JP4405185B2 - In-situ purification method for soil contaminated with organochlorine compounds - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an in-situ purification method for soil contaminated with an organic chlorinated compound, or contaminated soil for detoxifying soil and groundwater.
[0002]
[Prior art]
For industrial cleaning such as oil removal of machinery, organochlorine compounds such as trichlorethylene have been used in large quantities so far. From the viewpoint of environmental pollution, the use of such organochlorine compounds has recently been regulated. However, a large amount of organochlorine compounds have already been used, and as a result, soil contamination or water pollution is also progressing. That is, organochlorine compounds such as trichlorethylene are stable and difficult to break down into microorganisms. Organochlorine compounds dumped in the natural environment not only contaminate the soil, but ultimately pollute rivers and groundwater, This can be a source of drinking water, which is problematic.
[0003]
Known methods for purifying soil contaminated with volatile organic compounds such as organic chlorine compounds include the soil gas suction method, the groundwater pumping method, and the soil excavation method. The soil gas suction method forcibly sucks the target substances present in the unsaturated zone. A suction well is installed in the ground by boring, and the inside of the suction well is depressurized by a vacuum pump, and the vaporized organic The compounds are collected in a suction well, guided to the underground, and treated by a method such as adsorption of organic compounds in soil gas onto activated carbon. When the contamination by the organic compound extends to the aquifer, a method is adopted in which a submersible pump is installed in the suction well and the water is pumped and treated simultaneously with the soil gas.
[0004]
The underground pumping method is a method of setting up a pumping well in soil and pumping up contaminated groundwater. Furthermore, the soil excavation method is a method in which contaminated soil is excavated, and the excavated soil is subjected to wind drying and heat treatment to remove and collect organic compounds.
[0005]
However, these methods are not methods for directly purifying soil, but are methods for purifying contaminated water collected by the soil gas suction method, groundwater pumping method, etc., or contaminated water such as rivers and groundwater. The amount is extremely large, and the treatment often takes a long time. It is also a drawback that the processing steps are often complicated. For this reason, a method for directly and simply purifying soil that is a source of contamination is required.
[0006]
As described above, the conventional method of purifying soil contaminated with organochlorine compounds collects contaminated water from the contaminated soil and either purifies it or collects the soil itself and purifies it. It is not a method of purifying itself directly and simply.
[0007]
In WO-01 / 08825, iron particles are finely divided to increase the surface area of iron to increase the processing capacity of pollutants, and in addition to atomization, the shape of the particles is made spherical. A soil purification agent comprising a spherical iron fine particle slurry having a particle size of less than 10 μm, which enables rapid penetration of iron into the inside, is disclosed.
[0008]
[Patent Document 1]
WO-01 / 08825
[0009]
[Problems to be solved by the invention]
According to the study of the present inventors, when a spherical iron fine particle slurry having a particle size of less than 10 μm described in WO-01 / 08825 is directly injected into contaminated soil, the iron fine particles are relatively uniformly distributed in the sandy layer or the like. Although slurry can be introduced, it cannot be uniformly introduced into silt layer, clay layer, Kanto loam layer, etc., and there is a problem that detoxification of organochlorine compounds may not be performed sufficiently. Became clear.
[0010]
Accordingly, an object of the present invention is to provide a method for efficiently purifying soil contaminated with organochlorine compounds in situ by agitation without excavation or the like.
[0011]
In order to realize the above object, the present inventors apply solidified powder such as lime-based, cement-based, or polymer-based to the soil of the ground and stir to construct a structure or the like. We paid attention to the deep mixing method, which is a ground improvement method.
[0012]
That is, the deep mixing treatment method includes a high pressure injection stirring method including a grout / slurry injection method, a slurry / air injection method, a slurry / air / water injection method, or a mechanical stirring method including a slurry method and a powder method. There were various studies on these.
