bluuebunny/crossref_metadata_2025_split huggingface dataset:
Planning Urban Growth in Ground Water Recharge Areas: Central Valley, Costa Rica
Authors: Rodriguez‐Estrada Hugo , Loaiciga Hugo A. 
Published: February 2007

AbstractNitrate levels in the ground water of the Central Valley of Costa Rica have increased in relation to the past. Previous studies determined that the unseweved sanitation systems in the recharge areas are the main source of nitrogen. Calculations are made in this study to estimate the maximum population density allowable without improved sewage systems in order to keep the nitrogen levels in ground water below the World Health Organization (WHO) criteria. Results were achieved employing a mass balance that involved the concentration and rate of domestic effluents and the flow rate in the aquifer, as well as an estimation of the effects caused by the agricultural activity. It was concluded that, in general terms, the population density must not exceed 45 inhabitants per hectare. Otherwise, sewage systems and treatment plants are necessary. These conclusions provide a basis for urban growth planning, which will protect ground water quality. The method used in this case should apply to similar situations.
Investigation of Ground Water Contamination by Fenamiphos and Atrazine in a Residential Area: Source and Distribution of Contamination
Authors: Appleyard Stephen J. 
Published: February 2007

AbstractGround water in a residential area of Perth. Western Australia, was contaminated with fenamiphos and atrazine. probably as a result of the storage and handling of these chemicals at a residential properly. Sampling of existing wells indicated that atrazine and fenamiphos concentrations in ground water beneath a neighboring property were 2000 μg/L and 1000 μg/L, respectively. Fenamiphos concentrations were sufficiently high to be toxic on prolonged skin contact, and contamination posed a public health threat to nearby residents with private wells. Management of the contamination problem included restricting ground water use in the area and using a recovery well to pump contaminated ground water.
The Application of a Statistical Trend Analysis Model to Ground Water Monitoring Data from Solid Waste Landfills
Authors: Lachance Amy D. , Stoline Michael R. 
Published: February 2007

AbstractA statistical trend methodology is used to compare ground water quality between eight landfill sites in western Michigan as a case study. Monitoring data were collected over a 15‐year period on 36 parameters at an upgradient and downgradient well selected at each of the eight sites. This yielded a total of 576 monitoring data sets available for analysis. New trend and contamination indices are introduced that are used to compare ground water contamination between these eight sites. These indices are used to assess each landfill's relative potential for environmental harm.Many questions remain unanswered, but what is demonstrated here is that this type of methodology has the potential to be used to assess trends of ground water chemistry concentrations at landfill sues in a region. A specific purpose of such an assessment could be to provide a quantified basis for the prioritization of funds allocated for cleanup of contaminated landfill sites. Having a technical capability to reduce large amounts of ground water monitoring data to appropriate summaries, which then can be used to assess environmental contamination between several sites, could also have important economic and health implications in other settings. Hopefully this paper will encourage further development of such technologies for these purposes.
Inexpensive Electronic Water Level Recorders for Hydrologic Studies
Authors: Keenan R. , Dickerson J. , Gardner L. , Reeves H. 
Published: February 2007

AbstractHydrologic investigations typically involve the collection of water level measurements at discrete points in space and time. The high cost of commercial electronic recorders can be a burden. We have developed an inexpensive (∼$200) electronic water level recorder consisting of a Motorola microcontroller, a clock, memory, pressure transducers, and associated circuitry. The instrument is powered by a 6‐V battery. These devices, each capable of monitoring up to eight channels of analog input, are presently providing continuous monitoring of nested piezometers, tide gauges, and rain gauges in hydrologic studies at the Savannah River site and the North Inlet (South Carolina) Long‐Term Ecological Research (LTER) site. The instruments can be custom tailored to record water levels at any specified time interval, or whenever the water level changes by a specified amount, and can store up to 32,000 water level observations. These instruments have been used to conduct slug tests and can be configured to monitor observation wells for pumping tests. Simplicity of construction and availability of components offer hydrologists an inexpensive but reliable method of water level recording. Several examples of the use of this instrumentation in diverse hydrologic settings are described.
The Rehabilitation of Monitoring Wells Clogged by Calcite Precipitation and Drilling Mud
Authors: Kroening David E. , Snipes David S. , Brame Scott E. , Hodges Rex A. , Price Van , Temples Tom J. 
Published: February 2007

