JP2018122289A - Water treatment method and water treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method having excellent efficiency of Fenton reaction in water treatment using Fenton reaction accompanied by reduction reaction. A water treatment method including steps (i) to (iii). (I) Ferric ion and hydrogen peroxide are added to the wastewater satisfying the following condition (A) so as to satisfy the following condition (B) to oxidize aldehydes and oxidizable contaminants in the wastewater. Reaction step to obtain a reaction solution by performing an oxidation treatment and a reduction treatment of reducing ferric ions to ferrous ions in the presence of an iron reduction catalyst (ii) The pH of the reaction solution is 6.0 or more and 10.0. The insolubilization step (iii) suspension is adjusted as follows to insolubilize the ferric and ferric ions in the reaction to obtain a suspension in which the ferric compound and the ferric compound are suspended. The first separation step to separate sludge and treated water. <Reaction conditions> (A) The pH of wastewater is 1.0 or more and 4.0 or less. (B) 0.17 ≦ T1 / (CA × CB) ≦ 1.2 [Selection diagram] FIG. 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 a strong oxidizing power, and are expected to be applied in various fields such as sterilization, decomposition of harmful substances such as aldehydes and decomposition of persistent pollutants using the strong oxidizing power. The ferrous ions used in the Fenton reaction are oxidized as the reaction proceeds to become ferric ions. For example, when wastewater containing oxidizable pollutants is treated using the Fenton reaction, sludge containing ferric compounds becomes waste, and the treatment cost is high. Further, since ferrous ions are consumed as the Fenton reaction proceeds, it was necessary to continue to generate ferrous ions even during the treatment.

  It is known that some of the ferric ions generated by the Fenton reaction 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. On the other hand, a technique is known in which an iron reduction catalyst that promotes the reduction reaction is added to simultaneously perform the Fenton reaction and the reduction reaction. As such an example, the example which adds activated carbon as an iron reduction catalyst is mentioned (patent documents 1 and patent documents 2).

  The water treatment methods described in Patent Literature 1 and Patent Literature 2 can reduce the cost of waste treatment compared to a water treatment method using only the Fenton reaction. Moreover, since the ferrous ion produced | generated by the said reduction reaction can be reused, the quantity of the ferrous ion generated additionally can be decreased.

JP 56-48290 A Japanese Patent No. 5215578

  However, when treating wastewater containing aldehydes as harmful substances using the methods described in Patent Document 1 and Patent Document 2, the reaction of reducing ferric ions to ferrous ions may be inhibited. It was. In that case, the efficiency of the Fenton reaction may decrease.

  Thus, one embodiment of the present invention is a water treatment using a Fenton reaction involving a reduction reaction of ferric ions, and the reduction reaction is not inhibited by the aldehydes contained in the waste water, and water having excellent Fenton reaction efficiency. A treatment apparatus and a water treatment reaction using the same are provided.

