Biochemical Oxygen Demand (BOD) of a water sample measures:
- A The amount of oxygen consumed by microorganisms to biochemically oxidize organic matter over 5 days at 20°C ✓
- B The amount of dissolved oxygen available in the sample
- C The total bacterial count per milliliter of the sample
- D The concentration of dissolved nitrates and phosphates available for aquatic organism growth
Correct answer: A. The amount of oxygen consumed by microorganisms to biochemically oxidize organic matter over 5 days at 20°C
Explanation
BOD is the amount of dissolved oxygen consumed by biological activity (microbial decomposition) when a water sample is incubated at 20°C for 5 days (BOD₅). It is an indirect measure of organic pollution — higher BOD indicates more organic matter and greater pollution. Clean river water has BOD <3 mg/L; raw sewage typically has BOD of 200–400 mg/L. COD (Chemical Oxygen Demand) measures all chemical oxidation.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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