JP2011251275A - Water treatment method and water treatment apparatus used for water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method by which water treatment is carried out efficiently without requiring excessive energy cost and making an apparatus large-sized and to provide the water treatment apparatus using the water treatment method.SOLUTION: The water treatment method includes supplying water droplets made from water W to be treated in a discharge space, and decomposing a substance to be treated in the water drops by active species generated by electric discharge in the discharge space. The water droplets passed through the discharge space and treated is stored as the treated water W1 in an oxidation prompting treatment part 51a of a treated water tank 5a and the remaining substance to be treated in the treated water W 1 is promptly oxidized by supplying iron powder 91 into the treated water W1 stored in the oxidation prompting treatment part 51a.

Description

  The present invention relates to a water treatment method for decomposing organic substances, inorganic substances, and microorganisms contained in tap water, sewage, waste water, and the like, and a water treatment apparatus used in this water treatment method.

Conventionally, ozone has been used for treatments such as oxidative decomposition, sterilization, and deodorization of organic substances in water in fields such as clean water, sewage, industrial wastewater, and pools (see Patent Document 1).
However, ozone has a weak oxidizing power and cannot be mineralized even if it can be made hydrophilic and low molecular. In addition, hardly decomposable organic substances such as dioxins cannot be decomposed.

Therefore, in order to improve the treatment capacity, ozone is generated by discharge, and OH radicals, O radicals, and the like that have stronger oxidizing power than ozone are generated, and the water to be treated is discharged in a discharge space (discharge field) containing the ozone and radicals. A water treatment apparatus has been proposed in which oxidation treatment is performed not only by ozone but also by radicals by exposure to water (see Patent Document 2).
However, radicals have a short lifetime and tend to disappear, so that the efficiency is low, and the water treatment apparatus previously proposed cannot sufficiently exhibit the oxidizing action by radicals.

Therefore, the inventor of the present invention provides a linear electrode as a voltage application electrode along the central axis of the cylindrical electrode as a ground electrode, and applies a high voltage to the linear electrode to cause discharge between both electrodes. At the same time, a water treatment apparatus is provided in which water to be treated is supplied to the discharge space in the form of water droplets, and the treatment target substance in the water to be treated is decomposed by active species such as radicals and ozone generated in the discharge space. It has been proposed (see Patent Document 3).
In other words, this water treatment apparatus generates radicals and ozone one after another by electric discharge, and improves the treatment efficiency by increasing the surface area of contact with the radicals and ozone by forming water to be treated into water droplets.

Japanese Patent Laid-Open No. 9-267096 JP 2000-279977 A JP 2009-241055 A

However, in the case of the water treatment apparatus proposed above, the treatment efficiency was better than that of the conventional method, but it is required to further improve the treatment efficiency when put into practical use.
That is, in the above water treatment apparatus, it is necessary for water droplets to remain in the discharge space for as long as possible, but in order to keep the water droplets in the discharge space for a long time, it is necessary to make the electrode large and long. As a result, there is a problem that the apparatus is increased in size, and a large amount of electric energy is required for discharging, which is costly.

  In view of the above circumstances, the present invention provides a water treatment method capable of efficiently performing water treatment without much energy cost and without increasing the size of the device, and a water treatment device used in the water treatment method. It is intended to provide.

  In order to achieve the above object, a water treatment method according to the present invention (hereinafter referred to as “water treatment method of the present invention”) supplies water to be treated in the form of water droplets in a discharge space, and discharges in the discharge space. A water treatment method in which a substance to be treated in water droplets is decomposed by active species generated by the method, wherein water droplets that have passed through the discharge space are treated as treated water and stored in a treated water storage tank. It is characterized in that iron powder is supplied into the treated water stored in the storage tank to promote oxidation of the remaining treatment target substance in the treated water.

  Further, the water treatment apparatus according to the present invention (hereinafter referred to as “the water treatment apparatus of the present invention”) supplies water to be treated in the form of water droplets in the discharge space, and depending on the active species generated by the discharge in the discharge space. A water treatment apparatus for decomposing a treatment target substance in water droplets, receiving a treated water droplet through the discharge space and storing it as treated water, and iron powder in the treated water storage tank And an iron powder supply means for supplying.

  In the present invention, the active species means radicals such as O radical and OH radical, and ozone.

