As per Central Pollution Control Board (CPCB), the permissible limit for oil and grease in industrial effluent discharged into inland surface water is
- A5 mg/L
- B10 mg/LCorrect
- C30 mg/L
- D100 mg/L
Solution
Concept
CPCB discharge standards for oil and grease in inland surface water
Formula
CPCB Inland Surface Water Standard: Oil & Grease ≤ 10 mg/L
Step-by-step solution
1. CPCB prescribes environmental effluent discharge standards under Schedule VI of EP Rules. 2. For discharge into inland surface waters (rivers, streams, lakes), the limit for oil and grease is 10 mg/L. 3. For discharge into public sewers, the limit is 20 mg/L. 4. Hence, the permissible limit for inland surface water is 10 mg/L. Answer: B
Explanation
Under the Environment (Protection) Rules, 1986 and CPCB General Standards for Discharge of Environmental Pollutants (Schedule VI), the maximum permissible concentration of oil and grease in treated effluents discharged into inland surface waters is 10 mg/L (10 ppm). For public sewers and marine coastal waters, the limit is 20 mg/L.
Why the other options are wrong
A) 5 mg/L is overly stringent compared to standard Indian environmental discharge norms. C) 30 mg/L is the standard limit for BOD, not oil and grease. D) 100 mg/L is the standard limit for suspended solids (TSS).
Shortcut
CPCB Oil & Grease limit: Inland surface water = 10 mg/L; Sewer/Marine = 20 mg/L.
Common mistake
Selecting 20 mg/L or confusing with BOD limits (30 mg/L for inland surface waters).
Correct answer: B) 10 mg/L