The minimum recommended conecntration of free chlorine (mg/L) in drinking water at the end of 1 hour is -: (A) 0.1, (B) 0.5, (C) 1, (D) 1.5
Answer is B. Recommended contact period of free residual Chlorine in water : 1 hour Level of free residual chlorine (FRC) recommended : Water type Residual chlorine level (Recommended) Contact period Drinking water >0.5 mg per litre (ppm) 1 hour Water bodies, post disaster >0.7 mg per litre (ppm) 1 hour Swimming pool sanitation >1.0 mg per litre (ppm) 1 hour Ref: Park 25th edition Pgno : 752