JP5621260B2 - Wastewater coagulation method - Google Patents

Description

  The present invention relates to a flocculation treatment method for wastewater, and more particularly to a flocculation treatment method for purifying various wastewaters using an inorganic flocculant, a water-soluble weak cationic polymer, and a polymer flocculant.

  As agglomeration treatment of wastewater generated in automobile manufacturing factories, steel mills, pulp and paper manufacturing industry, cleaning, gravel industry, other chemical factories, etc., generally aluminum-based or sulfuric acid band, polyaluminum chloride (PAC) etc. A method is employed in which after adding an iron-based inorganic flocculant, a polymer flocculant is further added to form a floc floc and then treated by a flocculent precipitation or a flocculent levitation method. The purified treated water is generally discharged into rivers and sewage.

  By the way, with the stricter regulation of the discharged water quality, the water quality is improved by improving the treatment apparatus and the wastewater treatment method, and it is indispensable to increase the amount of inorganic flocculant added. However, when the amount of the inorganic flocculant used is increased, the chemical cost is increased, the amount of generated sludge is increased, and the generated sludge treatment cost is increased. Moreover, since it is difficult to sufficiently remove the low-molecular-weight COD component in the wastewater only by the power of the inorganic flocculant, there remains anxiety about the quality of the treated water discharged. In the case where advanced processing is performed at a later stage in order to eliminate this anxiety, the load on the advanced processing step becomes high.

  Under the circumstances as described above, application of an organic coagulant, which is a kind of cationic coagulant, has been promoted for the purpose of reducing the amount of inorganic coagulant used while maintaining and improving the quality 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, like the inorganic coagulant. In addition, since the organic coagulant has a higher charge density of the cation than the inorganic coagulant, the coagulation action is much larger than that of the inorganic coagulant. Organic coagulants not only neutralize suspended substances but also react with negatively charged dissolved substances such as lignin sulfonic acid and humic acid to form insoluble salts. A reduction effect is also expected.

  Typical organic coagulants currently used are low molecular weight, strong compounds such as alkylamine / epichlorohydrin condensate, alkylene dichloride and polyalkylene polyamine condensate, dicyandiamide / formalin condensate, and dimethyldiallylammonium chloride polymer. Examples thereof include water-soluble polymers having a cation density. Furthermore, various polymers and waste water treatment methods have been proposed as novel organic coagulants.

  For example, an alkylamine-epichlorohydrin condensate having an intrinsic viscosity of 0.002 to 0.5 dl / g, polydimethyldiallylammonium halide having an intrinsic viscosity of 0.01 to 0.5 dl / g, and an intrinsic viscosity of 0.05 to 1. A deinking wastewater treatment method (Patent Document 1), in which any charge control agent is added in 0 dl / g of polydimethylaminoalkyl (meth) acrylate and then agglomeration treatment is performed using a polymer flocculant (Patent Document 1), inorganic agglomeration And a treatment method using a polymethacrylate ester cationic polymer flocculant and an anionic polymer flocculant (Patent Document 2) have been proposed.

  However, the above prior art is common in that it uses a water-soluble polymer having a high cation density, and may have an effect, but for various wastewaters, the amount of inorganic flocculant used is reduced, It has not yet been possible to stably obtain good treated water quality.

JP-A-10-118660 JP 2004-249182 A

  Therefore, regarding the organic flocculant used in the flocculation treatment of wastewater, (1) the amount of inorganic flocculant used can be further reduced, (2) good floc flocs are formed, and solid-liquid separability is excellent ( 3) Good treatment water quality (COD, oil content, SS, etc.) can be obtained, (4) Appropriate reaction conditions in the actual apparatus can be set easily and stably, and (5) Treatment costs can be further reduced. That is required.

  The present invention has been made in view of the above circumstances, and its purpose is to reduce the amount of the inorganic flocculant used in the flocculation / separation treatment of the wastewater, reduce the processing cost, and obtain good water quality. To provide wastewater treatment technology.

  As a result of intensive studies on the condensation mechanism in order to achieve the above object, the present inventors have obtained the following surprising findings. That is, the action of the organic coagulant in the prior art is mainly based on the charge neutralization action due to its strong cationic property. However, a specific weakly cationic polymer has an adsorbing action in addition to charge neutralization, and therefore has an excellent coagulation action due to a synergistic effect when used in combination with an inorganic flocculant. Therefore, by using the water-soluble weak cationic polymer, the amount of the inorganic flocculant used can be greatly reduced, and good treated water quality (COD, turbidity, SS, etc.) can be stably obtained.

