DRAFT
MARCH 31, 1989
GUIDANCE MANUAL
FOR
COMPLIANCE WITH THE
FILTRATION AND DISINFECTION REQUIREMENTS
FOR
PUBLIC WATER SYSTEMS
USING
SURFACE WATER SOURCES
SCIENCE AND TECHNOLOGY BRANCH
CRITERIA AND STANDARDS DIVISION
OFFICE OF WATER
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C.
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GUIDANCE MANUAL
FOR
COMPLIANCE WITH THE
FILTRATION AND DISINFECTION REQUIREMENTS
FOR
PUBLIC WATER SYSTEMS
USING
SURFACE WATER SOURCES
for
Science and Technlogy Branch
Criteria and Standards Division
Office of Drinking Water
U.S. Environmental Protection Agency
Washington, D.C.
Contract No. 68-01-6989
DRAFT
by
Malcolm Pirnie, Inc.
100 Eisenhower Drive
Paramus, NJ 07653
CWC-HDR, Inc.
3461 Robin Lane
Cameron Park, California 95682
March 31, 1989
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TABLE OF CONTENTS
1. INTRODUCTION 1~1
2. GENERAL REQUIREMENTS 2-1
2.1 Application 2-1
2.1.1 Types of Water Supplies 2-2
2.1.2 Determination of Applicable Services 2-2
2.2 Treatment Requirements 2-11
2.3 Operator Personnel Requirements 2-13
3. SYSTEMS NOT FILTERING 3-1
3.1 Source Water Quality Criteria 3-2
3.1.1 Coliform Concentrations 3-2
3.1.2 Turbidity Levels 3-4
3.2 Disinfection Criteria 3-5
3.2.1 Inactivation Requirements 3-5
3.2.2 Determination of Overall Inactivation
for Residual Profile, Multiple
Disinfectants and Multiple Sources 3-23
and Multiple Sources
3.2.3 Demonstration of Maintaining a Residual 3-31
3.2.4 Disinfection System Redundancy 3-34
3.3 Site-Specific Conditions 3-35
3.3.1 Watershed Control Program 3-35
3.3.2 On-site Inspection 3-37
3.3.3 No Disease Outbreaks 3-40
3.3.4 Monthly Coliforn MCL ' 3-41
3.3,5 Total Trihalomethane (TTHM) Regulations 3-43
4. CRITERIA FOR DETERMINATION OF FILTRATION AND DISINFECTION 4-1
TECHNOLOGY TO BE INSTALLED
4.1 introduction 4-1
4.2 Selection of Appropriate Filtration Technology 4-1
4.2.1 General Descriptions 4-2
4.2.2 Capabilities 4-3
4.2.3 Selection 4~7
4.3 Available Filtration Technologies 4-9
4.3.1 Introduction 4-9
4.3.2 General 4-9
4.3.3 Conventional Treatment 4-11
4.3.4 Direct Filtration 4-12
4.3.5f,-Slow Sa^id^Filtration 4-14
44.3;.6 Diatomacepus Earth Filtration 4-16
'4.3V7 Alternate^Technologies 4-18
4.3.8 Other Alternatives 4-19
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TABLE OF CONTENTS (Continued)
Page
4.4 Disinfection 4-19
4.4.1 General 4-19
4.4.2 Recommended Removal/Inactivation 4-20
4.4.3 Total Trihalomethane (TTHM) Regulations 4-22
5. CRITERIA FOR DETERMINING IF FILTRATION AND DISINFECTION
ARE SATISFACTORILY PRACTICED • 5-1
5.1 Introduction 5-1
5.2 Turbidity Monitoring Requirements 5-1
5.2.1 Sampling Location 5-1
5.2.2 Sampling Frequency 5-2
5.2.3 Additional Monitoring • 5-2
5.3 Turbidity Performance Criteria 5-4
5.3.1 Conventional Treatment or
Direct Filtration 5-4
5.3.2 Slow Sand Filtration 5-6
5.3.3 Diatomaceous Earth Filtration 5-6
5.3.4 Other Filtration Technologies 5-7
5.4 Disinfection Monitoring Requirements 5-7
5.5 Disinfection Performance Criteria 5-7
5.5.1 Minimum Performance Criteria Required
Under the SWTR 5-7
5.5.2 Recommended Performance Criteria 5-8
5.5.3 Disinfection By-Product Considerations 5-9
5.5.4 Determination of Inactivation by
Disinfection 5-11
5.6 Other Considerations 5-21
6. REPORTING 6-1
6.1 Reporting Requirements for Public Water Systems
Not Providing Filtration 6-1
6.2 Reporting Requirements for Public Water Systems
Using Filtration 6-2
7. COMPLIANCE 7-1
7.1 Introduction 7-1
7.2 Systems Using a Surface Water Source
(Not Ground Water Under the Direct
Influence of Surface Water) 7-1
7.3 Compliance Transition with Current NPDWR
Turbidity Requirements 7-3
7.4 Systems Using a Ground Water Source Under
the Direct Influence of a Surface Water 7-3
7.5 Responses for Systems not Meeting the SWTR Criteria 7-5
7.5.1 Introduction 7-5
7.5.2 Systems Not Filtering 7-5
7.5.3 Systems Currently Filtering 7-7
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TABLE OF CONTENTS (Continued)
Page
8. PUBLIC NOTIFICATION 8-1
9. EXEMPTIONS 9-1
9.1 Overview of Requirements 9-1
9.2 Recommended Criteria 9-2
9.3 Compelling Factors 9-3
9.4 Evaluation of Alternate Water Supply Sources 9-6
9.5 Protection of Public Health 9-7
9.6 Notification to EPA 9-10
LIST OF TABLES
Table Following
No. Description Page
2-1 Survey Form for the Classification of Drinking
Water Sources 2-6
4-1 Removal Capabilities of Filtration Processes 4-3
4-2 Generalized Capability of Filtration Systems to 4-8
Accommodate Raw Water Quality Conditions
6-1 Source Water Quality Conditions for Unfiltered systems 6-3
6-2 Long Term Turbidity Record Sheet for Unfiltered systems 6-3
6-3 CT Determination for Unfiltered Systems 6-3
6-4 Disinfection Information for Compliance Determination for
Unfiltered Systems 6-3
6-5 Distribution Ssystem Disinfectant Residual Data for
Unfiltered and Filtered Systems 6-3
6-6 Monthly Report to Primacy Agency for Compliance
Determination - Unfiltered Systems 6-3
6-7 Daily Data Sheet for Filtered Systems 6-3
6-8 Monthly Report to Primacy Agency Compliance Deterimination
Filtered Systems 6-3
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TABLE OF CONTENTS (Continued)
LIST OF FIGURES
Figure Following
No. Description Page
2-1 Steps to Source Classification 2-3
3-1 Single Chamber Contactor 3-16
3-2 Multiple Chamber Contactor 3-17
3-3 Turbine Contactor 3-18
3-4 City of Tuscon Ozone Contactor 3-20
3-5 Average Ozone Residuals Los Angeles Aqueduct Filtration
Plant . 3-21
3-6 Determination of Inactivation for Multiple 3-24
Disinfectant Application to a Surface Water Source
3-7 Individually Disinfected Surface Sources Combined 3-27
at a Single Point
3-8 Multiple Combination Points for Individually 3-27
Disinfected Surface Sources
4-1 Flow Sheet for a Typical Conventional Water 4-11
Treatment Plant
4-2 Flow Sheet for a Typical Direct Filtration Plant 4-13
4-3 Flow Sheet for a Typical Direct Filtration Plant 4-13
.with Flocculation
LIST OF APPENDICES
Appendix Description Page
A Use of Particulate Analysis for Source and Water
Treatment Evaluation , A-l
B Institutional Control of Legionella B-l
C Tracer Test Procedures C-l
D A Survey of the Current Status of Residual Disinfectant D-l
Measurement Methods for all Chlorine Species and Ozone
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TABLE OF CONTENTS (Continued)
LIST OF FIGURES
Figure Following
No. Description Page
2-1 Steps to Source Classification 2-3
3-1 Single Chamber Contactor 3-16
3-2 Multiple Chamber Contactor 3-17
3-3 Turbine Contactor 3-18
3-4 City of Tuscon Ozone Contactor 3-20
3-5 Average Ozone Residuals Los Angeles Aqueduct Filtration
Plant 3-21
3-6 Determination of Inactivation for Multiple 3-24
Disinfectant Application to a Surface water Source
3-7 Individually Disinfected Surface Sources Combined 3-27
at a Single Point
3-8 Multiple Combination Points for Individually 3-27
Disinfected Surface Sources
4-1 Flow Sheet for a Typical Conventional Water 4-11
Treatment Plant
4-2 Flow Sheet for a Typical Direct Filtration Plant 4-13
4-3 Flow Sheet for a Typical Direct Filtration Plant 4-13
with Flocculation
LIST OF APPENDICES
Appendix Description . Page
A Use of Particulate Analysis for Source and Water
Treatment Evaluation A-l
B Institutional Control of Legionella B-l
C Determination Of Disinfectant Contact Time C-l
D A Survey of the Current Status of Residual Disinfectant D-l
Measurement Methods for all Chlorine Species and Ozone
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TABLE OF CONTENTS (Continued)
Appendix
E
F
G
H
I
J
K
L
M
N
0
LIST OF APPENDICES
Description
Inactivation Achieved by Various Disinfectants
Basis for CT Values
Protocol for Demonstrating Effective Disinfection
Sampling Frequency for Total Coliforms in the
Distribution System
Maintaining Redundant Disinfection Capability
Watershed Control Program
Sanitary Survey
Small System Considerations
Pilot Study Protocol for Alternate Filtration Technology
Protocol for the Demonstration of Effective Treatment
Protocols for Point-of-Use Treatment Devices
Page
E-l
F-l
G-l
H-l
1-1
J-l
K-l
L-l
M-l
N-l
0-1
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1. INTRODUCTION
This Guidance Manual complements the filtration and disinfection treat-
ment requirements for public water systems using surface water sources or
ground water under direct influence of surface water as presented in the
Surface Water Treatment Rule (SWTR).
The purpose of this manual is to provide guidance to United States
Environmental Protection Agency (USEPA) Regional Offices, individual states
and affected utilities in the implementation of the SWTR, and to help assure
that actions taken toward implementation are consistent. This manual is
advisory in nature and is meant to 'supplement the criteria of the SWTR. For
example, the SWTR sets treatment requirements which encompass a large range of
source water conditions. The guidance manual suggests design, operating and
performance criteria for specific surface water quality conditions to provide
the optimum protection from microbiological contaminants. These
recommendations are presented as guidelines rather than an extension of the
rule. They are offered to give the Primacy Agency flexibility in establishing
the most appropriate treatment requirements for the waters within their
jurisdiction.
Throughout this document, the term "Primacy Agency" refers to a State
with primary enforcement responsibility for public water systems or "primacy,"
or to mean EPA in the case of a State that has not obtained primacy.
In order to facilitate the use of this manual, it has been structured to
follow the framework of the SWTR as closely as possible. In this manual, the
term "SWTR" will always refer to the criteria of the rule. Brief descriptions
of the contents of each section of this manual are presented in the following
paragraphs.
Section 2
This section provides guidance for determining whether a water supply
source is subject to the requirements of the SWTR; including the determination
of whether a ground water source is under direct influence of surface water
and at risk to the presence of Giardia cysts or other large microorganisms.
The overall treatment requirements of the SWTR are also presented, along with
recommendations for the qualifications of operator personnel.
1-1
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Section 3
For systems which are subject to the requirements of the SWTR and which
do not currently provide filtration, this section provides guidance to the
Primacy Agency for determining if a given source:
- Meets the source water quality criteria
- Meets the disinfection requirements including:
- Maintenance of adequate disinfection
- Provision for disinfection system redundancy
- Maintains an adequate watershed control program
- Meets the on-site inspection requirements
- Has not had an identified waterborne disease outbreak
- Complies with the requirements of the Total Coliform Rule
- Complies with total trihalomethane (TTHM) regulations
Section 4
This section pertains to systems which do not meet the requirements to
avoid filtration outlined in Section 3 and therefore are required to install
filtration. Guidance is given for the selection of an appropriate filtration
technology based on the source water quality and the capabilities of the
technology in achieving the required performance criteria. In addition,
recommended design and operating criteria are provided for the available
filtration technologies.
Section 5
Section 5 presents guidance to the Primacy Agency for determining
compliance with the turbidity and disinfection performance requirements to
determine if filtration and disinfection are satisfactorily practiced.
Recommendations are made for the level of disinfection to be provided in order
to meet the overall treatment requirements of the SWTR. This section includes
the recommended use of CT (disinfectant residual concentration x contact time)
tables for chlorine, chlorine dioxide, ozone and chloramines, or demonstration
of effective disinfection for chlorine dioxide, ozone and chloramines.
1-2
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Section 6
Section 6 provides guidelines to the Primacy Agency for establishing the
reporting requirements associated with the SWTR. The requirements include the
report content and frequency, and are applicable to both filtering and nonfil-
tering systems.
Section 7
This section provides an overview of the time schedule for Primacy
Agencies and utilities to meet the requirements of the SWTR. Examples are
presented to provide guidance for corrective measures which can be taken by
systems which are not in compliance with the treatment requirements.
Section 8
This section of the manual presents guidance on public notification.
Included are examples of occurrences which would require notification, lang-
uage of notices and the method of notification.
Section 9
Section 9 provides guidance to the Primacy Agency for determining whether
a system is. eligible for an exemption. The criteria for eligibility for an
exemption include:
- Compelling factors (economic or resource limitations)
- - No available alternate source
- The protection of public health
This section also covers an evaluation of the financial capabilities of a
water system, the review of the availability of alternate sources and measures
for protecting public health.
1-3
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Appendices
The manual also contains several appendices which provide more detailed
guidance in specific areas. These include:
Appendix A - Use of Particulate Analysis
for Source and Water Treatment Evaluation
A study involving 150 water sources resulted in the identification of
particulate matter which is indicative of a surface water or ground water
under the influence of surface water. A paper summarizing the results of the
study is included in this appendix.
Appendix B - Institutional
Control of Legionella
Filtration and/or disinfection provides protection from Legionella.
However, it does not assure that recontamination or regrowth will not occur in
the hot water or cooling systems of buildings within the distribution system.
This appendix provides guidance for the monitoring and treatment which can be
used by institutional systems for the control of Legionella.
Appendix C - Tracer Test Procedures
In many cases, the determination of disinfectant contact times needed to
evaluate the CT of a water system will necessitate the use of tracer studies.
This appendix provides guidance for conducting these studies. In some cases
it may not be practical to conduct a tracer study. For such cases guidance is
given for estimating the detention time based on the physical configuration of
the system.
Appendix D - A Survey of the Current
Status of Residual Disinfectant
Measurement Methods for all Chlorine
Species and Ozone
This appendix includes a listing of the analytical methods required under
the SWTR. A copy of an executive summary of a report on the analytical
methods used to measure the residual concentrations of the various
1-4
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disinfectants is also included. The reliability and limitations of each of
the methods are also presented.
Appendix E - Inactivations Achieved
by the Various Disinfectants
This appendix presents the log inactivations of Giardia cysts and enteric
viruses which are achieved at various CT levels by chlorine, chlorine dioxide,
chloramines and ozone. Inactivations of enteric viruses achieved by UV
absorbance are also included.
Appendix F - Basis for CT Values
This appendix provides the background and rationale utilized in develop-
ing the CT values for the various disinfectants. Included is a paper by Clark
et al.f 1988, in which a mathematical model was used in the calculation of CT
values for free chlorine.
Appendix G - Protocol for Demonstrating
Effective Disinfection
This appendix provides the recommended protocols for demonstrating the
effectiveness of chloramines, chlorine dioxide and ozone as primary
disinfectants.
Appendix H - Sampling Frequency for
Total Colifoms in the Distribution System
The sampling frequency required by the Total Coliform Rule ( FR )
is presented in this appendix.
Appendix I - Maintaining
Redundant Disinfection Capability
This appendix details the disinfection conditions which should be
maintained by a system using chlorine, chlorine dioxide, ozone or chloramines,
to assure that compliance with the SWTR requirement for redundant disinfection
is met.
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Appendix J - Watershed Control Program
This appendix provides a detailed outline of a watershed program which
may be adjusted by the Primacy Agency to serve the specific needs of a par-
ticular water system.
Appendix K - Sanitary Survey
This appendix provides guidance for a comprehensive sanitary survey of a
supply source, its treatment and delivery to the consumer. The contents for
an annual on-site inspection are included in Section 3.
Appendix L - Small System Considerations
This appendix presents difficulties which may be faced by small systems
in complying with the SWTR along with guidelines for overcoming these diffi-
culties.
Appendix M - Pilot Study Protocol
for Alternate Filtration Technology
. This appendix presents pilot study protocols to evaluate the effective-
ness of an alternate filtration technology in attaining the performance
requirements of the SWTR.
Appendix N - Protocol for the
Demonstration of Effective Treatment
This appendix provides guidance for conventional and direct filtration
plants to demonstrate that adeguate filtration is being maintained at effluent
turbidities between 0.5 and 1 Nephelometric Turbidity Unit (NTU).
Appendix O - Protocol for
Point-of-Use Treatment Devices
In some limited cases, it may be appropriate to install point-of-use
(POU) or point-of-entry (POE) treatment devices as an interim measure to
provide protection to the public health. This appendix provides a protocol
for evaluating and determining the efficacy of POU/POE treatment devices.
1-6
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2. GENERAL REQUIREMENTS
2.1 Application
The SWTR pertains to all public water systems which utilize a surface
water source or ground water source under the direct influence of surface
water. The SWTR defines a surface water as all waters which are open to the
atmosphere and subject to surface runoff. Ground water under the direct
influence of surface water is defined as: any water beneath the surface of
the ground with (i) significant occurrence of insects or other macroorganisms,
algae, organic debris, or large-diameter pathogens such as Giardia lamblia, or
(ii) significant and relatively rapid shifts in water characteristics such as
turbidity, temperature, conductivity, or pH which closely correlate to
climatological or surface water conditions. Direct influence must be
determined for each individual source in accordance with criteria established
by the Primacy Agency. The Primacy Agency criteria may provide for
documentation of well construction and geology, with field evaluation, or
site-specific measurements of water quality as explained in Section 2.1.2.
The traditional concept that all water in subsurface aquifers is free
from pathogenic organisms is based upon soil being an effective filter that
removes microorganisms and other relatively large particles by straining and
antagonistic effects (Bouwer, 1978). In most cases pathogenic bacteria
retained in the soil find themselves in a hostile environment, are not able to
multiply'and eventually die. However, some underground sources of drinking
water may be subject to contamination by pathogenic organisms from the direct
influence of nearby surface waters.
Only those subsurface sources which are at risk to contamination from
large microorganisms such as protozoa (specifically Giardia cysts) will be
subject to the requirements of the SWTR. Subsurface sources which may be at
risk to contamination from bacteria and enteric viruses, but which are not at
risk from Giardia cysts will be regulated either under the Total Coliform Rule
or forthcoming disinfection treatment requirements for ground waters. EPA
intends to promulgate disinfection requirements for ground water systems in
conjunction with regulations for disinfection by-products by 1991.
2-1
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2.1.1 Types of Water Supplies
Surface Waters
Surface water supplies that are often used as sources of drinking water
include two major classifications, running and quiescent waters. Streams,
rivers and brooks are examples of running water, while lakes, reservoirs/
impoundments and ponds are examples of quiescent waters. The exposure of
surface waters to the atmosphere results in exposure to precipitation events,
surface water runoff and contamination with micro and macroorganisms resulting
from activities in their surrounding areas. These sources are subject to the
requirements of the SWTR.
Systems with rain water catchments not subject to surface runoff (e.g.
roof catchment areas) are not considered vulnerable to contamination from
animal populations which carry protozoan cysts pathogenic to humans and are
thus not subject to the SWTR requirements. However, such systems should at
least provide disinfection to treat for potential bacterial and viral
contamination coming from bird populations.
Ground Waters under Direct Influence of Surface Water
Ground water sources which may be subject to contamination with
pathogenic organisms from surface waters include, springs, infiltration gal-
leries, wells or other collectors in subsurface aquifers. The following
section presents a recommended procedure for determining whether a source will
be subject to the requirements of the SWTR.
2.1.2 Determination of Applicable Sources
The Primacy Agency has the responsibility for determining which water
supplies must meet the requirements of the SWTR. However, it is the
responsibility of the water purveyors to provide the Primacy Agency with the
information needed to make this determination. This section provides guidance
to the Primacy Agency for determining which water supplies are surface waters
or ground waters directly influenced by a surface water and are thereby
1. One study (Markwell and Shortridge, 1981} indicates that a cycle of
water borne transmission and maintenance of influenza virus may
exist within duck communities, and that it is conceivable for virus
transmission to occur in this manner to other susceptible animals,
including humans.
2-2
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subject to the requirements of the SWTR. Following the determination that the
source is subject to the SWTR the requirements enumerated in Sections 2.2 and
2.3 must be met.
The Primacy Agency must develop a program for evaluating ground water
sources for direct influence within 18 months of the promulgation of the rule.
All community ground water systems must be evaluated within 5 years of the
SWTR promulgation/ while all non-community systems must be evaluated within 10
years. Primacy Agencies with an approved Wellhead Protection (WHP) Program,
may be able to use the WHP program's requirements which include delineation of
wellhead protection areas, assessment of sources of contamination and
implementation of management control measures. These same requirements can be
used for meeting the requirements of the watershed control program for ground
water under the direct influence of a surface water.
A multiple step approach has been developed as the recommended method of
determining whether a ground water source is under direct influence of a
surface water. This approach includes the review of information gathered
during sanitary surveys. As defined by the USEPA, a sanitary survey is an
on-site review of the water source, facilities, equipment operation and
maintenance of a public water system for the purpose of evaluating the
adequacy of such source, facilities, equipment, operation and maintenance for
producing and distributing safe drinking water. Sanitary surveys are required
under the Total Coliform Rule and may be required under the forthcoming
disinfection requirements for ground water systems as a condition for
obtaining a variance or for determining the level of disinfection required.
Therefore, it is recommended that the determination of direct influence be
correlated with the sanitary surveys conducted under these other requirements.
As illustrated on Figure 2-1, the determination of whether a source is
subject to the requirements of the SWTR may involve one or more of the
following steps:
1. A review of the records of the system's source(s) to determine
whether the source is obviously a surface water, i.e. pond, lake,
streams, etc.
2. If the source is a well, determination of whether it is clearly a
ground water source, or whether further analysis is needed to
determine possible surface water influence.
2-3
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Obvious Surface
Sources:
Lakes, Reservoirs,
Streams, Creeks,
Rivers, etc.
j
SWTR Applies
~^-(Yes J
All Public Water
Systems
Identify Source Type
Source is Spring
Infiltration Gallery, or
Ranney Well
Review System File
and Conduct
Sanitary Survey
Source Influenced by
Surface Water?
Source is Well
Well is Protected from
Surface Influence
Based on State
Criten'a?
\ 6S J
SWTR Does Not Apply
Undecided -
«
Conduct Paniculate
Analysis. Monitor
Changes :n Water
Quality, Temperature,
etc.
Summary of Findings
Indicate Source is
Influenced by Surface
Water and Could
Contain Giardial
FIGURE 2-1 STEPS TO SOURCE CLASSIFICATION
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3. A complete review of the system's files followed by a field sanitary
survey. Pertinent information to gather in the file review and
field survey includes: source design and construction; evidence of
surface water contamination; water quality analysis; indications of
waterborne disease outbreaks; operational procedures; and customer
complaints regarding water quality or water related infectious
illness.
4. Conducting particulate analysis and other water quality sampling and
analyses.
Step 1. Records Review
A review of information pertaining to each source should be carried out
to identify those sources which are obvious surface waters. These would
include ponds, lakes, streams, rivers, reservoirs, etc. If the source is a
surface water, then the SWTR would apply, and criteria in the rule would need
to be applied to determine if filtration is necessary. If the source is not
an obvious surface water, then further analyses, as presented in Steps 2, 3,
or 4, are needed to determine if the SWTR will apply. If the source is a
well, go to Step 2. If the source is a spring, infiltration gallery, Ranney
well, or any other subsurface source, proceed to Step 3 for a more detailed
analysis.
Step 2. Review of Well Sources
While most well sources have historically been considered to be all
ground water, recent evidence suggests that some wells, especially shallow
wells constructed near surface waters, may be influenced by surface water.
One approach in determining whether a well is subject to contamination by
surface water would be to evaluate the water quality of the well by the
criteria in Step 4. However, this process is rather time consuming and labor
intensive. In an attempt to reduce the effort needed to evaluate well
sources, a set of criteria have been developed to identify wells in deep, well
protected aquifers which are not subject to contamination from surface water.
While these criteria are not as definitive as water quality analysis, it is
believed that they provide a reasonable degree of accuracy, and allow for a
relatively rapid determination for a large number of well sources in the U.S.
Wells less than or equal to 50 feet in depth are considered to be shallow
wells, and should be evaluated for surface influence according to steps 3
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and/or 4. For wells greater than 50 feet in depth, State or system files
should be reviewed for the criteria listed below:
1. The well construction should include:
- A surface sanitary seal using bentonite clay, concrete or other
acceptable material.
- A well casing that penetrates consolidated (slowly permeable)
material.
- A well casing that is only perforated or screened below consol-
idated (slowly permeable) material.
2. The source should be located at least 200 feet from any surface
water.
3. The water quality records should indicate:
- No record of total coliform or fecal coliform contamination in
untreated samples collected over the past three years.
- No history of turbidity problems associated with the source.
- No history of known or suspected outbreak of Giardia, or other
pathogenic organism associated with surface water (e.g.
Cryptosporidium), which has been attributed to that source.
4. If data is available for particulate matter in the well; or
turbidity or temperature data from the well and a nearby surface
water there should be:
- No evidence of particulate matter associated with surface
water.
- No turbidity or temperature data which correlates to that of a
nearby surface water.
Wells that meet all of the criteria listed above are not subject to the
requirements of the SWTR, and no additional evaluation is needed. Wells that
do not meet all the requirements listed require further evaluation in
accordance with Steps 3 and/or 4 to determine whether or not they are directly
influenced by surface water.
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Step 3. Sanitary Survey
For sources other them a well source, the State or system files should be
reviewed for the well construction and water quality conditions as listed in
Step 2. Reviewing historical records in State or system files is a valuable
information gathering tool. However, the results may be inconclusive. A
sanitary survey in the field may be helpful in establishing a more definite
determination of whether the water source is at risk to pathogens from surface
water influence.
Information to obtain during a sanitary survey include:
- Evidence that surface water enters the source through defects in the
source such as lack of a surface seal on wells, infiltration gallery
laterals exposed to surface water, springs open to the atmosphere,
surface runoff entering a spring or other collector, etc.
- Distances to obvious surface water sources.
If the survey indicates that the well is subject to surface water
influence, the source must either be reconstructed as explained later in this
section or it must be treated in accordance with the requirements for the
SWTR. If the survey does not show conclusive evidence of surface water
influence,' the analysis outlined in Step 4 should be conducted.
The Washington State Department of Social and Health Services has devel-
oped a form to guide them and provide consistency in their evaluation of
sources for surface water influence (Notestine & Hudson, 1988). Table 2-1
provides a copy of this form as a guide for evaluating sources.
Step 4. Particulate Analysis and Other Indicator Parameters.
Particulate analysis is intended to identify organisms which only occur
in surface waters as opposed to ground waters, and whose presence in a ground
water would clearly indicate that at least some surface water has been mixed
with it. Method 912K in Standard Methods, for Giardia cyst analysis, can be
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TABLE 2-1
SURVEY FORM FOR THE CLASSIFICATION OF DRINKING WATER SOURCES
General
1. Utility Name (ID#)
2. Utility Person(s) Contacted
3. Source Type (As shown on state inventory)
________ Spring _________ Ranney Well
Infiltration System Shallow Well
4. Source Name ' Year constructed
5. Is this source used seasonally or intermittently? No Yes
If yes, are water quality problems the reason? No Yes
6. Has there ever been a waterborne disease outbreak associated with this
source? Yes No If yes, explain
7. Have there been turbidity or bacteriological MCL violations within the
last five years associated with this source? No Yes
If yes, describe frequency, cause, remedial action (s) taken
8. Have there been consumer complaints within the past five years associated
with this source? No Yes If yes, discuss nature,
frequency, remedial action taken
9. Is there any evidence of surface water intrusion (pH, temperature,
conductivity, etc. changes) during the year? Yes No
If yes, describe
10. Sketch of source in plan view (on an additional sheet)
Shallow Wells
1. Does the well meet good sanitary practices regarding location, con-
struction, seal etc. to prevent the entrance of surface water?
Yes No If no, describe the deficiencies
- 1 -
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2. Hydrogeology (Attach copy of well log or summarize it on reverse)
a. Depth to static water level? (Feet)
b. Drawdown? (Feet)
c. What is the depth to the highest screen or perforation? (Feet)
d. Are there impervious layers above the highest screen or perforation?
Yes No Unknown
If yes, please describe
3. Is there a permanent or intermittent surface water within 500 feet of the
well? Yes No If yes, describe (type, distance etc.)
4. Additional comments:
Springs
1. a. What is the size of the catchment area (acres)?
b. Give a general description of the area (terrain; vegetation; soil
etc.) '
2. What is the vertical distance between the ground surface and the nearest
point of entry to the spring collector(s) (feet)?
3. How rapidly does rainfall percolate into the ground around the spring?
Percolates readily; seldom if ever any runoff.
_____ Percolates readily but there is some runoff in heavy rain.
Percolates slowly. Most local rainfall ponds or runs off.
Other
4. Does an impervious layer prevent direct percolation of surface water to
the collector (s)? Yes No Unknown
5. Is the spring properly constructed to prevent entry of surface water?
Yes No
6. Sediment
a. Is the spring box free of debris and sediment? Yes No
b. When was it last cleaned (Date)
c. How often does it need to be cleaned? (month)
- 2 -
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d. How much sediment accumulates between cleaning? (estimate in
inches)
7. Additional comments:
Infiltrations System and Ranney Wells
1. What are the shortest distances (vertical and horizontal separating the
collector from the nearest surface water? (Feet)
2. Does turbidity of the source vary 0.2 NTU or more throughout the year?
Yes No ^^^^^^ Not measured
If yes, describe how often and how much (pH, temperature, conductivity,
etc.)
3. Additional Comments
Survey Conducted By: ________________^_^_— Date:
Decision? Surface Impacted Source Yes No If no, further
evaluation needed (particulate analysis, etc.)
-------
applied for general particulate analysis as discussed in the paper in Appendix
A (Hoffbuhr, et al, 1986).
In 1986 Hoffbuhr et. al. listed six parameters identifiable in a
particulate analysis which were believed to be valid indicators of surface
contamination of ground water. These were: diatoms, rotifers, coccidia,
plant debris, insect parts, and Giardia cysts. Later work by Notestine and
Hudson (1988) found that microbiolegists did not all define plant debris in
the same way, and that deep wells known to be free of surface water influence
were shown by particulate analysis to contain "plant debris" but none of the
other five indicators. Their work suggests that "plant debris" may not cur-
rently be a useful tool in determining surface water influence, but may be in
the future when a standard definition of "plant debris" is developed. There-
fore, it is recommended that only the presence of the other five parameters;
diatoms, rotifers, coccidia, insect parts, and Giardia, be used as indicators
of direct surface contamination. In addition, if other large diameter
(> 7 urn) organisms which are clearly of surface water origin are present,
these should also be considered as indicators of direct surface water
influence. Methods of collecting samples and interpreting results are listed
below:
Sampling Protocol
- Sampling Procedure
Samples should be collected using the equipment outlined in Standard
Methods 912K.
- Location
Samples should always be collected as close to the source as possi-
ble, and prior to any treatment. If samples must be taken after
disinfection, samples should be noted and analyzed as soon as
possible.
- Number
A minimum of two samples should be collected during the period the
source is most susceptible to surface water influence. Such crit-
ical periods will vary from system to system and will need to be
determined case by case. For some systems, it may be one or more
days following a significant rainfall (eg. 2" in 24 hours) . For
other systems it may be a period of maximum flows and stream
turbidities following spring snowmelt, or during the summer months
when water tables are elevated as a result of irrigation. In each
2-7
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case, particulate samples should be collected when the source in
question is most effected. A surrogate measure such as source
turbidity or depth to water table may be useful in making the
decision to monitor. If there is any ambiguity in the particulate
analysis results, additional samples should be collected when there
is the greatest likelihood that the source will be contaminated by
surface water.
- Volume
Sample volume should be between 500 and 1000 gallons, and should be
collected over a 4 to 8 hour time period. It is preferable to
analyze a similar (+/- 10%) volume of water for all sources,
preferably a large volume, although this may not always be possible
due to elevated turbidity' or sampling logistics. The volume
filtered should be recorded for all samples.
Interpretation
A standardized process for sampling and analyzing particulates in drink-
ing water has not been established. Therefore the interpretation of results
may differ depending on the sampling and analytical procedures used, and also
on the training and experience of the microbiologist. At present the methods
simply do not have the precision to establish a numerical ranking of the
degree to which a source is influenced, or the risk that it presents. Until
such time as the particulate analysis process is standardized, the presence of
any of the five (or other) surface water indicators should be considered
strong evidence of surface water influence.
There may be times when the particulate results are not definitive. For
example when only a single rotifer is observed in a sample collected during a
critical period, and ^11 other information indicates the source is a ground
water. For such ambiguous results, it is recommended that several other
particulate analyses be collected at critical times in an attempt to reproduce
the original results.
Consistent identification of surface indicators, even few in numbers, is
strong evidence of surface influence. However, if the initial results cannot
be reproduced during critical times, it may be concluded that the source is
more likely a ground water.
Other Indicators
A number of other indicators could be used to provide supportive evidence
of surface influence. While particulate analysis probably provides the most
- fl
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direct evidence that pathogens from surface water could be migrating into a
ground water source, other parameters such as turbidity, temperature, pH and
conductivity could provide supportive, but less direct, evidence.
Turbidity fluctuations of greater than 0.5 - 1 NTU over the course of a
year may be indicative of surface water influence. Considerable caution
should be used when evaluating turbidity changes though, since the turbidity
could be caused by very small particles (< lum) not originating in a surface
water or it could be that larger particles are being filtered out and only the
very smallest particles migrate into the water source.
Temperature fluctuations may also indicate surface water influence.
Fortunately these are easy to obtain and if there is a surface water within
500 feet of the water source, measurements of both should be recorded for
comparison. Large changes in surface water temperature closely followed by
similar changes in source temperature would be indicative of surface water
influence. Also, temperature changes of greater than 15- 20% over the course
of a year appear to be a characteristic of some sources influenced by surface
water (Randall, 1972) . Changes in other chemical parameters such as pH,
conductivity, hardness,etc. could also be monitored. Again, these would not
give a direct indication of whether pathogens originating in surface water
were present, but could indicate whether the water chemistry was or was not
similar to a nearby surface water and/or whether source" water chemistry
changed in a similar pattern to surface water chemistry. At this time no
numerical- guidelines are available to differentiate what is or is not similar,
so these comparisons are more qualitative than quantitative.
Seasonal Sources
Some sources may only be used for part of the year, for example during
the summer months when water usage is high. These sources should not be
excluded from evaluation and, like other sources, should be evaluated during
their period(s) of highest susceptibility. Particular attention should be
given to those sources which appear to be influenced by surface water during
part of the year. There may be times during which these subsurface water
sources are not influenced by•surface water and other times when they are part
or all surface water. If that is the case, then it is critical that careful
testing be done prior to, during and at the end of the use of the source.
2-9
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This should be done over several seasons to account for seasonal variation.
In practice, it is preferable to use sources which are less vulnerable to
contamination since susceptible sources will necessitate ongoing monitoring
and close attention to operation.
Modification of Sources
Sources influenced by surface water may be altered in some cases to
eliminate the surface water contamination. States may elect to allow systems
with such sources to modify the construction of the source and/or the area
surrounding the source in an effort to eliminate surface water contamination.
Since this could be expensive and take considerable time to evaluate for
effectiveness, careful consideration should be given to the decision to modify
a source. In deciding whether source modification is appropriate, systems and
States should consider the following points:
- Is the cause of the surface water contamination known? If the
specific cause or point of surface water contamination is not known,
it will not be possible to determine an effective control strategy.
Further, there may be several reasons why the source is susceptible
to surface water influence. For example, an infiltration gallery
may receive surface water because some of its laterals are exposed
in the bed of a nearby stream, and also because laterals distant
from the stream are shallow and are affected by surface runoff.
Simply modifying or eliminating one or the other set of laterals in
this case would not entirely eliminate surface water influence.
* What is the likelihood that modification of the source will be
effective? Assuming that the source of contamination has been
. identified, the expected effectiveness of control measures should be
evaluated. If the cause is relatively discreet, a crack in a well
casing or an uncovered spring box for example, then there is a high
degree of confidence that an effective solution could be developed.
Should the nature of the contamination be more diffuse, or wide-
spread, then the merits of spending time and money to modify the
source should be carefully considered. In the case of the example
above, eliminating the use of the laterals under the stream will
solve part of the problem. Without considerably more hydrogeologic
information about the aquifer and the placement of the other
laterals, though, it is not clear what, if any, control measures
would effectively eliminate surface water influence in those later-
als distant from the stream.
If a source is identified as being influenced by surface water, and it is
decided to attempt to modify it, interim disinfection practices which will
ensure at least 99.9% inactivation of Giardia should be considered. Methods
2-10
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and levels of disinfection which can be used to achieve such removals can be
found in Subsection 141.72 (a) of the SWTR and in Section 3.2 of this manual.
A partial listing of types of modifications which could be undertaken
includes:
i) Diverting surface runoff from springs by trenching, etc.
ii) Redeveloping springs to capture them below a confining layer.
iii) Covering open spring collectors
iv) Reconstructing wells to install sanitary seals, and/or to screen
them in a confined (protected) aquifer.
v) Repairing cracks or breaks in any type of source collector that
allows the entry of surface contaminants.
vi) Discontinue the use of infiltration laterals which intercept surface
water.
An extended period of monitoring should follow reconstruction (eg.
through at least two years or critical periods) to evaluate whether the source
is still influenced by surface water. Preferably particulate analysis would
be used to make such evaluations, but it may be helpful to use simpler mea-
sures, such as temperature and turbidity, as screening tools. Longer term
monitoring at critical times may also be an appropriate agreement between the
system and the Primacy Agency if there is still doubt about the long term
effectiveness of the solution.
If modification is not feasible, another alternative to avoid having to
comply with the SWTR may be to develop a new well either deeper or at a
different location.
2.2 Treatment Requirements
According to the SWTR, all community and noncommunity public water
systems which use a surface water source or a ground water under the direct
influence of a surface water must achieve a minimum of 99.9 percent (3 log)
removal and/or inactivation of Giardia cysts, and a minimum of 99..99 percent
(4 log) removal and/or inactivation of viruses. In the SWTR and this manual,
"viruses" means viruses of fecal origin which are infectious to humans by
waterborne transmission. Filtration plus disinfection or disinfection alone
2-11
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may be utilized to achieve these performance levels, depending on the source
water quality and site specific conditions. The SWTR establishes these
removal and/or inactivation requirements based on Giardia and viruses because
this level of treatment will also provide protection from heterotrophic plate
count (HPC) bacteria and Legionella as required in the SDWA amendments.
Guidelines for meeting the requirements of the SWTR are provided in the
remainder of this manual as outlined in Section 1. All systems must meet the
operator qualificiaitons presented in Section 2.3.
2.3 Operator Personnel Qualifications
The SWTR requires that all systems must be operated by qualified person-
nel. It is recommended that the Primacy Agency set standards for operator
qualifications, in accordance with the system type and size. In order to
accomplish this, the Primacy Agency should develop a method of evaluating an
operator's competence in operating a water treatment system. Primacy Agencies
which do not currently have a certification program are thereby encouraged, to
implement such a program. An operator certification program provides a
uniform base for operator qualifications and an organized system for
evaluating these qualifications.
It is recommended that plant operators have a basic knowledge of science,
mathematics and chemistry involved with water treatment and supply. The
minimum requirements for at least one key staff member should include an
understanding of:
- The principles of water treatment and distribution and their charac-
teristics
- The uses of potable water and variations in its demand
- The importance of water quality to public health
- The equipment, operation and maintenance of the distribution system
f. In the SWTR and this manual "Legionella" means a genus of bacteria,
some species of which have caused a type of pneumonia called
Legionnaires Disease; the etiologic agent of most cases of
Legionnaires Disease examined has been L. pneumophila.
2-12
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- The treatment process equipment utilized, its operational parameters
and maintenance
- The principles of each process unit (including the scientific basis
and purpose of the operation and the mechanical components of the
unit)
- Performance criteria such as turbidity, total colifonn, fecal
coliform, disinfectant residual, pH, etc. to determine operational
adjustments
- Common operating problems encountered in the system and actions to
correct them
- The current National Primary Drinking Water Regulations, the Secon-
dary Drinking Water Regulations and monitoring and reporting
requirements
- Methods of sample collection and sample preservation
- Laboratory equipment and tests used to analyze samples (where
appropriate)
- The use of laboratory results to analyze plant efficiency
- Record keeping
- Customer relations
- Budgeting and supervision (where appropriate)
Training in the areas listed above and others is available through the
American - Water Works Association (AWWA) training course series for water
supply operations. The course series includes a set of four training manuals
and one reference book as follows:
- Introduction to Water Sources and Transmission (Volume 1)
- Introduction to Water Treatment (Volume 2)
- Introduction to Water Distribution (Volume 3)
- Introduction to Water Quality Analyses (Volume 4)
- Reference Handbook: Basic Science Concepts and Applications
- Instructor Guide and Solutions Manual for Volumes 1, 2, 3 and 4
2-13
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These manuals are available through the American Water Works Association,
6666 West Quincy Avenue, Denver, Colorado 80235 USA, (303) 794-7711.
The State of California also offers a series of training manuals for
water treatment plant operators prepared by the California State University
School of Engineering in Sacramento. The manuals include:
1. Water Supply System Operation. (1 Volume)
2. Water Treatment Plant Operation. (2 Volumes)
These operator training manuals are available from California State
University, Sacramento, 6000 J Street, Sacramento, California 95819, phone
(916) 454-6142.
Completion of an established training and certification program will
provide the means of assuring that the operators have received training in
their respective area, and are qualified for their position. The education
and experience requirements for certification should be commensurate with the
size and the complexity of the treatment system. At the present time, some
states have instituted a certification program while others have not. Follow-
ing is a summary of the basic contents of a certification program, which can
serve as a guide to the Primacy Agency in developing a complete program.
- Board of examiners for the development and implementation of the
program.
- Classification of treatment facilities by grade according to the
size and technology of the facilities.
- * Educational and experience requirements for operators of the various
treatment facilities according to grade.
- A written/oral examination to determine the knowledge, ability and
judgement of the applicants with certification obtained upon receiv-
ing a passing grade.
- Renewal program for the license of certification, including the
requirement of additional coursework or participation in workshops.
The certification program should provide technically qualified personnel
for the operation of the plant.
The extensive responsibility which is placed on the operating personnel
warrants the development of an outline of the responsibilities and authority
of the personnel members to aid them in the efficient operation of the plant.
2-14
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The major responsibilities which should be delegated in the outline of re-
sponsibilities include: the normal day-to-day operations, preventive mainte-
nance, field engineering, water quality monitoring, troubleshooting, emergency
response, cross-connection control, implementation of improvements, budget
formulation, response to complaints and public/press contact. A reference
which the Primacy Agency may utilize in developing the outline is "Water
Utility Management Practices" published by AWWA.
2-15
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3.0 SYSTEMS NOT FILTERING
The provisions of the SWTR require that filtration or a particulate
removal technology as approved by the Primacy Agency, must be included in the
treatment train unless certain criteria are met. These criteria are enumerat-
ed in this chapter and include:
Source Water Quality Conditions
1. Coliform concentrations (total or fecal).
2. Turbidity levels.
Disinfection Criteria
1. System maintains at least 99.9 percent Giardia cyst inactivation and
99.99 percent virus inactivation, for all but one day per month.
2. System must have redundant backup components with an auxiliary power
supply, automatic start-up and alarm to ensure continuous disin-
fection, or automatic shutoff of delivery of water to the dis-
tribution system when the residual drops below 0.2 mg/L. To allow
the automatic shutoff, the Primacy Agency must determine that this
would not result in an unusal risk to health.
3. System maintains a minimum residual of 0.2 entering the distribution
system. The residual level must not drop below 0.2 mg/L for more
than a 4 hour period.
4. System maintains a detectable disinfectant residual in the distri-
bution system or a level of less than 500 HPC colonies/ml in no less
. than 95 percent of the samples each month for any two consecutive
months. For systems which cannot practically monitor for HPC, the
Primacy Agency may establish site specific criteria to ensure
adequate disinfection is provided.
Other Criteria
1. System maintains a watershed control program.
2. System has an on-site inspection each year conducted by the Primacy
Agency, or a party approved by the Primacy Agency, to demonstrate
that the system has adequate watershed control and disinfection.
3. System in its current configuration has not had a waterborne disease
outbreak, as determined by State or local health officials.
4. System complies with the total coliform MCL for the distribution
system.
5. System is in compliance with the Total Trihalomethane (TTHM) reg-
ulation. Currently this only applies to systems serving more than
10,000 people.
3-1
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The purpose of this section is to provide guidance to the Primacy Agency
for determining compliance with these provisions.
3.1 Source Water Quality Criteria
The first step in determining if filtration is required for a given sur-
face water supply is to determine if the supply meets the source water quality
criteria as specified in the SWTR. The site-specific criteria pertaining to
systems which do not filter are not applicable unless the source water quality
criteria are met.
Sampling Location
The SWTR requires that the source water samples be collected at a loca-
tion just prior to the point of disinfection where the water is no longer
subject to surface runoff. When multiple sources are used, sampling should be
conducted at a location just prior to the point of disinfection or disin-
fection sequences used for calculating the CT [disinfectant residual (mg/L) x
contact time (min.}]. Sampling at this location is appropriate because this
is the water which will be disinfected in accordance with the requirements of
the SWTR and is, therefore, the source water.
3.1.1 Coliform Concentrations; Specifically, the SWTR states that the
system must demonstrate that either the fecal coliform concentration is less
than 20/100 ml or the total coliform concentration is less than 100/100 ml in
•
the water prior to the point of disinfectant application in 90 percent of the
samples taken during any consecutive six month period. Where monitoring for
both parameters has been conducted, the rule only requires that the fecal
coliform limit be met. However, EPA recommends that the analytical results
for both total coliforms and fecal coliforms be reported, in addition, if the
turbidity of a surface water source is greater than 5 MTU and is blended with
a ground water to reduce the turbidity, EPA recommends that the high turbidity
water prior to blending meet the fecal coliform source water quality criteria.
Ongoing monitoring is required to ensure that these requirements are
continually met. The samples may be analyzed using either the multiple tube
3-2
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fermentation method or the membrane filter test (MF) as described in the 16th
Edition of Standard Methods.
Sampling Frequency
Minimum sampling frequencies are as follows:
Population Served Coliform Samples/Week*
<500 1
?01-3,300 2
3,301-10,000 3
10,001-25,000 4
>25,000 5
^Samples must be taken on different days as approved
by the Primacy Agency.
In addition, one sample must be taken every day during which the
turbidity exceeds 1 NTU. Also, under the Total Coliform Rule, systems must
take one coliform sample near the first service connection within 24 hours
after a source water turbidity measurement exceeds 1 NTU. This measurement
must be included in the total coliform compliance determination. The purpose
of these requirements is to ensure that the monitoring includes worst case
conditions. The Primacy Agency may determine on a case-by-case basis that
coliform samples do not have to be collected during times when the turbidity
exceeds 1 NTU on a weekend or holiday.
The initial evaluation of the source water quality is based on the data
from the previous 6 months. After the initial evaluation, systems must
continue to conduct the sampling each month to fulfill the source water
quality criteria. If the criterion has not been met, the system must filter.
Utilization of An Historical Data Base
Some systems may already monitor their source water for total and/or
fecal coliform concentration. The resulting historical data base may be
sufficient for the Primacy Agency to make the initial determination of whether
the system meets the source water quality criteria. The historical data base
is considered sufficient for making this determination if:
- The raw water sampling location is upstream of the point of disin-
fectant application as previously defined.
- The samples represent at least the minimum sampling frequency
previously mentioned.
- The sampling period covers at least the previous six months.
3-3
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3.1.2 Turbidity Levels; The SWTR requires that, prior to disinfection,
the turbidity of the water must not exceed 5 NTU, unless the following con-
ditions are met:
a. There are not more than two events in any 12 consecutive months and
not more than five events in any 120 consecutive months during which
the turbidity exceeds 5 NTU. An event is defined as any number of
consecutive days in which at least one turbidity measurement exceeds
5 NTU each day, and;
b. The Primacy Agency determines that exceedance of 5 NTU is unusual or
unpredictable.
Turbidity events which do not meet the above condition result in the
requirement to install filtration.
Utilizing the same sampling location requirements as stated in Sec-
tion 3.1, the determination of compliance is based upon the collection of grab
samples at least once every four hours. EPA recommends that the initial
determination of whether the turbidity criterion is met be based upon data
from 6 consecutive months. However, the Primacy Agency may be able to deter-
mine whether the criterion can be met based on historical data for a given
system.
Any system which exceeds the 5 NTU maximum limit at any time should
notify the Primacy Agency as soon as possible and no later than the end of the
next business day. The Primacy Agency should evaluate additional data from
the utility to determine the significance of the event with respect to the
potential health risk to the community and determine whether a boil water
notice is necessary. Boil water notices are not required under the SWTR
although they may be issued at the discretion of the Primacy Agency. Data
which may be .used to make this determination include raw water fecal coliform
1. The SWTR permits the use of continuous turbidity monitoring as a
substitute for grab sample monitoring if the measurement is validated
by the system for accuracy with grab sample measurements on a
regular basis as determined by the Primacy Agency. Validation
should be performed at least twice a week based on the procedure
outlined in Part 214A in the 16th Edition of Standard Methods.
3-4
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levels, duration and magnitude of the turbidity excursion, disinfectant
residual entering the system during the excursion and/or coliform levels in
the distribution system following the excursion.
In order to determine if the periods in which the turbidity exceeds 5 NTU
are unusual or unpredictable, it is recommended that in addition to the
historical turbidity data, the water purveyor should collect and provide to
the Primacy Agency current and historical information on flows, reservoir
water levels, climatological conditions, and any other information that the
Primacy Agency deems relevant. This information should be evaluated to
determine if the event was unusual or unpredictable. Examples of unusual or
unpredictable events include: hurricanes, floods, avalanches or earthquakes.
A system may be able to avoid a high turbidity event by:
- Utilization of an alternate source which is not a surface water and
does not have to meet the requirements of the SWTR.
- Utilization of an alternate source which is a surface water and
which does meet the requirements of the SWTR.
- Utilization of storage water to supply the community until the
source water quality meets the criteria.
3.2 Disinfection Criteria
3.2.1 Inactivation Requirements
To avoid filtration, a system must demonstrate that it maintains disin-
fection conditions which inactivate 99.9 percent of Giardia cysts and 99.99
percent of viruses every day of operation. If the disinfection level provides
less than these inactivations for more than one day of the month, the system
is in violation of a treatment technique requirement. If the system incurs
such a violation during any two months in any 12 consecutive months, the
system must install filtration. To make this demonstration, the system must
monitor and record the disinfectant(s) used, disinfectant residual(s),
disinfectant contact time(s), pH, and water temperature, and use these data to
determine if it is meeting the minimum total percent inactivation requirements
in the rule.
A number of disinfectants are available, including ozone, chlorine,
chlorine dioxide and chloramines. The SWTR establishes CT [disinfectant
residual concentration (mg/L) x contact time (min)] levels for these
3-5
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disinfectants which will achieve different levels of inactivation under
various conditions.
A system is deemed- in compliance with the inactivation requirements if
the CT value(s) calculated for its disinfection conditions meet (or exceed)
the CT value specified in the rule. The system must make this determination
each day that it is delivering water to its customers.
For the purpose of calculating CT values, disinfection contact time (in
minutes) is the time it takes the water, during peak hourly flow, to move
between the point of disinfectant application to a point where residual
disinfectant concentration is measured prior to the first customer. Residual
disinfectant concentration is the concentration of the disinfectant (in mg/1)
at a point before or at the first, customer. Contact time in pipelines must be
calculated based on "plug flow" (i.e., where all water moves homogeneously in
time between two points) by dividing the internal volume of the pipeline by
the peak hourly flow rate through that pipeline. Contact time within mixing
basins and storage reservoirs must be determined by tracer studies or an
equivalent demonstration as determined by the Primacy Agency. Guidance for
determining contact times for basins is provided in Appendix C.
Systems with only one point of disinfectant application may determine the
overall inactivation based on one point of residual measurement prior to the
first customer, or on a profile of the residual concentration after the point
of disinfectant application. Methods of disinfection measurement are present-
ed in Appendix D. The residual profile and the total inactivation provided is
calculated by:
Measuring the disinfectant residual, C, at any number of points
within the treatment train.
Determining the travel time, T, between the point of disinfectant
application and the point(s) where C is measured.
Calculating CT for each point of residual measurement (CT . ).
calc
3-6
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- Determining the inactivation ratio (CT . /^qq q' ^or eac^ se~
quence.
Calculating CT for each point of residual measurement (CT . ) .
Summing the inactivation ratios for each sequence, i.e. C T ', /CT
+ C.T./CT-- + C T /CTaQ . to determine the total inactivation
. ,i 2 99.9 n n 99.9
ratio.
If the total inactivation ratio (CT . / CTQ ) is equal to or greater than
CcL JLC -77 • y
1.0, the system provides greater than 99.9 percent inactivation of Giardia
lamblia cysts) , and the system is meeting the disinfection performance re-
quirement. Further explanation of this is contained in Section 3.2.2.
Systems need only calculate one CT (CT )' each day, for a point at or
calc
prior to the first customer, or alternatively they have the option of cal-
culating numerous CTs after the point of disinfectant application but prior to
the first customer to determine the inactivation ratio. Profiling the
residual gives credit for the higher residuals . which exist shortly after the
disinfectant is applied. However, if one CT is calculated (CT , ) and this
calc
exceeds the applicable CT , the system is meeting the disinfection perfor-
99 . 9
mance requirement. For systems with a very low oxidant demand in the water
and long contact times are available, this approach may be the most practical
to use.
For systems with multiple points of disinfectant application (e.g., if
ozone followed by chlorine, or chlorine is applied at two different points in
the treatment train) , the inactivation ratio of each disinfectant sequence
prior to the first customer must be used to determine the total inactivation
ratio. The disinfectant residual of each disinfection sequence and the
corresponding contact time must be measured at some point prior to the subse-
quent disinfection application point (s) to determine the inactivation ratio
for each sequence, and whether the total inactivation ratio of 1.0 or greater
CT is the CT value required to achieve 99.9 percent or 3-log
Giardia cyst inactivation for the conditions of pH, temperature and
residual concentration for each sequence. A sequence is the portion
of the system with a measurable contact time between two points of
disinfection application or residual monitoring.
3-7
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is achieved. For example, if the first disinfection sequence provided an
inactivation ratio of 2/3 (or 99 percent inactivation) and the second disin-
fection sequence provided an inactivation ratio of 1/3 (or 90 percent inac-
tivation) , the total inactivation ratio would equal 1.0 (2/3 + 1/3 = 1) .
Further explanation of this is contained in Section 3.2.2.
If the system fails to achieve at least 99.9 percent inactivation (i.e.,
the inactivation ratio is less than 1.0) any two or more days in one month,
the system is in violation of a treatment technique requirement. If the
system incurs such a violation during any two months in any 12 consecutive
months, the system must install filtration.
Maintaining Inactivation Level
The SWTR establishes CTs for chlorine, chlorine dioxide, ozone and
chloramines which will achieve various inactivations of Giardia cysts and
viruses, as presented in Appendix E. A system determines whether it is
meeting the inactivation requirements by measuring the residual disinfectant
concentration daily, during peak hourly flow for each disinfection sequence
prior to the first service connection in the distribution system or immediate-
ly following the point at which the contact time is determined and calculating
the overall inactivation ratio. Since a system can only identify peak hourly
flow after it has occurred, it is suggested that residual measurements be
taken each hour during the day. If the sampling points are remote, or manpow-
er is limited and it is impractical to collect hourly grab samples, continuous
monitors may be installed. Measurements for the hour of peak flow can then be
used in calculating CT. The temperature and pH (for systems using chlorine)
must be determined daily for each disinfection sequence prior to the first
customer.
Although the inactivation maintained in the system is determined during
peak hour flow, it should be noted that the disinfectant dosage applied to
maintain this inactivation may not be necessary during lower flow conditions.
Continuing to apply a disinfectant dosage based on the peak hourly flow could
possibly result in increased levels of disinfectant by-products, including
THMs. Under lower flow conditions, a higher contact time is available and a
lower residual may provide the CT needed to meet the inactivation require-
ments. The system should, however, maintain a disinfectant residual which
3-8
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will still provide a 3-log inactivation of Giardia cysts and a 4-log inac-
tivation of viruses at non-peak hourly flows. The system should therefore
evaluate the residual needed to provide the required inactivation under
different flow conditions and set the dosage accordingly. The following
provides an example of maintaining the required inactivation.
Example
A 5 mgd non-filtering system disinfecting with free chlorine at one point
of application, has a contact time of 165 minutes during a peak flow of 5 MGD.
The flow varies from 1 to 5 MGD. The pH and temperatures of the water are 7
and 5 C, respectively. At a residual 0.9 mg/L, a CT of 145 mg/L-min is
required to meet the disinfection requirements at a 5 MGD flow. Under lower
flow conditions, the available contact time is longer and a lower residual
would be needed to provide the required disinfection. Based on existing
contact time and using the appropriate CT tables (in this case. Table E-2) in
Appendix E for a 3-log Giardia cyst inactivation, the required disinfection
would be provided by maintaining the following chlorine residuals for the
indicated flow:
Contact CT (mg/l-min) Free Chlorine
Flow (MGD) Time (min) Required Residual (mg/L)
5 165 148 1.0
4 206 144 0.7
3 275 143 0.6
2" 412 139 0.4
1 825 139 0.2
This table indicates the variation of residuals needed for the system to
provide the required inactivation. For chlorine, the disinfectant residual
cannot be adjusted in direct proportion to the flow because the CT needed for
disinfection is dependent upon the residual. Since it is not practical to
continuously adjust the residual and, since a disinfection level for a 3-log
Giardia cyst inactivation must be maintained under all flow conditions, it is
suggested that the flow variation at the utility be divided into ranges and
the residual needed at the higher -flow rate of each range be maintained for
all flows within the range to ensure the required disinfection.
3-9
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The following flow ranges and residuals are suggested for the system:
Free Chlorine
Flow Range (MGD) Residual (mg/L) Maintained
1 - 1.9 0.4
2 - 3.9 0.6
4-5 0.9
By maintaining these residuals, the utility is ensuring the provision of the
required disinfection while minimizing the disinfectant application, which
should result in lower disinfection by-products.
Although these residuals will meet the inactivation requirements, main-
taining a residual in the distribution system must also be considered. If
there is no other point of disinfection prior to the distribution system, the
residual for disinfection must be maintained at a level which will also
provide a residual throughout the distribution system. The complete range of
flows occurring at the plant should be evaluated for determining the required
residual. The utilities may establish the residual requirements for as many
flow ranges as is practical.
The CTs determined from these data for the system each day should be
compared to the values in the table for the pH and temperature of the water,
to determine if the CT needed for the required inactivation has been achieved.
Only the analytical methods prescribed in the SWTR, or otherwise approved by
EPA, may be used for measuring disinfectant residuals. Methods prescribed in
the SWTR are listed in Appendix O. The Appendix also contains a paper to
offer guidance in selecting monitoring methods for various disinfectants and
conditions.
The Primacy Agency should make periodic checks on its utilities to assure
that they are maintaining adequate disinfection at non-peak flow conditions.
Meeting the Inactivation Requirement Using Free Chlorine
When free chlorine is used as a disinfectant, the efficiency of inactiva-
tion is influenced by the temperature and pH of the water. Thus, the measure-
ment of the temperature and pH for the determination of the CT is required.
The SWTR provides the CT requirements for free chlorine at various tempera-
tures and pHs which may occur in a source water. These values are presented
in Table E-l through Table E-7 in Appendix E. The basis for these values is
discussed in Appendix F. For free chlorine a 3-log inactivation of Giardia
3-10
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cysts will provide greater than a 4-log inactivation of viruses, thus meeting
the SWTR inactivation requirements.
As indicated in Table E-2, a raw water temperature of 5 C, a pH of 7.0,
and a residual chlorine concentration of 1.4 mg/L result in a CT of 155 to
provide a 3-log inactivation of Giardia cysts. Therefore, to meet the inac-
tivation requirement under these conditions with one point of residual mea-
surement, a contact time of 125 minutes prior to the first customer would be
required.
Meeting the Inactivation Requirement Using Chloramines
Chloramines are a much weaker oxidant than free chlorine, chlorine
dioxide and ozone. The CT values for Chloramines presented in Table E-12, are
based on disinfection studies using preformed Chloramines and in vitro
excystation of Giardia muris cysts (Rubin, 1988). No safety factor was
applied to the laboratory data on which the CT values were based since EPA
believes that chloramination, conducted in the-field, is more effective than
using preformed chloramines.
In the laboratory testing using preformed chloramines, ammonia and chlo-
rine were reacted to form chloramines before the addition of the microorga-
nisms. Under field conditions, chlorine is usually added first followed by
ammonia addition further downstream. Also, even after the addition of ammo-
nia, some free chlorine residual may persist for a period of time. Therefore,
free chlorine is present for a period of time prior to the formation of
chloramines. Since this free chlorine contact time is not duplicated in the
laboratory when testing with preformed chloramines, the CT values obtained by
such tests may provide conservative values when compared to those CTs actually
obtained in the field with chlorine applied before ammonia. Also, other
factors such as mixing in the field {versus no mixing in the laboratory) may
contribute to disinfection effectiveness. For these reasons, systems using
chloramines for disinfection may demonstrate effective disinfection in accor-
dance with the procedure in Appendix G in lieu of meeting the CT values in
Appendix E.
