JP2000312900A - Organic sludge dewatering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the water content of dewatered cake by dewatering it efficiently by dewatering with a tannin derivative having a cationic substituent and a polymeric flocculant added into organic sludge. SOLUTION: In dewatering organic sludge, a tannin derivative having a cationic substituent (cationic tannin) is used. The tannin including tannic acid is preferably extracted from a mimosa, a quebrachs, chestnuts, and others. The cationic substituent is not restricted in particular if it is a primary- quaternary amino group, and a trialkylammonium chloride group is especially preferable. A polymeric flocculant used with cationic tannin is not restricted in particular if it is not anionic, both cationic and amphoteric polymeric flocculants can be used, but a cationic flocculant is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for dehydrating organic sludge generated from a sewage treatment plant, a human waste treatment plant, various industrial wastewater treatment facilities, and the like.

[0002]

2. Description of the Related Art Organic sludge generated from sewage treatment plants, human waste treatment plants, various types of industrial wastewater treatment facilities, and the like usually has a stable dispersion of particles constituting the sludge with negative charges. Therefore, when such organic sludge is coagulated and dehydrated,
In the past, cationic polymer flocculants were used alone.

However, when a cationic polymer flocculant is used alone for organic sludge that has undergone decay, there is a problem that the recovery of suspended suspended matter is low and the water content of the dewatered cake is high.

[0004] In order to solve this problem, for example, a method using a combination of a cationic polymer flocculant and an anionic polymer flocculant (JP-A-58-215454, JP-A-58-215454).
JP-A-139799), a method of using an amphoteric polymer flocculant after adding an inorganic flocculant (JP-A-2-18070)
No. 0), a method using a cationic polymer flocculant having an amidine monomer unit (JP-A-5-192513), a method using tannin and a cationic polymer flocculant in combination (Japanese Patent Publication No. 57-52880). And the like have been proposed.

Further, tannin derivatives having a cationic substituent can be used alone or together with an inorganic coagulant in metallurgy, pulp,
It is known to be used as a flocculant for wastewater in the paper industry and the like.

[0006]

However, due to the recent change and diversification of the properties of organic sludge generated from sewage treatment plants, night soil treatment plants, various industrial wastewater treatment facilities, etc., the conventional dewatering method has a problem in filtering. However, there was a problem that only low sludge was obtained, and as a result, the water content of the dewatered cake was high.

Accordingly, it is an object of the present invention to provide an organic sludge which can efficiently dewater organic sludge generated from a sewage treatment plant, a human waste treatment plant, various industrial wastewater treatment facilities and the like, and in which the water content of a dewatered cake after the dewatering is reduced. To provide a dehydration method.

[0008]

The present invention is a method for dewatering organic sludge, comprising dehydrating organic sludge to which a tannin derivative having a cationic substituent and a polymer flocculant have been added.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, the subject of dehydration treatment is not particularly limited as long as it is an organic sludge. For example, organic sludge such as excess sludge generated from a sewage treatment plant, a human waste treatment plant, various industrial wastewater treatment facilities and the like is used. Sludge.

In the method for dewatering organic sludge of the present invention, a tannin derivative having a cationic substituent (hereinafter referred to as cationic tannin) is used. Here, the tannin is preferably a vegetable tannin that contains not only tannin but also tannic acid and is extracted from mimosa, kevracho, chestnut, and the like that are industrially produced in large quantities. The cationic substituent is not particularly limited as long as it is a primary to quaternary amino group, and examples thereof include a trialkylammonium chloride group. Of these, a trimethylammonium chloride group is preferred. The position of the cationic substituent is not particularly limited.

The method for producing such a cationic tannin is not particularly limited.
(2) a method in which aminomethylated by a Mannich reaction using a dialkylamine and formalin is converted to a tertiary ammonium salt with a mineral acid and an organic acid, or a compound obtained by the same aminomethylation in a Mannich reaction having 1 carbon atom ~
A quaternary ammonium salt with an alkyl halide of 2 or benzyl halide or a diester of sulfuric acid with an alcohol having 1 to 2 carbon atoms.

[0012] Commercially available cationic tannins can also be used. Such commercial products include, for example, Tanac S.A. A. Corporation (Brazil) "TANF
LOC SA ”(product name) and“ TANFLOC SS ”
(Product name) and the like. The cation degree by colloid titration using potassium polyvinyl sulfate at pH 4 was 0.84 meq / g for the former and 1.01 meq / g for the latter.
meq / g.

