Mention different measures for controlling water pollution. 

There are two major sources of water pollution i.e. sewage and industrial wastes. 
Treatment of sewage:
(i) Sewage must be churned by machines and churned sewage is passed into a tank with a gentle slope. Heavier particles settle and the water flowing down is relatively pure.
(ii) Water must be sterilised with the help of chlorination. It kills microbes of sewage fungus as well as some pathogens, spores.
(iii) Treatment of water with lime, alum etc also helps in its purification.
Treatment of industrial waste: The chemical substances present in the industrial waste products dissolved in water can be precipitated by suitable chemical reactions and removed later on from water. Photocatalysis and ion-exchanges have been developed for the treatment of industrial wastes.