What are Desalination plants? How can they curb the water crisis ?

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Maharashtra CM Uddhav Thackeray clears Mumbai’s first desalination plant. This plant is said to process 200 million liters of water daily (MLD), with the aim to overcome the water shortage faced by Mumbai in the months of May and June.

Desalination seems to be a perfect solution to water crisis. A desalination plant turns salt water into water that is fit to drink. The most commonly used technology used for the process is reverse osmosis where an external pressure is applied to push solvents from an area of high-solute concentration to an area of low-solute concentration through a membrane. The microscopic pores in the membranes allow water molecules through but leave salt and most other impurities behind, releasing clean water from the other side. Desalination plants are mostly set up in areas that have access to sea water.

Desalination is mostly used by developed countries such as in the Middle East and also has recently paved its way into United States and Australia. In India, the state that has been the pioneer in using this technology is Tamil Nadu, setting up  two desalination plants near Chennai in year of 2010 and then 2013. The two plants supply 100 million liters a day (MLD) each to Chennai. Two more plants are expected to be set up in Chennai. The other states that have proposed these plants are Gujarat, which has announced to set up a 100 MLD RO plant at the Jodiya coast in Jamnagar district. There are also proposals to set up desalination plants in Dwarka, Kutch, Dahej, Somnath, Bhavnagar and Pipavav, which are all coastal areas in Gujarat. Andhra Pradesh, too, has plans of setting up a plant.

According to Bombay Municipal Corporation’s calculated prediction, the population of Mumbai is anticipated to touch 1.72 crore by 2041 and accordingly, the projected water demand would be 6424 MLD by then. Currently, BMC supplies 3850 MLD as against the requirement of 4200 MLD each day. In 2007, a state government-appointed high-level committee had suggested setting up desalination plants in Mumbai, however, over the years the authorities have avoided building the project claiming that the cost is restricting the initiation of the project . However, with the city’s water problems on the rise owing to burgeoning population, Maharashtra Chief Minister Uddhav Thackeray has recently given the Brihanmumbai Municipal Corporation the go-ahead for the project. The project is proposed to be set up on 25 to 30 acres of land at Manori and will have a capacity of 200 MLD. It will take about two and a half to three years to complete and is expected to cost around Rs 1,600 crore. The BMC will be floating tenders for building the project.

Due to the high cost of setting up and running a desalination plant, the Maharashtra government has over the last decade been hesitant in building such a plant. Desalination is an expensive way of generating drinking water as it requires a high amount of energy. The other problem is the disposal of the byproduct — highly concentrated brine — of the desalination process. While in most places brine is pumped back into the sea, there have been rising complaints that it ends up severely damaging the local ecology around the plant.

Desalination is a costly project but access to potable water is quintessential. Tamil Nadu has already taken its steps towards this project. Mumbai has a few models to view in order to create such a plant. This plant can produce more than a million liter of water. Hence, it could be very beneficial but the Government must keep in check the disposal of brine.