Fluoride content in water is removed by:

Ans: c (Lime and Alum)Ref: Park, 20th ed. Pg. 636, 19th ed. Pg. 511, 582The recommended level of fluorides in drinking water in India is accepted as 0.5 to 0.8 mg/Lt. Endemic fluorosis has been observed in areas where the drinking water contains excessive amount of fluorine (3- 5 mg/L).Intervention:1. Changing of water source - running surface water contains lower quantities of fluorides than ground water.2. Chemical treatment - Nalgonda technique of deflouridation of water. It involves the addition of lime and alum in sequence followed by flocculation, sedimentation and filtration. Nalgonda technique is developed by The National Environmental Engineering Research Instistute, Nagpur.