JP2013215708A - Amphoteric water-soluble polymer flocculant and method for dehydrating sludge by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an amphoteric water-soluble polymer flocculant which is excellent in sludge dehydrating treatment performance.SOLUTION: An amphoteric water-soluble polymer flocculant is characterized by comprising amphoteric water-soluble polymers which contain 1 to 30 mol% of cationic monomer expressed by general formula (1): CH=C(CH)-CO-X-Q-NRRRZ, 1 to 30 mol% of cationic monomer expressed by general formula (2): CH=CH-CO-X-Q-NRRRZ, 2 to 50 mol% of anionic monomer expressed by general formula (3): RCH=CR-A-B, and 0 to 96 mol% of other monomers. When c1, c2 and a1 denote mol% of the monomers expressed by general formulas (1), (2), (3), respectively, and the range is within 1<c1/c2<2 and 0.8<a1/(c1+c2)<2. Also, the amphoteric water-soluble polymer flocculant comprises the amphoteric water-soluble polymers, and an anionic polymer which has anionic groups and weight average molecular weight of 1,000 to 1,000,000.

Description

  The present invention relates to an amphoteric water-soluble polymer flocculant and a method for dewatering sludge using the same.

  Conventionally, nonionic, cationic, anionic or amphoteric polymer flocculants have been used for the purpose of agglomerating, settling and separating suspensions contained in domestic wastewater and industrial wastewater. In particular, cationic polymer flocculants are frequently used for dewatering treatment of sewage sludge. However, sludge cannot be sufficiently dehydrated due to an increase in the amount of sludge generated and changes in sludge properties.

  In order to solve these problems, sludge dewatering methods using various amphoteric polymer flocculants have been proposed (Patent Documents 1 and 2). However, it is necessary to add a large amount of the conventional amphoteric polymer flocculant to the sludge depending on the type of sludge to be treated. In addition, when a conventional amphoteric polymer flocculant is used, the particle size of flocs formed is reduced and the filtration rate becomes insufficient, so that the throughput per unit time cannot be increased. Therefore, in the sludge dewatering method using the conventional amphoteric polymer flocculant, it is difficult to sufficiently reduce the water content of the obtained dewatered cake.

  In addition, a method for dewatering sludge using an inorganic coagulant and a polymer flocculant has been proposed. Patent Document 3 discloses a sludge dewatering method using an inorganic coagulant and an amphoteric polymer flocculant. However, this method makes it difficult for the dewatered cake to peel off from the filter cloth in the sludge dewatering step. Moreover, the moisture content of the dehydrated cake obtained cannot be reduced sufficiently.

  Patent Document 4 discloses a sludge dewatering method in which an inorganic coagulant is added, the pH is adjusted to 5 to 8, and then an amphoteric polymer flocculant is added. However, this method may not provide a sufficient effect depending on the properties of the sludge to be treated. Sludge properties vary depending on the location of the sludge, and it is difficult to treat sludge with various properties using one type of polymer flocculant. Therefore, there is a need for a sludge dewatering agent and a sludge dewatering method that can be used for sludge having various properties.

JP-A-62-205112 JP-A-53-149292 JP 59-16599 A JP 63-158200 A

  The problem to be solved by the present invention is to provide an amphoteric water-soluble polymer flocculant that solves the above problems and a method of dewatering sludge using the same.

  The inventors of the present invention have studied various water-soluble polymer compounds in order to solve the above problems, and have found that an amphoteric water-soluble polymer flocculant composed of an amphoteric water-soluble polymer having a predetermined structure is used for sludge dewatering treatment. It has been found that when used, it exhibits superior dehydration performance compared to conventional amphoteric water-soluble polymer flocculants. Moreover, it has been found that by including a polymer compound having a predetermined anionic group in the amphoteric water-soluble polymer flocculant, further excellent dehydration performance is exhibited, and the present invention has been completed. The present invention for achieving the above object is described below.

[1] At least the following general formula (1)
_{CH 2 = C (CH 3)} -CO-X-Q-N + R 1 R 2 R 3 · Z - (1)
[In the formula (1), X is O or NH, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, R ¹ is an alkyl group or benzyl group having 1 to 3 carbon atoms, R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Z ⁻ represents a counter anion. ]
1 to 30 mol% of a structural unit derived from a cationic monomer represented by the following general formula (2)
^{_{CH 2 = CH-CO-X}} -Q-N + R 1 R 2 R 3 · Z - (2)
[In the formula (2), X is O or NH, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, R ¹ is an alkyl group or benzyl group having 1 to 3 carbon atoms, R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Z ⁻ represents a counter anion. ]
1 to 30 mol% of a structural unit derived from a cationic monomer represented by the following general formula (3)
R ⁴ CH = CR ⁵ -A-B ¹ (3)
[In Formula (3), R ⁴ is a hydrogen atom, a methyl group or COOB ² , R ⁵ is a hydrogen atom, a methyl group or CH ₂ COOB ² , A is COO, SO ₃ , C ₆ H ₅ SO ₃ , CONHC (CH ₃₎ a ₂ CH ₂ SO ₃ or _C 6 _H 5 COO, ^{B 1} and ^{B 2} represents a hydrogen atom or a cation. ]
2 to 50 mol% of a structural unit derived from an anionic monomer represented by formula (0) and 0 to 96 mol% of a structural unit derived from another monomer, and represented by the general formulas (1), (2), ( When the mole% of the monomer represented by 3) is c1, c2, and a1, respectively,
An amphoteric water-soluble polymer flocculant comprising an amphoteric water-soluble polymer satisfying 1 <c1 / c2 <2, 0.8 <a1 / (c1 + c2) <2.

