United States

Environmental Protection Office of Water EPA-815-R-98-001

Agency 4607 September 1998

_______________________________________________________________________

Small System 

Compliance Technology

List for the Surface 

Water Treatment Rule

 and Total Coliform Rule 

 
TABLE OF CONTENTS

1. Introduction 1

Section 1.1: Safe Drinking Water Act Implementation 1

Section 1.2: Need for a Small System Technology Requirement 1

Section 1.3: Small System Treatment Technology Requirements 2

Section 1.4: Format of the Small System Compliance Technology 

List for the SWTR and TCR 5

Section 1.5: Content of the Small System Compliance Technology

List for the SWTR and TCR 5

Section 1.6: Stakeholder Involvement 6

Section 1.7: Key Stakeholder Input 7

Section 1.8: Organization of the Document 7 

2. Compliance Technology List for SWTR 8 

Section 2.1: Background of the Surface Water Treatment and 

Total Coliform Rules 8 

Section 2.2: Technologies Evaluated for the Compliance 

Technology List 8 

Section 2.3: Compliance Technology Evaluation of Disinfection

 Technologies 9

Disinfection Treatment Technologies Listed in the 1989 SWTR 

Ozone 10

Chlorine 11

Chloramines 12

Chlorine Dioxide 12

Additional Listed Disinfection Treatment Technologies 

UV Radiation 13

On-site Oxidant Generation 15

Section 2.4: Degree of Pilot Testing for Filtration Technologies 

on the Compliance Technology List 17

Section 2.5: Compliance Technology Evaluation of Filtration 

Technologies 17

Filtration Treatment Technologies Listed in the Original SWTR

Conventional Filtration 19

Direct Filtration 20
Slow Sand Filtration 21

Diatomaceous Earth (DE) Filtration 21

Additional Listed Filtration Technologies

 Membrane processes

Reverse Osmosis (RO) Filtration 24

Nanofiltration (NF) 24

Ultrafiltration (UF) 24

Microfiltration (MF) 25

 Bag and cartridge type filters

Bag Filtration 25

Cartridge Filtration 27

Backwashable Depth Filtration 28

Section 2.6: Summary of Compliance Technologies for the SWTR 29

3. Compliance Technologies for the Total Coliform Rule 38

4. Emerging Technologies and Issues for Further Consideration 40

Section 4.1: Emerging Technologies:

Advanced Ultraviolet Treatments 41

Advanced Oxidation Processes 43

Section 4.2: Additional Issues for Consideration 44

List of Figures

Figure 1. Compliance Technologies 4

List of Tables

Table 1. Surface Water Treatment Compliance Technologies

(A) Disinfection Technologies 31

(B) Filtration Technologies 34

Table 2. Total Coliform Rule Compliance Technologies 39
Appendices

Appendix A: Relevant Parts of Sections 1412 of the Revised 

Safe Drinking Water Act (SDWA)

Appendix B: Additional References on SWTR-Approved Filtration 

Technologies

Appendix C: Memorandum Regarding TCR Technologies
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. There are over 70 statutory deadlines in the 1996 SDWA for the Environmental Protection

Agency (EPA). The Amendments contain a challenging set of activities for EPA, States, Indian

tribes, public water systems, and other stakeholders.

Due to the 1996 SDWA Amendments’ 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. Many of the 70

statutory deadlines have been grouped into twelve project areas. Each of these areas has a broad set

of stakeholders that will provide information and comments. In addition to the stakeholders’

participation, the National Drinking Water Advisory Council (NDWAC) has formed working groups

to address several of the relevant issues. These working groups make recommendations to the full

Council, which in turn advises EPA on individual regulations, guidances, and policy matters.

One of the twelve project areas created by the 1996 SDWA is being addressed by EPA’s

Treatment Technology Team. 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. Short-term goals of this team were to prepare:

(1) the list of technologies that small systems can use to comply with the Surface Water Treatment

Rule (SWTR), completed August 6, 1997; (2) the list of technologies that small systems can use to

comply with all of the other National Primary Drinking Water Regulations (NPDWRs), by August

6, 1998; and (3) the list of variance technologies for small systems for the appropriate NPDWRs, by

August 6, 1998. Longer-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. This document relates

to the updating of the SWTR and the listing of Total Coliform Rule (TCR) small system compliance

technologies. These have been grouped into one publication as they both address microbial

contaminants and their indicators in drinking water.

Section 1.2: Small System Technology Definitions

The earlier 1986 SDWA Amendments identified a process for setting maximum contaminant
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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 amended

1996 SDWA. 

The Surface Water Treatment Rule (SWTR) requires compliance with a treatment technique

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 TCR, promulgated in 1989, requires compliance with an MCL

and specifies treatments and other means for water system compliance.

Before the 1996 SDWA 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 [H.R. Rep. No. 93-1185

at 18(1974)] and was carried over when the Act was amended in 1986 [132 Cong. Rec. S6287 (May

21, 1986)]. The service 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 SDWA Amendments attempt to redress this problem in

part through the previously described series of small system compliance technologies. This guidance

is the part of a series of publications (begun in 1997 for the SWTR) aimed at helping small systems

comply with drinking water standards.

Section 1.3: Small System Treatment Technology Requirements

Since large systems were previously used as the basis for all feasibility determinations, the

existing BATs for MCL compliance and the treatment techniques require further analysis for small

system applications. The 1996 SDWA Amendments specifically require EPA to make technology

assessments relevant to the three categories of small systems for both existing regulations (e.g.,

SWTR and TCR) and future requirements. The three population-based size categories of small

systems thus defined are: 10,000 - 3,301 persons, 3,300 - 501 persons, and 500 - 25 persons.

The 1996 SDWA Amendments identify 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
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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 was significantly revised in 1996. Under the 1986

SDWA Amendments systems were required to install a technology before applying for a variance;

if they were unable to meet the MCL, 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. Under the 1996 Amendments there is a new procedure available for small

systems (systems serving fewer than 10,000): the “small system variance”. The difference between

a regular variance and a small system variance 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, 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 additional SDWA requirements that affect the listing of variance technologies. Critical

in regard to this particular listing are the following: (1) 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)]; and, (2) small

system variances are not available for regulations addressing microbiological contamination (including

contamination by bacteria, viruses, or other organisms) or any indicator or treatment technique for

a microbial contaminant [Section 1415(e)(6)(B)]. Therefore, there are no variances or variance

technologies available for the SWTR and TCR.

In addition, since the SWTR and TCR address microbial contamination, the affordability criteria

discussed under the EPA/SDWA affordability project do not apply. For the SWTR and TCR the only

screening criterion beyond treatment efficacy will be the ability of small water systems to install and

reliably operate the process. 

The flow chart in Figure 1 depicts how the compliance technology and exemption processes may

be utilized in decision-making under the SWTR and TCR drinking water regulations.
4

Insert Fig. 1

(Not available in electronic format)
5

Section 1.4: Format of the Small System Compliance Technology List for the SWTR and TCR

The 1996 SDWA Amendments do 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 rather than through rule-making. Since the listing provided in this guidance is

meant to be informational and interpretative, 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 SWTR and TCR

requirements; it does not over-ride any of the regulatory requirements.

Both the SWTR and TCR were published in the Federal Register on June 29, 1989. Even

though many systems have already installed treatment, there are systems that still need to select a

treatment technology to comply with the SWTR and/or the TCR. The importance of meeting the

deadlines set forth under the rules further justifies EPA’s decision to issue this compliance technology

list as guidance.

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 and/or subsequent

updates. Issuing a list in this fashion will allow EPA to provide information to more small systems

and regulators in a timely manner as they make treatment technology decisions.

Section 1.5: Content of the Updated Small System Compliance Technology List for the SWTR

and TCR

The SDWA does not specify the content of the compliance technology lists. This listing provides

greater detail than earlier listings, on the capabilities, applicability ranges, water quality concerns, and

operational and maintenance requirements for the identified compliance technologies. This listing also

includes, in summary format, tabulations (at end of Chapters 2 and 3) which include details on issues

identified by EPA and its stakeholders in their review of draft materials.

Technologies with which the reader may be less familiar are included in the listing, and these are

given greater coverage; there are other technologies discussed in Chapter 4 as “emerging”

technologies, that is those technologies which indicate a likelihood of success in meeting the specific

treatment goals and which require further evaluation. The listing will evolve and be issued annually

or as required. The listing 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 and

since this would be beyond EPA’s purview. Information on specific products may be available

through other mechanisms:

(1) EPA’s Office of Research and Development and the National Sanitation Foundation (NSF)

International are conducting a pilot project under the Environmental Technology Verification (ETV)

Program designed to provide treatment purchasers with performance data from independent third
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party organizations. The EPA and NSF are cooperatively conducting this project to provide the

mechanism for “verification testing” of packaged drinking water treatment systems. This pilot project

includes: development of verification protocols and test plans; independent testing and validation of

packaged equipment; partnerships among test/verification entities to obtain credible cost and

performance data; and preparation of product verification reports for wide-spread distribution. It will

be through the distribution of this data by which EPA expects the greatest amount of performance

information sharing, leading to efficient and effective technology applications to meet safe drinking

water goals. (For more information on this project consult the NSF-ETV Web site http://www.

nsf.org/verification/verification.html)

(2) The National Drinking Water Clearinghouse, at West Virginia University, has developed the

RESULTS database. RESULTS was designed as an electronic means to access data on small water

treatment systems employing both conventional and non-conventional treatment technologies.

Information and on-site contacts may be obtained on these treatment applications. (Clearinghouse:

phone (304)293-4191, or Web site http://www.ndwc.wvu.edu)

Finally, it is likely that this SWTR and TCR listing may in future years develop in tandem with

or eventually merge with the long-term enhanced surface water treatment requirements (LTESWTR).

Obviously, as EPA develops information on technologies applicable to small public water systems for

microbial control under the SWTR and LTESWTR these efforts may completely merge.

Section 1.6: Stakeholder Involvement

EPA held stakeholder meetings in Washington, D.C., on July 22 and 23, 1997, and May 18 and

19, 1998. Stakeholders at the meetings included representatives of States, public water systems,

trade associations, and equipment manufacturers. At the 1998 meeting the proposed draft 1998

listings for SWTR and TCR were presented to stakeholders. Stakeholders were asked to consider

the revised compliance technology information, and to provide comments.

Section 1.7: Key Stakeholder Input

The May 18-19, 1998 SWTR/TCR stakeholder discussions centered on EPA’s tabulation of

listed and “emerging” technologies for the SWTR, and to a lesser extent on TCR technologies. EPA

tables provided detailed information on the following technology-specific subject areas: treatment

efficacy, including ranges of microbial inactivation; treatment complexity and operator skill levels

required; byproducts formed (both chemical and physical byproducts of treatment); raw water quality

concerns; and other important limitations of the listed treatments. Stakeholder discussions were very

fruitful and resulted in several proposed changes to EPA’s draft listing:

! Stakeholders suggested that EPA group several technologies into the “advanced oxidation”

heading; and, that modifications to traditional ultraviolet radiation be grouped together as

“advanced ultraviolet” treatment. Both groups are considered emerging treatments for

small drinking water systems. [Stakeholders generally agreed with EPA that the above-
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referenced treatment groups should still be considered “emerging” due to significant gaps

in information: such as the the lack of availability of treatment efficacy data and/or

operational data in a small systems or drinking water setting. It was also noted that the

above-cited EPA/NSF verification program may provide results on the testing of some of

the disinfection technologies later in the year, and that results may be available prior to the

next listing for the subject microbial regulations.

! EPA was advised to note (in guidance) that bag filters should be handled carefully due to

the fragility of the materials, and that seals on cartridge filters can damage and require

special attention.

! EPA was advised that in reference to bag and cartridge filtration it would not be advisable

to specify maximum raw water turbidity levels (i.e., the 2 to 3 NTU cited). Such limits may

be more a function of pretreatment and system economy, and that levels up to 10- 30 NTU

have been treated successfully.

! EPA was advised as to the use of ozonation at many small systems in the U.S. and that the

International Ozone Association has recently compiled and presented operational case study

data (copies of a tabulated listing and presentation by R. Rice at the May 1998

NSF/WHO/PAHO Small Systems Symposium were provided); however, it is generally

believed that “advanced” combinations involving ozone have yet to be demonstrated or

even practical for small supplies; ozone representatives also pointed out that previously

cited cleaning problems have been largely overcome in the past 5 years due to use of pure

oxygen feeds (in lieu of air feed) to newer ozone generators. 

! It was generally agreed by the participants that an annual update to the SWTR listing of

technologies would be appropriate in order to capture any developments in the treatment

technology field.

! Relative to the proposed TCR listing of compliance technologies, no specific changes or

sustantive comments were received.

EPA received and reviewed additional information from other sources who were not present at the

stakeholder meeting, and these are cited as needed within Chapter 2 technology discussions.

Section 1.8: Organization of the Document

This guidance document is organized into chapters describing the small systems compliance

treatment technologies for the SWTR and TCR. Chapter 1 discusses the requirements of the 1996

SDWA Amendments and the approach EPA is following to meet those requirements. Chapter 2

discusses the technologies that were evaluated including those previously listed by EPA in 1997. The

listing is found also in tabular format at the end of the chapter. Chapter 3 contains the Total Coliform

Rule compliance technology listing. Chapter 4 contains emerging technologies and additional criteria

that may require further consideration prior to future technology listings. Appendices contain

relavant background information.
8

 2. COMPLIANCE TECHNOLOGY LIST FOR SWTR

Section 2.1: Background of the Surface Water Treatment Rule

The SWTR, published in the Federal Register on June 29, 1989, set national standards for

treating public surface water supplies and ground water supplies under the direct influence of surface

water. The SWTR includes: (1) criteria under which filtration is required and procedures by which

the States are to determine which systems must install filtration; and (2) disinfection requirements.

