Which of the following is not affected by routine chlorination ?

Ans. is 'b' i.e., Polio virus Chlorination Chlorination is one of the greatest advances in water purification. Chlorine kills pathogenic bacteria, but has no effect on spores, ceain viruses (e.g., polio, viral hepatitis) and cyst of E.histolytica, in usual doses. Mechanism of action When chlorine is added to water, there is formation of hypochloric and hypochlorous acid The hypochloric acid is neutralized by the alkanity of the water. The hypochlorous acid ionizes to form hydrogen ions and hypochlorite ions. The disinfecting action of chlorine is mainly due to the hypochlorous acid and to a small extent due to the hypochlorite ions. The hypochlorous acid is the most effective form of chlorine for water disinfection, it is 70-80 times more effective than hypochlorite ion. Method of Chlorination For disinfecting large bodies of water, following methods of chlorination are available : ? Chlorine gas First choice Chloramine Perchloron or high test hypochlorite (HTH).