JP2000202500A - Method for dehydrating organic sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for dehydrating of organic sludge capable of lowering water content in organic sludge aggregate. SOLUTION: The treating method is executed by adding an anionic high molecular flocculant composed of a styrene based polymer having sulfonic group into the organic sludge and after that, adding a cationic high molecular flocculant. The cationic high molecular flocculant having >=2.5 meq./g ion equivalent is used. As the anionic high molecular flocculant, one having 50-500 mPa.s viscosity measured in a 1 wt.% Na2SO4 aq. solution having 0.2 normality at 25 deg.C is used. Or the organic sludge is flocculated and dehydrated by a dehydrating method using the cationic high molecular flocculant in the quantity equal to or above the quantity of the anionic high molecular flocculant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dehydrating an organic sludge using a polymer flocculant, and more particularly, to a method of adding a predetermined anionic polymer flocculant before adding a cationic polymer flocculant. The present invention relates to a method for dehydrating organic sludge, which comprises coagulating organic sludge by adding an agent, and dehydrating the resulting aggregate.

[0002]

2. Description of the Related Art Conventionally, as a method of purifying wastewater, a suspended substance in a waste liquid is aggregated and settled, and then treated with microorganisms.
Purification methods have been performed by appropriately combining methods such as adsorption treatment and reverse osmosis treatment. That is, the aggregation treatment has an important significance as a pretreatment step for performing various treatment steps. As described above, the substance added to the wastewater to coagulate the suspended matter in the wastewater is a coagulant, and in addition to the inorganic coagulant, a nonionic, cationic, anionic organic polymer coagulant. Etc. are used. For example, JP-A-2-298400 describes a sludge dewatering agent comprising a combination of a cationic polymer flocculant and a polystyrene sulfonate as active ingredients. In addition, JP-A-10-101730 discloses that the weight average molecular weight is 1
50,000 to 600,000 sulfonated styrenic polymers based polymeric flocculants are described.

[0003] Agglomerates of organic sludge are generated by coagulation and sedimentation of suspended matter in organic sludge by the above-mentioned coagulant. Such aggregates are incinerated after being subjected to a dehydration treatment such as a centrifugal dehydration method or a roll dehydration method. Therefore, even though the dewatering process is performed, if the water content of the generated organic sludge aggregate is high, not only the amount to be dewatered is increased, but also the subsequent incineration process is not desirable, which is not desirable. Therefore, there is a big problem as to how to reduce the water content of the generated organic sludge aggregate in the filtration and dewatering process of the generated organic sludge aggregate after coagulating and sedimenting the suspended substance with the coagulant. .

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and a dewatering treatment of organic sludge which can reduce the water content in an organic sludge aggregate using a polymer flocculant. It is intended to provide a method.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, (1) adding a cationic polymer flocculant after adding an anionic polymer flocculant; (2) Use of a styrene-based polymer having a sulfonate group and / or a sulfonate group as an anionic polymer coagulant, and use of specific anionic polymer coagulant and cationic polymer coagulant That, by using the amount of the cationic polymer flocculant equal to or more than the use weight of the anionic polymer flocculant,
The inventors have found that the water content of the organic sludge agglomerate can be greatly reduced, and completed the present invention.

