Impact of total carbon/sulfate on methane production and sulfate removal from co-digestion of sulfate-containing wastewater and corn stalk.

During the process of preparing furfural by straw depolymerization with dilute sulfuric acid, large amounts of high temperature sulfate-rich organic wastewater were produced. It cannot be treated directly by anaerobic digestion and converted to bioenergy due to high concentrations of sulfate. In this study, anaerobic co-digestion of sulfate containing wastewater and corn stalk was performed at thermophilic conditions to investigate the influences of total carbon (TC)/sulfate (6, 16, 35 and 110) on methane production and sulfate removal. The results showed that the highest methane production of 260.14 mL g volatile solid (VS) was achieved at TC/sulfate of 35, which was significantly higher than 12.53 mL g VS obtained at TC/sulfate of 6. Moreover, the results of sulfate balance analysis showed a maximum sulfate removal of 93.43% was achieved at TC/sulfate of 16, and sulfate concentration in biogas slurry was less than 0.1 g/L regardless of TC/sulfate after 28 days of co-digestion. The microbial community was analyzed using 16S rDNA sequencing technology, the results showed that methane was mainly produced by Methanoculleus and Methanosarcina, and sulfate was removed via Desulfotomaculum, and the relative abundance of methanogenic archaea (MA) and sulfate reducing bacteria (SRB) were significantly correlated with methane production and sulfate removal. It can concluded that higher methane production and sulfate removal can be obtained by anaerobic co-digestion of sulfate containing wastewater and corn stalk at properly TC/sulfate.