United States 

 Environmental Protection 

 Agency 

Water Treatment Technology Feasibility Support 

Document for Chemical Contaminants for the 

Second Six-Year Review of 

National Primary Drinking Water Regulations 
Office of Water (4607M) 

EPA 815-B-09-007 

October 2009 

www.epa.gov/safewater 
EPA-OGWDW Water Treatment Technology Feasibility Support EPA 815-B-09-007 

Document for Chemical Contaminants for the Second Six-Year October 2009 

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Table of Contents 

Executive Summary...................................................................................................................ES-1 

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

2 Measuring Treatment Effectiveness for Contaminants Regulated through MCLs.............. 2-1 

3 Treatment Reviews for Contaminants Regulated Through MCLs ......................................3-1 

3.1 2,4-D ............................................................................................................................3-1 

3.2 Endothall......................................................................................................................3-3 

3.3 Hexachlorocyclopentadiene......................................................................................... 3-3 

3.4 Oxamyl.........................................................................................................................3-3 

3.5 Toluene ........................................................................................................................3-4 

3.6 Xylenes ........................................................................................................................3-5 

3.7 Benzene........................................................................................................................3-5 

3.8 Chlordane.....................................................................................................................3-6 

3.9 1,2-Dibromo-3-chloropropane (DBCP)....................................................................... 3-6 

3.10 1,2-Dichloropropane ....................................................................................................3-7

3.11 Heptachlor....................................................................................................................3-7 

3.12 Heptachlor Epoxide ..................................................................................................... 3-8

3.13 Hexachlorobenzene...................................................................................................... 3-8

3.14 Toxaphene....................................................................................................................3-8 

3.15 1,1,2-Trichloroethane................................................................................................... 3-9 

3.16 Vinyl Chloride ............................................................................................................. 3-9 

3.17 Carbon Tetrachloride ................................................................................................... 3-9

3.18 1,2-Dichloroethane (Ethylene Dichloride)................................................................. 3-10 

3.19 Dichloromethane........................................................................................................ 3-10 

3.20 Tetrachloroethylene ...................................................................................................3-11

3.21 Trichloroethylene....................................................................................................... 3-12 

4 Review of Treatment Techniques for Acrylamide and Epichlorohydrin............................. 4-1 

4.1 Improvements in Manufacturing.................................................................................. 4-2 

4.2 Regulations and Guidelines in Other Countries........................................................... 4-2 

5 References............................................................................................................................5-1 

Appendix: Monomer Data from NSF International.................................................................... A-1 
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Table of Exhibits 

Exhibit ES-1. Summary of Treatment Feasibility Review for Contaminants Regulated 

through MCLs............................................................................................................................ES-3 

Exhibit 1-1. Contaminants Included in this Treatment Technology Feasibility Review............. 1-2 

Exhibit 3-1. Summary of Treatment Feasibility Review for Contaminants Regulated through 

MCLs ...........................................................................................................................................3-2 

Exhibit 4-1. Summary of NSF International Product Testing Results for Acrylamide and 

Epichlorohydrin ........................................................................................................................... 4-2 

Exhibit 4-2. Comparison of Acrylamide and Epichlorohydrin Drinking Water Guidelines .......4-3 
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Abbreviations and Acronyms 

ANSI American National Standards Institute 

atm m3/m3 atmospheres-cubic meter (of water) per cubic meter (of air) 

BAT Best Available Technology 

DBCP 1,2-dibromo-3-chloropropane 

EPA Environmental Protection Agency 

EQL Estimated Quantitation Level 

ETV EPA’s Environmental Technology Verification Program 

GAC Granular Activated Carbon 

lbs/1,000 gal pounds of carbon used per 1,000 gallons of water treated 

MCL Maximum Contaminant Level 

MCLG Maximum Contaminant Level Goal 

mg/kg milligrams per kilogram 

mg/L milligrams per liter 

NPDWRs National Primary Drinking Water Regulations 

PAC Powdered Activated Carbon 

POU Point-of-use 

POU-GAC Point-of-use Granular Activated Carbon 

PQL Practical Quantitation Level 

PTA Packed Tower Aeration 

SDWA Safe Drinking Water Act 

SOCs Synthetic Organic Compounds 

TCE Trichloroethylene 

TT Treatment Technique 

VOCs Volatile Organic Compounds 

WHO World Health Organization 

μg/L micrograms per liter 
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Document for Chemical Contaminants for the Second Six-Year October 2009 

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Executive Summary 

The U.S. Environmental Protection Agency (EPA) has completed its second Six-Year Review 

(Six-Year Review 2) of national primary drinking water regulations (NPDWRs). The 1996 Safe 

Drinking Water Act (SDWA) Amendments require the U.S. Environmental Protection Agency 

(EPA or the Agency) to periodically review existing National Primary Drinking Water 

Regulations (NPDWRs). Section 1412(b)(9) of SDWA reads: 

 ...[t]he Administrator shall, not less than every 6 years, review and revise, as 

appropriate, each primary drinking water regulation promulgated under this title. 

Any revision of a national primary drinking water regulation shall be promulgated 

in accordance with this section, except that each revision shall maintain, or 

provide for greater, protection of the health of persons. 

The primary goal of the Six-Year Review process is to identify NPDWRs for possible regulatory 

revision. Although the statute does not define when a revision is “appropriate,” as a general 

benchmark, EPA considered a possible revision to be “appropriate” if, at a minimum, it presents 

a meaningful opportunity to: 

• improve the level of public health protection, and/or 

• achieve cost savings while maintaining or improving the level of public health protection. 

For Six-Year Review 2, EPA implemented the protocol that it developed for the first Six-Year 

Review (USEPA, 2003), including minor revisions developed during the current review process 

(USEPA, 2009d). EPA obtained and evaluated new information that could affect a NPDWR, 

including information on health effects (USEPA, 2009f), analytical feasibility (USEPA, 2009b), 

and occurrence (USEPA, 2009a and 2009e). 

This technical support document provides the Agency’s findings for its review of treatment 

feasibility information. EPA identified potential to revise NPDWRs for 23 contaminants. 

Consequently, EPA reviewed the best available technologies (BATs) and treatment techniques 

(TTs) specified in NPDWRs, and any emerging technologies, to determine whether treatment 

performance would pose a limitation to such revisions. This document describes these treatment 

feasibility reviews. 

EPA reviewed the BATs and technologies to meet TTs to determine the potential to achieve 

concentrations based on estimated quantitation levels (EQLs) or new health effects information. 

USEPA (2009c) provides a description of the EQLs and USEPA (2009f) identifies the new 

health-based thresholds. EPA used these thresholds to evaluate potential for meaningful 

opportunity to improve public health protection. The result of the treatment review is a 

determination of whether treatment would pose a limitation to revising an NPDWR. 

EPA measured technology effectiveness for contaminants for which the enforceable standard is a 

maximum contaminant level (MCL) based on the following factors: 

• Removal efficiency, which is measured as the percentage of the influent concentration 

removed through treatment 
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• Qualitative conclusions about treatability from previous EPA rulemakings and other 

scientific and engineering sources 

• Other, technology-specific measures. 

Aeration and carbon adsorption are common contaminant removal technologies. In instances 

when BATs and/or small system compliance technologies include aeration technologies, EPA 

used Henry’s Law constants as indicators of likely treatment effectiveness. Aeration 

technologies, which include packed tower aeration (PTA), multi-stage bubble aeration, tray 

aeration, shallow tray aeration, spray aeration, and mechanical aeration, remove contaminants by 

passing air through the water to be treated. Aeration processes transfer, or “strip,” volatile 

contaminants from the water into the air. Henry’s Law constants, which can vary across 

contaminants, provide measures of the ease with which this stripping occurs. 

In instances when BATs and/or small system compliance technologies include carbon adsorption 

technologies, EPA used bed life and carbon usage rates as indicators of likely treatment 

effectiveness. Carbon adsorption technologies, which include granular activated carbon (GAC), 

powdered activated carbon (PAC), and point-of-use granular activated carbon (POU-GAC), 

remove contaminants through adsorption onto a carbon media. The length of time for which the 

carbon retains its capacity to absorb target contaminants provides a measure of treatment 

feasibility and effectiveness. 

EPA did not identify limitations of BAT, small system compliance technologies, or emerging 

technologies to achieve the EQL or health-based thresholds for most of the contaminants 

regulated through MCLs. Exhibit ES-1 summarizes these results. For oxamyl, however, data on 

removal efficiency and a lack of demonstrated treatment effectiveness at low concentrations 

suggest potential for limitation at concentrations as low as the health-based threshold. Similarly, 

for 1,2-dichloropropane, treatment to the estimated quantitation level may not be feasible. 

EPA established a TT in lieu of an MCL for acrylamide and epichlorohydrin because of the 

absence of standardized analytical methods for measurement in water. The TT limits the 

allowable monomer level in products used for water treatment and the dosage of polymers that 

contain them. EPA established the residual monomer level for each contaminant at the lowest 

level manufacturers could feasibly achieve at the time of regulation. A system can use third-party 

or manufacturer’s certification in lieu of testing for the residual monomer level. 

NSF International (NSF), a third party organization, tests and certifies water treatment chemicals 

that meet NSF/ANSI Standard 60, Drinking Water Treatment Chemicals – Health Effects, which 

sets out requirements for treatment chemicals based on human health protection (NSF, 1999a). 

