After the state government’s decision to carry out a feasibility study to decide whether desalinating sea water is an option to fight the water woes of Mumbai, experts say the membrane technology using is the best possible method that can be used to desalinate sea water.
The technology, using reverse osmosis, is the best possible option to convert sea water into drinking water. It works by using pressure to force a solution through a membrane, retaining the solute on one side and allowing the pure solvent to pass to the other.
This is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low-solute concentration, through a membrane, to an area of high solute concentration when no external pressure is applied. Reverse osmosis is similar to the technique used in dialysis, which is used by people with kidney failure. The kidneys filter the blood, removing waste products such as urea and water, which is then excreted as urine.
According to Dr Sunil Bhagwat from University Institute of Chemical Technology, countries in West Asia use such kind of technology to tackle water shortages.
“It is more feasible to use desalinated sea water for purposes other than drinking and bathing etc. Unfortunately, Mumbai has common connections for all the needs of the water and we can not bifurcate the use of water,” Dr Bhagwat said.
Similar to Chennai, the Brihanmumbai Municipal Corporation (BMC) also had a proposal to desalinate sea water a few years back. But it could not materialise due to high costs.
According to DT Dange, a senior official working with Mumbai Metropolitan Regional Development Authority’s hydraulic department, there is a lot of difference between normal filtration and desalination. “In BMC, the filtration is done using methods such as chlorination which are basic. But for desalination, we need much more complex techniques,” said Dange.
Even if the government is successful in desalinating sea water, it may not be of great help because Mumbai does not have separate water lines for drinking water and for other purposes, say experts.
