Yamuna water improves during lockdown period, CPCB analysis shows

There has been a “significant improvement” in the water quality of river Yamuna in the national capital during the lockdown period, thanks to polluting industries

There has been a “significant improvement” in the water quality of river Yamuna in the national capital during the lockdown period, thanks to polluting industries being shut and people keeping away from the river, as per an analysis done by the Central Pollution Control Board (CPCB) and submitted to the Yamuna monitoring committee, a body appointed by the National Green Tribunal.

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This came a day after the Delhi Pollution Control Committee (DPCC) came out with its report based on tests of samples collected from nine locations. It, too, had concluded that the overall water quality had improved by up to 33%, though it is still not being fit for bathing.

The CPCB report is based on water samples collected from three major locations --- Palla (the entry point of the river in Delhi), Nizamuddin bridge (between Wazirabad and Okhla barrages where 14 drains discharge into it) and Okhla barrage upstream (after discharge from 16 drains).

The CPCB also took samples from two major drains --- Najafgarh and Shahdara --- that contribute at least two-thirds of the hydraulic ( sand, silt and gravel) load in the river, the report said.

The samples were collected on April 6, 2020, and have been compared with the results of tests done in March 2020. The nationwide lockdown was announced on March 24 to contain the spread of the Covid-19 pandemic.

“The analysis indicates that there is considerable improvement in water quality, in terms of DO (dissolved oxygen), BOD (biochemical oxygen demand) and COD (chemical oxygen demand), when compared with the pre-lockdown period, at all three monitored locations. However, water quality at Nizamuddin and Okhla upstream did not meet the primary water quality criteria for bathing,” the report stated.

BOD means the amount of oxygen required by the river to maintain its flow. The prescribed BOD standards are 3 milligrams per litre (mg/l). The lower the BOD, the better the water quality.

COD indicates the presence of industrial effluents in a water body. A reduction in COD means that the amount of effluents in the river is also going down.

DO is an indicator of how much oxygen is present in the river for the survival of aquatic life. The higher the DO, the better the health of the river.

As per the report findings, at Palla, post-lockdown, the BOD was 2mg/l, down from 7.9mg/l (pre-lockdown).The DO here was 8.3mg/l, compared to 17.1mg/l (pre-lockdown) and COD was 6mg/l, down from 28mg/l (pre-lockdown).

The pH levels (a measure of acidity in the water measured on a scale of 0-14) were 7.8 in April as compared to that of 8.7 in March. “The results comply with the primary water quality criteria for outdoor bathing with respect to analysed parameters of pH, DO and BOD,” the report said.

At Nizamuddin Bridge, the analysis results showed that pH was 7.2 as compared to 7.3 in March, BOD levels were 5.6mg/l from.57 mg/l and COD was 16mg/l as compared to 90mg/l previously. DO levels were not detected.

“The results do not meet the primary criteria of being fit for bathing with respect to DO and BOD,” it said. At Okhla barrage (upstream), the report said the results do not meet the prescribed standards for bathing. The pH was 7.1 as compared to 7.2, BOD was 6.1mg/l from .27mg/l, COD level was 18mg/l from 95 mg/l.

DO was 1.2 mg/l, but could not be compared as values for March could not be detected. “Though water quality does not meet the primary criteria, there was a considerable reduction in concentration of BOD (77.41) and COD (81.05%) levels, which can be attributed to no industrial effluent discharges and the stretch of about 7.5km (after Nizamuddin Bridge) that might be helping in self-purification of river Yamuna,” it said.

It further said the waste water quality in the two drains ---Najafgarh and Shahdara --- has also shown improvement of about 30-45% in BOD levels, though the drains, even with this improvement, had BOD levels of 56 mg/l and 89mg/l, respectively.

The report has attributed the post-lockdown overall improvement in the water quality to various factors, including release of abundant fresh water from Wazirabad Barrage and availability of dilution in the river; no industrial effluent discharge (only about 35.9MLD); good penetration of solar radiation in water body, owing to the washing out of bottom sediments and colloidal form of pollutants; and reduced human activity such as throwing of religious offerings, materials and solid waste; bathing and washing of clothes in the river.

The two-member Yamuna monitoring committee had asked the CPCB and DPCC to test water quality during the lockdown period to ascertain the reasons behind the seemingly cleaner Yamuna.

Seeing both the reports, the committee has observed that one of the major reasons behind the water being cleaner was the availability of fresh water that allowed dilution of pollutants. “As per data obtained from the Delhi Jal Board (D JB), there was a fivefold increase in the water released into the river from Wazirabad during the lockdown, which was less than 1000 cusecs prior to the lockdown. Besides the closure of industries and reduced human activity too has contributed to the better health of the river,” the committee concluded in its report Tuesday.