Wastewater treatment agent with COD reduction effect

Abstract

To provide a wastewater treatment agent for use in coagulation treatment of wastewater, which not only has coagulation treatment performance but also can reduce the COD of the treated water, and a wastewater treatment method using the agent.SOLUTION: The reduction of the COD of treated water can be achieved by applying a wastewater treatment agent comprising a polymer obtained by polymerizing monomer components containing a cationic monomer represented by general formula (1) and / or an anionic monomer represented by general formula (2) in the presence of cyclodextrin. Preferably, the amount of the cyclodextrin present in the polymerization to obtain the polymer is 2 to 15 mass% based on the total monomer mass.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a wastewater treatment agent and a wastewater treatment method, and more particularly to a wastewater treatment agent and a wastewater treatment method capable of reducing COD as well as removing suspended substances by coagulation treatment.

Background Art

[0002] As a wastewater treatment method, a method of purifying water by coagulating and aggregating suspended substances in water with a coagulant or flocculant is applied. Among them, polyacrylamide-based (PAM-based) flocculants are particularly widely used, and effective compositions, physical properties, and formulations combined with coagulants have been proposed. For example, Patent Document 1 discloses a treatment method of adding a polyacrylamide-based anionic polymer flocculant having an anionic group ratio of 55 mol% or more and 85 mol% or less to wastewater with a high salt concentration. However, many of these mainly aim at the coagulation treatment of suspended substances, and improvement of treated water quality, particularly removal of COD (chemical oxygen demand) components, is not described. COD is an index of organic matter in wastewater. When discharging from a business site having a specific facility into the sea, lakes, etc., it is necessary to reduce the COD concentration below the reference value, and it is desired to reduce COD as much as possible by coagulation treatment. Patent Document 2 discloses a wastewater treatment method of adding a PAM-based organic coagulant to wastewater and then adding a polymer flocculant. Patent Document 3 discloses a coagulation treatment method of adding an inorganic flocculant to wastewater, then adding a PAM-based organic coagulant, and further adding a polymer flocculant, and it is described that a COD reduction effect can be obtained respectively. However, these formulations require the use of two or more liquids. Although a certain effect is recognized for reducing COD derived from suspended substances, the fact is that a satisfactory effect has not been obtained for dissolved COD. Therefore, there is a demand for a wastewater treatment agent that is excellent not only in the coagulation treatment of suspended substances but also in the COD reduction effect, particularly the dissolved COD reduction effect.

[0003]

Patent Document 1

[0004] The present invention relates to a wastewater treatment agent for coagulation treatment of wastewater and a wastewater treatment method using the same, and aims to provide a wastewater treatment agent and wastewater treatment method that can not only coagulate suspended solids but also reduce the COD of treated water, particularly the soluble COD components. [Means for solving the problem]

[0005] As a result of diligent research to solve the above problems, we discovered that by using a wastewater treatment agent made of a polymer obtained by polymerizing a monomer mixture having a specific monomer composition in the presence of cyclodextrin, it is possible to achieve not only the coagulation treatment of suspended solids but also an improvement in the COD reduction effect, leading to the present invention. [Effects of the Invention]

[0006] By using the wastewater treatment agent and wastewater treatment method of the present invention, it is possible to achieve coagulation treatment of suspended solids and reduction of COD in treated water. [Modes for carrying out the invention]

[0007] The wastewater treatment agent in the present invention consists of a polymer obtained by polymerizing monomer components containing a cationic monomer represented by the following general formula (1) and / or an anionic monomer represented by the following general formula (2) in the presence of cyclodextrin. JPEG0007870048000001.jpg2771 General formula (1) R1 represents hydrogen or a methyl group, R2 and R3 represent alkyl or alkoxy groups with 1 to 3 carbon atoms, R4 represents hydrogen or alkyl or alkoxy groups with 1 to 3 carbon atoms, or alkyl or aryl groups with 7 to 20 carbon atoms, A represents oxygen or NH, B represents an alkylene group with 2 to 4 carbon atoms, X1 - Each represents anion. JPEG0007870048000002.jpg2671 General formula (2) R5 is hydrogen, a methyl group, or a carboxymethyl group, and Q is SO3. - , C6H4SO3 - CONHC(CH3)2CH2SO3 - C6H4COO - Or COO - R6 represents hydrogen or COOY2, and Y1 or Y2 represents hydrogen or a cation.

