Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2000-11-22
2004-04-20
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S610000, C210S612000, C210S614000, C210S620000, C210S630000
Reexamination Certificate
active
06723242
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for processing organic chlorine compounds.
2. Related Background Art
There are cases where objects to be processed such as fly ash or main ash generated from waste incinerators, leachate from waste disposal facilities, suspended matters contained in the leachate, soils contaminated by inappropriately disposed wastes, and biological sludge subjected to leachate treatments contain a high concentration of hard-to-decompose organic chlorine compounds represented by dioxins. There are urgent social needs for eliminating or detoxifying the hard-to-decompose organic chlorine compounds. Recently, various methods for decomposing and processing materials containing such organic chlorine compounds have been proposed.
Among these methods, examples of physicochemical methods include high temperature incineration method, molten salt incineration method, active carbon adsorption method, gamma ray decomposition method, ozone decomposition method, wet type air oxidization method, catalyst incineration method, supercritical hydroxylation method, alkaline chemical decomposition method, alkaline catalyst decomposition method, thermal desorption method, and the like. On the other hand, as a biological method, Japanese Patent Application Laid-Open No. HEI 10-323646 and Japanese Patent Application Laid-Open No. HEI 10-257895 disclose methods using microorganisms having a lignin decomposing capability.
Also, literatures, e.g., Hiroyuki Nakagawa et al., “Bio-Remediation of Environment Contaminated with Aromatic Compounds,”
Water Purification and Liquid Wastes Treatment
, 39, 535-544 (1998), pp.539-540; Satoshi Takada, “Possibility of Decomposition of Dioxins by White-Rot Fungus,” the 23rd Lecture Meeting of Japan Society for Environmental Chemistry, Advanced Abstracts, 35-40 (1998); Tomohiko Ishiguro, “Decomposition and Elimination of Noxious Chemical Materials Such as Dioxins by Microorganisms,”
Journal of Water and Waste
, 33, 645-651 (1991); and the like generally describe methods using polychlorinated biphenyl (PCB) decomposing microorganisms, white-rot fungus, and the like. Further, a literature—C. Klimm et al.,
Chemosphere
, 37, 2003-2011 (1998)—reports an example of processing dioxins in a case where an object to be treated is kept under an anaerobic condition.
SUMMARY OF THE INVENTION
The inventors have studied the above-mentioned conventional methods and, as a result, have found the following problems. Namely:
(1) Conventional physicochemical methods often necessitate complicated, large-scale apparatus for fully decomposing organic chlorine compounds, such as dioxins, contained in the object to be processed. Among them, there are methods for which high temperature, high pressure, and the like are indispensable conditions. Therefore, if such methods are employed, then the processing tends to take time and labor, thereby raising the processing cost.
(2) Microorganisms employed in conventional biological methods tend to be hard to handle and collect. Also, there is a tendency that the kinds of dioxins fully decomposable thereby are limited, and the processing with a favorable stability and reproducibility is hard to carry out. As a result, the efficiency of decomposing dioxins may not always be sufficient.
(3) In the method in which the object to be processed is kept under an anaerobic condition, the effect of reducing dioxins with time cannot fully be obtained.
In view of such circumstances, it is an object of the present invention to provide a method and apparatus for processing organic chlorine compounds, which can decompose hard-to-decompose organic chlorine compounds such as dioxins by a treatment simpler than conventional ones, can remarkably improve the efficiency of decomposition, and can lower the processing cost.
For solving the above-mentioned problems, the inventors have repeated diligent studies, and have found that, if a specific microorganic body is caused to act on an object to be processed containing an organic chlorine compound such as a dioxin under a predetermined condition, the organic chlorine compound can be decomposed. Also, the inventors have found that the decomposing rate of organic chlorine compound can be enhanced if components inhibiting the decomposition of organic chlorine compound by the microorganic body are eliminated under a predetermined processing condition. The inventors have further repeated studies based on these findings, thereby accomplishing the present invention.
Namely, the method of processing an organic chlorine compound in accordance with the present invention is a method of decomposing and eliminating the organic chlorine compound in an object to be processed, the method comprising a biological treatment process of causing a first microorganic body capable of oxidizing reduced nitrogen to come into contact with the object to be processed, and biologically processing the object to be processed in a state containing the first microorganic body, so as to decompose the organic chlorine compound.
In such a method of processing an organic chlorine compound, if an aerobic treatment is carried out as the biological treatment, then a nitrifying reaction in which reduced nitrogen is oxidized by the first microorganic body is carried out. At this time, along with the nitrifying reaction, a reaction of decomposing the organic chlorine compound contained in the object to be processed proceeds, whereby the organic chlorine compound is decomposed, so as to turn into lower hydrocarbon, carbon dioxide, water, and the like.
Though the mechanism of decomposing the organic chlorine compound has not fully been elucidated, it is presumed that a conjugate reaction such as co-oxidation, for example, proceeds in an enzymatic reaction system in which an oxidase produced by the microorganic body involves, whereby the organic chlorine compound is oxidized and decomposed along with the oxidization (nitrification) of reduced nitrogen. However, the action is not restricted thereto. Such an enzymatic reaction does not necessitate severe reaction conditions such as high temperature and high pressure in particular, whereby hard-to-decompose organic chlorine compounds can be decomposed by very simple processing.
Preferably, a reduced nitrogen adding process for adding reduced nitrogen to the object to be processed is provided. As a consequence, an amount of reduced nitrogen sufficient for carrying out the aerobic treatment as the biological treatment can be supplied. Hence, the reaction of oxidizing reduced nitrogen by the first microorganic body and, consequently, the reaction of decomposing the organic chlorine compound can be caused to proceed reliably and sufficiently.
Thus, it is preferred that the biological treatment process comprises an aerobic treatment process of oxidizing reduced nitrogen contained in the object to be processed with the first microorganic body and decomposing the organic chlorine compound in an aerobic atmosphere. Here, as the first microorganic body, nitrite bacteria, nitrate bacteria, and the like which are easy to obtain and culture are preferably used. Examples of reduced nitrogen are those oxidized by such a first microorganic body, such as ammonium ion and urea, which may be originally contained in the object to be processed or be added thereto.
If the anaerobic treatment is carried out as the biological treatment, then the activity of first microorganic body for oxidizing reduced nitrogen tends to decrease. However, it has been verified that the organic chlorine compound in the object to be processed is favorably decomposed even in an anaerobic atmosphere in the state where the biological activity of the first microorganic body is maintained by way of a biologic treatment in an aerobic atmosphere (which may be the above-mentioned aerobic treatment process).
Though details of the mechanism of decomposing the organic chlorine compound have not been clear, it is presumed that, for example, an oxidase produced by the first microorganic bo
Inoue Isamu
Miki Kohei
Nishikawa Eiichi
Ohkata Masanobu
Satou Jirou
Arent Fox Kintner & Plotkin & Kahn, PLLC
Barry Chester T.
Sumitomo Heavy Industrie's, Ltd.
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