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Groundwater is susceptible to pollution due to improper waste disposal. Groundwater contamination continues to be a problem in areas where population relies on groundwater as a major source of drinking water. Development of technologies, such as in situ electrochemical transformation to clean contaminated groundwater is of great importance. Electrochemical systems, which mainly consist of two or more arranged electrodes that are immersed in wells in groundwater, are of interest because of their ability to manipulate redox conditions to transform contaminants into non-toxic forms. Aquifers in karst regions are very susceptible to contamination and present a significant exposure routes due to presence of fissures and channels that facilitate contaminant transport under high flow rate. Trichloroethylene (TCE), a toxic chlorinated solvent that causes major health problems, is present in many contaminated aquifers including many that reside in karst regions. Treatment of aquifers contaminated with TCE is difficult in the presence of other contaminants, such as chromate, selenate, and nitrate, which interfere with TCE transformation and degradation mechanisms. Moreover, presence of natural organic matter (NOM) in the groundwater can influence transformation of TCE and other contaminants. Therefore, it is important to evaluate transformation of TCE in the presence of contaminant mixtures in groundwater. In this study, a series of experiments are conducted to (1) evaluate of the effect of co-existing organic and inorganic compounds on the electrochemical dechlorination of trichloroethylene (TCE) in simulated karst media; and (2) assessment of the impacts of high groundwater flow rates in the presence of palladium (Pd) catalyst on TCE transformation rate and the accumulation of precipitates. A small-scale flow-through limestone column is used to simulate a karst aquifer media to evaluate dechlorination of TCE in the presence of organic and inorganic compounds. Iron anode was used to produce ferrous ions and promote reducing conditions in the column. Various current intensities (30, 60, and 90 mA) were applied under the flow rate of 1 mL min−1 and initial TCE concentration of 1 mg L−1. Under the same testing conditions, presence of chromate has the highest influence on TCE removal followed by selenate and then nitrate. The reduction of TCE under 90 mA current, 1 mL min−1 flow rate, and 1 mg L−1 initial TCE concentration, was inhibited in the presence of humic acids due to competition for direct electron transfer and/or reaction with atomic hydrogen produced at the cathode surface by water electrolysis. The use of iron anode creates favorable conditions for TCE reduction but produces aggregates in combination with ferrous ions, which may impact the long-term performance of the remedial system. A vertical acrylic column, with Pd pellets placed on the cathode surface, was used to investigate the impacts of Pd-based catalysis for the removal of TCE under high flow rate (1 L min−1). The effects of electrode materials and current intensities on precipitation, pH and ORP are assessed. The following electrode materials and arrangements were tested: (a) two MMO electrodes as an anode and a cathode, (b) a cast-iron anode and a MMO cathode, and (c) a cast-iron anode and a copper foam cathode. Current intensities of 500, 250, 125, and 62 mA were tested under the flow rate of 1 L min−1 and 5 mg L−1 of initial concentration of TCE. Under the conditions of 1 L min−1 flow, 500 mA current, and 5 mg L−1 initial concentration of TCE, removal efficacy using iron anodes (96%) is significantly higher than that of mixed metal oxide (MMO) anodes (66%) because the iron anode supports reduction conditions by electrolysis. Two types of cathodes (MMO and copper foam) in the presence of Pd/Al2O3 catalyst under various currents (250, 125, and 62 mA) were used to evaluate the effect of cathode materials on TCE removal efficacy. The similar removal efficiencies were achieved for both cathodes, but more precipitation generated with copper foam cathode. Palladium improved TCE degradation by 120% for 250 mA, 100% for 125 mA, 100% for 62 mA, under the conditions of using an iron anode followed by a copper foam cathode with 1 L min−1 flow rate. The high velocities of groundwater flow can have important implications since the groundwater flow rate can significantly fluctuate, especially in karst aquifers. The optimization of the electrochemical systems for successful operation under high flow rates allows the robustness and great flexibility for the application. It is assumed that the high flow rate would favor the transformation of contaminants since it would flush out precipitates and prevent clogging.
The world’s fresh water supplies are dwindling rapidly—even wastewater is now considered an asset. By 2025, most of the world's population will be facing serious water stresses and shortages. Aquananotechnology: Global Prospects breaks new ground with its informative and innovative introduction of the application of nanotechnology to the remediation of contaminated water for drinking and industrial use. It provides a comprehensive overview, from a global perspective, of the latest research and developments in the use of nanotechnology for water purification and desalination methods. The book also covers approaches to remediation such as high surface area nanoscale media for adsorption of toxic species, UV treatment of pathogens, and regeneration of saturated media with applications in municipal water supplies, produced water from fracking, ballast water, and more. It also discusses membranes, desalination, sensing, engineered polymers, magnetic nanomaterials, electrospun nanofibers, photocatalysis, endocrine disruptors, and Al13 clusters. It explores physics-based phenomena such as subcritical water and cavitation-induced sonoluminescence, and fog harvesting. With contributions from experts in developed and developing countries, including those with severe contamination, such as China, India, and Pakistan, the book’s content spans a wide range of the subject areas that fall under the aquananotechnology banner, either squarely or tangentially. The book strongly emphasizes sorption media, with broad application to a myriad of contaminants—both geogenic and anthropogenic—keeping in mind that it is not enough for water to be potable, it must also be palatable.
