WO2024116641A1

WO2024116641A1 - Water-treating agent and water treatment method

Info

Publication number: WO2024116641A1
Application number: PCT/JP2023/037910
Authority: WO
Inventors: 惇山口
Original assignee: 三洋化成工業株式会社
Priority date: 2022-11-30
Filing date: 2023-10-19
Publication date: 2024-06-06

Abstract

The present invention relates to: a water-treating agent that contains a quaternary ammonium salt (A) and at least one salt (S) selected from the group consisting of silicates, phosphates, and borates; and a water treatment method in which the water-treating agent is used. According to the present invention, it is possible to provide a water-treating agent and a water treatment method that have a remarkably exceptional effect for reducing the amount of water-soluble COD components, the agent and method stably reducing the amount of water-soluble COD components even if an excessive amount of water-treating agent is used in response to the type or amount of water-soluble COD components contained in water being treated or to the amount of water being discharged.

Description

Water treatment agent and water treatment method

The present invention relates to a water treatment agent and a water treatment method. More specifically, the present invention relates to a water treatment agent and a water treatment method for removing water-soluble COD components from water containing water-soluble COD components, such as various industrial wastewater, sewage, purified water, and sludge (organic sludge and inorganic sludge).

　Traditionally, methods proposed for removing water-soluble COD components contained in industrial wastewater, etc., include activated carbon treatment, ultraviolet irradiation, ozone treatment, and Fenton treatment, which combines ferrous sulfate and hydrogen peroxide. However, all of these methods are expensive to treat, and are not widely used.

In response to this, a method has been proposed for removing (reducing) water-soluble COD components using so-called polymer flocculants (for example, Patent Document 1). However, while conventional treatment methods use water-soluble COD component reducers such as polymer flocculants that can widely accommodate different types of water-soluble COD components in wastewater, they deal with fluctuations in the type and amount of water-soluble COD in the wastewater and fluctuations in the wastewater flow rate by adding an excess of polymer flocculant, which creates the problem that adding more polymer flocculant than the actual optimal amount makes the polymer flocculant itself a water-soluble COD component, increasing the amount of water-soluble COD components.

In addition, Patent Document 2 proposes a water treatment method that can stably reduce water-soluble COD components even if an excessive amount of water treatment agent is used in response to the type and amount of water-soluble COD components contained in the water to be treated or fluctuations in the amount of wastewater. The water treatment method includes a step of adding to the water to be treated a water treatment agent containing a copolymer having a weight average molecular weight of 10,000 to 600,000, which is obtained by polymerizing a monomer having a cationic functional group and a monomer having no cationic functional group in a specific molar ratio, and a water treatment agent containing at least one salt selected from the group consisting of silicates, phosphates, and borates. However, there is room for improvement in the water-soluble COD removal rate, and further improvement in the effect of reducing water-soluble COD components is desired.

Patent Publication No. 4923834 Patent Publication No. 6852113

The present invention has been made in consideration of the problems of the prior art, and the object of the present invention is to provide a water treatment agent and a water treatment method that can stably reduce water-soluble COD components even when an excessive amount of the water treatment agent is used in response to the type and amount of water-soluble COD components contained in the water to be treated or fluctuations in the amount of wastewater, and that is remarkably effective in reducing water-soluble COD components.

The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention is a water treatment agent containing a quaternary ammonium salt (A) represented by any one of the following general formulas (1) to (3) and at least one salt (S) selected from the group consisting of silicates, phosphates, and borates.

[In formula (1), n is an integer of 5 to 17 representing the number of repeating methylene groups, R ¹ to R ³ each independently represent a methyl group, an ethyl group, a propyl group, or a butyl group, and X ⁻ represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent.]

[In formula (2), n is an integer of 5 to 17 representing the number of repeating methylene groups, and X ⁻ represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent.]

[In formula (3), n is an integer of 5 to 17 representing the number of repeating methylene groups, ^X- represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent, and Y is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.]

The present invention also provides a water treatment method comprising a step (I) of adding a quaternary ammonium salt (A) represented by any one of the general formulae (1) to (3) to the water to be treated, and a step (II) of adding at least one salt (S) selected from the group consisting of silicates, phosphates, and borates to the water to be treated.

The present invention can suppress the increase of water-soluble COD components even under conditions where the amount of water treatment agent added is excessive, and can stably obtain an excellent water-soluble COD component reduction effect. In this specification, "water-soluble COD component reduction effect" means the effect of reducing the content of water-soluble COD components in water by forming water-insoluble complexes with the water-soluble COD components contained in the water to be treated, precipitating them, and separating and removing them.

1 is a graph showing the relationship between the amount (mg/L) of solids of a quaternary ammonium salt (A) added in a water treatment agent and COD (mg/L).

<Water treatment agent>
The water treatment agent of the present embodiment contains a quaternary ammonium salt (A) represented by any one of the following general formulas (1) to (3) and at least one salt (S) selected from the group consisting of silicates, phosphates, and borates.

The water treatment agent of this embodiment may be a one-component water treatment agent that is a composition containing the quaternary ammonium salt (A) and the salt (S), or may be a two-component water treatment agent consisting of a water treatment agent (P1) containing the quaternary ammonium salt (A) and a water treatment agent (P2) containing the salt (S). From the viewpoint of the effect of reducing water-soluble COD components, the water treatment agent of this embodiment is preferably a two-component water treatment agent consisting of a water treatment agent (P1) containing the quaternary ammonium salt (A) and a water treatment agent (P2) containing the salt (S).

[Quaternary ammonium salt (A)]
The quaternary ammonium salt (A) is a compound having a structure represented by any one of the general formulas (1) to (3). Hereinafter, a compound having a structure represented by the general formula (1) will be referred to as compound (A1), a compound having a structure represented by the general formula (2) will be referred to as compound (A2), and a compound having a structure represented by the general formula (3) will be referred to as compound (A3).

[Compound (A1)]
The compound (A1) has a structure represented by the general formula (1).

In the general formula (1), n is an integer of 5 to 17, representing the number of repeating methylene groups. If n is 4 or less, there is a tendency for the effect of reducing water-soluble COD components to decrease due to insufficient hydrophobicity (even if the water-soluble COD components and the quaternary ammonium ion form a complex, the complex is highly water-soluble and therefore difficult to precipitate and to separate as a precipitate), whereas if n is 18 or more, there is a tendency for the effect of reducing water-soluble COD components to decrease due to insufficient solubility in water (as the water solubility of the quaternary ammonium ion is low, it is difficult to form a complex with the water-soluble COD components and it is difficult to separate the water-soluble COD components as a precipitate). From the viewpoint of the effect of reducing water-soluble COD components, n is preferably 11 to 17.

In addition, it is presumed that linear alkyl groups have stronger intermolecular forces than branched alkyl groups with the same number of carbon atoms, and therefore tend to associate more easily, resulting in a larger particle size for the complex of water-soluble COD components and quaternary ammonium ions, and that the complex tends to separate more easily as a precipitate. Therefore, it is presumed that compound (A1) having a linear alkyl group with 6 to 18 carbon atoms is more effective at reducing water-soluble COD components than quaternary ammonium salts having branched alkyl groups with the same number of carbon atoms.

In the general formula (1), R ¹ to R ³ each independently represent a methyl group, an ethyl group, a propyl group, or a butyl group.

In the general formula (1), X ^- represents a counter anion of an ammonium ion, and is an anion group derived from a conjugate base of a Brønsted acid or a quaternizing agent. Examples of the Brønsted acid include inorganic acids (hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, etc.) and organic acids (sulfonic acids (methylsulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, etc.), carboxylic acids (oxalic acid, acetic acid, maleic acid, etc.), and phosphonic acids (methylphosphonic acid, phenylphosphonic acid, etc.)). From the viewpoint of the effect of reducing water-soluble COD components, hydrochloric acid (i.e., X ^- =Cl ^- ), hydrobromic acid (i.e., X ^- =Br ^- ), or sulfuric acid (i.e., X ^- =HSO ₄ ^- ) is preferred. Examples of the quaternizing agent include methyl chloride (i.e., X ⁻ ═Cl ⁻ ), methyl bromide (i.e., X ⁻ ═Br ⁻ ), dimethyl sulfate (i.e., X ⁻ ═CH ₃ SO ₄ ⁻ ), and benzyl chloride (i.e., X ⁻ ═Cl ⁻ ). From the viewpoint of the effect of reducing water-soluble COD components, X ⁻ is preferably Cl ⁻ , Br ⁻ or HSO ₄ ⁻ .