[0013]
Among them, a stirrer that can be used in a mechanical stirring type-slurry system, for example, a CDM method (the rotating direction of the adjacent rotating shaft is opposite), a DCS method, an epocolumn method (they have a rotating shaft concentric with the inner stirring blade The iron fine particles are put into the soil by rotating the agitator at the same time or alternately in the opposite direction to the normal direction, using the ones used in the opposite direction (rotating direction with the outer agitating blade), etc. It has been found that uniform dispersion can be achieved.
[0014]
[Means for Solving the Problems]
  In the present invention, a rotor blade is attached to soil contaminated with an organochlorine compound.TwoIn-situ purification of soil contaminated with organochlorine compound including a step of penetrating the stirring blade of the rotating shaft and applying an iron fine particle slurry, and stirring the soil to which the iron fine particle slurry is applied by the stirring blade A method,The rotating shaft having the stirring blade is composed of two of an inner rotating shaft and an outer rotating shaft, the two rotating shafts are concentric, and the inner rotating shaft has an inner stirring blade around the inner rotating shaft. Around the stirring blade, there is an outer stirring blade attached to the outer rotating shaft, the two rotating shaftsAt the same timeOpposite each otherIt is in the in-situ purification method characterized by rotating. Also, such a configurationHaveA stirrer is generally used.
  In the above method,The number of blades of the stirring blades on the inner and outer rotating shafts is 400 to 800 times / minute.It is preferable. Moreover, it is preferable that solid content of an iron fine particle slurry is 3-12 mass%.
[0015]
  In the present invention, a rotor blade is attached to soil contaminated with an organochlorine compound.2 or moreIn situ position of soil contaminated with organochlorine compound including the step of penetrating the stirring blade of the rotating shaft and applying the iron fine particle slurry, and stirring the soil to which the iron fine particle slurry is applied with the stirring blade A purification method,Soil contaminated with organochlorine compounds is in saturation zone,As the iron fine particle slurry, a slurry having a solid content of 3 to 12% by mass is used.The amount of iron fine particle slurry applied to the soil is adjusted to 1 m of soil. ^Three 50-200 liters perAn in-situ purification method comprising two or more rotating shafts having the stirring blades, the two or more rotating shafts being not concentric, and rotating adjacent rotating shafts simultaneously opposite each other; as well as
  The soil impregnated with the organic chlorine-based compound penetrates the stirring blades of two or more rotating shafts to which the rotor blades are attached and imparts an iron fine particle slurry, and the soil to which the iron fine particle slurry is imparted is added to the soil. An in-situ purification method for soil contaminated with organochlorine compounds including a step of stirring with a stirring blade,The soil contaminated with organochlorine compounds is in an unsaturated zone,As the iron fine particle slurry, a slurry having a solid content of 3 to 12% by mass is used.The amount of iron fine particle slurry applied to the soil is adjusted to 1 m of soil. ^Three 150-300 liters perAn in-situ purification method comprising two or more rotating shafts having the stirring blades, the two or more rotating shafts are not concentric, and adjacent rotating shafts are simultaneously rotated opposite to each other simultaneously. There is also. A stirrer having such a configuration is generally used.
[0016]
When soil contaminated with organochlorine compounds is in the saturation zone, the amount of iron fine particle slurry applied to this soil is 1 m of soil.³It is preferably 50 to 200 L (liter) per unit. Moreover, when the soil contaminated with the organic chlorinated compound is in an unsaturated zone, the amount of iron fine particle slurry applied to the soil is 1 m of soil.³It is preferably 150 to 300 L per unit.
[0017]
The solid content of the iron fine particle slurry is preferably 0.5 to 30% by mass, more preferably 3 to 12% by mass, and particularly preferably 4 to 8% by mass. Determined according to soil properties and degree of contamination.
[0018]
The stirrer used is preferably a stirrer that can be used in a mechanical stirrer-slurry system. The stirrer is preferably a relative stirrer. It is preferable that the blade cutting frequency with a relative stirrer is 400 to 800 times / minute, particularly 550 to 650 times / minute. The purification operation can be performed in a shorter time.
