Download or read book A Field Laboratory and Modeling Study of Natural Attenuation Processes Affecting the Fate and Transport of Hexavalent Chromium in a Redox Variable Groundwater Environment written by Lucas Ammi Hellerich and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2004 with total page 882 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Monitored Natural Attenuation of Inorganic Contaminants in Ground Water written by and published by . This book was released on 2007 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: V.3 ... consists of individual chapters that describe 1) the conceptual background for radionuclides, including tritium, radon, strontium, technetium, uranium, iodine, radium, thorium, cesium, plutonium-americium and 2) data requirements to be met during site characterization.
Download or read book Natural Attenuation of Hexavalent Chromium in Ground Water and Soils written by Carl D. Palmer and published by . This book was released on 1994 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book In Situ Treatment of Soil and Groundwater Contaminated with Chromium written by National Risk Management Research Laboratory (U.S.) and published by . This book was released on 2000 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Assessment of Hexavalent Chromium Natural Attenuation for the Hanford Site 100 Area written by and published by . This book was released on 2015 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hexavalent chromium (Cr(VI)) plumes are present in the 100 Area at the Hanford Site. Remediation efforts are under way with objectives of restoring the groundwater to meet the drinking-water standard (48 æg/L) and protecting the Columbia River by ensuring that discharge of groundwater to the river is below the surface-water quality standard (10 æg/L). Current remedies include application of Pump-and-Treat (P & T) at the 100-D, 100-H, and 100-K Areas and Monitored Natural Attenuation (MNA) at the 100-F/IU Area. Remedy selection is still under way at the other 100 Areas. Additional information about the natural attenuation processes for Cr(VI) is important in all of these cases. In this study, laboratory experiments were conducted to demonstrate and quantify natural attenuation mechanisms using 100 Area sediments and groundwater conditions.
Download or read book Chromium in Soil Perspectives in Chemistry Health and Environmental Regulation written by Paul T. Kostecki and published by CRC Press. This book was released on 1998-01-08 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: The importance of understanding complex toxicological and chemical properties of hexavalent and trivalent chromium has increased rapidly over the last few years as state and federal regulators reevaluate environmental standards. The risk management of chromium-contaminated soils continues to be a very dynamic process that presents interesting challenges. Chromium in Soil discusses the challenges faced by those investigating and remediating chromium-impacted soils and groundwater. The chapters address numerous ground-breaking developments in various fields of environmental chromium research, including toxicity, chemistry, environmental fate and transport, remediation technology, and health-based cleanup standards.
Download or read book Coupling of Oxidation reduction Reactions of Chromium Iron and Manganese written by Chao Pan (Environmental engineer) and published by . This book was released on 2017 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Both within the United States and internationally, hexavalent chromium (Cr(VI)) is a contaminant of concern in drinking water supplies. The U.S. Environmental Protection Agency is considering a Cr(VI)-specific standard. Thus improved technologies for Cr(VI) removal in drinking water are needed. Iron electrocoagulation for Cr(VI) removal was examined at conditions directly relevant to drinking water treatment, and humic acid (HA) affects the performance of electrocoagulation in multiple ways. The success of the chromium treatment or remediation also relies on the stability of the Cr(III)-containing solids with respect to reoxidation under groundwater conditions. Manganese is ubiquitous in aquatic and terrestrial environments, and the redox cycling of manganese may significantly impact the fate and transport of chromium. Coupling of redox reactions of chromium, iron and manganese involves multiple interaction pathways that occur in the aqueous phase as well as at solid-water interfaces. A mechanistic and quantitative understanding of these processes is needed to establish input parameters for kinetic and transport models and to enable decision-making for chromium treatment strategies.Iron electrocoagulation (EC) is a technology that can successfully achieve low concentrations of Cr(VI) in treated drinking water. In our research we have applied iron electrocoagulation (EC) with iron serving as the sacrificial anode to treat simulated drinking water solutions. Experiments have evaluated the effects of pH, dissolved oxygen, and common anions on Cr(VI) removal during batch EC treatment. In addition, the presence of humic acid (HA) inhibited the rate of Cr(VI) removal in electrocoagulation, with slower Cr(VI) removal at higher pH. This is due to dissolved oxygen competing with Cr(VI) for the oxidation of Fe(II) released from the anode. As determined using dynamic light scattering and wet chemistry experiments, the presence of HA resulted in the formation of Cr(III)-Fe(III)-HA colloids during electrocoagulation, which is difficult to remove in following water treatment steps of sedimentation