Effects of front aeration on the purification process in horizontal subsurface flow constructed wetlands shown with 2D contour plots

Two dimensional (2D) contour plots were used to visualize the effects of front-aeration on the nutrient removal processes in ceramsite-filled horizontal subsurface flow (HSSF) constructed wetlands (CWs) over a 14 month period. Heterogeneous redox conditions (with a high-low-high tendency in the oxidation-reduction potential (ORP) values) along the water flow direction were observed in the aerated CW (ACW). In contrast, the CW without aeration (NACW) was dominated by anoxic or anaerobic conditions. Good nitrogen and phosphate removal efficiencies were obtained with the ACW configuration, which outperformed the NACW configuration. 2D contour plots are convenient for providing an improved understanding of the removal processes in HSSF CWs, which will be helpful for the optimization of CWs. (C) 2014 Elsevier B.V. All rights reserved.