JPH08117358A - Method for decomposing polyclorinated biphfenyl - Google Patents

Abstract

PURPOSE: To provide a method for decomposing polyclorinated biphenyl that is safe and efficient, and allows decomposed substances to be easily dumped. CONSTITUTION: In the decomposition of polyclorinated biphenyl group, a polyclorinated biphenyl in a fluid to be processed is decomposed using a chemical decomposition process, and a dechlorination reaction is stopped at a point when all amount of a high-chlorinated polyclorinated biphenyl to be processed is dechlorinated to be a low chlorinated polyclorinated biphenyl group with mono-, di- or trichloride and the low chlorinated polyclorinated biphenyl group with mono-, di- or trichloride is decomposed using microorganism. To perform a microorganism decomposition, a product or a fractional distillation at 150 to 350 deg.C of the product resulted from a chemical decomposition process and a water solution containing nutrient salts and polyclorinated biphenyl group decomposing fungus are mixed under aerobic condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing polychlorinated biphenyls, and in particular, dechlorinating polychlorinated biphenyls by a chemical decomposing method to reduce chlorine and then decomposing and detoxifying by microorganisms. The present invention relates to a method for decomposing polychlorinated biphenyls.

[0002]

2. Description of the Related Art Halogenated organic compounds such as PCBs (polychlorinated biphenyls), dioxins and halogenated pesticides have become a serious problem as environmental pollutants. In particular, because PCB has excellent insulation and is flame retardant,
Mainly produced in large quantities as an electrical insulating oil and widely used, PCBs released into the environment have been found to accumulate in the human body and exhibit strong toxicity such as liver damage, and production and new use are prohibited. ing. PCB is difficult to dispose because it is difficult to decompose, and various disposal methods have been studied. For example, various treatment methods such as a high temperature combustion method, a microbial decomposition method, and a chemical decomposition method have been proposed.

As a chemical decomposition treatment method, for example, a high boiling point oil is used as a solvent and a hydrogen donor, and a halogenated organic compound is reductively dehalogenated to render it harmless (International Patent Application No. PCT / US / 01112 and Japanese Patent Application No. 6-39332). When treating highly chlorinated PCBs by these methods, the highly chlorinated PCBs are decomposed in a short time and the residual PCBs are also dechlorinated to trichlorinated PCBs at a temperature lower than that of the high temperature combustion method. There is a feature called. However, the residual PCB concentration decreases exponentially with the reaction time as in the normal chemical reaction. Therefore, in order to completely dechlorinate and decompose the remaining trichlorinated PCB, the first high chlorination There is a problem in that much processing time and energy are required, which is more than the time and energy required for the PCB to be decomposed and the residual PCB to be dechlorinated to the trichlorinated PCB.

On the other hand, it is known that PCBs released into the environment are gradually decomposed by microorganisms.
Many kinds of bacteria and actinomycetes have already been isolated as microorganisms that decompose lactic acid. Many of these PCB-degrading microorganisms
Under aerobic conditions, it is possible to easily decompose low chlorinated PCBs with trichlorination or lower, but the degradability of PCBs with 4 chlorination or higher is poor, and the number of bacteria capable of degrading pentachlorinated PCBs is extremely limited. Confirmed to be a type of bacteria (App
l. Environ. Microbiol., 35, 223, 1978, Basic Life
Sci., 45, 253, 1988).

This is supported by the fact that almost no mono- or di-chlorinated PCBs are detected in the natural world and the frequency of detection of relatively highly chlorinated PCBs is high. In the natural environment,
It is known that highly chlorinated PCBs are gradually dechlorinated by microorganisms under anaerobic conditions, but these anaerobic microorganisms have not yet been isolated. As described above, in general, highly chlorinated PCB is difficult to be decomposed by microorganisms and high concentration of P
Since CB cannot be decomposed, a microbial decomposition method has not hitherto been studied as a method for decomposing PCB.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and combines a microbial decomposition treatment method with a chemical decomposition treatment method to provide excellent safety and efficiency, and a decomposition-treated product. An object of the present invention is to provide a method for disassembling a PCB that can be easily disposed of.