[2] The cationic monomer represented by the general formula (1) is a methyl chloride quaternized product of dimethylaminoethyl methacrylate, and the cationic monomer represented by the general formula (2) is methyl chloride 4 of dimethylaminoethyl acrylate. The amphoteric water-soluble polymer flocculant according to [1], which is a graded product.

[3] The amphoteric water-soluble polymer and an anionic water-soluble polymer having an anionic group and having a weight average molecular weight of 1,000 to 1,000,000 are described in [1] or [2] Amphoteric water-soluble polymer flocculant.

[4] The amphoteric water-soluble polymer according to any one of [1] to [3], wherein the amphoteric water-soluble polymer is a polymer polymerized in the presence of the anionic water-soluble polymer. Molecular flocculant.

[5] An anionic water-soluble polymer is represented by the following general formula (4)
^{_{CH 2 = CR 6 -COOM (4}} )
[In the formula (4), R ⁶ represents a hydrogen atom or a methyl group, M represents a hydrogen atom, an ammonium ion, an alkali metal ion or an alkaline earth metal ion. ]
The amphoteric water-soluble polymer flocculant according to any one of [1] to [4], comprising a structural unit derived from an anionic monomer represented by the formula:

[6] A method for dewatering sludge, comprising adding the amphoteric water-soluble polymer flocculant according to any one of [1] to [5] to the sludge for dehydration.

[7] After adding an organic cationic coagulant and / or an inorganic coagulant to the sludge, the amphoteric water-soluble polymer flocculant according to any one of [1] to [5] is added for dehydration. Characterized sludge dewatering method.

[8] After adding an organic cationic coagulant and / or an inorganic coagulant to the sludge, the pH (25 ° C.) of the sludge is adjusted to 4 to 7, and then any one of [1] to [5] A method for dewatering sludge, comprising adding the amphoteric water-soluble polymer flocculant described above to dehydrate.

[9] The sludge dewatering method according to any one of [6] to [8], wherein the sludge is organic sludge.

  The amphoteric water-soluble polymer flocculant of the present invention exhibits a high coagulation action on a wide range of sludge, and when this is used for sludge dewatering treatment, the floc formed is high in strength and has a high filtration rate. Moreover, the moisture content of the dehydrated cake obtained is also low.

Hereinafter, the present invention will be described in detail.
In this specification, an acryloyl group or a methacryloyl group is represented as a (meth) acryloyl group, acrylic acid or methacrylic acid is represented as (meth) acrylic acid, and acrylate or methacrylate is represented as (meth) acrylate.

(A) Amphoteric water-soluble polymer flocculant The amphoteric water-soluble polymer and the anionic water-soluble polymer, which are water-soluble polymers used as the amphoteric water-soluble polymer flocculant in the present invention, will be described below.

(A-1) Amphoteric water-soluble polymer In the structure represented by the above formula (1), which is a structural unit of polymerization, as a counter anion, halogen ions such as chlorine ions, sulfate ions, nitrate ions, phosphate ions, Mention may be made of methylsulfonate ions. The cationic monomer represented by the above formula (1) is preferably a dimethylaminoethyl methacrylate salt, a quaternized product such as methyl chloride or benzyl chloride, and more preferably a dimethylaminoethyl methacrylate methyl chloride quaternized product.

  In the structure represented by the above formula (2) serving as a structural unit for polymerization, the same as the above formula (1) can be used as the counter anion. The cationic monomer represented by the above formula (2) is preferably a dimethylaminoethyl acrylate salt, a quaternized product such as methyl chloride or benzyl chloride, and more preferably a methyl chloride quaternized product of dimethylaminoethyl acrylate.

  Specific examples of the anionic monomer represented by the above formula (3) serving as a structural unit for polymerization include (meth) acrylic acid and salts thereof; unsaturated carboxylic acids such as crotonic acid, itaconic acid and maleic acid; Examples thereof include acrylamidoalkylalkanesulfonic acid such as acrylamido-2-methylpropanesulfonic acid and salts thereof, and vinylsulfonic acid and salts thereof and 4-vinylbenzoic acid and salts thereof. Examples of the salt include ammonium salts and alkali metal salts such as sodium and potassium. Among these, (meth) acrylic acid and its salt are preferable.

