Fouling control of pre-ozonation on a submerged ultrafiltration system: Characteristics and mechanisms

Conventional treatment such as coagulation and sand filtration prior to ultrafiltration (UF) is widely used for treating contaminated surface water sources for potable supply. While beneficial, conventional treatment alone is unable to control membrane fouling effectively in many cases, and there is continuing interesting in the use of additional, complementary methods such as oxidation and adsorption in the pre-treatment of raw water prior to UF. In this study, the applications of ozonation (O-3) and powdered activated carbon (PAC) in the submerged UF system (SUF) have been evaluated at laboratory-scale employing test water after conventional water treatment. In parallel tests with and without the pretreatment, the impact of O-3 on the increase of trans-membrane pressure was evaluated and with the analysis of membrane fouling resistance, both as the cake layer and within membrane pores. The results indicated that the O-3/SUF system can alleviate about 20.43% membrane fouling, compared with SUF system without pre-ozonation. Pre-ozonation combined with PAC removed protein-like substances, resulted in a 39.2% reduction of total organic carbon; increased the amount of attached biomass on the PAC and membrane surface, resulted in the improvement of the biodegradability of microorganisms. The application of O-3 can reduce the stickiness of surface of organic pollutants, which is beneficial to remove the pollutants deposited on membrane surface by chemical backwashing. Therefore, the application of pre-ozonation and PAC within SUF system is a potentially important approach for fully mitigating membrane fouling. (C) 2020 Elsevier B.V. All rights reserved.