and granular media filtration. Characterization of the solids by X-ray diffraction indicates that the iron oxides produced are lepidocrocite at pH 8, with more ferrihydrite in the presence of HA.Building on previous knowledge of MnO2 as an oxidant for Cr-containing solids, we systematically evaluated the rates and products of the oxidation of Cr(III) in iron oxides by MnO2. We found that Cr(III) dissolution from CrxFe1-x(OH)3 greatly influenced the Cr(VI) production rates. A multi-chamber reactor was used to assess the role of solid-solid mixing in CrxFe1-x(OH)3-MnO2 interactions. A dialysis membrane divided the reactor into two chambers, eliminating the possibility of direct contact of the solids in each chamber but allowing dissolved species to diffuse across the membrane. The Cr(VI) production rate was much lower in multi-chamber experiments (CrxFe1-x(OH)3||MnO2) than in completely mixed batch experiments under the same condition, indicating that the redox interaction is greatly accelerated by mixing of the two solids. The model was first established to predict Cr(VI) release in Cr(OH)3||MnO2 multichamber experiments, as dissolved Cr(III) concentration in equilibrium with Cr(OH)3 is higher at low pH and it’s easy to observe the behavior of Cr(VI) dynamics with more Cr(VI) generation. While solid phase Mn(IV) is well known oxidants of Cr(III)-containing solids, the localized oxidation of adsorbed Mn(II) by dissolved oxygen can also promote the oxidation of Cr(III) contained within CrxFe1-x(OH)3. The promotional effects was likely due to Mn redox cycling in which oxidized forms of Mn species were generated as oxidants of CrxFe1-x(OH)3 that were more potent than O2.
Download or read book Natural Attenuation written by Patrick V. Brady and published by CRC Press. This book was released on 2018-02-06 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: Natural Attenuation: CERCLA, RBCAs, and the Future of Environmental Remediation presents the concept of "natural attenuation"-the tendency of soils to severly limit the toxicity of many types of hazardous waste. It reviews and updates the most recent findings from the field and lab and shows how natural attenuation is rapidly changing the direction and focus of environmental remediation. Outlining the legal and regulatory framework that has made waste remediation so costly, this book shows how applying an understanding of natural attenuation can decrease cleanup outlays while lowering risks to human health. Natural Attenuation: CERCLA, RBCAs, and the Future of Environmental Remediation makes it clear why natural attenuation will be relied upon more and more in the future.
Download or read book An In situ Permeable Reactive Barrier for the Treatment of Hexavalent Chromium and Trichloroethylene in Ground Water Multicomponent reactive transport modeling written by and published by . This book was released on 1999 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Treatability Study of in Situ Technologies for Remediation of Hexavalent Chromium in Groundwater at the Puchack Well Field Superfund Site New Jersey written by Vincent R. Vermeul and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Evaluation and Chemical Modeling of Hexavalent Chromium Adsorption Desorption and Reduction in a Natural Soil written by Mohammed F. Azizian and published by . This book was released on 1993 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chromium and its compounds are widely used by modern industries, resulting in large quantities of this element being discharged into the environment. To remove chromium from contaminated soils and ground water, it is necessary to predict chemical and physical processes that control the rate of reactions and transport of chromium in soils and aquifers. The goals of this experimental study were to determine (i) kinetics and equilibrium adsorption of chromium(VI) in a natural soil, (ii) reduction of Cr(VI) to Cr(III) in the soil, and (iii) the effect of competing oxyanions on Cr(VI) adsorption in the soil. The TLM was used to interpret surface complexation reactions of the chromate ions in the soil. A laboratory investigation of reactions between hexavalent chromium, Cr(VI), and a natural soil was conducted to evaluate factors that influence sorption and reduction of Cr(VI) in natural soils. Both batch and soil column experiments were conducted to study the chemical behavior and transport of Cr(VI) in the soil. Results indicated that adsorption and reduction of Cr(VI) are the major processes that control the rate of transport and mobility of chromium in natural soils. Cr(VI) removal from solution increased with increasing solute concentration and with decreasing solution pH. This experimental study provides insight on how the residual amount of ferrous ions in minerals such as magnetite can effect the redox speciation of chromium in natural soils. Experimental results indicated that the small amounts of magnetite Fe3O4 contained in the soil caused reduction of Cr(VI) to Cr(III) even at pH above 8. The ferrous iron contained in magnetite provides a source of electrons for the reduction of Cr(VI) to Cr(III). Competing oxyanions, phosphate (H2PO4−/HPO42−) and sulfate (SO42−), increased Cr(VI) desorption by direct competition for adsorption sites. The equilibrium adsorption capacity of the soil was described with the Langmuir model, while a triple layer model (TLM) was employed to describe the surface complexation reactions. Outer-sphere surface complexation reactions and two-site (FeOH and AIOH) modeling were used to simulate adsorption of the chromate (CrO42−) and bichromate (HCrO4−) ions.
