Wave-pulse mixing coupled with powdered activated carbon enhances AnMBR in treating low temperature municipal wastewater and recovering dissolved CH4

The anaerobic membrane bioreactor (AnMBR) technology is increasingly applied in the treatment of municipal wastewater. However, its application in cold region still faces many challenges including low anaerobic digestion efficiency and high concentrations of dissolved methane (D-CH₄). In this study, powdered activated carbon (PAC) was incorporated into AnMBR operated under wave-pulse mixing mode (P-W-AnMBR) to enhance the operational performance under low temperature condition. As temperature decreased and organic loading rate (OLR) elevated, the COD removal efficiency in the P-W-AnMBR maintained at a high level (93.4 %∼95.8 %) and exhibited favorable stability. The P-W-AnMBR could effectively prevent volatile fatty acid (VFA) accumulation with the lowest VFA concentrations of 22.0 ± 3.9 mg·L^-1. Correspondingly, the methane yield in P-W-AnMBR system reached high as 0.22 ± 0.04 L·g^-1 which was 1.5 times of that in conventional biogas-recirculation mixing AnMBR (B-AnMBR), while the D-CH₄ supersaturation was only ∼1.05, showing a 52.4 % decrease compared to B-AnMBR. According to higher electron transfer system activity and Cyt-C content, electron transfer process was enhanced in P-W-AnMBR, accounting for superior organics conversion to methane. Through a high average K_La as 4.50 h⁻¹, the D-CH₄ readily transfer to the gas phase, thereby reducing the concentration of D-CH₄ as well as increasing the proportion of gaseous methane. Energy analysis showed generation of methane energy could be augmented in P-W-AnMBR as OLR was elevated at 15 °C, thereby significantly reducing the net energy consumption. The combination of wave-pulse mixing and conductive PAC within AnMBR provides insights into low temperature resource recovery from municipal wastewater.