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Arsenic
Chromium VI Dense Nonaqueous Phase Liquids (DNAPLs) 1,4-Dioxane Dioxins Mercury MTBE Perchlorate POPs PCBs TCE Other Contaminants
Treatment Technologies Roasting/retorting and incineration are thermal techniques and the most common techniques used for treating mercury-contaminated waste. Roasting/retorting operations separate the mercury from the rest of the waste stream and condense it for recovery or removal. Because the control of mercury emissions from incinerators is difficult, alternative technologies are sought that either recycle the mercury in the wastes, separate the mercury from the organics prior to incineration of the organics, or produce a stable residue for disposal that reduces the risks attributed to the organic and mercury constituents. The treatment approach depends on the type of waste being treated, and may require the use of a series of technologies. Mercury cannot be destroyed, so treaters have to rely on various methods to capture or recover it, depending on the mercury species present, its concentration, and the waste matrix or media involved. Selecting the appropriate treatment formula depends on the degree of organic destruction required prior to further mercury treatment, the degree of mercury speciation control required by the waste form, and other operating procedures to ensure mercury extraction. The final treatment step in non-thermal processes for mercury wastes generally involves either precipitation to produce a waste that can be retorted or immobilization prior to disposal. Chemical oxidation is applied to elemental mercury and organomercury compounds to destroy the organics and to convert mercury to a soluble form, such as HgCl2 or HgI2, which can then be separated from the waste matrix and treated. Oxidizing reagents used in these processes include sodium hypochlorite, ozone, hydrogen peroxide, chlorine dioxide, free chlorine (gas), and proprietary reagents. Chemical leaching is an aqueous process that depends on the ability of a leaching solution to solubilize mercury and remove it from the waste matrix. The solubilized mercury ideally partitions to the liquid phase, which is filtered off for further treatment (e.g., precipitation, ion exchange, carbon adsorption). This process can remove inorganic forms of mercury from inorganic waste matrices, but it is less effective for removing nonreactive elemental mercury unless the leaching formula is capable of ionizing mercury to an extractable form. Acid leaching is used most commonly to remove mercury from inorganic media. Chemical precipitation of mercury requires that the mercury be in an ionic state (e.g., Hg2+), which means that all organic content has been removed. Precipitation reagents include lye, caustic, sodium sulfide, and, to a lesser extent, soda ash, phosphate, and ferrous sulfide. Ion exchange resins have proven useful in removing mercury from aqueous media, particularly at concentrations on the order of 1 to 10 ppb. Ion exchange applications usually treat mercuric salts, such as mercuric chlorides. In other applications of resins, the resins can be cleaned (regenerated) and reused, but Hg is not readily removed; if a selective resin is used, the adsorption process is usually irreversible and the resin must be disposed of in a hazardous waste unit. Solidification/stabilization(S/S) processes are nondestructive methods to immobilize (encapsulate) the hazardous constituents in a matrix while decreasing the waste surface area and permeability. Conventional S/S agents include Type 1 Portland cement, lime, and fly ash, though more innovative forms also are available. The encapsulation process temperatures can volatilize mercury, so the mercury vapor and oxide that forms must be captured and recycled in the process. Amalgamation typically involves the mixing of elemental mercury with a powdered granular metal (typically zinc), forming a non-liquid, semi-solid matrix of elemental mercury and the metal. Other technologies being studied or developed for mercury remediation include thermal processes that mobilize the mercury for capture as vapor, electrokinetics, and phytoremediation. Adapted from:
"Potential Revisions to the Land Disposal Restrictions Mercury Treatment Standards"
The alternatives considered include chemical oxidation, chemical leaching, chemical precipitation, and ion exchange. Arsenic and Mercury, Workshop on Removal, Recovery, Treatment, and Disposal: Abstract Proceedings, Alexandria, Virginia, August 17-20, 1992 These proceedings also were published as Mercury and Arsenic Wastes, William Andrew Publishing, 1993.
