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Author: Publisher: ISBN: Category : Languages : en Pages : 68
Book Description
This work explores two innovative technologies for the remediation of chlorinated ethene solvents contaminating groundwater: (1) groundwater circulation wells (GCWs) with downwell zero-valent metal reductive dechlorination reactors, and (2) constructed vertical subsurface flow wetlands. Both the natural dechlorination in wetland sediments, and the engineered dechlorination in a well using zero-valent metals have major implications for the treatment of Air Force pollutants, with the potential to save millions of dollars annually in long term remediation at hundreds of sites across the Air Force. Complementary modeling and column studies examined the potential for controlling and treating groundwater contamination using groundwater circulation wells (GCWs) with downwell zero-valent metal reductive dechlorination reactors. The construction of the field scale wetland research facility includes two complete wetland cells (140 x 60 feet each), fully contained. Chemical analysis of samples drawn from the various depths of wetland sediment suggests a very heterogeneous development of microbial activity relevant to reductive dechlorination over the course of one year of operation. Concentration contours of PCE, TCE, and nitrate suggest that reductive dechlorination is taking place when more readily reducible electron acceptors (like nitrate) are depleted. PCE is reduced ten-fold from inflow to outflow, even with significant short-circuiting of flow from the bottom sediments to the outflow. Data suggests 100-fold treatment is possible.
Author: Publisher: ISBN: Category : Languages : en Pages : 68
Book Description
This work explores two innovative technologies for the remediation of chlorinated ethene solvents contaminating groundwater: (1) groundwater circulation wells (GCWs) with downwell zero-valent metal reductive dechlorination reactors, and (2) constructed vertical subsurface flow wetlands. Both the natural dechlorination in wetland sediments, and the engineered dechlorination in a well using zero-valent metals have major implications for the treatment of Air Force pollutants, with the potential to save millions of dollars annually in long term remediation at hundreds of sites across the Air Force. Complementary modeling and column studies examined the potential for controlling and treating groundwater contamination using groundwater circulation wells (GCWs) with downwell zero-valent metal reductive dechlorination reactors. The construction of the field scale wetland research facility includes two complete wetland cells (140 x 60 feet each), fully contained. Chemical analysis of samples drawn from the various depths of wetland sediment suggests a very heterogeneous development of microbial activity relevant to reductive dechlorination over the course of one year of operation. Concentration contours of PCE, TCE, and nitrate suggest that reductive dechlorination is taking place when more readily reducible electron acceptors (like nitrate) are depleted. PCE is reduced ten-fold from inflow to outflow, even with significant short-circuiting of flow from the bottom sediments to the outflow. Data suggests 100-fold treatment is possible.
Author: Michael L. Shelley Publisher: ISBN: 9781423549208 Category : Languages : en Pages : 68
Book Description
This work explores two innovative technologies for the remediation of chlorinated ethene solvents contaminating groundwater: (1) groundwater circulation wells (GCWs) with downwell zero-valent metal reductive dechlorination reactors, and (2) constructed vertical subsurface flow wetlands. Both the natural dechlorination in wetland sediments, and the engineered dechlorination in a well using zero-valent metals have major implications for the treatment of Air Force pollutants, with the potential to save millions of dollars annually in long term remediation at hundreds of sites across the Air Force. Complementary modeling and column studies examined the potential for controlling and treating groundwater contamination using groundwater circulation wells (GCWs) with downwell zero-valent metal reductive dechlorination reactors. The construction of the field scale wetland research facility includes two complete wetland cells (140 x 60 feet each), fully contained. Chemical analysis of samples drawn from the various depths of wetland sediment suggests a very heterogeneous development of microbial activity relevant to reductive dechlorination over the course of one year of operation. Concentration contours of PCE, TCE, and nitrate suggest that reductive dechlorination is taking place when more readily reducible electron acceptors (like nitrate) are depleted. PCE is reduced ten-fold from inflow to outflow, even with significant short- circuiting of flow from the bottom sediments to the outflow. Data suggests 100- fold treatment is possible.
