JPH1085799A - Sludge dehydrating agent and dehydrating method for sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dehydrating agent and a dehydrating method in which the agent is used, in which the dehydrating agent is added to sludge generated from a sewage treating plant, industrial waste treating facility, etc., to aggregate the sludge in the form of floc so that the strength of the floc can be increased and the moisture content of a dehydrated cake can be decreased. SOLUTION: The dehydrating agent is prepared by combining two kinds of flocculants or derivatives selected from the group consisting of a cationic cellulose derivative, acrylate polymer flocculant, amphoteric macromolecular flocculant or cationic polymer flocculant including amidine units. And in the dehydrating method, the polymer flocculant comprising two kinds of flocculants or derivative is added to a sludge at a time and mixed together, or after adding the cationic cellulose derivative to the sludge and mixing them, the acrylate polymer flocculant, amphoteric polymer flocculant or cationic polymer flocculant including amidine units are added separately and mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a sludge dewatering agent comprising a cellulose derivative having a cationic substituent as one component thereof and combining it with another coagulant component.
Also, the present invention relates to a method for dewatering sludge using the combined sludge dewatering agent for dewatering sludge generated from sewage treatment plants, human waste treatment plants, various industrial wastewater treatment facilities, and the like.

[0002]

2. Description of the Related Art Conventionally, sludge generated from sewage treatment plants, human waste treatment plants, various industrial wastewater treatment facilities, and the like cannot be dewatered as it is, and is usually added with a polymer flocculant and used in a screw decanter. It is mechanically dewatered by a dehydrator such as a belt press. Generally, the method of dewatering sludge using a polymer flocculant includes: (1) a method using a cationic polymer flocculant alone such as a quaternary salt of dimethylaminoethyl (meth) acrylate; (3) a method in which an inorganic flocculant and an amphoteric polymer flocculant are used in combination.

In recent years, however, sludge has become difficult to dewater due to the sophistication of water treatment, changes in the properties of wastewater to be treated, and diversification. For example, in the case of human waste treatment by seawater dilution, a large amount of inorganic salts are mixed. Also, fertilizer industry,
A large amount of inorganic salts are also mixed in sludge generated from industrial wastewater treatment facilities such as food and dye industries. Sludge from the treatment of industrial wastewater from the dye industry also contains a large amount of other surfactants. In addition, sludge from biological wastewater treatment performed in wastewater treatment in the pulp and paper industry is rich in water, its main component is cells of microorganisms, and furthermore, it contains a large amount of surfactant. As described above, the properties of the wastewater to be treated are diversified, and the properties of the wastewater constantly change. Therefore, in the conventional dehydration method using a flocculant as described in the above (1) to (3), the obtained floc is not sufficiently strong, the floc is easily broken, and the belt press dehydrator has a gravity filtration property. And the sludge throughput decreases. Therefore, the removability of the dewatered cake from the filter cloth becomes poor, and there is a problem that the dewatering cake must be stopped in a state where the water content of the dewatered cake is relatively high.

[0004]

Therefore, in view of such circumstances, the present inventors have added to the diversified mud generated from sewage treatment plants, human waste treatment plants, various industrial wastewater treatment facilities, and the like. A flocculant capable of flocculating the sludge and flocculant as a floc having a large and excellent strength, capable of efficiently dewatering and achieving a reduction in the water content of the dewatered cake after dewatering. As a result of intensive studies on the optimal sludge dewatering method using the flocculant,
The present invention has been completed.

[0005]

The object of the present invention is achieved by the following sludge dewatering method of the present invention. That is, (1) A sludge dewatering agent comprising a combination of a cellulose derivative having a cationic substituent and an acrylate polymer flocculant. (2) The sludge dewatering agent according to the above (1), wherein the acrylate polymer flocculant is a copolymer of acrylamide and a monomer represented by the following general formula (1). .

[0006]

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Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ and R ₃ are an alkyl group having 1 to 4 carbon atoms, R ₄ is a hydrogen atom, an alkyl group or a benzyl group having 1 to 4 carbon atoms, A represents an oxygen atom or NH, B represents an alkylene group having 2 to 4 carbon atoms or a hydroxypropylene group, and X ⁻ represents an anionic counter ion. (3) In the copolymer, acrylamide and the monomer represented by the general formula (1) have a polymerization ratio of 95 to 10: 5.
90. The sludge dewatering agent according to the above item (2), which is a copolymer obtained by copolymerization at 90. (4) A sludge dewatering agent comprising a combination of a cellulose derivative having a cationic substituent and an amphoteric polymer flocculant. (5) A sludge dewatering agent comprising a combination of a cellulose derivative having a cationic substituent and a cationic polymer flocculant having an amidine unit. (6) A method of dewatering sludge, comprising adding and mixing a cellulose derivative having a cationic substituent to sludge, followed by adding an acrylate polymer flocculant and performing dehydration treatment. (7) The sludge dehydration according to (6), wherein the acrylate polymer flocculant is a copolymer of acrylamide and a monomer represented by the following general formula (1). Method.

