Download or read book Modeling Chlorinated Ethene Removal in the Methanogenic Zone of Constructed Wetlands written by Randall L. Roberts and published by . This book was released on 2001-03 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study is to gain understanding of the dynamics of the processes that degrade Perchloroethene (PCE) to ethene, within the confines of the methanogenic zone of a constructed wetland. A system dynamics modeling approach is used. This model is focused on determining conditions that will enhance contaminant degradation. The chemical and biological processes within the methanogenic zone of a wetland system are extremely complex and dynamic processes. The model is broken up into three simultaneous processes: dechlorination, methanogenesis, and fermentation. The system behavior of the methanogenic zone can be adequately described by the classical formulations of representative microbial reactions acting simultaneously within each process in response to substrate limitation. The zone is assumed to be homogeneous and well mixed. This study provides a fundamental understanding of the complex interactions within the methanogenic zone of a constructed wetland and gives some insight for implementation. Testing identified flow rate, hydrogen concentration, and initial PCE biomass as specific parameters, which could be optimized to have the most effect on contaminant fate.
Download or read book Modeling Chlorinated Ethene Removal in the Methanogenic Zone of Constructed Wetlands A System Dynamics Approach written by and published by . This book was released on 2001 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study is to gain understanding of the dynamics of the processes that degrade Perchloroethene (PCE) to ethene, within the confines of the methanogenic zone of a constructed wetland. A system dynamics modeling approach is used. This model is focused on determining conditions that will enhance contaminant degradation. The chemical and biological processes within the methanogenic zone of a wetland system are extremely complex and dynamic processes. The model is broken up into three simultaneous processes: dechlorination, methanogenesis, and fermentation. The system behavior of the methanogenic zone can be adequately described by the classical formulations of representative microbial reactions acting simultaneously within each process in response to substrate limitation. The zone is assumed to be homogeneous and well mixed. This study provides a fundamental understanding of the complex interactions within the methanogenic zone of a constructed wetland and gives some insight for implementation. Testing identified flow rate, hydrogen concentration, and initial PCE biomass as specific parameters, which could be optimized to have the most effect on contaminant fate.
Download or read book Modelling Chlorinated Ethene Removal in the Methanogenic Zone of Constructed Wetlands written by Randall L. Roberts and published by . This book was released on 2001 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Comparison of Modeling Approaches in Simulating Chlorinated Ethene Removal in a Constructed Wetland by a Microbial Consortia written by Jason S. Campbell and published by . This book was released on 2002-03 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study is to compare different approaches to modeling the reductive dechlorination of chlorinated ethenes in the anaerobic region of an upward flow constructed wetland by microbial consortia. A controlled simulation experiment that compares three different approaches to modeling the degradation of chlorinated ethenes in wetland environments is conducted and investigates how each of the modeling approaches affect simulation results. Concepts like microbial growth in the form of a biofilm and spatially varying contaminant concentrations bring the validity of the CSTR assumption into question. These concepts are incorporated into the different modeling approaches to evaluate the CSTR assumption. Model simulations show that spatially varying contaminant concentrations have a significant effect on contaminant effluent concentrations. Additionally, the significance of the incorporation of a biofilm concept depends on the time characteristics of both diffusive mass transport and reaction kinetics.
