Transport of Manure-derived Escherichia coli within Naturally-Fractured Dolomite

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7/1/2012 - 6/30/2014

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  • Shangping Xu, UW-Milwaukee

In Northeastern Wisconsin, the unconfined dolomite aquifer represents a major source of drinking water. Well monitoring data showed that microbial contamination is prevalent in this aquifer. In general, manure is considered the most likely source of the microbial contamination. However, little is known about the transport behavior of manure-derived bacteria within the dolomite fractures under varying water chemistry and flow conditions. The primary goal of this proposed research is to fill this knowledge gap through a series of laboratory-scale experiments using naturally-fractured dolomite samples. Specifically, I plan to examine the transport behavior of manure-derived E. coli within natural dolomite fractures under a range of water chemistry and flow conditions. I will also investigate the remobilization kinetics of previously retained E. coli cells due to water chemistry and flow perturbations. Findings from this proposed research will advance our understanding of the mechanisms that control the retention and release of E. coli, a representative indicator bacterium, within natural dolomite fractures and will provide useful kinetics parameters for the future development, refinement and validation of predictive mathematical models. Combined with field observation data, the results obtained from this research will also provide a basis for evaluating the public health risks associated with the application of manure as a fertilizer in agricultural fields (e.g., to identify the private wells that are most susceptible to microbial contamination). Additionally, the findings can lead to improved manure management practices, such as the timing of manure application and the selection of agricultural fields for manure application, which can potentially reduce the risks of groundwater contamination by manure-derived bacteria. Because fractured carbonate aquifers represent important sources of drinking water in areas beyond the state of Wisconsin and bacterial contamination of fractured rock aquifers by livestock manure has been documented in many other places, the expected findings from this project will have broad applications by advancing our understanding of the spread of bacteria in saturated fractured geological formations.

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