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[[Image:membrane filtration icon.png|right|80px]]
[[Image:reverse osmosis.jpg|thumb|right|200px|Solar powered desalinisation plant using reverse osmosis to produce clean drinking water. Photo: [http://www.arkletontrust.co.uk/?q=node/459 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.]]]
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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====