  Although it does not specifically limit as iron powder used by this invention, It is preferable to use the reduced iron powder whose particle size is 500 micrometers or less, and it is more preferable to make 40 micrometers or less especially exist. That is, if the particle size of the reduced iron powder is too large, the reduced iron powder may immediately settle and the reaction may be difficult to proceed unless it is stirred vigorously with a stirrer or the like. On the other hand, when trying to perform strong stirring with a stirrer, a large-capacity stirrer is required, which may increase equipment costs and energy costs. Therefore, it is preferable to reduce the particle size of the reduced iron powder so that it does not settle and floats for a long time.

Although the addition amount of reduced iron powder is not specifically limited, It is preferable that 0.1-10 [g / L] is contained in treated water.
Moreover, although the reduced iron powder used by this invention is not specifically limited, For example, what was manufactured with the mill scale reduced iron powder method and the ore reduced iron powder method is mentioned.

Further, in the present invention, although not particularly limited, it is preferable to supply iron powder into the treated water and simultaneously bubble oxygen into the treated water.
That is, by bubbling oxygen, the iron powder can float for a longer time, promote the generation of OH radicals, and activate the decomposition process more.

The oxygen to be bubbled need not be pure oxygen as long as it contains oxygen to some extent, and may be air.
The bubble diameter of the bubbled oxygen is not particularly limited, but it is preferable to make the bubbles as fine as possible in consideration of the reaction rate.
The amount of oxygen supplied to the treated water is not particularly limited, but is preferably 0.2 to 2 [L / min · L-treated water].

In the present invention, the discharge method is not particularly limited as long as a discharge that generates high-energy electrons or ultraviolet rays occurs. However, one electrode is a voltage application electrode, the other electrode is a ground electrode, and the voltage application electrode is a high voltage. A method of applying a pulse voltage can be mentioned.
The materials for the voltage application electrode and the ground electrode are not particularly limited, but titanium and stainless steel are preferable in consideration of corrosion resistance.

The shape of the electrode is not particularly limited, but in the case of the ground electrode, it is not particularly limited, and examples thereof include a cylindrical electrode such as a cylindrical electrode and a cylindrical mesh electrode, a flat plate electrode, and the like, and a cylindrical electrode is preferable.
On the other hand, for example, when the ground electrode is a cylindrical electrode, the voltage application electrode includes a wire electrode, a screw electrode, a sword mountain electrode, a wire brush electrode, and the like provided along the central axis of the cylindrical electrode. When the electrode is a flat plate electrode, a flat plate electrode provided in parallel to the flat plate electrode is exemplified.

  Further, a plurality of pairs of voltage application electrodes and ground electrodes may be provided in the processing chamber instead of only one pair.

  The discharge voltage applied between the voltage application electrode and the ground electrode is not particularly limited as long as it is a voltage at which discharge occurs.

In the present invention, the substance to be treated is not particularly limited, and examples thereof include various organic compounds, organic substances such as bacteria and odor components.
In the present invention, the water droplet forming means is not particularly limited, and examples thereof include a spray nozzle and a shower nozzle.
In addition, although the said water droplet is not specifically limited, In order to improve the contact with the radical and ozone which generate | occur | produce in a discharge space, it is preferable to use a water droplet as fine as possible.

In the water treatment apparatus of the present invention, the treated water storage tank is not particularly limited, but the treated water is stored, and an accelerated oxidation treatment unit that promotes oxidation of the remaining treatment target substance, and a supernatant water that stores supernatant water of the accelerated oxidation treatment unit It is good also as a structure provided with the storage part.
That is, iron ions generated by supplying iron powder to the treated water storage tank act as a flocculant, and aggregates aggregated in the treated water are generated. Therefore, if the discharge is performed as it is, the agglomerates are also discharged together, so it is necessary to provide a separate solid-liquid separation device. However, it is not necessary to separately provide a solid-liquid separation device by leaving the agglomerate on the accelerated oxidation treatment unit side and discharging the supernatant water once stored in the supernatant water storage unit.

Moreover, the water treatment apparatus of this invention is good also as a structure provided with the circulation path which supplies the treated water of a treated water storage tank to discharge space again.
That is, the treatment water can be repeatedly treated in the discharge space and the treatment water storage tank by circulation, and high treatment performance can be obtained even if the entire apparatus is downsized.

  The water treatment method of the present invention is a water treatment method in which water to be treated is supplied in the discharge space as water droplets, and the treatment target substance in the water droplets is decomposed by active species generated by discharge in the discharge space. In addition, water droplets processed through the discharge space are stored in the treated water storage tank as treated water, and iron powder is supplied into the treated water stored in the treated water storage tank to promote oxidation of the remaining treatment target substances in the treated water. I tried to do it.

