Organoclay as variably permeable reactive barrier to manage NAPLs in groundwater

Organoclay as variably permeable reactive barrier to manage NAPLs in groundwater
이승학Craig H. Benson
organoclay; NAPL; permeable reactive barrier; PAHs; PRBs
Issue Date
2010년 한국지하수토양환경학회 추계학술발표회
, 215-215
Three commercial organoclays were evaluated as media for a variably permeable reactivebarrier (VPRB) to manage coal-tar creosote, a non-aqueous phase liquid (NAPL) consistingprimarily of polycyclic aromatic hydrocarbons (PAHs). Organoclays and organoclay-sand mixtureshaving at least 25% organoclay had NAPL conductivities less than 10U" m/s, whereas theirhydraulic conductivities to water were on the order of 0.001 m/s. Water migration was negligiblein organoclays solvated with NAPL. However, organoclays solvated with NAPL released PAHs tothe aqueous phase when contacted with fresh water, even under quiescent conditions. Adsorptionisotherms for aqueous phase PAHs tend to be convex upward within the range of concentrations ofenvironmental interest, and greater adsorption occurs when the aqueous phase contains multiplePAHs. Column tests were conducted with 100% organoclay and organoclay-sand mixtures using anaqueous solution containing dissolved naphthalene, acenaphthene, Phenanthrene, and fluoranthene for208-276 pore volumes of flow (PVF). Break through occurred at 190 PVF for only one organoclay(lowest organic carbon content) and only for naphthalene (lowest Kow). No other PAHs wereabove the detection limit in the effluent. Breakthrough predicted with solute transport analysesconducted using the batch isotherm parameters as input occurred later than observed in the columntest because isotherm models fit to the batch test data over-predicted sorption at lowconcentrations. The findings indicate that organoclays should be effective media for VPRBs tomanage creosote NAPL and associated PAHs dissolved in ground water. They block NAPLadvection, readily permit flow of water with dissolved PAHs, and sorb dissolved PAHs from waterflowing through the organoclay.
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