallow soil contamination.

Media Treated:

ï Soil

ï Groundwater

Types of Plants Used in Phytoremediation to

Treat Arsenic:

ï Poplar 

ï Cottonwood

ï Sunflower

ï Indian mustard

ï Corn

Summary

Phytoremediation is an emerging technology. The

data sources used for this report contained

information on only one applications of

phytoremediation to treat arsenic at full scale and

two at pilot scale. Experimental research into

identifying appropriate plant species for

phytoremediation is ongoing. It is generally

applicable only to shallow soil or relatively shallow

groundwater that can be reached by plant roots. In

addition, the phytoremediating plants may

accumulate high levels of arsenic during the

phytoremediation process, and may require

additional treatment prior to disposal.

O + exduates

e.g., CH C OOH

2

3

Degradation Root respiration

CO + H O2 2

Mineralization

Uptake

Transpiration

Phloem

Photosynthesis + O

Xylem

H O + nutrients

2

2

Photosynthesis Dark Respiration

Organic

chemicals

C H O x y z

Uptake (and

contaminant

removal)

Transpiration

15.0 PHYTOREMEDIATION TREATMENT

OF ARSENIC

Technology Description and Principles

Phytoremediation is an emerging technology generally

applicable only to shallow contamination that can be

reached by plant roots. Phytoremediation applies to all

biological, chemical, and physical processes that are

influenced by plants and the rhizosphere, and that aid in

cleanup of the contaminated substances. 

Phytoremediation may be applied in situ or ex situ, to

soils, sludges, sediments, other solids, or groundwater

(Ref. 15.1, 15.4, 15.5, 15.7). The mechanisms of

phytoremediation include phytoextraction (also known as

phytoaccumulation, the uptake of contaminants by plant

roots and the translocation/accumulation of contaminants

into plant shoots and leaves), enhanced rhizosphere

biodegradation (takes place in soil or groundwater

immediately surrounding plant roots), phytodegradation

(metabolism of contaminants within plant tissues), and

phytostabilization (production of chemical

compounds by plants to immobilize

contaminants at the interface of roots and

soil). The data sources used for this report

identified phytoremediation applications for

arsenic using phytoextraction and

phytostabilization.

The selection of the phytoremediating

species depends upon the species ability to

treat the contaminants and the depth of

contamination. Plants with shallow roots

(for example, grasses, corn) are appropriate

only for contamination near the surface,

typically in shallow soil. Plants with deeper

roots, (for example, trees) may be capable of

remediating deeper contaminants in soil or

groundwater plumes.

Examples of vegetation used in phytoremediation

include sunflower, Indian mustard, corn, and grasses

(such as ryegrass and prairie grasses) (Ref. 15.1). Some

plant species, known as hyperaccumulators, absorb and

concentrate contaminants within the plant at levels

greater than the concentration in the surrounding soil or

groundwater. The ratio of contaminant concentration in

the plant to that in the surrounding soil or groundwater

is known as the bioconcentration factor. A

hyperaccumulating fern (Pteris vittata) has been used in

the remediation of arsenic-contaminated soil, waste, and

water. The fern can tolerate as much as 1,500 parts per

million (ppm) of arsenic in soil, and can have a 

bioconcentration factor up to 265. The arsenic

concentration in the plant can be as high as 2 percent

(dry weight) (Ref. 15.3, 15.6).
15-2

2

1

4

01234

Bench

Pilot

Full

Factors Affecting Phytoremediation

Performance

ï Contaminant depth - The treatment depth is

limited to the depth of the plant root system

(Ref. 15.5).

ï Contaminant concentration - Sites with low

to medium level contamination within the root

zone are the best candidates for

phytoremediation processes (Ref. 15.4, 15.5). 

High contaminant concentrations may be toxic

to the remediating flora.

ï Climatic or seasonal conditions - Climatic

conditions may interfere or inhibit plant

growth, slow remediation efforts, or increase

the length of the treatment period (Ref. 15.4).

ï Contaminant form - In phytoaccumulation

processes, contaminants are removed from the

aqueous or dissolved phase. 

