A novel gravity-driven fixed-bed ceramic membrane filtration (GDFBCM) with critical PAC-MnOx-ceramsite filters for simultaneously removing hazardous manganese and ammonia from groundwater

Groundwater is widely threatened by hazardous manganese and ammonia. In present study, a novel gravity-driven fixed-bed ceramic membrane filtration (GDFBCM) with critical PAC-MnOx-ceramsite filters was built to address these issues. Static ceramsite filters in GDCM significantly increased membrane flux from 11 L/m²·h to 18 L/m²·h on the 50th day of filtration. Their synergistic effects with aerated fluidization further reduced membrane fouling by 29 %. Ammonia removal was improved from 62 % to 78 % by ceramsite filters after accelerating nitrification and denitrification by stimulating Nitrospira and Nitrosomonas. Metabolite secretion, ATP level, bacteria abundance and microorganism community analysis evidenced that ceramsite filters acted as immobilization carriers to stimulate Mn-oxidizing bacteria (e.g. Pseudomonas and Hyphomicrobium) for greater biological oxidation of dissolved manganese. According to FTIR, XRD, XPS spectra and SEM-EDS mapping, the facilitated formation of two-dimensional sheet-like birnessite on ceramsite filters established a virtuous cycle for continuous manganese removal. These processes further benefited from the increased hydraulic retention time by denser membranes. The excellent resistance to suddenly increasing pollution loading confirmed the outstanding applicability of GDFBCM. Energy consumption analysis also indicated that GDFBCM was an energy-saving system for groundwater treatment with the specific energy consumption of less than 4 × 10⁻³ kWh/m³.