How Reverse Osmosis Used For The Production Of Fresh Water In Ship

      Reverse osmosis is one of the modern methods used in ships for producing fresh water from sea water.

        If pure water and salt water are separated using a semi permeable membrane as shown in figure then the pure water flows through semi permeable membrane into salt water in
order to maintain the osmotic pressure of the two solutions. This is called osmosis.

 

     The flow direction in osmosis can be reversed by applying pressure in the salt solution. Then the water from the salt solution is forced to flow into pure water through semi permeable membrane. This process continues when the osmotic pressure of salt solution became equal to the applied pressure. The osmotic pressure of normal sea water is 28 bar and it increases as the salt concentration increases. The applied pressure varies with the plant size, generally in the range of 40 – 70 bar. A triplex plunger  pump is used for applying pressure on the salt solution.