Phytoaccumulation is generally not effective on

contaminants that are insoluble or strongly

bound to soil particles.

ï Agricultural factors - Factors that affect plant

growth and health, such as the presence of

weeds and pests, and ensuring that plants

receive sufficient water and nutrients will affect

phytoremediation processes.

Media and Contaminants Treated

Phytoremediation has been applied to contaminants from

soil, surface water, groundwater, leachate, and municipal

and industrial wastewater (Ref. 15.4). In addition to

arsenic, examples of pollutants it can potentially address

include petroleum hydrocarbons such as benzene,

toluene, ethylbenzene, and xylenes (BTEX), polycyclic

aromatic hydrocarbons (PAHs), pentachlorophenol,

polychlorinated biphenyls (PCBs), chlorinated aliphatics

(trichloroethylene, tetrachloroethylene, and 1,1,2,2-

tetrachloroethane), ammunition wastes (2,4,6-

trinitrotoluene or TNT, and RDX), metals (lead,

cadmium, zinc, arsenic, chromium, selenium), pesticide

wastes and runoff (atrazine, cyanazine, alachlor),

radionuclides (cesium-137, strontium-90, and uranium),

and nutrient wastes (ammonia, phosphate, and nitrate)

(Ref. 15.7).

Type, Number, and Scale of Identified Projects

Treating Soil, Waste, and Water Containing Arsenic

The data sources used for this report contained

information on phytoremediation of arsenic

contaminated soil at full scale at one Superfund site (Ref.

15.7). Two pilot-scale applications and four bench-scale

tests were also identified (Ref. 15.2, 15.3, 15.7-11). 

Figure 15.1 shows the number of identified applications

at each scale.

Figure 15.1

Scale of Identified Phytoremediation Projects for

Arsenic Treatment

Summary of Performance Data

Table 15.1 provides a performance summary of the

identified phytoremediation projects. Data on the effect

of phytoremediation on the leachability of arsenic from

soil were not identified. Where available, Table 15.1

provides total arsenic concentrations prior to and

following phytoremediation treatment. However, no

projects with arsenic concentrations in the treated soil,

waste, and water both prior to and after treatment were

identified. Bioconcentration factors were available for

one pilot- and two bench-scale studies, and ranged from

8 to 320.

Applicability, Advantages, and Potential Limitations

Phytoremediation is conducted in situ and therefore

does not require soil excavation. In addition,

revegetation for the purpose of phytoremediation also

can enhance restoration of an ecosystem (Ref. 15.5).

This technology is best applied at sites with shallow

contamination. If phytostabilization is used, the

vegetation and soil may require long-term maintenance

to prevent re-release of the contaminants. Plant uptake

and translocation of metals to the aboveground portions

of the plant may introduce them into the food chain if

the plants are consumed (Ref. 15.5). Products could

bioaccumulate in animals that ingest the plants (Ref.

15.4). In addition, the toxicity and bioavailability of

contaminants absorbed by plants and phytodegradation

products is not always known. 

Concentrations of contaminants in hyperaccumulating

plants are limited to a maximum of about 3% of the
15-3

Factors Affecting Phytoremediation Costs

ï Number of crops grown - A greater number

of crops may decrease the time taken for

contaminants to be remediated to specified

goals, thereby decreasing costs (Ref. 15.2). 

However, the number of crops grown will be

limited by the length of the growing season, the

time needed for crops to reach maturity, the

potential for multiple crops to deplete the soil

of nutrients, climatic conditions, and other

factors.

ï Factors affecting phytoremediation

performance - Items in the ìFactors Affecting

Phytoremediation Performanceî box will also

affect costs.

plant weight on a dry weight basis. Based on this

limitation, for fast-growing plants, the maximum annual

contaminant removal is about 400 kg/hectare/year. 

However, many hyperaccumulating species do not

achieve contaminant concentrations of 3%, and are slow

growing. (Ref. 15.12)

The case study at the end of this section further discusses

an application of phytoremediation to the treatment to

arsenic-contaminated soil. Information for this project is

summarized in Table 15.1, Project 1.

