bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory Evaluation of the Use of Surfactants for Ground Water Remediation and the Potential for Recycling Them
Authors: Lee Dal‐Heui , Cody Robert D. , Hoyle Elythe L. 
Published: February 2007

AbstractThe primary goal of this study was to develop a suitable experimental and laboratory methodology for investigating the efficiency of surfactants in removing hydrophobic contaminants from sand and the efficient recovery of used surfactant solutions for reuse. One of the goals of this study was to test the use of a hydrophile‐lipophile balance (HLB) number as a suitable selection criterion. We used toluene as a model contaminant, Ottawa sand as a model porous medium, and six nontoxic, water‐soluble anionic or nonionic surfactants with HLB numbers ranging from 12 to greater than 25.Four of the six surfactants were judged to be less suitable on the basis of their properties (less suitable HLB and surface tension), and on batch experiments using separatory funnel, shaker table, and centrifugation methods. The two most suitable surfactants were trideceth‐19‐carboxylic acid (TDCA), an anionic surfactant, and polyoxypropylene‐polyoxyethylene block copolymer (POP‐POE), a nonionic surfactant. These two surfactants were then used for sand column leach experiments, and two of the less suitable surfactants were also investigated to determine if HLB number and batch experiments satisfactorily predicted leaching effectiveness.In sand column experiments, an aqueous surfactant solution containing a mixture of 1% anionic and 1% nonionic surfactant in a 1.6% NaOH solution was the most effective in removing the toluene. Removal efficiency of alkylaryl ethoxylate carboxylic acid (AECA), which has an HLB number of 19, was only slightly less than for the chemically similar TDCA, but that of dioctyl sulfosuccinate (DOSS) with an HLB greater than 25 was much less effective. These results indicate that HLB number alone is not a perfect indicator of surfactant effectiveness for leaching hydrophobic contaminants because the chemical structure of the surfactant is also important. In the counter‐current solvent extraction experiments designed to allow reuse of surfactants, the anionic surfactant solution (2% TDCA) was the most effectively recycled.
Use of LIF for Real‐Time In‐Situ Mixed NAPL Source Zone Detection
Authors: Kram Mark L. , Lieberman Stephen H. , Fee Jerry , Keller Arturo A. 
Published: February 2007

AbstractThe site characterization and analysis cone penetrometer system (SCAPS), equipped with realtime fluorophore detection capabilities, was used to delineate subsurface contaminant releases in an area where plating shop waste was temporarily stored. Records indicated that various nonaqueous phase liquids (NAPLs) were released at the site. The investigators advanced the SCAPS laser‐induced fluorescence (LIF) sensor to depths beneath the water table of the principal water‐bearing zone. The water table was located approximately 6 feet (1.8 m) below ground surface (bgs) across the site. Fluorescence, attributed to fuel compounds commingled with chlorinated solvents, was observed at depths ranging from 4.0 to 11.5 feet (1.2 to 3.5 m) bgs. Fluorescence, attributed to naturally occurring organic materials (by process of elimination and spectral characteristics) commingled with chlorinated solvent constituents, was observed at depths ranging from approximately 13 to 40 feet (4.0 to 12.2 m) bgs. Fluorescence responses from compounds confirmed to be commingled with chlorinated solvents indicates that the SCAPS fluorophore detection system is capable of indirectly delineating vadose zone and subaqueous chlorinated solvents and other dense nonaqueous phase liquids (DNAPLs) at contaminant release sites. This confirmation effort represents the first documented account of the successful application of LIF to identify a mixed DNAPL/LNAPL source zone.
Field Measurement of Dissolved Oxygen: A Comparison of Methods
Authors: Wilkin Richard T. , McNeil Mary S. , Adair. Cherri. J. , Wilson John T. 
Published: February 2007

