Filtration with cornstalks as a pre-treatment process to control membrane fouling in the concentration of biogas slurry: performance, mechanism and economic analysis

Anaerobic fermentation produces biogas slurry as a by-product of clean energy, which poses a severe challenge for the sustainable management of livestock farms. Clean water can be obtained and nutrients can be enriched through membrane treatment of biogas slurry. Membrane processes without pre-treatment cause serious membrane fouling. In this study, three different densities of cornstalk filling were selected to filter biogas slurry and the impact of the pre-treatment on the subsequent membrane process was studied. The results demonstrate the techno-economic feasibility of filtration with cornstalks as a pre-treatment for membrane concentration. Control of membrane fouling after cornstalk filtration was achieved by intercepting suspended solids in the biogas slurry. Filtration through the high density (150 kg m(-3)) packing material had the best filtering effect. In particular, the best removal rates of TP, turbidity, and COD in the biogas slurry after filtration with cornstalk were more than 60%, 50%, and 25%, respectively. Resistance of the mud cake layer accounted for more than 80% of the total membrane resistance during the membrane treatment. The adsorption of pollutants inside the membrane pores is the main mechanism of membrane pore blockage. Membrane treatment after filtration would be more economically favorable than direct membrane treatment in practical applications despite the increased cost of using cornstalks. This study provides a technical reference for the high-value utilization of biogas slurry.