[0008]

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Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ and R ₃ are an alkyl group having 1 to 4 carbon atoms, R ₄ is a hydrogen atom, an alkyl group or a benzyl group having 1 to 4 carbon atoms, A represents an oxygen atom or NH, B represents an alkylene group having 2 to 4 carbon atoms or a hydroxypropylene group, and X ⁻ represents an anionic counter ion. (8) In the copolymer, acrylamide and a monomer represented by the general formula (1) have a polymerization ratio of 95 to 10: 5.
90. The sludge dewatering method according to the above item (7), wherein the sludge is a copolymer obtained by copolymerization at 90. (9) A method for dewatering sludge, which comprises adding and mixing a cellulose derivative having a cationic substituent, followed by adding an amphoteric polymer flocculant and performing a dehydration treatment. (10) A method for dewatering sludge, comprising adding and mixing a cellulose derivative having a cationic substituent, followed by adding a cationic polymer flocculant having an amidine unit and performing dehydration treatment.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As a cellulose derivative having a cationic substituent, which is one of the constituent elements of the present invention, existing chemical substance Nos. 8-651, for example,
It is possible to use one in which 1.6 to 1.8 moles of oxyethylene groups are added and 0.3 to 0.4 moles of quaternary ammonium bases are combined per anhydroglucose ring unit of cellulose. Specific examples include cationized hydroxyethyl cellulose represented by the following molecular formula (2).

[0011]

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As the cellulose derivative having a cationic substituent used in the present invention, commercially available products can be used. Specific examples of commercially available products include “Leogard G” and “Leogard G” available from Lion Corporation. LEOGARD GP, LEOGARD KGP, LEOGARD MG
P "and the like.

Another flocculant used in the present invention is a cationic polymer flocculant having a cationic monomer unit represented by the following general formula (3) as an essential component, and preferably the cationic monomer unit is It contains 5 mol% or more. Examples of the cationic monomer represented by the following general formula (3) include the following. That is, dimethylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diethylamino (methyl, ethyl, propyl or butyl)
Acrylate or methacrylate, di-n-propylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diisopropylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, di-n-butylamino (methyl, ethyl, propyl) Or butyl) acrylate or methacrylate, di-sec-butylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diisobutylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, dimethylamino (methyl, ethyl, propyl or Butyl) acrylamide or methacrylamide, diethylamino (methyl, ethyl, propyl or butyl) acrylamide Or methacrylamide, di -
n-propylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, diisopropylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, di-n
-Butylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, di-se
neutralizing salts with hydrogen halides such as c-butylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, diisobutylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, sulfuric acid, nitric acid, acetic acid, etc. Examples include alkyl halides, benzyl halides, quaternized compounds with dimethyl sulfate, diethyl sulfate, and the like, but are not limited thereto.

[0014]

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Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ and R ₃ are an alkyl group having 1 to 4 carbon atoms, R ₄ is a hydrogen atom, an alkyl group or a benzyl group having 1 to 4 carbon atoms, A represents an oxygen atom or NH, B represents an alkylene group having 2 to 4 carbon atoms or a hydroxypropylene group, and X ⁻ represents an anionic counter ion. In the present invention, among the above cationic polymer flocculants, those having an acrylate structure are more effective. Particularly preferred are those containing dimethylaminoethyl acrylate, neutralized salts of diethylaminoethyl acrylate, and quaternary salts. These cationic vinyl monomers may be used alone or in combination of two or more. Above all, it is a copolymer of acrylamide and a monomer represented by the following general formula (1), and the copolymerization ratio is 95 to 10: 5 to 90 in molar ratio.
Are preferred.

[0016]

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Wherein R ₁ is a hydrogen atom or a methyl group, R ₂ and R ₃ are an alkyl group having 1 to 4 carbon atoms, R ₄ is a hydrogen atom, an alkyl group or a benzyl group having 1 to 4 carbon atoms, A represents an oxygen atom or NH, B represents an alkylene group having 2 to 4 carbon atoms or a hydroxypropylene group, and X ⁻ represents an anionic counter ion. In addition, one of these cationic vinyl monomers copolymerized with acrylamide may be used alone, or two or more thereof may be used in combination.

