JPH06500A - Method for dehydrating sludge - Google Patents

Abstract

PURPOSE:To efficiently perform dehydration even when industrial waste liquid, raw sludge and sludge of excrement are acidic or alkaline by adding specified aqueous composition to the industrial waste liquid treated by an activated sludge method or a digested sludge method, raw sludge and sludge of excretions, filtering and dehydrating the produced cake. CONSTITUTION:The aqueous composition of the following acrylamide-based copolymer is added to industrial waste liquid treated by an activated sludge method or a digested sludge method, raw sludge and sludge of excrement or sludge. Produced cake is filtered and dehydrated. The acrylamide-based copolymer is constituted of 65-99mol% ethylene structural unit expressed by formula I, 0-15mol% acrylate structural unit expressed by formula II and 1-35mol% acrylamide structural unit expressed by formula III and arranged linearly and irregularly and has 1,000-50,000 weight average molecular weight. However R<1> denotes 1-4C alkyl group in the formula II and R<2> denotes 2-8C alkylene group, R<3> and R<4> denote 1-4C alkyl group and R<5> denote 1-12C alkyl group or 6-12C alicyclic alkyl group and X denote halogen atoms, CH3OSO3 pr C2 H5OSO3 in the formula III.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dewatering industrial waste liquor, raw sludge, night soil or sewage sludge treated by an activated sludge method or a digested sludge method.

[0002]

2. Description of the Related Art Conventionally, as a method of dehydrating sludge, as a dehydrating agent, for example, ferric chloride and slaked lime are used in combination,
A method in which a cationic polymer such as a dicyandiamide or dialkylaminoethylmethacrylate-based polymer, a chitosan or a dimethyldiallylammonium chloride-based polymer is added to sludge is used.

[0003]

However, in the method of using ferric chloride and slaked lime together, damage to the incinerator due to chlorine generation during cake incineration, which is produced in a large amount, and Cr contained in ferric chloride. It has been pointed out that the problem of secondary pollution due to heavy metals such as Cd, Cd, Pb and Mn.

Further, when a dicyandiamide or dialkylaminoethylmethacrylate type cationic polymer is used, there is a drawback that slaked lime which is also used as a dehydrating aid is hydrolyzed by the action of alkali to reduce its efficacy.

[0005] Chitosan has a drawback that it remains dissolved under acidic conditions but becomes insoluble under neutral and alkaline conditions and loses its efficacy.

The dimethyldiallylammonium chloride type cationic polymer does not have the above-mentioned drawbacks regardless of whether the system is acidic or alkaline, and acts as a dehydrating agent relatively stably, but it is still insufficient in terms of dehydration efficiency. There was a problem.

[0007]

The present invention has been made in view of the above, and has the formula:

[Chemical 4] An ethylene structural unit represented by

[Chemical 5] (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), 0 to 15 mol% of an acrylate structural unit represented by the general formula:

[Chemical 6] (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴ are respectively alkyl groups having 1 to 4 carbon atoms, R ⁵ is an alkyl group having 1 to 12 carbon atoms, and 6 to 12 carbon atoms. An arylalkyl group or an alicyclic alkyl group having 6 to 12 carbon atoms, X
Is a halogen atom, CH ₃ OSO ₃ or C ₂ H ₅ OSO
Acrylamide structural units 1 to 3 represented by ₃ are shown)
Factory waste liquor obtained by treating an aqueous composition of an acrylamide copolymer having a weight average molecular weight of 1,000 to 50,000 in a linearly irregular arrangement of 5 mol% by an activated sludge method or a digested sludge method. This is a sludge dewatering method characterized by adding to the wastewater, night soil or sewage sludge and filtering and dehydrating the produced cake.

[Requirements Constituting Means] Acrylic Copolymer Aqueous Composition The aqueous composition of the acrylamide copolymer used in the present invention has the formula:

[Chemical 7] An ethylene structural unit represented by

[Chemical 8] (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), 0 to 15 mol% of an acrylate structural unit represented by the general formula:

[Chemical 9] (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴ are respectively alkyl groups having 1 to 4 carbon atoms, R ⁵ is an alkyl group having 1 to 12 carbon atoms, and 6 to 12 carbon atoms. An arylalkyl group or an alicyclic alkyl group having 6 to 12 carbon atoms, X
Is a halogen atom, CH ₃ OSO ₃ or C ₂ H ₅ OSO
Acrylamide structural units 1 to 3 represented by ₃ are shown)
It is an aqueous composition obtained by emulsifying, dispersing, or solubilizing 5 mol% of an acrylamide copolymer having a weight average molecular weight of 1,000 to 50,000, which is randomly arranged in a linear fashion.

