Over 700 megaliters of untreated sewage discharged daily into 4 Mumbai rivers

A total of 747 megaliters of untreated sewage is released into four rivers in Mumbai each day, according to a civil appeal petition filed by the Municipal Corporation of Greater Mumbai (MCGM) in the Supreme Court

A total of 747 megaliters of untreated sewage is released into four rivers in Mumbai each day, according to a civil appeal petition filed by the Municipal Corporation of Greater Mumbai (MCGM) in the Supreme Court. These include the Mithi River, which receives the highest quantum of dry weather flow (DWF) at 285 ML per day, followed by the Poisar river (67 MLD), Dahisar river (56 MLD) and the Oshiwara/Walbut river (17 MLD). A single megaliter comprises 10 lakh litres.

Over 700 megaliters of untreated sewage discharged daily into 4 Mumbai rivers

Brihanmumbai Municipal Corporation (BMC) officials said that tenders for infra works, which will divert sewage away from these water bodies and into the municipal treatment and disposal system, are close to being awarded. Broadly, they involve laying down new sewer lines, building retaining walls, constructing small capacity sewage treatment plants and installing drainage interceptors at strategic locations. However, the commissioning of these works is still some time away.

“As per the instructions of the National Green Tribunal, we have already floated the tenders. Financial packages have also been opened, and we are in fact in the final process of awarding the work to appropriate contractors. But the work, being undertaken as part of the Municipal Sewerage Improvement Program, is expected to be finished only in about three to four years,” said P Velarasu, additional municipal commissioner, Mumbai.

A review of the MCGM’s submission to the Supreme Court (which challenges an NGT order from October last year, which penalised the former for repeatedly polluting city rivers, creek and drains), however, reveals that the planned interventions may not be sufficient to fix the problem.

“On completion of the river rejuvenation works, major DWF approximately 426 MLD will be anticipated and diverted into the existing municipal sewer lines/STPs,” stated the MCGM’s petition, a copy of which is with HT. This still leaves nearly 321 MLD of balance for which the corporation does not seem to have a clear plan of action, as per available documents.

“This is a glaring problem which the MCGM has not even acknowledged before the apex court,” said Stalin D, director of NGO Vanashakti, whose petition in the NGT led to its October 2020 order. When asked to clarify the MCGM’s strategy for the balance wastewater, Velarasu said, “We will aim to divert as much untreated sewage as possible, as well as reduce the quantum of DWF being generated.”

Meanwhile, the MCGM has proposed to carry out a range of infra works along the Mithi River in four packages. In package one, which runs from Filter pada to the WSSD garage in Tilak Nagar, an 8MLD STP is being built for the treatment of wastewater to meet revised effluent standards, as prescribed by the NGT.

“The work commenced from 27.11.2018 and was

likely to be completed within the period of 24 months. However, due to the present pandemic, the same is delayed... Due to the revision of the effluent norms, the project extended further by 14 months and is scheduled to be completed by 31.12.2021,” the MCGM told the apex court.

Fresh sewer lines, 1.65 kilometres in length, are also being built to channel DWF to the upcoming STP. “Also, the construction of... 24 MLD influent pumping station is in progress. The physical progress of work is till date 70%,” the MCGM’s civil appeal stated.

In package two (from WSSD garage to CTS Bridge) works are further divided into four different tenders. They include building an 8-kilometre-long sewer, installing 102 drainage interceptors, building a retaining wall of about 3 kilometres, and a service road of about 9 kilometres. Though the work order for these has been issued, the MCGM has not specified the degrees of progress achieved as on date. “Time period for package-II works is 24 months (excluding monsoon),” the corporation submitted.

Work on packages three and four are yet to commence. Package three (from CTS bridge to Mahim Causeway and Vakola nalla) involve the construction of fresh sewers (8km), retaining wall (also 8km) and service roads (7kms), in addition to the installation of more drainage interceptors, gate pumps, sewage pumping stations, and “beautification” of the riverfront. It is unclear whether tenders for the same have been awarded, and if so, when. The specified time period for this work is at least 36 months.

Package four, finally, comprises the construction of a 6.5kms tunnel to divert 168MLD of intercepted DWF (from Bapat nalla and Safed Pool nalla) to a proposed STP at Dharavi, which will be commissioned only in 2026. Tenders are invited. The contract period for the work is four years from the date of the award.

Similar interventions have been proposed along the Poisar, Dahisar and Oshiwara rivers. In all, about 17.5kms of fresh sewer lines, 16.5kms of stormwater drains, 16 drainage interceptors and 17 small capacity sewage treatment plants will be built over the next four years. Key locations for the installation of STPs include Sukurwadi and Indira Nagar along the Dahisar river; Kranti Nagar, Gokul Nagar. Durga Nagar, Poisar Subway and Sanjay Nagar along the Poisar river; and near the Hindu cemetery in Aarey Colony, which is aimed at tackling a significant quantity of wastewater that is discharged from the dairy industry there.

In all, the corporation has received 10 bids from contractors. The BMC’s tendering process, their civil appeal shows, has been considerably delayed due to the pandemic. Tenders that were invited in April and May last year are yet to be awarded for works on the three smaller rivers.