New Delhi: Seven out of 37 sewage treatment plants (STPs) in the city did not meet water-related standards, according to a Delhi Pollution Control Committee (DPCC) report based on samples collected in April. The same number of STPs failed to meet the parameters in March as well.
Capacity and Performance of Non-Compliant STPs
The seven non-compliant STPs have a total installed capacity of 62.4 million gallons per day (MGD). The worst performer was Yamuna Vihar Phase III, which failed on five parameters: total suspended solid (TSS), biochemical oxygen demand (BOD), ammonical nitrogen, dissolved phosphate, and faecal coliform. The Ghitorni STP also failed to meet five criteria: TSS, BOD, chemical oxygen demand, dissolved phosphate, and faecal coliform.
Yamuna Vihar Phase I, Mehrauli, Vasant Kunj 1, and Vasant Kunj 2 STPs did not meet four parameters, while Delhi Gate (old) Phase I and II plants failed to meet three criteria. Additionally, of the 37 STPs, two were non-operational or under upgradation.
Concerns Over Upgradation and Tighter Standards
Environmental activist Pankaj Kumar said the seven STPs have not been upgraded for years. “However, over the past few years, the parameters for BOD and TSS have become tighter. Also, tenders have not been released for the upgradation of Yamuna Vihar Phase I and II plants,” he noted.
Though the majority of the STPs in Delhi are now meeting the standards, this is not having any significant impact on the water quality in the Yamuna. “The river continues to have high faecal coliform levels, indicating untreated sewage is flowing into it,” said Kumar.
Role of STPs in River Restoration
STPs play an important role in river restoration by intercepting wastewater, treating it to reduce pollutants, and ensuring that cleaner water is discharged into the river system. The treated water from STPs is also used for various purposes, including horticulture and for rejuvenating lakes. Water from the seven non-compliant STPs is largely used for watering plants on roadsides and parks in the city.
Previous Penalties and Studies
In February, the DPCC told the National Green Tribunal (NGT) that it imposed an environmental compensation of Rs 2.9 crore on 15 STPs for not meeting prescribed standards between July and October 2025. A 2015 study by The Energy and Resources Institute (TERI), commissioned by the Delhi government on froth formation in the Yamuna, stated that the STPs have poor treatment efficiency in reducing BOD, COD, nitrate, and phosphate.
The Yamuna Vihar Phase 1, Phase 2, and Phase 3 STPs were prominent offenders as froth-laden wastewater from them was being directly discharged into the river through a combined outlet downstream of Wazirabad. “This suggests incomplete nutrient removal and the need for process optimisation for efficient BOD and COD removal,” noted the study.
