JP2007222823A - Cleaning method of soil polluted with chloroorganic compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently cleaning soil polluted with a chloroorganic compound by simply and quickly activating aerobic microorganism and anaerobic microorganism in the polluted soil. <P>SOLUTION: The cleaning method of polluted soil is a method for cleaning soil polluted with a chloroorganic compound and involves the step of loading and mixing the polluted soil with corn steep liquor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for purifying soil contaminated with a chlorinated organic compound with microorganisms.

  Chlorinated organic compounds have been used in large quantities due to their excellent solubility, volatility, and nonflammability. For example, tetrachlorethylene (hereinafter referred to as “PCE”), which is a representative chlorinated organic compound, has dry melting, metal parts, in addition to chlorofluorocarbon gas production materials, due to its excellent solubility, volatility, and nonflammability. It has been used for degreasing and cleaning, and fiber refining.

  On the other hand, organic compounds with a particularly high degree of chlorine substitution also have the disadvantage that they are chemically stable and difficult to decompose in the environment. In addition, since it is difficult to be metabolized in vivo, it has been reported that the central nervous system and liver / kidney are damaged. Therefore, when soil is contaminated with a chlorinated organic compound, there is a risk that secondary damage will occur in the living body. Therefore, various technologies have been developed for purifying such contaminated soil.

  Examples of such techniques include various chemical or physical treatment methods such as a method in which a chlorinated organic compound is sucked and adsorbed on activated carbon, a thermal decomposition method by heating, a method for insolubilizing contaminated soil, and the like. However, in recent years, treatment with microorganisms that can be carried out inexpensively under milder conditions and is excellent from the viewpoint of energy saving, that is, bioremediation has attracted attention and has been developed.

  Bioremediation includes a method disclosed in Patent Document 1. In this method, treatment with anaerobic microorganisms and treatment with aerobic microorganisms are alternately repeated. This technology is effective by dechlorinating compounds that are difficult to be decomposed by aerobic microorganisms, such as highly chlorinated organic compounds, by anaerobic microorganisms and treating the resulting dechlorinated compounds by aerobic microorganisms. Yes.

  However, soil contamination by chlorinated organic compounds is generally very wide, and the amount of soil to be purified is large. Therefore, further efficiency is required for the purification treatment of contaminated soil.

  Therefore, in the technology of Patent Document 2, a compound having a reducing power such as formic acid or oxalic acid is added to activate the anaerobic microorganisms to purify the soil. Patent Document 3 describes a method for purifying soil by adding an electron donor such as sodium benzoate to activate indigenous bacteria and decomposing a halogenated compound. In the technique of Patent Document 4, acetic acid, lactic acid, and the like are used as activators of microorganisms that purify soil, and in the technique of Patent Document 5, saponin and the like are used.

By the way, Patent Document 6 discloses a microorganism preparation for lyophilizing a liquid medium and microorganisms containing an organic nitrogen source and a carbon source and decomposing raw garbage, waste water, and the like. An example of the organic nitrogen source is corn steep liquor, which is a concentrated corn soak. However, the corn steep liquor in the art is attached as a nutrient for microorganisms in the lyophilized preparation, and is not added for a specific purpose.
JP 2003-164850 A (Claim 1, Example) Japanese Patent Laid-Open No. 7-136632 (Claims) Japanese Patent Laid-Open No. 10-225677 (Claims) JP 2003-326247 A (Claim 1) JP-A-2004-188406 (Claims) Japanese Patent Laying-Open No. 2005-278441 (Claims)

  As described above, various techniques for purifying soil contaminated with chlorinated organic compounds are known. In order to treat highly chlorinated organic compounds, the compounds are first removed by anaerobic microorganisms. A method for further degradation by aerobic microorganisms after chlorination is known.

  However, the amount of contaminated soil to be treated is generally extremely large, and it is preferable that the treatment period can be shortened even by one day. Moreover, since the soil is normally in an aerobic state, the formation of an anaerobic environment in the prior art often requires a cost such as requiring a sealed container or enclosing gas. Therefore, a method capable of easily and quickly activating these microorganisms has been demanded.

