JP2004195456A - Method for preventing water from being polluted by dioxins-containing bottom sediment, and covering material for the prevention - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing water from being polluted by scattering and diffusion of dioxins from dioxins-containing bottom sediment in harbors, rivers, and lakes, and a covering material for the prevention. <P>SOLUTION: The dioxins-containing bottom sediment is covered with a mixture prepared by adding one or more of steel slag, natural sand, and air-cooled blast furnace slag to water-granulated blast furnace slag. The ratio of the mixed water-granulated blast furnace slag is 5-95 mass%, and the particle size of the steel slag to be used is equal to or larger than the average particle size of the granulated blast furnace slag and ≤25 mm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method and a covering material for preventing dioxins from scattering or dispersing from dioxin-containing sediment of a harbor, river, lake, or marsh to contaminate water quality.

  2. Description of the Related Art As a method for preventing water pollution due to scattering and diffusion of pollutants from the bottom of harbors, rivers, lakes and marshes, a method such as sand covering with earth and sand is conventionally known. However, conventionally known methods such as sand covering with earth and sand may not sufficiently prevent contamination.

  As an improvement plan, Patent Literature 1 discloses a method of covering the surface layer of the sediment with sand, further covering the surface layer with an adsorptive inorganic substance such as granulated slag, and removing contaminants generated by elution from the sediment by adsorption. It has been disclosed. In this method, granulated slag is used as one of the adsorptive inorganic substances, and the shape is preferably in the form of powder. However, when the granulated slag is a granulated blast furnace slag, the granulated slag is firmly consolidated due to its hydraulic property, and if the granulated slag is further powdered, the tendency is remarkable, which is not preferable as the structure of the water bottom.

  As a solution to the above problem, Patent Literature 2 discloses a method in which a water bottom is covered with steelmaking slag, and an upper layer of granulated blast furnace slag is further formed thereon. In this method, the steelmaking slag purifies polluting components generated by elution from the sediment and the like, and it is preferable to use coarse slag in order to reduce the solidification of the steelmaking slag. Furthermore, by using a structure in which the upper layer of the steelmaking slag is covered with the granulated blast furnace slag, the solidification of the granulated blast furnace slag is reduced by the steelmaking slag of the lower layer while utilizing the purification effect of the granulated blast furnace slag. .

  As described above, the granulated blast furnace slag is effective in preventing water pollution by pollutants from the sediment, but has an unfavorable property of firmly consolidating the sediment due to its hydraulic property.

Many dioxins present in the sediment of water in harbors, rivers and lakes and in water are likely to be attached to suspended solids. For example, Non-Patent Document 1 describes that it was suggested that many dioxins in river water were present in suspended substances in water.
JP-A-4-215900 JP 2001-252693 A Ministry of Land, Infrastructure, Transport and Tourism "About the results of a survey on dioxins in national first-class rivers in 2000"

  An object of the present invention is to provide a method for effectively preventing water pollution particularly by dioxin-containing sediment by controlling and actively utilizing the hydraulic property of granulated blast furnace slag.

As described above, it has been suggested that many dioxins in rivers are present in suspended matter in water, so the present inventors have proposed that dioxins be prevented from scattering and spreading. We thought that it was only necessary to prevent scattering and diffusion of the suspended matter. However, in the conventional method in which sediment is covered with sediment or the like, the interval between the sediment particles hardly changes after the sand is covered. There is concern that it will spread to.
Therefore, the present inventors paid attention to the hydraulic property of the granulated blast furnace slag, and studied a method of coating sediment using the granulated blast furnace slag.

  When granulated blast furnace slag is placed in a water environment, calcium ions and silicate ions are eluted, these hydration products are deposited on the surface of slag particles, and the gap between slag particles is closed. Has a certain hydraulic property. The present inventors coated sediment with granulated blast furnace slag, and the effect of preventing suspended matter from scattering and diffusing was, in the initial stage of the coating, almost equal to or slightly inferior to conventional sediment-covered sand. However, it was confirmed that the hydraulic properties of the slag gradually improved, and in the long term, an effect higher than that of the conventional sand covering sand was obtained. Examples of the suspended substance include soil particles and organic substances. When the suspended substance to which dioxins are adhered is particularly siliceous, the effect of preventing scattering and diffusion was more observed. However, when the granulated blast furnace slag is coated alone, there are cases where the coating layer is almost solidified and clogged to form a disk-like shape, or the effect is almost the same as that of earth and sand in the long term.

