United States
Environmental Protection
Agency
LT1ESWTR Disinfection Profiling
and Benchmarking
Technical Guidance Manual
c
o
15
o
(0
1.400
1.200
1.000
0.800
0.600
0.400
0.200
0.000
Log Inactivation
0 4 8 12 16 20 24 28 32 36 40 44 48 52
Week Tested
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Office of Water (4606M)
EPA816-R-03-004
www.epa.gov/safewater
May 2003
Printed on Recycled Paper
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This document provides public water systems and States with Environmental Protection Agency's
(EPA's) current technical and policy recommendations for complying with the disinfection profiling
and benchmarking requirements of the Long Term 1 Enhanced Surface Water Treatment Rule
(LT1ESWTR). The statutory provisions and EPA regulations described in this document contain
legally binding requirements. This document is not a regulation itself, nor does it change or substitute
for those provisions and regulations. Thus, it does not impose legally binding requirements on EPA,
States, or public water systems. This guidance does not confer legal rights or impose legal obligations
upon any member of the public.
While EPA has made every effort to ensure the accuracy of the discussion in this guidance, the
obligations of the regulated community are determined by statutes, regulations, or other legally binding
requirements. In the event of a conflict between the discussion in this document and any statute or
regulation, this document would not be controlling.
The general description provided here may not apply to a particular situation based upon the
circumstances. Interested parties are free to raise questions and objections about the substance of this
guidance and the appropriateness of the application of this guidance to a particular situation. EPA and
other decisionmakers retain the discretion to adopt approaches on a case-by-case basis that differ from
those described in this guidance where appropriate.
Mention of trade names or commercial products does not constitute endorsement or recommendation
for their use.
This is a living document and may be revised periodically without public notice. EPA welcomes public
input on this document at any time.
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Acknowledgements
The Environmental Protection Agency gratefully acknowledges the individual
contribution of the following:
Mr. Kevin W. Anderson, Pennsylvania Department of Environmental Protection
Mr. John E. Brutz, Gallitzin Water Authority
Mr. Jerry Biberstine, National Rural Water Association
Ms. Alicia Diehl, Texas Natural Resource Conservation Commission
Mr. Bryce Feighner, Michigan Department of Environmental Quality
Mr. J.W. Heliums, Jr., Community Resource Group, Inc.
Mr. Allen J. Lamm, New Ulm Public Utilities
*Ms. Rebecca Poole, Oklahoma Department of Environmental Quality
Mr. Jack Schulze, Texas Natural Resource Conservation Commission
Mr. Brian Tarbuck, Tolt Treatment Facility, Azurix CDM
Mr. Ritchie Taylor, Center for Water Resource Studies, Western Kentucky University
Mr. Steve Via, American Water Works Association
*Participation supported by Association of State Drinking Water Administrators.
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CONTENTS
1. Introduction 1
1.1 Purpose of Document 1
1.2 Overview of Long Term 1 Enhanced Surface Water Treatment Rule 2
1.3 Overview of Disinfection Profiling and Benchmarking Requirements 3
1.3.1 Significant Changes to Disinfection Practices 6
1.3.2 Obtaining State Approval for Significant Changes to Disinfection
Practices 6
1.4 Using Disinfection Profiling and Benchmarking to Balance Rule
Requirements 8
1.5 Contents of this Guidance Document 9
2. Disinfection Segment 11
2.1 Introduction 11
2.2 Identifying Disinfection Segments 11
2.2.1 Single Disinfection Segment 12
2.2.2 Multiple Disinfection Segments 13
2.2.3 Disinfection Segments for Multiple Treatment Trains 16
2.3 Steps Completed 18
2.4 Next Step 18
3. Data Collection 19
3.1 Introduction 19
3.2 Data Needed for the Disinfection Profile 19
3.2.1 Peak Hourly Flow Rate 20
3.2.2 Residual Disinfectant Concentration 21
3.2.3 Temperature 22
3.2.4 pH 22
3.3 Data Collection Worksheets 25
3.4 Steps Completed 25
3.5 Next Step 25
3.6 References 26
4. Calculating CT 27
4.1 Introduction 27
4.2 What is CT? 27
4.3 Determining "C" 28
4.4 Determining "T" 28
4.4.1 Volume 29
4.4.2 Theoretical Detention Time 30
4.4.3 Baffling Factor 31
4.4.4 Calculate Contact Time 32
4.5 Calculate CTcak 35
4.6 Steps Completed 38
4.7 Next Step 38
4.8 References 38
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Contents
5. Calculating Inactivation 39
5.1 Introduction 39
5.2 Log Reduction 39
5.3 Determining CT Required 40
5.3.1 CT99.9 for Giardia 41
5.3.2 CT99.99 for Viruses 43
5.4 Calculating Actual Log Inactivation for One Disinfection Segment 43
5.5 Calculating Actual Log Inactivation for Multiple Disinfection Segments 46
5.6 Steps Completed 49
5.7 Next Step 49
6. Developing the Disinfection Profile and Benchmark 51
6.1 Introduction 51
6.2 Constructing a Disinfection Profile 52
6.3 The Disinfection Benchmark 55
6.4 Significant Changes to Disinfection Practices 56
6.5 Benchmark Calculations 56
6.6 Steps Completed 59
6.7 Next Step 59
7. Evaluating Disinfection Practice Modifications 61
7.1 Introduction 61
7.2 System Reporting Requirements 63
7.3 Simultaneous Compliance 63
7.3.1 Changes to the Point of Disinfection 65
7.3.2 Changes to the Disinfectant(s) Used in the Treatment Plant 66
7.3.3 Changes to the Disinfection Process 69
7.3.4 Other Modifications 70
7.4 How the State will Use the Benchmark 71
7.5 Steps Completed 72
7.6 References 72
8. Treatment Considerations 73
8.1 Introduction 73
8.2 Alternative Disinfectants and Oxidants 73
8.2.1 Chloramines (NH2C1) 74
8.2.2 Ozone (O3) 75
8.2.3 Chlorine Dioxide (C1O2) 76
8.2.4 Potassium Permanganate (KMnO4) 77
8.2.5 Ultraviolet Radiation (UV) 77
8.2.6 Comparison of Disinfectants 78
8.3 Enhanced Coagulation and Softening 80
8.4 Increasing Contact Time 82
8.5 Membranes 85
8.6 References 88
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Contents
Appendices
Appendix A. Glossary 91
Appendix B. CT Tables 101
Appendix C. Blank Worksheets 113
Appendix D. Examples 121
Appendix E. Tracer Studies 157
Appendix F. Calculating the Volume of Each Sub-Unit 167
Appendix G. Baffling Factors 171
Appendix H. Conservative Estimate and Interpolation Examples 187
Figures
Figure 1-1. Sample Disinfection Profile 4
Figure 1-2. Disinfection Profile and Benchmark Decision Tree 7
Figure 2-1. Plant Schematic Showing A Conventional Filtration Plant With One
Disinfection Segment 12
Figure 2-2. Plant Schematic Showing Two Disinfection Segments 13
Figure 2-3. Plant Schematic Showing One Injection Point with Multiple
Disinfection Segments 14
Figure 2-4. Plant Schematic Showing Two Injection Points with Multiple
Disinfection Segments 15
Figure 2-5. Plant Schematic Showing Identical Treatment Trains and Multiple
Disinfection Segments 16
Figure 2-6. Plant Schematic Showing Multiple Treatment Trains and Multiple
Disinfection Segments 17
Figure 4-1. Baffling Characteristics of a Pipe and Clearwell 31
Figure 6-1. Example of a Completed Disinfection Profile 52
Figure 7-1. Example of Moving the Point of Pre-disinfectant Application 65
Figure 7-2. Example of Changing Disinfectant Type 68
Figure 7-3. Changing Pre-disinfection Location and Type of Disinfectant 68
Figure 8-1. Particles Removed Through Membrane Technologies 87
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Contents
Tables
Table 4-1. Volume Equations for Shapes 30
Table 4-2. Baffling Factors 32
Table 7-1. Removal and Inactivation Requirements 62
Table 7-2. Typical Removal Credits and Inactivation Requirements for
Various Treatment Technologies 62
Table 8-1. Study Results on Changing Primary and Secondary Disinfectants 79
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Contents
ABBREVIATIONS
List of common abbreviations and acronyms used in this document:
American Water Works Association
Baffling Factor
AWWA
BF
C
CFR
CT
CWS
DBF
DOC
DOM
EPA
FBRR
GAC
gal
gpm
GWUDI
HAAS
hrs
IESWTR
LT1ESWTR
MCL
MG
mg/L
MGD
m/h
MRDL
NCWS
NTNCWS
Residual Disinfectant Concentration
Code of Federal Regulations
The Residual Disinfectant Concentration (mg/1) Multiplied by the
Contact Time (minutes)
Community Water System
Disinfection Byproduct
Dissolved Organic Carbon
Dissolved Organic Matter
Environmental Protection Agency
Filter Backwash Recycling Rule
Granular Activated Carbon
Gallons
Gallons per Minute
Ground Water Under Direct Influence of Surface Water
Haloacetic Acids
Hours
Interim Enhanced Surface Water Treatment Rule
Long Term 1 Enhanced Surface Water Treatment Rule
Maximum Contaminant Level
Million Gallons
Milligrams per Liter
Million Gallons per Day
Meters per Hour
Maximum Residual Disinfectant Level
Non-community Water System
Non-transient Non-community Water System
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Contents
PWS
PWSID
Q
RO
SCADA
SDWA
Stage 1 DBPR
SWTR
T
TDT
THM
TOC
TT
TTHM
UV
V
WTP
X log inactivation
X log removal
(^
Hg/L
Public Water System
Public Water System Identification
Peak Hourly Flow Rate
Reverse Osmosis
Supervisory Control and Data Acquisition
Safe Drinking Water Act
Stage 1 Disinfectants and Disinfection Byproduct Rule
Surface Water Treatment Rule
Contact Time (minutes)
Theoretical Detention Time
Trihalomethanes
Total Organic Carbon
Treatment Technique
Total Trihalomethanes
Ultraviolet
Volume
Water Treatment Plant
Reduction to 1/1 Ox of original concentration by disinfection
Reduction to 1/1 Ox of original concentration by physical removal
Micron (10"6 meter)
Micrograms per liter
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Contents
MARGIN ICONS
Icons and text in the margins of this document highlight information and additional
resources. These icons are shown below with brief descriptions of their uses or the types of
information they may be used to highlight.
Indicates a reference to the federal regulations.
Indicates the need to consult with the State.
Indicates additional references or highlights important
information.
Indicates worksheets.
Indicates sampling or data collection requirements.
Indicates applicability criteria.
Indicates a helpful hint or suggestion.
f
Highlights a key point or key information.
Indicates the next step.
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EPA Guidance Manual viii May 2003
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1. INTRODUCTION
In this Chapter:
• Purpose of Document
• Overview of
LT1ESWTR
• Overview of
Disinfection Profiling
and Benchmarking
Requirements
• Using Disinfection
Profiling and
Benchmarking to
Balance Rule
Requirements
• Contents of this
Guidance Document
40 CFR Section 141.501
1.1 PURPOSE OF DOCUMENT
This guidance manual is intended to help public water systems
(PWSs) comply with the disinfection profiling and
benchmarking requirements of the Long Term 1 Enhanced
Surface Water Treatment Rule (LT1ESWTR). The
requirements of the LT1ESWTR apply to PWSs that:
• Serve fewer than 10,000 people; and,
• Are classified as either surface water or ground water
under the direct influence of surface water (GWUDI).
This manual explains disinfection profiling and benchmarking,
discusses when and why they are necessary, and provides
guidance as to how to compile a disinfection profile and how to
calculate the benchmark. This guidance manual also discusses
how systems and States may use these data to make decisions
about disinfection practices. Copies of this document and other
documents that pertain to LT1ESWTR may be obtained by:
• Contacting the appropriate State office;
• Calling the Safe Drinking Water Hotline at
1-800-426-4791;
• Downloading from EPA's website at
http://www.epa.gov/safewater/mdbp/lt 1 eswtr.html; or,
• Calling the National Service Center for Environmental
Publications at 1-800-490-9198 or visiting their website
at http://www.epa.gov/ncepihom/.
Systems serving 10,000 people or more have different profiling
requirements and should refer to the Interim Enhanced Surface
Water Treatment Rule Guidance Document: Disinfection Profiling
and Benchmarking, August 1999 (EPA 815-R-99-013).
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1. Introduction
Key components of
LT1ESWTR.
1.2 OVERVIEW OF LONG TERM 1 ENHANCED
SURFACE WATER TREATMENT RULE
The LT1ESWTR is a Federal regulation that establishes a
treatment technique to control Cryptosporidium. The rule
applies to public water systems serving fewer than 10,000
people and classified as either a surface water system or a
GWUDI system. Key components of the LT1ESWTR are:
• Systems must provide a minimum of 2-log (99%)
removal of Cryptosporidium.
• Systems with conventional or direct filtration plants
must meet more stringent combined filter effluent
turbidity limits and must meet new requirements for
individual filter effluent turbidity.
• Systems using alternative filtration techniques (defined
as filtration other than conventional, direct, slow sand,
or diatomaceous earth) must demonstrate to the State the
ability to consistently achieve 2-log (99%) removal of
Cryptosporidium and comply with specific State-
established combined filter effluent turbidity
requirements.
• Systems that meet the filtration avoidance criteria must
comply with additional watershed control requirements
to address Cryptosporidium.
• Systems must develop a disinfection profile unless the
State determines that the disinfection profile is
unnecessary. The State can only make this determination
if the system can demonstrate that the levels of Total
Trihalomethanes (TTHM) and Haloacetic Acids
(HAAS) are below 0.064 mg/L and 0.048 mg/L,
respectively. The system must develop a benchmark if
the system was required to develop a disinfection profile
and subsequently plans a significant change to
disinfection practices.
• New, finished water reservoirs must be covered.
• Cryptosporidium is now included in the Federal
definition of GWUDI.
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1. Introduction
40 CFR Sections 141.503
(c) and 141.503 (d).
1.3 OVERVIEW OF DISINFECTION PROFILING
AND BENCHMARKING REQUIREMENTS
The requirements for disinfection profiling and benchmarking
described in this manual are part of the LT1ESWTR, published
by EPA on January 14, 2002. The disinfection profiling and
benchmarking requirements of the LT1ESWTR apply only to
community and non-transient non-community water systems
using surface water or GWUDI as a source and serving fewer
than 10,000 people.
Transient water systems are not required to create a disinfection
profile, unless directed by the State. However, transient systems
are encouraged to use the profile as a tool to help evaluate their
system.
40 CFR Section 141.530
Systems should balance
disinfection practices with
Stage 1 Disinfectants and
Disinfection Byproducts
Rule requirements. See
Section 1.4 for more
information on this topic.
A disinfection profile is a graphical representation of a
system's level ofGiardia lamblia (referred to as Giardia) or
virus inactivation measured during the course of a year.
A benchmark is the lowest monthly average microbial
inactivation during the disinfection profile time period. A
disinfection benchmark is required only if a system was required
to develop a disinfection profile and decides to make significant
changes to its disinfection practices.
The LT1ESWTR requires systems to analyze their current
disinfection practices before making changes to these practices.
This analysis will result in a disinfection profile. Figure 1-1
depicts a sample disinfection profile.
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1. Introduction
Sample Disinfection
Profile
40 CFR Section 141.531
Systems that believe they
have data that meet the
avoidance criteria should
consult with the State to
determine whether they are
required to profile.
Systems not required to
profile are encouraged to
complete and use the
profile as a tool to help
evaluate their system.
1.400 -,
1.200 -
1.000 -
0.800 -
0.600 -
0.400 -
0.200 -
0.000 -
0 4 8 12 16 20 24 28 32 36 40 44 48 52
Week Tested
Figure 1-1. Sample Disinfection Profile
Each system must complete a disinfection profile unless the
State determines that the system's profile is unnecessary. This
determination will be based on TTHM and HAAS levels in the
distribution system. States may determine that a profile is
unnecessary only if:
• TTHM and HAAS samples are collected after January 1,
1998.
• The samples are collected in the month with warmest
water temperature and at the point of maximum
residence time in the distribution system.
• TTHM and HAAS levels in the samples are less than
80% of the maximum contaminant level (MCL). This
equates to TTHM <0.064 mg/L and HAAS <0.048 mg/L.
Systems that do not have data meeting the avoidance criteria by
July 1, 2003, for systems serving 500 to 9,999 people and
January 1, 2004, for systems serving fewer than 500 people
MUST begin to create a disinfection profile.
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1. Introduction
40 CFR Section 141.532
40 CFR Section 141.536
CT = C x T
C = Residual disinfectant
concentration, mg/L
T = Contact time, minutes
See Chapter 4 for more
information on CT.
40 CFR Section 141.540
Systems serving 500 to 9,999 people must begin collecting data
for the disinfection profile by July 1, 2003. Systems serving
fewer than 500 people must begin collecting data for the
disinfection profile by January 1, 2004.
In order to create a disinfection profile, systems should:
• Identify disinfection segments;
• Collect required data for each segment;
• Calculate CT; and,
• Calculate inactivation.
These topics are described in more detail in Chapters 2 - 5 of
this document.
Systems must create and retain the profile in graphic form. The
profile must be made available for review by the State as part of
a sanitary survey.
Before any significant changes may be made to the disinfection
process, a system must calculate the benchmark value based on
disinfection practices. The benchmark is the lowest monthly
average microbial inactivation during the disinfection profile
time period (See Chapter 6 for more detail). The system is
required to calculate a benchmark if both of the following apply:
• The system is required to complete a disinfection profile;
and,
• The system plans to make a significant change to
disinfection practices.
Systems must also consult with the State for approval before
making any significant change to disinfection practices.
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1. Introduction
40 CFR Section 141.541
40 CFR Section 141.542
1.3.1 Significant Changes to Disinfection
Practices
Significant changes to disinfection practice include:
• Changes to the point of disinfection;
• Changes to the disinfectant(s) used in the treatment
plant;
• Changes to the disinfection process; or,
• Any other modification identified by the State.
1.3.2 Obtaining State Approval for Significant
Changes to Disinfection Practices
If a system is required to complete a disinfection profile and
intends to make a change as listed in Section 1.3.1, it must
consult with the State for approval. The following information
must be submitted to the State:
• A description of the proposed change;
• The disinfection profile for Giardia lamblia (and, if
necessary, viruses) and disinfection benchmark;
• An analysis of how the proposed change will affect the
current levels of disinfection; and,
• Any additional information requested by the State.
The flowchart in Figure 1-2 provides information on the
LT1ESWTR disinfection profiling and benchmarking
requirements.
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1. Introduction
Figure 1-2. Disinfection Profile and Benchmark Decision Tree
Is the source
water classified as either surface
or GWUDI?
Is the system
a transient non-commumtv
water system?
Does the
system serve fewer than
10,000 people?
No disinfection profiling
or benchmarking required
f System must comply with \
/ disinfection profiling and \
\ benchmarking requirements /
\. under IESWTR. J
under the LT1ESWTR
provisions.
Did the State
determine that a disinfection profile
was unnecessary?
Has the system tested
TTHM and HAAS after January 1, 1998
during the month of warmest water temperature
and at the point of maximum residence time
in the distribution system?
Was the annual
TTHM level < 0.064 mg/L and
the annual HAAS level
0.048 mg/L';
^
System must profile
Giardia inactivation.1'2
NO
Did the
system develop a disinfection
profile and keep it
on file?
YES
System must calculate
the benchmark for
Giardia inactivation and
consult with the State.2
Are there plans
to modify the existing
isinfection practice?
No disinfection
benchmark required.2
NO
Did the system
calculate the benchmark for Giardia inactivation^
and consult with the
State?
System is in compliance
with disinfection profiling
and benchmarking
requirements.
1. If using chlorine dioxide, ozone, or chloramines as a primary disinfectant the system must profile and benchmark viral
inactivation as well.
2. Disinfection profile must be kept on file for State to review during sanitary survey.
3. Tier 2 violation. Public notification is required within 30 days.
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1. Introduction
Systems must balance
disinfection practices with
Stage 1 DBPR
requirements. The
disinfection profile and
benchmark information
will assist systems and
States with achieving this
balance.
More information on the
Stage 1 DBPR is available
at EPA's website
(http://www.epa. gov/safewater/
mdbp/implement.html'l.
Systems may be
considering changes to
disinfection practices
during the disinfection
profiling process to
address Stage 1 DBPR
requirements. Systems
should contact the State
prior to making changes
to disinfection practices
and discuss how these
changes will affect the
disinfection profiling
process.
1.4 USING DISINFECTION PROFILING AND
BENCHMARKING TO BALANCE RULE
REQUIREMENTS
The LT1ESWTR disinfection profiling and benchmarking
requirements will protect public health by assessing the risk of
exposure to Giardia and viruses as systems begin to take steps
to comply with Stage 1 Disinfectants and Disinfection
Byproducts Rule (Stage 1 DBPR) requirements. For systems
classified as either surface water or GWUDI serving fewer than
10,000 people, the MCLs for TTHM and HAAS become
effective January 1, 2004. The Stage 1 DBPR established an
MCL of 0.080 mg/L for TTHM and 0.060 mg/L for HAAS.
TTHM are the sum of the concentrations in milligrams per
liter of the tribalomethane compounds (trichloromethane
[chloroform], dibromochloromethane, bromodichloromethane,
and tribromomethane [bromoform]). The MCL for TTHM is
0.080 mg/L starting January 1, 2004. Prior to January 1, 2004,
there is no Federal MCL for TTHM for systems serving fewer
than 10,000 people.
HAAS are the sum of the concentrations in milligrams per liter
of the haloacetic acid compounds (monochloroacetic acid,
dichloroacetic acid, trichloroacetic acid, monobromoacetic
acid, and dibromoacetic acid). The MCL for HAAS is 0.060
mg/L starting January 1, 2004. Prior to January 1, 2004, there
is no Federal MCL for HAAS for systems serving fewer than
10,000 people.
In order to meet the requirements of the Stage 1 DBPR,
systems may have to consider changes to their disinfection
practices. Disinfection byproducts (DBFs) such as TTHM and
HAAS are formed when organic materials react with
disinfectants such as chlorine. Therefore, systems with high
levels of DBFs may need to modify disinfection practices to
reduce the formation of DBFs. However, changes such as the
use of lower concentrations of disinfectant will also lessen
microbial inactivation. Decreasing the amount of disinfectant
too much may produce water of unsatisfactory microbial
quality. Disinfection profiling and benchmarking will help to
ensure that no significant reduction in microbial protection
results as a system changes disinfection practices to meet the
TTHM and HAAS MCLs under Stage 1 DBPR.
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1. Introduction
Contents of Document
1.5 CONTENTS OF THIS GUIDANCE
DOCUMENT
This document is organized in the following sections and
chapters:
• Chapter 1 - Introduction
• Chapter 2 -Disinfection Segment
This chapter defines the term disinfection segment
and describes how a system would identify the
disinfection segment(s).
• Chapter 3 - Data Collection
This chapter presents the data collection
requirements for creating a disinfection profile.
• Chapter 4 - Calculating CT
This chapter presents information and examples on
how to calculate CT to be used in the development
of a disinfection profile.
• Chapter 5 -Calculating Inactivation
This chapter presents information and examples on
how to calculate Giardia and virus inactivation
values to be used in the development of a
disinfection profile.
• Chapter 6 - Developing the Disinfection Profile and
Benchmark
This chapter provides information on how to
develop a disinfection profile using calculated
inactivation values. This chapter also presents
information on when the disinfection benchmark
must be calculated and how to calculate the
benchmark.
• Chapter 7 - Evaluating Disinfection Practice
Modificiations
This chapter discusses how the disinfection profile
and benchmark can be used to assess system
modifications that may be considered for
compliance. It also discusses the issues associated
with each modification.
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1. Introduction
Contents of Document
• Chapter 8 - Treatment Considerations
This chapter presents case studies and other
information that may assist systems with
LT1ESWTR and other rule compliance.
Appendices
Appendix A - Glossary
Appendix B - CT Tables
Appendix C - Blank Worksheets
Appendix D - Examples
Appendix E - Tracer Studies
Appendix F - Calculating the Volume of each
Sub-unit
Appendix G - Baffling Factors
Appendix H - Conservative Estimate and
Interpolation Examples
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2. DISINFECTION SEGMENT
In this Chapter:
• Identifying
Disinfection Segments
• Steps Completed
• Next Step
All monitoring points are
located before or at the
first customer (40 CFR
141.533(d)).
Systems need to identify
disinfection segments. A
disinfection profile must
be developed using all
disinfection segments.
2.1 INTRODUCTION
The first step in developing a disinfection profile should be to
identify the disinfection segments within the plant. A
disinfection segment is a section of a treatment system
beginning at one disinfectant injection or monitoring point and
ending at the next disinfectant injection or monitoring point.
Every disinfectant injection point is the start of a new
disinfection segment. Every injection point has an associated
monitoring point. However, a plant may have only one
disinfectant point, and choose to monitor at two or more points,
creating two or more disinfection segments. A system must
monitor the residual disinfectant before or at the first customer
(40 CFR Section 141.533(d)). The disinfection segment could
include distribution pipes and storage tanks located prior to the
first customer.
Plants with multiple treatment trains will have multiple
disinfection segments. If the treatment trains are identical, and
flow is split equally, the disinfection segments for each train
should be the same. If the treatment trains are very different,
the system should identify all disinfection segments and
develop a disinfection profile for each train separately.
2.2 IDENTIFYING DISINFECTION SEGMENTS
The suggested starting point for analyzing a plant is to develop
a summary of the unit processes, disinfectant injection and
monitoring points. It may be helpful to use a sketch or plan
drawing of the plant. Drawings like those shown in Figures 2-1
through 2-6 may help in defining disinfection segments.
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2. Disinfection Segment
Example:
Single Disinfection
Segment
2.2.1 Single Disinfection Segment
Figure 2-1 shows a simple plant, with one injection point and one
monitoring point, resulting in a single disinfection segment. The
disinfection segment begins at the chlorine injection point prior to
the clearwell and ends at the monitoring point after the clearwell.
One Disinfection Segment:
One injection point, one monitoring point
Chlorine
I njected
Sedimentation
Filtration
Monitoring Point
1,
Clearwell
Temperature
pH
Distribution
System
Figure 2-1: Plant Schematic Showing A Conventional
Filtration Plant With One Disinfection Segment
EPA Guidance Manual 12
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2. Disinfection Segment
2.2.2 Multiple Disinfection Segments
Figure 2-2 is an example of a system with two injection points
and two monitoring points, resulting in two disinfection
segments. Disinfection Segment 1 starts at the chlorine
injection point (prior to the coagulation basin) and ends at the
monitoring point after the filters. Disinfection Segment 2 starts
at the chlorine injection point after the first monitoring point
(between the filter and the clearwell) and ends at the
monitoring point after the clearwell and prior to the first
customer. Even for this simple plant, the analysis of how much
disinfection takes place in the plant may be complicated. In
this example, disinfection occurs in the coagulation basin,
flocculation basin, sedimentation basin, filter, and clearwell, as
well as in all the associated piping.
Example:
Two Disinfection
Segments
. L .
Disinfection Segment 1
Chlorine
Injected
/ / Intake — > * LTTJ t>A~J
, ..^ ^ y Q
\ \ Coagulation Flocculation
Sedimentation
Disinfection Segment 1
Monitor ng Point
CI2 residual
Temperature
PH
i r i
Disinfection
Segment 2
Chlorine
1 njected
1
Nitration 1
Disinfection Segment 2 gy
Monitoring Point
CI2 residual
Temperature
PH
arwell
bution
stem
Figure 2-2: Plant Schematic Showing Two
Disinfection Segments
May 2003
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LT1ESWTR Disinfection Profiling and Benchmarking
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2. Disinfection Segment
Example:
Multiple Disinfection
Segments
Chlorine residuals tend to
decline as water moves
through the treatment
plant. The benefit of
monitoring the chlorine
residual at multiple
locations is to obtain
additional credit for the
higher chlorine levels that
exist at intermediate
points in the plant. See
Chapter 4 for more on the
benefits of higher
measured chlorine
concentrations when
calculating log
inactivations.
Figure 2-3 is an example of a system with one injection point
and multiple monitoring points. Although the system is
required to have a minimum of one monitoring point, the
chlorine is sampled in four locations to obtain higher chlorine
residual values throughout the treatment train for Surface
Water Treatment Rule (SWTR) compliance as opposed to
monitoring at one location after the clearwell where the
chlorine residual will be much less than measurements prior to
the clearwell. The first disinfection segment starts at the
chlorine injection point and ends at the first sampling point
(between the coagulation and flocculation basins). The next
three disinfection segments begin at one sampling point and
end at the following sampling point. Therefore, even though
there is only one injection point at this system, there are four
disinfection segments.
Ch
Inj
/ /intake
Dis
Disinfection
Segment 1
orine
scted
— oil
Coagulation
Disinfection
Segment 2
> iff-1 C5/T:) -j-* Sed
Flocculation
Disinfection Segment 2
Monitoring Point
CI2 residual
Temperature
pH
infection Segment
Monitoring Point
CI2 residual
Temperature
pH
1
Disinfection Disinfection
Segment 3 Segment 4
Filtration
.
^ ' 'j
Disinfection Segment 3 |
Monitor ng Point I
CI2 residual
Temperature
PH
Disinfection Segment 4
Monitoring Point
CI2 residua
Temperature
PH
Clearwell
< i
Distribution
System
Figure 2-3: Plant Schematic Showing One Injection
Point with Multiple Disinfection Segments
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2. Disinfection Segment
Figure 2-4 is an example of a more complicated plant
schematic where the plant's multiple disinfection segments
have been defined. In Figure 2-4 chlorine is sampled in three
locations to obtain additional credit for higher chlorine residual
values that exist at intermediate points in the plant. Ammonia
is added prior to the clearwell to form chloramines. The use of
a different disinfectant results in a new disinfection segment.
Example:
Multiple Disinfection
Segments
Disinfection
Segment 1
Chlorine
Injected
/ /Intake— ^> H
( r oL=o
\ \ Coagulation
) ) ' J
Disinfection
Segment 2
H-> l~Tv=~' /ff^ -f-> Sed
Flocculation
Disinfection Segment 2
Monitoring Point
CI2 residual
Temperature
pH
Disinfection Segment 1
Monitoring Point
CI2 residual
Temperature
pH
Disinfection Dis
Segments Se
Amn
nje
Filtration ,
>infection
;g merit 4
non a
cted
.