[0008] Examples of tertiary amino group-containing cationic monomers represented by general formula (1) include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, and salts thereof. Examples of quaternary ammonium base-containing cationic monomers include (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxyethyldimethylbenzylammonium chloride, (meth)acryloylaminopropyltrimethylammonium chloride, and (meth)acryloylaminopropyldimethylbenzylammonium chloride. It is also possible to combine two or more of these.

[0009] Examples of anionic monomers represented by general formula (2) include (meth)acrylic acid, itaconic acid, maleic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and their salts. Two or more of these can also be combined. The anionic monomers can be used after being neutralized with sodium hydroxide or the like as appropriate.

[0010] The polymer in this invention may further contain nonionic monomers as monomer components. Examples of nonionic monomers include acrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, hydroxyethylacrylamide, vinylpyrrolidone, vinylformamide, glycerol (meth)acrylate, and hydroxyethyl (meth)acrylate. It is also possible to combine two or more of these.

[0011] Any of the following monomer combinations may be used: a cationic polymer obtained by polymerizing a cationic monomer represented by general formula (1) and a nonionic monomer; an anionic polymer obtained by polymerizing an anionic monomer represented by general formula (2) and a nonionic monomer; an amphoteric polymer obtained by polymerizing a cationic monomer represented by general formula (1) and an anionic monomer represented by general formula (2); or an amphoteric polymer obtained by polymerizing a cationic monomer represented by general formula (1), an anionic monomer represented by general formula (2), and a nonionic monomer. In the case of a cationic polymer, the cationic monomer is preferably 20 to 100 mol% of the total monomers. In the case of anionic polymers, the anionic monomer is preferably 10 to 80 mol% of the total monomers.

[0012] Furthermore, the monomer components may include crosslinkable monomers. Examples of crosslinkable monomers include methylenebisacrylamide, ethylene glycol di(meth)acrylate, N-methylolacrylamide, triallyl isocyanate, divinylbenzene, and triallylamine. It is also possible to combine two or more of these. The addition rate of crosslinkable monomers is preferably 100 ppm or less relative to the total monomers.

[0013] The wastewater treatment agent in the present invention is not particularly limited in its product form and can be manufactured by known methods. For example, after polymerization by aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, brine dispersion polymerization, etc., it can be made into any product form such as an aqueous solution, water-in-oil emulsion, brine dispersion, or powder. These various polymerizations are carried out by conventional methods. For example, radical polymerization is carried out under a nitrogen atmosphere with or without stirring after adding a polymerization initiator. Examples of polymerization initiators include azo-based polymerization initiators such as 2,2'-azobis[2-(5-methyl-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis-2-amidinopropane dihydrochloride, 2,2'-azobisisobutyronitrile, and dimethyl-2,2'-azobisisobutyrate. Other examples include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; peroxides such as hydrogen peroxide and benzoyl peroxide; lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy-2-ethylhexanoate, t-butyl hydroperoxide, cerium ammonium nitrate, and cerium ammonium sulfate. These can be used alone, but can also be used in combination with reducing agents such as sulfites and bisulfites as redox polymerization initiators. The addition rate of polymerization initiators is 0.001% to 1% by mass relative to the total monomers.

[0014] Furthermore, chain transfer agents can be used. Examples of chain transfer agents include alkyl mercaptans, thioglycolic acid and its esters, isopropyl alcohol, allyl alcohol, allylamine, and sodium hypophosphate. Other examples include monomers such as sodium methallyl sulfonate, potassium methallyl sulfonate, and ammonium methallyl sulfonate, which are methallyl sulfonates.

