JP5865629B2 - Method for suppressing foaming of detachment liquid - Google Patents

Description

  The present invention relates to a method for suppressing foaming of a detachment liquid. More specifically, the present invention suppresses foaming during solid-liquid separation of sludge such as sewage mixed raw sludge, sewage surplus sludge, or digested sludge into a desorbed liquid and a dehydrated cake using a centrifugal dehydrator. For technology.

Substances subject to wastewater treatment are of various sizes, from particles suspended in water to dissolved molecules, but particles with a diameter of about 10 ^-6 to 10 ^-2 cm are mainly used. Is removed by agglomeration. In the aggregation treatment, an aggregating agent or the like is added to the solution in which the particles are suspended, and the particles are aggregated and settled. The settled aggregated particles are called sludge. The sludge is solid-liquid separated into a dehydrated cake and a desorbed liquid by a dehydration process using a dehydrator such as a centrifugal dehydrator, a belt press dehydrator, or a screw press dehydrator.

  The flocculant is appropriately selected according to the type of wastewater to be treated, and powder type or emulsion type polymer flocculants are widely used. The emulsion type polymer flocculant is advantageous in that it improves the workability of the flocculant addition step and dispersion step because it is more soluble than the powder type polymer flocculant.

  As an emulsion type flocculant, Patent Document 1 discloses a water-in-oil emulsion using a nonionic surfactant and paraffin oil. More specifically, the examples include a water-in-oil emulsion containing a cationic polymer having a cationic monomer copolymerization rate of 35 mol%, and an amphoteric polymer having a cationic monomer copolymerization rate of 30 mol%. An example is described in which a mixture with a water-in-oil emulsion containing coalescence is used as a flocculant. In addition, the specific chemical composition of the nonionic surfactant in the said Example is unknown.

  Patent Document 2 describes a flocculant composition obtained by adding an inorganic flocculant to an aqueous phase and performing water-in-oil emulsion polymerization without the presence of a crosslinking agent. In the examples and comparative examples, a copolymer obtained by polymerizing acryloyloxyethyltrimethylammonium chloride at a copolymerization rate of 30 mol% to 90 mol% is described.

  Patent Document 3 describes a water-in-oil emulsion flocculant obtained by reverse-phase emulsion polymerization of acroyloxyethylbenzyldimethylammonium chloride and a bifunctional monomer in the presence of a chain transfer agent. Examples thereof include a crosslinked copolymer obtained by polymerizing acryloyloxyethylbenzyldimethylammonium chloride at a copolymerization rate of 29 to 70 mol%, and an acryloyloxyethylbenzyldimethylammonium chloride copolymerization rate of 29 to 70. Non-crosslinked copolymers polymerized in mol% are described. When producing a cross-linked copolymer, 300 ppm or more of a cross-linking agent is added to the monomer.

  Patent Document 4 describes a water-in-oil emulsion obtained by reverse-phase emulsion polymerization of a monomer containing a water-soluble cationic vinyl monomer. In the examples, a crosslinked copolymer obtained by polymerizing acryloyloxyethyltrimethylammonium chloride at a copolymerization rate of 100 mol% or 50 mol% is described. When producing a cross-linked copolymer, 300 ppm or more of a cross-linking agent is added to the monomer.

JP 2000-218297 A JP 2000-005507 A Japanese Patent Laid-Open No. 10-277600 JP 09-225499 A

  However, when solid-liquid separation of sludge by a centrifugal dehydrator is performed using the above-described conventional emulsion type polymer flocculant, there is a problem that the desorbed liquid foams. This problem is particularly noticeable in the solid-liquid separation of sludge such as sewage mixed raw sludge, sewage surplus sludge, or digested sludge. When foaming of the detachment liquid occurs, bubbles may cause the sensor of the detachment liquid storage tank to malfunction, or foaming may occur when returning the detachment liquid to the biological treatment tank, causing deterioration of sedimentation. There is a risk of causing such a situation. In addition, the above Patent Documents 1 to 4 do not disclose specific examples of solid-liquid separation of sludge such as sewage mixed raw sludge, sewage surplus sludge, or digested sludge by a centrifugal dehydrator.

  Therefore, the present invention provides a method for effectively suppressing foaming of the desorbed liquid when solid-liquid separation of sludge such as sewage mixed raw sludge, sewage surplus sludge, or digested sludge using a centrifugal dehydrator. For the purpose.

  The present inventors have intensively studied to solve the above problems. As a result, it was found that by adding a water-in-oil emulsion containing a water-soluble polymer having a predetermined structural unit to sludge that is prone to foaming, foaming of the desorbed liquid is remarkably suppressed. Completed.

  That is, the foam suppression method of the present invention includes the step A of adding a flocculant to at least one kind of sludge selected from the group consisting of raw sewage mixed sludge, sewage surplus sludge, and digested sludge; A step B in which the sludge containing the agent is subjected to solid-liquid separation using a centrifugal dehydrator, and separated into a desorbed liquid and a dehydrated cake. The flocculant is a water-soluble polymer (A) having at least one structural unit selected from the group consisting of the following (1) to (4) in a hydrocarbon which is a continuous phase by a nonionic surfactant. A water-in-oil emulsion in which an aqueous solution containing (D) is dispersed as a dispersed phase is included. The water-in-oil emulsion is obtained by emulsion polymerization of a monomer in the absence of a crosslinking agent or in the presence of a crosslinking agent of more than 0 and 50 mass ppm or less with respect to the total mass of the monomer. can get.

  (A) a water-soluble polymer containing 50 to 100 mol% of the following structural unit (1);

In the formula, R ¹ represents a hydrogen atom or a methyl group,
R ² and R ³ each independently represents an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms,
R ⁴ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group,
A represents an oxygen atom or -NH-,
B represents an alkylene group having 2 to 4 carbon atoms or an oxyalkylene group having 2 to 4 carbon atoms,
X ¹⁻ represents a 1-3 valent anion;
(B) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (2);

In the formula, R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group,
R ⁷ and R ⁸ each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group,
X ²⁻ represents a 1-3 valent anion;
(C) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (3);

In the formula, R ⁹ represents a hydrogen atom or a methyl group,
X ^3- represents a 1-3 valent anion;
(D) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (4);

In the formula, R ¹⁰ and R ¹¹ each independently represents a hydrogen atom or a methyl group,
X ⁴⁻ represents a 1-3 valent anion.

