JP4428125B2 - Pollution purification method - Google Patents

Description

  The present invention relates to a technique for activating anaerobic microorganisms using a bioremediation method, promoting the purification of soil and groundwater contaminated with organochlorine compounds, and purifying contaminated areas in situ in a short period of time. is there.

  Conventionally, soil and groundwater contamination purification equipment and methods include vacuum extraction method, pumped water aeration method, lime method, iron powder method, soil excavation replacement method, soil moisture cleaning method, insolubilization treatment method, gas / liquid mixing Well methods, air sparging methods, bioremediation methods, and various methods for purification are used, but iron powder method and bioremediation method can be raised as methods that can clean up soil and groundwater contamination in a short period of time and energy saving. .

  In recent years, attention has been focused on the purification of contaminated areas (bioremediation method) using microorganisms that save energy and are inexpensive.

In this bioremediation method, the indigenous microorganisms are propagated by injecting a nutrient source containing a substrate (carbon source), nitrogen, inorganic nutrient salts such as phosphorus and potassium, and a hydrogen donor into the contaminated area. It is known to activate and accelerate the degradation action of pollutants. As nutrient sources, compounds that are liquid at room temperature have been proposed. (For example, see Patent Document 1)
In another conventional example, the use of a nutrient source that is solid at room temperature, including a fatty acid having a specific carbon number, alcohol, and the like has been proposed. (For example, see Patent Document 2)
Japanese Patent Application Laid-Open No. 11-90484 JP 2002-370085 A

  However, liquid nutrient sources are excellent in fluidity, so even if injected into soil or groundwater, they penetrate into the bottom and dissolve in groundwater, and flow out of the contaminated area, causing microorganisms to grow and activate, causing contamination. The effect of promoting the degradation action was low, and there was a need to reinject nutrients in a relatively short cycle.

  In addition, solid nutrient sources are excellent in sustaining the effect of growing and activating microorganisms and accelerating the degradation action of pollutants, but they have multiple injection wells due to low diffusion and permeability to contaminated areas. Many injection sites were needed.

  Thus, conventional nutrient injections are difficult to achieve both the growth and activation of microorganisms and the sustainability of the effect of promoting the degradation action of pollutants, which limits the improvement of purification efficiency. was there.

Accordingly, the present invention enhances Oite diffusion nutrients, the persistence of penetration allowed effects contaminated region, the growth of microorganisms by nutrients, by activating, to decompose the pollutants in soil and groundwater contaminated region An object of the present invention is to improve the purification efficiency of a purification method in which a solid nutrient source is melted to form a liquid and injected into soil and groundwater.

In order to solve the above-mentioned problems, the present invention is a method for injecting a nutrient source for activating microorganisms that decompose organochlorine compounds into at least one of organochlorine compound-containing soil and groundwater, The source is a solid substance containing a straight-chain saturated monocarboxylic acid having 8 or more carbon atoms , dissolved in a volatile or water-soluble organic solvent, and liquid when injected into the soil and groundwater containing the organochlorine compound. In this method, after the injection, the organic solvent is volatilized or dissolved in moisture so that the nutrient source becomes solid or gel.

As a result, the nutrient source can be injected in a liquid state, and the diffusibility and permeability of the nutrient source can be enhanced in at least one of the soil and groundwater containing the organochlorine compound. On the other hand, due to volatilization of organic solvents (for example, ethanol, methanol, etc.), the nutrient source becomes solid or gel, thereby increasing the sustainability of the nutrient effect in situ, and growing microorganisms with the nutrient source. It can be activated to improve the purification efficiency by decomposing pollutants in soil and groundwater in the contaminated area.

According to the pollution purification method of the present invention, a solid nutrient source containing a linear saturated monocarboxylic acid having 8 or more carbon atoms is dissolved in a volatile or water-soluble organic solvent (for example, ethanol, methanol, etc.). When the liquid nutrient is pressurized and injected into at least one of the soil and groundwater, the organic solvent volatilizes or becomes a solid or gel in situ due to dissolution in moisture. Since the solid surface area can be increased by diffusing and penetrating into the gaps in the mesh, and the organic solvent can also be used as a nutrient source, the sustainability of the effect of nutrients over a wide range is increased. Purification efficiency can also be improved by microorganisms decomposing soil and groundwater pollutants containing organochlorine compounds.

