EVALUATION OF TREATMENT EFFECTIVENESS
FOR REDUCING
TRIHALOMETHANES IN DRINKING WATER
EPA CONTRACT
NO. 68-01-6292
FINAL REPORT
JULY 1983
-------
FINAL REPORT
EVALUATION OF TREATMENT EFFECTIVENESS FOR REDUCING
TRIHALOMETHANES IN DRINKING WATER
by
Robert C. Gumerman
Nancy Heim
Culp/Wesner/Culp
Consulting Engineers
Santa Ana, California 92707
Contract No. 68-01-6292
Project Officer
Jim Walasek
Technical Support Division
Office of Drinking Water
Cincinnati, Ohio 45268
Criteria and Standards Division
U. S. Environmental Protection Agency
Washington, D.C. 20460
-------
ABSTRACT
This report is concerned with preservation of the microbiological quality
of the finished water following implementation of treatment technique changes
for reduction of trihalomethanes (THMs).
An initial survey of utilities serving more than 75,000 individuals was
conducted in early 1981 to determine which utilities ware experiencing high
THM concentrations, what control strategies had been implemented, and how
successful these control strategies were in reducing THM concentrations and
maintaining microbiological quality of the finished water. Twenty-four utili-
ties were located which had made treatment technique changes and successfully
lowered THM concentrations to less than the THM Maximum Contaminant Level
(MCL). Of these, nine had changed the point of chlorine application, ten had
changed to use of chlorine plus ammonia (chloramines), and one had switched to
chlorine dioxide. In addition, two had reduced pH prior to chlorine
application, one had improved the coagulation process prior to chlorine
application, and one used granular activated carbon for THM precursor removal.
In early 1983, six utilities which were initially contacted were still
conducting testing of one or more control strategies, with full-scale
implementation scheduled for later dates.
A field monitoring program aimed at examination of microbiological char-
acteristics before, during, and after changes were made for THM control, was
conducted at three large utilities. At Shenango Valley Water Company, Sharon,
Pennsylvania, four phases of testing evaluated pre and postdisinfection using
combinations of chlorine, chloramines, and chlorine dioxide. At the Davenport
Water Company, Davenport, Iowa, the initial point of chlorine application was
moved to the mid-point of the settling basin, and at Topeka, Kansas, pre and
postdisinfection with chloramines was implemented. Field monitoring included
testing for coliform (standard and high volume testing procedures), plate
counts using a membrane technique, coliphage, virus testing (at Davenport
only), THM, and total organic carbon. Testing conducted by the utilities
i
-------
included temperature, pH, turbidity, and disinfectant residual. Testing
results and conclusions derived from the results are summarized in this
Report, with detailed results available in three separate reports prepared for
each field monitoring site.
A Guidance Manual intended for use by utilities planning to make
treatment technique changes for THM control is also included. This Guidance
Manual discusses the trihalomethane formation reaction and the impact of raw
water quality on the rate and extent of THM formation, the necessary steps
which must be followed for compliance with the THM MCL, and procedures to
ensure preservation of the microbiological quality of the finished water after
changes are made for THM control. Guidance examples are presented for systems
using chlorination only, systems using conventional treatment, and systems
using lime softening. Representative costs are presented for THM control using
Best Generally Available Treatment Methods.
-------
ACKN OWLED GEMEN TS
There were four groups of participants involved in the conduct of this
Report: (1) the Contractor, (2) the laboratory services subcontractor, (3) the
EPA technical directors, and (4) the personnel at the three utilities involved
in the field monitoring portion of the project. The contractor was
Culp/Wesner/ Culp, Santa Ana, California. Laboratory services were provided by
a subcontractor, James M. Montgomery, Consulting Engineers, Inc., Pasadena,
California. Technical direction was provided by U.S. Environmental Protection
Agency personnel from the Office of Drinking Water, in both Cincinnati, Ohio
and Washington, D.C. Personnel from the Shenango Valley Water Company,
Sharon, Pennsylvania, City of Topeka, Kansas, and the Davenport Water Company,
Davenport, Iowa, participated in the field monitoring portion of the project.
The membership of each group is listed below.
FINAL REPORT PREPARATION
Culp/Wesner/Culp, Santa Ana, CA
Authors: Robert C. Gumerman
Nancy Heim
Production Staff: Linda McKinney, Kay Erickson, A1 Herron (illustrations)
LABORATORY SERVICES
James M. Montgomery, Consulting Engineers, Inc.
Project Supervision: Lawrence Y.C. Leong, Ph.D.
Project Staff: Carole J. Leong
Gary C. Sears
Neal D. Buhler
Ghislaine M. Hawkins
Julie L. Bur bank
iii
-------
TECHNICAL DIRECTION
First Project Officer: Stig Regli, Science, and Technology Branch,
Office of Drinking Water, EPA, Washington, D.C.
Second Project Officer: James B. Walasek, Water Supply Technology Branch,
Technical Support Division, Office of Drinking Water,
EPA, Cincinnati, OH
UTILITY PERSONNEL
Shenango Valley Water Company, Sharon, PA
Kenneth W. Baumann - Vice President/Operations
Debera Truog, Water Quality Manager
City of Topeka, Kansas
Richard E. Pelton, Water Superintendent
Bruce Northrup, Chemist
Davenport Water Company, Davenport, Iowa
American Water Works Service Company Inc.
Clarence Blanck, Director Water Quality
Howard Thompson, Water Quality Supervisor
Dean Piatt, Chemist
Many other utilities were contacted during this project to obtain
information. These utilities and the personnel involved are to numerous to
mention, although their assistance is gratefully acknowledged.
iv
-------
CONTENTS
Chapter Page
ABSTRACT i
ACKNOWLEDGEMENTS iii
CONTENTS V
LIST OF FIGURES vii
LIST OF TABLES viii
1 INTRODUCTION 1
2 SUMMARY OF INTERIM REPORT 7
3 TREATMENT TECHNIQUES SUCCESSFULLY USED TO REDUCE TRIHALO-
METHANES AT UTILITIES SERVING OVER 75,000 INDIVIDUALS 11
Change in the Point of Chlorination 11
Change in the Type of Disinfectant 13
Other Plant Modifications For THM Control 19
Treatment Facilities With Modifications In Progress 21
Summary 23
4 FIELD MONITORING PROGRAM 24
Introduction 24
Criteria For Selection of Utilities 24
Rationale for Selection of the Three Utilities -
Shenango, Davenport, and Topeka 28
Rationale for Selection of Davenport, Iowa for
Virus Monitoring. 30
Quality Control - Collection, Shipment and Sample Analysis . 32
Analyses Conducted and Procedures Utilized 33
Other Quality Control Considerations 35
Shenango Valley Water Company Sampling Program 36
Davenport Water Company Sampling Program 44
Topeka Water Department Sampling Program 53
v
-------
Chapter Page
5 GUIDANCE CRITERIA FOR UTILITIES PROPOSING TREATMENT
TECHNIQUE CHANGES TO ACHIEVE THM COMPLIANCE 62
Introduction 63
The Trihalomethane Formation Reaction 64
Necessary Steps for Compliance With the THM MCL 69
Guidance For Systems Using Chlorination Only 79
Guidance For Systems Using Conventional Treatment 84
Guidance For Systems Using Lime Softening 90
Summary of Microbiological Concerns 95
Cost of Best Generally Available Treatment Methods 97
References For Chapter 5 107
REFERENCES 108
APPENDICES
A. The Trihalomethane Regulation A-1
B. Coliphage Test Results - Summer 1981 B-1
vi
-------
LIST OF FIGURES
Number Title Page
1 Flow Diagram and Sampling Points, Shenango Valley
Water Company, Sharon, PA 37
2 Davenport Water Company, Process Flow Diagram and Sampling
Points, Phase 1: Original Point of Chlorination 46
3 Davenport Water Company, Process Flow Diagram and Sampling
Points, Phase 2: Shifted Point of Chlorination 47
4 Aerial Photographs of the Davenport Water Treatment Plant ... 48
5 City of Topeka, Process Flow Diagram and Sampling
Points, Phase 1: Chlorine/Chlorine 55
6 City of Topeka, Process Flow Diagram and Sampling
Points, Phase 2: Chlorine/Chloramines 56
7 Aerial Photograph of the City of Topeka Water
Treatment Plant 57
8 THM Parameters and Their Relationships 6 5
9 Necessary Steps For Compliance With The THM MCL 70
10 Suggested Decision Format For THM Compliance in
Systems Using Chlorination Only 80
11 THM Control Measures For Systems Using Chlorination Only .... 81
12 Suggested Decision Format For THM Compliance in
Conventional Treatment Plants ........... 85
13 THM Control Measures For Systems Using Conventional Treatment . 86
14 Suggested Decision Format for THM Compliance in Lime
Softening Plants 91
15 THM Control Measures For Systems Using Lime Softening 92
vii
-------
LIST OF TABLES
Number Title Page
1 Utilities Controlling THMs by Changing the Point or Dosage
of Chlorine Application 12
2 Chlorine and Ammonia Application Points of Utilities
Using Chloramine Disinfection 14
3 THM Reduction for Utilities Operating with Free Chlorine
Through Filtration and Chloramines Formed After Filtration . . 16
4 THM Reduction for Utilities Operating with Chloramines Formed
Prior to Filtration 17
5 Average or Range in Instantaneous THM Concentrations at
Mobile, Alabama, Using Chlorine Dioxide and Free Chlorine
Disinfection 19
6 Miscellaneous Treatment Techniques Used for THM Control 20
7 Status of Utilities With THM Control Strategies in Progress . . 22
8 Mean Disinfectant Residuals (mg/liter), Shenango Valley
Water Company 40
9 Percentage of Samples Showing Positive Total Coliform
Tests, Shenango Valley Water Company 43
10 Disinfectant Dose and Mean Disinfectant Residual Information,
Davenport Water Company 49
11 Disinfectant Dose and Mean Disinfectant Residual Information,
City of Topeka 58
12 Geometric Mean Plate Count per 100 ml, City of Topeka 59
13 Most Suitable Treatment Technologies For Control of TTHM .... 76
14 Summary of Features of Best Generally Available
Treatment Methods 78
15 Assumptions Used in Development of Costs For THM
Control Technologies 98
16 Cost of Chlorination 99
viii
-------
List of Tables (continued)
Number Title Page
17 Cost of Chloramine Usage To Meet THM MCL 100
18 Cost of Chlorine Dioxide Usage To Meet THM MCL 102
19. Cost of Powdered Activated Carbon Use To Meet THM MCL 103
20. Cost of Increased Alum and Polymer Dosages To Meet THM MCL ... 105
21. Example Costs For a 0.219 m^/sec (5 mgd) Plant Using
Best Generally Available Treatment Methods ..........106
ix
-------
CHAPTER 1
INTRODUCTION
BACKGROUND
To control trihalomethane (THM) concentrations in drinking water, EPA
promulgated an amendment to the National Interim Primary Drinking Water
Regulations on November 29, 1979. This amendment established a maximum contam-
inant level (MCL) of 100 ug/L for total trihalome thanes (TTHMs), as well as
monitoring and reporting requirements for TTHMs.
Trihalome thanes included in the 100 ug/L MCL are chloroform,
bromodichloromethane, dibromochloromethane, and branoform. The MCL became
applicable to systems serving more than 75,000 people November 29, 1981, and
to systems serving between 10,000 and 75,000 people on November 29, 1983.
Monitoring requirements for systems serving between 10,000 and 75,000 people
became effective November 29, 1982, and require quarterly collection of
samples.
The intent of the THM Regulation is to ensure that utilities achieve
compliance with the THM MCL, while at the same time insuring that water
supplied to the customer continues to be free of pathogenic organisms. It is
essential that the microbiological integrity of the drinking water not be
compromised by changing the treatment technique to achieve compliance with the
THM MCL.
PURPOSE AND OBJECTIVES
This Project had three principal objectives, which were:
• Summarize THM control strategies which have been successfully
implemented by utilities serving greater than 75,000 people.
1
-------
• Conduct field sampling at three utilities, with special emphasis on
microbiological measurements, before, during, and after implementation
of a THM control strategy.
• Prepare a Guidance Manual, for utilities serving fewer than 75,000
people, to assist in the practical and economic selection of a treat-
ment modification to meet the THM MCL, while insuring that the micro-
biological integrity of the finished water is preserved. This Guidance
Manual will be based on experiences at utilities serving greater than
75,000 people.
Each of these objectives is briefly discussed in the following
paragraphs.
When this project was initiated in late 1980, there were over 380
utilities which served more than 75,000 people. At that time, most of these
utilities had performed some sampling for THMs, and some which were not in
compliance with the MCL had already made changes which brought them into
compliance. Many others which did not meet the MCL were only beginning their
investigation and evaluation of control techniques. In early 1981, a litera-
ture survey was undertaken to identify utilities which had a potential THM
problem, and this literature survey was followed by a telephone survey. The
intent of the telephone survey was to determine if the utility was in compli-
ance with the THM MCL, and if in compliance, whether any treatment changes had
been made to achieve compliance and whether there were any changes in finished
water bacteriological quality. For utilities not in compliance, discussions
centered around their plans for compliance. Because many utilities were only
beginning to investigate THM control strategies in early 1981, follow-up
contact with many utilities continued through 1981 and into mid-1982.
Many utilities were reluctant to provide microbiological and THM data
over the telephone, perhaps because it is difficult to sumnarize. In many
cases, follow-up letters were sent to obtain additional data. Some utilities
responded to these letters, but the majority did not. For these reasons, the
the data on microbiological, THM, and disinfectant dosage and residual is
2
-------
incomplete in some cases. Without actually visiting each utility, it is
believed that the data herein is complete to the extent possible.
When the project was funded by EPA, it was intended that field monitoring
be conducted at five utilities. This was decreased to three utilities for two
reasons. First, difficulty was experienced in locating suitable utilities
which were planning on implementing a treatment technique change during the
time-frame of this project. Second, it was determined that additional testing
at fewer utilities would produce more meaningful results. The three utilities
selected for inclusion in a field monitoring program were: Shenango Valley
Water Company, Sharon, Pennsylvania; City of Topeka, Kansas; and Davenport
Water Company, Davenport, Iowa. The field monitoring included testing for
total bacteria population using a membrane standard plate count technique,
total coliform organisms using the standard MPN technique and a high volume
sampling technique, coliphage, THMs, TOC, disinfectant residual, temperature,
pH, and turbidity. Enteric virus sampling was also conducted, but only at
Davenport. Samples were collected before and after changes for THM control.
Treatment techniques evaluated at Shenango Valley Water Company included
pre and postchlorination, prechlorination/post chlorine dioxide, pre chlorine
dioxide/postchloramine, and prechlorination/postchloramine. At Topeka,
prechlorination followed by ammonia addition and postchloramine production
were used. At the Davenport Water Company, the point of prechlorination was
shifted from the raw water intake to half way through the settling basin, and
ammonia and chlorine were added at the clearwell.
The Guidance Manual is intended to assist in the selection of a THM
control strategy, and is for use primarily by systems serving between 10,000
and 75,000 people, although it is also applicable to larger systems. This
Guidance Manual includes consideration of raw water quality, applicable treat-
ment technique modifications, maintenance of microbiological quality, and cost
of THM control strategies.
3
-------
SUMMARY AND CONCLUSIONS
A survey of utilities which served over 75,000 individuals and had THM
concentrations exceeding the regulations resulted in the identification of
twenty-four utilities which have made treatment technique changes for THM
control. Nine of these utilities have achieved compliance by moving the point
of initial chlorine application to after clarification, while ten have
switched to use of chlorine plus ammonia for the production of chloramines.
One has switched to chlorine dioxide. The remaining four used miscellaneous
techniques such as reduced pH before chlorination, improved coagulation, and
granular activated carbon.
In the three full-scale field monitoring programs, many conclusions were
reached. Several of the more significant conclusions of these three monitoring
programs are presented following. In reviewing these conclusions, particular
attention should be paid to the disinfectant dosages and residuals, as higher
or lower dosages or residuals could have produced different results- and thus
different conclusions. Among the more significant conclusions of these three
monitoring programs were the following:
Shenango Valley Water Company, Sharon, Pennsylvania
• Chlorine dioxide (0.62 mg/L dosage) is less effective a predisinfec-
tant than chlorine (4.0 mg/L dosage) when measured between raw water
and clarified water (after settling and before filtration) sampling
points. This conclusion is based on both plate counts and coliform
tests. No testing was conducted on equivalent dosages of the two
disinfectants.
• Postdisinfection with chloramines (4.5 mg/L dosage) is less effective
than with either chlorine (2.5 mg/L dosage) or chlorine dioxide (0.47
mg/L dosage) based on finished water plate counts (after GAC filtra-
tion and clearwell).
• Prechlorination (5 mg/L dosage) and post chlorine dioxide (0.47 mg/L
dosage) gave a higher percentage of positive coliform tests (50%
4
-------
positive) at the "dead-end" sample point in the distribution systan,
than other disinfectant combinations. Mean disinfectant residuals
during this prechlorination and post chlorine dioxide operating condi-
tion were 0.1 mg/L for free chlorine and 0.1 mg/L for chlorine
dioxide.
• Chlorine dioxide as a postdisinfectant (0.47 mg/L dosage) was poor at
suppressing bacterial regrowth in the distribution system (0.1 mg/L
residual), based on plate count bacteria.
• Postdisinfection with chloramines (4.5 mg/L dosage) was slower acting
than other postdisinfectants, but ultimately produced the lowest plate
counts in the distribution system.
• THM reductions occurred with all alternate disinfectant combinations
evaluated.
Davenport Water Company, Davenport, Iowa
• Moving the point of initial chlorine application to mid-way through
the clarification basin (4-6 mg/L dosage) did not degrade finished
water plate counts or change the percentage of positive coliform tests
in the finished water.
• Movement of the chlorination point did not reduce THM concentrations,
in contrast to results obtained in earlier studies performed by the
utility. The reason for this difference is not clear, but it may have
been caused by higher water temperatures during this monitoring
program, or due to changes in precursor concentration or type since
the earlier studies.
City of Topeka, Kansas
• Breakpoint prechlorination (8-13 mg/L) and postchlorination (2-3 mg/L)
provided plate count and coliform reductions between raw and finished
5
-------
water sampling points equivalent to those experienced with the use of
prechlorination (3.6 mg/L) followed by ammonia addition (after 2-3
hours) and postchloramine formation (2-3 mg/L).
• Use of prechlorination (3.6 mg/L dosage) for 2-3 hours followed by
ammonia addition to produce chloramines significantly reduced THM
formation relative to breakpoint chlorination (8-13 mg/L dosage). Mean
THM reductions were 74 percent for finished water and 71 percent in
the distribution system.
6
-------
CHAPTER 2
SUMMARY OF INTERIM REPORT
As a portion of this Report, an Interim Report1 was submitted on May 1,
1981. This Interim Report summarized progress to date, and in specific/ out-
lined information obtained from a literature search and telephone survey of
utilities serving over 75,000 people which were indicated to have THM concen-
trations exceeding the 0.1 mg/L MCL. THM concentrations were reported for over
50 utilities. Thirteen of these utilities were discussed in considerable
detail, including a description of the treatment facilities and unit processes
utilized, raw water quality microbiological data, THM results, plans (if any)
for treatment technique changes to control THMs, and a description of current
laboratory testing practices. Out of this list of thirteen utilities, seven
were recommended for further evaluation, as they were felt to be reasonable
candidates for inclusion in the field monitoring portion of the project.
These seven utilities were:
Shenango Valley Water Company, Sharon, Pennsylvania
Keystone Water Company, Norristown, Pennsylvania
Davenport Water Company, Davenport, Iowa
Abilene, Texas
Newport, Rhode Island
Topeka, Kansas
East St. Louis, Illinois
The Interim Report also discussed case studies of five other utilities
which had successfully made changes for THM control. These five utilities,
and the changes which they made, were:
1. Huron, South Dakota - Treatment consists of presedimentation, lime-
soda softening, recarbonation, and anthracite filtration. In the
initial phase of testing, the point of chlorination was moved from
7
-------
the rapid mix basin to the recarbonation basin. The objective of this
move was to eliminate chlorine addition during high pH water condi-
tions, which accelerate the rate of THM formation. Mention should be
made, however, that the high pH conditions which exist during lime
softening enhance bacterial kill during treatment. Chloroform concen-
tration in the finished water decreased by 75%.