In order to solve the above problems, the present invention has the following aspects.
[1] A method for treating wastewater containing aldehydes and oxidizable pollutants, comprising the following steps (i) to (iii):
(I) Ferrous ions and hydrogen peroxide are added so as to satisfy the following condition (B) with respect to the wastewater that satisfies the following condition (A) stored in the reaction tank, and the aldehydes in the wastewater And an oxidation treatment for oxidizing the oxidizable contaminant, and a reduction treatment for reducing ferric ions generated by the oxidation treatment to the ferrous ions in the presence of an iron reduction catalyst. Reaction step to be obtained (ii) The pH of the reaction solution obtained in the step (i) is adjusted to 6.0 or more and 10.0 or less, and the ferrous ions and the ferric ions in the reaction are adjusted. Insolubilization step of obtaining a suspension in which the ferrous compound and the ferric compound are suspended by insolubilizing to produce a ferrous compound and a ferric compound (iii) In the step (ii) The obtained suspension is The first separation step of separating the sludge containing iron compound, treated with water, the <Reaction conditions>
(A) The pH of the waste water is 1.0 or more and 4.0 or less.
(B) 0.17 ≦ T ₁ / (C _A × C _B ) ≦ 1.2
(T ₁ : time (unit: time) that the waste water stays in the reaction tank)
C _A : Concentration concentration of the aldehydes relative to the total amount of the reaction solution (unit: mol / L)
C _B : Addition concentration of hydrogen peroxide with respect to the total amount of the reaction solution (unit: mg / L))
[2] The water treatment method according to [1], further comprising the following step (iv).
(Iv) Sludge return step of returning at least a part of the sludge separated in the step (iii) to the step (i) [3] The aldehyde is propionaldehyde [1] or [2] Water treatment method.
[4] The water treatment method according to any one of [1] to [3], wherein in the step (i), the pH of the waste water is adjusted to 1.0 or more and 4.0 or less using an acid.
[5] The water treatment method according to any one of [1] to [4], wherein the iron reduction catalyst is at least one selected from the group consisting of activated carbon and zeolite.
[6] The water treatment method according to any one of [1] to [5], wherein a ferrous salt or a ferrous oxide is used for the oxidation treatment in the step (i).
[7] In any one of [1] to [6], in the step (iii), the suspension is separated into the sludge and the treated water using a microfiltration membrane or an ultrafiltration membrane. Water treatment method.
[8] Prior to the step (i), the method according to any one of [1] to [7], including a biological treatment step in which a part of the aldehydes is decomposed using a microorganism to form the waste water. Water treatment method.
[9] A second separation step of separating the treated water into the aldehydes and the oxidizable contaminants contained in the treated water and permeated water using a nanofiltration membrane or a reverse osmosis membrane [ The water treatment method according to any one of [1] to [8].
[10] A waste water treatment apparatus containing aldehydes and oxidizable pollutants, comprising the following (1) to (4).
(1) An oxidation treatment in which ferrous ions and hydrogen peroxide are added to the waste water to oxidize the aldehydes and the oxidizable contaminants in the waste water, and ferric ions generated by the oxidation treatment (2) The ferrous ion contained in the reaction solution supplied from the reaction unit. And insolubilizing part to obtain a suspension in which ferrous compound and ferric compound are suspended by insolubilizing ferric ion and generating ferrous compound and ferric compound (3) A first separation unit that separates the suspension supplied from the insolubilization unit into sludge containing the ferric compound and treated water. (4) The reaction unit so as to satisfy the following formula (1): controls the control unit 0.17 ≦ _{T 2 (C A × C B) ≦} 1.2 ... (1)
(T ₂ : time for which the reaction liquid stays in the reaction part (unit: time)
C _A : Concentration concentration of the aldehydes relative to the total amount of the reaction solution (unit: mol / L)
C _B : Addition concentration of hydrogen peroxide with respect to the total amount of the reaction solution (unit: mg / L))
[11] The water treatment apparatus according to [10], further comprising (5) below.
(5) Sludge return means for returning at least a part of the sludge generated in the first separation section to the reaction section [12] The first separation section includes a microfiltration membrane or an ultrafiltration membrane [10] Or the water treatment apparatus as described in [11].
[13] The water treatment device according to any one of [10] to [12], wherein the first separation unit is provided in the insolubilization unit.
[14] A first pH adjuster for adjusting the pH of the waste water by supplying an acid to the reaction section;
A water treatment device according to any one of [10] to [13], comprising: a second pH adjustment device that adjusts the pH of the reaction solution by supplying alkali to the insolubilized portion.
[15] The water treatment apparatus according to [14], wherein the acid is sulfuric acid or hydrochloric acid.
[16] The water treatment apparatus according to any one of [10] to [15], further comprising catalyst addition means for adding an iron reduction catalyst to the reaction unit.
[17] The water treatment apparatus according to any one of [10] to [16], further including a biological treatment unit that decomposes part of the aldehydes with microorganisms and uses the waste water upstream of the reaction unit.
[18] Having a nanofiltration membrane or a reverse osmosis membrane, and using the nanofiltration membrane or the reverse osmosis membrane, the treated water, the aldehydes and the oxidizable contaminant contained in the treated water, A water treatment device given in any 1 paragraph of [10]-[17] provided with the 2nd separation part separated into permeated water.

[1] A water treatment method having the following steps (i) to (v).
(I) A fenton reaction is performed on wastewater containing aldehydes and oxidizable contaminants under the following conditions (A) and (B) to oxidize the aldehydes and oxidizable contaminants. Oxidation process.
(Ii) adjusting the pH of the reaction solution obtained in the oxidation step to 6.0 or more and 10.0 or less to insolubilize ferrous ions and ferric ions generated by the Fenton reaction; An insolubilization step for producing a compound and a ferric compound.
(Iii) A first separation step of separating a suspension in which the ferrous compound and the ferric compound are suspended into sludge containing the ferric compound and treated water.
(Iv) A sludge return step for returning at least a part of the sludge generated in the first separation step to the oxidation step.
(V) A reduction step of reducing the ferric ion to the ferrous ion with an iron reduction catalyst. (A) The pH of the waste water is 1.0 or more and 4.0 or less.
(B) The following formula (S1) is satisfied.
0.17 ≦ T ₁ / (C _A × C _B ) ≦ 1.2 (S1)
T ₁ : Time required for the oxidation step (unit: time)
C _A : Concentration concentration of the aldehydes relative to the total amount of the reaction solution (unit: mol / L) C _B : Addition concentration of hydrogen peroxide relative to the total amount of the reaction solution (unit: mg / L)
[2] The water treatment method according to [1], wherein the aldehyde is propionaldehyde. [3] The water treatment method according to [1] or [2], wherein in the oxidation step, the pH of the waste water is adjusted to 1.0 or more and 4.0 or less using an acid.
[4] The water treatment method according to any one of [1] to [3], wherein the iron reduction catalyst is at least one selected from the group consisting of activated carbon and zeolite.
[5] The water treatment method according to any one of [1] to [4], wherein a ferrous salt or a ferrous oxide is used for the Fenton reaction.
[6] In any one of [1] to [5], in the first separation step, the suspension is separated into the sludge and the treated water using a microfiltration membrane or an ultrafiltration membrane. Water treatment method. [7] The water treatment according to any one of [1] to [6], further including a biological treatment step in which a part of the aldehydes is decomposed using a microorganism to form the waste water prior to the oxidation step. Method. [8] A second separation step of separating the treated water into the aldehydes and the oxidizable contaminants contained in the treated water and permeated water using a nanofiltration membrane or a reverse osmosis membrane. The water treatment method according to any one of [1] to [7].
[9] A water treatment apparatus comprising the following (1) to (5).
(1) A reaction tank that oxidizes aldehydes and oxidizable pollutants contained in wastewater by a Fenton reaction and reduces ferric ions generated by the Fenton reaction to ferrous ions by an iron reduction catalyst.
(2) An insolubilization tank in which the ferrous ions and ferric ions contained in the reaction solution supplied from the reaction tank are insolubilized to generate ferrous compounds and ferric compounds.
(3) A first separation device that separates a suspension in which the ferrous compound and the ferric compound are suspended into sludge containing the ferric compound and treated water.
(4) Sludge return means for returning at least a part of the sludge generated in the first separator to the reaction tank.
(5) Control means for controlling the Fenton reaction so as to satisfy the following condition (C).
(C) The following formula (1) is satisfied.
0.17 ≦ T ₂ / (C _A × C _B ) ≦ 1.2 (1)
T ₂ : Time for which the reaction solution stays in the reaction tank (unit: time)
C _A : Concentration concentration of the aldehydes relative to the total amount of the reaction solution (unit: mol / L) C _B : Addition concentration of hydrogen peroxide relative to the total amount of the reaction solution (unit: mg / L)
[10] The water treatment device according to [9], wherein the first separation device includes a microfiltration membrane or an ultrafiltration membrane.
[11] The water treatment device according to [9] or [10], wherein the first separation device is provided in the insolubilization tank.
[12] A first pH adjusting device for adjusting the pH of the waste water by supplying an acid to the reaction vessel;
A water treatment device according to any one of [9] to [11], comprising a second pH adjustment device that supplies alkali to the insolubilization tank to adjust the pH of the reaction solution.
[13] The water treatment apparatus according to [12], wherein the acid is sulfuric acid or hydrochloric acid.
[14] The water treatment apparatus according to any one of [9] to [13], comprising catalyst addition means for adding an iron reduction catalyst to the reaction tank.
[15] The water treatment apparatus according to any one of [9] to [14], further including a biological treatment tank upstream of the reaction tank, in which a part of the aldehydes are decomposed by microorganisms and used as the waste water.
[16] Having a nanofiltration membrane or a reverse osmosis membrane, and using the nanofiltration membrane or the reverse osmosis membrane, treating the treated water with the aldehydes and the oxidizable contaminant contained in the treated water The water treatment device according to any one of [9] to [15], further comprising a second separation device that separates into permeated water.

