United States

Environmental Protection Office of Water EPA 815-R-98-002

Agency 4607 September 1998

_____________________________________________________________________

Small System

Compliance Technology

List for the Non-Microbial 

Contaminants Regulated

Before 1996

 
ii

TABLE OF CONTENTS

Table of Contents ii

List of Figures iv

1. Introduction 1

Section 1.1: Safe Drinking Water Act Implementation 1

Section 1.2: Need for a Small System Technology Requirement 2

Section 1.3: Small System Treatment Technology Requirements 

of the 1996 SDWA 3

Section 1.4: Point-of-Entry and Point-of-Use Treatment Units as 

Compliance Technologies 10

Section 1.5: Format and Content of this Small System Compliance 

Technology List 10

Section 1.6: Stakeholder Involvement 11

Section 1.7: Organization of the Document 12 

2. Background on Existing National Primary Drinking Water Regulations 14

Section 2.1 National Interim Primary Drinking Water Regulations

(NIPDWRs) (40 FR 59566) 15

Section 2.2 Radionuclides NIPDWRs (41 FR 28402) 15

Section 2.3 Trihalomethanes NIPDWRs (44 FR 68624) 16

Section 2.4 Fluoride Rule (51 FR 11396) 16

Section 2.5 Phase I Rule (52 FR 25690) 16

Section 2.6 Phase II Rule (56 FR 3526) and 

Phase IIb Rule (56 FR 30266) 16

Section 2.7 Lead and Copper Rule (56 FR 26460) 17

Section 2.8 Phase V Rule (57 FR 31776) 18

Section 2.9 Summary of National Primary Drinking Water Regulations 18

3. Descriptions of Technologies 22

4. Affordable Technology Determinations 42

Section 4.1 National-Level Affordability Criteria 42

Section 4.2 Affordable Technology Analysis using National-Level 

Affordability Criteria 46

5. Small Systems Compliance Technologies for Inorganic Contaminants, 

Including Corrosion By-Products 48

Section 5.1: Background 48

Section 5.2: Evaluation of Technologies 50
iii

Section 5.3: Small Systems Compliance Technologies List 56

Section 5.4: Emerging Technologies 61

6. Small Systems Compliance Technologies for Radionuclides 65

Section 6.1: Background 65

Section 6.2: Evaluation of Technologies 67

Section 6.3: Small Systems Compliance Technologies List 81

Section 6.4: Emerging Technologies 83

7. Small Systems Compliance Technologies for Volatile Organic Contaminants 86

Section 7.1: Background 86

Section 7.2: Evaluation of Technologies 87

Section 7.3: Small Systems Compliance Technologies List 90

Section 7.4: Emerging Technologies 93

8. Small Systems Compliance Technologies for Other Synthetic 

Organic Contaminants 96

Section 8.1: Background 96

Section 8.2: Evaluation of Technologies 97

Section 8.3: Small Systems Compliance Technologies List 98

Section 8.4: Emerging Technologies 102

Appendix: Relevant Statutory Sections 106
iv

LIST OF FIGURES

Chapter 1

Figure 1. Small System Requirements: Compliance vs. 

Variance Technologies 5

Figure 2. Affordable Compliance Technologies 7

Figure 3. Compliance Technologies (No Affordability) 9

Chapter 6

Figure 1. Disposal of Liquid Wastes 78

Figure 2. Disposal of Solid Wastes 80
1

1. INTRODUCTION

Section 1.1: Safe Drinking Water Act Implementation

The Safe Drinking Water Act (SDWA) Amendments were signed by the President on August

6, 1996. The 1996 SDWA contains over 70 statutory deadlines for the Environmental Protection

Agency (EPA), presenting a challenging set of activities for EPA, States, Indian tribes, public water

systems, and other stakeholders.

Due to the 1996 SDWA’s emphasis on public information and participation, as well as EPA’s

desire to seek a broad range of public input, the stakeholder process that was begun during the 1995

drinking water program redirection effort has been greatly expanded. To provide focus, EPA has

grouped many of the statutory deadlines into more general project areas. Each of these areas has a

broad set of stakeholders that will provide information and comments.

One of these project areas focuses on small systems treatment technologies and is being

addressed by EPA’s Treatment Technology Team. This project area is a part of one of the primary

objectives of the 1996 SDWA, which is to more fully consider the needs of small drinking water

systems in developing and implementing drinking water regulations. The mission of the Treatment

Technology Team is to identify and/or develop high quality, cost-effective treatment technologies to

meet regulation development and program implementation objectives and deadlines. The team’s

short-term goals are to prepare: (1) by August 6, 1997, the list of technologies that small systems can

use to comply with the Surface Water Treatment Rule (SWTR); (2) by August 6, 1998, the list of

technologies that small systems can use to comply with all of the other (pre-August 1996) National

Primary Drinking Water Regulations (NPDWRs); and (3) by August 6, 1998, the list of variance

technologies for small systems for the appropriate NPDWRs. The long-term goals include the

identification of: (1) small system compliance and variance technologies for all future regulations; (2)

best available technologies (BATs) for larger systems in future regulations; and (3) emerging

technologies that should be evaluated as potential compliance or variance technologies for both

existing and future regulations.

The Environmental Protection Agency met the first of these short-term goals in August, 1997.

A Federal Register notice dated August 11, 1997 published the compliance technology list for the

surface water treatment rule (EPA 1997a). The notice also announced the availability of a guidance

manual entitled “Compliance Technology List for the Surface Water Treatment Rule” (EPA 1997b),

which provided more detailed background information supporting the list of technologies published

in the Federal Register notice.

The Environmental Protection Agency updated the list of compliance technologies for the SWTR

and published the list of compliance technologies for the total coliform rule in a Federal Register

notice on August 6, 1998 (EPA 1998a). EPA is also publishing an update to the guidance manual

that supported the original SWTR list of compliance technologies. The updated guidance manual is

entitled “Compliance Technology List for the Surface Water Treatment Rule and the Total Coliform
2

Rule” (EPA 1998b). This document covers both update of the SWTR list and the compliance

technologies identified for the Total Coliform Rule (TCR). These have been grouped into one

publication as they both address microbial contaminants and their indicators in drinking water. The

list of compliance technologies for the total coliform rule is one of the lists required by Section

1412(b)(4)(E)(iii) of the SDWA.

The Environmental Protection Agency met both the second and third of the short-term goals in

August 1998. A Federal Register notice dated August 6, 1998 (EPA 1998a) published the list of

compliance technologies that systems can use to comply with all of the other NPDWRs and the

findings concerning variance technologies for the contaminants regulated before 1996. EPA did not

list any variance technologies for contaminants regulated before 1996 in this notice. This guidance

manual was developed to provide more detail on the list of compliance technologies for the nonmicrobial contaminants regulated before 1996. A guidance manual entitled “Variance Technology

Findings for Contaminants Regulated before 1996" has been prepared to describe the procedures that

were used to make the determination that there would be no variance technologies for contaminants

regulated before 1996 at this time (EPA 1998c).

Section 1.2: Need for a Small System Technology Requirement

The 1986 SDWA identified a process for setting maximum contaminant levels (MCLs) as close

to the maximum contaminant level goal (MCLG) as is “feasible.” The Act states that the term

“feasible” means feasible with the use of the best technology, treatment techniques and other means

which the Administrator finds, after examination for efficacy under field conditions and not solely

under laboratory conditions, are available (taking cost into consideration) [Section 1412(b)(4)(D)].

The technologies that met this feasibility criterion are called “best available technologies” (BATs) and

are listed in the final regulations. This process is retained in the 1996 SDWA. All of the existing

MCLs covered in this document were developed using this process.

One of the regulations covered in this document is the Lead and Copper Rule, which requires

compliance with a treatment technique rule rather than an MCL. Section 1412(b)(7)(A) of the 1986

SDWA listed the conditions under which a treatment technique could be promulgated in lieu of an

MCL. When these conditions are met, the Act states that “. . . the Administrator must identify those

treatment techniques which, in the Administrator’s judgement, would prevent known or anticipated

adverse effects on the health of persons to the extent feasible”. The definition of feasible listed above

would also apply in the technology determinations for treatment techniques like the Lead and Copper

Rule.

There is one other treatment technique rule in the group of non-microbial contaminants regulated

before 1996: epichlorohydrin and acrylamide are regulated through the Phase II Rule (see Chapter

2) via a treatment technique rather than with MCLs. Unlike the technology-based treatment

techniques established by the SWTR or the Lead and Copper Rule, the treatment techniques for these

two contaminants are not based on the use of treatment technologies to remove or reduce the

contaminant concentration. Instead, the treatment technique for these two contaminants requires
3

those public water systems using acrylamide or epichlorohydrin in a treatment process to provide

written certification annually to the State that the combination of dose and monomer level does not

exceed specified levels. Since technologies are not being utilized for these NPDWRs, neither

compliance nor variance technologies will be listed for these contaminants.

Before the 1996 Amendments, cost assessments for the treatment technology feasibility

determinations were based upon impacts to regional and large metropolitan water systems. This

protocol was established when the SDWA was originally enacted in 1974 (Congressional Record

1974) and was carried over when the Act was amended in 1986 (Congressional Record 1986). The

population size categories that EPA has used to make feasibility determinations for regional and large

metropolitan water systems has varied among different regulation packages. The most common

population size categories used were 50,000 - 75,000 people and 100,000 - 500,000 people. The

technical demands and costs associated with technologies that are feasible based on regional and large

metropolitan water systems often make these technologies inappropriate for small systems. The 1996

Amendments attempt to redress this problem in part through the previously described series of small

system compliance technologies. This guidance is the second part of a series of publications aimed

at helping small systems comply with the existing regulations.

Section 1.3: Small System Treatment Technology Requirements of the 1996 SDWA

Since large systems were used as the basis for the feasibility determinations, some of the existing

BATs for MCLs and the existing treatment techniques may not be appropriate for small systems. In

response to this concern, the 1996 SDWA specifically requires EPA to make technology assessments

relevant to the three categories of small systems respectively for both existing and future regulations,

in addition to the pre-1996 Amendments BAT protocol. The three population-served size categories

of small systems defined by the 1996 SDWA are: 10,000 - 3,301 persons, 3,300 - 501 persons, and

500 - 25 persons.

The 1996 SDWA identifies two classes of technologies for small systems: compliance

technologies and variance technologies. A “compliance technology” may refer to both a technology

or other means that is affordable and that achieves compliance with the MCL and to a technology or

other means that satisfies a treatment technique requirement. Possible compliance technologies

include packaged or modular systems and point-of-entry (POE) or point-of-use (POU) treatment

units [see Section 1412(b)(4)(E)(ii)]. Variance technologies are only specified for those system

size/source water quality combinations for which there are no listed compliance technologies [Section

1412(b)(15)(A)]. Thus, the listing of a compliance technology for a size category/source water

combination prohibits the listing of variance technologies for that combination. While variance

technologies may not achieve compliance with the MCL or treatment technique requirement, they

must achieve the maximum reduction or inactivation efficiency that is affordable considering the size

of the system and the quality of the source water. Variance technologies must also achieve a level

of contaminant reduction that is protective of public health [Section 1412(b)(15)(B)].

The variance procedure for small systems has been significantly revised in the 1996 SDWA. The
4

1986 SDWA required non-compliant water systems to install a “best available technology” (BAT)

before applying for a variance: if they were unable to meet the MCL after treatment, they could then

apply for a variance. The 1996 Amendments have given the variance option additional flexibility in

that variances can be applied for and granted before the variance technology is installed, thus ensuring

that the system will have a variance before it invests in treatment. This new variance procedure

applies specifically to small water systems (systems serving less than 10,000) and is referred to as the

“small system variance”. The difference between the original variance and the small system variance

procedures is the basis for the feasibility (technical and affordability) determination. For the former,

large systems are the basis; for the latter, small systems are the basis. If there are no affordable

compliance technologies listed by the EPA for a small system size category/source water quality

combination and EPA has identified small systems variances technologies for that combination, then

the system may apply for a small system variance. One of the criteria for obtaining a small system

variance is that the system must install a variance technology listed for that size category/source water

quality combination [Section 1415(e)(2)(A)]. A small system variance may only be obtained if

alternate source, treatment, and restructuring options are unaffordable at the system-level.

There are some additional statutory requirements for small system variances that affect the listing

of variance technologies. Small system variances are not available for any MCL or treatment

technique for a contaminant with respect to which a national primary drinking water regulation was

promulgated prior to January 1, 1986 [Section 1415(e)(6)(A)]. The final Variance and Exemption

Rule provides EPA’s interpretation of this requirement (EPA 1998d). In a case where a pre-1986

NPDWR is updated, EPA has determined that small system variances would not be available if the

pre-1986 MCL is either retained or raised. Small system variance would only be available if the pre1986 MCL was lowered (could apply to updates of the existing arsenic and radionuclides MCLs if

the pre-1986 MCLs are lowered). Nor are small system variances allowable for NPDWRs (including

treatment techniques) for microbial contaminants or microbial contaminant indicators, i.e., bacteria,

viruses, other regulated pathogens, or regulated indicators, like turbidity [Section 1415(e)(6)(B)].

Variance technologies were not specified for those contaminants for which small system variances

are not allowable by the SDWA.

The process for identifying compliance and variance technologies for future regulations was

summarized in the preceding paragraphs. The language in the 1996 SDWA Amendments is different

for the existing regulations. There are two mandatory lists of compliance technologies that will be

developed for the existing rules. By August 6, 1997, the Administrator was required to list

technologies that meet the SWTR for each of the three size categories [Section 1412(b)(4)(E)(v)].

By August 6, 1998, after consultation with the States, the Administrator was required to issue a list

of technologies that achieve compliance with the MCLs or treatment technique requirements for other

existing NPDWRs. Also by August 6, 1998, after consultation with the States, the Administrator was

required to issue guidance or regulations for variance technologies for the existing NPDWRs for

which a small system variance can be granted. Figure 1 summarizes the requirements for compliance

and variance technologies and differentiates between existing and future regulations.
5

FIGURE 1

SMALL SYSTEM REQUIREMENTS

COMPLIANCE VS. VARIANCE TECHNOLOGIES

COMPLIANCE

TECHNOLOGY

VARIANCE

TECHNOLOGY

EXISTING

REGULATIONS:

 Meet affordable

 technology criteria

Not Explicitly Required Inherently Required

 Source Water Quality GOOD POOR

 Endpoint MCL Maximum Reduction

that is Affordable

 Health Requirements

 Separate from MCL

NONE Must be protective of

public health

FUTURE

REGULATIONS:

 Meet affordable

 technology criteria

Required Required

 Source Water Quality GOOD POOR

 Endpoint MCL Maximum Reduction

that is Affordable

 Health Requirements

 Separate from MCL

NONE Must be protective of

public health

The two major concerns regarding technologies for small systems are affordability and technical

complexity. Regarding affordability, per household costs tend to be higher for the smaller system

customers for most central treatment technologies, leading to many cases where small systems simply

cannot afford to install a prescribed technology. Regarding technical complexity, small systems often

do not have access to well-trained water system operators. Although the statute is silent concerning
6

whether small system compliance technologies for existing regulations should be affordable, EPA

believes that the better approach under the statute is that affordability should be evaluated for future

regulations and existing regulations where the statute allows variance technologies. If the candidate

technologies are not evaluated against an affordable technology criterion, then compliance

technologies would exist for all of the existing regulations regardless of the source water quality. The

existing best available technologies (BATs) or treatment techniques would automatically become the

compliance technologies for small systems, which was the case prior to the 1996 Amendments. EPA

does not believe that result to be what Congress intended. As a result, EPA will evaluate small

system technologies against an affordable technology criterion for those existing regulations where

small system variances or variance technologies are not prohibited by the SDWA. When affordable

compliance technologies are identified for these contaminants, technologies that can achieve

compliance but did not meet the affordability criterion will also be identified. This is consistent with

EPA’s approach to the compliance technology list for the SWTR and the views of stakeholders. EPA

will list these technologies and indicate that they did not pass the affordable technology criterion

rather than limit the information on options available to systems. For those regulations where the

SDWA prohibits small system variances or variance technologies, affordability will not be considered

in the evaluation of compliance technologies because there would be no function to doing so (all

systems subject to the rule must comply).

The flow chart in Figure 2 shows the role of the affordable technology criteria in the treatment

technology arena. The primary function of the criteria is to determine whether a system of a given

size/source water quality combination should proceed down the compliance or variance technology

pathway (assuming an affordable variance technology can be identified). The secondary function is

to define the universe of technologies within the compliance or variance technology pathway. These

affordable technology criteria are different from the affordability criteria to be used by States in

granting small system variances under Section 1415(e). The criteria used by States will be applicable

to individual systems (“system-level affordability criteria”). Options that States can use for systemlevel affordability criteria were developed in the Small System NDWAC Working Group process and

are available in “Information for States on Developing Affordability Criteria for Drinking Water.”

This document was published on February 4, 1998 (EPA 1998e) and can be downloaded at

http://www.epq.gov/OGWDW/smallsys/afford.html. In contrast, the affordable technology criteria

to be developed under Section 1412(b)(4) can be viewed as “national-level affordability criteria”

(EPA 1998f). Technologies that meet the national-level criteria may not be affordable for a particular

system within the size category (“system-level affordability criteria”). In these cases, the system

should explore the options of restructuring or finding an alternate source of water. If these options

are not available, grants and exemptions may be available. These issues are discussed in more detail

in Chapter 4. The respective roles of the national-level and system-level affordability criteria are

summarized in Figure 2.
7

System Out

of Compliance

Affordable

Compliance

Technology?

Can System

afford Treatment

Alt. Source or

Restructuring?

Can

system afford

a compliance

technology?

Can System

Restructure

or afford Alt

Source?

Implement

Compliance

Technology

Implement

Treatment,

Alt Source or

Restructuring

Implement

Affordable

variance

technology

FIGURE 2

AFFORDABLE COMPLIANCE TECHNOLOGIES*

Has

exemption

period run

out?

Obtain Small

System Variance

Exemption

Process (State

sets schedule

for compliance)

Is

Restructuring

practicable?

*NOTE: This approach covers the regulations that pass all of the

screening criteria for variance technologies.

Are

Exemptions

Available

YES NO

YES NO

YES

NO

NO

YES

YES

YES

YES

YES RS

NO

NO

YES

NO

NO
8

For those existing regulations where the SDWA prohibits small system variances or variance

technologies, the candidate technologies will not be evaluated against an affordable technology 

criterion. There are two statutory prohibitions on small system variances and one prohibition on

variance technologies. As previously mentioned, small system variances are not available for any

NPDWR for a microbial contaminant (or indicator). The compliance technologies for the six

microbial contaminants were not evaluated against the affordable technology criterion (EPA 1998b).

Small system variances are also not available for any MCL or treatment technique with respect to

which a NPDWR was promulgated prior to January 1, 1986. Technologies were not evaluated

against an affordable technology criterion for the 12 contaminants where the pre-1986 MCL has been

retained or raised. The statutory prohibition on variance technologies is found in Section

1412(b)(15)(B) of the SDWA. The Administrator shall not identify any variance technology under

this paragraph, unless the Administrator has determined, considering the quality of the source water

to be treated and the expected useful life of the technology, that the variance technology is protective

of public health. For 19 contaminants, it was determined that in order to be protective of public

health, the MCL had to be met. Thus, affordable compliance technology determinations were not

done for 31 of the 71 contaminants with listed compliance technologies or for the six microbial

contaminants, which are covered in another document. The flow chart in Figure 3 shows the

simplified process for these regulations. In this figure, “no affordability” refers to the fact that

affordability considerations are not allowed for these contaminants.
9

System Out

of Compliance

*NOTE: This approach covers all regulations where the contaminant

 failed to meet one of the screening criteria for variance technologies.

Are

Exemptions

Available

Can

system afford

a compliance

technology?

Can System

Restructure

or afford Alt

Source?

Implement

Compliance

Technology

Implement

Alt. Source

or

Restructuring

FIGURE 3 

COMPLIANCE TECHNOLOGIES (No affordability)*

Has

exemption

period run

out?

Exemption

Process(State

sets schedule

for compliance)

NO

YES

YES NO

YES

YES

NO

NO

YES

NO
10

Section 1.4: Point-Of-Entry and Point-of-Use Treatment Units as Compliance Technologies

Section 1412(b)(4)(E)(ii) of the SDWA identifies both Point-of-Entry (POE) and Point-of-Use

(POU) treatment units as options for compliance technologies. A POE treatment device is a

treatment device applied to the drinking water entering a house or building for the purpose of

reducing contaminants in the drinking water distributed throughout the house or building. A POU

treatment device is a treatment device applied to a single tap used for the purpose of reducing

contaminants in drinking water at that one tap. POU devices are typically installed at the kitchen tap.

The SDWA identifies requirements that must be met when POU or POE units are used by a

water system to comply with a NPDWR. Section 1412(b)(4)(E)(ii) stipulates that “point-of-entry

and point-of-use treatment units shall be owned, controlled, and maintained by the public water

system or by a person under contract with the public water system to ensure proper operation and

maintenance and compliance with the MCL or treatment technique and equipped with mechanical

warnings to ensure that customers are automatically notified of operational problems.” Other

conditions in this section of the SDWA include the following: “If the American National Standards

Institute has issued product standards applicable to a specific type of POE or POU treatment unit,

individual units of that type shall not be accepted for compliance with a MCL or treatment technique

unless they are independently certified in accordance with such standards.” 

In order to list POU treatment units as compliance technologies, EPA had to delete the part of

40 CFR §141.101 that prohibited POU devices to be used to comply with an MCL. A final rule was

published in the Federal Register on June 11, 1998 (EPA 1998g) deleting the prohibition on the use

of POU devices as compliance technologies. As previously mentioned, POU devices are listed as

compliance technologies for inorganic contaminants, synthetic organic contaminants, and

radionuclides. POU devices are not listed for volatile organic contaminants because they do not

address all routes of exposure. POE devices are still considered emerging technologies because of

waste disposal and cost considerations. POE devices may be included on an updated list in 1999.

For more detail on POU and POE devices, see the supporting document entitled “Cost Evaluation

of Small System Compliance Options: Point-of-Use and Point-of-Entry Treatment Units” (EPA

1998h). 

Section 1.5: Format and Content of the Small System Compliance Technology List for the

Non-Microbial Contaminants Regulated Before 1996

The 1996 SDWA does not specify the format for the compliance technology lists. Section

1412(b)(15)(D) states that the variance technology lists can be issued either through guidance or

regulations. EPA believes that the compliance technology list may also be appropriately provided

through guidance for pre-August 1996 rules, rather than through rule-making. Since the listing

provided in this guidance is meant to be informational, it does not require any changes to existing

rules or the promulgation of new ones. The purpose of this guidance is to provide small systems with

information concerning the types of technologies that can be used to comply with the requirements

of the existing non-microbial regulations. It does not over-ride any of the requirements of those
11

regulations. In summary, EPA has chosen to issue the list through a guidance document because

regulation development is unnecessary and could considerably delay publication of the list. Issuing

the list without rule-making allows EPA to meet the statutory deadline and to provide information

to more small systems as they make their treatment technology decisions. It is also much easier and

faster to update a guidance rather than a rule to incorporate advances in technology performance.

The SDWA does not specify the content of the compliance technology lists. These initial lists

(63 FR 42032) are very general and expand the lists of technology options listed in the existing nonmicrobial regulations. These lists may be updated to incorporate new technologies or additional

information on parameters that can affect the selection of treatment. The lists will evolve over time,

but will not be product-specific. The compliance technology lists will not be product-specific because

EPA’s Office of Ground Water and Drinking Water does not have the resources to review each

product for each potential application; nor does EPA feel it would be appropriate to do so.

Information on specific products will be available through another mechanism. EPA’s Office of

Research and Development has a pilot project under the Environmental Technology Verification

(ETV) Program to provide treatment system purchasers with performance data from independent

third parties. The EPA and National Sanitation Foundation International (NSF) are cooperatively

organizing and conducting this pilot project to allow for verification testing of packaged drinking

water treatment systems for meeting community and commercial needs. This pilot project includes

the development of verification protocols and test plans, the independent testing and validation of

packaged equipment, the fostering and supporting of government/industry partnerships to obtain

credible cost and performance data, and the preparation of product verification reports for widespread distribution. 

Section 1.6: Stakeholder Involvement

EPA held a stakeholder meeting on May 18 and 19, 1998. Approximately 50 people registered

and participated in the meeting. Key stakeholders included States, water systems, and equipment

manufacturers. Representatives from nine States were present at the meeting (either at the meeting

or on conference lines) and several others received the material that was sent out prior to the meeting

for review. A draft of the “Cost Evaluation of Small System Compliance Options: Point-of-Use and

Point-of-Entry Treatment Units” was sent out prior to the meeting. 

During the meeting, compliance technology options were presented for each group of

contaminants: inorganic contaminants (IOCs), volatile organic contaminants (VOCs), synthetic

organic contaminants (SOCs), and radionuclides. There was also a presentation on POU and POE

devices that followed the sessions on the contaminant groups. Since most of the compliance

technologies identified for these groups of contaminants were the BATs listed in the regulations, there

were few significant comments on those presentations.

One major topic discussed at the meeting was the format of the document. The two options

were separate documents for each contaminant group or one document with separate chapters
12

devoted to each contaminant group. Stakeholders preferred a document organized by contaminant

groups rather than by individual technologies, since many technologies can treat for more than one

contaminant group. For example, the technologies used for VOCs removal can also be used to

remove some SOCs. There is also a lot of cross-over between technologies that can treat IOCs and

radionuclides.

Stakeholders reiterated that they thought the list of compliance technologies should be as

comprehensive as possible. Rather than exclude possible options that have technical limitations,

stakeholders preferred EPA to list the technologies along with the discussions of and guidance for

dealing with these limitations. Examples of limitations include treatment technological complexity,

which raises the concern of whether small systems could successfully operate complex processes.

Stakeholders indicated that a more comprehensive compliance technology list that included more

technology options for individual systems would be preferable to a more conservative list that

disallows for the fact that many small systems have the capacity to operate more complex

technologies. EPA has also incorporated this philosophy into the identification of affordable

compliance technologies. EPA identified compliance technologies that did not meet the affordability

criteria in addition to those that did, as discussed in Section 1.3.

The initial lists of technologies are not intended to be definitive: systems may choose any

technologies that meet the requirements of the regulations. In each chapter, there are technologies

identified as “emerging technologies” that are not listed. These technologies either have data needs

or require further evaluation before being listed as compliance technologies. Data needs are identified

in the technology discussions in Chapter 3 and in the chapters discussing each of the individual

contaminant groups. List updates could include new technologies and could include additional

information regarding the already listed technologies. 

Section 1.7: Organization of the Document

This document is organized into several chapters describing the small system compliance

technologies for the non-microbial contaminants regulated before 1996. Chapter 1 discusses the

requirements of the 1996 SDWA and the approach EPA is following to meet those requirements.

Chapter 2 provides background on the existing non-microbial regulations, including the dates of

promulgation. Chapter 3 provides a description of technologies that can be used to treat more than

one group of contaminants. Technologies that only apply to one group of contaminants are described

in the chapter devoted to that contaminant group. Chapter 4 summarizes the national-level

affordability criteria and describes when and how these criteria were used to identify affordable

compliance technologies. Chapter 5 describes the compliance technologies for each of the IOCs,

including corrosion by-products. Chapter 6 describes the compliance technologies for each of the

radionuclides. Chapter 7 describes the compliance technologies for each of the VOCs. Chapter 8

describes the compliance technologies for each of the SOCs.
13

References

Congressional Record. 1974. House of Representatives 93-1185 at 18. The 93rd Congress, Second

Session. 13. Microfilm #H503-28.

Congressional Record. 1986. Vol. 132. 99th Congress, Second Session. No. 69. May 21, 1986.

