Water treatment method and water treatment apparatus

Abstract

To provide a water treatment method and a water treatment device capable of safely and efficiently decomposing a soluble organic material included in water to be treated using a simple device.SOLUTION: A water treatment method comprises the steps of: storing water to be treated containing a soluble organic material in a treatment tank 21; injecting oxygen-containing gas to a gas flowing region 126 formed on the circumference of a light source 122 irradiating the water to be treated present in the treatment tank 21 with UV rays; radiating UV rays in a wavelength range capable of generating ozone from the light source to the gas flowing region 126, to generate ozone in the gas flowing region 126; and mixing the ozone generated by radiating the UV rays and the water to be treated present in the treatment tank 21; and irradiating the ozone-containing water to be treated with the UV rays from the light source 122 to carry out accelerated oxidation, thereby removing the soluble organic material present in the water to be treated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a water treatment method and a water treatment apparatus.

Background Art

[0002] Various types of water to be treated, such as river water, leachate, industrial water, agricultural water, tap water, pure water, sewage, industrial wastewater, and organic wastewater, contain various impurities. For example, the water to be treated contains contaminants such as dust, dirt, or clay, aquatic organisms such as bacteria or microorganisms, algae, organic substances such as organic fluorine compounds such as PFOS (perfluorooctanesulfonic acid), PFOA (perfluorooctanoic acid), PFHxS (perfluorohexanesulfonic acid) and its salts, inorganic salts such as calcium, magnesium, or sodium, gases such as carbon dioxide, carbon, or hydrogen sulfide, and metal substances such as iron or manganese. In order to remove these impurities, various water treatments such as coagulation sedimentation treatment, biological treatment, and filtration treatment are performed on the water to be treated.

[0003] The water to be treated is further subjected to sterilization treatment as necessary. For example, Japanese Patent No. 5802558 describes an example of a sterilization treatment using a hydroponics system that exhibits a bactericidal action and an organic matter decomposition action by the synergistic effect of a sterilization and purification unit having an ozone supply function, an ultraviolet irradiation function, and a photocatalytic action function on a culture solution that is a liquid fertilizer. Japanese Patent No. 5191782 describes an example of a hydroponics system for sterilizing a culture solution that is a liquid fertilizer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Ultraviolet (UV) sterilization is useful because, compared to sterilization using disinfectants and other chemicals, it leaves less residue, is safe, and effectively decomposes dissolved organic matter in a short time. However, if the water to be treated is highly turbid or if there are substances that block the light, the UV light may not reach sufficiently, resulting in insufficient sterilization. In general ozone oxidation treatment, relatively high concentrations of ozone gas are supplied for treatment, which may generate odors in the surrounding area during the oxidation process. Furthermore, there are concerns that ozone remaining in the water after ozone oxidation treatment may have various effects on organisms living in the discharge destination of the treated water.

[0006] In view of the above issues, the present invention provides a water treatment method and a water treatment apparatus that can safely and efficiently decompose dissolved organic matter contained in water to be treated using a simple apparatus. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the present inventors have found that it is useful to perform accelerated oxidation treatment on water to be treated that contains dissolved organic matter, using ultraviolet light and ozone generated by ultraviolet irradiation.

[0008] Based on the above findings, this disclosure is a water treatment method characterized in that, in one aspect, it includes: placing water to be treated containing dissolved organic matter in a treatment tank; injecting an oxygen-containing gas into a gas flow region formed around a light source that irradiates the water to be treated in the treatment tank with ultraviolet light; irradiating the gas flow region from the light source with ultraviolet light in a wavelength range that generates ozone, thereby generating ozone in the gas flow region; mixing the ozone generated by the irradiation of ultraviolet light with the water to be treated in the treatment tank; and performing an accelerated oxidation treatment by irradiating the water to be treated containing ozone with ultraviolet light from the light source, thereby removing dissolved organic matter in the water to be treated.

[0009] In one embodiment of the water treatment method according to the present invention, a gas containing ozone and oxygen generated in a gas flow region is supplied to the water to be treated at a rate of 0.005 to 1 L / L - water to be treated, such that the gas-liquid ratio of the water to be treated and the gas containing ozone and oxygen is 1 to 200 by volume.

[0010] In another embodiment of the present invention, the water treatment method further comprises the step of generating oxygen-containing bubbles with a bubble diameter of 100 μm or less, and injecting the generated bubbles into the water to be treated.

[0011] In another embodiment of the present invention, the water treatment method further includes a step of performing a pretreatment to remove chromatic components from the water to be treated before placing the water to be treated into the treatment tank.

[0012] In another embodiment of the water treatment method according to the present invention, the water to be treated contains at least one of bacteria, fungi, microorganisms, algae, cyanobacteria, or organofluorine compounds.

[0013] In another embodiment of the present invention, the water treatment method further comprises the step of performing a water treatment on the water to be treated, before placing the water to be treated into the treatment tank, which includes at least one of the following: solid-liquid separation treatment, coagulation and sedimentation treatment, biological treatment, ion exchange treatment, filtration treatment, physical adsorption treatment, and electrolysis treatment.

[0014] In one aspect, the water treatment apparatus according to an embodiment of the present invention comprises: a treatment tank that contains water to be treated containing dissolved organic matter and decomposes the dissolved organic matter in the water to be treated by performing an accelerated oxidation treatment on the water to be treated using ultraviolet light and ozone; an ultraviolet irradiation means that includes a light source for irradiating the water to be treated with ultraviolet light in the wavelength range of 100 to 300 nm and a gas flow region formed around the light source for circulating gas; a gas injection means for supplying an oxygen-containing gas to the gas flow region; and an introduction means for introducing ozone generated by irradiation of the gas flow region into which the oxygen-containing gas has been injected with ultraviolet light from the light source into the water to be treated in the treatment tank.

[0015] In one embodiment, the water treatment apparatus according to an embodiment of the present invention further includes a bubble injection means for generating bubbles containing oxygen with a bubble diameter of 100 μm or less and injecting the generated bubbles into the water to be treated.

[0016] In another embodiment, the water treatment apparatus according to an embodiment of the present invention further includes a pretreatment means connected to the front stage of the treatment tank for performing pretreatment to remove the chromaticity components in the water to be treated.

Effects of the Invention

[0017] According to the present invention, it is possible to provide a water treatment method and a water treatment apparatus capable of safely and efficiently decomposing and treating the dissolved organic matter contained in the water to be treated with a simple apparatus.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic diagram showing an example of the water treatment apparatus according to the first embodiment of the present invention. [Figure 2] It is a schematic diagram showing an example of the water treatment apparatus according to the second embodiment of the present invention. [Figure 3] It is a schematic diagram showing an example of the water treatment apparatus according to the third embodiment of the present invention. [Figure 4] It is a schematic diagram showing an example of the water treatment apparatus according to a modified example of the embodiment of the present invention. [Figure 5] It is a schematic diagram showing an example of the water treatment apparatus according to a modified example of the embodiment of the present invention. [Figure 6] It is a schematic diagram showing an example of the water treatment apparatus according to a modified example of the embodiment of the present invention.