Another flocculant used in the present invention includes:
A polymer coagulant comprising an amphoteric polymer obtained by copolymerizing a vinyl cationic monomer unit, a vinyl anionic monomer unit and a vinyl nonionic monomer unit in a molecule. Examples of the vinyl-based cationic monomer used as a raw material include neutralized salts of the cationic monomers exemplified as the cationic monomer unit represented by the general formula (1) with hydrogen halide, sulfuric acid, nitric acid, acetic acid, etc., and alkyl halides. And quaternary compounds such as dimethyl sulfate, diethyl sulfate and the like. These vinyl-based cationic monomers may be used alone or in a combination of two or more. As a method for introducing a cationic unit into an acrylic polymer, a method in which (meth) acrylamide is first polymerized and then aminomethylated by a Mannich reaction using a dialkylamine having 1 to 4 carbon atoms and formalin. There is. This product can be used as a salt with a mineral acid or an organic acid and a quaternary ammonium salt with an alkyl halide having 1 to 4 carbon atoms, benzyl halide or a diester of an alcohol having 1 to 4 carbon atoms and sulfuric acid.

The vinyl anionic monomers used as raw materials include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, -Acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamidoethanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 3-acryloyloxypropane Sulfonic acid, 4-acryloyloxybutanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3
-Metal salts such as methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfonic acid and alkali metals and alkaline earth metals or ammonium salts thereof. These anionic monomers may be used alone or in combination of two or more.

Examples of the vinyl nonionic monomer used as a raw material include (meth) acrylamide, (meth) acrylic acid ester, (meth) acrylonitrile, and vinyl acetate. Among them, acrylamide is particularly desirable.

Another flocculant used in the present invention is a cationic polymer flocculant having an amidine unit. The cationic polymer flocculant having an amidine unit contains 20 to 90 mol%, preferably 50 to 90 mol% of an amidine unit represented by the following general formula (4) and / or (5). Further, in addition to the amidine unit represented by the general formula (4) and / or the general formula (5), a repeating unit represented by the following general formula (6), the general formula (7) and the general formula (8) May be included.

[0022]

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In the formula, R ¹ and R ² represent a hydrogen atom or a methyl group, R ³ represents an alkyl group having 1 to 4 carbon atoms or a hydrogen atom,
X ^- represents an anion.

The cationic polymer flocculant having an amidine unit has a reduced viscosity of 0.1 to 10 dl / ml measured at 25 ° C. as a 0.1 g / dl solution in 1 N saline.
g, and the reduced viscosity is 0.1 dl /
If it is less than g, the cohesive strength is weak, and the sludge treatment amount tends to decrease. A method for producing a cationic polymer flocculant having an amidine unit is described in JP-A-5-19251.
No. 3 publication. That is, it is represented by the general formula (9) CH ₂ ＝ CR ² —NHCOR ³ (wherein R ² represents a hydrogen atom or a methyl group, and R ³ represents an alkyl group having 1 to 4 carbon atoms or a hydrogen atom). It can be obtained by producing a copolymer of a compound and acrylonitrile or methacrylonitrile, generating an amino group in the copolymer, and simultaneously or subsequently reacting with an amino group and a cyano group to form an amidinate. .
In use, the cationic polymer flocculant having an amidine unit may be used in combination with another cationic or amphoteric polymer flocculant as long as its performance is not impaired.

As described above, the sludge dewatering agent of the present invention comprises a combination of two types of polymer flocculants, a type A component and a type B component, and the type A component is a cellulose derivative having a cationic substituent (hereinafter referred to as cationic type). Abbreviated as cationic cellulose), and the addition ratio of the cationic cellulose to the sludge is as follows:
Since it fluctuates depending on the properties of the sludge, it cannot be unconditionally specified, but it is 0.01 to 5% by weight per solid sludge (TS).
Preferably it is 0.1 to 2% by weight. On the other hand, the B-class component
The cationic polymer flocculant having a cationic monomer unit represented by the general formula (1) as an essential component,
Either the amphoteric polymer flocculant obtained by copolymerizing a vinyl cationic monomer unit, a vinyl anionic monomer unit and a vinyl nonionic monomer unit in the molecule, or the cationic polymer flocculant having an amidine unit One type of polymer flocculant.

