Filtration is a method of separation using filter media. Filters are typically able to remove particles as small as about 1 micron, but are unable to remove some dissolved chemicals. Ultrafiltration is a filtration method based on hollow fiber membranes. Ultrafiltration membranes have very tiny pore sizes, usually between 0.01 and 0.1 microns, and are able to filter out even smaller particles and microorganisms, and even viruses and most bacteria.

Ultrafiltration water treatment systems utilize mechanical filtration of hollow fibers or sheet membranes to treat water. These membranes have micropores that filter out extremely small particles and microorganisms in the water, making the water purer.

Ultrafiltration membranes can become contaminated with NOM (non-biodegradable organic matter), which can significantly affect the performance of the ultrafiltration process. NOM pollution will cause the pores of the ultrafiltration membrane to be blocked, reducing the filtration efficiency and increasing the frequency and cost of cleaning and maintenance.