  Therefore, the problem to be solved by the present invention is to provide a method that can easily and quickly activate aerobic microorganisms and anaerobic microorganisms in soil contaminated with chlorinated organic compounds and efficiently purify the contaminated soil. is there.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, organic acids such as formic acid, oxalic acid, butyric acid, and lactic acid have been conventionally used as additive components for activating microorganisms in contaminated soil. By using corn steep liquor, chlorine-based organic acids have been used. The present invention has been completed by finding that organic compounds can be efficiently purified.

That is, the soil purification method by microorganisms according to the present invention,
A method for purifying soil contaminated with chlorinated organic compounds,
It includes a step of adding and mixing corn steep liquor to the contaminated soil.

  The purification method preferably further includes a step of adding a basic pH adjuster to the contaminated soil. Although soil contaminated with chlorinated organic compounds is acidic, microorganisms may not be able to fully function. In such a case, the microorganism can be activated by adding a basic pH adjuster to adjust the soil pH to about 6-9.

  As such a basic pH adjusting agent, a carbonate or bicarbonate is suitable. The release of carbon dioxide gas can further reduce the redox potential of the soil environment, and can increase the efficiency of dechlorination of chlorinated organic compounds by anaerobic microorganisms.

  The addition amount of the corn steep liquor is preferably 0.05 to 5.0% by mass with respect to the dry weight of the contaminated soil. If it is less than 0.05% by mass, the effect of each component may not be sufficiently exhibited. On the other hand, by adding corn steep liquor in excess, anaerobic microorganisms will become nutrient sources when corn steep liquor remains in large quantities even after anaerobic environment has been formed in the contaminated soil. May not be rapidly dechlorinated.

  Preferably, the purification method further includes a step of adding soil contaminated with a chlorinated organic compound and purified by microorganisms to the contaminated soil. In contaminated soil once purified, there are many cases where the balance of microorganisms necessary for the decomposition of chlorinated organic compounds and the soil environment are in place. In the said aspect, this purification | cleaning soil is reduce | restored to contaminated soil and the efficient purification | cleaning of contaminated soil is aimed at.

  When there are not enough anaerobic microorganisms capable of dechlorinating chlorinated organic compounds in the contaminated soil to be treated, it is preferable to add and mix anaerobic microorganisms having the ability to dechlorinate chlorinated organic compounds. . By such an embodiment, a more efficient purification process can be achieved.

  Furthermore, as an anaerobic microorganism to add, a KBC-1 strain (FERM BP-08573) is suitable. The KBC-1 strain dechlorinates highly chlorinated organic compounds such as PCE even under microaerobic conditions and at low temperatures, where conventional dechlorinated microorganisms were unable to exert their dechlorination ability. Can be

  According to the soil purification method of the present invention, the environment in the contaminated soil can be quickly changed to an anaerobic environment. As a result, anaerobic microorganisms capable of dechlorinating chlorinated organic compounds can be activated, and the decomposition of chlorinated organic compounds can be promoted. Therefore, the present invention is extremely useful industrially as being applicable to large-scale treatment of contaminated soil with a chlorinated organic compound such as PCE that has been used in a large amount and has a large contamination range.

  The soil purification method according to the present invention is a method for purifying soil contaminated with a chlorinated organic compound, and includes a step of adding and mixing corn steep liquor to the contaminated soil.

  The chlorinated organic compound to be treated according to the present invention refers to those which have been used in large quantities in the past or present, but are hardly decomposed in the environment and are required to be treated. For example, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene (hereinafter referred to as “cis-DCE”), 1,1,1-trichloroethane, trichloroethylene ( Hereinafter, “TCE”), tetrachloroethylene (PCE) and the like, dichlorobenzene, polychlorinated biphenyl, dioxin and the like can be mentioned. In the present invention, an organic compound having a high degree of chlorine substitution, such as PCE, which has been difficult to process by conventional methods, can be efficiently processed. Therefore, the present invention is effective for treating contaminated soil with PCE alone or complex contaminated soil of PCE and other chlorinated organic compounds.

  The contaminated soil to be treated according to the present invention refers to soil in which the concentration of each harmful chlorinated organic compound exceeds the official environmental standard value. For example, according to “Environmental Standards Concerning Soil Contamination (August 23, 1991, Environment Agency Notification No. 46)”, the environmental standard value of PCE is 0.01 mg / L and TCE is 0.00. Since 03 mg / L and cis-DCE are 0.04 mg / L, the soil whose concentration of PCE and the like exceeds these reference values is treated.