That is, according to the present invention, after adding an anionic polymer flocculant comprising a styrene polymer having a sulfonic acid group and / or a sulfonic acid group to an organic sludge,
The present invention relates to a method for dehydrating an organic sludge, which comprises adding a cationic polymer coagulant and performing coagulation and dehydration. In the method, an ion equivalent is 2.
A method for dehydrating organic sludge, characterized by using a cationic polymer flocculant of 5 meq / g or more, and further comprising a 0.2 N Na ₂ SO ₄ aqueous solution (1.
A method of dehydrating an organic sludge, comprising using an anionic polymer flocculant having a viscosity of 10 to 500 mPa · s at 25 ° C. at a concentration of 1% by weight (corresponding to a concentration of 42% by weight). The present invention relates to a method for dehydrating an organic sludge, wherein the amount of the coagulant used is equal to or more than the used weight of the anionic polymer coagulant.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method for dehydrating organic sludge of the present invention will be described in detail. (1) Polymer flocculant Anionic polymer flocculant The anionic polymer flocculant used in the present invention is a styrene-based polymer having a sulfonic acid group and / or a sulfonate group (hereinafter, both are referred to as a sulfone group). It becomes. Sulfone groups are generally present on the benzene ring of styrene, and such are preferred in the present invention. Further, in the present invention, a sulfonate group in which a sulfonic acid group is neutralized by an alkali is preferable. Examples of alkalis that neutralize sulfonic acid groups include alkali metals such as sodium, potassium, magnesium, and calcium, hydroxides of alkaline earth metals, ammonia, lower alkylamines, lower alkanolamines, and tetraalkyl quaternary ammoniums. Can be These can be used alone or in combination. Styrene-based polymer having a sulfone group, homopolymerization of styrenesulfonic acid or a salt thereof, or butadiene copolymerizable with them, acrylonitrile, acrylic acid, methacrylic acid and those obtained by copolymerizing their esters, polystyrene or styrene Examples thereof include sulfonated polymers obtained by copolymerization with other monomers, and preferred examples of the present invention include sulfonated styrene polymers. A method for sulfonating a styrene-based polymer is known in Japanese Patent Application Laid-Open No. 10-101730 and the like. The styrene-based polymer is sulfonated using a conventional sulfonating agent such as sulfuric anhydride, sulfuric anhydride / Lewis base complex, and fuming sulfuric acid. A particularly preferable method is a method using sulfuric anhydride or a sulfuric anhydride / Lewis base complex. Styrene polymers used for sulfonation include polystyrene (homopolymer) and copolymers of styrene and other monomers. Styrene-based polymers are used as they are or in combination with various resins, and are widely used in various containers, cushioning materials, heat-insulating materials, etc. It is used in the invention and is preferable in terms of waste treatment and resource reuse. As the sulfonated styrene-based polymer, one obtained by subjecting a part of sulfone groups to a desulfurization reaction is preferable. As the desulfurization ratio, [(theoretical ion equivalent value of the sulfonated polymer−the measured ion equivalent value after desulfation) / theoretical ion equivalent value of the sulfonated polymer]
It is estimated from the reduction rate of the ion equivalent value calculated by the above, and the value is preferably 5 to 70%, more preferably 10 to 40%, and particularly preferably 15 to 38%. If the desulfurization ratio is less than 5%, the ratio of the sulfone groups exhibiting hydrophilicity increases, and the organic sludge cannot be sufficiently hydrophobized, and the water content of the organic sludge increases, which is not preferable.
On the other hand, if it exceeds 50%, it is not preferable because it becomes difficult to dissolve in sludge. The theoretical ion equivalent value of the sulfonated polymer was calculated assuming that one sulfone group is added to one aromatic ring present in the styrene-based polymer. Such a sulfonated styrenic polymer is considered to form a crosslinked structure by a desulfurization reaction,
In order to impart the same effect to the styrene sulfonic acid polymer, it is necessary to change the structure by introducing a small amount of a crosslinking component such as divinylbenzene. The desulfurization reaction of the sulfonated styrene-based polymer can be easily controlled by the reaction conditions using a sulfonating agent.

As the anionic polymer flocculant, neutral salts such as sodium chloride, sodium sulfate and sodium nitrate can be used in an amount of 0.1%.
25% of a 1% by weight aqueous solution added in an amount of 01 to 5 N
The viscosity at 25 ° C of 1% by weight in an aqueous solution containing 0.2 N of a neutral salt is 10 to 500 mPa · s, more specifically, the viscosity at 25 ° C of 10 to 2,000 mPa · s. It is preferable that the viscosity at 25 ° C. of a 1% by weight aqueous solution containing 1N of a neutral salt is 10 to 300 mPa · s. In addition, the salt viscosity of 0.5% by weight (viscosity at a concentration of 0.5% by weight in a 4% by weight aqueous NaCl solution at 25 ° C.) used as an index of the performance of the flocculant is 1 to 30 m
Pa · s is preferable, and more preferably 2 to 20 mPa · s
s, particularly preferably 2 to 12 mPa · s. This viscosity is correlated with the molecular weight of the anionic polymer flocculant and the degree of crosslinking. If the viscosity is less than 10 mPa · s at the above viscosity, the ratio of hydrophilic sulfone groups increases, and the organic sludge is sufficiently reduced. Hydrophobicization is not possible, and the coagulation effect of the organic sludge is reduced, and the water content is increased, which is not preferable. On the other hand, if it exceeds 2,000 mPa · s, it is difficult to dissolve in the sludge, which is not preferable. Furthermore, since the sulfone group is hydrophilic, when the ionic equivalent is large, water is easily retained in the polymer, and the water content of the generated organic sludge increases. Therefore, the anionic polymer flocculant used in the present invention. It is preferable that the ion equivalent of is small, 5meq / g
The following is preferable, more preferably 3.0 to 4.5 meq / g, and particularly preferably 3.5 to 4.5 meq / g.

