Removal of pharmaceutically active compounds (PhACs) and toxicological response of Cyperus alternifolius exposed to PhACs in microcosm constructed wetlands

Abstract

This study investigated the effects of selected four pharmaceutically active compounds (PhACs) (carbamazepine, sulfamethoxazole, ofloxacin, and roxithromycin) on the photosynthesis and antioxidant enzymes of Cyperus alternifolius in constructed wetlands (CWs). Moreover, the removal and kinetics of PhACs in CWs were evaluated to explore the related removal mechanisms. Results showed that C. alternifolius can uptake and withstand certain PhACs. The PhAC tolerance of C. alternifolius might be attributed to their capacity to maintain relatively normal photosynthetic activity and elevated antioxidative defense. CWs offered comparable or even higher removal efficiencies for the selected PhACs compared with conventional WWTPs. The removal of the target PhACs was enhanced in the planted CWs versus the unplanted CWs mostly because of plant uptake and rhizosphere effects. In particular, carbamazepine, which is considered the most recalcitrant of the PhACs, was significantly reduced (p<0.05). The removal of target PhACs fitted into two distinct periods. The initial fast step (within the first 2h) was essentially attributed to the adsorption onto the CW medium surface. The subsequent slow process (2–12h) closely followed first-order kinetics probably because of the interaction between microorganisms and plants. The obtained results indicate that C. alternifolius can phytoremediate PhAC-contaminated waters in CWs.