Author :
Publisher :
Page : 31 pages
File Size : 42,20 MB
Release : 1998
Category :
ISBN :
This effort was conducted to determine the flow rate of the groundwater at NAS Fallon, Nevada, in support of research advancing in situ anaerobic dechlorination of chlorinated solvents. The study was conducted at an existing array of groundwater wells in an area contaminated by chlorinated solvents. Fresh water was used as the tracer due to the heavy loading of chlorides in the area. The tracer tests were inconclusive regarding groundwater transport in the treatment lanes.
Author : Victor Magar
Publisher :
Page : 408 pages
File Size : 45,6 MB
Release : 2001
Category : Science
ISBN :
The symposium included 600 presentations in 50 sessions on bioremediation and supporting technologies used for a wide range of contaminants already in, or poised to invade, soil, groundwater, and sediment. Three hundred and fifty-two papers were selected and organized into ten volumes. Volume seven's articles examine the use of enhanced anaerobic biotransformation processes for treatment of chlorinated solvents in soil and groundwater. Electron donors used to stimulate reductive dechlorination processes in lab- and field-scale demonstrations are also presented. Articles average eight pages, and contain abstracts and references. Annotation copyrighted by Book News Inc., Portland, OR.
Author : Sebastien Roupen Kaskassian
Publisher :
Page : 394 pages
File Size : 25,81 MB
Release : 2002
Category :
ISBN :
Bioventing under anaerobic reductive conditions has been presented as a potential bioremediation technology for dealing with highly chlorinated compounds present in the capillary fringe of a contaminated soil. Anaerobic reductive bioventing is similar to aerobic bioventing, providing the gas injected is free of oxygen and contains an electron donor, here hydrogen. The concept of bioventing is reported to be cost effective because of the in-situ solution it provides. Tetrachloroethylene (PCE) typically degrades under anaerobic, reductive conditions to Vinyl Chloride (VC), which can then be readily oxidized to environmentally benign products. In this study, enhanced anaerobic degradation of PCE in the unsaturated zone of the soil was simulated in soil microcosms. Four 15 cm high and 8 cm in diameter reactors were filled with a contaminated soil sampled at an Air Force base site. Each reactor allowed for a different set of conditions in components concentration in the gas feed. The work focused on optimizing the injection gas composition, monitoring electron donor delivery and utilization, and evaluating the treatment performance of PCE. Only one microcosm, fed with 0.5 % of hydrogen and 0.5 % of carbon dioxide, showed dechlorination of PCE into Trichloroethylene (TCE) and Cis-Dichloroethylene (Cis-DCE). This microcosm completely consumed hydrogen and produced little methane, thus proving that the feeding conditions favored dechlorinators over methanogenes. PCE sequential dehalogenation did not proceed further than Cis-DCE but the total quantity of intermediates produced accounted for more than 40 % of the PCE removed in that dechlorinating microcosm. In the other microcosms, PCE removal was mainly due to adsorption of PCE onto the soil organic matter. Adding biomass to the microcosm or increasing the gas retention time did not result in significant improvements of the microcosm dechlorinating activity. Pre-existing soil contaminants, mainly hydrocarbons, were not responsible for the lack of dechlorination. Gas feeding concentrations were the only parameters proved to trigger PCE sequential dechlorination since they helped maintaining reducing conditions. This study was useful to assess the potential for dechlorination of highly chlorinated compounds in a specific soil sample and to optimize the feed conditions to be applied when testing anaerobic bioventing in-situ.
Author : DEREK. VEERKAMP
Publisher :
Page : 119 pages
File Size : 15,3 MB
Release : 1999-03-01
Category :
ISBN : 9781423545804
Chlorinated solvents and their daughter products are the most common contaminants of groundwater at industrial and military facilities in the United States. Limitations of conventional technologies have intensified efforts to find alternative methods to remediate contaminated sites to regulatory goals set by CERCLA. Natural attenuation of chlorinated solvents is a promising alternative to traditional pump and treat methods but has not been well understood or widely accepted. This modeling study investigated the ability of TCE to completely degrade under various aquifer conditions and rate order constants. It also examined a case study of a former landfill site at Moody AFB. We found unusually high flow of ground water by advection or dispersion inhibits the complete degradation of TCE. High concentrations of sulfate or nitrate inhibit the creation of methanogenic conditions and therefore inhibit reductive dechlorination of TCE. We also found an electron donor co-contaminant a critical factor for the complete destruction of TCE because it creates anaerobic conditions. The model illustrated a possible explanation for the lack of down gradient contaminants at the landfill site may be the coupling of reductive dechlorination and cometabolism naturally attenuation the contaminants.
