JPH11253926A - Purifycation of polluted substance by halogenated organic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a gas of offensive odor which is generated secondarily in the decomposition of polluted substances and the discoloration of soil to mix a reducing agent and others uniformly in the purification of a large amount of a polluted substance. SOLUTION: In a method for purifying a substance polluted with halogenated organic compounds having a process in which a reducing agent in which standard electrode potential to a standard hydrogen electrode at 25 deg.C is -2400-30 mV and the nutrition source of conventional nutrition type anaerobic microorganisms are added to the polluted substance, the reducing agent is the alloy of reduced iron, cast iron, and an iron-silicon alloy and others or a water soluble compound. The nutrition source contains organic carbon and 20-50 wt.% based on the carbon of oxidized nitrogen. A process in which a nutrient solution and the reducing agent are mixed with the polluted substance, a process in which the pH of the polluted substance is adjusted at 4.5-9.0, and a process in which the mixture is allowed to stand under low ventilation conditions are included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying contaminants by halogenated organic compounds, especially chlorinated organic compounds, such as soil, sediment, sludge, and water. The present invention relates to a method for purifying contaminants by decomposing a halogenated organic compound by a combined reductive dehalogenation reaction.

[0002]

2. Description of the Related Art In recent years,
Pollution of soil and groundwater by halogenated organic compounds such as tetrachloroethylene, trichloroethylene, 1,1,1-trichloroethane, and dichloroethylene, which are widely used as degreasing and cleaning agents for metal parts of electronic equipment and dry cleaning Have been. Since these halogenated organic compounds are not easily decomposed in the natural world and are poorly water-soluble, they easily accumulate in soil and permeate into groundwater in a contaminated area. In addition, the halogenated organic compound causes liver damage and has carcinogenicity. Therefore, it is desired to decompose halogenated organic compounds such as chlorinated organic compounds contained in soil and the like.

Recently, a microorganism treatment method (bioremediation) has attracted attention as a method for purifying soil, groundwater, and the like contaminated with a halogenated organic compound. The microorganism treatment method is cost-effective and safe. However, in the microorganism treatment method, as described below, the treatment takes a long time, and the types and concentrations of decomposable substances are limited.

[0004] As an example of the microorganism treatment method, many aerobic decomposition treatment methods of trichloroethylene by methane assimilating bacteria, toluene / phenol decomposing bacteria, ammonia oxidizing bacteria, and alkene assimilating bacteria have been reported. However, 1)
The decomposition reaction is unstable, 2) the range of substances to be decomposed is extremely narrow, and 3) high chlorinated substances such as tetrachloroethylene and carbon tetrachloride have the disadvantage that they have no decomposition action.

On the other hand, many anaerobic microorganisms can widely decompose highly chlorinated organic compounds such as tetrachloroethylene, trichloroethylene and carbon tetrachloride.
However, there are drawbacks such as 1) very slow growth of microorganisms, and 2) production and accumulation of highly toxic intermediate metabolites in the anaerobic decomposition process (Hiroo Uchiyama and Osamu Yagi, Bioscience and Industry, 1). 1994, Vol. 52, No. 11, 879-884).

On the other hand, as a technique for decomposing a halogenated organic compound by a chemical reaction, a reductive treatment of a chlorinated organic compound with metallic iron has been reported (Tetsuo Sanezaki, Treatment of groundwater contaminated with organochlorine compounds-activated carbon attached to metallic iron) Low-temperature processing technology, "PPM", 1995, Vol. 26,
No. 5, pages 64-70). Therefore, the present inventor tried a dechlorination test by adding metallic iron to soil in the absence of a microbial carbon source. However, no dechlorination reaction was observed under conditions where the microorganisms were not cultured, especially when the reducing atmosphere and neutral conditions were not maintained. Further, even when iron salts such as FeCl ₂ , FeCl ₃ and FeSO ₄ were added instead of metallic iron, no dechlorination reaction was observed.

Furthermore, a method has been reported in which metallic iron and high-pressure air are injected into contaminated soil to cause a halogenated organic compound to react with iron powder to make it inorganic and detoxify (Japanese Patent Application Laid-Open No. 8-257570). ). Also in this method, there are problems such as a problem of an air injection facility and a possibility of volatilization of a halogenated organic compound. Furthermore, since high-pressure air is used, a cost problem occurs, which is not practical.

Further, a method of removing organic chlorine compounds contaminating soil and groundwater by combining a natural substance having a dehalogenation catalytic action with a microorganism treatment has been reported (Nikkei Biotech, published by Nikkei BP). 1996 10
Issued on March 7, No. 361, pp. 14-15). But,
No specific natural substances and microorganisms are described.

US Pat. No. 5,411,664 describes a method for decomposing halogenated organic compounds by adding fibrous organic substances and polyvalent metal particles such as iron to contaminants. However, this US patent does not describe reducing agents such as reduced iron, cast iron, alloys, and water-soluble reducing agents. Further, it is not described that the contaminants are maintained in a reducing atmosphere and a predetermined pH after the addition of the reducing agent.

Furthermore, depending on the composition of the nutrient source to be added,
Since biological reduction reactions such as sulfuric acid reduction and methane fermentation occur in soil, sulfur-based odorous gas such as hydrogen sulfide and mercaptan, and combustible gas such as methane gas may be generated. In addition, the soil may change color to black with the production of iron sulfide and the like. Further, the reaction between the metal powder and water may generate flammable hydrogen gas.

Furthermore, it is easy to uniformly mix reducing agents, nutrients and contaminants in the laboratory. On the other hand, in order to actually purify soil and other contaminants,
A large amount of reducing agents and nutrients are mixed, and civil works are required. Also, it is not always easy to mix uniformly. Furthermore, it is assumed that the conditions at the time of kneading affect the decomposition rate of the halogenated organic compound. In particular, in order to purify contaminants having a volume of 1 m ³ or more, especially 10 m ³ or more, a method of kneading is required.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for purifying contaminants caused by a halogenated organic compound by decomposing the halogenated organic compound by combining a chemical reaction and a biological reaction. And

A first aspect of the present invention aims at decomposing a halogenated organic compound by a reductive dehalogenation reaction.

A second aspect of the present invention aims at decomposing a halogenated organic compound by a chemical dehalogenation reaction.

According to a third aspect of the present invention, it is possible to prevent the generation of sulfur-based malodorous gas or combustible gas which is produced as a by-product in a reductive dehalogenation reaction, and to prevent excessive discoloration of soil and other contaminants. With the goal.

According to a fourth aspect of the present invention, it is an object of the present invention to effectively mix a nutrient source and a reducing agent with a contaminant when the contaminant has a large volume.

The first aspect of the present invention is characterized in that a predetermined reducing agent is added, thereby promoting a reductive dehalogenation reaction.

The second aspect of the present invention is characterized in that a predetermined reducing agent is added, thereby promoting a chemical dehalogenation reaction. Unlike the first aspect of the present invention, a biological reaction need not necessarily be involved. By using a predetermined reducing agent, a halogenated organic compound can be decomposed only by a chemical reaction.

In a third aspect of the present invention, the organic carbon 2
By using a nutrient source containing 0 to 50% by weight of oxidized nitrogen, a microorganism group involved in a reductive dehalogenation reaction is changed when a halogenated organic compound is decomposed,
Blackening of soil due to iron sulfide and the like, and generation of malodorous gas such as mercaptan can be suppressed.

According to a fourth aspect of the present invention, the process is characterized in that the reducing agent and the nutrient source are mixed with the contaminant.
1 m ³ or more, especially when purifying contaminants 10 m ³ or more volumes, it is possible to mix these more uniformly.

In the third and fourth aspects of the present invention, the reducing agent used in the first or second aspect of the present invention is preferably used. However, the invention is not limited to the reducing agent used in the first aspect or the second aspect of the present invention.

According to a first aspect of the present invention, there is provided a method for purifying contaminants caused by a halogenated organic compound, wherein a standard electrode potential with respect to a standard hydrogen electrode at 25 ° C. is 130 mV.
A step of adding a reducing agent of about −2400 mV and a nutrient of a heterotrophic anaerobic microorganism to the contaminant, wherein the reducing agent is reduced iron, cast iron, iron-silicon alloy,
A method is provided which is at least one selected from the group consisting of a titanium alloy, a zinc alloy, a manganese alloy, an aluminum alloy, a magnesium alloy, a calcium alloy, and a water-soluble compound. In the presence of such a reducing agent, reductive dehalogenation by a combination of a chemical reaction and a microorganism can be promoted.

In the present invention, the reducing agent has a standard electrode potential of -400 m with respect to a standard hydrogen electrode at 25 ° C.
V to -2400 mV and reduced iron, cast iron, iron
Silicon alloy, titanium alloy, zinc alloy, manganese alloy,
It is preferably at least one selected from an aluminum alloy, a magnesium alloy, and a calcium alloy. Further, it is preferable that the reducing agent contains reduced iron. Alternatively, it is preferable that the reducing agent contains cast iron. Alternatively, the reducing agent is an iron-silicon alloy, a titanium-silicon alloy, a titanium-aluminum alloy, zinc-
It is at least one selected from the group consisting of an aluminum alloy, a manganese-magnesium alloy, an aluminum-zinc-calcium alloy, an aluminum-tin alloy, an aluminum-silicon alloy, a magnesium-manganese alloy, and a calcium-silicon alloy. preferable.

It is preferred that the reducing agent is a water-soluble compound. The reducing agent is an organic acid or a derivative thereof,
More preferably, it is hypophosphorous acid or a derivative thereof, or a sulfide salt.

It is preferable that the reducing agent is a powder having a particle size of 500 μm or less. In this specification, the powder is not limited to a powder having a particle size of 500 μm or less. Preferably, the contaminant has a water content of at least 25% by weight.

Preferably, after the adding step, the method further comprises a step of maintaining the contaminants in a pH range of 4.5 to 9.0 in order to promote reductive dehalogenation of the halogenated organic compound. More preferably, after the adding step, the method further comprises a step of maintaining the contaminants in a pH range of 4.5 to 9.0 and in a reducing atmosphere.

Various organic composts, composted organic matter,
Alternatively, it is preferable to include a step of adding wastewater or waste containing organic matter to the contaminants, and then mixing them.

In a first aspect of the present invention, the water-soluble reducing agent has 1 to 20 carbon atoms and may be substituted with a hydroxyl group, such as monocarboxylic acid, dicarboxylic acid, tricarboxylic acid, Alternatively, it is preferably tetracarboxylic acid or a salt thereof, polyhydroxyaryl, or hypophosphorous acid or a salt thereof. Preferably, the water-soluble reducing agent is hypophosphorous acid or a salt thereof. Further, the water-soluble reducing agent may be a salt composed of an organic acid or hypophosphorous acid and iron, titanium, zinc, manganese, aluminum or magnesium.

In order to adjust the pH of the contaminant, it is preferable to include a step of adding at least one of an alkali metal compound and an alkaline earth metal compound to the contaminant. In the holding step, it is preferable that the halogenated organic compound is converted into an organic compound containing no halogen atom. In the holding step, it is preferable that the halogenated organic compound is converted into a hydrocarbon containing no halogen atom.

According to a second aspect of the present invention, there is provided a method for purifying contaminants caused by a halogenated organic compound, wherein a standard electrode potential with respect to a standard hydrogen electrode at 25 ° C. is 130 mV.
A step of adding a reducing agent of about −2400 mV to the contaminants, wherein the reducing agent is reduced iron, cast iron, iron-silicon alloy, titanium alloy, zinc alloy, manganese alloy, aluminum alloy, magnesium alloy, A method is provided that is at least one selected from the group consisting of a calcium alloy and a water-soluble compound.

In a second aspect of the present invention, the reducing agent has a standard electrode potential of −445 mV to −2400 mV with respect to a standard hydrogen electrode at 25 ° C., and comprises an iron-silicon alloy, a titanium alloy, a zinc alloy, and manganese. It is preferably at least one selected from alloys, aluminum alloys, magnesium alloys, and calcium alloys.

The contaminants have a dry weight of 1 k
Preferably, the contaminant contains from 0.1 g to 100 g of an iron compound based on 1 kg of the dry weight of the contaminant. More preferably, the compound contains iron hydroxide (Fe (OH) ₃ ) or triiron tetroxide (Fe ₃ O ₄ ).

Further, the reducing agent is an iron-silicon alloy, a titanium-silicon alloy, a titanium-aluminum alloy, a zinc-aluminum alloy, a manganese-magnesium alloy, an aluminum-zinc-calcium alloy, an aluminum-tin alloy, an aluminum-silicon alloy. It is preferably at least one selected from the group consisting of a silicon alloy, a magnesium-manganese alloy, and a calcium-silicon alloy.

Alternatively, the reducing agent is preferably a water-soluble compound. Preferably, the reducing agent is an organic acid or a derivative thereof, hypophosphorous acid or a derivative thereof, or a sulfide salt. The reducing agent is 5
It is preferable that the powder has a particle size of 00 μm or less. In addition, in this specification, a powder has a particle diameter of 500.
It is not limited to powder having a size of μm or less.

According to a third aspect of the present invention, there is provided a method for purifying contaminants caused by a halogenated organic compound, wherein a standard electrode potential at 25 ° C. with respect to a standard hydrogen electrode is 130 mV.
A step of adding a reducing agent of about −2400 mV and a nutrient of a heterotrophic anaerobic microorganism to the contaminant, wherein the nutrient contains organic carbon and 20 to 20% of the organic carbon. A method is provided that contains 50% by weight nitrogen oxide.