  According to one embodiment of the present invention, in water treatment using a Fenton reaction involving a reduction reaction of ferric ions, the aldehydes contained in the wastewater do not inhibit the reduction reaction, and the water has excellent Fenton reaction efficiency. A treatment apparatus and a water treatment reaction using the same are provided.

The figure which shows schematic structure of the water treatment apparatus 1 of 1st Embodiment. The figure which shows schematic structure of the water treatment apparatus 2 of 2nd Embodiment. The figure which shows schematic structure of 1 A of water treatment apparatuses which are the modifications of 1st Embodiment. The figure which shows schematic structure of 2 A of water treatment apparatuses which are the modifications of 2nd Embodiment.

  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.

<First Embodiment>
[Water treatment equipment]
The structure of the water treatment apparatus 1 used for the water treatment method of 1st 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 unit 10, an insolubilizing unit 20, an adjustment tank 41, a storage tank 61, and a control unit 70.

  The reaction unit 10 includes a reaction tank 11, an iron reagent addition means 15 for adding an iron reagent into the reaction tank 11, a hydrogen peroxide addition means 16 for adding hydrogen peroxide into the reaction tank 11, and a reaction tank 11 Catalyst addition means 17 for adding an iron reduction catalyst to the reaction tank 11 and dilution water addition means 18 for adding dilution water to the reaction tank 11.

  The insolubilizing unit 20 includes an insolubilizing tank 21.

Further, the water treatment apparatus 1 includes a pH adjuster 14 that adjusts the pH in the reaction tank 11 and a pH adjuster 24 that adjusts the pH in the insolubilization tank 21.
In the present specification, the pH adjusting device 14 corresponds to a first pH adjusting unit in claims. The pH adjuster 24 corresponds to a second pH adjuster in the claims.

  Further, the water treatment apparatus 1 includes a sludge return means 32 that returns at least a part of the sludge generated in the insolubilization tank 21 from the insolubilization tank 21 to the reaction tank 11.

A first separation portion 22 is provided in the insolubilization tank 21.
A second separation unit 42 is provided between the adjustment tank 41 and the storage tank 61.

(Drainage)
In the water treatment by the water treatment apparatus 1, wastewater containing aldehydes and oxidizable contaminants is oxidized using the Fenton reaction. Examples of aldehydes include propionaldehyde.
In this embodiment, the aldehyde concentration in the waste water is 0.5 × 10 ⁻³ mol / L or more.

  Examples of oxidizable contaminants 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.

(Reaction part)
The reaction unit 10 oxidizes aldehydes and oxidizable contaminants contained in the wastewater by the Fenton reaction, and reduces ferric ions (Fe ³⁺ ) generated by the Fenton reaction to ferrous ions (Fe ²⁺ ). To do. The reaction tank 11 is filled with at least an iron reagent that generates ferrous ions, hydrogen peroxide, and an iron reduction catalyst.

