Characterization of anaerobic methanogenic process in the goethite dosed continuous reactors under different pH

Although conductive materials (CM) gained increasing attention over the last decades to facilitate methane production, its influence on the whole process of anaerobic digestion was not clear yet, especially for the acidogenesis. The purpose of this study was to investigate the role of goethite on methane production and its effects on the volatile fatty acids (VFAs) in acidogenesis under different pH conditions. Results showed that the methane production and chemical oxygen demand (COD) removal efficiency in continuous stirring tank reactors (CSTRs) were increased with the addition of goethite. The promotion effects of goethite were particularly significant under acidic conditions. Microbial community analysis indicated that Clostridium and Syntrophic bacteria were enriched in goethite-dosed reactors, while methanogens community was mainly affected by pH. Goethite inhibited the generation of acetate and increased the butyrate production, which may benefit to keep the pH of the reactors stable. The results revealed the underlying mechanism of goethite to promote performances of anaerobic digestion and confirmed goethite was a potential additive under different pH conditions.