JP3178224B2 - Sludge dewatering agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel sludge dewatering agent and a method for dewatering sludge using the same. More specifically, the present invention provides a sludge dewatering agent that gives a dewatered cake having a low water content, in which the sludge coagulation state is good even when the amount of the inorganic coagulant used is small, as compared with a conventional sludge dewatering agent. The present invention relates to a method for efficiently dewatering sludge using the wastewater.

[0002]

2. Description of the Related Art In recent years, sludge generated from municipal sewage and human waste treatment has been hardly dehydrated due to an increase in the ratio of organic substances and decay. Moisture content of cake after mechanical dehydration is about 80%
The above-mentioned sludge is regarded as a hardly dewaterable sludge. As an efficient treatment method, a so-called sludge using two kinds of cationic and anionic polymer flocculants instead of the conventional cationic polymer flocculant alone. A two-liquid method and a method using an inorganic flocculant and an amphoteric polymer flocculant in combination have been developed and put into practical use. Particularly, the latter method is disclosed in JP-A-59-16599 (inorganic coagulant and Mannich-modified composition),
3-158200 (Amphoteric polymer flocculant having cation and anion in the same molecule as inorganic flocculant) and JP-A-2-180700 (Amphoteric polymer having cation and anion in the same molecule as inorganic flocculant) (Coagulant) and are widely used for improving the dewatering treatment of hardly dewaterable sludge. However, the amount of the inorganic coagulant added is usually required to be 10 to 20% as a product per sludge solid. Therefore, it is necessary to use sludge pH lowering machinery and equipment, especially in the combustion furnace when using iron salts, incinerators when using iron salts. In addition, various problems that do not occur in the conventional treatment of a single polymer flocculant, such as the generation of clinker and an increase in the melting point in the incineration ash melting treatment when an aluminum salt is used, are caused. For this reason, a polymer flocculant which can perform efficient dehydration with the addition of a small amount of the inorganic flocculant and without the addition has been desired.

[0003]

SUMMARY OF THE INVENTION The present invention overcomes such disadvantages of the conventional sludge dehydrating agent and can be used even if the amount of the inorganic coagulant is small or no inorganic coagulant is added. An object of the present invention is to provide an organic sludge dewatering agent capable of efficiently dewatering sludge with a small amount, and a method for dewatering sludge using the dewatering agent.

[0004]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above-mentioned object, and as a result, the present inventors have found that a water-soluble polymer containing amidine units, a specific amphoteric water-soluble polymer and a combination of an acidic substance are used. It has been found that the purpose can be achieved by a dehydrating agent, and the present invention has been completed based on this finding. That is, the present invention consists of the following items. (1) (A) a cationic water-soluble polymer containing amidine units, (B) an amphoteric water-soluble polymer obtained by copolymerizing a cationic vinyl monomer, an anionic vinyl monomer and a nonionic vinyl monomer. (C) A sludge dewatering agent comprising an acidic substance.

Hereinafter, the present invention will be described in detail. The water-soluble polymer having an amidine unit used as the component (A) of the dehydrating agent of the present invention is a cationic polymer having an amidine unit represented by the following general formula [1] and / or general formula [2]. is there. In the formula, R ¹ and R ² are a hydrogen atom or a methyl group, X ⁻ is a halogen ion such as a chloride ion, an iodine ion, a bromine ion, NO ₃ ⁻ , CH ₃ COO ^−.
And the like.

Embedded image In the present invention, the water-soluble polymer having an amidine unit used as the component (A) contains the amidine unit represented by the general formula [1] and / or the general formula [2] in an amount of 20 to 90 mol%, preferably 50 to 90 mol%. It contains 90 mol%. The water-soluble polymer having an amidine unit used as the component (A) includes, in addition to the amidine unit represented by the general formula [1] and / or the general formula [2], a general formula [3] and a general formula [4] And a repeating unit represented by the general formula [5]. In the formula, R ¹ and R ² are a hydrogen atom or a methyl group, R ³
Is an alkyl group or a hydrogen atom having 1 to 4 carbon atoms, X ^-
Is a halogen ion such as chlorine ion, iodine ion and bromine ion, and an anion such as NO ₃ ⁻ and CH ₃ COO ⁻ .