  According to the present invention, when a sludge such as raw sewage mixed sludge, sewage surplus sludge, or digested sludge is solid-liquid separated using a centrifugal dehydrator, foaming of the desorbed liquid can be effectively suppressed. Become.

  Hereinafter, preferred modes of the present invention will be described. However, the technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited to the following modes.

  The foam suppression method of the present invention includes a step A in which a flocculant is added to at least one kind of sludge selected from the group consisting of sewage mixed raw sludge, sewage surplus sludge, and digested sludge; and the flocculant obtained in step A. A step B in which the sludge contained is subjected to solid-liquid separation using a centrifugal dehydrator to separate the sludge into a desorbed liquid and a dehydrated cake;

<Process A>
In step A, a flocculant is added to at least one kind of sludge selected from the group consisting of raw sewage mixed sludge, sewage surplus sludge, and digested sludge.

[Sludge]
In the foam suppression method of this embodiment, it is essential to use at least one selected from the group consisting of sewage surplus sludge, sewage mixed raw sludge, and digested sludge as sludge. Here, the classification of sludge will be described. First, sludge that is generated when wastewater is collected in the first sedimentation tank and settled is called “raw sludge”. On the other hand, the supernatant of the initial sedimentation tank is biologically treated in an aeration tank, the suspension in the treated water is precipitated, and the suspension is returned to the aeration tank. At this time, excess sludge is removed from the treatment system. It is burned. The sludge generated at this time is called “surplus sludge”. Moreover, the sludge which mixed raw sludge and excess sludge is called "mixed raw sludge." Furthermore, sludge generated when raw sludge is subjected to anaerobic fermentation is called “digested sludge”.

  The sewage surplus sludge, sewage mixed raw sludge, or digested sludge, which is the target of the foam suppression method of this embodiment, has a characteristic that it tends to foam when solid-liquid separation is performed using a centrifugal dehydrator compared to other sludge. Have. In particular, digested sludge is more suitable as a target of the foaming suppression method of the present embodiment because foaming is more remarkable than sewage surplus sludge and sewage mixed raw sludge. The type of digested sludge applied to this form is not particularly limited, and is generated from fishery processing wastewater, food processing wastewater, petrochemical wastewater, livestock wastewater, etc., sewage digested sludge, human waste digested sludge, livestock digested sludge, etc. Various digested sludges can be used.

[Flocculant]
The flocculant added in the foam suppression method of this embodiment essentially contains a water-in-oil emulsion. The water-in-oil emulsion has at least one structural unit selected from the group consisting of the following (1) to (4) in a hydrocarbon that is a continuous phase by a nonionic surfactant. An aqueous solution containing the molecules (A) to (D) is dispersed as a dispersed phase.

(hydrocarbon)
The hydrocarbon has a role as a continuous phase (oil phase) of the water-in-oil emulsion. The hydrocarbon is not particularly limited as long as it is immiscible with water used as the dispersed phase. For example, paraffins, mineral oil such as kerosene, light oil, and middle oil, or 150 having a boiling point and viscosity equivalent to these. A hydrocarbon-based synthetic oil such as isoparaffin having a temperature of from 250C to 250C may be used. These hydrocarbons may be used alone or in combination of two or more.

  The hydrocarbon content is not particularly limited, but is usually 20% by mass to 50% by mass, preferably 20% by mass to 40% by mass with respect to the total mass of the water-in-oil emulsion. When the hydrocarbon content is 20% by mass or more, heat generation during polymerization can be suppressed, so that the production can be easily controlled. On the other hand, when the hydrocarbon content is 40% by mass or less, the concentration can be increased, which is advantageous for transportation and the stability of the emulsion can be maintained.

(Nonionic surfactant)
Nonionic surfactants function as emulsifiers in water-in-oil emulsions. There is no restriction | limiting in particular in the nonionic surfactant used with the water-in-oil emulsion of this form, Both water-soluble nonionic surfactant and oil-soluble nonionic surfactant can be used. Among these, it is preferable to use a nonionic surfactant having an HLB value of 3 to 11 at the time of polymerization. Examples of such a nonionic surfactant include polyoxyethylene nonylphenyl ether and polyoxyethylene stearyl. Ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene tridecyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristeale -Water-soluble nonionic surfactants such as polyoxyethylene sorbitan trilaurate, polyoxyethylene sorbitan tripalmitate, sorbitan monooleate, sorbitan dioleate, sorbitan monostearate And sorbitan distearate Sorbitan monolaurate - DOO, sorbitan distearate laurate, sorbitan monopalmitate, and the like nonionic surface active agent oil-soluble, such as sorbitan distearate palmitate. Among these, it is preferable to use a water-soluble nonionic surfactant from the viewpoint of further improving the foaming suppression effect of the detachment liquid.

  Furthermore, after the polymerization, it is preferable to add a water-soluble surfactant to make the emulsion particles covered with the oil film easy to adjust to water and to dissolve the water-soluble polymer. Then, the obtained emulsion is diluted with water and used for each application. As the water-soluble surfactant, either an ionic surfactant or a nonionic surfactant can be used, but a water-soluble nonionic surfactant having an HLB of 8 to 15 is preferable, and is represented by the following general formula 5. It is more preferable to use a water-soluble nonionic surfactant having an HLB value of 8 to 15.

In the formula, P represents an aliphatic hydrocarbon group having 8 to 17 carbon atoms,
Q represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms,
p represents the number of 5-20 which is the average addition mole number of ethylene oxide,
q represents the number of 0-20 which is the average addition mole number of isopropylene oxide.

  Examples of the aliphatic hydrocarbon group having 8 to 17 carbon atoms include nonylphenyl group, stearyl group, lauryl group, cetyl group, dodecyl group, and oleyl group.

  Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group.

  Specific examples of the water-soluble nonionic surfactant represented by the above general formula 5 include polyoxyethylene nonyl phenyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene Tridecyl ether, polyoxyethylene oleyl ether, etc., all of which are random copolymers such as polyoxyethyleneoxyisopropylene nonylphenyl ether, polyoxyethyleneoxyisopropylene stearyl ether, polyoxyethyleneoxyisopropylene lauryl ether, polyoxy Ethyleneoxyisopropylene cetyl ether, polyoxyethyleneoxyisopropylene tridecyl ether, polyoxyethyleneoxyisopropylene oleyl ether Le and the like. The reason why the foaming suppression effect of the detachment liquid is improved by using the nonionic surfactant represented by the general formula 5 is that the nonionic surfactant represented by the general formula 5 is a polyoxyalkylene sorbitan fatty acid. One of the reasons is thought to be that it has the property of being less susceptible to hydrolysis than an ester or the like.

  The content of the surfactant is preferably 0.5 to 10% by mass and more preferably 1 to 5% by mass with respect to the total mass of the water-in-oil emulsion. In addition, only 1 type of surfactant may be used independently and 2 or more types may be used together.

(Water-soluble polymer)
In the water-in-oil emulsion of this embodiment, an aqueous solution containing water-soluble polymers (A) to (D) having at least one structural unit selected from the group consisting of (1) to (4) below is a dispersed phase. It is characterized by being distributed as follows.

  The water-soluble polymer (A) contains 50 to 100 mol% of the following structural unit (1).

In the formula, R ¹ represents a hydrogen atom or a methyl group,
R ² and R ³ each independently represents an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms,
R ⁴ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group,
A represents an oxygen atom or -NH-,
B represents an alkylene group having 2 to 4 carbon atoms or an oxyalkylene group having 2 to 4 carbon atoms,
X ¹⁻ represents a 1-3 valent anion.

  Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group.

  Examples of the alkoxy group having 1 to 3 carbon atoms include methoxy group, ethoxy group, n-propoxy group, and isopropoxy group.

  Examples of the alkylene group having 2 to 4 carbon atoms include a methylene group, an ethylene group, a trimethylene group, a propylene group, a tetramethylene group, a 1-methyltrimethylene group, a 2-methyltrimethylene group, and a 1-ethylethylene group. , 2-ethylethylene group, 1,2-dimethylethylene group.

  Examples of the oxyalkylene group having 2 to 4 carbon atoms include oxymethylene group, oxyethylene group, oxytrimethylene group, oxypropylene group, oxytetramethylene group, oxy (1-methyltrimethylene) group, oxy ( 2-methyltrimethylene) group, oxy (1-ethylethylene) group, oxy (2-ethylethylene) group, and oxy (1,2-dimethylethylene) group.

  Examples of the anion include fluoride ion, chloride ion, bromide ion, iodide ion, hydroxide ion, sulfate ion, phosphate ion, nitrate ion, carbonate ion, borate ion, tartrate ion, acetate ion. , Propionate ion, p-toluenesulfonate ion, trifluoroacetate ion, trifluoromethanesulfonate ion and the like. Of these, chloride ions are preferred.

  The water-soluble polymer (A) having the structural unit (1) can be obtained by (co) polymerizing the following monomers. Examples of the monomer include quaternary alkyl halides such as methyl chloride of tertiary amine monomers such as dimethylaminoethyl (meth) acrylate and diallylalkylamine. Specific examples include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxy-2-hydroxypropyltrimethylammonium chloride, and (meth) acryloylaminopropyltrimethylammonium chloride. Examples of the monomer include a quaternized product of a tertiary amine monomer such as dimethylaminoethyl (meth) acrylate with an aryl halide compound such as benzyl chloride. Specific examples include (meth) acryloyloxyethylbenzyldimethylammonium chloride, (meth) acryloyloxy-2-hydroxypropylbenzyldimethylammonium chloride, (meth) acryloylaminopropylbenzyldimethylammonium chloride, and the like. Only one type of the above monomers may be used alone, or two or more types may be used in combination.

  The water-soluble polymer (A) may be obtained by copolymerization of a monomer that forms the structural unit (1) and an ethylenically unsaturated compound that can be copolymerized with the monomer. The ethylenically unsaturated compound is not particularly limited, and any of an anionic ethylenically unsaturated compound and a nonionic ethylenically unsaturated compound can be used. Examples of the anionic ethylenically unsaturated compound include (meth) acrylic acid or an alkali metal salt or ammonium salt such as a sodium salt thereof; maleic acid or an alkali metal salt thereof; acrylamide-2-methylpropanesulfonic acid or the like Acrylamide alkanesulfonic acid, or an alkali metal salt or ammonium salt thereof. On the other hand, examples of nonionic ethylenically unsaturated compounds include (meth) acrylamide, N, N-dimethylacrylamide, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, acryloylmorpholine and the like can be mentioned. These ethylenically unsaturated compounds may be used alone or in combination of two or more.

  The water-soluble polymer (A) essentially contains 50 to 100 mol% of the structural unit (1) when the total number of repeating units is 100 mol%. When the content of the structural unit (1) is less than 50 mol%, the hydrophobicity of the water-soluble polymer contained in the resulting water-in-oil emulsion is relatively high, and the affinity for water may be reduced. There is sex. As a result, the stability of the water-in-oil emulsion in water may be reduced, and foaming may easily occur. In addition, the structural unit derived from the anionic ethylenically unsaturated compound in the water-soluble polymer (A) is preferably 0 to 30 mol% from the viewpoint of maintaining the foaming suppression effect of the detachment liquid.

  The water-soluble polymer (B) contains 40 to 100 mol% of the following structural unit (2).

In the formula, R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group,
R ⁷ and R ⁸ each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group,
X ²⁻ represents a 1-3 valent anion.

  Examples of the alkyl group having 1 to 3 carbon atoms, the alkoxy group having 1 to 3 carbon atoms, and the anion include the same as those exemplified in the above general formula 1.

