Effects of ammonium ions from the anolyte within bio-cathode microbial fuel cells on nitrate reduction and current density

Abstract

This study was to determine the effects of the ammonium ion in the anolyte of the two-chamber biocathode MFC, which uses nitrate ions as the final electron acceptor, on the nitrate reduction and the current density. The ammonium nitrogen mass transfer coefficient was 3 x 10(-6) cm/s and the diffusivity was 6 x 10(-8) cm(2)/s through Nafion 117 under abiotic conditions, with the circuit disconnected. When the TCBC-MFC was operated at 96.6 +/- 11.2 mg/L of SCODcr in the anode chamber and 37.9 +/- 2.8 mg/L of nitrate nitrogen in the cathode chamber at an external resistance 100 Omega, the analytical denitrification rate was being 7.89 +/- 0.78 g/m(3) d in the presence of ammonium ions and 3.07 +/- 0.26 g/m(3) d in the absence of ammonium ions. The current density was 176.1 +/- 31.7 mA/m(2) when NH4+-N was present in the anolyte and 28.2 +/- 19.4 mA/m(2) without NH4+-N. Thus, it was determined that the ammonium ions in the anolyte were promoted electron movement, which increased the denitrification rate to twice that in the ammonium-free system. (C) 2014 Elsevier Ltd. All rights reserved.