22 out of 35 Delhi sewage treatment plants do not meet standards

Delhi already has a gap of 160 million gallons per day (MGD) in its sewage treatment capacity. While Delhi generates 792MGD of sewage each day, the 35 STPs can only treat a combined total of 632MGD

As many as 22 out of Delhi’s 35 presently operational sewage treatment plants (STPs) are not meeting one or more of the prescribed standards, which may be impacting Yamuna’s water quality, data gathered by the Delhi Pollution Control Committee (DPCC) in May 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. (HT PHOTO)

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 12 MGD 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.

One of Delhi’s largest STPs, the old 40 MGD Nilothi STP, was found not meeting the standards at the outlet for TSS, BOD, and COD, while 15 MGD Rohini STP failed to meet five of the seven criteria including BOD, COD, TSS, ammonical nitrogen and dissolved phosphates. The parameters ranged from 1.5 times to twice the prescribed standards at Rohini, to up to four times the standard at Nilothi.

The only 13 plants currently meeting all standards are the Coronation Pillar Phase III STP, Delhi Gate STPs (both old and new), Sen Nursing Home STP, the new Nilothi STP, the new Pappankalan STP, the Okhla STP (new), the Kondli Phase I, II STP, the Kondli Phase III STP, Kapashera STP, Chilla STP, Akshardham STP, and another 16 MGD Okhla STP.

Delhi already has a gap of 160MGD in its sewage treatment capacity. While Delhi generates 792MGD of sewage each day, the 35 STPs can only treat a combined total of 632MGD. The gap is further widened when one looks at the actual sewage being treated by these plants each day, which is just 547 MGD, as per the latest Delhi Jal Board (DJB) data.

Experts said a large chunk of this treated water was being released back into the Yamuna, meaning pollution could be entering back into the river if the norms were not being met.

“Only a small chunk of the STP water is recycled at present, which is being used to revive lakes and water parks. But, over 50% of this treated water is released back into the river. If parameters are not being met, then we are again polluting the river, albeit at lower levels. Even with plans to increase STP capacity, it is more important that these plants first meet the standards,” said Bhim Singh Rawat, a Yamuna activist, and member of the South Asia Network on Dams, Rivers and People (SANDRP).

Rawat said if such treated water is used to revive lakes, then there is also a possibility of groundwater contamination. “Once the groundwater aquifers are polluted, there is no way of reversing that, so it becomes even more important that the water being used for recycling purposes also meets the standards,” he added.

According to a DJB official, a timeline has been set to increase the STP capacity to 814MGD by December this year and up to 964.5MGD by June 2024. “Not only will the total capacity increase for Delhi, by adding both STPs and decentralised STPs, but by June 2024, all 964.5MGD of STPs will meet the prescribed norms too, as they are being upgraded,” the official said.

During the Budget session in May, finance minister Kailash Gahlot released the 2022-23 economic survey which said the water treatment capacity of the DJB has seen an increase of 13% over the past decade to 943 million gallons per day in 2022 from 906 MGD in 2014.

Delhi water minister Saurabh Bhardwaj said his government was working actively to rehabilitate its STPs, admitting that there cannot be an improvement in the Yamuna’s water quality unless the STPs work better.

“There cannot be an improvement in Yamuna’s pollution, unless the STPs work better, both in terms of quality as well as increased capacity. The reference parameters for STP functioning were changed in the recent past across the country and now most states are rehabilitating STPs to better parameters,” said Bhardwaj, referring to the Union ministry’s notification of October 2017 for revised STP norms.

He said the DJB had already awarded the work of rehabilitation of eleven STPs so far to professional firms, which will bring both BOD and TSS levels below 10mg/l.