[0019]
It is preferable to apply the iron fine particle slurry while stirring and / or continuously apply the iron fine particle slurry. It is preferable that the iron fine particles of the iron fine particle slurry have an average particle diameter of 0.3 to 1.5 μm. The penetration of fine iron particles into the soil is excellent.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The purification method of the present invention is intended to directly purify soil contaminated with organochlorine compounds in situ without excavation. The soil is relatively agitated (reverse to the normal direction) while applying the iron fine particle slurry. This is basically done by stirring in the direction).
[0021]
As a stirrer used in the purification method of the present invention to relatively stir the soil while applying the iron fine particle slurry, a stirrer that can be used in a mechanical stirring type-slurry system, such as a CDM method, a DCS method, an epocolumn method, etc. These are generally used as relative stirrers. That is, they have two or more, preferably two, rotating shafts for stirring in the stirrer. In particular, there is a relative stirrer in which the rotation shaft is composed of two inner rotation shafts and outer rotation shafts, the two rotation shafts are concentric, and the rotation directions of the inner rotation shaft and the outer rotation shaft are opposite to each other. preferable.
[0022]
The purification method of the present invention uses, for example, the above-mentioned stirrer, applies the iron fine particle slurry (generally sprayed) while penetrating the tip of the stirring blade into the soil and rotating the stirring blade (generally composed of a plurality of stirring blades). And by vigorously mixing the iron fine particle slurry and the soil. As a result, the iron fine particle slurry and the soil are sufficiently mixed and the uniformity is dramatically improved, and the reaction between them is promoted, so that there is almost no soil left unpurified.
[0023]
As the agitator, an agitator used in the DCS method is particularly preferable. The structure of this stirrer is shown in FIGS.
[0024]
FIG. 1 shows a sectional view of an example of a stirrer used in the DCS method. In FIG. 1, an inner stirring blade (owned by two sets of three inner stirring blades) 12 is attached around the inner rotating shaft 11, and an outer stirring blade (outer stirring) attached to the outer rotating shaft 10 around the inner rotating blade 11. 3) and 13 vertical blades 14 for supporting them are provided. The inner rotary shaft 11 and the outer rotary shaft 10 are installed concentrically. The stirring blades of the inner stirring blade 12 are provided so as to be positioned between the stirring blades of the outer stirring blade 13 in the height direction. A stirring head 15 is provided at the tip of the stirrer, and a tip discharge port 16 is provided in the center thereof. In general, a discharge port is also provided at the center of the rotating shaft 11.
[0025]
FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1. The inner stirring blade 12 and the outer stirring blade 13 rotate in opposite directions opposite to each other as indicated by arrows. As described above, two inner stirring blades are owned by one set of three stirring blades, and three outer stirring blades are owned by one set of three stirring blades. The number of stirring blades can be set as appropriate. 6-12 sheets are preferable.
[0026]
The DCS method stirrer shown in FIGS. 1 and 2 rotates the stirring head 15, the inner stirring blade 12 and the outer stirring blade 13 with a large torque while penetrating the iron fine particle slurry, and penetrates into the soil. That is, first, the iron fine particle slurry is ejected from the discharge port 16 and penetrates into the soil while stirring the soil with the stirring head 15, and is sufficiently stirred by the inner stirring blade 12 and the outer stirring blade 13 that rotate opposite to each other. . In addition, iron fine particle slurry or other chemical | medical agent can be discharged from the discharge port (not shown) of the center part of the inner side rotating shaft 11 as needed. By such ejection and stirring of the slurry, the soil and the iron fine particles in the slurry are particularly efficiently brought into contact, and the reduction reaction proceeds rapidly. The number of times that the blades of the inner stirring blade 12 and the blades of the outer stirring blade 13 intersect (that is, increases in proportion to the number of blades and the number of rotations). The number of blade cutting is too small or too large. In general, it is preferably 400 to 800 times / minute, particularly preferably 550 to 650 times / minute. Thereby, purification in a short time becomes possible.
