In order to preserve groundwater as a viable source of drinking water, remedial measures must be applied where appropriate. The application of the various remedial technologies is site and contaminant dependent. Differing geology, subsurface soil, groundwater geochemistry, type of contaminant present, cost and even accessibility to the site are all considerations when selecting an appropriate remedial system. At many sites oxygen is a limiting factor for aerobic degradation of many organic compounds like methyl tert butyl ether (MTBE) and hydrocarbons found in diesel and fuel oil, etc. (Nyer et al, 2002). Mechanisms limiting the success of getting the oxygen out of the passive release well include: · Slow chemical diffusion of oxygen in water; · Limited cross section of the groundwater flowing into the well and advecting oxygenated water back into the aquifer; and · Generally weak transverse dispersion, both horizontal and vertical, during subsequent advection of the oxygenated water in the porous media. These issues must be recognized even in the design of a passive release well remediation system. For example, a typical remedial objective is to deliver dissolved oxygen across the width and vertical extent of a contaminant zone in an aquifer. The width of the oxygen plume around the injection well defines how many oxygen-release wells are required to create a curtain of oxygen. Cost-effective design dictates fewer wells, while effective coverage may dictate more wells placed closer together. Thus, understanding the transverse width over which significant oxygen is passively released to the aquifer (the “radius of influence”) is a critical design parameter and the focus of this thesis. Due to the difficulty in getting a passively released dissolved oxygen plume to transversely encompass the total width of a contaminant plume, other more efficient means of introducing oxygen into the subsurface are required. Injecting amended water directly into a release well would increase the transverse distance in which dissolved oxygen would spread. A series of experiments were conducted at CFB Borden to assess the efficacy of an oxygen releasing technology called the iSOC™. The experiments were all conducted in the same manner, by connecting a tank of oxygen to the iSOC™ unit, which then was placed in a release well and allowed to run in experiment 1 for 103 days, experiment 2 for 132 days and experiment 3 for 29 days. iv Dissolved oxygen concentrations were measured at varying time intervals throughout each experiment using an Orion dissolved oxygen probe. Results of each of the three experiments were very similar in that dissolved oxygen was only detected in a very narrow plume (10 cm to 25 cm in width) within 1 m of the release well. The presence of BTEX, BOD and COD within the groundwater and soil at the site were investigated to assess if presented a significant enough sink for the oxygen and thereby limiting the transverse growth of the dissolved oxygen plume. Groundwater results indicated that while dissolved oxygen was utilized for BTEX degradation and to overcome the natural oxygen demand (both BOD and COD) at the site, the amount of oxygen released into the aquifer would have satisfied both of these processes. The COD of the soil at the site presented a higher oxygen demand than the groundwater and presented a greater limiting factor to the transverse growth of the oxygen plume. By releasing oxygen passively with the iSOC™ only a small transverse portion of the Borden aquifer was likely influenced. This limitation has been noted in general for passive release technologies (Wilson & Mackay, 1995). While the iSOCÔ technology develops very high oxygen levels in the groundwater in the release well, it does not overcome the hydrogeological constraint of limited transverse dispersion. Thus, a high oxygen concentration is delivered to a very narrow segment of the aquifer. Overall, transverse dispersion has a minimal impact on a passively release oxygen plume, particularly in close proximity to the release well, but once the plume has migrated a distance away from the release well the effect of transverse dispersion increases. The oxygen demand of an aquifer can also limit the effect of transverse and longitudinal dispersion. If a site has a high chemical or biological oxygen demand the released gas will be consumed before dispersion can have an effect on the plume. By injecting nutrient rich water into a release well the water will forcibly overcome any influence transverse dispersion will have in and around a release well, thereby relying on longitudinal dispersion to create a larger area for contaminant degradation to occur.

