Determining Kinetic Parameters of a Nitrite-Accumulating, Denitrifying, Cathode-Oxidizing Biofilm

Microbial fuel cells (MFCs) can simultaneously oxidize dissolved organic compounds in an anode and reduce nitrate in a cathode while producing electricity from municipal wastewater. However, previous studies have reported nitrite accumulation in denitrifying biocathodes. In this study, nitrite accumulation of 64% of the total initial nitrogen concentration was observed in batch cycles of a denitrifying biocathode. Elimination of possible environmental inhibitors, including dissolved oxygen, pH and carbon limitation did not reduce nitrite accumulation. Batch kinetic parameters for nitrate and nitrite reduction were determined using a cross-competitive inhibition model. For nitrate reduction, a maximum utilization rate (qmax, NA) of 0.0199 ± .0031 (mg NO3-N/mgVSS•day) was observed and for nitrite reduction, the maximum utilization rate (qmax, NI) was 0.0157 ± 0.00026 mg NO2-N/mgVSS•day. Though these parameters are unique for this nitrite-accumulating denitrifying biocathode community, the determining kinetic parameters is important in designing full-scale reactors and predicting biocathode performance.