Integrated Assessment of Wastewater Reuse, Exposure Risk, and Fish Endocrine Disruption in the Shenandoah River Watershed.

Reuse of municipal and industrial wastewater treatment plant (WWTP) effluent is used to augment freshwater supplies globally. The Shenandoah River Watershed (U.S.A.) was selected to conduct on-site exposure experiments to assess endocrine disrupting characteristics of different source waters. This investigation integrates WWTP wastewater reuse modeling, hydrological and chemical characterization, and in vivo endocrine disruption bioassessment to assess contaminant sources, exposure pathways, and biological effects. The percentage of accumulated WWTP effluent in each river reach (ACCWW%) was used to predict environmental concentrations for consumer product chemicals (boron), pharmaceutical compounds (carbamazepine), and steroidal estrogens (estrone, 17-ß-estradiol, estriol, and 17-α-ethinylestradiol). Fish endocrine disruption was evaluated using vitellogenin induction in adult male or larval fathead minnows. Water samples were analyzed for >500 inorganic and organic constituents to characterize the complex contaminant mixtures. Municipal ACCWW% at drinking water treatment plant surface water intakes ranged from <0.01 to 2.0% under mean-annual streamflow and up to 4.5% under mean-August streamflow. Measured and predicted environmental concentrations resulted in 17-ß-estradiol equivalency quotients ranging from 0.002 to 5.0 ng L-1 indicating low-to-moderate risk of fish endocrine disruption. Results from the fish exposure experiments showed low (0.5- to 3.2-fold) vitellogenin induction in adult males.

Spatial and temporal variation in de facto wastewater reuse in drinking water systems across the U.S.A.

De facto potable reuse occurs when treated wastewater is discharged into surface waters upstream of potable drinking water treatment plant (DWTP) intakes. Wastewater treatment plant (WWTP) discharges may pose water quality risks at the downstream DWTP, but additional flow aids in providing a reliable water supply source. In this work de facto reuse is analyzed for 2056 surface water intakes serving 1210 DWTPs across the U.S.A. that serve greater than 10,000 people, covering approximately 82% of the nation's population. An ArcGIS model is developed to assess spatial relationships between DWTPs and WWTPs, with a python script designed to perform a network analysis by hydrologic region. A high frequency of de facto reuse occurrence was observed; 50% of the DWTP intakes are potentially impacted by upstream WWTP discharges. However, the magnitude of de facto reuse was seen to be relatively low, where 50% of the impacted intakes contained less than 1% treated municipal wastewater under average streamflow conditions. De facto reuse increased greatly under low streamflow conditions (modeled by Q95), with 32 of the 80 sites yielding at least 50% treated wastewater, this portion of the analysis is limited to sites where stream gauge data was readily available.

Assessment of De Facto Wastewater Reuse across the US: trends between 1980 and 2008.

De facto wastewater reuse is the incidental presence of treated wastewater in a water supply source. In 1980 the EPA identified drinking water treatment plants (DWTPs) impacted by upstream wastewater treatment plant (WWTP) discharges and found the top 25 most impacted DWTPs contained between 2% and 16% wastewater discharges from upstream locations (i.e., de facto reuse) under average streamflow conditions. This study is the first to provide an update to the 1980 EPA analysis. An ArcGIS model of DWTPs and WWTPs across the U.S. was created to quantify de facto reuse for the top 25 cities in the 1980 EPA study. From 1980 to 2008, de facto reuse increased for 17 of the 25 DWTPs, as municipal flows upstream of the sites increased by 68%. Under low streamflow conditions, de facto reuse in DWTP supplies ranged from 7% to 100%, illustrating the importance of wastewater in sustainable water supplies. Case studies were performed on four cities to analyze the reasons for changes in de facto reuse over time. Three of the four sites have greater than 20% treated wastewater effluent within their drinking water source for streamflow less than the 25th percentile historic flow.