In Situ Mixed Region Vapor Stripping in Low-Permeability Media. 1. Process Features and Laboratory Experiments

Abstract

This is the first paper in a three-part series on mixed region vapor stripping (MRVS) for in situ treatment of fine-grained soils contaminated by volatile organic compounds (VOCs). In this paper, the MRVS process is described followed by the results of laboratory experiments in which the efficiency of MRVS for removing trichloroethene (TCE) was measured. These experiments revealed that MRVS could rapidly remove >90% of the initial TCE from fine-grained, silty clay soils (>80% silt and clay particles, and hydraulic conductivity cm s-'). A spherical diffusion model for TCE mass removal during MRVS was developed and used to simulate the measured reductions in soil TCE level as a function of treatment time. The conceptual model for VOC transport was subsequently used to simulate VOC removals measured in the MRVS field tests. The field-scale evaluation of MRVS is the subject of the second paper, while model simulations of field VOC removals are described in the third paper in this series.

X-231A demonstration of in-situ remediation of DNAPL compounds in low permeability media by soil fracturing with thermally enhanced mass recovery or reactive barrier destruction

“…DOE was confronting these problems at several sites across the United States including the Portsmouth Gaseous Diffusion Plant (PORTS) near Piketon, Ohio. In attempting to implement effective solutions, PORTS and other sites were supporting technology development activities and these were enabling some advancements (e.g., West et al 1995;Siegrist et al 1995a;Gierke et al 1995). In addition, there were some research and demonstration efforts ongoing at the DOE national level through funding from the Office of Science and Technology (OST).…”

“…The PORTS plant has several Resource Conservation and Recovery Act (RCRA) regulated units where assessment and remediation of DNAPL compounds in LPM is required as part of the RCRA Corrective Measures and Corrective Actions program and the DOE accelerated clean-up plan. Previous work at the site had included a major demonstration of in situ mixed region vapor stripping that supported full-scale application of the technology for closure of the X-231B unit (Davenport et al 1994;West et al 1995;Siegrist et al 1995a;Gierke et al 1995). The adjacent X-231A site was chosen as a location to carry out another in situ remediation technology demonstration with joint funding from DOE OST and the PORTS environmental restoration program.…”

“…A fugacity based model (Dawson 1997) was used for this purpose to asses the TCE distribution within the Minford. Based on literature data for key properties of TCE and using representative measured values , and Gierke et al 1995 of porosity (40% v/v), volume fraction of water (36% v/v), and mass fraction of organic carbon (500 mg/kg) for the Minford, a bulk concentration of 300 mg TCE per kg of soil can result in 15% of the mass of TCE being present in a nonaqueous phase with 69% in the soil water, 14% on the soil solids, and 2% in the soil air.…”

Alkaline dechlorination of chlorinated volatile organic compounds

“…For example, biodegradation of TCE is a very slow process that requires specific conditions (e.g., adding nutrients) and a source of acclimated or specialized microorganisms (Fiorenza et al 1991;Brown et al 1993). Vacuwdvapor extraction followed by adsorption on activated carbon is effective and commonly used (Brown 1992;Hinchee 1994;Siegrist et al 1995;West et al 1995). Carbon adsorption is especially effective for the treatment of effluents with low VOC concentrations.…”

In Situ Mixed Region Vapor Stripping in Low-Permeability Media. 3. Modeling of Field Tests

“…The comprehensive study consisted of laboratory experiments, field testing, and mathematical modeling. The first paper (1) describes the treatment process and laboratory results. The results of full-scale field experiments are given in the second paper (2).…”