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MEMBRANE PROCESSES Membrane processes include microfiltration, ultrafiltration, nanofiltration, reverse osmosis and electrodialysis. This typology of treatment is not usually used for municipal wastewaters, but it is often employed for the production of drinkable water and for particular reuse alternatives (recharge of potable aquifer through direct injection and industrial reuse). Microfiltration and ultrafiltration use a synthetic porous membrane to separate the small dimension contaminants. The dimension of the removed contaminants depends on the membrane pore amplitude; information are provided in the following Table . The ultrafiltration process can also be utilised as a reverse osmosis pre-treatment to assure the water quality requirements necessary for industrial cooling water. Ultrafiltration can remove suspended and colloidal material, bacteria and virus and organic compounds, while reverse osmosis is also able to remove dissolved salts. The useful life of a membrane is dependent on avoiding conditions that can cause fouling, scaling, or chemical interactions, trough an appropriate pre-treatment. A key issue is to prevent biological growth on membrane surface that can result in membrane integrity damage.
Comparison
of different membrane processes
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