HR: 1340h
AN: H23A-1409    [Abstracts]
TI: Experimental Investigation of In-Situ Chemical Oxidation of Complex DNAPL Source Zones by Permanganate
AU: * Heiderscheidt, J L
EM: e Jeffrey.Heiderscheidt@afit.edu
AF: Air Force Institute of Technology, 2950 Hobson Way, Bldg 643, Wright-Patterson AFB, OH 45433 United States
AU: Illangasekare, T H
EM: tissa@mines.edu
AF: Center for the Experimental Study of Subsurface Environmental Processes (CESEP), ESE, Colorado School of Mines 1600 Illinois St, Golden, Co 80401 United States
AU: Siegrist, R L
EM: siegrist@mines.edu
AF: Center for the Experimental Study of Subsurface Environmental Processes (CESEP), ESE, Colorado School of Mines 1600 Illinois St, Golden, Co 80401 United States
AB: Remediation of aquifers contaminated with organic waste chemicals that are in the form of dense non-aqueous phase liquids pose many challenges. The contaminated source zones are naturally heterogeneous and the unstable behavior of DNAPLs results in complex entrapment architecture. Some of the remediation schemes rely on effective delivery of treating agents to the locations where the DNAPLs are entrapped. During remediation, the source zone conditions may change, thus affecting the delivery efficiency of the treating agent. One such technology of DNAPL source zone treatment, in-situ chemical oxidation is designed to speed up remediation of a contaminant source zone by inducing increased mass transfer from DNAPL sources into the aqueous phase for subsequent destruction. Individual sources may be present as pools of high saturation, regions of disconnected ganglia at residual saturation, or some combination. Oxidation using permanganate generates manganese oxide (MnO2 (s)) precipitates. Research has shown that these solids, as with other remedial technologies, can result in permeability reductions in the bulk source zone reducing the ability for oxidant to be transported to individual sources. Solids can also form at the DNAPL-water interface, decreasing contact of the oxidant with the DNAPL source. Consequently, MnO2 (s) formation may alter the mass transfer rate from DNAPL into the aqueous phase, diminishing the magnitude of any mass depletion increase induced by oxidation. A two-dimensional intermediate scale tank experiment was performed, spatially monitoring permeability changes and relating them to MnO2 (s) distribution measured through post-oxidation soil coring. Sampling of aqueous PCE, chloride, and permanganate concentrations was used to relate changes in mass flux from DNAPL residual and pool source zones to MnO2 (s) formation. For the conditions of this experiment, MnO2 (s) formation reduced aqueous permeability in and around DNAPL sources resulting in changes to the flow pattern, with source zone configuration and soil property contrasts partly determining the effects. A pool with little or no residual around it, in a relatively homogeneous flow field, appeared to benefit from resulting MnO2 (s) pore-blocking that substantially reduced mass transfer from the pool with relatively little mass removed from the pool. On the other hand, a pool with residual around it (in a more complex heterogeneous flow field) appeared to undergo increased mass transfer as MnO2 (s) reduced permeability, complicating flow, and increasing mixing at the NAPL-water interface. Further, magnitude of increased PCE mass depletion during oxidation appeared to depend on PCE configuration (pool versus ganglia) and decreased as MnO2 (s) was formed and deposited at the DNAPL-water interface.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: Fall Meeting 2005