The nutrient source is the organic carbon.
More preferably, it contains 0 to 30% by weight of nitrogen oxide. Preferably, the organic carbon is supplied as a water-soluble organic carbon source.

Further, the reducing agent has a standard electrode potential at −25 m ° C. with respect to a standard hydrogen electrode of −400 mV to −24.
It is preferable that the metal substance be 00 mV. It is preferable that the reducing agent is at least one selected from the group consisting of reduced iron, cast iron, iron-silicon alloy, titanium alloy, zinc alloy, manganese alloy, aluminum alloy, magnesium alloy, and calcium alloy.

Alternatively, the reducing agent is preferably a water-soluble compound. It is preferable that the reducing agent is a powder having a particle size of 500 μm or less.

In the third aspect of the present invention, the nitrogen oxide is preferably in the form of a nitrate. The nitrate is an alkali metal nitrate, an alkaline earth metal nitrate,
It preferably contains iron nitrate, titanium nitrate, zinc nitrate, manganese nitrate, aluminum nitrate or magnesium nitrate, and more preferably the nitrate contains sodium nitrate, potassium nitrate or calcium nitrate.

The organic carbon source is preferably a saccharide, an organic acid or a derivative thereof, a lower alcohol, a molasses waste liquid, a brewery waste liquid, or a mixture thereof.

According to a fourth aspect of the present invention, there is provided a method for purifying contaminants containing a halogenated organic compound and a solid, comprising: a nutrient solution containing a nutrient source of a heterotrophic anaerobic microorganism and water; A reducing agent having a standard electrode potential of 130 mV to −2400 mV with respect to a standard hydrogen electrode at 25 ° C.
Mixing the contaminant, wherein the mixing includes adjusting the contaminant to a pH in the range of 4.5 to 9.0; and allowing the mixture to stand under low aeration conditions. A method comprising:

In the present invention, it is preferable that the reducing agent is in powder form, the nutrient solution is added to the contaminant, and then mixed, and the reducing agent is added to the mixture and then mixed. preferable.

Further, it is preferable that the reducing agent is a powder having a particle size of 500 μm or less. In this specification, the powder is not limited to a powder having a particle size of 500 μm or less.

Further, the reducing agent is selected from reduced iron, cast iron, iron-
Silicon alloy, titanium alloy, zinc alloy, manganese alloy,
It is preferably at least one selected from the group consisting of an aluminum alloy, a magnesium alloy, and a calcium alloy.

As a first step, a step of adding and mixing 1 to 10% by volume of the nutrient solution based on the contaminant with the contaminant, and then adding a larger amount than the amount added in the first step Preferably, the method further comprises a step of adding the nutrient solution to the contaminants and mixing the nutrient solution.

Alternatively, as a first step, 1 to 5 vol% of the nutrient solution based on the contaminant is added to the contaminant and mixed, and then as a second step, the first step
Adding the nutrient solution to the contaminant so that the amount becomes 5 to 10 vol% based on the contaminant in combination with the step, and further mixing the nutrient solution in an amount larger than the amount added in the first step or the second step Preferably, the method further comprises a step of adding the nutrient solution to the contaminants and mixing the nutrient solution.

Further, the reducing agent is a water-soluble compound,
Preferably, the reducing agent is dissolved in the nutrient solution. Further, at least the first 3
It is preferable to maintain the contaminants at 17C to 60C for days.

In the fourth aspect of the present invention, it is preferable that 15 to 25 vol% of the nutrient solution based on the contaminant is finally added to the contaminant.

Further, in the standing step, it is preferable that the contaminants are kept at 17 ° C. to 60 ° C. for at least the first 5 days. Further, in the standing step, it is preferable that the contaminants are kept at 20 ° C to 40 ° C for at least the first 3 days, preferably 5 days.

It is preferable that the stationary step is performed in a state of being separated from the surroundings. Preferably, the contaminants are coated with an impermeable material to maintain low aeration conditions. In order to maintain low aeration conditions, it is preferable to immerse the contaminants in an aqueous liquid. Preferably, the nutrient solution, the reducing agent, and the contaminant are mixed in a container.

According to a fifth aspect of the present invention, there is provided a method for purifying contaminants caused by a halogenated organic compound, wherein a standard electrode potential at 25 ° C. with respect to a standard hydrogen electrode is 130 mV.
A method comprising the steps of: mixing a solid reducing agent with a nutrient of a heterotrophic anaerobic microorganism, and adding the mixture to the contaminant, at ~ -2400 mV.

In the fifth aspect of the present invention, it is preferable to mix the solid reducing agent with a nutrient solution containing the nutrient source and water.

The solid reducing agent includes, for example, a powdery or powdery reducing agent.

Preferably, the adding step is started within 24 hours after the mixing step, more preferably, within 6 hours, more preferably, within 2 hours. Is still more preferred.

[0055]

DETAILED DESCRIPTION OF THE INVENTION In the first, second, and third aspects of the present invention, contaminants due to halogenated organic compounds are purified. In the present specification, halogen is
Refers to fluorine, chlorine, bromine and iodine. In the present invention, contaminants due to organic compounds having a halogen atom can be purified, in particular, contaminants due to organic compounds having a chlorine atom and a bromine atom can be purified, and more particularly, organic compounds having a chlorine atom can be purified. Contamination can be purified. The chlorinated organic compound is not limited to, for example, aliphatic compounds such as tetrachloroethylene, trichloroethylene, 1,1,1-trichloroethane, and dichloroethylene, and can also decompose aromatic compounds such as pentachlorophenol.

The contaminants that can be treated in the first, second, third, and fourth aspects of the present invention include soil, sediment, sludge, and the like. Also, compost, composted organic matter and waste can be treated. In the first, second, and third aspects of the present invention, aqueous liquids such as groundwater and wastewater can be treated. As used herein, aqueous liquids include aqueous solutions, suspensions, emulsions, and mixtures thereof.

When the contaminant is soil, sediment, sludge, or the like, the water content is preferably at least 25% by weight, more preferably 40 to 60% by weight. This is because it is preferable to make it difficult for air to enter soil, sludge, and the like in order to grow anaerobic microorganisms. This moisture content (%) is defined as follows.

Water content = (weight of water / weight of contaminants including water) × 100 When the contaminants are water such as groundwater and wastewater, the water content is necessarily 25% by weight or more.

In the first aspect of the present invention, the standard electrode potential at 25 ° C. with respect to the standard hydrogen electrode is 130 mV to −2.
By adding a reducing agent of 400 mV and a nutrient of heterotrophic anaerobic microorganisms to the contaminants, both chemical reaction and biological reaction are promoted to decompose the halogenated organic compound.

If the standard electrode potential is higher than 130 mV, sufficient reducing power cannot be obtained. On the other hand, substances having a standard electrode potential lower than −2400 mV, for example, alkali metals such as metal sodium and metal potassium have an excessively strong reducing power, and thus react explosively with water to generate hydrogen gas, which is extremely low. It is not preferable because it is dangerous. 25 ° C
The standard electrode potential (E °) with respect to the standard hydrogen electrode is shown in the following table.

[0061]

[Table 1] The standard electrode potential refers to the measurement using a hydrogen electrode as a reference electrode when all species involved in the battery reaction are in a standard state (pure solid phase, standard concentration, standard pressure, etc.). This is the potential measured when the test is performed, and is equal to the standard potential E ⁰ . This value is expressed using the following equation.

E ⁰ = −ΔG ⁰ / nF Here, ΔG ⁰ is a standard change of the free energy of the cast in a battery reaction, n is the number of electrons involved in the reaction, and F is a Faraday constant. Usually, the oxidation-reduction potential is often indicated by a potential measured using a saturated silver chloride electrode as a reference electrode. In this case, the measured value is about 200 mV compared to a standard potential measured using a hydrogen standard electrode as a reference electrode. Note that the value is low.

In the present invention, the reducing agent is selected from the group consisting of reduced iron, cast iron, iron-silicon alloy, titanium alloy, zinc alloy, manganese alloy, aluminum alloy, magnesium alloy, calcium alloy, and a water-soluble compound. At least one type.

When the reducing agent has a standard electrode potential with respect to a standard hydrogen electrode at 25 ° C. of −400 mV to −2400 m
V is preferably a metal substance.

In one embodiment of the present invention, reduced iron is used as the reducing agent. The surface of the iron powder is usually oxidized to form an oxide film. In contrast, with reduced iron,
Less oxide film, easily oxidized, high reactivity.

Here, reduced iron refers to a kind of metallic iron produced by reduction of oxides, which is in a very fine powder form and is easily oxidized (Chemical Dictionary 2, Chemical Dictionary Dictionary Editing Committee, Kyoritsu Publishing Co.). Typically,
It is reduced with hydrogen gas at high temperature. Iron oxide may be reduced, but the oxide is not limited to iron oxide. Some reduced irons have a Fe content of 90% or more. For example, it can be obtained from Wako Pure Chemical Industries, Ltd.

In another embodiment of the present invention, cast iron is preferably used as a reducing agent. This is because cast iron is safe, easy to handle, and can achieve a high purification rate. Further, shavings of a cast product, that is, cast iron shavings are more preferable. This is because the shavings can be reused.

In general, of pig iron produced by reducing iron ore, iron is industrially used by further removing impurities.
A steel having a carbon concentration of about 2% or less (weight) is referred to as steel, and a steel containing more carbon is referred to as cast iron.
987, pp. 411).

Since steel has excellent mechanical properties, it is used in many industrial products. We examined whether the steel shavings released at that time could be used in a method for purifying substances contaminated with halogenated organic compounds, and found that oil was used in the cutting process. Contains oil. If the method for purifying contaminants with an organic chlorine compound according to the present invention is carried out using this, there is a risk of causing secondary contamination with oil. On the other hand, since cast iron used for casting does not use oil at the time of cutting, cast product shavings (cast iron shavings) are 2% like the steel product shavings.
There is no risk of secondary contamination.

In another embodiment of the present invention, an alloy is used as the reducing agent. That is, iron-silicon alloy,
Titanium, zinc, manganese, aluminum, magnesium, and calcium alloys are also used. Examples of the titanium alloy include a titanium-silicon alloy and a titanium-aluminum alloy. Examples of the zinc alloy include a zinc-aluminum alloy. Examples of the manganese alloy include a manganese-magnesium alloy. Examples of the aluminum alloy include an aluminum-zinc-calcium alloy, an aluminum-tin alloy, and an aluminum-silicon alloy.

Examples of the magnesium alloy include a magnesium-manganese alloy. Examples of the calcium alloy include a calcium-silicon alloy.

The action of the reducing agent will be described with reference to the case of reduced iron. The reaction mechanism of the anaerobic dehalogenation reaction with metallic iron is described in Sakizaki's report on the reaction of reduced iron ("Treatment of groundwater contaminated with organochlorine compounds-Treatment technology at low temperatures with activated carbon attached to metallic iron", PPM, 1995).
, Vol. 26, No. 5, pp. 64-70), adsorption of halogenated organic compounds occurs on the surface of reduced iron, and at the same time, the anode and the anode are reduced due to the difference in conditions between the metal side and the environment side on the surface of reduced iron. Cathode polarization occurs, causing current to flow. Along with this, iron is eluted as iron ions at the anode, while electrons flow into the cathode,
It is considered that a reduction reaction such as a dehalogenation reaction occurs.

Anode: Fe → Fe²⁺ + 2e^-  As mentioned above, cast iron has a carbon concentration of 2% or more.
Generally 3 to 3.5% by weight and 13 to 14% by volume
Contains a large amount of carbon as graphite. Iwayu
Casting product shavings (cast iron shavings), called luk, are waste
Before being discharged as, they are generally ground in a mill.
During the grinding, some of the graphite is separated and
Attaches to surface. This cast iron powder is covered with a water film
And graphite act as cathodes, while iron
The current acts as described above,
Elutes iron at the cathode, and reduces the reduction
It is thought that a response will occur. The above alloys also work as anodes
It is believed that the alloy elutes when used. Meanwhile, the cathode
It is thought that a dehalogenation reaction occurs in the reaction.

In the case of an alloy having a stronger reducing power than metallic iron, the reducing atmosphere is more easily maintained, the potential difference with the halogenated organic compound becomes larger, and the dehalogenation reaction is accelerated.

Further, when an alloy such as a magnesium-manganese alloy, a zinc-aluminum alloy, an aluminum-zinc-calcium alloy, or an aluminum-tin alloy is used, an oxide film or a corrosion product may not adhere to the metal surface. Alternatively, even if it adheres, it does not become a dense film that inhibits the reaction (it is not passivated), so that the reduction reaction does not cause a problem of reducing the contact efficiency, and the purification reaction can be performed efficiently.

In one embodiment of the present invention, the reducing agent is
It is preferably a water-soluble compound.

As compared with the case where a solid such as a powder is added, the contact efficiency with the halogenated organic compound is dramatically increased, and the dehalogenation reaction is accelerated. Further, since the water-soluble reducing agent permeates the soil or the like, the reducing agent can be injected using an injection well or the like, and no physical excavation and mixing work is required. Furthermore, if the reducing state becomes unstable during the purification operation, it is possible to recover the reducing state easily by collecting leachate of contaminants, adding a water-soluble reducing agent, and re-injecting. It is.

