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GATE 2022 CE (CE1) – Question 26

Water and Waste Water Quality and Treatment · Water quality standards, parameters and water quality index · 1 mark · Multiple select

For wastewater coming from a wood pulping industry, Chemical Oxygen Demand (COD) and 5-day Biochemical Oxygen Demand (BOD5) were determined. For this wastewater, which of the following statement(s) is/are correct?

  1. COD > BOD5
  2. COD ≠ BOD5
  3. COD < BOD5
  4. COD = BOD5

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Show answer and explanation

Correct answer: (A) COD > BOD5; (B) COD ≠ BOD5

Explanation

COD includes chemically oxidizable material, including the refractory organic material typically present in wood-pulping wastewater. Five-day BOD measures the oxygen consumed biologically within that finite period.

Therefore **COD > BOD₅**, which also implies **COD ≠ BOD₅**. **Answer: A and B**.