13 research outputs found
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In situ, field scale evaluation of surfactant enhanced DNAPL recovery using a single-well, push-pull test. 1998 annual progress report
'The overall goal of this project is to develop the single-well, push-pull test method as a new site characterization and feasibility assessment tool for studying the fundamental fate and transport behavior of injected surfactants and their ability to solubilize and mobilize dense nonaqueous phase liquids (DNAPLs) in the subsurface. The specific objectives are: (1) to develop a modified push-pull test for use in identifying and quantifying the effects of sorption, precipitation, and biodegradation on the fate and transport of injected surfactants, (2) to use the developed test method to quantify the effects of these processes on the ability of injected surfactants to solubilize and mobilize residual phase trichloroethylene, and (3) to demonstrate the utility of the developed test method for performing site characterization and feasibility studies for surfactant enhanced DNAPL recovery systems. This report summarizes work as of June 1, 1998 (after 20 months of a 36-month project); laboratory and field work as been successfully completed for all three objectives.
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In situ, field scale evaluation of surfactant enhanced DNAPL recovery using a single-well, push-pull test. 1997 annual progress report
'Surfactant enhanced DNAPL recovery involves the use of injected surfactants to increase the solubility and/or mobility of DNAPL in the subsurface to reduce the time and cost required for site remediation. The successful design of a surfactant enhanced DNAPL recovery system requires a quantitative understanding of the competing processes of DNAPL solubilization and mobilization, and sorption, precipitation, and microbial degradation of injected surfactant components. An innovative new site-characterization technology, the single-well, push-pull test method, is currently under development at Oregon State University and has been successfully used in the field to determine a wide range of aquifer physical, chemical, and biological characteristics. A push-pull test consists of the controlled injection of a prepared test solution into a single monitoring well followed by the extraction of the test solution/groundwater mixture from the same well. The type, combination, and concentration of injected solutes is selected to investigate specific aquifer characteristics. The overall goal of this project is to further develop the single-well, push-pull test method as a new site characterization and feasibility assessment tool for studying the fundamental fate and transport behavior of injected surfactants and their ability to solubilize and mobilize DNAPLs in the subsurface. The specific objectives are: (1) to develop a modified push-pull test for use in identifying and quantifying the effects of sorption, precipitation, and biodegradation on the fate and transport of injected surfactants, (2) to use the developed test method to quantify the effects of these processes on the ability of injected surfactants to solubilize and mobilize residual phase trichloroethylene, and (3) to demonstrate the utility of the developed test method for performing site characterization and feasibility studies for surfactant enhanced DNAPL recovery systems.
Microbial nitrate respiration of lactate at in situ conditions in ground water from a granitic aquifer situated 450 m underground
There is widespread interest in developing methods to investigate in situ microbial activity in subsurface environments. Novel experiments based on single borehole push–pull methods were conducted to measure in situ microbial activity at the \uc4sp\uf6 Hard Rock Laboratory (HRL). Microbial nitrate reduction and lactate consumption were measured at in situ conditions at a depth of 450 m in the HRL tunnel. A circulation system was used to circulate ground water from the aquifer through pressure-maintaining flow cells containing coupons for biofilm growth. The system allows microbial investigations at in situ pressure, temperature and chemistry. Four experiments were conducted in which a combination of a conservative tracer, nitrate and lactate was injected into the circulation system. Rate of nitrate utilization was 5 \ub5m h-1 without lactate and 13 \ub5m h-1 with lactate. Lactate consumption increased from 30 to 50 \ub5m h-1 with the addition of an exogenous electron acceptor (nitrate). Attached and unattached cells were enumerated using epifluorescence microscopy to calculate cell-specific rates of activity. The biofilm had an average cell density of 1
7 106 cells cm-2 and there was an average of 6
7 105 unattached cells mL-1 in circulation. Cell-specific rates of lactate consumption were higher than previously reported using radiotracer methods in similar environments. The differences highlight the importance of conducting microbial investigations at in situ conditions. The results demonstrate that an indigenous community of microbes survives at a depth of 450 m in the Fennoscandian shield aquifer with the potential to oxidize simple organic molecules such as lactate
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Physical and hydrologic properties of rock outcrop samples at Yucca Mountain, Nevada
Studies are underway at Yucca Mountain to characterize physical and hydrologic conditions for a potential high-level radioactive waste repository. Site characterization requires the development of three- dimensional models describing hydrogeologic units in terms of inputs for numerical models. It is also important to understand the spatial distribution of these properties, vertical and horizontally, in order to estimate values at unmeasured points. Deterministic processes of volcanism caused the initial formation of the rock units, and it is useful to be able to correlate rock properties with the more qualitative descriptions of rock lithology that occur on a larger scale. Preliminary data were collected to develop methods and evaluate spatial relations to determine sampling frequency. In addition, a data base was developed to provide some of the parameters needed for preliminary flow-modeling exercises. Surface transects of rock outcrops facilitated rapid collection of closely spaced samples of all units exposed at and around Yucca Mountain. This report presents the data collected, descriptive statistics for various units, preliminary hydrogeologic units, and analyses of porosity compared with flow properties
Spatially-distinct redox conditions and degradation rates following field-scale bioaugmentation for RDX-contaminated groundwater remediation
Simplified Method of "Push-Pull" Test Data Analysis for Determining In Situ Reaction Rate Coefficients
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Techniques for assessing the performance of in situ bioreduction and immobilization of metals and radionuclides in contaminated subsurface environments
Department of Energy (DOE) facilities within the weapons complex face a daunting challenge of remediating huge below inventories of legacy radioactive and toxic metal waste. More often than not, the scope of the problem is massive, particularly in the high recharge, humid regions east of the Mississippi river, where the off-site migration of contaminants continues to plague soil water, groundwater, and surface water sources. As of 2002, contaminated sites are closing rapidly and many remediation strategies have chosen to leave contaminants in-place. In situ barriers, surface caps, and bioremediation are often the remedial strategies of chose. By choosing to leave contaminants in-place, we must accept the fact that the contaminants will continue to interact with subsurface and surface media. Contaminant interactions with the geosphere are complex and investigating long term changes and interactive processes is imperative to verifying risks. We must be able to understand the consequences of our action or inaction. The focus of this manuscript is to describe recent technical developments for assessing the performance of in situ bioremediation and immobilization of subsurface metals and radionuclides. Research within DOE's NABIR and EMSP programs has been investigating the possibility of using subsurface microorganisms to convert redox sensitive toxic metals and radionuclides (e.g. Cr, U, Tc, Co) into a less soluble, less mobile forms. Much of the research is motivated by the likelihood that subsurface metal-reducing bacteria can be stimulated to effectively alter the redox state of metals and radionuclides so that they are immobilized in situ for long time periods. The approach is difficult, however, since subsurface media and waste constituents are complex with competing electron acceptors and hydrogeological conditions making biostimulation a challenge. Performance assessment of in situ biostimulation strategies is also difficult and typically requires detailed monitoring of coupled hydrological, geochemical/geophysical, and microbial processes. In the following manuscript we will (1) discuss contaminant fate and transport problems in humid regimes, (2) efforts to immobilize metals and radionuclides in situ via bioremediation, and (3) state-of-the-art techniques for assessing the performance of in situ bioreduction and immobilization of metals and radionuclides. These included (a) in situ solution and solid phase monitoring, (b) in situ and laboratory microbial community analysis, (c) noninvasive geophysical methods, and (d) solid phase speciation via high resolution spectroscopy