osmosis is the natural process where water moves from a less saline solution to a more saline solution across a semi-permeable membrane. It is the process used by plants to take water from the ground through their roots.Therefore a reverse osmosis (RO) process will involve water moving from saline solution (sea water) to a less saline solution a more across a semi-permeable membrane (Figure 3.26). The great advantage of the RO plant is that it produces a substantial amount of water that is closer to the quality of drinking water than it is to the quality of feed water with the flash evaporators the water produced is distilled water which means that the water needs separate p before it is suitable as drinking water. This usually means passing the water over a charcoal bed.