  In the method of the present invention, corn steep liquor is added to and mixed with the contaminated soil. Thereby, anaerobic microorganisms in the soil are activated quickly, oxygen is consumed to form an anaerobic environment in the soil, and then anaerobic microorganisms with excellent dechlorination ability of chlorinated organic compounds are activated, As a result, the decomposition of harmful chlorinated organic compounds is accelerated. Here, the microorganisms in the soil include microorganisms added for dechlorination and decomposition of chlorinated organic compounds in addition to indigenous microorganisms.

  Corn steep liquor is a by-product in the production of corn starch, and is obtained by concentrating the immersion liquid produced in the wet milling process of corn starch. More specifically, the corn is immersed in warm water containing sulfite, and the immersion liquid from which the extract is eluted is separated in the swelling process, concentrated after lactic acid fermentation, and is generally commercially available. Its components include proteins, peptides, amino acids, lactic acid, sulfurous acid, sugar, minerals, vitamins and the like. By adding and mixing this corn steep liquor to the contaminated soil, it is possible to activate aerobic microorganisms in the contaminated soil remarkably compared to the case where conventional nutrient sources are added, and quickly form an anaerobic environment in the soil. can do.

  The addition amount of the corn steep liquor is preferably 0.05 to 5.0% by mass with respect to the dry weight of the contaminated soil. If it is less than 0.05% by mass, the effect of each component may not be sufficiently exhibited. On the other hand, if the added amount exceeds 5.0% by mass, a large amount of corn steep liquor remains after anaerobic conditions are formed in the contaminated soil, and anaerobic microorganisms use this as a nutrient source, resulting in chlorinated organic compounds. May not be rapidly dechlorinated. More preferably, they are 0.1 mass% or more and 1.5 mass% or less.

  In the method of the present invention, it is preferable to add and mix a basic pH adjuster in addition to corn steep liquor to the contaminated soil. Soil contaminated with chlorinated organic compounds is diverse, and its pH varies depending on the type and concentration of the pollutant, the type of indigenous microorganism, the number of bacteria, and the like. As a result, in the conventional treatment, the period until the formation of the anaerobic conditions by the aerobic microorganisms, and thus the concentration of the chlorinated organic compound is reduced below the environmental standard value, is not stable. In particular, soil contaminated with chlorinated organic compounds is acidic and often has an environment in which microorganisms do not actively work. Therefore, in this aspect, when the soil pH is excessively reduced, a basic pH adjuster is added and mixed to adjust the pH of the contaminated soil to about 6 to 9, thereby enabling a stable purification treatment.

  The basic pH adjuster is not particularly limited as long as it can raise the pH of acidic contaminated soil and does not excessively increase the pH with an appropriate buffer capacity. However, carbonates or bicarbonates are preferred. This is because the redox potential of the soil can be lowered chemically and the anaerobic environment can be formed more rapidly by the release of carbon dioxide. Such basic pH adjusters include alkali metal or alkaline earth metal hydrogen carbonates such as sodium hydrogen carbonate, potassium hydrogen carbonate, calcium hydrogen carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, etc. Mention may be made of carbonates of alkali metals or alkaline earth metals. Among these, sodium hydrogen carbonate and / or calcium carbonate is preferable because it is inexpensive and safe.

  The added amount of the basic pH adjuster is such that the pH of the contaminated soil to be treated is about 6 to 9 in order to activate the microorganisms in the soil. A specific addition amount may be determined by a preliminary experiment.

  The addition amounts of the corn steep liquor and the basic pH adjuster may be added and mixed with the contaminated soil as they are. However, in order to facilitate the addition and mixing, and to suppress the uneven distribution of corn steep liquor or the like, it is preferable that these are once made into an aqueous solution and the aqueous solution is added and mixed. What is necessary is just to adjust the density | concentration of aqueous solution suitably.

  In the method of the present invention, soil contaminated with a chlorinated organic compound and purified by microorganisms (hereinafter sometimes referred to as “purified soil”) may be added to the contaminated soil. In contaminated soil once purified, there are many cases where the balance of microorganisms necessary for the decomposition of chlorinated organic compounds and the soil environment are in place. In this aspect, the purified soil is reduced to contaminated soil, and the contaminated soil is efficiently purified.

