Performance Characterization of Pharmaceutical Removal by Horizontal Subsurface Flow Constructed Wetlands Using Multivariate Analysis

Three horizontal subsurface flow constructed wetlands and three sand filters (without plants) were set up at the campus of Nanyang Technological University, Singapore. Eight pharmaceuticals including carbamazepine, naproxen, diclofenac, ibuprofen, caffeine, ketoprofen, salicylic acid, and clofibric acid were enriched in the wetland inflow. Three factors, namely, with/without the presence of vegetation, operational modes (batch and continuous), and hydraulic residence time were investigated by a polynomial regression model with analysis of variance, including factorial design, to find the relationships between contaminant removal and the affecting factors, as well as to determine the dominant variables and how each of them interact for each parameter. The objective of this study was to compare the removal efficiencies of selected pharmaceuticals under different wetland retention times, planted versus unplanted modes, and feeding strategies. A polynomial regression model with ANOVA was used to develop the relationships between pharmaceutical removal and the affecting factors in wetland systems. The presence of higher macrophytes, batch feeding strategies, and longer hydraulic residence time were important for pharmaceutical elimination.