Enhancing Biogas Production of Corn Stover by Biogas Slurry Reflux Based on Microfiltration Membrane Filtration and Biochar Adsorption

Abstract

Reflux of biogas slurry is an effective way to reduce the discharge of wastewater. In order to improve the utilization efficiency of reflux fluid and reduce ammonia inhibition in an anaerobic digestion (AD) system, biogas slurry was pretreated by microfiltration membrane and biochar adsorption. In this study, the suspension solid (SS), biochemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) were investigated, as well as the gas production effect of the reflux of biogas slurry in AD, so as to evaluate the filtration effect of the microfiltration membrane with different pore sizes and the adsorption effect of biochar with different dosages. The results showed that 0.65 μm microfiltration had the best interaction effect and 7 g/L biochar had the best adsorption effect. The results of anaerobic co-digestion of the biogas slurry and corn stover showed the peak gas production of the pretreated reflux fluid was advanced by 1 day, and the maximum daily methane production and maximum cumulative methane production reached 39.20 mL·g−1 VS and 137.14 mL·g−1 VS, respectively. These results indicated that the combined treatment of biogas slurry by microfiltration membrane and biochar could have potential applications for the treatment and recycling of biogas slurry.