In water treatment, membranes are barriers that allow water to pass through but stop unwanted substances from passing through with it. Working much like the cell walls in our bodies, technical membranes filter out salts, impurities, viruses, and other particles from water.
A membrane process is any method that relies on a membrane barrier to filter or remove particles from water. Fluid is passed through the membrane because of the pressure difference between one side of the membrane and the other. Contaminants remain on one side. Although many types of filtering media are used for water treatment — for instance, clay, silt, and sand — one of the properties that distinguishes membranes is their ability to separate smaller substances such as salts and ions from a liquid.
Membranes were first applied to water treatment processes in the 1960s, but in the next decade, they became increasingly used for desalination. Now, the list of membrane processes used in water treatment has lengthened to include:.