Characteristics of removal of waste-water marking pharmaceuticals with typical hydrophytes in the urban rivers

Abstract

The investigations on their variation and distribution of 13 called waste-water marking pharmaceuticals (WWMPs) were conducted under 4 hydrophyte conditions (without plants, with submerged aquatic plant (Myriophyllum verticillatum L.), emergent aquatic plant cattail (Typha orientalis Presl) and floating aquatic plant (Lemna minor L.)) in a simulated urban river system. By the calculation of mass balance, the quantitative distribution of WWMPs in water phase, sediment and plant tissues was identified, and the overall removal efficiencies of target pharmaceuticals in the whole system could be determined. Without plants, high persistence of atenolol (ATL) (97.7%), carbamazepine (CBM) (102.8%), clofibric acid (CLF) (101.8%) and ibuprofen (IBU) (80.9%) was detected in water phase, while triclosan (TCS) (53.5%) displayed strong adsorption affinity in sediment. The removal under the planted conditions was considerably raised, compared with no plant condition for most WWMPs. However, TCS did not show obvious differences among the hydrophyte conditions due to its strong adsorption affinity and high hydrophobicity. The relatively higher removal was found for the hydrophilic (logKow<1) or moderately hydrophobic (1<logKow<3) pharmaceuticals with submerged and emergent aquatic plants. The highly hydrophobic pharmaceuticals (logKow>4.0) did not show significant differences among the whole tests in sediment. Mass balance calculation displayed the removal of CBM (5.6%–13.6%), CLF (4.0%–17.8%) and caffeine (8.4%–17.2%) through the plant uptake was relatively higher. For the rest WWMPs, only small parts (<6.0%) of the initial concentrations were found in plant tissues. The higher removal efficiencies of most WWMPs under the planted conditions indicated that aquatic plants indeed played an important role in the removal of WWMPs although the direct uptakes might not be a dominant pathway to the overall removal of WWMPs. Besides, the floating aquatic plant removed most WWMPs from the water phase efficiently. In contrast, submerged and emergent aquatic plants could effectively remove them in sediment.