Social & Preventive Medicine Residual chlorine required for normal supply of water system in order to disinfect water born pathogen is A 0.5mg/L B 1mg/L C 0.1mg/L D 2.5mg/L 💡 Explanation Residual chlorine required for normal supply of water system in order to disinfect water born pathogen is ✓ Correct Answer: A. 0.5mg/L