AbstractThe ability to confidently measure the concentration of dissolved oxygen (D.O.) in ground water is a key aspect of remedy selection and assessment. Presented here is a comparison of the commonly practiced methods for determining D.O. concentrations in ground water, including colorimetric, membrane‐covered electrode, and modified Winkler techniques. The Winkler titration (azide and permanganate modifications) is the most accurate and precise technique for determining D.O. and is appropriate for applications with stringent data quality objectives. In addition, excellent correlation over a wide range of D.O. concentrations was found between Winkler titrations and colorimetric tests using the rhodazine D (below 1 part per million [ppm]) and indigo carmine reagents (above 1 ppm). Electrode measurements represent the simplest method for determining D.O. concentrations on a continuous basis and electrode determinations positively correlate with Winkler results above 1 ppm. Below 1 ppm, electrodes provide only a qualitative measure of low D.O. level, apparently due to slow electrode response.
DNAPL Removal from a Heterogeneous Alluvial Aquifer by Surfactant‐ Enhanced Aquifer Remediation
Authors: Londergan John T. , Meinardus Hans W. , Manner Paul E. , Jackson Richard E. , Brown Chris L. , Dwarakanath Varadarajan , Pope Gary A. , Ginn Jon S. , Taffinder Sam 
Published: February 2007

AbstractA demonstration of surfactant‐enhanced aquifer remediation (SEAR) was conducted at Hill Air Force Base (AFB), Utah. Two surfactant floods were undertaken in a test section of a heterogeneous alluvial aquifer with a hydraulic conductivity range of 2.8 to 8.6 ft/day (10‐5 to 10‐4 m/sec) and a pore volume of approximately 15,000 gallons (57 m3). The wellfield installed for the demonstration consisted of lines of three injection and three extraction wells, a central monitoring well, and a single hydraulic control well. No physical barriers to flow, such as sheet‐pile walls, were employed; surfactant flooding was controlled entirely by hydraulic manipulation of the flow field. The inter‐well distance between injectors and extractors was 20 feet (6 m); the distance between individual injectors and extractors in line was 10 feet (3 m). The water table was 25 feet (7.6 m) below ground surface with a saturated zone approximately 19‐feet thick (5.8 m). Residual dense nonaqueous phase liquids (DNAPL) remained in a zone of alluvium 42 to 46 feet (13 to 14 m) below ground surface following extraction of free‐phase DNAPL. The injectors and extractors were screened in this DNAPL zone. Three partitioning interwell tracer tests (PITTs) and two surfactant floods were conducted over four months during 1996. The surfactant floods removed 341 out of 346 gallons of residual DNAPL (1290 of 1310 L), according to the PITTs. This represents a total recovery of about 98.5% of the DNAPL volume present in the zone of residual DNAPL as determined by comparing the initial and final PITTs. There was no reduction in hydraulic conductivity due to colloid mobilization during the surfactant floods; in fact, the hydraulic gradient across the test zone decreased as the floods progressed. Concentrations of dissolved total chlorinated hydrocarbons in the test section decreased from 1000 mg/L before the floods to less than 10 mg/L following the floods. This demonstration is evidence of the technical practicability of DNAPL removal from alluvium.
Evaluation of BTEX Remediation by Natural Attenuation at a Coastal Facility
Authors: Suarez Monica P. , Rifai Hanadi S. 
Published: February 2007

AbstractNatural attenuation has emerged as a potential alternative for remediating sites contaminated with fuel hydrocarbons. This paper examines the viability of using attenuation through natural processes to remediate ground water at an industrial facility. The research combined field assessments with data analysis and modeling to evaluate plume stability and predict remediation times. Field data on natural attenuation indicate that BTEX contamination at the site is being attenuated at rates that vary within the range of 0.0001 to 0.0073/day. Stability analyses confirm that the BTEX plume has reached steady state. An analysis on mass flux showed that between 1979 and 1996, 95,000 pounds of BTEX were lost via biodegradation, while 8000 pounds were lost through other mechanisms. A first‐order biodegradation rate of 0.0002/day for BTEX was obtained from the change in the total mass of dissolved BTEX with time. Cleanup times in excess of 200 years for the site were estimated using analytical modeling of natural attenuation, which agreed well with the remediation times estimated using the attenuation rates calculated for the site.
A New Multilevel Ground Water Monitoring System Using Multichannel Tubing
Authors: Einarson Murray D. , Cherry John A. 
Published: February 2007