  The type of the purified soil is not particularly limited, but an embodiment in which the soil purified by the method of the present invention is reduced is efficient. That is, if the contaminated soil to be treated is divided into appropriate sections and the first section is purified, and then the purified soil is added to the contaminated soil in the next section, efficient purification can be performed.

  The amount of the purified soil added is only required to allow more efficient treatment, but is usually about 1 to 20% by mass with respect to the contaminated soil. If the addition amount is too small, the effect may not be obtained. On the other hand, if the addition amount is too large, the overall processing efficiency may be reduced.

  In the method for purifying contaminated soil according to the present invention, indigenous aerobic microorganisms and anaerobic microorganisms may be used, but in particular, there are not enough anaerobic microorganisms for treating highly chlorinated organic compounds in the soil. In addition, anaerobic microorganisms having the ability to dechlorinate chlorinated organic compounds may be separately added and mixed.

  Whether or not anaerobic microorganisms having the ability to dechlorinate chlorinated organic compounds contained in the contaminated soil are present in the contaminated soil to be purified may be determined by a conventional method. For example, a sample collected from contaminated soil is inserted into an ampoule together with nutrient sources of anaerobic microorganisms, and a medium supplemented with a chlorinated organic compound is added and sealed as necessary. By measuring, it is possible to determine the presence or absence of anaerobic microorganisms having the ability to dechlorinate chlorinated organic compounds.

Regardless of the presence or absence of dechlorinated anaerobic microorganisms in the contaminated soil to be purified, anaerobic microorganisms having the ability to dechlorinate chlorinated organic compounds may be added. Amount of anaerobic microorganisms varies depending like amount and degree of contamination of soil or the like to be treated (soil concentration of chlorinated organic compounds), for example, 10 ⁸ corresponding bacterial solution per 1 mL, with respect to contaminated soil What is necessary is just to add about 0.1-10 mass%. However, such addition amount needs to be adjusted as appropriate according to the actual treatment state, and can be specifically determined by preliminary experiments.

  Further, the anaerobic microorganism to be added may be selected from those that can dechlorinate the chlorinated organic compound to be treated. For example, when purifying contaminated soil by PCE, Desulfitobacterium genus bacteria or the like that have been demonstrated to dechlorinate PCE may be used.

  Among the Desulfitobacterium bacteria, the KBC-1 strain is preferable. The KBC-1 strain can dechlorinate PCE even under microaerobic conditions and at low temperatures, where conventional dechlorinated microorganisms could not exert dechlorination ability. Furthermore, since the KBC-1 strain can be dechlorinated mainly to TCE without producing vinyl chloride having higher toxicity than PCE, safer processing is possible.

The KBC-1 strain is deposited with the depository as follows.
(I) Names and destinations of depositary institutions Name: National Institute of Advanced Industrial Science and Technology, Patent Biological Depositary Center Address: 1-chome, East 1-chome, Tsukuba City, Ibaraki Prefecture, Japan
(Ii) Date of deposit: December 11, 2003 (iii) Deposit number: FERM BP-08573

  In addition, in order to treat the contaminated soil with anaerobic microorganisms more efficiently, nutrient sources (nitrogen nutrient sources, carbon nutrient sources, organic acids, inorganic salts, vitamins necessary for the growth of anaerobic dechlorinated microorganisms) Etc.) may be added as appropriate. However, the type and amount of addition need to be in a range that does not inhibit the effects of basic pH adjuster, purified soil, and / or added anaerobic microorganisms in addition to corn steep liquor.

  The order of addition of the corn steep liquor, the basic pH adjuster, the clarified soil, and the added anaerobic microorganisms, that is, the order of carrying out the additive mixing step of these additive components is not particularly limited. These additive components may be added and mixed sequentially, or two or more of them may be added simultaneously and mixed.

  In the present invention, in addition to corn steep liquor as it is for the contaminated soil to be treated, basic pH adjuster, purified soil and / or added anaerobic microorganisms (hereinafter referred to as “corn steep liquor or the like together”) May be added). However, since it may be difficult to mix, it is preferable to excavate and collect the contaminated soil once to purify it.

  In order to add and mix corn steep liquor and the like into the collected soil, it is preferable to use a stirring means corresponding to the scale of implementation. As such a stirring means, a conventional method can be used. For example, a rotary stirring device, a scribing stirring device, a tiller stirring device, a stirring device equipped with a stirring blade, or the like can be used. Using these stirring means, the contaminated soil and corn steep liquor are well stirred and mixed so that the added components do not segregate.

