Cyclodextrin-enhanced in situ flushing of multiple-component immiscible organic liquid contamination at the field scale: Analysis of dissolution behavior

There is great interest in the potential use of solubility-enhancing agents for subsurface remediation of non-aqueous-phase organic liquid (NAPL) contamination. Cyclodextrin was demonstrated to be effective for NAPL removal during a recent pilot-scale field study. The study provides an opportunity to investigate the mechanisms controlling mass transfer between a multicomponent NAPL and an enhanced-flushing agent solution at the field scale. A relationship is developed to describe enhanced dissolution of a multiple- component NAPL and is used to analyze the field data. While NAPL dissolution behavior was generally complex during the cyclodextrin flush, the initial peak and final effluent concentrations for most of the target contaminants were within a factor of 2 of the equilibrium values predicted using the ideal enhanced-dissolution theory. This suggests that the dissolution of the multicomponent NAPL during the cyclodextrin flush may be approximately treated, at least for practical purposes, as an ideal, equilibrium process. It appears that the dissolution theory successfully predicted the observed behavior for this system. Thus, it may be useful for assisting in the planning, design, and evaluation of other enhanced-flushing applications involving multicomponent NAPL.