Simulation of the Kinetic Sorption and Desorption of Trichloroethene (TCE) and Surfactant in Ground Water at Picatinny Arsenal, New JerseyEPA Grant Number: R824365
Title: Simulation of the Kinetic Sorption and Desorption of Trichloroethene (TCE) and Surfactant in Ground Water at Picatinny Arsenal, New Jersey
Investigators: Smith, James A. , Imbrigiotta, Thomas E.
Institution: University of Virginia , United States Geological Survey [USGS]
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 1995 through April 1, 1997
Project Amount: $79,000
RFA: Exploratory Research - Engineering (1995) Recipients Lists
Research Category: Engineering and Environmental Chemistry , Land and Waste Management
Description:The objective of this project is to calibrate a mathematical model to field data on the transport of a nonionic surfactant, Triton X-100, and trichloroethene (TCE) through an unconfined, sand-and-gravel aquifer at Picatinny Arsenal. As part of a previously supported EPA project, laboratory and field experiments were conducted to study the effects of aqueous Triton X-100 concentrations less than critical micelle concentration on the rate of TCE desorption from natural soil to water. It was hypothesized that low surfactant concentrations can increase the hydration of soil organic matter and thereby lower the diffusive resistances for TCE desorption by providing a less tortuous path for TCE diffusion from the soil organic matter to the bulk aqueous phase. Based on laboratory batch and column desorption experiments, it was determined that Triton X-100, at aqueous equilibrium concentrations as low as 30 mg/L, increased the rate of TCE desorption from soil collected at the field site.
These experiments were followed by a field test of this technology at a TCE-contaminated aquifer at Picatinny Arsenal undergoing pump-and-treat remediation. For the field test, a series of injection and monitoring wells were installed in the center of the contaminant plume. A bromide-ion tracer test was conducted to quantify advection velocities and dispersivities. An aqueous solution of Triton X-100 was injected and the movement of the surfactant through the aquifer was monitored over time. The TCE concentration in the ground-water was also monitored. At present, the surfactant and TCE concentration data are being analyzed by a two-dimensional model that accounts for advection, dispersion, and both equilibrium and rate-limited sorption/desorption. The model that accounts for equilibrium sorption has been unsuccessful at representing either the surfactant or TCE transport through the aquifer. Kinetic imulations are ongoing, but preliminary results suggest the rate-limited sorption model will better describe the observed surfactant and TCE concentration data. Furthermore, preliminary simulations reveal that the surfactant has increased the rate of TCE desorption from soil to water at the field site by increasing the mass-transfer coefficient for desorption. It appears that even relatively low concentrations of Triton X-100 can improve the remediation efficiency of existing pump-and-treat ground-water remediation systems.