  By adding and mixing corn steep liquor, such as corn steep liquor and basic pH adjuster, to the soil contaminated with chlorinated organic compounds, the activity of aerobic microorganisms is first activated, and the anaerobic environment in the soil has been conventional. It is formed more rapidly than the method, and as a result, the anaerobic microorganisms are then activated, whereby the chlorinated organic compound can be efficiently decomposed.

  At this time, the contaminated soil may be sealed in a reaction vessel or the like so that an anaerobic environment is easily formed. However, soil contamination by chlorinated organic compounds is often widespread, and the amount of contaminated soil to be purified is often large. In such a case, if a method of sealing the soil is adopted, a large reaction container is required, and it is difficult to seal the large reaction container. Therefore, the contaminated soil can be stacked in a predetermined space and preferably covered with a sheet to create an anaerobic environment. According to this method, at least the soil interior can be naturally anaerobic environment, and dechlorination by anaerobic microorganisms can be promoted. This method also has an advantage that a large-scale reaction apparatus is not required. However, harmful organic compounds may leak into the atmosphere. In this case, it is preferable to recover the organic compound by adsorbing it on an adsorbent such as activated carbon.

  The conditions for activating the aerobic microorganism with a corn steep liquor or the like to form the anaerobic environment are not particularly limited as long as the aerobic microorganism can actively grow. For example, the temperature and humidity may be the optimum conditions for the aerobic microorganism to be used or the same. However, as long as aerobic microorganisms can sufficiently grow, the reaction may be performed at normal temperature and normal humidity.

  The “anaerobic environment” in the present invention includes a case where it can be said to be a microaerobic environment, and if dechlorination by anaerobic microorganisms proceeds, it is not always necessary to set anaerobic conditions in a strict sense. . More specifically, it refers to a state where the oxygen concentration is within a range where anaerobic microorganisms capable of dechlorinating chlorinated organic compounds can grow and chlorinated organic compounds can be dechlorinated, for example, minus 50 mV at the redox potential. The following shall be said.

  According to the present invention, the soil can be made an anaerobic environment more quickly than the conventional method, and the indigenous or newly added anaerobic microorganisms having the ability to dechlorinate chlorinated organic compounds can be activated. it can. In the present invention, the boundary between an anaerobic environment formation process and an anaerobic microorganism dechlorination process is not always clear, and the transition is natural and gradual. Therefore, it is not particularly necessary to change conditions such as the temperature in the anaerobic environment formation process, that is, the aerobic microorganism activation process and the anaerobic microorganism dechlorination process. However, the oxidation-reduction potential may be measured as appropriate so that the conditions are suitable for anaerobic microorganisms used when an anaerobic environment is formed.

  The time required for dechlorination by anaerobic microorganisms depends on the amount of soil to be treated, the degree of contamination, etc., but the progress of treatment by measuring the type and concentration of chlorinated organic compounds released into the soil sample and gas phase The situation may be grasped and the time until the end of the dechlorination of the chlorinated organic compound (the time when the concentration of the organic chlorinated compound targeted for dechlorination falls below the environmental standard value) may be used.

  After the anaerobic environment is formed in the contaminated soil by the method of the present invention and the chlorinated organic compound is dechlorinated by the anaerobic microorganism, the dechlorinated compound may be further decomposed. Since the dechlorination compound is easier to dechlorinate and decompose than a highly chlorine-substituted compound, such decomposition treatment is not particularly limited. For example, further dechlorination by anaerobic microorganisms, decomposition treatment by aerobic microorganisms, or physical or chemical treatment may be performed. A specific method for performing these subsequent methods may be a conventional method or a conventional method.

  According to the method for purifying contaminated soil with a chlorinated organic compound according to the present invention, anaerobic microorganisms can be activated to quickly form an anaerobic environment, and the efficiency of dechlorination by anaerobic microorganisms can be improved. it can.

  Although an anaerobic environment can be formed by addition of lactic acid or the like in the conventional method, it may take time. As a result, not only the time required for the purification treatment itself is increased, but also anaerobic microorganisms may be killed before the chlorinated organic compound is dechlorinated. Further, in the conventional method, there are cases where the purification treatment cannot be stably performed depending on the state of the contaminated soil. Furthermore, some conventional methods are difficult to implement on a large scale, such as requiring a large sealed container.

