In this article we will discuss about:- 1. Development of Public Water Supply System 2. Need for Protected Water Supplies 3. Objectives 4. Planning 5. Components.
Contents:
- Development of Public Water Supply System
- Need for Protected Water Supplies
- Objectives of Public Water Supply System
- Planning of Water Supply Scheme for a Town or City
- Components of Public Water Supply Scheme
1. Development of Public Water Supply System:
Since very early times man has obtained water from the surface sources such as rivers, lakes, etc., as well as from the subsurface or groundwater sources such as springs, wells, etc. Due to relatively less requirement of water in the early times, which was mainly for domestic purposes, these sources were deemed to be sufficient to meet the requirements of the persons residing in the nearby areas. Further water was directly procured from these sources by the persons as per their requirements and there was no public water supply system.
ADVERTISEMENTS:
However, with the growth of population the demand of water also increased which led to the development of new sources of water, construction of conduits and aqueducts for the conveyance of water from a distance and subsequent storage to be ultimately distributed to the inhabitants through a pipe system.
Where the source of water happened to be situated at a level lower than that of the areas to be served, it became necessary to lift water by the installation of pumps, which was therefore the next step in the development of the public water supply system.
With the rapid expansion in the fields of industry and commerce, the demand of water correspondingly increased, thus requiring large quantities of water at greater and more dependable pressure of supply. This led to the construction of elevated or overhead reservoirs, known as service reservoirs, located in the hearts of towns or cities close to the areas to be supplied water. The service reservoirs, besides supplying water at adequate pressures, serve to balance the variations in the public demand of water.
Development of Public Water Supply System in India:
ADVERTISEMENTS:
In India, Calcutta (at present Kolkata) was the first city to have a modem water supply system installed in the year 1870. The other big cities developed their water supply schemes in due course of time. However, even at present times the progress in this direction is not very much encouraging. Although after independence attention was focussed on this vital issue, but due to shortage of funds and other difficulties it has not been able to make the desired progress in the matter.
At present only about 16 per cent of Indian towns are provided with water supply systems serving about 5 per cent population of the whole of the country. Moreover none of the metropolitan cities of India (including Delhi) is being supplied water for 24 hours of the day. As such our country has yet to make serious efforts to provide treated water to the most of the population.
2. Need for Protected Water Supplies
:
It is necessary that the water which is supplied to the public must be invariably free from all types of impurities both suspended and/or dissolved in it, any kind of bacteria and any other contamination which may cause serious harm to the health of the public. It is therefore imperative to plan and build such a water supply scheme which would provide potable water free from any kind of contamination.
ADVERTISEMENTS:
In general the water obtained from wells or springs i.e., groundwater is free from impurities and it may be supplied to public without adopting arty method of purification. This is so because in the course of its movement through the porous sub-strata the water is completely relieved of its suspended impurities. However, before supplying to the public this water may have to be disinfected by chlorination (i.e., by adding chlorine or chlorine compound to water) or any other method, in order to remove any harmful bacteria responsible for causing diseases.
The water obtained from any of the surface sources of water needs to be purified before it can be supplied to the public. The most commonly adopted method of purification of Water is filtration. In the process of filtration water is allowed to pass through beds of sand and gravel whereby minute suspended and dissolved particles are removed.
It has been found that the process of filtration is greatly accelerated if water is pretreated with certain substances which when added to water forms large masses of precipitates or floes out of the impurities present which in the process settle down and are ultimately removed. This pre-filtration treatment of water is known as coagulation which involves the use of alum.
The water having undergone through the process of filtration is still found to contain some harmful disease producing bacteria which are minutely-sized living organisms not visible to naked eye. As such in order to ensure protected supplies of water free from any health hazard, it is necessary to kill these bacteria by disinfecting water.
ADVERTISEMENTS:
The most commonly adopted method of disinfection is chlorination which is a process of adding chlorine or chlorine compound to water. Other methods of disinfecting water viz., treatment through ozone or ultra-violet rays or excess lime are also in use.
Thus it may be seen that a public water supply system should be such that it is able to provide an adequate and reliable supply of water catering to all the public needs and also ensure that the supplies so made are not only potable but also fully protected against any infection which might pollute water and cause epidemics resulting in human sufferings and loss.
3. Objectives of Public Water Supply System
:
The main objectives of any public water supply system are as follows:
ADVERTISEMENTS:
(1) To supply safe and wholesome water to the consumers.