^^ ' '
I
Disinfection Segment 3
Monitoring Point
CI2 residual
Temperature
pH
Disinfection Segmen
Monitoring Point
Chloramine residua
Temperature
Distr bution
System
4
Figure 2-4: Plant Schematic Showing Two Injection
Points with Multiple Disinfection Segments
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LT1ESWTR Disinfection Profiling and Benchmarking
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2. Disinfection Segment
2.2.3 Disinfection Segments for Multiple
Treatment Trains
For some system configurations, one profile would not
accurately characterize the entire treatment process. In these
cases, multiple profiles are suggested. Figure 2-5 shows a
plant with multiple treatment trains and multiple disinfection
segments. In this example, the treatment trains are identical in
that all unit processes in both trains have the same dimensions,
operating rates, and hydraulic capacity. Since the treatment
trains are identical, and flow is split equally between the
treatment trains, the disinfection profile for Disinfection
Segments la and Ib should be identical. Similarly, the
disinfection profile for Disinfection Segments 2a and 2b should
be identical. However, systems should check with the State to
determine if separate disinfection profiles are required for each
treatment train.
Example: Disinfection
Segments for Identical
Treatment Trains
Disinfection Segment 1a
Chlorine
Flow Injected
] J^Controner j ^
/ /mtake -»| 1/2ofFlow J^ |
\ \ Coagulation
] ) Chlorine
Injected
I, I J.
1/2 of Flow I
ok) |
Coagulation
L
Disinfection Segment 1 a Disinfection Segment 2a
Monitoring Point Monitoring Point
CI2 residual CI2 residual
Temperature Temperature
pH PH
0 0 Sedimentation ^ Filtration
A° ^fi0 | |^
Flocculation ^^^
C
I
\L, ,-JuU I I Sedimentation Filtration
A° iP [ J
Flocculation ^ — ^
Disinfection Segment 1b Disinfection Segment 2b
Monitoring Point Monitoring Point
CI2 residual CI2 residual
Temperature Temperature
pH pH
1 Disinfection Segment 1b
*Note: Flow is split equally between treatment trains.
Disinfection
Segment 2a
1
Injected j
I Distribution
-JT.I.,,,
hlorine
ijected
1
I Distribution
T o:
-------
2. Disinfection Segment
Example: Disinfection
Segments for Multiple
Treatment Trains
Figure 2-6 shows a plant with two treatment trains and multiple
disinfection segments. Although the treatment trains are
identical, in this example, the flow is not split equally between
the treatment trains. The disinfection profile for Disinfection
Segments la and Ib may not be identical. Similarly, the
disinfection profile for Disinfection Segments 2a and 2b may
not be identical. Therefore, this plant should develop a
separate disinfection profile for each treatment train. Again,
the system should check with the State on this issue.
Disinfection Segment 1a
Disinfection Segment 1a Disinfection Segment 2a
Monitoring Point Monitoring Point
Temperature Temperature
pH pH
Chlorine
. . Flow lnJefted I
// — rM ^. > &Y<*"""*" , Fi"raiion
/ /lnlake --J 1/3ofFow J^ &A A 1
\ \ Coagulation Flocculation ^^^
) J Chlorine C
Injected ,
1 1 90 Sedimentation Flltratlon
2/3 of Flow |__ I
Coagulation Flocculation —
Disinfection Segment 1b Disinfection Segment 2b
Monitoring Point Monitoring Point
Temperature Temperature
pH pH
" Disinfection Segment 1b
*Note: Flow is NOT split equally between treatment trains.
Disinfection
I Segment 2a i
I I
Chlorine i
Injected
I Distribution
„,.[„„
hlorine
n ected
I Distribution
| ^ C'"
i i
' Disinfection '
Segment 2b
Figure 2-6: Plant Schematic Showing Multiple
Treatment Trains and Multiple Disinfection Segments
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LT1ESWTR Disinfection Profiling and Benchmarking
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2. Disinfection Segment
2.3 STEPS COMPLETED
Calculate
In activation
the
Disinfection
Profile
Benchmark
and
the
Disinfection
Profile and
Benchmark
CT
Identify
Disinfection
Segments
2.4 NEXT STEP
After all of the disinfection segments have been identified, data
must be collected for each disinfection segment. See Chapter 3
for more information on disinfection profiling data collection
requirements.
EPA Guidance Manual 18
LT1ESWTR Disinfection Profiling and Benchmarking
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3. DATA COLLECTION
In this Chapter:
• Data Needed for the
Disinfection Profile
• Data Collection
Worksheets
• Steps Completed
• Next Step
• References
40 CFR Section 141.532
40 CFR Section 141.533
3.1 INTRODUCTION
Once a system has identified all disinfection segments, data
must be collected for each segment to create the disinfection
profile. For systems serving 500 to 9,999 people, data
collection must begin no later than July 1, 2003. For systems
serving fewer than 500 people, data collection must begin no
later than January 1, 2004. Systems that are required to
develop a disinfection profile must collect data once a week, on
the same day of the week, for twelve consecutive months (one
year). The State may allow the use of a more representative
data set for disinfection profiling, so systems with sufficient
historic data should check with the State prior to collecting data
(40 CFR Section 141.530).
3.2 DATA NEEDED FOR THE DISINFECTION
PROFILE
To develop a disinfection profile, data must be collected once
per week on the same day of the week for one year. The
following data are needed for each disinfection segment
identified (See Chapter 2 for information on disinfection
segments):
• Peak Hourly Flow;
• Residual Disinfectant Concentration;
• Temperature; and,
• pH (if chlorine is used).
Measurements must be taken on the same day of the week,
every week, for one year (52 measurements), during peak
hourly flow for that day. Data can be measured manually or
with on-line instrumentation.
Systems that already have existing data that meet the criteria of
Section 3.2 may wish to contact the State to determine if the
existing data can be used to create a disinfection profile in lieu of
collecting new data.
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LT1ESWTR Disinfection Profiling and Benchmarking
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3. Data Collection
All data must be collected
at peak hourly flow.
Data needed for each
disinfection segment:
• Peak Hourly Flow
• Residual Disinfectant
Concentration
• Temperature
• pH (if chlorine is
used)
• Volumes and Baffling
Factors (See Chapter
4)
3.2.1 Peak Hourly Flow Rate
The amount of time the water is in contact with the disinfectant
is a function of flow rate. When the flow rate increases, the
time the water spends in the plant decreases. Using the peak
hourly flow rate (required by LT1ESWTR) for analysis
provides a conservative value for contact time. Some systems
may be able to use a single peak hourly flow across the plant.
In some systems, the peak hourly flow may vary across the
plant. If the system has multiple disinfection segments and
flow does vary across the plant, the disinfection segments may
have different peak hourly flows.
Each system will determine its peak hourly flow rate
differently. Some possible ways to determine the flow rate are:
• Flow meter records;
• Design flow rate;
• Maximum loading rates to the filters or other treatment
process units;
• Raw water pump records; or,
• Historical maximum flow rate.
When determining peak hourly flow, systems may want to take
into consideration the location of their disinfection segment.
For example, a system with a single disinfection segment with
disinfection prior to the clearwell may consider using clearwell
pumping rates versus raw water pump records to determine the
peak hourly flow rate.
When compiling data for the disinfection profile, systems will
monitor once per week on the same calendar day during peak
hourly flow for residual disinfectant concentration, pH (if
chlorine is used), and temperature.
Systems with supervisory control and data acquisition
(SCADA) systems will be able to review records, identify the
peak hourly flow, and then obtain the residual disinfectant
concentration, temperature, and pH (if chlorine is used) that
were recorded during peak hourly flow. Those systems
without SCADA will need to coordinate with the State to
develop a procedure that allows the system to best identify
peak hourly flow to allow data collection. Some suggested
approaches are:
EPA Guidance Manual 20
LT1ESWTR Disinfection Profiling and Benchmarking
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3. Data Collection
CT = C x T
C = Residual disinfectant
concentration, mg/L
T = Contact time, minutes
See Chapter 4 for more
information on CT.
Determine when peak hourly flow occurred the day
before data must be collected. Collect the residual
disinfectant concentration, temperature, and pH (if
chlorine is used) on the required day at the time peak
hourly flow occurred on the previous day.
Using the above approach, collect residual disinfectant
concentration, temperature, and pH (if chlorine is used)
at three different times (such as before, during, and
after) near the time peak hourly flow occurred on the
previous day. Then, based on pump records or other
information, determine when peak hourly flow actually
occurred and use the data that were collected nearest to
the time of peak hourly flow.
3.2.2 Residual Disinfectant Concentration
The residual disinfectant concentration is monitored for each
disinfection segment during peak hourly flow and is measured
in milligrams per liter (mg/L). At least one monitoring point
must be associated with each disinfectant injection point.
However, systems may choose to sample for residual
disinfectant concentration at more than one location for each
unique injection point. The residual disinfectant concentration
must be measured using methods listed in Standard Methods
for the Examination of Water and Wastewater, 18th (1992), 19th
(1995), or 20th (1998) editions. For those systems using ozone,
Method 4500-03 B, contained in Standard Methods for the
Examination of Water and Wastewater, 18th (1992) or 19th
(1995) editions must be used. If approved by the State,
residual disinfectant concentrations for free chlorine and
combined chlorine may be measured using DPD colorimetric
test kits.
CT is a measure of the strength of the disinfectant for the time
that the water and disinfectant are in contact. CT is determined
by multiplying the residual disinfectant concentration (C) by
contact time (T). Monitoring the residual disinfectant at more
than one location results in higher CT values since the residual
disinfectant concentration decreases with each subsequent
treatment process. For more information on CT refer to
Chapters 4 and 5.
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3. Data Collection
If monitoring in °F, use
the following formula to
convert from °F to °C:
°C = 5 x (°F - 32)
9
Example: Collecting data
for a single disinfection
segment.
3.2.3 Temperature
The temperature is measured at each monitoring point and at
the same time as the residual disinfectant concentration (during
peak hourly flow). The temperature should be measured in
degrees Celsius (°C) because the CT Tables in Appendix B are
based on temperature as measured in °C (See Chapter 5 for an
explanation of CT tables). Temperature is important since the
effectiveness of all disinfectants is temperature sensitive.
Temperature must be measured using Method 2550 in
Standard Methods for the Examination of Water and
Wastewater,
18th (1992), 19th (1995), or 20th (1998) editions.
3.2.4 pH
If a system uses chlorine as a disinfectant, pH must be
monitored because chlorine is pH-sensitive and is more
effective at lower pH values. The pH is sampled at each
sampling point and at the same time as the residual disinfectant
concentration (during peak hourly flow). The CT tables in
Appendix B for chlorine are based on pH. Systems must
measure pH using EPA Method 150.1 or 150.2, ASTM method
D1293-95, or Method 4500-H+ in Standard Methods for the
Examination of Water and Wastewater, 18th (1992), 19th
(1995), or 20th (1998) editions.
Example 3-1: Collecting Data for a Disinfection
Profile
Collect the data necessary for developing a disinfection profile
for the system shown below.
One Disinfection Segment:
One injection point, one monitoring point L T J
Distribution
System
EPA Guidance Manual 22
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3. Data Collection
Some systems may
operate the plant at a low
pH (for instance, a pH of
6) to achieve enhanced
coagulation or more
microbial inactivation (if
chlorine is used).
However, systems should
consider increasing the pH
prior to sending the
finished water to the
distribution system to
avoid corrosion issues.
Example 3-1 continued
Step 1. Determine the peak hourly flow.
From the clearwell pump records the peak hourly flow
is determined to be 347 gallons per minute (gpm).
Step 2. Measure the chlorine residual, temperature, andpH
(since chlorine is used) during peak hourly flow at the same
monitoring point and at the same time.
During peak hourly flow the following measurements
are recorded at the same monitoring point at the same
time:
Chlorine residual = 0.8 mg/L
pH = 6
Temperature = 0.5 °C
Worksheet #1 in Appendix C can be used to record water
quality data for the disinfection profile. The worksheet excerpt
on this page demonstrates how to record the data from this
example using Worksheet #1 in Appendix C.
WORKSHEETS
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA1234567
System/Water Source: XYZ Water Plant
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
Viruses
Prepared by: Joe Operator
Disinfection Segment/Sequence of Application: Clearwell/1st
Week
#
1
2
3
4
5
6
3
Residual
D is inf.
Cone.
C (mg/L)
0.8
4
PH
6
5
Water
Temp.
(°C)
0.5
6
Peak
Hourly
Flow
(gpm)
347
7
Volume
(gai)
8
TDT
(min.)
9
Baffling
Factor
10
Disinf.
Contact
Time
T (min.)
11
CTCaic =
(CxT)
(min-mg/L)
12
CT
Req'd
(min-mg/L)
13
Inactivation
Ratio
(Col 11 /Col 12)
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
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3. Data Collection
Example: Collecting data
for multiple disinfection
segments.
Example 3-2: Collecting Data for Multiple
Disinfection Segments
Collect the data necessary for developing a disinfection profile
for the system shown below.
Disinfection Disinfection
Segment 1 Segment 2
Chlorine
Injected
V
' i I c^ac^a
ntake > -*> ^f3 ^f3 -f-*
olo
. Coagulation
) I l
Disinfection Segment 2
Monitoring Point
CI2 residual = 0.7 mg/L
Temperature = 5 °C
pH = 7.5
Disinfection
Segment 3
Filtration
^ [
Disinfection Segment 3
Monitoring Point
CI2 residua = 0.3 mg/L
Temperature = 5 °C
pH = 7.5
1 1
Disinfection
Segment 4
Chlorine
Injected
I
=" |
I
Disinfection Segment 1 Disinfection Segment 4
Monitoring Point Monitoring Point
CI2 residual = 1.0 mg/L CI2 residual = 0.8 mg/L
Temperature = 5 °C Temperature = 5 °C
pH = 7.5 pH = 7.5
:iearwell
Distrbutior
System
Step 1. Determine the peak hourly flow for Disinfection
Segments 1 through 4.
From the raw water pump records the peak hourly flow is
determined to be 347 gpm for Disinfection Segments 1, 2,
and 3.
From the clearwell pump records the peak hourly flow is
determined to be 370 gpm for Disinfection Segment 4.
Step 2. Measure the chlorine residual, temperature, andpH
(since chlorine is used) during peak hourly flow at the same
monitoring point and at the same time.
During peak hourly flow the following measurements are
recorded at the same monitoring point at the same time:
Disinfection
Segment
1
2
3
4
Chlorine
Residual (mg/L)
1.0
0.7
0.3
0.8
Temperature
(°C)
5
5
5
5
PH
7.5
7.5
7.5
7.5
EPA Guidance Manual 24
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3. Data Collection
Example 3-2 continued
Again, Worksheet #1 in Appendix C can be used for data
collection, as shown in Example 3-1. A new copy of
Worksheet #1 should be used for each disinfection segment for
systems with multiple segments. Example D-2 in Appendix D
illustrates how to complete Worksheet #1 for multiple
disinfection segments.
3.3 DATA COLLECTION WORKSHEETS
The worksheets in Appendix C are helpful for recording
collected data. Systems should verify that their State will
accept the worksheets for recordkeeping and reporting
purposes.
3.4 STEPS COMPLETED
r
Calculate
the
and
the
Disinfection
CT
Collect Data
Identify
Disinfection
Segments
3.5 NEXTSTEP
Now that data have been collected for each disinfection
segment, the CT value can be calculated. Chapter 4 explains
how to calculate CT.
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3. Data Collection
3.6 REFERENCES
APHA, AWWA, WEF. 1998. Standard Methods for the Examination of Water and
Wastewater, 20th Edition. APHA, Washington, D.C.
APHA, AWWA, WEF. 1995. Standard Methods for the Examination of Water and
Wastewater, 19th Edition. APHA, Washington, D.C.
APHA, AWWA, WEF. 1992. Standard Methods for the Examination of Water and
Wastewater, 18th Edition. APHA, Washington, D.C.
EPA Guidance Manual 26 May 2003
LT1ESWTR Disinfection Profiling and Benchmarking
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4. CALCULATING CT
In this Chapter:
• CT
• Determining "C"
• Determining "T"
• CTcaic
• Steps Completed
• Next Step
• References
40 CFR Section 141.532
CTcaic - The CT that is
calculated for a given
disinfection segment.
Equation 4-1
CTca,c = C x T
4.1 INTRODUCTION
If a system is required to complete a disinfection profile, it must
calculate the CT value for each disinfection segment, known as
CTcaic. System operational data and other data must be
collected to determine CTcaic weekly for one year. Systems will
collect data once a week, on the same day of the week, for
twelve consecutive months (one year). For systems serving 500
to 9,999 people, data collection must begin no later than July 1,
2003. For systems serving fewer than 500 people, data
collection must begin no later than January 1, 2004 (40 CFR
Section 141.532). See Chapter 3 for more information on data
collection. The CTcaic value derived for each disinfection
segment will be used to calculate the inactivation ratio for each
disinfection segment on a weekly basis.
4.2 WHAT is CT?
CT simply stands for concentration (C) and contact time (T)
It is the result of multiplying the disinfectant residual
concentration by the contact time. CT is a measure of
disinfection effectiveness for the time that the water and
disinfectant are in contact. "C" is the disinfectant residual
concentration measured in mg/L at peak hourly flow and "T" is
the time that the disinfectant is in contact with the water at peak
hourly flow. The contact time (T) is measured from the point of
disinfectant injection to a point where the residual is measured
before the first customer (or the next disinfection application
point) and is measured in minutes.
Equation 4-1
c (minutes-mg/L) = C x T
C = Residual disinfectant concentration measured during
peak hourly flow in mg/L.
T = Time, measured in minutes, that the water is in
contact with the disinfectant.
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LT1ESWTR Disinfection Profiling and Benchmarking
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4. Calculating CT
Contact Time = T
(Sometimes referred to as
Tio)
4.3 DETERMINING "C"
"C" is the residual disinfectant concentration measured during
peak hourly flow in mg/L. The residual disinfectant
concentration must be measured for each disinfection segment.
In addition, the residual disinfectant concentration must be
measured once per week on the same day of the week during
peak hourly flow. See Chapter 3 for information on the residual
disinfectant concentration.
4.4 DETERMINING "T"
The disinfectant contact time (T), also referred to as TIO in the
Guidance Manual for Compliance with the Filtration and
Disinfection Requirements for Public Water Systems Using
Surface Water (EPA, 1991), is an estimate of the detention time
within a basin or treatment unit at which 90 percent of the water
passing through the unit is retained within the basin or treatment
unit. T can be determined through a tracer study or estimated
based on the theoretical detention time and baffling factor.
Before measuring or calculating T, a system may want to check its
permits or other documentation that the State may have to see if a
tracer study has been conduced for its facility. T can be
determined based on the results of a tracer study. See Appendix E
for more information on tracer studies.
The peak hourly flow rate is used to calculate the contact time
within the treatment plant. Using the peak hourly flow rate for
analysis provides a conservative value for the contact time.
The following steps may be used to calculate T for a treatment
system:
• Define the disinfection segments in the system.
• Determine the peak hourly flow in the disinfection
segment.
T must be calculated
based on peak hourly
flow.
EPA Guidance Manual 28
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4. Calculating CT
• Calculate the volume of each basin, pipe, or unit
process in each disinfection segment (See Section
4.4.1).
• Calculate the theoretical detention time for each basin,
pipe, or unit process (See Section 4.4.2).
• Determine the baffling factor (BF) of each basin, pipe,
or unit process (See Section 4.4.3).
• Determine T for each basin, pipe, or unit process based
on the theoretical detention time and baffling factor
(See Section 4.4.4).
• Sum the Ts of each basin, pipe, or unit process for a
total contact time for the disinfection segment.
Defining disinfection segments and measuring peak hourly
flow have already been discussed in Chapters 2 and 3. The
following sections discuss the remaining topics.
4.4.1 Volume
The volume of each basin, pipe, or unit process is used to
calculate T. Since some treatment units, such as clearwells,
can have fluctuating levels that affect volume, systems should
consult the State on what volume should be used for the
disinfection profile. Systems and States may want to consider
the following options:
• Volumes can be based on the minimum volume that can
occur in the treatment unit. This approach is the most
conservative.
• Volumes can be based on the actual volume realized in
the treatment unit during peak hourly flow if adequate
information is available to identify the actual volume.
• Volumes can be based on the lowest volume realized in
the treatment unit for that day.
Table 4-1 provides the equations used to find the volume of the
specific sub-units or segments. See Appendix F for detailed
examples of sub-units and volume equations.
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29 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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4. Calculating CT
Volume Equations
See Appendix F for more
information on volume
calculations.
1 cubic foot = 7.48
gallons
Equation 4-2
TDT = V/Q
Table 4-1: Volume Equations for Shapes
SHAPE
Cylindrical
Pipes
Rectangular
Basins
Cylindrical
Basins
Rectangular
Filters
EXAMPLE OF UNIT
WITH THIS SHAPE
Raw Water Pipe
Plant Piping
Finished Water Pipe
Rapid Mix,
Flocculation, and
Sedimentation
Basins, Clean/veils
Rapid Mix,
Flocculation, and
Sedimentation
Basins, Clean/veils
Filtration
VOLUME EQUATION
Length x Cross-
sectional Area
Length x Width x
Minimum Water Depth
Minimum Water Depth
x Cross-sectional Area
Surface Area of Filter x
Depth of Water Above
Filter Surface (Volume
of water in the media
pores may also be
used.)
4.4.2 Theoretical Detention Time
The theoretical detention time (TDT) is the time that the water
is in a basin, pipe, or unit process assuming perfect plug flow.
Perfect plug flow assumes no short-circuiting within the basin,
pipe, or unit process. The TDT is calculated by dividing the
volume based on low water level by the peak hourly flow
(Equation 4-2).
Equation 4-2
TDT = V / Q
TDT = Theoretical Detention Time, in minutes
V = Volume based on low water level, in gallons
Q = Peak hourly flow, in gpm
EPA Guidance Manual 30
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
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4. Calculating CT
Plug Flow - The water
travels through a basin,
pipe, or unit process in
such a fashion that the
entire mass or volume is
discharged at exactly the
TDT of the unit and no
short-circuiting occurs.
Short-circuiting - A
hydraulic condition in a
basin or unit process in
which the actual flow time
of water through the basin
is less than the basin or
unit process volume
divided by the peak hourly
flow.
4.4.3 Baffling Factor
The T in each basin, pipe, or unit process is a function of
configuration and baffling. The flow through a pipe is very
different than the flow through an unbaffled basin (See Figure
4-1). The longest path a particle can take through a pipeline is
not that different from the shortest path. In the case of an
unbaffled basin, one particle may flow through directly from
the inlet to the outlet. This short-circuiting particle will be in
contact with the disinfectant for a relatively short time.
Baffling Factor= 1.0
/ :'" •
> »i • i •
^* * #»
'••«.» '
-
Baffling Factor = 0.1
Top: This pipe demonstrates a plug flow condition in which all of
the material sent through the pipe discharges at the theoretical
hydraulic detention time of the pipe.
Bottom: This unbaffled basin demonstrates short-circuiting in
which some of the material entering the basin would come out
almost immediately, while other material that enters at the same
time will be detained for a longer period of time. Short-circuiting
occurs in basins with poor baffling.
Figure 4-1: Baffling Characteristics of a Pipe and
Clean/veil
May 2003
31 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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4. Calculating CT
See Appendix G for more
information on baffling
factors.
Table 4-2
Baffling Factors
Equation 4-3
T = TDT x BF
Baffling factors (BF) have been developed that allow the
contact time of a basin, pipe, or unit process to be estimated,
based on the volume of and flow rate through a basin, pipe, or
unit process. Baffling factors were developed based on
numerous tracer studies of basins with different sizes and
configurations. Table 4-2 and Appendix G provide a summary
of theoretical baffling factors for various baffling conditions
and basins.
Table 4-2: Baffling Factors
Baffling
Condition
Unbaffled
(mixed
flow)
Poor
Average
Superior
Perfect
(plug flow)
Baffling
Factor
0.1
0.3
0.5
0.7
1.0
Baffling Description
None, agitated basin, very low
length to width ratio, high inlet
and outlet flow velocities.
Single or multiple unbaffled
inlets and outlets, no intra-basin
baffles.
Baffled inlet or outlet with some
intra-basin baffles.
Perforated inlet baffle,
serpentine or perforated intra-
basin baffles, outlet weir or
perforated launders.
Very high length to width ratio
(pipeline flow), perforated inlet,
outlet, and intra-basin baffles.
4.4.4 Calculate Contact Time
T can be calculated once the TDT and baffling factor are
known (Equation 4-3).
Equation 4-3
T = TDT x BF
T = Time, measured in minutes, that the water is in
contact with the disinfectant.
TDT = Theoretical detention time, in minutes
BF = Baffling factor
EPA Guidance Manual 32
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
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4. Calculating CT
Example 4-1: Determining "T"
Determine T for the conventional filtration system discussed in Example 3-1.
Diameter = 40ft
Depth = 30 ft
Chlorine
Injected
Minimum Operating Level
Side View
Residual Monitoring
Point
To
> Distribution
Peak Hourly System
Flow = 347 gpm
To
->• Distribution
Peak Hourly System
Flow = 347 gpm
Top View
Step 1. Measure the physical dimensions of the clearwell.
Measure the inner tank diameter to obtain the volume of water in the clearwell rather
than the volume of the tank itself.
Diameter = 40 ft
Measure the minimum operating depth in the clearwell to obtain a conservative
estimate of the volume of water in the tank.
Minimum Water Depth = 30 ft
May 2003
33 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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4. Calculating CT
Example 4-1 continued
Step 2. Calculate the volume of the clearwell based on low water level.
From Table 4-1 the equation for calculating the volume of a cylindrical basin is:
Volume (V) = minimum water depth x cross-sectional area (rcr2)
where
TT =3.14
radius (r) = diameter / 2 = 40 ft / 2 =20 ft
V = 30 ft x 3.14 x (20 ft)2 = 37,680 ft3
V = 37,680 ft3 x (7.48 gal / ft3)
V = 282,000 gallons
The volume of the clearwell = 282,000 gallons
Note: More information on volume equations and calculations can be found in Appendix F.
Step 3. Calculate the theoretical detention time.
TDT = V / Q (Note: Q = peak hourly flow) (Eq. 4-2)
TDT = 282,000 gal / 347 gpm
TDT = 813 minutes
The TDT in the clearwell is 813 minutes
Step 4. Determine the baffling factor for the clearwell.
From the diagram shown above there is no baffling in the clearwell. From Table 4-2,
the baffling factor (BF) for an unbaffled basin is 0.1.
The baffling factor for the clearwell = 0.1
Step 5. Calculate the contact time of the disinfectant in the clearwell.
Contact Time = TDT x BF (Eq. 4-3)
T=813 minx 0.1
T= 81.3 minutes
The contact time in the clearwell = 81.3 minutes
Worksheet #1 in Appendix C can be used to record data and calculate contact time. The
worksheet excerpt on the next page demonstrates how data may be recorded from this
example and previous examples using Worksheet #1 in Appendix C.
EPA Guidance Manual 34 May 2003
LT1ESWTR Disinfection Profiling and Benchmarking
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4. Calculating CT
Example 4-1 continued
WORKSHEETS
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA1234567
System/Water Source: XYZ Water Plant
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
Viruses
Prepared by: Joe Operator
Disinfection Segment/Sequence of Application: Clearwell/1st
Week
#
1
2
3
4
5
6
3
Residual
D is inf.
Cone.
C (mg/L)
0.8
4
PH
6
5
Water
Temp.
(°C)
0.5
6
Peak
Hourly
Flow
(gpm)
347
7
Volume
(gai)
282,000
8
TDT
(min.)
813
9
Baffling
Factor
0.1
10
Disinf.
Contact
Time
T (min.)
81.3
11
CTCaic =
(CxT)
(min-mg/L)
12
CT
Req'd
(min-mg/L)
13
Inactivation
Ratio
(Col 11 /Col 12)
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
4.5 Calculate CTcaic
To calculate CTcaic, a system must monitor the residual
disinfectant concentration and the amount of time that the
water is in contact with the disinfectant. A system that is
required to complete a disinfection profile must determine
CTca]c values once per week, on the same day of the week, for
one year.
The disinfection effectiveness for the time that the water and
disinfectant are in contact is calculated as follows:
Equation 4-1
CTcaic = C X T
Equation 4-1
ic (minutes-mg/L) = C x T
C = Residual disinfectant concentration measured during
peak hourly flow in mg/L.
T = Time, measured in minutes, that the water is in
contact with the disinfectant.
May 2003
35 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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4. Calculating CT
Example 4-2 demonstrates how to determine CTca]c for one
disinfection segment. If more than one disinfectant is used or
if residual disinfectants are measured in more than one
location, then CTcak: must be calculated for each disinfection
segment. See the examples in Appendix D for more
illustrations of calculating CTcaic under different operating
conditions.
Example 4-2: Calculate CTcalc
Calculate CTcaic for the conventional filtration system in the previous examples.
One Disinfection Segment:
One injection point, one monitoring point
Step 1. Determine "C".
From example 3-1, C = 0.8 mg/L
Step 2. Determine "T".
From example 4-1, T = 81.3 minutes
Step 3. Calculate CTcaic.
CT = C x T
CT = 0.8 mg/L x 81.3 minutes
CT = 65.0min-mg/L
ic = 65.0 min-mg/L
Chlorine
Injected
Filtration
Monitoring Point
CI2 residual = 0.8 mg/L
Distribution
System
EPA Guidance Manual 36
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
4. Calculating CT
Worksheet #1 in Appendix C can be used to record data and calculate CTcaic. The worksheet
excerpt below demonstrates how to record the data from this example and previous
examples using Worksheet #1 in Appendix C.
WORKSHEETS
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA1234567
System/Water Source: XYZ Water Plant
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
Prepared by: Joe Operator
Viruses
Disinfection Segment/Sequence of Application: Clearwell/1st
Week
#
1
2
3
4
5
6
3
Residual
D is inf.
Cone.
C (mg/L)
0.8
4
PH
6
5
Water
Temp.
(°C)
0.5
6
Peak
Hourly
Flow
(gpm)
347
7
Volume
(gai)
282,000
8
TDT
(min.)
813
9
Baffling
Factor
0.1
10
Disinf.
Contact
Time
T (min.)
81.3
11
CTCaic =
(CxT)
(min-mg/L)
65.0
12
CT
Req'd
(min-mg/L)
13
Inactivation
Ratio
(Col 11 /Col 12)
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
May 2003
37 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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4. Calculating CT
4.6 STEPS COMPLETED
Calculate
Inactivation
the
Disinfection
and
Benchmark
the
and
Calculate CT
Collect Data
Identify
Disinfection
Segments
4.7 NEXT STEP
In addition to CTcaic, CT required must also be determined to
calculate log inactivation. Chapter 5 describes how to
determine CT required and calculate log inactivation.
4.8 REFERENCES
EPA. 1991. Guidance Manual for Compliance with the Filtration and Disinfection
Requirements for Public Water Systems Using Surface Water. Washington, D.C.