The requirements for acrylamide- and epichlorohydrin-based polymers in Standard 60 are based 

on EPA’s TT standards. Thus, NSF 60 certification of a polymeric coagulant aid containing 

acrylamide or epichlorohydrin indicates that users are in compliance with EPA’s regulation when 

a product is used as specified (i.e., for the intended purpose and up to the maximum usage level 

indicated by NSF). EPA obtained NSF data indicating that manufacturers now produce polymers 

with substantially lower residual monomer content than the TTs require. This new information, 

viewed in conjunction with regulations and guidelines in other countries, suggests there is 

potential to revise the TTs to reflect a lower feasible monomer content 
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Exhibit ES-1. Summary of Treatment Feasibility Review for Contaminants 

Regulated through MCLs

Contaminant 

Current MCL 

(mg/L) 

Threshold 

Evaluated 

(mg/L) BAT 

Treatment 

Limitation 

Potential 

2,4-D 0.07 0.04 GAC1 No 

Endothall 0.1 0.05 GAC1 No 

Hexachlorocyclopentadiene 0.05 0.04 GAC and PTA2 No 

Oxamyl 0.2 0.002 GAC1,3 Uncertain 

Toluene 1.0 0.6 GAC and PTA4 No 

Xylenes 10.0 1.0 GAC and PTA4 No 

Benzene 0.005 0.0005 GAC and PTA3,4 No 

Chlordane 0.002 0.001 GAC1 No 

DBCP 0.0002 0.0001 GAC and PTA5 No 

1,2-dichloropropane 0.005 0.0005 GAC and PTA4 Uncertain 

Heptachlor 0.0004 0.0001 GAC1 No 

Heptachlor epoxide 0.0002 0.0001 GAC1 No 

Hexachlorobenzene 0.001 0.0001 GAC1 No 

Toxaphene 0.003 0.001 GAC1 No 

1,1,2-trichloroethane 0.005 0.003 GAC and PTA4 No 

Vinyl chloride 0.002 0.0005 PTA4 No 

Carbon tetrachloride 0.005 0.0005 GAC and PTA4 No 

1,2-dichloroethane 

(ethylene dichloride) 0.005 0.0005 GAC and PTA4 No 

Dichloromethane 0.005 0.0005 PTA4 No 

Tetrachloroethylene 0.005 0.0005 GAC and PTA4 No 

Trichloroethylene 0.005 0.0005 GAC and PTA6 No 

1. Small system compliance technologies are: GAC, PAC, and POU-GAC. 

2. Small system compliance technologies are: GAC, POU-GAC, PTA, diffused aeration, multi-stage bubble aeration, tray 

aeration, and shallow tray aeration. 

3. Although not currently listed as BAT, promising emerging technologies include: RO, RO followed by GAC, and advanced 

oxidation (ultraviolet light combined with ozone) followed by GAC. 

4. Small system compliance technologies are: GAC, PTA, diffused aeration, multi-stage bubble aeration, tray aeration, and 

shallow tray aeration. 

5. Small system compliance technologies are: GAC, PAC, PTA, diffused aeration, multi-stage bubble aeration, tray aeration, 

and shallow tray aeration. 

6. Small system compliance technologies are: GAC, PTA, diffused aeration, multi-stage bubble aeration, tray aeration, 

shallow tray aeration, spray aeration, and mechanical aeration. 

BAT = best available technologies 

DBCP = 1,2-dibromo-3-chloropropane 

GAC = granular activated carbon 

MCL = maximum contaminant level 

Mg/L = milligrams per liter 

PAC = powdered activated carbon 

POU = point-of-use 

PTA = packed tower aeration 

RO = reverse osmosis 
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1 Introduction 

The U.S. Environmental Protection Agency (EPA) has completed its second Six-Year Review 

(Six-Year Review 2) of national primary drinking water regulations (NPDWRs). The 1996 Safe 

Drinking Water Act (SDWA) Amendments require the U.S. Environmental Protection Agency 

(EPA or the Agency) to periodically review existing National Primary Drinking Water 

Regulations (NPDWRs). Section 1412(b)(9) of SDWA reads: 

 ...[t]he Administrator shall, not less than every 6 years, review and revise, as 

appropriate, each primary drinking water regulation promulgated under this title. 

Any revision of a national primary drinking water regulation shall be promulgated 

in accordance with this section, except that each revision shall maintain, or 

provide for greater, protection of the health of persons. 

The primary goal of the Six-Year Review process is to identify NPDWRs for possible regulatory 

revision. Although the statute does not define when a revision is “appropriate,” as a general 

benchmark, EPA considered a possible revision to be “appropriate” if, at a minimum, it presents 

a meaningful opportunity to: 

• improve the level of public health protection, and/or 

• achieve cost savings while maintaining or improving the level of public health protection. 

For Six-Year Review 2, EPA implemented the protocol that it developed for the first Six-Year 

Review (USEPA, 2003), including minor revisions developed during the current review process 

(USEPA, 2009d). EPA obtained and evaluated new information that could affect a NPDWR, 

including information on health effects (USEPA, 2009f), analytical feasibility (USEPA, 2009b), 

and occurrence (USEPA, 2009a and 2009e). 

This technical support document provides the Agency’s findings for its review of treatment 

feasibility information. EPA identified potential to revise NPDWRs for 23 contaminants. 

Consequently, EPA reviewed the best available technologies (BATs) and treatment techniques 

(TTs) specified in NPDWRs, and any emerging technologies, to determine whether treatment 

performance would pose a limitation to such revisions. This document describes these treatment 

feasibility reviews. 

EPA reviewed treatment feasibility for contaminants regulated through MCLs for which there is 

potential to revise the MCL due to: 

• New health effects assessments suggesting potential for a lower MCLG and potential to set 

the MCL equal to a lower MCLG is not limited by practical quantitation levels (PQLs) 

• Analytical methods review findings indicating the potential for lower PQLs 

• A health effects assessment is ongoing, but the MCLG is less than the MCL and there is 

potential to lower the PQL, which originally limited the MCL 
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EPA also reviewed the treatment feasibility for two contaminants that are regulated through TTs 

and are not the subjects of recent or ongoing regulatory action. Exhibit 1-1 identifies the 

contaminants included in the review. 

Exhibit 1-1. Contaminants Included in this Treatment Technology Feasibility 

Review 

Contaminants regulated through MCLs and potential to revise the MCL 

New health effects assessment indicates potential MCLG decrease, PQL does not currently limit 

the MCL or there is potential to decrease PQL 

1 2,4-D 

2 Endothall 

3 Hexachlorocyclopentadiene 

4 Oxamyl 

5 Toluene 

6 Xylenes 

New health effects assessment, MCLG = 0, MCL = PQL and there is potential to decrease PQL 

7 Benzene 

No new health effects assessment, MCL = PQL and there is potential to decrease PQL 

8 Chlordane 

9 1,2-Dibromo-3-chloropropane (DBCP) 

10 1,2-Dichloropropane 

11 Heptachlor 

12 Heptachlor epoxide 

13 Hexachlorobenzene 

14 Toxaphene 

15 1,1,2-Trichloroethane 

16 Vinyl chloride 

Ongoing health effects assessment, MCL > MCLG and there is potential to decrease PQL 

17 Carbon tetrachloride 

18 1,2-Dichloroethane (Ethylene Dichloride) 

19 Dichloromethane 

20 Tetrachloroethylene 

21 Trichloroethylene 

Contaminants regulated through TTs and potential to revise the TT 

22 Acrylamide 

23 Epichlorohydrin 

This document primarily discusses best available technologies (BATs) specified by EPA to meet 

MCLs and technologies to meet TT-type NPDWRs. It provides supplemental information on 

small systems compliance technologies and other related treatment information. EPA relies on 

available scientific and engineering data to support this process. The purpose of this report is to 

document EPA’s evaluation of the potential for BATs to remove contaminants to achieve 

concentrations comparable to the estimated quantitation level (EQL) or health-based threshold 

for each contaminant. USEPA (2009c) provides a description of how EPA developed the EQLs 

or health-based thresholds. EPA used these thresholds to evaluate potential occurrence and 

exposure effects in addition to treatment feasibility. The end result of each of the following 
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contaminant-specific reviews is a determination of whether treatment would pose a limitation to 

revising an NPDWR. 

Section 2 provides background information on the methods the Agency used to evaluate the 

effectiveness of treatment technologies for contaminants regulated through MCLs. Section 3 

presents the treatment reviews for individual contaminants regulated through MCLs. Finally, 

section 4 provides a review of the potential to revise TTs for two contaminants (acrylamide and 

epichlorohydrin) regulated through this method. 
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2 Measuring Treatment Effectiveness for Contaminants 

Regulated through MCLs 

As discussed above, the treatment analysis in this document uses treatment benchmarks for the 

contaminants that are based on either an EQL or a health-based threshold, which were developed 

for the Six-Year Review 2 occurrence analysis (USEPA, 2009c). EPA evaluated technology 

effectiveness against this benchmark based on the following factors: 

• Removal efficiency, which is measured as the percentage of the influent concentration 

removed through treatment 

• Qualitative conclusions about treatability from previous EPA rulemakings and other 

scientific and engineering sources 

• Other, technology-specific measures, discussed in more detail below. 

Aeration and carbon adsorption are the most common technologies used for the removal of the 

contaminants with MCLs in this document. The following discussion describes technologyspecific measures that EPA used in evaluating treatment effectiveness for these technologies. 

