Water-containing sediment remover

Abstract

The present invention provides a water-containing sediment removal agent that can effectively soften water-containing sediments, particularly iron bacteria sludge, using a simple method, and a method for removing water-containing sediments using the removal agent. [Solution] A water-containing sediment remover containing 50% to 100% by mass of organic acid powder, wherein the median diameter (D50) of the organic acid powder is 0.3 mm or more, is used to remove water-containing sediment, especially iron bacteria sludge.

Description

[Technical Field]

[0001] The present invention relates to a water-containing sediment removal agent and a method for removing water-containing sediments. [Background technology]

[0002] Water-containing deposits that form in culverts and tunnels can cause water stagnation and lead to various problems. For example, sludge-like deposits produced by bacteria, especially iron bacteria sludge, when produced and accumulated in large quantities, are not only unsightly but can also cause scattering and contamination due to wind from passing vehicles. Furthermore, if iron bacteria sludge accumulates in equipment such as water collection pipes, drainage ditches, and drainage pipes installed in culverts and tunnels, insufficient drainage can lead to water stagnation and flooding, making it impossible for vehicles to pass, and causing metal components such as rails and fasteners to rust.

[0003] Patent Document 1 discloses a cleaning agent in the form of a solution for elevated water tanks or underground water tanks, in which two or more organic acids selected from the group consisting of oxalic acid, lactic acid, tartaric acid, citric acid, gluconic acid, ascorbic acid, and malic acid are dissolved in water as active ingredients. Patent Document 2 discloses a softening agent for hydrated sediments containing a hydroxypolycarboxylic acid, and the examples disclose that a powdered softening agent containing various acids was packed into a rice ball mold and compressed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 59-164398 [Patent Document 2] Japanese Patent Publication No. 2023-163132 [Overview of the project] [Problems that the invention aims to solve]

[0005] Citric acid is a versatile material with many uses, such as being dissolved in a solvent (water) and used as a solution-type cleaning agent, as described in Patent Document 1. When used as a cleaning agent, it is usually used in solution form. Examples of its use in powder form include lemonade mixed with other materials and acidulants, but there have been no prior disclosures of powdered citric acid being used as a cleaning agent, and no prior examples regarding suitable particle size or particle size distribution for such applications are known.

[0006] Generally, when using powders by scattering them, the selection of particle size is important depending on the application. Larger particle sizes result in better fluidity, but inferior dissolution speed and uniformity of mixing with other powders. Conversely, while smaller particle sizes result in better dissolution speed and uniformity of mixing with other powders, it is known that powder fluidity tends to deteriorate.

[0007] Furthermore, when distributing powder by hand or with tools, it is preferable that the particles are moderately large (i.e., have a moderately large mass) because they are less affected by air resistance and can be dispersed forcefully to the desired area. On the other hand, if the particles are too large, although they may have force, their mass is too great, and they may not adhere effectively to the desired area, sometimes falling due to their own weight.

[0008] Furthermore, when the particle size is small (i.e., has a small mass), it is difficult to accurately apply the substance to the desired area due to dust generation during application and the effects of air resistance.

[0009] As a result of diligent research, the inventors found that citric acid powder with a median diameter (D50) of 0.3 mm to 2.0 mm is suitable for application as a cleaning agent and the like.

[0010] The present invention provides a water-containing sediment removal agent that can effectively soften water-containing sediments, particularly iron bacteria sludge, using a simple method, and a method for removing water-containing sediments using the removal agent. [Means for solving the problem]

[0011] The present invention relates to a water-containing deposit remover containing an organic acid powder having a specific median diameter, particularly a hydroxypolycarboxylic acid powder.

[0012] Furthermore, this invention relates to a method for removing water-containing sediments, particularly iron bacteria sludge, by applying a water-containing sediment removal agent to the water-containing sediments. [Effects of the Invention]

[0013] The present invention provides a water-containing sediment remover containing a hydroxypolycarboxylic acid that can effectively soften water-containing sediments, particularly iron bacteria sludge, to facilitate their removal. Furthermore, the present invention provides a simple and effective method for removing water-containing sediments, particularly iron bacteria sludge.

