- 2069 Poush · 3+2 marks
Water pollutants, harmful effects, control measures
Short answer
Major water pollutants are organic waste, heavy metals, pathogens, and suspended solids. They cause waterborne diseases, eutrophication, bioaccumulation, and degrade water quality. Control requires sewage treatment, reduced fertilizer use, preventing waste dumping, and strict environmental laws.
What are the major water pollutants and their harmful effect? Mention the possible measures to control water pollution.
Major water pollutants
| Type | Pollutants | Source |
|---|---|---|
| Organic | Sewage, detergents, pesticides, oil, phenols, food waste | Households, farms, industries |
| Inorganic | Heavy metals (Pb, Hg, Cd, As), nitrates, phosphates, acids, alkalis, salts | Industries, mines, fertilisers |
| Biological | Bacteria, viruses, protozoa, worms | Sewage, animal waste |
| Physical | Suspended solids, heat, radioactive material | Erosion, power plants |
Harmful effects
- Health: waterborne diseases (cholera, typhoid, dysentery, hepatitis, diarrhoea); Hg causes Minamata disease, Cd causes itai-itai disease, As causes arsenicosis (found in groundwater of the Terai), Pb damages the brain; nitrate in water causes blue-baby syndrome.
- Eutrophication: excess nitrate and phosphate cause algal blooms; when the algae die, their decay uses up dissolved oxygen (high BOD, low DO) and fish die.
- Bioaccumulation and biomagnification of pesticides and metals in the food chain.
- Bad taste, smell and colour; water is unfit for drinking, irrigation and industry.
- Thermal pollution reduces oxygen solubility and disturbs aquatic life.
Control measures
- Treat sewage and industrial effluents before discharge (primary, secondary and tertiary treatment).
- Use less fertiliser and pesticide; use organic farming; ban phosphate detergents.
- Prevent dumping of solid waste in rivers; build proper sanitation and toilets.
- Cool hot water before discharge; recycle and reuse water.
- Strict laws (polluter pays), regular monitoring, public awareness and river-cleaning programmes (such as for the Bagmati).
✓ Answer checked by Claude Opus 5.5 (high effort)
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