Bioelectrochemical systems for production of commodity chemicals with simultaneous wastewater treatment

Abstract

Bioelectrochemical systems (BESs) have been emerging as promising sustainable biotechnology for wastewater treatment and production of value-added chemicals (such as H2O2, acetate, and ethanol). However, BESs still face economic and technical challenges, which need considerable attention for achieving full potential at commercial scale. The main objective of this study was to improve the performance and reduce the cost of BESs for chemicals production and pollutants removal. Firstly, a novel bipolar membrane microbial electrolysis cell (MEC)-Fenton system was developed for the efficient treatment of aniline wastewater. In such system, H2O2 was in situ generated at the cathode of MEC, which was simultaneously used as a source of •OH for the degradation of aniline. The aniline was effectively degraded under an applied voltage of 0.5 V with aniline removal efficiency of 97.1±1.2%. Moreover, energy balance demonstrated that the MEC-Fenton system is a promising strategy for removal of persistent organic pollutants from wastewater. In order to reduce the consumption of applied voltage, a hybrid system of the MEC and reverse electrodialysis (RED) technology was developed, for value-added chemicals production and wastewater treatment, which was named microbial reverse-electrodialysis electrolysis cell (MREC). In the MREC, electrical potential generated by the exoelectrogenic microbes and salinity-gradient energy between seawater and river water were utilized to drive H2O2 production. Operational parameters such as air flow rate, pH, cathode potential, flow rate of salt and fresh water were investigated. The MREC was further integrated with Fenton system for removal of persistent organic pollutants. This hybrid system has several advantages, such as lower operational costs, lower electrical energy consumption, and higher safety level, which provide an efficient and cost-effective system for the degradation of persistent organic pollutants. Biological conversion of CO2 to value-added chemicals (e.g., acetate and ethanol) in microbial electrosynthesis (MES) has emerged as an attractive approach to address the energy and environmental concerns caused by the fossil fuels. In this study, we designed an innovative MREC system to achieve efficient CO2 conversion. This work expanded the potential of the MREC as an efficient technology platform for simultaneous CO2 capture and synthesis of value-added chemicals.