Cyclodextrin-enhanced in situ flushing of multiple-component immiscible organic liquid contamination at the field scale: Mass removal effectiveness

The feasibility of 'enhanced-solubility remidiation technologies, designed to enhance the removal of nonaqueous-phase organic liquids (NAPLs) from the subsurface, must be tested at the field scale. Herein are reported the results of an experiment designed to evaluate the effectiveness of a cyclodextrin (sugar) solution for enhanced-solubilization removal of a multicomponent NAPL from an aquifer. This effort is the first field test of this innovative technology, termed a 'complexing sugar flush' (CSF). The saturated zone within an enclosed cell was flushed with 8 pore volumes of a 10 wt % cyclodextrin solution. The cyclodextrin solution increased the aqueous concentrations of all the target contaminants to values from about 100 to more than 20 000 times the concentrations obtained during a water flush conducted immediately prior to the CSF. The degree of solubility enhancement was greater for the more-hydrophobic contaminants. Conversely, the relative mass removal was greater for the less-hydrophobic compounds due to their generally higher apparent solubilities, which effected a significant reduction in the initial mass during the relatively short experiment. The average reduction in soil-phase concentrations for the target contaminants was 41%. This mass-removal percentage corresponds well to the results of partitioning-tracer tests, which indicated a 44% reduction in the average NAPL saturation.