Nitrogen Removal in A Redox-Stratified Constructed Wetland System

M. Khajah, A.O. Babatunde



A redox-stratified multi-stage vertical flow constructed wetland system was designed to enhance the removal of nitrogen from synthetic domestic wastewater with high nitrogen concentration. The overall aim was to further our mechanistic understanding of nitrogen removal in such systems and in constructed wetlands in general, and to determine the impact of design and operational variables on the overall removal efficiency. A tidal flow operational strategy was used to enhance aeration and thus promote nitrogen removal in the system. The system was designed and operated as a multi-stage system with a hydraulic loading rate and retention time of 0.76 m³/m²·d and 8 hours, respectively. Results obtained over a 7 month period showed that the multi-stage system was able to efficiently remove the contaminants with average removal efficiencies of 97% for chemical oxygen demand, 97% for ammonium-nitrogen and 75% for total nitrogen; however, only 12% of TP was removed in the system. Results further reveal that the oxidation redox potential and dissolved oxygen are the significant operational variables impacting upon nitrogen removal in the system.