Variations and behavior of wastewater-marking pharmaceuticals influenced under hydrodynamic conditions in urban river systems

Thirteen wastewater-marking pharmaceuticals were selected to explore their variations and behavior under hydrodynamic conditions in urban river systems. Four flow velocities were set, i.e., 0 cm/s for static condition, and 5, 10 and 20 cm/s for dynamic conditions. In the water phase, most of target compounds emerged big fluctuations between static and dynamic conditions. The lower concentrations were detected in the dynamic conditions. However, carbamazepine had minimum relative change during the whole 15-day tests with at least 85% of the initial concentration remaining. In the sediment, the concentrations of most pharmaceuticals in the dynamic conditions were higher than in the static condition, whereas carbamazepine showed big fluctuation in both static and dynamic conditions. With the change of the flow velocities, all target pharmaceuticals showed obviously different variation tendencies mainly due to the changes of environmental parameters, such as turbidity, dissolved matters, microbial biomass, and suspended particulates. In addition, five metabolites were selected to further investigate the transformation of diclofenac and carbamazepine with different flow velocities in the water phase. More diclofenac were transformed into 4-Hydroxy diclofenac in the water phase in the dynamic conditions. Moreover, in the case of a set flow velocity, the concentrations of some pharmaceuticals changed remarkably between the straight and turning channels of an urban river system. Overall, hydrodynamic conditions showed significant influences on the levels of target compounds in the aquatic environment and, therefore, could be taken into account in the risk assessment and control of these compounds.