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Title: Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau

Abstract

Uranium is present in the vadose zone at the Hanford Central Plateau and is of concern for protection of groundwater. The Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau identified gas-phase treatment and geochemical manipulation as potentially effective treatment approaches for uranium and technetium in the Hanford Central Plateau vadose zone. Based on laboratory evaluation, use of ammonia vapor was selected as the most promising uranium treatment candidate for further development and field testing. While laboratory tests have shown that ammonia treatment effectively reduces the mobility of uranium, additional information is needed to enable deployment of this technology for remediation. Of importance for field applications are aspects of the technology associated with effective distribution of ammonia to a targeted treatment zone, understanding the fate of injected ammonia and its impact on subsurface conditions, and identifying effective monitoring approaches. In addition, information is needed to select equipment and operational parameters for a field design. As part of development efforts for the ammonia technology for remediation of vadose zone uranium contamination, field scale-up issues were identified and have been addressed through a series of laboratory and modeling efforts. This report presents a conceptual description for field application of themore » ammonia treatment process, engineering calculations to support treatment design, ammonia transport information, field application monitoring approaches, and a discussion of processes affecting the fate of ammonia in the subsurface. The report compiles this information from previous publications and from recent research and development activities. The intent of this report is to provide technical information about these scale-up elements to support the design and operation of a field test for the ammonia treatment technology.« less

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1170499
Report Number(s):
PNNL-23699
830403000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; urnaium; remediation; vadose zone

Citation Formats

Truex, Michael J., Szecsody, James E., Zhong, Lirong, Thomle, Jonathan N., and Johnson, Timothy C.. Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau. United States: N. p., 2014. Web. doi:10.2172/1170499.
Truex, Michael J., Szecsody, James E., Zhong, Lirong, Thomle, Jonathan N., & Johnson, Timothy C.. Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau. United States. doi:10.2172/1170499.
Truex, Michael J., Szecsody, James E., Zhong, Lirong, Thomle, Jonathan N., and Johnson, Timothy C.. Mon . "Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau". United States. doi:10.2172/1170499. https://www.osti.gov/servlets/purl/1170499.
@article{osti_1170499,
title = {Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau},
author = {Truex, Michael J. and Szecsody, James E. and Zhong, Lirong and Thomle, Jonathan N. and Johnson, Timothy C.},
abstractNote = {Uranium is present in the vadose zone at the Hanford Central Plateau and is of concern for protection of groundwater. The Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau identified gas-phase treatment and geochemical manipulation as potentially effective treatment approaches for uranium and technetium in the Hanford Central Plateau vadose zone. Based on laboratory evaluation, use of ammonia vapor was selected as the most promising uranium treatment candidate for further development and field testing. While laboratory tests have shown that ammonia treatment effectively reduces the mobility of uranium, additional information is needed to enable deployment of this technology for remediation. Of importance for field applications are aspects of the technology associated with effective distribution of ammonia to a targeted treatment zone, understanding the fate of injected ammonia and its impact on subsurface conditions, and identifying effective monitoring approaches. In addition, information is needed to select equipment and operational parameters for a field design. As part of development efforts for the ammonia technology for remediation of vadose zone uranium contamination, field scale-up issues were identified and have been addressed through a series of laboratory and modeling efforts. This report presents a conceptual description for field application of the ammonia treatment process, engineering calculations to support treatment design, ammonia transport information, field application monitoring approaches, and a discussion of processes affecting the fate of ammonia in the subsurface. The report compiles this information from previous publications and from recent research and development activities. The intent of this report is to provide technical information about these scale-up elements to support the design and operation of a field test for the ammonia treatment technology.},
doi = {10.2172/1170499},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2014},
month = {Mon Sep 01 00:00:00 EDT 2014}
}

Technical Report:

