JP5659746B2 - Water treatment apparatus and water treatment method - Google Patents

Description

  The present invention relates to a water treatment apparatus and a water treatment method.

  In a manufacturing process of an aqueous dispersion in a manufacturing factory of an electrostatic charge image developing toner (hereinafter sometimes simply referred to as “toner”), water containing a coloring component or the like is generated. Since these waters may contain coloring components such as pigments, dyes, surfactants, etc., the chemical oxygen demand (COD) is large as well as the solids concentration. It cannot be discharged into sewers. Therefore, these waters are reused after being processed at a water treatment facility in the factory or discharged to the outside.

  In particular, as a method for producing toner, various chemical toner production methods such as emulsion polymerization method, suspension polymerization method, dissolution suspension method and the like have been developed and implemented instead of conventional kneading and pulverization methods. . For example, in the emulsion polymerization method, a resin dispersion formed by emulsion polymerization of a polymerizable monomer of a binder resin, a colorant, a release agent, and a charge control agent as necessary in the presence of a surfactant, While stirring and mixing in an aqueous solvent, the toner particles are aggregated and heated and fused to produce toner particles that are colored resin particles having a predetermined particle size, particle size distribution, shape, and structure.

  In such an aggregation process of toner production, an organic compound such as ethylenediamine disuccinic acid (hereinafter sometimes referred to as “chelating agent”) that forms a coordinate bond with a metal ion may be used. . For this reason, a chelating agent-containing solution containing an organic compound that forms a coordination bond with a metal ion may be generated in the toner manufacturing process.

  Usually, as a general water treatment, a coagulation sedimentation treatment is often used. Coagulation and sedimentation treatment is the most common in the field of water treatment, as described on pages 141 to 153 of the technology and legal water quality edition (supervised by the Ministry of International Trade and Industry, Environmental Location Bureau, published in 2001). It is a solid-liquid separation operation used in Japan and is widely used. The coagulation sedimentation treatment is a treatment method in which flocs (coarse particles generated by aggregation) are generated by adding a flocculant to raw water, and solids and liquids are separated by precipitating the flocs due to the specific gravity difference between water and flocs. . The floc thus separated as a solid is treated as sludge for industrial waste, and the water from which the solid has been separated is reduced in chemical oxygen demand and reused or discharged into rivers and sewers.

  Further, Fenton treatment is known as a method for decomposing organic substances in water. The Fenton treatment is a method in which an organic substance is oxidatively decomposed by hydroxy radicals generated by a reaction between hydrogen peroxide and divalent iron ions.

  For example, Patent Document 1 discloses that the oxygen content of the raw water in a reaction tank containing iron powder is low for treating the COD and chromaticity of industrial wastewater generated from factories and livestock farms at low cost. A wastewater treatment method using iron powder is described in which an oxidizing agent is added and stirred so that the concentration becomes 1/20 to 1 times as a quantity, and a precipitation chamber is installed in the reaction tank or after the reaction tank It describes that a precipitation tank is installed in the process, and the precipitated iron powder is returned to the reaction tank.

Patent Document 2 discloses that wastewater containing organic substances is treated with Fenton using iron salt and hydrogen peroxide for the purpose of treating organic wastewater efficiently with a small amount of iron compounds, enabling the recycling of iron compounds. In this method, there is described a wastewater treatment method in which an electrode is provided in a reaction tank for performing Fenton treatment, and Fenton treatment is performed while Fe ³⁺ is electrochemically reduced.

  In Patent Document 3, for the purpose of reducing the burden on the environment, an oxidizing agent and an iron salt are added to a stock solution containing a hardly-decomposable organic substance to decompose the hardly-decomposable organic substance, and used. A method for treating a liquid containing a hardly decomposable organic substance that regenerates an iron salt and reuses it as an iron salt is described.

JP 2003-300083 A JP 2004-181329 A JP 2004-243162 A

  An object of the present invention is to provide a water treatment apparatus and a water treatment method for treating water containing an organic compound that forms a coordination bond with metal ions and reducing the amount of sludge generated.

The invention according to claim 1 is directed to water discharged from a manufacturing process of an electrostatic charge image developing toner containing an organic compound forming a coordinate bond with a metal ion, and subjecting the water to be processed to Fenton treatment. Fenton treatment means to be performed, solid-liquid separation means to perform solid-liquid separation of sludge of the Fenton-treated water subjected to the Fenton treatment, and the treatment target without reducing at least a part of the solid-liquid separated sludge And a return means for returning the water to the water treatment device.

  The invention according to claim 2 is the water treatment apparatus according to claim 1, further comprising a pH adjustment unit that adjusts the pH of the Fenton-treated water on a front side of the solid-liquid separation unit.

According to a third aspect of the present invention, water discharged from a manufacturing process of an electrostatic charge image developing toner containing an organic compound that forms a coordination bond with a metal ion is treated, and Fenton treatment of the water to be treated is performed. A Fenton treatment step to be performed; a solid-liquid separation step to perform solid-liquid separation of sludge of the Fenton-treated water subjected to the Fenton treatment; and water to be treated without reducing at least a part of the sludge separated into solid and liquid And a return process for returning to the water.

  The invention according to claim 4 is the water treatment method according to claim 3, further comprising a pH adjustment step of adjusting the pH of the Fenton-treated water on the upstream side of the solid-liquid separation step.

  According to the invention according to claim 1, the amount of generated sludge is reduced as compared with the case where there is no return means for returning at least part of the solid-liquid separated sludge to the water to be treated without reducing it. A water treatment apparatus is provided.

  According to the invention which concerns on Claim 2, compared with the case where it does not have the pH adjustment means which adjusts pH of Fenton treated water, the water treatment apparatus which the separability of the sludge in a solid-liquid separation means improves is provided.

  According to the invention of claim 3, water that reduces the amount of sludge generated compared to a case in which at least a part of the sludge separated into solid and liquid is not returned to the water to be treated without being reduced. A processing method is provided.

