Dysfunctional Delhi STPs pose Yamuna clean-up hurdle | Latest News Delhi

New Delhi

Over half or 19 of Delhi’s 37 sewage treatment plants (STPs) are failing to meet the treatment standards set by the Central Pollution Control Board (CPCB), thereby posing a key challenge to the Yamuna clean-up due to the release of effluents with alarming levels of faecal coliform, experts and stakeholders said, citing the latest data shared by the Delhi Pollution Control Committee (DPCC).

The faecal coliform level in some cases is ten times more than the prescribed limits at the Ghitorni STP, while several units of the Okhla plant were closed, according to a DPCC report dated January 30. Activists have recently flagged that sludge was observed in Yamuna near the Kalindi Kunj barrage.

To be sure, as many as 22 drains empty into the Yamuna, with Najafgarh being the largest of all and solely accounting for around 65% of the discharge.

The report, a monthly assessment for January, reveals that the majority of the STPs do not meet the prescribed norms set for parameters, such as faecal coliform, biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS), among others.

STPs are the primary tools to clean the Yamuna in the city, which has an estimated sewage generation of 3,600 MLD (million litres per day) or 792 MGD (million gallons per day). According to estimates, around 80% of Delhi’s water supply (990 MGD) reverts to wastewater, but 37 STPs at 20 locations have an installed capacity to treat only 667 MGD.

The Delhi Economic Survey underlines that the city’s capacity utilisation is only 565 MGD and the gap in sewage treatment is 227 MGD, which ends up in drains, water bodies and the Yamuna. Experts have pointed out that this estimated sewage generation does not take into account groundwater used by people.

Underperforming plants

According to CPCB standards, the faecal coliform rate should at most be 230 most probable number (MPN)/100 m/l or less, but the levels at Delhi STPs were found to be over 10 times this limit, even after treatment. The highest value, of 2,400 MPN, was recorded at the Ghitorni STP, followed by 1,800 MPN at Keshopur-2, 1,700 MPN at Vasant Kunj -2, Delhi gate and Mehrauli, each, in January, according to the report.

Similarly, plants also exceeded the BOD and TSS levels: TSS of 57mg/L at Ghitroni, 55mg/L at Vasant Kunj-1, 43 mg/L at Molarband and 34 mg/L at Mehrauli; BOD of 34mg/l at Vasant Kunj, 30 mg/l at Ghitorni, and 26 mg/l at Molarband. The standard for BOD is also 10 mg/l.

Last year, the National Green Tribunal (NGT) observed that the Delhi Jal Board (DJB) has built only 17 STPs over the past nine years, and noted that these plants are yet to be completed at 15 drains, which contribute to the high pollution levels in Delhi’s drain network and eventually, the Yamuna. It had sought a response from DJB on the status of Delhi’s STPs and trapping of sewage.

Bhim Singh Rawat, a Yamuna activist and member of the South Asia Network on Dams, Rivers and People (SANDRP), said that the agencies are focusing on symptoms by clearing floating waste while neglecting the root cause. “For years, we have been hearing about STPs not meeting norms but no accountability is fixed. There is no monitoring mechanism which involves people and civil society and violations continue month after month without any repercussion,” he said.

Rawat said the DJB estimates sewage generation without taking into account extracted groundwater. “The real quantum of sewage is much more; STPs are inadequate and underperforming and even the water that gets treated does not meet norms,” Rawat said, calling on the new government to focus on improving STP management.

“Commercial use and ornamental plants which change the natural character of the river floodplain should be avoided,” he said.

The DJB did not respond to requests for comment.