P. S6287. Statement of Senator Durenberger. [132 Cong. Reg.]

USEPA. “Four Documents Required Under the Safe Drinking Water Act as Amended”. Federal

Register. 62(154): 42986. August 11, 1997. (EPA 1997a).

USEPA. “Small System Compliance Technology List for the Surface Water Treatment Rule”. EPA815-R-97-002. Office of Water. August 1997. (EPA 1997b).

USEPA. “Announcement of Small Systems Compliance Technology Lists for Existing National

Primary Drinking Water Regulations and Findings Concerning Variance Technologies”. Federal

Register. 63(151): 42032. August 6, 1998. (EPA 1998a).

USEPA. “Small System Compliance Technology List for the Surface Water Treatment Rule and

Total Coliform Rule”. EPA-815-R-98-001. Office of Water. September 1998. (EPA 1998b).

USEPA. “Variance Technology Findings for Contaminants Regulated before 1996". EPA 815-R-98-

003. Office of Water. September 1998. (EPA 1998c). 

USEPA. “Revision of Existing Variance and Exemption Regulations To Comply With Requirements

of the Safe Drinking Water Act; Final Rule”. Federal Register. 63(157): 43834. August 14, 1998.

 (EPA 1998d).

USEPA. “Information for States on Developing Affordability Criteria for Drinking Water”. EPA816-R-98-002. Office of Water. February, 1998. (EPA 1998e).

USEPA. “National-Level Affordability Criteria Under the 1996 Amendments to the Safe Drinking

Water Act”. Prepared by International Consultants, Inc., Hagler Bailly Services, Inc. and Janice A.

Beecher, Ph.D. for the EPA. August 1998. (EPA 1998f).

USEPA. “Removal of the Prohibition on the Use of Point of Use for Compliance with National

Primary Drinking Water Regulations”. Federal Register. 63(112): 31932. June 11, 1998. (EPA

1998g).

USEPA. “Cost Evaluation of Small System Compliance Options: Point-of-Use and Point-of-Entry

Treatment Units”. Prepared by The Cadmus Group, Inc. September 1998. (EPA 1998h).
14

2. BACKGROUND ON EXISTING NATIONAL PRIMARY DRINKING WATER

REGULATIONS

This chapter discusses the regulatory history that has resulted in the existing drinking water

regulations. The discussion is meant to briefly describe the relevant parts of the charge given to EPA

by the 1974 Safe Drinking Water Act (SDWA) and its 1986 Amendments and to briefly explain the

evolution of the National Primary Drinking Water Regulations (NPDWRs) that were promulgated

in response. It is not meant to be a detailed explanation or history of these events, but rather is

intended to provide the reader with enough information regarding the NPDWRs so that he or she will

know which NPDWR is associated with a particular contaminant. It also meant as a catalogue of the

Federal Register citations of the various NPDWRs.

 Through the SDWA, Congress requires EPA to regulate contaminants which present health

risks and which are known to occur in some public drinking water supplies. Under the current

SDWA, EPA sets legal limits on the levels of certain contaminants in drinking water through

Maximum Contaminant Levels (MCLs) and treatment techniques. The legal limits are as protective

of human health as is “feasible”, where feasibility is determined by treatment removal efficiencies

using the best available technologies, the levels of the contaminant found in drinking water sources

and other water quality parameters, and the levels at which the contaminant can be accurately

quantified analytically. In cases where available analytical methods are inadequate or normal

monitoring schemes are inadequate, EPA may impose treatment techniques to be followed under

specified conditions. For rules that involve MCLs, “best available technologies” for treating

contaminated water and analytical methods are listed. SDWA gives individual states the opportunity

to set and enforce their own drinking water standards as long as the standards are at least as stringent

as EPA's national standards. Most states and territories directly oversee the regulatory programs for

water systems within their borders. 

The United States Congress enacted the Safe Drinking Water Act (SDWA) on December 16,

1974 (Public Law 93-523). In response to SDWA, EPA regulated 23 contaminants between 1975

and 1985. The 1974 SDWA called for EPA to regulate drinking water contaminants in two steps.

The first step involved the creation of the National Interim Primary Drinking Water Regulations

(NIPDWRs), based largely on the 1962 U.S. Public Health Service standards. The second step

involved the revision of these standards, as deemed necessary, following a comprehensive review by

the National Academy of Sciences of the risks posed to water consumers from the regulated

contaminants. The NIPDWRs were fully enforceable after their respective stated “effective dates”.

The first NIPDWRs were promulgated in 1975, the Radionuclides NIPDWRs in 1976, the

Trihalomethanes NIPDWRs in 1979, and the Fluoride Rule in 1986, shortly before the 1986

Amendments. 

Congress amended SDWA on June 19, 1986 (Public Law 99-339). The 1986 Amendments

required EPA to set Maximum Contaminant Level Goals (MCLGs) and National Primary Drinking

Water Regulations (NPDWRs) for 83 specific contaminants. The Amendments declared that the

existing NIPDWRs were finalized as NPDWRs upon enactment of the 1986 SDWA, included
15

provisions for periodic review of the data and studies affecting the basis of the MCLGs and MCLs,

and made provisions for allowing variances under specified conditions.

 The list of 83 contaminants included 22 with NIPDWRs (excluded total trihalomethanes) and

remainder were new contaminants. The amendments also required EPA to regulate 25 additional

contaminants every three years, effective January of 1991 and continuing indefinitely. In addition,

each NPDWR was to be reviewed triennially to ensure the continued adequacy of the MCLG and

MCL. In 1987, EPA exercised discretion provided by SDWA in substituting ethylbenzene, styrene,

heptachlor, heptachlor epoxide, nitrite, aldicarb sulfoxide, and aldicarb sulfone for 7 of the 83

contaminants listed for regulation. EPA chose to regulate the 83 contaminants in phases, according

to the availability of data and studies supporting the setting of MCLGs and NPDWRs. The Phase

I Rule, otherwise known as the VOC/Unregulated Contaminants Rule, was promulgated in 1987, the

Phase II Rule, the Lead and Copper Rule, and the Phase II-b Rule in 1991, and the Phase V Rule in

1992. The Phase III Rule became known as the Radionuclides Rule and is currently being reviewed.

The Phase IV Rule became known as the Disinfection-By-Products Rule, which is due to be

promulgated in November of 1998. All of the relevant rules are discussed in more detail below. 

Congress again amended SDWA on August 6, 1996. The 1996 Amendments resulted in several

provisions related to the Small Systems Compliance Technology Lists, as discussed in the first

chapter. However, the Small Systems Compliance Technology List deadline covered by this

document applies only to the pre-1996 regulated contaminants, so the impact of the 1996 SDWA on

future rules and updates need not be discussed here.

Section 2.1 National Interim Primary Drinking Water Regulations (NIPDWRs) (40 FR 59566)

The National Interim Primary Drinking Water Regulations (NIPDWRs) were promulgated on

December 24, 1975. This rule established Maximum Contaminant Levels (MCLs) for 6 synthetic

organic contaminants, 10 inorganic contaminants, turbidity, and total coliform. The rule also

established requirements for monitoring, analytical methods, reporting, record keeping, and public

notification for each of the contaminants. The MCLs established by this rule were designed to be

enforceable until revised.

Section 2.2: Radionuclides NIPDWRs (41 FR 28402)

The Radionuclides NIPDWRs were promulgated on July 9, 1976. This rule established MCLs

for combined radium-226 and -228 and two classes of radionuclide contaminants. It also established

requirements for monitoring, analytical methods, reporting, and record keeping for these

contaminants. The MCLs established by this rule were designed to be enforceable until revised. The

MCLs established by this rule are currently in effect, although the rule is being reviewed at the time

of this writing.
16

Section 2.3: Trihalomethanes NIPDWRs (44 FR 68624)

The Trihalomethanes NIPDWRs were promulgated on November 29, 1979. This rule

established MCLs and requirements for monitoring, analytical methods, and reporting for total

trihalomethanes. “Total trihalomethanes” is defined as the summed concentrations of the four

trihalomethane chemicals defined in the rule. This rule only applies to community water systems

serving 10,000 persons or more that add a chemical disinfectant during any part of the drinking water

treatment process. Since this rule does not apply to small drinking water systems, total

trihalomethanes will not be considered in terms of small systems compliance or variance

technologies.

Section 2.4: Fluoride Rule (51 FR 11396)

The Fluoride Rule was promulgated on April 2, 1986, updating the Fluoride NIPDWR, which

was included in the 1975 NIPDWRs. This rule established an MCL and secondary MCL for fluoride

and applies only to community water systems. The rule also established a procedure by which public

water systems could obtain variances from the interim and revised regulations for fluoride. The

variance procedure includes the identification and installation of best available technology (BAT) for

fluoride removal. EPA later revised the monitoring requirements (EPA 1995b) for fluoride by

including it into the Standardized Monitoring Framework promulgated under the Phase II Rule

(January 30, 1991).

Section 2.5: Phase I Rule (52 FR 25690)

The Phase I Rule was promulgated on July 8, 1987. This rule establishes MCLs and

requirements for monitoring, reporting, and public notification for 8 volatile organic contaminants

(VOCs). The rule also establishes monitoring requirements for 51 other synthetic organic

contaminants not regulated by NPDWRs, i.e., unregulated contaminant monitoring. The rule applies

to community water systems and non-transient, non-community water systems.

Section 2.6: Phase II Rule (56 FR 3526) and Phase II-b Rule (56 FR 30266)

The combined Phase II Rule was promulgated in two rule makings, the “Phase II Rule” on

January 30, 1991 and the “Phase IIb Rule” on July 1, 1991. Combined, the two rule makings

establish new requirements for the regulation of 38 chemicals, 11 of which were previously regulated

under the 1975 NIPDWRs, including barium, cadmium, chromium, mercury, nitrate, selenium, 2,4-D,

lindane, methoxychlor, toxaphene, and 2,4,5-TP. Additionally, the Phase II Rule removed silver from

the list of NPDWRs and developed SMCLs for silver and aluminum.

The Phase II Rule (January 30, 1991) establishes Maximum Contaminant Level Goals (MCLGs),

MCLs, and requirements for monitoring, analytical methods, and public notification for 26 synthetic

and volatile organic contaminants (SOCs, VOCs) and 7 inorganic contaminants (IOCs). The rule also

reproposes MCLs for 5 contaminants. Some of the regulations apply to all public water supplies and
1

 Action levels are different from MCLs in that, rather than being a legal limit on a

contaminant like an MCL, they are triggers for taking prescriptive prevention or removal steps.

17

others only to community water systems and non-transient, non-community water systems. 

The Phase IIb Rule finalizes the MCLGs and NPDWRs for the 5 contaminants reproposed in the

Phase II Rule. It also changes the monitoring requirements to the standardized monitoring

framework for the 8 VOCs regulated in the Phase I Rule.

Two contaminants regulated by the Phase II Rule, acrylamide and epichlorohydrin, are not

applicable to the determination of small system compliance technology lists or small system variances.

These two compounds are associated with chemical additives used in drinking water treatment and

are regulated through a treatment technique that requires a certification that the product of the dose

and monomer concentration will not exceed certain levels. No treatment technology is required to

be installed to reduce contaminant levels under this treatment technique. As such, there are no

compliance or variance technologies for either acrylamide or epichlorohydrin.

On May 27, 1992 EPA postponed the effective date of the MCLs and amended the monitoring

requirements for aldicarb, aldicarb sulfone, and aldicarb sulfoxide (56 FR 221778). This stay will

remain in effect while EPA conducts a revised risk assessment and solicits public comment on the risk

assessments. During this time, these pesticides are being monitored as unregulated contaminants.

Section 2.7: Lead and Copper Rule (56 FR 26460)

The Lead and Copper Rule was promulgated on June 7, 1991 and became effective on December

7, 1992. This rule establishes MCLGs and NPDWRs for controlling lead and copper levels in

drinking water. Although all rules establishing treatment techniques are unique, the Lead and Copper

Rule stands out because it is the only NPDWR that attempts to minimize contamination introduced

by the action of the water itself on the distribution system. Other treatment techniques either address

contaminants in the source water (e.g., the Surface Water Treatment Rule) or contaminants that may

result from the treatment processes themselves (e.g., NPDWR for epichlorohydrin). 

Lead and copper contamination of drinking water mainly occurs after the water is in the

distribution system, so monitoring at the treatment plant is not adequate. The contamination results

from corrosion of pipes and plumbing in the distribution system. The Lead and Copper Rule requires

community water systems and non-transient, non-community water systems to complete a materials

evaluation of their distribution system and/or review other information to target homes that are at

high risk of lead and copper contamination. Water systems are required to monitor at the tap in these

high risk homes, with the number of tap-sampling sites being proportional to the population served.

Those systems with lead levels above the action level1 are required to apply a treatment technique for

mitigation, that may include corrosion control treatment, source water treatment, lead service line

replacement, and public education. Replacement of lead containing materials within a distribution

system is only required if corrosion control measures do not bring lead levels below the action level.
18

Systems with elevated copper levels should apply corrosion control treatment, since replacement of

the copper piping source material is generally cost prohibitive.

Section 2.8: Phase V Rule (57 FR 31776)

The Phase V Rule established MCLGs and promulgated NPDWRs for 18 synthetic organic

contaminants and 5 inorganic contaminants. The monitoring framework for these contaminants are

in the standardized monitoring framework format. This rule applies to community water systems and

non-transient, non-community water systems. The NPDWR for nickel was revoked.

Section 2.9: Summary of National Primary Drinking Water Regulations (NPDWRs)

Table 2.11 tabulates the various regulated drinking water contaminants, providing information

on contaminant type, the governing NPDWR, and the promulgated MCLs and BATs. For more

information on the NPDWRs, visit the Office of Ground Water and Drinking Water’s Internet

homepage (http://www.epa.gov/OGWDW). The homepage has a table

(http://www.epa.gov/OGWDW/wot/appa.html) of current NPDWRs that includes information on

health effects from ingestion of the regulated contaminants and the sources responsible for their

occurrence in drinking water. Further information on the drinking water regulatory history can be

found on the OGWDW homepage at “http://www.epa.gov/safewater/source/therule.html”. Each of

the BATs is discussed in later chapters.

Summary of Current National Primary Drinking Water Regulations (NPDWRs)

Contaminant Type NPDWR BATs MCL

(Fg/L)

Benzene VOC Phase I Rule GAC, PTA 5

Carbon Tetrachloride VOC Phase I Rule GAC, PTA 5

Chlorobenzene VOC Phase II Rule GAC, PTA 100

cis-1,2 Dichlorobenzene VOC Phase II Rule GAC, PTA 7

Dibromochloropropane VOC Phase II Rule GAC, PTA 0.2

1,2- Dichloroethane VOC Phase I Rule GAC, PTA 5

1,1- Dichloroethylene VOC Phase I Rule GAC, PTA 7

Dichloromethane VOC Phase II Rule GAC, PTA 5

1,2- Dichloropropane VOC Phase II Rule GAC, PTA 5

Ethylbenzene VOC Phase II Rule GAC, PTA 700

Ethylene dibromide VOC Phase II Rule GAC, PTA 0.05

o-Dichlorobenzene VOC Phase II Rule GAC, PTA 600
19

p-Dichlorobenzene VOC Phase I Rule GAC, PTA 78.5

Styrene VOC Phase II Rule GAC, PTA 100

Tetrachloroethylene (PCE) VOC Phase II Rule GAC, PTA 5

Toluene VOC Phase II Rule GAC, PTA 1000

trans-1,2-Dichloroethylene VOC Phase II Rule GAC, PTA 100

1,2,4- Trichlorobenzene VOC Phase V Rule GAC, PTA 70

1,1,1- Trichloroethane VOC Phase I Rule GAC, PTA 200

1,1,2- Trichloroethane VOC Phase V Rule GAC, PTA 5

Trichloroethylene (TCE) VOC Phase I Rule GAC, PTA 5

Vinyl Chloride VOC Phase I Rule GAC, PTA 2

Xylenes (total) VOC Phase II Rule GAC, PTA 10,000

Alachlor SOC Phase II Rule GAC 2

Atrazine SOC Phase II Rule GAC 3

Carbofuran SOC Phase II Rule GAC 40

Chlordane SOC Phase II Rule GAC 2

Dibromochloropropane SOC Phase II Rule GAC, PTA 0.2

2,4-D SOC Phase II Rule GAC 70

Ethylene Dibromide SOC Phase II Rule GAC, PTA 0.05

Heptachlor SOC Phase II Rule GAC 0.4

Heptachlor Epoxide SOC Phase II Rule GAC 0.2

Lindane SOC Phase II Rule GAC 0.2

Methoxychlor SOC Phase II Rule GAC 40

Polychlorinated Biphenyls SOC Phase II Rule GAC 0.5

Pentachlorophenol SOC Phase II Rule GAC 1

Toxaphene SOC Phase II Rule GAC 3

2,4,5-TP SOC Phase II Rule GAC 50

Benzo(a)pyrene SOC Phase V Rule GAC 0.2

Dalapon SOC Phase V Rule GAC 200

Di(2-ethylhexyl) adipate SOC Phase V Rule GAC, PTA 400
20

Di(2-ethylhexyl) phthalate SOC Phase V Rule GAC 6

Dinoseb SOC Phase V Rule GAC 7

Diquat SOC Phase V Rule GAC 20

Endothall SOC Phase V Rule GAC 100

Endrin SOC Phase V Rule GAC 2

Glyphosate SOC Phase V Rule oxidation (Cl2 or O3) 700

Hexachlorobenzene SOC Phase V Rule GAC 1

Hexachlorocyclopentadiene SOC Phase V Rule GAC, PTA 50

Oxamyl SOC Phase V Rule GAC 200

Picloram SOC Phase V Rule GAC 500

Simazine SOC Phase V Rule GAC 4

2,3,7,8-TCDD (Dioxin) SOC Phase V Rule GAC 3 x 10-5

Acrylamide SOC Phase II Rule treatment technique TT

Epichlorohydrin SOC Phase II Rule treatment technique TT

Antimony IOC Phase V Rule CF, RO 6

Asbestos IOC Phase II Rule CF, Corrosion Control,

Direct Filt, Diatom Filt

7 million

fibers/liter

(longer than

10 Fm)

Cyanide IOC Phase V Rule IX, RO, alkaline Cl2 200

Lead IOC Lead and Copper,

Final Rule

treatment technique TT

Arsenic IOC NIPDWR for

arsenic

CF, LS, IX, RO, EDR 50

Barium IOC Phase II Rule IX, LS, RO, EDR 2000

Beryllium IOC Phase V Rule AA, CF, LS, IX, RO 4

Cadmium IOC Phase II Rule CF, IX, LS, RO 5

Chromium IOC Phase II Rule CF, IX, LS, RO 100

Copper IOC Lead and Copper,

Final Rule

treatment technique TT

Fluoride IOC Fluoride, Final

Rule

AA, RO 4000
21

Mercury IOC Phase II Rule CF, GAC, LS, RO 2

Nitrate IOC Phase II Rule IX, RO, EDR 10000 

(as N)

Nitrite IOC Phase II Rule IX, RO 1000 

(as N)

Nitrate + Nitrite IOC Phase II Rule - See individual

contaminants -

10000 

(as N)

Selenium IOC Phase II Rule AA, CF, IX, LS, RO,

EDR

50

Thallium IOC Phase V Rule AA, IX 2

combined radium-226 and

radium-228

RAD Radionuclides

Rule

IX, LS, RO 5 pCi/L

gross alpha particle activity RAD Radionuclides

Rule

RO 15 pCi/L

total beta particle activity and

photon activity

RAD Radionuclides

Rule

IX, RO 4 mrem/yr

Notes: GAC = granular activated carbon, PTA = packed tower aeration, IX = ion exchange, LS = lime

softening, RO = reverse osmosis, CF = coagulation/filtration, EDR = electrodialysis/electrodialysis reversal, AA

= activated alumina.
22

3. DESCRIPTIONS OF TREATMENT TECHNOLOGIES FOR SMALL SYSTEMS

This chapter discusses small systems treatment technologies that can be used for the removal of

more than one class of the currently regulated drinking water contaminants. Each process is briefly

described and issues specific to small systems needs are highlighted. Advantages, limitations, and

special considerations are emphasized where applicable. Small systems treatment strategies include

centralized treatment, including package plants, and point-of-use/entry (POU/E) technologies. Each

strategy is discussed in general, then individual technologies are discussed. The choice of strategy

to be used in a specific situation depends on the source water quality, the nature of the contaminant

to be removed, the desired qualities of the finished water, and the size of the drinking water system.

Centralized Treatment

For small systems, centralized treatment refers to both full scale conventional treatment and to

centrally located package plant treatment. This section will focus on full scale conventional

treatment; package plants are discussed below. Centralized treatment refers to the practice of treating

water at a centralized location before it enters the distribution system. Centralized treatment at more

than one entry point is sometimes referred to as “de-centralized treatment”. This point is important

because it clarifies the differentiation between multiple entry point centralized treatment and POU/E

treatment. Within this document, “centralized treatment” will include both single entry point

centralized treatment and multiple entry point treatment. 

In general, centralized treatment is preferred to POU/E technologies since monitoring and

maintenance can be centrally managed, which is the most reliable way to ensure safe water. Full scale

conventional treatment is the most common strategy for systems serving more than a few thousand

persons (EPA 1993, p. 97). Full scale treatment is designed by a consulting engineer and makes use

of originally designed and fabricated concrete and steel structures, as opposed to pre-fabricated

package plant units. Larger systems can pass the higher engineering and construction costs through

the large customer base at a generally reasonable per user cost. The costs associated with fully

engineered treatment technologies can be prohibitive for the smallest of water systems, but for some

technologies, e.g., packed tower aeration, full scale treatment may be cost-effective down to very

small system sizes.

Package Plant Treatment

Package plants are skid mounted factory assembled centralized treatment units that arrive on site

“virtually ready to use” (Goodrich et al. 1992, EPA 1993). Package plants offer several advantages.

First, since they combine elements of the treatment process into a compact assembly (such as

chemical feeders, mixers, flocculators, basins, and filters), they tend to require lesser construction and

engineering costs. Another advantage is that many package plant technologies are becoming more

automated and thus can be less demanding of operators than their fully engineered counter-parts

(EPA 1990). However, pilot testing requirements can significantly increase package treatment costs.

Some states require pilot tests of all package plant installations. Often package plant pilot testing is
23

required on a case by case basis, so that results from one situation can not be “transferred” to another

situation, regardless of how similar the situations may be. Since pilot testing is resource intensive and

can last from several weeks to a year or more, it can add significant costs, e.g., more than thirty

percent to the original equipment costs in some cases (Goodrich et al. 1992). Since it is, of course,

essential to confirm that installed treatment is working properly, the need for site specific pilot testing

can not be entirely eliminated, but it can be reduced (EPA 1993). To this end, verification of package

plant performance by an independent party would reduce costs by reducing in degree the need for

pilot testing. It is important to keep in mind that pilot testing needs are specific both to the

technology in question and to source water quality. For a discussion of pilot testing needs for

individual technologies, see, e.g., NRC’s Safe Water from Every Tap (NRC 1997).

This need for package plant performance verification is currently being addressed by EPA in

cooperation with National Sanitation Foundation (NSF) International through an EPA Environmental

Technology Verification project. Together they are cooperatively organizing and developing a pilot

project (Package Drinking Water Treatment Systems Pilot Project) to allow for verification testing

of package plant units. The aims of the project include developing verification testing protocols and

test plans, independently testing and validating package plant equipment, conveying and supporting

government/industry partnerships to obtain credible cost and treatment performance data, and

preparing product verification reports for public use. It is expected that the program will become

financially self-sustaining through user fees and leveraged resources. More information regarding this

program may be found on the NSF Internet website a t

“http://www.nsf.org/verification/html/overview.html”.

Whether or not a small system can afford a package plant technology is only part of the question.

In addition, the system must have an operator or contractor who can properly operate and maintain

the equipment. Fortunately, many package plant technologies are becoming more automated and

simpler to use. For example, modern filtration membrane technologies have the ability to backwash

automatically, greatly simplifying their use. In cases where a technology requires more advanced

skills, recent advances (NRC 1997) in telemetry devices or remote monitoring and control devices

have made it possible for a single operator to monitor and operate several small water systems within

a given area. These “circuit rider” operators can work from a central location while receiving

information (including alarms) from the various plants via FAX or modem. Remote control

capabilities allow the circuit rider operator to control certain aspects of the treatment process (e.g.,

chemical coagulant dosage or disinfection dosage) via a modem or other means. This reduces

operator costs to a single system and can reduce the amounts of chemicals required for treatment.

These telemetric devices may make those technologies requiring a full-time operator more feasible

for many small systems. The combined use of package plants and telemetric monitoring and control

may well extend many of the more complex water treatment technologies to the universe of

technologies appropriate for small systems.
24

Point-of-Use/ Point-of-Entry Technologies

Point-of-entry (POE) treatment units (Goodrich et al. 1992, Lykins et al. 1992) treat all of the

water entering a household or other building, with the result being treated water from any tap. Pointof-use (POU) treatment units treat only the water at a particular tap or faucet, with the result being

treated water that one tap, with the other taps serving untreated water. POE and POU treatment

units often use the same technological concepts employed in the analogous central treatment

processes, the main difference being the much smaller scale of the device itself and the flows being

treated. Sometimes the POE/U technology uses essentially the same process as its full-scale

counterpart, but in some instances process modifications are required to account for the much smaller

flows being treated. For example, full-scale filtration technologies often use periodic backwashings

to extend the lifetime of the filter bed, whereas POU filtration technologies are often used until

exhausted and then simply discarded.

POE/U devices have disadvantages to their use and so are generally used only when a centralized

treatment facility is not technically or financially feasible for a water system. Regarding POU devices,

if one is placed under the kitchen sink to treat food for drinking and cooking, only that water is

potable; water from a bathroom tap would be untreated, and thus exposure to contaminants during

teeth brushing, etc. is possible (NRC 1997). In some cases, POU technologies are simply not

applicable, e.g., in cases of volatile contaminants which would volatilize into the indoor air during

showering and other water uses. In these cases, only POE treatment or centralized treatment is

appropriate. POE treatment units also have limitations. For example, some POE filters require

backwashing or regeneration to maintain a reasonable filter bed/resin lifetime (number of bed volumes

before the filter bed or resin needs replacement). If the backwash requires special disposal methods,

costs may increase prohibitively. In the case of acute contaminants, which can cause adverse health

effects after short term exposures, POE/U treatment is generally not viewed as appropriate (NRC

1997). For example, the 1998 Small Systems Compliance Technologies Lists for the Surface Water

Treatment Rule and the Total Coliform Rule (EPA 1998a) does not list any POE/U devices for the

microbial contaminants or microbial indicators. The legal requirements for the use of POE/U devices

as compliance technologies are discussed in Section 1.4.

Technologies that are amenable to POE/U scale treatment include activated alumina, granular

activated carbon, reverse osmosis, ion exchange, and air stripping. Each of these applications is

discussed below along with its centralized treatment analogue. There are also discussions of POE/U

technologies in the chapters dealing with compliance technologies for specific contaminants.

Before installing POE/U treatment units, water systems should evaluate the units for treatment

efficacy and efficiency. For devices that employ cartridges (e.g., GAC and activated alumina), the

NRC (1997) recommends that water systems pilot test to develop estimates of the unit’s service life

for their particular source water. In other cases, evaluations may be simpler, e.g., for RO it may only

be necessary to confirm that membrane fouling will not be a problem. These concerns are discussed

in more detail in the individual technologies discussions below.
25

Effective operation, monitoring, and maintenance are vital to the successful use of POE/U

treatment units for compliance purposes (Goodrich et al. 1992, NRC 1997). As discussed in Section

1.4, the units are required by the SDWA to be “owned, controlled, and maintained by the public water

system or by a person under contract with the public water system to ensure proper operation and

maintenance and compliance with the MCL or treatment technique and equipped with mechanical

warnings to ensure that customers are automatically notified of operational problems”. Proper

installation is of course essential. After installation, the PWS needs a well-defined operation and

maintenance program to assure a continuous supply of safe drinking water. The PWS also needs a

routine monitoring program to confirm that the operation and maintenance program is adequate and

that the treated water meets drinking water standards.