  Therefore, the present inventors considered that if the hydraulic property of the granulated blast furnace slag could be controlled, water pollution by dioxin-containing sediment could be prevented, and a preferable structure of the water bottom could be obtained, and various studies were conducted. .

  As a result of investigating the factors affecting the hydraulic properties of the granulated blast furnace slag used in the water area, the inventors have found that the particle size distribution of the slag is the largest factor. And, depending on the water area to be used, the coarse grain ratio is about 2.0 to 2.7 or less, and the more fine grains there are, the easier it is to consolidate. Conversely, the coarse grain rate is about 2.0 to 2.7. It was also found that the larger the coarse particles, the harder it was to consolidate. In addition, the coarse particle ratio complies with the definition of JISA0203, and in the present invention, the measurement was performed according to this definition. Specifically, sieving is performed using a set of 80 mm, 40 mm, 20 mm, 10 mm, 5 mm, 2.5 mm, 1.2 mm, 0.6 mm, 0.3 mm, and 0.15 mm mesh sieves. The sum of the percentages of all samples that did not pass was determined by dividing by 100.

  Based on the above findings, the present inventors considered that, when fine granules are easily formed in granulated blast furnace slag, the hydraulic property can be reduced by mixing natural sand with granulated blast furnace slag. On the other hand, when it was difficult to solidify a large amount of coarse particles, it was considered that hydraulic properties could be improved by mixing steelmaking slag and blast furnace slag.

  The present invention has been achieved based on the above findings, and the gist thereof is as follows.

(1) A method for preventing water pollution by dioxin-containing sediment, wherein the dioxin-containing sediment is coated with a mixture of granulated blast furnace slag and steelmaking slag and / or natural sand.

(2) The method according to (1), wherein the blended amount of the granulated blast furnace slag in the mixture is 5 to 95% by mass.

(3) The method according to (1) or (2), wherein a particle size of the steelmaking slag is not less than an average particle size of the granulated blast furnace slag and not more than 25 mm.

(4) A coating material for preventing water pollution by dioxin-containing sediment, wherein granulated blast furnace slag and steelmaking slag and / or natural sand are mixed.

(5) Instead of steelmaking slag and / or natural sand, one or more of steelmaking slag, natural sand, and blast furnace slow-cooling slag are added, and any one of (1) to (3) is characterized. 3. The method for preventing water pollution by dioxin-containing sediments described in 1. above.

(6) A coating material for preventing water pollution by dioxin-containing sediment, characterized by mixing one or more of granulated blast furnace slag, steelmaking slag, natural sand, and slowly cooled blast furnace slag.

  Advantageous Effects of Invention According to the present invention, water pollution due to scattering and diffusion of dioxins contained in sediment of a port, river, lake or marsh can be more effectively prevented than sand covering by conventional methods such as earth and sand. In addition, since slag, which is a by-product generated from a steel mill, can be used, the amount of use of natural resources, such as earth and sand, can be reduced, and a favorable effect on resource utilization can be obtained.

  The method for preventing water pollution by dioxin-containing sediments of the present invention is intended to prevent dioxins from scattering or dispersing from dioxin-containing sediments of harbors, rivers, and lakes to prevent water pollution. And a method in which sediment is covered with a mixture of at least one or more of granulated blast furnace slag, steelmaking slag, natural sand, and slowly cooled blast furnace slag.

  The granulated blast furnace slag has a particle size distribution, and the particle size or average particle size of the granulated blast furnace slag in the present invention refers to the sieve size at which the cumulative percentage passing through the sieve is 50% based on the definition of JISA1102. Equivalent.