The filtration and disinfection requirements are treatment technique requirements to protect the public

against potential adverse health effects of exposure to the protozoa Giardia lamblia, viruses,

Legionella, and heterotrophic bacteria, as well as many other pathogenic organisms that are removed

by these treatment techniques. The SWTR also contains certain limits on turbidity as criteria for: (1)

determining whether a public water system is required to filter; and (2) determining whether filtration

is alone adequate. [Note: additional surface water treatment requirements for small water systems

are expected to come into effect under the Long Term Enhanced Surface Water Treatment Rule

(LTESWTR), including provisions for control of Cryptosporidium through filtration and revised

turbidity standards. These will be addressed as in subsequent listings.]

Section 2.2: Technologies Evaluated for the Compliance Technology List

The SWTR enables EPA to issue “log removal credits” to water utilities through requirements

for particular water treatments, rather than a requirement for utilities to meet an MCL: a microbial

MCL would require the technically difficult feat of monitoring for the microorganisms. Inactivation

requirements are 99.9% (3 log) for Giardia cysts and 99.99% (4 log) for viruses. The inactivation

requirements can be met through disinfection alone or a combination of filtration and disinfection.

The 1989 SWTR listed four filtration technologies: conventional filtration including sedimentation;

direct filtration; diatomaceous earth filtration; and slow sand filtration. Disinfection treatment is

required to follow all of these filtration treatments. The disinfection technologies listed in the 1989

SWTR were chlorine, ozone, chlorine dioxide, and chloramines. Additional filtration and disinfection

technologies were subsequently listed by EPA as discussed below.

 In 1997 EPA began evaluating information on the originally listed technologies and several

alternate technologies (i.e., treatments not listed in the 1989 rule), for SWTR application at small

public water supplies. Among the alternative treatments considered were: mixed-oxidant disinfection

(on-site oxidant generation); ultraviolet (UV) disinfection; four membrane filtration technologies

(reverse osmosis, microfiltration, ultrafiltration, nanofiltration); bag filtration; and cartridge filtration.

The Agency presented a proposed listing of these technologies and, after receiving considerable input

from its stakeholders, listed all the proposed technologies in August 1997 (EPA 815-R-97-002). In

addition, while some small system caveats were included in that listing, the technologies were listed

for all the SDWA-specified small system size categories. As part of the 1997 listing EPA included

abbreviated information on any known limitations regarding each of the compliance technologies;

operator skill levels; and other issues that would be important to consider before site-specific choices

are made. 
9

EPA undertook the following in 1998: (1) to further organize specific operational characteristics

of treatment and data on treatment efficacy, and to specify any other known limitations on the listed

treatments; and (2) to determine if other emerging treatments may be considered viable for the SWTR

small systems compliance technology listing. The emerging treatments were identified as advanced

oxidation (or perozone), pulsed ultraviolet, and ultraviolet oxidation (i.e., UV plus peroxide or

ozone).

In identifying the disinfection and filtration compliance technologies in this chapter, EPA

discusses disinfection technologies in Section 2.3; pilot testing for filtration treatment systems in

Section 2.4; and filtration technologies in Section 2.5; also, a tabular summary of compliance

technologies for the SWTR is provided in Section 2.6.

EPA notes that the listing of SWTR technologies is not intended to be a comprehensive or

exclusive list. Systems may choose alternative treatment technologies: i.e., technologies not listed

which may be found to meet the requirements of the SWTR. EPA lists in Chapter 4 “emerging

technologies” that in the future may be evaluated more fully and, if found applicable, would be listed

as small systems compliance technologies under SWTR.

The removal and/or inactivation of target or surrogate microorganisms is considered the primary

test of a treatment technology’s efficacy; however, other factors are considerably important in

evaluating treatment including the plausibility of operating the system under a range of conditions.

EPA researched available information on each disinfection and filtration treatment type and has

written up those listed in this document in accordance with available data. Most references cited are

from the published literature except in cases where ongoing research results are mentioned. There

is not a single template from which to determine viability of a technology for listing; a certain level

of judgement is required when evaluating data on new or emerging technologies. Finally, it is noted

that additional pertinent information on each of the disinfection and filtration technologies has been

included in a table at the end of this chapter.

Section 2.3: Compliance Technology Evaluation of Disinfection Technologies

Since passage of the 1996 SDWA amendments, several disinfection technologies have been

evaluated by EPA as possible compliance technologies. The viability of four disinfection technologies

listed in the 1989 SWTR (i.e., free chlorine, ozone, chlorine dioxide, and preformed chloramines) was

discussed at length in the 1989 EPA SWTR guidance manual (3), therefore those technology

summaries in this report are relatively brief.

CT values required for achieving a certain degree of inactivation for each disinfectant are listed

in CT tables in the above-cited SWTR guidance manual. CT refers to the product of the residual

disinfectant concentration in mg/L, “C”, and the disinfectant contact time in minutes, “T”. The

disinfectant contact time is defined as the time required for the water being treated to flow from the

point of disinfectant application to a point before or at the first customer during peak hourly flow.

There is a relationship between CT values and inactivation rates (or log inactivation) for a given
10

disinfectant. Since the determination of log inactivation of a microbiological contaminant is more

technically demanding than the calculation of CT, CT is used as a surrogate for log inactivation for

a given disinfectant under specific water quality conditions (e.g., temperature, pH). The SWTR and

associated guidance provide CT values for free chlorine, ozone, chlorine dioxide, and preformed

chloramines that correspond to 1-log inactivation of Giardia lamblia cysts. Viruses are generally

inactivated at much lower dosages of disinfectant (inactivations of the more resistant surrugate MS-2

bacteriophage are in several cases mentioned in this and other reference material). Where this report

mentions information on inactivation of Cryptosporidium oocysts it is for informational purposes

since the SWTR does not specifically address Cryptosporidium.

DISINFECTION TREATMENT TECHNOLOGIES LISTED IN THE ORIGINAL SWTR

Ozone Ozone is a powerful oxidant with high disinfectant capacity. A study found that within a pH

range of 6 to 10, at 3 to 10 EC, and with ozone residuals between 0.3 to 2.0 mg/L, bacteriophage

MS-2 (a surrogate test organism) and Hepatitis A virus were completely inactivated. Inactivations

ranged from >3.9-log to >6-log, and occurred within very short contact periods (i.e., 5 seconds) (1).

A 1992 research report describes treatment studies conducted on MS-2, poliovirus, and Giardia

cysts. It found that MS-2 in natural waters are very sensitive to ozone in comparison to poliovirus

type 3. In addition, Giardia muris and enteric viruses may be inactivated by ozone (as the primary

disinfectant) with 5 minutes contact time and ozone residuals of 0.5 to 0.6 mg/L to 3-log and 4-log

removals, respectively. The report concludes that design of ozone as a primary treatment should be

based on simple criteria including ozone contact concentrations, competing ozone demands, and a

minimum contact time to meet the required cyst and viral inactivation requirements, in combination

with USEPA guidance recommendations (2). Viral inactivation CT values for ozone were published

in the original USEPA guidance manual for the SWTR (3).

EPA notes that ozonation technology requires careful monitoring for ozone leaks which

pose a hazard. Also, use of ozonation may increase biodegradable organics in water which may affect

distributed water quality. Additional treatment may be used as necessary. Also, where bromides

are present in raw water there is an increased potential for formation of disinfection byproducts, i.e.,

brominated organics and bromate, which should be minimised. Secondary disinfection with chlorine

or chloramines may help in this regard, by balancing treatment needs with the need for also protecting

distributed water quality.

It has been brought to EPA’s attention at stakeholder meetings that recent advancements in

ozonation technology include use of high purity oxygen feed systems, rather than ambient air feed

systems. Ozonation treatment is therefore said to run cleaner and require less cleaning-related

maintenance than had the earlier versions of this technology.

EPA has reviewed survey data submitted by the International Ozone Association and found that

ozonation has been applied at many drinking water treatment facilities in the U.S. Ozonation systems

with capacities greater than 100,000 gal/day, as well as small water systems serving as little as 500

gal/day, have been documented (4,5). Ozonation, according to these same sources, is often applied
11

for drinking water disinfection as well as for other water treatment objectives, such as for oxidation

of dissolved iron and manganese, and control of taste and odor and/or trihalomethanes. Ozonation

technology for the subject public water system application is available from a number of suppliers.

Ozone treatment is a listed compliance technology for all size categories of public water systems. 

 References

1. Hall, R.M., and Sobsey, M.D. Inactivation of Hepatitis A Virus and MS2 by Ozone and OzoneHydrogen Peroxide in Buffered Water. Water Science and Technology, Vol. 27, No. 3-4, pp. 371-

378.

2. Finch, G.R., Labatiuk, C.W., Helmer, R.D. and Belosevic, M. Ozone and Ozone-Peroxide

Disinfection of Giardia and Viruses. Prepared for AWWA Research Foundation, Denver (1992).

3. U.S. Environmental Protection Agency. Guidance Manual for Compliance with the Filtration and

Disinfection Requirements for Public Water Systems Using Surface Water Sources (1989 and 1991).

4. Dimitriou, M.A. Letter with attachments attributed to R.G. Rice, from the International Ozone

Association to U.S. Environmental Protection Agency, May 23, 1997.

5. Rice, R. Small (<10,000 persons or < 1 MGD) U.S. Potable Water Treatment Plants Using

Ozone- In Operation. Assembled for the International Ozone Association. March 11, 1998. 

Chlorine Chlorine in its several forms is the most widely used disinfectant at public water supplies.

Hypochlorites are available in solid (e.g., tablet) or liquid (solution pump-fed) forms. The use of

gaseous chlorination (while available) at small water supplies may not be among the best disinfection

options due to the hazardous nature of the material. Use of gaseous chlorine places greater demand

on the need for isolated plant space, on providing trained and attentive operating staff and their

protection from any hazards, and, possibly, on liability issues which may boost insurance costs for

small public water systems. 

Stakeholders have indicated that provision of adequate CTs for chlorination may be problematic

and require additional consideration, particularly where contact time (basins) may be an expensive

option for small systems. However, stakeholders agree that all public water supply systems,

regardless of size, would benefit from the listing of chlorine for meeting the SWTR. Chlorination

technologies for even the smallest public water system applications are available, in gaseous, solid and

liquid-feed forms, from a number of suppliers. Cautions regarding use of gaseous chlorine are

appropriate, and attention should be paid to staffing and their protection, as noted above. Use of

hypochlorite solutions also warrants the following precautions: with time the disinfectant strength of

the solution decreases; and, toxic chlorate levels in solution can increase. Awareness regarding the

potential for producing elevated levels of halogenated disinfection byproducts, e.g., trihalomethanes,

inorganic byproducts, and others, is also essential. Chlorination treatment is a listed compliance

technology for all size categories of public water systems.
12

Reference

1. U.S. Environmental Protection Agency. Guidance Manual for Compliance with the Filtration and

Disinfection Requirements for Public Water Systems Using Surface Water Sources (1989 and 1991).

Chloramines Chloramines, while possessing certain advantages over other disinfectants (e.g., long

residual effect and low production of disinfection byproducts), have not been widely used in

disinfection at small public water systems. Compared to free chlorine and ozone, chloramines

possess less potency as a germicidal agent, and would therefore require longer CTs; and, as noted

above, stakeholders have informed the USEPA that provision of suitable CTs for such chemical

disinfection may be costly and/or problematic and requires adequate consideration. 

Chloramine disinfection requires careful monitoring of the ratio of added chlorine to ammonia.

Failure to do so can result in odor and taste problems or biological instability of water in the

distribution system. Excess ammonia (i.e., low chlorine:ammonia) can promote growth of nitrifying

bacteria, which convert ammonia to nitrates and nitrates. Ammonia dose should be tempered by any

natural ammonia occurring in raw water (1).

USEPA and stakeholders agree that all public water supply systems, regardless of size, would

benefit from the listing of chloramines for SWTR small systems application, with the caveats

mentioned above. The Agency has not seen documentation of applied use at small facilities.

Chloramination technologies for even the smallest public water system applications may be available

from treatment vendors. Chloramination is a listed compliance technology for all size categories of

public water systems.

Reference

1. White, G.C. Handbook of Chlorination and Alternate Disinfectants. Volume 3. Van Nostrand

Co., N.Y., N.Y. (1992).

Chlorine Dioxide Chlorine dioxide, although a powerful oxidant, may be more difficult to handle

than other forms of chlorine. Chlorine dioxide requires trained staff to manage its use and is so

reactive (thus, is consumed very readily) that it may not provide a residual disinfectant in the

distribution system. Photochemical decomposition of ClO2 in reservoirs may increase chlorate

concentrations, and other factors including the generation process used and water pH can affect

chlorate and chlorite levels. The Agency has not seen documentation of applied use of this

technology at small facilities. However, stakeholders have urged USEPA not to exclude this

treatment for disinfection. It is noted that chlorine dioxide units for small public water system

applications may be available from treatment vendors. Chlorine dioxide is a listed treatment for all

categories of public water systems.

ADDITIONAL LISTED DISINFECTION TREATMENT TECHNOLOGIES
13

UV Radiation Ultraviolet (UV) radiation has been found to be an effective disinfectant in treatment

of relatively clean source waters. Historically, UV has been adapted to disinfect reclaimed water,

treated sewage, industrial process water, and small groundwater supplies. Simplicity of installation,

ease of operation and maintenance, and low costs relative to chemical disinfection, make UV a useful

small systems disinfection technology option. Stakeholders have suggested that users of this

technology consider UV within the framework of the multiple barrier approach as put forward by the

Agency under the SWTR. 

UV radiation as a germicidal agent is effectively applied at a wavelength of 253.7 nanometers

(or a range of 250-270 nanometers) through application of low-pressure mercury lamps. Other

wavelengths are effective in the destruction of chemical contaminants, but this is not addressed in this

guidance. UV dose is expressed in units of milliwatt-sec per square centimeter (mW-sec/cm2), the

product of the intensity (I) of the UV lamp (mW/cm2) and time (T) of exposure (sec). UV treatment

of water is therefore comparable to the CT as described above for chemical disinfection, since UV

dose is expressed in terms of the IT values.

