Field Implementation of a Winsor Type I Surfactant/Alcohol Mixture for in Situ Solubilization of a Complex LNAPL as a Single-Phase Microemulsion

Abstract

A Winsor Type I surfactant/alcohol mixture was used as an in situ flushing agent to solubilize a multicomponent nonaqueous phase liquid (NAPL) as a single-phase microemulsion (SPME) in a hydraulically isolated test cell at Hill Air Force Base (AFB), Utah. The surfactant (polyoxyethylene(10) oleyl ether) and alcohol (1-pentanol) together comprised 5.5 wt % of the flushing solution. The NAPL was extremely complex, containing more than 200 constituents and a ‘pitch' fraction that was not solvent-extractable. The NAPL removal effectiveness of the SPME flood was evaluated using information from soil cores, partitioning tracer tests, and NAPL constituent breakthrough curves (BTCs) measured at three extraction wells. Soil core data indicated that approximately 90−95% of the most prevalent NAPL constituents were removed from the cell by the SPME flood. A comparison of pre- and postflushing partitioning tracer data indicated that about 72% of the measured NAPL volume was removed by the SPME flood. Integration of NAPL constituent BTCs indicated 55−75% removal of the target NAPL constituents when partitioning tracer data were used to estimate the initial amount of NAPL present and 60−175% removal of two target constituents when soil core data were used to estimate the amount of NAPL initially present. These results indicate that the SPME flood effectively removed the NAPL constituents of concern, but an insoluble anthropogenic residue was left behind.