WHY WATER PURIFICATION AND TREATMENT GIVEN TO THE WATER FOUND IN THE NATURE

Water found in nature is seldom, if ever, all pure and free from danger for human consumption and most waters require treatment for the removal of germs of diseases, solid impurities, taste, odour, colour, iron and mineral salts, etc. In general the treatment given to water is adjusted suitably to the characteristics of the raw water and the nature of impurities to be dealt with. The main treatment required for surface waters is for contamination, corrosion, turbidity, taste and colour;and for underground waters is for removal of hardness and scale farming salts, corrosive salts and excess iron and other minerals. Particular attention should be paid to planning and lay -out of water treatment works in such a way that its capacity may be enlarged without difficulty in future for any of population. The treatment works should be located as near the source of supply as possible. Storage tends to improve the quality of water through sedimentation of silt and other suspended matter and by the oxidation of dissolved impurities. Colour and turbidities are reduced to a considerable extent and bacteria also disappears to as much as 90 to 95 percent which in many cases offers an effective substitute for pre sedimentation and pre chlorination. Polluted water derived from rivers is stored undisturbed in large impounding reservoirs which may be for a period of 2 to 4 weeks, but the stored water deteriorates biologically. Penetration of sunlight into water disinfecting effect and its bleaching action on the colouring matter is limited to a depth of 1.5 metres in the clear water and upto only a few centimeters in turbid waters. For this reason the growths of the organisms are much less likely in turbid silt bearing waters than in clear waters.