  As the granulated blast furnace slag used in the present invention, the granulated blast furnace slag can be used as it is after the granulation treatment, but the shape and particle size may be adjusted by processing. The slag particles after granulation are angular and have less good filling of particles than sand, but one or more of the steelmaking slag, natural sand, and blast furnace slowly cooled slag according to the present invention are mixed. In addition to controlling the hydraulic properties of the granulated blast furnace slag, it is also possible to fill the particle spacing of the granulated blast furnace slag, and by filling the gaps, the same as conventional sand and sand covering from the beginning of coating. Some degree of effect can be obtained.

  If the granulated blast furnace slag is processed to adjust its shape and particle size, the filling properties of the granulated blast furnace slag can be improved. Is also improved. At this time, one or more of steelmaking slag, natural sand, and blast furnace slow cooling slag may be mixed to control the hydraulicity of the granulated blast furnace slag. Normally, granulated blast furnace slag having a coarse particle ratio of about 4 to 2.5 is obtained as it is after the granulation treatment. When this is processed, it can be adjusted from the coarse particle ratio as it is after the water granulation treatment to 0, but in the present invention, a slag having a lower limit of the coarse particle ratio of about 1 is used.

  In the present invention, a mixture of granulated blast furnace slag and at least one or more of steelmaking slag, natural sand, and slowly cooled blast furnace slag is used for coating the sediment. The blending amount of the granulated blast furnace slag in the mixture is preferably from 5 to 95% by mass. As described above, depending on the water area to be used, the granulated blast furnace slag has a very high hydraulicity, such as a case where the granulated blast furnace slag has a coarse particle ratio of about 2.0 to 2.7 or less and is fine. In this case, sufficient hydraulic properties can be obtained with a small amount of the granulated blast furnace slag, but if the proportion occupies less than 5% by mass, the hydraulic properties of the granulated blast furnace slag are not sufficiently exhibited. On the other hand, if the blending amount of the granulated blast furnace slag is more than 95% by mass, the ratio of the steelmaking slag, natural sand, and blast furnace slowly cooled slag to the entire mixture becomes small. Hydraulic control effect of slag is not so much exhibited.

  As natural sand used in the present invention, mountain sand, river sand, sea sand and the like can be used. If the chemical component is natural, it is also possible to use crushed sand from rock. The average particle size of the natural sand used is preferably 0.3 to 1.2 mm, but the average particle size is not necessarily limited by the combination with the particle size of the granulated blast furnace slag.

  Examples of the steelmaking slag used in the present invention include converter slag and hot metal pretreatment slag, and the higher the pH when immersed in water, the smaller the amount of mixing, the more the effect of improving the hydraulic properties of the granulated blast furnace slag is improved. It is preferable because there is. For example, when a mixture containing granulated blast furnace slag and steelmaking slag is immersed in water, the pH of the particle interstitial water is sufficient if it is about 12 when the total amount is steelmaking slag, but 9 or more, more preferably 9 or more. The material and the amount of the steelmaking slag may be determined so as to be 10 or more.

  The blast furnace slow cooling slag used in the present invention increases the pH when immersed in water in the same manner as steelmaking slag, and improves the hydraulic properties of the granulated blast furnace slag. Chemical components are almost the same as granulated blast furnace slag, but those having a higher pH than granulated blast furnace slag are used. In addition, when covering the sediment of the sea area, if the pH is excessively increased by mixing steelmaking slag, white turbidity may occur. Since the blast furnace slow cooling slag does not have a sharp increase in pH as compared with the steelmaking slag, the blast furnace slow cooling slag can be used when suppressing cloudiness.