In instances when BATs and/or small system compliance technologies include aeration 

technologies, EPA uses the Henry’s Law constant as an indicator of likely treatment 

effectiveness. Aeration technologies, which include packed tower aeration (PTA), multi-stage 

bubble aeration, tray aeration, shallow tray aeration, spray aeration, and mechanical aeration, 

remove contaminants by passing air through the water to be treated. This process transfers, or 

“strips,” volatile contaminants from the water into the air. The Henry’s Law constant provides a 

measure of the ease with which this stripping occurs. The units for the Henry’s Law constant in 

this document are atmospheres-cubic meter (of water) per cubic meter (of air) (atm m3/m3); a 

higher Henry’s Law constant indicates greater strippability, and easier contaminant removal by 

aeration. 

In instances when BATs and/or small system compliance technologies include carbon adsorption 

technologies, EPA uses bed life and carbon usage rates as indicators of likely treatment 

effectiveness. The use of these indicators is a refinement of the method EPA previously used to 

assess treatment technology feasibility during First Six-Year Review. Carbon adsorption 

technologies, which include granular activated carbon (GAC), powdered activated carbon 

(PAC), and point-of-use granular activated carbon (POU-GAC), remove contaminants through 

adsorption onto a carbon media. In GAC and POU-GAC, water to be treated passes through a 

fixed bed of the media; in PAC, the media is mixed into the water to be treated. In either case, 

the media has a specific capacity for adsorbing a given contaminant. In GAC and POU-GAC, 

once this capacity is exhausted, the media must be removed and regenerated or replaced with 

fresh media. In PAC, this capacity influences the quantity, or “dose,” of powdered carbon 

required to remove the contaminant. In either case, the length of time for which the carbon 

retains its capacity to absorb target contaminants provides a measure of treatment feasibility and 

effectiveness. For example, a GAC medium will be more useful for a contaminant that it can 

continue to remove for several months than for a contaminant that exhausts its capacity quickly. 

With GAC treatment, this length of time is typically called “bed life,” and can be measured in 
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months, or in the volume of water treated, called “bed volumes.” Another measure of carbon 

capacity is carbon usage rate, with units of pounds of carbon used per 1,000 gallons of water 

treated (lbs/1,000 gal). A lower carbon usage rate reflects a greater capacity for the contaminant, 

and more efficient treatment. 
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3 Treatment Reviews for Contaminants Regulated Through 

MCLs 

The results of EPA’s review of health effects or analytical feasibility indicated the potential to 

revise the NPDWRs for each of the contaminants in this section. Consequently, EPA reviewed 

treatment feasibility for each to determine whether treatment feasibility would limit the potential 

to revise. Each treatment review includes the following: 

• The current MCL for the contaminant and the EQL or health-based threshold developed 

during Six-Year Review 2 

• Identification of current BATs and small system compliance technologies 

• Where appropriate, identification of new or emerging treatment technologies 

• Available information on the treatment effectiveness of these technologies for the 

contaminant 

• Discussion of whether treatment is known to be a limiting concern under the current 

NPDWR 

• A conclusion regarding whether treatment would be expected to be a limiting concern should 

the Agency revise the NPDWR. 

Based on the treatment reviews, EPA did not identify limitations of BAT, small system 

compliance technologies, or emerging technologies to achieve the EQL or health-based 

thresholds for most of the contaminants regulated through MCLs. However, for oxamyl, data on 

removal efficiency and a lack of demonstrated treatment effectiveness at low concentrations 

suggest potential for limitation at concentrations as low as the health-based threshold. Similarly, 

for 1,2-dichloropropane, treatment to the estimated quantitation level may not be feasible. 

Exhibit 3-1 summarizes these results. 

3.1 2,4-D 

The current MCL for 2,4-D is 0.07 mg/L and the current BAT is GAC (40 CFR 141.61). Small 

system compliance technologies include: GAC, PAC, and POU-GAC (USEPA, 1998). The 

health-based threshold used for the Six-Year Review 2 is 0.04 mg/L (USEPA, 2009f). 

According to the World Health Organization (WHO), the achievable GAC removal efficiency 

for 2,4-D is more than 80%, to concentrations lower than 0.0001 mg/L (WHO, 2006). Carbon 

usage rates for 2,4-D (0.1224 lbs/1,000 gal) are relatively low compared with other organic 

contaminants, indicating good treatment feasibility (56 FR 3526, January 30, 1991). 

Treatment is not known to be a limiting concern for the current MCL for 2,4-D. The Agency’s 

current assessment is that treatment technology would not pose a feasibility limitation at the 

health-based threshold of 0.04 mg/L. 
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Exhibit 3-1. Summary of Treatment Feasibility Review for Contaminants 

Regulated through MCLs 

Contaminant 

Current MCL 

(mg/L) 

Threshold 

Evaluated 

(mg/L) BAT 

Treatment 

Limitation 

Potential 

2,4-D 0.07 0.04 GAC1 No 

Endothall 0.1 0.05 GAC1 No 

Hexachlorocyclopentadiene 0.05 0.04 GAC and PTA2 No 

Oxamyl 0.2 0.002 GAC1,3 Uncertain 

Toluene 1.0 0.6 GAC and PTA4 No 

Xylenes 10.0 1.0 GAC and PTA4 No 

Benzene 0.005 0.0005 GAC and PTA3,4 No 

Chlordane 0.002 0.001 GAC1 No 

DBCP 0.0002 0.0001 GAC and PTA5 No 

1,2-dichloropropane 0.005 0.0005 GAC and PTA4 Uncertain 

Heptachlor 0.0004 0.0001 GAC1 No 

Heptachlor epoxide 0.0002 0.0001 GAC1 No 

Hexachlorobenzene 0.001 0.0001 GAC1 No 

Toxaphene 0.003 0.001 GAC1 No 

1,1,2-trichloroethane 0.005 0.003 GAC and PTA4 No 

Vinyl chloride 0.002 0.0005 PTA4 No 

Carbon tetrachloride 0.005 0.0005 GAC and PTA4 No 

1,2-dichloroethane 

(ethylene dichloride) 0.005 0.0005 GAC and PTA4 No 

Dichloromethane 0.005 0.0005 PTA4 No 

Tetrachloroethylene 0.005 0.0005 GAC and PTA4 No 

Trichloroethylene 0.005 0.0005 GAC and PTA6 No 

1. Small system compliance technologies are: GAC, PAC, and POU-GAC. 

2. Small system compliance technologies are: GAC, POU-GAC, PTA, diffused aeration, multi-stage bubble aeration, tray 

aeration, and shallow tray aeration. 

3. Although not currently listed as BAT, promising emerging technologies include: RO, RO followed by GAC, and advanced 

oxidation (ultraviolet light combined with ozone) followed by GAC. 

4. Small system compliance technologies are: GAC, PTA, diffused aeration, multi-stage bubble aeration, tray aeration, and 

shallow tray aeration. 

5. Small system compliance technologies are: GAC, PAC, PTA, diffused aeration, multi-stage bubble aeration, tray aeration, 

and shallow tray aeration. 

6. Small system compliance technologies are: GAC, PTA, diffused aeration, multi-stage bubble aeration, tray aeration, 

shallow tray aeration, spray aeration, and mechanical aeration. 

BAT = best available technologies 

DBCP = 1,2-dibromo-3-chloropropane 

GAC = granular activated carbon 

MCL = maximum contaminant level 

Mg/L = milligrams per liter 

PAC = powdered activated carbon 

POU = point-of-use 

PTA = packed tower aeration 

RO = reverse osmosis 
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3.2 Endothall 

The current MCL for endothall is 0.1 mg/L and the current BAT is GAC (40 CFR 141.61). Small 

system compliance technologies include: GAC, PAC, and POU-GAC (USEPA, 1998). The 

health-based threshold used for the Six-Year Review 2 is 0.05 mg/L (USEPA, 2009f). 

In proposing GAC as the BAT for endothall, EPA concluded that GAC is effective in removing 

synthetic organic compounds (SOCs) including endothall (55 FR 30370, July 25, 1990), based 

on model predictions that took into account endothall’s chemical/physical characteristics. 

Subsequent treatability studies in support of the final EPA rulemaking demonstrated that GAC 

was as effective as predicted by the model (57 FR 31776, July 17, 1992). 

Treatment is not known to be a limiting concern for the current MCL for endothall. The 

Agency’s current assessment is that treatment technology would not pose a feasibility limitation 

at the health-based threshold of 0.05 mg/L. 

3.3 Hexachlorocyclopentadiene 

The current MCL for hexachlorocyclopentadiene is 0.05 mg/L and the current BATs are GAC 

and PTA (40 CFR 141.61). Small system compliance technologies include: GAC, POU-GAC, 

PTA, diffused aeration, multi-stage bubble aeration, tray aeration, and shallow tray aeration 

(USEPA, 1998). The health-based threshold used for the Six-Year Review 2 is 0.04 mg/L 

(USEPA, 2009f). 

EPA has categorized hexachlorocyclopentadiene among the more volatile SOCs (55 FR 30370, 

July 25, 1990). For the volatile SOCs, properly designed PTA facilities can achieve removal 

efficiencies of 90% to more than 99% (55 FR 30370, July 25, 1990). For 

hexachlorocyclopentadiene, Henry’s Law constants reported in several sources are high, ranging 

from 0.6701 to 1.105 atm m3/m3, indicating good treatment feasibility (Sander, 1999). EPA has 

concluded that GAC also is effective in removing SOCs including hexachlorocyclopentadiene 

(55 FR 30370, July 25, 1990). 