EPA Guidance Manual 38
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
5. CALCULATING INACTIVATION
In this Chapter:
• Log Reduction
• Determining CT
Required
• Calculating Actual
Log Inactivation for
One Disinfection
Segment
• Calculating Actual
Log Inactivation for
Multiple Disinfection
Segments
• Steps Completed
• Next Step
1-log reduction = 90%
2-log reduction = 99%
3-log reduction = 99.9%
4-log reduction = 99.99%
A spreadsheet (in
Microsoft® Excel) has
been developed that can
be used by systems to
calculate log inactivations.
The spreadsheet is
available on EPA's
website at
http://www.epa.gov/safe-
water/mdbp/ltleswtr.html.
5.1 INTRODUCTION
In order to develop a disinfection profile, the Giardia log
inactivation must be calculated. The log inactivation of viruses
must also be calculated if the system uses ozone, chloramines,
or chlorine dioxide for primary disinfection. Ozone,
chloramines, and chlorine dioxide are not as effective for
inactivating viruses as for inactivating Giardia, and systems
must make sure the appropriate virus inactivation is achieved.
To determine log inactivation achieved through disinfection, a
series of calculations are completed. First, CTca]c is determined
(See Chapter 4). Then CTcaic is related to the required CT using
CT tables (See Section 5.3). The CT required for a desired log
inactivation is dependent upon pH (if chlorine is used),
temperature, and residual disinfectant concentration (for
chlorine). Individual CT tables are used for each type of
disinfectant because the effectiveness of different disinfectants
varies with each type of microorganism. For this reason,
separate CT tables have been developed for chlorine, chlorine
dioxide, ozone, and chloramines for both Giardia and viruses
(See Appendix B).
5.2 LOG REDUCTION
The concept of log reduction (removal and inactivation) is used
extensively in discussions of compliance with microbiological
requirements. The term refers to logarithmic theory.
Essentially, in this context, log reduction relates to the
percentage of microorganisms physically removed or
inactivated by a given process. One log reduction means that
90% of the microorganisms are removed or inactivated. Two
log corresponds to 99%, three log corresponds to 99.9% and
four log corresponds to 99.99%. The removal or inactivation
"log number" coincides with the number of nines in the
percentage reduction. This chapter will discuss log inactivation
achieved through disinfection only; however, it should be
remembered that when determining the total system reduction,
the physical log removal is added to the log inactivation
through disinfection for total reduction of microorganisms (See
Chapter 7).
May 2003
39 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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5. Calculating Inactivation
CT99 9 for Giardia :
3-log inactivation
CT99 99 for viruses
4-log inactivation
If the temperature, pH, or
residual disinfectant
concentration falls
between or outside the
values listed in the
columns or rows on the
table, systems should
contact the State for the
appropriate method to
determine CT required.
Appendix H presents two
different interpolation
methods.
5.3 DETERMINING CT REQUIRED
After determining CTcaic (See Chapter 4) based on system
operating parameters and configuration, CT tables are used to
determine the required CT value for a certain level of
inactivation. The CT tables in Appendix B give CT values that
achieve a 3-log inactivation of Giardia and viruses, as a
function of disinfectant type, temperature, pH and residual
disinfectant concentration. The following guidelines can be
used to obtain the required CT value from the CT tables:
• Find the appropriate table based on the disinfectant
used.
• Find the appropriate table based on the microorganism
of concern (Giardia or viruses).
• Find the appropriate portion of the table (for chlorine)
or column based on measured temperature.
• Find the appropriate column (for chlorine) based on the
measured pH. Systems should contact the State if the
pH value is not included in the CT tables in Appendix
B.
• Find the appropriate row based on the measured
disinfectant residual (for chlorine only).
• Identify the CT value based on the above information.
The CT tables in Appendix B for chlorine are based on pH.
The CT tables in Appendix B for Giardia inactivation by
chloramines and virus inactivation by chlorine dioxide also list
a range for pH. Although systems are not required to monitor
the pH for chloramines and chlorine dioxide, systems should
ensure that the pH falls between the range of 6-9 when this pH
range is specified in the CT tables.
The following sections discuss how to obtain 3-log CT required
for Giardia inactivation (CT99.9) and 4-log CT required for
virus inactivation (CT99.99).
EPA Guidance Manual 40
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
5. Calculating Inactivation
The CT table for
inactivation of Giardia by
chloramines (Table B-7)
lists values between the
pH range 6 to 9.
5.3.1 CT99 9 for Giardia
All surface water systems or GWUDI systems are required to
achieve 3-log (99.9%) reduction of Giardia through removal
(filtration) and/or inactivation (disinfection) (See 40 CFR
141.70(a)(l)). States generally grant log removal credits for
filtration which typically vary depending on the treatment
process (such as conventional, direct, or alternative filtration).
For unfiltered systems, all three logs must be achieved through
disinfection. For filtered systems, refer to Table 7-2 for typical
log removal credits and resulting inactivation values that must
be achieved by disinfection. Inactivation through disinfection
can be achieved by one disinfectant or a combination of
disinfectants. The method used to calculate log inactivation
under the LT1ESWTR requires that the CT99.9 value for
Giardia be determined. Example 5-1 illustrates how to obtain
CT.99.9.
Example 5-1: Determining CT999
The conventional filtration system discussed in Examples 3-1, 4-1, and 4-2 uses chlorine
disinfectant only; therefore the system only needs to calculate CT99.9 for Giardia because
chlorine is significantly more effective against viruses than Giardia. Find the required CT
to achieve 3-log inactivation of Giardia, or CT99.9.
One Disinfection Segment:
One injection point, one monitoring point
Chlorine
Injected
Filtration
Monitoring Point
CI2 residual = 0.8 mg/L
Temperature = 0.5 °C
pH = 6
Distribution
System
May 2003
41 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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5. Calculating Inactivation
Example 5-1 continued
Step 1. Gather required data during peak hourly flow.
Water temperature = 0.5 °C
Chlorine residual = 0.8 mg/L
pH = 6.0
Step 2. Locate appropriate CT table.
The table for 3-log inactivation ofGiardia by free chlorine is Table B-l in Appendix B.
Step 3. Identify the appropriate portion of the table based on operating conditions and
3-log Giardia inactivation.
The first section of the table is for temperatures less than or equal to 0.5 °C. The first
column in that section is for pHs less than or equal to 6.0. The disinfectant residual of 0.8
mg/L is found in the third row down on the chart. The relevant portion of Table B-l is
reprinted below.
Excerpt from Table B-l:
CT values for 3-Log Inactivation ofGiardia Cysts by Free Chlorine (0.5 °C portion of table
for 0.4 to 1.2 mg/L)
Chlorine
Concentration
(mg/L)
<=0.4
0.6
0.8
1.0
1.2
Temperature <=
<=6.0
137
141
145
148
152
6.5
163
169
172
176
180
7.0
195
200
205
210
215
pH
7.5
237
239
246
253
259
0.5
8.0
277
286
295
304
313
°C
8.5
329
342
354
365
376
9.0
390
407
422
437
451
Step 4. Obtain CT99.9 value.
From this chart, the value of CT for 3-log inactivation at 0.8 mg/L and pH of 6 is 145 min-
mg/L.
CT99.9 for Giardia = 145 min-mg/L
Worksheet #1 in Appendix C can be used to record data needed to determine CT99 9 and to
record the value of CT99.9. The worksheet excerpt on the next page demonstrates how to
record the data from this example and previous examples using Worksheet #1 in
Appendix C.
EPA Guidance Manual 42
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
5. Calculating Inactivation
Example 5-1 continued
WORKSHEETS
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA1234567
System/Water Source: XYZ Water Plant
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
Viruses
Prepared by: Joe Operator
Disinfection Segment/Sequence of Application: Clearwell/1st
Week
#
1
2
3
4
5
6
3
Residual
D is inf.
Cone.
C (mg/L)
0.8
4
PH
6
5
Water
Temp.
(°C)
0.5
6
Peak
Hourly
Flow
(gpm)
347
7
Volume
(gai)
282,000
8
TDT
(min.)
813
9
Baffling
Factor
0.1
10
Disinf.
Contact
Time
T (min.)
81.3
11
CTCaic =
(CxT)
(min-mg/L)
65.0
12
CT
Req'd
(min-mg/L)
145
13
Inactivation
Ratio
(Col 11 /Col 12)
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
The CT table for
inactivation of viruses by
chlorine dioxide (Table B-
4) lists values between the
pH range 6 to 9.
5.3.2 CTgg.gg for Viruses
All surface water systems or GWUDI systems are required to
achieve 4-1 og (99.99%) reduction of viruses through removal
(filtration) and/or inactivation (disinfection) (See 40 CFR
141.70(a)(2)). States generally grant log removal credits for
filtration which typically vary depending on the treatment
process (such as conventional, direct, or alternative filtration).
For unfiltered systems, all four logs must be achieved through
disinfection. One method used to calculate log inactivation
uses the CT99.99 value for viruses. Virus inactivation must be
determined if chloramines, chlorine dioxide, or ozone are used
for primary disinfection (See 40 CFR 141.535). Example D-3
in Appendix D illustrates a method for obtaining CT99.99 for a
system using ozone.
5.4 CALCULATING ACTUAL LOG
INACTIVATION FOR ONE DISINFECTION
SEGMENT
Actual log inactivation can be calculated as a ratio of the CTcaic
value achieved by the system to the CT value required for 3-log
inactivation of Giardia or 4-log inactivation of viruses.
40 CFR Section 141.534
May 2003
43 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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5. Calculating Inactivation
Equation 5-1
The following equation must be used to calculate Giardict log
inactivation for one disinfection segment:
Equation 5-1
Actual Log Inactivation of Giardia = 3 x (CTcaic / CT99.9)
Example 5-2 shows how a system may calculate the Giardia
log inactivation achieved in a system with one disinfection
segment.
Example 5-2: Determine Actual Log Inactivation for Giardia
The conventional filtration system discussed in Examples 3-1, 4-1, 4-2 and 5-1 uses chlorine
disinfectant only; therefore the system only needs to calculate actual Giardia log
inactivation because chlorine is significantly more effective against viruses than Giardia.
Determine the actual Giardia log inactivation achieved by the system.
Step 1. Determine CTcaic and CTgg.g for the disinfection segment.
The following table summarizes the values determined for CTcaic and CT99.9:
Disinfection Segment
1 -Chlorine
^ A calc
min-mg/L
65.0
CT99.9 for Giardia
min-mg/L
145
Step 2. Calculate the inactivation ratio for the clearwell.
Inactivation Ratio = CTcaic / CT99.9
Inactivation Ratio = 65.0/145
Inactivation Ratio = 0.448
Step 3. Calculate Giardia log inactivation for the clearwell.
Giardia log inactivation = 3 x (CTcaic / CT99.9)
Giardia log inactivation = 3 x 0.448
Giardia log inactivation = 1.34
Refer to Chapter 7 for more information on interpreting log inactivation values.
EPA Guidance Manual 44
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
5. Calculating Inactivation
Example 5-2 continued
Worksheet #1 in Appendix C can be used to record data and calculate log inactivation. The
worksheet excerpt below demonstrates how data may be recorded from this example and
previous examples using Worksheet #1 in Appendix C.
WORKSHEETS
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA1234567
System/Water Source: XYZ Water Plant
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
Viruses
Prepared by: Joe Operator
Disinfection Segment/Sequence of Application: Clearwell/1st
Week
#
1
2
3
4
5
6
3
Residual
D is inf.
Cone.
C (mg/L)
0.8
4
PH
6
5
Water
Temp.
(°C)
0.5
6
Peak
Hourly
Flow
(gpm)
347
7
Volume
(gai)
282,000
8
TDT
(min.)
813
9
Baffling
Factor
0.1
10
Disinf.
Contact
Time
T (min.)
81.3
11
CTCaic =
(CxT)
(min-mg/L)
65.0
12
CT
Req'd
(min-mg/L)
145
13
Inactivation
Ratio
(Col 11 /Col 12)
0.448
14
Log
Inactivation*
1.34
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
Systems should check with their State to determine the
appropriate method for calculating virus inactivation. The
following equation was used for the examples presented in this
document:
Equation 5-2
Check with the State on
the approved method to
calculate virus
inactivation.
Equation 5-2
Actual Log Inactivation of Viruses = 4 x (CTcaic / CT9999)
Additional examples of calculating the actual log inactivation
of Giardia and viruses are contained in Appendix D. A
spreadsheet has also been developed that can be used by
systems to calculate log inactivations. The spreadsheet is
available on EPA's website
fwww.epa.gov/safewater/mdbp/ltleswtr.html).
May 2003
45 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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5. Calculating Inactivation
Equation 5-3
£ = Sum of.
Systems must sum the
CTcaic / CT99 9 inactivation
ratios for each
disinfection segment if the
system has multiple
disinfection segments.
5.5 CALCULATING ACTUAL LOG
INACTIVATION FOR MULTIPLE
DISINFECTION SEGMENTS
Actual log inactivation for a system with more than one
disinfection segment is calculated as a sum of the ratios of the
CTcaic value achieved by each disinfection segment to the CT
value required for 3-log inactivation of Giardia or 4-log
inactivation of viruses in each disinfection segment.
The following equation must be used to calculate Giardia log
inactivation for a system with multiple disinfection segments:
Equation 5-3
Actual Log Inactivation of Giardia = 3 x £ (CTcaic / CT99.9)
Example 5-3 shows how a system may use the worksheets in
Appendix C to calculate the Giardia log inactivation achieved
in a system with multiple disinfection segments.
Example 5-3: Determine Total Log Inactivation for Giardia
The conventional filtration system discussed in Example D-2 in Appendix D uses chlorine
as a pre-disinfectant and a primary disinfectant and uses chloramines as a secondary
disinfectant. Determine the total Giardia log inactivation achieved by the system.
The worksheets in Appendix C can be used to record data and calculate log inactivation.
The following table summarizes the calculations for each unit process in Disinfection
Segment 1 in Example D-2.
Unit Process
Coagulation
Flocculation
Sedimentation
Filtration
Total:
Volume (qal)
24,000
80,000
100,000
45,000
249,000
Peak Hourly
Flow (qpm)
5,000
5,000
5,000
5,000
TDT
(min)
4.8
16
20
9
BF*
0.1
0.1
0.5
0.7
Contact Time (min)
0.48
1.6
10
6.3
18.4
* See Appendix G for baffling factors.
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5. Calculating Inactivation
Example 5-3 continued
The worksheet excerpt below demonstrates how a system may record the data from
Disinfection Segment 1 in Example D-2 using Worksheet #1 in Appendix C. For this
example, Worksheet #1 should be copied so the data from each disinfection segment can be
entered.
WORKSHEETS
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA7654321
System/Water Source: ABC Water Plant
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
Prepared by: Jon Operator
Viruses
Disinfection Segment/Sequence of Application: Coagulation, Flocculation, Sedimentation, Filtration/1 st
Week
#
1
2
3
4
5
6
3
Residual
Disinf.
Cone.
C (mg/L)
1.0
4
PH
7.5
5
Water
Temp.
(°C)
10
6
Peak
Hourly
Flow
(gpm)
5,000
7
Volume
(gai)
249,000
8
TDT
(min.)
**
9
Baffling
Factor
**
10
Disinf.
Contact
Time
T (min.)
18.4
11
CTCaic =
(CxT)
(min-mg/L)
18.4
12
CT
Req'd
(min-mg/L)
134
13
Inactivation
Ratio
(Col 11 /Col 12)
0.137
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
"See the previous table showing details of each unit process for theoretical detention times and baffling factors.
The worksheet excerpt below demonstrates how a system may record the data from
Disinfection Segment 2 in Example D-2 using Worksheet #1 in Appendix C.
WORKSHEETS
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA7654321
System/Water Source: ABC Water Plant
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
Viruses
Prepared by: Jon Operator
Disinfection Segment/Sequence of Application: Clearwell/2nd
Week
#
1
2
3
4
5
6
3
Residual
Disinf.
Cone.
C (mg/L)
1.2
4
PH
7.5
5
Water
Temp.
(°C)
10
6
Peak
Hourly
Flow
(gpm)
5,000
7
Volume
(gai)
300,000
8
TDT
(min.)
60
9
Baffling
Factor
0.7
10
Disinf.
Contact
Time
T (min.)
42
11
CTCaic =
(CxT)
(min-mg/L)
50
12
CT
Req'd
(min-mg/L)
137
13
Inactivation
Ratio
(Col 11 /Col 12)
0.365
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
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5. Calculating Inactivation
Example 5-3 continued
The worksheet excerpt below demonstrates how a system may record the data from
Disinfection Segment 3 in Example D-2 using Worksheet #1 in Appendix C.
WORKSHEET #1
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
Disinfectant Type: Chloramine
Profile Type (check one): X Giardia
PWSID: AA7654321 System/Water Source: ABC Water Plant
Prepared by: Jon Operator
Viruses
Disinfection Segment/Sequence of Application: Transmission Pipe/3rd
Week
#
1
2
3
4
5
6
3
Residual
D is inf.
Cone.
C (mg/L)
0.6
4
PH
N/A
5
Water
Temp.
(°C)
10
6
Peak
Hourly
Flow
(gpm)
5,000
7
Volume
(gai)
31 ,000
8
TDT
(min.)
6.2
9
Baffling
Factor
1.0
10
Disinf.
Contact
Time
T (min.)
6.2
11
CTCalc =
(CxT)
(min-mg/L)
3.7
12
CT
Req'd
(min-mg/L)
1,850
13
Inactivation
Ratio
(Col 11 /Col 12)
0.002
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
The worksheet excerpt below demonstrates how a system may determine total Giardia log
inactivation for the system in Example D-2 using Worksheet #2 in Appendix C.
WORKSHEET #2
TOTAL LOG INACTIVATION DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA7654321
System/Water Source: ABC Water Plant
Disinfectant Type: Chlorine/Chloramine
Profile Type (check one): X Giardia
Prepared by: Jon Operator
Viruses
Week
#
1
2
3
4
5
6
Inactivation Ratio for each disinfection segment from Worksheet #1
Disinfection
Segment
1
0.137
Disinfection
Segment
2
0.365
Disinfection
Segment
3
0.002
Disinfection
Segment
4
Disinfection
Segment
5
Sum
of
Inactivation
Ratios
0.504
Total
Log
Inactivation1
1.51
1 Giardia : Log Inactivation = 3 x Sum of Inactivation Ratios
Viruses: Log Inactivation = 4 x Sum of Inactivation Ratios (or a method approved by the State)
Refer to Chapter 7 for more information on interpreting log inactivation values.
EPA Guidance Manual 48
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5. Calculating Inactivation
Equation 5-4
£ = Sum of.
Systems must sum the
CTcalc / CT99 99 inactivation
ratios for each disinfection
segment if the system has
multiple disinfection
segments.
Check with the State on
the approved method to
calculate virus
inactivation.
Systems should check with their State to determine the
appropriate method to use for calculating virus
inactivation. The following equation was used for the
examples presented in Appendix D of this document:
Equation 5-4
Actual Log Inactivation of Viruses = 4 x £ (CTcaic / 0X99.99)
Example D-3 in Appendix D presents one method for
determining virus log inactivation for a system using ozone.
5.6 STEPS COMPLETED
Calculate CT
Calculate
Inactivation
the
and
the
and
Collect Data
Identify
Disinfection
Segments
5.7 NEXT STEP
Once a system has determined log inactivation values once per
week for a full year, then a disinfection profile and benchmark
(if required) can be developed. Chapter 6 presents information
on how to develop the disinfection profile and calculate a
benchmark.
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5. Calculating Inactivation
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6. DEVELOPING THE DISINFECTION PROFILE
AND BENCHMARK
In this Chapter:
• Constructing a
Disinfection Profile
• The Disinfection
Benchmark
• Significant Changes
to Disinfection
Practices
• Benchmark
Calculations
• Steps Completed
• Next Step
40 CFR Section 141.534
Systems that use chlorine
as a disinfectant must
create a disinfection
profile for Giardia only.
40 CFR Section 141.535
Systems that use
chloramines, chlorine
dioxide, or ozone for
primary disinfection must
create a disinfection
profile for Giardia and
viruses. The method used
to calculate virus
inactivation must be
approved by the State.
6.1 INTRODUCTION
Once the log inactivation has been calculated, a disinfection
profile can be developed. A disinfection profile is a graphical
representation of a system's level of Giardia or virus
inactivation measured during the course of a year (Figure 6-1
provides an example disinfection profile). The disinfection
profile is the log inactivation (of Giardia or viruses) graphed as
a function of time. It can be used as a tool in the decision
making process for a system's disinfection practices.
For systems that use chlorine as a disinfectant, Giardia is the
more difficult organism to treat; therefore it is the limiting
parameter and the only pathogen for which a disinfection
profile is required. Viruses may be the limiting parameter for
systems that use chloramines, chlorine dioxide, or ozone.
Therefore, systems that use these disinfectants for primary
disinfection must create a disinfection profile for both Giardia
and viruses. The method used to calculate viral log
inactivations must be approved by the State.
If a system was required to develop a disinfection profile and
decides to make a significant change to disinfection practices,
then a disinfection benchmark must be calculated. The
disinfection benchmark is the lowest monthly average log
inactivation. The disinfection benchmark will be used by both
the system and the State to evaluate proposed modifications to
disinfection practices.
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6. Developing the Disinfection Profile and Benchmark
40 CFR Section 141.536
Example Disinfection
Profile
6.2 CONSTRUCTING A DISINFECTION
PROFILE
After log inactivation values have been calculated once each
week for one year (using the method presented in Section 5.4),
the system must produce a disinfection profile. A disinfection
profile is a graph of log inactivation data. The log inactivations
may be plotted along the vertical axis of a graph with the
corresponding weeks of the year plotted along the horizontal
axis, as shown in Figure 6-1. Systems are required to retain the
disinfection profile in graphic form and it must be available for
review by the State as part of a sanitary survey. Example 6-1
demonstrates how to create a disinfection profile.
Figure 6-1. Example of a Completed Disinfection
Profile
Disinfection Profile for System X, 2004
1.400 -,
1.200 -
1.000 -
0.800 -
0.600 -
0.400 -
0.200 -
0.000 -
Log Inactivation
0 4 8 12 16 20 24 28 32 36 40 44 48 52
Week Tested
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6. Developing the Disinfection Profile and Benchmark
Example 6-1: Disinfection Profile for Giardia
Create a disinfection profile for Giardia for the conventional filtration system that was
discussed in Examples 3-1, 4-1, 4-2, 5-1, and 5-2..
Step 1. Calculate the Giardia log inactivations once per week on the same day of the
week for one year.
The table below shows the Giardia log inactivations that were calculated each week for one
year using the methods presented in Section 5.4 and Example 5-2. This information can also
be obtained from the first and last columns of Worksheet #1 in Appendix C for systems with
one disinfection segment or Worksheet #2 in Appendix C for systems with multiple
disinfection segments.
Month
JAN
FEB
MARCH
APRIL
MAY
JUNE
Week
1
2
3
4
5
Q
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Log Inact.
1.34
1.35
1.38
1.37
1.38
1.38
1.39
1.40
1.40
1.40
1.41
1.42
1.43
1.46
1.50
1.54
1.57
1.64
1.66
1.70
1.72
1.74
1.77
1.79
1.82
1.81
Month
JULY
AUG
SEP
OCT
NOV
DEC
Week
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
Log Inact.
1.86
1.82
1.76
1.74
1.71
1.70
1.66
1.61
1.60
1.55
1.56
1.52
1.51
1.47
1.48
1.47
1.47
1.45
1.41
1.43
1.41
1.40
1.40
1.40
1.40
1.37
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6. Developing the Disinfection Profile and Benchmark
Example 6-1 continued
Step 2. Plot the disinfection profile.
The log inactivations are plotted along the vertical axis with the corresponding weeks of the
year plotted along the horizontal axis. The log inactivation value for week 1 (1.34) is
plotted on the vertical axis at a point corresponding to week 1 on the horizontal axis, as
shown below. The log inactivation value for week 2 (1.35) is plotted on the horizontal axis
at a point corresponding to week 2 on the horizontal axis. The log inactivation value for
week 3 (1.38) is plotted on the horizontal axis at a point corresponding to week 3 on the
horizontal axis. After the points are plotted, lines are drawn to connect the points in order
by the week tested.
1.30
Week Tested
(Horizontal Axis)
Continue to plot the points for each week until all 52 weeks have been plotted. The
completed disinfection profile is shown below.
2.0
ra 1.5
'o
ro
^ 1.0
O)
| 0.5 H
ro
0.0
1/1/2004
3/25/2004 6/17/2004 9/9/2004
Sample Date
12/2/2004
EPA Guidance Manual 54
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6. Developing the Disinfection Profile and Benchmark
40 CFR Section 141.540
System must consult the
State prior to making
modifications to
disinfection practices.
Once a disinfection profile has been completed for a system,
the system will have all of the data required to calculate a
benchmark (which is necessary if the system contemplates
making a significant change to its disinfection practices). The
next sections discuss what a benchmark is and how it is
calculated.
6.3 THE DISINFECTION BENCHMARK
The LT1ESWTR requires systems to develop a disinfection
benchmark if the system is required to create a disinfection
profile and decides to make a significant change to disinfection
practices. The system must consult with the State for approval
prior to making a significant change to disinfection practices
(See Section 6.4 for a description of significant changes).
Systems may be considering disinfection modifications for
compliance with the Stage 1 DBPR requirements or for other
reasons. The disinfection profile and benchmark information
will allow the State to assess appropriate modifications to
disinfection practices, as necessary. As explained in Chapter 1,
benchmarking is used to characterize the minimum level of
Giardia, and in some cases, virus log inactivations that are
provided under current disinfection practices. The benchmark
calculated under existing conditions can be compared to the
benchmark calculated under the proposed modifications to
ensure that changes to disinfection practices do not result in
inactivation levels lower than the required inactivation values
without appropriate State consultation and review.
A benchmark is required if both of the following criteria apply:
• A disinfection profile is required;
AND,
• The system decides to make a significant change(s) to
disinfection practices.
Systems that do not use chloramines, ozone, or chlorine
dioxide as primary disinfection will calculate a profile and
benchmark for Giardia only. Systems that use chloramines,
ozone, or chlorine dioxide for primary disinfection must also
calculate a profile and benchmark based on virus inactivation
in addition to those for Giardia inactivation. Virus inactivation
must be determined for these systems to address the possibility
of reduced inactivation for viruses when using an alternative
disinfectant.
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6. Developing the Disinfection Profile and Benchmark
40 CFR Section 141.541
40 CFR Section 141.543
Equation 6-1
Monthly Average Log
Inactivation
6.4 SIGNIFICANT CHANGES TO DISINFECTION
PRACTICES
The LT1ESWTR describes four types of significant
modifications to disinfection practices:
• Changes to the point of disinfection;
• Changes to the disinfectant(s) used in the treatment
plant;
• Changes to the disinfection process; or,
• Any other modification identified by the State.
Systems may consider one or more of the above-mentioned
modifications to comply with Stage 1 DBPR. These
modifications will require the system to calculate its benchmark.
The benchmark will be used for discussion with the State on
disinfection modifications. The significant modifications are
discussed in more detail in Chapter 7.
6.5 BENCHMARK CALCULATIONS
A disinfection benchmark is calculated using the following
steps:
• Complete a disinfection profile that includes the
calculation of log inactivation ofGiardia and viruses (if
required) for each week of the profile.
• Compute the average log inactivation for each calendar
month of the profile by averaging the weekly log
inactivation values for each month (See Equation 6-1).
Equation 6-1
Monthly Average
Log Inactivation =
Sum of Weekly Log Inactivation Values
Number of Weekly Values per Month
• Select the month with the lowest average log inactivation
for the 12-month period. This value is the benchmark.
Example 6-2 demonstrates how to calculate the disinfection
benchmark.
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6. Developing the Disinfection Profile and Benchmark
Example 6-2: Calculating a Benchmark
Calculate the disinfection benchmark for the conventional filtration system discussed in
Examples 3-1, 4-1, 4-2, 5-1, 5-2, and 6-1.
Step 1. Calculate weekly Giardia log inactivations.
This step was completed in Example 6-1. The data is summarized below:
Month
JAN
FEB
MARCH
APRIL
MAY
JUNE
Week
1
2
3
4
5
Q
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Log Inact.
1.34
1.35
1.38
1.37
1.38
1.38
1.39
1.40
1.40
1.40
1.41
1.42
1.43
1.46
1.50
1.54
1.57
1.64
1.66
1.70
1.72
1.74
1.77
1.79
1.82
1.81
Month
JULY
AUG
SEP
OCT
NOV
DEC
Week
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
Log Inact.
1.86
1.82
1.76
1.74
1.71
1.70
1.66
1.61
1.60
1.55
1.56
1.52
1.51
1.47
1.48
1.47
1.47
1.45
1.41
1.43
1.41
1.40
1.40
1.40
1.40
1.37
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6. Developing the Disinfection Profile and Benchmark
Example 6-2 continued
Step 2. Calculate the monthly average log inactivation for each month.
Begin by averaging January's inactivations:
Average log inactivation for January = ( Sum of Weekly Log Inactivation Values )
(Number of Weekly values in Month)
= 1.34 + 1.35 + 1.38+ 1.37+ 1.38
5 values
= (6.82)7 (5) = 1.36
Continue this process for each month. The following are the results for the Example system:
January 1.36 July 1.78
February 1.39 August 1.64
March 1.41 September 1.52
April 1.54 October 1.47
May 1.71 November 1.41
June 1.80 December 1.39
Step 3. Identify the month with the lowest monthly average log inactivation. The log
inactivation for this month is the disinfection benchmark.
The month with the lowest monthly average log inactivation is January, with a value of 1.36.
The benchmark is 1.36.
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6. Developing the Disinfection Profile and Benchmark
6.6 STEPS COMPLETED
••*
Calculate
Inactivation
Develop the
Disinfection
Profile and
Benchmark
the
and
Calculate CT
Collect Data
Identify
Disinfection
Segments
6.6 NEXTSTEP
By calculating the benchmark, the system has identified its
lowest monthly average inactivation value. This benchmark is
used as a guide when evaluating disinfection practice
modifications. Chapter 7 provides information on how to
evaluate disinfection practice modifications.
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7. EVALUATING DISINFECTION PRACTICE
MODIFICATIONS
In this Chapter:
• System Reporting
Requirements
• Simultaneous
Compliance
• How the State will
Use the Benchmark
• Steps Completed
Systems must consult the
State prior to making
modifications to
disinfection practices.
7.1 INTRODUCTION
The benchmark is a system's lowest monthly average Giardia
(or virus) inactivation based on the disinfection profile. The
benchmark must be calculated if a system is required to develop
a disinfection profile and decides to make a significant
modification to disinfection practices. The benchmark will help
in evaluating alternatives to the current disinfection practices.
Remember, a system must reliably and consistently provide the
necessary log inactivation through disinfection to achieve
adequate Giardia and virus log reduction as required by the
SWTR (See Table 7-1). Table 7-2 provides typical removal
credits and inactivation requirements for different processes.
Systems should check with the State on the specific removal
credits and inactivation requirements since Table 7-2 contains
typical values.