Summary of Cost Data

Cost data specific to phytoremediation of arsenic were

not identified. The estimated 30-year costs (1998

dollars) for remediating a 12-acre lead site were

$200,000 for phytoextraction (Ref. 15.15). Costs were

estimated to be $60,000 to $100,000 using

phytoextraction for remediation of one acre of

20-inch-thick sandy loam (Ref. 15.14). The cost of

removing radionuclides from water with sun-flowers has

been estimated to be $2 to $6 per thousand gallons of

water (Ref. 15.16). Phytostabilization system costs have

been estimated at $200 to $10,000 per hectare,

equivalent to $0.02 to $1.00 per cubic meter of soil,

assuming a 1-meter root depth (Ref. 15.17).

References

15.1 U.S. EPA. Treatment Technologies for Site

Cleanup: Annual Status Report (Tenth Edition). 

Office of Solid Waste and Emergency Response. 

EPA-542-R-01-004. February 2001.

http://www.epa.gov/ncepi/Catalog/

EPA542R01004.html

15.2 Cost and Performance Case Study.

Phytoremediation at Twin Cities Army

Ammunition Plant Minneapolis-St.Paul,

Minnesota. Federal Remediation Technologies

Roundtable (FRTR).

http://www.frtr.gov/costperf.htm.

15.3 Ma LQ, Komar KM, Tu C, Zhang WH, Cai Y,

Kennelly ED. A fern that hyperaccumulates

arsenic. Nature 409:579. February 2001.

http://www.ifas.ufl.edu/~qma/PUBLICATION/

Nature.pdf

15.4 Federal Remediation Technologies Screening

Matrix and Reference Guide Version 3.0. FRTR. 

http://www.frtr.gov/matrix2/top_page.html

15.5 U.S. EPA. Introduction to Phytoremediation.

National Risk Management Research

Laboratories. Office of Research and

Development. EPA 600-R-99-107. February

2000. http://www.clu-in.org/download/remed/

introphyto.pdf

15.6 Zhang W, Cai Y, Tu C, Ma LQ. Speciation and

Distribution of Arsenic in an Arsenic

Hyperaccumulating Plant. Biogeochemistry of

Environmentally Important Elements. Symposia

Papers Presented Before the Division of

Environmental Chemistry. American Chemical

Society. San Diego, CA. April 1-5, 2001.

15.7 Schnoor JL. Phytoremediation. Technology

Evaluation Report. Prepared for Ground-Water

Remediation Technologies Analysis Center

(GWRTAC). 1997. 

http://www.gwrtac.org/html/

tech_eval.html#PHYTO

15.8 U.S. EPA. Phytoremediation Resource Guide. 

Office of Solid Waste and Emergency Response. 

EPA 542-B-99-003. June 1999.

http://www.clu-in.org/download/remed/

phytoresguide.pdf

15.9 Compton A, Foust RD, Salt DA, Ketterer ME. 

Arsenic Accumulation in Potomogeton

illinoiensis in Montezuma Well, Arizona.

Biogeochemistry of Environmentally Important

Elements. Symposia Papers Presented Before

the Division of Environmental Chemistry.

American Chemical Society. San Diego, CA. 

April 1-5, 2001.

15.10 Redwine JC. Innovative Technologies for

Remediation of Arsenic in Soil and

Groundwater. Southern Company Services, Inc. 

15.11 Qian JH, Zayed A, Zhu YL, Yu M, Terry N. 

Phytoaccumulation of Trace Elements by

Wetland Plants: III. Uptake and Accumulation

of Ten Trace Elements by Twelve Plant Species. 

Journal of Environmental Quality. 1999.

15.12 Lasat, M. The Use of Plants for the Removal of

Toxic Metals from Contaminated Soil. 

American Association for the Advancement of

Science.
15-4

15.13 Lasat, M. Phytoextraction of Toxic Metals: A

review of Biological Mechanisms. J. of Environ.

