Osmosis
Osmosis is a natural process in which water flows through a semipermeable membrane from a region of lower solute concentration to a region of higher concentration. This process serves to equalize the concentrations on both sides of the membrane.
In water treatment, osmosis is used in reverse osmosis technology to remove impurities such as salts, bacteria and other dissolved substances from the water. Water is pressed through a membrane that is only permeable to water molecules, while pollutants are retained. Reverse osmosis thus ensures highly pure drinking water.