Control strategy to improve sustainable flux for a high-solid AnMBR in co-digesting food waste and sewage sludge

This study extends the previous research focused on enhancing the sustainable flux of a high-solid anaerobic membrane bioreactor (AnMBR) for the food waste (FW) and sewage sludge (SeS) co-digestion. A control strategy was implemented by adjusting instantaneous flux and filtration-to-relaxation (F/R) ratio under different total solid (TS) concentrations. The maximum sustainable fluxes of 8.7 ± 0.1, 13.3 ± 0.2, 20.3 ± 0.2, and 20.3 ± 0.6 LMH were achieved at the TS concentrations of 30, 25, 20, and 15 g/L, respectively, with corresponding optimal F/R ratios of 3:1, 5:1, 9:1, and 9:1, respectively. These sustainable fluxes were significantly improved, 4.24, 3.33, 2.18, and 2.01 times of those observed in the mono FW digestion at the same TS concentrations. Furthermore, a mathematical simulation in the form of an exponential function was developed to forecast the optimal sustainable flux at other TS levels. The improved sustainable flux of FW and SeS co-digestion than mono FW digestion might due to (1) the lower apparent viscosity, (2) the larger particle size, and (3) the synergistic effect existed in this co-digestion system. Based on the control strategy of membrane filtration, a TS concentration of 20 g/L is recommended for the AnMBR in the anaerobic co-digestion of FW and SeS. This research provides a valuable guidance for optimizing working mode of high-solid AnMBRs.