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Innovative Green Treatment of Former Manufactured Gas Plant Dense Non Aqueous Phase Liquids using Surfactant-Enhanced In-Situ Chemical Oxidation (S-ISCOTM)

ABSTRACT

Surfactant-Enhanced In-Situ Chemical Oxidation (S-ISCOTM), is a new type of Coelution TechnologyTM for environmental remediation of complex sites. Traditional In Situ Chemical Oxidation (ISCO) methods have had limited success in degrading non-aqueous phase liquids (NAPLs) because of mass transfer limitations controlling the rate of dissolution of NAPL constituents into groundwater. ISCO reactions predominantly take place in the aqueous phase in the subsurface. S-ISCO™ Coelution Technology™ is more efficient at degrading NAPLs than ISCO, as the recations do not have the same limitations. The effectiveness of, Surfactant- Enhanced In-Situ Chemical Oxidation (S-ISCOTM), in reducing the amount of Former Manufactured Gas Plant (MGP) dense non-aqueous phase liquids (DNAPLs) in soils was demonstrated in a field verrified pilot study. The S-ISCOTM technology, patent-pending by VeruTEK Technologies, Inc., uses biodegradable, U.S. Food and Drug Administration (USFDA) Generally Recognized as Safe (GRAS) food-grade cosolvents and surfactants (VeruSOLTM) (for example, coconut oil, castor oil and citrus extracts) to solubilize immiscible phase MGP DNAPL organic compounds into groundwater. Application of S-ISCOTM with VeruSOLTM destroys contaminants in-place using traditional ISCO processes, particularly activated persulfate which generates a variety of powerful free radical species. S-ISCOTM involves coeluting both the cosolvent-surfactant mixture with the oxidant enabling simultaneous dissolution and oxidation. Selection of the specific VeruSOLTM mixture is dependent on the nature of the MGP DNAPL components, particularly, the mole fractions and octanol-water partition coefficients (Kow) of the individual organic compounds. The coelution involves controlling the rate of DNAPL compound dissolution and the oxidation reaction rates. Laboratory treatability studies demonstrated that the solubilization reaction by surfactant and surfactant/cosolvent mixtures resulted in significant increases in dissolved phased COCs without mobilizing NAPL. Soil column tests were run using homogenized soil from an MGP site and spiking the soil with DNAPL from the MGP site to approximate residual saturation with respect to MGP DNAPL. Various surfactants and cosolvent- surfactant mixtures were flushed through replicate columns. VOCs and SVOCs were periodically monitored in the column effluent using USEPA Methods 8260 and 8270. The simultaneous addition of Fe(II)-EDTA activated persulfate to a column being flushed with VeruSOLTM reduced total effluent COCs flushed from the column by 87 percent.

A large field pilot test confirmed that the S-ISCOTM process effectively degrades MGP tar- saturated soils without any significant increases of groundwater contaminant flux. The Pilot Test consisted of four injection phases and three post-injection monitoring Phases. Both the field and laboratory treatability studies found that VeruSOLTM treatment was able to solubilize both high and low molecular weight PAHs. Soils mass destruction analysis from more than 50 soil sampling locations collected before and after the S-ISCOTM Pilot Test indicates that polycyclic aromatic hydrocarbons (PAHs) and medium weight petroleum hydrocarbons (MPH) were significantly removed from the Pilot Test area. Thirty days after the termination of S- ISCOTM injection and 75 feet downgradient of injection wells, the mass flux was less than the pre-Pilot Test mass flux for PAH and MPH compounds and slightly greater for BTEX compounds.

Analysis of quarterly groundwater monitoring VOC and SVOC data from 18 monitoring wells in and downgradient of the Pilot Test Area was conducted for 1.5 years following completion of the Field Trial. Non Parametric Wilcoxon Signed Rank Test statistical methods were used to compare mean pre-S-ISCOTM PAH data from several years of data with quarterly sampling results for more than one year following completion of injections. The results of this analysis indicated that the PAH concentrations in the 18 groundwater monitoring well samples statistically decreased with a 99.8 confidence interval.

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