bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNAPL Characterization Methods and Approaches, Part 2: Cost Comparisons
Authors: Kram Mark L. , Keller Arturo A. , Rossabi Joseph , Everett Lome G. 
Published: February 2007

AbstractContamination from the use of chlorinated solvents, often classified as dense nonaqueous phase liquids (DNAPLs) when in an undissolved state, pose environmental threats to ground water resources worldwide. DNAPL site characterization method performance comparisons are presented in a companion paper (Kram et al. 2001). This study compares the costs for implementing various characterization approaches using synthetic unit model scenarios (UMSs), each with particular physical characteristics. Unit costs and assumptions related to labor, equipment, and consumables are applied to determine costs associated with each approach for various UMSs. In general, the direct‐push sensor systems provide cost‐effective characterization information in soils that are penetrable with relatively shallow (less than 10 to 15 m) water tables. For sites with impenetrable lithology using direct‐push techniques, the Ribbon NAPL Sampler Flexible Liner Underground Technologies Everting (FLUTe) membrane appears to be the most cost‐effective approach. For all scenarios studied, partitioning interwell tracer tests (PITTs) are the most expensive approach due to the extensive pre‐and post‐PITT requirements. However, the PITT is capable of providing useful additional information, such as approximate DNAPL saturation, which is not generally available from any of the other approaches included in this comparison.
Experimental Evaluation of Fouling Processes in Porous Polyethylene Well Screens Used for Horizontal Wells
Authors: Logan Andrew J. , Siegrist Robert L. , Munakata‐Mars Junko 
Published: February 2007

AbstractThe hydraulic performance of porous polyethylene well screens was examined in laboratory columns to understand the processes that affect well performance in many field applications. Conditions studied included (1) well‐screen pore size; (2) the presence of biodegradable drilling fluid, biological electron acceptors, and biofouling organisms; and (3) chlorine development. Custom‐fabricated, segmentable acrylic columns (8.9 cm diameter. 64 cm length) were employed using a factorial design statistical approach to mimic a variety of representative field conditions experienced during field applications. After circular well‐screen coupons (circular sections of the well screen cut to match the diameter of the columns) were cut and secured horizontally in the columns, sand media, and, in some cases, biodegradable drilling fluid were packed on top of the well screens. Those columns receiving chlorine development were allowed to sit overnight after a 1000 ppm chlorine solution was introduced beneath the well screen following upflow saturation. The columns were upflow saturated and then operated with simulated ground water in a down flow mode under constant hydraulic head for up to 75 days. Residual head with depth was measured and flux density values were recorded over time. Effluent samples were collected and analyzed for dissolved oxygen (D.O.), electrical conductance, pH, and total solids. After achieving pseudo‐steady‐state throughput condition as indicated by relatively constant effluent flux densities, the columns were dismantled and the well‐screen coupons were examined under a scanning electron microscope to observe causes of any loss in flow observed. The hydraulic conductivities of the well screens were also measured before and after operation in the columns. Results show that these porous polyethylene well screens resist fouling due to microbial colonization or chemical precipitation. Scanning electron microscopy revealed little or no colonization of the surfaces by microbes or blockage of pores by particle entrapment. Hydraulic head measurements revealed that the cause of headloss in the columns was a result of processes that occurred in the overlying sand media and not within the well screens themselves.
Field Evaluation of In Situ Chemical Oxidation Through Vertical Well‐to‐Well Recirculation of NaMnO4
Authors: Lowe K.S. , Gardner EG. , Siegrist R.L. 
Published: February 2007

