JP2012005993A - Coagulation treatment method for colored waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coagulation treatment method capable of drastically reducing chromaticity and obtaining good treated water in coagulation treatment of colored waste water.SOLUTION: Inorganic coagulant and amidine-based coagulant are added to and mixed with the colored waste water and pH control to a range of 5.0-7.0 is performed as necessary. Then, polymer coagulant is added to generate coagulation flock. Next, solid-liquid separation of the generated coagulation flock is performed. In this favorable embodiment, the polymer coagulant is anionic or non-ionic polymer coagulant including a sulfonic acid group, and consecutive addition is performed when the polymer coagulant is added to generate the coagulation flock.

Description

  The present invention relates to a coagulation treatment method for colored wastewater, and more particularly to a coagulation treatment method for colored wastewater that can significantly reduce the chromaticity of the treatment water.

  In the agglomeration treatment of dyeing wastewater, washing wastewater for dust control products, laundry wastewater, and other colored wastewater generated from various factory facilities, an inorganic polymer flocculant is generally added after adding an inorganic flocculant. , Agglomerating flocs are generated and agglomerated sedimentation or pressurized levitation is performed. The purified treated water is generally discharged into rivers and sea areas.

  Conventionally, in order to cope with stricter regulations on the quality of discharged water, water quality has been improved by improving treatment equipment and wastewater treatment methods. However, colored wastewater often has high chromaticity even if BOD, SS, etc. satisfy the regulation values, and often gives a significant sense of contamination to local residents. Therefore, there are cases where chromaticity regulations are set, and there is a strong demand for efficient decolorization of colored wastewater.

  In general, the quality of treated water is determined by the amount of inorganic flocculant added, such as aluminum sulfate (hereinafter referred to as “band”), polyaluminum chloride (hereinafter referred to as “PAC”), ferric chloride, and the like used for coagulation and separation. Increase to increase. However, the chromaticity can be removed to some extent by adding an inorganic flocculant, but it is often difficult to decolorize to a satisfactory level. Furthermore, it is often difficult to obtain a stable decolorization performance because the causative substances of coloring are various and the coagulation effect is affected by various substances coexisting in the wastewater.

  Under the circumstances as described above, application of an organic coagulant, which is a kind of water-soluble cationic polymer, has been proposed for the purpose of improving the decolorization of treated water. Since the organic coagulant is a polyelectrolyte having a large number of cationic groups in the molecule, it is used for the purpose of neutralizing the charge of the suspended substance in the water to be treated in the same manner as the inorganic coagulant. Since the organic coagulant has a higher charge density of the cation than the inorganic coagulant, the coagulant has a feature that it is much larger than the inorganic coagulant. In addition, the organic coagulant not only neutralizes suspended substances but also reacts with negatively charged dissolved substances such as lignin sulfonic acid and humic acid to form insoluble salts. The reduction effect of COD is also expected.

  Representative organic coagulants currently used include low molecular weights such as alkylamine / epichlorohydrin condensates, alkylene dichloride and polyalkylene polyamine condensates, dicyandiamide / formalin condensates, and dimethyldiallylammonium chloride polymers. Examples include water-soluble polymers having a strong cation density.

  As a decoloring treatment method using the organic coagulant as described above, for example, an inorganic flocculant and an organic coagulant (secondary amine) are added to treated water obtained by biological treatment of waste water with high chromaticity such as coffee waste water. A method of coagulating and separating using a polymer flocculant after adding a polycondensation polymer of chloroquine and epichlorohydrin, polydiallyldimethylammonium chloride, dicyandiamide cationic coagulant, polyacrylamide cationic coagulant, etc. (patent) Document 1), a decolorization method (Patent Document 2) in which an inorganic flocculant is added to dye wastewater and then agglomeration treatment is performed using polyvinylamine has been proposed.

  However, although any method can obtain a certain degree of decolorization effect, no coagulation treatment method has yet been proposed so that a satisfactory decolorization effect can be obtained for various colored wastewaters.

