Remediation of Coal Tar Contaminated Porous Medium Systems

The legacy practice of municipal gas production has led to thousands of tar contaminated subsurface systems, which have resulted from the disposal and handling practices of combustion by-products formed during gas manufacturing. These tar wastes can vary widely in composition, but they are essentially always complex mixtures that contain all of the 16 poly-nuclear aromatic hydrocarbon (PAH) priority pollutants, and lOO's of other compounds as well. Conventional physicochemical remediation methods have not proven effective for remediating such sites. In this work, a novel approach is investigated based upon alkaline flushing to mobilize the residual tar contamination using a one-dimensional column. A follow-up approach is performed with an ethanol flush to further reduce the flux of PAHs from the treated source zone. More than 50% of the tar residual was removed during the alkaline flushing. Mechanistic understanding of the effects of alkaline solution flushing on wettability and tar mobilization deserve further consideration.Master of Science in Environmental Engineerin

Mobilization of Manufactured Gas Plant Tar with Alkaline Flushing Solutions

This experimental study investigates the use of alkaline and alkaline-polymer solutions for the mobilization of former manufactured gas plant (FMGP) tars. Tar-aqueous interfacial tensions (IFTs) and contact angles were measured, and column flushing experiments were conducted. NaOH solutions (0.01–1 wt.%) were found to significantly reduce tar-aqueous IFT. Contact angles indicated a shift to strongly water-wet, then to tar-wet conditions as NaOH concentration increased. Column experiments were conducted with flushing solutions containing 0.2, 0.35, and 0.5% NaOH, both with and without xanthan gum (XG). Between 10 and 44% of the residual tar was removed by solutions containing only NaOH, while solutions containing both NaOH and XG removed 81–93% of the tar with final tar saturations as low as 0.018. The mechanism responsible for the tar removal is likely a combination of reduced IFT, a favorable viscosity ratio, and tar bank formation. Such an approach may have practical applications and would be significantly less expensive than surfactant-based methods

Mobilization of Manufactured Gas Plant Tar with Alkaline Flushing Solutions

This experimental study investigates the use of alkaline and alkaline–polymer solutions for the mobilization of former manufactured gas plant (FMGP) tars. Tar–aqueous interfacial tensions (IFTs) and contact angles were measured, and column flushing experiments were conducted. NaOH solutions (0.01–1 wt.%) were found to significantly reduce tar–aqueous IFT. Contact angles indicated a shift to strongly water-wet, then to tar–wet conditions as NaOH concentration increased. Column experiments were conducted with flushing solutions containing 0.2, 0.35, and 0.5% NaOH, both with and without xanthan gum (XG). Between 10 and 44% of the residual tar was removed by solutions containing only NaOH, while solutions containing both NaOH and XG removed 81–93% of the tar with final tar saturations as low as 0.018. The mechanism responsible for the tar removal is likely a combination of reduced IFT, a favorable viscosity ratio, and tar bank formation. Such an approach may have practical applications and would be significantly less expensive than surfactant-based methods