Field and Laboratory Evaluation of the Treatment of DNAPL Source Zones Using Emulsified Zero-Valent Iron
Emulsified zero-valent iron (EZVI) is a surfactant-stabilized, biodegradable emulsion that forms droplets consisting of a liquid-oil membrane surrounding zero-valent iron (ZVI) particles in water. This article summarizes the results obtained during the first field-scale deployment of EZVI at NASA’s Launch Complex 34 (LC34) located on Cape Canaveral Air Force Station, Florida, in August 2002 and presents the results of recent follow-on laboratory tests evaluating the mechanisms, which contribute to the performance of the technology. The field-scale demonstration evaluated the performance of EZVI containing nanoscale zero-valent iron (NZVI) when applied to dense, nonaqueous phase liquid (DNAPL) trichloroethylene (TCE) in the saturated zone. Results of the field demonstration indicate substantial reductions in TCE soil concentrations (greater than 80 percent) at all but two soil boring locations and significant reductions in TCE groundwater concentrations (e.g., 60 percent to 100 percent) at all depths targeted with EZVI. Laboratory tests conducted in 2005 suggest that both NZVI particles and EZVI containing NZVI can provide significant reductions in TCE mass when used to treat TCE DNAPL in small test reactors. However, EZVI was able to reduce TCE concentrations to lower levels than were obtained with NZVI alone, likely as a result of the combined impact of sequestration of the TCE into the oil phase and degradation of the TCE with the NZVI. © 2006 Wiley Periodicals, Inc.