Microbial fuel cells inoculated with French vertical flow treatment wetland sludge: A step towards clogging...

Clogging is considered an operational challenge in French vertical flow treatment wetlands (VFTWs), causing hydraulics and aeration problems. The available monitoring methods are labor intensive. Microbial fuel cells (MFCs) have emerged as real-time biosensors, including for treatment wetlands (TW) systems. In this study, French VFTW sludge was investigated as inoculum in MFCs, to assessing its adaptation into electrochemical environment as a step for clogging MFC-based biodetector implementation in such systems. The results show that the inoculum was successfully adapted, with stable current generation at 0.4 mA. The electrochemical impedance spectroscopy (EIS) demonstrated the establishment of a biofilm with electroactive characteristics and non-limiting anode. Metagenomic analysis showed that the French VFTW harbor electroactive species, and the MFC created a selective pressure on the VFTW sludge inoculum and significantly shaped the microbial community and function, stimulating the enrichment of electroactive bacteria (EAB), such Geobacterales (4.11% to 5.83%), with potential expression of cytochrome-c for extracellular electron transference (EET). This study illustrates the feasibility of developing electroactive biofilms from French VFTW and suggests its use as an inoculum, improving the integration of TW-MFC systems. Considering these results, the well-adapted anodic biofilm could enable the detection of aeration limitations via cathodic reactions in future studies.