  The amphoteric water-soluble polymer of the present invention can be obtained by polymerizing a monomer mixture containing at least one of the above cationic monomer and anionic monomer. Furthermore, you may copolymerize with another monomer.

Examples of other monomers include nonionic monomers and hydrophobic monomers.
As the nonionic monomer, various compounds can be used as long as they have radical polymerizability. Specifically, dialkyl (meth) acrylamides such as (meth) acrylamide, dimethyl (meth) acrylamide and diethyl (meth) acrylamide are used. , Hydroxyalkyl (meth) acrylates such as hydroxylethyl (meth) acrylate, dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate, dialkylaminoalkyl (meth) acrylamides such as dialkylaminopropyl (meth) acrylamide, etc. Can be mentioned. Among these, (meth) acrylamide is preferable.

Also, other hydrophobic monomers can be used as long as the effects of the present invention are not impaired.
As the hydrophobic monomer, various compounds can be used as long as they have radical polymerizability. Specifically, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, ethyl carbitol (meth) acrylate, methyl (Meth) acrylate, ethyl (meth) acrylate, vinyl acetate and the like can be mentioned. These other monomers may be used alone or in combination of two or more.

  In the amphoteric water-soluble polymer, the structural unit derived from the cationic monomer represented by the formula (1) is 1 to 30 mol%, preferably 5 to 30 mol%, more preferably 5 to 25 mol%. preferable. Moreover, the structural unit derived from the cationic monomer represented by the said Formula (2) is 1-30 mol%, 5-30 mol% is preferable and 5-25 mol% is more preferable. Furthermore, the structural unit derived from the anionic monomer represented by the above formula (3) is 2 to 50 mol%, preferably 5 to 40 mol%, more preferably 10 to 40 mol%. Furthermore, the structural unit derived from another monomer is in the range of 0 to 96 mol%.

  Further, the amphoteric water-soluble polymer has a ratio of 1 <c1 / c2 <2 when the molar percentages of the monomers represented by the formulas (1), (2), and (3) are c1, c2, and a1, respectively. 1 <c1 / c2 <1.5 is preferable, and 1 <c1 / c2 <1.1 is more preferable. Further, 0.8 <a1 / (c1 + c2) <2, preferably 0.8 <a1 / (c1 + c2) <1.5, and particularly preferably 0.8 <a1 / (c1 + c2) <1.1. If it is out of this range, the wastewater treatment performance deteriorates.

As is clear from the relationship between the contents of the above monomers, the amphoteric water-soluble polymer of the present invention contains the anionic monomer at the same level as the cationic monomer or more than the cationic monomer. Such an amphoteric water-soluble polymer is particularly effective in dewatering sludge when an inorganic coagulant is used in combination.
Further, the amphoteric water-soluble polymer of the present invention contains both methacrylate and acrylate monomers as the cationic monomer, and the content of the methacrylate cationic monomer is higher than the content of the acrylate cationic monomer. It is a feature. Since the methacrylate-based cationic monomer has a methyl group bonded to the α-carbon, the methacrylate-based cationic monomer has a feature of higher hydrophobicity than the acrylate-based cationic monomer. Therefore, it contains only acrylate-based cationic monomers and sludge when it is used as a flocculant because of its superior dehydration effect compared to amphoteric water-soluble polymers that contain both but have a high content of acrylate-based cationic monomers. The water content is reduced, and good peelability is exhibited for belts and filter cloths. However, there is a problem that methacrylate-based cationic monomers have poor granulation properties of flocs formed when sludge is treated as compared with acrylate-based cationic monomers. In addition, methacrylate-based cationic monomers are less reactive in radical polymerization reactions than acrylate-based cationic monomers, and there are problems in terms of copolymerization and high molecular weight. Therefore, when only a methacrylate-based cationic monomer is used, it may be difficult to obtain a polymer that satisfies the required physical properties and performance. Therefore, an amphoteric water-soluble polymer excellent in aggregating performance can be obtained by polymerizing using both methacrylate and acrylate monomers as cationic monomers and using more methacrylate monomers than acrylate monomers.

  As the polymerization method for obtaining the amphoteric water-soluble polymer, radical polymerization is preferable. As the radical polymerization method, conventionally known radical polymerization methods such as bulk polymerization, suspension polymerization, emulsion polymerization, and aqueous gel polymerization can be used. Among these radical polymerization methods, aqueous solution gel polymerization and emulsion polymerization are preferred from the viewpoint of production cost and ease of handling of the polymer.

  Which polymerization method is used is appropriately selected depending on the physical properties required for the polymer flocculant. When the degree of crosslinking is high, it is preferable to select emulsion polymerization, and when it is low, aqueous gel polymerization is selected.