[0027]
For example, the number of blade cutting is calculated as follows.
[0028]
Inner stirring blades: 6 blades, rotation speed: 21 times / minute at low speed (when penetrating), 42 times / minute at high speed (when pulling out),
Outer stirring blades: 9 blades, number of rotations: 8.1 times / minute at low speed (when penetrating), 16.3 times / minute at high speed (when pulling out),
When the stirring process is performed at a penetration speed of 1.0 m / min and a drawing speed of 1.0 m / min under the above conditions, the number of blade cuts is calculated as follows:
Number of blade cuts =
Number of blade cuts during penetration (number of inner blades x rotation speed ÷ penetration speed + number of outer blades x rotation speed ÷ penetration speed) + number of blade cuts during extraction (number of inner blades x rotation speed ÷ extraction speed + number of outer blades x rotation speed ÷ (Pullout speed) =
(6 sheets × 21 ÷ 1.0 + 9 sheets × 8.1 ÷ 1.0) + (6 sheets × 42 ÷ 1.0 + 9 sheets)
× 8.1 ÷ 1.0) = 198.9 + 398.7 = 597.6 (times / minute)
The size of the agitator for the DCS method is preferably about 1 to 3 m, particularly about 1 to 2 m in terms of the diameter of the outer stirring blade.
[0029]
As a relative stirrer similar to the DCS method stirrer, an epocolumn method stirrer can also be used.
[0030]
As the stirrer used in the method of the present invention, a stirrer used in the CDM method (mechanical stirring type-slurry method) is also preferable. The structure of this stirrer is shown in FIG.
[0031]
In FIG. 3, rotary shafts 33A and 33B having a large number of stirring blades 32A and 32B (stirring blades) are attached to hydraulic motors 31A and 31B. The iron fine particle slurry is applied to the soil from the discharge ports 35A and 35B at the tip of the rotating shaft via the pressure feed pipes 34A and 34B in the rotating shafts 33A and 33B. Generally, a stirring blade as a set of 2 to 4 stirring blades is attached to the rotating shaft. In general, 6 to 8 sets of such a plurality of stirring blades are attached to form a stirring blade. This improves the stirring efficiency. The stirrer penetrates into the contaminated soil by, for example, supplying iron fine particle slurry to the pressure feeding pipes 34A, 34B, and spraying the slurry from the discharge ports 35A, 35B at the tip thereof while rotating the stirring blade 33A to the right. This is performed by rotating 33B counterclockwise and the stirring blade penetrates into the soil. By such ejection and stirring of the slurry, the soil and the iron fine particles in the slurry are efficiently contacted, and the reduction reaction proceeds rapidly.
[0032]
When a stirrer having only one stirring shaft is used, in the present invention, it is necessary to perform stirring with the rotation direction of the stirring shaft alternately and in the reverse direction. It is preferable to change the direction of rotation as frequently as possible because the reaction between the iron fine particles and the soil proceeds efficiently.
[0033]
Alternatively, using two or more stirrers with only one stirring blade, using a plurality of stirrers close to each other and rotating the stirring blades in the ground so that they are opposite to each other, The slurry and soil can be mixed.
[0034]
The method of the present invention can be applied to any soil contaminated with organochlorine compounds. For example, any of a sandy layer, a clay layer, a silt layer, etc. is possible.
[0035]
When soil contaminated with organochlorine compounds is in the saturation zone, the amount of iron fine particle slurry applied to this soil is 1 m of soil.³It is preferable that it is 20-400L per hit, especially 50-200L. Moreover, when the soil contaminated with the organic chlorinated compound is in an unsaturated zone, the amount of iron fine particle slurry applied to the soil is 1 m of soil.³It is preferable that it is 50-500L per hit, especially 150-300L.
[0036]
The pollution source to be purified according to the present invention is an organic chlorinated compound. Examples of organic chlorinated compounds include 1,1-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2 -Trichloroethane, 1,1,2,2-tetrachloroethane, dichlorodifluoroethane and the like can be mentioned. These organochlorine compounds are thought to be removed from the soil by losing halogen to the corresponding hydrocarbons due to the dehalogenation action (reduction action) of iron.