Despite this reduction, the continued formation of Tttls in the
distribution system produced unacceptably high concentrations. In the
second phase of this study, ammonium sulfate addition after recarbon-
ation was used to produce chloramines, which resulted in a reduction
in distribution system THMs from 154 ug/L to 37 ug/L. Of signifi-
cance, the distribution system total plate counts were reduced by 75%
(compared to use of free chlorine) when use of chloramines was
implemented.
Louisville, Kentucky - At Louisville, treatment consisted of
prechlorination, presedimenation without coagulants, lime-soda
softening, rapid sand filtration and postchlorination. Using this
treatment configuation, the THM concentration in the finished water
exceeded 100 ug/L. Two disinfectant practices were evaluated in
detail. The first was application of chlorine dioxide (plus a small
amount of free chlorine) following coagulation, followed by ammonia
addition 10 minutes later at the start of the softening basin.
Pos tdi sinf ection was accomplished by the addition of combined
chlorine following filtration. This treatment technique change
reduced the THM concentration to 5 ug/L. Although standard plant
count reductions following coagulation were essentially equivalent to
those experienced with free chlorine, the filtered water plate count
was over 10 times greater than with free chlorine. This regrowth was
attributed to a rapid decrea^p in the chlorine dioxide residual after
its initial application, and establishment of a population of
nitrifying bacteria in the filters. These bacteria apparently were
using added ammonia as a food and energy source. However, in the
distribution system, both the chlorine dioxide/chloramine concept and
-------
the initial free chlorine concept produced equivalent standard plate
count results, and no coliforms were observed for either approach.
In the second phase of testing, free chlorine addition following
coagulation, with ammonia addition 10 minutes later, was practiced.
Combined chlorine was also used as the final disinfectant. In
contrast to the prior testing with chlorine dioxide, plate counts
decreased steadily through the treatment processes, and lower values
were observed in the distribution system than in the finished water.
Distribution system THM concentrations averaged 25 ug/L. The use of
this this approach was implemented on a continuous basis as a result
of this testing.
3. Cincinnati, Ohio - Treatment consists of two large, uncovered
settling reservoirs (2-3 days detention time), coagulation, settling,
and rapid sand filtration. Alum was added prior to presedimentation.
In the first phase of testing, the point of initial chlorination was
changed from before the presedimentation reservoirs to after these
reservoirs. In the second phase of testing, the point of initial
chlorine addition was moved further back, to just prior to filtra-
tion. The first phase testing demonstrated an 80% reduction in
distribution system THMs, due to a shorter chlorine contact time and
greater THM precursor removal prior to chlorine addition. No signif-
icant reduction in the distribution system THM concentration occurred
in the second phase, and there was no change in finished water
bacterial quality based on coliform and SPC testing. In the second
phase, finished water coliform concentration was less than 1/100 ml
and finished water SPC was less than 1/ml. These results are
comparable to those which were achieved before changing the point of
chlorination.
4. Beaver Falls, Pennsylvania - At Beaver Falls, two stages of coagula-
tion were used prior to filtration. Chlorine was added after the
first stage settling. During the testing, three of the eight filters
had the top 24 inches of sand replaced with granular activated
9
-------
carbon. Three different carbons were utilized, with the objective of
testing their capability for taste and odor control as well as for
THM control. Results of the THM testing showed very effective THM
removal by the carbon until exhaustion, which occurred between 10-15
weeks, depending on the carbon. Coliform density and SPC values were
higher in the GAC product water than in the feed water, at least
during the warmer summer months. However, postchlorination was
effective in the reduction of both coliform and standard plate count
organisms in the GAC product water. Finished water coliform concen-
tration was less than 1/100 ml and SPC values were less than 500/ml.
5. Durham, North Carolina - Treatment of river water consisted of a
presedimentation storage reservoir, alum coagulation and sedimenta-
tion, and dual media filtration. Before changes for THM control,
chlorine was added ahead of the rapid mix at an average dosage of 5.8
mg/L. After changes were made, chlorine was added just prior to
filtration, at an average dosage of 3.7 mg/L. Results showed a 40%
reduction in finished water THMs, dropping from an average of 1 29
ug/L (July through December) before changeover, down to 77 ug/L
(January through March) after changeover. This represented an average
reduction of 48%. During the Spring months when water temperatures
increased and flocculation improved, finished water THM concentra-
tions of 60 ug/L were noted.
Bacteriological testing was conducted, but it was not indicated
whether this was plate count or coliform testing. Results of the
bacteriological testing, after moving the point of chlorination,
indicated that adequate disinfection was maintained, according to the
plant staff.
10
-------
CHAPTER 3
TREATMENT TECHNIQUES SUCCESSFULLY USED TO REDUCE TRIHALOMETHANES AT UTILITIES
SERVING OVER 75,000 INDIVIDUALS
One of the objectives of this study was to investigate the types of TtM
control strategies which have been successfully instituted by utilities
serving greater than 75,000 people. During the course of this study, many
utilities conducted extensive pilot and plant-scale tests to determine the
most feasible methods of reducing THM's in their water supplies. This section
summarizes the permanent plant modifications that resulted from the initial
tests conducted by twenty-four utilities which experienced THM problems.
Additionally, six utilities that are currently (early 1983) in the process of
making treatment technique changes for THM control are also discussed. The
relative effectiveness of different treatment modifications to reduce THMs is
discussed.
Based upon the survey of these utilities, the two most commonly used
methods for controlling the formation of THMs are to change the point of
chlorine addition or to use chloramines. Other less commonly used techniques
were reduction in the chlorine dose, improved coagulation, lowering the pH
after lime softening, use of chlorine dioxide disinfection, and GAC for
precursor removal.
CHANGE IN THE POINT OF CHLORINATION
Table 1 lists nine utilities which have successfully reduced TFM
concentrations by shifting chlorination to a point later in the treatment
train, or reducing the prechlorination dosage. In most cases, effective THM
control was achieved by eliminating prechlorination and/or chlorinating at a
point just prior to filtration. Several facilities, including Philadelphia,
Pennsylvania, Lubbock, Texas, and Chesterfield, Virginia, also have tried to
further reduce THM formation by reducing chlorine dosages. Of these three,
11
-------
TABLE 1
UTILITIES CONTROLLING THMS BY CHANGING THE POINT OR DOSAGE OF CHLORINE APPLICATION
Average
or Range in THM
Concentration (ug
Source
Original Point
Revised Point
Before Change
After Change
Utility
Population
of Water
of Chlorination
of Chlorination
Plant
Distribution
Plant
Distribut
Philadelphia, PA*
950,000
Surface
Before presedimentation
basin
After presedimentation
basin; before rapid mix
140
1 40*
50-70
50-70*
Chesterfield, VA
130,000
Surface
Before rapid mix
Between primary and
secondary clarification
-
>100
-
50-90
Montgomery, AL
175,000
Ground &
Surface
Before rapid mix
Before sand filters
-
100
-
1 5
Indianapolis, IN
80,000
Surface
Before rapid mix
Before sand filters
-
20-1 50
-
25-1 00
Lubbock, TX**
250,000
Unknown
**
»»
-
-
45
50-70
Newport News, VA
330,000
Surface
Before sedimentation
Before saraJ filters
102
-
18
50
Keystone Water Co.
Norristown, PA
80,000
Surface
Before flocculation
After new GAC filters
70
78-1 2 2
-
35-60
Cincinnati, OH
860,000
Surface
Prior to presedimentation
Before sand filters
106
-
65
-
Davenport, IA***
135,000
Surface
Raw water pump station
Halfway through
sedimentation basin
1 15
1 16-1 27
133
1 30-1 36
~Operated continuously with ammonia addition
**Reduced chlorine dosage only.
to plant product water. This
stops subsequent THM formation.
'•~Results are from sampling program conducted as a portion of this project. Higher concentrations after the change may have resulted fran a 6°C
increase in mean water temperature. Prior testing by the utility indicated a reduction in THMs due to the change in the point of chlorination.
Chloramines are used for postdisinfection.
-------
only the City of Lubbock, Texas, was able to reduce THM concentrations to an
acceptable level with only a reduction of chlorine dosage. Except for Norris-
town, Pennsylvania, all of the utilities shown in Table 1 operate their faci-
lities for THM control year round, rather than on a seasonal basis when THM's
present a problem. Only Davenport, Iowa, had higher THM concentrations after
the change in point of chlorination. These results were from the sampling
program conducted as a part of this project. According to the utility, these
results are contrary to earlier data collected by the utility. However, the
utility did not furnish this earlier data. If it is true that there was a
variation from earlier testing, this may be due to an increase in water
temperature, a change in precursor concentration or type during the sampling
program, a difference in analytical technique, or sample preservation.
Based upon the limited data collected in the telephone survey, none of
the utilities reported a significant change in the bacteriological quality of
treated water as a result of treatment technique changes for THM control.
However, none of the utilities were willing to furnish results of bacterio-
logical sampling. Operating without prechlorination, several facilities did
report an experienced algae buildup in sedimentation basins and filters, which
leads to increased maintenance. Due to the severity of the algae problem in
Norristown, Pennsylvania, however, the original scheme of adding chlorine to
the mixing chamber is practiced (at a reduced dosage) during the summer
months. One possibility for controlling algae growth in the filters would be
copper sulfate addition, but none of these utilities were using this
technique.
CHANGE IN THE TYPE OF DISINFECTANT
Chloramines
A large number of utilities have chosen alternative methods of
disinfection as a means of controlling THM's. Among the methods available,
disinfection using chloramines has become the most widely practiced. The
locations used for ammonia application, however, are quite varied from one
plant to another. Table 2 lists ten utilities which recently modified their
treatment facilities for disinfection using combined chlorine. The various
-------
TABLE 2
CHLORINE AND AMMONIA APPLICATION POINTS OF UTILITIES USING CHLORAMINE DISINFECTION
Utility
Population
Chlorine Application Points
NH-j Application Points
Kansas City, KS
190,000
After sand filters
Following chlorine addition
Louisville, KY
333,000
After coagulation
After sand filers
10 minutes after each
application of chlorine
Contra Costa, CA
150,000
Before sand filters
After sand filters
Miami, FL
1 ,500,000
Before sand filters
30 - 60 Sec. after chlori-
nation, before sand filters
Occoquan, VA
700,000
Before sand filters
After sand filters
Tampa, FL
455,000
Before sand filters
After sand filters
After sand filters
San Diego, CA
850,000
Before sand filters
1 mg/1 free CI2 residual
maintained through filters
before NH2 addition
Brownsville, TX
85,000
Before mixing chamber
After sand filters
Before distribution
Raw water
Houston, TX
2,000,000
After raw water pump
and at clearwell before
distribution
Raw water
Topeka, KS
180,000
After presedimentation
and before rapid mix.
Also before sand filters
Rapid mix and before filters
-------
points of chlorine and ammonia application for each plant are compared in
Table 2. With the exception of Brownsville and Houston, Texas, where the raw
water is ammoniated prior to chlorine addition, in order to insure adequate
ammonia mixing, all other facilities add ammonia at some point following
chlorination. As illustrated in Table 2, most utilities add chlorine just
before filtration (Louisville, Kentucky applies chlorine slightly earlier,
immediately following coagulation and Topeka uses prechlorination to the
extent possible while still meeting regulations). Several facilities also
apply chlorine at a second point in the treatment train, usually after sand
filtration.
Of the ten utilities listed in Table 2, five add chlorine before sand
filtration and ammonia after sand filtration. Thus, a free chlorine residual
is maintained through the filters. The remaining five utilities listed in
Table 2 operate with combined chlorine formation prior to filtration.
Table 3 shows THM reductions for the five utilities which maintain a free
chlorine residual through the sand filters, and Table 4 shows similar data for
the five utilities operating with combined chlorine through the filters.
Comparing these two tables indicates that a higher reduction in THM1s gener-
ally resulted at facilities operating with chloramines, rather than with a
free chlorine residual, through their filters.
By operating without free chlorine prior to the filters, some plants have
experienced operating problems during the summer months due to algae growth on
the settling basin and filter walls, and algae carry over from the settling
basin to the filter. For a short period of time, Brownsville Texas, attempted
to eliminate prechlorination at the mixing chamber (this was before the
recently installed ammonia feed facilities were on-line), but found it
impractical due to excessive algae growth in clarifiers and filters. Conse-
quently, prechlorination is still practiced at Brownsville. Topeka, Kansas
prefers to use prechlorination to the extent possible while still meeting the
regulations. Such prechlorination is preferred for bacterial disinfection
purposes as well as reducing algae growth in the treatment basins and
filters.
15
-------
TABLE 3
THM REDUCTION FOR UTILITIES OPERATING WITH FREE CHLORINE THROUOT FILTRATION
AND CHLORAMINES FORMED AFTER FILTRATION
Average or Range in THM Concentration (ug/L)
Before Change* After Change**
Utility
Water Source
Plant
Distribution
Plant
Distribution
% Reduction
in Distribution
System THMs
Kansas City
Contra Costa, CA
Occoquan, VA
Tampa, FL
San Diego, CA
Surface
Surface
Surface
Ground &
Surface
Surface
85
80
100 - 150
110
80
150 - 200
300
90 - 95
25 - 40
50
89
40
50
90
60 - 65
24
50
67 - 75
70
33
~Before condition refers to use of chlorination for disinfection prior to use of chloramines for THM
control.
**After condition is with use of chloramines for THM control. The location of ammonia addition is shown
in Table 2.
-------
TABLE 4
THM REDUCTION FOR UTILITIES OPERATING WITH
CHLORAMINES FORMED PRIOR TO FILTRATION
Average
or Range in THM
Concentration (ug/L)
% Reduction
Before
Change*
After Change**
in Distribution
Utility
Water Source
Plant
Distribution
Plant Distribution
System THMs
Louisville, KY
Surface
— 100—
—25--
75
Miami, FL
Ground
100
200 - 300
50
75 - 83
Brownsville, TX***
Surface
200
450
87 180
60
Houston, TX
Surface
>100
125 - 150
30 - 65 80
36 - 47
Topeka, KS****
Surface
297
304 - 334
78 76 - 105
71
~Before condition refers to use of chlorination for disinfection prior to use of chloramines
for THM control.
**After condition is with use of chloramines for THM control. The location of ammonia addition
is shown in Table 2.
***0ther plant modifications in progress to further reduce THM's.
****Results from sampling program conducted as a portion of this project.
-------
With the exception of Kansas City and Topeka, Kansas, all of the
utilities using chloramine disinfection operate their facilities for THM
control on a year round basis, and none reported a noticeable drop in
bacteriological quality of the finished water, based generally on coliform and
I
SPC testing. The results of water quality sampling before and after introduc-
tion of chloramines into several water supply systems indicate that certain
quality characteristics actually are enhanced by the use of chloramines. For
example, the City of San Diego no longer finds it necessary to rechlorinate
standpipes and various locations within the distribution system since
conversion to chloramine disinfection. Also, standard plate counts have proven
to be as low, if not lower, than with free chlorine, and city residents have
noticed an improvement in the taste of the water. The City of Contra Costa,
f
California, reported a definite improvement in turbidity of the finished water
both at the plant and in the distribution system. Miami, Florida, was the only
utility reporting ill-effects from the use of chloramines. Although bacterio-
logical quality of the product water remained unchanged, the utility has
received some complaints on color. When Miami previously operated with break-
point chlorination, treated water typically contained 3 to 5 color units.
Since conversion to chloramines, the plant now produces a water with an
average of 13 color units.
Chlorine Dioxide
Although several utilities have experimented with chlorine dioxide as an
alternative disinfectant for THM control, Mobile, Alabama is the only utility
serving more than 75,000 where permanent plant modifications have been made at
present (early 1933). Chlorine dioxide is used year round, with chlorine
dioxide addition at the raw water pumping station and following treatment, a
combination of chlorine dioxide and free chlorine is added before pumping
finished water to the distribution system. Table 5 shows the results of TtW
sampling before and after the plant's conversion to the use of chlorine
dioxide.
18
-------
TABLE 5
AVERAGE OR RANGE IN INSTANTANEOUS THM CONCENTRATIONS AT MOBILE,
ALABAMA USING CHLORINE DIOXIDE AND FREE CHLORINE DISINFECTION
Sample
Location
Before Conversion,
Free Chlorine
Disinfection
After Conversion,
Chlorine Dioxide
Disinfection
Plant product water 140 ug/L
Distribution system-average 200 ug/L
40 ug/L
40-90 ug/L
The data indicates that although some trihalomethanes are still formed,
the use of chlorine dioxide clearly reduced THM formation relative to use of
free chlorine only.
OTHER PLANT MODIFICATIONS FOR THM CONTROL
Improved Clarification
Table 6 summarizes the effectiveness of other treatment techniques used
by various utilities for THM control. Lowering the pH after softening,
improved coagulation to remove precursors, and GAC were the techniques used.
In Columbus, Ohio, lime/soda softening results in a water with a pH of about
10.6. With recarbonation to a pH of 8.0, prior to chlorine addition, TFW
concentrations in the distribution system were lowered fran an average of 110
ug/L to an average of 70 ug/L. No changes in distribution system coliform
concentrations were noted following this change. In Benton, Illinois,
eliminating prechlorination and reducing lime dosages to achieve a lower pH
has reduced average THMs in the distribution system from 208 to 80 ug/L, or by
about 60%. Without prechlorination in the summer, however, it is necessary for
the utility to add copper sulfate to help control the algae growth in
clarifiers. There also are plans to use chlorine dioxide at the facility's
original point of prechlorination to further control summer algae blooms.
Normal practice at Melbourne, Florida, included the use of lime and
magnesium as coagulants during treatment. By switching to alum, coagulation
was improved sufficiently to reduce THMs in the distribution system
19
-------
TABLE 6
MISCELLANEOUS TREATMENT TECHNIQUES USED FOR THM CONTROL
Distribution System
THM Concentration (ug/L)
Utility
Water Source
THM Treatment Technique
Before
After
Morse Rd Plant
Columbus, OH
Surface
Lower pH after softening
to 8.0 by recarbonation
150
60
Dublin Rd. Plant
Columbus, OH
Surface
Lower pH after softening
to 8.0 by recarbonation
1 10
70
Rend Lake Intercity
Water Company
Benton, IL
Surface
Lower pH by reducing lime
dosage, eliminate
prechlorination
180 - 235
76 - 84
Melbourne, FL*
Surface
Improved coagulation
using alum
300 - 1200
100 - 400
Passaic Valley Water
Commission
Little Falls, NJ
Surface
GAC in sand replacement
mode
Not Obtained
46
*Other plant modifications in progress to futher reduce THMs.
-------
from a range of 1200 ug/L down to 100-400 ug/L. Because THM concentrations
after this change still exceed the MCL, Melbourne, has plans to convert their
post chlorination facilities to chloramination.
Granular Activated Carbon
Granular activated carbon (GAC), used in the sand replacement mode, has
proven to effectively remove THM precursors, and thus control THMs at Little
Falls, New Jersey. The Passaic Valley Water Commission operates two plants
which draw water from the Passaic River. Although modifications were made at
only one facility, the data in Table 6 indicates that THM concentrations in
the distribution system are reduced to an acceptable level by blending the
treated water from the two plants. The GAC facilities have been operating
successfully in Little Falls since October, 1981.
TREATMENT FACILITIES WITH MODIFICATIONS IN PROGRESS
Several utilities not previously discussed are in various stages of
implementing THM control strategies. Table 7 summarizes the planned modifica-
tions and current status (as of early 1983) of these changes. As illustrated
in Table 7, all of the anticipated changes involve changing the location of
chlorine addition, the use of chloramines as a disinfectant, or chlorine
dioxide as a predisinfectant.
In addition to the utilities shown in Table 7, there are several others
planning additional modifications for further THM reduction. The following
briefly summarizes these future plans:
Melbourne, FL - Ammonia to be added to clearwell following chlorina-
tion (March, 1983).
Brownsville, TX - Ammonia installation at second plant is complete and
will be operational by January, 1983.
Chesterfield, VA - Falling Creek Plant will be using chlorine dioxide
for predisinfection in January, 1983.
21
-------
TABLE 7
STATUS
OF UTILITIES WITH THM CONTROL
STRATEGIES IN PROGRESS
Utility
Plant Modification
Current Status
Raleigh, NC
Move point of chlorination to
precede filters
City has 2 plants; one plant
already changed, but THM data
not available
Jackson, MS
Ammonia to be injected in 5
points located after existing
chlorination points
System due on line May 1983
Metropolitan Water
District of Southern
California,
Los Angeles, CA
Ammonia to be added at all
plants and in finished water
reservoirs
Implementation of ammonia system
January 1984. Currently, pre-
chlorination reduced to 1 mg/L
at 1 plant has reduced THM's by
10 - 15%
Abeline, TX
Move point of chlorination
As of June 1982, ammonia added
to raw water before mixing. City
continuing experiments with the
point of chlorination
Ft Lauderdale, FL
Ammonia to be added following
chlorination points
Construction of ammonia facili-
ties to begin Jan - March, 1983
Corpus Christi, TX
Ammonia to be added
Investigating various locations
of use at two major treatment
facilities
Evansvilie, IN
Chlorine dioxide used as a
predisinfectant
Facilities to be on-line in the
Summer of 1983
-------
Norristown, PA - Ammonia to be added to provide a combined chlorine
residual through the filters. Also, plans for GAC
use in a sand replacement mode, at second plant in
March, 1983.