  According to the invention which concerns on Claim 4, compared with the case where the pH adjustment process which adjusts pH of Fenton treated water is not included, the water treatment method which the separability of the sludge in a solid-liquid separation process improves is provided.

It is a schematic structure figure showing an example of the water treatment equipment concerning the embodiment of the present invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  In order to make the Fenton reaction more efficient, the sludge generated in the Fenton treatment is reduced to ferrous ions contained in the sludge by electrical treatment or reducing agent addition treatment and reused as a catalyst for the Fenton reaction. It is known that when water containing an organic compound (chelating agent) that forms a coordinate bond with metal ions is treated with Fenton, some or all of the ferrous ions produced by reducing sludge May coordinate with the chelating agent and may not be effectively used as a catalyst for the Fenton reaction. For this reason, wasteful reduction treatment is performed, the amount of chemicals used is increased, the amount of sludge generated as a result is increased, and the cost is increased.

  The present inventors treated water containing an organic compound that forms a coordinate bond with a metal ion, performed solid-liquid separation of sludge from Fenton-treated water subjected to Fenton treatment, and at least one of the sludge separated into solid and liquid. It was found that the amount of chemical used or the amount of sludge generated is reduced by returning the water to the water to be treated as it is without reducing it. Since it is not necessary to perform sludge reduction treatment, capital investment required for reduction is suppressed. Moreover, the water quality of the treated water obtained improves.

  FIG. 1 shows a schematic configuration of an example of a water treatment apparatus for performing water treatment according to the present embodiment. The water treatment apparatus 1 according to the present embodiment includes a first Fenton reaction tank 12 and a second Fenton reaction tank 14 as Fenton treatment means, and a solid-liquid separation tank 18 as a solid-liquid separation means. On the front side of the first Fenton reaction tank 12, a raw water tank 10 for storing raw water may be provided, and the solid-liquid separation tank 18 on the rear side of the first Fenton reaction tank 12 and the second Fenton reaction tank 14 is provided. You may have the pH adjustment tank 16 as a pH adjustment means in the front | former stage side. The Fenton reaction tank as the Fenton treatment means may be composed of one tank or may be composed of two or more tanks.

  In the water treatment apparatus 1, piping or the like is connected to the inlet of the raw water tank 10, and the outlet of the raw water tank 10 and the inlet of the first Fenton reaction tank 12, the outlet of the first Fenton reaction tank 12, and the second Fenton reaction tank 14. The inlet, the outlet of the second Fenton reaction tank 14 and the inlet of the pH adjustment tank 16, and the outlet of the pH adjustment tank 16 and the inlet of the solid-liquid separation tank 18 are each connected by a pipe or the like. Etc. are connected. The lower part of the solid-liquid separation tank 18 and the first Fenton reaction tank 12 are connected by a return pipe 20 as a return means. The first Fenton reaction tank 12 and the pH adjustment tank 16 are provided with pH measuring devices 22 and 24 such as a pH meter, respectively, as pH measuring means. The first Fenton reaction tank 12, the second Fenton reaction tank 14, and the pH adjustment tank 16 may be provided with a stirring device having stirring blades or the like as stirring means. A coagulation treatment apparatus provided with an inorganic coagulant addition tank, a polymer coagulant addition tank, and a precipitation tank as a coagulation treatment means on the rear stage side of the solid-liquid separation tank 18, a biological treatment apparatus as a biological treatment means, and activated carbon adsorption treatment You may have the activated carbon adsorption processing apparatus etc. as a means.

  The operation of the water treatment apparatus 1 and the water treatment method according to this embodiment will be described with reference to FIG.

Raw water containing a chelating agent, which is water to be treated, is sent from the raw water tank 10 or the like to the first Fenton reaction tank 12 through piping or the like. In the first Fenton reaction vessel 12, a predetermined amount of ferrous ion catalyst (divalent iron salt) is added to the raw water through an addition pipe or the like. A pH adjuster may be added as necessary to adjust the pH to a predetermined range. The raw water to which the ferrous ion catalyst has been added is sent to the second Fenton reaction tank 14 through a pipe or the like. In the second Fenton reaction tank 14, a predetermined amount of hydrogen peroxide is added through an addition pipe or the like. In the 2nd Fenton reaction tank 14, a Fenton process is performed using a ferrous ion catalyst and hydrogen peroxide (Fenton process process). In the Fenton treatment step, ferrous ions (Fe ²⁺ ) react with hydrogen peroxide to generate hydroxy radicals, and organic substances such as chelating agents in the raw water are oxidatively decomposed by the generated hydroxy radicals.

The chelating agent is not particularly limited as long as it is an organic compound that forms a coordination bond with a metal ion. For example, an organic compound having 2 to 6 acid groups that form a coordination bond with a metal ion. Compounds. Examples of the acid group include a carboxyl group (—COOH group), a sulfo group (—SO ₃ H), and a phospho group (—P (═O) (OH) ₂ ). Examples of such chelating agents include nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), triethylenetetraaminehexaacetic acid (TTHA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethyliminodiacetic acid (HIDA), Dicarboxymethylglutaric acid tetrasodium salt (GLDA), dihydroxyethylglycine (DHEG), hydroxyethylethylenediaminetetraacetic acid (HEDTA), hydroxyethylethylenediaminetriacetic acid, ethylenediamine disuccinic acid (EDDS), L-glutamic acid diacetic acid (GLDA) 3-hydroxy-2,2′-iminodisuccinic acid (HIDS), L-aspartic acid-N, N-diacetic acid (ASDA), methylglycidin diacetate (MGDA), heptoglu Conic acid (GH-NA), amino polyvalent carboxylic acid compounds such as taurine-N, N-diacetic acid, polyvalent phosphonic acid compounds such as hydroxyethylidene diphosphonic acid (HEDP), or alkali metals such as sodium Examples thereof include salts and hydrates. The chelating agent is preferably water soluble.

  In the first Fenton reaction tank 12, the raw water is adjusted to an acidity of, for example, pH 2 or more and 3 or less by a pH adjusting agent such as an acid.

  Examples of the divalent iron salt include ferrous sulfate and ferrous chloride.

