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Enhanced nitrogen removal in single-chamber microbial fuel cells with increased gas diffusion areas

Authors

  • Hengjing Yan,

    1. Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802; telephone: +1-814-865-9436; fax: +1-814-863-7304
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  • John M. Regan

    Corresponding author
    1. Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802; telephone: +1-814-865-9436; fax: +1-814-863-7304
    • Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802; telephone: +1-814-865-9436; fax: +1-814-863-7304.
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Abstract

Single-chamber microbial fuel cells (MFCs) with nitrifiers pre-enriched at the air cathodes have previously been demonstrated as a passive strategy for integrating nitrogen removal into current-generating bioelectrochemical systems. To further define system design parameters for this strategy, we investigated in this study the effects of oxygen diffusion area and COD/N ratio in continuous-flow reactors. Doubling the gas diffusion area by adding an additional air cathode or a diffusion cloth significantly increased the ammonia and COD removal rates (by up to 115% and 39%), ammonia removal efficiency (by up to 134%), the cell voltage and cathode potentials, and the power densities (by a factor of approximately 2). When the COD/N ratio was lowered from 13 to 3, we found up to 244% higher ammonia removal rate but at least 19% lower ammonia removal efficiency. An increase of COD removal rate by up to 27% was also found when the COD/N ratio was lowered from 11 to 3. The Coulombic efficiency was not affected by the additional air cathode, but decreased by an average of 11% with the addition of a diffusion cloth. Ammonia removal by assimilation was also estimated to understand the ammonia removal mechanism in these systems. These results showed that the doubling of gas diffusion area enhanced N and COD removal rates without compromising electrochemical performance. Biotechnol. Bioeng. 2013; 110: 785–791. © 2012 Wiley Periodicals, Inc.

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