The correlation between post-in situ chemical oxidation concentration rebound and molecular diffusion

Sodium permanganate and potassium permanganate have been used for in situ chemical oxidation (ISCO) projects for approximately two decades now. After decades of application, concentration rebound has emerged as a common problem for this remediation strategy. Unfortunately after decades of research on ISCO, there has been very little research on the question of concentration rebound. Most research on the topic of ISCO has focused on demonstrating effectiveness, estimating kinetics, or quantifying the effects of reaction products. Only one study has demonstrated that a correlation between concentration rebound and hydrogeological parameters exists. This study uses a numerical solution to an advection-dispersion-reaction equation in order to quantify a correlation between the rate of rebound and molecular diffusivity in pure water. It accomplishes this by simulating a variety of sites contaminated with tetrachloroethene or trichloroethene that also had an ISCO with permanganate. Each simulation included advection, two-dimensional dispersion, oxidation, concentration rebound, natural oxidant demand, and retardation. Six sites were suitable for simulation and nine cells were delineated within the six sites. These cells allowed for a variety of soils, contaminants, injection methods (i.e. frequency, depth, mass of oxidant, duration, etc...), time scales, spatial scales, and hydrogeological variables to be examined. A robust correlation (R2=0.9257) was identified with a regression analysis between the molecular diffusion coefficient in pure water and the rate of concentration rebound. The correlation identified by this research offers several useful applications. One application of this research is that it is now possible to optimize the information gained by a thorough site characterization. For example, a more predictable rate of concentration rebound can be used to optimize the time intervals between oxidant injections. In addition, choosing injection well locations can be optimized by modeling the boundaries of an oxidant's effectiveness. Another application of this research is that a more predictable rate of concentration rebound can be used to compare the effectiveness of ISCO to other remediation technologies. This reduces a variety of uncertainties by allowing more informed decisions between very expensive remediation strategies.Ph. D.Includes bibliographical referencesIncludes vitaby Adam Karl Tressle