JP2004313865A - Underground cleaning body arranged with hardly water-permeating division layer and construction method for underground cleaning body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To totally generate no residual soil, to exhibit large water-permeability and to individually clean contaminated underground water in respective aquifers by one cleaning body without making underground water flowing in one aquifer flow to the other aquifer through the cleaning body. <P>SOLUTION: The underground cleaning body 10 has a hardly water-permeating layer 23 between the aquifer 22 and the aquifer 24 is made on a contaminated ground 30 existed with two or more of aquifers. The cleaning body divisions 11, 13, 15 positioned on the aquifer are formed by a mixture body including at least a cleaning material, a bioerodible polymer and original ground soil. Hardly water-permeating division layers 12, 14 for shutting off mutual communication of underground water flowing in aquifers at both vertical sides clamping a hardly water-permeating layer are arranged in the cleaning body division positioned in the hardly water-permeating layers 12, 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an underground purifying body which does not generate residual soil, exhibits large water permeability, and can separately purify each contaminated groundwater flowing through a plurality of aquifers having different pore water pressures with a single purifying body. It relates to a construction method for constructing an underground purification body.
[0002]
[Prior art]
For example, volatile organic compounds such as trichloroethylene, which are used in large quantities in cleaning processes at semiconductor manufacturing plants, may contaminate soil or groundwater due to leakage, etc. And the use of groundwater is limited.
[0003]
In order to solve this, a purification continuous wall containing a metallic reducing agent is formed in the ground in a direction of blocking the flow of groundwater contaminated with volatile organic compounds, and when groundwater passes through the purification continuous wall. There is a method of decomposing pollutants by a reduction reaction to make the pollutants non-polluting (International Publication No. WO91 / 08176 of Patent Document 1). Further, the purification wall continuously arranged in the ground is a continuous pillar or an intermittent pile of a cylinder, and separation of the metallic reducing agent is prevented by stacking the cylindrical bags containing the metallic reducing agent on the cylinder, and water permeability is also provided. There has also been disclosed a method that improves the above (Japanese Patent Application Laid-Open No. H11-156351 of Patent Document 2).
[0004]
On the other hand, the structure of the ground generally has a plurality of aquifers with different pore water pressures. That is, as shown in FIG. 7, the normal ground 50 has a surface layer 51, an aquifer 52, a poorly permeable layer 53, an aquifer 54, and a base 55 in the depth direction of the ground, or It has a structure in which a poorly permeable layer is further repeatedly present in the depth direction. In such a ground 50, the contaminants leaked from the factory 56 and the like selectively pass through a portion having good water permeability and diffuse, but when the contamination history is old, the contaminants infiltrate into the inside of the poorly permeable layer 53. In some cases, it may penetrate through the poorly permeable layer 53 to reach the lower aquifer 54. Moreover, the flow of groundwater is often different between the upper and lower aquifers 52, 54 sandwiching the poorly permeable layer 53, and when contaminants are dissolved in the groundwater, the contamination moves and diffuses with the flow of the groundwater, It is not rare that the underground pollution source 57 spreads in the horizontal direction and extends deep in the depth direction, and the pollution concentration in each aquifer naturally differs at present.
[0005]
[Problems to be solved by the invention]
However, the conventional underground purification wall as disclosed in JP-A-11-156351 does not adopt a structure corresponding to the above-described ground structure. Therefore, when such an underground purification wall is disposed underground, there is a problem that contaminated groundwater flowing in an aquifer having a low pore water pressure hardly passes through the purification wall and is difficult to be purified. The reason will be described with reference to FIG. That is, the underground purification wall 58 disposed on the ground downstream of the pollution source 57 normally has the same or larger permeability as the aquifer in order to smoothly pass the contaminated groundwater through the purification wall. Designed. However, in this case, the underground purification wall 58 communicates the two aquifers 52 and 54 at the same time. For example, the contaminated groundwater X of the upper aquifer 52 having a high pore water pressure partially passes through the purification wall 58. Although it passes through and becomes purified groundwater X1, the remaining groundwater X2 flows into the lower aquifer 54 having a low pore water pressure and stays around the underground purification wall 581 located in the aquifer 54 portion. For this reason, the contaminated groundwater Y in the aquifer 54 cannot smoothly pass through the underground purification wall 58, and a flow that flows around the underground purification wall 58 is generated. This phenomenon is the same also when the lower aquifer 54 has a higher pore water pressure than the upper aquifer 52, and contaminated groundwater in the lower aquifer 52 is not purified.
