Reverse Osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. There are various systems and processors used to produce reverse osmosis water. Portable water processors are used and sold for purification in various locations. To work effectively, the water should normally be under 40psi or greater. Portable RO processors can be used by people who live in areas without clean water. As the device is easy to use they are able to filter river or seawater themselves. Travellers on long trips like camping and touring in countries where the water is polluted use RO processors coupled with one or more UV sterilisers. RO systems are now used extensively by marine aquarium enthusiasts to feed their tanks with RO water. In the production of bottled mineral water the water is passed through an RO system to remove pollutants and microorganisms.