[0006]

Embedded image Water-soluble polymers having the amidine unit represented by the general formula CH ^₂ = CR ₂ -NHCOR ³ (wherein, the R ² is a hydrogen atom or a methyl group, R ³ is C 1 -C
To 4) and a copolymer of acrylonitrile or methacrylonitrile to produce an amino group,
It can be obtained by simultaneously or subsequently reacting an amino group with a cyano group to form an amidine. The polymer having an amidine unit has an intrinsic viscosity of not less than 1.0 dl / g, more preferably 3.0 dl / g, measured at 30 ° C. using a 1N aqueous solution of sodium chloride as a solvent.
It is desirable that this is the case. This intrinsic viscosity is 1.0 dl /
If it is less than g, the cohesive strength is weak and the sludge treatment amount tends to decrease, which is not preferable. The amphoteric water-soluble polymer used as the component (B) in the sludge dewatering agent of the present invention is obtained by copolymerizing a cationic vinyl monomer, an anionic vinyl monomer and a nonionic vinyl monomer. As the cationic vinyl monomer, for example, a compound represented by the general formula [6]:

[0007]

Embedded image Can be used. In the formula, R ⁴ is a hydrogen atom or a methyl group, and R ⁵ is a carbon atom having 1 to 4 carbon atoms such as a methylene group, an ethylene group, a propylene group, and a butylene group.
Wherein the propylene and butylene groups may be linear or branched. R ⁶ is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, s
an alkyl group having 1 to 4 carbon atoms such as an ec-butyl group and a t-butyl group; R ⁷ is a hydrogen atom;
Is an alkyl group or a benzyl group. The A is -O- or -NH-, Y ^- is a chlorine ion, an iodine ion, a halogen ion such as a bromine ^{_{ion, 1 / 2SO 4 2-, NO}} 3 -,
An anion such as CH ₃ COO ⁻ , CH ₃ SO ₄ ^— or C ₂ H ₅ SO ₄ ^— .

The monomer represented by the general formula [6] includes, for example, 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-sec-butylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, diisobutylamino (methyl, ethyl, propyl or butyl) acrylamide or Examples include hydrogen halides such as methacrylamide, neutralized salts with sulfuric acid, nitric acid, acetic acid, etc., and quaternized compounds with alkyl halides, dimethyl sulfate, diethyl sulfate, and the like. Is, but not of course not limited thereto. Examples of the hydrogen halide include hydrogen chloride, hydrogen bromide, and examples of the alkyl halide include methyl chloride, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, and benzyl chloride. One of these cationic vinyl monomers may be used, or two or more thereof may be used in combination.

The anionic vinyl monomers include, for example, acrylic acid, methacrylic acid, α-ethylacrylic acid and their sodium, potassium, ammonium salts, vinyl sulfonic acid, vinyl methyl sulfonic acid, allyl sulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 3-methacrylamidopropanesulfonic acid,
Examples include, but are not limited to, 3-methacryloyloxypropanesulfonic acid and their sodium, potassium, and ammonium salts. These anionic vinyl monomers may be used alone or in combination of two or more. Further, nonionic vinyl monomers include, for example, vinyl group-containing amides such as acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, and vinyl cyanide compounds such as acrylonitrile and methacrylonitrile. , Methyl acrylate,
(Meth) acrylic acid alkyl esters such as ethyl acrylate, methyl methacrylate, and ethyl methacrylate; carboxylic acid vinyl esters such as vinyl acetate;
Examples include aromatic vinyl compounds such as styrene, α-methylstyrene, and p-methylstyrene, but are not limited thereto. These nonionic vinyl monomers may be used alone or in combination of two or more.

The proportion of each component in the amphoteric water-soluble polymer of the component (B) is not particularly limited, but the content of the cationic vinyl monomer unit is C mol%, and the content of the anionic vinyl monomer unit is A mol%, and when the content of the nonionic vinyl monomer unit is N mol%, the formula:

(Equation 1) It is preferable that each component is contained so as to satisfy the following relationship. The molecular weight of the amphoteric water-soluble polymer is
1N aqueous sodium nitrate solution (pH = 3) as solvent
It is desirable that the intrinsic viscosity measured at ℃ is 5.0 dl / g or more. If the intrinsic viscosity is less than 5.0 dl / g, the cohesive strength is weak, and the sludge treatment amount tends to decrease, which is not preferable. The method for producing the amphoteric water-soluble polymer of the component (B) is not particularly limited, and any method such as ordinary solution polymerization, suspension polymerization, and emulsion polymerization can be used. For example, in aqueous solution polymerization, ammonium persulfate, potassium persulfate,
A predetermined amount of each of the above monomers may be polymerized under ordinary polymerization conditions using 2′-azobis (2-amidinopropane) dihydrochloride or the like.

