Abstract
The factors that affect microbial community assembly and its effects on the performance of bioelectrochemical systems are poorly understood. Sixteen microbial fuel cell (MFC) reactors were set up to test the importance of inoculum, temperature and substrate: Arctic soil versus wastewater as inoculum; warm (26.5°C) versus cold (7.5°C) temperature; and acetate versus wastewater as substrate. Substrate was the dominant factor in determining performance and diversity: unexpectedly the simple electrogenic substrate delivered a higher diversity than a complex wastewater. Furthermore, in acetate fed reactors, diversity did not correlate with performance, yet in wastewater fed ones it did, with greater diversity sustaining higher power densities and coulombic efficiencies. Temperature had only a minor effect on power density, (Q10: 2 and 1.2 for acetate and wastewater respectively): this is surprising given the well-known temperature sensitivity of anaerobic bioreactors. Reactors were able to operate at low temperature with real wastewater without the need for specialised inocula; it is speculated that MFC biofilms may have a self-heating effect. Importantly, the warm acetate fed reactors in this study did not act as direct model for cold wastewater fed systems. Application of this technology will encompass use of real wastewater at ambient temperatures.
Highlights
Bioelectrochemical Systems (BESs) are a suite of technologies that exploit the ability of an anaerobic microbial community to donate electrons from organic matter to a solid anode in an electrical circuit, treating wastewater and generating a current
This study presents a simple yet rigorous experiment to explore the link between microbial community diversity and BES performance, and how the choice of inoculum, temperature and substrate may affect this
Realistic temperatures and substrate quality are currently two of the most important discrepancies between prevailing laboratory research and plausible pilot scale BES reactors pre-requisite to the application of BES technologies
Summary
Bioelectrochemical Systems (BESs) are a suite of technologies that exploit the ability of an anaerobic microbial community to donate electrons from organic matter to a solid anode in an electrical circuit, treating wastewater and generating a current. Community assembly is poorly understood in the microbial world in general and in BES in particular [1] it might be reasonable to assume that it is affected by both the temperature, substrate and inocula [2, 3]. Most of the putative applications of BES anticipate using a feed composed of complex waste organic matter at ambient temperatures [4], many studies use an acetate feed at controlled and elevated temperatures (typically ~30 oC). These simplified conditions cannot be an accurate reflection of the real life scenarios BES technologies will have to work in to be commercially viable
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