JP 2003-181491 A Japanese Patent Laid-Open No. 8-81519

  The present invention has been made in view of the above circumstances, and its purpose is to agglomerate that can greatly reduce the chromaticity of the treated water in the agglomeration treatment of the colored wastewater, and can provide a decoloring effect that is also satisfactory in appearance. It is to provide a processing method.

  In principle, purification of wastewater by coagulation treatment is carried out by charging negatively charged dissolved substances (suspended substances, colloidal substances, BOD and COD components, etc. in wastewater) with inorganic coagulants and organic coagulants. This is achieved by adding and insolubilizing and then aggregating and separating.

  Suspended substances and colloidal substances are water-insoluble particles having a relatively large particle size, so that they are condensed to form fine flocs when neutralized by charge. However, even if inorganic flocculants and organic coagulants are added, coloring substances such as dyes that dissolve in water will remain dissolved in water if they are highly hydrophilic even if they are neutralized by charge, and water-insoluble fine flocs will not be produced. May not form. For this reason, even when a polymer flocculant is added and agglomerated and separated, agglomerated flocs are not formed, the colored substance remains in water, and the treated water chromaticity often remains high.

  As a result of intensive studies on methods for insolubilizing coloring substances such as dyes, the present inventors have obtained the following various findings. That is, according to the addition of the amidine-based flocculant, a coloring substance such as a dye is insolubilized and a good decoloring effect is obtained. This is a peculiar effect of amidine-based flocculants, and reacts with colored substances such as negatively charged soluble dyes to neutralize the charge, and the amidine-based flocculants react with polyanions to form complexes. This is considered to be insolubilized in water. A reaction product of a coloring substance such as a dye insolubilized in water and an amidine-based flocculant generates a fine floc that is insoluble in water, and a good decoloring effect can be obtained by adding a polymer flocculant and aggregating and separating. Furthermore, the use of an anionic or nonionic polymer flocculant containing a sulfonic acid group as the polymer flocculant, or by adding the polymer flocculant in portions, enables more efficient decolorization.

  The present invention has been completed based on the above findings, and the gist thereof is that an inorganic flocculant and an amidine flocculant are added to and mixed with colored wastewater, and after adjusting the pH as necessary, the polymer flocculant is added. In addition, the present invention resides in a coagulation treatment method for colored wastewater, characterized in that coagulation flocs are generated and then the generated coagulation flocs are subjected to solid-liquid separation. In a preferred embodiment of the present invention, the polymer flocculant is an anionic or nonionic polymer flocculant containing a sulfonic acid group, and is added sequentially when the polymer flocculant is added to form an aggregate floc. To do.

  According to the present invention, it is possible to obtain treated water having excellent decoloring effect and low chromaticity in the coagulation treatment of colored wastewater.

  Hereinafter, the present invention will be described in detail. Examples of the colored wastewater that is the subject of the present invention include, but are not limited to, dyeing wastewater, washing wastewater for dust control products, laundry wastewater, and other colored wastewater generated from various factory facilities.

  In the present invention, as the inorganic flocculant, a commercially available aluminum-based or iron-based inorganic flocculant is used. Examples of the aluminum-based inorganic flocculant include band, PAC, and aluminum chloride. Examples of the iron-based inorganic flocculant include ferric chloride and polyiron sulfate. The amount of the inorganic flocculant added is usually 500 to 3,000 mg / L, although it varies depending on the properties of the colored waste water to be treated.

  The “repeat unit” of the amidine-based flocculant used in the present invention is represented by the following chemical formula.

  The amidine-based flocculant can be produced by the method described in Japanese Patent No. 2624089. Specifically, N-vinylformamide and acrylonitrile are copolymerized, and the resulting copolymer is hydrolyzed under hydrochloric acid acidity, and then heat-treated to cyclize the primary amino group and cyano group of the inner chain of the molecule. To form an amidine ring.

  The molecular weight of the amidine-based flocculant is usually 100,000 to 5,000,000, preferably 1,000,000 to 5,000,000. When the molecular weight is less than 100,000, the coagulation force is reduced, and when it exceeds 5 million, it is difficult to produce on a commercial basis.

