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Treatment of environmental contaminantsRelated Patent Categories: Hydraulic And Earth Engineering, Soil Remediation, With Treatment, ChemicalTreatment of environmental contaminants description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070189855, Treatment of environmental contaminants. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application claims the benefit of U.S. Provisional Application No. 60/491,007, filed Jul. 29, 2003. FIELD OF THE INVENTION [0002] The present invention relates to the in situ and ex situ oxidation of organic compounds in soils, groundwater, process water and wastewater and especially relates to the in situ oxidation of volatile and semi-volatile organic compounds, pesticides and other recalcitrant organic compounds in soil and groundwater. BACKGROUND OF THE INVENTION [0003] The presence of volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), pesticides, polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) in subsurface soils and groundwater is a well-documented and extensive problem in industrialized and industrializing countries. Notable among these are the volatile organic compounds or VOCs which include any at least slightly water soluble chemical compound of carbon, with a Henry's Law Constant greater than 10.sup.-7 atm m.sup.3/mole, which is toxic or carcinogenic, is capable of moving through the soil under the influence of gravity and serving as a source of water contamination by dissolution into water passing through the contaminated soil due to its solubility, including, but not limited to, chlorinated solvents such as trichloroethylene (TCE), vinyl chloride, tetrachloroethylene (PCE), methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane (TCA), 1,1-dichloroethane, 1,1-dichloroethene, carbon tetrachloride, benzene, chloroform, chlorobenzenes, and other compounds such as ethylene dibromide, and methyl tertiary butyl ether. [0004] In many cases discharge of VOCs and other contaminants into the soil leads to contamination of aquifers resulting in potential public health impacts and degradation of groundwater resources for future use. Treatment and remediation of soils contaminated with VOCs and other organic contaminants have been expensive, require considerable time, and in many cases are incomplete or unsuccessful. Treatment and remediation of compounds that are either partially or completely immiscible with water (i.e., Non Aqueous Phase Liquids or NAPLs) have been particularly difficult. Also treatment of highly soluble but biologically stable organic contaminants such as MTBE and 1,4-dioxane are also quite difficult with conventional remediation technologies. This is particularly true if these compounds are not significantly naturally degraded, either chemically or biologically, in soil environments. NAPLs present in the subsurface can be toxic to humans and other organisms and can slowly release dissolved aqueous or gas phase volatile organic compounds to the groundwater resulting in long-term (i.e., decades or longer) sources of chemical contamination of the subsurface. In many cases subsurface groundwater contaminant plumes may extend hundreds to thousands of feet from the source of the chemicals resulting in extensive contamination of the subsurface. These chemicals may then be transported into drinking water sources, lakes, rivers, and even basements of homes through volatilization from groundwater. [0005] The U.S. Environmental Protection Agency (USEPA) has established maximum concentration limits for various hazardous compounds. Very low and stringent drinking water limits have been placed on many halogenated organic compounds. For example, the maximum concentration limits for solvents such as trichloroethylene, tetrachloroethylene, and carbon tetrachloride have been established at 5 .mu.g/L, while the maximum concentration limits for chlorobenzenes, polychlorinated biphenyls (PCBs), and ethylene dibromide have been established by the USEPA at 100.mu.g/L, 0.5.mu./L, and 0.05.mu.g/L, respectively. Meeting these cleanup criteria is difficult, time consuming, costly, and often virtually impossible using existing technologies. [0006] Many methods exist for the remediation of soil, groundwater and wastewater to meet the clean-up standards. Examples include dig-and-haul, pump-and-treat, biodegradation, sparging, and vapor extraction. However, meeting stringent clean-up standards is often costly, time-consuming, and often ineffective for many compounds that are recalcitrant--i.e. not responsive to such treatment. [0007] Chemical oxidation, either applied in situ or ex situ of the subsurface or waste stream, is an approach to treat contaminants with strong oxidizing chemicals, with the ultimate goal of complete mineralization, or conversion to carbon dioxide and water. Examples of oxidants that have been utilized for this purpose include Fenton's chemistry (activated hydrogen peroxide), permanganate and ozone. Persulfates, and in particular sodium persulfate, have more recently been suggested for use in environmental remediation