Organic sludge dewatering agent

Abstract

To provide a sludge dehydrating agent to be used for sludge dehydration treatment, having a deodorant function and higher in performance, and a sludge dehydration method.SOLUTION: A sludge dehydrating agent can deodorize or diminish a sulfur-based odor such as hydrogen sulfide or methyl mercaptan that causes a foul smell and achieve improvement in sludge dehydrating performance by using the sludge dehydrating agent containing water-soluble polymer having a specified composition and isothiazoline compound. It is preferable that a content ratio of the isothiazoline compound to the water-soluble polymer be 0.005-0.1 mass% in a sludge dehydrating agent product.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a water-soluble polymer widely used as a sludge dewatering agent, and more particularly to a sludge dewatering agent containing a water-soluble polymer having a deodorizing effect and improved sludge dewatering performance, and a sludge dewatering method using the same.

Background Art

[0002] Water-soluble polymers are used as sludge dewatering agents for the dewatering treatment of organic sludges such as primary settled sludge sedimented from sewage, excess sludge sedimented from the effluent of an activated sludge tank or mixed raw sludge, digested sludge obtained by anaerobically digesting these sludges, or livestock manure sludge. Polyacrylamide (PAM)-based water-soluble polymers are widely used as general sludge dewatering agents. Sludge added with a sludge dewatering agent is dehydrated with an appropriate dehydrator such as a belt press or a screw press and treated as a dewatered cake. These sludges and dewatered cakes generate sulfur-based odors caused by hydrogen sulfide, methyl mercaptan, etc., which may deteriorate the working environment and living environment in the sludge dewatering process and subsequent treatment processes, posing a problem. Therefore, the application of various compounds has been devised as deodorants for sludge or dewatered cakes. For example, Patent Document 1 discloses a deodorant for dewatered cakes using 1,2-benzisothiazolin-3-one salt. Patent Document 2 discloses a deodorant for sludge or dewatered cakes containing 1,2-benzisothiazolin-3-one and a pyrithione compound. In addition, a method for preventing odor generation using a deodorant and a polymer flocculant in the sludge dewatering process is disclosed. Patent Document 3 discloses a method for preventing odor generation in which a metal salt of 2-mercaptobenzimidazole or a divalent metal salt of 2-mercaptobenzothiazole is added to sludge and then a polymer flocculant is added. Furthermore, a sludge dewatering agent containing a deodorant and a polymer flocculant is disclosed. Patent Document 4 discloses an emulsion-type PAM-based polymer sludge dewatering agent containing terpenes such as menthol and essential oils such as peppermint oil and eucalyptus oil as deodorants. Patent Document 5 discloses a polymer flocculant having a deodorizing function by mixing a PAM-based polymer flocculant with humus soil adsorbed with p-dichlorobenzene and plant essential oils. However, there are cases where a satisfactory deodorizing effect cannot be obtained with these, or where the addition rate needs to be increased to obtain a deodorizing effect or a dewatering effect. Therefore, there is a demand for a more efficient sludge dewatering agent having both a deodorizing effect and a dewatering effect.

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention relates to a sludge dewatering agent used for sludge dewatering treatment, and an object thereof is to provide a sludge dewatering agent and a sludge dewatering method having a deodorizing action and higher performance.

Means for Solving the Problems

[0005] As a result of intensive studies to solve the above problems, it has been found that by using a sludge dewatering agent containing a water-soluble polymer having a specific composition and an isothiazoline-based compound, a deodorizing action can be achieved and an improvement in sludge dewatering performance can be achieved, leading to the present invention.

Effects of the Invention

[0006] By using the sludge dewatering agent in the present invention, it is possible to deodorize or suppress sulfur-based odors such as hydrogen sulfide and methyl mercaptan, which are the causes of bad odors, in organic sludge that generates bad odors and poses a problem, and to achieve an improvement in sludge dewatering performance.

Embodiments for Carrying Out the Invention

[0007] The water-soluble polymer in the present invention comprises 1 to 99 mol% of a cationic monomer represented by the following general formula (1), 0 to 99 mol% of an anionic monomer represented by the following general formula (2), and 1 to 99 mol% of a nonionic monomer as constituent units. Preferably, 20 to 99 mol% of the cationic monomer represented by the general formula (1), more preferably 30 to 99 mol%, and even more preferably 40 to 99 mol%. This is because the higher the proportion of the cationic monomer in the middle to high molar amount, the more versatile it is for different types of sludge. When containing the anionic monomer represented by the general formula (2), preferably 1 to 20 mol% of the anionic monomer, more preferably 1 to 15 mol%. JPEG0007709700000001.jpg2771 General formula (1) R1 is hydrogen or a methyl group, R2 and R3 are alkyl or alkoxy groups having 1 to 3 carbon atoms, R4 is an alkyl or alkoxy group having 1 to 3 carbon atoms, an alkyl group or aryl group having 7 to 20 carbon atoms, A is oxygen or NH, B represents an alkylene group having 2 to 4 carbon atoms, X1 - each represents an anion. TIFF0007709700000002.tif2771 General formula (2) R5 is hydrogen, a methyl group or a carboxymethyl group, Q is SO3 - , C6H4SO3 - , CONHC(CH3)2CH2SO3 - , C6H4COO - or COO - , R6 is hydrogen or COOY2, and Y1 or Y2 each represents hydrogen or a cation.

