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What is False statement regarding chlorination of water: and explain in detail?
(Refer: K. Park’s Textbook of Preventive and Social medicine, 24th edition, pg no: 765, 766)
Recommended minimum contact period is 1 hour for chlorination
Principles of chlorination

Water should be clear, turbid free
Chlorine demand should be estimated, which is the amount of chlorine needed to destroy bacteria, oxidize all organic matter, neutralise all ammoniacal substances in water
Breakpoint chlorination – The point a which chlorine demand of the water is met Free chlorine begins to appear in water, if further chlorine is added beyond breakpoint
Recommended minimum  contact period is 1 hour for chlorination
Recommended Residual chlorine for drinking water is 0.5 mg / litre
For water bodies, post disaster – 0.7 mg / litre
For swimming pool sanitation, it is 1.0 mg/ litre