The rate of addition of any one of the cationic polymer flocculant, the amphoteric polymer flocculant or the cationic polymer flocculant having an amidine unit to the sludge, and the properties of the sludge Although it cannot be unconditionally specified because it fluctuates depending on the solid content of the sludge, it is in the range of 0.1 to 3.0% by weight, preferably 0.2 to 2.0% by weight. If necessary, an inorganic flocculant such as a sulfate band, polyaluminum chloride, or polyiron sulfate can be used in combination. In this case, the inorganic coagulant is usually added in an amount of 100 to 5000 ppm based on the sludge slurry.

Here, the A-class component may be a cellulose derivative having a cationic substituent, for example, a cellulose compound represented by the molecular formula (2) alone, and other cationic compounds may be used. It may be a mixture with a cellulose compound having a substituent. In addition, the B type component is
Explaining the above-mentioned cationic polymer flocculant, which is one of them, for example, the cationic polymer having the cationic monomer unit represented by the general formula (1) or (3) as an essential component. As long as it is a molecule, a (30/70) copolymer of methyl quaternary chloride of dimethylaminoethyl acrylate and acrylamide alone may be used, and a (30/70) copolymer of methyl quaternary chloride of dimethylaminoisopropyl acrylate and acrylamide may be used. ) A cationic polymer flocculant comprising a mixture with a copolymer may be used, but it does not mean, for example, a mixture with a cationic polymer flocculant having an amidine unit.

The sludge dewatering agent of the present invention can be applied to a sludge simultaneously as a combined flocculant of two types of polymer flocculants of a type A component and a type B component. When it is applied to cases where it is difficult to dehydrate such as containing a surfactant, the above-mentioned cationic cellulose is first added, thoroughly mixed and stirred, and then the cationic polymer aggregation shown as above or One of a coagulant or an amphoteric polymer coagulant is added and a floc is formed by stirring, and the floc is dehydrated by a dehydrator such as a screw decanter or a belt press dehydrator to obtain a dehydrated cake having a low water content. The dehydration method is more preferable. In this case, since the mixing and stirring of the cationic cellulose derivative and the sludge is not intended to generate flocs, it is preferable to perform stronger stirring than usual stirring so that the cationic cellulose derivative and the sludge are sufficiently mixed. Next, one of the above-mentioned cationic polymer flocculant or amphoteric polymer flocculant is added and floc is formed by stirring. In this case, floc is formed as large as possible with stirring. It is good to stir it.

In the combination dehydrating agent of the present invention, which is a combination of two types of polymer flocculants, a type A component and a type B component, the mixing ratio of the type A component polymer flocculant is 5 to 50% by weight, preferably 1%.
-10% by weight. This is because the synergistic effect of both components is high in such a range. Further, the amount of the sludge dewatering agent of the present invention added to the sludge is usually the total amount of the type A component and the type B component with respect to the solid content of the slurry sludge, that is,
The amount of the combined sludge dewatering agent of the present invention is 0.1 to 3.0% by weight, preferably 0.2 to 1.0% by weight.

[0030]

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to only these examples. Examples 1 to 9 below describe the case where the A-type component and the B-type component of the dehydrating agent of the present invention are added to sludge by a simultaneous addition method. Next, in Examples 10 to 19, a case where the type A component of the dehydrating agent of the present invention is preliminarily added to the sludge, and then the type B component is added and the addition and dehydration are performed by a sequential addition method will be described. The results displayed in the examples are as follows. ◎ ・ ・ ・ very good ○ ・ ・ ・ good △ ・ ・ ・ Somewhat bad × ・ ・ ・ bad

Examples 1-2, Comparative Examples 1-2 The sludge discharged from the M City human waste treatment facility was treated with cationic cellulose (Leoguard G: manufactured by Lion Corporation).
Is 20% by weight and 80% by weight of a cationic polymer flocculant a shown in Table 2 below (0.2% by weight of distilled water).
Dissolved in weight%. ) Was tested. The properties of the excess sludge are as follows. pH 7.0; TS 1.5%; SS 1.4%; VT
S 74.5%; Electric conductivity 1.1 mS / cm

(Testing method)
ml beaker and 20% by weight of cationic cellulose
80% by weight of cationic polymer flocculant a shown in Table 2 below
Was dissolved in distilled water to 0.2% by weight of distilled water
Are added as shown in Table 1 below and at 500 rpm
Stir for 1 minute. Size of flocculated floc generated by stirring
After measuring its height, transfer it onto a polyester filter cloth and
Transients were observed. The sludge after gravity filtration is applied to two polyester
And a filter pressure of 0.4kg / with an air cylinder.
cm ^TwoSqueezed and dewatered for 1 minute at the pressure of
Observe the water content and measure the water content of the dehydrated cake by the usual method.
Was. The results are shown in Table 1. As a comparative example,
The test was performed using only the on-polymer flocculant. The result
Also shown in Table 1. Here, the sludge dewatering agent of the present invention is
Implementation of Table 1 means adding as shown in Table 1.
To explain Example 1, dissolve in distilled water to 0.2% by weight
Sludge dewatering agent into sludge TS (dry solids of sludge)
Here, the sludge contains 1.5%. ) Based on
Then, 1.3% is added.