  The steelmaking slag used in the present invention is obtained by crushing a solidified mass of molten slag and adjusting the particle size by classification. The particle size of the steelmaking slag is expressed by the upper limit of the size of the sieve when classified and the lower limit of the size. The grain size of the steelmaking slag used in the present invention is more effective when the upper limit value and the lower limit value are not less than the average particle size of the granulated blast furnace slag and not more than 25 mm. That is, if the steelmaking slag contained free calcium oxide, the surface activity is high if the particle size of the steelmaking slag is less than the average particle size of the granulated blast furnace slag, and the reaction between free calcium oxide and water Since the amount of collapsing steelmaking slag increases, the particle gap of the coating material may increase or the coating layer may be partially broken. The maximum particle size of the steelmaking slag is preferably 25 mm or less. When it is larger than 25 mm, when the sediment is coated with the mixture with the granulated blast furnace slag, separation occurs due to a difference in specific gravity and a difference in particle size, and a uniform coating layer cannot be formed. The blast furnace slow cooling slag used in the present invention has no restriction on the particle size. The chemical composition of the blast furnace slowly cooled slag is almost the same as that of the granulated blast furnace slag, and there is no fear of collapse like steelmaking slag. Further, there is almost no difference in specific gravity from the granulated blast furnace slag as compared with the steelmaking slag, which is preferable for avoiding separation at the time of coating.

Hereinafter, although an example of the present invention is shown, the present invention is not limited to this example.
Examples 1 to 16:
In rivers and harbors where the concentration of dioxins in water quality exceeds the environmental standard of 1 pg-TEQ / L, one or more of blast furnace granulated slag, mountain sand, steelmaking slag, and blast furnace decooled slag according to the present invention are used. A test of coating the sediment with the mixture was performed. In the river, the sediment dioxin concentration was 26 pg-TEQ / g, the water dioxin concentration was 4 pg-TEQ / L, and the suspended solids were 20 mg / L. At the port, the sediment dioxins concentration was 28 pg-TEQ / g, the water dioxins concentration was 1.2 pg-TEQ / L, and the suspended solids were 10 mg / L.

  The sediment of the designated water area was covered with a covering material, and about one year later, the quality of the water and the covering layer were investigated to evaluate the pollution prevention effect. In the evaluation of the curing state of the coating layer, a part of the coating layer was core-sampled, and it was considered that the sample material had cured when the sample material maintained its shape independently without collapsing. The water quality was measured by sampling about 500 mm of water on the sediment or on the sand.

  Tables 1 and 2 show the results.

  In Example 1, since the granulated blast furnace slag was slightly fine with a coarse particle ratio of 2.5, mountain sand was blended at 5% by mass to form a coating material. The water quality dioxin concentration was 0.1 pg-TEQ / L after the implementation, which satisfied the environmental standards. The suspended solids concentration dropped to 5 mg / L after the run. In addition, when a part of the coating layer was subjected to core sampling in order to check the curing state of the coating layer, it was confirmed that the sampled material had maintained its shape independently without collapsing, and was thus cured. No cracks or the like were found in the coating layer.

  In Example 2, the granulated blast furnace slag was a fine particle having a coarse particle ratio of 2.2, and therefore, 20 mass% of mountain sand was blended to obtain a coating material. The water quality dioxin concentration was 0.08 pg-TEQ / L after the implementation, which satisfied the environmental standards. Further, the concentration of the suspended substance was reduced to 4 mg / L after the operation. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 3, since the granulated blast-furnace slag had a fine grain ratio of 2, the sand was blended at 70% by mass to form a coating material. The water dioxin concentration was 0.07 pg-TEQ / L after the implementation, which satisfied the environmental standards. Further, the concentration of the suspended substance was reduced to 4 mg / L after the operation. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 4, the granulated blast furnace slag had a coarse particle ratio of 3 and was slightly coarse, so that 7% by mass of steelmaking slag was blended as a coating material to increase hydraulicity. The particle size range of the steelmaking slag used was 1 to 5 mm. The average particle size of the granulated blast furnace slag was 0.9 mm. The water quality dioxin concentration was 0.07 pg-TEQ / L after the implementation, which sufficiently satisfied the environmental standards. The suspended solids concentration dropped to 4 mg / L after the run. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 5, a coating material was prepared by mixing 90 mass% of a steelmaking slag having a particle size of 1 to 25 mm with a slightly fine-grained granulated blast furnace slag having a coarse particle ratio of 2.5 and an average particle size of 0.7 mm. The water dioxin concentration was 0.08 pg-TEQ / L after the operation, which satisfied the environmental standards, and the suspended solid concentration was reduced to 5 mg / L after the operation. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 6, 3 mass% of steelmaking slag having a particle size of less than 1 mm was blended with a relatively coarse-grained granulated blast furnace slag having a coarseness ratio of 3.5 to obtain a coating material. Since the steelmaking slag was smaller than the average particle size of the granulated blast furnace slag and there was a fear of collapse, the blending amount was reduced. The water quality dioxin concentration was 0.2 pg-TEQ / L after the implementation, which satisfied the environmental standards. The suspension concentration also dropped to 5 mg / L after the run. The sampling material maintained its shape independently, and no signs of collapse were seen in the coating layer.

