To control the RO membrane fouling, all the organic, colloidal, and biological matter needs to be removed from the feedwater to the RO system. Hence, a proper pretreatment process capable of producing a substantial reduction in the fouling potential of the membrane is very important to the functioning of a RO filtration process. Conventionally disinfection, fast mixing, coagulation, flocculation, sedimentation, and deep bed filter application are used together as a pretreatment approach after which SDI measurements are used as a criterion to evaluate the efficiency of the pretreatment. However, minute changes occurring in conventional treatment can have adverse effect on the RO filtration process. Factors such as chemical overdose, improper chemical use in pretreatment will result in irreversible fouling, resulting in the increase of TMP, power consumption and increased cleaning operations. Due to these limitations, many seawater reverse osmosis (SWRO) plants are using membrane filtrations such as MF and UF as pretreatment techniques. Application of UF as a pretreatment technique results in the usage of fewer chemicals, less floor space, and higher water recovery than conventional methods. It also eliminates the need for cartridge filter/sludge disposal with similar energy requirements as conventional pretreatment processes .
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