Groundwater contamination impacts a significant portion of our nation's water supply. In-situ air sparging has proven to be both an efficient and a cost-effective method for remediating saturated soils and groundwater contaminated with volatile organic compounds (VOCs), including light nonaqueous phase liquids (LNAPLs) such as benzene as well as dense nonaqueous phase liquids (DNAPLs) such as trichloroethylene. The current design of field air sparging systems is empirical, based solely on pilot tests and past experience. As a result, the present implementation of field systems often requires extensive modification in design during the remediation program in order to improve air sparging performance - leading to larger expenditures of time and money. This research will develop a rational design basis for air sparging field operations by: 1) conducting controlled, idealized laboratory experiments to investigate air flow patterns and the resulting mass transfer/transport processes that occur during air sparging; 2) developing a comprehensive mathematical model that accurately incorporates the major contaminant mass transfer/transport mechanisms and validating it using the results f the laboratory testing; 3) assembling and assessing the performance of air sparging systems implemented in the field under different geologic and contaminant conditions, and 4) using the extensive field air sparging data to validate the numerical model. The laboratory experiments will have the following specific objectives: 1) investigate the effects of soil stratigraphy and groundwater flow on air sparging performance; 2) evaluate the effects of VOC type, form, and location, including LNAPL and DNAPL pools on air sparging removal efficiency; 3) verification of laboratory studies through the laboratory remediation of actual field soils, and 4) perform a comparison on laboratory simulation results with field performance data and develop a conceptual air sparging model. The resulting conceptual model can be used to develop or validate mathematical models, permitting field systems to be designed on a rational basis in the future. Because air sparging is a viable remedial option at so many contaminated sites, an optimization of the design process that this research will provide will offer enormous financial benefits.
