COMPARISON OF TWO CYCLODEXTRIN REMEDIATION APPROACHES: LINE-DRIVE VERSUS PUSH-PULL

Cyclodextrin enhanced flushing of a military site contaminated with TCE-DNAPL was carried out under full scale conditions. Although initially setup as a line-drive system (i.e., injection of cyclodextrin flushing solution into dedicated injection wells and extraction from dedicated extraction wells after passage of the flushing solution through the DNAPL source zone), the remediation scheme was later modified to run in push-pull mode (i.e., injection and extraction of the cyclodextrin flushing solution from the same well(s)). Both remediation schemes were closely monitored and contaminant and cyclodextrin mass recoveries were calculated for each scenario. The field experiments revealed that the push-pull approach significantly outperformed the line-drive scheme. Not only was the contaminant mass recovery higher on a per-flushing-volume basis, but the overall cyclodextrin mass recovery achieved during push-pull operation far exceeded the line-drive mass recoveries. These findings have important implications regarding the feasibility of the cyclodextrin enhanced remediation technology in particular. Beyond that, our results may provide guidance for the design of other remediation strategies that are based on chemically enhanced flushing of a DNAPL source zone.