Q.What are the major causes of water pollution? Explain.
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Start your 14-day free trial to unlock the full solution →Water gets polluted by a variety of sources, which can be grouped as follows:
1. Pathogens: The most serious water pollutants are disease-causing organisms (bacteria and other microorganisms) that enter water from domestic sewage and animal excreta. Sewage carries bacteria such as Escherichia coli and Streptococcus faecalis, which cause gastrointestinal diseases.
2. Organic wastes: These include plant and animal materials that are decomposed by bacteria and consume dissolved oxygen from water. Excess organic waste leads to a high BOD (Biochemical Oxygen Demand) and reduces the oxygen available to aquatic life.
3. Plant nutrients (fertilisers): Nitrates and phosphates from agricultural runoff (fertilisers) and detergents cause eutrophication — an excessive growth of algae and phytoplankton on the water surface. When these die, their decomposition by bacteria further depletes dissolved oxygen, killing fish and other aquatic organisms.
4. Chemical pollutants: These include:
- Heavy metals (e.g. mercury, lead, cadmium) from industrial effluents, which are toxic and can bio-accumulate in the food chain.
- Pesticides and herbicides washed off from agricultural fields.
- Detergents and synthetic organic compounds. …
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