JP7505340B2 - Decomposition promoter and method for decomposing volatile organic halogen compounds - Google Patents

Description

The present invention relates to a decomposition promoter capable of promoting the decomposition of volatile organic halogen compounds by microorganisms, and a decomposition method using the same.

As a method for purifying soil or groundwater contaminated with volatile organic halogen compounds such as volatile organic chlorine compounds, when the contaminated area is widespread or when there are facilities in operation above ground, biostimulation, in which nutrients are injected into the ground to grow and activate microorganisms living at the contaminated site, and bioaugmentation, in which microorganisms with excellent decomposition properties are injected into the ground to break down contaminants, are used. In either case, nutrients are needed to efficiently grow and activate the pollutant-decomposing microorganisms and the microorganisms that support their functions, and various nutrients have been proposed, including organic materials that have the effect of activating chlorinated ethylene-decomposing microorganisms.

Examples of decomposition promoters that activate microorganisms that decompose volatile organic chlorine compounds are described in Patent Documents 1 to 5.

Patent Document 1 describes a composition containing an ester with a polyfunctional alcohol, Patent Document 2 describes a composition containing yeast, fatty acids, carbohydrates, etc., Patent Document 3 describes a condensation reaction product of an amino acid and an oxycarboxylic acid, and Patent Document 4 describes an extract obtained from the fruit and peel of citrus fruits. Patent Document 5 describes citric acid as a nutrient for microorganisms that decompose chlorinated ethylene compounds.

JP 2000-511969 A JP 2005-185870 A JP 2010-104962 A Patent No. 6126588 JP 2002-1304 A

The methods described in Patent Documents 1 and 3 have the problem that the activity of the microorganisms is low in the initial stage of administration, and it takes a long time to completely purify soil, especially in soil containing a large amount of chlorinated ethylene compounds. In addition, the method described in Patent Document 2 also has the problem that, although it has an effect of promoting the decomposition of chlorinated ethylenes, the degree of promotion is not sufficient, and it takes a long time to completely purify soil. In addition, there are problems in terms of cost, such as the need to combine multiple commercially available products as materials, including the glycerin/yeast extract/vitamin mixture described in Patent Document 4.

The extract obtained from citrus fruits and peels proposed in Patent Document 4 is advantageous in terms of cost and safety. However, citrus fruits and peels contain large amounts of substances with antibacterial properties, such as nobiletin and tangeretin, and there are concerns that they may have adverse effects, such as inhibiting the growth of target microorganisms. There are also concerns that when injected into the ground as a nutrient for biological purification technology, they may have an effect of significantly changing the indigenous microbial ecosystem.

The present invention aims to provide a decomposition promoter and a decomposition method for volatile organic halogen compounds that are excellent in terms of cost, safety, and environmental compatibility, and can be used in biological purification technology to achieve purification at low cost and safely by using the agent and method in biological purification technology to remove soil contaminated with organic chlorine compounds.

The gist of the present invention is as follows:

[1] A decomposition promoter for volatile organic halogen compounds that promotes the decomposition of volatile organic halogen compounds by microorganisms, the decomposition promoter being characterized in that it contains at least one of pineapple juice, an extract obtained from pineapple fruit (including the peel), and an extract obtained from pineapple fruit juice residue (including the peel).

[2] The decomposition promoter for volatile organic halogen compounds according to [1], characterized in that the pineapple is one belonging to the genus Ananas in the family Bromeliaceae.

[3] A method for decomposing volatile organic halogen compounds by microorganisms, comprising supplying a liquid containing the decomposition promoter of [1] or [2] to soil and/or groundwater containing volatile organic halogen compounds.

[4] The method for decomposing a volatile organic halogen compound according to [3], wherein the volatile organic halogen compound is an organic chlorine compound.

[5] The method for decomposing a volatile organic halogen compound according to [ 3 ] or [4], wherein the microorganism is at least one selected from the group consisting of bacteria of the genus Dehalococcoides, Clostridium, Dehalobacter , Sulfurospirillum, Desulfobacterium, Desulfomonas, and Desulfomonile.

Pineapple juice is rich in citric acid, which is used as a nutrient for microorganisms that break down chlorinated ethylene. Some citrus fruits are also rich in citric acid, but many of them also contain large amounts of substances with antibacterial properties, such as nobiletin and tangeretin, so various restrictions may be required for its use as a nutrient for biological purification technology.

