Surfactant Flushing/Enhanced Biodegradation at a Dry Cleaner Site

A pilot-scale field test of in-situ alcohol flushing for enhanced solubilization and extraction of a dense nonaqueous phase liquid (DNAPL) source zone was conducted at a former dry cleaner site located in Jacksonville, Florida. This study was conducted to evaluate the feasibility of in-situ flushing for remediation of DNAPL sites in Florida. Groundwater at this site was contaminated with tetrachloroethylene (PCE) that had migrated below the water table, located at 3 m below ground surface (bgs), and collected at high saturations in thin, discontinuous layers in the 7.9 m to 9.4 m bgs depth interval. An oblong source zone (7.3 m × 2.7 m) was delineated using direct-push technologies, and further characterized using soil coring and partitioning tracer techniques. Tracer tests and in-situ alcohol flushing were conducted using three injection wells that approximately bisected the source zone and six recovery wells located on the outer perimeter of the source zone. A partitioning tracer test conducted before the alcohol flood provided an estimate of about 68 L of PCE within the zone swept by the wells. The test zone was flushed with 34 kL (equivalent to 2 pore volumes) of a 95% ethanol/5% water mixture over a period of 3 days. Alcohol flushing removed approximately 43 L of PCE from the test zone (62% removal effectiveness). These results were in agreement with soil core data that indicated approximately 65% removal and a postflushing partitioning tracer test that indicated approximately 26 L of PCE remaining (63% removal). Postflushing groundwater concentrations were monitored for a period of four years both in the source area and at multilevel samplers in the plume. Increased degradation products were quantified at a plume transect.