JP4721312B2 - Groundwater purification pile material, manufacturing method thereof, and groundwater purification pile - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is for a groundwater purification pile that can be stably held in sand or gravel without separating a metallic reducing agent used to purify groundwater contaminated with volatile organic compounds and the like. The present invention relates to a material, a manufacturing method thereof, and a groundwater purification pile using the material.
[0002]
[Prior art]
Volatile organic compounds such as trichlorethylene, which are used in large quantities in the cleaning process of semiconductor manufacturing plants, etc., may contaminate the soil or groundwater due to leakage, etc. There is a problem that the use of groundwater is restricted.
[0003]
As a solution to this problem, a continuous purification wall containing a metallic reducing agent is formed in the ground in a direction to block the flow of groundwater contaminated with volatile organic compounds, and the groundwater passes through the purification continuous wall. There is a method of decomposing pollutants and making them non-polluting by a reduction reaction (International Publication No. WO91 / 08176).
[0004]
This treatment method is a useful technique because pollutants in groundwater are effectively decomposed. However, this method, when installing a purification continuous wall in the ground, because the metallic reducing agent is dense, it separates from the bulking material such as sand or gravel, reducing the purification function of groundwater There is a problem. In order to solve such a problem, the purification wall continuously disposed in the ground is a cylindrical continuous pile or intermittent pile, and a cylindrical bag containing a metallic reducing agent is stacked on the column, and the cylindrical bag is further added to a donut. There is also disclosed one in which separation of the metallic reducing agent is prevented by using a mold and water permeability is improved (Japanese Patent Laid-Open No. 11-156351).
[0005]
[Problems to be solved by the invention]
However, the method of stacking a cylindrical bag containing a metallic reducing agent in a column is complicated and troublesome, and increases the construction cost. It is even more so if the cylindrical bag is donut shaped. Also, as a groundwater purification method, instead of constructing a continuous underground purification wall and treating it as a whole amount of contaminated groundwater, that is, a transmittance of 100%, the conventional well for pumping contaminated water is effectively utilized, There is also a demand for the installation of underground purification walls that reduce the processing load of pollutants in the country.
[0006]
Accordingly, an object of the present invention is to use a groundwater purification pile material that does not cause separation of a high-density powdery metallic reducing agent, a method for producing the same by a simple method, and the groundwater purification pile material. It is to provide constructed groundwater purification piles.
[0007]
[Means for Solving the Problems]
In such a situation, as a result of intensive studies, the present inventors used a specific particle size range of sand or gravel as an extender, and when mixing and stirring a metal powder as a reducing agent, If the water is so wet that the sand or gravel surface is wet, the powder adheres to the surface of the sand or gravel as if it were so-called kinako, There is no separation in the series of vibration processes leading to unloading and purification pile driving, and if this is used as a material for groundwater purification piles, the reduction purification function of the purification piles will be maintained continuously and effectively. As a result, the present invention has been completed.
[0008]
That is, the present invention sprays water onto sand or gravel having a particle size of 0.5 to 20 mm , stirs and moves to uniformly wet the surface of the sand or gravel, and then applies a metal powder as a reducing agent. An object of the present invention is to provide a material for groundwater purification piles, which is obtained by charging and moving by stirring .
[0009]
In the present invention, 3 to 11 parts by weight of water is sprayed on 100 parts by weight of sand or gravel on sand or gravel having a particle size of 0.5 to 20 mm , and moved by stirring to move the sand or gravel. a state moistened and then, mixing the metal powder is a reducing agent of 10 to 200 parts by weight relative to sand or gravel per 100 parts by weight, groundwater purification pile material, characterized in that the stirring movement It is in providing the manufacturing method of.
[0010]
Further, the present invention, the purification pile made of the material for groundwater purification pile is arranged intermittently and in a row in the ground, the purification pile is arranged deeper than the groundwater level, shallower than the groundwater level Is to provide a groundwater purification pile characterized by being an empty-placed portion.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the groundwater purification pile material of the present invention, the sand or gravel having a particle diameter of 0.5 to 20 mm refers to medium sand, coarse sand, fine gravel and medium gravel, among natural soils, A mixture of two or more can be used. Artificial crushed stone having a particle diameter of 0.5 to 20 mm and general crushed stone 7 for civil engineering can also be used. When the particle size of the sand or gravel is within the above range, uniform mixing with a metallic reducing agent such as iron powder is possible, and appropriate water permeability is obtained when used as a purification pile. The sand or gravel having a particle size of 0.5 to 20 mm has a fine gravel of 2 to 5 mm in the material of 80% or more, preferably 90% or more, and the balance is 0.5%. Those within the range of ˜20 mm are more preferred. The particle size of the sand or gravel is within the above range, but may contain a small amount of fine sand or coarse gravel that is less than 0.5 mm in particle size and 20 mm in particle size as long as the effect of the present invention is not impaired. Good.
