In a bid to rejuvenate the Yamuna and restore its environmental flow—the volume of water essential to sustain freshwater ecosystems—the Delhi Jal Board (DJB) is preparing to release over 1,200 million litres per day (MLD) of highly treated wastewater into the river from three advanced sewage treatment plants (STPs). Senior DJB officials said that a separate conveyance system will be developed to transport the treated effluent directly to the river, bypassing open drains that often re-contaminate the water.
According to the rejuvenation plan, treated water from the Coronation Pillar and Yamuna Vihar STPs will be released near Wazirabad through a closed-duct system – a water transportation pipeline system – while the Okhla STP will discharge into the Yamuna via the Abul Fazal drain. Combined, these facilities are expected to add 1,244 MLD of treated water to the Yamuna’s depleted stream.
The 22km stretch of Yamuna in Delhi, from Wazirabad barrage to Okhla Barrage, is less than 2% of the river’s total length, but accounts for nearly 76% of the total pollution in the river, a Yamuna monitoring committee report noted.
The Yamuna’s water quality deteriorates sharply downstream of Wazirabad, as untreated sewage and industrial waste enter the river. Officials hope that the infusion of treated water—with biochemical oxygen demand (BOD) and total suspended solids (TSS) levels below 10mg/L—will dilute the pollution load and improve oxygen levels for aquatic life.
Environmental flow, or e-flow, refers to the minimum water required in a river to maintain its ecological health. Experts and agencies such as the Delhi Pollution Control Committee (DPCC) and the environment department have pegged this requirement for the Yamuna at 23 cubic metres per second (cumecs), but current flows hover around 10 cumecs. A 2023 parliamentary panel had also urged immediate action to improve e-flow to prevent the river’s visible pollution symptoms, such as frothing and foul odours, particularly in areas like Kalindi Kunj and Okhla.
Of the three STP projects, the most ambitious is the Coronation Pillar STP. When it was inaugurated in March 2022, it was tied to an earlier plan inspired by Singapore’s NEWater model to pump treated water upstream to Palla to augment drinking water supply. However, despite receiving approval from the Upper Yamuna Board, the plan was shelved amid objections from Haryana and its concerns over using treated wastewater for drinking purposes.
A DJB official explained that for the first two years, the project remained pending with the Upper Yamuna River Board (UYRB) for approval which was finally granted in 2020 with many riders including further purification of water with the use of advanced technology and microfiltration to 3:3 levels, which is Class C level for clean inland surface water level. Even as the Coronation Pillar plant became operational in 2022, but the process to install another advanced treatment facility could not be executed.
Under the revised strategy, DJB now plans to release a total of 453 MLD of treated water from Coronation Pillar STP downstream of Wazirabad (instead of Palla), requiring the installation of a 2,000mm pipeline and a pumping system. An additional 227 MLD from the upgraded Yamuna Vihar STP will be directed to the same location after building a missing section of the conveyance system. Officials have set a July 2026 deadline for both projects.
The third part of the project includes the release of 563 MLD Okhla Sewage Treatment Plant (STP) — the largest such facility in Asia. Officials said that Okhla water will be added via Abul Fazal area and almost half of the work to set up the conveyance system has been completed. “In the long term, the idea is that instead of releasing treated water via drains which gets contaminates, a closed duct system should be in place to improve e-flow in the river,” the official added. “This is part of a broader effort to restore the Yamuna’s ecological balance.”
The government is hoping that this treated discharge will aid in diluting the chemical and organic load in the river, particularly around the Kalindi Kunj and Okhla areas where foam formation and foul odour are common due to sewage accumulation.
Bhim Singh Rawat, an activist and member of the South Asia Network on Dams, Rivers and People (SANDRP), said while some marginal dilution will take place, the flow seems insufficient. “Quality of treated water will have to be ensured. The water being dumped in the river should be further purified to the inland water level. In the previous case of using it for potable water, strict monitoring would have been ensured as it impacts health of people but the agencies become lax when it comes to the river’s health. In long term, we need to focus on ensuring more fresh water in the river stream. Use highly treated water for secondary uses like washing and horticulture and equal amount of fresh water be allowed to flow in the river. At present, the Yamuna is acting as a large drain. The long-term solution remains ensuring our drains are no longer carrying sewage into the river directly,” said Rawat.