JP2004195322A - Soil or ground water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil or ground water treatment method for avoiding secondary pollution effectively by fixing a carbon source at a soil or ground water position as a solid to supply carbon by minute quantity over a long period of time. <P>SOLUTION: The representative constitution of this soil or ground water treatment method is set so that the carbon source, which contains a specific number of carbon atoms and has a specific molecular structure, and a water absorbing material with a specific water absorption are allowed to coexist and a means which performs stirring in soil or ground water is provided. As the carbon source, a specific carbon source, which has biodegradability, contains a specific number of carbon atoms and has a specific molecular structure is selected to be used in such a state that the carbon source and the water absorbing material are allowed to coexist. As a carbon source which is solid on the ground and insoluble in water, an ester of a 14C or more straight chain saturated fatty acid and a monohydric alcohol is used. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a soil and groundwater treatment method for purifying in situ an organic chlorine compound such as trichlorethylene, and more particularly to a microorganism treatment method for adding a carbon source to microorganisms living in situ.
[0002]
[Prior art]
The conventional method of treating soil and groundwater using in situ microorganisms involves adding a carbon source of a microorganism (also referred to as a hydrogen donor or an electron donor) as a liquid to soil or groundwater.
[0003]
[Patent Document 1]
JP-A-9-276894 [Patent Document 2]
JP-A-11-90484
[Problems to be solved by the invention]
In these conventional techniques, the liquid carbon moves in the flow of the groundwater, deviates from the intended pollution source, does not achieve the original purpose, and has a problem of secondary pollution by the added carbon source.
[0005]
The present invention effectively solves these conventional problems, and it is possible to effectively avoid secondary pollution by stopping the carbon source as a solid at the soil for purification and groundwater, and supplying carbon for a long period of time. The present invention provides a method for treating soil and groundwater.
[0006]
[Means for Solving the Problems]
In order to solve these conventional problems, the present inventors have made intensive studies and found that a carbon source (hydrogen donor) having a specific structure having a specific carbon number and a water absorbing material having a specific water absorption rate coexist, When added to soil or groundwater by a specific method, the present invention has found an outstanding effect that cannot be obtained by the conventional technology, and has completed the present invention.
[0007]
That is, the soil and groundwater treatment method of the present invention has the following main requirements.
1. A composition comprising a carbon source which is solid on the ground and insoluble in water and a water-absorbing material is added to soil through holes or grooves provided from the ground.
2. A composition comprising a carbon source and a water-absorbing material which is solid and insoluble in water on the ground is added to the groundwater through a hole provided on the ground, or a hole or groove provided in advance.
(3) A method of adding a composition comprising a carbon source and a water-absorbing material which is solid and water-insoluble on the ground added through a hole provided in soil or a hole provided in advance or a groove, or to ground water or both soil and ground water. Stir mechanically with.
4 While excavating the soil, a composition comprising a carbon source which is solid and insoluble in water on the ground and a water absorbing material is added.
5 While digging the soil while adding a composition consisting of a carbon source which is solid and insoluble in water and a water-absorbing material on the ground, stirring the added carbon source.
(6) adding a composition comprising a carbon source and a water-absorbing material which are solid and insoluble in water on the ground to soil or groundwater or both soil and groundwater from at least two or more points; An operation for stirring groundwater is provided.
[0008]
Further, as a carbon source, a fatty acid having 10 or more carbon atoms, an alcohol having 12 or more carbon atoms, an ester of a linear saturated fatty acid having 14 or more carbon atoms and a monohydric alcohol, a linear saturated fatty acid having 14 or more carbon atoms and a polyhydric alcohol Esters or derivatives thereof, esters of fatty acids having 16 or more carbon atoms and glycerin, fatty amines having 12 or more carbon atoms or amides having 12 or more carbon atoms, fatty amines having 12 or more carbon atoms or fatty acid amides having 12 or more carbon atoms, A degradable plastic is selected, and a material having a water absorption of 60% or more is selected as the water absorbing material.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The carbon source used in the present invention must be solid on the ground and insoluble in water. (Hereinafter referred to simply as a carbon source.)
The carbon source existing as a solid at the target purification position does not easily move due to the flow of groundwater or the like, but undergoes a biodegradation reaction by microorganisms living at the purification position, and releases carbon for a long time.
[0010]
Although the melting point of the carbon source used in the present invention is generally a value specific to the substance, a carbon source having an arbitrary melting point can be prepared by mixing a plurality of carbon sources having different melting points.
[0011]
As a means for providing a hole or a groove from the ground, a known means widely used in civil engineering work can be easily used.
[0012]
Examples of the known means include a boring means using a boring machine in the case of a hole, and a soil cement method (such as Japanese Patent No. 1954875) and a subsurface vertical impermeable wall method in the case of a groove (Patent No. 1575294, No. 2698768).