[0012]
Examples of the metal powder as the reducing agent include iron or zinc simple substance, or an alloy or compound powder thereof. Of these, iron powder is preferable in that it is inexpensive and can be used as waste. The metal powder as the reducing agent has an average particle size of about 1/2 to 1/100 of the particle size of sand or gravel, and in the presence of an appropriate amount of water described later, sand or gravel and metal powder. And a uniform mixture can be formed. Moreover, if the compounding quantity of this metal powder is the range of 10-200 weight part with respect to 100 weight part of materials for groundwater purification piles, Preferably it is 10-50 weight part, It is enough for exhibiting a reduction purification function. The amount can be made small.
[0013]
The material for groundwater purification piles of the present invention is a mixture in which sand or gravel having the above particle size and metal powder as a reducing agent are uniformly mixed, and has a water content of 1 to 10% by weight, preferably 3 ~ 5% by weight. The uniformly mixed mixture means a state in which the metal powder is uniformly distributed in the sand or gravel, and according to visual observation, the surface of the sand or gravel is visible to the extent that water floats. It is in a wet state, in which the metal powder adheres to the surface of the sand or gravel as if so-called kina powder was evenly coated. That is, it is presumed that the sand or gravel surface and the metal powder are in an adsorbed state due to the suction action of the water meniscus existing between them. When the water content is less than 1% by weight or more than 10% by weight, the above suction action hardly occurs. Therefore, even with slight vibration, the high-density metal powder tends to be separated.
[0014]
According to the groundwater purification pile material of the present invention, the sand or gravel of the above particle size and the metal powder as the reducing agent become a hardly separable mixture that is uniformly mixed by the presence of an appropriate amount of water, The metal powder as the reducing agent is not separated from the mixture in a series of vibration processes from the purification pile material manufacturing process, unloading and purification pile placement. Moreover, since the metal powder which is a reducing agent distributes uniformly in sand or gravel, it is suitable as a material for groundwater purification piles.
[0015]
The material for groundwater purification piles of the present invention comprises a sand or gravel having a particle size of 0.5 to 20 mm, 3 to 11 parts by weight of water with respect to 100 parts by weight of the sand or gravel, and the sand or gravel 100 It is produced by mixing 10 to 200 parts by weight of metal powder as a reducing agent with respect to parts by weight and stirring to obtain a mixture in which the sand or gravel and the metal powder are uniformly mixed. However, preferably, sand or gravel having a particle size of 0.5 to 20 mm and 3 to 11 parts by weight of water are mixed in advance with respect to 100 parts by weight of the sand or gravel and stirred to remove the sand or gravel. Then, the sand or gravel content and the metal powder are mixed with 10 to 200 parts by weight of the reducing agent, and then stirred with respect to 100 parts by weight of the sand or gravel content. Is produced by obtaining a mixture that is uniformly mixed. It is preferable that the surface of the sand or gravel is moistened with an appropriate amount of water in advance and then the metal powder is added, in that the adhesion of the metal powder to the sand or gravel proceeds smoothly due to the adsorption action.
[0016]
The stirring method is not particularly limited as long as it sufficiently stirs the sand or gravel and the metal powder. In particular, the mixture of sand or gravel and the metal powder is rotated and stirred in the vertical direction. That is, it is preferable to perform stirring with movement in the vertical direction. Such agitation is performed by a paddle mixer having a rotating shaft that is horizontal or inclined with respect to a horizontal plane, or a concrete mixer that agitates by rotating a container in a vertical direction. In the case of a paddle mixer whose rotation axis is inclined with respect to a horizontal plane, the maximum inclination angle is about 30 degrees, and usually 3 to 5 degrees. In the paddle mixer, if the rotating shaft has a slight inclination, the residence time of the agitated material in the paddle becomes longer, and more sufficient stirring is performed. Among the above stirring means, it is possible to use a concrete mixer that stirs by rotating the container in the vertical direction, so that a relatively large volume of stirring is possible, and the entire mixture of sand or gravel and metal powder is It is suitable in that it is stirred by rotating in the vertical direction. Moreover, in the preferable production method, it is efficient that the stirring of the sand or gravel and water and the stirring of the wet sand or gravel and the metal powder are both performed with the same stirring device. The conditions for stirring the sand or gravel and the metal powder are not particularly limited, but in the case of a concrete mixer, 5 to 15 rpm and several to ten and several minutes are preferable.
