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__NOTOC__ <small-title />[[Image:membrane filtration icon.png|right|80px]][[Image:reverse osmosis.jpg|thumb|right|300px200px|Solar powered desalinisation plant using reverse osmosis to produce clean drinking water. Photo: [http://www.arkletontrust.co.ukcom/?q=node/459 179 Solar panel project for the Lower Kolyma region of the Republic of Sakha-Yakutia, Russia: A four year collaboration.]]][[Image: ultrafiltration water bottle.jpg|thumb|right|200px|LIFESAVER: World’s First Ultra Filtration Water Bottle. Photo: [http://www.lifesaversystems.com/ Lifesaversystems.com.]]][[Image:microfiltration kiosk.jpg|thumb|right|200px|Opening day for the safe water kiosk. Designed for affordable community water supply or disaster relief applications, the system combines microfiltration and chlorine disinfection to produce potable water. It removes particulate, bacteria, protozoa, virus and other contaminants greater than 0.1 micron (μm). Photo: [http://www.waterworld.com/index/display/article-display/318311/articles/water-wastewater-international/volume-22/issue-6/editorial-spotlight/innovative-lsquosafe-water-kioskrsquo-ensures-quality-water-for-kenyan-community.html Water World.]]]
The membrane processes of most significance in water treatment are reverse osmosis, ultrafiltration, microfiltration and nanofiltration. These processes have traditionally been applied to the production of water for industrial or pharmaceutical applications, but are now being applied to the treatment of drinking-water.
====High-pressure processes====
If two solutions are separated by a semipermeable membrane (i.e. a membrane that allows the passage of the solvent but not of the solute), the solvent will naturally pass from the lower-concentration solution to the higher-concentration solution. This process is known as osmosis. It is possible, however, to force the flow of solvent in the opposite direction, from the higher to the lower concentration, by increasing the pressure on the higher-concentration solution. The required pressure differential is known as the osmotic pressure, and the process is known as reverse osmosis.
'''Microfiltration''' is a direct extension of conventional filtration into the submicrometre range. Microfiltration membranes have pore sizes typically in the range 0.01–12 μm and do not separate molecules but reject colloidal and suspended material at operating pressures of 1–2 bar. Microfiltration is capable of sieving out particles greater than 0.05 μm. It has been used for water treatment in combination with coagulation or PAC to remove particulates and some dissolved organic carbon prior to reverse osmosis membranes and to improve permeate flux.
==Construction=Suitable conditions===The [https://sites.google.com/site/lifefiltasenseseveri/home LifeFilta] products (nanofiltration) are distributed worldwide by the SenseSeveri group, operations with offices in Europe (Belgium), Africa (Bénin, Burundi, Cameroun, Kenya, Uganda) and maintenanceNorth America (New York). ===Manuals, videos and links===* [http://wn.com/nanofiltration Nanofiltration]. World News Inc.* Trotter, Cate. [http://inhabitat.com/milan-2008-lifesaver-flask-cleans-and-filters-with-ease/ LIFESAVER: World’s First Ultra Filtration Water Bottle.] May, 2008.* [https://www.waterworld.com/international/potable-water/article/16201009/innovative-safe-water-kiosk-ensures-quality-water-for-kenyan-community Innovative ‘Safe Water Kiosk’ Ensures Quality Water for Kenyan Community.] Water World. ===Acknowledgements===* [http://whqlibdoc.who.int/publications/2011/9789241548151_eng.pdf Guidelines for Drinking-water Quality.] Fourth edition. WHO, 2011.