Evaluation of inoculation method and limiting conditions on bacterial activity in microbial electrochemical cells

Abstract

There is growing interest in the potential of microbial electrochemical systems (microbial electrochemical cells – MXCs) for sustainable wastewater treatment and energy production, and extensive research has been undertaken to improve their power production. To optimize MXCs, their performance under technical and operational deficiencies should also be characterized. Using experiments with fed-batch reactors, this study investigated the effects of seeding method, electron donor and acceptor limitations, mixing, salinity, and substrate concentration on performance.The MXCs required 0–8 days for current generation depending on the inoculum source; the most rapid generation was achieved with attached electrogenic bacteria. When the electrogenic bacteria were exposed to air for 3h, the current production was deferred for 5h. The bacteria could handle the lack of an electron donor for at least 3 days, and the lack of a solid electron acceptor for at least 5 days, which would facilitate long distance delivery. A 1.54-fold increase in electron donor concentration contributed to a 1.7-fold enhancement in peak current. The addition of 75mM NaCl increased the power density from 1.64mWm−2 to 2.16mWm−2, whereas optimal mixing increased the power from 0.613mWm−2 to 1.786mWm−2. Thus, electrogenic bacteria may endure some unfavorable conditions, but optimization of operational conditions is necessary to maximize MXC performance.