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Title: 100-D Area In Situ Redox Treatability Test for Chromate-Contaminated Groundwater

Abstract

No abstract prepared.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab., Richland, WA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
765145
Report Number(s):
PNNL-13349; 820201000
R&D Project: 30352; 820201000; TRN: US0100102
DOE Contract Number:
AC06-76RL01830
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 12 Oct 2000
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; CHROMATES; GROUND WATER; WATER POLLUTION; REDOX REACTIONS; REMEDIAL ACTION; IN-SITU PROCESSING; HANFORD RESERVATION

Citation Formats

Williams, M.D., Vermeul, V.R., Szecsody. J.E., and Fruchter, J.S.. 100-D Area In Situ Redox Treatability Test for Chromate-Contaminated Groundwater. United States: N. p., 2000. Web. doi:10.2172/765145.
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Williams, M.D., Vermeul, V.R., Szecsody. J.E., & Fruchter, J.S.. 100-D Area In Situ Redox Treatability Test for Chromate-Contaminated Groundwater. United States. doi:10.2172/765145.
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Williams, M.D., Vermeul, V.R., Szecsody. J.E., and Fruchter, J.S.. Thu . "100-D Area In Situ Redox Treatability Test for Chromate-Contaminated Groundwater". United States. doi:10.2172/765145. https://www.osti.gov/servlets/purl/765145.
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@article{osti_765145,
title = {100-D Area In Situ Redox Treatability Test for Chromate-Contaminated Groundwater},
author = {Williams, M.D. and Vermeul, V.R. and Szecsody. J.E. and Fruchter, J.S.},
abstractNote = {No abstract prepared.},
doi = {10.2172/765145},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Oct 12 00:00:00 EDT 2000},
month = {Thu Oct 12 00:00:00 EDT 2000}
}
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Technical Report:
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DOI:  10.2172/765145
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  • ; ; ; ...
    A treatability test was conducted for the In Situ Redox Manipulation (ISRM) technology at the US Department of Energy's Hanford, Washington 100D Area. The target contaminant was dissolved chromate [Cr(VI)] in groundwater. The ISRM technology involves creating a permeable subsurface treatment zone to reduce mobile chromate in groundwater to an insoluble form. The ISRM permeable treatment zone is created by reducing ferric iron [Fe(III)] to ferrous iron [Fe(II)] within the aquifer sediments. This is accomplished by injecting aqueous sodium dithionite into the aquifer and withdrawing the reaction products. The goal of the treatability test was to create a linear ISRMmore » barrier by injecting sodium dithionite into five wells. Well installation and site characterization activities began in the spring of 1997. The first dithionite injection took place in September 1997. The results of this first injection were monitored through the spring of 1998; the remaining four dithionite injections were carried out in May through July of 1998. These five injections created a reduced zone in the Hanford unconfined aquifer 150 feet in length (perpendicular to groundwater flow) by 50 feet wide. The reduced zone extended over the thickness of the unconfined zone, which is approximately 15 feet. Analysis of recent groundwater sampling events shows that the concentrations of chromate [Cr(VI)] in groundwater in the reduced zone have been decreased from starting concentrations of approximately 900 ppb to below analytical detection limits (<7 ppb). Chromate concentrations are also declining in some downgradient monitoring wells. Laboratory analysis of iron in the soil indicates that the barrier should remain in place for approximately 20 to 25 years. These measurements will be confirmed by analysis of sediment cores in FY 1999.« less

  • ; ; ; ...
    A treatability test was conducted for the In Situ Redox Manipulation (ISRM) technology at the 100 D Area of the U. S. Department of Energy's Hanford Site. The target contaminant was dissolved chromate in groundwater. The ISRM technology creates a permeable subsurface treatment zone to reduce mobile chromate in groundwater to an insoluble form. The ISRM permeable treatment zone is created by reducing ferric iron to ferrous iron within the aquifer sediments, which is accomplished by injecting aqueous sodium dithionite into the aquifer and then withdrawing the reaction products. The goal of the treatability test was to create a linearmore » ISRM barrier by injecting sodium dithionite into five wells. Well installation and site characterization activities began in spring 1997; the first dithionite injection took place in September 1997. The results of this first injection were monitored through the spring of 1998. The remaining four dithionite injections were carried out in May through July of 1998.These five injections created a reduced zone in the Hanford unconfined aquifer approximately 150 feet in length (perpendicular to groundwater flow) and 50 feet wide. The reduced zone extended over the thickness of the unconfined zone. Analysis of post-emplacement groundwater samples showed concentrations of chromate, in the reduced zone decreased from approximately 1.0 mg/L before the tests to below analytical detection limits (<0.007 mg/L). Chromate concentrations also declined in downgradient monitoring wells to as low as 0.020 mg/L. These data, in addition to results from pre-test reducible iron characterization, indicate the barrier should be effective for 20 to 25 years. The 100-D Area ISRM barrier is being expanded to a length of up to 2,300 ft to capture a larger portion of the chromate plume.« less