The proportion of the water-soluble polymer having an amidine unit of the component (A) and the amphoteric water-soluble polymer of the component (B) in the sludge dewatering agent of the present invention is not particularly limited. The amount is preferably at least 50% by weight based on the total amount of the components (A) and (B). If the amount of the component (B) is less than 30% by weight, the effects of the present invention cannot be sufficiently exhibited. In the production of the sludge dewatering agent of the present invention, when the components (A) and (B) are mixed and dissolved in the same tank, a reaction product of both polymers is generated. An acidic substance is added as the component (C) in order to suppress the dissociation of. As the acidic substance, for example, sulfamic acid,
Sodium hydrogen sulfate, hydrogen chloride, sulfuric acid and the like can be used. The amount of the component (C) used is at least the amount required to neutralize the alkalinity component in the dissolved water. M of dissolved water
Alkalinity, industrial water, not more than city water at 50mg / l (CaCO ₃ conversion), in the well water of sewage water or high alkalinity, an 100~150mg / l (CaCO ₃ conversion).
Therefore, the M alkalinity of dissolved water is at most 150 mg.
/ L (in terms of CaCO ₃ ), and 291 mg / l is required to neutralize this with, for example, sulfamic acid. When the dissolution concentration of the polymer is set to 0.3% (3000 mg / l), about 10% by weight of sulfamic acid with respect to the weight of the polymer may be previously mixed with the polymer.
The component (A) and the component (B) may be dissolved after the component (C) is put into the dissolving water and dissolved.

By using the sludge dewatering agent of the present invention, it is possible to easily and efficiently dewater hardly dewaterable sludge without using an inorganic coagulant. Since an inorganic coagulant is not used in the dehydration treatment, there is no possibility of causing a problem in corrosion of equipment and a combustion furnace and in incineration ash melting treatment. However, a small amount of an inorganic flocculant may be used in combination with the sludge dewatering agent of the present invention, if necessary, as long as these problems do not significantly hinder. Examples of the inorganic coagulant used in combination include a sulfuric acid band, ferric chloride, ferrous sulfate, and polyaluminum chloride. In the sludge dewatering method of the present invention, the cationic water-soluble polymer containing amidine units (A) and the amphoteric water-soluble polymer (B) are simultaneously added to the sludge. The method of adding one of the components first to coagulate the sludge and then adding the other component is not preferable because a sufficient dehydration effect cannot be obtained. As a dehydrator used for dewatering sludge,
Equipment used for ordinary sludge treatment can be used without any particular limitation, and examples thereof include a centrifugal dehydrator, a belt press dehydrator, a screw press dehydrator, a filter press dehydrator, and a vacuum dehydrator. The sludge to which the method of the present invention can be applied is not particularly limited, and can be effectively applied to, for example, mixed sludge including organic sludge and coagulated sludge generated in sewage, human waste, general industrial wastewater treatment, and the like.

[0013]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Production Example 1 (Water-soluble polymer containing amidine unit) 5 equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube
In a 00 ml flask, 35.5 g of N-vinylformamide
(0.5 mol), 26.5 g (0.5 mol) of acrylonitrile and 310 g of water, and the atmosphere was replaced with nitrogen.
The temperature was raised to 60 ° C. with stirring, 1.0 g of a 10% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride was added, and polymerization was continued for 5 hours while maintaining the temperature at 60 ° C. 98.1 g of concentrated hydrochloric acid (1.0 mol as hydrogen chloride) was added to the suspension in which the polymer was precipitated in water, and the mixture was reacted for 4 hours while heating and refluxing to convert the polymer into amidine. The obtained polymer solution was added to acetone, and the precipitated polymer was dried under vacuum. The intrinsic viscosity of this polymer measured at 30 ° C. using a 1N aqueous solution of sodium chloride as a solvent was 4.2 dl / g. Production Example 2 (Amphoteric water-soluble polymer) 5 equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube
In a 00 ml flask, 15.6 g (0.075 mol) of methyl chloride quaternary compound of diethylaminoethyl methacrylate were added.
9.7 g (0.05 mol) of methyl quaternary methyl chloride of diethylaminoethyl acrylate, 6.3 g (0.0%) of acrylic acid
88 mol), 20.4 g (0.288 mol) of acrylamide and 400 g of water, and the atmosphere was replaced with nitrogen.
The temperature was raised to 60 ° C. with stirring, 1.0 g of a 10% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride was added, and polymerization was continued for 5 hours while maintaining the temperature at 60 ° C. The obtained polymer solution was added to acetone, and the precipitated polymer was dried under vacuum. The intrinsic viscosity of this polymer measured at 30 ° C. using a 1N aqueous solution of sodium nitrate as a solvent is 9.0 dl / g.
Met. Production Example 3 (sludge dewatering agent) 6.7 g of the polymer powder obtained in Production Example 2, 3.3 g of the polymer powder obtained in Production Example 1, and 1.0 g of sulfamic acid
Was mixed to obtain a sludge dehydrating agent mixture 2.a. This mixture was dissolved in water and used for the following sludge treatment. Table 1 shows the sludge dewatering agents composed of polymers used in Examples and Comparative Examples.

