Estimation of influent concentrations of estrogens and select prescription drugs in wastewater treatment plants

Due to the high costs associated with laboratory analysis, load estimation of pharmaceuticals is necessary to identify compounds that may have high influent and effluent concentrations in wastewater treatment plants (WWTPs). The load estimation model presented in this paper was developed to estimate the influent concentration of prescription and over-the-counter (OTC) drugs in WWTPs. It accounts for the demographic profile of the population served by the WWTP and was based on a previous estimation model for estrogens. The model was applied to: 1) two statin compounds prescribed for lowering cholesterol levels, and 2) acetaminophen, an OTC drug for pain relief. The previous estrogen model was also used, with minor modification to conform to our proposed model, to estimate the influent concentration of 17-β estradiol in two medium-scale WWTPs. Differences between model predictions and actual measured concentrations ranged from 1.2% to 130%, suggesting model calibration is needed to improve reliability.