JP2019198856A - Water treatment method and water treatment apparatus - Google Patents

Abstract

To provide a water treatment method for decomposition of a substance to be oxidized by elevating a decomposition ability by Fenton reaction, and a water treatment apparatus using the same.SOLUTION: The water treatment method includes an oxidation process (A2) for conducting light irradiation to a mixed liquid (A) containing a water to be treated containing a substance to be oxidized, a ferrous ion, hydrogen peroxide, and an iron reduction catalyst for decomposition of the substance to be oxidized, and the water treatment apparatus has a reaction tank for conducting Fenton reaction under light irradiation in the presence of a mixed liquid (A) containing a water to be treated containing a substance to be oxidized, a ferrous ion, hydrogen peroxide, and an iron reduction catalyst for decomposition of the substance to be oxidized.SELECTED DRAWING: Figure 1

Description

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

  The Fenton reaction is a reaction in which hydrogen peroxide is reacted with ferrous ions to generate hydroxy radicals. Hydroxyl radicals have strong oxidizing power, and are expected to be applied in various fields such as sterilization, decomposition of harmful substances and persistent pollutants by using the strong oxidizing power.

  The ferrous ions used in the Fenton reaction are oxidized as the reaction proceeds to become ferric ions. It is known that some of ferric ions are reduced to ferrous ions in the presence of hydrogen peroxide. However, this reduction reaction is known to be very slow compared to the Fenton reaction. Therefore, there is a problem that the resolution of the oxidizable substance is reduced by reducing the concentration of ferrous ions supplied to the Fenton reaction.

  In Patent Document 1, in addition to the Fenton reaction, it is proposed to irradiate ultraviolet rays having a low wavelength (λ = 254 nm) and to decompose the oxidizable substance by utilizing the resolution of the oxidizable substance of ultraviolet rays.

JP 2003-285083 A

  However, if the oxidizable substance is directly decomposed by the low wavelength ultraviolet ray, the ultraviolet ray irradiation device is expensive, the electric cost is increased, and the processing cost is increased. Furthermore, there is a problem that a special countermeasure is required because of the low wavelength.

  Therefore, an object of the present invention is to provide a water treatment method for decomposing an oxidizable substance by increasing the resolution by the Fenton reaction, and a water treatment apparatus using the same.

That is, the present invention has the following aspects.
[1] The mixture (A) containing water to be treated containing an oxidizable substance, ferrous ions, hydrogen peroxide, and an iron reduction catalyst is irradiated with light to decompose the oxidizable substance. The water treatment method which has an oxidation process (A2).
[2] The water treatment method according to [1], wherein the mixed solution (A) includes a complex-forming substance, and the complex-forming substance is a substance that forms a complex with the ferrous ion.
[3] The water treatment method according to [1] or [2], wherein the mixed solution (A) contains ferric ions.
[4] The mixed solution (A) includes a complex-forming substance, and the complex-forming substance is a substance that forms a complex with the ferric ion, [1] to [3] Water treatment method.
[5] The water treatment method according to any one of [1] to [4], wherein in the oxidation step (A2), the wavelength of the light is 380 nm or more.
[6] In any one of [1] to [5], in the oxidation step (A2), the concentration of the iron reduction catalyst is 100 to 10000 mass ppm with respect to the total mass of the mixed solution (A). The water treatment method according to item.
[7] The mixture (B) containing water to be treated containing an oxidizable substance, ferrous ions, hydrogen peroxide, and a complex-forming substance is irradiated with light to decompose the oxidizable substance. The water treatment method which has an oxidation process (B2).
[8] A Fenton reaction is performed under light irradiation in the presence of a mixed liquid (A) containing water to be treated containing an oxidizable substance, ferrous ions, hydrogen peroxide, and an iron reduction catalyst, A water treatment apparatus comprising a reaction tank for decomposing oxidizable substances.

  ADVANTAGE OF THE INVENTION According to this invention, the water treatment method which improves the resolution | decomposability by a Fenton reaction and decomposes | disassembles an oxidizable substance, and a water treatment apparatus using the same can be provided.

1 is a schematic diagram showing a schematic configuration of a water treatment device 1. It is a graph showing the oxide resolution in Example 1 and Comparative Examples 1 and 2. It is a graph showing the oxide resolution in Example 2 and Comparative Example 3. It is a graph showing the oxide resolution in Example 3 and Comparative Example 4.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easy to see.

[Water treatment equipment]
The structure of the water treatment apparatus 1 used for the water treatment method of this embodiment is demonstrated. FIG. 1 is a diagram illustrating a schematic configuration of a water treatment apparatus 1 according to the present embodiment. As shown in FIG. 1, the water treatment apparatus 1 includes a reaction tank 11, an insolubilization tank 21, an adjustment tank 41, and a storage tank 61.

  The water treatment apparatus 1 includes a first pH adjusting unit 14, an iron reagent adding unit 15, a hydrogen peroxide adding unit 16, a catalyst adding unit 17, and a light irradiation unit 18 in the reaction tank 11.

  The water treatment apparatus 1 includes a second pH adjusting unit 24 in the insolubilization tank 21. A concentrating device 22 is provided in the insolubilization tank 21.

  The water treatment apparatus 1 includes a suspension returning means 32 between the insolubilization tank 21 and the reaction tank 11.

