Microfiltration is a filter process which removes contaminants from a fluid (liquid & gas) by passage through a micro porous membrane. A typical microfiltration membrane pore size range is 0.1 to 10 micrometers (m). Microfiltration is not fundamentally different from reverse osmosis, ultra filtration or nanofiltration, except in terms of the size of the molecules it retains.

Microfiltration membranes remove all bacteria. Only part of the viral contamination is caught up in the process, even though viruses are smaller than the pores of a micro filtration membrane. This is because viruses can attach themselves to bacterial biofilm.

Increasingly used in drinking water treatment, it effectively removes major pathogens and contaminants such as Giardia lamblia cysts, Cryptosporidium oocysts, and large bacteria. For this application the filter has to be rated for 0.2 m or less. For mineral and drinking water bottlers, the most commonly used format is pleated cartridges usually made from polyethersulfone (PES) media. This media is asymmetric with larger pores being on the outside and smaller pores being on the inside of the filter media.

Micro filter can be implemented in many different water treatment processes when particles with a diameter greater than 0.1 mm need to be removed from a liquid.

Examples of micro filter applications are
  • Cold sterilisation of beverages and pharmaceuticals
  • Clearing of fruit juice, wines and beer
  • Separation of bacteria from water (biological wastewater treatment)
  • Effluent treatment
  • Separation of oil/ water emulsions
  • Pre-treatment of water for nano filter or Reverse Osmosis
  • Solid-liquid separation for pharmacies or food industries
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