Modes for Carrying Out the Invention

[0019] Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals. The embodiments shown below are illustrative examples of devices and methods for realizing the technical idea of ​​this invention, and the technical idea of ​​this invention is not limited to the structure, arrangement, etc., of the components described below.

[0020] (First Embodiment) As shown in Figure 1, the water treatment apparatus 100 according to the first embodiment of the present invention comprises a water treatment means 1 that treats raw water to obtain water to be treated, and an accelerated oxidation treatment means 2 that performs accelerated oxidation treatment (AOP treatment) on the water to be treated using ultraviolet light and ozone.

[0021] The water treatment means 1 is a device that performs predetermined water treatment in order to utilize raw water for a predetermined purpose, and various water treatment devices 100 can be used. Preferably, the water treatment means 1 is a device that performs water treatment including at least one of the following: solid-liquid separation treatment, coagulation and sedimentation treatment, biological treatment, ion exchange treatment, filtration treatment, physical adsorption treatment, and electrolysis treatment.

[0022] For example, if the water treatment means 1 is a water purification treatment device, the water treatment device 100 may include an intake well for storing the water to be treated, a mixing tank for mixing chemicals such as inorganic coagulants with the water to be treated, a floc formation tank for adding polymer coagulants to form flocs, a sedimentation tank for settling the flocs, a filtration tank for filtering the treated water, a distribution tank for storing the filtered water, and so on.

[0023] For example, if the water treatment means 1 is a sewage treatment facility, the water treatment device 100 may include receiving and storage equipment for receiving water to be treated such as septic tank sludge, sewage and / or sewage; slag removal equipment for removing impurities from the water to be treated; biological treatment equipment for biologically treating the water to be treated by biological denitrification treatment or anaerobic digestion treatment; and advanced treatment equipment for performing advanced treatment on the biologically treated water obtained from biological treatment, such as coagulation and sedimentation treatment, sand filtration, activated carbon treatment, desalination, evaporation, and disinfection.

[0024] For example, if the water treatment means 1 is a pure water production device, the water treatment device 100 may include a sand filter for filtering the water to be treated, an activated carbon device, a cation exchange column, an anion exchange column, an ultraviolet irradiation (UV) device, a reverse osmosis (RO) device, and a degassing device equipped with a mixed bed column and a degassing membrane.

[0025] For example, if the water treatment means 1 is a water treatment device 100 for a closed-loop land-based aquaculture facility, it may include rearing tanks for raising fish, shellfish, etc., a filtration device for filtering the water to be treated, a nitrogen treatment device for removing nitrogen components derived from fish waste, a filtration device or foam separation device for removing suspended solids in the water to be treated after nitrogen treatment, and a sterilization device.

[0026] For example, if the water treatment means 1 is a pure water production device for water to be treated that contains organic fluorine compounds such as PFOS, PFOA (perfluorooctanoic acid), PFHxS (perfluorohexanesulfonic acid) and their salts, the water treatment device 100 may include a sand filter for filtering the water to be treated, an activated carbon device, a cation exchange tower, an anion exchange tower, an ultraviolet irradiation (UV) device, a reverse osmosis (RO) membrane device, and a deaeration device equipped with a mixed bed tower and a deaeration membrane. Furthermore, if the water treatment means 1 is a water purification facility for water containing organic fluorine compounds (PFOS and PFOA), the water treatment device 100 may include an intake well for storing the water to be treated, a mixing tank for mixing chemicals such as inorganic coagulants with the water to be treated, a floc formation tank for adding polymer coagulants to form flocs, a sedimentation tank for settling the flocs, a filtration tank for filtering the settled water, and a distribution tank for storing the filtered water. It may also include disinfection of combined sewer overflow (CSO) or purification devices for lake and river water.

[0027] In the example shown in Figure 1, an example is described in which the accelerated oxidation treatment means 2 is connected to the downstream of the water treatment means 1. However, the example is not limited to this, and the accelerated oxidation treatment means 2 may be incorporated into a part of the various equipment that constitutes the water treatment means 1. For example, the accelerated oxidation treatment means 2 may be incorporated into an advanced treatment device that performs advanced treatment such as disinfection on biologically treated water, or into an ultraviolet irradiation device for sterilization of pure water in a pure water system.

[0028] The treated water contains dissolved organic matter. In this embodiment, dissolved organic matter refers to the total amount of organic matter in the filtrate filtered through a filter paper with a pore size of 1 μm. Specifically, dissolved COD Cr , soluble COD Mn This includes soluble BOD, soluble TOC, soluble reducing sugars, soluble starch, and organofluorine compounds.

[0029] The treated water may further contain nutrients or trace metal components. Specifically, the nutrients or trace metals include nitrogen (N) and its compounds, phosphorus (P) and its compounds, Na, K, Ca, Mg, Fe, B, and hydrates or compounds of each metal.

[0030] The treated water contains at least one of the following: bacteria, fungi, microorganisms, algae, cyanobacteria, or organofluorine compounds. The dissolved organic matter in the treated water is often composed of dissolved organic components derived from these bacteria, fungi, microorganisms, algae, cyanobacteria, organofluorine compounds, etc. Therefore, the concentration of dissolved organic matter changes depending on the concentration of dissolved organic matter components derived from bacteria, fungi, microorganisms, algae, cyanobacteria, organofluorine compounds, etc. in the treated water.

[0031] The bacteria contained in the treated water (hereinafter also referred to as "bacteria" or "general bacteria") refer to bacteria (especially heterotrophic bacteria) that form colonies on a semi-agar medium when cultured at 36±1°C for 24±2 hours, and are measured by a method compliant with the Water Supply Test Method (published by the Japan Water Works Association, Water Supply Test Method) or the Wastewater Test Method (published by the Japan Sewerage Association, Wastewater Test Method). The number of colonies formed on the medium is expressed as cells / mL or CFU / mL. Bacteria include general viable bacteria. When a culture solution is used as the treated water, it is required that the bacterial levels be kept below a certain standard value, as the culture solution is used for growing food such as vegetables and fruits.

[0032] Algae typically include phytoplankton, etc. Specifically, algae include green algae, cyanobacteria, golden algae, diatoms, etc., and in particular, green algae that have photosynthetic pigments (chlorophyll a) in their cells. When using treated water such as culture solutions or culture solutions from plant production systems, problems such as increased frequency of water replacement and cleaning of flow channels may occur due to the growth of algae. When using raw water such as river water as treated water, the concentration of phytoplankton may fluctuate due to weather conditions such as torrential downpours, which may cause a rapid increase in algae.