  A first flow path 12 and a second flow path 13 are connected to the reaction tank 11. The first flow path 12 allows wastewater containing aldehydes and oxidizable contaminants to flow into (suppli to) 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.
In addition, in this specification, the 1st reaction tank and the 2nd reaction tank comprise the reaction tank in a claim.

(First pH adjuster)
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. Therefore, it is preferable to install a measuring device (not shown) for measuring the pH in the tank in the reaction tank 11.

  In the present embodiment, the pH in the reaction vessel 11 is adjusted to a 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 contact efficiency between the ferric ion and the iron reduction catalyst can be increased while maintaining good solubility of the iron reagent in water. When the pH in the reaction tank 11 is less than 1.0 or exceeds 4.0, the pH adjuster 14 adds acid or alkali to the reaction tank 11 to adjust the pH in the reaction tank 11. The pH in the reaction tank 11 is preferably 2.0 or more and 3.0 or less, and more preferably 2.5 or more and 3.0 or less.

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, and sulfuric acid or hydrochloric acid is preferable. Among these, 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.

(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 a ferrous salt or a ferrous oxide is 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, in this embodiment, since ferric iron is reduced and ferrous iron is regenerated by the iron reduction catalyst, ferric iron can be used from the beginning 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.

(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 by hydrogen peroxide to regenerate ferrous ions. The iron reduction catalyst is preferably at least one selected from the group consisting of activated carbon and zeolite, and activated carbon is more preferable from the viewpoint of catalyst efficiency and waste catalyst treatment.

  The shape of the iron reduction catalyst is preferably powder from the viewpoint of catalyst efficiency. In addition, the particle size of the iron reduction catalyst is preferably 0.05 μm to 100 μm because the catalyst can be easily recovered.

  In the reaction tank 11, ferric iron is reduced and ferrous iron is regenerated in the presence of an iron reduction catalyst simultaneously with the normal Fenton reaction. Thereby, the ferric iron discarded in the water treatment using only the Fenton reaction can be reused. For this reason, the cost of ferric iron treatment can be reduced, and the amount of iron reagent added from the iron reagent addition means 15 can be reduced.

(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. The aldehydes and oxidizable pollutants contained in the wastewater are oxidatively decomposed by the generated hydroxyl radicals. In addition, when the wastewater contains inorganic substances such as phosphorous acid and hypophosphorous acid, these are oxidized by hydroxy radicals, 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.

  In this embodiment, hydrogen peroxide is used for the above-described reduction reaction of ferric ions in addition to the normal Fenton reaction. Therefore, it is preferable that the amount of hydrogen peroxide added from the hydrogen peroxide adding means 16 is larger than that in the first embodiment.

(Control part)
The control unit 70 controls the reaction unit 10 to satisfy the following condition (C). Specifically, the control unit 70 controls the hydrogen peroxide addition unit 16 and the dilution water addition unit 18 of the reaction unit 10. Thereby, the control unit 70 controls the Fenton reaction.
(C) Time reaction solution remaining in the reaction vessel 11: a value T ₂ of the (unit time), concentration of the aldehydes for reaction total amount (unit: mol / L) over the value C _A of the relative reaction total volume addition concentration (unit: mg / L) of hydrogen peroxide value obtained by dividing the product of the value C _B of satisfies the following equation (1).
0.17 ≦ T ₂ / (C _A × C _B ) ≦ 1.2 (1)

In the present embodiment, the value of T ₂ / (C _A × C _B ) is preferably 0.20 or more and 0.80 or less, more preferably 0.22 or more and 0.70 or less, and 0.30 or more and 0.60 or less. Is more preferably 0.40 or more and 0.50 or less.

  The control unit 70 preferably has a measuring device that measures the concentration of aldehydes contained in the total amount of the reaction solution.

When the value of T ₂ / (C _A × C _B ) is less than 0.17, the time that the reaction liquid stays in the reaction tank 11 is lengthened. Alternatively, the reaction solution is diluted by adding dilution water so that the addition concentration of hydrogen peroxide or the aldehyde content concentration satisfying the above formula (1) is added by the dilution water adding means 18.
The amount of hydrogen peroxide added is determined according to the target treated water quality. At that time, the amount of hydrogen peroxide added is controlled so that the value of T ₂ / (C _A × C _B ) satisfies the above formula (1).

  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.

(Insolubilized part)
The insolubilized part 20 insolubilizes the ferrous ions and ferric ions generated by the Fenton reaction to remove them from the reaction solution, thereby generating ferrous compounds and ferric compounds. The reaction solution is supplied from the reaction tank 11 to the insolubilization tank 21.

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

(Second pH adjuster)
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 adjusted to a range of 6.0 or more and 10.0 or less. Therefore, it is preferable to install a measuring device (not shown) for measuring the pH in the tank in the insolubilizing tank 21. The pH adjusting device 24 adds alkali to the insolubilizing tank 21 according to the pH in the tank. The pH in the insolubilization tank 21 is preferably from 7.0 to 9.0, more preferably from 7.5 to 8.5, and even more preferably from 7.8 to 8.3.

  Examples of the kind of alkali to be added include the same alkalis that can be added by the pH adjuster 14.

