bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory Study of Air Sparging of TCE‐Contaminated Saturated Soils and Ground Water
Authors: Adams Jeffrey A. , Reddy Krishna R. 
Published: February 2007

AbstractAir sparging has proven to be an effective remediation technique for treating saturated soils and ground water contaminated by volatile organic compounds (VOCs). Since little is known about the system variables and mass transfer mechanisms important to air sparging, several researchers have recently performed laboratory investigations to study such issues. This paper presents the results of column experiments performed to investigate the behavior of dense nonaqueous phase liquids (DNAPFs). specifically trichloroethylene (TCE), during air sparging. The specific objectives of the study were (1) to compare the removal of dissolved TCE with the removal of dissolved light nonaqueous phase liquids (LNAPLs). such as benzene or toluene; (2) to determine the effect of injected air‐flow rate on dissolved TCE removal; (3) to determine the effect of initial dissolved TCE concentration on removal efficiency; and (4) to determine the differences in removal between dissolved and pure‐phase TCE. The test results showed that (1) the removal of dissolved TCE was similar to that of dissolved LNAPL: (2) increased air‐injection rates led to increased TCE removal at lower ranges of air injection, but further increases at higher ranges of air injection did not increase the rate of removal, indicating a threshold removal rate had been reached; (3) increased initial concentration of dissolved TCE resulted in similar rates of removal: and (4) the removal of pure‐phase TCE was difficult using a low air‐injection rate, but higher air‐injection rates led to easier removal.
Installing Multilevel Sampling Arrays to Monitor Ground Water and Contaminant Discharge to a Surface Water Body
Authors: Dean Sean M. , Lendvay John M. , Barcelona Michael J. , Adriaens Peter , Katopodes Nikolaos D. 
Published: February 2007

AbstractA simple, effective method for the installation and sampling of vertically discrete points in a dynamic beach environment was developed and tested on the eastern shore of Lake Michigan, The installation permitted the vertical resolution of a ground water plume discharging to the lake and allowed monitoring of temporal variations during relatively calm and stormy periods of the year. These installations permit the definition of vertical heterogeneities such as oxidation‐reduction conditions and geochemical characteristics that are expected to impact the transport and fate of ground water contaminants discharged to the surface water.
Ellog Auger Drilling: Three‐in‐One Method for Hydrogeological Data Collection
Authors: Sørensen Kurt , Larsen Flemming 
Published: February 2007

AbstractThe Ellog auger drilling method is an integrated approach for hydrogeological data collection during auger drilling in unconsolidated sediments. The drill stem is a continuous flight, hollow‐stem auger with integrated electrical and gamma logging tools. The geophysical logging is performed continuously while drilling. Data processing is carried out in the field, and recorded log features are displayed as drilling advances. A slotted section in the stem, above the cutting head, allows anaerobic water and soil‐gas samples to be taken at depth intervals of approximately 0.2 m. The logging, water, and gas sampling instrumentation in the drill stem is removable; therefore, when the drill stem is pulled back, piezometers can be installed through the hollow stem. Cores of sediments can subsequently be taken continuously using a technique in which the drill bit can be reinserted after each coring. The Ellog auger drilling method provides detailed information on small‐scale changes in lithology, sediment chemistry, and water, as well as gas compositions in aquifer systems–data essential to hydrogeological studies.
In‐Well Hydraulics of the Electromagnetic Borehole Flowmeter: Further Studies
Authors: Arnold Katrin B. , Molz Fred J. 
Published: February 2007

AbstractThe electromagnetic borehole flowmeter (EBF) is finding increasing application as a method for measuring hydraulic conductivity (K) distributions. A recent paper details an experimental/theoretical study of the effect of in‐well hydraulics on calculated K distributions based on EBF measurements (Dinwiddie et al. 1999). Results showed that minimizing head loss associated with flow through the meter was the key to producing accurate K values. Using the same experimental procedures, the previous study has been extended to develop data from a larger diameter (1 inch) EBF, and to determine if an EBF can be calibrated effectively without using an inflatable packer to force all flow through the meter annulus. Both experiments were aimed at producing low head loss conditions. Results show that overall calibration can be accomplished in the absence of a packer, which reduces head losses to nonmeasurable levels, and use of the 1‐inch EBF with a packer reduces head losses by a factor of 16 when compared with the 0.5‐inch EBF studied by Dinwiddie et al. (1999).
An Analysis of Low‐Flow Ground Water Sampling Methodology
Authors: Sevee John E. , White Carol A. , Maher David J. 
Published: February 2007

