Ultrafiltration – A Membrane Filtration Technology

Ultrafiltration (UF) is used to remove essentially all colloidal particles (0.001 to 1.0 microns) from water and some of the largest dissolved contaminants. The pore size in a UF membrane is mainly responsible for determining the type and size of contaminants removed. In general, membrane pores have size ranging from 0.005 to 0.1 micron. UF membrane manufacturers classify each UF product as having a specific molecular weight cutoff (MWC), which is a rough measurement of the size of contaminants removed by a given UF membrane. A 100,000 MWC UF membrane means that when water containing a given standard compound with a molecular weight of around 100,000 daltons is fed to the UF unit, nearly all of the compound will not pass through the membrane.

Ultrafiltration is used in:

• Laboratory grade water purification
• Wastewater treatment
• Drinking water treatment
• Paint Recovery in the automotive industry
• Desalting and solvent-exchange of proteins
• Dialysis and other blood treatments

Substances with a molecular weight of 100,000 daltons have a size of about 0.05 microns to about 0.08 microns in diameter. UF membranes are used where essentially all colloidal particles (including most pathogenic organisms) must be removed, but most of the dissolved solids may pass through the membrane without causing problems downstream or in the finished water. UF will remove most turbidity from water.