Cincinnati, OH - Plans for GAC installation. Although not being
installed specifically for THM control, GAC is
expected to result in further reduction of finished
water THM concentrations.
SUMMARY
The results of this study indicate that although there are many options
available for reducing trihalomethane formation, only two methods are used
extensively by most utilities: changing the point of chlorination and the use
of chloramines as a disinfectant. The information which was collected
indicates, however, that the application of these techniques, and the
efficiency of these techniques, can vary significantly between treatment
plants. For example, with the use of chloramines, ammonia may be added at only
one point, or several points of application may be used. Also, some utilities
add ammonia before chlorination, vftiile others add ammonia at some point
following chlorination. The variations are almost limitless depending on the
plant design, source and quality of the raw water, and ambient environmental
conditions such as water temperature. State regulations and cost factors also
can have a major effect on not only the treatment technique selected, but also
on its precise application. For example, some state health departments require
that a free chlorine residual be maintained through the filter system. This
situation would, therefore, preclude the use of ammonia at any point prior to
filtration.
Finally, it should be recognized that nany utilities operate more than
one treatment plant. In some cases, the utility was able to control
distribution system THMs sufficiently by merely making modifications at a
single plant. In other situations, THM concentrations in the distribution
system could only be brought into compliance with MCL by making modifications
at all plants feeding the distribution system.
23
-------
CHAPTER 4
FIELD MONITORING PROGRAM
INTRODUCTION
Field monitoring programs were conducted at three utilities:
• Shenango Valley Water Company, Sharon, Pennsylvania
• City of Topeka, Kansas
• Davenport Water Company, Davenport, Iowa
During the field monitoring programs, chemical, microbiological and THM
data were collected before, during, and after changes were implemented for
control of THMs. The objective of collecting this data was to determine the
effect on the microbiological quality of the finished water as a result of
treatment changes to control THMs. Data were collected for total coliform
organisms, coliphage, enteric virus (Davenport only), THM, TOC (Shenango
only), disinfectant residual, pH, temperature, turbidity, and total bacteria
population using a membrane standard plate count. A Quality Assurance Project
Plan^ was prepared for this project, and was approved by EPA on August 5,
1982.
CRITERIA FOR SELECTION OF UTILITIES
The three utilities which were included in the field monitoring program
were selected after a screening of approximately 400 utilities, each of which
served more than 75,000 individuals. Criteria used to select these three
utilities were:
• Service to more than 75,000 individuals
• Existing THM concentrations exceeding the Regulation
• Quality of the raw water supply
• Planned treatment modifications to be made in the near future for
control of THMs
m Willingness to participate in the monitoring program
• Type of treatment modification planned
24
-------
These criteria are discussed in the following sections:
Service to More Than 75,000 Individuals
Only community water systems serving 75,000 or more individuals were
considered for inclusion in the field monitoring program. This decision was
based upon the necessity of locating utilities which intended to make treat-
ment technique changes during the contract period of this project (originally
scheduled to terminate on March 31, 1982, but subsequently extended to
December 31, 1982, exclusive of the Final Report). Since testing during warm
water conditions was desired, the time of testing was restricted to either
during the Summer of 1981 or 1982. The Regulations required conformance of
utilities serving more than 75,000 individuals within 2 years of promulgation
(i.e., by November 29, 1981 ) and utilities serving between 10,000 and 75,000
individuals within 4 years of promulgation (i.e., by November 29, 1983), mean-
ing that only the larger utilities could be sampled within the timeframe of
this contract.
Sampling during the spring and summer months was preferred, because raw
water quality is generally poor, microbial populations in the raw water are
usually high and water temperatures are high. All of these factors act to
place stress of the treatment process, particularly from the standpoint of
microbial quality improvement.
Existing THM Concentrations Exceeding the Regulations
The Trihalomethane Regulation2 which was promulgated November 29, 1979,
established a maximum total trihal one thane concentration of 0.10 mg/L, based
upon a twelve-month running average of a minimum of 4 samples per quarter per
treatment plant. Samples are to be collected on the same day for each
treatment plant. This Regulation is presented in Appendix A.
Only utilities which did not meet the requirements of the Regulation were
considered for inclusion in the Monitoring Program. Other utilities were not
included, as it was considered that none would make changes for reduction in
the THM concentration if they did not actually exceed the maximum contaminant
level (MCL) in the Regulation.
25
-------
Quality of the Raw Water Supply
Treatment facilities with poor raw water quality were desired, since this
situation would create the greatest stress on the treatment works, and a
higher chance of significant microbial penetration through the treatment
barrier. Of particular significance were coliform organisms, as they are an
indicator of fecal contamination, and total plate count. Also of importance in
the selection was turbidity. Overall, poor raw water microbial quality was the
most important factor.
An average total coliform concentration of at least 5000 organisms/100 ml
was desired, since this concentration is usually indicative of heavy fecal
contamination of the raw water. The ability of a treatment nradification to
provide satisfactory disinfection even with high raw water coliform concentra-
tions is mandatory, and thus it was felt desireable to include such utilities
in the monitoring program.
THM precursors, although not directly measured, are important because
they lead to high finished water THM concentrations. Without a THM concentra-
tion exceeding 100 ug/L. in the distribution system, treatment changes would
probably not be made, and the utility would not be a likely candidate for
inclusion. High raw water turbidity is important because of the stress it
places on the treatment system, particularly the disinfection capability, due
to the "shielding" of microbes from the disinfectant.
Coliphage were also considered important, as they are considered a better
indicator of potential pathogenic virus presence than others parameters.
Coliphage sampling was conducted at five plants as part of the screening
process. The results of the phage sampling are presented later in this
chapter. In general, the results were inconclusive due to the small number of
samples collected and problems encountered with the temperature of the samples
during shipment. This coliphage sample collection, shipment, and analysis was
conducted before the Quality Assurance Project Plan was developed, although
procedures used were identical to those included in the Quality Assurance
Project Plan.3 in general, the high temperature problems resulted from the
utilities not complying with directions furnished to them.
26
-------
Planned Treatment Modifications to be Made in the Near Future
The objective of the monitoring program was to sample before, during and
after a treatment change. Therefore, it was necessary to locate utilities
which were planning a change in the near future, but had not yet made the
change.
As the screening process for selection of utilities continued, it became
apparent that the majority of utilities being considered had already nade
treatment changes necessary to reduce THM concentrations, or were in the
process of studying alternative concepts and did not plan to make treatment
technique changes until the Fall of 1982, or later. Ultimately, two utilities
were selected (Topeka and Davenport) that had already made treatment technique
changes. These utilities agreed to change back to their conventional prechlor-
ination and postdis infection for a six week period of time to allow
"background" data to be collected, and to then revert to their selected THM
control strategy. Prior to making these changes, approval was obtained fran
EPA Region 7, and in the case of Topeka, from the State of Kansas, Division of
Environment, Bureau of Water Supply.
Willingness to Participate in the Monitoring Program
Utilities selected for the monitoring program were responsible for a
number of items, including:
• Collection of samples
• Preparation of samples for shipping and coordination of shipping
arrangements with the overnight courier service
• Analysis of certain parameters: temperature, pH, disinfectant
residual, and turbidity
• Notation of any variations in raw water quality or treatment plant
operation during the monitoring program
27
-------
Satisfactory conduct of these items required considerable effort on the
part of the selected utilities. Without the wholehearted cooperation of these
utilities, the field monitoring programs would not have been successful. Thus,
only utilities which were willing and expressed enthusiam about participation
were considered.
Type of Treatment Modification Planned
The ideal mix of utilities would result in the selection of three
utilities using different treatment modifications. Anticipated modifications
to be considered included:
• Use of chloramines
• Use of ozone
• Use of chlorine dioxide
• Changing the point of chlorination
• Use of granular activated carbon for precursor removal
RATIONALE FOR SELECTION OF THE THREE UTILITIES—SHENANGO, DAVENPORT, AND
TOPEKA
As discussed in Chapter 2, seven utilities were identified (page 7) by
the Interim Report1 as suitable candidates for the Field Monitoring Program.
Shortly after preparation of the Interim Report, the Shenango Valley Water
Company was selected as a location for field monitoring, because this utility
met the above criteria and was embarking on a test of several alternate
disinfectants for THM control. The list of six remaining utilities was further
narrowed to four using raw water quality as a basis for eliminating one
utility (Abilene, Texas) and prior implementation of a THM control strategy
for elimination of a second (Newport, Rhode Island).
The remaining four utilities were:
• Keystone Water Company, Norristown, Pennsylvania
• Davenport Water Company, Davenport, Iowa
• Illinois American Water Company, East St. Louis, Illinois
• City of Topeka, Kansas 28
-------
At these remaining four utilities, as well as at the previously selected
Shenango Valley Water Company, raw water coliphage testing was initiated
during the summer of 1981 with the results intended to be used in the selec-
tion of two additional utilities. The rationale for using coliphage as a
screening tool was that high coliphage concentrations would be an indicator of
the presence of enteric virus, a condition which would be conducive to placing
a high degree of "stress" on the treatment works.
Complete results for the raw water coliphage testing for the five
utilities are shown in Appendix B, Tables B-1 to B-5. Sample analysis was
performed by Dr. Robert Safferman in EPA's Cincinnati laboratories. As shown
in these tables, difficulty was experienced in maintaining a shipping tempera-
ture less than the desired 10°C, prior to the samples arriving at EPA's
Cincinnati labs, where they were analyzed. Also, a number of samples took more
than the desired one day to reach Cincinnati.
Averaging the results in Tables B-1 to B-5, using only samples with
temperatures less than 10°C, yielded the following results:
Raw Water Coliphage - PFU/100 ml
Single Layer Test Method Double Layer Test Method
Utility RNA Phage DNA Phage RNA Phage DNA Phage
Shenango Valley Water Co. 30 35 55 39
Keystone Water Co. 50 200 74 352
Davenport Water Co. 0 2 0 2
Illinois American Water Co. All Samples Over 10°C
City of Topeka 60 99 80 128
The numbers of samples included in the above averages were:
Shenango-3; Keystone-4; Davenport-1 ; Illinois American-0; and Topeka-4. RNA
phage are- those which replicate using cellular RNA (ribonucleic acid) from
E. Coli and DNA phage replicate using cellular DNA (deoxyribonucleic acid)
from E. Coli.
29
-------
On the basis of these results alone, it was difficult to draw
conclusions, although it would appear that Shenango (sampling program was
already completed at this time), Keystone, and Topeka had the worst water
quality from the standpoint of coliphage. After this testing, two of the four
utilities were deleted from the list of candidates: Keystone Water Company
and Illinois American Water Company. These deletions were not on the basis of
the coliphage test results, however. Keystone was dropped because the utility
had no firm plans for implementing a treatment technique change in 1982.
Illinois American was dropped because the utility was not responsive in
sendLng requested microbiological data, because the coliphage results were not
valid, and because no firm plans had been made for a treatment technique
change in early 1982.
This screening procedure resulted in the selection of the Shenango Valley
Water Company (sampled during the summer of 1981) and the City of Topeka and
the Davenport Water Company (sampled during the summer of 1982) for the field
monitoring program. Of these three utilities, Davenport was ultimately
selected as the site for virus monitoring.
RATIONALE FOR SELECTION OF DAVENPORT, IOWA FOR VIRUS MONITORING
The two candidate sites for virus monitoring were Davenport, Iowa, and
Topeka, Kansas. The criteria used to select between these two was the limited
coliphage test results from samples collected during the summer of 1981, and
the initial sampling results from Davenport and Topeka between May and early
June, 1982. Based upon the coliphage results from the 1981 sampling, Topeka
would probably have been selected, as coliphage concentrations over 50 times
higher were detected. However, the Davenport results were only based on one
sample (all others arrived at more than 10°C) and may not have been
representative.
The results from the first part of the 1982 sampling were felt to be more
significant however. Conclusions from this early sampling were:
1. The log reduction of m-SPC between raw and finished water was lower
at Davenport (3.359 log reduction) than at Topeka (5.08 log
reduction). 30
-------
2. Detention time in the Davenport treatment plant was relatively short
(4.5-5 hours) compared to Topeka (over 8 hours). Also, at Davenport,
the planned treatment technique change would not use any disinfectant
until over half way through the treatment facility. This was felt to
be particularly significant from the standpoint of disinfection
efficiency.
3. Coliphage concentrations in raw water were higher at Topeka (an
average of 1976 PFU/100 ml) than at Davenport (an average of 440
PFU/100 ml), as shown following. However, coliphage were detected in
finished water at Davenport on one date, while no coliphage were
detected in finished water at Topeka.
Utility
Sampling Date
Raw Water Coliphage - PFU/100 ml
RNA Phage
DNA Phage
Total Phage
Davenport
Topeka
May 24, 1982
June 1, 1982
June 7, 1982
June 14, 1982
May 24, 1982
June 1, 1982
June 7, 1982
June 14, 1982
26
59
12
68
17
803
163
7
107 133
1 291 1350
74 86
126 194
Average = 440
NA NA
4175 4978
648 81 1
132 139
Average = 1976*
~Excluding May 24, 1982 sample.
Overall, it can be stated that the decision between these two utilities
was not clear-cut. After evaluation of all factors, the decision was made by
Culp/Wesner/Culp and James M. Montgomery Consulting Engineers to conduct virus
monitoring at Davenport, principally because the plant was providing less
effective treatment than at Topeka, and the planned treatment technique change
was felt to be more critical at Davenport (from a disinfection standpoint)
than at Topeka.
31
-------
QUALITY CONTROL - COLLECTION, SHIPMENT AND SAMPLE ANALYSIS
A Quality Assurance Project Plan3 was completed for this project, and
approved by EPA on August 5, 1982. The purpose of this Quality Assurance (QM
document was to present the policies, organization, objectives, functional
activities and specific QA and quality control activities which were used to
achieve the desired data quality goals. The QA Project Plan was prepared in
accordance with EPA's "Interim Guidelines and Specifications for Preparing
Quality Assurance Project Plans".4 Dr. Larry Leong, James M. Montgomery
Consulting Engineers (JMM) had primary QA responsibility for .laboratory
analytical data generated during this project.
After the three utilities were selected, they were visited by Dr. Larry
Leong (Shenango) or Dr. Robert Gumerman (Topeka, Davenport). The objectives of
these site visits were to meet the people with whom we would be working, to
inspect the treatment and laboratory facilities, to select sampling points at
the plant and in the distribution system, and to discuss protocol for sample
collection and shipment. Only sampling points which were currently used by the
utility were considered, as these sample points would be familiar to personnel
collecting the samples.
The Quality Assurance Project Plan outlines the custody of samples during
collection and shipment. In summary, the laboratory subcontractor for this
project, JMM, prepared and labeled all sample bottles prior to shipment to the
utilities. Listed on each label were plant location, sample location, and
sample type. Two blank spaces were provided on the label for the sample
collector to list time and date of sample collection. Bottles were shipped to
the utilities in ice chests, which were also used by the utilities to return
the refrigerated samples to JMM.
After sample collection, samples were placed in a freezer for several
hours to reduce the temperature to 4°C or less (but not to the point of
freezing the samples). The refrigerated samples were then packed in ice and
frozen "blue ice" packages and were sent by Federal Express or an equivalent
overnight courier service. Samples generally arrived at JMM laboratories
32
-------
within 24 hours of sample collection. A criterion for sample acceptability was
that samples be received at a temperature of 10°C or less.
Upon arrival at JMM, samples were logged into the laboratory computer
system, and microbiological tests were initiated immediately. The maximum
holding time for THM samples after collection was 30 days.
ANALYSES CONDUCTED AND PROCEDURES UTILIZED
The following sections discuss for each parameter measured, the location
of sampling within the plant and the test procedures which were utilized.
Standard Plate Count (Membrane Technique)
These samples were collected on raw water, water partially through the
treatment process (usually after settling), plant product water, vand at two
locations in the distribution system.
The test is a measure of the bacterial density in a water sample. It is
an empirical method, with the total number of cells measured being dependent
upon the media utilized and the incubation temperature. The media used by JMM
is called m-Standard Plate Count Media (m-SPC media) which contains: 2%
peptone, 2.5% gelatin, 1% glycerol, and 1.5% agar in distilled water. A 0.45
um (micron) pore size membrane filter was used and incubation was at 35°C.
This media was selected by JMM after an evaluation of several medias,
which included m-SPC media, R-2A media, and standard plate count agar.
Reference for the m-SPC media is: Taylor, R.H. and Geldrich, E.E. , "A New
Membrane Filter Procedure for Bacterial Counts in Potable Water and Swimming
Pools", JAWWA, Vol. 78, p. 402, July 19 79.
Total Coliform
Most Probable Number Technique —
Raw water samples were analyzed using the standard MPN test. Five tubes
per dilution were utilized. Reference is Standard Methods, 14th Edition, pp.
913-926. 33
-------
Modified Most Probable Number Technique --
Samples were collected at an intermediate point in the treatment plant
(usually after settling), plant product water, and at two locations in the
distribution system.
This technique is designed for the measurement of relatively dilute
coliform concentrations, as would typically be found in the treatment plant
product water. This technique combines the filtration of large quantities of
water with the most probable number test, and as such is referred to as high
volume testing. The volume of sample used in the testing was one liter. The
test allows for the quantification of low densities of total coliforms (0.02
per 100 ml). The reference for this technique is: Levin, M.A., Fischer, J.R.,
Cabelli, V.J., 1974. "Quantitative Large-Volume Sampling Technique", Appl.
Microbiology 28: 515-517.
Enteric Virus
Virus testing was only conducted at the Davenport Water Company Plant,
and only on raw water and plant product water.
The concentration of virus is based upon the adsorption of virus on a
filter during the filtration of large quantities of water, followed by the
elution (desorption) with approximately one liter of 3% beef extract at pH =
9.0. This one liter of extract can then be further concentrated to about 100
ml. A complete description of the equipment utilized, as well as the
procedures used for concentration, elution, reconcentration, and equipment
calibration are listed in the Quality Assurance Project Plan3, Appendix D,
pages D-21 to D-3 3.
Virus testing was only conducted at the Davenport Water Company Plant,
and only on raw water and plant product water.
E. Coli phage
Escherichia coli phage (referred to as coliphage in this report) testing
was conducted on raw water and plant product water.
34
-------
Coliphage testing was conducted using procedures recently developed by
Dr. Robert Safferman at the Virology Section, Environmental Monitoring and
Support Laboratory, EPA, Cincinnati. Coliphage analyses were conducted because
coliphage is an indicator of the presence of enteric virus, analagous to the
use of coliform tests as an indicator of the presence of pathogens. A complete
description of the procedures utilized is outlined in the Quality Assurance
Project Plan3, Appendix D, pp. D-7 to D—11.
Trihalomethanes
Trihalomethanes were sampled at all sampling points except the raw water.
The procedure utilized was EPA Method 501.2, modified by use of a phosphate
buffer. The THMs were concentrated by liquid-liquid extraction, then analyzed
by gas chromatography using an electron capture detector.
Temperature, pH, Turbidity, and Disinfectant Residual
Testing was conducted at various sampling points, depending upon the
parameter. These tests were conducted by the utilities and supplied to JMM on
data sheets prepared specifically for this project.
Total Organic Carbon (TOC)
TOC testing was conducted only at the Shenango Valley Water Company. The
testing procedure utilized was EPA Method 415.1.
OTHER QUALITY CONTROL CONSIDERATIONS
The Quality Assurance Project Plan3 contains detailed information
related to internal quality control checks, corrective action procedures, and
data handling for the laboratory analytical data generated during this
project.
35
-------
SHENANGO VALLEY WATER COMPANY SAMPLING PROGRAM
During the Summer of 1981, full scale testing was conducted at the
Shenango Valley Water Company, Sharon, Pennsylvania. Three different treatment
techniques capable of reducing THM concentrations in finished water were
evaluated in this testing. Techniques included prechlorination and post
chlorine dioxide, pre chlorine dioxide and postchloramines, prechlorination
and postchloramines. The sampling program conducted as a portion of this
project was accomplished between June 22, 1981 and October 14, 1981. A Final
Report^ on the sampling program was completed by JMM in July 1982.