[0008] As the cationic monomer represented by the general formula (1), it is a quaternary compound of dimethylaminoethyl (meth) acrylate or dimethylaminopropyl acrylamide with a halide of a lower alkyl group such as methyl chloride or ethyl chloride. For example, (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, (meth) acryloyloxy-2-hydroxypropyltrimethylammonium chloride, etc. Two or more of these can be combined without any problem. As the anionic monomer represented by the general formula (2), (meth) acrylic acid or its alkali metal salt or ammonium salt such as sodium salt, maleic acid or its alkali metal salt, acrylamidealkanesulfonic acid such as acrylamide-2-methylpropanesulfonic acid or its alkali metal salt or ammonium salt, etc. are mentioned. Two or more of these can be combined without any problem.

[0009] As the nonionic monomer used in the present invention, (meth) acrylamide, N,N'-dimethylacrylamide, acrylonitrile, 2-hydroxyethyl (meth) acrylate, diacetoneacrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, acryloylmorpholine, etc. are mentioned. Among these, (meth) acrylamide is preferable. Two or more of these can be combined without any problem.

[0010] The water-soluble polymer in the present invention can be produced by known methods. It can be produced by copolymerizing one or more monomers or monomer mixtures selected from cationic monomers, nonionic monomers, and anionic monomers. The copolymerization can be carried out by any polymerization method. For example, after polymerization by aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, dispersion polymerization in salt water, etc., it can be made into any product form such as an aqueous solution, a dispersion in salt water, a water-in-oil emulsion, or a powder. Among these, water-in-oil emulsion polymerization, which is easy to adjust the molecular weight and polymer structure, is preferred.

[0011] In the case of a water-in-oil emulsion, it can be appropriately produced according to the methods described in, for example, JP-A-10-140496 and JP-A-2011-99076. That is, a monomer mixture containing one or more selected from cationic monomers, nonionic monomers, and anionic monomers is mixed with water, an oily substance composed of at least a hydrocarbon immiscible with water, and at least one surfactant having an HLB effective for forming a water-in-oil emulsion, and strongly stirred to form a water-in-oil emulsion, followed by polymerization.

[0012] Examples of the oily substance composed of hydrocarbons used as the dispersion medium include paraffins, naphthenes, or mineral oils such as kerosene, light oil, and middle oil, or hydrocarbon-based synthetic oils having properties such as boiling point and viscosity in substantially the same range as these, or mixtures thereof. The content ranges from 20% to 50% by mass, preferably from 20% to 35% by mass, based on the total amount of the water-in-oil emulsion.

[0013] Examples of at least one surfactant having an HLB and an amount effective to form a water-in-oil emulsion include nonionic surfactants having an HLB of 1 to 15. Specific examples thereof include sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate, polyoxyethylene nonylphenyl ether, and the like. The addition amount of these surfactants is 0.5 to 10% by mass, preferably 1 to 5% by mass, based on the total amount of the water-in-oil emulsion.

[0014] The polymerization concentration of the monomer is in the range of 20 to 60% by mass, and the polymerization concentration and temperature are appropriately set according to the monomer composition and the choice of initiator. The polymerization temperature is in the range of 20 to 80°C, preferably 20 to 60°C. Radical polymerization initiators are used for polymerization initiation. These initiators can be either oil-soluble or water-soluble, and any of azo-based, redox-based, and peroxide-based initiators can polymerize. Examples of oil-soluble azo-based initiators include 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2-methylbutyronitrile), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and the like.

[0015] Examples of water-soluble azo-based initiators include 2,2'-azobis(amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-imidazolin-2-yl)propane] dihydrochloride, 4,4'-azobis(4-cyanovaleric acid), and the like. Examples of redox systems include combinations of ammonium peroxodisulfate with sodium sulfite, sodium bisulfite, trimethylamine, tetramethylethylenediamine, and the like. Further examples of peroxide-based initiators include ammonium or potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy-2-ethylhexanoate, t-butyl hydroperoxide, and the like.