[0014] The present invention provides a method for removing water-containing sediments (hereinafter referred to as the "removal method") that uses a water-containing sediment removal agent containing organic acid powder (hereinafter referred to as the "removal agent") to break down the coagulation structure of accumulated water-containing sediments, particularly iron bacteria sludge, thereby promoting solid-water separation. This makes the separated solid components easily fluid, and after applying the removal agent, they can be easily washed away, for example, by a washing operation that reduces water flow and energy load. This prevents water stagnation caused by stagnant drainage flow, contamination of vehicles, equipment, tunnel interiors, etc., by scattered sediment, and rusting of metal components such as rails and fasteners. Using the removal method of the present invention makes water-containing sediments more fluid and sediment particles more easily dispersed, thus suppressing redeposition in drainage ditches and pipes and allowing for effective return to the natural environment. Furthermore, it reduces the effort required for sediment collection and treatment, and the sludge produced by iron bacteria is particularly desirable because it is rich in iron, making it a nutrient source for aquatic organisms. [Modes for carrying out the invention]

[0015] The remover of the present invention contains an organic acid powder as an active ingredient. In the present invention, the powder refers to an aggregate of particles that can be recognized as isolated grains, and even if it is not composed of particles of a single composition, and a plurality of types of particles having different compositions may be mixed as long as it has the following predetermined average particle diameter.

[0016] From the viewpoint of improving the removal effect, the content of the organic acid powder in the remover of the present invention is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and 100% by mass or less, preferably 95% by mass or less, more preferably 80% by mass or less.

[0017] The content may be 100% by mass, that is, the remover of the present invention may consist only of the organic acid powder.

[0018] From the viewpoint of improving the removal effect, the median diameter (D50) of the organic acid powder is 0.3 mm or more, preferably 0.35 mm or more, more preferably 0.4 mm or more. Also, from the same viewpoint, it is preferably 2.0 mm or less, more preferably 1.8 mm or less, and still more preferably 1.5 mm or less. The median diameter (D50) of the organic acid powder can be measured by the method of the examples using sieving.

[0019] Also, from the viewpoint of improving the removal effect, the organic acid powder preferably contains 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less of the powder having a particle size of less than 0.3 mm.

[0020] From the viewpoint of improving the removal effect, as the organic acid constituting the organic acid powder, a hydroxy polyvalent carboxylic acid is preferable. Examples of the hydroxy polyvalent carboxylic acid include compounds having one or more hydroxyl groups and two or more carboxyl groups. From the viewpoint of improving the removal effect, the total number of carbon atoms of the hydroxy polyvalent carboxylic acid is preferably 3 or more, more preferably 4 or more, and from the same viewpoint, it is preferably 8 or less, more preferably 6 or less. From the perspective of improving the removal effect, the number of hydroxy groups in the hydroxy polycarboxylic acid is preferably 1 or more, and from the same perspective, it is preferably 4 or less, more preferably 2 or less. From the perspective of improving the removal effect, the number of carboxy groups in the hydroxy polycarboxylic acid is preferably 2 or more, and from the same perspective, it is preferably 4 or less, more preferably 3 or less.

[0021] Examples of the hydroxy polycarboxylic acid include hydroxy polycarboxylic acids represented by the following general formula (1).

Chemical formula

[0022] Regarding the hydroxy polycarboxylic acid of the general formula (1), a compound in which a part of the carboxyl group is in the form of a salt with an alkali metal ion, an alkaline earth metal ion, an ammonium ion, etc. may be used, but from the perspective of improving the removal effect, it is preferable to use a compound in which all carboxyl groups are in the acid form.

[0023] Among the hydroxypolycarboxylic acids of general formula (1), those containing an asymmetric carbon can be used as optical isomers alone or as mixtures. Mixtures are preferred from the viewpoint of availability and cost-effectiveness.

[0024] Examples of hydroxypolycarboxylic acids include citric acid, malic acid, tartaric acid, 2-hydroxycitric acid, 2-methylcitric acid, isocitric acid, 2-hydroxyglutaric acid, citramaric acid, tartronic acid, 2-methyltartronic acid, hydroxyfumaric acid, hydroxymaleic acid, hydroxymethanetricarboxylic acid, aldaric acid, and their isomers. Hydrates of these can also be used.

