Simultaneous recovery of salt differential energy and chemical energy from wastewater by bioelectrochemical system

Abstract

Bioelectrochemical systems (BESs) serve as an emerging renewable energy technology that presents great potential for wastewater treatment and energy recovery. Microbial desalination cell (MDC), as a type of BES, is capable of desalination while realizing wastewater treatment and recycling of electric energy, which has become a research hotspot in recent years. However, research that has been conducted tends to focus only on the desalination capacity of the MDC and pays less attention to its electricity generation performance. The electricity derived from the recovery of chemical energy in the wastewater by the system has also not been well utilized. In this study, a microbial reverse-electrodialysis cell (MRC), which is capable of obtaining the salt difference energy from high-salt wastewater, was constructed and coupled with an electrodialysis cell (EDC), ultimately constructing a new type of BES named MRC-EDC. It can synchronize the recovery of chemical energy and salt difference in high-salt wastewater, realizing the in-situ use of electric energy and wastewater desalination. The maximum power production performance of MRC-EDC reached 2.44 W m⁻², which was 67.1% higher than that of conventional MFC. The COD removal rate of the system reached 34.16% after 10 h of operation, and the average desalination rate per hour was 5.15%. This study provides a reference for the construction of high-efficiency BESs.