AbstractBased on aquifer performance tests, 13 out of 15 wells situated at the Mixed Waste Disposal (MWD) area located at the Savannah River site. South Carolina, exhibited high skin factors and low well efficiencies indicative of severely damaged wells. The use of damaged wells in aquifer testing can lead to inaccurate determinations of aquifer properties, and such wells are unusable in future remediation programs. Moreover, damaged wells can go dry during purging, thus compromising sample collection. Pump tests, chemical analyses, and biological investigations revealed that the poor well performance at MWD was attributable to calcite precipitation on the well screen and drilling mud in the filter pack. The calcite problem resulted from improper well installation, and the drilling mud in the filter pack was due to inadequate well development.Experimental rehabilitation procedures employed on two wells, MWD 5A and 1A, included acidification, swabbing, introduction of surfactants, and surging. Treatment of the wells substantially improved well yields, skin factors, and well efficiencies. Moreover, well rehabilitation was determined to be a reasonable alternative to drilling new wells at the MWD wellfield.
Cryogenic Drilling: A New Drilling Method for Environmental Remediation
Authors: Simon Rafael D. , Cooper George A. 
Published: February 2007

AbstractCryogenic drilling is a technique developed at the University of California (UC), Berkeley, for drilling in unstable sediments of environmental monitoring, for characterizing, and for remediation wells, The method uses standard air rotary drilling techniques, but with cold nitrogen rather than ambient air as the circulating fluid in order to freeze and stabilize the borehole wall. Several laboratory and full‐scale field tests have been performed. A.52‐foot‐deep (16 m) soil boring and 24 foot (7 m) monitoring well have been drilled as part of the Lawrence Berkeley Laboratory Site Characterization Project. Continued testing and refinement of the equipment and operational method are in progress. The method has been proposed for use as part of the Department of Energy (DOE) weapons site cleanup at locations with unstable sediments such as Hanford, Sandia, and Idaho National Engineering Laboratory (INEL).
Secondary Effects of Soil Venting and Potential Low‐Cost Enhancements
Authors: Walton John C. , Anker Charles B. 
Published: February 2007

AbstractSoil venting, in addition to removing volatile organic compounds, has secondary effects on soil temprature and moisture content. A simple enthalpy balance model is used to illustrate the maganitude and direction of temperature and moisture content changes in the soil during ordinary venting and with several potential modifications to venting. Because of the importance of latent heat of vaporization, injection of warm, dry air into the substance is generally ineffective in heating the soil. In contrast, injection of humidified, slightly heated air is found to result in significant soil warming even at low flow rates. Soil warming is thought to be an important mechanism for enhancing remediation, particularly in the final or tail stage of cleanup where concentrations slowly decline wiht time. A variety of soil venting alternatives are simulated at hypothetical sites in Chicago, Illinois, and Tucson, Arizona, including simple humidification, humidification with solar heating, and venting under positive pressure. All there methods result in higher final soil temperatures than the control case of normal soil venting. Humidification of the input air at the rates applied does not result in significant change in average soil moisture content or saturation of the soil wtih water.
Analysis of Petroleum‐Contaminated Water by GC/FID with Direct Aqueous Injection
Authors: Potter Thomas L. 
Published: February 2007

