Assume a membrane is semipermeable allowing water to pass through while being closed to dissolved salts. Place a membrane between two compartments in a container. Then place a salt solution in one half of the container and pure water in the other half. Now a fundamental scientific principle comes into play. The two different concentrations of liquids will try to reach equilibrium on both sides of the membrane. The only way for this to occur is for the pure water to pass through the membrane to the salt-water side in an attempt to gain equilibrium. This is called osmosis.
Reverse Osmosis is the reversal of the natural flow of osmosis. It is a technology where the goal is not to dilute the salt solution but separate the pure water from the salt and other unwanted contaminants. When the natural osmotic flow is reversed, water from the salt solution is forced through the membrane in the opposite direction by application of pressure and consequently the term REVERSE OSMOSIS has been created.
