Method for removing water-containing sediments

Abstract

To effectively remove hydrous deposits by a simple method, with reduced load to the natural environment.SOLUTION: A method for removing hydrous deposits induces foaming at the original location of hydrous deposits and removes the hydrous deposits through the foaming.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for removing water-containing sediment.

Background Art

[0002] Water-containing sediment generated in culverts and tunnels can cause water flow to stagnate and may lead to various problems. For example, sludge-like sediment generated by bacteria, particularly iron bacteria sludge, when it is generated and deposited in large quantities, not only looks dirty, but also causes the sediment to scatter and become contaminated by the wind when vehicles pass by. In addition, when iron bacteria sludge accumulates on facilities such as water collection pipes, drainage ditches, and drain pipes installed in culverts and tunnels, insufficient drainage occurs, resulting in stagnant water and flooding, making it impossible for vehicles to pass, and metal components such as rails and fixtures rusting.

[0003] Conventionally, as countermeasures for suppressing sludge-like sediment generated by bacteria, compositions using compounds having bactericidal properties for killing the bacteria themselves, and devices for fixing such compositions are known (Patent Documents 1 to 4).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] Regularly removing water-containing deposits that form in culverts and tunnels requires considerable time and effort. While there are methods to mechanically remove the water-containing deposits, the need to transport equipment, power sources, and washing water to the work site means that preparation and operation are time-consuming, and it is difficult to address this issue in limited workspace and time. It is also possible to suppress the formation of water-containing deposits by using disinfectants to kill bacteria, but from the perspective of the natural environment, it is desirable to reduce the use of such compounds as much as possible.

[0006] This invention provides a method for removing water-containing sediments that is simple, effective, and has minimal impact on the natural environment. [Means for solving the problem]

[0007] The present invention relates to a method for removing water-containing sediments, which involves generating foam in the water-containing sediments at their original location and removing the water-containing sediments by said foaming. [Effects of the Invention]

[0008] The present invention provides a method for removing water-containing sediments that is simple, effective, and has minimal impact on the natural environment.

[0009] The present invention provides a simple and safe method for fluidizing and washing away accumulated water-containing sediment. This prevents waterlogging caused by stagnant drainage flow and contamination of vehicles, equipment, tunnel interiors, etc., by scattered sediment. The present invention's removal method makes water-containing sediment easier to fluidize and sediment particles easier to disperse, thus suppressing redeposition in drainage ditches and pipes and effectively returning it to the natural environment. Furthermore, it reduces the effort required for sediment collection and treatment, and sediment produced by iron bacteria is particularly desirable because it is rich in iron, serving as a nutrient source for aquatic organisms. [Modes for carrying out the invention]

[0010] As a result of diligent research to solve the above problems, the inventors have found that water-containing sediments can be easily removed from their locations by softening them with foamed bubbles while they are in their original state, for example, on the inner walls of tunnels or in culverts, and then leaving them to flow with the flow of groundwater, leaks, or drainage, and / or by simply spraying them with water.

[0011] The water-containing sediments targeted by this invention may be of a physical property and scale that can be removed by foaming. For example, materials that require significant mechanical force to move, such as riverbed gravel and geological strata, or materials that inherently possess high fluidity, are excluded from the water-containing sediments targeted by this invention. In other words, the water-containing sediments targeted by this invention are those that can be fluidized and removed by foaming. Examples of water-containing sediments targeted by this invention include iron bacteria sludge, biofilms, biomats, etc., derived from the metabolism of microorganisms such as bacteria, as well as particles such as sand, clay, and mud, fallen leaves, animal and plant fragments and decaying matter, and mixtures thereof.

[0012] The removal method of the present invention is suitable for removing hydrated sediments containing metabolites of iron bacteria. In hydrated sediments containing metabolites of iron bacteria, iron bacteria (also called iron-oxidizing bacteria, iron-oxidizing bacteria, iron bacteria, etc.) obtain their own energy, which is produced by divalent iron ions (Fe 2+ ) trivalent iron ions (Fe 3+ It is a sediment containing water-insoluble 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, sob, etc. In other words, as a result of the life activities of iron bacteria, hydrated sediments containing the metabolites of iron bacteria are formed.