The cationic polymer flocculant used in the present invention includes, for example, quaternized poly-N, N-dialkylaminoalkyl (meth) acrylate and quaternary N, N-dialkylaminoalkyl (meth) acrylate. And a acrylamide copolymer. These can be used alone or in combination of two or more. In the case of a copolymer, the proportion of the quaternized N, N-dialkylaminoalkyl (meth) acrylate, such as a cationizing monomer, is preferably 60 to 99% by weight, more preferably 70 to 99% by weight, and particularly preferably. Is 80-99% by weight
It is.

[0010] The cationic polymer flocculant preferably has an ion equivalent of 2.5 meq / g or more. The cationic polymer flocculant electrically neutralizes the negatively charged suspended substance and the anionic polymer flocculant to form a strong floc and to improve the dehydration performance, Is preferable. On the other hand, if the ion equivalent is too high in cationicity, the water content of the organic sludge can be reduced, but there is a problem that the filtration amount is reduced and the efficiency of the dehydration treatment is reduced. Therefore, the upper limit of the ion equivalent is preferably 5.5 meq / g, and more preferably 4.5 meq / g.
It is 9 meq / g. Therefore, the cationic equivalent of the cationic polymer flocculant is preferably 2.5 to 5.5 meq / g, more preferably 4.0 to 4.9 meq / g, and particularly preferably 4.5 meq / g.
４4.9 meq / g.

The amount of each polymer flocculant varies depending on the concentration of the suspended matter in the sludge.
1 to 5% by weight (to the suspension) is added, and the combined ratio of the polymer coagulant used in combination is 0.1 to 50% by weight of the anionic polymer coagulant when the total amount is 100% by weight. It is preferably 5 to 40% by weight, particularly preferably 5 to 30% by weight, and therefore the cationic polymer flocculant is preferably 50 to 99.9% by weight, more preferably The amount is 60 to 95% by weight, particularly preferably 70 to 95% by weight, and it is preferable to use the same amount or more as the amount of the anionic polymer coagulant used. If the amount of the anionic polymer coagulant is less than 0.1% by weight, the effect of the addition of the anionic polymer coagulant becomes unclear, so that it is not preferable. If the amount exceeds 50% by weight, the dehydration performance deteriorates.

According to the present invention, the water content can be reduced to 80% or less by the measuring method shown in the examples. In particular, the anionic polymer flocculant is obtained by sulfonating polystyrene, the anion equivalent of which is 5 meq / g or less, and the ion equivalent of the cationic polymer flocculant is 3 to 5.5 m.
eq / g (especially 4.5 to 4.9 meq / g) and when the desulfurization ratio is 5 to 70% (especially 10 to 40%), the water content is 79% or less (especially 78.5% Below) and the filtration amount is 7
It can be 0 ml / 10 s or more (particularly 70 to 75 ml / 10 s).

[0013]

According to the method for dehydrating organic sludge of the present invention, the cationic polymer flocculant is added after the anionic polymer flocculant is added to the wastewater. Suspended matter in wastewater is usually negatively charged, and conventionally, by adding a cationic polymer flocculant, it is electrically neutralized to form floc by flocculation. Was sinking. Further, by adding an anionic polymer flocculant, flocs are aggregated to form a large floc, thereby increasing the sedimentation speed and improving wastewater treatment efficiency. However, when an excessively large floc is formed, the sedimentation speed is increased, while the moisture is retained in the floc, resulting in an increase in the water content of the generated organic sludge. On the other hand, in the present invention, the cationic polymer flocculant is added after the anionic polymer flocculant is added first, and the anionic polymer flocculant is added to the electrolyte contained in the water to be treated. Even in the coexistence system, since the viscosity of the aqueous solution is high, the aggregation performance is not reduced.

[0014]

