Filter membranes are used in various industries such as food and beverage, medical and pharmaceutical, municipal water treatment, industrial high purity water, boiler make-up water, seawater desalination, electronic industry ultra-pure water, wastewater treatment and reuse, material concentration and purification, and so on.

The flow rate of water through the membrane is not large, so in order to pass the required amount of water, the monomer area of the membrane device should be large, and many membrane tubes should be installed in a small space. There are five types of membrane: plate and frame type, spiral type, bridge type, tubular type, and hollow fiber type. Plate and frame type membranes should use porous materials, and spiral and bridge type membranes are the same as plate and frame type membranes. The spiral type is coiled, while the bridge type is folded into a small volume and stuffed with a large area of membrane. Tubular membranes also require porous materials, with raw water flowing through the inside of the tube and permeated water flowing out of the tube. This type of membrane is commonly used by customers, as well as externally pressurized tubular membranes. The outer diameter of the hollow system is several hundred um, and the system is surrounded by most fiber tubes. Because the fiber tubes are small, it is not necessary to use high strength fiber tubes. The membrane itself is sufficient to resist the pressure given. There are two types of hollow fiber systems: internal pressure type where raw water passes through the inner side of the hollow system, and external pressure type where external pressure is applied.