Which among the following is used in deflouridation of water?

Ans: a (Alum and Lime) Ref: Park, 19th ed, p. 511,582The addition of lime and alum in sequence followed by flocculation, sedimentation and filtration for defluridation of water is Nalgonda technique.The recommended level of fluorides in drinking water in India accepted as 0.5 to 0.8 mg/ltr.Endemic fluorosis.It has been observed in areas where the drinking water contains excessive amount of fluorine (3-5 mg/L).Intervention:i) Changing of water source - running surface water contains lower quantities of fluorides than ground water.ii) Chemical treatment - Nalgonda technique of deflouridation of waters It involves the addition of lime and alum in sequence followed by flocculation, sedimentation and filtration.BRIDGEStabilising bleaching powder by adding lime is called Clarke's methodNalgonda technique - developed by The National EnvironmentalEngineering Research Institute, Nagpur.