The relatively resistant test organisms MS-2 and Bacillus subtilis have been inactivated by UV

at a level of 3-logs at dosages of approximately 20 to 40 mWsec/cm2, and a level of 4-logs at dosages

of approximately 60 to 90 mWsec/cm2. These test results were reported in a 1996 USEPA overview

of UV disinfection efficacy, operation, and cost (1). In addition, a recent pilot study on groundwater

containing 0.65 ppm iron indicated a 4-log inactivation of MS-2 at 87 mWsec/cm2 (2). These doses

would likely inactivate poliovirus, Hepatitis A, and rotavirus. Rotavirus, a UV-resistant virus, was

the subject of testing in buffered, distilled water, which yielded 3- and 4-log inactivations at

approximately 30 and 40 mWsec/cm2, respectively (3).

Research has confirmed that UV effectiveness is relatively insensitive to temperature and pH

differences, and that application of UV as a primary disinfectant (followed by chlorination or

chloramination) does not contribute to disinfection by-product formation. In addition, UV application

was found not to convert nitrate to nitrite or bromide to bromines or bromates (3).

However, it has long been observed that turbidity, natural organics, iron, calcium hardness,

suspended solids, and other factors can reduce UV transmission and cause lamp fouling, thus

lowering disinfection effectiveness. Studies have tracked UV performance and transmission, through

use of new-generation electronic UV sensors. (Some older UV sensors exhibited erratic readings and

a loss of performance over time.) Testing found that correlations may be established between system

performance (MS-2 inactivation) and UV sensor readings. This may prove invaluable in maintaining

the reliability of UV sensor readings. Bioassay techniques and chemical actinometry were cited by

researchers as tools available for obtaining appropriate correlations, and for recalibrating sensors

periodically. The same studies found that manual cleaning of fouled UV sleeves and sensors, with

commercially-available, 20 percent muriatic acid solution, was effective and not labor-intensive, i.e.,

requiring one-half to one hour of labor (2). 

The UV dose needed for a particular application may vary depending on source water quality.
14

A suggested lower bound of 38 mWsec/cm2 is based on ANSI/NSF standard 55, which is intended

for disinfecting visually clear water pre-filtered for cyst reduction. That dose corresponds to an

approximate 4-log rotavirus inactivation, utilizing no multiplier/factor-of-safety. An upper bound of

140 mWsec/cm2 is based on above-cited lab and field study data, i.e., 4-log viral or MS-2

inactivations (1, 4), and use of a factor-of-safety or multiplier of 2 to 3.

[Note: Table E-14 of the SWTR Guidance Manual, Inactivation of Viruses by UV, was based on less

resistant Hepatitis A virus, at 2- and 3-log inactivations in lab-prepared media. The current guidance

may be more conservative in approaching UV design needs.]

Protozoan cysts require greater UV doses for inactivation. For example, one test in a distilled

water medium indicated a 2-log inactivation of Giardia lamblia at a UV dose of 180 mWsec/cm2 and

a 1-log inactivation of Giardia lamblia at a UV dose of approximately 40 mWsec/cm2 (5). A factor

of safety or multiplier of 2 to 3 applied to this dosage produces a dose of 80 to 120 mWsec/cm2 to

achieve a 1-log inactivations of Giardia lamblia. As a practical matter, conventional UV systems

may not be cost effective for control of Giardia at greater than 1-log removal, although advanced

ultraviolet treatment systems which may produce 2- to 4-log inactivations of Cryptosporidium are

being investigated (see Chapter 4) for potential application under the forthcoming EPA Enhanced

Surface Water Treatment Regulation.

In addition to pretreatment and/or automatic cleaning systems to remove above-cited dissolved

and/or suspended materials, which can impede UV performance, a secondary disinfectant is necessary

to provide a residual protection of water in distribution systems. Continuous dose measurement,

remote alarms, automatic cleaning of UV components, and annual UV sensor maintenance may also

be important design components to prevent deposition or scaling and to minimize on-site operator

attention. UV treatment systems appear to be commercially available for drinking water application,

within the dose ranges suggested above. Ultraviolet disinfection is a listed technology for all three

categories of small public water systems.

[Note: The Agency expects, as data become available, to improve upon and possibly refine the

recommended UV doses for meeting viral inactivations requirements. In addition, EPA briefly

discusses as “emerging” technologies the following variations on conventional UV treatment: pulsed

UV; medium pressure UV; and UV oxidation (i.e., as used in combination with peroxide or ozone

(see Chapter 4).]

References

1. U.S. Environmental Protection Agency. Ultraviolet Light Disinfection Technology in Drinking

Water Application: An Overview. Office of Water. EPA 811-R-96-002 (1996).

2. Snicer, G.A., Malley, J.P., Margolin, A.B. and Hogan, S.P. Evaluation of Ultraviolet (UV)

Technology for Groundwater Disinfection. Prepared for AWWA Research Foundation, Denver

(1997).
15

3. Malley, J.P., Shaw, J.P, and Roppy. J.R. Evaluation of By-Products Produced by Treatment of

Groundwaters With Ultraviolet Irradiation. Prepared for AWWA Research Foundation, Denver

(1995).

4. Wilson, B.R. et al. Coliphage MS-2 as a UV Water Disinfection Efficacy Test Surrogate for

Bacterial and Viral Pathogens. Proceedings of Water Quality Technology Conference; Part I,

Toronto, Canada (1993).

5. Karanis, P., et al. UV Sensitivity of Protozoan Parasites. Journal of Water Supply Research and

Technology-Aqua. Vol. 41, No. 2, pp. 95-100 (1992).

On-Site Oxidant Generation (Also known as anodic oxidation and salt brine electrolysis) On-site

oxidant generation may be accomplished by an electrolytic process which generates a concentrated

solution of oxidants, mainly free chlorine. This process involves passage of an electric current

through a continuous-flow brine (salt) solution within a cell. The electrolyzed brine solution

containing the concentrated disinfectant is injected into water for treatment. The concentrated

solution is diluted approximately one hundred-fold in drinking water treatment. 

EPA’s previous listing included “mixed oxidant disinfection,” and the Agency has decided to

characterize this technology in another manner. Recently completed research, as discussed below,

has not determined that additional oxidants (other than free chlorine) are produced to a significant

degree by the electrolytic action within this process. In its application this treatment is similar to

chlorination, however rather than apply commercially available gaseous, solid or liquid forms of

chlorine, the process produces a strong disinfectant solution on-site. This treatment method has been

successfully tested, applied, and accepted mainly due to the convenience, ease of operation, and basic

level of operator skill required.

On-site oxidant generators have been reported to produce multiple oxidants. However, the

individual oxidants in solution have proven to be difficult to characterize. Recent research,

sponsored by EPA, investigated the composition of the generated solutions as well as the analytical

techniques available for measurement of the individual species. Lab and full-scale units were studied,

and a variety of analytical methods and chemical masking techniques were tested for blocking the

interference of free chlorine in the measurement of ozone in solution. The experiments confirmed that

chlorine is the primary oxidant in the electrolyzed solution (measured at 200 to 400 mg/L), with

ozone, hydrogen peroxide, and chlorine dioxide undetected. Lab-prepared solutions containing free

chlorine and ozone were also tested and it was shown that, due to the rapid rate of reaction between

the two oxidants (in the millisecond time-scale), any ozone that may be in solution becomes, in a very

short time, unavailable for the purpose of disinfection. Based on kinetic studies, ozone levels were

calculated by researchers to be less than 0.5 mg/L immediately following generation (1).

It may be assumed until further investigations bear results that units of this type may use various

grades of raw material, salt, and this may in turn result in differing amounts of oxidants and associated

byproducts in solution. It is noteworthy that this process may also produce chlorate (ClO3

-) and
16

bromate (BrO3

-

) in solution: the former species being a function of free chlorine decomposition, the

latter, a human carcinogen, is produced as a result of reactions with bromide in the salt used in

preparation of the electrolytic solution. The above-cited study (1) reported relatively low levels of

chlorite, chlorate and bromate ions in solution in concentrated anolyte liquor (less than 0.05 mg/L

chlorite, and 1 to 2 mg/L both chlorate and bromate in full-scale system); the study also detected

bromate in finished water but was not specific about concentration.

Researchers have studied the effects on-site electrolysed salt brine disinfection in relation to

Cryptosporidium oocysts and Clostridium perfringens spores as an indicator of oocyst inactivation:

at a dosage of 5 mg/L, mixed oxidation achieved greater than 2-log Cryptosporidium inactivation at

1-hour contact time (2). A technical report by the Los Alamos Technical Associates, Inc., reported

a 4-log inactivation of/ f-2 bacteriophage in water at a relatively short contact time, i.e., CT of 4 (3).

In order to provide a complete and useful set of data, studies on inactivation of Cryptosporidium are

under way by EPA (4) and by others, including the American Water Works Research Foundation,

with results anticipated in 1999.

On-site oxidant generation for disinfection purposes has been used in full scale water treatment

applications at a variety of locations. Field applications have indicated the ease of operation and

effectiveness of these systems. Examples of full-scale applications of on-site generation of

disinfectants, in several U.S. states, may provide some guidance to interested parties on the use and

efficacy of this technology.

Given that on-site generation of oxidants may have advantages over other treatment methods,

EPA suggests that small systems consider this disinfection technique for compliance purposes. Given

information regarding the disinfectant generated, EPA suggests taking a course of utilizing

chlorination CT tables when designating chemical dosing for these systems. Additional studies in

1998-99 may yield appropriate data on CT requirements for this technology.

References

1. Gordon, G. “Electrochemical Mixed Oxidant Treatment: Chemical Detail of Electrolyzed Salt

Brine Technology.” Miami University Department of Chemistry and Biochemistry, Oxford OH.

Prepared for IT Corporation and U.S. Environmental Protection Agency. May, 1998.

2. Venczel, L.V., Arrowood, M., Hurd, M., Sobsey, M.D., “Inactivation of Cryptosporidium parvum

Oocysts and Clostridium perfringens Spores by a Mixed-Oxidant Disinfection and by Free Chlorine,”

Applied and Environmental Microbiology (April 1997): 1598-1601.

3. Bradford, W.L., Baker, F.A. Design, Fabrication and Testing of a Laboratory Test Electrolytic

Water Disinfection Unit (EWDU): Adendum Number 2. Los Alamos Technical Report LATA/MX94/0009. Los Alamos Technical Associates, Inc. Los Alamos, NM (1994).

4. Goodrich, J. Personal communication with Marc Parrotta. U.S. Environmental Protection
17

Agency (June 1998).

Section 2.4: Degree of Pilot testing for New Filtration Technologies on the Compliance

Technology List

The current SWTR lists four types of filtration technologies and associated requirements. These

are described in 40 CFR §141.73(a) - (d): (1) conventional filtration treatment or direct filtration; (2)

slow sand filtration; (3) diatomaceous earth filtration; and (4) other (alternative) filtration

technologies. A public water system could not use an alternative filtration technology unless it could

demonstrate to the State through the use of pilot plant studies or other means that the technology,

in combination with disinfection as described under §141.72(b), meets the required three log removal

of Giardia and four log removal of viruses.

For these alternative filtration technologies, there are typically two stages of evaluation prior to

approval. The first stage is to determine if the process effectively removes the contaminants of

concern. The second stage is to determine if the individual system can effectively operate the process

and to assess site-specific considerations that can affect the technology’s performance. Under the

SWTR, the filtration processes listed in §141.73(a)-(c) already meet the first stage requirement, but

generally require some degree of site-specific testing to meet the second stage. The “other filtration

technologies” [§141.73(d)] require pilot testing to meet both criteria.

For alternative filtration technologies on the SWTR compliance technology list, the national-level

pilot testing for viability may be waived under §141.73(d). Pilot plant studies are just one mechanism

identified in §141.73(d) to demonstrate that the process is capable of meeting the goals of the SWTR.

The filtration technology can be demonstrated using “other means” besides pilot testing. Those

alternative filtration technologies on the compliance technology list have been determined by EPA

to be effective under §141.73(d) and thus do not require national-level pilot testing for viability. This

puts new filtration technologies on the same regulatory footing as the technologies listed in

§141.73(a) - (c) in terms of national-level pilot testing. A State may still require site-specific pilot

testing to assess factors that affect technology performance for all of the compliance technologies.

A State may as a practical measure require such testing to demonstrate that a system is capable of

operating a given treatment process.

For filtration technologies that are not on the compliance technology list, the existing mechanism

in the SWTR for alternative filtration technologies can still be used. Pilot testing for viability could

be required for these systems under §141.73(d).

Section 2.5: Compliance Technology Evaluation of Filtration Technologies

Filtration technologies have been evaluated and listed as compliance technologies. Since the

viability of the four technologies listed in §141.73(a)-(c) has already been summarized in the SWTR

guidance manual, those technology summaries do not contain all information previously reported by

EPA. (Appendix B contains references published on the filtration technologies listed in the SWTR
18

since 1989.) Seven filtration technologies have been added as compliance technologies for small

systems. Summary information on the filtration technologies is included in a table at the end of this

chapter.

FILTRATION TREATMENT TECHNOLOGIES LISTED IN THE 1989 SWTR 

Filtration is the most commonly used treatment for reducing turbidity and microbial contaminant

levels in domestic water supplies. Common drinking water filtration processes involve passing water

through a filter media to remove suspended particulate material, larger colloidal materials, and, for

some filter media, to reduce levels of smaller colloidal and dissolved contaminants. Examples of

suspended particulates include clay and silt, microorganisms, humic and other aggregated organic

materials, and aluminum and iron oxide precipitates. Typical filter media include silica sand,

diatomaceous earth, garnet or ilmenite, and a combination of coarse anthracite coal overlaying finer

sand. Filtration may involve single media, dual media (e.g., coal-sand), and tri-media (e.g., an added

third layer of sand). Filtration may be rapid or slow, depending upon the application, and may involve

different removal processes, cleaning methods, and operation methods (1, 2, 3).

