Editing Microfiltration (section)

==General principles==

Microfiltration usually serves as a pre-treatment for other separation processes such as [[ultrafiltration]], and a post-treatment for [[Sand filter|granular media filtration]]. The typical particle size used for microfiltration ranges from about 0.1 to 10 [[micrometre|μm]].<ref name="micrio1">Baker, R 2012, ''Microfiltration, in Membrane Technology and Applications'', 3rd edn, John Wiley & Sons Ltd, California. p. 303</ref> In terms of approximate molecular weight these [[Synthetic membrane|membranes]] can separate macromolecules of molecular weights generally less than 100,000 g/mol.<ref name="micrio2">Microfiltration/Ultrafiltration, 2008, Hyflux Membranes,  accessed 27 September 2013. <{{cite web |url=http://www.hyfluxmembranes.com/microfiltration.html |title=Microfiltration &#124; Hyflux Membranes |access-date=2013-10-15 |url-status=dead |archive-url=https://web.archive.org/web/20131015201250/http://www.hyfluxmembranes.com/microfiltration.html |archive-date=2013-10-15 }} rel="nofollow>"</ref> The filters used in the microfiltration process are specially designed to prevent particles such as, [[sediment]], [[algae]], [[protozoa]] or large [[bacteria]] from passing through a specially designed filter. More microscopic, atomic or ionic materials such as water (H<sub>2</sub>O), [[monovalent ion|monovalent]] species such as Sodium (Na<sup>+</sup>) or Chloride (Cl<sup>−</sup>) ions, dissolved or natural [[organic matter]], and small [[colloids]] and [[viruses]] will still be able to pass through the filter.<ref name="micrio3">Crittenden, J, Trussell, R, Hand, D, Howe, K & Tchobanoglous, G. 2012, ''Principles of Water Treatment'', 2nd edn, John Wiley and Sons, New Jersey. 8.1</ref>

The suspended liquid is passed through at a relatively high velocity of around 1–3&nbsp;m/s and at low to moderate pressures (around 100-400 [[kilopascal|kPa]]) parallel or tangential to the semi-permeable membrane in a sheet or tubular form.<ref name="Perry, RH 2007">Perry, RH & Green, DW, 2007. ''Perry's Chemical Engineers' Handbook'', 8th Edn. McGraw-Hill Professional, New York. p. 2072</ref>  A [[pump]] is commonly fitted onto the processing equipment to allow the liquid to pass through the membrane filter. There are also two pump configurations, either pressure driven or [[vacuum]]. A differential or regular [[pressure gauge]] is commonly attached to measure the pressure drop between the outlet and inlet streams.  See Figure 1 for a general setup.<ref>Baker, R 2000, ''Microfiltration, in Membrane Technology and Applications'', John Wiley & Sons Ltd, California. p. 279.</ref>

[[File:Overall setup for the Microfiltration system - PNG.png|thumb|right|Figure 1: Overall setup for a microfiltration system]]

The most abundant use of microfiltration membranes are in the [[water]], [[beverage]] and [[Bioprocess|bio-processing]] industries (see below). The exit process stream after treatment using a micro-filter has a recovery rate which generally ranges to about 90-98 %.<ref>Kenna, E & Zander, A 2000, ''Current Management of Membrane Plant Concentrate'',  American Waterworks Association, Denver. p.14</ref>