Simulation of dense non-aqueous phase liquid remediation through steam-enhanced extraction

Abstract

Steam-enhanced extraction has been reviewed by many researchers as an innovative technology to remediate dense non-aqueous phase liquid (DNAPL) from subsurface. However, the application of steam-enhanced extraction to heterogeneous subsurface conditions is still obscurity and its implementation is limited due to steam flow sensitivity to site characterization. Two-dimensional (2-D) simulations were performed to assess the efficiency of steam-enhanced extraction in remediation of heterogeneous subsurface contaminated with tetrachloroethylene (PCE) spill. The simulation was performed with four different steam injection rates. The results shows that increased in steam injection rate will increase the PCE remediation time. The steam injection with the rate of 1.0 x 10-4 kg/s was successfully removing 100% of the PCE. There are significant impacts in the difference in remediation time with the increment approximately 20 min, 40 min and 70 min for every 2.0 x 10-5 kg/s increment. The dominant mechanisms of PCE removal is physical displacement through vaporization and co-boiling enhanced by steam distillation and steam stripping. The simulation results of steam-enhanced extraction for PCE removal was compared with surfactant-enhanced method implemented in existing experimental study. It was discovered that the time required to remove PCE using steam-enhanced extraction is four times faster than the time required to remove PCE using surfactant-enhanced method. This shows the capability of steam-enhanced extraction to recover contaminant more effectively. Steam-enhanced extraction has a greatest potential to decrease clean-up time which will offset greater capitol cost of the system.