Mumbai: The proposed 200 million litres per day (MLD) desalination plant at Manori will draw seawater through a 2.4km intake tunnel at a depth of around 20m.Amid opposition over the potential impact of seawater intake and the discharge of concentrated brine on marine ecosystems and fishing livelihoods, BMC is incorporating advanced engineering measures for marine protection, said additional municipal commissioner Abhijit Bangar. Geotechnical surveys for the project have begun. The intake system will comprise two submerged intake heads, separated by 20-25m in a zigzag pattern to prevent interference. Suction velocity will be restricted to a maximum of 0.15m/s to reduce risks to marine organisms, while a multi-stage screening system will prevent marine life from entering the plant. According to BMC, the intake pipeline will be 2,360m long and the outfall pipeline will extend 2,420m from the landfall point. The brine discharge point will be located 728m north of the intake heads, with more than 15 diffuser units designed to disperse the concentrated saltwater. The civic body said the project will use tunnelling rather than conventional dredging for the first 2,000m of the intake and outfall pipelines. Pipe-jacking method will help avoid disturbing the seabed and the organisms living on it. Mechanical rock-cutting methods will be used instead of blasting. The project’s environmental impact assessment identifies no coral reefs, turtle nesting grounds or seagrass beds at the proposed site, and the nearest mangrove patch is about 505m away, said BMC. It also cited modelling studies to allay concerns over brine discharge. Residual chlorine will have to be neutralised before release to limit its toxicity to sensitive marine organisms. However, the plant’s substantial energy requirement is a key concern. It is expected to require around 45MW of electricity and BMC is planning a 180MW power plant to meet its energy needs. It estimates it will spend around Rs 3,500 crore on solar power over 20 years for the project. Mumbai receives around 4,100 MLD of water from its seven reservoirs. “We are trying to ensure that by 2030, the supply reaches 5,140 MLD. Of this, 600 MLD should come from desalination plants at Gorai and Versova and 440 MLD from the Gargai project,” said Bangar. The Manori project is expected to add 200 MLD once operational in Dec 2029. Another 200 MLD will be ready by Dec 2030.
