Mumbai’s proposed 200 million litres per day desalination plant at Manori will draw seawater through a 2.4-km intake tunnel built about 20 metres below the sea, with the Brihanmumbai Municipal Corporation planning multiple safeguards to limit harm to marine life and fishing activity.
Additional municipal commissioner Abhijit Bangar said the civic body was incorporating advanced engineering measures after concerns were raised about seawater intake and the discharge of concentrated brine. Geotechnical surveys for the project have begun.
The intake system will use two submerged intake heads placed 20 to 25 metres apart in a zigzag configuration. According to the BMC, suction velocity will be limited to a maximum of 0.15 metres per second to reduce the risk of marine organisms being drawn into the system. A multi-stage screening arrangement will also be installed before seawater enters the plant.
The intake pipeline will measure 2,360 metres, while the outfall pipeline will extend 2,420 metres from the landfall point. The brine discharge point is planned 728 metres north of the intake heads and will use more than 15 diffuser units to disperse the concentrated saltwater.
For the first 2,000 metres of both pipelines, the project will use tunnelling instead of conventional dredging. The BMC said pipe-jacking would reduce disturbance to the seabed and organisms living on it. Mechanical rock-cutting methods will be used instead of blasting during construction.
The project’s environmental impact assessment identified no coral reefs, turtle nesting grounds or seagrass beds at the proposed site, according to the civic body. The nearest mangrove patch is about 505 metres away. The BMC also cited modelling studies in support of its assessment of the proposed brine discharge. Residual chlorine will have to be neutralised before release to reduce toxicity to sensitive marine organisms.
Energy consumption remains a major component of the project. The plant is expected to require around 45 megawatts of electricity, while the BMC is planning a 180MW power plant to meet its energy needs. The civic body estimates that it will spend around Rs 3,500 crore on solar power over 20 years for the project.
Mumbai currently receives around 4,100 MLD of water from seven reservoirs. The BMC is targeting supply of 5,140 MLD by 2030, with 600 MLD expected from desalination plants at Gorai and Versova and another 440 MLD from the Gargai project, Bangar said.
The Manori plant is expected to add 200 MLD when it becomes operational in December 2029. A further 200 MLD of desalination capacity is expected to be ready by December 2030.
