Predicting EDC concentrations in a river mixing zone

The fate and transport of endocrine disrupting chemicals (EDCs) in ambient river waters is a major concern associated with effluents from municipal wastewater treatment plants (WWTPs). This paper presents a methodology for quantifying the spatial distribution of EDCs in a river mixing zone. The core of the technical analysis is based on a two-dimensional steady-state analytical model characterized by ambient turbulence in the receiving water. This model was first calibrated with mass transport data from field measurements for a conservative substance (electrical conductivity) and then used to predict aqueous-phase EDC concentrations throughout a WWTP mixing zone. To demonstrate the usefulness of this methodology for water quality management purposes, the modeling framework presented in this paper was used to determine a lumped in-stream attenuation rate constant (kd = 3 d−1) for 17β-estradiol under natural conditions. This rate constant likely accounts for the combined contributions of physical sorption, photolysis, microbial and chemical degradation, and the measured value is highly consistent with previously published results from bench-scale removal experiments.

► Field sampling in a river mixing zone enabled EDC fate and transport modeling. ► WWTP mixing zones are estrogenicity “hotspots” due to incomplete mixing. ► In-stream attenuation rate constant for 17β-estradiol was kd = 3 d−1 from model. ► Simple analytical model gives same accuracy as complex water modeling code. ► Modeling framework is suitable for future EDC regulation in river mixing zones.