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TRANSPORT OF CHEMICAL AND MICROBIAL CONTAMINANTS FROM KNOWN WSTEWATER DISCHARGES: POTENTIAL CHEMICAL INDICATORS OF HUMAN FECAL CONTAMINATION
Citation:
Glassmeyer, S, I. Ferrer, E. T. Furlong, J. D. Cahill, S. D. Zaugg, S. L. Werner, M. Meyer, D. W. Kolpin, AND D D. Kryak. TRANSPORT OF CHEMICAL AND MICROBIAL CONTAMINANTS FROM KNOWN WSTEWATER DISCHARGES: POTENTIAL CHEMICAL INDICATORS OF HUMAN FECAL CONTAMINATION. Presented at U.S. EPA's Research on Microorganisms in Drinking Water Workshop, Cincinnati, OH, August 5-7, 2003.
Impact/Purpose:
The objectives of this task are to evaluate a large suite of chemical compounds for their correlation with the concentration of indicator microbes, and determine their ability to monitor water quality in source and finished waters as a surrogate for traditional methods of human fecal contamination.
Description:
The quality of drinking and recreational water is currently ascertained using indicator bacteria, such as Escherichia coli and fecal enterococci. However, the tests to analyze for these bacteria require 24 to 48 hours to complete, and do not discriminate between human and animal fecal material sources. One solution to these problems is to use chemicals that are commonly found in human wastewater as supplementary tracer compounds. The chemicals have the advantage of requiring shorter analysis times (3-4 hours), and a suite of human specific markers can be selected that are unique to human wastewater. For this project, compounds includes those that are produced and excreted by humans (e.g. coprostanol), that are consumed and pass easily through humans (e.g. pharmaceuticals and caffeine), and that are associated with humans and deposited into the combined graywater/ blackwater household septic waste stream (e.g. surfactants). At ten wastewater treatment facilities, a treated effluent sample, as well as surface water samples from upstream, and at two successive points downstream from the facility were collected. This longitudinal sampling scheme was used to determine the persistence of the target compounds in streams. Compounds that are quickly removed or degraded may not be persistent enough to serve as tracers; those that are too recalcitrant would similarly not be suitable as they would be present after the pathogens have been eliminated. To estimate the environmental persistence of pathogens, the water samples were analyzed for E. coli and fecal enterococci in addition to the suite of chemicals being measured. For chemical analysis, the water samples were extracted using either solid phase extraction (for the pharmaceuticals) or liquid-liquid extraction (for the other wastewater contaminants) and were analyzed using either high-performance liquid chromatography/mass spectrometry (HPLC/MS; pharmaceuticals) or gas chromatography/mass spectrometry (GC/MS; other wastewater contaminants). The concentration of microbial indicators was determined using modified mTEC (E. coli) or mEI (enterococci) media. Of the 114 chemical analytes investigated in this project, more than 80 were found in at least one sample. While most concentrations were in the range of 0.1 to 1.0 mg/ L, in some of the more highly contaminated samples, concentrations were in the range of 5-20 mg/ L. The concentrations of the majority of the chemical compounds present in the samples generally followed the expected trend: they were either non-existent or at only trace levels in the upstream samples, had their maximum values in the wastewater effluent samples, and then declined in the two downstream samples. However, at most locations, there were indicator bacteria in the upstream samples, illustrating some of the difficulty in using bacteria to monitor water quality. This work indicates that these human wastewater constituents do have utility as tracers of human wastewater discharge. However, until the behavior of these chemical analytes is evaluated in a rigorous epidemiological study, their true potential as chemical indicators of human fecal contamination will not be determined. To begin this assessment, samples are currently being analyzed as part of the National Epidemiological and Environmental Assessment of Recreational Water Study, which should determine if there is a correlation between concentration of any of the chemicals and incidence of illness.