Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
1997-06-16
2001-02-13
Taylor, Dennis L. (Department: 3673)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
C405S128350
Reexamination Certificate
active
06186939
ABSTRACT:
BACKGROUND OF THE INVENTION
Leaching of heavy metal bearing wastes and direct discharges of heavy metal bearing waste waters has been of concern to environmental regulators, waste producers and various health officials since the 1970's. This concern resulted in the promulgation of the Resource Conservation and Recovery Act (RCRA) in 1979. Under RCRA, solid wastes may be considered hazardous if the waste leaches excessive heavy metals under the Toxicity Characteristic Leaching Procedure (TCLP) as set forth in the Federal Register, Vol. 55, No. 61 (Mar. 29, 1990) and which corresponds in pertinent part to the procedure set forth in the Federal Register, Vol. 55, No. 126, pp.26985-26998 (Jun. 29, 1990). In addition, there exist various states such as California, Michigan and Vermont which require additional leaching tests on solid waste in order to classify the waste and direct the more heavy metal leaching wastes to hazardous waste landfills.
In order to avoid having solid wastes be required to be handled at more expensive hazardous waste landfills, various researchers and solid waste businesses have investigated and developed methods to control the leaching of heavy metals, such as lead from the solid waste. The art has looked at the control of leaching by ex-situ methods involving portland cement, silicates, sulfates, phosphates and combinations thereof. See U.S. Pat. Nos. 4,629,509 (calcium sulfide); 4,726,710 (sodium sulfur oxide salt); the teachings of which are incorporated herein by reference in their entirety.
SUMMARY OF THE INVENTION
Existing heavy metal treatment processes are designed and operated in a post-waste production mode or remediation mode and thus ignore the advantages of adding stabilizing agents into the product stream prior to or during waste production. The invention is based upon the discovery that heavy metal in heavy metal bearing materials or wastes can be stabilized within a product stream or during waste production, such that the heavy metal does not leach from the waste under appropriate conditions known to cause leaching. The invention provides a method that effectively treats any heavy metal bearing material or waste by the use of stabilizing agents, such that the stabilized waste will resist the leaching of heavy metals such as, but not limited to copper, zinc, lead and cadmium.
The invention can be used for in-line heavy metal stabilization which allows for hazardous and solid waste treatment without the need for any post-waste production mixing device, yet permits the treated material or waste to remain free flowing. The stabilizing agent(s) can be added directly to the material prior to its generation as a waste which must then be classified pursuant to RCRA. An advantage of this process is the elimination of the need to treat the waste as a hazardous waste under RCRA. Hazardous waste treatment permitting can also be obviated. Furthermore, the USEPA requires that hazardous wastes be “treated in an enclosed form” prior to collection of wastes if one wishes to be exempt from permitting requirements.
The invention is particularly useful for pre-waste stabilization. This involves the injection of particulate water insoluble or water soluble precipitants, flocculants, coagulants and/or mineral salts directly into the processing lines of auto-shredders, wire stripper and wire-chopping systems such that the first generation point of fines, dust, waste, fluff and/or plastics have been seeded with such stabilizing agents and thus the produced waste will pass TCLP criteria and thus be exempt from RCRA Part B permitting.
The method can also be used for stabilizing heavy metal in a paint containing the same. A stabilizing agent or combination of stabilizing agents described herein is (are) applied onto a painted surface before the paint is removed from the surface by methods such as grit blasting or scraping. The advantage of the pre-waste stabilizer additive here is that the collection of the heavy metal bearing waste will not be as necessary for environmental and/or TCLP waste handling reasons, and upon any such collection the grit and paint products will have been seeded thus requiring no RCRA permitting for hazardous waste treatment or handling.
The invention provides a method of TCLP leaching criteria and/or other relevant leaching tests in order to characterize the waste as non-hazardous and/or to reduce the solubility of the heavy metal bearing waste to a point considered suitable by the appropriate local, state and/or federal leaching criteria.
DETAILED DESCRIPTION OF THE INVENTION
One of the most costly environmental tasks facing industry in the 1990's will be the clean-up and treatment of heavy metal bearing wastes, both solid and hazardous, at old dump sites, storage areas and retention areas and at existing waste generation sites, such as process facilities or incinerators throughout the world. Depending on the specific state and federal regulations, those wastes will be classified as either solid, special or hazardous. The management options for the waste producer vary greatly depending upon the waste classification and the regulatory requirements associated with that classification. The most stringent waste classification is that of hazardous.
There exist various methods of stabilizing and solidifying heavy metal bearing hazardous wastes. The most common method, using portland cement for physical solidification, is common knowledge in the environmental engineering field. There exist several patented processes for hazardous waste treatment such as using carbonates, polysilicates, phosphates and versions of portland cement. These patented methods and the use of portland cement all recognize the need to control chemistry and provide for mixing of the waste and the treatment chemicals in order to control heavy metal solubility, as tested by the TCLP Federal acetic acid leaching test, by either precipitation of the heavy metal into a less soluble compound or the physical encapsulation of the waste and surface area reduction.
Wastes subject to regulation are usually tested via the USEPA TCLP extraction method. The TCLP extraction method is referred to by the USEPA SW-846 Manual on how to sample, prepare and analyze wastes for hazardousness determination, as directed by the Resource Conservation and Recovery Act (RCRA). The TCLP test by definition assumes that the waste of concern is exposed to leachate from an uncovered trash landfill cell, thus the TCLP procedure calls for the extraction of the waste with a dilute acetic acid solution which simulates co-disposal with decaying solid waste.
Previous hazardous waste treatment processes for reducing the leachability of heavy metal bearing wastes have failed to consider the use of pre-waste stabilizer seeding. Prior methods failed to exploit using the TCLP extractor as a miniature Continuous Flow Stirred Tank Reactor (CFSTR) in which complex solubility, adsorption, substitution, exchange and precipitation can occur as well as macroparticle formations. The invention presented herein utilizes the TCLP, WET and/or distilled leaching (DI) extractor as a continuous stirred tank reactor similar to that used in the wastewater industry for formation of flocculants, coagulants and precipitant reactions. See Metcalf & Eddy, 2nd Ed., McGraw Hill, “Waste Water Engineering Treatment/Disposal/Reuse”, 1979. In addition, the invention presented herein utilizes post-extraction filtration with 0.45 micron filters as the method of formed particle capture and removal similar to that conducted by rapid sand filtrators used with the wastewater and water treatment fields. Existing heavy metal treatment processes are designed and operated relying upon a post-waste production treatment. However, these approaches ignore the regulatory, processing, handling and permitting advantages of combining stabilizing agents such as retaining matrices, coagulants and precipitants with the material to be wasted prior to such waste activity.
The invention relates to the pre-waste production stabilization of heavy metal bearing
Hamilton, Brook, Smith and Reynolds, P.C.
Taylor Dennis L.
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