UNCLEAR VERDICT

WHILE SOCIAL media platforms are flooded with videos that suggest the lockdown has drastically cleaned up the Ganga, the truth is that not much has changed. This becomes clear in the recently released report by the Central Pollution Control Board (CPCB) that analyses the water quality in the Ganga before (March 15-21) and during the lockdown (March 22-April 15). In contrast, the water quality in the Yamuna improved substantially during the lockdown, though the river remained polluted.

The report on the Ganga, which only shows overall trends and does not share the actual data, found that the biological oxygen demand (BOD) and chemical oxygen demand

(COD) levels of the river remained almost unchanged throughout the study period, indicating that wastewater flow did not drop during the lockdown (see ‘Little to show’ on p21). There has been marginal increase in dissolved oxygen (DO) and decrease in nitrates “due to the absence of industrial wastewater discharge, agricultural runoff and increased freshwater flow,” says the report. CPCB analysed water quality data from 18 realtime monitoring stations starting from Bijnor in Uttar Pradesh to Howrah in West Bengal. The agency also studied samples from 18 sites along the tributaries (9) and drains (9) of the Ganga. The tributaries showed a trend similar to that of the main stem of the river, while the wastewater quality in the drains remained unchanged during the lockdown.

The findings might be disheartening, but are on the expected lines. The 97 towns near the Ganga generate around 3,500 million litres of wastewater per day (MLD) and just that led to suspended solids and turbidity in the river. Of the 15 sites where DO levels were recorded throughout the study period, four sites in West Bengal saw a significant positive variation in the remaining three weeks of the lockdown, when compared to the pre-lockdown period. In the 11 sites in Uttar Pradesh, non-significant positive variations were found in the last three weeks.

Ujjwawl Mukherjee, former senior scientist with the pollution control board, says the high levels of DO in West Bengal only indicate eutrophication in the water and should not be confused as cleaner water.

has to check DO levels for 24 hours to get the real picture,” he adds. West Bengal scientists did not comment on this claim.

The overall BOD levels of samples collected from 17 sites remained high during the lockdown, especially in West Bengal—Behrampore, Behrampore downstream and Sirampur. Barring Deoriaghat site in Kanpur, where BOD levels peaked to 15 milligrams per litre (mg/l) in the third week of the lockdown, sites in Uttar Pradesh recorded little BOD variation before and during the lockdown. “BOD value ranged between 1.13 mg/l and

5.56 mg/l during the lockdown period, more or less similar to prelockdown range of 1.37 mg/l to 5.58 mg/l,” says the report.

Also, the sites did not record significant reduction in COD levels during the lockdown. While some of the stations in the upper stretches of the river recorded marginal decrease through the four weeks, several sites downstream had higher COD levels than before the lockdown. Ammoniacal Nitrogen levels also remained high in 11 of the 15 sites, which shows “increased discharge of untreated and partially treated sewage into the river,” admits the report. The nitrate levels came down (varying from 2 to 66 per cent) in most sites due to the shutting down of industrial and agricultural activities.

“The closing of industrial units improved the DO levels and closing of the ghats reduced the organic load. As a result, a marked difference can be seen in the colour of the river in Varanasi,” says Malika Singh, regional officer, Uttar Pradesh state pollution control board at Varanasi. He adds that the two monitoring sites in the city had cleaner water this April over the last year.