Electroactive bacteria-driven electron transfer accelerates molecular transformation of tetracycline in iron-carbon coupled wetland microbial fuel cells.

Abstract

Conventional constructed wetlands (CWs) often suffer from adsorption saturation and incomplete degradation when treating antibiotic wastewater, posing risks of pollutant re-release. An iron-carbon substrate was coupled with a microbial fuel cell in a vertical subsurface flow CW (FeC-MFC) based on the hypothesis that electroactive microbial enrichment and strengthened electron transfer would promote TC transformation and treatment stability under chronic TC stress (800 μg/L). FeC-MFC achieved 99.97% TC removal, reducing residual parent TC to 0.28 μg/L, while maintaining stable COD (86.95%) and TN (92.46%) removal. Bioelectrochemical coupling enriched Geobacter (10.09%) and maintained an electroactive microbial network under prolonged TC exposure, accompanied by enhanced functions related to xenobiotic transformation, stress response, cytochrome P450 metabolism and aromatic compound degradation. Enhanced electron transfer was associated with microbially mediated TC transformation. A greater diversity of transformation products included highly oxygenated and more polar intermediates was also detected. These findings associate electroactive bacterial enrichment and sustained electrical activity with more extensive TC transformation, highlighting the need to consider molecular transformation alongside removal efficiency when evaluating antibiotic treatment performance.