Liquid purification method and liquid purification system

Abstract

The purpose of the present invention is to provide a liquid purification method for purifying a liquid to be treated, the method configured such that a liquid is purified with high efficiency without incurring a large cost. This liquid purification method comprises: a step for preparing a first container and a liquid to be treated inside the first container; a generation step for generating fine droplets of the liquid above the surface of the liquid by oscillating an ultrasonic vibrator disposed in the liquid; and a purification step for purifying the liquid by bringing the fine droplets into contact with ozone.

Description

Liquid purification method and liquid purification system

[0001] The present disclosure relates to a liquid purification method and a liquid purification system for purifying a liquid to be treated.

[0002] Liquid purification methods using ozone gas are used in water supply and sewerage facilities. Unlike chemical sterilization, ozone self-decomposes into oxygen, leaving no residual residue. In addition, the raw material is generated from oxygen in the air or water, so there are advantages to adopting this method in terms of chemical procurement and management.

[0003] Bubbling is a method used to dissolve ozone gas in a liquid. However, when dissolving by gas bubbling, the bubbles rise to the surface and diffuse into the gas phase before the ozone has fully dissolved, making the use of ozone gas inefficient. Furthermore, the undissolved ozone gas that rises to the surface and diffuses into the gas phase cannot be released directly into the atmosphere, requiring the installation of a separate ozone gas exhaust treatment device, which tends to increase costs.

[0004] In Patent Document 1, the stirring force of a line mixer is used to reduce the bubble diameter when bubbling ozone gas, suppress the floating speed, and lengthen the residence time in the liquid, thereby making effective use of ozone gas.

[0005] Patent No. 4259797

[0006] However, the technology described in Patent Document 1 is an invention aimed at forming bubbles in ozone in the liquid to be treated, and the efficiency of dissolving ozone in the liquid to be treated is insufficient, resulting in high costs associated with purifying the liquid to be treated.

[0007] In view of the above problems, an object of the present invention is to provide a liquid purification method and a liquid purification system that can purify a liquid highly efficiently without incurring large costs.

[0008] A liquid purification method according to one embodiment of the present invention includes the steps of: preparing a first container and a liquid to be treated inside the first container; generating microdroplets of the liquid above the liquid surface by oscillating an ultrasonic vibrator disposed in the liquid; and purifying the liquid by bringing the microdroplets into contact with ozone.

[0009] According to the present disclosure, it is possible to provide a liquid purification method and a liquid purification system that purify a liquid to be treated highly efficiently without incurring large costs.

[0010] FIG. 1 is a diagram for explaining the configuration of a liquid purification system. FIG. 2 is a diagram for explaining a liquid purification method in which purified liquid is recovered in a second container by the liquid purification system. FIG. 3 is a diagram for explaining the functional configuration of a liquid purification system equipped with a mercury lamp. FIG. 4 is a diagram for explaining the functional configuration of a liquid purification system in which a plurality of ultrasonic vibrators are arranged. FIG. 5 is a diagram for explaining a liquid purification system that uses a mesh type ultrasonic vibrator. FIG. 6 is a diagram for explaining a liquid purification system in which the ultrasonic vibrator is inclined diagonally upward. FIG. 7 is a diagram for explaining a liquid purification system intended for in-line continuous operation. FIG. 8 is a diagram for explaining a liquid purification method at the liquid surface by the liquid purification system. FIG. 9 is a diagram for explaining a liquid purification system using a double-structured container.

[0011] Hereinafter, embodiments according to the present disclosure will be described. Note that the following embodiments are merely examples and are not intended to unnecessarily limit the concept of the present disclosure. In addition, in this specification, microdroplets refer to droplets having a diameter of 1 mm or less. It is preferable that the number average particle size of the microdroplets is 0.99 mm or less.

[0012] The liquid purification system and the liquid purification method using the liquid purification system according to this embodiment will be described below with reference to the drawings.

[0013] 1 is a diagram showing an example of the functional configuration of a liquid purification system 100. The liquid purification system 100 includes a first container, an ultrasonic vibrator 200 disposed in a liquid 300 to be treated that is prepared inside the first container, and an ozone generation unit 400 that generates ozone in the first container.