[0014]

[Table 1]

1) Intrinsic Viscosity Polymers 1, 2, 3, 4, c, d and e have an intrinsic viscosity of 1
The measurement was performed at 30 ° C. using an N sodium nitrate aqueous solution as a solvent. The intrinsic viscosities of the polymers a and b were measured at 30 ° C. using a 1N aqueous solution of sodium chloride as a solvent. 2) Abbreviations mean the following. DAM: Methyl quaternary chloride of dimethylaminoethyl methacrylate DAA: Methyl quaternary chloride of dimethylaminoethyl acrylate AA: Acrylic acid AAm: Acrylamide 3) Colloid equivalent The colloid equivalent is determined by the colloid titration method (Ryoichi Chitate). , Published by Nankodo Co., Ltd., November 30, 1969). The colloid equivalents of Polymers 1, 2 and 3 are as follows:
The measured cation equivalent value (pH = 3) is shown. 4) C / A indicates the molar ratio between the cationic monomer unit and the anionic monomer unit.

The capillary suction time (hereinafter abbreviated as CST) was measured using the apparatus shown in FIG. That is, when the sludge 3 is poured into a cylindrical tube 2 placed on a No. 17 filter paper 1 manufactured by Whatman, and the sample is absorbed by the filter paper and wet-expanded while drawing a concentric circle, the distance AB
The time (seconds) required to wet the space (diameter at point A 30 mm, diameter at point B 45 mm) was measured by the counter 4 to obtain the CST. The standard for completion of sludge reforming with inorganic coagulant is CST
The value of / SS is about 20 seconds /%. The evaluation of the sludge dewatering agent was based on the optimum sludge dewatering agent addition rate (vs. SS
%), The water content after filtration for 30 seconds, cake yield and water content of 4%.
For each item, assign a score of 0 to 3 to each value,
Performed by the total points. Table 2 shows the relationship between the value of each item and the score.

[0017]

[Table 2]

Examples 1-3 Coagulation and dehydration tests were carried out using mixed sludge from a sewage treatment plant. Sludge properties are pH 5.8, SS 3.7%, VSS / S
S77%, fiber content / SS3%. The CST of this sludge was 1350 seconds, and the CST / SS was 365 seconds /%. 200 g of this sludge was collected in a homogenizer container having a capacity of 500 ml, and various sludge dehydrating agents shown in the columns of Examples 1 to 3 in Table 3 were added thereto and reacted at 10,000 rpm for 7 seconds. In addition, this coagulation dehydration test is a test method assuming a centrifugal dehydrator in which the cohesive floc destruction resistance is required. After measuring the floc diameter, the sludge was subjected to gravity filtration for 30 seconds under the conditions of a 100 mesh filter cloth and a filtration area of 19.6 cm ² , and the filtration amount after 30 seconds was measured. The addition rate of the sludge dehydrating agent was changed by 0.2% per SS to carry out a coagulation test, and the addition rate at which the best gravity filterability was obtained was determined. Gravity filterability was evaluated based on the water content of coagulated sludge during filtration for 30 seconds. After packing the gravity-filtrated material into a compression column having a diameter of 30 mm and a height of 17.5 mm, the resultant was subjected to compression dehydration at 0.5 kg / cm ² for 60 seconds, and the yield per unit area of the cake (mg / cm ² ) The rate was measured. Among the measurement items, the water content is used to evaluate the quality of solid-liquid separation, and the cake yield is used to evaluate the strength of the pressed cake. As shown in Table 3, the overall score is 12
The scores were 9 to 10 out of a perfect score, indicating that these sludge dewatering agents have good dewatering performance.