Treatment is not known to be a limiting concern for the current MCL for 

hexachlorocyclopentadiene. The Agency’s current assessment is that treatment technology would 

not pose a feasibility limitation at the health-based threshold of 0.04 mg/L. 

3.4 Oxamyl 

The current MCL for oxamyl is 0.2 mg/L and the current BAT is GAC (40 CFR 141.61). The 

health-based threshold used for the Six-Year Review 2 is 0.002 mg/L (USEPA, 2009f). Small 

system compliance technologies include: GAC, PAC, and POU-GAC (USEPA, 1998). In 

addition, EPA’s Environmental Technology Verification (ETV) Program recently verified the 

performance of several POU devices for removal of chemical contaminants including oxamyl. 

The emerging technologies tested in the ETV verifications included reverse osmosis, reverse 

osmosis followed by GAC, and advanced oxidation (ultraviolet light combined with ozone) 

followed by GAC (NSF, 2005a, 2005b, 2005c, 2006, 2007a). 
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GAC removal efficiency for oxamyl ranges from 85% to 95%, depending on design parameters 

(USEPA, 1990). The ETV test of a POU device using advanced oxidation followed by GAC 

verified that the GAC filter component of the device removed greater than 98% of oxamyl from 

an influent concentration of 1.1 mg/L (NSF, 2005c). 

The ETV tests of POU devices using reverse osmosis verified that the reverse osmosis 

components of these devices removed 99% or more of oxamyl from influent concentrations of 

0.98 to 1.1 mg/L. Because of the high removals using the reverse osmosis components alone, the 

verifications did not test the GAC components of those devices that included the technology for 

oxamyl removal (NSF, 2005a, 2005b, 2006, 2007a). 

Treatment is not known to be a limiting concern for the current MCL for oxamyl. Given the 

above data on removal efficiency (85% to 98% for GAC and 99% for reverse osmosis) and a 

lack of demonstrated treatment effectiveness at low concentrations, however, treatment 

technology could pose a limitation at concentrations as low as the health-based threshold of 

0.002 mg/L. 

3.5 Toluene 

The current MCL for toluene is 1 mg/L and the current BATs are GAC and PTA (40 CFR 

141.61). Small system compliance technologies include: GAC, PTA, diffused aeration, multistage bubble aeration, tray aeration, and shallow tray aeration (USEPA, 1998). The health-based 

threshold used for the Six-Year Review 2 is 0.6 mg/L (USEPA, 2009f). 

According to the WHO, the achievable air stripping removal efficiency for toluene is more than 

80%, to concentrations lower than 0.001 mg/L (WHO, 2006). For PTA, field studies performed 

in three States demonstrated a removal efficiency of greater than 96% for toluene and other 

contaminants, with initial concentrations of up to 0.6 mg/L (Ram et al., 1990 as cited in USEPA, 

1998). Performance studies employing diffused aeration to treat toluene and other contaminants 

have demonstrated 50% to 90% removal efficiencies (USEPA, 1985 as cited in USEPA, 1998). 

For toluene, Henry’s Law constants reported in several sources are relatively high, ranging from 

0.126 to 0.314 atm m3

/m3, indicating good treatment feasibility (Sander, 1999; Cummins and 

Westrick, 1987). EPA has categorized toluene as a contaminant with good strippability (56 FR 

3526, January 30, 1991). 

According to the WHO, the achievable GAC removal efficiency for toluene is more than 80%, to 

concentrations lower than 0.001 mg/L (WHO, 2006). Carbon usage rates for toluene (0.3050 

lbs/1,000 gal) are higher than for other organic contaminants (56 FR 3526, January 30, 1991). 

Although EPA found that GAC may be more than twice as expensive as PTA for large systems 

on a dollar per household per year basis, if off-gas control of PTA is necessary, then costs 

between PTA and GAC are more competitive (56 FR 3526, January 30, 1991). 

Treatment is not known to be a limiting concern for the current MCL for toluene. The Agency’s 

current assessment is that treatment technology would not pose a feasibility limitation at the 

health-based threshold of 0.6 mg/L.
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3.6 Xylenes 

The current MCL for total xylenes is 10 mg/L and the current BATs are GAC and PTA (40 CFR 

141.61). Small system compliance technologies include: GAC, PTA, diffused aeration, multistage bubble aeration, tray aeration, and shallow tray aeration (USEPA, 1998). The health-based 

threshold used for the Six-Year Review 2 is 1 mg/L (USEPA, 2009f). 

According to the WHO, the achievable air stripping removal efficiency for xylenes is more than 

80%, to concentrations lower than 0.005 mg/L (WHO, 2006). Performance studies for diffused 

aeration used to treat xylenes and other contaminants have demonstrated 50% to 90% removal 

efficiencies (USEPA, 1985 as cited in USEPA, 1998). For xylenes, Henry’s Law constants 

reported in several sources are relatively high, ranging from 0.0973 to 0.341 atm m3/m3, 

indicating good treatment feasibility (Sander, 1999; Cummins and Westrick, 1987). EPA has 

categorized xylenes as a contaminant with good strippability (56 FR 3526, January 30, 1991). 

According to the WHO, the achievable GAC removal efficiency for xylenes is more than 80%, 

to concentrations lower than 0.005 mg/L (WHO, 2006). One case study, cited in the U.S. Army 

Corps of Engineers’ Adsorption Design Guide, shows GAC removal efficiencies for xylenes of 

greater than 99% at influent concentrations of 0.2 to 0.5 mg/L (U.S. Army Corps of Engineers, 

2001). Carbon usage rates for xylenes (0.2148 to 0.3718 lbs/1,000 gal) are higher than for other 

organic contaminants (56 FR 3526, January 30, 1991). Although EPA found that GAC may be 

more than twice as expensive as PTA for large systems on a dollar per household per year basis, 

if off-gas control of PTA is necessary, then costs between PTA and GAC are more competitive 

(56 FR 3526, January 30, 1991). 

Treatment is not known to be a limiting concern for the current MCL for xylenes. The Agency’s 

current assessment is that treatment technology would not pose a feasibility limitation at the 

health-based threshold of 1 mg/L.

3.7 Benzene 

The current MCL for benzene is 0.005 mg/L and the current BATs are GAC and PTA (40 CFR 

141.61). The EQL used for the Six-Year Review 2 is 0.0005 mg/L (USEPA, 2009c). Small 

system compliance technologies include: GAC, PTA, diffused aeration, multi-stage bubble 

aeration, tray aeration, and shallow tray aeration (USEPA, 1998). In addition, EPA’s ETV 

Program recently verified the performance of several POU devices for removal of chemical 

contaminants including benzene. The emerging technologies tested in the ETV verifications 

included reverse osmosis, reverse osmosis followed by GAC, and advanced oxidation 

(ultraviolet light combined with ozone) followed by GAC (NSF, 2005a, 2005b, 2005c, 2006, 

2007a). 

EPA pilot studies using PTA at more than 30 sites showed greater than 99% volatile organic 

compound (VOC) removals to be achievable. Based on these and other studies, EPA concluded 

that PTA systems designed using reasonable engineering practices could achieve 99% removal 

of nine VOCs, including benzene, under all anticipated circumstances. Removal could be as high 

as 99.9% under optimum conditions (50 FR 46902, November 13, 1985). For benzene, Henry’s 

Law constants in several sources are relatively high, ranging from 0.0584 to 0.341 atm m3

/m3, 
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indicating good treatment feasibility (Sander, 1999; Crittenden, 1988; Cummins and Westrick, 

1987). 

EPA has concluded that GAC can achieve a high level of removal of most VOCs. Although 

carbon usage rates are significantly higher for benzene than other VOCs, EPA concluded that 

removal is still feasible using GAC (50 FR 46902, November 13, 1985). One case study cited in 

the U.S. Army Corps of Engineers’ Adsorption Design Guide shows a GAC removal efficiency 

for benzene of greater than 99% at an influent concentration of 0.4 mg/L (U.S. Army Corps of 

Engineers, 2001). The ETV test of a POU device using advanced oxidation followed by GAC 

verified that the GAC filter component of the device removed greater than 99% of benzene, from 

an influent concentration of 0.44 mg/L (NSF, 2005c). 

The ETV tests of POU devices using reverse osmosis verified that the reverse osmosis 

components of these devices removed 85% to greater than 99% of benzene, from influent 

concentrations of 0.68 to 1.1 mg/L. Because of the high removals using the reverse osmosis 

components alone, the verifications did not test the GAC components of those devices that 

included the technology for benzene removal (NSF, 2005a, 2005b, 2006, 2007a). 

Treatment is not known to be a limiting concern for the current MCL for benzene. The Agency’s 

current assessment is that treatment technology would not pose a feasibility limitation at the EQL 

of 0.0005 mg/L. 

3.8 Chlordane 

The current MCL for chlordane is 0.002 mg/L and the current BAT is GAC (40 CFR 141.61). 

The EQL used for the Six-Year Review 2 is 0.001 mg/L (USEPA, 2009c). Small system 

compliance technologies include: GAC, PAC, and POU-GAC (USEPA, 1998). 

According to the WHO, the achievable air stripping removal efficiency for chlordane is more 

than 80%, to concentrations lower than 0.0001 mg/L (WHO, 2006). Carbon usage rates for 

chlordane (0.0379 lbs/1,000 gal) are lower than for other organic contaminants, indicating good 

treatment feasibility (56 FR 3526, January 30, 1991). 

