Method for treating water containing organofluorine compounds

Abstract

To provide a method for treating organofluorine compound-containing water, in which cavitation caused by a low-pressure jet stream can be utilized for decomposition treatment of a hardly decomposable organofluorine compound contained in environmental water.SOLUTION: The method for treating the water containing the organic fluorine compound comprises adding a gas to the water containing the organic fluorine compound, injecting the water containing the organic fluorine compound into water through an injection nozzle to cause cavitation and to generate bubbles of <1 μ m, and decomposing the organic fluorine compound contained in the water containing the organic fluorine compound by utilizing the cavitation and the bubbles of <1 μm. The discharge pressure of the injection nozzle is 0. 3MPa or less, and the number of circulations of the water containing the organic fluorine compound through the injection nozzle is set according to the content of the organic fluorine compound and the required reduction ratio.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for treating water containing organic fluorine compounds. [Background technology]

[0002] In recent years, attention has been focused on the contamination of environmental water and other areas by organic fluorine compounds, namely perfluoroalkyl and polyfluoroalkyl compounds (hereinafter sometimes referred to as "PFAS"). In particular, perfluorooctane sulfonic acid (hereinafter sometimes referred to as "PFOS") and perfluorooctanoic acid (hereinafter sometimes referred to as "PFOA") have been designated as Class I Specified Chemical Substances under the Act on the Evaluation of Chemical Substances and Regulation of Their Manufacture, etc., in light of their inclusion in Annex B and Annex A of the Stockholm Convention on Persistent Organic Pollutants (POPs Convention). In principle, their manufacture, import, and use are prohibited. Furthermore, perfluorohexane sulfonic acid (hereinafter sometimes referred to as "PFHxS") was also added to Annex A of the POPs Convention in June 2022, and was designated as a Class I Specified Chemical Substance in February 2024.

[0003] However, because these PFASs have water- and oil-repellent properties and excellent chemical and thermal stability, they have been widely used for many years in water repellents, coatings, firefighting foams, etc., and surveys by the Ministry of the Environment have shown that PFOS / PFOA and PFHxS have been widely detected in river water, groundwater, etc. In 2020, PFOS / PFOA were added to the water quality management target setting items in the drinking water quality standards and the monitoring items in the environmental water quality standards, respectively, with a target value and guideline value (provisional) of 50 ng / L (combined value of PFOS and PFOA). PFHxS was also added to the environmental water quality standards in March 2021 as an item requiring investigation, and in April 2021 as an item requiring consideration in the drinking water quality standards.

[0004] PFOS / PFOA and PFHxS are chemically extremely stable, water-soluble and non-volatile substances, so if released into the environment they are likely to migrate into water systems, and because they are difficult to decompose, they are thought to remain in the environment for long periods of time. Furthermore, because PFOS / PFOA and PFHxS have been widely detected in river water, groundwater, etc., there is a demand for the development of a low-cost method for decomposing PFAS contained in environmental waters such as river water, lake water, and groundwater (sometimes referred to as "environmental water" in this specification), but the reality is that there are no effective methods.

[0005] Specifically, advanced oxidation is widely used to decompose organic compounds, but it is said that it cannot be applied to decomposing PFOS / PFOA because the reactivity of the advanced oxidation with PFOS / PFOA's OH radicals is extremely low. In fact, advanced oxidation (O3 + H2O2, O3 + UV) was attempted using groundwater containing 2-6 ng / L of PFOS and 40-58 ng / L of PFOA, but no significant decomposition effect of PFOS / PFOA was confirmed.

[0006] On the other hand, methods that utilize cavitation have been proposed as methods for decomposing organic compounds other than the accelerated oxidation method (see, for example, Patent Documents 1 to 3).

[0007] Here, cavitation refers to a physical phenomenon in which a pressure difference in a liquid flow causes the liquid to boil when the pressure drops to the saturated vapor pressure of the liquid, resulting in the generation of tiny bubbles in a short period of time, which then disappear when the speed slows down (when the pressure recovers).