[0017]
According to the production method of the present invention, the obtained groundwater purification pile material, as described above, is uniformly mixed in the presence of an appropriate amount of water with the above-mentioned particle size sand or gravel and the reducing agent metal powder. Therefore, the metal powder as the reducing agent is not separated from the mixture even in a series of vibration processes from the process of producing the material for purification piles, carrying out, and placing the purification piles. Moreover, since the metal powder which is a reducing agent distributes uniformly in sand or gravel, it is suitable as a material for groundwater purification piles. Furthermore, since the manufacturing method of the present invention can be performed by a simple method using existing equipment, it can greatly contribute to cost reduction.
[0018]
The groundwater purification pile of the present invention is formed by disposing the purification pile made of the material for groundwater purification piles intermittently and in a row in the ground. That is, the groundwater purification pile material is carried in from a manufacturing factory to a construction site by a method that avoids mixing of rainwater, and the purification pile is placed by a known sand pile construction method. In the known sand pile construction method, for example, after the hollow tube has been penetrated to the design depth in the ground, the material is introduced, and in the process of pulling the hollow tube to the ground surface, the introduced material is discharged to sand. It is a method of creating a pile. In addition, examples of the row-like arrangement include one row and two or more rows.
[0019]
The example of arrangement | positioning of the groundwater purification pile of this invention is demonstrated with reference to FIG.1 and FIG.2. FIG. 1 is a longitudinal sectional view for explaining the arrangement of groundwater purification piles, and FIG. 2 is a view taken along line XX of FIG. 1 and 2, the groundwater purification pile 1 is formed downstream of the pollution source with respect to the groundwater flow, and the groundwater level W.V. L. A purification pile 1b disposed deeper and mixed with the metal powder as the reducing agent; L. It consists of the blanking part 1a arrange | positioned in a shallower part. Immersion refers to sand or gravel that is not mixed with metal powder as a reducing agent. Groundwater level W. L. By providing the blanking portion 1a in the shallower portion, it is possible to eliminate waste of using a reducing agent in a region where no volatile organic matter exists. In addition, although the effect of the present invention is achieved even if the empty portion is an unfilled space, it is dangerous that irregularities occur on the ground surface. As described above, the empty portion not filled with metal powder can be used for safety such as construction. Can be secured. The groundwater purification pile of this example is the groundwater level W. L. Although the empty portion 1a is arranged in a shallower portion, as another example, the groundwater level W.V. L. The form which arrange | positions the purification | cleaning pile in which the metal powder which is the said reducing agent was mixed also in a shallower part is mentioned. In this case, although there is a waste of using a reducing agent in an area where volatile organic substances do not exist, the groundwater level W.V. L. There is an advantage that continuous piles from deeper to the ground surface can be constructed with uniform material and construction efficiency is good. In the figure, the groundwater purification piles 1 are arranged in the ground intermittently at equal pitches and in two rows. In this example, there are a total of 36 purification piles in one row and two rows, and the purification pile 13 in the rear row 1B enters between the purification pile 11 in the front row 1A and the purification pile 12 adjacent thereto. In other words, the purification piles in the front row 1A and the purification piles in the rear row 1B are arranged in a staggered manner. And as shown in FIG. 1, it arrange | positions so that the ratio of the cross-sectional area which a purification | cleaning pile occupies in a front view and a purification | cleaning pile formation area cross section, ie, the permeability | transmittance of groundwater may be 75%. In FIG. 1, reference numeral 2 indicates a pavement portion of the ground surface 3.
[0020]
Next, a method for purifying contaminated groundwater by the groundwater purification pile 1 will be described. 75% of the contaminated groundwater permeates through the groundwater purification pile 1 arranged in two rows intermittently at an equal pitch in the ground. At that time, since the groundwater usually has a neutral pH range and a low redox potential, for example, the hardly decomposable halogenated hydrocarbon in the groundwater is dehalogenated in the presence of the reducing metal powder, It is converted into harmless hydrocarbons and generates hydrogen. Thereby, the hardly decomposable halogenated hydrocarbon is rendered harmless and the contaminated groundwater is purified. In this groundwater purification pile 1, since the reducing agent is uniformly distributed in the pile, the contaminated groundwater passing through the purification pile 1 is stably purified over a long period of time. And 25% of the contaminated groundwater passes through the groundwater purification pile 1 without passing through it, but in the downstream well not shown in the figure, it is pumped up as a groundwater whose pollutant concentration is diluted. It is purified on the ground based on this method. Thereby, compared with the continuous wall formed so that all the flows of contaminated groundwater may be interrupted, it becomes easier to perform the purification pile, and the purification pile material including the reducing agent can be saved. Moreover, the purification load in the existing well can be reduced.