AbstractLow‐flow ground water sampling methodology can minimize well disturbance and aggravated colloid transport into samples obtained from monitoring wells. However, in low hydraulic conductivity formations, low‐flow sampling methodology can cause excessive drawdown that can result in screen desaturation and high ground water velocities in the vicinity of the well, causing unwanted colloid and soil transport into ground water samples taken from the well. Ground water velocities may increase several fold above that of the natural setting. To examine the drawdown behavior of a monitoring well, mathematical relationships can be developed that allow prediction of the steady‐state drawdown for constant low‐flow pumping rates based on well geometry and aquifer properties. The equations also estimate the time necessary to reach drawdown equilibrium. These same equations can be used to estimate the relative contribution of water entering a sampling device from either the well standpipe or the aquifer. Such equations can be useful in planning a low‐flow sampling program and may suggest when to collect a water sample. In low hydraulic conductivity formations, the equations suggest that drawdown may not stabilize for well depths, violating the minimal drawdown requirement of the low‐flow technique. In such cases, it may be more appropriate to collect a slug or passive sample from the well screen, under the assumption that the water in the well screen is in equilibrium with the surrounding aquifer.
An Evaluation of Physicochemical Treatment Technologies for Water Contaminated with MTBE
Authors: Keller Arturo A. , Sandall Orville C. , Rinker Robert G. , Mitani Marie M. , Bierwagen Britta , Snodgrass Michael J. 
Published: February 2007

AbstractTreatment of methyl tertiary‐butyl ether (MTBE) from contaminated surface and ground water supplies presents specific challenges due to the physicochemical properties of MTBE that depend strongly on its hydrophilic nature, and translate into a high solubility in water, and low Henry's constant and low affinity for common adsorbents. We evaluate four treatment technologies‐air stripping, granular activated carbon (GAC), hydrophobic hollow fiber membranes, and advanced oxidation processes (AOP)‐using ozone or ozone/hydrogen peroxide. Experimental work was carried out to generate parameter values necessary for the design of these processes. Ten different flow rates/concentration combinations were evaluated in our designs to cover the range from high flow rate/low concentration typical of surface water and ground water drinking water supplies to low flow rate/high concentration typical of ground water remediation sites. For all cases, the processes were designed to produce effluent water of 5 μg/L or less. Capital costs and operation and maintenance costs were determined at the feasibility level by using standard engineering estimating practices.Air stripping is the lowest cost technology for high flow rales (100 to 1000 gpm) if no air treatment is required. Hollow fiber membranes are the lowest cost technology for flow rates of 10 to 100 gpm if no air treatment is required, which is typical at these low flow rates. GAC will be most costeffective at all flow rates if air treatment is required and the influent water has low levels of other organic compounds. AOP using ozone or ozone/hydrogen peroxide is in all cases more expensive than the alternative technologies, and there are sufficient uncertainties at this point with respect to byproducts of AOP to warrant further study of this technology. The cost of treating MTBE‐contaminated water for conventional technologies such as air stripping and GAC is 40% to 80% higher than treating water contaminated only with other hydrocarbons such as benzene.
DNAPL Removal from a Heterogeneous Alluvial Aquifer by Surfactant‐Enhanced Aquifer Remediation
Authors: Londergan John T. , Meinardus Hans W. , Mariner 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.
Experimental and Economic Assessment of Two Surfactant Formulations for Source Zone Remediation at a Former Dry Cleaning Facility
Authors: Ramsburg C. Andrew , Pennell Kurt D. 
Published: February 2007

AbstractTreatability tests and cost analyses were conducted to provide objective criteria for selection of a surfactant formulation to be used for surfactant enhanced aquifer remediation (SEAR) of a tetrachloroethene (PCE)‐contaminated site in Oscoda, Michigan. Two surfactant formulations, 4% Tween 80 + 500 mg/L CaCl2 and 8% Aerosol MA/IPA +15,000 mg/L NaCl + 1000 mg/L CaCl2, were considered based on their capacity to solubilize PCE and prior use in SEAR applications. Results of a two‐dimensional aquifer cell experiment indicated that 53% of the released PCE was recovered after flushing with approximately 8 pore volumes of 4% Tween 80. In contrast, only 3 pore volumes of 8% Aerosol MA/IPA solution were required to recover 78% of the PCE from the two‐dimensional aquifer cell, although the greater recovery of PCE was attributed, in large part, to the higher concentration of Aerosol MA. However, mobilization of PCE as free product was observed during the 8% Aerosol MA/IPA flood, which was consistent with total trapping number (NT) calculations. At the pilot‐scale, SEAR treatment costs were estimated to be $222,000 and $244,000 for 4% Tween 80 and 8% Aerosol MA/IPA, respectively, which compared favorably to the estimated pump‐and‐treat cost of $316,000. Projected full‐scale costs, based on a line‐drive flushing system, were $382,000 for 4% Tween 80 and $443,000 for 8% Aerosol MA/IPA. In contrast, full‐scale pump‐and‐treat costs were estimated to be $1,167,000. Surfactant recycling was shown to be logistically and economically infeasible at the pilot scale, and provided only a minimal cost benefit for 4% Tween 80 at the full scale. Based on the similarities in solubilization capacity and treatment cost, but substantially lower risk of PCE displacement, Tween 80 was recommended over Aerosol MA/IPA for pilot‐scale testing of SEAR.
Application Procedures for the Electromagnetic Borehole Flowmeter in Shallow Unconfined Aquifers
Authors: Crisman Stefanie A. , Molz Fred. J. , Dunn David L. , Sappington Frank C. 
Published: February 2007

