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close this book Water purification, distribution and sewage disposal for Peace Corps volunteers
close this folder Section 1: Water supply sources
View the document Overview:
View the document Background information
View the document Evaluation of sources
View the document Factors influencing the quality of water
View the document The quantity of water
View the document Types of sources
View the document Development of water sources
View the document The basic requirements of a water supply
View the document Selection of the source of supply
View the document Lesson plans

The basic requirements of a water supply

The Objectives of any water supply, big or small, are to provide the consumers with safe and wholesome water in adequate amounts and to make that water readily available to users.

SAFE AND WHOLESOME WATER

Safe and wholesome water is water that may be consumed without risk from its chemical and bacteriological contents. Its color and odor should be unobjectionable and it should be free of visible suspended matter.

Much information concerning its sanitary quality may be obtained by chemical examination of a water but it is impossible to say that a water is free of sewage pollution by chemical analysis alone. Where the presence of pollution is being investigated, bacteriological examination is essential. Water which the tests have shown to be safe may be polluted after the samples have been taken and the only way of ensuring the early detection of intermittent pollution is through frequent routine bacteriological examinations. In rural areas it is often difficult enough to have one such examination done but to insist on weekly repetitions would be quite unrealistic. The Bacillus cold which normally lives in the bowels of warm-blooded animals and which is present in human faeces in enormous numbers is used as the bacterial indicator of pollution. Unfortunately there is no ready method of differentiating B. cold of animal origin from those of human origin.

In view of the foregoing it is of the utmost importance that the supply system be correctly located and constructed so as to provide natural protection against outside contamination. A careful inspection of the pertinent area must, therefore, be carried out, and it should be repeated at regular intervals to ensure that this area is maintained in the necessary sanitary state.

ADEQUATE QUANTITY

The average amount of water required daily by an individual is about 10 gallons for domestic purposes, i.e. drinking, cooking, bathing and laundry. People can do with less for short periods when necessary, but public health is best served by encouraging the use of water and discouraging its waste. The provision of 25 or more gallons per person per day does not include water needed for gardening purposes or for animals.

The former usually affects only the bungalows and varies considerably in amount. The standard daily allowances for animals are: - for horses and cattle - 10 gallons per capita: and for sheep, goats and pigs, 2 gallons each. Hospitals require about 50 gallons per patient daily, and schools need approximately 10 gallons daily for each child.

AVAILABILITY

From the purely public health view-point there is no question but that the aim should be to supply safe and wholesome water in adequate quantity to every family in its home. Generally, when individual families are provided with taps in their own houses they look after the taps and the wastage of water is minimal. On the other hand, where the distribution of water is by public standpipes, the taps are generally left running and many of them are repeatedly broken so that they cannot be turned off. Unfortunately the capital cost of a water-point in each house is often too great and it is then necessary to compromise between economic realities and the desired sanitary conditions.

Until they actually experience the benefits of safe water, villagers rarely understand or appreciate its advantages and they will continue to use their old polluted sources unless the new sanitary supply is superior in some respects obvious to them, such as greater convenience or greater reliability. They may bathe themselves and wash their clothes at the new water-point hut the general standard of household cleanliness will vary inversely with the distance the water has to be carried. If the new water-points are not as handy or as dependable as the old ones the people will continue to use unprotected shallow wells near their homes or persist in going to the river for polluted water. Such practices defeat the real object for which the new supply is being installed, namely, to improve the public health. As many stand-pipes and household connections as possible should, therefore, be supplied and the layout of the whole pipe system should be such as to facilitate the future provision of a tap in each house. The following are suggested as minimum standards: - one stand-pipe should not serve much more than 40 people; and in the case of wells to which the people must 90 for their water there should be at least one well for every 250 people (approximately).