PILOT-SCALE STUDY OF IN-SITU STEAM EXTRACTION FOR THE RECOVERY OF DENSE NONAQUEOUS PHASE LIQUIDS FROM THE VADOSE ZONE

An environmental audit of a manufacturing site in eastern Pennsylvania revealed the presence of dense nonaqueous phase liquids (DNAPLs) in t he vadose zone. The principal analyte detected in this audit was chlor oform. The current recovery scheme, soil-vapor extraction (SVE), does not yield a sufficient rate of DNAPL recovery to be economically feasi ble. A pilot plant was constructed at the site to determine the effect s of steam injection on DNAPL recovery: Several large, stainless steel columns were packed with uncontaminated soil from the site and spiked with chloroform. Tio columns charged with saturated steam at 7.5 psig yielded 71 and 97% recoveries of the initial chloroform volume after the addition of less than one pore volume of steam. An average recover y of 15% was achieved by SVE. Significant levels of chloroform were de tected in the simulated water table of one of the steam-charged reacto rs.