The filtration technologies discussed in this section are used to remove suspended particulate

matter from water. For filtration processes that involve the addition of a chemical coagulant,

coagulation refers to the complex process of particle aggregation within a water being treated,

including coagulant formation, particle destabilization (surface charge alteration of suspended

particles), and inter-particle collisions. Flocculation may be considered a part of the coagulation

process and refers to the process of promoting inter-particle collisions and thus the aggregation of

larger particles (floc). Larger suspended particles may be removed by simple filtration or by

sedimentation (gravity settling) or flotation (floc rises to the surface and is skimmed off). Simple

filtration involves the physical trapping of suspended particles that are larger than the pore volumes

of the filter media; the bulk water passes through unimpeded and leaves the particles behind. As finer

suspended particles pass through the filter medium, they are destabilized, resulting in coagulation and

adherence to the filter medium (2, 4). In the case of slow sand filtration, which does not involve the

addition of coagulants, colloidal and dissolved organic materials may be removed by biological

processes in the schmutzdecke (“black layer” or biologically-active layer) and in the filter medium

below. In the case of direct filtration, which requires influent water with much less turbidity, the

coagulation and flocculation step is followed immediately by filtration. Since there is less aggregated

material to remove, sedimentation or flotation is not required to prolong the filter cycle. Some

dissolved chemicals may be removed by chemical sorption at the surface of the filter media, especially

in the cases of higher surface area filter media (e.g., fine sand and diatomaceous earth), but these

processes account for much less of the bulk contaminant removal compared to physical sorption

processes (1, 2, 3, 5).

For the purposes of meeting the performance criteria under the SWTR and to protect public

health, disinfection treatment is applied following filtration.

In regard to improving the operation of fitration plants, recent advances in telemetry devices
19

have made it possible for a single operator to remotely monitor and operate one or more small water

systems within a given area. These “circuit rider” operators can work from a central location,

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

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

coagulant or disinfection dosage) via modem or other means. This reduces operator costs, and can

reduce the amount of chemicals required for treatment (6). These telemetric devices may make

technologies that require full-time operator attention more feasible for many small systems. The

combined use of package plants and telemetric monitoring may well extend the use of the more

complex water treatment technologies to the universe of small systems.

The following technologies are listed in this guidance as compliance technologies for all three

size categories of small public water systems; disinfection is assumed to follow filtration treatment.

The first four filtration technologies were listed and described in the SWTR (5).

Conventional Filtration and Specific Variations Conventional filtration includes chemical

coagulation, rapid mixing, and flocculation, followed by floc removal via sedimentation (or flotation).

The clarified water is then filtered. Common filter media designs include sand, dual-media, and trimedia. 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. Conventional

treatment has demonstrated removal efficiencies greater than 99% for viruses and 97 to 99.9% (rapid

filtration with coagulation and sedimentation) for Giardia lamblia (5). 

There are a variety of coagulation/filtration package plants applicable to small systems (2, 6, 7,

8). In package plants that utilize sedimentation, the sedimentation step usually occurs in tube settlers.

In “dual-stage filtration” (8, 9), the sedimentation step is replaced by a passive

flocculation/clarification step that occurs in an initial “depth clarifier” tank. The clarified water is then

passed through a depth filter. Other modes of clarification are possible, including the use of the

various upflow and downflow flocculation/filtration processes, also known as “roughing filter”

processes. Typically, roughing filters are not as versatile as sedimentation or flotation, but some

varieties may perform comparably. One example of a package plant of this type uses a buoyant

crushed plastic medium used in an upflow mode as a contact flocculator and roughing filter ahead of

a downflow triple-media bed (2). Coagulation/filtration package units have demonstrated the ability

to effectively remove turbidity, color, disinfection by-product precursors, viruses, bacteria, and

protozoa (e.g., Cryptosporidium and Giardia cysts) (6, 7, 8, 9). 

The dissolved air flotation (DAF) process includes coagulation and flocculation, but instead of

gravity sedimentation, the floc is carried up to the water surface by rising air bubbles, where the floc

can be skimmed off (2, 6, 10). DAF may be more applicable than other conventional filtration

systems for removing particulate matter that does not readily settle, e.g., algae-rich waters, highly

colored waters, low turbidity/low alkalinity waters, and cold waters. DAF is less appropriate for very

turbid waters due to their higher silt and clay contents. The National Research Council suggests an

upper turbidity limit of 30 to 50 NTU for small systems using DAF (6). For lower turbidity waters,

DAF performance is comparable to conventional filtration employing sedimentation, and may be
20

superior in removal of turbidity, especially low density turbidity (11).

Conventional filtration is the most widely used technology for treating surface water supplies for

turbidity and microbial contaminants, but may be less applicable to the smallest water system size

category (those serving 25 to 500 persons) due to relatively high costs and technical complexity.

Although conventional filtration has the advantage that it can treat a wide range of water qualities,

it has the disadvantage that it requires advanced operator skill and has high monitoring requirements.

Thus, small systems without access to a skilled operator should not use conventional treatment, given

that waterborne pathogens are acute contaminants and that the disruption of chemical pre-treatment

can lead to pathogen introduction into the distribution system (2, 6, 9). The performance of

conventional filtration is extremely sensitive to the proper management of the coagulation chemistry

involved; if the coagulation step is disrupted or improperly executed, the removal efficiencies for

turbidity and microbiological contaminants decrease dramatically in a matter of minutes. For this

reason, EPA suggests that only those systems with full-time access to a skilled operator use

conventional filtration.

Direct filtration Direct filtration has several effective variations; all direct filtration systems include

a chemical coagulation step followed by rapid mixing, and all exclude the use of a sedimentation or

other clarification step prior to filtration. Following chemical mix, water is filtered through dual- or

mixed-media filters using pressure or gravity units. Pressure units, which are used primarily by small

systems (2), 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. In addition to the mode of filtration, variations of direct filtration include filter

media type and mixing requirements. In-line filtration (12) 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 because of its low cost relative to

conventional treatment (12, 13). The National Research Council (6) has suggested that small systems

not use direct filtration for waters with average turbidities above 10 NTU or maximum turbidities

above 20 NTU. Two other important considerations are color and algae. Since color removal

requires coagulant additions in proportion to the degree of color, an upper limit of color is

appropriate for direction filtration. An AWWA Committee report (14) suggests an upper limit of 40

color units. Algae removal must be evaluated on a case by case basis. Direct filtration has

demonstrated removal efficiencies of 90 to 99% for viruses, 50% for Giardia lamblia without

coagulation, and 95-99% for Giardia lamblia with coagulation pre-treatment (5).

Direct filtration has the disadvantage that it requires advanced operator skill and has high

monitoring requirements. Thus, small systems without access to a skilled operator should not use

direct filtration, given that waterborne pathogens are acute contaminants and that the disruption of

chemical pre-treatment can lead to pathogen introduction into the distribution system (2, 3, 6). The

performance of direct filtration is extremely sensitive to the proper management of the coagulation

chemistry involved; if the coagulation step is disrupted or improperly executed, the removal

efficiencies for turbidity and microbiological contaminants decrease dramatically in a matter of

minutes. For this reason, EPA suggests that only those systems with full-time access to a skilled

operator use direct filtration.
21

Slow sand filtration Slow sand filters are simple, are easily used by small systems, and have been

adapted to package plant construction (6, 7). Slow sand filters are similar to single media rapid-rate

filters in some respects, but there are crucial differences in the mechanisms employed (other than the

obvious difference in flow rate). The schmutzdecke, the top-most, biologically active layer of filter,

removes suspended organic materials and microorganisms by biodegradation and other processes,

rather than relying solely on simple filter straining or physico-chemical sorption. Advantages of slow

sand filtration include its low maintenance requirements (since it does not require backwashing and

requires less frequent cleaning) and the fact that its efficiency does not depend on actions of the

operator. However, slow sand filters do require time for the schmutzdecke to develop after each

cleaning: during this “ripening period,” however, filter performance steadily improves. The ripening

period can last from six hours to two weeks, but typically requires less than two days. A two day

filter-to-waste period is recommended for typical sand filters (2). Since few remedies are available

to an operator when the process is ineffective, particularly if a system has little storage capacity, slow

sand filtration should be used with caution and should not be used without pretreatment or process

modifications (e.g., GAC layer addition) unless the raw water is low in turbidity, algae, and color

(15). Package plant versions with a granular activated carbon layer located beneath the slow sand

can adsorb organic materials that are resistant enough to biodegradation to pass through the

schmutzdecke. When used with source water of the appropriate quality, slow sand filtration may be

the most suitable filtration technology for small systems (6). Slow sand filtration has demonstrated

removal efficiencies in the 90 to 99.9999% range for viruses and greater than 99.99% for Giardia

lamblia (5).

Diatomaceous earth (DE) filtration DE filtration, also known as pre-coat or diatomite filtration,

can be used to directly treat low turbidity raw water supplies or chemically coagulated, more turbid

water sources . DE filters consist of a pre-coat layer of DE, approximately 1/8-inch thick, supported

by a septum or filter element. To properly maintain the DE pre-coat layer, and to maintain porosity,

treatment is supplemented by a continuous-body feed of diatomite and recycled filtered water.

Intermittant operation of DE filters is not advised unless the system recycles water through the filter

during production down times. Maintaining the filter in this manner optimizes performance, extends

the filtration cycle, and lowers filter maintenance requirements.

Normally the DE filter is backwashed and the septum cleaned after each break in filtration. Then

a fresh layer of precoat is applied. If changes in water quality occur, body feed rates may be adjusted

immediately and/or a re-precoat may be applied. DE filtration plants can be designed to make such

adjustments automatically.

DE filtration is very effective for removing Giardia cysts, but filtration studies with plain DE

have not indicated a marked capability to remove very small particles, e.g., viruses (2, 6, 16). Some

research has shown that specific modifications can lead to 99 percent virus removal (2). In addition,

recent studies have indicated excellent removal rates (e.g., 6-log) of Cryptosporidium oocysts for DE

grades commonly used by smaller systems (17) .

Since chemical coagulation is not required, DE filtration is very attractive as a small systems

technology and it has been used successfully by small systems for many years. Waters that are low
22

in turbidity, color and other organic matter (disinfection by-product precursors) are most suitable for

direct application of DE technology (6).

References

1. U.S. Environmental Protection Agency. “Technologies and Costs for the Removal of

Microbiological Contaminants from Potable Water Supplies”. October 1988.

2. Cleasby, John L. “Filtration”. AWWA, Water Quality and Treatment: A Handbook of

Community Water Supplies, 4 ed. Pontius, F.W., ed. McGraw-Hill, Inc. New York. 1990.

3. Letterman, R.D. Filtration Strategies to Meet the Surface Water Treatment Rule. American

Water Works Association. Denver, CO. 1991.

4. Stumm, W. and Morgan, James J. Aquatic Chemistry, 2nd ed. John Wiley and Sons, Inc. New

York. 1981.

5. U.S. Environmental Protection Agency. 40 CFR Parts 141 and 142. Drinking Water; National

Primary Drinking Water Regulations; Filtration, Disinfection; Turbidity, Giardia lamblia, Viruses,

Legionella, and Heterotrophic Bacteria; Final Rule. Federal Register, 27486, V. 54, N. 124, June

29, 1989.

6. National Research Council (NRC). Safe Water From Every Tap: Improving Water Service to

Small Communities. National Academy Press. Washington, DC. 1997.

7. Campbell, Susan, Lykins, B.W., Jr., Goodrich, J.A., Post, D., and Lay, T. “Package plants for

small systems: a field study”. Journal of the American Water Works Association. November, 1995.

pp. 39-47.

8. Brigano, F.A., McFarland, J.P., Shanaghan, P.E., and Burton, B. “Dual-Stage Filtration Proves

Cost Effective”. Journal of the American Water Works Association. May 1994. p. 75.

9. Horn, J.B., Hendricks, D.W., Scanlan, J.M., Rozelle, L.T., and Trnka, C. “Removing Giardia

Cysts and Other Particles from Low Turbidity Waters Using Dual-Stage Filtration”. Journal of the

American Water Works Association. February 1988. pp. 68-77.

10. American Water Works Association. “International Conference Examines Flotation

Technology”. Journal of the American Water Works Association. March 1994. p. 26.

11. Malley, J.P., Jr. and Edzwald, J.K. “Laboratory Comparison of DAF with Conventional

Treatment”. Journal of the American Water Works Association. September 1991. pp. 56-61.

12. U.S. Environmental Protection Agency. “Very Small Systems Best Available Cost Document”.

September 1993.
23

13. Westerhoff et al. “Plant-Scale Comparison of Direct Filtration Versus Conventional Treatment

of a Lake Erie Water”. Journal of the American Water Works Association. March 1980. p. 148.

14. AWWA Committee Report. “The Status of Direct Filtration”. Journal of the American Water

Works Association. July 1980. p. 405.

15. Cleasby, J.L. “Source Water Quality and Pre-treatment Options for Slow Sand Filters”. Chapter

3 in Slow Sand Filtration. Gary Logsdon, ed. American Society of Civil Engineers. New York.

1991.

16. Logsdon, Gary S. “Comparison of Some Filtration Processes Appropriate for Giardia Cyst

Removal”. Presented at the Calgary Giardia Conference, Calgary, Alberta, Canada. February 23-25,

1987.

17. Ongerth, J.E. and Hutton, P.E. “DE Filtration to Remove Cryptosporidium”. Journal of the

American Water Works Association. December 1997. p. 39.

ADDITIONAL LISTED FILTRATION TREATMENT TECHNOLOGIES

Membrane Processes 

The four treatments listed below are membrane processes, which make use of pressure-driven

semi-permeable membrane filters. Membranes are manufactured in a variety of configurations,

materials and pore size distributions. The selection of membrane treatment for a particular drinking

water application would be determined by a number of factors, such as: targeted material(s) to be

removed, source water quality characteristics, treated water quality requirements, membrane pore

size, molecular weight cutoff (MWCO), membrane materials and system/treatment configuration (1).