[0033]

[Table 1]

[0034]

[Table 2]

(Test Results) As is clear from Table 1, in each of the examples, the formed flocs have a large diameter, excellent strength, good filterability, and low cake moisture content after dewatering. On the other hand, in the case of the comparative examples, the formed flocs were small in diameter, inferior in strength, and poor in filterability and peelability.

Examples 3-6, Comparative Examples 3-6 Catalytic cellulose (Leogard G: manufactured by Lion Co., Ltd.) was used for sludge discharged from the M City human waste treatment facility.
A test was conducted by adding a sludge dewatering agent consisting of 20% by weight and 80% by weight of one of the amphoteric polymer flocculants b and c shown in Table 4 below (dissolved in distilled water at 0.2% by weight). Was done. The properties of the excess sludge are as follows. pH 7.0; TS 1.5%; SS 1.4%; VT
S 74.5%; Electric conductivity 1.1 mS / cm

(Testing method)
In a beaker, 20% by weight of cationic cellulose and 80% by weight of cationic polymer flocculant b shown in Table 4 below
A solution obtained by dissolving a sludge dewatering agent consisting of (or a cationic polymer coagulant c 80% by weight) in distilled water at 0.2% by weight was added as shown in Table 3 below, and stirred at 500 rpm for 1 minute. After measuring the size of the aggregated floc generated by the stirring, the floc was transferred onto a polyester filter cloth, and the gravity filterability was observed. The sludge after gravity filtration is sandwiched between two polyester filter cloths, and the surface pressure is 0.4 kg / cm with an air cylinder.
After squeezing and dehydrating at a pressure of ² for 1 minute, the releasability from the filter cloth was observed, and the water content of the dehydrated cake was measured by a conventional method. The results are shown in Table 3. As a comparative example, a test was performed using only the amphoteric polymer flocculant. The results are shown in Table 3.

[0038]

[Table 3]

[0039]

[Table 4]

(Test Results) As is clear from Table 3, in each of the examples, the formed flocs have a large diameter, excellent strength, good filterability, and low cake moisture content after dewatering. On the other hand, in the case of the comparative examples, the formed flocs were small in diameter, inferior in strength, and poor in filterability and peelability.

Example 7 and Comparative Example 7 Except for the sludge having the following properties discharged from the municipal wastewater treatment facility, an addition test of a sludge dewatering agent was carried out in the same manner as in Example 3 and Comparative Example 3, and the results are shown in Table 5 below. The result was obtained. The properties of the sludge used in the test are as follows. pH 6.8; TS 2.4%; SS 2.3%; VT
S 79.1%; electric conductivity 1.4 mS / cm

[0042]

[Table 5]

(Test Results) As is clear from Table 5, in each of the examples, the formed flocs have a large diameter, excellent strength, good filterability, and low cake moisture content after dewatering. On the other hand, in the case of the comparative examples, the formed flocs were small in diameter, inferior in strength, and poor in filterability and peelability. The cationic polymer flocculants used in the tests of Example 7 and Comparative Example 7 are as shown in Table 4.

Examples 8 to 9 and Comparative Examples 8 to 9 For the sludge discharged from the M City human waste treatment facility, cationic cellulose (Leoguard G: manufactured by Lion Corporation) was used.
Cationic polymer flocculant having 20% by weight and amidine unit (N-vinylformamide / acrylonitrile (5
0/50) Test by adding a sludge dewatering agent (dissolved in distilled water to 0.2% by weight) consisting of 80% by weight of an amidine compound of the copolymer and a cationic polymer flocculant having a molecular weight of 3,000,000). Was done. The properties of the excess sludge are as follows. pH 7.0; TS 1.5%; SS 1.4%; VT
S 74.5%; Electric conductivity 1.1 mS / cm

(Testing method)
ml of a cationic polymer flocculant having 20% by weight of cationic cellulose and the above amidine unit.
A sludge dewatering agent consisting of 0.2% by weight dissolved in 0.2% by weight of distilled water was added as shown in Table 6 below, and 500 r
Stirred at pm for 1 minute. After measuring the size of the flocculated floc generated by stirring, transferred to a polyester filter cloth,
Gravity filterability was observed. The sludge after gravity filtration is sandwiched between two pieces of polyester filter cloth, and the surface pressure is 0.4 with an air cylinder.
After squeezing and dehydrating at a pressure of kg / cm ² for 1 minute, the releasability from the filter cloth was observed, and the water content of the dehydrated cake was measured by a conventional method. The results are shown in Table 6. As a comparative example, a test was performed using only a cationic polymer flocculant having an amidine unit. The results are shown in Table 6.