[0006]
On the other hand, since the purification continuous wall described in International Publication No. WO91 / 08176 excavates a slot, a large amount of residual soil is generated. Further, when a mixture of a metal-based reducing agent and sand is installed in the slot, it is difficult to uniformly disperse the metal-based reducing agent and the like, and stably maintain the water permeability of the aquifer. There is a problem that it cannot be secured. Further, in the case of an underground purification wall described in Japanese Patent Application Laid-Open No. H11-156351 of Patent Document 2, for example, in the case of a cylindrical purification wall, activated carbon or the like is formed by using a forming pipe in a hollow portion of a casing pipe formed by excavation by a digging method. After the casting, the casing pipe is pulled out, so that a large amount of residual soil is generated, which causes a problem of industrial waste treatment.
[0007]
[Patent Document 1]
International Publication No. WO91 / 08176 (Claims)
[Patent Document 2]
JP-A-11-156351 (Claims, paragraph number 0023)
[0008]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to generate almost no residual soil and exhibit large water permeability, and to prevent groundwater flowing in one aquifer from flowing into another aquifer through a purification body. It is an object of the present invention to provide an underground purifier capable of individually purifying contaminated groundwater in an aquifer with one purifier, and a construction method of the underground purifier.
[0009]
[Means for Solving the Problems]
That is, the present invention (1) that achieves the above object has an underground purification system that is formed on a contaminated ground having a poorly permeable layer between aquifers and two or more aquifers. Wherein the purifier section located in the aquifer is formed of a mixture containing at least a purifying material, a biodegradable polymer, and ground soil, and the purifier section located in the poorly permeable layer comprises the poorly permeable section. It is an object of the present invention to provide an underground purifier in which a poorly permeable partition layer for blocking the mutual flow of groundwater flowing in aquifers on both upper and lower sides of a layer is provided. Further, in the present invention (2), the contaminated ground has a repeating structure of an aquifer, a poorly permeable layer and an aquifer in the depth direction of the ground, and the third and subsequent aquifers are non-contaminated layers. In some cases, the underground purifier is provided with the lower end portion of the underground purifier being landed on a poorly permeable layer sandwiched between an aquifer of a deepest contaminated layer and an aquifer of a non-contaminated layer. is there. Further, the present invention (3) provides the underground purifying body, wherein the purifying material is at least one selected from a pollutant adsorbent and a pollutant decomposing material. Further, the present invention (4) provides the underground purification body in which the poorly permeable partition layer has the same or higher permeability than the poorly permeable layer connected to the partition layer. It is. Further, the present invention (5) is a method for constructing an underground purification body on a contaminated ground having a poorly permeable layer between aquifers and two or more aquifers. Supplying a mixed drug material containing a purification material and a biodegradable polymer from the ground to the ground, and mixing and mixing the mixed drug material and the original ground soil to form a purifier body section located in the aquifer; The water-impervious material is supplied from the ground to the ground, and the water-impervious material and the original ground are formed by stirring and mixing, and the mutual flow of groundwater flowing through the upper and lower aquifers sandwiching the impervious layer is cut off. The present invention provides a construction method of an underground purification body for performing a step of arranging a partition layer having poor water permeability.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the contaminated ground on which the underground purification body is formed is a ground having a poorly permeable layer between aquifers and two or more aquifers. That is, contaminated ground having a three-layer structure of an aquifer, a poorly permeable layer, and an aquifer in the depth direction of the ground, or a repetition of a poorly permeable layer and an aquifer further in the depth direction of the ground following the three-layer structure. The ground has a structure. The upper part of this laminated structure is the surface layer, and the lower part is the base of the hard layer. Therefore, for example, when there are two layers of impervious layers, the ground is deep from the surface of the ground to the surface layer, the first aquifer, the first impervious layer, the second aquifer, the second impervious layer, and the third impervious layer. Consists of aquifer and basement. Further, the pore water pressures of a plurality of aquifers may be the same or different from each other, but in most cases usually differ. In the present invention, a remarkable effect can be obtained when the pore water pressures are different. In addition, the flow directions of the groundwater in the plurality of aquifers may be the same or different from each other.
