Iron-carbon could enhance nitrogen removal in Sesuvium portulacastrum constructed wetlands for treating mariculture effluents

This study investigated an Iron-carbon (Fe-C) micro-electrolysis method to enhance nitrogen removal of Sesuvium portulacastrum constructed wetlands (CWs) when treating mariculture effluents. The main objective was to investigate the effects of Fe-C on nitrogen purification performance and microbial characteristics of Sesuvium portulacastrum CWs. Results showed that the presence of Fe-C and Sesuvium portulacastrum could improve nitrogen removal efficiency by 20-30% and 15-30%, respectively. CWs with 33% v/v Fe-C addition performed well on nitrogen removal: TAN, 41.49 ± 13.64%; NO₂^--N, 13.32%; NO₃^--N, 60.02 ± 6.17%; TIN, 63.40 ± 12.11%. Microbial analysis revealed that Fe-C altered the microbial communities, and improved the abundance of denitrification related genera. Based on microbial enzyme activities and genes abundance, the anammox and denitrification processes were promoted by Fe-C in CWs. These findings indicate that Sesuvium portulacastrum CWs with 33% v/v Fe-C represents an effective nitrogen removal for mariculture wastewater with insufficient carbon source.