On the other hand, unlike citrus fruits, pineapple contains almost no substances that exhibit strong antibacterial properties and has a low growth inhibitory effect on decomposing microorganisms. When the juice of the representative citrus fruit, Shikuwasa, is added to a culture solution of chlorinated ethylene-decomposing microorganisms, a strong decomposition retarding effect is observed even at around 0.1 g/L in TOC conversion, but no inhibitory effect is observed with the same amount of pineapple juice, and rapid decomposition of chlorinated ethylene is achieved.

The decomposition accelerator of the present invention is superior in terms of cost, safety, and environmental compatibility compared to conventional technologies that use commercially available pharmaceutical and food-grade products, and by using it in biological purification technology for soil contaminated with organic halogen compounds, purification can be achieved cheaply and safely.

In addition, because it contains almost no substances that exhibit antibacterial properties, purification by decomposing microorganisms proceeds more efficiently than with conventional technologies that use citrus juice, and the burden on the indigenous microbial ecosystem is also lower.

1 is a graph showing the results of an example. 13 is a graph showing the results of a comparative example.

The decomposition accelerator for volatile organic halogen compounds of the present invention is characterized by containing one or more of the following A to C:
A: Pineapple juice B: Extract obtained from pineapple fruit (including peel) C: Extract obtained from pineapple fruit juice residue (including peel)

The type of pineapple is not particularly limited, and any plant belonging to the Bromeliaceae family is acceptable, with those belonging to the Bromeliaceae family's Ananas genus being particularly preferred.

As the extracts of B and C above, extracts with water are preferred.

There are no particular limitations on the method of supplying the liquid containing the decomposition promoter for volatile organic halogen compounds to the soil or groundwater, but it is preferable to supply it through a well pipe. The decomposition promoter of the present invention is preferably injected into the soil or groundwater so that the concentration in the soil or groundwater is 0.01 to 0.5 g/L, particularly 0.05 to 0.1 g/L, calculated as TOC. However, the injection amount may be determined according to the degree of contamination, etc., and is not limited to this.

The decomposition accelerator for volatile organic halogen compounds of the present invention may contain other components in addition to the above components A to C.

The above-mentioned other components may be used together with, for example, glucose, fructose, ammonium sulfate, urea, ammonium salts, sulfur compounds, phosphorus compounds, potassium compounds such as potassium chloride, magnesium compounds such as magnesium chloride and magnesium sulfate, yeast extract, or peptone, which serve as nutrient sources for microorganisms.

The decomposition promoter of the present invention promotes the decomposition of volatile organic halogen compounds by microorganisms by contacting the decomposition promoter with soil, groundwater, or other samples contaminated with the volatile organic halogen compounds. The volatile organic halogen compounds that are the subject of the present invention are preferably organic chlorine compounds, such as carbon tetrachloride, chloroform, dichloromethane, monochloromethane, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, 1,3-dichloropropene, tetrachloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, vinyl chloride, and the like.

In particular, the decomposition accelerator of the present invention can effectively promote the decomposition of chloroethenes such as tetrachloroethylene, trichloroethylene, dichloroethylenes, and vinyl chloride. Tetrachloroethylene is decomposed by microorganisms into trichloroethylene, dichloroethylene, monochloroethylene (vinyl chloride), and ethylene in that order.

The decomposition accelerator of the present invention promotes the decomposition of volatile organic halogen compounds by microorganisms, and may utilize microorganisms that are originally present in the soil or groundwater to be purified, or may be used together with microorganisms that are useful for decomposing volatile organic halogen compounds. It may also be used together with a composition containing such microorganisms. That is, when the soil or groundwater to be purified contains a sufficient number of microorganisms that decompose volatile organic halogen compounds, the decomposition accelerator or decomposition accelerator composition of the present invention may be applied directly to the target soil. On the other hand, when the amount of microorganisms in the soil is small or when it is desired to accelerate decomposition, the decomposition accelerator or decomposition accelerator composition of the present invention may be applied together with previously prepared microorganisms or a composition containing microorganisms.

Microorganisms useful for decomposing volatile organic halogen compounds are preferably anaerobic microorganisms, such as those of the genera Dehalococcoides, Clostridium, Dehalobacter, Sulfurospirillum, Desulfobacterium, Desulfomonas, and Desulfomonile.