[0011]
In the contaminated ground on which the underground purification body of the present invention is formed, the contaminated layer in which the contaminant is present is one that exists over at least two aquifers. If only one of the shallowest aquifers is a contaminated layer, the underground purifier may be constructed such that the lower end of the underground purifier is settled on the first impervious layer to form one aquifer. There is no danger that groundwater flowing through the formation will flow to other aquifers. In addition, a plurality of aquifers may have the same or different contaminant concentrations, but in the present invention, a particularly remarkable effect is exerted when the plurality of aquifers have different contaminant concentrations. In addition, a non-polluted aquifer may be present in the contaminated ground in addition to the polluted layer. Examples of the contaminants include, but are not particularly limited to, volatile organic compounds such as trichloroethylene and heavy metals.
[0012]
In the present invention, prior to constructing the underground purification body on the contaminated ground, a preliminary investigation for grasping the underground ground structure and the state of contamination is performed in advance. The survey method is performed by a known method, and the survey items include, for example, the existence and depth of the aquifer and the impervious layer, the permeability coefficient of each aquifer and the impervious layer, the flow direction of each groundwater, And the presence of a contaminated layer and a non-contaminated layer. The permeability coefficient of the aquifer is usually 10 ^-1 -10 ^-4 cm / sec, and the permeability coefficient of the poorly permeable layer is usually 10 ^-6 -10 ^-8 cm / sec. According to the ground survey at a certain point in the country, the ground concerned is, in order in the depth of the ground, the first aquifer 10m, the first impervious layer 3m, the second aquifer 10m, the second impervious layer 5m, and the third aquifer 5m. The aquifer was 5 m, and of these layers, the first aquifer to the second aquifer were contaminated layers.
[0013]
Next, an underground purification body according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view of the underground purifier in the present embodiment. The underground purification body 10 of this example includes a surface layer 21, a first aquifer 22, a first poorly permeable layer 23, a second aquifer 24, a second poorly permeable layer 25, and a third terrain in the deep underground direction. An underground purifier formed downstream of the soil pollution source 19 comprising the water layer 26, the third water-impermeable layer 27, the fourth aquifer 28, and the base 29, and is located in the first aquifer 22. The purifying body section 11, the purifying body section 13 located in the second aquifer 24, and the purifying body section 15 located in the third aquifer 26 are a mixture containing at least a purifying material, a biodegradable polymer, and original ground soil. The purifying body sections formed and located in the first impervious layer 23 circulate the contaminated groundwater flowing through the first aquifer 22 and the second aquifer 24 located on both upper and lower sides of the first impervious layer 23. A barrier layer 12 that blocks water is provided, and the purifying body located in the second water-impermeable layer 25 has a second water-impervious section. It is obtained by providing the partition layer 14 of low permeability to block the mutual flow of contaminated groundwater flowing through the second aquifer 24 and the third aquifer 26 positioned above and below both sides of the 25.
