The Brihanmumbai Municipal Corporation has completed the interception and diversion of all 20 sewage outfalls flowing into Powai Lake, ending the direct discharge of sewage into the lake from October 1, the civic body said on September 30.
The sewage flows have been connected to sewage treatment plants through newly laid and existing sewer networks. Eighteen outfalls along Adi Shankaracharya Marg have been diverted to the Bhandup sewage treatment plant through gravity-based systems, while two flows near Perugate on the northern side of the lake have been routed to the Filterpada sewage treatment plant.
The work involved laying 3,056 metres of new sewer lines. The BMC’s Sewerage Projects and Mumbai Sewerage Disposal Project departments had inspected the 20 outfall points before undertaking the interception work. Restoration of trenches dug during construction is currently in progress.
Additional Municipal Commissioner (Projects) Abhijit Bangar inspected the project site on September 30 and reviewed the status of the completed work. He directed officials to finish the remaining associated works within the stipulated timeline and meet the required quality standards.
The civic body said the intervention is part of its efforts to conserve and rejuvenate Powai Lake, where urbanisation has increased the pressure on the water body. Around 18 million litres of sewage was being discharged into the lake daily, according to the BMC. The lake, created in 1891, has a water spread of 223 hectares, a circumference of about 6.6 kilometres and a catchment area of approximately 600 hectares. Its water-holding capacity is around 5,455 million litres, and the water is used for non-potable purposes.
Powai Lake has also seen extensive growth of water hyacinth. The BMC estimates that the quantity of the invasive aquatic plant in the lake was 24,000 metric tonnes. By September 29, two harvesting machines had removed 20,340 metric tonnes, or 85 per cent, of the estimated quantity.
Bangar said sewage had adversely affected the water quality of the lake, which is an ecologically sensitive ecosystem. He attributed the extensive growth of water hyacinth partly to the increase in organic content in the lake water. While harvesting operations are continuing, the BMC said the plant’s natural growth rate has led to repeated regrowth.
The civic body expects the stoppage of sewage inflow to reduce the spread of water hyacinth. However, organic content already present in the lake remains. Bangar said the BMC would undertake a special initiative to improve water quality and study available biological technologies, with suitable measures expected to begin within the next one to two months.
The sewage interception work began in August 2025 and was completed in 13 months. Alongside the diversion project, the BMC is constructing an 8-million-litre-per-day sewage treatment plant at the site of a disused sewage pumping station in Powai.
The new plant is designed to scientifically treat sewage and release 8 million litres of treated water back into Powai Lake. According to the tender schedule, the project is due for completion by December 2028, although the BMC is working to advance completion to May 2027. Once operational, 8 million litres of sewage will be treated at the new facility, while the remaining 8 million litres will be sent to the Bhandup sewage treatment plant.