Specific Technologies

Specific technologies that apply to more than a single class of chemical contaminants are

discussed below.

Activated Alumina

Activated Alumina (AA) is a physical and chemical process in which ions in the feed water are

sorbed to an oxidized AA surface. AA is prepared through dehydration of Al(OH)3 at high

temperatures and consists of amorphous and gamma alumina oxide. AA is used in packed beds to

remove contaminants such as fluoride, arsenic, selenium, silica, and natural organic matter. Feed

water is continuously passed through the bed to remove contaminants. The contaminant ions are

exchanged with the surface hydroxides on the alumina. The adsorption ability of AA media must

eventually be replenished. When all adsorption sites on the AA surface are filled, the bed must be

regenerated. Regeneration is accomplished through a sequence of rinsing with regenerant, flushing

with water, and neutralizing with acid. The regenerant is a strong base, typically sodium hydroxide;

the neutralizer is a strong acid, typically sulfuric acid (EPA 1998b). The alumina dissolves slightly

in sodium hydroxide. Over time the media will dissolve and require replacement.

AA is useful for removing negatively charged ions. AA displays amphoteric properties, meaning

its surface charge changes with solution pH. AA is not charged at a pH of 9.5, is positively charged

below this pH, and is negatively charged above it (NRC 1997). Anions are best adsorbed below this

pH.

Water quality strongly influences the residence times and flow rates necessary for proper

operation of activated alumina columns. In particular, the potential for preferential exchange of

anions other than the target compounds in the raw water must be evaluated for each source water that

will be treated with AA (NRC 1997).

As with ion exchange, regenerant disposal can be a problem. Some facilities discharge the

regenerant brine solution to lined evaporation ponds designed for this purpose. After the water

evaporates from the salts, the dried salts are disposed of in a landfill. Disposal costs can make up
26

much of the operating cost of this technology.

AA may be well suited for small systems. The columns can be scaled and more added if

necessary. Small systems should be concerned, however, about cost and operational complexity

(NRC 1997). For instance, small systems should be concerned about the chemicals that may be

required to operate AA. Stakeholders agreed that small systems would not likely regenerate on sight.

Regenerating the media off-site or disposing of the spent media may be possibilities. Small systems

should also be concerned about highly concentrated waste streams. 

Activated Carbon

Activated carbon is similar to charcoal in composition, but is surfacially altered to enhance its

sorption properties. The base carbon material (typically bituminous coat, lignite, petroleum coke, or

bone char) is carbonized through heating it in the absence of air and then activated by oxidation at

high temperature (200oC to 1000oC). The activation process results in a highly porous, high surface

area per unit mass material with a large sorption capacity for many water impurities, including

synthetic organic contaminants (SOCs), taste and odor causing compounds, and some species of

mercury. (Snoeyink 1990, NRC 1997, AWWA - ASCE 1998).

Granular activated carbon (GAC)

GAC treatment removes contaminants via the physical and chemical process of sorption, by

which the contaminants accumulate at the carbon surface as the water passes through the carbon bed.

Removal efficiencies for many organic contaminants are excellent under ideal circumstances, but can

be significantly affected by water quality parameters, like dissolved natural organic matter levels, pH,

and temperature. Removal efficiencies change drastically once the bed nears exhaustion. At

exhaustion, contaminant breakthrough occurs, which is often defined as the point in time when the

contaminant concentration in the effluent equals that in the influent. Before this occurs, the carbon

bed must be regenerated or replaced to ensure proper removals (Snoeyink 1990).

Information regarding GAC contactor configurations, operational modes, and design factors can

be found in many sources (e.g., AWWA 1990, EPA 1990, Snoeyink 1990, AWWA - ASCE 1998).

Operating problems encountered when using activated carbon are similar to those associated with

rapid sand and dual-media filters. Common operating problems include: controlling the carbon

depth, (when applicable) ensuring proper backwashing and maintaining depth and bed density after

backwashing, removing carbon from the contactors and storage tanks, regenerating the carbon,

controlling contactor flow rate, and controlling biological growth in the carbon bed (AWWA - ASCE

1998).

GAC often requires pre-filteration to remove particulate matter from the source water to prevent

clogging of the GAC bed. An alternative is to use the GAC column itself as a filter medium,

performing both filtration and sorption simultaneously. The disadvantage of this latter approach is

that frequent backwashing of the column is required. Backwashing may cause spent carbon to come
27

into contact with the treated water: if this can be tolerated, then the technology is straightforward

and compact (NRC 1997).

Competitive sorption can also significantly affect the removal efficiency of an activated carbon

system. Naturally occurring dissolved organic matter may compete with organic contaminants for

GAC sorption sites, decreasing the removal efficiency for a given GAC column and thus increasing

the amount of GAC needed to achieve the optimal efficiency. Competing organic compounds can

also displace (cause the desorption of) contaminants. If influent water quality changes result in a high

concentration of the competing compound, the contaminant desorption process may temporarily

cause the contaminant level in the effluent to exceed that in the influent. Because of this, competing

chemicals need to be removed from the water prior to GAC treatment, or the GAC system should

be designed to accommodate the fluctuation in concentrations of the competing compounds

(Snoeyink 1990).

Single-stage GAC systems (in which all of the water being treated flows through one column,

rather than through two or more in series) must be monitored to ensure that breakthrough does not

occur. If an exhausted GAC column is not regenerated or replaced, desorption may result in the

effluent having higher concentrations of the contaminant than the untreated water. Monitoring for

some organic compounds may require an advanced operator or the services of an outside laboratory.

In general, GAC is straightforward to apply on a small scale. Small columns may be easily obtained

and installed. If virgin carbon is required (which can be the case with drinking water applications),

the operating costs are often higher.

Powdered activated carbon (PAC)

Powdered activated carbon (PAC) treatment works in much the same way as GAC. The main

difference is the mode of application and the grain size of the activated carbon. PAC grains are ten

to one hundred times smaller than GAC grains, but the water being treated comes into contact with

much less carbon material per unit volume treated, so the process is not as efficient as GAC. The

carbon powder is added directly to the raw water line or to a mixing basin. For efficient removals,

all of the water being treated should come into contact with the carbon. The sorption process is very

quick because of the small carbon particle size (which increases the specific surface area of the

activated carbon) and thus the normal mixing basin contact times used for other elements of the

treatment train are sufficient for sorption. In such cases, no modifications to the existing structure

of the treatment plant need be made. Testing prior to design determines the required contact time.

After proper contact, the PAC is settled or filtered from the water and disposed of with the plant

sludge. Proper removal of the PAC after sorption is required to ensure contaminant removal and to

prevent discoloration of the effluent (NRC 1997). The same argument concerning competitive

sorption for GAC treatment applies to PAC treatment.

PAC can be very economical if required only periodically (e.g., seasonally) in response to

changes in water quality. If the dose can be optimized and adjusted in response to variations in

influent water quality, then further savings can be incurred. In general, PAC is simple to employ on
2

 The Henry’s Law coefficient (HL) can be defined any number of ways, and so can be

reported in various units. Here, we are assuming that HL = Ca / Cw, where Ca is the concentration

of the contaminant in air at equilibrium with Cw, the concentration of the contaminant in water.

28

a small scale if the plant already has a treatment train in place that includes mixing, precipitation or

sedimentation, and filtration.

PAC may adsorb some chemicals that are added during the treatment process, e.g., chlorine and

potassium permanganate. For this and other reasons, the best point of application is usually at the

head of plant, either in the source water pipeline or in a mixing basin (AWWA - ASCE 1998).

Air Stripping (Aeration)

Air stripping, or aeration, involves the continuous contact of air with the water being treated,

allowing volatile dissolved contaminants to transfer from the source water to the air. After contact,

the “contaminated air” is swept from the system, taking the contaminants, e.g., volatile organic

chemicals, taste- and odor- causing compounds, and radon, out of contact with the treated water.

The driving force for the water-to-air transfer of the volatile contaminants is related to the

contaminant concentration gradient between the water and air. In designing aeration treatment, it is

important to consider both the total amount of transfer possible, i.e., the amount that would be

transferred to reach equilibrium, and the rate at which transfer takes place. The amount of possible

transfer is dependent on a combination of the physiochemical characteristics of the contaminant (such

as molecular weight, molecular charge/polarity and shape, etc., all of which also affect the water

solubility), site specific conditions, like temperature and water quality, and the design of the aeration

system, e.g., air/water ratio. The Henry’s Law coefficient is a commonly used indicator of the

tendency of a contaminant to partition from water to air. A large value (by common definitions2)

indicates that the contaminant can be significantly stripped from water. Efficient stripping is also a

function of the rate of transfer, which depends on both the properties of the contaminant, the site

specific conditions, and the aeration design, e.g., an effective contact surface area between the air and

water (Cornwell 1990).

The key factors which are considered in the design of aeration systems include contact time (time

of exposure); air-to-water ratio; proper dispersal of waste gases into atmosphere; physical chemistry

of the contaminant; influent concentration of the contaminant; water and surrounding air temperatures

(AWWA and ASCE 1998). The most common types of aeration systems include packed tower

aerators, diffuser aerators, including multi-stage bubble aerators, multi- or shallow tray aerators, spray

aerators, mechanical aerators, and gas permeable membrane aerators. 
29

Packed tower aerators

In packed tower aerators (PTA), the contaminated water flows downward by gravity over a

bed of packing material such as fixed plastic grids, loose plastic rings, or loose ceramic saddles,

while air is blown upward through the column. The packing material breaks the surface area for

contact between air and water thus promoting transfer of the contaminant into the gaseous phase. 

The removal efficiency of contaminants using PTAs depends upon the air to water ratio,

contact time, available surface area, water loading rate, physical and chemical characteristics of

the contaminant, and water and air temperature. 

The air flow requirements for a packed tower depend on the Henry’s Law coefficient for the

particular compound to be removed from the water. In an ideal system, the greater the Henry’s

Law coefficient for a compound, the less air is required to remove a contaminant from water. 

However, air to water ratios used to achieve a given removal efficiency are greater than the ideal

system. 

The contact time is a function of the depth of the packing material. As the depth of packing

materials increases, the contact time between the water and air increases, thereby causing high

percent removals of the contaminant.

The available surface area for mass transfer depends upon the packing material. Smaller

packing materials provide greater available area for mass transfer per volume of material thus

increasing the mass of contaminant removed. The pressure drop for the air passing through the

column must be considered when selecting packing materials.

The water loading rate is the amount of water that passes through the tower and is largely a

function of diameter of the tower. The water loading rate typically ranges from 25 to 30 gpm/ft2

(AWWA and ASCE 1998).

PTAs are very efficient in removing several compounds from water. PTAs are considered

Best Available Technologies (BAT) for several organic compounds. PTA can generally be used

with systems of all sizes. A typical PTA consists of a packed column or tower, blower, pumping

unit, and an effluent storage unit. Pretreatment may be necessary for removal of microorganisms,

iron, Mn, and excessive particulate matter. PTAs are usually located outdoors, therefore piping

may need to be protected in cold climates. 
30

Diffuser aerators

Diffused aeration (DA) is the process of bubbling air into a water-filled contact chamber

through a diffuser mechanism located at or near the bottom of the chamber. The chamber can

either be a column or basin. The efficiency of diffused aeration for removing organics depends

upon the diffuser type, air-to-water ratio, depth of the water in the contact chamber, detention

time, and water temperature. Diffused aerators are generally used only to adapt existing plant

equipment. 

Multi-stage bubble aerators (MSBA) are a form of commercially available package plant. 

These are a variation to the traditional diffused aerator. Typical commercial units consist of a

high-density polyethylene vessel partitioned into multiple stages with an individual aerator for

each stage. MSBAs are compact, with water depths typically less than 1.5 ft (compared to depths

of 10 to 20 ft for typical aeration basins). If housing is required for the aeration unit, MSBA’s

compactness can be very attractive. Other advantages of MSBA include removal efficiencies that

are competitive with PTA.

The advantages of a diffuser aeration system is that an existing basin or storage tank can

be modified to be used as a diffuser aeration unit. Due to reduced pumping costs, no packing

material costs, and potentially lower energy costs, marginal savings may be incurred. However,

an increase in contact time and air-to-water ratios may be needed to achieve good removals

because DA generally does not provide for convective movement of the water and thus does not

allow as much contact between the air and water as other methods.

Point-Of-Use/Point-Of-Entry Aeration Technologies

Point-of-use aeration technologies are not practical for volatile contaminants because

routes of exposure can occur through inhalation, direct contact, and ingestion from a secondary

faucet. Therefore, POU aeration technologies are not considered for compliance technology

listing. 

Air stripping technologies such as PTA and diffused bubble aerators have been used in

POE systems to remove VOCs from ground water (NRC 1997). Similar to other aeration

technologies, these systems rely on mass transfer to remove VOCs from water. While POE

aeration is technically feasible, it is not commonly used for public water systems and may not be

as cost effective as other aeration systems.
31

Multiple tray aerators

Tray aerators (Cornwell 1990, AWWA-ASCE 1998) consist of a series of trays with slats,

perforations, or wire mesh bottoms over which water flows and collects at the base of the unit. 

The thin film of water formed as the water flows over the media provides a large surface area for

mass transfer of the contaminant from water to air. These aerators can be operated with a natural

draft or with a forced draft using an air compressor. Using the natural draft reduces operating

costs, but is less efficient than using a forced draft. 

Shallow tray aerators (STA) are another form of low-profile package plant. In STA, the

contaminated water flows along the trays while air is blown through hundreds of holes in the

bottom of the trays, creating a large mass-transfer surface area where contaminants are

volatilized. These units are analogous to MSBA in terms of their advantages, including

potentially high removal efficiencies and compactness.

Multiple tray aerators can be used with systems of all sizes. These aerators are very

efficient in removing co-occurring VOCs. However, higher air-to-water ratios may be required to

ensure volatilization of the contaminants. One disadvantage is that slime and algae can grow on

the trays, possibly necessitating the addition of copper sulfate or chlorine to control growth (NRC

1997). However, in shallow tray aerators, precipitation and biofilm development is minimal

because of the vigorous bubbling action created by air flowing through the tiny holes (Lamarre

1993).

Spray Aerators

Spray aerators produce small water droplets by spraying water through nozzles. The

small droplets produced expose a large interfacial surface area through which contaminants can

migrate from the liquid phase to the gaseous phase. Installations commonly consist of fixed

nozzles on a pipe grid. 

The factors which affect the removal efficiency of spray aerators are size of the water

droplets formed (area for mass transfer), height of spray (contact time), and temperature. The

advantages of spray aerators include the capability of achieving efficient mass transfer due to the

small water droplets created by the fixed nozzles and the lack of any packing costs. The

disadvantages includes the need for large operational area.
32

Mechanical aerators

Mechanical aeration introduces air into the water by rapidly agitating the water surface

with a mechanical mixer. The advantage to using mechanical aerators is that they are adaptable to

existing basins, and are often installed as a system retrofit. However, these units are not as

efficient as other aeration units. Because of the limited contacting system between air and water,

large basins, long residence times, and high energy inputs may be needed to increase the efficiency

of the aerator. These systems are applicable when low level contaminant removal is needed to

reach the MCL.

Gas-permeable membrane aeration

Gas-permeable membrane aeration processes consist of a membrane module made up of

highly porous, small diameter, hollow fiber membranes as a contacting device, providing an airwater contact area per equipment volume nearly an order of magnitude greater than packed tower

air strippers (Semmens et al.; Zander et al. 1989). Water flows through the interior of hollow

membrane tubes constructed of a material that allows gases but not liquids to pass through. The

large surface area for air-water contact allows for removal of semivolatile and volatile organic

chemicals (NRC 1997). Gas-permeable membrane systems offer the highest removal efficiencies

of all contacting devices. Membrane technology has to be considered emerging because longterm performance has not been evaluated.

Air Stripping Suitability for Small Systems

Overall an aeration system can generally be installed for a fairly low cost, and most

aeration units are not complex. The treatment process is highly adaptable to small treatment

plants, often involving a simple retrofit to existing treatment basins. Cost and treatment efficiency

both increase with increasing system complexity. If contaminant concentrations are high and

regulations require treatment of the air leaving the system, however, costs increase dramatically. 

The specific type of aerator depends only on the degree of contaminant reduction desired. Also,

because mixtures of contaminants exist in contaminated water and even though the effectiveness

of the process varies for each contaminant, aerating to remove one specific contaminant will also

reduce concentrations of the others.

Air Stripping Limitations

The secondary effects of aeration may be a problem. These include potential air quality

problems created by exhaust gases from the aerator, and the potential for water quality

deterioration from airborne particulates, oxidized inorganics, instability resulting in corrosion, and

biological growth in the aeration device. Post-treatment disinfection may be needed after

treatment with some of the aeration units. Depending on the water system’s location, off-gas may

have to be treated using a scrubber, thereby increasing the complexity and the cost of the aeration

units.
33

Coagulation/ Filtration

Coagulation/filtration (C/F) processes involve the addition of chemicals like iron salts,

aluminum salts, or cationic polymers that coagulate and de-stabilize particles suspended in the

influent, so that they may be ultimately removed via clarification and/or filtration. The C/F

processes described in “Small System Compliance Technology List for the Surface Water

Treatment Rule and Total Coliform Rule” (EPA 1998c) include “conventional filtration”, which

includes a clarification step before filtration, and “direct filtration”, which does not. This

discussion assumes that C/F processes would be added primarily to deal with microbial

contaminants. As such, it is recommended that the compliance technology guidance for the

SWTR (EPA 1998c) be consulted for details.

Conventional Filtration

Conventional filtration includes pre-treatment steps of chemical coagulation, rapid mixing,

and flocculation, followed by floc removal via sedimentation or flotation. After clarification, the

water is then filtered. Common filter media include sand, dual-media, and tri-media. Design

criteria for specific sites are influenced by site-specific conditions and thus individual components

of the treatment train may vary in design criteria between systems. Most of the concerns

regarding conventional filtration are specific to the Surface Water Treatment Rule (SWTR) and

are discussed elsewhere (EPA 1998c). The main issue is that conventional filtration does not

work properly if the coagulation chemistry is incorrect, so that operator skill is of paramount

importance, since the operator must frequently monitor water quality and must know how to

correct coagulant dosages in response to water quality changes (EPA 1990, NRC 1997).

Direct Filtration

Direct filtration has several effective variations, but all include a pre-treatment of chemical

coagulation followed by rapid mixing. The water is then filtered through dual- or mixed-media

using pressure or gravity filtration units. Pressure units, which are used primarily by small

systems, have the advantage of not requiring repumping for delivery of the filtrate to the point of

use. Gravity units have the advantage of allowing easy visual inspection of the filter medium

during and after backwash. Besides the mode of filtration, variations of direct filtration include

filter media and mixing requirements. In-line filtration is the simplest form of direct filtration and

consists of filters preceded by direct influent chemical feed and static mixing. In general, direct

filtration usually requires low turbidity raw water and is attractive mainly because of its low cost

relative to conventional treatment. Again, advanced operator skill and proper monitoring are

required.
34

Ion exchange

Ion exchange (IX) involves the selective removal of charged inorganic species from water

using an ion-specific resin (AWWA 1990, AWWA-ASCE 1998). The surface of the ion

exchange resin contains charged functional groups that hold ionic species by electrostatic

attraction. As water containing undesired ions passes through a column of resin beds, charged

ions on the resin surface are exchanged for the undesired species in the water. The resin, when

saturated with the undesired species, is regenerated with a solution of the exchangeable ion. A

large variety of synthetic resins is available for specific applications.

Generally, resins can be categorized as anion exchange or cation exchange resins. Anion

exchange resins selectively remove anionic species such as nitrate (NO3

-

) and fluoride (F-). Anion

exchange resins are often regenerated with sodium hydroxide or sodium chloride solutions, which

replace the anions removed from the water with hydroxide (OH-) or chloride (Cl-) ions,

respectively. Cation exchange resins are used to remove undesired cations from water and

exchange them for protons (H+), sodium ions (Na+) or potassium ions (K+).

Water to be treated by IX must be low in solids to avoid fouling the resin. In particular,

reduced iron species in ground water may become oxidized when the water is exposed to oxygen

in the atmosphere and form precipitates that can damage the resin.

A resin may preferentially remove certain ions from solution. In general, it will remove

highly charged ions more easily than it will remove monovalent ions. Calcium, magnesium, and

reduced iron ions will be removed preferentially to other cations. The presence of such species

may reduce removal efficiencies (NRC 1997).

An operator must monitor the system to determine the extent of resin saturation or the

breakthrough of the ion to be removed. On ion breakthrough, the resin must be removed from

service and regenerated. IX units can be controlled automatically, freeing the operator to make

daily visits (rather than attending to the systems full-time) to assure proper operation.

In either the cation or anion exchange process, the regeneration solution, which contains

high concentrations of the undesired ions, must be carefully disposed of. Disposal can be quite

costly, especially in the case of concentrated radionuclides (NRC, 1997).

Stakeholders requested that EPA state that IX can be operated in a “merry-go-round”

configuration to achieve low levels of contaminants in the effluent and to minimize regeneration

frequency. An example would be the use of three beds in series: two in production and one in

regeneration mode at any given time. When exchange capacity of the first bed in series is

exhausted, the first bed is removed from service to be regenerated. The second bed in series then

becomes the first and a fresh regenerated bed is brought on-line to become the second. This

maximizes the exchange capacity of the beds and prevents leakage since a fresh bed is always last

in line (EPA 1994). In addition to the “merry-go-round” approach, single, deep bed, counter-
35

current flow processes can also increase the usable capacity of the IX bed and reduce leakage

(EPA 1995).

IX is a common water treatment technology for small systems. IX is available in the form

of point-of-use (POU) and point-of-entry (POE) devices as well as in the form of full-scale

treatment. An advantage to IX is that it can be used under fluctuating flow rates (NRC 1997). 

The technology does produce highly concentrated waste by-product streams that may be an issue;

brine recycling might reduce this impact somewhat. With IX, the primary factor in calculating

costs is the regeneration frequency, and competition with other ions will affect the run length. 

For example, anion exchange would be recommended primarily for small ground water systems

with low sulfate and TDS. 

Lime softening

In the lime-softening (LS) process, the pH of the water being treated is raised sufficiently

to precipitate calcium carbonate and, if necessary, magnesium hydroxide. Calcium and

magnesium ions in water cause hardness; hard water can cause scaling problems in water heaters,

and soap lathers poorly in hard water. In small systems, LS would typically be practiced by

adding hydrated lime to raw water to raise the pH to approximately 10. This removes calcium

carbonate. If magnesium removal is also required, the pH during softening would need to be

closer to 11. In some waters, addition of soda ash is needed for effective hardness removal. 

After mixing, flocculation, sedimentation, and pH readjustment, the softened water is filtered

(NRC 1997). In addition to removing calcium and magnesium, LS also removes radium and

several inorganics (including arsenic).

Many large water systems use LS to treat surface waters. However, the combination of

variable source water quality and the complexity of the chemistry of LS may make it too complex

for small systems that use surface water sources. LS may be more appropriate for small systems

that use ground water because of the relative uniform quality of ground water. Once the

softening chemistry for a ground water is determined, it should not change much. In comparison,

chemical additions to surface waters need to be modified frequently in response to water quality

changes (NRC 1997).

One of the difficult aspects of LS is the operation and maintenance of lime feeders and

lines carrying lime slurry to the point of application. In addition, plant operators must understand

lime softening chemistry. Measurement of pH must be accurate, and the operator must know that

the pH meter is properly calibrated. Failure to maintain the proper pH in softened water prior to

filtration at a lime softening plant could result in precipitation of excess lime in the filter beds and

formation of calcium carbonate deposits within the filters. 

LS is similar to coagulation/filtration in that pre-fabricated equipment is available. LS may

be a feasible technology in the larger small ground water systems. For the smaller categories, LS

may be feasible by using some form of contract or satellite operation that would enable a trained
3

 MWCO is defined as an estimate of the molecular weight of the smallest molecule that

will be retained by the membrane.

36

operator to monitor the process periodically.

Membrane Processes

Four membrane processes are discussed in this document: reverse osmosis (RO),

ultrafiltration (UF), nanofiltration (NF), and electrodialysis/electrodialysis reversal (ED/EDR). All

of these processes share certain characteristics, since they all involve membranes, but RO is

distinct in that it involves a non-porous membrane and ED/EDR in that it involves a ion selective

membrane. Membranes are manufactured in a variety of configurations, materials and pore size

distributions. The selection of membrane treatment for a particular drinking water application is

determined by a number of factors, including: targeted material(s) to be removed, source water

quality characteristics, treated water quality requirements, membrane pore size, molecular weight

cutoff3 (MWCO), membrane composition, and system/treatment configuration (Jacangelo 1991).

In general, membrance processes show little economy of scale, since capital costs per

volume of water treated do not increase dramatically as design flows decrease. For this reason,

and others discussed below, membrane technologies can be a good choice for addressing many

small systems water quality problems. For ground water systems not requiring pre-treatment,

membrane technology addition requires little more than a feed pump, a cleaning pump, the

membrane modules, and holding tanks (NRC 1997). Membrane technologies can be more costeffective than more conventional treatments for controlling a host of water quality problems

(Wiesner et al. 1994, Bergman 1996).

Ultrafiltration and Nanofiltration

 Ultrafiltration and nanofiltration are “membrane filtration” processes, in that they work

by excluding contaminants due to pore size constraints (Adham et al. 1996, Agbekodo et al.

1996). The water is forced by pressure from the source water side (concentrate) through the

pores of a semi-permeable membrane to the produced water side (permeate). Impurities are

prevented from passing through the membrane by size exclusion, and so are retained in the

concentrate. The permeate is generally of a very high quality (NRC 1997).

Membrane classification standards vary between manufacturers. For example, one

supplier may classify a membrane as nanofiltration, while another supplier may classify a similar

membrane as ultrafiltration. Also, some manufacturers refer to average pore size and some to

maximum pore size. For these reasons, water systems should make sure that the reported pore

size is adequate for the required purposes by looking directly at pore size, MWCO, and the

required applied pressure.

The operation of ultrafiltration and nanofiltration processes are substantially less
4

 Osmotic pressure is defined as the pressure that arises from the natural tendency of a

solvent like water to pass from the dilute solution on one side of a semi-permeable non-porous

membrane to the concentrated solution on the other side.

37

complicated than the operation of the treatment trains needed to achieve similar removals via

conventional technologies. In particular, membrane processes may be very appropriate for small

systems attempting to remove multiple contaminants. If pre-treatment is required, the complexity

of the required operations can of course increase appreciably. In addition, specific site testing to

analyze the potential for organic fouling may be required. However, there are few limitations to

the types of raw water that can be handled by membrane processes and, if needed, pre-treatment

(NRC 1997, AWWA - ASCE 1998).

Reverse Osmosis

Reverse osmosis (RO) is a highly efficient removal process for inorganic ions, some

organic contaminants, and, in some cases, microbiological contaminants (EPA 1990, Logsdon et

al. 1990, NRC 1997, AWWA-ASCE 1998). RO resembles membrane filtration processes since

they all involve passing water through a semi-permeable membrane. However, in the case of RO,

the principle involved is not filtration. Instead, it involves the use of applied hydraulic pressure to

oppose the osmotic pressure4 across a non-porous membrane, forcing the water from the

concentrated solution side to the dilute solution side. Since the membrane is non-porous, the

water does not travel through pores, but rather dissolves into the membrane, diffuses across, then

dissolves out into the permeate. Any contaminant that can likewise dissolve into the membrane

and pass into the permeate will not be rejected by the RO membrane. However, most inorganic

contaminants of interest and many organic contaminants are rejected by the membrane and will be

retained in the concentrate. RO produces a larger volume of concentrate (reject) solution than

membrane filtration processes. The concentrate volume can be as much as 25 to 50 percent of the

raw water volume. Drinking water treatment can be accomplished with lower pressure versions

of RO (125 to 300 psi), with feasible recoveries of 70 to 85% (AWWA - ASCE 1998).

