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MANUAL
FOR EVALUATING
PUBLIC DRINKING WATER SUPPLIES
A Manual of Practice
\
SB
U. S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water and Hazardous Materials
Water Supply Division
LIP
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REPRINTED 1974
REPRINTED 1971
Previously Published in 1969 as
PHS Publication 1820
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PREFACE
Today much attention is being focused on water supply as
an aspect of man's environment that can be either (a) a
natural resource of great benefit to him or (b) a vehicle
by which disease organisms or toxic chemicals can be dis-
tributed widely. The public has no way of directly protect-
ing its own water supply. Constant vigilance by health and
waterworks officials is necessary for continued safe water
production and distribution. These professionals must exer-
cise this vigilance by regular evaluation of existing public
water supplies and thorough study of proposed installations.
The Manual for Evaluating Public Drinking Water Supplies
is designed to provide guidance to health and waterworks
officials in determining whether a public drinking water
supply satisfies modern health requirements. It replaces
the Manual of Recommended Water Sanitation Practice, which
for many years has been a reference document widely used by
the health and waterworks professions.
The Manual for Evaluating Public Drinking Water Supplies
has been prepared by the Water Hygiene Division of the
Office of Water Programs, Environmental Protection Agency.
Particular credit for assistance in its preparation is ex-
tended to members of the Advisory Committee on Use of the
Public Health Service Drinking Water Standards and to the
EPA Regional Office personnel responsible for the water
hygiene program. It is hoped that this manual will be found
useful by all whose duty it is to ensure safe drinking water
for the American people.
James H. McDermott
Director
Water Hygiene Division
Office of Water Programs
Environmental Protection Agency
111
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ADVISORY COMMITTEE
ON USE OF THE PUBLIC HEALTH SERVICE
DRINKING WATER STANDARDS0
Mr. George H. Eagle, Chief Sanitary Engineer, Ohio State
Department of Health
Mr. Eugene C. Meredith, Director, Division of Engineering,
Virginia Department of Health
Mr. Elwood Bean, Chief, Treatment Section, Philadelphia
Water Department
Mr. Oscar Gullans, Chief Filtration Engineer, South District
Filtration Plant (Chicago)
Dr. David McGuire, Director, Division of Laboratories,
Colorado State Health Department
Mr. Guy M. Tate, Jr., Director, Bureau of Sanitation,
Birmingham (Alabama) - Jefferson County Board of Health
Mr. Daniel A. Okun, Professor of Sanitary Engineering, Head,
Department of Environmental Sciences and Engineering,
The School of Public Health, University of North
Carolina.
Mr. Henry J. Ongerth, Assistant Chief, Bureau of Sanitary
Engineering, California State Department of Public
Health
Mr. H 0. Hartung, Executive Vice President, St. Louis
(Missouri) County Water Company
Public Health Service Personnel
Mr. Malcolm C. Hope (Chairman), Assistant Chief, 'Division
of Environmental Engineering and Food Protection,
Department of Health, Education, and Welfare, Washington
25, D.C.
a,The positions shown are those occupied in March 1966.
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Mr. Richard S. Mark (Co-Chairman), Chief, Interstate Carrier
Branch, Division of Environmental Engineering and Food
Protection, Department of Health, Education, and Wel-
fare, Washington 25, D.C.
Mr. Floyd B. Taylor (Secretary), Chief, Water Supply Sec-
tion, Interstate Carrier Branch, Division of Environ-
mental Engineering and Food Protection, Department of
Health, Education, and Welfare, Washington 25, D.C.
Mr. Morris B. Ettinger, Chief, Chemistry and Physics Section,
Water Supply and Pollution Control Research Branch,
Robert A. Taft Sanitary Engineering Center, Cincinnati,
Ohio
Dr. P. W. Kabler, Chief, Microbiology Section, Water Supply
and Pollution Control Research Branch, Robert A. Taft
Sanitary Engineering Center, Cincinnati, Ohio
Dr. Richard Woodward, Chief, Engineering Section, Water
Supply and Pollution Control Research Branch, Robert
A. Taft Sanitary Engineering Center, Cincinnati, Ohio
VI
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REGIONAL OFFICES
Region I - Connecticut, Maine,
Massachusetts, New Hampshire,
Rhode Island, Vermont.
J. F. Kennedy Federal Building
Boston, Massachusetts 02203
Region II - New Jersey, New York,
Puerto Rico, Virgin Islands.
Federal Building, 26 Federal Plaza
New York, New York 10007
Region III - Delaware, District of
Columbia, Maryland, Pennsylvania,
Virginia, West Virginia.
P.O. Box 12900
Philadelphia, Pennsylvania 19108
Region IV Alabama, Florida,
Georgia, Kentucky, Mississippi,
North Carolina, South Carolina,
Tennessee.
50 Seventh Street, N.E.
Atlanta, Georgia 30323
Region V - Illinois, Indiana,
Michigan, Minnesota, Ohio,
Wisconsin.
433 West Van Buren Street
Chicago, Illinois 60607
vii
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Region VI - Arkansas, Louisiana,
New Mexico, Oklahoma, Texas.
1114 Commerce Street
Dallas, Texas 75202
Region VII - Iowa, Kansas,
Missouri, Nebraska
601 East 12th Street
Kansas City, Missouri 64106
Region VIII - Colorado, Montana,
North Dakota, South Dakota, Utah.
19th and Stout Streets
Denver, Colorado 80202
Region IX - Arizona, California,
Hawaii, Nevada, American Samoa,
Guam
50 Fulton Street
San Francisco, California 94102
Region X - Alaska, Idaho, Oregon,
Washington
1321 Second Avenue
Seattle, Washington 98101
Vlll
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CONTENTS
INTRODUCTION
PART I - THE SANITARY SURVEY AND WATER TREATMENT
REQUIREMENTS 1
The Sanitary Survey 1
Basic Principle 1
Public Water Supplies - General Evaluation 1
The Survey Engineer 3
The Survey Report 3
Water Treatment Requirements 4
General Requirements 4
Extent of Treatment 5
Group I. Water Usable Without Treatment 6
Group II. Water Needing Disinfection Only 9
Group III. Water Needing Treatment by Complete
Conventional Means 9
PART II - RECOMMENDED SANITARY REQUIREMENTS FOR WATER
SOURCE PROTECTION AND TREATMENT 13
Ground Water Supplies 13
Geologic Factors for Source Protection 13
Distances from Sources of Contamination 14
Wells 14
Sp rings 18
Infiltration Galleries 19
Surface Water Used Without Filtration 19
General 19
Special Precautions to be Taken 22
Surface Waters Used with Chemical Treatment, Filtration,
and Disinfection 23
General Requirements 23
Plant Intake 24
Plant Delivery Capacity 25
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PI ant Location 25
Presettling Reservoirs 26
Coagulation and Sedimentation Basins 26
Chemical Feeding 27
Slow Sand Fil ters 27
Rapid Granular Filters 28
Alternate Forms of Treatment 29
Finished Water Storage Reservoirs 29
Cross-Connections, Open Connections, and Partition Walls
in a Water Treatment Plant 29
Drains 30
Finished Water Pumping Stations 30
Disinfection 31
Chlorination 31
Chlorination Equipment 31
Hypochlorite Solutions 34
Control of Chlorination 34
Other Methods of Disinfection 37
Fluoridation 41
Operation Control 42
Supervision 42
Laboratory Tests and Control 43
Summary 44
PART III - RECOMMENDED SANITARY REQUIREMENTS FOR WATER
DISTRIBUTION SYSTEMS 47
Water Distribution System 47
General Protection Principles 47
Protection for Pipe System 48
Storage Protection 49
Interconnections, Backflow Connections, Cross and Open
Connections 51
Cross-Connection 51
Open Connection 52
Backflow Connection 52
Interconnection 52
Water Distribution System Hazards 52
REFERENCES 55
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APPENDIX - EXCERPTS FROM THE UNITED STATES PUBLIC
HEALTH SERVICE DRINKING WATER STANDARDS 57
Bacteriological Quality 57
Physical Characteristics 61
Radioactivity 61
XI
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INTRODUCTION
Since 1914, Federal, state, and local health authori-
ties and waterworks officials have used the Public Health
Service Drinking Water Standards, in its original and re-
vised forms, as the standards for healthful public drinking
water supplies. An appendix in the 1942 revision sets forth
guidelines for evaluating a public water supply. This ap-
pendix, which was published separately in 1946 as the Manual
of Recommended Water Sanitation Practice, has now been re-
vised and updated to reflect important changes about organic
chemicals and radiochemicals and to include more details
of sanitary requirements for water source protection and
treatment. It is published here as the Manual for Evaluat-
ing Public Drinking Water Supplies.
The evaluation of a public drinking water supply ap-
praises the origin, treatment, distribution, and storage
of water, and the bacteriological, physical, chemical, and
radiochemical qualities of the water as it flows from the
tap. This Manual recommends procedures for surveying and
evaluating a water supply and describes the elements of
water treatment generally necessary to ensure the production
of water that continuously meets the requirements of the
Public Health Service Drinking Water Standards.
Adherence to the recommendations contained in this
Manual is not a requirement for approval of any public
drinking water supply, nor is it intended that these recom-
mendations supplant design criteria adopted by state or
local regulatory bodies. This Manual is intended to serve as
a guide to those whose task it is to evaluate public water
supply systems and deals primarily with health hazards at-
tendant on the production of a potable public water supply.
Xlll
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Factors such as the complexity of the system being eval-
uated, the nature of the raw water source, and the com-
petence of personnel engaged in operating the supply require
professional judgment to successfully apply the Manual's
recommendations.
The Manual supplements the Public Health Service Drink-
ing Water Standards with particular emphasis on those items
related to ''Source and Protection.'' The construction
criteria pertain to those features of a plant that are
essential to the continued production of a safe water
supply.
xiv
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Parti
THE SANITARY SURVEY AND WATER
TREATMENT REQUIREMENTS
A. THE SANITARY SURVEY
1. Basic Principle
Section 2.2 of the Public Health Service Drinking Water
Standards 1962 (PHS Drinking Water Standards)1 provides that
''Frequent sanitary surveys shall be made of the water sup-
ply system to locate and identify health hazards which might
exist in the system.''
2. Public Water Supplies - General Evaluation
In the PHS Drinking Water Standards, a water supply
system is defined to include ''the works and auxiliaries
for collection, treatment, storage, and distribution of
the water from the source of supply to the free-flowing
outlet of the ultimate consumer.'' Sanitary protection is
concerned with all those parts of a water system that come
within this definition. The responsibility of the water
purveyor for conditions in the water supply system gen-
erally ends at the connection to the consumer's piping, and
responsibility for the consumer's system rests with the
owner of the premises and with municipal, county, or other
legally constituted authorities.
Proper evaluation of a water supply requires a care-
ful study of the source and of the practices and protection
applied to the supply. Although no precise outline of such
a study can be given here, all studies should include, as a
minimum, a compilation and evaluation of the following basic
data:
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(a) a field and office sanitary survey of the water
and its environment from source to the consumer's tap;
(b) a description of the water system's physical fea-
tures including adequacy of supply, treatment processes
and equipment, storage facilities, and delivery capabilities
(sketches are invaluable);
(c) an analysis of 12-month bacterial records and
current chemical records on water from the source, the
treatment plant, and the distribution system;
(d) an analysis of operating records showing present
capacity, water demands, production to meet demands, and
anticipated future demands;
(e) a review of management and operation methods and of
the training, experience, and capabilities of personnel;
(f) a review of treatment plant and supporting labo-
ratory equipment and procedures, including the qualifica-
tions of the laboratory personnel;
(g) an examination of state and local regulations and
plumbing codes; and
(h) a summary and analysis of all facts pertinent to
all water-system-related health hazards that were observed
during a field survey.