If a system uses chloramines and is able to achieve the CT values for
99.9 percent inactivation of Giardia cysts, it is not always appropriate to
assume that 99.99 percent or greater inactivation of viruses was also
3-11
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achieved. New data indicate that Hepatitis A virus is more sensitive than
Giardia cysts to inactivation by preformed chloramines (Sobsey, 1986). The CT
values required to achieve 99.99 percent inactivation of Hepatitis A with
preformed chloramines are lower than those needed to achieve 99.9 percent
inactivation of Giardia cysts. These data contrast with other data which
indicate that rotavirus is more resistant than Giardia cysts to preformed
chloramines (Hoff, 1986). However, rotavirus is very sensitive to inac-
tivation by free chlorine, much more so than Hepatitis A (Hoff, 1986;
Sobsey, 1988). If chlorine is applied prior to ammonia, the short term
presence of free chlorine would be expected to provide at least 99.99 percent
inactivation of rotavirus prior to the addition of ammonia and subsequent
formation of chloramines. Thus, EPA believes it is appropriate to use
Hepatitis A data, in' lieu of rotavirus data, as a surrogate for defining
minimum CT values for inactivation of viruses by chloramines, under the
condition that chlorine is added to the water prior to the addition of am-
monia.
A system which achieves a 99.9 percent or greater inactivation of Giardia
cysts with chloramines can be considered to achieve at least 99.99 percent
inactivation of viruses, provided that chlorine is added to the water prior to
the addition of ammonia. Table E-13 provides CT values for achieving different
levels of virus inactivation. However, if ammonia is added first, the CT
values in the SWTR for achieving 99.9 percent inactivation of Giardia cysts
cannot be" considered adequate for achieving 99.99 percent inactivation of
viruses.
Under such cases of chloramine production, the SWTR requires systems to
demonstrate through on-site challenge studies, that the system is achieving at
least a 4-log inactivation of viruses unless the CTs for a 4-log virus inac-
tivation are maintained. Guidance for conducting such studies is given in
Appendix G.
3. CT values ranging from 0.025 to 2.2 achieve 99 percent inactivation
of rotavirus by free chlorine at pH = 6 -10 and 4 - 5~C (Hoff,
1986).
3-12
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Meeting the Inactivation Requirement Using Chlorine Dioxide
Under the SWTR, the CT values for the inactivation of Giardia cysts using
chlorine dioxide are independent of pH. Under the SWTR the only parameter
affecting the CT requirements associated with the use of chlorine dioxide is
temperature. Table E-8 in Appendix E presents the chlorine dioxide CT values
required for the inactivation of Giardia cysts at different temperatures. The
basis for these CT values is discussed in Appendix F. Systems which use
chlorine dioxide are not required to measure the pH of the disinfected water
for the calculation of CT. For chlorine dioxide, as for free chlorine, a
3-log inactivation of Giardia cysts will result in greater than a 4-log virus
inactivation, meeting the SWTR inactivation requirements. The Primacy Agency
may allow lower CT values than those specified in the SWTR for individual
systems based on information provided by the system. Protocols for demon-
strating effective disinfection at lower CT values is provided in Appendix G.
As indicated in Tables E-8 and E-9, the CT requirements for chlorine
dioxide are substantially lower than those required for free chlorine.
However, chlorine dioxide is not as stable as free chlorine or chloramines in
a water system and may not be capable of providing the required disinfectant
residual throughout the distribution system. In addition, out of concern for
toxicological effects, EPA's current guideline is that the sum of the chlo-
rine dioxide, chlorate and chlorite residuals, be less than 1.0 mg/L at all
consumer taps. This guideline may be lowered as more health effects data
become available. These concerns further reduce the feasibility of using
chlorine dioxide as a secondary disinfectant for distribution systems.
Therefore, the use of chlorine dioxide as a primary disinfectant may result in
the need for the application of a secondary disinfectant, such as chlorine or
chloramines, that will persist in the distribution system and provide the
required residual protection.
Meeting the Inactivation Requirement Using Ozone
A third disinfectant which can be used to inactivate Giardia cysts and
viruses is ozone. As with chlorine dioxide, under the SWTR, the CT values for
ozone are independent of pH. Tables E-10 and E-ll present the CT requirements
3-13
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for ozone at different source water temperatures. The SWTR does not require
the measurement of the finished water pH for purposes of CT calculations. The
basis for the CT values for ozone is given in Appendix F. As for free chlo-
rine and chlorine dioxide, a 3-log Giardia cyst inactivation with ozone will
result in greater than a 4-log virus inactivation. The Primacy Agency may
allow lower CT values for individual systems based on information provided by
the system. Recommended protocol for demonstrating effective disinfection is
provided in Appendix G.
Ozone is extremely reactive and dissipates quickly after application.
(4)
Therefore, a residual can only be expected to persist a short time after
application. In addition to this, the application of ozone to water is
dependent on mass transfer. For these reasons, the method of CT determination
used for the other disinfectants is impractical for ozone. The CT , must be
r calc
determined for the ozone basin alone. The portion of the ozone basin where
the ozone is applied will be referred to as the contactor, and the portion of
the basin where ozone is no longer applied will be referred to as the reactor.
For many ozone contactors, the residual in the contactor will vary in
accordance with the method and rate of application and there will be a portion
4. The residual must be measured using the Indigo Method (Bader &
Hoigne, 1981) or automated methods which are calibrated in reference
to the results obtained by the Indigo method, on a regular basis as
determined by the Primacy Agency. The Indigo method has been
submitted for inclusion in the 17 Edition of Standard Methods. This
method is preferable to current standard methods because of the
selectivity of the indigo-reagent in the presence of most
interferences found in ozonated waters. Indigo trisulfonate is the
indicator used in this test method. The ozone degrades an acidic
solution of indigo trisulfonate in a 1:1 proportion. The decrease
in absorbance is linear with increasing ozone concentrations over a
wide range. Malonic acid can be added to block interference from
chlorine. Interference from permanganate, produced by the ozonation
of manganese, is corrected by running a blank in which • ozone is
destroyed prior to addition of the indigo reagent. The samples can
be analyzed using a spectrophotometer at a 600 ran wavelength which
can detect residuals as low as 2 ug/L or a visual color comparison
method which can measure down to 10 ug/L ozone. Although currently
available monitoring probes do not use the Indigo Method, they can
be calibrated via this method.
3-14
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of the contactor which does not contain an ozone residual. As previously
indicated, the CT is based on the presence of a known residual during a
specific contact time. Thus disinfection credit is-only provided for the
time, T effective during which a residual is present. The method of monitor-
ing the residual will have an impact on the determination of the CT for each
basin, thereby affecting the disinfection credit.
In addition to the difficulty in determining the ozone residual for the
CT calculation, the contact time will vary between basins depending on their
configuration. Several types of contactors are available including porous
diffusers, submerged turbines, injector, packed towers and static mixers.
Each type of contactor is available in either single or multiple chamber
units. The flow through a single chamber turbine unit will approximate a
completely mixed unit, while flow through a single chamber diffused contactor,
or a multiple chamber diffused contactor, will more closely represent plug
flow. However, the contact time for the contactor should be determined
through a tracer study or an equivalent method with air or oxygen applied
during testing, as approved by the Primacy Agency. Guidance for the deter-
mination of detention time is included in Appendix C. The detention time
(T ) obtained from the tracer study should be used to determine the CT of
the ozone basin. The following section provides guidance for determining CT
for the two types of ozone contactors (diffused and turbine) most widely used
in the United States. A recent survey of operating ozone systems in drinking
water treatment plants in the United States indicated that all 40 plants
employ either bubble diffusers or submerged turbine contactors (Robson et al.
1988}. It should be noted that this does not preclude the use of other types
of contactors for disinfection.
Diffused Ozone Contactors
In diffused contactors, the ozone is bubbled into the water through
diffusers at the bottom of the basin. The contactor may be designed for even
application across the length of the basin, or tapered application where a
higher ozone dose is applied at the beginning of the basin.
Diffusers may also be operated in different flow regimes, either counter-
current or co-current. That is, the water flows in the same or opposite
3-15
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direction to the flow of rising gas bubbles. Regardless of the flow regime,
the ozone residual will vary throughout the contactor, depending on the rate,
and mode of application,, and the quality of the influent water (eg. pH, TOO.
In determining the CT, the portion of the basin containing a residual should
must be determined as explained later in this section.
Single Chamber Unit
A typical countercurrent flow single chamber contactor is illustrated on
Figure 3-1. The first step in determining the CT should be to ascertain the
point in the contactor at which a residual is first detected. A monitoring
probe should be placed within the contactor near the inlet at approximately
mid-depth and moved to sampling ports towards the effluent until a residual is
detected. The time (T,n) obtained from the tracer study should then be
multiplied by the fraction of the contactor volume which has a residual,
generating the time, T effective for the CT calculation. A second probe
should then be placed at the contactor effluent and the average residuals from
the two probes calculated. The CT provided by the basin can be approximated
as [average ozone residual x T effective]. An example of this follows.
Example
A 5 mgd utility has a single chamber ozone contactor. A tracer study for
the contactor indicated a 3 minute contact time. Using an ozone probe,
the first detectable residual, 0.1 mg/L, was detected one-third of the
way through the contactor volume. The time for disinfection, T effective
is therefore, two-thirds of the contact time, or 0.67 x 3 minutes = 2
minutes. The effluent residual is 1.0 mg/L. The CT , for the
calc
contactor is [(0.1 + 1.0)72] x 2 min = 1.1 mg/L-min.
A more accurate representation of the residual within the basin can be
obtained by placing a number of probes within the basin and taking the average
of the measured residuals. The probes should be located so that each probe
monitors a detectable residual. The probes should be equally spaced both
horizontally and from the top to bottom of the basin in the area of detectable
residual. Profiling the ozone concentration in this way will provide a more
accurate measurement of the ozone concentration gradient and may allow a
higher ozone concentration to be used in the CT calculation than the average
3-16
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UNOZONATED
WATER
CONTACT
CHAMBER
OFF-GAS
*'•
. *
^r-fej—
I •*"
OZONATED
WATER
OZONE —*
FLOW METER
VALVE
FIGURE 3-1 SINGLE CHAMBER CONTACTOR
-------
determined from only two points. The average of these measurements is then
used to calculate CT so that CT » average residual x T effective.
One way to increase the CT credit for the ozone basin may be to provide a
reactor following the contactors. Although ozone is not added in the reactor,
a residual is maintained to provide additional disinfectant contact time.
Ozone is not added to the reactor, therefore mixing will not interfere with
plug flow. The reactor can also be baffled to more closely approximate plug
flow, maximizing its detention time. The detention time of the reactor should
be determined through a tracer study and the average residual within the
reactor should be measured as it is for the contactor to determine the CT for
the reactor. If the reactor provides the necessary CT, the need to determine
the portion of the contactor that contains a residual would be eliminated.
Multiple Chamber Units
A multiple chamber diffuser contactor is a unit containing ozone dif-
fusers in each of the chambers separated by baffles, as illustrated on Figure
3-2. Initially the portion of the first chamber or chambers containing a
residual should be determined for use in generating CT for each chamber.
However, in multiple chamber contactors/reactors, the determination of CT may
be simplified by operating to satisfy the ozone demand in the first chamber,
using the remaining contactor/reactor volume for disinfection, similar to the
French application. This mode of operation would eliminate the need to
determine the portion of the first chamber containing a residual.
Monitoring probes can be placed near the inlet and outlet of each of the
subsequent chambers downstream of the first chamber. The average residual
measured will be used to determine the CT provided in each chamber.
CcL J.C
Within each chamber, additional probes may be placed to get a more accurate
representation of the average residual. The contact time for each chamber may
be calculated as a fraction of the overall detention time determined from the
tracer study. The fraction will be a ratio of the volume of the chamber to
the overall volume of the contactor, as follows:
- An ozone contactor has a total volume of 10,000 gallons and an
overall T of 10 minutes at peak flow. The contactor'is baffled into
four chambers. The volume of each chamber is 2,500 gallons.
Therefore, the detention time of each chamber is:
1 x 10 minutes = 2.5 minutes
10,000
3-17
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UNOZONATED
WATER
o ;-..;*/
OZONE-
CONTACT
CHAMBER
OFF-GAS
v
'•f
. 9' •
4
OZONATED
WATER
FLOW METER
VALVE
FIGURE 3-2 MULTIPLE CHAMBER CONTACTOR
-------
The CTcalc will then be calculated for each chamber using the correspond-
ing average residual and detention time. As with the single chamber basin, a
reactor may be used following the contactors to increase the disinfectant
contact time. The overall inactivation ratio for the ozone basin can then be
calculated as outlined in Section 3.2.2.
Turbine Contactors
In turbine contactors, the ozone is added across the entire depth of the
water as illustrated on Figure 3-3. This type of contactor approximates a
completely mixed system, and a residual should exist throughout the contactor.
Initially, probes should be placed in the contactor, evenly spaced horizon-
tally and from top to bottom to confirm that the contactor is completely
mixed, and to determine the average residual within the contactor. A com-
pletely mixed reactor can be assumed if all probes indicate approximately the
same measurement. A rule of thumb which may be used is for all the measure-
ments to be within 20 percent of each other. During daily operation one
monitoring probe within the contactor will be sufficient to measure the
average residual of a completely mixed reactor. The CT value for the
contactor will be [average residual x T ] . The contactor should be tested
following changes in ozone application rate and seasonal, changes to confirm
that it is a completely mixed unit. To increase the CT for the basin, a
reactor may be provided following the contactor as suggested for the diffused
contactor'.
The short life of ozone in water will usually result in a system which
utilizes ozone as a primary disinfectant and applies a secondary disinfectant,
such as chlorine or chloramines, in order to maintain a disinfectant residual
in the distribution system. However, consideration should be given to the
fact that when ozone comes in contact with either chlorine or chloramines,
reactions between the two may result in the mutual destruction of both disin-
fectants. In order to prevent the two disinfectants from destroying each
other, the secondary disinfectant should be applied after the ozone residual
has fully dissipated.
3-18
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OZONE
IN
WATEH
OUT
WATER
IN
FIGURE 3-3 TURBINE CONTACTOR
-------
Ozone Case Studies
Three case studies are presented here to demonstrate the determination of
CT for existing ozone basins. In cases 2 and 3, the basins are in use at
filtration plants, although the same method of CT determination is applicable
for ozone basins whether they are being used for a filtered or unfiltered
supply.
Case 1 - North Andover(from USEPA, 1988b)
During early 1986, 18 cases of Giardiasis were reported in the North
Andover, Massachusetts area. The outbreak was traced to the presence of
Giardia cysts in the raw water supply, Lake Colchichewick. At the time, lake
water was transported through two pumping stations and chlorinated (without
filtration) before entering the North Andover distribution system.
As an interim solution, while the design and construction of a new
treatment plant which included filtration was in progress, ozonation facil-
ities were installed at each pumping station. Each station pumps an average
of 2.5 to 3 mgd. Chlorine is added at four points in the distribution system,
to provide a residual.
Each ozone contactor is 10 ft wide and 20 ft long, with 16 ft water
depth. Baffles are included in the contactors to separate each into five
chambers, with ozone being applied equally in each chamber. Applied ozone
dosages are 5 mg/L.
At the outlet of the last chamber of each ozone contactor, the concen-
tration of dissolved ozone is between 0.9 and 1.0 mg/L. The total hydraulic
flow time of water through each ozone contactor is 10 minutes at peak flow in
summertime. During winter, with lower water demand, pumping rates are reduced
by 50%, thereby doubling the hydraulic residence time to 20 minutes.
Tracer studies need to be conducted at the plant to determine the T
values of the contactors. Additional probes are also needed within the
contactors to determine the ozone profile needed to calculate the inactivation
ratio.
Since the temperature of Lake Colchichewick varies from 5C in winter to
20C in summer, the CT values for attaining 3-log activation of Giardia cyst
inactivation range from 2 mg/L-min at 5~C to 0.75 mg/L-min at 20~C. If the
tracer study results in a T value which is one-half of the hydraulic
detention time, the contact time in the winter would be 10 minutes requiring
3-19
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an average ozone residual of 0.2 mg/L throughout the contactor to provide a CT
of 2 mg/L-min. During the summer months, the contact time would be approxi-
mately 5 minutes, requiring an average residual of 0.15 mg/L throughout the
contactor to provide a CT of 0.75 mg/L-min.
Case 2 - City of Tucson (from Joost et al., 1988 )
The City of Tucson is currently designing a 150 mgd direct filtration
plant. A single application of ozone is to be applied prior to the rapid mix,
for a number of oxidative purposes, including primary disinfection.
The Tucson plant will have four, parallel, countercurrent, 6-stage ozone
contactors, each with a 37.5 mgd design capacity and a 12 minute design
hydraulic residence time. The plant flow ranges between 60 to 150 mgd, and
one or two ozone contactors will be taken off-line during low flow periods,
varying the actual detention time of the basins. As illustrated on Figure
3-4, the contactors will be divided into six chambers. The T of this
configuration was estimated to be about half the hydraulic residence time.
A baffled section at the end of each of these contactors will not have
diffusers, although the ozone residual will be at least partially maintained
in these sections, which will contribute to the overall inactivation attained.
Based on pilot plant testing, applied ozone doses of 1.5 to 3.0 mg/L
should produce a maximum of 0.50 mg/L dissolved ozone residual in the contac-
tors, and a minimum of 0.25 mg/L providing CTs from 1 to 2 mg/L-min which
provides greater than a 1-log inactivation of Giardia cysts required for the
system. To assure that the CT values are being maintained, each contactor
will have several ozone residual analyzers operating continuously. A minimum
of three analyzers will be used per contactor, to generate a residual profile
across the contactor.
Case 3 - Los Angeles (from Stolarik et al., 1988)
At this 600 mgd plant, ozone was installed for pretreatment oxidation
ahead of coagulation, flocculation and filtration before the CT requirements
for primary disinfection were proposed in the SWTR . Consequently, the ozone
contactors were not.designed with CT considerations in mind.
There are four ozone contactors at the plant -- one for each of the
plant's four pretreatment process trains. Each ozone contactor is designed to
3-20
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UNOZONATEO
WATER
CONTACT
CHAMBER
OFF-OAS
fc.
OZONE
*J
*J
-_.
i
OZONATEO
WATER
FLOW METER
VALVE
FIGURE 3-4 CITY OF TUSCON OZONE CONTACTOR
-------
contain two ozone contact chambers, with ozone added to each chamber. Between
the two chambers is a baffled section in which no ozone is applied. The
purpose of this section is to allow the flow of water to change direction, so
that water in each contacting chamber flows downward, counter-current to the
flow of rising ozone/gas bubbles. After the second ozone contact chamber, the
water exiting the base of the chamber rises in a second baffled section to the
outlet of the ozone contactor, as it does for the Tucson contactor.
Dye tracer studies were performed in accordance with recommendations in
Appendix C in one of the process trains at this plant, and residual ozone was
measured by the Indigo trisulfonate method as well as by standard iodometxy.
Rhodamine WT was selected as the tracer for the studies. Since ozone
decolorizes this dye rapidly, when tracer tests were conducted, the ozone
generators were turned off, but the flow of oxygen was maintained through the
system / in order to induce the mixing and bulk fluid changes which occur
normally in the contactor. Sampling of dye tracer concentration was conducted
over a five day test period at 10 sample locations and at five different water
flow rates (40 to 100 percent of capacity). Samples taken during ozonation
(to measure dissolved ozone concentrations) were taken at taps located after
the first chamber, at the top of the intermediate flow-changing baffled
section, at the outlet of the second ozone contacting chamber, at the exit of
the ozone contactor, and at the inlet and outlet of the rapid mixers as shown
on Figure 3-5.
Analysis of the data collected showed that T times for the the entire
ozone contact system were approximately half of the theoretical hydraulic
detention time, depending upon the water flow rates. During periods when
ozone was applied, residual concentrations varied across the system as
follows: residuals were detected at 0.15 mg/L after the first chamber,
0.09 mg/L at the top of the intermediate flow-changing baffled section, 0.16
mg/L at the outlet of the second chamber, and 0.05 mg/L at the outlet of the
rapid mixers.
Based on determinations of actual contactor detention times and measure-
ments of ozone residuals, projected CT values were compared with EPA's crite-
ria for 1-log reduction of Giardia. It was determined that the plant's 7,900
Ibs./day design capacity ozonation system would be capable of meeting the CT
3-21
-------
OZONE CONTACT BASIN
RAPID MIXERS FLOCCULATORS
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 t 1 1
1 I 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
t 1 1 1 1 1
1 t 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
oooooo
.09 .2
n
.15
)A t t t t t
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
i i i i i i
oooooo
.21
.18
.16
.14
1
flC
.UO
IF
.00
70%
30%
BASED ON AVERAGE OF 7 DATA SETS
NOVEMBER 19. 1987 TO DECEMBER 1. 1987
APPLIED OZONE DOSE 1.10 - 1.65 mg/L
WATER TEMPERATURE RANGE: 11.8 - 14.5 °C
1. FROM STOLARIK AND CHRISTIE, 1988
2. RESIDUALS IN mg/L
-------
requirements throughout the year. However, reduced operating margins and
correspondingly higher costs for increased power consumption and supplemental
liquid oxygen feed would occur during seasonal periods of peak ozone demand.
Summary
Many systems which do not provide filtration will have difficulty in
providing the contact time necessary to satisfy the inactivation requirements
prior to the first customer. For example, a system using free chlorine at a
water temperature of 5 C, a pH of 7.0 and a chlorine residual of 1.4 mg/L
would require 111 minutes of contact time to meet the inactivation require-
ment. Options which are available to these systems include:
- Installation of storage facilities that will provide the required
contact time under maximum flow conditions.
- Use of an alternate disinfectant such as ozone or chlorine dioxide
which has CT values lower than those required for free chlorine for
the required inactivation.
For some systems, the difficulty in obtaining the required inactivation
may only be a seasonal problem. A system that has raw water temperatures
which reach 20 C during the summer months at a pH of 7.0, may have sufficient
contact time to meet the CT of 56 at a chlorine concentration of 1 mg/L.
However, assuming the same pH and chlorine concentration, it may not have
sufficient contact time to meet the CT requirement at 5 C (149) or at 0.5 C
(210). Under those conditions, a system could choose to use ozone or chlorine
dioxide on a seasonal basis, since they are stronger disinfectants requiring a
shorter contact time.
As indicated in Table E-12, the CT values for chloramines may be imprac-
tical to attain for most systems. Systems which currently utilize chloramines
as a primary disinfectant may need to use either free chlorine, chlorine
dioxide or ozone in order to provide the required disinfection. However,
systems using chloramines as a primary disinfectant may chose to demonstrate
the adequacy of the disinfection. Appendix G presents a method for making
this demonstration.
3-22
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3.2.2 Determination of Overall Inactivation for Residual Profile,
Multiple Disinfectants and Multiple Sources
For systems which apply disinfectant(s) at more than one point, or choose
to profile the residual from one point of application, the total inactivation
achieved is the sum of the inactivation ratios between each of the points of
disinfection or between each of the residual monitoring points respectively.
The portion of the system with a measurable contact time between two points of
disinfection application or residual monitoring will be referred to as a
section. The calculated CT (CT ) for each section is determined daily.
C21XC
The CT needed to fulfill the disinfection requirements is CT _, corre-
sponding to a 3-log inactivation of Giardia cysts and greater than or equal to
a 4-log inactivation of viruses (except for chloramines as explained in
Section 3.2.1). The inactivation ratio for each section is represented by
CT . /CT__ _, as explained in Section 3.2.1, and indicates the portion of the
caxc 77.9
required inactivation provided by the section. The sum of the inactivation
ratios from each section can be used to determine the overall level of disin-
fection provided. Because inactivation is a first order reaction, the inac-
tivation ratio corresponds to log and percent inactivations as follows:
CT , /CT__ _ Log Inactivation Percent Inactivation
—calc 99.9 —*
0.17 CT_. = 0.5 log = 68 %
77 • 7
0.33-CT99>9 = 1 log = 90%
0.50 CT = 1.5 log = 96.8%
0.67 CT99^g = 2 log = 99%
0.83 CToa = 2.5 log = 99.7%
.77 • 7
1.00 CTQQ » 3 log = 99.9%
77 • y
1.33 CT =4 log = 99.99%
77* 7
The CT can be determined for each section by referring to Tables E-l
through E-13 in Appendix E, using the pH (when chlorine is the disinfectant)
and temperatures of the water for the respective sections. These tables
present the log inactivation of Giardia cysts and enteric viruses achieved by
CTs at various water temperatures and pHs.
3-23
-------
Log inactivations are additive, so:
0.5 Log +1.0 Log =1.5 Log or
°-17CT99.9 + °'33CT99.9 = °'5CT99.9
If the sum of the inactivation ratios is greater than or equal to one,
the required 3-log inactivation of Giardia cysts has been achieved. An
inactivation ratio of at least 1.0 is all that is needed to demonstrate
compliance with the Giardia cyst inactivation requirements for unfiltered
systems.
The total log inactivation that is provided can be determined by multi-
plying the sum of the inactivation ratios, (CT /CTgg g' • fay three. The
total log inactivation can be determined in this way because CT is equiva-
yy • y
lent to a 3-log inactivation. The overall percent inactivation can then be
determined as follows:
y = 100 - 100 Equation (1)
10X
where: y = % inactivation
x = log inactivation
For example:
x = 3.0 log inactivation
y = 100 - 100 = 99.9 % inactivation
103'°
The following is an example of the determination of the overall percent
inactivation for multiple points of disinfection.
Example
A community of 6,000 people obtains its water supply from a lake which is
10 miles from the city limits. Two 0.5 MG storage tanks are located along the
12-inch transmission line to the city. The water is disinfected with chlorine
dioxide at the exit from the lake and with chlorine at the discharge from the
first and second storage tanks. The average water demand of the community is
1 MGD with a peak hourly demand of approximately 2 MGD. For the calculations
of the overall percent inactivation, the supply system is divided into three
sections as shown on Figure 3-6.
3-24
-------
1 st GUST!
1 STORAGE STORAGE
71
k TANK 1 + TANK 2
I I
1
t
CHLORINE CHLORINE CHLORINE
DIOXIDE
SECTION
SECTION
SECTION
FIGURE 3-6 DETERMINATION OF IN ACTIVATION FOR
MULTIPLE DISINFECTANT APPLICATION
TO A SURFACE WATER SOURCE
-------
Section 1 - from the lake to the discharge from the first storage tank,
Section 2 - from the discharge from the first storage tank to the dis-
charge from the second tank
Section 3 - from the discharge of the second storage tank to the first
customer
The overall inactivation is computed daily for the peak hourly flow condi-
tions. On the day of this example calculation, the peak hourly flow was
2 MGD. The pH, temperature and disinfectant residual of the water were
measured at the end of each section just prior to the next point of disinfec-
tion and the first customer during the hour of peak demand. The water travels
through the 12-inch transmission main at 237'ft/min at 2 MGD, The deten-
tion times of the storage tanks were determined to be 290 min and 285 man as
the result of tracer studies.
The data for the inactivation calculation are as follows:
Section 1 Section 2 Section 3
length of pipe (ft) 15,840 26,400 10,560
contact time (min)
pipe 67 111 . 45
tank 290 285 0
total 357 396 45
disinfectant chlorine chlorine chlorine
dioxide
residual (mg/L) 0.1 0.2 0.4
temperature (C) 5 5 5
pH 888
This information is then used in conjunction with the CT values in Appen-
yy • y
dix E to determine the (CT /CTQQ Q) in each section as follows:
yy * y
Section 1 - Chlorine dioxide
CT , - 0.1 mg/L x 357 minutes = 36 mg/L-min
calc
From Table E at a temperature of 5 C and pH = 8,
CT is 54 mg/L-min
yy • y
5.
2 -
A
2 X lO^gal/day X
(1 ft"fT /4)
1ft3
7.48 gal
X day
1440 min
= 237 ft/min
3-25
-------
CT , /CHnn „ = 36 mg/L-min » 0.67
calc 99'9 54 mg/L-min
Section 2 - Chlorine
CT , =0.2 mg/L x 396 minutes « 79 mg/L-min
calc
From Table E at a temperature of 5 C and pH = 8,
CT__ is 202 mg/L-min
99* 9
/ CT__ _ = 79 mg/L-min = 0.39
202mg/L-min
Section 3 - Chlorine
CT , = 0.4 mg/L-min x 45 min - 18 mg/L-min
calc
From Table E at a temperature of 5 C and pH = 8,
CT is 202 mg/L-min
CT , /CTQQ = 18 mg/L-min = 0.09 = 0(6)
calc 99.9
The sum of CT . /CT _ is egjual to 1.06, which is greater than 1, therefore,
the system meets the requirements of providing a 3-log inactivation of Giardia
cysts. The log inactivation provided is:
x = 3 x CT
caJ-C - 3 x 1.06 = 3.18
CT99.9
The percent inactivation can be determined using equation 1.
y - 100 - 100 = 100 - 100 = 100 - 0.07 = 99.93% inactivation
ID3*18 1514
The generation of reliable CT values for inactivations less than
(0.17CT } 0.5 log was not feasible by extrapolation from the
existing 3ata. Thus, no credit is given for less than a 0.5 log
inactivation.
3-26
-------
The system meets the requirement of providing a 99.9 percent inactivation of
Giardia cysts.
The SWTR also requires that the public be provided with protection from
Legionella as well as Giardia cysts and viruses. Inactivation levels have not
been set for Legionella because the required inactivation of Giardia cysts
will provide protection from Legionella. However, this level of disin-
fection cannot assure that all Legionella will be inactivated and that no
recontamination or regrowth in recirculating hot water systems of buildings or
cooling systems will occur. Appendix B provides guidance for monitoring and
treatment to control Legionella in institutional systems.
The above discussion pertains to one source with sequential disinfection.
However, other systems may blend more than one source, and disinfect one or
more of the sources independently prior to blending. System conditions which
may exist include:
- All the sources are combined at one point prior to supplying the
community but one or more of the sources are disinfected prior to
being combined, as shown on Figure 3-7.
- Each source is disinfected individually and enters the distribution
system at a different point, as shown on Figure 3-8.
For all systems combining sources, the first step in determining the CT
should be to determine the CT - provided from the point of blending closest
CclXC
to the first customer using the contact time and residual at peak hourly flow
for that portion of the distribution system. This corresponds to Section D on
Figure 3-7 and Section E on Figure 3-8. If the CT for section D or E
7. Kuchta et al. (1983) reported a maximum CT requirement of 22.5 for
a 99 percent inactivation of Legionella in a 21 C tap water at a pH
of 7.6-8.0 when using free chlorine. Using first order kinetics, a
99.9 percent inactivation requires a CT of 33.8. Table A-5 presents
the CTs needed for free chlorine to achieve a 99.9 percent
inactivation of Giardia cysts at 20 C. this table indicates that
the CT required for a 3 long inactivation of Giardia at the
temperature and pH of the Legionella test ranges from 67 to 108
depending on chlorine residual, this is 2 to 3 times higher than
that which is needed to achieve a 3 long inactivation of Legionella.
3-27
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1st CUSTOMER
FIGURE 3-7 INDIVIDUALLY DISINFECTED
SURFACE SOURCES COMBINED
AT A SINGLE POINT
•• c
e
1 st CUSTOMER
DISINFECTANT
APPLICATION
COMBINATION POINT
SAMPLING POINTS
FIGURE 3-8 MULTIPLE COMBINATION POII
FOR INDIVIDUALLY DISINFECl
SURFACE SOURCES
-------
provides the required inactivation, no additional CT credit is needed and no
further evaluation is required. However, if the CT for section D or E is not
sufficient to achieve the required inactivation, then the inactivation ratio
(CT )/(CT g) should be determined for each section to determine the
overall inactivation provided for each source. The overall inactivation
provided must be greater than or equal to one for all sources in order to
comply with the requirements for 3-log inactivation of Giardia cysts.
On Figure 3-7, sections A, B, C and D contain sampling points, a, b c and
d respectively. The sum of the inactivation ratios for sections A+D, B+D and
C+D must each be greater than or equal to one for the disinfection require-
ments to be met.
The overall inactivation provided for each source on Figure 3-7 should be
determined as:
Source I
- Determine CT . for sections A and D based on the residual measurements
at sample- point! a and d, and the travel time through each section under
peak hourly flow conditions for the respective section.
- Determine CT for the pH and temperature conditions in each section
using the tables in Appendix E
- Calculate the inactivation ratios ^CTcalc/CT99 9) for sections A and D.
- Calculate the sum of the inactivation ratios for sections A and D.
- If the sum of the inactivation ratios is greater than or equal to 1, the
system has provided the required 3-log Giardia cyst inactivation.
Source II
- Determine CT for section B based on the residual measured at sample
point b and ^e travel time through the section under peak hourly flow
conditions.
- Determine CT for section B for the pH and temperature conditions in
CfcQ Q
the section using the appropriate tables in Appendix E.
- Calculate the inactivation ratio f^/ } for section B.
3-28
-------
Add the inactivation ratios for Sections B and D to determine the overall
inactivation for source II.
If the sum of the inactivation ratios is greater than or equal to 1, the
system has provided the required 3-log Giardia cyst inactivation for the
source.
Source III
Determine CT , for section C based on the residual measured at sample
C3.J.C
point c and the travel time through the section under peak hourly flow
conditions.
Determine CT for section C for the pH and temperature conditions in
the section using the appropriate tables in Appendix E.
- Calculate the inactivation ratio (CT . /CTQQ Q) for section C.
CaXC 77. y
- Add the inactivation ratios for section C and D to determine the overall
inactivation for source III.
- If the sum of the inactivation ratios is greater than or equal to 1, the
system has provided, the required 3-log Giardia cyst inactivation for the
source.
'The determination of the overall inactivation provided for each source
may require more calculations for systems such as that on Figure 3-8 th>.n on
Figure 3-7. On Figure 3-8 sections A, B, C, D, and E contain sampling points
a, b, c, d, and e respectively. In order to minimize the calculations needed,
the determination of the overall inactivation provided should begin with the
source closest to the first customer.
The overall inactivation provided for each source on Figure 3-8 should be
determined as follows:
Source III
- Determine CT for sections C and E based on the residual measurement
at sample points c and e and the travel time through each section under
peak hourly flow conditions for the respective section.
- Determine CT for the pH and temperature conditions in each section
using the tables in Appendix E.
- Calculate the inactivation ratios (CT /CT _) for sections C and E.
caxc 99.9
3-29
-------
- Calculate the sum of the inactivation ratios for sections C and E.
- If the sum of the inactivation ratios is greater than or equal to 1, the
system has provided the required 3-log Giardia cyst inactivation for
source III.
Source II
- Determine CT . for section D based on the residual measured at sample
point D and Qie travel time through the section under peak hourly flow
conditions.
- Determine CT g for section D for the pH and temperature conditions in
the section using the appropriate tables in Appendix E.
- Calculate the inactivation ratio (CT . /CTQQ Q) f°r section D.
caj.c yy • y
- Add the inactivation ratios for sections D and E to determine the overall
inactivation.
- If the sum of the inactivation ratios is greater than or equal to 1, the
system has provided the required 3-log Giardia cyst inactivation for
source II, as well as source I since the water from each of these sources
are combined prior to sections D and E.
- If the total inactivation ratio for sections D and E is less than 1,
additional calculations are needed. Proceed as follows for source III.
- Determine CT . for section B based on the residual measured at sample
point B and ^le3 travel time through the section under peak hourly flow
conditions.
- Determine CT for section B for the pH and temperature conditions in
the section using the appropriate tables in Appendix E.
- Calculate the inactivation ratio
-------
inactivation. However, if this sum is less than 1 additional calculations
will be needed to determine the overall .inactivation provided for source I.
The calculation is as follows:
Source I
- Determine CT for section A based on the residual measured at sample
point b and Qie travel time through the section under peak hourly flow
conditions.
- Determine CT__ for section A for the pH and temperature conditions in
the section using the appropriate tables in Appendix E.
- Calculate the inactivation ratio (CT - /CT ) for section A.
caxc- 77.7
- Add the inactivation ratios for sections A, D, and E to determine the
overall inactivation for source I.
- If the sum of the inactivation ratios is greater than or equal to 1, the
system has provided the required 3-log Giardia cyst inactivation for the
source.
3.2.3 Demonstration of Maintaining a Residual
The SWTR establishes two requirements pertaining to the maintenance of a
residual. The first requirement is to maintain a minimum residual of 0.2 mg/L
entering the distribution system. Also, a detectable residual must be main-
tained throughout the distribution system, these requirements are further
explained in the following sections.
Maintaining a Residual Entering the System
The SWTR requires that a residual of 0.2 mg/L be maintained in the water
entering the distribution system at all times. Continuous monitoring at the
entry point (s) to the distribution system is required to ensure that a detect-
able residual is maintained. Any time the residual drops below 0.2 mg/L, the
system must notify the Primacy Agency prior to the end of the next business
day. The system is in violation of a treatment technique if the residual
level is not restored to 0.2 mg/L within four hours and filtration must be
installed. In cases where the continuous monitoring equipment fails, grab
samples every four hours may be used for a period of 5 working days while the
equipment is restored to operable conditions.
3-31
-------
The system must record, each day of the month, the lowest disinfectant
residual entering the system and this residual must not be less than 0.2 mg/L.
Systems serving less than or equal to 3,300 people may take grab samples in
lieu of continuous monitoring at frequencies as follows:
System Population Samples/day*
<500 1
501-1,000 2
1,101-2500 3
>2,501-3300 4
*Samples must be taken at dispersed time intervals as approved by the
Primacy Agency.
If the residual concentration falls below 0.2 mg/L, another sample must
be taken within 4 hours and sampling continued at least every four hours until
the disinfectant residual is at least 0.2 mg/L.
Maintaining a Residual Within the System
The SWTR also requires that a detectable disinfectant residual be main-
tained throughout the distribution system, with measurements taken at a
minimum frequency equal to that required by the Total Coliform Rule as pre-
sented in Appendix H. The same sampling locations as required for the
coliform regulation must be used for taking the disinfectant residual or HPC
samples. However, for systems with both ground water and surface water
sources or ground water under the direct influence of surface water, entering
the distribution system, residuals may be measured at points other than
coliform sampling points if these points are more representative of the
disinfected surface water and allowed by the Primacy Agency. An HPC level of
less than 500/ml is considered equivalent to a detectable residual for the
purpose of determining compliance with this requirement, since the absence of
a disinfectant residual does not necessarily indicate microbiological con-
tamination .
Disinfectant residual can be measured as total chlorine, free chlorine,
combined chlorine or chlorine dioxide (or HPC level). The SWTR lists the
approved analytical methods for these analyses. For example, several test
methods can be used to test for chlorine residual in the water, including
3-32
-------
amperometric titration, DPD colorimetric, DPD ferrous titrimetric method and
(8)
iodometric method, as described in the 16th Edition of Standard Methods.
Appendix D provides a review and summary of available disinfectant residual
measurement techniques.
The SWTR requires that a detectable disinfectant residual be present in
95 percent or more of the monthly distribution system samples. In systems that
do not filter, a violation of this requirement for two consecutive months
caused by a deficiency in treating the source water will trigger a requirement
for filtration to be installed. Therefore, a system which does not maintain a
residual in 95 percent of the samples for one month because of treatment defi-
ciencies, but is maintaining a residual in 95 percent of the samples for the
following month, will meet this requirement.
The absence of a detectable disinfectant residual in the distribution
system may be due to a number of factors, including:
- Insufficient chlorine applied at the treatment plant
- Interruption of chlorination
- A change in chlorine demand in either the source water or the
distribution system
- Long standing times and/or, long transmission distances
Available options for systems to correct the problem of low disinfectant
residuals within their distribution system include:
- " Routine flushing
- Increasing disinfectant doses at the plant
- Cleaning of the pipes (either mechanically by pigging or by the
addition of chemicals to dissolve the deposits) in the distribution
8. Also, portable test kits are available which can be used in the
field to detect residual upon the approval of the Primacy Agency.
These kits may employ titration or colorimetric test methods. The
colorimetric kits employ either a visual detection of a residual
through the use of a color wheel, or the detection of the residual
through the use of a hand held spectrophotometer.
3-33
-------
system to remove accumulated debris which may be exerting a
disinfectant demand;
- Flushing and disinfection of the portions of the distribution system
in which a residual is not maintained; or
- Installation of satellite disinfection feed facilities with booster
chlorinators within the distribution system.
For systems unable to maintain a residual, the Primacy Agency may determine
that it is not feasible for the system to monitor HPCs and judge that disin-
fection is adequate based on site-specific conditions.
Additional information on maintaining a residual in the system is
available in the AWWA Manual of Water Supply Practices and Water Chlorination
Principles and Practices.
3.2.4 Disinfection System Redundancy
Another disinfection requirement that unfiltered water supply systems
must meet is disinfection system redundancy. A system providing disinfection
as the only treatment is required to assure that the water delivered to the
distribution system is continuously disinfected. This can be accomplished by
providing either redundant disinfection equipment or an automatic shutoff of
delivery of water to the distribution system when the disinfectant residual
level drops below 0.2 mg/L. The provision of redundant disinfection equipment
includes:
- Both a primary and a secondary disinfection system in which all
components have backup 5inits with capacities equal to or greater
than the largest unit on-line.
- A minimum of two storage units of disinfectant which can be used
alternately - e.g., two cylinders of chlorine gas, two tanks of
hypochlorite solution
- Where generation of the disinfectant is needed (such as ozone), a
backup unit with a capacity equal to or greater than that of the
largest unit on-line.
- Automatic switchover equipment to change the feed from one storage
unit to the other before the first empties or becomes inoperable
- Feed systems with backup units with capacities equal to or greater
than the largest unit on-line.
3-34
-------
- An alternate power supply such as a standby generator with the
capability of running all the electrical equipment at the disinfec-
tion station. The generator should be on-site and functional with
the capability of automatic start-up on power failure
Appendix I contains more specific information for the Primacy Agency for
determining compliance with this requirement.
Providing automatic shutoff of water delivery requires approval by the
Primacy Agency. The Primacy Agency must determine that this action will not
result in an unreasonable risk to health. This determination should include
the evaluation of the system configuration to protect against negative pres-
sures in the system and high demand periods including fire flow requirements.
This provision should only be allowed if systems have adequate distribution
system storage to maintain positive pressure for continued water use.
3.3 SITE - SPECIFIC CONDITIONS
In addition to meeting source water quality criteria and disinfection
criteria, nonfiltering systems utilizing surface water supplies must meet the
following criteria:
- Maintain a watershed control program
- Conduct a yearly on-site inspection
- Determine that no waterborne disease outbreaks have occurred
- Comply with the revised annual total coliform MCt
- Comply with TTHM regulations (currently applies to systems serving
>10,000 people)
Guidelines for meeting these other criteria are presented in the follow-
ing sections.
3.3.1 Watershed Control Program
A watershed control program is a surveillance and monitoring program
which is conducted to protect the quality of a surface water source. It is
desirable to have an aggressive and detailed watershed control program to
effectively limit or eliminate potential contamination by human enteric
viruses. A watershed program may impact parameters such as turbidity, certain
organic compounds, viruses, and total and fecal coliforms and areas of wild-
life habitation. However, the'program is expected to have little or no impact
on parameters such as naturally occurring inorganic chemicals, naturally
occurring organic materials, and pathogens transmitted by wildlife with the
3-35
-------
exception of preventing animal activity near the source water intake prior to
disinfection.
It may be difficult to quantify the effect of a watershed program since
there are many variables which influence water quality that are beyond the
control or knowledge of the water supplier. ~~ As a result, the benefit of a
watershed control program or specific control measures must in many cases be
.based on accumulated cause and effect data and on the general knowledge of the
impact of control measures rather than on actual quantification. The effec-
tiveness of a program to limit or eliminate potential contamination by human
enteric viruses will be determined based on: the comprehensiveness of the
watershed review; the ability of the water system to effectively carry out and
monitor the management decisions regarding control of detrimental activities
occurring in the watershed; and the potential for the water system to maximize
land ownership and/or control of land use within the watershed. According to
the SWTR, a watershed control program should include as a minimum:
1. A description of the watershed including its hydrology and land
ownership
2. Identification, monitoring and control of watershed characteristics
and activities in the watershed which may have an adverse effect on
the source water quality
3. A program to gain ownership or control of the land within the
watershed through written agreements with land owners, for the
purpose of controlling activities which will adversely affect the
-microbiological quality of the water
4. An annual report which identifies special concerns in the watershed
and how they are being handled, identifies activities in the
watershed, projects adverse activities expected to occur in the
future and how the utility expects to address them.
Appendix J contains a more detailed guide to a comprehensive watershed
program.
For systems utilizing ground water sources under the influence of surface
water, the control measures delineated in the Wellhead Protection (WHP)
program encompass the requirements of the watershed control program, and can
be used to fulfill the requirements of the watershed control program. Guid-
ance on the content of State wellhead Protection Programs and the delineation
of wellhead protection areas is given in: "Guidance for Applicants for State
3-36
-------
Wellhead Protection Program Assistance Funds Under the Safe Drinking Water
Act," June, 1987, and "Guidelines for Delineation of Wellhead Protection
Areas," June, 1987, available from the EPA office of Ground-Water Protection
(WH-550G).
As a minimum, the WHP program must:
- Specify the duties of State agencies, local governmental entities and
public water supply systems with respect to the development and implemen-
tation of Programs;
- Determine the wellhead protection area (WHPA) for each wellhead as
defined in subsection 1428 (e) based on all reasonably available
hydrogeologic information ground-water flow, recharge and discharge and
other information the State deems necessary to adequately determine the
WHPA;
- Identify within each WHPA all potential anthropogenic sources of contami-
nants which may have any adverse effect on the health of persons;
- Describe a Program that contains, as appropriate, technical assistance,
financial assistance, implementation of control measures, education,
training and demonstration projects to protect the water supply within
WHPAs from such contaminants;
- Include contingency plans for the location and provision of alternate
drinking water supplies for each public water system in the event of well
or wellfield contamination by such contaminants;
- Include a requirement that consideration be given to all potential
sources of such contaminants within the expected wellhead area of a new
water well which serves a public water supply system; and
- Include a requirement for public participation.
3.3.2 On-site Inspection
The watershed control program and the on-site inspection are interrelated
preventive strategies. The on-site inspection is actually a program which
includes and surpasses the requirements of a watershed program. While the
watershed program is mainly concerned with the water source, the on-site
inspection includes some additional requirements for source water quality
control and is also concerned with the disinfection system. As defined by the
USEPA, an on-site inspection includes review of the water source, disinfection
facilities and operation and maintenance of a public water system for the
3-37
-------
purpose of evaluating the adequacy of such systems for producing safe drinking
water.
According to the SWTR, an on-site inspection to evaluate the watershed
control program and disinfection system is required to be conducted annually
by a party approved by the Primacy Agency. The inspection should be conducted
by competent individuals such as sanitary and civil engineers/ sanitarians,
and technicians who have experience and knowledge in the operation, mainte-
nance, and design of a water system, and who have a sound understanding of
public health principles and waterborne diseases. Guidance for the contents
of an inspection are included in the following paragraphs. Appendix K pre-
sents guidelines for a sanitary survey which includes and surpasses the
requirements of the on-site inspection.
At the onset of determining whether or not a source is to be classified
as a surface water, EPA recommends that utilities conduct a detailed, compre-
hensive sanitary survey. Appendix K presents a comprehensive list of water
system features that the person conducting the survey should be aware of and
review as appropriate. This initial investigation establishes the quality of
the water source, its treatment and delivery to the consumer. EPA recommends
that this comprehensive evaluation be repeated every three years for systems
serving 4,100 people or less and every five years for systems serving more
than 4,100 people. Also, under the Total Coliform rule, systems which take
less than 5 coliform samples per month must conduct such sanitary surveys
within every 5 or 10 years depending upon whether the source is protected and
disinfected.
The annual on-site inspection to fulfill the SWTR requirements must
include as a minimum:
A. Source Evaluation
1. Review of the effectiveness of the watershed control program
(Appendix J)
2. Review of the physical condition and protection of the source
intake
3. Review of maintenance program to insure that all to disinfec-
tion equipment is appropriate and has received repair as needed
to assure a high probability for prevention of disinfection
system failure
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B. Treatment Evaluation
1. Review of improvements and/or additions made to disinfection
processes during the previous year to fulfill inadequacies
detected in earlier surveys
2. Review of disinfection equipment for physical deterioration
3. Review of operating procedures
4. Review of data records to assure that all required tests are
being conducted and recorded and disinfection is effectively
practiced
5. Identification of any improvements which are needed in the
equipment, system maintenance and operation, or data collection
In addition to these requirements, it is recommended for all systems,
including those with filtered and unfiltered supplies, that a periodic sani-
tary survey also be conducted. The sanitary survey should include the items
listed in A and B above as well as:
C. Distribution System Evaluation
1. Review of storage facilities for construction condition
2. Determination that sufficient pressure has been maintained in
the system throughout the year
3. Verification that system equipment has received regular mainte-
nance
4. Review of additions/improvements incorporated during the year
to correct inadequacies detected in the initial inspection
5. Review of cross connection prevention program, including annual
testing of backflow prevention devices
6. Review of routine flushing program for effectiveness
7. Evaluation of the corrosion control program and impact on
distribution water quality
8. Review of the periodic storage reservoir flushing program for
adequacy
9. Review of practices in repairing water main breaks to assure
they include disinfection
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D. Management/Operation Evaluation
1. Review the operations to insure that any difficulties experi-
enced during the year have been adequately addressed
2. Review to decide whether a reorganization of management is
needed
3. Determine whether the budget is adequate
4. Review of staffing to insure adequate personnel are available
and they are adequately trained and/or certified
5. Verify that a regular maintenance schedule is followed
6. Review the systems records to verify that they are adequately
maintained
7. Review bacteriological data from the distribution system for
coliform occurrence, repeat samples and action response
3.3.3 No Disease Outbreaks
Under the provisions of the SWTR, a surface water system which does not
filter must not have had an identified waterborne disease outbreak in its
current configuration which has been determined by the Primacy Agency to be
attributable to a treatment deficiency. If an identified waterborne disease
outbreak has occurred in the past and the outbreak was attributed to a treat-
ment deficiency, then the system must install filtration unless the system has
upgraded its treatment system to remedy the deficiency which led to the out-
break and the Primacy Agency has determined that the system is satisfying this
requirement. The system may not be required to install filtration if the
Primacy Agency has determined the disease outbreak to be the result of a
distribution system problem rather than a source water treatment deficiency.
In order to determine whether the requirement is being met, the re-
sponsible federal, state and local health agencies should be surveyed to
obtain the current and historical information on waterborne disease outbreaks
which may have occurred within a given system. Whether conducted by the
Primacy Agency or submitted by the water purveyor, this information should
include:
A. Source of the Information:
1. Name of agency
2. Name and phone number of person contacted
3. Date of inquiry
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B. Outbreak Data
1. Known or suspected incidents of waterborne disease outbreaks
2. Date(s) of occurrence(s)
3. Type or identity of illness
4. Number of cases
C. Status of Disease Reporting:
- Changes in regulations; e.g., giardiasis was not a reportable
disease until 1985
D. If a Disease Outbreak has Occurred:
1. Was the reason for the outbreak identified; e.g., inadequate
disinfection
2. Did the outbreak occur while the system was in its current
configuration
3. Was remedial action taken
4. Have there been any further outbreaks since the remedial action
was taken
If a review of the available information indicates that the system or
network for disease reporting is inadequate within the Primacy Agency's area
of responsibility, efforts should be made to encourage the appropriate agen-
cies to upgrade the disease reporting capabilities within the area.
3.3.4 Monthly Coliform MCL
Monthly MCL
Systems must comply with the monthly coliform MCL on an ongoing basis in
order to avoid filtration. The monthly coliform MCL criteria include:
a. The three test methods which can be used within the distribution
system are the membrane filter technique (MF), the multiple tube
9. The P-A is a modification of the MPN method in which a single
3-41
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fermentation test reported in terms of the most probable number
(MPN).or the presence of coliforms using the presence-absence test
(P-A)Iy'.
b. Systems which analyze less than 40 samples/month for coliforms must
have coliform-positive results in no more than one sample/month.
c. Systems which analyze 40 or more samples/month must maintain coli-
form-positive results in 5.0 percent or less of the samples of each
month
d. For systems analyzing fewer than 1 sample/month, no more than 1
sample per 3-month period may be total coliform-positive, except
that, at the discretion of the Primacy Agency, compliance may be
based upon sampling during a one-month period.
e. Unfiltered surface water systems must analyze one coliform sample
each day the raw water turbidity exceeds one NTU.
The culture medium of each positive sample must be analyzed for fecal coli-
forms or Escherichia cgli and five repeat samples must be collected within
24 hours at the same sampling location or the next closest sampling point. If
any repeat sample is total-coliform positive but fecal-coliform-negative, five
additional repeat samples must be taken within 24 hours of being notified of
the results. The system must repeat this process until either coliforms are
not detected in one set of five repeat samples or the system determines that
the monthly coliform MCL has been exceeded and notifies the Primacy Agency.
If fecal coliforms or &._ coli are present in any repeat samples, the system
must notify the Primacy Agency. The results of the repeat sample are to be
included in the calculation of the MCL and can be used to satisfy the minimum
culture bottle is innoculated with a 100 ml sample. The test method
is currently listed as a tentative procedure; however, past research
has indicated that the P-A method has a detection efficiency which
surpasses that of the MPN test and is equivalent to that of the MF
method (Fujioka et al., 1986). The test procedure is also more
easily performed than the aforementioned methods.
10. Systems using an unfiltered surface supply are required to collect a
minimum of 5 samples per month, regardless of population.
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number of monthly coliform samples required. The frequency of monitoring to
meet the above regulations is based on population served, as indicated in
Appendix H.
Although a Maximum Contaminant Level Goal/Maximum Contaminant Level
(MCLG/MCL) for Heterotrophic Plate Count (HPC) has not been proposed, the
Total Coliform Rule uses the HPC to invalidate total coliform samples based on
interference from HPC. If a coliform sample produces a turbid culture in the
absence of gas production, using the multiple-tube fermentation technique, or
produces a turbid culture in the absence of an acid reaction using the
presence-absence (P/A) test, or produces confluent growth or a colony number
that is too numerous to count using the membrane filter technique, the system
may declare the sample invalid (unless total coliforms are detected), and
collect and analyze another water sample. The second sample is to be analyzed
for total coliform using a media less prone to interference by heterotrophic
bacteria. The sample is considered coliform-positive if the coliform test is
positive and is considered coliform-negative if the coliform test is negative.
Systems which fail to meet the total coliform MCL because of a failure in
the disinfection treatment of the source water is required to install filtra-
tion.
3.3.5 Total Trihalomethane (TTHM) Regulations
For the system to continue to use disinfection as the only treatment, it
must be in compliance with the total trihalomethane (TTHM) MCL regulation.
The current regulation has established an MCL for total TTHM of 0.10 mg/L for
systems serving a population greater than 10,000. This level may be reduced
in the future and this should be considered when planning disinfectant appli-
cation.
One alternative for utilities to meet the CT requirements of the SWTR is
to increase the disinfectant dose. However, for many systems, this will
result in an increased formation of TTHMs. Any increase which results in TTHM
levels greater than 0.10 mg/L is unacceptable. However, considering that more
stringent TTHM requirements are expected in the future, disinfection applica-
tion which increases THMs to levels close to 0.10 mg/L should not be imple-
mented. In such cases, an alternate disinfectant which produces fewer TTHMs
may be used. Alternate disinfectants include the use of ozone or chlorine
dioxide as primary disinfectants with chlorine or chloramines as secondary
(residual) disinfectants. However, the EPA will be promulgating a
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disinfection by-product regulation in 1991 which may put limitations on
by-products of these disinfectants also. EPA recommends that Primacy Agencies
require systems which are going to change their disinfection practices to
conduct testing prior to the change to determine the resulting by-products.
Any changes which will result in an exceedance of by-product regulations
should not be implemented.
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4. DESIGN AND OPERATING CRITERIA FOR
FILTRATION AND DISINFECTION TECHNOLOGY
4.1 Introduction
In accordance with the SWTR, public water systems must include filtra-
tion, or some other approved particulate removal technology, in their treat-
ment process unless they are able to satisfy certain conditions. Those
conditions include compliance with source water quality criteria and site-
specific criteria, for which guidance is provided in Section 3 of this manual.
Systems not able to satisfy these conditions will be required to provide
particulate removal and meet criteria pertaining to operation and design
(specified in part in the definitions of technologies in the SWTR and more
specifically as determined by the Primacy Agency), and performance.
This section provides guidance for those water systems which currently do
not have filtration equipment and must add it, and for systems which have
existing filtration processes. Guidance on additional alternatives for small
systems is discussed in Appendix L.
This section includes guidance on the following topics:
- Filtration Technology: Descriptions, capabilities, design criteria
and operating requirements for each technology, and a listing of
major factors to be considered in their selection, including raw
water quality considerations.
- Disinfection: Descriptions of the most applicable disinfection
* technologies used with filtration systems, and a presentation of the
relative effectiveness of the disinfection technologies with respect
to inactivation of bacteria, cysts and viruses.
- Alternate Technologies: Descriptions of some currently available
alternate filtration technologies.
- Other Alternatives: Includes a description of some nontreatment
alternatives including regionalization and use of an alternate
source.
4.2 Selection of Appropriate Filtration Technology
Filtration is generally provided by passing water through a bed of sand,
a layer of diatomaceous earth, or through a combination of coarse anthracite
coal overlaying finer sand. Filters are classified and named in a number of
4-1
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ways. For example, based on application rate, sand filters can be classified
as either slow or rapid; yet these two types of filters differ in many more
characteristics than just application rate. They differ in their removal
process, bed material, method of cleaning, and operation. Based on the type
of bed material, filters can be classified as sand, diatomaceous earth,
dual-media (coal-sand), or even tri-media in which a third sand layer is
added.
4.2.1 General Descriptions
Definitions of currently used technologies, as contained in the SWTR are
as follows:
a. Conventional Treatment: A series of processes including coagu-
lation, flocculation, sedimentation and filtration.
b. Direct Filtration: A series of processes including coagulation (and
perhaps flocculation) and filtration, but excluding sedimentation.
c. Slow Sand Filtration: A process which involves passage of raw water
through a bed of sand at low velocity [generally less than 0.4
meters/hour (1.2 ft/hr)] resulting in particulate removal by physi-
cal and biological mechanisms and changes in chemical parameters by
biological actions.
d. Diatomaceous Earth Filtration: A process that meets the following
conditions.
- A precoat cake of diatomaceous earth filter media is deposited
on a support membrane (septum)
" - The water is filtered by passing it through the cake on the
septum; additional filter media, known as body feed, is contin-
uously added to the feed water in order to maintain the per-
meability of the filter cake.
e. Alternate Technologies: The available alternate filtration tech-
nologies include, but are not limited to:
- Package Plants
Depending upon the type of treatment units in place, historical
performance and/or pilot plant work, these plants could be
categorized as one of the technologies in a-d above at the
discretion of the State. Several studies have already indicated
that some package plants effectively remove Giardia cysts. If such
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- Cartridge Filters
4.2.2 Capabilities
Filtration processes provide various levels of turbidity and microbial
contaminant removal. When properly designed and operated and when treating
source waters of suitable quality, the above filtration processes (with the
exception of cartridge filters regarding virus removal) are capable of achiev-
ing at least a 2-log (99 percent) removal of Giardia cysts and a 1-log
(90 percent) removal of viruses without disinfection (Logsdon, 1987b; USEPA,
1988a; Roebeck, 1962). A summary of the removal capabilities of the various
filtration processes is presented in Table 4-1.
As indicated in Table 4-1, conventional treatment without disinfection is
capable of achieving up to a 3-log removal of Giardia cysts and up to a. 3-log
removal of viruses. Direct filtration can achieve up to a 3-log removal of
Giardia cysts and up to a 2-log removal of viruses. Achieving the maximum
removal efficiencies of those constituents with these treatment processes
requires the raw water to be properly coagulated and filtered. Factors which
can adversely impact removal efficiencies include:
- Raw water turbidities less than 1 NTU
- Cold water conditions
- Non-optimum or no coagulation
- Improper filter operation including:
- No filter to waste
- Intermittent operation
- Sudden rate changes
- Poor housekeeping
- Operating the filters beyond turbidity breakthrough
Studies of slow sand filtration have shown that this technology (without
disinfection) is capable of providing greater than a 3-log removal of Giardia
cysts and greater than a 3-log removal of viruses. Factors which can adverse-
ly impact removal efficiencies include:
plants provided adequate disinfection as demonstrated by satisfying
CT values, so that the complete treatment train achieves at least
3-log removal/inactivation of Giardia cysts and 4 log
removal/inactivation of viruses, use of this technology would
satisfy the minimum treatment requirements.
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TABLE 4-1
REMOVAL CAPABILITIES OF FILTRATION PROCESSES
(1)
Log Removals
Process
Conventional Treatment
Direct Filtration
Slow Sand Filtration
Diatomaceous Earth
Filtration
Giardia
Cysts
2-3
2-3
(2)
2-3
2-3
(5)
(5)
Viruses
1-3
1-2
1-3
1-2
(3)
(3)
(4)
(2)
(2)
Total
Coliform
>4
1-3
1-2
1-3
Note:
1. Without disinfection
2. Logsdon, 1987b.
3. Roebeck et al 1962
4. Poynter and Slade, 1977
5. _These technologies generally achieve greater than a 3-log removal.
-------
- Poor source water quality
- Cold water conditions
- Increases in filtration rates
- Decreases in bed depth
- Improper sand size
- Inadequate ripening
Also, as indicated in Table 4-1, diatomaceous earth (DE) filtration can
achieve greater than a 3-log removal of Giardia cysts when sufficient precoat
and body feed are used. However, turbidity and total coliform removals are
strongly influenced by the grade of DE employed. Conversely, DE filtration is
not very effective for removing viruses unless the surface properties of the
diatomaceous earth have been altered by pretreatment of the body feed with
alum or a suitable polymer. In general, DE filtration is assumed to achieve
only a 1-log removal of viruses unless demonstrated otherwise. Factors which
can affect the removal of Giardia cysts and viruses include:
- Precoat thickness
- Amount of body feed
- Grade of DE
- Improper conditioning of septum
Package plants can be used to treat water supplies for communities as
well as for recreational areas, parks, construction camps, ski resorts,
military installations and others where potable water is not available from a
municipal supply. Operator requirements vary significantly with specific
situations. Under unfavorable raw water conditions they could demand full-
time attention. Package plants are most widely used to treat surface supplies
for removal of turbidity, color and coliform organisms prior to disinfection.