Examples of the water-soluble reducing agent include organic acids or derivatives thereof, hypophosphorous acid or derivatives thereof, and sulfide salts. Examples of the organic acid include carboxylic acid, sulfonic acid, phenol and derivatives thereof. Examples of the carboxylic acid include a monocarboxylic acid, a dicarboxylic acid, a tricarboxylic acid, and a tetracarboxylic acid each having 1 to 20 carbon atoms and optionally substituted with a hydroxyl group. Specifically, formic acid, acetic acid,
Preferred are citric acid, oxalic acid, terephthalic acid and the like, and particularly preferred are aliphatic dicarboxylic acids having 2 to 10 carbon atoms such as citric acid and oxalic acid.

The phenol derivative is preferably a polyhydroxyaryl. Polyhydroxyaryl is
An aryl substituted with two or more hydroxyl groups is mentioned, and the aryl includes benzene, naphthalene, anthracene and the like. Further, a condensed ring may be formed like naphthalene or indene. Examples of the polyhydroxyaryl include 1,2,3-trihydroxybenzene,
1,4-dihydroxybenzene is preferred. here,
1,2,3-Trihydroxybenzene is also called pyrogallic acid, pyrogallol. The alkaline solution reacts with oxygen to form an oxide.

The derivatives of organic acids include salts, esters,
Examples include amides and acid anhydrides, and salts are preferred. The counter ion is not particularly limited, and includes an alkali metal ion such as a sodium ion; an alkaline earth metal ion such as a calcium ion; an inorganic ion such as a transition metal ion such as an iron ion and a titanium ion; Organic ions may be used.

Examples of the derivatives of hypophosphorous acid include salts and esters, and salts are preferred. As the opposite ion,
There is no particular limitation, and alkali metal ions such as sodium ions; alkaline earth metal ions such as calcium ions;
It may be an inorganic ion such as a transition metal ion such as an iron ion or a titanium ion, or an organic ion such as a tetraalkylammonium ion.

Further, the reducing agent may be a salt comprising an organic acid or hypophosphorous acid and iron, titanium, zinc, manganese, aluminum or magnesium.

When these reducing agents are added, no intermediate metabolites such as vinyl chloride, which are frequently reported in the anaerobic dehalogenation reaction, are produced or accumulated at all, and all the reaction products are completely eliminated. It was found that it was converted to a dehalogenated substance and released into the gas phase. When a reducing agent having a standard electrode potential equal to or lower than that of metallic iron is used, the potential difference from the halogenated organic compound becomes larger, and the dehalogenation reaction is accelerated, which is preferable.

When the contaminant is soil, the amount of the reducing agent
The amount is preferably 0.01 to 20 g, more preferably 0.05 to 10 g, per 100 g of soil. When the contaminant is water, the amount is preferably 0.1 to 30 g per 100 ml of water,
More preferably, it is 0.2 to 20 g. In any case, when the contamination concentration of the halogenated organic compound to be dehalogenated exceeds 50 mg / kg (or 50 mg / l), 1 mg of the halogenated organic compound is used.
It is necessary to increase the addition amount of a reducing agent such as a metal powder at a ratio of 0.05 to 0.1 g. However, this is only a value under ideal conditions, and in an actual pollution site, if oxygen consumption by microorganisms is not performed smoothly, the reducing power of the reducing agent may be wasted. In addition, since the reducing power of the reducing agent is easily consumed even by the supply of oxygen or the like from rainwater or the outside air, a preliminary test should be performed on site at the time of implementation, and the addition concentration should be determined individually according to the conditions at the site. .

The reducing agent is preferably in the form of a powder or a solution in order to increase the contact efficiency between the reducing agent and the contaminants. However, most of the above-mentioned substances react with water and easily change to the oxidized state. In this case, it is desirable to directly mix the contaminants with the reducing agent or to dissolve the reducing agent in water immediately before mixing. In the case of a powder, it preferably has a particle size of 500 μm or less. This is because when the particle size is small, the decomposition rate of the halogenated organic compound is improved.

Further, depending on the use, the reducing agent is preferably a powder having a particle size of 0.001 mm to 5 mm, and more preferably a powder having a particle size of 0.01 mm to 1 mm.

The particle size governs the rate of the chemical reduction reaction,
It should be noted that the reduction reaction rate per unit weight decreases in proportion to the increase in the particle diameter. Further, when the particle diameter is 5 mm or more and the material is a metal substance, the surface of the metal particles is covered with a relatively thick oxide film, and thus there is a high possibility that the metal in the reduced state at the center is not used. On the other hand, when the particle diameter is 0.001 mm or less, the oxidation rate is extremely high, and the risk of being oxidized by contact with moisture during transportation and during mixing increases. In the case where the reducing agent is a metal substance, even if the surface of the powder is oxidized, it can be used if the inside is in a reduced state and is not oxidized.

Examples of heterotrophic anaerobic microorganisms include, for example, methanogens (eg, Methanosoarc).
Ina genus, Methanothrix genus, Methan
genus obacterium, Methanobrevib
acter), sulfate-reducing bacteria (eg, Desulf)
ovrio, Desulfotomaculum
Genus, Desulfobacterium Genus, Desul
genus fobacter, Desulfococcus
Genus), acid-producing bacteria (eg, Clostridium)
Genus, Acetivibrio, Bacteroide
sp., Ruminococcus sp., facultative anaerobic bacteria (eg Bacillus sp., Lactobacillus)
us genus, Aeromonas genus, Streptococ
genus cus, Micrococcus) and the like.

Also, Bacillus genus, Pseudo
genus monas, genus Aeromonas, Strepto
The genus coccus and the genus Micrococcus are preferable because they have an oxidized nitrogen reducing activity.

The nutrient source of the heterotrophic anaerobic microorganism is appropriately selected according to the microbial characteristics of the contaminant. For example,
It is sufficient to select one of a medium for methanogenic microorganisms, a medium for sulfate-reducing microorganisms, a medium for nitrate-reducing microorganisms, etc. In the selection, the purification efficiency of halogenated organic compounds is examined by a purification treatability test (purification applicability test). Can be determined.

As nutrients for the methane-producing microorganisms, nutrients generally known as growth nutrients for methane-producing microorganisms represented by lactic acid, methanol, ethanol, acetic acid, citric acid, pyruvic acid, polypeptone and the like may be used. In addition, as a growth nutrient of sulfate-reducing microorganisms, lactic acid, methanol, ethanol, acetic acid, citric acid, pyruvic acid, polypeptone, a nutrient generally known as a growth nutrient of sulfate-reducing microorganisms represented by sugar-containing organic substances and the like Is fine.

Further, organic wastewater / waste subjected to methane fermentation is effective as a growth nutrient for heterotrophic anaerobic microorganisms, such as brewery wastewater, starch wastewater, dairy wastewater. And sugar-making wastewater, beer lees, okara, and sludge.

When a liquid microbial medium is added, if an excessive amount is added, permeation of the halogenated organic compound into the underground may progress and contamination may be diffused. Conversely, if the amount is too small, microbial growth may occur. Proper water content cannot be secured, resulting in growth suppression. For this reason, it is good to adjust and add a liquid microbial medium so that the water content in soil (sludge etc. is equivalent to soil) is 25 to 60%, preferably 35 to 60%. The amount of the medium to be added should be determined in consideration of the soil moisture content, porosity, particle size composition, and hydraulic conductivity. Therefore, both the concentration of the microorganism medium and the amount of the medium used for addition differ depending on the state of the contaminated soil, and should be carefully determined by a purification treatability test.

In order to ensure a stable water content in the soil, it is effective to appropriately mix diatomaceous earth, various water retaining materials, humic soil, and the like.

When the contaminant is a substance having low water permeability such as clayey soil or consolidated silt, it takes a long time because the dechlorination treatment using only a reducing agent has low contact efficiency. It is conceivable that the reduction state becomes unstable depending on the supply conditions of the oxide from the outside. In this case, in addition to the reducing agent, an organic carbon source serving as a growth substrate for the microorganism is added,
By reducing and purifying under neutral conditions, the reduced state can be stabilized and complete dehalogenation purification can be achieved.

In the present invention, after adding the reducing agent,
Preferably, the contaminants are maintained in a reducing atmosphere. Here, the reducing atmosphere means, for example, that oxygen gas in the air is blocked by water or the like. This is because heterotrophic anaerobic microorganisms are involved in the degradation, and the presence of oxygen or the like inhibits the growth of such microorganisms. In addition, it is considered that a reducing atmosphere is easily achieved by oxidizing the reducing agent. When the reducing agent has been consumed, it may be difficult to maintain the reducing atmosphere.

As the reducing atmosphere, the standard electrode potential with respect to the standard hydrogen electrode at 25 ° C. is +200 to −24.
The range of 00 mV is preferable, and +200 to -1000 mV
Is more preferable, and the range of +100 to -600 mV is still more preferable.

In the present invention, it is preferable to maintain a predetermined pH during the progress of the reductive dehalogenation reaction. Specifically, pH 5.8 to 8.5 is preferable, pH 6 to 8 is more preferable, and pH 6.2 is still more preferable.
７7.6. When a predetermined pH and anaerobic environment are stably secured in this manner, the activity of dehalogenating the organic compound on the surface of the reducing agent can be kept high.

Further, a pH adjuster can be added to the contaminants in advance. As such a pH adjuster, in the case of an acidic soil, it is preferable to use an alkali metal compound or an alkaline earth metal compound, and specifically, to use those which have been conventionally used as an inorganic soil improver. Can be. Examples include limestone, quicklime, slaked lime, calcium sulfate (gypsum), magnesium oxide, bentonite, barlite, zeolite, and the like.

Further, when performing this treatment, it is preferable to mix various composts, composted organic substances and the like in view of the progress of the reaction. These mainly affect the effect of adding microorganisms, supply microbial nutrients, and retain water, and refer to those conventionally known as organic soil improvers.

These act to secure microbial nutrient sources and an anaerobic environment, and furthermore, to remove odorous gas generated by anaerobic fermentation of soil, particularly sulfur-based odorous gas such as hydrogen sulfide and methyl mercaptan. It is thought that it also acts on decomposition and removal.

It is well known that various composts contain various microorganisms such as actinomycetes and bacteria, and that there are many microorganisms capable of efficiently decomposing sulfur-based malodorous substances. In addition, it can be easily inferred from the fact that many useful odorless microorganisms are isolated from various composts and that compost is used as a countermeasure against malodor in livestock manure treatment.

According to the above-mentioned conditions, the pH of the soil, such as that of an alkali metal compound or an alkaline earth metal compound, is maintained.
Anaerobic substances present in soil by adding an inorganic substance as a regulator (often referred to as an inorganic soil amendment), an organic substance (organic soil amendment), and a microorganism medium Since the growth of sexual microorganisms starts immediately and the neutral and anaerobic environment of the soil is quickly formed, the mixing time of the reduced iron, which is responsible for the chemical dehalogenation reaction according to the present invention, into the soil is determined by the inorganic system. material,
Mix at the same time as adding organic substances and microbial medium,
There is no hindrance, rather it is better to mix them at the same time to secure an anaerobic environment for a long time,
It is inexpensive, and is advantageous in managing the pollution purification process.

In applying the reductive dehalogenation reaction according to the present invention to an actual contaminated site, it is not necessary to construct a large-scale facility at all, and various contaminated soils can be treated with various soil improving materials and reducing agents. After mixing, it is sufficient to add a microorganism growth medium and cover the purification area with a vinyl sheet or the like for the purpose of preventing water evaporation and rainwater mixing and keeping the temperature warm. In addition, it is desirable to spread humus or compost on the soil surface layer of the purification area as needed to prevent generation of offensive odor gas and to suppress moisture evaporation.

Although the mechanism of the reductive dehalogenation reaction according to the present invention has not been fully elucidated at present,
The present inventors consider as follows. First, the standard electrode potential with respect to the standard hydrogen electrode at pH 4.5 to 9.0 in contaminants such as soil and 25 ° C. is +200 to −24.
In order to secure an anaerobic environment in the range of 00 mV, an inorganic substance and an organic substance and a microorganism medium as a microorganism activator are added to the soil to create an anaerobic environment utilizing the growth reaction of microorganisms in the soil. Is preferred. In this case, since the anaerobic microorganisms in the soil rapidly grow, they hardly suppress the chemical dehalogenation reaction, and the biological dehalogenation reaction and the chemical dehalogenation reaction start almost simultaneously.

Although the mechanism of the biological anaerobic dehalogenation reaction is not clear because it has not been sufficiently pursued microbiologically and enzymatically, it is not clear. When obligate anaerobic microorganisms such as microorganisms and various anaerobic sludges and anaerobic microorganisms in bottom mud are growing, it is reported that chlorine is sequentially dechlorinated one by one by a very slow microbial reaction. Therefore, it is considered that a similar mild reductive dehalogenation reaction is also proceeding in the present invention.

In the present invention, the chemical dehalogenation reaction accounts for most of the initial stage of the reaction up to one month after the start of purification.
Thereafter, the chemical dehalogenation reaction converged with the decrease in the contaminant concentration of the halogenated organic compound and the reduction activity of the reducing agent, and instead, the biological dehalogenation reaction slowly became dominant, and Dechlorination proceeds over a long period of time. By the time this biological dehalogenation reaction begins to work, the concentration of halogenated organic compound contamination has been significantly reduced and will not result in a concentration inhibition of the organism's dehalogenation reaction; It acts more actively as a dehalogenation reaction for low-concentration contamination. Therefore, in the purification of the halogenated organic compound contamination according to the present invention, it is possible to purify to a very low concentration by the interaction between the chemical dehalogenation reaction and the biological dehalogenation reaction.

