Download or read book Mathematical Modelling of DNAPL Source Zone Remediation written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mathematical modelling was utilized to evaluate trichloroethylene (TCE) and tetrachloroethylene (PCE) dense non-aqueous phase liquid (DNAPL) source zone remediation in the subsurface environment. Semi-analytical solutions were derived, tested, and employed to evaluate the benefits of source zone concentration reduction and solute degradation mechanisms on the evolution of plumes in porous media and fractured rock domains. Simulations of treatment in complex DNAPL source zones using different remedial technologies were completed with a numerical model that was developed, tested, calibrated, and applied to nine idealized heterogeneous porous media sites. Analytical modelling revealed that, in domains dominated by matrix diffusion, aggressive and moderate source zone concentration reduction may have similar effects on the leading edge of the plume. The tailing (near source) edge of the plume may be more responsive to aggressive concentration reduction, particularly when diffusion processes are negligible. Both the near-field (near-source) and far-field plume responses were strongly influenced by the matrix decay half-life for both transient and steady-state conditions. The degradative capacity of the matrix largely dictated plume extent and life-span for the fractured bedrock site considered here. Numerical simulations of in situ source zone treatment with chemical oxidation (ISCO), enhanced bioremediation (ISEB), and surfactants (SEAR) were compared and contrasted. Treatment efficacy was site specific, with benefits observed at some sites, and detrimental impacts observed at others. Each technology demonstrated some degree of performance enhancement relative to dissolution only (no treatment). The maximum DNAPL mass depletion enhancement factors for ISCO, ISEB and SEAR, were 1.44, 2.91, and 2.70 after 10 years, respectively. Similarly, the maximum boundary mass flux enhancement factors for ISCO, ISEB and SEAR were 9.78, 3.32, and 3.97, respectively. While notable enha.

Download or read book A Numerical Investigation of Metabolic Reductive Dechlorination in DNAPL Source Zones written by John Anthony Christ and published by . This book was released on 2005 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among the most intractable environmental remediation problems are those involving the release of dense non-aqueous phase liquids (DNAPLs), such as chlorinated solvents, to the subsurface. Research efforts have focused on the use of numerical models to investigate reductions in contaminant concentrations due to partial mass removal and improvements in the performance of complementary source zone remediation technologies. Previous numerical investigations, however, have been limited to two-dimensional systems. Furthermore, a lack of models capable of simulating the most promising complementary technology, metabolic reductive dechlorination, has limited its application. This work developed and applied compositional multiphase numerical simulators to examine the influence of dimensionality (two-dimensions versus three-dimensions) on DNAPL source zone simulations and to investigate the benefits of stimulating metabolic reductive dechlorination at a chlorinated ethene-DNAPL contaminated site. Results from the dimensionality investigation showed that the simulation of DNAPL migration, entrapment, and dissolution in two dimensions provided reasonable approximations to the behavior simulated in three dimensions. Commonly employed saturation distribution and mass recovery metrics were approximately equivalent. Flux- averaged concentrations simulated in two dimensions, however, tended to be three to four times higher than those simulated in three dimensions. This difference was attributed to dilution at the down gradient boundary. An alternative metric, mass flux reduction, however, yielded better agreement.

Download or read book Chlorinated Solvent Source Zone Remediation written by Bernard H. Kueper and published by Springer Science & Business. This book was released on 2014-04-22 with total page 759 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this book is to help engineers and scientists better understand dense nonaqueous phase liquid (DNAPL) contamination of groundwater and the methods and technology used for characterization and remediation. Remediation of DNAPL source zones is very difficult and controversial and must be based on state-of-the-art knowledge of the behavior (transport and fate) of nonaqueous phase liquids in the subsurface and site specific geology, chemistry and hydrology. This volume is focused on the characterization and remediation of nonaqueous phase chlorinated solvents and it is hoped that mid-level engineers and scientists will find this book helpful in understanding the current state-of-practice of DNAPL source zone management and remediation.