  The water-soluble polymer (B) having the structural unit (2) can be obtained by (co) polymerizing the following monomers. Examples of the monomer include a quaternized product of diallylalkylamine with a halogenated lower alkyl quaternized product or a halogenated aryl compound such as benzyl chloride. Specific examples include diallyldimethylammonium chloride. Only one type of the above monomers may be used alone, or two or more types may be used in combination.

  The water-soluble polymer (B) may be obtained by copolymerization of a monomer that forms the structural unit (2) and an ethylenically unsaturated compound that is copolymerizable with the monomer. As the said ethylenically unsaturated compound, the thing similar to the ethylenically unsaturated compound illustrated in the said water-soluble polymer (A) can be used.

  The water-soluble polymer (B) essentially contains 40 to 100 mol% of the structural unit (2) when the total number of repeating units is 100 mol%. When the content of the structural unit (2) is less than 40 mol%, the hydrophobicity of the water-soluble polymer contained in the resulting water-in-oil emulsion is the same as in the case of the water-soluble polymer (A) described above. It may be relatively high and the affinity for water may be reduced. As a result, the stability of the water-in-oil emulsion in water may be reduced, and foaming may easily occur. In addition, the content of the structural unit derived from the anionic ethylenically unsaturated compound in the water-soluble polymer (B) is the same as in the case of the water-soluble polymer (A) described above, and suppresses foaming of the detachment liquid. From the viewpoint of maintaining the effect, the content is preferably 0 to 30 mol%.

  The water-soluble polymer (C) contains 40 to 100 mol% of the following structural unit (3). Hereinafter, the structural unit (3) is also referred to as “vinylamine structural unit”.

In the formula, R ⁹ represents a hydrogen atom or a methyl group,
X ³⁻ represents a 1-3 valent anion.

  As said anion, the thing similar to what was illustrated by the above-mentioned general formula 1 is mentioned.

  A method for producing a water-soluble polymer (C) having the vinylamine structural unit is disclosed in JP-A-6-65329. Specifically, if necessary, N-vinylformamide is (co) polymerized with another monomer in the presence of a radical polymerization initiator, and the formyl group in the resulting polymer is converted to an acid or caustic alkali (alkali metal). It can be easily obtained by modification using a hydroxide. At this time, the molar ratio of N-vinylformamide and other monomers used as necessary is preferably 50:50 to 100: 0, and preferably 80:20 to 100: 0. .

  Any acid can be used as the acid used for the modification as long as it is a strongly acidic compound. Specific examples include hydrochloric acid, bromic acid, hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid, sulfamic acid, alkanesulfonic acid, and the like. On the other hand, examples of the caustic used for modification include sodium hydroxide and potassium hydroxide. The amount of the modifier used is appropriately selected according to the target modification rate, usually in the range of 0.1 to 2 equivalents with respect to the formyl group in the polymer. Further, the denaturation reaction is usually carried out at 40 to 100 ° C. The content of the vinylamine structural unit in the water-soluble polymer (C) is 40 to 100 mol%, more preferably 50 to 100 mol%, when the total number of repeating units is 100 mol%.

  The water-soluble polymer (D) contains 40 to 100 mol% of the following structural unit (4). Hereinafter, the structural unit (4) is also referred to as “amidine structural unit”.

In the formula, R ¹⁰ and R ¹¹ each independently represents a hydrogen atom or a methyl group,
X ⁴⁻ represents a 1-3 valent anion.

  A method for producing a water-soluble polymer (D) having the amidine structural unit is disclosed in JP-A-5-192513. Specifically, N-vinylformamide and acrylonitrile are copolymerized in the presence of a radical polymerization initiator. The resulting copolymer is modified (hydrolyzed) with an acid to form a primary amino group, and then the primary amino group is reacted with the cyano group of the adjacent acrylonitrile. At this time, the molar ratio of N-vinylformamide and acrylonitrile is preferably 50:50 to 60:40.

  Any acid can be used as the acid used for the modification as long as it is a strongly acidic compound. Specific examples include hydrochloric acid and sulfamic acid. The amount of the acid used is appropriately selected from the range of usually 0.1 to 2 equivalents depending on the target modification rate with respect to the formyl group in the polymer. Further, the denaturation reaction is usually carried out at 40 to 100 ° C. The content of the amidine structural unit in the water-soluble polymer (D) is 40 to 100 mol%, more preferably 50 to 100 mol%, when the total number of repeating units is 100 mol%.

(Additive)
The monomer used in the method for producing the water-soluble polymers (A) to (D) can be emulsion-polymerized in the presence of an additive, if necessary. Although there is no restriction | limiting in particular as the said additive, For example, a crosslinking agent, a polymerization initiator, a chain transfer agent, etc. are mentioned.

  The crosslinking agent can be added for the purpose of modifying the molecular structure of the water-soluble polymer. For example, when the flocculant of this embodiment is applied to so-called hardly dewatering sludge having a low fiber content, the water-soluble polymer should be made into a crosslinked type by polymerizing in the presence of a water-in-oil emulsion polymerization in the presence of a crosslinking agent. Is preferred. On the other hand, for sludge that has a high fiber content and is easily separated into solid and liquid, it is preferable that the water-soluble polymer is polymerized without coexistence of a crosslinkable monomer during water-in-oil emulsion polymerization, so that the water-soluble polymer is linear. . By controlling the molecular structure of the water-soluble polymer in this way, large aggregated flocs can be generated, so that the filtration rate is increased and good solid-liquid separation performance can be obtained.

  The cross-linking agent that can be used in the present embodiment is not particularly limited. For example, N, N-methylenebis (meth) acrylamide, triallylamine, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, Tetraethylene glycol methacrylate, 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 and the like can be mentioned. Of these crosslinking agents, a water-soluble polyvinyl compound is preferable, and N, N-methylenebis (meth) acrylamide is most preferable. In addition, it is preferable that the addition amount in the case of adding a crosslinking agent exceeds 0 with respect to the total mass of a monomer, and is 50 mass ppm or less.

