9 of 37 STPs in Delhi failing norms or not working: DPCC

The report for March, dated April 13, showed that while seven STPs did not meet prescribed standards, another two were non-operational and undergoing rehabilitation

Nine out of 37 sewage treatment plants (STPs) in Delhi are either non-operational or do not meet the water treatment parameters set by the Central Pollution Control Board (CPCB), according to the latest monthly report on STP functioning in the Capital.

Experts flagged fluctuations in the quality of water being released into the Yamuna by STPs.

The report for March, dated April 13, showed that while seven STPs did not meet prescribed standards, another two were non-operational and undergoing rehabilitation.

Though an improvement from February, when 14 STPs were either non-operational or not meeting parameters, experts raised concerns that the improved STP data does not tally with Yamuna’s water quality, which deteriorated in March.

The monthly Yamuna water quality report, also published by DPCC, for March showed faecal coliform peaking at 400,000 units, compared to 110,000 units in February. Biological oxygen demand (BOD) peaked at 60 mg/l in March – 20 times the safe limit of 3 mg/l – compared to 36 mg/l in February.

The Ghitorni, Vasant Kunj-I, and Delhi Gate (Old) STPs fared the worst, failing on all four parameters: faecal coliform, BOD, chemical oxygen demand (COD), and total suspended solids (TSS). Vasant Kunj-II, Yamuna Vihar Ph-I, Yamuna Vihar Ph-III, and Mehrauli STPs failed on three parameters – TSS, BOD and faecal coliform.

Faecal coliform – an indication of sewage contamination – peaked at 28,000 most probably number (MPN) units per 100ml at Mehrauli – 121 times the standard of 230 MPN units per 100ml. This was followed by Ghitorni, which recorded 17,000 units.

STPs are a primarily tool for cleaning up the river – preventing sewage by treating it and releasing cleaner water back into the river. According to the standards, TSS and BOD should both be under 10 mg/l.

Experts flagged fluctuations in the quality of water being released into the Yamuna by STPs. They said that though the improvement reflects positively on paper, the river was still more polluted March than it was in February.

“On paper, this is an improvement but if one looks at Yamuna’s data, there was a clear deterioration in March. This does not tally with the improvement in STP data. In February, when we had 14 STPs not meeting norms, the Yamuna was much cleaner,” said Pankaj Kumar, a Yamuna activist.

In February, DPCC had informed the National Green Tribunal that it imposed an environmental compensation of ₹2.89 crore on 15 STPs for failing to meet prescribed standards between July and October 2025.

More recently, on April 17, HT had reported how after two decades and more than ₹2,454 crore poured into the Delhi Jal Board’s (DJB) flagship Interceptor Sewage Project (ISP), a significant chunk of that investment has likely gone down the drain. An inspection ordered by the Centre found that the project stopped only around 60% of the sewage volume DJB claimed to have halted from entering the Yamuna. While DJB claimed to have tapped and diverted 238 million gallons per day of sewage, only around 142 MGD had actually been halted, with over 117 MGD of untreated waste still flowing into the river from drains the board had declared “completed.”