[0021]
The arrangement of the groundwater purification pile according to the present invention is not particularly limited. For example, as shown in FIG. 3, intermittently and in two rows of staggered arrangement in the ground as a flow of contaminated groundwater as shown in FIG. On the other hand, if the angle α or smaller than the angle α is taken, the size of the gap 101 between one purification pile 11 in the front row 1A and the purification pile 12 adjacent thereto becomes narrower with respect to the flow direction of the contaminated groundwater. The purification pile 13 is completely contained, and the transmittance can be almost 100%. Thus, in this invention, various arrangement | sequence forms can be taken so that the transmittance | permeability of groundwater may be 50-100%. Various arrangement forms include one row of intermittent arrangements, two rows or three or more rows of staggered intermittent arrangements, and further, an arrangement with an inclination with respect to the flow of groundwater.
[0022]
【Example】
EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.
Example 1
The axis of rotation is inclined 5 degrees from the horizontal plane, the total length is 2.3 m, each axis is rotated in the opposite direction of each other at 80 rpm, and the mixture is agitated while rotating in the vertical direction at a speed of 1 m / min in the left-right direction. A small biaxial paddle mixer was used that moved and discharged the mixture from the end of the shaft. First, dry silica sand No. 2 having a particle diameter of 2 to 5 mm accounted for about 90% of the whole, and an average particle diameter of 1.8 mm was introduced at 100 kg / min from the upper left end of the small biaxial paddle mixer. Further, water was sprayed at a rate of 5 liters / minute on the part where the silica sand No. 2 falls into a small two-shaft paddle mixer. Silica sand No. 2 and water were moistened and moved by a small biaxial paddle mixer, so that the surface of the silica sand No. 2 could be evenly moistened. Next, iron powder for powder metallurgy with an average particle size of 75 μm was charged from the top at a rate of 25 kg / min. The introduced iron powder was agitated and moved by a small two-shaft paddle mixer together with silica sand No. 2 whose surface was moistened, and discharged from the outlet as a uniform mixture. When the small biaxial paddle mixer after the mixture was discharged was inspected, it was not possible to confirm a portion where iron powder or silica sand No. 2 was unevenly attached. The total amount of raw materials used was 1000 kg for silica sand 2, 50 liters of water, and 250 kg of iron powder for powder metallurgy.
[0023]
(Evaluation of separability of mixture)
The mixture was filled and sealed in a 2 liter glass container so as to be 80% of the container volume, and the mixture was vibrated for 1 minute with an amplitude width of 30 mm and an amplitude of 120 times / minute, and visually observed. As a result, separation of iron powder for powder metallurgy was not recognized, and the content in the glass container was divided into three samples, upper, middle and lower, and the contents were analyzed. The variation was within 2% with respect to the amount ratio. Furthermore, when the mixture was observed with a microscope, iron powder was uniformly attached to the surface of silica sand No. 2 as if it was covered with kinako.
[0024]
Comparative Example 1
A mixture was obtained from the outlet of the small biaxial paddle mixer in the same manner as in Example 1 except that no water spraying was performed. The mixture seemed to be discharged as a homogeneous mixture. When the inside of the small biaxial paddle mixer was observed after the mixture was discharged, a lump of iron powder remained in the entire lower area of the small biaxial paddle mixer, particularly below the iron powder inlet. When the separability of the obtained mixture was evaluated by the same vibration method as in Example 1, the iron powder for powder metallurgy settled below the glass container, and the iron powder and quartz sand No. 2 were clearly separated.
[0025]
Reference example 1
The particle size of 2-5mm occupies about 90% of the total, 2.5 liters of water is added to 50kg of dry silica sand No. 2 with an average particle size of 1.8mm, the rotation axis is vertical, and the stirring blade rotates in the horizontal plane. The surface of silica sand No. 2 was evenly moistened (water content ratio 5%). Next, 12.5 kg of iron powder for powder metallurgy with an average particle diameter of 75 μm is mixed with 52.5 kg of wet silica sand No. 2 and, further, the mixture is stirred mainly in a horizontal plane using the same small mixer. 10 minutes. The resulting mixture of silica sand No. 2 and iron powder seemed to be homogeneously stirred and mixed, but it was found that a part of the iron powder was accumulated on the outer periphery of the stirring blade and the mixing was uneven did.
