Publications

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Geochemical Engineering Design (GED) is based on applications of the principles and various computer models that describe the biogeochemistry and physics of removal of contaminants from water by adsorption, precipitation and filtration. It can be used to optimize or evaluate the efficiency of all phases of in situ recovery (ISR). The primary tools of GED are reactive transport models; this talk describes the potential application of the HYDROGEOCHEM family of codes to ISR. The codes can describe a complete suite of equilibrium or kinetic aqueous complexation, adsorption-desorption, precipitation-dissolution, redox, and acid-base reactions in variably saturated media with density-dependent fluid flow. Applications to ISR are illustrated with simulations of (1) the effectiveness of a reactive barrier to prevent off-site uranium migration and (2) evaluation of the effect of sorption hysteresis on natural attenuation. In the first example, it can be seen that the apparent effectiveness of the barrier depends on monitoring location and that it changes over time. This is due to changes in pH, saturation of sorption sites, as well as the geometry of the flow field. The second simulation shows how sorption hysteresis leads to observable attenuation of a uranium contamination plume. Different sorption mechanisms including fast (or reversible), slow, and irreversible sorption were simulated. The migration of the dissolved and total uranium plumes for the different cases are compared and the simulations show that when 50-100% of the sites have slow desorption rates, the center of mass of the dissolved uranium plume begins to move upstream. This would correspond to the case in which the plume boundaries begin to shrink as required for demonstration of natural attenuation.

This session will explore the current technical approaches to reducing the environmental effects of uranium ISR in comparison to the historical environmental impact of uranium mining to demonstrate advances in this controversial subject.

The dose limits for emissions from the nuclear fuel cycle were established by the Environmental Protection Agency in 40 CFR Part 190 in 1977. These limits were based on assumptions regarding the growth of nuclear power and the technical capabilities of decontamination systems as well as the then-current knowledge of atmospheric dispersion and the biological effects of ionizing radiation. In the more than thirty years since the adoption of the limits, much has changed with respect to the scale of nuclear energy deployment in the United States and the scientific knowledge associated with modeling health effects from radioactivity release. Sandia National Laboratories conducted a study to examine and understand the methodologies and technical bases of 40 CFR 190 and also to determine if the conclusions of the earlier work would be different today given the current projected growth of nuclear power and the advances in scientific understanding. This report documents the results of that work.

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Sandia National Laboratories (SNL) is conducting pilot scale evaluations of the performance and cost of innovative water treatment technologies aimed at meeting the recently revised arsenic maximum contaminant level (MCL) for drinking water. The standard of 10 {micro}g/L (10 ppb) is effective as of January 2006. The pilot tests have been conducted in New Mexico where over 90 sites that exceed the new MCL have been identified by the New Mexico Environment Department. The pilot test described in this report was conducted in Anthony, New Mexico between August 2005 and December 2006 at Desert Sands Mutual Domestic Water Consumers Association (MDWCA) (Desert Sands) Well No.3. The pilot demonstrations are a part of the Arsenic Water Technology Partnership program, a partnership between the American Water Works Association Research Foundation (AwwaRF), SNL and WERC (A Consortium for Environmental Education and Technology Development). The Sandia National Laboratories pilot demonstration at the Desert Sands site obtained arsenic removal performance data for fourteen different adsorptive media under intermittent flow conditions. Well water at Desert Sands has approximately 20 ppb arsenic in the unoxidized (arsenite-As(III)) redox state with moderately high total dissolved solids (TDS), mainly due to high sulfate, chloride, and varying concentrations of iron. The water is slightly alkaline with a pH near 8. The study provides estimates of the capacity (bed volumes until breakthrough at 10 ppb arsenic) of adsorptive media in the same chlorinated water. Adsorptive media were compared side-by-side in ambient pH water with intermittent flow operation. This pilot is broken down into four phases, which occurred sequentially, however the phases overlapped in most cases.

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The lowering of the drinking water standard (MCL) for arsenic from 50 {micro}g/L to 10 {micro}g/L in January 2006 could lead to significant increases in the cost of water for many rural systems throughout the United States. The Arsenic Water Technology Partnership (AWTP), a collaborative effort of Sandia National Laboratories, the Awwa Research Foundation (AwwaRF) and WERC: A Consortium for Environmental Education and Technology Development, was formed to address this problem by developing and testing novel treatment technologies that could potentially reduce the costs of arsenic treatment. As a member of the AWTP, Sandia National Laboratories evaluated cutting-edge commercial products in three annual Arsenic Treatment Technology Vendors Forums held during the annual New Mexico Environmental Health Conferences (NMEHC) in 2003, 2004 and 2005. The Forums were comprised of two parts. At the first session, open to all conference attendees, commercial developers of innovative treatment technologies gave 15-minute talks that described project histories demonstrating the effectiveness of their products. During the second part, these same technologies were evaluated and ranked in closed sessions by independent technical experts for possible use in pilot-scale field demonstrations being conducted by Sandia National Laboratories. The results of the evaluations including numerical rankings of the products, links to company websites and copies of presentations made by the representatives of the companies are posted on the project website at http://www.sandia.gov/water/arsenic.htm. This report summarizes the contents of the website by providing brief descriptions of the technologies represented at the Forums and the results of the evaluations.

