JPH0871599A - Sludge dehydrating agent - Google Patents

Abstract

PURPOSE: To obtain a sludge dehydrating agent excellent in flocculation properties and capable of forming a dehydrated cake low in water content by adding a cationic polymeric flocculant having a structure represented by a specific general formula in its molecule and an anionic polymeric flocculant. CONSTITUTION: At the time of the dehydration treatment of flocculated sludge, a cationic polymeric flocculant having a structure of dialkylaminopropylacrylamide or dialkylaminopropylmethacrylamide in its molecule and an anionic polymeric flocculant are together used. That is, a dehydrating agent is prepared from the cationic polymeric flocculant having a structure represented by formula I or II and the anionic polymeric flocculant. In the formulae I, II, R<1> is hydrogen or a methyl group, R<2> is a methyl group, an ethyl group, a propyl group or an isopropyl group, R<3> is hydrogen, a methyl group, an ethyl group, a propyl group, an isopropyl group or a benzyl group and X<-> is C1<-> , 1/2SO4 <2-> , HSO4 <-> , NO3 <-> , CH3 COO<-> , HCOO<-> or CH3 SO4 <-> .

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a sludge dehydrating agent.
More specifically, the present invention relates to a sludge dewatering agent which is excellent in cohesiveness and can obtain a dewatered cake having a low water content.

[0002]

2. Description of the Related Art Organic sludge such as excess sludge and coagulated sludge is generated by biological treatment of sewage, night soil or various industrial wastewater. So far, a cationic polymer dehydrating agent has been used alone for the dehydration treatment of these sludges, but in recent years, due to an increase in the amount of sludge generated with an increase in the amount of discharged water, and deterioration of sludge properties, conventional cationic Since the polymeric dehydrating agent has poor cohesive strength, there is a limit to the amount of sludge that can be processed, and the processing conditions are satisfactory in terms of dehydrated cake water content, SS recovery rate, and cake peelability from filter cloth. Instead, improvement is urged. Although some proposals have been made to solve these problems, none of them are satisfied at present. An example will be described below. (1) Intramolecular amphoteric polymer dehydrating agent. Compared to the conventional cationic polymer dehydrating agent, it produces larger flocs and can improve the sludge throughput, but
Since the floc strength is relatively weak, the water content of the dehydrated cake is almost unchanged from the current state, and the cake peelability from the filter cloth may not be sufficient. (2) A method in which a cationic polymer dehydrating agent is added first, and then an anionic polymer dehydrating agent is added to perform dehydration treatment. Cationic polymer dehydrating agent and anionic polymer dehydrating agent 2
Since the agents are used together, two dissolution tanks are required, it is difficult to control the addition amount of each polymer dehydrating agent, and skill is required to perform stable treatment. (3) A dehydrating agent containing a Mannich modified product of polyacrylamide and an anionic polymer as active ingredients (Japanese Patent Publication No. Sho 60-
No. 43800). The Mannich modified product of polyacrylamide is a cation modified product based on polyacrylamide, which is a material that forms strong and large flocs and has excellent aggregation performance. However, this product is produced by allowing formalin and dimethylamine to act on polyacrylamide, and a highly reactive methylol group remains in the polymer, and Mannich base itself is unstable and easily deteriorates, resulting in product stability. The fact is that there is a big problem in terms of.

[0003]

The present invention has excellent product stability and is capable of treating a large amount of sludge.
It was made for the purpose of providing a sludge dehydrating agent which gives a dehydrated cake which has a low water content during filtration and has good releasability from a filter cloth.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have dialkylaminopropyl acrylamide, dialkylaminopropyl methacrylamide, salts thereof or quaternized salts thereof. It was found that by using a cationic polymer flocculant having a structure in the molecule and an anionic polymer flocculant in combination, good sludge dewatering property can be obtained, and based on this finding, the present invention was completed. I arrived. That is, the present invention is
An organic sludge dehydrating agent comprising a cationic polymer flocculant having a structure represented by the following general formula [1] or general formula [2] in the molecule and an anionic polymer flocculant:

Embedded image (In the formula, R ¹ is hydrogen or methyl group, R ² is methyl group, ethyl group, propyl group or isopropyl group, R 2
³ is hydrogen, methyl group, ethyl group, propyl group, isopropyl group or benzyl group, X ⁻ is Cl ⁻ , 1 / 2S
O ₄ ²⁻ , HSO ₄ ⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , HCOO ⁻ or CH ₃ SO ₄ ⁻ . ).

