Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

Denis M. O'Carroll

Abstract

Nano-scale zero valent iron (nZVI) has shown promising mobility and in-situ reactivity with chlorinated volatile organic compounds when injected into saturated porous media. The current study evaluated nZVI mobility and subsequent reactivity with in-situ contaminants in a variably saturated porous media. The nZVI particles, synthesized onsite at subzero temperatures, demonstrated complete trichloroethene (TCE) degradation within the target area. Furthermore, a three dimensional finite difference model (CompSim) was utilized to investigate nZVI mobility in variably saturated zones. Model predicted well head data were in very good agreement with field observations. Simulation results showed that the injected slurry migrated radially outward from the injection well and that nZVI travel distance increases were not proportional to the increase in injected nZVI volume. This study suggested that the numerical simulator can be a practical tool for optimal design of nZVI field applications.

The second study aimed at alleviating back diffusion from low permeability porous media observed at numerous field studies. Experiments were conducted in a two-dimensional sandbox with alternate vertical layers of coarse sand and silt flooded with TCE at aqueous solubility. Electrokinetics (EK) was used to enhance permanganate delivery through the silt layers. The suite of experiments demonstrated that EK was able to drive more permanganate at a faster rate throughout the silt layers in comparison to no-EK experiments. The combined EK and permanganate application resulted in 4.4 orders of magnitude reduction in TCE concentrations compared to a 3.5 orders of magnitude reduction without EK application. This experiment demonstrated that EK coupled with permanganate application can be used to remediate low permeability strata.

The third study investigated a novel approach of EK assisted persulfate delivery followed by electrical resistance heating (ERH) for persulfate activation for low permeability soil remediation. The study showed that EK delivered persulfate throughout the silt. The application of ERH was successfully able to activate the persulfate within the porous matrix leading to complete in-situ tetrachlorothene (PCE) degradation. To the authors’ knowledge, this study was the first to combine EK and ERH for persulfate delivery and activation for low permeability soil remediation.

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