Anaerobic digestibility of up-concentrated organic matter obtained from direct membrane filtration of municipal wastewater

Direct membrane filtration (DMF) process is a promising technology for up-concentration and recovery of organic matter (OM) from municipal wastewater. This study investigates anaerobic digestibility of up-concentrated OM obtained from the DMF process. Effluent from a primary sedimentation basin was used as feed water. Effect of polyaluminum chloride (PACl) addition to the DMF process on the anaerobic digestibility of obtained upconcentrated OM was also investigated because PACl is sometimes used as a coagulant in the DMF process for improving effluent quality and OM recovery, and for mitigating membrane fouling. Batch anaerobic digestion experiments were conducted to achieve these objectives. Fitting the obtained data to the reaction curve model revealed that maximum biogas production based on feed volatile solids (VSfed) from up-concentrated OM containing PACl reached 0.56 L-Biogas/g-VSfed, which was higher than from up-concentrated OM without PACl (0.47 L-Biogas/g-VSfed), waste activated sludge (0.35 L-Biogas/g-VSfed), and mixed sludge (0.48 L-Biogas/g-VSfed). Methane yield based on degraded VS (VSdeg) of up-concentrated OM containing PACl was 0.56 L-CH4/g-VSdeg, which was also highest. These results indicate the up-concentrated OM obtained from the DMF process has high potential for biogas production, and the addition of PACl in the DMF process (similar to 4.3 mg-Al/L) could enhance the biogas production.