¹Department of Civil Engineering, University of Colorado at Boulder, Boulder, CO 80309, 303-492-6754 and ²Department of Civil Engineering, University of Colorado at Boulder, Boulder, CO, 80309, 303-492-6644
Use of thermal processes, such as hot water flooding and steam injection for the enhanced recovery of entrapped hydrocarbons from petroleum reservoirs have been practiced in the oil industry. The potential exists for the use of similar techniques for the mobilization and recovery of non-aqueous phase (NAPL) waste products from soils in contaminated aquifers. However, the direct application of these techniques for aquifer remediation is precluded due to some basic differences associated with the problem of scale, types of chemicals, expected cleanup levels and heterogeneities in aquifers. In our ongoing research, we are investigating the use of hot water for the mobilization of entrapped NAPLs under micro and macroscale entrapment saturations. The objectives of this research are to understand and model the mobilization process at various scales of interest, from the laboratory to the field scale.
This paper presents preliminary results from mobilization experiments that were conducted in soil columns. Sand is packed homogeneously in a vertical column that was placed in a temperature controlled insulated chamber. The bottom of the column is fitted with a base to which a high-suction (bubbling pressure) porous plate can be attached. After saturating the dry soil with the test NAPL, the column was drained at the bottom. Suction was then applied at the bottom to create residual saturation. After removing the porous plate, hot water at a known constant temperature was pumped from the bottom of the column. The effluent was sampled continuously to determine the volume of mobilized NAPL. The NAPL saturation in the column was monitored using a dual gamma attenuation system. The experiments were repeated for different temperatures of hot water (10º-50º C), sand types and flooding velocities. The data was analyzed to determine the recovery efficiencies. The research results from these experiments will be used to design mobilization experiments in two-dimensional tanks to evaluate the recovery efficiencies in more realistic field systems where the flow is multi-dimensional and heterogeneities control the flow behavior.
ground water, NAPL, remediation, thermally enhanced recovery, up-scaling
This paper is from the Proceedings of the 10th Annual Conference on Hazardous Waste Research 1995, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.