Specific examples of the cation (ammonium ion) in the compound (A1) include hexyltrimethylammonium ion, heptyltrimethylammonium ion, octyltrimethylammonium ion, nonyltrimethylammonium ion, decyltrimethylammonium ion, undecyltrimethylammonium ion, dodecyltrimethylammonium (lauryltrimethylammonium) ion, tridecyltrimethylammonium ion, tetradecyltrimethylammonium (myristyltrimethylammonium) ion, pentadecyltrimethylammonium ion, hexadecyltrimethylammonium ion, heptadecyltrimethylammonium ion, octadecyltrimethylammonium (trimethylstearylammonium) ion, and mixtures thereof. From the viewpoint of the effect of reducing water-soluble COD components, the hexadecyltrimethylammonium ion or octadecyltrimethylammonium (trimethylstearylammonium) ion is preferred.

[Compound (A2)]
The compound (A2) has a structure represented by the general formula (2).

In the general formula (2), n is an integer of 5 to 17, representing the number of repeating methylene groups. If n is 4 or less, there is a tendency for the effect of reducing water-soluble COD components to decrease due to insufficient hydrophobicity (even if the water-soluble COD components and the quaternary ammonium ion form a complex, the complex is highly water-soluble and therefore difficult to precipitate and to separate as a precipitate), whereas if n is 18 or more, there is a tendency for the effect of reducing water-soluble COD components to decrease due to insufficient solubility in water (as the water solubility of the quaternary ammonium ion is low, it is difficult to form a complex with the water-soluble COD components and it is difficult to separate the water-soluble COD components as a precipitate). From the viewpoint of the effect of reducing water-soluble COD components, n is preferably 11 to 17.

In addition, it is presumed that linear alkyl groups have stronger intermolecular forces than branched alkyl groups with the same number of carbon atoms, and therefore tend to associate more easily, resulting in a larger particle size for the complex of water-soluble COD components and quaternary ammonium ions, and that the complex tends to separate more easily as a precipitate. Therefore, it is presumed that compound (A2) having a linear alkyl group with 6 to 18 carbon atoms is more effective at reducing water-soluble COD components than quaternary ammonium salts having branched alkyl groups with the same number of carbon atoms.

In the general formula (2), X ^- represents a counter anion of an ammonium ion, and is an anion group derived from a conjugate base of a Brønsted acid or a quaternizing agent. Examples of the Brønsted acid include inorganic acids (hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, etc.) and organic acids [sulfonic acids (methylsulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, etc.), carboxylic acids (oxalic acid, acetic acid, maleic acid, etc.), and phosphonic acids (methylphosphonic acid, phenylphosphonic acid, etc.)], and the like. From the viewpoint of the effect of reducing water-soluble COD components, hydrochloric acid (i.e., X ^- =Cl ^- ), hydrobromic acid (i.e., X ^- =Br ^- ), or sulfuric acid (i.e., X ^- =HSO ₄ ^- ) is preferred. Examples of the quaternizing agent include methyl chloride (i.e., X ⁻ ═Cl ⁻ ), methyl bromide (i.e., X ⁻ ═Br ⁻ ), dimethyl sulfate (i.e., X ⁻ ═CH ₃ SO ₄ ⁻ ), and benzyl chloride (i.e., X ⁻ ═Cl ⁻ ). From the viewpoint of the effect of reducing water-soluble COD components, X ⁻ is preferably Cl ⁻ , Br ⁻ or HSO ₄ ⁻ .

Specific examples of the cation (ammonium ion) in the compound (A2) include benzylhexyldimethylammonium ion, benzylheptyldimethylammonium ion, benzyloctyldimethylammonium ion, benzylnonyldimethylammonium ion, benzyldecyldimethylammonium ion, benzylundecyldimethylammonium ion, benzyldodecyldimethylammonium (benzyllauryldimethylammonium) ion, benzyltridecyldimethylammonium ion, benzyltetradecyldimethylammonium (benzylmyristyldimethylammonium) ion, benzylpentadecyldimethylammonium ion, benzylhexadecyldimethylammonium ion, benzylheptadecyldimethylammonium ion, benzyloctadecyldimethylammonium (benzyldimethylstearylammonium) ion, and mixtures thereof. From the viewpoint of the effect of reducing water-soluble COD components, benzylhexadecyldimethylammonium ion or benzyloctadecyldimethylammonium ion is preferred.

[Compound (A3)]
The compound (A3) has a structure represented by the general formula (3).

In the general formula (3), n is an integer of 5 to 17, representing the number of repeating methylene groups. If n is 4 or less, there is a tendency for the effect of reducing water-soluble COD components to decrease due to insufficient hydrophobicity (even if the water-soluble COD components and the quaternary ammonium ion form a complex, the complex is highly water-soluble and therefore difficult to precipitate and to separate as a precipitate), whereas if n is 18 or more, there is a tendency for the effect of reducing water-soluble COD components to decrease due to insufficient solubility in water (as the water solubility of the quaternary ammonium ion is low, it is difficult to form a complex with the water-soluble COD components and it is difficult to separate the water-soluble COD components as a precipitate). From the viewpoint of the effect of reducing water-soluble COD components, n is preferably 11 to 17.

In addition, it is presumed that linear alkyl groups have stronger intermolecular forces than branched alkyl groups with the same number of carbon atoms, and therefore tend to associate more easily, resulting in a larger particle size for the complex of water-soluble COD components and quaternary ammonium ions, and that the complex tends to separate more easily as a precipitate. Therefore, it is presumed that compound (A3) having a linear alkyl group with 6 to 18 carbon atoms is more effective at reducing water-soluble COD components than quaternary ammonium salts having branched alkyl groups with the same number of carbon atoms.

In the general formula (3), X ^- represents a counter anion of an ammonium ion, and is an anion group derived from a conjugate base of a Brønsted acid or a quaternizing agent. Examples of the Brønsted acid include inorganic acids (hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, etc.) and organic acids [sulfonic acids (methylsulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, etc.), carboxylic acids (oxalic acid, acetic acid, maleic acid, etc.), and phosphonic acids (methylphosphonic acid, phenylphosphonic acid, etc.)], and the like. From the viewpoint of the effect of reducing water-soluble COD components, hydrochloric acid (i.e., X ^- =Cl ^- ), hydrobromic acid (i.e., X ^- =Br ^- ), or sulfuric acid (i.e., X ^- =HSO ₄ ^- ) is preferred. Examples of the quaternizing agent include methyl chloride (i.e., X ⁻ ═Cl ⁻ ), methyl bromide (i.e., X ⁻ ═Br ⁻ ), dimethyl sulfate (i.e., X ⁻ ═CH ₃ SO ₄ ⁻ ), and benzyl chloride (i.e., X ⁻ ═Cl ⁻ ). From the viewpoint of the effect of reducing water-soluble COD components, X ⁻ is preferably Cl ⁻ , Br ⁻ or HSO ₄ ⁻ .

In the general formula (3), Y is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and from the viewpoint of the effect of reducing water-soluble COD components, a hydrogen atom or a methyl group is preferred.