Author :
Publisher :
Page : 0 pages
File Size : 46,84 MB
Release : 2002
Category :
ISBN :
Enhanced biological reductive dechlorination (EBRD) shows a great deal of promise for efficiently treating groundwater contaminated with chlorinated solvents, but demonstration sites around the country were reporting mixed results. Because individual demonstrations commonly used dissimilar methods, the limitations of the technology were not clear and its applicability at any given site was unknown. As a result, the Environmental Security Technology Certification Program (ESTOP) invested in the development of a standardized protocol to test the technology's effectiveness at any site. A draft protocol was developed that included microcosm and field-testing and an extensive array of sampling and monitoring. Once developed, the draft protocol was applied at four sites to evaluate its overall effectiveness. Data generated at the four sites was used to refine the protocol by eliminating less valuable components while maintaining a testing methodology that provides scientifically defensible data that would satisfy the regulatory community at a reasonable cost. Microcosm testing was used to evaluate the performance of a suite of electron donors, which included yeast extract, lactate, butyrate, benzoic add, propionic add, and acetic add. The testing examined the rate, onset, and extent of dechlorination as well as donor fermentation pathways. Microcosm testing data revealed an apparently heterogeneous distribution of dechlorinating organisms within Individual sites, and that most electron donors will eventually yield the same dechlorination endpoint, though the onset and rate of dechlorination may differ significantly. The electron donor showing the most rapid and complete dechlorination in microcosm studies (usually butyrate) was used in the four 6-month field demonstrations.
Author : Erica S. Becvar
Publisher :
Page : 10 pages
File Size : 29,14 MB
Release : 1996
Category :
ISBN :
Use of chlorinated solvents has led to extensive soil and groundwater contamination. Current aerobic treatment methods, such as pump-and-treat with carbon sorption or air stripping, are limited and often cost-prohibitive. Researchers have isolated microbial cultures capable of reductively dechlorinating tetrachloroethene (PCE) to ethene (ETH). Field studies have shown reductive dechlorination of chlorinated solvents to be stimulated by the addition of electron donors. Based on these results, this project utilizes indigenous bacteria and added electron donors for degradation of PCE in the field. The approach is designed to achieve a rigorous mass balance on electron donors, electron acceptors, and microbial carbon/energy sources. The effort is aimed at validating reductive dechlorination in a realistic field situation.
Author :
Publisher :
Page : 268 pages
File Size : 50,2 MB
Release : 1993
Category : Groundwater
ISBN :
Author : Robert D. Norris
Publisher : CRC Press
Page : 377 pages
File Size : 21,88 MB
Release : 2017-11-22
Category : Science
ISBN : 1351363441
Written by leading soil and ground-water remediation scientists, Handbook of Bioremediation presents information regarding the processes, application, and limitations of using remediation technologies to restore contaminated soil and ground water. It covers field-tested technologies, site characterization requirements for each remediation technology, and the costs associated with their implementation. In addition to discussions and examples of developed technologies, the book provides insights into technologies ranging from theoretical concepts to limited field-scale investigations. In situ remediation systems, air sparging and bioventing, the use of electron acceptors other than oxygen, natural bioremediation, and the introduction of organisms into the subsurface are among the specific topics covered in this invaluable handbook.
Author : Thomas K.G. Mohr
Publisher : CRC Press
Page : 552 pages
File Size : 12,30 MB
Release : 2016-04-19
Category : Science
ISBN : 0203489373
A ubiquitous, largely overlooked groundwater contaminant, 1,4-dioxane escaped notice by almost everyone until the late 1990s. While some dismissed 1,4-dioxane because it was not regulated, others were concerned and required testing and remediation at sites they oversaw. Drawing years of 1,4-dioxane research into a convenient resource, Environmental
Author :
Publisher :
Page : 152 pages
File Size : 10,32 MB
Release :
Category : Sewage disposal
ISBN :
