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A proposed strategy for the remediation of uranium (U) contaminated sites is based on immobilizing U by reducing the oxidized soluble U, U(VI), to form a reduced insoluble end product, U(IV). Due to the use of nitric acid in the processing of nuclear fuels, nitrate is often a co-contaminant found in many of the environments contaminated with uranium. Recent studies indicate that nitrate inhibits U(VI) reduction in sediment slurries. However, the mechanism responsible for the apparent inhibition of U(VI) reduction is unknown, i.e. preferential utilization of nitrate as an electron acceptor, direct biological oxidation of U(IV) coupled to nitrate reduction, and/or abiotic oxidation by intermediates of nitrate reduction. Recent studies indicates that direct biological oxidation of U(IV) coupled to nitrate reduction may exist in situ, however, to date no organisms have been identified that can grow by this metabolism. In an effort to evaluate the potential for nitrate-dependent bio-oxidation of U(IV) in anaerobic sedimentary environments, we have initiated the enumeration of nitrate-dependent U(IV) oxidizing bacteria. Sediments, soils, and groundwater from uranium (U) contaminated sites, including subsurface sediments from the NABIR Field Research Center (FRC), as well as uncontaminated sites, including subsurface sediments from the NABIR FRC and Longhorn Army Ammunition Plant, Texas, lake sediments, and agricultural field soil, sites served as the inoculum source. Enumeration of the nitrate-dependent U(IV) oxidizing microbial population in sedimentary environments by most probable number technique have revealed sedimentary microbial populations ranging from 9.3 x 101 - 2.4 x 103 cells (g sediment)-1 in both contaminated and uncontaminated sites. Interestingly uncontaminated subsurface sediments (NABIR FRC Background core FB618 and Longhorn Texas Core BH2-18) both harbored the most numerous nitrate-dependent U(IV) oxidizing population 2.4 x 103 cells (g sediment)-1. The nitrate-dependent U(IV) oxidizing microbial population in groundwaters is less numerous ranging from 0 cells mL-1 (Well FW300, Uncontaminated Background NABIR FRC) to 4.3 x 102 cells mL-1 (Well TPB16, Contaminated Area 2 NABIR FRC). The presence of nitrate-dependent U(IV) oxidizing bacteria supports our hypothesis that bacteria capable of anaerobic U(IV) oxidation are ubiquitous and indigenous to sedimentary and groundwater environments.

Abstract Bacterial community succession was investigated in a field-scale subsurface reactor formed by a series of wells that received weekly ethanol additions to re-circulating groundwater. Ethanol additions stimulated denitrification, metal reduction, sulfate reduction and U(VI) reduction to sparingly soluble U(IV). Clone libraries of SSU rRNA gene sequences from groundwater samples enabled tracking of spatial and temporal changes over a 1.5-year period. Analyses showed that the communities changed in a manner consistent with geochemical variations that occurred along temporal and spatial scales. Canonical correspondence analysis revealed that the levels of nitrate, uranium, sulfide, sulfate and ethanol were strongly correlated with particular bacterial populations. As sulfate and U(VI) levels declined, sequences representative of sulfate reducers and metal reducers were detected at high levels. Ultimately, sequences associated with sulfate-reducing populations predominated, and sulfate levels declined as U(VI) remained at low levels. When engineering controls were compared with the population variation through canonical ordination, changes could be related to dissolved oxygen control and ethanol addition. The data also indicated that the indigenous populations responded differently to stimulation for bioreduction; however, the two biostimulated communities became more similar after different transitions in an idiosyncratic manner. The strong associations between particular environmental variables and certain populations provide insight into the establishment of practical and successful remediation strategies in radionuclide-contaminated environments with respect to engineering controls and microbial ecology.

There is concern that mercury (Hg) in coal combustion by-products might be emitted into the environment during processing to other products or after the disposal/landfill of these by-products. This perception may limit the opportunities to use coal combustion by-products in recycle/reuse applications and may result in additional, costly disposal regulations. In this program, CONSOL conducted a comprehensive sampling and analytical program to include ash, flue gas desulfurization (FGD) sludge, and coal combustion by-products. This work is necessary to help identify potential problems and solutions important to energy production from fossil fuels. The program objective was to evaluate the potential for mercury emissions by leaching or volatilization, to determine if mercury enters the water surrounding an active FGD disposal site and an active fly ash slurry impoundment site, and to provide data that will allow a scientific assessment of the issue. Toxicity Characteristic Leaching Procedure (TCLP) test results showed that mercury did not leach from coal, bottom ash, fly ash, spray dryer/fabric filter ash or forced oxidation gypsum (FOG) in amounts leading to concentrations greater than the detection limit of the TCLP method (1.0 ng/mL). Mercury was detected at very low concentrations in acidic leachates from all of the fixated and more than half of the unfixated FGD sludge samples, and one of the synthetic aggregate samples. Mercury was not detected in leachates from any sample when deionized water (DI water) was the leaching solution. Mercury did not leach from electrostatic precipitator (ESP) fly ash samples collected during activated carbon injection for mercury control in amounts greater than the detection limit of the TCLP method (1.0 ng/mL). Volatilization tests could not detect mercury loss from fly ash, spray dryer/fabric filter ash, unfixated FGD sludge, or forced oxidation gypsum; the mercury concentration of these samples all increased, possibly due to absorption from ambient surroundings. Mercury loss of 18-26% was detected after 3 and 6 months at 100 F and 140 F from samples of the fixated FGD sludge. Water samples were collected from existing ground water monitoring wells around an active FGD disposal site (8 wells) and an active fly ash slurry impoundment (14 wells). These were wells that the plants have installed to comply with ground water monitoring requirements of their permits. Mercury was not detected in any of the water samples collected from monitoring wells at either site. A literature review concluded that coal combustion byproducts can be disposed of in properly designed landfills that minimize the potentially negative impacts of water intrusion that carries dissolved organic matter (DOM). Dissolved organic matter and sulfate-reducing bacteria can promote the transformation of elemental or oxidized mercury into methyl mercury. The landfill should be properly designed and capped with clays or similar materials to minimize the wet-dry cycles that promote the release of methylmercury.

