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, “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 CPCB report notes. The lower these numbers are the better they indicate river health.
“Reduction in BOD concentration has been less significant owing to continual discharge of untreated or inadequately treated sewage. Marginal reduction can be seen only in the 4th week of the lockdown. Further, there is gradual increase in BOD levels towards downstream stretches of the river, with the maximum values in West Bengal,” according to the CPCB report. “Reduction in COD concentration has also been less significant. Few locations show increase in the COD values, while in remaining stations reduction in COD levels was not significant. 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, with an estimated quantity of 3,500 MLD (Million Litres per Day) of sewage, out of which 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.
Highest in U.P.
The CPCB assessed pollution a week before lockdown and weeks after at 36 locations in Uttar Pradesh and West Bengal. The pollution in the river is highest in Uttar Pradesh. The bulk of the sewage treatment plants commissioned under Ganga are in Uttar Pradesh towns and 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 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,” the CPCB notes. However, this was done basis an assessment at only three locations in Delhi and the gains were significantly due to reduced industrial activity.