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

Abstract

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.

Key findings

• ▸Doubling the gas diffusion area increased ammonia and COD removal rates by up to 115% and 39%.
• ▸Lowering the COD/N ratio from 13 to 3 increased ammonia removal rate by up to 244%.
• ▸Lowering the COD/N ratio from 11 to 3 increased COD removal rate by up to 27%.

Keywords

Identifiers

DOI

10.1002/bit.24769

Journal

Biotechnology and Bioengineering

Year

2012