[0007]

In order to solve the above-mentioned problems, in the present invention, in a method for decomposing polychlorinated biphenyls, a dechlorination reaction by a chemical decomposition treatment method for polychlorinated biphenyls to be treated is performed. When the total amount of treated high chlorinated polychlorinated biphenyls was reduced to 3 chlorine or less to low chlorinated polychlorinated biphenyls, it was stopped and produced.
It biodegrades chlorinated polychlorinated biphenyls below chlorination. Thus, in the present invention,
The dechlorination reaction of the chemical decomposition treatment method is stopped when the total amount of highly chlorinated PCBs to be treated has been dechlorinated to a low chlorinated PCB of 3 chlorination or less, and the generated low chlorination of 3 chlorination or less is chlorinated. This is a method for decomposing PCB, which is characterized by biodegrading PCB. The chemical decomposition treatment method used in the present invention includes dehalogenation by a chemical reaction,
Any method can be applied as long as it can decompose and detoxify the harmful halogenated organic compound.

Specific examples of the chemical decomposition treatment method include a hydrogenation method in which hydrogen is added for dehalogenation in the presence of a noble metal catalyst, a metal sodium method in which reductive dehalogenation is performed with metal sodium, and polyethylene. There is a KPEG method in which glycol and potassium hydroxide are added to reductively dehalogenate. Particularly preferably, a high boiling point oil is used as a solvent and a hydrogen donor to reductively dehalogenate a halogenated organic compound. To make it harmless (International Patent Application No. PCT / US / 01112 and Japanese Patent Application No. 6-3933)
No. 2) can be applied. In the present invention, the dechlorination reaction of these chemical decomposition treatment methods is stopped when the total amount of harmful polychlorinated biphenyls is dechlorinated into low-chlorinated polychlorinated biphenyls having a trichlorination or less, and 4 chlorine is added. After it is confirmed that the above-described compound does not exist, it can be subjected to a microbial decomposition method.

In the present invention, as a microorganism for decomposing low chlorinated PCBs having a trichlorination or less produced by dechlorinating harmful PCBs by a chemical decomposition treatment method, a low chlorination PCB having a trichlorination or less is preferable. Any microorganism can be used as long as it can be decomposed aerobically. Microorganisms capable of aerobically decomposing low-chlorinated PCBs with a trichlorination or less include a group of microorganisms having a biphenyl degrading enzyme, for example, Achromobacter, Pseudomonas, Aeromonas, Micrococcus, Acinetobacter, Vibrio. , Bacteria of the genus Alcaligenes, genus Bacillus, genus Klebsiella, etc., but particularly preferably bacteria of the genus Achromobacter, genus Pseudomonas, genus Aeromonas, genus Alcaligenes can be applied. In addition, genes involved in PCB degradation (Appl. Microbiol. Biotechnol. 2
9, 363, 1988) can also be used.

These microorganisms aerobically decompose low chlorinated PCBs having a trichlorination or less to produce benzoic acid chloride as a final product. The benzoic acid chloride is subjected to ordinary organic wastewater treatment. It can be easily decomposed by microorganisms present in activated sludge. Further, since these microorganisms have a biphenyl degrading enzyme, they decompose biphenyl and produce benzoic acid that is easily degraded by ordinary microorganisms. In the present invention, low chlorinated P of 3 chlorination or less
The CB-containing product of chemical decomposition of PCB is directly mixed with an aqueous solution containing nutrients and PCB-decomposing bacteria and reacted under aerobic conditions to allow microbial decomposition. When the chemical decomposition product is contained in the high boiling point oil, the high boiling point oil concentration is 30% as a concentration mixed with an aqueous solution containing nutrient salts and PCB degrading bacteria.
Below, low chlorinated PCB concentration of less than 3 chlorination is 500 mg
/ L or less is desirable.