AbstractIt is increasingly common for the electromagnetic borehole flowmeter (EBF) to he used to measure hydraulic conductivity (K) distributions in subsurface flow systems. Past applications involving the EBF have been made mostly in confined aquifers (Kabala 1994; Boman et al. 1997; Podgorney and Ritzi 1997; Ruud and Kabala 1997a, 1997b; Flach et al. 2000), and it has been common to set up a flow field around a test well using a small pump that is located near the top of the well screen (Mob, and Young 1993). In thin, unconfined aquifers that exhibit ground water tables near the ground surface and that undergo drawdown during pumping, such a configuration can be problematical because pumping and associated drawdown may effectively isolate the upper portion of the aquifer from the flowmeter. In these instances, a steady‐state flow field in the vicinity of the test well may be created using injection rather than pumping, allowing for testing in the otherwise isolated upper portion of the aquifer located near the initial water table position. Using procedures developed by Molz and Young (1993), which were modified for an injection mode application, testing was conducted to determine whether or not the injection mode would provide useful information in a shallow, unconfined aquifer that required the collection of data near the initial water table position. Results indicated that the injection mode for the EBF was well suited for this objective.
In Situ Measurement of Electro‐Osmotic Fluxes and Conductivity Using Single Wellbore Tracer Tests
Authors: McNab Walt W. , Ruiz Roberto 
Published: February 2007

AbstractElectro‐osmosis (EO), the movement of water through porous media in response to an electric field, offers a means for extracting contaminated ground water from fine‐grained sediments, such as clays, that are not easily amenable to conventional pump‐and‐treat approaches. The EO‐induced water flux is proportional to the voltage gradient in a manner analogous to the flux dependence on the hydraulic gradient under Darcy's law. The proportionality constant, the soil electro‐osmotic conductivity or keo, is most easily measured in soil cores using bench‐top tests, where flow is one‐dimensional and interfering effects attributable to Darcy's law can be directly accounted for. In contrast, quantification of EO fluxes and keo in the field under deployment conditions can be difficult because electrodes are placed in ground water wells that may be screened across a heterogeneous mixture of lithologies. As a result, EO‐induced water fluxes constitute an approximate radial flow system that is superimposed upon a Darcy flow regime through permeable pathways that may or may not be coupled with hydraulic head differences created by the EO‐induced water fluxes. A single well comparative tracer test, which indirectly measures EO fluxes by comparing wellbore tracer dilution rates between background and EO‐induced water fluxes, may provide a means for routinely quantifying the efficacy of EO systems in such settings. EO fluxes measured in field tests through this technique at a ground water contamination site were used to estimate a mean keo value through a semianalytic line source model of the electric field. The resulting estimate agrees well with values reported in the literature and with values obtained with bench‐top tests conducted on a soil core collected in the test area.
Remediation of Sea Water Intrusion: A Case Study
Authors: Tsanis Ioannis K. , Song Li‐Fan 
Published: February 2007

AbstractSea water intrusion and remediation in the Upper Floridan Aquifer in South Carolina is simulated using the finite‐element model SUTRA developed by the U.S. Geological Survey. A sensitivity analysis of the effect of the hydrogeologic parameters on the sea water recharge and seepage velocities is performed. An increase in confining unit and/or in aquifer conductivity results in an increase of the sea water recharge. An increase in aquifer porosity results in a decrease of the sea water recharge. Among the three remedial techniques simulated—reduced aquifer withdrawals, an injection well, and a combined injection and capture well—the reduced aquifer withdrawals and injection well are the best methods for preventing sea water intrusion.
Analytical Model for Removal of a Uniformly Distributed Single‐Component NAPL Under Nonequilibrium Conditions
Authors: Brouwers H.J.H. , Augustijn D.C.M. 
Published: February 2007

