Osmosis in reverse is referred to as reverse osmosis. Whereas osmosis happens naturally without the need of energy, reversing the process requires the application of energy to the more saline solution. The majority of dissolved salts, organics, bacteria, and pyrogens flow through a reverse osmosis membrane, but not the majority of dissolved salts, organics, bacteria, and pyrogens. However, in order to desalinate (demineralize or deionize) water, you must apply pressure to the reverse osmosis membrane that is larger than the naturally occurring osmotic pressure. This allows pure water to pass through while keeping the bulk of impurities out.