If a benchmark value is less than the required log inactivation
for disinfection, then the system will probably need to modify
disinfection practices, such as increasing the amount of
disinfectant or the contact time. Increasing the amount of
disinfectant will probably require the system to evaluate
disinfection byproducts more closely.
If the benchmark is greater than the required inactivation in
Table 7-2 (or as required by the State), the system can consider
decreasing the amount of disinfectant added, contact time, or
altering other disinfection practices. Systems must consult the
State for approval prior to making a significant change to their
disinfection practices. The State will work with the system to
determine if the change is significant and whether it triggers any
additional requirements under LT1ESWTR.
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7. Evaluating Disinfection Practice Modifications
Microbial removal and
inactivation requirements.
Table 7-1: Removal and Inactivation Requirements
Microorganism Required Log Treatment
Reduction
Giardia 3-log (99.9%) Removal and/or
Inactivation
Viruses 4-log (99.99%) Removal and/or
Inactivation
Cryptosporidium 2-log (99%) Removal
Table 7-2: Typical Removal Credits and Inactivation
Requirements for Various Treatment Technologies
Process
Conventional
Treatment
Direct
Filtration
Slow Sand
Filtration
Diatomaceous
Earth Filtration
Alternative
(membranes,
bag filters,
cartridges)
Unfiltered
Typical Log
Removal Credits
Giardia
2.5
2.0
2.0
2.0
*
0
Viruses
2.0
1.0
2.0
1.0
*
0
Resulting
Disinfection Log
Inactivation
Requirements
Giardia
0.5
1.0
1.0
1.0
*
3.0
Viruses
2.0
3.0
2.0
3.0
*
4.0
* Systems must demonstrate to the State by pilot study or other means
that the alternative filtration technology provides the required log
removal and inactivation shown in Table 7-1.
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7. Evaluating Disinfection Practice Modifications
40 CFR Section 141.542
Stage 1 DBPR = Stage 1
Disinfectants and
Disinfection Byproducts
Rule
7.2 SYSTEM REPORTING REQUIREMENTS
A system that is considering a significant change to its
disinfection practice must calculate the disinfection benchmark,
provide the benchmark to the State, and consult with the State
for approval before making the significant change. The
LT1ESWTR describes four types of significant changes to
disinfection practices:
• Changes to the point of disinfection;
• Changes to the disinfectant(s) used in the treatment
plant;
• Changes to the disinfection process; or,
• Any other modification identified by the State.
As part of the consultation and approval process, a system must
submit the following information to the State:
• A description of the proposed change.
• The disinfection profile and disinfection benchmark for
Giardia. If the system uses chloramines, ozone, or
chlorine dioxide for primary disinfection, the system
must also submit a profile and benchmark for viruses.
• An analysis of how the proposed change will affect the
current levels of disinfection.
• Any additional information requested by the State.
Disinfection profiling and benchmarking will help ensure that
microbial protection is not compromised by any modifications
to disinfection practices. These modifications are discussed in
more detail in Section 7.3.
7.3 SIMULTANEOUS COMPLIANCE
The LT1ESWTR is not the only rule that affects or dictates
disinfection practices. The Stage 1 DBPR applies to some or
all PWSs (depending on the disinfectant used) that add
chlorine, chloramines, chlorine dioxide, or ozone. This rule
establishes MCLs for TTHM and HAAS, in addition to other
byproducts (depending on the disinfectant used). The MCLs
are 0.080 mg/L for TTHM and 0.060 mg/L for HAAS under
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7. Evaluating Disinfection Practice Modifications
Disinfection Byproducts
DBF
the Stage 1 DBPR. Surface water systems and systems
classified as GWUDI that serve less than 10,000 people must
comply with this rule by January 1, 2004. The Stage 1 DBPR
also establishes maximum residual disinfectant levels
(MRDLs) for systems using chlorine, chloramines, and
chlorine dioxide.
The following terms may be helpful for understanding
disinfection practices:
• Disinfection Byproduct (DBF) Precursors - DBF
precursors are constituents naturally occuring in source
water that react with a disinfectant to form DBFs. The
primary DBF precursor is natural organic matter, which
is monitored as total organic carbon (TOC). Organic
matter reacts with the disinfectant to form TTHM,
HAAS, and other DBFs. The Alternative Disinfectants
and Oxidants Guidance Manual (EPA, 1999a) provides
more detailed information on DBF formation.
• Pre-disinfection - Pre-disinfection occurs when a
disinfectant is added to the treatment train prior to the
primary disinfectant injection location. The purpose of
pre-disinfection is to obtain additional inactivation
credits, to control microbiological growth in subsequent
treatment processes, to improve coagulation, and/or to
reduce tastes and odors.
• Primary Disinfection - The disinfectant used in a
treatment system with the primary objective to achieve
the necessary microbial inactivation.
• Secondary Disinfection - The disinfectant applied
following primary disinfection in a treatment system
with the primary objective to maintain the residual
disinfectant throughout the distribution system.
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7. Evaluating Disinfection Practice Modifications
Example:
Moving the point of pre-
disinfectant application
7.3.1 Changes to the Point of Disinfection
Any change in the location of the disinfectant application
constitutes a significant change to disinfection practices. For
instance, a water system that uses pre-disinfection may consider
moving the point of disinfectant application further into the
treatment train (See Figure 7-1). This modification will result in
a reduction of contact time between DBF precursors and the
disinfectant(s) with corresponding reduction (typically) in the
production of DBFs. Also, moving the pre-disinfection to a
location after some of the treatment processes where organics
have been removed will result in less contact between organic
matter (precursors) and disinfectant; therefore, fewer DBFs
should be created.
Figure 7-1. Example of Moving the Point of Pre-
disinfectant Application
CI2
Feed
Sedimentation
0
Filtration
Clean/veil
Distri
ution
Predisinfection
Location
System
® Potential locations for pre-disinfection. For example,
the system may consider relocating the pre-disinfection
location from the intake to one of three other possible
locations. The potential for DBF formations decreases
further down the treatment train for two reasons:
1. Contact time between DBF precursors and
disinfectants is reduced.
2. DBF precursors are removed with each subsequent
treatment process.
A system that is considering moving the point of
disinfectant application further into the treatment process
should make sure that it can maintain adequate contact time
and meet required log inactivations.
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7. Evaluating Disinfection Practice Modifications
Systems should identify all
impacts on the treatment
process and maintain
compliance with all rules
when moving the point of
disinfectant application.
When moving the point of disinfection further into the treatment
process, a system should consider whether adequate contact time
will still be available to achieve sufficient disinfection. This
type of modification may affect the amount of inactivation
achieved by the system. Systems may find that seasonal use of
this type of modification is helpful in reducing summertime
DBF levels, which are typically the highest.
In conventional treatment, DBF precursors are removed through
coagulation, sedimentation, and filtration. Moving the point of
disinfectant application to another point downstream from these
processes can reduce the concentration of DBF precursors that
come in contact with the disinfectant. However, moving the
disinfectant application point downstream also reduces the time
that the disinfectant is in contact with the water and the CTcaic
for the disinfectant. Increasing the disinfectant concentration
can help maintain a higher CTcaic, but greater disinfectant
concentrations also lead to increased DBF formation. In
addition, the disinfectant concentration may be limited
(depending on the disinfectant used) by the MRDL for the
disinfectant. Another alternative for maintaining CT is to add
baffling to the clearwell or to storage tanks downstream in order
to increase the disinfectant contact time. An increase in the
contact time value may allow a lower disinfectant concentration
and may result in fewer disinfection byproducts. However, the
system must make sure it provides enough disinfectant to
achieve the required microbial inactivation values.
7.3.2 Changes to the Disinfectant(s) Used in
the Treatment Plant
Water systems typically use one or more of the following
disinfectants:
• Chlorine;
• Chloramines;
• Chlorine Dioxide;
• Ozone; or,
• Ultraviolet (UV).
A water system may consider changing the disinfectant used in
its treatment plant to comply with the Stage 1 DBPR MCLs.
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7. Evaluating Disinfection Practice Modifications
Considerations for
alternative disinfectants.
Systems may also consider changing both the disinfectant and
point of disinfection application. For example, a system may
shift from chlorine as the sole source of disinfection to chlorine
prior to the clearwell (primary disinfection) and ammonia
added after the clearwell for chloramine (secondary
disinfection) (See Figure 7-2). This configuration allows for
chlorine to achieve Giardict and virus inactivation in the
clearwell. The addition of ammonia after the clearwell to
produce chloramines can reduce the formation of DBFs in the
distribution system. In another example, a system may move
the pre-disinfection location from a point prior to the
presedimentation basin to a point prior to coagulation. In
addition, the system may change the pre-disinfectant from
chlorine to ozone to reduce TTHM and HAAS formation (See
Figure 7-3).
As a system considers different disinfectants, it should evaluate
the following:
• What DBFs are created by the disinfectant?
• What concentrations and contact times are required to
provide adequate microbial inactivation?
• Where is the best point of application in the treatment
train to minimize DBF's and maximize inactivations?
For more information on disinfectants, refer to Chapter 8 of
this guidance manual and the Alternative Disinfectants and
Oxidants Guidance Manual (EP'A, 1999a), available on EPA's
website http ://www. epa. gov/safewater/mdbp/implement.html.
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7. Evaluating Disinfection Practice Modifications
Example:
Changing disinfectant
type
Example:
Changing pre-disinfection
location and type of
disinfectant
Figure 7-2. Example of Changing Disinfectant Type
Primary Disinfectant
(Existing)
CI2
Feed
From Filtration
Secondary Disinfectant (New)
Ammonia Feed for
Monochloramine Formation
Distribution
System
Chlorine is used as the sole disinfectant and is added prior
to the clearwell to obtain Giardia and virus inactivation.
The system decides to add ammonia after the clearwell to
produce chloramine. Using chloramine as a secondary
disinfectant has two advantages:
1) Chloramine typically has a lower potential for
TTHM and HAAS formation than chlorine.
Chloramine should result in lower TTHM and
HAAS formation in the distribution system.
2) Chloramine residuals last longer than chlorine.
Figure 7-3. Changing Pre-disinfection Location and
Type of Disinfectant
Cl
Feed
Filtration
Clearwell
System
Change pre-disinfection location from prior to the pre-
sedimentation basin (point 1) to prior to coagulation (point
2). Changing from chlorine to ozone may also be
considered to reduce TTHM and HAAS formation.
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7. Evaluating Disinfection Practice Modifications
Chlorine is pH sensitive
and more effective at
lower pHs.
7.3.3 Changes to the Disinfection Process
Other changes to the disinfection process also require water
systems to consult with the State before making the treatment
change. Some modifications to the disinfection process include
the following:
• Changing the contact basin geometry and baffling
conditions to provide additional contact time;
• Increasing or decreasing the pH during disinfection; or,
• Decreasing the disinfectant dose during warmer
temperatures.
The LT1ESWTR requires water systems to submit information
to the State prior to making a change (See Section 7.2).
Effects of Basin Geometry and Baffling Conditions on
Contact Time
Changing the contact basin geometry or baffling conditions
may result in more inactivation by changing the T value in the
CTcaic value. With this modification, additional inactivation is
achieved without increasing the disinfectant concentration.
pH Effects on Chlorine
Chlorine is very sensitive to pH. Decreases in pH provide
increased inactivation ofGiardia and viruses. Therefore, at
lower pHs a lower chlorine dose or contact time can be applied
while achieving a sufficient level of inactivation of both
Giardia and viruses. This in turn can reduce the potential for
DBF formation. However, decreasing the pH is a process-
sensitive issue and could result in other system changes, such as
increased coagulant demand for proper floe formation,
distribution system corrosion problems, or precipitation of
certain inorganics. Extensive jar tests and pilot scale studies
may be necessary before adjusting the pH.
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7. Evaluating Disinfection Practice Modifications
Chlorine is temperature
sensitive and more
effective at higher
temperatures.
Temperature Effects on Chlorine and DBF Formation
Chlorine is more effective at higher temperatures, which results
in faster chemical reactions and consequently, a higher
potential for DBF formation. Warmer surface waters also
support more organic growth, increasing the potential for DBF
formation. However, since chlorine is more reactive at higher
temperatures, it is also more effective against microorganisms
such as Giardia and viruses. Thus, when water temperatures
are warmer the chlorine dose or contact time can be decreased
while achieving the same amount of microbial inactivation as
in cooler temperatures. However, if a system decreases the
chlorine dose or contact time, the system should ensure that it
is maintaining sufficient log inactivations of both Giardia and
viruses.
7.3.4 Other Modifications
The State may determine that other changes in water system
operations should be considered significant changes in
disinfection practices. If the State makes such a determination,
systems that make these other significant changes must develop
and submit a disinfection benchmark.
The modifications listed in Sections 7.3.1 through 7.3.3 are not
an exhaustive list. States may determine that other types of
changes are also significant. Therefore, a water system should
check with the State program office for assistance in
determining whether a proposed change triggers the
disinfection benchmarking procedure. Other modifications that
may require State consultation and approval are enhanced
coagulation, enhanced softening, or oxidation. Water systems
can refer to the Alternative Disinfectants and Oxidants
Guidance Manual (EPA, 1999a) and the Enhanced
Coagulation and Enhanced Precipitative Softening Guidance
Manual (EPA, 1999b) for additional information. Copies of
these guidance manuals can be obtained by downloading from
EPA's website at
http ://www. epa. gov/safewater/mdbp/implement.html.
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7. Evaluating Disinfection Practice Modifications
The State may use the
benchmark to make sure
that modifications to
disinfection practices still
maintain required
microbial inactivation.
7.4 How THE STATE WILL USE THE
BENCHMARK
The State is expected to use the benchmark to evaluate the
microbial inactivation the system has achieved over time and
compare this with the expected microbial inactivation the
system will achieve by disinfection practice modifications.
Systems with a benchmark that is less than the inactivation
requirements in Table 7-2 or those required by the State will
probably need to modify disinfection practices in order to
provide the necessary level of disinfection. For instance, a
conventional treatment plant has calculated a benchmark of 0.3
for Giardia but is required to achieve 0.5-log Giardia
inactivation through disinfection. This system would need to
provide additional disinfection to achieve the required 0.5-log
Giardia inactivation. At the same time, systems must also
make sure that they maintain compliance with the Stage 1
DBPR. The system must consult with the State for approval
and provide all necessary information prior to any significant
modification, as described in Section 7.2.
Systems may consider modifying disinfection practices if the
benchmark is greater than the inactivation requirements in
Table 7-2 or the inactivation required by the State. For
instance, a conventional treatment plant has calculated a
benchmark of 1.3 for Giardia but is only required to achieve a
0.5-log Giardia inactivation through disinfection. The system
uses chlorine and is having difficulties complying with TTFDVI
and HAAS MCLs established by the Stage 1 DBPR. The
system considers decreasing the amount of chlorine, but must
determine what level of chlorine is needed to meet the 0.5-log
Giardia inactivation and still maintain compliance with the
Stage 1 DBPR. Again, the system must consult with the State
for approval prior to making any significant modifications and
must provide all necessary information.
The benchmark may be used by the State as a minimum level
of inactivation of Giardia and viruses that must be maintained
by water systems when modifying disinfection practices. The
State may also use the disinfection profile and benchmark to
determine an appropriate alternative benchmark under different
disinfection scenarios. The LT1ESWTR Implementation
Guidance Manual (under development at this time) will
provide additional information on how States will use the
disinfection profile and benchmark.
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7. Evaluating Disinfection Practice Modifications
7.5 STEPS COMPLETED
Calculate
In activation
Develop the
Disinfection
Profile and
Benchmark
Calculate CT
Collect Data
Identify
Disinfection
Segments
Report and
Evaluate the
Disinfection
Profile and
Benchmark
7.6 REFERENCES
EPA. 1999a. Alternative Disinfectants and Oxidants Guidance Manual (EPA 815-R-99-
014). Washington, D.C.
EPA. 1999b. Enhanced Coagulation and Enhanced Precipitative Softening Guidance
Manual (EPA 815-R-99-012). Washington, D.C.
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8. TREATMENT CONSIDERATIONS
In this Chapter:
• Alternative
Disinfectants and
Oxidants
• Enhanced
Coagulation and
Softening
• Increasing the Contact
Time
• Membranes
For more information on
alternative disinfectants
and oxidants, see the
Alternative Disinfectants
and Oxidants Guidance
Manual (EPA, 1999a),
available on EPA's
website
http ://www. epa. gov/safewater/
mdbp/implement. html.
8.1 INTRODUCTION
In order to comply with the requirements of the LT1ESWTR
and the Stage 1 DBPR, water systems may decide to make
changes to their disinfection practices or other treatment
processes. Disinfection profiling and benchmarking will help
ensure that microbial protection is not compromised by any of
these modifications. Since DBFs are formed when organic
material reacts with disinfectants such as chlorine, water
systems may choose to use less chlorine or modify treatment
processes to reduce the formation of DBFs. Some methods
that water systems may use to control disinfection byproducts,
while meeting the required inactivation levels for Giardia and
viruses, include the use of alternative disinfectants and
oxidants, enhanced coagulation and softening, increasing the
contact time, or the use of alternative filtration techniques, such
as membranes. Pilot testing is generally recommended before
any of these major modifications are made to plant processes.
The State must also be consulted for approval prior to any
modifications.
8.2 ALTERNATIVE DISINFECTANTS AND
OXIDANTS
This section discusses various alternative disinfectants and
oxidants that may be considered for meeting both inactivation
and Stage 1 DBPR requirements. A more complete discussion
of this topic is provided in the Alternative Disinfectants and
Oxidants Guidance Manual (EP'A, 1999a).
Chlorine has long been considered an effective disinfectant in
water systems and is the most widely used disinfectant by
small systems. Chlorine is typically used in one of three forms:
chlorine gas, sodium hypochlorite (typically liquid), and
calcium hypochlorite (typically solid). Chlorine effectively
inactivates a wide range of pathogens, including Giardia and
viruses. Chlorine residuals are generally carried into the
distribution system for further protection. The Stage 1 DBPR
established an MRDL of 4.0 mg/L measured as chlorine if
chlorine is used (community and non-transient non-community
water systems). Remember, surface water and GWUDI
systems must maintain a residual disinfectant concentration of
0.2 mg/L at the entry point to the distribution system and must
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8. Treatment Considerations
Alternative disinfectants
and oxidants to consider
are chloramines, ozone,
chlorine dioxide, ultra-
violet radiation, and
potassium permanganate.
Stage 1 DBPR
For community and non-
transient non-community
water systems using
chloramines:
MRDLof4.0mg/Las
chlorine.
maintain a detectable residual disinfectant in the distribution
system (40 CFR Section 141.72).
The use of chlorine as a disinfectant, particularly as a pre-
disinfectant, has typically been found to increase the formation
of DBFs. One option to resolve this problem is to use a
different pre-disinfectant or an oxidant such as chlorine
dioxide, ozone, or potassium permanganate. The type of
oxidant used and its concentration have significant effects on
DBF formation. Consideration should also be given to the pH
of the water, since lowering the pH decreases TTHM formation
but increases formation of other chlorinated organic species
(Dowbiggin and Thompson, 1990). In addition, higher
temperatures speed up the reaction between chlorine and
organic material, thus increasing finished water TTHM and
HAAS levels (Singer, 1999).
Retaining adequate disinfectant residual at all points in the
water distribution system is important to inhibit bacteriological
growth, and using chlorine to achieve this has been a widely
accepted practice. However, the long detention time for water
at the ends of water mains promotes DBF formation when
chlorine is used. An alternative disinfectant, such as
chloramines, may then be an option.
8.2.1 Chloramines (NH2CI)
Chloramines are formed when chlorine and ammonia are added
together, either simultaneously or sequentially. The ammonia
can be applied before or after the chlorine. However, applying
ammonia after the chlorine has been found to inactivate
pathogens more effectively (AWWA, 1999). Chloramination
is normally practiced as a ratio of approximately 1 part of
ammonia to 4 parts of chlorine (on a mg/L basis) to ensure
monochloramine formation (Kawamura, 2000). Chloramines
are typically used as a secondary disinfectant since they are
more stable than chlorine and can provide better protection in
the distribution system (Kawamura, 2000). To meet required
inactivations of Giardia and viruses, chloramines require more
contact time than chlorine. Chloramines typically have a lower
potential than chlorine for producing DBFs. The Stage 1
DBPR established an MRDL of 4.0 mg/L as chlorine for
systems using chloramines. The CT tables presented in
Appendix B of this guidance document assume ammonia is
added after chlorine to form chloramines.
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8. Treatment Considerations
Stage 1 DBPR
For community and non-
transient non-community
water systems using
ozone:
MCL for bromate
= 0.010mg/L
8.2.2 Ozone (O3)
Over the last fifteen years, the most widely studied alternative
to chlorine as a disinfectant has been ozone (Schneider and
Tobiason, 2000). Ozone is used for both oxidation and
disinfection. It must be generated at the point of application,
since it is an unstable molecule. Ozone is a powerful oxidant
and is more effective than chlorine, chloramines, and chlorine
dioxide for inactivation of viruses, Cryptosporidium, and
Giardia(EPA, 1999a).
Ozone effectively oxidizes DBF precursors, but its
effectiveness is pH and temperature dependent. It can only be
used as a primary disinfectant, since it is unable to maintain a
residual in the distribution system. Chlorine or chloramines
should also be applied as a secondary disinfectant to maintain
the residual.
The use of ozone poses some health and safety concerns that
should be addressed by a utility considering its use.
Instrumentation should be provided for ozone systems to
protect both personnel and the equipment. Ozone is highly
corrosive and toxic, and ozonation systems are relatively
complex. While ozone does not form halogenated DBFs
except in bromide-rich waters, it does form a variety of organic
and inorganic byproducts, such as bromate. Bromate is
regulated by the Stage 1 DBPR at 0.010 mg/L.
Case Study — Schneider and Tobiason (2000)
Jar-testing was used to study the effects of preozonation on interactions among
coagulants, particles, and natural organic matter. Synthetic water (deionized, distilled
water with organic matter, particles, and background ions added) and waters from
Lake Gaillard in Branford, Connecticut; the Oradell reservoir in Oradell, New Jersey;
and the Passaic River in Little Falls, New Jersey, were tested. Experiments were run
with ozone only and with ozone followed by coagulation. The research found that
when alum was used as a coagulant, preozonation hindered the removal of turbidity
and dissolved organic matter (DOM) at the conditions tested. Cationic polymers,
however, allowed small increases in the removal of turbidity and DOM. It was found
that varying the preozone contact time from 4 to 28 minutes had little effect on settled
water turbidity, TOC, and dissolved organic carbon for the conditions tested.
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8. Treatment Considerations
Case Study -Ashe, et al (1994)
The Brewer Water District, serving 9,100 customers, operates pumping and treatment
facilities in Eddington, Maine. The water system draws its water from Hatcase Pond,
disinfects with sodium hypochlorite, adjusts the pH with caustic soda, adds sodium fluoride
for fluoridation, and sends the treated water to a 50,000-gallon clearwell. In order to
comply with new and pending regulations, the system needed to reduce TTHMs and
achieve a 3-log inactivation ofGiardia cysts and a 4-log inactivation of viruses. The
District began addressing its disinfection concerns by studying its present water quality and
disinfection practices. The raw water supply was found to exhibit a high chlorine demand
and a rapid rate of TTHM formation. The use of ozone, chlorine dioxide, and chloramines
were considered in place of chlorine disinfection. The use of chloramines was determined
to be economically unfeasible due to the large volume of additional storage required in
order to meet CT criteria. Pending legislation for the regulation of chlorine dioxide
byproducts (chlorite is now regulated) eliminated it from further consideration. Ozone was
therefore chosen as a primary disinfectant for pilot plant study. Results showed that
ozonation at a dose of 2.0 mg/L to 3.5 mg/L and a contact time of 6 to 9 minutes would
provide the required CT value for this system under all water temperatures and pH
conditions, and adequately destroy the organic compounds that form DBFs. Chloramines
were chosen for use as a secondary disinfectant in order to maintain a residual throughout
the distribution system while reducing trihalomethane formation in the distribution system.
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Hatcase Pond Pump
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r >
r
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40,000 Gallon Ozone
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250,000 Gallon
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Brewer Water District proposed treatment process.
8.2.3 Chlorine Dioxide (CIO2)
Chlorine dioxide is a powerful oxidant and disinfectant that is
effective at inactivating bacterial, viral, and protozoan
pathogens. Chlorine dioxide is generated on-site and is equal
or superior to chlorine in its disinfection ability. Chlorine
dioxide is primarily used in the United States as a means of
taste and odor control, oxidation of iron and manganese, and
control of TTHM and HAAS (Kawamura, 2000). Chlorine
dioxide doses are limited due to production of chlorite. The
Stage 1 DBPR regulates chlorite. Utilities using chlorine
dioxide may have to use granular activated carbon (GAC) or a
chemical reducing agent, such as sulfur dioxide, to remove the
chlorite residual.
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8. Treatment Considerations
Stage 1 DBPR
For water systems using
chorine dioxide:
MRDLof0.8mg/Las
C1O2.
MCL of chlorite of 1.0
mg/L (only applies to
community and non-
transient non-community
systems).
EPA is currently
developing a UV
Guidance Manual.
Chlorine dioxide is a strong oxidant and aids in reducing
TTHM and HAAS by oxidizing precursors. Chlorine dioxide
can also be used to reduce taste and odors or as a primary or
secondary disinfectant. Chlorine dioxide has the ability to
maintain a residual in the distribution system for an extended
period of time (Kawamura, 2000). The Stage 1 DBPR
establishes an MRDL of 0.8 mg/L as C1O2 for systems
(community, non-transient non-community, and transient non-
community) using chlorine dioxide.
8.2.4 Potassium Permanganate (KMnO4)
Potassium permanganate is primarily used as a pre-oxidant to
control algal growth, tastes, and odors, and to remove iron,
manganese, and color. It may also be used to control DBF
formation by oxidizing organic precursors and reducing the
demand for other disinfectants (EPA, 1999a). It is not allowed
under the Surface Water Treatment Rule to be used as a
disinfectant to achieve microbial inactivation. A water
treatment plant may choose to use potassium permanganate as a
pre-oxidant, in lieu of chlorine, and then move the chlorination
point further into the treatment train. This configuration may
help in the control of DBFs by reducing the concentration of
natural organic matter and delaying the introduction of chlorine
until after the majority of precursors have been removed in the
treatment process.
There are some disadvantages to using potassium
permanganate. Potassium permanganate must be handled
carefully when preparing the feed solution, since it can cause
serious eye injury, irritate the skin and respiratory system, and
can be fatal if swallowed. It also tends to turn the water a pink
color.
8.2.5 Ultraviolet Radiation (UV)
UV light is becoming an increasingly popular method of
disinfecting drinking water. One advantage of UV is that it
does not cause the formation of harmful disinfection
byproducts. Recent studies also show that UV can inactivate
Cryptosporidium and Giardia. An additional advantage is that
there are fewer safety concerns with using UV than with
chemical disinfectants such as chlorine gas or chlorine dioxide.
UV rays inactivate microorganisms by penetrating their cell
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8. Treatment Considerations
Systems should conduct a
pilot study prior to
eliminating or adding a
disinfectant.
walls to damage essential cell components. UV is not effective
on all pathogens, and studies are being done to identify UV's
effectiveness.
The UV dose is the product of the irradiance and the time that
an organism is exposed to that irradiance. The dose is
expressed in millijoules per square centimeter (mJ/cm2) or the
equivalent, milliwatt-seconds per square centimeter
(mW-s/cm2). A common UV dose used in drinking water
disinfection is 38-40 mJ/cm2 (Cotton, et al., 2001). Data from
recent research indicate that a dose of 40 mJ/cm2 will achieve
at least a 2-log inactivation of Cryptosporidium (Cotton, et al.,
2001). Giardici is thought to be equally as sensitive as or more
sensitive than Cryptosporidium to UV light. Bacteria are more
susceptible to UV disinfection than Cryptosporidium. Some
viruses are significantly less susceptible to UV disinfection
than Cryptosporidium and bacteria. Thus, virus inactivation is
likely to control the dose when UV is used as the only
disinfectant in drinking water treatment.
Despite the many advantages of UV systems, these systems
also have some shortcomings. Since UV is a physical
disinfectant, not a chemical disinfectant, it does not leave a
residual in the water. Thus, a secondary disinfectant must be
applied to maintain distribution system residuals. Another
disadvantage is that higher turbidity may shield organisms and
prevent them from being exposed to UV. Additionally, organic
material absorbs UV light and can increase the UV demand of
the water. Therefore, it is recommended that systems apply UV
light as a disinfectant after filtration, where turbidity and
organics in the water are reduced. Another potential problem is
that scale can form on the quartz sleeves that house the UV
lamps, depending on the ions, hardness, alkalinity, and pH of
the water. This in turn causes a reduction in the amount of UV
energy that is transmitted to the water. However, regular
cleaning of the sleeves can reduce the effects of scaling.
Finally, the operation of the UV lamps may be temperature
dependent.
8.2.6 Comparison of Disinfectants
EPA and the Association of Metropolitan Water Agencies
(AMWA) funded a two-year study of 35 water treatment
facilities to evaluate DBF production based on various
combinations of primary and secondary disinfectants. Among
four of the facilities, alternative disinfection strategies were
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8. Treatment Considerations
investigated to evaluate the difference in DBF production from
the systems' previous disinfection strategies (or base
disinfection conditions). The results were analyzed in three
reports (Metropolitan and Montgomery, 1989; Jacangelo, et al.,
1989; Malcolm Pirnie, Inc., 1992) that documented different
aspects of the study. Table 8-1 summarizes the results of the
study. This study illustrates that a change in primary
disinfectant from chlorine to ozone or to chloramines may help
reduce TTHM and HAAS.
Table 8-1. Study Results on Changing Primary and Secondary Disinfectants
Change in Disinfection Practice1
(Primary Disinfectant/Secondary Disinfectant)
Chlorine/Chlorine
To
Chlorine/Chloramines2
Chlorine/Chlorine
To
Ozone/Chlorine
Chlorine/Chloramines
To
Ozone/Chloramines
Chlorine/Chlorine
To
Chloramines/Chloramines
Ozone/Chlorine
To
Ozone/Chloramines
Chloramines/Chloramines
To
Ozone/Chloramines
Chlorine/Chlorine
To
Ozone/Chloramines
Utility #7
Utility #19
Utility #36
Utility #7
Utility #36
Utility #36
Utility #25
Utility #36
Utility #7
Utility #36
DBF
Concentration Change
TTHM
Decrease
Decrease
No change
Decrease
Decrease
Decrease
Decrease
No change
Decrease
Decrease
HAAS
Decrease
Decrease
No change
Decrease
Decrease
Decrease
Decrease
No change
Decrease
Decrease
1 Several studies were conducted to examine the effects of changing primary and secondary disinfectants on
DBF levels. For instance, changing the secondary disinfectant from chlorine to chloramines resulted in a
decrease in both TTHM and HAAS. Results are based on full-scale evaluations at Utilities #19 and #25 and on
pilot scale evaluations at Utilities #7 and #36.
