The WHO and BIS standard for residual free chlorine in treated piped water supply at consumer's tap is:

• A 0.2–0.5 mg/L ✓
• B 0.1–0.2 mg/L
• C 0.5–1.0 mg/L
• D 1.0–2.0 mg/L

Explanation

BIS (IS 10500:2012) and WHO guidelines recommend a residual free chlorine of 0.2–0.5 mg/L at the consumer's tap to ensure microbiological safety without excessive chlorine taste or disinfection by-product formation. At water works, a contact time of 30 minutes with a minimum contact-product (CT) of 0.2 mg-min/L is required before distribution.

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.