Ultra-filtration (UF) utilizes a semipermeable membrane to physically remove suspended particles from water based on particle size and the pore size rating of the UF membrane. Among membrane technologies commonly used, UF is typically one step “tighter” (meaning it has smaller pore size) than micro-filtration.

Ultrafiltration is a type of membrane filtration in which hydrostatic pressure forces a liquid against the semipermeable membrane. The semipermeable membrane is a thin layer of material capable of separating substances when a driving force is applied across it. Suspended solids and solutes of high molecular weight are retained, while water and low molecular weight solutes can pass through the membrane.

Similar to the Reverse Osmosis technology, but differing in terms of the size of the molecules it retains.