That is, by subjecting the water to be treated to water droplets and passing through the discharge space, the material to be treated in the water droplets is brought into contact with ozone and radicals generated in the discharge space to decompose the material to be treated in the water droplets. Can do.
Moreover, hydrogen peroxide and nitrogen oxides are also formed by discharge, and this hydrogen peroxide dissolves in the treated water received in the treated water storage tank. In addition, nitrogen oxides dissolve in the treated water to become nitric acid, and the treated water becomes acidic.

  In the treated water storage tank, ferrous ions formed on the surface of the iron powder react catalytically with hydrogen peroxide generated by the discharge to generate OH radicals with strong oxidizing power and remain in the treated water. The target substance to be processed is decomposed. Therefore, the organic matter in the for-treatment water is decomposed quickly and efficiently.

  As described above, according to the water treatment method of the present invention, the decomposition of the organic compound is not only caused by ozone and radicals generated in the discharge space, but also by adding iron powder without applying electric energy, so-called Since the residual material to be treated is subjected to accelerated oxidative decomposition using the Fenton reaction, water treatment can be efficiently performed without much energy cost and without increasing the size of the apparatus.

It is a schematic diagram explaining 1st Embodiment of the water treatment apparatus concerning this invention. It is a circuit diagram of the high voltage pulse generator of the water treatment apparatus of FIG. It is a schematic diagram explaining 2nd Embodiment of the water treatment apparatus concerning this invention. It is a graph which compares and shows the indigo carmine density | concentration change of the to-be-processed water accompanying progress of the processing time investigated in Example 1 and the comparative example 1. FIG. 6 is a graph showing a change in the concentration of hydrogen peroxide with the lapse of treatment time examined in Experimental Example 1. It is a graph showing the concentration change of nitrate ion with progress of processing time investigated in example 1 of an experiment.

Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof.
FIG. 1 shows a first embodiment of a water treatment apparatus according to the present invention.

As shown in FIG. 1, the water treatment apparatus 1a includes a treatment chamber 2, a cylindrical electrode 3, a linear electrode 4, a treated water storage tank 5, a pump 6, and a shower nozzle 7 as a water droplet forming means. The water supply hose 71 to be treated as a circulation path, the mixed gas supply means 8a, the iron powder supply device 9a, and the high voltage pulse generator 10 as a high voltage power source are provided.
The processing chamber 2 is formed of, for example, an insulating material such as an acrylic resin, or the inner surface of a stainless steel cylindrical body is covered with an insulating material, and has a cylindrical shape.

The processing chamber 2 includes an upper lid 23, and a shower nozzle installation hole 23 a is provided in the upper lid 23.
An exhaust pipe 25 is provided at the lower end of the processing chamber 2. It is preferable to provide an ozone removing device such as an ozone removing filter in the middle or the outlet of the exhaust pipe 25.

The cylindrical electrode 3 is obtained, for example, by processing a stainless steel 2.5 mesh, wire net of 1.1 mm into a cylindrical shape, and the outer diameter is slightly smaller than the inner diameter of the processing chamber body 21. .
The linear electrode 4 is formed of, for example, a titanium steel wire having a diameter of 1 mm, and is provided along the central axis of the cylindrical electrode 3.

The treated water storage tank 5 a includes a tank body 51 and a lid 52.
The inside of the tank body 51 is divided into an accelerated oxidation treatment part 51a and a supernatant water storage part 51b through a partition wall 53 having a height at which an overflow gap 54 is formed between the tank body 51 and the lid 52.

The lid 52 covers the upper opening of the tank body 51 so as to face the lower end opening of the processing chamber 2 and all the portions other than the supply port of the iron powder supply device 9a described later, and supports the processing chamber 2 from below. It has been.
The supernatant water reservoir 51 b of the tank body 51 is connected to the pump 6.
The pump 6 is configured to send the separated water W2 (or water to be treated W) in the supernatant water reservoir 51b to the shower nozzle 7 via the water to be treated supply hose 71.

The shower nozzle 7 turns the separated water W2 (or treated water) sent through the treated water supply hose 71 into a mist state composed of water droplets having a particle size of 1500 μm or less toward the upper opening of the cylindrical electrode 3. To be injected.
Moreover, the spray angle of the shower nozzle 7 is adjusted to an angle along the inner wall surface of the cylindrical electrode 3 that is the outermost edge of the discharge space at the maximum spread portion of the sprayed water mist M to be sprayed.

