Liquid treatment device

A liquid treatment device that achieves an effective treatment by forcibly contacting a swirl flow of a hydrogen peroxide-containing treated liquid with a liquid to be treated that has been processed to contain copper ions or iron ions includes a rod-like first electrode, a plate-like second electrode formed of a copper- or iron-containing metal, and a first treatment vessel that causes a liquid to swirl and generate a gas phase in a swirl flow of the liquid. A pulse voltage is applied to the generated gas phase to generate a plasma. The second electrode serves as an anode, and reaches inside of a supply section for a liquid to be treated. The liquid to be treated containing the generated copper ions or iron ions is forcibly brought into contact with hydrogen peroxide generated by the plasma. In this way, the Fenton's reaction effectively takes place, and the liquid treatment performance improves.

TECHNICAL FIELD

The technical field relates to a liquid treatment device that electrochemically treats liquid. Specifically, the present disclosure relates to a liquid treatment device that treats liquid by generating a plasma in liquid, and forcibly mixing hydrogen peroxide generated by the plasma with a liquid to be treated containing copper ions or iron ions generated from an anode by electrolysis, whereby suspended substances or microorganisms contained in the liquid are decomposed or sterilized through the Fenton's reaction caused by mixing these chemical species.

BACKGROUND

FIG. 14shows an example of a traditional liquid treatment device. A pair of electrodes401is disposed in water, and a high-voltage generator400applies voltage to these electrodes401. This causes discharge in water, and generates hydrogen peroxide. At least one of the electrodes401is configured from a copper- or iron-containing metal, and the discharge causes an electrolysis whereby the copper atoms or iron atoms in the electrode dissolve into water, and produce copper ions or iron ions. In the presence of hydrogen peroxide, a Fenton's reaction occurs upon generation of copper ions or iron ions, and produces highly reactive active species OH radicals under the catalytic effect of the copper ions or iron ions. These active species, with their oxidative power, react with the contaminants or other foreign substances contained in the liquid, and treat the liquid by decomposing these substances. With an added configuration that applies ultrasonic waves to the hydrogen peroxide generated by discharge, the device is able to improve its liquid treatment performance with the OH radicals generated by decomposition of the hydrogen peroxide.

SUMMARY

The liquid treatment device described in Japanese Patent No. 5834912 generates hydrogen peroxide and copper or iron ions through discharge, and highly sterilizing OH radicals are generated by causing a Fenton's reaction. However, the OH radicals have a short life, and quickly turn into hydrogen peroxide, which is less sterilizing than OH radicals. This is problematic in terms of treatment efficiency because the OH radicals cannot effectively contact the suspended substance in the water to be treated when the water to be treated has high fluidity.

Under these circumstances, the present disclosure is intended to provide a liquid treatment device that can efficiently generate OH radicals through Fenton's reaction, and improve treatment efficiency even when the liquid to be treated has high fluidity.

A liquid treatment device according to an aspect of the present disclosure includes:

a first treatment vessel that is cylindrical in shape and having a closed end at a first end of a central axis of the vessel and a circular cross section orthogonal to the central axis, the first treatment vessel on a first end side of the central axis having a liquid inlet through which liquid is introduced in a tangential direction of the circular cross section of the vessel, and that causes the liquid to swirl around the central axis and generate a gas phase in a swirl flow of the liquid;

a first electrode that is rod-like in shape and disposed on the first end side of the central axis of the first treatment vessel;

a second electrode made of a copper- or iron-containing metal and disposed on a second end side of the central axis of the first treatment vessel;

a liquid ejecting section through which the liquid is ejected from the first treatment vessel in the form of a treated liquid;

a second treatment vessel in which the treated liquid ejected through the liquid ejecting section mixes with a liquid to be treated;

a power supply that applies a voltage between the first electrode and the second electrode in a way that applies a positive voltage to the second electrode, and causes copper ions or iron ions to dissolve out of the second electrode into the liquid to be treated in the second treatment vessel; and

a supply section that supplies the liquid to be treated to the second treatment vessel in a direction that differs from a direction of a jet of the treated liquid ejected from the first treatment vessel.