According to the chemical and biological anaerobic dechlorination method of the present invention, the halogenated organic compound is eluted from the contaminated soil by combining the inorganic and organic substances of the soil improvers with low solubility. Without doing, and
By purifying the halogenated organic compound contaminated soil easily and in a short period of time without penetrating the halogenated organic compound contamination deeper than the contaminated location by maintaining the water retention of the contaminated soil appropriately. Is possible.

In the reaction of the present invention, the above-mentioned dechlorination reaction can be allowed to proceed until a completely chlorine-free organic compound is obtained as a main product. This is preferable from the viewpoint of sufficiently purifying contaminants due to the above. For example, in the purification of contaminants by tetrachloroethylene and trichlorethylene, the main products, which are completely chlorine-free organic compounds are ethylene and ethane, and in this reaction, almost no intermediate products containing harmful chlorine are produced. Very good results are obtained since no formation occurs.

[0110] In the second aspect of the present invention, the reducing agent used in the first aspect of the present invention is used. Even when a predetermined nutrient is not added and a biological reaction is not involved, the halogenated compound can be decomposed.

In a second aspect of the present invention, the reducing agent has a standard electrode potential of −445 mV to −2400 mV with respect to a standard hydrogen electrode at 25 ° C., and comprises an iron-silicon alloy, a titanium alloy, a zinc alloy, It is preferably at least one selected from a manganese alloy, an aluminum alloy, a magnesium alloy, and a calcium alloy. These reducing agents have a stronger reducing power than iron. Therefore, when contaminants such as soil contain iron compounds, particularly divalent or trivalent iron compounds, these iron compounds may be reduced to iron to participate in the dehalogenation reaction. May be possible.

In view of the above, it is preferable that the contaminant contains 0.1 g to 100 g of an iron compound based on 1 kg of the dry weight of the contaminant. 1 kg to 1 g of iron compound is contained based on 1 kg, and the iron compound is iron hydroxide (Fe (O
It is more preferably contains H) ₃₎ or triiron tetraoxide (Fe ₃ O _4). Further, as the iron compound, FeO, F
Iron oxide such as e ₂ O _{3 and} iron chloride may be contained. Further, it is more preferable that the reducing agent has a standard electrode potential with respect to a standard hydrogen electrode at 25 ° C. of −450 mV to −2400 mV. Alternatively, the reducing agent may be a water-soluble compound.

The reducing agent used in the third and fourth aspects of the present invention will be described below. In the third and fourth aspects of the present invention, a reducing agent having a standard electrode potential of 130 mV to -2400 mV with respect to a standard hydrogen electrode at 25C is used. First aspect or second aspect of the present invention
Is preferably used.

However, the reducing agent used in the third and fourth aspects of the present invention is different from the first and second aspects of the present invention.
Not limited to the reducing agent used for the side surface of (1), for example, iron (not limited to reduced iron and cast iron), manganese, nickel, magnesium, and copper can also be used. Since metal iron or metal manganese naturally exists in soil in an oxidized state in a large amount, even if added, it has little effect on the ecosystem and is safe. Also, it is easily available because it is commercially available. The amount of the reducing agent used is as described above.

The reducing agent used in the third and fourth aspects of the present invention is preferably a metal substance having a standard electrode potential at 25 ° C. with respect to a standard hydrogen electrode of −400 mV to −2400 mV. The reducing agent is reduced iron,
It is preferably at least one selected from the group consisting of cast iron, iron-silicon alloy, titanium alloy, zinc alloy, manganese alloy, aluminum alloy, magnesium alloy, and calcium alloy.

Alternatively, the reducing agent is preferably a water-soluble compound. It is preferable that the reducing agent is a powder having a particle size of 500 μm or less.

Hereinafter, the third aspect of the present invention will be mainly described. Descriptions common to the first aspect of the present invention are omitted.

In the third aspect of the present invention, the standard electrode potential at a temperature of 25 ° C. with respect to a standard hydrogen electrode is 130 mV to −2.
Adding a reducing agent of 400 mV and a nutrient of a heterotrophic anaerobic microorganism to the contaminant. Thereby, as described above, the halogenated organic compound can be decomposed by reductive dehalogenation.

[0119] In a third aspect of the present invention, the nutrient source is an organic carbon and 20 to 5 of the organic carbon.
0% by weight of nitrogen oxides, and 20% of the organic carbon
It preferably contains up to 30% by weight of oxidized nitrogen.
Thereby, when decomposing the halogenated organic compound, the microorganism group involved in the reductive dehalogenation reaction is changed,
Blackening of soil due to iron sulfide and the like, and generation of malodorous gas such as mercaptan can be suppressed. Here, the content of oxidized nitrogen means, for example, in the case of nitrate, the weight of nitrogen atoms contained in the nitrate. Similarly, the content of organic carbon refers to the weight of carbon atoms contained in the organic matter.

In the reductive dehalogenation, a biological reduction reaction such as sulfuric acid reduction and methane fermentation occurs in soil according to the composition of the nutrient source to be added. Therefore, malodorous gases such as hydrogen sulfide and mercaptan and methane gas and the like are produced. Combustible gas may be generated. Further, under reducing conditions, hydrogen gas is generated by the reaction between the metal powder and water. Further, as a result of the sulfate reduction, iron sulfide may be formed and the soil may turn black.

However, in the nutrient source, 20 to 20 organic carbon atoms are contained.
When 50% by weight of oxidized nitrogen is contained, these reactions can be suppressed. That is, it has been confirmed by soil tests that the organic carbon source, which is a growth substrate, is mainly used by microorganisms having an oxidized nitrogen reducing activity, and methane fermentation and a sulfate reduction reaction are suppressed. Nitrogen gas is mainly generated from the soil, and hydrogen gas is also generated. However, since the gas is diluted with the nitrogen gas, there is no danger of ignition explosion. Furthermore, the generation of hydrogen sulfide, mercaptan-based gas and iron sulfide can be suppressed more reliably by not using salts containing sulfur or sulfate as a substance to be added as a nutrient.

When an excessive amount of nitrogen oxide salt is added to contaminants, nitrogen oxide remains after consumption of organic carbon.
A sufficient reducing atmosphere cannot be maintained. For example,
It should be noted that the oxidation-reduction potential with respect to the saturated silver chloride electrode decreases only to about +100 mV, and the reductive dehalogenation reaction hardly proceeds. Conversely, if the amount of the oxidized nitrogen salt is extremely insufficient with respect to the amount of the organic carbon source added, the oxidized nitrogen is exhausted by the initial generation of nitrogen gas, and then the normal biomass such as methane fermentation is used. A catalytic reduction reaction will occur. Therefore, the ratio between the organic carbon source and the nitrogen oxide salt to be added is important.

In Alcaligenes eutrophus and Paracoccus denitrificans, which are generally known as microorganisms having an oxidizing nitrogen reducing activity, the consumption rate of oxidizing nitrogen in an aqueous solution is 40 to 50% by weight of the organic carbon source. As a result of the inventors performing the reduction reaction of the present invention using indigenous bacteria in various soils, it was found that nitrogen oxide was added at a ratio of 20 to 50 wt% of organic carbon source, preferably 20 to 30 wt%. In this case, no odorous gas of methane or sulfur was generated, and the oxidized nitrogen salts were completely eliminated, so that complete dehalogenation of the halogenated organic compound was achieved.

Hitherto, it has been considered that the addition of nitric oxide in the progress of the reductive dehalogenation reaction inhibits the reaction (Fujita et al., Proc. 8th In.
ternational Cont.on anaerobic Digestion, 1997,
2, 492-499). However, in the present invention, by appropriately adjusting the addition ratio of oxide nitrogen and organic carbon, the generation of combustible gas such as sulfur-based odorous gas or methane is prioritized by microorganisms having an oxide nitrogen reduction activity. Thus, a stable and efficient dehalogenation reaction, which cannot be achieved with metal powder alone, has been made possible by stably maintaining the reduced state in contaminants. Thus, it can be said that the present invention is a novel purification method that breaks the conventional common sense.

Preferably, the oxidized nitrogen is in the form of a nitrate. The nitrate preferably contains an alkali metal nitrate, an alkaline earth metal nitrate, iron nitrate, titanium nitrate, zinc nitrate, manganese nitrate, aluminum nitrate or magnesium nitrate, wherein the nitrate is sodium nitrate, potassium nitrate or nitric acid. More preferably, it contains calcium.

In the present invention, organic carbon is preferably supplied as a water-soluble organic carbon source. this is,
The present invention is not necessarily limited to the third aspect of the present invention, and may be applied to the first and fourth aspects of the present invention. The water-soluble organic carbon is preferably a saccharide, an organic acid or a derivative thereof, a lower alcohol, a molasses waste liquid, a brewery waste liquid, or a mixture thereof. Organic carbon acts as a growth substrate for growing microorganisms. In addition, sugars such as glucose and sucrose, organic acids or organic acid salts such as acetic acid, citric acid and lactic acid, organic waste liquid such as molasses waste liquid, brewery waste liquid, beer lees, and okara are used as organic carbon. can do. The amount of organic carbon to be added should be determined in consideration of the oxidizing power of the contaminant and the contaminant concentration of the halogenated organic compound. However, when the contaminant is ordinary unsaturated soil, 1 to 1 kg of soil is required.
About g of organic carbon is necessary for maintaining the reduced state. Further, when the contamination concentration of the halogenated organic compound to be dehalogenated exceeds 50 mg / kg,
It is necessary to increase the amount of organic carbon added at a ratio of 10 to 20 mg per 1 mg of the halogenated organic compound. However, this is only a guideline, and in actual pollution sites, not only the oxidizing power of contaminants but also the supply of oxygen and the like by rainwater or air consumes the reducing power of organic carbon and metal powder described below. Preliminary tests should be performed to determine the individual concentration.

[0127] A fourth aspect of the present invention is a method for purifying contaminants including a halogenated organic compound and a solid.
Contaminants are as described above. Fourth Embodiment of the Present Invention
The method includes mixing a predetermined nutrient solution and a predetermined reducing agent with contaminants. Then, in this mixing step, the contaminants are adjusted to a range of pH 4.5 to 9.0.

Preferably, the reducing agent is in powder form, the nutrient solution is added to the contaminant, then mixed, and the reducing agent is added to the mixture, and then mixed. Thereby, the reducing agent can be prevented from being oxidized by the nutrient solution, and its reducing power can be exerted in the contaminants.

On the other hand, the reducing agent is a water-soluble compound,
The reducing agent may be dissolved in the nutrient solution. It is easier to apply on site than a solid reducing agent. In addition, it becomes easy to store and transfer a large amount of nutrient solution. In order to prevent the reducing agent from being oxidized during storage, the nutrient solution containing the reducing agent is preferably stored in a closed container.

Alternatively, in the mixing step, the nutrient solution may be added to the contaminants in two or more portions. When a large amount of nutrient solution is mixed with, for example, soil, a shearing force hardly acts on the soil mass in the liquid, and the soil mass may move in the liquid without being collapsed. On the other hand, when a small amount of nutrient solution is added, the lump of soil is easily disintegrated due to the shearing force, and can be more uniformly mixed. Then, more nutrient solution may be further added. In one embodiment, as a first step, 1-10 vol% of the nutrient solution based on the contaminant is added to the contaminant and mixed, and then more than the amount added in the first step Preferably, the method further comprises the step of adding and mixing an amount of the nutrient solution to the contaminant. In another embodiment, as a first step, 1-5 v based on the contaminants.
ol% of the nutrient solution to the contaminant and mixing, and then, as a second step, combining the nutrient solution with 5 to 10 vol% based on the contaminant in conjunction with the first step. Adding to the contaminants and mixing;
It is preferable that the method further comprises a step of adding a larger amount of the nutrient solution than the amount added in the step or the second to the contaminant and mixing. In any of the embodiments, a small amount of the nutrient solution is added in the first stage, so that a shear force acts on the mixture, which facilitates more uniform mixing. In any embodiment, it is preferred that 15 to 25 vol% of the nutrient solution is finally added to the contaminant based on the contaminant. The final means the sum of these nutrient solutions when they are added in several portions.

Next, the mixture is allowed to stand under a low aeration condition. In this standing step, contaminants are removed by reductive dehalogenation. For example, it is allowed to stand for two weeks or more, preferably one month or more.

It is preferable that the standing step is performed in a state of being separated from the surroundings. This can prevent the halogenated organic compound in the mixture from diffusing and penetrating into the surroundings.

Further, in order to maintain low ventilation conditions, it is preferable to coat the contaminants with an impermeable material. For example,
The soil may be covered with a vinyl sheet. This is for promoting the culture of anaerobic microorganisms. In order to maintain low aeration conditions, it is preferable to immerse the contaminants in an aqueous liquid.

Further, in the standing step, the contaminants are preferably kept at 17 ° C. to 60 ° C. for at least the first three days. This particularly promotes the cultivation of the microorganisms in the mixture and increases the concentration. In the standing step, it is preferable that the contaminants are kept at 17 ° C to 60 ° C for at least the first 5 days. Further, in the standing step, it is preferable that the contaminants are kept at 20 ° C to 40 ° C for at least the first 3 days, preferably 5 days.