Raw water for the treatment works was pumped directly from the Shenango
River. The treatment plant was a 0.438 m^/s (10 mgd) conventional alum
coagulation plant, as shown in the process schematic flow diagram, Figure 1.
Instead of using sand filtration, the dual media (anthracite and sand)
originally used in the filters had been replaced with granular activated
carbon (GAC) to remove taste and odor. The GAC was several years old at the
time of the field monitoring program.
Chemical addition capability at the raw water pump station included lime,
soda ash, and potassium permanganate. Lime and soda ash additions are used
during the winter months to increase alkalinity and improve coagulation.
Neither chemical was added during the sampling program. Potassium perman-
ganate, used for taste and odor control and to oxidize raw water manganese,
was added during the sampling program.
At the rapid mix basin, alum, powdered activated carbon (PAC) and the
initial dosage of disinfectant were added. The final disinfectant dose,
fluoride, and sodium hydroxide can be added to the clearwell; all three were
added during the course of the sampling program.
The sampling phases evaluated in the program were:
Phase 1 - Prechlorination and postchlorination - 16 days duration (June
22 - July 7)
36
-------
DISTRIBUTION
34) DEAD END" (43) FLOWING
o-
SAMPLING POINT
FIGURE 1
FLOW DIAGRAM AND SAMPLING POINTS
8HENANGO VALLEY WATER CO.. SHARON, PA.
37
-------
Phase 2 - Prechlorination and post chlorine dioxide - 23 days duration
(July 8 - July 30)
Phase 3 - Pre chlorine dioxide and postchloramines - 28 days duration
(July 31 - August 27)
Phase 4 - Prechlorination and postchloramines - 28 days duration (August
28 - September 24)
Phase 1A - Prechlorination and postchlorination -¦ 21 days duration
(September 24 - October 14)
.Five sampling points were used, each an existing sampling point of the
Shenango Valley Water Company. The sampling points are shown in Figure 1.
Sample point 1 was raw water, prior to the addition of any chemicals. Sample
point 2 was located after clarification, after the flow from the two
clarifiers had been blended together. Finished water samples, sample point 3,
were taken about 10 feet after the main booster pumps which pump from the
clearwell to the distribution system. Two sample points ( 34, 48) were located
in the distribution system. Sample point 34 was located at the dead end of a
pipeline, while sample point 48 was located on a main trunk line.
The number of samples taken in the different phases of the sampling
program were as shown following. The number of samples collected at each
sampling point are also shown, according to the order sample point 1, 2, 3, 34
and 48.
Number of Samples Collected
Phase m-SPC and coliform TOC THM
1 9+3+9+9+9=39 1+1+1+1+1= 5 1+0+1+1+1= 4
2 12+12+12+12+12=60 4+3+3+4+4=18 4+1+4+4+4=17
3 12+12+12+12+12=60 3+3+3+3+3=15 3+0+3+3+3=12
4 12+11+12+12+12=59 3+2+3+3+3=14 3+0+3+3+3=12
1A 3+3+3+3+3=15 1 + 1+1+1+1= 5 1+0+1+1+1= 4
Totals 233 57 49
The number of samples collected in each phase was equally divided among
the five sampling points, except for sample point 2 which had seven fewer
microbiological samples, 2 fewer TOC samples, and eleven fewer THM samples.
Sample point 2 was considered to be of less significance than the other four
sampling points. 38
-------
Records of disinfectant dosage and measurements for disinfectant
residuals are presented in Table 8. Based upon the results of the sampling
program, the following conclusions were reached.
1. When either chlorine dioxide or chloramines were used as the
postdisinfectant (Phases 2, 3, 4), a residual was measured in all
samples collected at both distribution system sample points. This was
not true in Phase 1A when postchlorination was used. In Phase 1A
(2.5 mg/1 post chlorine dose), all four samples collected at sample
point 34 measured zero free chlorine residual, and at sample point 48
one of the two samples measured showed zero free chlorine.The other
data point for sample point 48 was recorded as "about 1.5 mg/l."
This may have been an incorrect reading.
2. Comparisons of the plate count data using two different medias (m-SPC
and R2-A) were made at all five sampling locations. The results for
m-SPC media gave plate counts between one and two logs greater than
the R-2A media. On the basis of these results, no further testing
with R2-A media was undertaken in either the Shenango sampling
program or the subsequent sampling programs at Davenport, Iowa, or
Topeka, Kansas.
3. Geometric mean m-SPC values for raw water were relatively constant in
the first three phases, decreased slightly in the fourth phase, and
then decreased sharply in phase 1A. Mean raw water temperature
showed similar changes, and possibly were the cause of the m-SPC
decreases.
Phase
Raw Water
Geometric Mean Raw Water Mean
m-SPC - No./ml Temperature - °C
1
2
3
4
1 -A
1 4,000
13,000
12,100
4,800
1,170*
24.1
25. 2
24.3
20.6
14.0
~Based on three samples only
39
-------
TABLE 8
MEAN DISINFECTANT RESIDUALS (mg/L)
SHENANGO VALLEY WATER COMPANY
Phase
Average Sample Point 3 Sample Point 34 Sample Point 48
Dosage Finished Dead End Flowing
Free
Free
ci2 cio2 nh2ci ci2 cio2 NH0C1 Cl0 C10o NH0C1
Free
*2^-l C12 ^^2 ""2V
1 Pre C12
2 Pre Cl2
4.0
Pftst Cl2 2.5
5.06
Post C102 0.47
1 .7
1.0 0.4
0.2
0.1 0.1
0.3
0.2 0.1
3 Pre C102 0.62
Post NH2C1 4.78
0.2
2.6 0.1
1.2 0.2
1.5
4 Pre C12
4.0
Post NH2C1 4.5
2.8
0.3
0.9
0.4
1 .4
1A Pre C12
Post CI-
4.0
2.5
2.5
0.75 —
Notes
1. Dash means no sample was collected. Also, no samples were collected
at sample point no. 2 (clarified water).
2. In Phase 3, approximately 1.0 mg/L of free chlorine was added in
conjunction with the chlorine dioxide.
3. In Phase 3 on August 18 and 19, a 2.1 mg/L dose of chlorine was added
to the raw water due to the presence of high algae concentrations in
the raw water.
4. No sampling for chlorite or chlorate was performed in Phases 2 and 3,
when chlorine dioxide was one of the disinfectants utilized.
40
-------
4. Geometric mean m-SPC reductions between raw water and clarified
water (sample pt. 2) indicate about a 3.3 log reduction when
chlorine was the predisinfectant (Phase 1), and a 2.6 log reduction
when chlorine dioxide was the predisinfectant (Phase 3). Between
these two sampling points and for the dosages which were used,
chlorine dioxide was a less effective predisinfectant. Much of this
difference in disinfection effectiveness may be the result of the
relatively low chlorine dioxide dose (0.62 mg/L) which was used,
compared to 4.0 mg/L of chlorine in Phase 1 (see Table 8). This low
chlorine dioxide dosage was selected because of EPA's concern for
high chlorine dioxide plus chlorite residuals; the sum of these two
constituents was recommended by EPA not to exceed 0.5 mg/L at the
time the sampling program was conducted. Also to be noted is the lack
of any chlorine dioxide residual measurements when chlorine dioxide
was used as a predisinfectant.
5. Using the number of positive coliform tubes at the clarified sample
point (#2) as a basis, chlorine dioxide as a predi sinf ectant was
statistically less effective than the use of chlorine as a
predisinfectant. However, during this Phase 3 testing, chlorine
dioxide residual was not measured, and it is not known if a chlorine
dioxide residual existed.
6. Based upon a statistical analysis of mean m-SPC reductions between
raw water and finished water (sample point 3), the effectiveness of
the different phases (from most effective to least effective) and the
mean log reductions were:
Chlorine/chlorine dioxide (Phase 2) -4.81 logs
Chlorine/chlorine (Phase 1) -4.24 logs
Chlorine/chloramines (Phase 4) -3.73 logs
Chlorine dioxide/chloramines (Phase 3) -3.55 logs
For the dosages utilized, this indicates that chlorine dioxide was a
more effective postdisinfectant than chlorine, between the raw water
41
-------
and finished water sampling points, and a less effective
predisinfectant. Also to be noted are the low chlorine dioxide
dosages, relative to the chlorine dosages (Table 8).
7. Based upon finished water coliform samples (sample point #3) the
data indicate that predi s infect ion with chlorine dioxide and
postdisinfection with chloramines had an occurrence of total
coliforms in the finished water which was significantly higher than
when chlorine was used as a predisinfectant in combination with
either chlorine, chlorine dioxide, or chloramines as post
disinfectants. See Table 9.
8. Based upon m-SPC test results, all disinfectant combinations allowed
regrowth at the "dead end" sampling point (#34) and post
disinfection with chlorine and chlorine dioxide allowed regrowth at
the trunk line sampling location (#48). Disinfectant residuals are
shown in Table 8. Only pos tdi sinf ection with chloramines prevented
regrowth at the trunk line sampling point. Fran the standpoint of
distribution system regrowth, use of chlorine dioxide as a post-
disinfectant allowed the maximum regrowth.
9. At sample point 34, the dead end point in the distribution system,
significant regrowth of coliform organisms occurred (50% of samples
had positive tubes) using prechlorination and post chlorine dioxide,
as shown in Table 9. This was significantly higher than in the
finished water (sample pt. 3) which had only 8% of the coliform
samples with positive tubes. At the flowing point in the
distribution system (sample pt. 48), all disinfectant combinations
were equally effective, although the pre chlorine di oxide/pos t-
chloramine combination had 17% of the coliform samples with positive
tubes.
42
-------
TABLE 9
PERCENTAGE OF SAMPLES SHOWING POSITIVE TOTAL COLIFORM TESTS
SHENANGO VALLEY WATER COMPANY
Phase
Sample Pt. 2
(Clarified)
Sample Pt. 3
(Finished)
Sample
Point 34
(Dead End)
Sample
Point 48
(Flowing)
1
Pre Cl2
Post CI2
0% (3)
0% (9)
22% (9)
0% (9)
2
Pre CI2
Post C102
17% (12)
8% (12)
50% (12)
0% (12)
3
Pre CIO2
Post NH Cl2
83% (12)
75% (12)
8% (12)
17% (12)
4
Pre Cl2
Post NH Cl2
0% (11)
0% (12)
25% (12)
8% (12)
1 A
Pre Cl2
0% (3)
0% (3)
0% (3)
0% (3)
Post CI2
Note: Number of samples collected is shown in parenthesis.
43
-------
10. Mean THM concentrations for sample points 3, 34, and 48 appeared to
be a function of both the disinfectant(s) used and the mean raw water
temperature, as shown below.
Instantaneous Mean Mean Raw Water
Phase Disinfectant THM Levels, ug/L Temperature, °C
Raw
Finished Water
Water
and Dist System
1
ci2/ci2
1.8
165
24
2
ci2/cio2
3.3
107
25
3
cio2/nh2ci
0. 3
54
24
4
C12/NH2C1
1.1
89
21
1 -A
C12/C12
4.2
99
14
Based on this data, use of either chlorine dioxide and/or chloramines
as a replacement for chlorine, results in a reduction in THM concen-
tration. Also, the reduction in mean THM concentration from 165 to 99
between Phase 1 to 1A is most likely a function of the mean raw water
temperature decrease from 24°C to 14°C.
General conclusions of the Shenango sampling program were: chlorine
dioxide was a less effective predisinfectant than chlorine and when used as a
postdisinfectant, allowed significant regrowth in the distribution system;
postchloramination is able to further inactivate coliform organisms which pass
through the treatment barrier; and postchloramination is a slow acting
disinfection technique which does not significantly reduce coliforms in the
finished water, but which does inactivate coliforms in the distribution system
after a longer period of contact.
DAVENPORT WATER COMPANY SAMPLING PROGRAM
The treatment strategy used for THM control at the Davenport Water
Company, Davenport, Iowa, was to shift the initial point of chlorination
application from the raw water to a point half way through the settling basin.
As a part of this project, sampling was conducted between May 17, 1982 and
August 4, 1982. A final report^ on this sampling program was prepared by
JMM and submitted in December 1982.
44
-------
The Davenport Water Company plant has a capacity of 1.314 m3/s (30
mgd), which is comprised of two parallel 0.657 m3/s (15 mgd) treatment
trains. Raw water is pumped directly from the Mississippi River, which is
adjacent to the plant. Treatment consists of alum flocculation, settling,
granular activated carbon (GAC) filtration, and clearwell storage. The GAC is
contained in structures which were previously sand filters, but have been
converted to GAC contactors. The GAC had been replaced within several weeks
of the initiation of the sampling program. Typically, the GAC is replaced once
per year, and has an intended purpose of taste and odor reduction; it is not
used specifically for removal of THM precursors. Sampling was divided into two
phases:
Phase 1 - No treatment change for THM control. Chlorine was added to the
raw water prior to the raw water pumping station. Following GAC
filtration, chlorine was added in conjunction with ammonia.
Phase 2 - Shifted point of chlorination for THM control. Chlorine was
added half-way through the settling basin, and in conjunction
with ammonia, after the GAC filtration.
A four day period was allowed between Phase 1 and Phase 2 to allow the
treatment process and distribution system to equilibriate to the changed
conditions. Treatment process flow diagrams for these two phases are shown in
Figures 2 and 3, respectively. Also shown are the point of addition of
chlorine and other chemicals and the five sampling points: 1 - raw water; 2 -
after flocculation and settling; 3 - product water clearwell; and 4 and 5 -
distribution system.
Sampling point 4 (Palmer Hills) in the distribution system was located
about 2 hours detention time from the treatment plant, and sampling point 5
(Leisure Lane) was one of the longest detention times in the distribution
system, an estimated 5 to 6 hours of detention time from the plant. There was
no rechlorination within the distribution system which would affect sampling
points 4 and 5.
An aerial photograph of the treatment plant is shown in Figure 4.
45
-------
ALUM
LIME (PH ADJUST)
POTASSIUM
PERMANGANATE
•u
o
o-
FIGURE 2
DAVENPORT WATER COMPANY
PROCESS FLOW DIAGRAM AND SAMPLING POINTS
PHASE 1: ORIGWAL POINT OF CHLORINATION
-------
ALUM
COAGULANT
AID P.A.C.
(EMERGENCY)
RAW
®\
MISSISSIPPI
RIVER
LOW LIFT
PUMP
STATION
FLOCCULATION
BASIN
LIME (PH ADJUST)
POTASSIUM
PERMANGANATE
SETTLING
BASIN
t
CHLORINE
BASIN
-
f
CHLORINE
o-
FIGURE 3
DAVENPORT WATER COMPANY
PROCESS FLOW DIAGRAM AND SAMPLING POINTS
PHASE 2: SHIFTED POINT OF CHLORINATION
-------
Photo Upper - Davenport Water Company, Davenport, Iowa
Credits: Lower - Mr. James Walasek, U.S. Environmental Protection Agency,
Cincinnati, Ohio
Figure 4. Aerial Photographs of the Davenport Water Company Water Treatment
Plant.
48
-------
The number of samples collected at the various sampling points was as
follows:
Phase
1
Original Point
of Chlorination
Total
Shifted Point
of Chlorination
Total
Sampli ng
Point
1-Raw
2-Settled
3-Finished
4-Palmer Hills
5-Leisure Lanes
1-Raw
2-Settled
3-Finished
4-Palmer Hills
5-Leisure Lanes
m-SPC and
Coliform Phage
16
16
16
16
1£
80
17
17
17
17
11
85
6
6
f2
4
4
Viruses
2
2
THM
4
5
_4
18
4
4
_4
16
No TOC samples were collected at Davenport, as it was felt that resources
would be more beneficially utilized by sampling other parameters.
Table 10 presents results of sampling for the disinfectant dosage and
mean disinfectant residual. As shown, the initial chlorine dosage was somewhat
higher in Phase 1 than in Phase 2, but the post chlorine dosage and the
residuals at the three sampling points measured were essentially equal.
Table 10 - Disinfectant Dose and Mean Disinfectant Residual Information
Davenport Water Company
Phase 1
Phase 2
Initial Chlorine Application
Prechlorination
After partial
6-7 mg/L
settling
4-6 mg/L
Post Chloramine Dose
1.5-2.0 mg/L
1.5-2.0 mg/L
Settled Water Disinfectant Residual
(Samp.
Pt. 2)
Free
0.49 mg/L
0. 48 mg/L
Total
0.79 mg/L
0.80 mg/L
Finished Water Disinfectant Residual
(Samp.
Pt. 3)
Free
0.05 mg/L
0.04 mg/L
Total
1.56 mg/L
1.46 mg/L
Distribution System Total Disinfectant Residual
Sampling Point No. 4
0. 74 mg/L
0.55 mg/L
Sampling Point No. 5
0.80 mg/L
0.72 mg/L
49
-------
On the basis of the sampling results contained in the Final Report^ for
the Davenport sampling program, the following conclusions were reached.
1. Raw water m-SPC plate counts during the 2 1/2 month period of
sampling (May 17, 1982 to August 4, 1982) were relatively constant
(counts were 0.4 logs less in Phase 1 than Phase 2), even though the
mean raw water temperature increased by about 6°C, from 19.2 to
25.2°C.
2. m-SPC plate counts showed mean log reductions through treatment of
3.34 and 3.61 for Phases 1 and 2, respectively. A statistical
comparison indicated that both of the two points of initial chlorine
application are equally effective in reducing the finished water
plate count.
3. In both phases, the m-SPC median (50%) values in the distribution
system were higher than the median values in the finished water.
This indicates that there was regrowth of bacteria within the distri-
bution system. A statistical comparison of the geometric mean plate
counts indicated however, that this difference was not statistically
significant.
4. The total coliform concentration in the raw water was essentially the
same in both phases. The data indicated that the point of chlorine
addition made no difference in the number of positive coliform tubes
at sample points 2, 3, 4 and 5 (settled water, finished water and in
the distribution system) and that the levels of coliform bacteria
were consistently low (less than 1/100 ml) at all sampling points
except raw water, in each phase. Coliform removals of up to 5.4 logs
were detected.
5. In Phase 1, six sets of raw and finished water samples were collected
for analysis of RNA and DNA coliphage, and in Phase 2, four paired
raw and finished water samples were collected. For raw water
analyses, one liter of water was concentrated, and for finished water
50
-------
samples, 10 liters of water were concentrated. A summary of data
collected on raw water coliphage quality in Phases 1 and 2 follows.
Phase 1 Phase 2
Range of Phage Concentrations - PFU/100 ml 39-1350 105-3978
Median (50%) Concentration - PFU/100 ml 119 222
Ratio of DNA to RNA Phage - Based on median
(50%) concentration 9:1 4:1
Coliphage were detected in the finished water on one sampling day in
Phase 1 (DNA phage detected), and on one sampling day in Phase 2 (RNA
phage detected). On June 1, when coliphage were detected in Phase 1,
the coliphage removal efficiency was 4 logs, compared to removals on
other days of 3.6 to 4 logs. Thus, on June 1, the plant was operating
within the upper range of its experienced phage removal capability.
This was not true in Phase 2 when coliphage was found in the finished
water on July 6. On this date, 2.9 logs of coliphage were being
removed, in contrast to the normal coliphage removal limits of 4.0 to
5.6 logs. Information on the dates of coliphage occurrence in the
finished water is shown following:
Phase 1 Phase 2
Coliphage removals when no coliphage 3.6-4.3 4.0-5.6
were detected in finished water logs logs
Information on date of detection in
finished water
Date June 1 July 6
Concentration in raw water - PFU/100 ml 1350 258
Concentration in finished water -
PFU/100 ml 0.14 0.33
Coliphage removal 4 logs 2.9 logs
It is important to note the following additional information on the
day of phage detection in the finished water in Phase 1.
• Raw water phage concentration was the highest of any sample in
this Phase 51
-------
• Coliform removal rate was 5.1 logs and no coliform were detected
in finished water
• m-SPC counts in the raw and finished water were the highest levels
detected in this Phase.
• Turbidity was the highest on this date of any day in Phase 1, 3 4
NTU in contrast to a median value of 22 NHJ.
Due to the small number of coliphage samples collected, no
statistical comparison could be made.