[0046]

[Table 6]

(Test Results) As is clear from Table 6, in each of the examples, the formed flocs have a large diameter, excellent strength, good filterability, and low cake moisture content after dehydration. On the other hand, in the case of the comparative examples, the formed flocs were small in diameter, inferior in strength, and poor in filterability and peelability.

Examples 10 to 12 and Comparative Examples 10 to 11 Concentrated sludge having the following properties discharged from the K sanitation facility association was treated with cationic cellulose (Leogard G, manufactured by Lion Corporation) and the cationic sludge shown in Table 9 below. The test was conducted by adding the polymer coagulant d dissolved in distilled water at 0.2% by weight in the order shown in Table 7 as shown in Table 7. Here, the meaning of performing the test by adding the sludge dewatering agent of the present invention at the fraction shown in Table 7 will be described with reference to Example 10 in Table 7. First, distilled water was added to 0.2% by weight. The dissolved cationic cellulose was added in an amount of 0.3% based on the sludge TS (a dried solid matter of the sludge, which is contained in the sludge in this case at 1.5%), and stirred at 1000 rpm for 10 seconds. Next, it means that 0.7% of the cationic polymer coagulant d shown in Table 9 dissolved in distilled water at 0.2% by weight was added based on the TS of the sludge. (Hereinafter, in addition to Example 11 in Table 7, the same applies to Table 8 and thereafter.) The properties of the concentrated sludge are as follows. pH 7.1; TS 2.8%; SS 2.7%; VT
S 67.2%; electric conductivity 1.6 mS / cm

(Testing method)
The mixture was placed in a ml beaker, cationic cellulose (dissolved in distilled water at 0.2% by weight) was added at the fraction shown in Table 7, and the mixture was stirred at 1000 rpm for 10 seconds. Next, a cationic polymer flocculant d (dissolved in distilled water at 0.2% by weight) shown in Table 9 below was added at a fraction shown in Table 7, and stirred at 500 rpm for 1 minute. After measuring the size of the aggregated floc generated by the stirring, the floc was transferred onto a polyester filter cloth, and the gravity filterability was observed. The sludge after gravity filtration is sandwiched between two pieces of polyester filter cloth, pressed and dewatered with an air cylinder at a surface pressure of 0.4 kg / cm ² for 1 minute, and then observed for releasability from the filter cloth. The water content of the dehydrated cake was measured by the above method. The results are shown in Table 7. As a comparative example, a test was performed using only a cationic polymer flocculant. The results are shown in Table 7.

[0050]

[Table 7]

Examples 13 to 14 and Comparative Examples 12 to 13 For the sludge having the following properties discharged from the municipal wastewater treatment facility, cationic cellulose (Leogard G: manufactured by Lion Corporation) and cationic properties shown in Table 9 below were used. The test was performed by adding, in the order of the polymer flocculant e, those dissolved in distilled water at 0.2% by weight. The properties of the sludge are as follows. pH 7.0; TS 1.5%; SS 1.4%; VT
S 74.5%; electric conductivity 1.1 mS / cm (Test method) 200 ml of the above-mentioned sludge was placed in a 300 ml beaker, and cationic cellulose (dissolved in distilled water at 0.2% by weight) was as shown in Table 8. Add 10% at the indicated fraction.
The mixture was stirred at 00 rpm for 10 seconds. Next, a cationic polymer flocculant e (dissolved in distilled water at 0.2% by weight) shown in Table 9 below was added at the fraction shown in Table 8, and 5
The mixture was stirred at 00 rpm for 1 minute. Hereinafter, the test was performed according to the test method in Example 10 and Comparative Example 10. The results are shown in Table 8.

[0052]

[Table 8]

[0053]

[Table 9]

(Test Results) As is clear from Tables 7 and 8, in the case of the examples, the flocs produced in each case were large in diameter, excellent in strength, good in filterability, and wet with cake after dehydration. The rate is also low. On the other hand, in the case of the comparative examples, the formed flocs were small in diameter, inferior in strength, and poor in filterability and peelability.