  In the present invention, due to the effect of corn steep liquor and the like, the contaminated soil can be easily and quickly made an anaerobic environment, and the dechlorination of the chlorinated organic compound that is the cause of the contamination can be stably and efficiently performed. Can be done.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

Reference example 1
To examine the effect of carbonate or bicarbonate as a basic pH adjuster, the redox potential was measured. For details, add 100 mL of distilled water to a 100 mL beaker, add 1.5 g of corn steep liquor, 1 g of calcium carbonate, and 1 g of sodium bicarbonate in order from the left to the right in Table 1, and sequentially add a redox potentiometer (Toko Chemical Research). The redox potential was measured. The results are shown in Table 1. In addition, the number in Table 1 is an oxidation-reduction potential, and a unit is mV.

  As shown in Table 1, it was found that by adding corn steep liquor and adding basic carbonate or bicarbonate, the redox potential can be significantly reduced even in the absence of microorganisms. From this result, if basic carbonate or hydrogen carbonate is added to the contaminated soil in addition to corn steep liquor, the soil environment can be quickly brought into anaerobic conditions, and chlorinated organic compounds are eliminated by anaerobic microorganisms. It is believed that chlorination occurs efficiently.

Example 1 Purification of PCE-contaminated soil by the method of the present invention Soil contaminated with about 1 mg of PCE per liter was prepared, and 1 kg of fresh soil (800 g of dry soil) was collected. A solution prepared by dissolving 2.4 g of corn steep liquor in 2.4 mL of water was added to this PCE-contaminated soil, and mixed with a small mixer for 30 seconds. Next, 0.8 g of sodium hydrogen carbonate was added and mixed for 30 seconds using the same small mixer. This mixed soil was put into a 500 mL beaker, covered with a polyvinylidene chloride film (Asahi Kasei Co., Ltd., Saran Wrap), and stored in a dark place at 25 ° C.

Comparative Example 1 Treatment with Conventional General Lactic Acid 1 kg of the PCE-contaminated soil used in Example 1 (800 g as dry soil) was collected. To this PCE-contaminated soil, a solution prepared by dissolving 2.4 g of sodium lactate, which is a typical nutrient source of microorganisms, and 0.24 g of diammonium hydrogen phosphate, in 2.4 mL of water is added, and a small mixer is used for 30 seconds. Mixed. Next, 0.8 g of sodium bicarbonate was added and mixed for 30 seconds with a small mixer. This mixed soil was put into a 500 mL beaker, covered with a polyvinylidene chloride film (Asahi Kasei Co., Ltd., Saran Wrap), and stored in a dark place at 25 ° C.

Comparative Example 2 Control 1 kg of the PCE-contaminated soil used in Example 1 was collected as raw soil (800 g as dry soil). 2.4 mL of water was added to this PCE-contaminated soil and mixed for 1 minute with a small mixer. This soil was put into a 500 mL beaker, covered with a polyvinylidene chloride film (Asahi Kasei Co., Ltd., Saran Wrap), and stored in a dark place at 25 ° C.

Test Example 1 Measurement of Redox Potential The soils of Example 1 and Comparative Examples 1 and 2 were periodically sampled and their redox potential was measured. Specifically, first, 7 g of each soil was accurately weighed every day and placed in a 50 mL disposable tube. Separately, anaerobic water was prepared. That is, about 500 mL of distilled water was put into a 750 mL pressure-resistant glass container and sealed with a butyl rubber stopper. Next, using a vacuum pump, the inside of the glass container was deaerated for about 30 minutes. Then, the stopper of the glass container was opened and nitrogen gas was blown into the deaerated water for 20 minutes to make anaerobic water. The glass container was again sealed with a butyl rubber stopper, and anaerobic water was stored. Next, 15 mL of this anaerobic water was added to the soil sample, and it was gently shaken up and down and stirred for 1 minute. After standing for about 20 minutes, measurement was performed using an oxidation-reduction potentiometer (manufactured by Toko Chemical Laboratory). The results are shown in FIG. In the figure, “CSL” is an abbreviation for corn steep liquor.

