TW201912588A - Water treatment method and water treatment device excellent in treatment efficiency and capable of facilitating a reduction reaction of ferric ions in water treatment using a Fenton reaction involving a reduction reaction of ferric ions - Google Patents

Abstract

The present invention provides a water treatment method, which is excellent in treatment efficiency and capable of facilitating a reduction reaction of ferric ions in water treatment using a Fenton reaction involving a reduction reaction of ferric ions. The water treatment method includes the following steps (a-i) and (a-ii): (a-i) the oxidization step for adjusting the pH value of the effluent containing pollutants under oxidization to be more than 1.0 and less than 4.0, and performing the Fenton reaction to oxidize the pollutants under oxidization; (a-ii) the reduction step for reducing the ferric ions in the reaction solution obtained from the oxidization step to ferrous ions in the presence of the iron reduction catalyst and metal ions other than iron.

Description

Water treatment method and water treatment device

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

Fenton Reaction is a reaction in which hydrogen peroxide is reacted with divalent iron ions to generate hydroxyl radicals. Hydroxyl radicals have strong oxidizing power and can be expected to be used in various fields such as sterilization, harmful substances, or decomposition of pollutants that are difficult to decompose by utilizing their strong oxidizing power.

The divalent iron ions used in the Fenton reaction are oxidized as the reaction progresses, thereby becoming ferric ions. For example, when the wastewater containing the oxidizing pollutant is treated by the Fenton reaction, the sludge containing the ferric compound becomes waste, and there is a problem that the treatment cost is high. In addition, as the Fenton reaction progresses, divalent iron ions are consumed, so that it is necessary to continue to generate divalent iron ions even during the treatment.

It is known that a part of the ferric ion generated in the Fenton reaction is partially reduced to a divalent iron ion in the presence of hydrogen peroxide. However, it is known that the reduction reaction is very slow compared to the Fenton reaction. On the other hand, a method of adding an iron reduction catalyst for promoting the reduction reaction and simultaneously performing a Fenton reaction and the reduction reaction is known. As an example of the above, an example in which activated carbon is added as an iron reduction catalyst is mentioned (Patent Document 1 and Patent Document 2).

According to the processing methods described in Patent Document 1 and Patent Document 2, the cost of processing waste can be suppressed as compared with the water treatment method using only the Fenton reaction. Further, since the divalent iron ions generated by the reduction reaction can be reused, the amount of divalent iron ions added can be reduced.

In the treatment methods described in Patent Document 1 and Patent Document 2, solid activated carbon is added to the reaction system. At this time, the activated carbon tends to aggregate, and it takes time to unravel the aggregate of the produced activated carbon. Therefore, the processing methods described in Patent Document 1 and Patent Document 2 may have low workability. In addition, once the agglomerated activated carbon is sometimes difficult to disperse in the reaction system.

On the other hand, a method of adding activated carbon to a reaction system after suspending it in a dispersion medium such as water is known (Patent Document 3). According to the treatment method described in Patent Document 3, a suspension obtained by suspending activated carbon in the dispersion medium can be supplied (added) to the waste liquid. Therefore, the processing method described in Patent Document 3 is excellent in workability. [Prior Art Document] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei.

[Problems to be Solved by the Invention] However, the treatment method described in Patent Document 3 may have lower treatment efficiency of the waste liquid than the method of adding solid activated carbon to the reaction system. Further, even when an iron reduction catalyst other than activated carbon is used, the same problem as described above may occur.

On the other hand, in the methods described in Patent Document 1 and Patent Document 2, the reduction reaction of ferric ions may be hindered. In this case, the processing efficiency in the water treatment may be lowered.

Therefore, in one aspect of the present invention, in the water treatment using the Fenton reaction accompanying the reduction reaction of ferric ions, a water treatment method which promotes a reduction reaction of ferric ions and is excellent in treatment efficiency and the water treatment are provided. The water treatment device used in the method.

In another aspect of the present invention, in the water treatment using the Fenton reaction accompanying the reduction reaction of ferric ions, a water treatment method which maintains the treatment efficiency and is excellent in workability and water treatment used in the water treatment method are provided. Device.

Further, in the present specification, the treatment efficiency in the water treatment is evaluated by the removal rate of total organic carbon (Total Organic Carbon) and the consumption of hydrogen peroxide. [Means for solving the problem]

The inventors have conducted efforts to promote the reduction reaction of ferric ions and improve the treatment efficiency in water treatment. As a result, it was found that the ferric ion and the iron-reducing catalyst and the metal ions other than iron coexist, and the reduction reaction of the ferric ion is carried out under the following condition (A), thereby satisfying the drainage standard and promoting the ferric iron. Reduction of ions. Further, it has been found that the treatment efficiency in water treatment is improved by promoting the reduction reaction of ferric ions, thereby completing the present invention.

On the other hand, the inventors have estimated that the reason for the decrease in the treatment efficiency in the water treatment is that the iron reduction catalyst is easily dispersed in contact with the air dissolved in the water due to dispersion in water, and the iron reduction catalyst is deactivated. In order to solve the above problems, the inventors have repeatedly conducted intensive studies, and as a result, it has been found that the reaction system is mixed with water selected from the group consisting of a divalent iron salt, a divalent iron oxide, a trivalent iron salt, and a ferric iron. The mixture of at least one of the groups consisting of oxides and the iron reduction catalyst suppresses deactivation of the iron reduction catalyst, thereby completing the present invention.

That is, the present invention has the following aspects. [1] A water treatment method comprising the following steps (ai) and (a-ii), (ai) an oxidation step of adjusting a pH of a wastewater containing an oxidizing pollutant by 1.0 or more and 4.0 or less, And performing a Fenton reaction to oxidize the oxidized pollutant, (a-ii) a reduction step, and reacting the oxidation step in the presence of a metal ion other than iron in the iron reduction catalyst The ferric ion in the liquid is reduced to a divalent iron ion. [2] The water treatment method according to [1], wherein the molar amount of the metal ion other than the iron in the reducing step/the mass of the iron reducing catalyst is represented by a ratio X of 0.3 mmol/ Above g and below 60 mmol/g. [3] The water treatment method according to [1] or [2] wherein, in the reducing step, a metal reagent for generating a metal ion other than the iron is used, the metal reagent being selected from the group consisting of a divalent metal, and a second At least one of the group consisting of a valence metal salt and a divalent metal oxide. [4] The water treatment method according to [3], wherein the metal reagent is at least one selected from the group consisting of manganese, manganese salts, manganese oxides, copper, copper salts, and copper oxides. [5] The water treatment method according to [3] or [4] wherein, in the oxidizing step, the use is selected from the group consisting of a divalent iron salt, a divalent iron oxide, a trivalent iron salt, and a trivalent iron oxide. At least one iron reagent in the group consisting of oxidizing the oxidized pollutant, before the oxidizing step, comprising a mixing step, the mixing step is to reduce the catalyst, the metal reagent and At least two of the groups consisting of the iron reagents are mixed. [6] A water treatment method comprising the following steps (bi) and (b-ii), the step (bi) comprising the following step (A), (bi) an oxidation step, which comprises oxidizing The pH of the drain of the pollutant is adjusted to 1.0 or more and 4.0 or less, and the Fenton reaction is performed to oxidize the oxidized pollutant, and the (b-ii) reduction step is carried out in the presence of the iron reduction catalyst. The ferric ion in the reaction liquid obtained in the step (bi) is reduced to a divalent iron ion, (A) an addition step in which the addition of water in the drainage is selected from the group consisting of a ferrous salt and a ferrous iron. a mixture of at least one of the group consisting of an oxide, a ferric salt, and a trivalent iron oxide with the iron reduction catalyst. [7] The water treatment method according to any one of [1] to [6] comprising the following steps (iii) to (v), (iii) an insolubilization step, the obtained in the oxidation step The pH of the reaction liquid is adjusted to 6.0 or more and 10.0 or less, and the divalent iron ions and the ferric ions generated by the Fenton reaction are insolubilized to form a divalent iron compound and a ferric iron compound, and (iv) concentrated. a step of separating a suspension in which the divalent iron compound and the ferric iron compound are suspended into a sludge containing at least the ferric compound and treated water to obtain the suspended suspension in which the sludge is concentrated The liquid, (v) the suspension is returned to the step, and at least a portion of the suspension is returned to the oxidation step. [8] The water treatment method according to [7], wherein in the concentration step, the suspension is obtained using a filtration membrane. [9] The water treatment method according to [7] or [8], comprising a separation step of separating the treated water into the treated water using a nanofiltration membrane or a reverse osmosis membrane The oxidized pollutants and the permeated water. [10] The water treatment method according to any one of [1] to [9] wherein the iron reduction catalyst is at least one selected from the group consisting of activated carbon and zeolite. [11] The water treatment method according to any one of [1] to [10] wherein, in the oxidizing step, the pH of the drainage water is adjusted to 1.0 or more and 4.0 or less using an acid. [12] A water treatment apparatus comprising the following (a-1), (a-1) reaction tank for oxidizing an oxidizing pollutant contained in the drainage by a Fenton reaction, and reducing the iron The trivalent iron ions generated by the Fenton reaction are reduced to divalent iron ions in the presence of a catalyst and a metal ion other than iron. [13] The water treatment device according to [12], wherein the molar amount of metal ions other than the iron in the reaction tank/the mass of the iron reduction catalyst is represented by a ratio X of 0.3 mmol/ Above g and below 60 mmol/g. [14] The water treatment device according to [12] or [13], comprising: an iron reagent addition mechanism, wherein the reaction tank is added with a salt selected from the group consisting of a divalent iron salt, a divalent iron oxide, and a trivalent iron salt. And at least one iron reagent in the group consisting of trivalent iron oxide; a catalyst addition mechanism, adding the iron reduction catalyst to the reaction tank; and a metal reagent addition mechanism added to the reaction tank A metal reagent for generating metal ions other than the iron. [15] The water treatment device according to [14], wherein the metal ion concentration measuring unit measures the total amount of the drainage water flowing into the reaction tank. The metal reagent addition means adds the metal reagent based on the measurement result of the metal ion concentration measuring unit. [16] The water treatment device according to [14] or [15], which has a mixing mechanism upstream of the reaction tank, the mixing mechanism will be composed of the iron reagent, the iron reduction catalyst, and the metal At least two of the groups consisting of reagents are mixed to obtain a mixture. [17] The water treatment device according to [16], which has an intermediate tank that stores the mixture and supplies the stored mixture to the reaction tank. [18] A water treatment apparatus comprising the following (b-1) and (b-2), (b-1) reaction tanks for oxidizing pollutants contained in the drainage by a Fenton reaction; Oxidizing, and using iron reducing catalyst to reduce ferric ions generated by the Fenton reaction into divalent iron ions, (b-2) a mixture adding mechanism, and adding the mixed water in the reaction tank A mixture of at least one of the group consisting of a divalent iron salt, a divalent iron oxide, a trivalent iron salt, and a trivalent iron oxide and an iron reduction catalyst is selected. [19] The water treatment device according to [18], which has a mixing mechanism selected from the group consisting of the divalent iron salt, the divalent iron oxide, the trivalent iron salt, and the trivalent iron oxide. At least one of the group consisting of is mixed with the iron reduction catalyst in water. [20] The water treatment device according to [18] or [19], which includes an intermediate tank that stores the mixture. [21] The water treatment device according to any one of [12] to [20], comprising the following (3) to (5), (3) an insolubilization tank, the reaction liquid supplied from the reaction tank The divalent iron ion and the ferric ion contained therein are insolubilized to form a divalent iron compound and a ferric iron compound, and (4) a concentration device that suspends the divalent iron compound and the third The suspension of the ferrous compound is separated into a sludge containing at least the ferric compound and treated water to obtain the suspension in which the sludge is concentrated, and (5) the suspension is returned to the mechanism, and the suspension is suspended. At least a portion of the liquid is returned to the reaction tank. [22] The water treatment device according to [21], comprising: a first pH adjusting device that supplies an acid or a base to the reaction tank to adjust a pH of the drainage; and a second pH adjusting device that A base is supplied to the insolubilization tank to adjust the pH of the reaction liquid. [23] The water treatment device according to [22], wherein the acid is sulfuric acid or hydrochloric acid. [24] The water treatment device according to any one of [21], wherein the concentrating device has a filtration membrane, and the suspension is obtained using the filtration membrane. [25] The water treatment device according to any one of [21], wherein the concentration device is disposed in the insolubilization tank. [26] The water treatment device according to any one of [21], comprising a separation device having a nanofiltration membrane or a reverse osmosis membrane, and using the nanofiltration membrane or The reverse osmosis membrane separates the treated water into the oxidized pollutants and permeate water contained in the treated water. [Effects of the Invention]

According to an aspect of the present invention, in a water treatment using a Fenton reaction accompanied by a reduction reaction of ferric ions, a water treatment method which promotes a reduction reaction of ferric ions and is excellent in treatment efficiency and the water treatment is provided. The water treatment device used in the method.

