According to WHO guidelines 2017, the minimum free residual chlorine (FRC) required at the consumer's end in a piped water supply for safe drinking water is:

• A 0.5 mg/L ✓
• B 0.1 mg/L
• C 0.2 mg/L
• D 1.0 mg/L

Explanation

For piped water systems serving populations at risk, WHO recommends maintaining a minimum free residual chlorine of 0.5 mg/L (0.5 ppm) at the point of delivery (consumer's tap). In normal low-risk situations, the minimum is 0.2 mg/L at the tap. After chlorination at source, the FRC at the treatment point should be 0.5 mg/L so that 0.2 mg/L persists at distant points after distribution losses. This is distinct from hyperchlorination (used in emergency disinfection) where levels of 5 mg/L are used.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.