The first comprehensive guide to one of today's most innovative approaches to environmental contamination Natural attenuation is gaining increasing attention as a nonintrusive, cost-effective alternative to standard remediation techniques for environmental contamination. This landmark work presents the first in-depth examination of the theory, mechanisms, and application of natural attenuation. Written by four internationally recognized leaders in this approach, the book describes both biotic and abiotic natural attenuation processes, focusing on two of the environmental contaminants most frequently encountered in groundwater--fuels and chlorinated solvents. The authors draw on a wealth of combined experience to detail successful techniques for simulating natural attenuation processes and predicting their effectiveness in the field. They also show how natural attenuation works in the real world, using numerous examples and case studies from a wide range of leading-edge projects nationwide involving fuel hydrocarbons and chlorinated solvents. Finally, they discuss the evaluation and assessment of natural attenuation and explore the design of long-term monitoring programs. An indispensable reference for anyone working in environmental remediation, Natural Attenuation of Fuels and Chlorinated Solvents in the Subsurface is essential reading for scientists and engineers in a range of industries, as well as state and federal environmental regulators, and professors and graduate students in environmental or chemical engineering.
Bioavailability refers to the extent to which humans and ecological receptors are exposed to contaminants in soil or sediment. The concept of bioavailability has recently piqued the interest of the hazardous waste industry as an important consideration in deciding how much waste to clean up. The rationale is that if contaminants in soil and sediment are not bioavailable, then more contaminant mass can be left in place without creating additional risk. A new NRC report notes that the potential for the consideration of bioavailability to influence decision-making is greatest where certain chemical, environmental, and regulatory factors align. The current use of bioavailability in risk assessment and hazardous waste cleanup regulations is demystified, and acceptable tools and models for bioavailability assessment are discussed and ranked according to seven criteria. Finally, the intimate link between bioavailability and bioremediation is explored. The report concludes with suggestions for moving bioavailability forward in the regulatory arena for both soil and sediment cleanup.
This publication comprises the presentations made at the NATO Advanced Research Workshop held in Sinaia, Romania 9 – 11 October, 2006. The contributions represent a unique cross section of issues and challenges related to contaminated site management. These range from low cost solutions to petroleum contaminated sites to advances in biological treatment methods. The publication is meant to foster links between groups facing challenges cleaning up contaminated sites.
The suitability of Advanced Oxidation Processes (AOPs) for pollutant degradation was recognised in the early 1970s and much research and development work has been undertaken to commercialise some of these processes. AOPs have shown great potential in treating pollutants at both low and high concentrations and have found applications as diverse as ground water treatment, municipal wastewater sludge destruction and VOCs control. Advanced Oxidation Processes for Water and Wastewater Treatment is an overview of the advanced oxidation processes currently used or proposed for the remediation of water, wastewater, odours and sludge. The book contains two opening chapters which present introductions to advanced oxidation processes and a background to UV photolysis, seven chapters focusing on individual advanced oxidation processes and, finally, three chapters concentrating on selected applications of advanced oxidation processes. Advanced Oxidation Processes for Water and Wastewater Treatment will be invaluable to readers interested in water and wastewater treatment processes, including professionals and suppliers, as well as students and academics studying in this area. Dr Simon Parsons is a Senior Lecturer in Water Sciences at Cranfield University with ten years' experience of industrial and academic research and development.
Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.
We are proposing this comprehensive volume aimed at bridging and bonding of the theory and practical experiences for the elimination of a broad range of pollutants from various types of water and soil utilizing innovative nanotechnologies, biotechnologies and their possible combinations. Nowadays, a broad range of contaminants are emerging from the industry (and also representing old ecological burdens). Accidents and improper wastewater treatment requires a fast, efficient and cost-effective approach. Therefore, several innovative technologies of water and soil treatments have been invented and suggested in a number of published papers. Out of these, some nanotechnologies and biotechnologies (and possibly also their mutual combinations) turned out to be promising for practical utilization – i.e., based on both extensive laboratory testing and pilot-scale verification. With respect to the diverse character of targeted pollutants, the key technologies covered in this book will include oxidation, reduction, sorption and/or biological degradation. In relation to innovative technologies and new emerging pollutants mentioned in this proposed book, an important part will also cover the ecotoxicity of selected pollutants and novel nanomaterials used for remediation. Thus, this work will consist of 8 sections/chapters with a technical appendix as an important part of the book, where some technical details and standardized protocols will be clearly presented for their possible implementation at different contaminated sites. Although many previously published papers and books (or book chapters) are devoted to some aspects of nano-/biotechnologies, here we will bring a first complete and comprehensive treatise on the latest progress in innovative technologies with a clear demonstration of the applicability of particular methods based on results of the authors from pilot tests (i.e., based on the data collected within several applied projects, mainly national project “Environmentally friendly nanotechnologies and biotechnologies in water and soil treatment” of the Technology Agency of the Czech Republic, and 7FP project NANOREM: “Taking Nanotechnological Remediation Processes from Lab Scale to End User Applications for the Restoration of a Clean Environment”). This multidisciplinary book will be suitable for a broad audience including environmental scientists, practitioners, policymakers and toxicologists (and of course graduate students of diverse fields – material science, chemistry, biology, geology, hydrogeology, engineering etc.).
This book summarizes the current state of knowledge concerning bacteria that use halogenated organic compounds as respiratory electron acceptors. The discovery of organohalide-respiring bacteria has expanded the range of electron acceptors used for energy conservation, and serves as a prime example of how scientific discoveries are enabling innovative engineering solutions that have transformed remediation practice. Individual chapters provide in-depth background information on the discovery, isolation, phylogeny, biochemistry, genomic features, and ecology of individual organohalide-respiring genera, including Dehalococcoides, Dehalogenimonas, Dehalobacter, Desulfitobacterium and Sulfurospirillum, as well as organohalide-respiring members of the Deltaproteobacteria. The book introduces readers to the fascinating biology of organohalide-respiring bacteria, offering a valuable resource for students, engineers and practitioners alike.