Specific examples of the cation (ammonium ion) in the compound (A3) include 1-hexylpyridinium ion, 1-hexyl-4-methylpyridinium ion, 1-heptylpyridinium ion, 1-heptyl-4-methylpyridinium ion, 1-octylpyridinium ion, 1-octyl-4-methylpyridinium ion, 1-nonylpyridinium ion, 1-nonyl-4-methylpyridinium ion, 1-decylpyridinium ion, 1-decyl-4-methyl ... 1-ethylpyridinium ion, 1-undecylpyridinium ion, 1-undecyl-4-methylpyridinium ion, 1-dodecylpyridinium ion (1-laurylpyridinium ion), 1-dodecyl-4-methylpyridinium ion (1-lauryl-4-methylpyridinium ion), 1-tridecylpyridinium ion, 1-tridecyl-4-methylpyridinium ion, 1-tetradecylpyridinium ion (1-myristylpyridinium ion), 1-tetradecylpyridinium ion (1-myristylpyridinium ion), 1-pentadecylpyridinium ion, 1-pentadecyl-4-methylpyridinium ion, 1-hexadecylpyridinium ion, 1-hexadecyl-4-methylpyridinium ion, 1-heptadecylpyridinium ion, 1-heptadecyl-4-methylpyridinium ion, 1-octadecylpyridinium ion (1-stearylpyridinium ion), 1-octadecyl-4 -methylpyridinium ion (1-stearyl-4-methylpyridinium ion) and mixtures thereof, and from the viewpoint of the effect of reducing water-soluble COD components, 1-hexadecylpyridinium ion, 1-hexadecyl-4-methylpyridinium ion, 1-octadecylpyridinium ion (1-stearyl-4-methylpyridinium ion), or 1-octadecyl-4-methylpyridinium ion (1-stearyl-4-methylpyridinium ion) are preferred.

[At least one salt (S) selected from the group consisting of silicates, phosphates and borates]
The salt (S) is at least one selected from the group consisting of silicates, phosphates, and borates. The salt (S) may be used alone or in combination of two or more.

The silicate may be an alkali metal salt or an alkaline earth metal salt of silicic acid, or an alkali metal salt or an alkaline earth metal salt of condensed silicic acid. The silicate is preferably at least one selected from the group consisting of lithium silicate, sodium silicate, potassium silicate, and calcium silicate, and more preferably sodium silicate. The silicate may be in the form of a solid or an aqueous solution, and aqueous solutions of sodium silicate (No. 1, No. 2, No. 3, No. 4, No. 5), so-called water glass, may be used.

The phosphate salt may be an alkali metal salt or an alkaline earth metal salt of phosphoric acid, or an alkali metal salt or an alkaline earth metal salt of condensed phosphoric acid (polyphosphoric acid, metaphosphoric acid, etc.). The phosphate salt is preferably at least one selected from the group consisting of monosodium phosphate, disodium phosphate, trisodium phosphate, potassium hydrogen phosphate, and sodium polyphosphate, and more preferably trisodium phosphate.

The borate salt may be an alkali metal salt or an alkaline earth metal salt of boric acid, an alkali metal salt or an alkaline earth metal salt of polyboric acid, or a hydrate thereof. The borate salt is preferably at least one selected from the group consisting of trisodium borate, sodium metaborate, and sodium tetraborate, and more preferably sodium tetraborate decahydrate.

From the viewpoint of the effect of reducing water-soluble COD components, the salt (S) preferably contains the silicate, and more preferably contains sodium silicate.

The weight ratio [(S)/(A)] of the quaternary ammonium salt (A) to the salt (S) in the water treatment agent of this embodiment is preferably 0.01 to 30, more preferably 0.1 to 20, and even more preferably 1 to 10, from the viewpoints of the effect of reducing water-soluble COD components, the amount of sludge generated, and treatment costs.

The water treatment agent of this embodiment may further contain water in addition to the quaternary ammonium salt (A) and the salt (S) from the viewpoint of operability (handling ability) and the like. When the water treatment agent contains water, the total content of the quaternary ammonium salt (A) and the salt (S) in the water treatment agent of this embodiment is preferably 0.1 to 80% by weight, more preferably 1 to 50% by weight, based on the total weight of the quaternary ammonium salt (A), the salt (S), and the water. The content of the quaternary ammonium salt (A) in the water treatment agent of this embodiment is preferably 0.1 to 30% by weight, more preferably 1 to 15% by weight, based on the total weight of the quaternary ammonium salt (A), the salt (S), and the water.

The total content of the quaternary ammonium salt (A), the salt (S), and water is preferably 90 to 100% by weight based on the weight of the water treatment agent.

When the water treatment agent of this embodiment is the above-mentioned "two-agent type water treatment agent consisting of a water treatment agent (P1) containing the quaternary ammonium salt (A) and a water treatment agent (P2) containing the salt (S)," the water treatment agent (P1) may contain water in addition to the quaternary ammonium salt (A). When the water treatment agent (P1) contains water, the content of the quaternary ammonium salt (A) in the water treatment agent (P1) is preferably 0.1 to 50% by weight, more preferably 1 to 30% by weight, based on the weight of the water treatment agent (P1) from the viewpoint of operability and the effect of reducing water-soluble COD components. The total content of the quaternary ammonium salt (A) and water in the water treatment agent (P1) is preferably 90 to 100% by weight based on the weight of the water treatment agent (P1).

When the water treatment agent of this embodiment is the above-mentioned "two-agent type water treatment agent consisting of a water treatment agent (P1) containing the quaternary ammonium salt (A) and a water treatment agent (P2) containing the salt (S)," the water treatment agent (P2) may contain water in addition to the salt (S). When the water treatment agent (P2) contains water, the content of the salt (S) in the water treatment agent (P2) is preferably 0.1 to 80% by weight, more preferably 1 to 50% by weight, based on the weight of the water treatment agent (P2) from the viewpoint of operability and the effect of reducing water-soluble COD components. The content of the salt (S) in the water treatment agent (P2) is preferably 90 to 100% by weight based on the weight of the water treatment agent (P2).

The water treatment agent of this embodiment may contain an organic coagulant to the extent that the effect of the present invention is not impaired in order to further improve the removal performance of water-soluble COD components. Examples of the organic coagulant include polycondensates of epihalohydrin and amine and their hydrochlorides, polycondensates of epihalohydrin and alkylenediamine and their hydrochlorides, polyethyleneimine and its hydrochlorides, alkylenedihalide-alkylenepolyamine polycondensates and their hydrochlorides, aniline-formaldehyde polycondensates and their hydrochlorides, polyvinylbenzyltrimethylammonium chloride, polyvinylpyridine and its hydrochlorides, (di)methyldi(meth)allylammonium chloride, and polyvinylimidazoline and its hydrochlorides. The organic coagulant may be used alone or in combination of two or more types. The organic coagulant may be contained in both or either of the water treatment agent (P1) and the water treatment agent (P2).

The method for producing the water treatment agent of this embodiment is not particularly limited, but it can be produced, for example, as follows.

When the water treatment agent is a one-component type, it can be produced by mixing the quaternary ammonium salt (A) diluted with water as necessary, the salt (S) diluted with water as necessary, and additives as necessary. The mixing method is not particularly limited, and for example, mixing may be performed using a stirrer in a container such as a bucket. The quaternary ammonium salt (A) and the salt (S) may form a complex and become cloudy, but it can be used without problems by stirring and mixing again immediately before use.

When the water treatment agent is a two-component type, the water treatment agent (P1) can be produced by mixing the quaternary ammonium salt (A), optionally diluted with water, with additives, and the water treatment agent (P2) can be produced by mixing the salt (B), optionally diluted with water, with additives, and the water treatment agent (P2) can be produced.

In the production of the water treatment agent, the method of diluting the quaternary ammonium salt (A) and/or the salt (S) with water is not particularly limited, but for example, a method can be used in which a predetermined amount of the quaternary ammonium salt (A) and/or the salt (S) is added to a previously measured amount of water while stirring it using a known stirring device (such as a jar tester), and the water is stirred for several hours (approximately 1 to 4 hours).