  The polymerization initiator that can be used in this embodiment is not particularly limited, and any of oil-soluble or water-soluble azo radical polymerization initiator, peroxide radical polymerization initiator, and redox radical polymerization initiator is used. Is possible. Examples of the oil-soluble azo radical polymerization initiator include 2,2′-azobisisobutyronitrile, 1,1-azobiscyclohexanecarbonitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis-2-methylpropionate, 4,4′-azobis- (4-methoxy-2,4-dimethyl) valeronitrile and the like. Examples of the water-soluble azo radical polymerization initiator include 2,2′-azobis (amidinopropane) dihydrochloride and 2,2′-azobis [2- (5-methyl-imidazolin-2-yl) propane. ] Dihydrochloride, 4,4'-azobis (4-cyanovaleric acid) and the like. Examples of the redox radical polymerization initiator include a combination of ammonium peroxodisulfate and sodium sulfite, sodium hydrogensulfite, trimethylamine, tetramethylethylenediamine, or the like. Further, examples of peroxide radical polymerization initiators include ammonium peroxodisulfate, potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic acid peroxide, tert-butylperoxy-2-ethyl. Hexanoate is mentioned. In addition, it is preferable that the addition amount of a polymerization initiator is 0.001-0.1 mass% with respect to the total mass of a monomer.

  The chain transfer agent is added as necessary to adjust the molecular weight and crosslinkability of the water-soluble polymer. In particular, when adding about 10 to 50 ppm by mass of the crosslinking agent with respect to the total mass of the monomer, it is preferable to add a chain transfer agent. Examples of the chain transfer agent include sodium formate and isopropyl alcohol. The addition amount of the chain transfer agent is preferably 0.001 to 1.0% by mass and more preferably 0.001 to 0.2% by mass with respect to the total mass of the monomers. By making the addition amount of the chain transfer agent 0.001% by mass or more, the effect of the chain transfer agent can be expressed. On the other hand, when the addition amount of the chain transfer agent is 1.0% by mass or less, an extreme decrease in molecular weight can be prevented.

  The water-in-oil emulsion in this embodiment can be obtained by emulsion polymerization of the above-described monomer in a solution containing a hydrocarbon and a nonionic surfactant in the presence of an additive that is included as necessary. More specifically, the monomer, water, hydrocarbon, and nonionic surfactant are mixed, sufficiently stirred and emulsified, and then polymerized. The polymerization conditions vary depending on the type of monomer, the type of polymerization initiator, and the like, but can be appropriately determined by those skilled in the art based on known knowledge in the field. In general, the polymerization temperature is 20 to 80 ° C, preferably 20 to 60 ° C. The polymerization concentration is usually 20 to 50% by mass, preferably 25 to 40% by mass.

  The salt aqueous solution viscosity of the water-soluble polymer contained in the water-in-oil emulsion obtained by the emulsion polymerization is preferably 5 to 120 mPa · s, and more preferably 10 to 80 mPa · s. In the present specification, the viscosity of the aqueous salt solution was measured using a B-type viscometer at 25 ° C. when completely dissolved so that the water-soluble polymer concentration was 0.5% in 1N saline. Adopt value at the time. The weight average molecular weight of the water-soluble polymer contained in the water-in-oil emulsion is preferably 2,000,000 to 15,000,000, more preferably 3,000,000 to 10,000,000. 000, more preferably 6,000,000 to 10,000,000. In the present specification, a value calculated by a static light scattering method is adopted as the weight average molecular weight.

  In addition, the flocculant of this form does not prevent other flocculants having a flocculant action from being included as long as the effect of the present invention is not significantly inhibited other than the above-described water-in-oil emulsion. The ratio of the water-in-oil emulsion contained in the flocculant of this embodiment is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and still more preferably 90 to 100% by mass, Especially preferably, it is 95-100 mass%, Most preferably, it is 100 mass%.

  In step A, a flocculant containing the water-in-oil emulsion is added to the sludge. The method for adding the flocculant to the sludge is not particularly limited, and the flocculant may be added to the sludge as it is, but in order to further improve the dispersibility of the flocculant, it is diluted with water before adding to the sludge. It is preferable to do. At this time, in order to improve the dispersibility of the water-in-oil emulsion in water, a water-soluble surfactant may be added separately from the surfactant added during the polymerization. In this case, as the water-soluble surfactant, either an ionic surfactant or a nonionic surfactant can be used, but a nonionic surfactant of HLB 8 to 15 is preferably used. Specifically, polyoxyethylene polyoxypropylene alkyl ether-based or polyoxyethylene alcohol ether-based surfactants are preferably used.

  The amount of the flocculant added to the sludge is appropriately determined depending on the type of sludge. For example, when the sludge is sewage digested sludge, the addition amount of the flocculant is usually 0.5 to 2.0 mass%, preferably 1.0 to 2.0 mass% with respect to SS. Moreover, the addition amount of the flocculant when sludge is a sewage mixing raw sludge is 0.1-1.5 mass% normally, Preferably it is 0.5-1.0 mass%. Moreover, when the sludge is sewage surplus sludge, the addition amount of the flocculant is usually 0.5 to 1.5% by mass, preferably 1.0 to 1.5% by mass. By making the addition amount of a flocculant into the said range, while being able to fully exhibit the cohesiveness of sludge, foaming of a desorption liquid can be suppressed effectively.

<Process B>
The process B includes a process B in which the sludge containing the flocculant obtained in the process A is subjected to solid-liquid separation using a centrifugal dehydrator, and separated into a desorbed liquid and a dehydrated cake.

[Centrifuge dehydrator]
There is no restriction | limiting in particular in the centrifugal dehydrator which can be used with this form, The thing used in the said field | area can be employ | adopted suitably. Moreover, the conditions for centrifugal dehydration are not particularly limited.