Further, in the present invention, a chemical decomposition treatment product of PCB containing a low chlorinated PCB having a trichlorination or lower is fractionally distilled, and a low chlorinated PCB having a trichlorination or lower is boiling point 150.
After concentrating in a condensate at ˜350 ° C., the concentrate can be mixed with an aqueous solution containing nutrient salts and PCB-decomposing bacteria and reacted under aerobic conditions to effect microbial decomposition. As a result, when the chemical decomposition product is contained in the high boiling point oil, the capacity of the high boiling point oil used for microbial decomposition can be significantly reduced, and the remaining high boiling point oil is used as fuel or the like. Can be used for. In the step of microbial decomposition, the concentration of a mixture of an aqueous solution containing nutrients and PCB-decomposing bacteria is set to a low chlorination P of 3 chlorination or less.
It is desirable that the CB concentration is 500 mg / l or less.

As described above, in the present invention, the dechlorination reaction of the chemical decomposition treatment method is performed at the time when the total amount of the highly chlorinated PCB to be treated is dechlorinated to the low chlorinated PCB having 3 or less chlorinations. By stopping and microbially decomposing the produced low chlorinated PCB having 3 or less chlorination, harmful highly chlorinated PCB can be efficiently decomposed. Further, biphenyl, which is a dechlorinated compound of PCB that is considered to be produced in the chemical decomposition treatment method, is harmful in itself, but in the present invention, biphenyl can be decomposed by the PCB-degrading microorganisms. It is also possible to easily dispose of decomposition products.

[0013]

EXAMPLES The present invention will be specifically described below with reference to Reference Examples and Examples, but the present invention is not limited to these. Reference Example 1 Chemical Decomposition Treatment of PCB To 150 ml of mineral oil in which PCB containing 3 chloride as a main component was dissolved at a concentration of 50 g / l, 20 g of sodium hydroxide and 1.5 g of amorphous carbon powder were added, and the mixture was placed under a nitrogen atmosphere at 330 ~
The mixture was heated and stirred at 350 ° C., and the concentration and composition ratio of the residual PCB were examined at regular intervals. The results are shown in Table 1. Highly chlorinated P
CB was decomposed to 0.05 mg / l after 6 hours.

[0014]

[Table 1]

Reference Example 2 Chemical Decomposition Treatment of PCB To 12 ml of sodium hydroxide and 1.5 g of amorphous carbon powder was added to 150 ml of mineral oil in which PCB containing tetrachloride as a main component was dissolved at a concentration of 50 g / l, and nitrogen atmosphere was added. Bottom 320-3
The mixture was heated and stirred at 40 ° C., and the concentration and composition ratio of residual PCB were examined at regular intervals. Table 2 shows the results. Highly chlorinated PC
Since B was decomposed to 1.0 mg / l after 6 hours, the reaction was stopped.

[0016]

[Table 2]

Example 1 Microbial Degradation of Low Chlorinated PCB To 150 ml of mineral oil in which PCB containing trichloride as a main component was dissolved at a concentration of 50 g / l, 20 g of sodium hydroxide and 1.5 g of amorphous carbon powder were added, and used as a reference. In the same manner as in Example 1, the mixture was heated and stirred at 330 to 350 ° C under a nitrogen atmosphere, and the reaction was stopped after 2 hours. As shown in Table 1, 1
And dichlorinated PCB were contained at about 500 mg / l, and highly chlorinated PCB having trichlorination or higher was not contained. 20 ml of the reaction-treated oil was mixed with 80 ml of a Pseudomonas culture solution having a PCB decomposing ability separated from soil,
C., and cultivated under aerobic conditions. After 24 hours, the initial concentration is about 1
It was confirmed that PCB of 00 mg / l was decomposed to 0.05 mg / l or less. It was also confirmed that biphenyl was not present in the microbially treated water.

