Reverse osmosis is basically the process of forcing a solvent particularly from a region of very high solute concentration via a membrane to a region of very low solute concentration particularly by applying an absolute pressure in excess of the respective osmotic pressure. This is actually the reverse of the osmosis process that is quite normal, which is basically the natural movement of solvent from an area of very low solute concentration, via a membrane, to an area of particularly high solute concentration when absolutely no external pressure is been applied. The membrane here is called semi-permeable, meaning it allows the complete passage of solvent but not exactly of solute.
To illustrate, let us imagine a semi-permeable membrane contains fresh water on one side and an aqueous solution that is concentrated on the other side. If osmosis that is normally taking place, the fresh water will basically cross the membrane to completely dilute the solution that is concentrated. In Commercial RO Plant, the entire pressure is basically exerted on the side with the solution that is concentrated to force the molecules of the water across the membrane to the complete fresh side of the water.
The membranes generally used for systems of reverse osmosis have quite a dense polymer barrier layer particularly in which separation takes usually place. Since Reverse Osmosis does not generally occur quite naturally, it must be created by properly applying pressure to the high solids water basically in order to force it via the membrane, with pressures ranging from 8 – 14 bar for completely fresh and brackish water, and range of 40 – 70 bar for seawater, that has around 24 bar osmotic pressure that is natural which must be overcome. There are a lot of Commercial RO Plant Manufacturer or RO Plant Manufacturer in the market.
Design Considerations for Reverse Osmosis Plant:-
Fluid Systems Reverse Osmosis Plants work on the method of the Cross flow Filtration, which usually takes the feed water and uses a bit percentage of it as a reject or washes stream, removing the solids during the process of filtration.
The product flow of a RO Plant is mainly a function of pressure and temperature. System recovery, that is product divided by feed is quite limited by the characteristics of the water of the feed and can be easily controlled through the use of recycle stream.