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Sandia National Laboratories (SNL) is conducting pilot scale evaluations of the performance and cost of innovative drinking water treatment technologies designed to meet the new arsenic maximum contaminant level (MCL) of 10 {micro}g/L (effective January 2006). As currently envisioned, pilots tests may include multiple phases. Phase I tests will involve side-by-side comparisons of several commercial technologies primarily using design parameters suggested by the Vendors. Subsequent tests (Phase II) may involve repeating some of the original tests, testing the same commercial technologies under different conditions and testing experimental technologies or additional commercial technologies. This Pilot Test Specific Test Plan (PTSTP) was written for Phase I of the Socorro Springs Pilot. The objectives of Phase I include evaluation of the treatment performance of five adsorptive media under ambient pH conditions (approximately 8.0) and assessment of the effect of contact time on the performance of one of the media. Addenda to the PTSTP may be written to cover Phase II studies and supporting laboratory studies. The Phase I demonstration began in the winter of 2004 and will last approximately 9 months. The information from the test will help the City of Socorro choose the best arsenic treatment technology for the Socorro Springs well. The pilot demonstration is a project of the Arsenic Water Technology Partnership program, a partnership between the American Water Works Association (AWWA) Research Foundation, SNL, and WERC (A Consortium for Environmental Education and Technology Development).

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Recent reduction of drinking water Maximum Concentration Level (MCL) for arsenic from 50 ppb to 10 ppb was intended to reduce incidence of bladder cancer and other cancers in US. Southwestern United States is characterized by high and variable background levels for arsenic. Estimated national annual costs of implementing 10 ppb MCL range from $165M to $605M to save 7 - 33 lives. - $5M - $23.9M /life saved - $1.3M - $6.6M/ year of life saved. About 1 life/500,000 exposed persons per year. New MCL is controversial due to high costs and uncertain health benefits.

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This report documents a field trial program carried out at Well No.15 located at Kirtland Air Force Base, Albuquerque, New Mexico, to evaluate the performance of two relatively new arsenic removal media, ALCAN-AASF50 (ferric coated activated alumina) and granular ferric hydroxide (US Filter-GFH). The field trial program showed that both media were able to remove arsenate and meet the new total arsenic maximum contaminant level (MCL) in drinking water of 10 {micro}g/L. The arsenate removal capacity was defined at a breakthrough effluent concentration of 5 {micro}g/L arsenic (50% of the arsenic MCL of 10 {micro}g/L). At an influent pH of 8.1 {+-} 0.4, the arsenate removal capacity of AASF50 was 33.5 mg As(V)/L of dry media (29.9 {micro}g As(V)/g of media on a dry basis). At an influent pH of 7.2 {+-} 0.3, the arsenate removal capacity of GFH was 155 mg As(V)/L of wet media (286 {micro}g As(V)/g of media on a dry basis). Silicate, fluoride, and bicarbonate ions are removed by ALCAN AASF50. Chloride, nitrate, and sulfate ions were not removed by AASF50. The GFH media also removed silicate and bicarbonate ions; however, it did not remove fluoride, chloride, nitrate, and sulfate ions. Differences in the media performance partly reflect the variations in the feed-water pH between the 2 tests. Both the exhausted AASF50 and GFH media passed the Toxicity Characteristic Leaching Procedure (TCLP) test with respect to arsenic and therefore could be disposed as nonhazardous waste.