Health hazards are defined in the PHS Drinking Water
Standards as ''any conditions, devices, or practices in the
water supply system and its operation which create, or may
create, a danger to the health and well-being of the water
consumer. An example of a health hazard is a structural
defect in the water supply system, whether of location,
design, or construction, which may regularly or occasion-
ally prevent satisfactory purification of the water supply
or cause it to be polluted from extraneous sources.'1 De-
tection of such health hazards requires a careful survey of
the entire water supply system. The complexity of this
task varies from the relatively simple investigation of a
single well supply and limited distribution system to the
involved survey of a supply that includes complete treat-
ment facilities and complex distribution systems.
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3. The Survey Engineer
A qualified person should make the sanitary survey of a
water supply; his competence determines the reliability of
the data collected. Although the qualifications constituting
competence cannot be precisely defined, he should have a
technical education in basic sanitary sciences and engi-
neering and a broad knowledge of sanitary features and
physical facts concerning potable water supplies and their
sources. The essential features of water purification plants
and systems, including their operation and methods of labo-
ratory control, must also be understood by the investigator.
4. The Survey Report
The basic survey objective is to collect sufficient
information to determine conclusively the capability of a
water supply to continuously provide water that meets the
PHS Drinking Water Standards. An engineering assessment of
the adequacy of the source, the treatment plants, and the
distribution system to meet normal and peak demands and to
maintain adequate pressures should be included. Existing
supplies should be surveyed frequently enough to control
health hazards and maintain good sanitary quality, and the
survey report of each public water supply system should be
reviewed annually and updated when necessary.
A brief, general description of the physical features
of the water supply from source to tap, employing maps and
sketches where appropriate, should include:
(a) the name and owner of the supply;
(b) a description of sources and catchment areas;
(c) a description of the storage available before and
after treatment; and
(d) a description of the system including date of in-
stallation of the main works and a record of major exten-
sions or alterations made since the last survey.
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B. WATER TREATMENT REQUIREMENTS
1. General Requirements
The water quality requirements of the PHS Drinking Water
Standards are minimum requirements, and good quality water
should have physical and chemical characteristics con-
siderably better than the limiting values established in the
PHS Drinking Water Standards (Sections 4.2, 5.1, 5.2, 6.1,
and 6.2). For example, water with turbidity of 5 units and
a color of 15 units may be acceptable, but in a coagulated,
filtered water such values could indicate serious malfunc-
tioning of the purification process. (The PHS Drinking Water
Standards are being revised current]y,and will contain a
recommendation that the turbidity standard be reduced to 1
turbidity unit. This and other revisions of the Drinking
Water Standards, proposed at the time of this printing, are
shown on the following pages.) Similarly, increased concen-
trations of copper and iron could indicate a corrosiveness
that would be objectionable to consumers, even though the
concentrations of the metals did not exceed recommended
limits. In well water an increase in chlorides over the
normal amount found in ground waters in the area may be the
first indication of pollution.
The type of treatment required depends on the charac-
teristics of the watershed, the raw water quality, and the
desired finished water quality. If pollution of the source
water is increasing, plant facilities, which were adequate
for treatment of a nonpolluted water, may become inadequate.
The production of water that is free from pathogenic orga-
nisms, aesthetically satisfactory to the senses, and reason-
ably acceptable chemically becomes increasingly difficult
when the raw water has a high and varying chlorine demand,
contains large numbers of coliform bacteria, or contains
high concentrations of dissolved solids, toxic substances,
or taste and odor producing substances.
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When evaluating the ability of a water supply system
to constantly produce a safe and satisfactory water, these
factors should be considered:
(a) the quality of water produced at times of unusual
stress, such as during heavy run-offs, periods of drought,
or periods of excessive demand as shown in the records;
(b) the quality of the raw and finished waters, as
determined by laboratory data and sanitary surveys, and any
trends in improvement or deterioration;
(c) the purification processes, including the facilities
used to apply disinfectants at various locations in the
treatment process, and their capacities compared with the
capacities considered necessary to meet maximum anticipated
requi rements;
(d) the treatment processes used and their reliability
in changing raw water characteristics to produce a fin-
ished water that continuously meets the PHS Drinking Water
Standards;
(e) the minimum residual chlorine concentration in the
plant effluent water, when chlorine is used, together with
the time that this or greater chlorine levels were main-
tained;
(f) the qualifications of the operators and laboratory
personnel, as indicated by appropriate training, or certi-
fication, or both; and
(g) the laboratory facilities and analytical procedures,
frequency and extent of their use, and application of the
data to operational control.
2. Extent of Treatment
The Public Health Service recommends that all municipal
water supplies, whether they be ground water or surface
water, receive treatment by disinfection regardless of the
quality of the water. The benefits from the added protection
provided by disinfection far outweigh the increased cost and
the added maintenance incurred by the water utility. When
coliform density is used as one criterion for judging treat-
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ment requirements, raw waters can be divided into three
groups: clean, clear, and polluted waters. The coliform
densities of the raw waters can be expressed in terms of the
most probable number (MPN) from the multiple-tube fermen-
tation technique, or actual coliform counts determined by
the membrane filter (MF) technique.
The requirements are given for three groups of water:
those usable without treatment, those needing disinfection
only, and those needing complete treatment. The quality re-
quirements listed below are the recommended Technical Review
Committee Tentative Standards, that are proposed as re-
visions to the current PHS Drinking Water Standards. They
differ from the current PHS Standards in that some standards
have been added, some have been deleted, and others modified.
Group I. Requirements for Water Usable Without Treat-
ment 1
A. Bacteriological Quality: The coliform standard
remains the same as the PHS Drinking Water Stand-
ards, 1962, plus the inclusion of a standard
plate count limit of 500 organisms per ml.
B. Physical Quality: should meet the following
standards.
Color 15
Turbidity 1 turbidity unit
Taste and odor 2 threshold odor number
Recommended Technical Review Committee Tentative Standards.
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C. Chemical Quality: chemical concentrations should
not exceed the following:
Maximum Allowable
Limits
Substance
concentration -
mg/liter
Arsenic (As) 0. 1
Barium (Ba) ]
Cadmium (Cd) 0.010
Chloride (Cl) 250
Chromium (Cr) 0. 05
Copper (Cu) 1
Cyanide (CN) 0. 2
Fluoride (F)a
50. 0-53. 7°F 1.8
53.8-58.3 1.7
58.4-63.8 1.5
63.9-70.6 1.4
70.7-79.2 1.2
79.3-90.5 1.1
Foaming Agents as Methylene Blue Active
Substances 0.5
Iron (Fe) 0.3
Lead (Pb) 0.05
Manganese (Mn) 0. 05
Mercury (Hg) 0. 005
Nitrate Nitrogen 10
Organics - Carbon Absorbable
CCE 0.3
CAE 1.5
Selenium (Se) 0. 01
Silver (Ag) 0. 05
Sodium (Na) 270
Sulfate (SO4) 250
Zinc (Zn) 5
Annual average of maximum daily air temperature.
Substances not included in the above table that may have
deleterious physiological effect or that may be excessively
corrosive to the water supply system should not be permitted
in the raw water supply.
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D. Radioactivity: should comply with the following
certification limits:
ALPHA ACTIVITY
Gross Alpha Activity - 1 pCi/1, or Radium 226 -
1 pCi/1 when the gross activity is greater than
1 pCi/1 but less than 10 pCi/1.
BETA ACTIVITY
Gross Beta Activity - 10pCi/l, or Strontium 90
- 10 pCi/1 when gross beta activity, after the
Potassium 40 activity has been subtracted, is
greater than 10 pCi/1 but less than.100 pCi/1.
The recommended technical task force tentative standards
provide for provisional arrangements to be made by further
community surveillance of radioactivity to modify the above
listed certification limits.
E. Pesticides: should not exceed the following
1imi ts:
_, . . . Maximum permissible
Jr esticide , /
concentration, mg/1
Aldrin 0.01
Aldrin and Dieldrin 0. 01
Dieldrin 0. 01
Chlordane 0.01
DDT 0. 1
Endrin 0. 003
Heptachlor 0. 02
Heptachlor epoxide 0. 02
Heptachlor and Heptachlor epoxide 0. 02
Lindane 0.1
Methoxychlor 0. 5
Organophosphate and carbamate
insecticides3- 0. 1
Toxaphene 0. 1
2,4-D 1
2,4,5-T 0.005
2,4,5-TP 0.2
Expressed in terms of parathion equivalent cholinester-
ase inhibition.
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Group II. Requirements for Water Needing Disinfection
Only
A. Physical, Chemical, Radioactivity, and Pesticide
Requirements: the requirements as shown for un-
treated raw ground water (Groups I.B, I.C, I.D,
and I.E) should be met. If the water does not
consistently meet all these requirements, con-
sideration should be given to providing addition-
al treatment during periodic decreases in quality
that result from high turbidity, tastes, etc.
B. Bacteriological Quality:
1. Fecal Coliform Density: If fecal coliform density
is measured, the total coliform density discussed
below may be exceeded, but fecal coliform density
should not, in any case, exceed 20 per 100 milli-
liters as measured by a monthly arithmetic mean.
When the fecal coliform vs. total coliform cri-
terion is used for Group II water, the fecal
coliform count should never exceed the 20 per 100
milliliters monthly arithmetic mean. This fecal
coliform standard only applies when it is being
measured on a regular basis.
2. Total Coliform Density: Less than 100 per 100
milliliters as measured by a monthly arithmetic
mean.
Group III. Requirements for Water Needing Treatment by
Complete Conventional Means Including Coagulation,
Sedimentation, Rapid Granular Filtration, and Disin-
fection (Pre and Post)
A. Bacteriological Quality:
1. Fecal Coliform Density: If fecal coliform density
is measured, the total coliform density discussed
below may be exceeded, but fecal coliform should
not exceed 2,000 per 100 milliliters as measured
by a monthly geometric mean.
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2. Total Coliform Density: Less than 20,000 per 100
mil 1iliters as measured by a monthly geometric
mean.
The same rationale applies here as in the Group II
waters concerning the use of the fecal coliform vs.
total coliform criterion. In no case should the
fecal coliform count exceed the 2,000 per 100
milliliters monthly geometric mean.
The arithmetic mean is used with the Group II
waters because the bacteriological data from these
waters will be of lesser magnitude than that from
the Group III waters; this difference in magnitude
between the monthly means of the Group II and
Group III waters is best reflected by the arith-
metic and geometric means, respectively.
These bacteriological limits may possibly be ex-
ceeded if treatment (in addition to coagulation,
sedimentation, rapid granular filtration, and
disinfection) is provided and is shown to be doing
a satisfactory job of providing health protection.
B. Physical Quality: Elements of color, odor, and
turbidity contribute significantly to the treat-
ability and potability of the water.
1. Color: A limit of 75 color units should not be
exceeded. This limit applies only to nonindustrial
sources; industrial concentrations of color should
be handled on a case-by-case basis and should not
exceed levels that are treatable by complete con-'
ventional means..