[0135]

The present invention will be described below in more detail with reference to examples. However, the present invention is not limited by these examples.

In the experiment for purifying tetrachloroethylene conducted in the examples of the present invention, a medium for methane-producing microorganisms in Table 2 or a medium for sulfate-reducing microorganisms in Table 3 was used as a microorganism medium. Also, in any purification tests,
Performed at room temperature (12-23 ° C).

The pH was measured by adjusting the soil: pure water = 1: 1 (weight ratio), and using a pH meter HM-5B manufactured by Toa Denpa Kogyo.
It was measured with a mold. In the measurement of the oxidation-reduction potential with respect to the saturated silver chloride electrode, soil: oxygen-free water = 1: 1 (weight ratio)
The ORP composite electrode model PS-8160 was immersed in an ORP Mei ODIC-3 model manufactured by Toa Denpa Kogyo Kogyo Co., Ltd., and measured after being left for 30 minutes.

The analysis of ethylene chloride in soil was carried out by a method developed at Yokohama National University (Kenichi Miyamoto et al., “Method for measuring the content of low-boiling organic pollutants in soil”, Journal of Japan Society on Water Environment, 199).
5 years, Vol. 18, No. 6, pp. 477-488), the sample soil was immersed in ethanol, ethylene was extracted with ethanol, and then the ethylene was re-extracted in decane.
A solution of ethylene in decane was converted to Hitachi Gas Chromatograph G-
The mixture was put into a column of 5000 type and analyzed by an FID detector.

On the other hand, for the measurement of the ethylene chloride gas generated in the gas phase, the generated ethylene chloride gas was measured using a Hitachi Gas Chromatograph G-5000 type 20% TCP Chromium.
mosorb WAW DMCS 60-80 mesh
Analysis was performed by injecting into a column and detecting with a FID detector. In the case of measuring ethylene and ethane gas generated in the gas phase, Porapack is used as a column.
Using a Hitachi Gas Chromatograph G-50 using a Q column
Analysis was performed by detecting with a 00 type FID detector. Further, for measurement of hydrogen, carbon dioxide gas, and methane generated in the gas phase, GL Science Gas Chromatograph-32 is used.
Type 0, TCD detector, activated carbon 30/60 or M
The analysis was carried out on a molecular sleeve 13X.

Examples of the reduced iron include Wako Pure Chemical Industries, Ltd.
Wako first grade reduced iron, product code 096-00785 was used. Unless otherwise specified, reduced iron refers to powder.

Examples 1 to 5 and 7 to 10 mainly relate to the first aspect of the present invention.

Example 1 In Example 1, reduced iron powder was used as a reducing agent.

The contaminated soil collected from the surface layer of the contaminated soil of Factory A was used. The contaminants in the contaminated soil are mainly tetrachlorethylene, and the amount of tetrachlorethylene contained in 1 kg of the dry contaminated soil is 25 mg. With respect to 14 samples obtained by collecting 30 g of this contaminated soil in a 125-ml vial, the time-dependent changes in the pH of the contaminated soil, the oxidation-reduction potential with respect to the saturated silver chloride electrode, and the amount of tetrachloroethylene reduction were determined under the following 14 types of experimental conditions. Examined. The water content in each experimental system was set in the range of 48 to 53%. During sample preparation and after sampling, the gas phase of the vial was replaced with nitrogen gas.

The test contaminated soil was obtained from the loam layer, and its physical properties were a water content of 47% and a water permeability of 10 ^-4 .
It had an oxidation-reduction potential of 380 mV with respect to a saturated silver chloride electrode at 10 ^-5 cm / sec, pH 6.6.

Experimental conditions Reaction system using medium for methanogen (Table 2) Control of contaminated soil Contaminated soil + methanogenic medium 9.0 ml Contaminated soil + methanogenic medium 9.0 ml + reduced iron 1.0
g Contaminated soil + 9.0 ml of methanation medium + 1.0 reduced iron
g + mixed calcareous fertilizer A (main limestone) 1.0 g + cow dung compost 1.0 g + humus 0.5 g contaminated soil + methane production medium 9.0 ml + reduced iron 1.0
g + mixed calcareous fertilizer B (main components limestone and amine)
0 g Tensewage sludge compost 1.0 g + humus 0.5 g Contaminated soil + methanation medium 9.0 ml + reduced iron 1.0
g + mixed shell fossil fertilizer (main component shell fossil) 1.0 g + sewage sludge compost 1.0 g + humus 0.5 g contaminated soil + methane production medium 9.0 ml + reduced iron 1.0
g + mixed calcareous fertilizer A 1.0 g + humus 1.0 g "Azumine" is a humic acid magnesia fertilizer, and its component composition is humic acid (50-60%), magnesia (15%),
Total nitrogen (3%), silicic acid (3%).

Table 2 shows the media for methanogenic microorganisms.

[0147]

[Table 2] * One mineral liquid is 6 g of K in 1 liter of distilled water.
₂ Refers to the liquid contained in HPO ₄ .

* 2 mineral liquids are 1 g of distilled water, 6 g of KH ₂ PO ₄ , 6 g of (NH ₄ ) ₂ SO ₄ , 1
2g of NaCl, MgSO ₄ · 7H ₂ O of 2.6 g, and refers to a liquid CaCl ₂ · 2H ₂ O of 0.16g is contained.

* A trace amount of mineral liquid is 1.5 g of nitrilotriacetic acid and 3.0 g of MgS in 1 liter of distilled water.
_{O 4 · 7H 2 O, MnSO} 4 · 2H 2 O of 0.5 g, 1.0
g of NaCl, FeSO ₄ · 7H ₂ O of 0.1 g, 0.1
g CoSO ₄ or CoCl ₂ , 0.1 g CaCl _2.
2H ₂ O, 0.1 g ZnSO ₄ , 0.01 g CuSO
₄ · 5H ₂ O, 0.01g of AlK (SO _{4) 2,} 0.01
g of H ₃ BO _3, and, 0.01 g of Na ₂ MoO ₄ · 2H
_This refers to the liquid contained in ₂ O. First, nitrilotriacetic acid is dissolved while adjusting the pH to 6.5 with KOH, and then other minerals are added. Finally, the pH is adjusted to 7.0 with KOH.

* The trace amount of vitamin liquid is 2 mg of biotin and 2 mg of folic acid (f) in 1 liter of distilled water.
olic acid), 10 mg of pyridoxine / hydrochloric acid, 5 mg of thiamine / hydrochloric acid, 5 mg of riboflavin (r
iboflavin), 5 mg of nicotinic acid, 5
mg of DL-calcium pantothate
enate), vitamin B _12, 5mg of p- aminobenzoic acid 0.1 mg, and refers to a liquid containing a 5mg of lipoic acid (lipoic acid).

In the above experimental conditions, the meaning of the equation representing the reaction system is as follows when the experimental conditions are described, for example.

In a vial bottle of 125 ml capacity obtained by collecting 30 g of contaminated soil, 1.0 g of reduced iron, mixed calcareous fertilizer A
After mixing 1.0 g, 9.0 ml of the medium for methane-producing microorganisms shown in Table 2 was added to this mixture, and then 1.0 g of cow dung compost and 0.5 g of humus were added, followed by a butyl stopper and an aluminum seal. Sealed. This series of operations for preparing the experimental sample was performed promptly without any pause.

As shown in FIG. 1, the content of tetrachloroethylene for three days passed, the pH value for seven days passed, and the oxidation-reduction against a saturated silver chloride electrode were measured for the seven samples thus prepared. Measure the potential.

The following measurement intervals are as shown in FIG.

B. Reaction system using medium for sulfate-reducing microorganisms (Table 3) Control of contaminated soil 9.0 ml of contaminated soil + 9.0 ml of sulfate-reduced medium + 1.0 g of reduced iron Contaminated soil + 9.0 ml of contaminated soil + sulfate-reduced medium 1.0 g of reduced iron
+ Mixed calcareous fertilizer A (main component limestone) 1.0 g + cow dung compost 1.0 g + humus 0.5 g contaminated soil + sulfuric acid reduction medium 9.0 ml + reduced iron 1.0 g
+ Mixed calcareous fertilizer B (main component limestone and aluminum) 1.0
g + 1.0 g of sewage sludge compost + 0.5 g of humus soil Contaminated soil + 9.0 ml of sulfate reduction medium + 1.0 g of reduced iron
+ Mixed shell fossil fertilizer (main component shell fossil) 1.0 g + sewage sludge compost 1.0 g + humus 0.5 g contaminated soil + sulfuric acid reduction medium 9.0 ml + reduced iron 1.0 g
+ Mixed calcareous fertilizer A (main component lime right) 1.0 g + humus 1.0 g Table 3 shows a medium for sulfate-reducing microorganisms.

[0156]

[Table 3] * The trace vitamin solution is the same as the trace vitamin solution in Table 2.

The test results in Example 1 are shown in FIGS. In Experiment A- and Experiment B-, tetrachloroethylene was reduced almost in the same manner as in Experiment A-1 or Experiment B-, and therefore, the description in the figures is omitted.

From this, by mixing reduced iron, inorganic fertilizers and various composts with the contaminated soil, and mixing the medium for methane-producing microorganisms or the medium for sulfate-reducing microorganisms, the neutral environment and the anaerobic environment around the soil pH of 7 were obtained. It is clear that is stable and tetrachlorethylene in the soil is rapidly decomposed. FIGS. 1 and 2 also show that tetrachloroethylene degradation is scarcely recognized only by mixing a contaminated soil with a medium for methanogenic microorganisms or a medium for sulfate-reducing microorganisms. The same effect was obtained by using slaked lime instead of the mixed calcareous fertilizer A.

Example 2 In Example 2, reduced iron powder was used as a reducing agent. Iron (II) chloride or iron (II) sulfate was used as a control.

Tetrachlorethylene was added to the soil contaminated with tetrachloroethylene, which was collected from the same factory as in Example 1, and the final contaminated concentration was adjusted so that the dry soil per kg was about 75 mg of tetrachloroethylene. The experiment was performed on soil. In the same manner as in Example 1, 30 g of contaminated soil was taken in a vial bottle having a capacity of 125 ml, and pH, redox potential with respect to a saturated silver chloride electrode, tetrachloroethylene reduction amount, ethylene / ethane production amount, hydrogen under the following eight kinds of experimental conditions were measured.・ The amount of carbon dioxide and methane generated was examined. The water content in each experimental system was 4
Performed in the range of 8-53%. In Experiments A- and B-, the contaminated soil, the sewage sludge compost, and the mulch were sterilized by steam pressure in an autoclave for 60 minutes to sterilize the microorganisms originating from them, and the microorganisms in the tetrachloroethylene decomposition reaction system were sterilized. The effect was examined.

During sample preparation, the gas phase of the vial was replaced with nitrogen.

Experimental conditions A. Reaction system using medium for methanogenic microorganisms (Table 2) Contaminated soil + 9.0 ml of methanogenic medium + 1.0 reduced iron
g + mixed calcareous fertilizer B (main component lime right and amine)
0 g + 1.0 g of sewage sludge combo + 0.5 g of humus soil Contaminated soil + 9.0 ml of methanation medium + FeCl
₂ 1.0 g + mixed calcareous fertilizer B (main component limestone and amine) 1.0 g + sewage sludge compost 1.0 g + humus 0.5 g contaminated soil + methane generation medium 9.0 ml + FeSO
₄ 1.0 g + mixed calcareous fertilizer B (main component limestone and amine) 1.0 g + sewage sludge compost 1.0 g + humus 0.5 g sterilized contaminated soil + methane generating medium 9.0 ml + reduced iron 1.0 g + mixed calcareous fertilizer B (main Ingredients: limestone and amine) 1.0 g + sterilized sewage sludge compost 1.0 g +
0.5 g of sterilized humus. Reaction system using medium for sulfate-reducing microorganisms (Table 3) Contaminated soil + 9.0 ml of sulfate-reduction medium + 1.0 g of reduced iron
+ Mixed calcareous fertilizer B (main component limestone and Azmin) 1.0
g + sewage sludge compost 1.0g + mulch 0.5g contaminated soil + sulfate-reducing medium 9.0ml + FeCl ₂ 1.
0g + mixed calcareous fertilizer B (main component limestone and Azmin)
1.0 g + sewage sludge compost 1.0 g + humus 0.5
g Contaminated soil + 9.0 ml of sulfate reduction medium + FeSO ₄ l.
0g + mixed calcareous fertilizer B (main component limestone and amine)
1.0 g + sewage sludge compost 1.0 g + humus 0.5
g Sterile contaminated soil + 9.0 ml of sulfuric acid reduction medium + 1.0 g of reduced iron + 1.0 g of mixed calcareous fertilizer B (main lime right and amine) + 1.0 g of sterilized sewage sludge compost +
0.5 g of sterilized humus The results of Example 2 are shown in Tables 4 and 5.

Tables 4 and 5 show that tetrachloroethylene was decomposed in the reduced iron. That is, by mixing reduced iron, an inorganic fertilizer (pH adjuster) and various composts with contaminated soil, and mixing a medium for methane-producing microorganisms or a medium for sulfate-reducing microorganisms,
It is clear that a neutral environment and an anaerobic environment around pH 7 are stably secured, and that tetrachloroethylene in soil is rapidly decomposed. On the other hand, instead of reduced iron, F
It is apparent that tetrachlorethylene decomposition hardly progresses when eCl ₂ or FeSO ₄ is added. That is, it does not decompose with a ferrous salt such as FeCl ₂ or FeSO ₄ or a ferric salt such as FeCl ₃ .