In the water treatment agent of this embodiment, the quaternary ammonium salt (A) forms a water-insoluble complex with the water-soluble COD components contained in the water to be treated, causing them to become insoluble and precipitate, and the precipitate is separated and removed, thereby reducing the water-soluble COD components. Since the water treatment agent further contains the salt (S), the complex between the quaternary ammonium salt (A) and the water-soluble COD components is coarsened, facilitating the separation and removal of the precipitate, and a further reduction effect in the water-soluble COD components can be expected. Furthermore, even if the quaternary ammonium salt (A) is added in excess to the water to be treated, the salt (S) precipitates the excessively added quaternary ammonium salt (A), and the quaternary ammonium salt (A) itself becomes a water-soluble COD component and can suppress the increase in the water-soluble COD components, so it is presumed that a stable water-soluble COD reduction effect can be expressed. In addition, even when the amount of the quaternary ammonium salt (A) added is small, the salt (S) can precipitate a complex of the water-soluble COD components dissolved in water and the quaternary ammonium salt (A), and is presumed to have an effect of reducing water-soluble COD components.

The water treatment agent of the present invention is very useful because, when added to various industrial wastewater (wastewater from factories in the paper pulp, dyeing, automobile, metal processing, steel, food, gravel, semiconductor-related and cleaning industries, etc.), sewage, purified water, sludge (organic sludge and inorganic sludge) generated in the treatment of industrial wastewater, etc., it can suppress the increase in water-soluble COD components, even under conditions where the amount of water treatment agent added is excessive, and can exhibit a stable water-soluble COD component reduction effect, and has a significantly excellent effect in reducing water-soluble COD components.

<Water treatment method>
The water treatment method of this embodiment includes a step (I) of adding the quaternary ammonium salt (A) to water to be treated (hereinafter, in this specification, may be referred to as water to be treated) containing water-soluble COD components, such as various industrial wastewater, sewage, purified water, and sludge (organic sludge and inorganic sludge), and a step (II) of adding the salt (S) to the water to be treated.

[Step (I)]
The step (I) is a step of adding the quaternary ammonium salt (A) to the water to be treated.

In step (I), the amount of the quaternary ammonium salt (A) added to the water to be treated can be adjusted depending on the type of water to be treated, the content of particles suspended in the water to be treated, the amount of water-soluble COD components, etc., and is not particularly limited. From the viewpoint of water-soluble COD component reduction performance, however, 1 mg to 10 g per 1 L of the water to be treated is preferable, 3 mg to 8 g is more preferable, 5 mg to 5 g is even more preferable, and 5 mg to 3 g is even more preferable.

In step (I), the method for adding the quaternary ammonium salt (A) to the water to be treated is not particularly limited, and the quaternary ammonium salt (A) can be added to the water to be treated and mixed by a known method.

[Step (II)]
The step (II) is a step of adding the salt (S) to the water to be treated.

In step (II), the amount of the salt (S) added to the water to be treated is preferably an amount such that the weight ratio of the salt (S) to the weight of the quaternary ammonium salt (A) [(S)/(A)] is 0.01 to 30, more preferably an amount such that the weight ratio is 0.1 to 20, and even more preferably an amount such that the weight ratio is 1 to 10.

In step (II), the method for adding the salt (S) to the water to be treated is not particularly limited, and the salt (S) can be added to the water to be treated and mixed using a known method.

The steps (I) and (II) may be carried out separately or simultaneously. When the steps (I) and (II) are carried out separately, the water treatment agent (P1) containing the quaternary ammonium salt (A) and the water treatment agent (P2) containing the salt (S) are added separately. When the steps (I) and (II) are carried out simultaneously, the quaternary ammonium salt (A) and the salt (S) are mixed in advance and added as a one-agent type water treatment agent. From the viewpoint of the effect of reducing water-soluble COD components, it is preferable to carry out the steps (I) and (II) separately, and it is more preferable to carry out the step (II) after carrying out the step (I).

[Other steps]
[Step (III)]
The water treatment method of the present embodiment may further include, in addition to the step (I) and the step (II), a step (III) of adding an inorganic flocculant to the water to be treated.

The inorganic flocculants include aluminum sulfate, polyaluminum chloride, ferric chloride, polyferric sulfate, and hydrated lime. Each of the inorganic flocculants may be used alone or in combination of two or more.

The amount of inorganic flocculant added when the water treatment method of this embodiment includes step (III) varies depending on the type of sludge or wastewater, the size and content of suspended particles, the total sludge and the amount of water-soluble COD components in the wastewater, etc., but is preferably 0.001 to 1% by weight, more preferably 0.005 to 0.8% by weight, and even more preferably 0.01 to 0.5% by weight based on the weight of the sludge or wastewater. If it is 0.001% by weight or more, the effect of reducing water-soluble COD components will be more pronounced, and if it is 1% by weight or less, the amount of sludge generated can be reduced.

When the water treatment method of the present embodiment includes the step (III), the steps (I) to (III) may be performed separately or simultaneously. The steps (I) to (III) are preferably performed in any one of the following procedures (i) to (iv).
Step (i)
After step (I), step (III) is carried out, and then step (II) is carried out.
Step (ii)
After step (III), step (I) is carried out, and then step (II) is carried out.
Step (iii)
Step (I) and step (III) are carried out simultaneously {i.e., the quaternary ammonium salt (A) and the inorganic flocculant are mixed in advance and then added to the water to be treated}, and then step (II) is carried out.
Step (iv)
After step (I), step (II) is carried out, and then step (III) is carried out.

When the water treatment method of this embodiment includes the step (III), from the viewpoint of treatment costs, it is preferable to carry out the step (II) after carrying out the steps (I) and (III). In other words, it is preferable to carry out the steps (I) to (III) in any of the above procedures (i) to (iii).

[pH adjustment step]
The pH of the water to be treated after the steps (I) and (II) have been performed, or after the steps (I) to (III) have been performed if the water treatment method of the present embodiment has the step (III), is preferably 1 to 12, more preferably 3 to 10, and even more preferably 5 to 8. In this range, the effects of the present invention, such as reduction of water-soluble COD components, can be more effectively achieved. Therefore, the water treatment method of the present embodiment may have a pH adjustment step of adding an inorganic acid (hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc.), an inorganic solid acidic substance (acidic sodium phosphate, acidic sulfuric acid, ammonium chloride, ammonium sulfate, ammonium bicarbonate, sulfamic acid, etc.), an organic acid (oxalic acid, succinic acid, malic acid, etc.), an inorganic alkaline substance (e.g., sodium hydroxide, potassium hydroxide, ammonia, etc.), and an organic alkaline substance (e.g., guanidine, etc.) or an aqueous solution thereof, in order to adjust the pH of the water to be treated after the steps (I) and (II), etc. have been performed.

[Polymer flocculant addition process]
From the viewpoint of facilitating solid-liquid separation, the water treatment method of the present embodiment preferably further comprises a polymer flocculant addition step of adding and mixing a polymer flocculant to the water to be treated after carrying out the steps (I) and (II) or, in the case where the water treatment method of the present embodiment comprises the step (III), after carrying out the steps (I) to (III) to form coarse flocs.

The polymer flocculant is not particularly limited, and any commonly used known polymer flocculant can be suitably used. The polymer flocculant may be any of cationic, nonionic, anionic, and amphoteric polymer flocculants, and these may also be used in combination.

The cationic polymer flocculant may be a homopolymer of polyethyleneimine, a Mannich modified poly(meth)acrylamide, a quaternized dialkylaminoethyl (meth)acrylate, or a copolymer with other monomers such as (meth)acrylamide, or a copolymer containing the cationic monomer as a constituent unit.

The nonionic polymer flocculant may be polyacrylamide or the like with a Mw of more than 1,000,000.

The anionic polymer flocculant may, for example, be sodium poly(meth)acrylate, hydrolyzed poly(meth)acrylamide, (meth)acrylamide-sodium (meth)acrylate copolymer, (meth)acrylamide-sodium (meth)acrylate-sodium 2-acrylamido-2-methylpropane-1-sodium sulfonate copolymer, (meth)acrylamide-sodium 2-acrylamido-2-methylpropane-1-sodium sulfonate copolymer, and other (co)polymers containing the anionic monomers described above.