According to another aspect of the present invention, in the water treatment using the Fenton reaction accompanying the reduction reaction of ferric ions, a water treatment method which maintains the treatment efficiency and is excellent in workability and a method used in the water treatment method are provided. Water treatment unit.

<<Embodiment of the Invention>> Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, in all of the following drawings, the size, ratio, and the like of the respective constituent elements are appropriately changed in order to facilitate the observation of the drawings.

<First Embodiment> The water treatment method according to the first embodiment includes the following step (ai), the following step (a-ii), the following step (iii), the following step (iv), and the following steps (v). ). (a-i) The oxidation step adjusts the pH of the wastewater containing the oxidizing pollutants to 1.0 or more and 4.0 or less, and performs a Fenton reaction to oxidize the oxidized pollutants. (a-ii) a reduction step of reducing ferric ions in the reaction liquid obtained in the oxidation step to divalent iron ions in the presence of a metal ion other than iron in the iron reduction catalyst. (iii) In the insolubilization step, the pH of the reaction liquid obtained in the oxidation step is adjusted to 6.0 or more and 10.0 or less, and the divalent iron ion and the ferric ion are insolubilized to form a divalent iron compound and a ferric iron compound. (iv) a concentration step of separating a suspension in which the divalent iron compound and the ferric compound are suspended into a sludge containing at least the ferric compound and treated water to obtain a concentrated suspension of the sludge liquid. (v) a suspension return step, at least a portion of the suspension being returned to the oxidation step.

Hereinafter, "metal ions other than iron" may be simply referred to as "metal ions". The combination of divalent iron ions and ferric ions is sometimes referred to as "iron ion". The combination of a divalent iron compound and a trivalent iron compound is sometimes referred to as an "iron compound". The sludge typically comprises a divalent iron compound and a ferric iron compound. In the present embodiment, the insolubilization step may be a step of adjusting the pH of the reaction liquid obtained in the oxidation step to 6.0 or more and 10.0 or less to insolubilize the divalent iron ions and the ferric ions to form a divalent iron compound and three. The iron compound is valence, and the metal ion is insolubilized to form a metal compound. In this case, the suspension separated into the sludge and the treated water in the concentration step is suspended in an iron compound and a metal compound, and the sludge contains a metal compound and an iron compound.

[Water Treatment Apparatus] Hereinafter, the configuration of the water treatment apparatus used in the water treatment method of the first embodiment will be described. Fig. 1 is a view showing a schematic configuration of a water treatment device according to a first embodiment. The water treatment device 1 shown in FIG. 1 includes a reaction tank 11, an insolubilization tank 21, an adjustment tank 41, and a storage tank 61.

In the present specification, when water flows from the reaction tank 11 to the storage tank 61, the side of the reaction tank 11 may be referred to as "upstream", and the side of the storage tank 61 may be referred to as "downstream".

The water treatment device 1 includes a pH adjustment device 14 , an iron reagent addition mechanism 15 , a hydrogen peroxide addition mechanism 16 , a catalyst addition mechanism 17 , and a metal reagent addition mechanism 18 in the reaction tank 11 .

Regarding the water treatment device 1, the pH adjustment device 24 is included in the insolubilization tank 21. Further, a concentration device 22 is provided in the insolubilization tank 21.

In the present specification, the pH adjusting device 14 corresponds to the first pH adjusting device in the patent application. Further, the pH adjusting device 24 corresponds to the second pH adjusting device in the patent application.

The water treatment device 1 includes a metal ion concentration measuring unit 19 upstream of the reaction tank 11.

In the water treatment device 1, a suspension return mechanism 32 is included between the insolubilization tank 21 and the reaction tank 11.

Regarding the water treatment device 1, a separation device 42 is included between the adjustment tank 41 and the storage tank 61.

(Drainage) In the water treatment by the water treatment device 1, the wastewater containing the oxidizing pollutants is oxidized by the Fenton reaction. Examples of the oxidizing contaminant include an organic substance which is difficult to be decomposed by biological treatment, or an inorganic substance such as phosphorous acid or hypophosphorous acid.

Examples of the organic substance include an organic solvent such as 1,4-dioxane, a humic substance, and an aldehyde which is not equivalent to any of an organic solvent and a humic substance. The term "humic substance" refers to a fraction obtained by extracting soil with an alkali such as sodium hydroxide, or an extract obtained by extracting soil with natural water is adsorbed to XAD resin (styrene or acrylic acid and divinylbenzene). The copolymer), and further a fraction which is eluted from the adsorbate by a dilute aqueous alkali solution.

Examples of the aldehydes include propionaldehyde.

Phosphorous acid and hypophosphorous acid are contained in the factory drainage of the plating plant.

(Reaction tank) In the reaction tank 11, the oxidizing pollutant contained in the wastewater is oxidized by the Fenton reaction, and is generated by the Fenton reaction in the presence of the iron reduction catalyst and the metal ion. The ferric ion is reduced to a divalent iron ion. The reaction tank 11 is a metal reagent containing at least hydrogen peroxide, iron reagent (Fe ²⁺ ), iron reduction catalyst, and metal reagent for generating metal ions. In the present specification, the metal reagent means a reagent containing a metal other than iron.

The first flow path 12 and the second flow path 13 are connected to the reaction tank 11. The first flow path 12 inflows (supplies) the drainage containing the oxidizing pollutants into the reaction tank 11. The second flow path 13 allows the reaction liquid discharged from the reaction tank 11 to flow (feed) into the insolubilization tank 21.

In the present embodiment, the metal ion concentration measuring unit 19 is included in the middle of the first flow path 12. The metal ion concentration measuring unit 19 will be described later.

In the water treatment device 1 shown in FIG. 1, the method of supplying the reaction liquid from the reaction tank 11 to the insolubilization tank 21 is not particularly limited, and the reaction liquid may be supplied using a pump or may be supplied to the reaction liquid by overflow.

Further, an example in which one reaction tank 11 is provided in the water treatment device 1 shown in Fig. 1 is shown, but a plurality of reaction tanks 11 may be arranged in series. In this case, the time taken for the Fenton reaction can be lengthened, so that the hydrogen peroxide can be sufficiently consumed by the Fenton reaction.

Further, when a plurality of reaction tanks 11 are disposed, the method of supplying liquid from the first reaction tank to the second reaction tank is not particularly limited, and a pumping liquid may be used, or an overflow liquid may be used. Further, in the present specification, the first reaction tank and the second reaction tank constitute a reaction tank in the scope of the patent application.

(Iron reagent addition mechanism) The iron reagent addition mechanism 15 adds an iron reagent to the reaction tank 11.

The iron reagent is not particularly limited as long as it is dissolved in water to generate divalent iron ions. The oxidized contaminant contained in the drainage is oxidized by the generated divalent iron ions. The iron reagent is at least one selected from the group consisting of a divalent iron salt, a divalent iron oxide, a trivalent iron salt, and a trivalent iron oxide, preferably a divalent iron salt and a divalent iron oxide. At least one of them. Among them, iron sulfate or ferric chloride is preferred in that it is not required to be managed in the drainage standard and is excellent in solubility. Further, in terms of high versatility and low corrosivity, it is more preferably iron sulfate.

Further, in the present embodiment, since the ferric ion is reduced by the ferric reduction catalyst and the divalent iron ions are regenerated, a ferric compound can be used as the iron reagent.

As the iron reagent, a solid state may be added to the reaction vessel 11, or a liquid state such as an aqueous solution of an iron reagent may be added to the reaction vessel 11.

(Hydrogen peroxide addition means) The hydrogen peroxide addition means 16 adds hydrogen peroxide to the reaction tank 11.

The divalent iron ions in the reaction tank 11 react with hydrogen peroxide to generate hydroxyl radicals. When the oxidizing contaminant contained in the drainage is an organic substance, the organic substance is oxidatively decomposed by the generated hydroxyl radical. Further, in the case of an inorganic substance such as phosphorous acid or hypophosphorous acid, it is oxidized by a hydroxyl radical, and the phosphorous acid becomes orthophosphoric acid, and the hypophosphorous acid becomes phosphorous acid or orthophosphoric acid.

On the other hand, in the reaction vessel 11, by the action of hydrogen peroxide, the divalent iron ions are oxidized to become ferric ions.

In the present embodiment, in addition to the Fenton reaction, hydrogen peroxide can be used in the reduction reaction of ferric ions generated by the Fenton reaction. Therefore, it is preferred that the amount of hydrogen peroxide added from the hydrogen peroxide addition mechanism 16 is larger than the theoretical value used in the Fenton reaction.

When a plurality of reaction tanks 11 are disposed, it is preferable that the reaction tank 11 to which hydrogen peroxide is added from the hydrogen peroxide addition mechanism 16 is a tank other than the reaction tank 11 at the most downstream. The more upstream the reaction tank 11 to which hydrogen peroxide is added, the longer it takes for the Fenton reaction to take longer, so that the hydrogen peroxide can be sufficiently consumed by the Fenton reaction. Therefore, it is possible to suppress the unreacted hydrogen peroxide from leaking into the insolubilization tank 21 and the adjustment tank 41 downstream of the reaction tank 11. In addition, an increase in the amount of chemical oxygen required in the treated water caused by unreacted hydrogen peroxide can be suppressed.

(First pH Adjusting Device) The pH adjusting device 14 adjusts the pH in the reaction tank 11 by adding an acid or a base to the reaction tank 11 in accordance with the pH in the tank.

