<prompt> Minimum chlorine content of water after chlorination should be?0.5 mgL5 mgL0.05 mgL50 mgL  <response>: ANSWER: A 0.5 mgLREF: Park 20th edition page 625Minimum recommended concentration of free chlorine is 0.5 mgL for one hour.ALSO KNOW:Most effective and cheapest method of chlorination of wells in rural India is by bleaching powder chlorinationBleaching powder contains 33 of chlorine content, is unstable with rapid and brief action.PERCHLORON High test hypochloride is a calcium compound which contains 60-70 available chlorineChlorine demand of well wTater is estimated by Horrocks Apparatus.Roughly 2.5 gms of bleaching powder is required to disinfect 1000 lit of water.One tablet of chlorine 0.5 gm can disinfect 20 liters of waterChlorine acts best as a disinfectant wThen the pH of water is around 7 because of the predominance of hypochlorous acid.This wdll give an approximate dose of 0.7 mg of applied chlorine per liter of water.A contact period of 1 hour is allowed before the wTater is drawn for use.At the end of 1 hour the residual chlorine is tested by ORTHOTOLIDINE ARSENITE TEST modification of Orthotolidine test Orthotolidine test 0.1 ml of reagent 1 ml of water read after 10 sec Orthotolidine reagent Orthotolidine 10 solution of HCLIf free residual chlorine level is less than 0.5mglitre, the chlorination procedure should be repeated before any water is drawnDose of chlorine chlorine demand residual chlorine 0.5mglitWATER QUALITY CRITERIAS STANDARDS:Turbidity 5 Nephelometric turbidity unit NTUColor 15 True color unit TCUpH 6.5 to 8.5Total dissolved solids TDS: Good palatability 600 mgLAcceptable palatability 1000 mgLUnpalatable 1200 mgLChloride: Standard 200 mgLMaximum 600 mgL 