The amphoteric polymer flocculant may be a copolymer of a cationic monomer (such as dialkylaminoethyl (meth)acrylate quaternized products and other cationic monomers as described above) with an anionic monomer (such as (meth)acrylic acid (salt), 2-acrylamido-2-methylpropane-1-sulfonic acid (salt)), and, if necessary, a nonionic monomer (such as acrylamide).

In the polymer flocculant addition step, there is no particular limitation on the method of adding the polymer flocculant. The polymer flocculant may be added as is, but from the viewpoint of uniform mixing, it is preferable to add the polymer flocculant to the water to be treated after making it into an aqueous solution. When using the polymer flocculant as an aqueous solution, the concentration of the polymer flocculant is preferably 0.05 to 1% by weight, more preferably 0.1 to 0.5% by weight. There is no particular limitation on the dissolution method and the dilution method after dissolution, but when dissolving a powdered polymer flocculant in water, it is preferable to add it gradually, since adding the polymer flocculant all at once will cause lumps and make it difficult to dissolve in water.

In the polymer flocculant addition step, the amount of polymer flocculant added varies depending on the type of water to be treated, the size and content of suspended particles, and the molecular weight of the polymer flocculant, but from the viewpoint of general flocculation performance, it is preferably 0.0001 to 0.5% by weight, more preferably 0.0002 to 0.3% by weight, even more preferably 0.0003 to 0.2% by weight, and even more preferably 0.0004 to 0.1% by weight based on the weight of the water to be treated.

[Solid-liquid separation process]
The water treatment method of this embodiment may include a solid-liquid separation step of removing precipitates precipitated in the water to be treated that has been treated in the step (I), the step (II), and the like, from the water to be treated.

In the solid-liquid separation step, methods for separating the solid and liquid can be used, such as gravity settling, membrane filtration, column filtration, pressure flotation, concentrators (e.g., thickeners, etc.), and dehydrators (e.g., centrifuges, belt press dehydrators, filter press dehydrators, etc.).

Specific examples of the water treatment method include the following examples (1) to (4).
・Example (1)
After carrying out the step (I) and the step (II) and, if necessary, carrying out the pH adjustment step, a solid-liquid separation step is carried out.
・Example (2)
After carrying out the step (I) and the step (II) and, if necessary, carrying out the pH adjustment step, the polymer flocculant addition step is carried out, and further, the solid-liquid separation step is carried out.
・Example (3)
The steps (I), (II) and (III) are carried out, and the pH adjustment step is carried out as necessary, and then the solid-liquid separation step is carried out.
・Example (4)
After carrying out the steps (I), (II) and (III) and, if necessary, carrying out the pH adjustment step, the polymer flocculant addition step is further carried out, and then the solid-liquid separation step is further carried out.

Among the above examples (1) to (4), examples (2) and (4) are preferred from the viewpoint of forming coarser flocs and facilitating solid-liquid separation.

The water treatment method of this embodiment may also include an activated carbon treatment step in which the water to be treated after the solid-liquid separation step is treated with activated carbon.

To confirm the effect of reducing water-soluble COD components in this invention, the COD of the treated wastewater (CODMn below) may be measured directly, but the effect of reducing COD can also be evaluated using TOC (total organic carbon), which is commonly used in the field of wastewater treatment as an alternative means of monitoring COD and can be measured more easily than COD. In the following examples, both COD and TOC are shown.

The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to these. Note that unless otherwise specified, parts in the examples refer to parts by weight.

The raw materials represented by each symbol in Tables 1 to 5 are as follows. The amount of each raw material {quaternary ammonium salt (A), comparative quaternary ammonium salt (comparative A), cationic polymer (M) and salt (S)} added in Tables 1 to 5 is the amount (mg) of solids (components excluding water and volatile solvents) of each raw material added per 1 L of water to be treated (wastewater from chemical plant B described below).
<Quaternary ammonium salt (A)>
(A1-1): Hexyl trimethyl ammonium chloride (A1-2): Lauryl trimethyl ammonium chloride (A1-3): Hexadecyl trimethyl ammonium chloride (A1-4): Trimethylstearyl ammonium chloride (A1-5): Tetradecyl trimethyl ammonium chloride (A1-6): Tetradecyl trimethyl ammonium bromide (A1-7): Hexadecyl trimethyl ammonium bromide (A1-8): Hexadecyl trimethyl ammonium hydroxide (A2-1): Benzyl hexyl dimethyl ammonium chloride (A2-2): Benzyl lauryl dimethyl ammonium chloride (A2-3): Benzyl Benzylhexadecyldimethylammonium chloride (A2-4): Benzyldimethylstearylammonium chloride (A3-1): 1-hexylpyridinium chloride (A3-2): 1-laurylpyridinium chloride (A3-3): 1-hexadecylpyridinium chloride (A3-4): 1-stearylpyridinium chloride (A3-5): 1-hexyl-4-methylpyridinium chloride (A3-6): 1-lauryl-4-methylpyridinium chloride (A3-7): 1-hexadecyl-4-methylpyridinium chloride (A3-8): 1-stearyl-4-methylpyridinium chloride <Comparative quaternary ammonium salts (comparison A)>
(Ratio A1-1): Tetramethylammonium chloride (Ratio A2-1): Benzyltrimethylammonium chloride (Ratio A3-1): 1-methylpyridinium chloride <Cationic polymer (M)>
(M-1): Salt (S) produced in Comparative Production Example 1 below
(S-1): Sodium silicate solution (No. 3) [manufactured by Fuji Chemical Co., Ltd.]
(S-2): Trisodium phosphate dodecahydrate [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.]
(S-3): Sodium tetraborate decahydrate [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.]
(S-4): Sodium silicate solution (No. 1) [manufactured by Fuji Chemical Co., Ltd.]
(S-5): Sodium silicate solution (No. 2) [manufactured by Fuji Chemical Co., Ltd.]
(S-6): Sodium silicate solution (No. 4) [manufactured by Fuji Chemical Co., Ltd.]
(S-7): Sodium silicate solution (No. 5) [manufactured by Fuji Chemical Co., Ltd.]

Comparative Production Example 1: Production of cationic polymer (M-1) and comparative water treatment agent (Comparative PM-1)
A four-neck flask equipped with a stirrer, a temperature sensor, a cooling tube, a dropping funnel and a mantle heater was charged with 190 parts of isopropyl alcohol (hereinafter abbreviated as "IPA") and 69 parts of ion-exchanged water, and heated to reflux under stirring. A mixed solution of 80 parts of IPA, 20 parts of ion-exchanged water, and 0.7 parts of azobisisobutyronitrile (hereinafter abbreviated as "AIBN") was added as an initiator solution from the dropping port, and a homogeneous mixture of 80% by weight of trimethyl-2-methacryloyloxyethylammonium chloride aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd., reagent) 352 parts, styrene (manufactured by Tokyo Chemical Industry Co., Ltd., reagent) 48 parts, IPA 180 parts, and ion-exchanged water 60 parts was added dropwise to the flask simultaneously over 4 hours while stirring the flask at 80 to 85 ° C. After dropping, the mixture was aged for 2 hours at the same temperature, and a homogeneous mixture of 80 parts IPA, 20 parts ion-exchanged water, and 2.0 parts AIBN was dropped into a flask at 80 to 85 ° C. over 1 hour and aged at the same temperature for 180 minutes. Thereafter, 465 parts of ion-exchanged water was added to the flask, and the temperature was raised to 100 ° C. to remove the IPA, and 1,000 parts of an aqueous solution containing a cationic polymer (M-1) and a solid content of 40.0 wt % was obtained. The aqueous solution was diluted with ion-exchanged water to a solid content of 10.0 wt %, to obtain a comparative water treatment agent (PM-1) containing a cationic polymer (M-1). The comparative water treatment agent (PM-1) had a solid content of 40.0 wt %, a pH of 4.5, and the Mw (weight average molecular weight measured by GPC) of the cationic polymer (M-1) was 180,000, and the colloid equivalent value (colloid equivalent value measured by colloid titration using potassium polyvinyl sulfate) was 4.1.

