Microbial Processes at Interfaces Affect NAPL Distributions

Clarkson University, Potsdam NY

Investigators

Abstract

9981494 Grimberg The remediation of dense non-aqueous phase liquids (DNAPLs) in subsurface environments is often limited by the heterogeneous distribution of the organic fluid. The overall goal of this research is to quantify the nature, extent and significance of changes in NAPL-water interfacial processes that result from the presence of an active microbial community. It is hypothesized that interfacial phenomena in NAPL-water-mineral systems undergo dynamic changes as biological exudates are produced or microorganisms adhere at interfaces. For example, reductions in adhesion tension would reduce the entry pressure for a nonwetting NAPL to enter a pore, resulting in the potential distribution of NAPL in smaller pore spaces than would otherwise be expected. Due to the transient nature of the microbial growth and overall adsorption reactions, it is expected that capillary flow could also be very transient. Results of this effort could potentially be used to increase the accessiblility and, therefore, the recovery of DNAPL during remediation efforts. Three specific tasks have been identified: (1) Quantify the rates and define conditions under which dynamic changes in the interfacial processes occur in the presence of biological activity, (2) Characterize the primary mechanisms of the biological effects and (3) Quantify the significance of these dynamic processes on the flow of NAPLs in porous media. The research work to be conducted will provide a better understanding of the mechanisms governing the migration of NAPLs under environmentally significant conditions, which will allow for an improved assessment of potential environmental impacts and public risk of NAPL release to the environment. Modeling results will provide a framework for quantifying complexities asssociated with NAPL mixtures, the presence of natural surface-active materials, and bacterial adhesion. Results will therefore improve predictive tools, such as multiphase contaminant transport models that might predict conditions that result in drainage of NAPL into areas of higher permeability, thereby increasing the potential effectiveness of remediation efforts.***