[0019]

[Table 3]

Comparative Examples 1 to 14 The same sludge as used in Examples 1 to 3 was used, and the sludge dewatering agents shown in the columns of Comparative Examples 1 to 14 in Table 3 were used.
The same operation as in 3 was repeated. The overall score was 5 points or less, and the dewatering performance was poor. Example 4 200 g of the same sludge as used in Examples 1 to 3 was put in a volume of 50.
Samples were collected in a 0 ml homogenizer container, and the same amounts of polymer 2 and polymer a as contained in the sludge dehydrating agent used in Example 2 were simultaneously added to the container and reacted at 10,000 rpm for 7 seconds. Thereafter, the same operation as in Examples 1 to 3 was repeated to evaluate. The overall score was 9 points, and Polymer 2
It can be seen that, if the polymer 2 and the polymer a are added simultaneously, the same dewatering performance as the sludge dewatering agent produced by previously mixing the polymer 2, the polymer a and the sulfamic acid can be obtained. Comparative Example 15 The same 200 g of sludge as used in Examples 1 to 3
The sample was collected in a 0 ml homogenizer container, the same amount of polymer 2 contained in the sludge dehydrating agent used in Example 2 was added to the container, and agglutination reaction was performed at 700 rpm for 15 seconds.
The same amount of polymer a as that contained in the sludge dewatering agent used in Example 2 was added to the container, and further, at 10,000 rpm, 7
The reaction was performed for seconds. Thereafter, the same operation as in Examples 1 to 3 was repeated to evaluate. The overall score is 2 points, and even if the same amount of polymer 2 and polymer a is used, if polymer 2 and polymer a are added sequentially, the sludge dewatering agent produced by previously mixing polymer 2, polymer a and sulfamic acid can be obtained. It can be seen that the dewatering performance is significantly inferior.

Comparative Example 16 200 g of the same sludge as used in Examples 1 to 3
The sample was collected in a 0 ml homogenizer container, the same amount of polymer a as that contained in the sludge dehydrating agent used in Example 2 was added to the container, and agglutination reaction was performed at 700 rpm for 15 seconds.
The same amount of polymer 2 as that contained in the sludge dewatering agent used in Example 2 was added to the container, and further, 10,000 rpm, 7
The reaction was performed for seconds. Thereafter, the same operation as in Examples 1 to 3 was repeated to evaluate. The overall score is 4 points. Even if the same amount of polymer a and polymer 2 is used, if polymer a and polymer 2 are added sequentially, the sludge dehydrating agent produced by previously mixing polymer 2, polymer a and sulfamic acid can be obtained. It can be seen that the dewatering performance is inferior. Examples 5 to 7 200 g of the same sludge as used in Examples 1 to 3 were put in a volume of 50.
Collected in a 0 ml homogenizer container, polyaluminum chloride (PAC, liquid product containing 10% Al ₂ O ₃ ) 0.37
g (5% of SS) was added and reacted. CST of sludge under this addition condition is 530 seconds, CST / SS is 143 seconds /
%, And the sludge reforming with the inorganic flocculant was in an incomplete state. Next, various sludge dehydrating agents shown in the columns of Examples 5 to 7 of Table 4 were added, reacted at 10,000 rpm for 7 seconds, and the same operation as in Examples 1 to 3 was repeated to evaluate the sludge dehydrating agent. . The overall score is 9 to 11, indicating that these sludge dewatering agents show good dewatering performance even when sludge modification with an inorganic flocculant is not completed.

[0022]

[Table 4]

Comparative Examples 17 to 30 The same sludge to which polyaluminum chloride was added as used in Examples 5 to 7 was used, and the sludge dewatering agents shown in the columns of Comparative Examples 17 to 30 in Table 4 were used. The same operation as 5 to 7 was repeated. The overall score was 7 points or less in all cases, and the dewatering performance was poor. Examples 8 to 10 200 g of the same sludge as used in Examples 1 to 3 were put in a volume of 50.
Collected in a 0 ml homogenizer container, polyaluminum chloride (PAC, liquid product containing 10% Al ₂ O ₃ ) 0.74
g (vs. SS 10%) was added and reacted. CST of the sludge under these addition conditions is 264 seconds, and CST / SS is 71 seconds /
%, And the sludge reforming with the inorganic flocculant was still incomplete. Next, various sludge dehydrating agents shown in the columns of Examples 8 to 10 in Table 5 were added, reacted at 10,000 rpm for 7 seconds, and the same operations as in Examples 1 to 3 were repeated to evaluate the sludge dehydrating agents. . The overall score is 10 to 12, indicating that these sludge dewatering agents show good dewatering performance even when sludge modification with an inorganic flocculant is not completed.