  The water treatment device 1 includes a separation device 42 between the adjustment tank 41 and the storage tank 61.

(Treated water)
In the water treatment by the water treatment apparatus 1, the water to be treated containing an oxidizable substance is oxidized using the Fenton reaction. Examples of the oxidizable substance include organic substances that are difficult to decompose by biological treatment, or inorganic substances such as phosphorous acid and hypophosphorous acid.

Examples of the organic substance include organic solvents such as 1,4-dioxane, humic substances, and the like. The humic substance is an adsorbed fraction obtained by extracting soil with an alkali such as sodium hydroxide or an extract obtained by extracting soil with natural water to XAD resin (a copolymer of styrene or acrylic and divinylbenzene). The fraction eluted from the adsorbed material with a dilute alkaline aqueous solution.
Phosphorous acid and hypophosphorous acid are contained in the factory effluent of a plating plant.

The water to be treated may contain a complex forming substance. In the present specification, the “complex forming substance” means a substance that forms a complex with ferrous ions (Fe ²⁺ ) and / or ferric ions (Fe ³⁺ ). In the present invention, ferric ions are usually generated by oxidation of ferrous ions. Ferrous ions are generated by reduction of ferric ions. Examples of the complex-forming substance include aldehydes, cyanide compounds, amine compounds, chlorides, and carboxylic acid compounds. Of these, aldehydes, cyanide compounds, amine compounds, and chlorides are preferable.
As used herein, “aldehydes” means compounds having an aldehyde group in the molecule. Examples of aldehydes include formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, vinyl aldehyde, and glyoxal.
As used herein, “cyanide compound” means a compound having “CN” in the molecule. Examples of cyanide include cyanide such as potassium cyanide and sodium cyanide; nitriles such as acetonitrile and acrylonitrile.
In the present specification, the “amine compound” means a compound having a compound having one or more primary to tertiary amino groups in the molecule. Examples of the amine compound include a primary amine compound, a secondary amine compound, a tertiary amine compound, or a salt thereof.
As used herein, “chloride” means a compound having “Cl” in the molecule. Examples of the chloride include inorganic chlorides such as potassium chloride and sodium chloride; organic chlorides such as chloroform and dichloromethane.
In the present specification, the “carboxylic acid compound” means a compound having a carboxy group or a functional group derived from a carboxy group in the molecule. Examples of the carboxylic acid compound include organic acids such as oxalic acid, formic acid, acetic acid, citric acid, propionic acid, butyric acid, isobutyric acid, and acrylic acid; and organic acid esters such as ethyl propionate.

Although the oxidizable substance is more easily decomposed when the complex-forming substance is not contained in the water to be treated, according to the present invention, the oxidizable substance can be decomposed even if the water to be treated contains the complex-forming substance.
When the water to be treated contains a complex-forming substance, the concentration thereof is preferably 20000 mg / L or less, more preferably 10,000 mg / L or less, and further preferably 5000 mg / L or less with respect to the total mass of the water to be treated. Moreover, 1 mg / L or more is preferable, 10 mg / L or more is more preferable, and 100 mg / L or more is further more preferable.
If the concentration of the complex-forming substance is not less than the above lower limit, the complex structure formed from ferrous ions and / or ferric ions and the complex-forming substance is destroyed by light irradiation, and a complex is formed. Easy to prevent.
When the concentration of the complex-forming substance is less than or equal to the above upper limit value, it is easy to suppress the formation of the complex, and it is easy to prevent the Fenton reaction from becoming difficult to proceed.

(Reaction tank)
In the reaction tank 11, the oxidizable substance contained in the water to be treated is oxidized by the Fenton reaction in the presence of ferrous ions (Fe ²⁺ ) and hydrogen peroxide under light irradiation.
When an iron reduction catalyst is used, ferric ions (Fe ³⁺ ) generated by the Fenton reaction are reduced to ferrous ions by an iron reduction catalyst under light irradiation.
When the water to be treated contains a complex-forming substance, the complex structure formed from ferrous ions and / or ferric ions and the complex-forming substance is destroyed by irradiating light, and ferrous iron Liberates ions and / or ferric ions.

  A first flow path 12 and a second flow path 13 are connected to the reaction tank 11. The first flow path 12 is used to flow (supply) the water to be treated containing the oxidizable substance into the reaction tank 11. The second flow path 13 allows the reaction solution discharged from the reaction tank 11 to flow (supply) into the insolubilization tank 21.

  In the water treatment apparatus 1 shown in FIG. 1, the method for 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 reacted using an overflow. A liquid may be supplied.

  In addition, although the example in which one reaction tank 11 was provided in the water treatment apparatus 1 shown in FIG. 1, the some reaction tank 11 may be arrange | positioned in series. In that case, since the time required for the Fenton reaction can be increased, hydrogen peroxide can be sufficiently consumed by the Fenton reaction.

  In addition, when a plurality of reaction tanks 11 are arranged, a method for feeding liquid from the first reaction tank to the second reaction tank is not particularly limited, and liquid feeding may be performed using a pump, or an overflow may be utilized. You may send liquid.

(Iron reagent addition method)
The iron reagent adding means 15 is for adding an iron reagent into the reaction tank 11.

