RO Desalination is a treatment process for production of fresh, low- salinity potable water from saline water source (seawater or brackish water) via membrane separation. The mineral/salt content of the water is usually measured by the water quality parameter named total dissolved solids (TDS), concentration of which is expressed in milligrams per liter (mg/L), or parts per thousand (ppt). The World Health Organization and the United Sates Environmental Protection Agency (US EPA) under the Safe Drinking Water Act have established a maximum TDS concentration of 500 mg/L as a potable water standard. This TDS level can be used as a classification limit to define potable (fresh) water.

Typically, water of TDS concentration higher than 500 mg/L and lower or equal to 15,000 mg/L (15 ppt) is classified as brackish. Natural water sources such as sea, bay and ocean waters which have TDS concentration higher than 15,000 mg/L are generally classified as seawater.