The membrane technologies listed below have been historically employed for specific drinking

water uses: (1) reverse osmosis treatment in a high pressure mode, in removal of salts from brackish

water and seawater; (2) nanofiltration, also referred to as membrane softening or low pressure RO,

in removal of calcium and magnesium ions (hardness) and/or natural organics and disinfection

byproducts control; (3) ultrafiltration, characterized by a wide band of MWCs and pore sizes, for

removal of specific dissolved organics (e.g., humic substances, for control of disinfection byproducts

in finished water) and for removing particulates; and (4) microfiltration, as with ultrafiltration

utilizing low operating pressures, for removal of particulates including pathogenic cysts (1, 2).

Pre-filtration and scale-inhibiting chemical addition may be utilized to protect membranes from

plugging effects, fouling and/or scaling, and to reduce operational and maintenance costs. For the

purposes of meeting the performance criteria under the SWTR and as a safety measure, a disinfectant

is commonly applied following membrane treatment to protect distributed water quality.

Stakeholders have requested that USEPA include the following information as part of the listing
24

of these technologies: (1) the degree of operator skill level, which often depends on water quality and

amount of pre- and post-treatment required; (2) higher operator skills are often needed for chemical

cleaning of membranes; (3) test piloting of membrane filtration systems may be required; (4)

monitoring of membrane integrity, as well as alarm and back-up systems, may be required but that

state reviewers should have latitude to decide on such requirements; (5) while the first two listed

membrane treatments are absolute barriers to viruses, it should be noted that ultrafiltration and

microfiltration are not, therefore the latter two should not be given credit for viral reductions; (6) no

distinction is made in terms of membrane configuration type, e.g., spiral bound or other, in this

guidance; (7) regarding other treatment goals, microfiltration will pass all organic compounds in

water whereas ultrafiltration will capture some organics; and, (8) since designations of membrane

absolute or nominal pore size have often been irregularly specified, causing some confusion in

interpreting a membrane’s exclusion capability, state reviewers may wish to request specific

information from manufacturers or suppliers for particular applications.

The following membrane processes are listed SWTR technologies for all three categories of small

public water systems:

Reverse Osmosis (RO) Filtration RO is a listed technology for all three categories of small public

water systems. Due to typical RO membrane pore sizes and size exclusion capability (in the metallic

ion and aqueous salt range), RO filtration is effective for removal of cysts, bacteria and viruses (2,

3); however, RO produces the most wasted water, at between 25-50% of the feed.

Disinfection is also recommeded to ensure safety of water. 

Nanofiltration (NF) NF is a listed technology for all three categories of small public water systems.

Due to typical NF membrane pore sizes and size exclusion capability (1 nanometer range, e.g.,

organic compounds), NF is effective for removal of cysts, bacteria and viruses. Disinfection is also

recommeded to ensure safety of water. 

Ultrafiltration (UF) UF is a listed technology for all three categories of small public water systems.

Due to typical UF membrane pore sizes and size exclusion capability (e.g., 0.01 micron, molecular/

macromolecular range), UF is effective for absolute removal of Giardia cysts and partial removal of

bacteria and viruses, and when used in combination with disinfection appears to control these

microorganisms in water (4, 5). Tests have also shown that filtrate turbidity may be kept consistently

at or below 0.1 NTU (6). Due to the importance of disinfection providing a second barrier to

contamination, and due to stakeholders’ above-mentioned concern regarding maintenance of

additional non-membrane treatment for viral inactivation credit, EPA stresses the need for disinfection

in conjunction with membrane treatment.

Microfiltration (MF) MF is a listed technology for all three categories of small public water systems.

Due to typical MF membrane pore sizes and size exclusion (e.g., 0.1 to 0.2 micron, macromolecular/microparticle range), MF is effective for absolute removal of Giardia cysts and partial

removal of bacteria and viruses, and when used in combination with disinfection appears to control

these microorganisms in water (4, 5). Tests have also determined that filtrate turbidity may be kept

below 0.2 NTU (7), typically at or below 0.1 NTU (6). Due to the importance of disinfection
25

providing a second barrier to contamination, and due to stakeholders’ above-mentioned concern

regarding maintenance of additional non-membrane treatment for viral inactivation credit, EPA

stresses the need for disinfection in conjunction with membrane treatment.

References

1. 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).

2. Taylor, J.S., Duranceau, S.J., Barrett, W.M., and Goigel, J.F. Assessment of Potable Water

Membrane Applications and Research Needs. Prepared for AWWA Research Foundation, Denver

(1989). 

3. U.S. Environmental Protection Agency. Guidance Manual for Compliance with the Filtration and

Disinfection Requirements for Public Water Systems Using Surface Water Sources (1989 & 1991).

4. Jacangelo, J.G., Adham, S., and Laine, J-M. Application of Membrane Filtration Techniques for

Compliance With the Surface Water and Groundwater Treatment Rules. Prepared for AWWA

Research Foundation, Denver (1995).

5. Jacangelo, J.G., Laine, J-M., Carns, K.E., Cummins, E.W., and Mallevialle, J. “Low-Pressure

Membrane Filtration for Removing Giardia and Microbial Indicators.” Journ AWWA, September,

1991.

6. Letterman, R.D. et al. Evaluation of Alternative Surface Water Treatment Technologies.

Sponsored by New York State Department of Health (1991).

7. Olivieri, V.P., Parker, D.Y., Willinghan, G.A. and Vickers, J.C. Continuous Microfiltration of

Surface Water. AWWA Seminar Proceedings: Membrane Technologies in the Water Industry.

AWWA Membrane Processes Conference, Orlando (1991).

Bag and Cartridge Type Filtration

Bag filtration Bag filtration systems are based on the physical screening process to remove particles.

If the pore size of the bag filter is small enough, parasite removal will occur (1). In a bag filtration

unit system, water to be treated passes through a bag-shaped filter where the particulates are

collected allowing filtered water to pass to the outside of the bag (2). Bag filters are manufactured

and supplied by a variety of companies. Bags are available in a variety of material compositions and

pore size ratings (typically from 1 to 40 micron). The sizing of the bag filtration component is

conditional on the on raw water quality, including the amount of particulate matter and turbidity (3).

 Unless the quality of the raw water precludes the need for pre-treatment, EPA recommends

pretreatment of the raw water using sand or multimedia filters, followed by preliminary bag or

cartridge filters of 10 micron or larger pore size, and the use of 1-5 micron filters as final filters to
26

increase particulate removal efficiencies and to extend the life of the filter (2, 4). Contingent on the

filter manufacturer, bag filters can accommodate turbidity units from 0.1 to 10.0 NTU and flow

between 10 and 50 gpm (4). However, the bag filters will only last a few hours when turbidity

consistently exceeds 1 NTU.

Bag filters in combination with cartridge filtration units have been used to remove Giardia

lamblia at several locations serving small systems (3, 5). Bag filter studies have shown mixed results

in the removal of Cryptosporidium, ranging from approximately 70% to 99.9% (1). Studies of

various membranes using beads as surrogates for Cryptosporidium oocysts also showed variability

in the removal of this organism (6). 

Bag filtration field testing also showed poor to excellent reductions in turbidity. However, this

variability might be due to improper installation of the units, leaks or tears in the systems, or local

water quality conditions, or as a result of problems with pre-filters (2, 4). In any case, general trends

in field experience seems to show that the smaller the pore size rating, the better the filter efficiency.

Stakeholders emphasized that bag filters have been successfully used in water systems across the

country. Site-specific pilot testing has been used to determine applicability at individual systems. The

stakeholders also identified two other factors that can lead to variability in performance. The bag

filter must fit the housing, and different manufacturer’s products may not be interchangeable. Some

products use nominal pore size ratings rather than absolute pore size ratings, and since nominal pore

size ratings refer to some average pore size rather than the largest, particles larger than the nominal

pore size may pass through the filter. 

Stakeholders have indicated that bags can be fragile and that care must be taken during

installation of replacements, to prevent bag tearing. They also noted that monitoring of filter integrity

may be needed, but that State reviewers should have the latitude to decide on such requirements.

To further inactivate microorganisms, the final filter effluent would need disinfection to meet the

SWTR requirements.

Bag filters have been used successfully in water systems across the country. One key to success

is preliminary pilot testing of the process to ensure adequate removals. Pilot testing prior to

installation of a bag filter is recommended to address any performance variability factors. Bag filters

are best suited for systems in the first two small system size categories (i.e., systems serving up

to 3,300). However, bag filters are listed as a compliance technology for all three system size

categories.

References

1. Goodrich, J.A. and Fox, K. R., “Small System Control of Cryptosporidium for WQA

Recertification Credit,” Water Conditioning and Purification (February 1996): 50-58.

2. New York State Department of Health Bureau of Public Water Supply Protection, Alternative
27

Technology Filtration Study, May 1993.

3. Brandt, B. “‘Remote Control’ Used to Fight Giardia," Journal of the American Water Works

Association v 86 n 2 Feb 1994. p 137-138..

4. Smith, G.G., Small Surface Water Systems Alternate Filtration Report. Minnesota Department

of Health, June 1994.

5. The Greeley-Polhemus Group, Inc. and Malcolm Pirnie, Inc., “Case Studies Assessing Low-Cost,

In-Place Technologies At Small Water Systems,” Prepared for The Association of State Drinking

Water Administrators. July 1992.

6. Goodrich, J.A. et al, “Cost and Performance Evaluations of Alternate Filtration Technologies for

Small Systems.” Proceedings of the American Water Works Association, Annual Convention, 1995.

Cartridge filtration Cartridge filtration relies on a simple physical screening process to remove

particles. Due to materials used and the direction of flow, these are distinct from bag filters. Small

pore size openings prevent passage of contaminants through the filter (1). Typical cartridge filters

are pressure filters withglass fiber or ceramic membranes, or strings wrapped around a filter element,

housed in a pressure vessel (2). The pleating allows for higher surface area for filtration. These

filters are manufactured and supplied by a variety of companies with different pore size ratings (0.3

to 80 micron) and materials (2, 3). Similar to bag filtration, these units are very compact and do not

require much space. 

The pore size rating of the cartridge filtration component used is dependent on the on raw water

quality, including the amount of particulate matter and the turbidity (3). Depending on the quality

of the raw water, prefiltration of the raw water using sand or multimedia filter, followed by bag or

cartridge filters of 10 microns or larger pore size as preliminary filter, and the use of 1-5 micron filters

as final filters are recommended to increase particulate removal efficiencies and to extend the life of

the filter (6, 7).

Cartridge filters can be used for removal of Giardia lamblia (2, 3, 4). Filtration studies

conducted by EPA to determine Cryptosporidium removal using beads as surrogates showed that

cartridge filtration with 2 micron rated units exhibited log removals of 3.51 and 3.68 (5).

Stakeholders emphasized that cartridge filters have been successfully used in water systems

across the country. Site-specific pilot testing was used to determine applicability at individual

systems. The stakeholders also identified a factor that can lead to variability in performance. Some

products use nominal pore size ratings rather than absolute pore size ratings. Since nominal pore size

ratings refer to some average pore size rather than the largest, particles larger than the nominal pore

size may pass through the filter. 

Stakeholders have noted that cartridge filter seals are subject to damage, and that the housing

material may be improperly specified, resulting in leakage and/or other treatment malfunctions; they
28

also have noted that monitoring of filter integrity may need to be required, but that State reviewers

should have the latitude to decide on such requirements.

To further inactivate the microorganisms, the final filter effluent would need disinfection to meet

the SWTR requirements.

Cartridge filters have been used successfully in water system across the country for up to ten

years. One key to success is upfront pilot testing of the process to ensure adequate removals. Pilot

testing prior to installation of a cartridge filter is recommended to ensure adequate performance. 

Cartridge filters are best suited for systems in the first two small system size categories ( i.e.,

those serving up to 3,300 people). However, cartridge filters are listed as a compliance technology

for all three system size categories.

References

1. Goodrich, J.A. and Fox, K.R. “Small System Control of Cryptosporidium for WQA

Recertification Credit.” Water Conditioning and Purification (February 1996): 50-58.

 

2. U.S. Environmental Protection Agency. “Very Small Systems Best Available Technology Cost

Document”. September 1993.

3. Brandt, Barbara "'Remote control' used to fight Giardia," Journal of the American Water Works

Association. v. 86 n. 2, pp. 137-138. February 1994.

4. The Greeley-Polhemus Group, Inc. and Malcolm Pirnie, Inc. “Case Studies Assessing Low-Cost,

In-Place Technologies At Small Water Systems,” Prepared for The Association of State Drinking

Water Administrators. July 1992.

5. Goodrich, J.A. et al, “Cost and Performance Evaluations of Alternate Filtration Technologies for

Small Systems.” Proceedings of the American Water Works Association Annual Convention, 1995.

6. New York State Department of Health Bureau of Public Water Supply Protection. Alternative

Technology Filtration Study, May 1993.

 

7. Smith, G.G. Small Surface Water Systems Alternate Filtration Report. Minnesota Department

of Health, June 1994.

Backwashable depth filtration Backwashable depth filters operate in part like cartridge filters in

that water flows radially inward allowing the process of particle screening. In one system, bundles

of fibers (the filter medium) are rotated and compressed during the filtration mode; monitoring of

pressure is used to indicate clogging, which triggers a reverse flow of washwater under pressure;

during the backwash cycle the fibers are relaxed, stretched and squeezed to allow for the release of

trapped deposits. Tests in Europe have indicated greater than 2-log removal of the relatively small

microorganism, Cryptosporidium (1)(2). 
29

The NSF International protocol for testing backwashable depth filters (3) describes the

technology as such: a bag filter, cartridge filter, or granular media filter intended to filter

uncoagulated water and designed to be backwashed when terminal head loss is attained or turbidity

breakthrough occurs. The protocol notes that surface waters of high quality are the most appropriate

waters for backwashable depth filters, and that feed water turbidity may not be an adequate indicator

of suitability for this treatment. Particulate matter may consist of incompressible and/or compressible

substances such as algae or other biological matter (compressible particles being more problematic,

affecting frequency of filter backwashing). Therefore, the volume of water treated prior to

backwashing may vary greatly depending on the type of particulate matter in source water. NSF also

cautions that since backwashable depth filters are not intended to remove viruses, the burden of virus

control falls entirely on the disinfection process.