[0033] Organofluorine compounds, abbreviated as PFAS (Per- and Polyfluoroalkyl Substances), are organic compounds with carbon-fluorine bonds and are also found in soluble organic matter. Due to their unique properties (water-repellent, oil-repellent, heat-resistant, chemical-resistant, and non-absorbent), organofluorine compounds have been used in a variety of products. However, they are persistent, accumulate in living organisms, and have been reported to have adverse effects on these organisms. In particular, the toxicity and bioaccumulation of PFOS (perfluorooctanesulfonic acid) and PFOA (perfluorosulfonic acid), which have eight carbon atoms, are well known. PFHxS (perfluorohexanesulfonic acid) is used as a substitute for PFOS. Organofluorine compounds are quantified by high-performance liquid chromatography-mass spectrometry (LC / MS or LC / MS / MS) after pretreatment. Organofluorine compounds exist in various natural environments and in the human living environment, but they may also be present in groundwater, lake and river water, sewage, and factory or industrial wastewater. Internationally, PFOS and PFOA are regulated under the Stockholm Convention on Residual Organic Pollutants (POPs Convention). In Japan, PFOS and PFOA in river water and groundwater are designated as items requiring monitoring regarding water pollution, and PFOS and PFOA in drinking water are positioned as water quality management target items, with provisional target values ​​set.

[0034] The treated water may contain suspended solids (SS). SS refers to solid suspended matter floating in water, specifically the substances that remain on filter paper when filtered through a filter paper with a pore size of 1 μm. SS includes both inorganic and organic substances. Inorganic SS includes components derived from soil and clay. Organic SS includes components derived from animal, plant, and microbial cells, as well as components derived from factories. The SS contained in the treated water is not particularly limited, but examples include components generated in the manufacturing process of soft drink factories, activated sludge, sludge detached from fluidized carriers, and SS derived from sludge flocs generated in the coagulation process.

[0035] The properties of the water to be treated are not limited to the following, but for example, organic wastewater with a total organic carbon (TOC) of 0.1 to 5000 mg / L, more specifically 1 to 3000 mg / L, and in one embodiment 0.5 to 100 mg / L may be used. Alternatively, organic wastewater with a chemical oxygen demand (COD) of 0.1 to 10000 mg / L, more specifically 1 to 6000 mg / L may be used as the water to be treated. Alternatively, organic wastewater with suspended solids (SS) of 0.1 to 2000 mg / L, more specifically 1 to 1000 mg / L, and in one embodiment 0.1 to 100 mg / L may be used as the water to be treated.

[0036] In AOP treatment, the chromaticity, turbidity, and effectiveness in removing dissolved organic matter may be limited depending on the ultraviolet transmittance, although this is not limited to the following. In one embodiment, the chromaticity of the treated water is approximately 1 to 1000 degrees, more typically 5 to 1000 degrees, even more typically 50 to 500 degrees, and in one embodiment 5 to 10 degrees. The suspended solids (SS) of the treated water are typically 50 to 1000 mg / L, more typically 50 to 500 mg / L, and even more typically 50 to 300 mg / L. The dissolved organic matter (soluble TOC) is typically 0.01 to 50 mg / L, more typically 0.05 to 20 mg / L, and even more typically 0.1 to 10 mg / L. COD Mn The typical range is 100-1000 mg / L, more typically 200-1000 mg / L, and even more typically 200-550 mg / L. S-COD MnTotal manganese is typically 100–1000 mg / L, more typically 200–1000 mg / L, and even more typically 200–500 mg / L. BOD is typically 200–1500 mg / L, more typically 200–1000 mg / L. S-BOD is typically 200–1500 mg / L, more typically 200–600 mg / L. Total manganese is typically 0.01–5 mg / L, more typically 0.01–3 mg / L, and even more typically 0.01–1 mg / L. Soluble manganese is typically 0.01–5 mg / L, more typically 0.01–3 mg / L, and even more typically 0.01–1 mg / L. Total iron is typically 0.01–10 mg / L, more typically 0.01–7 mg / L, and even more typically 0.01–5 mg / L. Solubility of Fe is typically 0.01–10 mg / L, more typically 0.01–7 mg / L, and even more typically 0.01–5 mg / L. Color, SS, and COD of the treated water. Mn S-COD Mn BOD, S-BOD, soluble TOC, total Fe, total Mn, soluble Fe, and soluble Mn can each be measured according to known water supply testing methods or wastewater testing methods.

[0037] <Methods for accelerated oxidation treatment> The accelerated oxidation treatment means 2 is a device that sterilizes and purifies water to be treated by performing accelerated oxidation treatment on the water to be treated using ultraviolet light and ozone. The accelerated oxidation treatment means 2 includes a treatment tank 21 that contains water to be treated containing dissolved organic matter and decomposes the dissolved organic matter in the water to be treated by performing accelerated oxidation treatment on the water to be treated using ultraviolet light and ozone; an ultraviolet irradiation means 22 that includes a light source 122 that irradiates the water to be treated with ultraviolet light in the wavelength range of 100 to 300 nm and a gas flow region 126 formed around the light source 122 for circulating gas; a gas injection means 23 that supplies oxygen-containing gas to the gas flow region 126; and an introduction means 24 that introduces ozone generated by irradiation of ultraviolet light from the light source 122 into the gas flow region 126 into which oxygen-containing gas has been injected, into the water to be treated in the treatment tank 21.

[0038] The treatment tank 21 is equipped with an ultraviolet irradiation means 22 in its central part that can irradiate the water to be treated with ultraviolet light in the wavelength range of 100 to 300 nm. The water to be treated is contained in a water flow area 127 provided inside the treatment tank 21 on the outer periphery of the ultraviolet irradiation means 22. The configuration of the ultraviolet irradiation means 22 is not particularly limited. For example, the ultraviolet irradiation means 22 includes a light source 122 that irradiates ultraviolet light, a casing 25 arranged to cover the area around the light source 122, a power supply and wiring (not shown), etc. The space between the light source 122 and the casing 25 functions as a gas flow area 126 for circulating gas.

[0039] There are no particular restrictions on the type of light source 122, but hot cathode and cold cathode ultraviolet lamps are preferably used. The casing 25 functions to protect the light source 122 while allowing oxygen-containing gas injected from the gas injection means 23 to flow between the light source 122 and the casing 25. There are no restrictions on the material of the casing 25, but typically, a colorless and transparent material such as acrylic resin, polyvinyl chloride resin, or glass resin is preferred, as it does not absorb or reflect ultraviolet light in the wavelength range irradiated by the light source 122 of the ultraviolet irradiation means 22, and is less susceptible to degradation by ultraviolet light.

[0040] The ultraviolet irradiation means 22 irradiates the water to be treated with a first ultraviolet light having a wavelength range for sterilization and a second ultraviolet light having a wavelength range for generating ozone from oxygen. In the example shown in Figure 1, the ultraviolet irradiation means 22 is shown as being provided separately with a first ultraviolet irradiation means 22A (first light source) that irradiates the first ultraviolet light and a second ultraviolet irradiation means 22B (second light source) that irradiates the second ultraviolet light, but the configuration is not limited to this. Preferably, by using an ultraviolet irradiation means 22 equipped with a light source 122 that can irradiate the first ultraviolet light and the second ultraviolet light with different wavelength ranges with a single ultraviolet lamp, the device can be made smaller and simpler.

