title: Enhanced nitrogen removal in single-chamber microbial fuel cells with increased gas diffusion areas.
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.
authors.affiliation: Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Hengjing
authors.initials: H
authors.lastname: Yan
authors.forename: John M
authors.initials: JM
authors.lastname: Regan
mesh_terms: D001674:Bioelectric Energy Sources; D057919:Biological Oxygen Demand Analysis; D004058:Diffusion; D004560:Electricity; D004566:Electrodes / Q000382:microbiology; D005740:Gases / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism
chemical_list: D005740:Gases; D009584:Nitrogen; D010100:Oxygen