[0015] The polymerization concentration is 5% to 60% by mass as monomer concentration, but preferably 10% to 40% by mass. The polymerization reaction is usually carried out at a temperature of 30°C to 100°C for 0.5 to 20 hours.

[0016] The wastewater treatment agent comprising polymers in the present invention is produced by polymerizing the monomer components in the presence of cyclodextrin. The cyclodextrin may be added to the monomer component mixture beforehand, or it may be added continuously or intermittently during polymerization. For ease of operation, it is preferable to add it to the monomer component mixture before polymerization. Examples of cyclodextrins in the present invention include α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, methyl-α-cyclodextrin, methyl-β-cyclodextrin, methyl-γ-cyclodextrin, hydroxyethyl-α-cyclodextrin, hydroxyethyl-β-cyclodextrin, hydroxyethyl-γ-cyclodextrin, hydroxypropyl-α-cyclodextrin, hydroxypropyl-β-cyclodextrin, hydroxypropyl-γ-cyclodextrin, monochlorotriazino-β-cyclodextrin, and the like. These may also be used in combination. Among these, β-cyclodextrin, methyl-β-cyclodextrin, and hydroxypropyl-β-cyclodextrin are preferred. The addition rate of cyclodextrin is preferably 2 to 15% by mass relative to the total monomer. This is because a rate lower than 2% by mass results in a low COD component removal effect, and a rate higher than 15% by mass does not yield a significant improvement and increases costs.

[0017] In this invention, the polymer can be measured at 25°C when dissolved in 4% sodium chloride water to a polymer concentration of 0.5% by mass, and its molecular weight can be used as an indicator of its viscosity (viscosity of 0.5% by mass salt aqueous solution). A viscosity of 20 to 200 mPa·s for the 0.5% by mass salt aqueous solution is preferred. If the viscosity is lower than this, the flocculation treatment effect will be insufficient. Conversely, if the viscosity is higher than this, the solubility will decrease and handling will become difficult. The viscosity was measured at 25°C with a rotational speed of 60 rpm using a B-type viscometer. Also, the viscosity measured at 25°C when dissolved in water to a polymer concentration of 0.2% by mass (0.2% aqueous solution viscosity) is preferably 500 mPa·s or less. As the B-type viscometer, general-purpose products such as the B8M type and TVB-10M type manufactured by Toki Sangyo Co., Ltd. are appropriately used. When the viscosity exceeds 100 mPa·s, a No. 2 rotor is used; when it is 100 mPa·s or less, a No. 1 rotor is used.

[0018] It is speculated that the polymer in the present invention is a polymer obtained by grafting the monomer component onto cyclodextrin during polymerization. Cyclodextrin forms a complex called an inclusion complex by encapsulating another substance in the cavity within its molecule. By adding the polymer grafted onto cyclodextrin to the wastewater, the suspended substances in the wastewater are aggregated by the polymer, and at the same time, the COD component in the water is captured by the inclusion action of cyclodextrin, and it is considered that the COD component is removed. In the conventional coagulation treatment, it is possible to reduce the COD derived from the suspended substances in the wastewater, but the dissolved COD component can hardly be reduced or cannot be said to be sufficient. On the other hand, in the wastewater treatment in the present invention, the dissolved COD can be reduced. Wastewater containing 50 ppm or more of dissolved COD is preferable for exhibiting the effect of the wastewater treatment agent in the present invention, more preferably 80 ppm or more, and even more preferably 100 ppm or more. Here, the dissolved COD refers to the COD of the filtrate after filtering the wastewater with a filter paper (No. 5C). COD (CODMn) was measured based on the factory wastewater test method (JIS K0102). In addition, although it is speculated that the polymer in the present invention is obtained by grafting onto cyclodextrin, its structure is fine and it is impossible to directly specify it due to the structure or properties of the polymer, or it is not approximately practical.