The present invention has been completed based on the above findings, and the gist thereof is that the inorganic flocculant (A) and the water-soluble weak cationic polymer (B) are added to papermaking wastewater simultaneously or in any order, Subsequently, a polymer flocculant (C) is added to form agglomeration floc and solid-liquid separation is a wastewater flocculation treatment method, wherein the water-soluble weak cationic polymer (B) is dimethylamino as a cationic monomer unit. Ethyl (meth) acrylate methyl chloride quaternary salt, acrylamide as an essential component as a nonionic monomer unit, the total content thereof is 90% by weight or more, and the content of the cationic monomer unit is 5 to 30% by weight Moreover, it is a polymer having an intrinsic viscosity of 1 to 18 dl / g, and the constituents and ratio of the polymer flocculant (C) are acrylic acid / acrylamide = 1/99 to 1 / 85 Ri anionic polymeric flocculant der is a polymer of (% by weight), moreover, the addition of the addition amount of the inorganic coagulant (A) is 50 to 100 mg / l, a water-soluble weak cation polymer (B) the amount resides in the aggregation treatment method of the papermaking waste water, wherein 0.5 to 10 mg / l der Rukoto.

  According to the treatment method of the present invention, it is possible to reduce the amount of the inorganic flocculant used, to form a good flocculent floc and to have excellent solid-liquid separability and to obtain a good quality water.

  Hereinafter, the present invention will be described in detail.

  Examples of the waste water targeted by the present invention include waste water generated from the paper industry, dyeing industry, automobile industry, metal processing industry, iron industry, food industry, gravel collection, semiconductor and cleaning industry. In particular, it is particularly effective for aggregating wastewater generated from the paper industry.

  As the inorganic flocculant (A) used in the present invention, generally available are aluminum-based or iron-based inorganic flocculants. Specifically, examples of the aluminum-based inorganic flocculant include aluminum sulfate (sulfate band), polyaluminum chloride (PAC), and aluminum chloride. Examples of the iron-based inorganic flocculant include ferric chloride and polyiron sulfate.

  The water-soluble weak cationic polymer (B) used in the present invention has dimethylaminoethyl (meth) acrylate methyl chloride quaternary salt as a cationic monomer unit, acrylamide as a nonionic monomer unit as an essential component, and a total content thereof. Is a polymer having a cationic monomer unit content of 5 to 30% by weight and an intrinsic viscosity of 1 to 18 dl / g.

  If the monomer unit is included as an essential component, other cationic monomer units such as neutralized or quaternary salts of dialkylaminoalkyl (meth) acrylates, or other nonionic monomer units such as methacrylamide, N , N-dimethyl (meth) acrylamide or the like can be further used alone or in combination.

  In the present invention, the content of the cationic monomer unit is important. When the content is less than 5% by weight, the effect of reducing the amount of the inorganic flocculant used is insufficient. The strength becomes weaker and the quality of treated water decreases.

  Examples of the polymerization method of the water-soluble weak cationic polymer (B) include precipitation polymerization, bulk polymerization, dispersion polymerization, and aqueous solution polymerization. As an example, a manufacturing method using an aqueous solution polymerization method will be described below.

  First, a predetermined amount of dimethylaminoethyl (meth) acrylate methyl chloride quaternary salt, acrylamide, and ion-exchanged water are weighed and adjusted to a predetermined 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 its peak, it is aged for 1 hour, and the polymer gel is taken out from the reaction vessel. The polymer gel is shredded with a meat chopper and dried at a temperature of 80 ° C. with a blower dryer. The dried polymer is pulverized with a pulverizer to a particle size of about 0.5 to 1 mm to obtain a water-soluble weak cationic polymer.

  The intrinsic viscosity of the water-soluble weak cationic polymer (B) is 1 to 18 dl / g, preferably 3 to 15 dl / g, more preferably 5.0 to 12.0 dl / g. When the intrinsic viscosity is less than 1.0 dl / g, the cohesive force becomes weak and the quality of the treated water is lowered. Moreover, when it exceeds 18.0 dl / g, the reactivity becomes worse and the aggregated flocs become coarse, but the sedimentation of the aggregated flocs deteriorates and the quality of the treated water also decreases. The intrinsic viscosity is a value measured at a temperature of 30 ° C. in a 1N sodium nitrate aqueous solution.

  A solid acid can be added to the water-soluble weak cationic polymer (B) in the present invention in order to reduce viscosity or improve reactivity. As the solid acid, sulfamic acid, acidic sodium sulfite and the like are generally used.

  The polymer flocculant (C) used in the present invention is not particularly limited, and an optimum type may be selected for the waste water to which the inorganic flocculant (A) and the water-soluble weak cationic polymer (B) are added. . For example, an anionic polymer flocculant, a nonionic polymer flocculant, etc. can be used.