[0013]
After reaching the target purification position, the carbon source used in the present invention is preferably mechanically stirred in groundwater or soil in order to disperse as uniformly as possible in the purification position.
[0014]
The method of mechanically stirring in ground water or soil is not particularly limited, and refers to all means capable of mechanically dispersing the added carbon source of the present invention, such as wings, screws, and reamer shapes. An excavator having a stirring shaft provided with a rotating tool is exemplified.
[0015]
The carbon source used in the present invention can be added in the soil at the same time as digging, in addition to the method of adding from the hole or groove provided on the ground, for example, a bit portion for drilling at the tip of a drilling shaft. A hole or a groove for adding a carbon source near the ground, a carbon source is supplied from the ground using a pneumatic pumping means or the like, and a method of adding the carbon source into the soil from the hole or the groove provided near the bit portion or the like. No.
[0016]
By using this method, an operation of digging a hole or a groove for adding a carbon source and an operation of adding a carbon source to soil can be achieved at the same time.
[0017]
Further, the carbon source used in the present invention, in addition to the method of adding from the hole provided on the ground, or a hole provided in advance, or a groove, simultaneously adding in the soil while digging, simultaneously mechanically stirring It is also possible to provide a hole or a groove for adding a carbon source near a drill bit and a stirring blade provided at a tip of a drill shaft, for example, and pneumatically feed the carbon source from the ground. And a method in which the mixture is supplied to the soil through holes or grooves provided in the vicinity of the bit portion and the wings, and is simultaneously stirred in the soil and groundwater by a stirring means such as a stirring wing provided in the vicinity.
[0018]
By using this method, an operation of digging a hole or a groove for adding a carbon source, an operation of adding a carbon source into soil, and an operation of mechanically stirring the carbon source after the addition can be achieved at the same time.
[0019]
Here, excavation means all the concepts of excavating the soil with some mechanical force and simultaneously traveling in the soil, and the traveling direction can be arbitrarily selected from vertical, horizontal and diagonal directions, and excavate As the means, the above-mentioned bits are generally used, but the present invention is not limited to this.
[0020]
Further, the excavation operation is generally, but not limited to, rotation of the excavation axis, and includes, for example, an operation in the upper limit direction and a combined operation of the rotation and the vertical operation.
[0021]
In addition, wings for excavation refer to all shapes capable of digging operation, fixed wings fixed in advance on the ground and closed on the ground and during propulsion and can be arbitrarily opened and closed at points requiring excavation Opening and closing feathers can be selected.
[0022]
The depth of the hole or groove formed in the present invention or the depth of excavation can be arbitrarily selected depending on the distribution of pollution and the condition of soil quality. Examples of those that penetrate a saturated aqueous layer and reach a saturated aqueous layer, and those that also penetrate the saturated aqueous layer, and particularly, in the case of a hole formed by boring, those excavating horizontally in a specific layer, a plurality of A material that penetrates the layer at an angle can be exemplified.
[0023]
As the carbon source used in the present invention, a specific carbon source having biodegradability and a specific number of carbon atoms and a specific molecular structure is selected and used, and further used in a state where the carbon source and the water-absorbing material coexist. This is the greatest feature of the present invention.
[0024]
The first carbon source selected is a fatty acid, which must have at least 10 carbon atoms, more preferably a fatty acid in which the alkyl group is linear and consists only of a single bond.
[0025]
These fatty acids are essentially insoluble in water, but if they have less than 10 carbon atoms, they have a low melting point and become liquid above the ground (normal temperature), easily diffuse into soil and groundwater, and are highly likely to contaminate organic matter with secondary substances. For this reason, the presence of a double bond is not preferred because even if the number of carbon atoms is 10 or more, the melting point generally decreases. Furthermore, the presence of a side chain, a benzene ring, or the like lowers the biodegradability itself, which is not preferable for the treatment method using microorganisms as in the present invention.
[0026]
Examples of the fatty acids satisfying the above requirements include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, lignoceric acid, behenic acid, and mixtures, salts, and hydrogenated products of these fatty acids.
[0027]
As the mixture, a simple fatty acid may be artificially mixed, or a natural mixture of tallow fatty acid, coconut oil fatty acid, palm oil fatty acid, rapeseed oil fatty acid and the like may be used.
[0028]
Furthermore, beef tallow, lard, cocoa butter, coconut oil, palm oil, palm kernel oil, and soybean containing the fatty acid are also included.
[0029]
The selected second carbon source is an alcohol whose carbon number is essential to be 12 or more, and more preferably a straight-chain saturated alcohol having an alkyl group.