2. Odor: A limit of 5 threshold numbers should not
be exceeded.
3. Turbidity: The limits for turbidity are variable.
Factors of nature, size, and electrical charge for
the different particles causing turbidity require
a variable limit. Turbidity should remain within a
range that is readily treatable by complete con-
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ventional means. It should not overload the water
treatment works, and it should not change rapidly
either in nature or in concentration when such
rapid shifts would upset normal treatment opera-
tions.
C. Chemical Quality: Since there is little reduction
in chemical constituents with complete conventional
treatment, raw water should meet the limits given
for Group I.C.
D. Radioactivity: Should comply with Certification
Limits given in Group I.D.
E. Pesticides: Should comply with requirements for
pesticides as shown for untreated raw ground water
in Group I.E.
Infectious material, the increasing diversity of chemi-
cal pollutants found in Group III raw waters, and the many
different situations encountered in regional and local
problems make it impractical to prescribe a limited selec-
tion of facilities and processes that can effectively
handle all problems presented by raw water and its sources.
Future improvements in treatment technology cannot be
reasonably assisted or regulated by requiring the fixed
process steps considered good for today's technology.
Table 1 describes some factors that increase the diffi-
culty in securing disinfection, e.g., adequate disinfec-
tion with halogens depends or temperature, pH, contact
time, and concentration of disinfectant.
Types of disinfection other than chlorination must be
demonstrated to function effectively in all compositions
of water likely to be encountered from the source used.
If a distribution system is of any considerable length,
the disinfection method should provide a residual pro-
tection that can be easily measured.
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Table 1. CONDITIONS CREATING DIFFICULTIES AT THE WATER PLANT AND
IN THE WATER MAINS
Bacterial and biological
conditions
Chemical conditions
Physical and operational
conditions
Increasing numbers of
coliforms
Biological pollution, i. e. , algal
or fungal metabolic products
that effect chlorine demand
Filter clogging organisms that
effect chlorine demand
Ammonia nitrogen
Toxic materials or taste and
odor requiring removal
Color or organic dispersing
agents (anticoagulants), lignin
compounds
Chlorine demand
Iron and manganese
High organic content
High or organic content
High or fluctuating pH
Low temperature
Extended distribution sys-
tems
Highly variable water
quality
Rapid variation in flow and
turbidity of surface water
resource
Tidal effects
Where water sources show continuing quality deteriora-
tion or the quality of water available is not adequate for
future demand, the water purveyor bhould be examining al-
ternate or auxiliary sources of supply and should have
positive plans to procure adequate facilities and sources.
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Part II
RECOMMENDED SANITARY REQUIREMENTS FOR
WATER SOURCE PROTECTION AND TREATMENT
A. GROUND WATER SUPPLIES (Refer to Part I. B.2, Group I)
Adequate, natural protection of ground water involves
purification of water by infiltration into the soil, by
percolation through underlying material, and by storage
below the ground water table.
Ground water, when available in sufficient quantity, is
often a preferred source of water supply. Such water can be
expected to be clear, cool, colorless, and quite uniform in
character. Underground supplies are generally of better
bacterial quality and contain much less organic material
than surface water but may be more highly mineralized.
1. Geologic Factors for Source Protection
When water seeps downward through overlying material to
the water table, particles held in suspension, including
microorganisms, may be removed. The extent of removal de-
pends on the depth and character of the overlying material.
The bacterial quality of the water also generally improves
during storage in the aquifer because time and storage
conditions are usually unfavorable for bacterial multi-
plication or survival. Of course, the clarity of ground
water does not guarantee safe drinking water, and only
adequate disinfection can guarantee the absence of patho-
genic organisms. An important, naturally protected water
supply is available where sufficient artesian water is
present.
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2. Distances from Sources of Contamination
All ground water withdrawal points should be located
a ''safe1' distance from sources of pollution. Sources of
pollution include septic tanks and other individual or
semipublic sewage disposal facilities, sewers and sewage
treatment plants, industrial waste discharges, land drain-
age, farm animals, fertilizers, and pesticides. Where water
resources are severely limited, ground water aquifers
subject to contamination may be used for water supply if
adequate treatment is provided.
After the decision has been made to develop a water
supply in an area, the direction of water movement during
proposed withdrawal conditions and the ''safe'1 distance
from potential pollution sources should determine the with-
drawal point. A ''safe1' distance is the distance that
ensures no contamination will be drawn or will flow to the
withdrawal point when conditions of pollution sources,
withdrawal, and water table levels are the most adverse.
Because many factors affect the determination of
''safe*' distances between ground water supplies and sources
of pollution, it is impractical to set fixed distances.
Where insufficient information is available to determine
the ''safe1' distance, the distance should be the maximum
that economics, land ownership, geology, and topography
will permit. If possible, a well site should be located at
an elevation higher than that of any potential source of
contamination. It should be noted that the direction of
ground water flow does not always follow the slope of the
land surface.
3. Wells
All wells must be properly sealed against surface water
contamination (Figure 1). Ground water can be contaminated
by surface water entering through the top of the well or by
surface water or water from contaminated aquifers, through
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PUMP UNIT
SANITARY WELL SEAL
COBBLE DRAIN
REINFORCED CONCRETE
COVER SLAB SLOPED
AWAY FROM PUMP
:ARTESIAN PRESSURE SURFACE
OR PIEZOMETRIC SURFACE
'CASING
Figure 1. Drilled well showing sanitary
protective features.
which the well passes, that flow down outside of the well
casing to the intake point.
When shallow ground water is developed, pathogenic
organisms may penetrate the water table. Fluctuations of the
water table caused by periods of heavy precipitation may at
times bring the water table into contact with contaminated
zones near the surface. Wells that extend only a short
15
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distance into shallow water tables are more likely to be
contaminated than wells that penetrate more deeply. The con-
struction of wells with watertight casings surrounded by
cement grout protects against surface contamination being
drawn to or reaching the casing wall. The depth of grout
necessary depends on the individual characteristics of the
of the area involved. Wien a sanitary survey is made of an
existing or proposed well site, nearby sewage disposal fa-
cilities, caves, sink holes, abandoned borings used for
surface drainage or sewage disposal, and improperly sealed
wells should be located, mapped, and evaluated as to pos*
sible hazard. Investigation should be made for fissures
or faults in the stratum overlying the aquifer.
The following specifications for sanitary protection are
particularly applicable to wells producing water that is
not treated or that receives disinfection only. (See also
American Water Works Association [AWW.A] Specification
A100.2)
a. Exclusion of Surface Water from Site. The top of the
well must be so constructed that no foreign matter or
surface water can enter the well. The well site should be
properly drained and adequately protected against flooding.
Surface drainage should be diverted away from the well.
b. Earth Formations Above Water-Bearing Stratum. Recharge
formations above the tapped aquifer should provide suffi-
cient filtration to prevent contamination from sources of
pollution.
c. Distance to Source of Contamination. The horizontal
distance from a well to a source of contamination should be
as great as practical.
d. Depth of Casing and Curbings. Well casings should ex-
tend into and be sealed to the impermeable stratum immedi-
ately above the aquifer.
e. Construction and Use of Casing and Curbing. For drilled
wells, the space between casing and well hole should be
16
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filled with cement grout to a sufficient depth below grade
to prevent surface pollution. Aquifers containing water of
undesirable quality should be sealed off from the well cas-
ing. The casing must extend 6 inches or more above the
surface of the well house floor or collar. Casings should
not be used as suction pipes.
f. Gravel-Packed Wells. The top level of the gravel pack-
ing should be at least 50 feet below ground surface. The
remaining space above the gravel level should be filled
with impervious puddled clay or cement grout. Gravel fill
pipes must be securely capped and sealed.
g. Well Seals or Covers. A watertight seal or cover must
be provided at the top of the casing.
h. Well Vents. Vents necessary to maintain atmospheric
pressure in the casing should be screened (#24 mesh), with
the return bend facing downward, and terminate at least
18 inches above the floor level or above the maximum flood
level, whichever is higher.
i. Well Pits. Well pits should be used only where there
is adequate protection to prevent flooding.
j. Construction and Installation of Pumps.The connec-
tion between the top of the well casing and the power unit
must be watertight. The openings for pump suction lines,
water level measurement lines, power cables, and lubrication
lines must be tightly sealed. Where pump suction lines are
outside well casings, the suction lines should be positively
protected from environmental hazards. Submersible pumps are
considered safe.
k. Pump Houses. Pump houses should be adequately drained
and protected against flooding.
1. Disinfection and Other Unit Processes. All treatment
processes should be accomplished in accordance with pro-
visions contained in other sections of this Manual.
17
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4. Springs
Water appears at the ground surface from springs of
two types, gravity and artesian. Gravity springs occur
when the aquifer in which water is percolating laterally
comes to the surface because of a sharp drop in surface
elevation below the normal ground water table or when ob-
structions to flow result in an overflow at the surface.
Artesian springs are formed when faults in impermeable
strata permit artesian water to escape from confinement.
Artesian springs discharge from artesian aquifers at pres-
sure higher than the discharge elevation and are usually
freer from environmental hazards than are gravity springs.
The nature of the strata underlying porous strata should
be known, and the possibility should be considered that
water may enter the aquifer through sink-holes or other
large openings. The slope of the water table should be
ascertained. The quality of water derived from springs
should be protected from surface contamination even if pro-
cessed as a surface water. The following requirements should
be met:
a. Structure. Springs should be housed in permanent build-
ings or structures with watertight walls. For surface
springs, the walls should extend into the aquifer.
b. Drainage. , Direct suiface drainage should be diverted
away from the spring.
c. Fencing. The entire area within 100 feet of the spring
should be fenced to prevent trespass of livestock and un-
authorized persons. Any portion of surface drainage diver-
sion ditches lying above the spring should be within the
fenced area.
d. Disinfection and Other Unit Processes. Disinfection and
other unit processes should be accomplished in accordance
with provisions contained in other sections of this Manual.
18
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5. Infiltration Galleries
An infiltration gallery is essentially a horizontal
well that collects water along its entire length. Such
galleries are usually laid in the alluvium near a body of
surface water but are sometimes constructed beneath the
surface water. Infiltration galleries are subject to the
same sanitary hazards as shallow wells but have greater
exposure to pollution because of their horizontal posi-
tion. The following precautions should be taken to pro-
tect against contamination:
a. Soil Filtration. To ensure adequate removal of sus-
pended matter and bacteria, each infiltration gallery should
be constructed and located to provide the collected water
the maximum filtration through soil and sand.
b. Protection from Contamination. With the exception of
service facilities, the surface area above and within a
minimum of 100 feet or a ''safe'1 distance of each gal-
lery should be void of buildings and dwellings and should
be protected by a fence to prevent trespass of livestock
and unauthorized persons.
c. Disinfection and Other Unit Processes. Disinfection and
other unit processes should be accomplished according to
provisions contained in other sections of this Manual.
B. SURFACE WATER USED WITHOUT FILTRATION (Refer to Part
I.E.2, Group II)
1. General
It is increasingly difficult, because of recreational
use of streams, lakes, and watersheds, and urban and indus-
trial development, for unfiltered surface water supplies to
meet the requirements of the PHS Drinking Water Standards.