[0041] The wavelength range of the first ultraviolet light is not limited as long as it promotes the decomposition of dissolved organic matter in the treated water and the activation of ozone, and is typically in the 100-300 nm range. More typically, the first ultraviolet light irradiates with ultraviolet light in the 240-300 nm range, and even more typically, 240-260 nm. The wavelength range of the second ultraviolet light is not limited as long as it generates ozone by irradiation with ultraviolet light, but is typically in the 180-190 nm range, and more typically, 185 nm.

[0042] The gas injection means 23 consists of, for example, an air compressor, an air pressure gauge, an air flow meter, a pressure reducing valve, piping, and its associated devices. Air is most preferably used as the oxygen-containing gas due to its ease of handling, availability, and economic efficiency. In addition to oxygen, other gases such as ozone, carbon dioxide, and hydrogen may also be included, and it is possible to introduce two or more of these gases simultaneously. The gas injection means 23 is connected to a gas flow region 126 formed between the light source 122 and the casing 25. The gas injection means 23 injects an oxygen-containing gas, typically air, into the gas flow region 126 through an inlet 231 provided in the casing 25.

[0043] In the accelerated oxidation treatment means 2, the first ultraviolet light is irradiated onto the water to be treated, which contains ozone, by the ultraviolet irradiation means 22 to perform an accelerated oxidation treatment that decomposes dissolved organic matter in the water to be treated. The light source 122 irradiates the gas flow region 126, into which an oxygen-containing gas such as air is injected, with a second ultraviolet light. As a result, ozone is generated in the gas flow region 126 from a portion of the injected oxygen. The small amount of ozone generated by the irradiation of the second ultraviolet light is mixed with the oxygen-containing gas into the water to be treated in the treatment tank 21 via the introduction means 24. Then, the first ultraviolet light is irradiated onto the water to be treated containing ozone by the first ultraviolet irradiation means 22A, generating hydroxyl radicals in the water to be treated. As a result, in the accelerated oxidation treatment means 2, an accelerated oxidative decomposition reaction (AOP treatment) by ultraviolet light, ozone, and hydroxyl radicals proceeds. Through this AOP treatment, dissolved organic matter, bacteria, algae, suspended solids (SS), etc., in the water to be treated are efficiently decomposed.

[0044] AOP treatment is also called accelerated oxidation treatment or accelerated oxidation treatment. This AOP treatment is a method that promotes oxidative decomposition reactions by generating more hydroxyl radicals than single oxidation treatments through the reaction of several oxidizing agents with water. Examples of oxidizing agents used in AOP treatment include ozone and hydrogen peroxide. Unlike treatment methods using chemicals, AOP treatment is useful because it leaves no residue after treatment and has excellent decolorization properties. Therefore, by applying it to the decomposition treatment of dissolved organic matter, bacteria, algae, suspended solids (SS), etc. in the water to be treated, changes in the composition of the water to be treated are suppressed, dissolved organic matter is decomposed, and the growth of bacteria and algae, etc. is suppressed, while accelerated oxidation treatment can be safely performed with simple equipment. In this embodiment, by combining ultraviolet (UV) treatment with AOP treatment, oxidation treatment, organic matter treatment, and sterilization treatment can be promoted, resulting in an even higher accelerated oxidation treatment effect than UV treatment, ozone treatment, or AOP treatment alone.

[0045] There are no particular restrictions on the amount of gas injected by the gas injection means 23. However, if the amount injected is too large, the reaction between the air and ultraviolet light will be insufficient, resulting in insufficient ozone generation. On the other hand, if the amount injected is too small, the amount of ozone generated for the AOP treatment carried out by the accelerated oxidation treatment means 2 will be insufficient, which may reduce the effectiveness of the sterilization and purification treatment.

[0046] It is preferable, though not limited to, that ozone be generated in the gas flow region 126 as an oxygen-containing gas such that the ozone concentration in the gas flow region 126 becomes 0.005 to 0.5 mg-O3 / L-fluid, more preferably 0.005 to 0.3 mg-O3 / L-fluid, and even more preferably 0.01 to 0.5 mg-O3 / L-fluid liquid.

[0047] The ozone-containing gas in the gas flow region 126 is mixed with the water to be treated in the treatment tank 21 via an introduction means 24 consisting of piping and a pump, which is connected to one end of the gas flow region 126 and one end of the water to be treated flow region 127, which is located on the outer circumference of the ultraviolet irradiation means 22 in the treatment tank 21. The volume of the gas flow region 126 is preferably 1 / 1 to 1 / 200 of the volume of the water to be treated flow region 127, and more preferably 1 / 3 to 1 / 100. This allows a gas containing ozone at a constantly stable concentration to be introduced into the water to be treated flow region 127 via the introduction means 24. Thus, dissolved organic matter contained in the water to be treated can be safely and efficiently decomposed using a simple device.

[0048] The introduction means 24 preferably supplies the gas containing ozone and oxygen generated in the gas flow region 126 into the treatment tank 21 at a rate of 0.005 to 1 L / L of water to be treated, more preferably 0.01 to 0.5 L / L of water to be treated, and even more preferably 0.01 to 0.2 L / L of water to be treated. Alternatively, when supplying air as the oxygen-containing gas, the gas-liquid ratio (volume ratio of water to be treated / gas containing ozone and oxygen) of the water to be treated and the injected gas is preferably 1 to 200, more preferably 3 to 100, and even more preferably 5 to 50. The gas containing ozone and oxygen introduced into the treatment tank 21 from the introduction means 24 may be configured to be discharged from the treatment tank 21 and further circulated within the treatment tank 21.

[0049] The gas containing ozone and oxygen generated in the gas flow region 126 of the ultraviolet irradiation means 22 is injected into the water to be treated flowing in the water to be treated flow region 127 outside the casing 25 in the treatment tank 21 via the introduction means 24 connected to the gas flow region 126. This makes it possible to make more efficient use of the small amount of ozone generated by ultraviolet irradiation and perform AOP treatment. Furthermore, it is preferable to install a pretreatment device (not shown), such as a filter for removing suspended components, before the accelerated oxidation treatment means 2, as this can further improve the efficiency of decomposition of dissolved organic matter in the water to be treated.

[0050] If too much ozone is generated in the water to be treated in the treatment tank 21, depending on the ozone concentration, it may adversely affect organisms at the discharge destination or use site of the treated water. In this invention, instead of supplying a relatively high concentration of ozone to the treatment tank 21 from the outside, air is injected into the treatment tank 21 and further into the gas flow region 126 of the ultraviolet irradiation means 22, and a small amount of ozone is generated by reacting oxygen with ultraviolet light in the gas flow region 126. Then, the reaction between the generated ozone and ultraviolet light generates highly oxidative hydroxyl radicals. Since the amount of ozone in the water to be treated is small, there is no need to specially provide a decomposition treatment for the ozone dissolved in the water to be treated. Furthermore, since there is no external supply of ozone, the equipment configuration is simple and running costs can be reduced. Therefore, according to this invention, dissolved organic matter in the water to be treated can be decomposed with simpler and smaller equipment.