  The iron reagent is not particularly limited as long as it dissolves in water and generates ferrous ions, but ferrous salts or ferrous oxides are preferable. Among them, iron sulfate or iron chloride is preferable because it does not need to be managed according to wastewater standards and has excellent solubility. In addition, iron sulfate is more preferable because of its high versatility and low corrosivity.

  Moreover, when using an iron reduction catalyst, since a ferric ion is reduce | restored by an iron reduction catalyst and a ferrous ion is reproduced | regenerated, a ferric compound can also be used as an iron reagent.

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

  The concentration of ferrous ions is appropriately determined according to the type of waste water.

(Hydrogen peroxide addition means)
The hydrogen peroxide addition means 16 is for adding hydrogen peroxide into the reaction tank 11.

  In the reaction vessel 11, ferrous ions react with hydrogen peroxide to generate hydroxy radicals. When the oxidizable substance contained in the for-treatment water is an organic substance, the organic substance is oxidatively decomposed by the generated hydroxy radical. In addition, in the case of inorganic substances such as phosphorous acid and hypophosphorous acid, each is oxidized by a hydroxy radical, and phosphorous acid becomes orthophosphoric acid, and hypophosphorous acid becomes phosphorous acid and orthophosphoric acid.

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

  When a plurality of reaction vessels 11 are arranged, the reaction vessel 11 to which hydrogen peroxide is added from the hydrogen peroxide addition means 16 is preferably a vessel other than the most downstream reaction vessel 11. Since the time required for the Fenton reaction can be increased as the reaction tank 11 to which hydrogen peroxide is added is upstream, the hydrogen peroxide can be sufficiently consumed by the Fenton reaction. Therefore, leakage of unreacted hydrogen peroxide in the insolubilization tank 21 and the adjustment tank 41 downstream of the reaction tank 11 can be suppressed. In addition, an increase in chemical oxygen demand in the treated water due to unreacted hydrogen peroxide can be suppressed.

(First pH adjusting means)
The first pH adjusting means 14 adjusts the pH in the reaction tank 11 by adding acid or alkali to the reaction tank 11 according to the pH in the tank.

  The inside of the reaction tank 11 is adjusted to a pH range in which an iron reagent is dissolved in water to generate ferrous ions and to generate hydroxy radicals. In the present embodiment, the pH in the reaction vessel 11 is preferably adjusted to a range of 1.0 or more and 4.0 or less. The solubility of the iron reagent with respect to water can be kept favorable as pH in the reaction tank 11 is 1.0 or more and 4.0 or less. Moreover, when using an iron reduction catalyst, the contact efficiency of a ferric ion and an iron reduction catalyst can be improved. The pH in the reaction tank 11 is more preferably 2.0 or more and 3.0 or less, and further preferably 2.5 or more and 3.0 or less.

  The reaction tank 11 is preferably provided with a measuring device (not shown) for measuring the pH in the tank.

  Examples 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. Of these, sulfuric acid or hydrochloric acid is preferable, and sulfuric acid is more preferable because it is difficult to capture hydroxy radicals generated by the Fenton reaction. These acids may be used individually by 1 type, and may use 2 or more types together.

Examples of the alkali include sodium hydroxide, sodium carbonate, calcium hydroxide, magnesium hydroxide and the like. Of these, sodium hydroxide is preferred because it is highly versatile and does not react with substances generated by the Fenton reaction.
These alkalis may be used individually by 1 type, and may use 2 or more types together.

(Catalyst addition means)
The catalyst addition means 17 is for adding an iron reduction catalyst into the reaction tank 11.

  Any iron reduction catalyst may be used as long as it does not substantially inhibit the Fenton reaction and promotes a reaction in which ferric ions are reduced and ferrous ions are regenerated. Examples of the iron reduction catalyst include activated carbon, zeolite, resin, quartz sand and the like. Among these, activated carbon is more preferable from the viewpoint of catalyst efficiency and waste catalyst treatment.

100-10000 mass ppm is preferable with respect to the total mass of a liquid mixture, and, as for the density | concentration of an iron reduction catalyst, 500-5000 mass ppm is more preferable.
When the concentration of the iron reduction catalyst is not less than the above lower limit, the efficiency of the reduction reaction of ferric ions generated by the Fenton reaction can be easily increased.
When the concentration of the iron reduction catalyst is not more than the above upper limit value, the amount of waste catalyst can be easily reduced.
Here, the “mixed liquid” includes water to be treated containing an oxidizable substance, ferrous ions, and hydrogen peroxide.
Furthermore, the mixed solution may contain a complex-forming substance and / or an iron reduction catalyst.

  The shape of the iron reduction catalyst is preferably powder from the viewpoint of catalyst efficiency. The average particle diameter of primary particles of the iron reduction catalyst is preferably 0.05 μm to 100 μm because the catalyst can be easily recovered. In the present specification, the average particle diameter can be measured by a laser diffraction method.

(Light irradiation means)
The light irradiation means 18 irradiates light in the reaction tank.
The wavelength of light is preferably 300 nm or more, more preferably 350 nm or more, and further preferably 380 nm or more. Moreover, as a wavelength of light, 650 nm or less is preferable and 540 nm or less is more preferable.
When the wavelength of light is equal to or greater than the lower limit, the amount of electricity consumed for light irradiation can be reduced.
When the wavelength of light is less than or equal to the above upper limit value, the reduction reaction of ferric ions is easily promoted, and the complex is broken to easily release ferrous ions.

