30 April 2020.

Introduction:

  The nationwide lockdown imposed to curb the spread of Covid-19 has improved the quality of water in the rivers, noticeably in Ganga and Yamuna.

A comparative assessment of pollution levels during pre-lockdown and lockdown periods was made through the analysis of data generated from 36 real-time water quality motoring systems.

Report of CPCB.

• The Central Pollution Control Broad (CPCB) in its latest report — ‘Impact of lockdown on water quality of river Ganga, April 2020 suggested that the main source of water pollution in the river are industrial effluents and the domestic wastewater. Due to lockdown and closure of industries there is significant reduction in effluents and quality of water has improved.
• However, in areas near the settlement where drains continue to discharge wastewater into river Ganga, no significant improvement has been noted due to the undeterred flow of wastewater throughout the lockdown period.
• According to The CPCB, there was notable improvement in water quality in the Yamuna,with respect to DO, BOD and COD when compared with pre-lockdown and lockdown period.
• The river Ganga’s water quality has improved with the increase in dissolved oxygen (DO) and reduced nitrate concentration. The tributaries of Ganga have also refined due to the concentration of DO increase during the lockdown period.
• According to the Uttarakhand Environment Protection and Pollution Board, there has been a 34 per cent reduction in faecal coliform and 20 per cent in biochemical oxygen demand in Haridwar.
• According to the Uttar Pradesh Pollution Control Board (UPPCB), healthy water should have a dissolved oxygen level of at least 7 mg/litre. The dissolved oxygen level upstream in river Ganga is 8.9 mg per litre while in the downstream it is 8.3 mg per litre. This clearly shows that water quality has improved significantly and is optimal for bathing.
• Water in Har-ki-Pauri has ranked in Class A for the first time in recent history.The water has always been placed in Class B .
• The Delhi Pollution Control Committee (DPCC) in its report submitted to the Yamuna Monitoring Committee (YMC) has also stated that the absence of industrial effluents and reduced human activities has improved the water quality of river Yamuna.

Reasons for improvement:

• According to CPCB,this improvement  may primarily be attributed to absence of industrial wastewater discharge, agricultural runoff and increased fresh water flow in the river. (A decline in) general human activities at ghats and entrainment of solid organic waste into the river.
• It, however, clarified that the improvement was “not substantial” as there was no significant reduction in other indicators- biochemical oxygen demand (BOD) and chemical oxygen demand (COD) and concentrations of ammoniacal nitrogen, which is seen to have gone up in certain locations.
• According to the analysis, this could be due to the unabated discharge of domestic wastewater from over 97 towns situated along the river in different states.

What is BOD/COD /DO?

BOD: Biochemical Oxygen Demand

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.  When BOD levels are high, dissolved oxygen (DO) levels decrease because the oxygen that is available in the water is being consumed by the bacteria. Water with a BOD level of 3-5 ppm is considered moderately clean. In water with a BOD level of 6-9 ppm, the water is considered somewhat polluted.

COD:Chemical Oxygen Demand.

. Chemical Oxygen Demand (COD) is an important measurement for the amount of oxygen that is required to break down pollutants (organic substances) in water.

DO: Dissolved Oxygen

Dissolved Oxygen is the amount of gaseous oxygen (O2) dissolved in the water. Oxygen enters the water by direct absorption from the atmosphere, by rapid movement, or as a waste product of plant photosynthesis. Healthy water should generally have dissolved oxygen concentrations above 6.5-8 mg/L.