Ultrafiltration belongs to the family of liquid membrane filtration processes that include reverse osmosis, nanofiltration, ultrafiltration and microfiltration. Whereas reverse osmosis and nanofiltration reject inorganic molecules and ions present in water, ultrafiltration removes organic molecules such as proteins and polysaccharides with molecular weights of 10,000 and higher. It is also used for removal of particles such as viruses, bacteria, parasites and suspended solids from a fluid. The ultrafilter pore size can be from 0.005 micron to 0.1 micron, and a specific pore size range is selected for each application as a compromise between filtration efficiency and rates. Ultrafilters used for water filtration fall in the range of 0.01-0.1 microns to achieve high removal efficiency of viruses and bacteria.