  The addition amount of the divalent iron salt is, for example, in the range of 250 mg / L to 1,000 mg / L with respect to the raw water to be treated. The amount of hydrogen peroxide added is, for example, in the range of 2,500 mg / L to 10,000 mg / L with respect to the raw water to be treated.

  In this embodiment, when the amount of the chelating agent in the raw water to be treated is in the range of 100 mg / L or more and 1,000 mg / L or less, the water treatment apparatus and the water treatment method according to this embodiment are suitable. Applies to When the amount of the chelating agent in the raw water is less than 100 mg / L, the coagulation sedimentation in the subsequent aggregation process of the Fenton treatment may be deteriorated due to an excessive reaction, and when it exceeds 1,000 mg / L, the Fenton reaction Decomposition by may be insufficient.

  The Fenton-treated water that has been subjected to the Fenton treatment may be sent to the pH adjustment tank 16, and the pH adjustment agent may be added to the pH adjustment tank 16 to adjust the pH (pH adjustment step). For example, by adjusting the pH within the range of 5 to 10, the sludge separability in the subsequent solid-liquid separation process is improved due to the aggregation of the sludge. Moreover, the residual hydrogen peroxide in the Fenton-treated water is reduced by adding a pH adjuster to adjust the pH.

  The pH-adjusted liquid whose pH has been adjusted is sent to the solid-liquid separation tank 18. In the solid-liquid separation tank 18, solid-liquid separation is performed into sludge generated by Fenton treatment and treated water (solid-liquid separation step).

  Examples of the solid-liquid separation means include a centrifugal separation tank, in addition to the solid-liquid separation tank by natural sedimentation.

  At least a part of the solid-liquid separated sludge is returned to the first Fenton reaction tank 12 through the return pipe 20 and the like without being reduced (returning step). Sludge that has been subjected to solid-liquid separation At least a part of the sludge that has been subjected to solid-liquid separation may be returned to the raw water to be treated as it is without being reduced, for example, may be returned to the raw water tank 10, You may return to the piping etc. which connect the water tank 10 and the 1st Fenton reaction tank 12. FIG.

The generated sludge contains iron hydroxide (Fe (OH) ₃ ) as the main component and contains ferric ions (Fe ³⁺ ), so the raw water to be treated as it is without reducing the sludge. The ferric ions are coordinated with the chelating agent in the raw water. Chelating agents having acid groups such as carboxyl group (—COOH group), sulfo group (—SO ₃ H), phospho group (—P (═O) (OH) ₂ ), especially amino polyvalent carboxylic acids such as EDTA It is considered that the compound is more easily coordinated with ferric ion (Fe ³⁺ ) than ferrous ion (Fe ²⁺ ). When the amount of ferric ions returned is larger than the amount of chelating agent in the raw water, the surplus ferric ions are used as a catalyst for Fenton treatment.

  Here, as a catalyst for the Fenton treatment, ferrous ions are known to have better reaction efficiency of the Fenton reaction than ferric ions, the amount of sludge to be returned is large, and the excess ferric iron If the number of ions increases, the reaction efficiency of the Fenton treatment decreases, and the COD-Mn removal rate tends to decrease. For this reason, the ferric ion necessary for the coordination bond with the chelating agent in the raw water is supplemented with the ferric ion contained in the return sludge, and the ferrous ion is used as the catalyst necessary for the Fenton treatment. Is preferred. The amount of sludge to be returned is preferably 0.67 or more and 1.33 or less in terms of a molar ratio with respect to the chelating agent as the amount of ferric ions contained in the sludge.

  The treated water separated in the solid-liquid separation tank 18 is sent to a coagulation treatment device on the rear stage side of the water treatment device 1 as needed, and a flocculant is added to grow the floc to perform the coagulation treatment. (Aggregation process). The aggregating apparatus is not particularly limited as long as it can perform the aggregating process. For example, the coagulation treatment apparatus includes an inorganic coagulant addition tank, a polymer coagulant addition tank, and a precipitation tank. In the agglomeration treatment, for example, in an inorganic flocculant addition tank, an inorganic flocculant is added to the treated water and an agglomeration reaction is performed to obtain an agglomerate. The polymer flocculant is added to the flocculent reaction liquid in the flocculant addition tank and the floc formation process for forming flocs from the flocculant, and the sludge slurry containing flocs and the separation liquid are separated by flocculent precipitation in the precipitation tank And a solid-liquid separation step. Note that a solid-liquid separation process such as a pressure levitation process may be performed instead of the coagulation sedimentation process.

  The agglomerated water that has been agglomerated in the agglomeration process is reused or discharged into a river or the like. If necessary, biological treatment, activated carbon adsorption treatment, sand filtration treatment, or the like may be performed after the aggregation treatment.

  For example, the separated liquid separated from the sludge slurry in the settling tank is sent to the biological treatment apparatus. Biological treatment is performed on the separated liquid in the biological treatment apparatus, and dissolved organic substances are removed (biological treatment step). In biological treatment, for example, dissolved organic matter is decomposed by bacteria or the like that live in activated sludge in a biological treatment tank, and separated into activated sludge and supernatant water by natural sedimentation or the like in the next sludge settling tank.

  The supernatant water (biologically treated water) separated in the biological treatment apparatus is sent to the activated carbon adsorption treatment apparatus. Activated carbon adsorption treatment is performed on the supernatant water in the activated carbon adsorption treatment apparatus, and COD components contained in the supernatant water are mainly adsorbed and removed by activated carbon (activated carbon adsorption treatment step).

  On the other hand, the sludge slurry separated from the separated liquid in the sedimentation tank is sent to a sludge concentrator or the like by a pump or the like. In the sludge concentrator, the sludge slurry is separated into a sludge separation liquid that is moisture and a solid content (separation step).

