According to a report by the Delhi Pollution Control Committee (DPCC), the quality of water in the Yamuna river has improved along the Delhi stretch during the COVID-19 lockdown, compared to April 2019. On April 6, 2020 the DPCC had collected water samples from 9 locations along the Yamuna and 20 locations of drains.
Major outcomes of the report
- The Yamuna has still not met the “water quality criteria”.
- The pollution has reduced by 21% at ITO Bridge, 20% at Nizamuddin Bridge, and 18% at Okhla Barrage.
- Pollution has reduced in five out of the six major drains, which flow into the Yamuna.
- Of the nine locations of the river, an increase in pollution was observed only in Khajuri Paltoon Pool, according to the report.
- Out of the 9 locations, 5 have shown 18%-33% reduction in biochemical oxygen demand (BOD) levels. The rest of the four locations have shown slight to considerable increase in BOD levels.
- Four of the nine locations where dissolved oxygen (DO) was nil in 2019 showed DO levels of 2.3-4.8 mg/l.
What is Biochemical Oxygen Demand (BOD)?
Biochemical oxygen demand (BOD) represents the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter under aerobic (oxygen is present). A higher BOD level means that more oxygen is needed to decompose a large quantity of organic matter (waste or pollutants) present in the water. So higher value of BOD means that the water is more polluted.
What is Dissolved oxygen?
Dissolved oxygen is the amount of dissolved oxygen present in the water. The presence of a sufficient concentration of dissolved oxygen is critical to maintaining the aquatic life and aesthetic quality of streams and lakes. The quality of water increases with an increase in DO levels.
A DO level of 5 mg/l or above is the recommended level for bathing in a river and DO levels over 5 mg/l were found only in two locations closer to where the river enters Delhi.
Sources
- The Hindu
- USGS
