Ultra Filtration is a membrane filtration procedure similar to RO, using hydrostatic pressure to fore water via a semi-permeable membrane. The pore size of the Ultra Filtration membrane is usually 103-106 Daltons. Ultra Filtration in India is a variety of membrane filtration in which hydrostatic pressure forces a liquid against a semi-permeable membrane. Suspended solids as well as solutes of high molecular weight are retained while water and low molecular weight solutes pass via the membrane. It is not basically different from RO, microfiltration, or nano-filtration except in terms of the size of the molecules it actually retains.