In the liquid treatment device of the aspect of the present disclosure, generation of copper ions or iron ions, and generation of hydrogen peroxide simultaneously take place in the discharge, and the liquid ejected in the form of a hydrogen peroxide-containing jet is forcibly mixed with a liquid to be treated containing copper ions or iron ions. Here, these liquids are forcibly mixed by introducing the liquid to be treated in a different direction from the swirl direction of the jet of the ejected liquid. In this way, the liquid to be treated can be efficiently treated. That is, OH radicals can efficiently generate in the Fenton's reaction, and the treatment efficiency can improve even when the liquid to be treated has high fluidity.

DESCRIPTION OF EMBODIMENTS

Embodiment

A liquid treatment device200according to an embodiment of the present disclosure is described below in detail, with reference to the accompanying drawings. In the drawings, the same or corresponding features are referred to by using the same reference numerals, and the same descriptions will not be repeated. To help understand the descriptions, the configurations in the drawings referred to in the following descriptions may be shown in simplified or schematic forms, or with omission of some of the constituting members. The dimensional ratios of the constituting members shown in the drawings are not necessarily true to the actual dimensional ratios.

Overall Configuration

The overall configuration of the liquid treatment device200is described first.

FIG. 1is a side cross sectional view showing a configuration of the liquid treatment device200according to First Embodiment of the present disclosure. In the diagrams referred to below, the arrow F represents the front of the liquid treatment device200, and arrow B represents the back of the liquid treatment device200. Arrow U represents the top of the liquid treatment device200, and arrow D represents the bottom of the liquid treatment device200. Arrow R represents the right as viewed from the back, and arrow L represent the left as viewed from the back.

The liquid treatment device200shown inFIG. 1is configured from a discharge treatment unit100and a liquid mixing unit110. The discharge treatment unit100causes a plasma discharge in the liquid inside a first treatment vessel12, and adds active species to the liquid. The present embodiment will be described through the case of treating an aqueous solution containing contaminants. The liquid mixing unit110has a second treatment vessel90in which a treated liquid L2containing active species after the treatment in the first treatment vessel12of the discharge treatment unit100is stored by being ejected in the form of a jet.

The discharge treatment unit100includes at least a discharge treatment unit main body10, and a pulse power supply60. The discharge treatment unit100may also include a liquid supply section50connected to an inlet portion15(described below).

The discharge treatment unit main body10includes the first treatment vessel12, the inlet portion15serving as an example of a liquid inlet, a liquid ejecting section17, a first electrode30, and a second electrode31.

The first treatment vessel12is where the introduced liquid (for example, water) L1is treated. The first treatment vessel12has a cylindrical treatment chamber having a circular front cross section. The inlet portion15is disposed at one end of the first treatment vessel12, and the liquid ejecting section17is disposed at the other end of the first treatment vessel12. The material of the first treatment vessel12may be an insulator or a conductor. In the case of a conductor, the first treatment vessel12must be separated from the electrodes30and31via an insulator.

The liquid L1is introduced into the first treatment vessel12through the inlet portion15. The inlet portion15is in communication with the liquid supply section50via a pipe51.

The treated liquid L2treated in the first treatment vessel12is ejected from the first treatment vessel12through the liquid ejecting section17. In the present embodiment, the liquid ejecting section17is connected to an intake opening91of the second treatment vessel90. The treated liquid L2ejected through the liquid ejecting section17enters the second treatment vessel90of the liquid mixing unit110in the form of a swirling flow of ejected liquid F2through the intake opening91, and is stored in the second treatment vessel90.

The liquid mixing unit110is configured from the second treatment vessel90and a supply section80.

The second treatment vessel90is disposed adjacent the first treatment vessel12, and the liquid ejecting section17of the first treatment vessel12is connected to the intake opening91of the second treatment vessel90. The treated liquid L2ejected through the liquid ejecting section17of the first treatment vessel12enters the second treatment vessel90through the intake opening91, and is stored in the second treatment vessel90. The liquid to be treated L3in the second treatment vessel90is then treated with the treated liquid L2. The supply section80is disposed at an end portion of the second treatment vessel90on the side of the first treatment vessel12. The material of the second treatment vessel90may be an insulator or a conductor. In the case of a conductor, the second treatment vessel90must be separated from the second electrode31via an insulator.

The supply section80is configured as a supply pipe disposed along the wall at an end portion of the second treatment vessel90adjacent the first treatment vessel12. Through the supply section80, the liquid to be treated L3is introduced into the second treatment vessel90, for example, into a region near the liquid ejecting section17, through a supply opening81at an end of the supply pipe. The liquid to be treated L3is introduced into the second treatment vessel90from the supply section80in a direction different from the direction the treated liquid L2is ejected into the second treatment vessel90from the first treatment vessel12through the liquid ejecting section17and the intake opening91. Specifically, the liquid to be treated L3and the treated liquid L2cross, and efficiently mix together. The material of the supply section80may be an insulator or a conductor. In the case of a conductor, the supply section80must be separated from the second electrode31via an insulator.