[0013] The hydrated sediment may include the portion that is exposed to the atmosphere.

[0014] The water-containing sediment may contain, for example, 50% by mass or more, further 60% by mass or more, further 70% by mass or more, and 99.5% by mass or less, further 97% by mass or less, and further 95% by mass or less of water.

[0015] The hydrated sediment may contain, for example, 0.5% by mass or more, further 3% by mass or more, further 5% by mass or more, and 50% by mass or less, further 40% by mass or less, and further 30% by mass or less of solids. Here, the solids of the hydrated sediment may consist of components other than water, and may also include liquid components.

[0016] Hydrated sediments may contain iron. The iron content in the solids of hydrated sediments may be, for example, 0.1% by mass or more, further 1% by mass or more, further 5% by mass or more, and 77% by mass or less, further 60% by mass or less, and further 50% by mass or less. In hydrated sediments, iron exists as iron compounds such as hydroxides and oxides. In this invention, the iron content in hydrated sediments refers to the amount of iron present as an element. Furthermore, this iron content can be measured, for example, by atomic absorption spectrophotometry.

[0017] From the viewpoint of the removal effect by foaming, the flow value of the water-containing sediment may be, for example, between 21 mm and 45 mm. Here, the flow value of the water-containing sediment is the diameter of the horizontal surface of the remaining water-containing sediment after placing a cylinder with an inner diameter of 20 mm and a height of 20 mm on a horizontal surface, quietly filling the space inside the cylinder with water-containing sediment without any gaps, scraping the top surface flat with a smooth metal plate, and then quietly lifting the cylinder vertically. If the shape is not a perfect circle, the average of the major and minor axes shall be used as the diameter. Furthermore, if water separates and seeps out from the water-containing sediment after the flow stops, the portion of the sediment remaining as solid matter shall be measured.

[0018] Examples of the water-containing sediment having the flow value as described above include sediments derived from metabolism such as bacteria, water-containing sediments derived from microorganisms such as biofilms and biomat, inorganic substances such as sand, clay, and mud containing water, organic substances such as fallen leaves, fragments of animals and plants, and / or putrefied substances, etc., and mixtures thereof may also be possible. The water-containing sediment containing water and solid components within the above range is preferable because it is likely to have the flow value.

[0019] [[ID=�]]From the viewpoint of the removal effect by foaming, the thickness of the water-containing sediment may be, for example, 0.1 cm or more, further 1 cm or more, further 3 cm or more, and 50 cm or less, further 30 cm or less, further 20 cm or less. Here, the thickness of the water-containing sediment is the thickness of the portion judged to be the thickest by visual confirmation. The thickness is actually measured using a vernier caliper, a ruler, etc.

[0020] In the present invention, foaming is caused to occur in situ in the water-containing sediment. In the present invention, foaming may be carried out on the surface of the water-containing sediment, or foaming may be carried out inside the water-containing sediment. That is, in the present invention, foaming can be carried out on the surface and / or inside of the water-containing sediment. In the present invention, foaming may be caused by the generation of gas. From the viewpoint of safety, the gas is preferably carbon dioxide or oxygen, and more preferably carbon dioxide having no flammability-supporting property.

[0021] In the present invention, foaming can be carried out using a foaming agent that foams upon contact with water. Examples of the foaming agent include a foaming agent containing the following component (a) and component (b). Component (a): One or more compounds selected from organic acids and inorganic acids Component (b): One or more compounds selected from carbonates and bicarbonates

[0022] Component (a) may be either an inorganic acid or an organic acid. From the viewpoint of being easily adaptable to the dissolution rate of component (b) and effectively causing reaction and foaming, component (a) is preferably an organic acid, and more preferably one or more compounds selected from organic acids having 1 to 18 carbon atoms. The number of carbon atoms of the organic acid may be, for example, 2 or more, further 3 or more, and 14 or less, further 10 or less.