[0025] From the viewpoint of improving the removal effect, one or more hydroxypolycarboxylic acids selected from citric acid, malic acid, and tartaric acid are preferred, and from the same viewpoint, citric acid is more preferred.

[0026] From the viewpoint of improving the removal effect, the organic acid constituting the organic acid powder of the present invention is preferably one or more selected from citric acid, malic acid, and tartaric acid, and from the same viewpoint, citric acid is more preferred.

[0027] The form of the removal agent of the present invention is not particularly limited, but from the viewpoint of convenience, it is preferably a solid. If the removal agent consists only of organic acid powder, the powder can be used as is. Furthermore, if it contains optional components as described later, it can be used in the form of powder, particles, granules, pellets, rods, or other tablet-like forms.

[0028] When the remover of the present invention is a solid, the median diameter (D50) of the remover is preferably 0.3 mm or more, more preferably 0.35 mm or more, and even more preferably 0.4 mm or more, from the viewpoint of improving the removal effect. Also from the same viewpoint, it is preferably 2.0 mm or less, more preferably 1.8 mm or less, and even more preferably 1.5 mm or less.

[0029] The removal agent of the present invention may contain one or more compounds selected from carbonates and bicarbonates as optional components to improve its removal effect. Alternatively, hydrogen peroxide adducts (percarbonates) to carbonates can also be used. Specifically, sodium carbonate, potassium carbonate, ammonium carbonate, calcium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium percarbonate, potassium percarbonate, etc., can be used. These may be used individually or in combination.

[0030] When using one or more compounds selected from carbonates and bicarbonates, the content of the compound in the removal agent is preferably 5 parts by mass or less per 100 parts by mass of the removal agent.

[0031] When using one or more compounds selected from carbonates and bicarbonates, the content of the compound in the removal agent is preferably 5 parts by mass or less per 100 parts by mass of the removal agent.

[0032] Other optional components that may be contained in the removal agent of the present invention include inorganic salts such as sodium sulfate, magnesium sulfate, and sodium chloride, colorants, preservatives, rust inhibitors, fragrances, disinfectants, rodenticides, and bittering agents to prevent accidental ingestion. The content of these components can be appropriately set depending on the component, but it is preferable to have 5 parts by mass or less per 100 parts by mass of the removal agent.

[0033] The removal agent of the present invention may optionally be used as a powder formed by adding appropriate additives (such as excipients) as needed, or it may be subjected to operations such as pulverization and sieving after molding. As excipients used during molding, hydrophilic polymers such as polyethylene glycol, polyvinyl alcohol, and celluloses, or naturally derived polymers such as agar and gelatin can be used. It may also be used wrapped in a water-soluble or water-soluble film or paper.

[0034] When the material is crushed and sieved after molding, the excipient containing the organic acid is preferably a powder with a median diameter (D50) of 0.3 mm or more and 2.0 mm or less, similar to the organic acid powder. Similarly, when the material is wrapped in a water-soluble or hydrolyzable film or paper, it is preferable that the median diameter (D50) is 0.3 mm or more and 2.0 mm or less, similar to the organic acid powder.

[0035] When using additives (such as excipients), the amount of these additives in the remover is preferably 5 parts by mass or less per 100 parts by mass of the remover.

[0036] The removal agent of the present invention may be used as a dispersion containing organic acid powder and optional components. From the viewpoint of safety, water, ethanol, and isopropyl alcohol are preferred as the dispersion medium for the dispersion. A dispersion containing organic acid powder can be obtained by saturating the organic acid and optional components in these dispersion mediums and then adding the organic acid and optional components to the resulting saturated solution.

[0037] The removal agent of the present invention may take the form of organic acid powder, powder molded by adding an excipient to an organic acid, or the above-mentioned dispersion liquid, but from the viewpoint of improving the removal effect, it is preferable to use it as a powder.