  In the present invention, the pH of the waste water when the polymer flocculant is added and agglomerated is usually 5.0 to 7.0, preferably 5.5 to 6.5. The pH of the wastewater can be adjusted with an alkaline agent such as mineral acid such as hydrochloric acid and sulfuric acid, caustic soda and slaked lime.

  The addition amount of the amidine-based flocculant varies depending on the quality of the colored wastewater, but is usually 1 to 100 mg / L, preferably 10 to 60 mg / L. When the addition amount is too small, the cohesiveness and decoloring effect are poor, and when it exceeds 100 mg / L, the processing cost becomes high.

  The order of adding the inorganic flocculant and the amidine flocculant is not particularly limited, but a method of adding the inorganic flocculant first is common.

  In the present invention, as the polymer flocculant, an anionic polymer flocculant, a nonionic polymer flocculant and the like can be used.

  Examples of the anionic polymer flocculant include a polyacrylamide partial hydrolyzate, a copolymer of acrylamide and acrylic acid, a copolymer of 2-acrylamide 2-methylpropanesulfonic acid and acrylamide, and 2-acrylamide 2- Examples thereof include a copolymer of methylpropanesulfonic acid, acrylic acid, and acrylamide. Among them, a copolymer containing a sulfonic acid group, such as a copolymer of 2-acrylamide 2-methylpropanesulfonic acid and acrylamide and a copolymer of 2-acrylamide 2-methylpropanesulfonic acid, acrylic acid and acrylamide, is preferably used. . The anionic polymer flocculant may be copolymerized with other monomers that do not adversely affect the aggregation effect. On the other hand, examples of nonionic polymer flocculants include polymers of acrylamide and copolymers with other nonionic monomers.

  The anionic group copolymerization ratio of the anionic polymer flocculant is not particularly limited, but is usually 1 to 25% by weight. The copolymerization ratio of the sulfonic acid-containing monomer in the anionic polymer flocculant containing a sulfonic acid group is usually 2 to 25% by weight. When the copolymerization ratio of the sulfonic acid-containing monomer is less than 2% by weight, the decoloring effect tends to be inferior. When it exceeds 25% by weight, there is no problem in the decoloring effect, but the cohesiveness tends to be inferior. The intrinsic viscosity of the anionic or nonionic polymer flocculant is not particularly limited, but is usually 15 dl / g or more.

  The addition amount of the polymer flocculant is usually 0.1 to 50 mg / L, although it varies depending on the SS concentration of the colored waste water to be treated.

  Examples of the polymerization method of the anionic and nonionic polymer flocculants include precipitation polymerization, bulk polymerization, dispersion polymerization, and aqueous solution polymerization, but are not particularly limited. As an example, a manufacturing method using an aqueous solution polymerization method will be described below.

  First, a predetermined amount of 2-acrylamido-2methylpropanesulfonic acid, acrylamide, and ion exchange water are weighed and adjusted to a predetermined pH and temperature, and then charged into a heat-insulating container that can be sealed. Next, the dissolved oxygen is replaced with nitrogen gas, and chemicals such as a polymerization initiator and a continuous transfer agent are added. As the polymerization initiator, known general azo initiators, redox initiators and the like can be used.

  As the polymerization proceeds, the polymerization temperature rises, but after the temperature reaches the peak, it is aged for 1 hour, and the polymer gel is taken out from the reaction vessel. The polymer gel is chopped with a meat chopper or the like and dried at a temperature of 80 ° C. with a blow dryer. The dried polymer is pulverized with a pulverizer to a particle size of about 0.5 to 1 mm to obtain an anionic polymer flocculant.