AbstractA direct aqueous injection capillary gas chromatography/flame ionization (GC/FID) procedure for the analysis of petroleum‐contaminated water was developed and applied to seven water samples saturated with different petroleum products. Separation of C1 to C4 alcohols, C6 to C9 monoaromatics, MTBE, phenol, aniline, and other compounds, and the detection of BTEX compounds at concentrations at or below their maximum contaminant levels (MCLs) is reported. Among the test compounds analyzed, the only pair found to coelute were 1‐butanol and benzene. A method for confirmation of alcohols and polar compounds in the presence of dissolved petroleum hydrocarbons was also evaluated. In this case, water samples were analyzed before and after purging. Polar compounds were found to be significant components of the water soluble fractions of commercial petroleum products.
Micellar‐Enhanced Ultrafiltration and Air Stripping for Surfactant‐Contaminant Separation and Surfactant Reuse
Authors: Lipe K. Michelle , Sabatini David A. , Hasegawa Mark A. , Harwell Jeffrey H. 
Published: February 2007

AbstractMicellar‐enhanced ultrafiltration (MELT) and air stripping were evaluated for surfactant‐contaminant separation and surfactant recovery. Two linear alkyl diphenyloxide disulfonate (DPDS) surfactants were evaluated with the contaminants naphthalene and trichloroethylene. A separation model developed from micellar partitioning principles showed a good correlation to batch MEUF studies, whereas flux analysis highlighted concentration polarization effects in relation to hydrophobe length. MEUF effectively concentrated the surfactant‐contaminant system (93 to 99 percent retention); however, this did not result in surfactant‐contaminant separation. Batch and continuous flow air stripping models were developed based upon air/water ratio, surfactant concentration, and Micellar partitioning; model predictions were validated by experimental data. Sensitivity analyses illustrated the decline in contaminant‐surfactant separation with increasing surfactant concentration (e.g., TCE removal efficiency declines from 83 percent to 37 percent as C‐16 DPDS concentration increases from 0 to 55 mM). This effect is greater for more hydrophobic contaminants (naphthalene vs. TCE) and surfactants with greater solubilization potential (C16‐DPDS vs. C‐12 DPDS). The resulting design equations can account for this effect and thus properly size air strippers to achieve the desired removal efficiency in the presence of surfactant micelles. Proper selection and design of surfactant‐contaminant separation and surfactant recovery systems are integral to optimizing surfactant‐enhanced subsurface remediation.
Performance of the In Situ Microcosm Technique for Measuring the Degradation of Organic Chemicals in Aquifers
Authors: Nielsen Per H. , Christensen Thomas H. , Albrechtsen Hans‐Jørgen , Gillham Robert W. 
Published: February 2007

AbstractAn in situ microcosm (ISM) consists of a stainless steel cylinder isolating about 2 L of the aquifer and is equipped with valves allowing for loading and sampling from the ground surface. During the last five years, this technique has been used frequently to study the degradation of organic chemicals in polluted and pristine aquifers representing different redox environments. The ISM technique has great potential for providing field‐relevant degradation potentials and rate constants, but care must be taken in using the equipment and interpreting the results. This paper provides details concerning the installation and operation of an ISM and presents experiences concerning data interpretation and monitoring of redox conditions.
Allocation of Environmental Remediation Funds Using Economic Risk‐Cost‐Benefit Analysis: A Case Study
Authors: James Bruce R. , Huff Dale D. , Trabalka John R. , Ketelle Richard H. , Rightmire Craig T. 
Published: February 2007

AbstractEfficient allocation of remediation resources is a critical need throughout the nation. Economic risk‐cost‐benefit analysis is an important tool for meeting this need. This paper provides site engineers, geologists, and managers with a conceptual understanding of economic risk‐cost‐benefit analysis and shows how it can be applied, even in situations where existing data are sparse or poor in quality. An example analysis is applied to the remediation of radioactive waste at Oak Ridge National Laboratory, in which the cost‐effectiveness is compared for two remediation alternatives: containment of the waste or monitoring only. A data‐worth analysis is also carried out to estimate the maximum justifiable exploration budget and the cost‐effectiveness of two proposed data collection programs. Results indicate that the methodology has potential in making robust remediation decisions regarding certain types of questions.
Intercomparison of Waterborne222Rn Collection Methods: Professional Vs. Homeowner Collection
Authors: Field R. William , Kross Burton C. 
Published: February 2007

