A Obtaining pure water from water containing a salt, as in desalination.
Pure water and the salt water are separated by a semipermeable membrane and the
pressure of the salt water is raised above the osmotic pressure, causing water
from the brine to pass through the membrane into the pure water. This process
requires a pressure of some 25 atmospheres, which makes it difficult to apply
on a large scale.
Pressure 8-9 psi
The membrane assembly consists of a pressure vessel with a membrane that allows
feedwater to be pressed against it. The membrane must be strong enough to
withstand whatever pressure is applied against it. RO membranes are made in a
variety of configurations, with the two most common configurations being
spiral-wound and hollow-fiber.