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  • This laboratory-scale investigation is focused on decreasing mobility of uranium in subsurface contaminated sediments in the vadose zone by in situ geochemical manipulation at low water content. This geochemical manipulation of the sediment surface phases included reduction, pH change (acidic and alkaline), and additions of chemicals (phosphate, ferric iron) to form specific precipitates. Reactants were advected into 1-D columns packed with Hanford 200 area U-contaminated sediment as a reactive gas (for CO2, NH3, H2S, SO2), with a 0.1% water content mist (for NaOH, Fe(III), HCl, PO4) and with a 1% water content foam (for PO4). Uranium is present in themore » sediment in multiple phases that include (in decreasing mobility): aqueous U(VI) complexes, adsorbed U, reduced U(IV) precipitates, rind-carbonates, total carbonates, oxides, silicates, phosphates, and in vanadate minerals. Geochemical changes were evaluated in the ability to change the mixture of surface U phases to less mobile forms, as defined by a series of liquid extractions that dissolve progressively less soluble phases. Although liquid extractions provide some useful information as to the generalized uranium surface phases (and are considered operational definitions of extracted phases), positive identification (by x-ray diffraction, electron microprobe, other techniques) was also used to positively identify U phases and effects of treatment. Some of the changes in U mobility directly involve U phases, whereas other changes result in precipitate coatings on U surface phases. The long-term implication of the U surface phase changes to alter U mass mobility in the vadose zone was then investigated using simulations of 1-D infiltration and downward migration of six U phases to the water table. In terms of the short-term decrease in U mobility (in decreasing order), NH3, NaOH mist, CO2, HCl mist, and Fe(III) mist showed 20% to 35% change in U surface phases. Phosphate addition (mist or foam advected) showed inconsistent change in aqueous and adsorbed U, but significant coating (likely phosphates) on U-carbonates. The two reductive gas treatments (H2S and SO2) showed little change. For long-term decrease in U reduction, mineral phases created that had low solubility (phosphates, silicates) were desired, so NH3, phosphates (mist and foam delivered), and NaOH mist showed the greatest formation of these minerals. In addition, simulations showed the greatest decrease in U mass transport time to reach groundwater (and concentration) for these silicate/phosphate minerals. Advection of reactive gasses was the easiest to implement at the laboratory scale (and presumably field scale). Both mist and foam advection show promise and need further development, but current implementation move reactants shorter distances relative to reactive gasses. Overall, the ammonia and carbon dioxide gas had the greatest overall geochemical performance and ability to implement at field scale. Corresponding mist-delivered technologies (NaOH mist for ammonia and HCl mist for carbon dioxide) performed as well or better geochemically, but are not as easily upscaled. Phosphate delivery by mist was rated slightly higher than by foam delivery simply due to the complexity of foam injection and unknown effect of U mobility by the presence of the surfactant.« less
  • Technetium-99 (Tc-99) is present in the vadose zone of the Hanford Central Plateau and is a concern with respect to the protection of groundwater. The persistence, limited natural attenuation mechanisms, and geochemical behavior of Tc-99 in oxic vadose zone environments must be considered in developing effective alternatives for remediation. This report describes a new in situ geochemical manipulation technique for decreasing Tc-99 mobility using a combination of geochemical Tc-99 reduction with hydrogen sulfide gas and induced sediment mineral dissolution with ammonia vapor, which create conditions for deposition of stable precipitates that decrease the mobility of Tc-99. Laboratory experiments were conductedmore » to examine changes in Tc-99 mobility in vadose zone sediment samples to evaluate the effectiveness of the treatment under a variety of operational and sediment conditions.« less
  • Historically, uranium was disposed in waste solutions of varying waste chemistry at the Hanford Site Central Plateau. The character of how uranium was distributed in the vadose zone during disposal, how it has continued to migrate through the vadose zone, and the magnitude of potential impacts on groundwater are strongly influenced by geochemical reactions in the vadose zone. These geochemical reactions can be significantly influenced by the disposed-waste chemistry near the disposal location. This report provides conceptual models and supporting information to describe uranium fate and transport in the vadose zone for both acidic and alkaline wastes discharged at amore » substantial number of waste sites in the Hanford Site Central Plateau. The conceptual models include consideration of how co-disposed acidic or alkaline fluids influence uranium mobility in terms of induced dissolution/precipitation reactions and changes in uranium sorption with a focus on the conditions near the disposal site. This information, when combined with the extensive information describing uranium fate and transport at near background pH conditions, enables focused characterization to support effective fate and transport estimates for uranium in the subsurface.« less