  When inorganic substances such as phosphorous acid and hypophosphorous acid are contained in the wastewater as oxidizable contaminants, when calcium hydroxide is added as alkali, the phosphorous acid and calcium hydroxide in the reaction solution react to precipitate. Form things. Therefore, in the 1st separation part 22 mentioned below, it can precipitate-separate into the precipitate 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 1st separation part 22 mentioned below, it can precipitate-separate into the precipitate containing orthophosphoric acid, and treated water.

(Sludge return means)
The sludge return means 32 returns at least a part of the sludge containing the iron compound and the iron oxidation catalyst from the insolubilization tank 21 to the reaction tank 11. The sludge return means 32 includes a fifth flow path 33. The fifth flow path 33 discharges at least a part of the sludge containing the iron compound and the iron reduction catalyst 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 sludge containing the iron compound and the iron reduction catalyst 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 part of the sludge 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 sludge is, the longer the time from the generation of ferrous iron to the use of the Fenton reaction can be increased. Therefore, the ferric iron in the returned sludge can be effectively reused for the Fenton reaction.

<First separator>
The first separation unit 22 performs solid-liquid separation of a suspension in which the ferrous compound and the ferric compound are suspended into sludge containing the iron compound and the iron oxidation catalyst and treated water. The first separation unit 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.
The first membrane module 23 is preferably provided with a microfiltration membrane or an ultrafiltration membrane. Examples of the microfiltration membrane include 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 difluoride (PVDF), polytetrafluoroethylene (PTFE), and the like. 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 and the iron reduction catalyst from leaking into the treated water.

  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 first membrane module 23 from the first separation unit 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 first separation unit 22 may be provided with a membrane surface cleaning aeration means disposed below the first membrane module 23. A well-known thing can be employ | adopted as said aeration means.

  In addition, in this embodiment, although the 1st separation part 22 was set as the structure provided with the 1st membrane module 23, it is not limited to this. The first separation unit 22 may include separation means other than the filtration membrane. Examples of separation means other than the filtration membrane include sand filtration, pressurized flotation separation, centrifugal separation, belt press, and sedimentation by a sedimentation basin.

(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 second separation unit 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 second separation unit 42 separates the treated water separated in the first separation step into oxidizable contaminants contained in the treated water and permeated water. The second separation unit 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 oxidizable contaminants on the membrane surface and maintain the filtration flux.

  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 second separation unit 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 at the second separation unit 42. ing. The flow rate can be adjusted by adjusting the output of the pump 55a.

(Reservoir)
The storage tank 61 stores the permeated water supplied from the second separation unit 42 via the fourth flow path 51. The permeated water stored in the storage tank 61 may be returned to a factory or the like that has discharged wastewater and reused, or may be diluted with industrial water or the like, and may be discharged into a river or the like.

  According to the water treatment apparatus 1 configured as described above, in the water treatment using the Fenton reaction accompanied by the reduction reaction of ferric ions, the reduction reaction is not inhibited by the aldehydes contained in the wastewater, and the Fenton reaction Excellent efficiency.

[Water treatment method]
The water treatment method of the first embodiment includes a reaction step including an oxidation treatment and a reduction treatment, an insolubilization step, a first separation step, a second separation step, and a sludge return step.
In the present embodiment, first, the aldehyde concentration in the waste water is measured upstream of the reaction tank 11, and the obtained measurement result is larger than the lower limit value of the aldehyde concentration (C _A ), and the production method of the present invention is applied. Determine if it is possible. And the process after a reaction process is performed with respect to the waste_water | drain which is larger than the lower limit of an aldehyde density | concentration (C _<A> ) and was judged that the manufacturing method of this invention is applicable.

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, a fenton reaction is performed on the wastewater containing aldehydes and oxidizable contaminants in the reaction tank 11 under the following conditions (A) and (B). And oxidizes oxidizable pollutants (oxidation treatment / reaction process).
(A) The pH of the waste water is 1.0 or more and 4.0 or less.
(B) The value T _{1 of the} time required for the reaction step (unit: time) is the value C _A of the content concentration (unit: mol / L) of aldehydes relative to the waste water and the concentration of hydrogen peroxide added to the waste water (unit: mg). / L) divided by the product of the value C _B satisfies the following formula (1).
0.17 ≦ T ₁ / C _A × C _B ≦ 1.2 (1)

Next, in the insolubilization tank 21, the pH of the reaction solution obtained in the reaction step is adjusted to 6.0 or more and 10.0 or less to insolubilize ferrous ions and ferric ions generated by the Fenton reaction, A ferrous compound and a ferric compound are produced (insolubilization step).
Further, the suspension in which the ferrous compound and the ferric compound are suspended is solid-liquid separated into sludge containing the iron compound and the iron reduction catalyst by the first separation unit 22 and the treated water (first separation step). ).

Furthermore, the treated water separated in the first separation step is stored in the adjustment tank 41. Then, the treated water is caused to flow out from the adjustment tank 41 to the second separation unit 42, and membrane separation is performed by the second separation unit 42 (second separation step). In the second separation step, the treated water is separated into aldehydes and oxidizable contaminants contained in the treated water and permeated water.
In the storage tank 61, the permeated water separated in the second separation step is stored.

Moreover, in the sludge return means 32 provided in the insolubilization tank 21, the sludge containing the ferric compound and the iron reduction catalyst separated in the first separation step is returned from the insolubilization tank 21 to the reaction tank 11 (sludge return step). . The ferric compound returned to the reaction tank 11 dissolves to become ferric ions, and is further reduced to ferrous ions by hydrogen peroxide and an iron reduction catalyst (reduction treatment / reaction process).