[0051] It is preferable, but not limited to, that the ozone treatment in the accelerated oxidation treatment means 2 is performed such that the ozone concentration in the treated water discharged from the accelerated oxidation treatment means 2 is 0.005 to 0.5 mg-O3 / L-treated water, more typically 0.01 to 0.4 mg-O3 / L-treated water, and even more typically 0.01 to 0.3 mg-O3 / L-treated water.

[0052] Alternatively, it is preferable to inject an oxygen-containing gas and / or bubbles into the treated water so that the DO of the treated water in the accelerated oxidation treatment is 5 to 20 mg / L, more preferably to inject so that the DO is 6 to 15 mg / L, and even more preferably to control the amount of oxygen-containing gas injected so that the DO is 6 to 12 mg / L.

[0053] According to the water treatment apparatus 100 of the first embodiment of the present invention, first and second ultraviolet rays are irradiated via the ultraviolet irradiation means 22 of the accelerated oxidation treatment means 2, and an oxygen-containing gas is injected from the gas injection means 23 into the gas flow region 126 of the ultraviolet irradiation means 22, and the second ultraviolet rays are irradiated into the gas flow region 126 from the light source 122, thereby generating a small amount of ozone. This ozone and oxygen-containing gas are mixed into the water to be treated in the treatment tank 21 via the introduction means 24, and hydroxyl radicals are generated when the first ultraviolet rays are irradiated in the presence of ozone. As a result, AOP treatment by ultraviolet rays and ozone is accelerated in the treatment tank 21, and this accelerating effect decomposes dissolved organic matter in the water to be treated. According to the embodiment of the present invention, since ozone is not supplied from an external source as in the conventional method, and no chemicals for sterilization are used, safe treatment can be performed without the use of chemicals and at a low ozone concentration.

[0054] (Water treatment method) A water treatment method according to the first embodiment of the present invention can be carried out using the water treatment apparatus 100 shown in Figure 1. Specifically, the water treatment method includes treating water containing dissolved organic matter, placing the water containing dissolved organic matter in a treatment tank 21, injecting an oxygen-containing gas into a gas flow region 126 formed around a light source 122 that irradiates the water in the treatment tank 21 with ultraviolet light, irradiating the gas flow region 126 from the light source 122 with ultraviolet light in a wavelength range that generates ozone, thereby generating ozone in the gas flow region 126, mixing the ozone generated by the irradiation of ultraviolet light with the water in the treatment tank 21, and performing an accelerated oxidation treatment by irradiating the water containing ozone with ultraviolet light from the light source 122 to remove dissolved organic matter from the water.

[0055] According to the water treatment method of the first embodiment of the present invention, first and second ultraviolet rays are irradiated onto the water to be treated in the presence of oxygen, and AOP treatment (UV-AOP treatment) using ultraviolet rays and ozone can be performed. Therefore, a water treatment method is obtained that can safely decompose dissolved organic matter in the water to be treated using a simple device while suppressing changes in the components of the water to be treated.

[0056] (Second Embodiment) As shown in Figure 2, the water treatment apparatus 100 according to the second embodiment of the present invention further comprises a bubble injection means 6 that generates oxygen-containing bubbles with a bubble diameter of 100 μm or less and injects the generated bubbles into the water to be treated.

[0057] In the bubble injection means 6, a portion of the oxygen-containing gas supplied from the gas injection means 23 is injected into the bubble injection means 6 to generate minute bubbles, which are then dissolved in the water to be treated, and the water containing the bubbles is sent to the accelerated oxidation treatment means 2. The smaller the diameter of the bubbles generated by the bubble injection means 6, the longer the time it takes for the bubbles to dissolve in the water to be treated. Therefore, by reducing the diameter of the bubbles generated by the bubble injection means 6, the amount of bubbles remaining in the water to be treated is increased, thereby adjusting the DO in the water to a more suitable range.

[0058] The bubble injection means 6 is not particularly limited, but various devices can be used, such as ejector type, injector type, swirling flow type, Venturi type, two-phase critical current type, rotor blade negative pressure self-priming type (static mixer), aura jet type, devices that utilize shear force or swirling flow due to water flow, devices that utilize cavitation, devices that use pressurized dissolution, and devices that use porous membranes.

[0059] In particular, the bubble injection means 6 is preferable because it uses a bubble generation device equipped with a porous membrane, which allows for miniaturization and simplification of the device. In a bubble generation device equipped with a porous membrane, gas is supplied to the porous membrane, and the fine bubbles generated on the surface of the porous membrane are carried away by the shear force of the water flow, generating tiny bubbles in the water. The bubble injection means 6 can inject gas into the bubble injection means 6 via a branch line that branches off from the gas supply line that supplies gas from a compressor or the like to the gas injection means 23. By adjusting the amount of gas branched off from the branch line, the ratio of the amount of gas injected by the bubble injection means 6 into the water to be treated and the ratio of the amount of gas supplied by the gas injection means 23 to the accelerated oxidation treatment means 2 can be adjusted.

[0060] In the present invention, although not limited to the following, the ratio of the amount of gas injected by the bubble injection means 6 into the water to be treated to the ratio of the amount of gas supplied by the gas injection means 23 to the accelerated oxidation treatment means 2, i.e., the supply ratio of bubbles to oxygen-containing gas supplied to the water to be treated (amount supplied by bubble injection means 6 / amount supplied by gas injection means 23), is set to be greater than 0.0 and less than 1.0 in volume ratio. Preferably, the oxygen-containing gas and bubbles are injected such that the supply ratio of bubbles to oxygen-containing gas supplied to the water to be treated is 0.1 or more in volume ratio. The supply ratio is more preferably 0.2 or more, and even more preferably 0.3 or more. The supply ratio is more preferably 0.9 or less, even more preferably 0.2 or more and 0.8 or less, and even more preferably 0.3 or more and 0.6 or less.

[0061] The bubbles generated by the bubble injection means 6 are preferably microbubbles with a diameter of 100 μm or less, and more preferably microbubbles with a diameter of 10 μm or less, and even more preferably microfine bubbles with a diameter of 1000 nm or less. The microbubbles slowly rise to the surface due to buoyancy while contracting in the water being treated. Therefore, when the second ultraviolet light is irradiated by the ultraviolet irradiation means 22, the ultraviolet irradiation time can be longer compared to millibubbles with a bubble diameter of about 1 mm, thereby increasing the amount of ozone generated.

[0062] Ultrafine bubbles, also commonly called ultrafine bubbles or nanobubbles, refer to bubbles with a diameter of several tens of nanometers to 1000 nm (1 μm). Ultrafine bubbles are distinguished from microbubbles or microfine bubbles, which are known as fine bubbles with a diameter of 1 μm to 100 μm. The main properties of ultrafine bubbles include their extremely small diameter and extremely slow rising speed, allowing them to exist in liquids for long periods of time; the generation of hydroxyl radicals when the bubbles collapse; extremely high dissolution efficiency; a negative surface charge; and repulsion when bubbles come into close proximity.