Methods for treating aqueous mercury discussed in this report include activated carbon adsorption, precipitation, coagulation/co-precipitation, ion exchange, chemical reduction, membrane separation, as well as emerging technologies involving macrocycles adsorption, biological treatment, and membrane extraction.
This report describes the results of four vendor demonstrations of new mercury cleanup technologies: Brookhaven National Laboratory offered a sulfur polymer stabilization/solidification process; Nuclear Fuel Services (NFS) presented the DeHg (de-merk) stabilization process; Allied Technology Group introduced a chemical stabilization treatment; and SepraDyne-Raduce demonstrated a vacuum thermal desorption technology. Economic and Environmental Analysis of Technologies to Treat Mercury and Dispose in a Waste Containment Facility This analysis considers three treatment technologies that convert elemental mercury into a stable form of mercury. The report is restricted to the treatment and disposal or long-term storage of elemental mercury and does not consider the treatment and disposal of mercury-containing wastes or radioactive mercury.
This paper discusses the following remediation technologies: immobilization [containment (caps, vertical barriers, horizontal barriers), solidification/stabilization (cement-based, polymer microencapsulation), and vitrification]; and separation and concentration (soil washing, pyrometallurgy, and soil flushing). Use of treatment trains is addressed also.
This report presents results of a DOE-sponsored project carried out by Florida State University and the Institute for Ecology of Industrial Areas (IETU), Katowice, Poland. The IETU is evaluating several potential approaches for managing mercury contamination in soil. The technologies addressed in this manuscript include chemical/plant stabilization and volatilization.
This report reviews technologies for removing mercury from surfaces, water, and mixed wastes (solid media). Surface methods: strippable coatings, chemical cleaning with iodine/iodide lixiviant, chemisorbing surface wipes with forager sponge and grafted cotton, and surface/pore fixation through amalgamation or stabilization. In liquids: precipitation processes (sulfide precipitation, coagulation/co-precipitation), adsorption processes (e.g., activated carbon adsorption), ion exchange, chemical reduction, membrane separation, membrane extraction, Self-Assembled Mercaptan on Mesoporous Silica (SAMMS), and graft copolymer of acrylamide onto cellulose. In solid media: separation/removal (thermal treatment processes and chemical leaching), immobilization, stabilization, and amalgamation. Mercury Contaminated Sites: Characterization, Risk Assessment and Remediation Unlike other metals, which generally are not very volatile, mercury from contaminated sites can have a significant impact on remote ecosystems via the atmospheric pathway. This book summarizes work on mercury characterization, risk assessment and remediation from Europe, Russia, and the American continent. Technology review chapters are supplemented by detailed international case studies. Mercury in Buildings: Construction and Demolition Contractor's Guide to Dealing with Mercury in Buildings Much Ado about Mercury: Evaluation of Treatment Options for Mercury Contaminated Soil at BNL Oak Ridge Mercury Forum: Presentations Oak Ridge National Laboratory held a Mercury Forum in Knoxville, TN, in May 1999, in search of a viable solution to mercury contamination in soil at the Oak Ridge facility. Vendors presented PowerPoint overviews of 14 remediation technologies for mercury cleanup.