through chemical oxidation. [0008] The use of hydrogen peroxide, and in particular metal-activated hydrogen peroxide (Fenton's chemistry) has been employed in the field application of chemical oxidation remediation over the past decade. Metals and chelated metals have been utilized to generate hydroxy radicals, which are capable of destroying a wide range of contaminants. However, there is significant demand on the hydrogen peoxide form nascent organics in the soil or groundwater, and from reduced metals. Thus, a significant amount of the hydrogen peroxide is expended on non-critical reaction pathways. In addition, transportation of the metal activators within the environmental medium is a key technological factor in the efficient use of hydrogen peroxide as an oxidant. Also, there is little data demonstrating that Fenton's chemistry is effective against highly recalcitrant contaminants. SUMMARY OF THE INVENTION [0009] The present invention relates to a method for the treatment of contaminated soil, sediment, clay, rock, and the like containing organic contaminants, as well as the treatment of groundwater, process water or wastewater containing organic contaminants. [0010] The method of the present invention uses a combination of water soluble oxidants, namely a persulfate and hydrogen peroxide. The combination is introduced into soil or water in amounts, under conditions and in a manner which assures that the oxidizing compounds are able to contact and oxidize most, and preferably substantially all, the target contaminants rendering the target contaminants harmless. [0011] In a preferred embodiment the composition of the present invention is introduced into soil in sufficient quantities to satisfy the soil oxidant demand and to oxidize the target contaminants and render them harmless. This methodology may also be used ex situ to treat quantities of contaminated soil which have been removed from the ground. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0012] In accordance with the present invention it has been found that a broad range of contaminants in an environmental medium can be effectively reduced or removed by treatment with a composition comprising a persulfate and hydrogen peroxide. Further improvements have been found when an activator is included in the composition. [0013] Contaminants susceptible to treatment by the compositions of the present invention include: volatile organic compounds (VOCs); semi volatile organic compounds (SVOCs); polychlorinated biphenyls (PCBs); polyaromatic hydrocarbons (PHHs); total petroleum hydrocarbons (TPHs) including benzene, toluene, xylene and ethylbenzene; methyl t-butyl ether (MTBE); brominated solvents; 1,4-dioxane; and pesticides (insecticides, herbicides, etc.). [0014] In accordance with the method of the present invention the contaminants are treated in an environmental medium. As used herein "environmental medium" refers to an environment where contaminants are found including, without limitation, soil, rock, groundwater, contaminated plumes, process water, waste water and the like. [0015] The process of the present invention may be carried out in situ or ex situ. In situ treatment is conducted in the physical environment where the contaminant(s) are found. [0016] Ex situ treatment involves removal of the contaminated medium from the location where it is found and treatment at a different location. [0017] In accordance with one embodiment of the present invention, the oxidation of volatile organic compounds at a contaminated site is accomplished by the injection of a combination of a persulfate and hydrogen peroxide into soil. [0018] In a preferred form of the invention, sodium persulfate (Na.sub.2S.sub.2O.sub.8) is introduced into contaminated soil along with hydrogen peroxide. [0019] For in situ soil treatment, injection rates must be chosen based upon the hydro geologic conditions, that is, the ability of the oxidizing solution to displace, mix and disperse with existing groundwater and move through the soil. Additionally, injection rates must be sufficient to satisfy the soil oxidant demand and chemical oxidant demand in a realistic time frame. It is advantageous to clean up sites in both a cost effective and timely manner. Careful evaluation of site parameters is crucial. It is well known that soil permeability may change rapidly both as a function of depth and lateral dimension. Therefore, injection well locations are also site specific. Proper application of any remediation technology depends upon knowledge of the subsurface conditions, both chemical and physical, and this process is not different in that respect. [0020] While sodium persulfate is the preferred persulfate compound for oxidizing the contaminants, other solid phase water soluble persulfate compounds can be used. These include monopersulfates and dipersulfates. Dipersulfates are preferred because they are inexpensive and survive for long periods in the groundwater saturated soil under typical site conditions. Continue reading about Treatment of environmental contaminants... 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