Remediation of PAH DNAPLs From a Former Manufactured Gas Plant Using Chemical Flooding

The remediation of dense nonaqueous phase liquids (DNAPLs) from subsurface systems remains one of the most persistent and challenging environmental problems. DNAPLs containing polycyclic aromatic hydrocarbons (PAHs), including coal tar and creosote, are especially challenging due to their multicomponent nature and complex physicochemical nature leading to complicated phase behavior. Former manufactured gas plants (MGPs) located around the country often contain considerable PAH DNAPL plumes from past coal tar disposal practices. Evidence suggests that the NAPL composition from these sites varies with distance from the source zone, possibly leading to a need for different remedial strategies within a single site. We examine chemical flooding methods to remediate DNAPLs from former MGPs via mobilization. We show that synthetic PAH mixtures can be successfully mobilized in one-dimensional column experiments using isopropyl alcohol. We also examine mobilization of NAPL from a former MGP as a function of location relative to the initial source, showing variability that can occur at such sites. In addition to mobilization, we also examine aqueous phase concentrations of PAHs pre and post alcohol flooding, which are a common end point of concern.