[0038] When the removal agent of the present invention is used in powder form, the median diameter (D50) of the removal agent is preferably 0.3 mm or more, more preferably 0.35 mm or more, and even more preferably 0.4 mm or more, from the viewpoint of improving the removal effect. Also from the same viewpoint, it is preferably 2.0 mm or less, more preferably 1.8 mm or less, and even more preferably 1.5 mm or less.

[0039] Next, a method for removing water-containing sediments using the removal agent of the present invention will be described. The water-containing sediments targeted by the removal method of the present invention may have physical properties and scale such that the removal effect of the removal agent of the present invention, such as the ability to break down cohesive structures and the ability to separate solids and water, can be exhibited. For example, materials that require a large amount of mechanical force to move, such as gravel and strata in riverbeds, or materials that inherently have high fluidity, are excluded from the water-containing sediments targeted by the present invention. In other words, the water-containing sediments targeted by the present invention are those that can be removed by separating solids and water and further fluidizing them with the removal agent of the present invention. Examples of water-containing sediments targeted by the removal method of the present invention include sludge, preferably sludge containing organic matter. Examples of sludge containing organic matter include iron bacteria sludge derived from the metabolism of microorganisms such as bacteria, biofilms, biomats, etc., as well as sludge containing fallen leaves, animal and plant fragments, and decaying matter, and mixtures thereof. Also, sludge containing particles such as sand, clay, and mud can be mentioned. The organic matter in the sludge containing organic matter is preferably sludge containing one or more selected from iron oxide and iron hydroxide, and more preferably iron bacteria sludge, from the viewpoint of the sludge having low fluidity. The content of one or more selected from iron oxide and iron hydroxide in the sludge is preferably 5% by mass or more, more preferably 30% by mass or more, and preferably 70% by mass or less, in terms of iron in terms of solid content.

[0040] The present invention relates to a method for removing water-containing sediments, which involves applying a removal agent containing organic acid powder to the water-containing sediment in situ. Furthermore, the removal agent of the present invention can be used in a method for removing water-containing sediments that promotes solid-water separation, thereby fluidizing and removing the sediment. The removal agent is preferably applied to the surface and / or interior of the water-containing sediment.

[0041] Methods for adding the remover in the removal method of the present invention include: scattering a solid remover on the surface of the water-containing sediment; placing a tablet-shaped remover on the surface of the water-containing sediment; embedding a solid, for example, granular, remover inside the water-containing sediment; or embedding a tablet-shaped remover inside the pre-water-containing sediment. Furthermore, if the remover is a dispersion, general methods such as spraying can be used.

[0042] From the viewpoint of removal effectiveness, the water content of the water-containing sediment targeted by the removal method of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 94% by mass or more, and preferably 99.5% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less.

[0043] From the viewpoint of removal effectiveness, the solid content of the water-containing sediment targeted by the removal method of the present invention is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 6% by mass or less. The solid content of the water-containing sediment refers to the residue remaining after the water has evaporated.

[0044] The water-containing sediment targeted by the removal method of the present invention may contain iron. The iron content in the solids of the water-containing sediment may be, for example, preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, and preferably 77% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. In water-containing sediment, iron exists, for example, as iron compounds such as hydroxides and oxides. In the present invention, the iron content in water-containing sediment refers to the amount of iron present as an element. Furthermore, this iron content can be measured, for example, by atomic absorption spectrophotometry.

[0045] The removal method of the present invention is suitable for removing sludge containing metabolites of iron bacteria (hereinafter abbreviated as iron bacteria sludge). Sludge containing metabolites of iron bacteria contains divalent iron ions (Fe) in order for iron bacteria (also called iron-oxidizing bacteria, iron-oxidizing bacteria, iron bacteria, etc.) to obtain their own energy. 2+ ) trivalent iron ions (Fe 3+This is a sediment containing sparingly water-soluble iron compounds (hydroxides, oxides, etc.) formed from trivalent iron ions after oxidation, and is also called slime, gel, biomat, brown agar-like substance, red water, red mud, or sob. In other words, it is a sludge containing metabolites of iron bacteria, resulting from the life activities of iron bacteria.