Examples 15-18, Comparative Examples 14-15 Regarding the excess sludge discharged from the H sanitation center, first, cationic cellulose (Leogard G: manufactured by Lion Corporation) was added to the excess sludge. The cationic polymer flocculant f or g shown in Table 12 is added to the excess sludge. Each coagulant was dissolved in distilled water at a concentration of 0.2% by weight, and a test was conducted. The properties of the sludge are as follows. pH 7.3; TS 2.6%; SS 2.5%; VT
S 71.5%; electric conductivity 2.0 mS / cm

(Test Method) 200 ml of the excess sludge was
In a 00 ml beaker, cationic cellulose (dissolved in distilled water at 0.2% by weight) was added at the fraction shown in Table 10 and stirred at 1000 rpm for 10 seconds. Then, amphoteric polymer flocculants f or g shown in Table 12 below
(All dissolved in distilled water at 0.2% by weight) were added at the fractions shown in Table 10, and the mixture was stirred at 500 rpm for 1 minute. After measuring the size of the aggregated floc generated by the stirring, the floc was transferred onto a polyester filter cloth, and the gravity filterability was observed. The sludge after gravity filtration is sandwiched between two polyester filter cloths, and the surface pressure is 0.4 kg / cm with an air cylinder.
After squeezing and dehydrating at a pressure of ² for 1 minute, the releasability from the filter cloth was observed, and the water content of the defatted cake was measured by a conventional method. The results are shown in Table 10. As a comparative example, a test was performed using only the amphoteric polymer flocculant f or g. The results are shown in Table 10.

[0057]

[Table 10]

Example 19, Comparative Example 16 Cationic cellulose (Leogard G, manufactured by Lion Corporation) was added to the excess sludge having the following properties discharged from an I-shiseki treatment facility at the fractions shown in Table 11. 10
The mixture was stirred at 00 rpm for 10 seconds. Next, a test was carried out by adding an amphoteric polymer flocculant g shown in Table 12 below (each dissolved in distilled water at 0.2% by weight) at a fraction shown in Table 11. The properties of the sludge are as follows. pH 6.8; TS 2.4%; SS 2.3%; VT
S 79.1%; Electric conductivity 1.8 mS / cm

(Testing method)
The mixture was placed in a ml beaker, and cationic cellulose (dissolved in distilled water at 0.2% by weight) was added at the fractions shown in Table 11 and stirred at 1000 rpm for 10 seconds. Then, an amphoteric polymer flocculant g (dissolved in distilled water at 0.2% by weight) shown in Table 12 below was added at a fraction shown in Table 11, and stirred at 500 rpm for 1 minute. Less than,
The test was performed according to the test method in Example 15 and Comparative Example 14. The results are shown in Table 11.

[0060]

[Table 11]

[0061]

[Table 12]

(Test Results) As is clear from Tables 10 and 11, in the case of the examples, the flocs produced in each case were large in diameter, excellent in strength, good in filterability, and water-containing cake after dehydration. The rate is also low. In contrast, in the case of the comparative example,
In each case, the generated floc has a small diameter, poor strength,
The filterability was poor and the water content of the dehydrated cake was high.

Examples 20 to 21 and Comparative Examples 17 to 18 For sludge discharged from the M city human waste treatment facility, cationic cellulose (Leogard G, manufactured by Lion Corporation) dissolved in distilled water at 0.2% by weight was used. It was added at the fractions shown in Table 13 and stirred at 1000 rpm for 10 seconds. Next, a cationic polymer flocculant having an amidine unit dissolved in distilled water at 0.2% by weight [amidine compound of N-vinylformamide / acrylonitrile (50/50) copolymer: molecular weight 3,000,000] h It was added at the fractions shown in the table and stirred at 500 rpm for 1 minute. After measuring the size of the aggregated floc generated by the stirring, the floc was transferred onto a polyester filter cloth, and the gravity filterability was observed. The sludge after gravity filtration is sandwiched between two pieces of polyester filter cloth, pressed and dewatered with an air cylinder at a surface pressure of 0.4 kg / cm ² for 1 minute, and then peeled from the filter cloth is observed. The moisture content of the defatted cake was measured by the above method. The results are shown in Table 13. As a comparative example, a test was performed using only the cationic polymer flocculant h having an amidine unit. The results are shown in Table 13. The properties of the sludge are pH 7.0; TS
1.5%; SS 1.4%; VTS 74.5%; electrical conductivity 1.1 mS / cm.