[0014] In this embodiment, the liquid purification system 100 prepares a liquid in a first container and generates microdroplets of the liquid above the liquid surface by oscillating an ultrasonic vibrator 200 disposed in the liquid. The first container is filled with ozone by an ozone gas generation unit 400, and the microdroplets generated by the ultrasonic vibrator 200 come into contact with the ozone, thereby purifying the liquid. The mist-like microdroplets generated by the ultrasonic vibrator 200 ensure a sufficient floating time in the ozone-filled space, and the large volume per droplet allows for efficient purification of the liquid to be treated. Note that the liquid purification systems described in this and other embodiments are merely exemplary configurations, and it is within the scope of the present invention to implement various configurations in combination as appropriate.

[0015] Here, there are no particular limitations on the ultrasonic vibrator 200, but a device used for piezoelectric atomization is a preferred form. Piezoelectric atomization devices are broadly classified into a throw-in type, which is installed in a liquid and turns the liquid near the gas-liquid interface into fine droplets, as shown in Figure 1, and a mesh type, which will be described later using Figure 5, in which piezoelectric elements are arranged around a mesh plate and fine droplets of liquid are supplied through the mesh holes. In this liquid purification system 100, the throw-in type is more preferred because there is no risk of clogging.

[0016] Furthermore, in the present invention, the liquid purification system 100 is characterized in that the ultrasonic vibrator 200 supplies microdroplets above the liquid surface of the liquid to be treated, and this functional configuration is an effective embodiment for ensuring the time for the microdroplets to contact with ozone. Furthermore, it is a particularly preferable embodiment that the microdroplets generated by the ultrasonic vibrator 200 are mist-like droplets in size.

[0017] The ultrasonic vibrator 200 constituting the liquid purification system 100 of the present invention generates minute droplets of mist-like droplet size, which allows the droplets to float for a long time in the gas phase containing ozone, and further increases the ratio of the gas-liquid interface per droplet volume, thereby enabling the ozone gas to be efficiently dissolved and utilized.

[0018] Methods for generating ozone gas using the ozone gas generating unit 400 include irradiation of oxygen with a low-pressure mercury lamp, discharge, and electrolysis of water. There are no particular limitations on the method for generating ozone, but ozone generation by irradiation with a Xe excimer lamp is preferred because ozone is generated by reacting only with oxygen in the air. Of course, there are no particular limitations on the gas as long as it contains oxygen, and pure oxygen can also be used.

[0019] It is also a preferred embodiment to include fine bubbles in the microdroplets. Fine bubbles refer to small gas bubbles (bubbles) of less than 100 μm in size. It has been reported that the inclusion of fine bubbles prolongs the deactivation of the effects of ozone water, and this is also a preferred embodiment in the present invention. In particular, ultrafine bubbles with a diameter of 1 μm or less are a preferred embodiment because they do not rise to the surface in the liquid.

[0020] The ultrasonic vibrator 200 is preferably a throw-in type ultrasonic vibrator, and the thickness from the ultrasonic vibrator to the liquid surface is preferably 15 cm or less. If the thickness is greater than this, there is a concern that the efficiency of generating microdroplets may decrease.

[0021] Furthermore, it is preferable that the particle size distribution of the fine bubbles of 20 μm or less generated by the ultrasonic vibrator 200 is 5 or less. If the particle size is greater than this, the bubbles will rise faster, which may hinder the efficient use of ozone. The particle size distribution is defined as the ratio (dw / dn) of the volume average particle size (dw) to the number average particle size (dn).

[0022] Furthermore, it is preferable that the ozone be brought into contact with the ozone in an environment with an average relative humidity of 90% or higher. This is because low humidity can cause the microdroplets to evaporate, resulting in insufficient purification. For example, it is expected that coloring materials will be more easily decolorized in a molecularly dissolved state than in a solid state.

[0023] In the first embodiment, the liquid purification system 100 returns the purified liquid to the liquid 300 to be treated and repeats the purification process, thereby diluting and clarifying the liquid to be treated.

[0024] Second Embodiment In the first embodiment, a liquid purification system was described in which the purified liquid is returned to the liquid to be treated. A liquid purification system 100 of the present embodiment will be described with reference to FIG.

