Solid-chemical composition for sustained release of organic...

Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Destruction of hazardous or toxic waste

Reexamination Certificate

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C210S600000, C210S610000, C435S176000, C435S178000, C435S179000, C435S187000, C435S243000, C435S252500, C435S252700, C435S253300, C435S254220, C435S254300

Reexamination Certificate

active

06620611

ABSTRACT:

BACKGROUND—FIELD OF THE INVENTION
This invention discloses advanced solid-chemical compositions which provide balanced, sustained-release sources of soluble and insoluble organic substrates and complex inorganic phosphates, as well as other beneficial agents, which when used as intended, promote the bioremediation of contaminated environmental media. Specifically, the present invention was developed to provide a relatively simple and inexpensive means of enhancing the anaerobic bioremediation and dehalogenation of halogenated organic contaminants, such as trichloroethene (TCE), as well as the biologically mediated chemical reduction of oxidized forms of certain inorganic contaminants, such as chromium (VI), uranium (VI), and arsenate-based pesticides. Either alone or in combination with other liquid- and solid-chemical compositions, it is the inventor's belief that the present invention also has the potential for the remediation of the gasoline additive methyl tertiary butyl ether (MTBE).
The disclosed solid-chemical compositions of the present invention provide improved means for (1) creating, enhancing, and maintaining anaerobic if not anoxic conditions by facilitating the biologically mediated removal of the available oxygen from the media; and (2) creating and maintaining reducing conditions (i.e., negative Eh values) and near neutral to slightly acidic pH conditions (6≦pH≦8) which favor anaerobic, biologically mediated chemical-reduction reactions, e.g., the reductive dehalogenation of halogenated organic contaminants and the reduction of the oxidized forms of certain metals. The disclosed solid-chemical compositions also provide means for maintaining the aforementioned conditions for sufficiently long periods of time to enable the biologically mediated degradation, transformation, and/or detoxification reactions to proceed to the extent that the concentrations and/or toxicity of the contaminants are reduced to acceptable levels.
BACKGROUND—DESCRIPTION OF PRIOR ART
Soil and ground-water pollution caused by chemical contaminants released into the environment is a well documented, world-wide problem. Such chemical contamination is associated with many different types of industrial activities over the last two centuries. Common environmental contaminants include several different types and forms of petroleum hydrocarbons, halogenated organic compounds including solvents (e.g., tetra- and trichloroethene, methylene chloride), organochlorine pesticides (e.g., DDT and toxaphene), polychlorinated biphenyls (i.e., PCBs), and heavy metals and other inorganic contaminants such as cyanides. The available toxicological data indicates that many of these contaminants, in particular many of the halogenated organic compounds, are toxic, carcinogenic or potentially carcinogenic to humans, animals and other environmental receptors. In addition, the available environmental and ecological data have shown that many of these contaminants tend to persist in the environment for long time periods. The long-term stability and extremely slow degradation of many such environmental contaminants presents a substantial, long-term hazard to human health and the environment throughout the industrialized world.
Many of the so-called conventional methods for the remediation or clean-up of chemically contaminated wastes, waters, soils, and sediments have generally involved either the physical removal of the contaminated media or the simple mass transfer of the contaminants from one media (e.g., soil) to another (e.g., air). In general, such physical-treatment technologies do not involve the chemical and/or biological destruction, breakdown, transformation, or detoxification of the contaminants. Two of the most common categories of physical environmental-remediation technologies are the excavation and off-site disposal (or treatment) of contaminated soils and the pumping and subsequent treatment of contaminated ground water. The excavation of contaminated soils is often followed by their disposal in a landfill, which can pose a potential long-term risk to the environment, or their incineration, which may result in the release of air pollution. Many ground-water pump-and-treat processes involve the simple mass-transfer or “stripping” of the contaminants from the water into the air. Another common physical-treatment method involves the use of granular activated carbon (GAC) reactors to treat chemically contaminated waters. When contaminated water is passed through a GAC reactor, the contaminants are physically adsorbed onto the carbon particles, thereby producing another contaminated media which requires subsequent disposal and/or treatment. Each of these physical-treatment technologies share the same disadvantage—they do not reduce the actual amount or toxicity of the chemical contaminants, but rather they simply move the contamination from one place to another or from one media to another.
Another category of environmental-remediation technologies, termed bioremediation, involves the use of microorganisms to convert chemical compounds into innocuous or less harmful chemical compounds. Bioremediation technologies generally have lower costs associated with their use and implementation than do the competing physical technologies. Bioremediation technologies can also be adapted to a broader range of contamination problems and variations in field conditions than other types of remediation technologies.
The most promising bioremediation technologies provide the additional capability of treating contaminated media in-situ, i.e., in place, without the need for ground-water pumping or soil excavation. Current trends in bioremediation technology indicate that the most technically feasible and commercially successful bioremediation technologies are those which promote bioremediation processes mediated by indigenous or “native” contaminant-degrading bacteria, fungi and other microorganisms which are naturally present in the, contaminated media. The presence of naturally occurring, contaminant-degrading microorganisms in many different types of environmental media has been extensively documented in the scientific literature. There is an extensive body of prior-art literature and patents concerning various means of using both aerobic and anaerobic bioremediation processes, engineered bacteria, and the “bioaugmentation” of contaminated media with cultured microorganisms and fungi to promote the biodegradation of organic contaminants in water, soil, and industrial wastes. For example, it has been reported that native Alcaligenes spp., Pseudomonas spp., and Enterobacter spp. can degrade a number of pesticides and polychlorinated biphenyls (Nadeau et al., 1994,
Applied and Environmental Microbiology;
Aislabie et al., 1997, New Zealand
Journal of Agricultural Research;
Galli et al., 1992,
Pseudomonas: Molecular Biology and Biotechnology
). Recent trends in the art and literature acknowledge a growing understanding of the use of anaerobic biological processes in the treatment of many different types of contaminants that are otherwise recalcitrant under aerobic conditions. In particular, trends in the art reflect a growing understanding of the need and importance of achieving and maintaining anaerobic conditions and other factors which favor the biologically mediated chemical reduction, dehalogenation, biodegradation, transformation, and/or detoxification of recalcitrant organic and inorganic contaminants in the environment.
U.S. Pat. No. 6,066,772 to Hater et al. (to Waste Management, Inc. and International Technologies Corporation) discloses a two-step, biologically mediated process for converting hazardous explosives such as nitroaromatic and nitramine explosives in soil, resulting in soils free of explosive contaminants and their reduced derivatives. The anaerobic step involves mixing natural microorganisms and an oxidizable carbon source (e.g., dextrose, molasses, beet juice, potatoes, sweet potatoes, corn starch, potato starch) into the soil to produce reduced residues of the explosives. The second, aerobi

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