Download or read book An Anion Characterization of a Constructed Wetland Used for Chlorinated Ethene Remediation written by Bradley M. Bugg and published by . This book was released on 2001-03 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chlorinated ethene's physical properties as well as its ubiquitous state at DOD installations makes it a priority for innovative remediation efforts. Current techniques are expensive and time consuming to maintain. Constructed wetlands suggest an inexpensive and operational alternative to conventional technologies. Sub-surface flow wetlands provide the anaerobic zones necessary to reduce the recalcitrant chlorinated solvents prior to anaerobic or aerobic mineralization of its daughter products. A vertical flow cell to include sequential sedimentary layers of two hydric soil lifts and a mix of hydric soil and woody compost was the subject of this investigation. This study focused on the statistical significance among the three constructed strata. Concentrations of mono-carboxylic acids and other anions are indicators of the reductive conditions necessary for remediation. Acid anion concentrations were expected to be higher in the assumed anaerobic strata of the constructed cell as a result of the fermentation of humic substances. Decreases in sulfate and nitrate were also expected over the upward flowing, wetland profile due to the reductive, anoxic conditions. Evidence in this study validate these assumptions and suggest that constructed wetlands are a viable alternative to current remediation methods. Findings also suggest manipulation of the physical parameters such as strata depth, soil type, flow rate, etc of a wetland could increase the cell's remediation effectiveness.
Download or read book Characterization of Chlorinated Solvent Degradation in a Constructed Wetland written by Nathan D. Clemmer and published by . This book was released on 2003-03 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: Widespread chlorinated ethene contamination of aquifers coupled with high costs of current treatment technologies demand innovative remediation solutions. Wetlands, maintaining anaerobic and aerobic zones promoting the complete degradation of chlorinated ethenes such as Tetrachloroethylene (PCE), could be the answer. This thesis characterized the chlorinated solvent contamination levels in three strata of an upward flow constructed wetland. Analysis of samples was accomplished by purge-and-trap gas chromatography. Water quality parameters, Dissolved Oxygen (DO), Oxidation Reduction Potential (ORP), pH, Conductivity, and Temperature, were also measured in monitoring wells with a water monitoring sonde. After removing data outliers caused by short-circuiting flow, PCE concentrations declined from an average of 32,59 +/- 0,699 ppb (+/- 95% confidence interval) in the inflow stream to an average of 0.171 +/- 0.079 ppb in the upper layer (99,3% reduction). Concentration trends of PCE degradation products cis-1,1 -Dichloroethylene (cis-DCE), Vinyl Chloride (VC), and Trichloroethylene TCE) indicate dechlorination processes are occurring. In addition to PCE, TCE at concentrations below 0,6 ppb was the only other analyte detected in the inflow and outflow, Water quality measurements (DO and 0RP) decreased from the bottom to the middle layer to a level that supports anaerobic reductive dechlorination but not methanogenesis. The DO increased slightly from the middle to the top layer while 0RP continued to decrease.
Download or read book Determination of Chlorinated Solvent Contamination in an Upward Flow Constructed Wetland written by Bryan C. Opperman and published by . This book was released on 2002-03-01 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study is to determine chlorinated solvent contamination levels in an upward flow constructed wetland at Wright-Patterson Air Force Base (WPAFB), Ohio. A stratified grid sampling methodology will be used in sampling the contaminated groundwater. Analysis will be accomplished by means of purge-and-trap gas chromatography. The contaminant concentration levels will be used to enhance the design and construction of man-made wetlands used to remove chlorinated solvents from aquifers. PCE levels declined from an average of 33.97 ppb in the inflow stream to an average of 3.65 ppb in the upper layer, a 91% reduction. High concentrations occurred in areas where high hydraulic pressure gradients and hydraulic conductivities combined to allow contaminated water to migrate to the upper layers of the wetland with minimal contact time for reduction. Removing these areas from the data set increased the PCE reduction efficiency to nearly 98% with an upper level concentration average of 0.84 ppb. Trichloroethene (TCE) inflow rates averaged 0.63 ppb while TCE concentrations in the upper layer averaged 0.175 ppb. TCE concentrations peaked in the middle layer of the wetland suggesting that reduction of PCE was occurring there and in the bottom layer.