[0023] Examples of inorganic acids in component (a) include hydrochloric acid, sulfuric acid, sulfurous acid, nitric acid, phosphoric acid, phosphorous acid, diphosphorous acid, and boric acid.

[0024] The organic acids in component (a) include (1) sulfamic acid, sulfanilic acid, p-toluenesulfonic acid, p-toluenesulfonic acid hydrate, m-xylenesulfonic acid, m-xylenesulfonic acid hydrate, benzenesulfonic acid, naphthalenesulfonic acid, alkylnaphthalenesulfonic acid (e.g., butylnaphthalenesulfonic acid), alkylbenzenesulfonic acid (e.g., dodecylbenzenesulfonic acid), phenolsulfonic acid, alkanesulfonic acid (e.g., hexanesulfonic acid, heptanesulfonic acid, tetradecanesulfonic acid), α-olefinsulfonic acid, hydroxya (1) Organic sulfonic acids such as lucansulfonic acid, taurine, N-methyltaurine, isethionic acid, (2) monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, oleic acid, stearic acid, benzoic acid, hydroxybenzoic acid, salicylic acid, partially neutralized products of the monocarboxylic acids, acid anhydrides of the monocarboxylic acids, and mixtures of esterified products of the monocarboxylic acids, (3) oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, malic acid, tartaric acid, oxaloacetic acid, aconitic acid, isocitric acid, oxalosuccinic acid, α-ketoglutaric acid, Dicarboxylic acids such as itaconic acid, citraconic acid, citramaric acid, glutaric acid, diethylglutaric acid, adipic acid, pimelic acid, suberic acid, 2-butyloctanedioic acid, azelaic acid, sebaciic acid, dodecanediic acid, nonenylucuccinic acid, dodecenyllucuccinic acid, alkenyllucuccinic acid, phthalic acid, isophthalic acid, terephthalic acid, sulfophthalic acid, sulfisophthalic acid, sulfotephthalic acid, cyclohexanedicarboxylic acid, cyclohexenedicarboxylic acid, partially neutralized products of the dicarboxylic acids, acid anhydrides of the dicarboxylic acids, and partially esterified products of the dicarboxylic acids, (4 (1) Tricarboxylic acids such as propanetricarboxylic acid, citric acid, trimellitic acid, benzenetricarboxylic acid, cyclohexanetricarboxylic acid, partially neutralized pretricarboxylic acids, acid anhydrides of the tricarboxylic acids, and partially esterified tricarboxylic acids, (5) Polycarboxylic acids of tetravalent or higher such as butanetetracarboxylic acid, pyromellitic acid, poly(meth)acrylic acid, polymaleic acid, polyepoxysuccinic acid, partially neutralized polycarboxylic acids, acid anhydrides of the polycarboxylic acids, and partially esterified polycarboxylic acids, (6) Acids other than (1) to (5),Examples include compounds with a phenol skeleton that exhibit acidity in water, such as phenol, resorcinol, and pyrogallol, and polyhydric phosphoric acids such as phytic acid. Component (a) can be used individually or in combination of two or more.

[0025] In addition, as component (a), other substances that become protonic acids through hydrolysis or thermal decomposition, as well as Lewis acids that exhibit acidity through hydrolysis, can also be used. Examples of substances that become protonic acids through hydrolysis or thermal decomposition include sodium persulfate, potassium persulfate, ammonium persulfate, potassium monopersulfate (oxon), and aluminum chloride, while examples of Lewis acids include boron trifluoride.

[0026] Component (a) is preferably used in an unneutralized state because it can increase the effective content as an acid necessary for foaming. However, it can also be used as a partially neutralized product neutralized with a suitable base to improve the dissolution rate and powder properties, or it can be used in combination with separately prepared partially neutralized or fully neutralized products. Examples of partially neutralized products include monosodium citrate, monosodium fumarate, monosodium maleate, sodium bisulfate, potassium bisulfate, ammonium bisulfate, sodium bissite, potassium bisulfite, and ammonium bisulfite.