With suitable catchment areas, adequate storage in impound-
19
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ing reservoirs, strict control of pollution sources on the
catchment and storage areas, and effective disinfection,
unfiltered water can quite often meet the bacteriological
requirements. Most unfiltered supplies, however, are unable
to consistently produce suitably clear and colorless water,
usually because of the influence of seasonal changes in
human activity and weather.
Special emphasis must be placed on prevention of pol-
lution of watersheds, or reservoir inspection and policing
procedures, and on disinfection. Terminal reservoirs3
and Class A upstream reservoirs" should never be used for
o
recreation. Upstream reservoirs are classed as follows:
Class A: Water derived from an uninhabited or sparsely
inhabited area, at or near the point of rainfall or
snow melt; collected in a storage reservoir, clean and
clear enough to be distributed to the consumers with
disinfection only. (See Figure 2 for illustration.)
Class B: Water impounded from an area not heavily in-
habited and allowed to flow from storage in a natural
stream to the point of withdrawal and requiring treat-
ment in varying degree in addition to disinfection.
Class C: Water which has flowed in a natural stream
before storage for a considerable distance, having re-
ceived polluting materials from municipalities, indus-
tries, or agricultural areas; confined in a reservoir
primarily for purposes of storage until such time as
low stream flow makes the stored water necessary for the
use of the downstream city; and later allowed to flow
from the reservoir to the tributary water works in an
open stream accessible to the public; and requiring
complete treatment.
"Terminal Reservoirs: areas providing end storage of water prior to treatment.
Upstream Reservoirs: reservoirs providing storage of untreated water at
various points in the watershed to provide or supplement the supply at the
terminal reservoir.
20
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Figure 2. Chester Morse Reservoir.
Ceda r River Watershed.
near Seattle, Washington.
Multipurpose reservoirs are those constructed for pur-
poses in addition to the supply of domestic water. The water
purveyor does not have complete control over the reservoir,
and the water requires the same complete treatment as Class
C water.
When the watershed cannot be owned completely or nearly
completely by the water purveyor, ownership of marginal land
around the reservoirs is recommended and ownership of the
land for a considerable area around the supply intake is
mandatory.
Although the beneficial effects of storage are con-
siderable, they cannot approach those obtained from chemical
21
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treatment and filtration. Such treatment should be con-
sidered when the pollution loading, expressed as the average
monthly concentration of total coliforms, approaches 100
per 100 milliliters.
2. Special Precautions to be Taken
Some precautions that must be taken with unfiltered
surface sources are:
(a) The character of the watershed area should be such
that heavy rainfall does not excessively increase the tur-
bidity in the storage reservoir. The area of swampland
should be small, and the water draining therefrom should
have a minor effect on the color of the impounded water.
Excessive turbidity exceeds 5 units, and excessive color
exceeds 15 units.
(b) Because the ideal of 100 percent ownership or con-
trol of the watershed of a surface supply cannot usually
be obtained, one protective measure is a strong program for
pollution control and abatement. The entire watershed area
should be surveyed periodically to detect existing or poten-
tially dangerous sources of pollution. If polluting emis-
sions can not be eliminated, they must be treated. A permit
to discharge waste should be given to those who treat wastes
adequately, as determined by health authorities, or the
water purveyor, or both, with the understanding that such
permits may be revoked and all emissions prohibited, if
necessary to protect the water supply.
(c) The population density of the watershed should be
determined yearly to forecast the future need for more
extensive treatment. This should include assessment of
possible pollution from industrial, agricultural, or recrea-
tional sources.
(d) When permission is given for limited recreational
use of upstream reservoirs, permission should be only by
permit and under proper supervision and should be revok-
able. Sufficient laboratory testing should be conducted to
evaluate the effect of such use.
22
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(e) Where disinfection is the only treatment, exception-
al precautions should be exercised to ensure the effective-
ness and reliability of this treatment. (See Part I. B.2) If
the flow of water to the supply system is variable, the
chlorinators should be of the proportional feed type, and
standby units should always be available.
C. SURFACE WATERS USED WITH CHEMTCAL TREATMENT, FILTRATION,
AND DISINFECTION (Refer to Part I.B.2, Group III)
1. General Requirements
Most surface waters require chemical treatment, coagula-
tion, sedimentation, filtration, and disinfection to make
them suitable for use as public water supplies. A combina-
tion of treatment methods will, if properly carried out,
convert a moderately polluted water into a safe drinking
water. Filtration systems such as diatomite, slow sand, and
certain patented processes may also be used under certain
conditions. The limitations of each treatment process must
not be exceeded.
In general, the design and construction (see Figure 3)
of water treatment plants vary with local circumstances.
Each plant should be designed and constructed to deal with
the characteristics of the water being treated in accord-
ance with state standards and generally accepted good prac-
Figure 3. Centraj District Filtration Plant, Chicago,
Illinois.
23
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tice. The following recommendations are intended only as a
general guide to good practice and should be interpreted
somewhat broadly in the light of specific raw water charac-
teristics and other conditions that may be involved. Older
plants may be expected to produce safe, palatable, econom-
ically useful water if modifications and improvements have
made the treatment facilities adequate and if they are
properly maintained and operated.
2. Plant Intake
The purpose of the plant intake is to withdraw con-
tinuously adequate quantities of the best available grade
of raw water. When selecting the intake location, the stream
or lake bottom character, currents, and potential sources
of pollution must be considered. To provide for the varia-
bility of environmental influences, the intake structure
should be designed and built to permit raw water withdrawal
at various levels, or locations, or both. The intake capac-
ity, including pumping facilities, should provide suffi-
cient raw water for the treatment plant at all times. The
quantity of finished water in storage provides a buffer and
is a factor in determining the necessary intake capacity.
This intake capacity generally equals the average rate of
demand on the maximum day. Dual facilities should be pro-
vided for mechanical equipment. Pump priming must not create
a cross connection between the finished and raw water
supplies.
Intake facilities should also be constructed to ensure
continuous raw water flow despite floods, icing, plugging
with debris or sand, high winds, power failure, damage by
boats, or any other occurrences; be inaccessible to tres-
pass; contain adequate toilet facilities, located and in-
stalled to prevent chance contamination of the raw water
supply; and contain an immediate warning system for the
treatment plant operator in case of failure of automatic
or semiautomatic pumping stations.
24
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3. Plant Delivery Capacity
The delivery capacity of a treatment plant, including
finished water storage should exceed the maximum anticipated
demand for a reasonable time period. A sufficient time
margin should be allowed for future expansion as the com-
munity grows. Water systems that are experiencing demands
approaching, equalling, or greater than this delivery capac-
ity and that are not progressing with construction plans
or the acquisition of auxiliary supplies to meet these
demands cannot be considered satisfactory. A capacity of
sufficient margin is one that can reasonably be expected
to meet all demands 5 years in the future.
4. Plant Location
The treatment plant should be located so that no con-
duit, basin, or other structure containing or conducting
water in the process of treatment can possibly be affected
by leakage from any sewer, drain, or other source of con-
tamination. The site should be drained so that no surface
water can enter into wells, basins, filter tanks, or other
process units.
Protection against floods may be provided by locating
the plant on high ground above flood levels or by con-
structing levees. The adequacy of flood protection would
depend on the flood heights to be expected, the structural
soundness of the protective works, the availability of ade-
quate auxiliary power, and the availability of pumping
equipment to assure the continuous removal of interior
drainage under emergency conditions. Facilities must be
provided to remove filter wash water, plant wastes, and
sanitary wastes during floods. All drainage and sewer lines
for the plant facilities must be designed and constructed
to prevent backflow from submerged outlets.
25
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5. Presettling Reservoirs
Presettling reservoirs are those removing turbidity by
plain sedimentation, supplemented in special cases by the
addition of coagulants, chlorine, or both. Not included are
the relatively small, so-called grit reservoirs commonly
used in the Mississippi Valley for removing coarse silt and
sand.
If presettling reservoirs are used, they should be
located above the influence of flood waters and should have
sufficient capacity to remove sand, silt, and clay with an
efficiency that will prevent overloading of subsequent
treatment facilities. The reservoir shape, inlet and outlet
design, and location should minimize potential short cir-
cuiting.
Provision should be made for rapid, convenient removal
of sludge from the reservoirs and for duplicate reservoirs,
a bypass with special treatment, adequate storage, or some
other means to avoid interruption of service during clean-
ing periods. Where highly polluted waters of variable qual-
ity are involved, coagulation at the inlet and prechlorina-
tion at the inlet or the outlet of the reservoirs should
be provided.
6. Coagulation and Sedimentation Basins
Coagulation and sedimentation properly prepare the
water for filtration. Coagulation and flocculation, which
precede sedimentation, are generally accomplished by rapid
distribution of the coagulating agent followed by gentle
agitation to promote flocculation.
Sedimentation basins should be sized and arranged to
ensure the settling of the floe developed and the delivery
of relatively clear water to the filters. Basins should be
of sufficient number and hydraulic flexibility to ensure
the continuous operation of the treatment plant. Provisions
should be made for satisfactory removal of sludge. The
26
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critical displacement velocity of the floe must not be
exceeded by water flowing through the sedimentation basins.
The flow over discharge weirs should be less than 20,000
gallons per day per foot of weir to prevent surges.
7. Chemical Feeding
Treatment plants should be provided with modern devices
for accurately measuring and adding to the water each chem-
ical used for coagulation or other purposes, with at least
one reserve unit for all chemical feed equipment, whether
of a dry feed or solution feed type. This chemical feed
equipment should have continuous recording devices and alarm
devices to ensure continuity of treatment and should be
capable of ready adjustment to variations in the flow of
water being treated. Where flows vary considerably through-
out a 24-hour period, the chemical feed adjustment should
be automatic. Sufficient chemicals should be stored to pre-
vent shortages caused by any unforeseeable interruption of
chemical supply. An up-to-date inventory of chemical stock
should be kept, and the oldest chemicals in stock should
be used first. The minimum chemical inventory should be a
30-day supply; this required inventory will vary from month
to month because of varied raw water quality and varied
demands.
8. Slow Sand Filters
Properly designed and operated slow sand filters are
suitable for the treatment of certain types of relatively
clear water. Preferably they should be covered, and they
should be operated at rates (normally about 4 million gal-
lons per acre per day) consistent with the continuous
production of water meeting the PHS Drinking Water Stand-
ards. Care should be taken to avoid any sudden increases
in the filtration rate of slow sand filters. The filter
area should consist of several independent units so that the
quality and quantity of water required at times of maximum
27
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draft can be supplied when some units are out of service
for cleaning (normally done every 20 to 60 days) or repair
work. To provide for more efficient filtration by the slow
sand filters and particularly to remove turbidity, the
raw water is sometimes given pretreatment consisting of
simple sedimentation, coagulation and sedimentation, pre-
liminary rapid filtration with or without coagulation and
sedimentation, or microstraining. Filtratio.n rates for slow
sand filters may be appreciably increased (by a factor of
2 or 3) over normally acceptable rates if enough preliminary
treatment is provided.
9. Rapid Granular Filters
Rapid granular filters should preferably be of the open,
gravity type to permit ready and continuous inspection. The
depth, effective size, and uniformity coefficient of the
media should meet the requirements of adequate yield and
filter efficiency. The rate of filtration should be consis-
tent with the production of a water that meets or exceeds
the requirements of the PHS Drinking Water Standards.