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 American Doctoral Dissertations written by and published by . This book was released on 1999 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Biogeochemistry of Wetlands written by K. Ramesh Reddy and published by CRC Press. This book was released on 2022-09-10 with total page 926 pages. Available in PDF, EPUB and Kindle. Book excerpt: The globally important nature of wetland ecosystems has led to their increased protection and restoration as well as their use in engineered systems. Underpinning the beneficial functions of wetlands are a unique suite of physical, chemical, and biological processes that regulate elemental cycling in soils and the water column. This book provides an in-depth coverage of these wetland biogeochemical processes related to the cycling of macroelements including carbon, nitrogen, phosphorus, and sulfur, secondary and trace elements, and toxic organic compounds. In this synthesis, the authors combine more than 100 years of experience studying wetlands and biogeochemistry to look inside the black box of elemental transformations in wetland ecosystems. This new edition is updated throughout to include more topics and provide an integrated view of the coupled nature of biogeochemical cycles in wetland systems. The influence of the elemental cycles is discussed at a range of scales in the context of environmental change including climate, sea level rise, and water quality. Frequent examples of key methods and major case studies are also included to help the reader extend the basic theories for application in their own system. Some of the major topics discussed are: Flooded soil and sediment characteristics Aerobic-anaerobic interfaces Redox chemistry in flooded soil and sediment systems Anaerobic microbial metabolism Plant adaptations to reducing conditions Regulators of organic matter decomposition and accretion Major nutrient sources and sinks Greenhouse gas production and emission Elemental flux processes Remediation of contaminated soils and sediments Coupled C-N-P-S processes Consequences of environmental change in wetlands# The book provides the foundation for a basic understanding of key biogeochemical processes and its applications to solve real world problems. It is detailed, but also assists the reader with box inserts, artfully designed diagrams, and summary tables all supported by numerous current references. This book is an excellent resource for senior undergraduates and graduate students studying ecosystem biogeochemistry with a focus in wetlands and aquatic systems.
Download or read book Natural Attenuation of Fuels and Chlorinated Solvents in the Subsurface written by Todd H. Wiedemeier and published by John Wiley & Sons. This book was released on 1999-03-08 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Pollution Abstracts written by and published by . This book was released on 1996 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt: Indexes material from conference proceedings and hard-to-find documents, in addition to journal articles. Over 1,000 journals are indexed and literature published from 1981 to the present is covered. Topics in pollution and its management are extensively covered from the standpoints of atmosphere, emissions, mathematical models, effects on people and animals, and environmental action. Major areas of coverage include: air pollution, marine pollution, freshwater pollution, sewage and wastewater treatment, waste management, land pollution, toxicology and health, noise, and radiation.
Download or read book Wastewater Treatment in Constructed Wetlands with Horizontal Sub Surface Flow written by Jan Vymazal and published by Springer Science & Business Media. This book was released on 2008-07-15 with total page 579 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wetlands have been used for uncontrolled wastewater disposal for centuries. However, the change in attitude towards wetlands during the 1950s and 1960s caused the minimization of the use of natural wetlands for wastewater treatment (at least in developed countries). Constructed wetlands have been used for wastewater treatment for about forty years. Constructed wetland treatment systems are engineered systems that have been designed and constructed to utilize the natural processes for removal of pollutants. They are designed to take advantage of many of the same processes that occur in natural wetlands, but do so within a more controlled environment. The aim of this book is to summarize the knowledge on horizontal s- surface flow constructed wetlands (HF CWs) and objectively evaluate their treatment efficiency under various conditions. The information on this type of wastewater treatment technology is scattered in many publications but a comprehensive summary based on world-wide experience has been lacking. The book provides an extensive overview of this treatment technology around the world, including examples from more than 50 countries and examples of various types of wastewater treated in HF CWs.
