Reverse osmosis (RO inverted osmosis) or RO is a method of water filter that can filter various big molecules and ions from a solvent by using pressure to the solvent when the solvent is on one side of the selection membrane (filter layer). This kind of methods has been widely used in water purifiers, especially the purifiers to make alkaline water such as the reverse osmosis countertop water filter.
The process causes the solute to settle in the pressure-laden layer so that the pure solvent can flow to the next layer. The selection membrane must be selective or can be sorted out which means it can pass its solvent (or smaller part of the solution) but can not pass solutes such as large molecules and ions. Osmosis is a natural phenomenon occurring within a living cell where the solvent molecule (usually water) flows from a low concentration region to a highly concentrated area through a semi-permeable membrane. This semi-permeable membrane refers to any cell membrane or membrane having a similar structure or portion of the cell membrane. The movement of the solvent continues until a balanced concentration is reached on both sides of the membrane.
Other than that, reverse osmosis can also mean a process of forcing a dissolved from a high soluble concentration region through a membrane to a low solute area using a pressure beyond the osmotic pressure. In easier terms, reverse osmosis works to push a solvent within a filter that captures the solute from one side and allows the solvent income purely from the other side.
To get fresh water from seawater can be done by reverse osmosis, a process of filtering seawater by using pressure flow through a filter membrane. This system is called SWRO or Seawater Reverse Osmosis and is widely used on ships or water supply installations on the coast with seawater raw materials. This process has been used to treat seawater for fresh water, since the early 1970s.