The inside of the reaction tank 11 is adjusted so that the iron reagent can be dissolved in water to generate divalent iron ions and the pH of the hydroxyl radicals is generated. In the present embodiment, the inside of the reaction vessel 11 is acidic, and specifically, it is adjusted to be in the range of 1.0 or more and 4.0 or less. When the pH in the reaction tank 11 is 1.0 or more and 4.0 or less, the solubility of the iron reagent with respect to water can be favorably maintained, and the contact efficiency between the ferric ion and the iron reduction catalyst can be improved. The pH in the reaction tank 11 is preferably 2.0 or more and 3.0 or less, more preferably 2.5 or more and 3.0 or less.

Moreover, it is preferable to provide a measuring apparatus (not shown) which measures the pH in the tank in the reaction tank 11.

Examples of the type of the acid include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and organic acids such as oxalic acid, citric acid, formic acid, and acetic acid. Among them, sulfuric acid or hydrochloric acid is preferred, and in view of the difficulty in capturing the hydroxyl radical generated in the Fenton reaction, sulfuric acid is more preferred. These acids may be used alone or in combination of two or more.

Examples of the type of the base include sodium hydroxide, sodium carbonate, calcium hydroxide, and magnesium hydroxide. Among them, sodium hydroxide is preferred because it is highly versatile and does not react with a substance formed in the Fenton reaction. These bases may be used alone or in combination of two or more.

(Ceramic Addition Mechanism) The catalyst addition mechanism 17 adds an iron reduction catalyst to the reaction tank 11.

The iron reduction catalyst may be a reactor which does not substantially inhibit the Fenton reaction and promotes reduction of ferric ions by hydrogen peroxide and reduction of ferric ions. The iron reduction catalyst is preferably at least one selected from the group consisting of activated carbon and zeolite, and more preferably activated carbon from the viewpoint of catalyst efficiency or treatment of the spent catalyst. The iron reduction catalyst can also be supported on the substrate.

The mass concentration of the iron reduction catalyst relative to the total amount of the reaction liquid is preferably 50,000 mg/L or less. When the mass concentration of the iron reduction catalyst is 50,000 mg/L or less, the decomposition reaction of hydrogen peroxide by the iron reduction catalyst can be suppressed. Further, it is easy to concentrate the sludge containing the iron compound in which iron ions are insolubilized by using a concentration device to be described later. Further, when the suspension is returned to the reaction tank 11 under the above conditions, when the pH is adjusted in the reaction tank 11, the amount of the acid used can be suppressed. In the case where the iron reduction catalyst is supported on the substrate, the mass of the iron reduction catalyst is the mass after removing the mass of the substrate.

The shape of the iron reduction catalyst is preferably in the form of a powder from the viewpoint of catalyst efficiency. Further, the particle diameter of the iron reduction catalyst is preferably from 0.05 μm to 100 μm from the viewpoint of easy recovery of the catalyst.

(Metal Reagent Adding Mechanism) The metal reagent adding mechanism 18 adds a metal reagent to the reaction tank 11.

Previously, in the water treatment using the Fenton reaction accompanying the reduction reaction of ferric ions, the reduction reaction of ferric ions may be hindered. In this case, the processing efficiency in the water treatment may be lowered.

In the present specification, the treatment efficiency in the water treatment is evaluated by the removal rate of total organic carbon (hereinafter, TOC) and the consumption amount of hydrogen peroxide.

The so-called TOC is the total amount of oxidizable organic matter in water expressed by the amount of carbon. The TOC removal rate was calculated based on the TOC concentration in the drain (raw water) and the TOC concentration in the treated water obtained after the water treatment, based on the formula (S1).

[Number 1] ···(S1)

In the present embodiment, it can be said that the higher the TOC removal rate of the treatment in a certain period of time, the more excellent the processing efficiency.

Further, the amount of hydrogen peroxide consumed is determined by the mass concentration of hydrogen peroxide with respect to the total amount of treated water.

As a method of measuring the mass concentration of hydrogen peroxide with respect to the total amount of treated water, a method of sampling the treated water and developing the hydrogen peroxide of the sampled treated water using potassium iodide by absorbance luminosity is exemplified. The measurement is carried out (for example, manufactured by Kyoritsu Chemical Co., Ltd., product name "Digital PACK TEST"). Further, as another method, a method in which the relative refractive index of the sampled water to be sampled is measured by a refractometer, and the mass concentration of hydrogen peroxide is calculated from the relative refractive index. Further, a method of measuring the density of the sampled treated water by a densitometer and calculating the mass concentration of hydrogen peroxide based on the density may be mentioned. Further, a method of measuring the mass concentration of hydrogen peroxide by an oxygen electrode method may be mentioned.

In the present embodiment, it can be said that the lower the mass concentration of hydrogen peroxide with respect to the total amount of treated water after the treatment for a certain period of time, the higher the consumption amount of hydrogen peroxide, and the more excellent the treatment efficiency.

In the present embodiment, evaluation is performed by either or both of the TOC removal rate and the mass concentration of hydrogen peroxide with respect to the total amount of treated water.

In order to solve the above problems, the inventors and others have made an effort to study. As a result, it was found that the ferric ion was efficiently reduced to divalent iron ions by coexisting the iron reducing catalyst with the metal ions, thereby completing the invention of the present aspect.

The metal reagent used in the present embodiment is not particularly limited as long as it is dissolved in water and generates metal ions. The metal ions generated by the metal reagent do not substantially hinder the Fenton reaction and promote the reduction reaction of ferric ions caused by hydrogen peroxide and an iron reduction catalyst.

The metal reagent used in the present embodiment is preferably at least one selected from the group consisting of a divalent metal salt and a divalent metal oxide. Further, the metal reagent is preferably at least one selected from the group consisting of a manganese salt, a manganese oxide, a copper salt, and a copper oxide in terms of being inexpensive, easy to obtain, and easy to manage in the drainage standard. Further, the metal reagent used in the present embodiment is preferably a sulfate or a hydrochloride in that it is not required to be managed in the drainage standard and is excellent in solubility.

As the metal reagent in the present embodiment, a solid state may be added to the reaction vessel 11, or a liquid state may be obtained by adding an aqueous solution of a metal reagent to the reaction vessel 11.

The ratio X of the amount of metal ions in the reaction vessel 11 / the mass of the iron reduction catalyst is preferably 0.3 mmol / g or more and 60 mmol / g or less. That is, when the mass concentration of the iron reduction catalyst relative to the total amount of the reaction liquid in the reaction tank 11 is 1000 mg/L, it is preferable that the metal is relative to the total amount of the reaction liquid in the reaction tank 11. The molar concentration of the ions is set to be 0.3 mmol/L or more and 60 mmol/L or less. When the ratio X is within the above range, the reduction reaction of ferric ions can be promoted and managed within the drainage standard.

When the ratio X is 0.3 mmol/g or more, the effect of promoting the reduction reaction of ferric ions can be sufficiently obtained. Further, when the ratio X is 60 mmol/g or less, the metal ions in the treated water can be managed within the drainage standard. On the other hand, in the case where the ratio X exceeds 60 mmol/g, especially in the case where the metal reagent is a manganese salt or a manganese oxide, manganese ions promote the decomposition reaction of hydrogen peroxide. As a result, the amount of hydrogen peroxide which can be used in the reduction reaction of the Fenton reaction or ferric ion is small. Therefore, there is a drop in processing efficiency in water treatment.

The ratio X is preferably 5 mmol/g or more, more preferably 15 mmol/g or more, and still more preferably 30 mmol/g or more. Further, the ratio X is preferably 50 mmol/g or less, more preferably 45 mmol/g or less, and still more preferably 40 mmol/g or less. The upper limit and the lower limit of the ratio X of the present embodiment can be arbitrarily combined. The ratio X may be, for example, 5 mmol/g or more and 50 mmol/g or less, or may be 15 mmol/g or more and 45 mmol/g or less, and may be 30 mmol/g or more and 40 mmol/g or less.

(Metal Ion Concentration Measurement Unit) The metal ion concentration measurement unit 19 measures the concentration of the metal ions of the present embodiment with respect to the total amount of the drainage water flowing into the reaction tank 11. The metal reagent addition mechanism of the present embodiment is based on the measurement result of the metal ion concentration measuring unit 19, and the molar concentration of the metal ions in the present embodiment with respect to the total amount of the reaction liquid in the reaction tank 11 is in the above range. Add a metal reagent.

The method for measuring the concentration of the metal ions in the present embodiment includes a method of sampling the drainage, and coloring the metal ions of the embodiment contained in the sampled drainage using a colorimetric reagent, and using the spectrophotometer. (For example, the company is manufactured by Kyoritsu Chemical Co., Ltd., and the product name is "Digital PACK TEST Multi").

In addition, the method of measuring the concentration of the metal ions in the present embodiment is not limited to the above method, and for example, a flame according to Japanese Industrial Standards (JIS) K 0102:2013 "factory drainage test method" may be used. Atomic absorption method, electric heating atomic absorption method, Inductively Coupled Plasma (ICP) luminescence spectrometry, ICP mass spectrometry.

(Insolubilization Tank) The insoluble tank 21 is formed by removing the divalent iron ions and ferric ions contained in the reaction liquid from the reaction liquid to insolubilize them, thereby producing a divalent iron compound and a ferric iron compound. Further, the insolubilization tank 21 insolubilizes metal ions contained in the reaction liquid to form a metal compound.

In the present embodiment, the divalent iron compound, the ferric ion, and the metal ion of the present embodiment are insolubilized as an oxide, a hydroxide or a chloride.

(Second pH Adjustment Device) The pH adjustment device 24 adjusts the pH in the insolubilization tank 21 by adding an alkali to the insolubilization tank 21 in accordance with the pH in the tank. The inside of the insolubilization tank 21 is adjusted so that the pH of the divalent iron ion, the trivalent iron ion, and the metal ion of this embodiment may be insolubilized. The pH in the insolubilization tank 21 is adjusted to be in the range of 6.0 or more and 10.0 or less. The pH in the insolubilization tank 21 is preferably 7.0 or more and 9.0 or less, more preferably 7.5 or more and 8.5 or less, and still more preferably 7.8 or more and 8.3 or less.

Further, it is preferable to provide a measuring device (not shown) for measuring the pH in the tank in the insolubilizing tank 21.

The type of the base to be added is the same as the base which can be added to the pH adjusting device 14.

When the oxidizing contaminant contained in the drainage is an inorganic substance such as phosphorous acid or hypophosphorous acid, when calcium hydroxide is added as a base, the phosphorous acid in the reaction liquid reacts with calcium hydroxide to form a precipitate. Therefore, in the concentrating device 22 to be described later, it is possible to precipitate and separate into a precipitate containing phosphorous acid and treated water. Further, orthophosphoric acid in the reaction liquid reacts with ferric ion to form a precipitate. Therefore, in the concentrating device 22 to be described later, it is possible to precipitate and separate into a precipitate containing orthophosphoric acid and treated water.

(concentrating device) The concentrating device 22 solid-liquid separation of a suspension in which a divalent iron compound, a ferric compound, and a metal compound is suspended into a sludge containing a divalent iron compound, a trivalent iron compound, a metal compound, and an iron reduction catalyst With the treatment of water, a concentrated suspension of sludge is obtained. The concentrating device 22 employs a full amount of filtration using the first membrane module 23. By using the first membrane module 23, even when the sludge is contained in a high concentration in the suspension, it is possible to separate with high separation ability.