[0008] Cavitation generates strong shock waves at the gas-liquid interface when the bubbles disappear. This can cause noise and vibration in pumps, for example. This causes erosion of the impeller surface.

[0009] Regarding the decomposition of PFOS / PFOA using cavitation, it has been reported that PFOS / PFOA in pure water can be thermally decomposed by cavitation caused by ultrasonic irradiation (see Non-Patent Document 1).

[0010] As mentioned above, cavitation has been used to decompose organic compounds, but there has been no method that can be used to decompose persistent organic fluorine compounds contained in environmental water.

[0011] Therefore, the present inventors previously proposed a method for treating water containing organic fluorine compounds, in which cavitation, which is used to decompose organic compounds, can be used to decompose persistent organic fluorine compounds contained in environmental water (see Patent Document 4). [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-253 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-305546 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-192914 [Patent Document 4] Japanese Patent Publication No. 2023-176073 [Non-patent literature]

[0013] [Non-Patent Document 1] Hiroshi Moriwaki, Youichi Takagi, Masanobu Tanaka, Kenshiro Tsuruho, Kenji Okitsu, and Yasuaki Maeda: Sonochemical Decomposition of Perfluorooctane Sulfonate and Perfluorooctanoic Acid, Environ. Sci. Technol., Vol.39, No.9, pp.3388-3392, 2005 Summary of the Invention [Problem to be solved by the invention]

[0014] Incidentally, the method for treating water containing organic fluorine compounds, which was previously proposed by the present inventors and disclosed in Patent Document 4, has the advantage of causing cavitation by injecting water containing organic fluorine compounds with added inert gas bubbles of less than 1 μm from an injection nozzle, thereby making it possible to decompose persistent organic fluorine compounds contained in environmental water. However, because strong cavitation is generated at a high discharge pressure of 10 MPa or more, there are problems with the durability of the injection nozzle as well as the need for an expensive high-pressure pump and large energy consumption in terms of equipment.

[0015] In view of the above-mentioned problems associated with the method for treating water containing organic fluorine compounds, as disclosed in Patent Document 4, in which cavitation, which is used for decomposing organic compounds, is adapted to decompose persistent organic fluorine compounds contained in environmental water, the present invention aims to provide a method for treating water containing organic fluorine compounds in which cavitation generated by a low-pressure jet flow is adapted to decompose persistent organic fluorine compounds contained in environmental water. [Means for solving the problem]

[0016] In order to achieve the above object, the present invention provides a method for treating water containing organic fluorine compounds, which comprises adding a gas to water containing organic fluorine compounds and injecting the water into the water through a spray nozzle to cause cavitation and generate bubbles of less than 1 μm, and decomposing the organic fluorine compounds contained in the water using the cavitation and the bubbles of less than 1 μm, wherein the discharge pressure of the spray nozzle is 0.3 MPa or less, and the amount of the organic fluorine compounds in the water is adjusted according to the content and required reduction rate of the organic fluorine compounds. The number of circulation times is set.

[0017] In this case, the number of times that the water containing the organic fluorine compound is circulated through the spray nozzle may be 400 to 2000 times.

[0018] In addition, the energy required to treat the water containing the organic fluorine compound per unit amount of water is 150 kWh / m 3 It can be:

[0019] The organic fluorine compounds to be decomposed may be C6 or higher perfluoroalkyl sulfonic acids (PFSAs) and C7 or higher perfluoroalkyl carboxylic acids (PFCAs).