AbstractA field pilot test was conducted at a U. S. Department of Energy site to evaluate in situ chemical oxidation of trichloroethene (TCE) in a silty‐sandy gravel aquifer located at 26 to 30 feet (8 to 9 m) below ground surface. A vertical well‐to‐well recirculation system was designed and implemented by placing four corner extraction wells in a square grid, with each well 45 feet (13.7 m) from a center injection well. Ground water was extracted from the four perimeter wells, combined aboveground in a piping network, and then amended inline with sodium permanganate (NaMnO4) before reinjection into the aquifer through a center injection well. During the pilot test, oxidant amended ground water (250 mg/L NaMnO4) was injected at 18 gpm (68.1 L/m) for 10 days, during which time‐354 pounds (160.6 kg) of NaMnO4 were delivered and approximately 240,660 gallons (911 kL) of ground water were recirculated and treated. NaMnO4 injection using vertical wells in a five‐spot pattern was capable of providing sufficient hydraulic control to deliver oxidant throughout the permeable zones of the 4100 ft2 (380 m2) test area within three days. TCE concentrations were reduced, from 2,000 μg/L to <10 μg/L, throughout all but the lower permeable eastern edge of the test region, indicating an apparent reduction in contaminant levels of 92% within three days and 97% within 10 days (two hours after the end of active recirculation). One month after system shut down, residual oxidant concentrations in the ground water had declined to <1 mg/L, while a gradual increase in TCE concentrations was observed. Oxidant consumption over time is expected due to a combination of factors, including oxidation of the natural organic material present, oxidation of TCE that diffused out from the finer‐grained and less permeable zones, and advection of TCE into the test area from the upgradient plume. No adverse effects to system toxicity, generation of reaction intermediates and products (e.g., chlorinated organic acids or partially degraded chlorocarbons), or reduction in formation permeability were observed.
Urban Ground Water Pollution: A Case Study in Cuttack City, India
Authors: Das Jyotirmaya , Sahoo Rama Krishna , Sinha B.K. 
Published: February 2007

AbstractA large number of ground water samples (360) was collected from 60 stations over six consecutive seasons to study the influence of the main sewerage drain on shallow ground water table beneath the municipal area of Cuttack, India. A majority of the samples collected from stations close to the drain exceeded the maximum permissible limits set by the World Health Organization (WHO). Almost all the samples near the drain exceeded the WHO limit for NO3‐ and Na+. However, the concentrations decreased as the distance from the drain increased. The winter season registered the maximum concentrations of NH4+, NO3‐, and SO42‐ ions whereas the minimum values always coincided with the rainy season. R‐mode factor analysis was conducted to find relationships amongst the 16 chemical parameters studied. Fluoride showed a negative correlation with Cl‐, Na+, NO3‐, SO42‐, and PO43‐. The concentration of F‐ may be lower in raw waste water than naturally occurs in the ground water. Therefore, a decrease in the concentration of F‐ near the drain may be attributed to dilution by contributions of waste water to the ground water. The rest of the parameters were found to be directly related to the distance of collection points to the sewerage. The distribution of nutrients is strongly affected by leaching of waste water into the ground water.
Biocurtain Design Using Reactive Transport Models
Authors: Phanikumar M.S. , Hyndman David W. , Criddle Craig S. 
Published: February 2007

AbstractBioremediation is an attractive alternative to traditional remediation methods for a variety of ground water contaminants. However, widespread implementation of bioremediation is currently limited by the complexity of the dynamic chemical and biological processes that need to be understood and incorporated into the design approach. Reactive transport models provide a powerful tool to simulate these complex interactions and, thus, can be used to improve and guide the design of bioremediation systems. We present a remediation design approach for intermittently stimulated biodegradation using multicomponent reactive transport models, parameterized using a series of nondimensional Damkohler numbers. Designs were based on either (1) a target aqueous phase concentration at the exit of the treatment system, or (2) the total contaminant mass fraction removed from a region of interest. The equation set used to develop this design approach is specific to the case of intermittent electron donor addition to drive cometabolic transformations. We illustrate the design procedure for a biocurtain that removes carbon tetrachloride. Our results for this case indicate that intermittent injection is significantly more efficient than strategies based on continuous pumping. Example design parameters include the length of the biologically active zone (i.e., biocurtain), the effective rate of degradation in this zone, and the interval between electron donor injection cycles. The presented dimensionless parametric approach can be used to design bench‐scale column studies and should be helpful for scale‐up to field‐scale remediation systems.
Designing Monitoring Programs to Effectively Evaluate the Performance of Natural Attenuation
Authors: Wiedemeier Todd H. , Haas Patrick E. 
Published: February 2007

