whereas the ATS and STS both had retention times of 2.3 d based on dye tracer studies. Subsequently, 5 L of
effluent from each treatment plant was collected on its corresponding sample day on six sampling dates over a three week period during summer conditions. Effluents were collected from the on-site systems prior to soil infiltration, which was intended to model worst case loadings to the environment with limited to no soil treatment. Because population demographics may influence estrogenicity of wastewater effluent (Brooks et al., 2003; Hemming et al., 2004; Martinovic et al., 2008), a sampling design included three samples to evaluate weekend influent wastewater and three samples were selected to represent influent on weekdays.