  The mixed gas supply means 8 a includes an oxygen cylinder 81, an oxygen supply pipe 82, a nitrogen cylinder 83, a nitrogen supply pipe 84, a mixer (GM-A2 manufactured by Matsumoto Kikai) 85, and a mixed gas supply pipe 86. ing.

The mixer 85 mixes oxygen sent from the oxygen cylinder 81 through the oxygen supply pipe 82 and nitrogen sent from the nitrogen cylinder 83 through the nitrogen supply pipe 84 to a predetermined mixing ratio. It is like that.
The mixed gas supply pipe 86 supplies the mixed gas obtained by mixing with the mixer 85 into the processing chamber 2 from the upper end portion of the processing chamber 2.
The oxygen concentration in the mixed gas is set to 25 to 90% by volume.

  The iron powder supply device 9a can supply a fixed amount of iron powder 91 from the supply port provided in the lid 52 to the accelerated oxidation processing unit 51a.

  As shown in FIG. 2, the high-voltage pulse generator 10 includes a high-voltage DC power supply 101, a capacitor 102, a resistor 103, a trigger tron gap switch 104, a pulse transformer 105, and a trigger circuit 106.

The high voltage pulse generator 10 operates as follows.
That is, the current from the high voltage DC power supply 101 is supplied to the capacitor 102 via the resistor 103, and the capacitor 102 is charged. After the capacitor 102 is charged to the target voltage, the trigger tron gap switch 104 is turned on by a high voltage trigger pulse from the trigger circuit 106. At this time, the electric charge charged in the capacitor 102 flows into the primary side of the pulse transformer 105, and a pulse-like induced voltage is generated on the secondary side due to the mutual inductance.

The high voltage pulse generated on the secondary side of the pulse transformer 105 in this way is applied between the linear electrode 4 and the cylindrical electrode 3.
That is, the terminal 107 is brought into conduction with the linear electrode 4, and the terminal 108 is brought into conduction with the cylindrical electrode 4.

  The number of repetitions of pulses output between the terminals 107 and 108 is controlled by changing the output frequency of the trigger pulse in the trigger circuit 106. The voltage of the output pulse is controlled by switching the output voltage of the high-voltage DC power supply 101.

The water treatment device 1a decomposes organic compounds in the water to be treated as follows.
That is, water to be treated W containing organic matter and the like is charged to the accelerated oxidation treatment part 51a and the supernatant water storage part 51b of the treated water storage tank 5a up to the upper end of the partition wall 53, and a predetermined amount (of the organic compound in the treated water). Iron powder 91 is supplied from the iron powder supply device 9a into the accelerated oxidation treatment unit 51a.

  Then, a high voltage pulse generator 10 applies a high voltage between the cylindrical electrode 3 and the linear electrode 4 in a pulsed manner, and a discharge space having a cylindrical shape in the vertical direction is formed in the cylindrical electrode 3. The pump 6 is driven and the water to be treated W (supernatant water W2) in the supernatant water reservoir 51b is sent to the shower nozzle 7 via the water to be treated supply hose 71, and above the cylindrical electrode 3. From this, water droplets are formed and ejected in the direction of the central axis of the cylindrical electrode 3.

The water treatment apparatus 1a is configured as described above. First, the water to be treated is brought into contact with ozone and radicals generated in the discharge space formed inside the cylindrical electrode 3, and the water in the water to be treated The organic compound is decomposed to become treated water W1, which is received by the accelerated oxidation treatment unit 51a from the lower end of the treatment chamber 2, and is mixed into the water stored in the accelerated oxidation treatment unit 51a.
In addition, hydrogen peroxide and nitrogen oxides are generated by the discharge generated in the discharge space, and the hydrogen peroxide dissolves in the treated water W1, and the nitrogen oxide becomes nitric acid and dissolves in the treated water W1, thereby promoting oxidation. It enters into the processing unit 51a.

On the other hand, since the iron powder 91 is supplied into the accelerated oxidation treatment unit 51a, the surface of the iron powder 91 is dissolved by the nitric acid contained in the treated water W1, and ferrous ions are generated. Iron ions act as a catalyst on the hydrogen peroxide contained in the treated water, and OH radicals are generated in the accelerated oxidation treatment portion 51a.
And the organic compound contained in the water in the promotion oxidation process part 51a is decomposed | disassembled by this OH radical.

