Why in news?
The lockdown in the wake of coronavirus (COVID-19) outbreak may have dramatically reduced air pollution across the country but it hasn’t significantly reduced pollution in the Ganga, according to a report by the Central Pollution Control Board (CPCB).
- The dissolved oxygen (DO) concentration, a measure of the amount of free oxygen available in river systems, only rose marginally from March 22-April 15. (A high DO value is considered a good indicator of river health.)
- However, two other measures, BOD (Biological Oxygen Demand) and COD (Chemical Oxygen Demand) both indicators of the amount of oxygen necessary to break down organic and inorganic pollution showed insignificant reductions. (The lower the BOD and COD numbers are the better the river health.)
Why are these improvements only marginal?
- Reduction in BOD concentration has been less significant owing to continual discharge of untreated or inadequately treated sewage.
- Reduction in COD concentration has also been less significant while in a few locations show increase in the COD values and this marginal reduction can be attributed due to stoppage of industrial activities.
- Domestic wastewater from 97 towns situated near river Ganga, and industrial effluents, are the main sources of water pollution in the river.
- When it comes to sewage: out of an estimated quantity of 3,500 MLD (Million Litres per Day – only 1,100 MLD is treated and remaining 2,400 MLD gets discharged untreated.
- Industrial effluent is estimated to be about 300 MLD, which is about 9% of total wastewater being discharged into the river every day.
- Though projects worth ₹23,000 crore have been commissioned (across 11 Ganga basin States), a noticeable increase in the cleanliness of the river isn’t yet apparent.
The silver lining: The CPCB, however, said that there was notable improvement in water quality in the Yamuna.
Analysis results indicate there is considerable improvement in the water quality of river Yamuna with respect to DO, BOD and COD when compared with pre-lockdown and lockdown period.