  As the polymerization initiator in radical polymerization, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide atom, peracetic acid, t-butyl hydride peroxide, benzoyl peroxide, peroxide such as di-t-butyl peroxide, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, azobiscyanovaleric acid, 2,2'-azobisisobutyronitrile and 2,2'-azobis [2-methyl-N- (2 -Hydroxyethyl) -propionamide], azo initiators such as azobiscyanovaleronitrile, azobisisobutyronitrile, peroxides such as hydrogen peroxide and sodium persulfate, sodium bisulfite, potassium bisulfite, A redox initiator composed of a combination with a reducing agent such as ferrous sulfate and ascorbic acid, and a photopolymerization initiator, It can be properly used in accordance with the focus method. The amount of the polymerization initiator used is preferably 0.001 to 5% by mass with respect to the total mass of the monomers.

  Moreover, you may use a chain transfer agent as needed. Examples of chain transfer agents include alcohols such as methanol, isopropyl alcohol, ethylene glycol and propylene glycol, amines such as methylamine and dimethylamine, thiols such as methanethiol and ethanethiol, methallylsulfonic acid and salts thereof Etc.

  Moreover, you may use a crosslinking agent as needed. Examples of the crosslinking agent include N, N-methylenebis (meth) acrylamide, glycidyl acrylate, ethylene glycol dimethacrylate, N-vinylacrylamide and the like.

  When the water-soluble polymer used in the present invention is produced by aqueous gel polymerization or emulsion polymerization, it can be produced under known polymerization conditions.

  In the case of aqueous gel polymerization, the polymerization initiation temperature is preferably 0 to 35 ° C. The polymerization time is preferably from 0.1 to 3 hours. The polymerization reaction is preferably carried out in an inert atmosphere in the absence of oxygen. In the case of aqueous gel polymerization, the concentration of the monomer mixture is preferably 25 to 60% by mass, particularly preferably 30 to 50% by mass. The pH of the aqueous monomer solution is preferably adjusted to 2-4. After completion of the polymerization reaction, heat treatment or drying is appropriately performed as necessary.

  In the case of emulsion polymerization, in order to form a water-in-oil emulsion, an aqueous phase containing the predetermined monomer, radical initiator, chain transfer agent, etc. used in the present invention, an oily substance consisting of immiscible hydrocarbon atoms And an effective amount of a surfactant to form a water-in-oil emulsion. A water-soluble polymer used in the present invention can be synthesized by polymerizing the formed water-in-oil emulsion.

  Examples of oily substances include paraffins, various mineral oils, hydrocarbon atomic oils having characteristics equivalent to these, and mixtures thereof. The content of the oily substance is 20% by mass to 50% by mass, preferably 25% by mass to 40% by mass with respect to the total amount of the water-in-oil emulsion.

  The surfactant for forming the water-in-oil emulsion preferably has an HLB of 3-11. Examples of such surfactants include nonionic surfactants such as sorbitan monooleate and sorbitan monostearate. The effective addition amount of these surfactants is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass with respect to the total amount of the water-in-oil emulsion.

  When emulsion polymerization is performed, the polymerization conditions are appropriately set according to the monomers and initiators used and the physical properties of the polymer. Polymerization temperature is 0-100 degreeC, 20-80 degreeC is preferable and 20-60 degreeC is more preferable. The polymerization concentration of the monomer is preferably 20 to 50% by mass, and more preferably 25 to 40% by mass. The polymerization reaction is preferably performed in an inert atmosphere free of oxygen. The polymerization time is preferably 1 to 10 hours, more preferably 2 to 6 hours.

  The 0.5% salt viscosity of the amphoteric water-soluble polymer of the present invention is preferably 10 to 60 mP · s, more preferably 15 to 50 mP · s, and still more preferably 20 to 50 mP · s. If it is 10 mPa · s or less, the cohesive force is insufficient and a sufficient dehydrating effect is not exhibited. If the viscosity is 60 mPa · s or more, the solution viscosity becomes too high and the dispersibility in the sludge during the agglomeration treatment is poor, or the agglomerate becomes sticky and the peelability is lowered. The molecular weight can be adjusted by a known method such as the use of a polymerization catalyst concentration, a crosslinking agent, or a chain transfer agent. By adding an amphoteric water-soluble flocculant containing such an amphoteric water-soluble polymer to waste water, dehydration treatment can be performed effectively.

(A-2) Anionic water-soluble polymer The amphoteric water-soluble polymer flocculant of the present invention exhibits a sufficient effect only with the amphoteric water-soluble polymer, but the anionic water-soluble polymer described in detail below. When used in combination, it exhibits even better effects.
The anionic water-soluble polymer preferably has an anionic monomer of the above formula (4) as a structural unit. As the anionic monomer represented by the above formula (4), acrylic acid and methacrylic acid and salts thereof are preferable, and as the alkali metal ion, Na ⁺ and K ⁺ are preferable.