[0026]
As is apparent from Example 1, the mixture obtained by adding iron powder for powder metallurgy to wet silica sand No. 2 having a water content of 5% and further stirring in a vertical direction is composed of iron powder for powder metallurgy and silica sand. The adhesion of No. 2 was strong and did not easily fall off. On the other hand, in Comparative Example 1, no matter how hard the dried silica sand No. 2 and iron powder for powder metallurgy are stirred firmly, the iron powder for powder metallurgy is separated and the presence of an appropriate amount of water is important. I understood. On the other hand, it was found that the agitation method is superior to the agitation in the horizontal plane.
[0027]
【The invention's effect】
According to the material for groundwater purification piles of the present invention, the sand or gravel having the above particle size and the metal powder as the reducing agent become a uniform mixture due to the presence of an appropriate amount of water, and the metal powder on the surface of the sand or gravel. Since the body is in an adsorbed state, the metal powder as a reducing agent is not separated from the mixture even in a series of vibration processes from the purification pile material manufacturing process, unloading and purification pile placement. Moreover, since the metal powder which is a reducing agent distributes uniformly in sand or gravel, it is suitable as a material for groundwater purification piles.
Moreover, according to the manufacturing method of the material for groundwater purification piles of this invention, the obtained material for groundwater purification piles has an effect similar to the above. Moreover, since the manufacturing method of the present invention can be performed by a simple method using existing equipment, the manufacturing cost can be reduced.
Further, according to the groundwater purification pile of the present invention, for example, the hardly decomposable halogenated hydrocarbon in the groundwater is dehalogenated in the presence of the reducible metal powder and converted into a harmless hydrocarbon. Thereby, the hardly decomposable halogenated hydrocarbon is rendered harmless and the contaminated groundwater can be purified. In the groundwater purification pile, since the reducing agent is uniformly distributed in the pile, the contaminated groundwater that passes through the purification pile is stably purified over a long period of time. Furthermore, compared to a continuous wall formed so as to block all the contaminated groundwater flow, the purification pile can be easily constructed, and the purification pile material including the reducing agent can be saved. Moreover, it is possible to reduce the purification load in the existing wells installed downstream [Brief description of the drawings]
FIG. 1 is a diagram for explaining the arrangement of groundwater purification piles.
2 is a view taken along line XX in FIG. 1. FIG.
FIG. 3 is a diagram illustrating another arrangement of groundwater purification piles.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 11, 12, 13 Groundwater purification pile 1a Empty casting part 1b Purification pile 1A Front row of groundwater purification pile 1B Rear row of groundwater purification pile 2 Pavement part 3 Ground surface 101 Clearance between groundwater purification pile and adjacent groundwater purification pile α Flow of contaminated groundwater And the angle formed by the row direction of the groundwater purification pile L. Groundwater level

Claims (5)

Water is sprayed onto sand or gravel with a particle size of 0.5 to 20 mm , stirring and moving to evenly wet the surface of sand or gravel, then metal powder as a reducing agent is added, stirring and moving A material for groundwater purification piles obtained by 3-11 parts by weight of water is sprayed onto 100 parts by weight of sand or gravel on sand or gravel with a particle size of 0.5 to 20 mm, and the mixture is stirred and moved to wet the sand or gravel. Then, 10 to 200 parts by weight of metal powder, which is a reducing agent, is mixed with 100 parts by weight of the sand or gravel, and stirred and moved . The groundwater purification pile material according to claim 2, wherein the agitation movement is performed by a paddle mixer having a rotation axis that is horizontal or inclined with respect to a horizontal plane, or a concrete mixer that agitates by rotating a container in a vertical direction. Manufacturing method. The purification pile made of the groundwater purification pile material according to claim 1 is arranged intermittently and in a row in the ground, and the purification pile is arranged deeper than the groundwater level, and the shallower portion than the groundwater level is empty. A groundwater purification pile characterized by being a striking part. The groundwater purification piles on an intermittent and multiple rows in the ground, further a staggered, groundwater purification according to claim 4, wherein the transmittance of the groundwater, characterized in that it is arranged to be 50-100% Pile.

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