They are available in capacities up to 6 mgd.
Colorado State University conducted a series of tests on one package
plant over a 5-month period during the winter of 1985-86 (Horn and Hendricks,
1986). Existing installations in Colorado had proven effective for turbidity
removal, and the tests at the university were designed to evaluate the sys-
tem's effectiveness in removing coliform bacteria and Giardia cysts from low
turbidity, low temperature source waters. The test results showed that the
filtration system could remove greater than 99 percent of Giardia cysts for
waters which had less than 1 MTU turbidity and less than 5 C temperatures, as
long as proper chemical treatment was applied, and the filter rate was
4-4
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10 gpm/ft or less. In addition, an alternate water source having a turbidity
ranging from 3.9 to 4.5 NTU was used in 12 test runs with coagulant doses
ranging from 15 to 45 mg/L. The effluent turbidities from these runs were
consistently less than 0.5 NTU.
Surveys of existing facilities indicate that while package plants may be
capable of achieving effective treatment, many have not consistently met the
MCL for turbidity, and in some cases, colifonns were detected in the filtered
water (Morand et al., 1980; Morand and Young, 1983). The performance diffi-
culties were related to the short detention time inherent in the design of the
treatment units, the lack of skilled operators with sufficient time to devote
to operating the treatment facilities and the wide-ranging variability in
quality of the raw water source. Raw water turbidity was reported to often
exceed 100 NTU at one site. Improvements in operational techniques and
methods at this site resulted in substantial improvement in effluent quality.
After adjustments were made, the plant was capable of producing a filtered
water with turbidities less .than 1 NTU, even when influent turbidities in-
creased from 17 to 100 NTU within a 2-hour period as long as proper coagu-
lation was provided.
One of the major conclusions of these surveys was that package water
treatment plants manned by competent operators can consistently remove turbid-
ity and bacteria from surface waters of a fairly uniform quality. Package
plants applied where raw water turbidities are variable require a high degree
of operational skill and nearly constant attention by the operators. Regard-
less of the quality of the raw water source, all package plants require at
least a minimum level of maintenance and operational skill and proper chemical
treatment if they are to produce satisfactory water quality.
Cartridge filters using microporous filter elements (ceramic, paper or
fiber) with pore sizes as small as 0.2 urn may be suitable for producing
potable water from raw water supplies containing moderate levels of turbidity,
algae and microbiological contaminants. The advantage to small systems of
these cartridge filters is that, with the exception of disinfection, no other
chemicals are required. The process is one of strictly physical removal of
small particles by straining as the water passes through the porous cartridge.
Other than occasional cleaning or cartridge replacement, operational
4-5
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requirements are not complex and do not require skilled personnel. Such a
system may be suitable for some small systems where, generally, only mainte-
nance personnel are available for operating water supply facilities. However,
the use of cartridge filters should be limited to low turbidity source waters
because of their susceptibility to rapid headless buildup. For example,
manufacturer's guidelines for achieving reasonable filter run lengths with
certain polypropylene filter elements are that the raw water turbidity be 2
NTU or less (USEPA, 1988a).
Lcr-7 (1983) analyzed the efficacy of a variety of cartridge filters using
turbidir. • measurements, particle size analysis, and scanning electron micro-
scope ar. -lysis. The filters were challenged, with a solution of microspheres
averaging 5.7 urn in diameter (smaller than a Giardia cyst) , at a concentration
of 40,000 to 65,000 spheres per mL. Ten of 17 cartridge filters removed over
99.9 percent of the microspheres.
In tests using live infectious cysts from a human source, cartridge
filters were found to be highly efficient in removing Giardia cysts (Hibler,
1986). Each test involved challenging a filter with 300,000 cysts. The
average removal for five tests was 99.86 percent, with removal efficiencies
ranging from 99.5 percent to 99.99 percent.
The application of cartridge filters to small water systems using either
cleanable ceramic or disposable polypropylene cartridges, appears to be a
feasible method for removing turbidity and most microbiological contaminants,
although data are needed regarding the ability of cartridge filters to remove
viruses. Since disinfection by itself could achieve a 4-log inactivation of
viruses, if the cartridge filter removes greater than or equal to 3 logs of
Giardia, then the filter plus disinfection would achieve the overall minimum
requirements. However, consideration should be given to the feasibility of
multiple barriers of treatment for each target organism, i.e., some Giardia
and virus removal by each barrier as a protection if one of the barriers
fails. The efficiency and economics of the process must be closely evaluated
for each application. Pretreatment in the form of roughing filters (rapid
sand or multi-media) or fine mesh screens may be needed to remove larger
suspended solids, which could cause the rapid buildup of headloss across the
cartridges. (USEPA, 1988a)
4-6
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In general, conventional treatment, direct filtration, slow sand filtra-
tion and diatomaceous earth filtration can be designed and operated to achieve
the maximum removal of water quality parameters of concern. However, for the
purpose of selecting the appropriate filtration and disinfection technologies
and for determining design criteria, these filtration processes should be
assumed to achieve a 2-log reduction in Giardia cysts and a 1-log reduction of
viruses. This conservative approach will assure that the treatment facility
has adequate capabilities to respond to non-optimum performance due to
changes in raw water quality, plant upsets, etc. The balance of the required
removals and/or inactivation of Giardia cysts and viruses must therefore be
achieved through the application of appropriate disinfection. The performance
of alternate technologies such as cartridge filters, and possibly package
plants, depending upon the unit under consideration, however, cannot be stated
with certainty at this time. These performance uncertainties necessitate the
use of pilot studies in order to demonstrate their efficacy for a given water
supply.
4.2.3 Selection
For any specific site and situation, a number of factors will determine
which filtration technology is most appropriate. Among these are: raw water
quality conditions, site specific factors, and economic constraints. A
discussion of the impact of raw water quality on the technology selection is
presented here. The impact of site specific factors and economic constraints
are presented in the USEPA document "Technologies and Costs for the Removal of
Microbial Contaminants from Potable Water Supplies" (USEPA, 1988a).
Raw Water Quality Conditions
The number of treatment barriers provided should be commensurate with the
degree of contamination in the source water. The four available technologies
vary in their ability to meet the performance criteria when a wide range of
raw water quality is considered. While numerical values of raw water quality
that can be accommodated by each of the four technologies will vary from site
to site, general guidance can be provided. General guidelines for selecting
filtration processes, based on total coliform count, turbidity, and color are
presented in Table 4-2. It is not recommended that filtration systems other
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than those listed in Table 4-2 be utilized when the general raw water quality
conditions exceed the values listed, unless it has been demonstrated through
pilot testing that the technology can meet the performance criteria under the
raw water quality conditions expected to occur at the site. The filtration
processes listed in Table 4-1 are capable of achieving the required perfor-
mance criteria when properly designed and operated if they are treating a
source water of suitable quality. One of the causes of filtration failures is
the use of inappropriate technology for a given raw water quality (Logsdon,
1987b).
However, these criteria are general guidelines. Periodic occurrences of
raw water coliform, turbidity or color levels in excess of the values present-
ed in Table 4-2 should not preclude the selection or use of a particular
filtration technology. For example, the following alternatives are available
for responding to occasional raw water turbidity spikes:
- Direct Filtration
- Continuous monitoring and coagulant dose adjustment
- More frequent backwash of filters
- Use of presedimentation
- Slow Sand Filtration
- Use of a roughing filter
- Use of an infiltration gallery
- Diatomaceous Earth Filtration
- Use of a roughing filter
- Use of excess body feed
For the above alternatives, it is recommended that pilot testing be
conducted to demonstrate the efficacy of the treatment alternative.
The characteristics of each filtration technology are a major factor in
the selection process. Characteristics of significance include performance
capabilities (contaminant removal efficiencies), design and construction
requirements, and operation and maintenance requirements. Details regarding
each of the four filtration technologies are presented in the following sub-
section.
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TABLE 4-2
GENERALIZED CAPABILITY OF FILTRATION SYSTEMS
TO ACCOMMODATE RAW WATER QUALITY CONDITIONS
Treatment
Conventional with predisinfection
Conventional without predisinfection
Direct filtration with flocculation
Direct filtration without flocculation
Slow sand filtration
Diatomaceous earth filtration
General Restrictions
Total
Col {forms
(#/100 ml)
ion (20,000(3)
(3)
ection (5,000
ation (500(3)
ouia«-,«(3)
Notes:
(800
(5)
(50
(3)
(5
(3)
(5
(3)
(5
(3)
1. Depends on algae population, alum or cationic polymer coagulation — (Cleasby et al., 1984.)
2. USEPA, 1971.
3. Letter-man, 1966.
4. Bishop et al., 1980.
5. Slezak and Sims, 1984.
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4.3 Available Filtration Technologies
4.3.1 Introduction
As indicated in the SWTR, the historical responsibility of the states to
establish design and operating criteria for public drinking water plants will
continue. The purpose of the following sections is to provide guidance on how
the design and operating criteria may need to be changed in order to assure
that the performance criteria in the SWTR are met.
The design criteria for the various filtration technologies found in the
1987 edition of the Recommended Standards for Water Works (Ten States Stan-
dards) are the minimum design criteria that a majority of states are currently
following. The design criteria contained in the Ten States Standards have
not been duplicated here. Rather, the reader is referred to the Ten States
Standards. EPA recommends the following additions and/or changes to the Ten
State Standards in order to assure compliance with the performance criteria of
the SWTR.
4.3.2 General
The following recommendations apply to all filtration plants:
A. All filtration plants should provide continuous turbidity monitoring
of the effluent turbidity from each individual filter.
B. All new water treatment plants should include the capability of
filter-to-waste on each filter, and where possible, existing filtra-
tion plants should install a filter-to-waste capability.
2. Based upon the results of a survey conducted for the American Water
Works Association Research Foundation (AWWARF), some 38 states use
the Ten States Standards entirely or in modified form (AWWARF,
1986).
3. Although this is not part of the requirements of the SWTR, it is
recommended because of .the possibility that not all filters in a
treatment plant will produce the same effluent turbidity. This may
be due to a variety of conditions that include bed upsets, failure
of media support or underdrain systems, etc. Although the combined
effluent from all the filters may meet the turbidity requirements of
the SWTR, the turbidity level from an individual filter may
substantially exceed the limits. This may result in the passage of
Giardia cysts, or other pathogens.
4. For most high rate granular bed filters, there is a period of
conditioning, or break-in, immediately following backwashing, during
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C. In order to establish filter-to-waste operating guidelines, the
following procedure is suggested:
a. Review the performance (effluent turbidity) data for each
filter and determine which filter has the poorest performance
historically (highest effluent turbidity).
b. Following backwashing of the filter with the poorest perfor-
mance, place that filter into service and collect grab .samples
every minute for a period of at least 30 minutes.
c. Analyze the grab samples for turbidity and determine how long
the filter must be in operation before the effluent turbidity
drops to less than or equal to 0.5 NTU (or 1.0 NTU in cases
where a filtered water turbidity of less than or equal to 1.0
NTU is allowed).
d. The filter to waste period is then defined as the time it takes
for the filter effluent of the worst filter to reach a turbid-
ity of less than or equal to 0.5 NTU (or 1.0 NTU) following
filter start-up at the normal production flow rate. If the raw
water is less than 1.0 NTU then at least 50 percent turbidity
removal across the filter should be achieved before the filter
is brought back on-line.
e. Since not all filters may be capable of filtering to waste at
normal production flow rates, an alternative may be to define
the quantity of water which must be filtered to waste.
f. In addition, the filter-to-waste period should be determined
during each of the seasonal variations in water quality to
account for their impact on filter performance.
D. All water treatment plants should increase filtration rates gradual-
j/p when placing filters back into service following backwashing
and/or after the filter-to-waste valve is closed.
which turbidity and particle removal is at a minimum. In some cases
the addition of a suitable polymer to the backwash water or starting
the filter at a low rate and gradually increasing the rate may
reduce the amount of time required for the break-in of a filter.
5. Continuous turbidity monitoring can be used in place of grab
sampling.
4-10
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4.3.3 Conventional Treatment
Conventional treatment is the most widely used technology for removing
turbidity and microbial contaminants from surface water supplies. Convention-
al treatment includes the pretreatment steps of chemical coagulation, rapid
mixing, flocculation and sedimentation followed by filtration. The filters
can be either sand, dual-media, or multi-media. Figure 4-1 is a flow sheet
for a conventional treatment plant.
Single media rapid sand filters are generally designed with a filtration
rate of 2 gpm/ft . Newer plants which use dual- or tri-media filters often
have a design filtration rate of 4 to 6 gpm/ft . When properly operated,
filter plants are generally capable of producing filtered water turbidities of
0.1 or 0.2 NTU. Site-specific raw water quality conditions influence the
design criteria for each component of a conventional treatment system.
Design Criteria
The minimum design criteria presented in the Ten State Standards for
conventional treatment are considered sufficient for the purposes of the SWTR
except for the following addition:
- The criteria for sedimentation should be expanded to include other
methods of solids removal including plate separation, dissolved air
flotation, and upflow-solids-contact clarifiers.
Operating Requirements
In addition to the operating requirements in the Ten State Standards, a
primary coagulant must be used at all times during which the treatment plant
is in operation. The operation of conventional and direct filtration
plants is more demanding than for DE or slow sand filter plants. Conventional
and direct filtration plants must be monitored carefully because failure to
maintain optimum coagulation can result in poor filter performance and break-
through of cysts and viruses. Although the detention time provided by the
6. Dependable removal of Giardia cysts can not be guaranteed if a clear
water (raw water turbidity less than 1 NTU) is filtered without
being properly coagulated (Logsdon, 1987b; Al-Ani et al., 1985).
7. As indicated in the preamble to the proposed SWTR, 33 percent of the
4-11
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COAGUL/i
kNTS
RAPID MIX
30 SEC-2 MIN
DETENTION
FLOCCULATION
20-45 MIN
SEDIMENTATION
1-4 HOURS
FILTRATION
RAPID SANO: 2 gpm/ft*
DUAL AND TRI-MIXEO
MEDIA: 4-6 gpm/ft?
FIGURE 4-1 FLOW SHEET OF A TYPICAL CONVENTIONAL
WATER TREATMENT PLANT
-------
settling basins results in some margin of safety, the loss of coagulation
control at the chemical feed and rapid mix points may not be noticed until the
poorly coagulated water reaches the filters and the process has failed.
Failure to effectively monitor and control filter operation can result in
undetected poor filter performance (Logsdon, 1987a; Logsdon, 1987b).
Effective operation of a conventional treatment plant requires careful
monitoring and control of:
- Chemical Feed
- Rapid Mix
- Flocculation
- Sedimentation
- Filtration
For the purposes of the SWTR, effective operation of a conventional water
treatment plant can be summarized as follows:
a. The application of a primary coagulant and the maintenance of
effective coagulation and flocculation at all times when a treatment
plant is in operation.
b. Maintenance of effective filtration. Unless terminal headless
occurs before the effluent turbidity exceeds 0.5 NTU, the filter
effluent turbidity of less than 0.5 NTU should be used to initiate:
1) the start of a backwash cycle
2) the start of a filter run at the end of a filter-to-waste cycle
c. Filters removed from service should always be backwashed upon start
up.
4.3.4 Direct Filtration
A direct filtration plant can include several different pretreatment unit
processes depending upon the application. In its simplest form, the process
reported cases of giardiasis in waterborne disease outbreaks were
attributed to improperly operated filtration plants.
8. Some conventional water treatment plants which treat low turbidity
source waters (<1 NTU) reportedly discontinue the application of
coagulant (s) during periods of low turbidity since the raw water
already meets the turbidity MCL. However, studies have shown that
cyst removal for low turbidity waters is the most difficult to
achieve and requires optimum pretreatment (including coagulation) to
achieve effective removals (Al-Ani et al., 1985).
4-12
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includes only in-line filters (often pressure units) preceded by chemical
coagulant application and mixing. The mixing requirement, particularly in
pressure filters, can be satisfied by influent pipeline turbulence. In larger
plants with gravity filters, an open rapid-mix basin with mechanical mixers is
typically used. Figure 4-2 illustrates the unit processes of a typical direct
filtration plant.
Another variation of the direct filtration process consists of the
addition of a coagulant to the raw water followed by rapid mixing and floccu-
lation, as illustrated on Figure 4-3. The chemically conditioned and floccu-
lated water is then applied directly to a dual or mixed-media filter. Floccu-
lation results in better performance of certain dual-media filter designs for
specific water supplies (USEPA, 1988a).
Design Criteria
The 1982 edition of Ten State Standards requires pilot studies to deter-
mine most of the design criteria. The requirement is considered sufficient
for the purposes of the SWTR with the following exception:
A. Primary coagulant must be used at all times when the treatment plant
is in operation.
Operating Requirements
Operating considerations and requirements for direct filtration plants
are essentially identical to those for conventional treatment plants. The
major difference is that a direct filtration plant^wi11 not have a clarifier,
and may or may not have a flocculation or contact basin. In addition, it is
recommended that all direct filtration plants, both new and existing, be
(10)
required to initiate a filter-to-waste period following backwashing.
9. Optimum coagulation is critical for effective turbidity and
microbiological removals with direct filtration (Al-Ani et al.,
1985).
10. As with conventional treatment, direct filtration produces a
relatively poor quality filtrate at the beginning of filter runs and
therefore requires a filter-to-waste period (Cleasby et al., 1984).
4-13
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COAGULANTS
INFLUENT'
RAPID MIX
30 SEC - 2 Mil
DETENTION
DUAL OR MIXED
MEDIA FILTER
4-5 Bpm/ft 2
FIGURE 4-2 FLOW SHEET FOR A TYPICAL
DIRECT FILTRATION PLANT
COAGULANTS
INFLUENT
RAPID MIX
30 SEC • 2 MtN
DETENTION
— ^
FLOCCULATION
15-40 MIN
•*
DUAL OR MIXED
MEDIA FILTER
4-5 opm/ft 2
FIGURE 4-3 FLOW SHEET FOR A TYPICAL DIRECT
FILTRATION PLANT WITH FLOCCULATION
-------
As with conventional treatment, the priorities for initiating the back-
washing of a filter should be filter effluent turbidity values, followed by
headloss and run time. Effluent turbidity monitoring equipment should be set
to initiate filter backwash at an effluent value lower than 0.5 NTU, in order
to meet finished water quality requirements. Also, any filters removed from
service, should always be backwashed upon start up.
4.3.5 Slow Sand Filtration
Slow sand filters differ from single-media rapid-rate filters in a number
of important characteristics. In addition to the difference of flow rate,
slow sand filters:
A. Function using biological mechanisms as well as physical-chemical
mechanisms
B. Use smaller sand particles
C. Are not backwashed, but rather are cleaned by removing the surface
media
D. Have much longer run times between cleaning
E. Require a ripening period at the beginning of each run
Although rapid rate filtration is the water treatment technology used
most extensively in the United States, its use has often proved inappropriate
for small communities since rapid-rate filtration is a technology that requir-
es skille'd operation by trained operators. Slow sand filtration requires very
little control by an operator. Consequently, use of this technology may be
more appropriate for small systems where source water quality is within the
guidelines recommended in Section 4.2.3.
As indicated in this section, slow sand filtration may be applicable to
other source water quality conditions with the addition of pretreatment such
as a roughing filter or presedimentation.
Design Criteria
The minimum design criteria presented in the Ten State Standards for slow
rate gravity filters are considered sufficient for the purposes of the SWTR
with the following exceptions:
4-14
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a. Raw water quality limitations should be changed to reflect the
values given in table 4-2.
b. The effective sand size should be between 0.15mm and 0.35mm rather
than the current 0.30 mm to 0.45 mm.
Operating Requirements
Maintenance of a slow sand filter requires two periodic tasks: removal
of the top 2 to 3 cm (0.79-1.2 inches) of sand and replacement of the sand
(Bellamy et al., 1985). The top 2 to 3 cm (0.79-1.2 inches) of the surface of
the sand bed should be removed when the headless exceeds 1 to 1.5 m.
Slow-sand filters produce poorer quality filtrate at the beginning of a
run (right after scraping), and require a filter-to-waste (or ripening) period
of one to two days before being used to supply the system. The ripening
period is an interval of time immediately after a scraped filter is put back
on-line, when the turbidity or particle count results are significantly higher
than the corresponding values for the operating filter. Filter effluent
monitoring should be used to determine the end of the ripening period. For
example, a turbidimeter could be set at 1.0 NTH or less to initiate start of
the filter run.
When repeated scrapings of the sand have reduced the' depth of the sand
bed to approximately one-half of its design depth, the sand should be re-
placed. Filter bed depths of less than 0.3 to 0.5 m (12 to 20 inches) have
11. Without pretreatment, limitations exist in the quality of water that
is suitable for slow sand filtration (Logsdon, 1987b; Cleasby et
al., 1984; Bellamy et al., 1985; Fox et al., 1983).
12. Significant decreases in total coliform removals were shown at
effective sand sizes greater than 0.35 mm (Bellamy et al., 1985).
As defined in the AWWA Standard for Filtering Material, effective
size is the size opening that will pass 10 percent by weight of a
sample of filter material.
13. Removal of this top layer of the "Schmutzdecke" should restore the
filter to its operational capacity and initial headloss.
4-15
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been shown to result in poor filter performance (Bellamy et al., 1985). The
replacement procedure should include removal of the remaining sand down to the
gravel support, the addition of the new sand to one half of the design depth
and placement of the sand previously removed on top of the new sand.
The amount of time for the biological population to mature in a new sand
filter (also called curing) and to provide stable and full treatment was found
to vary. The World Health Organization (1980) reported that curing requires a
few weeks to a few months. Fox et al., (1983) found that "about 30 days" were
required to bring particle and bacterial effluents down to a stable level.
All researchers agree that a curing time for a new filter is required before
the filter operates at its fullest potential (Bellamy et al., 1985).
4.3.6 Diatomaceous Earth Filtration
Diatomaceous earth (DE) filtration, also known as precoat or diatomite
filtration, is applicable to direct treatment of surface waters for removal of
relatively low levels of turbidity and microorganisms.
Diatomite filters consist of a layer of DE about 3 mm (1/8 inch) thick
supported on a septum or filter element. The thin precoat layer of DE must be
supplemented by a continuous body feed of diatomite, which is used to maintain
the porosity of the filter cake. If no body feed is added, the particles
filtered out will build up on the surface of the filter cake and cause rapid
increases in headless. The problems inherent in maintaining a perfect film of
DE on the septum have restricted the use of diatomite filters for municipal
purposes," except under certain favorable raw water quality conditions, i.e.,
low turbidity and good bacteriological quality. Specific upper limits of raw
water quality parameters are not well-defined because dratomaceous earth
14. This procedure results in clean sand being placed in the bottom half
of the filter bed and biologically active sand in the top half
reducing the amount of. time required for the curing period. It also
provides for a complete exchange of sand over time, alleviating
potential problems of excessive silt accumulation and clogging of
the filter bed (Bellamy et al., 1985).
4-16
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process performance depends on the nature, as well as the concentration, of
the raw water particles and the grades of diatomite employed. Logsdon (1987b)
reported that littered water turbidities above 1 NTU and short filter runs
were observed for several diatomaceous earth plants having maximum raw water
turbidities above 20 NTU.
Design Criteria
The minimum design criteria presented in the Ten State Standards for
diatomaceous earth filtration are considered sufficient for the purposes of
the SWTR with the following exceptions:
A. The recommended quantity of precoat is 1 kg/m (0.2 pounds per
square foot) of filter area, and the minimum thickness of the
precoat filter cake is 3mm to 5mm (1/8 to 1/5-inch). '
B. Treatment plants should be encouraged to provide a coagulant coating
[alum or suitable polymer] of the body feed.
Operating Requirements
Operating requirements specific to DE filters include:
- Preparation of body feed and precoat
- Verification that dosages are proper
- Periodic backwashing and disposal of spent filter-cake
- Periodic inspection of the septum(s) for cleanliness or damage
- Verification that the filter is producing a filtered water that
.meets the performance criteria
4.3.7 Alternate Technologies
15. Studies"have shown that a precoat thickness of 1 kg/m (0.2 Ibs/ft )
was most effective in Giardia cyst removal and that the precoat
thickness was more important than the grade size in cyst removal
(DeWalle et al., 1984; Logsdon et al., 1981; Bellamy et al., 1984).
16. Although enhancement of the DE is not required for Giardia cyst
removal, coagulant coating of the body feed has been found to
significantly improve removals of viruses, bacteria and turbidity.
(Brown et al., 1974; Bellamy et al., 1984).
4-17
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The SWTR indicates that filtration technologies other than those speci-
fied above may be used following demonstration (e.g., through the use of
on-site pilot studies) that the alternate technology is at least as effective
as conventional treatment. Guidance for the pilot studies required to demon-
strate this effectiveness is given in Appendix M of this manual.
Alternate filtration technologies which are currently available include:
- Package Plants
- Cartridge Filters
Package plants are not a separate technology in principle from the
preceding technologies. They are, however, different enough in design crite-
ria, operation and maintenance requirements that they should be handled as an
alternate technology. The package plant is designed as a factory-assembled,
skid-mounted unit generally incorporating a single, or at the most, several
tanks. A complete treatment process typically consists of chemical coagula-
tion, flocculation, settling and filtration. Package plants generally can be
applied to flows ranging from about 25,000 gpd to approximately 6 mgd (USEPA,
1988a).
The application of cartridge filters using either cleanable ceramic or
disposable polypropylene cartridges to small water systems may be a feasible
method for removing turbidity and some microbiological contaminants, such as
Giardia cysts although no data are available regarding the inability to remove
viruses. As previously indicated, pilot studies are required to demonstrate
the efficacy of this technology for a given supply. If the technology were
demonstrated to be effective through pilot plant studies at one site, then the
technology could be considered to be effective at another site which had
similar source water quality conditions. Pilot plant testing at the new site
might not be necessary.
Design Criteria
Upon completion of the pilot studies and assuming successful demonstra-
tion of performance, design criteria should be established and approved by the
Primacy Agency. Eventually, a sufficiently large data base will become
available to apply the alternate technology on other water supplies of similar
quality.
4-18
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Operating Requirements
Upon completion of the pilot studies and assuming successful demonstra-
tion of performance, operating requirements should be established and approved
by the Primacy Agency.
4.3.8 Other Alternatives
Under certain circumstances, some systems may have other alternatives
available. These alternatives include regionalization and the use of alter-
nate sources.
For small water systems which must provide filtration, a feasible option
may be to join with other small or large systems to form a regional water
supply system. Alternative water sources located within a reasonable distance
of a community which meet the requirements of the SWTR and other applicable
drinking water regulations may be developed to provide a satisfactory solution
to a community water quality problem. Alternative ground water sources may be
available depending upon the size and location of the system and the costs
involved.
4.4 Pi s infection
4.4.1 General
The SWTR requires that disinfection be included as part of the treatment
of water for potable use. EPA has already recommended that the number of
treatment barriers be commensurate with the degree of contamination in the
source water in accordance with Table 4-2. For example, as indicated in Table
4-2, when the total coliforms in the source water are greater than 5,000/100
ml, conventional treatment with predisinfection is recommended. However, the
selection of appropriate disinfection requires more detailed considerations
than those provided in Table 4-2. These considerations include:
- Source water quality and the overall removal/inactivation of Giardia
cysts and viruses
- Formation of TTHMs
- Need for an oxidant for purposes other than disinfection, e.g.,
control of taste, odor, iron, manganese, color, etc.
4-19
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4.4.2 Recommended Removal/Inactivation
The SWTR requires a minimum 3-log removal/inactivation of Giardia cysts
and a minimum 4-log removal/inactivation of viruses. For purposes of design-
ing disinfection systems, filtration which is operated to meet the turbidity
performance requirements presented in Section 5 should be assumed to achieve a
2-log removal of Giardia cysts and a 1-log removal of viruses.
However, well operated conventional treatment plants optimized for
turbidity removal can be expected to achieve a 2.5 to 3-log removal of Giardia
cysts and diatomaceous earth, slow sand filtration and direct filtration
plants can be expected to achieve greater than a 2-log removal of Giardia
cysts. EPA recommends that conventional filtration systems provide disin-
fection to achieve a minimum of 0.5-log inactivation of Giardia cysts and a
2-log inactivation of viruses. Other systems should provide sufficient
disinfection to achieve a minimum of 1-log inactivation of Giardia cysts and a
3-log inactivation of viruses as a margin of safety. CT values for achieving
these inactivations are given in Appendix E. Systems which achieve a 0.5-log
inactivation of Giardia cysts, using free chlorine, would achieve greater than
a 4-log inactivation of viruses. Ozone and chlorine dioxide are generally
more effective at inactivating viruses than Giardia cysts however, there are
some conditions at which the viruses are more difficult to inactivate (see
Tables E-8 to E-12). Because of this, a system utilizing ozone or chlorine
dioxide for disinfection must check the CT values needed to provide the
required inactivation of both Giardia and viruses and provide the higher of
the two disinfection levels.
Chloramines are much less effective for inactivating Giardia cysts and
viruses than the other disinfectants. Also, chloramines may be applied to the
system in sevejral ways, either with chlorine added prior to ammonia, ammonia
added prior to chlorine or performed. For systems applying chlorine ahead of
ammonia, the required level of disinfection may be determined as follows:
- determine the CT needed to provide the required inactivation of
Giardia and viruses
- provide the higher of the two levels
- follow the protocol in Appendix G to demonstrate effective inacti-
vation, allowing lower levels of disinfection.
4-20
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For systems applying ammonia ahead of chlorine or preformed chloramines,
the EPA recommends that the system demonstrate effective virus inactivation
according to the protocol in Appendix G. The CT values for virus inactivation
in Table E-13 only apply to the addition of chlorine prior to ammonia.
Although the SWTR requires a minimum of a 3-log removal/inactivation of
Giardia cysts and a minimum of a 4-log removal/inactivation of viruses, it may
be appropriate for the Primacy Agency to require greater removals/inactiva-
tions depending upon the degree of contamination within the source water.
Rose, 1988 conducted a survey of water sources to characterize the level
of Giardia cyst occurrence for "polluted" and "pristine" waters. Polluted
waters are defined as waters receiving sewage and agricultural wastes, while
pristine waters are those originating from protected watersheds with no
significant sources of microbiological contamination from human activities.
EPA believes that treatment should be provided to assure less than one case of
microbiologically-caused illness per year per 10,000 people. In order to
provide this level of protection, 3, 4 or 5-log Giardia cyst should be provid-
ed for the following source water qualities:
Giardia Cyst Removal/inactivation Required Based
on Source Water Cyst Concentration
Giardia Inactivation 3-log 4-log 5-log
Allowable daily avg
cyst concentration/100 L <1 >1-10 >10-100
(geometric mean)
According to these guidelines, systems with sewage and agricultural
discharges to the source water should provide disinfection to achieve an
overall 5-log removal/inactivation of Giardia cysts, while 3-log removal/inac-
tivation should be provided for sources with no significant microbiological
contamination from human activities. A 4-log removal/inactivation of cysts
17. Rose, 1988.
-4
18. 10 annual risk per person based on consumption of 2 liters of
water daily.
4-21
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should be provided for source waters with some microbiological contamination
between these two extremes. These levels of treatment for different general-
ized source water characterizations are presented as guidelines. The Primacy
Agency could develop disinfection requirements based on these guidelines or it
may require systems which have the resources available to conduct raw water
monitoring for Giardia cyst concentrations to establish the appropriate level
of overall treatment and disinfection needed.
In the absence of a risk analysis for exposure to viruses, a guideline
for virus inactivation, can be based on the occurrence of viruses vs. Giardia
cyst occurrence. Using a direct proportion between occurrence and inac-
tivation provided, for a 4-log Giardia cyst removal/inactivation a 5-log virus
removal/inactivation is recommended, and for 5-log Giardia re-
moval/inactivation, 6-log virus removal/inactivation if recommended.
CT tables for each of the disinfectants for various removals are
presented in Appendix E. These tables should be reviewed in order to
determine the minimum dosage and contact time required for the selected
disinfectant in preparation for ascertaining the chemical feed and storage
requirements.
In order for systems to meet the levels of inactivation recommended here,
significant changes in the system may be required. To avoid changes in the
system which may result in conflicts with future regulations, the EPA has
given the Primacy Agency discretion in establishing interim disinfection
levels to" provide protection of public health prior to the promulgation of the
disinfection byproduct regulations. Guidance for establishing interim disin-
fection requirements is provided in Section 5.5.
4.4.3 Total Trihalomethane (TTHM) Regulations
In addition to complying with disinfection requirements, systems must
conform to the TTHM regulation. Currently, this regulation includes an MCL
for TTHMs of 0.1 mg/L for systems which serve greater than 10,000 people. EPA
expects to issue more stringent regulations in the near future. These regu-
lations may also pertain to systems serving less than 10,000 people. There-
fore, the selection of an appropriate disinfectant must include consideration
of current and future regulations.
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5. CRITERIA FOR DETERMINING IF FILTRATION
AND DISINFECTION ARE SATISFACTORILY PRACTICED
5.1 Introduction
Under the SWTR, new and existing filtration plants must meet specified
monitoring and performance criteria in order to assure that filtration and
disinfection are satisfactorily practiced. These criteria include:
- Turbidity monitoring requirements
- Turbidity performance criteria
- Disinfection monitoring requirements
- Disinfection performance criteria
The overall objective of these criteria is to provide control of: Giardia
cysts; viruses; turbidity; HPC and Legionella by assuring a high probability
that:
a. Filtration plants are well operated and achieve maximum removal
efficiencies of the water quality parameters of concern.
b. Disinfection will provide adequate inactivation of viruses, HPC and
Legionella, and added protection against Giardia cysts.
5.2 Turbidity Monitoring Requirements
5.2.1 Sampling Location
The purpose of the turbidity requirements for systems which utilize
filtration include:
a. To provide an indication of:
- Giardia cyst and general particulate removal for conventional
treatment and direct filtration
- General particulate removal for diatomaceous earth filtration
and slow sand filtration
b. To indicate possible interference with disinfection
To accomplish the purposes of the turbidity requirements, the SWTR
requires that the turbidity samples be representative of the system's filtered
5-1
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water. The sampling locations which would satisfy this requirement include:
a. Combined filter effluent prior to entry into a clearwell
b. Clearwell effluent
c. Plant effluent or immediately prior to entry into the distribution
system
d. Average of measurements from each filter effluent.
The selection of one of these sampling locations for demonstrating
compliance with the turbidity performance criteria is left to the system or
the preference of the Primacy Agency.
5.2.2 Sampling Frequency
The SWTR requires that the turbidity of the filtered water must be
determined:
a. At least once every four hours that the system is in operation, or
b. The Primacy Agency may reduce the sampling frequency to once per day
for systems using slow sand filtration or filtration treatment other
than conventional treatment, direct filtration or diatomaceous earth
filtration. For systems serving less than 500 people, the Primacy
Agency may reduce the sampling frequency to once per day regardless
of the type of filtration used; if the historical performance and
operation of the system indicate there is effective turbidity
removal under variety of conditions expected to occur in that
system.
A system may substitute continuous turbidity monitoring for grab sample
monitoring if it validates the continuous measurement for accuracy on a
regular basis using a protocol approved by the Primacy Agency. EPA recommends
that the calibration of continuous turbidity monitors be verified at least
twice per week according to the procedures established in Method 214A of the
16th Edition of Standard Methods.
5.2.3 Additional Monitoring
As indicated in Section 4.3.2, it has been recommended that systems equip
each filter with a continuous turbidity monitor. This recommendation is not
part of the requirements of the SWTR and is not required for establishing
compliance. Rather, it is recommended as a tool for systems to use to better
monitor their treatment efficiency and to provide a method for detecting a
deterioration in filter performance.
5-2
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In filtration, effective particle removal depends on both physical and
chemical factors. The particles to be removed must be transported to the
surface of the media and they must attach to the media. When efficient
particle removal does not occur, the deterioration of filter performance can
be due to either physical problems with the filters or problems with the
treatment chemistry.
Physical problems which can result in a deterioration of filter perfor-
mance include:
- Media loss
- Media deterioration
- Mud ball formation
- Channeling or surface cracking
- Underdrain failure
- Cross-connections
In addition, the treatment chemistry has a significant impact on filtra-
tion. Specifically, effective particle removal is a function of the:
- Raw water chemistry and the changes induced by the chemicals added;
- Surface chemistry of the particles to be removed
- Surface chemistry of the media
Consequently, when a filter experiences particle breakthrough or turbidity
breakthrough prior to the development of terminal headless/ the search for
alternatives to correct the problem must include not only an evaluation of the
potential physical causes but the treatment chemistry as well. Generally this
involves an evaluation of one or more of the following:
a. Alternate coagulant type and/or dose
b. Alternate coagulant aid or flocculant aid type and/or dose
c. Need for an alternate oxidant type and/or dose
d. Need for a filter aid or alternate dose
5-3
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If continuous monitoring of each filter effluent cannot be implemented,
then it is recommended that at least the following be conducted on a quarterly
basis:
- Monitor each filter, either by grab samples or continuous monitors,
through the course of a routine cycle of operation, i.e., from
restart to backwash, and
- Visually inspect each filter where appropriate for indications of
physical deterioration of the filter.
These are general suggestions. The Primacy Agencies are encouraged to
work with the systems to determine the best overall monitoring program(s) for
their particular filtration plants in order to assess the status of the filter
units.
5.3 Turbidity Performance Criteria
The SWTR establishes turbidity performance criteria for each of the
filtration technologies. As previously indicated, these criteria provide an
indication of:
a. Effective particle and microbial removal and
b. Potential for interference with disinfection
5.3.1 Conventional Treatment or Direct Filtration
Based upon the requirements of the SWTR, the minimum turbidity perfor-
mance criteria for systems using conventional treatment or direct filtration
are:
- Filtered water turbidity must be less than or equal to 0.5 NTU in
95 percent of the measurements taken every month.
- At the discretion of the Primacy Agency, filtered water turbidity
levels of less than or equal to 1 NTU in 95 percent of the measure-
ments taken every month may be permitted on a case-by-case basis if
the Primacy Agency determines that the system is capable of achiev-
ing the minimum overall performance requirements of 99.9 percent
removal/inactivation of Giardia cysts at the higher turbidity level.
Such a determination could be based upon an analysis of existing
design and operating conditions and/or performance relative to
certain water quality characteristics. The design and operating
conditions to be reviewed include the adequacy of treatment prior to
filtration, the percent turbidity removal across the treatment train
and level of disinfection. Water quality analysis which may also be
used to evaluate the treatment effectiveness include particle size
5-4
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counting before and after the filter. Pilot plant challenge studies
simulating a full size operation may also be used to demonstrate
effective treatment. Depending on the source water quality and
system size, the Primacy Agency will determine the extent of the
analysis and whether a pilot plant demonstration is needed. For
this demonstration, systems are allowed to include disinfection in
the determination of the overall performance by the system.
- Filtered water turbidity may not exceed 5 NTU at any time.
Conventional treatment plants that are meeting the minimum performance
criteria and have well operating settling basins are assumed to be achieving
at least a 2.5-log removal of Giardia cysts and at least a 2-log removal of
(2)
viruses prior to disinfection.
Direct filtration plants that are meeting the minimum performance
criteria are assumed to be achieving at least a 2-log removal of Giardia cysts
and a 1-log removal of viruses.
Although the minimum turbidity performance criterion has been set at 0.5
NTU, treatment facilities using conventional treatment or direct filtration,
whose raw water supplies have turbidity levels of 1 NTU or less, should be
(4)
encouraged to achieve filtered water turbidity levels of less than 0.2 NTU.
1. Recommended protocol for this demonstration is presented in Appendix N.
2.
The literature indicates that well operated conventional treatment and plants
can achieve up to a 3-log reduction of Giardia cysts and viruses (Logsdon,
1987b and Roebeck et al., 1962). Limiting the credit to 2.5-logs for Giardia
cysts and 2-logs for viruses provides a margin of safety and is consistent
with the multiple barrier concept.
3.
Literature indicates that well operated direct filtration plants can achieve
up to a 3-log "removal of Giardia cysts and up to a 2-log removal of viruses
(Logsdon, 1987b; Roebeck et al., 1962). Limiting the credit to 2-log for
Giardia cysts and 1-log for viruses provides a margin of safety and is
consistent with the multiple barrier concept.
4.
Research has demonstrated that difficulty in obtaining effective removals of
Giardia cysts and viruses with low turbidity source waters (Logsdon, 1987b;
Al-Ani et al., 1985).
5-5
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5.3.2 Slow Sand Filtration
For systems using slow sand filtration, the turbidity performance re-
quirements are:
- The filtered water turbidity must be less than or equal to 1 NTU in
95 percent of the measurements for each month.
- At the discretion of the Primacy Agency, a higher filter effluent
turbidity may be allowed for well operated plants (Section 4.3.5) on
a case-by-case basis, if there is no interference with disinfection
and the turbidity level never exceeds 5 NTU. Non interference with
disinfection could be assumed if the finished water entering the
distribution system is meeting the coliform MCL and HPC levels are
less than 10/ml during times of highest turbidity.
- Filtered water turbidity may not exceed 5 NTU at any time.
Slow sand filtration plants, with appropriate design and operating
conditions and which meet the minimum turbidity performance criteria are
considered to be well operated and achieving at least a 2-log removal of
Giardia cysts and 2-log removal of viruses without disinfection.(5)
5.3.3 Diatomaceous Earth Filtration
For systems using diatomaceous earth filtration, the turbidity perfor-
mance criteria are:
a. The filtered water turbidity must be less than or equal to 1 NTU in
95 percent of the measurements for each month.
b. - The turbidity level of representative samples of filtered water must
at no time exceed 5 NTU.
Diatomaceous earth systems, with appropriate design and operating con-
ditions and which meet the minimum turbidity performance criterion are to be
considered well operated and achieving a minimum 2-log removal of Giardia
cysts and a 1-J.og. removal of viruses without disinfection.
5.
As indicated in Section 4, pilot studies have shown that with proper nurturing
of the schmutzdecke, operation at a maximum loading rate of 0.2 m/h will
provide optimum removal of Giardia cysts and viruses (Logsdon, 1987b; Bellamy
et al., 1985).
5-6
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5.3.4 Other Filtration Technologies
As specified in the SWTR, the turbidity performance criteria for filtra-
tion technologies, other than the ones presented above, are the same as for
conventional treatment and direct filtration.
5.4 Disinfection Monitoring Requirements
The SWTR requires that each system continuously monitor the disinfectant
residual of the water as it enters the distribution system and record the
lowest disinfectant residual each day. Systems serving less than or equal to
3300 people may take grab samples in lieu of continuous monitoring at fre-
quencies as follows:
System Population Samples/Day*
<500 1
"501-1,000 2
1,001 - 2,500 3
2,501 - 3,300 4
* Samples must be taken at dispersed time intervals as approved
by the Primacy Agency.
If the residual concentration falls below 0.2 mg/L, the system must take
another sample within 4-hours and notify the Primacy Agency by the end of the
next business day. Each system must also measure the disinfectant residual in
the distribution system at the same frequency and locations for which total
coliform measurements are made pursuant to the requirements in the revised
coliform -rule (proposed at the same time as the SWTR). For systems which use
both surface and ground water sources, the Primacy Agency may allow sampling
sites which are more representative of the surface water supply.
5.5 DISINFECTION PERFORMANCE CRITERIA
5.5.1 Minimum Performance Criteria Required by the SWTR
For systems which provide filtration, the disinfection requirements of
the SWTR are:
The system must demonstrate by continuous monitoring and recording
that a disinfectant residual in the water entering the distribution
system is never less than 0.2 mg/L for more than 4 hours. If at any
time the residual falls below 0.2 mg/L for more than 4 hours the
5-7
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system is in violation. The system must notify the Primacy Agency
whenever the residual falls below 0.2 mg/L before the end of the
next business day.
b. The system must demonstrate detectable disinfectant residuals or HPC
levels less than 500 colonies/ml in at least 95 percent of the
samples from the distribution system each month, for any two
consecutive months.
5.5.2 Recommended Performance Criteria
The SWTR requires that the overall treatment provided must achieve a
minimum of a 3-log removal/inactivation of Giardia cyst and a 4-log re-
moval/ inacti vat ion of viruses. As outlined in Section 5.3, it can be assumed
that well operated filter plants achieve between a 2 to 2.5-log removal of
Giardia cysts and between a 1 to 2-log removal of viruses. It is therefore
recommended that the Primacy agencies adopt additional disinfection perfor-
mance criteria that includes:
a. As a minimum, primary disinfection requirements that are consistent
with the overall treatment requirements of the SWTR, or preferably.
b. Establishes primary disinfection requirements as a function of raw
water quality as outlined in Section 4.4.
Recommended Minimum Disinfection
The recommended minimum primary disinfection to be provided is the
disinfection needed to provide the additional inactivation for the entire
treatment process to meet the overall treatment requirement of 3-log Giardia
and 4-log virus inactivation. The following table provides a summary of the
treatment performance and the recommended level of disinfection.
Recommended Disinfection
Log Removal (Log Removals)
Treatment Giardia Viruses Giardia Viruses
Conventional
Filtration 2.5 2 0.5 2
Direct Filtration 2 1 1.0 3.0
Slow Sand 2 2 1.0 2.0
Diatomaceous
Earth 2 1 1.0 3.0
5-8
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Recommended Disinfection as a Function of Raw Water Quality
Although the SWTR requires the overall treatment to provide a minimum of
a 3-log Giardia and a 4-log virus removal/inactivation, it may be appropriate
for the Primacy Agency to require greater removals/inactivations depending on
the degree of contamination in the source water as presented in Section 4.4.
Following is a summary of the recommended overall treatment which should be
provided for the specified source water quality:
Allowable daily avg
cyst concentration/100 L £1 >1-10 >10-100
(geometric mean)
Giardia Removal/inactivation 3-log 4-log 5-log
Virus Removal/inactivation 4-log 5-log 6-log
Since it is not possible to increase removals previously outlined through
filtration, in order to provide this overall treatment, the disinfection
provided will need to be increased accordingly. For example, if for a
particular slow sand filtration plant on overall treatment for 4-log Giardia
removal/inactivation and 5-log virus removal/inactivation is recommended,
disinfection for a 2-log Giardia inactivation and 3-log virus inactivation
would be needed to meet the overall recommended removal/inactivation.
5.5.3 Disinfection By-Product Considerations
Although the EPA suggests increased levels of disinfection for various
source water conditions, it is also recommended that a utility should not
implement such a change without considering the potential conflict with the
requirements of existing or future disinfection by-product regulations. EPA
intends to promulgate National Primary Drinking Water Regulations to regulate
levels of disinfectants and disinfectant by-products when it promulgates
disinfection requirements for ground water systems (anticipated by the end of
1991). EPA is concerned that changes required in utilities' disinfection
practices to meet the recommended inactivations for the SWTR might be
inconsistent with treatment changes needed to comply with the forthcoming
regulations for disinfectants and disinfection by-products. For this reason,
the EPA is allowing Primacy Agencies discretion in determining the
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disinfection conditions needed for filtered systems to meet the overall
treatment requirements specified in the rule or recommended based on source
water quality.
During the interim period, prior to promulgation of the disinfection
by-product regulation, EPA recommends that the Primacy Agency allow more
credit for Giardia cyst and virus removal than generally recommended. This
interim level is recommended in cases where the Primacy Agency determines that
a system is not currently at a significant risk from microbiological concerns
at the existing level of disinfection and that a deferral is necessary for the
system to upgrade its disinfection process to optimally achieve compliance
with the SWTR as well as the forthcoming disinfection by-product regulations.
The following paragraphs outline the recommended interim disinfection levels
for various treatment processes.
For well operated conventional filtration plants that meet the minimum
turbidity requirements at all times, the Primacy Agency may consider giving
the system credit for 3-log Giardia cyst removal (in lieu of the generally
recommended 2.5-log credit). EPA recommends that credit be given for 3-log
Giardia cyst removal by conventional treatment only if:
a. The total treatment train achieves at least 99 percent turbidity
removal, or filtered water turbidities are consistently less than
0.5 NTU, whichever is lower;
b. The level of HPC in the finished (disinfected) water entering the
distribution system is consistently less than 10/ml;
c. The source water generally has Giardie cyst concentrations less than
1 cyst/100 L.
In establishing interim disinfection requirements for systems using slow
sand filtration and diatomaceous earth filtration, these systems may be
allowed credit, for 2.5 or 3-log Giardia cyst removal in lieu of the generally
recommended guideline of 2-logs. Pilot plant studies have demonstrated
(USEPA, 1988a) that these technologies, when well operated, generally achieve
at least 2.5-log removals.
The EPA feels that interim disinfection requirements are appropriate in
some cases depending upon source water quality, reliability of system opera-
tion and potential increased health risks from disinfection by-products.
5-10
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Since EPA intends to regulate disinfectants and disinfection by-products
before 1992 and compliance with the SWTR is not required until June of 1993,
it is anticipated that most systems will not need significant time delays or
long interim periods to optimally address the requirements of both rules.
5.5.4 Determination of Inactivation by Disinfection
The inactivations recommended above can be achieved by disinfection at
any point in the treatment or distribution system prior to the first customer.
Disinfection provided prior to filtration is referred to as pre-disinfection
while disinfection after filtration is referred to as post-disinfection. As
presented in Section 3.2, the inactivation of Giardia cysts and viruses
provided by disinfection are correlated to CT values.
The SWTR defines CT as the residual disinfectant concentration(s) in mg/L
multiplied by the contact time(s) in minutes measured from the point of
application to the point of residual measurement or between points of residual
measurement. The inactivation maintained can be determined by calculating CT
at any point along the process after disinfectant application prior to the
first customer. A system may determine the inactivation based on one point of
residual measurement prior to the first customer, or on a profile of the
residual concentration after the point of disinfectant application. The
residual profile is generated by monitoring the residual at several points
between the point(s) of disinfectant application and the first customer. The
system can then use the method described in Section 3.2 for determining the
total inactivation credit. Profili^j the residual allows for credit of the
higher residuals which exist shortly after the disinfectant is applied.
Appendix D presents methods for determining various disinfectant residuals.
In pipelines, the contact time is calculated by dividing the internal
volume of the-pipeline by the peak hourly flow rate through the pipeline.
Within mixing basins and storage reservoirs, there may be short circuiting.
Therefore, the hydraulic detention time may not represent the actual disin-
fectant contact time. The contact time should be determined by tracer studies
or an equivalent demonstration. The time determined from the tracer study to
be used for calculating CT is T . T is equivalent to the time for 10
percent of the water to pass through the basin, thus 90 percent of the water
5-11
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will be in the basin for this length of time. Guidance for determining
detention time in basins is provided in Appendix C.
The residual disinfectant concentration should be measured daily, during
peak hourly flow for each disinfectant section prior to the first customer in
the distribution system. Unless a system knows from experience when peak flow
will occur, a system can only identify peak hourly flow after it has passed.
Therefore, it is suggested that residual measurements be taken every hour. If
it is not practical to take grab samples each hour, continuous monitors may be
used. The measurements taken during the hour of peak flow can then be used to
determine the CT for each section (CT , }. The determination of CTs for
calc
ozone contactors is explained in Section 3.2.1.
Although the inactivation maintained in the system is determined during
peak hourly flow, it should be noted that the disinfectant dosage applied to
maintain this inactivation may not be necessary under lower flow conditions.
Under lower flow conditions, a higher contact time is generally available and
the CT needed to meet the required inactivation may be met with a lower
residual. Continuing to apply a disinfectant dosage based on the peak hourly
flow may provide more disinfection than is needed, possibly resulting in
increased levels of disinfectant by-products. However, the system should also
maintain the required inactivation levels at non-peak hourly flows. There-
fore, the system should therefore evaluate the dose needed to provide the CT
necessary for maintaining the required inactivation under different flow
conditions and set the dosage accordingly. The following example provides
guidelines for determining flow ranges and disinfection levels to maintain the
required disinfection.
Example
A 20 mgd direct filtration plant applying free chlorine as a disinfectant
has a contact" time of 27 minutes under peak flow conditions. The pH and
temperature of the water are 7 and 5 C, respectively. Utilizing Table E-2, a
CT of 54 at a residual of 2 mg/L is required to achieve 1-log Giardia cyst
inactivation. However, under low flow conditions the available contact time
is longer, and lower residuals are needed to provide the same level of inacti-
vation. Based on the calculated contact time under various flow rates and the
5-12
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CT values in Table E-2, adequate disinfection would be provided by maintaining
the following chlorine residuals for the indicated flows:
CT
Contact (mg/l-min) Free Chlorine
Flow (MGD) the (min) Required Residual (mg/L)
20 27 54 2.0
15 36 51 1.5
10 54 48.5 0.9
5 108 46.5 0.5
The variation in CT required with respect to the residual for chlorine
makes it impractical for the utility to continually change the disinfectant
dose as the flow changes. Therefore, EPA suggests that the flow variation at
the utility be divided into ranges and the residual needed at the higher flow
of the range be maintained for all flows within the range to ensure adequate
disinfection. The following flow ranges and residuals are suggested for this
plant:
Free Chlorine
Flow Range (MGD) Residual (mg/L)
5-10 0.9
10-15 1.5
15-20 2.0
In this way, the utility is assuring the provision of the required
disinfection while minimizing the disinfectant application and possibly
lowering disinfection by-products.
Although these residuals will meet the recommended CT, maintaining a
residual in the distribution system must also be considered. If there is no
other point of disinfection prior to the distribution system, the residual for
disinfection must' be maintained at a level which will also provide a residual
throughout the distribution system. The complete range of flows occurring at
the plant should be evaluated for determining the required residual. The
utilities may establish the residual needs for as many flow ranges as is
practical.
The Primacy Agency should make periodic checks to ensure that the utility
is maintaining adequate disinfection at both peak and non-peak flow condi-
tions.
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Meeting the Recommended Inactivation Using Free Chlorine
As previously indicated in Section 3.2.1, the effectiveness of free
chlorine as a disinfectant is influenced by both the temperature and pH of the
water. The inactivation of Giardia cysts by free chlorine at various tempera-
tures and pHs are presented in Appendix E (Table E-l through Table E-6). The
CT value for the inactivation of viruses by free chlorine are presented in
Table E-7.
To determine whether a system is meeting these inactivations, the free
chlorine residual, pH and temperature must be measured, at one point or
several points prior to the first customer where contact time is measured. The
contact time should be determined from the point of application of the
disinfectant to points where the residual is measured for determining CTs
prior to the first customer. The CTs actually achieved in the system should
then be compared to the values in the table for the pH and temperature of the
source water. Guidance on calculating the CT for chlorine is presented in
Section 3.2.1.
Meeting the Recommended Inactivation Using Chlorine Dioxide
CT values for the inactivation of Giardia cysts by chlorine dioxide are
presented in Table E-8 and the CT values for the inactivation of viruses are
presented in Table E-9. The disinfection efficiency of chlorine dioxide may
be significantly increased at higher pHs. According to the Tables E-8 and
E-9, the only parameter affecting the CT requirements associated with the use
of chlorine dioxide is temperature. The CT values in Tables E-8 and E-9 were
based on data at pH 6 and 7. Thus, systems with high pHs may wish to demon-
strate that CT values lower than those presented in Tables E-8 and E-9 may
achieve the desired level of inactivation.
Chlorine dioxide residuals are short-lived. Therefore, sampling and
residual analysis- at various points in the treatment process downstream of the
point of application may be necessary to establish the last point at which a
residual is present. Subsequent sampling and residual analyses conducted
upstream of this point can .be used to determine the CT credit by utilizing the
demonstrated detention time between the point of application and the sampling
location. Methods for calculating CT values are presented in Section 3.2.
Systems using chlorine dioxide may conduct pilot studies to demonstrate
effective disinfection in lieu of calculating CT, or for determing that lower
5-14
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CT values than those in Appendix E are appropriate. Guidelines for conducting
these studies are presented in Appendix G.
Meeting the Recommended Inactivation using Ozone
CT values for the inactivation of Giardia cysts by ozone are presented in
Table E-10 for various temperatures and inactivation rates. As indicated in
this table, the CTs needed for inactivation with ozone are substantially lower
than those required for free chlorine. This reflects the fact that ozone is a
more powerful disinfectant. The CT requirements for inactivation of viruses
using ozone are presented in Table E-ll. Because of the reactivity of ozone,
it is unlikely that a residual will exist for more than a few minutes. As a
result, the application of a persistent disinfectant such as chlorine or
chloramines is needed to maintain the required disinfectant residual in the
distribution system. Guidance for calculating CT values for ozone are
presented in Section 3.2.1. In lieu of calculating the CT for an ozone
contactor or to demonstrate that lower CTs are effective, the disinfection
efficiency can be demonstrated through pilot studies as presented in
Appendix G.
Meeting the Recommended Inactivation Requirements using Chloramines
CT values for the inactivation of Giardia cysts by preformed chloramines
are presented in Table E-12. The high CT values associated with the use of
preformed chloramines may be unachievable for some systems. In these cases,
chlorine, ozone, or chlorine dioxide should be used for primary disinfection,
and chloramines for residual disinfection, as necessary. Table E-13 presents
CT values for the inactivation of viruses with preformed chloramines. For
systems applying chloramines to meet the virus inactivation; it is suggested
that these systems also monitor for HPC in the finished water, as presented in
Section 5.6. Systems may demonstrate effective disinfection with chloramines
as outlined in Appendix G. Further guidance on chloramines is located in
Section 3.2.1.
Examples for Determining the Disinfection to be Provided
Recommended 0.5-log Giardia, 2-log Virus Inactivation
A community of 70,000 uses a river as its drinking water source.
Ozonation prior to a conventional treatment plant is used to treat the water.
5-15
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The source has a protected watershed with limited human activity and no sewage
discharge. The river water has the following water quality characteristics:
turbidity 10 - 200 NTU
total estimated Giardia cyst level <1/100 ml
total coliforms 20 - 100/lOOml
pH 7.0-7.5
temperature 5-15
The treatment plant has a design capacity of 15 mgd and treats an average
flow of 10 mgd. A three chamber ozone contactor precedes the rapid mix. Alum
and polymer are added as a coagulant and coagulant aid. The finished water
turbidity at the plant is maintained within the range of 0.1 to 0.2 NTU.
Chloramines are applied after the filters, but prior to the clearwells, to
maintain a residual entering and throughout the distribution system.
Based on the raw water quality and source water protection, an overall
3-log Giardia and 4-log virus removal/inactivation is appropriate for this
water source. However, as noted in Section 5.3, Primacy Agencies may credit
well operated conventional filtration plants with 2.5-log Giardia removal and
2-log virus removal. Therefore, disinfection for 0.5-log Giardia and 2-log
viruses is recommended to meet the overall treatment requirements of the SWTR.
On the day of this example calculation, the peak hourly flow rate of the
plant was 13 mgd. The contact time of the ozone basin, T determined from
tracer study data is 6 minutes for this flow. The water had a pH of 7 and a
temperature of 5 C on the day of the calculation. For ozone under these
conditions of pH and temperature the following CTs are needed for inactivation
(Tables E-10, E-ll):
0.5-log Giardia 2-log virus
CT 0.3 0.6
The CT values "indicate that viruses are the controlling parameter for disin-
fection and the overall inactivation provided will be calculated based on
viruses. The overall virus inactivation provided by the ozone" contactor is
determined as follows:
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Average
Residual
C (mg/L)
0.1
0.2
0.2
T
(minutes)
2
2
2
CT ,
(vfflS
0.2
0.4
0.4
CT
99 9
Minutes
0.9
0.9
0.9
CT , /C
calc
0.22
0.44
0.44
r99.9
Chamber
1
2
3
The sum of CT , /CT is 1.1. This corresponds to more than a 3-log virus
inactivation determined as 3 X CT . /CT_g . = 3 X 1.1 = 3. 3-log. Therefore,
the system exceeds the recommended inactivation.
Recommended 1-log Giardia, 2-log Virus Inactivation
A 2 MGD slow sand filtration plant treating reservoir water provides
drinking water for a community of 8,000 people. The source has a protected
watershed and the following water quality characteristics:
turbidity 5-10 MTU
total coliforms 100 - 500/lOOml
total estimated Giardia cyst level < 1/100 ml
pH 6.5 - 7.0
temperature 5 - 15 C
The filtered water turbidity ranges from 0.6 - 0.8 MTU. Considering the
source water quality and plant performance, an overall 3-log Giardia and 4-log
virus removal/inactivation is considered sufficient for this system. As noted
in Section 5.3, the Primacy Agency may credit slow sand plants with 2-log
Giardia and 2-log virus removal. Therefore disinfection for 1-log Giardia and
2-log virus is recommended for the system to meet the overall treatment
requirements .
Chlorine is added prior to the clearwells to provide disinfection. The
clearwells have a capacity of 80,000 gallons. A one mile, 16-inch trans-
mission main transports the water from the treatment plant to the first
customer. The inactivation provided is determined daily for the peak hourly
flow conditions. Tracer studies have been conducted to determine the T for
the clearwells for different flow rates. For the purposes of calculating the
inactivation the system is divided into two sections.
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Section 1 - clearwell
Section 2 - transmission main
The flowrate at peak hourly flow was 1.5 mgd on the day of this example.
At this flowrate, the T of the clearwell is 67 minutes, as determined from
the results of the tracer studies. At this flowrate, water travels through
the transmission main at 99 ft/min. The data for the calculation of the
inactivation is as follows:
Section 1 Section 2
length of pipe (ft) 0 5280
contact time (min)
pipe 0 53
basin 67 . 0
total 67 53
disinfectant chlorine chlorine
residual (mg/L) 1.0 0.6
temperature C 5 5
pH 7.5 7.5
For free chlorine, a 1-log Giardia cyst inactivation provides greater than a
4-log virus inactivation; therefore, Giardia is the controlling parameter, and
the inactivation provided is determined based on Giardia. The calculation is
as follows:
Section 1 - Chlorine
CT . = 1.0 mg/L x 67 minutes = 67 mg/L-min
From Table E-2, at a temperature of 5 C and a pH of 7.5, CT is 179
mg/L-min '
CTcalc/CT99.9
179 mg/L-min
Section 2 - Chlorine
CT = 0.6 mg/L x 53 minutes = 32 mg/L-min
From Table E-2, at a temperature of 5 C and a pH of 7, CT is 179
t— . yy * y
mg/L-min
CTcalc/CT99.9 = 32mg/l-min = 0.18
179 mg/L-nun
The sum of CT /CTQQ Q is equal to 0.85. This is equivalent to a 2.5-log
Ca J.C yy . y
Giardia inactivation determined as 3x CT . /CTQQ Q = 3 x 0.85 = 2.5.