The first membrane module 23 includes a filter membrane. Examples of the filtration membrane include a microfiltration membrane, an ultrafiltration membrane, and the like. As a precision filtration membrane, a monolith type membrane is mentioned. Examples of the ultrafiltration membrane include a hollow fiber membrane, a flat membrane, and a tubular membrane. Among them, a hollow fiber membrane can be preferably used in terms of a high volume filling ratio.

In the case where a hollow fiber membrane is used in the first membrane module 23, examples of the material thereof include cellulose, polyolefin, polyfluorene, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (polyvinyl fluoride). Polytetrafluoroethylene, PTFE), etc. Among them, as a material of the hollow fiber membrane, polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE) is preferred in terms of chemical resistance and strong pH change.

In the case where a columnar film is used in the first membrane module 23, a ceramic membrane is preferably used.

The average pore diameter of the fine pores formed in the filtration membrane is preferably from 0.01 μm to 1.0 μm, more preferably from 0.05 μm to 0.45 μm. When the average pore diameter of the fine pores is at least the lower limit value, the pressure required for solid-liquid separation can be sufficiently suppressed. On the other hand, when the average pore diameter of the fine pores is at most the upper limit value, sludge containing the iron compound, the metal compound, and the iron reduction catalyst can be prevented from leaking into the treated water.

In the present embodiment, it is preferred to carry out concentration as follows with respect to the total amount of the suspension based on the mass concentration of the iron reduction catalyst with respect to the total amount of the reaction liquid in the reaction tank 11. The magnification of the mass concentration of the iron reduction catalyst (hereinafter sometimes referred to as "concentration ratio") is about 4 to 20 times. When the suspension is returned to the reaction tank 11 under the condition that the concentration ratio is 4 times or more, when the pH is adjusted in the reaction tank 11, the amount of the acid used can be suppressed. In addition, when the concentration ratio is 20 times or less, the concentration of the sludge by the concentration device 22 and the return of the suspension by the suspension return mechanism 32 are facilitated.

A third flow path 31 is connected to the first membrane module 23. The third flow path 31 discharges the treated water that has passed through the filtration membrane of the first membrane module 23 from the concentration device 22 and flows into the adjustment tank 41. A pump 31a is provided in the third flow path 31. Thereby, the treated water can be discharged from the insoluble tank 21.

Further, it is preferable that the third flow path 31 is provided with a measuring device that measures the total iron concentration in the treated water. When it is judged by the measuring device that the total iron concentration in the treated water exceeds 0.04 mg/L, the pH in the insolubilizing tank 21 or the solid-liquid separation in the first membrane module 23 or both becomes Appropriate ways to respond appropriately.

Further, in the present specification, the total iron is also referred to as total iron, and is iron (dissolved iron) in an ionic state like divalent iron ions or ferric ions, and is like a divalent iron compound or a trivalent iron compound. A general term for iron (suspended iron) that does not dissolve in water. That is, the total iron concentration is the total concentration of the irons. In addition, "all manganese" or "all copper" described later is also used in the same meaning.

Further, the concentrating device 22 may include a diaphragm cleaning vent mechanism disposed below the first membrane module 23. As the ventilating mechanism, a known person can be employed.

Further, in addition to the first membrane module 23, the concentrating device 22 may use other separation mechanisms in combination. Examples of the other separation means include sand filtration, pressurized floating separation, centrifugal separation, belt pressing, and precipitation by a sedimentation tank.

(suspension return mechanism) The suspension return mechanism 32 returns at least a part of the sludge-concentrated suspension from the insolubilization tank 21 to the reaction tank 11. The suspension return mechanism 32 includes a fifth flow path 33. The fifth flow path 33 discharges at least a part of the suspension from the insolubilization tank 21, and flows (feeds) into the reaction tank 11. A pump 33a is provided in the fifth flow path 33. Thereby, at least a part of the suspension in the insolubilization tank 21 can be sent back to the reaction tank 11 from the insolubilization tank 21.

When a plurality of reaction tanks 11 are disposed, it is preferable that the reaction tank 11 that returns at least a part of the suspension from the insolubilization tank 21 is a tank other than the most downstream reaction tank 11 . The more upstream the reaction tank 11 that returns at least a portion of the suspension, the more the ferric compound in the suspension is dissolved to become ferric ions and further reduced to divalent iron ions for use in the Fenton reaction. It takes longer. Therefore, the ferric compound in the returned suspension can be effectively reused in the Fenton reaction.

In the present embodiment, the trivalent iron compound discarded in the water treatment by the Fenton reaction can be reused. Therefore, in addition to the cost of reducing the treatment of the ferric compound, the amount of the iron reagent added from the iron reagent addition mechanism 15 can be reduced.

(Adjustment Tank) The adjustment tank 41 stores the treated water supplied from the insolubilization tank 21 via the third flow path 31.

A seventh flow path 55 is connected to the adjustment groove 41. The seventh flow path 55 discharges the treated water stored in the adjustment tank 41 and flows into the separation device 42. A pump 55a and an adjustment valve 55b are provided in the seventh flow path 55. Thereby, the treated water can be discharged from the adjustment tank 41.

The separation device 42 separates the treated water separated in the concentration step into an oxidized pollutant contained in the treated water and permeated water. The separation device 42 employs a cross flow filtration method using the second membrane module 43. By using the cross-flow filtration method, accumulation of oxidized pollutants on the surface of the membrane can be suppressed, and the filtration stream can be maintained.

A nanofiltration membrane or a reverse osmosis membrane is included in the second membrane module 43. In the case where a nanofiltration membrane is used in the second membrane module 43, the material thereof may be, for example, a polyethylene-based, a polyamidoamine-based or a cross-linked polyamine-based polyamine or a fat. A metal condensate polymer, a heterocyclic polymer system, a polyvinyl alcohol system, a cellulose acetate polymer, or the like.

When a reverse osmosis membrane is used for the second membrane module 43, the material thereof may be polyamine, polyfluorene or cellulose acetate, and preferably contains aromatic polyamine or crosslink. A polyamine of an aromatic polyamine.

A fourth flow path 51 is connected to the second membrane module 43. The fourth flow path 51 discharges the permeated water that has passed through the nanofiltration membrane or the reverse osmosis membrane of the second membrane module 43 from the separation device 42 and flows into the storage tank 61. Pressure is applied to the filtration surface side (upstream side) of the second membrane module 43 by the pump 55a, whereby the permeated water can be discharged from the adjustment tank 41, and membrane separation can be performed by the separation device 42. The adjustment of the flow rate can be performed by the output adjustment of the pump 55a.

(Storage Tank) The storage tank 61 stores the permeated water supplied from the separation device 42 via the fourth flow path 51. The permeated water stored in the storage tank 61 is returned to the factory that discharges the drainage, for example, and is reused by industrial water or the like, and may be discharged to the river or the like.

[Water Treatment Method] A water treatment method using the water treatment device 1 shown in Fig. 1 will be described. In the water treatment method of the present embodiment, the pH of the drainage water is first adjusted to 1.0 or more and 4.0 or less in the reaction tank 11, and the oxidizing pollutant contained in the drainage is oxidized by the Fenton reaction (oxidation). step).

Then, in the insolubilization tank 21, the pH of the reaction liquid obtained in the oxidation step is adjusted to 6.0 or more and 10.0 or less, and the divalent iron ion and the ferric ion are insolubilized to form a divalent iron compound and a ferric iron compound. Further, the metal ions contained in the reaction liquid are insolubilized to form a metal compound (insolubilization step).

Further, the suspension in which the divalent iron compound, the trivalent iron compound, and the metal compound are suspended is solid-liquid separated into a sludge containing a divalent iron compound, a trivalent iron compound, a metal compound, and an iron reduction catalyst by the concentration device 22. The treated water is treated with a concentrated suspension of the sludge (concentration step).

Then, the treated water separated in the concentration step is stored in the adjustment tank 41. Then, the treated water flows out of the adjustment tank 41 to the separation device 42, and the separation device 42 performs membrane separation (separation step). In the separation step, the treated water is separated into oxidized contaminants contained in the treated water and permeated water. Further, in the storage tank 61, the permeated water separated in the separation step is stored.

Further, in the suspension returning mechanism 32, the suspension concentrated in the concentration step is returned from the insolubilizing tank 21 to the reaction tank 11 (suspension returning step).

The ferric compound which is sent back to the suspension in the reaction tank 11 is dissolved in the reaction tank 11 to become ferric ions, and is hydrolyzed by hydrogen in the presence of an iron reduction catalyst and metal ions. Reduction to divalent iron ions (reduction step).

In the present embodiment, the ratio X of the amount of metal ions in the reduction step and the mass of the iron reduction catalyst is preferably 0.3 mmol/g or more and 60 mmol/g or less. When the ratio X is within the above range, the Fenton reaction can be substantially prevented, and the reduction reaction of ferric ions caused by hydrogen peroxide and an iron reduction catalyst can be promoted. In addition, metal ions in the treated water can be managed within the drainage standard. A better ratio X is as described above.

According to the above, according to the water treatment method of the water treatment device of the present embodiment, the reduction reaction of ferric ions is promoted, and water treatment having excellent treatment efficiency can be realized.

<Second Embodiment> [Water Treatment Apparatus] Hereinafter, a water treatment apparatus used in the water treatment method of the second embodiment will be described. Fig. 2 is a view showing a schematic configuration of a water treatment device according to a second embodiment. The water treatment device 2 shown in FIG. 2 includes an intermediate groove 71 upstream of the reaction tank 11. Further, a mixing mechanism 72 is provided in the intermediate groove 71 of Fig. 2 .

(Mixing Mechanism) The mixing mechanism 72 shown in Fig. 2 mixes at least two of the group consisting of an iron reagent, an iron reduction catalyst, and a metal reagent to obtain a mixture. The mixing mechanism 72 is not particularly limited as long as at least two of the group consisting of the iron reagent, the iron reduction catalyst, and the metal reagent are uniformly dispersed or mixed. Fig. 2 shows a case where at least two of the group consisting of an iron reagent, an iron reduction catalyst, and a metal reagent are dispersed or mixed in water. In the case where the mixture is in a solid state, as the mixing means 72, for example, a stirrer can be used. In the case where the mixture is in a liquid state, as the mixing mechanism 72, for example, a stirrer or a ventilating device can be used.

(Intermediate Tank) The intermediate tank 71 shown in FIG. 2 stores the mixture mixed by the mixing mechanism 72 and supplies the stored mixture to the reaction tank 11.

A supply path 73 is connected to the intermediate tank 71. The supply path 73 supplies the mixture from the intermediate tank 71 to the reaction tank 11.

In the water treatment device 2 shown in FIG. 2, the method of supplying the mixture from the intermediate tank 71 to the reaction tank 11 is not particularly limited. When the mixture is in a solid state, for example, a method of transporting (supplying) a mixture using a carrier gas can be mentioned. Further, in the case where the mixture is in a liquid state, for example, a method of supplying a mixture using a pump can be mentioned.

Further, an example in which one intermediate tank 71 is provided in the water treatment device 2 shown in Fig. 2 is shown, but a plurality of intermediate grooves 71 may be included.

Further, in the present embodiment, an example in which the mixing mechanism 72 is included in the intermediate groove 71 is shown, but the invention is not limited thereto. The mixing mechanism 72 may also be included upstream of the intermediate tank 71 independently of the intermediate tank 71.

[Water Treatment Method] The water treatment method using the water treatment device 2 shown in Fig. 2 includes a mixing step before the oxidation step, the mixing step of at least a group consisting of an iron reduction catalyst, a metal reagent, and an iron reagent. Two kinds of mixing.