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Sandia National Laboratories (SNL) is collaborating with the Awwa Research Foundation (AwwaRF) and WERC (A Consortium for Environmental Education and Technology Development) in a program for the development and testing of innovative technologies that have the potential to substantially reduce the costs associated with arsenic removal from drinking water. Sandia National Laboratories will administer contracts placed with AwwaRF and WERC to carry out bench scale studies and economic analyses/outreach activities, respectively. The elements of the AwwaRF program include (1) identification of new technologies, (2) proof-of-concept laboratory studies and, (3) a research program that will meet the other needs of small utilities by providing solutions to small utilities so that they may successfully meet the new arsenic MCL. WERC's activities will include development of an economic analysis tool for Pilot Scale Demonstrations and development of educational training and technical assistance tools. The objective of the Sandia Program is the field demonstration testing of innovative technologies. The primary deliverables of the Sandia program will be engineering analyses of candidate technologies; these will be contained in preliminary reports and final analysis reports. Projected scale-up costs will be generated using a cost model provided by WERC or another suitable model.

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As part of the Arsenic Water Technology Partnership program, Sandia National Laboratories will carry out field demonstration testing of innovative technologies that have the potential to substantially reduce the costs associated with arsenic removal from drinking water. The scope for this work includes: (1) selection of sites for pilot demonstrations, (2) identification of candidate technologies through Vendor Forums, proof-of-principle bench-scale studies managed by the American Water Works Association Research Foundation (AwwaRF) or the WERC design contest, and (3) pilot-scale studies involving side-by-side tests of innovative technologies. The goal of site selection is identification of a suite of sites that exhibit a sufficiently wide range of groundwater chemistries to allow examination of treatment processes and systems under conditions that are relevant to different geochemical settings throughout the country. A number of candidate sites have been identified through reviews of groundwater quality databases, conference proceedings and discussions with state and local officials. These include sites in New Mexico, Arizona, Colorado, Oklahoma, Illinois, Michigan, Florida, Massachusetts and New Hampshire. In New Mexico, discussions have been held with water utility board staffs in Chama, Jemez Pueblo, Placitas, Socorro and several communities near Las Cruces to determine the suitability of those communities for pilot studies. The initial pilot studies will be carried at Socorro and Jemez Pueblo; other communities will be included as the program progresses. The proposed pilot test at a hot spring water source near Socorro will provide an opportunity to test treatment technologies at relatively high temperatures. If approved by the Tribal Government, the proposed pilot at the Jemez Pueblo would provide an opportunity to test technologies that will remove arsenic in the presence of relatively high concentrations of iron and manganese while leaving the beneficial levels of fluoride unchanged. Candidate technologies for the pilot tests are being reviewed by technical evaluation teams. The initial reviews will consider as many potential technologies and screen out unsuitable ones by considering data from past performance testing, expected costs, complexity of operation and maturity of the technology. The pilot test configurations will depend on the site-specific conditions such as access, power availability, waste disposal options and availability of permanent structures to house the test. Most of the treatment technologies that will be evaluated can be separated into two broad categories: (1) sorption processes that use fixed bed adsorbents and (2) membrane processes. The latter include processes that involve formation of a floc or precipitate that contains the arsenic in a reactor followed by separation of the solids from the water by filtration. Several innovations that could lead to lower treatment costs have been proposed for adsorptive media systems. These include: (1) higher capacity and selectivity using mixed oxides composed of iron and other transition metals, titanium and zirconium based oxides, or mixed resin-metal oxides composite media, (2) improved durability of virgin media and greater chemical stability of the spent media, and (3) use of inexpensive natural or recycled materials with a coating that has a high affinity for arsenic. Improvements to filtration-based treatment systems include: (1) enhanced coagulation with iron compounds or polyelectrolytes and (2) improved filtration with nanocomposite materials. In the pilot tests, the innovative technologies will be evaluated in terms of: (1) their ability to reduce arsenic to levels below the EPA Maximum Contaminant Level (MCL) of 10 ppb, (2) site-specific adsorptive capacity, robustness of performance with respect to likely changes in water quality parameters including pH, TDS, foulants such as Fe, Mn, silica, and organics, effect of competing ions such as other metals and radionuclides, and potentially deleterious effects on the water system such as pipe corrosion from low pH levels, fluoride removal, and generation of disinfection by-products. The new arsenic MCL will result in modification of many rural water systems that otherwise would not require treatment. Opportunities for improvement of water quality in systems that currently do not comply with other standards would be an added benefit from the new arsenic MCL that has both economic and public health value.