[0020] Furthermore, the method for treating water containing organic fluorine compounds of the present invention can be used to decompose persistent organic fluorine compounds contained in environmental water. [Effects of the Invention]

[0021] The method for treating water containing organic fluorine compounds of the present invention involves adding a gas to water containing organic fluorine compounds and injecting the water through an injection nozzle, thereby causing cavitation and generating bubbles of less than 1 μm in size, and using the cavitation and bubbles of less than 1 μm to decompose the organic fluorine compounds contained in the water containing organic fluorine compounds.Therefore, it is possible to treat large quantities of water containing organic fluorine compounds using a simple mechanism. Furthermore, this method for treating water containing organic fluorine compounds has a discharge pressure of 0.3 MPa or less, and the number of times that the water containing organic fluorine compounds is circulated through the spray nozzle is set according to the content of the organic fluorine compounds and the required reduction rate. Therefore, it overcomes the problems associated with conventional methods for treating water containing organic fluorine compounds, such as the durability of the spray nozzle, the need for expensive high-pressure pumps, and high energy consumption, and is capable of treating large amounts of water containing organic fluorine compounds, making it possible to use the method for decomposing persistent organic fluorine compounds contained in environmental water. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is an explanatory diagram showing a test facility for carrying out the method for treating water containing organic fluorine compounds of the present invention. [Figure 2] An explanatory diagram of the bubble generating device used in the test facility, (a) being a front view and (b) being a side view. [Figure 3] 1 is a graph showing the results of decomposition treatment test (1). [Figure 4] 1 is a graph showing the results of decomposition treatment test (2). [Figure 5] 1 is a graph showing the results of decomposition treatment test (3). [Figure 6] 1 is a graph showing the results of decomposition treatment test (4). [Figure 7] 1 is a graph showing the results of decomposition treatment test (5) (comparative example (high pressure treatment)). DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the method for treating water containing organic fluorine compounds of the present invention will be described with reference to the drawings.

[0024] The method for treating water containing organic fluorine compounds of the present invention involves adding a gas to water containing organic fluorine compounds and injecting the water into the water through an injection nozzle, thereby causing cavitation and generating bubbles of less than 1 μm, and decomposing the organic fluorine compounds contained in the water using the cavitation and bubbles of less than 1 μm, and the discharge pressure of the injection nozzle is 0.3 MPa or less (energy consumption). The pressure is preferably 0.2 MPa or less, more preferably 0.1 MPa or less, in consideration of reducing energy and supplying gas to generate bubbles, and the number of times that the water containing the organic fluorine compound is circulated through the spray nozzle is set according to the content of the organic fluorine compound and the required reduction rate. Here, various gases such as nitrogen gas and air can be used as the gas to be added to the water containing the organic fluorine compound. Furthermore, the organic fluorine compounds to be decomposed include perfluoroalkyl compounds and polyfluoroalkyl compounds, in particular PFOSs (PFSAs: perfluoroalkyl sulfonic acids) and PFOAs (PFCAs: perfluoroalkyl carboxylic acids).

[0025] [Testing equipment] 1 and 2 show a test facility for carrying out the method for treating water containing organic fluorine compounds of the present invention. In this test facility, one or two (in parallel) "FoamJet" (registered trademark) units (FJP-3-SP; 50 L / min / unit) manufactured by YBM Corporation are installed in the water tank 1 as bubble generators (UFB generators) 2 that generate bubbles smaller than 1 μm (ultrafine bubbles (sometimes referred to as "UFB" in this specification)), to generate UFB (nitrogen UFB, oxygen UFB) that can become the nucleus for generating cavitation. The sample water (water containing organic fluorine compounds) in the water tank 1 circulating through the bubble generator 2 is cooled by a cooling coil 3 to which cooling water is supplied from a cooling water tank 4, or heated by a water tank heater, so that the water temperature can be maintained at a predetermined temperature, for example, in the range of 45 to 48°C.