The cationic polymer flocculant used in the sludge dewatering agent of the present invention is a dialkylaminopropyl acrylamide, a dialkylaminopropyl methacrylamide, a salt thereof or a compound thereof represented by the general formula [1] or [2]. Having a quaternized structure in the molecule, and in the general formula [1] and general formula [2], R ¹
Is hydrogen or methyl group, R ² is methyl group, ethyl group, propyl group or isopropyl group, R ³ is hydrogen, methyl group, ethyl group, propyl group, isopropyl group or benzyl group, X ⁻ is Cl ⁻ , 1 / 2SO _{^{4 2-, HSO 4 -, NO}} 3
^- , CH ₃ COO ⁻ , HCOO ⁻ or CH ₃ SO ₄ ⁻ . The cationic polymer flocculant used for the sludge dewatering agent of the present invention preferably has 10 mol% or more of the structural unit represented by the general formula [1] or the general formula [2] in the molecule. When the amount of the structural unit represented by the general formula [1] or the general formula [2] is less than 10 mol% in the molecule, the cohesive force of the cationic polymer coagulant becomes weak. The cationic polymer flocculant used in the sludge dewatering agent of the present invention has an intrinsic viscosity value of 2. used as an index of molecular weight.
It is preferably 0 dl / g or more. Here, the value of the intrinsic viscosity is a value measured at 30 ° C. using 1N-NaNO ₃ as a solvent. When the intrinsic viscosity of the cationic polymer flocculant is less than 2.0 dl / g, the cohesive force of the cationic polymer flocculant becomes weak. The cationic polymer flocculant used in the sludge dewatering agent of the present invention is not particularly limited in the structural unit other than the structural unit represented by the general formula [1] or the general formula [2], and any monomer unit is selected. be able to. Examples of such a monomer unit include nonionic monomer units such as acrylamide, methacrylamide, dimethylacrylamide, acrylonitrile, styrene, methyl methacrylate and methyl acrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate and diethylaminoethyl methacrylate. Etc. are quaternized with methyl chloride, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, benzyl chloride, etc., or with a tertiary salt with hydrogen chloride, sulfuric acid, nitric acid, acetic acid, formic acid, etc. Examples of the cationic monomer unit, anionic monomer units such as acrylic acid, methacrylic acid, or alkali metal salts thereof, and the like.

The method for introducing the structural unit represented by the general formula [1] or [2] into the cationic polymer flocculant used in the sludge dewatering agent of the present invention is not particularly limited.
For example, after copolymerizing acrylamide or methacrylamide, it can be reacted with a dialkylaminopropyl halide or the like to introduce a dialkylaminopropyl group into the nitrogen atom and further converted into a salt or quaternary product. The dialkylaminopropyl methacrylamide can be copolymerized and then made into a salt or quaternary compound, or the salt or quaternary dialkylaminopropyl acrylamide or dialkylaminopropyl methacrylamide can be copolymerized. It is desirable that the monomer giving the structure represented by the general formula [1] or the general formula [2] is selected from those having compatibility with other monomers to be copolymerized and copolymerized. The anionic polymer flocculant used for the sludge dewatering agent of the present invention preferably has 5 mol% or more of anionic monomer units in the molecule. When the amount of the anionic monomer unit is less than 5 mol% in the molecule, the cohesive force of the anionic polymer coagulant becomes weak.
The anionic polymer flocculant used in the sludge dewatering agent of the present invention has an intrinsic viscosity value of 1 used as an index of molecular weight.
It is preferably at least 0.0 dl / g. Here, the value of the intrinsic viscosity is a value measured at 30 ° C. using 1N-NaCl as a solvent. When the intrinsic viscosity of the anionic polymer coagulant is less than 10.0 dl / g, the cohesive force of the anionic polymer coagulant becomes weak. Examples of the anionic polymer flocculant used in the sludge dewatering agent of the present invention include polyacrylic acid, acrylamide, a copolymer of methacrylamide and acrylic acid, methacrylic acid or an alkali metal salt thereof, polyacrylamide, and polyacrylamide. Examples thereof include a hydrolyzate of methacrylamide with an acid or an alkali, acrylic acid, methacrylic acid or an alkali metal salt thereof and acrylamide, and a copolymer of methacrylamide and a sulfonic acid vinyl monomer. Examples of the sulfonic acid vinyl monomer include 2-acrylamide-
2-methyl propane sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid or salts thereof, and the like,
It is not limited to these.