  The weight average molecular weight of the anionic water-soluble polymer of the present invention is 1,000 to 1,000,000, preferably 5,000 to 500,000, and particularly preferably 8,000 to 250,000. When the weight average molecular weight is less than 1000, the aggregation ability is poor. On the other hand, when the weight average molecular weight exceeds 1,000,000, the insoluble matter increases and it is difficult to exhibit the function as a flocculant. The weight average molecular weight of the anionic water-soluble polymer is a value measured by gel permeation chromatography using standard PEO as a molecular weight standard.

As the polymerization method, aqueous gel polymerization, reverse phase suspension polymerization, reverse phase emulsion polymerization and the like can be employed. Aqueous gel polymerization is preferred because it can be easily and easily handled.
An anionic water-soluble polymer is produced by polymerization of an unsaturated carboxylic acid monomer having one vinyl group. Particularly preferred are polymer compounds produced by polymerization of (meth) acrylic acid.

  The anionic water-soluble polymer can be obtained by polymerization using a known polymerization method. The known polymerization method is as described above.

In the polymerization, other anionic monomers that can be copolymerized or other monomers may be contained. Although it does not restrict | limit especially as a monomer which can be copolymerized, The same thing as the anionic monomer used for manufacture of the said amphoteric water-soluble polymer and another monomer can be used. These other copolymerizable monomers may be used alone or in admixture of two or more.
Commercially available poly (meth) acrylic acid (salts) can also be used as the anionic water-soluble polymer.

(A-3) Amphoteric water-soluble polymer flocculant containing an amphoteric water-soluble polymer and an anionic water-soluble polymer The amphoteric water-soluble polymer flocculant of the present invention exhibits a sufficient effect even with only the amphoteric water-soluble polymer. However, the amphoteric water-soluble polymer described in the above (a-1) and the anionic water-soluble polymer described in the above (a-2) are further improved.

  When the amphoteric water-soluble polymer flocculant is a mixture of an amphoteric water-soluble polymer and an anionic water-soluble polymer, the amount of the anionic water-soluble polymer to the amphoteric water-soluble polymer is On the other hand, it is 0.1-10 mass%, 0.5-8 mass% is preferable and 0.75-5 mass% is especially preferable. When the blending amount is less than 0.1% by mass, the effect of the aggregating ability of the obtained aggregating agent is the same as that of the composition containing no anionic water-soluble polymer. On the other hand, when it exceeds 10% by mass, the resulting polymer is insolubilized and does not function as a flocculant.

  The mixing method may be mixing the anionic water-soluble polymer and the amphoteric water-soluble polymer in a dry powder state, or mixing each solution of the anionic water-soluble polymer and the amphoteric water-soluble polymer, respectively. good. Moreover, you may mix by melt | dissolving the other dry powder in one solution of an anionic water-soluble polymer or an amphoteric water-soluble polymer.

  The amphoteric water-soluble polymer flocculant of the present invention is particularly preferable when the amphoteric water-soluble polymer described in the above (a-1) is produced in the presence of the anionic water-soluble polymer (a- This is a method using an amphoteric water-soluble polymer obtained by polymerizing the monomer mixture described in 1).

  In the amphoteric water-soluble polymer flocculant containing the anionic polymer of the present invention, it is preferable that a part of the anionic water-soluble polymer and the amphoteric water-soluble polymer are chemically bonded. That is, the amphoteric water-soluble polymer flocculant of the present invention comprises a main chain having a cationic monomer unit and an anionic monomer unit, and a side chain having an anionic group and having a weight average molecular weight of 1,000 to 1,000,000. It is preferable to comprise a graft copolymer.

  The amphoteric water-soluble polymer flocculant produced by such a method has a main chain having a cationic monomer unit and an anionic monomer unit, a side chain having an anionic group and a weight average molecular weight of 1,000 to 1,000,000, It is thought that the graft copolymer comprised from this is included.

  The amount of the anionic water-soluble polymer based on the monomer mixture is 0.1 to 10% by mass, preferably 0.1 to 8% by mass, and 0.3 to 5% by mass with respect to the monomer mixture. Particularly preferred. When the blending amount is less than 0.1% by mass, the effect of the aggregation ability of the obtained polymer is not different from that of the polymer containing no anionic water-soluble polymer. On the other hand, when it exceeds 10% by mass, the resulting polymer is insolubilized and does not function as a flocculant.

  The polymerization method is not particularly limited, and can be obtained by polymerization using a known polymerization method. Known polymerization methods are as described above, and aqueous gel polymerization that can be easily and easily handled is preferred.