In general, rapid granular filters should be designed
and operated to maintain high efficiency in particulate
removal and to keep the filtering medium free of mud balls,
cracks, and other hindrances to efficient filtration. The
total available filter area should be divided into several
independent units so that maximum demands occurring during
cleaning or repair of individual units can be met. Rapid
granular filters are opera-ted at 1.5 to 3.0 gallons per
square foot per minute and are usually cleaned every 12
to 40 hours. Cleaning is normally done when sufficient
head loss has been established to put the bed and its under-
drainage system under partial vacuum or when there seems to
be danger of 0. breakthrough. This partial vacuum should not
be allowed to become large enough to cause air binding or
shrinkage cracks to occur; backwashing should be done before
evidence of a breakthrough is seen.
28
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Rapid granular filters operated at rates higher than
those mentioned above can still produce high quality water
depending on the incoming water quality, the efficiency of
the treatment units preceding the filters, the capabilities
of the filters, and the degree of quality control exercised.
10. Alternate Forms of Treatment
Other treatment processes may be used either as an
added degree of treatment or to replace one of the afore-
mentioned units (sections 5 through 9 above). The more
common processes are diatomaceous earth filters, filter
beds with more than one type of media, and high rate fil-
ters. Use of these and other alternate forms of treatment
will depend on incoming water quality and volume, economic
feasibility, performance of the other units of the treatment
process, and degree of quality control exercised.
11. Finished Water Storage Reservoirs
All finished water reservoirs should be covered. If
such reservoirs are located below adjacent structures or
below ground elevation, adequate protection against leakage
of nonpotable or drainage water from such higher elevations
should be provided. If practical, such reservoirs should
be situated above the ground water table and should have
no common wall with any other plant units containing water
in a prior stage of treatment.
12. Cross-Connections, Open Connections, and Partition Walls
in a Water Treatment Plant
No cross-connection should exist between any conduit
carrying filtered or postchlorinated water and another
conduit carrying nonpotable water, or water in any prior
stage of treatment.
No conduit or basin containing finished water should
have a common division wall with another conduit or basin
29
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containing nonpotable water. Vertical double division walls,
where separated sufficiently to permit ready access for
inspection, are permissible where the division walls are
monolithic in construction and are properly keyed into their
footings or are cast monolithically with the footings.
Filter-to-waste conduits should not be directly con-
nected to any drainage conduit if backflow can occur.
No conduit carrying nonpotable or partially treated
water, no center-passage type conduits, and no conduits
having double separation walls should be located directly
above any conduit or basin containing finished water.
13. Drains
All drainage conduits should be watertight against
leakage. Where drains discharge into bodies of water serving
as raw water supplies, the discharge points should be lo-
cated so that no drain water can, under any circumstances,
be carried to the plant intake, or to any other water intake
located in the vicinity of the plant. No sanitary sewer or
process wastes sewer should be permitted to discharge waste
water into the raw water supply in the vicinity of any
treatment plant intake; nor should any drain carrying con-
taminated surface water be permitted to be so discharged.
''In the vicinity of* means any discharge point from which
the waste water may adversely affect the raw water supply,
and should be evaluated in terms of flow conditions for the
raw water supply and for the waste water.
14. Finished Water Pumping Stations
For sanitary protection, the precautions given below
should be taken:
(a) Pumping stations should be protected against in-
terruption of operation because of floods. Similarly, pro-
tection against fire should be provided, and plans should
be established for operation under all natural or man-made
disaster situations.
30
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(b) The required number, types, and capacities of pumps
depend on the conditions peculiar to the system involved.
The pumps should be able to meet existing load conditions
with ample reserve. In addition, sufficient standby capacity
should be available to meet maximum demands when the largest
pumping unit is out of service. All pumps should be main-
tained in good condition and periodically operated and
checked for proper performance. The suction pipes should
be examined frequently to determine that they are water-
tight.
(c) Proper plumbing and proper location of sewer lines
protect clear wells from pollution. Pump priming, if re-
quired, should be accomplished with potable water.
(d) Both design and operation should minimize any condi-
tions that might lead to negative pressures in the distribu-
tion system. This includes providing surge suppressors,
closing and opening valves slowly, and avoiding unnecessary
starting and stopping of pumps.
D. DISINFECTION
1. Chlorination
a. Chlorination Equipment. Chlorination equipment should be
selected, installed, and operated to achieve continuous and
effective disinfection under all possible conditions, with
enough stand-by units to ensure uninterrupted operation.
The capacity of the regular chlorination equipment, stand-
by equipment excluded, should exceed the highest anticipated
dosage. The determination of this maximum dosage (and normal
dosages) should be made with the guidance and approval of
the appropriate health agency. The characteristics of the
water to be treated, conditions of water use, and type of
chlorination provided, i.e., free or combined chlorine re-
sidual, should be considered. Frequent operation of stand-by
units to ensure reliability can be accomplished by rotating
the stand-by assignment from unit to unit on a monthly
31
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basis. Adding the plumbing necessary for feeding chlorine
from any prechlorination, postchlorination, or stand-by
equipment to any chlorination point in the treatment pro-
cess provides flexibility to the chlorine feeding facili-
ties. A complete stock of spare parts and tools should be
maintained for emergency replacements or repairs, and pre-
ventive maintenance (scheduled inspection and repair before
breakdown) should be practiced. Chlorination equipment
should be capable of satisfactory operation under every
probable hydraulic condition.
Manual control of the chlorine dosage is permissible
if the rate of flow is relatively constant and an attendant
is always on duty to promptly make the necessary adjust-
ments in dosage. Automatic proportioning of the chlorine
dosage to the chlorine demand of the water is particularly
desirable where the quality of the water is subject to
change without warning. If the instantaneous flow rate
varies more than 25 percent above or below the daily av-
erage, the chlorine dosage to the flow of water being treat-
ed should be automatically proportioned. If the water being
chlorinated is pumped by manually controlled pumps, manual
adjustment of the chlorine dosage is permissible, provided
there is assurance that chlorine dosage will be changed
to compensate for changes in the pumping rates. Whether
manual or automatic chlorinators are used, the operator
should frequently check both the chlorinators and the chlo-
rine residuals.
A reliable and uninterrupted supply of potable water,
under proper pressure and free from coarse, suspended mat-
ter, should be available to ensure the continuous operation
of solution-free chlorinators. Hydraulically or electrical-
ly-driven pumping equipment used for maintaining pressure
should be provided with alternate sources of power to ensure
continuous operation.
Scales for measuring the quantity of chlorine used in a
given time period provide information needed for a chlorine
inventory and for a check on the dosage rates. Such scales,
32
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preferably of the recording type, should be rugged, easily
read, and sufficiently accurate and sensitive to measure
chlorine withdrawal with suitable precision. A visual or
audible pressure drop warning device installed on the feed
lines gives supplementary protection against interruption
of supply.
A sufficient number of cylinders or containers of chlo-
rine should be connected to the chlorinator in use through a
manifold header to maintain adequate operating pressures
throughout any unattended periods. A sufficient reserve
supply of chlorine should be connected at all times to as-
sure continuous chlorination of the Water, even when cylin-
ders or containers are being changed. Minimum chlorine in-
ventory should be sufficient for the plant to satisfy a
maximum 30-day demand. If chlonnators are remote from the
chlorine supply, dual feed lines should be provided and
should be installed along different routes.
If simple chlorination is the only treatment, frequent
residual chlorine determinations should be made. In the
absence of full time treatment, supervision consisting of
frequent manual determinations or residual chlorine record-
ers with alarms should be used. Such alarms must be placed
where frequent servicing is convenient and where they will
be easily heard. Daily service and calibration of these
recorders and alarms should be under the supervision of
skilled personnel.
The water plant should have sufficient chlorination
capacity to provide free residual chlorination.
Chlorination enclosures should be adequately ventilated
to permit exhaust by gravity or mechanical means from the
lowest point of the enclosure. The chlorinator installation
and the handling and storage of chlorine containers should
conform to safety requirements recommended by the Chlorine
Institute.a
*The Chlorine Institute, Inc., 342 Madison Avenue, New York, New York 10017
33
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b. Hypochlorite Solutions. Solutions of calcium or sodium
hypochlorite should be prepared in a mixing tank, diluted,
and allowed to settle before the clear supernatant liquid
is withdrawn to the solution storage tank and subsequently
to the hypochlorinator.
The strength of the clear supernatant hypochlorite
solution should be checked frequently by laboratory test and
appropriate adjustment should be made in either its strength,
by dilution, or in the rate of feed to provide proper chlo-
rine application. Batches of calcium hypochlorite solution
should not be stored for more than '5 days, unless the solu-
tion is properly alkalinized with sodium carbonate. If
hard water is used to make the hypochlorite solution, the
addition of sodium hexametaphosphate will stabilize the
solution and will aid in preventing the fouling and clogging
of equipment.
c. Control of Chlorination. Chlorine should be continuously
applied to the water being treated in a manner that ensures
rapid and thorough dispersion of the chlorine throughout
the water.
The proper dosage of chlorine should be determined by
regular and frequent free chlorine residual tests, both at
the plant and at various points in the distribution system.
In general, a minimum free chlorine residual of 0,1 milli-
gram per liter at distant points in the distribution system
helps maintain a system free from bacterial growths. If
chloramines are used, the desirable residual is 1.0 to 2.0
milligrams per liter at distant points in the distribution
system. The residual chlorine carried in the finished water
leaving the treatment plant should be regulated accordingly.
At times of threatened or actual outbreaks of waterborne
disease, such as during floods, the residual chlorine should
be maintained at a minimum of 1.0 milligram per liter for
free chlorine and 6.0 milligrams per liter for chloramine
in all parts of the distribution system despite resulting
tastes, odors, or both in the delivered water. Where a
34
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short contact time exists to the first consumer's service
line or where waters of high pH are to be treated, residuals
should be increased.
Routine sampling points should be established at the
treatment plant and at several representative points in the
water distribution system. Samples from these distribution
points should be tested for chlorine residuals on the same
scheduled basis as for bacteria, and the residuals should
be recorded as free chlorine and combined chlorine on the
bacteriological report form. Any abnormal decrease in the
normal free or combined chlorine at any point in the dis-
tribution system should be checked, and if the abnormality
persists, a thorough investigation of that portion of the
system should be made.
The frequency at which chlorine residual tests should
be made is related to the contact period. If the contact
time is short (less than 15 minutes), frequent tests are
needed, often at less than hourly intervals. If the contact
time is long (several hours), tests of the plant effluent
should be made at least once in each 8-hour period of opera-
tion, and at least daily at regular sampling points on the
distribution system.
Special care should be taken to maintain a detailed,
accurate daily record of chlorination practice and chlorine
residuals.
Such a record should include:
(a) rate of flow and volume of water treated per unit
time, (continuous record);
(b) gross weight of chlorine cylinders or containers
in use and the weight at the end of a selected time period
(24 hours or less) (continuous record);
(c) the pounds of chlorine used in a selected time
period (24 hours or less);
(d) the gallons of water treated in a selected time
period (24 hours or less);
(e) the applied dose for the selected time period;
(f) chlorinator control settings; and
35
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(g) time and location of sampling, and the type and
results of residual chlorine tests.
