Groundwater has been urgently confronted with extensive manganese contamination nowadays. In this study, a novel fixed-bed ceramic membrane bioreactor (FBCMBR) coupled with intermittently fluidized ceramsite-PACMnOx filters by high-pressure gas was developed for efficient manganese removal. The results indicated FBCMBR 1# with full-filled ceramsite-PAC-MnOx filters reduced transmembrane pressure by 61.2 %, compared to FBCMBR 2# with less-filled filters, and achieved an average manganese removal of 82.8 % during 55-day filtration. Confocal laser scanning microscope (CLSM) images evidenced regular swabbing of apoptotic microorganisms and metabolites from membranes by fluidized filters eliminated reversible fouling. Dispersed active film was retained by membranes and still responsible for manganese removal. Stimulated microbial activities to 25.7 mu mol/L adenosine triphosphate and enriched manganese oxide bacteria (i.e, Pseudomonas) to 2 x 105 MPN/ mL by abundant ceramsite promoted biological oxidation of manganese. SEM-EDS mapping, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) spectra demonstrated filters were covered by threedimensional flower-like structure birnessite, in which Mn(III) contributed to catalytic oxidation of Mn(II) as dominated valence and Mn(IV) was responsible for concentration, facilitating the formation of birnessite and autocatalytic oxidation cycle. Sterilization experiments confirmed catalytic oxidation rather than biological oxidation predominated in manganese removal in FBCMBR, which also showed great self-repair ability with exposure to extremely bio-adverse conditions. For further FBCMBR optimization, flux was stepwise increased or exogenous mature birnessite was introduced during startup period. Both remarkably reduced ripening time (more than 50 days earlier) and reliably stabilized effluent manganese concentration at less than the threshold value of China's standard for drinking water quality (0.1 mg/L).