  • This investigation is focused on refining an in situ technology for vadose zone remediation of uranium by the addition of ammonia (NH3) gas. Objectives are to: a) refine the technique of ammonia gas treatment of low water content sediments to minimize uranium mobility by changing uranium surface phases (or coat surface phases), b) identify the geochemical changes in uranium surface phases during ammonia gas treatment, c) identify broader geochemical changes that occur in sediment during ammonia gas treatment, and d) predict and test injection of ammonia gas for intermediate-scale systems to identify process interactions that occur at a larger scalemore » and could impact field scale implementation.Overall, NH3 gas treatment of low-water content sediments appears quite effective at decreasing aqueous, adsorbed uranium concentrations. The NH3 gas treatment is also fairly effective for decreasing the mobility of U-carbonate coprecipitates, but shows mixed success for U present in Na-boltwoodite. There are some changes in U-carbonate surface phases that were identified by surface phase analysis, but no changes observed for Na-boltwoodite. It is likely that dissolution of sediment minerals (predominantly montmorillonite, muscovite, kaolinite) under the alkaline conditions created and subsequent precipitation as the pH returns to natural conditions coat some of the uranium surface phases, although a greater understanding of these processes is needed to predict the long term impact on uranium mobility. Injection of NH3 gas into sediments at low water content (1% to 16% water content) can effectively treat a large area without water addition, so there is little uranium mobilization (i.e., transport over cm or larger scale) during the injection phase.« less
  • This report is the second of two studies on potential applications for vadose zone monitoring (VZM) at the Hanford Site. The U.S. Department of Energy (DOE) agreed to perform the studies in a letter from M. S. Schlender, DOE, to M. L. Goldstein, Environmental Protection Agency (EPA), and M. A. Wilson, Washington State Department of Ecology (Ecology), subject ''Vadose Zone Monitoring Study,'' 02-ERD-0055, dated March 11, 2002. The first study evaluated the potential for performance monitoring at the Environmental Restoration Disposal Facility (ERDF) and was published as ''Study of Vadose Zone Monitoring at the Hanford Site, Task I . Usemore » in New Cells at the Environmental Restoration Disposal Facility'', dated May 2003 (DOE/RL-2003-31). This report is Task 2 and examines the potential for VZM at waste sites and tank farms in the 200 East and West Areas of the Central Plateau Remediation Project (Central Plateau). The potential benefits of VZM are discussed in the introduction, as well as the objectives of the study. A summary of the hydrogeology of the central plateau is presented. This includes a discussion of the stratigraphy, vadose zone transport, and groundwater characteristics. A chapter on the regulatory framework is presented in the context of the anticipated remediation, Environmental Protection Agency regulations, and the regulations of other western states. While the previous Task I study presented a survey of commercial sites in the western part of the United States, this report surveys vadose zone monitoring at other government sites in the western United States. Most of the significant Department of Energy Sites are discussed and compared. Since the western part of the United States contains many of the DOE research facilities, a discussion is presented on the vadose zone research and development activities at these facilities. The ongoing development and use of VZM by the Air Force, Navy, and Army is presented. A summary is presented of the planned remediation on the Central Plateau in order to identify the relevant types of remediations that would be candidates for VZM. A short discussion of the existing groundwater plumes is given to complete the picture of how vadose zone contamination eventually becomes groundwater contamination. The technology is surveyed and categorized by type. These types include moisture change methods, moisture sampling methods, geophysical techniques, and remote sensing techniques. Future trends are identified. The probable course will be the development of methods that can integrate the information over larger volumes, particularly those that will use less invasive or remote sensing technologies. A discussion of deployment methods is given. These include basin lysimeters, access tubes, sensors placed inside landfills, and cover monitoring. In order to match the technologies with the planned remedies the current technologies are discussed in the context of specific types of site remediations. These include waste sites such as cribs and trenches, tank farm sites, and other facilities. Conclusions are reached, which include an analysis of the different types of conditions appropriate for VZM, considerations in the selections of the appropriate technologies, and issues associated with adapting to the development of new technologies. Also, a short discussion is given of the operational facilities that will be used during the cleanup efforts.« less