[0025] The liquid purification system 100 of this embodiment includes a first container for storing the liquid 300 to be treated, and a second container for collecting droplets that have come into contact with ozone. As in the first embodiment, the system also includes an ultrasonic vibrator 200 placed in the liquid stored in the first container, and an ozone generation unit 400 that generates ozone in the first container. The system converts the liquid into fine droplets by ultrasonic vibration and brings the fine droplets into contact with ozone, thereby purifying the liquid.

[0026] With this configuration, the purified liquid is collected in the second container, thereby enabling highly efficient purification and collection of the purified liquid.

[0027] [Modification 1] Modification 1 will be described with reference to Fig. 3. In Modification 1, the liquid purification system 100 further includes an ultraviolet light 600 that generates ultraviolet light.

[0028] Here, the wavelength of the ultraviolet light 600 preferably includes 254 nm, which is absorbed by ozone. By irradiating ultraviolet light using the ultraviolet light 600, the ozone generated by the ozone generation unit 400 becomes hydroxyl radicals. In this state, accelerated oxidation functions during the purification process, and when the liquid purification system 100 is opened to the outside air, the ozone in the system can be deactivated, making this a useful embodiment. Of course, when quenching the ozone in the recovery mechanism after the purification process is completed, known methods such as manganese-based catalysts or activated carbon can also be used. In other words, the liquid purification system 100 described in this modified example includes an irradiation process in which ultraviolet light is irradiated using the ultraviolet light 600 as a post-process of the purification process.

[0029] Modification 2 will be described with reference to Figure 4. Liquid purification system 100 in Modification 2 is characterized by having a plurality of ultrasonic vibrators 200. By having a plurality of ultrasonic vibrators 200, the rate at which microdroplets are generated from the liquid to be treated is increased, thereby improving the purification rate.

[0030] [Variation 3] Variation 3 will be described using Figure 5. Figure 5 shows a mesh-type ultrasonic vibrator 200 in which piezoelectric elements are arranged around a mesh plate, and minute droplets of liquid can be generated from the mesh holes. When the ultrasonic vibrator 200 is of the mesh type, the liquid purification system 100 is configured to include a supply unit 700 for supplying the liquid 300 to be treated, which is stored in a first container, to the ultrasonic vibrator 200.

[0031] [Variation 4] Variation 4 will be described using Figure 6. Figure 6 shows a liquid purification system 100 in which the ultrasonic vibrator 200 is tilted toward the opening of the first container. By positioning the ultrasonic vibrator at an angle toward the opening of the first container, the liquid purification system 100 can collect the generated droplets with high efficiency.

[0032] Modification 5 will be described using Figure 7. In this modification, liquid purification system 100 further includes a supply path 800 that supplies untreated liquid to the first container, and a discharge path 900 that discharges the purified liquid recovered in the second container. This configuration makes it possible to continuously supply the liquid to be treated and discharge the treated liquid, and enables liquid purification system 100 to purify large amounts of liquid highly efficiently by operating for long periods of time.

[0033] [Variation 6] Variation 6 will be described using Figure 8. Figure 8 shows a liquid purification system installed on the surface of a liquid to be treated, such as a liquid in a reservoir such as a pond, lake, ocean, or pool, to purify the liquid. In this variation, the liquid purification system has a collection container 900 for collecting dispersed microdroplets and an agitation mechanism 1000 for agitating the liquid. This liquid purification system may be installed floating on the liquid to be treated, or may even be moved above the liquid to purify it.

[0034] [Variation 7] Variation 7 will be described using Figure 9. In Variation 7, the liquid purification system has a first container for storing the liquid to be treated, and a liquid tank 1100 is provided outside the first container, so that the liquid to be treated is purified without directly contacting the ultrasonic vibrator 200. Note that the ultrasonic vibrator 200 may be provided on the back side of the first container.

[0035] The following examples illustrate the results of verification conducted by varying the conditions of the liquid purification method using the liquid purification system 100, focusing on the following points. The droplet diameter was measured using water-sensitive paper. Specifically, the droplet diameter was calculated from the volume using the water-sensitive paper.

[0036] The cumulative FB concentration (100 million particles / ml) of 20 μm or less, the particle size (nm) of UFB of 20 μm or less, the number ratio of UFB in FB of 20 μm or less, and the particle size distribution of UFB of 20 μm or less were all measured using a measuring instrument manufactured by Shimadzu Corporation (model number SALD-7500nano).