  In Example 7, the granulated blast furnace slag had a coarse particle ratio of 3.5 and an average particle diameter of 1 mm, and was relatively coarse. However, mountain sand was added in an amount of 50% by mass, and steelmaking slag was added in an amount of 5% by mass. The effect of promoting the solidification of steelmaking slag was confirmed as the coating material thus obtained. The particle size range of the steelmaking slag was 1 to 5 mm. The water dioxin concentration was 0.07 pg-TEQ / L after the operation, sufficiently satisfying the environmental standards, and the suspended solid concentration was reduced to 4 mg / L after the operation. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 8, in order to enhance hydraulicity, 10% by mass of blast furnace slowly cooled slag was blended with granulated blast furnace slag having a coarse particle ratio of 3 to obtain a coating material. The particle size of the blast furnace slow cooling slag used is 5 mm or less. The water quality dioxin concentration was 0.07 pg-TEQ / L after the implementation, which sufficiently satisfied the environmental standards. The suspended solids concentration dropped to 4 mg / L after the run. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 9, similarly to Example 8, a blast furnace granulated slag was blended with 10% by mass of blast furnace slowly cooled slag to obtain a coating material. The particle size of the blast-furnace slow cooling slag used was 25 mm or less, and there were more coarse particles than in Example 7. The water quality dioxin concentration was 0.08 pg-TEQ / L after the implementation, which sufficiently satisfied the environmental standards. The suspended solids concentration dropped to 4 mg / L after the run. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  Example 10 is an example in which treatment was performed on the sediment of a port, and 10 mass% of mountain sand was mixed with granulated blast furnace slag having a coarse particle ratio of 2.5 to obtain a coating material. The water dioxin concentration was 0.02 pg-TEQ / L after the operation, sufficiently satisfying the environmental standards, and the suspended solid concentration was reduced to 3 mg / L after the operation. Since the sampling material maintained its shape independently without collapsing, it was confirmed that it was cured. No cracks or the like were found in the coating layer.

  In Example 11, 70 mass% of mountain sand was mixed with fine-grained granulated blast furnace slag having a coarse particle ratio of 2.2 to obtain a coating material. The water dioxin concentration was 0.03 pg-TEQ / L after the operation, which satisfies the environmental standards, and the suspended solid concentration was reduced to 3 mg / L after the operation. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 12, the granulated blast furnace slag was a relatively coarse particle having a coarse particle ratio of 3.2 and an average particle size of 0.9 mm. Therefore, 5 mass% of steelmaking slag having a particle size range of 1 to 5 mm was blended and coated. Material. The water quality dioxin concentration after the implementation was 0.02 pg-TEQ / L, which sufficiently satisfied the environmental standards, and the suspended solid concentration was reduced to 3 mg / L. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 13, 70% by weight of steelmaking slag containing coarse grains having a grain size range of 1 to 25 mm was blended with granulated blast furnace slag having a coarse grain rate of 2.7 and an average grain size of 0.7 mm to obtain a coating material. The water quality dioxin concentration after the implementation was 0.02 pg-TEQ / L, which sufficiently satisfied the environmental standards, and the suspended solid concentration was reduced to 3 mg / L. Regarding the curing state of the coating layer, the core sample material was independent and sound. No cracks or the like were found in the coating layer.