[0014]
Further, in the underground purifier 10 of this example, it is not necessary to perform any special construction on the surface layer 112 above the purifier section 11 located in the first aquifer 22 at the lowest depth. However, in FIG. 1, since the original ground soil of the surface layer 112 is stirred and mixed in the construction process and the water permeability is enhanced, the impervious rainwater infiltration prevention layer 17 is provided on the head of the underground purification body 10. ing. Further, the lower end portion 16 of the underground purification body 10 is landed on a third water-impermeable layer 27 sandwiched between a third aquifer 26 as a deepest contaminated layer and a fourth aquifer 28 as a non-contaminated layer. When the lower end portion 16 of the underground purification body 10 is settled by penetrating the third water-impermeable layer 27, the contaminated groundwater in the third aquifer 26 may flow into the fourth non-contaminated aquifer 28. There is. In this case, similarly to the purifying body section located in the other water-impermeable layer, if the water-impermeable partition layer is arranged in the purifying body portion located in the third water-impermeable layer 27, the lower end portion 16 of the underground purifying body 10 can be provided. May be penetrated through the third water-impermeable layer 27 and landed, but this is not preferable because a wasteful construction portion occurs.
[0015]
The purifier section located in the aquifer of the underground purifier 10 of this example is made of a mixture containing a purifying material, a biodegradable polymer, and original ground soil. Examples of the purification material include a contaminant adsorbent and a contaminant decomposer. The contaminant adsorbent is not particularly limited as long as it mainly removes contaminants such as organic halogen compounds or heavy metals by adsorption, and examples thereof include activated carbon. The contaminant decomposing material is not particularly limited as long as the contaminant is mainly removed by decomposition, and examples thereof include a metal-based reducing material and an iron oxide-based decomposing material. Examples of the metal-based reducing material include metal powders of iron or zinc, or powders of alloys or compounds thereof, and among them, those in which iron powder is inexpensive and discharged as waste can also be used. It is preferable in this respect. As the iron oxide-based decomposition material, for example, a commercially available iron oxide-based by-produced magnetite-based titanium oxide synthesized from iron-containing sulfuric acid produced as a by-product from the titanium oxide production process can be used. Further, a composite material of a metal-based reducing material and an iron oxide-based decomposing material as described in JP-A-2002-317202 can also be used. Among these purifying materials, it is preferable to use a pollutant decomposing material in that pollutants can be decomposed and made harmless. These purification materials can be used alone or in combination of two or more.
[0016]
When the biodegradable polymer is mixed with the purification material and supplied to the in-situ soil from the ground, the biodegradable polymer acts as a dispersion aid to uniformly disperse the purification material in the mixed drug material, and after being supplied to the original ground soil. Is decomposed in about one week, for example, and flows out together with the groundwater, so that it has a function of creating voids in the original ground soil and giving water permeability. The action of the biodegradable polymer in the mixed drug material for dispersing the purification material becomes more remarkable particularly when the mixed drug material is a slurry-type mixed drug solution because the mixed drug solution has a high viscosity. The biodegradable polymer is not particularly limited, and includes, for example, a natural or synthetic water-soluble polymer. Specific examples include polylactic acid; cellulose-based polymers such as carboxymethyl cellulose (CMC); Examples include starch-based polymers such as methyl starch (CMS). Among them, when the cellulose-based polymer is used as a mixed drug material in the form of a slurry, the mixed drug material exhibits a purifying material dispersing function by a thickening action of the polymer and is preferable in that it is decomposed in a relatively short time. .