Example 1
1 L of wastewater from a chemical plant B containing an anionic surfactant was collected in a beaker, and under stirring, 2,500 mg of water treatment agent (P1-1) (250 mg of quaternary ammonium salt (A) solid content equivalent) was added, which is an aqueous solution in which a quaternary ammonium salt (A1-1) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After stirring for 1 minute, 7,500 mg of water treatment agent (P2-1) (750 mg of (S) solid content equivalent) was added, which is an aqueous solution in which a salt (S-1) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After 3 minutes, a 1 wt% aqueous sulfuric acid solution was added dropwise while continuing to stir, and the pH was adjusted to 7.0. After stirring for 3 minutes, the mixture was left to stand for 5 minutes. The left-standing supernatant was filtered through a filter paper (No. 5C), and the COD of the filtrate was measured in accordance with the CODMn analysis method described in JIS K0102:2016. The TOC was measured using a total organic carbon analyzer [multi N/C 3100, manufactured by Analytik Jena Japan Co., Ltd.]. The COD was 8 mg/L and the TOC was 12 mg/L.

<Examples 2 to 30, 35 to 36, 38 to 43, and 59 to 62>
The supernatant was filtered in the same manner as in Example 1, except that the types and amounts of the quaternary ammonium salt (A) and the water treatment agent (P1) and the salt (S) and the water treatment agent (P2) were changed to those shown in Table 1, Table 2, Table 3, or Table 4. The COD and TOC of the filtrate were measured in the same manner as in Example 1, and the results are shown in Tables 1 to 4.

<Example 31>
1 L of wastewater from a chemical plant B containing an anionic surfactant was collected in a beaker, and under stirring, 2,500 mg of water treatment agent (P1-3) (250 mg of quaternary ammonium salt (A) solid content equivalent) was added, which is an aqueous solution in which a quaternary ammonium salt (A1-3) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After stirring for 1 minute, 7,500 mg of water treatment agent (P2-1) (750 mg of salt (S) solid content equivalent) was added, which is an aqueous solution in which a salt (S-1) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After 3 minutes, a 1 wt% aqueous sulfuric acid solution was added dropwise while continuing to stir, and the pH was adjusted to 7.0. Subsequently, while stirring, a 0.2 wt% aqueous solution of Sanfloc CE-706P (manufactured by Sanyo Chemical Industries, Ltd.) as a cationic polymer flocculant was added in an amount to a solid content concentration of 10 mg/L, and the mixture was stirred for 3 minutes and then allowed to stand for 5 minutes. The supernatant was filtered through a filter paper (No. 5C) and the filtrate was measured for COD and TOC in the same manner as in Example 1. The COD was 4 mg/L and the TOC was 6 mg/L.

<Example 32>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 31, except that the quaternary ammonium salt (A1-3) was replaced with (A1-4) {the water treatment agent (P1-3) was replaced with (P1-4)}, were measured. The COD was 6 mg/L and the TOC was 9 mg/L.

<Example 33>
1 L of wastewater from B chemical plant containing an anionic surfactant was collected in a beaker, and under stirring, polyaluminum chloride ["Taipac 6010", manufactured by Taimei Chemical Industry Co., Ltd.] as an inorganic flocculant was added in an amount to a solid content concentration of 50 mg/L. Further, under stirring, 2,500 mg of water treatment agent (P1-3) (250 mg of quaternary ammonium salt (A) solid content equivalent) was added, which is an aqueous solution in which quaternary ammonium salt (A1-3) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight, and after stirring for 1 minute, 7,500 mg of water treatment agent (P2-1) (750 mg of salt (S) solid content equivalent) was added, which is an aqueous solution in which salt (S-1) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After 3 minutes, 1 wt% sulfuric acid aqueous solution was added dropwise while continuing stirring to adjust the pH to 7.0. After stirring for 3 minutes, the mixture was left to stand for 5 minutes. The supernatant was filtered through a filter paper (No. 5C) and the filtrate was measured for COD and TOC in the same manner as in Example 1. The COD was 4 mg/L and the TOC was 6 mg/L.

<Example 34>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 33, except that the quaternary ammonium salt (A1-3) was replaced with (A1-4) {the water treatment agent (P1-3) was replaced with (P1-4)}, were measured. The COD was 7 mg/L and the TOC was 10 mg/L.

<Example 37>
50 parts of an aqueous solution in which a quaternary ammonium salt (A1-3) was dissolved in ion-exchanged water to a solids concentration of 10% by weight was added to a 100 ml beaker. 50 parts of an aqueous solution in which a salt (S-1) was dissolved in ion-exchanged water to a solids concentration of 10% by weight was added and mixed under stirring to obtain a one-form water treatment agent (P-37) containing (A1-3) and (S-1).
1 L of wastewater from chemical factory B containing an anionic surfactant was collected in a beaker, and 5,000 mg of the above water treatment agent (P-37) (including 250 mg of solids of quaternary ammonium salt (A) and 250 mg of solids of salt (S)) was added under stirring. After 3 minutes, 1 wt % aqueous sulfuric acid solution was added dropwise while continuing stirring to adjust the pH to 7.0. After 3 minutes of stirring, the solution was allowed to stand for 5 minutes. The supernatant liquid that had been allowed to stand was filtered through filter paper (No. 5C), and the COD and TOC of the filtrate were measured in the same manner as in Example 1. The COD was 21 mg/L, and the TOC was 32 mg/L.

<Example 44>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 3, except that the salt (S-1) was replaced with (S-4) {the water treatment agent (P2-1) was replaced with (P2-4)}, were measured. The COD was 7 mg/L and the TOC was 10 mg/L.

<Example 45>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 3, except that the salt (S-1) was replaced with (S-5) {the water treatment agent (P2-1) was replaced with (P2-5)}, were measured. The COD was 6 mg/L and the TOC was 9 mg/L.

<Example 46>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 3, except that the salt (S-1) was replaced with (S-6) {the water treatment agent (P2-1) was replaced with (P2-6)}, were measured. The COD was 5 mg/L and the TOC was 7 mg/L.

<Example 47>
The same procedure as in Example 3 was repeated except that the salt (S-1) was replaced with the salt (S-7) {the water treatment agent (P2-1) was replaced with the water treatment agent (P2-7)}, and the COD and TOC of the filtrate of the supernatant were measured. The COD was 5 mg/L and the TOC was 7 mg/L.

<Example 48>
The same procedure as in Example 33 was repeated except that polyaluminum chloride was replaced with aluminum sulfate (manufactured by Taimei Chemical Industry Co., Ltd.), and the COD and TOC of the filtrate of the supernatant were measured. The COD was 5 mg/L and the TOC was 7 mg/L.

<Example 49>
The same procedure as in Example 33 was repeated except that polyaluminum chloride was replaced with polyferric sulfate (manufactured by Taiki Pharmaceutical Co., Ltd.), and the COD and TOC of the filtrate of the supernatant were measured. The COD was 6 mg/L and the TOC was 9 mg/L.

<Example 50>
The same procedure as in Example 33 was repeated except that polyaluminum chloride was replaced with ferric chloride (manufactured by Taiki Pharmaceutical Co., Ltd.), and the COD and TOC of the filtrate of the supernatant were measured. The COD was 5 mg/L and the TOC was 7 mg/L.

<Example 51>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 3, except that the quaternary ammonium salt (A1-3) was replaced with (A1-5) {the water treatment agent (P1-3) was replaced with (P1-5)}, were measured. The COD was 7 mg/L and the TOC was 10 mg/L.

<Example 52>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 3, except that the quaternary ammonium salt (A1-3) was replaced with (A1-6) {the water treatment agent (P1-3) was replaced with (P1-6)}, were measured. The COD was 9 mg/L and the TOC was 13 mg/L.