6. Cumulative total probability plots of total coliform and coliphage
data indicated a mean log ratio of 1:1.4, and the similarity in the
slope of the lines indicated a similar population distribution of
these two organism groups,
7. Two paired samples of raw and finished water were concentrated and
assayed for enteric virus in both Phase 1 and Phase 2. No enteric
virus were detected in any of these samples#
8. Mean THM levels increased from Phase 1 to Phase 2, and exceeded the
THM MCL in both phases, as shown following!
Phase 1 Phase 2
May 17 to June 28 to
Location June 24 August 4
Finished Water iTS 133
Distribution System - Sampling Pt, 4 127 136
Distribution System - Sampling Pt. 5 116 130
Relative to these increases, it should be noted that the mean water
temperature increased 6°C from Phase 1 to Phase 2.
The overall conclusion of this monitoring program is that the change in
the point of chlorination did not decrease the bacterial quality of the
finished water* This was true in spite of the absence of any disinfection
until the mid-point of the settling basin, where chlorine was first intro-
duced, Significantly^ there was no THM reduction due to the changed point of
chlorination, which is in contrast to data collected earlier by the utility,
52
-------
The differences between earlier THM data collected by the utility and data
collected during this monitoring program may be due to different water
temperatures, different precursor types or concentrations, different
analytical techniques, or sample preparation differences.
TOPEKA WATER DEPARTMENT SAMPLING PROGRAM
At Topeka, Kansas, the treatment strategy used for THM reduction was to
use ammonia in conjunction with chlorine for formation of chloramines. The
sampling program at Topeka was conducted between May 17, 1982 and August 4,
1982, and a Final Report? on this sampling program was submitted by JMM in
December 19 82.
The City of Topeka treatment plant pumps raw water frcm the Kansas River,
which is adjacent to the plant site, and is about four miles upstream of down-
town Topeka. There are actually three different treatment plants built at
different times on the plant site, and the South Plant was selected for this
study. The South Plant is a lime softening plant with a capacity of 0.876
m^/s (20 mgd). The treatment train consists of presedimentation, a
prechlorination basin (called the "breakpoint chlorination basin"),
first-stage rapid mix/flocculation/settling, second-stage rapid
mix/flocculation/settling, rapid sand filtration, and clearwell storage.
Two sampling phases were used:
Phase 1 - No treatment change for THM control. Breakpoint chlorina-
tion was used after presedimentation and prior to the first
stage rapid mix basin. Postchlorination was used.
Phase 2 - Prechlorination dose was reduced, and ammonia was added
after the "breakpoint basin" (2-3 hours after chlorine
addition), to convert remaining free chlorine to
chloramines. Prior to rapid sand filtration, ammonia and
chlorine were added for post disinfection.
A four day period was allowed between the two phases to allow the treatment
process and the distribution system to come to equilibrium after the change in
disinfection practices. c.
-------
A process flow diagram of the treatment plant in Phases 1 and 2 is shown
in Figures 5 and 6, respectively. Also shown are the five sampling points: 1 -
raw water; 2 - after second stage settling; 3 - after clearwell storage; and 4
and 5 - distribution system locations. One distribution system sampling point
(Sample Point 4) was located near a major trunk line conveying water to a
37,850 m^ (10 MG) terminal storage reservoir. The detention time (after
treatment) at this location was less than 8 hours. The second distribution
system sampling point (Sample Point 5) was at a remote location, and the
detention time prior to water reaching this location was 2-3 days. In the
past the City had noted no or low chlorine residuals at this location. Both
of the distribution system sampling points were existing sampling points used
by the City.
An aerial photo of the treatment works is presented in Figure 7.
The number of samples collected at the various sampling points was as
follows:
m-SPC and
Phase
Sampling Point
Coliform
Phage
THM
1
1-Raw
16
5
5
Pre- and
2-Settled
16
Pos tchlorination
3-Finished
16
5
5
4-Near Reservoir
16
5
5-Near Airport
16
5
2
1-Raw
17
4
3
Combined Chlorine
2-Settled
17
3-Finished
17
3
3
4-Near Reservoir
17
3
5-Near Airport
17
3
Chlorine and post disinfectant dosages, as well as results of sampling for
total and free chlorine residuals are shown in Table 11. As shown, no free
chlorine residual was measured in Phase 2.
54
-------
CLEARWELL
RAPID SAND
FILTERS
(«T^
3) FINISHED
CHLORINE
CARBON DIOXIDE
SODIUM HEX.
FLUORIDE
RAPID MIX
-
FLOCCULATION
a
-SAMPLING POINT
FIGURE 5
CITY OF TOPEKA
PROCESS FLOW DIAGRAM AND SAMPLING POINTS
PHASE 1: CHLORINE/CHLORINE
-------
Ul
CI
POLYMER
PiA.C.
CHLORINE
HAW
°v
AMMONIA
LIME
ALUM
CARBON DIOXIDE
KANSAS
RIVER
PI1E
SEDIMENTATION
BASIN
BREAKPOINT
CHLORIN ATION
BASIN
ASH
RAPID MIX
FLOCCULATION
\ SETTLED
3 ) FINISHED
AMMONIA
CHLORINE
CARBON DIOXIDE
SODIUM HEX.
FLUORIDE
CLEAIIWELL
RAPID SAND
FILTERS
SETTLING
RAPID MIX
FLOCCULATION
1
I
O SAMPLING POINT
FIGURE 6
CITY OF TOPEKA
PROCESS FLOW DIAGRAM AND SAMPLING POINTS
PHASE 2: CHLORINE/CHLOR AMINES
-------
Photo Mr. James Walasek, U.S. Environmental Protection Agency,
Credit: Cincinnati, Ohio
Figure 7. Aerial Photograph of the City of Topeka Water Treatment Plant.
57
-------
Table 11 - Disinfectant Dosage and Mean Disinfectant Residual Information
City of Topeka
Initial Chlorine Dosage
Phase 1
8-13 mg/L
Phase 2
3.6 mg/L
followed by NH^
after 2-3 hours
Post Disinfectant Dosage
2-3 mg/L of
chlorine
2-3 mg/L of
chloramine
Settled Water Disinfectant Residual
(Sample Point 2)
Free
Total
Finished Water Disinfectant Residual
(Sample Point 3)
Free
Total
Distribution System Disinfectant Residual
0.48 mg/L
0.64 mg/L
3.08 mg/L
3.19 mg/L
0.0 mg/L
0.26 mg/L
0.0 mg/L
2.97 mg/L
Sample Point 4 Free
Total
2.40 mg/L
2.50 mg/L
0.0 mg/L
2.73 mg/L
Sample Point 5 Free
Total
1.02 mg/L
1.13 mg/L
0.0 mg/L
1 .89 mg/L
Based upon the results contained in the Final Report? for sampling
program, the following conclusions were reached.
1. Raw water m-SPC plate count values were relatively constant during
both phases of the study, as shown in Table 12.
58
-------
TABLE 12. GEOMETRIC MEAN PLATE COUNT PER 100 ML
CITY OF TOPEKA
Sampling Point
Raw
Settled
Finished
Distribution, Sample Pt. 4
Distribution, Sample Pt. 5
Phase
1
T70 x-TO?
5.99 x 101
9.95 x 101
2.42 x 101
8.05 x 102
4.67 x 10°
2.14 x 1 03
5.2 x 101
3.39 x 101
8.4 x 102
Table 12 indicates that breakpoint chlorination in Phase 1 is
substantially more effective at reducing the m-SPC values between raw
water and settled water, relative to Phase 2. However, no
statistical difference occurred in plate count reductions between raw
and finished water in Phases 1 and 2. Both forms of disinfection
removed 5 logs of plate count bacteria between raw water and finished
water in Phases 1 and 2.
In both phases, there was an increase in plate count bacteria in the
distribution system, although the increase was not statistically
significant. Both types of disinfection appear equally effective in
maintaining microbial quality in the distribution system at detention
times between 8 hours and 2-3 days.
Raw water coliform concentrations were relatively constant during
both phases. The geometric mean was 1.2 x 104 MPN/100 ml in Phase 1
and 5.5 x 103 MPN/100 ml in Phase 2. Total coliform destruction in
both phases was at least 5.7 logs of coliform organisms, and except
for the raw water, the coliform levels at the other four sampling
points were consistently low (less than 1/100 ml). Due to the low
concentration of coliform organisms at all points other than raw
water, comparing log reductions or the MPN of coli forms is not
useful. Instead, a statistical analysis of the frequency of positive
and negative tubes in the coliform tests was conducted. This analysis
indicated that the disinfection procedures used in Phases 1 and 2
were equally effective in reduction of coliform bacteria during
treatment and in the distribution system.
-------
4. Four paired samples of raw and finished water in each phase were
concentrated and assayed for E. coliphage. In these tests, one liter
of sample was concentrated for raw water testing, and 10 liters was
concentrated for finished water testing. Total raw water phage
detected in Phase 1 were between 139 and 4,978 PFU/100 ml (geometric
mean was 824 PFU/100 ml) and in Phase 2 were between 738 and 2,193
PFU/100 ml (geometric mean was 1,140 PFU/100 ml). DNA phage were 4-20
times higher in concentration than RNA phage. Importantly, no DNA or
RNA phage were detected in any of the eight finished water samples
tested. Both disinfectants were capable of inactivating at least 5
logs of coliphage.
5. During the softening process, pH was increased over 2 units above raw
water pH (from about 8 to 10), and water in the distribution system
was about 1.5 units higher than raw water pH values (frcm about 8 to
about 9.5). Such high pH values are above optimum conditions for
microbiological cells, and thus high pH aids the disinfection
process. Conversely, high pH decreases the efficiency of
chlorination, by shifting the HOC1/OC1- equilbrium toward 0C1~,
which is a less powerful disinfectant. Average pH values at each of
the five sampling points in Phases 1 and 2 are shown following:
Average pH values
Phase
2
Sample Point
3
4
5
2
8.00
8.1 1
10. 22
10.1 2
9.56
9.59
9. 49
9.47
9.55
9.52
6. Use of chloramines in Phase 2 significantly reduced mean THM
concentrations, as shown following:
Finished Water
Distribution System (Sample Pt. 4)
Distribution System (Sample Pt. 5)
Sampling Location
Phase 1 Phase 2
29 7 ug/L 78 ug/L
304 ug/L 76 ug/L
334 ug/L 105 ug/L
The average raw water temperature in Phases 1 and 2 was 20.2°C and
24.9°C, respectively. 60
-------
Overall conclusions of the Topeka sampling program were that chloramines
are just as effective a disinfectant as free chlorine, after a contact time of
11 to 12 hours and that THM concentrations can be effectively reduced.
Although mean THM values (105 ug/L) at the distribution sampling point with
the longest detention time were above the THM MCL, it would be reasonable to
expect that conformance with the THM MCL would be achieved on an annual basis
if a running average of quarterly samples were used, as required by the TtW
Regulations.
61
-------
CHAPTER 5
GUIDANCE CRITERIA FOR UTILITIES PROPOSING TREATMENT
TECHNIQUE CHANGES TO ACHIEVE THM COMPLIANCE
Beginning on the following page is a Guidance Manual which EPA plans to
publish as a separate document. The Guidance Manual is intended for use by
utilities serving fewer than 75,000 individuals, although most of the exper-
ience data used in the development of this Guidance Manual is based upon
larger utilities.
A separate set of references is provided for the Guidance Manual.
62
-------
SECTION 1
INTRODUCTION
Utilities which serve between 10,000 and 75,000 individuals, and which
use a disinfectant were required to begin monitoring for trihalomethanes
(THMs) by November 29, 1982, and to be in compliance with the THM Maximum
Contaminant Level (MCL) no later than November 29, 1983.1 This Guidance
Manual has been prepared to assist these utilities in achieving compliance.
Discussed within this Manual are:
• The trihalomethane formation reaction.
• Necessary steps for compliance with the THM MCL.
• Guidance for systems using chlorination only.
• Guidance for systems using conventional treatment.
• Guidance for systems using lime softening.
• A summary of microbiological concerns.
• Costs of best generally available treatment methods.
Throughout this Guidance Manual, the importance of insuring continuous
protection against pathogenic organisms in the treated water is stressed. This
is particularly important. The intent of the regulations relating to THMs is
twofold; first to achieve compliance with the THM MCL, and secondly to
preserve microbiological integrity of the finished water.
63
-------
SECTION 2
THE TRIHALOMETHANE FORMATION REACTION
The generalized reaction for formation of THMs is:
Free chlorine Organic
and/or bromine + Precursors ^ Trihalomethanes + Byproduct Compounds
Reactants in this equation are free chlorine (or bromine) and organic
precursors (humic and fulvic substances), and the products are TH4s and
byproduct compounds. The byproduct compounds include both halogenated and
nonhalogenated reaction byproducts. THMs can be considered to be a byproduct
of disinfection.
TRIHALOMETHANE PARAMETERS
Four THM parameters are important to the understanding of the THM
Regulations and THM control strategies. These parameters are shown graphically
in Figure 8 and are discussed below:
Instantaneous THM
Instantaneous THM (Inst THM) is the THM concentration at the moment of
sampling. Compliance with the THM MCL is determined using Inst THM. It can be
expressed in terms of the sum of the individual species, or as each of the
four major species (chloroform, bromodichloromethane, dibramochlorcmethane,
and bromoform). Although, other THM species may be formed, the Ttti MCL
includes only these four species.
Terminal THM
Terminal THM (Term THM) is a measurement of the TfW present after a
specified time period. In most cases, the time utilized is equivalent to the
time of treatment plus the distribution system detention time. The temperature
of the test is the distribution system water temperature.
64
-------
FIGURE 8
THM PARAMETERS AND THEIR RELATIONSHIPS
65
-------
THM Formation Potential
Trihalomethane Formation Potential (THMFP) is the increase in TH4
concentration during the storage period for the Terminal THM test. In other
words, Terminal THM minus Instantaneous THM equals THMFP.
Maximum Total Trihalomethane Potential
Maximum Total Trihalomethane Potential (MTP) is an attempt to maximize
the formation of THMs, with the test results being indicative of how high the
total trihalomethane (TTHM) concentration in the distribution system might
become under conditions favoring TTHM formation. The test is conducted over 7
days at a temperature of 25°C (77°F) or above. A chlorine residual of at least
0.2 mg/L must be present at the completion of the test, or the MTP test must
be rerun using an initial chlorine concentration of 5 mg/L and a solution pH
buffered to 9.0 - 9.5 (EPA Method 510.1). Reference 2 presents additional
information on conduct of the MTP test.
FACTORS INFLUENCING THE RATE OF THM FORMATION
The rate of the THM formation reaction is influenced by a number of
factors. Among the more important are:
• Temperature
• pH
• Organic Precursors
• Free Chlorine Concentration
• Bromide Concentration
Temperature
Higher water temperatures increase the rate of THM formation. Utilities
using surface water supplies generally experience highest THM concentrations
during the summer months, when temperatures are highest. For groundwater
supplies, temperature variations are less dramatic, and seasonal variation in
66
-------
THMs will be less pronounced. Many utilities have found that treatment
techniques for THM control are not necessary during the winter months, vrtien
lower water temperatures decrease the reaction rate and when organic precursor
concentrations are lower.
pH
Higher pH values increase the rate of THM formation, and generally also
the terminal THM. This impact is believed to be due to changes which occur in
the qrganic precursors, making them more reactive. The impact of high pH is
most evident in lime softening plants, which often operate at pH values up to
11.0.
Organic Precursors
The type and concentration of organic precursors influence the reaction
rate. Due to the diverse nature of the precursors, the best measure of their
impact is to conduct a THMFP test. This test will indicate the quantity of
precursor which is available to react with free chlorine. At the completion of
the Terminal THM test, all of the organic precursors will not have reacted, as
shown in Figure 8. Under other test conditions, such as longer time of
reaction or higher temperature, a portion of this precursor material nay
react. Thus, it is important when measuring THMFP to select test conditions
representative of the water supply system being evaluated.
Free Chlorine Concentration
The presence of free chlorine is necessary for the THM formation reaction
to proceed. However, free chlorine residuals in excess of the chlorine demand
have little impact on accelerating the rate of Ttt4 formation. Initial mixing
and reactor design may impact the rate of formation even when the chlorine
residual is in excess of the demand.
67
-------
Bromide Concentration
Bromide ion is oxidized to bromine by free chlorine. The bromine molecule
can then react with organic precursors to form THMs. Three of the four
trihalomethanes included in the THM MCL require the presence of bromine for
formation. Importantly, the rate of formation of bromine containing TfWs is
faster than the rate of chloroform (a nonbramine TIM) formation, because
bromine competes more effectively than chlorine for the active sites on the
organic precursor molecules. Bromide ions are naturally accuring in many water
supplies, while in some surface or groundwater supplies, the bromide ion is
the result of sea water intrusion.
68
-------
SECTION 3
NECESSARY STEPS FOR COMPLIANCE WITH THE THM MCL
The necessary steps for compliance with the THM MCL are shown in
Figure 9. Each of these steps is discussed in the sections which follow.
COLLECTION OF QUARTERLY SAMPLES
The first step is collection of quarterly samples, for quarters ending on
March 31, June 30, September 30, and December 31, 1983. These quarterly sample
results must be submitted to the primacy agency within 30 days of the system's
receipt of the results, unless otherwise stipulated by the primacy agency. In
States which have been granted primary enforcement responsibility by the EPA,
the primacy agency is the agency of the State government with jurisdiction
over public water systems. In States without primary enforcement responsibil-
ity, the primacy agency is the Regional Office of the U.S. Environmental
Protection Agency.
Sampling requirements and conditions for reduced sampling frequency are
different for surface water and groundwater supplies. The following two
sections discuss principal differences. A more complete discussion of sampling
requirements is included in the EPA publication, "Guidance For the Sampling,
Analysis and Monitoring of Trihalomethanes in Drinking Water,"2
Quarterly Sampling For Surface Water Supplies
For surface water systems, a minimum of four samples per quarter are
required for each treatment plant. Quarterly samples from the distribution
system are to be collected within a 24 hour period, and at least 25 percent
are to be at locations in the distribution system which reflect the maximum
residence time. The remaining 75 percent are also to be collected from the
distribution system, at representative locations based on individuals served,
sources of water, and treatment methods utilized.
69
-------
FIGURE 9
NECESSARY STEPS FOR COMPLIANCE WITH THE THM MCL
-------
Compliance is based upon an annual running average of the four quarterly
averages. After one year of compliance monitoring, a request to decrease the
monitoring frequency can be made to the primacy agency if the instantaneous
TTHM concentration has never exceeded 0.1 mg/L. The decision to reduce the
sampling frequency should be made on a case-by-case basis by the primacy
agency. If a reduced sampling frequency of one sample per quarter is allowed,
this sample should be collected at the point in the distribution system with
the maximum residence time.
When there is more than one treatment plant, more than one surface
supply, or a combination of surface and groundwater supplies, the number of
samples can be reduced, but generally not to a frequency as low as one sample
per quarter. Also, if a system is operating on a reduced monitoring frequency
and there is a significant change in the source water or the type of treatment
utilized, the sampling frequency must immediately be increased to four samples
per quarter. A discussion of the probable number of reduced samples for such
situations is presented in Reference 2.
Quarterly Sampling For Groundwater Supplies
Groundwater supplies generally are more consistent in quality and have
lower precursor concentrations than surface supplies. Thus, monitoring
requirements for THMs are less restrictive for groundwater supplies.
For systems using only groundwater, the monitoring frequency can be as
low as one MTP (maximum total trihalomethane potential) test per year for each
aquifer. This sample must be collected from the distribution system location
having the longest residence time. Before the primacy agency will permit this
reduced frequency, substantiation must be presented by the utility that the
MTP is less than 0.1 mg/L during the time of the year when maximum TTHM
formation and/or when the highest TOC concentration occurs.
EVALUATION OF TREATMENT OPTIONS
If the quarterly monitoring results indicate that a utility is not in
compliance with the THM MCL, and an alternate water supply is not available, a
71
-------
treatment technique change should be considered. In some cases only minor
modifications will be necessary to achieve compliance. Examples of minor
modifications are improved precursor removal by seasonal use of PAC, or
increased coagulant or coagulant aid dosages. Assuming that the disinfectant
practices remain unchanged, these changes are considered minor because they
would not significantly impact the microbial quality of the finished water.
A treatment modification is considered significant if the impact on
microbial quality of the finished water has not been established. Examples of
such significant changes are:
• Change in disinfectant type, dosage, point of application, or contact
time.
• Change in the source water, either partially or completely.
• Addition of granular activated carbon in the treatment process.
• Addition of an open finished water reservoir.