Unless bacteriological or other tests indicate a need
for maintaining a higher minimum concentration of residual
chlorine, a minimum of at least 0.4 milligram of free chlo-
rine per liter should be maintained in the treated water for
an actual contact period of at least 30 minutes before de-
livery to the first consumer. If chloramine (combined chlo-
rine) treatment is used for disinfection, the residual
chlorine concentration as indicated by the orthotolidine
method should be at least 2.0 milligrams per liter after
at least 3 hours of contact before delivery to the first
consumer. When required, the state health department should
direct that the minimum concentration of residual chlorine
and the minimum retention period for the chlorinated water
should be increased.
Efficient disinfection of a water supply with chlorine
depends on the type of chlorine residual and the factors
of contact time, temperature, pH, and the presence of sus-
pended material (nature and amount). Free chlorine, a more
effective bactericide than combined chlorine, kills bacteria
and viruses in less time or in the same time at lower con-
centrations than combined chlorine. Information on the bac-
tericidal and viricidal effect of free chlorine is given in
Table 2 and Figure 4. Note that most laboratory studies
have been performed under ideal conditions with water free
from suspended matter (other than organisms) and free from
chlorine demand. Practical plant operation requires higher
chlorine residuals or longer contact times than those in-
dicated by laboratory tests. Free chlorine and combined
chlorine are most effective at low pH values (Figures 5 and
6) and at higher temperatures (Figure 5).
The relationship between the chlorine added and the type
of chlorine residual obtained (a chlorine residual curve)
is illustrated in Figure 7. A chlorine residual curve plots
data obtained from a specific test conducted under estab-
lished conditions. These test results may vary considerably
36
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Table 2. GERMICIDAL EFFICIENCY OF FREE CHLORINE IN WATER
Microorganism
Salmonella typhosa suspended in DFW
(Butterfleld et al.)
Eschenchia coll suspended in DFW
Aerobacter aerogenes suspended in DFW
Shigella dysentenae suspended in DFW
f t
in distilled water (Neefe et al. )
Purified Coxsackie A2 in DFW
(Clarke and Kabler)
Purified poliovirus I (Mahoney) m DFW
(Weldenkopf)
Purified poliovirus I (Mahoney) in DFW
(Kelly and Sanderson)
Purified poliovirus III (Saukett) in DFW
(Kelly and Sanderson)
Purified Coxsackie B5 in DFW
(Kelly and Sanderson)
Purified adenovirus 3 in DFW
(Clarke et al )
Temp. ,
deg cent.
20-25
20-25
20-25
20-25
20-25
20-25
Room
1-6
3-6
27-29
27-29
0
0
25-28
25-28
25-28
25-28
25-28
25-28
25
25
Final pH
7 0
8. 5
7 0
8. 5
7.0
7.0
6. 7-6. 8
6.8-7 1
8 8-9.0
6.9-7. 1
8. 8-9.0
7. 0
8.5
7. 0
9.0
7 0
9.0
7 0
9. 0
6. 9-7. 1
8. 8-9.0
Free Cl ,
mg /liter
.06
.06
. 04
. 07
. 05
. 05
.04
1.9-2.2
7.4-8. 3
. 16-. 18
. 92-1. 0
. 53
5.0
. 21-. 30
.21-. 30
1 1-.20
1 1-.20
.21- 30
.21-. 30
.20
. 20
Destruction, "'t /no
o of mm.
> 99. 99/5
> 99. 99/5
> 99. 99/5
> 99. 99/5
> 99. 99/5
> 99. 99/5
c
99.6/4
99.6/5
99.6/4
99.6/3
99.6/4 1/2
99.6/3
09.9/3
99.9/8
99. 0/2
99 9/16
99. 9/1
99. 9/8
99 8/8-16 sees
99 8/40-50 sees
Water Supplies.
5th Sanit. Eng.
81. Univ. Bull.
P. W. Kabler
Conf. , Urbana,
61(22)-72-78.
S L, Chang,
111. , Jan. 29-30,
aFrom "Pathogenic Bacteria and Viruses in
N. A. Clarke, and H F. Clark. In- Proc
1963. Univ. 111. Eng. Exp. Sta. Cir. No.
^Demand-free water.
cThirty-mmutes contact time protected all of 12 volunteers.
with changes in temperature, contact time, and pH. The
breakpoint shown in Figure 7 determines the amount of chlo-
rine that will react with ammonia, organic nitrogen com-
pounds, and/or other substances to form combined chlorine
before free chlorine will be present. Any increase in the
amount of chlorine applied past the breakpoint results in a
corresponding increase in the free chlorine residual.
Treatment to obtain a free chlorine residual means the
addition of chlorine beyond the breakpoint. In actual prac-
tice, the character of the water, including its pH, tempera-
ture, and analysis, may vary over relatively short periods
of time to cause variations in the breakpoint. Not all
waters show a typical breakpoint.
2. Other Methods of Disinfection
Disinfection methods other than chlorination, which
have been advocated or introduced from time to time, include
37
-------
10.0
1.0
CJ
LU Q
_l
CQ
0.01
COXSACKIE A2 VIRUS
(CLARKE AND KABLER)
E. COLI
(BUTTERFIELD
AND WATT IE)
POLIOVIRUS
TYPE 1
(WEIDENKOPF)
ADENOVIRUS
(TYPE 3
(CLARKE, STEVENSON
KABLER)
0.1
1.0
10
100
MINUTES
Figure 4. Concentration-time relationship for 99
percent destruction of Escherichia coll
and several viruses by HOCl at 0 to 6°C.
the use of ionic silver, ozone, bromine, iodine, and ultra-
violet light. For the most part, recommended use has been
limited to individual or semipublic water supplies or swim-
ming pools. Any system of disinfection other than chlorina-
tion should be approved by the proper health agency before
the method in question is applied to public water supplies.
All methods of disinfection (including chlorination)
should satisfy the following criteria:
(a) the disinfectant must contact all particles of the
water treated;
(b) The disinfectant must be effective despite any
possible change in the conditions of treatment or in the
characteristics of the water being treated, i.e., color,
38
-------
0.1 0.2 0.3 0.4 0.5 0.6
CHLORINE, ppm
Figure 5. pH-temperature relationship
in chlorine disinfection.
*
cr
i
^
*«
ae.
LU
/u
60
50
40
30
20
10
n
-A
_
~
-J
_
;
-
t
i i i i i i I i i i i i i i
AV>A ORGANISM
\ O Escherichia coli
\ + Salmonella typhosa
\ Q Escherichia coli
\ Salmonella typhosa
1 \ 9 Escherichia coli
, . X Salmonella typhosa
^ \ A Escherichia coli
\ \ ^ A Salmonella typhosa
*VNN>
nSi 1 S^~ s~ ^^1 : SA--
f&& \ 1 i T i T T^T" 1 1 i~T^T~
1 '
PH
7.0
7.0
8.5
8.5
9.8
9.8
10.7
10.7
T rj
1 _
.
:
r ~1i
-T1
0.1 0.2 fi.3 0.4 0.5 0.6 0.7 0.8 0.9
CHLORINE, ppm
Figure 6. Residual requirement for tOO percent
kill.
39
-------
4.
e 3.
2.
1.
0.9 NH3-N
/ , I .FREE CHLORINE I
0 1234567
9 10 11 12
CHLORINE ADDED, ppm
Figure 7. Chlorine residual curve.
turbidity, pH, total dissolved solids, temperature, or other
factors;
(c) The disinfectant must not be toxic to people using
the water supply;
(d) The disinfectant must have a residual action suffi-
cient to protect the distribution system from bacterial
growths;
(e) The disinfectant can be readily measured in water
in the concentrations expected to be effective for disin-
fection;
(f) The disinfectant (bactericidal and viricidal ef-
fectiveness) will destroy virtually all microorganisms,
and
(g) The disinfection system is practical.
40
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E. FLUOBIDATION
The Public Health Service recommends an optimum level
of fluoridation for all public water supplies. PHS Drinking
Water Standards state ''Fluoride in drinking water will
prevent dental caries. When the concentration is optimum,
no ill effects will result and caries rates will be 60-65
percent below the rates in communities using water supplies
with little or no fluoride.'*
Fluoridation operations in public water supplies should
be checked very carefully in the course of a sanitary survey.
Accurate and complete records should be kept at the plant,
and all responsible personnel should be competent to operate
the fluoridation equipment, with strict attention paid to
the operation of the dosing equipment. Dry chemical feeders
can be clogged by lumps formed in the holding bin, and
hydrofluosilicic acid feed equipment can be corroded because
of the active nature of the chemical. Fluoride dosing de-
vices should be checked frequently by the operators to as-
sure accurate dosing. All dosing devices, whether they are
single-set constant flow dispensers or dispensers paced to
the flow of water through the plant, should be checked to
see that they perform reliably. The loss of as little as
0.3 milligram of fluoride per liter that might result from
inaccurate dosing will noticeably reduce the dental health
benefits. In some cases, there is an appreciable amount of
natural fluoride in the Water and normally used amounts of
fluoride compound do not have to be used to bring the water
up to the optimum level. The optimum level of fluoride ion
may be determined for each location by consulting Table 3.
Local health departments occasionally set seasonal levels
in which the dosage varies according to the month of the
year. The amount of control by the local health agency
should be noted in the sanitary survey, and the existence
of some office to handle the complaints received is often
beneficial.
41
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Table 3. FLUORIDE LEVEL DETERMINATION
Annual average of maximum
daily air temperatures4
50.0 - 53.7°F
53.8 - 58.3°F
58.4 - 63.8T
63.9 - 70.6°F
70.7 - 79.2°F
79.3 - 90.5°F
Fluoride
Minimum
0.9
0.8
0.8
0.7
0.7
0.6
ion concentration
Op timum
1.2
1. 1
1.0
0.9
0.8
0.7
Maximum
1.7
1. 5
1.3
1.2
1.0
0.8
Based on temperature data obtained for a minimum of
5 years.
The treatment plant records of the fluoridation opera-
tion should include:
(a) amount of Water treated in each 24-hour period;
(b) amount of fluoride compound used;
(c) amount of fluoride ion used;3
(d) theoretical dosage in milligrams of fluoride ion
per liter in the water treated;
(e) setting on the dosing machine;
(f^ amount of fluoride compound on hand; and
(g) fluoride ion concentration as measured by analytical
means.
F. OPERATION CONTROL
1. Supervision
Every water treatment plant producing water for public,
domestic use should be under the full-time control of a
technically trained and state certified supervisor. For
certain types of small plants, part-time trained super-
vision may be permissible; in such cases, the supervisor
The fluoride compound will vary in purity (e.g., NaF = 98 percent pure,
and of this 96 percent Only a certain percentage of the compound is available
fluoride). Sodium fluoride (98 percent pure) contains 44.4 percent available
fluoride.
42
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should be on call for any emergency and should inspect the
plant at least twice each week.
2. Laboratory Tests and Control
All water quality tests should be made in accordance
with the current edition of Standard Methods for the Exami-
nation of Water and Waste Water. The schedule of laboratory
tests followed in controlling the operation of a water
treatment plant will vary with the volume and character of
the water being treated.