[0017]
The poorly permeable partition layers 12 and 14 of the underground purifier are not particularly limited as long as they are formed of a water-blocking material. Examples of the water blocking material include cement milk and the like. The water-impermeable partition layers 12 and 14 may be formed on at least a part of the purifying body sections located in the first water-impermeable layer 23 and the second water-impermeable layer 25, respectively. In other words, if the first water-impermeable layer 23 has a thickness H, as shown in FIG. What is necessary is just to form a part of 111 (thickness H) with a layer having a thickness h smaller than H. The thickness h of the partition layer 12 is appropriately determined based on the thickness of the water-impermeable layer, its water-impermeability, and the like. If the thickness h of the partition layer 12 is too large, not only excessive water permeability will be caused, but also material waste will be caused. On the other hand, if the thickness h is too small, stable water permeability may not be obtained. Further, the impervious partition layers 12 and 14 have the same impermeability as the first impervious layer 23 and the second impervious layer 25 connected to the divider layers 12 and 14 or have greater impermeability. Among them, the same imperviousness to the continuous first impervious layer 23 and the second impervious layer 25 can be used, so that waste of materials can be omitted and the flow of groundwater in the vertical direction can be reliably shut off. Is preferred.
[0018]
The underground purification body 10 supplies a mixed drug material containing a purification material and a biodegradable polymer into the ground from the ground, stirs and mixes the mixed drug material and the original ground soil, and is located in the aquifer. A step of forming a purifier body section, supplying the water-impervious material into the ground from the ground, stirring and mixing the water-impervious material and the original ground soil, and forming the upper and lower aquifers sandwiching the poorly permeable layer. It can be obtained by performing a step of arranging a poorly permeable partition layer that blocks mutual flow of flowing groundwater. The method of installing this underground purification body in the ground is not particularly limited, and is a mechanical stirring and mixing method using a so-called mechanical stirring device, a jet stirring and mixing method using a jet stirring and mixing device, a mechanical stirring method. A combined method using a stirring / mixing method and a jet-type stirring / mixing method, and a compound method using an apparatus having a mechanical stirring function and a jet-type stirring function can be applied. All of these methods generate little residual soil and do not cause problems with industrial waste disposal. Among these methods, it is preferable to use the mechanical stirring and mixing method in that the uniform mixing of the purification material, the biodegradable polymer and the ground soil can be performed relatively easily and reliably.
[0019]
The mixing ratio of the purification material and the biodegradable polymer in the mixed chemical varies depending on the degree of contamination of the contaminated groundwater, the geology of the original ground soil, the degree of decomposition of the biodegradable polymer, and the like, and is appropriately determined. In addition, an auxiliary agent for adjusting the degree of progress of the decomposition of the biodegradable polymer can be added to the mixed drug material, if necessary. The supply form of the mixed drug material is a powdery substance and a liquid substance. Of these, a slurry-like liquid substance containing a purification material, a biodegradable polymer, and water can be used as described above. This is preferable in that the function of dispersing the purification material of the conductive polymer can be effectively exhibited.
[0020]
Hereinafter, a method of constructing the underground purifier 10 of the present embodiment underground using a mechanical stirrer will be described. As the mechanical stirring device, for example, a plurality of stirring blades provided below the stirring shaft, a first opening for discharging a mixed chemical solution provided in the vicinity of the stirring blades, and a second opening for discharging a water-blocking material Or a plurality of similar stirring blades, a single opening provided near the stirring blades for supplying a mixed chemical solution and a water-blocking material, and a material supply for switching the supply of the mixed chemical solution and the water-blocking material There is an apparatus provided with a switching unit. Further, on the ground, a first plant facility for supplying a slurry-type mixed chemical solution containing a purification material, a biodegradable polymer and water, and a second plant facility for supplying a water-blocking material such as cement milk will be installed. When material supply switching means for switching the supply of the mixed chemical liquid and the water-blocking material is provided, the material supply switching means can change a material discharged from a single opening provided near the stirring blade. it can.