ACTION PLAN
If minor modifications do not achieve compliance, and a significant
treatment modification is deemed to be necessary, an action plan must be
submitted to the primacy agency. The three minimum components of the action
plan are:
• Evaluation of System for Sanitary Defects
• Baseline Water Quality Survey
• Evaluation of Treatment Options
Evaluation of System for Sanitary Defects
The intent of the sanitary survey is to identify and correct any sanitary
defects, unsound treatment practices, or inadequate operation and maintenance
practices, before any changes are implemented for the control of Tttls. This
survey should include the entire system: source(s), treatment plant(s), and
distribution system.
72
-------
No exact survey protocol must be followed, although Reference 2 presents
the minimum recommended elements of a sanitary survey.
Baseline Water Quality Survey
The action plan must include a detailed description of a baseline water
quality monitoring survey. This water quality survey should be conducted for a
minimum of six months before making a significant treatment technique change,
and twelve months afterward. Detection of changes in finished water quality
which result from changes in the treatment technique is the purpose of the
survey. In specific, the survey is aimed at detecting changes which may lead
to increased public health risk due to the presence of pathogenic organisms in
the finished water. To account for seasonal variations, the survey period
before the treatment technique change should include the warmest month of the
year.
Parameters which must be evaluated in this baseline survey have not been
established by the EPA. However, consideration of the following parameters is
recommended by the EPA. 2
Microbial Parameters
9 Total coliforms
• Standard plate counts (20°C and 35°C)
• Heterotrophic plate count (at temperature of water)
• Total fecal coliforms
• Fecal streptococci
• Enteric virus (grossly polluted source waters)
• Coliphage
Other Parameters
• THM
• Disinfectant residual
• pH
• Temperature
• Turbidity
• Total organic carbon
• Orthophosphate
• Ammonia nitrogen ^
-------
Recommended analytical procedures for each of these parameters are
included in Reference 2.
While total coliforms are an essential parameter to be monitored, it is
strongly recommended that other microbial parameters also be measured, to
insure that subtle water quality changes do not go undetected. Monitoring
other microbial parameters is important because many pathogenic bacteria and
virus are more resistant to environmental stress than coliform, and these
pathogens may multiply in the finished water even though coliform counts
remain low.
The minimum recommended sampling locations for the baseline survey are:
• Raw water
• Immediately prior to final disinfection
• Treatment plant finished water, immediately before distribution
system
• At end(s) of distribution system
Generally, wsekly analysis of coliforms, plate count organisms, and
disinfectant residuals would be satisfactory. However, during periods of
abnormally poor raw water quality, daily monitoring may be justified.
The information in the water quality survey should be used in conjunction
with the sanitary survey and analysis of existing treatment facilities to
determine if there is a potential public health risk due to microbial penetra-
tion of the treatment barrier. When evaluating data, any water quality
deterioration in the plant finished water or the distribution system should be
carefully evaluated. This evaluation should include consideration of seasonal
changes in raw water quality and unusual weather conditions.
Evaluation of Treatment Options
The third step in the action plan is to outline the approach to be
followed to evaluate treatment techniques for THM control. In developing and
presenting an approach, it is important that existing processes be evaluated
74
-------
and optimized for THM control. To assist in this evaluation, a THM profile
(Inst THM and THMFP) through the existing plant should be prepared. This
profile will indicate the extent of THM formation, as well as the rate of THM
formation as water moves through each of the unit treatment processes. This
knowledge is essential in the optimization of existing unit processes for THM
control.
If the utility believes that optimization of existing unit processes will
not be sufficient to achieve compliance, the action plan should present the
approach which will be followed to evaluate other treatment options. In
deciding which treatment options should be evaluated, factors to consider are
the ability to lower THMs, impact on disinfection efficiency and finished
water quality, and cost. Thus, the utility must have a defined plan of
\
evaluation submitted as part of the action plan.
A discussion of the best alternatives available for THM control and their
cost is presented in the following section.
TREATMENT METHODS FOR CONTROL OF THM FORMATION
Since the initial discovery in 1974 that THMs may be formed during the
chlorination of drinking water, many treatment technologies have been
evaluated for reduction of THM formation. References 3 and 4 present detailed
evaluations of treatment techniques which are suitable for control of THM
formation.
The February 28, 1983, amendment-* to the TTHM implementation
regulations defines two general categories of technology for controlling THMs.
These categories are defined following, and the treatment techniques included
in each category are listed in Table 13.
Best Generally Available Treatment Methods For Reducing TTHMs
These treatment methods, which are listed in Table 13, are the
methods of choice for the control of THM formation. Each is relatively
low in cost, simple in operation, and generally effective for THM
control. 7 c
-------
TABLE 13
MOST SUITABLE TREATMENT TECHNOLOGIES FOR CONTROL OF TTHM
BEST GENERALLY AVAILABLE TREATMENT METHODS
• Use of chlorine dioxide as an alternate or supplemental disinfectant
or oxidant.
• Use of choramines as an alternate or supplemental disinfectant or
oxidant.
• Improvement of existing clarification for THM precursor removal.
• Change point of chlorination. When necessary, use a substitute
pre-oxidant such as chloramines or chlorine dioxide. Potassium
permanganate may be useful in some situations, but not as a total
substitute for chlorine or other pre-oxidant.
• Use powdered activated carbon on a seasonal basis to reduce precursor
or THM concentrations. Dosage not to exceed 10 mg/L on an average
annual basis.
OTHER TREATMENT METHODS
• Add off-line storage for precursor reduction.
• Add aeration for THM reduction.
0 Add clarification to the treatment train.
• Consider alternative source of raw water.
9 Use ozone as an alternative or supplemental disinfectant or oxidant.
76
-------
Other Treatment Methods
These treatment methods, while effective for THM control, may not be
technically feasible or economically reasonable. In such cases a variance
(a permanent or temporary relief) may be granted by the primacy agency.
When a variance is issued, a schedule of compliance nay require
examination of these methods to determine if they could significantly
reduce TTHM concentrations, and whether these reductions are commensurate
with costs incurred.
A summary of the advantages and disadvantages of the Best Generally
Available Treatment methods is presented in Table 14. Also shown in Table 14
are the most suitable applications for each of these treatment methods.
-------
TABLE 14
SUMMARY OF FEATURES OF BEST GENERALLY AVAILABLE TREATMENT METHODS
Treatment Method
Advantages
Disadvantages
Most Suitable Applications
Chlorine Dioxide
1. Easy to prepare and feed
2. Good disinfectant
3. Also useful for iron and
manganese oxidation
4. Destroys taste and odor
producing phenolic compounds
5. No demand due to NH3 in raw
water
1. If not controlled, free chlorine
can be present along with generated
chlorine dioxide
2. Distribution system concentrations
of total oxidants must be less than
1.0 mg/L, due to potential Averse
health effects
3. High cost
1. Pre and postriisfectant
Chlorine dioxide residual
should be above 0.2 mg/L
Chloramines
-J
00
Improve Existing
Clarification For
Precursor Removal
1. Easy to produce
2. Excellent for maintaining a
residual in the distribution
system
3. Does not form THMs
4. Most effective in high pH
wa ters
1. Cost is generally low
2. Usually results in increased
removal of turbidity and
microorganisms
3. Generally results in lower
oxidant demand
1. Weaker disinfectant than chlorine or
chlorine dioxide
2. Slew reacting disinfectant
3. Poor viricide
1. Increased sludge quantities
2. May require baffling changes
settling basin
Should not be used as a
primary disinfectant
Good use is as a po6t-
disinfectant, with either
chlorine or chlorine dioxide
as a predi sinfectant
Good for use in lime soften-
ing plants, due to high pH
Where residual is above 0. 5
mg/L in distribution systen
1. Any plant with existing
clarification facilities
Moving Point of
Chlorination
Potential decrease in oxidant
dosage
Costs will decrease or remain
the same
Chlorine dioxide or chloramines
say be used as pre-oxidants
Potassium permanganate may be
used in combination with other
pre-oxidants
1. If an alternate predisinfectant is
not used, disinfection contact time
is reduced, allowing microbial
penetration further into the treat-
ment works
2. Can lead to slime growths in settling
basin if an alternate predisinfectant
is not used
1. Plants where a high percent-
age of precurors, or rapidly
reacting precursors, are
removed during coagulation/
se ttli ng
2. Plants with bromide in raw
water, as Titos containing
bromine are very rapidly
formed
3. Free chlorine residual in the
distribution system should be
saintained above 2.0 mg/L
Seasonal Use of
Powdered Activated
Carbon
1. Can be used intermittently
during periods of poor raw
water quality
2. Can be used for removal of
either precursors or THMs
3. Also removes taste and odor
May have high cost, if storage and
feed facilities are not already in
place
Additional slud^p generation
Annual averaqe not to exceed
10 mg/L
1. Plants with TTH4s slightly
above MCL due to seasonal
variations in raw water
quali ty
-------
SECTION 4
GUIDANCE FOR SYSTEMS USING CHLORINATION ONLY
Many systems with low turbidity and coliform concentrations in the raw
water supply use chlorination as the only form of treatment, principally for
disinfection. Such treatment may be used for either groundwater or surface
supplies, although it is much more predominant, and generally more appro-
priate, for groundwater supplies.
The choices for Best Generally Available Treatment are few, as shown in
Figure 10. The principal factors to be considered in the decision making
process are discussed in the following sections, with reference to Figure 11,
which shows Instaneous THM, THMFP, and Terminal THM for a hypothetical water
supply.
ORIGINAL CONDITION
Figure 11A shows the original treatment, vrtiich consists of chlorine
addition to a trunk pipeline which feeds the distribution system. Following
chlorine addition, Inst THM before entering the distribution system is 50 ug/L
and THMFP is 90 ug/L. In the distribution system, the average Inst THM is 140
ug/L, which is a noncompliance situation.
TREATMENT OPTIONS
Chloramine Disinfection
There are two options for producing chloramines. One is to add ammonia
concurrently with chlorine, resulting in immediate chloramine formation
(Figure 11B). This approach results in only minimal THM formation, during the
time that the chlorine and ammonia have not reacted. The second chloramine
approach (Figure 11C) is to add chlorine with amnonia addition somewhat later.
Figure 11C illustrates ammonia addition 15 minutes after chlorine
79
-------
FIGURE 10
SUGGESTED DECISION FORMAT FOR THM COMPLIANCE
IN SYSTEMS USING CHLORI NAT I ON ONLY
80
-------
CHLORINE
ADDITION
DISTRIBUTION
SYSTEM
11+0
120
100
80
60
4o
20
0
140
120
100
80
60
40
20
PROCESS FLOW DIAGRAM
140
ORIGINAL CONDITIONS
140
50
• AMMONIA
CHLORINE
tl
140
10
140
140
120
100
80
60
40
20
0
140
120
100
80
60
40
20
0
CHLORINE
j-'S M
IN
11)0
nAMMI
n
AMMONIA
40
80
50
140
80
CHLORINE
DIOXIDE
+
140
140
15
LEGEND
m
~
~~[=~
IIA - ORIGINAL CONDITION
CHLORINATION ONLY
IB
IMMEDIATE CHLORAMINE
FORMATION
I1C
CHLORINE ADDITION WITH
AMMONIA ADDTION 15 MIN.
LATER
ID - CHLORINE DI OX IDE
ADDITION
INSTANTANEOUS THM CONCENTRATION
THM FORMATION POTENTIAL
TERMINAL THM CONCENTRATION
FIGURE 11
THM CONTROL MEASURES FOR SYSTEMS
USING CHLORINATION ONLY
81
-------
addition. This approach allows free chlorine disinfection until chloramine
formation. THMs are formed during the free chlorine contact period, but THM
formation ceases with the addition of sufficient quantities of ammonia. This
technique may be useful if the system can be operated in this manner, and if
concentration of Inst THM production during the free chlorine stage does not
lead to subsequent problems with exceeding the MCL.
Chlorine Dioxide
Substitution of chlorine dioxide at the original chlorination point will
reduce THMs (Figure 11D). As shown, only moderate THM formation occurs, due to
the presence of some residual free chlorine in the chlorine dioxide. Providing
the residual chlorine is not excessive, the MCL can generally be achieved with
this approach. If the quantity of chlorine used is carefully controlled, it is
possible to generate chlorine dioxide containing very little free chlorine,
and the resultant formation of THMs will be minimized.
Microbiological Considerations
For systems using only chlorination, the raw water can be assumed to have
low levels of bacterial contamination. The following discussion of micro-
biological considerations is based upon this assumption.
The microbiological significance of any of these changes depends to a
great degree upon the detention time between the point of disinfectant
addition and the first service connections in the distribution system. If this
time is short, immediate chloramine formation (Figure 11B) may not provide
adequate disinfection, due to the slow rate of chloramine disinfection. In
such a case, 15 or more minutes of free chlorine contact prior to ammonia
addition (Figure 11C) would provide better disinfection. For systems with long
detention times between chloramine formation and service connections,
immediate chloramine formation may be adequate.
82
-------
Chlorine dioxide addition (Figure 11D) should provide good disinfection
if a chlorine dioxide residual can be maintained in the distribution system.
The presence of some free chlorine in the chlorine dioxide will enhance
disinfection, although it will result in some THM formation. EPA recommends
that the combined residual of chlorine dioxide, chlorite ion, and chlorate ion
should not exceed 1.0 mg/L at any point in the distribution system. Use of
chlorine dioxide may be precluded in systems with water having a high oxidant
demand, because it may be impossible to maintain a residual in the extremities
of the distribution system while complying with this recommendation.
83
-------
SECTION 5
GUIDANCE FOR SYSTEMS USING CONVENTIONAL TREATMENT
The majority of systems using surface water supplies use conventional
treatment. In this context, conventional treatment is defined as the following
unit processes: rapid mix; flocculation; settling; filtration; and clearwel.l
storage. Chlorine addition is before rapid mix and after filtration.
The choices for Best Generally Available Treatment are shown in
Figure 12, arranged in a recommended order of consideration. For a hypotheti-
cal water supply, bar graphs for Inst THM, TMFP, and Term THM at various
stages of treatment and in the distribution system are shown in Figure 13.
ORIGINAL CONDITION
Chlorine is added as a predisinfectant prior to rapid mix, and as a post
disinfectant after filtration. THM formation begins with the initial chlorine
dose, continuing throughout the treatment train (assuming a residual is
maintained) and in the distribution system. As shown in Figure 1 3A, TfMFP
decreases during settling and filtration due to removal of organic precursors.
Also, the Inst THM increases throughout the plant as the Tttl formation
reaction proceeds. The distribution system Inst Tttl averages 140 ug/L and is
not in compliance.
TREATMENT OPTIONS
Improve Precursor Removal
One of the first treatment options which should be evaluated for this
noncompliant system is to improve precursor removal during clarification and
filtration. This concept is particularly suited to highly turbid waters.
Increased precursor removal may be accomplished at existing treatment plants
in several ways:
84
-------
THM SAMPLE
ANALYSIS
ABOVE
MCL
BELOW MCL
COMPLIANCE
> t y
FIGURE 12
SUGGESTED DECISION FORMAT FOR THM COMPLIANCE
IN CONVENTIONAL TREATMENT PLANTS
85
-------
CHLORINE CHLORINE
PROCESS FLOW DIAGRAM - ORIGINAL CONDITION
200
160
120
80
^0
0
200
160
120
80
1)0
0
180
CHLORINE
180
180
80
15
150
100
20
1^0
50
90
^0
11)0
60
hO
90
50
90
13A ORIGINAL
CONDITION
13B IMPROVED
PRECURSOR
REMOVAL
200
160
120
80
hO
0
200
160
120
80
i<0
0
200
160
120
80
1(0
0
180
CHLORINE
180
CHLORINE
D10 XI OE
180
180 CHLORINE
I
125
180
15
180
150
UO
130
10
50
CHLORINE
I
CHLORINE +
AMMONIA
+
hO I hO
50
110
1 10
1 10
100
10
20
lhO
50
120
120
15
25
13C CHANGE IN
CHLORI NAT I ON
POINT TO AFTER
SETTLING
1 3D PRECHLORINATION,
POSTCHLORAMINE
FORMATION
120
I3C PRE CHLORINE
80 DIOXIDE,
POSTCHLORINAT I ON
LEGEND
I 1 INSTANTANEOUS THM CONCENTRATION
~ THM FORMATION POTENTIAL
r~H 1 TERMINAL THM CONCENTRATION
FIGURE 13
THM CONTROL MEASURES FOR SYSTEMS
USING CONVENTIONAL TREATMENT
86
-------
# Increase coagulant dose, use a different coagulant, or use a
combination of coagulants
m Use a polymer, increase polymer dose, or use a different polymer
• Use powdered activated carbon
Figure 13B shows hypothetical THM reductions. Note that a greater
reduction of THMFP occurs during settling and filtration than in the original
condition (Figure 13A), due to the improved removal of precursors. The Inst
THM formation rate is also slower, due to the enhanced removal during settling
and filtration of some of the faster reacting precursors. Since there is no
change in chlorination dosage or point of chlorine addition, disinfection
efficiency will not be compromised. Rather, disinfection efficiency may be
enhanced due to the increased removal of turbidity, which in many cases
decreases disinfection efficiency. This is based upon the assumption that the
pH is not raised to improve coagulation. If pH is increased, disinfection
efficiency will probably be decreased due to the shift in free chlorine
concentration from hypochlorous acid (H0C1) to hypochlorite ion (OCL-).
In many, if not most cases, the point of chlorination is shifted at the
same time that increased precursor removal is implemented. The two techniques
are not necessarily interdependent, however.
Shift Point of Chlorination To After Settling
When the initial application of chlorine is delayed until after settling,
substantial precursor removal will have occurred during settling and the Term
THM concentration will be lower. In many cases, this technique is used in
conjunction with "Improved Precursor Removal" (discussed previously) to
produce even greater THM reductions. This approach should be used with some
caution, because it may allow significant penetration of pathogenic organisms
further into the treatment works. In situations where remaining THM precursors
are fast reacting and/or the distribution system has a relatively long
detention time, this technique may not be adequate to achieve compliance. In
such cases, compliance would depend upon the amount of precursor removal which
is achieved during settling.
87
-------
Figure 13C shows changes in Inst THM formation rate relative to original
conditions. Following settling, the THMFp is slightly greater than original
conditions, because not all of the precursors that form Inst THM at this point
in the original condition are removed during settling. In the distribution
system, Inst THM is less than the original condition because some of the
precursor material removed during settling is rapid reacting material, which
would have been converted to THM in the original condition.
Prechlorination, Postchloramine Formation
This technique, shown in Figure 13D, combines the continued use of
prechlorination with the long-term residual application of chloramines. Inst
THM formation and THMFP reduction are equivalent to the original conditions,
until chloramine formation. When postchlorine is added with ammonia to form
chloramines, essentially no further production of THMs occurs. In the
distribution system, there is some unreacted THMFP; however, this could only
be converted to Inst THM by free chlorine. This unreacted THMFP illustrates
the Inst THM reduction attributable to the use of chloramines as a
postdisinfectant. This technique is useful when THM formation is slow.
Pre Chlorine Dioxide, Postchlorination
In this concept, chlorine dioxide is used as a predisinfectant. Low
chlorine dioxide dosages must be used in order to keep the residual chlorine
dioxide/chlorite/chlorate concentration below EPA's recommended level of 1.0
mg/L. If the chlorine dioxide contains some chlorine, as a result of
incomplete reaction during chlorine dioxide generation, some Inst THM will be
formed. This technique, shown in Figure 1 3E is advantageous because
predisinfection is achieved with little THM formation, and precursors are
removed during settling and filtration, prior to chlorine application.
MICROBIOLOGICAL CONSIDERATIONS
Systems using conventional treatment for surface supplies typically have
moderate, and sometimes seasonally heavy bacterial contamination in the raw
88
-------
water supply. To a large extent, the disinfection efficiency of the different
concepts discussed depends upon the extent of this bacterial contamination in
the raw water. For moderate to heavy bacterial contamination, more than 500
coliforms per 100 ml, daily sampling for SPC and coliforms is recommended as a
minimum. If there are upstream wastewater discharges, virus sampling should be
considered, and coliphage and fecal strep monitoring are recommended. For
supplies with only light to moderate bacterial contamination, less than 500
coliforms per 100 ml, weekly sampling for SPC and coliform is generally
adequate.
A discussion of the microbiological considerations of each treatment
technique previously discussed follow:
Improved Precursor Removal
Disinfection will probably be better than the original condition, due to
increased removals of turbidity, organics, and bacteria during settling. A
potential for decrease in pre and postchlorine dosages exists, without a
change in disinfection efficiency.
