Biological Oxygen Demand (BOD) is a standard criterion for:
✓ Correct answer: c) Pollution assay in aquatic ecosystems
ExplanationBOD measures the amount of dissolved oxygen re- quired by microorganisms to break down organic material in water over a specific time.BOD is the amount of dissolved oxygen needed by bacteria in decomposing the organic wastes present in water.It is measured in milligrammes per litre of water of ox- ygen.The higher value of BOD indicates low (Dissolved Oxygen) DO content of water.BOD is not a reliable method for assessing water pollution because it only includes biodegradable elements.Standard Method 5210B is the most widely used method for determining Biological Oxygen Demand (BOD).It measures the difference in dissolved oxygen (DO) over a five-day incubation period at 20°C.The initial DO is recorded, and after incubation, the final DO is measured.The BOD value is then calculated based on oxygen depletion.Higher BOD indicates poor water quality due to higher oxygen demand, while lower BOD suggests purer water with less oxygen consumption.DO levels are lower in summer as warm water holds less oxygen.83
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