Presentation Abstract

Occurrence and Fate of High-Volume Pharmaceuticals in Wastewater-Impacted Environments
Mark Benotti and Bruce Brownawell
State University of New York at Stony Brook, Stony Brook, NY

Pharmaceutically active compounds (PhACs) are readily detected in surface waters that receive municipal wastewaters. To understand possible human or ecological exposure risk, a greater understanding of the processes controlling environmental fate of these compounds needs to be developed. In this work, the occurrence and fate of a selection of water-soluble PhACs are compared in wastewater-impacted groundwater and estuarine surface water environments. This research project also has been aimed at determining whether selected PhACs may be useful as tracers of wastewater and other wastewater-derived contaminants in surface and groundwater environments.

Analytical methods employed in this research project were modified from those developed for high volume pharmaceuticals by the U.S. Geological Survey. High performance liquid-chromatography is coupled with time-of-flight mass-spectrometry (HPLC-ToF-MS), a novel MS approach offering unique advantages for this study. The full-spectral sensitivity of the instrument allows for the analyses of non-target compounds and provides indications of analytical interferences or false positive detections of PhACs. The moderately high resolution of ToF-MS and its ability to estimate analyte accurate mass provide enhanced analyte confirmation, determination of elemental formula, and identification of interferences with the same nominal mass.

Studies on the occurrence and fate of PhACs in groundwater focused on field measurements in the upper glacial aquifer of Suffolk County, New York; a region where approximately 75 percent of municipal wastewater is discharged to ground, mostly from cesspools and septic tanks. Groundwater concentrations of detected PhACs were generally low (low to mid ng/L range) with the highest concentrations being immediately adjacent to known point source wastewater introduction. Migration from one treatment plant was followed in more detail. The extent of transport of individual PhACs in the plume tended to be inversely related to their tendency to adsorb to aquifer material. Microbial transformation of some poorly sorbed pharmaceuticals (e.g., metformin) was inferred from their lack of transport. The tendency of PhACs to be detected in groundwater is a function of source strength, analytical sensitivity, and mobility in subsurface environments. The PhACs that were most readily detected included caffeine, paraxanthine (a caffeine metabolite), carbamazepine, and to a lesser extent, sulfamethoxazole and codeine. The transport of caffeine appears to depend on poorly understood biogeochemical transformations. Whereas caffeine distributions were consistent with conservative transport in an oxic wastewater plume at one site, it was rapidly removed within another plume emanating from a septic tank, particularly in an oxidized zone proximate to the main anaerobic plume. A role of abiotic oxidation reactions has been hypothesized to account for this observation and is part of an ongoing doctoral dissertation study.

A wider range of PhACs is readily detected and typically in higher concentrations (low ng/L to low μg/L range) in surface waters of Jamaica Bay, an estuary in New York City highly impacted by municipal wastewaters. The persistence of pharmaceuticals in Jamaica Bay (residence time of a couple of weeks) was demonstrated by both laboratory die-away experiments and by relating chemical concentrations to salinity (freshwater inputs controlled by wastewater discharges to the bay). Of the 12 pharmaceuticals detected throughout the entire salinity range of Jamaica Bay, only nicotine degraded much faster than the residence time of the bay. Diltiazem and, to a lesser extent, trimethoprim were PhACs that were persistent in Jamaica Bay but not transported well in groundwater because of sorption. Of the PhACs measured in Jamaica Bay, caffeine, paraxanthine, nicotine, and cotinine (a nicotine metabolite) had the highest analytical signals and have the potential to serve as the best tracers of wastewater inputs in estuaries.

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