--- title: "Sources, effects and remedies of water pollution" subject: "Engineering Chemistry" chapter: 3 key: "semester_2/engineering_chemistry:water-pollution-sources" source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/water-pollution-sources site: BCT Engineering --- # Sources, effects and remedies of water pollution Engineering Chemistry · Chapter 3: Environmental Chemistry - Asked in: 2075 Baisakh, 1+2+2 marks; 2069 Bhadra, 1+2+2 marks (asked 2 times) - Video: [Water Pollution: Sources, Effects, and Prevention | Pollution Awareness | Free Online Course](https://www.youtube.com/watch?v=0A6sDFFLa8U) — Learning by ThePoemStory - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/water-pollution-sources - Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-3 ## Question What are the major sources of water pollution? Mention their adverse effects and possible remedies. ## Short answer Major sources: domestic sewage, industrial effluents, agricultural runoff, mining and oil spills, thermal discharges. Adverse effects: waterborne diseases, eutrophication (algal blooms, low dissolved oxygen), biomagnification of toxins, bad taste and odor. Remedies: effluent treatment, organic farming, waste segregation, cooling hot water, strict monitoring. ## Answer **Water pollution** is the contamination of water bodies by substances that make water unfit for its use and harm living things. #### Major sources - **Domestic sewage:** human waste, kitchen waste, detergents. - **Industrial effluents:** acids, alkalis, dyes, heavy metals (Pb, Hg, Cd, As, Cr), oils and phenols, from tanneries and from paper, textile, sugar and chemical industries. - **Agricultural runoff:** fertilisers (nitrates, phosphates), pesticides (DDT) and animal wastes. - **Mining and oil:** acid mine drainage, oil spills. - **Thermal pollution:** hot water from power plants and industries. - **Others:** radioactive wastes, landfill leachate, siltation from soil erosion, religious and cultural offerings, municipal solid waste dumping into rivers. #### Adverse 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. #### Possible remedies - 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). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which is an agricultural source of water pollution? A. Hot cooling water from power plants B. Acid mine drainage C. Tannery effluents with phenols D. Runoff of fertilisers (nitrates, phosphates), pesticides and animal wastes Answer: D. Agricultural runoff carries fertilisers, pesticides and animal wastes; the others are thermal, mining and industrial sources. (Key point: Sources) 2. Which source produces thermal pollution? A. Hot water discharged from power plants and industries B. Fertiliser runoff from farms C. Domestic sewage and detergents D. Oil spills at sea Answer: A. Power plants and industries release hot water, causing thermal pollution. (Key point: Thermal source) 3. How does excess nitrate and phosphate in a lake kill fish? A. They make the water too alkaline for fish gills B. They cause algal bloom; on decay the algae use up dissolved oxygen (high BOD, low DO) C. They directly poison fish with nitrate crystals D. They raise dissolved oxygen so much that fish burst Answer: B. Nutrients cause algal bloom; decay of the algae consumes dissolved oxygen, so fish suffocate. (Key point: Eutrophication) 4. Which pairing of pollutant and disease is correct? A. Hg - itai-itai disease; Cd - Minamata disease B. As - Minamata disease; Pb - arsenicosis C. Hg - Minamata disease; Cd - itai-itai disease D. Cd - blue-baby syndrome; Hg - arsenicosis Answer: C. Mercury causes Minamata disease and cadmium causes itai-itai disease; arsenic causes arsenicosis and nitrate causes blue-baby syndrome. (Key point: Metal diseases) 5. Which is a key remedy for water pollution from sewage and industry? A. Discharge them directly into rivers so they dilute B. Add more phosphate detergents C. Dump solid waste into rivers so it settles D. Treat sewage and industrial effluents (primary, secondary, tertiary) before discharge Answer: D. Treating effluents before discharge removes pollutants at the source. 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