  In addition, according to the present invention, when the groundwater flow is fast (for example, the flow of groundwater is 5 cm to 8 cm per day) by pressurizing and injecting a liquid nutrient source, the layer (road) ) Is formed, the infused nutrient source becomes solid and becomes resistance of the layer formed by the groundwater, so that the knitting of the groundwater flow can be suppressed.

  The pollution purification method according to the present invention is particularly suitable for the purification of soil and / or groundwater containing an organochlorine compound as a contaminant. Examples of organochlorine compounds include tetrachloroethylene, trichloroethylene, dichloroethylene, vinyl chloride, dichloromethane, chloroform, carbon tetrachloride, chloroethane, dichloroethane, trichloroethane, dichloropropane, dichlorobroethylene, bromodichloromethane, chlorodibumomethane, and dioxin. Can be mentioned. It is particularly suitable for the purification of soil and / or groundwater containing at least one contaminant of tetrachlorethylene, trichlorethylene and carbon tetrachloride.

In the contamination purification method of the present invention, as described above, as a nutrient source for growing and activating microorganisms, a solid nutrient source is liquefied with an organic solvent and injected into soil and / or groundwater, Use nutrient sources that solidify in the soil and / or groundwater area after injection.

  The solid nutrient source contains a component that activates the pollutant decomposing action of microorganisms (anaerobic microorganisms) and can exist in a solid state in soil or groundwater. Examples of components of nutrient sources that activate microorganisms include components that serve as nutrient salts of microorganisms (such as phosphorus and nitrogen) and temperament components (that is, organic substances as energy sources), components that serve as hydrogen donors, and the like. It is. The hydrogen donor is a substance that supplies hydrogen to microorganisms, and the supplied hydrogen replaces, for example, chlorine of the organic chlorine compound that is a pollutant, thereby reducing the molecular weight of the organic chlorine compound. Used to promote further biological degradation.

  The solid nutrient source is selected from those containing a linear saturated monocarboxylic acid having 8 or more carbon atoms, and at least one kind can be used. These substances function not only as substrates but also as hydrogen donors for microorganisms.

  This is because a linear saturated monocarboxylic acid having 8 or more carbon atoms has a sufficiently high melting point, so that a nutrient source containing this easily maintains a solid state in soil or groundwater. The upper limit of the carbon number of the straight-chain saturated monocarboxylic acid is not particularly limited, but those having 22 or less carbon atoms are preferred because they are industrially and easily available from natural materials. Further, in consideration of liquefaction from the solid state, the carbon number is most preferably 8 to 18.

  In addition, by selecting a linear saturated monocarboxylic acid that is not a multiple bond such as a double bond, the melting point of the carboxylic acid does not decrease and the specific gravity with water is almost the same, so it is solid in soil and groundwater. It is easy to maintain the state. A linear saturated monocarboxylic acid, that is, a fatty acid is also excellent in efficiency as a hydrogen donor.

  Examples of the linear saturated monocarboxylic acid include caprylic acid (melting point: 16.5 ° C., specific gravity: 0.91), pelargonic acid (melting point: 15 ° C., specific gravity: 0.90552), capric acid (melting point: 31.3 ° C., specific gravity: 0) 8931), lauric acid (melting point 44 ° C., specific gravity 1.0099), myristic acid (melting point 53.5 ° C., specific gravity 0.8533), palmitic acid (melting point 62.65 ° C., specific gravity 0.8414), stearic acid ( Melting point 71 ° C., specific gravity 0.8428) and mixtures of these carboxylic acids. Among these, myristic acid, palmitic acid, and stearic acid are particularly preferable. Moreover, as a mixture, the mixture of the fatty acid extracted from natural raw materials, such as what selected several carboxylic acid and artificially mixed, beef tallow fatty acid, coconut oil fatty acid, may be sufficient.