  As shown in FIG. 1, in the case of the control in which no nutrient source for aerobic microorganisms is added, the oxidation-reduction potential hardly changes. When sodium lactate and diammonium hydrogen phosphate are added as nutrient sources, the redox potential decreases, but it is not sufficient to activate anaerobic microorganisms. On the other hand, when corn steep liquor and sodium hydrogen carbonate are added, it becomes 0 mV or less on the 5th day, and on the 6th day, the redox potential can be lowered to −50 mV, which is sufficient to activate anaerobic microorganisms. . Therefore, according to the method of this invention, it turned out that the environment which activates the anaerobic microorganism which decomposes | disassembles PCE can be formed earlier than before.

Test Example 2 PCE Concentration Measurement The soils of Example 1 and Comparative Examples 1 and 2 were sampled periodically to measure the PCE concentration. Specifically, first, 50 g of each soil was collected every day and placed in a 500 mL Erlenmeyer flask. Next, a stirring bar was added, and water was added so that the Erlenmeyer flask was almost full. Here, the amount of water added was recorded. The flask was stirred for about 4 hours with a stirrer, and after standing for 30 minutes, 10 mL of the supernatant was collected, placed in a 25 mL vial, and sealed with a Teflon (registered trademark) coated butyl rubber stopper. The vial was allowed to stand at 60 ° C. for about 30 minutes, and then 100 μL of the gas phase portion of the vial was collected with a microsyringe and inserted into a gas chromatography (GC-ECD) apparatus for gas chromatography analysis. In addition, the measurement conditions of gas chromatography are as follows.
Analytical instrument: Shimadzu Gas Chromatograph with Electron Capture Detector (ECD) Capillary column: DB-624 manufactured by J & W Scientific (inner diameter 0.2 mm, length 60 m, film thickness 1.4 μm)
Analysis conditions: temperature of each part; column tank 150 ° C., inlet / outlet 250 ° C., detector 250 ° C.
Carrier gas; high purity helium 1.0 ml / min.
Split ratio; 1:10
Injection volume: 100 μL

  The measurement results are shown in FIG. As a result of FIG. 2, in the case of the control in which no nutrient source for microorganisms is added, PCE can hardly be reduced. When sodium lactate and diammonium hydrogen phosphate were added as nutrient sources, PCE could be reduced to the environmental standard value of 0.01 mg / L on the 9th day. On the other hand, when corn steep liquor and sodium bicarbonate were added, PCE could be reduced below the environmental standard value on the seventh day. Therefore, according to the method of the present invention, it was demonstrated that PCE can be decomposed more efficiently than the conventional method.

Test Example 3 Measurement of the number of microorganisms contained in the soil The soils of Example 1 and Comparative Examples 1 and 2 were periodically sampled, and the number of aerobic microorganisms was measured. Specifically, 1 g of each soil was collected and diluted 10-fold using sterilized distilled water. Next, 100 μL of each diluted solution was applied to a plate for aerobic microorganisms which is a standard agar medium (JIS K0101 63.2), and then the lid of the plate was closed. The plate was allowed to stand for 3 to 7 days in a dark place at 25 ° C., and the colonies that appeared were counted. From the results, the number of aerobic microorganisms present in 1 g of dry soil was calculated by a dilution plate method using a plate.

  In addition, the number of anaerobic microorganisms was measured as follows. First, a diluted bacterial solution was prepared in the same manner as in the case of an aerobic microorganism, and this was applied to an anaerobic microorganism plate (manufactured by Nissui Pharmaceutical Co., Ltd.), then the lid was closed, and it was sealed in an anero pack. The plate was allowed to stand for 10 days in a dark place at 25 ° C., and the colonies that appeared were counted. From the results, the number of anaerobic microorganisms present in 1 g of dry soil was calculated. Both results are shown in FIG. 3 as daily CFUs.

  As shown in FIG. 3, the growth of both aerobic and anaerobic microorganisms is more active when corn steep liquor and sodium bicarbonate are added than when lactic acid is added as a carbon nutrient source for microorganisms according to the prior art. I understand. Therefore, according to the method of the present invention, it was proved that the activity of microorganisms in the contaminated soil can be activated and the pollutants can be decomposed more efficiently.

