Synergistic effects of biochar addition and filtration mode optimization on mitigating membrane fouling in high-solid anaerobic membrane bioreactors.

In this study, a high-solid anaerobic membrane bioreactor was established for treating food waste, and membrane fouling rates were regulated through multivariate modulation. The anaerobic membrane bioreactor operated stably at a high organic loading rate of 28.75 gCOD/L/d achieved a methane production rate of 8.03 ± 0.61 L/L/d. Experimental findings revealed that the most effective control of membrane fouling was achieved at a filtration- relaxation ratio (F/R) of 10/90 s. This indicates that a higher relaxation frequency provided improved the mitigation of membrane fouling. Compared with single F/R modulation, the combined modulation of biochar and F/R provided enhanced control over membrane fouling. Moreover, the addition of biochar altered the sludge properties of the reactor, thereby preventing the formation of a dense cake layer. Additionally, biochar enhanced the sheer force of the fluid on the membrane surface and facilitated the separation of pollutants during the relaxation stage, thereby contributing to improved control of membrane fouling.

Process characteristics and energy self-sufficient operation of a low-fouling anaerobic dynamic membrane bioreactor for up-concentrated municipal wastewater treatment.

Up-concentration of municipal wastewater using physico-chemical methods can effectively enrich organic matter, facilitating subsequent anaerobic digestion of up-concentrated wastewater for enhanced methanogenesis at reduced energy consumption. An anaerobic dynamic membrane bioreactor (AnDMBR) assisted with biogas-sparging was developed to treat up-concentrated municipal wastewater, focusing on the effects of operating temperature and hydraulic retention time (HRT) as well as COD mass balance and energy balance. The COD removal stabilized at about 98 % over the experimental period, while gaseous and dissolved methane contributed 43-49 % and 2-3 % to the influent COD reducing greenhouse gas emissions. The formed dynamic membrane exists mainly as a heterogeneous cake layer with a uneven distribution feature, ensuring the stable effluent quality. Without adopting any physico-chemical cleaning, the transmembrane pressure (TMP) maintained at a low range (2.7 to 14.67 kPa) with the average TMP increasing rate of 0.089 kPa/d showing a long-term low-fouling operation. Increasing the concentration ratio, the methane production rate decreased from 0.18 to 0.15 L CH4/gCOD likely due to the accumulation of particulate organics. Microbial community analysis indicated the predominant methanogenic pathway shifted from hydrogenotrophic to acetoclastic methanogenesis in response to the temperature change. Net energy balance (0.003-0.600 kWh/m3) can be achieved only under room temperature (25 °C) rather than mesophilic conditions (36 °C).