For the conventional plant treating lightly polluted
water, the scheduled laboratory tests should be sufficient
to assure conformance with the bacteriological, physical,
and chemical requirements of the PHS Drinking Water Stand-
ards. Such tests should include: turbidity, color, alkalin-
ity, temperature, pH, hardness, residual chlorine, and ex-
aminations for coliform bacteria by both presumptive and
confirmed tests or by membrane filter. Completed tests
should be conducted to verify positive results of confirmed
tests. Special tests, such as for residual alum, iron, man-
ganese, taste, odor, or other undesirable constituents in
the final effluent, may be necessary. Where prechlorination
is used in addition to postchlorination, tests for residual
chlorine should be made at each major stage of treatment.
Personnel in the average water plant laboratory are not
expected to make tests for all the trace elements and chem-
icals listed in the PHS Drinking Water Standards (e.g.,
ABS, arsenic, CGE, cyanide, etc.). Such tests should be
made, however, by qualified laboratories at sufficient
intervals to ensure that the waters reaching the consumer
meet the provisions of the PHS Drinking Water Standards.
Although the frequency of tests, particularly for tur-
bidity and coliform organisms, depends on the character
and variability of the quality of the water treated, at
least one test should be conducted every 24 hours, on each
day of the week. Since the turbidity and residual chlorine
43
-------
in finished water concentrations are valuable indices of
the effectiveness of treatment processes, these tests should
be made often, sometimes at hourly intervals, when the
character of the raw or partly treated water is changing
rapidly. Where possible, recording turbidimeters and chlo-
rine residual recorders should be used.
An important element in judging the efficiency of plant
operation is the general appearance of the plant and its
surroundings. A neat, well-kept plant with attractive
grounds is an indication of good operation, although this
criterion is not infallible. Neatness in the appearance of
a plant can not offset insufficient supervision and operator
training. The following items are important in the evalua-
tion of the general efficiency of operation and maintenance
control:
(a) training and experience of the supervisory and
operating staff;
(b) adequacy of operation records;
(c) adequacy of laboratory control;
(d) suitability of plant design and construction for
adequate treatment of available raw water; and
(e) capacity of the plant and finished water storage
in relation to average and maximum demands.
G. SUMMARY
Part I.E.2, Groups I, II, and III, provides guidance on
the relationship between pollution loadings and extent of
treatment required. Each purification plant should be oper-
ated to handle adequately any loading placed upon it. The
extent of this loading will be determined by the climate;
the character of the supply's watershed, including its
size, vegetation, and topography; the characteristics and
volume of sewage and other wastes entering the raw water
source.
For an evaluation of a plant's operating effectiveness,
information must be available on raw water characteristics:
44
-------
turbidity, color, alkalinity, hardness, iron, bacterial
quality, and average and ranges of variations in quality,
especially after heavy rainfall or at times of high runoff,
as well as the finished water's characteristics.
Complete records should be maintained and should include
equipment, maintenance, and operating data. Data such as
the rated capacity of raw and finished water pumps; charac-
ter, types, number, and reliability of pumps, and other
equipment including standby units; average and maximum daily
delivery; and maintenance records are important to an ade-
quate evaluation of plant adequacy.
45
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-------
Part III
RECOMMENDED SANITARY REQUIREMENTS FOR
WATER DISTRIBUTION SYSTEMS
A. WATER DISTRIBUTION SYSTEM
A number of principles of protection required by good
sanitary engineering practice are:
1. General Protection Principles
(a) A water distribution system should be designed and
constructed to provide, at all times, an adequate supply of
water, at ample pressure, in all parts of the system.
(b) The safety and palatahility of potable water should
not be degraded in any manner while flowing through the
distribution system.
(c) The system should be provided with sufficient bypass
and blow-off valves to make necessary repairs without undue
interruption of service over any appreciable area. Blow-off
connections to Sewers or sewer manholes should be pro-
hibited.
(d) Open finished water reservoirs should not be per-
mitted. If there are such reservoirs, chlorine residuals
should be maintained into the distribution system. Where
this is not practical, booster chlorination facilities
should be provided at the reservoir site and ample contact
time must be provided to ensure complete disinfection before
distribution to the first consumer.
(e) Physical cross-connections should not be permitted
that allow unsafe water to enter the distribution system.
47
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(f) The system should not permit excessive leakage
(greater than 10 percent).
(g) Special precautions should be taken to prevent
possible damage to submarine lines.
(h) The distribution system should be maintained to
prevent contamination of any part of the system during
necessary repairs, replacements, or extensions of mains.
When pressure in any part of the distribution system be-
comes abnormally low, provisions should be made to notify
consumers in the area of necessary protective health pre-
cautions .
(i) The frequency of bacteriological sample collection
should be in accord with the requirements of the PHS Drink-
ing Water Standards. Samples should be collected at repre-
sentative points on the distribution system, and the proper
location of these representative points should be routinely
evaluated.
2. Protection for Pipe System
(a) The pipe system and its appurtenances should be
designed to maintain an adequate positive water pressure
throughout the system.
(b) Materials used for caulking should not be capable
of supporting growth of pathogenic bacteria and should be
free from oil, tar, or greasy substances. Joint packing
materials should meet the latest AWWA specification.
(c) Corrective water treatment should be practiced where
lime deposits in the mains tend to reduce the effective size
and capacity of the pipes. To prevent and destroy biological
deposits, heavy chlorination may be effective.
(d) The pipe layout should be designed for future addi-
tions and connections to provide circulation where deadends
are necessary in the growth stage of the pipe system.
(e) The corrosive effects of finished water on non-
ferrous metal pipe used for water-service lines should be
considered, together with possible toxicological effects
upon consumers resulting from solution of the metals.
48
-------
(f) Only nontoxic plastic pipe shall be used, where
plastic pipe is acceptable.
(g) Sanitary precautions should be taken in laying new
water pipes.
Insofar as possible, pipes should not be laid in
water or where they can be flooded with water or sewage
in the laying process.
Leakage should be determined by hydrostatic pressure
tests.
New mains and repaired main sections should be dis-
infected by the latest AWWA procedure before being
placed in or returned to service.
Underground drains from fire hydrants and valve
chambers should not be connected directly to sewers or
storm drains.
The absence of pollution should be demonstrated by
bacteriological examination before new lines and ap-
purtenances are placed in service.
Water pipes should be laid at an elevation above
that of nearby sewers, with water pipe joints preferably
no closer than 10 feet from the sewer pipe center line.
Where this is not possible, extra durable and corrosion-
resistant water and sewer pipe should be specified and
special care should be taken to ensure proper installa-
tion, with durable water-tight tested joints.
Where water pipes cross sewer lines, the water pipes
must be laid above the sewer pipes.
3- Storage Protection
(a) Storage reservoirs and elevated tanks should be
operated and maintained to ensure the highest sanitary qual-
ity of the water.
(b) Storage reservoirs should be located above probable
ground water levels. Surface runoff and underground drainage
should be away from the structure. Provisions should be
included to guard against the sanitary hazards related to
location; ground water levels, movements, and quality;
49
-------
character of soil; possibility of sewage pollution; and
overtopping by floods. Sites in ravines or low areas subject
to periodic flooding should be avoided. Any sewer located
within 50 feet of a storage reservoir with a below-ground
level floor should be considered carefully. Such sewers
should be constructed of extra heavy or service-weight me-
chanical-joint cast-iron pipe with tested, water-tight
joints. No sewer should be located less than 10 feet from
the reservoir.
(c) All storage reservoirs should be protected against
flood waters or high water levels in any stream, lake, or
other body of water. The reservoir should be placed above
the high water level, and the structure and appurtenances
should be watertight.
(d) The ground surface above the reservoir should be
graded to drain surface water away from the reservoir and to
prevent pooling of surface water within the vicinity. Walls
or fencing should surround open reservoirs and public access
should be prohibited.
(e) Any overflow, blow-off, or clean-out pipe from a
storage reservoir should discharge freely into an open basin
from a point not less than three diameters of the discharge
pipe above the top or spill line of the open basin. All
overflow, blow-off, or clean-out pipes should be turned
downward to prevent entrance of rain and should be screened
with removable 24-mesh screen to prevent the entrance of
birds, insects, rodents, and contaminating materials. If the
discharge pipes are likely to be submerged by surface or
flood water, a watertight blind flange should be provided to
attach to the pipe opening to prevent contaminated water
backflowing into the reservoir. If the reservoir must be
emptied when the normal outlet is submerged by surface or
flood waters, pumps with outlets above the flood water
should be used for emptying.
(f) All inlet and outlet pipes of storage reservoirs
should be properly supported and constructed to minimize
the effects of settling, and wall castings should be pro-
50
-------
vided with suitable collars to ensure watertight connec-
tions .
(g) A suitable and substantial cover should be provided
for any reservoir, elevated tank, or other structure used
for finished water storage. Covers should be watertight,
made of permanent material, and constructed to drain freely
and to prevent contamination from entering the stored water.
The surface of a storage reservoir cover should not be used
for any purpose that may result in contamination of the
stored water.
(h) Manholes and manhole frames used on covered storage
reservoirs and elevated tanks should be fitted with raised,
watertight walls projecting at least 6 inches above the
level of the surrounding surface. Manholes used for ground
level reservoirs in heavy snowfall areas should be elevated
24 to 36 inches. Each manhole frame should be closed with
a solid watertight cover, preferably with edges projecting
downward at least 2 inches around the outside of the frame.
The manhole covers should be provided with a sturdy locking
device and should be kept locked when not in use.
(i) Any vents or openings for water-level control gauges
or other purposes that project through covers on storage
reservoirs and elevated tanks should be constructed to pre-
vent the entrance of dust, rain, snow, birds, insects, or
other contaminants.
(j) Reservoirs and elevated tanks on the distribution
system should be disinfected before being put into service
or after extensive repairs or cleaning have been completed.
Steel tanks and ground level water reservoirs should be
disinfected in accord with AWWA standards.
4. Interconnections, Backflow Connections, Cross and Open
Connections
a. Cross-Connection. A cross-connection is any physical
connection or arrangement between two otherwise separate
piping systems, one of which contains potable water, and
the other, water of unknown or questionable safety, or
51
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steam, gases, or chemicals, whereby there may be a flow
from one system to the other. No physical cross-connection
should be permitted between public or private water dis-
tribution systems containing potable water and any other
system containing water of questionable quality or contain-
ing contaminating or polluting substances.
b. Open Connection. An open connection is a piping arrange-
ment that provides an air gap between two water supply sys-
tems. The arrangement may become a cross-connection or in-
terconnection by the insertion of a length of pipe into the
air gap. Open connections may be permiss.ible under the
regulation and supervision of the appropriate health agen-
cies .
c. Backflow Connection. A backflow connection is any ar-
rangement whereby water or other liquids, mixtures, or
substances can flow into the distribution pipes of a potable
water supply from any source or sources other than its in-
tended source. Backsiphonage is one type of backflow. House
or industrial toilet or sink fixtures that contain or may
contain fluids that may be siphoned into the water system
should be classed as backflow connections and should be
prohibited.
d. Interconnection. An interconnection is a physical con-
nection between two potable water supply systems. Inter-
connection may be allowed when the sources of supply in-
volved are approved by the appropriate health agencies.
B. 1&ATER DISTRIBUTION SYSTEM HAZARDS
Many failures to meet the bacteriological requirements
of the PHS Drinking Water Standards are directly related to
the use of poor operating and maintenance procedures for
distribution systems or to the presence of sanitary defects
52
-------
in the system. Some causes that contribute to poor bacteri-
ological quality are:
(a) insufficient treatment at the point of production;
(b) cross-connections;
(c) improperly protected distribution system storage;
(d) inadequate main disinfection;
(e) unsatisfactory main construction, including improper
joint-packing;
(f) close proximity of sewer and water mains;
(g) improperly constructed, maintained, or located blow-
off, vacuum, and air relief valves; and
(h) negative pressures in the distribution system.
