Simulated formation and flow of microemulsions during surfactant flushing of contaminated soil

Contamination of groundwater resources by non-aqueous phase liquids (NAPLs) has become an issue of increasing environmental concern. This study invest igated the formation and flow of microemulsions during surfactant flushing of NAPL-contaminated soil using the finite difference model UTCHEM, which w as verified with our laboratory experimental data. Simulation results showe d that surfactant flushing of NAPLs (i.e., trichloroethylene and tetrachlor oethylene) from the contaminated soils was an emulsion-driven process. Form ation of NAPL-in-water microemulsions facilitated the removal of NAPLs from contaminated soils. Changes in soil saturation pressure were used to monit or the mobilization and entrapment of NAPLs during surface flushing process . In general, more NAPLs were clogged in soil pores when the soil saturatio n pressure increased. Effects of aquifer salinity on the formation and flow of NAPL-in-water microemulsions were significant. This study suggests that the formation and flow of NAPL-in-water microemulsions through aquifer sys tems are complex physical-chemical phenomena that are critical to effective surfactant flushing of contaminated soils. (C) 2001 Elsevier Science Ltd. All rights reserved.