Enhancing manganese redox-driven nitrogen removal by integrating manganese ore with microelectrolysis into constructed wetlands.

Microelectrolysis-integrated constructed wetlands (e-CWs) typically exhibit limited total phosphorus (TP) removal performance, while manganese ore-amended CWs (MOCWs) encounter challenges associated with the interplay between Mn redox cycling and nitrogen transformation. To overcome these limitations, this study introduced MO around the cathode or anode regions in e-CWs, designated as e-CMOCW and e-AMOCW, respectively. Results demonstrated that manganese oxides accelerated NH4+-N removal. Additionally, microelectrolysis enhanced the reductive dissolution of MO, increasing Mn2+ production. This process significantly enriched diverse denitrifying bacteria within e-CMOCW and e-AMOCW, promoting Mn redox cycling and nitrogen transformation, thereby achieving higher NO3--N and total nitrogen removal efficiencies. Moreover, elevated Mn2+ concentrations facilitated TP removal by forming Mn-P precipitates. Canna indica L. mitigated oxidative stress induced by MO and microelectrolysis through increased activity of superoxide dismutase (SOD) and catalase (CAT), ensuring its growth remained unaffected. This study proposes a novel optimization strategy to enhance pollutant removal efficiency in CWs.