 Removal efficiencies for inorganic contaminants range from 85 to > 99%. Removal for

organic contaminants are highly variable depending upon the contaminant and the water quality. 

Lower molecular weight organic molecules and organic molecules that have an affinity for the

membrane may diffuse through the membrane. The degree to which the contaminant passes

depends on the contaminant’s molecular weight and its chemical nature. Removal efficiencies for

organic compounds range from greater than 99% to no removal at all.

An RO membrane can foul if the influent is not pre-treated, depending upon the quality of

the raw water (AWWA-ASCE 1998). Influent total organic carbon (TOC) levels can be as high

as 20 mg/L without requiring pre-treatment (NRC 1997), but the influent have low turbidity, iron,

manganese, and chlorine or pre-treatment is required. Groundwater waters may have low enough

TOC levels and turbidity, but may require removal of iron and manganese. Applying disinfection

after the membrane process can obviate the need to remove chlorine beforehand.
38

Since the permeate has very low mineral content and alkalinity, it can be quite corrosive. 

The usual practice to reduce corrosivity is to blend, i.e., bypass a pre-determined percentage of

the raw water to the permeate. Other possible measures include de-gasification of carbon dioxide

and/or hydrogen sulfide (both are acids in water) or pH adjustment through the addition of a

chemical base, like sodium hydroxide. Post-treatment disinfection is also a common practice.

Usually, RO systems have automatic backwash features, reducing labor requirements. The

skill requirements for the daily operation of common pre-treatment processes are often greater

than the membrane process itself. However, periodic cleaning of the membrane surface is

required. Care must be taken to avoid contamination of the raw or finished water with the acidic

post-wash solution. Also, the membrane should be flushed with permeate to prevent later scaling. 

If the plant is taken out of operation for days at a time, the membranes should be filled with a

disinfection solution to prevent biological growth, which can damage the membrane (NRC 1997).

Electrodialysis (ED) and electrodialysis reversal (EDR)

Electrodialysis (ED) and electrodialysis reversal (EDR) are usually used for demineralizing water from brackish water sources. They involve electrochemical separation

processes to concentrate salts from the feed water into smaller-volume, higher-concentration

solutions within collection channels. ED and EDR systems consist of stacks of alternating anionic

and cationic selective membranes. The ionic constituents pass through the membranes in response

to an electric current applied perpendicularly to the membrane surfaces. This results in an

alternating sequence of de-mineralized water streams and concentrate streams (NRC 1997,

AWWA - ASCE 1998). The principal difference between ED and EDR is that EDR involves the

additional step of a change in electrode polarity every 15 to 20 minutes, causing a reversal in ion

movement. This step minimizes scale buildup on the membranes and thus EDR can operate for

longer time periods between cleanings. The majority of plants using ED technology in the United

States use EDR (NRC 1997).

ED/R systems require feed water pre-treatment. Cartridge filtration is often the minimum

requirement. Turbidity should be less than 2 NTU, free chlorine levels less than 0.5 mg/L,

manganese less than 0.3 mg/L, and hydrogen sulfide less than 0.3 mg/L (Conlon 1990). Total

dissolved solids up to 4,000 mg/L have been successfully handled by EDR plants (NRC 1997).

Unlike membrane filtration and RO, the product water does not pass through the ED/R

membranes, so the potential for organic fouling is reduced. Unfortunately, another consequence

is that microbiological, most organic, and colloidal/particulate contaminants are not removed from

the product water. Standards for these contaminants must be met through pre-treatment or other

means, if necessary. And like other membrane processes, some bypassed water (or other

measures) may be required to reduce the corrosivity of the product water. ED/R systems usually

operate at 70% recovery (NRC 1997).

A principal disadvantage of ED/R is the high energy consumption. Pumping costs are
39

similar to costs for ultrafiltration, but process power costs roughly equal pumping costs for ED/R.

More than half of the ED/R systems in operation in North America serve fewer than 3,500

persons, with some serving fewer than 200. Since ED/R plants are amenable to automatic

operation, part-time operators may be sufficient, depending upon pre- and post-treatment

requirements.

Membrane Process Waste Disposal Considerations

Waste stream disposal is often the most important consideration (NRC 1997). Waste

stream disposal can pose a significant problem in some areas, since waste volumes are larger than

for conventional treatment . Because membrane filtration processes require little or no chemical

addition, the concentrate usually contains only the contaminants found in the source water, and so

disposal of the concentrate into the source water may be feasible. Other alternatives include

sanitary sewer discharge, deep well injection, dilution, and spray irrigation (Pontius et al. 1996,

USEPA 1996). Careful planning may be required to legally and safely dispose of membrane

concentrate wastes. A potentially time consuming part of the process involves obtaining

regulatory permits. In the vast majority of cases, an acceptable waste disposal method can be

successfully implemented and permitted (Pontius et al. 1996).

Disposal of RO and ED/R reject water poses a potentially more serious problem than the

membrane filtration processes, because of the large concentrate volumes. Municipal sewer

disposal and deep well injection are conventional waste handling strategies. The use of

evaporation ponds is another possibility, but is normally used only when conventional means are

not possible, because of the high associated costs and land requirements. For areas with very low

land costs, this may be a feasible alternative for small systems (EPA 1997a).

References

Adham, S.S., Jacangelo, J.G., and Laine, J-M. “Characteristics and Costs of MF and UF Plants”. 

JAWWA 88(5). p. 22. May 1996.

Agbekodo, K.M., Legube, B., and Cote, P. “Nanofiltration Yields High-Quality Drinking Water

in a Paris Suburb”. JAWWA 88(5). p. 67. May 1996.

American Water Works Association. Water Quality and Treatment: A Handbook of Community

Water Supplies, 4th ed.. Pontius, F., ed. McGraw-Hill. New York. 1990.

American Water Works Association and American Society of Civil Engineers (AWWA and

ASCE). Water Treatment Plant Design. Third Edition. McGraw-Hill. New York. 1998.

Bergman, R.A. “Cost of Membrane Softening in Florida”. JAWWA 88(5). p. 32. May 1996.
40

Cornwell, D.A. “Air Stripping and Aeration”. AWWA, Water Quality and Treatment: A

Handbook of Community Water Supplies, 4th ed.. Pontius, F., ed. McGraw-Hill, Inc. New

York. 1990.

Goodrich, J.A., Adams, J.Q., Lykins, B.W., Jr., and Clark, R.M. “Safe Drinking Water from

Small Systems: Treatment Options”. JAWWA. 84(4). p. 49. May 1992.

Jacangelo, J.G. “The Development of Membrane Technology”. International Report (IR 3)

Water Supply: Review Journal of the International Water Supply Association. Vol. 9, Numbers

3/4. 1991.

Lamarre, B. Selecting an Air Stripper–What to Consider. The National Environmental Journal,

July/August. 1993.

Logsdon, G.S., Sorg, T.J., and Clark, B.M. “Capability and Cost of Treatment Technologies for

Small Systems”. JAWWA. 82(6). p. 60. June 1990.

Lykins, B.W., Jr., Clark, R.M., and Goodrich, J.A. Point-of-Use / Point-of-Entry for Drinking

Water Treatment. Lewis Publishers. Ann Arbor, MI. 1992.

National Research Council (NRC). (1997). Safe Water From Every Tap: Improving Water

Service to Small Communities. Committee on Small Water Supply Systems. Water Science and

Technology Board, Commission on Geosciences, Environment, and Resources. National

Academy Press, Washington, DC. 1997.

Pontius, F.W., Kawczynski, E., and Koorse, S.J. “Regulations Governing Membrane Concentrate

Disposal”. JAWWA 88(5). p. 44. May 1996.

Semmens, M.J., R. Qin, and A.K. Zander. “Using Microporous Hollow-Fiber Membranes to

Separate VOCs from Water”. Journal of the American Water Works Association 81(4):162-167. 

1989.

Snoeyink, V. L. “Adsorption of Organic Compounds”. AWWA, Water Quality and Treatment: 

A Handbook of Community Water Supplies, 4th ed.. Pontius, F., ed. McGraw-Hill, Inc. New

York. 1990.

USEPA. “Technologies for Upgrading Existing or Designing New Drinking Water Treatment

Facilities”. Office of Drinking Water. EPA/625/4-89/023. March 1990.

USEPA. “Technical and Economic Capacity of States and Public Water Systems to Implement

Drinking Water Regulations: Report to Congress”. Office of Water. EPA 810-R-93-001. 

September 1993.
41

USEPA “Summary of Arsenic Treatment Workshop”, January 18, 1994.

USEPA. “An SAB Report: Review of Issues Related to the Regulation of Arsenic in Drinking

Water”, EPA-SAB-DWC-95-015, July 1995.

USEPA. “Technology Transfer Handbook: Management of Water Treatment Plant Residuals”. 

Office of Research and Development. EPA/625/R-95/008. April 1996.

USEPA. “Announcement of Small Systems Compliance Technology Lists for Existing National

Primary Drinking Water Regulations and Findings Concerning Variance Technologies”. Federal

Register. Vol. 63, No. 151, p. 42032. August 6, 1998. (EPA 1998a).

USEPA. “Draft Technologies and Costs for the Removal of Arsenic from Potable Water

Supplies”. July 1998. (EPA 1998b). 

USEPA. “Small System Compliance Technology List for the Surface Water Treatment Rule and

Total Coliform Rule”. EPA 815-R-98-001. Office of Water. September 1998. (EPA, 1998c)

Wiesner, M. R., Hackney, J., Sethi, S., Jacaneglo, G., and Laine, J. M. “Cost Estimates for

Membrane Filtration and Conventional Treatment”. JAWWA. 86(12). pp. 33 - 41. 1994.
42

4. AFFORDABLE TECHNOLOGY DETERMINATIONS

Section 4.1: National-Level Affordability Criteria

As discussed in Section 1.3, EPA did evaluate technologies for each small size category

against an affordable technology criterion for those regulations where a small system variance

could be granted. The size category-dependent affordable technology criteria are collectively

referred to as “national-level affordability criteria.” This nomenclature has been used to

distinguish the national-level affordability criteria from the affordability criteria that States will use

for determinations affecting individual systems. EPA published information regarding these

“system-level affordability criteria” in February, 1998 (EPA 1998a). This information was

required by Section 1415(e)(7)(B) of the SDWA. There are three provisions of the SDWA that

refer to these “system-level affordability criteria.” Section 1415(e) provides for affordabilitybased variances, under certain circumstances, for small drinking water systems. Section 1416

allows for exemptions that provide systems facing compelling economic factors additional time to

comply with SDWA requirements. Small systems could receive as long as nine additional years to

comply. Finally, Section 1452(b) provides that affordability on a per household basis shall be one

of the three factors used to prioritize systems for assistance from the new Drinking Water State

Revolving Fund (DWSRF). The system-level affordability criteria can be different for different

purposes. For example, States can use different affordability criteria to make decisions about

whether a system should receive a small system variance and when a system should receive

additional subsidization from the DWSRF. In fact, the threshold used for additional assistance for

systems meeting a NPDWR would likely be lower than the threshold used to determine when a

system would operate at a level that does not provide an equivalent level of protection as meeting

the MCL.

The national-level affordability criteria used to determine if there is an affordable variance

technology will also be different from the system-level criteria used by the State to determine if a

system should receive a small system variance. Technologies determined to be “unaffordable”

under the national-level affordability criteria may still be affordable for a specific system within

the size category, in which case the system may install that technology if it so chooses. 

Conversely, if a financially disadvantaged small water system out of compliance with a NPDWR

cannot afford any of the compliance technologies that are determined to be “affordable” under the

nation-level affordability criteria, one option for that system would be to apply to the State for an

exemption. This process is available for regulations promulgated after 1996. Such a system

cannot apply for a new exemption for the regulations issued prior to August 6, 1998. Those small

systems with existing exemptions for rules in effect on August 6, 1998 may continue to get

renewals of their exemptions until the exemption period has run out. That means that a small

system can have no more than 9 years after the Section 1412 compliance date to meet the

applicable MCL/treatment technique even if the exemption was issued prior to the 1996 SDWA

Amendments.

To determine if there are any affordable compliance technologies for a given NPDWR, the
43

national-level affordability criteria are compared against the cost estimates for the applicable

treatment technologies. To make this comparison, there must be a consistent unit of measure for

both parameters. The selected approach was to measure user burden as the increase to annual

household water bills that would result from installation of treatment. For community water

systems, the household was selected as the most sensitive user for cost increases (EPA 1998b). 

Non-community water systems (NCWSs) were also evaluated by comparing their vulnerability to

cost increases with households in community water systems. The conclusion, based on this

comparison, was that the categories of NCWS were either not vulnerable to SDWA-related

treatment cost increases or were less vulnerable to SDWA-related treatment cost increases than a

typical household (EPA 1998c).

A summary of the methodology used to determine the national-level affordability criteria is

described below. The household is the focus of the national-level affordability analysis. 

Treatment technology costs are presumed affordable to the typical household if they can be shown

to be within a range (defined as a range of percentages of median household income) that appears

reasonable when compared to other household expenditures. This approach is based on the

assumption that affordability to the median household served by the CWS can serve as an

adequate proxy for the affordability of technologies to the system itself. EPA has chosen to

express the water system financial and operational characteristics using their median values, which

is a measure of their respective central tendencies. EPA believes that the national-level

affordability criteria should describe the characteristics of typical systems and should not address

extreme situations where costs might be extremely low or excessively burdensome.

After selecting the impacts on households as the measure for comparing national-level

affordability and treatment costs, a consistent set of units was needed to make the comparison. 

The treatment cost models produce rate increases measured in dollars/thousand gallons ($/kgal). 

Annual household water consumption is needed to convert the treatment technology costs into

the increase in annual household water bills. The water consumption estimates were multiplied by

1.15 to account for lost water due to leaks. Since the water lost to leaks is unbilled, the water

bills for the actual water used needed to be adjusted to cover this lost water by increasing the

household consumption. Multiplying the rate increase by the adjusted annual household

consumption yields the increase to annual household water bills ($/household/year increase).

The national-level affordability criteria have two major components: current annual water

bills (baseline) and the affordability threshold. The current annual household water bills were

subtracted from the affordability threshold to determine the maximum increase that can be

imposed by treatment and still be considered affordable. This difference was compared with the

converted treatment costs to make the affordable technology determinations. This difference is 

called the available expenditure margin.

The baseline costs include existing water quality, water production, and water distribution

costs. Water production costs include labor and energy for pump operation to supply water to

customers. Water distribution costs include costs of infrastructure repair (mains and service lines)
44

and administrative costs (customer billing and meter checking). The existing water quality costs

include both treatment and monitoring. The data utilized to determine the baseline were collected

in 1995, so treatment costs for many of the regulated contaminants may already be accounted for

in the baseline. 

The affordability threshold was determined by comparing the cost of public water supply

for households with other household expenditures and risk-averting behavior. National

expenditure estimates were derived to illustrate the current allocation of household income across

a range of general household expenditures. This consumer expenditure data provided a basis for

determining the affordability threshold by comparing baseline household water costs to median

household income (MHI) to determine the financial impact of increased water costs on

households.

There are three parameters needed for each size category to perform the affordable

technology analysis. These parameters are: annual household consumption, current annual water

bills, and median household income (MHI). The annual household water consumption and the

current annual water bills were derived directly from data in the 1995 Community Water System

Survey (EPA 1997a, EPA 1997b). The MHI data were derived by linking the CWSS data with

data in the 1990 Census using zip codes. 

The national-level affordability criteria are based on an affordability threshold of 2.5% of

the MHI for each size category (EPA 1998d). For each size category, median values have been

used for annual household water consumption, baseline annual water bills, and median household

income. The baseline water bills ranged from 0.65% to 0.69% MHI in the three size categories. 

Thus, the available expenditure margin were approximately 1.8% MHI for each size category. 

Table 4-1 summarizes the national-level affordability criteria and shows the maximum increase

that could occur using these criteria. The numbers in this table are slightly different from the

numbers in the Federal Register notice (EPA 1998e). There were some minor changes in the

baseline values for current water bills and median household income (EPA 1998d). Most systems

would not be expected to actually experience cost increases of this magnitude if a compliance

technology was installed. Many compliance technologies impose substantially lower household

costs. For example, the screening process examined several technologies that imposed less than

$300/household per year increases in all three size categories. Appendix F of the “National-Level

Affordability Criteria Under the 1996 Amendments to the Safe Drinking Water Act” report lists

mitigating measures that could reduce the impact on households. In addition, the national-level

affordability criteria do not consider the impact of financial assistance from State Revolving Fund

loans or other sources. This financial assistance could also reduce the impact on households in

those systems that qualify for financial assistance. For more detail on the national-level

affordability criteria, see the “Variance Technology Findings for Contaminants Regulated Before

1996"(EPA 1998d) and the National-Level Affordability Criteria Under the 1996 Amendments to

the Safe Drinking Water Act” (EPA 1998b) documents. 
45

Table 4-1: National-Level Affordability Criteria

System Size Baseline Affordability Available Expenditure

Population Served MHI

($/yr)

Water Bills

($/hh/yr)

Water Bills

 ( %MHI) 

Threshold

(2.5% MHI)

Margin

($/hh/year increase)

25 - 500 $30,785 $211 0.69% $770 $559

501 - 3,300 $27,058 $184 0.68% $676 $492

3,301 - 10,000 $27,641 $181 0.65% $691 $474
46

Section 4.2: Affordable Technology Analysis using National-Level Affordability Criteria

Compliance technologies were evaluated against the national-level affordability criteria for

those existing regulations where small system variances or variance technologies are not

prohibited by the SDWA. When affordable compliance technologies are identified for these

contaminants, technologies that can achieve compliance, but did not meet the affordability

criterion will also be identified.

In general, technology cost estimates to treat all of the water were compared against the

available expenditure margin for each size category (see Table 4-1). Technology cost estimates

were derived for both central treatment options and centrally-managed Point-of-Use and Point-ofEntry device options. The procedures followed for this analysis are described in detail in Chapter

4 of the background document entitled “Variance Technology Findings for Contaminants

Regulated Prior to 1996” (EPA 1998d). Based on this analysis, an affordable compliance

technology was found for each of the five contaminants for all system sizes and expected source

water qualities. For most of the system size/source water quality combinations, there are multiple

affordable technologies.

The national-level affordability criteria only played a role in removing some of the options

in the smallest size categories. The technologies that did not meet the affordability criteria in the

smallest size category are also identified as “other compliance technologies.” Since the

technology costs were based on treatment of all of the water for this analysis, systems requiring

lower removals may find that the “other compliance technologies” would pass the national-level

affordability criteria if a lower removal efficiency is required. A portion of the influent water

could be treated and blended with an untreated portion and the system could still meet the MCL. 

Under this approach, both the capital and operating and maintenance costs for the process would

be reduced. Systems and States should consider the “other compliance technologies” under those

circumstances.
47

References

USEPA. “Community Water System Survey Volume 1: Overview”. EPA 815-R-97-001a. 

Office of Water. January 1997. (EPA 1997a).

USEPA. “Community Water System Survey Volume II: Detailed Survey Result Tables and

Methodology Report”. EPA 815-R-97-001b. Office of Water. January 1997. (EPA 1997b).

USEPA. “Information for States on Developing Affordability Criteria for Drinking Water”. 

EPA-816-R-98-002. Office of Water. February, 1998. (EPA 1998a).

USEPA. “National-Level Affordability Criteria Under the 1996 Amendments to the Safe

Drinking Water Act”. Prepared by International Consultants, Inc., Hagler Bailly Services, Inc.

and Janice A. Beecher, Ph.D. for the EPA. August 1998. (EPA 1998b).

USEPA. “An Assessment of the Vulnerability of Non-Community Water Systems to SDWA Cost

Increases”. Prepared by Science Applications International Corporation for the EPA. July 1998. 

(EPA 1998c).

USEPA. “Variance Technology Findings for Contaminants Regulated before 1996". EPA 815-

R-98-003. Office of Water. September 1998. (EPA 1998d).

USEPA. “Announcement of Small Systems Compliance Technology Lists for Existing National

Primary Drinking Water Regulations and Findings Concerning Variance Technologies”. Federal

Register. 63(151): 42032. August 6, 1998. (EPA 1998e).
48

5. SMALL SYSTEMS COMPLIANCE TECHNOLOGIES FOR INORGANIC

CONTAMINANTS, INCLUDING CORROSION BY-PRODUCTS

Section 5.1: Background

Seventeen inorganics are regulated. The interim MCL for arsenic was issued in 1975. A

proposal for a new regulation for arsenic is expected by January 2000, and a final rule is expected

by January 2001. The final rule for fluoride was promulgated in April 1986. The final rule for the

Phase II inorganics (asbestos, cadmium, chromium, mercury, nitrate, nitrite and selenium) was

promulgated in January 1991. The lead and copper rule was promulgated in June 1991. The final

rule for Phase IIb (barium) was promulgated in July 1991. The final rule for the Phase V

inorganics (antimony, beryllium, cyanide and thallium) was promulgated in July 1992. 

Issues with compliance technologies for inorganics treatment are discussed in Section

5.2.2. A general description of these technologies can be found in Chapter 3. Corrosion control

technologies are relevant for inhibiting lead and copper dissolution in the distribution system. In

addition, corrosion control reduces release of other inorganics such as asbestos and cadmium. 

The corrosion control technologies are described in Section 5.2.1. Section 5.3 lists the

compliance technologies for small systems and Section 5.4 describes emerging technologies. 

A short description of some of the key inorganics are given below:

Lead and Copper: 

In June 1991, EPA promulgated a NPDWR for lead and copper consisting of a treatment

technique requirement that includes corrosion control treatment, source water treatment, lead

service line replacement and public education. Lead occurs in drinking water from two sources:

(1) Lead in raw water supplies and (2) corrosion of plumbing materials in the water distribution

system (corrosion by-products). Most lead contamination is from corrosion by-products. The

primary source of copper in drinking water is corrosion of copper pipes, which are widely used

throughout the United States for interior plumbing of residences and other buildings. In some

cases, copper is a component of additives to drinking water used by systems to control the growth

of algae (EPA 1991a).

 

Asbestos: 

Asbestos fibers are relatively large particles. Asbestos fibers are generally of two types:

chrysotile and amphibole. Chrysotile fibers are more common in water supplies and are usually

less than 5 microns in length and approximately 0.1 microns in width. Amphiboles are on the

order of 0.4 to 1.7 microns in length and 0.1 to 0.4 microns in width (Logsdon 1979, Kirmeyer

1979a, Kirmeyer 1979b, Black & Veatch 1975). Because of the large size of the particles, the

potential for using inexpensive membrane technologies exists. However, further research is

required. 
49

Antimony:

Antimony is found in over 100 mineral species; however, it does not occur in abundance. 

Metallic antimony is blueish white in color, with a metallic luster, and is extremely brittle, with a

flaky, crystalline texture. Antimony has valence states in the -3, 0, +3, and +5 forms; antimony

does not seem to occur in drinking water in the +3 and +5 states. Though ion exchange (IX) is an

affordable, effective treatment technology for most inorganics, IX does not appear to be effective

in removing antimony (EPA 1990).

Fluoride:

Fluoride commonly occurs in the earth’s crust as fluorspar (CaF2), cryolite (Na3AlF6) and

fluorapatite (Ca10F2(PO4)6) and ranks thirteenth among the elements in order of abundance. 

Concentrations as high as 9 to10 mg/l are not uncommon in some ground waters (Benefield

1982). Fluoride has beneficial and detrimental effects. It can help prevent dental cavities when an

optimum amount is present in drinking water. However, long-term consumption of water

containing excessive amounts of fluoride can lead to fluorosis of the teeth and bones. The MCL

for fluoride is 4.0 mg/l, and the secondary maximum contaminant level (SMCL) is 2.0 mg/l. The

SMCL was set at 2 mg/l because that level would prevent the majority of cases of water-related

cosmetically objectionable dental fluorosis while still allowing for the beneficial effects of fluoride

(EPA 1986a). 

Nitrate:

Nitrate is a common ion found in most natural waters. It is the end product of the

oxidation of ammonia. Because it is an algal nutrient it can promote algal blooms (Benefield

1982). Nitrate is also a potential hazard to infants. Serious and occasionally fatal poisonings in

infants have occurred following ingestion of well waters shown to contain nitrate at

concentrations greater than 10 mg/l of nitrate (as Nitrogen). Well water, particularly shallow well

waters, tend to have higher concentrations of nitrates than surface waters. The major sources of

nitrate contamination has been from septic tank discharges, fertilizer in agricultural drainage,

animal feedlots, domestic and municipal sewage, and industrial wastes (EPA 1984a). 

Arsenic:

Arsenic occurs in two primary forms: organic and inorganic. Inorganic arsenic occurs in

two valence states, arsenite (As III) and arsenate (As V). Most natural waters contain the

inorganic forms of arsenic. Groundwaters generally contain As (III) and surface waters generally

contain As (V). Arsenate is removed more efficiently that arsenite by the treatment technologies

listed here. Therefore, if arsenite is the predominant species present, oxidation to arsenate may be

required to achieve the desired removal.
50

Section 5.2 Evaluation of Technologies

Corrosion Control Technologies

There are primarily three different approaches to control for corrosion in the distribution

system. One approach is to cause a calcium carbonate precipitate to form inside the distribution

system to protect the inside of the pipes. Another approach, referred to as passivation, is to

change the water to be less corrosive without causing a precipitate to form. There are two

methods of passivation. The first is to change the alkalinity and pH of the water. The second is

to add an inhibitor (EPA 1992). The third approach to control for corrosion is to use aeration. 

Calcium carbonate precipitation 

The principle behind calcium carbonate precipitation is to maintain the concentration of

calcium and carbonate high enough in the product water so that calcium carbonate precipitates

out in the distribution system. The solids form a protective coating. This approach is only

practical if the concentration of the calcium and carbonate are high enough in the influent water. 

If necessary, calcium can be added in the form of hydrated or quick lime. The carbonate can be

adjusted by adding soda ash, sodium bicarbonate or carbon dioxide. The pH can be adjusted, if

necessary, by adding these aforementioned chemicals and/or caustic soda, hydrochloric acid or

sulfuric acid. Small systems should be aware of the complexities inherent in using lime and soda

ash systems. These methods require a high degree of operator attention because the calcium

carbonate plugs bins, tanks, pumps and piping. To keep downtime to a minimum the bins have to

be kept dry. In addition, the feed systems must be acid cleaned. Small systems should also be

aware of complexities in operating a sodium hydroxide system. In addition to avoiding calcium

carbonate plugging of the sodium hydroxide feed system, small systems should also be aware that

employees may have to handle a strong base; sodium hydroxide is usually delivered as a 50

percent solution (EPA 1992). Stakeholders expressed a concern that this approach may also

cause a build-up of precipitate in consumers’ hot water heaters.

This control strategy is only appropriate for lead. It is not an effective strategy for copper

for several reasons. First, a much larger surface area would need to be coated. Second, a calcium

carbonate film may not establish on copper piping. Third, adjusting alkalinity for precipitation

may produce a high alkalinity finished water which can be corrosive to copper. 
51

Passivation 

The other approach to corrosion control is passivation. In this case, the goal is to produce

less corrosive water. A precipitate need not be created. 

