Electrokinetic Remediation of Heterogeneous and Low Permeability Soils Contaminated by Hydrophobic Organic Compounds

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Throughout the United States, hydrophobic organic compound (HOC) contamination has become a widespread and pervasive problem. HOCs, which include tars, creosotes, petroleum residues, and chlorinated solvents, are commonly used in a myriad of different industries. They are generally classified as irritants and/or toxins, and many have been identified as lethal carcinogens. Therefore, in order to protect public health and the environment, sites with existing contamination urgently need remediation. Unfortunately, removing HOC contamination has proved to be very difficult. These compounds are extremely persistent due to their low aqueous solubilities, and their distribution within the subsurface is highly dependent on particle and macro-scale heterogeneities. In spite of attempts to develop efficient HOC remediation technologies, very few have been successful. In-situ flushing with surfactants/cosolvents, though, has been shown to be promising. Surfactants/cosolvents are pumped into the subsurface to increase HOC desorption/solubilization by lowering interfacial tension. Once in solution, the contaminants are mobilized towards wells where the solution is commonly pumped out and treated. The effectiveness of the flushing process, however, depends largely on the extent of contaminant desorption and solubilization, and the degree of interaction between the solution, contaminant, and soil.The objective of this research is therefore to characterize the distribution of HOCs in heterogeneous soil environments and develop and evaluate the electrokinetic enhancement technique for the remediation of HOCs under difficult heterogeneous subsurface conditions. Though electrokinetically enhanced flushing has great potential, the physicochemical reactions and transport mechanisms are complex. A complete fundamental and conceptual understanding of the various components of the process is essential. To achieve this goal, the following tasks will be performed: (1) characterization of the HOCs in heterogeneous soils, (2) evaluation of surfactants/cosolvents for enhanced HOC desorption and solubilization, (3) assessment of HOC removal from particle-scale heterogeneous soils, (4) assessment of HOC removal from macro-scale heterogeneous soils, and (5) development of design guidelines for remediating HOC-contaminated soils.In conjunction with the research objectives, the project will offer educational opportunities and infrastructure improvements for geotechnical and geoenvironmental education at both the graduate and undergraduate student levels. Equipment for the research, especially the physical two-dimensional simulation models, will serve as important demonstration tools for classroom instruction.