[0046] Examples of methods for adding a removal agent in the iron bacteria sludge removal method of the present invention include sprinkling a solid, for example, granular, removal agent on the surface of the iron bacteria sludge generated in the tunnel; placing a tablet-shaped removal agent on the surface of the iron bacteria sludge; embedding a solid, for example, granular or powdered, removal agent inside the iron bacteria sludge; and embedding a tablet-shaped removal agent inside the iron bacteria sludge.

[0047] The amount of the removal agent of the present invention used is not particularly limited, but can be appropriately adjusted according to the thickness, hardness, moisture content, and desired level of removal of the water-containing sediment. For example, the amount of the removal agent of the present invention used per liter of water-containing sediment is preferably 1 g or more, more preferably 5 g or more, even more preferably 10 g or more, and preferably 300 g or less, more preferably 200 g or less, and even more preferably 100 g or less.

[0048] The removal agent of the present invention, upon contact with the water-containing sediment, disrupts the cohesive structure of the sediment, promoting solid-liquid separation and softening and fluidizing any remaining solid components. After applying the removal agent of the present invention, the water-containing sediment can be easily washed away from the sediment site by applying water to it, for example, by using water present in the surrounding environment, such as leaks, springs, or drainage, or by performing simple operations. [Examples]

[0049] <Water-containing sediment> The sediment sampled from a reservoir in Wakayama City, Wakayama Prefecture, as shown in Table 1 below, was used as a model sludge for hydrated sediment. This sediment has a high moisture content of 95.6% by mass and also contains 8.2% by mass of iron, making its properties similar to those of iron bacteria sludge. [Table 1]

[0050] <Manufacturing of Removal Agents> Commercially available citric acid powder was sieved using the following method to obtain powder with a predetermined D50. Sifts with mesh sizes of 0.15 mm, 0.30 mm, 0.50 mm, 0.60 mm, 0.71 mm, 1.18 mm, and 2.36 mm were assembled on the bottom of the container in that order, and 100 g of commercially available citric acid powder was sieved through them. This operation was repeated to obtain citric acid powders with D50 values ​​as shown in Examples 1 to 6 and Comparative Example 1 in Table 1. The value of D50 was defined as the average of the mesh size of the sieve through which all the powder passed and the mesh size of the sieve one size smaller, through which no powder passed. For example, in Example 1, the powder that passed through the 3.35 mm sieve but not the 2.36 mm sieve was collected. In this case, the value of D50 was: (3.55mm + 2.46mm) ÷ 2 = 2.86mm This was the calculation. The granulated sugar, saccharin sodium dihydrate, and sand (mountain sand from Joyo, Kyoto Prefecture) used in Comparative Examples 2-4 were similarly sieved, and the D50 value was calculated.

[0051] Furthermore, if the powder is distributed across two or more sieves, a graph can be created with the average value obtained from the mesh opening of each sieve on the horizontal axis and the sum of the mass percentage of the powder in that sieve and the mass percentage of the powder that passed through the sieve before (cumulative value) on the vertical axis. An approximation curve can then be drawn connecting the cumulative values ​​in order of particle size, and the particle size at which the value of this approximation curve becomes 50% can be determined as D50.

[0052] <Flowability test using model sludge> 30g of the model sludge was placed on a smooth metal plate that was set horizontally, so that when the plate was placed vertically, the center of the model sludge would be 30cm from the bottom. Then, the metal plate was gently placed vertically, creating a state where the model sludge adhered to the wall surface. 20g of the removal agent was then manually sprinkled onto the model sludge from a distance of 30cm from the metal plate. The time from application to the start of flow was defined as the flow start time. This was evaluated as follows: less than 5 seconds was rated as excellent, 5 seconds or more but less than 15 seconds as good, and 15 seconds or more as bad. The results are shown in Table 2.

[0053] In Examples 1-6, which used citric acid powder with a D50 of 0.40 mm or more, flow started in less than 15 seconds in all cases. In Example 1, where the D50 was 2.86 mm, the flow start time was slightly longer than in Examples 2-6, where the D50 was 1.77 mm or less. Comparative Example 1, which used citric acid powder with a D50 of 0.23 mm, required more than 15 seconds to begin flowing. Similarly, Comparative Examples 2-4, which did not use organic acids, also required more than 15 seconds to begin flowing.

