Pilot‐scale study of in situ steam extraction for the recovery of dense nonaqueous phase liquids from the vadose zone

Abstract

An environmental audit of a manufacturing site in eastern Pennsylvania revealed the presence of dense nonaqueous phase liquids (DNAPLs) in the vadose zone. The principal analyte detected in this audit was chloroform. The current recovery scheme, soil‐vapor extraction (SVE), does not yield a sufficient rate of DNAPL recovery to be economically feasible. A pilot plant was constructed at the site to determine the effects of steam injection on DNAPL recovery: Several large, stainless steel columns were packed with uncontaminated soil from the site and spiked with chloroform. Two 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 recovery of 15% was achieved by SVE. Significant levels of chloroform were detected in the simulated water table of one of the steam‐charged reactors.