[0030]
These alcohols are essentially insoluble in water, but have a low melting point if the number of carbon atoms is less than 12, become liquid at room temperature, easily diffuse into soil or groundwater, and are highly likely to cause secondary contamination of organic substances. In addition, the presence of a double bond is not preferable because even if the number of carbon atoms is 12 or more, the melting point generally decreases.
[0031]
Examples of the alcohol satisfying the above requirements include lauryl alcohol, myristyl alcohol, stearyl alcohol, cetyl alcohol, behenyl alcohol, and mixtures and salts of these alcohols.
[0032]
As the mixture, a simple alcohol may be artificially mixed, or a natural mixture may be used.
[0033]
The third carbon source selected is an ester of a fatty acid and a monohydric alcohol, and it is essential that the fatty acid has 14 or more carbon atoms and the fatty acid is linear and saturated. There is no.
[0034]
If the fatty acid has less than 14 carbon atoms, it has a low melting point, becomes a liquid at room temperature, easily diffuses into soil and groundwater, and is highly likely to cause secondary contamination of organic substances. If the number is 14 or more, the melting point generally decreases, which is not preferable. Furthermore, the presence of a side chain, a benzene ring, or the like lowers the biodegradability itself, which is not preferable for the treatment method using microorganisms as in the present invention.
[0035]
Fatty acids satisfying the above requirements include myristyl myristate, cetyl palmitate, stearyl stearate, methyl stearate, butyl stearate, cholesteryl stearate, batyl stearate, octyl dodecyl behenate, behenyl behenate, and these esters. Examples thereof include a mixture and distearyl phthalate in which the fatty acid is a dibasic acid.
[0036]
The fourth carbon source selected is an ester of a fatty acid and a polyhydric alcohol or a derivative thereof, and the fatty acid must have at least 14 carbon atoms and be linear and saturated. Is not particularly limited.
[0037]
If the fatty acid has less than 14 carbon atoms, it has a low melting point, becomes a liquid at room temperature, easily diffuses into soil and groundwater, and is highly likely to cause secondary contamination of organic substances. Even if the number is 14 or more, it is generally not preferable because the melting point is generally lowered. Furthermore, the presence of a side chain, a benzene ring, or the like lowers the biodegradability itself, which is not preferable for the treatment method using microorganisms as in the present invention.
[0038]
Fatty acids satisfying the above requirements include sorbitan monomyristylate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monobehenate, polyoxyethylene sorbitan monostearate, polyethylene Glycol monostearate, polyethylene glycol distearate, sorbitan sesquistearate, sorbitan tristearate, polyoxyethylene sorbite hexastearate, and mixtures of these esters, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxy Ethylene stearyl ether, polyoxyethylene behenyl ether, glycerin cetyl ether, glycerin stearyl ether, poly Alkoxy polyoxypropylene cetyl ether, polyoxyethylene polyoxypropylene decyl tetradecyl ether, ethers such as polyoxyethylene octylphenyl ether are exemplified.
[0039]
The fifth carbon source selected is an ester of a fatty acid and glycerin, and it is essential that the fatty acid has 16 or more carbon atoms, but the carbon number of glycerin is not particularly limited.
[0040]
If the fatty acid has less than 16 carbon atoms, the fatty acid has a low melting point, is in a liquid state at room temperature, easily diffuses into soil or groundwater, and has a high risk of secondary contamination of organic substances, which is not preferable.
[0041]
Fatty acids satisfying the above requirements include stearic acid monoglyceride, palmitic acid stearic acid monoglyceride, oleic acid monoglyceride, stearic acid monodiglyceride, oleic acid stearic acid monoglyceride, oleic acid stearic acid monoglyceride, behenic acid monoglyceride, monostearic acid tetraglyceride, triglyceride Tetraglyceryl stearate, tetraglyceryl pentastearate, hexaglyceryl monostearate, hexaglycel pentastearate, decaglyceryl monostearate, decaglyceryl distearate, decaglyceryl tristearate, decaglicel pentastearate, decaglicel heptastearate, decaglicel decastearate, monostearin Acid polyoxyethylene glycerin, Nosutearin acid Polo propylene glycol, and mixtures of these esters are exemplified.
[0042]
The sixth carbon source selected is a fatty amine, and is a general term for a substance comprising an alkyl group and a primary amine, a secondary amine, a tertiary amine, a diamine, an alkylamine acetate, and the like. It is essential that it be 12 or more.
[0043]
More preferably, it is a fatty amine in which the alkyl group is linear and saturated, and even more preferably, it is a secondary amine having 16 or more carbon atoms, a tertiary amine having 22 or more carbon atoms, and a diamine. Is a fatty amine having 16 or more carbon atoms and, in the case of an alkylamine acetate, having 14 or more carbon atoms.