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 Bioreduction of Hexavalent Chromium written by Md Mahbub Alam and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evaluation of Chromium Speciation and Transport Characteristics in the Hanford Site 100D and 100H Areas written by and published by . This book was released on 1995 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Field and laboratory investigations have been conducted to define the fate and transport characteristics of chromium contamination present in the 100D/H Areas of the Hanford Site. This information is relevant to assessing the impact of the release of hexavalent chromium to the Columbia River. Included in this study was the determination of the concentration and aqueous speciation of chromium in the unconfined acquifer and an assessment of potential changes in speciation as groundwater passes through the river/acquifer transition zone and mixes with the Columbia River. The results of this study indicate that chromium present within the Hanford acquifer is predominantly in the oxidized hexavalent state. Chromium is apparently stable in the oxidized form owing to its lack of organic matter within the acquifer. A portion of the chromium is removed as groundwater passes through the transition zone due to reduction and precipitation associated with sediment/water interaction processes. Chemical data collected from seep water samples, however, suggests, that most of the hexavalent chromium ultimately discharges into the Columbia River. Dilution of hexavalent chromium subsequently occurs during the mixing of groundwater and river water, with relatively little change taking place in speciation.
Download or read book A Steady state Model for Hexavalent Chromium Reduction in Simulated Biological Reactive Barrier written by Phalazane Johanna Mtimunye and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Biological remediation of Cr(VI) contaminated soil and groundwater is an emerging field. In this study, the in situ bioremediation technology for treating Cr(VI) contaminated groundwater aquifers was evaluated using a laboratory microcosm system. The study was conducted using columns with five equally spaced intermediate sampling ports along the length to facilitate finite difference modelling of the Cr(VI) concentration profile within the column. Cr(VI) concentration was continuously measured in the influent, in five equally spaced intermediate ports within the column and in the effluent port. The change or the shift in microbial community within the inoculated column was also monitored due to exposure to toxic conditions after seven weeks of operation using the 16S rRNA genotype fingerprinting method. The effect of introducing a natural carbon source (sawdust) in inoculated columns in comparison with the performance of sterile controls under various loading conditions was also evaluated. Near complete Cr(VI) removal was achieved in an inoculated carbon source reactor, whereas only 69.5% of Cr(VI) removal was achieved in an inoculated column without an added carbon source after 4 days of operation at 20 mg/L. In a sterile control reactor less than 2% of Cr(VI) was removed after 4 days of operation at 20 mg/L. Experimental cores demonstrated a successful Cr(VI) reduction process in the simulated microbial barrier system that was evaluated internally. The model that simulates Cr(VI) removal and transport in the subsoil environment was developed. The Cr(VI) mass balance model across the reactor that accounts for the flow characteristics and biological removal mechanism successfully captured the trends of Cr(VI) response profiles under quasi-steady state conditions for different loading conditions. This study demonstrate the potential of applying effective Cr(VI) reducers in the reactive barrier systems to contain or attenuate the spread of Cr(VI) contaminant in groundwater aquifer systems. The finite difference model developed in this study to evaluate the behaviour of Cr(VI) in the reactor could contribute towards improved designs of future in situ bioremediation systems that can be implemented for remediation of Cr(VI) on site.