[0037] The relative humidity was measured using a temperature and humidity data logger (model number KT-255F) manufactured by Fujita Electric Works.

[0038] The bactericidal activity was measured using a Biochecker (product number TTC) manufactured by Sanai Co., Ltd.

[0039] The odor was determined using a detector tube for ammonia (product number 3HM) manufactured by Gastec Corporation.

[0040] Regarding the verification of the effect on the liquid to be treated, the following evaluation items were evaluated before and after treatment according to the following criteria (some items were not evaluated).

[0041] In evaluating decolorization, a liquid that has absorption in the wavelength range of 300 nm to 800 nm can be said to be a liquid with room for improvement in transparency, regardless of whether it is chromatic or achromatic. In particular, at colorant manufacturing sites where decolorization is required, each color is manufactured separately to avoid color mixing. For yellow colorants (e.g., DY132), wastewater that absorbs light slightly above 300 nm needs to be treated, while for blue colorants (e.g., AB9), wastewater that absorbs light slightly below 800 nm needs to be treated. Decolorization: Reduction rate of absorbance at 640 nm for Blue No. 1 aqueous solution A Less than 10% B 10% or more, less than 50% C 50% or more, less than 80% D Less than 80% or more Deodorization: Reduction rate of ammonia odor measured with a gas detection tube A Less than 10% B 10% or more, less than 50% C 50% or more, less than 80% D Less than 80% or more Bactericidal activity: Reduction rate of colony count of Escherichia coli (JM109) A Less than 10% B 10% or more, less than 50% C 50% or more, less than 80% D Less than 80% or more Degradability: PEG200 aqueous solution was used. Percentage of decrease in peak area in liquid chromatography A Less than 10% B 10% or more but less than 50% C 50% or more but less than 80% D Less than 80% or more Effective utilization of ozone gas: Ratio of ozone concentration in the surrounding environment to the ozone concentration in the space in contact with the droplets A Less than 10% B 10% or more but less than 50% C 50% or more but less than 80% D Less than 80% or more Productivity: Relative ratio to the amount of liquid treated per hour in normal upward direction compared to Example 4 A 99% or more B 80% or more but less than 99% C 50% or more but less than 80% D Less than 50%

[0042] Example 1 With reference to Figure 1, a Seiko Giken piezoelectric atomization element (1.6 MHz) was used as the ultrasonic vibrator 200. The ultrasonic vibrator 200 was installed at the bottom of a 500 ml glass container (first container), the top was sealed, and 200 ml of the liquid 300 to be treated was poured into it. The installation position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 2 cm, and the liquid purification process was carried out. A Xe excimer lamp (manufactured by Oak Manufacturing, model: SE172-035HEC1) was used as the ozone gas generation unit 400.

[0043] The droplets generated by the ultrasonic vibrator had an average diameter of 20 μm.

[0044] Example 2 A purification process was carried out in the same manner as in Example 1, except that a mesh-type ultrasonic vibrator 200 and a KMJ diffuser (model number GXZ-J626) were provided as the first container, the liquid 300 to be treated was set to 200 ml, and the liquid purification system 100 shown in FIG. 5 was used as a reference.

[0045] The droplets generated by the ultrasonic vibrator had an average diameter of 5 μm.

[0046] Example 3 A liquid purification process was carried out in the same manner as in Example 1, except that a Seiko Giken immersion type ultrasonic atomization unit (IMA-SG1 (hood for IM1-24)) was provided above the installation position of the ultrasonic vibrator 200.

[0047] The droplets generated by the ultrasonic atomization unit had an average diameter of 5 μm.

[0048] Example 4 A purification process was carried out in the same manner as in Example 1, except that 300 ml of the liquid 300 to be treated was poured in and the installation position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 3 cm.

[0049] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0050] Example 5 Referring to FIG. 6, a liquid purification process was carried out in the same manner as in Example 4, except that the ultrasonic vibrator 200 in the liquid was tilted by 5°.

[0051] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 18 μm.

[0052] Example 6 Referring to FIG. 6, the purification process was carried out in the same manner as in Example 4, except that the ultrasonic vibrator 200 in the liquid was tilted at an angle of 45°.

[0053] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 18 μm.

