DJB wraps up delayed sewer interceptor project

The ISP was meant to cut off the sewage flowing into Yamuna through building trunk drains and treat it before it entered the river, thus boosting the water quality

The Delhi Jal Board’s interceptor sewer project (ISP), aimed at cutting the sewage flowing into Yamuna, has been finally completed after almost a decade of delays. However, the project’s benefits in terms of reducing untreated sewage load is likely to take more time, DJB has said.

The target of the project was tapping sewage flow of 1,100 MLD of untreated sewage which amounts to 242 MGD wastewater. (HT Archive)

Planned in 2006 with an estimated cost of ₹2,454 crore, the ISP was meant to cut off the sewage flowing into Yamuna through building trunk drains and treat it before it entered the river, thus boosting the water quality. The idea was to intercept the smaller sewers by the trunk sewer line running along the large drains and block them from meeting the main drains while diverting the raw sewage to treatment plants.

The Delhi government, in its report to the Centre, has stated that the ISP has been completed and verified through an independent assessment. “Yamuna monitoring committee got an independent assessment of the ISP done through a team comprising RS Tyagi (former member DJB) and HOD of environmental engineering at Delhi Technical University. The team has confirmed that the sewage trapping part of ISP has been completed,” the report, also seen by HT, stated.

“However, treatment of 242 million gallon of sewage per day, as planned, will take place only after the construction and rehabilitation of Rithala and Kondli sewage treatment plants.”

A DJB official said that work on upgradation and rehabilitation of the nine STPs is likely to be completed by December 2027 in phases.

The target of the project was tapping sewage flow of 1,100 MLD of untreated sewage which amounts to 242 MGD wastewater.

In 1994, after the Supreme Court took cognisance of Yamuna’s poor condition, Delhi government had proposed installation of STPs at the mouths of 23 drains discharging sewage into Yamuna. The project was marred at the planning stage due to land availability problems.

In 2005-06, DJB submitted its ISP plan to the Supreme Court and in 2007, the apex court constituted a high-level committee to study the ISP proposal. In 2011, the work was awarded to contractors, and construction began, four years after the plan was approved. Initially, it was estimated to be completed by 2015.

The project was initially estimated to cost around ₹1,200 crore, but its expenditure doubled to over ₹2,454 crore, officials said.

“The scheme was also revised midway as more illegal colonies and drains kept getting added,” an official said.

The plan sees minor drains discharging sewage into the three largest drains being trapped and transferring the contaminated water to the nearest STP. “The three big drains currently carry 242 MGD of sewage into Yamuna. The treated water was then to be channelled to the river through the drains, in the process raising the biological oxygen demand (BOD) level to an acceptable limit,” the official explained.