In order to preserve groundwater as a viable source of drinking water, remedial measures must be applied where appropriate. The application of the various remedial technologies is site and contaminant dependent. Differing geology, subsurface soil, groundwater geochemistry, type of contaminant present, cost and even accessibility to the site are all considerations when selecting an appropriate remedial system. At many sites oxygen is a limiting factor for aerobic degradation of many organic compounds like methyl tert butyl ether (MTBE) and hydrocarbons found in diesel and fuel oil, etc. (Nyer et al, 2002). Mechanisms limiting the success of getting the oxygen out of the passive release well include: · Slow chemical diffusion of oxygen in water; · Limited cross section of the groundwater flowing into the well and advecting oxygenated water back into the aquifer; and · Generally weak transverse dispersion, both horizontal and vertical, during subsequent advection of the oxygenated water in the porous media. These issues must be recognized even in the design of a passive release well remediation system. For example, a typical remedial objective is to deliver dissolved oxygen across the width and vertical extent of a contaminant zone in an aquifer. The width of the oxygen plume around the injection well defines how many oxygen-release wells are required to create a curtain of oxygen. Cost-effective design dictates fewer wells, while effective coverage may dictate more wells placed closer together. Thus, understanding the transverse width over which significant oxygen is passively released to the aquifer (the “radius of influence”) is a critical design parameter and the focus of this thesis. Due to the difficulty in getting a passively released dissolved oxygen plume to transversely encompass the total width of a contaminant plume, other more efficient means of introducing oxygen into the subsurface are required. Injecting amended water directly into a release well would increase the transverse distance in which dissolved oxygen would spread. A series of experiments were conducted at CFB Borden to assess the efficacy of an oxygen releasing technology called the iSOC™. The experiments were all conducted in the same manner, by connecting a tank of oxygen to the iSOC™ unit, which then was placed in a release well and allowed to run in experiment 1 for 103 days, experiment 2 for 132 days and experiment 3 for 29 days. iv Dissolved oxygen concentrations were measured at varying time intervals throughout each experiment using an Orion dissolved oxygen probe. Results of each of the three experiments were very similar in that dissolved oxygen was only detected in a very narrow plume (10 cm to 25 cm in width) within 1 m of the release well. The presence of BTEX, BOD and COD within the groundwater and soil at the site were investigated to assess if presented a significant enough sink for the oxygen and thereby limiting the transverse growth of the dissolved oxygen plume. Groundwater results indicated that while dissolved oxygen was utilized for BTEX degradation and to overcome the natural oxygen demand (both BOD and COD) at the site, the amount of oxygen released into the aquifer would have satisfied both of these processes. The COD of the soil at the site presented a higher oxygen demand than the groundwater and presented a greater limiting factor to the transverse growth of the oxygen plume. By releasing oxygen passively with the iSOC™ only a small transverse portion of the Borden aquifer was likely influenced. This limitation has been noted in general for passive release technologies (Wilson & Mackay, 1995). While the iSOCÔ technology develops very high oxygen levels in the groundwater in the release well, it does not overcome the hydrogeological constraint of limited transverse dispersion. Thus, a high oxygen concentration is delivered to a very narrow segment of the aquifer. Overall, transverse dispersion has a minimal impact on a passively release oxygen plume, particularly in close proximity to the release well, but once the plume has migrated a distance away from the release well the effect of transverse dispersion increases. The oxygen demand of an aquifer can also limit the effect of transverse and longitudinal dispersion. If a site has a high chemical or biological oxygen demand the released gas will be consumed before dispersion can have an effect on the plume. By injecting nutrient rich water into a release well the water will forcibly overcome any influence transverse dispersion will have in and around a release well, thereby relying on longitudinal dispersion to create a larger area for contaminant degradation to occur.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

