Total nitrogen removal in a single-chamber, plug-flow microbial fuel cell

Microbial fuel cells (MFCs) can produce energy while removing BOD from wastewater, and MFCs with a biocathode can additionally achieve denitrification. However, MFCs cannot achieve nitrification. We propose a novel plug-flow MFC for BOD and total nitrogen removal, where nitrifying hollow-fiber membranes (HFMs) are integrated into the cathode. The process consists of a plug-flow reactor receiving BOD and ammonium. BOD is oxidized at the anode. Protons from BOD oxidzation and the influent ammonium, are conveyed by the flow to the cathode. In the cathode, racks of nitrifying HFMs are alternated with denitrifying biocathodes, providing nitrification and denitrification. No proton exchange membrane (PEM) is required and pH shifts are minimized. This configuration obtained a power density of 296 mW/m³ (5 mW/m² cathode) and a coulombic efficiency of 17%. Nitrification and denitrification fluxes were up to 1.7 g NH₄⁺-N/m² HFM/d and 1.6 g NO₃^--N/m² cathode/d, respectively. We currently are developing a mathematical model to identify optimal operating conditions and potential configurations for scale-up.