The amphoteric water-soluble polymer flocculant produced by such a method is considered to be a mixture of an anionic water-soluble polymer, an amphoteric water-soluble polymer, and a graft copolymer. The graft copolymer is preferably contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the amphoteric water-soluble polymer flocculant.
The weight average molecular weight of the graft copolymer is 1 million to 20 million.

The reason why this graft copolymer exhibits good dehydration performance is presumed to be that an anionic group localized away from the main chain can be effectively neutralized with an organic cationic coagulant or an inorganic coagulant.
The amphoteric water-soluble polymer flocculant of the present invention may be added with additives such as an antifoaming agent, an antioxidant and a pH adjuster as long as the effects of the present invention are not impaired.

(B) Sludge dewatering method In the sludge dewatering treatment using the amphoteric water-soluble polymer flocculant of the present invention, the sludge to be treated is not particularly limited. Sewage, human waste, and domestic wastewater treatment sludge, food factory wastewater treatment sludge, chemical factory wastewater treatment sludge, pig farm wastewater treatment sludge, and organic sludge generated in general industrial wastewater (so-called raw sludge, surplus sludge, etc.) Mixed sludge, digested sludge, coagulated sedimentation / floating sludge, and mixtures thereof), and mixed sludge containing coagulated sedimented sludge.

  Specifically, in the dehydration method, if necessary, an inorganic coagulant and / or an organic cationic coagulant is added to the sludge, and the pH is preferably adjusted to 4-7. As a method for adjusting the pH, after adding an inorganic coagulant or an organic cationic coagulant, when the pH value is satisfied, there is no need for pH adjustment, but when the range limited in the present invention is not satisfied, Adjust by adding acid or alkali. Examples of the acid include hydrochloric acid, sulfuric acid, acetic acid and sulfamic acid. Examples of the alkali include caustic soda, caustic potash, slaked lime, and ammonia. Thereafter, the amphoteric polymer flocculant of the present invention is added to the sludge to form a sludge floc. In addition, when aiming at deodorization, dephosphorization, denitrification, etc., it is preferable that pH is less than 5. The flock formation method is in accordance with a known method.

  Examples of the inorganic coagulant include sulfate band, polyaluminum chloride, aluminum chloride, ferric chloride, ferrous sulfate, and polyferric sulfate.

  Examples of organic cationic coagulants include (meth) acryloyloxyethyltrimethylammonium chloride polymer, (meth) acrylamide copolymer, epichlorohydrin and dimethylamine condensate, polyethyleneimine hydrochloride, polyallylamine hydrochloride, Examples thereof include polydimethyldiallylammonium chloride, polyamidine, and a cationic surfactant.

Each addition amount of an amphoteric water-soluble polymer flocculant, an inorganic coagulant, and an organic cationic coagulant, a stirring speed, a stirring time, etc. are based on conventionally well-known conditions.
The amphoteric water-soluble flocculant of the present invention may be used in combination with other cationic polymers or anionic polymers.

The formed floc is dehydrated by a known means to obtain a dehydrated cake.
Examples of the dehydrator include a screw press dehydrator, a belt press dehydrator, a filter press dehydrator, and a screw decanter.

Moreover, the flocculant of this invention is applicable also to the dehydration method which uses the granulation concentration tank which has a filtration part.
Specifically, after adding an inorganic coagulant and / or an organic cationic coagulant to sludge, and further adding a polymer flocculant, or together with the polymer flocculant, the granulation concentration tank having the filtration unit for the sludge And a method of taking out the filtrate from the filtration unit and granulating it, and dehydrating the granulated product with a dehydrator.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
The measuring method of each physical property is as follows. The temperature condition for measuring various physical properties is 25 ° C. unless otherwise specified.

[0.5% salt viscosity]
Add 20.8 g of sodium chloride to 500 mL of pure water and 0.5% by mass of the sample (polymer), and screw blades (about 6 cmφ) in a constant temperature water bath at 25 ± 1 ° C. until the sample is completely dissolved. Was stirred at 200 rpm. The viscosity of this sample solution was read for 3 minutes at 60 rpm and 25 ± 1 ° C. using a TV-10M type B viscometer manufactured by Toki Sangyo Co., Ltd. with an M1 rotor. The salt viscosity was used. When the viscosity exceeded the measurement upper limit of the M1 rotor, the M2 rotor was used.
A sample solution was prepared. Using a B-type rotational viscometer, the viscosity of this sample solution at 25 ° C. was measured.

[10 seconds filtration rate]
The sludge floc dispersion was gravity filtered using a resin filter cloth filter with a 60 mesh screen (mesh opening 273 μm). The volume of the filtrate after 10 seconds was measured, and this was defined as a 10-second filtration rate.