The distribution system of a water supply presents
many opportunities to impair water quality. The time of de-
tention within the system's mains may be quite long, and
many potential inlets for polluting materials, such as
services, blow-off and relief valves, and cross-connections,
usually exist. Any list of protective measures must include
proper procedures for the laying, flushing, and disinfecting
of new or repaired mains; maintenance of chlorine residuals
when a main is returned to service; and adequate separation
of water and sewer lines. Blow-off and relief valves can
adversely affect water quality if improperly constructed or
installed, or if located in sumps subject to flooding or
in other places subject to inundation by wastes or poor
quality water.
The system should be designed to supply adequate quanti-
ties of water under ample pressure and should be operated to
prevent, as far as possible, conditions leading to the
occurrence of negative pressure. Steps to prevent negative
pressure should include minimizing planned shutdowns, pro-
viding adequate supply capacity, correcting under-sized con-
ditions, and properly selecting and locating booster pumps
to prevent the occurrence of a negative head in piping
subject to suction. Continuity of service and maintenance
of adequate pressure throughout a public water supply system
are essential to prevent back-siphonage.
53
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Contaminated secondary water sources, where; cross-
connected to a community system, can seriously degrade
the water in the system. Many water-borne disease outbreaks
have resulted from such connections. Cross-connection haz-
ards may be divided into those resulting from the inter-
connection of a nonpotable water supply with a potable
supply, and those resulting from backflow caused by the
development of negative pressure in the water distribution
systems of premises having internal piping defects. Negative
pressure can develop from such causes as main breaks, inade-
quate supply pressure, undersized mains, unusual water de-
mands, and shutdowns for maintenance or repair. On the con-
sumer's premises, backflow can also be caused by back
pressure from cross-connections to boilers, elevated storage
tanks, hydro-pneumatic systems, pumps, circulating systems,
and auxiliary water supply systems. To deal with these
problems, an active cross-connection control and elimination
program and an aggressive program of reducing, to a minimum,
the frequency of occurrence of negative pressure in the
system should be established.
Stored, treated water in the distribution system may
be contaminated by substances that fall into uncovered
finished water storage tanks or reservoirs, by wind-blown
material entering vents, and by ground or surface water
seepage. Open storage is subject to pollution from gulls,
ducks, and other birds; animals, such as rodents; wind-
blown contaminants; human activities such as bathing, fish-
ing, and deliberate contamination; and many other sources.
The best method to prevent deterioration of the quality of
water stored in tanks and reservoirs is to provide water-
tight storage facilities that are constructed with roofs to
afford protection against surface runoff. In the absence of
such cover, disinfection of all water fed to the system from
storage is essential and tends to offset, but does not
prevent, the ill effects from this introduced contamination.
54
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REFERENCES
1. Public Health Service drinking water standards. PHS
Publ. No. 956. 1962. 61 pp.
2. AWWA standard for deep wells. AWWA Standard A100-66.
Jan. 1966. 61 pp.
3. Recreational use of domestic water supply reservoirs.
AWWA Statement of Policy. JAWWA (Reference Edition).
59:(No. 10, Part 2)51-52. Oct. 1967.
4. Standard methods for the examination of water and waste-
water . 12th ed. Prepared and published jointly by
APHA, AWWA, and WPCF- American Public Health Asso-
ciation, Inc., New York. 1965- 769 pp.
5. AWWA standard for painting and repainting steel tanks,
standpipes, reservoirs, and elevated tanks for water
storage. AWWA Standard D102-64. Feb. 1964. 33 pp.
6. Potable-water storage reservoirs. AWWA Committee Report.
JAWWA 45:1079-89. Oct. 1953.
7. Water supply and plumbing cross-connections. PHS Publ.
No. 957. 1963. 69 pp.
55
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APPENDIX
EXCERPTS FROM
THE UNITED STATES PUBLIC HEALTH SERVICE
DRINKING WATER STANDARDS a
3. Bacteriological Quality
3. 1 Sampling
3.11 Compliance with the bacteriological require-
ments of these Standards shall be b^sed on examinations
of samples collected at representative points throughout
the distribution system. The frequency of sampling and
the location of sampling points shall be established
jointly by the Reporting Agency and the Certifying
Authority after investigation by either agency, or both,
of the source, method of treatment, and protection of
the water concerned.
3.12 The minimum number of samples to be collected
from the distribution system and examined each month
should be in accordance with the number on the graph in
Figure Al, for the population served by the system. For
the purpose of uniformity and simplicity in application,
the number determined from the graph should be in ac-
cordance with the following: for a population of 25,000
and underto the nearest 1; 25,001 to 100,000to the
nearest 5; and over 100,000to the nearest 10.
3.13 In determining the number of samples examined
monthly, the following samples may be included, pro-
vided all results are assembled and available for in-
spection and the laboratory methods and technical compe-
"Public Health Service drinking water standards. PHS Publ. No. 956- 1962-
61 PP.
57
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1.000
MINIMUM NUMBER OF SAMPLES PER MONTH
2 3 4 5 10 50 100
500
10,000
100,000
1,000,000
10,000,000
Figure A1. Recommended minimum monthly samples
per population served by water supply.
tence of the laboratory personnel are approved by the
Reporting Agency and the Certifying Authority:
(a) Samples examined by the Reporting Agency.
(b) Samples examined by local government labora-
tories.
(c) Samples examined by the water works authority.
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(d) Samples examined by commercial laboratories.
3.14 The laboratories in which these examinations are
made and the methods used in making them shall be sub-
ject to inspection at any time by the designated repre-
sentatives of the Certifying Authority and the Reporting
Agency. Compliance with the specified procedures and the
results obtained shall be used as a basis for certifica-
tion of the supply.
3.15 Daily samples collected following a bacterio-
logically unsatisfactory sample as provided in sections
3.21, 3.22, and 3.23 shall be considered as special
samples and shall not be included in the total number
of samples examined. Neither shall such special samples
be used as a basis for prohibiting the supply, provided
that; (1) When waters of unknown quality are being
examined, simultaneous tests are made on multiple por-
tions of a geometric series to determine a definitive
coliform content; (2) Immediate and active efforts are
made to locate the cause of pollution; (3) Immediate
action is taken to eliminate the cause; and (4) Samples
taken following such remedial action are satisfactory.
3.2 Limits.-The presence of organisms of the coliform
group as indicated by samples examined shall not exceed the
following limits:
3.21 When 10 ml standard portions are examined, not
more than 10 percent in any month shall show the pres-
ence of the coliform group. The presence of the coliform
group in three or more 10 ml portions of a standard
sample shall not be allowable if this occurs:
(a) In two consecutive samples;
(b) In more than one sample per month when less
than 20 are examined per month; or
(c) In more than 5 percent of the samples when 20
or more are examined per month.
When organisms of the coliform group occur in 3 or
more of the 10 ml portions of a single standard sample,
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daily samples from the same sampling point shall be
collected promptly and examined until the results ob-
tained from at least two consecutive samples show the
water to be of satisfactory quality.
3.22 When 100 ml standard portions are examined, not
more than 60 percent in any month shall show the pres-
ence of the coliform group. The presence of the coliform
group in all five of the 100 ml portions of a standard
sample shall not be allowable if this occurs:
(a) In two consecutive samples;
(b) In more than one sample per month when less
than five are examined per month; or
(c) In more than 20 percent of the samples when
five or more are examined per month.
When organisms of the coliform group occur in all five
of the 100 ml portions of a single standard sample,
daily samples from the same sampling point shall be
collected promptly and examined until the results ob-
tained from at least two consecutive samples show the
water to be of satisfactory quality.
3.23 When the membrane filter technique is used, the
arithmetic mean coliform density of all standard samples
examined per month shall not exceed one per 100 ml.
Coliform colonies per standard sample shall not exceed
3/50 ml, 4/100, 7/200, or 13/500 ml in:
(a) Two consecutive samples;
(b) More than one standard sample when less than 20
are examined per month; or
(c) More than five percent of the standard samples
when 20 or more are examined per month.
When coliform colonies in a single standard sample
exceed the above values, daily samples from the same
sampling point shall be collected promptly and examined
until the results obtained from at least two consecutive
samples show the water to be of satisfactory quality.
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4. PHYSICAL CHARACTERISTICS
4.1 Sampling.The frequency and manner of sampling shall
be determined by the Reporting Agency and the Certifying
Authority. Under normal circumstances samples should be
collected one or more times per week from representative
points in the distribution system and examined for turbid-
ity, color, threshold odor, and taste.
4.2 Limits.-Drinking water should contain no impurity
which would cause offense to the sense of sight, taste, or
smell. Under general use, the following limits should not be
exceeded:
Turbidity 5 units
Color 15 units
Threshold Odor Number 3
6. RADIOACTIVITY
6 .1 Sampl i rig.
6.11 The frequency of sampling and analysis for
radioactivity shall be determined by the Reporting
Agency and the Certifying Authority after consideration
of the likelihood of significant amounts being present.
Where concentrations of Ra or Sr90 may vary consider-
ably, quarterly samples composited over a period of
three months are recommended. Samples for determination
of gross activity should be taken and analyzed more
frequently.
6.12 As indicated in paragraph 5.1, data from ac-
ceptable sources may be used to indicate compliance with
these requirements.
6.2 Limits.
6.21 The effects of human radiation exposure are
viewed as harmful and any unnecessary exposure to ioniz-
ing radiation should be avoided. Approval of water sup-
plies containing radioactive materials shall be based
upon the judgment that the radioactivity intake from
such water supplies when added to that from all other
sources is not likely to result in an intake greater
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than the radiation protection guidance3 recommended by
the Federal Radiation Council and approved by the Presi-
dent. Water supplies shall be approved without further
consideration of other sources of radioactivity intake
of Radium-226 and Strontium-90 when the water contains
these substances in amounts not exceeding 3 and 10
/^we/liter, respectively. When these concentrations are
exceeded, a water supply shall be approved by the certi-
fying authority if surveillance of total intakes of
radioactivity from all sources indicates that such in-
takes are within the limits recommended by the Federal
Radiation Council for control action.
6.22 In the known absence of Strontium-90 and alpha
emitters, the water supply is acceptable when the gross
beta concentrations do not exceed 1,000 /x/jc/liter. Gross
beta concentrations in excess of 1,000 /u/uc/liter shall
be grounds for rejection of supply except when more com-
plete analyses indicates that concentrations of nuclides'
are not likely to cause exposures greater than the Ra-
diation Protection Guides as approved by the President
on recommendation of the Federal Radiation Council.
The Federal Radiation Council, in its Memorandum for the President, Sept. 13,
1961, recommended that "Routine control of useful applications of radiation
and atomic energy should be such that expected average exposures of suitable
samples of an exposed population group will not exceed the upper value of
Range II (20 /fie/day of Radium-226 and 200 tfic/day of Strontium-90)."
Absence is taken here to mean a negligibly small fraction of the above sep-
cific limits, where the limit for unidentified alpha emitters is taken as the
listed limit for Radium-226.
62 6 US GOVERNMENT PRINTING OFFICE 1972- T59-281/2113
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