Author: Annamarie F. Therrien Publisher: ISBN: Category : Biogeochemistry Languages : en Pages : 77
Book Description
Constructed wetlands are an efficient and cost effective means for chlorinated aliphatic hydrocarbon remediation, and will therefore continue to gain momentum as an accepted treatment by the US EPA (U.S. EPA, 1995; Amarante, 2000; Lien, 2001; WETPOL, 2009). The treatment options for chlorinated aliphatic hydrocarbons (CAHs), including wetlands, capitalize on aerobic/anaerobic interfaces in which bacterially mediated reduction-oxidation reactions degrade pollutants (Li, 1997; Bradley, 1998; Lorah and Voytek, 2004; Amon, 2007; Imfeld, 2008). In August 2000, researchers at Wright State University (WSU) combined efforts with the United States Air Force Institute of Technology (AFIT) to construct a pilot-scale upward-flow treatment wetland on Wright-Patterson Air Force Base with parameters that could remediate perchloroethene (PCE) found in a nearby aquifer (Amon et al., 2007). Eleven studies of short duration have since documented the existance of anerobic and aerobic interfaces by measuring various terminal electron acceptors (sulfate, nitrate, methane, iron) and numerous other parameters. The studies evaluated PCE degradation rates, geochemical profiles, hydraulic conductivity and chlorinated ethene concentrations. (Bugg, 2002; Opperman, 2002; Clemmer, 2003; Kovacic, 2003; BonDurant, 2004; Sobolewski, 2004; Lach, 2004; Schlater, 2006; Mohamud, 2007; Waldron, 2007, Corbin, 2008). The present research has attempted to compile, organize, and re-analyze the data collected by AFIT and WSU researchers during 2001-2006. Data was analyzed using Jenks Optimization (goodness of variance fit) method to identify and remove outliers. Meta analysis of CAH concentrations and redox parameters was performed by creating data subsets of individual piezometer and depths, influent to effluent transect data and ArcGIS maps. The present analysis concludes that a fully functioning wetland with strongly reducing geochemical conditions and flow patterns capable of PCE destruction developed at this site within 18-24 months. Dechlorination of CAHs was observed at every depth and at 63 of 66 sampled locations despite significant differences in hydraulic conductivity and available electron acceptors. Rate of dechlorination varied with depth and hydraulic conductivity. Strongest reducing conditions developed at Middle layer (0.69 m) and demonstrated the highest rates of PCE dechlorination. Maximum degradation of vinyl chloride (VC) and 1,2 dichloroethenes (DCE) occurred in Upper layer (0.23m) where conditions may have been more oxidizing. The size of the pilot-scale treatment wetland generally allowed adequate residence time despite short circuits. However, two exceptions were observed: (i) near the effluent, increases in head pressure, due to laminar flow bring higher concentrations from gravel layer to surface quickly, and (ii) CAHs re transmitted quickly along the wetland’s outer boundary, possibly along the soil-PVC liner. Despite these effects, with the exception of one researcher’s results, the effluent concentrations for all CAH species remained below their respective MCLs after January 2003. The study suggests that the construction of wetland for the treatment PCE-contaminated groundwater include establishing and employing a grid monitoring system to ascertain geographical boundaries for problem areas, frequent sampling in initial 24 months and establishing controls on influent pumping system to adjust residence time as needed.
Author: Michael R. Staples Publisher: ISBN: 9781423511700 Category : Chlorohydrocarbons Languages : en Pages : 108
Book Description
Past research has shown that there is a rising public concern with environmental issues in the Republic of Korea (ROK). As Korean government and public interest in the environment grow, there is likely to be increased pressure to remediate environmental contamination at United States Department of Defense (DoD) installations in Korea. Impacting DoD's ability to remediate contaminated sites overseas is the fact that limited environmental funds must compete with high priority mission requirements. Thus, particularly at overseas bases, there is an urgent need for inexpensive and effective groundwater remediation technologies. Horizontal Flow Treatment Well (HFTW) systems have been demonstrated in the U.S. to be an effective technology for managing groundwater contamination. However, the problem of finding a technology that is appropriate for use in Korea is particularly challenging due to the fractured aquifer systems that are ubiquitous throughout the Korean peninsula. The model analyses conducted in this study found that HFTWs have the potential to be a cost effective alternative to conventional technologies for contaminant management in the fractured media found in Korea. This study focused on the containment of groundwater contaminated with chlorinated solvents in the fractured rock aquifers that are commonly encountered at DoD installations in the ROK. Horizontal Flow Treatment Wells were analyzed as a potentially cheaper, safer, and more effective technology for the containment of chlorinated solvent contaminated groundwater. In this study, an HFTW numerical model that was developed for porous media was applied to the fractured systems encountered in the ROK. It was concluded that at the scale of interest, use of a porous media model was appropriate. Both hydrogeologic and design parameters were varied to determine their effects on the technology performance.
