Seasonal Removal Efficiency and Degradation Products of Two Typical PPCPs in Subsurface Flow Constructed Wetlands

Abstract

The pollution of surface waters by pharmaceuticals and personal care products (PPCPs) has aroused widespread concern. Constructed wetlands (CWs) have outstanding advantages in the removal of PPCPs; however, few studies have focused on the interaction of different types of PPCPs in CWs. In this study, two typical PPCPs[broad-spectrum antimicrobial agents triclosan (TCS) and non-steroidal anti-inflammatory drug diclofenac (DCF)] were selected as target pollutants and their removal behavior in subsurface flow CWs was analyzed. The effects of different seasons and influent conditions (i.e., single and combined addition of TCS and DCF) on removal efficiency was also examined. The main parameters of the CW system were as follows:the up-flow subsurface CW had a hydraulic load of 0.20 m·d-1 and a hydraulic residence time of 3 d with a continuous flow inlet. The initial influent concentration of PPCPs was 80 g·L-1 for TCS and 25 g·L-1 for DCF. The results showed that the average removal efficiencies for TCS and DCF in summer (91.72% and 85.86%, respectively) were significantly higher than in winter (52.88% and 32.47%, respectively). Independent sample t-tests confirmed that there was no significant difference in the removal efficiency of TCS and DCF under the different influent conditions (single and combined addition). The degradation products of TCS and DCF were also no different between the influent systems, and the representative degradation products of TCS were not detected in all systems. The main degradation products of DCF in the different systems were 3,5-dichlorobenzoic acid and m-dichlorobenzene. The two studied PPCPs showed no significant antagonism and competition effects at trace levels.