Treatment is not known to be a limiting concern for the current MCL for chlordane. The 

Agency’s current assessment is that treatment technology would not pose a feasibility limitation 

at the EQL of 0.001 mg/L. 

3.9 1,2-Dibromo-3-chloropropane (DBCP) 

The current MCL for DBCP is 0.0002 mg/L and the current BATs are GAC and PTA (40 CFR 

141.61). The EQL used for the Six-Year Review 2 is 0.0001 mg/L (USEPA, 2009c). Small 

system compliance technologies include: GAC, PAC, PTA, diffused aeration, multi-stage bubble 

aeration, tray aeration, and shallow tray aeration (USEPA, 1998). 

The Henry’s Law constant (0.00486 atm m3

/m3) for DBCP is at least an order of magnitude 

lower than for other contaminants such as benzene (Cummins and Westrick, 1987). EPA has 

categorized DBCP as a contaminant with difficult strippability (56 FR 3526, January 30, 1991). 
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Carbon usage rates for DBCP are significantly lower (0.0448 lbs/1,000 gal) than for other 

organic contaminants, indicating good treatment feasibility (56 FR 3526, January 30, 1991). The 

City of Redlands, California, operates a GAC treatment plant to remove DBCP and 

trichloroethylene (TCE) from groundwater. The carbon adsorbers typically operate for 18 

months between reactivations (GWRTAC, 2001). Thus, while both aeration and carbon 

adsorption are BATs, adsorption may, in some cases, be the preferred treatment. 

Treatment is not known to be a limiting concern for the current MCL for DBCP. The Agency’s 

current assessment is that treatment technology would not pose a feasibility limitation at the EQL 

of 0.0001 mg/L. 

3.10 1,2-Dichloropropane 

The current MCL for 1,2-dichloropropane is 0.005 mg/L and the current BATs are GAC and 

PTA (40 CFR 141.61). Small system compliance technologies include: GAC, PTA, diffused 

aeration, multi-stage bubble aeration, tray aeration, and shallow tray aeration (USEPA, 1998). 

The EQL used for the Six-Year Review 2 is 0.0005 mg/L (USEPA, 2009c). 

Performance studies for diffused aeration used to treat 1,2-dichloropropane and other 

contaminants have demonstrated 50% to 90% removal efficiencies (USEPA, 1985 as cited in 

USEPA, 1998). For 1,2-dichloropropane, Henry’s Law constants reported in several sources are 

moderately high, ranging from 0.0481 to 0.136 atm m3/m3, indicating good treatment feasibility 

(Sander, 1999; Cummins and Westrick, 1987). EPA has categorized 1,2-dichloropropane as a 

contaminant with average strippability (56 FR 3526, January 30, 1991). 

According to the WHO, the achievable GAC removal efficiency for 1,2-dichloropropane is more 

than 80%, to concentrations lower than 0.001 mg/L (WHO, 2006). Carbon usage rates for 1,2-

dichloropropane (0.2857 lbs/1,000 gal) are somewhat higher than for other organic contaminants 

(56 FR 3526, January 30, 1991). Although EPA found that GAC may be more than twice as 

expensive as PTA for large systems on a dollar per household per year basis, if off-gas control of 

PTA is necessary, then costs between PTA and GAC are more competitive (56 FR 3526, January 

30, 1991). 

Treatment is not known to be a limiting concern for the current MCL for 1,2-dichloropropane. 

However, given the above data (removal efficiency 50% to 90% for aeration, with only 

moderately high Henry’s Law constants; removal efficiency more than 80%, to concentrations 

lower than 0.001 mg/L, for GAC), treatment technology could pose a feasibility limitation at the 

EQL of 0.0005 mg/L.

3.11 Heptachlor 

The current MCL for heptachlor is 0.0004 mg/L and the current BAT is GAC (40 CFR 141.61). 

Small system compliance technologies include: GAC, PAC, and POU-GAC (USEPA, 1998). 

The EQL used for the Six-Year Review 2 is 0.0001 mg/L (USEPA, 2009c). 

Carbon usage rates for heptachlor are significantly lower (0.0556 lbs/1,000 gal) than for other 

organic contaminants, indicating good treatment feasibility (56 FR 3526, January 30, 1991). 
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Treatment is not known to be a limiting concern for the current MCL for heptachlor. The 

Agency’s current assessment is that treatment technology would not pose a feasibility limitation 

at the EQL of 0.0001 mg/L. 

3.12 Heptachlor Epoxide 

The current MCL for heptachlor epoxide is 0.0002 mg/L and the current BAT is GAC (40 CFR 

141.61). Small system compliance technologies include: GAC, PAC, and POU-GAC (USEPA, 

1998). The EQL used for the Six-Year Review 2 is 0.0001 mg/L (USEPA, 2009c). 

Carbon usage rates for heptachlor epoxide are significantly lower (0.0271 lbs/1,000 gal) than for 

other organic contaminants, indicating good treatment feasibility (56 FR 3526, January 30, 

1991). EPA has categorized heptachlor epoxide as a strongly adsorbed organic contaminant (54 

FR 22062, May 22, 1989). 

Treatment is not known to be a limiting concern for the current MCL for heptachlor epoxide. 

The Agency’s current assessment is that treatment technology would not pose a feasibility 

limitation at the EQL of 0.0001 mg/L. 

3.13 Hexachlorobenzene 

The current MCL for hexachlorobenzene is 0.001 mg/L and the current BAT is GAC (40 CFR 

141.61). Small system compliance technologies include: GAC, PAC, and POU-GAC (USEPA, 

1998). The EQL used for the Six-Year Review 2 is 0.0001 mg/L (USEPA, 2009c). 

EPA has categorized hexachlorobenzene among moderately adsorbed contaminants, exhibiting 

an intermediate carbon usage rate (55 FR 30370, July 25, 1990). The agency concluded that 

GAC is effective in removing SOCs including hexachlorobenzene (55 FR 30370, July 25, 1990). 

Treatment is not known to be a limiting concern for the current MCL for hexachlorobenzene. 

The Agency’s current assessment is that treatment technology would not pose a feasibility 

limitation at the health-based threshold of 0.0001 mg/L. 

3.14 Toxaphene 

The current MCL for toxaphene is 0.003 mg/L and the current BAT is GAC (40 CFR 141.61). 

Small system compliance technologies include: GAC, PAC, and POU-GAC (USEPA, 1998). 

The EQL used for the Six-Year Review 2 is 0.001 mg/L (USEPA, 2009c). 

Carbon usage rates for toxaphene are significantly lower (0.0432 lbs/1,000 gal) than for other 

organic contaminants, indicating good treatment feasibility (56 FR 3526, January 30, 1991). 

Treatment is not known to be a limiting concern for the current MCL for toxaphene. The 

Agency's current assessment is that treatment technology would not pose a feasibility limitation 

at the EQL of 0.001 mg/L. 
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3.15 1,1,2-Trichloroethane 

The current MCL for 1,1,2-trichloroethane is 0.005 mg/L and the current BATs are GAC and 

PTA (40 CFR 141.61). Small system compliance technologies include: GAC, PTA, diffused 

aeration, multi-stage bubble aeration, tray aeration, and shallow tray aeration (USEPA, 1998). 

The health-based threshold used for the Six-Year Review 2 is the current MCLG of 0.003 mg/L 

(USEPA, 2009c). 

EPA indicates that 1,1,2-trichloroethane may be among the less volatile organic chemicals (55 

FR 30370, July 25, 1990). Still, for 1,1,2-trichloroethane, Henry’s Law constants reported in 

several sources are moderately high, ranging from 0.0314 to 0.0487 atm m3

/m3, indicating good 

treatment feasibility (Sander, 1999). 

For carbon adsorption, EPA has categorized 1,1,2-trichloroethane among moderately adsorbed 

contaminants, exhibiting an intermediate carbon usage rate (55 FR 30370, July 25, 1990). 

Treatment is not known to be a limiting concern for the current MCL for 1,1,2-trichloroethane. 

The Agency’s current assessment is that treatment technology would not pose a feasibility 

limitation at the health-based threshold of 0.003 mg/L. 

3.16 Vinyl Chloride 

The current MCL for vinyl chloride is 0.002 mg/L and the current BAT is PTA (40 CFR 141.61). 

Small system compliance technologies include: GAC, PTA, diffused aeration, multi-stage bubble 

aeration, tray aeration, and shallow tray aeration (USEPA, 1998). The EQL used for the Six-Year 

Review 2 is 0.0005 mg/L (USEPA, 2009c). 

EPA pilot studies at more than 30 sites showed that PTA can achieve greater than 99% VOC 

removals. Because vinyl chloride is more easily removed by aeration than other VOCs, EPA 

concluded that PTA systems designed using reasonable engineering practices could achieve 

99.9% removal of vinyl chloride under most circumstances (50 FR 46902, November 13, 1985). 

Case studies using spray aeration demonstrated greater than 99% removal for vinyl chloride and 

other contaminants, with initial concentrations of 100 to 200 mg/L (USEPA, 1985 as cited in 

USEPA, 1998). For vinyl chloride, Henry’s Law constants reported in several sources are very 

high, ranging from 0.889 to 265 atm m3

/m3, indicating very good treatment feasibility (Sander, 

1999; Crittenden, 1988; Cummins and Westrick, 1987; Rauschert Industries, undated). 

