Ultrafiltration (UF) is a type of membrane filtration in which hydrostatic pressure forces a liquid against a semipermeable membrane. A semipermeable membrane is a thin layer of material capable of separating substances when a driving force is applied across the membrane. Once considered technology viable only for desalination, membrane filtration is increasingly being used to remove particulates, natural organic material, bacteria and other microorganisms which can impart undesirable color, off-tastes and odors to your water. It also remove contaminants that can react with disinfectants to form disinfection byproducts (DBP) in drinking water, including trihalomethanes, haloacetic acids, bromate, and chlorite.
Ultrafiltration uses hollow fibers of membrane material and the feed water flows either inside the shell, or in the inside space of the tubular-shaped fibers. Suspended and dissolved solids of high molecular weight are retained, while water and low molecular weight solutes pass through the membrane. Ultrafiltration is not fundamentally different from reverse osmosis, microfiltration or nanofiltration, except in terms of the size of the molecules it retains. When strategically combined with other purification technologies in a complete water system, UF is ideal for the removal of colloids, viruses, bacteria, and microorganisms larger than the membrane pore size from water. Its primary removal mechanism is size exclusion, though surface chemistry of the particles or the membrane may affect the purification efficiency. UF can be used as pretreatment for reverse osmosis systems or as a final filtration stage for deionized water.
The primary advantages of ultrafiltration:
- Constant, high quality water production.
- Operational convenience: the procedure adapts automatically to the quality of the raw water.
- Does not use chemicals.
- No risk of dangerous by-products.
- Cost-effective to operate.
- Compact footprint.
- Environmentally-friendly technology.