The formula in the acrylamide-based copolymer:

[Chemical 10] The proportion of ethylene structural units represented by is 65 to 99 mol%. When the proportion of the ethylene structural unit is less than 65 mol%, the dehydration efficiency is lowered and the water content of the cake after dehydration is increased. On the other hand, when it exceeds 99 mol%, the aggregating action of the acrylamide-based copolymer becomes too small, and blocks are less likely to be formed. In addition, in the present invention, the ratio of the ethylene structural unit is 85 to 97 mol% from the viewpoint of the balance of dehydration efficiency and aggregation action.
Is particularly preferable.

The general formula in the acrylamide-based copolymer:

[Chemical 11] The ratio of the acrylate structural unit represented by the formula (wherein R ¹ is the same as above) is 0 to 15 mol%. When the proportion of the acrylate structural unit exceeds 15 mol%, the produced block becomes sticky. In the present invention, the case where the acrylate structural unit is contained is preferable because the water content of the cake is lowered as a result of imparting hydrophobicity. In the present invention, the proportion of the acrylate structural unit is preferably 1 to 15 mol%, and more preferably 3 to 7 mol%, from the viewpoint of the balance between tackiness and cake water content.

In the acrylate structural unit, R ¹
Is an alkyl group having 1 to 4 carbon atoms. Specific examples of R ¹ include methyl group, ethyl group, n-propyl group, i
-Propyl group, n-butyl group and i-butyl group are mentioned, and these groups may be mixed in one molecule. Among these groups, the methyl group and the ethyl group are preferable from the viewpoint of not causing any adverse effect due to adhesiveness.

The general formula in the acrylamide-based copolymer:

[Chemical 12] (In the formula, R ² , R ³ , R ⁴ and R ⁵ are the same as above), and the proportion of the acrylamide structural unit is 1 to 35 mol%. When the proportion of this acrylamide structural unit is less than 1 mol%, the aggregation action becomes too small,
On the other hand, when it exceeds 35 mol%, the water content of the cake becomes large, which is inconvenient. In the present invention, the ratio of the acrylamide structural unit is particularly preferably 3 to 15 mol% from the viewpoint of the balance between the aggregating action and the cake water content.

In the acrylamide structural unit, R
² is an alkylene group having 2 to 8 carbon atoms. Specific examples of R ² include ethylene group, propylene group,
Hexamethylene group, neopentylene group and the like,
These groups may be mixed in one molecule. Among these groups, an ethylene group and a propylene group are preferable, and a propylene group is particularly preferable, from the viewpoint of easy production and economy.

R ³ and R ⁴ are each 1 to 1 carbon atoms.
4 is an alkyl group. Specific examples of R ³ and R ⁴ include a methyl group, an ethyl group, a propyl group, and a butyl group, and these groups may be mixed in one molecule. Among these groups, a methyl group and an ethyl group are preferable from the viewpoint of aggregation action.

R ⁵ is an alkyl group having 1 to 12 carbon atoms,
Arylalkyl group having 6 to 12 carbon atoms or 6 to carbon atoms
12 is an alicyclic alkyl group. Specific examples of R ⁵ include methyl group, ethyl group, n-propyl group,
i-propyl group, n-butyl group, sec-butyl group, n
Alkyl groups such as octyl group and n-lauryl group; arylalkyl groups such as benzyl group and 4-methylbenzyl group; alicyclic alkyl groups such as cyclohexyl group and methylcyclohexyl group, and these groups are included in one molecule. May be mixed in. In addition, as R ⁵ , a linear alkyl group and an arylalkyl group are preferable from the viewpoint of adhesiveness, and a lower alkyl group is preferable from the viewpoint of aggregation action. Particularly preferred R ⁵ includes a methyl group and an ethyl group.

The X is, for example, a halogen atom such as Cl, Br or I, CH ₃ OSO ₃ or C ₂ H ₅ OSO ₃
And these may be mixed in one molecule. Among these, Cl, CH ₃ OSO ₃ and C ₂
H ₅ OSO ₃ is preferable.