(2) To supply water in adequate quantity.
(3) To make water available within easy reach of the consumers so as to encourage the general cleanliness.
Each of these objectives is briefly discussed below:
A safe and wholesome water is the one which is unpolluted, free from disease producing bacteria, toxic substances as well as excessive amounts of mineral and organic matter that may impair the quality of water. Thus water would be safe and wholesome if it is not harmful when consumed.
In order to ensure that water which is supplied is safe and wholesome, standards of quality for drinking water have been established. By supplying water which satisfies these standards of quality the first objective of the public water supply system can be attained.
In order to supply water in adequate quantity it would be necessary to select the source of water which would ensure that the quantity of water as required by the consumers would be available. Further the units required to store requisite quantity of water for continuous supply must also have sufficient capacities.
In order to make water available within easy reach of the consumers it would be necessary to provide a well laid-out system of distribution with adequate capacity so that the system could be fully relied upon to meet the requirements of the consumers at all hours of the day.
The later two objectives of public water supply system have to be studied in relation to the urban and rural areas to be served. The urban areas are well developed and it is normally ensured that water would be made available in sufficient quantities through well laid-out system of distribution. On the other hand the rural areas are underdeveloped and due to paucity of funds it may not be possible to supply water in sufficient quantity within the close proximity of the entire rural population.
The net result of this would be that the amount of water which could be made available to the rural population would be bare minimum required for their survival i.e., for drinking, cooking, etc., and very little water left for the purposes of general cleanliness. Thus both these objectives of the public water supply system have to be viewed from the point of public health necessity as well as the economic consideration.
However, where the requirements of water supply may not be easily satisfied because of the paucity of funds available with the executing authority a compromise in between may offer a satisfactory solution. For example in the case of a rural water supply system a well may be constructed and either one or two hydrants may be provided close to the well or a number of hydrants may be provided close to the houses of the residents.
In the first case although the funds required would be less but the greater distance in reaching the well may preclude people using water frequently. On the other hand in the second case the funds available may not be enough for the purpose. As such a probable solution may be to provide the public hydrants at one or two places centrally located with a number of water taps provided at each hydrant.
4. Planning of Water Supply Scheme for a Town or City
:
In planning a water supply scheme for a town or city the following points need to be considered:
1. Source of water
2. Quality of water
3. Population
4. Rate of consumption
5. Topography of area
6. Financial aspects
7. Trends of future development
1. Source of Water:
A search has to be made for a good perennial source of water in the vicinity of the town or city for which the water supply scheme is being planned. Sometimes the source of water may not be available in the near vicinity in which case the water may have to be procured from a far off place. The source of water should therefore be selected keeping in view quantity, quality and cost involved.
2. Quality of Water:
On the basis of the quality of water available from the source the line of treatment of water would be decided. If the water available is relatively pure the cost involved for its treatment would be less and vice versa.
3. Population:
From the available data of census of the last few decades, the future population may be predicted. Various units of the scheme should be so designed that the scheme is able to cater the needs for the future population.
4. Rate of Consumption:
The demand of water would depend on the various uses such as domestic, commercial and industrial, civic or public, etc. The rate of consumption per capita per day should be decided by carefully considering all these uses. This rate when multiplied by the population will give the total quantity of water required for the water supply scheme.
5. Topography of Area:
Topographical map of the area to be served by the water supply scheme should be prepared. This map will be quite useful in the location of the various units of the scheme, and help in the formulation of the most economical scheme.
6. Financial Aspects:
This involves the consideration of the total funds that would be available for the water supply scheme. The scheme should be so planned that it is as economical as possible and the entire scheme is adjusted within the available funds.
7. Trends of Future Development:
The trends of the future development of the town or city should be predicted and properly adjusted while planning the water supply scheme. Some of the possible trends of the future development may be in the form of new industries, public institutions, public recreation centres, new residential blocks, etc., coming up.
5. Components of Public Water Supply
Scheme:
The various components of a public water supply scheme are as indicated below:
1. Source of water supply—surface and sub-surface sources.
2. Intakes for collecting surface water.
3. Water treatment plant having screening, sedimentation, filtration, disinfection units, etc.
4. Service reservoirs.
5. Control valves
6. Distribution system comprising mains, sub-mains, branch pipelines, etc.
7. Hydrants for firefighting, flushing streets, etc.