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A comparative study of pre-ozonation and in-situ ozonation on mitigation of ceramic UF membrane fouling caused by alginate

Song, Jia, Zhang, Zhenghua, Zhang, Xihui
Journal of membrane science 2017 v.538 pp. 50-57
alginates, artificial membranes, ceramics, fouling, hydroxyl radicals, microfiltration, models, molecular weight, oxidation, ozonation, ozone, ultrafiltration, water treatment
Pre-ozonation or in-situ ozonation coupled with membrane filtration has been actively utilized for membrane fouling control in water treatment, however, the comparative analysis of these two ozonation processes on membrane fouling control has not been reported so far. In this study, the comparative effect of pre-ozonation and in-situ ozonation on mitigation of ceramic UF (ultrafiltration) membrane fouling caused by alginate was systematically investigated through characterization of TMP, fouling resistance, MW distribution, dissolved ozone concentration, the formation of hydroxyl radical and modeling. Results showed that both pre-ozonation and in-situ ozonation were effective in alleviating the cake layer fouling. Ozonation efficiently broke down the high molecular weight (MW) fractions (>150kDa and 80–150kDa) of alginate into the low MW fractions (6–80kDa; 0.4–6kDa and 0.1–0.4kDa), reducing the membrane interception of alginate. Pre-ozonation achieved better fouling mitigation performance compared with in-situ ozonation at low ozone dosages of 2 and 4mg/L. However, in-situ ozonation had better fouling control performance at high ozone dosage of 10mg/L with the normalized TMP (ΔTMP) maintaining below 0.2 kPa after 60min filtration. Besides, in-situ ozonation was more effective in hydraulically irreversible fouling control than pre-ozonation regardless of ozone dosage. Integration of in-situ ozonation and ceramic membrane filtration catalyzed ozone decomposition with the increased generation of hydroxyl radical, which further strengthened the oxidation of the accumulated foulants on the membrane surface and within the membrane pores and thus effectively alleviated the reversible and irreversible fouling.