|Characterization and optimization of microbial fuel cells for sustainable wastewater treatment |
|Kartik Chandran, Columbia University |
CCR 201, 12:10 PM
Microbial fuel cells (MFCs) are at the most fundamental level anaerobic bioreactors in which bacteria oxidize energy yielding substrates to produce electricity. MFCs are a sustainable alternate to several physical-chemical waste treatment options owing to their biological nature in that they are environmentally benign and have the added benefit of generating electrochemical potential energy from waste. This research aims to biokinetically, thermodynamically and ecologically characterize and engineer microbial communities that are most efficient at simultaneously degrading pollutants and generating electrochemical potential.
The MFCs in this study consisted of carbon cloth anodes and open-air cathodes. The anode biofilm community was enriched for an electrogenic bacterial community by spraying a solution of iron(III) chloride on the anode prior to initiating the MFC. This in-situ anode enrichment technique significantly enhanced power output from the MFC (up to 1.2 W/m2) at a coulombic efficiency of 62%. Biofilm thickness also correlated positively with increased electricity production (compared to the electrode treated with sodium sulfate, where little biofilm was observed). Most of the electricity production on exogenic substrates (such as glucose) was attributed to the anode biofilm. However, an equally high amount of electricity was also produced by endogenous anaerobic metabolism likely involving fermentation intermediates such as volatile fatty acids.
Based on shotgun cloning and sequencing of 16S ribosomal DNA genes, the carbon-cloth anodes were colonized by a broad diversity of bacteria that have been found previously in activated sludge but not shown to have electrogenic properties thus far. These results are significant, since they show that the bacterial species known to be electrogenic may not include several guilds abundant in activated sludge.
In sum, our preliminary results suggest that the anode enrichment technique can facilitate the “engineering” of anode biofilms in MFCs to maximize electricity production. Additionally, our microbial ecology results suggest that a vast proportion of electrogenic bacteria have not yet been implicated as such.