Further, in the accelerated oxidation treatment unit 51a, fine floating components contained in the water in the accelerated oxidation treatment unit 51a aggregate due to the aggregating action of iron ions, but only the supernatant water gets over the upper end of the partition wall 53. It enters into the supernatant water reservoir 51b.
Then, the supernatant water that has entered the supernatant water storage section 51b is mixed with the water stored in the supernatant water storage section 51b, and is sent again as treated water to the shower nozzle 7 via the pump 6 and the treated water supply hose 71. The water droplets are supplied to the discharge space.

  Finally, when the predetermined time has elapsed and the decomposition process is sufficiently performed, the water in the supernatant water storage unit 51b is discharged as it is, and the accelerated oxidation processing unit 51a removes the aggregated precipitate and iron powder residue stored at the bottom. After filtration and separation, the filtrate is discharged.

  As described above, the water treatment apparatus 1a supplies the iron powder 91 to the accelerated oxidation treatment unit 51a to promote oxidation of the residual treatment target substance by using the organic compounds that could not be decomposed by ozone or radicals generated in the discharge space. Therefore, even if the processing chamber 2 is small, the processing efficiency is improved. In addition, since it is not necessary to enlarge and lengthen the discharge space, the electrical energy required for the discharge can be reduced.

  Further, as described above, the water treatment apparatus 1a is supplied into the processing chamber 2 by the mixed gas supply means 8a so that the mixed gas in which oxygen is 25 to 90% by volume and nitrogen is the remainder is filled. Therefore, a large amount of OH radicals and O radicals are efficiently generated, and the treatment can be performed faster.

FIG. 3 shows a second embodiment of the water treatment apparatus according to the present invention.
As shown in FIG. 3, the water treatment apparatus 1b is the same as the water treatment apparatus 1a except for the configuration described below.

That is, in this water treatment apparatus 1b, the tank body 51 includes a water storage tank 51c that is completely partitioned through the partition wall 55, adjacent to the accelerated oxidation treatment section 51a.
And the to-be-processed water W of the to-be-processed water storage tank 51c is sent to the shower 7 via the hose 71.

An air diffuser 92 is provided at the bottom of the accelerated oxidation treatment unit 51a, and air sent from the blower 9b is bubbled from the air diffuser 92 into fine bubbles.
The supernatant water storage tank 51b is provided with a discharge pipe 56 so that the supernatant water W2 in the supernatant water storage tank 51b can be discharged from the discharge pipe 56.

As described above, the water treatment apparatus 1b is drained as the supernatant water W2 without circulating the treated water W1.
An air diffuser 92 is provided at the bottom of the accelerated oxidation treatment part 51a, and the air sent from the blower 9b is bubbled from the air diffuser 92 into fine bubbles, so that the iron powder 91 is more uniform. Will float in a dispersed state. That is, the iron powder 91 works efficiently as a catalyst, and oxygen in the air works as an oxidizing agent, so that accelerated oxidation can be performed more efficiently.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the high voltage pulse generator is provided, but a commercially available high voltage pulse generator may be separately provided.
In the above embodiment, the water treatment apparatus includes the mixed gas supply unit or both the mixed gas supply unit and the oxidant supply unit. However, the mixed gas supply unit and the oxidant supply unit may be omitted. I do not care.

  In the above-described embodiment, the water to be treated is sprayed from above and sprayed. However, when the cylindrical electrode is a mesh, the cylindrical electrode is connected from the side of the cylindrical electrode through the mesh. The water to be treated may be supplied into the inside.

  Specific examples of the present invention will be described below in comparison with comparative examples.

Example 1
In the processing chamber 2, six pairs of cylindrical electrodes 3 and linear electrodes 4 are centered on one pair of cylindrical electrodes 3 and linear electrodes 4, and the other five pairs of cylindrical electrodes 3 and linear electrodes are centered. Except that 4 are arranged radially at equal intervals, the water treatment apparatus 1a shown in FIG. 1 is used to decompose indigo carmine as a treatment target substance in the water W to be treated under the following experimental conditions, and ultraviolet visible Using a spectrophotometer (trade name U-1900, manufactured by Hitachi High-Technologies Corporation), the change in the concentration of indigo carmine with the lapse of the treatment time of the water to be treated W was examined by the absorbance at 610 nm.
[Experimental conditions]
Indigo carmine initial concentration in treated water W: about 20 ppm
Amount of treated water W: 7 liters Injection speed (circulation speed) of treated water W: 14 L / min Charging voltage: 20 kV
Number of discharges: 100 times / second Properties of cylindrical electrode 3: 2.5 mesh, wire diameter 1.1 mm, hole area ratio 79.5%, welded wire mesh Outer diameter of cylindrical electrode 3: 39.5 mm
Length of cylindrical electrode 3 (length in the central axis direction): 200 mm × 6 Particle diameter of water mist to be treated: 750 to 970 μm
Spray angle of shower nozzle 7: 30 °
Iron powder: 7g / L
Distance from shower nozzle 7 to cylindrical electrode: The outermost edge of the water mist M to be treated was adjusted to be the upper end of the outer edge of the cylindrical electrode located at the outermost part.
Oxygen / nitrogen ratio of the mixed gas: Oxygen: nitrogen = 10: 90
Mixed gas supply condition: The mixed gas was supplied into the processing chamber 2 at 10 L / min (normal temperature and normal pressure).