[0027] Since the component (b) to be combined is preferably a solid, a solid acid is more preferable for component (a) from the viewpoint of being able to be handled similarly. Furthermore, from the viewpoint of safety in use, a carboxylic acid, which is a weak acid, is more preferable.

[0028] From the viewpoint of increasing the amount of foam, the foaming agent used in the present invention may contain component (a) in proportions of, for example, 35% by mass or more, 40% by mass or more, 45% by mass or more, and 80% by mass or less, 75% by mass or less, and 70% by mass or less, of the total content of component (a) and component (b) (however, if component (c) described later is included, the content of component (c) is also included in this total).

[0029] Component (b) is one or more compounds selected from carbonates and bicarbonates, and a hydrogen peroxide adduct (percarbonate) to a carbonate can also be used. Examples of component (b) include sodium carbonate, potassium carbonate, ammonium carbonate, calcium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium percarbonate, and potassium percarbonate. These may be used alone or in combination. Due to their availability and ease of handling, component (b) is preferably a compound selected from sodium carbonate and sodium bicarbonate.

[0030] From the viewpoint of increasing the amount of foam, the foaming agent used in the present invention may contain component (b) in proportions of, for example, 25% by mass or more, further 30% by mass or more, further 35% by mass or more, and 60% by mass or less, further 55% by mass or less, and further 50% by mass or less, of the total content of component (a) and component (b) (however, if component (c) described later is included, the content of component (c) is also included in this total).

[0031] The form of the foaming agent used in the present invention is not particularly limited, but it is preferably solid. Specifically, it can be in the form of powder, granules, tablets, etc. If it is solid, it may be molded with appropriate additives (such as excipients) as needed, or it may be wrapped in a soluble film or paper. The foaming agent used in the present invention may be liquid, but in order to avoid reactions (performance degradation) before use, it is preferable that it does not contain both component (a) and component (b) in a liquid state. In addition, in the foaming agent used in the present invention, component (a) and component (b) may be added to the deposit separately.

[0032] The foaming agent used in the present invention is preferably one that foams upon contact with water, such as moisture in water-containing sediments. More specifically, the foaming agent used in the present invention is preferably one that generates gas upon contact with water and forms foam through foaming. More preferably, it is one that generates highly safe carbon dioxide or oxygen through neutralization or oxidation-reduction reactions. Even more preferably, it is one that generates carbon dioxide that does not support combustion.

[0033] In the foaming agent used in the present invention, the combination of component (a) and component (b) is not particularly limited, but as described above, a combination that generates carbon dioxide upon contact with water is preferred. From the viewpoint of efficiently generating carbon dioxide upon contact with water, the foaming agent used in the present invention is preferably a combination in which component (a) is a compound selected from dicarboxylic acids and tricarboxylic acids, and component (b) is a compound selected from sodium carbonate and sodium bicarbonate.

[0034] Examples of foaming agents used in the present invention that generate oxygen and carbon dioxide include a combination in which component (a) is one or more compounds selected from persulfates and monopersulfates, and component (b) is a percarbonate. Among these, a combination of potassium monopersulfate (oxon) and sodium percarbonate is preferred.

[0035] Examples of foaming agents used in the present invention that generate oxygen include a combination in which component (a) is one or more compounds selected from persulfates and monopersulfates, and component (b) is hydrogen peroxide. Among these, the combination of sodium persulfate and hydrogen peroxide is preferred.

[0036] It is preferable to use components (a) and (b) in a molar ratio that theoretically allows for complete reaction without leaving any unreacted substances and to bring the pH to near neutral after the reaction is complete. In the foaming agent used in the present invention, the molar ratio of component (a) to component (b) may be, for example, 0.02 or more, further 0.04 or more, further 0.1 or more, further 0.2 or more, and 50 or less, further 25 or less, further 10 or less, and further 5 or less. It is preferable to select the molar ratio of component (a) to component (b) taking into consideration the pH of the environment in which it is used.

