Ultrafiltration is a low-pressure membrane process used to separate bacteria, viruses, and high molecular weight compounds colloidal and particulate matters from a feed stream. Ultrafiltration has larger pores and high permeability with less osmotic effects that allows ultrafiltration to operate at relatively lower pressure than nanofiltration and reverse osmosis and is therefore it is least costly to operate.

Ultrafiltration is widely used in industry as pretreatment for other forms of purification such as ion exchange and reverse osmosis, gelatin and protein concentration in the pharmaceutical industry, sugar clarification in the food and beverage industry, cheese and whey concentration, production of ultra pure water, clarification of juice, downstream processing, membrane bioreactors, treatment of bleach plant effluents, and recovery of lignin compounds in the pulp and paper industry. Ultrafiltration can be used to reject virus, bacteria, pyrogens, endotoxins, and particulates but not ionic species.

Hollow fiber configuration is widely used in the ultrafiltration processes. The benefit of this construction is that it allows for backwashing of the membrane when the filtrate or product flow rate has decreased due to accumulation of material on the membrane. The ultrafiltration membrane is capable of removing colloidal materials, fine suspensions, bacteria, virus, suspended material and large dissolved molecular weight organic materials.