Working Principle of Membrane Filter

A comparatively short definition of membrane filter could be just like this: membranes filters are something to separate and enrich solutes in solution, and separate colloidal suspensions.

Water flow through the membrane is not very fast, so in order to pass the required amount of water, the monomer area of the membrane device should be large, and many thin membrane tubes should be filled in a small space. In addition, the film with a thickness of less than 100um must have the ability to withstand high pressure, so we should try to make various kinds of pressure-resistant films.

There are five types of the membrane filter: plate-frame type, spiral type, bridge type, tubular type, and hollow fiber type. Porous materials should be used for the plate-and-frame membranes. The spiral type is coiled, and the bridge type is to insert a large area of the membrane into a small folded volume.

Tube membranes also need porous materials. Raw water passes through the inner side of the pipe and seepage flows out of the pipe. This kind of membranes is commonly used for passengers, but also for externally pressurized ones. The outer diameter of the hollow system is several hundred um, and most fiber tubes are packed in the system.