According to structural，the ultrafiltration membrane is divided into a plate-and-frame type (plate type), a hollow fiber type, a nanometer membrane type ultrafiltration membrane, a tube type, a coil type, and the like.
Among them, hollow fiber ultrafiltration membrane is the most mature and advanced form of ultrafiltration technology. The hollow fiber has an outer diameter of 0.4-2.0 mm and an inner diameter of 0.3-1.4 mm. The hollow fiber tube wall is covered with micropores, and the pore diameter is expressed by the molecular weight of the retentate substance, and the molecular weight cut off can be several thousand to several hundreds of thousands. The raw water is pressurized and flows outside or inside the hollow fiber to form an external pressure type and an internal pressure type hollow ultrafiltration membrane. Ultrafiltration is a dynamic filtration process in which the trapped material can be removed with the concentrate without clogging the membrane surface and can be continuously operated for a long period of time.