  In Example 14, the particle size of the granulated blast furnace slag was almost the same as in Example 6, and 50% by mass of mountain sand and 4% by mass of steelmaking slag were blended to form a coating material. The particle size of the steelmaking slag was 1 to 5 mm. The water-based dioxin concentration was 0.03 pg-TEQ / L after the implementation, sufficiently satisfying the environmental standards, and the suspended solid concentration was also 3 mg / L. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 15, in place of the steelmaking slag used in Example 11, 30% by mass of blast furnace slow cooling slag having a particle size of 5 mm or less was blended to form a coating material. The water quality dioxin concentration after the implementation was 0.02 pg-TEQ / L, which sufficiently satisfied the environmental standards, and the suspended solid concentration was reduced to 3 mg / L. It was confirmed that the sampling material maintained its shape by itself and was hardened. No cracks or the like were found in the coating layer.

  In Example 16, the granulated blast furnace slag having a coarse particle ratio of 3.5 was mixed with 5% by mass of mountain sand of 5 mm or less, 5% by mass of steelmaking slag of 1 to 5 mm, and 10% by mass of slowly cooled slag of 5 mm or less. To obtain a coating material. The water dioxin concentration was 0.03 pg-TEQ / L after the operation, sufficiently satisfying the environmental standards, and the suspended solid concentration was reduced to 3 mg / L after the operation. There were no cracks in the coating layer, and the sampling material maintained its shape by itself.

Comparative Examples 1-3:
In the same region as in Examples 1 to 16, in rivers and ports where the dioxin concentration of water quality exceeds environmental standards, using natural sand, blast furnace granulated slag, a mixture of blast furnace granulated slag and natural sand or steelmaking slag. A coating test on the sediment was performed in the same manner as in the examples, and after about one year, the water quality and the coating layer were investigated in the same manner as in the examples to evaluate the effect of preventing contamination.

  Table 3 shows the results.

  Comparative Example 1 is an example in which the sediment of a river was covered with mountain sand. The water dioxins concentration was 0.8 pg-TEQ / L after the implementation, which satisfied the environmental standards, and the suspended solids concentration was also reduced to 10 mg / L after the implementation. Could not be obtained. When core sampling was performed on a part of the coating layer, the sampled material collapsed without maintaining its shape due to mountain sand.

  Comparative Example 2 is an example in which the sediment of a river was covered only with granulated blast furnace slag, but the coating layer was partially solidified in a disc shape, and its core sampling material was free standing while maintaining its shape. However, the coating layer had cracks. As a result, the concentration of suspended solids was reduced to 10 mg / L, but the concentration of dioxins was 1 pg-TEQ / L, which was about environmental standards. In addition, since cracks were observed in the coating layer, there was concern about the long-term prevention effect.

  Comparative Example 3 is an example in which the sediment of the port was covered with mountain sand. The water dioxin concentration was 0.5 pg-TEQ / L after the implementation, which satisfies environmental standards, and the suspended solids concentration also decreased to 5 mg / L after the implementation. However, high contamination as in Examples 7 to 11 was observed. No substance prevention effect was obtained.

Claims (6)

  A method for preventing water pollution by dioxin-containing sediment, comprising coating dioxin-containing sediment with a mixture of granulated blast furnace slag and steelmaking slag and / or natural sand.   The method according to claim 1, wherein the blended amount of the granulated blast furnace slag in the mixture is 5 to 95% by mass.   3. The method according to claim 1, wherein a particle size of the steelmaking slag is not less than an average particle size of the granulated blast furnace slag and not more than 25 mm. 4.   A coating material for preventing water pollution by dioxin-containing sediment, characterized by mixing granulated blast furnace slag with steelmaking slag and / or natural sand.   The steelmaking slag, natural sand, or one or more of blast furnace slow cooling slag is added in place of the steelmaking slag and / or natural sand, The method according to any one of claims 1 to 3, wherein The described method.   A coating material for preventing water pollution by dioxin-containing sediment, characterized by mixing one or more of granulated blast furnace slag, steelmaking slag, natural sand, and slowly cooled blast furnace slag.