At least seven sewage treatment plants have failed the prescribed discharge standards for total suspended solids, biochemical oxygen demand and faecal coliform levels in May, the latest DPCC report said.
Testing standards across more than 30 STPs in the national capital, the report provides data for samples collected from both inlet and outlet points.
Flagging the STP at Yamuna Vihar Ph-III for non-compliance, the report said the outlet sample from the facility exceeded the set limits for total suspended solids, biological oxygen demand and faecal coliform.
According to the report by Delhi Pollution Control Committee (DPCC), the treated discharge from the STP showed a faecal coliform level of 7,600 MPN/100 ml, against the permissible level of 230 MPN/100 ml.
The outlet sample at the Yamuna Vihar Ph-III also showed a TSS level of 17 mg/l against the prescribed limit of 10 mg/l and BOD of 28 mg/l against the permissible level of 10 mg/l.
The sample collected from the STP at Mehrauli showed a faecal coliform level of 15,000 MPN/100 ml, along with high TSS, BOD, ammoniacal nitrogen and dissolved phosphate.
The other STPs that have not met the prescribed limits included those at Yamuna Vihar Ph-I, Ghitorni, Coronation Pillar and two in Vasant Kunj.
The STP at Ghitorni showed extremely high level of faecal coliform, reaching up to 17,000 MPN/100 ml, as compared to 16,000 MPN/100 ml in April and 17,000 MPN/100 ml in March.
One of the STPs at Vasant Kunj showed a faecal coliform level of 17,000 MPN/100 ml, while the outlet sample of the other recorded a level of 8,100 MPN/100 ml.
The DPCC conducts periodic monitoring of STPs in Delhi to assess the efficiency of sewage treatment and ensure compliance with environmental norms aimed at reducing pollution in the Yamuna River and other water bodies.
