No abstract

A field demonstration of surfactant‐enhanced solubilization was completed in a shallow unconfined aquifer located at a Coast Guard Station in Traverse City, Michigan. The primary objectives of the study were: (1) to assess the ability of the vertical circulation well (VCW) system for controlling chemical extractants added to the subsurface; and (2) to assess the behavior of the surfactant solution in the subsurface, with a goal of maximum surfactant recovery. A secondary objective was to demonstrate enhanced removal of PCE and recalcitrant components of a jet fuel. The analytical results showed that the surfactant increased the contaminant mass extracted by 40–fold and 90–fold for the PCE and jet fuel constituents, respectively. The surfactant solution demonstrated minimal sorption (retardation) and did not precipitate in the subsurface formation. In addition, the VCW system was able to capture in excess of 95% of the injected surfactant solution. Additional field testing and full‐scale implementation of surfactant‐enhanced subsurface remediation should be performed.

No abstract

Surfactant‐enhanced subsurface remediation is being evaluated as an innovative technology for expediting ground‐water remediation. This paper reports on laboratory and modeling studies conducted in preparation for a pilot‐scale field test of surfactant‐enhanced subsurface remediation. Laboratory batch and column studies evaluated the surfactant‐contaminant ground‐water interactions in an effort to properly design the field‐scale demonstration. A series of laboratory tracer tests and numerical simulations were completed to demonstrate the effectiveness of the hydraulic system (a vertical circulation well—VCW) for capturing injected solutions in a shallow, highly conductive, unconfined ground‐water formation. The results of these studies were then used to optimize the performance of the VCW system during the subsequent field‐scale demonstration study which utilized the VCW for injecting and extracting a surfactant solution. Information from the simulation studies, combined with the results of the batch and column tests, was crucial for procuring regulatory approval for the field demonstration, and successful design of the field‐scale demonstration.

A glacio-fluvial aquifer located at Wurtsmith Air Force Base, Michigan, has been contaminated with JP-4 fuel hydrocarbons released by the crash of a tanker aircraft in October of 1988. A comprehensive analysis of the inorganic and organic geochemical constituents and geomicrobiological markers has documented the occurrence of in situ biodegradation of hydrocarbons in the aquifer.Concentration profiles of aromatic hydrocarbons, aromatic acids, and phospholipid ester-linked fatty acids (PLFA) in aquifer solids suggest microbially mediated degradation of hydrocarbons and production of aromatic acid metabolites. Microbial community structure as indicated by the PLFA patterns shows an absence of polyunsaturated fatty acids characteristic of microeukaryotes and high proportions of C 12 -C 20 fatty acids typical of bacteria. Contamination increased microbial biomass by one order of magnitude and shifted the community to a more anaerobic bacterial consortium.Jet fuel-4 (JP-4) spillage has been a source of contamination for soils and ground water. Monoaromatic and aliphatic hydrocarbons are major constituents of this fuel. Because the aromatic fraction of the fuel mixture is relatively water soluble, these compounds tend to migrate from contaminated soils into aquifers (7). A dissolved plume typically develops downgradient from the point of free product release. Physical (dispersion, volatilization), chemical (sorption, dissolution), and biological processes (microbial degradation) control the subsequent fate and transport of the dissolved contaminants in the subsurface. Aromatic hydrocarbons are subject to degradation by a variety of microbial transformation processes in the subsurface (2-3). Degradation of monoaromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylenes (BTEX) has been demonstrated in numerous laboratory studies. Biodegradation has been documented under aerobic (4), denitrifying (5-72), dissimilatory iron-reducing (75), sulfate-reducing (14-17), and methanogenic conditions (18)(19)(20)(21).Direct measurement of in situ biodegradation of contaminants is often difficult (22). The field evidence for potential microbial remediation of organic contaminants involves demonstration of compound mass removal, production of metabolites, functional microbial activities, and indirect measures of redox changes and isotopic composition of dissolved