[Filter cloth peelability]
The filtered sludge floc was squeezed at 170 kPa for 3 minutes using a test belt press machine to perform a dewatering test of the sludge, and the peelability of the dewatered cake from the filter cloth after the test was evaluated according to the following criteria.
A: Very easy to peel off (almost no filter cloth deposits)
○: Easy to peel off (slightly attached filter cloth)
Δ: Hard to peel off (many filter cloth deposits)

[Moisture content]
The dehydrated cake after the belt press was weighed in an aluminum pan, dried in a circulating drier at 105 ° C. for 16 hours, the weight of the dried cake was measured, and the water content was calculated.

[Flock diameter]
It was measured visually.

(Production example)
In a stainless steel reaction vessel, sodium polyacrylate (hereinafter abbreviated as “PANa”), 79% dimethylaminoethyl acrylate methyl chloride quaternary salt (hereinafter abbreviated as “DAC”) aqueous solution, 78% dimethylaminoethyl methacrylate Put methyl chloride (hereinafter abbreviated as “DMC”), 50% acrylamide (hereinafter abbreviated as “AM”) aqueous solution, acrylic acid (hereinafter abbreviated as “AA”), add distilled water and add the total mass Was 1 kg. The blending ratio of each monomer is shown in Table 1. The concentration of each monomer in this solution is 40% by mass in total.

The solution was adjusted to pH = 4, and the solution temperature was adjusted to 20 ° C. while nitrogen gas was blown into the solution for 60 minutes. Thereafter, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (hereinafter abbreviated as “V-50”) was added to 1500 ppm with respect to the total mass of each monomer. Subsequently, the solution was polymerized by irradiating light from above the reaction vessel with a 13 W black light at an irradiation intensity of 0.4 mW / cm ² for 60 minutes to obtain a hydrogel polymer. The obtained hydrogel polymer was taken out of the container and chopped. This was dried at a temperature of 80 ° C. for 5 hours and then pulverized to obtain a powdery polymer A11. A sample of the obtained polymer A11 was taken, and 0.5% salt viscosity was measured with a B-type viscometer. The 0.5% salt viscosity was 22.2 mPa · s.

  Polymers A1 to A10, A12 to A16, B1 are prepared by appropriately adjusting the reaction conditions in the same manner as in Production Examples, except that the molecular weight and blending ratio of PANa and the blending ratio of each monomer are changed as described in Table 1. ~ B4 was obtained.

(Examples 1-16, Comparative Examples 1-4)
200 mL of organic sludge (pH 7.8, suspended matter (SS) = 12,500 mg / L, total evaporation residue (TS) = 29200 mg / L) collected from a chemical factory was placed in a 300 mL beaker. To this organic sludge, 2000 ppm of ferric sulfate was added until the pH reached 5.0. To this, a 0.1 mass% aqueous solution of the flocculant shown in Table 1 was added in an amount of 100 ppm in terms of solid content with respect to the sludge weight. The mixed sludge was stirred at 300 rpm for 1 minute using a jar tester to form a sludge floc, and the floc diameter was measured visually. Then, using a test belt press, the sludge was dehydrated by pressing at 170 kPa for 3 minutes to obtain a dehydrated cake.
The floc diameter and the 10-second filtration rate of the sludge floc and the water content of the dewatered cake were measured, and the results are shown in Table 2.

  Examples 1-16 used the predetermined amphoteric water-soluble flocculant of the present invention. The flocculant of the present invention has a higher filtration rate for 10 seconds than the flocculant of the comparative example, and the water content of the resulting dehydrated cake is also low. Moreover, the peelability of the filter cloth was also good. Further, Examples 11 to 16 using a flocculant containing an amphoteric water-soluble polymer and an anionic polymer showed better results than Examples 1 to 10 using a flocculant containing no anionic polymer. It was.

In Comparative Examples 1 and 2, c1 / c2 of the flocculant deviated from the specified range of the present invention. The results were inferior to Examples 1-16 in both the 10 second filtration rate and the cake moisture content.
In Comparative Examples 3 and 4, a1 / (c1 + c2) of the flocculant deviated from the specified range of the present invention. As a result, both the 10 second filtration rate and the cake moisture content were inferior to those of Examples 1-16.

(Examples 17 to 32, Comparative Examples 5 to 8)
200 mL of mixed sludge (set to pH 5.7, SS = 10500 mg / L, TS = 13200 mg / L) composed of coagulated sludge and excess sludge collected from a public sewage treatment plant was collected in a 300 mL beaker. To this sludge, 2500 ppm of polyferric sulfate (18.9 mass% with respect to TS of sludge) was added. The pH was 4.3. To this, a 0.1% by mass aqueous solution of each polymer shown in Table 1 was added in an amount of 1.2% by mass with respect to the sludge TS. Using a jar tester, this sludge was stirred at 200 rpm for 1 minute to form a sludge floc, and the floc diameter was visually measured. Then, using a test belt press, the sludge was dehydrated by pressing at 170 kPa for 3 minutes to obtain a dehydrated cake.
The floc diameter and sludge floc diameter of the sludge floc and the water content of the dewatered cake were measured. The results are shown in Table 3.