The intensity of the light is preferably ^{100~5000W / m 2, 500~5000W / m} 2 is more preferable.
When the light intensity is equal to or higher than the lower limit, the amount of electricity consumed for light irradiation can be reduced.
When the light intensity is less than or equal to the above upper limit value, the reduction reaction of ferric ions is easily promoted, and the complex is broken to easily release ferrous ions.

(Insolubilization tank)
The insolubilization tank 21 is insolubilized in order to remove ferrous ions and ferric ions generated by the Fenton reaction from the reaction solution, thereby generating ferrous compounds and ferric compounds.

  In this embodiment, ferrous ions and ferric ions become insoluble as iron compounds such as iron oxide, iron hydroxide, or iron chloride.

(Second pH adjusting means)
The second pH adjusting means 24 adjusts the pH in the insolubilization tank 21 by adding alkali to the insolubilization tank 21 according to the pH in the tank. The inside of the insolubilization tank 21 is adjusted to a pH range in which ferrous ions and ferric ions can be insolubilized. The pH in the insolubilization tank 21 is preferably adjusted to a range of 6.0 or more and 10.0 or less. The pH in the insolubilization tank 21 is more preferably 7.0 or more and 9.0 or less, further preferably 7.5 or more and 8.5 or less, and particularly preferably 7.8 or more and 8.3 or less.

  The insolubilizing tank 21 is preferably provided with a measuring device (not shown) for measuring the pH in the tank.

  Examples of the alkali to be added include the same alkalis that can be added by the first pH adjusting means 14.

  When the oxidizable substance contained in the water to be treated is an inorganic substance such as phosphorous acid or hypophosphorous acid, when calcium hydroxide is added as an alkali, phosphorous acid in the reaction solution reacts with calcium hydroxide. A precipitate is formed. Therefore, in the concentration apparatus 22 mentioned later, it can precipitate-separate into the deposit containing phosphorous acid, and treated water. In addition, orthophosphoric acid in the reaction solution reacts with ferric ions 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.

(Concentrator)
The concentration device 22 obtains a suspension in which sludge containing the iron compound, the iron reduction catalyst, and the complex is concentrated from the suspension in which the ferrous compound, the ferric compound, the iron reduction catalyst, and the complex are suspended. Is. The concentrator 22 employs a total filtration method using the first membrane module 23. By using the first membrane module 23, even when sludge is contained in the suspension at a high concentration, it can be separated with high separation ability. In this embodiment, a concentration method using a total filtration method is employed, but a cross flow filtration method may be employed.

  The first membrane module 23 includes a filtration membrane such as a microfiltration membrane or an ultrafiltration membrane. Examples of the microfiltration membrane include a hollow fiber membrane, a flat membrane, a tubular membrane, and a monolith type membrane. Examples of the ultrafiltration membrane include a hollow fiber membrane, a flat membrane, and a tubular membrane. Among these, a hollow fiber membrane is preferably used because of its high volume filling rate.

  When a hollow fiber membrane is used for the first membrane module 23, examples of the material include cellulose, polyolefin, polysulfone, polyvinylidene fluoride difluoride (PVDF), and polytetrafluoroethylene (PTFE). Among these, as the material for the hollow fiber membrane, polyvinylidene difluoride (PVDF) and polytetrafluoroethylene (PTFE) are preferable from the viewpoint of chemical resistance and resistance to pH change.

  When a monolith type membrane is used for the first membrane module 23, a ceramic membrane is preferably used.

  The average pore diameter of the micropores formed in the microfiltration membrane or ultrafiltration membrane is preferably 0.01 μm to 1.0 μm, and more preferably 0.05 μm to 0.45 μm. If the average pore diameter of the micropores is not less than the lower limit value, the pressure required for solid-liquid separation can be kept sufficiently small. On the other hand, if the average pore diameter of the micropores is not more than the upper limit value, it is possible to prevent the sludge containing the iron compound, the iron reduction catalyst, and the complex from leaking into the treated water.

  In this embodiment, the magnification of the mass concentration of the iron reduction catalyst relative to the total amount of the suspension when the mass concentration of the iron reduction catalyst relative to the total amount of the reaction solution is used as a reference (hereinafter, this may be referred to as “concentration magnification”). Is preferably concentrated so as to be about 4 to 20 times. If the concentration factor is 4 times or more, the amount of acid used for pH adjustment in the reaction tank 11 can be suppressed when the suspension is returned to the reaction tank 11 by the suspension return means 32 described later. Further, if the concentration factor is 20 times or less, the concentration of sludge using the concentration device 22 and the return of the suspension using the suspension return means 32 are facilitated.

  A third channel 31 is connected to the first membrane module 23. The third flow path 31 discharges the treated water that has passed through the microfiltration membrane or the ultrafiltration membrane of the first membrane module 23 from the concentrating device 22 and flows it into the adjustment tank 41. A pump 31 a is installed in the third flow path 31. Thereby, the treated water can be discharged from the insolubilization tank 21.