AbstractAn intercomparison between trained professional and homeowner water collection techniques was conducted to assess the validity of using both inexperienced homeowner water collectors and mail‐in return of point‐of‐use water samples. The findings indicate that homeowner‐collected water samples obtained at the point of use inside the home and professionally collected water samples collected at an outside tap are comparable, especially if confounders, such as air bubbles in the sampling vials, are minimized.
Effects of Process Control Changes on Aquifer Oxygenation Rates During In Situ Air Sparging in Homogeneous Aquifers
Authors: Rutherford Kyle W. , Johnson Paul C. 
Published: February 2007

AbstractIn situ air sparging is used to remediate petroleum fuels and chlorinated solvents present as submerged contaminant source /ones and dissolved contaminant plumes, or to provide barriers to dissolved contaminant plume migration. Contaminant removal occurs through a combination of volatilization and aerobic biodegradation: thus, the performance at any given site depends on the contaminant and oxygen mass transfer rates induced by the air injection. It has been hypothesized that these rates are sensitive to changes in process flow conditions and site lithology, but no data is available to identify trends or the magnitude of the changes. In this work, oxygenation rates were measured for a range of air injection rates, ground water flow rates, and pulsing frequencies using a laboratory‐scale two‐dimensional physical model constructed to simulate a homogeneous hydrogeologic setting. Experiments were conducted with water having low chemical and biochemical oxygen demand. Results suggest the following: that there is an optimum air injection rate: advective How of ground water can be a significant factor when ground water velocities are > 0.3 m/d: and pulsing the air injection had little effect on the oxygenation rate relative lo the continuous air injection case.
History of the Sole Source Aquifer Program: A Community‐Based Approach for Protecting Aquifers Used for Drinking Water Supply
Authors: McCabe William J. , Job Charles A. , Simons John J. , Graves John S. , Terada Calvin J. 
Published: February 2007

AbstractThe Sole Source Aquifer Program has helped prevent contamination of many community drinking water supplies. If an aquifer supplies the sole or principal source of a community's drinking water, a local ground water user may petition the Environmental Protection Agency (EPA) under the Safe Drinking Water Act for its designation and protection as a “sole source aquifer.” Since 1974, residents and officials of 65 communities and multi‐community areas have petitioned and received assistance from the EPA to prevent contamination of their local ground water source of drinking water. This designation means that EPA may review federal financially assisted projects to determine if they would contaminate the aquifer and cause a public health hazard. If they could cause contamination, EPA can request that the project be modified or stopped. The significance of this program in terms of population served and funds affected has been substantial, indicating the Sole Source Aquifer Program has been an important local tool for protecting ground water used as a source of drinking water. Information is given on three different examples of sole source aquifer designations protected under this program: the New Jersey Coastal Plain Aquifer System, the Great Miami River Buried Valley Aquifer System (Ohio), and the Eastern Snake River Plain Aquifer (Idaho), serving populations of 543,000, 921,000, and 275,000, respectively. In all three examples, preventing ground water contamination through the Sole Source Aquifer Program has protected the community drinking water supply.
Field Evaluation of Ultrasonic Method for Assessing Well Seals
Authors: Yesiller Nazli , Benson Craig H. , Edil Tuncer B. 
Published: February 2007

AbstractField tests were conducted in three boreholes using an ultrasonic testing method to evaluate its ability to assess contact between the seal and riser (casing). The ultrasonic method is used inside the riser without disturbing the riser, seal, or formation soil. The risers were 50‐mm‐diameter (2‐inch) Schedule 40 steel pipes that are used for ground water monitoring wells. Different types of seals were placed around the risers and defects were purposely introduced in the seals to test the ultrasonic method. The ultrasonic response changed as the neat‐cement seals cured or hydration of the bentonite seals changed. When adequate moisture was not available, the bentonite seals deteriorated, losing contact with the riser. When adequate moisture was available, however, the seals swelled into contact with the riser. Both conditions were detected with the ultrasonic method. The method also detected the intentional defects, as well as defects that were not intended. The boreholes were excavated to compare results of the ultrasonic tests with the actual condition of the seals. The condition of the seals agreed well with the results of the ultrasonic tests.
Three‐Dimensional Experimental Testing of a Two‐Phase Flow‐Modeling Approach for Air Sparging
Authors: Hein Gretchen L. , Gierke John S. , Hutzler Neil J. , Falta Ronald W. 
Published: February 2007

