DNAPL Source Zone Depletion During In Situ Chemical Oxidation (ISCO): Experimental and Modeling Studies
Abstract
In situ chemical oxidation (ISCO) using permanganate is a promising technology for remediating groundwater and soil contaminated by chlorinated solvents present as dense non-aqueous phase liquids (DNAPLs). However, there remain gaps in knowledge about ISCO effects on mass depletion from complex DNAPL source zones and effects of MnO2(s) formation, impacting field application of the technology. Further, a simulation tool is needed for studying ISCO under typical complex field conditions. A 2D experiment was performed investigating oxidation of a complex DNAPL source zone composed of tetrachloroethylene (PCE) within a simulated aquifer, to qualitatively understand ISCO effects on mass depletion and permeability, and generate quantitative data for ISCO model testing. Hydraulic head and aqueous concentrations were monitored and soil cores were analyzed to evaluate permeability effects and mass depletion rate changes due to changes in DNAPL saturation and MnO2(s) formation. For this experiment, MnO2(s) formation depended partly on source configuration, and did not noticeably reduce permeability or alter flow patterns until exceeding 0.1g MnO2(s)/kg soil. Oxidation effects on mass depletion depended on source configuration (ganglia versus pool and location of ganglia related to pool); effects were dramatically different for a complex source zone than a lone pool or residual source, highlighting the importance of source architecture characterization to performance of an ISCO field application. The Chemical Oxidation Reactive Transport in 3D (CORT3D) model code was developed as a decision tool for simulating ISCO, and tested by modeling experiments focusing on important ISCO processes. Simulations confirmed the importance of accounting for changing permeability and multiple natural oxidant demand (NOD) fractions. Simulations also verified oxidation can increase mass depletion from a PCE DNAPL source more than can be attributed solely to increased concentration gradient.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2005
- Accession Number
- ADA511158
Entities
People
- Jeffrey L. Heiderscheidt
Organizations
- Colorado School of Mines