Biochemical Oxygen Demand (BOD) may not be a good index for pollution for water bodies receiving eff

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Question

Biochemical Oxygen Demand (BOD) may not be a good index for pollution for water bodies receiving effluents from:

Accepted Answer

Correct Answer: 1 — Petroleum industryStep-by-step Solution:BOD (Biochemical Oxygen Demand) measures the amount of dissolved oxygen consumed by microorganisms while decomposing organic matter in water. It is a reliable indicator of pollution only when the pollutants are biodegradable organic substances that microorganisms can break down.Petroleum industry effluents contain hydrocarbons (crude oil, refined petroleum products), heavy metals, and other inorganic and non-biodegradable pollutants. Many of these compounds are not easily degraded by the microorganisms used in the BOD test, so the BOD values may appear deceptively low even though the water is severely polluted with toxic substances. Therefore, BOD is not a reliable indicator for petroleum-based pollution.Why other options are incorrect:Option 2: Sugar industry effluents are rich in biodegradable organic matter (sugars, molasses), which microorganisms readily decompose. BOD accurately reflects the level of organic pollution here.Option 3: Domestic sewage is rich in biodegradable organic matter (faeces, food waste, detergents). BOD is the standard and most appropriate measure of domestic sewage pollution.Option 4: Dairy industry effluents (milk, whey, lactose) are highly biodegradable organic wastes. BOD accurately measures the oxygen demand in such cases.Key Concept: BOD (Biochemical Oxygen Demand) — the amount of dissolved oxygen (in mg/L) needed by aerobic decomposers to break down organic matter in water at a fixed temperature (usually 20°C) over 5 days. High BOD = high organic pollution = low dissolved oxygen. BOD is only effective for measuring biodegradable organic pollution. For toxic, non-biodegradable pollutants (heavy metals, petroleum hydrocarbons, pesticides), Chemical Oxygen Demand (COD) is a more appropriate parameter.

Biochemical Oxygen Demand (BOD) may not be a good index for pollution for water bodies receiving effluents from:

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Biochemical Oxygen Demand (BOD) may not be a good index for pollution for water bodies receiving effluents from:

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