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Water pollution and river rejuvenation

Polluted rivers and lakes and what cleans them: sewage treatment and reuse, industrial effluent, contaminants in drinking water, and the programmes that rejuvenate rivers. Prelims has asked what biological oxygen demand measures and which pollutants are found in drinking water in parts of India.

UPSC has asked

  • Prelims 2017: what biological oxygen demand is a standard criterion for
  • Prelims 2013: pollutants found in drinking water in parts of India

Showing 1 of 6 subjects, those that changed from 1 to 15 July 2026.Show all

Constructed wetlands for city drains

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Prelims and Mains

A constructed wetland treats sewage where it flows, with stone structures that slow the water, rock filters and plants that take up nutrients, so it needs far less energy than a mechanical treatment plant.

What changed

  1. 9 Jul 2026New subject

    • The National Mission for Clean Ganga is treating drains where they flow instead of piping sewage to a plant. Pilots on the Shastri Park and Kailash Nagar drains, which discharge into the Yamuna, will treat about 10 million litres a day.
    • The systems combine stone structures that slow the flow, rock filters, and plants that take up nutrients and pollutants, so they need far less energy than mechanical plants.

    PIB, 9 Jul 2026: NMCG's focus on Nature Based Solutions: Initiation of two pilot projects and training programs on NbS (opens in a new tab)

Also filed elsewhere

  • Fluorosis · on Non communicable diseases, nutrition and food safety

    Fluorosis is not a poisoning that arrives from a factory: the fluoride is in the rock the groundwater passes through, so a village can drink it for years with nothing having gone wrong upstream.