Change in Chlorination Point To After Settling
This technique may be suitable for low to moderate bacterial contamina-
tion, but probably not for supplies with high bacterial concentrations, or
during periods of heavy contamination. From a disinfection standpoint, the
problem is the increased penetration of microorganisms into the treatment
plant. This could be particularly critical in systems with a short clearwell
or distribution system detention time prior to service.
Prechlorination/Postchloramines
If adequate prechlorination is used, good overall disinfection should
occur. Postchloramines have a relatively slow rate of disinfection, but
maintain a very effective residual in the distribution system. A long distri-
bution system detention time is beneficial when postchloramines are used.
Pre Chlorine Dioxide/Postchlorination
This is a highly satisfactory technique, assuming correct dosages.
89
-------
SECTION 6
GUIDANCE FOR SYSTEMS USING LIME SOFTENING
Lime softening plants using prechlorination generally produce high TH4
concentrations because of the high pH conditions, used during softening. The
typical unit operations used in lime softening include rapid mix,
flocculation/settling, recarbonation, filtration, and clearwell storage.
Feasible THM control measures which use Best Generally Available
Treatment Methods are arranged in a decision format in Figure 14. THM forma-
tion for a hypothetical supply using conventional pre and postchlorination, as
well as these feasible control measures, is shown in Figure 15. The bar graphs
in Figure 15 show Inst THM, THMFP, and Terminal THM at various stages of
treatment.
The most feasible control measures are to change the point of chlorina-
tion to after recarbonation or to use a prechlorination/postchloramine
approach. If these techniques are not effective, a secondary choice would be
prechlorine dioxide/postchloramines. This technique is a second choice due to
the high cost of constructing and operating chlorine dioxide facilities.
ORIGINAL CONDITIONS
Using prechlorination, there is normally a rapid formation of Inst TH4
during rapid mix, flocculation, and settling. This rapid rate of formation is
to a great degree attributable to the high pH during softening. After
recarbonation, when the pH is lowered, the rate of formation slows. Figure 8-A
illustrates an increase in the THMFP and Term THM following lime addition
(which increases pH), and a subsequent decrease in THMFP and Term THM follow-
ing settling and filtration, due to removal of precursors. Inst THM formation
continues throughout the treatment train, and the system is not in compliance,
as the distribution system Inst THM concentration is 140 ug/L.
90
-------
THM SAMPLE
ANALYSIS
ABOVE
MCL
BELOW MCL
-*¦ COMPLIANCE
COMPLIANCE
PRE CHLORINE DIOXI
POSTCHLORAMINES
DE
COMPLIANCE
ABOVE
MCL
EVALUATE OTHER TREATMENT
METHODS OR OBTAIN VARIANCE
FIGURE \k
SUGGESTED DECISION FORMAT FOR THM COMPLIANCE
IN LIME SOFTENING PLANTS
91
-------
CI.
LIME
IV
RAPID
MIX
FLOC-
CULAT1 ON
SETTLING
RECAR-
BONATI ON
Fl LTRA-
TI ON
CI,
CLEAR-
WELL
DISTRI-
BUTION
SYSTEM
PROCESS FLOW DIAGRAM - ORIGINAL CONDITION
21(0
200
160
120
80
1(0
0
2l»0
200
160
120
80
1(0
0
I5A ORIGINAL
CONDITION
15B CHANGE IN
CHLORI NAT I ON POINT
TO AFTER
RECARBONATI ON
21(0
200
160
120
80
1(0
0
CHLORINE
t
80
220
30
CHLORINE
2^0 r DIOXIDE
I
180
200
160
120
80
1(0
0
220
10
160
75
30
CHLORINE
AMMONIA
H
1)0
80
CHLORINE
I AMMONIA
\ t
120
30
11)0
15C PRECHLORINATION,
80 POSTCHLORAMINE S
120
30
150 PRE CHLORINE
DIOXIDE,
POSTCHLORAMINES
LEGEND
n INSTANTANEOUS THM
THM FORMATION POTENTIAL
1 i TERMINAL THM CONCENTRATION
FIGURE 15
THM CONTROL MEASURES FOR SYSTEMS
USING LIME SOFTENING
92
-------
TREATMENT OPTIONS
Change in Point of Chlorination To After Recarbonation
Figure 15B shows the impact of changing the point of chlorination to
after recarbonation. Such a change prevents any Inst THM formation until after
recarbonation. Also, additional removal of rapidly acting precursor material
occurs during flocculation/settling, reducing the THMFP to 130 ug/L. This
example shows a distribution system Inst THM concentration of 90 ug/L. To
achieve such an Inst THM, either the precursors removed during softening and
filtration would have to be predominantly rapidly reacting precursors and/or
the detention time in the distribution system would have to be short.
Prechlorination, Postchloramines
This approach combines use of a strong predisinfectant with a long
lasting postdisinfectant which does not produce THMs. As shown in Figure 15C,
Inst THM and THMFP are identical to the original condition up to the point of
chlorine/ammonia addition, which results in chloramine formation. At this
point, formation of Inst THM ceases, and there is unreacted THMFP in the
distribution system.
Pre Chlorine Dioxide; Postchloramines
Only very low Inst THM concentrations are produced in this concept, and
only if there is residual free chlorine in the chlorine dioxide. THM concen-
trations are shown in Figure 15D. The cost of this concept is higher than the
other suggested control techniques, due to the high cost of the chlorine
dioxide generation facilities.
MICROBIOLOGICAL CONSIDERATIONS
During lime softening, the high pH conditions aid in the disinfection
process. Thus, there is additional protection which is not provided by conven-
tional treatment. Principal microbiological considerations are discussed in
the following paragraphs for each suggested technique.
93
-------
Change in Point of Chlorination To After Recarbonation
Increased microbial penetration into the treatment plant will be
experienced. High pH will curtail this penetration to a degree, but an
increase in microbiological monitoring to once per day is recanmended,
particularly during periods of high raw water bacterial concentration.
Prechlorination, Postchloramines
' Use of a strong predisinfectant, combined with high pH should produce
excellent disinfection. Then, use of long lasting chloramines will provide
additional disinfection as necessary.
Pre Chlorine Dioxide, Postchloramines
Results should be comparable to the previously discussed concept, as long
as a chlorine dioxide residual is maintained through filtration. Overall
comparability depends upon residual of the predisinfectant.
94
-------
SECTION 7
SUMMARY OF MICROBIOLOGICAL CONCERNS
One of the principal functions of a water treatment plant is to act as a
barrier to microorganisms, particularly pathogens. This barrier is especially
important in surface supplies, which in many cases contain discharges fran
upstream wastewater treatment plants, as well as stonnwater runoff and animal
waste discharges.
To meet the requirements of the Trihalomethane Regulation, it is
essential that adequate disinfection be provided. Two general THM control
concepts which can place additional stress on the microbial removal efficiency
of the treatment works are:
• Changing the initial point of chlorine addition to after settling.
• Use of alternate disinfectants (chloramines and chlorine dioxide).
The impact of these changes on the microbial population is most
significant during periods of poor raw water quality and during varm water
conditions. When the water is warmest, microbial activity is at or near its
maximum, and disinfection efficiency is also enhanced.
The objective of the Baseline Water Quality Survey is to collect adequate
microbiological data before any treatment changes are made, as well as after
changes are made. The baseline data collected before any changes are made for
THM control should verify that adequate disinfection is being achieved.
Secondly, the data collected will be a basis for comparison after changes are
made.
Following changes, microbiological monitoring should continue for at
least one year, and even longer where chloramines are used. Particularly
important in this phase of the water quality survey are:
1. Increased monitoring during abnormally heavy pollution loads in the
raw water. 95
-------
2. Monitoring at dead-end or slow-flow portions of the distribution
s ys tern.
In most situations, weekly monitoring of microbial parameters (coliforms
and SPC as a minimum) is sufficient. However, during high raw water bacterial
concentrations, daily sampling is recommended. Where upstream wastewater
treatment plant discharges occur, periodic enteric virus or coliphage testing
should be considered.
Long-term bacteriological changes are often noted first at dead-ends, or
slow-flow locations. These locations are often the first to show the effect of
insufficient disinfectant residuals and intermittent penetration of the treat-
ment barrier. For systems using chloramines, it is important to monitor over
even longer periods than a year, as long-term problems such as increased
bacteria levels, drop off of chloramine residual, and taste and odor
complaints may occur.
96
-------
SECTION 8
COST OF BEST GENERALLY AVAILABLE TREATMENT METHODS
Determining and comparing the cost of different THM control strategies is
very site specific, as costs are strongly influenced by total disinfectant
dose and by existing disinfection facilities. Within this section, costs are
presented for 0.0438, 0.219, 0.438, and 0.657 m^/sec (1, 5, 10, and 15 mgd)
plants. These costs were developed using Reference 6 and the assumptions shown
in Table 15. Additional information on cost of THM control strategies can be
found in References 3, 4 and 7.
CHLORINATION
Use of pre and pos tchlori nation is generally the original condition,
prior to any changes for THM control. Thus, the cost of chlorination is the
reference point to which potential control strategies are compared.
Table 16 presents chlorination costs for existing chlorination systems.
These costs are for O&M and chlorine costs only, and do not include capital
amortization. Costs are also shown in Table 16 for new chlorination systems,
which include capital amortization as well as O&M and chlorine cost.
CHLORAMINE FORMATION
Addition of ammonia to a solution containing free chlorine, or
vice-versa, results in the formation of chloramines. For most plants, the
addition of ammonia storage and feed facilities and piping to the point of
application are the only changes necessary. This assumes that chlorination
facilities already exist, and the piping exists for conveyance of a chlorine
solution to the desired point of addition.
In some cases, both chlorine and ammonia storage and feed facilities will
be required. Table 17 presents costs for both of these situations. In this
table, the ratio of chlorine to ammonia is 3:1.
97
-------
TABLE 15
ASSUMPTIONS USEE IN DEVELOPMENT OF COSTS FOR
THM CONTROL TECHNOLOGIES
Parameter
Value or Cost
Electrical Energy
Labor
Interest Rate
Amortization Period
ENR Construction Cost Index (January, 1983)
Producer Price Index - Finished Goods
(January, 1983)
Average Operating Capacity of Plant
Chlorine Cost
Ammonia Cost
Sodium Chlorite Cost
Powdered Activated Carbon Cost
Alum Cost
Polymer Cost
$0.06/kwh
$10.00/hr
8%
20 years
369.80
$0.33/kg
$0.22/kg
$2.21/kg
$0.66/kg
$0.15/kg
$5.51/kg
283.6
70%
($300/ton)
($200/ton)
($2000/ton)
($600/ton)
($140/ton)
($2.50/lb)
98
-------
TABLE 16
COST OF CHLORINATION
EXISTING CHLORINATION SYSTEM
Plant Design
Capacity Chlorine Dosage - mg/L
m^/sec (mgd) 1 3 6 1_0
0.0438 (1) 0.74 (2.80) 0.95 (3.60) 1.14 (4.30) 1.35 (5.10)
0.219 (5) 0.21 (0.80) 0.32 (1.20) 0.45 (1.70) 0.63 (2.40)
0.438 (10) 0.13 (0.50) 0.24 (0.90) 0.37 (1.40) 0.53 (2.00)
0.657 (15) 0.11 (0.40) 0.21 (0.80) 0.32 (1.20) 0.50 (1.90)
NEW CHLORINATION SYSTEM
0.438 (1)
0.219 (5)
0.438 (10)
0.657 (15)
0.98 (3.70)
0.29 (1.10)
0.18 (0.70)
0.15 (0.55)
1.37 (5.20)
0.42 (1.60)
0.32 (1.20)
0. 27 (1 .00)
1.64 (6.20)
0.61 (2.30)
0.48 (1.80)
0.40 (1.50)
1.85 (7.00)
0.82 (3.10)
0.69 (2.60)
0.63 (2.40)
Notes:
1. Costs are in
-------
TABLE 17
COST OF CHLORAMINE USAGE TO MEET THM MCL
WITH NEW AMMONIA FEED FACILITIES ONLY;
CHLORINE FEED FACILITIES EXIST
Plant Design
Capaci ty Chlorine Dosage - mg/L
m^/sec (mgd) 0. 75 1. 50 2. 20 3« 70
0.0438 (1) 1. 29 (4.90) 1.56 (5.90) 1.90 (7.20) 2. 17 (8. 20)
0.219 (5) 0.40 (1.50) 0.48 (1.80) 0.58 (2.20) 0.74 (2.80)
0.438 (10) 0.24 (0.90) 0.32 (1.20) 0.40 (1.50) 0.53 (2.00)
0.657 (15) 0.18 (0.70) 0.29 (1.10) 0.34 (1.30) 0.48 (1.80)
WITH NEW CHLORINE AND AMMONIA FEED FACILITIES
0.4 38 (1 )
0.219 (5)
0.438 (10)
0.657 (15)
1.53 (5.80)
0.48 (1.80)
0.29 (1.10)
0.24 (0.90)
1.82 (6.90)
0.58 (2.20)
0.40 (1.50)
0.34 (1.30)
2.22 (8.40)
0.71 (2.70)
0.48 (1.80)
0.42 (1.60)
2.53 (9.60)
0.90 (3.40)
0.63 (2.40)
0.55 (2.10)
Notes:
1. Costs are in with <£/1000 gallons shown in parenthesis.
2. Facilities are operating at 70% of design capacity.
3. Costs do not include a chlorine contact basin/clearwell.
4. Ratio of chlorine to ammonia is 3:1.
5. Costs when chlorine facilities exist do not include capital
amortization of chlorine facilities.
100
-------
CHLORINE DIOXIDE
Chlorine dioxide is generally produced by mixing a chlorine solution with
a sodium hypochlorite solution. The reaction is:
Cl2 + 2NaC102 —2C102 + 2NaCl
The optimum pH for this reaction is about 3.5, which can be achieved by
addition of excess chlorine or by acid addition. For water treatment applica-
tions, the use of acid is generally the desirable approach, as the use of
excess chlorine would result in the presence of free chlorine in the chlorine
dioxide solution, which would lead to THM formation.
Generally this reaction is only 85-90% complete. Based upon a 90%
complete reaction, 0.268 kg (0.59 lb) of chlorine and 0.849 (1.87 lb) of 80%
pure technical grade sodium chlorite are required to produce 0.454 kg (one
pound) of chlorine dioxide.
Similar to the production of chloramines, most plants will already have a
chlorination system installed. For these situations, only the chlorine dioxide
generator and the sodium chlorite feed facilities are needed to convert
existing gas chlorination systems to chlorine dioxide feed systems.
In other situations, both chlorine and sodium chlorite storage and feed
facilities, as well as the chlorine dioxide generator, will be required. Table
18 presents costs for both of these situations.
POWDERED ACTIVATED CARBON
Powdered activated carbon (PAC) can be used to increase removal of Tttl
precursors, as well as to remove THMs after formation. EPA has placed a 10
mg/L limit on PAC dosage, based upon the average annual dosage.
Table 19 presents costs for PAC feed at design capacities of 5, 15, and
30 mg/L.
101
-------
TABLE 18
COST OF CHLORINE DIOXIDE USAGE TO MEET THM MCL
WITH NEW CHLORINE AND SODIUM CHLORITE FEED FACILITIES
Plant Design
Capaci ty Chlorine Dosage - mg/L
m^/sec (mgd) 1 3 5
0.0438 (1) 1.74 (6.60) 2.72 (10.30) 3.64 (13.80)
0.219 (5) 0.74 (2.80) 1.61 (6.10) 2.38 (9.00)
0.438 (10) 0.58 (2.20) 1.37 (5.20) 2.14 (8.10)
0.657 (15) 0.50 (1.90) 1.29 (4.90) 2.06 (7.80)
WITH NEW SODIUM CHLORITE FEED FACILITIES ONLY;
CHLORINE FEED FACILITIES EXIST
0.0438 (1) 1.48 (5.60) 2.38 (9.00) 3.25 (12.30)
0.219 (5) 0.66 (2.50) 1.48 (5.60) 2.21 (8.40)
0.438 (10) 0.53 (2.00) 1.29 (4.90) 2.03 (7.70)
0.657 (15) 0.48 (1.80) 1.24 (4.70) 1.98 (7.50)
Notes:
1. Costs are in 4/m^, with
-------
TAHLE 19
COST OF POWDERED ACTIVATED CARBON USE TO MEET THM MCL
Plant Design Capacity
3
m /sec (mgd)
Powdered Activated Carbon Feed Capacity - mg/L
15
30
0.438
0.219
0.438
0.657
(1)
(5)
(10)
(15)
2.64 (10.0)
0.85 (3.20)
0.61 (2.30)
0.55 (2.10)
3.09 (11.70)
1.24 (4.70)
1.03 (3.90)
0.95 (3.60)
3. 19 (12.10)
1.29 (4.90)
1.06 (4.00)
0.98 (3.70)
Notes:
1. All costs are in m^/sec, with 4/1000 gallons shown in parenthesis.
2. Average annual dosage is 5 mg/L for the 5 mg/L feed capacity, and is
10 mg/L for the 15 and 30 mg/L feed capacities. This is necessary
because the Regulations (Reference 5) restrict average annual dosage
to an upper limit of 10 mg/L.
103
-------
IMPROVED PRECURSOR REMOVAL
Enhancement of THM precursor removal can generally be accomplished by
increasing the dosage of coagulant and/or coagulant aid. Changes in the clari-
fier inlet baffling may also be necessary to optimize removals. Although there
may be some cost associated with baffling changes or changing the point of
chlorination addition, the principal cost is for additional chemical usage.
Costs for additional alum and polymer dosages are shown in Table 20. These
costs are additive, if dosages of both chemicals are increased.
Usually, changes for enhanced precursor removal are made in conjunction
with a movement in the point of prechlorination to after the sedimentation
process.
EXAMPLE OF COSTS FOR A HYPOTHETICAL 0.219 m3/sec (5 MGD) PLANT
Shown in Table 21 are costs of THM control strategies for a hypothetical
0.219 m^/sec (5 mgd) treatment plant operating at 70% of design capacity.
Using assumed dosages for disinfectants, as well as coagulant, polymer, and
PAC dosages, costs for Best Generally Available Treatment Methods are
compared in Table 21 using information in Tables 16 to 20 as a basis. Users
should understand that this is a hypothetical example, and that site specific
conditions may lead to large differences in the cost of treatment.
104
-------
TABLE 20
ALUM
POLYMER
COST OF INCREASED ALUM AND POLYMER DOSAGES TO MEET THM MCL
Cost - (j:/m3
Increased Dosage - mg/L (^/1000 gallons)
10 0.16 (0.60)
20 0.32 (1.20)
30 0.45 (1.70)
40 0.61 (2.30)
50 0.77 (2.90)
0.2 0.1 1 (0.40)
0.4 0.21 (0.80)
0.6 0.34 (1.30)
0.8 0.45 (1 .-70)
1.0 0.55 (2.10)
Notes Costs include only the additional chemical cost. No additional capital
facilities or O&M requirements are included.
105
-------
TABLE 21
EXAMPLE COSTS FOR A 0.219 m3/sec (5 MGD) PLANT USING
BEST GENERALLY AVAILABLE TREATMENT METHODS
Chlorination - Original Condition
Dosage = 10 mg/L
No amortization of
facilities included
Cost -
0.634
(2.44
/m3
/1000 gal)
Chloramines
Prechlorination = 3 mg/L
Postchloramines = 3.65 mg/L
Chlorination facilities exist - no capital amortization included
Cost = 0.32 + 0.74 = 1 .06<}:/m3
(1.2 + 2.8 = 4.04/1000 gal)
Chlorine Dioxide
Pre Chlorine Dioxide = 3 mg/L
Postchlorination = 3 mg/L
Chlorination facilities exist - no capital amortization included
Cost = 1.48 + 0.32 = 1.804/m3
(5.6 + 1.2 = 6.84/1000 gal)
Powdered Activated Carbon
30 mg/L feed capacity installed
10 mg/L average annual dose
Cos t = 1.29 4/m3
(4.94/1000 gal)
Improved Precursor Removal - Change Point of Chlorine Addition
Alum dose increased by 20 mg/L
Polymer dose increased by 0.8 mg/L
No piping or buffling changes required
Cost = 0.32 + 0.45 = 0.774/m3
(1.2 + 1.7 = 2.94/1000 gal)
Note: Plant is operating at 70% of the 0.219 m3/sec (5 mgd) design capacity
106
-------
REFERENCES FOR CHAPTER 5
1. "Guidance for the Sampling, Analysis, and Monitoring of Trihalomethanes in
Drinking Water," Science and Technology Branch, Criteria and Standards
Division, U.S.E.P.A., Washington, D.C. February, 1983.