— ^— ~— ~ caic yy . y
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Therefore, the system exceeds the disinfection recommended to meet the overall
treatment requirements.
Recommended 2-log Giardia, 4-log Virus Inactivation
A community of 200,000 people uses a reservoir treated by direct filtra-
tion for its water supply. The reservoir is fed by a river which receives the
discharge from a wastewater treatment plant upstream of the reservoir. The
reservoir water quality is as follows:
turbidity 5-15 NTU
total coliforms 200 - 500/100 ml
total estimated Giardia cyst level 5/100 L
pH 6 - 7
temperature 5 - 15 C
Based on the source water quality, an overall removal/inactivation of
4-log Giardia and 5-log virus is recommended as outlined in Section 4.4.
The source water flows by gravity to a 3 MG storage reservoir prior to
pumping to the water treatment plant. Chloramines are added to the water at
the inlet of the storage reservoir and chlorine dioxide is added to the
filtered water prior to the clearwells. Chloramines are applied after the
clearwells to maintain a residual in the distribution system. The system
design flow is 8 mgd with an average flow of 5 mgd. For. the calculation of
the overall inactivation, the system is divided into 2 sections.
Section 1 - the storage reservoir and the transmission to the treatment
plant
Section 2 - the clearwells
The overall inactivation for the system is computed daily at the peak
hourly flow conditions. The pH, temperature, and disinfectant residual is
measured at the end of each section prior to the next point of disinfectant
application and the first customer. On the day of this example calculation
the peak hourly flow was 6 mgd. The water flow rate through the 20-inch
transmission main is 256 ft/min at a flow of 6 mgd. Tracer studies were
conducted on the storage reservoir and clearwells. As determined from the
testing the detention times, T , of the basins at a flow of 6 mgd are 380 and
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80 minutes for the storage reservoir and clearwells, respectively. The data
for the calculation of inactivation is as follows:
Section 1 Section 2
length of pipe (ft) 4500 0
contact time (min)
pipe 18 0
basin 380 130
total 398 130
disinfectant chloramines chlorine dioxide
residual (mg/L) 1.5 0.1
temperature C 15 C 5 C
pH 77
For each of the disinfectants used, the following CTs are needed for
2-log Giardia and 4-log virus inactivation for the pH and temperature
conditions of the system.
CT for 2-log CT for 4-log
Giardia Virus
chloramines 1435 1988
chlorine dioxide 27 33.5
The CT required for the virus inactivation is higher than that needed for
Giardia inactivation for each of the disinfectants. Since the viruses are the
controlling parameter, the inactivation calculation will be based on the
viruses. The calculation is as follows:
Section 1 - Chloramines
CT , =1.5 mg/L x 398 minutes = 597 mg/L-min
calc
From Table E-13, at a temperature of 5 C and a pH of 7, CT is 1988
/_ • • yy • yy
mg/L-min
CTcalc/CT99.99 = 597 mg/l-min = 0.3
1988 mg/L-min
Section 2 - Chlorine Dioxide
CT =0.2 mg/L x 130 minutes = 26 mg/L-min
Oci-LC
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From Table E-9, at a temperature of 5 C and a pH of 7, CT qq is
33.5 mg/L-min
CTcalc/CT99 99 = 26 *<3/l-*^ = 0.78
calc 99.99 33_5 mg/L.min
The sum of CT /CT _ OQ is equal to 1.08, which is equivalent t<-> a 4.2-log
CalC 99.99
inactivation of viruses, determined as follows:
CT
CT
CT
x = 4 x calc = 4 x 1.08 = 4.3-logs
99.99
Therefore, the system provides sufficient disinfection to meet the overall
recommended treatment performance.
5.6 Other Considerations
Monitoring for HPC is not required under the SWTR. However, such moni-
toring may provide a good operational tool for:
- Measuring microbial breakthrough
- Evaluating process modifications
- Detecting loss of water main integrity
- Detecting bacterial regrowth conditions within the distribution
system
- Determining interference with the coliform measurements (AWWA, 1987)
Therefore, EPA recommends routine monitoring of HPC on the plant effluent
and within the distribution system whenever the analytical capability is
available inhouse or nearby. Systems which do not have this capability should
consider using a semiquantitative bacterial water sampler kit, although this
is not acceptable.for compliance monitoring.
As presented in the preamble to the SWTR, EPA believes that it is
inappropriate to include HPC as a treatment performance criterion in the rule
since small systems would not have in-house analytical capability to conduct
the measurement, and they would need to send the samples to a private
5-21
-------
laboratory. Unless the analysis is conducted rapidly, HPC may multiply and
the results may not be representative.
EPA recommends that an HPC level of less than 10/ml in the finished water
entering the distribution system and levels of less than 500/ml throughout the
distribution system be maintained.
Legionella is another organism which is not included as a treatment
performance criterion. Inactivation information on Legionella is limited.
The available information indicates that the filtration and disinfection
requirements of the SWTR will remove or inactivate substantial levels of
Legionella which might occur in source waters. Since these organisms are
similar in size to coliform organisms, removal by filtration should be similar
to those reported for total coliforms. In addition, the available disin-
fection information indicates that the CT requirements for inactivation of
Legionella are lower than those required for the inactivation of Giardia
cysts.
6. These treatment requirements do not guarantee that these organisms will
not be present in numbers sufficient to colonize hot water systems within
homes and institutions (Muraca et al., 1986). Guidance for control of
Legionella by institutions is provided in Appendix B.
5-22
-------
6. REPORTING
6.1 Reporting Requirements for Public Water Systems Not Providing Filtration
The SWTR requires unfiltered systems to prepare monthly reports for the
Primacy Agency to determine compliance with the requirements for:
- source water fecal and/or total coliform levels
- source water turbidity levels
- disinfection level
- disinfectant residual entering the distribution system
- disinfectant residuals throughout the distribution system.
The monthly reports must be prepared and submitted to the Primacy Agency
within 10 days after the end of the month. The utility must maintain a daily
data log used to prepare the monthly reports. Tables 6-1 through 6-5 are
examples of daily data sheets which the utilities may find useful for logging
the data needed to prepare reports for the Primacy Agency.
Table 6-6 presents a concise format which can be used for the monthly
reports to the Primacy Agency. Tables 6-3 and 6-4 must also be submitted with
the monthly report. After the initial 12 months of reporting, the Primacy
Agency may remove the requirement for reporting the information contained in
Table 6-3 if it is satisfied that the system is computing compliance with the
CT requirements. correctly. The individual sample results summarized in the
monthly reports should be kept on file at the utility for a minimum of
5 years.
In addition to the monthly reporting requirements for source water
quality conditions and disinfection information, systems with unfiltered
supplies are also required to submit annual reports for the watershed control
program and the on-site inspection within 10 days after the end of the federal
fiscal year.
6-1
-------
The Primacy Agency will review the reports to determine whether or not
compliance has been met. A recommended report format for the watershed
control program is:
Summarize all activities in the watershed(s) for the previous year.
Identify activities or situations of actual and potential concern in
the watershed(s).
3. Describe how the utility is proceeding to address them.
The SWTR requires each system to provide the Primacy Agency with a report
of the on-site inspection unless the inspection is conducted by the Primacy
Agency. EPA suggests that:
1. A report of the inspection containing the findings, suggested
improvements and dates by which to complete improvements is to be
prepared following the initial system review.
2. To lessen the burden on utilities, a report containing results of
the general survey should be submitted in subsequent years.
In addition to these reporting requirements, the SWTR requires that the
reporting requirements of the Total Trihalomethane Regulation and the Coliform
Rule are also met.
Records of waterborne disease outbreaks also must be maintained. In the
event of a waterborne disease outbreak, as defined in part 141.2 of the SWTR,
the Primacy Agency must be notified within 48 hours.
The report of the outbreak should contain:
1. Date of occurrence
2. Type of illness
3. Number of cases
4. System conditions at the time of the outbreak, including
disinfectant residuals, pH, temperature, turbidity, and
bacteriologicol results.
The records of an outbreak must be maintained permanently.
6.2 Reporting Requirements for Public Water Systems Using Filtration
The SWTR requires filtered water systems to submit monthly reports to the
Primacy Agency for determination of compliance with the requirements for:
- treated water turbidity
- disinfectant residual entering the distribution system
- disinfectant residuals throughout the distribution system
6-2.
-------
Tables 6-7 and 6-8 present a format which the utility can use as a daily data
log and to submit monthly reports to the Primacy Agency.
Recommended Reporting Not Required by the SWTR
The Primacy Agency may also want filtered water systems to report some
information associated with recommendations made in this manual which are not
requirements of the SWTR. EPA recommends that filtered water systems:
1. Report the percent inactivation of Giardia cysts and enteric
viruses, recommended by the Primacy Agency.
2. Report point of application for all disinfectants used.
3. Report the daily CT(s) used to calculate the percent inactivation of
Giardia cysts and viruses.
4. If more than one disinfectant is used, report the CT(s) and inac-
tivation (s) achieved for each disinfectant and the total percent
inactivation achieved.
5. Report the percent inactivation determined prior to filtration and
the data used to make this determination.
6. Note any difference between the measured CT(s) and the CT required
to meet the overall minimum treatment performance requirement
specified by the Primacy Agency.
Tables 6-3 and 6-4 can be used to maintain the records necessary for numbers 2
through 6.
This information can be used to determine the disinfection level
maintained by the system to assure that the overall removal/inactivation
required is maintained.
The Primacy Agency may make provisions to minimize the reporting
requirements for systems with reservoirs, large amounts of storage or long
transmission mains which provide a long disinfectant contact time. Since
these systems -typically provide inactivation in excess of that needed, the
Primacy Agency may require the system only to report the minimum daily
residual at the end of the disinfectant contact time. The CT maintained can
then be estimated based on this residual and the contact time under the system
design flow. This method of CT determination will eliminate the need for the
system to determine the contact time under maximum flow conditions each day.
6-3
-------
TABLE 6-1
Month
Year
Page 1
Date
1
2
3
k
5
6
7
8
9
10
11
12
13
H
15
16
17
IS
SOURCE WATER QUALITY CONDITIONS FOR UNFfLTERED SVS
CoHform Measurements*
No. of Samples .
Fecal
Total
No. of Samples Meeting Specified Limits
Fecal «= 20/100 mL)
Total ((= 100/100 mL)
TEMS1
System/Treatment Plant
PWSID
Turbldits
Maximum
Turbidity
(NTU)
Measurements
Turbidity
"Event"
(Yes or No)
Notes:
1.
2.
3.
Samples are taken from the source water immediately prior to the first disinfection point included in the CT determination.
As specified in 40 CFR HI.7<»(b)(1), a fecal or total coliform sample must be taken on each day that the
system operates and a source water turbidity measurement exceeds 1 NTU.
For each day that the maximum turbidity exceeds 5 NTU, the date should be entered for the day that the State was notified
of this exceedance; e.g., "5.8-22".
A "yes" response is required each day the maximum turbidity exceeds 5 NTU and the previous day did not. This is indicative
of the beginning of a turbidity "event". The total number of "yes" responses equals the number of turbidity "events" in
the month.
-------
TABLE 6-1
Month
Year
Page 2
Date
19
20
21
22
23
24
25
26
27
28
29
30
31
Totals:
SOURCE WATER QUALITY CONDITIONS FOR UNFILTERED SYSTEMS1
System/Treatment Plant
PWSID
Colt form Measurements'
No, of Samples •
Fecal
Total
No. of Samples Meeting Specified Limits
Fecal «» 20/100 ml)
Total «= 100/100 mi.)
Turbidity
Maximum
Turbidity
(NTU)
Measurements
Turbidity
"Event"
(Yes or No)
t
Maximum daily turbidity = NTU
Total number of turbidity "events" »
-------
TABLE 6-2
Year
Month
January
February
March
April
May
June
July
August
September
October
November
December
LONG-TERM SOURCE MATER QUALITY CONDITIONS RECORD SHEET
FOR UNFILTERED SYSTEMS
System
PWSID
Treatment Plant
Collform Measurements Turbidity Measurements
No. of Samples
Fecal
' Total
No. of Samples Meeting Specified Limits
Fecal «* 20/100 ml)
Total «- 100/100 ml)
Dates with
Turbidity )5 NTU
Total
Number of
Turbidity
Events
-------
TABLE 6-3
Month
Year
CT DETERMINATION FOR UNFILTERED SYSTEMS*
System/Treatment Plant
Date
1
2
3
4
S
6
7
8
9
10
11
12
13
1*
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Disinfectant
Concentration,
C (mg/L)
-
PWSID
2
Oi si nf ectant
Contact Time,
T (min)
Disinfectant/Sequence of Application
CTcalc3
(=CxT)
PH2'"
Water
Temp
(°C)
CT99.95
(CTca1c/CT99.9)
Notes:
1.
2.
3.
4.
5.
Use a separate sheet for each disinfectant/sampling site. Enter disinfectant and
sequende position; e.g., "ozone/1st" or "C10 /3rd".
Measurement taken at peak hourly flow.
CTcalc = C (mg/L) x T (min).
Only required if the disinfectant is free chlorine.
From Tables 1.1 - 1.6, 2.1, and 3.1, 40 CFR U1,7«i(b)(3).
-------
TABLE 6-A
Month
Year
Page 1
Date
1
2
3
it
5
6
7
8
9
10
11
12
13
T>
Minimum Disinfectant Residual
at Point-of-Entry to
Distribution System(mg/L)
DISINFECTION INFORMATION FOR COMPLIANCE DETERMINATION
FOR UNFILTERED SYSTEMS
System/Treatment Plant
PWSID
(CTcalc/CT99.9)2
Disinfectant Sequence
1st
2nd
3rd
<>th
5th
6th
£ (CTcalc/CT99.9)
£ (CTcalc/CT99.9) <13
(Yes or No)
Notes:
1.
2.
For multiple disinfectants, this column must only be completed for the last disinfectant added prior to entering the distribution system.
If less than 0.2 mg/L, the duration of the period must be reported; e.g., "0.1-3 hrs".
If (CTcalc/CT99.9) (.17, no disinfection credit is given. Enter zero for that sequence. To determine I (CTcalc/CT99.9),
add (CTcalc/CT99.9) values from the first disinfectant sequence to the last.
If I (CTcalc/CT99,9) (1, a treatment technique violation has occurred, and a "yes" response must be entered.
-------
TABLE 6-
-------
TABLE 6-5
Month
Year
Page 1
Date
1
2
3
<*
5
6
7
8
9
10
It
12
13
n
15
16
17
18
19
20
21
22
23
2 it
25
26
27
28
29
30
31
Total
No. of Sites Where
Disinfectant
Residua) Measured
<=a)
a=
DISTRIBUTION SYSTEM DISINFECTANT RESIDUAL DATA
FOR UNFILTERED AND FILTERED SYSTEMS
System/ Treatment Plant
PNSID
•
No. of Sites Where No
Disinfectant Residual
Measured but HPC
Measured (=b)
b=
No. of Sites Where
Disinfectant Residual
Not Detected, No HPC
Measured (=c)
c=
No. of Sites Where
Disinfectant Residual
Not Detected,
HPC >= 500/mL (=d)
d=
No. of Sites Where
Disinfectant Residual
Not Measured,
HPC )= 500 ml (=e)
e=
V~
=(
) x 100 =
-------
TABLE 6-6
MONTHLY REPORT TO PRIMACY AGENCY FOR
COMPLIANCE DETERMINATION
UNFILTERED SYSTEMS
Month ^__________ System/Treatment Plant
Year
Page 1
bouree Water Quality Conditions
A. Cumulative number of months for which results are reported «
1. Earliest of 6 previous months and the year , e«9-» if the current reporting month ij
January 1989, the earliest of 6 previous months is July 1988.
2. Earliest of 12 previous months and the year . i.e., the current month one year ago.
3. ?arT$est of 120 previous months and the year , i.e., the current month ten years ago,
B. Coliform Criteria1
No. of Samples No. of Samples Meeting Specified Limits
Fecal Total Fecal((« 20/100 mL) Total«= 100/100 mL)
Previous 6-month cumulative: ____
Current month's: + _ + _____ + . + '
Earliest of 6 previous month's: - - - ____^______ -
Current 6-month cumulative: *» x» y» z»
Percentage of samples (* 20/100 ml fecal coliforms, F = y/w x 100 « %
Percentage of samples (= 100/100 ml total coliforms, T » z/x x 100 = %
Is F < 90% ?: Yes No 5 is T < 90% ?: Yes No
6
If F and T < 90% system is in violation — Violation?
C. Turbidity Criteria
Maximum turbidity level for reporting (current) month * NTU
Reporting Month-
Oate of
5 NTU Date Dates of 5 NTU Exceedance
Exceedance Reported Previous 12 months Previous 120 months
-------
TABLE 6-6
MONTHLY REPORT TO PRIMACY AGENCY FOR
COMPLIANCE DETERMINATION
UNFILTERED SYSTEMS (Continued)
Month • System/Treatment Plant
Year PWSID
Page 2
Number of Turbidity Events
Previous 120-month cumulative: (= PI20)
Previous 12-month cumulative: (= P12)
Earliest of 120 previous month's; (= E120)
Earliest of 12 previous month's: (= E12)
Current month: (= C)
Cunulative number of periods during which the turbidity exceeded 5 NTU in the previous 12 months
P12 - E12 + C * . If ) 2, system is in violation -- Violation?
Cumulative number of periods during which the turbidity exceeded 5 NTU in the previous 120 months
P120 - E120 + C • . If ) 5, system is in violation — Violation?
The system is in violation if the Primacy Agency does not determine that any 5 NTU exceedances during the
current month were unusual and unpredictable — Violation?
Disinfection Criteria
A. Point-of-Entry Minimum Disinfectant Residual Criteria
Days the residual was (0.2mg/L
Day Duration of Low Level
Based on the minimum disinfectant residual data reported for the month, if the residual disinfectant
concentration was less than 0.2 mg/L for more than 4 hours at one time, the system is in violation —
Violation?
B. Distribution System. Disinfectant Residual Criteria
The values of a, b, c, d, and e from Table 6-5, as specified in «> CFR HI .75 (b)(2)(iii)(A)-(E):
a« . b= , c= , d= , e=
The value of "V" from Table 6-5 calculated for the reporting month is %. If V )5%, the system
is in violation of a treatment technique -- Violation?
-------
TABLE 6-6
MONTHLY REPORT TO PRIMACY AGENCY FOR
COMPLIANCE DETERMINATION
UNFILTERED SYSTEMS (Continued)
Month System/Treatment Plant
Year PWSID
Page 3
C. Disinfection Requirement Criteria
Based on the disinfection information reported for the month in Table 6-<», if I (CTca1c/CT99.9) (1 for
any 2 days, a treatment technique violation has occurred — Treatment technique violation?
If a treatment technique violation occurred and this is the second (or higher) such violation within tii
past 12-month period, the system is in violation — Violation?
Notes:
1. The current 6-month cumulatives are required to determine whether compliance with the col iform cri;
has been achieved. These totals are calculated front: the previous 6-month cumulatives, the currn
month's, and totals from the earliest of 6 previous months.
2. Enter cumulatives as appropriate from the previous month's monthly report (Table 6-6).
3. Enter totals from Table 6-1 for the current month.
4. Enter totals from Tables 6-2 for the month and year shown in A(1), A(2), and A(3), as appropriate
5. Determine the 6-month cumulatives for the currant month by performing the indicated computations,
6. Evaluate fecal or total coliform data as appropriate -- for systems which monitor both fecal am)
coliforms only F must be 2. 90* for compliance,
7. A turbidity "event" consists of a series of consecutive days in which the maximum turbidity excee
5 NTU.
-------
TABLE 6-7
Month
Year
Page 1
Date
1
2
3
4
5
6
7
a
9
Minimum Disinfectant Residual
at Point-of-Entry to
Distribution System (mg/L)
DAILY DATA SHEET FOR
FILTERED SYSTEMS
2
Maximum Filtered Water Turbidity
Filter
#
Combined Filter
Effluent
Clear-well
Effluent
Plant
Effluent
System/Treatment Plant
PWSID
Filtration Techno 1 ogy
No. of Turbidity
Measurements
it
No. of Turbidity
Measurements (=
Specified Limit
No. of Turbidity5
Measurements
) 5 NTU
Notes:
1.
2.
For multiple disinfectants, this column must only be completed for the last disinfectant added prior to entering the distribution
system. If less than 0.2 mg/L, the duration of the period must be reported; e.g., "0.1-3 hrs".
For systems using conventional treatment, direct filtration, or technologies other than slow sand or diatomaceous earth filtration,
turbidity measurements may be taken at the combined filter effluent, clearwell effluent, or plant effluent prior to entry into the
distribution system. The turbidity may also be measured for each individual filter with a separate sheet maintained for each.
3. For continuous monitors count each
-------
TABLE fi-7
Month
Year
Page 2
Date
10
11
12
13
H
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Minimum Disinfectant Residual
at Point-of-Entry to
Distribution System (mg/L)
DAILY DATA SHEET FOR
FILTERED SYSTEMS
System/Treatment Plant
PWSID
Filtration Technology
2
Maximum Filtered Water Turbidity
Filter
i
*
Combined Filter
Effluent
Clearwell
Effluent
Plant
Effluent
Totals:
No. of Turbidity
Measurements
No. of Turbidity*
Measurements («*
Specified Limit
No. of Turbidity
Measurements
> 5 NTU
-------
TABLE 6-8
MONTHLY REPORT TO PRIMACY AGENCY
COMPLIANCE DETERMINATION - FILTERED SYSTEMS
Month _^^^^^^_^__ System/Treatment Plant
Year PWSID
Page 1
Turbidity Performance Criteria
A. Total number of filtered water turbidity measurements =
B. Total number of filtered water turbidity measurements which are less than or equal to the specified limits
for the filtration technology employed =
C. The percentage of turbidity measurements meeting the specified limits = B/A x 100
= / x 100 = %
If C ( 95%, system is in violation — Violation?
0. If the effluent turbidity exceeded 5 NTU at any time during the month, the system is in violation —
Violation?
If so, record the date and turbidity value for any measurements exceeding 5 NTU:
Date Turbidity. NTU
Disinfection Performance Criteria
A. Point-of-Entry Minimum Disinfectant Residual Criteria
Days the residual was (0.2 mg/L
Day Duration of low level
-------
TABLE 6-8
MONTHLY REPORT TO PRIMACY AGENCY
COMPLIANCE DETERMINATION - FILTERED SYSTEMS
Month System/Treatment Plant
Year PWSID
Page 2
Based on the minimum disinfectant residual data reported for the month, if the residual disinfectant
concentration was less than 0.2 mg/L for more than 4 hours at one time, the system is in violation —
Violation?
B. Distribution System Disinfectant Residual Criteria
The values a, b, c, d, and e from Table 6-5, as specified in 40 CFR U1.75(b)(2)(iii)(A)-(E):
a* , b» , c* , d* , e=
The value of "V" from Table 6-5 calculated for the reporting month is %. If V ) 5%, the system is
in violation of a treatment technique -- Violation?
If a treatment technique violation occurred and this is the second such violation in two consecutive montt
the system is in violation — Violation?
-------
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Committee Report. J.AWWA, 72(7):405-411, 1980.
Bouwer, H. Ground Water Hydrology. McGraw Hill Book Co., New York,
pp. 339-356, 1978.
Brown, T. S.; Malina, J. F., Jr.; Moore, B. D. Virus Removal by Diatomaceous
Earth Filtration - Part 1 S 2. J.AWWA 66(2):98-102, (12):735-738, 1974.
Clark, R. M. ;-Read, E. J.; Hoff, J. C. Inactivation of Giardia lamblia by
Chlorine: A Mathematical and Statistical Analysis. Unpublished Report,
EPA/600/X-87/149, DWRD, Cincinnati, OH, 1987.
Cleasby, J. L.; Hilmoe, D. J.; Dimitracopoulos, C. J. Slow-Sand and Direct
In-Line Filtration of a Surface Water. J.AWWA, 76(12}:44-55, 1984.
Cotruvo, J. A.; Vogt, C. D. USEPA Office of Drinking Water, Regulatory
Aspects of Disinfection. AWWA Seminar Proceedings, AWWA Conference, pp. 27-32,
June, 1984.
-1-
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DeWalle, F. B.; Engeset, J.; Lawrence, W. Removal of Giardia lamblia Cysts by
Drinking Water Plants. EPA-600/52-84-069, United States Environmental Pro-
tection Agency, MERL, Cincinnati, Ohio, May 1984.
Fox, K. R.; Miltner, R. J.; Logsdon, G. S.; Dicks, D. L.; Drolet, L. F. Pilot
Plant Exploration of Slow Rate Filtration. Presented at the AWWA Annual
Conference Seminar, Las Vegas, Nevada, June 1983.
Fujioka, R.; Kungskulniti, N.; Nakasone, S. Evaluation of the Presence -
Absence Test for Colifonns and the Membrane Filtration Method for Heterotro-
phic Bacteria. AWWA Technology Conference Proceedings, November, 1986.
Geldreich, E.; Nash, H.; Reasoner, D.; Taylor R. Necessity of Controlling
Bacterial Populations in Potable Waters: Community Water Supply. J.AWWA,
64:596-602, 1972.
Geldreich, E.; Greenberg, A.; Haas, C.; Ho'ff, R.; Karlin, J.; Means, E.;
Moser, R.; Regunathan, P.; Reich, K. and Victoreen, H. Microbiological
Considerations for Drinking Water Regulation Revisions, Committee Report,
Organisms in Water Committee. JAWWA, 79(5):81, 1987.
Great Lakes-Upper Mississippi River Board of State Public Health and Environ-
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Hibler, C. P. Evaluation of the 3M Filter 124A in the FS-SR 122 Type 316 S/S
#150 Housing for Removal of Giardia Cysts. Department of Pathology, Colorado
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Colorado State University, Undated.
Hoffbuhr, J. W.; Blair, J.; Bartleson, M.; Karlin, R. Use of Particulate
Analysis "for Source and Water Treatment Evaluation. AWWA Water Quality
Technology Conference Proceedings, November 1986.
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Research Laboratory, Drinking Water Research Division, Cincinnati, Ohio,
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Horn, J. B.; Hendricks, D. W. Removals of Giardia Cysts and other Particles
from Low Turbidity Waters Using the Culligan Multi-Tech Filtration System.
Engineering Research Center, Colorado State University, Unpublished, 1986.
Joost, R. D.; Long, B. W.; Jackson, L. Using Ozone as a Primary Disinfectant
for the Tucson CAP Water Treatment Plant, presented at the IOA/PAC Ozone
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Kelly, Gidley, Blair and Wolfe, Inc. Guidance Manual - Institutional Alterna-
tives for Small Water Systems. AWWA Research Foundation Contract 79-84, 1986.
-2-
-------
Kuchta, J. M.; States, S. J.; McNamara, A. M.; Wadowsky, R. M.; Yee, R. B.
Susceptibility of Legionella pneumophila to Chlorine in Tap Water. Appl.
Environ. Microbiol., 46(5): 1134-1139, 1983.
Letterman, R. D. The Filtration Requirement in the Safe Drinking Water Act
Amendments of 1986. U.S. EPA/AAAS Report, August 1986.
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Filtration Methods for Removal of Giardia Cysts and Cyst Model. J.AWWA,
73:111-118, 1981.
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February 12, 1987a.
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Giardia Cyst Removal. USEPA Drinking Water Research Division; Presented at
Calgary Giardia Conference, Calgary; Alberta, Canada, February 23-25, 1987b.
Long, R. L. Evaluation of Cartridge Filters for the Removal of Giardia
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Systems. J.AWWA, 62:11:670, 1970.
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System. Appl. Environ. Microbiol., 53(2):447-453, 1987.
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Bacteria at Each Step of Treatment During Preparation of Drinking Water at
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-------
Poynter, S. F. B.; Slade, J. S. The Removal of Viruses by Slow Sand Filtra-
tion, Prog. Wat. Tech. Vol. 9, pp. 75-88, Pergamon Press, 1977. Printed in
Great Britain.
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-4-
-------
World Health Organization Collaborating Center. Slow Sand Filtration of
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-5-
-------
- APPENDIX A
USE OF PARTICULATE ANALYSIS FOR
SOURCE AND WATER TREATMENT EVALUATION
Reprinted from 1986 Annual
Conference Proceedings, by
permission
Copyright © 1986, American
Work Works Association
-------
USE OF PARTICULATE ANALYSIS FOR SOURCE
AND WATER TREATMENT EVALUATION
Jack w. Hoffbuhr; P.E.
Deputy Director
Water Management Division
U.S. E.P.A., Region 8
Denver, Colorado 8202-2413
John Blair, P.E.
District Engineer
Colorado Department of Health
Grand Junction, Colorado 81501
Michael Bartleson
Director of Water Treatment Operations
City of Broomfield
Brcornfield, Colorado 80020
Richard Karlin, P.E.
Chief, Drinking Water Section
Colorado Department of Health
Denver, Colorado 80220
Coliform bacteria and turbidity have been traditional procedures for
evaluating the quality of source waters and the effectiveness of treatment
processes. Many water systems have used these measures exclusively to deter-
mine the microbiological quality of their finished water. This sense of
security has been severly diminished in recent years due to the increasing
frequency of reported waterborne disease outbreaks where' water quality was
judged to be excellent by the traditional measures. It is evident that
additional tools are needed to determine the quality of source and treated
waters. The recent enactment of the 1986 Amendments to the Safe Drinking
Water Act (SDWA) also highlights this need.
Background
Giardia Lamblia has become a most famous (or infamous) parasite to the
water utility industry. Its presence in source waters across the U.S. and
role in numerous waterborne outbreaks has:
1. Emphasized the importance of the multiple barrier concept in water
treatment;
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2. Illustrated the need for additional techniques to evaluate the
quality of water; and
3. Caused a major increase in sampling and analysis for Giardia
These points were clearly emphasized in epidemiological and engineering
studies conducted by the Colorado Department of Health (1) . These studies
also indicated that all surface waters are susceptible to contamination by
Giardia. As a result, the Department of Health adopted regulations requiring
filtration of all surface water sources.
Ground water sources weren't included since it was felt that they were
protected by the natural barrier provided by the layers of earth. However, it
quickly became apparent that not all ground waters are created equally. Wells
and springs that are properly sited, designed and constructed certainly
provide a larger degree of protection from contamination due to surface
influences. However, many alluvial wells plus wells and springs that are
poorly constructed don't provide that same level of protection.
Infiltration galleries fall into a gray area since they can collect
surface and ground water. In most cases, they are heavily influenced by
surface water conditions.
It was clear that a technique was needed to determine if the so-called
ground waters were susceptible to surface water and, therefore, Giardia
contamination. Sanitary surveys can identify problem areas and potential
pathways- of contamination but aren't conclusive evidence. Turbidity and
coliform results, as shown by the previous study aren't reliable indicators
(1).
Sampling to determine the presence of only Giardia cysts isn't helpful
either since not finding Giardia in a single sample doesn't obviate the
potential for -contamination. However, the sampling and analysis procedure for
Giardia does offer a useful alternative. A variety of other particulate
matter is trapped on the sampling filter and appears on the microscope slide
along with any Giardia cysts. These particulates can be identified and
evaluated to provide a valuable insight into the quality of the water.
To further explore the usefulness of this procedure the Colorado Depart-
ment of Health conducted a study of 70 water systems in Colorado. (A special
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study examined 10 systems in depth (2)). The Region 8 office of the Environ-
mental Protection Agency conducted a study of SO systems in Wyoming using the
same procedures (3). The objectives of the studies were to (1) identify
particulate types that, by their presence in water, indicate surface water
contamination and (2) to determine the efficacy of water treatment systems.
This paper discusses the results obtained pertaining primarily to the first
objective.
Methods
The 150 systems selected for the studies included surface water sources,
wells, springs and infiltration galleries. This paper presents the results of
16 systems representing a cross-section of both studies.
Untreated source water was sampled at each site using a one micron
cartridge filter apparatus and the protocols for pathogenic protozoans de-
scribed in the 16th edition of Standard methods (4). All samples were shipped
packed in ice and analyzed within 48 hours. The Colorado samples were an-
alyzed by the Health Department's Parasitology Laboratory. Split samples were
analyzed by Or. Charles Hibler at Colorado State University for quality
control. The Wyoming samples were all analyzed by Or. Hibler. In all cases
the particulate analysis was conducted using the zinc sulfate flotation
techniques (4,5). This procedure does not produce 100 percent cyst recovery
or precise particulate analysis, but it does provide results which provide
invaluable information about the quality of the sampled water.
The particulate analyses provided results for 14 particulate categories
which have been summarized into 12 groups for purposes of this paper. The
particulates, except for Giardia, were enumerated using the general quantities
shown in Table 1. For Giardia cysts the numbers shown are estimated total
numbers of cysts -in the samples.
Discussion of Results
The particulate categories shown in Table 2 constitute a broad spectrun
of what could be found in water. Not all of them are good indicators of
surface water contamination of ground water. By considering these categories
in detail a more concise list of possible indicators can be developed.
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Sediment - Includes all the particulate matter in a sample. Since
this group is so inclusive, it is not a good indicator.
Amorphous Debris - Consists of pieces of silica, decaying vegeta-
tion, micro-organisms and unrecognizable matter with a wide size
range. Since this material is non-specific and ubiquitous in all
water sources it is not a good indicator.
Algae - Comprises a large group of microorganisms which have a wide
variety of sizes and shapes. Algae have been found in all types of
water sources, therefore, as a group they are not a good indicator.
Diatoms - A particular type of algae that contain silica in their
cell walls. Since diatoms require sunlight they are not normally
found in ground water, therefore they are a good indicator.
Plant Debris - This category consists of undigested fecal material
from herbivorous mammals such as beavers and muskrats. This catego-
ry should be an excellent indicator of animal activity in the
watershed and of surface water influence.
Giardia - This infamous protozoan pathogen ranges in size from
7-14 microns. The organism is transported by beavers, muskrats,
dogs, humans and other mammals. In the cyst form the organism is
fairly resistant to environmental conditions and chlorine. Giardia
cysts are excellent indicators of surface water influence.
Free-living and Parasitic Nematodes - Worm-like microorganisms that
can exist in a wide variety of water environments including filter
beds, infiltration galleries and wells, therefore, they are not good
indicators.
Coccidia - Host specific parasites found in animals and fish. They
range in size from 10 to 20 microns and make excellent indicators of
surface water influence.
Pollen - Powder-like material produced by plants and found every-
where, therefore not a good indicator.
Protozoa (other than Giardia cysts) - Microorganisms which live in a
variety of water sources, therefore they are not good indicators.
Crustacea - Large microorganisms ranging in size from 250 to 500 mi-
crons, with eggs from 50 to 150 microns. Since they can live in
many types of water sources they are not good indicators of surface
water influence. However, their presence in finished water can
indicate poor treatment performance.
Insects - This category includes insects, insect parts, larvae and
eggs. Since many insects live in or near surface water they can be
good indicators.
-------
- Rotifers - Microscopic animals commonly found in surface waters
ranging in size from 150 - 600 microns. They require sunlight so
are good indicators of surface water influence.
Based on these points, the list of particulate types that can indicate a
surface water impact on ground water are shown in Table 3. A key to their
usefulness is that they are the same size or larger than Giardia cysts. If
they are not removed by natural processes in the earth or by treatment pro-
cesses, Giardia cysts probably would not be removed either. Therefore, the
presence of these indicator particulates in wells, springs, infiltration
galleries or treatment plant effluents indicates that these water systems are
also at risk of becoming contaminated by Giardia cysts.
The particulate data from the studies were reviewed to determine if the
above reasoning was valid. Table 4 shows data from 16 of the water systems
surveyed. The symbols used are the same as those in Table 1.
The streams contained a broad spectrum of all the particulate types
including Giardia cysts. The influence of animals on these sources is in-
dicated by the presence of plant debris, coccidia and Giardia. It is clear
that if adequate treatment isn't provided to these sources that the respective
water systems would be at risk.
The infiltration galleries (except for gallery 5} also contained a wide
range of particulate matter including plant debris and Giardia cysts. This
indicates that little filtering action was being accomplished by galleries 6,
7, and 8. These installations had collection systems buried from a few inches
to about six feet below the streams. Gallery. 5 had a collection system
constructed 10 feet deep and 20 feet away from and parallel to the stream
which allowed for better filtration. Many times infiltration galleries are
constructed as low cost alternatives to more complete treatment. It is
evident that such installations may be providing a false sense of security.
The well data indicate a much different pattern. The wells only con-
tained a few particulate types and, with the exception of well 12, none of the
types indicated surface water intrusion. The characteristics of these wells
are listed by Table 5. Wells 9 and 11 would have the most potential for
contamination (assuming the geologic formations are roughly the same and good
construction practices were followed) since they are closest to surface water.
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Well 12 did exhibit some plant debris and should be investigated further.
Well 9 showed the smallest amount of particulate matter. However, a sample
taken during the spring runoff contained plant debris and Giardia cysts which
illustrate an important consideration. Since surface water quality can
fluctuate widely, judgments based on one sample can lead to serious errors.
The springs showed even less particulate matter than the wells.
Spring 14 did contain rotifers and spring 16 some plant debris indicating
surface water influence. The sanitary surveys revealed that the catchment
areas in both cases were not fenced and there was evidence of heavy animal and
human traffic, illustrating the importance of proper source protection.
Overall, the data support the indicators shown by Table 3. The six
particulate types are present in surface waters and absent in properly pro-
tected ground waters. The results of these studies indicate that particulate
analysis can provide an excellent tool in evaluating source water quality, the
potential for surface water contamination of ground water and the effective-
ness of infiltration galleries.
Conclusions
1. Particulate analysis can provide valuable information for evaluating
source water quality, the potential for surface water contamination
of ground waters and the effectiveness of infiltration galleries.
2. Diatoms, rotifers, coccidia, plant debris, insect parts and Giardia
cysts are valid indicators of surface water contamination of ground
- water systems.
3. Infiltration galleries are providing a false sense of security in
many instances particularly if the collection system is directly
under the stream. Infiltration galleries must be carefully evalu-
ated to determine if treatment beyond chlorination is needed.
4. Sampling for particulate analysis should be done seasonally to gain
an understanding of the fluctuation of surface water quality and the
impact on ground water.
5. Particulate analysis can also provide information on the effective-
ness of water treatment processes in removing particulate matter.
Acknowledgements
The authors express their sincere thanks to Mr. Kurt Albrecht of the
Colorado Department of Health's Laboratory Division and Dr. Charles Hibler and
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his staff at Colorado State University's Pathology Laboratory. Mr. Albrecht
spent many hours analyzing the samples. Dr. Hibler and his staff analyzed
numerous samples and provided expert advice on the studies.
References
1. Karlin, R.V. and Hopkins, R.S., "Engineering Defects Associated With
Colorado Giardiasis Outbreaks June 1980 - June 1982." Proc. AWWA
ACE, Las Vegas, Nev. (June 1983).
2. Bartleson, M.E. "Particulate Indicators for Assessing Protected
Ground Water Sources and Water Treatment Efficacy." Report to
Colorado Dept. of Health, Denver, Co. (June 1986).
3. Wiley, B.R., Harman, D.J., and Benjes, Jr., H.H. "Survey and
Evaluation of 80 Public Water Systems in Wyoming - Project Summary."
Culp/Wesner/Culp, Denver, Co. (January 1986).
4. Standard Methods for the Examination of Water and Wastewater, APHA,
AWWA & WPCF, Washington, D.C. (16th ed., 1985).
5. Logsdon, G.S., et. all "Control of Giardia Cysts By Filtration:
The Laboratory's Role." Proc. AWWA WQTC, Norfolk, Va. (December
1983) .
-------
TABLE 1
PARTICULATE ANALYSIS QUANTITY DESIGNATIONS
Symbol
EH
H
M
S
0
R
VR
T
Verbal Rating
Extremely heavy
Heavy
Moderate
Small
Occasional
Rare
Very rare
Trace
Description
4 or more particles per microscope
field
3 particles per microscope field
2 particles per microscope field
1 particle per microscope filed
1 "particle every 3 or 4 microscope
fields
2 to 3 particles in entire slide
1 particle in entire slide
Visual observation, typically used
only for sediment
N None Not detected
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TABLE 2
SUMMARY OF PARTICULATE TYPES
Sediment: Coccidia
Large Amorphous Debris Pollen
Fine Amorphous Debris Protozoa
Algae Crustacea
Diatoms Insect Parts & Larvae
Plant Debris Rotifers
Giardia
Free Living & Parasitic Nematodes
-------
TABLE 3
PARTICULATE TYPES INDICATING SURFACE WATER
Diatoms Plant Debris
Rotifers Insect Parts & Larvae
Coccidia Giardia
-------
TABLE 4
•RESULTS OF PARTICIPATE ANALYSES
Source
Infiltration
Particulate Type
Amorphous Material
Protozoa
Algae
Diatoms
Plant Debris
Nematodes
Rotifers
Crustacea
Coccidia
Insect Parts
Pollen
Giardia Cysts
Streams
1
H
T
T
H
O
T
N
N
T
R
N
4
2
M
T
T
T
O
M
I)
T
T
VR
N
20
3
0
R
R
O
II
N
R
R
R
R
N
98
4
O
R
O
O
S
0
R
0
N
O
O
129
Galleries
5
M
T
N
R
0
T
N
N
N
R
N
N
6
M
T
H
H
T
T
N
T
R
H
T
80
7
M
T
EH
T
T
T
R
N
N
N
N
20
8
0
N
R '
O
M
O
N
O
0
O
O
71
9
S
N
T
N
N
N
N
11
N
U
N
U
Wells
10
M
R
H
N
N
0 .
N
U
N
N
N
N
11
S
R
N
N
N
N
N
N
N
N
N
N
12
H
T
N
N
T
N
N
N
N
N
N
N
13
R
R
T
N
N
N
N
N
N
N
N
N
Springs
14
R
N
N
N
N
N
R
N
N
N
N
N
15
0
R
0
N
N
N
N
N
N
N
O
N
16
T
N
N
N
T
T
N
N
N
N
T
N
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TABLE 5
V7ELL CHARACTERISTICS
Source
9
10
11
12
Depth, ft.
100
40
60
72
• i
Distance From Stream, ft.
20
300
20
100
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APPENDIX B
INSTITUTIONAL CONTROL OF LEGIONELLA
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APPENDIX B
INSTITUTIONAL CONTROL OF LEGIONELLA
Introduction
Legionella is a genus name for bacteria commonly found in lake and river
waters. Some species of this genus have been identified as the cause of the
disease legionellosis. In particular, Legionella pneumophila has been
identified as the cause of Legionnaires disease, the pneumonia form of
legionellosis and with Pontiac Fever, a nonpneumonia disease. Outbreaks of
legionellosis are primarily associated with inhalation of water aerosols or,
less commonly, with drinking water containing Legionella bacteria with
specific virulence factors not yet identified. Foodborne outbreaks have not
been reported (USEPA, 1985).
As discussed in this document, treatment requirements for disinfection of
a municipal water supply are thought to provide at least a 3 log reduction of
Legionella bacteria (see Section 3.2.2). However, some recontamination may
occur in the distribution system due to cross connections and during
installation and repair of water mains. It has been hypothesized that the low
concentrations of Legionella entering buildings due to these sources may
colonize and regrow in hot water systems (USEPA, 1985). Although all of the
criteria required for colonization are not known, large institutions, such as
hospitals, hotels, and public buildings with recirculating hot water systems
seem to.be the most susceptible. The control of Legionella in health care
institutions, such as hospitals, is particularly important due to the
increased susceptibility of many of the patients.
The colonization and growth of Legionella in drinking water primarily
occurs within the consumer's plumbing systems after the water leaves the
distribution .system. Therefore, the control of these organisms must be the
consumer's responsibility. This appendix is intended to provide guidance to
these institutions for the detection and control of the Legionella bacteria.
Monitoring
It is suggested that hospitals, and other institutions with potential for
the growth of Legionella, conduct routine monitoring of their hot water
3-1
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systems at least quarterly. The analytical procedures for the detection of
these organisms can be found in Section 912.1 "Legionellaceae" of the 16th
edition of Standard Methods. Samples should be taken at, or closely
following, the hot water storage reservoir and from a number of shower heads.
It is recommended that showers with the least frequent usage be included in
the sampling program. Follow-up testing is suggested for all positive
indications prior to the initiation of any remedial measures. If the the
presence of Legionella is confirmed, then remedial measures should be taken.
Although the regrowth of Legionella is commonly associated with hot water
systems, hot and cold water interconnections may provide a pathway for cross
contamination. For this reason, systems detecting Legionella in hot water
systems should also monitor their 'cold water systems.
Treatment
Because the primary route of exposure to Legionella is probably
inhalation, rather than ingestion, it is recommended that disinfection
procedures include an initial shock treatment period to disinfect shower heads
and hot water taps where the bacteria may colonize and later become airborne.
The shock treatment period should also include disinfection of hot water
tanks. After this time, a point-of entry treatment system can be installed to
provide continual disinfection of the hot water system.
Initial Disinfection
The. most applicable method for the initial disinfection of shower heads
and water taps is heat eradication. The fittings can be removed and held at
temperatures greater than 60 C for at least 24 hours. Disinfection of fit-
tings can also be achieved by soaking or rinsing with a strong chlorine
solution. When soaking the fittings, a minimum chlorine strength of 50 mg/L
should be used for a period of no less than 3 hours. Rinsing with chlorine
should be performed with more concentrated solutions. Care nust be taken not
1. Monitoring frequency based on the reported rate of Legionella
regrowth observed during disinfection studies (USEPA, 1985).
3-2
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to corrode the finished surface on the fittings. Commercially available
bleaches, for example, are typically 5.25 percent chlorine by weight.
Long-Term Disinfection
Heat - Numerous studies have shown that increasing the hot water tempera-
ture to 50 - 70 C over a period of several hours may help to reduce and
inhibit Legionella populations. However, some instances of regrowth after 3
to 6 months have been reported. In these cases, the authors have concluded
that a periodic schedule of short-term temperature elevation in the hot water
may be an effective control against legionellosis (USEPA, 1985; Muraca, 1986).
Disinfection by this method also requires periodic flushing of faucets and
shower heads with hot water. Although heat eradication is easily implemented
and relatively inexpensive, a disadvantage is the potential need for periodic
disinfection. The potential for scalding from the unusually hot water also
exists (USEPA, 1985; Muraca, et al. 1986).
Chlorination - Several studies have suggested that a free chlorine
residual of 4 mg/L will eradicate Legionella growth. There is, however, a
possibility for recontamination in areas of the system where the chlorine
residual drops below this level. A stringent monitoring program is therefore
required to ensure that the proper residual is maintained throughout the
system and under varying flow conditions. It may also be necessary to apply a
large initial chlorine dose to maintain the 4 mg/L residual. This may cause
problems of pipe corrosion and, depending on water quality, high levels of
trihalomethanes (THMs).
Ozone - Ozone is the most powerful oxidant used in the potable water
industry. One study indicated that an ozone dosage of 1 to 2 mg/L was suffi-
cient to provide a 5 log reduction of Legionella (Muraca, et al. 1986). Ozone
is generated by passing a high voltage current of electricity through a stream
of dry air or oxygen. The use of high voltage electricity requires proper
handling to avoid creating hazardous conditions. The ozone is applied by
bubbling the ozone containing gas through the water in a chamber called a
contactor.
One of the disadvantages of this system is its complexity. It requires a
dry air or oxygen source, a generator, and a contactor sized to provide 2 to 5
minutes of contact time and an ambient ozone monitor. All materials in
3-3
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contact with the ozone must be constructed of special ozone resistant mat-
erials to prevent leakage. Leak detection is also required because of the
toxic nature of ozone and possible explosive conditions if pure oxygen is used
for generation.
Another disadvantage of ozonation is the rapid decomposition of ozone
residuals. The half-life of ozone in drinking water is typically around 10
minutes. This makes it difficult, if not impossible, to maintain a residual
throughout the water system and may require the use of a supplementary
disinfectant such as chlorine or heat. For these reasons it is not thought
that ozonation is viable for institutional applications.
Ultraviolet Irradiation - Ultraviolet (UV) light, in the 254 nanometer
wavelength range can be used as a disinfectant. UV systems typically contain
low-pressure mercury vapor lamps to maximize output in the 254 nm range.
Water entering the unit passes through a clear cylinder while the lamp is on,
exposing bacteria to the UV light. Because UV light can not pass through
ordinary window glass, special* glass or quartz sleeves are used to assure
adequate exposure.
t
The intensity of UV irradiation is measured in microwatt-seconds per
square centimeter (uW-s/cm2). Several studies have shown a 90 percent reduc-
tion of Legionella with a UV dosage of 1000 - 3000 uW-s/cm2, compared to 2000
to 5000 uW-s/cm2 for E. coli, Salmonella and Pseudpmonas (USEPA, 1985). In
another study, a 5 log reduction of Legionella was .achieved at 30,000
uW-s/cm2j and the reduction was more rapid than with both ozone and chlorine
disinfection (Muraca, et al. 1986).
The major advantage of UV disinfection is that it does not require the
addition of chemicals. This eliminates the storage and feed problems associ-
ated with the use of chlorine, chlorine dioxide and chloramines. In addition,
the only maintenance required is periodic cleaning of the quartz sleeve and
replacement of bulbs. UV monitors are available which measure the light
intensity reaching the water and provides a signal to the user when
maintenance is required. These monitors are strongly suggested for any
application of UV irradiation for disinfection. It should be noted, however,
that these monitors measure light intensity which may not be directly related
to disinfection efficiency. The UV lamps should therefore not be operated
past the manufacturers use rating even with a continuous L'V monitor installed.
3-4
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Another disadvantage of UV disinfection, as with ozonation, is that a
residual is not provided. A supplementary disinfectant may therefore be
required to provide protection throughout the system. In addition, turbidity
may interfere with UV disinfection by blocking the passage of light to the
microorganisms.
Other Control Methods - In addition to chemical and heat disinfection,
there are system modifications which can be made to inhibit Legionella growth.
Many institutions have large hot water tanks heated by coils located midway in
the tank. This type of design may result in areas near the bottom of the tank
which are not hot enough to kill Legionella. Designing tanks for more even
distribution of heat may help limit bacterial colonization. In addition,
sediment build-up in the bottom of storage tanks provides a surface for
colonization. Periodic draining and cleaning may therefore help control
growth. Additionally, other studies have found that hot water systems with
stand-by hot water tanks used for meeting peak demands, still tested positive
for Legionella despite using elevated temperature (55 C) and chlorination
(2 ppm) (Fisher-Hoch, et al. 1984.) Stringent procedures for the cleaning,
disinfection and monitoring of these stagnant tanks should be set up and
followed on a regular basis.
In another study, it was reported that black rubber washers and gaskets
supported Legionella growth by providing habitats protected from heat and
chlorine; It was found, after replacement of the black rubber washers with
Proteus BO compound washers, that it was not possible to detect Legionella
from any of the fixtures (Colbourne, et al. 1984).
Conclusions
Legionella bacteria have been identified as the cause of the disease
legionellosis., of which the most serious form is Legionnaires Disease.
Although conventional water treatment practices are sufficient to provide
disinfection of Legionella, regrowth in buildings with large hot water
heaters, and especially with recirculating hot water systems, is a significant
problem. This problem is of particular concern to health care institutions,
such as hospitals, where patients may be more susceptible to the disease.
3-5
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This guideline suggests a program of quarterly monitoring for Legionella.
If the monitoring program suggests a potential problem with these organisms, a
two stage disinfection program is suggested consisting of an initial period of
shock treatment followed by long term disinfection.
Four methods of disinfection for the control of Legionella were presented
in this appendix; heat, chlorination, ozonation, and ultraviolet irradiation.
All four of the methods have proven effective in killing Legionella.
Ultraviolet irradiation and heat eradication are the suggested methods of
disinfection due, primarily, to advantages in monitoring and maintenance.
However, site specific factors may make chlorination or ozonation more feas-
ible for certain applications. In addition, it is recommended that all
outlets, fixtures and shower heads be inspected and all black rubber washers
and gaskets replaced with materials which do not support the growth of
Legionella organisms.
One problem associated with the application of point-of-entry treatment
systems is the lack of an approved program for certifying performance claims.
However, the National Sanitation Foundation (NSF), Ann Arbor, MI an
unofficial, non-profit organization, does have a testing program to verify
disinfection efficiencies and materials of construction. Certification by the
NSF, or other equivalent organizations, is desirable when selecting a
treatment system.
References
Colbourne, J.; Smith, M. G.; Fisher-Hoch, S. P. and Harper, D. Source of
Legionella pneumophila Infection in a Hospital Hot Water System: Materials
Used in Water Fittings Capable of Supporting L. pneumophila Growth. In:
Thornsberry, C.; Balows, A.; Feeley, J. C. and Jakubowski, w. Legionella -
Proceedings of the 2nd International Symposium. American Society for
Microbiology, pp. 305-307, 1984.
Fisher-Hoch, S. P.; Smith, M.G.; Harper, D. and Colbourne, J. Source of
Legionella pneumonia in a Hospital Hot Water System, pp. 302-304 in
Thornsberry, C.; Balows, A.; Feeley, J.C. and Jakubowski, W. Legionella
Proceedings of the 2nd International Symposium, American Society for
Microbiology, pp. 302-304, 1984.
3-6
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Muraca, P.; Stout, J. E. and Yu, V. L. Comparative Assessment of Chlorine,
Heat, Ozone, and UV Light for Killing Legionella pneumophila Within a Model
Plumbing System. Appl. Environ. Microbiol. 53(2):447-453, 1986.
U.S. Environmental Protection Agency, Office of Drinking Water. Control of
Legionella in Plumbing Systems, Health Advisory (1985).
3-7
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APPENDIX C
DETERMINATION OF DISINFECTANT
CONTACT TIME
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APPENDIX C
DETERMINATION OF DISINFECTANT CONTACT TIME
As indicated in Section 3, for pipelines, all fluid passing through the
pipe is assumed to have a detention time equal to the theoretical or mean
residence time at a particular flow rate. However, in mixing basins, storage
reservoirs, and other treatment plant process units, utilities may be required
to determine the contact time for the calculation of CT through tracer studies
or other methods approved by the Primacy Agency.
For the purpose of determining compliance with the disinfection require-
ments of the SWTR, the contact time of mixing basins and storage reservoirs
used in calculating CT should be the detention time which is equalled or
exceeded by ninety percent (90%) of the fluid passing through the system.
This has been designated as T according to the convention adopted by
Thirumurthi (1969). A profile of the flow through the basins over time can be
generated by tracer studies. Information provided by these studies is used
for estimating the detention time, T , required for calculating CT.
This appendix is divided into two sections. The first section presents a
brief synopsis of tracer study methods, procedures, and data evaluation. In
addition, an example is presented for a hypothetical tracer study conducted to
determine the T contact time in a clearwell. The second section presents a
method of determining T from theoretical detention times in systems where it
is impractical to conduct tracer studies.
C.I Tracer Studies
Tracer Study Considerations
Because detention time (T) is proportional to flow rate (Q), a relation-
ship between these parameters is necessary to determine T under different flow
conditions. Therefore, tracer tests should be performed for at least four
flow rates. The flow rates should be separated by approximately equal
intervals with one near average flow, two greater than average, and one at a
.less than average flow. The flows should also be selected to avoid
extrapolating to more than 110 percent of the highest tested flow.
C - 1
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Under normal treatment plant operation, the plant flow is indicative of
the flow passing through any particular process unit. An increase or re-
duction in plant flow will impart a proportional change in flow through each
process unit in the plant's treatment train. Therefore, "flow rate" in the
previous paragraph refers to plant flow.
In addition to plant flow, detention times determined by tracer studies
are also dependent on the water level in the contact basin. This is particu-
larly pertinent to storage tanks and clearwells which are often used as
equalization storage for distribution system demands, as well as being contact
basins for disinfection. In such instances, the water levels in the reser-
voirs vary to meet the system demands. The actual detention time of these
contact basins will also vary depending on whether they are emptying or
filling.
Tracer studies should be conducted during periods when the water level is
maintained in accordance with normal plant operation. In the ideal case where
the water level is maintained at a near constant level, that is, flow in
equals flow out, the detention time determined by tracer tests is valid for
calculating CT when the tank is operating at water levels greater than or
equal to the level at which the test was performed. If the water level during
testing increases above the normal operating level, the resulting concen-
tration profile will predict an erroneously high detention time. Conversely,
extremely low water levels during testing may lead to an overly conservative
contact time. Therefore, when a tracer study is conducted to determine the
contact time of a basin with a constant water level, the recommended test
procedure is to maintain the basin's water level at or slightly below, but not
above, the normal operating level.
For many plants, the water level in a clearwell or storage tank varies
between high and low levels in response to distribution system demands. In
such instances, in order to obtain a conservative estimate of the contact
time, the tracer study should be conducted during a period when the tank level
is falling (flow out greater than flow in). This procedure will provide a
detention time for the contact basin which is also valid when the water level
is rising (flow out less than flow in) from a level which is at or above the
level at which the T detention time was determined during the tracer study.
C - 2
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Whether the water level is constant or variable, the tracer study should be
repeated for several different plant flows, as described above.
For clearwells which are operated with extreme variations in water level,
conducting a tracer study is impractical. Under such operating conditions, a
reliable detention time is not provided for disinfection, and disinfection
contact time will need to be provided elsewhere in the system.
Detention time may also be influenced by differences in water temperature
within the plant. For plants with potential for thermal stratification,
additional tracer studies are suggested under the various seasonal conditions
which are likely to occur. The contact times determined by the tracer studies
under the various seasonal conditions should remain valid as long as no
physical changes are made to the mixing basin(s) or storage reservoir(s).
As defined in Section 3.2.2, the portion of the system with a measurable
contact time between two points of disinfection or residual monitoring is
referred to as a section. For systems which apply disinfectant(s) at more
than one point, or choose to profile the residual from one point of applica-
tion, tracer studies should be conducted to determine T for each section
containing process unit(s). The T • obtained for a section is used along with
the residual disinfectant concentration prior to the next disinfectant appli-
cation or monitoring point to determine the CT for that section. The
C3i±C
inactivation ratio for the section is then determined. The total inactivation
achieved in the system is the "sum" of the inactivation ratios for all
sections, and the log inactivation can be determined from this total as
explained in Section 3.2.2.
Systems with more than one section in the treatment plant should begin
sequential tracer studies at the last section and complete the studies with
the first section of the treatment train. Therefore, residual concentrations
of the tracer material will not affect successive tracer studies, and the
required time for performing the studies will be minimized.
If disinfectant application and/or residual monitoring is discontinued at
any point between two sections with known T values, the sum of these indi-
vidual T values should be used in calculating CT for the combined sections.
This detention time is conservative in terms of calculating CT. A separate
C - 3
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tracer study could be conducted for the combined sections, resulting in a
greater T Q value.
When conducting tracer studies in ozone contactors, flocculators or any
basin containing mixing, tracer studies should be conducted for the range of
mixing used in the process. In ozone contactors, air should be added in lieu
of ozone to prevent degradation of the tracer. Tracer studies should then be
conducted at several air to water ratios to provide data for the complete
range of ratios used at the plant. For flocculators, tracer studies should be
conducted for various mixing intensities to provide data for the complete
range of operations.
Tracer Study Methods
Tracer study methods involve the application of chemical dosages to a
system and tracking the resulting effluent concentration as a function of
time. An evaluation of the effluent concentration profile is used for de-
termining the detention time, T . Two common methods of tracer addition
employed in water treatment evaluations are available:
the step-dose method
the slug-dose method
The step-dose method entails introduction of a tracer chemical at a
constant dosage until the concentration at the desired endpoint reaches a
steady-state level. Step-dose method tracer studies are. frequently employed
in drinking water applications for the following reasons:
- the resulting normalized concentration vs. time profile is directly
used to determine, T , the contact time required for calculating CT
- very often, the necessary feed equipment is available to provide a
constant rate of application of the tracer chemical
One other advantage of the step-dosage method is that the data may be
verified by comparing the concentration vs. elapsed time profile for samples
collected at the start of dosing with the profile obtained when the tracer
feed is discontinued.
Alternatively, with the slug-dose method, a large instantaneous dose of
tracer is added to the water and timed as it passes through 'the mixing basin
or storage reservoir. A disadvantage of this technique is that very concen-
trated solutions are needed for the dose in order to adequately define the
C - 4
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concentration versus time profile. Intensive mixing may therefore be required
to minimize potential density-current effects. Other disadvantages of using
the slug-dose method include:
- the resulting concentration vs. time profile cannot be used to
directly determine T without further mathematical manipulation
- a mass balance on the treatment section is required to determine
whether the tracer was completely recovered
For these reasons, the step-dose method is more easily applied in drinking
water tracer studies and will be discussed for the remainder of this section.
Tracer Selection
The first step in any tracer study is the selection of a chemical to be
used as the tracer. The most common tracer chemicals employed in drinking
water plants are chloride and fluoride. Both of these chemicals are readily
available, conservative (that is, they are not consumed or removed during
treatment), and are easily monitored. These chemicals are also nontoxic and
approved for potable water use.
Tracer Addition
The tracer chemical should be added at the same point(s) in the treatment
train as the disinfectant to be used in the CT calculations.
The duration of tracer addition is mainly dependent on the volume of the
contact basin, and hence, its theoretical detention time. In order to ap-
proach a steady-state concentration in the contact basin effluent, the dose
usually should be continued for a period of two to three times the theoretical
detention time (Hudson, 1981) .
In all cases, the tracer chemical should be dosed in sufficient concen-
tration to easily monitor a residual at the contact basin outlet throughout
the test. The required tracer chemical concentration, is generally dependent
upon the nature of the chosen tracer chemical, including its background
concentration, and the mixing characteristics of the contact basin to be
tested. Recommended chloride doses for step-method tracer studies where the
background chloride level is less than 10 mg/L are on the order of 20 mg/L
(Hudson, 1975). Also, fluoride concentrations as low as 1.0 to 1.5 mg/L are
practical when the raw water fluoride level is not significant (Hudson, 1975).
However, tracer studies conducted on systems suffering from serious
C - 5
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shortcircuiting of flow may require substantially larger step-doses. This
would be necessary to detect the tracer chemical and to adequately define the
effluent tracer concentration profile.