(Comparative Example 1)
The change in the concentration of indigo carmine was examined in the same manner as in Example 1 except that iron powder was not used.

The result of the concentration change of indigo carmine examined in Example 1 and Comparative Example 1 is shown in comparison with FIG.
As shown in FIG. 4, it can be seen that the decomposition treatment speed is increased by using the water treatment method of the present invention, that is, by adding iron powder to the treated water storage tank.

(Experimental example 1)
The water treatment apparatus was operated under the same processing conditions as in Example 1 above except that the tank body 51 was filled only with ion-exchanged water and the iron powder was not supplied to the accelerated oxidation treatment unit 51a. The time-dependent changes in the hydrogen peroxide concentration and nitric acid concentration dissolved in the water in 51a were examined. The time-dependent change in hydrogen peroxide concentration is shown in FIG. 5, and the time-dependent change in nitric acid concentration is shown in FIG.

  5 and 6 that hydrogen peroxide and nitric acid are generated over time by the discharge.

  Although the water treatment apparatus of this invention is not specifically limited, For example, it can use for purification | cleaning of the waste_water | drain containing organic substance, disinfection of contaminated water, etc.

DESCRIPTION OF SYMBOLS 1a, 1b Water treatment apparatus 2 Processing chamber 3 Cylindrical electrode 4 Linear electrode 5a, 5b Treated water storage tank 51 Tank main body 51a Promotion oxidation processing part 51b Supernatant water storage part 51c To-be-processed water storage tank 6 Pump 7 Shower nozzle (water droplet forming means )
71 Untreated water supply hose (circulation path)
8a Mixed gas supply means 81 Oxygen cylinder 82 Oxygen supply pipe 83 Nitrogen cylinder 84 Nitrogen supply pipe 85 Mixer 86 Mixed gas supply pipe 9a Iron powder supply apparatus 91 Iron powder 9b Blower 92 Aeration pipe 10 High voltage pulse generator (high voltage power supply)
W treated water W1 treated water W2 supernatant water M treated water mist

Claims (8)

A water treatment method in which water to be treated is supplied as water droplets in a discharge space, and a treatment target substance in the water droplets is decomposed by active species generated by discharge in the discharge space,
Water droplets processed through the discharge space are stored in the treated water storage tank as treated water, and iron powder is supplied into the treated water stored in the treated water storage tank to promote oxidation of the remaining treatment target substances in the treated water. Water treatment method.   The water treatment method according to claim 1, wherein the iron powder is reduced iron powder having a particle size of 500 μm or less.   The water treatment method according to claim 1 or 2, wherein oxygen is bubbled into the treated water. A water treatment apparatus that supplies water to be treated into water droplets in the discharge space, and decomposes the substance to be treated in the water droplets by active species generated by discharge in the discharge space,
The treated water storage tank which receives the water droplet processed through the discharge space and stores it as treated water, and the iron powder supply means for supplying the iron powder to the treated water storage tank are provided. A water treatment apparatus used in a water treatment method.   The water treatment apparatus according to claim 4, further comprising oxygen supply means for bubbling oxygen in the treated water storage tank.   6. The apparatus according to claim 4, further comprising at least a pair of cylindrical electrodes and linear electrodes, and a high-voltage power source that applies a high voltage between the cylindrical electrodes and the linear electrodes to form a discharge space. Water treatment equipment.   The treated water storage tank includes treated water, and an accelerated oxidation treatment unit that promotes oxidation of the remaining treatment target substance, and a supernatant water storage unit that stores supernatant water of the accelerated oxidation treatment unit. 6. The water treatment apparatus according to any one of 6.   The water treatment apparatus according to any one of claims 4 to 7, further comprising a circulation path for supplying treated water from the treated water storage tank to the discharge space again.

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