  According to the water treatment method of the above method, in the water treatment using the Fenton reaction accompanied by the reduction reaction of ferric iron, the reduction reaction is not inhibited by the aldehydes contained in the waste water, and the efficiency of the Fenton reaction is improved. Are better.

Second Embodiment
Hereinafter, the water treatment apparatus 2 of 2nd Embodiment of this invention is demonstrated. FIG. 2 is a diagram illustrating a schematic configuration of the water treatment device 2 of the second embodiment.
As shown in FIG. 2, the water treatment device 2 of the second embodiment includes a biological treatment unit 80 upstream of the reaction tank 11. Moreover, the water treatment apparatus 2 includes a microorganism addition unit that adds microorganisms to the biological treatment unit 80.

(Biological Processing Department)
The biological treatment unit 80 includes a biological treatment tank 81. The biological treatment tank 81 stores raw water (drainage) before being oxidized in the reaction tank 11.

  A sixth channel 82 and a first channel 83 are connected to the biological treatment tank 81. The sixth channel 82 allows raw water containing aldehydes and oxidizable contaminants to flow into (be supplied to) the biological treatment tank 81. The first flow path 83 allows the waste water discharged from the biological treatment tank 81 to flow into (supply to) the reaction tank 11.

  In the water treatment device 2 shown in FIG. 2, the method for supplying wastewater from the biological treatment tank 81 to the reaction tank 11 is not particularly limited, and the wastewater may be supplied using a pump, or the wastewater may be discharged using an overflow. You may supply.

  In the water treatment apparatus 2 shown in FIG. 2, an example in which one biological treatment tank 81 is provided is shown, but a plurality of biological treatment tanks 81 may be arranged in series. In that case, since the time required for biological treatment of aldehydes can be increased, the aldehyde concentration in the waste water can be sufficiently reduced.

In addition, when a plurality of biological treatment tanks 81 are arranged, a method for feeding liquid from the first biological treatment tank to the second biological treatment tank is not particularly limited, and liquid feeding may be performed using a pump, or overflow may be caused. You may use and send liquid.
In addition, in this specification, the 1st biological treatment tank and the 2nd biological treatment tank comprise the reaction tank in a claim.

The water treatment method of the second embodiment has a biological treatment step prior to the reaction step.
In the biological treatment tank 81, a part of the aldehydes are decomposed by microorganisms and used as waste water (biological treatment step).

  According to the water treatment apparatus 2 configured as described above, since aldehydes contained in the wastewater can be reduced before being oxidized in the reaction tank 11, the reduction reaction of ferric ions is not inhibited, and the Fenton reaction Excellent efficiency.

  According to the water treatment method as described above, the aldehydes contained in the wastewater can be reduced before the reaction step, so that the reduction reaction of ferric ions is not inhibited and the Fenton reaction is excellent in efficiency.

  Note that the water treatment apparatus and the water treatment method of one embodiment of the present invention are not limited to the above-described embodiments. For example, in the said embodiment, although the example which provides the 1st isolation | separation part 22 in the insolubilization tank 21 was shown, the 1st isolation | separation part 22 does not need to be provided in the insolubilization tank 21. FIG. In that case, another tank may be arrange | positioned between the insolubilization tank 21 and the adjustment tank 41, and the 1st separation part 22 may be provided in this tank.

  When the 1st separation part 22 is not provided in the insolubilization tank 21, the structure shown below as a structure of the 1st membrane module 23 may be sufficient. 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 and an iron reduction catalyst is stored, and the secondary side of the filtration membrane is suctioned. It may be connected to a pump.

  Further, for example, in the first embodiment, the example in which the second separation unit 42 is provided between the insolubilization tank 21 and the storage tank 61 has been described, but the second separation unit 42 may be omitted. FIG. 3 is a diagram illustrating a schematic configuration of a water treatment apparatus 1A that is a modification of the first embodiment. As shown in FIG. 3, in the water treatment apparatus 1 </ b> A, treated water may be allowed to flow into the storage tank 61 via the third flow path 31.

  Similarly, in the second embodiment, the second separator 42 may be omitted. FIG. 4 is a diagram illustrating a schematic configuration of a water treatment apparatus 2A that is a modification of the second embodiment. As shown in FIG. 4, in the water treatment apparatus 2 </ b> A, the treated water may be flowed into the storage tank 61 through the third flow path 31.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.

<Measurement of residual concentration of hydrogen peroxide in treated water>
[Example 1]
In a 500 mL container, put the model wastewater whose propionaldehyde content concentration is adjusted to 5.2 × 10 ⁻³ mol / L with respect to the total amount of the reaction solution, and add sulfuric acid into the container to adjust the pH to 3.0. did. Next, activated carbon (manufactured by Mitsubishi Chemical Aqua Solutions Co., Ltd., product name “DiaFellow CT”) was added to the container so that the concentration of the iron reduction catalyst with respect to the total amount of the reaction solution was 1000 mg / L. Further, iron (II) sulfate heptahydrate (FeSO ₄ .7H ₂ O) was added so that the concentration of the iron reagent added to the total amount of the reaction solution was 250 mg / L. By stirring these mixed solutions, they were sufficiently dispersed and dissolved in the model waste water. Next, while stirring this solution, hydrogen peroxide was added to the vessel so that the concentration of hydrogen peroxide added to the total amount of the reaction solution was 2500 mg / L, thereby preparing a reaction solution. Further, the Fenton reaction was carried out for 4 hours while stirring the reaction solution (reaction step).