[0037]
The iron fine particle slurry that can be used in the method of the present invention may be any iron fine particle slurry, but an iron fine particle slurry having a small average particle diameter is preferred. The iron fine particles preferably have an average particle size of less than 10 μm, more preferably 0.1 to 3 μm, particularly 0.3 to 1.5 μm, and the shape is preferably spherical.
[0038]
The iron fine particle slurry is preferably a steelmaking dust slurry. The steelmaking dust slurry is preferably a steelmaking dust slurry before being concentrated with a thickener, or a fine iron powder which has been concentrated with a thickener and finally selected into only fine particles by a filter press.
[0039]
The solid content of the slurry is preferably 0.5 to 30% by mass, more preferably 3 to 12% by mass, and particularly preferably 4 to 8% by mass. Further, the slurry preferably contains an antioxidant. Thereby, it can maintain so that iron may not be oxidized. In the solid content, 90% by mass or more is metallic iron and iron-containing compounds. In solid content, metal iron accounts for 30 mass% or more.
[0040]
The iron fine particles contained in the slurry used in the method of the present invention are generally very fine particles, and therefore, when applied directly to contaminated soil, they rapidly penetrate into the soil. By using such ultrafine iron powder, the detergency can be greatly improved. Further, the iron fine particles are ultrafine particles as described above, and particularly when the shape is a sphere, when applied to the contaminated soil, the iron fine particles penetrate into the soil very quickly and exhibit a purification action.
[0041]
The iron fine particle slurry can be used in combination with metals other than iron, such as Mn, Mg, Zn, Al, and Ti, which have a reducing action. These metals also preferably have an average particle size as small as possible.
[0042]
Since the fine iron powder has a large surface area and is easily oxidized (passivated) on the surface, it is preferable to use a hydrophilic binder and / or a metal halide together in the present invention to prevent this.
[0043]
Metal halides are NaCl, KCl, MgCl₂, CaCl₂In particular, NaCl is preferable. Metal halides have the function of reducing iron hydroxide and oxide to metallic iron. The amount used is generally 0.5 to 200% by mass, preferably 0.5 to 50% by mass, based on the solid content.
[0044]
Furthermore, the iron fine particle slurry used in the present invention may contain a hydrophilic resin. The hydrophilic resin has a function of covering the surface of the iron fine particles and protecting the organic halide from being oxidized before exhibiting a reducing action. Examples of such hydrophilic resins include disaccharides such as sucrose, sucrose derivatives (eg, sucrose higher fatty acid esters), monosaccharides such as glucose, alginic acid; pullulan, PVA (polyvinyl alcohol), CMC (carboxyl methylcellulose), Examples thereof include water-soluble resins such as polyacrylamide, guar gum, methylcellulose, and hydroxyethylcellulose. Pullulan (particularly preferred because of its low viscosity when made into an aqueous solution), hydroxyethyl cellulose, sucrose, glucose, and PVA are preferred. Using a biodegradable polymer as the hydrophilic resin is particularly effective against secondary environmental pollution. The amount used is generally 0.01 to 200% by mass, preferably 0.01 to 100% by mass, based on the solid content.
[0045]
Further, since the iron fine particle slurry is in the form of a slurry, oxidation of the iron particle surface can be prevented, and therefore oxidation during transportation can also be prevented. During transportation, it is preferable to stir so that the iron particles do not precipitate and solidify. Moreover, in order to prevent the oxidation of the iron particle surface, it is preferable to add an antioxidant to the slurry. Examples of the antioxidant include organic acids (eg, ascorbic acid (vitamin C), citric acid, malic acid, particularly ascorbic acid) and salts thereof. 01-10 mass% is common, and 0.1-3 mass% is preferable.
[0046]
The iron fine particle slurry preferably further contains a metal sulfate (particularly ferrous sulfate) as a reducing agent. Since this reacts with oxygen in the air, it is possible to prevent the surface of the metal iron fine particles from being oxidized.
