Multi-phase partitioning, ecological risk and fate of acidic pharmaceuticals in a wastewater receiving river: the role of colloids.

The occurrence and multi-phase distribution of five pharmaceutical compounds were investigated in an urban wastewater treatment plant (WWTP) receiving river by analysis of pharmaceuticals in sediment, particulate matter, conventional dissolved phase (>0.7 μm), colloidal phase (5 kDa to 0.7 μm), and truly dissolved phase (<5 kDa) water. Diclofenac was found in all samples, followed by clofibric acid, ibuprofen, ketoprofen, and naproxen with the decreasing detection frequency. All targets in WWTP outfall site were higher than those in the upstream and downstream, indicating that the WWTP is an important input source of pharmaceuticals in the river. The colloidal phase contributed 10-14% of ketoprofen, 8-26% of naproxen, 17-36% of clofibric acid, 22-33% of diclofenac, and 9-28% of ibuprofen in the aquatic system, suggesting the colloids will play an important role as carrier to contaminants in the aquatic environment. Based on truly dissolved concentrations of pharmaceuticals in water, only the risk quotient (RQ) value for diclofenac towards fish was higher than 1, indicating it poses a potential risk to aquatic organisms. Finally, a Level III fugacity model was used to further assess the environmental fate of the selected pharmaceuticals (exemplified for clofibric acid and diclofenac). Both clofibric acid and diclofenac tend to accumulate in water compartment with the percentage of 99.7% and 60.6%, respectively. Advection in river is a significant loss process for clofibric acid (56.4%) and diclofenac (54.4%).