  The water treatment apparatus and the water treatment method according to the embodiment of the present invention treat water containing a chelating agent, and in particular, are discharged from a manufacturing process of an electrostatic charge image developing toner using a chelating agent. It is preferably applied to the treatment of water discharged from the production process by various chemical toner production methods such as an emulsion polymerization method, an emulsion aggregation method, a suspension polymerization method, and a dissolution suspension method. In the emulsion polymerization method, a resin dispersion formed by emulsion polymerization of a binder resin polymerizable monomer, a colorant, a release agent, and, if necessary, a charge control agent are stirred and mixed in an aqueous solvent. Then, toner particles that are colored resin particles having a predetermined particle size, particle size distribution, shape, and structure are produced by aggregation and heat fusion. The emulsion polymerization method is roughly divided into a production process of resin particles as a raw material of toner, a production process of a dispersion such as a colorant dispersion and a release agent dispersion, and a production process of an electrostatic charge image developing toner. . Each will be described below with an example.

<Process for producing toner for developing electrostatic image>
(Production process of resin particles)
In order to produce resin particles, a polymerizable monomer and a surfactant are usually added to water and stirred to form an emulsion. When a polymerizable monomer emulsion is formed, preferably 25% by mass or less (that is, a small amount of emulsion) of the emulsion and a free radical initiator are added to the aqueous phase and mixed, and seed polymerization is performed at a desired reaction temperature. To start. After the seed particles are generated, the remaining emulsion is further added to the seed particle-containing composition, and polymerization is continued at a predetermined temperature for a predetermined time to complete the polymerization, thereby generating resin particles (resin particle dispersion). . From this resin particle manufacturing process, a resin particle dispersion containing a solid content such as a surfactant, resin particles, or the like, which is no longer necessary in the manufacturing process or is generated by equipment maintenance in the manufacturing process, an aqueous surfactant solution Etc. are discharged. When the resin particles are produced, they are aggregated together with a colorant dispersion, a release agent dispersion and the like to form aggregate particles, which are then fused to form toner particles.

  The type of the polymerizable monomer is not particularly limited as long as it can react with a free radical initiator. Specific examples of the polymerizable monomer include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, Esters having a vinyl group such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile These polymerizable monomers are polymerized to form a homopolymer or a copolymer.

  Further, resins such as polyesters and polyurethanes may be sheared and dispersed in an aqueous medium together with a surfactant. Moreover, what contains an ammonia component as a resin particle is also used.

  As the surfactant used for the production of the resin particles, an anionic surfactant, a cationic surfactant or a nonionic surfactant may be used. Generally, an anionic surfactant is dispersed. It is preferably used because of its strong force and excellent dispersion of resin particles. The nonionic surfactant is preferably used in combination with the anionic surfactant or the cationic surfactant. The said surfactant may be used individually by 1 type, and may be used in combination of 2 or more type.

  Specific examples of anionic surfactants include fatty acid soaps such as potassium laurate, sodium oleate, and castor oil sodium; sulfate esters such as octyl sulfate, lauryl sulfate, lauryl ether sulfate, and nonyl phenyl ether sulfate; lauryl sulfonate , Sodium alkylarylsulfonates such as dodecylbenzenesulfonate, triisopropylnaphthalenesulfonate, dibutylnaphthalenesulfonate; sulfones such as naphthalenesulfonate formalin condensate, monooctylsulfosuccinate, dioctylsulfosuccinate, lauric acid amide sulfonate, oleic acid amide sulfonate Acid salts; lauryl phosphate, isopropyl phosphate, nonylphenyl ether phosphate Phosphoric acid esters such as Feto; dialkyl sulfosuccinate salts such as sodium dioctyl sulfosuccinate; sulfosuccinate salts such as sulfosuccinate lauryl disodium; and the like.

  Specific examples of the cationic surfactant include laurylamine hydrochloride, stearylamine hydrochloride, oleylamine acetate, stearylamine acetate, stearylaminopropylamine acetate, and other amine salts; lauryltrimethylammonium chloride, dilauryldimethylammonium Chloride, distearyldimethylammonium chloride, distearyldimethylammonium chloride, lauryldihydroxyethylmethylammonium chloride, oleylbispolyoxyethylenemethylammonium chloride, lauroylaminopropyldimethylethylammonium ethosulphate, lauroylaminopropyldimethylhydroxyethylammonium perchlorate, alkylbenzene Trimethylammonium chloride, Quaternary ammonium salts such as quilts trimethyl ammonium chloride; and the like.

  Specific examples of the nonionic surfactant include alkyl ethers such as polyoxyethylene octyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether; polyoxyethylene octyl phenyl ether, polyoxy Alkyl phenyl ethers such as ethylene nonyl phenyl ether; alkyl esters such as polyoxyethylene laurate, polyoxyethylene stearate, polyoxyethylene oleate; polyoxyethylene lauryl amino ether, polyoxyethylene stearyl amino ether, polyoxyethylene Alkylamines such as oleyl amino ether, polyoxyethylene soybean amino ether, polyoxyethylene beef tallow amino ether; Alkyl amides such as ethylene lauric acid amide, polyoxyethylene stearic acid amide, polyoxyethylene oleic acid amide; vegetable oil ethers such as polyoxyethylene castor oil ether and polyoxyethylene rapeseed oil ether; lauric acid diethanolamide, stearic acid Alkanolamides such as diethanolamide and oleic acid diethanolamide; sorbitan ester ethers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate And so on.

  There is no restriction | limiting in particular as a free radical initiator. Specifically, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide , Ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide and the like.

  In the present embodiment, the size of the resin particles is about 0.05 μm or more and 1 μm or less in terms of a volume average particle size measured with a laser diffraction particle size distribution measuring apparatus (Microtrack manufactured by Nikkiso Co., Ltd.).

(Manufacturing process of colorant dispersion and release agent dispersion)
The colorant dispersion is obtained by mixing a colorant, a surfactant and the like in an aqueous phase and performing a dispersion treatment. Similarly, the release agent dispersion is obtained by mixing a release agent, a surfactant and the like in an aqueous phase and performing a dispersion treatment. Coloring that contains solids such as surfactants and colorants, which are no longer necessary in the manufacturing process from the manufacturing process of the colorant dispersion and the release agent dispersion, or are generated by equipment maintenance in the manufacturing process. An agent dispersion, a release agent dispersion containing a solid content such as a surfactant and a release agent, an aqueous surfactant solution and the like are discharged.

  Examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, selenium yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, and Dupont. Oil red, pyrazolone red, resol red, rhodamine B rake, lake red C, rose bengal, aniline blue, ultramarine blue, chalcoa oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green oxalate, etc. Pigment: Acridine, xanthene, azo, benzoquinone, azine, anthraquinone, dioxadi System, thiazine, azomethine, indigo, thioindigo, phthalocyanine, aniline black, polymethine, triphenylmethane dyes, diphenylmethane dyes, and various dyes such as thiazole system. These colorants may be used alone or in combination of two or more.

  The size of the colorant in the colorant dispersion is, for example, about 0.05 μm or more and 0.5 μm or less in the volume average particle size measured by the laser diffraction particle size distribution measuring apparatus (Microtrack manufactured by Nikkiso Co., Ltd.). It is.

  The type of wax that acts as a mold release agent is not particularly limited. For example, low molecular weight polyolefins such as polyethylene, polypropylene, and polybutene; silicones having a softening point; oleic acid amide, erucic acid amide, ricinoleic acid amide, Fatty acid amides such as stearamide; plant waxes such as carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, micro And mineral waxes such as crystallin wax and Fischer-Tropsch wax; and ester waxes of higher fatty acids such as stearyl stearate and behenyl behenate and higher alcohols.

  The size of the release agent in the release agent dispersion is, for example, 0.05 μm or more and 0.5 μm in volume average particle diameter measured with the laser diffraction particle size distribution measuring apparatus (Microtrack manufactured by Nikkiso Co., Ltd.). It is about the following.

  Examples of the surfactant include the same surfactants used for the production of the resin particles.

(Toner manufacturing process)
The resin particles obtained by the above preparation method are used for toner preparation by the following method. Resin particles obtained by the above preparation method, a colorant dispersion, a release agent dispersion, an aggregating agent if necessary, a charge control agent if necessary, and other additives as necessary And the resulting mixture at a temperature near the glass transition temperature (Tg) of the resin particles, preferably Tg ± 10 ° C. of the resin particles, for a time effective to produce an aggregate, for example, 1 hour Heating for 8 hours or less produces a toner-sized aggregate. Next, this aggregate suspension is heated to a Tg of the resin particles or higher, preferably Tg + 40 ° C. of the resin particles, for example, about 60 ° C. to about 120 ° C. The toner particles are granulated, separated from the mother liquor by means of filtration or the like, washed with ion exchange water or the like (washing step), and then dried.

  The resin particles are usually used as a binder resin for toner, and are present in the toner in an amount of 75% by mass to 98% by mass with respect to the solid content of the toner.

  The colorant is usually present in the toner in an amount effective for coloring, for example, about 1 to 15% by mass, preferably about 3 to 10% by mass, based on the solid content of the toner.

  A preferable amount of the wax that functions as a release agent is about 5% by mass or more and 20% by mass or less based on the solid content of the toner.

  The coagulant used as necessary may be used in an amount effective for fusion, for example, about 0.01% by mass to 10% by mass with respect to the solid content of the toner. As the flocculant to be used, a compound having a monovalent or higher charge is preferable. Specific examples of the compound include the aforementioned anionic surfactants; acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid and oxalic acid; Examples include, but are not limited to, salts such as magnesium, sodium chloride, aluminum sulfate, calcium sulfate, ammonium sulfate, aluminum nitrate, silver nitrate, copper sulfate, sodium carbonate, and polyaluminum chloride. Preferred flocculants include those having a nitrogen component such as nitric acid.

  In addition, an organic compound (chelating agent) that forms a coordinate bond with a metal ion may be used in an aggregation step for generating an aggregate.

  The charge control agent may be used in an amount effective for charging, for example, 0.1% by mass or more and 5% by mass or less based on the solid content of the toner. Suitable charge control agents include, but are not limited to, alkyl pyridinium halides, bisulfates, charge control agents such as silica, and negative charge control agents such as aluminum complexes.

  In addition, inorganic particles or the like may be wet-added as an additive as necessary. Examples of inorganic particles to be wet-added include silica, alumina, titania, calcium carbonate, magnesium carbonate, and tricalcium phosphate, all of which are usually used as external additives on the toner surface, such as ionic surfactants and polymers. You may disperse | distribute in water with an acid, a polymer base, etc., and add wet as an inorganic particle dispersion liquid, such as a silica.

  The size of the inorganic particles used in the present embodiment in the dispersion is a volume average particle size measured by the laser diffraction particle size distribution measuring apparatus (Microtrack manufactured by Nikkiso Co., Ltd.) and is about 4 nm to 150 nm.

  The manufacturing process (including the toner cleaning process) such as the resin particle manufacturing process, the colorant dispersion manufacturing process, the release agent dispersion manufacturing process, and the toner manufacturing process is not necessary in the manufacturing process. Or a surfactant aqueous solution containing solids such as a surfactant, a colorant, a release agent, inorganic particles, and a toner, a resin particle dispersion, and a colorant dispersion generated during equipment maintenance in the manufacturing process. The surfactant-containing liquid such as the release agent dispersion, the inorganic particle dispersion, the toner dispersion, and the apparatus cleaning water is discharged. In addition, when a chelating agent is used in an aggregating step or the like for generating an aggregate, a chelating agent-containing solution that is not required in this manufacturing step or generated during equipment maintenance in the manufacturing step is generated. Sometimes. These raw waters are collected in a raw water tank or the like and treated by the above water treatment method.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

(Preparation of resin particle dispersion)
Styrene 320 parts by mass n-butyl acrylate 80 parts by mass Acrylic acid 10 parts by mass Dodecanethiol 10 parts by mass This solution 420 parts by mass, nonionic surfactant (manufactured by Sanyo Chemical Co., Ltd., Nonipol 400) 6 parts by mass, and anionic system A solution obtained by dissolving 10 parts by weight of a surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen SC) in 550 parts by weight of ion-exchanged water is placed in a flask to disperse and emulsify, and while stirring and mixing slowly for 10 minutes, 50 parts by mass of ion-exchanged water in which 4 parts by mass of ammonium persulfate was dissolved was added. Thereafter, the inside of the flask was sufficiently replaced with nitrogen and heated with stirring in an oil bath until the temperature in the system reached 70 ° C., and emulsion polymerization was continued for 5 hours to obtain a resin particle dispersion.