2Free chlorine contact time was 4 hours for Utility #7 during use of chlorine/chloramine strategy.
Source: Malcolm Pirnie, Inc., 1992; Jacangelo, etal., 1989.
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8. Treatment Considerations
Enhanced softening
means the improved
removal of DBF precursors
by precipitative softening.
Enhanced coagulation
means the addition of
sufficient coagulant for
improved removal of DBF
precursors by conventional
filtration treatment.
Guidance for
implementing enhanced
coagulation or enhanced
precipitative softening is
provided in the Enhanced
Coagulation and
Enhanced Precipitative
Softening Guidance
Manual (EPA, 1999b).
8.3 CHANGES IN ENHANCED COAGULATION
AND SOFTENING
In conventional water treatment plants, precursors of DBFs
may be removed through the coagulation process with
aluminum or ferric salts and/or polymers. If a greater reduction
in the DBF level is required, then the treatment techniques of
either enhanced coagulation or enhanced precipitative softening
can be employed.
With fewer precursors present, the formation of DBFs is
thereby reduced. Enhanced coagulation also allows for more
effective disinfection, since the chlorine demand is lower in
water treated by enhanced coagulation. In addition, the lower
pH resulting from enhanced coagulation allows chlorine to
inactivate Giardia more effectively, since chlorine is more
effective at lower pHs.
One way to implement enhanced coagulation is to change the
type or dose of coagulant and/or polymer aid. However, before
either enhanced coagulation or enhanced softening is
implemented at a water treatment plant, the proposed changes
should be evaluated through pilot-testing or bench-scale
studies. Jar testing is commonly used to simulate coagulant
dose changes and its effectiveness. A water treatment plant
should first determine the present status of the coagulation
process by taking TOC samples from the raw water and the
finished water. With this data, the percent removal of TOC
may be calculated and a desired TOC removal level may be
determined.
Changes to the coagulation and softening processes may have
secondary effects on a water treatment plant. The pH of the
water may be altered by the changes, thus affecting the
disinfection process. Over the typical plant pH operating range
of 5.5 to 9.5, decreasing the pH values improves the
disinfection characteristics of chlorine and ozone and decreases
the effectiveness of chlorine dioxide (EPA, 1999b). Another
secondary effect of enhanced coagulation or softening may be
the production of a lighter and more fragile floe that can carry
over into the filters, thus shortening filter runs and increasing
the amount of filter backwash water produced. Efficient
sedimentation is extremely important prior to the filters to
prevent filter overload. More sludge may also result from
enhanced coagulation and enhanced softening, because of
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8. Treatment Considerations
increased coagulant and lime dosages and more TOC removal.
In addition, inorganic contaminant levels for iron, manganese,
aluminum, sulfate, chloride, and sodium in finished water may
increase with increased coagulant dosages (depending on type
of coagulant used). A recent study by Carlson, et al. (2000)
presents secondary effects of enhanced coagulation and
softening.
Case Study — Kramer andHorger (1998)
The Samuel S. Baxter Water Treatment Plant in Philadelphia conducted a series of jar tests to
look at enhanced coagulation and its impact on TOC removal from the source water. At the
time of the study, the 200 MOD Baxter plant used pre-treatment, flocculation/sedimentation,
filtration, and disinfection to treat its water. It seasonally used potassium permanganate as a
preoxidant to control algae and its associated tastes and odors. Ferric chloride was used as the
primary coagulant. This enhanced coagulation study considered the pH of coagulation as well
as the coagulant dose. lar tests using treatment plant water showed that the optimal pH was
significantly less than the pH that was being used in the plant for coagulation and that the
coagulant dose could be reduced by 10-30%. Full scale testing at the water treatment plant
showed that by reducing the pH of coagulation, TTHM formation was significantly reduced
and TOC removal increased significantly. Further investigation is necessary to determine the
impact of lower pH on the formation of haloacetic acids.
Case Study - Bell-Ajy, et al (2000)
Research, including jar tests using raw water from 16 water utilities throughout the United
States and two full-scale evaluations, was conducted to evaluate the optimal coagulation
conditions for removal of TOC and DBFs. lar test results showed that when optimized
coagulation was implemented, treatment effectiveness seemed pH dependent. lar tests using
alum, ferric chloride, and polyaluminum chloride coagulants with sulfuric acid for pH
reduction removed more TOC than those at higher pH levels. In the full-scale applications,
enhanced coagulation effectively increased TOC removal and reduced trihalomethanes and
trihalomethane formation potentials. With a lowering of pH during the coagulation process,
turbidity and particle removals were improved. The researchers recommended that sludge
generation, floe carryover, and dewatering, along with the point of chlorine addition and
alkalinity consumption, be considered in the treatment scheme before enhanced coagulation is
implemented.
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8. Treatment Considerations
8.4 INCREASING CONTACT TIME
Increasing either C (the disinfectant residual concentration) or
T (the contact time for the disinfectant) will increase the CT
value and provide additional credit for Giardia cyst and virus
reductions. The value of CT can be increased by constructing
additional storage, increasing the disinfectant residual,
changing the disinfectant, lowering the pH, increasing the
minimum clearwell depth, lowering high service peak flows, or
improving clearwell hydraulics to allow for a greater detention
time (Bishop, 1993). Increasing disinfectant concentrations to
improve CT poses the problem of increasing the formation of
DBFs, particularly with chlorine. One way to gain additional
disinfection credit without increasing the disinfectant dosage is
to increase the detention time in the clearwell. Increased
detention time serves to allow more contact time, thus
providing more opportunity for the destruction of
microorganisms.
Another way to increase CT is to construct additional storage
prior to high service pumping. However, the cost and
utilization of available space makes this option less preferred
(Bishop, 1993). These suggested operating scenarios may limit
DBF formations if the majority of DBF precursors have been
removed. If a significant amount of DBF precursors, such as
organic matter, is present when the disinfectant is added, these
scenarios may not be advantageous.
As discussed in Chapter 4 of this manual, the detention time
used in the CT calculation is not the theoretical detention time
(basin volume divided by flow rate), but rather the amount of
time in which 10 percent of the fluid passes through a basin,
process, or system in which a disinfectant residual is
maintained. This value is determined from tracer tests or is
estimated with the use of a baffling factor. Certain basin
shapes and designs allow good mixing, while others allow
short-circuiting. The baffling factors listed in Table 4-2
account for various baffling conditions, inlet/outlet designs, and
basin configurations. A water system desiring more contact
time in order to increase its CT value may improve the
hydraulics of its existing clearwell by improving the detention
time within the unit through baffling or inlet/outlet changes.
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8. Treatment Considerations
Possible clearwell changes are:
• Relocating the inlet and/or outlet to maximize the
separation distance between them;
• Perforating the distribution and collection piping to
disperse flow across the clearwell;
• Using overflow inlets to disperse existing horizontal
inlet flows;
• Using baffles to disperse inlet flow;
• Perforating baffle walls to disperse flows into and out of
basins; and,
• Using inlet or outlet weirs or launderers to distribute
flow (Bishop, 1993).
Case Study - Pinsky, et al (1991)
The South Central Connecticut Regional Water Authority (RWA) hired a consulting firm
to conduct a comprehensive study of current disinfection practices at three of its surface
water treatment plants. Two of these plants (Lake Gaillard and West River) are direct
filtration plants and the third one (Lake Saltonstall) is a conventional water treatment
plant. Where current disinfection practices were found to be inadequate, disinfection
strategies and alternatives for satisfying CT requirements were investigated and
recommendations were developed. Tracer studies confirmed that the filtered water
reservoirs experienced short-circuiting. After research of various physical and chemical
alternatives, the recommendation for the West River plant was the construction of a
single vertical baffle in the finished water reservoirs at a total cost of $147,000. At the
Lake Gaillard Plant, it was determined that a single vertical baffle in each of the two
finished water reservoirs, at a total project cost of $ 120,000, would meet the CT
requirement.
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8. Treatment Considerations
Case Study - Teefy, et al. (1995)
The Alameda County Water District (ACWD) in Fremont, California, was not meeting the
disinfection requirements of the SWTR or its DBF requirements. The existing water
treatment plant was a conventional surface water treatment plant that used free chlorine for
disinfection, alum and cationic polymer for coagulation and filtration, and chloramines for
secondary disinfection. In order to receive additional disinfection credit, it was decided that
the plant's 750,000-gallon reservoir should be modified to obtain more detention time for
the chlorine. The common inlet/outlet configuration of the tank did not allow for any
contact time credit. In order to determine the best type and location of the new inlet and
outlet structures, more than 50 configurations were tested in a scale modeling study.
Twenty minutes was determined to be the desired T10 after the improvements were
completed. Based on the model results, a spiral-type arrangement with the inlet coming in
tangential to the side of the tank and the outlet line coming directly out of the bottom center
of the tank was chosen. In addition to these changes to the reservoir, the point of sodium
hydroxide and aqua ammonia addition was moved from immediately after the filters to
downstream of the newly-modified reservoir. This move was made to slow the formation of
trihalomethanes and to make the required CT requirement easier to achieve. The total
project cost of $1,800,000 included the modeling study, engineering design, and actual
construction of the improvements. The full-scale results were close to the model
predictions, but agreement was not always good. Tests at the mid-range operating depth
agreed best with the model predictions.
>> t
1 1
To Distribution
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8. Treatment Considerations
For more information on
membranes, refer to
Membrane Practices for
Water Treatment (AWWA,
2001).
8.5 MEMBRANES
Four basic classes of membrane technology are currently used
in the water treatment industry: reverse osmosis, nanofiltration,
ultrafiltration, and microfiltration. Figure 8-1 presents the
typical pore size range and removal capabilities for these
membrane process classes. Membranes have a distribution of
pore sizes, and this distribution will vary according to the
membrane material and manufacturing process. When a pore
size is stated, it can be presented as either nominal (i.e., the
average pore size) or absolute (i.e., the maximum pore size) in
terms of microns (|im). The removal capabilities of reverse
osmosis and nanofiltration membranes are typically not stated
in terms of pore size, but instead as a molecular weight cutoff
representing the approximate size of the smallest molecule that
can be removed by the membrane.
All of these membrane processes are effective at removing
Giardia, Cryptosporidium, and most bacteria (provided the
membrane has no leaks). The amount of removal will depend
on the type of membrane used. Reverse osmosis,
nanofiltration, and ultrafiltration should remove viruses,
assuming there are no leaks in the membranes. Reverse
osmosis and nanofiltration are capable of removing inorganic
and organic contaminants, including DBF precursors (AWWA,
1999).
Membranes can be effective in decreasing the amount of DBFs
formed:
• The removal of pathogens by membranes should reduce
the amount of disinfectant required for inactivation and
should result in lower finished water DBF
concentrations; and,
• The removal of DBF precursors should result in lower
finished water DBF concentrations (when reverse
osmosis or nanofiltration is used).
It is important to remember that these membrane processes are
physical barriers only, and must be followed by disinfection to
ensure inactivation of pathogens not removed by the membrane
barrier, control of bacterial regrowth in downstream system
plumbing, and an adequate distribution system residual.
Membranes can also be used to achieve other treatment
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8. Treatment Considerations
objectives. More information on membranes can be obtained
from the Guidance Manual for Membrane Filtration (under
development by EPA-OGWDW).
Case Study - Bing, et al (2001)
The Delta Water Treatment Plant in Delta, Ohio, which serves approximately
3,200 people, treats river water with lime-soda softening and filtration. In order
to meet increasing demand and upcoming regulations the plant needed to
upgrade the facility. An integrated membrane system, consisting of
microfiltration and reverse osmosis, was chosen for a pilot study. The
microfiltration filtrate was blended with the reverse osmosis permeate to reduce
the demand on the reverse osmosis system while still meeting water quality
objectives. The dissolved organic carbon, trihalomethane formation potential,
and haloacetic acid formation potential were substantially reduced by reverse
osmosis and in the blended water were well within the compliance levels of the
Stage 1 DBPR. Turbidity, hardness, and particulate removal goals of 0.05 NTU,
110-150 mg/L, and 2 logs, respectively, were also surpassed in the blended
water. An additional benefit of this system was that the pH of the finished water
was lower than in the existing system, meaning that a lower chlorine dose could
be used to meet CT requirements, further reducing the formation of DBFs. This
study showed that this integrated membrane system is suitable for small systems
using surface water sources.
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8. Treatment Considerations
Figure 8-1. Particles Removed Through Membrane Technologies
Micron Scale
Approximate
Molecular
Weight
Typical Size
Range of
Selected
Water
Constituents
Membrane
Process*
* Particle Fill
• r, 1 .. , in 1 Macro Molecular
Ionic Range 1 Molecular Range 1 _
O.C
100
Sa
—
ation is shown f
01 0.
1000 10,000
Dissolved
Its
•
^^| Nanof
| Reverse Osn
or reference onl>
31 0
100,000
>ganics
Viruses
Co
•
—
Itration
nosis
i. It is not a men
1 1
500,000
loids
Particle Filtra
^| Ultrafiltra
nbrane separatio
Micro Particle Range 1 Macro Particle Range
0 1
Giar
Bacteria
Cryptospork
tion ^^^^^1
^| Microfiltra
tion
n process.
0 1C
fe)
Hum
—
tion
)0 10
Sand
^^m
00
•
Source: AWWA/ASCE, 1998.
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8. Treatment Considerations
8.6 REFERENCES
Ashe, C.R., V.F. Coletti, and R.A. Stoops. 1994. Small System Compliance: CT versus
DBFs. 1993 AWWA Annual Conference Proceedings.
AWWA. 2001. Membrane Practices for Water Treatment. Denver, CO.
AWWA. 1999. Water Quality & Treatment - Handbook of Community Water Supplies.
Fifth Edition. McGraw-Hill. New York, NY.
AWWA/ASCE. 1998. Water Treatment Plant Design. Third Edition. McGraw-Hill. New
York, NY.
Bell-Ajy, K., M. Abbaszadegan, E. Ibrahim, D. Verges, and M. LeChevallier. 2000.
Conventional and Optimized Coagulation for NOM Removal. Journal AWWA, 92(10):44-
58.
Bing, J., R. Jackson, D. Heyman, L. Born, and R. Huehmer. 2001. Compliance with
M/DBP Rules Using Integrated Membrane Systems. 2001 AWWA Annual Conference
Proceedings.
Bishop, M.M. 1993. The CT Concept and Modifications to Improve Detention Times. 1992
AWWA Annual Conference Proceedings.
Bishop, M.M., J.M. Morgan, B. Cornwell, and D.K. Jamison. 1993. Improving the
Disinfection Time of a Water Plant Clearwell. Journal AWWA, 85(3):68-75.
Carlson, K., S. Via, B. Bellamy, M. Carlson. 2000. Secondary Effects of Enhanced
Coagulation and Softening. Journal AWWA, 92(6):63-75.
Cotton, C.A., D.M. Owen, G.C. Cline, T. P. Brodeur. 2001. UV Disinfect!on Costs for
Inactivating Cryptosporidium. Journal AWWA, 93 (6): 82-94.
Dowbiggin, W.B. and J.C. Thompson. 1990. Preparing for the Disinfection Byproducts
Regulations Case Studies. 1989 AWWA Annual Conference Proceedings.
EPA. 1999a. Alternative Disinfectants and Oxidants Guidance Manual (EPA 815-R-99-
014). Washington, D.C.
EPA. 1999b. Enhanced Coagulation and Enhanced Precipitative Softening Guidance
Manual (EPA 815-R-99-012). Washington, D.C.
Jacangelo, J.G., N.L. Patania, K.M. Reagan, E.M. Aieta, S.W. Krasner, and M.J. Mcguire.
1989. Impact of Ozonation on the Formation and Control of Disinfection Byproducts in
Drinking Water. Journal AWWA, 81(8):74.
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8. Treatment Considerations
Kawamura, Susumu. 2000. Integrated Design and Operation of Water Treatment
Facilities. Second Edition. John Wiley & Sons. New York, NY.
Kramer, L.A. and J. Horger. 1998. The Optimization of Coagulation Using Dual pH
Adjustment: The Philadelphia Water Department Prepares to Meet Stage 1 D/DBP. 1997
AWWA Water Quality Technology Conference Proceedings.
Malcolm Pirnie, Inc. 1992. Technologies and Costs for Control of Disinfection Byproducts.
Prepared for EPA, Washington, D.C.
Metropolitan and Montgomery. 1989. Disinfection Byproducts in United States Drinking
Waters. Metropolitan Water District of Southern California and James M. Montgomery
Consulting Engineers, Inc. Prepared for EPA, Washington, D.C.
Pinsky, D.E., H.J. Dunn, and A.F. Hess. 1991. CT Compliance Strategies: Three Case
Studies. 1990 AWWA Annual Conference Proceedings.
Schneider, O.D. and J.E. Tobiason. 2000. Preozonation Effects on Coagulation. Journal
AWWA, 92(10):74-87.
Singer, P.C., editor. 1999. Formation and Control of Disinfection By-Products in Drinking
Water. AWWA. Denver, CO.
Teefy, S., R. Shaver, and Almeda County Water District. 1995. From Model to Full Scale:
Modification of a Reservoir to Improve Contact Time. 1994 AWWA Annual Conference
Proceedings.
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Appendix A
Glossary
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Appendix A. Glossary
A.1 GLOSSARY
baffle. A flat board or plate, deflector, guide or similar device constructed or placed in
flowing water or slurry systems to cause more uniform flow velocities, to absorb energy,
and to divert, guide, or agitate liquids (water, chemical solutions, slurry).
baffling factor (BF). The ratio of the actual contact time to the theoretical detention time.
clarifier. A large circular or rectangular tank or basin in which water is held for a period of
time, during which the heavier suspended solids settle to the bottom by gravity. Clarifiers
are also called settling basins and sedimentation basins.
clearwell. A reservoir for the storage of filtered water with sufficient capacity to prevent
the need to vary the filtration rate in response to short-term changes in customer demand.
Also used to provide chlorine contact time for disinfection.
coagulant. A chemical added to water that has suspended and colloidal solids to destabilize
particles, allowing subsequent floe formation and removal by sedimentation, filtration, or
both.
coagulation. As defined in 40 CFR 141.2, a process using coagulant chemicals and mixing
by which colloidal and suspended materials are destabilized and agglomerated into floes.
community water system (CWS). A public water system which serves at least 15 service
connections used by year-round residents or regularly serves at least 25 year-round
residents.
conventional filtration treatment. As defined in 40 CFR 141.2, a series of processes
including coagulation, flocculation, sedimentation, and filtration resulting in substantial
particulate removal.
Cryptosporidium. A disease-causing protozoan widely found in surface water sources.
Cryptosporidium is spread by the fecal-oral route as a dormant oocyst from human and
animal feces. In its dormant stage, Cryptosporidium is housed in a very small, hard-shelled
oocyst form that is resistant to chlorine and chloramine disinfectants. When water
containing these oocysts is ingested, the protozoan may cause a severe gastrointestinal
disease called cryptosporidiosis.
CT or CTcaic- As defined in 40 CFR 141.2, the product of "residual disinfectant
concentration" (C) in mg/1 determined before or at the first customer, and the corresponding
"disinfectant contact time" (T) in minutes, i.e., "C" x "T". If a public water system applies
disinfectants at more than one point prior to the first customer, it must determine the CT of
each disinfectant sequence before or at the first customer to determine the total percent
inactivation or "total inactivation ratio". In determining the total inactivation ratio, the
public water system must determine the residual disinfectant concentration of each
disinfection sequence and corresponding contact time before any subsequent disinfection
application point(s). "CT99.9" is the CT value required for 99.9 percent (3-log) inactivation
of Giardia lamblia cysts. CT99.9 for a variety of disinfectants and conditions appear in
Tables 1.1- 1.6, 2.1, and 3.1 of §141.74(b)(3) inthe Code of Federal Regulations.
CTcaic/CT99.9 is the inactivation ratio. The sum of the inactivation ratios, or total inactivation
ratio shown as £ [(CTcaic) / (CT99.9)] is calculated by adding together the inactivation ratio
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Appendix A. Glossary
for each disinfection sequence. A total inactivation ratio equal to or greater than 1.0 is
assumed to provide a 3-log inactivation ofGiardia lamblia cysts.
detention time. The average length of time a drop of water or a suspended particle remains
in a tank or chamber. Mathematically, it may be determined by dividing the volume of
water in the tank by the flow rate through the tank.
diatomaceous earth filtration. As defined in 40 CFR 141.2, a process resulting in
substantial particulate removal, that uses a process in which: (1) a "precoat" cake of
diatomaceous earth filter media is deposited on a support membrane (septum), and (2) while
the water is filtered by passing through the cake on the septum, additional filter media,
known as "body feed," is continuously added to the feed water to maintain the permeability
of the filter cake.
direct filtration. As defined in 40 CFR 141.2, a series of processes including coagulation
and filtration, but excluding sedimentation, and resulting in substantial particulate removal.
disinfectant. As defined in 40 CFR 141.2, any oxidant, including but not limited to
chlorine, chlorine dioxide, chloramines, and ozone added to water in any part of the
treatment or distribution process, that is intended to kill or inactivate pathogenic
microorganisms.
disinfectant contact time. As defined in 40 CFR 141.2, the time in minutes that it takes for
water to move from the point of disinfectant application or the previous point of disinfectant
residual measurement to a point before or at the point where residual disinfectant
concentration ("C") is measured. Where only one "C" is measured, "T" is the time in
minutes that it takes for water to move from the point of disinfectant application to a point
before or at where residual disinfectant concentration ("C") is measured. Where more than
one "C" is measured, "T" is (a) for the first measurement of "C", the time in minutes that it
takes for water to move from the first or only point of disinfectant application to a point
before or at the point where the first "C" is measured and (b) for subsequent measurements
of "C", the time in minutes that it takes for water to move from the previous "C"
measurement point to the "C" measurement point for which the particular "T" is being
calculated. Disinfectant contact time in pipelines must be calculated based on "plug flow"
by dividing the internal volume of the pipe by the maximum hourly flow rate through that
pipe. Disinfectant contact time within mixing basins and storage reservoirs must be
determined by tracer studies or an equivalent demonstration.
disinfection. As defined in 40 CFR 141.2, a process which inactivates pathogenic
organisms in water by chemical oxidants or equivalent agents.
disinfection benchmark. The lowest monthly average microbial inactivation during the
disinfection profile time period.
disinfection byproduct precursors. Substances that can be converted into disinfection
byproducts during disinfection. Typically, most of these precursors are constituents of
natural organic matter. In addition, the bromide ion (Br") is a precursor material.
disinfection byproducts (DBFs). Inorganic and organic compounds formed by the reaction
of the disinfectant, natural organic matter, and the bromide ion during water disinfection
processes. Regulated DBFs include trihalomethanes, haloacetic acids, bromate, and chlorite.
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Appendix A. Glossary
disinfection profile. As stated in 40 CFR 141.530, a graphical representation of your
system's level of Giardia lamblia or virus inactivation measured during the course of a year.
disinfection segment. A section of the system beginning at one disinfectant injection or
monitoring point and ending at the next disinfectant injection or monitoring point.
effluent. Water or some other liquid that is raw, partially or completely treated that is
flowing from a reservoir, basin, treatment process or treatment plant.
enhanced coagulation. As defined in 40 CFR 141.2, the addition of sufficient coagulant
for improved removal of disinfection byproduct precursors by conventional filtration
treatment.
enhanced softening. As defined in 40 CFR 141.2, the improved removal of disinfection
byproduct precursors by precipitative softening.
filtration. As defined in 40 CFR 141.2, a process for removing particulate matter from
water by passage through porous media.
finished water. Water that has passed through a water treatment plant such that all the
treatment processes are completed or "finished" and ready to be delivered to consumers.
Also called product water.
flocculation. As defined in 40 CFR 141.2, a process to enhance agglomeration or collection
of smaller floe particles into larger, more easily settleable particles through gentle stirring by
hydraulic or mechanical means.
Giardia lamblia. Flagellated protozoan, which is shed during its cyst-stage with the feces of
man and animals. When water containing these cysts is ingested, the protozoan causes a
severe gastrointestinal disease called giardiasis.
ground water under the direct influence of surface water (GWUDI). As defined in 40
CFR 141.2, any water beneath the surface of the ground with significant occurrence of
insects or other macroorganisms, algae, or large-diameter pathogens such as Giardia
lamblia or Cryptosporidium, or 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 individual sources in
accordance with criteria established by the State. The State determination of direct influence
may be based on site-specific measurements of water quality and/or documentation of well
construction characteristics and geology with field evaluation.
haloacetic acids five (HAAS). As defined in 40 CFR 141.2, the sum of the concentrations
in milligrams per liter of the haloacetic acid compounds (monochloroacetic acid,
dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid),
rounded to two significant figures after addition.
influent water. Raw water plus recycle streams.
interpolation. A technique used to determine values that fall between the marked intervals
on a scale.
log inactivation. The percentage of microorganisms inactivated through disinfection by a
given process.
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Appendix A. Glossary
log reduction. The percentage of microorganisms reduced through log removal added to
the log inactivation. One log reduction means that 90% of the microorganisms are removed
or inactivated. Two log corresponds to 99%, three log is 99.9% and four log corresponds to
99.99%.
log removal. The percentage of microorganisms physically removed by a given process.
maximum contaminant level (MCL). As defined in 40 CFR 141.2, the maximum
permissible level of a contaminant in water which is delivered to any user of a public water
system.
membrane filtration. A filtration process (e.g., reverse osmosis, nanofiltration,
ultrafiltration, and microfiltration) using tubular or spiral-wound elements that exhibits the
ability to mechanically separate water from other ions and solids by creating a pressure
differential and flow across a membrane.
micrograms per liter (|J,g/L). One microgram of a substance dissolved in each liter of
water. This unit is equal to parts per billion (ppb) since one liter of water is equal in weight
to one billion micrograms.
micron. A unit of length equal to one micrometer (|im). One millionth of a meter or one
thousandth of a millimeter. One micron equals 0.00004 of an inch.
milligrams per liter (mg/L). A measure of concentration of a dissolved substance. A
concentration of one mg/L means that one milligram of a substance is dissolved in each liter
of water. For practical purposes, this unit is equal to parts per million (ppm) since one liter
of water is equal in weight to one million milligrams. Thus a liter of water containing 10
milligrams of calcium has 10 parts of calcium per one million parts of water, or 10 parts per
million (10 ppm).
non-community water system (NCWS). As defined in 40 CFR 141.2, a public water
system that is not a community water system. A non-community water system is either a
"transient non-community water system (TWS)" or a non-transient non-community water
system (NTNCWS)."
non-transient non-community water system (NTNCWS). As defined in 40 CFR 141.2, a
public water system that is not a community water system and that regularly serves at least
25 of the same persons over six months per year.
organics. Carbon-containing compounds that are derived from living organisms.
oxidant. Any oxidizing agent; a substance that readily oxidizes (removes electrons from)
something chemically. Common drinking water oxidants are chlorine, chlorine dioxide,
ozone, and potassium permanganate. Some oxidants also act as disinfectants.
oxidation. A process in which a molecule, atom, or ion loses electrons to an oxidant. The
oxidized substance (which lost the electrons) increases in positive valence. Oxidation never
occurs alone, but always as part of an oxidation-reduction (redox) reaction.
pathogens, or pathogenic organisms. Microorganisms that can cause disease (such as
typhoid, cholera, or dysentery) in other organisms or in humans, animals and plants. They
may be bacteria, viruses, or protozoans and are found in sewage, in runoff from animal
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Appendix A. Glossary
farms or rural areas populated with domestic and/or wild animals, and in water used for
swimming. There are many types of microorganisms which do not cause disease. These
microorganisms are called non-pathogens.
pH. pH is an expression of the intensity of the basic or acid condition of a solution.
Mathematically, pH is the negative logarithm (base 10) of the hydrogen ion concentration,
[H+]. [pH = log (1/H+)]. The pH may range from 0 to 14, where 0 is most acidic, 14 most
basic, and 7 neutral. Natural waters usually have a pH between 6.5 and 8.5.
plug flow. The water travels through a basin, pipe, or unit process in such a fashion that the
entire mass or volume is discharged at exactly the theoretical detention time of the unit.
pre-disinfection. The addition of a disinfectant to the treatment train prior to the primary
disinfectant injection location. Generally, the purpose of pre-disinfection is to obtain
additional inactivation credits, to control microbiological growth in subsequent treatment
processes, to improve coagulation, or to reduce tastes and odors.
primary disinfection. The disinfectant used in a treatment system to achieve the necessary
microbial inactivation.
public water system (PWS). As defined in 40 CFR 141.2, a system for the provision to the
public of water for human consumption through pipes or, after August 5, 1998, other
constructed conveyances, if such system has at least fifteen service connections or regularly
serves an average of at least twenty-five individuals daily at least 60 days out of the year.
Such term includes: any collection, treatment, storage, and distribution facilities under
control of the operator of such system and used primarily in connection with such system;
and any collection or pretreatment storage facilities not under such control which are used
primarily in connection with such system. Such term does not include any "special irrigation
district." A public water system is either a "community water system" or a "non-community
water system".
reservoir. Any natural or artificial holding area used to store, regulate, or control water.
secondary disinfection. The disinfectant application in a treatment system to maintain the
disinfection residual throughout the distribution system.
sedimentation. As defined in 40 CFR 141.2, a process for removal of solids before
filtration by gravity or separation.
short-circuiting. A hydraulic condition in a basin or unit process that occurs when the
actual flow time of water through the basin is less than the basin or unit process volume
divided by the peak hourly flow.
State. As defined in 40 CFR 141.2, the agency of the State or Tribal government which has
jurisdiction over public water systems. During any period when a State or Tribal
government does not have primary enforcement responsibility pursuant to Section 1413 of
the Safe Drinking Water Act, the term "State" means the Regional Administrator, U.S.
Environmental Protection Agency.
surface water. As defined in 40 CFR 141.2, all water which is open to the atmosphere and
subject to surface runoff.
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Appendix A. Glossary
total organic carbon (TOC). As defined in 40 CFR 141.2, total organic carbon in mg/L
measured using heat, oxygen, ultraviolet irradiation, chemical oxidants, or combinations of
these oxidants that convert organic carbon to carbon dioxide, rounded to two significant
figures.
total trihalomethanes (TTHM). As defined in 40 CFR 141.2, the sum of the concentration
in milligrams per liter of the trihalomethane compounds (trichloromethane [chloroform],
dibromochloromethane, bromodichloromethane and tribromomethane [bromoform]),
rounded to two significant figures.
trihalomethane (THM). As defined in 40 CFR 141.2, one of the family of organic
compounds, named as derivatives of methane, wherein three of the four hydrogen atoms in
methane are each substituted by a halogen atom in the molecular structure.
tracer. A foreign substance mixed with or attached to a given substance for subsequent
determination of the location or distribution of the foreign substance.
tracer study. A study using a substance that can readily be identified in water (such as a
dye) to determine the distribution and rate of flow in a basin, pipe, ground water, or stream
channel.
transient non-community water system. As defined in 40 CFR 141.2, means a non-
community water system that does not regularly serve at least 25 of the same persons over
six months per year.
virus. As defined in 40 CFR 141.2, a virus of fecal origin which is infectious to humans by
waterborne transmission.
water supply system. The collection, treatment, storage, and distribution of potable water
from source to consumer.
