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 a viable technology only for desalination, membrane processes are
increasingly employed for removal of bacteria and other microorganisms, particulate material,
and natural organic material, which can impart color, tastes, and odors to the water and
react with disinfectants to form disinfection byproducts.
As advancements are made in membrane production and module design, capital and
operating costs continue to decline.
Ultrafiltration uses hollow fibers of membrane material and the feed water flows either inside the shell,
or in the lumen of the fibers. Suspended solids and solutes of high molecular weight are retained,
while water and low molecular weight solutes pass through the membrane.
UF is utilised to remove a variety of contaminants. The proper UF membrane must be selected to
meet the performance requirements.Organic molecules can be rejected well, but the rating of
UF membranes varies in molecular weight cut-offs from 1,000 to 100,000.
Reduction of typical raw water organics is not as effective as Reverse Osmosis.
Pressure drops vary with membrane selection and operating temperature.
Some UF membranes are capable of continuous operation at temperatures up to 90ºC,
to provide excellent microbial control.
UF reduction of Endotoxin (pyrogens) varies from 2 log10 to 4 log10 as a function of membrane selection.
UF has been shown to be capable of consistent production of purified water meeting the USP WFI Endotoxin
limit of 0.25 Eu/ml in typical system applications.
UF produces excellent microbial reduction with typical ratings of 3 log10 to 4 log10 reduction.
UF produces excellent particle reduction and is frequently used in other applications,
such as semiconductor production when particle control is far more critical than purified water.
- UF can remove contaminants, such as Endotoxin and organics.
- UF offers effective operating costs in high particle loading applications.
- Some UF elements can tolerate rigorous sanitisation procedures using steam or ozone.
- The waste stream is generally much less than waste from Reverse Osmosis units.
- Ultrafiltration has low energy requirements.
Typical applications include:
- RO and NF pre-treatment.
- Industrial and municipal wastewater reclamation.
- Ultrapure water production.
- Seawater desalination.
- Ion-exchange pre-treatment.
- Potable water production.
- Industrial wastewater treatment for discharge.
- Resource recovery from industrial waste streams.
- Ground water treatment for industrial or municipal use.
- Surface water treatment for industrial or municipal use.
- Seawater reverse osmosis pre-treatment.
- Industrial water treatment effluent reclamation.
- Municipal or sewage treatment effluent reclamation.
- Reuse (water recycling).