The first electrode30is rod-like in shape, and is disposed in the first treatment vessel12. The first electrode30is disposed via, for example, an insulating section on the wall surface opposite the wall surface where the liquid ejecting section17of the first treatment vessel12is formed.

The second electrode31is configured as a plate-like member formed of a copper- or iron-containing metal. As an example, the second electrode31is disposed so that, as shown inFIG. 1, one end of the second electrode31is on the outer side of the wall of the first treatment vessel12where the liquid ejecting section17is formed, specifically, on the wall surface of the second treatment vessel90adjacent the first treatment vessel12where the first treatment vessel12and the second treatment vessel90join together. The other end of the second electrode31is on the inner wall surface of the supply section80through and around the intake opening91. This arrangement of the second electrode31is merely an example, and the second electrode31may be disposed any other way, provided that it is at least disposed at one end of a central axis X1of the first treatment vessel12. Here, the one end of the central axis X1is not limited to the wall surface at one end of the first treatment vessel12, and may be in the vicinity of the region where the first treatment vessel12and the second treatment vessel90join together, outside of the first treatment vessel12, or may be in the vicinity of the region where the first treatment vessel12and the second treatment vessel90join together, inside the second treatment vessel90. This will be described later as variations of the embodiment.

The pulse power supply60is connected to the first electrode30and the second electrode31, and applies a high pulse-voltage with the second electrode31serving as an anode. That is, a positive voltage is applied to the second electrode31.

The liquid supply section50is, for example, a pump that supplies a liquid (for example, water) L1into the first treatment vessel12. The liquid supply section50is connected to the pipe51. At one end, the pipe51is connected to the inlet portion15. The other end of the pipe51is connected to a liquid source (for example, a water tank or a faucet; not illustrated). Alternatively, the other end of the pipe51is connected to the second treatment vessel90so as to circulate a liquid (liquid to be treated L3) containing the treated liquid L2sent from the first treatment vessel12and stored in the second treatment vessel90.

The pulse power supply60applies a bipolar high pulse-voltage of several kilovolts between the first electrode30and the second electrode31, with the second electrode31serving as an anode.

Device Main Body

The discharge treatment unit main body10is described below in detail.FIG. 2is a side cross sectional view of the discharge treatment unit main body10.

The first treatment vessel12has a first inner wall21, a second inner wall22, and a third inner wall23. The first inner wall21is a cylindrical wall portion. The second inner wall22is provided at a first end portion of the first inner wall21(for example, the left end portion ofFIG. 2). The third inner wall23is provided at a second end portion of the first inner wall21(for example, the right end portion ofFIG. 2). The second inner wall22and the third inner wall23are substantially circular in shape as viewed from side. The first inner wall21, the second inner wall22, and the third inner wall23form a substantially cylindrical housing83inside the first treatment vessel12. Here, the first inner wall21has a central axis X1, that is, an imaginary central axis of the substantially cylindrical housing83formed inside the first treatment vessel12.

The second inner wall22has an electrode supporting tube24projecting out into the first treatment vessel12from the center of the second inner wall22. The electrode supporting tube24is tubular in shape, and extends toward the third inner wall23(i.e., toward the right inFIG. 2). The electrode supporting tube24is disposed in such an orientation that its central axis lies on the central axis X1. The first electrode30is supported in the electrode supporting tube24, via an insulator53. The first electrode30, which is rod-like in shape, is surrounded by the insulator53having a form of a tube. Accordingly, the first electrode30is in such an orientation that its longitudinal axis lies on the central axis X1. The inner end portion of the first electrode30projects out toward the third inner wall23(i.e., toward the right inFIG. 2) by about the same length as the electrode supporting tube24, past the insulator53.

The inlet portion15is provided through the discharge treatment unit main body10, and has an open end151formed in the first inner wall21. The inlet portion15is disposed at a location adjacent the second inner wall22as viewed from side.FIG. 3is a cross sectional view at line III-III ofFIG. 2. The inlet portion15is disposed in the wall surface of the first inner wall21.