  Examples of the anionic polymer flocculant include polyacrylic acid soda, partially hydrolyzed polyacrylamide, a copolymer of acrylamide and sodium acrylate, a polymer of 2-acrylamide-2methylpropanesulfonic acid, acrylamide, and the like. And the like. Examples of nonionic polymer flocculants include polymers of acrylamide or copolymers with other nonionic monomers. The intrinsic viscosity of the polymer flocculant (C) is not particularly limited, but is usually 15 dl / g or more.

  In the present invention, the inorganic flocculant (A) and the water-soluble weak cationic polymer (B) are added to the wastewater simultaneously or in any order, and then the polymer flocculant (C) is added. Specifically, two tanks are installed, each chemical is added to a separate tank and mechanically stirred, the addition position is shifted to the same tank and mechanically stirred, and one chemical is added to the wastewater line. A method of adding, guiding to the mixing tank and adding the other drug and mechanically stirring, a method of adding each drug to the wastewater line and further adding a shifted position to mix the lines, etc. are conceivable. In these, the method of installing 2 tanks and adding each to a separate tank and carrying out mechanical stirring is preferable. Further, in the case of line mixing, it is necessary that the turbulent flow is sufficient, and when it is insufficient, installation of a line mixer or the like is also effective.

  The amount of each chemical added varies depending on the water quality such as the type of wastewater, SS, and turbidity. The amount of the inorganic flocculant (A) added is usually 50 to 600 ppm, the amount of the water-soluble weak cationic polymer (B) is usually 0.5 to 10 mg / l, and the polymer flocculant (C) is added. The amount is 0.1-10 ppm. Moreover, after adding an inorganic flocculant (A) and a water-soluble weak cationic polymer (B) simultaneously or in arbitrary orders, the space | interval (stirring mixing time) at the time of adding a polymer flocculant (C) is then set. For example, it is about 30 seconds to 3 minutes. Solid-liquid separation of the flocs produced by agglomeration can be performed according to a conventional method.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to a following example at all unless the summary is exceeded. In addition, each measuring method employ | adopted in the following examples 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. (edited by the Society of Polymer Science, “New Edition Polymer Dictionary”, Asakura Shoten, p. 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) Supernatant turbidity (SS):
Turbidity was measured based on JIS K 0101.

(5) Supernatant COD:
COD was measured based on JIS K 0101.

  SS and COD were measured by measuring the floc particle size and settling time, and then allowing to stand for 2 minutes, collecting treated water from a depth of 3 cm from the surface.

Examples 1-10:
The total wastewater from the N paper mill was collected and used as wastewater. The properties of the wastewater were pH = 7.5, SS = 320 mg / l, COD = 390 mg / l.

  First, 500 ml of waste water was collected in a 500 ml beaker, PAC was added as an inorganic flocculant, and the mixture was stirred and mixed at a rotation speed of 150 rpm for 1 minute. The inorganic flocculant was diluted 10 times with water and used.

  Subsequently, the water-soluble weak cationic polymer shown in Table 1 was added on the conditions shown in Table 2, and it stirred and mixed for 1 minute at the rotation speed of 150 rpm. The water-soluble weak cationic polymer was used as a 0.1 to 0.3% by weight aqueous solution.

  Next, the polymer flocculant shown in Table 1 was added under the conditions shown in Table 2, and the mixture was stirred for 2 minutes at a rotation speed of 100 rpm to form an aggregate floc. The polymer flocculant was used as a 0.1 to 0.3% by weight aqueous solution. The results of the aggregation performance test are shown in Table 2.

Comparative Examples 1-7:
The drug was added under the conditions shown in Table 2 with or without using the water-soluble polymer shown in Table 1, and the aggregation performance test was performed under the same test conditions as described above. The results are shown in Table 2.

Examples 11-14:
The waste water from the F paper company was collected and used. The properties of the wastewater were pH = 6.8, SS = 256 mg / l, turbidity = 450 NTU, COD = 96 mg / l.

  First, 500 ml of waste water was collected in a 500 ml beaker, and the water-soluble weak cationic polymer shown in Table 1 was added under the conditions shown in Table 3, and the mixture was stirred and mixed for 1 minute at a rotation speed of 150 rpm. The water-soluble weak cationic polymer was used as a 0.1 to 0.3% by weight aqueous solution.

  Next, a band was added as an inorganic flocculant, and the mixture was stirred and mixed for 1 minute at a rotation speed of 150 rpm. The inorganic flocculant was diluted 10 times with water and used.

  Next, the polymer flocculant shown in Table 1 was added under the conditions shown in Table 3, and stirred for 2 minutes at a rotation speed of 100 rpm to form agglomerated floc. The polymer flocculant was used as a 0.1 to 0.3% by weight aqueous solution. The results of the aggregation performance test are shown in Table 3.

