Fourteen of the 37 sewage treatment plants (STPs) in Delhi are either non-operational (undergoing rehabilitation) or do not meet the water treatment parameters set by the Central Pollution Control Board (CPCB), the February report on STP functioning shows.
Mehrauli and Vasant Kunj STP fare worst with violations in all four parameters, including faecal coliform, biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS), while the units at Kapashera and Molarband are undergoing repair and upgradation.
Several STPs, which are a primary tool for cleaning up the Yamuna, are also unable to meet the standards.
According to the latest report of the Delhi Pollution Control Committee (DPCC) announced on March 6, the STPs which failed to meet the criterion include Delhi Gate phase 1 and 2; Sen Nursing Home Phase 1 and 2; Okhla (old); Okhla (new) Yamuna Vihar-3; Yamuna Vihar Phase-1; Vasant Kunj1 and 2, Ghitorni; Mehrauli; Rithala Phase-2 and Keshopur-1.
The faecal coliform level was 24,000most probable number (MPN)/100ml at Mehrauli STP–104 times that the prescribed limit of 230 units. It was 18,000 units at Ghitorni and 15,000 units at Vasant Kunj.
Faecal coliform levels indicate sewage contamination, with safe recreational water generally requiring less than 500 MPN/100 mL and drinking water requiring 0/100 mL.
The number of STPs failing to meet the parameters has increased, with nine such plants flagged by the DPCC in its September and October reports, 12 in December and 14 in February.
The report, dated March 6, is part of the monthly assessment report for STPs, Common Effluent Treatment Plants (CETPs), river and drains. The DPCC collects and analyses samples of STPs every month. No sample could be taken from Kapashera and Molarband STPs as there was no flow during inspection.
According to the parameters, the TSS and BOD levels should be less than 10mg/L. Six STPs —Yamuna Vihar ph-3, Yamuna Vihar, Vasant Kunj1,2 and Ghitorni and Mehrauli — failed to meet these standards, the report shows.
DJB spokesperson did not respond to HT’s request for a comment. However, an official said several of DJB plants are very old and the CPCB norms have become more tough over the years. “DJB is undertaking a phased action plan to upgrade the old STPs and nine more plants will be revamped under the project,” official said.
STPs are a key component in efforts clean the Yamuna. Delhi estimates that 80% of its water supply (1,000 MGD) comes back as wastewater. Delhi has 37 STPs at 20 locations with an installed capacity to treat764 MGD water in 2025. Experts have earlier raised concerns about the method used in estimating sewage generation, saying it fails to account for groundwater and non-DJB sources.
The government stated that of the 37 STPs found substandard, 28 have been upgraded and work continues on the remaining nine. “Tenders have been completed for 35 decentralised STPs costing ₹2,400 crore, and plans for 12 additional STPs worth ₹7,200 crore are underway. Treatment capacity has been increased from 700 MGD to 814 MGD,” the government said.