[0044]
When the number of carbon atoms is less than these limited numbers, the melting point is low, the liquid state is formed at room temperature, and it is easily diffused into soil or groundwater, and the possibility of secondary contamination of organic matter is high. Even if it is more than the limit, the melting point is generally lowered, which is usually not preferable. Furthermore, the presence of a side chain, a benzene ring, or the like reduces the biodegradation itself, which is not preferable for the treatment method using a microorganism as in the present invention.
[0045]
Fatty amines meeting the above requirements include laurylamine, myristylamine, stearylamine, dipalmitylamine, distearylamine, dimethylbehenylamine, palmitylpropylenediamine, stearylpropylenediamine, myristylamine acetate, stearylamine acetate, stearin Examples thereof include diethylaminoethylamide acid, diethylaminopropylamide stearate, and mixtures and salts of these fatty amines.
[0046]
The seventh carbon source selected is a fatty acid amide, and it is essential that the carbon number be 12 or more.
[0047]
If the number of carbon atoms is less than 12, the melting point is low, the liquid state is formed at room temperature, and it is not preferable because it easily diffuses into soil or groundwater and the secondary contamination of organic matter is high.
[0048]
Examples of the fatty acid amide satisfying the above requirements include lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, ethylenebisstearic acid amide, dipalmityl ketone, distearyl ketone, and A mixture of these fatty acid amides is exemplified.
[0049]
The eighth carbon source selected is a biodegradable resin, more preferably a biodegradable resin having an ester bond having excellent biodegradability.
[0050]
Specific examples include lactic acid polymers, copolymers of hydroxybutyric acid and hydroxyvaleric acid, condensation polymers of polyols and aliphatic dicarboxylic acids, and poly (ε-caprolactone).
[0051]
The biodegradable resin generates carboxylic acids and alcohols by hydrolysis in the presence of water present in soil and groundwater, and any of these carboxylic acids and alcohols is a carbon source that can be used in the microbial reaction of the present invention. It is what becomes.
[0052]
Nutrients of microorganisms other than carbon (such as nitrogen and phosphorus) may be added and injected separately from the carbon source used in the present invention. Even if the nutrient salt is water-soluble, it is preferable because it is immobilized by the solid carbon source at the same position as the carbon source and the elution can be controlled.
[0053]
In order to realize these configurations, for example, a predetermined amount of nitrogen such as ammonium sulfate and potassium dihydrogen phosphate and a phosphorus source are mixed with the carbon source used in the present invention, and the mixture is extruded at a temperature raised to near the melting point of the carbon source. A composition in which a nitrogen source and a phosphorus source are dispersed in a carbon source can be obtained by ordinary granulation means such as a granulator.
[0054]
In the composition, as the carbon source is gradually biodegraded, the nitrogen and phosphorus sources present therein are gradually exposed to the surface, and as a result, a sustained-release body of carbon, nitrogen and phosphorus is formed.
[0055]
The carbon source having a specific carbon number and structure used in the present invention, itself is insoluble in water but has high biodegradability, and a small amount of biodegradation products generated when undergoing biodegradation in soil, or Release to groundwater environment.
[0056]
Since these biodegradation products usually have fewer carbon atoms than the original carbon source, and are easily soluble in water, microorganisms contributing to purification readily utilize these biodegradation products and mainly use trichlorethylene by co-metabolism. And other pollutants are made harmless by a dechlorination reaction.
[0057]
That is, in the soil and groundwater treatment method of the present invention, by selectively using a carbon source having a specific structure having a specific carbon number as a carbon source of the microbial reaction, the biodegradation reaction of in situ indigenous microorganisms is extremely utilized. It uses the property as a sustained-release substance of a carbon source that elutes in small amounts, and since it releases carbon in small amounts for a long time with a single addition, the possibility of secondary contamination by organic substances is low, and it is used in conventional technology. There is no need to continuously add the liquid carbon source that has been used.
[0058]
It is essential that the water-absorbing material used in the present invention has a self-water absorption of 60% or more.
[0059]
If the water absorption is less than 60%, the constitution of the present invention does not produce an essential synergistic effect with the carbon source, which is not preferable.
[0060]
Examples of suitable water-absorbing materials include starch styrene sulfonic acid graft polymer, starch acrylic acid graft polymer, starch acrylonitrile graft polymer, starch acrylamide graft polymer, starch vinyl sulfonic acid graft polymer, cellulose acrylonitrile graft polymer , Polyvinyl alcohol and polymers, crosslinked carboxymethylcellulose, substances called superabsorbent polymers such as crosslinked products of sealonic acid, agarose and polyacrylic acid, perlite, verculite, rock wool, activated carbon, silica gel, charcoal, porous Examples include porous ceramics, sponges such as urethane, nonwoven fabrics, fiber aggregates, mica, and talc.