Test Procedure
In preparation for beginning a tracer study, the raw water background
concentration of the chosen tracer chemical must be established. The
background concentration is essential, not only for aiding in the selection of
the tracer dosage, but also to facilitate proper evaluation of the data.
Pre-tracer study monitoring should be performed at the same sampling
point(s) selected for the tracer study to determine that the tracer concen-
tration is at or below this background level. The monitoring procedure is
outlined in the following steps:
- If the tracer chemical is normally added for treatment, discontinue
its addition to the water in sufficient time to permit the tracer
concentration to recede to its background level before the test is
begun.
- Prior to the start of the test, regardless of whether the chosen
tracer material is a treatment chemical, the tracer concentration in
the water is monitored at the sampling point where the disinfectant
residual will be measured for CT calculations.
- If a background tracer concentration is detected, monitor it until a
constant concentration, at or below the raw water background level
is achieved. This measured concentration is the baseline tracer
concentration.
Following the determination of the tracer dosage, feed and monitoring
point(s), and a baseline tracer concentration, tracer testing can begin.
At time zero, the tracer chemical feed will be started and left at a
constant rate for the duration of the test. Over the course of the test, the
tracer residual should be monitored at the required sampling point(s) every 2
to 3 minutes to provide data for a well-defined plot of tracer concentration
vs. time. Depending on the size of the contact basin and flow (theoretical
residence time), less frequent residual monitoring may be possible until a
change in residual concentration is first detected. In systems which have a
theoretical detention time greater than 2 hours, sampling may be conducted
every 10 minutes for the first 40 minutes, or until a tracer concentration
above the baseline level is first detected. At this time, sampling should
C - 6
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continue at 2 to 3-minute intervals until the residual concentration reaches a
steady-state value. The time and tracer residual of each measurement should
be recorded on a data sheet. In addition, the water level, plant flow, and
temperature should be recorded during the test.
If verification of the test is desired, the tracer feed should be discon-
tinued, and the receding tracer concentration at the effluent should be
nonitored at the same frequency until tracer concentrations corresponding to
the background level are detected. The time at which tracer feed is stopped
is time zero for the receding tracer test and must be noted. The receding
tracer test will provide a replicate set of measurements which can be compared
with data derived from the rising tracer concentration vs. time curve.
Data Evaluation
Data from tracer studies should be summarized in tables of time and
residual concentration. These data are then analyzed to determine the deten-
tion time, T to be used in calculating CT. The TIQ values may be found by
a graphical method. This method involves plotting a graph of diraensionless
concentration vs. time and reading the value for T directly from the graph
at the appropriate dimensionless concentration. The specific details and
steps involved with this method of data evaluation are illustrated in the
following example.
Data Evaluation for Determining T in a Clearwell
A tracer study employing the step-dose method of tracer addition was
conducted" for a clearwell with a theoretical detention time, T, of 30 minutes
at an average plant flow of 2.5 MGD. Because fluoride is added at the inlet
to the clearwell as a water treatment chemical, necessary feed equipment was
in place for dosing a constant concentration of fluoride throughout the tracer
study. Based on this convenience, fluoride was chosen as the tracer chemical.
Prior to the start of testing, a fluoride baseline concentration of 0.2 mg/L
was established for the water exiting the clearwell. A constant fluoride
dosage of 2.0 mg/L was added to the clearwell inlet. Fluoride levels in the
clearwell effluent were monitored and recorded every 3 minutes. The raw
tracer study data, along with the results of further analyses are shown in
Table C-l.
C - 7
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TABLE C-l
CLEARWELL TRACER TEST DATA
(1,2,3)
t, minutes
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
Fluoride Concentration
Measured, mg/L
0.20
0.20
0.20
0.20
0.29
0.67
0.94
1.04
1.44
1.55
1.52
1.73
1.93
1.85
1.92
2.02
1.97
1.84
2.06
2.05
2.10
2.14
Tracer, mg/L
0
0
0
0
0.09
0.47
0.74
0.84
1.24
' 1.35
1.32
1.53
1.73
1.65
1.72
1.82
1.77
1.64
1.86
1.85
1.90
1.94
Normalized, C/Co
0
0
0
0
0.045
0.24
0.37
0.42
0.62
0.68
0.66
0.76
0.86
0.82
0.86
0.91
0.88
0.82
0.93
0.92
0.95
0.96
Notes:
1.
2.
3.
Measured cone. = Tracer cone. + Baseline cone.
Baseline cone. =0.2 mg/L, fluoride dose =2.0 mg/L
Tracer cone. = Measured cone. - Baseline cone.
-------
The steps in evaluating the raw data shown in the first and second
columns of Table C-l are as follows for the graphical method of analysis.
First, the baseline fluoride concentration, 0.2 mg/L, is subtracted from the
measured concentration to give the fluoride concentration resulting from the
tracer study addition alone. For example, at elapsed time = 39 minutes, the
tracer fluoride concentration, C, is obtained as follows:
C = C - C
measured baseline
= 1.85 mg/L - 0.2 mg/L
= 1.65 mg/L
This calculation was repeated at each time interval to obtain the data shown
in the third column of Table C-l. As indicated, the fluoride concentration
rises from 0 mg/L at t = 0 minutes to the applied fluoride dosage of 2 mg/L,
at t = 63 minutes.
The next step is to normalize or develop dimensionless concentrations by
dividing the tracer concentrations in the second column of Table C-l by the
applied fluoride dosage, Co = 2 mg/L. For time = 39 minutes, C/Co is cal-
culated as follows:
C/Co = (1.65 mg/L)/(2.0 mg/L)
= 0.82
The resulting normalized data, presented in the fourth column of Table C-l, is
the basis- for completing the determination of TIQ.
In order to determine T by the graphical method, a plot of C/Co vs.
time should be generated using the data in Table C-l. A smooth curve should
be drawn through the data as shown on Figure C-l.
T is read directly from the graph at a dimensionless concentration
(C/Co) corresponding to the time for which 10 percent of the tracer has passed
at the effluent end of the contact basin (TIQ). For step-dose method tracer
studies, this normalized concentration is C/Co = 0.10 (Levenspiel, 1972).
T should be read directly from Figure C-l at C/Co = 0.1 by first
drawing a horizontal line (C/Co = 0.1) from the Y-axis (t = 0) to its inter-
section with the smooth curve drawn through the data. At this point of
intersection, the time read from the X-axis is TIQ and may be found by
C - 3
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RGURE 0-1
C/Co vs. Time
Graphical Analysis for T10
o
10
20 30 40 50
TIME (MINUTES)
-------
extending a vertical line downward to the X-axis. These steps have been
performed as illustrated on Figure C-l, resulting in a value for T of
approximately 13 minutes.
Plant Flow Dependency of T
As previously stated, tests should be conducted for at least four plant
flows. The TIQ detention time should be determined by the above procedure for
each of the tested plant flows. The detention times should then be plotted
versus plant flow. For the example presented in the previous section, tracer
studies were conducted at additional plant flows of 1.1, 4.2, and 5.6 MGD.
The T values at the various plant flows are:
Plant Flow T
1.1 20
2.5 13
4.2 7
5.6 4
T data for these tracer studies were plotted as a function of the plant
flow, Q, as shown on Figure C-2.
C.2 Determination of T Without Conducting a Tracer Study
In some situations, conducting tracer studies for determining the
disinfectant contact time, T10/ may be impractical or prohibitively expensive.
The limitations may include a lack of funds, manpower or equipment necessary
to conduct the study. For these cases, the Primacy Agency may allow the use
of standard fractions representing the ratio of T to T, and the theoretical
detention time, to determine the detention time, T , to be used for
calculating CT values. This method for finding T involves multiplying the
theoretical detention time by the fraction, T /T, that is representative of
the particular contact basin configuration for which T is desired.
Tracer studies conducted by Marske and Boyle (1973) and Hudson (1975) on
chlorine contact chambers and flocculators/settlirg basins, respectively, were
used as a basis in determining representative T10/T values for various basin
configurations. Marske and Boyle (1973) performed tracer studies on 15 dis-
tinctly different types of full-scale chlorine contact chambers to evaluate
design characteristics that affect the actual detention time. Hudson (1975)
- 9
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35
30
25
RGURE C-2
Detention Time vs. Flow
CO
LU
20
O 15
10
AVERAGE
MAXIMUM
EXTRAPOLATION
I
23456
PLANT FLOW (MGD)
8
-------
conducted 16 tracer tests on several flocculation and settling basins at six
water treatment plants to identify the effect of flocculator baffling and
settling basin inlet and outlet design characteristics on the actual detention
time.
Impact of Design Characteristics
The design characteristics evaluated include: length-to-width ratio, the
degree of baffling within the contact basins, and the effect of inlet baffling
and outlet weir configuration. These physical characteristics of the contact
basins affect their hydraulic efficiencies in terms of dead space, plug flow,
and mixed flow proportions. The dead space zone of a basin is basin volume
through which no flow occurs. The remaining volume where flow occurs is
comprised of plug flow and mixed flow zones. The plug flow zone is the
portion of the remaining volume in which no mixing occurs in the direction of
flow. The mixed flow zone is characterized by complete mixing in the flow
direction and is the complement to the plug flow zone. All of these zones
were identified in the studies for each contact basin. Comparisons were then
made between the basin configurations and the observed flow conditions and
design characteristics.
The ratio T10/T was calculated from the data presented in the studies and
compared to its associated hydraulic flow characteristics. Both studies
resulted in T10/T values which ranged from 0.3 to 0.7. The results of the
studies indicate a correlation between T /T and the contact basin baffling
conditions, particularly at the inlet and outlet to the basin. As the basin
baffling conditions improved, higher T /T values were observed, with the
outlet conditions generally having a greater impact than the inlet conditions.
As discovered from the results of the tracer studies performed by Marske
and Boyle (1973) and Hudson (1975) , the effectiveness of baffling in achieving
a high T10/T fraction is more related to the quality of the baffling design
than the nature and function of the contact basin in which it is utilized.
For this reason, T /T values may be defined for three levels of baffling
conditions rather than for particular types of contact basins. General
guidelines were developed relating the T /T values from these studies to the
respective baffling characteristics. These guidelines can be used to
determine the T values for specific basins.
C - 10
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Baffling Classifications
The purpose of baffling is to maximize utilization of basin volume,
increase the plug flow zone in the basin, and minimize short circuiting. Some
form of baffling at the inlet and outlet of the basins is used to evenly
distribute flow across the basin. Additional baffling may be provided within
the interior of the basin (intra-basin) in circumstances requiring a greater
degree of flow distribution or redistribution. Ideal baffling design reduces
the inlet and outlet flow velocities, distributes the water as uniformly as
practical over the cross section of the basin, minimizes mixing with the water
already in the basin, and prevents entering water from short circuiting to the
basin outlet as the result of wind or density current effects. Three general
classifications of baffling conditions — poor, average, and superior — were
developed to categorize the results of the tracer studies for use in determin-
ing T from the theoretical detention time of a specific basin. The T /T
fractions associated with each degree of baffling are summarized in Table C-2.
Factors representing the ratio between T and the theoretical detention time
for plug flow in pipelines and flow in a completely mixed chamber have been
included in Table C-2 for comparative purposes. However, in practice the
theoretical T /T values of 1.0 for plug flow and 0.1 for mixed flow are
seldom achieved because of the potential effect of dead space, which reduces
their actual values by a proportional amount. Conversely, the T /T values
shown for the intermediate baffling conditions already incorporate the effect
of the dead space zone, as well as the plug flow zone, because they were
derived empirically rather than from theory.
As indicated in Table C-2, poor baffling conditions consist of an unbaf-
fled inlet and outlet with no intra-basin baffling. Average baffling con-
ditions consist of intra-basin baffling and either a baffled inlet or outlet.
Superior baffling conditions consist of at least a baffled inlet and outlet,
and possibly some intra-basin baffling to redistribute the flow throughout the
basin's cross-section.
The three basic types of basin inlet baffling configurations are: a
target-baffled pipe inlet, an overflow weir entrance, and a baffled submerged
orifice or port inlet. Typical intra-basin baffling structures include:
diffuser (perforated) walls; launders; cross, longitudinal, or maze baffling
C - 11
-------
to cause horizontal or vertical serpentine flow; and longitudinal divider
walls, which prevent mixing by increasing the length-to-width ratio of the
basin(s). Commonly used baffled outlet structures include free-discharging
weir, e.g., sharpcrested and V-notch, and submerged ports or weirs. Weirs
that do not span the width of the contact basin, such as Cipolleti weirs,
should not be considered baffling as their use may substantially increase weir
overflow rates and the dead space zone of the basin.
Examples of Baffling
Examples of these levels of baffling conditions for rectangular and
circular basins are explained and illustrated in the following section.
Typical uses of various forms of baffled and unbaffled inlet and outlet
structures are also illustrated.
The plan and section of a rectangular contact basin with poor baffling
conditions, which can be attributed to the unbaffled inlet and outlet pipes,
is illustrated on Figure C-3. The flow pattern shown in the plan view indi-
cates straight-through flow with dead space occurring in the regions between
the individual pipe inlets and outlets. The section view reveals additional
dead space from a vertical perspective in the upper inlet and lower outlet
corners of the contact basin. Vertical mixing also occurs as bottom density
currents induce a counter-clockwise flow in the upper water layers.
The inlet flow distribution is markedly improved by the addition of an
inlet diffuser wall and intra-basin baffling as shown on Figure C-4. However,
only average baffling conditions are achieved for the basin as a whole because
of the inadequate outlet structure — a Cipolleti weir. The width of the weir
is short in comparison with the width of the contact basin. Consequently,
dead space exists in the corners of the contact basin, as shown by the plan
view. In addition, the small weir width causes a high weir overflow rate,
which results in short circuiting in the center of the contact basin.
Superior baffling conditions are exemplified by the flow pattern and
physical characteristics of the contact basin shown on Figure C-5. The inlet
to the basin consists of submerged, target-baffled ports. This inlet design
serves to reduce the velocity of the incoming water and distribute it uniform-
ly throughout the basin's cross-section. The outlet structure is a sharp-
crested weir which extends for the entire width of the contact basin. This
C - 12
-------
PLAN
(
/\.
77.
,
f,
3
3
>
SECTION
FIGURE C-3 POOR BAFFLING CONDITIONS --
RECTANGULAR CONTACT BASIN
-------
I I
PLAN
r
SECTION
FIGURE C-4 AVERAGE BAFFLING CONDITIONS
RECTANGULAR CONTACT BASIN
-------
X
171
Vf
^y
\
;
v
^
•••B
/
^
PLAN
/I
/
X
>
X
/
n-*-
/
X
r\
'
xx/
X
SECTION
FIGURE C-5 SUPERIOR BAFFLING CONDITIONS
RECTANGULAR CONTACT BASIN
-------
type of outlet structure will reduce short circuiting and decrease the dead
space fraction of the basin, although the overflow weir does create some dead
space at the lower corners of the effluent end. These inlet and outlet
structures are by themselves sufficient to attain superior baffling con-
ditions; however, maze-type intra-basin baffling was included as an example of
how this type of baffling aids in flow redistribution within a contact basin.
The plan and section of a circular contact basin with poor baffling
conditions, which can be attributed to flow short circuiting from the center
feed well directly to the effluent trough is shown on Figure C-6. Short
circuiting occurs in spite of the outlet weir configuration because the center
feed inlet is not baffled. The inlet flow distribution is improved somewhat
on Figure C-7 by the addition of an annular ring baffle at the inlet which
causes the inlet flow to be distributed throughout a greater portion of the
basin's available volume. However, the baffling conditions in this contact
basin are only average because the inlet center feed arrangement does not
entirely prevent short circuiting through the upper levels of the basin.
Superior baffling conditions are attained in the contact basin configura-
tion shown on Figure C-8 through the addition of a perforated inlet baffle and
submerged orifice outlet ports. As indicated by the flow pattern, more of the
basin's volume is utilized due to uniform flow distribution created by the
perforated baffle. Short circuiting is also minimized because only a small
portion of flow passes directly through the perforated baffle wall from the
inlet to the outlet ports.
Additional Considerations
Flocculation basins and ozone contactors represent water treatment
processes with slightly different characteristics from those presented in
Figures C-3 through C-8 because of the additional effects of mechanical
agitation and mixing from ozone addition, respectively. Studies by Hudson
(1975) indicated that a single-compartment flocculator had a T /T value less
than 0.3, corresponding to a dead space 'zone of about 20 percent and a very
high mixed flow zone of greater than 90 percent. In this study two four-
compartment flocculators, one with and the other without mechanical agitation,
exhibited Tin/T va^-ues ^n *-he range of 0.5 to 0.7. This observation
C - 13
-------
PLAN
SECTION
FIGURE C-6 POOR BAFFLING CONDITIONS
CIRCULAR CONTACT BASIN
-------
PLAN
i^
/fZ"
/////////////////// / / / / s
SECTION
FIGURE C-7 AVERAGE BAFFLING CONDITIONS
CIRCULAR CONTACT BASIN
-------
PLAN
SECTION
FIGURE C-8 SUPERIOR BAFFLING CONDITIONS
CIRCULAR CONTACT BASIN
-------
indicates that not only will compartmentation result in higher T10/T values
through better flow distribution, but also that the effects of agitation
intensity on T /T are reduced where sufficient baffling exists. Therefore,
regardless of the extent of agitation, baffled (two or more compartments)
flocculation basins should be considered to possess average baffling
conditions (T /T = 0.5), whereas unbaffled (single compartment) flocculation
basins are characteristic of poor baffling conditions (TIO/T = 0.3).
Similarly, multiple stage ozone contactors are baffled contact basins
which show characteristics of average baffling conditions. Single stage ozone
contactors should be considered as being poorly baffled. However, circular,
turbine ozone contactors may exhibit flow distribution characteristics which
approach those of completely mixed basins, with a T10/T of 0.1, as a result of
the intense mixing.
In many cases, settling basins are directly connected to the
flocculators. Data from Hudson (1975) indicates that poor baffling conditions
at the flocculator/settling basin interface can result in backmixing from the
settling basin to the flocculator. Therefore, settling basins that have inte-
grated flocculators without effective inlet baffling should be considered as
poorly baffled, with a T /T of 0.3, regardless of the outlet conditions,
unless intra-basin baffling is employed to redistribute flow. If intra-basin
and outlet baffling is utilized, then the baffling conditions should be
considered average with a T1O/T of 0.5.
Filters are special treatment units because their design and function is
dependent on flow distribution that is completely uniform. Except for a small
portion of flow which short circuits the filter media by channeling along the
walls of the filter, filter media baffling provides a high percentage of flow
uniformity and can be considered superior baffling conditions for the purpose
of determining T . As such, the T value can be obtained by subtracting the
volume of the filter media, support gravel, and underdrains from the total
volume and calculating the theoretical detention time by dividing this volume
by the flow through the filter. The theoretical detention tine is then
multiplied by a factor of 0.7, corresponding to superior baffling conditions,
to determine the T value.
C - 14
-------
Conclusions
The recommended T10/T values and examples are presented as a guideline
for use by the Primacy Agency in determining T values in site specific
conditions and when tracer studies cannot be performed because of practical
considerations. Selection of T10/T values in the absence of tracer studies
was restricted to a qualitative assessment based on currently available data
for the relationship between contact basin baffling conditions and their
associated T10/T values. Conditions which are combinations or variations of
the above examples may exist and warrant the use of intermediate T /T values
such as 0.4 or 0.6. As more data on tracer studies become available, specif-
ically correlations between other physical characteristics of contact basins
and the flow distribution efficiency parameters, further refinements to the
T /T fractions and definitions of baffling conditions may be appropriate.
References
Hudson, H. E. , Jr.. "Residence Times in Pretreatment", J. AWWA, pp. 45-52,
January, 1975.
Hudson, H. E. , Jr.. Water Clarification Processes; Practical Design and
Evaluation, Van Nostrand Reinhold Company, New York, 1981.
Levenspiel, 0.. Chemical Reaction Engineering, John Wiley £ Sons, New York,
1972.
Marske, D. M. and Boyle, J. D.. "Chlorine Contact Chamber Design - A Field
Evaluation", Water and Sewage Works, pp. 70-77, January, 1973.
Thirumurthi, D.. "A Break-through in the Tracer Studies of Sedimentation
Tanks", J. WPCF, pp. R405-R418, November, 1969.
-------
APPENDIX E
INACTIVATIONS ACHIEVED
3Y VARIOUS DISINFECTANTS
-------
TABLE E-1
CT VALUES FOR 1NACTIVATION
OF CIARDIA CYSTS BY FREE CHLORINE
AT 0.5 C
CHLORINE
CONCENTRATION •
(ng/L>
o0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
CHLORINE
rnurPiiTPATtfm *
IUNWCN 1 KA 1 1 UH *
(ag/D
<«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8-
3
CHLORINE
rnumiTV AT I ny
I WHICH I KM I I UH
«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
0.5
23
24
24
25
25
26
26
27
28
28
29
»
30
30
0.5
40
40
41
42
43
44
46
47
48
50
50
51
52
53
0.5
65
68
70
73
75
77
80
82
83
85
87
Of
91
92
PH«6
Log Inactivations
1.0 1.5 2.0 2.5 3.0
46 69 91 114 137
47 71 94 118 141
48 73 97 121 145
49 74 99 123 148
51 76 101 127 152
52 78 103 129 155
52 79 105 131 157
54 81 108 135 162
55 83 110 138 165
56 85 113 141 169
57 86 115 143 172
SB 88 117 146 175
59 89 119 148 178
60 91 121 151 181
pH»7.5
Leg Inactivations
1.0 1.5 2.0 2.5 3.0
79 119 158 198 237
80 ltd lav IT* ti'j
82 123 164 205 246
84 127 169 211 253
86 130 173 216 259
89 133 177 222 266
91 137 182 228 273
93 140 186 233 279
95 143 191 238 286
99 149 198 248 297
99 149 199 248 298
101 152 203 253 304
103 155 207 258 310
105 158 211 263 316
pN-9.0
Leg Inactivations
1.0 1.5 2.0 2.5 3.0
130 195 260 325 390
136 204 271 339 407
141 211 281 352 422
146 219 291 364 437
ISO 226 301 376 451
155 232 309 387 464
159 239 318 398 477
163 245 326 408 489
167 250 333 417 500
170 256 341 426 511
174 261 348 435 522
178 267 355 444 533
181 272 362 453 5- T
184 276 368 460 552
0.5
27
28
29
29
30
31
32
32
33
T/
34
35
36
36
0.5
46
io
49
51
52
54
55
56
58
59
60
61
63
64
Log
1.0
54
56
57
59
60
61
63
64
66
*7
68
70
71
72
Log
1.0
92
;.
98
101
104
107
110
113
115
118
120
123
125
127
pH«6.5
p«»7.0
Inactivations
1.5
' 82
84
86
88
90
92
95
97
99
101
103
105
107
109
2.0
109
112
115
117
120
123
126
129
131
134
137
139
142
145
pH*8.0
2.5
136
140
143
147
150
153
158
161
164
168
171
174
178
181
3.0
163
168
172
176
180
184
189
193
197
201
205
209
213
217
0.5
33
33
34
35
36
37
38
39
J9
40
41
42
43
44
Inactivations
1.5
139
1*3
148
152
157
161
165
169
173
177
181
184
188
191
2.0
185
191
197
203
209
214
219
225
231
235
241
245
250
255
2.5
231
238
246
253
261
268
274
282
288
294
301
307
313
318
3.0
277
286
295
304
313
321
329
338
346
353
361
368
375
382
Note: CTOQ {
0.5
55
57
42
44
46
48
SO
68
70
71
73
74
75
77
109
1.0
65
67
68
70
72
74
75
77
79
81
82
84
86
87
log
1.0
110
114
85
88
92
96
99
136
139
142
145
148
151
153
Inactivations
1.5
98
100
103
105
108
111
113
116
118
121
124
126
129
131
pi
2.0
130
133
137
140
143
147
151
154
157
161
165
168
171
174
H=8.s
2.5 3.0
163 195
167 200
171 205
175 210
179 215
184 221
188 226
193 231
197 236
202 242
206 247
210 252
214 257
218 261
Inactivations
1.5
165
171
127
133
138
144
149
204
209
213
218
222
226
230
=CT for 3-loq
2.0
219
228
169
177
184
191
198
271
278
284
290
296
301
307
2.5 3.0
274 J29
285 342
212 254
221 265
230 276
239 287
248 297
339 407
348 417
355 426
363 435
370 444
377 452
383 460
inactivatii
-------
TABLE E-2
CT VALUES FOR IMACT I VAT I ON
OF 5IAROIA CTSTS BY FREE CHLORINE
AT 5 C
CHLORINE
CONCENTRATION
(ng/L)
<«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
CHLORINE
CONCENTRATION •
(ng/L)
<-0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2*6
2.8
3
CHLORINE
CONCENTRATION
(•9/L)
•»0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
O.S
16
17
17
18
18
18
19
19
19
20
20
20
21
21
O.S
28
29
29
30
31
31
32
33
33
34
35
36
36
37
0.5
47
49
SO
52
53
55
56
SB
59
60
61
63
64
65
Log
1.0
32
33
34
35
36
36
37
38
39
39
40
41
41
42
Log
1.0
55
57
58
60
61
62
64
65
67
68
70
71
72
74
Log
1.0
93
97
100
104
107
110
112
115
118
120
123
125
127
130
pH»6
Inactivations
1.5 2.0 2.5
49 65 81
SO 67 83
52 69 86
53 70 88
54 71 89
55 73 91
56 74 93
57 76 95
58 77 97
59 79 98
60 80 100
61 81 102
62 S3 103
63 84 105
pN>7.5
Inactivations
1.5 2.0 2.5
83 111 138
86 114 143
88 117 146
90 119 149
92 122 153
94 125 156
96 128 160
98 131 163
100 133 167
102 136 170
IDS 139 174
107 142 178
109 US 181
111 147 184
pH«9.0
Inactivations
1.5 2.0 2.S
140 186 233
146 194 243
1S1 201 251
1S6 208 260
160 213 267
16S 219 274
169 225 281
173 230 288
177 235 294
181 241 301
184 245 307
IBS 2SO 313
191 255 318
195 259 J24
pH-6.5
Log Inactivations
3.0
97
100
103
105
107
109
111
114
116
118
120
122
124
126
0.5
20
20
20
21
21
22
22
23
23
23
24
24
25
25
1.0 1.5
39 59
40 60
41 61
42 63
42 64
43 65
44 66
45 68
46 69
47 70
48 72
49 73
49 74
SO 76
2.0 2.5
78 98
80 100
81 102
S3 104
85 106
87 108
88 110
90 113
92 115
93 117
95 119
97 122
99 123
101 126
pH«8.0
3.0
117
120
122
125
127
130
132
135
133
140
143
146
148
151
0.5
23
24
24
25
25
26
26
27
28
28
29
29
30
30
Log Inactivations
3.0
166
171
175
179
183
187
192
196
200
204
209
213
217
221
3.0
279
291
301
312
320
329
337
345
353
361
368
375
382
339
33
34
35
36
37
38
39
40
41
41
42
43
44
45
AX 04
68 102
70 105
72 108
74 111
76 114
77 116
79 119
81 122
83 124
84 127
86 129
88 132
89 134
13? 165
136 170
140 175
144 180
147 184
151 189
155 193
159 198
162 203
165 207
169 211
172 215
175 219
179 223
3>%
.0
198
204
210
216
221
227
232
238
243
248.
253
258
263
268
fJote: CTQQ =
O.S
39
41
42
43
45
46
47
48
49
50
51
52
53
54
pH*7.0
Log Inactivations
1.0
46
48
49
50
51
52
53
54
55
56
57
58
59
61
Log
1.0
79
C i
84
87
89
91
94
96
98
100
102
104
106
108
1.5 2.0
70 93
72 95
73 97
75 99
76 101
78 103
79 105
81 108
83 r.O
85 113
86 115
88 117
89 119
91 121
pH*8.5
2-5 3.0
1 '6 139
•19 uj
122 U6
124 U9
127 152
129 155
132 15g
135 162
138 165
141 ;:?
1*3 172
146 175
148 178
152 182
Inactivations
1.5 2.0
118 157
.;; 163
126 163
130 173
134 178
137 183
141 187
144 191
147 196
150 200
153 204
156 208
159 212
162 216
2.S 3.0
197 236
203 2(4
210 252
217 260
223 267
228 274
234 281
239 287
245 274
2SO 300
255 304
260 312
265 318
270 324
CT for 3-Toq inactivatif
-------
TABLE E-3
CT VALUES FOR INACTIVATIOH
OF GIAROIA CYSTS BY FREE CHLORINE
AT 10 C
f>H«6
CHLORINE
CONCENTRATION
(ng/L)
<*0.«
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
Log Inactivations
0.5
12
13
13
13
13
U
14
U
IS
15
15
15
16
16
1.0
24
25
26
26
27
27
28
29
29
30
30
31
31
32
1.5
37
38
39
40
40
41
42
43
44
45
45
46
47
48
2.0
49
50
52
S3
S3
55
55
57
58
59
60
61
62
63
2.5
61
63
65
66
67
68
69
72
73
74
75
77
78
79
3.0
73
75
78
79
80
82
83
86
22
23
23
24
25
25
26
26
27
27
28
1.0
42
43
n
45
46
47
48
49
50
51
52
S3
54
55
1.5
63
64
66
67
69
70
72
74
75
77
79
80
82
83
2.0
83
85
87
89
91
93
96
98
100
102
105
107
109
111
2.5
104
107
109
112
114
117
120
123
125
128
131
133
136
138
3.0
125
128
131
134
137
140
144
147
ISO
153
157
160
163
166
0.5
25
26
26
27
28
28
29
30
30
31
32
32
33
34
pH«8.0
Log Inactivations
1.0
50
51
53
54
55
57
58
60
61
62
63
65
66
67
1.5
75
77
79
81
83
85
87
90
91
93
95
97
. 9*
101
2.0
99
102
105
108
111
113
116
119
121
124
127
129
131
134
2.5
124
128
132
135
138
142
145
149
152
155
158
162
164
168
3.0
149
153
158
162
166
170
174
179
182
186
190
194
197
201
0 S
30
3i
32
33
33
34
35
36
37
38
38
39
40
41
pH«8.5
Log Inactivations -
1.0
59
6.
63
65
67
69
70
72
74
75
77
78
80
81
1.5
89
TC
95
98
100
103
106
108
111
113
115
117
120
122
2.0
118
lta»
126
130
133
137
141
143
147
150
153
156
159
162
2.5
us
><«tf
158
163
167
172
176
179
184
188
192
195
199
203
177
189
195
200
206
211
215
221
225
230
234
239
243
pH-9.0
CHLORINE Log Inactivations
CONCENTRATION
-------
TABU E-4
CT VALUES FOR 1NACTIVATION
OF GIARDIA CYSTS BY FREE CHLORINE
AT 15 C
CHLORINE
CONCENTRATION
C«g/L>
«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
CHLORINE
CONCENTRATION
(•a/i)
«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
" 3
pH«6
p»U6.5
Log Inactivations
0.5
10
10
10
10
10
10
11
1.0
16
17
17
18
18
18
19
19
19
20
20
20
21
21
1.5
25
25
26
27
27
28
28
2?
29
30
30
31
31
32
2.0
33
33
35
35
36
37
37
38
39
W
40
41
41
42
pH-7.5
2.5
41
42
43
44
45
46
47
48
48
49
50
51
52
53
3.0
49
50
52
53
54
55
56
57
58
59
60
61
62
63
O.S
10
10
10
11
11
11
11
11
12
12
12
12
12
13
Log Inactivations
O.S
14
14
IS
IS
15
16
16
16
17
17
18
18
IB
19
1.0
28
?9
29
30
31
31
32
33
33
34
35
36
36
37
1.5
42
43
44
45
46
47
48
49
SO
51
53
54
55
56
2.0
55
57
59
60
61
63
64
65
67
68
70
71
73
74
2.5
69
72
73
75
77
78
80
82
83
85
88
89
91
93
3.0
83
86
88
90
92
94
96
98
100
102
105
107
109
111
O.S
17
17
i»
18
19
19
19
20
20
21
21
22
22
22
Log Inactivations
1.0
20
20
20
21
21
22
22
23
23
23
24
24
25
25
1.5
30
30
31
32
32
33
33
34
35
35
36
37
37
38
2.0
39
40
41
42
43
43
44
45
46
47
48
49
49
51
pd-a.O
2.5
49
50
51
S3
53
54
55
57
58
58
60
61
62
63
3.0
59
60
61
63
64
65
66
68
69
70
72
73
74
76
0.5
12
12
12
13
13
13
13
14
14
14
14
IS
IS
15
Log Inactivations
1.0
33
34
«
36
37
38
39
40
41
41
42
43
44
45
1.5
50
51
S3
54
56
57
58
60
61
62
64
65
66
67
2.0
66
68
70
72
74
76
77
79
81
83
85
86
88
89
2.5
83
85
88
90
93
95
97
99
102
103
106
108
110
112
3.0
99
102
105
108
111
114
116
119
122
124
127 .
129
132
134
O.S
20
20
21
22
22
23
24
24
25
25
26
26
27
27
P»U7.0
Log Inactivations
1.0
23
24
24
25
25
26
26
27
28
28
29
29
30
30
1.5
35
36
37
38
38
39
40
41
42
43
43
44
45
46
2.0
47
48
49
SO
51
52
53
54
5K
57
57
59
59
61
PH«8.5
2.5
58
60
61
63
63
£5
66
68
"0
71
72
73
74
76
3.0
Tn
fw
75
ft
7»
I)
ye
13
7A
fQ
78
10
70
tr
8'
*1
84
89
91
Log Inactivations
1.0
39
41
42
43
45
46
47
48
49
50
51
52
S3
54
1.5
59
61
63
65
67
69
71
72
74
75
77
78
80
81
2.0
79
81
84
87
89
91
94
96
98
100
102
104
106
103
2.5
98
102
105
108
112
114
118
120
123
125
128
130
133
135
3.0
118
122
126
130
134
137
141
144
U7
ISO
153
154
159
162
ptW.O
CHLORINE Log Inactivations
CONCENTRATION
(•g/L) O.S 1.0 1.5 2.0 2.5 3.0
«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
23
24
25
26
27
28
28
29
30
30
31
31
32
33
47
49
SO
52
53
SS
56
58
59
60
61
63
64
65
70
73
76
78
80
83
85
87
89
91
92
94
94
98
93
97
101
104
107
110
113
IIS
118
121
123
125
12'
130
117
122
126
130
133
138
141
144
148
151
153
157
159
163
140
146
151
156
160
165
169
173
177
181
184
188
191
195
Note: CTgg g= CT for 3-1 og inactivaticn
-------
TABLE E-5
CT VALUES FOR INACTIVATION
OF GIAROIA CYSTS BY FREE CHLORINE
AT 20 C
CHLORINE
rfiuraiTRATlOM ' -
UUMVCN 1 KM 1 * IM
<«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
CHLORINE
CONCENTRATION -
008/L)
«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
CHLORINE
CONCENTRATION
(•9/L)
«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
pH«6
Log Inactivations
0.5 1.0 1.5 2.0 2.5 3.0
6 12 18 24 30 36
6 13 19 25 32 38
7 13 20 26 33 39
7 13 20 26 33 39
7 13 20 27 33 40
7 14 21 27 34 41
7 14 21 28 35 42
7 14 22 29 36 43
7 15 22 29 37 44
7 IS 22 29 37 44
8 15 23 30 38 45
8 IS 23 31 38 46
8 16 24 31 39 47
8 16 24 31 39 47
pH«7.5
Log Inactivations
0.5 1.0 1.5 2.0 2.5 3.0
10 21 31 41 52 62
11 21 32 43 53 6*
11 22 33 44 55 66
11 22 34 45 56 67
12 23 35 46 58 69
12 23 35 47 58 70
12 24 36 48 60 72
12 25 37 49 62 74
13 25 38 50 63 75
13 26 39 51 64 77
13 26 39 52 65 78
13 27 40 53 67 80
14 27 41 54 68 81
14 28 42 55 69 83
pH«9.0
Log Inactivations
18 35 53 70 88 105
18 36 55 73 91 109
19 38 57 75 94 113
20 39 59 78 98 117
20 40 60 80 100 120
21 41 62 82 103 123
21 42 63 W 105 126
22 43 65 86 108 129
22 44 66 88 110 132
23 45 68 90 113 135
23 46 69 92 115 138
24 47 71 94 118 141
24 48 72 95 119 143
24 49 73 97 122 146
pH«6.5
O.S
7
10
Log
1.0
15
15
15
16
16
16
17
17
17
18
18
18
19
19
Inactivations
1.5
22
23
23
24
24
25
25
26
76
27
27
28
28
29
2.0
29
30
31
31
32
33
33
34
35
35
36
37
37
38
2.5
37
38
38
39
40
41
42
43
43
44
45
46
47
48
3.0
44
45
46
47
48
49
50
51
52
53
54
55
56
57
Log
O.S 1
9
9
9
9
10
10
10
10
10
11
11
11
11
11
.0
17
18
18
19
19
19
20
20
21
21
22
22
22
23
pH»7.0
Inactivations
1.5
26
27
28
28
29
29
30
31
31
-;
33
33
34
34
pH*8.0
0.5
12
ij
13
14
14
14
15
15
IS
16
16
16
17
17
Log
1.0
25
ia
26
27
28
28
29
30
30
31
32
32
33
34
Inactivations
1.5
37
ji
40
41
42
43
44
45
46
" 47
48
49
50
51
Note
2.0
49
J 1
53
54
55
57
S3
59
61
62
63
65
66
67
:
2.5
62
o.
66
68
69
71
73
74
76
78
79
81
83
84
CTog
5 "
3.0
74
r*
79
81
83
85
87
39
91
93
95
97
99
101
q =
• •
L09
O.S 1
15
15
16
16
17
17
18
18
18
19
19
20
20
20
CT for
.0
30
31
32
33
33
34
35
36
37
33
33
39
40
41
2.0
35
36
37
37
38
39
39
41
41
i;
43
44
45
45
pH=8.5
2.5 3.0
43 S2
45 54
46 55
47 56
48 57
48 53
49 59
51 61
52 62
53 63
54 65
55 66
56 67
57 63
Inactivations*
1.5
45
46
48
49
50
52
53
54
55
57
58
59
60
61
3-log
2.0
59
61
63
65
67
69
70
72
73
75
77
78
79
81
2.5 3.0
74 89
77 92
79 95
32 98
33 100
86 103
88 105
90 108
92 110
94 113
96 115
98 117
99 119
102 122
Inactivatio
-------
TABU E-6
CT VALUES FOR IN ACTIVATION
OF CIAROIA CYSTS BY FREE CHLORINE
AT 25 C
CHLORINE
CONCENTRATION
(•g/D
«0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
pH«6
Log Inactivation*
0.5 1.0 1.5
4
4
4
4
5
5
5
12
13
13
13
14
14
14
5 10 15
5 10 15
5 10 15
5 10 15
5 10 16
5 10 16
5 11
16
2.0
16
17
17
17
18
18
19
19
19
20
20
21
21
21
pH.7.5
2.5
20
21
22
22
23
23
23
24
24
25
25
26
26
27
3.0
24
25
26
26
27
27
28
29
29
30
30
31
31
32
0.5
5
5
5
5
5
6
6
6
6
6
6
6
6
6
pH«6.S
Log Inactivations
1.0
10
10
10
10
11
11
11
11
12
•^
12
12
12
13
1.5
15
15
16
16
16
17
17
17
18
18
18
19
19
19
2.0
19
20
21
21
21
22
22
23
23
23
24
25
25
25
pH«8.0
2.5
24
25
26
26
27
28
28
28
29
29
30
31
31
32
3.0
29
30
31
31
32
33
33
34
35
35
36
37
37
38
0.5
6
6
6
6
6
7
7
7
7
7
7
7
8
8
PH"7.0
log Inaeti vat ions
1.0
12
12
12
12
13
13
13
14
14
14
14
15
15
15
1.5
18
18
19
19
19
20
20
21
21
21
22
22
23
23
2.0
23
24
25
25
25
26
27
27
27
28
29
29
30
31
PN»«.5
2.5
29
30
31
31
32
33
33
34
34
35
36
37
38
38
3.0
3j
37
37
jj
3;
(g
41
(I
<;
(3
U
ii
W
CHLORINE
Log {Motivations
Leg Inaotivations
Log Inactivations
IKAI IUH
•B/L)
"0.4
0.6
:.;
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
-2.8
3
0.5
7
7
7
8
9
9
9
9
9
1.0
14
14
15
IS
15
16
16
16
17
17
17
18
18
18
21
22
22
23
23
24
24
25
25
26
26
27
27
28
28
29
29
30
31
31
32
33
33
34
35
35
36
37
35
36
37
38
38
39
40
41
42
43
43
44
45
46
42
43
44
45
46
47
48
49
SO
51
52
53
54
55
0.5
10
10
10
10
10
11
11
11
11
1.0
17
17
18
18
18
19
19
20
20
21
21
22
22
22
1.5
25
26
27
27
28
29
29
30
31
31
32
33
33
34
2.0
33
34
35
36
37
38
39
40
41
41
42
43
44
45
2.5
42
43
44
45
46
48
48
50
51
52
S3
54
55
56
3.0
SO
jl
S3
54
55
57
58
60
61
62
63
65
66
67
O.S
10
IU
11
11
11
12
12
12
12
13
13
13
13
14
1.0
20
in
21
22
22
23
23
24
25
25
26
26
27
27
1.5
30
ii
32
33
34
35
35
36
37
33
39
3?
40
41
2.0
39
<• i
42
43
45
46
47
48
49
50
51
52
53
54
2.5
49
3i
53
54
56
58
58
60
62
63
64
65
67
68
3.0
59
61
a
65
a
69
70
72
74
75
77
78
80
81
pH«9.0
CHLORINE Log Inaetivations
MIMIIUI '
(•g/D
<«o.«
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
0.5
12
12
13
13
13
14
14
14
IS
15
IS
16
16
16
1.0
23
24
25
26
27
27
28
29
29
30
31
y.
32
32
1.5
35
37
38
39
40
41
42
43
44
45
46
47
48
49
2.0
47
49
SO
52
S3
ss
56
57
59
60
61
63
64
65
2.5
58
61
63
65
67
68
70
72
73
75
77
78
80
81
3.0
70
73
75
78
30
82
84
86
88
90
92
94
96
97
Note: CTQQ 0= CT for 3-loq inactivatio"
r*.» • .*•
-------
TABLE E-7
CT VALUES FOR
INACTIVATION OF VIRUSES BY FREE CHLORINE(1'2*
Log Inactivatlon
Temperature (C)
0.5
5
10
15
20
25
2.0
PH
6-9 (3)
6
4
3
2
1
1
10
45
30
22
15
11
7
3.0
PH
6-9(3)
9
6
4
3
2
1
10
66
44
33
22
16
11
4.0
pH
6-9 (3)
12
8
6
4
3
2
10
90
60
45
30
22
15
Notes:
.1.
2.
Data adapted from Sobsey (1988) for inactivation of Hepatitus A
Virus (HAV) at pH = 6, 7, 8, 9, and 10 and temperature = 5 C. CT
values include a safety factor of 3.
CT values adjusted to other temperatures by doubling CT for each
10 C drop in temperature.
-------
TABLE E-8
CT VALUES FOR
INACTIVATION OF GIARDIA CYSTS
BY CHLORINE DIOXIDE pH 6-9
Temperature (C)
Inactivation
0.5
1
1.5
2
2.5
3
log
log
log
log
log
log
0.5
10
20
30
40
50
60
5
7
13
20
27
33
40
10
5
10
15
20
25
30
15
3.3
5
10
13
17
20
20
3
5
7.5
10
13
15
25
1.
3.
5.
6.
8.
10
7
3
0
7
3
-------
2.
TABLE E-9
CT VALUES FOR
INACTIVATION OF VIRUSES
BY CHLORINE DIOXIDE pH 6-9
(1,2)
Source: Sobsey 1988
Temperature (C)
Removal 0.5 5 10 15 20
2 log 8.4 5.6 4.2 2.8 2.1
3 log 25.6 17.1 12.8 8.6 6.4
4 log 50.3 33.5 25.1 16.8 12.6
Notes:
1. Data adapted from Sobsey (1988) for inactivation of Hepatit
_25
1.4
4.3
8.4
us A Vin
(HAV) at pH « 6.0 and temperature = 5 C. CT values include a safety
factor of 3.
CT values adjusted to other temperatures by doubling CT for each 10 C
drop in temperature.
-------
TABLE E-10
CT VALUES FOR
INACTIVATION OF GIARDIA CYSTS
BY OZONE pH 6-9
Temperature (c)
Inactivation 0 . 5
0.5 log
1 log
1.5 log
2 log
2.5 log
3 log
0.48
0.97
1.5
1.9
2.4
2.9
5
0.32
0.63
0.95
1.3
1.6
1.9
10
0.23
0.48
0.72
0.95
1.2
1.4
15
0.16
0.32
0.48
0.63
0.79
0.95
20
0.12
0.24
0.36
0.48
0.60
0.72
25
0.08
0.16
0.24
0.32
0.40
0.48
-------
TABLE E-ll
CT VALUES FOR
INACTIVATION OF VIRUSES BY OZONE '
Temperature (C)
Inactivation 0 . 5
2 log 0.9
3 log 1.4
4 log 1.8
5 10 15 20 25
0.6 0.5 0.3 0.25 0.15
0.9 0.8 0.5 0.4 0.25
1.2 1.0 0.6 0.5 0.3
Notes:
1. Data adapted from Roy (1982) for inactivation of poliovirus for
pH = 7.2 and temperature = 5 C. CT values include a safety
factor of 3.
2. CT values adjusted to other temperatures by doubling CT for each
10 C drop in temperature.
-------
TABLE E-12
CT VALUES FOR
INACTIVATION OF GIARDIA CYSTS
BY CHLORAMINE pH 6-9
Temperature (C)
Inactivation 0.5
0.5 log
1 log
1.5 log
2 log
2.5 log
3 log
690
1,295
1,900
2,590
3,154
3,800
5
363
737
1,100
1,435
1,826
2,200
10
337
675
925
1,349
1,536
1,850
15
250
505
750
1,009
1,245
1,500
20
181
366
550
738
913
1,100
25
130
260
375
532
623
750
-------
TABLE E-13
CT VALUES FOR
INACTIVATION OF VIRUSES BY CHLORAMINE '2'3'
Temperature (C)
Inactivation 0 . 5
2
3
4
log 1,243
log 2,063
log 2,883
5
857
1,423
1,988
10
643
1,067
1,491
15
428
712
994
20 25
321 214
534 356
746 497
Notes:
1. Data from Sobsey (1988) for inactivation of Hepatitus A Virus (HAV)
for pH = 8.0 and temperature = 5 C, and assumed to apply for pHs in
the range of 6.0 to 10.0.
2. CT values adjusted to other temperatures by doubling CT for each
10 C drop in temperature.
3. This table of CT values applies for systems using combined chlorine
where chlorine is added prior to ammonia in the treatment sequence.
CT values in this table should not be used for estimating the
adequacy of disinfection in systems applying preformed chloramines
or ammonia ahead of chlorine.
-------
TABLE E-14
CT VALUES FOR
INACTIVATION OF VIRUSES BY UV {*•'
Log Inactivation
Notes:
1. Data adapted from Sobsey (1988) for UV inactivation of Hepatitus A
Virus (HAV). Units of CT values are mW-sec/cm. CT values include
a saftey factor of 3.
2. For UV inactivation, CT values are independent of temperature.
Dependencies of pH on UV inactivation are related to changes to
the viruses and not the UV intensity.
3. CT values based on UV inactivation of Coxsackie B-5 (Sobsey 1988)
and UV inactivation of Poliovirus type 1 and Simian Rotavirus Chang
et al. (1985) are lower from those indicated in this Table.
-------
APPENDIX P
BASIS FOR CT VALUES
-------
APPENDIX F
BASIS OF CT VALUES
F.I Inactivation of Giardia Cysts
F.I.I Free Chlorine
The CT values for free chlorine in Tables E-l through E-6 are based on a
statistical analysis (Clark et al., 1988; attached to this appendix), which
considered both animal infectivity studies (Hibler et al., 1987) and
ex cyst at ion studies (Jarroll et al., 1981; Rice et al., 1982; Rubin et al. ,
1988). A multiplicative model was selected to best represent the chemical
reactions during the inactivation process. This model was applied to each of
the data sets, listed above, and in various combinations. The animal
infectivity data were included in all the combinations studied. The animal
infectivity data was considered essential for inclusion in all the analysis of
combined data sets because it included many more data points than the other
data sets, all of which represented inactivation levels at 99.99 percent.
Because of limitations with the excystation methodology, only data for
achieving less than 99.9 percent inactivation was available from such studies.
Statistical analysis supported the choice of combining the Hibler et al.
and the Jarroll et al. data (and excluding the Rice et al. (1981) and Rubin et
al. (1987) data) , to form the best fit model for predicting CT values for
different levels of inactivation. As a conservative regulatory strategy the
authors recommended that CT values for different* levels of inactivation be
determined by applying first order kinetics to the 99 percent upper confidence
interval of the CT values predicted by the model.
77* 99
The model was applied using the above strategy, as a safety factor, to
determine the CT values ranging from 0.5-log to 3-log inactivation at 0.5 and
5 C. CT values for temperatures above 5 C were estimated assuming a twofold
decrease for every 10 C. CT values .for temperatures at 0.5 C were estimated
assuming a 1.5 times increase to CT values at 5 C. This general principle is
supported by Hoff (1986).
F-l
-------
Application of the model to pHs above 8, up to 9, was considered reason-
able because the model is substantially sensitive to pH (e.g., CTs at pH 9 are
over three times greater than CTs at pH 6 and over two times greater than CTs
at pH 7). At a pH of 9, approximately four percent of the hypochlorous acid
fraction of free chlorine is still present. Recent data indicate that in
terms of HOC1 residuals (versus total free chlorine residuals including HOC1
and OC1~) the CT products required for inactivation of Giardia muris and
Giardia lamblia cysts decrease with increasing pH from 7 to 9 (Leahy et al.,
1987; Rubin et al., 1988b). However, with increasing pH, the fraction of free
chlorine existing as the weaker oxidant species (OC1 ) increases. In terms of
total free chlorine residuals (i.e., HOC1 and OCl") the CT products required
for inactivation of Giardia muris cysts increase with increasing pH from 7 to
9 but less than by a factor of 2 at concentrations of less than 5.0 mg/L (see
Table F-l). Also, the significance of pH on the value of CT products achiev-
ing 99 percent inactivation appears to decrease with decreasing temperature
and free chlorine concentration. The relative effects of pH, temperature, and
chlorine concentration, on inactivation of Giardia muris cysts appears to be
the same for Giardia lamblia cysts (Rubin et al., 1988b), although not as much
data for Giardia lamblia cysts for high pH and temperature values as for
Giardia muris cysts is yet available.
F.I.2 Ozone and Chlorine Dioxide
The CT values for ozone in Table E-10 are based on disinfection studies
using in vitro excystation of Giardia lamblia (Wickramanayake, G. B., et al.,
1985). CT values at 5 C and pH 7 for ozone ranged from 0.46 to 0.64 (disin-
fectant concentrations ranging from 0.11 to 0.48 mg/L). No CT values were
available for other pHs. The highest CTgg value, 0.64, was used as a basis
for extrapolation to obtain the CT values at 5~C, assuming first order kinet-
ics and applying a safety factor of 2, e.g., (.64) X 3/2 X 2 = 1.9). CT
values for temperatures above 5 C were estimated assuming a twofold decrease
for every 10~C. CT values for temperatures at 0.5 C were estimated assuming a
1.5 times increase to CT values at 5 C.
The CT values for chlorine dioxide in Table E-8 are based on disinfection
studies using _in vitro excystation of Giardia muris CTgg values at 5 C and
F-2
-------
TABLE F-l
CT VALUES TO ACHIEVE 99 PERCENT
INACTIVATION OF GIARDIA MURIS CYSTS BY FREE CHLORINE
£H
7
8
9
Temperature
(C)
1
15
1
15
1
15
(Source: Rubin
0.2-0.5
500
200
510
440
310
, et al., 1988b)
Concentration (mg/L)
0.5-1.0
760
290
820
220
1,100
420
1.0-2.0
1,460
360
1,580
1,300
620
2.0-5.0
1,200
290
1,300
320
2,200
.760
-------
pH 7 ranged from 7.2 to 17.6 (disinfectant concentrations ranging from 0.1 to
5.5 mg/L). The highest CT value, 17.6, was used as a basis for
extrapolation to obtain the values in Table E-8, assuming first order kinetics
and a safety factor of 1.5 , i.e.,
CT Q = 1 x CTQQ x 1-5 or 3 x 17.6 x 1.5 = 40
yy. y ^T y y TT
A lower safety factor is used for chlorine dioxide than for ozone,
because the data was generated using Giardia muris cysts which are more
resistant than Giardia lambia cysts. CT values at other temperatures were
estimated, based on the same rule of thumb multipliers assumed for ozone.
A larger safety factor was applied to the ozone and chlorine dioxide
data than to the chlorine data because:
a. Less data were available for ozone and chlorine dioxide than for
chlorine;
b. Data available for ozone and chlorine dioxide, because of the
limitations of the excystation procedure, only reflected up to or
slightly beyond 99 percent inactivation. Data for chlorine, based
on animal infectivity studies rather than excystation procedures,
reflected inactivation of 99.99 percent. Extrapolation of data to
achieve CT values for 99.9 percent inactivation with ozone and
chlorine dioxide, involved greater uncertainty than the direct
determination of CT values for 99.9 percent inactivation using
chlorine.
c. The CT values for ozone and chlorine dioxide to achieve 99.9 percent
-inactivation are feasible to achieve; and
d. Use of ozone and chlorine dioxide is likely to occur within the
plant rather than in the distribution system (versus chlorine and
chloramines which are the likely disinfectants for use in the
distribution system). Contact time measurements within the plant
will involve greater uncertainty than measurement of contact time in
pipelines.
EPA recognizes that the CT values for ozone and chlorine dioxide are
based on limited data. Therefore, EPA encourages the generation of
additional data in accordance with the protocols provided in
Appendix G to determine conditions other than the specified CT
values, for providing effective disinfection at a particular system.
F-3
-------
F.I.3 Chloramines
The CT values for chloramines in Table E-12 are based on disinfection
studies using preformed chloramines and in vitro excystation of Giardia muris
(Rubin, 1988). Table F-2 summarizes CT values for achieving 99 percent
inactivation of Giardia muris cysts. The highest CT values for achieving
99 percent inactivation at 1 C (2,500) and 5 C (1,430) were each multiplied by
1.5 (i.e., first order kinetics were assumed) to estimate the CT g values at
0.5 C and 5 C, respectively, in Table E-12. The CT value of 970 at 15 C was
multiplied by 1.5 to estimate the CT value. The highest CT value of
yy • " yy
1,500 at 15 C and pH 6 was not used because it appeared anomalous to the other
data. Interesting to note is that among the data in Table F-2 the CT values
in the lower residual concentration range (<2 mg/L) are higher than those in
the higher residual concentration range (2-10 mg/L). This is opposite to the
relationship between these variables which exists for free chlorine,
indicating that for chloramines, within residual concentrations practiced by
water utilities (less than 10 mg/L), residual concentration may have greater
influence than contact time on the inactivation of Giardia cysts. No safety
factor was applied to these data since chloramination, conducted in the field,
is more effective than using preformed chloramines. Also, Giardia muris
appears to be more resistant than Giardia lamblia to chloramines (Rubin,
1988b).
F.2 Inactivation of Viruses
F.2.1 Free Chlorine
CT values for free chlorine are based on data by Sobsey (1988) for
inactivation of Hepatitus A virus (HAV), Strain HM175, at pH 6,7,8,9 and 10,
chlorine concentrations of 0.5 to 0.2, and a temperature of 5 C, as contained
in Table F-3. The highest CT value for the pH range 6-9 for achieving 2, 3,
and 4-log inactivation of HAV were multiplied by a safety factor of 3 to
obtain the CT values listed in Table E-7. (e.g., the CT value for achieving
4-log inactivation at pHs 6-9 was determined by multiplying
2.55 X 3 = 7.6 = 8). The CT values at pH 10 were significantly higher than
those for pHs 6-9 and are considered separately. The CT values in Table E-7
for pH 10 also include a safety factor of 3. CT values at temperatures other
F-4
-------
TABLE F-2
CT VALUES FOR 99 PERCENT
INACTIVATION OF GIARDIA MURIS CYSTS BY MONOCHLORAMINE*
£H
6
(Source:
Temperature
(C)
15
5
1
15
5
1
15
5
1
15
5
1
Rubin, 1988)
Monochloramine
<0.2
1,500
>1,500'
>1,500
>970
>970
2,500
1,000
>1,000
>1,000
890
>890
>890
Concentration (mg/L)
2.0-10.0
880
>880
>880
970
1,400
>1,400
530
1,430^
1,880
560
>560
>560
*CT values with ">" signs are extrapolated from the known data.
-------
TABLE F-3
CT VALUES FOR INACTIVATION OF HEPATITUS A VIRUS
BY FREE CHLORINE
LOG INACTIVATION
2
3
4
(Source: Sobsey 1988)
PH
6 2. * 1 12
1.18 0.70 1.00 1.25 19.3
1.75 1.07 1.51 1.9 14.6
2.33 1.43 2.03 2.55 9.8
-------
than 5 C were determined assuming a two fold decrease for every 10 C increase.
CT values for inactivating viruses in general are based on HAV data since they
give higher CT values than those for inactivation of polio and rotaviruses
under similar conditions of pH and temperature (Hoff, 1986).
F.2.2 Chlorine Dioxide
Data by Sobsey (1988) for inactivation of Hepatitus A virus, strain Hm
175, by chlorine dioxide concentrations of 0.14 to 0.5 mg/1 at 5 C is shown in
Table F-4. The CT values in Table E-9 for pHs 6-9 were determined by applying
a safety factor of 2 to the above average CT values at pH 6. This safety
factor is lower than that used to determine CT values for chlorine because
chlorine, dioxide appears to be significantly more effective at higher pHs and
most waters are assumed to have a higher pH than 6.
CT values at temperatures other than 5 C in Table E-9 were determined by
applying a twofold decrease for every 10 C increase. The data for pH 9 was
not considered because it is very limited and other viruses are more resistant
to chlorine dioxide than Hepatitus A is at pH 9. According to Hoff (1986) at
a pH of 9 and a temperature of 21 C, a CT of 0.35 provides a 2-log
inactivation of poliovirus 1. Applying the same safety factor and rule of
thumb multipliers to this data results in a CT of 2.8 for a 4-log virus
inactivation at 0.5~C, in contrast to a CT of 50.3 resulting from the
Hepatitus A data at pH 6. Therefore, in order to assure inactivation of
Hepatitus A, the higher CT values are needed. Systems with high pHs may wish
to demonstrate the effectiveness of chlorine dioxide at lower CT values bases
on the protocol in Appendix G. Chlorine dioxide is much more effective for
inactivating rotavirus and polio virus than it is for inactivating HAV (Hoff
1986) .
F.2.3 Chloramines
The CT values in Table E-13 at 5 C were based directly on data by Sobsey
(1988) using preformed chloramines at pH 8. No safety factor was applied to
the laboratory data since chloramination in the field, where some transient
presence of free chlorine would occur, is assumed more effective than pre-
formed chloramines.
F-5
-------
TABLE F-4
CT VALUES FOR INACTIVATION OF HEPATITUS A VIRUS
BY CHLORINE DIOXIDE (SOBSEY 1988)
Log Inactivation
pH6 2
3
4
pH9 >2.5
>3.6
CT
3.78, 2.97, 1.8, 2.59
9.3, 9.57, 7.92, 7.4
17.6, 19.47, 15.48, 14.43
<0.165
<0.165
Avg. CT
2.79
8.55
16.75
-------
HAV is less resistant to preformed chloranrnes than are other viruses.
For example, CTs of 3,800-6,500 were needed for 2-log inactivation of Simian
Rotavirus at pH = 8.0 and temperature = 5 C (Herman and Hoff, 1984) . However,
these same viruses are very sensitive to free chlorine. CT values ranging
from less than 0.025 to 2.16 were required to achieve 99 percent inactivation
of rotavirus by free chlorine at pH = 6-10 and temperature = 4-5 C (Hoff,
1986). HAV is more resistant to free chlorine than are rotaviruses.
The CT values in Table E-13 apply for systems using combined chlorine
where chlorine is added prior to ammonia in the treatment sequence. This
should provide sufficient contact with free chlorine to assure inactivation of
rotaviruses. CT values Table E-13 should not be used for estimating the
adequacy of disinfection in systems applying preformed chloramines or ammonia
ahead of chlorine, since CT values based on HAV inactivation with preformed
chloramines may not be adequate for destroying rotaviruses. In systems
applying preformed chloramines, it is recommended that inactivation studies as
outlined in Appendix G be performed with Bacterio-phage MS2 as the indicator
virus to determine sufficient CT values. Also, the protocol in Appendix G can
be used by systems applying chlorine ahead of ammonia to demonstrate lower
CT's than those indicated in Table E-13.
F.2.4 Ozone
No laboratory CT values based on inactivation of HAV virus are yet
available for ozone. Based on data from Roy (1982), a mean CT value of 0.2
achieved 2-log inactivation of poliovirus 1 at 5 C and pH 7.2. Much lower CT
values are needed to achieve a 2-log inactivation of rotavirus (Vaughn, 1985).
No CT values were available for achieving greater than a 2-log inactivation.
The CT values in Table E-ll for achieving 2-log inactivation at 5 C was
determined by applying a safety factor of 3 to the data from Roy (1982) . CT
values for 3 and 4-log inactivation were determined by applying first order
kinetics and assuming the same safety factor of 3. CT values were adjusted
for temperatures other than 5 C by applying a two fold decrease for every 10 C
increase. Based on the available data, CT values for ozone disinfection are
not strongly dependent on pH. Therefore, data obtained at pH = 7.2 is assumed
F-6
-------
to apply for pHs in the range of 6.0 to 9.0. However, it should be noted that
the maintenance of an ozone residual is affected by pH.
References
American Water Works Association. Water Chlorination Principles and Prac-
tices, 1973.
