Key operational parameters assessment for a chromium (VI)-reducing annular upflow microbial fuel cell

Abstract

Development of upflow microbial fuel cells (MFCs) is of importance since these types of MFCs can be integrated in wastewater treatment plants for the provision of continuous treatment and energy recovery. In this study, key operational parameters were assessed for a hexavalent chromium [Cr(VI)] reducing annular upflow MFC (approximately 5 L total liquid volume). The optimized operational parameters were cathode and anode hydraulic retention times of 2 days, temperature of 34 °C, influent Cr(VI) concentration of 800 mg L−1, and anode and cathode pH of 7 and 4 respectively. This study demonstrated that a parallel configuration is advantageous since it leads to a high current and power density operation due to low internal resistance when compared to series configuration. The precipitation of Cr(III) over time was demonstrated to have a potential to reduce MFC performance and operating at high influent Cr(VI) pHs (7–10) should be avoided. The optimized peak output potential difference and maximum power density achieved under parallel configuration were 896 mV and 994 mW m−3 respectively, at a current density of 1191 mA m−3. This study provides a step into developing continuous metal reducing MFCs for use in simultaneous treatment of heavy metals in wastewater and energy recovery.