Delhi govt to release treated wastewater into Yamuna to boost water quality

Delhi’s stretch of the Yamuna requires a minimum e-flow of 23 cumecs to remain ecologically functional, as per estimates by expert institutions and parliamentary panels.

In a bid to improve the Yamuna’s water quality, the Delhi government plans to release treated wastewater from the 564 million litres per day (MLD) Okhla sewage treatment plant (STP) — the largest such facility in Asia — to boost the river’s environmental flow (e-flow). The plan aims to add 5.69 cubic metres per second (cumecs) of treated effluent to the river, which currently falls far short of the minimum flow required to sustain its ecological health.

Pollution seen in the Yamuna during pollution season in Delhi. (HT Archive)

Delhi’s stretch of the Yamuna requires a minimum e-flow of 23 cumecs to remain ecologically functional, as per estimates by expert institutions and parliamentary panels. However, the river presently flows at just 10 cumecs. Officials said the additional treated water will offer partial relief to heavily polluted stretches near Okhla and further downstream.

“The additional flow — equivalent to 5.69 cumecs — will be discharged from the Okhla STP outfall into the Yamuna via the canal downstream of the Okhla barrage. This will particularly benefit areas around Okhla where water quality is currently poor,” said a government official.

Environmental flow or e-flow refers to the minimum volume of water that must flow through a river to maintain its ecological balance. In 2023, a parliamentary standing committee on water resources recommended an e-flow of 23 cumecs for the Yamuna. The Delhi Pollution Control Committee (DPCC) and the environment department reiterated this target earlier this year in meetings on river rejuvenation.

The project had been delayed for months due to pending permissions from the Uttar Pradesh Irrigation Department, which controls the Yamuna downstream. The clearance was finally granted on March 1 this year, and the remaining work is expected to be completed by the end of 2025. Officials expect to begin releasing the additional e-flow by February 2026.

The government hopes that the treated discharge will dilute chemical and organic pollutants in the river, particularly in the Kalindi Kunj and Okhla zones, where frothing and foul odour are common due to high sewage accumulation.

The Okhla STP was made fully operational in April this year. It is a joint initiative of the National Mission for Clean Ganga (NMCG) and the DJB, with construction having started in 2017.

However, experts warned that the move, while helpful, is far from sufficient. Bhim Singh Rawat, a Yamuna activist and member of the South Asia Network on Dams, Rivers and People (SANDRP), said, “At present, the Yamuna is acting like a giant drain. Adding cleaner water via the Abul Fazal drain may cause some dilution, but it won’t be enough. The real solution is to stop sewage discharge into the river entirely.”

Rawat also stressed the need for stringent quality control at the Okhla plant. “If the treated water doesn’t meet high standards, it won’t make a meaningful difference. We need a clear policy for using treated water in other parts of the city — for non-potable purposes — so it doesn’t all go to waste.”