The weight average molecular weight of the acrylamide copolymer is 1,000 to 50,000. The term "weight average molecular weight" as used herein means a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography.
Vol. 44, No. 2, 139 to 141 (1987)). When the molecular weight is less than 1,000, the aggregating action is poor and the dehydration performance aimed at by the present invention is not sufficiently exhibited, and when it exceeds 50,000, the block produced is coarse and soft. Too much, filtration becomes difficult and workability deteriorates.
A preferred weight average molecular weight is 3,000 to 30,000.

The acrylamide copolymer used in the present invention is, for example, an ethylene-acrylic acid ester copolymer obtained by copolymerizing ethylene and an acrylic acid ester by a high-pressure polymerization method, for example, JP-A-60-7900.
After hydrolysis and thermal degradation by the method described in JP-A No. 8 to a desired molecular weight, the obtained ethylene-acrylic acid ester-acrylic acid copolymer was amidated with N, N-dialkylaminoalkylamine. It is obtained by cation modification with a quaternizing agent.

Method for Preparing Aqueous Solution of Acrylamide Copolymer The aqueous composition of the above acrylamide copolymer is, for example, a high pressure emulsification method, that is, 110 to 140 are prepared by charging the acrylamide copolymer and water into an autoclave. It can be easily prepared by stirring under pressure at a temperature of ° C and emulsifying or dispersing.

Amount to be added Although it depends on the amount of suspended solids in the sludge, the solid content is usually 10 to 10,000 ppm, preferably 100 to
It is 1,000 ppm. If it is less than 10 ppm, the aggregation effect is no longer present, and if it exceeds 10,000 ppm, it is uneconomical.

Dehydration aids If necessary, slaked lime, fly ash, carbide slag,
Perlite, bentonite, diatomaceous earth, wood flour, chaff,
Dehydration aids such as silica can be used.

Filtration method Conventional ones such as a vacuum dewatering machine, a belt filter, a filter press, an Oliver type dewatering machine and the like can be used.

Applicable sludge pH pH = 1 to 14, that is, any of acidic, neutral and alkaline.

Applicable types of sludge The sludge can be used for factory effluent treated by activated sludge method or digested sludge method, raw sludge, or human waste or sewage sludge.

[0025]

[Operation] The acrylamide-based copolymer used in the present invention is considered to have an action of removing water from the production block because the site having an ethylene structure has strong hydrophobicity.

Further, the cation group portion of the acrylamide copolymer is adsorbed on the suspended substance of sludge and agglomerates to form a block.

[0027]

EXAMPLES The acrylamide copolymers used in the present invention were synthesized according to the following Production Examples 1-9.

<Production Example 1> 400 ml of xylene, ethylene-ethyl acrylate-acrylic acid copolymer (in a 1-liter four-necked flask equipped with a thermometer, a stirrer, a dropping funnel and a Dean-Stark water diverter ( 150 g of ethylene / ethyl acrylate / acrylic acid = 93/3/4) and 1.0 g of paratoluenesulfonic acid were charged.

Next, 21.1 g of N, N-dimethylaminopropylamine was charged and the temperature was adjusted to 140 ° C. using an oil bath.
The mixture was heated to 1, the water formed was continuously removed by azeotropy with xylene, and the mixture was further reacted at 140 ° C. for 17 hours, and the amidation reaction was continued until no water was formed and no water azeotropy was observed. .

458 g of the obtained reaction product was cooled to 80 ° C., and methyl iodide 2 was added to the reaction mixture from a dropping funnel.
8.7 g was gradually added dropwise over 1 hour. During this time, an exotherm was observed, but the reaction temperature was lowered to 90 ° C by cooling.
Maintained at. After completion of dropping, an aging reaction was carried out at 100 ° C. for 4 hours. The reaction product thus obtained was poured into a large amount of methanol, and the produced precipitate was collected and dried to obtain an acrylamide copolymer. The weight average molecular weight of the acrylamide copolymer was measured to be 19,4.
It was 00.

<Production Examples 2 to 9> In the same manner as in Production Example 1, the acrylamide copolymers shown in Production Examples 2 to 9 in Table 1 were prepared according to the method described in Japanese Patent Application No. 2-331082. Manufacturing Examples 2 to 9 differ from Manufacturing Example 1 in the following points.