[0016] When producing the water-soluble polymer in the present invention, a crosslinkable monomer can be used as a structure modifier during or after polymerization. From the perspective of product stability when mixed with an isothiazoline-based compound, a crosslinked water-soluble polymer produced by allowing the crosslinkable monomer to be present in the range of 0.00005 to 0.050% by mass based on the total amount of monomers is preferred. Although it varies depending on the monomer composition and polymerization conditions, if it exceeds 0.050% by mass, the crosslinking progresses too much and it becomes water-insoluble, which is not preferable for the use of the present invention. Examples of the crosslinkable monomer include N,N'-methylenebis(meth)acrylamide, triallylamine, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, polyethylene glycol di(meth)acrylate, N-vinyl(meth)acrylamide, N-methylallylacrylamide, glycidyl acrylate, polyethylene glycol diglycidyl ether, acrolein, glyoxal, vinyltrimethoxysilane, etc., and N,N'-methylenebis(meth)acrylamide is preferred.

[0017] Also, it is effective to use isopropyl alcohol in an amount of 0.1 to 5% by mass based on the monomer or sodium formate in an amount of 0.01 to 0.5% by mass based on the monomer in combination to adjust the degree of polymerization.

[0018] After polymerization, if necessary, a hydrophilic surfactant called a phase inversion agent is added to make the emulsion particles covered with an oil film more compatible with water and make the water-soluble polymer therein more easily soluble, and then it is diluted with water and used for each application. Examples of the hydrophilic surfactant include cationic surfactants and nonionic surfactants with an HLB of 9 to 15, such as polyoxyethylene polyoxypropylene alkyl ether-based and polyoxyethylene alcohol ether-based surfactants.

[0019] The water-soluble polymer in the present invention requires a certain molecular weight to exhibit performance as a sludge dewatering agent. In the present invention, the viscosity of a 4% by mass aqueous sodium chloride solution (SLV; viscosity of 0.5% by mass aqueous solution) measured with a rotational viscometer at 25°C when completely dissolved so that the polymer concentration becomes 0.5% by mass can be used as an index of the molecular weight. For the water-soluble polymer in the present invention, the SLV is preferably 5 mPa·s or more and 100 mPa·s or less, more preferably 10 mPa·s or more and 100 mPa·s or less, and even more preferably 10 mPa·s or more and 70 mPa·s or less. This viscosity of the 0.5% by mass aqueous solution is a value measured with a No. 1 rotor at 60 rpm using a B-type viscometer. As the B-type viscometer, Toki Sangyo TVB-10M or the like is used. Incidentally, the polymer solution is prepared by stirring at 800 rpm for 30 minutes. Furthermore, in terms of the weight average molecular weight, 1 million to 8 million is preferable, 2 million to 8 million is more preferable, and 2 million to 6 million is even more preferable.

[0020] The isothiazoline-based compounds in the present invention use one or more selected from 1,2-benzisothiazolin-3-one, N-butyl-1,2-benzisothiazolin-3-one, 2-methylisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 4,5-dichloro-2-methyl-4-isothiazolin-3-one, 2-ethyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-ethyl-4-isothiazolin-3-one, 5-chloro-2-t-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-cyclohexyl-4-isothiazolin-3-one, and their salts. Among these, 1,2-benzisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and their salts are preferred, and 1,2-benzisothiazolin-3-one and its salts are most preferred. This is because when mixed with the water-soluble polymer in the present invention, the product stability tends to be higher compared to other isothiazoline-based compounds.

[0021] The mixing of the water-soluble polymer and the isothiazoline-based compound can be carried out by preparing an aqueous solution containing the isothiazoline-based compound and then mixing it with the water-soluble polymer product. Alternatively, the isothiazoline-based compound can be added to the water-soluble polymer solution for preparation, or the aqueous solution of the isothiazoline-based compound can be prepared and then mixed with the water-soluble polymer solution. From the perspective of practicality, it is preferable to prepare an aqueous solution of the isothiazoline-based compound and mix it with the water-soluble polymer product to obtain a sludge dewatering agent. In this case, the aqueous solution of the isothiazoline-based compound is preferably contained at 1% by mass or less based on the sludge dewatering agent product, although it depends on the aqueous solution concentration. This is because when it exceeds 1% by mass, problems may occur in the stability and solubility of the sludge dewatering agent product. Note that the aqueous solution of the isothiazoline-based compound refers to an isothiazoline-based compound solution containing 50% by mass or more of water.

[0022] When preparing an aqueous solution containing an isothiazoline compound and then mixing it with a water-soluble polymer product, first, in order to dissolve the isothiazoline compound in the aqueous solution, glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, glycol ethers such as propylene glycol ether, diethylene glycol monobutyl ether, ethylene glycol ethyl ether, ethylene glycol monobutyl ether, and alcohols such as methanol, ethanol, propanol, isopropanol are used to dissolve it at an arbitrary concentration. Also, inorganic salts may be used or used in combination during dissolution. Examples of inorganic salts include sodium chloride, potassium chloride, lithium chloride, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, sodium phosphate, potassium phosphate, calcium chloride, magnesium chloride, magnesium sulfate, sodium nitrate, calcium nitrate, magnesium nitrate, etc.

