Enhanced medicinal herbs wastewater treatment in continuous flow bio-electro-Fenton operations along with power generation

In this study, we proposed a microbial fuel cell (MFC) system with anodic bio-oxidation inoculated with seed sludge as active biocatalyst coupled to cathodic electro-Fenton equipped with a composite electrode of Fe@Fe2O3/graphite for the enhanced medicinal herbs wastewater treatment as a bio-electro-Fenton (BEF) system. The influence of hydraulic retention time (HRT) and influent organic loading rate (OLR) on the treatment performance and energy balance of the BEF system was examined. The maximum chemical oxygen demand (COD) removal of 93% and the BOD5/COD of 0.89 in the continuous BEF system were desirable with an OLR of 0.58 g L−1 d−1 and HRT of 83.33 h. The maximum current density of 603.86 mA m−2, a voltage of 892 mV, a power density of 183.06 mW m−2 were achieved with an OLR 5.77 g L−1 d−1 and HRT 5.21 h. The coulombic and energy efficiencies were 5.36 and 65.33%, respectively. The optimum HRT was found to be around 11–21 h for electricity production and COD removal simultaneously from the wastewater.