A community's water supply has a residual chlorine level of 0.2 mg/L at the point of consumption after municipal treatment. Which conclusion is MOST correct?
- A Insufficient — WHO recommends at least 0.5 mg/L at point of use
- B Excessive — chlorine above 0.1 mg/L is toxic
- C Adequate chlorination — WHO recommends 0.2 mg/L as the minimum residual at point of use ✓
- D Adequate — India's standard requires only 0.1 mg/L residual at distribution point
Correct answer: C. Adequate chlorination — WHO recommends 0.2 mg/L as the minimum residual at point of use
Explanation
WHO guidelines recommend a minimum free residual chlorine of 0.2 mg/L at the point of use to ensure microbiological safety for water distribution systems under normal conditions. At the point of treatment (entry to distribution system), a higher residual (0.5 mg/L) is typically targeted to ensure 0.2 mg/L reaches distant points. India's BIS standard (IS 10500:2012) also specifies 0.2 mg/L as the maximum desirable limit and 1.0 mg/L as the permissible limit at point of delivery. A residual of 0.2 mg/L at consumption point thus meets the minimum WHO requirement.
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.