Water discharged by STPs in Delhi falls short of national norms, shows DPCC analysis
Despite the Delhi government’s claim that sewage treatment plants are operating at over 88 per cent capacity, DPCC data shows treated wastewater from most drains continues to exceed national pollution norms.
The Delhi government maintains that its sewage treatment plants (STPs) are operating at more than 88% capacity, suggesting most wastewater is being processed. Yet, analysis by the Delhi Pollution Control Committee (DPCC) paints a different picture: water discharged from the city’s plants continues to fall short of national quality norms. Of 17 drains carrying treated effluent, 16 showed pollutant levels above permissible limits.
Tests revealed breaches across key parameters — pH, total suspended solids (TSS), chemical oxygen demand (COD), and biological oxygen demand (BOD). Elevated BOD, for example, reflects organic waste that depletes dissolved oxygen, threatening aquatic life. DPCC’s October report recorded severe exceedances, with BOD reaching 145 mg/l in the Sahibabad drain, 110 mg/l in Shahdara, and 60 mg/l in Najafgarh. COD levels also overshot safe limits, peaking at 296 mg/l in Shahdara and 152 mg/l in Najafgarh, compared with 50 mg/l standards.
“Such high values, especially in a non-lean month, indicate that large amounts of untreated or poorly treated sewage are entering these drains, carrying organic waste and chemicals that the treatment system should have removed,” said Pankaj Kumar, a Delhi-based Yamuna activist.
In an affidavit to the National Green Tribunal, DPCC said that 22 drains ultimately feed the Yamuna within Delhi. Ten drains have been fully tapped and two partially, while Najafgarh and Shahdara — carrying roughly 800 million gallons per day (MGD) — are technically difficult to tap fully and are being partially addressed through the Interceptor Sewer Project. Eight drains remain untapped, with flows still needing diversion to sewers or treatment plants.
The DPCC has also said that discharge of treated, partially treated, and untreated sewage as the primary cause of pollution, particularly along the 22-km stretch between Wazirabad barrage and Asgharpur village, where the Yamuna receives nearly all of Delhi’s sewage with minimal dilution. The current treatment shortfall is estimated at 88 MGD, largely due to unauthorised colonies lacking complete sewer networks, according to DPCC.
To address existing shortfalls and prepare for future volumes, according to senior DJB officials, four key measures are being taken including rehabilitating three STPs mainly Kondli Phase II, Rithala Phase I and Yamuna Vihar Phase II, where work has been completed, upgrading and expanding eight more STPs which are at different stages of execution, constructing three new STPs at Okhla, Sonia Vihar and Delhi Gate, and building 40 decentralised treatment units, including 26 DSTPs across the city and 14 in the Najafgarh drainage zone. In addition, the DJB has floated a tender for a long-term Sewerage Improvement Scheme 2043, covering surveys, DPRs, gap analysis and a citywide sewerage master plan.
As per an internal DJB document, senior DJB officials have recently said that, “there is… requirement in future for installation of additional STPs to meet the increasing sewage generation due to population growth, urban expansion, and redevelopment of residential and commercial areas,” senior DJB officials have said.
Sophiya Mathew is a Correspondent at The Indian Express, based in New Delhi. She joined the Delhi bureau in 2024, and has specialization in Integrated Multimedia Journalism from the Asian College of Journalism (ACJ), Chennai.
Professional Background
Core Beats: Her reporting is primarily focused on the Environment and Education.
Specialization: She has gained recognition for her ground-level reporting on the Yamuna floodplains and the socio-economic challenges faced by those living on its banks. She also focuses on the disparities in Delhi's education system, ranging from elite private schools to government institutions and refugee education.
Recent Notable Articles (December 2025)
Her recent work has been heavily centered on Delhi's severe winter pollution crisis and the government's regulatory responses:
1. The Air Pollution Crisis
"A tale of two cities: Delhi govt schools choke in bad air, private classrooms set up air filters" (Dec 20, 2025): A high-impact feature contrasting the "Clean Air Bubbles" in elite schools with the reality of government school students who are exposed to an equivalent of 17 cigarettes a day due to outdoor exposure.
"Delhi sees season's worst air day, second worst December AQI in nearly a decade" (Dec 15, 2025): An analytical report on the meteorological patterns trapping pollutants in the NCR.
"Delhi bans non-BS VI vehicles from outside: Why curbing vehicular pollution is key" (Dec 17, 2025): Explaining the science behind targeting specific vehicle vintages to lower particulate matter.
2. Enforcement & Regulations
"No fuel at pumps in Delhi without valid PUC certificate from December 18" (Dec 17, 2025): Breaking the news on the environment ministry's strict "No PUC, No Fuel" policy.
3. Education Policy
"Law to regulate school fee in Delhi risks becoming procedural, say parents" (Dec 13, 2025): Investigating the loopholes in the new Delhi School Education (Transparency in Fixation and Regulation of Fees) Bill, 2025.
"Monsoon Session: Private school fee regulation Bill cleared after four-hour debate" (Aug 9, 2025): Covering the legislative passage of the controversial fee hike regulation.
Signature Style
Sophiya is known for her observational depth. Her reporting often includes vivid details from school corridors, hospital waitlists, or the banks of the Yamuna to illustrate how policy failures affect the city's most vulnerable residents. She is a frequent expert guest on the 3 Things podcast, where she explains the complexities of Delhi’s environmental laws.
X (Twitter): @SophiyaMathew1 ... Read More