[0063] Ultrafine bubbles have very small diameters, resulting in low buoyancy, and can remain in water for extended periods, from several weeks to several months. Therefore, they reside in the treated water for even longer periods than microbubbles. Because ultrafine bubbles remain in the treated water for extended periods without disappearing, the oxygen concentration in the treated water can be maintained for a long time. Furthermore, ozone-containing bubbles generated from ultrafine bubbles, so-called ozone ultrafine bubbles, remain in the treated water for extended periods, generating hydroxyl radicals through bubble collapse or reaction with second ultraviolet light irradiated from the ultraviolet irradiation means 22. Because ultrafine bubbles have high dissolution efficiency, their oxidizing, sterilizing, and decolorizing effects are higher compared to cases where ozone gas, which is difficult to dissolve in liquid, is injected from an external source. The bubble injection means 6 may also generate millibubbles with a diameter of approximately 1 μm to 1 mm as a byproduct when generating microbubbles or ultrafine bubbles. By generating various bubbles with different diameters and injecting them into the treated water, the maintenance of oxygen (DO) in the treated water and sterilization and purification treatment can be performed efficiently.

[0064] The bubble diameter is not particularly limited, but it can be measured using measurement methods such as dynamic light scattering and laser diffraction / scattering. Dynamic light scattering involves irradiating a group of gas particles undergoing Brownian motion with laser light and detecting the scattered light with a photomultiplier tube. The autocorrelation function is calculated from the temporal change in scattering intensity (fluctuation in scattering intensity) of the gas particles undergoing Brownian motion, the diffusion coefficient is determined, and the relative particle size distribution is obtained using the Einstein-Stokes equation. Laser diffraction / scattering, on the other hand, involves irradiating gas particles passing through a flow cell with a laser, detecting the scattered light emitted from them with a forward scattering light sensor, a side scattering light sensor, and a back scattering light sensor, and calculating the particle size distribution of the bubbles from the light intensity distribution pattern.

[0065] In order to generate ultrafine bubbles or microbubbles using a device with a porous membrane as the bubble injection means 6, it is preferable to set the pressure of the injected gas to 0.1 MPa or higher, and more preferably to 0.5 MPa or higher. If the gas pressure is too high, it may not be efficient from the standpoint of device maintenance and high-pressure processing, so the upper limit of the gas pressure can be, for example, 1 MPa or less.

[0066] The gas supplied to the bubble injection means 6 is most preferably air, but it may also contain any other gas such as oxygen, ozone, carbon dioxide, or hydrogen, and it is also possible to introduce two or more gases simultaneously. A filter for removing suspended components can also be installed before the bubble injection means 6. By injecting bubbles into the water to be treated by the bubble injection means 6, bubbles can be present in the water to be treated at a high concentration for a long period of time, thereby improving the ozone concentration during ozone generation. As a result, the treatment during AOP treatment can be accelerated.

[0067] (Water treatment method) A water treatment method according to a second embodiment of the present invention can be carried out using the water treatment apparatus 100 shown in Figure 2. Specifically, the water treatment method includes the steps of: treating water containing dissolved organic matter; placing the water containing dissolved organic matter in a treatment tank 21; injecting an oxygen-containing gas into a gas flow region 126 formed around a light source 122 that irradiates the water in the treatment tank 21 with ultraviolet light; irradiating the gas flow region 126 from the light source 122 with ultraviolet light in a wavelength range that generates ozone to generate ozone; mixing the ozone generated by the irradiation of ultraviolet light with the water in the treatment tank 21; and performing an accelerated oxidation treatment on the water containing ozone by irradiating it with ultraviolet light from the light source 122 to remove dissolved organic matter from the water; and generating oxygen-containing bubbles with a bubble diameter of 100 μm or less; and injecting the generated bubbles into the water.

[0068] According to the water treatment method of the second embodiment of the present invention, bubbles with a diameter of 100 μm or less, preferably 1000 nm or less, can be dissolved in the water to be treated from the bubble injection means 6, and the water to be treated containing bubbles is supplied to the accelerated oxidation treatment means 2. Bubbles with small diameters, such as bubbles with a diameter of 100 nm or less, remain in the treatment tank 21 of the accelerated oxidation treatment means 2 for a long period of time once dissolved in the water to be treated. A small amount of ozone is generated from the oxygen in the bubbles by irradiation with a second ultraviolet light. The reaction between the generated ozone, ultraviolet light, and hydroxyl radicals increases the treatment efficiency of the AOP treatment in the accelerated oxidation treatment means 2, thereby increasing the decomposition efficiency of dissolved organic matter in the water to be treated. Furthermore, by providing the bubble injection means 6, the DO of the water to be treated can be improved, so the amount of air injected into the accelerated oxidation treatment means 2 can be reduced. As a result, the amount of air injected into the water to be treated can be reduced overall, reducing the power required for bubble injection, thus enabling more economical and efficient treatment.

[0069] (Third embodiment) As shown in Figure 3, the water treatment apparatus 100 according to the third embodiment of the present invention further comprises a pretreatment means 5 connected to the front of the treatment tank 21 and performing pretreatment to remove chromatic components from the water to be treated.

[0070] Various devices for removing chromatic components can be used as pretreatment means 5. For example, an acid treatment device that injects acid into the water to be treated to lower the pH of the water to 6 or less, further to 5.5 or less, and even further to 5 or less can be used as pretreatment means 5. A filtration device that passes the water to be treated through a sand filter or a microfiltration membrane to remove suspended solids contained in the water can also be suitably used as pretreatment means 5. Alternatively, an activated carbon treatment device that uses activated carbon or the like to physically adsorb suspended solids contained in the water to be treated can also be used as pretreatment means 5. Furthermore, a coagulation and sedimentation treatment device using inorganic or organic coagulants, an adsorption treatment device using physicochemical adsorbents other than activated carbon, and an electrolysis device that performs electrolysis can also be used as pretreatment means 5. It is also possible to apply the accelerated oxidation treatment means 2 as pretreatment means 5 and perform the accelerated oxidation treatment two or more times.

[0071] (Water treatment method) The water treatment method according to the third embodiment of the present invention can be carried out using the water treatment apparatus 100 shown in Figure 3, and differs from the water treatment apparatus 100 shown in Figures 1 and 2 in that it includes a step of performing a pretreatment to remove the chromatic component from the water to be treated before placing the water to be treated in the treatment tank.

[0072] According to the water treatment apparatus 100 and water treatment method of the third embodiment of the present invention, chromatic components are removed by a pretreatment to remove chromatic components from the water to be treated. If the water to be treated contains metals such as Mn, oxidation of metal ions may occur due to ultraviolet irradiation or accelerated oxidation treatment by the accelerated oxidation treatment means 2 described later, which may increase the chromaticity of the water to be treated. In the third embodiment, since the pretreatment means 5 is provided, the increase in the chromaticity of the water to be treated caused by the oxidation of metal components in the water to be treated, especially iron and manganese, can be suppressed, and thus changes in the composition of the water to be treated can be effectively suppressed.

[0073] (modified version) Although the present invention has been described by the embodiments described above, the descriptions and drawings that constitute part of this disclosure should not be understood as limiting the invention. This disclosure is not limited to the embodiments described above, and it goes without saying that the components can be combined and modified to embody the invention without departing from its spirit.

