Performance, bacterial community dynamics, and key mechanisms of electric field enhanced vertical flow constructed wetlands treating domestic wastewater

Insufficient carbon availability, limited microbial activity, and low simultaneous nitrogen and phosphorus removal constrain the performance of conventional vertical flow constructed wetlands (VFCWs) for domestic wastewater treatment. Here, an electric field-enhanced VFCW system (EF-VFCWs) was established and compared with conventional VFCWs for rural domestic wastewater treatment. EF-VFCWs generally achieved higher removal of NH₄⁺-N, NO₃^--N, COD, and TP under different hydraulic retention times, with more pronounced enhancement in nitrogen and COD removal. High-throughput sequencing showed that electric field exposure reshaped the bacterial community and increased the relative abundance of taxa associated with denitrification, phosphorus transformation, and organic matter degradation. Functional prediction further suggested higher relative abundance of multiple KEGG orthologs and pathway groups involved in carbon, nitrogen, and phosphorus transformation in EF-VFCWs. PLS-PM analysis indicated that environmental factors indirectly affected pollutant removal by modulating microbial community structure and functional potential. Overall, electric field coupling strengthened bio-electrochemical interactions within the wetland system and was associated with improved treatment performance.