In wastewater reuse projects, UF technology has become the mainstream process of reverse osmosis pretreatment, which not only broadens the scope of reverse osmosis treatment water sources, reduces the pollution load of reverse osmosis membrane systems, prolongs the cleaning cycle and replacement cycle of membrane elements, and reduces The operating cost of the system is reduced; the design average water flux of the reverse osmosis membrane is even increased, thereby reducing the investment in the equipment of the reverse osmosis system. However, in the wastewater reuse system, there are many factors that affect the service life of ultrafiltration as reverse osmosis pretreatment.
UF technology is a kind of membrane separation technology. It uses the pressure difference of 0.1 to 0.5 MPa as the driving force and uses the interception ability of porous membrane to separate the particles of different sizes in the solution by physical interception, so as to achieve The purpose of purifying and concentrating, sieving different components in a solution.
1. Fouling. The fouling of UF membrane elements is mainly due to concentration polarization. Higher pressure difference across the membrane, lower membrane flow rate, and higher pollutant concentration contribute to the formation of concentration polarization. When there is no concentration polarization, the pressure difference of the filtration membrane increases, and the filtration flux increases accordingly; when the concentration polarization is serious to a certain extent, the filtration flux almost remains unchanged when the pressure difference of the filtration membrane increases. When the pressure difference across the membrane is large, the gel layer formed by the pollutants on the membrane surface will be compacted and gradually form an irreversible blockage. Therefore, controlling the pressure difference across the membrane is the main method to achieve membrane flux recovery. .
2. Oxidation and hydrolysis. Oxidation and hydrolysis will greatly reduce the service life of UF membrane elements, especially in wastewater reuse, which requires a large amount of oxidants for frequent cleaning to solve microbial and organic pollution. Therefore, the oxidation resistance and hydrolysis resistance of UF membrane element materials are Sex is especially important.
3. Overpressure. If the operating pressure of UF technology is too high, it will cause irreversible damage to the UF membrane elements. When the influent water is overpressured or the ultrafiltration product water pressure is held back, the pump will be alarmed and stopped, which ensures that the ultrafiltration device operates under normal pressure and differential pressure.
4. Temperature. The temperature of wastewater discharged from the production line is related to the survival process. Excessive temperature may cause irreversible damage to the membrane or lead to leakage. Different UF membrane materials such as ceramic UF membranes have different temperature tolerances, so the UF membrane should be prevented from being affected by extreme high temperatures.