Sulfur and iron cycles promoted nitrogen and phosphorus removal in electrochemically assisted vertical flow constructed wetland treating wastewater treatment plant effluent with high S/N ratio

Phosphate (PO43--P) and nitrate (NO3--N) in the effluent of wastewater treatment plants are the predominant sources of eutrophication. In this study, a bench-scale electrochemically assisted vertical flow constructed wetland (E-VFCW) was developed, which exhibited favorable PO43--P (89.7-99.4%), NO3--N (82.7-99.6%), and TN (51.9-93.7%) removal efficiency in tertiary wastewater treatment. In addition, little N2O accumulation (0.32-2.19% of △NO3--N) was observed. The study further elucidated that PO43--P was removed mainly in the anode chamber by co-precipitation (Fe(n+)OH-PO4) and adsorption (FeOOH-PO4) pathways. Multi-pathway of NO3--N reduction was proposed, with 13.9-30.2% of NO3--N predominantly eliminated in the anode chamber by ferrous-dependent NO3--N reduction bacteria. In the cathode chamber, electrons storage and resupply modes during S cycle exerted crucial roles in NO3--N reduction, which enhanced the…