Membrane FiltrationMembrane filtration is a rapidly expanding field in water treatment. There are many different types of filters available in a wide range of pore sizes and configurations. In addition, there are numerous possible applications for membrane filtration ranging from the removal of relatively large particulate material to the removal of dissolved compounds.DefinitionAmembraneis a semi-permeable thin layer of material capable of separating contaminants as a function of their physical/chemical characteristics.A more common way to express this is: A membrane is a thin layer of material that will only allow certain compounds to pass through it. Which material will pass through the membrane is determined by the size and the chemical characteristics of the membrane and the material being filtered.Comparison to Conventional TreatmentConventional Filtration DesignConventional filtration relies on a number of mechanisms to remove particulate and dissolved material from the filter influent; these mechanisms are adsorption, settling, and straining.These mechanisms are illustrated in the following graphic.