AbstractAir sparging has been used for several years as an in situ technique for removing volatile compounds from contaminated ground water, but few studies have been completed to quantify the extent of remediation. To gain knowledge of the air flow and water behavior around air injection wells, laboratory tests and model simulations were completed at three injection flow rates (62, 187, and 283 lpm) in a cylindrical reactor (diameter ‐ 1.2 m, depth = 0.65 m). Measurements of the air flux distribution were made across the surface of the reactor at 24 monitoring locations, six radial positions equally spaced along two orthogonal transects. Simulations using a multiphase flow model called T2VOC were completed for a homogeneous, axisymmetric configuration. Input parameters were independently measured soil properties. In all the experiments, about 75 percent of the flow injected exited the water table within 30 cm of the sparge well. Predictions with T2VOC showed the same. The averages of four flux measurements at a particular distance from the sparge well compare satisfactorily with T2VOC predictions. Measured flux values at a given radius varied by more than a factor of two, but the averages were consistent between experiments and agreed well with T2VOC simulations. The T2VOC prediction of the radial extent of sparging coincided with the distance out to which air flow from the sparge well could not be detected in the reactor. The sparging pattern was relatively unaffected by the air injection rate over the range of conditions studied. Changes in the injection rate resulted in nearly proportional changes in flux rates.
Analytical Model for Contaminant Mass Removal by Air Sparging
Authors: Rabideau Alan J. , Blayden James M. 
Published: February 2007

AbstractAn analytical model was developed lo predict the removal of volatile organic compounds (VOCs) from ground water by air sparging (AS). The model treats the air sparging zone as a completely mixed reactor subject to the removal of dissolved contaminants by volatilization, advection, and first‐order decay Nonequilibrium desorption is approximated as a first‐order mass transfer process. The model reproduces the tailing and rebound behavior often observed at AS sites, and would normally require the estimation of three site‐specific parameters. Dimensional analysis demonstrates that predicted tailing can be interpreted in terms of kinetic desorption or diffusion of aqueous phase contaminants into discrete air channels. Related work is ongoing to test the model against field data.
Removal of Volatile Organic Compounds from Surfactant Solutions by Flash Vacuum Stripping in a Packed Column
Authors: Choori Umesh N. , Scamehorn John F. , O'Haver John H. , Harwell Jeffrey H. 
Published: February 2007

AbstractVolatile organic compounds (VOCs) am be removed from contaminated ground water and subsurface media by surfaclant‐enhanced remediation processes. For the process to be economically competitive it is necessary to recover and reuse the surfactant from this concentrated solution. The VOC can be removed from this concentrated solution by flash vacuum stripping, leaving the surfactant solution for reuse. In this study, the flash vacuum stripping of trichloroethylene (TCE) from an anionic surfactant solution in a co‐current packed column was studied under rough vacuum conditions. The presence of surfactants lead to a reduction in the overall liquid phase volumetric mass transfer coefficient (MTC) of 40 to 95%. depending on flow rate and surfactant concentration at 50°C and 16 kPa. At liquid loading rates of less than 13 cm3/cm2min, the MTC of TCE decreases rapidly with an increase in liquid loading rate, and at liquid loading rates above that, the MTC decreases slightly with an increase in the liquid loading rate. This trend may have been due to foaming. At surfactant concentrations above the critical micelle concentration, the effect of surfactant concentration was not significant at liquid loading rates less than 13 cm3/cm2min. However, beyond that rate, the MTC of TCE decreased drastically with an increase in surfactant concentration. The MTC of TCE increased with an increase in temperature. A large pressure drop (3 to 4 kPa/m) was observed across the packed bed due to foaming.