Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Destruction of hazardous or toxic waste
Reexamination Certificate
1999-04-28
2001-07-31
Beisner, William H. (Department: 1744)
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Destruction of hazardous or toxic waste
C405S128350, C588S253000, C210S631000, C210S759000, C210S747300
Reexamination Certificate
active
06268205
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of treating underground carbon-based contaminants using an injected fluid.
BACKGROUND OF THE INVENTION
Metallic peroxide compounds have been formulated for the purpose of releasing oxygen in situ to support biodegradation of contaminants. U.S. Pat. No. 5,264,018 issued Nov. 23, 1993 to Koenigsberg, et al. describes the use of magnesium peroxide in soils as an oxygen releasing compound. Such material is described in (U.S. Pat. No. 5,395,419 issued Jan. 14, 1993 to Koenigsberg, et al.) as being an oxygen liberating compound for the enhancement of aerobic microbes in the biodegradation of waste materials and as a Therapeutic and Preventative Treatment of Anaerobic Plant and Soil Conditions.
FMC Corporation has sold a product trademarked “Permeox” which includes Calcium Peroxide. This product is marketed as an “oxygen source” for bioremediation. FMC points out in their literature that the intermediate step for oxygen generation is the formation of hydrogen peroxide. This reaction is as follows:
CaO
2
+2H
2
0Ca(OH)
2
+H
2
0
2
The second stage of the reaction which liberates molecular oxygen is as follows:
2H
2
0
2
O
2
+2H
2
0
Numerous papers have been written on the benefits of using oxygen releasing materials on aerobic bacterial degradation processes. Examples of these are: Jane L. Vernalia, 1977, “Bioremediation of Pentachlorophenol in Soil Under Anaerobic and Aerobic Conditions”
ORC Oracle
, vol. 1, no. 4; Michael A. Heitkamp, 1997, “Effects of Oxygen-Releasing Materials on Aerobic Bacterial degradation Processes”,
Bioremediation Journal I
(2):105-114 (1997); Bianchi-Mosquera, G. C., R. M. Allen-King, and D. M. Mackay, 1994, “Enhanced Degradation of Dissolved Benzene and Toluene Using a Solid Oxygen-releasing Compound”
Ground Water Monitoring Rem
. 14 (1):120-128; and Vesper, S. J., L. C. Jurdoch, S. Hayes, and W. J. Davis-Hoover, 1994, “Solid Oxygen Source for Bioremediation in Subsurface Soils”,
J. Hazard Materials
, 36:265-274.
The use of hydrogen peroxide with iron as a co-reagent, was first reported by the English chemist, Dr. H. J. H. Fenton in 1894. Research has been conducted and reported describing Fenton's chemistry which is based on the production of the hydroxyl and perhydroxyl radicals from hydrogen peroxide. See for example: Richard J. Watts, Matthew D. Udell, and Robert M. Monsen, 1992, “Use of Iron Minerals in Optimizing the Peroxide Treatment of Contaminated Soils”,
Water Environment Research
, 65(7):839-844 and Richard J. Bigda, 1996, “Fentons Chemistry: An Effective Advanced Oxidation Process”,
Environmental Technology
. May-June 1996:34-39. These highly reactive compounds rapidly oxidize carbonaceous materials.
However, hydrogen peroxide is relatively unstable, potentially unsafe and typically does not survive in the subsurface long enough to be effective or practical as either an oxygen supplement or as an oxidizing reagent. In addition, the technical difficulties involved in delivering hydrogen peroxide to the contaminated media have limited its use. Hydrogen peroxide is also toxic to microorganisms in higher concentrations.
It has been reported by Bryan W. Tyre, Richard J. Watts, and Glen C. Miller, 1991, “Treatment of Four Biorefractory Contaminants in Soils Using Catalyzed Hydrogen Peroxide”, J. of
Environmental Quality
20:832-838, that bio-refractory organic pollutants such as chlorinated compounds can be oxidized using catalyzed hydrogen peroxide (Fenton's reagent). These materials, along with certain hydrocarbons, present a challenge to biodegradation because of the lack of reactive sites on the molecules.
Traditional remedial technologies such as a simple pumping and treating of groundwater, vacuum extraction of volatile organic compounds, thermal treatment of contaminated soil or excavation and landfilling of contaminated soil are typically costly, disruptive to normal site activities and may only transfer contaminants to another location or convert them to another form.
While these techniques and systems have advantages in some circumstances, they all suffer from economical, technical or time drawbacks. That is, they are either quite expensive to carry out and disruptive of the site, or they are technically limited by the site hydrology and the nature of the contaminant, or they take a very long time to be effective. There thus exists a need for an economical method that is less disruptive to site activities, less restricted by site hydrology, contaminant type and concentration and still achieve substantial results within a reasonable period of time.
Although in situ bioremediation is becoming increasingly popular as a remedial technology, this process is typically slow and may be inhibited by high contaminant concentrations or the presence of free phase contaminants. In addition, many organic contaminants are biorefractory and, therefore, resistant to biodegradation. The technical difficulties involved in delivering nutrients and oxygen supplements such as metallic peroxide into the subsurface media has also restricted the effectiveness of in situ bioremediation.
SUMMARY OF THE INVENTION
In overcoming one or more of the drawbacks of the prior art, the present invention provides a method of treating organic contaminants in soil and/or groundwater.
Soil and/or groundwater contaminated with organic pollutants are decontaminated in accordance with the present invention by a two stage process. The first stage involves the in situ generation of hydrogen peroxide on a desired, time-released basis which reacts with natural and/or introduced co-reagents to produce hydroxyl and perhydroxyl radicals which act as powerful oxidizing agents to oxidize a wide variety of organic contaminants. Complete oxidization of organic contaminants results in carbon dioxide and water as the end products. Any remaining intermediate byproducts are more easily mineralized by intrinsic biodegradation processes.
The inventors have determined that significant oxidative activities occur with the present invention at a pH range of approximately 6 to 9, which is the range typically encountered in the subsurface media. This is also the optimum pH range for microbial activity. The oxidative reaction potentially occurs for the site-specific life of the formulation dependant upon availability of co-reagents (such as iron salts) and the availability of carbonaceous material. If a co-reagent or a carbon source is not available, the hydrogen peroxide will eventually decompose to produce oxygen. Although oxidative chemistry is not necessarily selective in the destruction of organic compounds, the inventors have determined that, unless the composition is over-applied, the controlled generation of hydrogen peroxide, and subsequently, free radicals over a longer period of time prevents significant negative impact to the indigenous microbial community. In the event of over-application the microbial community will quickly re-establish itself due to the resulting oxygen and nutrient enriched environment.
The second stage of this process involves enhancing intrinsic biodegradation processes. Once the initial oxidation phase is completed, the composition continues to produce molecular oxygen on a timed-release basis, dependant upon site chemistry, formulation and dosage rate. The oxygen enriched environment and the presence of less biorefractory carbon sources from incomplete oxidation have been observed to increase total heterotrophic plate counts and the number and quality of indigenous contaminant degraders.
This invention includes the application of an on-site mixture with water of a novel formulation, finely powdered, and the subsurface injection of the fluid. The formulation is a blend of environmentally safe compounds formulated to provide a timed-release (over a relatively short period) of hydroxyl radicals and perhydroxyl radicals to relatively quickly oxidize a variety of organic contaminants and to subsequently provide residual and timed-release (over a relatively long period) molecular ox
Kiest John L.
Trezzo Jerrold A.
Beisner William H.
Biomanagement Services, Inc.
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