Social & Preventive Medicine Resdiual chlorine in chlorination of water should be – A 1 mg/l after 1 hr B 0.5 mg/l after 1 hr C 1 mg/l after 30 mins D 0.5mg/l after 30 mins 💡 Explanation Resdiual chlorine in chlorination of water should be - ✓ Correct Answer: B. 0.5 mg/l after 1 hr