  The third channel 31 is preferably provided with a measuring device for measuring the total iron concentration in the treated water. When the measurement apparatus determines that the total iron concentration in the treated water exceeds 0.04 ppm, the pH in the insolubilization tank 21 and / or the solid-liquid separation in the first membrane module 23 are appropriate. Appropriate measures are taken so that

  Further, the concentrating device 22 may include an aeration means for cleaning the membrane surface arranged below the first membrane module 23. A well-known thing can be employ | adopted as said aeration means.

  Furthermore, the concentrating device 22 may use another separating means in addition to the first membrane module 23. Examples of other separation means include sand filtration, pressurized flotation separation, centrifugal separation, belt press, and sedimentation by a sedimentation basin.

(Suspension return means)
The suspension return means 32 returns at least a part of the suspension in which sludge is concentrated from the insolubilization tank 21 to the reaction tank 11. The suspension return means 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 causes the reaction tank 11 to flow (supply).
A pump 33 a is installed in the fifth flow path 33. Thereby, at least a part of the suspension in the insolubilization tank 21 can be returned from the insolubilization tank 21 to the reaction tank 11.

  When a plurality of reaction tanks 11 are arranged, the reaction tank 11 that returns at least a part of the suspension from the insolubilization tank 21 is preferably a tank other than the most downstream reaction tank 11. The more upstream the reaction tank 11 that returns at least a part of the suspension is, the more the ferric compound in the suspension dissolves to become ferric ions, which are further reduced to ferrous ions before the Fenton reaction. It is possible to increase the time for which the cycle of turning to ferric ions and reducing to ferrous ions is performed. Therefore, the ferric compound in the returned suspension can be effectively reused for the Fenton reaction.

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

  A seventh channel 55 is connected to the adjustment tank 41. The seventh channel 55 discharges the treated water stored in the adjustment tank 41 and flows it into the separation device 42. A pump 55a and an adjustment valve 55b are installed in the seventh flow path 55. Thereby, the said treated water can be discharged | emitted from the adjustment tank 41 now. The adjustment valve 55b may not be provided.

  The separation device 42 membrane-separates the treated water separated in the concentration step into an oxidizable substance contained in the treated water and permeated water. The separator 42 employs a cross flow filtration method using the second membrane module 43. By adopting the cross flow filtration method, it is possible to suppress the deposition of the oxidizable substance on the film surface and maintain the filtration flux.

  The second membrane module 43 includes a nanofiltration membrane or a reverse osmosis membrane. When a nanofiltration membrane is used for the second membrane module 43, the material thereof is a polyethylene, an aromatic polyamide or a polyamide including a crosslinked polyamide, an aliphatic amine condensation polymer, a heterocyclic polymer, a polyvinyl alcohol, Examples thereof include cellulose acetate polymers.

  When a reverse osmosis membrane is used for the second membrane module 43, examples of the material include polyamide, polysulfone, cellulose acetate, and the like, and polyamide containing aromatic polyamide or crosslinked aromatic polyamide is preferable.

  A fourth channel 51 is connected to the second membrane module 43. The fourth flow channel 51 discharges the permeated water that has passed through the nanofiltration membrane or reverse osmosis membrane of the second membrane module 43 from the separation device 42 and causes the water to flow into the storage tank 61. By applying pressure to the filtration surface side (upstream side) of the second membrane module 43 with the pump 55a described above, the permeated water can be discharged from the adjustment tank 41, and membrane separation can be performed by the separation device 42. . The flow rate can be adjusted by adjusting the output of the pump 55a.

(Reservoir)
The storage tank 61 stores permeated water supplied from the separation device 42 via the fourth flow path 51. The permeated water stored in the storage tank 61 is diluted with industrial water or the like and discharged into a river or the like.

  When an iron reduction catalyst is used, ferric compounds that have been conventionally discarded can be reused in water treatment using the Fenton reaction. Therefore, the amount of the iron reagent added from the iron reagent adding means 15 can be reduced, and the generation of sludge derived from the ferric compound can be reduced. In particular, when an iron reduction catalyst is used, the oxidation reaction of the oxidizable substance and the reduction reaction of ferric ions generated by the Fenton reaction are performed in one reaction tank 11 equipped with light irradiation means. Thereby, the water treatment apparatus 1 can be made more compact. Further, since the concentration of ferrous ions supplied to the Fenton reaction is increased by reduction of ferric ions, the reaction efficiency of the oxidative decomposition reaction of the oxidizable substance can be further increased.

  Further, when the water to be treated contains a complex-forming substance, the complex structure formed from the ferrous ion and / or ferric ion and the complex-forming substance can be destroyed by irradiating light. Ferrous and / or ferric ions can be liberated. Therefore, the amount of the iron reagent added from the iron reagent adding means 15 can be reduced, and the generation of sludge derived from the complex can be reduced. When the water to be treated contains a complex-forming substance, the oxidation reaction of the oxidizable substance and the destruction of the complex structure are performed in one reaction tank 11 provided with light irradiation means. Thereby, the water treatment apparatus 1 can be made more compact. Moreover, since the density | concentration of the ferrous ion supplied to Fenton reaction increases by destruction of a complex structure, the reaction efficiency of the oxidative decomposition reaction of an oxidizable substance can be raised more.

[Water treatment method]
In the water treatment method of the first embodiment of the present invention, the pH adjustment step (A1), the oxidation step (A2), the insolubilization step (A3), the concentration step (A4), the separation step (A5), Suspension return step (A6).