[0054] Example 7 Referring to FIG. 6, the purification process was carried out in the same manner as in Example 4, except that the ultrasonic vibrator 200 in the liquid was tilted by 60°.

[0055] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 18 μm.

[0056] Example 8 A liquid purification process was carried out in the same manner as in Example 4, except that the ozone gas generating unit 400 was changed from a Xe excimer lamp to a low-pressure mercury lamp (manufactured by Sankyo Electric, model number GLK8MQ-ZH).

[0057] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0058] Example 9 A purification treatment was carried out in the same manner as in Example 4, except that the ozone gas generation unit 400 was changed from a Xe excimer lamp to a discharge-type ozone generation unit (product name O3 PREMIμM, manufactured by Growth, model AL-11ES3).

[0059] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0060] Example 10 A liquid purification process was carried out in the same manner as in Example 1, except that 350 ml of the liquid 300 to be treated was poured in and the installation position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 4 cm.

[0061] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0062] Example 11 A liquid purification process was carried out in the same manner as in Example 4, except that a 1 L glass container (first container) was used, the top of which was sealed, 700 ml of the liquid 300 to be treated was poured into it, and the installation position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 15 cm.

[0063] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0064] Example 12 A liquid purification process was carried out in the same manner as in Example 4, except that a 1 L glass container (first container) was used, the top of which was sealed, 800 ml of the liquid 300 to be treated was poured into it, and the installation position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 16 cm.

[0065] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0066] Example 13 A liquid purification process was carried out in the same manner as in Example 4, except that a 1 L glass container (first container) was used, the top of which was sealed, 800 ml of the liquid 300 to be treated was poured into it, and the installation position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 7 cm.

[0067] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0068] Example 14 A liquid purification process was carried out in the same manner as in Example 4, except that a 1 L glass container (first container) was used, the top of which was sealed, 800 ml of the liquid 300 to be treated was poured into it, and the installation position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 8 cm.

[0069] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0070] Example 15 The liquid purification system shown in Figure 8 was manufactured as follows. A 2 L PFA hemispherical cover was used for the microdroplet collection container, a Tamiya submersible motor (ITEM70154) was used for the screw (propulsion mechanism / liquid stirring mechanism), and the ultrasonic vibrator and ozone gas generation unit were the same as in Example 1. The liquid purification system was floated on 50 L of a 100 ppm Blue No. 1 aqueous solution, and the installation position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 3 cm, and a purification process was performed.

[0071] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 20 μm.

[0072] 2, a 500 ml glass container was used as the first container, and the second container was a 20 L Tedlar bag made of polyvinyl fluoride, and the container was sealed inside. 300 ml of the liquid 300 to be treated was poured into the glass container, and the position of the ultrasonic vibrator 200 was adjusted so that the distance between the gas-liquid interface and the piezoelectric element surface was 8 cm. A liquid purification process was carried out in the same manner as in Example 4.

[0073] The droplets generated by the ultrasonic vibrator 200 had an average diameter of 6 μm.

[0074] Example 17 In the same manner as in Example 4, the driving of the ultrasonic vibrator 200 was controlled so that the average relative humidity was 90%, and a liquid purification process was carried out.

[0075] Example 18 In the same manner as in Example 4, the driving of the ultrasonic vibrator 200 was controlled so that the average relative humidity was less than 90%, and a liquid purification process was carried out.

[0076] Example 19 Purification treatment was carried out in the same manner as in Example 16, except that an ultraviolet light was provided with reference to FIG.

[0077] The low-pressure mercury lamp used was a Sankyo Electric product, model number GLK8MQ.

[0078] The decolorization reaction was accelerated by ultraviolet irradiation using the ultraviolet light 600. When the spatial gas concentration in the purified liquid purification system after ultraviolet irradiation was measured, no ozone was detected.

[0079] Comparative Example 1 The liquid to be treated was supplied by a submersible pump and sprayed into a 20 L polyvinyl fluoride resin Tedlar bag equipped with an ozone generation unit 400 and a shower head (Tanaka Metal, Bollina Pulito) on the waste liquid side.

[0080] The average diameter of the droplets generated by the showerhead was 2 mm.

[0081] Comparative Example 2 Referring to FIG. 6, the liquid purification process was carried out in the same manner as in Example 4, except that the ultrasonic vibrator 200 in the liquid was tilted by 90°. As a result, no microdroplets were generated, and the treated liquid could not be collected in the second container.