[0054] <Measuring the removal rate of sediment using model sludge> 30g of the model sludge was placed on a smooth metal plate that was set horizontally, so that when the plate was placed vertically, the center of the model sludge would be 30cm from the bottom. Then, the metal plate was gently placed vertically, creating a state where the model sludge adhered to the wall surface. 20g of the removal agent was then manually sprinkled onto the model sludge from a distance of 30cm from the metal plate. Five minutes after the application of the removal agent, the mass of the model sludge remaining attached to the metal plate was measured, and the removal rate was calculated using the following formula. The results are shown in Table 2. Removal rate = [(30g - amount of residual deposited material (g)) ÷ 30g] × 100 (%)

[0055] In Examples 1-6, which used citric acid powder with a D50 of 0.40 mm or more, a removal rate of 68% or more was obtained in all cases. In Example 1, where the D50 was 2.86 mm, the removal rate was slightly lower than in Examples 2-6, which used citric acid powder with a D50 of 1.77 mm or less. Comparative Example 1, which used citric acid with a D50 of 0.23 mm, had a removal rate of 63%, which was lower than that of Examples 1-6. Furthermore, in Comparative Examples 2-4, which used organic compounds other than organic acids or sand, no sediment was removed at all.

[0056] [Table 2]

Claims

1. A water-containing sediment remover containing 50% by mass or more and 100% by mass of organic acid powder, wherein the median diameter (D50) of the organic acid powder is 0.3 mm or more.

2. The water-containing sediment remover according to claim 1, wherein the form is solid.

3. The water-containing sediment remover according to claim 1, wherein the median diameter (D50) of the organic acid powder is 0.3 mm or more and 2.0 mm or less.

4. The water-containing sediment remover according to claim 1, wherein the organic acid powder is a powder containing 50% by mass or less of particles smaller than 0.3 mm.

5. The water-containing sediment remover according to claim 1, further comprising 100% by mass of the aforementioned organic acid powder.

6. The water-containing deposit remover according to any one of claims 1 to 5, wherein the organic acid constituting the organic acid powder is one or more selected from hydroxypolycarboxylic acids.

7. The water-containing deposit remover according to any one of claims 1 to 5, wherein the organic acid constituting the organic acid powder is a hydroxypolycarboxylic acid having 4 to 6 carbon atoms.

8. The water-containing deposit remover according to any one of claims 1 to 5, wherein the organic acid constituting the organic acid powder is one or more selected from hydroxypolycarboxylic acids represented by general formula (1). 【Chemistry 1】 [In the formula, n represents an integer from 0 to 3. The dotted line indicates no bond or a single bond when n is 1, and no bond when n is 0, 2, or 3. When the dotted line represents no bond, R １ , R ２ and R ３ each independently represent a hydrogen atom, a methyl group, a hydroxyl group, or -R ４ -COOH [R ４ represents an alkylene group having 1 to 4 carbon atoms.], which represents a carboxyalkyl group. When the dotted line represents a single bond, R １ and R ２ are absent, and R ３ represents a hydrogen atom, a methyl group, a hydroxyl group, or -R ４ -COOH [R ４ represents an alkylene group having 1 to 4 carbon atoms.], which represents a carboxyalkyl group.]

9. The water-containing sediment remover according to any one of claims 1 to 5, wherein the organic acid constituting the organic acid powder is one or more selected from citric acid, malic acid, and tartaric acid.

10. The water-containing deposit remover according to any one of claims 1 to 5, wherein the organic acid constituting the organic acid powder is citric acid.

11. A method for removing water-containing sediment, comprising spraying the water-containing sediment removal agent described in claim 1 or 2 onto the water-containing sediment, wherein the water content of the water-containing sediment is 80% by mass or more and 99.5% by mass or less.

12. The method for removing water-containing sediment according to claim 11, wherein the water-containing sediment is iron bacteria sludge.

13. A method for removing water-containing deposits according to claim 11, applicable to water-containing deposits adhering to a wall surface.

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