Download or read book Biochar for Environmental Management written by Dr. Johannes Lehmann and published by Earthscan. This book was released on 2009 with total page 449 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Biochar is the carbon-rich product when biomass (such as wood, manure, or crop residues) is heated in a closed container with little or no available air. It can be used to improve agriculture and the environment in several ways, and its stability in soil and superior nutrient-retention properties make it an ideal soil amendment to increase crop yields. In addition to this, biochar sequestration, in combination with sustainable biomass production, can be carbon-negative and therefore used to actively remove carbon dioxide from the atmosphere, with major implications for mitigation of climate change. Biochar production can also be combined with bioenergy production through the use of the gases that are given off in the pyrolysis process.This book is the first to synthesize the expanding research literature on this topic. The book's interdisciplinary approach, which covers engineering, environmental sciences, agricultural sciences, economics and policy, is a vital tool at this stage of biochar technology development. This comprehensive overview of current knowledge will be of interest to advanced students, researchers and professionals in a wide range of disciplines"--Provided by publisher.
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 Nano and Bio Based Technologies for Wastewater Treatment written by Elvis Fosso-Kankeu and published by John Wiley & Sons. This book was released on 2019-05-21 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents recent challenges related to new forms of pollution from industries and discusses adequate state-of-the-art technologies capable to remediate such forms of pollution. Over the past few decades the boom in the industrial sector has contributed to the release in the environment of pollutants that have no regulatory status and which may have significant impact on the health of humans and animals. These pollutants also referred to as "emerging pollutants", are mostly aromatic compounds which derive from excretion of pharmaceutical, industrial effluents and municipal discharge. It is recurrent these days to find water treatment plants which no longer produce water that fits the purpose of domestic consumption based on newly established guidelines. This situation has prompted water authorities and researchers to develop tools for proper prediction and control of the dispersion of pollutants in the environment to ensure that appropriate measures are taken to prevent the occurrence of outbreaks due to sudden load of these pollutants in the water system. The chapters in this book cover a wide range of nano and bio-based techniques that have been designed for the real time detection of emerging contaminants in environmental water sources, geochemical models that are continuously improved for the prediction of inorganic contaminants migration from the mine solid wastes into ground and surface waters. Remediation strategies are also discussed and include effective techniques based on nanotechnology, advanced membrane filtration, oxidative and bio-degradation processes using various types of nanocatalysts, biocatalysts or supporting polymer matrices which are under advanced investigations for their implementation at large scale for the removal of recalcitrant pollutants from polluted water. Nano and Bio-Based Technologies for Wastewater Treatment: Prediction and Control Tools for the Dispersion of Pollutants in the Environment is divided is two sections. The first section covers the occurrence of emerging pollutants in environmental water while the second section covers state-of-the-art research on the removal of emerging pollutants from water using sustainable technologies. A total of 13 chapters addressing various topics related to the two sections are essentially based on recent developments in the respective field which could have a significant impact on the enhancement of the performance of wastewater treatment plants around the world, and especially in developing countries where access to clean and safe water remains a daily challenge.
Download or read book Lake Kinneret written by Tamar Zohary and published by Springer. This book was released on 2014-09-29 with total page 674 pages. Available in PDF, EPUB and Kindle. Book excerpt: This condensed volume summarizes updated knowledge on the warm-monomictic subtropical Lake Kinneret, including its geophysical setting, the dynamics of physical, chemical and biological processes and the major natural and anthropogenic factors that affect this unique aquatic ecosystem. This work expands on a previous monograph on Lake Kinneret published in 1978 and capitalizes on the outcome of more than 40 years of research and monitoring activities. These were intensively integrated with lake management aimed at sustainable use for supply of drinking water, tourism, recreation and fishery. The book chapters are aimed at the limnological community, aquatic ecologists, managers of aquatic ecosystems and other professionals. It presents the geographic and geological setting, the meteorology and hydrology of the region, continues with various aspects of the pelagic and the littoral systems. Finally, the last section of the book addresses lake management, demonstrating how the accumulated knowledge was applied in order to manage this important source of freshwater. The section on the pelagic system comprises the heart of the book, addressing the major physical processes, external and internal loading, the pelagic communities (from bacteria to fish), physiological processes and the major biogeochemical cycles in the lake.
