Environment › Pollution
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
6 Aug 2026 · Prelims and Mains
Namami Gange
The test of a river cleaning programme is not the plants it builds but whether a stretch of the river stops failing the bathing water standard. In the Central Pollution Control Board's count for 2025, one stretch of the Ganga did.
- Namami Gange, launched in 2014 and run by the National Mission for Clean Ganga, pays for sewage treatment in the Ganga basin and for the surveys of the river's fauna.
- The Central Pollution Control Board (CPCB) lists a river stretch as polluted when its biochemical oxygen demand stays above the bathing water standard, and drops the stretch once it complies.
- The CPCB's Polluted River Stretch report 2025 left the Haridwar to Sultanpur stretch in Uttarakhand off the list.
- Stretches in Uttar Pradesh and West Bengal improved in part.
- Namami Gange has created 4,263 million litres a day of sewage treatment capacity, and 146 of its 219 sewage projects are complete.
- Minimum environmental flow norms for the Ganga, notified in October 2018, are monitored by the Central Water Commission.
- Surveys counted 3,037 gharials, and a National Gharial Conservation Action Plan followed.
- The Gangetic dolphin estimate for 2021 to 2023 is 6,327, and India's first Dolphin Rescue Ambulance is in service.
UPSC has asked
- Prelims 2016: key features of the National Ganga River Basin Authority
31 Aug 2026 · Prelims and Mains
Reuse of treated wastewater
Sewage that is treated and then let into the river uses the treatment capacity once. A reuse policy sends that water to a farm or a factory instead, and two States have now written one.
Treat
Sewage treatment capacity built under the Atal Mission for Rejuvenation and Urban Transformation (AMRUT)
Match the quality
Treat only to the standard the end use needs
Use it
Treated water reaches farms and industry, and reuse is tied to river rejuvenation
- The National Framework on Safe Reuse of Treated Water, 2022, asks every State to frame its own reuse policy.
- Uttar Pradesh and Uttarakhand notified policies for the reuse of treated wastewater, one written for the plains and one for hill conditions.
- Each builds in fit-for-purpose reuse, blended finance and digital monitoring, and ties reuse to river rejuvenation.
The Hindu, 31 Aug 2026: Mainstreaming reuse of treated wastewater (opens in a new tab)
25 Aug 2026 · Prelims and Mains
The Jojari
The Jojari carries industrial effluent rather than sewage, and the remedy asked of the court was distance rather than treatment. In August 2026 the Supreme Court fixed that distance in metres.
- The Supreme Court barred construction within 100 metres of the Jojari and hazardous industry within 500 metres of its flood line.
- The Jojari carries Jodhpur's industrial effluent to the Luni near Balotra, as the Bandi carries Pali's.
- Effluent in the Jojari, Bandi and Luni affects about two million people in Rajasthan.
17 Aug 2026 · Prelims and Mains
Hexavalent chromium in the Kanpur region
Chromium sulphate for the tanneries was made around Kanpur for decades, and the waste from making it was left on the ground. It has since worked its way down into the water people drink.
- Groundwater in about a dozen areas of Kanpur Nagar, Kanpur Dehat and Fatehpur was reported to hold hexavalent chromium, from decades of waste dumped by factories making chromium sulphate for tanneries.
- A 2025 State report found excess chromium (VI) in 73 to 96 per cent of the blood samples tested.
- National Green Tribunal orders in 2005 and 2017 had sought closures and the removal of the dumps.
- It is a carcinogen, and long inhalation raises the risk of lung cancer.
- Swallowed in water, it injures the liver, kidneys and gut.
- Skin contact causes ulcers and allergic dermatitis.
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.