[Example 1, Comparative Example 1]
The following experiment was carried out to verify the effect of pineapple juice on the decomposition reaction of chlorinated ethylenes by anaerobic microorganisms.
<Experimental conditions>
[Evaluation of the decomposition activity of tetrachloroethylene as chlorinated ethylene under various nutrient addition conditions]
Dehalococcoides bacteria were used as the chlorinated ethylene decomposition microorganisms. Pineapple juice (Example 1) and Citrus depressa juice (Comparative Example 1), which belong to the citrus fruits, were used as decomposition promoters at 0.1, 0.3, and 0.8 g/L in terms of TOC. A trisodium citrate solution at 0.8 g/L in terms of TOC was used as a control series.

A seed culture pre-cultured in advance using a citric acid-added artificial medium was inoculated into a vial containing an artificial medium (liquid volume 100 mL) described in the following literature to which each decomposition promoter had been added, to a final concentration of 1%. 0.2 mL of a 100 mg/mL tetrachloroethylene (PCE) solution was added, and cultivation was started under anaerobic conditions at a cultivation temperature of 25°C.

The decomposition activity of chlorinated ethylene compounds was evaluated by monitoring the concentrations of gas components in the headspace of the culture tank. The ethylene concentration was measured by gas chromatography, and the concentrations of PCE and its decomposition products (trichloroethylene (TCE), dichloroethylene (DCE), and chloroethylene (CE)) were measured by headspace-gas chromatography mass spectrometry.

*Artificial culture medium description literature: N. Okutsu, W. Tamura, M. Mizumoto, T. Ueno, H. Ishida, T. Iizumi. (2012) Field demonstration of bioaugmentation in trichloroethane-contaminated groundwater. Water Practice Technol. 7: wpt2012053

<Results and Discussion>
[Evaluation of chlorinated ethylene decomposition activity under various nutrient addition conditions]
The results for the series with pineapple juice added are shown in FIG. 1, and the results for the series with shekwasha juice added are shown in FIG.

As shown in Figure 1, the pineapple juice (labeled "Pine" in Figure 1) added series showed a high decomposition rate at TOC conversion of 0.3 g/L or less. In particular, at 0.1 g/L, decomposition activity was observed to be at the same level as the control series (citric acid 0.8 g/L).

On the other hand, in the series in which Shikwasha juice, a citrus fruit, was added, a strong decomposition delay effect was observed at all juice concentrations, as shown in Figure 2. In particular, there was a tendency for decomposition to almost stop after DCE. The decomposition from PCE to DCE is catalyzed by a relatively large number of microbial species, but the microorganisms that have the activity to decompose CE to ethylene are limited to some Dehalococcoides bacteria. It is presumed that the antibacterial substances contained in citrus fruits inhibit the growth of chlorinated ethylene decomposing microorganisms, including Dehalococcoides bacteria, or the microorganisms that support them, and the chlorinated ethylene decomposition reaction.

Claims (5)

A decomposition promoter for volatile organic halogen compounds that promotes the decomposition of volatile organic halogen compounds by microorganisms, comprising:
pineapple juice,
A decomposition accelerator for volatile organic halogen compounds, comprising at least one of an extract obtained from pineapple fruit (including the peel) and an extract obtained from pineapple fruit juice residue (including the peel). The decomposition accelerator for volatile organic halogen compounds according to claim 1, characterized in that the pineapple is one belonging to the genus Ananas of the family Bromeliaceae. A method for decomposing volatile organic halogen compounds by microorganisms, comprising supplying a liquid containing the decomposition promoter of claim 1 or 2 to soil and/or groundwater containing volatile organic halogen compounds. The method for decomposing a volatile organic halogen compound according to claim 3, wherein the volatile organic halogen compound is an organic chlorine compound. 5. The method for decomposing volatile organic halogen compounds according to claim 3 or 4, wherein the microorganism is at least one selected from the group consisting of bacteria of the genus Dehalococcoides, bacteria of the genus Clostridium, bacteria of the genus Dehalobacter, bacteria of the genus Sulfurospirillum, bacteria of the genus Desulfobacterium, bacteria of the genus Desulfomonas, and bacteria of the genus Desulfomonile.

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