What is ultrafiltration?


What is ultrafiltration?

This is a membrane filtration process that removes suspended solids, dissolved solids, bacteria, viruses, endotoxins and other pathogens to produce pure water with a low TDS content. It can retain particles of 0.001 – 0.1 microns (µm) in a fluid.

Ultrafiltration membranes are more closed compared to microfiltration, but more open than nanofiltration and Reverse osmosis ROThe membranes work with low pressure, which results in lower operating costs. In addition, they are very effective as a pretreatment for Reverse osmosis RO, and they also have a backwash system, which gives them a longer life.

How does it work?

Ultrafiltration uses hydrostatic pressure to force water through a semi-permeable membrane. The type of membranes that constitute ultrafiltration can be spirals that use cross-flow separation, hollow fiber membranes and tubular. The ultrafiltration system works to remove contaminants with molecular weights of 300 to 500’000 Dalton (1).

The membranes remove very small particles, such as chlorine-resistant organisms, bacteria, organics, sediments, high molecular weight solutes and other suspended solids. As in microfiltration, ultrafiltration is mostly applied as a pre-treatment for Reverse osmosis RO, as well as a stand-alone treatment.

What are the applications of ultrafiltration?

Ultrafiltration has a wide filed of application, working as a pretreatment and in processes where excellent quality water is needed. It also a fundamental part in the separation of food grade emulsions, specifically in the processes of milk, serum, cheese, etc. Some examples of its main applications are:

  • Whey protein concentration.
  • Concentration of vegetable proteins such as oats, canola or soya.
  • Starch recovery.
  • Water Treatment
  • Fruit juice, wine and beer clarification.
  • Starch recovery.

Classification by particle size.

Remember that 1 micron (μm) is equivalent to 0.0001 Å.


  1. Cheryan, M. MEMBRANE SEPARATIONS | Ultrafiltration. Reference Module in Chemistry, Molecular Sciences and Chemical Engineering. s.l. : Elsevier, 2013.