Treatment is not known to be a limiting concern for the current MCL for vinyl chloride. The 

Agency’s current assessment is that treatment technology would not pose a feasibility limitation 

at the EQL of 0.0005 mg/L. 

3.17 Carbon Tetrachloride 

The current MCL for carbon tetrachloride is 0.005 mg/L and the current BATs are GAC and 

PTA (40 CFR 141.61). Small system compliance technologies include: GAC, PTA, diffused 

aeration, multi-stage bubble aeration, tray aeration, and shallow tray aeration (USEPA, 1998). 

The EQL used for the Six-Year Review 2 is 0.0005 mg/L (USEPA, 2009c). 
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EPA pilot studies at more than 30 sites showed that PTA can achieve greater than 99% VOC 

removals. Based on these and other studies, EPA concluded that PTA systems designed using 

reasonable engineering practices could achieve 99% removal of nine VOCs, including carbon 

tetrachloride, under all anticipated circumstances. Removal could be as high as 99.9% under 

optimum conditions (50 FR 46902, November 13, 1985). For carbon tetrachloride, Henry’s Law 

constants reported in several sources are high, ranging from 0.204 to 1.36 atm m3/m3, indicating 

good treatment feasibility (Sander, 1999; Crittenden, 1988; Cummins and Westrick, 1987; 

Rauschert Industries, undated). 

EPA indicates that GAC can achieve high level of removal (up to 99.9%) of VOCs, including 

carbon tetrachloride, under all anticipated conditions (50 FR 46902, November 13, 1985). Case 

studies cited in the U.S. Army Corps of Engineers’ Adsorption Design Guide show GAC 

removal efficiencies for carbon tetrachloride of greater than 99.9%, at influent concentrations of 

1.0 to 135 mg/L (U.S. Army Corps of Engineers, 2001). 

Treatment is not known to be a limiting concern for the current MCL for carbon tetrachloride. 

The Agency’s current assessment is that treatment technology would not pose a feasibility 

limitation at the EQL of 0.0005 mg/L. 

3.18 1,2-Dichloroethane (Ethylene Dichloride) 

The current MCL for 1,2-dichloroethane is 0.005 mg/L and the current BATs are GAC and PTA 

(40 CFR 141.61). Small system compliance technologies include: GAC, PTA, diffused aeration, 

multi-stage bubble aeration, tray aeration, and shallow tray aeration (USEPA, 1998). The EQL 

used for the Six-Year Review 2 is 0.0005 mg/L (USEPA, 2009c). 

EPA pilot studies using PTA at more than 30 sites showed greater than 99% VOC removals to be 

achievable. Based on these and other studies, EPA concluded that PTA systems designed using 

reasonable engineering practices could achieve 99% removal of nine VOCs, including 1,2-

dichloroethane, under all anticipated circumstances. Removal could be as high as 99.9% under 

optimum conditions (50 FR 46902, November 13, 1985). For 1,2-dichloroethane, Henry’s Law 

constants reported in several sources are moderately high, ranging from 0.023 to 0.0639 atm 

m3

/m3, indicating good treatment feasibility (Sander, 1999; Crittenden, 1988; Cummins and 

Westrick, 1987). 

EPA has concluded that GAC can achieve a high level of removal of most VOCs. Although 

carbon usage rates are significantly higher for 1,2-dichloroethane than other VOCs, EPA 

concluded that removal is still feasible using GAC (50 FR 46902, November 13, 1985). 

Treatment is not known to be a limiting concern for the current MCL for 1,2-dichloroethane. The 

Agency’s current assessment is that treatment technology would not pose a feasibility limitation 

at the EQL of 0.0005 mg/L. 

3.19 Dichloromethane 

The current MCL for dichloromethane is 0.005 mg/L and the current BAT is PTA (40 CFR 

141.61). Small system compliance technologies include: GAC, PTA, diffused aeration, multi-
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stage bubble aeration, tray aeration, and shallow tray aeration (USEPA, 1998). The EQL used for 

the Six-Year Review 2 is 0.0005 mg/L (USEPA, 2009c). 

EPA has categorized dichloromethane among the more volatile SOCs (55 FR 30370, July 25, 

1990). For the volatile SOCs, properly designed PTA facilities can achieve removal efficiencies 

of 90% to 99% or more (55 FR 30370, July 25, 1990). For dichloromethane, Henry’s Law 

constants reported in several sources are moderately high, ranging from 0.0341 to 0.132 atm 

m3/m3, indicating good treatment feasibility (Sander, 1999). For GAC, EPA has concluded that 

the technology is capable of removing SOCs, but is a more costly technique than PTA for 

dichloromethane (55 FR 30370, July 25, 1990). 

Treatment is not known to be a limiting concern for the current MCL for dichloromethane. The 

Agency’s current assessment is that treatment technology would not pose a feasibility limitation 

at the EQL of 0.0005 mg/L. 

3.20 Tetrachloroethylene 

The current MCL for tetrachloroethylene is 0.005 mg/L and the current BATs are GAC and PTA 

(40 CFR 141.61). Small system compliance technologies include: GAC, PTA, diffused aeration, 

multi-stage bubble aeration, tray aeration, and shallow tray aeration (USEPA, 1998). The EQL 

used for the Six-Year Review 2 is 0.0005 mg/L (USEPA, 2009c). 

EPA pilot studies at more than 30 sites showed that PTA can achieve greater than 99% VOC 

removals. Based on these and other studies, EPA concluded that PTA systems designed using 

reasonable engineering practices could achieve 99% removal of nine VOCs, including 

tetrachloroethylene, under all anticipated circumstances. Removal could be as high as 99.9% 

under optimum conditions (50 FR 46902, November 13, 1985). According to the WHO, the 

achievable air stripping removal efficiency for tetrachloroethylene is more than 80%, to 

concentrations lower than 0.001 mg/L (WHO, 2006). Field studies of PTA performed in three 

States demonstrated a removal efficiency of greater than 96% for tetrachloroethylene and other 

contaminants, with initial concentrations of up to 0.6 mg/L (Ram et al., 1990 as cited in USEPA, 

1998). Performance studies employing multiple tray aeration to treat tetrachloroethylene and 

other contaminants have demonstrated 50% to 90% removal efficiencies (USEPA, 1985 as cited 

in USEPA, 1998). For tetrachloroethylene, Henry’s Law constants reported in several sources 

are high, ranging from 0.214 to 1.20 atm m3

/m3, indicating good treatment feasibility (Sander, 

1999; Cummins and Westrick, 1987; Rauschert Industries, undated). EPA has categorized 

tetrachloroethylene as a contaminant with good strippability (56 FR 3526, January 30, 1991). 

According to the WHO, the achievable GAC removal efficiency for tetrachloroethlyene is more 

than 80%, to concentrations lower than 0.005 mg/L (WHO, 2006). Case studies cited in the U.S. 

Army Corps of Engineers’ Adsorption Design Guide show GAC removal efficiencies for 

tetrachloroethylene of greater than 99.9%, at influent concentrations of 4.5 to 170 mg/L (U.S. 

Army Corps of Engineers, 2001). EPA has concluded that GAC can achieve a high level of 

removal (up to 99.9%) of VOCs, including tetrachloroethlyene, under all anticipated conditions 

(50 FR 46902, November 13, 1985). Carbon usage rates for tetrachloroethylene (0.1144 

lbs/1,000 gal) are relatively low compared with other organic contaminants, indicating good 

treatment feasibility (56 FR 3526, January 30, 1991). 
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Treatment is not known to be a limiting concern for the current MCL for tetrachloroethylene. 

The Agency’s current assessment is that treatment technology would not pose a feasibility 

limitation at the EQL of 0.0005 mg/L. 

3.21 Trichloroethylene 

The current MCL for trichloroethylene is 0.005 mg/L and the current BATs are GAC and PTA 

(40 CFR 141.61). Small system compliance technologies include: GAC, PTA, diffused aeration, 

multi-stage bubble aeration, tray aeration, shallow tray aeration, spray aeration, and mechanical 

aeration (USEPA, 1998). The EQL used for the Six-Year Review 2 is 0.0005 mg/L (USEPA, 

2009c). 

EPA pilot studies at more than 30 sites showed that PTA can achieve greater than 99% VOC 

removals. Based on these and other studies, EPA concluded that PTA systems designed using 

reasonable engineering practices could achieve 99% removal of nine VOCs, including 

trichloroethylene, under all anticipated circumstances. Removal could be as high as 99.9% under 

optimum conditions (50 FR 46902, November 13, 1985). Field studies of PTA performed in 

three States demonstrated a removal efficiency of greater than 96% for trichloroethylene and 

other contaminants, with initial concentrations of up to 0.6 mg/L (Ram et al., 1990 as cited in 

USEPA, 1998). Performance studies employing multiple tray aeration to treat trichloroethylene 

and other contaminants have demonstrated 50% to 90% removal efficiencies (USEPA, 1985 as 

cited in USEPA, 1998). Other case studies using spray aeration demonstrated greater than 99% 

removal for trichloroethylene and other contaminants, with initial concentrations of 100 to 200 

mg/L (USEPA, 1985 as cited in USEPA, 1998). For trichloroethylene, Henry’s Law constants 

reported in several sources are relatively high, ranging from 0.116 to 0.552 atm m3

/m3, indicating 

good treatment feasibility (Sander, 1999; Crittenden, 1988; Cummins and Westrick, 1987; 

Rauschert Industries, undated). 

