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More river stretches are now critically polluted: CPCB
Why in news?
- The number of polluted stretches in India’s rivers has increased to 351 from 302 two years ago
- And the number of critically polluted stretches — where water quality indicators are the poorest — has gone up to 45 from 34, according to an assessment by the Central Pollution Control Board (CPCB).
- While the Rs. 20,000 crore clean-up of the Ganga may be the most visible of the government’s efforts to tackle pollution, the CPCB says several of the river’s stretches — in Bihar and Uttar Pradesh — are actually far less polluted than many rivers in Maharashtra, Assam and Gujarat.
- These three States account for 117 of the 351 polluted river stretches.
- Based on the recommendations of the National Green Tribunal, the CPCB last month apprised the States of the extent of pollution in their rivers.
Mithi among the worst
- The most significant stretches of pollution highlighted by the CPCB assessment (which is yet to be published) include
- The Mithi river from Powai to Dharavi — with a BOD (Biochemical Oxygen Demand) of 250 mg/l,
- The Godavari — from Someshwar to Rahed — with a BOD of 5.0-80 mg/l;
- The Sabarmati — Kheroj to Vautha — with a BOD from 4.0-147 mg/l; and
- The Hindon — Saharanpur to Ghaziabad — with a BOD of 48-120 mg/l.
- In its compilation of polluted stretches in Uttar Pradesh, the Ganga with a BOD range of 3.5-8.8 mg/l is indicated as a ‘priority 4’ river.
Graded scale
- The CPCB, since the 1990s, has a programme to monitor the quality of rivers primarily by measuring BOD, which is a proxy for organic pollution — the higher it is, the worse the river.
- The health of a river and the efficacy of water treatment measures by the States and municipal bodies are classified depending on BOD, with a BOD greater than or equal to 30 mg/l termed ‘priority 1,’ while that between 3.1-6 mg/l is ‘priority 5.’
- The CPCB considers a BOD less than 3 mg/l an indicator of a healthy river.
- In its 2015 report, the CPCB had identified 302 polluted stretches on 275 rivers, spanning 28 States and six Union Territories.
Source
The Hindu