  In Examples 17 to 32, the predetermined amphoteric water-soluble flocculant of the present invention was used. The flocculant of the present invention has a higher filtration rate for 10 seconds than the flocculant of the comparative example, and the water content of the resulting dehydrated cake is also low. Moreover, the peelability of the filter cloth was also good. Furthermore, Examples 27 to 32 using an aggregating agent containing an amphoteric water-soluble polymer and an anionic polymer showed better results than Examples 17 to 26 using an aggregating agent containing no anionic polymer. It was.

In Comparative Examples 5 and 6, c1 / c2 of the flocculant deviated from the specified range of the present invention. The results were inferior to Examples 17-32 in both the 10 second filtration rate and the cake moisture content.
In Comparative Examples 7 and 8, a1 / (c1 + c2) of the flocculant deviated from the specified range of the present invention. The results were inferior to Examples 17-32 in both the 10 second filtration rate and the cake moisture content.
That is, the flocculant of the present invention is superior in performance to the flocculant of the comparative example.

Claims (9)

At least the following general formula (1)
_{CH 2 = C (CH 3)} -CO-X-Q-N + R 1 R 2 R 3 · Z - (1)
[In the formula (1), X is O or NH, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, R ¹ is an alkyl group or benzyl group having 1 to 3 carbon atoms, R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Z ⁻ represents a counter anion. ]
1 to 30 mol% of a structural unit derived from a cationic monomer represented by the following general formula (2)
^{_{CH 2 = CH-CO-X}} -Q-N + R 1 R 2 R 3 · Z - (2)
[In the formula (2), X is O or NH, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, R ¹ is an alkyl group or benzyl group having 1 to 3 carbon atoms, R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Z ⁻ represents a counter anion. ]
1 to 30 mol% of a structural unit derived from a cationic monomer represented by the following general formula (3)
R ⁴ CH = CR ⁵ -A-B ¹ (3)
[In Formula (3), R ⁴ is a hydrogen atom, a methyl group or COOB ² , R ⁵ is a hydrogen atom, a methyl group or CH ₂ COOB ² , A is COO, SO ₃ , C ₆ H ₅ SO ₃ , CONHC (CH ₃₎ a ₂ CH ₂ SO ₃ or _C 6 _H 5 COO, ^{B 1} and ^{B 2} represents a hydrogen atom or a cation. ]
2 to 50 mol% of a structural unit derived from an anionic monomer represented by formula (0) and 0 to 96 mol% of a structural unit derived from another monomer, and represented by the general formulas (1), (2), ( When the mole% of the monomer represented by 3) is c1, c2, and a1, respectively,
An amphoteric water-soluble polymer flocculant comprising an amphoteric water-soluble polymer satisfying 1 <c1 / c2 <2, 0.8 <a1 / (c1 + c2) <2.   The cationic monomer represented by the general formula (1) is a dimethylaminoethyl methacrylate methyl chloride quaternized product, and the cationic monomer represented by the general formula (2) is a dimethylaminoethyl acrylate methyl chloride quaternized product. The amphoteric water-soluble polymer flocculant according to claim 1.   3. The amphoteric water-soluble polymer according to claim 1, comprising the amphoteric water-soluble polymer and an anionic water-soluble polymer having an anionic group and having a weight average molecular weight of 1,000 to 1,000,000. Polymer flocculant.   The amphoteric water-soluble polymer flocculant according to any one of claims 1 to 3, wherein the amphoteric water-soluble polymer is a polymer polymerized in the presence of the anionic water-soluble polymer. The anionic water-soluble polymer is represented by the following general formula (4)
^{_{CH 2 = CR 6 -COOM (4}} )
[In the formula (4), R ⁶ represents a hydrogen atom or a methyl group, M represents a hydrogen atom, an ammonium ion, an alkali metal ion or an alkaline earth metal ion. ]
The amphoteric water-soluble polymer flocculant according to any one of claims 1 to 4, comprising a structural unit derived from an anionic monomer represented by the formula:   A method for dewatering sludge, comprising adding the amphoteric water-soluble polymer flocculant according to any one of claims 1 to 5 to dewatering the sludge.   After adding an organic cationic coagulant and / or an inorganic coagulant to sludge, the amphoteric water-soluble polymer flocculant according to any one of claims 1 to 5 is added for dehydration. Sludge dewatering method.   After adding an organic cationic coagulant and / or an inorganic coagulant to the sludge, the pH (25 ° C) of the sludge is adjusted to 4-7, and then the amphoteric according to any one of claims 1 to 5. A method for dewatering sludge, comprising adding a water-soluble polymer flocculant and dewatering.   The sludge dewatering method according to any one of claims 6 to 8, wherein the sludge is organic sludge.