<Example 53>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 3, except that the quaternary ammonium salt (A1-3) was replaced with (A1-7) {the water treatment agent (P1-3) was replaced with (P1-7)}, were measured. The COD was 8 mg/L and the TOC was 12 mg/L.

<Example 54>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 3, except that the quaternary ammonium salt (A1-3) was replaced with (A1-8) {the water treatment agent (P1-3) was replaced with (P1-8)}, were measured. The COD was 5 mg/L and the TOC was 7 mg/L.

<Example 55>
1 L of wastewater from a chemical plant B containing an anionic surfactant was collected in a beaker, and 2,500 mg of a water treatment agent (P1-3) (250 mg of quaternary ammonium salt (A) solid content equivalent) was added, which was an aqueous solution in which a quaternary ammonium salt (A1-3) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After stirring for 1 minute, 7,500 mg of a water treatment agent (P2-1) (750 mg of salt (S) solid content equivalent) was added, which was an aqueous solution in which a salt (S-1) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After 3 minutes, a 1% by weight aqueous sulfuric acid solution was added dropwise while continuing the stirring to adjust the pH to 7.0. After 30 minutes, polyaluminum chloride ["Taipac 6010", manufactured by Taimei Chemical Industry Co., Ltd.] was added as an inorganic flocculant under stirring in an amount such that the solid content concentration was 100 mg/L. After 3 minutes, a 1% by weight aqueous sodium hydroxide solution was added dropwise while continuing the stirring to adjust the pH to 7.0. After stirring for 3 minutes, the mixture was allowed to stand for 5 minutes. The supernatant was filtered through a filter paper (No. 5C), and the COD and TOC of the filtrate were measured in the same manner as in Example 1. The COD was 4 mg/L, and the TOC was 6 mg/L.

<Example 56>
1 L of wastewater from a chemical plant B containing an anionic surfactant was collected in a beaker, and 2,500 mg of a water treatment agent (P1-3) (250 mg of quaternary ammonium salt (A) solid content equivalent) was added, which was an aqueous solution in which a quaternary ammonium salt (A1-3) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After stirring for 1 minute, 7,500 mg of a water treatment agent (P2-1) (750 mg of salt (S) solid content equivalent) was added, which was an aqueous solution in which a salt (S-1) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After 3 minutes, a 1% by weight aqueous sulfuric acid solution was added dropwise while continuing the stirring to adjust the pH to 7.0. After 30 minutes, polyaluminum chloride ["Taipac 6010", manufactured by Taimei Chemical Industry Co., Ltd.] was added as an inorganic flocculant under stirring in an amount such that the solid content concentration was 100 mg/L. After 3 minutes, a 1% by weight aqueous sodium hydroxide solution was added dropwise while continuing the stirring to adjust the pH to 7.0. Next, while stirring, a 0.2 wt% aqueous solution of Sanfloc CE-706P (manufactured by Sanyo Chemical Industries, Ltd.) as a cationic polymer flocculant was added in an amount to give a solids concentration of 1 mg/L, and the mixture was stirred for 3 minutes and then allowed to stand for 5 minutes. The supernatant liquid that had been allowed to stand was filtered through filter paper (No. 5C), and the COD and TOC of the filtrate were measured in the same manner as in Example 1. The COD was 6 mg/L and the TOC was 9 mg/L.

<Example 57>
The same procedure as in Example 56 was repeated except that the 0.2% by weight aqueous solution of the cationic polymer flocculant "Sunfloc CE-706P" was replaced with a 0.2% by weight aqueous solution of the anionic polymer flocculant "Sunfloc AH-400P (manufactured by Sanyo Chemical Industries, Ltd.)," and the COD and TOC of the filtrate of the supernatant were measured. The COD was 4 mg/L and the TOC was 6 mg/L.

<Example 58>
The same procedure as in Example 56 was repeated except that the 0.2% by weight aqueous solution of the cationic polymer flocculant "Sunfloc CE-706P" was replaced with a 0.2% by weight aqueous solution of the nonionic polymer flocculant "Sunfloc NOP (manufactured by Sanyo Chemical Industries, Ltd.)," and the COD and TOC of the filtrate of the supernatant were measured. The COD was 5 mg/L and the TOC was 7 mg/L.

<Example 63>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 57 were measured, except that an aqueous solution of an acrylamide-diallyldimethylammonium chloride copolymer, "Unisense FCA1000L (manufactured by Senka Corporation)," which is an organic coagulant, was added to a solids concentration of 50 mg/L instead of polyaluminum chloride ["Taipac 6010" manufactured by Taimei Chemical Industry Co., Ltd.] (solids concentration 100 mg/L). The COD was 4 mg/L and the TOC was 6 mg/L.

<Example 64>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 57 were measured, except that an aqueous solution of poly(diallyldimethylammonium chloride), an organic coagulant, "Unisense FPA100L (manufactured by Senka Corporation)" was added to a solids concentration of 50 mg/L instead of polyaluminum chloride ["Taipac 6010" manufactured by Taimei Chemical Industry Co., Ltd.] (solids concentration 100 mg/L). The COD was 4 mg/L and the TOC was 6 mg/L.

<Example 65>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 57 were measured, except that an aqueous solution of dimethylamine-ammonia-epichlorohydrin condensate "Unisense KHE100L (manufactured by Senka Corporation)" as an organic coagulant was added to a solids concentration of 50 mg/L instead of polyaluminum chloride ["Taipac 6010" manufactured by Taimei Chemical Industry Co., Ltd.] (solids concentration 100 mg/L). The COD was 7 mg/L and the TOC was 10 mg/L.

<Example 66>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 57 were measured, except that an aqueous solution of dicyandiamide-formalin condensate, "Unisense KHF11L (manufactured by Senka Corporation)," an organic coagulant, was added to a solids concentration of 50 mg/L instead of polyaluminum chloride ["Taipac 6010," manufactured by Taimei Chemical Industry Co., Ltd.] (solids concentration 100 mg/L). The COD was 8 mg/L and the TOC was 11 mg/L.

<Example 67>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 57 were measured, except that an aqueous solution of dicyandiamide-diethylenetriamine condensate "Unisense KHP10P (manufactured by Senka Corporation)" which is an organic coagulant was added to a solids concentration of 50 mg/L instead of polyaluminum chloride ["Taipac 6010" manufactured by Taimei Chemical Industry Co., Ltd.] (solids concentration 100 mg/L). The COD was 7 mg/L and the TOC was 10 mg/L.

<Comparative Example 1>
The COD and TOC of the wastewater from Chemical Factory B were measured. The COD was 80 mg/L and the TOC was 122 mg/L.

<Comparative Examples 2 to 4>
The type of quaternary ammonium salt (A) was changed to a comparative quaternary ammonium salt (comparison A-1) shown in Table 5 {the water treatment agent (P1-1) was changed to (comparison P1) shown in Table 5}, and the amount of salt (S-1) {and water treatment agent (P2-1)} added was changed to the amount shown in Table 5. The supernatant filtrate was treated in the same manner as in Example 1, except that the amount of salt added was changed to the amount shown in Table 5. The COD and TOC of the supernatant filtrate were measured in the same manner as in Example 1. The results are shown in Table 5.

<Comparative Example 5>
1 L of wastewater from a chemical factory B containing an anionic surfactant was collected in a beaker, and while stirring, polyaluminum chloride ["Taipac 6010", manufactured by Taimei Chemical Industry Co., Ltd.] was added as an inorganic flocculant in an amount to give a solids concentration of 100 mg/L. After 1 minute, a 1 wt% aqueous solution of sulfuric acid was added dropwise while continuing the stirring to adjust the pH to 7.0. Then, while stirring, a 0.2 wt% aqueous solution of Sanfloc CE-706P (manufactured by Sanyo Chemical Industries Co., Ltd.) as a polymer flocculant was added in an amount to give a solids concentration of 10 mg/L, and the mixture was stirred for 3 minutes and then allowed to stand for 5 minutes. The left-standing supernatant was filtered through a filter paper (No. 5C), and the COD and TOC of the filtrate were measured in the same manner as in Example 1. The COD was 42 mg/L, and the TOC was 64 mg/L.