Qual. 31:109-120. 2002.

15.14 Salt, D. E., M. et al. Phytoremediation: A Novel

Strategy for the Removal of Toxic Metals from

the Environment Using Plants. Biotechnol.

13:468-474. 1995.

15.15 Cunningham, S. D. The Phytoremediation of Soils

Contaminated with Organic Pollutants: Problems

and Promise. International Phytoremediation

Conference. May 8-10. Arlington, VA. 1996.

15.16 Dushenkov, S., D. et al.. Removal of Uranium

from Water Using Terrestrial Plants. Environ, Sci.

Technol. 31(12):3468-3474. 1997. 

15.17 Cunningham, S. D., and W. R. Berti, and J. W.

Huang. Phytoremediation of Contaminated Soils.

Trends Biotechnol. 13:393-397. 1995.
Table 15.1

Arsenic Phytoremediation Treatment Performance Data for Arsenic

15-5

Project

Number

Industry or Site

Type

Waste or

Media Scale

Site Name or

Location

Initial Arsenic

Concentration

Final Arsenic 

Concentration

Bioconcentration

Factor

Remediating

Flora Source

1 Mining Deep soil Full Whitewood Creek

Superfund Site, SD

1,000 mg/kg Performance data

not available due

to death of

remediating flora.

Hybrid poplar

(specific

variety not

identified)

15.7

2 Munitions

Manufacturing/S

torage

Surface soil Pilot Twin Cities Army

Ammunition Plant, Site

C and Site 129-3,

Minneapolis-St. Paul,

MN

-- -- -- Corn (specific

variety not

identified), 

white mustard

(Sinapis alba)

15.2

3 -- Groundwater

(ex situ)

Pilot Montezuma Well, AZ 100 mg/L (Well

water)

4.59 mg/kg

(shoots)

8.87 mg/kg

(roots)

8 Potomogeton

illinoiensis

15.9

4 -- Surface soil Bench -- 650 -- 20 - 75 (leaves) Moss verbena

(V. tenuisecta)

15.10

-- -- 60 - 320 (shoots) Saw palmetto

(S. repens)

5 Wood

Preserving

Surface soil Bench FL 400 -- 265 Brake fern

(Pteris vittata)

15.3

6 -- Soil Bench East Palo Alto, CA -- -- -- Tamarisk

(Tamarix

ramosissima),

Eucalyptus

15.8

7 -- Soil Bench -- -- 34 mg/kg

(shoots)

177 mg/kg (roots)

-- Water lettuce

(Pistia

stratiotes)

15.11
16 - 1

Summary

Biological treatment designed to remove arsenic

from soil, waste, and water is an emerging

remediation technology. The information sources

used for this report identified a limited number of

projects treating arsenic biologically. Arsenic was

reduced to below 0.050 mg/L in one pilot-scale

application. This technology promotes

precipitation/coprecipitation of arsenic in water or

leaching of arsenic in soil and waste. The leachate

from bioleaching requires additional treatment for

arsenic prior to disposal.

Technology Description: Biological treatment of

arsenic is based on the theory that microorganisms 

that act directly on arsenic species or create ambient

conditions that cause arsenic to precipitate/

coprecipitate from water and leach from soil and

waste. 

Media Treated:

• Soil

• Waste

• Water

Microbes Used:

• Sulfate-reducing bacteria

• Arsenic-reducing bacteria

Effluent

Packed

media and

microbes

Influent

Model of a Biological Treatment System

16.0 BIOLOGICAL TREATMENT FOR

ARSENIC

Technology Description and Principles

Although biological treatments have usually been

applied to the degradation of organic contaminants,

some innovative techniques have applied biological

remediation to the treatment of arsenic. This

technology involves biological activity that promotes

precipitation/coprecipitation of arsenic from water and

leaching of arsenic in soil and waste. 

Biological precipitation/coprecipitation processesfor

water create ambient conditions intended to cause

arsenic to precipitate/coprecipitate or act directly on

arsenic species to transform them into species that are

more amenable to precipitation/coprecipitation. The

microbes may be suspended in the water or attached to

a submerged solid substrate. Iron or hydrogen sulfide

may also be added (Ref. 16.2, 16.3, 16.4, 16.4).