AbstractA new multilevel ground water monitoring system has been developed that uses custom‐extruded flexible 1.6‐inch (4.1 cm) outside‐diameter (O.D.) multichannel HOPE tubing (referred to as Continuous Multichannel Tubing or CMT) to monitor as many as seven discrete zones within a single borehole in either unconsolidated sediments or bedrock. Prior to inserting the tubing in the borehole, ports are created that allow ground water to enter six outer pie‐shaped channels (nominal diameter = 0.5 inch [1.3 cm]) and a central hexagonal center channel (nominal diameter = 0.4 inch [1 cm]) at different depths, facilitating the measurement of depth‐discrete piezometric heads and the collection of depth‐discrete ground water samples. Sand packs and annular seals between the various monitored zones can be installed using conventional tremie methods. Alternatively, bentonite packers and prepacked sand packs have been developed that are attached to the tubing at the ground surface, facilitating precise positioning of annular seals and sand packs. Inflatable rubber packers for permanent or temporary installations in bedrock aquifers are currently undergoing site trials. Hydraulic heads are measured with conventional water‐level meters or electronic pressure transducers to generate vertical profiles of hydraulic head. Ground water samples are collected using peristaltic pumps, small‐diameter bailers, inertial lift pumps, or small‐diameter canister samplers.For monitoring hydrophobic organic compounds, the CMT tubing is susceptible to both positive and negative biases caused by sorption, desorption, and diffusion. These biases can be minimized by: (1) purging the channels prior to sampling, (2) collecting samples from separate 0.25‐inch (0.64 cm) O.D. Teflon sampling tubing inserted to the bottom of each sampling channel, or (3) collecting the samples downhole using sampling devices positioned next to the intake ports. More than 1000 CMT multilevel wells have been installed in North America and Europe to depths up to 260 feet (79 m) below ground surface. These wells have been installed in boreholes created in unconsolidated sediments and bedrock using a wide range of drilling equipment, including sonic, air rotary, diamond‐bit coring, hollow‐stem auger, and direct push. This paper presents a discussion of three field trials of the system, demonstrating its versatility and illustrating the type of depth‐discrete data that can be collected with the system.
Pulsed Air Sparging in Aquifers Contaminated with Dense Nonaqueous Phase Liquids
Authors: Heron Gorm , Gierke John S. , Faulkner Barton , Mravik Susan , Wood Lynn , Enfield Carl G. 
Published: February 2007

AbstractAir sparging was evaluated for remediation of tetrachloroethylene (PCE) present as dense nonaqueous phase liquid (DNAPL) in aquifers. A two‐dimensional laboratory tank with a transparent front wall allowed for visual observation of DNAPL mobilization. A DNAPL zone 50 cm high was created, with a PCE pool accumulating on an aquitard. Detailed process control and analysis yielded accurate mass balances and insight into the mass‐transfer limitations during air sparging.Initial PCE recovery rates were high, corresponding to fast removal of residual DNAPL within the zone influenced directly by air channels. The vadose zone DNAPL was removed within a few days, and the recovery in the extracted soil vapors decreased to low values. Increasing the sparge rate and pulsing the air injection led to improved mass recovery, as the pulsing induced water circulation and increased the DNAPL dissolution rate. Dissolved PCE concentrations both within and outside the zone of air channels were affected by the pulsing. Inside the sparge zone, aqueous concentrations decreased rapidly, matching the declining effluent PCE flux. Outside the sparge zone, PCE concentrations increased because highly contaminated water was pushed away from the air injection point.This overall circulation of water may lead to limited spreading of the contaminant, but accelerated the time‐weighted average mass removal by 40% to 600%, depending on the aggressiveness of the pulsing. For field applications, pulsing with a daily or diurnal cycling time may increase the average mass removal rate, thus reducing the treatment time and saving in the order of 40% to 80% of the energy cost used to run the blowers. However, air sparging will always fail to remove DNAPL pools located below the sparge point because the air will rise upward from the top of a screen, unless very localized geological layers force the air to migrate horizontally. Unrecognized presence of DNAPL at chlorinated solvent sites residual and pools could potentially hamper success of air sparging cleanups, since the presence of small DNAPL pools, ganglia or droplets can greatly extend the treatment time.
Recovery of Coal Tar and Creosote from Porous Media: The Influence of Wettability
Authors: Hugaboom Daniel A. , Powers Susan E. 
Published: February 2007