[0021]
In this example, first, a step of forming a purifying body section located in the aquifer is performed. A mechanical stirring device (not shown) penetrates into the ground downstream of the contaminated layer 19 to a predetermined depth. After the penetration, the first plant equipment is driven to supply the mixed chemical solution in the form of slurry to the original ground soil from the first opening, and the mixed chemical solution and the original ground soil are uniformly stirred and mixed by the stirring blade, and the stirring shaft is further pulled up. The purification body section 15 is formed at the position of the aquifer 26. Next, a step of arranging the impervious partition layer 14 that blocks the mutual flow of groundwater flowing through the second aquifer 24 and the third aquifer 25 on the upper and lower sides sandwiching the second impervious layer 25 is performed. I do. That is, during the formation of the purifying body section 15, the supply of the mixed chemical solution is stopped, the second plant equipment is driven to supply the water-blocking material to the original ground soil from the second opening, and the water-blocking material and the raw ground soil are separated. The mixture is uniformly stirred and mixed with a stirring blade to form a poorly permeable partition layer 14 at the position of the poorly permeable layer 25. This operation is further successively repeated to form the purifier section 13, the poorly permeable partition layer 12, the purifier section 11, and the poorly permeable rainwater infiltration prevention layer 17 in order above the poorly permeable partition layer 14. . The rainwater intrusion prevention layer 17 is made of the same material as the hardly permeable partition layer, and the water permeability may be the same. In addition, the surface layer 112 above the underground purification body from the groundwater level WL to the poorly permeable rainwater infiltration prevention layer 17 does not supply the mixed chemical solution or the water-blocking material, and remains as the soil that has been stirred and loosened during the construction process. It may be.
[0022]
Next, the process in which the purifier body section located in the aquifer of the underground purifier constructed underground becomes a structure that actually purifies the contaminated groundwater will be described with reference to FIG. FIG. 3 is a conceptual diagram for explaining a structural change in an aquifer portion of an underground purification body constructed underground. The underground structure before the underground purification body is constructed is generally composed of soil particles 31 and gaps 32 (portions through which groundwater flows) between the soil particles 31 (FIG. 3A). Due to the presence of the gap 32, appropriate water permeability is obtained. When the underground purifying body is constructed in the ground, the underground structure includes a high-viscosity slurry 34 composed of, for example, a purifying material, a biodegradable polymer, and water between the soil particles 31 ( FIG. 3 (B)). The purifier in this state does not show water permeability. Thereafter, the biodegradable polymer in the purifying body is gradually decomposed due to the biological activity or the like of the microorganism, for example, the thickening action disappears and flows out together with the groundwater, and the disappeared portion appears as a gap 32 (FIG. C)). When the biodegradable polymer is completely decomposed and disappears, for example, within 5 to 10 days after the construction of the underground purification body, the purification material 33 remaining in the gap moves with gravity settling or the flow of groundwater, and the nearby soil particles are removed. 31 (FIG. 3D). The structure of the underground purification body in this state has soil particles 31, a purification material 33 attached to the surface of the soil particles, and a gap 32 between the soil particles 31 that exhibits appropriate water permeability. Thereby, the water permeability of the purifier becomes substantially the same as the underground water permeability before construction of the purifier, and the purification efficiency is improved.
[0023]
In the process of constructing the underground purifier, the purifier body section of the underground purifier is kept impermeable for about 5 to 10 days due to the effect of the biodegradable polymer as described above. On the other hand, when constructing a poorly permeable compartment, cement milk, a preferred water-blocking material, solidifies in three days. As described above, by controlling the decomposition time of the biodegradable polymer to be longer than the solidification time of the cement milk, it is possible to reliably construct a partition having poor water permeability. Conversely, if the decomposition time of the biodegradable polymer is shorter than the solidification time of the cement milk, pressure acts before the hardly permeable section, which is the solidified cement milk, is formed, so that pores are opened and difficult. A water-permeable partition layer cannot be created.
[0024]
Although the underground purifier is formed at a predetermined depth in a contaminated ground having a plurality of aquifers having different pore water pressures, for example, a permeable purifying section is provided at the position of the aquifer on the ground. In the purifier body formed and located in the impervious layer, the impervious partition layer is formed and adopts a structure corresponding to the ground structure, so that the flow of contaminated groundwater in each aquifer is as if the underground purifier is It maintains its flow as if it had not been created and passes through the permeable purifier section. For this reason, the problem that the contaminated groundwater in the aquifer with high pore pressure flows into the aquifer with low pore pressure and the contaminated groundwater in that part is not purified is not caused.
