Demineralisation is a chemical-physical treatment process of water intended for the elimination, in whole or in part, of dissolved salts. It can be achieved in two different ways: either by using ion exchange resins or by reverse osmosis.

Water Energy reverse osmosis systems, of the series WO, are based on the phenomenon that occurs when to the surface of a semi-permeable membrane, which separates two solutions with different concentration, is applied a pressure difference versus and higher than osmotic pressure, so that the solvent flow occurs from the more concentrated to the more diluted solution. Reverse osmosis is one of the technologies used to desalinate sea water.