MANUAL
   FOR EVALUATING
PUBLIC DRINKING WATER
      SUPPLIES

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              MANUAL
         FOR EVALUATING
PUBLIC DRINKING WATER SUPPLIES
            A Manual of Practice
                    \
              \m
       U. S. ENVIRONMENTAL PROTECTION AGENCY
      Office of Water and Hazardous Materials
            Water Supply Division

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Reprinted 1975
Reprinted 19J4
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.  Bichard  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  	  ]_
   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
   Springs  	 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
                             IX

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    Plant Location 	 25
    Presetting 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  wa'ter  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)^  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.'1

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
 ar cause it to be polluted from  extraneous  sources.'*  De-
 tection of such  health hazards requires a careful  survey of
 the  entire  water  supply system. The complexity of this
 cask 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.
    579-607 O - 75 - 2

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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]yfand 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
requirements;
    (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 *

       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)                                   o. 1
Barium (Ba)                                   j
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                                 Ji8
  53.8-58.3                                    !*7
  58.4-63.8                                    1*5
  63.9-70.6                                    1.'4
  70.7-79.2                                    i.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
3.
 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
             IpCi/l but less than 10 pCi /I.
            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
            Pesticide                        ,  f.       „
            	                 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
  insecticidesa                               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.
8

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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
       rnilliliters 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-
10

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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.  Radioactivi ty:  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 on  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.
                                                      11

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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
 coli forms
 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), Hgnin
compounds
Chlorine demand
Iron and manganese
High organic content
High or organic content
High or fluctuating  pH
Low temperature
Extended distribution ey»-
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  should  be  examining al-
ternate or  auxiliary  sources  of supply  and  should  have
positive plans  to  procure  adequate  facilities  and  sources.
12

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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.
                           13

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 2.   Distances from Sources of Contamination

     All  ground  water withdrawal points should be located
 a  ''safe''  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''  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  ''safe'' 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
14

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                PUMP UNIT
      SANITARY WELL SEAL
   COBBLE DRAIN
REINFORCED CONCRETE
COVER SLAB SLOPED
AWAY FROM PUMP
  ARTESIAN PRESSURE SURFAC
  OR  PIEZOMETRIC SURFACE
         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.  When 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  surface dr*i-age 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''  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.B.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
  579-697 O - 75 - 3

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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  reservoirs9
and Class A upstream  roservoirsb should never be used  for
                                                          Q
recreation. Upstream  reservoirs  are classed  as  follows;-3

    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:   \Nater 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  tlow 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 stora9e of water prior to treatment.
 bUpstrea» Reservoirs:  reservoirs providing storage of untreated  water at
  various points  in the .atershed  to provide or supplement  the supply at the
  terminal reservoir.
 20

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            Figure 2.  Chester Morse Reservoir,
                      Cedar  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

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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 CHEMICAL TREATMENT,  FILTRATION,
     AND DISINFECTION  (Refer to  Part I.B.2,  Group  III)

1.   General  Requirement^

    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.  Central  District  Filtration  Plant,  Chicago,
            I  11 ino i s.
                                                         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.  Presetting 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
duality  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.  Filtration  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 operated 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  a  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.
     FiIter-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 loca-ted 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 chlorinators  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.3
 *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
    579-697 O - 75 - 4

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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
 nave 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 Z. CERMICIDAL EFFICIENCY OF FREE CHLORINE IN WATER
Microorganism
Salmonella typhosa suspended in DFW
(Butterfield et al. )
Escherichia coli suspended in DFW

Aerobacter aerogenes suspended in DFW

Feces -borne infectious hepatitis virus
in distilled water {Neefe et al, )
Purified Coxsackie A2 in DFW
(Clarke and Kabler)


Purified poliovirus I (Mahoney) in 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
3-6
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
. 11-. 20
. 1 1-.20
.21-. 30
.21-. 30
.20
.20
Destruction, %/no.
o of min.
> 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
99.9/3
99.9/8
99.9/2
99.9/16
99.9/1
99.9/8
99.8/8-16 sees.
99.8/40-50 sees.
»From "Pathogenic Bacteria and Viruses in
 N. A, Clarke, and H. F. Clark. In: Proc
 1963. Univ. 111. Eng. Exp. Sta. Cir. No.
Water Supplies."  P. W. Kabler,
 5th Sanit. Eng, Conf. , Urbana,
81. Univ. Bull. 61(22):72-78.
 S. L. Chang,
III. , Jan. 29-30,
t>Demand-free water.
cThiTty-minutes 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

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                                  COXSACKIE A2 VIRUS
                                  (CLARKE AND KABLER)
                          E. COL I
                           (BUTTERFIELD
                           AND WATT IE)
                                          POLIOVIRUS
                                           TYPE 1
                                            (WEIDENKOPF)
ADENOVIRUS
 (TYPE 3
 (CLARKE. STEVENSON
  AND KABLER)
                         1.0              10
                              MINUTES
          Figure 4.  Concentration-time  relationship  for  99
                    percent destruction  of  Escherichia  coll
                    and several  viruses  by  HOCI  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

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     20 -|l
     10
0.2  0.3  0.4

CHLORINE, ppm
                              0.5  0.6
    Figure 5. pH- temperature  relationship
              in  chlorine di sinfection.
          0-2   n.3  0.4   0.5   0.6   0.7   0.8  0.9

                     CHLORINE,  ppm

Figure 6.   Residual requirement for 100 percent
            Kill.
                                                      39

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                 I   I   I   '    I   '   I   I    I   I   I
                        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 temperaturesa

50. 0 - 53.7T
53.8 - 58. 3°F
58.4 - 63.8°F
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
Optimum
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 98 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 FHS 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,  CCE,  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
     °f tne  week.  Since the  turbidity and residual chlorine
                                                         43

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 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

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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.
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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  anc
constructed  to  provide, at all  times,  an adequate supply of
water,  at ample pressure,  in all parts  of the system.
    (b) The  safety  and palatability 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.
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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  fojr 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.
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    (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;
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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-
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  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 reservoirs6 should be
 disinfected in accord with AWWA standards.
 4.  Interconnections. Backflow  Connections. Cross anri Op^n
    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
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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 permissible  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
p r oh i b i t ed.

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.  WATER 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

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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-
 offi 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.
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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.
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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, A\VWA, and WPCF.  American Public Health Asso-
        ciation,  Inc., New York. 1965- 769pp.
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 based 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 under—to  the nearest 1;  25,001 to 100,000—to the
  nearest 5; and over  100,000—to 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-

ftPublic Health Service drinking water standards.  PHS  Pobl.  No. 956. 1962-
 61 PP-
                            57

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        1,000
                      MINIMUM NUMBER OF SAMPLES PER MONTH
             1     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.
58

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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
                          """""•" — " — — —— — . . _ _ ™-__ *J

                   6-  RADIOACTIVITY
 6.1  Sampling.
     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 Ra2^  or Sr'O  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.
                                                     are
  6.21  The  effects of human  radiation exposure  „_
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 Fadium-226 and Strontiuro-90 when  the water contains
    these substances in amounts not  exceeding  3  and  10
    /^to/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 absenceb  of  Strontium-90  and alpha
    emitters, the water  supply  is  acceptable when  the gross
    beta concentrations  do not exceed 1,000 /^/^c/liter.  Gross
    beta concentrations  in  excess of 1,000  /^c/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 /ftc/day of Stront ium-90).
bAbsence 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
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