According to the above, the water treatment method using the water treatment device of the present embodiment promotes the reduction reaction of ferric ions in the same manner as in the first embodiment, and the water treatment excellent in the treatment efficiency can be realized.

Furthermore, the water treatment device and the water treatment method according to an aspect of the present invention are not limited to the above embodiment. For example, in the water treatment device 1, the adjustment tank 41 and the separation device 42 may be omitted without performing the separation step. In this case, the treated water that has passed through the concentrating device 22 can be directly stored in the storage tank 61.

Further, for example, in the above embodiment, the method of concentrating the sludge using the concentrating device 22 may not necessarily be a method using the first membrane module 23. For example, the sand filtration, the pressurized floating separation, the centrifugal separation, the belt pressing, the precipitation by the sedimentation tank, or the like may be used.

Further, although the example in which the concentrating device 22 is installed in the insolubilizing tank 21 is shown, the concentrating device 22 may not be provided in the insolubilizing tank 21. In this case, another groove may be disposed between the insolubilization tank 21 and the adjustment tank 41, and the concentration device 22 may be provided in the tank.

When the concentration device 22 is not provided in the insolubilization tank 21, the configuration of the first membrane module 23 may be as follows. For example, the filter membrane is fixed in a housing so that the primary side of the filtration membrane (precision filtration membrane or ultrafiltration membrane) is isolated from the secondary side. Further, the primary side of the filtration membrane in the casing communicates with a tank in which a sludge containing an iron compound and an iron reduction catalyst and a suspension of treated water are stored by a circulation flow path, and the filtration membrane is twice. The side can also be connected to the suction pump.

Further, in the above-described embodiment, the metal ion concentration measuring unit 19 is included in the middle of the first flow path 12, but the present invention is not limited thereto. Further, the metal ion concentration measuring unit 19 may not be included.

<<Another Aspect of the Present Invention>> Next, an embodiment of another aspect of the present invention will be described with reference to the drawings.

<Third Embodiment> The water treatment method according to the present embodiment includes the following step (bi), the following step (b-ii), the following step (iii), the following step (iv), and the following step (v); . (b-i) The oxidation step of adjusting the pH of the wastewater containing the oxidizing pollutants to 1.0 or more and 4.0 or less, and performing a Fenton reaction to oxidize the oxidized pollutants. (b-ii) a reduction step of reducing ferric ions in the reaction liquid obtained in the oxidation step to divalent iron ions in the presence of an iron reduction catalyst. (iii) In the insolubilization step, the pH of the reaction liquid obtained in the oxidation step is adjusted to 6.0 or more and 10.0 or less, and the divalent iron ion and the ferric ion are insolubilized to form a divalent iron compound and a ferric iron compound. (iv) a concentration step of separating a suspension in which the divalent iron compound and the ferric compound are suspended into sludge and treated water containing at least the ferric compound, and obtaining the sludge by concentration Said suspension. (v) a suspension return step, at least a portion of the suspension being returned to the oxidation step.

Further, in the present embodiment, the step (b-i) includes the following step (A). (A) an adding step of adding at least one selected from the group consisting of a divalent iron salt, a divalent iron oxide, a trivalent iron salt, and a trivalent iron oxide in water. A mixture of iron reduction catalysts.

[Water Treatment Apparatus] Hereinafter, the configuration of the water treatment apparatus used in the water treatment method of the present embodiment will be described. Fig. 3 is a view showing a schematic configuration of a water treatment device according to the embodiment. The water treatment device 3 shown in FIG. 3 includes a reaction tank 11, an insolubilization tank 21, an adjustment tank 41, and a storage tank 61.

The water treatment device 3 includes a pH adjusting device 14, a hydrogen peroxide adding mechanism 16, and a mixture adding mechanism 78 in the reaction tank 11.

The mixture addition mechanism 78 includes an intermediate tank 71, an iron reagent addition mechanism 15, and a catalyst addition mechanism 17. A mixing mechanism 72 is provided in the intermediate tank 71.

Regarding the water treatment device 3, the pH adjustment device 24 is included in the insolubilization tank 21. Further, a concentration device 22 is provided in the insolubilization tank 21.

As described above, the pH adjusting device 14 corresponds to the first pH adjusting device in the patent application. Further, the pH adjusting device 24 corresponds to the second pH adjusting device in the patent application.

In the water treatment device 3, a suspension return mechanism 32 is included between the insolubilization tank 21 and the reaction tank 11.

Regarding the water treatment device 3, a separation device 42 is included between the adjustment tank 41 and the storage tank 61.

(Drainage) In the water treatment by the water treatment device 3, the wastewater containing the oxidizing pollutants is oxidized by the Fenton reaction. Examples of the oxidizing contaminant include an organic substance which is difficult to be decomposed by biological treatment, or an inorganic substance such as phosphorous acid or hypophosphorous acid.

Examples of the organic substance include an organic solvent such as 1,4-dioxane, a humic substance, and an aldehyde which is not equivalent to any of an organic solvent and a humic substance.

(Reaction tank) In the reaction tank 11, the oxidizing pollutant contained in the drainage is oxidized by the Fenton reaction, and the ferric ion generated by the Fenton reaction is reduced by the iron reduction catalyst. Divalent iron ions. The reaction tank 11 is filled with at least an iron reagent, hydrogen peroxide, and an iron reduction catalyst which generate divalent iron ions (Fe ²⁺ ).

The first flow path 12 and the second flow path 13 are connected to the reaction tank 11. The first flow path 12 inflows (supplied) the drainage containing the oxidizing pollutants into the reaction tank 11. The second flow path 13 flows (supplies) the reaction liquid discharged from the reaction tank 11 into the insolubilization tank 21.

In the water treatment device 3 shown in FIG. 3, the method of supplying the reaction liquid from the reaction tank 11 to the insolubilization tank 21 is not particularly limited, and the reaction liquid may be supplied using a pump or may be supplied to the reaction liquid by overflow.

Further, an example in which one reaction tank 11 is provided in the water treatment device 3 shown in FIG. 3 is shown, but a plurality of reaction tanks 11 may be arranged in series. In this case, the time taken for the Fenton reaction can be lengthened, so that the hydrogen peroxide can be sufficiently consumed by the Fenton reaction.

Further, when a plurality of reaction tanks 11 are disposed, the method of supplying liquid from the first reaction tank to the second reaction tank is not particularly limited, and a pumping liquid may be used, or an overflow liquid may be used. Further, in the present specification, the first reaction tank and the second reaction tank constitute a reaction tank in the scope of the patent application.

(First pH Adjustment Device) The pH adjustment device 14 adjusts the pH in the reaction tank 11 by adding an acid or a base to the reaction tank 11 in accordance with the pH in the tank, which is the same as the pH adjustment device 14 of the first embodiment.

(Hydrogen peroxide addition means) The hydrogen peroxide addition means 16 adds hydrogen peroxide to the reaction tank 11, and is the same as the hydrogen peroxide addition means 16 of the first embodiment.

(Mixture Addition Mechanism) The mixture addition mechanism 78 adds a mixture in which iron reagent and iron reduction catalyst are mixed in water to the reaction tank 11. In the present embodiment, the mixture stored in the intermediate tank 71 is added to the reaction tank 11.

In the prior art, a method in which activated carbon as an iron reduction catalyst is suspended in a dispersion medium such as water and then added to a reaction system is treated in a water treatment as compared with a case where solid activated carbon is added to a reaction system. low efficiency.

The inventors have speculated that the reason for the decrease in the treatment efficiency in the water treatment is that the iron reduction catalyst is easily dispersed with the air dissolved in the water by the dispersion of the catalyst in the water, and the iron reduction catalyst is deactivated.

Therefore, the inventors of the present invention have made an effort to study a water treatment method that maintains the treatment efficiency in water treatment and is excellent in workability. As a result, the inventors found that at least one selected from the group consisting of a divalent iron salt, a divalent iron oxide, a trivalent iron salt, and a trivalent iron oxide is mixed with iron by addition to the reaction system. The invention of the present aspect is completed by reducing the mixture of the catalyst and suppressing the deactivation of the iron reduction catalyst.

In the present embodiment, it can be said that the higher the TOC removal rate of the treatment in a certain period of time, the more excellent the treatment efficiency in water treatment.

(Intermediate Tank) The intermediate tank 71 stores a mixture of iron reagent and iron reduction catalyst mixed in water.

A sixth flow path 82 and an eighth flow path 83 are connected to the intermediate groove 71. The sixth flow path 82 flows (supplies) water for dispersing or dissolving the iron reagent and the iron reduction catalyst into the intermediate tank 71. The eighth flow path 83 allows the mixture discharged from the intermediate tank 71 to flow (feed) into the reaction tank 11.

In the intermediate tank 71, the iron reagent and the iron reduction catalyst are mixed in water by the mixing mechanism 72. The mixing means 72 is not particularly limited as long as the iron reagent and the iron reducing catalyst are uniformly dispersed or dissolved. In Fig. 3, the mixing mechanism 72 is a mixer. The mixing mechanism 72 can be a venting device.

In the water treatment device 3 shown in FIG. 3, the method of supplying the mixture from the intermediate tank 71 to the reaction tank 11 is not particularly limited. For example, a pump may be used to supply the mixture from the intermediate tank 71 to the reaction tank 11.

(Iron reagent addition mechanism) The iron reagent addition mechanism 15 adds at least an iron reagent to the intermediate tank 71.

As the iron reagent, the same iron reagent as described above can be mentioned. The preferred aspect of the iron reagent is also the same as described.

In the present embodiment, most of the divalent iron ions generated from the iron reagent are used for the Fenton reaction, but some of them are combined with the iron reduction catalyst. Therefore, it is preferred to add an iron reagent in such a manner that the amount of divalent iron ions generated is larger than the amount of divalent iron ions bound to the iron reduction catalyst. For example, it is preferable to add an iron reagent so that the ferrous ion/iron reduction catalyst is 0.01 or more and 1 or less in terms of a mass ratio, and it is more preferable to add an iron reagent so as to be 0.03 or more and 0.5 or less.

Further, in the present embodiment, since the ferric ion is reduced by the ferric reduction catalyst and the divalent iron ions are regenerated, a ferric compound can be used as the iron reagent.

As the iron reagent, a solid state can be used, and a liquid state can also be obtained by using an aqueous solution such as an iron reagent.

Further, in the iron reagent addition mechanism 15, in order to adjust the concentration of divalent iron ions in the reaction liquid in the reaction tank 11, an iron reagent may be directly added to the reaction tank 11 as needed.

(Ceramic Addition Mechanism) The catalyst addition mechanism 17 adds an iron reduction catalyst to at least the intermediate tank 71.

As the iron reduction catalyst, the same iron reduction catalyst as described above can be cited. The preferred aspect of the iron reduction catalyst is also the same as described.

The mass concentration of the iron reduction catalyst with respect to the total amount of the mixture in the intermediate tank 71 is not particularly limited, but is preferably 2000 mg/L or more and 200,000 mg/L or less.

