Mumbai civic body’s desalination plant project: Why not focus on water conservation, ask experts

Even as the Brihanmumbai Municipal Corporation (BMC) is planning to revive its decade-old proposal to develop a desalination plant in the city to convert seawater into potable water, experts have said that the issue has brought back focus on the need for water conservation by way of harvesting and fixing leakages on Mumbai’s 6,000-km-long pipeline network.

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Ten days ago, Maharashtra environment minister Aaditya Thackeray had given his nod to BMC for preparing a feasibility report to revive the civic body’s plan for a desalination plant.

The plan was first proposed in 2007 to provide an alternative water source to the city, owing to poor rainfall in the catchment areas of the dams that supply water to Mumbai.

Later in 2016-17, the BMC had initiated the process to set up two desalination plants – one in south Mumbai and the other either at suburbs or any other location in the Mumbai Metropolitan Region (MMR) – with a capacity to process 100 million litres per day (MLD) of seawater into potable water. However, the project was put on hold owing to high cost.

Now the BMC has claimed that cost optimisation methods have been introduced for the project and the civic body estimates that a desalination plant for supplying 200 MLD of water can be constructed at an approximate cost of ₹1,800 crore.

Currently, the city gets drinking water from the Bhatsa, Vaitarna, Middle Vaitarna, Modak Sagar, Tulsi, Tansa and Vehar lakes, which are located in Mumbai and the neighbouring Thane and Palghar districts. The civic body supplies 3,850 million litres of water per day (MLD), even as the city needs 4,200 MLD of water.

The BMC has also proposed to construct the Gargai dam in Palghar district, which will supply around 440 MLD of water to the city. The civic body has anticipated the city’s water to surge to 5910 MLD by 2030.

However, experts have stated that as water infrastructure projects such as building dams and introducing desalination plants are expensive means to avail water for the city, emphasis must be laid on water conservation.

Commenting on BMC’s idea to revive the desalination plant project, Rakesh Kumar, director of CSIR-National Environmental Engineering Research Institute (CSIR-NEERI) last week told HT, “These are costlier options, and it brings back to the problem of how we handle our water resources and conservation.”

Rainwater harvesting

Around a decade ago, the civic body made it mandatory for residential and commercial buildings to install a rainwater harvesting system on their terraces. The BMC denies occupancy certificate (OC) to new projects if they did not implement the system.

During its financial budget for 2020-2021, the BMC had also announced that the recycled water will be used for flushing and other non-potable building activities to reduce the load on supply by at least 1,350 MLD. It also made it mandatory for bulk users to install sewage water treatment plants (STPs) in its premises.

However, the execution of the ambitious project on ground has not been encouraging and the ratio of rainwater lost continues to be substantial.

According to BMC’s estimates, between June 2007 and December 2015, at least 5,000 new constructions were approved of which only 1,848 (36%) new buildings have implemented the rainwater harvesting system on their premises.

Janak Daftari, a water conservationist who was associated with the BMC since the inception of the rainwater harvesting system project, said, “The implementation of rainwater harvesting system is poor. Typically, developers install an inadequately-designed tank to harvest water, merely for the sake of getting clearances from the BMC. Actually, it is ineffective for harvesting and provides little relief from water stress. Recycling waste water offers the most cost-effective solution for resolving water shortages in urban areas.”

However, the BMC claims that annually only around 2,000 to 2,500 building proposals get passed, and that it is also the responsibility of citizens to conserve rainwater.

Vinod Chithore, director of BMC’s engineering services, said, “We have made it mandatory for residential buildings to have rainwater harvesting plants on terraces and don’t give permissions to buildings without it. Now if the harvesting is not carried out, we cannot blame the administration alone. Annually more than 2,000 buildings get permissions, and it is also the moral responsibility of citizens to ensure that water is harvested.”

Leakages and unaccounted supply

Experts have also said that the city must tap on non-revenue water. Of the annual supply, around 20% of the water is lost owing to leakages and illegal water connections. The BMC has been working towards digitalising the water supply system of the city which is around 6,000 km long.

“Annually around 28% of the total water supply is not accounted for owing to illegal water connections or wastage due to leakages. This is a major problem with our water supply system and a big failure on part of the BMC to regulate water theft or misuse. We might not need costly projects if we execute basic water conservation methods properly,” Sitaram Shelar, convenor of Pani Haq Samiti, an organisation that works towards universal access to water.

“When it comes to water pipelines and unaccounted water, the department has been consistently working towards ensuring that the city’s water supply chain functions well. But we need to understand that in a city like Mumbai, maintenance of water supply is a challenging task. It is a continuous process in which if we fix one thing, something else may pop out. This process will go on,” said Chithore.