[0023] Furthermore, for adjusting the pH of the isothiazoline compound aqueous solution, one or more of acids such as sulfuric acid, hydrochloric acid, nitric acid, acetic acid, formic acid, sulfamic acid, citric acid, fumaric acid, phthalic acid, succinic acid, adipic acid, oxalic acid, malic acid, salicylic acid or their salts, sodium hydroxide, potassium hydroxide, ferric sulfate, ferric chloride, ferric nitrate, copper sulfate, copper chloride or their hydrates can be added. Adjusting the pH of the isothiazoline compound aqueous solution to 5.8 - 8.0 is preferable because the product stability and effect of the sludge dewatering agent in the present invention tend to be improved. The preparation of these isothiazoline compound aqueous solutions is carried out by mixing treatment under arbitrary mixing conditions using a stirrer, mixer, homogenizer, etc. Forming fine particle colloids by the mixing treatment is preferable because the diffusibility with the water-soluble polymer sample is further enhanced and the effect is improved. It is preferable to adjust the concentration of the isothiazoline compound in the isothiazoline compound aqueous solution to 3 - 20% by mass.

[0024] In addition, as the isothiazoline compound used in the present invention, those commercially available as general industrial raw materials can be used. For example, "PROXEL (registered trademark) GXL" (20% by mass of 1,2-benzisothiazolin-3-one, dipropylene glycol solution), "PROXEL (registered trademark) BDN" (35% by mass of 1,2-benzisothiazolin-3-one, dipropylene glycol solution) commercially available from Lonza Japan Co., Ltd., "ZONEN (registered trademark) FP" (a mixture of 11.2% by weight of 5-chloro-2-methyl-4-isothiazolin-3-one and 1.3% by mass of 2-methyl-4-isothiazolin-3-one, propylene glycol solution) commercially available from Chemclear Co., Ltd., "KATHON (registered trademark) LX1400" (10.6% by weight of 5-chloro-2-methyl-4-isothiazolin-3-one, sodium nitrate-containing solution) commercially available from Rohm and Haas Japan Co., Ltd., "KATHON (registered trademark) WT" (13.9% by weight as a 3:1 mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, magnesium nitrate-containing solution) commercially available from Rohm and Haas Japan Co., Ltd., etc. can be used.

[0025] As the isothiazoline compound, it is preferably contained in the sludge dewatering agent product in an amount of 0.005 to 0.1% by mass. This is because if it is less than 0.005% by mass, a significant improvement in the deodorizing effect and the dewatering effect cannot be obtained, and if it exceeds 0.1% by mass, the stability of the sludge dewatering agent product becomes poor and problems may occur in long-term storage.

[0026] Although the mechanism of action of the sludge dewatering agent in the present invention is unclear, an odor component adsorption action due to a chemical reaction between the sulfur-based odor component in the sludge suspension and the functional group of the isothiazoline compound is obtained. On the other hand, it is presumed that the cross-linking adsorption action between the water-soluble polymer and the suspended substances in the sludge is promoted by blocking the sulfur-based odor component that acts as an aggregation inhibitor, and the aggregation effect is improved. That is, it is considered that the effect of the sludge dewatering agent in the present invention is manifested by the synergism of the odor component adsorption action and the cross-linking adsorption action.

[0027] The sludge types to which the sludge dewatering agent of the present invention can be applied include surplus sludge generated during biological treatment of papermaking wastewater, chemical industry wastewater, food industry wastewater, etc., or organic sludge generated during the treatment of municipal sewage, night soil, and industrial wastewater (so-called raw sludge, surplus sludge, mixed raw sludge, digested sludge, sedimentation / floating sludge, and mixtures thereof), livestock sludge, etc. In particular, it is effective for organic sludge with a high organic content ratio that is more difficult to dewater and prone to odor problems. Specifically, it is sludge with an organic matter content (VSS, loss on ignition in suspended solids, mass% vs. SS) of 45 mass% or more, which is an indicator of organic matter. In recent years, in these organic sludges, VSS and VTS (loss on ignition in evaporation residue, mass% vs. TS) tend to increase, and the effect of the sludge dewatering agent of the present invention becomes more prominent compared to conventional sludge dewatering agents. Therefore, sludge with a VSS of 60 mass% or more is preferred, and 70 mass% or more is even more preferred. Incidentally, various measured values are based on measurements according to standard methods (sewage test methods).