EPA finds that backwashable depth filters, while not used and tested extensively in the U.S.,

present similar characteristics as the above cited bag and cartridge filters. These filters may be best

suited for systems in the first two small system size categories ( i.e., those serving up to 3,300

people). However, backwashable depth filters are listed as a compliance technology for all three

small system size categories.

References

1. Ives, K.J. et al. “An Evaluation of the Effectiveness of the Fibrotex Filter in Removing

Cryptosporidial Oocysts from a Surface Water Supply.” Protozoan Parasites and Water. Edited by

W.B. Betts, et al., University of York, United Kingdom (1995).

2. Bernhardt, H. et al. “Investigations of the Retention Efficiency of Fibrotex Filters for

Cryptosporidium Oocysts Applying Low Turbid Waters from a Water Treatment Plant.”

Unpublished study by Wahnbacktalsperrenverband Siegburg, Universitat Bonn, and Kalsep Ltd.

3. NSF International. Draft NSF Equipment Verification Testing Plan: Backwashable Depth

Filtration for the Removal of Microbiological and particulate Contaminants (1998).

Section 2.6: Summary of Compliance Technologies for the SWTR

The following Tables 1(a) and 1(b), on disinfection and filtration treatments, respectively,

summarize the current listing of small water system compliance technologies for the SWTR. Water

system managers and other reviewers should examine the several columns included in this tablulation.

The filtration and the disinfection treatment tables each are split into Parts 1 and 2 to accomodate the

information categories presented. Limitations included in the tabulation are also described in the text

of this chapter, and in references cited. The technologies are listed for all three of the subject size

categories unless otherwise indicated. 

EPA has assigned each technology a level of complexity, reflective of ease of treatment operation

and, quite generally, the level of operator skill and knowledge that would be required to run the water

treatment plant to meet the subject regulations. If a given treatment is operationally complex, or
30

“advanced,” then the plant operator must have some form of training for such “advanced” treatment.

The tables characterize the skill level for each listed technology, ranging from basic, through

intermediate and advanced. For a unit technology that requires “basic operator skill”, an operator

with minimal experience in the water treatment field can perform the necessary system operation and

monitoring if provided with written instruction. “Intermediate operator skill” implies that the

operator understands the principles of water treatment and has a knowledge of the regulatory

framework. “Advanced operator skill” implies that the operator possesses a thorough understanding

of the principles of system operation, including water treatment and regulatory requirements. If

pretreatment is required at a given site, it may be assumed that the required operator skill levels will

increase; likewise, if certain features of a treatment train advance technologically, such that operation

is simplified or automated, then skill level may decrease. Further information on skill levels may be

found in publications by the American Water Works Association, and in protocols developed by the

NSF International under the previously-cited treatment verification program.

The SWTR compliance technology list includes new technological, operational, and other

information not listed previously by EPA. Information is provided on important raw water

parameters, chemical and physical byproducts produced, and other possible limitations that should

be considered in selection and design of treatment. The following tabulation is meant for quick

reference regarding the listed compliance treatment technologies. It should be recognized that sitespecific conditions may preclude certain applications, and that conditions may necessitate other forms

or variants of the listed treatment to maximize control of the subject microbiological contaminants.
1CT (Concentration x Time), in mg-min/L, based upon 1989 Surface Water Treatment Rule Guidance Manual. Temp. 10 C, 

mid-pH range, unless otherwise indicated.

2UV dose is product of mW/cm2 (intensity) x sec (time); bases of viral inactivation ranges are rotavirus and MS-2 tests (see text).

3Unpublished research results of Malley et al. (1997-98) suggest correlations; groundwater principally studied.

31

Table 1a. SURFACE WATER TREATMENT COMPLIANCE TECHNOLOGY TABLE

DISINFECTION TECHNOLOGIES (Part 1)

Unit

Technologies

Removals:

Log Giardia & Log Virus w/CT’s

indicated in ( )1

Complexity: 

Ease of Operation

(Operator Skill)

Raw Water, Pretreatment

& Other Water Quality Issues

Free Chlorine 3 log (104) & 4 log (6) Basic Better with high quality. Pretreatment may be needed to reduce disinfection

byproduct (DBP) precursors; and/or to reduce pH, turbidity, and/or chlorine dose. If

high potential for DBPs, chloramination may be best for distribution protection. 

Where Fe/Mn high, sequestration or physical removal may be needed.

Ozone 3 log (1.43) & 4 log (1.0) Intermediate Better with high quality. pH 7 to 9 and/or above normal temperatures may increase

cyst inactivations. Pretreatment may control DBP formation; and Fe/Mn may

necessitate sequestration or physical removal.

Chloramines 3 log (1850) & 4 log (1491) Intermediate Better with high quality. Excess ammonia (low Cl2 to N ratio) can promote growth

of nitrifying bacteria in filters, which convert ammonia to nitrates and nitrites;

nitrification in covered reservoirs also likely. Ammonia dose should be tempered by

natural ammonia levels in water.

Ultraviolet

Radiation

1 log Giardia (80-120) & 

4 log viruses (90-140) mWsec/cm2

doses in parentheses2

Basic Relatively clean source water required. UV adsorption (e.g., Fe, NOM) and scattering

constituents (e.g., particles) affect dosage for microbial inactivation, and therefore

system design/cost. Data indicate strong correlation between dose required and iron;

bench-scale studies using microbial surrogate recommended.3

On-Site

Oxidant

Generation

Research pending on CT values Basic Better with high quality. Other factors: Chlorine production rates may vary; CT

based on chlorination is suggested. See also Free Chlorine.
32

Chlorine

Dioxide

3 log (23) & 4 log (25) Intermediate Better with high quality. DBPs include chlorite and chlorate. Photochemical

decomposition of ClO2 in uncovered reservoirs may increase chlorate concentrations

in water. Generation process, pH, and other factors, can affect chlorate/chlorite

levels.
33

Table 1a. SURFACE WATER TREATMENT COMPLIANCE TECHNOLOGY TABLE

DISINFECTION TECHNOLOGIES (Part 2)

Unit Technologies Disinfection Byproducts

Concerns

Other Limitations

Free Chlorine Trihalomethanes, haloacetic acids,

aldehydes, inorganic byproducts,

others.

Fe and Mn demand, pH and other factors influence dose. DBP production

should be monitored where precursors occur. Providing adequate CT

(time/storage) may be a problem for some supplies. Chlorine gas requires

special caution in handling and storage, and operator training.

Ozone Organic acids, aldehydes, AOC, and

others. If bromide present, brominated

organics and bromate.

Ozone leaks represent hazard: air monitoring required. Ozone used as primary

disinfectant (i.e., no residual protection). Biodegradable organics may affect

distributed water quality. Personnel time requirements for system cleaning may

be fairly substantial.

Chloramines Long CT. Requires care in monitoring of ratio of added chlorine to ammonia. 

Chlorine Dioxide Storage and handling precautions: exposure to heat, sunlight, or UV light may

decrease product strength; spillage would require rapid recovery/sumps, and

access to water for cleanup.

On-site Oxidant

Generation

Chlorate (ClO3

-

), bromate (BrO3

-

), and

chlorinated THMs

Research will determine CT values appropriate for electolyzed salt brine. Other

oxidants (other thatn chlorine) not detected in solution by significant research

effort.

Ultraviolet Radiation NA No disinfectant residual protection for distributed water. Periodic calibration of

UV sensors and other special maintenance may be required.
4National Research Council, Committee on Small Water Supply Systems. “Safe Water From Every Tap: Improving Water

Service to Small Communities.” National Academy Press, Washington, D.C. (1997).

34

Table 1b. SURFACE WATER TREATMENT COMPLIANCE TECHNOLOGY TABLE

FILTRATION TECHNOLOGIES (Part 1)

Unit Technologies Removals:

Log Giardia & Log Virus 

Raw Water, Pretreatment

& Other Water Quality Issues 

Conventional Filtration and

Specific Variations on

Conventional

2-3 log Giardia & 1 log viruses Wide range of water quality. DAF more applicable for removing

particulate matter that doesn’t readily settle: algae, high color, low turbidity

(up to 30-50 NTU) and low-density turbidity. Prior to filtration: chemical

coagulation, rapid mix, flocculation, sedimentation or flotation (depth

clarifiers or roughing filters may replace sedimentation).

Direct Filtration 0.5 log Giardia & 1-2 log 

viruses (and 1.5-2 log Giardia

with w/coagulation)

Suggested limits: average turbidity 10 NTU; maximum turbidity 20 NTU;

40 color units; algae on a case-by-case basis4. Prior to filtration: chemical

coagulation and rapid mixing.

Slow Sand Filtration 4 log Giardia & 1-6 log viruses “Schmutzdecke” formation prerequisite. Pretreatment or process

modifications required if raw water high in turbidity, color, and/or algae.

Diatomaceous Earth

Filtration

Very effective for Giardia (2

to3-log) and Cryptosporidium

(up to 6-log); low bacteria and

virus removal

Low turbidity, low color water; low organic DBP precursors. Pretreatment

may be used to decrease turbidity and DBP precursors, although chemical

coagulation is not typically necessary.
5Ref. “Recommended Standards for Water Works.” Policy Statement on Reverse Osmosis Treatment by the Great LakesUpper Mississippi River Board of State Public Health & Environmental Managers (1997).

6Ref. Chellam, S. Et al., “Effect of Pretreatment on Surface Water Nanofiltration.” JAWWA, October 1997 (Vol. 89, Issue 10). 

And, Lozier, J., et al, “Integrated Membrane Treatment in Alaska,” JAWWA, October 1997 (Vol. 89, Issue 10). It is noted that the use

of microfiltration as pretreatment may not result in removal of all foulants, i.e., nanofilters may require more frequent chemical cleaning

than when ultrafilter is used as pretreatment.

7Ref. Adham,S.S, Jacangelo, J.G., and Laine, J.M. “Characteristics and Costs of MF and UF Plants.” JAWWA, May 1996.

35

Reverse Osmosis Very effective, absolute barrier 

(cysts and viruses)

May require conventional or other pretreatment for surface water to

protect membrane surfaces: may include turbidity or Fe/Mn removal;

stabilization to prevent scaling; reduction of dissolved solids or hardness;

pH adjustment.5

Nanofiltration Very effective, absolute barrier

(cysts and viruses)

Very high quality or pretreatment required (e.g., micro- or ultra-filtration to

reduce fouling/extend cleaning intervals).6 See also Reverse Osmosis

pretreatments, above.

Ultrafiltration Very effective Giardia, >5-6

log7; Partial removal viruses

(disinfect for virus credit)

High quality or pretreatment required (e.g., microfiltration). TOC rejection

generally low, so if DBP precursors are a concern, NF may be preferable.

Microfiltration Very effective Giardia, >5-6 log; 

Partial removal viruses

(disinfect for virus credit)

High quality or pretreatment required. Same note as for ultrafiltration

regarding TOC.

Cartridge/

Bag/Backwashable Depth

Filtration

Variable Giardia removal &

Disinfection required for virus

removal 

Very high quality or pretreatment required, due to low particulate loading

capacity. Depending on raw water quality, sand or multi-media prefilter,

and 10 micron preliminary filter prior to 1 to 5 micron filter, recommended. 

See also NSF protocols.
36

Table 1b. SURFACE WATER TREATMENT COMPLIANCE TECHNOLOGY TABLE

FILTRATION TECHNOLOGIES (Part 2)

Unit Technologies Complexity: 

Ease of Operation

(Operator Skill Level)

Secondary Waste

Generation

Other Limitations/Drawbacks

Conventional Filtration and

Specific Variations on

Conventional

Advanced Sludge (varying solids %),

backwash, filter to waste

High monitoring requirements; full-time operator or

“circuit rider” attention.

Direct Filtration Advanced Filter backwash High monitoring requirements; full-time operator or

“circuit rider” attention.

Slow Sand Filtration Basic Filter cake. Filter to waste

(2-day) each ripening period

Algae (especially seasonal blooms) in raw water can clog

filters and cause variations in run length. Not very

effective in removal of DBP precursors or color. Most

effective on high quality source water, i.e., those of low

turbidity, algae and color.

Diatomaceous Earth Intermediate Diatomaceous filter residue

(substantial amounts)

Intermittent operation of DE filters not advised unless the

system recycles water through the filter: this will extend

the filtration cycle and lower filter maintenance. Low raw

water turbidity/color water.

Reverse Osmosis Intermediate: increases with

pre/post-treatment and

membrane cleaning needs.

Briney waste. High volume,

e.g.,25 to 50 percent. May

be toxic to some species

Bypassing of water (to provide blended/stabilized

distributed water) cannot be practiced at risk of increasing

microbial concentrations in finished water. Postdisinfection required under regulation, and recommended

as a safety measure and for residual maintenance. Other

post-treatments may include degassing of CO2 or H2S,

and pH adjustment.

Nanofiltration Intermediate: increases with

pre/post-treatment and

membrane cleaning needs.

Concentrated waste. 5 to 20

percent volume

Disinfection required under regulation, and recommended

as a safety measure and residual protection.
37

Ultrafiltration Basic:increases with

pre/post-treatment and

membrane cleaning needs.

Concentrated waste. 5 to 20

percent volume. Waste may

include sand, silt, clays,

cysts, algae, viruses and

humic material (Ref. 2).

