Social & Preventive Medicine Recommended level of residual chlorine for disinfection of water is:- A >0.1 mg/L for a contact period of half hour B >0.5 mg/L for a contact period of half hour C >0.5 mg/L for a contact period of 1 hour D >1.0 mg/L for a contact period of 1 hour 💡 Explanation Recommended level of residual chlorine for disinfection of water is:- ✓ Correct Answer: C. >0.5 mg/L for a contact period of 1 hour