  Note that the amount of the solid nutrient source used is not particularly limited, and can be appropriately set according to the type of the nutrient source, the area of the contaminated region, the amount of the contaminant, and the like. For example, the type and amount of pollutants contained in the soil or groundwater sampled by surface surveys, shallow surveys, and deep surveys in contaminated areas, types and amounts of competing substances (oxidizing substances), and geological conditions (penetration, temperature) Analyze, identify, etc., determine the concentration from the pollutant mass, the mass of the pollutant contained in the soil and groundwater mass, and replace the pollutant type, concentration, nutrient source diffusivity and chlorine with hydrogen Purification efficiency by injecting 0.1 to 20 times, preferably 1 to 12 times, solid nutrient source under pressure relative to the amount of pollutants in the contaminated area Can be improved. For example, in the case of contamination of 10 ppm of tetrachlorethylene on a soil area of 200 m2, use of a solid nutrient source of about 600 Kg is exemplified.

In addition, organic solvents for liquefying solid nutrient sources are organic solvents composed of carbon, hydrogen, and oxygen, such as ethanol, methanol, and ethyl ether. And ethanol, which is a substance that does not pollute the environment of groundwater, is desirable. Ethanol is also a nutrient source for microorganisms (anaerobic microorganisms) and contributes to the degradation of pollutants.

  A dissolution apparatus for supplying a solid nutrient source and an organic solvent has a stirring means, can efficiently promote dissolution, and can prevent separation due to the difference in specific gravity between the solid nutrient source and the organic solvent. .

Reference example 1

  Hereinafter, the contamination purification method according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an outline of soil and groundwater contamination purification of Reference Example 1 of the present invention. In the example of this figure, since the organic chlorinated compound (for example, tetrachloroethylene, trichlorethylene, etc.) that is a pollutant has been used as a cleaning agent in the factory 1 (home appliance manufacturing factory, cleaning factory, etc.) in the past, the factory 1 The contaminated area of soil and groundwater containing pollutants spreads and remains stable around the site.

  The soil in the contaminated area has a geological structure in which the top soil 2, the upper silt layer 3, the sandy soil layer 4 and the lower silt layer 5 are accumulated in order from the ground surface. The sandy soil layer 4 is a layer containing groundwater, that is, an aquifer.

  In the soil having such a stratum structure, as shown in FIG. 1, the pollutant penetrates from the factory 1 to the topsoil 2 and then penetrates further downward to reach the upper silt layer 3. Since the upper silt layer 3 is a soil layer with a lot of clay, and is impermeable or hardly permeable, the contaminants stay on the surface of the upper silt layer 3 as a contaminated portion 6. However, it does not stay completely in the upper silt layer 3 and penetrates the upper silt layer 3 and reaches the sandy soil layer 4 (aquifer). And the contamination range is expanded as shown in the contamination expansion region 7 by the flow of groundwater. From the actual situation of such contamination, it is important to effectively purify the contaminated part 6 and the contamination enlarged region 7.

  In this contamination purification method, the solid nutrient source 8 is dissolved in the soil and / or ground water in the contaminated part 6 and the contamination expansion region 7 and is injected under pressure as a liquid nutrient source 9.

  In soil and / or groundwater, there are microorganisms that can degrade pollutants to low molecular weight. Examples of microorganisms having such a decomposing action include the genus Ssccharomyces, the genus Hansenula, the genus Candida, and the genus Dehalococides. The microorganism may be a microorganism artificially introduced from the outside into soil and / or groundwater.

  In the method of injecting the nutrient source, the solid nutrient source 8 filled in the nutrient source reservoir 10 is connected to the nutrient source reservoir 10 and the melting bath 12 by a signal from the control device 11. The valve (A) 13 is opened, and the solid nutrient source 8 is put into the melting tank 12. The input amount is determined by the control device 11 inputted in advance, and the valve (A) 13 is opened and closed by a signal from the control device 11.

