No improvement in Ganga water quality during lockdown
But pause in industrial activity has aided Yamuna
The lockdown may have dramatically reduced air pollution across the country but it hasn’t significantly reduced pollution in the Ganga.
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.
There is gradual increase in BOD levels towards downstream stretches of the river, with the maximum values in West Bengal. 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 the remaining 2,400 MLD gets discharged untreated.
Industrial effluent is estimated to be about 300 MLD. 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.