In the sludge dewatering agent of the present invention, the ratio of the cationic polymer coagulant and the anionic polymer coagulant is not particularly limited, but the weight ratio of both is 90:10 to 10: 9.
Those having a ratio of 0, preferably 80:20 to 40:60 can be suitably used. The method of using the sludge dehydrating agent of the present invention is not particularly limited, and it can be used by any method. For example, the cationic polymer aggregating agent of the present invention and the anionic polymer aggregating agent can be separately dissolved and sequentially added to sludge for aggregation and dehydration treatment. Alternatively,
The cationic polymer flocculant and the anionic polymer flocculant can be dissolved in the same dissolution tank and added to the sludge as a mixture. In this case, there is no problem in performance even if an acid such as hydrochloric acid, sulfuric acid, acetic acid, sodium hydrogensulfate, sulfamic acid or the like or an alkali agent such as sodium hydroxide, sodium carbonate, potassium hydroxide or calcium hydroxide is used in combination, if necessary. . In advance, a cationic polymer flocculant, an anionic polymer flocculant and an acid or alkali are mixed,
This is preferably dissolved in water to form an aqueous solution and added to sludge. Before adding the sludge dehydrating agent of the present invention to sludge,
An inorganic flocculant can be added to the sludge. Examples of the inorganic coagulant include a sulfuric acid band, polyaluminum chloride, ferric chloride, ferrous sulfate, polyferrous sulfate and the like. There is no particular limitation on the sludge for which the sludge dewatering agent of the present invention is used, and sewage, night soil treatment plant, excess sludge of general industrial wastewater or a mixture of these with the first settling tank sludge, or a mixture of the tertiary treatment sludge. Examples include sludge. The dehydrator used for dehydrating sludge aggregated by the sludge dehydrating agent of the present invention is not particularly limited, and equipment used for ordinary sludge treatment can be used. As such a dehydrator, for example, a belt press dehydrator,
A centrifugal dehydrator, a screw press dehydrator, a vacuum dehydrator, a filter press dehydrator and the like can be mentioned.

[0008]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Table 1 shows the composition and intrinsic viscosity of the polymer flocculant used in the examples.

[0009]

[Table 1]

[Caution] 1) C-1 to 6 are prepared by using 1N-NaNO ₃ as a solvent and A-
1 and 2 are 1 N-NaCl as a solvent, all 30 ℃
It was measured at. DMAPAA: dimethylaminopropylacrylamide _{DMAPAA (1 / 2H 2 SO 4} ): sulfates of dimethylaminopropyl acrylamide DMAPAA (CH ₃ Cl): dimethylaminopropyl acrylamide methyl chloride quaternized DAA (CH ₃ Cl): dimethylaminoethyl Methyl chloride quaternary of acrylate DAM (CH ₃ Cl): Methyl chloride quaternary of dimethylaminoethyl methacrylate AA: Acrylic acid AAm: Acrylamide NaA: Sodium acrylate NaAMPS: 2-Acrylamido-2-methylpropanesulfonic acid Na salt The clarity of the filtrate and the peelability of the cake from the filter cloth were evaluated according to the following criteria. Clarity of filtrate ◯: The filtrate is completely transparent. ○ △: The filtrate was slightly turbid. Δ: Slight turbidity is observed in the filtrate. X: The filtrate is cloudy. Peelability ◯: The cake peels cleanly from the filter cloth. B: The cake slightly adheres to the filter cloth. X: The cake adheres to the filter cloth. Example 1 A Nutsche test and a squeeze test were performed using mixed sludge (pH 6.1, SS 1.9%) at a sewage treatment plant. Sludge 2
Take 00 ml in a 300 ml beaker and use 5 g of a 0.4% by weight aqueous solution of a mixture of a cationic polymer flocculant C-1 and an anionic polymer flocculant A-1 at a weight ratio of 70/30 as a sludge dewatering agent (pH 3.0). After adding, the mixture was stirred at 200 rpm for 30 seconds with a stirrer equipped with turbine blades. After measuring the floc diameter at that time, a polyvinyl chloride pipe having an inner diameter of 5 cm was placed in a nutcheroth laid with a nylon filter cloth, coagulated sludge was poured into the pipe, and the filtrate amount after 10 seconds was measured. Further, the clarity of the filtrate at this time was evaluated by visual observation. A certain amount of the sludge after filtration was put on a filter cloth for belt press and squeezed at 0.5 kg / cm ² and 1.0 kg / cm ² for 1 minute to visually evaluate the peelability of the cake from the filter cloth. Then, the water content of the cake was measured. The results are shown in Table 2. Example 2 As Example 1 except that a mixture of a cationic polymer flocculant C-2, an anionic polymer flocculant A-1 and sodium carbonate in a weight ratio of 50/30/20 was used as a sludge dewatering agent. The exact same operation was repeated. The results are shown in Table 2. Example 3 Example 1 except that a mixture of a cationic polymer flocculant C-3, an anionic polymer flocculant A-1 and sodium hydrogen sulfate in a weight ratio of 50/30/20 was used as the sludge dewatering agent. The exact same operation was repeated. The results are shown in Table 2. Comparative Example 1 The same operation as in Example 1 was repeated except that a mixture of the cationic polymer flocculant C-2 and sodium carbonate in a weight ratio of 80/20 was used as the sludge dewatering agent. Second result
Shown in the table. Comparative Example 2 Except for using the cationic polymer flocculant C-3 as the sludge dewatering agent, the same operation as in Example 1 was repeated. The results are shown in Table 2. Comparative Example 3 The same operation as in Example 1 was repeated except that the cationic polymer flocculant C-5 was used as the sludge dewatering agent. The results are shown in Table 2. Comparative Example 4 As Example 1 except that a mixture of a cationic polymer flocculant C-5, an anionic polymer flocculant A-1 and sodium carbonate in a weight ratio of 50/30/20 was used as a sludge dewatering agent. The exact same operation was repeated. The results are shown in Table 2.

