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 Py-CW 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 NH 4 + -N removal efficiency and produced lower NO 3 − -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/m 3 , 29.14 mW/m 3 , and 23.81 mW/m 3 , 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. • Performance comparison of two inexpensive and conductive anode fillers • Evaluation of three anodic configurations of constructed wetland-microbial fuel cell • Pyrite multi-anode CW-MFC achieved COD (95.15 %), NH 4 + -N (73.80 %) and TP (41.32 %). • Pyrite multi-anode CW-MFC achieved V max (609.36 mV), PD (78.49 mW/m 3 ) and CE (2.58 %). • Increasing anode number increased nitrogen, phosphorus removal and power generation.