The liquid ejecting section17is provided through, for example, a central portion of the third inner wall23. The liquid ejecting section17is formed in such a fashion that its central axis lies on the central axis X1. The liquid ejecting section17is connected to the intake opening91of the second treatment vessel90.

The second electrode31is a copper- or iron-containing plate-like metallic member. The second electrode31is disposed in such an orientation that it reaches into the supply section80through the supply opening81around the liquid ejecting section17of the first treatment vessel12, as shown inFIG. 4, which shows a cross sectional view at line IV-IV ofFIG. 2.

Operation

The operation of the liquid treatment device200is described below.

For the purpose of explanation, the operation of the liquid treatment device200will be described for a state in which a gas phase G is generated in the first treatment vessel12(FIG. 6), and a state in which a plasma P is generated by applying a pulse voltage to the gas phase G from the pulse power supply60(FIG. 7).FIG. 6is a side cross sectional view showing a swirl flow F1that has generated inside the first treatment vessel12, in the absence of an applied pulse voltage.

As shown inFIG. 6, a liquid (for example, water) L1is introduced into the first treatment vessel12through the inlet portion15under a predetermined pressure, specifically, under the pressure of a pump, or under the pressure of running water in the case of using tap water instead of a pump. In response, the liquid L1moves toward the right-hand side ofFIG. 6from the inlet portion15as it generates a swirl flow F1along the first inner wall21. The swirl flow F1traveling rightward inFIG. 6is directed toward the liquid ejecting section17.

By the presence of the swirl flow F1, the pressure around the central axis X1drops below the saturated water vapor pressure, and the liquid L1partially vaporizes, and generates a gas phase G in the vicinity of the central axis X1. The gas phase G occurs around the swirl axis, specifically, on and along the central axis X1from the right end portion301of the first electrode30ofFIG. 6to regions near the intake opening91. The gas phase G is in contact with the swirl flow F1, and swirls with the swirl flow F1in the same direction. In the vicinity of the liquid ejecting section17and the intake opening91, the swirling gas phase G experiences resistance from the treated liquid L2present in the second treatment vessel90, and is sheared into microbubbles or nanobubbles. These bubbles diffuse into the second treatment vessel90as soon as the treated liquid L2containing large quantities of bubbles is ejected into the second treatment vessel90through the liquid ejecting section17, and through the intake opening91connected to the liquid ejecting section17.

FIG. 7is a side cross sectional view showing a state in which the pulse power supply60has applied a pulse voltage between the first electrode30and the second electrode31in the presence of the swirl flow F1generated inside the first treatment vessel12as shown inFIG. 6. As shown inFIG. 7, the pulse power supply60applies a high pulse-voltage between the first electrode30and the second electrode31with the gas phase G being present over the region from the first electrode30to the intake opening91after the vaporization of the liquid L1. Applying a high pulse-voltage between the first electrode30and the second electrode31generates a plasma P in the gas phase G, and this produces radicals (e.g., OH radicals) or ions. The radicals or ions dissolve into the swirl flow F1from the gas phase G, and decompose the contaminants dissolving in the liquid L1. The plasma P in the gas phase G near the liquid ejecting section17experiences resistance from the treated liquid L2present in the second treatment vessel90, and this produces a large quantity of bubbles B containing active species such as OH radicals and ions. The liquid L2is ejected into the second treatment vessel90through the liquid ejecting section17with the bubbles B or active species. That is, the OH radicals and other chemical species generated by plasma P dissolve into the treated liquid L2stored in the second treatment vessel90, either directly or through bubbles B. After a lapse of a predetermined time period, the treated liquid L2in the second treatment vessel90turns into relatively stable hydrogen peroxide. The plasma P generated in response to high pulse-voltage application becomes extinguished upon ending voltage application.

The plasma generates ultraviolet (UV) light as it discharges. The generated UV light can decompose and sterilize contaminants or microorganisms upon falling on these substances. The UV light also generates OH radicals upon falling on the hydrogen peroxide water generated in the treated liquid, and the contaminants and microorganisms can be decomposed and sterilized also by these OH radicals.