[0011]

[Table 2]

Example 1 using the sludge dewatering agent of the present invention
3, the floc diameter, the filtration rate, the clarity of the filtrate,
It shows good results in all respects of cake water content and peelability. On the other hand, Comparative Example 1 using a sludge dewatering agent containing a cationic polymer flocculant having the same structure as that used for the sludge dewatering agent of the present invention, but containing no anionic polymer flocculant In No. 2 and No. 2, the floc diameter was small, the water content of the cake was high, and the releasability of the cake from the filter cloth was poor when the cake was squeezed at 1.0 kg / cm ² . In Comparative Example 3 in which only the cationic polymer flocculant having a structure different from that used for the sludge dewatering agent of the present invention was used as the sludge dewatering agent, the floc diameter was small, the cake water content was high, and 1.0 kg / The peelability of the cake from the filter cloth when it was squeezed at cm ² was slightly poor. Even if it contains a cationic polymer flocculant and an anionic polymer flocculant, the cationic polymer flocculant is a sludge dewatering agent having no structure represented by the general formula [1] or the general formula [2]. In Comparative Example 4 used, all of the floc diameter, the filtration rate, the clarity of the filtrate, the water content of the cake, and the peeling property are different from Example 2 only in the structure of the cationic polymer flocculant. In terms of, it shows extremely bad results. Example 4 As the sludge, a mixed sludge (pH 7.0, SS 2.6%) of surplus sludge from a human waste treatment plant and a tertiary treatment coagulated sludge was used, and a cationic polymer coagulant C-1 and an anionic substance were used as sludge dewatering agents. 0. 0 of a mixture of polymeric flocculant A-1 in a weight ratio of 70/30.
The exact same procedure as in Example 1 was repeated except that 14 g of a 4% by weight aqueous solution was added. The results are shown in Table 3. Example 5 Example 4 except that a mixture of a cationic polymer flocculant C-3, an anionic polymer flocculant A-1 and sodium hydrogen sulfate in a weight ratio of 50/30/20 was used as the sludge dewatering agent. The exact same operation was repeated. The results are shown in Table 3. Comparative Example 5 The same operation as in Example 4 was repeated except that a mixture of the cationic polymer flocculant C-2 and sodium carbonate in a weight ratio of 80/20 was used as the sludge dehydrating agent. The result is the third
Shown in the table. Comparative Example 6 The same operation as in Example 4 was repeated except that the cationic polymer flocculant C-3 was used as the sludge dewatering agent. The results are shown in Table 3.

[0013]

[Table 3]