  • The U.S. Department of Energy (DOE) has committed to accelerate cleanup of contaminated groundwater along the Columbia River. The current treatment approach was driven by a series of Interim Action Records of Decision (IAROD) issued in the mid-1990s. Part of the approach for acceleration involves increasing the rate of groundwater extraction for the chromium plume north of the 100-D Reactor and injecting the treated water in strategic locations to hydraulically direct contaminated groundwater toward the extraction wells. The current treatment system uses ion exchange for Cr(VI) removal, with off-site regeneration of the ion exchange resins. Higher flow rates will increasemore » the cost and frequency of ion exchange resin regeneration; therefore, alternative technologies are being considered for treatment at high flow rates. One of these technologies, electrocoagulation (EC), was evaluated through a pilot-scale treatability test. The primary purpose of the treatability study was to determine the effectiveness of Cr(VI) removal and the robustness/implementability of an EC system. Secondary purposes of the study were to gather information about derivative wastes and to obtain data applicable to scaling the process from the treatability scale to full-scale. The treatability study work plan identified a performance objective and four operational objectives. The performance objective for the treatability study was to determine the efficiency (effectiveness) of hexavalent chromium removal from the groundwater, with a desired concentration of {le} 20 micrograms per liter ({micro}g/L) Cr(VI) in the effluent prior to re-injection. Influent and effluent total chromium and hexavalent chromium data were collected using a field test kit for multiple samples per week, and from off-site laboratory analysis of samples collected approximately monthly. These data met all data quality requirements. Two of three effluent chromium samples analyzed in the off-site (that is, fixed) laboratory met the performance objective during the continuous operational testing. Effluent hexavalent chromium analyzed by the field laboratory met the performance goal in over 90 percent of the samples. All effluent hexavalent chromium samples during the batch testing with high influent hexavalent chromium concentrations ({approx}2000 {micro}g/L) met the performance objective. Although the EC system was able to meet the performance goal, it must be noted that it was not uncommon for the system to be operated in recycle mode to achieve the performance goal. The EC unit was sometimes, but not always, capable of a single pass treatment efficiency high enough to meet the performance goal, and recycling water for multiple treatment passes was effective. An operational objective was to determine the volume and composition of the waste streams to enable proper waste designation. The toxicity characteristic leaching procedure (TCLP) concentrations, pH, and free liquids were determined for solid material from the EC electrodes (mechanically removed scale), the filter press, and the tank bottoms for the effluent and waste collector tanks. These data met all data quality requirements. All solid-phase secondary waste streams were found to be below the TCLP limits for the toxicity characteristic, and a pH value within the limits for the corrosivity characteristic. Out of three samples, two (one of scale from the EC unit and one from filter press solids) failed the free liquid (paint filter) test, which is one of the acceptability criteria for Hanford's Environmental Restoration Disposal Facility (ERDF). The solid-phase waste generation rate was about 0.65-gallon of solid waste per 100 gallons of water treated. It is concluded that the solid-phase secondary waste generated from this technology under the conditions at the test site will meet the toxicity and corrosivity criteria for disposal. It is also concluded that with engineering and/or operational improvements, a solid-phase secondary waste could be produced that would meet the free liquid disposal requirements. The second operational objective was to assess the operational reliability and safety of the system. For the continuous operations testing period from July 23 to September 12,2007, the system was not able to operate unattended. An extensive period of startup and adjustment preceded continuous operations, but was unsuccessful in providing a suitable and robust operating condition. Primary operational reliability problems were related to the sensitivity of the solid separation process to operational conditions such that a robust operating procedure (for example, chemical dosage) was not identified during the treatability test. Poor solids separation and high effluent iron concentrations also led to operational difficulties associated with injection well fouling.« less

  • ; ; ; ...
    This work plan supports a new, integrated approach to accelerate cleanup of chromium in the Hanford 100 Areas. This new approach will provide supplemental treatment upgradient of the ISRM barrier by directly treating chromium and other oxidizing species in groundwater (i.e., nitrate and dissolved oxygen), thereby increasing the longevity of the ISRM barrier and protecting the ecological receptors and human health at the river boundary.

  • ; ; ; ...
    Pacific Northwest National Laboratory conducted a treatability test designed to demonstrate that in situ biostimulation can be applied to help meet cleanup goals in the Hanford Site 100-D Area. In situ biostimulation has been extensively researched and applied for aquifer remediation over the last 20 years for various contaminants. In situ biostimulation, in the context of this project, is the process of amending an aquifer with a substrate that induces growth and/or activity of indigenous bacteria for the purpose of inducing a desired reaction. For application at the 100-D Area, the purpose of biostimulation is to induce reduction of chromate,more » nitrate, and oxygen to remove these compounds from the groundwater. The in situ biostimulation technology is intended to provide supplemental treatment upgradient of the In Situ Redox Manipulation (ISRM) barrier previously installed in the Hanford 100-D Area and thereby increase the longevity of the ISRM barrier. Substrates for the treatability test were selected to provide information about two general approaches for establishing and maintaining an in situ permeable reactive barrier based on biological reactions, i.e., a biobarrier. These approaches included 1) use of a soluble (miscible) substrate that is relatively easy to distribute over a large areal extent, is inexpensive, and is expected to have moderate longevity; and 2) use of an immiscible substrate that can be distributed over a reasonable areal extent at a moderate cost and is expected to have increased longevity.« less