Hibler, C. P.; C. M. Hancock; L. M. Perger; J. G. Wegrzn; K. D. Swabby Inacti-
vation of Giardia cysts with Chlorine at 0.5 C to 5.0 C American Water Works
Association Research Foundation, In press, 1987.
Hoff, J. C. Inactivation of Microbial Agents by Chemical Disinfectants,
EPA/600/52-86/067, U.S. Environmental Protection Agency, Water Engineering
Research Laboratory, Cincinnati, Ohio, September, 1986.
Jarroll, E. L.; A. K. Binham; E. A. Meyer Effect of Chlorine on Giardia
lamblia Cyst Viability. Appl. Environ. Microbiol., 41:483-487, 1981.
Leahy, J. G.; Rubin, A. J.; Sproul, O. J. Inactivation of Giardia muris Cysts
by Free Chlorine. Appl. Environ. Microbiol., July 1987.
Liu, O. C.; Seraichekas, H. R. ; Akin, E. W.; Brashear, D. A.; Katz, E. L.;
Hill, Jr., W. L. Relative Resistance of Twenty Human Viruses to Free Chlorine
in Potomac Water. 1971.
Payment, P.; Trudel, M.; Plante, P. Elimination of Viruses and Indicator
Bacteria at Each Step of Treatment During Preparation of Drinking Water at
Seven Water Treatment Plants. Appl. Environ. Microbiol., 49:1418, 1985.
Regli, S. USEPA Disinfection Regulations. Presented at AWWA Seminar Proceed-
ings: Assurance of Adequate Disinfection, or CT or Not CT. Kansas City,
Missouri, June 14, 1987.
Rubin, A. J. "CT Products for the Inactivation of Giardia Cysts by Chlorine,
Chloramine, Iodine, Ozone and Chlorine Dioxide" submitted for publication in
J. AWWA, December, 1988b.
Rubin, A. J. Factors Affecting the Inactivation of Giardia Cysts by Mono-
chloramine and Comparison with other Disinfectants. Water Engineering Re-
search Laboratory, Cincinnati, OH March 1988a.
Sobsey, M D. Detection and Chlorine Disinfection of Hepatitus A in Water.
CR-813-024. EPA Quarterly Report. Dec., 1988.
Wickramanayake, G. B.; A. J. Rubin; Sproul, 0. J. Effects of Ozone and
Storage Temperature on Giardia Cysts. J.AWWA, 77(8):74-77, 1985.
F-7
-------
INACTIVATION OF GIARDIA LAMBLIA BY FREE CHLORINE:
A MATHEMATICAL MODEL
Robert M. Clark, Director
Drinking Water Research Division
Risk Reduction Engineering Laboratory
Cincinnati, OH 45268
Stig Regli
USEPA-Office of Drinking Water
Criteria and Standards Division
Washington, DC 20460
Dennis A. Black
Instructor in Mathematics
University of Nevada
Las Vegas, Nevada
INTRODUCTION
Amendments to the Safe Drinking Water Act (PL93-523) highlight the
continuing problem of waterborne disease and mandate EPA to promulgate
(a) criteria by which filtration will be required for surface water
supplies and (b) disinfection requirements for all water supplies in
the United States. EPA's Office of Drinking Water is proposing to use
the C*t (Concentration times Time - disinfectant residual concentration
in mg/L multiplied by the disinfectant concentration contact time in
minutes) concept for determining the inactivation of Giardla lamblia
cysts, one of the most resistant pathogens, likely to be present in
surface waters*
Among individual agents, Giardia ranks number one as a cause of water-
borne illnesses and number four as a cause of waterborne outbreaks,
even though it was first identified as a causative agent in the mid-
19601 s.l The Office of Drinking Water is developing criteria under
which utilities using surface water would be required to meet source
water quality conditions, maintain a protected watershed and achieve
C*t values which provide a 99.9% inactivation of Giardla lamblia cysts,
In order to avoid filtration. If, for example, a utility in addition
to meeting other requirements, can demonstrate that through effective
disinfection, manifested by a sufficient C't value, it can reduce
Giardla levels by 99.9Z, then it would not be required to filter.
In this paper a mathematical model is developed based on the C*t con-
cept, for inactivation of G_. lamblia cysts by free chlorine. The model
is applied first to inactivation data from animal infectivity studies.
A procedure is then developed to select the best combination of data
sets available assuming that the animal infectivity data is included in
each combination. The model is then applied to the "best" data set to
calculate the model parameters. A regulatory strategy is proposed for
applying this model for the determination of C't values under the
surface water treatment rule (SWTR).
-------
THE C»t CONCEPT
The C*t concept Chat is in current use is an empirical equation stemming
from the early work of Watson and is expressed as:2
K - C»t (1)
where
K * constant for a specific microorganism exposed under specific
conditions
C » disinfectant concentration
n - constant, also called the "coefficient of dilution"
t - the contact time required for a fixed percent inactivation
It is based on the van't Hoff equation used for determining the nature
of chemical reactions in which the value n determines the order of the
chemical reaction*3»*
The application of this equation to disinfection studies requires
multiple experiments where the effectiveness of several variables, such
as pH, temperature, and the disinfectant concentration are examined to
determine how they affect the inactivation of microbial pathogens* The
disinfection concentration (C) and time (t) necessary to attain a
specific degree of inactivation (e.g. 99Z) are plotted on double log-
arithmic paper* Such a plot results in a straight line with slope
n.5'6 Figure 1 Illustrates data plotted In this manner and also the
significance of the value of n in extrapolation of disinfection data.?
When n equals 1, the C*t value remains constant regardless of the
disinfectant concentration used, i.e., disinfectant concentration and
exposure time are of equal importance in determining the inactivation
rate, or the C*t product, K. If n is greater than U disinfectant
concentration is the dominant factor in determining the inactivation
rate while if n Is less than 1, exposure time is more important than
disinfectant concentration* Thus, the value of n is a very important
factor in determining the degree to which extrapolation of data from
disinfection experiments is valid* In addition, Morris pointed out
that the evaluation of n is valid only if the original experimental
data follow Chick's Law (i.e., the rate of organism distruction is
directly proportional to the number of living organisms remaining at
any specified time) which is normally not the case.**
FACTORS AFFECTING C't
The destruction of pathogens by chlorlnation is dependent on a number
of factors, including water temperature, pH, disinfectant contact time,
degree of mixing, presence of interfering substances (which may be
related to turbidity), and concentrations of chlorine available*7 The pH
especially, has a significant effect on inactivation efficiency because
it determines the species of chlorine found in solution*
The impact of temperature on disinfection efficiency is also signifi-
cant. For example, Clarke determined that in order to maintain the
same level of virus destruction by chlorine, contact time must be in-
creased two to three times when the temperature is lowered 1CTC.9
Disinfection by chlorination can inactivate Giardia cysts, but only
-------
under rigorous conditions. Most recently, Hoff e_£ jl^. concluded that
these cysts are among the most resistant pathogens known, and that in-
activation by disinfection at low temperatures is especially difficult.10
Using in vitro excystation, Jarroll ££ .al.. have shown that 99.8 percent
of G. lamblia cysts can be killed by exposure to 2.5 mg/L of chlorine
for 10 minutes at 15°C at pH 6, or after 60 minutes at pH 7 or 8.11
At 5*C, exposure to 2 mg/L of chlorine killed 99.8 percent of all cysts
at pH 6 and 7 after 60 minutes.11 While it required 8 mg/L to kill the
same percentage of cysts at pH 6 and 7 after 10 minutes, it required 8
mg/L to inactivate cysts to the same level at pH 8 after 30 minutes.
Inactivation rates decreased at lower temperatures and at higher pHs as
indicated by the higher C*t values. Figures 2 and 3 summarize the data
developed by Jarroll et al» It should be noted that the nature of the
excystation method limits the ability to measure percent survival at
high inactivation levels. The assay involves microscopic observation
of the cysts. Therefore, to detect one viable cyst in 1000 (99.9%
inactivation), several thousand cysts must be observed to count enough
viable cysts for statistical confidence at this level. Since this has
not been done, no data for achieving 99.9% or higher inactivation
levels is available from studies involving excystation procedures.
Quantification of the combined effects of pH, temperature and disinfect-
ant concentrations require special techniques which take into account
.the interaction of these variables so they can be described by a single •
value. In the following section, cyst inactivation data from animal
infectivity studies conducted by Hibler, e± al^ are described.12 The
Hibler data are unique, in that unlike data from excystation studies,
they indicate the disinfectant conditions necessary to achieve greater
than 99.9 percent inactivation of (». lamblia cysts. These data could
be combined with excystation data for £. lamblia by Rice, et al.,
Jarroll, e£ al. and Rubin e£ al. to show the combined effects of
chlorine concentration, pH and temperature on different levels of
inactivation of £. lamblia cysts.1*»12»13»14
ANIMAL INFECTIVITY DATA
Hibler acquired O^ lamblia isolates from several human sources and
maintained them by passage in mongolian gerbils.12 Cysts obtained from
these animals were used to develop C-t values for 99.99 percent in-
activation of G. lamblia cysts with chlorine at temperatures of 0.5, 2.5
and 5.0°C and at pH values of 6, 7 and 8.
In these experiments clean G. lamblia cysts at a concentration of 1.02
x 10^ cysts/mL were exposed to selected chlorine concentrations at
appropriate pH and temperature. At specified time intervals for each
temperature and pH condition, chlorine activity was stopped by the
addition of sodium thiosulfate. The treated cyst suspension was centri-
fuged, the supernatant poured off and the cysts resuspended in a small
volume of buffer. Each of 5 gerbils, per test run, was fed 5 x 10* of
the concentrated chlorine exposed cysts. Equal numbers of positive
control animals were each orally inoculated with 50 unchlorinated cysts
maintained and buffered at the same temperature and pH as the chlorine
exposed cysts. Infectivity studies with unchlorinated cysts showed
that approximately 5 cysts usually constituted an infective dose.
Table 1 shows a distribution of the number of animals infected by
chlorine exposed cysts.
-------
In order to analyze these data the following assumptions were made.
If all five animals were infected, then it can be assumed that the C*t
of the test run produced less than 99.99Z inactivation. If no animals
were infected, then the C*t had produced greater than 99.99Z inactivation,
and if 1-4 animals were infected, the C*t produced 99.992 inactivation.
The limitation of this experiment is that it is only appropriate to
assign a specific level of inactivation (i.e. 99.992) to the case of
1-4 animals infected.
MODEL DEVELOPMENT
Statistical analysis was performed on the infectivity and excystation
data sets to determine the effects of inactivation level, temperature,
pH, and concentration of disinfectant on time to inactivation.15 A
multiplicative model was selected to best represent the chemical re-
actions during the inactivation process:
t - R Ia Cb pHc tempd (2)
where
t * time to inactivation in minutes
I • inactivation level
C - concentration of disinfectant in mg/L
pH « pH at which experiment was conducted
temp * temperature at which experiment was conducted
R, a, b, c, d » model parameters.
A log transformation of equation 2 yields: LOG}()(t) - LOG}Q(R) +
aLOGujd) * t> LOGio(C) + cLOGjo(pH) + dLOGjo
-------
differences. Significance of the indicator random variable (Z) would
support the hypothesis of different regression surfaces, i.e., incom-
patibility of the data sets chosen. The indicator random variable was
created in such a way as to always differentiate between the Hibler
data and other data sets considered. l1*^, 13, 14 Table 2 contains the
data set combinations and regression diagnostics.
As can be seen from from Table 2 the indicator random variable combining
the Hibler, e£ al^. and Jarrol, et_ al^. data bases was not significant.
All other data bases considered had a significant indicator random
variable at the 0.05 level of significance. A formal test for differ-
ences of intercept and/or slope between the Hibler, et_ al. and Jarroll
et al. data sets was conducted using the BMDP PIR procedure in the BMDP
statistical programming language. Test results indicated no difference
between the data sets. Thus, statistical analysis supports the choice
of the Hibler et al. and Jarroll et al. data as the data base for
Giarida cyst modeling procedures.
The resulting regression equation is
t - 0.12 1-0-27 c-0.81 pH2.54 Cenp-0-15 (5)
Equation 5 multiplied by C yields
Ct » 0.12 1-0-27 CO-19 pH2-54 temp-0-15 (6)
which is the Ct equation utilized. It can be shown that equation 6 is
equivalent to the Watson equation (Appendix A). The Confidence inter-
vals for parameter estimated of equation 6 are:
R; ( 0.0384, 0.4096)
a; (-0.2321, -0.3031)
1+b; ( 0.0792, 0.2977)
c; ( 1.9756, 3.1117)
d: (-0.0724, -0.2192)
The confidence intervals were calculated using the Bonferroni met hod. 16
REGULATORY APPLICATION
There are many uncertainties regarding the various data sets that might
be utilitzed for calculating C*t values. The random variable analysis
shows the statistical incompatibility among these data sets. More work
needs to be done to define the impact of strain variation, and in. vivo
versus in vitro techniques on C«t values. In order to provide conser-
vative estimates for C*t values the authors suggest the approach illus-
trated in Figure 4.
In Figure 4 the 99Z confidence interval at the 4 log inactivation level
is calculated. First order kinetics are then assumed so that the in-
activation "line" goes through 1 at C*t - 0 and a C*t value equal to the
upper 99Z confidence interval at 4 logs of inactivation (Appendix B) .
As can be seen the inactivation line bounds higher C*t values then all
of the mean C*t values from equation 6 as well as all of the Jarroll,
£t_ ja.1. data points (at inactivation levels of 0.1 and 0.015) and the
Hibler e_t £.1. data points (at inactivation level of 0.0001). Conser-
vative C*t values, for a specified level of inactivation, can be obtained
-------
from the inactivation line prescribed by the disinfection conditions.
For the example indicated in Figure 4, the appropriate C't for achieving
99.9Z inactivation would be 160. This approach (assumption of first
order kinetics) also provides the basis for establishing credits for
sequential disinfection steps.
SUMMARY AND CONCLUSIONS
Amendments to the Safe Drinking Water Act clearly require that all
surface water suppliers in the U.S. to filter and/or disinfect to pro-
tect the health of their customers. G^ lamblia has been identified as
one of the leading causes of waterborne disease outbreaks in the U.S.
G. lamblia cysts are also one of the most resistant organisms to
disinfection by free chlorine. EPA's Office of Drinking Water has
adopted the C*t concept to quantify the inactivation of £. lamblia
cysts by disinfection. If a utility can assure that a large enough C*t
can be maintained to ensure adequate disinfection then, depending upon
site specific factors, it may not be required to install filtration.
Similarly, the C*t concept can be applied to filtered systems for
determining appropriate levels of protection.
In this paper, an equation has been developed that can be used to
predict C*t values for inactivation of G. lamblia by free chlorine based
on the interaction of disinfectant concentration, temperature and, and
inactivation level. The parameters for this equation have been derived
from a set of animal infectivity data (Hibler, e£ al.)12 and excyscation
data (Jarroll, e£ al.)11 The equation can be used to predict C't values
for achieving 0.5 to 4 logs of inactivation and, within temperature
ranges of 0.5-5*C, chlorine concentration ranges up to 4 mg/L, and at pH
levels of 6 to 8. While the model was not based on pH values above 8,
the model is still considered applicable to pH levels of 9 for reasons
discussed elsewhere.17 The equation shows the effect of disproportionate
increases of C't versus inactivation levels. Using 99 confidence inter-
vals at the 4 log inactivation levels and applying first order kinetics
to these end points a conservative regulatory strategy for defining C-t
at various levels of inactivation has been proposed. This approach
represents an alternative to the regulatory strategy previously proposed.1
REFERENCES
1. Craun, G.F. "Waterborne Outbreaks from Giardia" in Giardia and
giardiasis. Editor: Erlandson Plenum Publishing Corporation (In
press).
2. Watson, H. E. A note on the variation of the rate of disinfection
with change in the concentration of the disinfectant. J. Hyg.
8^:536-592, 1908.
3. Berg, G., S. L. Chang, .and E. K. Harris. Devitalization of micro-
organisms by iodine 1. dynamics of the devitalization of entero-
viruses by elemental iodine. Virol. ^2:469-481, 1964.
4. Fair, G. M., J. C. Geyer, and D. A. Okun. Water and Wastewater
Engineering. Vol. 2. Water purification and wastewater treatment
and disposal. John Wiley and Sons, Inc., New York, NY, 1968.
5. Fair, G. M., J. C. Morris, and S. L. Chang. The dynamics of
water chlorination. J. New Eng. Water Works Assoc. 61:285-301,
1947.
-------
6. Fair, G. M., J. C. Morris, S. L. Chang, II Weil, and R. P. Burden.
1948. The behavior of chlorine as a water disinfectant. J. Am.
Water Works Assoc. 40:1051-1061.
7. Hoff, J. C., "Inactivation of Microbial Agents by Chemical Disin-
fectants" EPA/600/2-86-067, 1986.
. 8. Morris, J. C., "Disinfectant Chemistry and Biocidal Activities" in
Proceedings of the National Specialty Conference on Disinfection,
American Society of Civil Engineers, New York, NY, 1970.
9. Clarke, N. A., G. Berg, P. W. Kabler, and L. L. Chang. "Human
Enteric Viruses in Water: Source, Survival, and Removability".
International Conference on Water Pollution Research, Landar,
September, 1962.
10. Hoff, J. C., E. W. Rice, and F. W. Schaefer III, "Disinfection
and the Control of Waterborne Giardiasis", In proceedings of the
1984 Specialty Conference, Environmental Engineering Division,
ASCE, June 1984.
11. Jarroll, E.L., Bingham, A.K., and Meyer, S.A. "Effect of Chlorine
on Giardia Lamblia Cyst Viability". Applied and Environmental
Microbiology. Vol. 41, pp. 483-487, February, 1981.
12. Hibler, C. P., Hancock, C. M., Perger, L. M., Wegrzn, J. G. and
Swabby, K. D., Inactivation of Giardia Cysts with Chlorine at
0.5*C to 5.0°C.t American Water Works Association Research Found-
ation, 6666 West Quincy
13. Rice, E. W., Hoff, J. C., and Schaefer III, F.W. "Inacti-
vation of Giardia Cysts by Chlorine", Applied and Environmental
Microbiology. Vol. 41, pp 250-251, January 1982.
14. Rubin, A., Internal Report of Progress, Through June 1, 1988,
EPA Project CR812238.
15. Clark, R.M., Read, E.J. and Hoff, J. C. "Inactivation of Giardia
Lamblia by Chlorine: A Mathematical and Statistical Analysis", Ac-
cepted for publication by the Journal of Environmental Engineering.
16. Neter, J. and Wasserman, W. Applied Linear Statistical Models,
Irwin: Homewood, IL, 1974.
17. Regli, S. "EPA Disinfection Regulations", in Seminar Proceedings
Assurance of Adequate Disinfection or C*t or not C*t, pp. 1-7,
American Water Works Association Annual Meeting 1987.
-------
APPENDIX - A
Equation 6 can be shown to be equivalent to equation (1) by divid-
ing equation 6 by C*"* which yields:
C-bt - RI« pflc tempd (A-l)
Assuming a constant pfl * pS, temp - temp and I » I yields
K -~Ria~~pHb tempc" Id (A-2)
therefore
• C-* - K (A-3)
where
—b « n in equation 1
-------
APPENDIX - B
A general relationship that relates C*t values at different inactiva-
tion levels is:
In (Ni/N0)
In (Nj/N0)
(B-l)
where N^ is the number of organism left at time tj_ and Nj is the number
of organisms left at time tj. Table B-l summarizes the multiplication
factors to be applied, assuming first order kinetics, to convert a
value of Ki to an equivalent value of Kj.
TABLE B-l. MULTIPLICATION FACTORS TO CONVERT C't VALUES FROM ONE
INACTIVATION LEVEL K£ TO INACTIVATION LEVEL Kj
From to Inactivation
Inactivation Level j
Level i
90
99
99.9
99.99
Multiplier for Ki
90
^
1/2
1/3
1/4
99
2.0
-
2/3
1/2
99.9
3.0
1 1/2
-
3/4
99.99
4.0
2.0
1 1/3
-------
TABLE 1. DISTRIBUTION OF ANIMALS INFECTED BY CHLORINE EXPOSED CYSTS
# of Infected Animals
pH
6
6
6
7
7
7
8
8
8
Temp
0.5
2.5
5
0.5
2.5
5
0.5
2.5
5
0
58
54
23
35
62
61
36
68
45
1
15
7
10
7
6
7
10
12
9
2
5
4
6
5
4
4
8
4
3
3
3
3
5
1
4
4
3
3
2
4
2
1
5
1
0
0
1
2
1
5
5
7
15
25
4 "
12
2
6
6
-------
TABLE 2. REGRESSION DIAGNOSTICS FOR DATA SET COMBINATIONS
Data Sets considered
Hibler,
Hibler,
Hibler,
Hibler,
Hibler,
Hibler,
Hibler,
Hibler,
pTI -^- M -*-? ^ y
Hibler,
Hibler,
Hibler,
Hibler,
Hibler,
Rice, Jarroll, Rubin
Rice, Jarroll, Rubin, ^
Rice , Rubin
Rice, Rubin, Z
Jarroll, Rubin
Jarroll, Rubin, Z
Rice, Jarroll
Rice, Jarroll, Z
Rubin
7
Rice
Ricef Z
Jarroll
Jarroll, Z
R-sauare
0.6801
0.7316
0.6649
0.7899
0.6424
0.6879
0.8619
0.865
0.6483
0.7593
0.8548
0.8678
0.8452
0.8459
Variables
intercept, temp
not significant
intercept, temp
not significant
intercept, tenp
not significant
intercept
not significant
intercept, tenp
not significant
intercept, temp
not significant
all variables
significant
all variables
significant
temp
not significant
intercept
not significant
all variables
significant
all variables
significant
all variables
significant
Z not
sienificanc
Plots
non normal data
non constant var
non normal data
"non constant var
non normal data
non constant var
non normal data
non constant var
non normal data -
non constant var
non normal data
non constant var
non normal data
non constant var
non normal data
non constant var
non normal data
non constant var
non normal data
constant var
non normal data
constant var
non normal data
constant var
non normal data
constant var
non normal data
constant var
-------
z
2:
111
5
O)
O)
10000E
ioooa
100 =
I I I IMIIll I I I I HH
I I I I Mill I I I I 11Jl
10000
1000
100
0.01
1 10 100
DISINFECTANT CONG. (MG/L)
1000
FIGURE 1. EFFECT OF n VALUE ON Ot VALUES AT
DIFFERENT DISINFECTANT CONCENTRATIONS
(Ot VALUES GIVEN IN PARENTHESES)
-------
too
0 10
CONTACT TIME (»tawt««)
FIGURE 2. INACTIVATION OF G. LAMBLIA CYSTS BY
FREE RESIDUAL CHLORINE AT 5°C
lOOi
0Mt
OM7
OH«
<
>
>
C
K
•
>
•I
O
K
01
10
0.2
CMLOHIMg COMCENTSATIOMS
O 3.0 aig/l
• 2.5 mg/l
'0 30 «o 010 « «0 0 10 30 «0
CONTACT TIME
FIGURE 3. INACTIVATION OF G. LAMBLIA CYSTS BY
TOTT OTQinilA!
OOIMC AT
-------
I
N
A
C
T
I
V
A
T
I
O
N
L
E
V
E
L
1.0000
0.1000 =
CI-PRED.
ACTUAL Ct
99% CONF. INTERVAL
0.0100 =
0.0010
0.0001
0.0000
20 40 60 80 100 120 140 160 180 200 220 240 260 280
Ct VALUES
FIGURE 4. 99% CONFIDENCE LEVELS USING HIBLER-
JARROLL EQUATION FOR CHLORINE - 2 mg/l;
PH-7; TEMPERATURE * 5° C
-------
Tables 6-7 and 6-8 present a format which the utility can use as a daily data
log and to submit monthly reports to the Primacy Agency.
Recommended Reporting Not Required by the SWTR
The Primacy Agency may also want filtered water systems to report some
information associated with recommendations made in this manual which are not
requirements of the SWTR. EPA recommends that filtered water systems:
\
1. Report the percent inactivation of Giardia cysts and enteric
viruses, recommended by the Primacy Agency.
\
2. Report point of application for all disinfectants used.
\
\
3. Report the daily CT(s) used to calculate the percent inactivation of
Giardia cysts-and viruses.
\
4. If more than one disinfectant is used, report the CT(s) and inac-
tivation (s) achieved for each disinfectant and the total percent
inactivation achieved.
5. Report the percent inactivation determined prior to filtration and
the data used to make this determination.
6. Note any difference between the measured CT(s) and the CT required
to meet the overall minimum treatment performance requirement
specified by the Primacy Agency.
\
Tables 6-3 and 6-4 can be used to maintain^ the records necessary for numbers 2
through 6.
This information can be used to determine the disinfection level
maintained by the system to assure that the overall removal/inactivation
required is maintained.
The Primacy Agency may make provisions to minimize the reporting
requirements for systems with reservoirs, large amounts of storage or long
transmission mains which provide a long disinfectant contact time. Since
these systems typically provide inactivation in excess of that needed, the
Primacy Agency may require the system only to report the minimum daily
residual at the end of the disinfectant contact time. The CT maintained can
then be estimated based on this residual and the contact time under the system
design flow. This method of CT determination will eliminate the need for the
system to determine the contact time under maximum flow conditions each day.
6-3
-------
APPENDIX G
PROTOCOL FOR DEMONSTRATING
EFFECTIVE DISINFECTION
-------
LIST OF APPENDICES
G-l Determining Chloramine Inactivation of Giardia for the Surface
Water Treatment Rule
G-2 Determining Chloramine Inactivation of Virus for the Surface Water
Treatment Rule
G-3 Determining Chlorine Dioxide Inactivation
G-4 Determining Ozone Inactivation
-------
02/06/89
DETERMINING CHLORAMINE INACTIVATION OF GIARDIA
FOR THE SURFACE WATER TREATMENT RULE
Microbiological Treatment Branch
Risk Reduction Engineering Laboratory
and
Parasitology and Immunology Branch
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
-------
TABLE OF CONTENTS
I. Materials 3
II. Reagents 4
III. Giardia muris Assay 7
IV. Disinfection Procedures for Giardia 10
V. Procedure for Determining Inactivation 12
VI. Bibliography 13
VII. Technical Contacts 14
Appendix
A. Use of the Hemocytometer 15
B. Preparation and Loading of Chamber Slides 20
-------
The Surface Water Treatment Rule requires 99.9% or greater removal/
Inactivation of Giardla. The following protocol may be used to determine
the percentage of Giardia inactivation obtained by a treatment plant
using chloramine disinfection.
I. MATERIALS
A. Materials for Disinfection
1. Stock chlorine solution
2. Stock ammonia solution
3. Stirring device
4. Incubator or water bath for temperatures below ambient
5. Water from treatment plant
6. Giardia muris cysts
7. Assorted glassware
8. Assorted pipettes
9. Reagents and instruments for determining disinfectant residual
10. Sterile sodium thiosulfate solution
11. Vacuum filter device, for 47mm diameter filters
12. 1.0 urn pore size polycarbonate filters, 47 mm diameter
13. Vacuum source
14. Crushed ice and ice bucket
15. Timer
B. Materials for Excystation
1. Exposed and control Giardia muris cysts
2. Reducing solution
3. 0.1 M sodium bicarbonate
4. Trypsin-Tryode's solution
5. 15 ml conical screw cap centrifuge tubes
6. Water bath, 37°C
7. Warm air incubator or slide warming tray, 37°C
- 8. Aspirator flask
9. Vacuum source
10. Assorted pipettes
11. Vortex mixer
12. Centrifuge with swinging bucket rotor
13. Chamber slides
14. Phase contrast microscope
15. Differential cell counter
16. Timer
-------
II. REAGENTS
A. Reducing Solution
Ingredient Amount
glutathione (reduced form) 0.2 g
L-cysteine-HCl 0.2 g
IX Hanks balanced salt solution 20.0 ml
Dissolve the dry ingredients in the IX Hanks balanced salt
solution and warm to 37° C before use in the experiment.
Prepare fresh, within 1 hour of use.
B. Sodium Bicarbonate Solution, 0.1 M
Ingredient Amount
Sodium bicarbonate 0.42 g
Dissolve the salt in 10 to 15 ml distilled water. Adjust
the volume to 50 ml with additional distilled water and
warm to 37°C before use in the experiment. Prepare fresh,
within 1 hour of use.
C. Sodium Bicarbonate Solution, 7.5%
Ingredient Amount
Sodium bicarbonate ' 7.5 g
Dissolve the sodium bicarbonate in 50 ml distilled water.
Adjust the volume to 100 ml with additional distilled
water. Store at room temperature.
D. Sodium Thiosulfate Solution, 10%
Ingredient Amount
Sodium thiosulfate 10.0 g
Dissolve the sodium thiosulfate in 50 ml distilled water.
Adjust the volume to 100 ml with additional distilled
water. Filter sterilize the solution through a 0.22 um
porosity membrane or autoclave for 15 minutes at 121°C.
Store at room temperature.
-------
E. Tyrode's Solution, 20X
Ingredient
NaCl
KC1
CaCl 2
MgCl2*6H20
NaH2P04*H20
Glucose
Amount
160.0 g
4.0 g
4.0 g
2.0 g
1.0 g
20.0 g
Dissolve the dry ingredients in the order listed in 750 ml
distilled water. Adjust the volume to 1.0 liter with addi-
tional distilled water. If long term storage (up to 1
year) is desired, filter sterilize the solution through a
0.22 urn porosity membrane.
F. Tyrode's Solution, IX
Ingredient . Amount
20X Tyrode's solution 5.0 ml
Dilute 5 ml of the 20X Tyrode's solution to a final volume
of 100 ml with distilled water.
G. Trypsin-Tyrode's Solution
Ingredient Amount
Trypsin, 1:100, U.S. Biochemical Co. 0.50 g
NaHC03 0.15 g
IX Tyrode's solution 100.00 ml
With continuous mixing on a stirplate, gradually add 100 ml
IX Tyrode's solution to the dry ingredients. Continue
stirring until the dry ingredients are completely dissolved.
Adjust the pH of the solution to 8.0 with 7.5% NaHC03.
Chill the trypsin Tyrode's solution to 4°C. NOTE: Trypsin
lots must be tested for their excystation efficiency.
Prepare fresh, within 1 hour of use.
H. Polyoxyethylene Sorbitan Monolaurate (Tween 20) Solution, 0.01%
(v/v)
Ingredient Amount
Tween 20 0.1 ml
Add the Tween 20 to 1.0 liter of distilled water. Mix
well.
-------
I. Vaspar
Ingredient Amount
Paraffin I part
Petroleum jelly 1 part
Heat the two ingredients in a boiling water bath until melt-
ing and mixing is complete.
-------
III. GIARDIA MURIS ASSAY
A. Cysts
Giardla muris cysts may be available from Swabby GERBCO, Inc.,
2319 East Grovers #260, Phoenix, AZ 85022; phone (602) 9712115,
or from other commercial sources. The cysts are produced in Mon-
golian gerbils (Meriones unguiculatus).
No commercial source of G_* muris cysts produced in mice is cur-
rently known. Mus musculus, the laboratory mouse, CF-1, BALBc,
and C3H/he strains have been used successfully to produce G_.
muris cysts. The method is labor intensive and requires a good
animal facility.
In order for the disinfection procedure to work properly, the £.
muris cysts used must be of high quality. Evaluation of a cyst
suspension is a subjective procedure involving aspects of morpho-
logy and micobial contamination as well as excystment. A good
quality G_. muris cyst preparation should exhibit the following:
1. Examine cyst stock suspension microscopically for the presence
of empty cyst walls (ECW). Cyst suspensions containing equal
to or greater than 12 ECW should not be used for determining
inactivation at any required level. However, if a 99.9%
level of disinfection inactivation is required, the stock
cyst suspension must contain <0.1% ECW.
2. Excystation should be 902 or greater.
3. The cyst suspension should contain little or no detectable
microbial contamination.
4. Good G. muris cysts are phase bright with a, defined cyst wall,
peritrophic space, and agranular cytoplasm. Cysts which are
phase dark, have no detectable peritrophic space, and have a
granular cytoplasm may be non-viable. There should be no more
than 4 to 5% phase dark cysts in a preparation.
Good £. muris cyst preparations result when the following guide-
lines are followed during cyst purification from feces:
1. Use feces collected over a period of 24 hours or less.
2. The isolation of the cysts from the feces should be done
immediately after the fecal material is collected.
3. Initially, (3. muris cysts should be purified from the fecal
material by flotation using 1.0 M sucrose.
4. If the (5. muris cyst suspension contains an undesirable den-
sity of contaminants after the first sucrose float, further
purification is necessary. Two methods for further purifica-
tion are suggested.
-------
a. Cysts may be reconcentrated over a layer of 0.85 M sucrose
in a 50 ml conical centrifuge tube. If this second ex-
posure to sucrose is not done quickly, high cyst losses
can occur due to their increased bouyant density in the
hyperosmotic sucrose medium. The cysts must be thoroughly
washed free of the sucrose immediately after collection
of the interface.
b. Cysts can be separated from dissimilar sized contaminants
by sedimentation at unit gravity, which will not adversely
affect cyst bouyant density, morphology, or viability.
B. Maintenance of Cysts
1. Preparation of stock suspension
Determine the suspension density of the (5. muris cyst prepara-
tion using a heraocytometer (see Appendix A). Adjust the cyst
suspension density with distilled'water to approximately 3-5
x 106 cysts/ml.
2. Storage
Store cysts in distilled water in a refrigerator at 4°C.
Cysts should not be used for disinfection experiments if they
are more than 2 weeks old (from time of feces deposition).
C. Excystation Assay
A number of G_. muris excystation procedures have been described in
the scientific literature (see Bibliography, Section VI). Any of
these procedures may be used provided 90% or greater excystation
of control, undisinfected G. muris cysts is obtained. The
following protocol is used to evaluate the suitability of cysts in
the stock suspension, and to determine excystation in control and
disinfected cysts.
1. For evaluating a cyst suspension or for running an unexposed
control, transfer 5 x 10^ G. muris cysts from the stock
preparation to a 15 ml conical screw cap centrifuge tube. An
unexposed control should be processed at the same time as the
disinfectant exposed cysts.
2. Reduce the volume of £. muris cyst suspension in each 15 ml
centrifuge tube to 0.5 ml or less by centrifugation at 400 x
g for 2 minutes. Aspirate and discard the supernatant to no
less than 0.2 ml above the pellet.
3. Add 5 ml reducing solution, prewarmed to 37°C, to each tube.
4. Add 5 ml 0.1 M NaHC03, prewarmed to 37°C, to each tube. NOTE:
Tightly close the caps to prevent the loss of CO2* If the
C02 escapes, excystation will not occur.
5. Mix the contents of each tube by vortexing and place in
a 37°C water bath for 30 minutes.
-------
6. Remove the tubes from the water bath and centrifuge each for
2 minutes at 400 x g.
7. Aspirate and discard the supernatant to no less than 0.2 ml
above the pellet and resuspend the pellet in each tube in 10
ml trypsin-Tyrode's solution chilled to 4°C.
8. Centrifuge the tubes for 2 minutes at 400 x g.
9. Aspirate and discard the supernatant to no less than 0.2 ml
above the pellet.
10. Add 0.3 ml trypsin-Tyrode's solution, prewarmed to 37"C, to
each tube. Resuspend the G. muris cysts by low speed vortex-
ing.
11. Prepare a chamber slide for each tube (see Appendix 8).
12. Seal the coverslip on each chamber slide with melted vaspar
and incubate at 37°C for 30 minutes in an incubator or on a
slide warmer.
13. After incubation, place a chamber slide on the stage of an
upright phase contrast microscope. Focus on the slide with a
low power objective. Use a total magnification of 400X or
more for the actual quantitation. NOTE: Be careful to keep
the objectives out of the vaspar.
14. While scanning the slide and using a differential cell coun-
ter, enumerate the number of empty cyst walls (ECW), partial-
ly excysted trophozoites (PET), and intact cysts (1C) observed
(see Section V for a further description of these forms and
the method for calculating percentage excystation). If the
percentage excystation in the stock suspension is not 90% or
greater, do not continue with the disinfection experiment.
-------
10
IV. DISINFECTION PROCEDURES FOR GIARDIA
A. The treatment plant water to be used should be the water influent
into the chloratnine disinfection unit process used in the plant.
If chloraraine disinfection is performed at more than one point in
the treatment process, e.g., prefiltration and postfiltration,
the procedure should simulate as closely as possible actual
treatment practice.
B. Prepare stock ammonia and chlorine solutions to be added to the
treatment plant water to achieve the same stoichiometric relation-
ship between chlorine and ammonia that is used in the water
treatment plant. These solutions should be concentrated enough
so that no more than 2 ml of each solution will be added to the
treatment plant water being disinfected.
C. Determine the contact time by the methods described in the Surface
Water Treatment Rule and/or the associated Guidance Manual.
D. Rinse a 600 ml beaker with treatment plant water to remove any
extraneous material that may cause disinfectant demand. Then
add 400 ml treatment plant water to the beaker.
E. Mix the contents of the beaker short of producing a vortex in the
center and continue until the conclusion of the experiment.
F. Equilibrate the 600 ml beaker and its contents as well as the dis-
infectant reagents to the desired experimental temperature.
G. Adjust the stock (I. muris cyst suspension with distilled water so
that the concentration is 2-5 x 10° cysts/ml.
H. Add 0.5 ml of the adjusted cyst suspension to the contents of the
600 ml beaker.
I. Add the disinfectant reagents to the beaker using the same rea-
gents, the same sequence of addition of reagents, and the same
time interval between addition of reagents that is used in the
disinfection procedure in the treatment plant.
J. Just prior to the end of the exposure time, remove a sample ade-
quate for determination of the disinfectant residual concentra-
tion. Use methods prescribed in the Surface Water Treatment Rule
for the determination of combined chlorine. This residual should
be the same (±20%) as residual present in the treatment plant
operation.
K. At the end of the exposure time, add 1.0 ml 10% sodium thiosulfate
solution to the contents of the 600 ml beaker.
L. Concentrate the G. muris cysts in the beaker by filtering the
entire contents through a 1.0 urn porosity 47 mm diameter polycar-
bonate filter.
-------
11
M. Place the filter, cyst side up, on the side of a 150 ml beaker.
Add 10 ml 0.01% Tween 20 solution to the beaker. Using a Pasteur
pipette, wash the G. muris cysts from the surface of the filter
by aspirating and expelling the 0.01% Tween 20 solution over the
surface of the filter.
N. Transfer the contents of the 150 ml beaker to an appropriately
labeled 15 ml screw cap conical centrifuge tube.
0. Keep the tube on crushed ice until the excystation assay is
performed (see Section III, C) on the disinfectant exposed cysts
and on an unexposed control preparation obtained from the stock
cyst suspension.
-------
12
V. PROCEDURE FOR DETERMINING INACTIVATION
A. Giardia muris Excystation Quantitation Procedure
The percentage excystation is calculated using the following for-
mula:
% excystation - ECW + PET v 100
ECW + PET + 1C
where ECW is the number of empty cyst walls,
PET is the number of partially excysted trophozoites, and
1C is the number of intact cysts.
An ECW is defined as a cyst wall which is open at one end and is
completely devoid of a trophozoite. A PET is a cyst which has
started the excystation process and progressed to the point where
the trophozoite has either started to emerge or has completely
emerged and is still attached to the cyst wall. An 1C is a
trophozoite which is completely surrounded with a cyst wall
showing no evidence of emergence. For the control, generally 100
forms are counted to determine the percent excystation.
The number of cysts that must be observed and classified (ECW,
PET, 1C) in the disinfected sample is dependent on the level of
inactivation desired and on the excystation percentage obtained
in the control.
For 0.5, 1 and 2 Iog10 reductions, (68%, 90% and 99% inacti-
vation, respectively), the minimum number of cysts to be
observed and classified is determined by dividing 100 by the
percentage excystation (expressed as a decimal) obtained in
the control.
For a 3 log^ reduction (99.9% inactivation) the minimum
number of cysts to be observed and classified is determined
by dividing 1,000 by the percentage excystation (expressed
as a decimal) obtained in the control.
B. Determining Inactivation
The amount of inactivation is determined by comparing the percent-
age excystation of the exposed cyst preparation to the percentage
excystation in the control preparation using the following for-
mula:
% inactivation = 100% - [(exposed % excysted/control % excysted) x 100]
If the percentage excystation in the exposed preparation is zero,
i.e., only 1C (no ECW or PET) are observed and counted, use <1 as
the value for "exposed % excysted" in the formula for calculating
% inactivation.
-------
13
VI. BIBLIOGRAPHY
American Public Health Association; American Water Works Association;
Water Polution Control Federation. Standard Methods for the Examina-
tion of Water and Wastewater, 16th ed. (1985).
Belosevic, M. & G.M. Faubert. Giardia muris; correlation between
oral dosage, course of infection, and trophozoite distribution in the
mouse small intestine. Exp. Parasitol., 56:93 (1983).
Erlandsen, L.S. and E.A. Meyer* Giardia and Giardiasis. Plenum
Press, New York, (1984).
Faubert, G.M. et al. Comparative studies on the pattern of infec-
tion with Giardia spp. in Mongolian gerbils. J. Parasitol., 69:802
(1983).
Feely, D.E. A simplifed method for in vitro excystation of Giardia
muris. J. Parasitol., 72:474-475 (1986).
Feely, D.E. Induction of excystation of Giardia muris by C02» 62nd
Annual Meeting of the American Society of Parasitologists, Lincoln,
Nebraska, Abstract No. 91 (1987).
Gonzalez-Castro, J., Bermejo-Vicedo, M.T. and Palacios-Gonzalez, F.
Desenquistamiento y cultivo de Giardia muris. Rev. Iber. Parasitol.,
46:21-25 (1986).
Melvin, D.M. and M.M. Brooke. Laboratory Procedures for the Diagnosis
of Intestinal Parasites. 3rd ed., HHS Publication No. (CDC) 82-8282
(1982).
Miale, J.B. Laboratory Medicine Hematology, 3rd ed. C. V. Mosby
Company, St. Louis, Missouri (1967).
Roberts-Thomson, I.C. et al. Giardiasis in the mouse: an animal
model. Gastroenterol., 71:57 (1976).
Sauch, J.F. Purification of Giardia muris cysts by velocity sedi-
mentation. Appl. Environ. Microbiol., 48:454 (1984).
Sauch, J.F. A new method for excystation of Giardia. Advances in
Giardia Research. University of Calgary, Calgary, Canada (In Press).
Schaefer, III, F.W., Rice, E.W., & Hoff, J.C. Factors promoting
In vitro excystation of Giardia muris cysts. Trans. Roy. Soc. Trop.
Med. Hyg., 78:795 (1984).
-------
14
VII. TECHNICAL CONTACTS:
A. Eugene W. Rice
Microbiological Treatment Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
Phone: (513) 569-7233
B. Frank W. Schaefer, III
Parasitology and Immunology Branch
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
Phone: (513) 569-7222
-------
15
Appendix A: Use of the Hemocytoraeter
Suspension Density Determination Using the Improved Neubauer (Bright-line)
Hemocytoraeter
The heraocytometer consists of two chambers separated by a transverse
trench and bordered bilaterally by longitudinal trenches. Each chamber
is ruled and consists of nine squares, each 1 x 1 x 0.1 mm with a
volume of 0.1 nmv*. Each square mm is bordered by a triple line. The
center line of the three is the boundary line of the square. (See
Figure 1).
According to the U. S. Bureau of Standards' requirements, the cover
glass must be free of visible defects and must be optically plane on
both sides within plus or minus 0.002 mm. ONLY HEMOCYTOMETER COVER
GLASSES MAY BE USED. ORDINARY COVER GLASSES AND SCRATCHED HEMOCYTOMETERS
ARE UNACCEPTABLE, as they introduce errors into the volume relationships.
The suspension to be counted must be evenly distributed and free of
large debris, so that the chamber floods properly. The suspension to be
counted should contain 0.01Z Tween 20 solution to prevent Giardia cysts
from sticking and causing improper hemocytometer chamber flooding. Cyst
suspensions should be adjusted so that there are a total of 60 to 100 cysts
in the four corner counting squares. Counts are statistically accurate
in this range. If the suspension is too numerous to be counted, then it
must be diluted sufficiently to bring it into this range. In some cases,
the suspension will be too dilute after concentration to give a statisti-
cally reliable count in the 60-100 cyst range. There is nothing that can
be done about this situation other than to record the result as question-
able.
To use the hemocytometer:
1. Dilute or concentrate the suspension as required.
2. Apply a clean cover glass to the hemocytoraeter and load the
hemocytometer chamber with 8-10 pi of vortexed suspension per
chamber. If this operation has been properly executed, the
liquid should amply fill the entire chamber without bubbles or
overflowing into the surrounding moats. Repeat this step with a
clean, dry hemocytometer and cover glass, if loading has been
incorrectly done. See step (1) below for the hemocytometer
cleaning procedure.
3. Do not attempt to adjust the cover glass, apply clips, or in any
way disturb the chamber after it has been filled. Allow the
Giardia cysts to settle 30 to 60 seconds before starting the
count.
4. The Giardia cysts may be counted using a magnification 200-600X.
5. Move the chamber so the ruled area is centered underneath it.
6. Then, locate the objective close to the cover glass while watch-
ing it from the side of rather than through the microscope.
-------
16
7. Focus up from the coverslip until the hemocytoraeter ruling
appears.
8. At each of the four corners of the chamber is a 1 tmn^ divided
into 16 squares in which Giardia cysts are to be counted (see
Figure 1). Beginning with the top row of four squares, count
with a hand tally counter in the directions indicated in Figure
2. Avoid counting Giardia cysts twice by counting only those
touching the top and left boundary lines and none of those touch-
ing the lower and right boundary lines. Count each square mm in
this fashion.
9. The formula for determining the number of Giardia cysts per ml
suspension is:
# of cysts counted 10 dilution factor 1,000 mm _
# of sq. mm counted 1 mm 1 1 ml
# cysts/ml
10. Record the result on a data sheet similar to that shown in
Figure 3.
11. A total of six different hemocytometer chambers must be loaded,
counted, and then averaged for each Giardia cyst suspension to
achieve optimal counting accuracy.
12. After each use, the heraocytometer and coverslip must be cleaned
immediately to prevent the cysts and debris from drying on it.
Since this apparatus is precisely machined, abrasives eannot be
used to clean it as they will disturb the flooding and volume
relationships.
a. Rinse the hemocytoraeter and cover glass first with tap
water, then 70% ethanol, and finally with acetone.
b. Dry and polish the hemocytometer chamber and cover glass
with lens paper. Store it in a secure place.
13. A number of factors are known to introduce errors into heraocyto-
meter counts. These include:
a. Inadequate suspension mixing before flooding the chamber.
b. Irregular filling of the chamber, trapped air bubbles,
dust, or oil on the chamber or coverslip.
c. Chamber coverslip not flat.
d. Inaccurately ruled chamber.
e. The enumeration procedure. Too many or too few Giardia
cysts per square, skipping or recounting some Giardia cysts.
-------
17
f. Total number of Giardia cysts counted is too low to
give statistical confidence in result.
g. Error in recording tally.
h. Calculation error; failure to consider dilution factor,
or area counted.
i. Inadequate cleaning and removal of cysts from the previous
count.
j. Allowing filled chamber to sit too long so that chamber sus-
pension dries and concentrates.
-------
18
I mm.
*
I/9MM. /
ji
«
"A!
E
s
c
i
<
i
••
<
f
*
.. — 0«pth of Chamber • O.I mm.
«JL
AssJ&g
Figure 1. Hemocytoraeter platform ruling. Squares 1, 2, 3, and 4 are
used to count Giardia cysts. (From Miale, 1967)
Figure 2. Manner of counting Giardia cysts in 1 square mra. Dark cysts
are counted and light cysts are omitted. (After Miale, 1967)
-------
19
Date
Person
Counting
Count
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
f Cells
Counted
l«2
Counted
Dilution
Factor
Lcjp-
Remarks
•
t cysts/ml _ I of cysts counted x 10 x dilution factor x 1,000 mm3
t of sq. mm counted 1 mm 1 1 ml
Figure 3. Hemocytometer Data Sheet for Giardia Cysts.
-------
20
Appendix B. Preparation and Loading of Excystation Chamber Slides
1. Using tape which is sticky on both sides, cut strips approximately 12
x 3 mm.
2. Apply a strip of the tape to one side of a 22 x 22 mm coverslip.
3. Apply a second strip of tape to the opposite edge but same side of
the coverslip.
4. Handling the coverslip by the edges only, attach the coverslip to the
center of a 3 x 1 inch glass slide by placing the taped sides of the
coverslip down along the long edge of the glass slide.
5. Make sure the coverslip is securely attached to the slide by lightly
pressing down on the edges of the coverslip with your fingers. Care
should be taken to keep finger prints off the center of the coverslip.
6. To load the chamber slide, place a Pasteur or microliter pipette
containing at least 0.2 ml of the Giardia cyst suspension about 2 ran
from an untaped edge of the coverslip. Slowly allow the cyst suspen-
sion to flow toward the coverslip. As it touches the coverslip it
will be wicked or drawn rapidly under the coverslip by adhesive forces.
Only expell enough of the cyst suspension to completely fill the
chamber formed by the tape, slide, and coverslip.
7. Wipe away any excess cyst suspension which is not under the coverslip
with an absorbant paper towel, but be careful not to pull cyst
suspension from under the coverslip.
8. Seal all sides of the coverslip with vaspar to prevent the slide from
drying out during the incubation.
NOTE: Prepared excystation chamber slides may be commercially avail-
able from Spiral Systems, Inc., 6740 Clough Pike, Cincinnati,
Ohio 45244, (513) 231-1211 or 232-3122, or from other sources.
-------
02/06/89
DETERMINING CHLORAMINE INACTIVATION OF VIRUS
FOR THE SURFACE WATER TREATMENT RULE
Microbiological Treatment Branch
Risk Reduction Engineering Laboratory
and
Parasitology and Immunology Branch
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
-------
TABLE OF CONTENTS
I. Materials 3
II. Reagents and Media 4
III. MS2 Bacteriophage Assay 6
IV. Disinfection Procedure 8
V. Procedure for Determining Inactivation 9
VI. Bibliography 10
VII. Technical Contacts 11
-------
The Surface Water Treatment Rule requires 99.99% or greater removal/
inactivation of viruses. The following protocol may be used to determine
the percentage of virus inactivation obtained by a treatment plant using
chloramine disinfection.
I. MATERIALS
A. Materials for Disinfection
I* Stock chlorine solution
2. Stock ammonia solution
3. Stirring device
4. Incubator or water bath for less than ambient temperature
5. Water from treatment plant
6. MS2 bacteriophage
7. Assorted glassware
8. Assorted pipettes
9. Aqueous, sterile sodium thiosulfate solution
10. Refrigerator
11. Vortex mixer
12. Timer
B. Materials for MS2 Assay
1. MS2 bacteriophage and its Escherichia coli host
2. Assorted glassware
3. Assorted pipettes
4. Incubator, 37°C
5. Refrigerator
6. Petri dishes, 100 x 15 ram, sterile
7. Vortex mixer
8. Water bath, 45°C
9. Sterile rubber spatula
10. EDTA, disodium salt
11. Lysozyme, crystallized from egg white
12. Centrifuge with swinging bucket rotor
-------
II. REAGENTS AND MEDIA
A. Tryptone-Yeast Extract (TYE) Broth
Ingredient _ Amount
Bacto tryptone 10.0 g
Yeast extract 1.0 g
Glucose 1.0 g
NaCl 8.0 g
1.0 M CaCl2 2.0 ml
Dissolve in distilled water to a total volume of 1.0 liter,
then add 0.3 ml of 6.0 M NaOH. This medium should be steri-
lized either by autoclaving for 15 minutes at 121°C or
filtration through a 0.22 yra porosity membrane and then
stored at approximately 48C. It is used in preparing
bacterial host suspensions for viral assays.
B. Tryptone-Yeast Extract (TYE) Agar
Ingredient _ Amount
TYE broth 1.0 liter
Agar 15.0 g
The agar should be added to the broth prior to steriliza-
tion. The medium should be sterilized by autoclaving for
15 minutes at 121°C. This medium is used to prepare slant
tubes for maintenance of bacterial stock cultures. The
prepared slant tubes should be stored at approximately 4°C.
C. Bottom Agar for Bacteriophage Assay
Ingredient
Bacto tryptone
Agar
NaCl
KC1
1.0 M CaCl2
Amount
10.0 g
15.0 g
2.5 g
2.5 g
1.0 ml
Dissolve the ingredients in distilled water to a total
volume of 1 liter. The medium should be sterilized by
autoclaving for 15 minutes at 121°C. After autoclaving and
cooling, store at 4°C. Immediately prior to use, liquefy
the medium by heating. Add approximately 15 ml of lique-
fied agar into each Petri dish. This bottom layer serves
as an anchoring substrate for the top agar layer.
-------
D. Top Agar for Bacteriophage Assay
Ingredient Amount
Bacto tryptone 10.0 g
Agar 8.0 g
NaCl 8.0 g
Yeast extract 1.0 g
Glucose 1.0 g
1.0 M CaCl2 1.0 ml
Dissolve the ingredients in distilled water to a total
volume of 1 liter. This medium should be sterilized by
autoclaving 15 minutes at 121°C. After cooling, store at
4°C until needed in bacteriophage assays. Immediately
prior to use in assays, liquefy the medium by heating and
then cool to and maintain at a temperature of 45°C.
E. Salt Diluent for Bacteriophage Assay
Ingredient Amount
NaCl 8.5 g
1.0 M CaCl2 2.0 ml
Dissolve in distilled water to a total volume of 1 liter.
This diluent should be sterilized either by autoclaving
for 15 minutes at 121°C or filtration through a 0.22 um
porosity membrane. Store at room temperature.
F. CaCl2, 1.0 M
Ingredient Amount
CaCl2 11-1 g
Dissolve in distilled water to a total volume of 100 ml.
Autoclave 15 minutes at 121°C or filter sterilize the
solution through a 0.22 urn porosity membrane. Store at
room temperature.
G. Sodium Thiosulfate, 10Z and 1Z
Ingredient Amount
Sodium thiosulfate 10.0 g
Dissolve the sodium thiosulfate in 50 ml distilled water.
Adjust the volume to 100 ml with additional distilled
water. Filter sterilize the solution through a 0.22 um
porosity membrane or autoclave 15 minutes at 121°C. Store
at room temperature. Prepare 1% sodium thiosulfate solution
by aseptically adding 1 ml of sterile 10% sodium thiosulfate
solution to 9 ml of sterile distilled water.
-------
III. MS2 BACTERIOPHAGE ASSAY
A. Microorganisms
1. MS2 bacteriophage: catalog number 15597-B1, American Type
Culture Collection, 12301 Parklawn Drive, Rockville, MD 20852
2. Bacterial host: Escherichia coli, catalog number 15597,
American Type Culture Collection.
B. Growth and Maintenance of Microorganisms
1. Preparation of bacterial host stock cultures
Inoculate host bacteria onto TYE agar slant tubes, incubate
24 hours at 37°C to allow bacterial growth, and then refriger-
ate at 4°C. At monthly intervals the cultured bacterial
hosts should be transferred to a new TYE agar slant.
2. Preparation of bacteriophage stock suspension
Melt top agar and maintain at 45°C. Add 3 ml of the agar to
a 13 x 100 mm test tube contained in a rack in a 45°C water
bath. Add 0.5 to 1.0 ml of the bacteriophage suspension
diluted so that the host bacterial "lawn" will show nearly
complete lysis after overnight incubation. Add 0.1 to 0.2 ml
of a TYE broth culture of the host bacteria that has been
incubated overnight. Mix gently and pour the contents on the
surface of bottom agar contained in a Petri dish that has
been prepared previously. Rock the Petri dish to spread the
added material evenly over the agar surface. After the top
agar solidifies (about 15 minutes), invert the Petri dish
and incubate overnight at 37°C. Repeat the above procedure
so that a minimum of 5 but no more than 10 Petri dishes are
prepared.
Following this incubation and using a sterile rubber spatula,
gently scrape the top and bottom agar layers into a large
beaker. Add to this pool of agar layers an amount of TYE
broth sufficient to yield a total volume of 80 ml. To this
mixture add 0.4 g of EDTA (disodium salt) and 0.052 g of
lysozyme (crystallized from egg white). Incubate this mixture
at room temperature for 2 hours with continuous mixing. Then
centrifuge the mixture for 15 minutes at 3,000 x g. Carefully
remove the upper fluid layer. This fluid layer constitutes a
viral stock suspension for use in subsequent testing and
assays. The viral stock suspension may be divided into
aliquots and stored either frozen or at 4°C.
C. Performance of Bacteriophage Assay
A two-week supply of Petri dishes may be poured with bottom agar
ahead of tine and refrigerated inverted at 4°C. If stored in a
refrigerator, allow agar plates to equilibrate to room temperature
-------
before use. Eighteen hours prior to beginning a bacteriophage
assay, prepare a bacterial host suspension by inoculating 5 ml of
TYE broth with a small amount of bacteria taken directly from a
slant tube culture. Incubate the broth containing this bacterial
inoculum overnight (approximately 18 hours) at 37°C i^jnediately
prior to use in bacteriophage assays as described below. This
type of broth culture should be prepared freshly for each day's
bacteriophage assays. If necessary, a volume greater than 5 ml
can be prepared in a similar manner.
On the day of assay, melt a sufficient amount of top agar and
maintain at 45°C in a water bath. Place test tubes (13 x 100 mm)
in a rack in the same water bath and allow to warm, then add 3 ml
of top agar to each tube. Inoculate the test tubes containing
top agar with the bacteriophage samples (0.5 to 1.0 ml of the
sample/tube) plus 0.1 to 0.2 ml of the overnight bacterial host
suspension. Dilute the bacteriophage samples from 10"* to 10~^
in salt diluent prior to inoculation and assay each dilution in
triplicate. In addition, assay the uninoculated salt diluent as
a negative control. Agitate :he test tubes containing top agar,
bacteriophage inoculum, and bacterial host suspension gently on a
vortex mixer, and pour the contents of each onto a hardened
bottom agar layer contained in an appropriately numbered dish.
Quickly rock the Petri dishes to spread the added material evenly,
and place on a flat surface at room temperature while the agar
present in the added material solidifies (approximately 15 min-
utes). Invert and incubate the dishes at 37°C overnight (approxi-
mately 18 hours). The focal areas of viral infection which
develop during this incubation are referred to as "plaques" and,
if possible, should be enumerated immediatly after the incubation.
If necessary, the incubated Petri dishes can -be refrigerated at
4°C overnight prior to plaque enumeration. As a general rule,
count only those plates that contain between 20 and 200 plaques.
-------
IV. DISINFECTION PROCEDURE
A. The treatment plant water to be used should be the water influent
into the chloramine disinfection unit process used in the plant.
If chloramine disinfection is performed at more than one point in
the treatment process, e.g. prefiltration and postfiltration, the
procedure should simulate as closely as possible actual treatment
practice.
B. Prepare stock ammonia and chlorine solutions to be added to the
treatment plant water to achieve the same stoichloraetric relation-
ship between chlorine and ammonia that is used in the water
treatment plant. These solutions should be concentrated enough
so that no more than 2 ml of each solution will be added to the
treatment plant water being disinfected.
C. Determine the contact time by the methods described in the Surface
Water Treatment Rule and/or the associated Guidance Manual.
D. Rinse two 600 ml beakers with treatment plant water to remove any
extraneous material that may cause disinfectant demand. Then add
400 ml treatment plant water to the beaker. The first beaker
will be seeded with MS2 before the contents are chloraminated.
The second beaker will be an indigenous virus control and will
be chloraminated without addition of extraneous phage.
E. Mix the contents of the beaker short of producing a vortex in the
center and continue until the conclusion of the experiment.
F. Equilibrate the 600 ml beakers and their contents as well as the
disinfectant reagents to the desired experimental temperature.
G. Dilute the stock MS2 bacteriophage so that the bacteriophage con-
centration is 1 to 5 x 108 PFU/ml.
H. Add 1.0 ml of the diluted MS2 bacteriophage to the contents of the
first 600 ml beaker.
I. Remove a 10 ml sample from the contents of the first beaker after
2 minutes of mixing. Assay the MS2 bacteriophage concentration
in this sample within 4 hours and record the results as PFU/ml.
This value is the initial MS2 concentration.
J. Remove a 10 ml sample from the contents of the second beaker
after 2 minutes of mixing. Assay the indigenous bacteriophage
concentration in this sample within 4 hours (at the same time as
you assay the sample from the first beaker) and record the
results as PFU/ml. This value is the initial unseeded concentra-
tion.
K. Add the disinfectant reagents to the contents of both beakers
using the same sequence, time, and concentrations as are used in
the actual treatment plant operations.
-------
L. Just prior to the end of the contact time, remove a volume of sam-
ple adequate for determination of the disinfectant residual con-
centration from both beakers. Use methods prescribed in the
Surface Water Treatment Rule for the determination of combined
chlorine. This residual should be the same (±20%) as the
residual present in the treatment plant operation.
M. At the end of the exposure time, remove a 10 ml sample from the
first 600 ml beaker and neutralise with 0.25 ml of 1.0% aqueous,
sterile sodium thiosulfate. Assay for the MS2 bacterionhage
survivors and record the results as PFU/ml. This value is the
exposed MS2 concentration.
N. At the end of the exposure time, remove a 10 ml sample from the
second 600 ml beaker and neutralize with 0.25 ml of 1.0% aqueous,
sterile sodium thiosulfate. Assay for the indigenous bacterio-
phage survivors and record the results as PFU/ml. This value is
the exposed unseeded concentration.
V. PROCEDURE FOR DETERMINING INACTIVATION
A. Calculation of Percentage Inactivation
Use the following formula to calculate the percent inactivation
of MS2:
1. % inactivation - 100% - [(exposed MS2/initial MS2) x 100]
Using values from Section IV steps I, J, M and N calculate initial
MS2 and exposed MS2 as follows:
2. Initial MS2 (PFU/ml) = I - J.
3. Exposed MS2 (PFU/ml) - M - N.
If the number of PFU/ml in exposed MS2 is zero, i.e., no plaques
are produced after assay of undiluted and diluted samples, use <1
PFU/ml as the value in the above formula.