Alkalinity and pH 

One method of passivation is to alter the alkalinity and the pH. This is appropriate when

the water is not very hard and low in alkalinity. This essentially involves use of the same

chemicals (lime, soda ash, etc.) and feed systems as in calcium carbonate precipitation. An

advantage of this approach is that small systems do not have to attempt the difficult task of

forming a precipitate throughout the distribution system. Small systems should, however, be

aware that employees might have to handle chemicals such as strong bases (EPA 1992).

Limestone contactors 

A method of altering the alkalinity and pH that might be particularly applicable to the

smaller systems is the use of limestone contactors (EPA 1987). This method would be applicable

if the raw water was soft and slightly acidic. With this technology, the water flows through and

dissolves a packed bed of crushed limestones. Because the raw water is slightly soft and slightly

acidic, the calcium carbonate dissolves. Consequently, the pH, calcium and alkalinity increases. 

Limestone contactors have low capital and operation and maintenance costs. This technology is

primarily recommended for the smallest category (25-500 only). Stakeholders expressed a

concern that limestone contactors are presently not widely in use.

Inhibitors 

The other approach to passivation for corrosion control is to use inhibitors. These are

usually phosphate or silicate based. The principal type of phosphates used are orthophosphates;

all are measured as orthophosphate as residual. Polyphosphates have a record of successful

corrosion suppression in some waters, but in others they can increase corrosivity. Polyphosphates

are primarily used as sequesterants. The chemicals are not dangerous, have a long shelf life, and

are highly soluble. Small systems would be able to use small tanks and feed pumps. Systems

should be aware, however, that tanks containing a phosphate-rich solution may experience some

biological growth. Consequently, routine cleaning would be recommended. Another potential

problem with inhibitors is that when first added, previously corroded material may be released

(EPA 1992).
52

Aeration

Aeration removes carbon dioxide, which directly affects pH and dissolved inorganic

carbon (DIC), the parameters that most influence lead and copper solubility. As a result, aeration

can be an effective corrosion control strategy, presuming the initial pH and DIC are appropriate. 

A suitable water must have a significant carbon dioxide concentration and a corresponding

relatively low pH. Carbon dioxide concentrations less than about 4 to 10 mg/L CO2 are not

suitable for aeration.

 Mineral precipitation brought about by water quality changes resulting from

aeration may present operational constraints under some conditions. Aeration produces

consistent water quality and may be advantageous to smaller utilities because of relatively low

costs and simple operational and maintenance needs (Lytle et al, 1998). 

Compliance Technologies for Inorganics

Activated Alumina 

In the application of activated alumina (AA) for treatment of inorganics such as arsenic,

fluoride and selenium, the pH must be lowered to the optimal range. When treated with an acid

solution, alumina is strongly positively charged and will select highly for fluoride (F-), selenium

species (SeO4

2-, HSeO32-), and arsenic (H2AsO4-

). Activated alumina displays a selectivity

sequence, which refers to an order in which ions are preferred by the alumina. Table 9.2 in Water

Quality and Treatment (AWWA 1990) shows the most preferred ions (i.e. those with the highest

separation factors) at the top of the table and the least preferred ions at the bottom. The greatest

adsorption capacity for fluoride occurs at pH 5.5. The greatest adsorption capacity for arsenic

occurs at approximately between 5.5 to 6.0 (Rosenblum 1984). To lower the pH, systems would

have to use acids, which may be problematic for small systems, since some degree of oversight

would be required to ensure that the pH adjustment chemicals are added without causing

significant water chemistry problems. However, many small systems have only part-time

operators. Small systems should also be concerned that it may be necessary to raise the pH after

treatment to avoid corrosion problems. In addition, chemicals involved in the regeneration

process (sodium hydroxide and sulfuric acid) may be difficult for small system operators to

handle. Consequently, small systems will likely need to regenerate the media off-site or dispose of

the spent media rather than regenerate it. AA media will likely pass toxicity tests (in the case of

arsenic) and therefore will be suitable for landfilling (EPA 1998a). Small systems should also be

concerned about highly concentrated waste streams that can be produced. Spent regenerant from

arsenic treatment cannot likely be discharged to a sanitary sewer without pre-treatment. 

Coagulation/filtration 

Coagulation/filtration (C/F) units are available as package plants, however, it may not be

advisable to install a C/F unit solely for inorganics removal. It may be a relevant technology if the

raw water is also high in turbidity. Stakeholders mentioned that some manufacturers are making

C/F units solely for arsenic removal. Stakeholders also expressed concerns about solids handling. 
53

For instance, disposal of arsenic contaminated sludge may be an issue, especially if it is deemed

hazardous. Sludges are evaluated by the toxicity characteristic leaching procedure (TCLP) to

determine if a sludge should be classified as hazardous. Sludges from four different water

treatment plants were evaluated (Bartley 1992) for a variety of inorganic contaminants, including

arsenic. One plant had a C/F process, one plant had a C/F and LS process, and two had LS

processes. All TCLP extracts were considerably below the current criterion (5 mg/L of arsenic)

for being designated a hazardous waste.

Lime softening 

Lime softening (LS), like coagulation/filtration, is not advisable solely for inorganics

removal. However, if systems have hard water and inorganics problems, LS would be

recommended as a compliance technology. Stakeholders agreed with this approach. Arsenic

TCLP extracts from the LS sludges (from the study mentioned above) were also well below the

criterion for being designated a hazardous waste. 

Ion exchange 

In considering application of ion exchange (IX) for inorganics removal, it is important to

understand what the effect of competing ions will be, and to what extent the brine can be

recycled. Similar to activated alumina, ion exchange exhibits a selectivity sequence, which refers

to an order in which ions are preferred. Table 9.2 in Water Quality and Treatment (AWWA

1990) shows the most preferred ions (i.e. those with the highest separation factors) at the top of

the table and the least preferred ions at the bottom. Barium, lead and copper are highly preferred

cations. Sulfate competes with both nitrate and arsenic, but more aggressively with arsenic in

anion exchange. The presence of TDS also impairs aresenic removal. Source waters with TDS

levels above 500 mg/L and sulfate levels above 120 mg/L are not amenable to IX treatment (EPA

1998a). Spent regenerant is produced during IX bed regeneration and this spent regenerant may

have high concentrations of sorbed contaminants and can be expensive to treat and/or dispose. 

Research has been conducted to minimize this effect: recent research on arsenic removal has

shown that the brine can be reused as many as 25 times (Clifford 1998). Though ion exchange

(IX) is an affordable, effective treatment technology for most inorganics, IX does not appear to be

effective in removing antimony. In a bench scale study of ion exchange a removal of only 40

percent was obtained from an influent antimony concentration of 120 ug/l after processing 700

bed volumes (EPA 1990). The charges on a ion also effect the removal efficiency. For instance,

ion exchange will remove arsenic (V), but won’t remove arsenic (III), because the predominant

species in natural water is uncharged. 
54

Reverse osmosis 

A concern with reverse osmosis (RO) for inorganics treatment is that if the full stream is

treated, then most of the alkalinity and the hardness would also be removed. In this case, posttreatment may be necessary to avoid corrosion problems. If feasible, a way to avoid this issue is

to blend the water rather than treat the full stream. The amount of water that is rejected is also an

issue with RO. Discharge concentrate can be between 10 and 50 percent of the influent flow

(EPA 1998a). For that reason it may not be an appropriate technology for all parts of the U.S. 

RO involves passing water through a semi-permeable membrane by forcing the water from the

concentrated solution side to the dilute solution side. Any contaminant that cannot dissolve into

the membrane and pass into the permeate will be rejected by the RO membrane. Most inorganic

contaminants of interest are rejected by the membrane and will be retained in the concentrate. 

Because of the small pore size, RO can remove both As(III) and As(V). However, as with the

other treatment technologies, RO removes As(V) to a greater degree than As(III). Consequently

pre-oxidation will improve removal efficiencies. For asbestos removal, RO and ultrafiltration

techniques have problems with asbestos fibers accumulating on the membrane surfaces. 

Conventional flushing techniques may not be effective. 

Oxidation 

Several oxidants are available for precipitating inorganics from drinking water, including

chlorine, ozone, chlorine dioxide and permanganate. In general, inorganics removal by oxidation

involves the conversion of the contaminant to a higher valence state which may be less soluble and

subject to precipitation. The oxidized inorganic can then be removed by clarification and/or

filtration. However, oxidation of cyanide is a physical break-up. Oxidation has been evaluated

for cyanide removal and the oxidants which have been evaluated include chlorine and ozone. 

Bench and pilot evaluations of chlorine oxidation were performed on wastewaters where cyanide

concentrations and oxidant dosages were higher than those typically encountered in drinking

water treatment. The results indicate that chlorine oxidation could achieve significant cyanide

removal. Oxidation with chlorine is not a new technology; it has been frequently applied in small

ground water systems. Chlorine oxidation is fairly inexpensive and not difficult to implement. A

concern with chlorine, however, is the formation of disinfection by-products, especially since the

chlorination should be conducted at a pH greater than or equal to 8.5. The use of chlorine to

oxidize cyanide results in the formation of cyanogen chloride. Chronic exposure to cyanogen

chloride may be as harmful as chronic exposure to cyanide at and above the MCL. Chlorine

quickly and effectively oxidizes cyanide and cyanogen chloride in a process called alkaline

chlorination. Alkaline chlorination oxidizes cyanide to harmless bicarbonate and nitrogen gas by

using excess chlorine at pH values greater than at least 8.5. The higher the pH the faster the

reaction proceeds. Alkaline chlorination is prescribed over simple chlorination because of the

need to destroy cyanide and cyanogen chloride as quickly as possible. 
55

Corrosion control

In addition to preventing dissolution of lead and copper, corrosion control is relevant for

inorganics removal because asbestos and cadmium can also be released from distribution systems. 

Corrosion control would minimize this release. Please refer to Section 5.2.1 for information on

corrosion control technologies. In some cases where corrosion control is not possible, the only

alternative may be to replace the piping.

Direct filtration 

Direct filtration is a compliance technology for asbestos removal and can achieve 95%

removal. In the application of this technology, proper chemical pretreatment is necessary. The

chemical treatment may consist of conditioning the feed water with alum or iron coagulants and

addition of polymers prior to filtration. The chemicals, when so added, destabilize the suspended

asbestos particles in the water making them easier to remove in the filter. Higher asbestos levels

in plant effluents are associated with poor destabilization of particles in the water and filter

breakthroughs (EPA 1986b). 

Diatomaceous earth filtration

Diatomaceous earth filtration is a compliance technology for asbestos removal and capable

of 95% removal. Improved removal of asbestos fibers has been obtained with a two-step precoating procedure. A coarse grade of diatomite is first applied. A second pre-coat of a finer

grade of diatomite that has been conditioned with alum or an anionic polymer is then applied. 

Similar conditioning of the diatomite used for body feed, by the continuous addition of a polymer

to the raw water, also improves the fiber removal efficiency (EPA 1986b). 

Granular activated carbon 

Granular Activated Carbon (GAC) is a compliance technology for treatment of mercury. 

GAC columns are used in water treatment systems primarily for the removal of organics by

adsorption and are particularly effective in removing those organics which contribute to taste and

odor problems in drinking water. High removal efficiencies of mercury have been obtained with

GAC and usually the capacity of GAC for organic mercury is greater than its capacity for

inorganic mercury (EPA 1984b).

Electrodialysis reversal 

Electrodialysis reversal (EDR) is a compliance technology for barium, selenium and

arsenic. In the removal of arsenic, fairly high recoveries can be obtained by using an internal brine

recycle system (EPA 1998a). EDR can be quite expensive to run because of the energy it uses. 

However, because it is generally automated and allows for part-time operation, it may be an

appropriate technology for small systems.
56

POU Reverse Osmosis and Ion Exchange

POU Reverse Osmosis (POU-RO) and/or Ion Exchange (POU-IX) units are affordable

compliance technologies for antimony, lead, arsenic, barium, beryllium, cadmium, chromium,

copper, fluoride, selenium and thallium. For antimony, the only compliance technology listed for

the smallest size category is POU-RO. POU units essentially use the same technology concepts as

in centralized treatment, and so the comments regarding the treatment technologies made above

also apply for POU treatment. Waste disposal is not likely to be an issue with POU-RO (please

refer to Section 6.2). POU-RO units need to be provided with a means of discharging reject

water to a drain; the reject water will likely be dilute enough to discharge directly into a drain. 

The EPA Drinking Water Research Division (DWRD) conducted POU studies in Alaska and

Oregon where POU-RO and POU-IX were demonstrated to be viable treatment alternatives. 

DWRD entered into a cooperative agreement with San Ysidro, New Mexico to study POU-RO

removal of arsenic, fluoride and other contaminants. Again, POU units were shown to be

effective. Since the conclusion of the San Ysidro study, the village has assumed ownership of the

units and is now responsible for operating and maintaining the units (EPA 1998a).

Section 5.3 Small Systems Compliance Technology List

Compliance Technologies for Inorganic Contaminants (IOCS)

Table 5.1 contains the technologies that have been identified as compliance technologies

for at least one IOC. The table contains the same structure as other tables with a list of limitations

that are contained in the footnotes and operator skill level and raw water quality issues for general

operation of the technology. 

Table 5.1: Technologies for IOCs

Unit technology Limitations

(see footnotes)

Operator Skill

Level Required Raw Water Quality Range

1. Activated

 Alumina

(

a

)

(

b

)

Advanced Ground waters, Competing anion

concentrations will affect run length 

2. Ion

 Exchange

 (IX)

(

c

) Intermediate Ground waters with low total dissolved

solids. Competing ion concentrations

will affect run length. Water should be

low in solids to avoid fouling the resin.

3. Lime

 Softening

(

d

)

(

e

)

(

f

)

Advanced Hard ground and surface waters. 

Variable source water quality may

make LS too difficult.
57

4. Coagulation/

 Filtration

(

g

)

(

h

)

Advanced Can treat wide range of water quality

5. Reverse

 Osmosis (RO)

(

i

)

(

j

)

(

k

)

Advanced Surface water usually require prefiltration

6. Alkaline

 Chlorination

(

l

)

(

m

)

Basic All ground waters

7. Ozone

 Oxidation

Intermediate All ground waters

8. Direct

 Filtration

(

n

) Advanced Needs high raw water quality

9.

Diatomaceous

earth filtration

(

o

)

(

p

) Intermediate Needs very high raw water quality

10. Granular

 Activated

 Carbon

(

q

) Basic Surface waters may require prefiltration

11.

Electrodialysis

Reversal

Advanced Requires prefiltration for surface water

12. POU - IX (

r

) Basic Same as Technology #2

13. POU - RO (

r

) Basic Same as Technology #5

14. Calcium

 Carbonate

 Precipitation

(

s

)

(

t

)

(

u

)

Basic Waters with high levels of alkalinity and

calcium

15. pH and 

 alkalinity

adjustment

(chemical feed)

(

s

) Basic All ranges

16. pH and

 alkalinity

 adjustment

(limestone

contactor)

(

v

) Basic Waters that are low in iron and

turbidity. Raw water should be soft

and slightly acidic.
58

17. Inhibitors (

w

)

(

x

)

Basic All ranges

18. Aeration (

y

) Basic Waters with moderate to high carbon

dioxide content.

Limitations Footnotes to the Technology Tables for IOCs

a

 Chemicals required during regeneration and pH adjustment may be difficult for small

systems to handle.

b

 May create highly concentrated waste streams.

c

 Disposal of regeneration solution containing high concentrations of undesired ions may

be problematic.

d

 Softening chemistry may be too complex for small systems.

e

 Operation and maintenance of lime feeders and lines carrying lime slurry may be too

complex for small systems.

f In LS, there is a potential for precipitation of excess lime in filter beds and formation of

calcium carbonate deposits within filters.

g

 It may not be advisable to install coagulation/filtration solely for inorganics removal.

h Solids handling may be an issue. For instance, disposal of arsenic contaminated sludge

may be an issue, especially if deemed hazardous.

i

 If all of the influent water is treated, then most of the alkalinity and hardness would also

be removed; post-treatment corrosion control will be necessary.

j

 Amount of water that is rejected can be substantial. RO may not be appropriate for all

parts of the U.S.

k

 For asbestos removal, RO has problems with asbestos fibers accumulating on the

membrane surfaces. Conventional flushing techniques may not be effective.

l

 pH must exceed pH 8.5 to ensure complete oxidation without build-up of cyanogen

chloride

m

 With alkaline chlorine oxidation, there is the potential for formation of disinfection byproducts.

n

 Conditioning the feed water with alum or iron coagulants and addition of polymers prior

to filtration may be necessary for asbestos removal (EPA 1986b).

o

 Two-step precoating procedure may be necessary for asbestos removal. A coarse grade

is first applied. A second coat conditioned with alum or an anionic polymer may be necessary

(EPA 1986b).

p

 Continuous addition of a polymer to the raw water may be necessary to improve

asbestos fiber removal efficiency (EPA 1986b).

q

 Usually, the capacity of GAC for organic mercury removal is greater than its capacity for

inorganic mercury removal (EPA 1984b).

r

 When POU devices are used for compliance, programs for long-term operation,

maintenance, and monitoring must be provided by water utility to ensure proper performance (see

Section 1.4).
59

s Small systems should be aware of the complexities inherent in using lime and soda ash

systems. These methods require a high degree of operator attention because the calcium

carbonate plugs bins, tanks, pumps and piping (EPA 1992).

t

 In operating a sodium hydroxide feed system, employees may have to handle the strong

base. 

u

 This approach may cause a build-up of precipitate in consumers’ hot water heaters. 

v This technology is recommended primarily for the smallest size category.

w

 Tanks containing a phosphate-rich solution may experience some biological growth. 

Routine cleaning is recommended.

x

 When first added, previously corroded material may be released (EPA 1992).

y

 Any of the first five aeration technologies listed for volatile organic contaminants can be

used.

Section 1.3 indicated that EPA would identify affordable compliance technologies for

those existing regulations where small system variances or variance technologies are not

prohibited by the SDWA. There are statutory prohibitions against small system variances or

variance technologies for 13 of the 17 IOCs. Table 5.2 contains the compliance technologies for

the four IOCs where affordability was considered. Affordability only plays a role in removing

some of the options in the smallest size category. The technology costs are based on treatment of

all of the water. The technologies that did not meet the affordability criteria in the smallest size

category are also identified in the next column called other compliance technologies. These

technologies may be affordable if the concentration of the contaminant is low enough that a

portion of the influent stream can be treated and blended with an untreated portion to still meet

the MCL. Systems and States should consider these options under those circumstances. Table

5.3 contains the compliance technologies for the remaining thirteen IOCs where affordability was

not considered due to statutory prohibitions (EPA 1998b). 

Table 5.2: Compliance Technologies by System Size Category for those IOC NPDWRs where

Affordability is Considered

Inorganic

Contaminant

Compliance Technologies for System Size Categories

(Population Served)

25 - 500 

(afford)

25 - 500 

(other)

501 - 3,300

(afford)

3,301 - 10,000

(afford)

Antimony 13 4, 5 4, 5, 13 4, 5, 13

Asbestos 8, 9, 15, 17 4 4, 8, 9, 15, 17 4, 8, 9, 15, 17

Cyanide 2, 6, 7 5 2, 5, 6, 7 2, 5, 6, 7
60

Lead 2, 12, 13, 14,

15, 16, 17, 18

3, 4, 5 2, 3, 4, 5, 12,

13, 14, 15, 16,

17, 18

2, 3, 4, 5, 12,

13, 14, 15, 16,

17, 18

Table 5.3: Compliance Technologies by System Size Category for those IOC NPDWRs where

Affordability is Not Considered

Inorganic

Contaminant

Compliance Technologies for System Size Categories

(Population Served)

25 - 500 501 - 3,300 3,301 - 10,000

Arsenic 1, 2, 3, 4, 5, 11, 12,

13

1, 2, 3, 4, 5, 11, 12,

13

1, 2, 3, 4, 5, 11, 12,

13

Barium 2, 3, 4, 5, 11, 12, 13 2, 3, 4, 5, 11, 12, 13 2, 3, 4, 5, 11, 12, 13

Beryllium 1, 2, 3, 4, 5, 12, 13 1, 2, 3, 4, 5, 12, 13 1, 2, 3, 4, 5, 12, 13

Cadmium 2, 3, 4, 5, 12, 13 2, 3, 4, 5, 12, 13 2, 3, 4, 5, 12, 13

Chromium 2, 3 a, 4, 5, 12, 13 2, 3 a, 4, 5, 12, 13 2, 3 a, 4, 5, 12, 13

Copper 2, 3, 4, 5, 12, 13, 15,

16, 17, 18

2, 3, 4, 5, 12, 13, 15,

16, 17, 18

2, 3, 4, 5, 12, 13, 15,

16, 17, 18

Fluoride 1, 5, 13 1, 5, 13 1, 5, 13

Mercury 3

b

, 4b, 5b, 10 3

b

, 4b, 5b, 10 3

b

, 4b, 5b, 10

Nitrate 2, 5, 11 2, 5, 11 2, 5, 11

Nitrite 2, 5 2, 5 2, 5

Nitrate + Nitrite 2, 5, 11 2, 5, 11 2, 5, 11

Selenium 1, 2c, 3, 4d, 5, 11d, 13 1, 2c, 3, 4d, 5, 11d, 13 1, 2c, 3, 4d, 5, 11d, 13

Thallium 1, 2, 12 1, 2, 12 1, 2, 12

Footnotes for Table 5.3: Compliance Technologies for IOCs (affordability not considered)

a

 Compliance technology for Chromium III only.

b

 Compliance technologies only when influent mercury concentrations 10 Fg/L.

c

 Compliance technology for Selenium VI only.

d

 Compliance technology for Selenium IV only.
61

Section 5.4: Emerging Technologies

Following is a listing of technologies that EPA did not list as compliance technologies. 

However, EPA is monitoring the development of these technologies and may list them as

compliance technologies in future updates of this guidance.

Biological denitrification 

For nitrate removal, another appropriate technology may be biological denitrification. In

biological denitrification, micro-organisms are fed some form of carbon, and use the nitrate as an

electron acceptor instead of oxygen. The micro-organisms reduce the nitrate to nitrogen. 

Though this technology has been used in wastewater treatment, its use in the United States in

water treatment is limited. The primary reason is that there is concern that since bacteria are

being used to treat the water, there is a potential for bacterial contamination of the water supply. 

Nanofiltration, ultrafiltration and microfiltration

Asbestos:

The MCL for asbestos is 7 million fibers/liter and refers only to those fibers longer than 10

microns (EPA 1991b). For particles of that size, reverse osmosis, nanofiltration, ultrafiltration

and microfiltration would be effective removal technologies. The membrane pore size for

microfiltration varies from approximately 0.1 to 1.0 microns (AWWA 1998); therefore, the

technology can be expected to remove asbestos fibers larger than 10 microns. For asbestos

removal, membrane techniques, however, have problems with asbestos fibers accumulating on the

membrane surfaces. Conventional flushing techniques may not be effective. The issue requires

further research. 

Arsenic:

Nanofiltration (NF) membranes have pore sizes that vary from approximately 0.001

microns to 0.005 microns. Because of the small pore size, NF can remove both As(III) and

As(V), but as with the other treatment technologies, NF removes As(V) more effectively. The

small pore size, however makes NF membranes more prone to fouling than ultrafiltration or

microfiltration membranes. The application of NF for surface water treatment is typically not

accomplished without extensive pretreatment for particle removal and possible pretreatment for

dissolved constituents to prevent fouling (EPA 1998a). NF can be operated at lower pressures

then reverse osmosis, which translates into lower operation and maintenance costs. However, a

recent study with arsenic removal revealed that the removal efficiency dropped significantly

during pilot-scale tests where the process was operated at more realist recoveries. When the

membrane unit was operated at a recovery of 65%, the arsenic removal efficiency dropped to

65% and when the recovery was increased to 90%, the arsenic removal efficiency dropped down

to 16% (Chang 1994). 
62

POU Activated Alumina Units

Activated Alumina (AA) units are often used for fluoride removal and are also applicable

for arsenic and selenium removal. Since the greatest adsorption capacity occurs at pH 5.5 for

fluoride, and between 5.5 and 6.0 for arsenic, and the pH will not be adjusted in a POU unit, the

removal efficiency will not be optimum. This implies that the exchange/adsorption capacity of the

activated alumina will be reached in a shorter time, and the spent cartridge will need to be

replaced more often. If, after investigation, EPA determines that this is not a major issue, POU

AA units will be added as compliance technologies in the next update of this list.

POU Ion Exchange and Reverse Osmosis Units for Nitrate 

Ion exchange and reverse osmosis are appropriate technologies for nitrate removal. If

they are used as POU devices, it is important to educate consumers as to potential health effects. 

Since POU devices do not treat all the water taps in a house, there is a potential health risk of

household residents drinking untreated water. Nitrate, as mentioned previously, is a potential

hazard to young infants; serious and occasionally fatal poisonings in infants have occurred

following ingestion. Households need to be informed about the importance of meeting

replacement schedules for media, cartridges, filters, and modules associated with POU systems. 

Households also must be careful not to use untreated water to make infant formula. Almost all

established cases of water related nitrate-induced methemoglobinemia in the United States have

resulted from the ingestion of private well water used to make infant formula. Stakeholders

suggested that EPA investigate the feasibility of public awareness projects such as using print,

radio and television media and public forums. Public outreach would, however, have significant

costs and may offset any savings of using POU devices. 

POE Units

POE units are relatively expensive, and not likely an affordable technology for small

systems. In addition, waste disposal issues remain with POE units. The disposal of the brine or

concentrate stream may be problematic. In addition, EPA needs to investigate if the usage of a

limestone contactor after a reverse osmosis unit will be adequate for corrosion control of internal

plumbing. 

References

American Water Works Association and American Society of Civil Engineers. Water Treatment

Plant Design. Third Edition. McGraw-Hill. 1998. 

American Water Works Association. Water Quality and Treatment. A Handbook of Community

Water Supplies. Fourth Edition. McGraw-Hill. 1990.

 

Bartley, C.B., Colucci, P.M. and Stevens, T. “The inorganic chemical characterization of water
63

treatment plant residuals”. EPA/600/SR-92-117, U.S. Environmental Protection Agency,

Cincinnati. 1992.

Benefield, L.D. et al., Process Chemistry for Water and Wastewater Treatment, Prentice-Hall,

1982.

Black and Veatch Consulting Engineers. “ Direct Filtration of Lake Superior Water for

Asbestiform Fiber Removal”. U.S. Environmental Protection Agency, EPA-670/2-75-050a,

1975.

Chang, S.D., Ruiz, H., Bellamy, W.D. et al. “Arsenic Removal by Enhanced Coagulation and

Membrane Technology. Proceedings of the 1994 American Water Works Association Annual

Conference”, American Water Works Association, New York, 1994.

Clifford, D., G. Ghurye and A. Tripp (1998). “Arsenic removal by Ion Exchange With and

Without Brine Reuse,” AWWA Inorganic Contaminants Workshop, San Antonio, TX, February

23-24, 1998.

Kirmeyer, G.J. “Seattle Tolt Water Supply Mixed Asbestiform Removal Study”. U.S.

Environmental Protection Agency, EPS-600/2-79-125, 1979. (Kirmeyer 1979a)

Kirmeyer, G.J. “Seattle Tolt Water Supply Mixed Asbestiform Removal Study. Appendices B

and C”. U.S. Environmental Protection Agency, EPA-600/2-79-153, 1979. (Kirmeyer 1979b)

Logsdon, G.S. “Water Filtration for Asbestos Fiber Removal”. U.S. Environmental Protection

Agency, EPA-600/2-79-206, 1979.

Lytle, D.A., Schock, M.R., Clement, J.A., Spencer, C.M. “Using Aeration for Corrosion

Control”, Journal AWWA, March 1998.

Rosenblum, E.R. and D.A. Clifford (1984). The Equilibrium Arsenic Capacity of Activated

Alumina, PB 84/10 527, NTIS, Springfield.

USEPA. “Technology and Costs for the Removal of Nitrates from Potable Water Supplies”.

