Modelling Concentrations of Pharmaceuticals and Personal Care Products in a Canadian Watershed

The concentrations of several pharmaceuticals and personal care products (PPCPs) were simulated in the Grand River watershed using the PhATE (Pharmaceutical Assessment and Transport Evaluation) model. PPCPs that were previously measured in the Grand River watershed were selected as the target compounds for this study. The application of the PhATE model was adapted to account for Canadian climatic conditions and its seasonal variability. In this regard, seasonal hydrological parameters (i.e., stream flow and velocity) were estimated based on historical data. Chemical loss parameters, including in-stream decay, human loss, and removal efficiency of treatment plants, were initially extracted from the literature and then calibrated to the site data. In general, the adapted PhATE model reasonably simulated pharmaceuticals with continuous use by humans such as ibuprofen, naproxen, carbamazepine, and gemfibrozil. Validation, which was performed only for ibuprofen, naproxen, and carbamazepine suggests that the calibrated model is able to reliably simulate concentrations. The model is the most accurate in validation when simulating carbamazepine which is the most persistent substance tested in this study, and as such, variations in its concentration primarily follow variation in stream flow.