[0061]
The main subject of the present invention is that the carbon source used in the present invention is added to soil groundwater in a solid state, but the presence of sufficient moisture around the carbon source is an essential condition for performing the biodegradation reaction. In particular, in the case of purifying an unsaturated water layer, the difference in the purifying effect depending on the presence or absence of this requirement is remarkable.
[0062]
When a material having a water absorption of 60% or more coexists around the carbon source of the present invention, sufficient water can be supplied and held around the carbon source, and when there is no water absorbing material. As compared with the case where only the carbon source of the present invention is simply added to soil or groundwater, it shows an excellent purification effect.
[0063]
Further, in addition to the coexistence of the carbon source and the water-absorbing material, it is further possible to perform some kind of stirring operation in soil and groundwater, and to make the carbon source and the water-absorbing material exist as uniformly dispersed in the soil and groundwater as possible. It acts synergistically and exhibits an outstanding purification effect.
[0064]
The microbial reaction that contributes to the implementation of the present invention is an anaerobic reaction in a state where the oxygen concentration is limited, and it is preferable to use another means for improving the anaerobic state using a chemical reduction reaction.
[0065]
【Example】
Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
(Example 1)
A 10 cm diameter pipe made of embi was inserted into a well dug in advance with 80 kg of a mixture of 45 wt% lauric acid, 35 wt% myristic acid, and 20 wt% cellulose acrylonitrile polymer (average particle size: 1 mm) as a carbon source from the ground. It was added to an unsaturated water layer 10 m below the ground through the book.
[0066]
Next, as a result of analyzing the water quality of the aquifer at the point where the mixture was added 111 days later, trichlorethylene, which had been present at 4.5 mg / L at the initial stage, was reduced to 0.9 mg / L.
[0067]
This is the result of biodegradation of the carbon source in the added mixed solution, and microbial decomposition of trichlorethylene using a trace amount of eluted organic matter as the carbon source.
[0068]
In addition, no increase in organic matter (measured by TOC) was observed from the observation well located downstream for the flow of groundwater 1.5 m from the point of addition, indicating that the carbon source of this example was added. No secondary contamination of organic matter was observed.
[0069]
In addition, as a comparison, at another place at the same point, as a result of performing the same experiment in which only the cellulose acrylonitrile polymer was removed, the trichloroethylene concentration was 3.2 mg / L, and the effect of coexisting the cellulose acrylonitrile polymer was remarkable. Admitted.
(Example 2)
A 30cm mixture of 55% by weight of tallow fatty acid, 10% by weight of stearyl alcohol, 15% by weight of lactic acid polymer, and 20% by weight of pearlite as a carbon source from the ground was passed through a 15cm diameter pipe inserted into a well dug in advance. It was added to a 5.5 m underground unsaturated water layer.
[0070]
Further, a stirring shaft having a wing with a radius of 20 cm for stirring was inserted into the tip through the well, and the shaft was propelled while rotating the stirring shaft from the ground to a position of 6.5 m below the ground. To stir and disperse.
[0071]
Next, as a result of sampling and analyzing the soil of the unsaturated aqueous layer at the point where the carbon source was added 105 days later, trichlorethylene, which was initially present at 7.9 mg / L, was reduced to 0.1 mg / L or less, and initially 1.4 mg / L. / L The tetrachlorethylene present was reduced by 0.2 mg / L.
[0072]
This is the result of biodegradation of the added carbon source and decomposition of trichlorethylene and tetrachloroethylene by a trace amount of eluted organic matter as a carbon source.
[0073]
In addition, no increase in organic matter (measured by TOC) was observed from the observation well located downstream for the flow of groundwater 1.5 m from the point of addition, indicating that the carbon source of this example was added. No secondary contamination of organic matter was observed.
[0074]
Also, as a comparison, at another place at the same point, the same experiment was carried out with only perlite removed.As a result, both the addition of perlite and the stirring with the wing after the addition were not performed, and the trichlorethylene concentration was 3.2 mg in all cases. / L and the concentration of tetrachloroethylan were 1.0 mg / L, and the effect of coexisting pearlite and the effect of stirring by feathers were remarkably recognized.
(Example 3)
FIG. 1 shows an excavation shaft for excavation used in the present embodiment.
[0075]
In FIG. 1, reference numeral 11 denotes a main body of a digging shaft, which is rotated by a motor in a direction indicated by an arrow in FIG. Reference numeral 12 denotes a wing for excavation provided at the tip of a digging shaft, 13 denotes an inlet pipe for a carbon source, and 14 denotes an outlet of the carbon source.
[0076]
First, a 30% by weight monodiglyceride stearate, 25% by weight lauric acid, 15% by weight palm oil, 30% by weight starch acrylamide polymer composition (average particle size: 1 mm) as a carbon source from the ground using compressed air from a 80 kg compressor. It was led to the introduction pipe of the carbon source of the 13th.