A water treatment method using the water treatment apparatus 1 shown in FIG. 1 will be described. In the water treatment method of the present embodiment, first, the pH of the water to be treated containing the oxidizable substance is adjusted to 1.0 or more and 4.0 or less in the reaction tank 11 (pH adjustment step (A1)).
Subsequently, in the presence of an iron compound, hydrogen peroxide, and an iron reduction catalyst, a Fenton reaction is performed while irradiating light to oxidize an oxidizable substance. The ferric ions generated by the Fenton reaction are reduced to ferrous ions by light irradiation in the presence of an iron reduction catalyst (oxidation step (A2)).

Next, in the insolubilization tank 21, the pH of the reaction solution obtained in the oxidation step (A2) is adjusted to 6.0 or more and 10.0 or less to insolubilize ferrous ions and ferric ions generated by the Fenton reaction. To produce a ferrous compound and a ferric compound (insolubilization step (A3)).
Furthermore, the suspension in which the ferrous compound, the ferric compound and the iron reduction catalyst are suspended is solid-liquid separated into sludge containing the iron compound and the iron reduction catalyst and the treated water by the concentrating device 22, and the sludge is separated. A concentrated suspension is obtained (concentration step (A4)).

Next, the treated water separated in the concentration step (A4) is stored in the adjustment tank 41. Then, the treated water is allowed to flow from the adjustment tank 41 to the separation device 42, and membrane separation is performed by the separation device 42 (separation step (A5)). In the separation step (A5), the treated water is separated into an oxidizable substance contained in the treated water and permeated water.
Furthermore, in the storage tank 61, the permeated water separated in the separation step (A5) is stored.

In the suspension return means 32, the suspension concentrated in the concentration step (A4) is returned from the insolubilization tank 21 to the reaction tank 11 (suspension return step (A6)).
The ferric compound in the suspension returned to the reaction tank 11 dissolves in the reaction tank 11 to become ferric ions, and is reduced to ferrous ions by the iron reduction catalyst and light irradiation (reduction step). (A7)).

  In the water treatment method of the first embodiment of the present invention, the oxidation reaction of the oxidizable substance and the reduction reaction of ferric ions generated by the Fenton reaction are performed in one-pot while irradiating light. Therefore, the amount of the iron reagent added from the iron reagent adding means 15 can be reduced, and the generation of sludge derived from the ferric compound can be reduced. Further, since the concentration of ferrous ions supplied to the Fenton reaction is increased by reduction of ferric ions, the reaction efficiency of the oxidative decomposition reaction of the oxidizable substance can be further increased.

  In the water treatment method of the second embodiment of the present invention, the pH adjustment step (B1), the oxidation step (B2), the insolubilization step (B3), the concentration step (B4), the separation step (B5), Suspension return step (B6).

A water treatment method using the water treatment apparatus 1 shown in FIG. 1 will be described. In the water treatment method of this embodiment, first, in the reaction tank 11, the pH of the water to be treated containing the oxidizable substance and the complex forming substance is adjusted to 1.0 or more and 4.0 or less (pH adjustment step (B1 )).
Subsequently, the Fenton reaction is performed while irradiating light in the presence of an iron compound and hydrogen peroxide to oxidize the oxidizable substance (oxidation step (B2)).
The insolubilization step (B3), the concentration step (B4), the separation step (B5), and the suspension return step (B6) are the insolubilization step (A3), the concentration step (A4), the separation step (A5), and It can be performed in the same manner as the suspension return step (A6).

  In the water treatment method of the second embodiment of the present invention, the oxidation reaction of the oxidizable substance and the liberation of ferrous ions due to the destruction of the complex are performed in one-pot while irradiating light. Therefore, the amount of the iron reagent added from the iron reagent adding means 15 can be reduced, and the generation of sludge derived from the complex can be reduced. Moreover, since the density | concentration of the ferrous ion supplied to Fenton reaction increases by destruction of a complex, the reaction efficiency of the oxidative decomposition reaction of an oxidizable substance can be improved more.

In addition, the water treatment apparatus and the water treatment method of the present invention are not limited to the above-described embodiments. For example, the water treatment apparatus 1 may further include a complex-forming substance concentration measuring unit (not shown). The complex-forming substance concentration measuring means is for measuring the concentration of the complex-forming substance contained in the water to be treated supplied to the reaction tank 11. Moreover, when not using an iron reduction catalyst, you may abbreviate | omit a catalyst addition means in the water treatment apparatus 1. FIG.
Furthermore, in the water treatment apparatus 1, the insolubilization tank 21, the adjustment tank 41, the separation apparatus 42, and the storage tank 61 may be omitted.
In the water treatment method of the first embodiment of the present invention, since ferric ions are reduced and reused as ferrous ions in the reaction tank 11, there is little generation of sludge derived from ferric compounds. . Therefore, the insolubilization tank 21, the adjustment tank 41, the separation device 42, and the storage tank 61 can be omitted.
Moreover, in the water treatment method of the second embodiment of the present invention, in the reaction tank 11, the complex is destroyed and ferrous ions are liberated, so that the generation of sludge derived from the complex is small. Therefore, the insolubilization tank 21, the adjustment tank 41, the separation device 42, and the storage tank 61 can be omitted.