2. Federal Register, Vol. 44, No. 231, 28641-28642 (November 29, 1979) as
corrected by Federal Register, Vol 45, No. 49, 15542-15547 (March 11,
1980)
3. Symons, J.M., Stevens, A.A., Clark, R.M., Geldreich, E.E., Love, O.T., and
Demarco, J., "Treatment Techniques for Controlling Trihalomethanes in
Drinking Water," EPA 600/2-81-156, USEPA, Cincinnati, OH (September 1981)
289 pp.
4. "Technologies and Costs for the Removal of Trihalomethanes From Drirking
Water," Science and Technology Branch, Criteria and Standards Division,
Office of Drinking Water, USEPA, Washington, D.C. , February, 1982.
5. Federal Register, Vol. 48, No. 40, 8406-8414, (February 28, 1983).
6. Gumerman, R.C., Culp, R.L., and Hansen, S.P., "Estimating Water Treatment
Costs," Volume 2, Cost Curves Applicable to 1 to 200 mgd Treatment
Plants," EPA 600/2-79-162b, USEPA, Cincinnati, OH (August 1979), 506 pp.
7. Clark, R.M., "Evaluating Costs and Benefits of Alternative Disinfectants*"
JAWWA, 73, 89-93 (February 1981).
107
-------
REFERENCES
1. Interim Report, "Evaluation of Treatment Effectiveness for Reducing
Trihalomethanes in Drinking Water", Culp/Wesner/Culp, EPA Contract No.
68-01-6992, May 1, 1981.
2. Federal Register, 44, No. 231, 68628-68707 (November 29, 1979) as
corrected by Federal Register, 45, No. 49, 15542-15547 (March 11, 1980).
3. "Quality Assurance Project Plan - Evaluation of Treatment Effectiveness
For Reducing Trihalomethanes In Drinking Water", Contract 68-01-6292,
Culp/Wesner/Culp, approved by EPA September 5, 1982.
4. Interim Guidelines and Specifications for Preparing Quality Assurance
Project Plans, QAMS-005/80, Office of Monitoring Systems and Quality
Assurance, Office of Research and Development, United States
Environmental Protection Agency, Washington, D.C. 20460, December 29,
1980.
5. "Shenango Valley Water Company, Final Report, July, 1982", prepared as a
portion of EPA Contract No. 68-01-6992, Evaluation of Treatment
Effectiveness For Reducing Trihalomethanes in Drinking Water.
6. "Davenport Water Company, Final Report, December, 1982", prepared as a
portion of EPA Contract No. 68-01-6992, Evaluation of Treatment
Effectiveness For Reducing Trihalomethanes in Drinking Water.
7. "City of Topeka Water Department, Final Report, December, 1982", prepared
as a portion of EPA Contract No. 68-01-6992, Evaluation of Treatment
Effectiveness For Reducing Trihalomethanes in Drinking Water.
8. Miller, W.G., Rice, R.G., Robson, C.M., Scullin, R.L., Kuhn, W., and
Wolf, H., "An Assessment of Ozone and Chlorine Dioxide Technologies for
Treatment of Municipal Water Supplies," EPA 600/2-78-147, USEPA,
Cincinnati, OH (August 1978) 571 pp., NTIS Accession No. PB 285972/AS.
9. Symons, J.M., Stevens, A.A., Clark, R.M., Geldreich, E.E., Love, O.T.,
and Demarco, J., "Treatment Techniques for Controlling Trihalomethanes in
Drinking Water," EPA 600/2-81-156, USEPA, Cincinnati, OH (September 1981)
289 pp.
10. Committee Report, "Organics Removal by Coagulation: A Review and
Research Needs," JAWWA, 71, 588-603 (October 1979).
11. Singer, P.C., Borchardt, J.H., and Colthurst, J.M., "The Effects of
Potassium Permanganate Pretreatment on Trihalomethane Formation in
Drinking Water," JAWWA, 72, 573-578 (October 1980).
108
-------
APPENDIX A
THE TRIHALOMETHANE REGULATION
-------
Accordingly, Part 141. Title 40 of the Code of Federal Regulations is hereby
amended as follows:
1. By amending § 141.2 to include the following new paragraphs (p) through (t):
§ 141.2 Definitions
(p) "Halogen" means one of the chemical elements chlorine, bromine or iodine.
(q) "Trihalomethane" (THM) means 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
(r) "Total trihalomethanes" (TTH M) means the sum of the concentration in milli-
grams per liter of the trihalomethane compounds (trichloromethane [chloroform],
dibromochloromethane, bromodichloromethane and tribromomethane [bromo-
form]), rounded to two significant figures.
(s) "Maximum Total Trihalomethane Potential (MTP)" means the maximum
concentration of total trihalomethanes produced in a given water containing a
disinfectant residual after 7 days at a temperature of 25°C or above.
(t) "Disinfectant" means 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 micro-
organisms.
2. By revising § 141.6 to read as follows:
§ 141.6 Effective dates.
(a) Except as provided in paragraph (b) of this section, the regulations set forth in
this part shall take effect on June 24, 1977.
(b) The regulations for total trihalomethanes set forth in § 141.12(c) shall take
effect 2 years after the date of promulgation of these regulations for community
water systems serving 75,000 or more individuals, and 4 years after the date of
promulgation for communities serving 10,000 to 74,999 individuals.
3. By revising the introductory paragraph and adding a new paragraph (c) in
§ 141.12 to read as follows:
§ 141.12 Maximum contaminant levels for organic chemicals.
The following are the maximum contaminant levels for organic chemicals. The
maximum contaminant levels for organic chemicals in paragraphs (a) and (b) of this
section apply to all community water systems. Compliance with the maximum con-
taminant levels in paragraphs (a) and (b) is calculated pursuant to § 141.24. The
maximum contaminant level for total trihalomethanes in paragraph (c) of this
section applies only to community water systems which serve a population of 10,000
or more individuals and which add a disinfectant (oxidant) to the water in any part of
the drinking water treatment process. Compliance with the maximum contaminant
level for total trihalomethanes is calculated pursuant to § 141.30.
•f-rom Frtlrral 44 No 2*1. 2RMI-2RM2 (Nov 29, 1979) ai corrected hy Ftilerat Rffnter 45, No 49 HM2 13^*7
(March II I9K0)
A-l
-------
• •••••••••
(c) Total trihalomethanes (the sum of the concentration of bromodichloro-
methane, dibromochloromethane. tribromomethane [bromoform] and trichloro-
methane [chloroform]) 0.10 mg/ L.
4. By revising the title, the introductory text of paragraph (a) and paragraph (b) of
§ 141.24 to read as follows:
§ 141.24 Organic chemicals other than total trihalomethanes, sampling, and
analytical requirements.
(a) An analysis of substances for the purpose of determining compliance with
§ 141.12(a) and § 141.12(b) shall be made as follows:
(b) If the result of an analysis made pursuant to paragraph (a) of this section indi-
cates that the level of any contaminant listed in § 141.24 (a) and (b) exceeds the
maximum contaminant level, the supplier of water shall report to the State within 7
days and initiate three additional analyses within one month.
5 By adding a new § 141 30 to read as follows:
§ 141.30 Total trihalomethanes sampling, analytical and other requirements.
(a) Community water systems which serve a population of 10.000 or more indi-
viduals and which add a disinfectant (oxidant) to the water in any part of the
drinking water treatment process shall analyze for total trihalomethanes in accor-
dance with this section. For systems serving 75,000 or more individuals, sampling
and analyses shall begin not later than I year after the date of promulgation of this
regulation. For systems serving 10.000 to 74,999 individuals, sampling and analyses
shall begin not later than 3 years after the date of promulgation of this regulation.
For the purpose of this section, the minimum number of samples required to be
taken by the system shall be based on the number of treatment plants used by the
system, except that multiple wells drawing raw water from a single aquifer may, with
the State approval, be considered one treatment plant for determining the minimum
number of samples. All samples taken within an established frequency shall be
collected within a 24-hour period.
(b)( I) For all community water systems utilizing surface water sources in whole or
in part, and for all community water systems utilizing only ground water sources that
have not been determined by the State to qualify for the monitoring requirements of
paragraph (c) of this section, analyses for total trihalomethanes shall be performed at
quarterly intervals on at least four watersamplesforeachtreatment plant used bythe
system. At least 25 percent of the samples shall be taken at locations within the distri-
bution system reflecting the maximum residence time of the water in the system The
remaining 75 percent shall be taken at representative locations in the distribution
system, taking into account number of persons served, different sources of water and
different treatment methods employed. The results of all analyses per quarter shall
be arithmetically averaged and reported to the State within 30 days of the system's
receipt of such results. Results shall also be reported to EPA until such monitoring
requirements have been adopted by the State. All samples collected shall be used in
the computation of the average, unless the analytical results are invalidated for tech-
nical reasons. Sampling and analyses shall be conducted in accordance with the
methods listed in paragraph (e) of this section.
(2) Upon the written request of a community water system, the monitoring
frequency required by paragraph (b)( I) of this section maybe reduced bythe State to
a minimum of one sample analyzed for TTHMs per quarter taken at a point in the
distribution system reflecting the maximum residence time of the water in the
system, upon a written determination by the State that the data from at least I year of
monitoring in accordance with paragraph (b)( I) of this section and local conditions
demonstrate that total trihalomethane concentrations will be consistently below the
maximum contaminant level.
(3) If at anytime during which the reduced monitoring frequency prescribed under
this paragraph applies, the results from any analysis exceed 0.10 mg/ L of TTHMs
A-2
-------
and such results are confirmed by at least one check sample taken promptly after
such results are received, or if the system makes any significant change to its source of
water or treatment program, the system shall immediately begin monitoring in
accordance with the requirements of paragraph (b)(1) of this section, which
monitoring shall continue for at least I year before the frequency may be reduced
again. At the option of the State, a system's monitoring frequency may and should be
increased above the minimum in those cases where it is necessary to detect variations
of TTHM levels within the distribution system.
(c)( I) Upon written request to the State, a community water system utilizing only
ground water sources may seek to have the monitoring frequency required by sub-
paragraph (I) of paragraph (b) of this section reduced toaminimum of one sample
for maximum TTH M potential per year for each treatment plant used by the system
taken at a point in the distribution system reflecting maximum residence time of the
water in the system. The system shall submit to the State the results of at least one
sample analyzed for maximum TTH M potential for each treatment plant used by the
system taken at a point in the distribution system reflecting maximum residence time
of the water in the system. The system's monitoring frequency may only
be reduced upon a written determination by the State that, based upon the data sub-
mitted by the system, the system has a maximum TTHM potential of less than 0 10
mgI L and that, based upon an assessment of the local conditions of the system, the
system is not likely to approach or exceed the maximum contaminant level for total
TTH Ms. The results of all analyses shall be reported to the State within 30 days of
the system's receipt of such results. Results shall also be reported to EPA until such
monitoring requirements have been adopted by the State. All samples collected shall
be used for determining whether the system must comply with the monitoring
requirements of paragraph (b) of this section, unless the analytical results are
invalidated for technical reasons. Sampling and analyses shall be conducted in
accordance with the methods listed in paragraph (e) of this section.
(2) If at any time during which the reduced monitoring frequency prescribed under
paragraph (c)(1) of this section applies, the results from any analysis taken by the
system for maximum TTH M potential are equal to or greater than 0.10 mg/ L, and
such results are confirmed by at least one check sample taken promptly after such
results are received, the system shall immediately begin monitoring in accordance
with the requirements of paragraph (b) of this section and such monitoring shall
continue for at least one year before the frequency may be reduced again. In the event
of any significant change to the system's raw water or treatment program, the system
shall immediately analyze an additional sample for maximum TTHM potential
taken at a point in the distribution system reflecting maximum residence time of the
water in the system for the purpose of determining whether the system must comply
with the monitoring requirements of paragraph (b) of this section. At the option of
the State, monitoring frequencies may and should be increased above the minimum
in those cases where this is necessary to detect variation of TTH M levels within the
distribution system.
(d) Compliance with § 141.12(c) shall be determined based on a running annual
average of quarterly samples collected by the system as prescribed in subparagraphs
(I) or (2) of paragraph (b) of this section. If the average of samples covering any 12
month period exceeds the Maximum Contaminant Level, thesupplierof watershall
report to the State pursuant to § 141.31 and notify the public pursuant to§ 141.32.
Monitoring after public notification shall be at a frequency designated by the State
and shall continue until a monitoring schedule as a condition to a variance, exemp-
tion or enforcement action shall become effective.
(e) Sampling and analyses made pursuant to this section shall be conducted by one
of the following EPA approved methods:
(1) "The Analysis of Trihalomethancs in Drinking Waters by the Purge and Trap
Method." Method 501.1. EMSL, EPA Cincinnati, Ohio.
(2) "The Analysis of Trihalomethanes in Drinking Water by l.iquid/l.iquid
Extraction." Method 501.2. EMSL. EPA Cincinnati. Ohio.
A-3
-------
Samples for TTH M shall be dechlorinated upon collection (o prevent further pro-
duction of Trihalomethanes. according to the procedures described in the above two
methods. Samples for maximum TTH M potential should not be dechlorinated, and
should be held for seven days at 25°C (or above), prior to analysis, according to the
procedres described in the above two methods.
(0 Before a community water system makes any significant modifications to its
existing treatment process for the purposes of achieving compliance with § 141.12(c),
such system must submit and obtain State approval of a detailed plan setting forth its
proposed modification and those safeguards that it will implement to ensure that the
bacteriological quality of the drinking water served by such system will not be
adversely affected by such modification. Each system shall comply with the
provisions set forth in the State-approved plan. At a minimum, a State approved
plan shall require the system modifying its disinfection practice to:
(1) Evaluate the water system for sanitary defects and evaluate the source water for
biological quality:
(2) Evaluate its existing treatment practices and consider improvements that will
minimize disinfectant demand and optimize finished water quality throughout the
distribution system;
(3) Provide baseline water quality survey data of the distribution system Such
data should include the results from monitoring for coliform and fecal coliform
bacteria, fecal streptococci, standard plate counts at 35°C and 20°C. phosphate,
ammonia nitrogen and total organic carbon. Virus studies should be required where
source waters are heavily contaminated with sewage effluent;
(4) Conduct additional monitoring to assure continued maintenance of optimal
biological quality in finished water, for example, when chloramines are introduced
as disinfectants or when pre-chlorination is being discontinued. Additional
monitoring should also be required by the State for chlorate, chlorite and chlorine
dioxide when chlorine dioxide is used. Standard plate count analyses should also be
required by the State as appropriate before and after any modifications:
(5) Consider inclusion in the plan of provisions to maintain an active disinfectant
residual throughout the distribution system at all times during and after the
modification.
This paragraph (0 shall become effective on the date of its promulgation.
-------
APPENDIX B
COLIPHAGE TEST RESULTS - SUMMER 1981
-------
TABLE B-1
Coliphage Sampling Results - Raw Water
May to October, 1981
Shenango Valley Water Company, Sharon, Pennsylvania
Temperature on
E. coli
PFU/100 ml
Date
Receipt by EPA
Host
Single Layer
Double Layer
Collected
Cincinnati - °C
(ATCC No.)
Test Method
Test Method
5/26/81
15
15597
4
10
1 37 06
8
0
6/15/81
15
15597
69
79
1 3706
173
2 37
6/22/81
16
15597
162
300
1 3706
1 28
394
7/13/81
12
15597
20
0
1 3706
22
26
7/27/81
9
15597
24
80
1 3706
67
69
8/10/81
9
15597
36
84
1 3706
10
12
9/21/81
9
15597
0
0
13706
38
36
10/05/81
1 3
15597
6
1 2
1 3706
6
1 2
Notes:
1. Sensitivity Limits: Single Layer Test Method - 4 PFU/100 ml
Double Layer Test Method - 10 PFU/100 ml
2. El. coli host ATCC No. 15597 is the host for RNA phages, and it is
sensitive to some DNA phages.
3. J2. coli host ATCC No. 1 3706 is the host for DNA phages.
4. Source of water is the Shenango River.
B-1
-------
TABLE B-2
Coliphage Sampling Results - Raw Water
May to October, 1981
City of Topeka, Kansas
Date
Collected
5/26/81
6/15/81
6/22/81
7/13/81
7/27/81
9/21/81
10/05/81
Temperature on
Receipt by EPA
Cincinnati - °C
17
10
E. coli
PFU/100 ml
22
10
SAMPLE
FROZEN
Host
(ATCC No.)
15597
13706
15597
1 3706
15597
13706
15597
1 3706
15597
1 3706
15597
1 3706
15597
1 3706
Single Layer
Test Method
8
1 12
44
150
928
2720
4
4
178
186
0
0
14
56
Double Layer
Test Method
40
70
78
150
161 0
6152
4
10
228
290
0
0
10
60
Notes:
1. Sensitivity Limits: Single Layer Test Method - 4 PFU/100 ml
Double Layer Test Method - 10 PFU/100 ml
2. E. coli host ATCC No. 15597 is the host for RNA phages, and it is
sensitive to some DNA phages.
3. 12. coli host ATCC No. 1 3706 is the host for DNA phages.
4. Source of water is the Kansas River.
5. Sample collected on June 22 was not received at EPA Cincinnati until
June 24.
B-2
-------
TABLE B-3
Coliphage Sampling Results - Raw Water
May
to June, 1981
Davenport Water
Company, Davenport, Iowa
Temperature on
E. coli
PFU/100
' ml
Date
Receipt by EPA
Host
Single Layer
Double Layer
Collected
Cincinnati - °C
(ATCC No.)
Test Method
Test Method
5/26/81
20
15597
0
0
1 3706
0
10
6/15/81
21
15597
16
34
1 3706
196
258
6/22/81
24
15597
42
84
1 3706
148
142
7/13/81
7
15597
0
0
13706 2 2
Notes:
1. Sensitivity Limits: Single Layer Test Method - 4 PFU/100 ml
Double Layer Test Method - 10 PFU/100 ml
2. E:. coli host ATCC No. 15597 is the host for RNA phages, and it is
sensitive to some DNA phages.
3. E. coli host ATCC No. 13706 is the host for DNA phages.
4. Source of water is the Mississippi River.
5. Samples collected on May 26, June 15, and June 22 were not received at
EPA Cincinnati laboratories until two days later.
B-3
-------
TABLE B-4
Coliphage Sampling Results - Raw Water
May to October, 19 81
Keystone Water Company, Norristown, Pennsylvania
Date
Collected
5/26/81
6/15/81
6/22/81
7/13/81
7/27/81
8/1 1/81
9/21/81
10/05/81
Temperature on
Receipt by EPA
Cincinnati - °C
20
17
E. coli
13
11
Host
(ATCC No.)
15597
1 3706
15597
1 3706
15597
1 3706
15597
1 3706
15597
1 3706
15597
1 37 06
15597
1 3706
15597
1 3706
Single Layer
Test Method
0
4
105
92
75
194
8
32
54
94
22
1 32
62
362
176
310
PFU/100 ml
Double Layer
Test Method
0
0
1 25
164
207
302
70
50
70
86
22
284
56
858
100
414
Notes:
1. Sensitivity Limits: Single Layer Test Method - 4 PFU/100 ml
Double Layer Test Method - 10 PFU/100 ml
2. _E. coli host ATCC No. 15597 is the host for RNA phages, and it is
sensitive to some DNA phages.
3. E. coli host ATCC No. 13706 is the host for DNA phages.
4. Source of water is the Schuykill River.
5. Sample collected on May 26 was not received at EPA Cincinnati until May
-------
TABLE B-5
Coliphage Sampling Results - Raw Water
May to June, 1981
Illinois American Water Company, East St. Louis, Illinois
Temperature on ,
E. coli
PFU/100 ml
Date
Receipt by EPA
Host
Single Layer
Double Layer
Collected
Cincinnati - °C
(ATCC No.)
Test Method
Test Method
5/26/81
17
15597
40
20
1 3706
192
210
6/15/81
14
15597
44
54
1 3706
1 28
1 32
6/22/81
16
15597
274
330
1 3706
471
575
7/13/81
22
15597
28
1 4
13706
848
92 0
Notes:
1. Sensitivity Limits: Single Layer Test Method - 4 PFU/100 ml
Double Layer Test Method - 10 PFU/100 ml
2. Ej. coli host ATCC No. 15597 is the host for RNA phages, and it is
sensitive to some DNA phages.
3. coli host ATCC No. 1 3706 is the host for DNA phages.
4. Source of water is the Mississippi River.
B-5
------- |