Reverse osmosis (RO), is the process of forcing a solvent from a region of high solute concentration through a semipermeable membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. This membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as the solvent) to pass freely. The largest and most important application of reverse osmosis is the separation of pure water from seawater and brackish waters; seawater or brackish water is pressurized against one surface of the membrane, causing transport of salt-depleted water across the membrane and emergence of potable drinking water from the low-pressure side.
Factors affecting system and process performance
The performance of a system depends on factors such as membrane type, flow control, feed water quality, temperature and pressure.
Also only part of the water entering the unit is useable; this is called the % recovery. This is affected by the factors listed above.
Systems must be well maintained to ensure good performance with any fouling requiring cleaning maximizing the output of water.
General treatment may be needed and the choice of general treatment would depend on the raw water quality and membrane type, alternatively other filters may be required to remove chlorine from water to protect the life of the membranes.
Where it is needed?
The water which contaminated with more TDS (Total Dissolved Solids) in simply salty water is needed this RO treatment.
RO Treated water is a must for medical use such as labs, dialysis unit etc.