Even when the microorganisms were sterilized (Experiment A)
-, B-1) The decomposition amount of tetrachloroethylene is considerably low, indicating that in the method of the present invention, the reductive dehalogenation reaction proceeds by a synergistic action of a biological reaction and a chemical reaction.

Table 5 shows the analysis results of the gas components generated in the vials in Experiments A and B. In all of these experimental systems, a large amount of hydrogen, carbon dioxide, and ethylene / ethane were produced. In both experiments A- and B-, only trace amounts of tetrachloroethylene and cis-DCE were detected. Also, almost no vinyl chloride was detected, and no accumulation was found. Calculating the material balance in Experiments A-1 and B-, it is calculated that about 71% and 58% of the decomposition amount of tetrachloroethylene in the soil was converted to ethylene and ethane.

Similar results were obtained by using livestock compost instead of sewage sludge compost.

Table 4 shows the results of the dehalogenation reaction test (after 55 days of culture) using highly contaminated soil.

[0168]

[Table 4] Table 5 shows the generated gas (after 55 days of culture) when a tetrahaloethylene was subjected to a dehalogenation reaction under anaerobic conditions.

[0169]

[Table 5] Even when tetrachloroethylene is decomposed, ethylene,
It can be decomposed to ethane.

Example 3 In Example 3, reduced iron was used as a reducing agent.

Tetrachloroethylene was added to the lake sediment (X) adjacent to the industrial zone and the surface sediment (Y) of the wetland to obtain 35 mg of tetrachloroethylene / 1 k of dry mud.
g to a final concentration. In a 25-liter cylindrical stainless steel can (diameter: 300 mm x height: 370 mm), four experimental systems (X-type control and purification section, Y-type control and purification section) were provided with four experimental systems in which 15 kg of contaminated bottom mud was collected. . The conditions of each experimental system are as follows. In addition, these experimental containers were covered with covers for the purpose of preventing evaporation of water and mixing of water and keeping the temperature warm. Laying compost and humus on the bottom mud surface was not an essential condition and was not performed in this experiment. These three series of experiments were installed outdoors, and the pH, the oxidation-reduction potential with respect to a saturated silver chloride electrode, and the decrease in tetrachloroethylene were examined with time. The outdoor temperature range during the experiment was 7 to 18 ° C, and the water content of the sediment was about 4
1 to 50%.

(Experimental conditions) X system control: contaminated bottom mud + pure water 3000 ml X system purification zone: contaminated bottom mud beer saccharified cake wastewater 3200 ml
+ 500 g of reduced iron + 500 g of mixed calcareous fertilizer B (main component of limestone and azumi) + 500 g of sewage sludge compost + 250 g of humus Y control: contaminated bottom mud + pure water 3300 ml Y system purification zone: contaminated bottom mud beer saccharified wastewater 3500 ml
+500 g of reduced iron + 500 g of mixed calcareous fertilizer B (main component of limestone and amine) +500 g of sewage sludge compost + 250 g of humus The main component of beer saccharified wastewater is reducing sugar 9600
mg / l, acetic acid 180mg / l, lactic acid 31
00 mg / l, suspended material 8100 mg / l, BOD (biochemical oxygen demand) 12700 mg / l
Liter and the total organic carbon concentration is 5100 mg / liter.

Table 6 shows the results of the change in the concentration of tetrachloroethylene. The pH and the oxidation-reduction potential with respect to the saturated silver chloride electrode were pH 4.6 to 5.3 and ORP 180 to 30 for both the X-based control and the Y-based control.
It is about 0 mV, and both X system purification zone and Y system purification zone
H7 to 7.4, ORP-400 to -570 mV. Thereby, in any of the X system purification zone and the Y system purification zone,
It can be seen that tetrachloroethylene can be effectively decomposed by the purification method according to the present invention.

Table 6 shows changes in the concentration of tetrachlorethylene in the bottom mud (unit: mg / kg of dry mud).

[0175]

[Table 6] In the present invention, by combining a chemical reaction and a biological anaerobic reaction, contaminants of a halogenated organic compound such as soil and groundwater can be quickly and easily purified. Further, according to the method of the present invention, contaminants can be purified without eluting the halogenated organic compound. For example, in the case of contaminated soil or the like, by maintaining the water retention of the contaminated soil or the like appropriately, it is possible to purify the halogenated organic compound contamination without penetrating into the underground deeper than the contamination position.

In the present invention, the halogenated organic compound can be converted into an organic compound containing no chlorine such as ethylene or ethane, and the reaction is not stopped by a harmful intermediate product. The problem of accumulation of data does not occur.

Example 4 In Example 4, reduced iron or cast iron waste was used as a reducing agent.

In the tetrachloroethylene soil purification experiment in Example 4, a medium for methane-producing microorganisms shown in Table 7 was used. The oxidation-reduction potential shown in Example 4 was
The potential measured using a platinum electrode as a metal electrode and a saturated silver chloride electrode as a comparative electrode is shown.

Table 7 shows the media for methanogenic microorganisms.

[0180]

[Table 7] Mineral 1 liquid, mineral 2 liquid, trace mineral liquid, and
The trace vitamin solution is the same as that used in Table 2.

A purification experiment was carried out on tetrachlorethylene-contaminated soil collected from Factory A (contamination concentration is 25 mg of tetrachloroethylene in soil in an amount corresponding to 1 kg of dry soil).

In the experiment, 30 g of contaminated soil was collected in a vial bottle having a capacity of 125 ml, and a methane-producing microorganism medium, reduced iron or cast iron scrap, and sewage sludge compost were mixed under the following conditions, and the decomposition of tetrachloroethylene was examined. The addition amount of reduced iron, cast iron waste, and sewage sludge compost to the soil was 5% (weight). Cast iron shavings are sifted and the particle size is 5
A cast iron swarf A of 500 μm or less was designated as a cast iron swarf B 50,000 to 800 μm, and a cast iron swarf C of 800 μm or more. In addition,
At the time of sample preparation, the gas phase of the vial was replaced with nitrogen.

The soil moisture content at the time of soil purification is 48.4 to
48.9%. The water content (%) here means
(Water weight / wet soil weight) × 100.

In the experiment, the cells were cultured for 60 days. And
PH in soil, redox potential against saturated silver chloride electrode,
The decrease in tetrachloroethylene, the amount of ethylene / ethane produced in the gas phase, and the amount of hydrogen / carbon dioxide / methane produced were investigated.

The reduced iron used here was, as described above,
It is commercially available from Wako Pure Chemical Industries as first-class reduced iron powder.

Experimental conditions 30 g of contaminated soil (control, comparative example) 30 g of contaminated soil + 9.0 ml of methane generation medium + 1.5 g of reduced iron + 1.5 g of sewage sludge compost 30 g of contaminated soil + 9.0 ml of methane generation medium + 1.5 g of cast iron waste A + sewage sludge Compost 1.5g Contaminated soil 30g + Methanogenic medium 9.0ml + Cast iron waste B 1.5g + Sewage sludge compost 1.5g Contaminated soil 30g + Methanogenic medium 9.0ml + Cast iron waste C 1.5g + Sewage sludge compost 1.5g Test in Example 4 The results are shown in Tables 8 and 9.

Table 8 shows the concentration of tetrachlorethylene in the soil when purified with cast iron chips or the like.

Table 9 shows the gas generated when purifying tetrachlorethylene in the soil with cast iron scraps or the like.

Table 8 shows the results of purification of tetrachloroethylene in soil by cast iron chips and the like (after 60 days of culture).

[0190]

[Table 8] Table 9 shows the amount of generated gas (after 60 days of culture) when purifying tetrachloroethylene in soil with cast iron scraps or the like.

[0191]

[Table 9] In Table 8, "tetrachloroethylene in soil (PC
"E), pH, ORP" represents the value after 60 days of culture.
“Ethylene / ethane conversion rate of tetrachloroethylene (PCE)” in Table 9 indicates the ratio of tetrachloroethylene converted to ethylene / ethane during 60 days of culture. "H
_“2 , CH ₄ , CO ₂ ” represent the amount of gas generated during the period per kg of dry soil.

In the system using the reduced iron and the system using the cast iron waste A, tetrachloroethylene in the soil was purified to a level at which it was not detected.

It can be seen that tetrachlorethylene can be dechlorinated and converted to ethylene and ethane using cast iron chips as in the case of reduced iron. In particular, it can be understood that tetrachlorethylene is dechlorinated very efficiently by using the cast iron scrap A, that is, cast iron scrap having a small particle size.

When tetrachloroethylene-contaminated soil was purified with cast iron shavings, the soil pH was 7.2-7.3, which was neutral, and the oxidation-reduction potential with respect to the saturated silver chloride electrode was -225 to 225.
A reducing environment of -375 mV was maintained. Therefore,
When comparing the soil purification method using reduced iron and the soil purification method using cast iron scrap, it can be said that there is no difference between the two soil environments.

Furthermore, in the systems to which the methane-producing microorganism medium was added, and in each of the systems in which carbon dioxide gas was generated in the gas phase of the vial, it can be said that the microorganisms are growing. That is, it can be said that the cast iron scrap is a substance that does not inhibit the growth of soil microorganisms.

Example 5 Samples of contaminated soils having different tetrachloroethylene contents were prepared by further adding tetrachloroethylene to the same tetrachloroethylene contaminated soil as in Example 4. As a result, 1 kg of soil converted to dry soil,
Contaminated soil containing 50mg of tetrachlorethylene, 75m
g and contaminated soil containing 140 mg were obtained.
Then, a purification test was performed on each contaminated soil.

In the experiment, 30 g of various contaminated soils were collected in a vial bottle having a capacity of 125 ml in the same manner as in Example 4, and 9.0 ml of the methane-producing microorganism medium shown in Table 7 and cast iron chips A1. 5 g and 1.5 g of sewage sludge compost were mixed, and the decomposition of tetrachlorethylene was examined. In addition,
At the time of sample preparation, the gas phase of the vial was replaced with nitrogen.

In the experiment, cultivation was continued at room temperature, and after 63 days, pH in soil, oxidation-reduction potential against a saturated silver chloride electrode,
The amount of reduction of tetrachloroethylene and the amount of ethylene / ethane produced in the gas phase were examined.

Experimental conditions Contaminated soil (50 mg-tetrachloroethylene / kg)
-Dry soil) 30 g (control) Contaminated soil (50 mg-tetrachloroethylene / kg)
-Dry soil) 30 g + Methanogenic medium 9.0 ml + Cast iron scrap A 1.5 g + Sewage sludge compost 1.5 g Contaminated soil (75 mg-tetrachloroethylene / k)
g-dry soil) 30 g (control) Contaminated soil (75 mg-tetrachloroethylene / k)
g-dry soil) 30 g + methane production medium 9.0 ml + cast iron waste A1.5 g + sewage sludge compost 1.5 g contaminated soil (140 mg-tetrachloroethylene /
kg-dry soil) 30 g (control) Contaminated soil (140 mg-tetrachloroethylene / k)
g-dry soil) 30 g + 9.0 ml of methane production medium + 1.5 g of cast iron waste A + 1.5 g of sewage sludge combo Table 10 shows the test results of Example 5. From this, by using cast iron shavings A having a particle size of 500 μm or less even in highly contaminated soil containing 50 mg, 75 mg, and 140 mg of tetrachloroethylene in a 1 kg amount of soil in terms of dry soil, Dehalogenation to ethylene / ethane was possible, indicating that the effectiveness of this soil purification method was demonstrated. In this soil purification experiment, slight trichlorethylene and cis-DCE were generated in the gas phase and in the soil as tetrachlorethylene decomposition products, but vinyl chloride was hardly detected.

In the purification of soil contaminated with high concentration of tetrachloroethylene using the cast iron shavings A, the soil pH was 7.2.
The oxidation-reduction potential with respect to neutral and saturated silver chloride electrodes was -350 to -380 mV, and the reducing environment was stably maintained.

In Table 10, "tetrachloroethylene in soil, pH, ORP" represents the value after 63 days of culture. Table 10
"Ethylene / ethane conversion rate of tetrachloroethylene" in the above means the ratio of tetrachloroethylene converted to ethylene / ethane during 63 days of culture.

Table 10 shows the purification results (after 63 days of culturing) of soil contaminated with high-concentration tetrachlorethylene using cast iron chips.

[0203]

[Table 10] In the present invention, it has been found that by using cast iron powder or reduced iron powder as the metal powder, a high purification rate can be achieved for a wide range of contamination concentrations from low to high concentrations of the halogenated organic compound. By using cast iron, for example, cast iron shavings, low-cost, safe and simple treatment system removes contaminants by halogenated organic compounds.
It can be purified and industrial waste can be effectively used.

Further, by combining a soil improver having low solubility, the elution of the halogenated organic compound from the contaminated soil can be suppressed. Moreover, if the water retention of the contaminated soil is appropriately maintained, purification can be achieved without spreading and penetrating the contamination from the contamination position of the organic chlorine compound contamination already generated underground to a deeper depth.

Embodiment 6 Embodiment 6 corresponds to the second aspect of the present invention. Example 6
Shows that a halogenated organic compound can be decomposed even when a nutrient of a heterotrophic anaerobic microorganism is not added.