[0025]
Examples of the underground purifying body constructed by the mechanical stirring / mixing method, the jet stirring / mixing method, the combined method using these two methods, or the combined method include, for example, a ground purifying body having a circular cross section. The underground purification body having a circular cross section is generally formed by arranging a large number of the underground purification bodies in the ground, and for example, the underground continuous wall constructed by tangently or partially overlapping the underground purification body and the underground purification body Purifiers in which the underground purifiers are arranged intermittently and in a plurality of rows in the ground and further in a staggered manner, and the like. The purifying body arranged so as to have a shape is suitable in that a plurality of groundwaters having different flow directions can be effectively purified, and further, the plurality of groundwaters having different flow directions are arranged so that the transmittances of the respective groundwaters become 100%. Is particularly preferable in that the purification can be reliably performed. As the staggered planar form, for example, a form in which one underground purifier is arranged alternately, a form in which W-shapes are arranged continuously (FIG. 4), and a rhombus are arranged continuously Form (FIG. 5). The schematic shape in plan view of the whole underground purifier formed by intermittently arranging a large number in the ground is not particularly limited, and examples thereof include a long rectangular shape, a bow shape, a donut shape, and an irregular shape. . The donut shape has a contaminated layer at its center, and purifies the so-called contaminated source by containing it. The schematic shape of the continuous wall-shaped underground purifier in plan view includes a long rectangular shape, a bow shape, an irregular shape, and the like.
[0026]
Another form of the continuous wall includes a combination of a water impermeable wall such as a flexible synthetic resin plate and a steel thin plate and the underground purification body of the present invention. The continuous wall may be, for example, a donut that contains the source of contamination. In addition, as a method of constructing a continuous wall combining the impermeable walls, for example, a jet-type stirring and mixing method, a combined method of a mechanical stirring and mixing method and a jet-type stirring and mixing method, and a mechanical stirring function and a jet-type stirring function. A composite construction method using an equipped device can be applied. In particular, when underground structures such as buried pipes become obstacles, the injection type mixing and mixing method and the combined method performed with a device equipped with a mechanical stirring function and an injection type stirring function enable the construction of a continuous wall, This is preferable in that close contact between the underground purifier and the underground structure can be ensured.
[0027]
FIG. 6 is a schematic plan view showing an example of an underground purifier constructed underground. In FIG. 6, reference numeral 41 denotes an average projection width W1 of the underground purification body 40 with respect to the flow direction A, and reference numeral 42 denotes an average projection width W2 of the underground purification body 40 with respect to the flow direction B for reference. Not an underground purifier. The underground purifier 40 of this example is such that a plurality of the underground purifiers 10 having a circular cross section are intermittently arranged in the ground in two rows and further in a zigzag pattern so that the overall schematic shape becomes a long rectangular shape. At an angle α perpendicular to the groundwater I in the flow direction A passing through the pollution layer 44 and the groundwater II in the flow direction B passing through the pollution layer 43 located in a different aquifer. Are arranged so that the transmittance of both groundwaters is 100%. Permeability refers to the ratio of the cross-sectional area occupied by the purifier in the cross-section of the purifier formation area when viewed along the direction of groundwater flow. Means passing through.
[0028]
Next, a method for purifying contaminated groundwater in the ground 30A having two aquifers using the underground purifier 40 arranged as shown in FIG. 6 will be described. Here, the underground purification body 40 is in a state where the biodegradable polymer is decomposed and shows stable water permeability. The groundwater passing through the underground purifier 40 has, for example, a neutral pH range and a low oxidation-reduction potential, and the purifying material uniformly dispersed in the purifier section located in the aquifer is, for example, a reducing material. It is a metal powder. When each of the groundwater flowing in the two aquifers in the flow direction A and the flow direction B reaches the underground purifier 40, it flows into the purifier section of the underground purifier 40 located in the aquifer. In this case, the flow of the contaminated groundwater in each aquifer is maintained by maintaining the natural flow as if the purifier 10 had not been created due to the high permeability of the purifier section located in the aquifer. Pass through the section of the purifier. At this time, for example, the hardly decomposable halogenated hydrocarbons in the two contaminated groundwaters are dehalogenated and converted into harmless hydrocarbons in the respective purifier sections in the presence of the reducing metal powder. Is purified.