B. Comparison of Percentage Inactivation to LogjQ of Inactivation
68% inactivation is equivalent to 0.5 logjo inactivation
90% inactivation is equivalent to 1 log^o inactivation
99% inactivation is equivalent to 2 log^o inactivation
99.9% inactivation is equivalent to 3 log^g inactivation
-------
10
VI. BIBLIOGRAPHY
Adams, M.H. Bacteriophages. Interscience Publishers, New York (1959).
American Public Health Association; American Water Works Association;
Water Pollution Control Federation. Standard Methods for the Examina-
tion of Water and Wastewater. 16th ed. (1985).
Grabow, W.O.K. et al. Inactivation of hepatitus A virus, other enter-
ic viruses and indicator organisms in water by chlorination. Water
Sci. Technol., 17:657 (1985)
Jacangelo, J.D.; Olivieri, V.P.; & Kawata, K. Mechanism of inactiva-
tion of microorganisms by combined chlorine. AWWARF Rept., Denver,
CO (1987).
Safe Drinking Water Committee. The disinfection of drinking water.
In: Drinking Water and Health, National Academy Press, Washington,
D.C., 2:5 (1980).
Shah, P. & McCamish, J. Relative resistance of poliovirus 1 and coli-
phages f£ and T2 in water. Appl. Microbiol. 24:658 (1972).
U.S. Environmental Protection Agency. Guidance Manual for Compliance
with the Filtration and Disinfection Requirements for Public Water
Systems Using Surface Water Sources. Appendix G. U.S. EPA, Office
of Water, Criteria and Standards Division, Washington, D.C. (1988).
Ward, N.R.; Wolfe, R.L.; & Olson, B.H. Effect of pH, application
technique, and chlorine-to-nitrogen ratio on disinfectant activity of
inorganic chloramines with pure culture bacteria. Appl. Environ.
Microbiol., 48:508 (1984).
-------
11
VII. TECHNICAL CONTACTS;
A. Donald Herman
Microbiological Treatment Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
Phone: (513) 569-7235
B. Christon J. Hurst
Microbiological Treatment Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
Phone: (513) 569-7331
-------
APPENDIX G 3 CHLORINE DIOXIDE INACTIVATION
The basis for the chlorine dioxide CT values for Giardia cyst in
the manual is given in Appendix F (pp 2-3). The CT valves are based on
data collected from five experiments conducted at five different
chlorine dioxide concentrations ( 0.1 to 5.5 mg/L) at pH 7 and 5 C.
The highest single value was used to calculate the CT values and a 2
fold safety factor was applied. A review of data from Hoff, 1986
indicated that the disinfection efficiency of chlorine dioxide for
bacteria and viruses increases approximately 2 to 3 fold as pH increases
from 7 to 9. Data from the report on which the CT values are based
(Leahy, 1985) indicate that at 25 C, G. Muris cyst inactivation CT's
were approximately 2 fold higher at pH 7 than at pH 9. In addition, the
data also indicate that chlorine dioxide efficiency increases as
disinfectant concentration increases within the range stated.
Because the CT values in the Manual are very conservative, and
because the data suggest that site specific conditions, i.e. water pH
and disinfectant concentration used, can have significant effects on
chlorine dioxide effectiveness, the option of allowing the Primacy
Agency to consider the use of lower CT valves by individual systems has
been provided.
This approval should be based on acceptable experimental data
provided by the system. The data should be collected using the protocol
provided in Appendix G-l for determining Giardia cyst inactivation by
chloramine with appropriate changes in Section IV A, B, and I to reflect
the use of chlorine dioxide rather than chloramine.
References:
Hoff, T.C. Inactivation of Microbial Agents By Chemical Disinfectants
EPA/600/52-86/067, U.S. Environmental Protection Agency, Water Engineer
Research Laboratory, Cincinnati, Ohio, September, 1986.
Leahy, J.G. Inactivation of Giandia Muris Cysts by Chlorine and Chlorine
Dioxide. Thesis, Department of Civil Engineering, Ohio State Universi-
ty, 1985.
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APPENDIX G-4 OZONE INACTIVATION
The basis for the ozone CT values in this manual is given in
Appendix F. As indicated in Appendix F, the ozone data base is very
limited. The CT values are for Giardia cysts derived from one publica-
tion (Wickramanyake et al, 1985) in which experiments were conducted at
one pH (7) and two temperatures (5 C and 25 C). Because of this limita-
tion, a large safety factor was applied in establishing the CT values.
Also, the experiments were conducted under steady state ozone concen-
trations with ozone continually added during the contact period. In
contrast, as pointed out on p. 3-14, of this manual, steady state ozone
concentrations are not maintained in field use. In addition to these
factors, the effectiveness of ozone contactors used in field applica-
tions may vary from each other and from the mixing efficiencies applied
in the laboratory experiments used to establish the CT valves.
The net effect of all of these differences limits the applicability
of the CT values to individual systems. Therefore, the option of
allowing the Primacy Agency to consider the use of lower CT valves by
individual systems has been provided.
This approval should be based on acceptable experimental data
provided by the system. In general, the procedure provided in Appendix
G-l for determining Giardia cyst inactivation by chloramine for de-
termining cyst viability before and after exposure to ozone can be used.
Because of the importance of ozone transfer efficiency and the impact of
the ozone application on the contactor hydraulics, use of a pilot plant
of the ozonation process used is essential. The ozone pilot unit should
have the capacity for a 1 to 10 gpm flow and should simulate the hydrau-
lics and ozone transfer efficiency of the full scale unit. the effi-
ciency of the contactor in activating the cysts can be determined from
the viability of cysts in the influent and effuent of the contactor,
determined as outlined in Appendix G-l. A recommended cyst concen-
tration for the raw water is 1x10 cysts/gallon. However, the influent
-------
concentration and the pilot plant flow rates may need to be adjusted
according to the availability of cysts. Additional information on the
&«•
design of specific pilot studies can
-------
References:
Wickramanayake, G.B., Rubin, A.J., and Sproul, O.J. Effects of Ozone and
Storage Temperatures on Giardia Cysts. J. AWWA, 77(8)-74-77, 1989
Wallis, P.M., Davies, J.S., Nuthonn, R., Bichanin-Mappin, J.M., Roach,
P.D., and Van Roodseloon, A. Removal and Inactivation of Giardia Cysts
in a Mobile Water Treatment Plant Under Field Conditions: Preliminary
Results. In Advances in Giardia Research. P.M. Wallis and B.R. Hammand,
eds, Union of Calgary Press, p. 137-144, 1989.
Wolfe, R.L., Stewart, M.H., Liang, S.L., and McGuire, M.J., submitted
for publication, 1989.
Olivieri, V.P. and Sykora, J.L., Field Evaluation of CT for Determining
the Adequacy of Disinfection. American Water Works Association Water
Quality Technology Conference. In press, 1989.
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APPENDIX H
SAMPLING FREQUENCY FOR TOTAL COLIFORMS
IN THE DISTRIBUTION SYSTEM
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APPENDIX I
MAINTAINING REDUNDANT
DISINFECTION CAPABILITY
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APPENDIX I
REDUNDANT DISINFECTION CAPABILITY
In reviewing water disinfection facilities for compliance with redundancy
requirements, the following items should be checked:
I. General
A. Are the capacities of all components of both the primary system and
the backup system equal to or greater than the required capacities?
Some systems may have two or more units that provide the required
dosage rates when all units are operating. In these cases, an
additional unit is needed as backup, during the downtime of any of
the operating units. The backup must have a capacity equal to or
greater than that of the largest on-line unit.
B. Are adequate safety precautions being followed, relative to the type
of disinfectant being used?
C. Are redundant components being exercised or alternated with the
primary components?
D. Are all components being properly maintained?
E. Are critical spare parts on hand to repair disinfection equipment?
F. Are spare parts available for components that are indispensible for
disinfecting the water?
II. Disinfectant Storage
A minimum of two storage units capable of being used alternately should
be provided. However, it is not necessary for both systems to have full
design capacity.
A. Chlorine
Storage for gaseous chlorine will normally be in 150-lb cylinders,
2,000-lb containers, or larger on-site storage vessels.
1. Is there automatic switchover equipment if one cylinder or
container empties or becomes inoperable?
2. Is the switching equipment in good working order, (manually
tested on a regularly scheduled basis), and are spare parts on
hand?
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3. Are the scales adequate for at least two cylinders or contain-
ers.
B. Hypochlorite
Storage of calcium hypochlorite or sodium hypochlorite is normally
provided in drums or other suitable containers. Redundancy requirements are
not applicable to these by themselves, so long as the required minimum storage
quantity is on hand at all times.
C. Ammonia
Anhydrous ammonia is usually stored in cylinders as a pressurized liquid.
Aqua ammonia is usually stored as a solution of ammonia and water in a hori-
zontal pressure vessel.
1. Is the available storage volume divided into two or more usable
units?
2. Is automatic switching equipment in operation to change over
from one unit to another when one is empty or inoperable?
3. Are there spare parts for the switching equipment?
III. Generation
Ozone and chlorine dioxide are not stored on-site. Rather, because of
their reactivity, they are generated and used immediately.
To satisfy the redundancy requirements for these disinfectants it is
recommended that two generating units, or two sets of units, capable of
supplying the required feed rate be provided. In systems where there is more
than one generation system, a standby unit should be available for times the
on-line units need repair. The backup unit should have a capacity equal to or
greater than the units it may replace.
A. Chlorine Dioxide
Chlorine, sodium chlorite, or sodium hypochlorite should be stored in
accordance with storage guidelines previously described.
B. Ozone
Are all generation components present and in working order for both the
primary and the redundant units (whether using air or oxygen)?
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C. Common
Is switchover and automatic start-up equipment installed and operable to
change from the primary generating unit(s) to the redundant unit(s)?
IV. Feed Systems
Redundancy in feed systems requires two separate units, or systems, each
capable of supplying the required dosage of disinfectant. If more than one
unit is needed to apply the required feed rate, a third unit should be avail-
able to replace any of the operating units during times of malfunction. The
replacement unit should, therefore, have a capacity equal to or greater than
that of the largest unit which it may replace-. This requirement applies to
all disinfection methods, and is best implemented by housing the primary and
redundant components in separate rooms, enclosures, or areas, as appropriate.
In reviewing these systems for redundancy, the following components
should be checked:
A. Chlorine
1. Evaporators
2. Chlorinators
3. Injectors
B. Hypochlorite
1. Mixing tanks and mixers
2. Chemical feed pumps and controls
3. Injectors
Dissolution equipment, including compressor and delivery piping
systems
Chlorine Dioxide
1. Chlorine feed equipment
2. Sodium chlorite mixing and metering equipment
3. Day tank and mixer
4. Metering pumps
5. If a package CIO unit is used, two must be provided
Chloramination
1. Chlorine feed equipment
1-3
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2. Ammonia feed equipment, including applicable equipment for
either:
a. Anhydrous ammonia (gas)
b. Aqua ammonia (solution)
V. Residual Monitoring
The best method of monitoring a disinfection facility for continuous
operation is by continuous recording equipment. To improve reliability, it is
suggested that duplicate continuous monitors are present for backup in the
event of monitor failure. However, if there is a failure in the monitoring
system for indicating that a continuous residual is being maintained, this
would be a violation of a monitoring requirement, not a treatment requirement.
A. Chlorine
1. Does the facility have a continuous monitor for chlorine
residual at the disinfection system site with an alarm or
indicator to show when the monitor is not functioning? For
added assurance, the provision of a backup monitoring unit is
also recommended.
2. Is there instrumentation in place to automatically switch from
one monitor to the other if the first one fails?
B. Hypochlorite
Same as for chlorine system.
C. Ozone
. 1. Does the facility have a continuous ozone monitor with automa-
tic switchover capability and alarms?
2. Does the facility have a continuous ozone residual monitor with
automatic switchover capability and alarms?
D. Chlorine Dioxide
1. Does the facility have a continuous chlorine dioxide monitor
with automatic switchover capability and alarms?
2. Does the facility have a continuous chlorine dioxide residual
monitor with automatic switchover capability and alarms?
E. Chloramination
1. Does the facility have a continuous ammonia monitor with
automatic switchover capability and alarm?
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2. Does the facility also have a continuous chlorine residual
monitor on-site with automatic switchover capability and
alarms?
VI. Power Supply
A permanently installed standby generator, capable of running all elec-
trical equipment at the disinfection station, and equipped for automatic
start-up on power failure, should be on-site and functional.
Alternatives to a standby generator, such as a feed line from a different
power source, are acceptable if they can be shown to have equal reliability.
VII. Alarms
Indicators and alarms, both local and remote, should be capable of
promptly alerting operating and supervisory personnel of problem conditions.
A. Local
Lights, buzzers, and horns should be installed and functioning to alert
on-site personnel to problem conditions.
B. Remote
Alarm signals should be relayed to a central control panel which is
manned 24 hours per day and whose operators can notify response personnel
immediately.
C. Problem Conditions
A minimum list of problem conditions which should have indicators and
alarms, both locally and at a 24-hour per day switchboard, are as follows:
•
1. Disinfectant leak
2. Feeder pump failure
3. Power outage
4. Generator or alternate power source on
5. Disinfectant residual less than setpoint value
VIII. Facility Layout
Maximum reliability is ensured when redundant units are separated from
primary units. The type of separation should be appropriate to the type of
potential malfunction. For example, any area within a building subject to a
chlorine leak should have primary components separated from redundant compo-
nents by an airtight enclosure, i.e., separate rooms of varying sizes.
1-5
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IX. Separate Facility
Under certain conditions, such as location of a disinfection facility in
an area of high earthquake potential, the most reliable means of providing
redundant facilities may be to house them in a completely separate structure
at a different site.
1-6
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APPENDIX J
WATERSHED CONTROL PROGRAM
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APPENDIX J
WATERSHED CONTROL PROGRAM
The following is a guideline for documenting a watershed control program.
All systems are expected to conduct the basic elements of a watershed control
program. However, the scope of the program should increase as the complexity
and size of the watershed/system increases. The program could be more or less
comprehensive than this outline, and will be determined on a case-by-case
basis by the utility and the Primacy Agency. In addition to the guidelines
below, a wellhead protection program could be the basis of a watershed control
program in many states. All of the elements found below would also be part of
a local Wellhead Protection Program.
A. Watershed Description
1. Geographical location and physical features of the watershed.
2. Location of major components of the water system in relation-
ship to the watershed.
3. Hydrology: Annual precipitation patterns, stream flow charac-
teristics, etc.
4. Agreements and delineation of land use/ownership.
B. Identification of the Watershed Characteristics
and Activities Detrimental to Water Quality
' 1. Naturally Occurring:
a. Effect of precipitation, terrain, soil types and land
cover
b. Animal populations (describe) — include a discussion of
the Giardia contamination potential, any other microbial
contamination transmitted by animals
c. Other - any other activity which can adversely affect
water quality
2. Man-Made:
a. Point sources of contamination such as wastewater treat-
ment plant, industrial discharges, barnyard, feedlots, or
private septic systems
J-l
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b. Nonpoint Source of Contamination:
1) Road construction - major highways, railroads
2) Pesticide usage
3) Logging
4) Grazing animals
5) Discharge to ground water which recharges the surface
source
6) Recreation activities
7) Potential for unauthorized activity in the watershed
8) Describe any other human activity in the watershed
and its potential impact on water quality
It should be noted that grazing animals in the watershed may
lead to the presence of Cryptosporidium in the water. Crypto-
sporidium is a pathogen which may result in a disease outbreak
upon ingestion. No information is available on its resistance
to various disinfectants, therefore grazing should not be
permitted on watersheds of non-filtering systems. The utility
should set priorities to address the impacts in B.I. and 2.,
considering their health significance and the ability to
control them.
C. Control of Detrimental Activities/Events
Depending on the activities occurring within the watershed, various
techniques could be used to eliminate or minimize their effect.
Describe what techniques are being used to control the effect of
activities/events identified in B.I. and 2. in its yearly report.
Example:
Activity; Logging in the watershed.
Management Decision; Logging effects are unacceptable, there-
fore, do not allow logging in watershed.
Procedure; Buy out all logging rights within the watershed.
Monitoring; Periodically tour watershed to ensure no logging
is conducted.
J-2
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Controlled logging may sometimes be more cost effective. Measures
should, however, be taken to:
- Limit access
- Ensure cleanup
- Control erosion
Example:
Activity; Point sources of discharge within the watershed.
Management Decision; Eliminate those discharges or minimize
their impact.
Procedures; Actively participate in the review of discharge
permits to alert the reviewing agency of the potential (actual)
impacts of the discharge and lobby for its elimination or
strict control.
Monitoring; Conduct special monitoring to ensure conditions of
the permit are met and to document adverse effects on water
quality.
D. Monitoring
1. Routine: Minimum specifications for monitoring several raw
water quality parameters are listed in Section 3.1. Describe
when, where and how these samples will be collected. These
results will be used to evaluate whether the source may con-
tinue to be used without filtration.
2. Specific: Routine monitoring may not provide information about
all parameters of interest. For example, it may be valuable to
conduct special studies to measure contaminants suspected of
being present (Giardia, pesticides, fuel products, enteric
viruses, etc.). Frequent presence of either Giardia or enteric
viruses in raw water samples prior to disinfection would
indicate an inadequate watershed control program. Monitoring
may also be useful to assess the effectiveness of specific
control techniques, and to audit procedures or operational
requirements instituted within the watershed. Utilities are
encouraged to conduct additional monitoring as necessary to aid
them in controlling the quality of the source water.
E. Management/Operations
1. Management
a. Organizational structure
b. Personnel and education/certification requirements
J-3
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2. Operations
a. Describe system operations and design flexibility.
b. The utility should conduct some form of ongoing review or
survey in the watershed to identify and react to potential
impacts on water quality. The scope of this review should
be documented and agreed upon by the utility and Primacy
Agency on a case-by-case basis.
c. Specifically describe operational changes which can be
made to adjust for changes in water quality. Example:
Switching to alternate sources; increasing the level of
disinfection; using settling basins. Discuss what trig-
gers, and who decides to make, those changes.
3. Annual Report: As part of the watershed program, an annual
report should be submitted to the Primacy Agency. The contents
of the report should:
a. Identify special concerns that occurred in the watershed
and how they were handled (example: herbicide usage, new
construction, etc.).
b. Summarize other activities in the watershed such as
logging, hunting, water quality monitoring, etc.
c. Project what adverse activities are expected to occur in
the future and describe how the utility expects to address
them.
F. Agreements/Land Ownership
The goal of a watershed management program is to achieve the highest
level of raw water quality practicable. This is particularly
critical to an unfiltered surface supply.
1. The utility will have maximum opportunity to realize this goal
if they have complete ownership of the watershed. Describe
efforts to obtain ownership, such as any special programs or
budget. When complete ownership of the watershed is not
practical, efforts should be taken to gain ownership of
critical .elements, such as, reservoir or stream shoreline,
highly erodable land, and access areas to water system
facilities.
2. Where ownership of land is not possible, written agreements
should be obtained recognizing the watershed as part of a
public water supply. Maximum flexibility should be given to
the utility to control land uses which could have adverse
effect on the water quality. Describe such agreements.
J-4
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3. Describe how the utility ensures that the landowner complies
with these agreements.
J-5
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APPENDIX K
SANITARY SURVEY
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APPENDIX K
SANITARY SURVEY
The SWTR requires that an on-site inspection be conducted each year as
outlined in Section 3. It is recommended that at the onset of determining the
classification of a source water that a detailed sanitary survey be conducted.
In addition, it is recommended that a sanitary survey such as contained in
this appendix be conducted every 3 to 5 years to ensure that the quality of
the water and service is maintained. This time period is suggested since the
time and effort needed to conduct the comprehensive survey makes it
impractical for it to be conducted annually. A periodic sanitary survey is
also required under the Total Coliform Rule for systems collecting less than 5
samples/month. The survey must be conducted every 5 years for all systems
except for protected ground water systems which disinfect. These systems must
conduct the survey every 10 years.
The sanitary survey involves three phases, including planning the survey,
conducting the survey and compiling the final report of the survey, as will be
presented in the following pages.
1. Planning the Survey
Prior to conducting or scheduling a sanitary survey, there should be
a detailed review of the water system's file to prepare for the
survey. The review should pay particular attention to past sanitary
survey reports and correspondence describing previously identified
-problems and their solutions. These should be noted, and action/in-
action regarding those problems should be specifically verified in
the field. Other information to review includes: any other corre-
spondence, water system plans, chemical and microbiological sampling
results, operating reports, and engineering studies. This review
will aid in the familiarization with the system's past history and
present conditions, and the agency's past interactions with the
system.
The initial phase of the water quality review will be carried out
prior to conducting the survey as well, and will consist of review-
ing the water system's monitoring records. Records should be
reviewed for compliance with all applicable microbiological, inor-
ganic chemical, organic chemical, and radiological contaminant MCLs,
and also for compliance with the monitoring requirements for those
contaminants. The survey will provide an opportunity to review
these records with the utility, and to discuss solutions to any MCL
or monitoring violations. The survey will also provide an
K-l
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opportunity to review how and where samples are collected, and how
field measurements (turbidity, chlorine residual, fluoride, etc.)
are made. Points to cover include:
a. Is the system in compliance with all applicable MCLs (organic
chemical, inorganic chemical, microbiological, and radio-
logical) ?
b. Is the system in compliance with all monitoring requirements?
The pre-survey file review should generate a list of items to check
in the field, and a list of questions about the system. It will
also help the survey or plan the format of the survey and to esti-
mate how much time it may take. . The next step is to make the
initial contact with the system management to establish the survey
date(s) and time. Any records, files, or people that will be
referenced during the survey should be mentioned at the outset.
Clearly laying out the intent of the survey up front will greatly
help in managing the system, and will ensure that the survey goes
smoothly without a need for repeat trips.
2. Conducting the Survey
The on-site portion of the survey is the most important and will
involve interviewing those in charge of managing the water system as
well as the operators and other technical people. The survey will
also review all major system components from the source(s) to the
distribution system. A standard form is frequently used to ensure
that all major components and aspects of each system are consis-
tently reviewed. However, when in the field, it is best to have an
open mind and focus most attention on the specifics of the water
system, using the form only as a guide. The surveyor should be
certain to be on time when beginning the survey. This consideration
" will help get the survey started smoothly with the operator and/or
manager.
As the survey progresses, any deficiencies that are observed should
be brought to the attention of the water system personnel, and the
problem and the corrective measures should be discussed. It is far
better to clarify technical details and solutions while standing
next to the problem than it is to do so over the telephone. Points
to cover include:
a. Is the operator competent in performing the necessary field
testing for operational control?
b. Are testing facilities and equipment adequate, and do reagents
used have an unexpired shelf life?
c. Are field and other analytical instruments properly and regu-
larly calibrated?
K-2
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d. Are records of field test results and water quality compliance
monitoring results being maintained?
e. Conduct any sampling which will be part of the survey.
Also, detailed notes of the findings and conversations should be
taken so that the report of the survey will be an accurate recon-
struction of the survey.
Specific components/features of the system to review and some
pertinent questions to ask are:
A. Source Evaluation
All of the elements for a source elevation enumerated below may also
be part of a Wellhead Protection Program.
1. Description: based on field observations and discussion
with the operator, a general characterization of the
watershed should be made. Features which could be includ^-
ed in the description are:
a. Area of watershed or recharge area.
b. Stream flow.
c. Land usage (wilderness, farmland, rural housing,
recreational, commercial, industrial, etc.).
d. Degree of access by the public to watershed.
e. Terrain and soil type.
f. Vegetation.
g. Other.
2. Sources of contamination in the watershed or sensitive
areas surrounding wells or well fields should be identi-
fied. Not only should this be determined by physically
touring and observing the watershed and its daily uses,
but the surveyor should also actively question the water
system manager about adverse and potentially adverse
activities in the watershed. An example of types of
contamination includes:
a. Man Made.
1. Point discharges of sewage, stormwate'r, and
other wastewater.
K-3
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2. On-site sewage disposal systems.
3. Recreational activities (swimming, boating,
fishing, etc.).
4. Human habitation.
5. Pesticide usage.
6. Logging.
7. Highways or other roads from which there might
be spills.
8. Commercial or industrial activity.
9. Solid waste or other disposal facilities.
10. Barnyards, feed lots, turkey and chicken farms
and other concentrated domestic animal activity*.
11. Agricultural activities such as grazing, till-
age, etc., which affects soil erosion, ferti-
lizer usage, etc.
12. Other.
b. Naturally Occurring.
1. Animal populations, both domestic and wild.
2. Turbidity fluctuations (from precipitation,
landslides, etc.).
3. Fires.
4. Inorganic contaminants from parent materials
(e.g., asbestos fibers).
5. Algae blooms.
6. Other.
This list is by no means all inclusive. The surveyor
should rely principally on his observations and
thorough questioning regarding the unique properties
of each watershed to completely describe what may
contaminate the source water.
K-4
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3. Source Construction.
a. Surface Intakes.
1. Is the source adequate in quantity?
2. Is the best quality source or location in that
source being used?
3. Is the intake protected from icing problems if
appropriate?
4. Is the intake screened to prevent entry of
debris, and are screens maintained?
5. Is animal activity controlled within the immedi-
ate vicinity of the intake?
6. Is there a raw water sampling tap?
b. Infiltration Galleries.
1. Is the source adequate in quantity?
2. Is the best quality source being used?
3. Is the lid over the gallery watertight and
locked?
4. Is the collector in sound condition and main-
tained as necessary?
5. Is there a raw water sampling tap?
c. Springs.
1. Is the source adequate in quantity?
2. Is there adequate protection around the spring
such as fencing to control the area within 200
feet?
3. Is the spring constructed to best capture the
spring flow and exclude surface water infiltra-
tion?
4. Are there drains to divert surface water from
the vicinity of the spring?
5. Is the collection structure of sound construc-
tion with no leaks or cracks?
K-5
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6. Is there a screened overflow and drain pipe?
7. Is the supply intake located above the floor and
screened?
8. Is there a raw water sampling tap?
d. Catchment and Cistern.
1. Is source adequate in quantity?
2. Is the cistern of adequate size?
3. Is the catchment area protected from potential
contamination?
4. is the catchment drain properly screened?
5. Is the catchment area and cistern of sound
construction and in good condition?
6. Is catchment constructed of approved non-toxic,
non-leaching material?
7. Is the cistern protected from contamination —
manholes, vents, etc?
8. Is there a raw water tap?
e. Other Surface Sources.
1. Is the source adequate in quantity?
2. Is the best possible source being used?
3. Is the immediate vicinity of the source pro-
tected from contamination?
4. Is the structure in good condition and properly
constructed?
5. Is there a raw water sampling tap?
4. Pumps, Pumphouses, and Controls.
a. Are all intake pumps, booster pumps, and other pumps
of sufficient capacity?
b. Are all pumps and controls operational and maintained
properly?
K-6
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c. Are check valves, blow off valves, water meters and
other appurtenances operated and maintained properly?
d. Is emergency power backup with automatic start-up
provided and does it work (try it)?
e. Are underground compartments and suction wells
waterproof?
f. Is the interior and exterior of the pumphouse in good
structural condition and properly maintained?
g. Are there any safety hazards (electrical or mechan-
ical) in the pumphouse?
h. Is the pumphouse locked and otherwise protected
against vandalism?
i. Are water production records maintained at the
pumphouse?
Watershed Management (controlling contaminant sources) :
The goal of the watershed management program is to ident-
ify and control contaminant sources in the watershed (see
Section 3.3.1 of this document, "Watershed Control Pro-
gram"). Under ideal conditions each source of contamina-
tion identified in 2 will already have been identified by
the utility, and some means of control instituted, or a
factual determination made that its impact on water
quality is insignificant. To assess the degree to which
the watershed management program is achieving its goal,
the following types of inquiries could be made:
a. If the watershed is not entirely owned by the util-
ity, have written agreements been made with other
land owners to control land usage to the satisfaction
of the utility? Are appropriate regulations under
the contract of state/local department of health in
effect?
b. Is the utility making efforts to obtain as complete
ownership of the watershed as possible? Is effort
directed to control critical elements?
c. Are there means by which the watershed is regularly
inspected for new sources of contamination or tres-
passers where access is limited?
d. Are there adequately qualified personnel employed by
the utility for identifying watershed and water
K-7
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quality problems and who are given the responsibility
to correct these problems?
e. Are raw water quality records kept to assess trends
and to assess the impact of different activities and
contaminant control techniques in the watershed?
f. Has the system responded adequately to concerns
expressed about the source or watershed in past
sanitary surveys?
g. Has the utility identified problems in its yearly
watershed control reports, and if so, have these
problems been adequately addressed?
h. Identify what other agencies have control or juris-
diction in the watershed. Does the utility actively
interact with these agencies to see that .their
policies or activities are consistent with the
utility's goal of maintaining high raw water quality?
B. Treatment Evaluation
1. Disinfection.
a. Is the disinfection equipment and disinfectant
appropriate for the application (chloramines, chlor-
ine , ozone, and chlorine dioxide are generally
accepted disinfectants)?
b. Are there back-up disinfection units on line in case
of failure, and are they operational?
c. Is there auxiliary power with automatic start up in
case of power outage? Is it tested and operated on a
regular basis, both with and without load?
d. Is there an adequate quantity of disinfectant on hand
and is it properly stored (e.g., are chlorine cylin-
ders properly labeled and chained)?
e. In the case of gaseous chlorine, is there automatic
switch over equipment when cylinders expire?
f. Are critical spare parts on hand to repair disin-
fection equipment?
g. Is disinfectant feed proportional to water flow?
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h. Are daily records kept of disinfectant residual near
the first customer from which to calculate CTs?
i. Are production records kept from which to determine
CTs?
j. Are CTs acceptable based on the level of treatment
provided (see Surface Water Treatment Rule for
filtered sources, and Section 3.2.2 of this guidance
manual for unfiltered sources, to determine the
appropriate CT)?
k. Is a disinfectant residual maintained in the dis-
tribution system, and are records kept of daily
measurements?
1. If gas chlorine is used, are adequate safety pre-
cautions being followed (e.g., exhaust fan with
intake within six inches of the floor, self-contained
breathing apparatus that is regularly tested, regular
safety training for employees, ammonia bottles and/or
automatic chlorine detectors)? Is the system ade-
quate to ensure the safety of both the public and the
employees in the event of a chlorine leak?
2. Other.
a. Are other treatment processes appropriate and are
they operated to produce consistently high water
quality?
b. Are pumps, chemical feeders, and other mechanical
equipment in good condition and properly maintained?
c. Are controls and instrumentation and adequate for the
process, operational, well maintained and calibrated?
d. Are accurate records maintained (volume of water
treated, amount of chemical used, etc.)?
e. Are adequate supplies of chemical on hand and pro-
perly stored?
f. Are adequate safety devices available and precautions
observed?
Sections of a sanitary survey pertaining to systems
containing filtration facilities have been omitted, as
this section of the guidance document pertains to non-
filtering systems.
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C. Distribution System Evaluation
After water has been treated, water quality must be protected
and maintained as it flows through the distribution system to
the customer's tap. The following questions pertain to the
water purveyor's ability to maintain high water quality during
storage and distribution.
1. Storage.
a. Gravity.
1. Are storage reservoirs covered and otherwise
constructed to prevent contamination?
2. Are all overflow lines, vents, drainlines, or
cleanout pipes turned downward and screened?
3. Are all reservoirs inspected regularly?
4. Is the storage capacity adequate for the system?
5. Does the reservoir (or reservoirs) provide
sufficient pressure throughout the system?
6. Are surface coatings within the reservoir in
good repair and acceptable for potable water
contact?
7. Is the hatchcover for the tank watertight and
locked?
8. Can the reservoir be isolated from the system?
9. Is adequate safety equipment (caged ladder, OSHA
approved safety belts, etc.) in place for
climbing the tank?
10. Is the site fenced, locked, or otherwise pro-
tected against vandalism?
11. Is the storage reservoir disinfected after
repairs are made?
12. Is there a scheduled program for cleaning
storage reservoir sediments, slime on floor and
side walls.
b. Hydropneumatic.
1. Is the storage capacity adequate for the system?
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2. Are instruments, controls, and equipment ade-
quate, operational, and maintained?
3. Are the interior and exterior surfaces of the
pressure tank in good condition?
4. Are tank supports structurally sound?
5. Does the low pressure cut in provide adequate
pressure throughout the entire system?
6. Is the pump cycle rate acceptable (not more than
15 cycles/hour)?
2. Cross Connections.
a. Is the system free of known uncontrolled cross
connections?
b. Does the utility have a cross connection prevention
program, including annual testing of backflow preven-
tion devices?
c. Are backflow prevention devices installed at all
appropriate locations (wastewater treatment plant,
industrial locations, hospitals, etc.)?
3. Other.
a. Are proper pressures and flows maintained at all
times of the year?
b. Do all construction materials meet AWWA or equivalent
standards?
c. Are all services metered and are meters read?
d. Are plans for the system available and current?
e. Does the system have an adequate maintenance program?
- Is there evidence of leakage in the system?
- Is there a pressure testing program?
- Is there a regular flushing program?
- Are valves and hydrants regularly exercised and
maintained?
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- Are AWWA standards for disinfection followed
after all repairs?
- Are there specific bacteriological criteria and
limits prescribed for new line acceptance or
following line repairs?
- Describe the corrosion control program.
- Is the system interconnected with other systems?
D. Manageme nt/Ope ration
1. Is there an organization that is responsible for providing
the operation, maintenance, and management of the water
system?
2. Does the utility regularly summarize both current and
long-term problems identified in their watershed, or other
parts of the system, and define how they intend to solve
the problems i.e., is their planning mechanism effective;
do they follow through with plans?
3. Is the budget and financing satisfactory to provide
continuous high quality service, and allow for future
replacements and improvements?
4. Are customers charged user fees and are collections
satisfactory?
5. Are there sufficient personnel to operate and manage the
system?
6. Are personnel (including management) adequately trained,
educated, and/or certified?
7. Are operation and maintenance manuals and manufacturers
technical specifications readily available for the system?
8. Are routine preventative maintenance schedules established
and adhered to for all components of the water system?
9. Are sufficient tools, supplies, and maintenance parts on
hand?
10. Are sufficient operation and maintenance records kept and
readily available?
11. Is an emergency plan available and usable, and are em-
ployees aware of it?
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12. Are all facilities free from safety defects?
When the survey is completed, it is always preferable to
briefly summarize the survey with the operator(s) and manage-
ment. The main findings of the survey should be reviewed so it
is clear that there are not misunderstandings about find-
ings/conclusions. It is also good to thank the utility for
taking part in the survey, arranging interviews with employees,
gathering and explaining their records, etc. The information
and help which the utility can provide are invaluable to a
successful survey, and every attempt should be made to continue
a positive relationship with the system.
3. Reporting the Survey
A final report of the survey should be completed as soon as possible
to formally notify the system and other agencies of the findings.
There is no set or necessarily best format for doing so, and the
length of the report will depend on the findings of the survey and
size of the system. Since the report may be used for future compli--
ance actions and inspections, it should include as a minimum:
1) the date of the survey; 2) who was present during the survey;
3) the findings of the survey; 4) the recommended improvements to
identified problems; and 5) the dates for completion of any improve-
ments. Any differences between the findings discussed at the
conclusion of the survey and what's included in the final report
should be discussed and clarified with the utility prior to sending
out the final report. In other words, the utility should be fully
aware of the contents of the final report before receiving it.
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APPENDIX L
SMALL SYSTEM CONSIDERATIONS
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APPENDIX L
SMALL SYSTEMS CONSIDERATIONS
Introduction
Under the provisions of the SWTR, systems with fewer than 500 service
connections may be eligible for an exemption. Guidance on the requirements
for an exemption is provided in Section 9. For systems which are not eligible
for an exemption, compliance with the SWTR is mandatory. It is recognized
that the majority (approximately 75 percent) of people in the United States
are served by a relatively small number of large systems. However, most water
systems in the United States are small. For small systems, compliance with
the various provisions of the SDWA has traditionally been a problem. Records
show small systems have a disproportionately higher incidence of drinking
water quality and monitoring difficulties. The reasons for these difficulties
can generally be broken down into the following three categories:
- Economics
- Treatment Technologies
- Operations (lack of qualified personnel)
Small water systems typically face severe economic constraints. Their
lack of operating revenues results in significant limitations on their ability
to respond to the requirements of the SDWA. These systems cannot benefit from
the economies of scale which are available to larger systems.
The second difficulty facing the small systems has been the lack of
appropriate treatment technologies. Although methods for removing most of the
contaminants known to occur in drinking water are available, many of these
technologies have only recently been scaled down for the smaller systems.
The third problem which has traditionally plagued small systems is the
lack of well trained operators. This deficiency is the result of many com-
bined factors. First of all, many of these operators are employed only on a
part-time basis or if they are employed on a full-time basis they have a
myriad of additional duties. In addition, the operator's technical background
may be limited as well. This results from the low salary of the position,
which is uninviting to qualified operators. Also, in spite of the requirement
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of retaining certified operators upheld in many states, it seems to be diffi-
cult to enforce this requirement in small systems.
The purpose of this appendix is to provide assistance to the Primacy
Agency in defining the problems and potential solutions typically associated
with small systems. It is beyond the scope of this document to provide an
indepth dicussion of the needs of small systems. However, over the past
several years the needs of the small water systems have been recognized to be
of primary concern and numerous workshops, seminars and committees have been
attempting to more clearly define workable solutions. A partial listing cf
the papers, reports and proceedings which discuss problems and solutions
pertaining to small systems beyond that which is possible in this manual is
presented in the reference list of this appendix.
Economics
One of the most severe constraints of small systems is the small economic
base from which to draw funds." Certain treatment and services must be pro-
vided for a community regardless of how few people are served. Thus, as the
number of connections to the system decrease, the cost per connection in-
creases. The economic limitations of small utilities makes it difficult to
provide needed upgrading of existing facilities or an adequate salary to
maintain the employment of a qualified operator to monitor and maintain the
system. Adding to the severity of the economic hardships of small systems is
the fact that many of the small water systems are privately owned, with
private ownership increasing as system size decreases. The ownership of the
plant presents difficulties since privately owned systems are subject to rate
controls by the local public utility commission, are not eligible for public
grants and loans, and may find commercial loans hard to obtain.
Financing options for small systems include; federal and state loan and
grant programs, federal revenue sharing and revenue bonds (for municipal
systems) and loans through the United States Small Business Administration
(SBA) and use of industrial development bonds or privatization (for private
utilities). These options are explained in greater detail in the "Guidance
Manual - Institutional Alternatives for Snail Water Systems" (ANWA, 1986).
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The following paragraphs will explain some existing options which may ease the
hardship of financing small water treatment facilities.
The major cause of small system difficulties arises from the lack of
funds and resources. It is therefore in the best interest of small utilities
to expand their economic base and the resources available to them, to achieve
the economies of scale available to larger systems. Regionalization is the
physical or operational union of small systems to effect this goal. This
union can be accomplished through the physical interconnection of two or more
small systems or the connection of a smaller system to a pre-existing larger
system. Water supply systems can also join together for the purchase of
supplies, materials, engineering services, billing and maintenance. The union
of the small systems increases the population served, thereby dispersing the
operational costs and decreasing the cost per consumer.
The creation of utility satellites is another form of regionalization. A
satellite utility is one which taps into the resources of an existing larger
facility without being physically connected to, or owned by, the larger facil-
ity. The larger system may provide any of the following for the smaller
system:
1. Varying levels of technical operational, or managerial assistance on
a contract basis.
2. Wholesale treated water with or without additional services.
3. Assuming ownership, operation and maintenance responsibility when
. the small system is physically separate with a separate source.
The formation of a satellite offers many advantages for both the
satellite and the parent utility. These advantages include: an improved
economy of scale for satellites, an expanded revenue base for the parent
utility, provisions of needed resources to satellites, the retention of the
satellites' local autonomy, improved water quality management of the
satellite, improved use of public funds for publicly owned satellites.
In order to create a more definite structure for the union of resources
of water treatment facilities, water districts may be created. Water
districts are formed by county officials and provide for the public ownership
of the utilities. The utilities in any given district would combine resources
and/or physically connect systems so that one or two facilities would provide
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water for the entire district. The creation of water districts creates
eligibility for public monies, has the potential for economies of size,
facilitates the takeover or contract services with publicly owned non-commun-
ity systems and small privately owned systems, and offers a tax advantage.
Drawbacks include subjection to politics, a strong local planning effort is
needed for success, and competition with private enterprises.
The centralization of utilities can be taken one step further through the
creation of county utilities or even state utilities. The government will
create a board which may then act to acquire, construct, maintain and operate
any public water supply within its district, the system may provide water on
its own or purchase water from any municipal corporation. The board may adopt
and administer rules for the construction, maintenance, protection and use of
public water supplies and the fixation of reasonable rates for water supplies.
The cost of construction and/or upgrading of facilities may be defrayed
through the issuance of bonds and/or property assessment. As with all the
alternatives, the creation of government control of the utilities has its
advantages and disadvantages. The advantages include: the creation of
central management, creation of economy of scale for utilities, eligibility
for public grants and loans, savings through centralized purchasing, manage-
ment, consultation, planning and technical assistance, and possible provision
for pool of trained operators. The disadvantages include the subjectivity to
politics, the slow response caused by bureaucracy, and competition to private
contractors.
Treatment Technologies
The high cost of available treatment technologies has limited their use
in small water supply systems. Recently prefabricated package plants and
individual treatment units have been developed to lessen these costs. At the
present time, the treatment technologies which are available to enable systems
to comply with the Safe Drinking Water Act are identified to be the following:
- Package plants
- Slow-sand filters
- Diatomaceous earth filters
- Cartridge filtration
A brief discussion of each treatment method is provided belcw.
-------
Package Plants
Clarification and filtration units which require minimal assembly in the
field can now be manufactured. To minimize required operator skill level and
operational attention, the equipment should be automated. Continuous effluent
turbidity and disinfectant residual monitoring systems with alarms and
emergency shutdown provisions are features that safeguard water quality and
should be provided for unattended plants.
Slow-Sand Filters
Slow-sand filters are applicable to small water supply systems. Their
proven record of effective removal of turbidity and Giardia cysts makes them
suitable for application where operational attention is minimal. Since no
chemicals other than a disinfectant are needed, and no mechanical equipment is
involved, the required operator skill level is the lowest of the filtration
alternatives available to small systems.
Diatomaceous Earth Filters
Diatomaceous earth (DE) pressure and vacuum filters can be used on
relatively low turbidity surface waters (less than 1 to 2 NTU) for removal of
turbidity and Giardia cysts. DE filters can effectively remove particles as
small as 1 micron, but would require coagulating chemicals and special filter
aids to provide significant virus removal.
Cartridge Filters
Cartridge filters using microporous ceramic filter elements with pore
sizes as" small as 0.2 um may be suitable for producing potable water, in
combination with disinfection, from raw water supplies containing moderate
levels of turbidity, algae, protozoa and bacteria. The advantage to a small
system, is, with the exception of chlorination, that no other chemicals are
required. The process is one of strictly physical removal of small particles
by straining as the water passes through the porous membranes. Other than
occasional cleaning or membrane replacement, operational requirements are not
complex and do not require skilled personnel.
Selection of a Filtration Technology
The criteria for selection of a filtration technology for a small commun-
ity are essentially the same as those for a larger community. That is, the
utility must first screen the complete list of available alternatives to
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eliminate those which are either not technically suited to the existing
conditions (Table 4-1) or not affordable by the utility. Remaining alterna-
tives should then be evaluated based on both cost (capital, annual, and
life-cycle) and non-cost bases (operation and maintenance, technical require-
ments versus personnel available; flexibility regarding future needs; etc.).
In these evaluations it should be noted that even though automated package
plants are cost-competitive with slow sand filters, their operation require-
ments to achieve optimum performance could be complicated. Also, the
maintenance requirements for package plants would be mechanically and
electrically oriented and might require a maintenance agreement with the
manufacturer.
During the process of installing the treatment system, interim measures
should be taken to ensure the delivery of a reasonably safe water to the
consumers. In addition to the available interim measures listed In
Section 9.3, temporary installation of mobile filtration plants may be
possible. These trailer-mounted units are sometimes available from state
agencies for emergencies, but more often may be rented or leased from an
equipment manufacturer.
Modification of Existing Filtration Systems
Small treatment systems that arc already in existence should comply with
the performance criteria of the SWTR. If the systems are not found to be
performing satisfactorily, modifications to the existing process may be
required*. Improvement in treatment efficiency depends on the type of filtra-
tion system in use. Operation of slow sand filters could be checked for bed
depth, short-circuiting, excessive hydraulic loading, and for the need to pre-
treat the raw water. Infiltration galleries, or sometimes, roughing filters
ahead of a slow sand filter may provide for better performance by reducing the
solids load on the filters. However, the design criteria and costs for this
alternative have not yet been defined. Site specific studies may be required
before roughing filters could be used to achieve compliance with the regula-
tions. Diatomaceous earth (DE) filters should be checked for appropriate
precoat and body feed application, hydraulic loading, grade (size) of DE being
used, and possible need for chemical pretreatment. Package plants would have
to be checked process-by-process, similar to the system used for a
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conventional plant. Other filtration processes would have to be checked for
hydraulic loading rate, appropriateness of the filter material (pore size),
and possible need for additional pretreatment.
Disinfection
Disinfection (CT) requirements for small systems can be met in several
different ways. The most obvious method of maintaining a disinfectant
residual in the distribution system is to add disinfectant at one or more
additional locations. An alternate method is to increase the disinfectant
dose at the existing application point(s). The latter alternative, however,
may increase disinfectant byproducts, including THMs, in the system.
If it is a relatively short distance between the treatment system and the
first customer, additional contact time can be provided so that the
disinfectant dose does not have to be increased beyond desirable residuals.
Two specific methods of increasing contact time for small systems are
1) installing a pressure vessel or closed storage vessel, baffled to provide
adequate contact time, or 2) constructing a looped pipeline, on the finished
water line between the filtration-disinfection system and the first customer.
The feasibility of either of these methods would depend on system specifics
that include size, physical conditions, and cost.
If it is not practical to provide additional storage time to achieve the
desired CT, an alternate, more effective disinfectant may be used. An
alternate disinfectant may provide a sufficient CT without altering the system
configuration.
Operations
Water treatment facilities need to be operated properly in order to
achieve maximum treatment efficiencies. There is currently a lack of well
trained operators at many small treatment plants. The main cause is lack of
awareness of the importance of correct plant operation, lack of training
programs, lack of enforcement of the requirement for employment of a certified
operator and lack of funds to employ such an operator.
Small systems may wish to implement a circuit rider/operator program. In
this program a qualified, certified, experienced operator works for several
water supply systems. The rider can either directly operate the plants, or
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provide technical assistance to individual plant operators, by acting as a
trainer through on-the-job supervision. The latter would be preferable since
it could create a pool of well trained operators.
The main cause of inadequately trained operators is the lack of well
established training programs. Until such training programs are begun,
systems must depend on other training means, such as seminars and books. One
resource which may be helpful in running the plant is "Basic Management
Principles for Small Hater Systems - An AWWA Small-Systems Resource Book",
1982.
Host package plant manufacturers' equipment manuals include at least
brief sections on operating principles, methods for establishing proper
chemical dosages, instructions for operating the equipment, and troubleshoot-
ing guides. An individual who studies these basic instructions and receives
comprehensive start-up training should be able to operate the equipment
satisfactorily. These services are vital to the successful performance of a
package water treatment plant and should be a requirement of the package plant
manufacturer. The engineer designing a package plant facility should specify
that start-up and training services be provided by the manufacturer, and also
should consider requiring the manufacturer to visit the plant at 6-month and
1-year intervals after start-up to adjust the equipment, review operations,
and retrain operating personnel. Further, this program should be ongoing and
funds should be budgeted every year for at least one revisit by the package
plant manufacturer.
Another way for small systems to obtain qualified plant operation would
be to contract the services of administrative, operations, and/or maintenance
personnel from a larger neighboring utility, government agencies, service
companies or consulting firms. These organizations could supply assistance in
financial and legal planning, engineering, purchasing accounting and collec-
tion services, laboratory support, licensed operators or operator training,
treatment and water quality assurance, regulatory liaison, and/or emergency
assistance. Through the contracting of these services the utility provides
for the resources needed, improves water quality management and retains its
autonomy. However, if and when the contract is terminated, the utility
returns to its original status.
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References
American Water Works Association. Basic Management Principles for Small Water
Systems, 1982.
American Water Works Association. Design and Construction of Small Water
Systems, 1984.
Kelly, Gidley, Blair and Wolfe, Inc. Guidance Manual - Institutional
Alternatives for Small Water Systems. AWWA Research Foundation Contract
79-84, 1986.
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APPENDIX M
PILOT STUDY PROTOCOL
FOR ALTERNATE FILTRATION TECHNOLOGY
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APPENDIX M
If a system desires to use an alternate filtration technology, then the
system must demonstrate through pilot testing that the alternate technology
can meet the performance criteria for virus and Giardia removal and/or
inactivation. However, pilot testing for virus removal is not required if the
water to be disinfected has a turbidity less than 1 NTD and sufficient CT is
provided to achieve 4-log virus inactivation. Alternate technologies may
include demonstrated technologies operating outside the range of accepted
design criteria.
This appendix provides a recommended protocol for evaluating alternate
filtration methods through pilot testing. This protocol is divided into
sections:
- Pilot Plant
- Testing Program
- Monitoring and analyses.
Pilot Plant
The primary consideration in design of the pilot plant is to adequately
simulate the treatment provided by the full scale facility. Criteria which
should be considered in the pilot plant design include but are not limited to
the parameters in the following list.
Treatment Process Criteria
Rapid Mix Number of Stages
Detention Time
Mixing Intensity
Flocculation Number of Stages
Detention Time
Mixing Intensity(ies)
Sedimentation Unit Type (plate, tube, etc.)
Loading Rates
Filtration Media type and size
Media depth
Loading Rate
Operation Mode (constant rate,
declining rate)
Chemical Addition Location
Dosage
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Testing Program
In developing a pilot testing procedure or study to evaluate an alternate
filtration technology, seasonal water quality variations should be reviewed in
order to establish the annual worst case water quality conditions for an
individual source water. The water quality parameters which should be re-
viewed include:
- Total and/or Fecal Coliforms
- Heterotrophic plate count
- Turbidity
- Temperature
- PH
- Color
- Chlorine demand
As a minimum, pilot testing should be conducted when the source exhibits
its worst case annual conditions. However, it is preferable to perform
testing under all seasonal water quality conditions.
The design of pilot plant studies will depend on a variety of factors
including the technology being evaluated and individual site constraints. Any
pilot study should include consideration of the following (Thompson, 1982) :
- Definition of purpose of study
- Identification of end product of study
- Collection of available background information
- Acquisition of additional information required
- Establishment of size of pilot plant and available space
- Determination of who will operate pilot plant
- Ascertainment of how it should be operated
- Establishment of life of pilot plant
- Determination of frequency and location of sample collection and
_ analysis
- Modification of pilot plant (if required)
- Revision of goals and budget if necessary
- Preparation of design and construction of pilot plant based on above
- Recording of all pilot plant data
1.Additional information on the design of specific pilot studies can be
found in the following references:
- Overview of Pilot Plant Studies. (Thompson, 1982)
- Water Treatment Principles and Design, James M. Montgomery.
- Al-Ani, C.S.U., Filtration of Giardia Cysts and Other Substances:
Volume 3. Rapid Rate Filtration (EPA/600/2-85/027).
M-2
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- Performance of critical data analysis
- Reporting of Substantiated Conclusion
Monitoring Requirements
The purpose of the pilot testing program is to demonstrate that the
alternate filtration technology can meet the performance criteria for virus
and Giardia removal/inacti vat ion outlined in Section 5. The monitoring
locations and frequency should therefore be selected to comply with these
requirements. For example, filter effluent turbidity should be monitored
continuously or, at a minimum every four hours. Disinfectant residual should
also be monitored as outlined in Section 5.
References
J. C. Thompson, "Overview of Pilot Plant Studies in Proceedings AWWA
Seminar on Design of Pilot-Plant Studies," May 16, 1982.
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APPENDIX N
PROTOCOL FOR DEMONSTRATION
OF EFFECTIVE TREATMENT
-------
APPENDIX N
PROTOCOL FOR DEMONSTRATION
OF EFFECTIVE TREATMENT
Based upon the requirements of the SWTR, the minimum turbidity perform-
ance criteria for systems using conventional treatment or direct filtration is
filtered water turbidity less than or equal to 0.5 NTU in 95 percent of the
measurements taken each month. However, at the discretion of the Primacy
Agency, filtered water turbidity levels of less than or equal to 1 NTU in 95
percent of the measurements taken every month may be permitted on a case-by-
case basis depending on the capability of the total system to remove and/or
inactivate at least 99.9 percent of Giardia lamblia cysts. This appendix
presents several approaches which could be taken to demonstrate overall
effective removal and/or inactivation of Giardia cysts and when higher tur-
bidity limits might be appropriate.
Optimize Turbidity Removal
Since turbidity measures the scattering of visible light {wavelength -
0.5 um) it will be particularly sensitive on an equivalent-weight basis to the
presence of particles of this size (O'Melia, 1987). Filtration theory indi-
cates that on a per-weight basis, particles between 0.1 and 2 um (depending on
filtration rate, media size and temperature) should be removed to a lesser
degree than particles that are either larger or smaller (Yao, et al, 1971) .
Thus, turbidity measurements are likely to be most sensitive to particles that
are least likely to be removed.
Since the principal consideration for filtered systems under the SWTR is
the removal of Giardia cysts which are considerably larger than 2 um (7-12
um), good turbidity removal should be tantamont to good Giardia cyst removal.
Therefore, depending on the type of turbidity, it may be possible to effec-
tively remove Giardia cysts without producing extremely low filtered water
turbidities.
Treatment plants that use settling followed by filtration, or direct
*
filtration are generally capable of producing a filtered water with a
N-l
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turbidity of 0.2 NTU or less. The most likely cause of high turbidities in
the filtered water is incorrect coagulant dosing (O'Melia, 1974). Regardless
of the turbidity of the raw or finished water, coagulant addition at some
point prior to filtration is required to destabilize particles for removal in
the filter. Only plants documenting continuous coagulant feed prior to
filtration should be eligible for being allowed higher filtered water turbid-
ities than the 0.5 NTU requirement. At plants that continuously feed coag-
ulant and do not meet the 0.5 NTU requirement, a series of jar tests, and
perhaps sand column filtration tests (in batch) should be performed to evalu-
ate the optimum coagulant dose for turbidity removal.
In the event that plants can document continuous coagulant feed, and,
after running the plant under conditions determined in batch testing to be
optimal for turbidity removal, still do not meet the 0.5 NTU requirement,
effective filtration status might be appropriate. This would further be
supported if it can be shown that the full scale plant is capable of achieving
a 2-log reduction in the concentration of particles between 5 and 15 urn in
size. Where a full scale plant does not yet exist, appropriately scaled-down
pilot filters might be used for such a demonstration. "Appropriate scale-
down" involves the following:
- filtration rate of the pilot equal to filtration rate on full scale
unit,
- pilot filter diameter greater than or equal to 50 times the media
diameter, (Robeck, et al 1959)
- media diameter, depth, and size gradation should be identical to
full scale,
- coagulant dosing identical to full scale
- any mixing and settling occurring before filtration in the full
scale plant should be reproduced as closely as possible in the
pilot. Mixing should be of the same G value(s) , and the detention
time for settling should be close to the average flow detention time
for the projected full scale plant.
In the case of either a full scale or pilot scale demonstration, removal
of particles in the range of 5 to 15 urn in diameter should be determined using
an electronic particle counter that has been calibrated with latex spheres.
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If a light blockage device is used (e.g. HIAC) this calibration will have been
done at installation of the device. The calibration should be checked before
taking measurements for the purposes of this demonstration. Samples should be
diluted appropriately to ensure that measurements do not reflect coincident
error. An electrical sensing zone device (e.g. Coulter Counter or Elzone) may
also be used. Appropriate dilutions, electrolyte strength, and calibration
procedures should be followed (these are scheduled to be outlined in the 17th
edition of Standard Methods). when using an electrical sensing zone instru-
ment, an orifice no larger than 125 urn and no smaller than 40 um should be
used since only particles between 2% and 40% of the orifice are accurately
sized and counted (Karuhn et al 1975).
Samples of the filter influent and effluent should be taken 5 minutes
after the backwashed filter is placed in operation, and every 30 minutes
thereafter for the first 3 hours of operation, followed by hourly samples up
until backwash (Wiesner et al 1987). All samples should show a 2-log removal.
Samples from repeated filter runs may be averaged at each sampling time, but
samples should not be averaged within one filter run.
Additional suggestions on particle counting technique (Wiesner 1985) :
1) If particle counts are not determined immediately upon sampling
(within 10 minutes) samples should be diluted.
2) For an electrical sensing zone measurement, samples should be
diluted 1:5 to 1:20 with a "particle-free" electrolyte solution
(approximately 1% NaCl) containing 100 particles per ml or fewer.
3) For a light blockage measurement, particle free water should be used
to dilute samples.
4) Dilutions should be done to produce particle concentrations as close
to the tolerance for coincident error as possible to minimize
background counts.
5) Particle counts should be determined within 8 hours of sampling.
6) All sampling vessels should be washed with laboratory detergent,
double rinsed in particle free water, and rinsed twice with the
water being sampled at the time of sampling.
N-3
-------
Disinfection
The level of disinfection could also be considered for determining when
to allow a higher turbidity performance criterion for a system. For example,
if a system achieves 3-log Giardia cyst inactivation through disinfection, as
determined by CT values, it may be appropriate to allow higher filtered water
turbidities (i.e., greater than 0.5 NTU but less than 1 NTU in 95 percent of
the measurements and never exceeding 5 NTU) . As an extension of this concept,
if a system achieves 2-log Giardia cyst inactivation and is able to demon-
strate greater than a 1-log reduction in concentration of particles between 5
and 15 um, in accordance with the procedure discussed in the previous section,
this could provide a basis for allowing filtered water turbidity limits above
0.5 NTU but less than 1 NTU in 95 percent of the measurements.
The expected level of fecal contamination and Giardia cyst concentrations
in the source water should be considered in the above analysis. In many
cases, high levels of disinfection (e.g., 2 to 3-log inactivation of Giardia
cysts), in addition to filtration which achieves less than 0.5 NTU in 95
percent of the measurements may be appropriate, depending upon source water
quality. Further guidance on the level of disinfection to be provided for
various source water conditions is provided in Section 4.4.2.
References
Coulter Electronics 600 W. 20th Street, Hialeah, FL 33010-2428
Karuhn, R.; Davies, R.; Kaye, B. H.; Clinch, M. J. Studies on the Coulter
Counter Part I. Powder Company Volume II, pp. 157-171, 1975
O'Melia, C. R. The Role of Polyelectrolytes in Filtration Processes, EPA -
67012-74-032, 1974T~~~
Robeck, G. G.; Woodword, R. L. Pilot Plants for Water Treatment Research,
Journal of Sanitary Engineering ASCE Vol. 85;SA4; 1, August 1959.
Wiesner, M. R.; Rook, J. J.; Fiessinger, F. Optimizing the Placement of GAC
Filters, J. AWWA VOL 79, pp. 39-49, Dec 1987.
Wiesner, M. R. "Optimum Water Treatment Plant Configuration Effects of Raw
Water Characteristics," dissertation John Hopkins University, Baltimore, MD,
1985.
N-4
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APPENDIX O
PROTOCOLS FOR POINT-OF-USE
DEVICES
-------
UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
Registration Division
Office of Pesticide Programs
Criteria and Standards.Division
Office of Drinking Water
GUIDE STANDARD AND PROTOCOL FOR
TESTING MICROBIOLOGICAL WATER PURIFIERS
Report of Task Force
Submitted April, 1986
Revised April, 1987
-------
CONTENTS
Page
PREFACE
1. GENERAL 1
2. PERFORMANCE REQUIREMENTS 6
3. MICROBIOLOGICAL WATER PURIFIER TEST PROCEDURES 8
APPENDIX 1 SUMMARY FOR BASIS OF STANDARDS AND 21
TEST WATER PARAMETERS
APPENDIX 2 LIST OF PARTICIPANTS IN TASK FORCE 29
APPENDIX 3 RESPONSE BY REVIEW SUBCOMMITTEE TO 31
PUBLIC COMMENTS
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Preface
The protocol presented in this paper can be applied to demonstrate the
effectiveness of new technologies as well as point-of-use devices. The
evaluation presented here deals with the removal of particulates and
disinfection. In areas which pertain to disinfection, the guidelines
contained in Appendix G take precedence.
-------
1. GENERAL
1.1 Introduction
The subject of microbiological purification for waters of unknown micro-
biological quality repeatedly presents itself to a variety of governmental and
non-governmental agencies, consumer groups, manufacturers and others. Exam-
ples of possible application of such purification capabilities include:
- Backpackers and campers
- Non-standard military requirements
- Floods and other natural disasters
- Foreign travel and stations (however, not for extreme contamination
situations outside of the U.S.)
Contaminated individual sources, wells and springs (however, not for
the conversion of waste water to microbiologically potable water)
- Motorhomes and trailers
Batch methods of water purification based on chlorine and iodine disin-
fection or boiling are well known, but many situations and personal choice
call for the consideration of water treatment equipment. Federal agencies
specifically involved in responding to questions and problems relating to
microbiological purifier equipment include:
- Registration Division, Office of Pesticide Programs (OPP), Environ-
mental Protection Agency (EPA): registration of microbiological
purifiers (using chemicals);
- Compliance Monitoring Staff, EPA: control of microbiological
purifier device claims (non-registerable products such as ultra-
violet units, ozonators, chlorine generators, others);
- U.S. Army Medical Bioengineering Research and Development Laboratory
(USAMBRDL), U.S. Army Natick Research and Development Center and
other Army and military agencies: research and development for
possible field applications;
- Criteria and Standards Division, Office of Drinking Water (ODW) ,
EPA: Consideration of point-of-use technology as acceptable tech-
nology under the Primary Drinking Water Regulations; consumer
information and service;
-------
- Drinking Water Research, Water Engineering Research Laboratory
(WERL), EPA; responsible for water treatment technology research;
- Microbiology Branch, Health Effects Research Laboratory (HERL), EPA;
responsible for study of health effects related to drinking water
filters.
A number of representatives of the above mentioned agencies provided
excellent participation in the task force to develop microbiological testing
protocols for water purifiers. Major participation was also provided by the
following:
- A technical representative from the Water Quality Association;
- A technical representative from the Environmental Health Center,
Department of Health and Welfare of Canada; and
- An associate professor (microbiology) from the University of
Arizona.