Comparative Examples 8-11;
A drug was added under the conditions shown in Table 3 with or without using the water-soluble polymer shown in Table 1, and an aggregation performance test was performed under the same test conditions as described above. The results are shown in Table 3.

  Table 2 shows the following.

  Examples 1 to show good coagulation performance and good turbidity of treated water. In particular, when the intrinsic viscosity of the water-soluble weak cationic polymer (B) is in a preferred range, Examples 1 to 8 are compared to Example 9 (low intrinsic viscosity) and Example 10 (high intrinsic viscosity), It is excellent also in the sedimentation property of the aggregation floc and the turbidity of treated water.

  Comparative Example 1 is an example in which a copolymer (B1) having a composition of methylaminoethyl (meth) acrylate methyl chloride quaternary salt (DME) lower than the range specified in the present invention was used, but the floc was small and the sedimentation was carried out. Both inferior in nature and turbidity of treated water. Comparative Example 2 is an example in which the copolymer (B2) having a DME composition higher than the range specified in the present invention was used. Like Comparative Example 1, the floc was small, the sedimentation property was inferior, and treated water was used. Turbidity is inferior. Comparative Example 3 is an example in which dimethyldiallylammonium chloride polymer is used as a water-soluble weak cationic polymer, but compared to the examples, the floc is small, the sedimentation is inferior, and the turbidity of treated water is significantly inferior. . Comparative Example 4 is an example in which the inorganic flocculant and the water-soluble weak cationic polymer were added, but the polymer flocculant was not added. However, the floc was very small, the sedimentation property, and the turbidity of the treated water were extremely low. Inferior to Comparative Examples 5 and 6 are examples in which a water-soluble weak cationic polymer was not used, and an inorganic flocculant and a polymer flocculant were used. However, in PAC 50 mg / l, the coagulability was poor due to insufficient addition of PAC, and 150 mg Although it aggregated to the same extent as an Example with the addition amount of / l, a process water turbidity is inferior compared with an Example. Comparative Example 7 is an example in which an inorganic flocculant is not used and a water-soluble weak cationic polymer and a polymer flocculant are used, but the floc is small and the sedimentation rate and the turbidity of treated water are inferior to those of the examples.

  Table 3 shows the following.

  Examples 11 to 14 show good aggregation performance, and the turbidity and COD of treated water are good.

  Comparative Example 8 is an example in which the copolymer (B1) having a DME composition lower than the range specified in the present invention was used, but the floc particle size and sedimentation were slightly inferior, but the turbidity of the treated water And COD is significantly inferior. Comparative Example 9 is an example in which a copolymer (B2) having a DME composition higher than the range specified in the present invention was used, but as in Comparative Example 8, the floc particle size and sedimentation were similar. The turbidity and COD of treated water are inferior. Comparative Example 10 is an example in which a dimethyldiallylammonium chloride polymer is used as the water-soluble cationic polymer, but the floc is small, the sedimentation property is inferior, and the turbidity and COD of the treated water are also inferior. Comparative Example 11 is an example using an inorganic flocculant and a polymer flocculant without using a water-soluble weak cationic polymer, but the amount of the inorganic flocculant used is three times that of Examples 11-14. Thus, although the size of the floc is about the same as that of the example, the sedimentation, turbidity of treated water, and COD are inferior to those of the example.

Claims (2)

After adding the inorganic flocculant (A) and the water-soluble weak cationic polymer (B) to papermaking wastewater simultaneously or in an arbitrary order, the polymer flocculant (C) is then added to produce agglomerated flocs. A method for aggregating wastewater to be liquid-separated, wherein the water-soluble weak cationic polymer (B) contains dimethylaminoethyl (meth) acrylate methyl chloride quaternary salt as a cationic monomer unit and acrylamide as a nonionic monomer unit. A polymer having a total content of 90% by weight or more, a content of cationic monomer units of 5 to 30% by weight, and an intrinsic viscosity of 1 to 18 dl / g, and a polymer. components and a polymeric anionic polymeric flocculant der the ratio of acrylic acid / acrylamide = 1 / 99-15 / 85 (weight%) of the coagulant (C) is, Duck, aggregation added amount of the additive amount is 50 to 100 mg / l, a water-soluble weak cationic polymerization of the inorganic coagulant (A) (B) of paper waste, wherein 0.5 to 10 mg / l der Rukoto Processing method.   The method for coagulating wastewater according to claim 1, wherein the water-soluble weak cationic polymer (B) has an intrinsic viscosity of 3 to 15 dl / g.