[0029]
【The invention's effect】
According to the present invention, in a contaminated ground having a plurality of aquifers having different pore water pressures, when groundwater flowing in one aquifer passes through an underground purification body, another groundwater flows through the purification body.
Contaminated groundwater in each aquifer can be individually purified by one purifier without flowing into the aquifer, and when constructing this underground purifier, hardly any residual soil is generated and The resulting purifier compartment exhibits high water permeability.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an underground purification body according to an embodiment of the present invention.
FIG. 2 is a schematic enlarged view of a circle X in FIG.
FIG. 3 is a conceptual diagram for explaining a structural change in an aquifer portion of an underground purifier constructed underground.
FIG. 4 is a diagram showing a form of a staggered arrangement in a plan view.
FIG. 5 is a diagram showing another form of the staggered arrangement in plan view.
FIG. 6 is a schematic plan view of the underground purification body according to the embodiment of the present invention.
FIG. 7 is a schematic sectional view showing a structure of a general contaminated ground.
FIG. 8 is a schematic sectional view of a conventional underground purifier.
[Explanation of symbols]
10 Underground purification body
11 Purification body section located in the first aquifer
12 Impervious partition layer connected to the first impervious layer
13 Purification body section located in the second aquifer
14 Impervious partition layer connected to the second impervious layer
15 Purification body section located in the third aquifer
16 Lower end of underground purification body
17 Rainwater infiltration prevention layer
19, 57 Source of pollution
21,51 Surface layer
22 First aquifer
23 First impervious layer
24 Second Aquifer
25 Second impervious layer
26 Third Aquifer
27 Third impervious layer
28 4th aquifer
29, 55 Base
31 soil particles
32 gap
33 Purification materials
34 High viscosity slurry
40 Underground Purifier
43, 44 Contamination layer
52, 54 Aquifer
53 impervious layer
58 Underground Purification Wall
WL groundwater level

Claims (5)

An underground purifier constructed on a contaminated ground having an aquifer between two aquifers and having two or more aquifers, wherein the purifier is located in the aquifer. The compartments are formed of a mixture containing at least a purification material, a biodegradable polymer, and ground soil. An underground purification body characterized in that it is provided with a poorly permeable partition layer that blocks the flow of water. The contaminated ground has a repeating structure of an aquifer, a poorly permeable layer and an aquifer in the depth direction of the ground, and when the third and subsequent aquifers are non-contaminated layers, The underground purifying body according to claim 1, wherein the lower end portion is landed on a poorly permeable layer sandwiched between an aquifer of the deepest contaminated layer and an aquifer of the non-contaminated layer. The underground purifying body according to claim 1, wherein the purifying material is at least one selected from a pollutant adsorbing material and a pollutant decomposing material. The ground according to any one of claims 1 to 3, wherein the poorly permeable partition layer has the same poor permeability or a greater poor permeability than the poorly permeable layer connected to the partition layer. Medium purifier. A method for forming an underground purification body on a contaminated ground having an aquifer between two aquifers and having two or more aquifers, wherein the purification material and the biodegradable polymer are mixed. A step of supplying the mixed drug material to the ground from the ground, stirring and mixing the mixed drug material and the original ground soil to form a purifying body section located in the aquifer; and And a water impervious partition layer for blocking the mutual flow of groundwater flowing through the upper and lower aquifers sandwiching the water impervious layer. A construction method of an underground purification body characterized by performing an installation step.

Images