Nano filtration is a pressure driven separation process. It is much the same as reverse osmosis. The key difference is the high degree of removal of monovalent ions, multivalent salts and low molecular weight organics in the reject. Reverse osmosis removes the monovalent ions at 98-99% level at 200 psi. Nano filtration membranes removal of monovalent ions varies between 50% to 90% depending on the material and manufacture of the membrane. There is variety of Nano filtration membranes available. Each type is particularly suited to a certain application and may not be acceptable to a different application.