Disinfection required for viral inactivation.

Microfiltration Basic:increases with

pre/post-treatment and

membrane cleaning needs.

Low volume waste may

include sand, silt, clays,

cysts, and algae.

Disinfection required for viral inactivation.

Cartridge/Bag/Backwashable

Depth Filtration

Basic Discarding of cartridges and

filters. Backwashable depth

filters may be equipped with

inactivation devices to

disinfect waste.

Requires relatively pure raw water. Care must be taken

not to damage clean cartridges, or tear bags, upon

installation. Cartridge replacement may be frequent,

increasing O&M requirements. Algae and fragments of

biological material may disrupt filter. Disinfection is

required for viral inactivation, i.e., disinfection CxT,

following filtration. May be more applicable to systems

serving fewer than 3,300.
38

3. COMPLIANCE TECHNOLOGIES FOR THE TOTAL COLIFORM RULE 

EPA promulgated the total coliform rule (TCR) in June 1989. The TCR contains a listing of “best

technologies, treatment techniques, or other means available for achieving compliance with the maximum

contaminant level (MCL) for total coliforms” [ from 40 CFR Ch. 1, §141.63 (d)]. Listed as best techniques

under TCR are:

 • Protection of wells from contamination (ground water)

 • Maintenance of disinfection residual for distribution

 • Proper maintenance of distribution systems

 • Filtration and/or disinfection

• State WHPP (ground water)

At the time these techniques were codified, no specific notation as to applicability to categories of public

water system size was included. However, with passage of the Safe Drinking Water Act of 1996, EPA is

to specify compliance technologies for three small water system size categories, defined by the Act as those

serving 10,000 - 3,301 persons; 3,300 - 501 persons; and 500 - 25 persons. 

As mentioned in Chapter 1, there are no variance provisions for regulations that control

microbiological contamination.

Following presentation at the May 1998 meeting with stakeholders of EPA’s proposed TCR

compliance technology listing, which essentially is the same as the above-cited 1989 listing, EPA has not

received substantive comments on this listing. Therefore, the Agency is listing the same treatment

techniques and other means for small systems compliance as were codified in the 1989 rule.

The following Table 2 contains some explanatory comments regarding each of the treatments and

other means listed. The comments are only meant as additional guidance in that certain codes of practice

may be useful in addressing a problem; or in terms of pointing out where additional constituents in water

may need additional attention (e.g., iron and manganese, ammonia, THM precursors).

It is also necessary to note that determining application of a treatment technique or other means to

comply would be highly dependent upon what factors are contributing to an MCL violation. For example,

faulty maintenance procedures and/or a leaking pipeline that may have triggered an MCL violation would

obviously require a different technological response than where a compromised well structure has been

found to be the cause of microbiological pollution. In addition, depending on the number and types of

faults that are found, a system may need to implement more than one compliance technology to adequately

safeguard its water system.
39

Table 2: TOTAL COLIFORM RULE COMPLIANCE TECHNOLOGIES

40 CFR Ch. 1 §141.63(d) 

Best Technologies or Other Means to Comply

(Complexity Level Indicated)

Comments/Water Quality Concerns

Protection of wells from contamination, i.e.,

placement and construction of well(s) 

 (Basic)

Ten States Standards and others (AWWA A100-90) apply; setback distances and protective vadose

zones; interfacing with other programs essential (e.g., source water protection program).

Maintenance of a disinfection residual for

distribution system protection

 (Intermediate)

Source water constituents may affect disinfection: Fe/Mn, organics, ammonia, other factors may affect

dosage and water quality. TTHM production and corrosion (Pb/Cu) may be issues. Biofilm formation

and other deposits in pipes may affect water quality.

TCR remains unspecific on type/amount of disinfectant, as each type differs in concentration, time,

temperature, pH, interaction with other constituents, etc.

Proper maintenance of distribution system: pipe

repair/replacement, main flushing programs,

storage/ reservoir and O&M programs 

(including cross-connection control/ backflow

prevention), and maintenance of positive

pressure throughout 

 (Intermediate)

O&M programs particularly important for smaller systems needing to maintain water purity. States may

vary on distribution protection measures. See also Appendix C EPA memorandum (Issue #2) in

reference to cross-connection control as proper maintenance; and EPA’s Cross-Connection Control

Manual (# EPA 570/9-89-007).

Filtration and/or Disinfection of surface water or

other groundwater under direct influence

(Subpart H/SWTR); or disinfection of

groundwater (Basic thru Advanced)

Same issues as cited above under maintaining disinfection residual; pretreatment requirements affect

complexity of operation.

Refer to SWTR Compliance Technology List; and other regulations under development.

Groundwaters: Compliance with State WellHead Protection Program

 (Intermediate)

EPA/State WHPP implementation (per §1428 SDWA): may be used to assess vulnerability to

contamination, and in determination of sampling and sanitary survey frequencies.
40

4. “EMERGING” TECHNOLOGIES AND ISSUES FOR FURTHER CONSIDERATION 

Section 4.1: Emerging Technologies

In 1997 EPA listed additional new or “emerging” technologies that merit further consideration as small

system compliance technologies under the SWTR and/or TCR. The Agency stated that if found to be

viable, these newer technologies would be incorporated in forthcoming lists. Identified were the following

emerging treatments or means to comply:

 • Advanced oxidation or perozone

 • Pulsed ultraviolet 

 • Ultraviolet oxidation

 • Point-of-entry (POE) devices*

*NOTE: POE treatment as a centrally managed treatment option was considered by EPA, however, the

Agency feels that POE application for addressing microbial contamination would be very limited due to

the concern for disinfecting water properly (following filtration) and the complexity of monitoring POE

systems individually.

Stakeholders at the May 1998 meeting agreed that this listing of technologies should remain very

inclusive, and that the emerging technologies should be investigated as more data on their use become

available. Stakeholders also advised that EPA should not be overly “prescriptive” in this listing on specific

factors that would impinge on site-specific designs. The listing should, therefore, continue to develop as

a tool for State regulatory personnel and small water system managers in their decision making.

EPA reviewed available information and industry-supplied data on the above emerging treatment

technologies, and determined that current data do not support the listing of the “advanced ultraviolet” and

“advanced oxidation” type processes in this context. In most cases, while appropriate in treating water

contaminated with other substances (such as organic contaminants), these treatments have not yet found

use at water systems for inactivating the target microorganisms. Two main reasons are cited for not

listing these as compliance technologies at this time:

(1) The Agency has not reviewed data on inactivation by these advanced processes of Giardia cysts

and viruses subject to the requirements of the SWTR.

(2) These processes may not have been tested/piloted in the field for meeting the subject regulatory

requirements. This may be due to a lack of penetration into and/or acceptance within the small

systems market at this time, or due to a perception that advanced treatments are not necessary, or may

be burdensome to operate for smaller systems, given that simpler, single-oxidant treatment

technologies have proven effective for the purposes stated.

The following is a brief summary of information EPA has reviewed on the above-mentioned advanced

treatment technologies. It should be noted that the Agency would continue to accept and review data that

may indicate progress in application of these treatments for control of microorganisms in water.
41

ADVANCED ULTRAVIOLET TREATMENTS

Pulsed Ultraviolet (UV) Pulsed ultraviolet radiation treatment is application of UV technology to a water

column via repeated high intensity bursts (or “high power density” pulses (1)) of radiation, as opposed to

continuous wave UV application which typically applies constant but lower levels of power and irradiation.

Tests on this technology have centered on efficacy of pulsed-UV treatment in treating oocysts of

Cryptosporidium (2)( 3) (4), and to some extent on inactivation of bacteria (5). A study presented in 1997

indicated that a pulsed UV system had produced an approximate 2-log inactivation of Cryptosporidium

oocysts (4). EPA has not viewed data on Giardia inactivation, or small systems applications of this

technology; American Water Works Association Research Foundation research results may be of assistance

in determining pulsed UV efficacy, likely targeting Cryptosporidium in water.

(1) LaFrenz, R. Application of Pulsed UV for Water Disinfection. Innovatech, Inc. Presented at AWWA

Water Quality Technology Conference, 1997.

(2) Cryptosporidium Testing Using Pulsed UV Light. US Centers for Disease Control, Atlanta Georgia,

February 10, 1994.

(3) Lorenzo-Lorenzo, M.J. et al. Effect of Ultraviolet Disinfection of Drinking Water on the Viability of

Cryptosporidium parvum Oocysts. Journal of Parasitology. 79(1)67-70 (1993).

(4) Clancy, J.L. et al. Inactivation of Cryptosporidium parvum Oocysts in Water Using Ultraviolet Light.

Clancy Environmental Consultants, University of Arizona, and United Water- N.J. in collaboration:

Presented at the AWWA International Symposium on Cryptosporidium and Cryptosporidiosis, Newport

Beach CA (March 1997).

(5) Bank, H.L. et al. Bactericidal Effectiveness of Modulated UV Light. Applied and Environmental

Microbiology, 56(12)3888-3889.

Ultraviolet Oxidation This treatment is the combination of ultraviolet and a strong chemical oxidant such

as hydrogen peroxide (or ozone). One study indicates 3-4 log reductions of coliphages, at doses of 10

mmol/L H2O2 and ultraviolet at 0.8 W/L (no time indicated) (1). One stakeholder reported that the

combination of UV and ozone has been in use overseas, though apparently not in the U.S. Ultraviolet

oxidation appears to have been applied more so in non-drinking water settings, e.g., in control of organic

compounds in wastewater. Testing on Giardia cysts (for characterizing of dosing requirements) have

apparently not been conducted. This treatment combination may be useful in pre-oxidizing iron,

manganese, and/or Arsenic (III) in raw water and providing disinfection credit. 

(1) Rajala R.L., et al. Effect of Advanced Oxidation Processes on Inactivation of Coliphages, Water

Science and Technology (1995).

Other Ultraviolet Variations Other modifications of the conventional or continuous wave UV application

include: 
42

! A medium pressure lamp system using a collimated beam was been pilot tested in an advanced

wastewater treatment application, at the Montreal wastewater plant. Fecal coliforms were inactivated

(over 3-logs) at doses of approximately 35 mWs/cm2, and other factors were investigated such as

turbidity, particle size distribution, UV transmittance, dissolved organics and iron. Photoreactivation

and dark repair mechanisms were found to increase microbial counts at higher UV doses (1). 

! An advanced ultraviolet cryptosporidium inactivation device incorporates within its design two

chambers that successively screen/trap microorganisms and irradiate them while trapped, at successive

doses of 4,000 mWs/cm2 (i.e., total dose approx. 8,000 mWs/cm2). Results of testing have been

presented to EPA and others: the tests indicate that greater than 4-log (99.99%) of Cryptosporidium

oocysts were inactivated by the process in a full-scale “pilot” test; results also indicated a need to

assess the maximal levels of inactivation, which may exceed 4-log, and to demonstrate the efficacy and

applicability of the treatment in real world applications, i.e., beyond the test’s carefully controlled trial

conditions (2). An additional challenge test using E.coli bacteria and B. subtilis (more resistant

bacterial endospores) on this same device resulted in a 4.9 log reduction in E. Coli, and a 1.3 log

reduction in B. subtilis (3). AWWA’s Opflow (4) monthly included an article on a demonstration of

the UV treatment unit (and ozonation) at a plant in Wisconsin.

! Additional research has been conducted on medium-pressure UV systems, and on pulsed UV using

xenon lamps. Also, thin film UV designs are being considered , possibly for reduction of dose and

power requirements. More research may result in more efficient designs for SWTR or enhanced

SWTR applications.

(1) Cairns, W.L., Sakamoto, G., Comair, C.B., and Gehr, R. Assessing UV Disinfection of a Physicochemical Effluent by Medium Pressure Lamps Using a Collimated Beam and Pilot Plant.” Trojan

Technologies, DigiPen Computer Graphics, and McGill University in collaboration: Presented at the WEF

Specialty Conference on Effluent Disinfection Systems. New Jersey (May 1993).

(2) Clancy, J.L. et al. Inactivation of Cryptosporidium parvum Oocysts in Water Using Ultraviolet Light.

Clancy Environmental Consultants, University of Arizona, and United Water- N.J. in collaboration:

Presented at the AWWA International Symposium on Cryptosporidium and Cryptosporidiosis, Newport

Beach CA (March 1997).

(3) Evaluation of the Disinfection Capabilities of the Safe Water Solutions L.L.C. Cryptosporidium

Inactivation Device. Clancy Environmental Consultants, report commissioned by Safe Water Solutions

L.L.C. (December 1996).

(4) Johnson, R.C. Getting the Jump on Cryptosporidium with UV. Opflow: American Water Works

Association, v.23, no.10 (October 1997).
43

ADVANCED OXIDATION PROCESSES

Advanced oxidation processes (AOPs) are oxidation processes that generate highly reactive hydroxyl

radicals. Hydroxyl radicals are produced by an accelerated the ozone decomposition rate, through the

addition of hydrogen peroxide (H2O2) and/or ultraviolet (UV) light to ozonated water. The most

commonly used AOP is the combination of hydrogen peroxide and ozone, also referred to as peroxone or

perozone (see above section on ultraviolet oxidation for more information on the UV-chemical oxidation

disinfection process).

Peroxide-ozone treatment has primarily been used to treat organics in water such as taste and odor

compounds and chlorinated organics. Metropolitan Water District (MWD) of Southern California

conducted extensive research into the removal of geosmin and 2-methylisoborneol (MIB). MWD also

performed studies on the inactivation of microorganisms using the peroxone process. The inactivation rates

were comparable to ozone at hydrogen peroxide to ozone ratios ranging from 0.2-0.3. E. coli, MS2 and

f2 coliphages were inactivated at rates greater than 5 log10, and hetrotrophic plate count (HPC) bacterium

was inactivated at approximately 1.2-2.5 log10. In other studies, inactivation of Giardia muris cysts using

peroxone was also comparable to ozone. The inactivation rate for Giardia muris was 2.3 ± 0.2 log10,

suggesting that peroxone is slightly more potent in inactivating this microbe than ozone. This advanced

process may also be of use in lowering brominated disinfection byproducts where bromides are present.