As the reducing agent, (1) metallic iron (comparative example),
(2) manganese, (3) aluminum-silicon alloy,
(4) Four types of sodium hypophosphite were compared.

Table 11 shows the standard electrode potential of each reducing agent.

Table 11 shows the standard electrode potential of the reducing agent.

[0209]

[Table 11] For 6500 g of loamy soil containing 150 mg / kg of tetrachlorethylene (water content 60%), (1) 20 g of metallic iron, (2) 10 g of manganese,
(3) 10 g of aluminum-silicon alloy or (4) 20 g of sodium hypophosphite is added, and the temperature is 2
The temperature was maintained at 0 ° C., and the state thereafter was measured.

In (2) and (3), the oxidation-reduction potential was lowered to -500 mV or less within 1 hour, and then -50 mV for 10 days.
It was kept below 0 mV. Tetrachloroethylene is 10
By the end of the day, ethylene and ethane were completely dehalogenated. In (4), the oxidation-reduction potential was -450 within one hour.
mV or less, and then maintained at -450 mV or less for 10 days. Tetrachloroethylene was completely dehalogenated to ethylene and ethane by 10 days. On the other hand, in (1), it took 5 days for the oxidation-reduction potential to drop to -400 mV, and thereafter maintained at -400 mV or less for 5 days. 2 days after 10 days of tetrachloroethylene
Only dehalogenated ethylene and ethane.

Example 7 A comparison was made between (1) a system to which only a reducing agent was added and no organic carbon source was added and (2) a system to which a reducing agent and an organic carbon source were added. Calcium-silicon alloy (standard electrode potential -1900 mV) was used as a reducing agent, and sodium acetate was used as an organic carbon source.

In (1) and (2), 100 g of a calcium-silicon alloy was added to 65 kg of clayey soil (water content: 55%) on which 200 mg / kg of trichlorethylene had been adsorbed. In (2), in addition to this, 70 g of sodium acetate and 7 g of nutrients were added. In each case, the temperature was maintained at 20 ° C., and the subsequent state was measured.

In both (1) and (2), the oxidation-reduction potential dropped to -500 mV or less within one hour. In (1), the oxidation-reduction potential was maintained at -500 mV or less for 10 days, and then gradually shifted to the oxidized state, and the oxidation-reduction potential increased to 0 mV by 40 days later. 80% of trichlorethylene was reduced to ethylene and ethane, but 20% remained in soil. On the other hand, (2) sets the oxidation-reduction potential to -500 mV
Maintained below, 99% of trichlorethylene was reduced to ethylene and ethane.

The surface of the reducing agent of the present invention is not easily covered with a stable oxide film and is easily dissolved in water, so that the reducing agent is easily brought into contact with contaminants and the decomposition rate is improved. Further, even if the contaminant is a substance having low water permeability such as clayey soil or consolidated silt, a dehalogenation reaction can be performed by combining the contaminant with an organic carbon source serving as a growth substrate for microorganisms.

Example 8 As the reducing agent, (1) metallic iron powder (control),
A comparison was made between (2) sodium hypophosphite powder and (3) titanium citrate aqueous solution.

(Test conditions) In terms of dry soil, loamy soil containing 120 mg / kg of tetrachloroethylene was used. The initial oxidation-reduction potential is +350 mV,
The amount of soil was 100 m ³ .

(Test Results) In (2) and (3), the oxidation-reduction potential decreased to -450 mV or less within 1 hour, and was maintained at -450 mV or less for 5 days thereafter. Tetrachloroethylene was completely dehalogenated to ethylene and ethane by 5 days.

On the other hand, in (1), it takes 10 days to completely knead the soil and metal using one backhoe, and then it takes 5 days until the oxidation-reduction potential drops to −400 mV, and then 5 days. It was maintained below -400 mV for days. By 20 days, only 20% of tetrachloroethylene had been dehalogenated to ethylene and ethane.

Example 9 In each system, ascorbic acid was used as a reducing agent. In system (1), no organic carbon source was added. On the other hand, in the system (2), sodium acetate was also used as an organic carbon source.

Clay containing 100 mg / kg of tetrachloroethylene in terms of dry soil was used. The initial redox potential was +320 mV and the initial pH was 6.5.

(Test Results) In each of the systems (1) and (2), the oxidation-reduction potential dropped to +130 mV or less within one hour after the injection of the reducing solution. (1) Increases the oxidation-reduction potential by +130 for 10 days.
mV or less, and then gradually shifted to an oxidized state,
After that, the oxidation-reduction potential increased to +300 mV.
The pH gradually decreased from 6.3 on day 0, and after 40 days.
It was 5. Trichloroethylene was reduced to 50% by ethylene and ethane, but 50% remained in soil.

On the other hand, in (2), after that, the oxidation-reduction potential gradually decreased and became -150 mV or less after 20 days.
-150 mV or less was maintained until 40 days later. The pH gradually decreased from 7.5 on day 0 to 6.8 after 40 days. 99.9% of trichlorethylene was reduced to ethylene and ethane.

In this embodiment, since the water-soluble reducing agent is used, the contaminants of the halogenated organic compound can be brought into good contact with the reducing agent, and the reductive dehalogenation reaction can be promoted.

The reducing agent used in this embodiment has the advantage that the standard electrode potential is equal to or lower than that of metallic iron, the potential difference between the reducing agent and the halogenated organic compound becomes larger, and the dehalogenation is accelerated. is there. Further, even if the contaminant is a substance having low water permeability such as clayey soil or consolidated silt, a dehalogenation reaction can be performed by combining the contaminant with an organic carbon source serving as a growth substrate for microorganisms. Also, these reducing agents, like metallic iron,
Does not passivate.

Example 10 The present invention shows that halogenated aromatic compounds can be decomposed.

20 g of metallic iron was added to 6 kg of loam soil having a concentration of 10 mg / kg of pentachlorophenol (hereinafter abbreviated as PCP). In system 10-1, 1 liter of a medium for nitrate-reducing microorganisms shown in Table 12 was further added. On the other hand, in the system 10-2, 1 liter of water was added as a control.

Table 12 shows the medium for nitrate-reducing microorganisms.

[0228]

[Table 12] Next, the temperature was maintained at 28 ° C. after kneading, and changes in PCP concentration and product concentration were examined.

Tables 13 and 14 show the results.

Table 13 shows the results of the system 10-1.

[0231]

[Table 13] Table 14 shows the results for system 10-2.

[0232]

[Table 14] In Tables 13 and 14, TeCP and CP are 2, 3, respectively.
Shows 5,6-tetrachlorophenol and 3-chlorophenol. Eh is a value converted into a standard electrode potential with respect to a standard hydrogen electrode.

In the system 10-1, compared with the system 10-2,
It can be seen that pentachlorophenol was rapidly decomposed. In system 10-1, pentachlorophenol is
2,3,5,6-tetrachlorophenol and / or 3
-Probably degraded to phenol via chlorophenol. Also, 2,3,5,6-tetrachlorophenol and 3-chlorophenol were finally dehalogenated and did not accumulate. In addition, it is considered that phenol was further decomposed into other compounds.

Embodiment 11 Embodiment 11 mainly corresponds to the third aspect of the present invention.

In Example 11, the tetrachloroethylene-contaminated soil was purified using the microorganism medium for reducing oxidized nitrogen shown in Table 15 and the medium for methane-producing microorganisms shown in Table 16 (control). Nitrogen oxide in the medium composition in Table 15 corresponds to 23% by weight of organic carbon. Purification test is performed at room temperature (12 ~
(23 ° C.) for 30 days, and changes in soil properties were measured.

The pH was measured as follows: soil: pure water = 1: 1 (Wt)
And measured with a pH meter HM-5B manufactured by Toa Denpa Kogyo. In the measurement of the oxidation-reduction potential (ORP) with respect to the saturated silver chloride electrode, soil: oxygen-free water = 1: 1 (W
t), Central Science ORP meter UK-2
At 030, the measurement was performed after the electrode was immersed and left for 30 minutes. In addition, the oxidation-reduction potential of the saturated silver chloride electrode shown in this example indicates a potential measured using a platinum electrode as a metal electrode and a saturated silver chloride electrode as a comparative electrode. Analysis of ethylene chloride in soil was carried out by a method developed at Yokohama National University (Kenichi Miyamoto et al., "Method for measuring the content of low-boiling halogenated organic compounds in soil", Journal of Japan Society on Water Environment, 1995, Vol. 18, No. 6)
No. pp. 577-488), ethanol extraction followed by conversion to decane and Hitachi Gas Chromatograph G-5000.
Type, 20% TCP Chromoso with FID detector
Analysis was performed using an rb WAW DMCS60-80 mesh column. Further, for measurement of hydrogen, carbon gas, methane, and nitrogen generated in the gas phase, Ac was measured with a GL Science Gas Chromatograph GC-320, TCD detector.
live carbon 30/60 or Molec
ulal sieve 13X was used. Further, the concentrations of nitrate nitrogen and nitrite nitrogen ions in the soil were measured using a Hitachi anion chromatograph 2010i for the extracted water adjusted to soil: pure water = 1: 1 (Wt).

Table 15 shows the microorganism medium for reducing oxidized nitrogen.

[0238]

[Table 15] Table 16 shows media for methanogenic microorganisms.

[0239]

[Table 16] A purification experiment was performed on tetrachlorethylene-contaminated soil (contamination concentration: about 25 mg / kg-dry soil) collected from a chemical factory. In the experiment, 30 g of contaminated soil was dispensed into a 50 ml vial bottle, and a medium and metal powder were mixed under the following conditions, and after 30 days, changes in soil properties such as tetrachloroethylene decomposition (Table 17) were determined. Examined. First-class reduced iron powder manufactured by Wako Pure Chemical Industries was used as the metal powder. At the time of sample preparation, the gas phase of the vial was replaced with helium gas.

Experimental conditions 30 g of contaminated soil 30 g of contaminated soil + 9.0 ml of water + 0.07 g of reduced iron 30 g of contaminated soil + 9.0 microbial medium for reducing oxidized nitrogen
ml + reduced iron 0.07g contaminated soil 30g + methanogenic microorganism 9.0ml
+ Reduced iron 0.07 g The test results are shown in Table 17. It was confirmed that when an oxidized nitrogen reduction medium was used, not only tetrachlorethylene was dechlorinated with ethylene and ethane, but also blackening of soil, generation of methane gas, and generation of mercaptan odor could be suppressed. It has also been found that hydrogen gas generated by the generation of nitrogen gas is diluted. In addition, no oxidized nitrogen or suboxide nitrate remained in the soil.

On the other hand, in a system to which only metal and water are added, pH
Was significantly reduced, and the oxidation-reduction potential with respect to the saturated silver chloride electrode also increased to +2 mV after 30 days, so that sufficient reductive dechlorination and decomposition could not be performed. As a result, tetrachloroethylene partially remained in the soil, and the conversion to ethylene was only 26%. From these facts, it is difficult to maintain an appropriate reduced state over a long period of time in a system to which only metal powder is added, and stable decomposition can only be achieved by coexisting a biological reaction due to the addition of a nutrient. It was shown that. Further, in the system to which only the metal powder was added, hydrogen gas of almost 100% concentration was generated, and it was considered that there was a risk of explosion. On the other hand, it was shown that nitrogen was reduced in the system to which the microbial medium for reducing oxidized nitrogen was added, and carbon dioxide was generated in the system to which the methanogenic microbial medium was added to dilute the hydrogen gas, so that the safety was high. However, in the system to which the methane-producing microorganism medium was added, generation of odor and discoloration of the soil were observed.

Table 17 shows the results of purification of tetrachloroethylene (PCE) in soil (after 30 days of culture).

[0243]

[Table 17] In a third aspect of the present invention, the use of a nutrient source containing 20-50% by weight of organic carbon, nitrogen oxides,
When the halogenated organic compound is decomposed, blackening of the soil and generation of odorous gas such as methane gas and mercaptan can be suppressed.

Example 12 In Example 12, organic carbon was supplied as a water-soluble organic carbon source.

To 5 kg of soil (60% moisture) containing 10 mg / kg of an organic chlorine compound, 6 g each of (1) glucose, (2) molasses waste liquid, and (3) compost were separately added as organic carbon sources. In addition, 200 mg of nutrients were added and maintained at a temperature of 28 ° C.

The following state was measured.

In (1) and (2), the number of anaerobic bacteria grew to 10 ⁷ viable bacteria / g soil in a few days, and the oxidation-reduction potential (ORP) against a saturated silver chloride electrode was maintained at −600 mV or less for 30 days. And tetrachloroethylene was dehalogenated to ethylene and ethane.

On the other hand, in (3), the number of microorganisms was 10
^It took 20 days to grow to ⁷ viable bacteria / g soil, and the ORP increased after 13 days and became -23 mV after 30 days.
Tetrachlorethylene remained 50% in the form of cDCE (cis-dichloroethylene) and was not completely dehalogenated.

Example 13 To 200 kg of soil (65% moisture) containing 30 mg / kg of a halogenated organic compound, 240 g of glucose was added as an organic carbon source, and 8 g of nutrients were added to purify it in winter. The work was performed under the conditions of (1) a plastic greenhouse, heated with warm water (average temperature: 22 ° C.), and (2) outdoor field loading.

In (1), the number of anaerobic bacteria was 10 ^{7 in} several days.
Proliferates to viable bacteria / g soil, ORP is -600 mV for 30 days
Maintained below, tetrachloroethylene was dehalogenated by ethylene and ethane.