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Appendix A. Glossary
A.1 REFERENCES
Calabrese, E.J., C.E. Gilbert, and H. Pastides, editors. 1988. Safe Drinking Water Act
Amendments, Regulations and Standards. Lewis Publishers. Chelsea, MI.
California State University. 1988. Water Treatment Plant Operation. School of Engineering,
Applied Research and Design Center, Sacramento, CA.
Dzurik, A. A., Rowman, and Littlefield. 1990. Water Resources Planning. Savage, MD.
Symons, J., L. Bradley, Jr., and T. Cleveland, editors. 2000. The Drinking Water
Dictionary. AWWA. Denver, CO.
USEPA. 2002. Code of Federal Regulations, Title 40, Chapter I, Section 141.2. July 1.
von Huben, H. 1991. Surface Water Treatment: The New Rules. AWWA.
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Appendix A. Glossary
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Appendix B
CT Tables
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Appendix B. CT Tables
TABLE B-1
CT VALUES* FOR 3-LOG INACTIVATION
OF GIARDIA CYSTS BY FREE CHLORINE
Chlorine Concentration
(mg/L)
<=0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
Chlorine Concentration
(mg/L)
<=0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
Temperature <=0.5°C
pH
<=6.0 6.5 7.0 7.5 8.0 8.5 9.0
137
141
145
148
152
155
157
162
165
169
172
175
178
181
163
168
172
176
180
184
189
193
197
201
205
209
213
217
195
200
205
210
215
221
226
231
236
242
247
252
257
261
237
239
246
253
259
266
273
279
286
297
298
304
310
316
277
286
295
304
313
321
329
338
346
353
361
368
375
382
329
342
354
365
376
387
397
407
417
426
435
444
452
460
390
407
422
437
451
464
477
489
500
511
522
533
543
552
Temperature = 15°C
pH
<=6.0 6.5 7.0 7.5 8.0 8.5 9.0
49
50
52
53
54
55
56
57
58
59
60
61
62
63
59
60
61
63
64
65
66
68
69
70
72
73
74
76
70
72
73
75
76
78
79
81
83
85
86
88
89
91
83
86
88
90
92
94
96
98
100
102
105
107
109
111
99
102
105
108
111
114
116
119
122
124
127
129
132
134
118
122
126
130
134
137
141
144
147
150
153
156
159
162
140
146
151
156
160
165
169
173
177
181
184
188
191
195
Temperature =5°C
pH
<=6.0 6.5 7.0 7.5 8.0 8.5 9.0
97
100
103
105
107
109
111
114
116
118
120
122
124
126
117
120
122
125
127
130
132
135
138
140
143
146
148
151
139
143
146
149
152
155
158
162
165
169
172
175
178
182
166
171
175
179
183
187
192
196
200
204
209
213
217
221
198
204
210
216
221
227
232
238
243
248
253
258
263
268
236
244
252
260
267
274
281
287
294
300
306
312
318
324
279
291
301
312
320
329
337
345
353
361
368
375
382
389
Temperature = 20 °C
pH
<=6.0 6.5 7.0 7.5 8.0 8.5 9.0
36
38
39
39
40
41
42
43
44
44
45
46
47
47
44
45
46
47
48
49
50
51
52
53
54
55
56
57
52
54
55
56
57
58
59
61
62
63
65
66
67
68
62
64
66
67
69
70
72
74
75
77
78
80
81
83
74
77
79
81
83
85
87
89
91
93
95
97
99
101
89
92
95
98
100
103
105
108
110
113
115
117
119
122
105
109
113
117
120
123
126
129
132
135
138
141
143
146
Temperature = 10°C
pH
<=6.0 6.5 7.0 7.5 8.0 8.5 9.0
73
75
78
79
80
82
83
86
87
89
90
92
93
95
88
90
92
94
95
98
99
101
104
105
107
110
111
113
104
107
110
112
114
116
119
122
124
127
129
131
134
137
125
128
131
134
137
140
144
147
150
153
157
160
163
166
149
153
158
162
166
170
174
179
182
186
190
194
197
201
177
183
189
195
200
206
211
215
221
225
230
234
239
243
209
218
226
234
240
247
253
259
265
271
276
281
287
292
Temperature = 25°C
pH
<=6.0 6.5 7.0 7.5 8.0 8.5 9.0
24
25
26
26
27
27
28
29
29
30
30
31
31
32
29
30
31
31
32
33
33
34
35
35
36
37
37
38
35
36
37
37
38
39
40
41
41
42
43
44
45
46
42
43
44
45
46
47
48
49
50
51
52
53
54
55
50
51
53
54
55
57
58
60
61
62
63
65
66
67
59
61
63
65
67
69
70
72
74
75
77
78
80
81
70
73
75
78
80
82
84
86
88
90
92
94
96
97
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
TABLE B-2
CT VALUES* FOR
4- LOG INACTIVATION OF VIRUSES BY FREE CHLORINE
Temperature (°C)
0.5
5
10
15
20
25
6-9
12
8
6
4
3
2
PH
10
90
60
45
30
22
15
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
TABLE B-3
CT VALUES* FOR
3-LOG INACTIVATION OF GIARDIA CYSTS
BY CHLORINE DIOXIDE
Temperature (°C)
< = 1 5
63 26
10
23
15
19
20
15
25
11
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
TABLE B-4
CT VALUES* FOR
4-LOG INACTIVATION OF VIRUSES
BY CHLORINE DIOXIDE pH 6-9
Temperature (°C)
< = 1
50.1
5
33.4
10
25.1
15
16.7
20
12.5
25
8.4
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
TABLE B-5
CT VALUES* FOR
3-LOG INACTIVATION OF GIARDIA CYSTS
BY OZONE
Temperature (°C)
<= 1
2.9
5
1.90
10
1.43
15
0.95
20
0.72
25
0.48
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
TABLE B-6
CT VALUES* FOR
4-LOG INACTIVATION OF VIRUSES BY OZONE
Temperature (°C)
<= 1 5 10 15 20 25
1.8 1.2 1.0 0.6 0.5 0.3
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
TABLE B-7
CT VALUES* FOR
3-LOG INACTIVATION OF GIARDIA CYSTS
BY CHLORAMINE pH 6-9
Temperature (°C)
10 15 20 25
3,800 2,200 1,850 1,500 1,100 750
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
TABLE B-8
CT VALUES* FOR
4-LOG INACTIVATION OF VIRUSES BY CHLORAMINE
Temperature (°C)
10 15 20 25
2,883 1,988 1,491 994 746 497
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
TABLE B-9
CT VALUE* FOR
INACTIVATION OF VIRUSES BY UV
Log Inactivation
ZO 3J)
21 36
*Although units did not appear in the original tables, units are min-mg/L.
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Appendix B. CT Tables
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Appendix C
Blank Worksheets
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Appendix C. Blank Worksheets
The following worksheets can be used to record and report information to the State on
Giardia or virus inactivation. Systems should check with their State prior to using these
worksheets for acceptability.
A completed example of the Log Inactivation Ratio Determination worksheet
(Worksheet#l) can be found in Chapters 3 through 5 and Appendix D of this Guidance
Manual.
A completed example of the Total Log Inactivation Determination worksheet (Worksheet
#2) can be found in Chapter 5 and Appendix D of this Guidance Manual.
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Appendix C. Blank Worksheets
WORKSHEET #1
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER1
Starting Month:,
Year:
PWSID:
System/Water Source:_
Disinfectant Type:
Profile Type (check one):
Prepared by: _
_Giardia
_Vi ruses
Disinfection Segment/Sequence of Application :
Week
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
3
Residual
Disinf.
Cone.
C (mg/L)
4
pH
5
Water
Temp.
(°C)
6
Peak
Hourly
Flow
(gpm)
7
Volume
(gal)
8
TDT
(min.)
9
Baffling
Factor
10
Disinf.
Contact
Time
T (min.)
11
CTCalc =
(CxT)
(min-mg/L)
12
CT
Req'd
(min-mg/L)
13
Inactivation
Ratio
(Col 11 /Col 12)
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
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Appendix C. Blank Worksheets
Notes:
1. The system is only required to calculate log inactivation values once per week on the same day
of the week. For instance, the system may choose to calculate log inactivation values on
Wednesday of every week. If the system has more than one point of disinfectant application or
uses more than one type of disinfectant, then the system can calculate log inactivation ratios on
separate sheets and sum the log inactivation ratios to obtain the total inactivation achieved by
the plant using Worksheet #2 in Appendix C of the LT1ESWTR Disinfection Profiling and
Benchmarking Technical Guidance Manual.
2. Use a separate form for each disinfectant application point and related residual sample site.
Enter the disinfectant and sequence position, e.g., "ozone/1st" or "chlorine dioxide/3rd".
3. Disinfectant concentration must be measured during peak hourly flow.
4. If the system uses chlorine, the pH of the disinfected water must be measured at the same
location and time the chlorine residual disinfectant concentration is measured during peak hourly
flow.
5. The water temperature must be measured at the same location and time the residual disinfectant
concentration is measured during peak hourly flow. Temperature must be in degrees Celsius
(°C).
6. Peak hourly flow for the day must be provided for the disinfection segment.
7. The volume is the operating volume in gallons realized by the pipe, basin, or treatment unit
process during peak hourly flow.
8. Theoretical detention time in minutes equals the volume in gallons in column 7 divided by the
peak hourly flow in gpm in column 6.
9. Enter the baffling factor for the system's pipe, basin(s), or treatment unit process as determined
by a tracer study or assigned by the State.
10. Disinfectant contact time in minutes is determined by multiplying the theoretical detention time in
minutes in column 8 by the baffling factor in column 9.
11. CTcaic is determined by multiplying the residual disinfectant concentration in mg/L in column 3 by
the disinfectant contact time in minutes in column 10.
12. The CTrequired value should be determined based on the tables contained in Appendix B of the
LT1ESWTR Disinfection Profiling and Benchmarking Technical Guidance Manual or tables in the
Surface Water Treatment Rule Guidance Manual. CTreqUired for Giardia is CT99 9 (or 3-log
inactivation) and CTreqUired for viruses is CT9999(or4-log inactivation).
13. Inactivation ratio equals CTca|C in column 11 divided by CTrequired in column 12.
14. Log Inactivation for Giardia = 3 x Inactivation ratio in column 13.
Log Inactivation for viruses = 4 x Inactivation ratio in column 13.
For multiple disinfection segments, Worksheet #2 should be used to sum inactivation ratios for
each disinfection segment to calculate system log inactivation.
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Appendix C. Blank Worksheets
WORKSHEET #2
TOTAL LOG INACTIVATION DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: _
Year:
PWSID:
System/Water Source:
Disinfectant Type:
Profile Type (check one):
Prepared by: _
Giardia
Viruses
Week
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
Inactivation Ratio for each disinfection segment from Worksheet #1
Disinfection
Segment
1
Disinfection
Segment
2
Disinfection
Segment
3
Disinfection
Segment
4
Disinfection
Segment
5
Sum
of
Inactivation
Ratios
Total
Log
Inactivation1
1 Giardia : Log Inactivation = 3 x Sum of Inactivation Ratios
Viruses: Log Inactivation = 4 x Sum of Inactivation Ratios (or a method approved by the State)
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Appendix D
Examples
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Appendix D. Examples
This appendix provides example of ways a system may comply with the regulations for a
disinfection profile and a disinfection benchmark. This appendix does not establish any
additional requirements for completing a disinfection profile or a disinfection benchmark
beyond the regulations established in the LT1ESWTR.
The following examples are presented in this appendix:
• Example D-l: Calculate Actual Log Inactivation for One Disinfectant Page 125
• Example D-2: Calculate Actual Log Inactivation for Three Disinfection Segments
and Two Disinfectants Page 129
• Example D-3: Develop a Disinfection Profile and Benchmark for a System
with Multiple Disinfection Segments Page 143
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Appendix D. Examples
Example D-l: Calculate Actual Log Inactivation for One Disinfectant
One Disinfection Segment:
One injection point, one monitoring point
Chlorine
Injected
CT Monitoring Point
CI2 residual = 1.0 mg/L
Temperature = 10 °C
pH = 6
Distribution
System
In this example, the direct filtration treatment system added chlorine prior to the clearwell
and it was required to create a disinfection profile. The system must determine the log
inactivation for Giardia achieved through disinfection.
Step 1. Determine the peak hourly flow.
From the raw water pump records the peak hourly flow (Q) is determined to be 5,000
gallons per minute (gpm).
Step 2. Measure the chlorine residual, temperature, andpH (since chlorine is used)
during peak hourly flow at the monitoring point and at the same time.
Temperature = 10°C
pH = 6
Chlorine residual = CChiorine =1.0 mg/L
Step 3. Measure the physical dimensions of the clearwell.
Minimum Operating Depth
75 ft
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Appendix D. Examples
Example D-l continued
Measure the inner tank length and width to obtain the volume of water in the
clearwell rather than the volume of the tank itself.
Length = 75 ft
Width = 35 ft
Measure the minimum operating depth in the clearwell to obtain a conservative
estimate of the volume of water in the tank.
Minimum Operating Depth = 15.3 ft
Step 4. Calculate the volume of the water in the clearwell based on low water level.
Volume (V) = minimum water depth x length x width
V= 15.3 ft x 75 ft x 35 ft = 40,160 ft3
V = 40,160 ft3 x (7.48 gal/ft3)
V = 300,000 gal
Step 5. Calculate the Theoretical Detention Time (TDT) in the clearwell.
TDT = V / Q
TDT = 300,000 gal / 5,000 gpm
TDT = 60 minutes
Step 6. Determine the baffling factor (BF)for the clearwell
Clearwell BF = 0.5 (from Table G-l in Appendix G for average baffling condition
as shown below.)
Step 7. Calculate the contact time of the disinfectant in the clearwell.
Contact Time (T) = TDT x BF
T =60 minx 0.5
T = 30 minutes
EPA Guidance Manual 126
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
Appendix D. Examples
Example D-l continued
Step 8. Calculate the CT for the disinfection segment.
^ A calc ^chlorine X 1
CTcaic = 1.0 mg/L x 30 min
k = 30 min-mg/L
Step 9. Determine the required CT '99.9 necessary to obtain 3-log Giardia inactivation.
The required CT value for 3-log Giardia inactivation (CT99.9) may be obtained by
using CT Table B-l in Appendix B, CT Values for 3-Log Inactivation of Giardia
Cysts by Free Chlorine. In this example, the required CT99.9 is 79 min-mg/L for a
pH of 6, temperature of 10 °C, and Cchiorine of 1.0 mg/L. The relevant section of
Table B-l is reprinted below and the pertinent section of the table is highlighted.
Excerpt from Table B-l:
CT Values for 3 -Log Inactivation of Giardia Cysts by Free Chlorine
(10 °C portion of table, for concentrations from 0.4 to 1.2)
Chlorine
Concentration
(mg/L)
<=0.4
0.6
0.8
1.0
1.2
Temperature =
<=6.0
73
75
78
79
80
6.5
88
90
92
94
95
7.0
104
107
110
112
114
nH
pn
7.5
125
128
131
134
137
10 °C
8.0
149
153
158
162
166
8.5
177
183
189
195
200
9.0
209
218
226
234
240
Step 10. Calculate the inactivation ratio for the clearwell.
Inactivation ratio = CTcaic / CT99 9
= (30 min-mg/L) / (79 min-mg/L)
Inactivation ratio = 0 380
Step 11. Calculate the actual Giardia log inactivation for the clearwell.
Log inactivation = 3 x CTcaic / CT99.9
Log inactivation = 3 x 0.380
Log inactivation = 1.14
The Giardia log inactivation for this system is 1.14.
May 2003 127 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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Appendix D. Examples
Example D-l continued
Assuming the system received a 2.0 log Giardia removal credit from the State for direct
filtration, it must achieve at least 1.0 log Giardia inactivation for a total 3.0 log Giardia
reduction as required in the Surface Water Treatment Rule (40 CFR Section
141.70(a)(l)). The value of 1.14 log Giardia inactivation exceeds the required 1.0 log
Giardia inactivation. A calculation for virus inactivation does not need to be
performed since only free chlorine is used as a disinfectant.
The worksheets in Appendix C can be used to record data and calculate log inactivation.
The table below demonstrates how to record the data from this example using Worksheet #1
in Appendix C.
WORKSHEET #1
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
PWSID: AA6543210 System/Water Source: LMN Water Plant
Prepared by: Jim Operator
Viruses
Disinfection Segment/Sequence of Application: Clearwell/1st
Week
#
1
2
3
4
5
6
3
Residual
Disinf.
Cone.
C (mg/L)
1.0
4
PH
6
5
Water
Temp.
(°C)
10
6
Peak
Hourly
Flow
(gpm)
5,000
7
Volume
(gal)
300,000
8
TDT
(min.)
60
9
Baffling
Factor
0.5
10
Disinf.
Contact
Time
T (min.)
30
11
CTCalc =
(CxT)
(min-mg/L)
30.0
12
CT
Req'd
(min-mg/L)
79
13
Inactivation
Ratio
(Col 11 /Col 12)
0.38
14
Log
Inactivation*
1.14
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
EPA Guidance Manual 128
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
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Appendix D. Examples
Example D-2: Calculate Actual Log Inactivation for Three Disinfection
Segments and Two Disinfectants
Disinfection Segment 1
Chlorine
Sedimentation lk I -> 0=2-, c=$O C=$O -» Sedim8nt
I cJo 0 A 0 ^
Flocculation
ation ^
^
Dis
Se
Filtration
Disinfection Segment 1
Monitoring Point
CI2 residual = 1.0 mg/L
Temperature = 10°C
pH = 7.5
C
infect
gmen
ilorine
-
l~
Disinfection Segment 2
Monitoring Point
CI2 residual = 1.2 mg/L
Temperature = 1 0 °C
pH = 7.5
Disinfection Segment 3
Monitoring Point
Chloramine residual = 0.6 mg/L
Temperature = 10 °C
I '
I
I
I
I
J
on
2
rwell
I
\
Distribution
System
in 5
(D tfl
« =
3 =f
In this example chlorine is added to the conventional treatment system before coagulation as
a predisinfectant and again prior to the clearwell as a primary disinfectant. Ammonia is
added to the system after the clearwell to create chloramines as the secondary disinfectant to
maintain a residual throughout the distribution system. The system was required to create a
disinfection profile. Therefore, the system must determine the actual log inactivation for
Giardia (Note: In this example virus log inactivations do not need to be calculated because
chloramine is being used as a secondary disinfectant).
Since there are three points where the disinfectant is added, the inactivation ratio must be
calculated for each disinfection segment.
A. Determine the Giardia Inactivation Ratio for Disinfection Segment 1
Disinfection Segment 1 begins at the chlorine injection location just prior to coagulation and
ends at the chlorine monitoring point just after the filters.
Step 1. Determine the peak hourly flow.
From the raw water pump records the peak hourly flow (Q) is determined to be 5,000
gpm.
Step 2. Measure the chlorine residual, temperature, andpH (since chlorine is used)
during peak hourly flow at the chlorine monitoring point and at the same time.
Temperature = 10°C
pH = 75
Chlorine residual = CChiorine =1.0 mg/L
May 2003
129 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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Appendix D. Examples
Example D-2 continued
Step 3. Measure the physical dimensions of the sub-units in Disinfection Segment 1.
Measure inner tank diameter or length and width to obtain the volume of water in the
tanks rather than the volume of the tanks themselves.
Measure the minimum operating depth in the tanks, where applicable, to obtain
conservative estimates of the volume of water in the tanks.
Coagulation:
Length = 13.7ft
Width = 13.7ft
Depth =17.1 ft
Flocculation:
*;
q
•*
I
-66.4 ft-
Length = 66.4 ft
Width = 11.5ft
Depth = 14.0 ft
EPA Guidance Manual 130
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
Appendix D. Examples
Example D-2 continued
Sedimentation:
-39.9ft-
Diameter = 39.9ft
Depth = 10.7 ft
Filtration:
Top of Filter Media
20ft
°>-
Depth above filter media = 4 ft
Length = 20 ft
Width = 9.4 ft
Number of filters = 8
Step 4. Calculate the volume of the water in each sub-unit in Disinfection Segment 1.
Coagulation:
Volume (V) = Length x Width x Depth
V= 13.7 ft x 13.7 ft x 17.1 ft =3,210 ft3
V= 3,210 ft 3x (7.48 gal / ft3)
V= 24,000 gallons
Flocculation:
Volume (V) = Length x Width x Depth
V= 66.4 ft x 11.5 ft x 14.0 ft = 10,690ft3
V= 10,690 ft3 x (7.48 gal / ft3)
V= 80,000 gallons
May 2003
131 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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Appendix D. Examples
Example D-2 continued
Sedimentation:
Volume (V) = K x Radius2 x Depth
71 =3.14 (constant)
Radius = Diameter / 2 = 39.9 / 2 = 19.95 ft
V= 3.14 x (19.95 ft)2 x 10.7 ft = 13,370 ft3
V= 13,370 ft3 x (7.48 gal / ft3)
V= 100,000 gallons
Filtration:
Volume (V) = Length x Width x Depth of Water Above Media x # of Filters
V= 20 ft x 9.4 ft x 4 ft x 8 filters = 6,020 ft3
V= 6,020 ft3 x (7.48 gal / ft3)
V= 45,000 gallons
Step 5. Calculate the Theoretical Detention Time (TDT) in the sub-units in Disinfection
Segment 1.
TDT = V / Q
Coagulation:
TDT = 24,000 gal / 5,000 gpm
TDT = 4.8 minutes
Flocculation:
TDT = 80,000 gal / 5,000 gpm
TDT = 16 minutes
Sedimentation:
TDT = 100,000 gal / 5,000 gpm
TDT = 20 minutes
Filtration:
TDT = 45,000 gal / 5,000 gpm
TDT = 9 minutes
EPA Guidance Manual 132 May 2003
LT1ESWTR Disinfection Profiling and Benchmarking
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Appendix D. Examples
Example D-2 continued
Step 6. Determine the baffling factors (BF)for the sub-units in Disinfection Segment 1.
The table below summarizes the baffling factors in this example for the sub-units in
Disinfection Segment 1.
Unit Process
(1) Coagulation
(2) Flocculation
(3) Sedimentation
(4) Filtration
BF*
0.1
0.1
0.5
0.7
*See Appendix G for Baffling Factors
Step 7. Calculate the contact time (T) in the sub-units in Disinfection Segment 1.
T = TDT x BF
Coagulation:
T= 4.8 minx 0.1
T= 0.48 minutes
Flocculation:
T= 16 minx 0.1
T= 1.6 minutes
Sedimentation:
T= 20 minx 0.5
T= 10 minutes
Filtration:
T= 9 minx 0.7
T= 6.3 minutes
Step 8. Calculate the total contact time in Disinfection Segment 1.
Total Contact Time (Ttotai) = Sum of T in each sub-unit
Ttotai = 0.48 min +1.6 min + 10 min + 6.3 min
= 18.4 minutes
May 2003
133 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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Appendix D. Examples
Example D-2 continued
Step 9. Calculate the CTfor Disinfection Segment 1 (CTcaic)
^ A calc ^chlorine X 1 total
CTcalc = 1.0 mg/L x 18.4 min
CTcaic = 18.4 min-mg/L
The CTcaic for Disinfection Segment 1 = 18.4 min-mg/L
Step 10. Determine the required CTV? necessary to obtain 3-log Giardia inactivation.
The required CT value for 3-log Giardia inactivation (CT99.9) may be obtained by
using CT Table B-l in Appendix B, CT Values for 3-Log Inactivation of Giardia
Cysts by Free Chlorine. The CT99.9 in this example is 134 min-mg/L for a pH of 7.5,
temperature of 10 °C, and Chorine of 1.0 mg/L. The relevant section of Table B-l is
reprinted below and the pertinent section of the table is highlighted.
Excerpt from Table B-l:
CT Values for 3-Log Inactivation of Giardia Cysts by Free Chlorine
(10 °C portion of table, for concentrations from 0.6 to 1.4)
Chlorine
Concentration
(mg/L)
0.6
0.8
1.0
1.2
1.4
Temperature =
<=6.0
75
78
79
80
82
6.5
90
92
94
95
98
7.0
107
110
112
114
116
nH
pn
7.5
128
131
134
137
140
10 °C
8.0
153
158
162
166
170
8.5
183
189
195
200
206
9.0
218
226
234
240
247
Step 11. Calculate the inactivation ratio for Disinfection Segment 1.
Inactivation ratio = CTcaic /
Inactivation ratio = (18.4 min-mg/L) / (134 min-mg/L)
Inactivation ratio = 0.137
EPA Guidance Manual 134
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
Appendix D. Examples
Example D-2 continued
B. Determine the Giardia Inactivation Ratio for Disinfection Segment 2
Disinfection Segment 2 in this example begins at the chlorine injection location just prior to
the clearwell and ends just after the clearwell.
Step 1. Determine the peak hourly flow.
The peak hourly flow (Q) for Disinfection Segment 2 is the same as the peak hourly
flow in Disinfection Segment 1.
Peak hourly flow = 5,000 gpm.
Step 2. Measure the chlorine residual, temperature, andpH (since chlorine is used)
during peak hourly flow at the chlorine monitoring point and at the same time.
Temperature = 10°C
Chlorine residual = CChiorine =1.2 mg/L
pH = 7.5
Step 3. Measure the physical dimensions of the clearwell.
Minimum Operating Depth
75 ft
Measure the inner tank length and width to obtain the volume of water in the
clearwell rather than the volume of the tank itself.
Length = 75 ft
Width = 35 ft
Measure the minimum operating depth in the clearwell to obtain a conservative
estimate of the volume of water in the tank.
Minimum Operating Depth = 15.3 ft
May 2003
135 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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Appendix D. Examples
Example D-2 continued
Step 4. Calculate the volume of the water in the clearwell based on low water level.
Volume (V) = minimum water depth x length x width
V= 15.3 ft x 75 ft x 35 ft = 40,160 ft3
V = 40,160 ft3 x (7.48 gal / ft3)
V = 300,000 gal
Step 5. Calculate the Theoretical Detention Time in the clearwell.
Theoretical Detention Time (TDT) = V / Q
TDT = 300,000 gal / 5,000 gpm
TDT = 60 minutes
Step 6. Determine the baffling factor for the clearwell.
Clearwell Baffling Factor (BF) = 0.7 (from Table G-l for superior baffling
condition as shown below.)
"D
;
u
•a
_TL
Jl
I
I
Step 7. Calculate the contact time of the disinfectant in the clearwell.
Contact Time (T) = TDT x BF
T =60 minx 0.7
T = 42 minutes
Step 8. Calculate the CTfor the disinfection segment.
^ A calc ^chlorine X 1
CTcaic = 1.2 mg/L x 42 min
k = 50 min-mg/L
EPA Guidance Manual 136
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
Appendix D. Examples
Example D-2 continued
Step 9. Determine the required CT99,9 necessary to obtain 3-log Giardia inactivation.
The required CT value for 3-log Giardia inactivation (CT99.9) may be obtained by
using CT Table B-l in Appendix B, CT Values for 3-Log Inactivation of Giardia
Cysts by Free Chlorine. The CT99.9 in this example is 137 min-mg/L for a pH of 7.5,
temperature of 10 °C, and Chorine of 1.2 mg/L. The relevant section of Table B-l is
reprinted below and the pertinent section of the table is highlighted.
Excerpt from Table B-l:
CT Values for 3-Log Inactivation of Giardia Cysts by Free Chlorine
(10 °C portion of table, for concentrations from 0.8 to 1.6)
Chlorine
Concentration
(mg/L)
0.8
1.0
1.2
1.4
1.6
Temperature =
<=6.0
78
79
80
82
83
6.5
92
94
95
98
99
7.0
110
112
114
116
119
nH
pn
7.5
131
134
137
140
144
10 °C
8.0
158
162
166
170
174
8.5
189
195
200
206
211
9.0
226
234
240
247
253
Step 10. Calculate the inactivation ratio for the clearwell.
Inactivation ratio = CTcaic / CT99.9
Inactivation ratio = (50 min-mg/L) / (137 min-mg/L)
Inactivation ratio = 0.365
C. Determine the Giardia Inactivation Ratio for Disinfection Segment 3
Disinfection Segment 3 in this example begins at the chloramine injection location after the
clearwell and ends at the monitoring point in the transmission pipe, which is prior to the first
customer.
Step 1. Determine the peak hourly flow.
The peak hourly flow (Q) for Disinfection Segment 3 is the same as the peak hourly
flow in Disinfection Segment 1.
Peak hourly flow = 5,000 gpm.
May 2003 137 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
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Appendix D. Examples
Example D-2 continued
Step 2. Measure the chloramine residual and temperature during peak hourly flow at the
chlorine monitoring point and at the same time.
Temperature = 10°C
Chloramine residual = CChioramine = 0.6 mg/L
Step 3. Measure the physical dimensions of the pipe.
, 5,280 Feet ,
Q )
Side View
Diameter = 12 in
h
End View
(Closeup)
Measure the length of the pipe and the inner pipe diameter to obtain the volume of
water in the pipe rather than the volume of the pipe itself.
Diameter = 12 in x (1 ft / 12 in) = 1 ft
Length = 5,280 ft
Step 4. Calculate the volume of the water in the pipe.
Volume (V) = TT x Radius2 x Length
71 =3.14 (constant)
Radius = Diameter / 2 = 1.0 / 2 = 0.5 ft
V= 3.14 x (0.5 ft)2 x 5,280 ft = 4,140 ft3
V= 4,140 ft3 x (7.48 gal/ft3)
V= 31,000 gallons
Step 5. Calculate the Theoretical Detention Time in the pipe.
Theoretical Detention Time (TDT) = V / Q
TDT = 31,000 gal / 5,000 gpm
TDT = 6.2 minutes
EPA Guidance Manual 138 May 2003
LT1ESWTR Disinfection Profiling and Benchmarking
-------
Appendix D. Examples
Example D-2 continued
Step 6. Determine the baffling factor for the pipe.
Baffling Factor (BF) = 1.0 (from Table G-l in Appendix G for a pipe)
Step 7. Calculate the contact time of the disinfectant in the pipe.
Contact Time (T) = TDT x BF
T =6.2 minx 1.0
T = 6.2 minutes
Step 8. Calculate the CTfor the disinfection segment.