[0077]
At the same time, the excavating shaft 11 starts excavating with the wings 12 from the ground while rotating, propelling to a point about 12 m immediately above the aquifer, and the carbon source used in this embodiment guided through the introduction pipe 13 is the carbon source. It was added into the soil from the outlet 14.
[0078]
Thereafter, the excavation shaft was pulled out to the ground while rotating in the reverse direction, so that the carbon source used in the present example could be stopped as a solid at the destination in a columnar shape.
[0079]
Next, after 207 days, the soil of the unsaturated aqueous layer at the point where the carbon source was added was sampled and analyzed. As a result, trichlorethylene, which had initially been present at an average of 18.0 mg / L, was reduced to 0.2 mg / L.
[0080]
In this method, the added carbon source is biodegraded, and microorganisms decompose trichloroethylene using a trace amount of eluted organic matter as a carbon source.
[0081]
In addition, no increase in organic matter (measured by TOC) was observed from the observation well located downstream of the flow of groundwater 1 m from the point of addition, and the organic matter due to the addition of the carbon source of this example was not observed. No secondary contamination was observed.
[0082]
As a comparison, the same experiment was conducted at another point at the same point, except that only the starch acrylamide polymer was removed.As a result, the trichlorethylene concentration was 3.2 mg / L, and the effect of coexisting with the starch acrylamide polymer was remarkably recognized. Was.
(Example 4)
FIG. 2 shows an excavation shaft for excavation used in this example.
[0083]
In FIG. 2, reference numeral 21 denotes a main body of an excavating shaft, which is rotated by a motor in a direction indicated by an arrow 25 in FIG. Reference numeral 22 denotes a digging wing provided at the tip of the digging shaft, 23 denotes a carbon source introduction pipe, 24 denotes a carbon source discharge port, 26 denotes a stirring wing, and a stirring wing 26 in a direction of an arrow 27. Can be opened and closed.
[0084]
First, a mixture of 45% by weight of stearyl alcohol, 35% by weight of myristic acid, 15% by weight of ammonium sulfate (anhydride) and 5% by weight of sodium dihydrogen phosphate as a carbon source added from the ground is an extrusion granulator set at a die temperature of 65 ° C. Was used to obtain a carbon source mixture granulated into a pellet having a length of 5 mm and a diameter of 1 mm.
[0085]
EDX analysis revealed that the obtained carbon source mixture had a structure in which ammonium sulfate and sodium dihydrogen phosphate were encapsulated by the carbon source.
[0086]
A mixture of 100 parts by weight of the obtained mixture, 10 parts by weight of silica gel, and 10 parts by weight of a crosslinked polyvinyl alcohol was introduced into a carbon source inlet pipe 23 in the figure by the force of compressed air by a compressor.
[0087]
At the same time, the excavating shaft 21 starts excavating from the ground with the feathers 22 while rotating, propelling to a point of about 25 m directly below the aquifer, and the mixture containing the carbon source used in the present example guided through the introduction pipe 23 is It was added to the soil and groundwater from the outlet 24 of the carbon source.
[0088]
At a point 3 m from the ground, the agitating wings 26 open at right angles to the propulsion direction (longitudinal direction of the excavation axis), and immediately after the carbon source used in this embodiment is added to the soil and groundwater from the discharge port 24. The stirring operation was started.
[0089]
After that, the excavating shaft closes the agitating wings 26 in parallel to the propulsion direction, and is pulled out to the ground while rotating in the reverse direction, whereby the carbon source used in this embodiment is agitated and dispersed as a solid at the destination in a dispersed state. I was able to stop.
[0090]
Next, 120 days later, as a result of sampling and analyzing the soil of the unsaturated aqueous layer at the point where the carbon source was added and the groundwater of the saturated aqueous layer, tetrachloroethylene, which was initially present on average at 22.0 mg / L, was 0.1 mg / L. It had dropped below.
[0091]
In this method, the added carbon source is biodegraded, and the microorganisms decompose tetrachlorethylene using a trace amount of eluted organic matter as a carbon source.
[0092]
In addition, no increase in organic matter (measured by TOC) was observed from the observation well located downstream of the flow of groundwater 1 m from the point of addition, and the organic matter due to the addition of the carbon source of this example was not observed. No secondary contamination was observed.
I was not able to admit.
[0093]
In addition, as a comparison, at another point at the same point, the same experiment was conducted in which only the silica gel and the polyvinyl alcohol cross-linked product were removed, and both the addition of the silica gel and the polyvinyl alcohol cross-linked product and the stirring by the blade after the addition were not performed. As a result, the tetrachloroethylene concentration was 18.1 mg / L or more, and the effect of coexisting the silica gel and the crosslinked polyvinyl alcohol and the effect of stirring by the feathers were remarkably observed.