Example 2 Microbial Decomposition of Fractionated Distillate Concentrated Liquid of Low Chlorinated PCB 150 g of mineral oil in which PCB containing chloride as a main component was dissolved at a concentration of 50 g / l, 20 g of sodium hydroxide and amorphous carbon powder 5 g was added, and similarly to Reference Example 1, the mixture was heated and stirred at 330 to 350 ° C. in a nitrogen atmosphere, and the reaction was stopped after 2 hours. As shown in Table 1, 1
And dichlorinated PCB were contained at about 500 mg / l, and highly chlorinated PCB having trichlorination or higher was not contained. When 150 ml of the reaction-treated oil was heated at 220 to 230 ° C. to condense the evaporated components, 3 ml of condensed oil was obtained. The condensed oil contained about 25 g / l of 1- and 2-chlorinated PCBs. The PCB concentration in the remaining reaction-treated oil was below the detection limit. A culture fluid of Pseudomonas having a PCB decomposing ability obtained by separating 0.2 ml of the condensed oil from soil
It was mixed with 0 ml and cultured at 28 ° C. under aerobic conditions. 24
After an hour, PCB with an initial concentration of about 50 mg / l was 0.05 m
It was confirmed that it was decomposed to g / l or less. Also,
It was confirmed that biphenyl was not present in the microbial-treated water.

Example 3 Microbial Degradation of Low Chlorinated PCB To 150 ml of mineral oil in which PCB containing tetrachloride as a main component was dissolved at a concentration of 50 g / l, 12 g of sodium hydroxide and 1.5 g of amorphous carbon powder were added to be used as a reference. In the same manner as in Example 2, the mixture was heated and stirred under a nitrogen atmosphere at 320 to 340 ° C., and the reaction was stopped after 3 hours. As shown in Table 2, the reaction-treated oil contained about 300 mg / l of 1, 2, and 3 chlorinated PCBs, and did not contain highly chlorinated PCBs of 4 chlorination or higher. PCB separated from soil with 20 ml of the reaction-treated oil
It was mixed with 80 ml of a Pseudomonas culture medium having a resolution and cultured at 28 ° C. under aerobic conditions. After 24 hours, it was confirmed that PCB having an initial concentration of about 60 mg / l was decomposed to 0.05 mg / l or less. It was also confirmed that biphenyl was not present in the microbially treated water.

[0020]

INDUSTRIAL APPLICABILITY As described above, in the present invention, the dechlorination reaction of the chemical decomposition treatment method is performed by treating the highly chlorinated PCB to be treated.
The energy required for the chemical decomposition treatment method can be significantly reduced by stopping when the total amount of chlorinated PCBs is dechlorinated to a low chlorinated PCB of 3 chlorinated or less, and the highly chlorinated PCB can be reduced in a short time. Since it can be converted to a structure and concentration that can be easily decomposed by microorganisms, harmful highly chlorinated PCBs can be efficiently decomposed by microbial decomposition of the produced trichlorinated or less low-chlorinated PCB. Further, in the present invention, biphenyl can also be decomposed by a PCB-decomposing microorganism, and the produced benzoic acid chloride and / or benzoic acid can be easily decomposed by an ordinary microorganism, so that the decomposed product can also be disposed of. You can easily.

Claims (3)

[Claims] 1. In the method for decomposing polychlorinated biphenyls, the dechlorination reaction by the chemical decomposition treatment method of the polychlorinated biphenyls to be treated is carried out by reducing the total amount of the highly chlorinated biphenyls to be treated to a low level of 3 chlorine or less. A method for decomposing polychlorinated biphenyls, which comprises stopping at the time of dechlorination to chlorinated polychlorinated biphenyls and microbially degrading the produced low-chlorinated polychlorinated biphenyls having a trichlorination or less. 2. The microbial degradation comprises a chemical degradation treatment product of polychlorinated biphenyls containing polychlorinated biphenyls having a low chlorination level of 3 or less, and nutrient salts and polychlorinated biphenyls degrading bacteria. The method for decomposing polychlorinated biphenyls according to claim 1, which is carried out under aerobic conditions by mixing with an aqueous solution. 3. The microbial decomposition is carried out by fractionally distilling a chemical decomposition treatment product of polychlorinated biphenyls containing low chlorinated polychlorinated biphenyls having a trichlorination or less, and boiling point 150.
A condensate of a fraction containing concentrated and low-chlorinated polychlorinated biphenyls having a trichlorination level of up to 350 ° C. and an aqueous solution containing nutrient salts and polychlorinated biphenyl degrading bacteria are mixed under aerobic conditions The method for decomposing polychlorinated biphenyls according to claim 1, which is carried out below.