EVALUATION OF SURFACTANT ENHANCED AQUIFER REMEDIATION PROCESSES FOR TRICHLOROETHYLENE RECOVERY IN A FIELD-SCALE THREE-DIMENSIONAL SANDPACK

This research focuses on the optimization of trichloroethylene (TCE) recovery in a field-scale three-dimensional sandpack model (8 m long, 4 m wide, and 2 m deep) which provides a realistic representation of a granular aquifer. The sandpack was fully saturated with water initially, inducing groundwater flow of approximately 1.72 m/d by implementing different hydrostatic heads in both ends. The pack, mostly consisting of 0.075 mm to 4.75 mm range sand diameters, was contained within concrete walls which worked as an impermeable barrier in this study.

30 ml of TCE was then released in the middle of the sandpack at the depth of 0.3 m from the floor in order to artificially create a TCE plume. When 24 hours was elapsed since then for TCE to be redistribute in the pack, water was first injected to recover the contaminant, by measuring TCE concentration at a 6.6 cm diameter extraction well located 2 m away downstream from injection well. There were three 2.54 cm diameter monitoring wells located approximately 0.72 m away downstream from the extraction well. During 3 and half days water injection at the bottom of the injection well (flow rate= 0.42 L/min ), the concentration of TCE collected at the extraction and monitoring wells was examined.

After waiting for two more days during which the TCE plume is allowed to migrate the imposed groundwater pressure gradient, 1 vol. % non-ionic Tween-80 surfactant was injected during 11.5 hours to increase the dissolution of TCE at the flow rate of 0.37 L/min, then followed by another water injection at 0.37 L/min flow rate for 2 days. The concentration of TCE was measured at extraction well and 3 monitoring wells simultaneously to determine the recovery and migration of TCE plume three days.

The analysis and simulation results imply that the initial TCE plume migrated under the groundwater pressure gradient somewhat towards the extraction well. 12 percent of the contaminant was produced by the initial water injection, followed by the recovery of additional 33 % of contaminant during subsequent surfactant and water injection.

This study shows that how DNAPL such as TCE can migrate under natural groundwater flow and during the injection water and surfactant solutions, which is important not only in the conceptual understanding of TCE movement but also the optimization of field-scale remediation process design.