The basic technology of Reverse Osmosis Desalination uses a feed pump to draw in sea water and a high pressure pump to force the feed water through a semi-permeable membrane to remove the salt. This leaves a high salinaity solution (reject water) and a very low salinity solution (fresh drinking water). The reject water is disguarded and the fresh water is diverted to fresh water storage tanks for use.

Reverse Osmosis as a technology derives from reversing the natural process of Osmosis.

Osmosis is a process that occurs when a high salinity solution and a low salinity solution are separated by an organic semi-permeable membrane. A semi-permeable membrane can be penetrated by certain solutions but not others. In osmosis the lower salinity solution will pass through the membrane into the higher salinity solution without any pressure required. This will occur until the solutions are of the same salinity or until the lower salinity solution has expended.

Reverse Osmosis however is not a naturally occurring process.

Using a high pressure pump salt water is forced over a synthetic membrane forcing some of the salt water to be stripped of its salt as it is forced through the membrane to the low pressure side. In a desalination system, excess salt water and salts that cannot penetrate the membrane are rejected from the system as waste and the fresh water that penetrates the membrane is diverted to fresh water tanks.

With a high pressure pump, pressurised sea water is continuously pumped through the pressure vessel against the membrane surface. The sea water will be separated into a low salinity product called the ‘Permeate’ and a high salinity product called the ‘Concentrate’.