Mumbai Turns To Sea As Water Demand Outpaces Supply

Countries in the Gulf and Israel have been relying on desalination for decades. For Mumbai, however, the idea has taken more than 15 years to move from a proposal to reality.

By 2029, the city is expected to get up to 400 million litres of drinking water every day from one of India's largest desalination plants. It will make Mumbai only the second Indian city, after Chennai, to turn seawater into drinking water on this scale.

The plan to supply desalinated water to Mumbai was first seriously considered after the severe water shortage of 2009, when the city faced daily water cuts. The civic body had proposed desalination to reduce the city's dependence on the monsoon.

Now, the Brihanmumbai Municipal Corporation (BMC) is building a Rs 4,007-crore desalination plant at Manori, a coastal village near Malad in northwestern Mumbai.

Once both phases are completed, the plant is expected to produce 400 Million Liters per Day (MLD) of drinking water, making it the largest desalination plant in India by capacity.

How Does A Desalination Plant Work?

Desalination essentially involves removing salt and other impurities from seawater to make it suitable for drinking.

• Seawater is drawn into the plant through intake pipes
• It is filtered to remove sand, seaweed and other debris
• The filtered water is pushed through specialised semi-permeable membranes at very high pressure
• The membranes allow water molecules to pass through while blocking dissolved salts and impurities
• Minerals are added back to the treated water to make it suitable for drinking
• The highly concentrated leftover water, known as brine, is discharged back into the sea with safeguards

The cost of desalination membranes has fallen over the years, while improvements in efficiency, durability and flow rates have made the technology more viable.

What Will Mumbai's Desalination Plant Deliver?

The Manori plant will spread across 12 acres.

Israel-based IDE Technologies will construct the desalination system and operate the plant for 20 years. Hyderabad-based GVPR Engineers will undertake the civil infrastructure.

The first phase will have a capacity of 200 MLD. According to a senior civic official, if the second phase is commissioned within the next six months, the total capacity could reach 400 MLD by mid-2030.

The project received coastal zone clearances from state and national authorities in April.

The clearances came with several conditions, including safeguards for brine disposal, protection of the local environment, tunnelling for offshore pipelines and the use of renewable energy for part of the plant's substantial power requirements.

The work will start post-monsoon," said Abhijit Bangar, Additional Municipal Commissioner, BMC.

Why Mumbai Needs More Water

Mumbai's water supply is under growing pressure as demand continues to outpace availability.

The city draws around 4,100 million litres of water per day from its seven lakes and reservoirs. But the BMC estimates that Mumbai needs around 4,664 MLD every day - leaving a shortfall of nearly 500-600 MLD.

The gap becomes even more critical when the monsoon is delayed or rainfall is below normal. Mumbai remains heavily dependent on the rains to replenish its reservoirs, making the city vulnerable to water shortages during a weak monsoon.

This year, reservoir levels fell to around 23.5 per cent of the city's annual requirement, prompting the BMC to impose a 10 per cent water cut across Mumbai. The delayed arrival of the monsoon further heightened concerns over a possible shortage before the rains eventually brought relief.

With the city's population density and commercial activity continuing to grow, water demand is only expected to rise.