Field demonstration of in-situ microemulsion flushing for enhanced remediation of multiple chlorinated solvents contaminated aquifer

The remediation of in-situ microemulsion flushing for multiple chlorinated solvents contaminated groundwater is challenging, because different chlorinated solvent has major influence on microemulsion formation and solubilization behaviors. This work was conducted to evaluate the remediation effectiveness for various chlorinated solvents contaminated site and monitor the disturbance of groundwater during in-situ microemulsion flushing process. Groundwater at this site was contaminated with chlorobenzene (MCB), chloroaniline and nitrochlorobenzene. The medium layer was mainly composed of fine and silty sand, with average hydraulic conductivity of 4.97 m/d. Results of this field-scale test indicated in-situ microemulsion flushing successfully enhanced the apparent solubility of various chlorinated solvents. Post-flushing concentration of various chlorinated solvents were 1.33-71.6-fold the concentration of pre-flushing values at 10 sampling locations within the test zone. This field was flushed with 16.8 m3 microemulsion, removing approximately 18.49 kg chlorinated solvents. Besides, a trend in the desorption order of various chlorinated solvents was observed. The least hydrophobic pollutant was flushed first, followed by contaminants of increasing hydrophobicity. In addition, during remediation process, the indexes of groundwater fluctuated insignificantly, indicating the reagent had little disturbance to aquifer. This field work demonstrated the feasibility of in-situ microemulsion enhanced remediation via increasing apparent solubility of multiple chlorinated solvents.