A municipal corporation measures a Biochemical Oxygen Demand (BOD) of 250 mg/L in a river receiving industrial effluent. This value indicates:
- A Highly polluted water — safe drinking water has BOD <1 mg/L ✓
- B Marginally polluted water within acceptable standards for industrial discharge
- C Potable water quality by WHO standards
- D Safe for bathing but not drinking
Correct answer: A. Highly polluted water — safe drinking water has BOD <1 mg/L
Explanation
BOD measures the oxygen demand of organic matter decomposing in water. A BOD of 250 mg/L indicates grossly polluted water — drinking water standards require BOD <1 mg/L, clean unpolluted river water has BOD <3 mg/L, and moderately polluted water has BOD 5–10 mg/L. A BOD of 250 mg/L reflects massive organic load from industrial/sewage discharge, with severe depletion of dissolved oxygen, making the water uninhabitable for aquatic organisms and a public health hazard.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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