The ubiquitous presence of pharmaceuticals, hormones, and other contaminants of emerging concern (CECs) in surface-water resources have necessitated research that better elucidates pathways of transport and transformation for these compounds from their discharged wastewater, through surface water to the source and treated water distributed by drinking water treatment plants. A joint USGS-USEPA study used a sampling strategy to follow surface water from upstream of a wastewater discharge to the effluent discharge, downstream through the effluent-mixing zone, a point further downstream, a drinking water treatment plant intake, and through the plant to treatment. The timing of sample collection from these sites was planned with a goal of sampling the same water parcel as it transited the stream system. A suite of 109 human-use pharmaceuticals and related CECs, representative of many commonly used therapeutic classes, were determined in samples from the six sample collection points using a previously published LC/MS/MS method. Stringent field and laboratory QA/QC protocols were employed to minimize or account for effects from field or laboratory sample handling and analysis practices. Method reporting limits, typically less than 50 ng/L, provided sufficient sensitivity for the determination of ambient pharmaceutical concentrations. Mixtures of CECs were detected in all samples collected from the study reach in October 2014 under low-flow conditions. The upstream site contained 21 quantifiable CECs, with a maximum concentration of 389 ng/L (methyl-1H-benzotriazole, a corrosion inhibitor). Wastewater effluent contained 69 CECs, with methyl-1H-benzotriazole (5060 ng/L) being found in the highest concentration followed by caffeine (4400 ng/L, stimulant) and desvenlafaxine (221 ng/L, antidepressant degradate). Numbers of CECs and maximum concentrations dropped markedly downstream as water moved from the discharge point. Substantially lower numbers and concentrations of CECs were detected in the effluent-mixing zone, the downstream location, and at the drinking water intake, (27, 22, and 22 compounds, respectively, with maximum concentrations of methyl-1H-benzotriazole of 439, 440 and 371 ng/L, respectively). Drinking water treatment, at the time of sampling chloramination, was effective in reducing the total number of detectable CECs to 3 (bupropion, cotinine, and meprobamate) at very low concentrations (0.76 [estimated], 3.74, and 7.58 ng/L, respectively).

Transport and transformation of pharmaceuticals and other contaminants of emerging concern from wastewater discharge through surface water to drinking water intake and treatment

253rd National Meeting (2017)

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