22 out of 35 sewage treatment plants do not meet standards

Data gathered by the Delhi Pollution Control Committee (DPCC) in May showed that 22 out of the 35 sewage treatment plants (STPs) presently operational in the city do not meet one or more of the prescribed standards, which may impact Yamuna's water quality.

- Jasjeev Gandhiok

This includes some new STPs too, like the Keshopur or Kondli plants, with parameters like total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), and dissolved phosphate levels being routinely breached at a number of the STPs, the data showed.

DPCC gathers monthly water samples from both the inlet and outlet of Delhi's STPs, comparing them to the prescribed standards of the Central Pollution Control Board (CPCB). A total of seven parameters are assessed, which include the PH level, TSS, BOD, COD, oil and grease levels, ammonical nitrogen levels, and dissolved phosphate in the water. In the readings gathered in May, data showed 62% of Delhi's plants did not meet one or more of these criteria.

For instance, at the Coronation Pillar's Phase I and II STP, the 20 million gallons per day (mgd) plant failed to meet the TSS, BOD, and dissolved phosphate criteria of 10 mg/litre, 10 mg/l, and 2 mg/l, respectively. At the new 12mgd Keshopur STP, BOD, COD, and TSS were beyond the prescribed standards, ranging from just over the standard, to two to three times the standard at both plants.