The process of separating dissolved salts in a salty water which has been physically treated (the particulate and suspended solids are separated by filtration) from the water by reverse osmosis is called water purification by RO. Reverse Osmosis is the artificial reversal of the natural osmosis process.
To reverse the osmosis mechanism, pressure must be applied to the brine side of the membrane. This pressure is the same with (osmotic pressure + net driving pressure).
All kinds of surface water (lakes, dams, etc.), well water, brackish well water and even sea water, which have been pre-treated with RO systems, can be treated.
Before the RO system, the direct filtration principle is utilized for physical pretreatment. (Mechanical filter, sand filter, cartridge filter, bag filter, etc.)