| Summary: | This work presents an effective approach for manganese-doped Al<sub>2</sub>O<sub>3</sub> ceramic membrane (Mn-doped membrane) fouling control by in-situ confined H<sub>2</sub>O<sub>2</sub> cleaning in wastewater treatment. An Mn-doped membrane with 0.7 atomic percent Mn doping in the membrane layer was used in a membrane bioreactor with the aim to improve the catalytic activity toward oxidation of foulants by H<sub>2</sub>O<sub>2</sub>. Backwashing with 1 mM H<sub>2</sub>O<sub>2</sub> solution at a flux of 120 L/m<sup>2</sup>/h (LMH) for 1 min was determined to be the optimal mode for in-situ H<sub>2</sub>O<sub>2</sub> cleaning, with confined H<sub>2</sub>O<sub>2</sub> decomposition inside the membrane. The Mn-doped membrane with in-situ H<sub>2</sub>O<sub>2</sub> cleaning demonstrated much better fouling mitigation efficiency than a pristine Al<sub>2</sub>O<sub>3</sub> ceramic membrane (pristine membrane). With in-situ H<sub>2</sub>O<sub>2</sub> cleaning, the transmembrane pressure increase (ΔTMP) of the Mn-doped membrane was 22.2 kPa after 24-h filtration, which was 40.5% lower than that of the pristine membrane (37.3 kPa). The enhanced fouling mitigation was attributed to Mn doping, in the Mn-doped membrane layer, that improved the membrane surface properties and confined the catalytic oxidation of foulants by H<sub>2</sub>O<sub>2</sub> inside the membrane. Mn<sup>3+</sup>/Mn<sup>4+</sup> redox couples in the Mn-doped membrane catalyzed H<sub>2</sub>O<sub>2</sub> decomposition continuously to generate reactive oxygen species (ROS) (i.e., HO• and O<sub>2</sub><sup>1</sup>), which were likely to be confined in membrane pores and efficiently degraded organic foulants.
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