^ A calc ^chloramine X 1
CTcaic = 0.6 mg/L x 6.2 min
CTcak = 3.7 min-mg/L
Step 9. Determine the required CT'99.9 necessary to obtain 3-log Giardia inactivation.
The required CT value for 3-log Giardia inactivation (CT99.9) may be obtained by
using CT Table B-7 in Appendix B, CT Values for 3-Log Inactivation of Giardia
Cysts by Chloramine pH 6-9. The CT99.9 in this example is 1,850 min-mg/L for a
temperature of 10 °C. Table B-7 is reprinted below and the pertinent section of the
table is highlighted.
Table B-7:
CT Values for 3-Log Inactivation of Giardia Cysts by Chloramine pH 6-9
Temperature (°C)
< = 1
3,800
5
2,200
10
1,850
15
1,500
20
1,100
25
750
Step 10. Calculate the inactivation ratio for the pipe.
Inactivation ratio = CTcaic / CT99.9
Inactivation ratio = (3.7 min-mg/L) / (1,850 min-mg/L)
Inactivation ratio = 0 002
May 2003 139 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
-------
Appendix D. Examples
Example D-2 continued
D. Determine Total Giardia Log Inactivation for the System.
Step 1. Determine the total Giardia inactivation ratio for the system,
Total Inactivation ratio = E (CTcaic / CT99.9) = 0.137 + 0.365 + 0.002 = 0.504
Step 2. Determine the total Giardia log inactivation for the system,
Total log inactivation = 3 x E (CTcaic / CT99.9)
Total log inactivation = 3 x (0.504)
Total log inactivation = 151
The total Giardia log inactivation for the system is 1.51.
Assuming the system received a 2.5 log Giardia removal credit from the State for
conventional filtration, it must achieve at least 0.5 log Giardia inactivation for a total
3.0 log Giardia reduction as required in the Surface Water Treatment Rule (40 CFR
Section 141.70(a)(l)). The value of 1.51 log Giardia inactivation exceeds the required
0.5 log Giardia inactivation. A calculation for virus inactivation does not need to be
performed since only free chlorine is used as the primary disinfectant.
E. Worksheets
The worksheets in Appendix C can be used to record data and calculate log inactivation.
The table below summarizes the calculations for each unit process in Disinfection
Segment 1.
Unit Process
Coagulation
Flocculation
Sedimentation
Filtration
Total:
Volume (gal)
24,000
80,000
100,000
45,000
249,000
Peak Hourly Flow (gpm)
5,000
5,000
5,000
5,000
BF*
0.1
0.1
0.5
0.7
Contact Time (min)
0.48
1.6
10
6.3
18.4
See Appendix G for baffling factors.
EPA Guidance Manual 140
LT1ESWTR Disinfection Profiling and Benchmarking
May 2003
-------
Appendix D. Examples
Example D-2 continued
The worksheet excerpt below demonstrates how data may be recorded from Disinfection
Segment 1 using Worksheet #1 in Appendix C. For this example, Worksheet #1 needs to be
copied so the data from each disinfection segment can be entered.
WORKSHEET #1
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
PWSID: AA7654321 System/Water Source: ABC Water Plant
Prepared by: Jon Operator
Viruses
Disinfection Segment/Sequence of Application: Coagulation, Flocculation, Sedimentation, Filtration/1 st
Week
#
1
2
3
4
5
6
3
Residual
Disinf.
Cone.
C (mg/L)
1.0
4
PH
7.5
5
Water
Temp.
(°C)
10
6
Peak
Hourly
Flow
(gpm)
5,000
7
Volume
(gai)
249,000
8
TDT
(min.)
»»
9
Baffling
Factor
»»
10
Disinf.
Contact
Time
T (min.)
18.4
11
CTcalc =
(CxT)
(min-mg/L)
18.4
12
CT
Req'd
(min-mg/L)
134
13
Inactivation
Ratio
(Col 11 /Col 12)
0.137
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
"See the previous table showing details of each unit process for theoretical detention times and baffling factors.
The worksheet excerpt below demonstrates how data may be recorded from Disinfection
Segment 2 using Worksheet #1 in Appendix C.
WORKSHEET #1
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
Disinfectant Type: Free Chlorine
Profile Type (check one): X Giardia
PWSID: AA7654321 System/Water Source: ABC Water Plant
Prepared by: Jon Operator
Viruses
Disinfection Segment/Sequence of Application: Clearwell/2nd
Week
#
1
2
3
4
5
6
3
Residual
Disinf.
Cone.
C (mg/L)
1.2
4
PH
7.5
5
Water
Temp.
(°C)
10
6
Peak
Hourly
Flow
(gpm)
5,000
7
Volume
(gai)
300,000
8
TDT
(min.)
60
9
Baffling
Factor
0.7
10
Disinf.
Contact
Time
T (min.)
42
11
CTcalc =
(CxT)
(min-mg/L)
50
12
CT
Req'd
(min-mg/L)
137
13
Inactivation
Ratio
(Col 11 /Col 12)
0.365
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
May 2003
141 EPA Guidance Manual
LT1ESWTR Disinfection Profiling and Benchmarking
-------
Appendix D. Examples
Example D-2 continued
The worksheet excerpt below demonstrates how data may be recorded from Disinfection
Segment 3 using Worksheet #1 in Appendix C.
WORKSHEET #1
LOG INACTIVATION RATIO DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
Disinfectant Type: Chloramine
Profile Type (check one): X Giardia
PWSID: AA7654321 System/Water Source: ABC Water Plant
Prepared by: Jon Operator
Viruses
Disinfection Segment/Sequence of Application: Transmission Pipe/3rd
Week
#
1
2
3
4
5
6
3
Residual
Disinf.
Cone.
C (mg/L)
0.6
4
PH
N/A
5
Water
Temp.
(°C)
10
6
Peak
Hourly
Flow
(gpm)
5,000
7
Volume
(gal)
31 ,000
8
TDT
(min.)
6.2
9
Baffling
Factor
1.0
10
Disinf.
Contact
Time
T (min.)
6.2
11
CTCalc =
(CxT)
(min-mg/L)
3.7
12
CT
Req'd
(min-mg/L)
1,850
13
Inactivation
Ratio
(Col 11 /Col 12)
0.002
14
Log
Inactivation*
*See worksheet #2 to determine total log inactivation if the system has multiple disinfection segments.
The worksheet excerpt below demonstrates how to determine total Giardia log inactivation
for the system using Worksheet #2 in Appendix C.
WORKSHEET #2
TOTAL LOG INACTIVATION DETERMINATION FOR SURFACE WATER SYSTEMS OR
GROUND WATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER
Starting Month: January
Year: 2004
PWSID: AA7654321
System/Water Source: ABC Water Plant
Disinfectant Type: Chlorine/Chloramine
Profile Type (check one): X Giardia
Prepared by: Jon Operator
Viruses
Week
#
1
2
3
4
5
6
Inactivation Ratio for each disinfection segment from Worksheet #1
Disinfection
Segment
1
0.137
Disinfection
Segment
2
0.365
Disinfection
Segment
3
0.002
Disinfection
Segment
4
Disinfection
Segment
5
Sum
of
Inactivation
Ratios
0.504
Total
Log
Inactivation1
1.51
Giardia: Log Inactivation = 3 x Sum of Inactivation Ratios
Viruses: Log Inactivation = 4 x Sum of Inactivation Ratios (or a method approved by the State)
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Appendix D. Examples
Example D-3: Develop a Disinfection Profile and Benchmark for a System
with Multiple Disinfection Segments
In this example a conventional filtration treatment plant added ozone in contact chambers at
the front of the plant as a primary disinfectant and used chlorine as the secondary
disinfectant after the clearwell. The ozone residual was measured at each ozone contact
chamber and the chlorine residual was measured in the transmission pipe. The system was
required to create a disinfection profile. Since ozone is used as a primary disinfectant, the
system must calculate both Giardict and virus log inactivations.
Disinfection Disinfection Disinfection
Segment 1 Segment 2 Segments
Ozone Contact Chambers
See enlarged drawing below
Flocculation
Sedimentation
Filtration
Clearwell
Chlorine -
Disinfection Segment 4
Monitoring Point
Chlorine Residual = 0.8 mg/L
Temperature = 0.5 °C
pH = 7.0
To
Distribution
System
Disinfection
Segment 1
C1in = 0.0 mg/L
C1out = °'
Disinfection
Segment 2
Temp = 0.5 °C
C2in = 0.4 mg/L
2out '
Temp = 0.5 °C
Disinfection
Segments
Temp = 0.5 °C
C, = 0
1
Chamber 1
° o0° °o
o °o ° °
1
Chamber 2
° o0° °o
o °o ° °
Chambers
° o0° °o
o °o ° °
4
k
C3in = 0.6 mg/L
Temp = 0.5 °C
NOTE: Following is one method for calculating Giardia inactivation for ozone using
the procedure presented in Guidance Manual for Compliance with the Filtration and
Disinfection Requirements for Public Water Systems Using Surface Water Sources (EPA,
March 1991). Systems must use a method approved by the State; therefore, systems
should check with the State to determine if it approves this method or if another
method is required.
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Appendix D. Examples
Example D-3 continued
A. Determine the Giardia Log Inactivation for Disinfection Segment 1
Step 1. Measure the ozone residual at the inlet and outlet of Contact Chamber 1 during
peak hourly flow.
Ciin = 0.0 mg/L
= 0.5mg/L
Table D-l. Correlations to Predict C Based on Inlet and Outlet Ozone
Concentrations
Flow Configuration
First Chamber
All Other
Chambers
Turbine
C
^ '-'OUt
Co-Current Flow
Partial Credit1
^ ^out
or
C = (C0ut+Cin)/2
Counter-Current
Flow
Partial Credit1
C = C0ut / 2
Reactive Flow
Not Applicable
^ ^out
1. 1-log of vims inactivation providing that Cout > 0.1 mg/L and 0.50 log Giardia inactivation providing that
Cout> 0.3 mg/L.
(Source: Guidance Manual for Compliance with the Filtration and Disinfection
Requirements for Public Water Systems Using Surface Water Sources, EPA, March 1991)
Step 2. Determine the Giardia log inactivation in Contact Chamber 1.
In Contact Chamber 1 the flow is counter-current since the water flows in the
opposite direction that the ozone flows (Note: Ozone is introduced in the bottom of
the chamber and bubbles upward). According to Table D-l, since the outlet ozone
concentration is 0.5 mg/L, which is greater than 0.3 mg/L, the Giardia log
inactivation in Contact Chamber 1 is 0.50.
B. Determine the Giardia Log Inactivation for Disinfection Segment 2
Step 1. Measure the temperature and the ozone residual at the inlet and outlet of Contact
Chamber 2 during peak hourly flow.
Temperature = 0.5 °C
C2in = 0.4 mg/L
C2out = 0.6 mg/L
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Appendix D. Examples
Example D-3 continued
Step 2. Determine C in Contact Chamber 2.
Table D-l. Correlations to Predict C Based on Inlet and Outlet Ozone
Concentrations
Flow Configuration
First Chamber
All Other
Chambers
Turbine
C
c — c
^ '-'OUt
Co-Current Flow
Partial Credit1
c — c
^ '-'OUt
or
C = (Gout + Gin) / 2
Counter-Current
Flow
Partial Credit1
C = C0ut / 2
Reactive Flow
Not Applicable
c — c
^ '-'OUt
1. 1-log of vims inactivation providing that Cout > 0.1 mg/L and 0.50 log Giardia inactivation providing that
Cout>0.3mg/L.
(Source: Guidance Manual for Compliance with the Filtration and Disinfection
Requirements for Public Water Systems Using Surface Water Sources, EPA, March 1991)
In Contact Chamber 2 the flow is counter-current since the water flows in the
opposite direction that the ozone flows. According to Table D-l, C = Cout / 2 for
contact chambers with counter-current flow.
C = C2out / 2
C = 0.6 mg/L / 2
C = 0.3 mg/L
Step 3. Determine the contact time in Contact Chamber 2.
The contact time for all of the ozone contact chambers taken together was
determined by a tracer study to be 15 minutes at peak hourly flow. The total contact
time can be divided proportionally by volume between all three chambers if the
chambers with final concentrations of zero (non-detectable) do not make up 50% or
greater of the total volume of the chambers. Since the final concentration in all
chambers is greater than zero and since the contact chambers are all identical with
equal volumes the contact time can be divided equally between all three chambers:
T = Ttot / 3 chambers =15 min / 3 chambers = 5 minutes per chamber
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Appendix D. Examples
Example D-3 continued
Step 4. Calculate CTcaic in Contact Chamber 2.
CTcalc = C x T
CTcaic = 0.3 mg/L x 5 min
k = 1.5 min-mg/L
Step 5. Locate appropriate CT table.
The table for 3-log inactivation ofGiardia by ozone is Table B-5 in Appendix B.
Step 6. Identify the appropriate portion of the table based on operating conditions.
Locate the column for 0.5 °C (< = 1 °C).
Table B-5
CT Values for 3 -Log Inactivation ofGiardia Cysts by Ozone
Temperature (°C)
< = 1
2.9
5
1.90
10
1.43
15
0.95
20
0.72
25
0.48
Step 7. Obtain CTw.? value.
From this chart it is determined that the value of CT for 3-log inactivation by ozone at 0.5°C
is 2.9 min-mg/L.
CT99.9 = 2.9 min-mg/L
Step 8. Calculate the Giardia inactivation ratio for Disinfection Segment 2.
Inactivation ratio = CTcaic / CT99.9
Inactivation ratio = (1.5 min-mg/L / 2.9 min-mg/L)
Inactivation ratio = 0.517
Step 9. Calculate Giardia inactivation for Disinfection Segment 2.
Giardia log inactivation = 3 x (CTcaic /
Giardia log inactivation = 3 x 0.517
Giardia log inactivation = 1.55
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Appendix D. Examples
Example D-3 continued
C. Determine the Giardia Log Inactivation for Disinfection Segment 3
Step 1. Measure the temperature and the ozone residual at the inlet and outlet of Contact
Chamber 3 during peak hourly flow.
Temperature = 0.5 °C
C3in = 0.6 mg/L
C3out = 0.1 mg/L
Step 2. Determine C in Contact Chamber 3.
Table D-l. Correlations to Predict C Based on Inlet and Outlet Ozone
Concentrations
Flow Configuration
First Chamber
All Other
Chambers
Turbine
C
c — c
^ '-'OUt
Co-Current Flow
Partial Credit1
^ ^out
or
C = (Cout + Gin) / 2
Counter-Current
Flow
Partial Credit1
C = C0ut / 2
Reactive Flow
Not Applicable
c — c
^ '-'OUt
1. 1-log of vims inactivation providing that Cout > 0.1 mg/L and 0.50 log Giardia inactivation providing that
Cout> 0.3 mg/L.
(Source: Guidance Manual for Compliance with the Filtration and Disinfection
Requirements for Public Water Systems Using Surface Water Sources, EPA, March 1991)
In Contact Chamber 3 the flow is co-current since the water flows in the same
direction that the ozone flows. According to Table D-l, C = (Cout + C;n) / 2 for
contact chambers with co-current flow.
C = (C3in + C3out) / 2
C = (0.6 mg/L + 0.1 mg/L) / 2
C = 0.35 mg/L
Step 3. Determine the contact time in Contact Chamber 3.
It was determined in Part B, Step 3 of this example that the contact time in each
chamber is 5 minutes.
T = 5 minutes
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Appendix D. Examples
Example D-3 continued
Step 4. Calculate CTcaic in Contact Chamber 3.
CTcalc = C x T
CTcaic = 0.35 mg/L x 5 min
k = 1.75 min-mg/L
Step 5. Locate appropriate CT table.
The table for 3-log inactivation ofGiardia by ozone is Table B-5 in Appendix B.
Step 6. Identify the appropriate portion of the table based on operating conditions.
Locate the column for 0.5 °C (< = 1 °C).
Table B-5
CT Values for 3 -Log Inactivation ofGiardia Cysts by Ozone
Temperature (°C)
< = 1
2.9
5
1.90
10
1.43
15
0.95
20
0.72
25
0.48
Step 7. Obtain CTw.? value.
From this chart it is determined that the value of CT for 3-log inactivation by ozone at 0.5°C
is 2.9 min-mg/L.
CT99.9 = 2.9 min-mg/L
Step 8. Calculate the Giardia inactivation ratio for Disinfection Segment 3.
Inactivation ratio = CTcaic / CT99.9
Inactivation ratio = (1.75 min-mg/L / 2.9 min-mg/L)
Inactivation ratio = 0.603
Step 9. Calculate Giardia inactivation for Disinfection Segment 3.
Giardia log inactivation = 3 x (CTcaic /
Giardia log inactivation = 3 x 0.603
Giardia log inactivation = 1.81
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Appendix D. Examples
Example D-3 continued
D. Determine Giardia Log Inactivation for Disinfection Segment 4
Step 1. Determine the peak hourly flow.
From the raw water pump records the peak hourly flow (Q) is determined to be 5,000
gpm.
Step 2. Measure chlorine residual, temperature, andpH during peak hourly flow at the
chlorine monitoring point and at the same time.
Temperature = 0.5 °C
pH = 70
Chlorine residual = CChiorine= 0.8 mg/L
Step 3. Measure the physical dimensions of the pipe.
I 5,280 Feet I
h— 'I
n)
Side View
Diameter = 12 in
H
End View
(Closeup)
Measure the length of the pipe and the inner pipe diameter to obtain the volume of
water in the pipe rather than the volume of the pipe itself.
Diameter = 12 in x (1 ft / 12 in) = 1.0 ft
Length = 5,280 ft
Step 4. Calculate the volume of the water in the pipe.
Volume (V) = K x Radius2 x Length
71 =3.14 (constant)
Radius = Diameter / 2 = 1.0 / 2 = 0.5 ft
V= 3.14 x (0.5 ft)2 x 5,280 ft = 4,140 ft3
V= 4,140 ft3 x (7.48 gal/ft3)
V= 31,000 gallons
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Appendix D. Examples
Example D-3 continued
Step 5. Calculate the Theoretical Detention Time in the pipe.
Theoretical Detention Time (TDT) = V / Q
TDT = 31,000 gal / 5,000 gpm
TDT = 6.2 minutes
Step 6. Determine the baffling factor for the pipe.
Baffling Factor (BF) = 1.0 (from Table G-l in Appendix G for a pipe)
Step 7. Calculate the contact time of the disinfectant in the pipe.
Contact Time (T) = TDT x BF
T =6.2 minx 1.0
T = 6.2 minutes
Step 8. Calculate the CT for the disinfection segment.
^ A calc ^chlorine X 1
CTcaic = 0.8 mg/L x 6.2 min
k = 5.0 min-mg/L
Step 9. Determine the required CT 99,9 necessary to obtain 3-log Giardia inactivation.
The required CT value for 3-log Giardia inactivation (CTgg.g) is obtained by using
CT Table B-l in Appendix B, CT Values for 3-Log Inactivation of Giardia Cysts by
Free Chlorine. The CTgg.g is 205 min-mg/L for a pH of 7.0, temperature of 0.5 °C,
and Cchiorine of 0.8 mg/L. The relevant section of Table B-l is reprinted below and
the pertinent section of the table is highlighted.
Excerpt from Table B-l:
CT Values for 3 -Log Inactivation of Giardia Cysts by Free Chlorine
(0.5 °C portion of table, for concentrations from 0.4 to 1.2 mg/L)
Chlorine
Concentration
(mg/L)
<=0.4
0.6
0.8
1.0
1.2
Temperature
<=6.0
137
141
145
148
152
6.5
163
169
172
176
180
7.0
195
200
205
210
215
PH
7.5
237
239
246
253
259
= 0.5°C
8.0
277
286
295
304
313
8.5
329
342
354
365
376
9.0
390
407
422
437
451
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Appendix D. Examples
Example D-3 continued
Step 10. Calculate the Giardia inactivation ratio for the pipe.
Inactivation ratio = CTcaic / CT99 9
Inactivation ratio = (5.0 min-mg/L / 205 min-mg/L)
Inactivation ratio = 0.024
Step 11. Calculate the actual Giardia log inactivation for the pipe.
Log inactivation = 3 x CTcaic / 0X99.9
Log inactivation = 3 x 0.024
Log inactivation = 0 07
The log inactivation of Giardia for Disinfection Segment 4 is 0.07.
E. Calculate the Total Giardia Inactivation for the System
Step 1. Sum the Giardia log inactivations for all of the disinfection segments to
determine the total Giardia log inactivation achieved by the system.
From Disinfection Segment 1:
Giardia log inactivation = 0.50
From Disinfection Segment 2:
Giardia log inactivation =1.55
From Disinfection Segment 3:
Giardia log inactivation =1.81
From Disinfection Segment 4:
Giardia log inactivation = 0.07
Total Giardia log inactivation = 0.50 + 1.55 + 1.81 + 0.07 = 3.93
Assuming the system received a 2.5 log Giardia removal credit from the State for
conventional filtration, it must achieve at least 0.5 log Giardia inactivation for a total
3.0 log Giardia reduction as required in the Surface Water Treatment Rule (40 CFR
Section 141.70(a)(l)). The value of 3.93 log Giardia inactivation exceeds the required
0.5 log Giardia inactivation.
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Appendix D. Examples
Example D-3 continued
F. Determine Virus Log Inactivation for Disinfection Segment 1
Since ozone is used as a primary disinfectant in this system, the log inactivation for viruses
must also be calculated.
Step 1. Determine the virus log inactivation in Contact Chamber 1.
Table D-l. Correlations to Predict C Based on Inlet and Outlet Ozone
Concentrations
Flow Configuration
First Chamber
All Other
Chambers
Turbine
C
^ '-'out
Co-Current Flow
Partial Credit1
p — p
^ '-'out
or
C = (C0ut+Cin)/2
Counter-Current
Flow
Partial Credit1
C = C0ut / 2
Reactive Flow
Not Applicable
^ '-'OUt
1. 1-log of vims inactivation providing that Cout > 0.1 mg/L and 0.50 log Giardia inactivation providing that
Cout>0.3mg/L.
(Source: Guidance Manual for Compliance with the Filtration and Disinfection
Requirements for Public Water Systems Using Surface Water Sources, EPA, March 1991)
In Contact Chamber 1 the flow is counter-current since the water flows in the
opposite direction that the ozone flows (Note: Ozone is introduced in the bottom of
the chamber and bubbles upward). According to Table D-l, since the outlet ozone
concentration is 0.5 mg/L (determined in Part A of this Example), which is greater
than 0.1 mg/L, the virus log inactivation in Disinfection Segment 1 (Contact
Chamber 1) is 1.0.
G. Determine Virus Log Inactivation for Disinfection Segment 2
Step 1. Determine the required CT'99.99 necessary to obtain 4-log virus inactivation for
Contact Chamber 2.
The required CT value for 4-log virus inactivation (CT99.99) is obtained by using CT Table
B-6 in Appendix B, CT Values for 4-Log Inactivation of Viruses by Ozone. In this example
the required CT99.99 is 1.8 min-mg/L for a temperature of 0.5 °C.
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Appendix D. Examples
Example D-3 continued
Table B-6
CT Values for 4-Log Inactivation of Viruses by Ozone
Temperature (°C)
< = 1
1.8
5
1.2
10
1.0
15
0.6
20
0.5
25
0.3
Step 2. Calculate the virus inactivation ratio for Contact Chamber 2.
CTcaic has already been calculated for Disinfection Segment 2.
CTcaic =1.5 min-mg/L
Inactivation ratio = CTcaic / 0X99.9
Inactivation ratio = (1.5 min-mg/L / 1.8 min-mg/L)
Inactivation ratio = 0.833
Step 3. Calculate the virus inactivation for Contact Chamber 2.
Virus log inactivation = 4 x CTcaic / CT99.99
Virus log inactivation = 4 x 0.833
Virus log inactivation = 3.3
The log inactivation of viruses for Disinfection Segment 2 is 3.3.
H. Determine Virus Log Inactivation for Disinfection Segment 3
Step 1. Determine the required CT'99.99 necessary to obtain 4-log virus inactivation for
Contact Chamber 3.
The required CT value for 4-log virus inactivation (CT99.99) is obtained by using CT Table
B-6 in Appendix B, CT Values for 4-Log Inactivation of Viruses by Ozone. The required
.gg is 1.8 min-mg/L for a temperature of 0.5 °C.
Table B-6
CT Values for 4-Log Inactivation of Viruses by Ozone
Temperature (°C)
<= 1 5
1.8 1.2
10 15 20 25
1.0 0.6 0.5 0.3
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Appendix D. Examples
Example D-3 continued
Step 2. Calculate the virus inactivation ratio for Contact Chamber 3.
CTcaic has already been calculated for Disinfection Segment 3.
CTcaic = 1.75 min-mg/L
Inactivation ratio = CTcaic / CT99.9
Inactivation ratio = (1.75 min-mg/L / 1.8 min-mg/L)
Inactivation ratio = 0.972
Step 3. Calculate the actual virus log inactivation for Contact Chamber 3.
Log inactivation = 4 x CTcaic / 0X99.99
Log inactivation = 4 x 0.972
Log inactivation = 3.9
The log inactivation of viruses for Disinfection Segment 3 is 3.9.
I. Determine Virus Log Inactivation for Disinfection Segment 4.
Even though chlorine is the only disinfectant used in Disinfection Segment 4, the virus
inactivation for Disinfection Segment 4 must also be calculated to determine the virus
inactivation for the whole system.
Step 1. Determine the required CT 99,99 necessary to obtain 4-log virus inactivation for
Disinfection Segment 4.
The required CT value for 4-log virus inactivation (CTgg.gg) is obtained by using CT Table
B-2 in Appendix B, CT Values for 4-log Inactivation of Viruses by Free Chlorine. The
required CT99.99 is 12 min-mg/L for a pH of 7.0 and temperature of 0.5 °C. Table B-2 is
reprinted on the next page and the pertinent section of the table is highlighted.
Table B-2:
CT Values for 4-Log Inactivation of Viruses by Free Chlorine
Temperature (°C)
0.5
5
10
15
20
25
6-9
12
8
6
4
3
2
PH
10
90
60
45
30
22
15
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Appendix D. Examples
Example D-3 continued
Step 2. Calculate the virus inactivation ratio for Disinfection Segment 4.
CTcaic has already been calculated for Disinfection Segment 4.
CTcaic = 5.0 min-mg/L
Inactivation ratio = CTcaic / CT99.9
Inactivation ratio = (5.0 min-mg/L / 12 min-mg/L)
Inactivation ratio = 0.417
Step 3. Calculate the actual virus log inactivation for Disinfection Segment 4.
Log inactivation = 4 x CTcaic / 0X99.99
Log inactivation = 4 x 0.417
Log inactivation =1.7
J. Calculate the Total Virus Inactivation for the System
Sum the virus log inactivations for all of the Disinfection Segments to determine the total
virus log inactivation achieved by the system,
From Disinfection Segment 1:
virus log inactivation =1.0
From Disinfection Segment 2:
virus log inactivation = 3.3
From Disinfection Segment 3:
virus log inactivation = 3.9
From Disinfection Segment 4:
virus log inactivation =1.7
Total virus log inactivation = 1.0 + 3.3 + 3.9 + 1.7 = 9.9
Assuming the system received a 2.0 log virus removal credit from the State for
conventional filtration, it must achieve at least 2.0 log virus inactivation for a total 4.0
log virus reduction as required in the Surface Water Treatment Rule (40 CFR Section
141.70(a)(2)). The value of 9.9 log virus inactivation exceeds the required 2.0 log virus
inactivation.
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Appendix D. Examples
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Appendix E
Tracer Studies
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Appendix E. Tracer Studies
E.1 INTRODUCTION
Information in this appendix is based on Appendix C in the Guidance Manual for
Compliance with the Filtration and Disinfection Requirements for Public Water Systems
Using Surface Water Sources (EPA, 1991). For more information on tracer studies, readers
are encouraged to consult Appendix C in the Guidance Manual for Compliance with the
Filtration and Disinfection Requirements for Public Water Systems Using Surface Water
Sources (EPA, 1991) or Tracer Studies in Water Treatment Facilities: A Protocol and Case
Studies (Teefy, 1996).
As indicated in Chapter 4, fluid passing through a 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 will be required to
determine the contact time for the calculation of CT through tracer studies or other methods
approved by the State.
The contact time of mixing basins and storage reservoirs used in calculating CT should be
the minimum detention time experienced by 90 percent of the water passing through the
unit. This detention time was designated as TIO according to the convention adopted by
Thirumurthi (1969). A profile of the flow through the basin over time can be generated by
tracer studies. Information provided by these studies may be used for estimating the
detention time, TIO, for the purpose of calculating CT. (Note: TIO is referred to as "T"
elsewhere in this document. However, for consistency with the Guidance Manual for
Compliance with the Filtration and Disinfection Requirements for Public Water Systems
Using Surface Water Sources (EPA, 1991), TIO is used in this appendix.)
This appendix presents a brief synopsis of tracer study methods, procedures, and data
evaluation. More detailed information about conducting tracer studies is available in
Appendix C of the lengthier Guidance Manual for Compliance with the Filtration and
Disinfection Requirements for Public Water Systems Using Surface Water Sources (EPA,
1991). It is important to obtain assistance from the State before conducting a tracer study to
ensure State approval of the results.
E.2 FLOW EVALUATION
Although detention time is proportional to flow, it is not generally a linear function. Tracer
studies may establish detention times for the range of flow rates experienced within each
disinfectant segment. Systems should note that a single flow rate might not characterize the
flow through the entire system. With a series of reservoirs, clearwells, and storage tanks,
flow will vary between each portion of the system.
Ideally, tracer tests should be performed for at least four flow rates that span the entire range
of flow for the segment being tested. The flow rates should be separated by approximately
equal intervals to span the range of operation, with one near average flow, two greater than
average, and one less than average flow. The flows should also be selected so that the
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Appendix E. Tracer Studies
highest test flow rate is at least 91 percent of the highest flow rate expected to ever occur in
that segment. Four data points should assure a good definition of the segment's hydraulic
profile.
The results of the tracer tests performed for different flow rates should be used to generate
plots of TIO versus flow (Q) for each segment in the system. A smooth line is drawn through
the points on each graph to create a curve from which TIO may be read for the corresponding
flow at peak hourly flow conditions. Refer to Appendix C, section C.I.7 of the Guidance
Manual for Compliance with the Filtration and Disinfection Requirements for Public Water
Systems Using Surface Water Sources (EPA, 1991), for an illustration of this procedure.
The most accurate tracer test results are obtained when flow is constant through the segment
during the course of the test. Therefore, the tracer study should be conducted at a constant
flow whenever practical. For a treatment plant consisting of two or more equivalent process
trains, a constant flow tracer test can be performed on a segment of the plant by holding the
flow through one of the trains constant while operating the parallel train(s) to absorb any
flow variations. Flow variations during tracer tests in systems without parallel trains or with
single clearwells and storage reservoirs are more difficult to avoid. In these instances, TIO
should be recorded at the average flow rate over the course of the test.