[0047]
The iron fine particle slurry preferably further contains an inorganic carbonate or carbonate-based mineral. Examples of these include calcium carbonate, precipitated calcium carbonate, magnesium carbonate, fossil limestone, limestone, and dolomite, and precipitated calcium carbonate is particularly preferable. Since the iron fine particle slurry of the present invention uses fine particle iron, it can be injected into the gap between the soil particles in the soil. However, since the possibility of leaching into groundwater and the like is increased by using fine particles, it is preferable in the present invention to fix the eluted iron ions and prevent this by using the carbonate.
[0048]
The iron fine particle slurry of the present invention can be obtained by suspending or dispersing an antioxidant, a metal halide or a hydrophilic resin, or a metal halide and a hydrophilic resin as required. In this case, it is preferable to use reducing electrolyzed water (preferably pH = 7 to 12) from the viewpoint of suppressing iron oxidation as much as possible. A surfactant such as naphthalene sulfonic acid may be used as the dispersant. The amount of the dispersant used is generally 0.01 to 10% by mass and preferably 0.1 to 5% by mass with respect to the solid content. Moreover, you may further use the above-mentioned antioxidant within the said range.
[0049]
The present invention has been described with respect to the method of injecting the iron fine particle slurry while stirring the soil contaminated with the organochlorine compound as described above. However, the present invention is similarly applied to soil contaminated with other pollution sources. can do. For example, the method of the present invention can also be used when iron fine particle slurry is injected into soil contaminated with hexavalent chromium.
[0050]
【Example】
[Example 1]
(1) Soil columnar layer and contamination distribution at the site to be purified
The sites targeted for purification are buried soil and loam layer in the range of 0m to 3.4m depth, 3.4 to 11.7m alternate layer of clay and sand, 11.7 to 16m sand layer, tetrachlorethylene (PCE) and contamination with trichlorethylene (TCE) revealed by prior investigation. The area was 3 m × 4 m. The soil columnar layer and the contamination distribution in this place are shown in FIG.
[0051]
(2) Purification experiment (stirring method A)
The contaminated soil shown in FIG. 4 was carried out using the same stirrer except for the following stirrer blades in the stirrer used in the CDM method (mechanical stirring type-slurry method) shown in FIG. That is, the CDM method stirrer used used two stirring rods having three stirring blades having a diameter of 1.0 m (consisting of three stirring blades having a length of about 0.5 m).
[0052]
As the iron fine particle slurry used, a 25% by mass aqueous dispersion of iron fine particles having an average particle diameter of 0.6 μm was used. The injection amount of the iron fine particle slurry was appropriately set for each penetration position according to the contamination concentration performed in advance. There were 20 penetration positions.
[0053]
The amount of iron fine particle slurry is 1m of soil³Use 50-200 liters per blade and set the blade cutting frequency to N₁, N₂, N₃, N₄, N₅I went there. N₁= 360, N₂= 450, N₃= 530, N₄= 610, N₅= 730 (unit: times / minute).
[0054]
[Example 2]
(1) Same as Example 1.
[0055]
(2) Purification experiment (stirring method B)
The contaminated soil shown in FIG. 4 was carried out using a stirrer used in the DCS method shown in FIG. The dimensions of the DCS method stirrer were 1.6 m for the outer stirring blade, 1.45 m for the longitudinal blade, and 1.75 m for the stirring head.
[0056]
As the iron fine particle slurry used, a 25% by mass aqueous dispersion of iron fine particles having an average particle diameter of 0.6 μm was used. The injection amount of the iron fine particle slurry was appropriately set for each penetration position according to the contamination concentration performed in advance. There were 20 penetration positions.
[0057]
The amount of iron fine particle slurry is 1m of soil.³Use 50-200 liters per blade and set the blade cutting frequency to N₁, N₂, N₃, N₄, N₅I went there. N₁= 360, N₂= 450, N₃= 530, N₄= 610, N₅= 730 (unit: times / minute).