[0037] The foaming agent used in the present invention preferably further contains the following component (c). Ingredient (c): Foam enhancer

[0038] Component (c) is present at and / or near the interfaces between solids, gases, and liquids, and is added to exhibit functions such as dispersion of solids, emulsification of liquids, reduction of interfacial tension at the interface, formation of an adsorption layer, and stabilization of bubbles. Component (c) is preferred from the viewpoint of enhancing the foaming removal effect of components (a) and (b). Regarding component (c), a foam increasing agent refers to a substance that slows down the coalescence of continuously generated bubbles, thereby suppressing the rapid disappearance of bubbles, while simultaneously increasing the amount of foam by forming stable foam.

[0039] Component (c) may be, for example, a foam-increasing agent with a molecular weight of 700,000 or less. Component (c) may include foam-increasing agents selected from high-molecular-weight compounds with molecular weights between 0.5 million and 700,000, and surfactants with molecular weights of less than 2,000. Examples of polymer compounds with a molecular weight of 0.5 million to 700,000 include natural polymers with a molecular weight of 0.5 million to 700,000, and semi-synthetic polymers with a molecular weight of 0.5 million to 700,000 obtained by chemically modifying natural polymers. Examples of polymer compounds with a molecular weight of 0.5 million to 700,000 include polymer compounds selected from proteins with a molecular weight of 0.5 million to 700,000, protein derivatives with a molecular weight of 0.5 million to 700,000, polysaccharides with a molecular weight of 0.5 million to 700,000, and polysaccharide derivatives with a molecular weight of 0.5 million to 700,000.

[0040] The polymer compound of component (c) may be a synthetic polymer or a natural polymer, as long as it has the aforementioned molecular weight, and may also be a semi-synthetic polymer obtained by chemically modifying a natural polymer.

[0041] Among the polymer compounds of component (c), natural polymers and semi-synthetic polymers obtained by chemically modifying natural polymers include proteins, polysaccharides, and their derivatives.

[0042] Examples of polysaccharides in component (c) include agar, curdlan, biopoly, gum arabic, alginic acid, cellulose, starch, sacran, guar gum, galactomannan, xanthan gum, and carrageenan. Examples of polysaccharide derivatives of component (c) include carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), hydroxypropylcellulose, methylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, and propylene glycol alginate. From the viewpoint of the effect of removing deposits by foaming, polysaccharides and their derivatives having β-bonds with a molecular weight of 700,000 or less are preferred.

[0043] Examples of proteins in component (c) include casein, gelatin, peptone, egg white protein, collagen, pea protein, and soy protein. Examples of protein derivatives of component (c) include sodium caseinate, protein hydrolysates, and protein enzyme hydrolysates.

[0044] Examples of synthetic polymers for component (c) include polyethylene glycol, polypropylene glycol, polyvinyl alcohol, partially saponified polyvinyl acetate, polystyrene sulfonate, poly(meth)acrylic acid-g-polyalkylene glycol, poly(meth)acrylic acid-g-alkoxypolyalkylene glycol, styrene-maleic acid copolymer, isobutylene-maleic acid copolymer, acrylic acid-maleic acid copolymer, and poly(meth)acrylic acid.

[0045] The molecular weight of the polymer compound of component (c) may be 0.5 million or more, further 10,000 or more, further 15,000 or more, and then 700,000 or less, further 500,000 or less, and further 300,000 or less, from the viewpoint of having a large amount of foam and excellent effect in removing sediment.

[0046] Examples of surfactants for component (c) include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactant for component (c) is preferably one or more surfactants selected from anionic surfactants and nonionic surfactants. The surfactant for component (c) is preferably a surfactant with a molecular weight of less than 2000.

[0047] Examples of anionic surfactants include alkyl sulfate salts, alkyl ether sulfate salts, alkanesulfonates, hydroxyalkanesulfonates, fatty acid salts, and alkyl ether carboxylates. Anionic surfactants may have a molecular weight of less than 2000. Salts of anionic surfactants include alkali metal salts. Anionic surfactants may have hydrocarbon groups with 8 to 18 carbon atoms, such as alkyl groups and alkenyl groups.

