--- title: "Sources and impacts of water pollution" subject: "Engineering Chemistry" chapter: 3 key: "semester_2/engineering_chemistry:water-sources-impacts" source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/water-sources-impacts site: BCT Engineering --- # Sources and impacts of water pollution Engineering Chemistry · Chapter 3: Environmental Chemistry - Asked in: 2072 Asoj, 3 marks - Video: [What Is Water Pollution | Environmental Chemistry | Chemistry | FuseSchool](https://www.youtube.com/watch?v=Zk1J2EW-nmQ) — FuseSchool - Global Education - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/water-sources-impacts - Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-3 ## Question What are the main sources of water pollution? Write the various impacts of water pollution. ## Short answer Main sources: domestic sewage, industrial effluents, agricultural runoff. Impacts: waterborne diseases (cholera, typhoid), heavy metal poisoning (Minamata from Hg, itai-itai from Cd, arsenicosis), eutrophication causing fish kills, bioaccumulation, and degraded water quality. ## Answer #### Main sources of water pollution - **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. #### Impacts - **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. ## 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. Runoff of fertilisers (nitrates, phosphates), pesticides and animal wastes B. Hot cooling water from power plants C. Acid mine drainage D. Tannery effluents with phenols Answer: A. Agricultural runoff carries fertilisers, pesticides and animal wastes; the others are thermal, mining and industrial sources. (Key point: Sources) 2. 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) 3. 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) 4. How does thermal pollution harm aquatic life? A. Hot water increases oxygen solubility and causes oxygen poisoning B. It makes water more acidic by dissolving CO2 C. It only changes the colour of the water D. Hot water holds less dissolved oxygen, disturbing aquatic life Answer: D. Oxygen solubility falls as temperature rises, so aquatic organisms get less oxygen. 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