Drinking Water and Health, Volume 4 (1982) / Chapter Skim
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II Elements of Public Water Supplies
II Elements of Public Water Supplies
Pages 9-17
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From page 9... ...
Groundwater is normally obtained by sinking wells into the saturated zone located beneath the water table. RAW WATER QUALITY AND TREATMENT The quality of surface waters varies.
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From page 10... ...
The temperatures of groundwaters are also more constant, normally approaching the average annual temperature of the region instead of the constant fluctuations reflected in the temperatures of surface waters. To be made acceptable for a public water supply, groundwater may require only disinfection to ensure adequate health protection.
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From page 11... ...
treated or finished Hater is transported in conduits or pipes rather than by open channels. In addition to a network of interconnecting mains or pipes, water distribution systems normally in clude storage facilities, valves, fire hydrants, service connections to user facilities, and perhaps pumping facilities.
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From page 12... ...
It may be necessary to control algae and microbial slime growths in open distribution reservoirs by adding copper sulfate and/or chlorine to the water. Furthermore, to ensure adequate disinfection, it is generally believed that there should be a sufficient chlorine residual throughout the distribution system.
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From page 13... ...
Plastic piping may also be used in water distribution systems, especially in household connections. Thermoplastic material used in plastic pipe include polyvinyl chloride (PVC)
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From page 14... ...
It is beyond the scope of this report to review established engineering practice as it relates to the proper design, construction, and operation of distribution systems. It should be recognized, however, that random or accidental events, such as pipe breakage, or situations leading to crossconnections or back-siphonage, may severely affect the chemical or bacteriological quality of water in distribution systems and, thus, the water delivered to the users.
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From page 15... ...
Prevention of back-flow may be accomplished by using vacuum breakers designed to admit air to break any vacuum in a water main or pipe, swing connections that permit a connection either to a potable water supply or to another source of water but not to both simultaneously, air gaps, and reduced pressure back-flow preventers, i.e., a device with at least two independently acting check valves separated by an automatic pressure differential relief valve. APPROACH TO THE STUDY Although the quality of water in a public water supply may be acceptable immediately after treatment, it may deteriorate before it reaches the users.
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From page 16... ...
Having reviewed and evaluated those conditions or factors influencing the deterioration of water quality in distribution systems and, in a sense, determined what is known and unknown, the committee was able to make recommendations regarding control procedures and to identify existing research needs. It is beyond the scope of this report to consider in depth the physical reliability or integrity of a public water supply system.
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From page 17... ...
Again, the importance of having a properly engineered and operated distribution system as it relates to reliability cannot be overemphasized. Water supply personnel must be constantly vigilant of defects and problems associated with distribution systems as they might impact water quality.
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