Pacific Northwest Laboratory (PNL) is studying possible mechanisms and fluid dynamics contributing to the periodic release of gases from the double-shell waste storage tanks at Hanford. This study is being conducted for Westinghouse Hanford Company (WHC), a contractor for the US Department of Energy (DOE). This interim report discusses the work done through November 1990. Safe management of the wastes at Hanford depends on an understanding of the chemical and physical mechanisms that take place in the waste tanks. An example of the need to understand these mechanisms is tank 101-SY. The waste in this tank is generating and periodically releasing potentially flammable gases into the tank vent system according to observations of the tank. How these gases are generated and become trapped, the causes of periodic release, and the mechanism of the release are not known in detail. In order to develop a safe mitigation strategy, possible physical mechanisms for the periodic release of flammable gases need to be understood.

An AFB fly ash sample from Georgetown University shows a significant difference in visual appearance to that of other AFB fly ash sources. Differences in the chemical composition of spent bed residue samples from Rivesville, West Virginia, are probably attributable to variations in the calcium to sulfur ratio in the fluidized-bed during combustion. Comparison of the particle size distribution of spent bed samples from Alliance, Ohio, and Georgetown University reveals a close similarity in the basic sizing of these materials, with each being considered in the medium to coarse sand size range. Visual inspection of the separated overflow sample from mineral cyclone separation indicates that this product may contain a relatively high percentage of lime. On the basis of available data, it appears that detrimental volume expansion in road base compositions containing AFB residue can be reduced to a tolerable level by pre-treatment, such as grinding and/or maximum hydration prior to use. Additions of relatively low percentages of AFB residue to acid mine waste-water resulted in significant increases in the percentage of solids of vacuum filtered samples, due to the low solids content of the wastewater sample. The addition of AFB residue to acid mine wastewater is effective in neutralizingmore » the pH and dewatering the waste, although previous neutralization tests have shown that milled AFB residue is generally more reactive and effective than as received AFB residue. Combinations of equal weights of AFB residue and fly ash appear to produce relatively high strength block. Blocks with 80 percent AFB residue and 20 percent fly ash exhibited somewhat lower strengths with little or no cracking.« less

The legal and institutional framework within which geothermal energy must develop has its origin in the early 1970s. In 1970, the Federal Geothermal Steam Act was passed into law and in 1974 the Washington State Geothermal Act was passed. The legal and institutional framework thus established by the state and federal governments differed substantially in format, content, and direction. In many instances, the legal and institutional framework established left as many questions unanswered as answered, and in some cases, the framework has proven to be more of an obstacle to development than an aid. From an examination of how the state and federal governments have addressed the varying needs of geothermal development and how the courts have interpreted some of their decisions, it is clear that in order to ensure that the legal and institutional framework is adequate to serve the needs of geothermal development, it must address, at a minimum, the following topics: (1) providing developers with access and a priority right to carry out exploration and development activities; (2) characterization of the resource so as to minimize conflicts with other natural resources; (3) establishing ownership; and (4) giving careful consideration to such lease terms as rentals and royalties,more » lease renewals, and diligence requirements. In addition, the framework must address groundwater law and its implications for geothermal development and how geothermal development will be considered in terms of establishing utility law. At the local level, it is imperative that geothermal be given careful consideration when decisions on resource management, zoning, and regulation are made. Local governments also have the power to establish programs which can provide substantial incentives for geothermal development and, by so doing, ensure that geothermal energy contributes to economic stability and growth.« less

A residential and industrial water-conservation scenario for California is constructed in which water consumption is disaggregated by residential end use, industrial sector, and hydrologic study area (HSA). The energy use associated with this water use was estimated for surface and groundwater delivery, distribution, heating, and waste-water treatment. For each end use and sector, water-conservation measures were delineated and their potential savings in terms of both water and attendant energy use were estimated. This material is combined to estimate the total water and energy savings potential by end use, sector, and HSA. This potential is then compared with the reported water savings to date, and finally, some conclusions and policy implications are drawn from the results. The general findings are discussed first, followed by a listing of the more important detailed results.

This report characterizes the ammonia industry operations, reviews current knowledge of ammonia release and subsequent impacts, summarizes the status of release prevention and control methods and identify research and development needs for safety and environmental control. Appendices include: accidental spills and human exposure; adiabatic mixing of liquid nitrogen and air; fire and explosion hazards; and environmental impact rating tables. (PSB)