  The solid nutrient source 8 put into the melting tank 12 is heated by the steam from the steam generator 14. The supply amount of the steam has a correlation with the input amount of the solid nutrient source 8 and the melting point, and is determined by adjusting the opening degree of the flow control valve 15 in response to a signal from the control device 11. This heating melts the solid nutrient source 8 into the liquid nutrient source 9, and when steam cannot be supplied, an electric heater may be used.

  When the melting tank 12 is stored in a heat retaining device 16 such as a container or a tank provided with heat retaining means, the stable liquid nutrient source 9 can be stably injected under pressure into soil and / or groundwater. , Proper management of energy for heating. Needless to say, the heat retaining device 16 includes a heat insulating material (not shown) and a heat retaining heater 17.

  Further, a temperature measuring device 18 is provided at the bottom of the melting tank 12, and a setting equal to or higher than the melting point of the solid nutrient source 8 input in advance to the control device 11 by the measured temperature of the temperature measuring device 18. When the temperature is reached, the supply valve 19 is opened, and the liquid nutrient source 9 is pressurized and injected into the soil and / or groundwater by the supply pump 21 through the injection hole 20. For example, when the solid nutrient source 8 is a nutrient source mainly composed of stearic acid having 18 carbon atoms, the supply valve 19 is heated after the temperature of the temperature measuring device 18 reaches 90 ° C. to 95 ° C. , And pressurized and injected into the soil and / or groundwater by the supply pump 21, it becomes easy to permeate into the soil and / or groundwater, and can be uniformly permeated into the gaps of the soil grains.

  Since the temperature of soil and groundwater is 5 ° C. to 20 ° C., the liquid nutrient source 9 injected under pressure is infused into a solid or gel form after being injected, so that it is in a wide range. Highly sustainable purification of pollutants can be realized.

  Further, regarding the state of purification, the observation well 22 is provided on the downstream side of the groundwater in the contaminated area, and the state of purification of the pollution can be determined by pumping and analyzing with the pump 23.

FIG. 2 is a schematic cross-sectional view showing an outline of soil and groundwater contamination purification of Example 1 of the present invention.

2 (Example 1 ) differs from the above-mentioned FIG. 1 ( Reference Example 1) in that the solid nutrient source 8 is dissolved into a liquid nutrient source 9. Therefore, the description of the overlapping part is omitted, and the different part will be described below.

  The nutrient source injecting method is such that the solid nutrient source 8 filled in the nutrient source storage tank 10 is connected to the nutrient source storage tank 10 and the dissolution stirring tank 24 by a signal from the control device 11. (A) 13 is opened, and the solid nutrient source 8 is put into the dissolution and agitation tank 24.

  Thereafter, ethanol, which is an organic solvent 27, is introduced into the dissolution and agitation tank 24 from a solvent storage tank (tank) 25 via a solvent supply pump 26. Input amounts of the solid nutrient source 8 and the organic solvent 27 are determined by the control device 11 inputted in advance, and the valve (A) 13 and a valve (B) 28 capable of controlling the flow rate according to a signal from the control device 11. Is opened and closed.

  The weight ratio of the solid nutrient source 8 and the organic solvent 27 is 40% for the solid nutrient source 8 and preferably 60% for the organic solvent 27, and most preferably the solid nutrient source 8 is 40%. The organic solvent 27 is 65% with respect to 35%. When the organic solvent 27 exceeds 60%, dissolution can be facilitated, but solid or gelation is difficult in soil and / or groundwater.

The correlation between the amounts of the solid nutrient source 8 and the organic solvent 27 charged in the dissolution and stirring tank 24 is correlated with the resolution of the organic solvent 27 and the temperature, and the adjustment is performed by adjusting the valve (A) 13 and the valve. (B) 28 is alternately opened and closed , and fine adjustment is performed by controlling the flow rate of the organic solvent 27 by the valve (B) 28. The solid nutrient source 8 is dissolved into the liquid nutrient source 9 by stirring and mixing in the dissolution stirring tank 24. Moreover, you may provide a heating apparatus for melt | dissolution promotion.