Author: Publisher: ISBN: Category : Languages : en Pages : 114
Book Description
The overall goal of this portion of the project was to package one or more unit processes, as modular components in vertical and/or horizontal recirculation wells, for treatment of volatile organic compounds (VOCs) [e.g., trichloroethene (TCE)] and radionuclides [e.g., technetium (Tc)99] in groundwater. The project was conceived, in part, because the coexistence of chlorinated hydrocarbons and radionuclides has been identified as the predominant combination of groundwater contamination in the US Department of Energy (DOE) complex. Thus, a major component of the project was the development of modules that provide simultaneous treatment of hydrocarbons and radionuclides. The project objectives included: (1) evaluation of horizontal wells for inducing groundwater recirculation, (2) development of below-ground treatment modules for simultaneous removal of VOCs and radionuclides, and (3) demonstration of a coupled system (treatment module with recirculation well) at a DOE field site where both VOCs and radionuclides are present in the groundwater. This report is limited to the innovative treatment aspects of the program. A report on pilot testing of the horizontal recirculation system was the first report of the series (Muck et al. 1996). A comprehensive report that focuses on the engineering, cost and hydrodynamic aspects of the project has also been prepared (Korte et al. 1997a).
Author: Derek R. Ferland Publisher: ISBN: 9781423539056 Category : Groundwater Languages : en Pages : 94
Book Description
The limitations of conventional containment technologies for groundwater contaminated with chlorinated solvents have motivated development of innovative technologies to achieve national groundwater remediation objectives. One inn9vative technology that is currently under development involves metal reductants or catalysts to chemically destroy the dissolved chlorinated solvent. Models are important tools that can be used to help transition this technology to the field. Model studies can be used to gain understanding about the technology, help determine when the prospective technology might work for a given site, and design full-scale field applications.
Author: Jeffrey C. Parr Publisher: ISBN: 9781423511878 Category : Groundwater Languages : en Pages : 155
Book Description
Groundwater contamination by perchlorate has recently been recognized as a significant environmental problem across the United States, and especially at Department of Defense facilities. In this study, a model is used to evaluate the potential of a innovative in situ bioremediation technology using Horizontal Flow Treatment Wells (HFTWs) to manage perchlorate-contaminated groundwater. The technology uses HFTWs to mix an electron donor into perchlorate-contaminated groundwater in order to promote reduction of the perchlorate by indigenous microorganisms in bioactive zones within the aquifer, as well as recirculate the contaminated water between treatment well pairs to achieve multiple passes of contaminated water through the bioactive zones. The model used in this study couples a three-dimensional fate and transport model, which simulates advective/ dispersive transport of solutes induced by regional groundwater flow and operation of the HFTW's, with a biodegradation model that simulates perchlorate reduction, as well as reduction of competing electron acceptors in the groundwater, by indigenous microorganisms. The model was applied to an example site to demonstrate how in situ perchlorate treatment might be implemented. A sensitivity analysis using the model is also conducted to evaluate which engineered and environmental parameters most affect technology performance. Model simulation results demonstrate that this technology may be effective in managing perchlorate-contaminated groundwater. The recirculation induced by the HFTW system results in increased treatment efficiency, as compared to treatment that would be achieved by a single pass of contaminated water through the bioactive zones. It was observed that the model was very sensitive to several kinetic parameters, indicating that a fruitful area for future research would be to study how these important parameters can be accurately quantified for given geochemical and microbiological conditions.
Author: Nathan D. Clemmer Publisher: ISBN: 9781423503132 Category : Constructed wetlands Languages : en Pages : 159
Book Description
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.
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Author: Michael L. Shelley
Author: Annamarie F. Therrien
Author: James M. Waldron
Author: Michael R. Staples
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Author: Derek R. Ferland
Author: Jeffrey C. Parr
Author: Nathan D. Clemmer