The impact of hospital sewage discharge on the assessment of environmental risk posed by priority pharmaceuticals: Hydrodynamic modelling and measurements

Hospital effluents can potentially increase the concentration of emerging pollutants in the influent of wastewater treatment plants (WWTP) and receiving water bodies. This paper presents a hydraulic model that predicts the transport of selected pharmaceuticals and personal care products (PPCP) in a municipal sewer system section of Oslo, Norway. The sewer section additionally collects sewage from a hospital, and the model output is calculated at the sewer discharge point, i.e. the WWTP influent. A set of reference simulations were carried out with PPCP input data obtained by transforming predicted environmental concentrations (PEC) into predicted sewer concentrations (PSC). The daily predicted sewer discharge concentrations (PSDC) were calculated using the simulation output. In the second set of simulations, also referred as the hospital scenario, PEC values were used to account for background PPCP concentrations in the sewer, and for the hospital effluent we used 24-h composite samples from a screening study. The potential of implementing theoretical PPCP concentrations, PSC, as model input was assessed by calculating the ratio of the PSDC values to WWTP influent data form the screening study. The impact of hospital sewage discharge into the sewer system was assessed by contrasting reference results to data obtained in the hospital scenario.