[0019] The wastewater treatment agent in the present invention can be applied to wastewater containing COD components. For example, it can be applied to COD-containing wastewater such as chemical factory wastewater, paper pulp manufacturing factory wastewater, petrochemical industry wastewater, plastic product manufacturing factory wastewater, dyeing wastewater, refining wastewater, printing factory wastewater, machinery manufacturing factory wastewater, food factory wastewater, industrial waste leachate, etc.

[0020] The wastewater treatment agent in the present invention is diluted with water to any concentration and then added. A range of 0.01 to 1.0% by mass is preferred. The addition rate to the wastewater is 1 to 1000 ppm based on the volume of the wastewater liquid. Also, it may be used in combination with inorganic flocculants such as aluminum sulfate, aluminum chloride, polyaluminum chloride, ferrous polysulfate, ferric polysulfate, ferric chloride, and other polymer flocculants.

Examples

[0021] The wastewater treatment agent in the present invention and the wastewater treatment method using the same will be specifically described below, but the present invention is not limited to the following examples.

[0022] (Wastewater treatment agent sample) Samples of the wastewater treatment agent composed of polymers in the present invention and comparative samples were prepared by the conventional method of aqueous solution polymerization. The monomer compositions and physical properties of these polymers are within the composition ranges commonly used as PAM-based flocculants. Also, β-cyclodextrin (manufactured by Fujifilm Wako Pure Chemical Corporation) was used as cyclodextrin.

[0023] (Example 1) 236.03 g of pure water and 7.58 g of 80% by mass acrylic acid were added to a 300 mL glass beaker, and 7.02 g of 48% by mass sodium hydroxide was slowly added dropwise while stirring to neutralize the acrylic acid. Next, 47.87 g of 50% by mass acrylamide and 1.50 g of β-cyclodextrin were added while stirring to form a homogeneous solution, which was then immersed in a 50°C oil bath to stabilize the temperature. The top of the beaker was covered with a plastic bag with a nitrogen inlet tube inserted to create a sealed state. 0.38 g of 0.2% by mass tert-butyl hydroperoxide was added as a polymerization initiator under a nitrogen atmosphere, and polymerization was carried out at 50°C for 18 hours under nitrogen aeration to obtain a water-soluble polymer solution. The viscosity of this solution when dissolved in pure water at a concentration of 0.2% by mass was 425 mPa·s, and the viscosity when dissolved in 4% by mass sodium chloride aqueous solution at a concentration of 0.5% by mass was 141 mPa·s. This is shown in Table 1 as Example 1.

[0024] (Example 2) 234.53 g of pure water and 7.58 g of 80% by mass acrylic acid were added to a 300 mL glass beaker. 7.02 g of 48% by mass sodium hydroxide was slowly added dropwise while stirring to neutralize the acrylic acid. Next, 47.87 g of 50% by mass acrylamide and 3.00 g of β-cyclodextrin were added while stirring to form a homogeneous solution, which was then immersed in a 50°C oil bath to stabilize the temperature. The top of the beaker was covered with a plastic bag with a nitrogen inlet tube inserted to create a sealed state. 0.38 g of 0.2% by mass tert-butyl hydroperoxide was added as a polymerization initiator under a nitrogen atmosphere, and polymerization was carried out at 50°C for 18 hours under nitrogen aeration to obtain a water-soluble polymer solution. The viscosity of this solution when dissolved in pure water at a concentration of 0.2% by mass was 471 mPa·s, and the viscosity when dissolved in 4% by mass sodium chloride aqueous solution at a concentration of 0.5% by mass was 164 mPa·s. This is shown as Example 2 in Table 1.