[0048] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene hydrogenated castor oil, polyoxyethylene castor oil, glycerin fatty acid esters, polyoxyethylene sorbitol fatty acid esters, sorbitan fatty acid esters, and alkyl monoglycerin ethers. Nonionic surfactants may have a molecular weight of less than 2000. Nonionic surfactants may have hydrocarbon groups with 8 to 18 carbon atoms, such as alkyl groups and alkenyl groups.

[0049] Examples of cationic surfactants include alkylamine salts, alkyltrimethylammonium salts, and dialkyldimethylammonium salts. Cationic surfactants may have a molecular weight of less than 2000. Cationic surfactants may have hydrocarbon groups with 8 to 18 carbon atoms, such as alkyl groups and alkenyl groups.

[0050] Examples of amphoteric surfactants include alkyl betaines and alkylamine oxides. Amphoteric surfactants may have a molecular weight of less than 2000. Amphoteric surfactants may have hydrocarbon groups with 8 to 18 carbon atoms, such as alkyl groups and alkenyl groups.

[0051] Component (c) is preferably one or more foam-increasing agents selected from proteins and their derivatives, polysaccharides having β-bonds with a molecular weight of 700,000 or less and their derivatives, anionic surfactants, and nonionic surfactants, from the viewpoint of the effect of removing deposits by foaming, and more preferably one or more foam-increasing agents selected from proteins and their derivatives, and polysaccharides having β-bonds with a molecular weight of 700,000 or less and their derivatives.

[0052] From the viewpoint of safety for living organisms and the environment, component (c) is preferably a foaming agent selected from casein, sodium caseinate, propylene glycol alginate, and hydroxyethylcellulose, which are also designated as food additives. Preferably, all of these have a molecular weight of 700,000 or less.

[0053] Of the components (c), the molecular weight of the polymer compound is the weight-average molecular weight, and for commercially available products, it may be the molecular weight based on the information attached to the product (e.g., catalog value). When measuring, it can be measured by known methods, such as GPC (gel permeation chromatography). When measuring, depending on the object, the following conditions may be adopted, for example. In addition, the molecular weight of the surfactant in component (c) can usually be calculated from its structure. <Polysaccharides and their derivatives> Equipment: HLC-8320 GPC (manufactured by Tosoh Corporation, with integrated detector) Column: GMPWXL + GMPWXL (anion) Eluent: 0.2M phosphate buffer / CH3CN=9 / 1 Flow rate: 0.5mL / min. Column temperature: 40℃ Detector: Schodex RI SE-61 differential refractive index detector Standard substance: Monodisperse polyethylene glycol with known molecular weight <Proteins and their derivatives> Equipment: HLC-8320 GPC (manufactured by Tosoh Corporation, with integrated detector) Column: Agilent Bio SEC-5 Eluent: 150 mM phosphate buffer, pH 7.0 Flow rate: 0.3mL / min. Eluent gradient conditions: Isocratic for 10-30 minutes Column temperature: 30°C Detector: Schodex RI SE-61 differential refractive index detector Standard substance: Monodisperse polyethylene glycol with known molecular weight

[0054] The foaming agent used in the present invention contains, from the viewpoint of ensuring that foam does not remain indefinitely after the foam removal process is complete, but disappears within a reasonable time, component (c) is preferably 0.1 parts by mass or more, preferably 200 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 25 parts by mass or less, per 100 parts by mass of the total of component (a) and component (b).

[0055] The foaming agent used in the present invention may contain surfactants other than anionic and nonionic surfactants in a content of 0.5% by mass or less, more preferably 0.3% by mass or less, more preferably 0.1% by mass or less, or even 0% by mass. Although the surfactants are components that improve foaming, the foaming agent used in the present invention is usually discharged into rivers and the like along with the water-containing sediment after being applied to the sediment, so it is desirable from the standpoint of reducing the content of the surfactants as much as possible to minimize environmental impact. In the present invention, even with such a reduction in the content of the surfactants in the foaming agent, an excellent removal effect is achieved.