One water treatment process depends upon biological

activity to produce and deposit iron oxides within a

filter media, which provides a large surface area over

which the arsenic can contact the iron oxides. The

aqueous solution is passed through the filter, where

arsenic is removed from solution through

coprecipitation or adsorption to the iron oxides. An

arsenic sludge is continuously produced (Ref. 16.3).

Another process uses anaerobic sulfate-reducing

bacteria and other direct arsenic-reducing bacteria to

precipitate arsenic from solution as insoluble arsenicsulfide complexes (Ref. 16.2). The water containing

arsenic is typically pumped through a packed-bed

column reactor, where precipitates accumulate until the

column becomes saturated (Ref. 16.5). The arsenic is

then stripped and the column is biologically regenerated

(Ref. 16.2). Hydrogen sulfide has also been used in

suspended reactors to biologically precipitate arsenic

out of solution (Ref. 16.2, 16.4). These reactors require

conventional solid/liquid separation techniques for

removing precipitates.

Removal of arsenic from soil biologically via

“accelerated bioleaching” has also been tested on a

bench scale. The microbes in this system produce

nitric, sulfuric, and organic acids which are intended to

mobilize and remove arsenic from ores and sediments

(Ref. 16.4). This biological activity also produces

surfactants, which can enhance metal leaching (Ref.

16.4).

Media and Contaminants Treated

Biological treatment typically uses microorganisms to

degrade organic contaminants in soil, sludge, solids 

groundwater, and wastewaters. Biological treatment
16 - 2

3

1

1

01234

Bench

Pilot

Full

Factors Affecting Biological Treatment

Performance

• pH - pH levels can inhibit microbial growth. 

For example, sulfate-reducing bacteria perform

optimally in a pH range of 6.5 to 8.0 (Ref.

16.5).

• Contaminant concentration - High arsenic

concentrations may be toxic to microorganisms

used in biological treatment (Ref. 16.1).

• Available nutrients - An adequate nutrient

supply should be available to the microbes to

enhance and stimulate growth. If the initial

solution is nutrient deficient, nutrient addition

may be necessary.

• Temperature - Lower temperatures decrease

biodegradation rates. Heating may be required

to maintain biological activity (Ref. 16.1).

• Iron concentration - For biologicallyenhanced iron precipitation, iron must be

present in the water to be treated. The optimal

iron level depends primarily on the arsenic

concentration. (Ref. 16.3).

Factors Affecting Biological Treatment Costs

• Pretreatment requirements - Pretreatment

may be required to encourage the growth of key

microorganisms. Pretreatment can include pH

adjustment and removal of contaminants that

may inhibit microbial growth.

• Nutrient addition - If nutrient addition is

required, costs may increase. 

• Factors affecting biological treatment

performance - Items in the “Factors Affecting

Biological Treatment Performance” box will

also affect costs.

has also been used to treat arsenic in water via

precipitation/coprecipitation and in soil through

leaching (Ref. 16.1, 16.3).

Type, Number, and Scale of Identified Projects

Treating Soil, Waste, and Water Containing Arsenic

The data sources used for this report contained

information on biological treatment of arsenic at full

scale at one facility, at pilot scale at three facilities, and

at bench scale for one project. Figure 16.1 shows the

number of identified applications at each scale. An

enhanced bioleaching system for treating soil

containing arsenic has been tested at bench scale (Ref.

16.4) (Table 16.1, Project 5). In addition, a biological

treatment system using hydrogen sulfide has been used

in a bioslurry reactor to treat arsenic at bench and pilot

scales (Ref. 16.4) (Table 16.1, Project 4). 

Figure 16.1

Scale of Identified Biological Treatment Projects for

Arsenic

Summary of Performance Data

Table 16.1 lists the available performance data for three

projects using biological treatment for arsenic

contamination in water. Of the two projects that treated

wastewaters containing arsenic, only one had both

influent and effluent arsenic concentration data (Project

1). The arsenic concentration was not reduced to below

0.05 mg/L in this project.

