Trade-off between treatment performance and ecological risks in different bioelectrochemical constructed wetlands with iron‑carbon substrates: Insights from sulfamethoxazole and nutrient removal

MFCMEcw achieved the highest sulfamethoxazole removal efficiency (69.66%) • Bioelectrochemistry alleviates greenhouse gas emissions under SMX stress • Bioelectrochemistry enriched electroactive bacteria • MFCMEcw increased the risk of resistance gene transmission Sulfamethoxazole (SMX) is widely detected in natural aquatic environments and poses increasing environmental concerns due to its persistence and incomplete removal in conventional treatment systems. Therefore, developing green and sustainable treatment technologies to remove SMX remains a critical challenge. In this study, the bioelectrochemical technologies including microbial fuel cell-integrated (MFCMEcw) and externally powered electrolysis cell (ECMEcw) were integrated with iron‑carbon micro-electrolysis constructed wetlands (MEcw) to evaluate their long-term (240 days) treatment performance, microbial responses, and ecological risks under SMX exposure. MEcw exhibited the highest removal efficiencies of total nitrogen (29.51%) and total phosphorus (57.77%), indicating greater resistance to antibiotic stress. In contrast, MFCMEcw achieved the highest SMX removal efficiency (69.63%), accompanied by significant reductions in greenhouse gas emissions and global warming potential. Metagenomic analysis revealed that MFCMEcw enriched electroactive microorganisms and extracellular electron transfer-related genes, suggesting increased electron transfer-related functional potential. However, antibiotic resistance genes, mobile genetic elements, and virulence factors were simultaneously enriched, indicating elevated ecological risks associated with resistance dissemination. Multivariate analyses further suggested that bioelectrochemical regulation, iron-associated processes, and microbial functional potential were closely associated with pollutant attenuation and environmental responses in the CWs. These findings provide insights for optimizing sustainable treatment technologies for antibiotic-contaminated wastewater. Download: Download high-res image (204KB) Download: Download full-size image