0303627 Sedlak Recent advances in analytical chemistry have led to the detection of numerous previously ignored chemical contaminants in municipal wastewater effluent. While the presence of these wastewater-derived contaminants has led to considerable scrutiny of projects in which highly treated wastewater is used to augment water supplies, little attention has been paid to the unintentional recycling of wastewater effluent. Results of a survey conducted during the 1970s suggested that over 7.7 million U.S. residents receive water from sources that consist of more than 50% wastewater effluent during some portion of the year. As a result of continued population growth, especially in arid regions, it is likely that the current number of people receiving wastewater-impacted water is even higher. Because many wastewater-derived contaminants are not removed during water treatment, this pathway could result in exposure of large populations to chemicals that are carcinogens or endocrine disrupters. Intellectual Merit The objective of this project is to assess the current extent of unintentional recycling of wastewater effluent and to develop tools that can be used to assess the potential presence of wastewater-derived contaminants in water supplies. These objectives will be accomplished through a combination of hydrologic modeling and field measurements. In the first phase of the project, locations where unintentional recycling is likely to be significant will be identified and a suite of conservative and reactive tracers will be evaluated under conditions found in surface waters. The hydrologic analysis will include estimation the fraction of wastewater effluent at drinking water intakes during average and low-flow conditions and the amount of time the water has spent in the river prior to abstraction. On the basis of this preliminary analysis, three sites will be chosen for further analysis during the second phase of the project. At each site, the hydrologic model will be refined using site-specific data including river morphology, precipitation and contaminant attenuation rates. Predictions from the model will be compared with measurements of conservative and reactive tracers made at locations throughout the contributing areas of the watershed. Discrepancies between model predictions and measurements will be used to refine the models and to obtain a better estimate of contaminant attenuation rates. Broader Impacts In addition to providing new insight into the risks posed by the unintentional recycling of wastewater effluent, the project will have a broad impact on science and engineering by providing new research opportunities for students from underrepresented groups. During the first phase of the research, high school students from low-performing local schools will assist in the collection of data needed to identify sites where unintentional recycling is significant. During the second phase of the project, undergraduate students from underrepresented groups will assist in field work and analysis of data.