  The method for adding the polymer flocculant to the waste water is not a problem even if a predetermined amount is added all at once, but the decoloring effect can be further improved by sequential addition. The number of sequential additions is not particularly limited, but is preferably added in two portions. Even if it is added in three or more times, there is no particular problem, but there is no further improvement in the decoloring effect, and the operation becomes complicated. The ratio of the added amount of the first stage and the second stage is usually 95/5 to 50/50. When the ratio is 50/50 or less, there is a tendency that the improvement of the decoloring effect is small as compared with the one-stage addition.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. Each measuring method in an Example is as follows.

(1) Intrinsic viscosity of the polymer flocculant:
Intrinsic viscosity was measured based on a conventional method using a Ubbelohde dilution type capillary viscometer in a 1N sodium nitrate aqueous solution at a temperature of 30 ° C. (Edition of Polymer Society, “New Edition Polymer Dictionary”, Asakura Shoten, page 107) ).

(2) Flock diameter:
The average floc diameter of the aggregated floc was measured visually.

(3) Settling time:
A predetermined amount of the polymer flocculant is added, and after stirring for a predetermined time, stirring is stopped. And the time until the produced | generated aggregation floc settles in the bottom of a 500 ml beaker was measured.

(4) Treated water SS:
A polymer flocculant was added and the amount of SS in the treated water 1 minute after stopping stirring was measured visually. A state in which almost no SS was visually recognized was indicated by a symbol “−”, and as SS increased, it was indicated by a symbol “+”, “++”, “++++”, or “x”.

(5) Chromaticity:
As a sample for measuring chromaticity, treated water having a depth of 3 cm was collected from the surface 2 minutes after the stirring was stopped, and measured by the transmitted light measurement method based on the factory drainage test method JIS K 0102. The measurement was performed at a wavelength of 420 nm, and the transmittance (%) of the sample was measured with the transmittance of pure water as 100 (%).

  Table 1 shows the coagulant and polymer flocculant used. The coagulant was dissolved at a concentration of 1.0% by weight, and the polymer flocculant was dissolved at a concentration of 0.1% by weight.

ＤＭＣ ：ジメチルアミノエチルメタクリレート・メチルクロライド４級塩
ＤＭＥ ：ジメチルアミノエチルアクリレート・メチルクロライド４級塩
ＡＡｍ ：アクリルアミド
ＡＭＰＳ：２−アクリルアミド２−メチルプロパンスルホン酸
ＡＡ ：アクリル酸

DMC: dimethylaminoethyl methacrylate / methyl chloride quaternary salt DME: dimethylaminoethyl acrylate / methyl chloride quaternary salt AAm: acrylamide AMPS: 2-acrylamide 2-methylpropanesulfonic acid AA: acrylic acid

[Examples 1 to 5]
A mop and mat washing waste water from a leasing company for A dust control products was collected and subjected to a coagulation test. The properties of the wastewater were pH = 10.5, SS = 490 mg / L, and transmittance at 420 nm = 1%.

  First, 500 ml of waste water was collected in a 500 ml beaker, aluminum chloride was added as an inorganic flocculant, and the mixture was stirred for 1 minute at a rotation speed of 150 rpm, and then adjusted to the pH shown in Table 2 using caustic soda. Subsequently, the amidine-based flocculant (K1) shown in Table 1 was added, and the mixture was further stirred and mixed for 1 minute at a rotation speed of 150 rpm. Next, a polymer flocculant was added, and further stirred for 1 minute at a rotation speed of 100 rpm to form an agglomerate floc. As shown in Table 2, Examples 1 to 5 were tested by changing the treatment pH and the type of the polymer flocculant containing a sulfonic acid group.

  Table 2 shows the results of Examples 1 to 5. In any of the examples, coagulation was good, transmittance (chromaticity) was good, and treated water that was satisfactory in appearance could be obtained.

[Examples 6 and 7]
The aggregation test was conducted under the same test conditions as in Examples 1-5. However, a carboxylic acid anionic polymer flocculant containing no sulfonic acid group was used as the polymer flocculant. The results are shown in Table 2. Although the coagulation property was good and treated water having a transmittance (chromaticity) could be obtained, the transmittance was inferior to the result of using a polymer flocculant containing a sulfonic acid group.