Resin particles obtained in the resin particle dispersion is 155nm where the laser diffraction particle size distribution measuring apparatus having a volume average particle diameter of the (manufactured by Nikkiso Co., Ltd. Microtrac) of resin particles (D ₅₀₎ was measured using a differential scanning calorimeter When the glass transition point of the resin was measured at a temperature rising rate of 10 ° C./min using Shimadzu Seisakusho Co., Ltd., DSC-50, it was 54 ° C., and a molecular weight measuring device (HLC-8020, manufactured by Tosoh Corporation) was used. The weight average molecular weight (polystyrene equivalent) was measured using THF as a solvent, and it was 33,000.

(Preparation of colorant dispersion)
Pigment 150 parts by weight Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 20 parts by weight Ion-exchanged water 400 parts by weight The above is mixed and dispersed with an optimizer, and a colorant dispersion is obtained. Prepared. The pigment is C.I. for yellow. I. Pigment Yellow 74 (manufactured by Dainichi Seika), C.I. I. Pigment Blue 15: 3 (manufactured by BASF), C.I. I. Pigment Red 122 (manufactured by Dainichi Seika Co., Ltd.) and carbon black (manufactured by Cabot Corp.) were used.

(Preparation of release agent dispersion)
Paraffin wax (manufactured by Nippon Seiwa Co., Ltd., HNP0190, melting point 85 ° C.) 50 parts by mass Cationic surfactant (manufactured by Kao Corporation, Sanisol B50) 5 parts by mass 200 parts by mass of ion-exchanged water Then, after dispersing using a homogenizer (IQA Ultra Turrax T50), the dispersion is performed with a pressure discharge type homogenizer, and a release agent having a volume average particle size of 550 nm is dispersed. A liquid was prepared.

(Preparation of toner for developing electrostatic image)
[Preparation of agglomerated particles]
Resin particle dispersion 200 parts by weight Colorant dispersion 30 parts by weight Release agent dispersion 70 parts by weight Cationic surfactant (manufactured by Kao Corporation, Sanisol B50) 1.5 parts by weight In a round stainless steel flask Then, the mixture was dispersed using a homogenizer (manufactured by IKA, Ultra Turrax T50), and then heated to 48 ° C. while stirring the inside of the flask in a heating oil bath. After maintaining at 48 ° C. for 30 minutes, observation with an optical microscope confirmed that aggregated particles (volume: 95 cm ³ ) having an average particle diameter of about 5 μm were formed. At the time of aggregation, 1.5 parts by mass of ethylenediaminetetraacetic acid tetrasodium (EDTA.4Na) (manufactured by Kirest Co., Ltd.) was used as a chelating agent.

[Preparation of adhered particles]
60 parts by mass of the resin particle dispersion was gently added to the prepared dispersion of aggregated particles. The volume of the resin particles contained in the resin particle dispersion was 25 cm ³ . And the temperature of the heating oil bath was raised to 50 degreeC, and was hold | maintained for 1 hour. When observed with an optical microscope, it was confirmed that adhered particles having an average particle diameter of about 5.7 μm were formed.

  Then, after adding 3 parts by mass of an anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) to the prepared dispersion of the adhered particles, the stainless steel flask was sealed and a magnetic seal was used. The mixture was heated to 105 ° C. and kept for 3 hours while stirring was continued. Then, after cooling, the reaction product was filtered, washed thoroughly with ion-exchanged water, and then dried to obtain an electrostatic image developing toner.

(Composition of water A to be treated)
The water A to be treated is water discharged from a toner production process such as the toner for developing an electrostatic image, and includes a colorant dispersion, a release agent (wax) dispersion, and resin particle dispersion. Water containing a liquid, a surfactant aqueous solution, a chelating agent-containing solution, and the like. The main composition of the water A to be treated is presumed to be as follows from the materials used in the preparation of the toner. Moreover, the measurement result of the chemical oxygen demand (COD-Mn) of this water was 1,600 mg / L.
Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2.0% by mass
Resin particles 2.0% by mass
Colorant 2.0% by mass
Wax (Polywax 725, manufactured by Toyo Petrolite Co., Ltd.) 1.0% by mass
Ethylenediaminetetraacetic acid tetrasodium (manufactured by Kirest Co., Ltd.) 0.08% by mass
92.92% by mass of water

  The chemical oxygen demand (COD-Mn) was measured by the method defined in JIS K 010217. Specifically, this is a test method in which an oxidant is added to a sample and allowed to react under a certain condition, and the amount of oxidant consumed at that time is expressed in terms of oxygen.

  The content of the chelating agent (here, EDTA) in water was measured using a high performance liquid chromatograph (manufactured by Hitachi High-Technologies).

(Pretreatment (sludge generation))
Fenton treatment was performed on the treatment target water A 1 L under the following conditions.
FeSO ₄ · _7H 2 O: iron as 600mg / L
Hydrogen peroxide (H ₂ O ₂ ): 6,000 mg / L
pH: 2.5
Reaction time: 2 hours Reaction temperature: 20 ° C
Sodium hydroxide (NaOH) was added to Fenton-treated water treated under the above conditions to adjust the pH to 9.5, and the mixture was allowed to stir and stay for 1 hour to decompose residual hydrogen peroxide. Filtered with 5A filter paper. The COD-Mn of filtered water was 595 mg / L, and the content of EDTA was 2 mg / L. The amount of sludge generated at this time was 1,435 mg / L. In the following examples, the sludge generated here was directly fed into the water to be treated without being subjected to reduction treatment as return sludge.

