The Process of Reverse Osmosis

Osmosis is a natural process. When two liquids with differing concentrations of a solute are separated by a semi-permeable membrane, the liquid tends to move from low to high solute concentrations to reach equilibrium.

Reverse osmosis is a process whereby a solvent of high solute concentration is forced through a semi-permeable membrane to an area of low solute concentration by applying pressure. The feed water pressure must exceed the osmotic pressure in order for the process to work. Thus, low pressure systems work with more dilute solutions, but highly concentrated solutions (such as sea water desalination) require greater pressures to work. The fact of the matter is that reverse osmosis is the most economical technology to purify water to extremely high quality standards.