(Example 5)
From the ground, a mixture of 100 parts by weight of palmitic acid and 45 kg of activated carbon 45% by weight as a carbon source was added to the soil in a grid pattern at intervals of 1 m from the surface of the ground at 15 points by means of a pneumatic pump using a compressor.
[0094]
After the addition is completed, mechanically agitate the section from the ground to a point 4 m above the ground using construction machinery (backhoe and power shovel) to uniformly disperse the mixture containing the carbon source, and uniformly disperse the carbon source as a solid at the destination. Could be stopped.
[0095]
Next, 105 days later, as a result of sampling and analyzing the soil of the unsaturated aqueous layer at the point where the mixture was added, trichlorethylene, which was present at 21.0 mg / L in the initial stage, was 0.4 mg / L, and 6.9 mg / L in the initial stage. The existing tetrachlorethylene was reduced to 0.2 mg / L or less.
[0096]
This is the result of biodegradation of the added carbon source and decomposition of trichlorethylene and tetrachloroethylene by a trace amount of eluted organic matter as a carbon source.
[0097]
In addition, no increase in organic matter (measured by TOC) was observed from the observation well located downstream for the flow of groundwater 1.5 m from the point of addition, indicating that the carbon source of this example was added. No secondary contamination of organic matter was observed.
[0098]
As a comparison, the results of the same experiment in which only the activated carbon was removed at another place at the same point, and the results of not performing both the addition of the activated carbon and the stirring by the construction machine after the addition, showed that the trichlorethylene concentration was low. It was 13.6 mg / L or more, and the effect of coexisting activated carbon and the stirring effect by construction machinery were remarkably recognized.
(Example 6)
While supplying 350 kg of the mixture containing the carbon source adjusted in Example 5 to the excavated portion by pneumatic pumping means using a compressor, it was previously contaminated with tetrachloroethylene and cis-1,2-dichloroethylene using the soil cement continuous wall method. A groove as shown in Fig. 3 was formed in a contaminated area that was found to be present.
[0099]
In FIG. 3, reference numeral 61 denotes a contaminated area, 62 denotes three parallel grooves formed in the longitudinal direction of the contaminated area, 63 denotes a diagonal groove obliquely (about 45 degrees) intersecting with the three parallel grooves, and 64 denotes a diagonal groove. This is a straight groove formed at right angles to the three parallel grooves.
[0100]
Each groove has a total length of 14.5m to 7m, width of 70cm, depth of 10.5m (penetrating through the saturated water layer). The cutter chain, which is a feature of the soil cement method, excavates while rotating like a caterpillar. The soil which has been simultaneously supplied and added with the carbon source of the present embodiment and is buried rearward (opposite to the traveling direction), so that the formed grooves uniformly disperse the soil at the site and the carbon source used in the present embodiment. The carbon source could be stopped at the destination as a solid.
[0101]
Next, 205 days later, as a result of sampling and analyzing the soil of the unsaturated aqueous layer and the groundwater of the saturated aqueous layer at the point where the mixture containing the carbon source was added, tetrachloroethylene and cis-1,2- The dichloroethylene removal rate was 91% or more.
[0102]
This is the result of microbial decomposition of tetrachloroethylene and cis-1,2-dichloroethylene using a trace amount of organic substances eluted by biodegradation of the added carbon source as a carbon source.
[0103]
Further, no increase in organic matter (measured by TOC) was observed from the observation well provided on the downstream side with respect to the flow of groundwater of 1.5 m from the contaminated area, and the addition of the carbon source of this example was not observed. No secondary contamination of organic matter was observed.
[0104]
As a comparison, the same experiment was conducted at another point at the same location, where only activated carbon was removed. As a result, the removal rate of tetrachloroethylene and cis-1,2-dichloroethylene was about 20%, and the effect of coexisting activated carbon was remarkable. Was recognized.
[0105]
The value of the addition amount of the carbon source used in this example is an example determined based on data obtained from various in-situ surveys performed in advance, and the addition amount is limited to this value. However, it goes without saying that it can be determined arbitrarily according to various conditions such as the concentration of pollutants, the type and activity of microorganisms contributing to in situ purification, soil properties, groundwater flow velocity and flow direction.
[0106]
Although not specifically exemplified in the present example, it is preferable to use various additives for accelerating a biological reaction and improving the dispersibility of the carbon source used in the present invention.
[0107]
Examples of these additives include fertilizer compositions as a source of nitrogen and phosphorus, powders of iron and copper to promote anxiety, sodium bisulfite, addition of hydrogen gas, and various surfactants as dispersants. And the like.
