Performance, process kinetics and functional microbial community of biocatalyzed electrolysis-assisted anaerobic baffled reactor treating carbohydrate-containing wastewater

Abstract

In this study, an anaerobic baffled reactor (ABR) coupled with a microbial electrolysis cell (MEC) was set up to treat carbohydrate-containing wastewater at 55 ± 1 °C. The MEC was employed to accelerate the degradation of volatile fatty acids (VFAs). The removal of chemical oxygen demand (COD) and production of methane and the corresponding kinetics were determined for different organic load rates (OLRs). The highest COD removal rate was 95.8% at an OLR of 7.0 kg COD m⁻³ d⁻¹, but it declined to 90.4% when the OLR was 19.4 kg COD m⁻³ d⁻¹ and finally stabilized at 65.3% when the OLR was increased to 34.3 kg COD m⁻³ d⁻¹. The volumetric production of methane was 1.5 L (L⁻¹ d⁻¹) when the OLR was 7.0 kg COD m⁻³ d⁻¹ and increased to 4.1 L (L⁻¹ d⁻¹) at an OLR of 34.3 kg COD m⁻³ d⁻¹, when the methane yield stabilized at 0.20–0.25 L g⁻¹ COD_removed. The kinetics and predictions according to the Stover–Kincannon and Van der Meer–Heertjes models closely agreed with the experimental data for the removal of COD and volumetric production of methane, respectively. An analysis of the microbial community suggested that hydrolytic bacteria, syntrophic fatty acid-oxidizing bacteria (SFOB), exoelectrogens and hydrogenotrophic methanogens achieved a significant synergistic effect and enhanced the degradation of VFAs, which made the thermophilic anaerobic system stable and efficient at high OLRs.