Prepared by V.J. Ciccone & Associates, Inc. August 1984 (EPA 1984a). 

USEPA. “Technologies and Costs for the Removal of Mercury from Potable Water Supplies”. 

Prepared by V.J. Ciccone & Associates, Inc. December 30, 1984 (EPA 1984b).

USEPA. “National Primary and Secondary Water Regulations; Fluoride; Final Rule.” Federal

Register. Vol. 51, No. 63, p. 11396. April 2, 1986 (EPA 1986a).

USEPA. “Technologies and Costs for the Removal of Asbestos from Potable Water Supplies”. 
64

Prepared by V.J. Ciccone & Associates, Inc. February 5, 1986 (EPA 1986b)

USEPA. “Limestone Bed Contactors for Control of Corrosion at Small Water Utilities”. 

February 1987.

USEPA. “Technologies and Costs for the Removal of Phase V Inorganic Contaminants from

Potable Water Souces.” Prepared by Malcolm Pirnie, Inc. January 1990.

USEPA. “Maximum Contaminant Level Goals and National Primary Drinking Water Regulations

for Lead and Copper; Final Rule.” Federal Register. Vol. 56, No. 110, p. 26460. June 7, 1991

(EPA 1991a)

USEPA. “National Primary Drinking Water Regulations; Final Rule.” Federal Register. Vol. 56,

No. 20, p. 3526. January 30, 1991. (EPA 1991b)

USEPA. “Lead and Copper Guidance Manual–Volume 2: Corrosion Control Treatment”. 

Prepared by Black & Veatch and Malcolm Pirnie, Inc. September 1992. 

USEPA. “Draft Technologies and Costs for the Removal of Arsenic from Potable Water

Supplies”. Prepared by International Consultants, Inc. July 1998 (EPA 1998a). 

USEPA. “Variance Technology Findings for Contaminants Regulated Before 1996". EPA 815-

R-98-003. Office of Water. September 1998. (EPA 1998b).
65

6. SMALL SYSTEMS COMPLIANCE TECHNOLOGIES FOR RADIONUCLIDES

Section 6.1: Background

The applicability of particular treatment technologies to the removal of radionuclides from

drinking water depends significantly on the chemical and physical characteristics of the

contaminants involved and the site specific characteristics of the water system, e.g., source water

quality and water system size. The considerations that determine feasibility include: high removal

efficiency, general geographic availability and applicability (e.g., climate considerations) of the

technology, cost, service life, and co-treatment compatibility.

The removal strategies for radium, gross-alpha emitters, and total beta and photon

emitters exploit the chemistries of the individual contaminants, as with any removal contaminant

removal strategy. The chemical properties of the contaminant to be removed, e.g., speciation,

solubility, tendency to sorb, etc., have a deciding influence on the choice of the best treatment

strategy. For example, some contaminants occur as either cations or anions depending upon the

source water conditions, e.g., pH, the presence of other complexing ions, including dissolved

organic compounds, etc. Thus, the choice of cation versus anion exchange treatment may depend

upon the site specific situation. As another relevant example, for coagulation/filtration treatment

processes to be effective for removing elevated gross alpha levels caused by uranium, uranium

must sorb to the floc or precipitate before settling or filtration. Highly efficient removal will only

occur for those uranium species that sorb significantly under the site specific conditions of the

source water as affected by the treatment process. For reverse osmosis treatment, the water

chemistry of the contaminants in question is less important since the removal mechanism tends to

remove both cations and anions and does not involve sorption.

Radionuclides occur naturally as trace elements in rocks and soils as the result of the

radioactive decay of the uranium-238 (U-238) and thorium-232 (Th-232). Of the U-238 and Th232 decay series, radon-222, radium-226, radium-228, U-238, and U-234 are the most common

in ground water (Zapecza and Szabo 1986). The other naturally occurring radionuclides are not

present in significant amounts in ground water, because of their environmental immobility and/or

short half-lives. The naturally occurring radionuclides of the uranium-238 decay series (uranium238, radium-226, and radon-222) are responsible for the majority of radiation exposure associated

with drinking water (e.g., Lowry and Lowry 1988, EPA 1991a). Radium-228 can also have

significant occurrence. Of these, only radium-226 and -228 currently have National Primary

Drinking Water Regulations. Total beta and photon emitter activity will be discussed only briefly
1

 Beta and photon activity is usually the result of releases from nuclear facilities. Since

releases from these facilities are strictly controlled, occurrence is rare. As such, total beta and

photon activity is of concern to only a few drinking water supplies.

2

 Uranium was proposed for regulation in 1991. A final NPDWR for uranium is expected

in the near future and will include a list of small systems compliance technologies.

3

 A revised Small Systems Compliance Technology list for gross alpha activity will be

issued with the future updated NPDWR for radionuclides.

66

since most are anthropogenic and their occurrence is very site specific1. Although uranium2

comprises the majority of “true total alpha activity” in surface waters (i.e., total alpha activity

without excluding radon-222 and uranium isotopes), it is exclude by definition from gross alpha

activity. This being the case, and since radium-226 primarily comprises gross alpha occurrence in

ground waters, radium will be the focus of the remainder of this discussion3.

When planning removal strategies for radionuclides, it is important to understand that

different isotopes of the same element (e.g., radium-226 versus radium-228) are chemically

indistinguishable from the perspective of treatment (Clifford 1990). In other words, when

planning treatment, “radium is radium”.
1

 Alpha-recoil refers to the recoil motion of the daughter product (the radium isotope, in

this case) resulting from the high energy ejection of the alpha particle during the alpha-decay of

the parent isotope, which was originally embedded in the aquifer solid phase. Analogous to the

recoil energy of a gun (Michel 1991), the high speed ejection of the alpha particle results in recoil

of the progeny radium isotope, imparting enough energy to eject it across the solid/water interface

into the ground water phase. This mechanism results in the enhanced solubility of the radium

isotope (Hess et al. 1985).

2

 1 pCi/L of radium roughly corresponds to 1 pg/L.

3

 For a discussion of competitive sorption, see Snoeyink 1990, p.788. Radium has the

largest atomic weight and hydrated ionic radius of the alkaline earth metal cations, which greatly

67

Chemical Behavior of Radium

Radium is primarily a ground water contaminant. Under oxidizing conditions (e.g.,

surface waters), it is very immobile. The sources of radium to ground water include dissolution of

radium-bearing aquifer solids, “alpha-recoil1” of radium isotopes from the aquifer solid matrix

across the solid/water boundary (Hess et al. 1985), and desorption of radium from aquifer solids

surfaces. Since radium itself is not very soluble in water and does not form strong complexes

with common solutes found in aquifers, the alpha recoil process is important in that it can

significantly increase the radium concentration above that due to dissolution from the aquifer

material. The radium “liberated” by the alpha recoil process may then stay in solution or sorb to

the aquifer matrix, where the fraction of radium in solution to that sorbed is determined by the

local geochemical conditions of the aquifer. For a more detailed discussion of how local geology

and geochemical processes control the occurrence of radium in aquifers, see, e.g., Hess et al.

1985, Zapecza and Szabo 1986, and Michel 1991. In general, radium occurs at higher ground

water concentrations under reducing conditions with high total dissolved solids content (Tanner

1964, as cited in Zapecza and Szabo 1986, and Michel 1991).

Radium, though much less soluble, behaves in water analogously to calcium and

magnesium (all are alkaline earth metals, group IIA), so water softening processes like ion

exchange and lime softening tend to remove radium also. Like the other alkaline earth metals,

radium remains a divalent cation (Ra2+

(aq)) up to the higher end of pH values normally found in

drinking water sources. In other words, radium does not significantly hydrolyze water (form

hydroxides or oxides) at ambient pH levels. This greatly simplifies the water chemistry of radium. 

One treatment strategy consequence of this is that cation exchange is usually the most appropriate

ion exchange type.

It is important to keep in mind that the radium ion is a problem at picogram (pg) per liter

levels2, whereas calcium concentrations of 100 mg/L are not unusual. To put this in perspective,

under those conditions, for every radium ion present in solution, there would be 1011, or one

hundred billion, calcium ions competing in the chemical processes3 that are exploited in water
increases its tendency to sorb to ion exchange resins relative to the other alkaline earth cations,

including Ca2+ and Mg2+.

68

softening. Fortuitously, radium preferentially sorbs relative to calcium or magnesium during

water softening processes to an extent that allows good radium removals. During lime softening,

which involves the precipitation of calcium carbonate and magnesium hydroxide, radium coprecipitates efficiently enough to achieve good removals (Clifford 1991). These and other

treatment processes will be discussed in more detail later in this chapter.

Another consequence of radium’s tendency to strongly sorb is that radium tends to

associate with suspended particulate matter. Colloid and micro-particulates in ground water

sources can include silica, high molecular weight organic matter, clays, and oxides precipitates of

Mn, Fe, and Al. Depending on the local chemical and physical conditions, a variable amount of

radium may be removed during the filtration removal of this suspended material. Unfortunately,

the average removal efficiency from simple filtration is often too low to be very useful (Clifford

1991).

Section 6.2: Evaluation of Technologies

Based on the properties of radium discussed above and the other criteria affecting

treatment technology selection, the treatment technologies evaluated for radium removal were

limited to: ion exchange (IE), point-of-use IE, point-of-entry IE, reverse osmosis (RO), point-ofuse RO, point-of-entry RO, lime softening (LS), greensand filtration, co-precipitation with barium

sulfate, selective sorbents, electrodialysis/electrodialysis reversal (ED/EDR), and pre-formed

hydrous manganese oxides (HMOs). For the removal of gross alpha emitters where radium

comprises most of the activity, these same technologies would apply. For the removal of gross

alpha activity caused by radionuclides other than the radium, which can include a variety of

contaminants, technologies should be evaluated on a case-by-case basis. This is also true for total

beta and photon emitter activity. However, ion exchange (IE), point-of-use IE, point-of-entry IE,

reverse osmosis (RO), point-of-use RO, and point-of-entry RO were determined to be robust

enough to merit a general evaluation.

The best available technologies (BATs) from the 1991 radionuclides proposed rule (EPA

1991a) were evaluated as small systems compliance technologies. The table below lists the MCLs

and the 1991 proposed BATs for the currently regulated radionuclides.

MCLs and BATs for Regulated Radionuclides

Contaminant MCL (1976) BAT (Proposed 1991)

combined radium-226 and radium2285 pCi/L Ion exchange (IE), lime softening

(LS), reverse osmosis (RO)
69

gross alpha particle activity 15 pCi/L RO

total beta particle activity and

photon activity, average annual

concentration

4 millirem/year IE, RO

Ion Exchange

The ion exchange (IX) process and general small systems concerns regarding the use of

ion exchange are discussed in Chapter 3. IX may be used to selectively remove radionuclide ions

from drinking water, e.g., the well known application of sodium ion exchange softening for

removing radium. As discussed in Chapter 3, IX treatment may be readily adapted for use by

small systems (NRC 1997) and may be used in a point-of-use and point-of-entry mode. The

effluent must be regularly monitored and/or the resin must be regenerated on a sufficiently

frequent basis to ensure that breakthrough has not occurred. However, the units may be

controlled automatically, so operator requirements may not be overly time intensive. 

Determination of regeneration frequency and trouble-shooting do require a skilled operator

(Clifford 1990a). It should be noted that disposal can be expensive in the case of concentrated

radionuclides.

Wastes generated by IX treatment include rinse and backwash water and, eventually, the

resin itself. The rinse and backwash liquid waste includes brine, radium, and any other

contaminants removed by the process. The contamination of the exhausted resin depends upon its

loading capacity and the degree of use since the last regeneration (EPA 1994). Disposal issues

specific to radium are discussed below.

Point-of-entry and point-of-use softening units are common and have been shown to be

consistent and effective in removing radium (AWWA-ASCE 1998, Clifford 1991a, Clifford

1991b). The general concerns regarding monitoring and performance that were discussed in

Chapter 3 apply here. Disposal of point-of-entry regenerant wastes are issue that remains to be

resolved before this technology will be listed as a small systems compliance technology. Point-ofuse softeners may be regenerable or disposable. Water systems must take care to ensure that

proper radium removal performance is being maintained through monitoring and/or maintenance. 

If drain disposal of regenerant wastes from point-of-use softeners to sanitary sewers is possible,

this technology may be an attractive option for small water systems. If disposal is not an option,

non-regenerable resins may be an attractive option.
70

Cation Exchange

Cation exchange resins are used to remove undesired cations from water by exchanging

them with protons (H+), sodium ions (Na+), or, in the case of sodium restrictions, potassium ions

(K+). Cation exchange is often used to reduce hardness through the removal of calcium and

magnesium cations, and thus is an efficient treatment for radium. Cation exchange is also a

treatment of choice for cationic beta and photon emitters.

As discussed in the introduction to this chapter, radium preferentially sorbs relative to

calcium and magnesium. Studies indicate that sodium cation exchange can remove 80 - 98% of

radium (Brink et al. 1978, as cited in Clifford 1990b, USEPA 1983, USEPA 1992). Significant

radium breakthrough was reported only after significant hardness breakthrough occurred (Clifford

1990b). Since treated water is often blended with some raw water (commonly 30 to 50%

blending) to reduce corrosivity in the effluent after softening, the radium influent levels must not

be so high that the blending process raises the radium effluent levels above the MCL. If the

radium influent levels are too high, corrosivity reduction other than blending or a treatment other

than softening must be used.

Weak acid cation (WAC) exchange resins may be used to remove radium from ground

water. For example, acid WAC resins may be used to exchange hydronium ion (H+) for radium. 

The exchange process removes hardness, alkalinity, and total dissolved solids from the influent

and is limited by carbonate alkalinity. Acid elution can be used to regenerate the resin. 

Although acid WAC resin exchangers are more expensive than sodium exchangers, they should be

considered when hardness and total dissolved solids reduction is desired along with radium

removal.

The liquid waste stream (rinse and backwash) volume produced by cation exchange for

radium removal typically ranges between 2 and 10% of the product water volume. The radium

concentration in the liquid waste depends upon the radium influent concentration, the volume of

regenerant solution used, and the frequency of regeneration. An Iowa case study showed liquid

waste radium levels between 110 and 530 pCi/L. Another showed an average and peak waste

level of 23 and 160 pCi/L, respectively. At the latter facility, the exhausted resin accumulated a

radium level of ca. 9 pCi/g (EPA 1994).

Anion exchange

A few studies have been conducted to specifically assess the effectiveness of anion

exchange for “gross alpha” removal, where either uranium is not the dominant source or the

speciation was not specified (EPA 1992). Removals between 85 and 95 percent can be achieved,

depending on which alpha emitters are present and on the water quality.
71

Lime Softening

Lime softening (Benefield et al. 1990, EPA 1992, NRC 1997) can be used to remove

radium from drinking water with removal efficiencies of 80 to 95%. This process involves

inducing precipitation of calcium carbonate and magnesium hydroxide by increasing the pH of the

treated water to ca. 10 through the addition of lime or lime-soda ash. The general process is

discussed in more detail in Chapter 3.

For surface water systems, lime softening technology is considered most feasible for large

systems (those that serve more than 10,000 persons) because of the difficulties resulting from the

combination of variable source water quality and the complexity of the chemistry involved. 

Changing water quality necessitates frequent monitoring and modification of the chemical dosage,

creating the need for intensive oversight by a highly qualified operator. This requirement may be

too burdensome for small surface water systems. 

For ground water systems, the relative uniformity in water quality makes lime softening a

more feasible technology, since the required dosages are relatively constant. However, the

operation and maintenance of lime feeders and the lines that carry the lime slurry to the treated

water are not simple matters, and they may prove too difficult for part-time operators. Since

many ground water systems are small, this limits the applicability of lime softening. Fortunately,

small package plants with labor saving devices and remote monitoring/control features are

becoming more common, making lime softening more accessible to small systems. The National

Research Council (1997) has suggested that while lime softening may be appropriate for small

ground water systems serving fewer than 3,300 persons, those serving fewer than 500 should only

use lime softening if they have a service contract or a satellite operation that would enable a

qualified operator to monitor the treatment process on a regular basis. Since radium is typically

found at higher levels only in ground waters, lime softening may be an appropriate radium

removal option for many small systems.

Wastes generated by lime softening include lime sludge, filter backwash liquid and sludge,

and sludge supernatant. Typical radium concentrations in waste products are reported to range

from 1,980 pCi/L in the wet lime sludge, 6 to 9 pCi/g in the dried sludge, 6 to 50 pCi/L in the

filter backwash liquid, and ca. 20 to 25 pCi/L in the sludge supernatant (EPA 1994).

Reverse Osmosis (RO)

The reverse osmosis process is described in Chapter 3 of this document. Reverse osmosis

has been shown to be highly effective for removing inorganic contaminants, including heavy

metals and radionuclides such as radium and uranium. RO can remove 87 to 98% of radium in

drinking water. Similar removals can be achieved for alpha particle activity and total beta and

photon emitter activity (EPA 1992, EPA 1998a).

Historically, RO membranes have required high operating pressure, in excess of 400 psi,
72

to provide adequate feed water recovery for brackish and fresh water supplies. However, recent

advances in membrane technology have led to the development of membranes capable of

operating at much lower pressures (100 to 200 psi). Low pressure membranes provide substantial

savings in process electric energy.

The performance of an RO system for radionuclide removal depends upon a number of

factors including pH, turbidity, iron/manganese content of the raw water, and membrane type. 

Design of a pretreatment system is dependent upon the quality and quantity of the feed water

source and may include one or more of the following: pH adjustment, filtration, iron and

manganese reduction, or additives for scale prevention. Existing treatment plants may already

provide much of the pretreatment required, for example, coagulation/filtration for highly turbid

surface water or iron removal for well waters. RO is adaptable to all systems sizes and can be

cost effective for small systems.

RO does not selectively remove dissolved contaminants. Therefore it is very effective for

removing multiple contaminants in one step.

RO systems produce very high quality water, removing 90 to >99% total dissolved salts

from the feed water, leading to demineralized product water. Demineralized water has low

alkalinity and can be corrosive. To reduce corrosivity in the product water, systems may by-pass 

some of the raw water and blend it with the permeate, raise the pH, or otherwise add alkalinity. 

The need for blending may be a factor in the selection of a RO system. In fact, the blending

process can make an RO process more economical than complete treatment of all raw water. The

fraction of the raw water to be treated will depend upon the removal efficiency of the selected RO

membrane, the initial concentration of contaminants in the raw water, and the required effluent

objective.

The reject water from RO is the only waste generated. However, reject water is

continuously generated during operation, so the volumes created are large compared to the

amount of water treated. The radium concentration in the reject water depends on the radium

concentration in the influent and the percent recovery of the operation. For example, if the RO

unit removes 98% of radium and rejects 50% of the influent water, then the reject water will

contain roughly two times the concentration of the influent water. Studies report ranges of ca. 8

to 40 pCi/L of radium in the reject water (EPA 1994).

Although point-of-use (POU) RO was not proposed as BAT in 1991 (see Chapter 1), it

appears to be a very promising small systems treatment option for inorganic contaminants removal

(NRC 1997), including radium, since it is reliable, effective, and simple to use on the small scale

(Clifford 1991a, Thomson and O’Grady 1998, EPA 1998c). A typical POU RO configuration for

radionuclides removal would include a 5 micron pre-filter to remove particulates, a GAC filter to

remove chlorine, taste, and odor, the RO unit itself, and a connection to the sink drain for reject

water disposal. The discharge line requires an air gap to prevent a cross-connection between

wastewater and drinking water. 
73

 Since general POU concerns are described above, this section will focus on reject water

disposal concerns. One of the primary advantages of POU RO is that reject water waste disposal

is straightforward if drain disposal to a sanitary sewer is possible. Although the total mass or

concentration of radionuclide contaminants discharged from the house would not significantly

change when RO treatment is installed, the reject water does contain higher radionuclides

concentrations than the untreated tap water. The actual degree of concentration depends on the

recovery percentage, as described above. Once the reject water sufficiently mixes with the other

drainage water, the radionuclide levels will be diluted until they approach those in the untreated

water. Since the drain water from a single tap is usually a small part of the drain water budget of

the entire household, this dilution should occur very quickly. The table below shows the

relationship between the % increase in radium concentration for the total household drainage

versus the RO recovery percentage:

Percent Increase in Radium Concentration in Household Drainage versus RO Rejection Percentage

% Recovery1 % [Ra] Increase2 Notes

50 5.0 1) “% Recovery” = 100*Volume of Product Water/ Volume of Total Water at

Tap).

40 3.3

30 2.1 2) “% [Ra] Increase” is the percentage increase in the concentration of radium in

the total house drainage, i.e., for a recovery of 50% and an untreated water

(influent) radium concentration of 10 pCi/L, the total house drainage would have

an average concentration of 10.5 pCi/L. 20 1.3

10 0.6

The table assumes that drinking and cooking water comprises 5% of the total household water

(EPA 1991) and that the rest of the water is returned to the drain. As the table shows, if the drain

water is discharged to a sanitary sewer, the concentration of radionuclides reaching the waste

water treatment plant should not be significantly affected by the addition of POU RO. Clifford

(1991a) reports a 15% recovery for spiral wound POU RO as typical. At this recovery, the reject

water is concentrated by a factor of about 1.18 relative to the raw water and, extrapolating from

the table, the increase in the average radium concentration in total household drainage is less than

one percent.

Stakeholders discussed the possibility of using POU RO with households connected to

septic tanks. While the above analysis would indicate that this may be feasible, EPA (1994) does

not suggest disposal of water treatment wastes into septic tanks. However, this suggestion is

based on centralized treatment assumptions and may not cover POU RO scenarios. This issue

deserves attention in the future. 
74

Technologies for Radionuclide Removal Not Proposed as BAT in 1991

Greensand Filtration for Radium Removal

Greensand filtration technology consists of a conventional filter box with the traditional

filtration medium replaced by manganese greensand. Manganese greensand has enhanced sorptive

abilities that allow it to remove certain dissolved ions in addition to normal filtration. The water is

pre-treated with potassium permanganate to oxidize dissolved materials into more insoluble

chemical species, which consequently are removed much more efficiently by the greensand filter. 

This is a continuous process, except when interrupted for filter backwashing. Studies indicate

that up to 56% of radium is also removed by greensand filtration. In a pilot plant study, the

radium removal efficiency was improved to 90% by passing the potassium permanganate pretreated water through a detention tank before filtration.

Wastes generated by this process include sludge and supernatant from the filter backwash,

and eventually the greensand media must be disposed of. Radium concentrations in the filter

backwash have been found to range from ca. 65 to 170 pCi/L. Dry weight concentrations of

radium in the greensand medium have been found to vary from ca. 30 to 46 pCi/g at one plant and

from 75 to 250 pCi/g at another (EPA 1994).

Pre-formed Hydrous Manganese Oxide (HMO) Filtration

Although no municipal installations are currently reported in the literature, pilot studies

have been completed and a full scale demonstration is planned (Clifford 1990a). Pilot studies

conducted in Illinois consisted of a pre-formed MnO2 (HMO) dosage of 2.0 mg/L, followed by a

minimum of ten seconds of mixing and post-mixing diatomaceous earth filtration or multi-media

filtration to remove the suspended MnO2 (which contains the sorbed radium). Greater than 96%

removals were consistently achieved over the five day run period (Clifford 1990a). Valentine et

al. (1992) reported average removals of 83%, 79%, and 71% for HMO dosages of 1.0, 0.5, and

0.2 mg/L (as Mn). Where applicable, costs for HMO treatment were projected to be quite low if

filtration is already in place (EPA 1994).

HMO filtration is similar to oxidation/filtration in complexity and operator skill

requirements. Proper dosages must be determined, and if water quality is variable, the dosage

must be re-calibrated. But, since radium is typically a ground water problem, this is less of a

concern for this application. Once the proper dose is determined, dosing is relatively easy,

requires simple equipment, and is fairly inexpensive (NRC 1997). Filters must be backwashed,

which may require intermediate operator skill. Radium containing wastes include HMO sludge,

filter backwash, and sludge supernatant.
75

Coprecipitation of Radium with Barium Sulfate

Addition of a soluble barium salt such as barium chloride to water contaminated with

radium and sulfate will result in the coprecipitation of a highly insoluble radium-containing barium

sulfate sludge. This process has been primarily used for wastewater treatment. Mine wastewater

treatment data indicates that up to 95% of radium is removed by this process. A full-scale

drinking water treatment plant in South Dakota currently uses this process to treat a radium

influent level of 16 pCi/L down to < 1 pCi/L.

Radium containing wastes generated by this process include the barium sulfate precipitate

sludge, filter backwash, and sludge supernatant.

Other Technologies

Other technologies exist which demonstrate promise for radionuclides removal from

drinking water. However, these technologies have not been fully tested in drinking water

treatment, or have been used only in industrial or experimental situations. Examples include

selective sorbents (e.g., acrylic fibers or resins impregnated with manganese dioxide) and nonsodium cation exchangers (e.g., hydrogen ion and calcium ion exchangers) for radium removal. 

POE IX and RO are not currently listed as compliance technologies because of unresolved issues

regarding waste disposal, post-treatment disinfection and corrosion control, and costs, but are

being further considered as small systems compliance technologies. 

Radiation Hazards Associated with Treatment

It should be noted that caution is required when choosing treatment technologies for

radionuclides removal, since many treatments may create radiation hazards through the

concentration of radionuclides within the treatment unit or in wastestreams.

Waste Generation and Disposal Guidelines
1Letter from Dr. R.C. Loehr and Dr. O.F. Nygaard, Science Advisory Board, to W.K.

Reilly, EPA, September 30, 1992.

76

Waste generation

In the 1991 proposed radionuclides rule (EPA 1991a), EPA referenced a 1990 EPA report

entitled “Suggested Guidelines for the Disposal of Naturally Occurring Radionuclides Generated

by Drinking Water Treatment Plants” (EPA 1990). In 1992, the Science Advisory Board (SAB)

reviewed the 1990 guidance and offered several recommendations.1 Among the most important

SAB recommendations which EPA has acted upon were: (1) the Agency should integrate

quantitative information on radioactivity in water treatment wastes within the document to

facilitate decision-making processes; and, (2) the Agency should select and provide rationale for

its occupational protection approach to water treatment plant workers.

In response to SAB’s first recommendation, EPA has developed a spreadsheet program on

floppy disk for computing waste volumes and radioactivity levels for several pertinent water

treatment processes, along with a user’s guide. This should aid in the planning and preengineering stages where managers will need information on the types of waste that may be

generated at new facilities. The spreadsheet program was developed by EPA in August 1993 and

is entitled “Spreadsheet Program to Ascertain Residuals Radionuclide Concentrations”

(SPAARC). The program and user’s guide can be obtained by contacting National Technical

Information Service (NTIS), 5285 Port Royal Rd., Springfield, VA 22161, (703) 487-4650; and

ERIC Clearinghouse, 1929 Kenny Road, Columbus OH 43210, (614) 292-6717. 

In response to SAB’s second recommendation, the occupational guidance has been

revised by the Office of Radiation and Indoor Air. It was determined that the doses that

personnel in water treatment facilities would receive would be substantially lower than the upper

bounds for workers in radiation facilities. In fact, it appears reasonable to keep treatment plant

workers’ doses to well within the levels recommended for the general public (100 mrem/yr). 

Consequently, the guidance recommends 100 mrem/yr as the maximum administrative control

level in water treatment facilities. The document also contains more guidance on seeking state

assistance and/or approval.

EPA has not yet finalized changes to the guidelines based on the SAB recommendation to

reevaluate the criteria for disposal of wastes containing lead-210, a byproduct of using activated

carbon for removal of radon, which is currently unregulated. Since this wastestream does not

affect disposal options for treatments concerning the currently regulated radionuclides, it will not

be discussed further here.