<Example 1>
Fenton treatment was performed on 500 mL of water A to be treated under the following conditions. The sludge generated in the pretreatment was directly fed to the water A to be treated as a return sludge without being reduced. The iron content in FeSO ₄ · 7H ₂ O is set to iron content so that the total amount of iron to be introduced into water A to be treated is 600 mg / L, and the proportion of iron in the return sludge is 25% by mass of the total iron content. 450 mg / L was added, and the iron content in the returned sludge was 150 mg / L as the iron content. Note that the iron content of 150 mg / L contained in the returned sludge corresponds to the amount of iron necessary for coordination with the chelating agent EDTA 800 mg / L of the water A to be treated.
Total iron amount: 600 mg / L
FeSO ₄ · _7H 2 O: iron as 450mg / L
Sludge: 150 mg / L as iron
Hydrogen peroxide (H ₂ O ₂ ): 6,000 mg / L
pH: 2.5
Reaction time: 2 hours Reaction temperature: 20 ° C
Sodium hydroxide was added to Fenton-treated water treated under the above conditions to adjust the pH to 9.5, and the mixture was allowed to stir for 1 hour to decompose residual hydrogen peroxide. Filtered with 5A filter paper. The COD-Mn of filtered water was 602 mg / L, and the residual amount of EDTA was 3 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 359 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

<Example 2>
The Fenton treatment is performed on 500 mL of the water A to be treated in the same manner as in Example 1 except that the ratio of the iron charged into the water A to be treated by the returned sludge is 16.7% by mass of the total iron amount as in the following conditions. Went.
Total iron amount: 600 mg / L
FeSO ₄ · 7H ₂ O: 500 mg / L as iron content
Sludge: 100mg / L as iron
Hydrogen peroxide (H ₂ O ₂ ): 6,000 mg / L
pH: 2.5
Reaction time: 2 hours Reaction temperature: 20 ° C
Sodium hydroxide was added to Fenton-treated water treated under the above conditions to adjust the pH to 9.5, and the mixture was allowed to stir for 1 hour to decompose residual hydrogen peroxide. Filtered with 5A filter paper. The COD-Mn of filtered water was 600 mg / L, and the residual amount of EDTA was 3 mg / L. The amount of sludge generated at this time was 1,435 mg / L, but since 287 mg / L was returned, the actual amount of sludge generated was 1,196 mg / L. The results are shown in Table 1.

<Example 3>
The Fenton treatment was performed on 500 mL of the water A to be treated in the same manner as in Example 1 except that the ratio of the iron introduced into the water A to be treated by the returned sludge was 33.3 mass% of the total iron amount as in the following conditions. Went.
Total iron amount: 600 mg / L
FeSO ₄ · _7H 2 O: iron as 400mg / L
Sludge: 200mg / L as iron
Hydrogen peroxide (H ₂ O ₂ ): 6,000 mg / L
pH: 2.5
Reaction time: 2 hours Reaction temperature: 20 ° C
Sodium hydroxide was added to Fenton-treated water treated under the above conditions to adjust the pH to 9.5, and the mixture was allowed to stir for 1 hour to decompose residual hydrogen peroxide. Filtered with 5A filter paper. The COD-Mn of filtered water was 610 mg / L, and the residual amount of EDTA was 4 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 478 mg / L was returned, so the actual amount of sludge generated was 956 mg / L. The results are shown in Table 1.

<Example 4>
The Fenton treatment is performed on 500 mL of the treatment target water A in the same manner as in Example 1 except that the ratio of iron to be introduced into the treatment target water A by return sludge is 50% by mass of the total iron amount as in the following conditions. It was.
Total iron amount: 600 mg / L
FeSO ₄ · _7H 2 O: iron as 300mg / L
Sludge: 300mg / L as iron
Hydrogen peroxide (H ₂ O ₂ ): 6,000 mg / L
pH: 2.5
Reaction time: 2 hours Reaction temperature: 20 ° C
Sodium hydroxide was added to Fenton-treated water treated under the above conditions to adjust the pH to 9.5, and the mixture was allowed to stir for 1 hour to decompose residual hydrogen peroxide. Filtered with 5A filter paper. The COD-Mn of filtered water was 680 mg / L, and the residual amount of EDTA was 15 mg / L. The amount of sludge generated at this time was 1,435 mg / L, but since 718 mg / L was returned, the actual amount of sludge generated was 718 mg / L. The results are shown in Table 1.

<Example 5>
Fenton treatment was performed on 500 mL of water A to be treated in the same manner as in Example 1 except that the following conditions were used.
Total iron amount: 550 mg / L
FeSO ₄ · _7H 2 O: iron as 450mg / L
Sludge: 100mg / L as iron
Hydrogen peroxide (H ₂ O ₂ ): 6,000 mg / L
pH: 2.5
Reaction time: 2 hours Reaction temperature: 20 ° C
Sodium hydroxide was added to Fenton-treated water treated under the above conditions to adjust the pH to 9.5, and the mixture was allowed to stir for 1 hour to decompose residual hydrogen peroxide. Filtered with 5A filter paper. The COD-Mn of filtered water was 650 mg / L, and the residual amount of EDTA was 12 mg / L. The amount of sludge generated at this time was 1,315 mg / L, but since 239 mg / L was returned, the actual amount of sludge generated was 1076 mg / L. The results are shown in Table 1.