AbstractIn this paper a simple analytical model is presented for the one‐dimensional transport equation describing the removal of a uniformly distributed, single‐component NAPL under nonequilibrium conditions. Both advective and dispersive transport are included in the model. The model describes two distinct stages: a solution for the time the amount of NAPL declines but the length of the NAPL‐containing region remains constant, and a solution from the moment the front, behind which all NAPL is depleted, starts to move. The model is valid for both dissolution (i.e., by water) or volatilization (i.e., by air). Dissolution (or volatilization) is considered a firstorder rate process with a constant mass‐transfer rate coefficient. As expected, the model approaches the solution for equilibrium conditions if the mass‐transfer coefficient tends to infinity. Even though the model is based on some rigorous assumptions, the simplicity of the model makes it useful for obtaining an initial mass‐transfer rate coefficient from experimental data, which can be used to estimate the time required to dissolve all NAPL, as shown for two data sets taken from the literature.
Tracer Tests and Image Analysis of Biological Clogging in a Two‐Dimensional Sandbox Experiment
Authors: Kildsgaard Jesper , Engesgaard Peter 
Published: February 2007

AbstractA two‐dimensional flow experiment on biological clogging was carried out by biostimulating a sandbox packed with sand inoculated with bacteria. Biostimulation consisted of continuously injecting nutrients (acetate and nitrate). Clogging was visualized by frequently carrying out colored tracer experiments using Brilliant Blue. The tracer experiments were recorded with a digital camera and converted to concentration maps using an image‐analysis method that revealed in detail the complex spreading pattern surrounding clogged areas. Clogging resulted in a finger‐like spreading of the tracer around the main clogged area. Fingers were asymmetric and their dominant direction changed over time. Although the flow field was complex around the main clogged area, the effect on the bulk hydraulic conductivity at the scale of the sandbox was very small.
Nitrate Source Identification Using δ15N in a Ground Water Plume Near an Intensive Swine Operation
Authors: Karr Jonathan D. , Showers William J. , Hinson Thomas H. 
Published: February 2007

AbstractNitrate‐contaminated ground water beneath and adjacent to an intensive swine (Sus scrofa domesticus) production facility in the Middle Coastal Plain of North Carolina was analyzed for δ15N of nitrate (δ15N‐NO3). Results show that the isotopic signal of animal waste nitrogen is readily identifiable and traceable in nitrate in this ground water. The widespread land application of animal wastes from intensive livestock operations constitutes a potential source of nitrogen contamination to natural water throughout large regions of the United States and other countries. The site of the present study has been suspected as a nitrate contamination source to nearby domestic supply wells and has been monitored for several years by government and private water quality investigators through sampling of observation wells, ditches, and streams. δ15N of nitrate allowed direct identification of animal waste‐produced nitrate in 11 of 14 wells sampled in this study, as well as recognition of nitrate contributions from non‐animal waste agricultural sources in remaining wells.
Laboratory Column Experiments Using Polymer Mats to Remove Selected VOCs, PAHs, and Pesticides from Ground Water
Authors: Patterson Bradley Mark , Davis Gregory Bruce , McKinley Allan James 
Published: February 2007

AbstractLarge‐scale column experiments were undertaken to evaluate the potential of polymer mats to remove selected volatile organic compounds, polycyclic aromatic hydrocarbons, and pesticides (atrazine and fenamiphos) from ground water and potentially to act as permeable reactive barriers in contaminated ground water environments. The polymer mats, composed of interwoven silicone (dimethylsiloxane) tubes and purged with air, were installed in 2 m long flow‐through columns. The polymer mats proved efficient in physically removing (stripping) benzene and naphthalene from contaminated water. Removal efficiencies for both these compounds from an aqueous phase flowing past a polymer mat were 75% or greater. However, for atrazine and fenamiphos, removal efficiencies were 5% or less, probably as a result of their lower Henry's law constants and possibly lower polymer diffusion coefficients.These experiments indicate that, at least for relatively volatile compounds, polymer mats can provide a remediation technique for the removal of organic compounds from contaminated water. Application of this technique may be well suited as a longer‐term, semipassive strategy to remediate contaminated ground water, using natural ground water flow to deliver contaminated ground water to polymer mats engineered as sorption‐stripping barriers.Additional benefits of this technique may include targeted delivery of gaseous chemical amendments, such as oxygen, to enhance aerobic biodegradation and to further reduce any residual concentrations of contaminants.