Download or read book Contaminants in the Subsurface written by National Research Council and published by National Academies Press. This book was released on 2005-04-23 with total page 371 pages. Available in PDF, EPUB and Kindle. Book excerpt: At hundreds of thousands of commercial, industrial, and military sites across the country, subsurface materials including groundwater are contaminated with chemical waste. The last decade has seen growing interest in using aggressive source remediation technologies to remove contaminants from the subsurface, but there is limited understanding of (1) the effectiveness of these technologies and (2) the overall effect of mass removal on groundwater quality. This report reviews the suite of technologies available for source remediation and their ability to reach a variety of cleanup goals, from meeting regulatory standards for groundwater to reducing costs. The report proposes elements of a protocol for accomplishing source remediation that should enable project managers to decide whether and how to pursue source remediation at their sites.

Download or read book Estimating Source Strength Functions of Dense Non aqueous Phase Liquids from Historical Field Datasets written by Brandon T. Wood and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Dense non-aqueous phase liquids (DNAPLs) pose a number of challenges in groundwater remediation design as well as prediction of contaminant fate. Previous research has suggested that flux based analysis may more closely relate a contaminant source zone to plume evolution and analysis of risk to human health and the environment. Several mathematical models have been developed to relate DNAPL mass and spatial distribution to contaminant mass flux. These functions were coupled with plume evolution models in order to assess their applicability to field settings using historical field data sets. These coupled solutions were used in an optimization framework in order to assess the applicability of source strength functions to field sites and the feasibility of characterizing a DNAPL source zone with historical data, mainly in the form of contaminant plume information both temporally and spatially. An efficient optimization technique, evolutionary optimization or genetic algorithm optimization was used to parameterize source strength functions for both known (synthetically generated data with known conditions) and unknown (field sites) historical datasets of various temporal record duration and resolution. This allowed for effective and accurate parameterization of source information for synthetically generated data, but due to the limitations of the analytical solutions to describe solute transport at field sites, failed to accurately parameterize certain cases. It is suggested that transport solutions that more accurately describe field settings are required for this type of analysis.

Download or read book Treating Dense Nonaqueous phase Liquids DNAPLs written by Godage B. Wickramanayake and published by . This book was released on 2000 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: - DNAPL Site Characterization- DNAPL Modeling- DNAPL Remediation Technologies- DNAPLs in Fractured Media- Surfactant/Cosolvent Flushing.

Download or read book Contaminated Ground Water and Sediment written by Calvin C. Chien and published by CRC Press. This book was released on 2003-11-24 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the documented result of an expert workshop, Modeling and Management of Emerging Environmental Issues, held at Penn State University. This event assembled four panels of modeling experts from the U.S. and Canada to discuss modeling technology development and application in order to promote sound and cost-effective environmental decision-making. This thorough analysis provides an overview on the state-of-the-art in current practice and identifies emerging research and development trends within modeling technology. Each of the discussions considers not only technical issues, but regulatory and cost factors as well.

Download or read book Assessing the Feasibility of DNAPL Source Zone Remediation Review of Case Studies written by and published by . This book was released on 2004 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall goal of this project was to gather information on the relative successes of remediation applications under different site conditions in order to initiate the development of guidelines on DNAPL source treatment. Members of the environmental community that had attempted to remediate DNAPL source zone areas were invited to participate in a web-based survey. which remained open for several months. Survey respondents were asked a number of questions dealing with site-specific issues (e.g. geology. hydrogeology. contaminant distribution. monitoring network) and technology specific issues (c-U. type of remedial technology. remediation stage. cost. treatment effectiveness). The number of survey respondents totaled 213. Of the 213. complete sets of data were obtained for 118 locations. Data from 21 published case studies was also entered into the survey. This report also includes a brief overview of chlorinated solvent DNAPL contamination and remediation processes. The data collected from this survey suggests that DNAPL remediation efficacy is extremely difficult to gauge. and although employing aggressive remedial technologies cannot achieve site closure. significant mass removal can be achieved.

