Natural Pressure-Driven Passive Bioventing
Cost and performance rept.
ENVIRONMENTAL SECURITY TECHNOLOGY CERTIFICATION PROGRAM ALEXANDRIA VA
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Bioventing is a process of aerating soils to stimulate in situ aerobic microbial activity and promote the bioremediation of water-unsaturated soils that have been contaminated with nonchlorinated hydrocarbons. Passive bioventing utilizes the gas pressure difference that develops between the atmosphere and the subsurface to drive air into the subsurface through vent wells. Conventional bioventing systems use at least one powered blower to inject air into the subsurface. This document provides information needed for comparing passive bioventing to conventional bioventing on the basis of performance, installation and operating costs, and implementation issues. The primary demonstration objective was to identify a site where passive bioventing would be successful. The secondary objective was to measure the rate of airflow and radius of oxygen influence as the result of operating a pilot-scale passive bioventing system that consisted of one vent well with a one-way passive valve and soil-gas monitoring points. Passive bioventing has been successfully demonstrated at four sites where the depth to groundwater is greater than 100 feet. This demonstration focused on determining if passive bioventing could be successfully applied at sites where the depth to groundwater is less than 100 feet. A search for suitable shallow groundwater sites where passive bioventing could be successfully applied was conducted by evaluating site documentation and performing field measurements. A total of 15 Department of Defense DoD sites located throughout the contiguous United States were identified as having features that could potentially lead to the successful application of passive bioventing. Short-term measurements were completed at each of the 15 sites, and passive bioventing was found to be feasible at three of the 15 sites based on measured rates of natural airflow into pre-existing vent wells of at least 1 cubic foot per minute cfm.
- Geology, Geochemistry and Mineralogy
- Fluid Mechanics
- Solid Wastes and Pollution and Control