  While stirring the reaction solution after completion of the Fenton reaction, an aqueous sodium hydroxide solution was added to adjust the pH of the reaction solution to 8.0, which was used as an insolubilizing solution (insolubilizing step). Next, using a syringe filter (product name “PequiQuy Nylon Non-sterile Syringe Filter”, manufactured by Rephile, pore size: 0.45 μm), the obtained insolubilized solution was treated with sludge containing iron compound and iron reduction catalyst, treated water, (First separation step).

  Hydrogen peroxide in the treated water was colored with potassium iodide and measured with an absorptiometer (product name “Digital Pack Test” manufactured by Kyoritsu Riken Co., Ltd.). The concentration was 48 mg / L. Further, the consumption rate of hydrogen peroxide calculated from the residual concentration of hydrogen peroxide in the treated water and the concentration of hydrogen peroxide added to the total amount of the reaction solution was 98.1%.

[Example 2]
The same procedure as in Example 1 was performed except that the Fenton reaction was performed for 6 hours. As a result of measuring the residual concentration of hydrogen peroxide in the obtained treated water, it was 3 mg / L or less of the lower limit of detection. The calculated consumption rate of hydrogen peroxide was 99.9% or more.
[Example 3]
The same procedure as in Example 1 was performed, except that the model wastewater prepared with a propionaldehyde content concentration of 1.0 × 10 ⁻² mol / L with respect to the total amount of the reaction solution was used to carry out the Fenton reaction for 6 hours. As a result of measuring the residual concentration of hydrogen peroxide in the obtained treated water, it was 68 mg / L. The calculated consumption rate of hydrogen peroxide was 97.3%.

[Example 4]
The same procedure as in Example 1 was performed, except that the model wastewater prepared with a propionaldehyde content concentration of 2.1 × 10 ⁻² mol / L with respect to the total amount of the reaction solution was used to carry out the Fenton reaction for 24 hours. As a result of measuring the residual concentration of hydrogen peroxide in the obtained treated water, it was 3 mg / L or less of the lower limit of detection. The calculated consumption rate of hydrogen peroxide was 99.9% or more.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the Fenton reaction was performed for 2 hours. As a result of measuring the residual concentration of hydrogen peroxide in the obtained treated water, it was 490 mg / L. The calculated consumption rate of hydrogen peroxide was 80.4% or more.

[Comparative Example 2]
The same procedure as in Example 3 was performed except that the Fenton reaction was performed for 4 hours. As a result of measuring the residual concentration of hydrogen peroxide in the treated water obtained, it was 265 mg / L. The calculated consumption rate of hydrogen peroxide was 89.4% or more.

[Comparative Example 3]
The same operation as in Example 4 was performed except that the Fenton reaction was performed for 4 hours. As a result of measuring the residual concentration of hydrogen peroxide in the obtained treated water, it was 356 mg / L. The calculated consumption rate of hydrogen peroxide was 85.8% or more.

[Comparative Example 4]
The same procedure as in Example 1 was performed except that the Fenton reaction was carried out for 24 hours using a model wastewater whose propionaldehyde content was adjusted to 0.21 mol / L with respect to the total amount of the reaction solution. It was 1060 mg / L as a result of measuring the residual density | concentration of the hydrogen peroxide in the obtained treated water. The calculated consumption rate of hydrogen peroxide was 57.6% or more.

The results of Examples and Comparative Examples are shown in Table 1. In Table 1, T ₁ represents a value of time (unit: time) required for the reaction step. The _{C A,} the content concentration of the aldehydes for reaction total amount (unit: mol / L) indicates the value of. The _{C B} are added the concentration of hydrogen peroxide to the reaction solution the total amount (unit: mg / L) indicates the value of.

  The consumption rate of hydrogen peroxide was evaluated according to the following criteria. In Table 1, the case where the consumption rate of hydrogen peroxide was 90% or more was designated as “◯”, and the case where the consumption rate of hydrogen peroxide was less than 90% was designated as “X”.

As shown in Table 1, in Examples 1 to 4 where the value of T ₁ / (C _A × C _B ) is in the range of 0.17 to 1.2, the consumption rate of hydrogen peroxide is 90% or more. Yes, the hydrogen peroxide consumption rate was excellent. On the other hand, in Comparative Examples 1 to 4 in which the value of T ₁ / (C _A × C _B ) is outside the range of 0.17 or more and 1.2 or less, the consumption rate of hydrogen peroxide is less than 90%. The consumption rate of hydrogen peroxide was inferior.

  From the above, it was shown that the present invention is useful.

