Use of Reverse osmosis in water purification
Reverse osmosis is extensively used in the desalination of sea water.
A porous film of cellulose acetate is used as a membrane which is permeable to water but impermeable to impurities and ions is placed over a support.
Pressure larger than the osmotic pressure is applied on the sea water solution which allows the passing out of the pure water holding back the bulk of contaminants through the membrane made of polymer.
The measure of pressure required relies upon the salt grouping of the food water. Greater concentration of feed water requires more pressure to defeat the osmotic pressure.
As the water enters the RO membrane under great pressure the water molecules pass through the semi-permeable membrane.
The membrane is impermeable to salts and other contaminants and hence is not allowed to pass through it.
These leftover contaminated water is then discharged through the reject stream and finally drained out or is fed back into the feed water supply. This water will again undergo same procedure and will be purified in some way.
