INVESTIGATING DNAPL DISSOLUTION KINETICS IN A SATURATED BENCH-SCALE FRACTURE NETWORK

Dense non-aqueous phase liquid (DNAPL) present in fractured bedrock settings introduces unique remediation challenges that are significantly different from porous media. Accurate characterization of DNAPL architecture and dissolution kinetics in a fractured network setting yield more efficient application of remedial actions on both the free and dissolved phases in field settings. However, to date, little research has been devoted to the kinetics of DNAPL dissolution in a fracture network setting. This research is the first to explore the dissolution behavior of tetrachloroethylene (PCE) DNAPL in a saturated three-dimensional, bench-scale fracture network comprised of low porosity sandstone. Dissolution mass-transfer rates and DNAPL interfacial areas are quantified using effluent aqueous phase PCE concentrations and interfacial area tracer testing from bench-scale fracture network experiments. Experimentally derived mass transfer rates are evaluated against system properties, such as interfacial area, Reynolds number, aperture and velocity, to determine the primary factors controlling DNAPL dissolution in a fracture setting. Dissolution mass transfer rates from the experimental fracture network are compared to analogous experiments of PCE dissolution in discrete fracture experiments. Additionally, preparations are currently under way for evaluating DNAPL dissolution kinetics during in situ chemical oxidation in the experimental fracture network.