Because the second electrode31is made of copper- or iron-containing metal, applying a positive voltage to the second electrode31causes an electrolysis in the voltage application by the pulse power supply60, and metal ions dissolve out of the second electrode31in the supply section80into the liquid to be treated L3passing through the supply section80. The liquid to be treated L3containing the metal ions leaves the supply opening81, and is introduced into the second treatment vessel90in the form of a directional liquid flow (for example, clockwise inFIG. 4), as shown in the supply liquid flow F3inFIG. 4. The supply liquid flow F3of the liquid to be treated L3is introduced into the second treatment vessel90in such a manner that the liquid L3forms a liquid flow of a direction different from the swirl direction of the ejected liquid flow F2(counter clockwise inFIG. 4) that occurs in the vicinity of the liquid ejecting section17when the treated liquid L2containing active species is ejected from the liquid ejecting section17.

In this way, the ejected liquid flow F2of the treated liquid L2containing active species ejected from the first treatment vessel12opposes the supply liquid flow F3of the copper or iron metal ion-containing liquid to be treated L3in the second treatment vessel90. That is, the ejected liquid flow F2and the supply liquid flow F3become forcibly mixed as they rotate in different directions (for example, opposite directions) and collide with each other, making it possible to more efficiently treat the liquid to be treated L3. The active species-containing treated liquid L2, and the copper or iron metal ion-containing liquid to be treated L3mix even more efficiently in the second treatment vessel90as the microbubbles or nanobubbles contained in the active species-containing treated liquid L2rise and diffuse in the liquid, and the Fenton's reaction takes place more efficiently. The OH radicals generated by the Fenton's reaction can then react with the organic materials and other substances contained in the liquid to be treated L3, and effectively decompose these substances. The second treatment vessel90has a larger inner space than the first treatment vessel12(for example, the second treatment vessel90is higher than the first treatment vessel12) in the vicinity of the line V-V ofFIG. 2(the cross section is shown inFIG. 5) where the supply liquid flow F3and the ejected liquid flow F2that generates in the vicinity of the liquid ejecting section17do not mix as effectively as in regions near the liquid ejecting section17, so that the treated liquid L2and the liquid to be treated L3can continuously mix as a result of the microbubbles or nanobubbles rising and diffusing in the liquid to be treated L3.

In the embodiment described above, generation of copper ions or iron ions from the second electrode31, and generation of hydrogen peroxide in the first treatment vessel12simultaneously take place in the discharge, and the treated liquid L2ejected in the form of a hydrogen peroxide-containing jet is brought into contact with the liquid to be treated L3containing copper ions or iron ions. Here, the treated liquid L2and the liquid to be treated L3are forcibly mixed by introducing the liquid to be treated L3in a different direction from the swirl direction of the ejected liquid flow F2, which is a swirling jet of the ejected liquid L2. In this way, the liquid to be treated L3can be efficiently treated. That is, OH radicals can efficiently generate in the Fenton's reaction, and the treatment efficiency improves even when the liquid to be treated L3has high fluidity. Because the plasma P is generated by vaporizing liquid L1in the swirl flow F1, and applying a pulse voltage from the pulse power supply60to the generated gas phase G, the efficiency of plasma P generation improves, and the liquid to be treated L3can be treated in a shorter time period.

Variations

In the foregoing descriptions, the first treatment vessel12is described as a vessel of a simple cylindrical shape. However, the first treatment vessel12may have a variety of other shapes, provided that it is a cylindrical vessel with a circular cross section and a closed end. For example, the same effect can be obtained with a first treatment vessel121that combines cylinders of different radii as shown inFIG. 8, or with a first treatment vessel122having a circular cone shape as shown inFIG. 9.

The second electrode31was described as being disposed in such a fashion that one end of the second electrode is in a region where the first treatment vessel12and the second treatment vessel90join together, and the other end of the second electrode31extends to the inner wall surface of the supply section80through the intake opening91. However, for example, the second electrode31may be disposed in the vicinity of the liquid ejecting section17of the first treatment vessel12, and the intake opening91. The same effect can be obtained with a second electrode311disposed on the side of the second treatment vessel90as shown inFIG. 10, which represents another example of the second electrode being disposed at one end of the central axis X1of the first treatment vessel12.

In the foregoing embodiment and variation, the supply section80is described through the case where the swirl flow of the ejected liquid flow F2of the active species-containing treated liquid L2mixes in a reverse direction with the supply liquid flow F3of the liquid to be treated L3in the vicinity of the liquid ejecting section17and the intake opening91. However, the present disclosure is not limited to this.

