Plant-associated microbial enrichment is linked to trace emerging contaminant removal in full-scale constructed wetland

Emerging contaminants (ECs) in wastewater treatment plant (WWTP) effluents pose increasing risks to aquatic ecosystems, necessitating advanced treatment solutions. Constructed wetlands offer a green, low-carbon approach for effluent polishing, yet field-scale evidence on EC removal mechanisms remains limited. This study conducted a 10-month operational monitoring (January–October 2025) of a full-scale constructed wetland receiving municipal WWTP effluent in Suzhou, China, to evaluate the removal of 154 ECs—including pharmaceuticals and personal care products (PPCPs), endocrine-disrupting chemicals (EDCs), per- and polyfluoroalkyl substances (PFAS), antibiotics, and pesticides—and elucidate the underlying mechanisms. The system achieved 40–50% EC removal alongside 14.7%-41.1% conventional pollutants reduction. EC removal efficiency correlated positively with influent concentration but showed no significant correlation with log Kow or molecular weight, indicating that mass transfer and metabolic thresholds govern trace-level EC removal. Direct plant uptake accounted for only 0.14% of the total mass of ECs removed. Instead, plants played an indirect role by shaping rhizosphere microbial communities: rhizosphere substrates exhibited higher microbial richness and greater abundance of complex organic pollutants degraders than deeper layers. Six plant species recruited distinct functional microbial assemblages, includingPantoeainAcorus calamus,ExiguobacteriuminCanna indicaandArundo donax, andComamonadaceaewithSphingobiuminThalia dealbata. Based on these findings, we propose several strategies to further enhance EC removal efficiency, including strengthening water-microorganism contact mechanisms, adopting mixed-species planting modes, and expanding the rhizosphere area. Collectively, these findings provide a theoretical foundation for optimizing plant–microbe-based technologies for EC removal in constructed wetlands and other nature-based systems.