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. HIGHLIGHTS De facto wastewater reuse demonstrates temporal variations.; Wastewater related to use as an indicator of precursors for disinfection byproducts.; De facto reuse related to trihalomethanes and haloacetic acids in drinking water water systems.; Threshold value for de facto wastewater reuse and safe drinking water.; Data to help inform decision-making about wastewater reuse to improve downstream water quality.;

Keywords

• dbp
• de facto reuse
• drinking water
• trihalomethanes
• water