When the mass concentration of the iron reduction catalyst relative to the total amount of the mixture is 2000 mg/L or more, the amount of the mixture to be added when the same amount of the iron reduction catalyst is added can be sufficiently reduced. Thereby, the amount of water required for water treatment can be sufficiently reduced. Further, in the case where the mass concentration of the iron reduction catalyst relative to the total amount of the mixture is 200,000 mg/L or less, the viscosity of the mixture is sufficiently low, and the mixture is easily mixed by the mixing mechanism 72. Thereby, the uniformity of the mixture in the intermediate tank 71 is easily maintained.

The concentration of the iron reduction catalyst relative to the total amount of the reaction liquid is preferably 50,000 mg/L or less. When the mass concentration of the iron reduction catalyst is 50,000 mg/L or less, the decomposition reaction of hydrogen peroxide by the iron reduction catalyst can be suppressed. Further, it is easy to concentrate the sludge containing the trivalent iron compound in which ferric ion is insolubilized by using a concentration device to be described later. Further, when the suspension is returned to the reaction tank 11 under the above conditions, when the pH is adjusted in the reaction tank 11, the amount of the acid used can be suppressed.

The shape of the iron reduction catalyst is preferably in the form of a powder from the viewpoint of catalyst efficiency. Further, the particle diameter of the iron reduction catalyst is preferably from 0.05 μm to 100 μm from the viewpoint of easy recovery of the catalyst.

Further, in order to adjust the concentration of the iron reduction catalyst in the reaction liquid in the reaction tank 11, the catalyst addition mechanism 17 may directly add the iron reduction catalyst to the reaction tank 11 as needed.

(Insolubilization Tank) The insolubilization tank 21 is formed by removing divalent iron ions and ferric ions generated by the Fenton reaction from the reaction liquid to form a divalent iron compound and a ferric iron compound.

In the present embodiment, the divalent iron ions and the ferric iron ions are insoluble as iron compounds such as iron oxide, iron hydroxide or ferric chloride.

(Second pH Adjustment Device) The pH adjustment device 24 is the same as the pH adjustment device 24 of the first embodiment.

(concentrating device) The concentrating device 22 solid-liquid separation of a suspension in which a divalent iron compound and a ferric iron compound are suspended into a sludge containing a divalent iron compound, a trivalent iron compound, and an iron reduction catalyst, and treated water, thereby obtaining A concentrated suspension of sludge. The concentrating device 22 employs a full amount of filtration using the first membrane module 23. By using the first membrane module 23, even when the sludge is contained in a high concentration in the suspension, it is possible to separate with high separation ability.

The first film module 23 is the same as the first film module 23 of the first embodiment. In the present embodiment, the preferable concentration ratio in the concentrating device 22 is the same as described above.

The third flow path 31 is connected to the first membrane module 23 in the same manner as in the first embodiment. A pump 31a is provided in the third flow path 31. Thereby, the treated water can be discharged from the insoluble tank 21.

Further, it is preferable that the third flow path 31 is provided with a measuring device that measures the total iron concentration in the treated water. When it is judged by the measuring device that the total iron concentration in the treated water exceeds 0.04 mg/L, the pH in the insolubilizing tank 21 or the solid-liquid separation in the first membrane module 23 or both becomes Appropriate ways to respond appropriately.

Further, the concentrating device 22 may include a diaphragm cleaning vent mechanism disposed below the first membrane module 23. As the ventilating mechanism, a known person can be employed.

Further, in addition to the first membrane module 23, the concentrating device 22 may use other separation mechanisms in combination. As another separation means, for example, sand filtration, pressurized floating separation, centrifugal separation, belt pressing, precipitation by a sedimentation tank, and the like can be mentioned.

(suspension return mechanism) The suspension return mechanism 32 returns at least a part of the concentrated sludge suspension from the insolubilization tank 21 to the reaction tank 11, and is the same as the suspension return mechanism 32 of the first embodiment.

In the present embodiment, the trivalent iron compound discarded in the water treatment by the Fenton reaction can be reused. Therefore, in addition to the cost of reducing the treatment of the ferric compound, the amount of the iron reagent added from the iron reagent addition mechanism 15 can be reduced.

(Adjustment Tank) The adjustment tank 41 stores the treated water supplied from the insolubilization tank 21 via the third flow path 31.

The seventh flow path 55 is connected to the adjustment groove 41 in the same manner as in the first embodiment. A pump 55a and an adjustment valve 55b are provided in the seventh flow path 55. Thereby, the treated water can be discharged from the adjustment tank 41.

The separation device 42 separates the treated water separated in the concentration step into an oxidized pollutant contained in the treated water and permeated water. Similarly to the separation device 42 of the first embodiment, the separation device 42 employs a cross flow filtration method using the second membrane module 43.

The fourth flow path 51 is connected to the second membrane module 43 in the same manner as in the first embodiment. Pressure is applied to the filtration surface side (upstream side) of the second membrane module 43 by the pump 55a, whereby the permeated water can be discharged from the adjustment tank 41, and membrane separation can be performed by the separation device 42. The adjustment of the flow rate can be performed by the output adjustment of the pump 55a.

(Storage Tank) The storage tank 61 stores the permeated water supplied from the separation device 42 via the fourth flow path 51. The permeated water stored in the storage tank 61 is returned to the factory that discharges the drainage, for example, and is reused by industrial water or the like, and may be discharged to the river or the like.

[Water Treatment Method] A water treatment method using the water treatment device 3 shown in Fig. 3 will be described. In the water treatment method of the present embodiment, the pH of the drainage water is first adjusted to 1.0 or more and 4.0 or less in the reaction tank 11, and the oxidizing pollutant contained in the drainage is oxidized by the Fenton reaction (oxidation). step). At the same time, a mixture of an iron reagent and an iron reduction catalyst mixed in water is added to the drainage (addition step). The iron reagent used in the addition step is as described above.

The iron reduction catalyst is difficult to aggregate by dispersing the iron reduction catalyst in water in advance. Therefore, the water treatment method of the present embodiment is excellent in workability. Further, in the presence of an iron reagent, by decomposing the iron reduction catalyst with water, the deactivation of the iron reduction catalyst can be suppressed.

Then, in the insolubilization tank 21, the pH of the reaction liquid obtained in the oxidation step is adjusted to 6.0 or more and 10.0 or less, and the divalent iron ions and the ferric ions generated by the Fenton reaction are insolubilized to generate divalent. Iron compound and ferric iron compound (insolubilization step).

Further, the suspension of the divalent iron compound and the ferric iron compound is solid-liquid separated into a sludge containing the divalent iron compound, the trivalent iron compound, and the iron reduction catalyst, and the treated water by the concentrating device 22, thereby obtaining The concentrated suspension of sludge (concentration step).

Then, the treated water separated in the concentration step is stored in the adjustment tank 41. Then, the treated water flows out of the adjustment tank 41 to the separation device 42, and the separation device 42 performs membrane separation (separation step). In the separation step, the treated water is separated into oxidized contaminants contained in the treated water and permeated water. Further, in the storage tank 61, the permeated water separated in the separation step is stored.

Further, in the suspension returning mechanism 32, the suspension concentrated in the concentration step is returned from the insolubilizing tank 21 to the reaction tank 11 (suspension returning step).

The ferric compound which is sent back to the suspension in the reaction tank 11 is dissolved in the reaction tank 11 to become ferric ions, and is reduced to divalent iron ions by hydrogen peroxide and an iron reduction catalyst ( Restore step). As described above, the water treatment method of the present embodiment can suppress the deactivation of the iron reduction catalyst, and therefore the reduction reaction of ferric ions proceeds efficiently. As a result, since a sufficient amount of divalent iron ions is supplied, sufficient processing efficiency can be obtained.

According to the above, according to the water treatment method using the water treatment device of the present embodiment, the treatment efficiency is maintained, and the water treatment excellent in workability can be realized.

Furthermore, the water treatment device and the water treatment method according to another aspect of the present invention are not limited to the embodiment. For example, in the water treatment device 3, the mixture addition mechanism 78 may not necessarily include the intermediate tank 71. In this case, the mixture may be directly added to the reaction tank 11. The mixture may be prepared in advance or may be prepared by natural mixing of an iron reagent, an iron reduction catalyst, and water in a flow path connected to the reaction tank 11.

Further, for example, an example in which the mixing mechanism 72 is provided in the intermediate tank 71 in the water treatment device 3 is shown, but the mixing mechanism 72 and the intermediate tank 71 may be provided separately. In this case, the tank may be relocated and a mixing mechanism 72 may be provided in the tank. After the mixture is prepared in the tank, the mixture may be added to the reaction tank 11 via the intermediate tank 71, or the mixture may be directly added to the reaction tank 11 from the tank.

Further, for example, in the water treatment device 3, the adjustment tank 41 and the separation device 42 may be omitted without performing the separation step. In this case, the treated water that has passed through the concentrating device 22 can be directly stored in the storage tank 61.

Further, for example, in the above embodiment, the method of concentrating the sludge using the concentrating device 22 may not necessarily be a method using the first membrane module 23. For example, the sand filtration, the pressurized floating separation, the centrifugal separation, the belt pressing, the precipitation by the sedimentation tank, or the like may be used.

Further, although the example in which the concentrating device 22 is installed in the insolubilizing tank 21 is shown, the concentrating device 22 may not be provided in the insolubilizing tank 21. In this case, another groove may be disposed between the insolubilization tank 21 and the adjustment tank 41, and the concentration device 22 may be provided in the tank.

When the concentration device 22 is not provided in the insolubilization tank 21, the configuration of the first membrane module 23 may be as follows. For example, the filter membrane is fixed in the casing with the primary side of the filtration membrane (precision filtration membrane or ultrafiltration membrane) isolated from the secondary side. Further, the primary side of the filtration membrane in the casing communicates with a storage tank storing a sludge containing a divalent iron compound, a ferric compound and an iron reduction catalyst, and a suspension of treated water by a circulation flow path, and is filtered. The secondary side of the membrane can also be connected to a suction pump. [Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by the following description. In the following tests, the concentration of each component was measured as follows.

[Measurement of mass concentration of hydrogen peroxide] "Measurement 1" A small amount of the reaction solution was sampled, and the test paper of Quantofix Peroxide 25 manufactured by MACHEREY-NAGEL was immersed in the test paper. In the sampled reaction solution, it was visually confirmed whether or not the test paper exhibited blue color. In the measurement 1, in the case where the test paper is blue, it means that the mass concentration of hydrogen peroxide in the reaction liquid is more than 25 mg/L.

"Measurement 2" The hydrogen peroxide in the treated water was developed with potassium iodide, and the measurement was carried out by an absorption photometer (manufactured by Kyoritsu Chemical Co., Ltd., product name "Digital PACK TEST").

[Determination of total iron concentration] The use of o-morpholine to develop iron ions or iron compounds in treated water by means of an absorptiometer (manufactured by Kyoritsu Chemical Co., Ltd., product name "Multiple Digital Packaging Test (Digital PACK TEST) Multi)") The measurement was carried out.

[Measurement of total copper concentration] Use 2,9-dimethyl-4,7-biphenyl-1,10-morpholine to develop copper ions or copper compounds in treated water by absorption spectrophotometer (co-chemistry) The company's manufacturing and product name "Digital PACK TEST Multi" was measured.

[Measurement of Total Manganese Concentration] Use potassium periodate to develop manganese ions or manganese compounds in treated water, and use a spectrophotometer (manufactured by Kyoritsu Chemical Co., Ltd., product name "Multiple Digital Packaging Test (Digital PACK) TEST Multi)") was measured.

