Water Info

The main uses of membrane separation in industry are: a. The filtration of micron and submicron particles b. The removal of molecules and colloids from liquids c. The separation of mixtures of miscible liquids d. The selective separation of ionic species e. The complete removal of all material suspended and dissolved from water The most common membrane procedures are : microfiltration , ultrafiltration , nanofiltration , reverse osmosis ( hyperfiltration) dyalisis , distillation and electrodyalisis. Microfiltration (MF) in combination with ultrafiltration (UF) may solve almost any separation problem involving particulates and material The reverse osmosis (RO) is not restricted to aqueous based solutions but can be applied to organic based solutions. The operating pressure of reverse osmosis is of higher magnitude that microfiltration and ultrafiltration being in the range of 10-100 bar. Nanofiltration is essentially a form of RO , a pressure driven process , which is applied in the area between the separation abilities of RO membranes and UF membranes.

The removal of contaminants from fluid is a major membrane application. A contaminant is defined as matter present in the fluid which must be removed or controlled.Contaminants may be solid , semi-solid or liquid eg SO2, SO4 CO2 H2S acid gases , waste gases , fertilizer , pesticides , solvents , nitrates , phosphates , heavy metals etc. Contaminants may be hard , rigid (will not deform under pressure) soft and liquid.

Reverse Osmosis is a membrane process aimed at removing low molecular solutes ( microrganic salts , small organic molecules ) from a solvent typically water.As the name reverse osmosis implies the process is the reversal of the natural osmosis by the application of a pressure higher than the osmotic pressure on the more concentrated solution in contact with the membrane. To better describe the RO first imagine the process of osmosis . Osmosis occurs when a semi-permeable membrane is used to separate two solutions of equal volume , one water and the other a dilute salt solution. Water is transferred from the water side of the membrane to the dilute solution side until an osmotic equilibrium is reached at which point a hydrostatic pressure , the osmotic pressure has built up on the solute solution side. By applying a pressure higher than the osmotic pressure on the salt solution the flow of water can be reversed.The main objective of the RO process is to remove water or another solvent from a solution in order to produce a more concentrated product and / or a pure water stream.