This report assists the remedy selection process by providing information on four in situ technologies for treating soil contaminated with metals: electrokinetic remediation, phytoremediation, soil flushing, and solidification/stabilization. Remediation Control Strategies and Cost Data for an Economic Analysis of a Mercury Total Maximum Daily Load in California A Total Maximum Daily Load (TMDL) value indicates a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and an allocation of that amount to the source(s) of the pollutant, such as a mine site. The purpose of the report is to illustrate the general costs associated with various remedial practices that are applicable to mercury sources in California. These costs encompass project development, environmental compliance, permit approval, cleanup approaches (including both conventional and innovative technologies), construction, and other transaction costs. Though the costs for remediation projects cited in the report are site-specific, methods for predicting costs through identification and assessment techniques are discussed. Removal of Mercury from Solids Using the Potassium Iodide/Iodine Leaching Process Treatment Technologies for Mercury in Soil, Waste, and Water This report contains information on the availability, performance, and cost of eight technologies for the treatment of mercury in soil, waste, and water. It describes the theory, design, and operation of the technologies; provides information on commercial availability and use; and includes site-specific data on performance and cost, where available. This information can help managers at sites with mercury-contaminated media and generators of mercury-contaminated waste and wastewater to:
The technologies for soil and waste that are included in the report are solidification and stabilization, soil washing and acid extraction, thermal treatment, and vitrification. Technologies for water include precipitation/coprecipitation, adsorption, membrane filtration, and biological treatment. The report also includes information on ongoing research on mercury treatment, including applications using nanotechnology, phytoremediation, air stripping, and in situ thermal desorption.
Phytoremediation of Toxic Metals: Using Plants to Clean Up the Environment
The phytoremediation project applied 0.5% granular sulfur and planted a site with meadow grass. The approach showed promise for stabilizing mercury contaminated soils in situ.
The soil washing process separates the contaminated feed soil into a coarse-grained fraction and a fine-grained fraction. Coarse soil with greater than or equal to 50 mg/kg Hg is crushed and treated in the vacuum-distillation process. Fine soil (< 2 mm) at Hg concentrations up to 5,000 mg/kg, is treated in the vacuum-distillation process, which heats the soil under a vacuum to volatilize and remove mercury. Mercury vapors removed from the vacuum-distillation unit enter a water-cooled multistep condenser unit that liquefies the vapors into elemental mercury. The treated fine soil fraction is mixed with any coarse soil fraction containing less than 50 mg/kg mercury and disposed of in a landfill.
This report describes the results of tests of stabilized mercury wastes undertaken to examine the consequences of mercury speciation on mercury release.
Stabilization and Testing of Mercury Containing Wastes: Borden Catalyst This report describes a demonstration of a technique to treat leachate with sulfide and phosphate binders. Stabilization and Testing of Mercury Containing Wastes: Borden Sludge This report details the stability assessment of a mercury-containing sulfide treatment sludge. Stabilization of Mercury in Waste Material from the Sulfur Bank Mercury Mine: Innovative Technology Evaluation Report Investigators examined the Silica Micro Encapsulation process developed by Klean Earth Environmental Company, an inorganic sulfide stabilization technology (ENTHRALL®) developed by E&C Williams, and a generic phosphate treatment.
A pilot-scale demonstration of the SPSS process for treatment of contaminated mixed-waste soils containing high concentrations (∼5,000 mg/L) of mercury and liquid elemental mercury was conducted at Brookhaven National Lab. SPSS chemically stabilizes the mercury to reduce vapor pressure and leachability and physically encapsulates the waste in a solid matrix to eliminate dispersion and provide long-term durability.
Encapsulation methods physically immobilize hazardous wastes to prevent contact with leaching agents such as water. This report summarizes the following methods: sulfur polymer stabilization/solidification and encapsulation by chemically bonded phosphate ceramic, polyethylene, asphalt, polyester resins, synthetic elastomers, polysiloxane, sol-gels (e.g., polycerams), and Dolocrete™.
SepraDyne™, through its subsidiary Raduce, has demonstrated a process for vacuum thermal desorption that can remove mercury from mixed wastes to levels below 10 ppm.
CLU-IN Site Profile Databases contain information on thousands of projects where innovative approaches have been used to deal with contamination problems. Completed North America Innovative Technology Demonstration Projects Lists field demonstrations of innovative remediation technologies sponsored by government agencies working in partnership with private technology developers. Cost and Performance Case Studies from the Federal Remediation Technologies Roundtable The FRTR Remediation Case Study Searchable Database provides capability to search all the case studies by keyword and category, including media/matrix, contaminant type, primary and supplemental technology type, specific site name, or state. Technology Innovation News Survey Archives |