<Example 6>
Fenton treatment was performed on 500 mL of water A to be treated in the same manner as in Example 1 except that the following conditions were used.
Total iron amount: 650 mg / L
FeSO ₄ · _7H 2 O: iron as 450mg / L
Sludge: 200mg / L as iron
Hydrogen peroxide (H ₂ O ₂ ): 6,000 mg / L
pH: 2.5
Reaction time: 2 hours Reaction temperature: 20 ° C
Sodium hydroxide was added to Fenton-treated water treated under the above conditions to adjust the pH to 9.5, and the mixture was allowed to stir for 1 hour to decompose residual hydrogen peroxide. Filtered with 5A filter paper. The COD-Mn of filtered water was 600 mg / L, and the residual amount of EDTA was 3 mg / L. The amount of sludge generated at this time was 1,555 mg / L. Of these, 479 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

<Example 7>
Fenton treatment was performed on 500 mL of the water to be treated A in the same manner as in Example 1 except that sodium hydroxide was not added to the Fenton-treated water, pH was not adjusted, and the reaction time was 1.6 h. Since pH adjustment was not performed on Fenton-treated water, solid-liquid separation was not performed, and in order to return 150 mg / L of iron to the raw water, it was necessary to return 125 mL corresponding to 1/4 of the total amount of Fenton-treated water as it was to the raw water. . In this case, in the continuous treatment as shown in FIG. 1, the reaction time (residence time) of the raw water is reduced and is inversely proportional to the total amount of the raw water and the return amount, so the reaction time is set to 1.6 h corresponding to the total amount. The COD-Mn of filtered water was 685 mg / L, and the residual amount of EDTA was 15 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 359 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

<Example 8>
Fenton treatment was performed on 500 mL of the water to be treated A in the same manner as in Example 1 except that sodium hydroxide was added to the Fenton-treated water to adjust the pH to 7. The COD-Mn of filtered water was 605 mg / L, and the residual amount of EDTA was 3 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 359 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

<Example 9>
Fenton treatment was performed on 500 mL of the water to be treated A in the same manner as in Example 1 except that sodium hydroxide was added to the Fenton-treated water to adjust the pH to 10. The COD-Mn of filtered water was 602 mg / L, and the residual amount of EDTA was 3 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 359 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

<Example 10>
Fenton treatment was performed on 500 mL of water A to be treated in the same manner as in Example 1 except that sodium hydroxide was added to the Fenton-treated water to adjust the pH to 4. The COD-Mn of filtered water was 625 mg / L, and the residual amount of EDTA was 7 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 359 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

<Example 11>
Fenton treatment was performed on 500 mL of water A to be treated in the same manner as in Example 1 except that sodium hydroxide was added to the Fenton-treated water to adjust the pH to 11. The COD-Mn of filtered water was 624 mg / L, and the residual amount of EDTA was 7 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 359 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

<Example 12>
Except for performing Fenton treatment on 500 mL of water B to be treated containing EDDS (ethylenediamine disuccinic acid) instead of EDTA so that COD-Mn of raw water is 1,600 mg / L, the same as in Example 1 Fenton treatment was performed. The COD-Mn of filtered water was 603 mg / L, and the residual amount of EDDS was 4 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 359 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

<Comparative Example 1>
About 500 mL of water to be treated A in the same manner as in Example 1 except that the return sludge was not charged as in the following conditions (the ratio of iron to be treated A is 0% by mass of the total amount of iron). Fenton treatment was performed.
Total iron amount: 600 mg / L
FeSO ₄ · _7H 2 O: iron as 600mg / L
Sludge: 0mg / L as iron (no charge)
Hydrogen peroxide (H ₂ O ₂ ): 6,000 mg / L
pH: 2.5
Reaction time: 2 hours Reaction temperature: 20 ° C
Sodium hydroxide was added to Fenton-treated water treated under the above conditions to adjust the pH to 9.5, and the mixture was allowed to stir for 1 hour to decompose residual hydrogen peroxide. Filtered with 5A filter paper. The COD-Mn of filtered water was 595 mg / L, and the residual amount of EDTA was 2 mg / L. The amount of sludge generated at this time was 1,435 mg / L. The results are shown in Table 1.

<Comparative example 2>
Fenton treatment was performed on 500 mL of water A to be treated in the same manner as in Example 1 except that the return sludge was reduced by an electrochemical method using an electrode. The COD-Mn of filtered water was 598 mg / L, and the residual amount of EDTA was 2 mg / L. The amount of sludge generated at this time was 1,435 mg / L. Of these, 359 mg / L was returned, so the actual amount of sludge generated was 1,076 mg / L. The results are shown in Table 1.

  As in Examples 1 to 12, the amount of sludge generated was reduced compared to Comparative Example 1 by returning at least a part of the solid-liquid separated sludge as it was to the water to be treated without reduction treatment. . Further, in Examples 1 to 6 and 8 to 11 in which the pH of the Fenton-treated water was adjusted, the separability of sludge was improved. Although the comparative example 2 which performed the reduction | restoration process compared with the comparative example 1, the amount of generated sludge was reduced, but the reduction process equipment and the reducing agent were needed.

  DESCRIPTION OF SYMBOLS 1 Water treatment apparatus, 10 Raw water tank, 12 1st Fenton reaction tank, 14 2nd Fenton reaction tank, 16 pH adjustment tank, 18 Solid-liquid separation tank, 20 Return piping, 22, 24 pH measurement apparatus.

Claims (4)

Water that is discharged from the manufacturing process of the toner for developing an electrostatic charge image containing an organic compound that forms a coordinate bond with a metal ion is a processing target.
Fenton treatment means for performing Fenton treatment of the water to be treated;
Solid-liquid separation means for performing solid-liquid separation of sludge of the Fenton-treated water subjected to the Fenton treatment;
A return means for returning to the water to be treated without reducing at least a part of the solid-liquid separated sludge;
A water treatment apparatus comprising:   2. The water treatment apparatus according to claim 1, further comprising a pH adjusting unit that adjusts the pH of the Fenton-treated water on a front side of the solid-liquid separating unit. Water that is discharged from the manufacturing process of the toner for developing an electrostatic charge image containing an organic compound that forms a coordinate bond with a metal ion is a processing target.
A Fenton treatment step of performing Fenton treatment of the water to be treated;
A solid-liquid separation step of performing solid-liquid separation of sludge of the Fenton-treated water subjected to the Fenton treatment;
A returning step of returning at least a part of the solid-liquid separated sludge to the water to be treated without reduction treatment;
A water treatment method comprising:   The water treatment method according to claim 3, further comprising a pH adjustment step for adjusting pH of the Fenton-treated water on a front stage side of the solid-liquid separation step.

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