Impact of enhanced-flushing reagents and organic liquid distribution on mass removal and mass discharge reduction

A series of column and flow cell experiments were conducted to investigate the impact of nonuniform organic liquid distribution on the relationship between reductions in contaminant mass discharge and reductions in source zone mass under conditions of enhancedsolubilization flushing. Trichloroethene was used as the model organic liquid, and sodium dodecyl sulfate and ethanol were used as representative enhanced-flushing reagents. The results were compared to those of waterflood control experiments. Concentrations of trichloroethene in the effluent exhibited a multi-step behavior with time, wherein multiple secondary periods of quasi steady state were observed. This nonideal behavior was observed for both the waterflood and enhanced-flushing experiments. For all flow cell experiments, the later stage of mass removal was controlled by the more poorly accessible mass associated with higher-saturation zones. The profiles relating reductions in contaminant mass discharge and reductions in mass exhibited a generally similar behavior for both the waterflood and enhanced-flushing experiments. This indicates that while the rates and magnitudes of mass removal are altered by the presence of a solubilization reagent solution, the fundamental mass removal process is not. The profiles obtained for the flow cell systems differed from those obtained for the column systems, highlighting the impact of source zone heterogeneity on mass removal behavior.