[0108]
As means for raising the temperature of soil and groundwater, means using Joule heat generated by passing an electric current from electrodes provided in the soil, hydration reaction with moisture in soil and groundwater in soil represented by lime and iron oxide Means utilizing the chemical reaction heat generated by the reaction can be exemplified.
[0109]
【The invention's effect】
As described above, the soil of the present invention, the groundwater treatment method is a target soil, a carbon source as a solid at the groundwater position, by supplying a trace amount of carbon for a long period of time, soil to effectively avoid secondary pollution, The present invention provides a groundwater treatment method.
[Brief description of the drawings]
FIG. 1 is a front view showing an excavation axis for excavating soil according to one embodiment of the present invention; FIG. 2 is a front view showing an excavation axis for excavating soil according to another embodiment of the present invention; FIG. 3 is a top view showing a cleaning groove according to an embodiment of the present invention.
11 Body of excavation shaft 12 Excavation wing 13 is inlet pipe 14 for carbon source.
21 Body of Drilling Shaft 22 Drilling Wing 23 Carbon Source Introducing Tube 24 Carbon Source Outlet 26 Stirring Wing 61 Contaminated Zone 62 Three Parallel Grooves 63 Formed in Longitudinal Direction of Contaminated Zone Diagonal groove 64 crossing obliquely (approximately 40 degrees) with the parallel groove of the straight groove formed at right angles to the three parallel grooves

Claims (20)

A method for treating soil, wherein a composition comprising a carbon source and a water-absorbing material which is solid and insoluble in water on the ground is added to the soil through holes or grooves provided in the soil. Groundwater treatment in which a composition comprising a carbon source and a water-absorbing material that is solid and insoluble in water on the ground is added to groundwater through a hole provided in the soil or a hole provided in advance or a groove provided in the soil. Method. The method for treating soil or groundwater according to claim 1, wherein there are two or more holes or grooves. The soil treatment according to claim 1 or 3, wherein a composition comprising a carbon source and a water-absorbing material which are solid and water-insoluble on the ground and added through a hole or a groove provided in the soil is mechanically stirred in the soil. Method. A composition comprising a ground solid and water-insoluble carbon source and a water-absorbing material added through a hole provided in the soil or a hole provided in advance or a groove, in groundwater, or in soil or groundwater. Soil mechanically stirred or groundwater treatment. A method for treating soil, wherein a composition comprising a carbon source which is solid and insoluble in water and a water-absorbing material is added while excavating the soil. A soil treatment method wherein a soil comprising a solid and water-insoluble carbon source on the ground and a water-absorbing material are added while excavating the soil and stirring the added carbon source. An operation of adding a composition comprising a carbon source and a water-absorbing material that are solid and insoluble in water on the ground to soil or groundwater or both soil and groundwater from at least two or more points; and Soil and groundwater treatment method comprising the action of stirring water. The method for treating soil or groundwater according to any one of claims 1 to 8, wherein a water absorption rate of the water-absorbing material is 60% or more. 9. The method for treating soil and groundwater according to claim 1, wherein a fatty acid having 10 or more carbon atoms is used as a carbon source which is solid and insoluble in water on the ground. The soil and groundwater treatment method according to claim 10, wherein the fatty acid is a linear saturated fatty acid. The soil and groundwater treatment method according to any one of claims 1 to 8, wherein an alcohol having 12 or more carbon atoms is used as a carbon source which is solid on the ground and insoluble in water. The soil and groundwater treatment method according to claim 12, wherein the alcohol is a saturated alcohol. 9. The method for treating soil and groundwater according to claim 1, wherein an ester of a linear saturated fatty acid having 14 or more carbon atoms and a monohydric alcohol is used as a carbon source which is solid and insoluble in water on the ground. 9. The method for treating soil and groundwater according to claim 1, wherein an ester of a linear saturated fatty acid having 14 or more carbon atoms and a polyhydric alcohol or a derivative thereof is used as a carbon source which is solid and insoluble in water on the ground. The soil and groundwater treatment method according to any one of claims 1 to 8, wherein an ester of a fatty acid having 16 or more carbon atoms and glycerin is used as a carbon source which is solid and insoluble in water on the ground. The soil and groundwater treatment method according to any one of claims 1 to 8, wherein a fatty amine having 12 or more carbon atoms or a fatty acid amide having 12 or more carbon atoms is used as a carbon source which is solid and insoluble in water on the ground. 9. The soil and groundwater treatment method according to claim 1, wherein the carbon source which is solid and insoluble in water on the ground is a fatty amine having 12 or more carbon atoms or a fatty acid amide having 12 or more carbon atoms. 9. The method for treating soil and groundwater according to claim 1, wherein the carbon source which is solid and insoluble in water on the ground is a biodegradable plastic. The method for treating soil and groundwater according to claim 19, wherein the biodegradable plastic has an ester bond.

Images