  Further, for example, in the above embodiment, the method for concentrating sludge using the concentrating device 22 is not necessarily a method using the first membrane module 23. For example, sand filtration, pressurized flotation separation, centrifugation, belt press, precipitation by a sedimentation basin, etc. may be used.

  Furthermore, although the example which provides the concentration apparatus 22 in the insolubilization tank 21 was shown, the concentration apparatus 22 does not need to be provided in the insolubilization tank 21. In that case, another tank may be arrange | positioned between the insolubilization tank 21 and the adjustment tank 41, and the concentration apparatus 22 may be provided in this tank.

  When the concentrating device 22 is not provided in the insolubilization tank 21, the following configuration may be used as the configuration of the first membrane module 23. For example, the filtration membrane is fixed in the housing so that the primary side and the secondary side of the filtration membrane (microfiltration or ultrafiltration) are isolated. The primary side of the filtration membrane in the housing communicates with a storage tank in which a suspension containing sludge and treated water containing an iron compound, an iron reduction catalyst, and a complex is stored in a circulation channel. The secondary side may be connected to a suction pump.

Although the water treatment method in the first embodiment of the present invention has a pH adjustment step (A1), if the water to be treated has a pH that can be used for the Fenton reaction, the pH adjustment step may be omitted. Good.
Further, the insolubilization step (A3), the concentration step (A4), the separation step (A5), and the suspension return step (A6) may not be performed. In the oxidation step (A2), ferric ions are reduced and reused as ferrous ions, so that there is little generation of sludge derived from ferric compounds. Therefore, it is not necessary to perform the insolubilization step (A3), the concentration step (A4), the separation step (A5), and the suspension return step (A6).

Although the water treatment method in the second embodiment of the present invention has a pH adjustment step (B1), if the water to be treated has a pH that can be used for the Fenton reaction, the pH adjustment step may not be performed. Good.
Further, the insolubilization step (B3), the concentration step (B4), the separation step (B5), and the suspension return step (B6) may not be performed. In the oxidation step (B2), ferrous ions are liberated from the complex structure formed from the ferrous ions and the complex-forming substance, so that there is little generation of sludge derived from the complexes. Therefore, it is not necessary to perform the insolubilization step (B3), the concentration step (B4), the separation step (B5), and the suspension return step (B6).

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description. In addition, about the structure which is common in the water treatment apparatus shown in FIG. 1, it demonstrates using the same name.
In addition, the following materials were used as each reagent.
Iron reagent: Iron (II) sulfate heptahydrate (FeSO ₄ · 7H ₂ O)
Iron reduction catalyst: Activated carbon (DiaFellow CT, manufactured by Mitsubishi Chemical Aqua Solutions Co., Ltd.)
Propionaldehyde (Fuji Film Wako Pure Chemical Industries, Ltd.)

[Example 1]
A water treatment device comprising a first pH adjusting unit, an iron reagent adding unit, a hydrogen peroxide adding unit, a catalyst adding unit, and a light irradiation unit in a reaction tank was prepared.
Orange II was added to pure water so as to have a concentration of 30 mg / L, and treated water was obtained.
The water to be treated was placed in the reaction vessel, and the pH was adjusted to 3.0 with sulfuric acid.
Subsequently, hydrogen peroxide was added to the reaction vessel so that the concentration of hydrogen peroxide relative to the total volume of water to be treated was 500 mg / L.
Further, the iron reagent was added to the reaction vessel so that the concentration of the iron reagent with respect to the total volume of the water to be treated was 5 mg / L (1 mg / L in terms of ferrous ion).
Furthermore, the iron reduction catalyst was added to the reaction tank so that the concentration of the iron reduction catalyst with respect to the total mass of the water to be treated was 100 ppm by mass.
The obtained water to be treated was irradiated with light having a wavelength of 380 nm and an intensity of 1600 W / m ² , and the concentration (mg / L) of Orange II in the water to be treated was measured every 5 minutes from the start of light irradiation. The obtained results are shown in Table 1 and FIG.
The concentration of Orange II was measured by absorptiometry.

[Comparative Example 1]
Water treatment was carried out in the same manner as in Example 1 except that no light was irradiated, and the concentration (mg / L) of Orange II in the water to be treated was measured every 5 minutes after the addition of the iron reduction catalyst. The obtained results are shown in Table 1 and FIG.

[Comparative Example 2]
Water treatment was carried out in the same manner as in Example 1 except that the iron reduction catalyst was not added, and the concentration (mg / L) of Orange II in the water to be treated was measured every 5 minutes from the start of light irradiation. The obtained results are shown in Table 1 and FIG.

In Example 1, Orange II in the water to be treated was almost completely oxidatively decomposed 20 minutes after the start of light irradiation.
In Comparative Example 1 where no light was irradiated, it took about 40 minutes for Orange II in the water to be treated to be almost completely oxidized and decomposed.
In Comparative Example 2 in which no iron reduction catalyst was added, it took about 40 minutes for Orange II in the water to be treated to be almost completely oxidatively decomposed.