Example 2 Purification treatment of PCE-contaminated soil by the method of the present invention 1 mass% of soil (purified soil) that has passed 2 days after the start of the treatment of Example 1 was added to new PCE-contaminated soil, and corn steep liquor And sodium bicarbonate were added in the same manner as in Example 1 to obtain a treated sample. With respect to this sample, the oxidation-reduction potential and the PCE concentration were measured by the methods of Test Examples 1 and 2. FIG. 4 shows the result of the oxidation-reduction potential, and FIG. 5 shows the result of the PCE concentration. The data with and without the addition of corn steep liquor in FIGS. 4 and 5 are the same as those in FIGS.

  As shown in FIGS. 4 and 5, the addition of clarified soil in addition to corn steep liquor and sodium hydrogen carbonate can lower the oxidation-reduction potential more rapidly, and decompose PCE more efficiently. be able to. This is thought to be due to the fact that the contaminated soil once purified has a well-balanced microorganism and a soil environment necessary for the decomposition of chlorinated organic compounds.

Example 3 Purification treatment of PCE-contaminated soil by the method of the present invention In Example 1, in addition to corn steep liquor and sodium hydrogencarbonate, 10 ⁵ strains of KBC-1 per 1 g of contaminated soil were added, or KBC- A sample was obtained by carrying out the same treatment except for adding 10% by mass of purified soil that had passed 3 days after the start of the treatment of Example 1 in addition to 1 strain. Further, the same processing as in Comparative Example 2 was performed to obtain a sample.

  For the above three samples, the PCE concentration was measured by the method of Test Example 2. The results are shown in FIG.

  As shown in FIG. 6, when the KBC-1 strain having high PCE resolution was added, PCE could be reduced to less than the environmental standard value on the third day from the start of the treatment. Furthermore, by adding the purified soil, the PCE could be reduced to less than the environmental standard value on the second day. Therefore, in the method of the present invention, in addition to the corn steep liquor, by adding a basic pH adjuster and an anaerobic microorganism excellent in dechlorination ability, by further adding purified soil, a more efficient purification treatment It has been demonstrated that

It is a figure which shows a time-dependent change of the oxidation-reduction potential in the case of the process by this invention, the process by the conventional lactic acid, or the case of no process (control) to PCE contaminated soil. It is a figure which shows the time-dependent change of the PCE density | concentration in soil when the process by this invention or the process by the conventional lactic acid is performed to the PCE contaminated soil, or in the case of no process (control). The time-dependent change of the number of aerobic microorganisms and anaerobic microorganisms in soil when PCE-contaminated soil is treated by the method of the present invention, or by conventional lactic acid treatment, or in the case of no treatment (control) is shown. FIG. It is a figure which shows a time-dependent change of the oxidation-reduction potential in the case of the process by this invention method using corn steep liquor, sodium hydrogencarbonate, and a purification | cleaning soil, or a no-treatment (control). It is a figure which shows the time-dependent change of the PCE density | concentration in the soil in the case of the process by this invention method using corn steep liquor, sodium hydrogencarbonate, and a purification | cleaning soil, or a no-treatment (control) for PCE contaminated soil. PCE-contaminated soil was treated with corn steep liquor, sodium bicarbonate and anaerobic microorganisms with excellent dechlorination ability, treated with the method of the present invention using purified soil, or untreated (control). It is a figure which shows the time-dependent change of the PCE density | concentration in the soil in a case.

Claims (7)

A method for purifying soil contaminated with chlorinated organic compounds,
A method for purifying soil with microorganisms, comprising a step of adding and mixing corn steep liquor to the contaminated soil.   Furthermore, the soil purification method of Claim 1 including the process of adding a basic pH adjuster to contaminated soil.   The soil purification method according to claim 2, wherein carbonate or bicarbonate is used as the basic pH adjuster.   The soil purification method according to any one of claims 1 to 3, wherein 0.05 to 5.0 mass% of corn steep liquor is added and mixed with respect to the dry weight of the contaminated soil.   Furthermore, the soil purification method in any one of Claims 1-4 including the process of adding to the contaminated soil what was soil contaminated with the chlorinated organic compound and purified by microorganisms.   Furthermore, the soil purification method in any one of Claims 1-5 which adds and mixes the anaerobic microorganisms which have the dechlorination ability of a chlorinated organic compound.   The soil purification method according to claim 6, wherein KBC-1 strain (FERM BP-08573) is used as an anaerobic microorganism.

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