Case studies cited in the U.S. Army Corps of Engineers’ Adsorption Design Guide show GAC 

removal efficiencies for trichloroethylene of greater than 99.9%, at influent concentrations of 3 

to 50 mg/L (U.S. Army Corps of Engineers, 2001). EPA has concluded that GAC can achieve a 

high level of removal (up to 99.9%) of VOCs, including trichloroethylene, under all anticipated 

conditions (50 FR 46902, November 13, 1985). The City of Redlands, California, operates a 

GAC treatment plant to remove trichloroethylene and DBCP from groundwater. The carbon 

adsorbers typically operate for 18 months between reactivations (GWRTAC, 2001). 

Treatment is not known to be a limiting concern for the current MCL for trichloroethylene. The 

Agency’s current assessment is that treatment technology would not pose a feasibility limitation 

at the EQL of 0.0005 mg/L. 
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4 Review of Treatment Techniques for Acrylamide and 

Epichlorohydrin 

Acrylamide and epichlorohydrin are introduced in drinking water primarily as impurities in 

polymers and copolymers used for water treatment and in contact surfaces used in storage and 

distribution systems. EPA proposed drinking water regulations for acrylamide and 

epichlorohydrin in 1989 (54 FR 22062, May 22, 1989) and promulgated final drinking water 

regulations in 1991 (56 FR 3526, January 30, 1991). As both these contaminants are classified as 

probable human carcinogens (B2), EPA established the MCLGs for both at zero. EPA has 

regulated these contaminants using a treatment technique requirement in lieu of a MCL because 

of the absence of standardized analytical methods for their measurement in water. The NPDWR 

limits the allowable monomer level in products used for water treatment and the dosage of 

polymers that contain them. EPA selected this option because methods are available for 

measurement of residual monomer in polymer products and these levels are routinely measured 

by manufacturers. These levels are: 

• Acrylamide: 0.05% residual acrylamide in polymers/copolymers and maximum dosage of 1 

ppm (or equivalent) 

• Epichlorohydrin: 0.01% residual epichlorohydrin in polymers/copolymers and maximum 

dosage of 20 ppm (or equivalent). 

The residual monomer level for each contaminant was considered to be the lowest level 

manufacturers could feasibly achieve at the time EPA promulgated the regulation (54 FR 22062, 

May 22, 1989). A system can use third-party or manufacturer’s certification in lieu of testing for 

the residual monomer level. 

NSF International (NSF), a third party organization, tests and certifies water treatment chemicals 

that meet NSF/ANSI Standard 60, Drinking Water Treatment Chemicals – Health Effects, which 

sets out requirements for treatment chemicals based on human health protection (NSF, 1999a). 

The requirements for acrylamide- and epichlorohydrin-based polymers in Standard 60 are based 

on EPA’s treatment technique requirements. Thus, NSF 60 certification of a polymeric coagulant 

aid containing acrylamide or epichlorohydrin indicates that users are in compliance with EPA’s 

regulation when a product is used as specified (i.e., for the intended purpose and up to the 

maximum usage level indicated by NSF). 

EPA obtained data during Six-Year Review 2 indicating that potential improvements in the 

technology or manufacturing now allow production of the polymer with lower residual monomer 

content. This new information viewed in conjunction with regulations and guidelines in other 

countries suggests there is potential for EPA to revise its TT requirement to reflect a lower 

feasible monomer content. 
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4.1 Improvements in Manufacturing 

In 2007, NSF provided EPA with results of NSF analyses between January 2005 and June 2007 

of acrylamide monomer in polyacrylamides and free epichlorohydrin in polyamines.1

 NSF 

performed the analyses for approval of these products against NSF/ANSI Standard 60. Exhibit 

4-1 provides a summary of the results. The Appendix contains the data NSF provided to EPA. 

Residual levels in the products tested and certified are well below the residual levels in the 

current TTs. The mean concentration among acrylamide tests is about one-fifth the residual level 

in the current TT, and the 90th percentile result is one-half the residual level in the current TT. 

All analyses for residual epichlorohydrin were non-detects, with a detection limit equal to onefifth the residual level in the current TT. 

Exhibit 4-1. Summary of NSF International Product Testing Results for Acrylamide 

and Epichlorohydrin 

Summary of Results (mg/kg) 

Contaminant 

Number of 

Analyses 

and 

Detections1 

Detection 

Limit 

(mg/kg) Maximum

90th

Percentile Mean2 Median2 Minimum

Current 

TT 

(mg/kg)3

Acrylamide4 66 [45] 10 420 250 98 60 10 500 

Epichlorohydrin5 84 [0] 20 NA NA NA NA NA 100 

NA = not applicable – all results are below the detection limit. 

1. Total number of analyses appears first. The number of results above the detection limit appears second, in brackets. 

2. Includes nondetected values for acrylamide, assumed to be 10 mg/kg. 

3. TT residual monomer content converted from percent to mg/kg; 1 mg/kg = 1/106 = 0.000001 = 0.0001%. 

4. Method: Per Skelly and Husser (1978). 

5. Method: Per section B.4.3.1 in NSF 60-2005. 

4.2 Regulations and Guidelines in Other Countries 

Regulations in other areas of the world are generally more stringent than the current EPA 

NPDWR for acrylamide and epichlorohydrin in drinking water. Exhibit 4-2 provides a 

comparison of recommendations and guidelines used elsewhere to EPA’s current regulations. 

Canada has no national regulations regarding acrylamide or epichlorohydrin. However, many 

provinces require NSF 60 certification for additives used in drinking water treatment (Lemieux, 

2007). The residual monomer and dosage requirements for NSF 60 certification are based on 

those in EPA’s current NPDWR. 

 

1

 NSF did not provide any confidential business information such as which manufacturers were included in the 

analyses. NSF only provided vectors of testing results. 
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Exhibit 4-2. Comparison of Acrylamide and Epichlorohydrin Drinking Water 

Guidelines 

Country/Region Regulation or Guideline Acrylamide Epichlorohydrin 

Residual Monomer 0.05% 0.01% 

US EPA Maximum Dosage 1 mg/L 20 mg/L 

Expected Concentration in Water1 0.5 μg/L 2 μg/L 

Canada NSF 60 certification required in many provinces; see text below

Residual Monomer 0.02% 0.002% 

Maximum Dosage 0.25 mg/L (average) 

0.5 mg/L (maximum) 

2.5 mg/L (average) 

United Kingdom 5 mg/L (maximum) 2 

Expected Concentration in Water1 0.05 μg/L (average) 

0.1 μg/L (maximum) 

0.05 μg/L (average) 

0.1 μg/L (maximum) 

European Union3 Concentration in Water 0.1 μg/L 0.1 μg/L 

WHO4 Concentration in Water 0.5 μg/L 0.4 μg/L 

Australia5 Concentration in Water 0.2 μg/L 0.5 μg/L 

1. The expected monomer concentration in water is the product of the maximum dosage and the residual monomer 

level, using the worst-case assumption that all residual monomer remains in finished water. 

2. DWI (2007) and Ashworth (2007). The UK limits both the average and the maximum polymer dose. 

3. OJEC (1998). The concentration is “the residual monomer concentration in the water as calculated according to 

specifications of the maximum release from the corresponding polymer in contact with the water.” 

4. WHO (2006). The World Health Organization’s recommendation for epichlorohydrin is a provisional guideline 

value because there is evidence of a hazard, but the available information on health effects is limited (WHO, 2004). 

5. NHMRC (2004). The guideline value for epichlorohydrin is below the limit of determination; improved analytical 

procedures are required for this compound. 
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5 References 

Ashworth, J. 2007. Personal communication from John Ashworth, UK Drinking Water 

Inspectorate, to Jitendra Saxena, U.S. EPA. 10 May. 

Crittenden, J. et al. 1988. “Using GAC to Remove VOCs from Air Stripper Off-Gas.” J.AWWA, 

80(5). (As cited in Clark, R. and J. Adams. EPA's Drinking Water and Groundwater 

Remediation Cost Evaluation: Air Stripping. Lewis Publishers.) 

Cummins, M. and J. Westrick. 1987. “Feasibility of Air Stripping for Controlling Moderately 

Volatile Synthetic Organic Chemicals.” Presented at 1987 AWWA Conference. Reprinted in 

Best Available Technology Peer Review Conference: Final Report. U.S. EPA. 

Drinking Water Inspectorate (DWI), United Kingdom. 2007. List of Approved Products. July. 

http://www.dwi.gov.uk/31/pdf/soslist06.pdf. 

Ground-Water Remediation Technologies Analysis Center (GWRTAC). 2001. Technology 

Status Report: Perchlorate Treatment Technologies, First Edition. Pittsburgh, PA. May. 

Lemieux, F. 2007. Personal communication from F. Lemieux, Health Canada, to Rajiv Khera, 

U.S. EPA. 16 October. 

National Health and Medicine Research Council (NHMRC), Australia. 2004. Australian 

Drinking Water Guidelines. http://www.nhmrc.gov.au/publications/synopses/eh19syn.htm. 

NSF International (NSF). 1999a. NSF Drinking Water Additives Program: The Second Decade. 

http://www.nsf.org/business/newsroom/waterworks99-1/index.html. 

