Water Supply System

COMMUNITY AND WATER SUPPLY:
Water is introduced into municipalities for many purpose:

1. For drinking and culinary uses,
2. for washing, bathing and laundering 
3. for cleaning windows, walls and floors,
4. for heating and air conditioning,
5. for watering lawns and gardens,
6. for filling swimming pools,
7. for display in fountains, 
8. for producing hydraulic and stream power,
9. for employing in numerous and varied industrial processes,
10. for protecting life and property against fire, and
11. for removing offensive and potentially dangerous wastes from household and industry.

To provide for these varying uses about 300 liters per capita per day is essential but many Indian cities have water supply much less than the required quality.

WATER SUPPLY SYSTEM OF A TOWN:
Water supply system of a town includes:

1. Sources of water supply,
2. Purification,
3. Transmission, and
4. Distribution of water.

SOURCES OF WATER SUPPLY:
There are various of water supply, they are:

• Rain water: This is collected from roof of building stored in cisterns of small individual supplies.
• Surface water: This is the run off water, which is collected putting dam across the natural streams or rivers. Usually water supply for a large town or city is derived from these sources.
• Ground water: Erecting wells and infiltration galleries across the river basin collects this water. This source of supply is suitable for small towns.

Municipal supplies may be drawn from a single source or from a number of different ones. The water from multiple sources is ordinarily mixed before distribution.

PURIFICATION OF WATER:
Some of the water collected from surface or ground source are satisfactory in quality for all common municipal uses. Such water needs to be protected only by disinfection. Other containing objectionable substances in varying quantities, and these substances must be removed, reduced to tolerable limit, destroyed, or otherwise changed in character before they are sent to the consumer. Impurities are acquired in normal passage of water through the atmosphere, over the earth's surface, or though the pores of the ground. They are associated in their pollution aspects with man's activities and, in particular, with his own use of water in household and industry and his discharge of spent water courses.
Purification works in public water supply system is employed to make water:

1. Hygienically safe,
2. Esthetically attractive and palatable, and
3. Economically satisfactory for the uses to which it is to be put.

The most common classes of municipal water purification works and their principal functions are:

1. Filtration plants that remove objectionable colour, turbidity and bacteria as well as other potentially harmful organisms by filtration through sand after necessary preparation of the water by coagulation and sedimentation.
2. Defferrization and demagnetization plants that remove excessive amounts of iron and manganese by oxidizing the soluble ferrous and manganeous compounds, which are removable by sedimentation and filtration.
3. Softening plants that removed excessive amounts of scale-forming soap consuming compounds, chiefly and soluble bicarbonate, chloride and sulphate of calcium and magnesium.

Most water supplies are chlorinated to assure their disinfection and many waters are treated with lime or other chemicals to reduce their tendency to corrode iron and other metals with they come into contact.

TRANSPORTATION OF WATER:
Supply conduits or adequate, transport water from the source of supply to the community and so form the connecting link between the collection works and the distribution system. The location of the source determines whether the conduits are short or long and whether the water is transported by gravity by pumping. Depending upon topography and available materials, conduits are designed to carry the water in open channel flow under pressure. They may follow the hydraulic grade line as:

1. Canals dug through the ground.
2. flumes elevated above the ground,
3. grade aqueducts laid in balanced cut and cover at ground surface,
4. grade tunnels penetrating hills, or they may depend from the hydraulic gradient as pressure aqueducts laid in balanced out and cover at the ground surfaces
5. pressure tunnels dipping beneath valleys or hills 
6. pipe lines of fabricated materials following the ground surface.

Size and shape of supply conduits are determined by hydraulic,structural and economic considerations. Velocities of flow are held ordinarily between 1 to 1.5m/sec. Requisite capacity depends upon the inclusion and size of service, or distributing reservoirs, in the supply system. 

The service reservoirs are designed to store enough water. Its capacity will be a day's consumption of water plus 50% excess of the average daily rate of use. Ordinarily, required storage is approximately a day's consumption.
Distribution reservoirs are constructed as open or covered basins at ground level or as elevated tanks. The choice depends upon their size and their location with particular reference to available elevation above the area served by them. A number of different reservoirs may be needed in large system.