Other revisions include: (1) a new section on mixed (or hazardous) wastes, (2) updates

reflecting U.S. Nuclear Regulatory Commission (NRC) and other federal regulations, and (3) a

new section on suggested wastestream sampling procedures.
77

The report was updated in 1994 with the abovementioned revisions and is entitled

“Suggested Guidelines for Disposal of Drinking Water Treatment Wastes Containing

Radioactivity” (EPA 1994). The updated guidelines are summarized in the following two figures

and table; for details, please refer to the guidelines. Summaries of the guidelines (e.g., EPA 1996)

and relevant background materials (e.g., Reid et al. 1983) may be obtained from EPA or the

literature. 

The table below summarizes estimated waste volumes, radioactivity levels and types of

waste generated by several of the above mentioned drinking water treatment processes. These

estimates are based on standard engineering assumptions and an assumed average daily water

production of 1.0 million gallons per day (MGD).

Characteristics of Selected Water Treatment Wastes (Computed Levels)

Treatment

Method

Raw/

Finished

Conc.

(pCi/L)

Waste Characteristics: 

Vol. and Radioactivity

Types of waste generated

Coagulation/

Filtration

50/10

(Uranium)

U Sludge volume: 10 kgpd

U sludge: 4,000 pCi/g

Iron or alum sludges from the contact and

settling basins and from the filter backwash. 

Supernatant from this sludge is a liquid waste. 

Additional liquid waste is generated when the

sludge is concentrated prior to disposal.

Lime

Softening

25/12.5

(Radium)

Ra Sludge volume: 22

kgpd

Ra sludge: 557 pCi/L

Settling tank sludge, which is precipitated

during the softening process. Filter backwash

(both solids and supernatant) and the sludge

supernatant are other wastes. 

Ion Exchange 25/5

(Radium)

Ra waste flow: 97 kgpd

Ra wastes: 207 pCi/L

Liquid waste containing brine, rinse and

backwash water, and contaminants stripped off

the resin. In addition, the resin itself is a solid

waste containing the contaminant exchanged. 

Reverse

Osmosis

50/15

(U)

U waste flow: 130 kgpd

U wastes: 320 pCi/L

Reject streams which are continuously generated

during the treatment process. 

Figure 1 is a flowchart summarizing the guidelines for disposal of radioactive liquids. The

Clean Water Act requires that dischargers of pollutants to navigable waters obtain a National

Pollutant Discharge Elimination Permit (NPDES), which contains, at a minimum, technologybased effluent limitations. Sufficient flow and channel geometry must be available to prevent a

buildup of radionuclides in the surface water or sediments to within limits set by the regulator. 

Pretreatment regulations prohibit discharge into sanitary sewers that would cause a municipal

wastewater treatment plant to violate a NPDES permit. The U.S. Nuclear Regulatory

Commission (NRC) limits the discharge of wastes containing radioactive materials into sanitary
78

sewers. A drinking water treatment plant owner interested in disposing of wastes containing

radionuclides into an injection well in a Primacy State should consult with the appropriate State

Agency first. State regulations may be more stringent than the Federal requirements and may ban

such practice. The plant owner in other States should consult with the appropriate Underground

Injection Control (UIC) Regional Branch office of the USEPA before deciding to dispose of

wastes containing radionuclides into an injection well. 
79

Figure 1. Disposal of Liquid 

Wastes

Surface

 Waters

Sanitary

 Sewers

Injection

 Wells

Water Treatment 

Liquid Wastes

Ra 226 < 60

Ra 228 < 60

 U < 300 

Ra 226 < 600

Ra 228 < 600

 U < 3000 

Ra 226 < 60

Ra 228 < 60

 U < 300 
80

 Figure 2 is a flowchart summarizing the guidelines for radioactive solids/sludges. Wastes

containing less than 3 pCi/g (dry) of radium and less than 50 ug/g (dry) of uranium may be

disposed of without the need for long-term institutional controls in a municipal landfill if the

wastes are first dewatered and then spread and mixed with other materials when emplaced. 

Solids/sludges containing 3 to 50 pCi/g (dry) of radium should be disposed of with a physical

barrier that would protect against radon release and isolate the wastes, and provided with

institutional controls designed to avoid inappropriate uses of the disposal site. The disposal

method for solids/sludges containing 50 to 2,000 pCi/g (dry) of radium should be determined on a

case by case basis. Recovery of the uranium resource may be considered for solids containing 50

to 500 ug/g (dry) of uranium. Wastes containing more than 2000 pCi/g (dry) of radium or more

than 500 ug/g (dry) of uranium should be disposed of only as permitted by State regulations.
81

Figure 2. Disposal of Solid 

Wastes

Case by 

Case

State

 Regs

Recovery

Water Treatment 

Solid Wastes

50 < Ra < 2000

Ra < 3

 U < 50 3 < Ra < 50 

50 <U < 500 

Ra > 2000

U > 500 

Physical

 Barrier

Municipal 

Landfill
82

Section 6.3: Small Systems Compliance Technologies List

Based on the evaluation of the technologies described in Section 6.2, the following table

lists the Small Systems Compliance Technologies for radionuclides (EPA 1998b).

Table 6.1: Technologies for Radionuclides

Unit Technologies Limitations 

(see footnotes)

Operator Skill

Level Required1

Raw Water Quality Range

& Considerations1

1. Ion Exchange

(IX)

(

a

) Intermediate All ground waters

2. Point of Use

(POU) IX

(

b

) Basic All ground waters

3. Reverse Osmosis

(RO)

(

c

) Advanced Surface waters usually

require pre-filtration

4. POU RO (

b

) Basic May require pre-filtration

5. Lime Softening (

d

) Advanced All waters

6. Green Sand

Filtration

(

e

) Basic

7. Co-precipitation

with Barium Sulfate

(

f

) Intermediate to

Advanced

Ground waters with suitable

water quality

8. Electrodialysis/

Electrodialysis

Reversal

Basic to

Intermediate

All ground waters

9. Pre-formed

Hydrous Manganese

Oxide Filtration

(

g

) Intermediate All ground waters

1

 National Research Council (NRC). Safe Water from Every Tap: Improving Water

Service to Small Communities. National Academy Press. Washington, D.C. 1997.

Limitations Footnotes to Table: Technologies for Radionuclides:

a

 The regeneration solution contains high concentrations of the contaminant ions. 

Disposal options should be carefully considered before choosing this technology.

b

 When POU devices are used for compliance, programs for long-term operation,

maintenance, and monitoring must be provided by water utility to ensure proper performance (see

Section 1.4).
83

c

 Reject water disposal options should be carefully considered before choosing this

technology. See other RO limitations described in Chapter 3 and Section 6.2.

d

 The combination of variable source water quality and the complexity of the chemistry

involved in lime softening may make this technology too complex for small surface water systems.

e

 Removal efficiencies can vary depending on water quality. 

f

 This technology may be very limited in application to small systems. Since the process

requires static mixing, detention basins, and filtration, it is most applicable to systems with

sufficiently high sulfate levels that already have a suitable filtration treatment train in place

g

 This technology is most applicable to small systems that already have filtration in place.

Chapter 1 indicated that EPA would identify affordable compliance technologies for those

existing regulations where small system variances or variance technologies are not prohibited by

the SDWA. There are statutory prohibitions against small system variances for all three

radionuclides, therefore affordability cannot be considered in listing these technologies. The

following table contains the compliance technologies the three radionuclides. The statutory

prohibitions on variance technologies and small system variances are discussed in detail in Chapter

1 of this document and Section IV of the “Small Systems Compliance Technology Lists for

Existing National Primary Drinking Water Regulations” (EPA 1998b).

Table 6.2: Compliance Technologies by System Size Category for Radionuclide 

NPDWRs, Affordability is Not Considered

Compliance Technologies1 for System Size Categories

(Population Served)

Contaminant 25 - 500 501 - 3,300 3,300 - 10,000

combined radium-226

and radium-228

1, 2, 3, 4, 5, 6, 7,

8, 9

1, 2, 3, 4, 5, 6,

7, 8, 9

1, 2, 3, 4, 5, 6, 7,

8, 9

gross alpha particle

activity

3, 4 3, 4 3, 4

total beta particle

activity and photon

activity, average annual

concentration

1, 2, 3, 4 1, 2, 3, 4 1, 2, 3, 4

Note: 1) Numbers correspond to those assigned to technologies found in the

Compliance Technologies Table for Radionuclides.
84

Section 6.4: Emerging Technologies

POE ion exchange and POE reverse osmosis have been determined to require further

evaluation. They have not been listed as compliance technologies since issues regarding ion

exchange regeneration, other maintenance, waste disposal, post-treatment disinfection, posttreatment corrosion control, etc. remain. EPA will evaluate information regarding these

technologies in the near future and will include them in future updates, if deemed appropriate.

References

Benefield, L.D. and Morgan, J.S. “Chemical Precipitation”. AWWA, Water Quality and

Treatment: A Handbook of Community Water Supplies, 4 ed. Pontius, F.W., ed. McGraw-Hill,

Inc. New York. 1990.

Clifford, D.A. “Removal of Radium from Drinking Water”, in Radon, Radium, and Uranium in

Drinking Water, Cothern and Rebers, eds., Lewis Publishers, Chelsea, Michigan, 1990. (Clifford

1990a).

Clifford, D.A. “Ion Exchange and Inorganic Adsorption”. AWWA, Water Quality and

Treatment: A Handbook of Community Water Supplies, 4 ed. Pontius, F.W., ed. McGraw-Hill,

Inc. New York. 1990. (Clifford 1990b).

Hess, C.T., Michel, J., Horton, T.R., Prichard, H.M., and Coniglio, W.A. “The Occurrence of

Radioactivity in Public Water Supplies in the United States”. Health Physics. Vol. 48. No. 5. 

pp. 553 - 586. May 1985.

Lowry, J.D. and Lowry, S.B. “Radionuclides in Drinking Water”. JAWWA. Vol. 80. No. 7. 

pp. 50 - 64. July 1988.

Michel, Jacqueline. “Relationship of Radium and Radon with Geological Formations”. In Radon,

Radium, and Uranium in Drinking Water. Cothern. C.R. and Rebers, P.A., eds. Lewis

Publishers, Inc. Chelsea, MI. 1991.

National Research Council (NRC). Safe Water From Every Tap: Improving Water Service to

Small Communities. National Academy Press. Washington, DC. 1997.

Reid, G.W., Lassovszky, P., and Hathaway, S. “Treatment, Waste Management, and Cost for

Radioactivity in Drinking Water”. USEPA. Committee Issue Papers. National Workshop on

Radioactivity in Drinking Water. May 1983.

Snoeyink, V.L. “Adsorption of Organic Compounds”. AWWA, Water Quality and Treatment: 

A Handbook of Community Water Supplies, 4 ed. Pontius, F.W., ed. McGraw-Hill, Inc. New

York. 1990.
85

Sorg, T.J. “Removal of Uranium from Drinking Water by Conventional Treatment Methods”. In

Radon, Radium, and Uranium in Drinking Water, Cothern and Rebers, eds., Lewis Publishers,

Chelsea, Michigan, 1990.

USEPA. “National Workshop on Radioactivity in Drinking Water: Committee Issue Papers”. 

Committee on Treatment, Waste Management, and Cost. Reid, G.W., Chairman. May 1983.

USEPA. “Suggested Guidelines for the Disposal of Drinking Water Treatment Wastes

Containing Naturally-Occurring Radionuclides”. Office of Drinking Water. July 1990.

USEPA. “National Primary Drinking Water Regulations; Radionuclides; Proposed Rule”. 

Federal Register. Vol. 56, No. 138, p. 33050. July 18, 1991. (EPA 1991a).

USEPA. “Manual of Individual and Non-Public Water Supply Systems”. Office of Water. EPA

570/9-91-004. May 1991. (EPA 1991b).

USEPA. “Technologies and Costs for the Removal of Radionuclides from Potable Water

Supplies”. Prepared by Malcolm Pirnie, Inc. July 1992.

USEPA. “Suggested Guidelines for Disposal of Drinking Water Treatment Wastes Containing

Radioactivity”. OGWDW. Draft, June 1994.

USEPA. “Technology Transfer Handbook: Management of Water Treatment Plant Residuals”. 

Office of Research and Development. EPA/625/R-95/008. April 1996.

USEPA. “Addendum to: Technologies and Costs for the Removal of Radionuclides from

Potable Water Supplies - Draft Report”. Prepared by International Consultants, Inc. Draft, June

1998. (EPA 1998a).

USEPA. “Announcement of Small Systems Compliance Technology Lists for Existing National

Primary Drinking Water Regulations and Findings Concerning Variance Technologies”. Federal

Register. Vol. 63, No. 151, p. 42032. August 6, 1998. (EPA 1998b).

USEPA. “Cost Evaluation of Small System Compliance Options: Point-of-Use and Point-ofEntry Treatment Units”. Prepared by Cadmus Group, Inc. Office of Ground Water and Drinking

Water. Draft. September, 1998. (EPA 1998c).

Valentine, R.L., Kurt, A., Meyer, J., Walsh, D., and Mielke, W. “Radium Removal Using Preformed Hydrous Manganese Dioxides”. Prepared for AWWA Research Foundation (Denver,

CO). 1992.

Zapecza, O.S. and Szabo, Z. “Natural Radioactivity in Ground Water - A Review”. National

Water Summary 1986: Hydrologic Events and Ground Water Quality. Water-Supply Paper
86

2325. p. 50-57. 1986. 
87

7. SMALL SYSTEMS COMPLIANCE TECHNOLOGIES FOR VOLATILE ORGANIC

CONTAMINANTS

Section 7.1: Background

Volatile organic contaminants (VOCs) are composed of a form of a carbon-based

molecule. These compounds dissipate or vaporize easily into air at room temperature. Volatile

organic compounds are usually used as solvents, degreasers, and fumigants. Table 2.11 lists the

National Primary Drinking Water Standards for regulated VOCs. 

VOCs typically are found in greater amounts in groundwater supplies than surface water

because exposure to air helps them dissipate from surface supplies. In groundwater supplies, the

compounds are very mobile and percolate into wells and aquifers. The compounds do not

degrade readily in the groundwater and, as known or suspected carcinogens, are a potentially

serious threat to drinking water safety. 

The technologies considered for the small systems compliance list are commonly used in

the drinking water industry. The BATs for removal of VOCs from drinking water are granular

activated carbon and packed tower aeration. The technologies listed for treatment of VOCs

include diffused aeration, multiple tray aeration, spray aeration, and mechanical aeration. The

other technologies that were considered are listed as emerging technologies due to lack of

performance data. These technologies include powdered activated carbon, gas permeable

membrane aeration, advanced oxidation processes, and point-of-entry technologies.

Point-Of-Use (POU)/Point-Of-Entry (POE) Technologies

POU technologies were not be considered for compliance technologies for VOCs because

POU units are attached only to the tap. Because of the volatile nature of VOCs, the indoor use

of VOC contaminated water can lead to significant human exposure through non-ingestion routes

such as inhalation following volatilization (e.g., while showering) or from direct contact with the

contaminated water. Stakeholders agreed that POU technologies should not be listed for

treatment of VOCs.

 POE technologies were not considered for compliance technologies for VOCs. The

potential for off-gas emissions from POE units is more likely to be a problem because these POE

units would be located near homes. Off-gases may have to be treated using a scrubber, thereby

increasing the complexity and the cost of the aeration units. Also, there is the potential for water

quality deterioration from airborne particulates, oxidized inorganics, instability resulting in

corrosion, and biological growth in the aeration device. Post-treatment disinfection may be

needed after treatment with POE aeration units. 
88

Section 7.2: Evaluation of Technologies

Packed Tower Aeration

 Packed tower aeration has been proven to effectively remove several VOCs from drinking

water. Packed tower aeration is considered a BAT for VOCs removal. The removal efficiency

for VOCs is primarily dependant on the air-to-water ratio, packing height, and available area for

mass transfer. The minimum air-to-water ratio needed to efficiently remove VOCs depends upon

Henry’s Law Coefficient. . The sizes of packing materials determine the available area for mass

transfer. Smaller materials may provide greater areas of mass transfer, however, an increased

pressure drop may occur if the materials are too small. 

Field tests performed in Brewster, NY, Wausau, WI, and Baldwin Park, CA resulted in

>96% removal efficiencies for VOCs such as tetrachloroethylene, trichloroethylene, cisdichloroethylene, and toluene. The influent concentrations were as great as 600 ug/L, using air to

water ratios of ~30:1 and tower heights ranging from 5.5-7.5 m packed with plastic saddles 

(Ram et al. 1990).

Some of the concerns with PTA units are that repressurization equipment and blowers

draw large amounts of electricity, therefore, electrical costs are high. If the unit is not adequately

ventilated, the contaminant removal efficiency will decrease due to mass transfer constraints. 

These systems may be limited for use in residential areas due to fan noise, and depending on the

location these systems may be subject to freezing. 

As with most aeration technologies, air quality regulations in certain localities may prevent

the implementation of these units since large quantities of a contaminant are vented into the air. 

Also, pretreatment for the removal of microorganisms, iron, manganese, and excessive particulate

matter may be needed. Post-treatment disinfection may have to be used to ensure no microbial

growth.

Diffused Aeration

Similar to PTAs, the efficiency of diffused aerators is dependant upon factors including

diffuser type, air-to-water ratio, depth of the water in the contact chamber, detention time, and air

and water temperature. Diffused aeration is considered an accepted technology for treatment of

VOCs (NRC 1997). 

Several performance studies have been conducted using diffused aerators. Studies

conducted in Glen Cove, New York (1984) showed that diffused aerators can efficiently treat

VOCs with influent concentrations ranging from 50-250 mg/l using air-to-water ratios of 15:1

(EPA 1985). The removal rates ranged from 50-90+% for 1,2-dichloropropane, cis-1,2-

dichloroethylene, trans-1,2-dichloroethylene, toluene, ethylbenzene, chlorobenzene, xylenes, odichlorobenzene, and ethylene dibromide. For the most part, the percent removals were higher
89

for VOCs with the higher Henry’s Law Coefficients. 

Diffused aeration units may not be as efficient as other aeration methods because it does

not provide for convective movement of the water thus limiting air-water contact. It is generally

used to adapt existing plant equipment such as storage tanks or basins. The removal efficiency of

these systems depends upon the gas to liquid mass transfer rate. The diffused aerator has less

interfacial area for mass transfer than the PTA; a longer contact time may be needed to achieve

sufficient removal of the VOCs. On the other hand, increased basin depth, contact basin

geometry, and turbines to reduce the air bubble size and increase bubble holdup can improve gas

transfer, thus improving the efficiency of the system. 

With diffused aerators, increased energy costs may be incurred due to post-treatment

repressurization. Also, post-treatment disinfection may have to be used to ensure no microbial

growth. 

Multiple Staged Bubble Aerators (MSBA)

MSBAs are variations to the traditional diffused aerator. These systems are typically

packaged plant commercial units that are more efficient than the traditional diffused aerator. 

MSBAs further reduce energy costs by optimizing the air to water ratio, contact time, and mass

transfer area. 

MSBA units are highly efficient, however the efficiency depends upon the air-to-waterratio. These units have the same limitations as the diffused aerator. 

Multiple Tray Aeration

Multiple tray aeration is considered a conventional technology for the removal of VOCs

from drinking water (NRC 1997). Multiple tray aerators consist of a series of trays with slats,

perforations, or wire mesh bottoms over which water falls and eventually collects at the base of

the unit. The thin film of water formed as the water flows over the media provides a large surface

area for mass transfer of the VOCs from water to air. Coke, coal, stone, or ceramic balls can be

placed in the trays to increase efficiency. 

Multiple tray aeration has been effective in removing 20 to 90 percent of VOCs from

drinking water (Robeck and Love 1983, Hess et al 1981). In studies performed in Smyrna,

Delaware reported removal efficiencies ranging from 50 to 90% of trichloroethylene and other

VOCs. In Camden, New Jersey (1979) conducted studies to determine the efficiency of the

aeration unit by testing trichloroethylene, tetrachloroethylene, carbon tetrachloride, and 1,2-

dichlorethane (EPA 1985). Preliminary results indicated that the aerator efficiency could be

improved by increasing the air-to-water ratio. 

The performance of tray aerators will be impaired in a poorly ventilated building. 
90

Artificial ventilation will be a requirement and may be provided by enclosure and provision of a

forced draft. The addition of the forced draft may increase the cost of the unit. Post-treatment

disinfection may be necessary because slime and algae growth can be a problem. Chemicals such

as copper sulfate or chlorine may have to be used to control the growth.

Shallow Tray Aeration (STA)

STAs involve the use of shallow trays, and are more efficient to multiple tray aerators. 

STAs increase the available area of mass transfer; thereby increasing the removal efficiency of

most VOCs. However, because of the high air-to-water ratio (100-900 m3/m3), greater energy

costs may be incurred. 

Spray Aeration

Spray aeration is an accepted technology where the contaminated water is sprayed

through nozzles. The small droplets produced expose a large interfacial surface area through

which VOCs can migrate from the liquid (water) phase to the gaseous (air) phase. Spray aerators

have been used to effectively treat VOCs (Wood 1982). Case studies (Florida) demonstrated that

> 99% of VOCs were removed from an influent total VOC concentration between 100-200 mg/l. 

The primary VOCs treated were 1,1-dichloroethane, and trichloroethylene, tetrachloroethylene,

vinyl chloride, and 1,1,1-trichloroethane (EPA 1985).

Although spray aerators are capable of achieving efficient removal of VOCs, this type of

aerator is for use only when low removal levels of VOCs are needed to reach an MCL. These

systems may not be as energy efficient as other aeration methods. Also, the spray aerator needs a

large operational area, which will increase building construction costs and may also increase

operating problems during cold weather when the temperature is below freezing. 

Mechanical Aeration

 Mechanical aerators are considered accepted technologies for the removal of VOCs from

drinking water (NRC 1997). Mechanical aerators introduce air into the water by rapidly agitating

the water surface with a mechanical mixer. They are not as efficient as other aeration systems at

removing VOCS. The contacting system between the air and water is not as effective for

volatilizing the contaminants. These systems often require large basins, long residence times, and

high energy inputs. However, these systems can be cost-effective because they are adaptable to

existing basins, and are often installed as a system retrofit. 

Mechanical aerators will probably not achieve VOC removals that are sufficient to attain

desired water qualities if influent levels are extremely high. Mechanical aerators should be used

when only low level removals are needed to reach the MCL.
91

Granular Activated Carbon

For the purposes of determining best available technologies (BATs) for removing

SOCs from drinking water, the Safe Drinking Water Act (§ 1412.b.4.D) explicitly states that any

BAT listed by EPA must be at least as effective as granular activated carbon (GAC). The various

BATs listed for the Phase II and V SOCs are GAC, packed tower aeration (PTA), and, in the case

of gylphosate, oxidation by chlorination or ozonation (EPA, 1991a, 1991b, and 1992b). 

However, for the purposes of determining the list of compliance technologies for small systems of

a given size category, the Safe Drinking Water Act (§ 1412.b.4.E) states that any listed

technology must be affordable and able to achieve compliance with the maximum contaminant

level. To emphasize the point, the listed small systems compliance technologies do not have to be

as effective as GAC in controlling SOCs.

Granular activated carbon (GAC) is most often used to treat VOCs in drinking water. 

GAC is listed as a BAT for removal of VOCs. It is packed into columns through which the raw

water flows. Packing the carbon in columns allows more complete contact between the water and

activated carbon, greater adsorption efficiency, and greater process control than is possible for

powdered activated carbon (Snoeyink 1990). In many cases GAC has been used to treat several

VOCs to the maximum contaminant levels with influent concentrations ranging up to 500 mg/l

(Ram et al. 1990). 

Although the adsorption characteristics of individual VOCs vary, they are amenable to

removal by activated carbon adsorption for a period of time or gallons of water treated. The

amount of water treated depends on the influent contaminant concentration, the amount of carbon

in the treatment unit, and the time the contaminant is in contact with the carbon. The removal

efficiency of the carbon system will deteriorate with use, and eventually breakthrough will occur. 

Section 7.3: Small System Compliance Technologies List

Table 7.1 contains the technologies that have been identified as compliance technologies

for at least one VOC. The table contains the same structure as other tables with a list of

limitations that are contained in the footnotes and operator skill level and raw water quality issues.

Table 7.1: Technologies for VOCs

Unit technology Limitations

(see footnotes)

Operator Skill

Level Required1 Raw Water Quality Range1

1. Packed Tower

Aeration (PTA)

(

a

) Intermediate All ground waters 

2. Diffused Aeration (

a. b) Basic All ground waters

3. Multi-Stage

Bubble Aerators

(

a, c) Basic All ground waters
92

4. Tray Aeration (

a, d) Basic All ground waters

5. Shallow Tray

Aeration 

(

a, e) Basic All ground waters

6. Spray Aeration (

a, f) Basic All ground waters

7. Mechanical

Aeration

(

a, g) Basic All ground waters

8. Granular Activated

Carbon (GAC)

(

h

) Basic All ground waters

1

 National Research Council (NRC). Safe Water from Every Tap: Improving Water Service to

Small Communities. National Academy Press. Washington, DC. 1997

Limitations Footnotes to the Technology Tables for VOCs

a

 Pretreatment for the removal of microorganisms, iron, manganese, and excessive

particulate matter may be needed. Post-treatment disinfection may have to be used.

b

 May not be as efficient as other aeration methods because it does not provide for

convective movement of the water thus limiting air-water contact. It is generally used only to

adapt existing plant equipment.

c

 This units are highly efficient, however the efficiency depends upon the air-to-water

ratio. 

d

 Costs may increase if a forced draft is used. Slime and algae growth can be a problem,

but can be controlled with chemicals such a copper sulfate or chlorine.

e These units require high air/water ratios (100-900 m3

/m3)

 

f

 For use only when a low removal levels are needed to reach an MCL because these

systems may not be as energy efficient as other aeration methods because of the contacting

system.

g

 For use only when a low removal levels are needed to reach an MCL because these

systems may not be as energy efficient as other aeration methods because of the contacting

system. The units often require large basins, long residence times, and high energy inputs which

may increase costs. 

h

 See the SOCs compliance technology table for limitation regarding these technologies.

Chapter 1 indicated that EPA would identify affordable compliance technologies for those

existing regulations where small system variances or variance technologies are not prohibited by

the SDWA. There are statutory prohibitions against small system variances or variance

technologies for 2 of the 21 VOCs. Table 7.2 contains the compliance technologies for the 19

VOCs where affordability was considered. Affordability only plays a role in removing options in

the smallest size category. The technology costs are based on treatment of all of the water. The
93

technologies that did not meet the affordability criteria in the smallest size category are also

identified in the next column called “other compliance technologies.” These technologies may be

affordable if the concentration of the contaminant is low enough that a portion of the influent

stream can be treated and blended with an untreated portion to still meet the MCL. This blending

would reduce both the capital and operating and maintenance costs of the process. Systems and

States should consider these options under those circumstances. Table 7.3 contains the

compliance technologies for the remaining two VOCs where affordability was not considered due

to statutory prohibitions (EPA 1998). 