AbstractThe recovery of coal tar or creosote, which are dense nonaqueous phase liquids (DNAPLs), from the subsurface has been used as a means of site remediation at several former manufactured‐gas plant sites and wood‐treating facilities. Surface‐active components in these complex DNAPL can have acid/base and surfactant characteristics that can significantly affect the wettability in these systems, with a reversal to DNAPL wetting at low pHs. These changes in wettability as a function of pH were employed to evaluate their significance on waterflooding efficiency in one‐dimensional soil columns. The use of pH as a means of controlling wettability resulted in identical density and viscosity properties between the water‐and DNAPL‐wet conditions. At some of the higher pHs, the interracial tension changed as well as the wettability. Maintaining a constant dimensionless capillary number was used to minimize the effect of this variable. DNAPL saturations remaining in the DNAPL‐wet systems after waterflooding ranged from 38% to 47%. Significantly lower final DNAPL saturations were achieved for water‐wetting systems (15% to 30%).
Fate of Pharmaceuticals During Ground Water Recharge
Authors: Drewes Jörg E. , Heberer Thomas , Rauch Tanja , Reddersen Kirsten 
Published: February 2007

AbstractPharmaceuticals and personal care products (PPCPs) have recently been detected in the aquatic environment. Many studies have identified domestic waste water discharge as the source for detectable concentrations of PPCPs in surface water. PPCPs are a concern for the aquatic environment when production and use are sufficiently large and physicochemical properties are appropriate. Hydrophilic PPCPs present in surface water or waste water may also affect ground water quality where water is used to recharge ground water. However, less is known about how efficiently PPCPs are removed during percolation through the subsurface. The scope of this study was to examine the fate of selected PPCPs during ground water recharge at two water reuse sites where secondary and tertiary treated waste water is used for subsequent ground water recharge. The ground water recharge sites selected differ in aboveground treatment and geohydrological settings. The selected pharmaceutials represent blood lipid regulators, analgesics/anti‐inflammatories, blood viscosity agents, and antiepileptics. Organic iodine was used as a surrogate parameter for X‐ray contrast agents. Composite samples of treated waste water and from ground water monitoring wells were collected and analyzed for Pharmaceuticals using gas chromatography with mass spectroscopic detection.The study revealed that the stimulant caffeine, analgesic/anti‐inflammatory drugs such as diclofenac, ibuprofen, ketoprofen, naproxen, and fenoprofen, and blood lipid regulators such as gemfibrozil were efficiently removed to concentrations near or below the detection limit of the analytical method after retention times of less than six months during ground water recharge. The antiepileptics carbamazepine and primidone were not removed during ground water recharge under either anoxic saturated or aerobic unsaturated flow conditions during travel times of up to eight years. Organic iodine showed a partial removal only under anoxic, saturated conditions as compared to aerobic conditions and persisted in the recharged ground water.
A Comparison of Benzene and Toluene Plume Lengths for Sites Contaminated with Regular vs. Ethanol‐Amended Gasoline
Authors: Ruiz‐Aguilar G.M.L , O'Reilly K. , Alvarez P.J.J. 
Published: February 2007

