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Ultrafiltration is a membrane technology that takes place within a membrane porosity range between 0.001 and 0.1 µm. This process is used for the selective removal of suspended matter, particles, large macromolecules, colloidal matter, or microorganisms, but does not remove ions or dissolved matter as reverse osmosis does.
Ultrafiltration membranes remove contaminants through a simple size-exclusion mechanism (sifting or sieving). A pressure difference makes the operation possible. Nominal pore size (pore diameter expressed in microns) or molecular weight cut-off (molecular weight of a solute that is over 90% retained, measured in Daltons) are commonly used to characterize ultrafiltration membranes.

It should be noted that different membrane materials with similar molecular cutoff weights may have different separation efficiencies. Regularity of the pore size distribution and the membrane chemistry itself also play an important role in separation.

Main types of ultrafiltration:

  • Hollow fiber
  • Tubular
  • Ceramic

Membranes can be found commercially in flat, tubular, spiral, or hollow fiber configuration, which are the most common in water treatment due to their high compactness and ability to be  washed hydraulically in the direction opposite the filtration direction.
However, these systems also require periodic chemical cleaning to restore the membranes.

Ceramic ultrafiltration, which is applied in wastewater with a high pollutant load, should be mentioned. This type of membrane is characterized by high chemical and mechanical resistance, as well as high thermal stability and durability, which makes them easier to wash using highly corrosive chemicals, guaranteeing a high quality effluent.


Ultrafiltration has a broad spectrum of uses, functioning as pretreatment and in processes where excellent water quality is required.

Some of its common uses are:

  • Reverse osmosis pretreatment
  • Potabilization of surface and well waters
  • For potable and wastewater reuse
  • Concentration and recovery of food industry products


Some of the advantages of this treatment system are:

  • Increased efficiency of contaminant removal
  • Increased and better continuity of filtration quality
  • Compact plants (they take up less space)
  • Simple automation
  • Reduction in chemical consumption