AbstractNatural attenuation processes affect the fate and transport of organic compounds in many hydrologic systems. Over the last several years, regulatory agencies and environmental professionals have come to recognize the importance of these natural processes in effecting contaminant attenuation. When they are shown to be protective of human health and the environment, and when a well‐designed monitoring program is in place to document the efficiency of these processes, they can be a valuable component of site remediation strategies.
Cautions and Suggestions for Geochemical Sampling in Fractured Rock
Authors: Shapiro Allen M. 
Published: February 2007

AbstractCollecting water samples for geochemical analyses in open bedrock boreholes or in discrete intervals of boreholes intersected by multiple fractures is likely to yield ambiguous results for ground water chemistry because of the variability in the transmissivity, storativity, and hydraulic head of fractures intersecting the borehole. Interpreting chemical analyses of water samples collected in bedrock boreholes requires an understanding of the hydraulic conditions in the borehole under the ambient flow regime in the aquifer as well as during sampling. Pumping in open boreholes, regardless of the pumping rate and the location of the pump intake, first draws water from the borehole and then from fractures intersecting the borehole. The time at which the volumetric rate of water entering the borehole from fractures is approximately equal to the pumping rate can be identified by monitoring the logarithm of drawdown in the borehole as a function of the logarithm of time. Mixing of water entering the borehole from fractures with water in the borehole must be considered in estimating the time at which the pump discharge is representative of aquifer water. In boreholes intersected by multiple fractures, after the contribution from the borehole volume has diminished, the contribution of fractures to the pump discharge will be weighted according to their transmissivity, regardless of the location of the pump intake. This results in a flux‐averaged concentration in the pump discharge that is biased by the chemical signature of those fractures with the highest transmissivity. Under conditions where the hydraulic head of fractures varies over the length of the borehole, open boreholes will be subject to ambient flow in the water column in the borehole. In some instances, the magnitude of the ambient flow may be similar to the designated pumping rate for collecting water samples for geochemical analyses. Under such conditions, the contributions to the pump discharge from individual fractures will be a function not only of the transmissivity of the fractures, but also of the distribution of hydraulic head in fractures intersecting the borehole. To reduce or eliminate the deleterious effects of conducting geochemical sampling in open boreholes, a straddle‐packer apparatus that isolates a single fracture or a series of closely spaced fractures is recommended. It is also recommended that open boreholes be permanently outfitted with borehole packers or borehole liners in instances where maintaining the hydraulic and chemical stratification in the aquifer is of importance. In a field example, a comparison of results from sampling in an open borehole and in discrete intervals of the same borehole showed dramatic differences in the concentrations of chemical constituents in the water samples, even though chemical field parameters stabilized prior to both open borehole and discrete interval sampling.
Efficacy of Annual Bacteria Monitoring and Shock Chlorination in Wells Finished in a Floodplain Aquifer
Authors: Oliphant J.A. , Ryan M.C. , Chu A. , Lambert T.W. 
Published: February 2007

AbstractPublic health authorities generally recommend annual water‐quality monitoring of rural water wells and shock chlorination if coliforms are detected. It is implicitly assumed that shock chlorination is effective in ridding most wells of bacteriological pathogens for months to years. Neither annual monitoring nor shock chlorination was effective in addressing coliform contamination of selected water wells in a small town developed on an alluvial aquifer where septic system effluents are impacting well water quality. Considerable temporal variation in total and fecal coliforms was observed in water wells monitored for a six‐month period. Individual wells intermittently met and exceeded the drinking water criteria, indicating annual sampling was insufficient. Shock chlorination of three contaminated wells and their associated distribution systems proved ineffective because colonies apparently originated from outside the wells and reappeared over relatively short time periods (ranging from less than one week up to 21 weeks). The relatively fast and similar rate of recovery of total heterotrophic bacteria suggested they are related to biofilm formation in the wells and not to ground water contamination.
Estimating Aquifer Sensitivity to Nitrate Contamination Using Geochemical Information
Authors: Trojan Michael D. , Campion Moira E. , Maloney Jennifers , Stockinger James M. , Eid Erin P. 
Published: February 2007