E.3 VOLUME EVALUATION
In addition to flow conditions, detention times determined by tracer studies depend on the
water level and subsequent volume in treatment units. This is particularly pertinent to
storage tanks, reservoirs, and clearwells, which, in addition to being contact basins for
disinfection are also often used as equalization storage for distribution system demands and
storage for backwashing. In such instances, the water levels in the reservoirs 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.
For some process units, especially sedimentation basins that are operated at a near constant
level (that is, flow in equals flow out), the detention time determined by tracer tests should
be sufficient for calculating CT when the basin is operating at water levels greater than or
equal to the level at which the test was performed. When conducting a tracer study to
determine the detention time, a water level at or slightly below, but not above, the normal
minimum operating level is recommended. 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).
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Appendix E. Tracer Studies
E.4 DISINFECTION SEGMENTS
For systems that apply disinfectant(s) at more than one point, or choose to profile the
residual from one point of application, tracer studies should be conducted to determine TIO
for each segment containing process unit(s). The TIO for a segment may or may not include
a length of pipe and is used along with the residual disinfectant concentration prior to the
next disinfectant application or monitoring point to determine the CTcaic for that segment.
The inactivation ratio for the section is then determined. The total log inactivation achieved
in the system can then be determined by summing the inactivation ratios for all sections as
explained in Chapter 5 of this document.
For systems that have two or more units of identical size and configuration, tracer studies
could be conducted on one of the units but applied to both. The resulting graph of TIO
versus flow can be used to determine TIO for all identical units.
Systems with more than one segment in the treatment plant that are conducting a tracer
study may determine TIO for each segment:
• By individual tracer studies through each segment; or,
• By one tracer study across the system.
If possible, tracer studies should be conducted on each segment to determine the TIO for each
segment. In order to minimize the time needed to conduct studies on each segment, the
tracer studies should be started at the last segment of the treatment train prior to the first
customer and completed with the first segment of the system. Conducting the tracer studies
in this order will prevent the interference of residual tracer material with subsequent studies.
For 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 or oxygen
should be added in lieu of ozone to prevent degradation of the tracer. The flow rate of air or
oxygen used for the contactor should be applied during the study to simulate actual
operation. Tracer studies should then be conducted at several air/oxygen 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.
E.5 TRACER STUDY METHODS
This section discusses the two most common methods of tracer addition employed in water
treatment evaluations, the step-dose method and the slug-dose method. Tracer study
methods involve the application of chemical dosages to a system, and tracking the resulting
effluent concentration as a function of time. The effluent concentration profile is evaluated
to determine the detention time, TIO.
In preparation for beginning a tracer study, the raw water background concentration of the
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Appendix E. Tracer Studies
chosen tracer chemical should be established. The background concentration is important,
not only to aid in the selection of the tracer dosage, but also to facilitate proper evaluation of
the data.
The background tracer concentration should be determined by monitoring for the tracer
chemical prior to beginning the test. The sampling point(s) for the pre-tracer study
monitoring should be the same as the points to be used for residual monitoring to determine
CT values. Systems should use the following monitoring procedure:
• 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.
Equal sampling intervals, as could be obtained from automatic sampling, are not required for
either tracer study method. However, using equal sample intervals for the slug-dose method
can simplify the analysis of the data. During testing, the time and tracer residual of each
measurement should also be recorded on a data sheet. In addition, the water level, flow, and
temperature should be recorded during the test.
E.5.1 Step-Dose Method
The step-dose method entails introduction of a tracer chemical at a constant dosage until the
concentration at the desired end point reaches a steady-state level. At time zero, the tracer
chemical feed is 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)
at a frequency determined by the overall detention time and site-specific considerations. As
a general guideline, sampling at intervals of 2 to 5 minutes should provide data for a well-
defined plot of tracer concentration versus time. If on-site analysis is available, less frequent
residual monitoring may be possible until a change in residual concentration is first detected.
Regular sampling is continued until the residual concentration reaches a steady-state value.
One graphical method of evaluating step-dose test data involves plotting a graph of
dimensionless concentration (tracer concentration (C) / applied tracer concentration (C0))
versus time and reading the value for TIO directly from the graph at the appropriate
dimensionless concentration. Alternatively, the data from step-dose tracer studies may be
evaluated numerically by developing a semi-logarithmic plot of the dimensionless data. The
semi-logarithmic plot allows a straight line to be drawn through the data. The resulting
equation of the line is used to calculate the TIO value, assuming that the correlation
coefficient indicates a good statistical fit (0.9 or above). Drawing a smooth curve through
the data discredits scattered data points from step-dose tracer tests.
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Appendix E. Tracer Studies
Step-dose tracer studies are frequently employed in drinking water applications for the
following reasons:
• The resulting normalized concentration versus time profile is directly used to
determine TIO, the detention time required for calculating CT; and,
• 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-dose method is that the data may be verified by comparing
the concentration versus elapsed time profile for samples collected at the start of dosing with
the profile obtained when the tracer feed is discontinued.
E.5.2 Slug-Dose Method
In the slug-dose method, a large instantaneous dose of tracer is added to the incoming water
and samples are taken at the exit of the unit over time as the tracer passes through the unit.
At time zero for the slug-dose method, a large instantaneous dose of tracer is added to the
influent of the unit. The same sampling locations and frequencies described for step-dose
method tests also apply to slug-dose method tracer studies. One exception with this method
is that the tracer concentration profile will not equilibrate to a steady-state concentration.
Because of this, the tracer should be monitored frequently enough to ensure acquisition of
data needed to identify the peak tracer concentration.
Slug-dose method tests should be checked by performing a material balance to ensure that
all of the tracer fed is recovered, or mass applied equals mass discharged.
Data from slug-dose tracer tests may be analyzed by converting it to the mathematically
equivalent step-dose data and using the techniques discussed above for the step-dose method
to determine TIQ. A graph of dimensionless concentration versus time should be drawn
which represents the results of a slug-dose tracer test. The key to converting between the
data forms is obtaining the total area under the slug-dose data curve. This area is found by
integrating the curve graphically or numerically. The conversion to step-dose data is then
completed in several mathematical steps involving the total area.
Slug-dose concentration profiles can have many shapes, depending on the hydraulics of the
basin. Therefore, slug-dose data points should not be discredited by drawing a smooth curve
through the data prior to its conversion to step-dose data.
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Appendix E. Tracer Studies
A disadvantage of the slug-dose method is that very concentrated solutions are needed for
the dose in order to adequately define the concentration versus time profile. Intensive
mixing is therefore necessary to minimize potential density-current effects and to obtain a
uniform distribution of the instantaneous tracer dose across the basin. This is inherently
difficult under water flow conditions often existing at inlets to basins. Other disadvantages
of using the slug-dose method include:
• The concentration and volume of the instantaneous tracer dose needs to be carefully
computed to provide an adequate tracer profile at the effluent of the basin;
• The resulting concentration versus time profile should not be used to directly
determine TIQ without further manipulation; and,
• A mass balance on the treatment segment should be used to determine whether the
tracer was completely recovered.
One advantage of this method is that it may be applied where chemical feed equipment is
not available at the desired point of addition, or where the equipment available does not
have the capacity to provide the necessary concentration of the chosen tracer chemical.
Although, in general, the step-dose procedure offers the greatest simplicity, both methods
are theoretically equivalent for determining TIQ. Either method or another method may be
used for conducting drinking water tracer studies, and the choice of method may be
determined by site-specific constraints or the system's experience.
E.6 TRACER SELECTION
An important step in any tracer study is the selection of a chemical to be used as the tracer.
Ideally, the selected tracer chemical should be readily available, conservative (that is, not
consumed or removed during treatment), easily monitored, and acceptable for use in potable
water supplies. Chloride and fluoride are the most common tracer chemicals employed in
drinking water plants that are nontoxic and approved for potable water use. Rhodamine WT
can be used as a fluorescent tracer in water flow studies in accordance with the following
guidelines:
• Raw water concentrations should be limited to a maximum concentration of 10
mg/L;
• Drinking water concentrations should not exceed 0.1 ug/L;
• Studies that result in human exposure to the dye should be brief and infrequent; and,
• Concentrations as low as 2 |ig/L can be used in tracer studies because of the low
detection level in the range of 0.1 to 0.2 ug/L.
The use of Rhodamine B as a tracer in water flow studies is not recommended by the EPA.
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Appendix E. Tracer Studies
The choice of a tracer chemical can be made based, in part, on the selected dosing method
and on the availability of chemical feeding equipment. For example, the high density of
concentrated salt solutions and their potential for inducing density currents usually precludes
chloride and fluoride as the selected chemical for slug-dose tracer tests.
Fluoride can be a convenient tracer chemical for step-dose tracer tests of clearwells because
it is frequently applied for finished water treatment. However, when fluoride is used in
tracer tests on clarifiers, allowances should be made for fluoride that is absorbed on floe and
settles out of water (Hudson, 1975). Additional considerations when using fluoride in tracer
studies include:
• It is difficult to detect at low levels,
• Many states impose a finished water limitation of 1 mg/L; and,
• The federal secondary and primary drinking water standards (i.e., the MCLs) for
fluoride are 2 and 4 mg/L, respectively.
For safety reasons, particularly for people on dialysis, fluoride is not recommended for use
as a tracer in systems that normally do not fluoridate their water. The use of fluoride is only
recommended in cases where the feed equipment is already in place. The system may wish
to turn off the fluoride feed in the plant for 12 or more hours prior to beginning the fluoride
feed for the tracer study. Flushing out fluoride residuals from the system prior to conducting
the tracer study is recommended to reduce background levels and avoid spiked levels of
fluoride that might exceed EPA's MCL or SMCL for fluoride in drinking water. In
instances where only one of two or more parallel units is tested, flow from the other units
would dilute the tracer concentration prior to leaving the plant and entering the distribution
system. Therefore, the impact of drinking water standards on the use of fluoride and other
tracer chemicals can be alleviated in some cases.
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Appendix E. Tracer Studies
E.7 REFERENCES
EPA. 1991. Guidance Manual for Compliance with the Filtration and Disinfection
Requirements for Public Water Systems using Surface Water Sources. Washington, D.C.
Hudson, H.E., Jr. 1975. Residence Times in Pretreatment. Journal AWWA, 67(1): 45-52.
Teefy, Susan. 1996. Tracer Studies in Water Treatment Facilities: A Protocol and Case
Studies. American Water Works Association Research Foundation. Denver, CO.
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Appendix F
Calculating the Volume of
Each Sub-Unit
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Appendix F. Calculating the Volume of Each Sub-Unit
Note: If dimensions are in feet and the volume is calculated in cubic feet, then the volume
should be converted to gallons by using the conversion: 1 ft3 = 7.48 gal.
Water Pipe (raw or treated):
Fluid Volume = Length x Cross-Sectional Area (Assumes full-pipe flow)
Side View
Length
Rectangular Basin:
Fluid Volume = Length x Width x
Minimum Water Depth
Cross-Section View
Cross-Sectional Area = 3.1416 * r2
r = inner radius = d / 2
d = inner diameter
Length
Width
\
\
Water Level
. . Minimum Water Depth
Cylindrical Basin:
Fluid Volume = Minimum Water Depth x Cross-Sectional Area
Side View
(^ ^j
.^Water Leyel^,
/
\
\
Minimum
Water Dep1
Top View
Cross-Sectional Area = 3.1416 * r2
r = inner radius = d / 2
d = inner diameter
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Appendix F. Calculating the Volume of Each Sub-Unit
Filters
Fluid Volume = Volume of Water Above Filter Surface
= Length x Width x Depth of Water Above Filter Surface
Length
"Width
Depth of
Water Above
Filter Surface
Note: Some States may give credit for volume in media. Check with the State for the
appropriate method to use for calculating volume in media.
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Appendix G
Baffling Factors
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Appendix G. Baffling Factors
G.1 INTRODUCTION
Information in this appendix is based on Appendix C in the Guidance Manual for
Compliance with the Filtration and Disinfection Requirements for Public Water Systems
Using Surface Water Sources (EPA, 1991). References to the main body of the report,
section headers, and some terminology have been modified to relate better to the content of
this Disinfection Profiling and Benchmarking Technical Guidance Manual. (Note: TIO is
referred to as "T" elsewhere in this document. However, for consistency with the
Guidance Manual for Compliance with the Filtration and Disinfection Requirements for
Public Water Systems Using Surface Water Sources (EPA, 1991), TIO is used in this
appendix.)
In some situations, conducting tracer studies for determining the disinfectant contact time,
TIO, may be impractical or prohibitively expensive. The limitations may include a lack of
funds, personnel, or equipment necessary to conduct the study. States may allow the use of
"rule of thumb" fractions representing the ratio of TIO to T, and the theoretical detention
time (TDT), to determine the detention time, TIO, to be used for calculating CT values. This
method for finding TIO involves multiplying the TDT by the rule of thumb fraction, Ti0/T,
which is representative of the particular basin configuration for which TIO is desired. These
fractions provide rough estimates of the actual TIO and systems should coordinate with their
State when selecting a baffling factor.
Tracer studies conducted by Marske and Boyle (1973) and Hudson (1975) on chlorine
contact chambers and flocculators/settling basins, respectively, were used as a basis in
determining representative Tio/T values for various basin configurations. Marske and Boyle
(1973) performed tracer studies on 15 distinctly different types of full-scale chlorine contact
chambers to evaluate design characteristics that affect the actual detention time. Hudson
(1975) 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.
G.2 IMPACT OF DESIGN CHARACTERISTICS
The significant design characteristics include length-to-width ratio, the degree of baffling
within the 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.
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The ratio Tio/T was calculated from the data presented in the studies and compared to its
associated hydraulic flow characteristics. Both studies resulted in Tio/T values that ranged
from 0.3 to 0.7. The results of the studies indicate how basin baffling conditions can
influence the Tio/T ratio, particularly baffling at the inlet and outlet to the basin. As the
basin baffling conditions improved, higher Tio/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 Tio/T fraction is more
related to the geometry and baffling of the basin than the function of the basin. For this
reason, Tio/T values may be defined for five levels of baffling conditions rather than for
particular types of contact basins. General guidelines were developed relating the Ti0/T
values from these studies to the respective baffling characteristics. These guidelines can be
used to determine the TIO values for specific basins.
G.3 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. 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. Five
general classifications of baffling conditions - unbaffled, poor, average, superior, and
perfect (plug flow) - were developed to categorize the results of the tracer studies for use in
determining TIO from the TDT of a specific basin. The Ti0/T fractions associated with each
degree of baffling are summarized in Table G-l. Factors representing the ratio between TIO
and the TDT for plug flow in pipelines and flow in a completely mixed chamber have been
included in Table G-l for comparative purposes. However, in practice the theoretical Tio/T
values of 1.0 for plug flow and 0.1 for mixed flow are seldom achieved because of the effect
of dead space. Conversely, the Tio/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.
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Appendix G. Baffling Factors
Table G-l. Baffling Classifications
Baffling Condition
Unbaffled (mixed flow)
Poor
Average
Superior
Perfect (plug flow)
TlO/T
0.1
0.3
0.5
0.7
1.0
Baffling Description
None, agitated basin, very low length to
width ratio, high inlet and outlet flow
velocities.
Single or multiple unbaffled inlets and
outlets, no intra-basin baffles.
Baffled inlet or outlet with some intra-basin
baffles.
Perforated inlet baffle, serpentine or
perforated intra-basin baffles, outlet weir or
perforated launders.
Very high length to width ratio (pipeline
flow), perforated inlet, outlet, and intra-
basin baffles.
As indicated in Table G-l, poor baffling conditions consist of an unbaffled inlet and outlet
with no intra-basin baffling. Average baffling conditions 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 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 to cause horizontal and/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 weirs, such as sharp-crested and
multiple 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.
G.4 EXAMPLES OF BAFFLING
Examples of these levels of baffling conditions for rectangular and circular basins are
explained and illustrated in this section. Typical uses of various forms of baffled and
unbaffled inlet and outlet structures are also illustrated.
The plan and section of a rectangular basin with poor baffling conditions, which can be
attributed to the unbaffled inlet and outlet pipes, are illustrated in Figure G-l. The flow
pattern shown in the plan view indicates 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
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Appendix G. Baffling Factors
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 in Figure G-2. 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 basin.
Consequently, dead space exists in the corners of the 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 basin.
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Appendix G. Baffling Factors
Figure G-l. Poor Baffling Conditions- Rectangular Contact Basin
Plan View
Section View
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Appendix G. Baffling Factors
Figure G-2. Average Baffling Conditions- Rectangular Contact Basin
Plan View
Section View
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Appendix G. Baffling Factors
Superior baffling conditions are exemplified by the flow pattern and physical characteristics
of the basin shown in Figure G-3. 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 uniformly throughout the basin's cross-section. The outlet structure is a sharp-
crested weir that extends for the entire width of the contact basin. This 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.
Figure G-3. Superior Baffling Conditions- Rectangular Contact Basin
a
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Appendix G. Baffling Factors
The plan and section of a circular basin with poor baffling conditions, which can be
attributed to flow short circuiting from the center feed well directly to the effluent trough are
shown in Figure G-4. 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 in Figure G-5 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.
Figure G-4. Poor Baffling Conditions- Circular Contact Basin
Plan View
Section View
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Appendix G. Baffling Factors
Figure G-5. Average Baffling Conditions- Circular Contact Basin
Plan View
Section View
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Appendix G. Baffling Factors
Superior baffling conditions are attained in the basin configuration shown on Figure G-6
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.
Figure G-6. Superior Baffling Conditions- Circular Contact Basin
Plan View
Section View
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Appendix G. Baffling Factors
G.5 ADDITIONAL CONSIDERATIONS
Flocculation basins and ozone contactors represent water treatment processes with slightly
different characteristics from those presented in Figures G-l through G-6 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 Tio/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 Tio/T values in the range of 0.5 to
0.7. This observation indicates that not only will compartmentation result in higher Tio/T
values through better flow distribution, but also that the effects of agitation intensity on
Tio/T are reduced where sufficient baffling exists. Therefore, regardless of the extent of
agitation, baffled flocculation basins with two or more compartments should be considered
to possess average baffling conditions (Ti0/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 that approach those of completely mixed basins, with a
Tio/T of 0.1, as a result of the intense mixing.
In many cases, settling basins are integrated with 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
integrated flocculators without effective inlet baffling should be considered as poorly
baffled, with a Tio/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 Tio/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 that 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 TIQ. 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 TDT by dividing this volume by the flow through the filter (Check with the
State on what volume may be allowed in a filter). The TDT may then be multiplied by a
factor of 0.7, corresponding to superior baffling conditions, to determine the TIO value.
G.6 CONCLUSIONS
The recommended Tio/T values and examples are presented as a guideline for use by the
State in determining TIQ. Conditions that are combinations or variations of the above
examples may exist and warrant the use of intermediate Tio/T values such as 0.4 or 0.6. As
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Appendix G. Baffling Factors
more data on tracer studies become available, specifically correlations between other
physical characteristics of basins and the flow distribution efficiency parameters, further
refinements to the Tio/T fractions and definitions of baffling conditions may be appropriate.
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Appendix G. Baffling Factors
G.7 REFERENCES
EPA. 1991. Guidance Manual for Compliance with the Filtration and Disinfection
Requirements for Public Water Systems using Surface Water Sources. Washington, D.C.
Hudson, H.E., Jr. 1975. Residence Times in Pretreatment. Journal AWWA, 67(1): 45-52.
Marske, D.M. and J.D. Boyle. 1973. Chlorine Contact Chamber Design - A Field
Evaluation. Water and Sewage Works, January, pp. 70-77.
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Appendix H
Conservative Estimate and
Interpolation Examples
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Appendix H. Conservative Estimate and Interpolation Examples
In some instances, the collected data for the disinfection profile will not coincide exactly
with the values in the CT tables. The following examples present two methods on how to
obtain 0X99.9 values. Systems should check with the State if these methods are acceptable
for obtaining CT99.9.
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Appendix H. Conservative Estimate and Interpolation Examples
Example H-l: Conservative Estimate Example for Obtaining CT99.9
One Disinfection Segment:
One injection point, one monitoring point U * »
Chlorine
Injected
Filtration
Monitoring Point
CI2 residual = 0.9 mg/L
Temperature = 6 °C
pH = 6.7
Distribution
System
This example will demonstrate one method, Conservative Estimate, for obtaining CT99.9
when collected data values are between values on the CT table. In this example a
conventional filtration treatment system added chlorine prior to the clearwell and it was
required to create a profile. The system must determine the Giardia log inactivation
achieved through disinfection.
A. Determine the required CT99.9 necessary to obtain 3-log Giardia
inactivation.
The required CT value for 3-log Giardia inactivation (CT99.9) may be obtained using CT
Table B-l in Appendix B, CT Values for 3-Log Inactivation of Giardia Cysts by Free
Chlorine.
Step 1. Round the temperature value.
Since the temperature of 6 °C is not shown in the table, the next lowest temperature
on the table, 5 °C, is used to obtain a conservative estimate of CT99.9. The lower
temperature value was chosen since chlorine is less effective at lower temperatures.
Step 2. Round the pH value.
Since the pH of 6.7 is not shown in the table, the next highest pH, 7.0, is used to
obtain a conservative estimate of CT99.9. The higher pH value was chosen since
chlorine is less effective at a higher pH.
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Appendix H. Conservative Estimate and Interpolation Examples
Example H-l continued
Step 3. Round the residual chlorine concentration value.
Since the residual chlorine concentration of 0.9 mg/L is not shown on the table, the
next highest residual chlorine concentration, 1.0 mg/L, is used to obtain a
conservative estimate of CT99.9. A higher residual chlorine concentration is used to
obtain a higher required CT99.9 value, which will result in a lower calculated log
inactivation ratio value.
Step 4. Determine CT99^
In this example the CT99.9 is 149 min-mg/L for a pH of 7.0, temperature of 5 °C, and Cchiorine
of 1.0 mg/L. The relevant section of Table B-l is reprinted below and the pertinent section
of the table is highlighted.
Excerpt from Table B-l:
CT values for 3-Log Inactivation ofGiardia Cysts by Free Chlorine (5°C portion of table for
0.4 to 1.2 mg/L)
Chlorine
Concentration
(mg/L)
<=0.4
0.6
0.8
1.0
1.2
Temperature
<=6.0
97
100
103
105
107
6.5
117
120
122
125
127
7.0
139
143
146
149
152
• 1
pH
7.5
166
171
175
179
183
5°C
8.0
198
204
210
216
221
8.5
236
244
252
260
267
9.0
279
291
301
312
320
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Appendix H. Conservative Estimate and Interpolation Examples
Example H-2: Interpolation Example for Obtaining CT99.9
One Disinfection Segment:
One injection point, one monitoring point
Chlorine
Injected
Filtration
Monitoring Point
CI2 residual = 0.9 mg/L
Temperature = 6 °C
pH = 6.7
T
Distribution
System
This example will demonstrate another method, interpolation, for obtaining 0X99.9 when
collected data values are between values on the CT table. In this example a conventional
filtration treatment system added chlorine prior to the clearwell and it was required to create
a profile. The system must determine the Giardia log inactivation achieved through
disinfection.
A. Determine the required CT99.9 necessary to obtain 3-log Giardia
inactivation.
The required CT value for 3-log Giardia inactivation (CT99 9) may be obtained using CT
Table B-l in Appendix B, CT Values for 3-Log Inactivation of Giardia Cysts by Free
Chlorine. Since the temperature of 6 °C, the pH of 6.7, and the residual chlorine
concentration of 0.9 mg/L are not shown on the table, interpolation is used to determine the
CT99 9 value.
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Appendix H. Conservative Estimate and Interpolation Examples
Example H-2 continued
Step 1. Interpolate for CTgg.g atpHof6. 7 at the next lowest temperature of 5 °C and the
next lowest residual chlorine concentration of0.8mg/L.
Excerpt from Table B-l:
CT Values for 3 -Log Inactivation ofGiardia Cysts by Free Chlorine (5°C portion of
table for 0.4 to 1.2mg/L)
Chlorine
Concentration
(mg/L)
<=0.4
0.6
0.8
1.0
1.2
<=6.0
97
100
103
105
107
6.5
117
120
122
125
127
Temperature
PH
7.0 7.5
139
143
146
149
152
166
171
175
179
183
5°C
8.0
198
204
210
216
221
8.5
236
244
252
260
267
9.0
279
291
301
312
320
(CT99.9 at pH 7.0) - (CT99.9 at pH 6.5) = (CT99.9 at pH 6.7) - (CT99.9 at pH 6.5)
pH7.0-pH6.5 pH6.7-pH6.5
146 min-mg/L - 122 min-mg/L = (CT99.9 at pH 6.7) - 122 min-mg/L
7.0-6.5
6.7-6.5
24 min-mg/L = (CT99.9 at pH 6.7) - 122 min-mg/L
0.5 0.2
24 min-mg/L x 0.2 = (CT99.9 at pH 6.7) -122 min-mg/L
0.5
9.6 min-mg/L = (CT99.9 at pH 6.7) - 122 min-mg/L
CT99.9 at pH 6.7 = 9.6 min-mg/L + 122 min-mg/L
CT999 at pH 6.7 = 131.6 min-mg/L
EPA Guidance Manual 194
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Appendix H. Conservative Estimate and Interpolation Examples
Example H-2 continued
Step 2. Interpolate for CTgg.g atpHof6. 7 at the next highest temperature of 10 °C and the
next lowest residual chlorine concentration of0.8mg/L.
Excerpt from Table B-l:
CT Values for 3 -Log Inactivation ofGiardia Cysts by Free Chlorine (10°C portion of
table for 0.4 to 1.2mg/L)
Chlorine
Concentration
(mg/L)
<=0.4
0.6
0.8
1.0
1.2
Temperature
<=6.0
73
75
78
79
80
6.5
88
90
92
94
95
7.0
104
107
110
112
114
• 1
pH
7.5
125
128
131
134
137
10 °C
8.0
149
153
158
162
166
8.5
177
183
189
195
200
9.0
209
218
226
234
240
(CT99.9 at pH 7.0) - (CT99.9 at pH 6.5) = (CT99.9 at pH 6.7) - (CT99.9 at pH 6.5)
pH7.0-pH6.5 pH6.7-pH6.5
110 min-mg/L - 92 min-mg/L = (CT99.9 at pH 6.7) - 92 min-mg/L
7.0-6.5
6.7-6.5
18 min-mg/L = (CT99.9 at pH 6.7) - 92 min-mg/L
0.5 0.2
18 min-mg/L x 0.2 = (CT99.9 at pH 6.7) - 92 min-mg/L
0.5
7.2 min-mg/L = (CT99.9 at pH 6.7) - 92 min-mg/L
CT99.9 at pH 6.7 = 7.2 min-mg/L + 92 min-mg/L
CT99.9 at pH 6.7 = 99.2 min-mg/L
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Appendix H. Conservative Estimate and Interpolation Examples
Example H-2 continued
Step 3. Interpolate for CTgg.g atpHof6. 7, temperature of6°C, and the next lowest
residual chlorine concentration of 0.8 mg/L.
The table below summarizes the 0X99.9 values determined at a pH of 6.7, residual
chlorine concentration of 0.8 mg/L, and temperatures of 5 °C and 10 °C.
pH = 6.7
Chlorine
Concentration
0.8 mg/L
Temperature
5°C
131.6 min-mg/L
10 °C
99.2 min-mg/L
(CT99.9 at 10 °C) - (CT99.9 at 5 °C) = (CT99.9 at 6 °C) - (CT99.9 at 5 °C)
10°C-5°C
6 °C - 5 °C
99.2 min-mg/L - 131.6 min-mg/L = (CT99.9at 6 °C) - 131.6 min-mg/L
10°C-5°C 6°C-5°C
-32.4 min-mg/L = (CT99.9at 6 °C) - 131.6 min-mg/L
5 V 1 V
—' V_x _L V_x
-32.4 min-mg/L x 1 °C = (CT99.9 at 6 °C) - 131.6 min-mg/L
5°C
-6.48 min-mg/L = (CT99.9at 6 °C) - 131.6 min-mg/L
CT99.9at 6 °C = -6.48 min-mg/L +131.6 min-mg/L
CT99.9at 6 °C = 125.1 min-mg/L
CT99.9 at a pH of 6.7, temperature of 6°C, and residual chlorine concentration of
0.8 mg/L is 125.1 min-mg/L.
EPA Guidance Manual 196
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Appendix H. Conservative Estimate and Interpolation Examples
Example H-2 continued
Step 4. Repeat steps 1 through 3 at the samepH and temperatures, but with a residual
chlorine concentration of 1.0 mg/L.
The results are summarized in the table, below.
pH
6.7
6.7
6.7
Temperature
TO
5
10
6
Residual Chlorine
Cone. (mg/L)
1.0
1.0
1.0
CT99.9
(min-mg/L)
134.6
101.2
127.9
CT99.9 at a pH of 6.7, temperature of 6°C, and residual chlorine concentration of
1.0 mg/L is 127.9 min-mg/L.
Step 5. Interpolate for CTw.c, atpHof6.7, temperature of 6°C, and residual chlorine
concentration of 0.9 mg/L.
The table below summarizes the CT99.9 values determined at a pH of 6.7, temperature
of 6°C, and residual chlorine concentrations of 0.8 mg/L and 1.0 mg/L.
pH = 6.7
Temperature
6°C
Chlorine Residual Cone.
0.8 mg/L
125.1 min-mg/L
1.0 mg/L
127.9 min-mg/L
(CT99.9 at 1.0 mg/L) - (CT99.9 at 0.8 mg/L) = (CT99.9 at 0.9 mg/L) - (CT99.9 at 0.8 mg/L)
1.0 mg/L-0.8 mg/L
0.9 mg/L-0.8 mg/L
127.9 min-mg/L - 125.1 min-mg/L = (CT99.9at 0.9 mg/L) - 125.1 min-mg/L
1.0 mg/L-0.8 mg/L 0.9 mg/L - 0.8 mg/L
2.8 min-mg/L = (CT99.9 at 0.9 mg/L) - 125.1 min-mg/L
0.2 mg/L
0.1 mg/L
2.8 min-mg/L x 0.1 mg/L = (CT99.9 at 0.9 mg/L) - 125.1 min-mg/L
0.2 mg/L
1.4 min-mg/L = (CT99.9 at 0.9 mg/L) - 125.1 min-mg/L
CT99.9at 0.9 mg/L = 1.4 min-mg/L + 125.1 min-mg/L
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Appendix H. Conservative Estimate and Interpolation Examples
Example H-2 continued
CT99.9 at 0.9 mg/L = 126.5 min-mg/L
CT99.9 at a temperature of 6°C, pH of 6.7, and residual chlorine concentration of
0.9 mg/L is 126.5 min-mg/L.
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