[0074] As shown in Figure 4, the treated water that has undergone accelerated oxidation treatment in the accelerated oxidation treatment means 2 may be circulated to the water treatment means 1 via a circulation means 7. In this case, a pH adjustment means 3 may be further provided to add a pH adjusting agent such as an acid or alkali to the treated water to adjust the pH of the treated water circulated to the water treatment means 1, as shown in Figure 5. Although not shown in Figures 1 to 5, a measuring unit (not shown) may be provided for measuring the flow rate, electrical conductivity, pH, turbidity, color, dissolved organic matter, SS, MLSS, etc. of the treated water treated in the water treatment means 1. When circulating the treated water that has undergone accelerated oxidation treatment in the accelerated oxidation treatment means 2 to the water treatment means 1, a function may be provided to adjust the flow rate by controlling the start and stop of the circulation based on the set values ​​of the items measured by the measuring unit. [Examples]

[0075] Examples of the present invention are shown below along with comparative examples. These examples are provided to help you better understand the present invention and its advantages, and are not intended to limit the invention.

[0076] <Device configuration> Figure 6 shows a schematic diagram of the water treatment device used in the test. This treatment device comprises a raw water tank 101 for containing the water to be treated, a circulation line 104 for taking the water to be treated from the raw water tank 101, performing accelerated oxidation treatment on it, and then returning it to the raw water tank 101, an accelerated oxidation treatment means 120 connected to the circulation line 104, and a bubble injection means 106 connected to the circulation line 104 for injecting bubbles into the water to be treated.

[0077] An air compressor 128 was connected to the bubble injection means 106 to inject air as an oxygen-containing gas. To inject air as an oxygen-containing gas into the accelerated oxidation treatment means 120, an air pump (not shown) was provided attached to the control panel 110, a flow meter and an air drain were provided on the air injection line 123, and air was injected into the treatment tank 121 by the air pump attached to the control panel 110. In the center of the treatment tank 121 of the accelerated oxidation treatment means 120, a single ultraviolet lamp capable of irradiating ultraviolet light in the wavelength range of 185 nm and 254 nm was installed, and a glass casing 125 was provided on the outside of the ultraviolet lamp. Air was injected from the air injection line 123 into the gas flow region 126 formed inside the casing 125. Ozone gas was generated from a portion of the air supplied into the casing 125 from the air injection line 123 by irradiation with ultraviolet light in the wavelength range of 185 nm. Air and ozone gas were introduced via the introduction section 124 into the treated water flow area 127, which is the liquid phase portion within the treatment tank 121 of the accelerated oxidation treatment means 120, and injected into the treated water. An agitator 142 was installed in the raw water tank 101, and the treated water was supplied to the circulation line 104 from a circulation pump 141 connected to the raw water tank 101.

[0078] <Test Conditions> Water containing dissolved organic matter was treated using the water treatment apparatus shown in Figure 6, according to the test conditions in Table 1. The TOC of the treated water in Tests 1-5 was 0.5-20 mg / L, the dissolved TOC was 5.4-5.8 mg / L, the chromaticity was 10 degrees or less, and the SS was 0.1-15 mg / L. The total volume of water used in the water treatment apparatus shown in Figure 6 was 50 L, and the water was circulated between the raw water tank 101 and the accelerated oxidation treatment means 120 with a circulation rate of 15 L / min, a circulation time of 10 minutes, and a water temperature of 20-30°C (unadjusted). The output of the ultraviolet lamp was 110 W, the ultraviolet irradiation dose was 0.37 Wh / L, and the ultraviolet irradiation time was 10 minutes. The ultraviolet irradiation dose was calculated based on the formula: ultraviolet irradiation dose = (ultraviolet output × ultraviolet irradiation time) ÷ (circulating water volume × circulation time).

[0079] For Test 1, no gas was injected, and only ultraviolet irradiation was performed. For Tests 2-4, gas was supplied into the casing 125 of the accelerated oxidation treatment means 120. In Test 5, ultrafine bubbles were further generated by the bubble injection means 106 and injected into the water to be treated. The injected gas was air, and the total injection amount was adjusted within the range of 0.38 to 1.9 L / min. The amount of air injected into the bubble injection means 106 was 0.19 L / min for Test 5. In Table 2, "gas-liquid ratio" refers to the volume ratio of the amount of injected air (circulating water volume / injected air volume) to the circulating water volume of the water to be treated.

[0080] [Table 1]

[0081] <Measurement items> Table 2 shows the water quality analysis results for raw and treated water. The water quality analysis items were pH, water temperature, DO, soluble TOC, color, turbidity, total bacterial count, total manganese (Mn), soluble Mn, total iron (Fe), and soluble Fe. These were measured in accordance with the Water Supply Test Method (published by the Japan Water Works Association) or the Sewage Test Method (published by the Japan Sewage Works Association), or JIS-K0102 (Japanese Industrial Standards). Electrical conductivity was measured using a commercially available conductivity meter.

[0082] The general bacterial reduction rate in Table 2 was calculated based on the formula: General bacterial reduction rate = (raw water concentration - treated water concentration) ÷ raw water concentration × 100. The "chromaticity increase rate" was calculated based on the formula: Chromaticity increase rate = (treated water concentration - raw water concentration) ÷ treated water concentration × 100. Samples for measuring dissolved components were filtered using glass filter paper with a pore size of 1 mm, and the filtrate after filtration was used.

[0083] [Table 2]

[0084] <Reduction rate of soluble TOC> The soluble TOC reduction rates were 6.9% for Test 1, 7.7% for Test 2, 8.6% for Test 3, 7.8% for Test 4, and 7.8% for Test 5. This shows that the soluble TOC reduction rate improved in Tests 2-5, which used accelerated treatment with ultraviolet light and ozone, compared to Test 1, which only used ultraviolet light.

[0085] <Total bacterial reduction rate> The general bacterial reduction rates were 94.8% for Test 1, 97.8% for Test 2, 98.7% for Test 3, 97.4% for Test 4, and 96.7% for Test 5. This shows that Tests 2-5, which used accelerated treatment with ultraviolet light and ozone, reduced general bacteria at a higher rate than Test 1, which only used ultraviolet light.

[0086] <Chromaticity> Although all the treated water samples contained trace amounts of Mn and Fe, it can be seen that the chromaticity of the treated water increased in all of the test examples 1 to 5 after ultraviolet treatment and oxidation acceleration treatment using ultraviolet light and ozone. From these results, it can be seen that if it is necessary to reduce the chromaticity of the treated water, it is better to perform a pretreatment before the oxidation acceleration treatment to remove substances that cause the chromaticity to increase due to the oxidation acceleration treatment, such as metallic components such as iron and manganese.

