An investigation of enhanced remediation techniques for the cleanup of subsurface DNAPL spills

Denser-than-water Non-Aqueous Phase Liquids (DNAPLs) are present at a significant fraction of contaminated groundwater sites. DNAPL spills have proven to be difficult to remediate, especially when the contaminants are present in the form of subsurface pools. In this work, novel strategies are presented for the remediation of spill sites containing DNAPLs pools along with improved methods for the study of DNAPL behavior within laboratory settings.; The first part of this work is an analysis of non-destructive measurement techniques for the observation of multiphase flow in porous media using x-ray absorption. A model of the physical process is constructed and new estimators are derived. Both the new estimators and existing analysis techniques are implemented as a suite of computer programs. The new estimators are compared to each other and to the existing techniques over a range of representative measurement problems. The estimators are shown to provide significantly improved accuracy and/or precision in return for the increased computational effort required.; The second part introduces a new class of DNAPL remediation techniques. The new remediation strategies employ controlled mobilization to remove the bulk of the DNAPL contaminant mass. The new strategies are implemented with a dense brine (sodium iodide) flushing solution and are tested in a series of laboratory flow cells representing a progression of increasingly realistic domains. The first is a one-dimensional tube packed with varying sand layers, the second is a two-dimensional vertical plate packed with a heterogeneous array of sands, and the third contains a fully three-dimensional and heterogeneous packing pattern. In all cells, DNAPL pools are created using trichlorethylene as the representative contaminant. The success of each remediation strategy is assessed by determining the relative masses of contaminant that are injected and subsequently recovered.; In many cases, the new strategies are able to remove the majority of pooled DNAPLs in relatively short time frames. These results are obtained across all of the heterogeneous domains tested. They are encouraging because they suggest that controlled mobilization strategies can overcome both the mass transfer limitations and the uncontrolled mobilization problems that plague competing technologies.