Ultrafiltration (UF) is the process of separating extremely small particles and dissolved molecules from fluids. The main base of separation is molecular size. Particles ranging from 1,000 to 1,000,000 of molecular weight are retained by ultrafiltration membranes.
While some dead-end cartridges are used, mainly in the pharmaceutical industry, ultrafiltration separations are carried out mainly in cross-flow mode. The systems operate at a relatively low transmembrane pressure, from 0.7 to 10.3 bar (10 to 150 psig).

The ultrafiltration membrane systems reduce operation and labor costs. The capacity to retain a high concentration minimizes disposal costs in a wide range of industries. In an attempt to preserve water, the use of ultrafiltration membrane systems to recycle water can provide zero disposal capabilities. The initial installation cost is low and a minimum of pretreatment chemicals is needed compared with conventional systems.