[0024]

[Table 5]

Comparative Examples 31 to 40 The same sludge to which polyaluminum chloride was added as used in Examples 8 to 10 was used, and the sludge dewatering agents shown in the columns of Comparative Examples 31 to 40 in Table 5 were used. The same operation as 8 to 10 was repeated. The overall score was 8 points or less, and the dewatering performance was poor. Example 11 A coagulation dehydration test was performed using a dehydration vehicle equipped with two reaction tanks and a belt press dehydrator having an effective filter cloth width of 0.75 m. The sludge used was mixed raw sludge from a sewage treatment plant, and the properties of the sludge during the test period were pH 5.9 to 6.1 and SS 1.50 to
1.72%, VSS / SS 80-82%, Fiber content / SS
18-22%. 0.8 for SS in the reaction tank
Add 0% sludge dewatering agent 2.a and treat sludge amount 5m ³ / h
Was performed. As shown in Table 6, despite the large CST / SS value, the SS recovery reached 99.8% and the cake moisture content was as good as 75.4%.

[0026]

[Table 6]

Example 12 Example 11 was repeated except that the amount of sludge dehydrating agent 2.a was 0.79% of SS and the amount of treated sludge was 10 m ³ / h.
A coagulation and dewatering test of sludge was performed under the same conditions as described above. As shown in Table 6, a high throughput with a filtration rate of 222 kg / m · h was obtained, and the SS recovery rate reached 99.6%. The water content of the cake was also good at 78.7%. Comparative Examples 41 to 45 The tests of Examples 11 and 12 were repeated using the sludge dewatering agents shown in the columns of Comparative Examples 41 to 45 in Table 6. As can be seen from the results shown in Table 6, when polymer 2 was used alone, dehydration was impossible, and when polymer a or c was used alone, the amount of treated sludge was 5 m ³ / h. The SS recovery rate did not reach 99%, and the amount of treated sludge was 10 m ³ / h.
Then, dehydration became impossible. Examples 13 and 14 In the first reaction tank, about 7.6% of polyaluminum chloride with respect to SS was added. In this state, CST /
SS was about 80 seconds /%, and sludge reforming with an inorganic flocculant was in an incomplete state. Further, in the second reaction tank, about 0.75% of the sludge dewatering agent 2.a was added to SS, and coagulation dewatering tests were performed at a treated sludge amount of 5 m ³ / h and 10 m ³ / h. As shown in Table 6, better results were obtained than when no polyaluminum chloride was added. Comparative Examples 46 to 49 Example 13 using polymers 2 and a each alone
A cohesive dehydration test was performed in the same manner as in No. 14. As shown in Table 6, the SS recovery rate was 9 even when the amount of treated sludge was 5 m ³ / h.
When the sludge amount did not reach 9% and the treated sludge amount was 10 m ³ / h, dehydration became impossible. Reference Example 1 In the first reaction tank, polymer 2 was added at 0.87% relative to SS to sludge having 17.3% of polyaluminum chloride relative to SS and CST / SS of 17 seconds /%. A coagulation and dehydration test was conducted in the same manner as in Example 14 with a treated sludge amount of 10 m ³ / h. The filtration speed is as high as 200 kg / m · h,
The SS recovery rate was as good as 99.8%. It can be seen that when the polymer 2 is used alone, good dehydration performance can be obtained only when an inorganic coagulant necessary for sufficiently reducing the value of CST / SS is used in combination.

[0028]

According to the sludge dewatering agent of the present invention, even if the amount of the inorganic coagulant added is small, a good sludge coagulation state can be obtained and a dewatered cake having a low moisture content can be obtained. It does not cause problems such as corrosion of the combustion furnace and an increase in melting point in the incineration ash melting treatment.

[Brief description of the drawings]

FIG. 1 is a plan view and a cc cross-sectional view of a CST measuring apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filter paper 2 Cylindrical tube 3 Sludge 4 Counter 5 Base 6 Cover 7 Electrode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-218399 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 11/14

Claims (1)

(57) [Claims] 1. A cationic water-soluble polymer containing (A) an amidine unit, and (B) an amphoteric water-soluble polymer obtained by copolymerizing a cationic vinyl monomer, an anionic vinyl monomer and a nonionic vinyl monomer. A sludge dewatering agent comprising a polymer and (C) an acidic substance.