For example, as another variation of the supply section80of the second treatment vessel90, a supply section801may be disposed by being separated from the wall surface of a second treatment vessel901adjacent the first treatment vessel12as shown inFIG. 11A, which represents another example of the supply section80of the second treatment vessel90being provided at one end of the central axis X1of the first treatment vessel12. The liquid to be treated L3can then be introduced from above the jet of the ejected liquid flow F2from the first treatment vessel12traveling toward the right-hand side ofFIG. 11A, at a right angle to the direction of rotation of the ejected liquid flow F2in the jet. The effects described in the embodiment also can be obtained with this configuration.

More specifically, the supply section801is missing a large portion of its wall at the bottom (bottom wall801a) on the side of the liquid ejecting section17of the first treatment vessel12, and a bottom wall801bopposite the liquid ejecting section17of the first treatment vessel12extends so as to block the imaginary line extending from the liquid ejecting section17.

With this configuration, the liquid to be treated L3supplied to the second treatment vessel901through the supply section801collides and mixes with the treated liquid L2ejected toward the bottom wall801bof the second treatment vessel901through the liquid ejecting section17, instead of simply traveling down to the bottom of the second treatment vessel901along the axial direction of the supply section801. Here, the collision occurs in the vicinity of the bottom wall801bas the liquid to be treated L3meets the treated liquid L2from above at a right angle to the direction of rotation of the ejected liquid flow F2.

The second electrode31is not limited to one disposed in the supply section801as in the foregoing embodiment and inFIG. 11A. As shown inFIG. 11B, the second electrode311, which corresponds to the second electrode31, may be disposed outside of the supply section801. For example, the second electrode311may be disposed on the wall surface of the second treatment vessel901adjacent the first treatment vessel12, separately from the supply section801. InFIG. 11B, the second electrode311is disposed outside of the supply section801, instead of inside, and the supply section801is disposed in the vicinity of the wall surface of the second treatment vessel901adjacent the first treatment vessel12.

In such a variation, the treated liquid L2enters the second treatment vessel901through the liquid ejecting section17, and the Fenton's reaction occurs as the treated liquid L2mixes with the liquid to be treated L3in the presence of metal ions dissolved out of the second electrode311in the second treatment vessel901.

The supply section801may be disposed in such an orientation that a supply opening81faces the liquid ejecting section17and the intake opening91in the second treatment vessel901, as shown inFIG. 11C. In such a configuration, the treated liquid L2enters the second treatment vessel90through the liquid ejecting section17, and the Fenton's reaction occurs as the treated liquid L2mixes with the liquid to be treated L3in the presence of metal ions dissolved out of the second electrode311in the second treatment vessel901. In this configuration, the liquid to be treated L3is supplied into the second treatment vessel901through the supply section801in a direction that crosses (or is orthogonal to) the jet direction of the treated liquid L2ejected from the first treatment vessel12, that is, the swirl direction of the ejected liquid flow F2.

As shown inFIG. 12, one end of the pipe51may be connected to a circulation pipe84so that the liquid to be treated L3containing the treated liquid L2in the second treatment vessel90can circulate through a water intake section16from regions near a stored water ejection opening82. The same effect also can be obtained with this configuration. It is also possible, as shown inFIG. 13, to branch the pipe51into the supply section80, and supply the liquid to be treated L3to both the first treatment vessel12and the supply section80. The same effect also can be obtained with this configuration.

While there have been described a certain embodiment and a variation of the present disclosure, the embodiment and the variation described above are merely examples of implementations of the present disclosure. Accordingly, the present disclosure is not limited to the foregoing embodiment and variation, and the foregoing embodiment and variation may be modified as appropriate within the gist of the present disclosure. For example, the foregoing embodiments and variations can exhibit their effects even when any of the embodiments or variations is appropriately combined with another embodiment or variation. It is also possible to combine different embodiments or different Examples, or combine embodiments and Examples. The features of different embodiments or Examples also may be combined.

In the liquid treatment device according to the aspect of the present disclosure, a plasma is generated in liquid, and the generated hydrogen peroxide is forcibly mixed with a liquid to be treated containing copper ions or iron ions generated through electrolysis at the anode. In this way, the Fenton's reaction occurs more effectively, and the liquid can be treated through decomposition and sterilization of suspended substances or microorganisms in the liquid. A liquid still containing contaminants or microorganisms after the treatment is introduced to generate plasma, and is brought into direct contact with the plasma or passed through a plasma generated regions. The UV light, radicals, and other chemical species generated by plasma discharge can then be used to treat liquid through decomposition and sterilization. This makes the liquid treatment device applicable to a wide range of environment improvements, such as sterilization and deodorizing.