Persistence and Potential
Effects of Complex Organic
Contaminant Mixtures in Wastewater-Impacted Streams
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Abstract
Natural and synthetic organic contaminants in municipal
wastewater
treatment plant (WWTP) effluents can cause ecosystem impacts, raising
concerns about their persistence in receiving streams. In this study,
Lagrangian sampling, in which the same approximate parcel of water
is tracked as it moves downstream, was conducted at Boulder Creek,
Colorado and Fourmile Creek, Iowa to determine in-stream transport
and attenuation of organic contaminants discharged from two secondary
WWTPs. Similar stream reaches were evaluated, and samples were collected
at multiple sites during summer and spring hydrologic conditions.
Travel times to the most downstream (7.4 km) site in Boulder Creek
were 6.2 h during the summer and 9.3 h during the spring, and to the
Fourmile Creek 8.4 km downstream site times were 18 and 8.8 h, respectively.
Discharge was measured at each site, and integrated composite samples
were collected and analyzed for >200 organic contaminants including
metal complexing agents, nonionic surfactant degradates, personal
care products, pharmaceuticals, steroidal hormones, and pesticides.
The highest concentration (>100 μg L<sup>–1</sup>)
compounds
detected in both WWTP effluents were ethylenediaminetetraacetic acid
and 4-nonylphenolethoxycarboxylate oligomers, both of which persisted
for at least 7 km downstream from the WWTPs. Concentrations of pharmaceuticals
were lower (<1 μg L<sup>–1</sup>), and several compounds,
including carbamazepine and sulfamethoxazole, were detected throughout
the study reaches. After accounting for in-stream dilution, a complex
mixture of contaminants showed little attenuation and was persistent
in the receiving streams at concentrations with potential ecosystem
implications