[Measurement of TOC Concentration] The TOC concentration in the treated water is measured in accordance with JIS K0102 "22. Organic Carbon (TOC)" and by the combustion type total organic carbon analyzer (manufactured by Mitsubishi Chemical Corporation, model "TOC-300V". ") Perform the measurement.

Hereinafter, the TOC removal rate is calculated based on the formula (S1) using the TOC concentration in the raw water (drainage) and the TOC concentration in the treated water.

[Number 2] ···(S1)

In the present embodiment, as the iron reduction catalyst, the iron reagent, and the metal reagent, the following materials were used. Iron reduction catalyst: activated carbon (DiaFellow CT manufactured by Chemical Aqua Solutions Co., Ltd.). Iron reagent: iron (II) sulfate heptahydrate (FeSO ₄ ·7H ₂ O). Metal reagent: manganese (II) sulfate pentahydrate (MnSO ₄ · 5H ₂ O), copper (II) sulfate pentahydrate (CuSO ₄ · 5H ₂ O).

<Water Treatment Test 1> A mixed liquid of ethanol and water adjusted to a total amount of TOC of 324 mg/L with respect to the total amount of the reaction liquid was placed in a 100 mL container, and this was set as a model drainage. The water treatment test of the simulated drainage was carried out.

In the water treatment test 1, the treatment time was defined as follows. In the "measurement 1" of the "measurement of the mass concentration of hydrogen peroxide", the time at which the test paper does not develop color is referred to as the end of the reaction, and the time elapsed until the end of the reaction is referred to as the treatment time. Further, in the case where the test paper was also colored in "Measure 1" after 180 minutes from the start of the reaction, the treatment time was set to 180 minutes.

[Examples A1 to A13, Comparative Example A1 to Comparative Example A4] Sulfuric acid was added to the simulated drainage to adjust the pH to 2.8. Then, an iron reduction catalyst, an iron reagent, and a metal reagent are added to the container. The iron reduction catalyst, the iron reagent, and the metal reagent are sufficiently dispersed or dissolved in the simulated drainage by stirring the solution.

Then, while stirring the solution, hydrogen peroxide was added to the vessel so that the mass concentration of hydrogen peroxide relative to the total amount of the reaction liquid became 3000 mg/L, and this was used as a reaction liquid. The Fenton reaction (oxidation step) was carried out while stirring the reaction liquid.

While stirring the reaction liquid after the reaction was stopped, the sodium hydroxide aqueous solution was added thereto, and the pH of the reaction liquid was adjusted to 8.0 to prepare an insoluble liquid (insolubilization step).

Then, the stirring of the insoluble solution was stopped, and a syringe filter (PephiQuik Nylon Non-sterile Syringe Filter, 0.45 μm) was used. The insoluble liquid is solid-liquid separated. Specifically, the insoluble liquid is separated into sludge containing iron compound, iron reduction catalyst, and metal compound, and treated water (concentration step). In this way, water treatment for simulated drainage is implemented.

The mass concentration of each reagent relative to the total amount of the reaction liquid in Example A1 to Example A13 and Comparative Example A1 to Comparative Example A4 of the water treatment test 1, and the molar amount of metal ions/iron reduction catalyst The ratio X represented by the mass is shown in Table 1. Further, the calculation results of the TOC removal rate, the treatment time, the mass concentration of hydrogen peroxide in the treated water, the total manganese concentration, and the total of the Examples A1 to A13 of the water treatment test 1, and the comparative examples A1 to A4. The measurement results of the copper concentration are shown in Table 1. In addition, the mass concentration of hydrogen peroxide in the treated water was measured by "Measure 2" of the "Measurement of the mass concentration of hydrogen peroxide".

[Table 1]

The TOC removal rate is preferably 48% or more. The mass concentration of hydrogen peroxide relative to the total amount of treated water is preferably 6 mg/L or less. It can be said that the lower the mass concentration of hydrogen peroxide relative to the total amount of treated water, the higher the consumption of hydrogen peroxide. The treated water preferably satisfies the drainage standard. More specifically, the total manganese concentration in the treated water is 10 mg/L or less, and the total copper concentration is 3 mg/L or less.

As shown in Table 2, in the water treatment methods of Examples A1 to A13 of the present invention, the TOC removal rate per unit treatment time was high and the consumption amount of hydrogen peroxide was also high. That is, in the water treatment methods of Examples A1 to A13, the treatment efficiency was excellent.

Further, in the water treatment methods of Examples A1 to A9 in which the molar ratio of the metal ions/the mass of the iron reduction catalyst represented by the mass X is 0.3 mmol/g or more and 60 mmol/g or less, It can be managed within the drainage standard. That is, it can be said that the water treatment methods of Examples A1 to A9 are suitable for reusing or discharging the treated water to the drainage treatment of rivers or the like.

On the other hand, in the water treatment method of Comparative Example A1, although the consumption amount of hydrogen peroxide was high, the TOC removal rate was low. It is presumed that the reason is that manganese ions promote the decomposition reaction of hydrogen peroxide, and as a result, the amount of hydrogen peroxide which contributes to the removal of TOC is small.

Further, in the water treatment method of Comparative Example A2, the TOC removal rate was low and the consumption amount of hydrogen peroxide was also low. That is, in the water treatment method of Comparative Example A2, the treatment efficiency was poor.

Further, in the water treatment methods of Comparative Examples A3 to A4, the TOC removal rate was high, but the consumption of hydrogen peroxide was low. That is, in the water treatment methods of Comparative Examples A3 to A4, the treatment efficiency was poor.

<Water Treatment Test 2> [Example A14] 400 mL of a chemical plant drain containing propionaldehyde was placed in a 500 mL vessel, and sulfuric acid was added to the vessel to adjust the pH to 2.8. Then, activated carbon was added in a container so that the mass concentration of the iron reduction catalyst relative to the total amount of the reaction liquid became 1042 mg/L. Further, FeSO ₄ ·7H ₂ O was added so that the mass concentration of the iron reagent relative to the total amount of the reaction liquid was 260 mg/L. Further, CuSO ₄ ·5H ₂ O was added so that the molar concentration of the metal ions relative to the total amount of the reaction liquid was 0.40 mmol/L. At this time, the concentration of the metal ion in the concentration of 1000 mg/L with respect to the iron reduction catalyst was 0.38 mmol/L. The iron reduction catalyst, the iron reagent, and the metal reagent are sufficiently dispersed or dissolved in the simulated drainage by stirring the solution.

Then, while stirring the solution, hydrogen peroxide was added in a container so that the mass concentration of hydrogen peroxide relative to the total amount of the reaction liquid became 2800 mg/L. Further, ultrapure water was added in such a manner that the total amount was 480 mL, and this was used as a reaction liquid. The Fenton reaction (oxidation step) was carried out while stirring the reaction liquid.

A small amount of the reaction solution was taken after 4 hours from the start of the reaction and after 24 hours. Sodium hydroxide was added to the sampled reaction solution, and the pH of the reaction liquid was adjusted to 8.0 to prepare an insoluble solution (insolubilization step).

Then, the insolubilizing solution was solid-liquid separated using the same syringe filter as in the water treatment test 1. Specifically, the insoluble liquid is separated into sludge containing iron compound, iron reduction catalyst, and metal compound, and treated water (concentration step).

In this way, water treatment of chemical plant drainage is carried out. As a result, the mass concentration of hydrogen peroxide in the treated water after 4 hours was 1900 mg/L. In addition, the mass concentration of hydrogen peroxide in the treated water after 24 hours was 1100 mg/L.

[Comparative Example A5] The treatment was carried out in the same manner as in Example A14 except that the metal reagent was not added.

In this way, water treatment of chemical plant drainage is carried out. As a result, the mass concentration of hydrogen peroxide in the treated water after 4 hours was 2,500 mg/L. In addition, the mass concentration of hydrogen peroxide in the treated water after 24 hours was 2,200 mg/L.

4 is a graph showing the consumption rate of hydrogen peroxide in the water treatment test 2. The horizontal axis of the graph of Fig. 4 indicates the processing time, and the vertical axis of the graph indicates the mass concentration of hydrogen peroxide with respect to the total amount of treated water. The greater the inclination of the graph of Fig. 4, the faster the consumption rate of hydrogen peroxide is. It can be said that if the consumption rate of hydrogen peroxide is fast, the treatment efficiency in water treatment tends to be excellent.

As shown in Fig. 4, in the water treatment method of the embodiment A14 to which the present invention is applied, the consumption rate of hydrogen peroxide is fast. On the other hand, in the water treatment method of Comparative Example A5 in which the metal reagent was not used, the consumption rate of hydrogen peroxide was slow.

[Example B1] An aqueous ethanol solution adjusted so as to have a total organic carbon concentration of 254 mg/L with respect to the total amount of the reaction liquid was placed in a container A of 250 mL, and pH was adjusted by adding sulfuric acid to the container. It is 2.8.

Further, after water was placed in another 100 mL of the container B, an iron reduction catalyst was added in the container so that the mass concentration of the iron reduction catalyst relative to the total amount of the mixture became 80,000 mg/L. Further, an iron reagent is added so that the mass concentration of the iron reagent relative to the total amount of the mixture becomes 60,000 mg/L. Thereafter, the contents were thoroughly stirred in a state in which the container was sealed, and a mixture in which iron reagent and iron reduction catalyst were mixed in water was obtained.

In the vessel A, the mass concentration of the iron reduction catalyst relative to the total amount of the reaction liquid is 667 mg/L, and the mass concentration of the iron reagent is 500 mg/L in terms of divalent iron ions. step). By stirring the mixed liquid, it is possible to sufficiently disperse and dissolve in the simulated drainage.

Then, while stirring the solution, hydrogen peroxide was added to the vessel so that the mass concentration of hydrogen peroxide relative to the total amount of the reaction liquid was 2770 mg/L, thereby preparing a reaction liquid. Further, the reaction solution was stirred while performing a Fenton reaction (oxidation step) for 2 hours.

The reaction solution after completion of the Fenton reaction was stirred, and an aqueous solution of sodium hydroxide was added thereto, and the pH of the reaction liquid was adjusted to 8.0 to prepare an insoluble solution (insolubilization step). Then, using a syringe filter (manufactured by Rephile Co., Ltd., product name "PephiQuik Nylon Non-sterile Syringe Filter", pore size 0.45 μm), the obtained insoluble liquid was separated. It is a sludge containing iron compound and iron reduction catalyst and treated water (first separation step).

The TOC concentration of the treated water was measured based on [Measurement of TOC concentration] and found to be 115 mg/L. The TOC removal rate was calculated based on the formula (S1), and the result was 55%.

[Example B2] The mixture was sufficiently contacted with air by agitating the mixture while stirring the mixture for one day. The same procedure as in Example B1 was carried out except that the mixture after the aeration was added to the vessel A.

The TOC concentration of the treated water was measured based on [Measurement of TOC concentration] and found to be 116 mg/L. The TOC removal rate was calculated based on the formula (S1), and the result was 54%.

[Comparative Example B1] Operations other than the preparation of the mixture and the addition of the iron reagent were carried out in the same manner as in Example B2. Specifically, after water is placed in the container B, an iron reduction catalyst is added in the container so that the mass concentration of the iron reduction catalyst relative to the total amount of the mixture becomes 80,000 mg/L. Thereafter, the contents were thoroughly stirred in a state where the container was sealed, and a mixture in which an iron reduction catalyst was mixed in water was obtained.