The Arsenic Water Technology Partnership (AWTP) program is a multi-year program funded by a congressional appropriation through the Department of Energy to develop and test innovative technologies that have the potential to reduce the costs of arsenic removal from drinking water. The AWTP members include Sandia National Laboratories, the American Water Works Association (Awwa) Research Foundation and WERC (A Consortium for Environmental Education and Technology Development). The program is designed to move technologies from bench-scale tests to field demonstrations. The Awwa Research Foundation is managing bench-scale research programs; Sandia National Laboratories is conducting the pilot demonstration program and WERC will evaluate the economic feasibility of the technologies investigated and conduct technology transfer activities. The objective of the Sandia Arsenic Treatment Technology Demonstration project (SATTD) is the field demonstration testing of both commercial and innovative technologies. The scope for this work includes: (1) Identification of sites for pilot demonstrations; (2) Accelerated identification of candidate technologies through Vendor Forums, proof-of-principle laboratory and local pilot-scale studies, collaboration with the Awwa Research Foundation bench-scale research program and consultation with relevant advisory panels; and (3) Pilot testing multiple technologies at several sites throughout the country, gathering information on: (a) Performance, as measured by arsenic removal; (b) Costs, including capital and Operation and Maintenance (O&M) costs; (c) O&M requirements, including personnel requirements, and level of operator training; and (d) Waste residuals generation. The New Mexico Environment Department has identified over 90 public water systems that currently exceed the 10 {micro}g/L MCL for arsenic. The Sandia Arsenic Treatment Technology Demonstration project is currently operating pilots at three sites in New Mexico. The cities of Socorro, Anthony, and Rio Rancho vary in population, water chemistry, and source of arsenic. Figure 1 shows the locations of each city. The following pages summarize the work being performed at each site. At each site, the owners (e.g. city utility) provide access to the site, water, electricity, means to discharge treated water, and daily operational checks. Daily checks include filling out a logsheet with information on the flow rates, pressure drops, flow adjustments (when needed), and notification of Sandia personnel if a leak is present. Sandia owns all equipment and is responsible for the disposal of spent media and other waste streams. Sandia also performs all field tests and collects water samples for laboratory analysis.

Contaminant release scenarios proposed for the Waste Isolation Pilot Plant (WIPP) repository suggest that the Culebra Dolomite member of the Rustler Formation could be an important radionuclide release path. This thin, vuggy, highly fractured unit is the most transmissive geologic unit overlying the WIPP. Many of the samples obtained from drill cores in the Culebra exhibit fractures that are lined with iron-oxyhydroxide-rich and clay-rich mineral coatings. The coatings are mineralogically distinct from the rock matrix, and may have sorptive characteristics that are different from a clay-poor dolomite matrix. Where locally abundant, such coatings could affect advective/diffusive exchange between matrix blocks and fractures and the accessible mineral surface area available for radionuclide adsorption. Clay minerals are present in the matrix and as fracture coatings in the samples from all the drill core locations examined in this study. Visual examination of rock sample surfaces in the H -19b7 core suggests that at least 7% of the total fracture surface area is coated with iron oxhydroxides or clays. In the samples from H-19b7, the amount of clay disseminated in the matrix varies from <1% to {approx}12 % by weight, and generally increases with stratigraphic height within the unit. In a suite of samples obtained from 12 other locations in the vicinity of the WIPP site, matrix samples from the Culebra contain 0.6--7% clay. These samples were taken from the more transmissive lower two-thirds of the unit (Culebra Units 2-4) which was considered to be the accessible portion of the unit in the WIPP Compliance Certification Application (CCA). Clay minerals also occur as clay-rich laminae and partings with the geometries of primary sedimentary structures and dissolution residues. Such partings are the loci of bedding plane fractures, and have the heaviest clay coatings found in the unit. Crosscutting fractures also commonly exhibit clay mineral coatings, but these are generally discontinuous and much thinner.

Groundwater plumes containing dissolved uranium at levels above natural background exist adjacent to uranium ore bodies, at uranium mines, milling locations, and at a number of explosive test facilities. Public health concerns require that some assessment of the potential for further plume movement in the future be made. Reaction-transport models, which might conceivably be used to predict plume movement, require extensive data inputs that are often uncertain. Many of the site-specific inputs are physical parameters that can vary spatially and with time. Limitations in data availability and accuracy means that reaction-transport predictions can rarely provide more than order-of-magnitude bounding estimates of contaminant movement in the subsurface. A more direct means for establishing the limits of contaminant transport is to examine actual plumes to determine if, collectively, they spread and attenuate in a reasonably consistent and characteristic fashion. Here a number of U plumes from ore bodies and contaminated sites were critically examined to identify characteristics of U plume movement. The magnitude of the original contaminant source, the geologic setting, and the hydrologic regime were rarely similar from site to site. Plumes also spanned a vast range of ages, and no complete set of time-series plume analyses based on the spatial extent of U contamination exist for a particular site. Despite the accumulated uncertainties and variabilities, the plume data set gave a clear and reasonably consistent picture of U plume behavior. Specifically, uranium plumes. © 2001 by AEHS.

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