[0082] Comparative Example 3 Comparative Example 3 was carried out in the same manner as Comparative Example 1, except that the shower head was changed to a JSA022 manufactured by Takagi.

[0083] The average diameter of the droplets generated by the showerhead was 5 mm.

[0084] Comparative Example 4 Referring to FIG. 6, the purification process was carried out in the same manner as in Example 4, except that the ultrasonic vibrator 200 in the liquid was tilted 180° downward. As a result, no microdroplets were generated, and the treated liquid could not be recovered in the second container.

[0085] Comparative Example 5 A purification treatment was carried out in the same manner as in Example 4, except that the ozone generation unit 400 was not driven.

[0086] The average diameter of the droplets was 20 μm.

[0087] Comparative Example 6 A Xe excimer lamp was placed in a 20 L polyvinylidene fluoride Tedlar bag, a PFA tube was placed in the bag, and one end of the tube was connected to an air pump, which was used to bubble the air into the liquid to be treated.

[0088] The smell of ozone emanated from the liquid being treated.

[0089] The processing conditions and effects of the above-mentioned Examples and Comparative Examples are summarized in Tables 1 and 2, respectively.

[0090]

[0091]

[0092] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0093] This application claims priority from Japanese Patent Application No. 2023-104197, filed on June 26, 2023, the contents of which are incorporated herein by reference.

Claims

1. A liquid purification method comprising the steps of: preparing a first container and a liquid to be treated inside the first container; generating microdroplets of the liquid above the liquid surface by oscillating an ultrasonic vibrator placed in the liquid; and purifying the liquid by bringing the microdroplets into contact with ozone.

2. A liquid purification method according to claim 1, wherein said generating step generates said minute droplets in a mist form and brings said droplets into contact with said ozone.

3. A liquid purification method according to claim 1 or 2, wherein the microdroplets contain fine bubbles of 20 μm or less.

4. A liquid purification method according to claim 3, characterized in that the fine bubbles include ultra-fine bubbles of 1 μm or less.

5. A liquid purification method as described in claim 4, characterized in that the proportion of said ultra-fine bubbles in the fine bubbles of 20 μm or less is 99% or more.

6. A liquid purifying method according to claim 1 or 2, characterized in that in said generating step, the liquid surface of said liquid has a thickness from said ultrasonic vibrator of 15 cm or less.

7. A liquid purifying method as claimed in either one of claims 4 or 5, characterized in that the ultra-fine bubbles have a ratio (dw / dn) of volume average particle diameter (dw) to number average particle diameter (dn) of bubbles of 20 μm or less of 5 or less.

8. A liquid purification method according to claim 1 or 2, further comprising a recovery step of recovering the purified liquid in a second container by said purification step.

9. A liquid purification method according to claim 1 or 2, further comprising an irradiation step of irradiating with ultraviolet light after said purification step.

10. A liquid purification method according to claim 1 or 2, characterized in that the purification step purifies the liquid in an environment having an average relative humidity of 90% or more.

11. A liquid purification method according to claim 1 or 2, characterized in that the liquid to be treated has absorption in the wavelength range of 300 nm or more and 800 nm or more.

12. A liquid purification system comprising: a first container for storing a liquid to be treated therein; an ultrasonic vibrator disposed in the liquid stored in the first container; and an ozone generation unit for generating ozone in the first container, the liquid being converted into microdroplets by ultrasonic vibrations produced by the ultrasonic vibrator, and the microdroplets being brought into contact with the ozone, thereby purifying the liquid.

13. A liquid purification system comprising an ultrasonic vibrator placed in a liquid to be treated, an ozone generation unit that generates ozone, and a collection container that covers at least a portion of the liquid to be treated, wherein the liquid is converted into fine droplets by ultrasonic vibrations produced by the ultrasonic vibrator, and the fine droplets are brought into contact with the ozone inside the collection container, thereby purifying the liquid.

14. The liquid purification system according to claim 13, wherein the liquid to be treated is any one of liquids in the sea, a lake, a pond, and a water tank.

15. The liquid purification system according to claim 13 or 14, further comprising an agitation mechanism for agitating the liquid to be treated, wherein the liquid to be treated is agitated.

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