[0028] The sludge dewatering agent in the present invention is diluted with water to an arbitrary concentration and added to these sludges. A range of 0.01 to 1.0 mass% is preferred. The addition rate to the sludge varies depending on the sludge type and the dewatering machine type, but it is 1 to 1000 ppm with respect to the sludge liquid volume. The types of dewatering machines that can be used can be applied to belt presses, centrifugal dewatering machines, screw presses, multi-disc type dewatering machines, rotary presses, filter presses, etc. Also, it may be used in combination with inorganic coagulants such as aluminum sulfate, aluminum chloride, polyaluminum chloride, ferrous polysulfate, ferric polysulfate, and ferric chloride.

Examples

[0029] The sludge dewatering agent in the present invention will be specifically described below, but the present invention is not limited to the following examples.

[0030] (Production of water-soluble polymer sample) Water-soluble polymer samples A to C in the present invention were produced by the conventional method of water-in-oil emulsions disclosed in JP-A-59-130397, JP-A-10-140496, JP-A-2011-99076, etc. These are products commonly used as sludge dewatering agents. Their compositions and physical properties are shown in Table 1.

[0031] (Table 1) TIFF0007709700000003.tif2691Monomer; DMQ: acryloyloxyethyltrimethylammonium chloride, AAM: acrylamide, AAC: acrylic acid Form; EM: water-in-oil emulsion Viscosity of 0.2 mass% aqueous solution: Viscosity (mPa·s) measured at 25 °C when dissolved in water so that the polymer concentration becomes 0.2 mass%. Viscosity of 0.5 mass% saline solution: Viscosity (mPa·s) measured at 25 °C when dissolved in 4 mass% saline so that the polymer concentration becomes 0.5 mass%.

[0032] (Preparation of isothiazoline-based compound aqueous solution) Ferric sulfate heptahydrate, 10 mass% sodium hydroxide, and pure water were added to a dipropylene glycol solution of 1,2-benzisothiazolin-3-one in proportions of 24:15:4:57 mass%, respectively, and mixed. An aqueous solution with a concentration of 5 mass% of 1,2-benzisothiazolin-3-one (pH 6) was prepared.

[0033] (Example 1) (Preparation of sludge dewatering agent) The water-soluble polymer sample A in the above (Table 1) was mixed with the prepared isothiazoline-based compound aqueous solution to prepare sludge dewatering agent samples containing 0.01 to 0.03% of the isothiazoline-based compound with respect to the sludge dewatering agent product. Similarly, water-soluble polymer samples B and C were mixed with the isothiazoline-based compound aqueous solution to prepare sludge dewatering agent samples containing 0.01 to 0.03% of the isothiazoline-based compound with respect to the sludge dewatering agent product. These were used as sludge dewatering agents in the following test examples as Example 1.

[0034] (Example of Performance Test 1, Sludge Dewatering Test) A dewatering test was conducted on livestock sludge generated from a livestock farm (pH 7.2, electrical conductivity 146 mS / m, SS content 14,250 mg / L, VSS 89.5% by mass, VTS 87.5% by mass, M-alkalinity 562 mg / L, anion amount 5.81 meq / L). 200 mL of sludge was collected in a poly beaker, and a 0.2% aqueous solution of a sludge dewatering agent containing 0.02% by mass of the water-soluble polymer sample A of Example 1 and an isothiazoline-based compound (relative to the sludge dewatering agent product) was added at 200 ppm relative to the sludge liquid volume (polymer pure content). After stirring by inverting up and down 10 times, filtration was performed through a 40-mesh sieve, and the filtrate volume was measured. Then, using a nylon filter cloth (#202), the sludge was dehydrated at a press pressure of 3 Kg / cm 2 for 30 seconds, and the cake moisture content (dried at 105°C for 20 hours) was measured. Also, the same test was conducted under the same conditions for the sludge dewatering agent containing 0.02% by mass of the water-soluble polymer sample B of Example 1 and an isothiazoline-based compound. The results are shown in Table 2.

[0035] (Comparative Test Example 1, Sludge Dewatering Test) Using the same sludge as in Performance Test Example 1, the same test as in Performance Test Example 1 was conducted using the water-soluble polymer samples A and B in Table 1. The results are shown in Table 2.

