Mediated anaerobic system performance, co-metabolizing flora and electron transfer by graphene oxide supported zero-valent iron composite

To enhance the traditional anaerobic treatment process, zero-valent iron (Fe 0 ) and graphene oxide (GO) have recently been used and studied. However, there are drawbacks in using GO and Fe 0 alone. In this study, Fe 0 /GO composite was utilized in anaerobic treatment of high strength wastewater to compensate for the drawbacks, and the promoting effects and the mechanism were investigated. The results verified that Fe 0 /GO improved COD removal rate and gas production which reached 91.8 % and 511 mL/12 h, respectively, and a better sludge flocculation performance was obtained. Furthermore, the fermentation type was optimized due to alteration of pH and oxidation-reduction potential by Fe 0 /GO, resulting in increment of acetic acid production and reduction of propionic acid accumulation. A detailed microbial characterization indicated that Fe 0 /GO had a significant effect on hydrotrophic methanogens ( Methanofastidiosum and Methanofastidiosales ), increasing from 1.79 % to 24.11 %. The distribution of hydrolytic fermentation bacteria, acetogenic bacteria and methanogens was more balanced and more diverse in the Fe 0 /GO system, indicating that a stable co-metabolizing microbial community was maintained. Moreover, the highest electron transport system activity and Fe 2+ and Fe 3+ concentration demonstrated that Fe 0 /GO could improve the intracellular and interspecific electron transfer. The conductivity, current response, cyclic voltammetry area were the highest and the internal resistance was the lowest, indicating that Fe 0 /GO could improve the extracellular electron transfer. The stable co-metabolizing microbial community and efficiency intra/extracellular electron transfer promoted the anaerobic wastewater treatment . This study could provide theoretical support for the practical application of developing technologies for anaerobic wastewater treatment.