  According to the foaming suppression method of this embodiment, foaming of the desorbed liquid can be effectively suppressed even when sludge is solid-liquid separated using a centrifugal dehydrator. Moreover, since the flocculant of this embodiment is also excellent in the flocculation performance, a good SS recovery rate (an index indicating how much solid matter in the sludge has been recovered as a dehydrated cake) can be achieved. Therefore, the dewatering efficiency of sludge can be significantly improved as compared with the conventional case. In addition, since malfunction of the apparatus due to foaming, which has been a problem in the past, can be reduced, the time and cost for maintenance can be reduced.

  The effect of this invention is demonstrated using a following example and a comparative example. However, the technical scope of the present invention is not limited only to the following examples.

<Manufacture of flocculant>
[Synthesis Example 1] Synthesis of flocculant 1 In a reaction vessel equipped with a stirrer and a temperature control device, 126.0 g of isoparaffin as a hydrocarbon (boiling point 190 to 230 ° C.) and polyoxyethylene decyl as a nonionic surfactant 12.5 g of ether (2.5% by mass with respect to the emulsion) was charged and dissolved to prepare an oil phase. Separately, 103.1 g of deionized water, 250.0 g of 80% aqueous solution of methacryloyloxyethyltrimethylammonium chloride (DAM), and 1.0 g of 1% by weight aqueous solution of methylenebisacrylamide as a cross-linking agent (total mass of monomers) 50 mass ppm) was mixed and completely dissolved to prepare an aqueous monomer solution. Thereafter, the pH of the aqueous monomer solution was adjusted to 3.95, the oil phase and the aqueous monomer solution were mixed, and the mixture was emulsified with stirring by a homogenizer at 1000 rpm for 15 minutes.

  To the obtained emulsion, 1.0 g of a 10% by mass aqueous solution of isopropyl alcohol as a chain transfer agent (0.05% by mass with respect to the total mass of the monomers) is added, and the temperature of the solution is kept at 30 to 33 ° C., Nitrogen replacement was performed for 30 minutes. Thereafter, 2.0 g of a 1% by weight aqueous solution of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride as a polymerization initiator (in total monomer mass) 0.01 mass%) was added to initiate the polymerization reaction. Polymerization was carried out for 12 hours while maintaining the reaction temperature at 32 ± 2 ° C. to complete the reaction, and flocculant 1 was obtained.

[Synthesis Examples 2 to 6 and Comparative Synthesis Examples 1 to 2] Synthesis of flocculants 2 to 6 and comparative flocculants 1 to 2 The composition of the monomer, the addition amount of the crosslinking agent, and the type of the surfactant are shown in Table 1 below. Flocculants 2-6 and comparative flocculants 1-2 were synthesized in the same manner as in Synthesis Example 1 except that the conditions were as described above.

[Synthesis Example 7]
N-vinylformamide 57.3 g, acrylonitrile 42.7 g, deionized water 87.2 g, 1% by mass in a 500 ml five-necked separable flask equipped with an anchor type stirrer, reflux condenser, thermometer, and nitrogen gas inlet / outlet Weigh out a monomer solution mixed with 0.35 g of methylenebisacrylamide (35 ppm of monomer) in an aqueous solution, 100 g of isoparaffin, 2 g of nonionic active agent HyperH1084 (manufactured by Croda), 6.5 g of sorbitan monooleate (HLB7), Nitrogen gas was introduced to perform deoxygenation operation. Thereafter, while stirring at a temperature of 52 ° C. and a rotation speed of 500 rpm, azo polymerization initiator [2,2′-azobis (2,4-dimethylvaleronitrile)] was added at 2500 ppm based on the total monomer mass, and then 60 ° C. The polymerization was carried out while maintaining the temperature for 18 hours.

  After cooling this polymer to room temperature, a stabilizer was added, 81.4 g of 36% hydrochloric acid was added, and hydrolysis was carried out at 85 ° C. for 12 hours. After the reaction, 8.0 g of polyoxyethylene decyl ether (HLB13.3) was added. The content of the amidine structural unit by NMR (nuclear magnetic resonance) was 88 mol%, and the weight average molecular weight by the static light scattering method was 3 million.

[Synthesis Example 8]
In a four-necked 500 mL separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 13.0 g of nonionic active agent Hypermer H1084 (manufactured by Croda) was charged into 185.6 g of isoparaffin having a boiling point of 190 ° C. to 230 ° C. Dissolved. Separately, N-vinylformamide (pure 99.8% by mass) 166.4 g, 1% by weight aqueous solution of methylene bisacrylamide 0.66 g (based on monomer 40 ppm), sodium formate 0.16 g (based on monomer 1000 ppm), Ion-exchanged water (134.9 g) was collected and added. The oil and the aqueous solution were mixed, and stirred and emulsified with a homomixer at 8000 rpm for 2 minutes. While stirring the resulting emulsion, the temperature of the monomer solution was kept in the range of 20 to 25 ° C., and after nitrogen substitution for 30 minutes, the polymerization initiator 2,2′-azobis (4-methoxy-2,4 -Dimethylvaleronitrile) (V-70, manufactured by Wako Pure Chemical Industries) 0.83 g (0.5% by mass of monomer) was added to initiate the polymerization reaction. The reaction was completed by polymerization for 12 hours while maintaining the temperature in the range of 20 to 25 ° C.

  In a four-necked 500 mL separable flask equipped with a stirrer, reflux condenser, thermometer and dropping funnel, 252.6 g of the above water-in-oil emulsion of N-vinylcarboxylic acid amide polymer oil and polyoxyethylene stearyl ether (manufactured by Kao Corporation) 12.6 g of Emulgen 306P (HLB 9.4)) was collected and stirred at 50 ° C. and sufficiently dissolved and mixed. After confirming dissolution, the mixture was heated to 80 ° C., 12.6 g of a 20% by mass hydroxylamine hydrochloride aqueous solution was added, and 98.7 g of an aqueous sodium hydroxide solution (pure 48% by mass) was added dropwise over 1 minute using a dropping funnel. The hydrolysis reaction was performed at 80 ° C. for 8 hours. After completion of the hydrolysis reaction, 123.5 g of an aqueous hydrochloric acid solution (pure content 35% by mass) was added with a dropping funnel to neutralize it. After neutralization, 20 g of polyoxyethylene decyl ether (HLB13.3) was added to obtain a water-in-oil emulsion of polyvinylamine. The vinylamine structural unit by the colloid titration method was 80 mol%, and the weight average molecular weight by the static light scattering method was 4.6 million.

