Microelectrolysis-integrated constructed wetland with sponge iron filler to simultaneously enhance nitrogen and phosphorus removal

Integrating sponge iron (SI) and microelectrolysis individually into constructed wetlands (CWs) to enhance nitrogen and phosphorus removal are challenged by ammonia (NH4+-N) accumulation and limited total phosphorus (TP) removal efficiency, respectively. In this study, a microelectrolysis-assisted CW using SI as filler surrounding the cathode (e-SICW) was successfully established. Results indicated that e-SICW reduced NH4+-N accumulation and intensified nitrate (NO3–-N), the total nitrogen (TN) and TP removal. The concentration of NH4+-N in the effluent from e-SICW was lower than that from SICW in the whole process with 39.2–53.2 % decrease, and as the influent NO3–-N concentration of 15 mg/L and COD/N ratio of 3, the removal efficiencies of NO3–-N, TN and TP in e-SICW achieved 95.7 ± 1.9 %, 79.8 ± 2.5 % and 98.0 ± 1.3 %, respectively. Microbial community analysis revealed that hydrogen autotrophic denitrifying bacteria of Hydrogenophaga was highly enriched in e-SICW.