[0036] (Table 2) TIFF0007709700000004.tif2691

[0037] (Example of Performance Test 2, Odor Measurement Test) 200 mL of the same sludge as in Performance Test Example 1 was collected in a poly beaker, and a 0.2% aqueous solution of a sludge dewatering agent containing 0.02% by mass of the water-soluble polymer sample A of Example 1 and an isothiazoline-based compound (relative to the sludge dewatering agent product) was added at 100 ppm relative to the sludge liquid volume (polymer pure content). After stirring by inverting up and down 10 times, 100 mL of the filtered sludge was put into a 300 mL Erlenmeyer flask, the Erlenmeyer flask was sealed with a rubber stopper with a rubber tube attached, fixed in a 40°C water bath, and the hydrogen sulfide (H2S) concentration after 3 hours was measured using a gas detector tube (manufactured by Gastec). Also, the same test was conducted under the same conditions for the sludge dewatering agent containing 0.02% by mass (based on the sludge dewatering agent product) of the water-soluble polymer sample B and the isothiazoline compound of Example 1. The results are shown in Table 3.

[0038] (Comparative Test Example 2, Odor Measurement Test) Using the same sludge as in Test Example 1, the same test as in Test Example 2 was conducted using the water-soluble polymer samples A and B in Table 1. The results are shown in Table 3.

[0039] (Table 3) TIFF0007709700000005.tif3075

[0040] In Test Examples 1 and 2 where the sludge dewatering agent of the present invention was added, compared with the case of using the same kind of water-soluble polymer samples in Comparative Test Examples 1 and 2, the amount of filtrate was larger, the cake moisture content decreased, and the hydrogen sulfide concentration decreased, indicating that the sludge dewatering agent containing the water-soluble polymer and the isothiazoline compound in the present invention has excellent dewatering effect and deodorizing effect.

[0041] (Test Example 3, Sludge Dewatering Test) A dewatering test was conducted on surplus sludge generated from a food factory (pH 7.2, electrical conductivity 199 mS / m, SS content 11750 mg / L, VSS 74.5% by mass, VTS 70.6% by mass, M-alkalinity 980 mg / L, anion amount 6.54 meq / L). 200 mL of sludge was collected in a poly beaker, and a 0.2% by mass aqueous solution of the sludge dewatering agent containing 0.01% by mass (based on the sludge dewatering agent product) of the water-soluble polymer sample A and the isothiazoline compound of Example 1 was added at 175 ppm based on the amount of the sludge liquid (pure polymer content). After stirring 20 times by transferring to another beaker, it was filtered through a 40-mesh sieve and the amount of filtrate was measured. Then, using a nylon filter cloth (#202), the sludge was dewatered at a press pressure of 3 Kg / cm 2 for 60 seconds, and the cake moisture content (dried at 105 °C for 20 hours) was measured. Also, the same test was conducted under the same conditions using other sludge dewatering agent samples of Example 1. The results are shown in Table 4.

[0042] (Comparative Test Example 3, Sludge Dewatering Test) Using the same sludge as in Test Example 3, the same test as in Test Example 3 was conducted using the water-soluble polymer samples A to C in Table 1. The results are shown in Table 4.

[0043] (Table 4) TIFF0007709700000006.tif4991

[0044] (Test Example 4, Sludge Dewatering Test) A dewatering test was conducted on the pressurized floatation floc sludge generated from a food factory (pH 6.5, electrical conductivity 209 mS / m, SS content 81500 mg / L, VSS 95.1 mass%, VTS 94.6 mass%, M-alkalinity 733 mg / L, anion amount 4.85 meq / L). 200 mL of sludge was collected in a poly beaker, and a 0.2 mass% aqueous solution of a sludge dewatering agent containing 0.01 mass% of the water-soluble polymer sample A of Example 1 and an isothiazoline-based compound (polymer pure content) was added at 200 ppm or 350 ppm based on the amount of the sludge liquid. After stirring 20 times by transferring the beaker, filtration was carried out through a 40-mesh sieve, and the amount of filtrate water was measured. Then, the sludge was dehydrated at a press pressure of 3 Kg / cm 2 for 60 seconds using a nylon filter cloth (#202), and the cake moisture content (dried at 105 °C for 20 hours) was measured. Also, the same test was conducted under the same conditions using other sludge dewatering agent samples of Example 1. The results are shown in Table 5.

[0045] (Comparative Test Example 4, Sludge Dewatering Test) Using the same sludge as in Test Example 4, the same test as in Test Example 4 was conducted using the water-soluble polymer sample A in Table 1. The results are shown in Table 5.

[0046] (Table 5) TIFF0007709700000007.tif3091

[0047] (Test Example 5, Sludge Dewatering Test) A dehydration test was carried out on livestock farm-derived livestock manure surplus sludge (pH 7.0, electrical conductivity 719 mS / m, SS content 17,500 mg / L, VSS 40.0 mass%, VTS 39.8 mass%, M-alkalinity 664 mg / L, anion amount 9.83 meq / L). 200 mL of sludge was collected in a poly beaker, and a 0.2 mass% aqueous solution of a sludge dewatering agent containing 0.02 mass% of the water-soluble polymer sample A and isothiazoline compound of Example 1 (based on the sludge dewatering agent product) was added at 75 ppm relative to the sludge liquid volume (polymer pure content). After stirring 10 times by inversion, filtration was carried out through a 40-mesh sieve, and the filtrate volume was measured. Then, using a nylon filter cloth (#202), the sludge was dewatered at a press pressure of 3 Kg / cm 2 for 30 seconds, and the cake moisture content (dried at 105 °C for 20 hours) was measured. Also, the same test was carried out under the same conditions using other sludge dewatering agent samples of Example 1. The results are shown in Table 6.

