Coupling iron pretreatment with a constructed wetland-microbial fuel cell to improve wastewater purification and bioelectricity generation

To evaluate the effects of Fe3C pretreatment on constructed wetland-microbial fuel cell performance, iron-free wastewater, ferric iron-containing wastewater, and ferric iron-containing wastewater pretreated with Fe3C were injected into laboratory fuel cells. Wastewater pretreatment can improve sewage treatment, power generation, and microbial growth in microbial fuel cells as ferric iron reacts with Fe3C to generate ferrous iron acting as electron acceptors, accumulating microbial to form cytochrome c, stimulating microbial production of extracellular polymers, reducing internal reactors resistance. Results show that the fuel cells pretreated with Fe3C had the highest removal efficiencies of ammonium nitrogen (96.38 ± 1.87%), total phosphorus (96.52 ± 1.25%) and chemical oxygen demand (74.70 ± 1.67%), and the greatest maximum power density (5.08 mW/m2) and greatest extracellular polymer content. The operational taxonomic units of the electrochemically active bacteria and ferric ammonium oxidizing bacteria Desulfobulbus and Pseudomonas increased significantly (p < 0.05) at the anode of the pretreated fuel cells (342 ± 11 and 98 ± 21) compared with the ferric iron (235 ± 11 and 155 ± 21)) and iron free fuel cells (226 ± 20 and 23 ± 1). This demonstrates that Fe3C pretreatment is environmentally friendly while improving the performance of the device.