On the other hand, in (2), 10
^It takes 30 days to grow to ⁷ viable bacteria / g soil, ORP
Increased after 10 days and reached +52 mV after 30 days. Tetrachloroethylene remained 20% undecomposed and 40% remained in the form of cDCE (cis-dichloroethylene) and was not completely dehalogenated.

Embodiment 14 Embodiment 14 mainly corresponds to the fourth aspect of the present invention.

A contaminated soil purification work for purifying the contaminants due to the halogenated organic compound in situ was performed.

The tetrachloroethylene-contaminated soil (average contaminant concentration: about 11 mg / kg-soil) excavated from the chemical plant site and stored in the concrete pit was purified.

This purification work was performed by the following three methods.

[Method 1] 5 m ³ of contaminated soil in a concrete pit was put into a 10 m ³ steel plate bucket, which is a non-leakage container, using a backhoe. Next, Table 15
Nutrient solution (hereinafter referred to as nutrient A) obtained by mixing the microbial medium for reducing oxidized nitrogen and the medium for methanogenic microorganisms in Table 16
0.2 m ³ (4 vol.% Of soil) was added to a steel plate bucket, and the soil and nutrient A were kneaded using a backhoe. Furthermore, nutritional supplement A 0.2 m ³ (4 vol.
%) Was added to a steel plate bucket, and the soil and nutrient A were kneaded using a backhoe. And further, nutritional supplement A
0.7 m ³ (14 vol.% Of soil) was added to the steel plate bucket and the soil and nutrient A were mixed. After the soil and nutrient A were sufficiently mixed, the reduced iron was sprayed on the soil in the steel plate bucket and kneaded again. The kneaded soil was returned to the concrete pit.

[Method 2] 5 m ³ of contaminated soil in a concrete pit was put into the steel plate bucket using a backhoe. Next, the nutrient A1.1m ³ (2 of soil)
2 vol. %) Was added to a steel plate bucket, and the soil and nutrient A were kneaded using a backhoe. Soil and nutrient A
After sufficient mixing, the reduced iron was sprayed on the contaminated soil in the steel plate bucket and kneaded again. The kneaded soil was returned to the concrete pit.

[Method 3] 5 m ³ of contaminated soil in a concrete pit was put into the steel plate bucket using a backhoe. Next, 15 to 20 hours before the addition, a suspension in which reduced iron was suspended in a microorganism medium for reducing oxidized nitrogen in Table 15 and a medium for methane-producing microorganisms in Table 16 (hereinafter referred to as nutrient B). 2 m ³ (4 vol.% Of soil) was added to a steel plate bucket, and the soil and nutrient B were kneaded using a backhoe. In addition, nutrient B 0.2m ³ (4vol of soil)
l. %) Was added to a steel plate bucket, and the soil and nutrient B were kneaded using a backhoe. Further, 0.7 m ^{3 of} nutrient B (14 vol.% Of soil) was added to a steel plate bucket, and these were thoroughly kneaded. The kneaded soil was returned to the concrete pit.

A part of the soil kneaded by the methods 1 to 3 was taken out, sieved with a 10 mm mesh sieve, and the amount of the soil clumps contained in the kneaded soil was visually checked. In the soil, the amount of the soil mass was 1 to 10% of the soil amount, whereas the soil obtained by the method 2 was 15 to 30%.
It was shown that the degree of kneading differs depending on the method of adding the nutrient and the method of kneading.

In any of the methods 1 to 3, after kneading, the entire upper surface of the soil in the concrete pit was fixed with an iron plate, which was often made of vinyl sheets, in order to suppress the ingress and egress of oxygen with the outside. In addition, besides the method of covering with a vinyl sheet, water is flooded to about 5 to 15 cm from the top surface of the soil so as to suppress the ingress and egress of oxygen from the outside and to keep moisture in the soil sufficiently, and to seal the soil with water. You may.

In all of the methods 1 to 3, the soil is returned to the concrete pit, in order to prevent tetrachloroethylene and the like from flowing out. In practice, underground contaminated soil may be put into a bucket, the contaminated soil and nutrient solution may be kneaded in the bucket, and then the kneaded material may be returned to the hole from which the contaminated soil has been removed. Alternatively, instead of kneading in a bucket, kneading may be performed in the ground at the site.

Two months after the covering with the vinyl sheet, the concentration of tetrachlorethylene in the soil was measured.
Table 18 shows the results. That is, Table 18 shows the results of the purification work for the soil contaminated with tetrachloroethylene.

[0263]

[Table 18] In the soil kneaded by Method 1, 99.8% was decomposed, 89% by Method 2 and 62% by Method 3.
From this, it can be seen that, as in Method 1, when the nutrient is added in several portions and kneading is performed each time, the decomposition rate is improved. Also, as in Method 2, when the powdery reducing agent is added after the nutrient solution and the soil are kneaded, the decomposition rate is improved.

The embodiments of the present invention include the following.

A method for purifying contaminants caused by a halogenated organic compound, comprising a step of adding a reducing agent having a standard electrode potential of 130 mV to −2400 mV with respect to a standard hydrogen electrode at 25 ° C. to the contaminants, The method wherein the reducing agent is at least one selected from the group consisting of reduced iron, cast iron, iron-silicon alloy, titanium alloy, zinc alloy, manganese alloy, aluminum alloy, magnesium alloy, calcium alloy, and a water-soluble compound.

When the reducing agent has a standard electrode potential with respect to a standard hydrogen electrode at 25 ° C. of −445 mV to −2400 m
V, and at least one selected from iron-silicon alloys, titanium alloys, zinc alloys, manganese alloys, aluminum alloys, magnesium alloys, and calcium alloys.

The contaminants have a dry weight of 1 k
The method wherein 0.1 g to 100 g of the iron compound is contained based on g.

The contaminants were added with a dry weight of 1 k
iron compounds 1g~100g based on g are contained, wherein said iron compound contains iron hydroxide (Fe (OH) ₃₎ or triiron tetraoxide (Fe ₃ O _4).

When the reducing agent is an iron-silicon alloy, a titanium-silicon alloy, a titanium-aluminum alloy, a zinc-aluminum alloy, a manganese-magnesium alloy, an aluminum-zinc-calcium alloy, an aluminum-tin alloy, an aluminum-silicon alloy, A method comprising at least one selected from the group consisting of a magnesium-manganese alloy and a calcium-silicon alloy.

[0270] The method wherein the reducing agent is a water-soluble compound.

A method wherein the reducing agent is an organic acid or a derivative thereof, hypophosphorous acid or a derivative thereof, or a sulfide salt.

A method wherein the reducing agent is a powder having a particle size of 500 μm or less.

A method for purifying contaminants caused by a halogenated organic compound, comprising a reducing agent having a standard electrode potential of 130 mV to −2400 mV with respect to a standard hydrogen electrode at 25 ° C., and a nutrient source of heterotrophic anaerobic microorganisms Adding to the contaminant, wherein the nutrient source contains organic carbon and 20 to 50% by weight of the organic carbon.

The nutrient source is 20 to 3 of the organic carbon.
A method containing 0% by weight of nitrogen oxide.

A method wherein the organic carbon is supplied as a water-soluble organic carbon source.

When the reducing agent has a standard electrode potential with respect to a standard hydrogen electrode at 25 ° C. of −400 mV to −2400 m
V is a metal material.

A method wherein the reducing agent is at least one selected from the group consisting of reduced iron, cast iron, iron-silicon alloy, titanium alloy, zinc alloy, manganese alloy, aluminum alloy, magnesium alloy, and calcium alloy. .

The method wherein the reducing agent is a water-soluble compound.

[0279] The method wherein the reducing agent is a powder having a particle size of 500 µm or less.

A method for purifying contaminants containing a halogenated organic compound and a solid, comprising a nutrient solution containing a nutrient source of heterotrophic anaerobic microorganisms and water, and a standard for a standard hydrogen electrode at 25 ° C. Electrode potential is 130mV ~ -24
Mixing a reducing agent of 00 mV with the contaminant, wherein the mixing step includes the step of mixing the contaminant with a pH of 4.5.
Adjusting the mixture to a range of from 9.0 to 9.0; and allowing the mixture to stand under low aeration conditions.

A method wherein the reducing agent is in powder form, wherein the nutrient solution is added to the contaminant and then mixed, and the reducing agent is added to the mixture and then mixed.

The method wherein the reducing agent is a powder having a particle size of 500 μm or less.

The method wherein the reducing agent is at least one selected from the group consisting of reduced iron, cast iron, iron-silicon alloy, titanium alloy, zinc alloy, manganese alloy, aluminum alloy, magnesium alloy, and calcium alloy. .

As a first step, based on the contaminants,
A step of adding and mixing 10 to 10 vol% of the nutrient solution to the contaminant; and a step of adding a larger amount of the nutrient solution to the contaminant than the amount added in the first step and mixing. How to have.

As a first step, based on the contaminants,
Adding and mixing the nutrient solution of 栄 養 5 vol% to the contaminant, and then, as a second step, in combination with the first step, the nutrient solution to be 5-10 vol% based on the contaminant. Adding to the contaminant and mixing, and further adding and mixing a larger amount of the nutrient solution to the contaminant than the amount added in the first or second step.

[0286] The method wherein the reducing agent is a water-soluble compound and the reducing agent is dissolved in the nutrient solution.

[0287] In the above stationary step, the contaminants are kept at 17 ° C to 60 ° C for at least the first three days.

[Brief description of the drawings]

FIG. 1 shows the use of a methane production medium according to the invention;
4 is a graph showing test results obtained by performing a reductive dehalogenation reaction on tetrachloroethylene-contaminated soil under anaerobic conditions.

FIG. 2 is a graph showing test results obtained by performing a dehalogenation reaction test on tetrachloroethylene-contaminated soil under anaerobic conditions using a sulfate reduction medium according to the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 11/02 (31) Priority claim number Japanese Patent Application No. 9-310599 (32) Priority date Hei 9 (1997) November 12, ( 33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 9-346511 (32) Priority date Hei 9 (1997) December 16, (33) Priority claim country Japan (JP) (31) ) Priority claim number Japanese Patent Application No. 9-357607 (32) Priority date Hei 9 (1997) December 25 (33) Priority claim country Japan (JP) (72) Inventor Koji Shinmura Hiyoshi, Kohoku-ku, Yokohama, Kanagawa Prefecture 2-33-1 Honmachi 351 Hiyoshi Ryo, Ebara Corporation

Claims (14)

[Claims] 1. A method for purifying contaminants caused by a halogenated organic compound, wherein a standard electrode potential with respect to a standard hydrogen electrode at 25 ° C. is 1
A step of adding a reducing agent of 30 mV to −2400 mV and a nutrient of heterotrophic anaerobic microorganisms to the contaminant, wherein the reducing agent is reduced iron, cast iron, iron-silicon alloy, titanium alloy , Zinc alloy, manganese alloy, aluminum alloy,
A method which is at least one selected from the group consisting of a magnesium alloy, a calcium alloy and a water-soluble compound. 2. The method according to claim 1, wherein the reducing agent has a standard electrode potential with respect to a standard hydrogen electrode at 25 ° C. of −400 mV to −2400.
mV, and reduced iron, cast iron, iron-silicon alloy,
The method according to claim 1, wherein the method is at least one selected from a titanium alloy, a zinc alloy, a manganese alloy, an aluminum alloy, a magnesium alloy, and a calcium alloy. 3. The method of claim 1, wherein said reducing agent comprises reduced iron. 4. The method of claim 1, wherein said reducing agent comprises cast iron. 5. The method according to claim 1, wherein the reducing agent is iron-silicon alloy, titanium-silicon alloy, titanium-aluminum alloy, zinc-
It is at least one selected from the group consisting of an aluminum alloy, a manganese-magnesium alloy, an aluminum-zinc-calcium alloy, an aluminum-tin alloy, an aluminum-silicon alloy, a magnesium-manganese alloy, and a calcium-silicon alloy. 2. The method according to 1. 6. The method according to claim 1, wherein said reducing agent is a water-soluble compound. 7. The method according to claim 6, wherein the reducing agent is an organic acid or a derivative thereof, hypophosphorous acid or a derivative thereof, or a sulfide salt. 8. The method according to claim 1, wherein the reducing agent is a powder having a particle size of 500 μm or less. 9. The method of claim 1, wherein the water content of the contaminant is at least 25% by weight. 10. The method according to claim 1, further comprising, after the adding step, maintaining the contaminant in a pH range of 4.5 to 9.0 to promote reductive dehalogenation of the halogenated organic compound. 2. The method according to 1. 11. After the adding step, remove the contaminants with p
2. The method according to claim 1, further comprising the step of maintaining H in the range of 4.5 to 9.0 and in a reducing atmosphere. 12. The method according to claim 1, further comprising a step of adding various kinds of organic compost, composted organic matter, or wastewater or waste containing organic matter to the contaminant, and then mixing. 13. A method for purifying contaminants due to a halogenated organic compound, wherein a standard electrode potential at 25 ° C. with respect to a standard hydrogen electrode is 1
A method comprising: mixing a solid reducing agent with a nutrient of a heterotrophic anaerobic microorganism at 30 mV to -2400 mV; and adding the mixture to the contaminant. 14. The method according to claim 13, wherein the solid reducing agent is mixed with a nutrient solution containing the nutrient source and water.