Evaluation of in-situ chemical flushing and oxidation technologies for the remediation of aquifer systems contaminated with DNAPLs

Organic compounds- such as petroleum hydrocarbons and chlorinated solvents- are widely used in numerous industrial applications. Because of their low solubility many of these compounds are often present in the environment in the form of dense non-aqueous phase liquids (DNAPLs) that act as long-term sources of pollutions. This study focuses on two technologies for the remediation of groundwater resources contaminated with DNAPLs: in-situ enhanced solubilization (ISES) and in-situ chemical oxidation (ISCO). The research aimed to investigate the synergetic benefits of combining these two technologies. Additionally, a numerical multiphase flow model was used to simulate the DNAPL fate and transport to improve our understanding of process mechanisms, and to explore alternative remediation methodologies and strategies. The performed laboratory experiments and modeling work show that the non-ionic surfactant Tween 80 is effective for the recovery of PCE entrapped in both silica sand and natural calcareous soil. For multicomponent DNAPL mixtures, the enhancement factor of each component plays an important role in determining the remediation efficiency. Combining surfactant enhanced dissolution with potassium permanganate produced improved overall mass removal. Pulse injection can yield longer contact times, resulting in more effective DNAPL removal. Heat-activated persulfate oxidation, whereby the system temperature is raised to about 50 ℃, can successfully activate the persulfate, resulting in improved DNAPL mass recovery. Furthermore, this study shows that multiphase modeling is an effective tool that can accurately simulate ISES and ISCO technologies, and potential help in the design and opitimization of field scale remediation of groundwater contaminated with DNAPLs.