 

Regarding raw water quality, higher levels of alkalinity affect the ozone residual, increasing

microorganism inactivations. Finch, et al., indicates O3 dose, pH, turbidity and temperature all affect

advanced oxidation efficiency. Also, above 0.5:1 application rate (hydrogen peroxide to ozone) there is no

apparent benefit; and as a precaution, above a 1:1 ratio of hydrogen peroxide to ozone the toxicity of H2O2

is an issue. 

Since the primary components in the peroxone system are ozone and hydrogen peroxide, it has the

same limitations as ozone. Peroxone can only be used as a primary disinfectant due to its high reactivity

rate; it does not maintain an appreciable residual level. Performance is based upon an optimal hydrogen

peroxide to ozone ratio of less than 0.5. Peroxone treatment may also have some small system limitations

because ozone must be generated at the point of use due to its instability, and hydrogen peroxide is

considered a hazardous material requiring secondary containment storage facilities.

Advanced oxidation is considered an emerging technology. The majority of advanced oxidation

research as been for treatment of organics. Because of peroxone’s oxidative properties, a system which

uses ozone as the primary disinfectant may want to consider advanced oxidation if they need to treat

organics as well. More studies will have to be performed before advanced oxidation becomes a common

technology for disinfection.

(1) Roy Wolfe, et al. Inactivation of Giardia muris and Indicator Organisms Seeded in Surface Water.

ES&T, 1989

(2) Roy Wolfe, et al. Disinfection of Model Indicator Organisms in a Drinking Water Pilot Plant by using

PEROXONE. Applied & Environmental Microbiology, 1989.
44

(3) Rajala, R.L. et al. Effect of Advanced Oxidation Processes on Inactivation of Coliphages.

Wat. Sci. Tech., 1995.

(4) McGuire, M.J., et al. Treating Water with Peroxone: A Revolution in the Making. 

WATER/Engineering & Management, May 1988.

(5) Finch, G.R. et al. Ozone and Ozone-Peroxide Disinfection of Giardia and Viruses.

AWWARF & AWWA, 1992.

Section 4.2: Additional Issues for Consideration

EPA will continue to seek, through voluntary submittal by stakeholders of on-going treatment

evaluations, and through other developmental activities, new information that may be useful to users of this

guide. It is anticipated that many of the technology issues discussed in this listing will be clarified when

further information is available. EPA particularly seeks information on treatment availability; design and

operational factors including raw water concerns and byproducts issues, system management, and of course

on treatment efficacy.

EPA will also keep abreast of other efforts underway in the fields of equipment testing, certification,

on-site verification, State-developed or other independently developed protocols for equipment tests,

operational issues, and other related concerns. The Agency is committed to continuing its dialogue with

stakeholders, both in terms of identifying issues and resolving them.

Finally, it should be noted that this listing may be viewed as a transitional listing as EPA considers

further regulations that will impact large, and small, water supplies; EPA has begun this transition by

including in this listing data that will be of greater import to systems as they prepare to provide the next

level of control of microbial pathogens in water, namely enhanced surface water treatment needs and

inactivation/removal of oocysts such as Cryptosporidium, which is to be addressed in later EPA rules.

Research in this area is moving rapidly, and results of national survey data will be forthcoming. These are

expected to be of use in regard to determining suitable compliance technologies for meeting the enhanced

surface water treatment requirements.
APPENDIX A

RELEVANT PARTS OF SECTIONS 1412 OF THE REVISED SAFE DRINKING WATER ACT 

(SECTION 1412(b)(4)(E)(ii) thru (v) as amended in 1996)
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 

 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).''.
APPENDIX B

ADDITIONAL REFERENCES ON SWTR-APPROVED FILTRATION TECHNOLOGIES
Cleasby, J.L. “Source Water Quality and Pre-treatment Options for Slow Sand Filters”. Chapter 3 in Slow

Sand Filtration. Gary Logsdon, ed. American Society of Civil Engineers. New York. 1991.

Collins, M. Robin. “Removing natural organic matter by conventional slow sand filtration”. American

Water Works Association Journal, v. 84 (May '92) p. 80-90. 

Collins, M. Robin. Evaluating modifications to slow sand filters. American Water Works Association

Journal, v. 83 (Sept. '91) p. 62-70.

Fogel, Doug. “Removing Giardia and Cryptosporidium by slow sand filtration”. American Water Works

Association Journal, v. 85 (Nov. '93) p. 77-84. 

Fulton, George P. "Diatomaceous earth filtration for reduced risk water treatment." PUBLIC WORKS v.

126 (Nov. '95) p. 34-6.

Gifford, John S. et al. "Synergistic effects of potassium permanganate and PAC in direct filtration systems

for THM precursor removal." WATER RESEARCH v. 23 (Oct. '89) p. 1305-12.

Goding, Clifford. "(Very) ancient filter medium." WATER/ENGINEERING & MANAGEMENT v. 136

(Oct. '89) p. 36.

Graham, Nigel J. D. et al. "Evaluating the removal of color from water using direct filtration and dual

coagulants." AMERICAN WATER WORKS ASSOCIATION JOURNAL v. 84 (May '92) p. 105-13.

Haarhoff, Johannes. et al. "Direct filtration of Chlorella with cationic polymer." JOURNAL OF

ENVIRONMENTAL ENGINEERING v. 115 (Apr. '89) p. 348-66.

Knocke, William R. et al. "Examining the reactions between soluble iron, DOC, and alternative oxidants

during conventional treatment." AMERICAN WATER WORKS ASSOCIATION JOURNAL v. 86 (Jan.

'94) p. 117-27.

Lay, Trudie. “Slow sand: timeless technology for modern applications”. American Water Works

Association Journal, v. 84 (May '92) p. 10. 

Leland, David E. Slow sand filtration in small systems in Oregon. American Water Works Association

Journal, v. 82 (June '90) p. 50-9.

Logsdon, Gary S. et al. "Testing direct filtration for the treatment of high-turbidity water." AMERICAN

WATER WORKS ASSOCIATION JOURNAL v. 85 (Dec. '93) p. 39-46.

Ongerth, Jerry E. "Evaluation of treatment for removing Giardia cysts.” AMERICAN WATER WORKS

ASSOCIATION JOURNAL v. 82 (June '90) p. 85-96.

Nieminski, Eva C. et al. "Removing Giardia and Cryptosporidium by conventional treatment and direct

filtration." AMERICAN WATER WORKS ASSOCIATION JOURNAL v. 87 (Sept. '95) p. 96-106.

Peer, George J. et al. "Spiking tests prove DE filtration works for high Giardia concentrations."
WATER/ENGINEERING & MANAGEMENT v. 140 (June '93) p. 18-19.

Randall, Nick. “A small town helps itself--to time-tested slow sand filter technology”. Public Works, v.

122 (Aug. '91) p. 104-6.

Rees, Robert H. et al. "Let diatomite enhance your filtration.” CHEMICAL ENGINEERING v. 97 (Aug.

'90) p. 76-9.

Rees, Robert. "Diatomites cut filtration costs.” POLLUTION ENGINEERING v. 22 (Apr. '90) p. 67-8+.

Riesenberg, F., Walters, B., Steele, A., and Ryder, R. Slow sand filters for a small water system. American

Water Works Association Journal, v. 87 (Nov. '95) p.48-56.

Schuler, Peter F. et al. "Diatomaceous earth filtration of cysts and particulates using chemical additives."

AMERICAN WATER WORKS ASSOCIATION JOURNAL v. 82 (Dec. '90) p. 67-75.

Schuler, Peter F. Slow sand and diatomaceous earth filtration of cysts and other particulates. Water

Research, v. 25 (Aug. '91) p. 995-1005. 

Spencer, Catherine M. et al. "Improving precursor removal." AMERICAN WATER WORKS

ASSOCIATION JOURNAL v. 87 (Dec. '95) p. 71-82.

Tobiason, John E. et al. "Pilot study of the effects of ozone and PEROXONE on in-line direct filtration."

AMERICAN WATER WORKS ASSOCIATION JOURNAL v. 84 (Dec. '92) p. 72-84.

VanArnam, David G. et al. "Diatomaceous-earth water filtration." WATER/ENGINEERING &

MANAGEMENT v. 136 (Oct. '89) p. 35-6.

Visscher, Jan Teun. Slow sand filtration: design, operation, and maintenance. American Water Works

Association Journal, v. 82 (June '90) p. 67-71. 

Walton, Harris G. "Diatomite filtration: why it removes Giardia from water." WATER/ ENGINEERING

& MANAGEMENT v. 136 (Oct. '89) p. 38.

Wiesner, Mark R. et al. "Cost estimates for membrane filtration and conventional treatment." AMERICAN

WATER WORKS ASSOCIATION JOURNAL v. 86 (Dec. '94) p. 33-41.
APPENDIX C

MEMORANDUM REGARDING TCR TECHNOLOGIES
MEMORANDUM

SUBJECT: Clarification of Issues Concerning the Revised Total Coliform Rule

FROM: Michael B. Cook, Director

Office of Drinking Water (WH-550D)

TO: Water Supply Branch Chiefs

Environmental Services Division Directors 

Quality Assurance Officers 

Regions-I-X

Several Regions and States have requested clarification on parts of the revised total coliform

rule, promulgated June 19, 1989. These clarifications appear below.

1. ISSUE: Why is it the total coliform rule does not distinguish between transient non-community

water systems and non-transient non-community water systems like some rules regulating chemical

contaminants?

Regulations on chemical contaminants generally deal with chronic exposure, i.e., lifetime

exposure; this differs from microbiological regulations where a single exposure may result in illness. 

Moreover, the vast majority of non-community water systems will sample fewer than five times per

month, and thus be required to have a sanitary survey every 5 years (with some exceptions), the same

as like-sized community water systems. For such systems, sanitary surveys are more important for

protecting public health than monitoring. Thus, it is less important to differentiate between the two

types of non-community water systems.

2. ISSUE: Is a cross-connection control program included as a best available means for achieving

compliance with the MCL?

§141.63(d) identifies the best technology, treatment techniques, or other means available for

achieving compliance with the MCL for total coliforms. This list includes paragraph (3) in that

section, "Proper maintenance of the distribution system including appropriate pipe replacement and

repair procedures, main flushing programs, proper operation and maintenance of storage tanks and

reservoirs, and continual maintenance of positive water pressure in all parts of the distribution

system...” EPA considers this statement as including a cross-connection control program.

3. ISSUE: Where is a fourth repeat sample collected?

§141.21(b)(2) states that a system which has a total coliform-positive sample must collect at

least one repeat sample from the sampling tap where the original total coliform-positive sample was

taken, and at least one repeat sample at a tap within five service connections upstream and at least one

repeat sample at a tap within five service connections downstream of the original sampling site. EPA
did not specifically state that a system required to take a fourth repeat sample by §141.21(b)(1) was to

take it within five service connections of the original sample, but that was implied in the rule in

§141.21(b)(2), and was the Agency's intention (see definition of repeat sample in the preamble on 54

FR 27553, column 1, first paragraph).

4. ISSUE: Where are additional sets of repeat samples collected?

§141.21(b)(4) states that if one or more samples in a set of repeat samples 4-s total coliformpositive, the system must collect an additional set of repeat samples. The rule, however, is not clear

on where the additional set is to be collected, five adjacent service connections from the original total

coliformpositive tap or the repeat total coliform-positive tap (assuming only one repeat sample is total

coliform-positive). EPA believe's that this situation would generally occur only when the distribution

system is contaminated, and consequently will allow the system to decide on which of the two taps to

center the second set of repeat samples.

5. ISSUE: If a system has a fecal col'iform-positive sample and all repeat samples are total

coliform-negative, does that system have an acute violation of the MCL for total coliforms?

§141.63(b) specifies the MCL for total coliforms, based upon the presence of fecal coliforms or

E. coli. Based upon this paragraph, if a system has a total coliform-positive routine sample which is

also fecal coliform-positive (or E. colipositive), and all repeat samples are total coliform-negative,

then the system has not violated the MCL in §141.63(b).

 6. ISSUE: Invalidation of total coliform-positive samples.

§141.21(c)(1) lists the conditions under which a State may invalidate a total coliform-positive

sample. A State may invalidate such a sample only on a case-by-case basis for eadh instance; the

State may not invalidate total coliform-positive samples prospectively or generically.

7. ISSUE: MCL violations for persistent violators of monitoring or reporting requirements.

No EPA rule, including the revised total coliform rule, states that systems which repeatedly

violate specified monitoring or reporting requirements are, as a consequence, in violation of the MCL. 

However, States should not be discouraged from choosing such an approach.

8. ISSUE: Collection of a routine sample(s) the next month by a small system after the State

waives the requirement for five samples the next month after a total coliform-positive sample.

§141.21(b)(5)(ii) states that when a State waives the requirement for a system which collects

fewer than five routine samples/month to collect at least five routine samples during the next month

after a total coliform-positive sample, the system must still take at least one routine sample before the

end of the next month, unless the State has determined that the system has corrected the

contamination problem before the system took the set of repeat samples. EPA did not intend to

suggest by this statement that systems could ignore the routine monitoring frequency requirements

specified under §§141.21(a)(2)-(3). A system must still collect the number of routine samples

specified by §§141.21(a) (2)-(3).
9. ISSUE: Mixed Medium ONPG-MUG (MMO-MUG) test

To date, the only commercially available formulation of the approved MMO-MUG test of which

EPA is aware is the Autoanalysis Colilert Test. Other methods which are identical in formulation and

procedure would also be acceptable. Variations in formulation or procedure of the MMO-MUG test

that was approved in the Federal Register (54 FR 27544; June 29, 1989) should be submitted to

EPA's Environmental Monitoring Systems Laboratory in Cincinnati for review.