<Comparative Example 6>
The COD and TOC of the filtrate of the supernatant obtained by treating in the same manner as in Example 1, except that the quaternary ammonium salt (A1-1) was replaced with the cationic polymer (M-1) (the water treatment agent (P1-1) was replaced with a comparative water treatment agent (Comparative PM-1)) in Example 1, were measured. The COD was 33 mg/L and the TOC was 50 mg/L.

<Comparative Example 7>
1 L of wastewater from a chemical factory B containing an anionic surfactant was collected in a beaker, and 1,000 mg (100 mg of quaternary ammonium salt (A) solid content equivalent) of a water treatment agent (P1-7) was added under stirring, which was an aqueous solution in which a quaternary ammonium salt (A2-3) was dissolved in ion-exchanged water to a solid content concentration of 10% by weight. After 3 minutes, a 1% by weight aqueous sulfuric acid solution was added dropwise while continuing stirring to adjust the pH to 7.0. After stirring for 3 minutes, the mixture was allowed to stand for 5 minutes. The supernatant liquid that had been allowed to stand was filtered through a filter paper (No. 5C), and the COD and TOC of the filtrate were measured in the same manner as in Example 1. The COD was 50 mg/L, and the TOC was 76 mg/L.

<Comparative Examples 8 to 9>
In Comparative Example 7, the amount of the quaternary ammonium salt (A2-3) {water treatment agent (P1-7)} added was changed to the amount shown in Table 5. The supernatant filtrate was obtained in the same manner as in Comparative Example 7, but the amount was changed to the amount shown in Table 5. The COD and TOC were measured in the same manner as in Example 1. The results are shown in Table 5.

FIG. 1 shows a graph plotting the COD (mg/L) values against the amount (mg/L) of the solids of the quaternary ammonium salt (A) in the water treatment agent or comparative water treatment agent for combination (1) [combination of Examples 3, 38, 39] containing the same quaternary ammonium salt (A) (water treatment agent (A2-3)) and salt (S) (salt (S-1)), combination (2) [combination of Examples 7, 40, 41] containing the same quaternary ammonium salt (A) (water treatment agent (A3-3)) and salt (S) (salt (S-1)), combination (3) [combination of Examples 11, 42, 43] containing the same quaternary ammonium salt (A) (water treatment agent (A3-3)) and salt (S) (salt (S-1)), and combination (4) [combination of Comparative Examples 7, 8, 9] containing the same quaternary ammonium salt (A) (comparative treatment agent (ratio P)) but not salt (S). In the case of the comparative water treatment agent not containing salt (S), the COD decreased up to an addition amount of 250 mg of quaternary ammonium salt (A), and the COD increased when the addition amount was further increased, and it can be seen that there is an optimum point for the addition amount of quaternary ammonium salt (A). In contrast, in the case of the water treatment agent of the example containing salt (S), no increase in COD was observed even when an amount of quaternary ammonium salt (A) exceeding 250 mg, which was the optimum point for the comparative water treatment agent, was used. In other words, it can be seen that even under conditions where the addition amount of the water treatment agent is excessive, the increase in water-soluble COD components is suppressed, and a stable water-soluble COD component reduction effect is expressed. Furthermore, in the case of the water treatment agent of the example, it can be seen that the water-soluble COD component reduction effect is excellent even when the addition amount of quaternary ammonium salt (A) is less than 250 mg, which was the optimum point for the comparative water treatment agent.

For Examples 1 to 58 and Comparative Examples 2 to 9, the COD removal rate and TOC removal rate were calculated from the obtained COD and TOC values according to the following formula, and the effect of reducing water-soluble COD components of each water treatment agent was evaluated. The obtained results are shown in Tables 1 to 5.
COD removal rate (%) = (COD value before treatment - COD value after treatment) / COD value before treatment x 100
TOC removal rate (%)=(TOC value before treatment−TOC value after treatment)/TOC value before treatment×100
However, the COD value and TOC value before treatment in the above formula are 80 mg/L and 122 mg/L, respectively, as described in Comparative Example 1.
For each of the Examples and Comparative Examples, the weight ratio [(S)/(A)] of the quaternary ammonium salt (A) to the salt (S) is shown in Tables 1 to 5.

The results in Tables 1 to 5 show that the water treatment agents according to Examples 1 to 67 have higher COD removal rates and TOC removal rates than the water treatment agents according to the comparative examples, and are significantly more effective at reducing water-soluble COD components. Furthermore, the results of (1) Examples 3, 38, and 39, (2) Examples 7, 40, and 41, and (3) Examples 11, 42, and 43 in Figure 1 show that the water treatment agent of the present invention can achieve a stable water-soluble COD reduction effect over a wide range of added amounts of the water treatment agent (addition amount of quaternary ammonium salt (A) in the water treatment agent).

The water treatment agent of the present invention is very useful because, by being added to various industrial wastewater (wastewater from factories in the paper pulp, dyeing, automobile, metal processing, steelmaking, food, gravel extraction, semiconductor-related, and cleaning industries, etc.), sewage, purified water, and sludge (organic sludge and inorganic sludge) generated in the treatment of industrial wastewater, etc., it can suppress an increase in water-soluble COD components, even under conditions where the amount of the water treatment agent added is excessive, and can exhibit a stable water-soluble COD component reduction effect, and can exhibit a significantly excellent effect of reducing water-soluble COD components.

Claims

A water treatment agent comprising a quaternary ammonium salt (A) represented by any one of the following general formulas (1) to (3) and at least one salt (S) selected from the group consisting of silicates, phosphates and borates:

[In formula (1), n is an integer of 5 to 17 representing the number of repeating methylene groups, R 1 to R 3 each independently represent a methyl group, an ethyl group, a propyl group, or a butyl group, and X − represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent.]

[In formula (2), n is an integer of 5 to 17 representing the number of repeating methylene groups, and X − represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent.]

[In formula (3), n is an integer of 5 to 17 representing the number of repeating methylene groups, X- represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent, and Y is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.]
The water treatment agent according to claim 1, wherein the salt (S) contains a silicate.
The water treatment agent according to claim 1 or 2, wherein the weight ratio [(S)/(A)] of the quaternary ammonium salt (A) to the salt (S) in the water treatment agent is 0.1 to 20.
A water treatment method comprising: a step (I) of adding a quaternary ammonium salt (A) represented by any one of the following general formulas (1) to (3) to water to be treated; and a step (II) of adding at least one salt (S) selected from the group consisting of silicates, phosphates, and borates to the water to be treated.

[In formula (1), n is an integer of 5 to 17 representing the number of repeating methylene groups, R 1 to R 3 each independently represent a methyl group, an ethyl group, a propyl group, or a butyl group, and X − represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent.]

[In formula (2), n is an integer of 5 to 17 representing the number of repeating methylene groups, and X − represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent.]

[In formula (3), n is an integer of 5 to 17 representing the number of repeating methylene groups, X- represents a counter anion of an ammonium ion and is an anion group derived from a conjugate base of a Bronsted acid or a quaternizing agent, and Y is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.]
The water treatment method according to claim 4, characterized in that the step (II) is carried out after the step (I).
The water treatment method according to claim 4, comprising a step (III) of adding an inorganic coagulant to the water to be treated.
The water treatment method according to claim 6, characterized in that the step (II) is carried out after the steps (I) and (III).
The water treatment method according to claim 4, further comprising a polymer flocculant addition step of adding and mixing a polymer flocculant to the water to be treated after steps (I) and (II) to form coarse flocs.
8. The water treatment method according to claim 6 or 7, further comprising a polymer flocculant addition step of adding and mixing a polymer flocculant to the water to be treated after the steps (I), (II), and (III) have been performed, thereby forming coarse flocs.