NSF International (NSF). 1999b. Summary Report: NSF International Extraction Results (1991 

to 1998), ANSI/NSF Standard 61: Drinking Water System Components – Health Effects. Report 

prepared for Health Canada. http://www.hc-sc.gc.ca/ewh-semt/water-eau/drinkpotab/mater/nsf_components_e.html. 

NSF International (NSF). 2000. Review of Contaminant Occurrences in Drinking Water 

Treatment Chemicals: A Summary Report of NSF International Results (1991 to 1999), 

ANSI/NSF Standard 60: Drinking Water Treatment Chemicals – Health Effects. Report prepared 

for Health Canada. 31 March. http://www.hc-sc.gc.ca/ewh-semt/water-eau/drinkpotab/mater/nsf_chemicals-chimiques_e.html. 

NSF International (NSF). 2005a. Environmental Technology Verification Report: Removal of 

Chemical Contaminants in Drinking Water, EcoWater Systems Incorporated ERO-R450E 

Drinking Water Treatment System. Prepared by NSF International under a Cooperative 

Agreement with U.S. Environmental Protection Agency. NSF 05/14b/EPADWCTR. September. 

NSF International (NSF). 2005b. Environmental Technology Verification Report: Removal of 

Chemical Contaminants in Drinking Water, Kinetico Incorporated Pall/Kinetico PurefectaTM 
EPA-OGWDW Water Treatment Technology Feasibility Support EPA 815-B-09-007 

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Drinking Water Treatment System. Prepared by NSF International under a Cooperative 

Agreement with U.S. Environmental Protection Agency. NSF 05/13b/EPADWCTR. September. 

NSF International (NSF). 2005c. Environmental Technology Verification Report: Removal of 

Chemical Contaminants in Drinking Water, Watts Premier Incorporated WP-4V Drinking Water 

Treatment System. Prepared by NSF International under a Cooperative Agreement with U.S. 

Environmental Protection Agency. NSF 05/12c/EPADWCTR. November. 

NSF International (NSF). 2006. Environmental Technology Verification Report: Removal of 

Chemical and Microbial Contaminants in Drinking Water, Watts Premier, Inc. M-2400 Point-ofEntry Reverse Osmosis Drinking Water Treatment System. Prepared by NSF International under 

a Cooperative Agreement with U.S. Environmental Protection Agency. NSF 

06/23/EPADWCTR. September. 

NSF International (NSF). 2007a. Environmental Technology Verification Report: Removal of 

Synthetic Organic Chemical Contaminants in Drinking Water, RASco, Inc. Advanced 

Simultaneous Oxidation Process (ASOPTM). Prepared by NSF International under a Cooperative 

Agreement with U.S. Environmental Protection Agency. NSF 06/25/EPADWCTR. September. 

NSF International (NSF). 2007b. NSF Product and Service Listings: NSF/ANSI Standard 60: 

Drinking Water Treatment Chemicals – Health Effects. List of search results with Chemical 

Name equal to Polyacrylamide. Search performed 25 October. 

http://www.nsf.org/Certified/PwsChemicals/Listings.asp?CompanyName=&TradeName=&Che

micalName=Polyacrylamide&ProductFunction=&PlantState=&PlantCountry=. 

NSF International (NSF). 2007c. NSF Product and Service Listings: NSF/ANSI Standard 60: 

Drinking Water Treatment Chemicals – Health Effects. List of search results with Chemical 

Name equal to Polyamines. Search performed 25 October. 

http://www.nsf.org/Certified/PwsChemicals/Listings.asp?ChemicalName=Polyamines&Product

Function=&PlantState=&PlantCountry= . 

NSF and Association of State Drinking Water Administrators (ASDWA). 2006. Survey of 

ASDWA Members: Use of NSF Standards and ETV Reports. March. 

http://www.nsf.org/business/water_distribution/pdf/ASDWA_Survey_2006.pdf. 

Official Journal of the European Communities (OJEC). 1998. Council Directive 98/83/EC of 3 

November 1998 on the quality of water intended for human consumption. 

Purkiss, D. 2007. Personal communication from D. Purkiss, NSF International, to Jitendra 

Saxena, U.S. EPA. 7 November. 

Ram, N.M., R.F. Christman, and K.P. Cantor. 1990. Significance and Treatment of Volatile 

Organic Compounds in Water Supplies. Lewis Publishers. (As cited in USEPA, 1998.) 

Rauschert Industries, Inc. Undated. Removal of Volatile Organic Compounds from Water. 

Brochure APP-02. 
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Sander, R. 1999. Compilation of Henry's Law Constants for Inorganic and Organic Species of 

Potential Importance in Environmental Chemistry (Version 3). http://www.mpchmainz.mpg.de/~sander/res/henry.html

Skelly, Norman E., and Edward R. Husser. 1978. “Determination of Acrylamide Monomer in 

Polyacrylamide and in Environmental Samples by High Performance Liquid Chromatography.” 

Analytical Chemistry, 50: 1959-1962. First page online at 

http://pubs3.acs.org/acs/journals/toc.page?incoden=ancham&indecade=3&involume=50&inissue

=14. 

U.S. Army Corps of Engineers. 2001. Adsorption Design Guide. Design Guide No. 1110-1-2. 

Department of the Army, U.S. Army Corps of Engineers. Washington, DC. 1 March. 

http://www.usace.army.mil/publications/design-guides/dg1110-1-2/entire.pdf

USEPA. 2009a. Analysis of Occurrence Data from the Second Six-Year Review of Existing 

National Primary Drinking Water Regulations. EPA 815-B-09-006. 

USEPA. 2009b. Analytical Feasibility Support Document for the Second Six-Year Review of 

Existing National Primary Drinking Water Regulations. EPA 815-B-09-003. 

USEPA. 2009c. Development of Estimated Quantitation Levels for the Second Six-Year Review 

of National Primary Drinking Water Regulations. EPA 815-B-09-005. 

USEPA. 2009d. EPA Protocol for the Second Review of Existing National Primary Drinking 

Water Regulations (Updated). EPA 815-B-09-002.

USEPA. 2009e. Occurrence Analysis for Potential Source Waters for the Second Six-Year 

Review of National Primary Drinking Water Regulations. EPA 815-B-09-004. 

USEPA. 2009f. Six-Year Review 2 – Health Effects Assessment – Summary Report. EPA 822-

R-09-006. 

USEPA. 2009g. Consideration of Other Regulatory Revisions in Support of the Second Six-Year 

Review of the National Primary Drinking Water Regulations. EPA 815-B-09-008. 

USEPA. 2007. Simultaneous Compliance Guidance Manual For The Long Term 2 And Stage 2 

DBP Rules. Office of Water. EPA 815-R-07-017. March. 

USEPA. 2003. EPA Protocol for Review of Existing National Primary Drinking Water 

Regulations. EPA 815-R-03-002. June. 

USEPA. 1999. Enhanced Coagulation and Enhanced Precipitative Softening Guidance Manual. 

Office of Water. EPA 815-R-99-012. May. 

USEPA. 1998. Small System Compliance Technology List for the Non-Microbial Contaminants 

Regulated before 1996. Office of Water. EPA 815-R-98-002. September. 
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USEPA. 1990. Technologies and Costs for the Removal of Phase V Synthetic Organic 

Chemicals from Potable Water Supplies. Office of Drinking Water. September. 

USEPA. 1985. Technologies and Costs for the Removal of Volatile Organic Chemicals from 

Potable Water Supplies. (As cited in USEPA, 1998.) 

World Health Organization (WHO). 2004. Epichlorohydrin in Drinking-water. 

WHO/SDE/WSH/03.04/94. 

World Health Organization (WHO). 2006. Guidelines for Drinking-water Quality: Incorporating 

First Addendum, Vol. 1, Recommendations. 3rd Edition. World Health Organization. Geneva, 

Switzerland. http://www.who.int/water_sanitation_health/dwq/gdwq3rev/en/index.html
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Appendix: Monomer Data from NSF International 

In 2007, NSF International (NSF) provided EPA with the results of NSF analyses of acrylamide 

monomer in polyacrylamides and free epichlorohydrin in polyamines certified to NSF/ANSI 

Standard 60. The analyses were performed between January 2005 and June 2007. The data that 

NSF provided is reproduced here. 

NSF determined the residual acrylamide content in 66 samples of commercial polyacrylamides, 

using the method described by Skelly and Husser (1978) with a detection limit of 10 mg 

acrylamide per kg polymer. NSF provided only a vector of test results; it did not provide 

manufacturer or product names or any other competition-sensitive information. Exhibit A-1

provides a frequency distribution for the data that NSF provided to EPA. 

Exhibit A-1. NSF International Data on Acrylamide Monomer in Polyacrylamide 

Measurement (mg/kg) Number of Samples 

ND1 21 

10 2 

20 1 

30 2 

40 6 

60 2 

70 3 

80 2 

90 2 

100 3 

110 1 

120 1 

140 3 

150 2 

170 2 

180 2 

210 2 

220 2 

280 1 

320 2 

340 1 

360 1 

410 1 

420 1 

ND = nondetect. 

1. Detection limit was 10 mg/kg. 

NSF provided EPA with measurements of the amount of residual epichlorohydrin in 84 samples 

of commercial polyamines, using the method described in section B.4.3.1 of NSF 60-2005 with a 

detection limit of 20 mg epichlorohydrin per kg polymer. NSF provided only a vector of test 
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results, with no manufacturer or product names or other competition-sensitive information. None 

of the 84 measurements found epichlorohydrin in a concentration greater than the detection limit.