In Examples 4 and 5 in which the sludge dehydrating agent of the present invention was used, the filtration rate was slightly slower, 0.5 kg / cm ^2.
Except for the fact that the cake water content is slightly higher when compressed with, the floc diameter, the clarity of the filtrate, and the cake water content and peelability when compressed with 1.0 kg / cm ² are all points. Shows good results. On the other hand, comparison using a sludge dewatering agent containing a cationic polymer flocculant having the same structure as that used for the sludge dewatering agent of the present invention, but containing no anionic polymer flocculant In Examples 5 and 6, the floc diameter was small and the filtration rate was slow.
The cake water content is high even when pressed at 0 kg / cm ² ,
When pressed at 1.0 kg / cm ² , the peelability of the cake from the filter cloth is not good. Example 6 As the sludge, excess sludge (pH 6.7, SS 0.9) of a food factory
%) Was used to perform a Nutsche test and a squeeze test. 200 ml of sludge was placed in a 300 ml beaker, 12 g of a 3.8 wt% aqueous solution of ferric chloride was added, and the mixture was stirred with a stirrer equipped with a turbine blade at 500 rpm for 20 seconds. Furthermore, as a sludge dewatering agent, a cationic polymer flocculant C-2,
4 g of a 0.4% by weight aqueous solution of a mixture of anionic polymer flocculant A-2 and sodium carbonate in a weight ratio of 50/30/20 was added, and the amount was 200 rp with a stirrer equipped with a turbine blade
Stirred for 30 seconds. After measuring the flock diameter at that time, the inner diameter is 5 cm on the nutcheroth lined with nylon filter cloth.
Place a PVC pipe and pour coagulated sludge into it 10
The amount of filtrate after 2 seconds was measured. Further, the clarity of the filtrate at this time was evaluated by visual observation. About sludge after filtration,
Transfer a certain amount to a filter cloth for belt press, 0.5kg / c
In m ² for 1 minute compression, visually evaluated releasability from filter cloth of the cake was measured moisture content of the cake. The results are shown in Table 4. Example 7 The addition amount of a 3.8 wt% aqueous solution of ferric chloride was 6 g,
Except for adding 3 g of a 0.4% by weight aqueous solution of a mixture of a cationic polymer flocculant C-4, an anionic polymer flocculant A-1 and sodium hydrogensulfate in a weight ratio of 50/30/20 as a sludge dehydrating agent. The exact same operation as in Example 6 was repeated. The results are shown in Table 4. Comparative Example 7 The same operation as in Example 7 was repeated except that a mixture of the cationic polymer flocculant C-2 and sodium carbonate in a weight ratio of 80/20 was used as the sludge dehydrating agent. The fourth result
Shown in the table. Comparative Example 8 A cationic polymer flocculant C-5 was used as a sludge dewatering agent without adding an aqueous solution of ferric chloride and subsequent stirring.
The exact same operation as in Example 7 was repeated except that was used. The results are shown in Table 4. Comparative Example 9 A cationic polymer flocculant C-6 was used as a sludge dehydrating agent without addition of an aqueous solution of ferric chloride and subsequent stirring.
The exact same operation as in Example 7 was repeated except that was used. The results are shown in Table 4. Comparative Example 10 Example 7 except that a mixture of a cationic polymer flocculant C-5, an anionic polymer flocculant A-1 and sodium hydrogen sulfate in a weight ratio of 50/30/20 was used as the sludge dehydrating agent. The exact same operation was repeated. The results are shown in Table 4. Comparative Example 11 Example 7 except that a mixture of a cationic polymer flocculant C-6, an anionic polymer flocculant A-1 and sodium hydrogen sulfate in a weight ratio of 50/30/20 was used as a sludge dewatering agent. The exact same operation was repeated. The results are shown in Table 4.

[0015]

[Table 4]

In Examples 6 and 7 using the sludge dewatering agent of the present invention, good results were shown in all respects of floc diameter, filtration rate, clarification of filtrate, cake water content and strippability. . On the other hand, Comparative Example 7 using a sludge dewatering agent containing a cationic polymer flocculant having the same structure as that used for the sludge dewatering agent of the present invention, but containing no anionic polymer flocculant. Comparative Examples 8 and 9 in which ferric chloride was not used in combination and only a cationic polymer flocculant having a structure different from that used in the sludge dewatering agent of the present invention was used as a sludge dewatering agent, and a cationic Use a sludge dewatering agent in which the cationic polymer flocculant does not have the structure represented by the general formula [1] or the general formula [2] even if it contains the polymer flocculant and the anionic polymer flocculant. In Comparative Examples 10 and 11, the satisfactory results were not obtained.

[0017]

According to the sludge dewatering agent of the present invention, the floc diameter of sludge and the filtration rate are large, and the clarity of the filtrate is excellent.
The water content of the cake obtained by filtration is low and the releasability from the filter medium is good. Therefore, in the sludge treatment facility, the amount of sludge treated increases, the amount of cake generated decreases, and the cake becomes easy to handle, and stable treatment can be performed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Matsushima 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. An organic sludge containing a cationic polymer flocculant having a structure represented by the following general formula [1] or general formula [2] in the molecule and an anionic polymer flocculant. Dehydrating agent. Embedded image (In the formula, R ¹ is hydrogen or methyl group, R ² is methyl group, ethyl group, propyl group or isopropyl group, R 2
³ is hydrogen, methyl group, ethyl group, propyl group, isopropyl group or benzyl group, X ⁻ is Cl ⁻ , 1 / 2S
O ₄ ²⁻ , HSO ₄ ⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , HCOO ⁻ or CH ₃ SO ₄ ⁻ . )