Bioenergy generation, organic matter, and simultaneous nitrogen and phosphorus removal in comparative pyrite and graphite-based constructed wetland-microbial fuel cells at different anode scales

To examine the comparative impact of pyrite (Py) and graphite (GG) anode fillers in different anode-number configurations of the constructed wetland-microbial fuel cell (CW-MFC), this study constructed two identical multi-anode (MA) CW-MFCs, two single-anode (SA) CW-MFCs, and two standard constructed wetlands (CWs) and evaluated their performances in bioenergy generation, COD removal, and simultaneous nitrogen and phosphorus removal. The results revealed a consistent advantage favoring the pyrite CW-MFCs and CW in power generation, energy recovery, organic matter, and nutrient removal. The Py-MACW-MFC, Py-SACW-MFC, and PyCW achieved COD removal efficiencies of 92 %, 95 %, and 84 %, which were on average 1.03 times higher than those of GG-MACW-MFC, GG-SACW-MFC and GG-CW, respectively. The Py-MACW-MFC (74 %), Py-SACW-MFC (59 %), and Py-CW (46 %) were also 1.17 times, 1.23 times and 1.24 times higher in NH4+-N removal efficiency and produced lower NO3--N and TP effluent concentrations than their respective CW-MFC/CW configurations. The maximum anodic power densities of the Py-MACW-MFC, 25.54 mW/m3, 29.14 mW/m3, and 23.81 mW/m3, for anode 1 (A1), anode 2 (A2), and anode 3 (A3) respectively, as well as its coulombic efficiencies, were higher than those of graphite CW-MFCs. The study demonstrated pyrite anode filler's capacity to outperform graphite's in all parameters and on every reactor scale despite being more affordable and readily available.