Editing Microfiltration (section)

===Process equipment===

====Membrane materials====

The materials which constitute the membranes used in microfiltration systems may be either organic or inorganic depending upon the contaminants that are desired to be removed, or the type of application.

* Organic membranes are made using a diverse range of polymers including [[cellulose acetate]] (CA), [[polysulfone]], [[polyvinylidene fluoride]], [[polyethersulfone]] and [[polyamide]]. These are most commonly used due to their flexibility, and chemical properties.<ref name="Perry, RH 2007"/>
* Inorganic membranes are usually composed of [[sintered]] metal or porous [[alumina]]. They are able to be designed in various shapes, with a range of average pore sizes and permeability.<ref name="Perry, RH 2007"/>

====Membrane structures====

General Membrane structures for microfiltration include

* [[Screen filter]]s (Particles and matter which are of the same size or larger than the screen openings are retained by the process and are collected on the surface of the screen)
* [[Depth filter]]s (Matter and particles are embedded within the constrictions within the filter media, the filter surface contains larger particles, smaller particles are captured in a narrower and deeper section of the filter media.)

====Membrane modules====
[[File:Cutaway of a microfiltration module with hollow fiber membranes at a NEWater plant.jpg|thumb|Cutaway of a microfiltration module with [[hollow fiber membrane]]s]]

;Plate and frame (flat sheet)
Membrane modules for dead-end flow microfiltration are mainly plate-and-frame configurations. They possess a flat and thin-film composite sheet where the plate is asymmetric. A thin selective skin is supported on a thicker layer that has larger pores. These systems are compact and possess a sturdy design, Compared to cross-flow filtration, plate and frame configurations possess a reduced capital expenditure; however the operating costs will be higher. The uses of plate and frame modules are most applicable for smaller and simpler scale applications (laboratory) which filter dilute solutions.<ref name="Seadler 2006, p.503">Seadler, J & Henley, E 2006, ''Separation Process Principles'', 2nd Edn,  John Wiley & Sons Inc. New Jersey p.503</ref>

;Spiral-wound
This particular design is used for cross-flow filtration. The design involves a [[pleated]] membrane which is folded around a [[perforation|perforated]] permeate core, akin to a spiral, that is usually placed within a pressure vessel. This particular design is preferred when the solutions handled is heavily concentrated and in conditions of high temperatures and extreme [[pH]]. This particular configuration is generally used in more large scale industrial applications of microfiltration.<ref name="Seadler 2006, p.503"/>

;Hollow fiber
This design involves bundling several hundred to several thousand [[hollow fiber membrane]]s in a tube filter housing. Feed water is delivered into the membrane module. It passes through from the outside surface of the hollow fibers and the filtered water exits through the center of the fibers. With the flux rate in excess of 75 gallon per square foot per day, this design can be used for large scale facilities.<ref>{{cite book |title=Water treatment. |date=2003 |publisher=American Water Works Association |location=Denver, CO |isbn=9781583212301 |pages=441–444 |edition=3rd |url=https://books.google.com/books?id=WO6A_4JAdVsC&pg=PA441 |access-date=14 November 2021}}</ref>