1.2 Basic Principles
1.2.1 Definition
As set forth in EPA Enforcement Strategy and as supported by a Federal
Trade Commission (FTC) decision (FTC v. Sibco Products Co., Inc., et al.,
Nov. 22, 1965), a unit, in order to be called a microbiological water
purifier, must remove, kill or inactivate all types of disease-causing micro-
organisms from the water, including bacteria, viruses and protozoan cysts so
as to render the processed water safe for drinking. Therefore, to qualify, a
microbiological water purifier must treat or remove all types of challenge
organisms to meet specified standards.
1.2.2 General Guide
The standard and protocol will be a general guide and, in some cases, may
present only the minimum features and framework for testing. While basic
features of the standard and protocol have been tested, it was not feasible to
conduct full-fledged testing for all possible types of units. Consequently,
protocol users should include pre-testing of their units in a testing rig,
including . the sampling techniques to be used. Where users of the protocol
find good reason to alter or add to the guide in order to meet specific
operational problems, to use an alternate organism or laboratory procedure, or
to respond to innovative treatment units without decreasing the level of
-------
testing or altering the intent of the protocol, they should feel free to do
so. For example, the OPP Registration Division might find it necessary to
amend the guide somewhat for different types of treatment units. Another
example would be ultraviolet (O.V.) units, which may have specific require-
ments in addition to the guide protocol.
1.2.3 Performance-Based
The standard will be performance-based, utilizing realistic worst case
challenges and test conditions and use of the standard shall result in water
quality equivalent to that of a public water supply meeting the
microbiological requirements and. intent of the National Primary Drinking Hater
Regulations.
1.2.4 Exceptions
A microbiological water purifier must remove, kill or inactivate all
types of pathogenic organisms if claims are made for any organism. However,
an exception for limited claims may be allowed for units removing specific
organisms to serve a definable environmental need (i.e., cyst reduction units
which can be used on otherwise disinfected and microbiologically safe drinking
water, such as a disinfected but unfiltered surface water containing cysts.
Such units are not to be called microbiological water purifiers and should not
be used as sole treatment for an untreated raw water.)
1.2.5 Not to Cover Non-Microbiological Reduction Claims
The treatment of water to achieve removal of a specific chemical or other
non-microbiological substances from water will not be a part of this standard.
National Sanitation Foundation (NSF) Standards 42 (Aesthetic Effects) and 53
(Health Effects) provide partial guides for chemical removal and other claims
testing.
1.2.6 Construction and Information Exclusions
While the standard recommends safe, responsible construction of units
with non-toxic materials for optimum operation, all such items and associated
operational considerations are excluded as being beyond the scope of the
standard. Included in the exclusion are materials of construction, electrical
and safety aspects, design and construction details, operational instructions
and information, and mechanical performance testing.
-------
1.2.7 Research Needs Excluded
The guide standard and protocol must represent a practical testing
program and not include research recommendations. For example, consideration
of mutant organisms or differentiation between injured and dead organisms
would be research items at this time and not appropriate for inclusion in the
standard.
1.2.8 Not to Consider Sabotage
Esoteric problems which could be presented by a variety of hypothetical
terrorist (or wartime) situations, would provide an unnecessary complication,
and are not appropriate for inclusion in the standard.
1.2.9 Continuity
The guide standard and protocol will be a living document, subject to
revision and updating with the onset of new technology and knowledge. It is
recommended that the responsible authorities for registration and drinking
water quality review potential needs every two to three years and reconvene
the task force upon need or upon request from the water quality industry, to
review and update the standard and testing protocol.
1.3 Treatment Units Coverage
1.3.1 Universe of Possible Treatment Units
A review of treatment units that might be considered as microbiological
purifiers discloses a number of different types covering treatment principles
ranging from filtration and chemical disinfection to ultraviolet light ra-
diation.
1.3.2 Coverage of This Standard
In view of the limited technical data available and in order to expedite
the work of the task force, the initial coverage is limited, on a priority
basis, to three basic types of microbiological water purifiers or active
components with their principal means of action as follows:
1.3.2.1 Ceramic Filtration Candles or Units (may or
may not contain a chemical bacteriostatic agent)
Filtration, and adsorption, and chemical anti-microbial activity if a
chemical is included.
-------
1.3.2.2 Halogenated Resins and Units
Chemical disinfection and possibly filtration. (Note: While not
included in this guide standard, halogen products for disinfection or systems
using halogen addition and fine filtration may be tested using many of its
elements, i.e., test water parameters, microbiological challenge and reduction
requirements, analytical techniques and other pertinent elements.)
1.3.2.3 Ultraviolet (UV) Units
0V irradiation with possible add-on treatment for adsorption and filtra-
tion (not applicable to 0V units for treating potable water from public water
supply systems).
1.3.3 Application of Principles to Other Units
While only three types of units are covered in this standard, the princi-
ples and approaches outlined should provide an initial guide for the testing
of any of a number of other types of units and/or systems for the microbiolo'g-
ical purification of contaminated water.
-------
2. PERFORMANCE REQUIREMENTS
2.1 Microbiological Water Purifier
In order to make the claim of "microbiological water purifier," units
must be tested and demonstrated to meet the microbiological reduction require-
ments of Table 1 according to the test procedures described in Section 3
(Appendix O-l) for the specific type of unit involved.
2.2 Chemical Health Limits
Where silver or some other pesticidal chemical is used in a unit, that
chemical concentration in the effluent water must meet any National Primary
Drinking Water Maximum Contaminant Level (MCL), additional Federal guidelines
or otherwise be demonstrated not to constitute a threat to health from con-
sumption or contact where no MCL exists.
2.3 Stability of Pesticidal Chemical
Where a pesticidal chemical is used in the treatment unit, the stability
of the chemical for disinfectant effectiveness should be sufficient for the
potential shelf life and the projected use life of the unit based on manufac-
turer's data. Where stability cannot be assured from historical data and
information, additional tests will be required.
2.4 Performance Limitations
2.4.1 Effective Lifetime
The manufacturer must provide an explicit indication or assurance of the
unit's effective use lifetime to warn the consumer of potential diminished
treatment capability either through:
a. Having the unit terminate discharge of treated water, or
b. Sounding an alarm, or
c. Providing simple, explicit instruction for servicing or replacing
units within the recommended use life (measurable in terms of volume
throughput, specific time frame or other appropriate method).
-------
2.4.2 Limitation on Use of Iodine
EPA policy initially developed in 1973 and reaffirmed in 1982 (memo of
March 3, 1982 from J. A. Cotruvo to G. A. Jones, subject: "Policy on Iodine
Disinfection") is that iodine disinfection is acceptable for short-term or
limited or emergency use but that it is not recommended for long-term or
routine community water supply application where iodine-containing species may
remain in the drinking water.
-------
3. MICROBIOLOGICAL WATER PURIFIER TEST PROCEDURES
3.1 Purpose
These tests are performed on ceramic filtration candles or units, halo-
genated resins and units and ultraviolet (UV) units in order to substantiate
their microbiological removal capabilities over the effective use life of the
purifier as defined in Table 1 and, where a pesticidal chemical is used, to
determine that said chemical is not present in the effluent at excessive
levels (see Section 3.5.3.4, Appendix O).
3.2 Apparatus
Three production units of a type are to be tested, simultaneously, if
feasible; otherwise, in a manner as similar to that as possible.
Design of the testing rig must parallel and simulate projected field use
conditions. For plumbed-in units a guide for design of the test rig may be
taken from "Figure 1: Test Apparatus-Schematic" (p. A-2 of Standard Number 53
"Drinking Water Treatment Units — Health Effects," National Sanitation
Foundation). Otherwise, the test rig must be designed to simulate field use
conditions (worst case) for the unit to be tested.
3.3 Test Waters — Non-Microbioloaical Parameters
In addition to the microbiological influent challenges, the various test
waters "will be constituted with chemical and physical characteristics as
follows:
3.3.1 Test Water #1 (General Test Water)
This water is intended for the normal non-stressed (non-challenge) phase
of testing for all units and shall have specific characteristics which may
easily be obtained by the adjustment of many public system tap waters, as
follows:
a. It shall be free of any chlorine or other disinfectant residual;
b. pH — 6.5-8.5;
c. Total Organic Carbon (TOO 0.1 - 5.0 mg/L;
d. Turbidity 0.1-5 NTU;
-------
e. Temperature 20 C ± 5 C; and
f. Total Dissolved Solids (TDS) 50 - 500 mg/L.
3.3.2 Test Water #2 (Challenge Test Water/Halogen Disinfection)
This water is intended for the stressed challenge phase of testing where
units involve halogen disinfectants (halogen resins or other units) and shall
have the following specific characteristics:
a. Free of chlorine or other disinfectant residual;
b. (1) pH 9.0 ± .2, and
(2) for iodine-based units a pH of 5.0 ± .2 (current information
indicates that the low pH will be the most severe test for virus
reduction by iodine disinfection);
c. Total Organic Carbon (TOO not less than 10 mg/L;
d. Turbidity not less than 30 NTU;
e. Temperature 4 C ± 1C; and
f. Total Dissolved Solids (TDS) 1,500 mg/L t 150 mg/L.
3.3.3 Test Water #3 (Challenge Test Water/Ceramic Candle
or Units With or Without Silver Impregnation)
This water is intended for the stressed challenge phase of testing for
the indicated units but not for such units when impregnated with a halogen
disinfectant (for the latter, use Test Water £2). It shall have the following
specific characteristics:
a. It shall be free of any chlorine or other disinfectant residual;
b. pH 9.0 ± .2;
c. Total Organic Carbon (TOO — not less than 10 mg/L;
d. Turbidity — not less than 30 NTU;
e. Temperature 4 C ± 1C; and
f. Total Dissolved Solids (TDS) — 1,500 mg/L ± 150 mg/L.
3.3.4 Test Water #4 (Challenge Test Water for Ultraviolet Units)
This water is intended for the stressed phase of testing for UV units and
shall have the following specific characteristics:
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a. Free of chlorine or other disinfectant residual;
b. pH 6.5 - 8.5;
c. Total Organic Carbon (TOO — not less than 10 mg/L;
d. Turbidity — not less than 30 NTU;
e. Temperature 4 C ± 1 C;
f. Total Dissolved Solids (TDS) — 1,500 mg/1 ± 150 mg/L;
g. Color U.V. absorption (absorption at 254 ran) — Sufficient para-
hydroxybenzoic acid (PHBH) to be just below the trigger point of the
warning alarm on the U.V. unit. (Note that Section 3.5.1.1 provides
an alternative of adjusting the U.V. lamp electronically, especially
when the U.V. lamp is preceded by activated carbon treatment.)
3.3.5 Test Water #5 (Leaching Test Water for Units Containing Silver)
This water is intended for stressed leaching tests of units containing
silver to assure that excess levels of silver will not be leached into the
drinking water. It shall have the following specific characteristics:
a. Free of chlorine or other disinfectant residual;
b. pH — 5.0 ± 0.2;
c. Total Organic Carbon (TOO — approximately 1.0 mg/L;
d. Turbidity — 0.1 - 5 NTU;
e. Temperature — 20 C ± 5 C; and
f. Total Dissolved Solids (TDS) — 25 - 100 mg/L.
3.3.6 Recommended Materials for Adjusting Test Water Characteristics
a. pH: inorganic acids or bases (i.e., HC1, NaOH);
b. Total Organic Carbon (TOO: humic acids;
c, Turbidity: A.C. Fine Test Dust (Park No. 1543094)
from: A.C. Spark Plug Division
General Motors Corporation
1300 North Dort Highway
Flint, Michigan 48556;
d. Total Dissolved Solids (TDS): sea salts, Sigma Chemical Co., S9883
(St. Louis,MO) or another equivalent source of TDS;
10
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e. Color U.V. Absorption: p-hydroxybenzoic acid (grade: general
purpose reagent).
3.4 Analytical Methods
3.4.1 Microbiological Methods
Methods in this section are considered "state-of-the-art" at the time of
its preparation and subsequent improvements should be expected. Methods used
for microbiological analyses should be compatible with and equal to or better
than those given below.
3.4.1.1 Bacterial Tests
a. Chosen Organism: Klebsiella terrigena (ATCC-33257).
b. Method of Production: Test organism will be prepared by overnight
growth in nutrient broth or equivalent to obtain the organism in the
stationary growth phase (Reference: Asburg, E.D., Methods of
Testing Sanitizers and Bacteriostatic Substances In: Disinfection,
Sterilization and Preservation, Seymour S. Block, ed., pp. 964-950,
1983}. The organism will be collected by centrifugation and washed
three times in phosphate buffered saline before use. Alternatively,
the organisms may be grown overnight on nutrient agar slants or
equivalent and washed from the slants with phosphate buffered
saline. The suspensions should be filtered through sterile Whatman
Number 2 filter paper (or equivalent) to remove any bacterial
clumps. New batches of organisms must be prepared daily for use in
challenge testing.
c. State of Organism: Organisms in the stationary growth phase and
suspended in phosphate buffered saline will be used.
d. . Assay Techniques: Assay may be by the spread plate, pour plate or
membrane filter technique on nutrient agar, M.F.C. or m-Endo medium
(Standard Methods for the Examination of Water and Wastewater, 16th
edition, 1985, APHA). Each sample dilution will be assayed in
triplicate.
3.4.1.2 Virus Tests
a. Chosen Organisms: Poliovirus type 1 (LSc) (ATCC-VR-59), and Rota-
virus Strain SA-11 (ATCC-VR-899) or WA (ATCC-VR-2018).
b. Method of Production: All stocks should be grown by a method
described by Smith and Gerba (in Methods in Environmental virology,
pp. 15-47, 1982) and purified by the procedure of Sharp, et al.
(Appl. Microbiol., 29:94-101, 1975), or similar procedure (Herman
and Hoff, Appl. Environ. Microbiol., 48:317-323, 1984), as these
methods will produce largely monodispersed virion particles.
11
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c. State of the Organism: Preparation procedure will largely produce
monodispersed particles.
d. Assay Techniques: Poliovirus type 1 may be grown in the BGM, MA-104
or other cell line which will support the growth of this virus. The
rotaviruses are best grown in the MA-104 cell line. Since both
viruses can be assayed on the MA-104 cell line, a challenge test may
consist of equal amounts of both viruses as a mixture (i.e., the
mixture must contain at least 1.0 x 10 /mL of each virus) . Assays
may be as plaque forming units (PFU) or as immunofluorescence foci
(IF) (Smith and Gerba, In: Methods in Environmental Virology,
PP- 15-47, 1982). Each dilution will be assayed in triplicate.
3.4.1.3 Cyst Tests
a. Chosen Organism
1. Giardia lamblia or the related organism, Giardia muris, may be
used as the challenge cyst.
2. Where filtration is involved, tests with 4-6 micron spheres or
particles have been found to be satisfactory and may be used as
a substitute for tests of occlusion using live organisms (see
Table 1) . Spheres or particles may only be used to evaluate
filtration efficacy. Disinfection efficacy can only be evalu-
ated with the use of viable Giardia cysts.
b. Method of Production: Giardia muris may be produced in laboratory
mice and Giardia lamblia may be produced in Mongolian gerbils;
inactivation results based on excystation measurements correlate
well with animal infectivity results.
c. State of the Organism: Organisms may be separated from fecal
. material by the procedure described by Sauch (Appl. Environ.
Microbiol., 48:454-455, 1984) or by the procedure described by
Bingham, et al. (Exp. Parasitol., 47:284-281, 1979).
d. Assay Techniques: Cysts are first reconcentrated (500 ml., minimum
sample size) according to the method of Rice, Hoff and Schaefer
(Appl. Environ. Microbiol., 43:250-251, 1982). The excystation
method described by Schaefer, et al. (Trans., Royal Soc. of Trop.
Med. & Hyg. 78:795-800, 1984) shall be used to evaluate Giardia
muris cyst viability. For Giardia lamblia cysts, the excystation
method described by Bingham and Meyer (Nature, 277:301-302, 1979) or
Rice and Schaefer (J. Clin. Microbiol., 14:709-710, 1981) shall be
used. Cyst viability may also be determined by an assay method
involving the counting of trophozoites as well as intact cysts
(Bingham, et al., Exp. Parasitol., 47:284-291, 1979).
12
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3.4.2 Chemical and Physical Methods
All physical and chemical analyses shall be conducted in accordance with
procedures in Standard Methods for the Examination of Water and Wastewater.
16th Edition, American Public Health Association, or equivalent.
3.5 Test Procedures
3.5.1 Procedure - Plumbed-in Units
a. 1. Install three production units of a type as shown in Figure 1
and condition each unit prior to the start of the test in
accordance with the manufacturer's instructions with the test
water without the addition of the test contaminant. Measure
the flow rate through each unit. The unit shall be tested ar
the maximum system pressure of 60 psig static and flow rate
will not be artificially controlled.
2. Test waters shall have the defined characteristics continuously
except for test waters 2, 3 and 4 with respect to turbidity.
The background non-sampling turbidity level will be maintained
at 0.1-5 NTU but the turbidity shall be increased to the
challenge level of not less than 30 NTU in the following
manner:
- In the "on" period(s) prior to the sampling "on" period.
- In the sampling "on" period when the sample actually will
be taken. (Note: at least 10 unit void volumes of the 30
NTU water shall pass through the unit prior to actual
sampling so as to provide adequate seasoning and uni-
formity before sample collection.-)
b. 1. Use appropriate techniques of dilution and insure continual
mixing to prepare a challenge solution containing the bacterial
contaminant. Then spike test water continuously with the
influent concentration specified in Table 1.
2. Use appropriate techniques to prepare concentrated virus and
Giardia suspensions. Feed these suspensions into the influent
stream so as to achieve the influent concentrations specified
in Table 1 in the following manner:
- In the "on" period(s) prior to the sampling "on" period.
- In the sampling "on" period when the sample actually will
be taken. (Note: at least 10 unit void volumes of seeded
water shall pass through the unit prior to sampling so as
to provide adequate seasoning and uniformity before sample
collection.)
13
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c. Purge the system of the uncontaminated water with a sufficient flow
of contaminated test water. Start an operating cycle of 10 percent
on, 90 percent off with a 15 to 40 minute cycle (Example: 3 minutes
on, 27 minutes off) with the contaminated test water. This cycle
shall be continued for not more than 16 hours per day (minimum daily
rest period of 8 hours) . The total program shall extend to 100% of
estimated volume capacity for halogenated resins or units and for
10-1/2 days for ceramic candles or units and U.V. units.
d. Sampling: Samples of influent and effluent water at the specified
sampling points shall be collected as shown below for the various
units; these are minimum sampling plans which may be increased in
number by the investigator. All samples shall be collected in
duplicate from the flowing water during the sampling "on" portion of
the cycle and they shall be one "unit void volume" in quantity (or
of appropriate quantity for analysis) and represent worst case
challenge conditions. Effluent samples shall usually be collected
near the middle of the sampling "on" period (or the whole volume
during one "on" period) except for samples following the specified
"stagnation" periods, for which sampling shall be conducted on the
first water volume out of the unit. Each sample will be taken in
duplicate and shall be retained and appropriately preserved, if
required, for chemical or microbiological analysis in the event
verification is required. (For units where the volume of a single
"on" period is insufficient for the required analysis, samples from
successive "on" periods may be accumulated until a sufficient volume
has been collected.)
l(a). Sampling Plan: Halogenated Resins or Units (Non-iodine Based)
Tests
Test Point
(% of Estimated
Capacity)
Start
25%
50%
After 48 hours
stagnation
Influent
Background
General
Active
Agent/
Residual
X
X
X
Microbiological
X
X
X
60%
75%
After 48 hours
stagnation
100%
Chal-
lenge
pH -
9.0 ± 0.2
X
X
X
X
X
X
X
X
14
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Kb). Sampling Plan: lodinated Resins or Units
Tests
Test Point
(% of Estimated
Capacity)
Start
25%
50%
After 48 hours
stagnation
Influent
Background
General
Active
Agent/
Residual
X
X
X
Microbiological
X
X
X
60%
75%
After 48 hours
stagnation
Chal-
lenge
pH -
9.0 ± 0.2
X
X
X
X
90%
100%
After 48 hours
stagnation
Chal-
lenge
pH -
5.0 ± 0.2
X
X
X
X
Sampling Plan: Ceramic Candles or Units and U.V. Units
Tests
Test Point
Influent
Backoround
Microbiolocical
Start -
Day 3 (middle)
Day 6 (middle)
After 48 hours
stagnation
General
X
X
X
Day 7 (middle)
Day 8 (near end)
After 48 hours
stagnation
Day 10-1/2
Chal-
lenge
X
X
X
X
(Note: All days are "running days" and exclude stagnation periods. When
the units contain silver, a leaching test shall be conducted as shown in
Section 3.5.1.e and silver residual will be measured at each microbiological
sampling point.)
-------
e. Leaching Tests for Silverized Units: Where the unit contains
silver, additional tests utilizing Test Water #5 will be conducted
as follows:
Tests
Influent
Test Point Background Silver/Residua^
Start X X
Day 2 x
After 48 hours
stagnation v
f. Alternate Sampling Plans:
1. Since some laboratories may find it inconvenient to test some
units on a 16 hour on/8 hour off cycle, two alternates are
recognized:
- Go to a shorter operational day but lengthen the days of
test proportionally
- Use up to 20 percent "on"/80 percent "off" for a propor-
tionally shorter operational day
2. Sampling points must be appropriately adjusted in any alternate
sampling plan.
g. Application of Test Waters: The application of test waters is
designed to provide information on performance under both normal and
stressed conditions; it should be the same or equivalent to the
following:
1. a. Halogenated Resins or Units (Non-iodine based) --
First 50% of test period: Test Water 1 (General)
Last 50% of test period: Test Water 2 (Challenge)
(pH - 9.0 ± 0.2)
b. lodinated Resins or Units —-
First 50% of test period: Test Water 1 (General)
Next 25% of test period: Test Water 2 (Challenge)
(pH - 9.0 ± 0.2)
Last 25% of test period: Test Water 2 (Challenge)
(but with pH - 5.0 ± 0.2)
2. Ceramic Candles or Units —
First 6 days of testing: Test Water 1 (General)
Last 4-1/2 days of testing: Test Water 3 (Challenge)
16
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3. Ultraviolet (U.V.) Units —
First 6 days of testing:
Last 4-1/2 days of testing:
h. Analyses and monitoring:
Test Water 1 (General)
Test Water 4 (Challenge)
i.
1. Microbiological sampling and analysis shall be conducted of the
specified influent and effluent sampling points during each
indicated sampling period.
2. Test Water Monitoring: The specified parameters of the various
test waters (see Section 3.3) will be measured and recorded at
each microbiological sampling point; the specified parameters
will be measured at least once on non-sampling days when the
units are being operated.
3. Background chemical analyses of influent water shall be con-
ducted at least once at the start of each test period to
determine the concentration of the U.S. EPA primary inorganic
contaminants, secondary contaminants and routine water para-
meters, not otherwise covered in the described test waters.
4. In addition, quality assurance testing shall be conducted for
the seed bacteria under environmental conditions on the first
and last days of testing to make sure that there is no signifi-
cant change over the test day. Populations will be measured
(for example, as dispersed in the supply tank) at the beginning
and end of the test day to detect possible incidenral effects
such as proliferation, die-off, adsorption to surfaces, etc.
Relatively stable bacterial seed populations are essential to
an acceptable test program.
5. When a unit contains a halogen or silver, the active agent
residual will be measured in the effluent at each microbiologi-
cal test (sampling) point.
6. Silver will additionally be measured three times in the efflu-
ent as specified in Section 3.5.I.e.
Neutralization of Disinfection Activity: Immediately after col-
lection, each test sample must be treated to neutralize residual
disinfectant. For halogen- and silver-based disinfectants this may
be done by addition of thioglycollate-thiosulfate neutralizer
solution (Chambers, et al., J. Amer. Water Works Assoc., 54:208-216,
1962). This solution should be prepared daily. All results are
invalid unless samples are neutralized immediately upon collection.
17
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j. Special Provisions for Ceramic Candles or Units:
1. Provisions for slow flow: Ceramic units may be subject to
clogging and greatly reduced flow over the test period. An
attempt should be made to maintain manufacturer rated or
claimed flow rates, but even at reduced flows the sampling
program set forth in Section 3.5.1.d.2 shall be maintained.
2. Cleaning of ceramic units: Units should be cleaned according
to manufacturer's directions. Two cleanings should occur
during the period of test (in order to prove the unit's
durability through the cleaning procedure). However, near the
time of microbiological sampling, the units should not be
cleaned until after the sampling. Further, no anti-microbial
chemical (for cleaning or sanitizing) may be applied to the
units during the test period unless the manufacturer specifies
the same as part of routine maintenance.
Jc. Halogenated units or U.V. units with mechanical filtration processes
separate from the microbiological disinfection components shall have
the mechanical filtration components replaced or serviced when
significant flow reduction (clogging) occurs in accordance with the
manufacturer's instructions in order to maintain the test flow rate.
Units with non-removable mechanical filtration components will be
run until . flow is below that considered acceptable for consumer
convenience. (If premature clogging presents a problem, some
specialized units may require a customized test plan.)
1. Special Provisions for Ultraviolet (U.V.) Units:
1. The units will be adequately challenged by the prescribed test
waters; consequently they will be operated at normal intensity.
However, where the U.V. treatment component is preceded by
activated carbon treatment, the output of the U.V. lamp shall
be adjusted electronically, such as by reducing the current to
the lamp or other appropriate means, to be just above the alarm
point. This option shall be available for use under other U.V.
configurations, at the choice of the persons responsible for
testing, as an alternative to the use of the U.V. absorbent,
p-hydroxybenzoic acid.
2. Fail/safe: Units will provide and will be tested for fail/safe
warnings in the event of water quality changes or equipment
failures which may interfere with its microbiological purifica-
tion function.
3. Cleaning: Manufacturer's guidance with respect to cleaning
will be followed.
18
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3.5.2 Procedure; Non-Plumbed Units
a. General: The basic procedures given in Section 3.5.1 shall be used
with necessary adaptations to allow for the specific design of the
unit. In any event, the testing procedures shall provide a test
challenge equivalent to those for plumbed-in units.
b. Test conditions and apparatus should be adapted to reflect proposed
or actual use conditions in consultation with the manufacturer,
including flow rate and number of people to be served per day. in
some cases variable flow or other non-standard conditions may be
necessary to reflect a worst-case test.
3.5.3 Acceptance and Records
3.5.3.1
To qualify as a microbiological water purifier, all three production
units of a type must continuously meet or exceed the reduction requirements of
Table 1, within allowable measurement tolerances for not more than ten percent
of influent/effluent sample pairs, defined as follows:
Virus: one order of magnitude
Bacteria: one order of magnitude
Cysts: one/half order of magnitude
The geometric mean of all microbiological reductions must meet or exceed
the requirements of Table 1. An example is given as follows:
- Unit: iodinated resin.
- Number of sample pairs over the completed test program:
10 per unit — 3 units = 30.
- Number of allowable sample pairs where log reduction is insuffi-
cient: 10% of 30 = 3 sample pairs.
- Allowable minimum log reductions in these 3 pairs:
0 Bacteria - 5 log
0 Virus - 3 log
8 Cyst - 2-1/2 log
- Conclusion: If the geometric mean of all reductions meets or
exceeds the requirements of Table 1, the indicated insufficient
sample pairs will.be allowed.
19
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3.5.3.2 Records
All pertinent procedures and data shall be recorded in a standard format
and retained for possible review until the report of results has been com-
pletely accepted by review authorities, in no case for less than a year.
3.5.3.3 Scaling Up or Down
Where a manufacturer has several similar units using the same basic
technology and parallel construction and operation, it may sometimes be
appropriate to allow the test of one unit to be considered representative of
others. Where any serious doubt exists, all units of various sizes may
require testing. A "rule of three" is suggested as a matter of judgment.
Scaling up to three times larger or on-third, based on the size of either the
test unit or of its operative element, may be allowed. However, for UV units,
any size scale-up must be accompanied by a parallel increase in radiation
dose.
3.5.3.4
Where silver or some other, chemical is used in the unit, concentrations
in the effluent water must meet any National Primary Drinking Water Maximum
Contaminant Level (MCL), additional Federal guidelines, or otherwise must not
constitute a threat to health-where no MCL exists.
20
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APPENDIX O-l
SUMMARY FOR BASIS OF STANDARDS AND TEST WATER PARAMETERS
A- Microbiological Reduction Requirements
1. Bacteria
Current standards for the microbiological safety of drinking
water are based on the presence of colifonn bacteria of which
Klebsiella is a member. Members of the genus Klebsiella are also
potential pathogens of man (Vlassof, 1977). Klebsiella terrigena is
designated as the test organism since it is commonly found in
surface waters (Izard, et al., 1981).
Experience with the use of colifonn bacteria to estimate the
presence of enteric bacterial pathogens in drinking water as per-
formed over the last 75 years indicates a high degree of reliabil-
ity. Required testing of more than one bacterial pathogen appears
unjustified since viral and Giardia testing will be required.
Enteric viruses and Giardia are known to be more resistant to common
disinfectants than enteric bacterial pathogens and viruses are more
resistant to removal by treatments such as filtration. Thus, any
treatment which would give a good removal of both virus and Giardia
pathogens would most likely reduce enteric bacteria below levels
considered infectious (Jarroll, et al., 1981; Liu, et al., 1971).
The concentration of coliform bacteria in raw sewage is approx-
imately 10/100 ml. Concentrations in polluted stream waters have
been found to exceed 10 per 100 ml (Gulp, et al., 1978, Table 10).
Based on the over 10 /100 ml concentrations observed in highly
polluted stream water and a target effluent concentration of less
than 1/100 ml, a 6 log reduction is recommended.
2. Virus
In the United States concentrations of enteroviruses are esti-
3 4
mated to range from 10 -10 /liter in raw sewage (Farrah and Schaub,
1971) . Based on this observation it is estimated that natural
waters contaminated with raw sewage may contain from 10 to 10
enteric viruses per liter.
There are currently no standards for viruses in drinking water
in the United States. However, EPA has proposed a non-enforceable
health-based recommended maximum contaminant level (RMCL) of zero
for viruses (EPA, 1985) . Several individuals and organizations have
developed guidelines for the presence of viruses in drinking water
and various experts have proposed standards (WHO, 1979, 1984; Berg,
1971; Melnick, 1976). It has generally been felt that
21
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drinking water should be free of infectious virus since even one
virus is potentially infectious and suggested standards are largely
based on technological limits of our detection methodology. Guide-
lines suggested by the World Health Organization (1984) and others
recommend that volumes to be tested be in the order of 100-1,000
liters and that viruses be absent in these volumes.
Assuming a target effluent level of less than one virus in 100
liters of water and a concentration of 10 enteric viruses in 100
liters of sewage-contaminated waters, the water purifier units
should achieve at least 4 logs of virus removal.
The relative resistance of enteric viruses to different dis-
infectants varies greatly among the enteric viruses and even among
members of the same group (i.e., enteroviruses). For example, while
f2 coliphage is one of the most resistant viruses to inactivation by
chlorine it is one of the most susceptible to inactivation by ozone
(Harakeh and Butler, 1984). Ionic conditions and pH can also affect
the relative resistance of different viruses to a disinfectant
(Engelbrecht, et al., 1980). On this basis it is felt that more
than one enteric virus should be tested to ensure the efficacy of
any disinfection system. Poliovirus type 1 (Strain LSc) was chosen
as one of the test viruses because it has been extensively used in
disinfection and environmental studies as representative of the
enterovirus family. It is recognized that it is not the most
resistant virus to inactivation by chlorine, but is still resistant
enough to serve as a useful indicator. Rotavirus is selected as the
second test enteric virus since it represents another group of
enteric viruses in nucleic acid composition and size. It is also a
major cause of viral gastroenteritis and has been documented as a
cause of water borne gastroenteritis (Gerba, et al., 1985). The
human rotavirus or the similar Simian rotavirus may be used in the
test procedure. A net 4-log reduction for a joint challenge of
" 1 x 10 /L each for poliovirus and rotavirus is recommended.
3. Cysts (Protozoan)
Over the past several years, giardiasis has consistently been
one of the most frequently reported waterborne diseases transmitted
by drinking water in the United States (Craun, 1984). EPA has
proposed a RMCL of zero for Giardia (EPA, 1985). Its occurrence has
generally been associated with treatment deficiencies including
either inadequate or no filtration. Giardiasis has not been known
to occur from drinking water produced by well-operated filtration
treatment plants. De Walle, et al. (1984), in a study of filtration
treatment plant efficiencies, cited percent removals for Giardia in
pilot plant tests as follows:
- Rapid filtration with coagulation-sedimentation: 96.6-99.9%;
- Direct filtration with coagulation: 95.9-99.9%.
22
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From this research and from the lack of Giardia cases in
systems where adequate filtration exists, a 3-log (99.9%) reduction
requirement is considered to be conservative and to provide a
comparable level of protection for water purifiers to a
well-operated filtration treatment plant.
Data on environmental levels for cysts in natural waters is
limited because of the difficulties of sampling and analysis.
Unpublished data indicate very low levels from less than 1/L to less
than 10/L. Here a 3-log reduction would provide an effluent of less
than 1/100 L, comparable to the recommended virus reduction require-
ments .
Either Giardia lamblia or the related organism, Giardia muris,
which is reported to be a satisfactory test organism (Hoff, et al.,
1985) , may be used as the challenge organism. Tests will be con-
ducted with a challenge of 10° organisms per liter for a 3-log
reduction.
Where the treatment unit or component for cysts is based on tjie
principle of occlusion filtration alone, testing for a 3-log reduc-
tion of 4-6 micron particles or spheres (National Sanitation Founda-
tion Standard 53, as an example) is acceptable. Difficulties in the
cyst production and measurement technologies by lesser-equipped
laboratories may require the use of such alternative tests where
applicable.
B. Microbiological Purifier Test Procedures^
1. Test Waters
a. The general test water (test water #1) is designed for the
normal, non-stressed phase of testing with characteristics that
may easily be obtained by the adjustment of many public system
tap waters.
b. Test water #2 is intended for the stressed phase of testing
where units involve halogen disinfectants.
1. Since the disinfection activity of some halogens falls
with a rising pH, it is important to stress test at an
elevated pH. The recommended level of 9.0 ± 0.2, while
exceeding the recommended secondary level (Environmental
Protection Agency, 1984) is still within a range seen in
some natural waters (Environmental Protection Agency,
1976). However, for iodine-based units, a second stress-
ful condition is provided — a pH of 5.0 ± 0.2 since
current information indicates that the disinfection
activity of iodine falls with a low pH (National Research
Council, 1980). While beneath the recommended secondary
-------
level (Environmental Protection Agency, 1984) a pH of 5.0
is not unusual in natural waters (Environmental Protection
Agency, 1976).
2. Organic matter as total organic carbon (TOO is known to
interfere with halogen disinfection. While this TOC is
higher than levels in many natural waters, the designated
concentration of 10 mg/L is cited as typical in stream
waters (Culp/Wesner/Culp, 1978).
3. High concentrations of turbidity can shield microorganisms
and interfere with disinfection. While the recommended
level of not less than 30 NTD is in the range of turbidi-
ties seen in secondary wastewater effluents, this level is
also found in many surface waters, especially during
periods of heavy rainfall and snow melt (Culp/Wesner/Culo,
1978).
4. Studies with Giardia cysts have shown decreasing halogen
disinfection activity with lower temperatures (Jarroll,
et al., 1980); 4 C, a common low temperature in many
natural waters, is recommended for the stress test.
5. The amount of dissolved solids (TDS) may impact the
disinfection effectiveness of units that rely on displace-
able or exchange elements by displacement of halogens or
resins, or it may interfere with adsorptive processes.
While TDS levels of 10,000 mg/L are considered unusable
for drinking, many supplies with over 2,000 mg/L are used
for potable purposes (Environmental Protection Agency,
1984). The recommended level of 1,500 mg/L represents a
realistic stress challenge.
c. Test water #3 is intended for the stressed phase of testing of
ceramic filtration candles or units with or without silver
impregnation.
1. Since viruses are typically eluted from adsorbing media at
high pHs (Environmental Protection Agency, 1978) it may be
concluded that a high pH will provide the most stressful
testing for a ceramic-type unit; consequently, the high
natural water pH of 9.0 is recommended.
2. Expert opinion also holds that organic material will
interfere with adsorption of viruses. Thus, a high total
organic carbon level of not less than 10 mg/L is recom-
mended .
3. Turbidity may enhance the entrapment and removal of
microorganisms but it also may stimulate "short-
circuiting" through some units. A turbidity level cf
24
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30 NTU will provide stress at time of sampling but the
non-sampling level of 0.1-5 NTU will allow routine opera-
tion of units.
4. Expert opinion holds that low water temperatures and high
TDS would most likely interfere with virus reduction by
adsorption; consequently, a 4 C temperature and 1,500 mg/L
TDS are recommended.
d. Test water #4 is intended for the stressed phase of testing for
ultraviolet (UV) units.
1. In general, high TOC, turbidity and TDS and low tempera-
ture are considered most stressful for UV, and the in-
dicated challenge levels are the same as for test
water #2.
2. The pH is not critical and may range from 6.5 to 8.5.
3. In order to test the UV units at their most vulnerable
stage of operation, a color challenge (light absorption'at
254 nm) is to be maintained at a level where UV light
intensity is just above the unit's low intensity warning
alarm point. However, an alternate to the absorption
challenge is provided through adjusting the light intensi-
ty output of the UV lamp electronically by reducing
current to the lamp, or other appropriate means, to be
just above the alarm point; this approach would be
particularly necessary where the UV lamp is preceded by
activated carbon treatment.
e. Test water #5 is intended for the stressed leaching tests of
units containing silver. Low pH, TOC, turbidity, and TDS and
higher temperature are felt to be the characteristics associ-
ated with increased leachability. The recommended pH of
5.0 ± .2, while being beneath the recommended secondary range
of 6.5-8.5 (Environmental Protection Agency, 1984) is still
found in some natural waters.
2. Test Procedures
The plan for testing and sampling is designed to reveal unit
performance under both "normal" and "stressed" operating conditions.
The stressed phase would utilize a set of water quality and opera-
tions conditions to give the units a realistic worst case challenge.
Testing plans for a specific model might involve modifications to
the recommended plan; more samples could be taken and analyzed; more
units could be studied. The principle of demonstrating adequate
performance even under realistic worst case conditions should be
maintained and the final selected test procedures should be agreed
as between investigators and reviewers or regulators.
25
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While some aspects of the testing procedures have been utilized
in actual experiments, the proposed protocol has not been verified
or utilized for the various units that may be considered. Conse-
quently, investigators and users of this protocol may find reasons
to alter some aspects through their practical experience; needed
changes should be discussed and cleared with involved reviewers/-
regulators.
26
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REFERENCES;
Berg, G. Integrated approach to the problem of viruses in water. J. ASCE,
Sanit. Eng. Div. 97:867-882, 1971.
Culp/Wesner/Culp. Guidance for planning the location of water supply intakes
downstream from municipal wastewater treatment facilities. EPA Report, Office
of Drinking Water. Washington, DC, 1978.
Craun, G. F. 1984. Waterborne outbreaks of giardiasis: Current status. In:
Giardia and giardiasis. D. L. Erlandsen and E. A. Meyer Eds., Plenum Press,
New York, pp. 243-261, 1984.
DeWalle, F. B.; J. Engeset; Lawrence, W. Removal of Giardia lamblia cyst by
drinking water treatment plants. Report No. EPA-600/52-84-069, Office of
Research and Development, Cincinnati, OH, 1984.
Engelbrecht, R. S., et al. Comparative inactivation of viruses by chlorine.
Appl. Environ. Microbiol. 40:249-256, 1980.
Environmental Protection Agency. Quality criteria for water. Washington, DC,
1976.
Environmental Protection Agency. National secondary drinking water
regulations. EPA-570/9-76-000, Washington, DC, 1984.
Environmental Protection Agency. National primary drinking water regulations;
synthetic organic chemicals, inorganic chemicals and microorganisms; Proposed
rule. Federal Register, Nov. 13, 1985.
Farrah, S. R. , and S. A. Schaub. Viruses in wastewater sludges. In: Viral
Pollution of the Environment, G. Berg, Ed. CRC Press, Boca Raton, Florida.
pp. 161-163, 1983.
Gerba, C. P.; Rose, J. B.; Singh, S. N. Waterborne gastroenteritis and viral
hepatitis. CRC Critical Rev. Environ. Contr. 15:213-236, 1985.
Harakeh, M.; Butler, M. Inactivation of human rotavirus, SA-11 and other
enteric viruses in effluent by disinfectants. J. Hyg. Camb. 93:157-163, 1984.
Hoff, J. C.; Rice, E. W.; Schaefer, F. W. Comparison of animal infectivity
and excystation as measures of Giardia muris cyst inactivation by chlorine.
Appl. Environ. Microbiol. 50:1115-1117, 1985.
Izard, D.; Farragut, C.;Gavini, F.; Kersters, K.; DeLey, J.; Leclerc, H.
Klebsiella terrigena, a new species from water and soil. Intl. J. Systematic
Eacteriol. 31:116-127, 1981.
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Jakubowski, W. Detection of Giardia cysts in drinking water. In: Giardia
and Giardiasis, Erlandsen, S. L.; Meyer, E. A. Eds., Plenum Press, NY.
pp. 263-286, 1984.
Jarroll, E. L.; Bingham, A. K.; Meyer, .E. A. Giardia cyst destruction:
Effectiveness of six small-quantity water disinfection methods. Am. J. Trop.
Med. 29:8-11, 1980
Jarroll, E. L.; Bingham, A. K.; Meyer, E. A. Effect of chlorine on Giardia
cyst viability. Appl. Environ. Microbiol. 43:483-487, 1981.
Liu, 0. C., et al. Relative resistance of 20 human enteric viruses to free
chlorine in Potomac River water. Proceedings of 13th Water Quality Conference
Snoeyink, V.; Griffin, V. Eds., pp. 171-195, 1971.
Melnick, J. L. Viruses in water. In: Viruses in Water Berg, G.;
Bodily, H. L.; Lennette, E. H.; Melnick, J. L.; Metclaf T. G., Eds. Amer.
Public Hlth. Assoc., Washington, OE, pp. 3-11, 1976.
National Research Council. The disinfection of drinking water, In: Drinking
Water and Health, Volume 2. Washington, DC, pp. 5-137, 1980.
National Sanitation Foundation. Drinking water treatment units: Health
effects. Standard 53. Ann Arbor, MI, 1982.
Vlassoff, L. T. Klebsiella. In: Bacterial Indicators/Health Hazards
Associated with Water Hoadley, A. W.; Dutka, B. J., Eds. American Society for
Testing and Materials, Philadelphia, PA. pp. 275-288, 1977.
World Health Organization. Human Viruses in Water, Technical Support
Series 639, World Health Organization, Geneva, 1979.
World Health Organization. Guidelines for Drinking Water Quality. Volume 1.
Recommendations. World Health Organization, Geneva, 1984.
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APPENDIX 0-2
LIST OF PARTICIPANTS; TASK FORCE ON GUIDE STANDARD AND PROTOCOL FOR
TESTING MICROBIOLOGICAL WATER PURIFIERS
Stephen A. Schaub, Chairman — U.S. Army Medical Bioengineering Research and
Development Laboratory (USAMBRDL), Fort Detrick, Maryland 21701, FTS:
8/935-7207 — Comm: 301/663-7207.
Frank A. Bell, Jr., Secretary — Criteria and Standards Division, Office of
Drinking Water (WH-550), Environmental Protection Agency, Washington,
D.C. 20460, Phone: 202/382-3037.
Paul Berger, Ph.D. — Criteria and Standards Division, Office of Drinking
Water (WH-550) , Environmental Protection Agency, Washington, D.C. 20460,
Phone: 202/382-3039.
Art Castillo — Disinfectants Branch, Office of Pesticide Programs (TS-767CO,
Environmental Protection Agency, Washington, D.C. 20460, Phone: 703/557-
3695.
Ruth Douglas — Disinfectants Branch, Office of Pesticide Programs (TS-767C) ,
Environmental Protection Agency, Washington, D.C. 20460, Phone: 703/557-
3675.
Al Dufour ~ Microbiology Branch, Health Effects Research Laboratory,
Environmental Protection Agency, 26 W. St. Clair Street, Cincinnati, Ohio
45268, Phone: FTS: 8/684-7870 — Comm: 513/569-7870.
Ed Geldreich — Chief, Microbiological Treatment Branch, Water Engineering
Research Laboratory, Environmental Protection Agency, 26 W. St. Clair
Street, Cincinnati, Ohio 45268, Phone: FTS: 8/684-7232 — Comm:
513/569-7232.
Charles Gerba — Associate Professor, Department of Microbiology and
Immunology, University of Arizona, Tucson, Arizona 85721, Phone:
602/621-6906.
John Hoff — Microbiological Treatment Branch, Water Engineering Research
Laboratory, Environmental Protection Agency, 26 W. St. Clair Street,
Cincinnati, Ohio 45268, Phone: FTS: 8/684-7331 — Comm: 513/569-7331.
Art Kaplan — Office of Research and Development (RD-681) Environmental
Protection Agency, Washington, D.C. 20460, Phone: 202/382-2583.
Bala Krishnan — Office of Research and Development (RD-681) Environmental
Protection Agency, Washington D.C. 20460, Phone: 202/382-2583.
29
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John Lee ~ Disinfectants Brcinch, Office of Pesticide Programs (TS-767C)
Environmental Protection Agency, Washington, D.C. 20460, Phone:
703/557-3663.
Dorothy Portner — Disinfectants Branch, Office of Pesticide Programs
(TS-767-C), Environmental Protection Agency, Washington, D.C. 20460,
Phone: 703/557-0484.
Don Reasoner — Microbiological Treatment Branch, Water Engineering Research
Laboratory, Environmental Protection Agency, 26 W. St. Clair Street,
Cincinnati, Ohio 45268, Phone: 312/654-4000.
P. Reguanthan (Regu) — Everpure, Inc., 660 N. Blackhawk Drive, Westmont,
Illinois 60559, Phone: 312/654-4000.
David Stangel — Policy and Analysis Branch, Office of Compliance Monitoring,
Environmental Protection Agency, Washington, D.C., Phone: 202/382-7845.
Richard Tobin — Monitoring and Criteria Division, Environmental Health
Center, Department of Health and Welfare of Canada, Tunney's Pasture,
Ottawa, Ontario, K1A OL2, Canada, Phone: 613/990-8982.
30
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APPENDIX O-3
RESPONSE BY REVIEW SUBCOMMITTEE(1) TO PUBLIC COMMENTS ON GUIDE STANDARD
AND PROTOCOL FOR TESTING MICROBIOLOGICAL WATER PURIFIERS
A. Recommendation for the use of Giardia lamblia cysts as a replacement for
Giardia muris cysts as the protozoan cyst test organisms.
Recommendation;
The subcommittee concurs with the recommendation and further endorses the
use of Giardia lamblia as the preferred cyst test for evaluation of all
treatment units and devices. Obviously the use of the protozoan orga-
nisms of actual health concern in testing is most desirable. Anyone
finding the Giardia lamblia strain feasible for testing and cost-
effective to work with is encouraged to use same instead of Giardia
muris.
B. Substitution of 4-6 micron bead or particle tests as an alternate option
instead of the Giardia cysts for evaluating devices that rely strictly on
occlusion filtration for microbiological removal: Several commenters
criticized the use of beads or particles (e.g., A.C. fine dust) and
recommended only use of live Giardia cysts for performance tests.
Discussion;
The subcommittee recognizes and favors the use of the natural human
parasite, Giardia lamblia, but was not aware of any convincing scientific
data which would disallow the optional use of testing with beads or
particles for units or devices using only occlusion filtration to remove
microorganisms. Previous development of the National Sanitation Standard
(NSF) 53 (1982) requirement for cyst reduction (using 4-6 micron parti-
cles as cyst models) was based on engineering and scientific opinion and
experimental evidence at that time. Specifically, Logsdon used
radioactive cyst models in the initial phase of a study of removal
efficiencies for diatomaceous earth filters; subsequent experiments with
Giardia muris cysts confirmed the efficacy of the diatomaceous earth
filters. Further studies by Hendricks and DeWalle with Giardia
lamblia cysts also showed comparable reduction efficiencies for
diatomaceous earth filters.
l.S.A. Schaub; F.A. Bell, Jr.; P. Berger; C. Gerba; J. Hoff;
P. Regunathan; and R. Tobin. [Includes additional revision pursuant to
Scientific Advisory Panel review (Federal Insecticide, Fungicide, and
Rodenticide Act).]
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Subsequently confirmatory parallel testing results have been developed
vis-a-vis 4-6 micron particles as compared to Giardia lamblia cysts.
Specifically, two units listed by NSF for cyst reduction (using 4-6
micron particles) have also been tested and lifted for 100% efficiency
reduction (using Giardia lamblia cysts) by Hibler :
1. Everpure Model QC4-SC
2. Royal Boulton Model F303.
Again we prefer the use of the human pathogen, Giardia lamblia; however,
no experimental data has been provided regarding the lack of validity or
of failure in previous tests utilizing beads or particles of 4-6 microns.
In most cases the bacterial or viral challenges to occlusion filters ill
represent a greater problem in terms of microbiological reduction
requirements than will cysts. Therefore, without substantiation of
deficiencies, the use of 4-6 micron beads or particles is considered to
be as feasible as the use of live cysts for routine performance testing
of water filtration (occlusion) devices.
Recommendation;
Recommend retaining the optional use of 4-6 micron particles or beads for
cyst reduction testing in occlusion filtration devices only.
References;
Logsdon, G. S., et al. Alternative Filtration Methods for Removal
of Giardia Cysts and Cyst Models, JAWWA, 73(2)111-118, 1981.
Logsdon, G. S.; Hendricks, D. W., et al. Control of Giardia Cysts
by Filtration: The Laboratory's Rose. Presented at the AWWA Water
Quality Technology Conference, December, 1983.
" OeWalle, et al. Removal of Giardia lamblia Cysts by Drinking Water
Treatment Plants, Grant No. R806127, Report to Drinking Water
Research Division, U.S. EPA (ORD/MERL), Cincinnati, Ohio.
(4)
National Sanitation Foundation, Listing of Drinking Water Treatment
Units, Standard 53. May, 1986.
Hibler, C. P. An Evaluation of Filters in the Removal of Giardia
lamblia. Water Technology, pp. 34-36. July, 1984.
C. Alternate assay techniques for cyst tests (Jensen): Proposed alterations
in cyst tests include a different method for separating cysts from fecal
material and an assay method involving the counting of trophozoites as
well as intact cysts. Both alterations have been used by Bingham, et al.
(Exp. Parasitol., 47:284-291, 1979).
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Recommendation;
These alterations appear to be reasonable laboratory procedures, support-
ed by a peer-reviewed article and will be included in the Report as
options for possible development and use by interested laboratories.
D. The use of pour plate techniques as an option for Klebsiella terrigena
bacteria analyses.
Recommendation;
The pour plate technique adds a heat stress factor to the bacteria which
constitutes a possible deficiency. However, it is a .recognized standard
method and probably will not adversely affect the Klebsiella terrigena.
Consequently, it will be added to the Report as one of the acceptable
techniques.
E. Option of using Escherichia coli in lieu of Klebsiella terrigena for the
bacterial tests.
Discussion:
Appendix 0-1, Section A.I. of the Guide Standard and Protocol sets forth
the basis for selection of K. terrigena as the test bacteria. The
selection was made along pragmatic line emphasizing the occurrence of j^i
terrigena in surface waters and that it would represent the enteric
bacteria. It was also pointed out that the tests with virus and Giardia
were expected to be more severe than the bacterial tests. For comprehen-
siveness, bacterial tests were included in the protocol but were not felt
to be as crucial as the virus and Giardia tests.
E. coli, or any number of other generally accepted indicator bacteria,
could be used for the test program if they were shown to have good
tes'ting and survival characteristics (equivalent to K. terriaena) by the
interested research laboratory.
Recommendation;
The intent of the Guide Standard and Protocol is to provide a baseline
program subject to modification when properly supported by an interested
laboratory. Consequently, any laboratory could propose and with proper
support (demonstrating challenge and test equivalency to K. terrigena)
use Escherichia coli or one of the other enteric bacteria. This idea
will be included in revised working in Section 1.2.2, "General Guide."
F. Performance requirements for Giardia cysts and virus in relation to the
EPA-Recommended Maximum Contamination Levels (RMCLs) of zero.
Discussion:
The RMCLs of zero for Giardia and viruses which have been proposed by EPA
are health goals. They are no enforceable srandards since to assure the
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presence of "no organisms" would require an infinite sample. The
rationale for the recommended performance requirements for Giardia cysts
and virus is set forth in Sections A.2 and A.3 of Appendix A. We feel
that these requirements together with the application of realistic worst
case test conditions will provide a conservative test for units resulting
in treated effluent water equivalent to that of a public water supply
meeting the microbiological requirements and intent of the National
Primary Drinking Water Regulations.
Recommendation;
Retain recommended performance (3,og reduction) requirements for cyst and
virus reduction.
G. Rotavirus and its proposed assay: One commenter states that the rota-
virus tests are impractical because Amirtharajah (J. AWWA, 78(3):34-49,
1976) cites "no satisfactory culture procedures available for analysis of
these pathogens and, therefore, monitoring would not be feasible."
Discussion;
Section 3.4.1.2, "Virus Tests" of the Report, presents means for cul-
turing and assaying rotaviruses. This means for doing the rotavirus
tests are available and are practical for application in the laboratory.
Dr. Amirtharajah was referring to the field collection, identification in
the presence of a wide variety of microorganisms, and quantification as
not being "satisfactory." Laboratory analysis of rotaviruses is practi-
cal but their field monitoring may not yet be feasible.
Further, the selection of both poliovirus and rotavirus as test viruses
was necessitated by the fact that the surface adsorptive properties and
disinfection resistance of the various enteric viruses have been shown to
differ significantly by virus group and by strains of a specific virus.
Whi-le all enteric viruses and their strains could not be economically
tested, it was determined by the task force that at least two distinctly
different virus types should be tested to achieve some idea of the
diversity of removal by the various types of water purifiers. Polio and
rota viruses have distinctly different physical and chemical charac-
teristics representative of the viruses of concern. Polioviruses are
small single stranded RNA viruses with generally good adsorptive proper-
ties to surfaces and filter media while rotaviruses are over twice as
large, are double stranded RNA and in some studies have been found to
possess less potential for adsorption onto surfaces or filter media.
These two viruses also have been demonstrated to have somewhat different
disinfection kinetics.
Recommendation:
Retain the rotavirus test requirements.
H. Definition of microbiological water purifier: One general comment
requested redefinition based on "lack of any virus removal "requirement:
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in the EPA primary drinking water regulations, so that no virus reduction
requirement should be included. Also, it was claimed that the separation
of purifiers from non-purifiers would be a "disservice to consumers and
other users."
Discussion;
Viruses are recognized in the EPA regulations vis-a-vis a proposed recom-
mended maximum contaminant level of zero. Since virus monitoring for
compliance with a possible MCL is not yet feasible, a treatment require-
ment is necessary. Virus control will be considered in the Safe Drinking
Water Act filtration and disinfection treatment regulations. The reduc-
tion of viruses by treatment is discussed by Amirtharajah (J. AWWA,
78:3:34-49, 1986).
With respect to consumers and other users, we feel that the current
definition is appropriate and necessary. The average consumer cannot be
expected to know the difference between viruses, bacteria and cysts, or
when a raw water will or will not contain any of these organisms. In
order to protect the average consumer, the subject units either alone jar
with supplementary treatment, should be able to cope with all of the
specified organisms.
Recommendation;
Retain the current definition for microbiological water purifier.
I. Coverage of units: Several comments related to the coverage of units.
These questions are addressed individually as follows:
1. Ultraviolet units that are used for supplemental treatment of water
from public water system taps would not be covered. We agree that
such units are not covered and parenthetical language has been
• included in Section 1.3.2.3 to clarify this point.
2. A special status should be given to units which remove Giardia and
bacteria but not virus. Specifically, the meaning of Section 1.2.4,
"Exceptions," was addressed. The "Exceptions" section was specif-
ically developed to relate to the problem of public water systems
having disinfection but no filtration on a surface supply. Cysts
alone have been found to survive disinfection treatment and could be
present in such treated waters. In this case an effective cyst
filter serves an independent, beneficial purpose and should not be
required to be a microbiological water purifier. However, such a
unit should not be used as sole treatment for untreated raw water.
Additional parenthetical language has been added to Section 1.2.4.
3. The entire treatment unit or system should be tested, not just a
single component. We agree but believe that it is sufficiently
clear without providing additional language.
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4. The protocol should be expanded to cover units for the reduction of
TCE, EDB and other chemical pollutants. We felt that the introduc-
tion of non-microbiological claims to the standard would make it
large, unwieldy and duplicative of an existing third-party standards
and testing program (see Section 1.2.5).
J. Alleged preference of National Sanitation Foundation (NSF) over other
laboratories for conducting the microbiological water purifier testing
protocol. The comment indicated that we were giving NSF preferential
treatment "to the detriment of other laboratories well qualified to
perform the required protocol."
Discussion;
We have made appropriate references to existing standards (#42 and #53)
developed by the NSF standards development process. Standard 53, the
health effects standard, was developed by a broadly based Drinking Water
Treatment Units Committee, including representatives from local, State
and Federal health and environmental agencies, universities, professional
and technical associations, as well as water quality industry
representatives. It was adopted in 1982 and the only test from it
utilized in our Report has been substantiated as described in Part B of
this "Response."
Nowhere in our report have we advocated NSF (or any other laboratory) as
the prime or only laboratory for implementing "the required protocol."
Recommendation;
No action needed.
K. Instruction concerning effective lifetime. One comment described an
alternate means for determining lifetime where a ceramic unit is
"brushed" to renew its utility and is gradually reduced in diameter. A
gauge is provided to measure diameter and to determine when replacement
is needed.
Recommendation;
Where a manufacturer provides a satisfactory "other" means of determining
lifetime, this should be accepted. Appropriate words have been added to
Section 2.4.I.C.
L. Ceramic candles should not be cleaned during testing because some
consumers would not clean them and this would provide the "worst case
test." One comment asserted this point.
Discussion:
There is some truth to this proposition. However, the other approach may
also have validity. Frequent brushing may reduce filtration efficiency.
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In any event, where a manufacturer prescribes filter cleaning and how to
do it, and provides a gauge to determine lifetime, we feel the testing
program is bound to follow the manufacturer's directions.
Recommendation;
No change needed.
M. Scaling up or down. One comment points out that one or more manufac-
turers may vary size of treatment units by increasing or decreasing the
number of operative units rather than the size of the operative unit.
The comment suggests allowing scaling based on size of operative unit.
Recommendation;
We agree with the comment and have added clarifying words to Sec-
tion 3.5.3.3.
N. Turbidity level of "not less that 30 NTU" for ceramic candles or units.
One comment states that "Such levels are impossible to utilize in testing
mechanical filtration devices which will clog entirely or require such
frequent brushing as to render the test impossible as a practical
matter."
Discussion;
We recognized the potential "clogging problems" in Section 3.5.1.a(2)
where the 30 NTU water is only to be applied immediately before and
during each sampling event; the non-sampling turbidity level, which will
be applied over 90% of the "on" time, is currently set at no less than
10 NTU.
Turbidity levels of 30 NTU are commonly found in surface waters during
heavy rainfall or snow melt. Treatment units may be used under these
circumstances, so this challenge level should be retained. However, most
usage will occur under background conditions so the non-sampling
turbidity levels should be 0.1-5 NTU.
Recommendations:
1. Retain sampling turbidity level of not less than 30 NTU, and
2. Change non-sampling turbidity to 0.1-5 NTU. Appropriate wording
changes have been introduced in Section 3.5.1.a(2) and in Appen-
dix O-l, Section B.
O. Chlorine in test water #5. One comment asserts that chlorine "tends to
increase silver ion leaching activity" and that a high chlorine level
should be included in the silver leaching test; but no reference or
evidence, however, is provided to back this assertion.
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Discussion;
We have no compelling evidence or reason to expect that chlorine will
enhance the leaching of silver. However, the prescribed low pH and TDS
levels will provide a clearly severe test for silver leaching.
Recommendation;
No change needed.
P. Unnecessary difficulty and expense of test protocols. Several comments
were made under this general heading. These comments are outlined and
discussed as follows:
1. Too many sampling events are required; sampling of a few units at
start, middle and finish should be satisfactory: The committee has
carefully laid out the standard and protocol and we feel the minimum
sampling plan must be maintained for the consumers' health pro-
tection.
2. Three units are too many to study; parallel testing of two units
should be satisfactory: For consumer protection, the Disinfectants
Branch, Office of Pesticide Programs, has traditionally required the
testing of three units. The committee recognizes the additional
cost involved in testing a third unit but feels that this will
provide a minimum level of assurance to prevent infectious disease
and recommends retention of the 3-unit requirement.
3. The protocol requires large tanks and microbiological reseeding on a
daily basis: We feel that the tank size requirements are not
extreme and can be met by an interested laboratory. With respect to
reseeding, it should be pointed out that virus and cyst seeding need
only be conducted immediately before and during the sampling "on"
- period (see Section 3.5.1.b(2)), equivalent to less that 10% of the
"on" time. This "spot" seeding for viruses and cysts recognized the
expense and difficulty of maintaining large populations of these
organisms. Continuous seeding was provided for bacteria because
they are easier to grow and maintain and might have the capacity to
grow through some units, given enough time and opportunity.
4. Challenge levels of contaminants are too high compared to known
environmental conditions and the required log reductions exceed Safe
Drinking Water Act requirements: As explained in a footnote to
Table 1, Section 2, the influent challenges may constitute greater
concentrations than would be anticipated in source waters. These
levels are necessary to test properly for the required log reduc-
tions without having to utilize sample concentration procedures
which are time/labor intensive and which may, on their own, intro-
duce quantitative errors to the microbiological assays. As men-
tioned in Part I of this paper, the log reductions for bacteria,
virus and Giardia have been suggested for public water system
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treatment in a paper by Amirtharajah (1986, JAWWA, 78:3:34-49). The
reductions in the microbiological purifier standard are entirely
compatible with the reductions cited for public water supply
treatment.
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