  DESCRIPTION OF SYMBOLS 1, 2 ... Water treatment apparatus, 10 ... Reaction part, 11 ... Reaction tank, 14, 24 ... pH adjuster, 17 ... Catalyst addition means, 20 ... Insolubilization part, 21 ... Insolubilization tank, 22 ... First separation part, 32 ... sludge return means, 42 ... second separation part, 70 ... control part, 80 ... biological treatment part, 81 ... biological treatment tank

Claims (18)

A method for treating wastewater containing aldehydes and oxidizable pollutants, comprising the following steps (i) to (iii):
(I) Ferrous ions and hydrogen peroxide are added so as to satisfy the following condition (B) with respect to the wastewater that satisfies the following condition (A) stored in the reaction tank, and the aldehydes in the wastewater And an oxidation treatment for oxidizing the oxidizable contaminant, and a reduction treatment for reducing ferric ions generated by the oxidation treatment to the ferrous ions in the presence of an iron reduction catalyst. Reaction step to be obtained (ii) The pH of the reaction solution obtained in the step (i) is adjusted to 6.0 or more and 10.0 or less, and the ferrous ions and the ferric ions in the reaction are adjusted. Insolubilization step of obtaining a suspension in which the ferrous compound and the ferric compound are suspended by insolubilizing to produce a ferrous compound and a ferric compound (iii) In the step (ii) The obtained suspension is The first separation step of separating the sludge containing iron compound, treated with water, the <Reaction conditions>
(A) The pH of the waste water is 1.0 or more and 4.0 or less.
(B) 0.17 ≦ T ₁ / (C _A × C _B ) ≦ 1.2
(T ₁ : time (unit: time) that the waste water stays in the reaction tank)
C _A : Concentration concentration of the aldehydes relative to the total amount of the reaction solution (unit: mol / L)
C _B : Addition concentration of hydrogen peroxide with respect to the total amount of the reaction solution (unit: mg / L)) The water treatment method according to claim 1, further comprising the following step (iv).
(Iv) Sludge returning step of returning at least a part of the sludge separated in the step (iii) to the step (i)   The water treatment method according to claim 1, wherein the aldehyde is propionaldehyde.   The water treatment method according to any one of claims 1 to 3, wherein in the step (i), the pH of the waste water is adjusted to 1.0 or more and 4.0 or less using an acid.   The water treatment method according to claim 1, 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 any one of claims 1 to 5, wherein a ferrous salt or a ferrous oxide is used for the oxidation treatment in the step (i).   The water treatment method according to any one of claims 1 to 6, wherein in the step (iii), the suspension is separated into the sludge and the treated water using a microfiltration membrane or an ultrafiltration membrane.   Prior to the step (i), the water treatment method according to any one of claims 1 to 7, further comprising a biological treatment step in which a part of the aldehydes is decomposed using microorganisms to form the waste water.   The method according to claim 1, further comprising a second separation step of separating the treated water into the aldehydes and the oxidizable contaminants contained in the treated water and permeated water using a nanofiltration membrane or a reverse osmosis membrane. The water treatment method according to claim 1. A water treatment apparatus comprising wastewater containing aldehydes and oxidizable pollutants and comprising the following (1) to (4).
(1) An oxidation treatment in which ferrous ions and hydrogen peroxide are added to the waste water to oxidize the aldehydes and the oxidizable contaminants in the waste water, and ferric ions generated by the oxidation treatment (2) The ferrous ion contained in the reaction solution supplied from the reaction unit. And insolubilizing part to obtain a suspension in which ferrous compound and ferric compound are suspended by insolubilizing ferric ion and generating ferrous compound and ferric compound (3) A first separation unit that separates the suspension supplied from the insolubilization unit into sludge containing the ferric compound and treated water. (4) The reaction unit so as to satisfy the following formula (1): controls the control unit 0.17 ≦ _{T 2 (C A × C B) ≦} 1.2 ... (1)
(T ₂ : time for which the reaction liquid stays in the reaction part (unit: time)
C _A : Concentration concentration of the aldehydes relative to the total amount of the reaction solution (unit: mol / L)
C _B : Addition concentration of hydrogen peroxide with respect to the total amount of the reaction solution (unit: mg / L)) The water treatment apparatus according to claim 10, further comprising the following (5).
(5) Sludge return means for returning at least a part of the sludge generated in the first separation part to the reaction part.   The water treatment device according to claim 10 or 11, wherein the first separation unit includes a microfiltration membrane or an ultrafiltration membrane.   The water treatment apparatus according to any one of claims 10 to 12, wherein the first separation unit is provided in the insolubilization unit. A first pH adjusting device for adjusting the pH of the waste water by supplying an acid to the reaction section;
The water treatment apparatus of any one of Claims 10-13 provided with the 2nd pH adjustment apparatus which supplies alkali to the said insolubilization part and adjusts the pH of the said reaction liquid.   The water treatment apparatus according to claim 14, wherein the acid is sulfuric acid or hydrochloric acid.   The water treatment apparatus according to any one of claims 10 to 15, further comprising catalyst addition means for adding an iron reduction catalyst to the reaction section.   The water treatment apparatus according to any one of claims 10 to 16, further comprising a biological treatment unit that decomposes a part of the aldehydes with microorganisms and uses the waste water upstream of the reaction unit.   A nanofiltration membrane or a reverse osmosis membrane, and using the nanofiltration membrane or the reverse osmosis membrane, the treated water, the aldehydes and the oxidizable contaminants contained in the treated water, and permeated water; The water treatment apparatus of any one of Claims 10-17 provided with the 2nd isolation | separation part isolate | separated into.

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