  Table 1 below shows the 0.5% salt viscosity and weight average molecular weight of each flocculant. As the comparative flocculant 3, “Himoloc MP-173H” manufactured by Hymo Co., Ltd. was used.

<Coagulation test and foaming test of sewage digested sludge>
[Example 1-1]
Sewage digestion sludge (pH 7.81, SS (floating matter): 17500 mg / L, TS (evaporation residue): 20500 mg / L, VSS (volatile floating matter): 73.9% by mass (vs. SS) generated from the sewage treatment plant For)), a coagulation test using a centrifugal dehydrator and a foaming test for filtration were performed. After 200 mL of sewage digested sludge was put into a 300 mL polypropylene beaker, a predetermined amount of 0.2% (w / v) aqueous solution of flocculant 1 was added, 1 minute at 1000 rpm using a tridental stirring rod, and then 1 at 30 rpm. Stirring was performed for a minute, and the floc state of the obtained sludge was observed.

Next, agglomerated sludge was poured all at once onto a filtration container having an inner diameter of 65 mm with a 40-mesh net attached to the bottom, and the amount of filtration per elapsed time was measured. Thereafter, the agglomerated sludge is placed on a water absorbent sponge and nylon # 202 filter cloth, and the filter cloth and the water absorbent sponge are further laminated thereon to sandwich the agglomerated sludge, and a press machine (cylinder pressure: 3 kg / cm ^2). ) For 30 seconds, and the moisture content of the dehydrated cake was measured.

  In addition, 100 mL of the obtained desorbing liquid was collected in a beaker, placed in a cylindrical cylinder (inner diameter: 36 mm, length: 300 mm), stirred up and down 20 times, allowed to stand for 10 seconds, Height was measured. The results are shown in Table 2.

[Examples 1-2 to 1-8, Comparative Examples 1-1 to 1-3]
In place of the flocculant 1, flocculants 2 to 8 or comparative flocculants 1 to 3 were used, respectively, except that the flocculence test and foamability test of sewage digested sludge were performed in the same manner as in Example 1-1. went.

  From the results of Table 2, according to the methods of Examples 1-1 to 1-8, it was shown that excellent cohesiveness was maintained for sludge and foaming was suppressed preferentially for the desorbed liquid. . On the other hand, in the methods of Comparative Examples 1-1 to 1-3, although the cohesiveness of sludge was good, remarkable foaming was observed in the desorbed liquid.

<Coagulation test and foaming test of sewage mixed raw sludge>
[Example 2-1]
Coagulation test and filtration using a centrifugal dehydrator for sewage mixed raw sludge (pH 5.3, SS: 19500 mg / L, TS: 21500 mg / L, VSS: 88.5% by mass (vs. SS)) generated from a sewage treatment plant The foamability test was conducted. After adding 200 mL of raw sewage mixed sludge to a 300 mL polypropylene beaker, add a predetermined amount of 0.2% (w / v) aqueous solution of flocculant 1 and use a tridental stirring rod for 1 minute at 1000 rpm, then at 30 rpm. Stirring was performed for 1 minute, and the floc state of the obtained agglomerated sludge was observed.

Next, agglomerated sludge was poured all at once onto a filtration container having an inner diameter of 65 mm with a 40-mesh net attached to the bottom, and the amount of filtration per elapsed time was measured. Thereafter, the agglomerated sludge is placed on a water absorbent sponge and nylon # 202 filter cloth, and the filter cloth and the water absorbent sponge are further laminated thereon to sandwich the agglomerated sludge, and a press machine (cylinder pressure: 3 kg / cm ^2). ) For 30 seconds, and the moisture content of the dehydrated cake was measured.

  In addition, 100 mL of the obtained desorbing liquid was collected in a beaker, placed in a cylindrical cylinder (inner diameter: 36 mm, length: 300 mm), stirred up and down 20 times, allowed to stand for 10 seconds, Height was measured. The results are shown in Table 3.

[Examples 2-2 to 2-8, comparative examples 2-1 to 2-3]
Instead of flocculant 1, flocculants 2 to 8 or comparative flocculants 1 to 3 were used, respectively, except that flocculant tests and foamability tests of raw sewage mixed sludge were performed in the same manner as in Example 2-1. Went.

  From the results of Table 3, it was shown that, according to the methods of Examples 2-1 to 2-8, excellent cohesiveness was maintained for sludge, and foaming was largely suppressed for the desorbed liquid. . On the other hand, in the methods of Comparative Examples 2-1 to 2-3, although the cohesiveness of the sludge was good, remarkable foaming was observed in the desorbed liquid.

<Agglomeration test and foaming test of sewage surplus sludge>
[Example 3-1]
For sewage surplus sludge (pH 6.4, SS: 12500 mg / L, TS: 13250 mg / L, VSS: 86.2% by mass (vs. SS)) generated from the sewage treatment plant, a coagulation test using a centrifugal dehydrator and filtration A foamability test was performed. After adding 200 mL of raw sewage mixed sludge to a 300 mL polypropylene beaker, add a predetermined amount of 0.2% (mass / mL) aqueous solution of flocculant 1 and use a tridental stirring rod at 1000 rpm for 1 minute, then at 30 rpm. Stirring was performed for 1 minute, and the floc state of the obtained agglomerated sludge was observed.

Next, agglomerated sludge was poured all at once onto a filtration container having an inner diameter of 65 mm with a 40-mesh net attached to the bottom, and the amount of filtration per elapsed time was measured. Thereafter, the agglomerated sludge is placed on a water absorbent sponge and nylon # 202 filter cloth, and the filter cloth and the water absorbent sponge are further laminated thereon to sandwich the agglomerated sludge, and a press machine (cylinder pressure: 3 kg / cm ^2). ) For 30 seconds, and the moisture content of the dehydrated cake was measured.