In Production Examples 8 and 9, R ¹ in the ethylene-ethyl acrylate-acrylic acid copolymer of the raw material copolymer was n-propyl group and n-butyl group, respectively. In Production Examples 5 and 7, the raw material copolymer was An ethylene-acrylic acid copolymer was used as the polymer. In Production Examples 4 and 8, N, N-dimethylaminoethylamine was used as the aminating agent, in Production Example 6, N, N-dimethylaminoneopentylamine was used as the aminating agent, and in Production Example 7, N, N-dimethylaminoethylamine was used as the aminating agent. N-diethylaminopropylamine was used, and in Production Example 9, N, N-diethylaminoethylamine was used as the aminating agent. In addition, Production Examples 2, 5, 6
In Examples 8 and 8, diethyl sulfate was used as the quaternizing agent, in Production Examples 4 and 9, benzyl chloride was used as the quaternizing agent, and in Production Example 3, p-methylbenzyl chloride was used as the quaternizing agent.

In Table 1, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and X of the acrylamide copolymers of Production Examples 1 to 9, the amount of ethylene structural units, the amount of acrylate structural units and the acrylamide structure are shown. The amount of unit and the weight average molecular weight are shown.

[0034]

[Table 1] Using the acrylamide copolymer obtained as described above, the aqueous composition was prepared as follows. formula:

[Chemical 13] An ethylene structural unit represented by the general formula:

[Chemical 14] An acrylate structural unit represented by and a general formula:

[Chemical 15] In an autoclave, an acrylamide-based copolymer having an acrylamide structural unit represented by
C., stirring was continued for 2 hours at a temperature of ^{2 to} 2.5 kg / cm.sup.2 and a pressure to obtain an aqueous composition having a solid content of 20%.

Using the aqueous composition of the acrylamide-based copolymer obtained as described above, the dehydration property was evaluated as follows.

(Examples 1 to 9) Sewage 20: Dehydration of digested sludge (suspended substance 6.92%, pH = 6.3) at a certain sewage treatment plant, which was digested by mixing a slight amount of excess sludge with human waste 60. The test was performed under the following conditions using a belt filter having a filtration area of 10 m ² . The evaluation was performed on the peelability and the water content of the cake after dehydration, and the results are shown in Table 2.

Comparative Example A dehydration test was conducted in the same manner as in Examples using polydimethyldiallylammonium chloride as a dehydrating agent, and the results are also shown in Table 2.

[0038]

(Test conditions) -Sludge supply amount: 5.8 m ³ / hr-Dehydrant addition amount: Concentration in sludge of the aqueous acrylamide copolymer composition of the present invention obtained in Production Examples 1-9 To 500 ppm based on solids content ・ Dehydration aid: Not used

(Evaluation) -Peelability: The ease with which the cake was peeled from the filter cloth was evaluated on a three-point scale: good for good, fair for moderate, and bad for bad.

Cake water content: Expressed in% by weight, the smaller the value, the better.

[0042]

[Table 2] As is clear from the results shown in Table 2, in all of Examples 1 to 9, as compared with the case of using the conventionally used polydimethyldiallylammonium chloride, the dehydration efficiency was excellent and the exfoliation of the cake was performed. The property is also good.

[0043]

As described above, according to the sludge dewatering method of the present invention, it is possible to efficiently dehydrate both acidic and alkaline.

Further, since the cake produced by adding the acrylamide copolymer to the sludge has a good peeling property and the water content of the cake after dehydration can be lowered, the energy burden at the time of burning the cake can be reduced. .

Claims (1)

[Claims] 1. A plant waste liquid, raw sludge, human waste or sewage sludge treated by the activated sludge method or the digested sludge method has the formula: An ethylene structural unit represented by the formula: 65 to 99 mol%, the general formula: (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), the acrylate structural unit is represented by 0 to 15 mol% and the general formula: (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴ are respectively alkyl groups having 1 to 4 carbon atoms, R ⁵ is an alkyl group having 1 to 12 carbon atoms, and 6 to 12 carbon atoms. An arylalkyl group or an alicyclic alkyl group having 6 to 12 carbon atoms, X
Is a halogen atom, CH ₃ OSO ₃ or C ₂ H ₅ OSO
Acrylamide structural units 1 to 3 represented by ₃ are shown)
It is characterized by adding an aqueous composition of 5 mol% of a acrylamide-based copolymer having a weight average molecular weight of 1,000 to 50,000 randomly arranged in a linear fashion, and filtering and dehydrating the produced cake. How to dehydrate sludge.