  When the dissolution and agitation tank 24 is stored in a heat retaining device 16 such as a container or a tank provided with heat retaining means, the stable liquid nutrient source 9 can be stably injected under pressure into soil and / or groundwater. At the same time, energy can be properly managed for heating. Needless to say, the heat retaining device 16 includes a heat insulating material (not shown) and a heat retaining heater 17.

  Further, the dissolution and stirring tank 24 is provided with a conductivity meter 29, and the concentration of the liquid nutrient source 9 input in advance to the control device 11 is set to a set concentration by the conductivity of the conductivity meter 29. In this case, the supply valve 19 is opened, and the supply source 21 pressurizes and injects the liquid nutrient source 9 into the soil and / or groundwater with an injection hole 20.

  For example, when the solid nutrient source 8 is a nutrient source mainly composed of stearic acid having 18 carbon atoms, after stirring and mixing until the conductivity of the conductivity meter 29 reaches an arbitrary value near the saturation point, The supply valve 19 is opened, and the supply pump 21 is pressurized and injected into the soil and / or groundwater, so that it can easily penetrate into the soil and / or groundwater, and uniformly penetrates the gap between the soil grains. be able to. Since the temperature of soil and groundwater is 5 ° C. to 20 ° C., the liquid nutrient source 9 injected under pressure is infused into a solid or gel form after being injected, so that it is in a wide range. Highly sustainable purification of pollutants can be realized.

  Further, regarding the state of purification, the observation well 22 is provided on the downstream side of the groundwater in the contaminated area, and the state of purification of the pollution can be determined by pumping and analyzing with the pump 23.

  Furthermore, it is self-evident that various embodiments can be appropriately combined and developed in a diversified manner corresponding to the contamination situation at the site.

  The contamination purification method of the present invention is, for example, soil contaminated with the contaminants around places where substances that can become contaminants are used or discharged, such as electronic parts factories, metal product factories, dry cleaning sites, and garbage incineration plants. It is extremely effective as a method for purifying groundwater.

Model sectional drawing which shows the outline | summary of the contamination purification of the soil and groundwater of the reference example 1 of this invention Model sectional drawing which shows the outline | summary of the contamination purification of the soil and groundwater of Example 1 of this invention

DESCRIPTION OF SYMBOLS 1 Factory 2 Topsoil 3 Upper silt layer 4 Sandy soil layer 5 Lower silt layer 6 Contaminated part 7 Contamination expansion area 8 Solid nutrient source 9 Liquid nutrient source 10 Nutrient source storage tank 11 Controller 12 Melting tank 13 Valve (A)
DESCRIPTION OF SYMBOLS 14 Steam generator 15 Flow control valve 16 Heat retention device 17 Heat retention heater 18 Temperature measurement device 19 Supply valve 20 Injection hole
21 Supply Pump 22 Observation Well 23 Pumping Pump 24 Dissolution Stirring Tank 25 Solvent Storage Tank (Tank)
26 Solvent Supply Pump 27 Organic Solvent 28 Valve B
29 Conductivity meter

Claims (4)

A method of injecting a nutrient source for activating microorganisms that decompose organochlorine compounds into at least one of soil and groundwater containing an organochlorine compound, wherein the nutrient source is linear saturated with 8 or more carbon atoms is dissolved in solid volatile or water-soluble organic solvent those containing monocarboxylic acid, wherein at the time of injection into the organochlorine compound contained in the soil and groundwater in a liquid form, after injection of the organic solvent A contamination purification method , wherein the nutrient source becomes solid or gel by volatilization or dissolution in water . 2. The contamination purification method according to claim 1, wherein the organic solvent is an organic solvent composed of carbon, hydrogen, and oxygen. The contamination purification method according to claim 1, wherein at least one of the soil and groundwater is purified in situ. The contamination purification method according to claim 1, wherein the nutrient source is pressurized and injected into soil.

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