title: A comparison of physicochemical methods for the remediation of porous medium systems contaminated with tar.
abstract: The remediation of former manufactured gas plant (FMGP) sites contaminated with tar DNAPLs (dense non-aqueous phase liquids) presents a significant challenge. The tars are viscous mixtures of thousands of individual compounds, including known and suspected carcinogens. This work investigates the use of combinations of mobilization, solubilization, and chemical oxidation approaches to remove and degrade tars and tar components in porous medium systems. Column experiments were conducted using several flushing solutions, including an alkaline-polymer (AP) solution containing NaOH and xanthan gum (XG), a surfactant-polymer (SP) solution containing Triton X-100 surfactant (TX100) and XG, an alkaline-surfactant-polymer (ASP) solution containing NaOH, TX100, and XG, and base-activated sodium persulfate both with and without added TX100. The effectiveness of the flushing solutions was assessed based on both removal of polycyclic aromatic hydrocarbon (PAH) mass and on the reduction of dissolved-phase PAH concentrations. SP flushes of 6.6 to 20.9 PV removed over 99% of residual PAH mass and reduced dissolved-phase concentrations by up to two orders of magnitude. ASP flushing efficiently removed 95-96% of residual PAH mass within about 2 PV, and significantly reduced dissolved-phase concentrations of several low molar mass compounds, including naphthalene, acenaphthene, fluorene, and phenanthrene. AP flushing removed a large portion of the residual tar (77%), but was considerably less effective than SP and ASP in terms of the effect on dissolved PAH concentrations. Persulfate was shown to oxidize tar components, primarily those with low molar mass, however, the overall degradation was relatively low (30-50% in columns with low initial tar saturations), and the impact on dissolved-phase concentrations was minimal.
authors.affiliation: Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, 148 Rosenau Hall, CB 7431, Chapel Hill, NC 27599, United States. Electronic address: shaus@live.unc.edu.
authors.forename: Scott C
authors.initials: SC
authors.lastname: Hauswirth
authors.affiliation: Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, 148 Rosenau Hall, CB 7431, Chapel Hill, NC 27599, United States. Electronic address: casey_miller@unc.edu.
authors.forename: Cass T
authors.initials: CT
authors.lastname: Miller
mesh_terms: D015142:Baltimore; D052918:Environmental Restoration and Remediation / Q000379:methods*; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D011108:Polymers; D012989:Soil Pollutants; D013501:Surface-Active Agents
keywords: Alkaline flushing; Alkaline–polymer; Alkaline–surfactant–polymer; Coal tar; Groundwater contamination; In situ chemical oxidation; Manufactured gas plant; PAH; Persulfate; Polymer flushing; Remediation; Surfactant; Surfactant–polymer; Xanthan gum