10.9 million litres of sewage flowing directly into Powai Lake daily, finds NGT-appointed panel
The committee has also sought an action plan from the civic body to connect the areas not covered by sewers to a sewerage network and their connectivity to STP.
4 min read
Powai lake. (File photo)The eight-member committee constituted by the National Green Tribunal (NGT) to draft a pollution remedial action plan for Powai Lake has noted that 10.9 million litres of sewage per day flow into the lake directly. The sewage directly flows into the lake through 19 culverts and natural drains from the adjoining areas including a slum, National Institute of Electrical Engineering (NITE) and Indian Institute of Technology (IIT)-B campuses.
The committee, which will initially meet every month for a year, has asked the Mumbai civic body to provide the zonal map of the sewerage network of the areas around Powai Lake, including the area in sq km covered with and without sewerage network ward-wise/area-wise and the status of its connectivity to a Sewage Treatment Plant (STP) for treatment, if any. The committee has also sought an action plan from the civic body to connect the areas not covered by sewers to a sewerage network and their connectivity to STP.
The committee has also asked the Brihanmumbai Municipal Corporation (BMC) to provide real-time updates of levels of dissolved oxygen in the Powai Lake on its website. Six real-time stations are monitoring dissolved oxygen at the site. The monitors were installed in 2019 after the then Union Environment Ministry told the Lok Sabha in a written statement that industrial effluents and household sewage flowing into the Powai Lake had raised its pollution levels eight times above safe standards.
In May 2017, the level of biochemical oxygen demand, which indicates the concentration of oxygen required for survival of aquatic life, had reached 150 milligrams per litre (mg/l) as against the accepted standards of 20mg/l.
The committee consists of members from the Ministry of Environment, Forest and Climate Change, the state and central boards of pollution, officials from BMC, the state forest and environment departments and Mumbai Police. It held its second meeting earlier this month.
Observing that the “ground situation is far from satisfactory”, the NGT in its order dated January 12, had constituted an eight-member committee to prepare an action plan covering all aspects, including steps to prevent discharge of sewage or any other effluents in Powai Lake and to monitor water quality to protect fish and other aquatic fauna and distinct sites of the marsh crocodile. The action plan may provide for the mode of execution, monitoring mechanism and budget allocation.
A presentation by BMC Additional Municipal Commissioner P Velrasu pointed out that discharge of untreated sewage from the surrounding areas into Powai Lake through 19 culverts caused the pollution problems and growth of water hyacinth. The committee has also asked BMC to carry out a detailed reconnaissance survey for identification of locations and estimation of the present quantity of sewage flowing into Powai Lake through the existing culverts and natural drains. The last such survey was undertaken in 2016.
The civic body listed the initiatives taken to rejuvenate Powai Lake, which includes installation of a new mobile barge-mounted subsurface aerator in 2019, six real-time monitoring stations for monitoring of dissolved oxygen, four jet fountains, five jet flow aerators and water hyacinth removal using mechanical operation. During its visit this month, the committee found all in working condition.
To reduce the discharge of sewage in the lake, BMC intercepted the sewage coming from Adi Shankaracharya Road and diverted it into the existing sewerage network for treatment at Bhandup STP, comprising of aeration lagoons. However, BMC has not quantified the sewage being diverted to Bhandup STP. Further, officials informed that due to ongoing Metro rail project work on Adi Shankaracharya Road, sewerage header lines were damaged. As a result, the sewage was entering Powai Lake through the culverts meant for the regulation of stormwater.
Recognised as a wetland, Powai Lake is a man-made lake constructed in 1891. The lake is also a habitat for crocodiles. Designated as unfit for drinking in 1893, the water from the lake is used for industrial purposes.
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