Table 7.2: Compliance Technologies by System Size Category for those VOC NPDWRs

where Affordability is Considered

Volatile Organic

Contaminant

Compliance Technologies for System Size Categories

(Population Served)

25 - 500 

(afford)

25 - 500

(other)

501 - 3,300

(afford)

3,301 - 10,000

(afford)

Benzene 1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Carbon

Tetrachloride

1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Chlorobenzene 1, 2, 3, 4, 5, 6, 7 8 1, 2, 3, 4, 5, 6,

7, 8

1, 2, 3, 4, 5, 6,

7, 8

cis-1,2-

Dichloroethylene

1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

1, 2 -

Dichloroethane

1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

1,1-

Dichloroethylene

1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Dichloromethane 1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

1, 2 -

Dichloropropane

1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Ethylbenzene 1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

o-Dichlorobenzene 1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

p-Dichlorobenzene 1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Tetrachloroethylene 1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8
94

Toluene 1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

trans-1, 2-

Dichloroethylene

1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

1, 2, 4-

Trichlorobenzene

1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

1, 1, 1-

Trichloroethane

1, 2, 3, 4, 5, 6 8 1, 2, 3, 4, 5, 6, 8 1, 2, 3, 4, 5, 6, 8

1, 1, 2-

Trichloroethane

1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Trichloroethylene 1, 2, 3, 4, 5, 6, 7 8 1, 2, 3, 4, 5, 6,

7, 8

1, 2, 3, 4, 5, 6,

7, 8

Xylenes (total) 1, 2, 3, 4, 5 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Table 7.3: Compliance Technologies by System Size Category for those VOC NPDWRs

where Affordability is Not Considered

Volatile Organic

Contaminant

Compliance Technologies for System Size Categories

(Population Served)

25 - 500 501 - 3,300 3,301 - 10,000

Styrene 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Vinyl Chloride 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8 1, 2, 3, 4, 5, 8

Section 7.4: Emerging Technologies

Powdered Activated Carbon

PAC is generally less than 50 mm in diameter and is added to the raw water line or to a

mixing basin. In order to treat VOCs effectively, PAC must contact all of the incoming water. 

Following adsorption, the carbon containing the organic compounds is settled or filter from the

water and disposed of with the plant sludge. In some cases no modifications other than the

addition of PAC dosing equipment need to be made to an existing plant because the normal

contact time used for other elements of water treatment is sufficient for contaminant adsorption

onto PAC. However, the contact time has to be determined prior to the design of the process.

The dose of PAC added to the system has to be adapted to deal with varying source water quality. 
95

The removal efficiencies of VOCs depend upon sufficient contact time, proper mixing,

effects of chlorine and other chemicals, and the removal method of spent PAC. However, PAC

requires coagulation/sedimentation facilities such as feed equipment, mixing chambers, clarifiers,

and filtration. If these facilities are in place, PAC is simple to employ on a small scale. PAC is

considered an emerging technology because long-term performance for treatment of VOCs has

not been evaluated. 

Gas-Permeable Membrane Aeration

Gas-permeable membrane aeration is an emerging technology (NRC 1997). In gas

permeable membrane systems, water flows through the interior of hollow membrane tubes

constructed of a material that allows gases but not liquids to pass through. The large surface area

for air-water contact allows for removal of VOCs (Semmens et al. 1989). Some studies have

shown that when compared with other aeration systems, gas-permeable membrane systems offer

the highest removal efficiencies of all contacting devices (NRC 1997). However, this technology

has to be considered emerging because long-term performance has not been evaluated.

Advanced Oxidation Processes

Advanced oxidation is considered an emerging technology. The majority of advanced

oxidation research as focused on treatment of chlorinated organics present in groundwater. 

Advanced oxidation processes can oxidize some volatile organic compounds such as

trichloroethylene and tetrachloroethylene to completion. An added benefit is that advanced

oxidation processes may used for disinfection. However, AOPs have only been used in one

drinking water system on the pilot level. Therefore, this technology is considered emerging

because long-term performance has not been evaluated.

References

Hess, A.F., Dysken, J.E., and Cline, G.C. “Case Studies Involving Removal of Organic Chemical

Compounds from Groundwater”. Presented at the Preconference Seminar Concerning Organic

Chemical Contaminants in Ground Water at the 1981 Annual Conference of the American Water

Works Association. St. Louis, Missouri. June 7-11, 1981.

National Research Council (NRC). Safe Water From Every Tap: Improving Water Service to

Small Communities. Committee on Small Water Supply. National Academy Press, Washington,

DC. 1997.

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

Compounds in Water Supplies. Lewis Publishers. pp. 363-391. 1990. 

Robeck, G.G. and Love, O.T. “Removal of Volatile Organic Contaminants from 

Ground Water”. Presented at the International Conference on Ground Water Contamination from
96

Organo-Chlorine Compounds of Industrial Origin. Milano, Italy. January 1983.

Semmens, M.J., Qin, R., and Zander, A.K. “Using Microporous Hollow-Fiber Membranes to

Separate VOCs from Water”. Journal of the American Water Works Association. 81(4):162-167. 

1989.

Snoeyink, V. L. “Adsorption of organic compounds”. Chapter 13 in Water Quality and

Treatment: A Handbook of Community Water Supplies, Fourth Edition. Denver: American

Water Works Association. 1990.

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

Water Supplies.” Prepared by Environmental Science and Engineering. May 1985.

USEPA. “National Primary Drinking Water Regulations; Final Rule.” Federal Register. Vol. 56,

No. 20, p. 3526. January 30, 1991. (EPA 1991a)

USEPA. “National Primary Drinking Water Regulations: Final Rule”. Federal Register. Vol.

56, No. 126, p. 30266. July 1, 1991. (EPA 1991b)

USEPA. “National Primary Drinking Water Regulations: Synthetic Organic Chemicals and

Inorganic Chemicals; Final Rule”. Federal Register. Vol. 57, No. 138, p. 31776. July 17, 1992.

USEPA. “Variance Technology Findings for Contaminants Regulated Before 1996". EPA 815-

R-98-003. Office of Water. September 1998. 

Wood, P. R. Removal of Volatile Organic Compounds from Water by Spray Aeration. Paper

presented at Seminar of Small Water Systems Technology. US Environmental Protection

Agency. Cincinnati, Ohio. April 1982.
97

8. SMALL SYSTEMS COMPLIANCE TECHNOLOGIES FOR OTHER SYNTHETIC

ORGANIC CONTAMINANTS

Section 8.1: Background

The Phase II and V SOCs are a diverse group of chemicals in terms of properties,

although most of them are used as pesticides and find their way into drinking water through this

common use. They vary widely with regard to chemical structure, make-up, and charge, which

causes them to exhibit a range of environmental behaviors. For the same reasons, the removal of

these compounds in drinking water treatment processes also varies. For example, Miltner et al.

(1989) demonstrated that water softening removed a significant percentage of carbofuran, but for

the other seven pesticides studied, softening was not effective. Miltner et al. (1989) also

demonstrated that clarification, filtration, and chlorination were not effective for any of the eight

pesticides studied. In general, less conventional treatment like activated carbon, membranes, air

stripping, ozonation, or advanced oxidation is required (Clark et al., 1990).

The physical and chemical properties (Schwarzenbach et al. 1993, Kamrin 1997) that

determine the behavior of SOCs in the environment and during treatment processes include

volatility (tendency to evaporate), water solubility, and resistance to chemical degradation. 

Volatile SOCs can enter the atmosphere and, if chemically persistent, travel great distances before

being deposited. Modes of atmospheric deposition of pollutants include dry-fall, or deposition of

the pollutant directly from the air or when attached to settling dust, etc. and wet-fall, or

deposition of the pollutant through rainfall, snow, or other precipitation (Schnoor 1996). 

Through atmospheric deposition, contaminants can reach surface waters and soils that are

otherwise pristine. For example, waters and soils that do not receive agricultural run-off can

become contaminated with pesticides because of atmospheric deposition. Water solubility is

another very important property that affects the environmental mobility and treatability of SOCs. 

If an SOC is very water soluble, it can be readily transported in run-off (Larson et al. 1997),

through ground water (Barbash and Resek 1996), and is more difficult to remove with granular

activated carbon (GAC) (Snoeyink 1990, p. 786). If the SOC is relatively insoluble, it tends to

sorb to the soil matrix in the case of ground water. In the case of surface water, insoluble SOCs

may sorb to suspended particles, some of which will settle out, or directly to the sediment matrix. 

In general, the less soluble an SOC, the greater its tendency to sorb to GAC (Snoeyink 1990,

Schwarzenbach et al. 1993).

Ten technologies for the removal of the Phase II and Phase V synthetic organic chemicals

(SOCs) have been evaluated as potential compliance technologies for small systems: GAC, PAC,

aeration, oxidation, advanced oxidation, ultrafiltration, nanofiltration, and reverse osmosis. For

the purposes of determining best available technologies (BATs) for removing SOCs from drinking

water, the Safe Drinking Water Act (§1412.b.4.D) explicitly states that any BAT listed by EPA

must be at least as effective as granular activated carbon (GAC). The various BATs listed for the

Phase II and V SOCs are GAC, packed tower aeration (PTA), and, in the case of gylphosate,

oxidation by chlorination or ozonation (EPA 1991a, 1991b and 1992a). However, for the
98

purposes of determining the list of compliance technologies for small systems of a given size

category, the Safe Drinking Water Act ( (§1412.b.4.E) states that any listed technology must be

affordable and able to achieve compliance with the maximum contaminant level. To emphasize

the point, the listed small systems compliance technologies do not have to be as effective as GAC

in controlling SOCs. 

Section 8.2: Evaluation of Technologies

Granular activated carbon (GAC) and powdered activated carbon (PAC)

The activated carbon processes are described in Chapter 3 of this document and in detail

in terms of SOCs removal in the “technologies and costs” regulatory support documents for the

Phase II and Phase V final rules (USEPA 1990 and 1992b). Based on past research and pilot

scale work, GAC is considered to be the best available broad spectrum removal process for

SOCs. PAC, when applied properly, works well for many of the SOCs. However, both

technologies exhibit a wide range of removal efficiencies, depending upon site specific conditions

and the identify of the SOC in question. Site specific conditions that may affect percent removal

include the presence of other “competing” contaminants, including natural organic matter, biofilm

development on the carbon surface, temperature, pH, variable influent concentrations (leading to

desorption), activated carbon particle size and specific surface area, and hydraulic loading rate

(AWWA - ASCE 1998). Due to the potential for variability in removal efficiencies, some degree

of source water-specific testing is needed to ensure adequate removal. In cases in which the raw

water has a low concentration of natural organic matter, such as most ground waters, inexpensive

bench-scale tests may be adequate to predict performance (NRC 1997). For surface water

systems, pilot tests may be required.

Discussions of models to predict full-scale performance that also discuss basic activated

carbon principles in the context of drinking water regulations are found in numerous sources (e.g.,

Sontheimer 1988, Snoeyink 1990, Speth 1990, Speth and Adams 1993). Design parameters are

discussed in a variety of text books (e.g., AWWA - ASCE 1998), journal articles (e.g., AWWA

1989), and EPA regulatory support documents (USEPA 1990 and 1992b).

POE and POU GAC are both potentially useful for small systems applications. However,

issues regarding cost-effectiveness and backwash waste disposal for POE GAC preclude its being

listed this year. POE GAC will continue to be evaluated as an emerging technology. POU GAC

is currently commonly used to remove taste and odor compounds and other organic contaminants

in a non-regulatory manner and is a potentially cost-effective way for small systems to remove

regulated SOCs. Regulatory issues regarding POU use were described in Chapters 1 and 3. The

performance and GAC bed life depend on the amount of GAC used in the device, the contact

time, and the nature of the contaminants being removed. A proper monitoring and unit

replacement schedule must be maintained to ensure that good removals are maintained (NRC

1997).
99

Packed Tower Aeration (PTA)

 Packed tower aeration (PTA) is BAT for several of the more volatile Phase II and Phase

V SOCs, namely dibromochloropropane, ethylene dibromide, di(2-ethylhexyl) adipate, and

hexachlorocyclopentadiene. The PTA process is described in Chapter 3. The issues and caveats

that apply to PTA treatment for VOCs removal, as described in chapter 7.

Other Aeration Technologies

Chapters 3 and 7 describe other aeration technologies relevant to the removal of the

volatile Phase II and V SOCs.

Oxidation

Oxidation by chlorination or ozonation is BAT for glyphosate. Other oxidation processes

are potentially applicable, but sufficient published data is not available. Issues and caveats

regarding chlorination and ozonation use by small drinking water systems are described elsewhere

(EPA 1997, EPA 1998b).

Section 8.3: Small Systems Compliance Technologies List

Based on the evaluation of the technologies described in Section 8.2, the following table

lists the Small Systems Compliance Technologies for at least one Phase II or V SOC (EPA

1998a). The table contains the same structure as other tables with a list of limitations that are

contained in the footnotes and operator skill level and raw water quality issues.

Table 8.1: Technologies for SOCs

Unit Technology Limitations

(see footnotes)

Operator Skill Level

Required1

Raw Water Quality Range

 and Considerations1

1. Granular

Activated Carbon

(GAC)

Basic Surface water may require

pre-filtration

2. Point of Use

(POU) GAC

(

a

) Basic Surface water may require

pre-filtration

3. Powdered

Activated Carbon

(

b

) Intermediate All waters

4. Chlorination (

c

) Basic Better with high quality

water
100

5. Ozonation (

c

) Basic Better with high quality

waters

6. Packed Tower

Aeration (PTA)

(

d

) Intermediate All ground waters 

7. Diffused

Aeration

(

d, e) Basic All ground waters

8. Multi-Stage

Bubble Aerators

(

d, f) Basic All ground waters

9. Tray Aeration (

d, g) Basic All ground waters

10. Shallow Tray

Aeration 

(

d, f) Basic All ground waters

1

 National Research Council (NRC). Safe Water from Every Tap: Improving Water

Service to Small Communities. National Academy Press. Washington, DC. 1997.

Limitations footnotes for Table 10: Technologies for SOCs

a

 When POU devices are used for compliance, programs for long-term operation,

maintenance, and monitoring must be provided by water utility to ensure proper performance.

b

 Most applicable to small systems that already have a process train including basins

mixing, precipitation or sedimentation, and filtration. Site specific design should be based on

studies conducted on the system’s particular water.

c See the SWTR compliance technology tables for limitations associated with this

technology.

d

 Pretreatment for the removal of microorganisms, iron, manganese, and excessive

particulate matter may be needed. Post-treatment disinfection may have to be used.

e

 May not be as efficient as other aeration methods because it does not provide for

convective movement of the water thus limiting air-water contact. It is generally used only to

adapt existing plant equipment.

f

 This units are highly efficient, however the efficiency depends upon the air-to-water ratio.

g

 Costs may increase if a forced draft is used.

 Chapter 1 indicated that EPA would identify affordable compliance technologies for those

existing regulations where small system variances or variance technologies are not prohibited by

the SDWA. There are statutory prohibitions against small system variances or variance

technologies for 14 of the 32 SOCs. The following table contains the compliance technologies

for the 18 SOCs where affordability was considered. Affordability only plays a role in removing

options in the smallest size category. The technology costs are based on treatment of all of the

water. The technologies that did not meet the affordability criteria in the smallest size category

are also identified in the next column called “other compliance technologies.” These technologies
1

 This affordability determination assumes that the small system already has the

appropriate treatment train in place for mixing, contact, and filtration. 

101

may be affordable if the concentration of the contaminant is low enough that a portion of the

influent stream can be treated and blended with an untreated portion to still meet the MCL. This

blending would reduce both the capital and operating and maintenance costs of the process. 

Systems and States should consider these options under those circumstances. The subsequent

table contains the compliance technologies for the remaining fourteen SOCs where affordability

was not considered due to statutory prohibitions. The statutory prohibitions on variance

technologies and small system variances are discussed in detail in the Variance Technologies

Findings Document (EPA 1998c).

Table 8.2: Compliance Technologies by System Size Category for those SOC NPDWRs

where Affordability is Considered

Contaminant Compliance Technologies for System Size Categories

(Population Served)

25 - 500 

(afford)

25 - 500

(other)

501 - 3,300

(afford)

3,301 - 10,000

(afford)

Alachlor 2, 311 1, 2, 3 1, 2, 3

Atrazine 2, 3 1 1, 2, 3 1, 2, 3

Carbofuran 2, 3 1 1, 2, 3 1, 2, 3

Dibromochloropropane 2, 3, 6, 7, 8,

9, 10

1 1, 2, 3, 6, 7,

8, 9, 10

1, 2, 3, 6, 7, 8, 9, 10

2,4-D 2, 3 1 1, 2, 3 1, 2, 3

Lindane 2, 3 1 1, 2, 3 1, 2, 3

Methoxychlor 2, 3 1 1, 2, 3 1, 2, 3

Pentachlorophenol 2, 3 1 1, 2, 3 1, 2, 3

Dalapon 2, 3 1 1, 2, 3 1, 2, 3

Di(2-ethylhexyl)

adipate

2, 3, 6, 7, 8,

9, 10

1 1, 2, 3, 6, 7,

8, 9, 10

1, 2, 3, 6, 7, 8, 9, 10

Di(2-ethylhexyl)

phthalate

2, 3 1 1, 2, 3 1, 2, 3

Dinoseb 2, 3 1 1, 2, 3 1, 2, 3
Table 8.2: Compliance Technologies by System Size Category for those SOC NPDWRs

where Affordability is Considered

Contaminant Compliance Technologies for System Size Categories

(Population Served)

25 - 500 

(afford)

25 - 500

(other)

501 - 3,300

(afford)

3,301 - 10,000

(afford)

102

Diquat 2, 3 1 1, 2, 3 1, 2, 3

Endothall 2, 3 1 1, 2, 3 1, 2, 3

Glyphosate 4, 5 4, 5 4, 5

Hexachlorocyclopentad

iene

2, 3, 6, 7, 8,

9, 10

1 1, 2, 3, 6, 7,

8, 9, 10

1, 2, 3, 6, 7, 8, 9, 10

Picloram 2, 3 1 1, 2, 3 1, 2, 3

Simazine 2, 3 1 1, 2, 3 1, 2, 3

Table 8.3: Compliance Technologies by System Size Category for those SOC

NPDWRs where Affordability is Not Considered

Contaminant

Compliance Technologies for System Size Categories

(Population Served)

25 - 500 501 - 3,300 3,300 - 10,000

Chlordane 1, 2, 3 1, 2, 3 1, 2, 3

Ethylene Dibromide 1, 2, 3, 6, 7, 8,

9, 10

1, 2, 3, 6, 7, 8,

9, 10

1, 2, 3, 6, 7, 8,

9, 10

Heptachlor 1, 2, 3 1, 2, 3 1, 2, 3

Heptachlor Epoxide 1, 2, 3 1, 2, 3 1, 2, 3

Polychlorinated

Biphenyls

1, 2, 3 1, 2, 3 1, 2, 3

Toxaphene 1, 2, 3 1, 2, 3 1, 2, 3

2,4,5-TP 1, 2, 3 1, 2, 3 1, 2, 3
Table 8.3: Compliance Technologies by System Size Category for those SOC

NPDWRs where Affordability is Not Considered

Contaminant

Compliance Technologies for System Size Categories

(Population Served)

25 - 500 501 - 3,300 3,300 - 10,000

103

Benzo(a)pyrene 1, 2, 3 1, 2, 3 1, 2, 3

Endrin 1, 2, 3 1, 2, 3 1, 2, 3

Hexachlorobenzene 1, 2, 3 1, 2, 3 1, 2, 3

Oxamyl 1, 2, 3 1, 2, 3 1, 2, 3

2,3,7,8-TCDD

(Dioxin)

1, 2, 3 1, 2, 3 1, 2, 3

Acrylamide N/A (treatment

technique)

N/A (treatment

technique)

N/A (treatment

technique)

Epichlorohydrin N/A N/A N/A

Section 8.4: Emerging Technologies

Membrane Processes

Reverse osmosis, including POE and POU RO, and nanofiltration show promise as

compliance technologies for SOCs. However, efficient rejection of a SOC depends upon the

specific membrane (surface charge, pore size and distribution, etc.), the source water quality, and

the environmental conditions of the test (AWWA - ASCE 1998). Very importantly, rejection of

SOCs must be confirmed through bench or pilot-scale testing. Because data on SOCs removal via

membranes are limited and because there are so many variables that affect membrane removal

efficiencies for SOCs, EPA will evaluate them further before listing any membrane technologies as

small systems compliance technologies.

POE GAC

As described above, POE GAC shows promise and will continue to be evaluated as a

potential small systems compliance technology.

References

AWWA. Organics Removal by Granular Activated Carbon. American Water Works Association. 

Denver, CO. 1989.
104

AWWA - ASCE. Water Treatment Plant Design, 3rd ed. American Water Works Association and

the American Society of Civil Engineers. McGraw-Hill, Inc. New York. 1998.

Barbash, J.E. and Resek, E.A. Pesticides in Ground Water: Distribution, Trends, and Governing

Factors. Vol. II of the Series, Pesticides in the Hydrologic System. USGS. Ann Arbor Press, Inc. 

1996.

Conlon, W. J. Membrane Processes. AWWA, Water Quality and Treatment: A Handbook of

Community Water Supplies, 4th ed.. Pontius, F., ed. McGraw-Hill, Inc. New York. 1990.

Jacangelo, J.G. The Development of Membrane Technology. International Report (IR 3) Water

Supply: Review Journal of the International Water Supply Association. Vol. 9, Numbers 3/4. 

1991.

Kamrin, M.A. Pesticide Profiles: Toxicity, Environmental Impact, and Fate. Lewis Publishers. 

New York. 1997.

Larson, S.J., Capel, P.D., and Majewski, M.S. Pesticides in Surface Waters: Distribution, Trends,

and Governing Factors. Vol. III of the Series, Pesticides in the Hydrologic System. USGS. Ann

Arbor Press, Inc. 1997.

National Research Council. Safe Water From Every Tap: Improving Water Service to Small

Communities. National Academy Press. Washington, D.C. 1997.

Schnoor, J.L. Environmental Modeling: Fate and Transport of Pollutants in Water, Air, and Soil. 

John Wiley & Sons, Inc. New York. p. 547. 1996.

Schwarzenbach, R. P., Gschwend, P., and Imboden, D. Environmental Organic Chemistry. J.

Wiley & Sons, Inc. New York. 1993.

Sontheimer, H., Crittendon, J. C., and Summers, R. S. Activated Carbon for Water Treatment.

DVGW-Forschungsstelle, 2nd ed. Karlsruhe, FRG. 1988.

Snoeyink, V. L. “Adsorption of Organic Compounds”. AWWA, Water Quality and Treatment: 

A Handbook of Community Water Supplies, 4th ed.. Pontius, F., ed. McGraw-Hill, Inc. New

York. 1990.

Speth, T. F. “Removal of VOCs from Drinking Water by Adsorption”. Significance and

Treatment of Volatile Organic Compounds in Water Supplies. N. Ram, K. Cantor, and R.

Christman, eds. Lewis Publishers, Inc. Ann Arbor, MI. 1990.

Speth, T. F. and Adams, J. Q. “GAC and Air Stripping Design Support for the Safe Drinking

Water Act”. Strategies and Technologies for Meeting SDWA Requirements. R. Clark and R.
105

Christman, eds. Lewis Publishers, Inc. Ann Arbor, MI. 1993. 

USEPA. “Technologies and Costs for the Removal of Synthetic Organic Chemicals from Potable

Water Supplies”. Office of Drinking Water. September, 1990.

USEPA. “National Primary Drinking Water Regulations; Final Rule.” Federal Register. Vol.

565, No. 20, p. 3526. January 30, 1991. (EPA 1991a)

USEPA. “National Primary Drinking Water Regulations; Final Rule”. Federal Register. Vol. 56,

No. 126, p. 30266. July 1, 1991. (EPA 1991b)

USEPA. “National Primary Drinking Water Regulations; Synthetic Organic Chemicals and

Inorganic Chemicals; Final Rule”. Federal Register. Vol. 57, No. 138, p. 31776. July 17, 1992. 

(EPA 1992a)

USEPA. “Technologies and Costs for the Removal of Phase V Synthetic Organic Chemicals from

Potable Water Supplies”. Prepared by Malcolm Pirnie, Inc.. January, 1992. (EPA 1992b)

USEPA. “Small System Compliance Technology List for the Surface Water Treatment Rule”. 

EPA 815-R-97-002. Office of Water. August, 1997.

USEPA. “Announcement of Small Systems Compliance Technology Lists for Existing National

Primary Drinking Water Regulations and Findings Concerning Variance Technologies”. Federal

Register. Vol. 63, No. 151, p. 42032. August 6, 1998. (EPA 1998a).

USEPA. “Small Systems Compliance Technology List for the Surface Water Treatment Rule and

the Total Coliform Rule”. EPA 815-R-98-001. September, 1998. (EPA 1998b).

USEPA. “Variance Technology Findings for Contaminants Regulated before 1996". EPA 815-R98-003. Washington, D.C.: EPA Office of Water. September 1998. (EPA 1998c).

Weber, W. J., Jr. Physicochemical Processes for Water Quality Control. Wiley - Interscience. 

New York. 1972.

Wiesner, M. R., Hackney, J., Sethi, S., Jacaneglo, G., and Laine, J. M. “Cost Estimates for

Membrane Filtration and Conventional Treatment”. Journal of the American Water Works

Association. 86(12). pp. 33 - 41. 1994.
106

APPENDIX A

RELEVANT PARTS OF SECTIONS 1412 OF THE REVISED (1996) SDWA 
107

SEC. 105. TREATMENT TECHNOLOGIES FOR SMALL SYSTEMS.

 Section 1412(b)(4)(E) (42 U.S.C. 300g-1(b)(4)(E)) is amended by 

adding at the end the following:

 ``(ii) List of technologies for small 

 systems.--The Administrator shall include in the 

 list any technology, treatment technique, or other 

 means that is affordable, as determined by the 

 Administrator in consultation with the States, for 

 small public water systems serving--

 ``(I) a population of 10,000 or 

 fewer but more than 3,300;

 ``(II) a population of 3,300 or 

 fewer but more than 500; and

 ``(III) a population of 500 or fewer 

 but more than 25;

 and that achieves compliance with the maximum 

 contaminant level or treatment technique, 

 including packaged or modular systems and point-

 of-entry or point-of-use treatment units. Point-

 of-entry and point-of-use treatment units shall be 

 owned, controlled and maintained by the public 

 water system or by a person under contract with 

 the public water system to ensure proper operation 

 and maintenance and compliance with the maximum 

 contaminant level or treatment technique and 

 equipped with mechanical warnings to ensure that 

 customers are automatically notified of 

 operational problems. The Administrator shall not 

 include in the list any point-of-use treatment 

 technology, treatment technique, or other means to 

 achieve compliance with a maximum contaminant 

 level or treatment technique requirement for a 

 microbial contaminant (or an indicator of a 

 microbial contaminant). If the American National 

 Standards Institute

[[Page 110 STAT. 1626]]

 has issued product standards applicable to a 

 specific type of point-of-entry or point-of-use 

 treatment unit, individual units of that type 

 shall not be accepted for compliance with a 
108

 maximum contaminant level or treatment technique 

 requirement unless they are independently 

 certified in accordance with such standards. In 

 listing any technology, treatment technique, or 

 other means pursuant to this clause, the 

 Administrator shall consider the quality of the 

 source water to be treated.

 ``(iii) List of technologies that achieve 

 compliance.--Except as provided in clause (v), not 

 later than 2 years after the date of enactment of 

 this clause and after consultation with the 

 States, the Administrator shall issue a list of 

 technologies that achieve compliance with the 

 maximum contaminant level or treatment technique 

 for each category of public water systems 

 described in subclauses (I), (II), and (III) of 

 clause (ii) for each national primary drinking 

 water regulation promulgated prior to the date of 

 enactment of this paragraph.

 ``(iv) Additional technologies.--The 

 Administrator may, at any time after a national 

 primary drinking water regulation has been 

 promulgated, supplement the list of technologies 

 describing additional or new or innovative 

 treatment technologies that meet the requirements 

 of this paragraph for categories of small public 

 water systems described in subclauses (I), (II), 

 and (III) of clause (ii) that are subject to the 

 regulation.

 ``(v) <<NOTE: Records.>> Technologies that 

 meet surface water treatment rule.--Within one 

 year after the date of enactment of this clause, 

 the Administrator shall list technologies that 

 meet the Surface Water Treatment Rule for each 

 category of public water systems described in 

 subclauses (I), (II), and (III) of clause (ii).''.