[0048] (Comparative Test Example 5, Sludge Dewatering Test) Using the same sludge as in Test Example 5, the same test as in Test Example 5 was carried out using the water-soluble polymer samples A and B in Table 1. The results are shown in Table 6.

[0049] (Table 6) TIFF0007709700000008.tif3391

[0050] (Test Example 6, Sludge Dewatering Test) A dehydration test was carried out on sludge generated from a pharmaceutical factory (pH 6.9, electrical conductivity 167 mS / m, SS content 21,500 mg / L, VSS 18.6 mass%, VTS 18.5 mass%, M-alkalinity 21 mg / L, anion amount 4.06 meq / L). 200 mL of sludge was collected in a poly beaker, and a 0.2 mass% aqueous solution of a sludge dewatering agent containing 0.02 mass% of the water-soluble polymer sample A and isothiazoline compound of Example 1 (based on the sludge dewatering agent product) was added at 320 ppm relative to the sludge liquid volume (polymer pure content). After transferring the beaker and stirring 20 times, filtration was carried out through a 40-mesh sieve, and the filtrate volume was measured. Then, using a nylon filter cloth (T-1179L), the sludge was dewatered at a press pressure of 3 Kg / cm 2It was dehydrated for 60 seconds, and the cake moisture content (dried at 105°C for 20 hours) was measured. In addition, the same test was conducted under the same conditions using other sludge dehydrating agent samples of Example 1. The results are shown in Table 7.

[0051] (Comparative Test Example 6, Sludge Dehydration Test) Using the same sludge as in Test Example 6, the same test as in Test Example 6 was conducted using the water-soluble polymer samples A to C in Table 1. The results are shown in Table 7.

[0052] (Table 7) TIFF0007709700000009.tif3391

[0053] (Test Example 7, Sludge Dehydration Test) A dehydration test was conducted on night soil sludge generated from a sewage treatment plant (pH 6.6, electrical conductivity 269 mS / m, SS content 2750 mg / L, VSS 90.0 mass%, VTS 76.5 mass%, M-alkalinity 790 mg / L, anion amount 1.30 meq / L). 200 mL of sludge was collected in a poly beaker, and a 0.2 mass% aqueous solution of a sludge dehydrating agent containing 0.02 mass% of the water-soluble polymer sample C of Example 1 and an isothiazoline-based compound (based on the sludge dehydrating agent product) was added at 40 ppm or 80 ppm (polymer pure content) to the amount of the sludge liquid. After stirring 20 times by transferring the beaker, it was filtered through a 40-mesh screen, and the amount of filtrate was measured. Then, using a nylon filter cloth (#202), the sludge was dehydrated at a press pressure of 3 Kg / cm 2 for 60 seconds, and the cake moisture content (dried at 105°C for 20 hours) was measured. The results are shown in Table 7.

[0054] (Comparative Test Example 7, Sludge Dehydration Test) Using the same sludge as in Test Example 7, the same test as in Test Example 7 was conducted using the water-soluble polymer sample C or A in Table 1. The results are shown in Table 8.

[0055] (Table 8) TIFF0007709700000010.tif3291

[0056] In Test Examples 3 to 7 where the sludge dewatering agent of the present invention was added, the amount of filtered water was larger and the cake moisture content showed a decrease compared to the case where the same kind of water-soluble polymer samples in Comparative Test Examples 3 to 7 were used. It was found that the sludge dewatering agent containing the water-soluble polymer and the isothiazoline-based compound in the present invention has excellent dewatering effects on various sludges.

[0057] (Test Example 8, Odor Measurement Test) Regarding the livestock manure surplus sludge generated from a pig farm (pH 7.4, electrical conductivity 708 mS / m, SS content 23,500 mg / L, VSS 69.1% by mass, VTS 63.4% by mass, M-alkalinity 2,613 mg / L, anion amount 8.73 meq / L) An odor measurement test was conducted. 200 mL of sludge was collected in a poly beaker, and a 0.2% aqueous solution of a sludge dewatering agent containing 0.02% by mass (based on the sludge dewatering agent product) of the water-soluble polymer sample A of Example 1 and the isothiazoline-based compound was added at 300 ppm (polymer pure content) based on the amount of the sludge liquid. After stirring 20 times by transferring to another beaker, 100 mL of the sludge filtered through a 40-mesh sieve was Put into a 300 mL Erlenmeyer flask, the Erlenmeyer flask was sealed with a rubber stopper equipped with a rubber tube, fixed in a 40 °C water bath, and the hydrogen sulfide (H2S) concentration after 2 hours was measured with a gas detector tube (manufactured by Gastech Co., Ltd.). Also, the same test was conducted under the same conditions using other sludge dewatering agent samples of Example 1. These results are shown in Table 9.

