Biologically enhanced dense non-aqueous phase liquid dissolution in a three-dimensional sandstone fracture network

Abstract

Chlorinated solvents are some of the more difficult organic groundwater contaminants at remedial sites in fractured geologic media. The complex nature of flow and transport through fractured systems makes remediation of these chemicals in fractures quite difficult. This research investigated the role of fracture aperture variability in the effectiveness of biodegradation of chlorinated solvents, specifically tetrachloroethene. Observed solvent dissolution enhancement ranged from 2.1 to 3.2, which is roughly a factor of 2 higher than single fracture experiments of the same rock type in less than half the time frame. Fracture intersections create more turbulent mixing and dispersion compared to a single fracture which allows for more efficient delivery of dissolved tetrachloroethene to microbes aiding in biodegradation. Additionally, results suggest that the natural flow heterogeneity found within bedrock fracture networks provide an ideal environment for segregating DNAPL-water interface and dechlorinating microbes which is beneficial biologically enhanced solvent dissolution.