[0058]
[Evaluation results]
The obtained results (purification rate of trichlorethylene) are shown in FIGS.
[0059]
FIG. 5 shows the purification rate according to Example 1 (Method A) and Example 2 (Method B) in the sand layer (depth 3.4 to 11.7 m), and FIG. 6 shows the clay layer (at depth 11.7 to 16 m). The purification rate by Example 1 (Construction A) and Example 2 (Construction B) was shown.
[0060]
The purification rate is expressed by the following formula:
Purification rate =
{(Number of samples satisfying environmental standards after 60 days) / (number of initial contaminated samples)}
× 100 (%)
The environmental standard value is 0.03 mg / L.
[0061]
From the results of FIGS. 5 and 6, it can be seen that there is a difference in the purification rate between the sand layer and the clay layer due to the difference in the construction method (A, B). The maximum purification rates of methods A and B are 65% and 100% for the sand layer and 20% and 100% for the clay layer, respectively. In both the sand layer and the clay layer, Method B shows a higher purification rate than Method A, and the tendency is particularly strong in the clay layer.
[0062]
It can be seen that there is a difference in the purification rate between the sand layer and the clay layer depending on the difference in the number of blade cuttings. In method B, the blade cutting frequency N in both the sand layer and the clay layer₄The purification rate was 100%. Number of blade cuts N₂~ N₅Is larger than the number of times of normal ground improvement (that is, the rotational speed is also high), but it can also be seen that the purification rate does not necessarily increase even if the rotational speed is too high.
[0063]
FIG. 7 shows the blade cutting frequency N in Example 2 (Method B).₄Shows the change over time in the TCE concentration of the contaminated soil when purification treatment (stir mixing) is performed. 58 days after the purification treatment, the amount of soil eluted by TCE satisfies the environmental standard value (0.03 mg / L).
[0064]
The soil elution amount was measured according to the official method.
[0065]
From the above results, it can be seen that there is an appropriate mixing method and an optimum number of blade cutting operations in the purification by mixing and stirring the organic chlorine compound in situ. This is because organochlorine compounds in contaminated soil may adhere to the surface of the soil particles or may dissolve in the groundwater. It is considered to be particularly effective for increasing the number of times of contact with the fine particles.
[0066]
【The invention's effect】
By using the method of the present invention, soil contaminated with organochlorine compounds can be efficiently purified in situ without excavation. That is, the method of the present invention can be uniformly introduced into soil that is difficult to permeate, such as silt layers, clay layers, and Kanto loam layers, by injecting the iron fine particle slurry into the soil with relative stirring. The reaction between the chlorine-based compound and the iron fine particles can be promoted. This makes it possible to quickly and almost completely detoxify organochlorine compounds in soil including silt layers, clay layers, Kanto loam layers, and the like.
[0067]
Therefore, the method of the present invention does not require complicated excavation work and can easily and efficiently purify organochlorine compound contaminated soil.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an example of a stirrer used in a DCS method used in the method of the present invention.
FIG. 2 is a cross-sectional view taken along line A-A ′ of FIG. 1;
FIG. 3 is a cross-sectional view of an example of a stirrer used in the CDM method used in the method of the present invention.
FIG. 4 is a soil columnar layer and contamination distribution of soil subjected to purification treatment in an example.
FIG. 5 is a graph showing the purification rate of Example 1 (Method A) and Example 2 (Method B) in a sand layer (depth 3.4 to 11.7 m).
FIG. 6 is a graph showing the purification rate according to Example 1 (Method A) and Example 2 (Method B) in a clay layer (at a depth of 11.7 to 16 m).
FIG. 7 shows the blade cutting frequency N in Example 2 (Method B)₄It is a graph which shows a time-dependent change of the TCE density | concentration of the contaminated soil at the time of performing a purification process in (3).
