Temporal variations of de facto wastewater reuse and disinfection by-products in public water systems in the Shenandoah River watershed, USA

Abstract

Temporal variations of de facto wastewater reuse are relevant to public drinking water systems (PWSs) that obtain water from surface sources. Variations in wastewater discharge flows, streamflow, de facto reuse, and disinfection by-products (DBPs – trihalomethane-4 [THM4] and haloacetic acid-5 [HAA5]) over an 18-year period were examined at 11 PWSs in the Shenandoah River watershed, using more than 25,000 data records, in gaged and ungaged reaches. The relationship of de facto reuse with DBPs by year and quarter at the PWSs was examined. A linear relationship was found between THM4 and de facto reuse on an annual average basis (p = 0.050), as well as in quarters 3 (July – September) (p = 0.032) and 4 (October – December) (p = 0.031). Using a t-test (p < 0.05), the study also showed that there were significant differences in DBP levels for PWSs relative to 1% de facto reuse. This was found for THM4 based on annual average and quarter 1 (January – March) data, and for HAA5 based on quarter 3 data during the period of record.

Wastewater reuse and predicted ecological risk posed by contaminant mixtures in Potomac River watershed streams

“…The advantage of using mean EROM streamflows compared to measured streamflow at streamgages, is that EROM streamflows allow consideration of stream dilution and time of travel at each ungaged reach in the watershed. Refinements to this approach have been demonstrated in the Shenandoah River watershed using local streamgage information to estimate ACCWW% for measured historic flows at ungaged reaches (Weisman et al, 2021).…”

“…Wastewater inputs consisted of average daily National Pollutant Discharge Elimination System (NPDES) permitted WWTP effluent discharges to surface waters during 2016 (U.S. Environmental Protection Agency, 2022). Effluent discharge volumes were obtained from the Chesapeake Assessment Scenario Tool (CAST) wastewater report (Chesapeake Bay Program, 2020) with the substitution of 79 Shenandoah River watershed facilities with previously published and quality‐assured 2016 discharge data (Weisman et al, 2021). The CAST tool is specific to Chesapeake Bay WWTPs; however, it synthesizes data from state databases and the U.S. Environmental Protection Agency (USEPA) Enforcement and Compliance History Online database (ECHO; U.S. Environmental Protection Agency, 2020b), which provides discharge volumes and outfall locations for facilities across the nation.…”

“…Similarly, the approach to estimate PECs and perform risk‐ranking assessments can be applied to any constituent for which reliable use, chemical, biological, and ecotoxicological benchmark parameters are available. This study focuses on the Potomac River watershed and is an expansion of studies on the Shenandoah River watershed (a Potomac River watershed subbasin) to examine de facto reuse and wastewater contaminants (Barber et al, 2022; Barber, Rapp, et al, 2019; Weisman et al, 2019, 2021). This study scales up from the 7920 km 2 Shenandoah River watershed with less than 100 WWTPs to the 36,750 km 2 Potomac River watershed with greater than 1800 WWTPs (U.S. Geological Survey, 2014).…”

Watershed-Scale Risk to Aquatic Organisms from Complex Chemical Mixtures in the Shenandoah River

“…SRW encompasses 9 counties and has 25 towns having 2014 populations ranging from 251 to 44,039 people, resulting in a population density of 51 people per km 2 . There are 106 municipal and industrial WWTPs with permitted surface water discharges and 13 municipal drinking water treatment facilities with surface water intakes. , Additional point- and non-point sources of chemicals include agricultural runoff, biosolids application, on-site wastewater disposal, urban development, atmospheric deposition, transportation networks, and recreation.…”

“…The RI results (Figure 1C) indicated that most of the WWTP-impacted stream reaches in SRW were at "risk" or "high risk" for adverse effects from exposure to chemical mixtures. Given that wastewater contributions to SRW have been relatively consistent over the past 2 decades, 35 it is likely that the fish and benthic communities have experienced long-term exposure to chemical mixtures from WWTP discharges.…”