[0025] (Example 3) 232.07 g of pure water and 15.13 g of 80% by mass acrylic acid were added to a 300 mL glass beaker. Under stirring, 14.01 g of 48% by mass sodium hydroxide was slowly added dropwise to neutralize the acrylic acid. Next, under stirring, 35.80 g of 50% by mass acrylamide and 3.00 g of β-cyclodextrin were added to form a homogeneous solution, which was then immersed in a 50°C oil bath to stabilize the temperature. The top of the beaker was covered with a plastic bag with a nitrogen inlet tube inserted to create a sealed state. Under a nitrogen atmosphere, 0.38 g of 0.2% by mass tert-butyl hydroperoxide was added as a polymerization initiator, and polymerization was carried out at 50°C for 18 hours under nitrogen aeration to obtain a water-soluble polymer solution. The viscosity of this solution when dissolved in pure water at a concentration of 0.2% by mass was 416 mPa·s, and the viscosity when dissolved in 4% by mass sodium chloride aqueous solution at a concentration of 0.5% by mass was 183 mPa·s. This is shown in Table 1 as Example 3.

[0026] (Example 4) In a 300 mL glass beaker, 194.02 g of pure water, 12.60 g of 50% by mass acrylamide, 85.87 g of 80% by mass acryloyloxyethyltrimethylammonium chloride, and 7.50 g of β-cyclodextrin were added under stirring to form a homogeneous solution, which was then immersed in a 50°C oil bath to stabilize the temperature. The top of the beaker was covered with a plastic bag with a nitrogen inlet tube inserted to create a sealed state. Under a nitrogen atmosphere, 0.94 g of 0.2% by mass tert-butyl hydroperoxide was added as a polymerization initiator, and polymerization was carried out at 50°C for 18 hours under nitrogen aeration to obtain a water-soluble polymer solution. The viscosity of this solution when dissolved in pure water at a concentration of 0.2% by mass was 162 mPa·s, and the viscosity when dissolved in 4% by mass sodium chloride aqueous solution at a concentration of 0.5% by mass was 24.2 mPa·s. This is shown as Example 4 in Table 1.

[0027] (Comparative Example 1) 234.53 g of pure water and 7.58 g of 80% by mass acrylic acid were added to a 300 mL glass beaker. 7.02 g of 48% by mass sodium hydroxide was slowly added dropwise while stirring to neutralize the acrylic acid. Next, 47.87 g of 50% by mass acrylamide was added while stirring to form a homogeneous solution, which was then immersed in a 50°C oil bath to stabilize the temperature. The top of the beaker was covered with a plastic bag with a nitrogen inlet tube inserted, creating a sealed state. 0.38 g of 0.2% by mass tert-butyl hydroperoxide was added as a polymerization initiator under a nitrogen atmosphere, and polymerization was carried out at 50°C for 18 hours under nitrogen aeration to obtain a water-soluble polymer solution. The viscosity of this solution when dissolved in pure water at a concentration of 0.2% by mass was 375 mPa·s, and the viscosity when dissolved in 4% by mass sodium chloride aqueous solution at a concentration of 0.5% by mass was 143 mPa·s. This is shown in Table 1 as Comparative Example 1.

[0028] (Comparative Example 2) 1.50 g of β-cyclodextrin was added to the water-soluble polymer solution obtained in Comparative Example 1 and stirred to obtain a homogeneous water-soluble polymer solution. This is shown in Table 1 as Comparative Example 2.

[0029] (Comparative Example 3) 3.00 g of β-cyclodextrin was added to the water-soluble polymer solution obtained in Comparative Example 1 and stirred to obtain a homogeneous water-soluble polymer solution. This is shown in Table 1 as Comparative Example 3.

[0030] (Comparative Example 4) 235.07 g of pure water and 15.13 g of 80% by mass acrylic acid were added to a 300 mL glass beaker. Under stirring, 14.01 g of 48% by mass sodium hydroxide was slowly added dropwise to neutralize the acrylic acid. Next, 35.80 g of 50% by mass acrylamide was added under stirring to form a homogeneous solution, which was then immersed in a 50°C oil bath to stabilize the temperature. The top of the beaker was covered with a plastic bag with a nitrogen inlet tube inserted to create a sealed state. Under a nitrogen atmosphere, 0.38 g of 0.2% by mass tert-butyl hydroperoxide was added as a polymerization initiator, and polymerization was carried out at 50°C for 18 hours under nitrogen aeration to obtain a water-soluble polymer solution. The viscosity of this solution when dissolved in pure water at a concentration of 0.2% by mass was 248 mPa·s, and the viscosity when dissolved in 4% by mass sodium chloride aqueous solution at a concentration of 0.5% by mass was 139 mPa·s. This is shown in Table 1 as Comparative Example 4.

