Bed electrodes in microbial electrochemistry: setup, operation and characterization

Abstract

Microbial electrochemical technologies have become a vital field of interest in the last two decades. Their reactors are of interest for a large community of scientists working in environmental engineering and technology, biochemistry, electrochemistry, physics, mathematical modeling, microbiology and other disciplines. Due to the fascinating fundamentals and the high promises for application at the horizon, the field is increasingly reflected in the curricula of students of the aforementioned disciplines. The main motivation for this article is to give scientists and students an overview on one specific sub-topic: bed electrodes and bed electrode reactors. After a brief introduction, these granulated electrodes are analyzed from an engineering, electrochemical and microbiological point of view. Thereby we guide the potential future operator for deciding which biotechnological processes and applications under which operational conditions (i.e. fixed-bed electrodes versus fluidized bed electrodes) may benefit by using bed electrodes. Special focus is given to the electrochemical and microbial characterization of granules. Thus we discuss a recent tool that opens the possibility to survey the electrochemical behavior of microbial biofilms on bed electrodes—the e-Clamp. Finally, two case studies of bed electrode reactors are briefly discussed.