Download or read book Dense Chlorinated Solvents and Other DNAPLs in Groundwater written by James F. Pankow and published by . This book was released on 1996 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Alternatives for Managing the Nation s Complex Contaminated Groundwater Sites written by National Research Council and published by National Academies Press. This book was released on 2013-02-27 with total page 423 pages. Available in PDF, EPUB and Kindle. Book excerpt: Across the United States, thousands of hazardous waste sites are contaminated with chemicals that prevent the underlying groundwater from meeting drinking water standards. These include Superfund sites and other facilities that handle and dispose of hazardous waste, active and inactive dry cleaners, and leaking underground storage tanks; many are at federal facilities such as military installations. While many sites have been closed over the past 30 years through cleanup programs run by the U.S. Department of Defense, the U.S. EPA, and other state and federal agencies, the remaining caseload is much more difficult to address because the nature of the contamination and subsurface conditions make it difficult to achieve drinking water standards in the affected groundwater. Alternatives for Managing the Nation's Complex Contaminated Groundwater Sites estimates that at least 126,000 sites across the U.S. still have contaminated groundwater, and their closure is expected to cost at least $110 billion to $127 billion. About 10 percent of these sites are considered "complex," meaning restoration is unlikely to be achieved in the next 50 to 100 years due to technological limitations. At sites where contaminant concentrations have plateaued at levels above cleanup goals despite active efforts, the report recommends evaluating whether the sites should transition to long-term management, where risks would be monitored and harmful exposures prevented, but at reduced costs.

Download or read book Natural Attenuation for Groundwater Remediation written by Commission on Geosciences, Environment, and Resources and published by National Academies Press. This book was released on 2000-08-31 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past decade, officials responsible for clean-up of contaminated groundwater have increasingly turned to natural attenuation-essentially allowing naturally occurring processes to reduce the toxic potential of contaminants-versus engineered solutions. This saves both money and headaches. To the people in surrounding communities, though, it can appear that clean-up officials are simply walking away from contaminated sites. When is natural attenuation the appropriate approach to a clean-up? This book presents the consensus of a diverse committee, informed by the views of researchers, regulators, and community activists. The committee reviews the likely effectiveness of natural attenuation with different classes of contaminants-and describes how to evaluate the "footprints" of natural attenuation at a site to determine whether natural processes will provide adequate clean-up. Included are recommendations for regulatory change. The committee emphasizes the importance of the public's belief and attitudes toward remediation and provides guidance on involving community stakeholders throughout the clean-up process. The book explores how contamination occurs, explaining concepts and terms, and includes case studies from the Hanford nuclear site, military bases, as well as other sites. It provides historical background and important data on clean-up processes and goes on to offer critical reviews of 14 published protocols for evaluating natural attenuation.

Download or read book Laboratory Investigation of Dense Non aqueous Phase Liquid DNAPL Partial Source Zone Remediation Using Cosolvents written by Andrew Joseph Kaye and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: There are hundreds of thousands of commercial, military, and industrial sites across the country where chemical wastes cause contamination to groundwater. Some of the more challenging sites to clean up contain contaminants as dense non-aqueous phase liquids (DNAPLs). There is currently no consensus in the academic, technical and regulatory communities on the ecological or environmental impacts of DNAPL source zone treatment. While many in-situ technologies have shown the ability to remove a significant portion of the contaminant mass, none are able to remove all of it from the source zone. This study investigates the benefits of partial source zone removal using cosolvent flushing. The benefits were assessed by characterizing the relationship between reductions in DNAPL mass and the corresponding reduction in contaminant mass discharge in several laboratory scale experiments. Also, the effects of fluid override and underride associated with cosolvent flushing on the mass reduction (MR) vs. flux reduction (FR) relationship were investigated. The results indicate a model with beta> 1 may be a good approximation of the MR vs. FR relationship using enhanced dissolution by the cosolvents in systems with similar degrees DNAPL and media heterogeneity. Also, the override and underride associated with cosolvents did not significantly affect their remediation.

Download or read book Mass Transfer from Entrapped DNAPL Sources Undergoing Remediation Characterization Methods and Prediction Tools written by and published by . This book was released on 2006 with total page 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary goal of this research was to understand and characterize mass transfer and tracer partitioning in physically heterogeneous DNAPL sources undergoing remediation. Four source zone treatment technologies were evaluated: (1) bio-treatment, (2) in situ chemical oxidation (ISCO), (3) surfactant enhanced dissolution and (4) thermal treatment. Fundamental knowledge was generated to improve and develop tools for evaluating the impact of remediation technologies on DNAPL distribution in heterogeneous systems. Experiments and modeling at column, flow cell and large tank scales were designed to understand how parameters that quantify laboratory-scale processes contributing to mass transfer and parameters that quantify the processes can be upscaled to describe and simulate the field-scale behavior, and to test hypotheses that mass transfer coefficients for entrapped DNAPL sources change during remediation. Large-tank experiments generated accurate data sets under controlled conditions suitable for model development and validation, and to obtain insight to mass transfer in physically heterogeneous system.