AbstractMethods for predicting aquifer sensitivity to contamination typically ignore geochemical factors that affect the occurrence of contaminants such as nitrate. Use of geochemical information offers a simple and accurate method for estimating aquifer sensitivity to nitrate contamination. We developed a classification method in which nitrate‐sensitive aquifers have dissolved oxygen concentrations > 1.0 mg/L, Eh values >250 mV, and either reduced iron concentrations < 0.1 mg/L or total iron concentrations < 0.7 mg/L. We tested the method in four Minnesota aquifer systems having different geochemical and hydrologic conditions. A surficial sand aquifer in central Minnesota exhibited geochemical zonation, with a rapid shift from aerobic to anaerobic conditions 5 m below the water table. A fractured bedrock aquifer in east‐central Minnesota remained aerobic to depths of 50 m, except in areas where anaerobic ground water discharged upward from an underlying aquifer. A bedrock aquifer in southeast Minnesota exhibited aerobic conditions when overlain by surficial deposits lacking shale, whereas anaerobic conditions occurred under deposits that contained shale. Surficial sand aquifers in northwest Minnesota contained high concentrations of sulfate and were anaerobic throughout their extent. Nitrate‐nitrogen was detected at concentrations exceeding 1 mg/L in 135 of 149 samples classified as sensitive. Nitrate was not detected in any of the 109 samples classified as not sensitive. We observed differences between our estimates of sensitivity and existing sensitivity maps, which are based on methods that do not consider aquifer geochemistry. Because dissolved oxygen, reduced iron, and Eh are readily measured in the field, use of geochemistry provides a quick and accurate way of assessing aquifer sensitivity to nitrate contamination.
An Evaluation of Tertiary‐Butyl Alcohol for the Development of a Drinking Water Action Level in Delaware
Authors: Fischer William “Tripp” 
Published: February 2007

AbstractFor regulators to develop risk‐based screening levels (RBSLs) for a petroleum constituent, a maximum allowable concentration at an exposure point, such as a drinking water action level, must be established. Of particular interest to regulators of leaking underground storage tank (LUST) sites in Delaware is the development of RBSLs for the oxygenated compounds that are added to gasoline to increase octane rating and promote cleaner burning fuel. Whereas methyl‐tertiary butyl ether (MTBE) became the first of the oxygenated compounds to gain regulatory attention in Delaware, tertiary‐butyl alcohol (TBA) is not far behind. TBA has been detected at LUST sites throughout Delaware and in some cases has been detected in private water supplies. However, Delaware does not currently have a drinking water action level, or maximum allowable exposure concentration, on which to base regulatory decisions regarding TBA.Toxicological data is inconclusive in classifying TBA as a carcinogen. However, carcinogenic responses are reported in rat and mice studies at extremely high doses. To address TBA in Delaware's Risk‐Based Corrective Action Program, the Delaware Division of Public Health must calculate drinking water action levels based on the results of the toxicological data. However, the establishment of TBA action levels could have a tremendous impact on the costs associated with investigating and remediating a LUST site. TBA may add $2000 to $5000 per year in analytical costs alone for an average LUST site in Delaware.
Simulation of a Ground Water Recirculation Well with a Dual‐Column Laboratory Setup
Authors: Lesage Suzanne , Brown Susan , Millar Kelly , Steer Helena 
Published: February 2007

AbstractThis paper describes a dual‐column laboratory setup consisting of a glass column and a stainless‐steel column filled with aquifer material. The setup was used to replicate a ground water recirculation well that serves as an in situ reactor and a combined injection/withdrawal well. The treatment solution consisted of a buffered titanium (III) citrate/vitamin B12 mixture. The first column, representing the well, was made of glass, allowing for visual inspection of the mixing. The stainless‐steel column was instrumented with redox (Eh) probes to monitor the changes in redox conditions. The redox measurement showed that, although the sand contained large quantities of iron oxides, the oxidation rate was relatively slow and the titanium solution would remain reduced for some time in the aquifer, continuing to react with the contaminants. This laboratory setup was used to optimize the reagent concentrations and rate of delivery for field implementation. It was found that 4 mM titanium citrate and 3 mg/L vitamin B12 were sufficient to degrade 1,1,2,2‐tetrachloroethane and carbon tetrachloride within one day, but not trichloroethylene, which required five days with 10 mM titanium citrate and 5 mg/L vitamin B12.
Optimizing Landfill Ground Water Analytes—New South Wales, Australia
Authors: Hart Barbara F. , Chaseling Janet 
Published: February 2007