In the sludge dewatering method of the present invention, the cationic tannin may be used alone or in combination of two or more.

The polymer flocculant used together with the cationic tannin in the method for dewatering organic sludge of the present invention is not particularly limited, except for the case of using an anionic polymer flocculant alone. Amphoteric polymer flocculants can be used, among which cationic polymer flocculants are preferred,
Particularly, a cationic polymer flocculant having an amidine unit is preferable.

Examples of the cationic polymer coagulant include a cationic polymer coagulant containing a cationic monomer unit represented by the following formula (1). Equation (1)
As the cationic monomer unit represented by, for example,
Neutralized salts of dimethylaminoethyl (meth) acrylate monomer units and dimethylaminopropyl (meth) acrylamide monomer units with hydrogen halides, sulfuric acid, nitric acid, acetic acid, etc., alkyl halides, benzyl halides, dimethyl sulfate and diethyl sulfate, etc. And quaternary compounds. Among them, those having a (meth) acrylate structure are preferable for improving dehydration,
Particularly, those containing a neutralized salt and a quaternary salt of dimethylaminoethyl (meth) acrylate are preferable.

[0016]

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In the formula (1), R ¹ is a hydrogen atom or a methyl group, and R ² and R ³ are each independently a carbon atom having 1 to 2 carbon atoms.
R ⁴ represents a hydrogen atom, an alkyl group having 1 to 2 carbon atoms or a benzyl group, A represents an oxygen atom or NH, B represents an alkylene group having 1 to 4 carbon atoms or a hydroxypropylene group, and X ⁻ represents an anionic group. Represents an ion.

Other cationic polymer flocculants include, for example, cationic polymer flocculants having an amidine unit represented by the following formula (2) or (3). The amidine unit represented by the following formula (2) and / or formula (3) is preferably contained in the cationic polymer in an amount of 20 to 90 mol%, particularly preferably 50 to 90 mol%. Further, the cationic polymer having an amidine unit may contain, in addition to the amidine unit, a repeating unit represented by the following formulas (4), (5) and (6).

[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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In the formulas (2) to (6), R ¹ and R ² represent a hydrogen atom or a methyl group, R ³ represents an alkyl group or a hydrogen atom having 1 to 2 carbon atoms, and X ⁻ represents an anion.

The cationic polymer flocculant having an amidine unit preferably has a reduced viscosity of 0.5 dl / g or more measured at 25 ° C. as a 0.1 g / dl solution in 1 N saline. If the reduced viscosity is less than 0.5 dl / 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, for example, in JP-A-5-192513. That is, a compound represented by the following formula (7) is copolymerized with acrylonitrile or methacrylonitrile, and the copolymer is hydrolyzed to generate an amino group. And a cyano group to produce a cationic polymer flocculant having an amidine unit.

[0027]

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In the formula (7), R ¹ represents a hydrogen atom or a methyl group, and R ³ represents an alkyl group having 1 to 2 carbon atoms or a hydrogen atom.

The kind of the cationic monomer unit contained in the cationic polymer flocculant may be one kind or a combination of two or more kinds, and may contain a nonionic monomer unit such as an acrylamide monomer unit.

The kind of the polymer flocculant used in the present invention may be one kind or a combination of two or more kinds. Further, it may be used in combination with an amphoteric polymer flocculant or an anionic polymer flocculant as long as the performance is not hindered.

The rate of addition of the cationic tannin to the organic sludge varies depending on the properties of the sludge, and cannot be said unconditionally.
ppm.

The rate of addition of the polymer flocculant to the organic sludge is the same, and cannot be said unconditionally, but is usually 20 to 1000 ppm based on the sludge slurry.

In the method for dewatering organic sludge of the present invention, an inorganic flocculant such as a sulfate band, polyaluminum chloride and polyiron sulfate may be added to the organic sludge, if necessary, in addition to the cationic tannin and the polymer flocculant. Is also good. In this case, the addition rate of the inorganic flocculant is usually 100 to 5000 ppm based on the sludge slurry.

The method of adding the cationic tannin and the polymer flocculant to the organic sludge is not particularly limited. First, the cationic tannin is added, mixed and stirred sufficiently, and then the polymer flocculant is added. It is preferable to use a dewatering method in which a floc is formed by stirring and then dewatered using a dehydrator such as a screw decanter or a belt press dehydrator to form a dewatered cake. When adding an inorganic flocculant, it is preferable to add it before adding a polymeric flocculant, and it is preferable to add simultaneously with or before and after a cationic tannin.

