Assessment of De Facto Wastewater Reuse across the
U.S.: Trends between 1980 and 2008
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Abstract
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