Ultrafiltration is a membrane separation technology that uses an asymmetric, microporous membrane and pressure differential to separate substances based on size. With pore sizes much smaller than most bacteria (≥0.2 μm), colloids (≥0.1 μm), and suspended particles (≥5 μm), UF membranes effectively remove these contaminants from liquids while allowing water and small dissolved molecules to pass through.

UF membranes are commonly made of polysulfone (PS), polypropylene (PP), or PVDF hollow fibers, which offer high chemical resistance and long service life. This technology is widely used for the production of mineral water, spring water, and as a pretreatment step for reverse osmosis and other advanced water treatment systems.