AbstractA study of analytes for ground water monitoring was conducted at 10 municipal solid waste landfills in northern New South Wales (NSW), Australia. From literature review, analytes were proposed and then approved by the NSW Environment Protection Authority (EPA) for initial ground water and leachate monitoring. Eight rounds of initial baseline monitoring using traditional geochemical analytes were conducted in uncontaminated ground water at a new, lined landfill. Four rounds of initial assessment monitoring were conducted at nine unlined or only partially lined old landfills. Analytes for the old landfills were selected with a health risk emphasis because ground water may already be contaminated.At the old landfill sites, analytes with values indicating contamination were often limited to one particular analytical group, although the analytical group represented differed from site to site. As a result, the most environmentally responsible suite of analytes for baseline monitoring is the traditional geochemical approach; free carbon dioxide for landfill gas; and organics in the form of volatile organic compounds for old landfills, but benzene, toluene, ethylbenzene, and xylene when wells are close to a new landfill. The current Subtitle D (U.S. EPA 1991) analytes proved inadequate. They would not have detected the majority of contaminants or contaminant indicators at the old landfills, i.e., organic nitrogen, ammonia, nitrate, iron, and manganese.After completion of initial monitoring at each site, reduced lists of analytes for ongoing monitoring were proposed and approved by the NSW EPA. The lists were based on literature evidence, contaminants, and contaminant indicators found in ground water at the old landfills, and in some cases leachate versus ground water concentrations. For the new landfill, the principle of limited analytes representing a broad range of analytical groups was used to assure precautionary environmental outcomes. At present‐day costs, cost savings for analyses alone at the new landfill are ÄD251, 160 over the 70‐year life of the landfill.
Application of Natural Attenuation to Ground Water Contaminated by Phenoxy Acid Herbicides at an Old Landfill in Sjoelund, Denmark
Authors: Tuxen Nina , Ejlskov Palle , Albrechtsen Hans‐Jørgen , Reitzel Lotte A. , Pedersen Jørn K. , Bjerg Paul L. 
Published: February 2007

AbstractInvestigations of geology, hydrogeology, and ground water chemistry in the aquifer downgradient from Sjoelund Landfill, Denmark, formed the basis for an evaluation of natural attenuation as a remediation technology for phenoxy acid herbicides at the site. Concentrations of phenoxy acids were up to 65 μg/L in the ground water, primarily 4‐chlor‐2‐methylphenoxypropionic acid (MCPP) and 2,4‐dichlorophenoxypropionic acid (dichlorprop). Mass removal of the phenoxy acids was shown within 50 to 100 m of the landfill by calculation of contaminant fluxes passing transects at three distances. There was accordance between increasing oxygen concentrations and decreasing phenoxy acid concentrations with distance from the landfill, indicating that aerobic degradation was a major mass removal process. Presence of high concentrations of putative anaerobic phenoxy acid metabolites suggested that anaerobic degradation was also occurring. Laboratory degradation experiments using sediment and ground water from the aquifer supported aerobic and anaerobic degradability of MCPP at the site. It was concluded that natural attenuation may be applicable as a remedy for the phenoxy acids at the Sjoelund Landfill site, although uncertainties related to calculations of chloride and phenoxy acid fluxes at a complex site and identification of specific in situ indicators were encountered. Thus, there is a pronounced need for development and broader experience with evaluation tools for natural attenuation of phenoxy acids, such as specific metabolites, changes in enantiomeric fractions, compound‐specific stable carbon isotope ratios, or microbial fingerprints.