[0035]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to only these examples. The water content is 110
The weight was calculated by the following equation from the weight before and after drying at 16 ° C. for 16 hours. Water content (%) = (weight before drying−weight after drying) / weight before drying × 100

[Example 1] Excess sludge 200 having a pH of 7.0 and a TS of 1.2% discharged from an A factory wastewater treatment facility
ml was placed in a 300 ml beaker, and TanacS. A. After adding 250 ppm of TANFLOC SA manufactured by the company, the mixture was stirred at 1000 rpm for 1 minute. Then, 50 ppm of a methyl chloride quaternary polymer of dimethylaminoethyl methacrylate was added as a cationic polymer coagulant, and the mixture was stirred at 1000 rpm for 1 minute. The slurry thus obtained was subjected to suction filtration using a Kiriyama funnel, and the time required for the filtrate to reach 100 ml (filtration time) was measured. The water content of the dehydrated cake on the filter paper was measured after draining. The results are shown in Table 1.

Example 2 Table 1 shows the results of the same operation as in Example 1 except that the addition ratio of the cationic tannin was changed to 500 ppm.

[Comparative Example 1] The results obtained in the same manner as in Example 1 except that the cationic tannin was not added are shown in Table 1.

[Comparative Example 2] The results obtained in the same manner as in Example 1 except that the cationic tannin was changed to ordinary tannic acid having no cationic substituent are shown in Table 1.

[0040]

[Table 1]

Example 3 B 200 ml of excess sludge discharged from a sewage treatment plant at pH 4.7 and TS 2.5% was placed in a 300 ml beaker, and T as cationic tannin was added.
anac S .; A. 10 TNFLOC SA
After adding 00 ppm, the mixture was stirred at 1000 rpm for 1 minute. Then, as an amphoteric polymer flocculant, a dimethylaminoethyl methacrylate methyl quaternary polymer / acrylamide / acrylic acid copolymer (molar ratio: 20/7)
0/10) was added at 250 ppm, and 1 at 1000 rpm.
Stirred for minutes. Table 2 shows the results obtained by measuring the filtration time of the slurry thus obtained and the water content of the dehydrated cake after filtration in the same manner as in Example 1.

Example 4 Table 2 shows the result of the same operation as in Example 3 except that the addition ratio of the cationic tannin was changed to 2000 ppm.

[Comparative Example 3] Table 2 shows the results obtained in the same manner as in Example 3 except that no cationic tannin was added.

[Comparative Example 4] The results obtained in the same manner as in Example 4 except that the cationic tannin was changed to ordinary tannic acid having no cationic substituent are shown in Table 2.

[0045]

[Table 2]

Example 5 Excess sludge 200 having a pH of 7.0 and a TS of 1.2% discharged from a wastewater treatment facility of Factory A
ml was placed in a 300 ml beaker, and TanacS. A. After adding 250 ppm of TANFLOC SA manufactured by the company, the mixture was stirred at 1000 rpm for 1 minute. Next, as a cationic polymer flocculant, a cationic polymer flocculant having amidine units, Diaclear (registered trademark) MK6450 manufactured by Mitsubishi Chemical Corporation, was added at 50 pp.
m and stirred at 1000 rpm for 1 minute. Table 3 shows the results obtained by measuring the filtration time of the slurry thus obtained and the water content of the dewatered cake after filtration in the same manner as in Example 1.

Example 6 Table 3 shows the result of the same operation as in Example 5 except that the addition ratio of the cationic tannin was changed to 500 ppm.

[Comparative Example 5] Table 3 shows the results of the operation in the same manner as in Example 5 except that the cationic tannin was not added.

[Comparative Example 6] The results are shown in Table 3 in the same manner as in Example 5, except that the cationic tannin was changed to ordinary tannic acid having no cationic substituent.

[0050]

[Table 3]

[0051]

According to the method for dewatering organic sludge of the present invention,
Organic sludge generated from sewage treatment plants, night soil treatment plants and various industrial wastewater treatment facilities can be efficiently dewatered in a short time,
Also, the water content of the dewatered cake after dehydration could be reduced.

Claims (2)

[Claims] 1. A method for dehydrating organic sludge, comprising dehydrating organic sludge to which a tannin derivative having a cationic substituent and a polymer flocculant have been added. 2. The method for dehydrating organic sludge according to claim 1, wherein the polymer flocculant is a cationic polymer flocculant.