Zero valent iron (ZVI) has demonstrated its reactivity and effectiveness for in-situ groundwater and soil remediation. The potential of the high reducing activity of nanoscale ZVI (nZVI) for environmental decontamination has attracted more attentions in recent years, as nZVI may be injected with water to the pollution sites for in-situ remediation. However, rapid oxidation and instant agglomeration of nZVI make it difficult for large-scale engineering application. Effort has been made to improve the stability and mobility of nZVI for effective in-situ remediation. In the present study, a novel Ca-based surface coating method has been developed for protection of nZVI and enhancement of its transport in environmental applications. A simple thermal deposition method was employed to coat a Ca-based layer on the surface of micro- or nano- ZVI particles in water or methanol environment. According to microscopic observations, Ca(OH)2 nano-layer was formed on the ZVI surface. A clear core-shell structure was observed for the coated nZVI/Ca(OH)2 particles based on the TEM observations. The Ca(OH)2 coating layer had a thickness about one fifth of the nZVI diameter and the Ca to Fe ratio was below 0.2. With the Ca(OH)2 shell, nZVI particles can be effectively protected against corrosion according to the standard natural spray corrosion tests. Thus, the Ca(OH)2 coating layer is able to greatly improve the stability of nZVI during storage, transportation and application. In addition, based on the result of the dissolution tests, the Ca(OH)2 shell could be readily dissolved in water with a low Ca content or a low ionic strength. After dissolution of the Ca(OH)2 shell, the reactivity of nZVI was found to be at the similar level as bare nZVI, which could remove Cr(VI) from water by more than 90% in about 20 min. The pseudo-first order rate constants for Cr(VI) reduction by bare nZVI and nZVI/ Ca(OH)2 after shell dissolution were 0.064 and 0.072 min-1, respectively. Moreover, the Ca(OH)2 coating shell would not only function as a protection layer but also improve the mobility of nZVI particles in in-situ applications. The aggregation and sedimentation of nZVI/Ca(OH)2 particles became considerably slower compared to bare nZVI without the coating. Clean-bed water filtration tests were conducted with sand and glass columns to evaluate the mobility and transport of nZVI in porous media. The results show that bare nZVI in the particle suspension deposited mostly at the top of the filters with little penetration. In comparison, the nZVI/Ca(OH)2 particles were able to penetrate through the filter media during the filtration process, and the dark iron particles could fill up the entire filter columns. The penetration rate increased from nearly 0 m/hr for bare nZVI to 0.43 m/hr for nZVI/Ca(OH)2 through the filter media. The Ca-based coating materials are known as of low cost and environmentally friendly. Thus, the new coating method developed in this study provides a cost-effective means for both the protection of nZVI and improvement of its transport and delivery in porous media for environmental decontamination. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 49-54).

Thesis (M.S.)--OGI School of Science & Engineering at OHSU, 2004. / Includes bibliographical references (leaves 59-65).

Thesis (Ph. D.)--Washington State University, August 2009. / Title from PDF title page (viewed on Sept. 9, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references.

Thesis (M.S. in environmental engineering)--Washington State University, May 2006. / Includes bibliographical references (p. 12-13).

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Polychlorinated Biphenyls (PCBs) are a group of 209 congeners that are regulated under the Toxic Substance Control Act. They enter the environment as a result of industrial processes and can travel long distances. PCBs are environmentally persistent and bioaccumulate in animal populations. Painted surfaces are a common point source for PCBs and there are few options for remediating structures painted with PCB-contaminated paint. Removal of the paint can often spread contamination and disposing or burning of large structures is expensive. Experiments employing reductive dehalogenation through the use of a bimetal have shown that PCBs can be degraded in mild laboratory conditions. This dissertation describes the process of developing an application media that will enable the degradation process reported in literature to be used in a field application. An environmentally friendly reaction environment had to be established as well as the treatment‟s operating parameters. In collaboration with researchers at the National Aeronautics Space Administration (NASA), Kenney Space Center (KSC), researchers at the University of Central Florida (UCF) developed a bimetallic treatment system (BTS) that can remove and degrade PCBs from painted surfaces. The technology was evaluated during a field demonstration at a decommissioned Department of Defense facility in Badger, Wisconsin. Samples of treatment paste, paint and concrete were analyzed over a three week period. The PCB concentrations in both the paint and concrete dropped dramatically as a result of the demonstration, and in many instances, were lowered below the EPA action limit of 50ppm. In the laboratory, additional studies were conducted to further the degradation in the treatment system. Through this process, a novel degradation system was established containing zero-valent magnesium and ethanol acidified with acetic acid. The use of acidified ethanol permitted the degradation to occur with iv just magnesium powder and eliminated the use of a bimetal and therefore palladium. The technology was incorporated into a modified treatment system termed Activate Metal Treatment System (AMTS). The AMTS was used on samples from a second field site where paint chips from an manufacturing warehouse in New York state were degraded to thousands of mg/kg (ppm) below their starting concentrations.