Download or read book Modeling Groundwater Flow and Contaminant Transport written by Jacob Bear and published by Springer Science & Business Media. This book was released on 2010-01-18 with total page 851 pages. Available in PDF, EPUB and Kindle. Book excerpt: In many parts of the world, groundwater resources are under increasing threat from growing demands, wasteful use, and contamination. To face the challenge, good planning and management practices are needed. A key to the management of groundwater is the ability to model the movement of fluids and contaminants in the subsurface. The purpose of this book is to construct conceptual and mathematical models that can provide the information required for making decisions associated with the management of groundwater resources, and the remediation of contaminated aquifers. The basic approach of this book is to accurately describe the underlying physics of groundwater flow and solute transport in heterogeneous porous media, starting at the microscopic level, and to rigorously derive their mathematical representation at the macroscopic levels. The well-posed, macroscopic mathematical models are formulated for saturated, single phase flow, as well as for unsaturated and multiphase flow, and for the transport of single and multiple chemical species. Numerical models are presented and computer codes are reviewed, as tools for solving the models. The problem of seawater intrusion into coastal aquifers is examined and modeled. The issues of uncertainty in model input data and output are addressed. The book concludes with a chapter on the management of groundwater resources. Although one of the main objectives of this book is to construct mathematical models, the amount of mathematics required is kept minimal.

Download or read book DNAPL Site Evaluation written by James W. Mercer and published by CRC-Press. This book was released on 1993-04-29 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: DNAPL Site Evaluation covers long-term contamination of ground water by DNAPL (dense non-aqueous phase liquids) chemicals. The book develops a framework for planning and implementing DNAPL site characterization activities. It provides detailed methods to identify, characterize, and monitor sites and analyzes their utility, limitations, risks, availability, and cost. Methods to interpret contaminant fate and transport are identified, and new site characterization methods are assessed. DNAPL Site Evaluation will maximize the cost-effectiveness of site investigation/remediation by providing the best information available to describe and evaluate methods to be used for determining the presence, fate, and transport of subsurface DNAPL contamination. The book will be a useful reference for groundwater professionals and environmental regulatory personnel.

Download or read book Development of Assessment Tools for Evaluation of the Benefits of DNAPL Source Zone Treatment written by and published by . This book was released on 2008 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its commencement in September 2002, SERDP Project ER-1293 has supported 4 doctoral students at three universities and resulted in over 40 conference proceedings/technical abstracts and over 20 peer-reviewed publications. These presentations and publications, as referenced in this final report, describe various aspects of the research investigations and tools that have been developed to enhance design and assessment of DNAPL source zone treatment. In general, research in ER-1293 has led to the development and validation of four important concepts: (i) partial source zone mass removal may result in substantial local concentration and mass flux reductions; (ii) potential remediation efficiency is closely linked to source zone architecture (ganglia to pool ratios); (iii) biostimulation and bioaugmentation approaches are feasible for treatment of DNAPL source zones; and (iv) the uncertainty in mass discharge ([M/T]) estimates can be quantified through application of geostatistical methods to field measurements. Major contributions of this research include (i) establishment that rates of metabolic reductive dechlorination can exceed rates of DNAPL dissolution, resulting in aqueous contaminant concentrations in the presence of DNAPL that are substantially lower than saturation levels and are not toxic to the dechlorinating organisms; (ii) enhancements in dissolution will be transient and a function of physico-chemical and biological conditions adjacent to the DNAPL; (iii) demonstration that mass flux reduction behavior can be directly linked to DNAPL source zone architecture; (iv) development of a series of geostatistical approaches capable of quantifying mass discharge uncertainty and guiding real-time sampling design for uncertainty reduction through hot spot delineation ; and (v) creation of a source zone remediation cost estimation tool.

Download or read book In Situ Chemical Oxidation for Groundwater Remediation written by Robert L. Siegrist and published by Springer Science & Business Media. This book was released on 2011-02-25 with total page 715 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume provides comprehensive up-to-date descriptions of the principles and practices of in situ chemical oxidation (ISCO) for groundwater remediation based on a decade of intensive research, development, and demonstrations, and lessons learned from commercial field applications.