[0064]

[Table 13]

(Test results) As is clear from Table 13,
In the case of the examples, the formed flocs have a large diameter, excellent strength, good filterability, and low cake moisture content after dehydration. On the other hand, in the case of the comparative examples, the formed flocs were small in diameter, inferior in strength, poor in filterability, and high in water content of the dehydrated cake.

[0066]

As described above, the sludge dewatering agent of the present invention, which is a combination of two types of polymer flocculants, a type A component and a type B component, is used in a sewage treatment plant, human waste treatment plant, various industrial wastewater treatment facilities, and the like. By adding to the generated sludge and coagulating the sludge, the sludge can be coagulated as a floc having a large and excellent strength, and can be efficiently dewatered.
A cake having a small water content after dehydration can be obtained. The type A component of the sludge dewatering agent is the above-mentioned polymer flocculant comprising a cellulose derivative having a cationic substituent,
The seed component includes the cationic polymer flocculant having a cationic monomer unit represented by the general formula (1) as an essential component, a vinyl cationic monomer unit, a vinyl anionic monomer unit, and a vinyl nonion in the molecule. A polymer flocculant comprising the amphoteric polymer obtained by copolymerizing a hydrophilic monomer unit, or one of the cationic polymer flocculants having an amidine unit.

In particular, for sludge which contains a large amount of inorganic salts and surfactants and is difficult to dehydrate, when applying a polymer flocculant to the sludge, first, cationic cellulose was added to the sludge and mixed. Thereafter, the sludge is flocculated into flocs by the method of dewatering sludge shown above or by adding and mixing a flocculant to the sludge, the flocculated flocs are dewatered, and the sludge is converted into flocs having a large and excellent strength. It can be coagulated, can be efficiently dewatered, and can obtain a cake having a small water content after dehydration. As described above, as the properties of wastewater subject to water treatment are diversifying,
In addition, the efficiency of the sludge dewatering step can be improved by the sludge dewatering method of the present invention despite the fact that the properties of the drainage constantly change.

Claims (10)

[Claims] 1. A sludge dewatering agent comprising a combination of a cellulose derivative having a cationic substituent and an acrylate polymer flocculant. 2. The sludge dewatering agent according to claim 1, wherein the acrylate polymer flocculant is a copolymer of acrylamide and a monomer represented by the following general formula (1). . Embedded image However, in the formula, R ₁ is a hydrogen atom or a methyl group, R ₂ ,
R ₃ is an alkyl group having 1 to 4 carbon atoms, R ₄ is a hydrogen atom, an alkyl group or benzyl group having 1 to 4 carbon atoms, A is an oxygen atom or NH, B is an alkylene group having 2 to 4 carbon atoms or hydroxypropylene. group, X ^- represents a Aanion counterions. 3. The copolymer according to claim 1, wherein the acrylamide and the monomer represented by the general formula (1) have a polymerization ratio of 95 to 1.
The sludge dewatering agent according to claim 2, which is a copolymer obtained by copolymerizing from 0: 5 to 90. 4. A sludge dewatering agent comprising a combination of a cellulose derivative having a cationic substituent and an amphoteric polymer flocculant. 5. A sludge dewatering agent comprising a combination of a cellulose derivative having a cationic substituent and a cationic polymer flocculant having an amidine unit. 6. A method for dewatering sludge, comprising adding and mixing a cellulose derivative having a cationic substituent to sludge, followed by adding an acrylate polymer flocculant and performing dehydration treatment. 7. The sludge dewatering method according to claim 6, wherein the acrylate polymer flocculant is a copolymer of acrylamide and a monomer represented by the following general formula (1). Method. Embedded image However, in the formula, R ₁ is a hydrogen atom or a methyl group, R ₂ ,
R ₃ is an alkyl group having 1 to 4 carbon atoms, R ₄ is a hydrogen atom, an alkyl group or benzyl group having 1 to 4 carbon atoms, A is an oxygen atom or NH, B is an alkylene group having 2 to 4 carbon atoms or hydroxypropylene. group, X ^- represents a Aanion counterions. 8. The copolymer according to claim 1, wherein the acrylamide and the monomer represented by the general formula (1) have a polymerization ratio of 95 to 1.
8. The method for dewatering sludge according to claim 7, wherein the copolymer is a copolymer obtained by copolymerizing from 0: 5 to 90. 9. A method for dewatering sludge, comprising adding and mixing a cellulose derivative having a cationic substituent, followed by addition of an amphoteric polymer flocculant and dehydration treatment. 10. A method for dewatering sludge, comprising adding and mixing a cellulose derivative having a cationic substituent, followed by adding a cationic polymer flocculant having an amidine unit and performing a dehydration treatment.