[0087] <Effects of air bubble injection treatment> Test 5, in which bubbles were injected into the treated water to accelerate oxidation treatment, showed a higher reduction rate of soluble TOC compared to Test 1, in which UV treatment was performed without bubbles. Furthermore, the general bacterial reduction rate was also higher in Test 5 than in Test 1. While DO decreased in Tests 1-3 after either UV treatment or accelerated oxidation treatment, Test 4, in which the total amount of gas injected was approximately five times greater than in Tests 2, 3, and 5, and Test 5, in which bubbles were injected into the treated water, both showed higher DO levels in the treated water after treatment. Additionally, comparing the total amount of gas injected, Test 5 maintained a higher DO level despite using less gas than Test 4, indicating that bubble injection treatment can maintain DO levels in the treated water for a longer period.

[0088] <Effects of ozone generation> For the treated water (Tests 6 and 7) after irradiation with ultraviolet light in the wavelength ranges of 185 nm and 254 nm, gas was collected from inside the casing of the accelerated oxidation treatment means 120, and the ozone concentration in the gas was measured. In Test 6, air was injected into the gas flow region 126 of the accelerated oxidation treatment means 120 from the air injection line 123 at a rate of 0.38 L / min. In Test 7, air was injected into the gas flow region 126 of the accelerated oxidation treatment means 120 from the air injection line 123 at a rate of 1.9 L / min. In Table 3, "Ozone Concentration in Air" was measured in accordance with the Sewage Test Method (published by the Japan Sewage Works Association, Sewage Test Method). In Table 3, "Air Injection Amount" indicates the flow rate of air injected from the air injection line 123 in Figure 6, and "Circulating Water Amount" indicates the supply flow rate of the treated water flowing into the accelerated oxidation treatment means 120. In Table 3, "Ozone supply" was calculated by multiplying the airborne ozone concentration by the air inflow rate, and the ozone concentration was evaluated by the ozone supply relative to the circulating water volume of the treated water. The airborne ozone concentrations were 0.6 mg-O3 / L-Air for Test 6 and 0.3 mg-O3 / L-Air for Test 7, and the ozone supply was 0.014 g-O3 / h for Test 6 and 0.034 g-O3 / h for Test 7. The ozone concentrations were 0.015 mg-O3 / L-treated water for Test 6 and 0.038 mg-O3 / L-treated water for Test 7. The ozone concentrations were lower than those in typical ozone oxidation treatments.

[0089] [Table 3]

[0090] According to this test, it is possible to safely and efficiently decompose dissolved organic matter contained in the treated water using a simple device by performing the oxidation acceleration treatment according to the embodiment of the present invention, compared to Test 1 which does not have a gas injection treatment step. It is also possible to reduce general bacteria in the treated water. [Explanation of symbols]

[0091] 1...Water treatment means 2... means of accelerated oxidation treatment 3...pH adjustment means 5…Pre-treatment means 6. Bubble injection method 7...Circulation means 21… Processing tank 22...Ultraviolet irradiation means 22A...First ultraviolet irradiation means 22B...Second ultraviolet irradiation method 23...Means of gas injection 24...Method of implementation 25…Casing 100...Water treatment equipment 101... Raw water tank 104... Circulation line 106... Air bubble injection means 110...Operation panel 120... means of accelerated oxidation treatment 121... Processing tank 122...Light source 123...Air injection line 124...Introduction 125...casing 126...Gas flow domain 127…Water distribution area to be treated 128... Air compressor 141... Circulation pump 142... Agitator 231…Inlet

Claims

1. The water to be treated, which contains dissolved organic matter, is placed inside the treatment tank. A gas containing oxygen is injected into a gas flow region formed around a light source that irradiates the water to be treated in the treatment tank with ultraviolet light. By irradiating the gas flow region with ultraviolet light in the wavelength range that generates ozone from the light source, ozone is generated within the gas flow region. The ozone generated by the irradiation of ultraviolet light is mixed with the water to be treated in the treatment tank. By irradiating the water to be treated, which contains ozone, with ultraviolet light from the light source to perform an accelerated oxidation treatment, dissolved organic matter in the water to be treated is removed. A water treatment method characterized by generating oxygen-containing bubbles with a diameter of 100 μm or less, and injecting the generated bubbles into the water to be treated.

2. The water to be treated, which contains dissolved organic matter, is contained in the treatment tank. Air is injected into a gas flow region formed around a light source that irradiates the water to be treated in the treatment tank with ultraviolet light. By irradiating the gas flow region with ultraviolet light in the wavelength range that generates ozone from the light source, ozone is generated within the gas flow region. The ozone generated by the irradiation of ultraviolet light is mixed with the water to be treated in the treatment tank. This includes removing dissolved organic matter from the water to be treated by irradiating the water to be treated, which contains ozone, with ultraviolet light from the light source to perform an accelerated oxidation treatment. A water treatment method characterized by supplying a gas containing ozone and oxygen generated in the gas flow region into the water to be treated at a rate of 0.005 to 1 L / L - water to be treated, such that the gas-liquid ratio of the water to be treated and the gas containing ozone and oxygen is 1 to 200 by volume.

3. The water to be treated, which contains dissolved organic matter, is contained in the treatment tank. A gas containing oxygen is injected into a gas flow region formed around a light source that irradiates the water to be treated in the treatment tank with ultraviolet light. By irradiating the gas flow region with ultraviolet light in the wavelength range that generates ozone from the light source, ozone is generated within the gas flow region. The ozone generated by the irradiation of ultraviolet light is mixed with the water to be treated in the treatment tank. This includes removing dissolved organic matter from the water to be treated by irradiating the water to be treated, which contains ozone, with ultraviolet light from the light source to perform an accelerated oxidation treatment. A water treatment method characterized by further comprising the step of performing a pretreatment to remove chromatic components from the water to be treated before placing the water to be treated into the treatment tank.

4. The water treatment method according to any one of claims 1 to 3, characterized in that the water to be treated contains at least one of bacteria, fungi, microorganisms, algae, cyanobacteria, or organofluorine compounds.

5. The water treatment method according to any one of claims 1 to 3, further comprising the step of performing a water treatment on the water to be treated, which includes at least one of a solid-liquid separation treatment, coagulation and sedimentation treatment, biological treatment, ion exchange treatment, filtration treatment, physical adsorption treatment, and electrolysis treatment, before the water to be treated is placed in the treatment tank.

6. A treatment tank that contains water to be treated containing dissolved organic matter, and decomposes the dissolved organic matter in the water to be treated by performing an accelerated oxidation treatment using ultraviolet light and ozone on the water to be treated, The ultraviolet irradiation means comprises a light source for irradiating the water to be treated with ultraviolet light in the wavelength range of 100 to 300 nm and a gas flow region formed around the light source for circulating gas, A gas injection means for supplying an oxygen-containing gas to the gas flow region, An introduction means for introducing ozone, generated by irradiation of ultraviolet light from the light source into the gas flow region into which an oxygen-containing gas has been injected, into the water to be treated in the treatment tank, A bubble injection means for generating oxygen-containing bubbles with a diameter of 100 μm or less and injecting the generated bubbles into the water to be treated. A water treatment apparatus characterized by comprising the following features.

7. The water treatment apparatus according to claim 6, further comprising a pretreatment means connected to the preceding stage of the treatment tank and performing pretreatment for removing chromatic components from the water to be treated.

Images