RO Desalination Sea Water Reverse Osmosis (SWRO) is a reverse osmosis desalination membrane process that has been commercially used since the early 1970s. Its first demonstration was done by Sidney Loeb and Srinivasa Sourirajan from UCLA in the California town of Coalinga. Because no heating or phase changes are needed, energy requirements are low in comparison to other processes of desalination.

Pre-treatment
Pre-treatment is important when working with RO and nanofiltration (NF) membranes due to the nature of their spiral wound design. The material is engineered in such a fashion to allow only one way flow through the system. As such the spiral wound design doesn't allow for back pulsing with water or air agitation to scour its surface and remove solids. Since accumulated material can not be removed from the membrane surface systems they are highly susceptible to fouling (loss or production capacity). Therefore, pretreatment is a necessity for any RO or NF system. Pretreatment in SWRO system has 4 major components:

• Screening of Solids
• Screening of Biological's
• Pre filtration pH Adjustment
• Cartridge Filtration
  

High Pressure Pump
The pump supplies the pressure needed to push water through the membrane, even as the membrane rejects the passage of salt through it. Typical pressures for brackish water range from 225 to 375 lbf/in² (1.6 to 2.6 MPa). In the case of seawater, they range from 800 to 1,180 lbf/in² (6 to 8 MPa).

Membrane Assembly
The Membrane Assembly consists of a pressure vessel with a membrane that allows feedwater to be pressed against it. The membrane must be strong enough to withstand whatever pressure is applied against it. RO membranes are made in a variety of configurations, with the two most common configurations being spiral-wound and hollow-fiber.

pH Adjustment
Liming material is used in order to adjust pH at 6.8 to 8.1 to meet the potable water specifications.

Disinfection
Post-treatment consists of stabilizing the water and preparing for distribution. Post Treatment of Drinking water is normally 6.8 (acidic) lower & in case of increasing the Ph indicates the rise in alkalinity which in both lower or higher can cause peptic cancer. Disinfection sometimes called germicidal or bactericidal to kill the bacteria's or life in the products by means of Ultra violet radiation by using of UV lamps directly on the product.

New Developments
General Electric has just developed a new membrane technique to pre-filter ocean water and allow it to be used for R.O. filtration. However, this means the water passes through two membranes against an osmotic gradient. While it is assumed the device will work as advertised this adds another layer of devices needed for filtering ocean waters before final treatment with R.O. membranes thus increasing the cost.