[0056] In this invention, as an example of a method for adding a foaming agent to water-containing sediment, when used for removing iron bacteria sludge generated in a tunnel, methods include sprinkling a powder mixture on the surface of the water-containing sediment, placing tablets on the surface of the water-containing sediment, spraying a liquid on the surface of the water-containing sediment, embedding powder inside the water-containing sediment, or embedding tablets inside the water-containing sediment. By these methods, foaming can be caused, and the water-containing sediment can be removed.

[0057] The foaming agent used in the present invention is preferably such that, from the viewpoint of effective removal of water-containing deposits, the maximum foam volume when 10 g of the foaming agent is brought into contact with 40 g of water at 20°C is 160 mL or more, 1000 mL or less, 900 mL or less, 800 mL or less, and 700 mL or less, and the maximum foam volume is reached in 1 second or more, 2 seconds or more, 3 seconds or more, 500 seconds or less, 460 seconds or less, 300 seconds or less, and 200 seconds or less. This maximum foam volume is the maximum amount of foam generated (the highest point reached on the graduated cylinder scale) when 10 g of the foaming agent is placed in a 1000 mL graduated cylinder (63 mm inner diameter, made of plastic) and 40 g of water adjusted to 20°C is added all at once, as shown in the examples described later.

[0058] In this invention, water-containing sediments can be removed with a removal rate of 30% or more, further 40% or more, and even further 50% or more. Here, the removal rate (%) is calculated as [1 - (T1 / T0)] × 100, where T0 is the thickness of the water-containing sediment before the removal operation and T1 is the thickness of the water-containing sediment after the removal operation. Furthermore, even if the removal rate of water-containing sediments in a single treatment is less than 30%, for example, the removal rate of water-containing sediments can be further increased by repeatedly performing removal by foaming.

[0059] In this invention, when removing water-containing sediments by foaming, external forces other than foaming, such as water flow, brush cleaning, or scraping, may be applied to the water-containing sediments. After removing the water-containing sediment by foaming, it can be left as is, or it can be washed with water if necessary. [Examples]

[0060] <Example of experiment> The powdered foaming agent shown in Table 1 was prepared using components (A) to (C) as shown in Table 1. 10 g of the powdered foaming agent was placed in a 1000 mL graduated cylinder (63 mm inner diameter, plastic), and 40 g of water adjusted to 20°C was added all at once. The volume scale at the top of the foam that was generated and rising was observed, and the maximum foam volume and the time to reach the maximum foam volume (referred to as "arrival time" in the table) were recorded. The results are shown in Table 1.

[0061] [Table 1]

[0062] • Sodium caseinate: Tokyo Chemical Industry Co., Ltd., reagent • Carboxymethylcellulose: Daicel Mirise Co., Ltd., CMC Daicel 1190, weight-average molecular weight 820,000 • Hydroxyethylcellulose: Daicel Mirise Co., Ltd., HEC Daicel SP400, weight-average molecular weight 250,000

[0063] <Example 1> (1) Iron bacteria sludge The following tests were conducted on the iron bacteria sludge used in this example. In this example, iron bacteria sludge that had formed in a drain outlet with an inner diameter of 5 cm installed in a retaining wall (Hannan City, Osaka Prefecture) was randomly selected and used.

[0064] (1-1) Flow value measurement test of iron bacteria sludge A polyvinyl chloride cylinder with an inner diameter of 20 mm and a height of 20 mm was placed on a horizontal surface, and iron bacteria sludge was quietly filled into the space inside the cylinder without any gaps. After the top surface was leveled with a smooth metal plate, the cylinder was quietly lifted vertically, and the diameter of the remaining sediment on the horizontal surface was measured. If the diameter was not perfectly circular, the average of the major and minor axes was used as the diameter. The results are shown in Table 2.

[0065] (1-2) Measurement test of solid content of iron bacteria sludge Approximately 3 g of iron bacteria sludge, which had been stirred and homogenized, was accurately weighed into a 100 mL beaker and dried at 105°C for 2 hours. The solid content of the iron bacteria sludge was determined from the difference in mass before and after drying. The results are shown in Table 2.

