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Why Pre-Filtration is Required for RO?

May. 15, 2020

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Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to remove ions, unwanted molecules and larger particles from drinking water. In an RO system, pressure is used to overcome natural osmotic pressure, forcing feedwater with its load of dissolved salt and other impurities through a semi-permeable membrane that removes a high percentage of the impurities. The product of this process is highly purified water.


Because the reverse osmosis membrane is a polymer semi-permeable membrane and the pore size is very precise, it's high requirement for the inlet water. And the inlet water particles should be less than 5 microns, otherwise, it will cause pollution to the reverse osmosis membrane module, thereby shortening the service life and increasing the filtration cost.


Therefore, if the inlet water particle are smaller than 5 microns, it meets the inlet water quality requirement for reverse osmosis. In this case, it is not necessary to install a pre-filtration device. If the inlet water particle are bigger than 5 microns, it's necessary to install a pre-filtration device. Before the reverse osmosis equipment, a pre-filtration device composed of single or multiple security filters is generally used.


In order to ensure that the inlet water particles of reverse osmosis are within 5 microns, reverse osmosis pre-filtration security filter is generally installed with 1 micron or 5 micron filter element or filter bag, such as High Flow Pleated Filter, Pleated Filter Cartridge, Melt Blown Cartridge, String Wound Cartridge, Activated Carbon Cartridge, Liquid Filter Bag. Here are some hot selling products from HONGTEK for your reference:


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In addition to microfiltration, ultrafiltration is also widely used in the pre-filtration of reverse osmosis. The water quality of ultrafiltration is stable, which can basically remove particles larger than 0.1μm, decrease the pollution of impurities on reverse osmosis and reduce the blocking of reverse osmosis membrane module, thus extend the service life of reverse osmosis membrane module and decrease the filtration cost. HONGTEK Ultrafiltration Membrane Modules for your reference:


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Whether microfiltration or ultrafiltration is selected as the pre-filtration of reverse osmosis, the purpose is to extend the service life of reverse osmosis membrane module and reduce the filtration cost. We should combine the pollution degree of water quality and the filtration cost when we choose the pre-filtration solution of reverse osmosis.


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