[Examples 8 and 9]
The aggregation test was conducted under the same test conditions as in Examples 1-5. However, a polymer flocculant having a sulfonic acid group content outside the preferred range was used. The results are shown in Table 2. Example 8 using A5 containing 1% by weight of a sulfonic acid group was better in chromaticity than a carboxylic acid-based anionic polymer flocculant, but was inferior to Example 3. Moreover, Example 9 was a result in which aggregating performance was inferior.

[Examples 10 and 11]
The aggregation test was conducted under the same test conditions as in Examples 1-5. However, the amount of amidine flocculant K1 added was changed. The results are shown in Table 2. Example 10 in which the addition amount of amidine-based flocculant K1 is 10 mg / L is inferior in chromaticity to Example 3 in which the addition amount is 20 mg / L, but shows better chromaticity than the comparative example in which K1 is not added. It was. Further, as shown in Example 11, even when the amidine flocculant K1 was added in an excessive amount of 40 mg / L, the chromaticity was not further improved.

[Examples 12 to 14]
The aggregation test was conducted under the same test conditions as in Examples 1-5. However, the method of dividing the addition of the polymer flocculant and adding it sequentially was adopted. The results are shown in Table 2. As shown in Example 12, chromaticity was improved by sequential addition in two steps. However, as shown in Example 13, even if it was divided into three, no further improvement effect was obtained. Further, as shown in Example 14, when the ratio of the polymer flocculant added to the first stage was 50% or less, the chromaticity was not improved.

Examples 15 and 16
The aggregation test was conducted under the same test conditions as in Examples 1-5. However, the type of inorganic flocculant was changed. The results are shown in Table 2. “Salt iron” in Table 2 means ferric chloride. In Examples 15 and 16, the cohesiveness and treated water chromaticity were the same as those in Example 3 and were good.

[Comparative Examples 1 and 2]
The aggregation test was conducted under the same test conditions as in Examples 1-5. However, Comparative Examples 1 and 2 did not use the amidine-based flocculant K1, and performed a flocculence test using a combination of an inorganic flocculant and a polymer flocculant. The results are shown in Table 2. The cohesiveness was good, but the chromaticity of the treated water was significantly inferior to that of the examples, and the color was visually brown, which was a bad result. Further, there was no significant improvement even when the amount of inorganic flocculant added was increased 1.5 times.

[Comparative Examples 3 to 7]
The aggregation test was conducted under the same test conditions as in Examples 1-5. However, the aggregation treatment was performed using various commercially available cationic organic coagulants instead of the amidine-based coagulant K1 as a coagulant. The results are shown in Table 2. The cohesiveness was not a problem except for Comparative Example 3, but the chromaticity of the treated water was inferior to that of the example using the amidine-based flocculant. In Comparative Example 3, the cohesiveness and the chromaticity of the treated water were inferior.

  In Table 2, the meanings of the abbreviations in the “inorganic flocculant type” column are as follows. That is, LAC: aluminum chloride, band: aluminum sulfate, salt iron: ferric chloride.

  In Table 2, the sign “+” in the column “Amount of polymer flocculant added” indicates that the addition of the polymer flocculant is divided. For example, “15” is 15 mg / l added at a time, “10 + 5” is 10 mg / l added and mixed, then 5 mg / l is added and mixed, “8 + 5 + 2” is 8 mg / l, It means that 5 mg / l and 2 mg / l are added and mixed in three stages.

Claims (3)

  An inorganic flocculant and an amidine flocculant are added to and mixed with colored wastewater, and after adjusting the pH to a range of 5.0 to 7.0 as necessary, a polymer flocculant is added to generate flocculent flocs, A method for coagulating colored wastewater, comprising solid-liquid separating the produced coagulated floc.   The aggregation treatment method according to claim 1, wherein the polymer flocculant is an anionic or nonionic polymer flocculant containing a sulfonic acid group.   The aggregating treatment method according to claim 1 or 2, wherein the polymer aggregating agent is added sequentially when a polymer flocculant is added to produce agglomerated floc.