NEW DELHI: The lockdown seems to have done what three decades of Ganga Cleaning Project could not do — improving quality of Ganga water.
An analysis of quality of water in Ganga and its tributaries revealed overall improvement especially with regard to increased Dissolved Oxygen (DO) and reduced nitrate concentration.
A Central Pollution Control Board (CPCB) report attributed the drop in pollution to reduced release of industrial waste and reduced discharges/dumping of wastes from various non-point sources in the river stream.
The reduction in Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) concentration was relatively less due to continuous discharge of domestic wastewater.
A comparative assessment of pollution levels during pre-lockdown and lockdown periods was made through analysis of data generated from 36 Real-Time Water Quality Motoring Systems.
During the first week of the lockdown period, DO concentration decreased slightly almost in all monitoring locations, due to heavy rain leading to increase in suspended solids, organic load and turbidity.
However, in the second, third and fourth week, the DO levels show marginal increment in most stations except in a few stations where it was even up to saturation values.
With regard to nine tributaries of the Ganga, the DO concentration increased during the lockdown period. Initially, the improvement was marginal due to heavy rains, but the substantial increase was noted from the second week onwards reaching saturation value at various locations.
Domestic wastewater from 97 towns and industrial effluent dump estimated 3,500 MLD 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 per cent of total wastewater being discharged every day.