The mixture was added in the vessel A in such a manner that the mass concentration of the iron reduction catalyst relative to the total amount of the reaction liquid was 667 mg/L. In addition, an aqueous FeSO ₄ ·7H ₂ O solution was added so that the mass concentration of the iron reagent relative to the total amount of the reaction liquid was 500 mg/L in terms of divalent iron ions.

The TOC concentration of the treated water was measured based on [Measurement of TOC concentration] and found to be 124 mg/L. The TOC removal rate was calculated based on the formula (S1), and the result was 51%.

[Comparative Example B2] The same procedure as in Example 1 was carried out except that the iron reagent and the iron reduction catalyst were separately added without preparing the mixture in advance. Specifically, an iron reduction catalyst was added to the container A so that the mass concentration of the iron reduction catalyst relative to the total amount of the reaction liquid was 667 mg/L. In addition, an aqueous FeSO ₄ ·7H ₂ O solution was added so that the mass concentration of the iron reagent relative to the total amount of the reaction liquid was 500 mg/L in terms of divalent iron ions.

The TOC concentration of the treated water was determined based on [Measurement of TOC concentration] and found to be 118 mg/L. The TOC removal rate was calculated based on the formula (S1), and the result was 54%.

The results of Examples B1 to B2 and Comparative Examples B1 to B2 are shown in Table 2.

In the evaluation of the workability in the water treatment, the aggregate of the iron reduction catalyst is not generated, and the iron reduction catalyst can be uniformly added to be "○", and the other is set to "x". In addition, the evaluation of the treatment efficiency in the water treatment is set to "x" in the case where the TOC removal rate is lower than in the case where the iron reduction catalyst is added in the powder state, and otherwise "○". In the comprehensive evaluation, the evaluation results of the workability and the treatment efficiency in the water treatment are "○" for both of them, and "X" for the other.

[Table 2]

As shown in Table 2, the example B1 and the example B2 to which the present invention was applied were the same as the comparative example B2 in which the iron reduction catalyst was added in the powder state, and the treatment efficiency in the water treatment was the same, and the workability in the water treatment was as follows. Excellent. Accordingly, it is considered that the deactivation of the iron reduction catalyst can be suppressed by mixing the iron reduction catalyst with water in the presence of an iron reagent.

On the other hand, in Comparative Example B1, compared with Comparative Example B2 in which an iron reduction catalyst was added in a powder state, workability in water treatment was excellent, but treatment efficiency in water treatment was lowered. Accordingly, in the case where only the iron reduction catalyst is mixed with water, it is considered that the deactivation of the iron reduction catalyst cannot be suppressed, and the treatment efficiency in the water treatment is lowered.

Based on the above results, the present invention was confirmed to be useful.

1, 2, 3‧‧‧ water treatment equipment

11‧‧‧Reaction tank

12‧‧‧First flow path

13‧‧‧Second flow path

14, 24‧‧‧ pH adjustment device

15‧‧‧ Iron reagent addition mechanism

16‧‧‧Hydrogen peroxide addition mechanism

17‧‧‧catalyst addition agency

18‧‧‧Metal reagent addition mechanism

19‧‧‧Metal ion concentration measurement department

21‧‧‧insoluble tank

22‧‧‧ Concentrated device

23‧‧‧First membrane module

31‧‧‧ third flow path

31a, 33a, 55a‧‧ ‧ pumps

32‧‧‧suspension return agency

33‧‧‧ fifth flow path

41‧‧‧Adjustment slot

42‧‧‧Separation device

43‧‧‧Second membrane module

51‧‧‧fourth flow path

55‧‧‧ seventh stream

55b‧‧‧Adjustment valve

61‧‧‧ storage tank

71‧‧‧Intermediate trough

72‧‧‧ Mixed institutions

73‧‧‧Supply road

78‧‧‧Mixed addition mechanism

82‧‧‧ sixth flow path

83‧‧‧ eighth flow path

Fig. 1 is a view showing a schematic configuration of a water treatment device according to a first embodiment. Fig. 2 is a view showing a schematic configuration of a water treatment device according to a second embodiment. Fig. 3 is a view showing a schematic configuration of a water treatment device according to a third embodiment. 4 is a graph showing the consumption rate of hydrogen peroxide in the water treatment test 2.

Claims (26)

A water treatment method comprising the following steps (ai) and (a-ii), (ai) an oxidation step of adjusting a pH of a drainage containing an oxidizing pollutant to 1.0 or more and 4.0 or less, and performing fen a reaction to oxidize the oxidized pollutant, (a-ii) a reduction step in the reaction solution obtained in the oxidation step in the presence of an iron reduction catalyst and a metal ion other than iron The ferric ion is reduced to a divalent iron ion. The water treatment method according to claim 1, wherein the molar amount of metal ions other than the iron in the reducing step/the mass of the iron reducing catalyst is represented by a ratio X of 0.3 mmol/ Above g and below 60 mmol/g. The water treatment method according to claim 1 or 2, wherein in the reducing step, a metal reagent for generating a metal ion other than the iron is used, and the metal reagent is selected from the group consisting of divalent metals and At least one of the group consisting of a valence metal salt and a divalent metal oxide. The water treatment method according to claim 3, wherein the metal reagent is at least one selected from the group consisting of manganese, manganese salts, manganese oxides, copper, copper salts, and copper oxides. The water treatment method according to claim 3, wherein in the oxidizing step, a group selected from the group consisting of a divalent iron salt, a divalent iron oxide, a trivalent iron salt, and a trivalent iron oxide is used. At least one iron reagent to oxidize the oxidized pollutant, before the oxidizing step, comprising a mixing step, the mixing step is to reduce the catalyst, the metal reagent and the iron reagent from the iron At least two of the group consisting are mixed. A water treatment method comprising the following steps (bi) and (b-ii), the step (bi) comprising the following step (A), (bi) an oxidation step, comprising a oxidizing pollutant The pH of the drainage is adjusted to 1.0 or more and 4.0 or less, and the Fenton reaction is performed to oxidize the oxidized pollutant, and the (b-ii) reduction step is performed in the presence of an iron reduction catalyst. The ferric ion in the reaction liquid obtained in the step is reduced to divalent iron ion, (A) an addition step, and the addition of the water to the drainage is selected from the group consisting of a divalent iron salt, a divalent iron oxide, and a trivalent A mixture of at least one of the group consisting of iron salts and ferric oxides and the iron reduction catalyst. The water treatment method according to claim 1 or 6, which comprises the following steps (iii) to (v), (iii) an insolubilization step, and a pH of the reaction liquid obtained in the oxidation step When it is adjusted to 6.0 or more and 10.0 or less, the divalent iron ion and the ferric ion generated by the Fenton reaction are insolubilized to form a divalent iron compound and a ferric iron compound, and (iv) a concentration step, which is suspended. A suspension having the divalent iron compound and the trivalent iron compound is separated into a sludge containing at least the ferric compound and treated water to obtain the suspension in which the sludge is concentrated, (v The suspension is returned to the step and at least a portion of the suspension is returned to the oxidation step. The water treatment method according to claim 7, wherein in the concentration step, the suspension is obtained using a filtration membrane. The water treatment method according to claim 7, comprising a separation step of separating the treated water into the contained in the treated water using a nanofiltration membrane or a reverse osmosis membrane Oxidizing pollutants and permeate water. The water treatment method according to claim 1 or 6, wherein the iron reduction catalyst is at least one selected from the group consisting of activated carbon and zeolite. The water treatment method according to claim 1, wherein in the oxidizing step, the pH of the drainage water is adjusted to 1.0 or more and 4.0 or less using an acid. A water treatment device comprising the following (a-1), (a-1) reaction tank for oxidizing an oxidizing pollutant contained in a drainage by a Fenton reaction, and an iron reduction catalyst and The ferric ion generated by the Fenton reaction is reduced to a divalent iron ion in the presence of a metal ion other than iron. The water treatment device according to claim 12, wherein a molar ratio of metal ions other than iron in the reaction tank/the mass of the iron reduction catalyst is 0.3 mmol/ Above g and below 60 mmol/g. The water treatment device according to claim 12 or 13, further comprising: an iron reagent addition mechanism, wherein the reaction tank is added with a salt selected from the group consisting of a divalent iron salt, a divalent iron oxide, and a ferric iron salt. And at least one iron reagent in the group consisting of trivalent iron oxide; a catalyst addition mechanism, adding the iron reduction catalyst to the reaction tank; and a metal reagent addition mechanism added to the reaction tank A metal reagent for generating metal ions other than the iron. The water treatment device according to claim 14, comprising a metal ion concentration measuring unit that measures a total amount of the drainage water flowing into the reaction tank. The metal reagent addition means adds the metal reagent based on the measurement result of the metal ion concentration measuring unit. The water treatment device according to claim 14, which has a mixing mechanism upstream of the reaction tank, the mixing mechanism comprising a composition of the iron reagent, the iron reduction catalyst and the metal reagent. At least two of the groups are mixed to obtain a mixture. The water treatment device of claim 16, which has an intermediate tank that stores the mixture and supplies the stored mixture to the reaction tank. A water treatment device comprising the following (b-1) and (b-2), (b-1) reaction tanks for oxidizing oxidized pollutants contained in the drainage by a Fenton reaction, and The ferric reducing catalyst is used to reduce ferric ions generated by the Fenton reaction into divalent iron ions, (b-2) a mixture adding mechanism, and the mixing in the reaction tank is selected from two in water. a mixture of at least one of a group consisting of a ferrous salt, a divalent iron oxide, a trivalent iron salt, and a trivalent iron oxide and an iron reduction catalyst. The water treatment device according to claim 18, which has a mixing mechanism selected from the group consisting of the divalent iron salt, the divalent iron oxide, the trivalent iron salt, and the trivalent iron oxide. At least one of the group consisting of is mixed with the iron reduction catalyst in water. The water treatment device of claim 18, wherein the water treatment device comprises an intermediate tank that stores the mixture. The water treatment device according to Item 12 or Item 18, comprising the following (3) to (5), (3) an insolubilizing tank for containing the reaction liquid supplied from the reaction tank; The divalent iron ion and the ferric ion are insolubilized to form a divalent iron compound and a ferric iron compound, and (4) a concentration device that suspends the divalent iron compound and the trivalent iron compound The suspension is separated into a sludge containing at least the ferric compound and treated water to obtain the suspension in which the sludge is concentrated, and (5) a suspension is returned to the mechanism to at least a part of the suspension. Returned to the reaction tank. The water treatment device according to claim 21, comprising: a first pH adjusting device that supplies an acid or a base to the reaction tank to adjust a pH of the drainage; and a second pH adjusting device that A base is supplied to the insolubilization tank to adjust the pH of the reaction liquid. The water treatment device according to claim 22, wherein the acid is sulfuric acid or hydrochloric acid. The water treatment device according to claim 21, wherein the concentration device has a filtration membrane, and the suspension is obtained using the filtration membrane. The water treatment device according to claim 21, wherein the concentration device is disposed in the insolubilization tank. The water treatment device according to claim 21, comprising a separation device having a nanofiltration membrane or a reverse osmosis membrane, and using the nanofiltration membrane or the reverse osmosis membrane to The treated water is separated into the oxidized pollutants and permeated water contained in the treated water.