[0058] (Comparative Test Example 8, Odor Measurement Test) Using the same sludge as in Test Example 8, the same test as in Test Example 8 was conducted using the water-soluble polymer samples A and B in Table 1. These results are shown in Table 9.

[0059] (Table 9) TIFF0007709700000011.tif3375

[0060] (Test Example 9, Odor Measurement Test) An odor measurement test was conducted on the raw sludge generated from the sewage treatment plant (pH 6.7, electrical conductivity 114 mS / m, SS content 6000 mg / L, VSS 87.5% by mass, VTS 84.6% by mass, M-alkalinity 260 mg / L, anion amount 1.48 meq / L). 200 mL of sludge was collected in a poly beaker, and a 0.2% aqueous solution of a sludge dewatering agent containing 0.01% by mass (based on the sludge dewatering agent product) of the water-soluble polymer sample A and the isothiazoline compound of Example 1 was added at 100 ppm with respect to the sludge liquid volume (pure polymer content). After stirring 20 times by transferring to a beaker, 200 mL of the sludge filtered through a 40-mesh screen was put into a 300 mL Erlenmeyer flask, the Erlenmeyer flask was sealed with a rubber stopper equipped with a rubber tube, fixed in a 40 °C water bath, and the concentrations of hydrogen sulfide (H2S) and methyl mercaptan (CH3SH) after 1 hour were measured with a gas detector tube (manufactured by Gastec Corporation). Also, the same test was conducted under the same conditions using other sludge dewatering agent samples of Example 1. The results are shown in Table 10.

[0061] (Comparative Test Example 9, Odor Measurement Test) Using the same sludge as in Test Example 9, the same test as in Test Example 9 was conducted using the water-soluble polymer samples A to C in Table 1. The results are shown in Table 10.

[0062] (Table 10) TIFF0007709700000012.tif5491

[0063] In Test Examples 8 and 9 to which the sludge dewatering agent according to the present invention was added, the concentrations of hydrogen sulfide or methyl mercaptan decreased compared to the case where the same kind of water-soluble polymer samples of Comparative Test Examples 8 and 9 were used, and it was found that the deodorizing effect of the sludge dewatering agent containing the water-soluble polymer and the isothiazoline compound according to the present invention is excellent.

[0064] It was confirmed that when the sludge dewatering agent containing the water-soluble polymer and the isothiazoline compound according to the present invention is applied to various sludges, particularly organic sludges containing a large amount of organic substances, sulfur-based odors are deodorized or the odor is suppressed, and the sludge dewatering performance is improved.

Claims

1. As the cationic monomer represented by the following general formula (1), 40 to 60 mol% of (meth)acryloyloxyethyltrimethylammonium chloride; as the anionic monomer represented by the following general formula (2), 0 to 5 mol% of an alkali metal salt or ammonium salt such as (meth)acrylic acid or its sodium salt; and as the nonionic monomer, 40 to 55 mol% of (meth)acrylamide. A water-soluble polymer having these as constituent units and, as the isothiazoline compound, at least one selected from 1,2-benzisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, and 2-methyl-4-isothiazolin-3-one, contained in a sludge dewatering agent product in an amount of 0.005 to 0.1% by mass. General formula (1) R １ is a hydrogen or methyl group, R ２ , R ３ is an alkyl or alkoxy group having 1 to 3 carbon atoms, R ４ is an alkyl or alkoxy group having 1 to 3 carbon atoms, an alkyl group having 7 to 20 carbon atoms or an aryl group, A is oxygen or NH, B represents an alkylene group having 2 to 4 carbon atoms, X １ － each represents an anion. General formula (2) R ５ is hydrogen, a methyl group or a carboxymethyl group, Q is SO ３ ― , C ６ H ４ SO ３ ― , CONHC(CH ３ ) ２ CH ２ SO ３ ― , C ６ H ４ COO ― or COO ― , R ６ is hydrogen or COOY ２ , Y １ or Y ２ each represents hydrogen or a cation.

2. The sludge dewatering agent according to claim 1, characterized in that the form of the sludge dewatering agent is a water-in-oil emulsion.

3. A method for dewatering sludge, characterized by adding the sludge dewatering agent according to any one of claims 1 to 2 to the sludge and performing dewatering.

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