[Example 2]
A water treatment apparatus including a first pH adjusting unit, an iron reagent adding unit, a hydrogen peroxide adding unit, and a light irradiation unit in a reaction tank was prepared.
To the pure water, Orange II was added to a concentration of 200 mg / L, and propionaldehyde was further added to a concentration of 800 mg / L to prepare treated water.
The water to be treated was placed in the reaction vessel, and the pH was adjusted to 3.0 with sulfuric acid.
Subsequently, hydrogen peroxide was added to the reaction vessel so that the concentration of hydrogen peroxide relative to the total volume of water to be treated was 500 mg / L.
Further, the iron reagent was added to the reaction vessel so that the concentration of the iron reagent with respect to the total volume of the water to be treated was 5 mg / L (3 mg / L in terms of ferrous ion).
The obtained water to be treated was irradiated with light having a wavelength of 380 nm and an intensity of 1600 W / m ² , and the concentration (mg / L) of Orange II in the water to be treated was measured every 5 minutes from the start of light irradiation. The obtained results are shown in Table 2 and FIG.
The concentration of Orange II was measured by absorptiometry.

[Comparative Example 3]
Water treatment was performed in the same manner as in Example 2 except that no light was irradiated, and the concentration (mg / L) of Orange II in the water to be treated was measured every 5 minutes after the addition of the iron reagent. The obtained results are shown in Table 2 and FIG.

In Example 2, about half of Orange II in the water to be treated was oxidatively decomposed about 40 minutes after the start of light irradiation.
In Comparative Example 3 where no light was irradiated, Orange II in the water to be treated was hardly oxidized and decomposed even after 40 minutes had passed since the start of light irradiation.

[Example 3]
A water treatment device comprising a first pH adjusting unit, an iron reagent adding unit, a hydrogen peroxide adding unit, a catalyst adding unit, and a light irradiation unit in a reaction tank was prepared.
To the pure water, Orange II was added to a concentration of 200 mg / L, and propionaldehyde was further added to a concentration of 800 mg / L to prepare treated water.
The water to be treated was placed in the reaction vessel, and the pH was adjusted to 3.0 with sulfuric acid.
Subsequently, hydrogen peroxide was added to the reaction vessel so that the concentration of hydrogen peroxide relative to the total volume of water to be treated was 500 mg / L.
Further, the iron reagent was added to the reaction vessel so that the concentration of the iron reagent with respect to the total volume of the water to be treated was 5 mg / L (3 mg / L in terms of ferrous ion).
Furthermore, the iron reduction catalyst was added to the reaction tank so that the concentration of the iron reduction catalyst with respect to the total mass of the water to be treated was 100 ppm by mass.
The obtained water to be treated was irradiated with light having a wavelength of 380 nm and an intensity of 1600 W / m ² , and the concentration (mg / L) of Orange II in the water to be treated was measured every 5 minutes from the start of light irradiation. The obtained results are shown in Table 3 and FIG.
The concentration of Orange II was measured by absorptiometry.

[Comparative Example 4]
Water treatment was carried out in the same manner as in Example 3 except that no light was irradiated, and the concentration (mg / L) of Orange II in the water to be treated was measured every 5 minutes after the addition of the iron reduction catalyst. The obtained results are shown in Table 3 and FIG.

In Example 3, more than half of Orange II in the water to be treated was oxidatively decomposed 40 minutes after the start of light irradiation.
In Comparative Example 4 in which light was not irradiated, about half of Orange II in the water to be treated was oxidized and decomposed after 40 minutes from the start of light irradiation. .

  DESCRIPTION OF SYMBOLS 1 ... Water treatment apparatus, 11 ... Reaction tank, 14 ... 1st pH adjustment means, 17 ... Catalyst addition means, 18 ... Light irradiation means, 21 ... Insolubilization tank, 22 ... Concentration apparatus, 24 ... 2nd pH adjustment means, 32 ... Suspension return means, 42 ... Separator

Claims (8)

  Oxidation step of decomposing the oxidizable substance by irradiating light to a liquid mixture (A) containing water to be treated containing the oxidizable substance, ferrous ions, hydrogen peroxide and an iron reduction catalyst ( A water treatment method comprising A2).   The water treatment method according to claim 1, wherein the mixed solution (A) contains a complex-forming substance, and the complex-forming substance is a substance that forms a complex with the ferrous ion.   The water treatment method according to claim 1 or 2, wherein the mixed solution (A) contains ferric ions.   The water treatment method according to any one of claims 1 to 3, wherein the mixed solution (A) includes a complex-forming substance, and the complex-forming substance is a substance that forms a complex with the ferric ion.   The water treatment method according to any one of claims 1 to 4, wherein in the oxidation step (A2), the wavelength of the light is 380 nm or more.   The water according to any one of claims 1 to 5, wherein in the oxidation step (A2), the concentration of the iron reduction catalyst is 100 to 10,000 ppm by mass with respect to the total mass of the mixed solution (A). Processing method.   Oxidation step of decomposing the oxidizable substance by irradiating the mixed liquid (B) containing the water to be treated containing the oxidizable substance, ferrous ions, hydrogen peroxide, and the complex-forming substance with light. A water treatment method comprising B2).   In the presence of a mixed liquid (A) containing water to be treated containing an oxidizable substance, ferrous ions, hydrogen peroxide, and an iron reduction catalyst, a Fenton reaction is performed under light irradiation, and the oxidizability A water treatment apparatus provided with a reaction tank for decomposing substances.

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