EXAMPLES Hereinafter, the method for dehydrating organic sludge of the present invention will be described more specifically with reference to examples and comparative examples. Examples 1 to 5, Comparative Examples 1 to 4 (1) Polymer flocculant Anionic polymer flocculant The following was used as the anionic polymer flocculant. PS-1: Styrofoam waste (polystyrene molecular weight 2
(0000,000) as a sodium salt and has the following properties. Viscosity (0.2 N Na ₂ SO ₄ aqueous solution, 1 wt% concentration, 25 ° C.) 195 mPa · s Viscosity (1.0 N Na ₂ SO ₄ aqueous solution, 1 wt% concentration, 25 ° C.) 89 mPa · s 0.5 wt% salt Viscosity (4 wt% NaCl aqueous solution, 0.5 wt% concentration, 25 ° C) 5.0 mPa · s Sulfone group introduction rate to benzene ring 100% Ion equivalent 3.5 meq / g Desulfurization rate 35% (to all benzene rings This is a comparison value with the case where one sulfone group is introduced). PS-2: Styrofoam waste (polystyrene molecular weight 2
(0000,000) as a sodium salt and has the following properties. Viscosity (0.2 N Na ₂ SO ₄ aqueous solution, 1 wt% concentration, 25 ° C.) 350 mPa · s Viscosity (1.0 N Na ₂ SO ₄ aqueous solution, 1 wt% concentration, 25 ° C.) 200 mPa · s 0.5 wt% salt Viscosity (4 wt% NaCl aqueous solution, 0.5 wt% concentration, 25 ° C) 9.0 mPa · s Sulfone group introduction rate to benzene ring 100% Ion equivalent 4.3 meq / g Desulfurization rate 20% (to all benzene rings This is a comparison value with the case where one sulfone group is introduced). PS-3: A television housing waste material (high impact polystyrene, molecular weight 200,000, polybutadiene content 5 mol%) is sulfonated into a sodium salt, and has the following characteristics. Viscosity (0.2 N Na ₂ SO ₄ aqueous solution, 1 wt% concentration, 25 ° C.) 52 mPa · s Viscosity (1.0 N Na ₂ SO ₄ aqueous solution, 1 wt% concentration, 25 ° C.) 27 mPa · s 0.5 wt% salt Viscosity (4 wt% NaCl aqueous solution, 0.5 wt% concentration, 25 ° C) 4.0 mPa · s Sulfone group introduction rate to benzene ring 100% Ion equivalent 3.5 meq / g Desulfurization rate 33% (to all benzene rings This is a comparison value with the case where one sulfone group is introduced). A-205: An anionic polymer (manufactured by Toagosei Co., Ltd.) containing sodium polyacrylate as a main component and having an ion equivalent of 4.0 meq / g (for comparison).

Cationic polymer flocculant The following was used as the cationic polymer flocculant. C-1; quaternary compound of dimethylaminoethyl acrylate with methyl chloride / acrylamide = 80/20 [mol%] Viscosity (4 wt% NaCl aqueous solution, 0.5 wt% concentration, 25 ° C.) 60 mPa · s ion equivalent 4. 7 meq / g C-2; quaternized product of dimethylaminoethyl acrylate with methyl chloride / acrylamide = 10/90 [mol%] Viscosity (4 wt% NaCl aqueous solution, 0.5 wt% concentration, 25 ° C) 80 mPa · s ion Equivalent 1.4 meq / g C-3; quaternary compound of dimethylaminoethyl acrylate with methyl chloride / acrylamide = 99/1 [mol%] Viscosity (4 wt% NaCl aqueous solution, 0.5 wt% concentration, 25 ° C) 50 mPa・ S ion equivalent 5.1meq / g

(2) Dehydration treatment and filtration test 100 ml of organic sludge for coagulation evaluation is collected in a 200 cc beaker. Thereafter, an anionic polymer flocculant is added in the ratio of the amount shown in Table 1. The numbers in Table 1 indicate the solid content (ppm) of the anionic polymer flocculant with respect to the sludge water.
It is. After the addition, 10 minutes at 1000 rpm using a stirrer.
Stir and mix for seconds. Next, a cationic polymer coagulant was added at a ratio of the addition amount (ppm) shown in Table 1, and the mixture was stirred and mixed at 1000 rpm for 30 seconds using a stirrer to generate flocs (Examples 1 to 5; Example 1). Thereafter, gravity dehydration is performed, and the filtration speed is measured. Next, the dewatered cake after the gravity dehydration was put into a table-top centrifugal sedimentation tube,
Centrifuge at 0 rpm for 10 minutes. After centrifugal dehydration,
Measure the moisture content of the dehydrated cake. In Comparative Examples 2 to 4, the cationic polymer flocculant was added first, and then the anionic polymer flocculant was added, followed by the same treatment. The test results are shown in Table 1 below.

[0017]

[Table 1]

(3) Effects of Example Comparative Example 2 in which the same amount of the same anionic polymer flocculant and cationic polymer flocculant was used and the order of addition to the waste liquid was reversed.
When comparing Examples 4 to 4 with Examples 1 to 3, the moisture content and the amount of filtration show significantly superior values in Examples 1 to 3 in which the anionic polymer flocculant was added first. I understand. That is, the difference in water content between Example 1 and Comparative Example 2 was 2.
0%, the difference in water content between Example 2 and Comparative Example 3 was 3.6%,
The difference in water content between Example 3 and Comparative Example 4 was 2.6%, which were all significantly different.

