What happens when domestic sewage mixes with river water?
Correct answer: C. The increased microbial activity uses up the dissolved oxygen.
- A. Small animals like rats will die after drinking river water.
- B. The increased microbial activity releases micronutrients such as iron.
- C. The increased microbial activity uses up the dissolved oxygen.
- D. The river water is still suitable for drinking as impurities are only about 0.1%.
Explanation
When sewage mixes with a water body, microorganisms present in it biodegrade the organic matter of the sewage using oxygen. This results in a sharp decline in dissolved oxygen which may cause mortality of aquatic creatures. Gradually, however, dissolved oxygen increases in concentration with the completion of biodegradation of sewage matter.
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Ecosystems include biotic and abiotic components, food chains and webs, energy flow, nutrient cycles, populations and ecological relationships. Pollution and conservation cover air, water, soil and noise pollution, their effects on organisms, biodiversity loss, protected areas, sustainable resource use and methods for reducing environmental damage.
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