AbstractThis article describes various statistical analyses of plume‐length data to evaluate the hypothesis that the presence of ethanol in gasoline may hinder the natural attenuation of hydrocarbon releases. Plume dimensions were determined for gasoline‐contaminated sites to evaluate the effect of ethanol on benzene and toluene plume lengths. Data from 217 sites in Iowa (without ethanol; set 1) were compared to data from 29 sites in Kansas that were contaminated by ethanol‐amended gasoline (10% ethanol by volume; set 2). The data were log‐normally distributed, with mean benzene plume lengths (± standard deviation) of 193 ± 135 feet for set 1 and 263 ± 103 feet for set 2 (36% longer). The median lengths were 156 feet and 263 feet (69% longer), respectively. Mean toluene plume lengths were 185± 131 feet for set 1 and 211 ±99 feet for set 2 (14% longer), and the median lengths were 158 feet and 219 feet (39% longer), respectively. Thus, ethanol‐containing BTEX plumes were significantly longer for benzene (p < 0.05), but not for toluene. A Wilcoxon signed rank test showed that toluene plumes were generally shorter than benzene plumes, which suggests that toluene was attenuated to a greater extent than benzene. This trend was more pronounced for set 2 (with ethanol), which may reflect that benzene attenuation is more sensitive to the depletion of electron acceptors caused by ethanol degradation. These results support the hypothesis that the presence of ethanol in gasoline can lead to longer benzene plumes. The importance of this effect, however, is probably site‐specific, largely depending on the release scenario and the available electron acceptor pool.
Evaluation of the Johnson and Ettinger Model for Prediction of Indoor Air Quality
Authors: Hers Ian , Zapf‐Gilje Reidar , Johnson Paul C. , Li Loretta 
Published: February 2007

AbstractScreening level models are now commonly used to estimate vapor intrusion for subsurface volatile organic compounds (VOCs). Significant uncertainty is associated with processes and models and, to date, there has been only limited field‐based evaluation of models for this pathway. To address these limitations, a comprehensive evaluation of the Johnson and Ettinger (J&E) model is provided through sensitivity analysis, comparisons of model‐predicted to measured vapor intrusion for 11 petroleum hydrocarbon and chlorinated solvent sites, and review of radon and flux chamber studies. Significant intrusion was measured at five of 12 sites with measured vapor attenuation ratios (αm's) (indoor air/source vapor) ranging from ∼1 × 10−6 to 1 × 10−4. Higher attenuation ratios were measured for studies using radon, inert tracers, and flux chambers; however, these ratios are conservative owing to boundary conditions and tracer properties that are different than those at most VOC‐contaminated sites. Reasonable predictions were obtained using the J&E model with comparisons indicating that model‐predicted vapor attenuation ratios (αp's) were on the same order, or less than the αm's. For several sites, the (m were approximately two orders of magnitude less than the a 's indicating that the J&E model is conservative in these cases. The model comparisons highlight the importance in using appropriate input parameters for the J&E model. The regulatory implications associated with use of the J&E model to derive screening criteria are also discussed.
In Situ Abiotic Detoxification and Immobilization of Hexavalent Chromium
Authors: Khan Faruque A. , Puts Robert W. 
Published: February 2007

AbstractDetailed site characterization data from the former electroplating shop at the U.S. Coast Guard Air Support Center, Elizabeth City, North Carolina, suggested that the elevated Cr(VI) in the capillary fringe area had contaminated the ground water at the site. Most of the mobile Cr(VI) is present in the capillary fringe zone of the aquifer under an oxidizing environment. Current literature suggests that the reduction of Cr(VI) to Cr(III) through in situ redox manipulation in the presence of a reductant is an innovative technique for remediating chromate‐contaminated sediments and ground water. The objective of this study was to evaluate the effectiveness of sodium dithionite in creating a reductive environment to remediate Cr(VI) present in soil. Sodium dithionite, a strong reductant, was injected into a small area of the vadose zone where elevated Cr(VI) was identified. Several striking changes observed in the target zone during the post‐injection monitoring periods include a significant decrease in Eh(SHE), as much as ∼700 mV, absence of dissolved oxygen for 48 weeks, and the increase of Fe(II) concentrations. Results indicated that the in situ remedial treatment of Cr(VI) in the capillary fringe area was effective and consequently the concentration of Cr(VI) in ground water dropped below the MCLG level. This research demonstrated the effectiveness of in situ abiotic remediation by reducing Cr(VI) concentrations, mobility, and toxicity in soils and ground water within a short period of time. Therefore, sodium dithionite would be a feasible and cost‐effective option for a full‐scale remedial approach for the contaminated site at the U.S. Coast Guard Facility.