Even in the same order of addition as in Examples 1 to 5, Comparative Example 1 using sodium acrylate having higher hydrophilicity than the sulfonated polystyrene-based polymer as the anionic polymer coagulant showed a water content of 81.5%. %) And the amount of filtration (51 ml / 10 s) are greatly reduced. This is presumed to be due to the fact that organic sludge could not be sufficiently hydrophobized by containing a large number of hydrophilic groups.

Further, according to the results of tests on the effects of the ion equivalent of the cationic polymer flocculant on the filtration amount and the water content, it was found that Example 5 (ion equivalent: 1) using a low cationic polymer flocculant was used. At 0.4 meq / g), the moisture content of the dehydrated cake is slightly poor at 80%, and the filtration amount is also slightly poor at 61 ml / 10 s. On the other hand, in Example 4 (ion equivalent: 5.1 meq / g) using a highly cationic polymer flocculant, the water content of the dehydrated cake was as excellent as 78.5%, as in Examples 1 to 3. . In addition, the filtration amount was slightly bad at 56 ml / 10 s. On the other hand, when the cation equivalent is moderately 4.7 meq / g (Example 1).
In (3), the water content of the dehydrated cake is remarkably small at 77.4 to 78.2% by weight, and the filtration amount is 70 to 74 ml / 1.
0s, which is very large, and the balance between them is remarkably excellent. From the above, it can be seen that the treatment method of this example is a method particularly suitable for a dehydration method using a centrifugal dehydrator. still,
The present invention is not limited to the specific embodiments described above, but may be variously modified embodiments within the scope of the present invention depending on the purpose and application.

[0021]

According to the method for dehydrating organic sludge of the present invention, that is, after adding an anionic polymer flocculant comprising a styrene-based polymer having a sulfone group first, contrary to the conventional addition method. By adding the same amount or more of the cationic polymer flocculant, the water content of the dewatered cake of organic sludge can be reduced. In particular, the ion equivalent is 3.
Using a cationic polymer flocculant of 0 meq / g or more and an anionic polymer flocculant having a viscosity of 10% to 500 mPa · s at 25 ° C. at a concentration of 1% by weight in a 0.2N Na ₂ SO ₄ aqueous solution. In the invention, not only the moisture content of the dewatered cake but also the filtration performance is excellent, and the performance balance is remarkably excellent. Therefore, the organic sludge dewatering process can be efficiently performed, and the organic sludge after dewatering can be easily processed. The treatment method of the present invention is particularly suitable for a dehydration method using a centrifugal dehydrator.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshio Mori 1 at Funami-cho, Minato-ku, Nagoya-shi, Aichi, Japan 1 Toagosei Co., Ltd. Nagoya Research Institute (72) Inventor Shigeo Kiuchi 1-chome, Sumida-ku, Tokyo 3-7 Inside Lion Corporation (72) Inventor Yasushi Inagaki 6-36 Kita-Shinagawa, Shinagawa-ku, Tokyo 7-36 Inside Sony Corporation (72) Inventor Kenji Ito 1 Funamicho, Minato-ku, Nagoya-shi, Aichi Prefecture Nagoya Research Institute, Toagosei Co., Ltd. (72) Katsuhide Higashi 1 Nagoya Research Institute, Minato-ku, Nagoya, Aichi Prefecture 1 Togosei Gosei Co., Ltd. Nagoya Research Institute (72) Inventor Takashi Tomizawa Sakaide, Kagawa Prefecture 2-4-1 Showa-cho F-term (reference) in the Sakaide Plant of Toagosei Co., Ltd. 4D015 BA09 BA12 BB17 CA11 DB02 DB04 DB30 DC07 DC08 EA02 EA04 EA06 EA36 F A03 FA19 4D059 AA30 BE13 BE37 BE57 BE59 BE61 DB11 DB24 DB25 DB26 EB04 EB11 EB12

Claims (4)

[Claims] The present invention relates to a method comprising: adding an anionic polymer flocculant comprising a styrene-based polymer having a sulfonic acid group and / or a sulfonic acid group to an organic sludge; Characteristic method of dehydrating organic sludge. 2. The method for dehydrating organic sludge according to claim 1, wherein a cationic polymer flocculant having an ion equivalent of 2.5 meq / g or more is used. 3. 1% by weight of a 0.2 N Na ₂ SO ₄ aqueous solution
2. The method for dehydrating organic sludge according to claim 1, wherein an anionic polymer flocculant having a viscosity of 10 to 500 mPa · s at a concentration of 25 ° C. is used. 4. The method for dehydrating organic sludge according to claim 1, wherein the amount of the cationic polymer flocculant used is equal to or greater than the weight of the anionic polymer flocculant used.