[0066] (1-3) Test to measure the iron content in the solids of iron bacteria sludge The solid content obtained in (1-2) above was analyzed by atomic absorption spectrophotometric analysis to determine the iron content in the solid content of the iron bacteria sludge. The results are shown in Table 2.

[0067] [Table 2]

[0068] (2) Example 1-1 In a 5cm diameter drain outlet installed in a retaining wall (Hannan City, Osaka Prefecture), 20g of the foaming agent from Experimental Example 2 in Table 1 was moistened with polyethylene glycol 400 (2g), rolled into a ball, and embedded in the 31mm thick iron bacteria sludge. Foaming began immediately, the foam mixed with the iron bacteria sludge, and flow began, gradually being discharged from the drain outlet. Upon inspection of the drain outlet after the foaming stopped, it was confirmed that the iron bacteria sludge had been reduced to a thickness of 3mm (90% removal rate).

[0069] (3) Examples 1-2 In a 5cm diameter drain outlet installed in a retaining wall (Hannan City, Osaka Prefecture), 29mm thick iron bacteria sludge was embedded in the sludge. 20g of the foaming agent from Experimental Example 1 in Table 1 was moistened with polyethylene glycol 400 (2g), rolled into a ball, and embedded in the sludge. Foaming began immediately, the foam mixed with the iron bacteria sludge, and flow began, gradually being discharged from the drain outlet. After the foaming stopped, the inside of the drain outlet was inspected and it was confirmed that the iron bacteria sludge had been reduced to a thickness of 5mm (83% removal rate).

[0070] (4) Examples 1-3 In a 5cm diameter drain outlet installed in a retaining wall (Hannan City, Osaka Prefecture), 20g of the foaming agent from Experimental Example 3 in Table 1 was moistened with polyethylene glycol 400 (2g), rolled into a ball, and embedded in the 32mm thick iron bacteria sludge. Foaming began immediately, the foam mixed with the iron bacteria sludge, and flow began, gradually being discharged from the drain outlet. Upon inspection of the drain outlet after the foaming had finished, it was confirmed that the iron bacteria sludge had been reduced to a thickness of 20mm (removal rate of 37%).

[0071] Based on the results of the examples, the effectiveness of the foaming agents listed in Table 1, which were not used in the examples, in removing iron bacteria sludge can be predicted by comparing their maximum foam volume and time to reach the foaming agent used in the examples.

Claims

1. A method for removing water-containing sediment, comprising using a foaming agent that foams upon contact with water to generate foam in the water-containing sediment at its original location, on and / or within the water-containing sediment, and removing the water-containing sediment by said foaming, The aforementioned water-containing sediment contains 50% by mass or more and 99.5% by mass of water, and also contains metabolites of iron bacteria. A method for removing water-containing sediments, wherein the foaming agent contains the following components (a) and (b). Component (a): One or more compounds selected from organic acids and inorganic acids. Component (b): One or more compounds selected from carbonates and bicarbonates.

2. The method for removing a water-containing sediment according to Claim 1, wherein the water-containing sediment includes a portion that is exposed to the atmosphere.

3. The method for removing water-containing sediment according to Claim 1, wherein the water-containing sediment contains 0.5% by mass or more and 50% by mass or less of solid content.

4. The method for removing water-containing sediment according to claim 1, wherein the water-containing sediment contains iron.

5. The method for removing water-containing sediment according to Claim 1, wherein the flow value of the water-containing sediment is 21 mm or more and 45 mm or less.

6. The method for removing water-containing sediment according to Claim 1, wherein the thickness of the water-containing sediment is 0.1 cm or more and 50 cm or less.

7. The method for removing water-containing sediment according to Claim 1, wherein component (a) is one or more compounds selected from organic acids having 1 to 18 carbon atoms.

8. The method for removing water-containing sediment according to claim 1, wherein the foaming agent is solid.

9. The method for removing water-containing sediment according to claim 1, wherein carbon dioxide is generated by the foaming.

10. The method for removing water-containing sediment according to any one of claims 1 to 9, wherein the water-containing sediment is removed with a removal rate of 30% or more.

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