Micron filtration is to segregate or separate particulate matter based on the size of the particulate matter. Sewing, screening or surface filtration are also the types of surface filtration based on size of the particulate matter. When the requirement of filtration is less than 0.2 microns, then membrane filtration is also used. In water and waste water treatment, this type of filters are very critical. It acts as a guard filter to further membrane treatment. Micron / membrane filtration also restricts the presence of the organics, bacteria and virus.