[Explanation of symbols]
10 Outer rotation axis
11 Inner axis of rotation
12 Inner stirring blade
13 Outer stirring blade
14 Longitudinal
15 Stirring head
16 Discharge outlet
31A, 31B Hydraulic motor
32A, 32B stirring blade
33A, 33B Rotating shaft
34A, 34B Pumping tube
35 Discharge port

Claims (12)

The soil impregnated with the organic chlorine compound penetrates the stirring blades of the two rotating shafts to which the rotor blades are attached, and gives the iron fine particle slurry to the soil to which the iron fine particle slurry is applied. An in-situ purification method for soil contaminated with organochlorine compounds including a step of stirring with a wing,
The rotating shaft having the stirring blade is composed of two of an inner rotating shaft and an outer rotating shaft, the two rotating shafts are concentric, and the inner rotating shaft has an inner stirring blade around the inner rotating shaft. An in-situ purification method comprising an outer stirring blade attached to an outer rotating shaft around the stirring blade and simultaneously rotating the two rotating shafts opposite to each other. 2. The in-situ purification method according to claim 1 , wherein the number of blades of the stirring blades on the inner and outer rotating shafts is 400 to 800 times / minute.   The purification method according to claim 1 or 2, wherein the solid content of the iron fine particle slurry is 3 to 12% by mass. The soil impregnated with the organic chlorine-based compound penetrates the stirring blades of two or more rotating shafts to which the rotor blades are attached and imparts an iron fine particle slurry, and the soil to which the iron fine particle slurry is imparted is added to the soil. An in-situ purification method for soil contaminated with organochlorine compounds including a step of stirring with a stirring blade,
Soil contaminated with organochlorine compounds is in saturation zone,
As the iron fine particle slurry, a slurry having a solid content of 3 to 12% by mass is used, and the amount of the iron fine particle slurry applied to the soil is 50 to 200 liters per 1 m ^{3 of} soil.
An in-situ purification method comprising two or more rotating shafts having the stirring blades, the two or more rotating shafts being not concentric, and rotating adjacent rotating shafts simultaneously opposite to each other. The soil impregnated with the organic chlorine-based compound penetrates the stirring blades of two or more rotating shafts to which the rotor blades are attached and imparts an iron fine particle slurry, and the soil to which the iron fine particle slurry is imparted is added to the soil. An in-situ purification method for soil contaminated with organochlorine compounds including a step of stirring with a stirring blade,
The soil contaminated with organochlorine compounds is in an unsaturated zone,
As the iron fine particle slurry, a slurry having a solid content of 3 to 12% by mass is used, and the amount of the iron fine particle slurry applied to the soil is 150 to 300 liters per 1 m ³ of the soil.
An in-situ purification method comprising two or more rotating shafts having the stirring blades, wherein the two or more rotating shafts are not concentric, and adjacent rotating shafts are simultaneously rotated opposite to each other simultaneously. The purification method according to any one of claims 1 to 3, wherein the soil contaminated with the organic chlorine compound is in a saturated zone, and the amount of the iron fine particle slurry applied to the soil is 50 to 200 liters per 1 m ^{3 of} the soil. . The soil according to claim 1, wherein the soil contaminated with the organic chlorine compound is in an unsaturated zone, and the amount of the iron fine particle slurry applied to the soil is 150 to 300 liters per 1 m ^{3 of} the soil. Method.   The purification method according to any one of claims 1 to 7, wherein the device having a rotating shaft and a stirring blade is a stirrer, and the stirrer is a stirrer that can be used in a mechanical stirring type-slurry system.   The purification method according to any one of claims 1 to 8, wherein the apparatus having a rotating shaft and a stirring blade is a stirrer, and the stirrer is a relative stirrer.   The purification method according to claim 1, wherein the application of the iron fine particle slurry is performed while stirring.   The purification method according to claim 1, wherein the application of the iron fine particle slurry is continuously performed.   The purification method according to any one of claims 1 to 11, wherein the iron fine particles of the iron fine particle slurry have an average particle diameter of 0.3 to 1.5 µm.

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