  In addition, 100 mL of the obtained desorbing liquid was collected in a beaker, placed in a cylindrical cylinder (inner diameter: 36 mm, length: 300 mm), stirred up and down 20 times, allowed to stand for 10 seconds, Height was measured. The results are shown in Table 3.

[Examples 3-2 to 3-8, Comparative examples 3-1 to 3-3]
Instead of the flocculant 1, flocculants 2-8 or comparative flocculants 1 to 3 were used, respectively, except that the sewage surplus sludge flocculation test and foamability test were performed in the same manner as in Example 3-1. went.

  From the results of Table 4, according to the methods of Examples 3-1 to 3-8, it was shown that excellent cohesiveness was maintained for sludge and foaming was suppressed preferentially for the desorbed liquid. . On the other hand, in the methods of Comparative Examples 3-1 to 3-3, although sludge coagulation was good, remarkable foaming was observed in the desorbed liquid.

Claims (6)

Step A of adding a flocculant to the digested sludge,
The sludge containing the flocculant obtained in the step A is subjected to solid-liquid separation using a centrifugal dehydrator, and separated into a desorbed liquid and a dehydrated cake.
The flocculant is a water-soluble polymer (A) having at least one structural unit selected from the group consisting of the following (1) to (4) in a hydrocarbon that is a continuous phase by a nonionic surfactant. A water-in-oil emulsion, in which an aqueous solution containing (D) is dispersed as a dispersed phase,
The water-in-oil emulsion is obtained by emulsion polymerization of a monomer in the absence of a crosslinking agent or in the presence of a crosslinking agent of more than 0 and 50 mass ppm or less with respect to the total mass of the monomer. A method for inhibiting foaming of the resulting detachment liquid;
(A) a water-soluble polymer containing 50 to 100 mol% of the following structural unit (1);
In the formula, R ¹ represents a hydrogen atom or a methyl group,
R ² and R ³ each independently represent an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms,
R ⁴ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group,
A represents an oxygen atom or -NH-,
B represents an alkylene group having 2 to 4 carbon atoms or an oxyalkylene group having 2 to 4 carbon atoms,
X ^1- represents a 1-3 valent anion;
(B) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (2);
In the formula, R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group,
R ⁷ and R ⁸ each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group,
X ²⁻ represents a 1-3 valent anion;
(C) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (3);
In the formula, R ⁹ represents a hydrogen atom or a methyl group,
X ^3- represents a 1-3 valent anion;
(D) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (4);
In the formula, R ¹⁰ and R ¹¹ each independently represent a hydrogen atom or a methyl group,
X ⁴⁻ represents a 1-3 valent anion. Step A of adding a flocculant to at least one kind of sludge selected from the group consisting of sewage mixed raw sludge, sewage surplus sludge, and digested sludge;
The sludge containing the flocculant obtained in the step A is subjected to solid-liquid separation using a centrifugal dehydrator, and separated into a desorbed liquid and a dehydrated cake.
The flocculant is selected from the group consisting of the following (1) to (4) in a hydrocarbon which is a continuous phase by a nonionic surfactant which is a polyoxyalkylene alkyl ether represented by the following general formula 5. A water-in-oil emulsion, in which an aqueous solution containing water-soluble polymers (A) to (D) having at least one structural unit is dispersed as a dispersed phase,
The water-in-oil emulsion is obtained by emulsion polymerization of a monomer in the absence of a crosslinking agent or in the presence of a crosslinking agent of more than 0 and 50 mass ppm or less with respect to the total mass of the monomer. A method for inhibiting foaming of the resulting detachment liquid;
(A) a water-soluble polymer containing 50 to 100 mol% of the following structural unit (1);
In the formula, R ¹ represents a hydrogen atom or a methyl group,
R ² and R ³ each independently represent an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms,
R ⁴ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group,
A represents an oxygen atom or -NH-,
B represents an alkylene group having 2 to 4 carbon atoms or an oxyalkylene group having 2 to 4 carbon atoms,
X ^1- represents a 1-3 valent anion;
(B) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (2);
In the formula, R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group,
R ⁷ and R ⁸ each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a benzyl group,
X ²⁻ represents a 1-3 valent anion;
(C) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (3);
In the formula, R ⁹ represents a hydrogen atom or a methyl group,
X ^3- represents a 1-3 valent anion;
(D) a water-soluble polymer containing 40 to 100 mol% of the following structural unit (4);
In the formula, R ¹⁰ and R ¹¹ each independently represent a hydrogen atom or a methyl group,
X ⁴⁻ represents a 1-3 valent anion;
In the formula, P represents an aliphatic hydrocarbon group having 8 to 17 carbon atoms,
Q represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms,
p represents the number of 5-20 which is the average addition mole number of ethylene oxide,
q represents the number of 0-20 which is the average addition mole number of isopropylene oxide. It said nonionic surfactant is a polyoxyalkylene alkyl ether represented by the following general formula 5, foam control method of desorption solution according to claim 1;
In the formula, P represents an aliphatic hydrocarbon group having 8 to 17 carbon atoms,
Q represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms,
p represents the number of 5-20 which is the average addition mole number of ethylene oxide,
q represents the number of 0-20 which is the average addition mole number of isopropylene oxide. The water-in-oil emulsion, the monomers, the obtained by emulsion polymerization in the presence or less of the cross-linking agent 50 mass ppm more than 0 with respect to the total weight of the monomers, according to claim 1 to 3 The method for suppressing foaming of the desorbed liquid according to any one of the above. The water-in-oil emulsion, wherein in presence of the total mass with respect to 10 to 10,000 ppm by weight of the chain transfer agent monomer, is obtained by formed by emulsion polymerization, according to claim 1-4 The method for suppressing foaming of a detachment liquid according to any one of the above. The method for inhibiting foaming of a detachment liquid according to any one of claims 1 to 5 , wherein the water-soluble polymer has a weight average molecular weight of 3,000,000 to 10,000,000.