[0031] (Comparative Example 5) In a 300 mL glass beaker, 201.52 g of pure water, 12.60 g of 50% by mass acrylamide, and 85.87 g of 80% by mass acryloyloxyethyltrimethylammonium chloride were added under stirring to form a homogeneous solution, which was then immersed in a 50°C oil bath to stabilize the temperature. The top of the beaker was covered with a plastic bag with a nitrogen inlet tube inserted to create a sealed state. Under a nitrogen atmosphere, 0.94 g of 0.2% by mass tert-butyl hydroperoxide was added as a polymerization initiator, and polymerization was carried out at 50°C for 18 hours under nitrogen aeration to obtain a water-soluble polymer solution. The viscosity of this solution when dissolved in pure water at a concentration of 0.2% by mass was 181 mPa·s, and the viscosity when dissolved in 4% by mass sodium chloride aqueous solution at a concentration of 0.5% by mass was 24.9 mPa·s. This is shown in Table 1 as Comparative Example 5.

[0032] (Table 1) TIFF0007870048000003.tif4990 Monomer; AAM: Acrylamide, AAC: Acrylic acid, DMQ: Acryloyloxyethyltrimethylammonium chloride 0.2% by mass aqueous solution viscosity: Viscosity (mPa·s) measured at 25°C when a polymer is dissolved in water to a concentration of 0.2% by mass. Viscosity of 0.5% by mass salt solution: Viscosity (mPa·s) measured at 25°C when a polymer is dissolved in 4% by mass sodium chloride water to a polymer concentration of 0.5% by mass.

[0033] (Example of a test conducted 1) A jar test was conducted using plastic washing wastewater (pH 6.3, SS content 1,850 mg / L, turbidity > 1,000 NTU, COD 680 mg / L) as the wastewater. 200 mL of wastewater was collected in a glass beaker, and 2,000 ppm of polyaluminum chloride was added to the wastewater, which was then stirred and mixed at 150 rpm for 60 seconds. Subsequently, 240 ppm of caustic soda was added to the wastewater, which was then stirred and mixed at 150 rpm for 60 seconds. Next, 15 ppm of the wastewater treatment agent sample from the present invention shown in Table 1, dissolved at a concentration of 0.1 mass%, was added to the wastewater, which was then stirred and mixed at 150 rpm for 30 seconds, 80 rpm for 30 seconds, and 40 rpm for 30 seconds. The floc diameter and soluble COD after standing for 5 minutes were measured according to the JIS K0102 method. The floc diameter can be used as an indicator of flocculation performance. These results are shown in Table 2.

[0034] (Comparative Test Example 1) The same wastewater as in Test Example 1 was used, and the same tests were conducted using the wastewater treatment agent samples of the comparative examples in Table 1. The results are shown in Table 2.

[0035] (Table 2) TIFF0007870048000004.tif4181

[0036] (Example of a test conducted 2) A jar test was conducted using wastewater from the manufacture of chemical products (pH 6.6, SS content 2,150 mg / L, turbidity > 1,000 NTU, COD 956 mg / L). 200 mL of wastewater was collected in a glass beaker, and 10 ppm of the wastewater treatment agent sample from the present invention (Table 1), dissolved at a concentration of 0.1% by mass, was added to the wastewater. The mixture was stirred and mixed under conditions of 150 rpm for 30 seconds, 80 rpm for 30 seconds, and 40 rpm for 30 seconds. The floc diameter and soluble COD after standing for 5 minutes were measured according to the JIS K0102 method. The results are shown in Table 3.

[0037] (Comparative Test Example 2) Using the same wastewater as in Test Example 2, a similar test was conducted using the wastewater treatment agent samples of the comparative examples in Table 1. The results are shown in Table 3.