One project (Project 3) treated groundwater spiked with

sodium arsenite. The groundwater had naturallyoccurring iron at 8 - 12 mg/L (Ref. 16.3). The initial

arsenic concentration ranged from 0.075 to 0.400 mg/L,

and was reduced by treatment to less than 0.050 mg/L. 

No data were available for the one soil bioleaching

project.

The case study at the end of this section further

discusses a pilot-scale application of biological

treatment to arsenic-contaminated groundwater. 

Information for this project is summarized in Table

16.1, Project 3.

Applicability, Advantages, and Potential Limitations

A variety of arsenic-contaminated soil, waste, and water

can be treated using biological processes. Biological

treatment of arsenic may produce less sludge than

conventional ferric arsenic precipitation (Ref. 16.2). A

high concentration of arsenic could inhibit biological

activity (Ref. 16.1, 16.2).
16 - 3

Case Study: Sodium Arsenite Spiked

Groundwater, Forest Row, Sussex, United

Kingdom

Groundwater with naturally-occurring iron between

8 and 12 mg/L was extracted in Forest Row,

Sussex, England and spiked with sodium arsenite. 

The arsenic concentration before treatment ranged

from 0.075 to 0.400 mg/L in the untreated water. 

The spiked groundwater was passed through a pilot

biological filtration unit, 3 m high with a 15 cm

diameter and filled to 1 m with silica sand. The

arsenic concentration was reduced to <0.04 mg/L

(Ref. 16.3) (see Project 3, Table 16.1).

Summary of Cost Data

The reported costs for biological treatment of arseniccontaminated soil, waste, and water range from less

than $0.50 to $2.00 per 1,000 gallons (Ref. 16.2, 16.4,

cost year not provided).

References

16.1 Remediation Technologies Reference Guide and

Screening Manual, Version 3.0. Federal

Remediation Technologies Roundtable.

http://www.frtr.gov/matrix2/top_page.html. 

16.2 Applied Biosciences. June 28, 2001.

http://www.bioprocess.com 

16.3 Use of Biological Processes for Arsenic

Removal. June 28, 2001. 

http://www.saur.co.uk/poster.html 

16.4 Center for Bioremediation at Weber State

University. Arsenic Treatment Technologies.

August 27, 2001. http://www.weber.edu/

Bioremediation/arsenic.htm

16.5 Tenny, Ron and Jack Adams. Ferric Salts

Reduce Arsenic in Mine Effluent by Combining

Chemical and Biological Treatment. August 27,

2001. http://www.esemag.com/0101/ferric.html
Table 16.1

Biological Treatment Performance Data for Arsenic

16 - 4

Project

Number

Industry or

Site Type Waste or Media Scale

Site Name

or Location

Initial Arsenic

Concentration

Final Arsenic

Concentration

Precipitate

Arsenic

Concentration Biological Process Source

1 -- Wastewater Full -- -- <0.05 mg/L -- Reduction and

precipitation from sulfate

reducing bacteria and

direct arsenic-reducing

bacteria

16.2

2 -- Wastewater Pilot -- 13 mg/L <0.5 mg/L -- Anaerobic sulfatereducing bacteria with a 

two-stage reactor, arsenic

precipitation and column

system

16.1

3 -- Groundwater

spiked with

sodium arsenite

Pilot -- 0.075 - 0.400

mg/L

0.010 - 0.040

mg/L

-- Biological filtration where

microbial activity

produces iron oxides for

coprecipitation or

adsorption of arsenic

16.3

4 – Groundwater Pilot – – – -- Precipitation of arsenic

sulfides using hydrogen

sulfide in a bioreactor

system

16.4

5 – Ores and

sediments

Bench – – – -- Enhanced bioleaching

system using microbialgenerated acids to

accelerate anion and

cation removal from ores

and sediments 

16.4

mg/L = Milligram per liter-- = Not available