[0038] (Table 3) TIFF0007870048000005.tif4182

[0039] (Example of a test conducted 3) A jar test was conducted using wastewater leachate (pH 9.2, SS content 17 mg / L, turbidity 9.1 NTU, COD 95 mg / L) as the wastewater sample. 200 mL of wastewater was collected in a glass beaker, and 8,000 ppm of aluminum sulfate was added to the wastewater. The mixture was stirred at 150 rpm for 60 seconds. Subsequently, 10 ppm of the wastewater treatment agent of the present invention (Table 1), dissolved at a concentration of 0.1 mass%, was added to the wastewater. The mixture was stirred at 150 rpm for 30 seconds, 80 rpm for 30 seconds, and 40 rpm for 30 seconds. The floc diameter and soluble COD after standing for 5 minutes were measured according to the JIS K0102 method. These results are shown in Table 4.

[0040] (Comparative Test Example 3) Using the same wastewater as in Test Example 3, a similar test was conducted using the wastewater treatment agent samples of the comparative examples in Table 1. The results are shown in Table 4.

[0041] (Table 4) TIFF0007870048000006.tif2482

[0042] (Examples of implemented tests 4-6) A jar test was conducted using simulated wastewater (pH 3.7, SS 100,000 mg / L, turbidity > 1,000 NTU, COD 790 mg / L) prepared by adding 100,000 mg / L of kaolin as suspended solids (SS) and 1,000 mg / L of tannic acid as a soluble COD component to water. 200 mL of wastewater was collected in a glass beaker, and the wastewater treatment agent of the present invention (Table 1), dissolved at a concentration of 1.0% by mass, was added at a concentration of 250 ppm or 150 ppm relative to the wastewater. The mixture was stirred and mixed under conditions of 150 rpm for 30 seconds, 80 rpm for 30 seconds, and 40 rpm for 30 seconds. The floc diameter and soluble COD after standing for 5 minutes were measured according to the JIS K0102 method. These results are shown in Table 5.

[0043] (Comparative Test Examples 4-6) Using the same wastewater as in Test Examples 4-6, similar tests were conducted using the wastewater treatment agent samples of the comparative examples in Table 1. The results are shown in Table 5.

[0044] (Table 5) TIFF0007870048000007.tif5782

[0045] In practical tests using the wastewater treatment agent sample of the present invention, the soluble COD decreased while the floc diameter of the suspended solids remained at or above the same level compared to comparative tests using a comparative wastewater treatment agent consisting of the same polymer monomer composition. Compared to conventional wastewater treatment agents, the wastewater treatment agent of the present invention was confirmed to be able to reduce soluble COD simultaneously with coagulation treatment in various types of COD-containing wastewater.

Claims

1. A wastewater treatment agent comprising a polymer obtained by polymerizing monomer components containing a cationic monomer represented by the following general formula (1) and / or an anionic monomer represented by the following general formula (2) in the presence of cyclodextrin. General formula (1) R １ R is a hydrogen or methyl group. ２ , R ３ R is an alkyl or alkoxy group having 1 to 3 carbon atoms. ４ is hydrogen or an alkyl or alkoxy group having 1 to 3 carbon atoms, or an alkyl or aryl group having 7 to 20 carbon atoms, A is oxygen or NH, B is an alkylene group having 2 to 4 carbon atoms, X １ － These represent anions, respectively. General formula (2) R ５ is hydrogen, a methyl group or a carboxymethyl group, Q is SO ３ － , C ６ H ４ SO ３ － , CONHC(CH ３ ) ２ CH ２ SO ３ － , C ６ H ４ COO － or COO － , R ６ is hydrogen or COOY ２ , Y １ or Y ２ each represents hydrogen or a cation.

2. The wastewater treatment agent according to claim 1, characterized in that the cyclodextrin is present in an amount of 2 to 15% by mass relative to the total monomer.

3. A method for treating wastewater, characterized by adding the wastewater treatment agent described in claim 1 or 2 to COD-containing wastewater.

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