[0026] The bubble generator 2 installed in the water tank 1 comprises an underwater pump 21 that sucks in sample water in the water tank 1 through an inlet 21a, a jet box 23 connected to the underwater pump 21 by piping 22, a gas supply pipe 24 connected to the middle of the piping 22 connected to the jet box 23 for supplying various gases such as nitrogen gas and air, and a discharge pipe 25 connected to the jet box 23 and discharging the sample water into the water tank 1 from an outlet 25a. As the sample water in the water tank 1 is sent by the submersible pump 21 through the pipe 22 to the jet box 23, gas (nitrogen gas, air) supplied from the gas supply pipe 24 is added, and the gas is sprayed into the sample water filling the jet box 23 through a spray nozzle (not shown) provided at the outlet of the pipe 22 facing the jet box 23. The resulting pressure drop causes cavitation, and the resulting swirling flow (a cavitation cloud state such as a ring vortex or spiral vortex) generates bubbles smaller than 1 μm, so that the organic fluorine compounds contained in the sample water are decomposed by the cavitation and bubbles smaller than 1 μm. Here, the ejection pressure of the injection nozzle of "Foam Jet" (registered trademark) (FJP-3-SP) is about 0.01 to 0.1 MPa. The sample water in the jet box 23 is discharged through the discharge pipe 25 and from the discharge port 25 a into the water tank 1 . Thereafter, the sample water in the water tank 1 is similarly circulated through the bubble generator 2 a predetermined number of times to decompose the organic fluorine compounds contained in the sample water.

[0027] [Decomposition treatment test] [Sample water to be treated] Actual river water (sample C) containing PFASs such as PFOS (PFSAs) / PFOA (PFCAs) was used as the target water for the degradation treatment test. The pH, TOC, iron and manganese concentrations, and PFAS concentrations such as PFOS (PFSAs) / PFOA (PFCAs) of sample C are shown in Table 1.

[0028] [Table 1]

[0029] Analysis of PFOS (PFSAs) / PFOA (PFCAs) in sample C and treated water was performed using solid-phase extraction-LC / MS / MS according to Appendix 1 of the Ministry of the Environment Notification (Enforcement of Environmental Standards for the Protection of Human Health Related to Water Pollution (Notification), Kansui Daisui-hatsu No. 2005281 and Kansui Daido-hatsu No. 2005282, May 28, 2020) and the method specified in JIS K 0450-70-10. Using a mixed standard solution, PFOS (PFSAs: perfluoroalkyl sulfonic acids) were quantified as C4-C10 (PFBS-PFDS) congeners, and PFOA (PFCAs: perfluoroalkyl carboxylic acids) were quantified as linear isomers only and linear and branched isomers. Results shown here are for linear isomers only. In addition, pH was measured in accordance with JIS K 0102-12.1, TOC in accordance with JIS K 0102-22.1, iron in accordance with JIS K 0102-57.4, and manganese in accordance with JIS K 0102-56.4. Sample C was river water and contained PFOS at 400-500ng / L, PFHxS at 660-1700ng / L, PFOA at 200-240ng / L, and PFHxA at 440-670ng / L. Other PFSAs included C4-C7 congeners, and PFCAs included C4-C11 congeners. Iron and manganese concentrations were also relatively high.

[0030] [Processing conditions] The amount of water to be treated was 30 L, and batch treatment was carried out on sample water C for a treatment time of 6 hours. To confirm the treatment effect over time, the minimum amount of water required was collected as an analytical sample after 3 hours and 6 hours and analyzed. Nitrogen was basically used as the UFB gas type, but a case was also carried out using air as a comparison to investigate the effect of the type of gas on the treatment effect. The treatment conditions for the decomposition treatment test are shown in Table 2.

[0031] [Table 2]

[0032] In Table 2, the low-pressure treatment is an example based on the method for treating water containing organic fluorine compounds of the present invention, and the high-pressure treatment is a comparative example based on the method for treating water containing organic fluorine compounds disclosed in Patent Document 4.

[0033] [Decomposition treatment test (1)] A decomposition test was conducted using one "Foam Jet" (registered trademark) unit, supplying nitrogen gas and generating nitrogen UFB. The sample water was heated to a temperature of approximately 45°C. The results are shown in Table 3 and Figures 3(a) and (b). Here, Figure 3(b) shows the vertical axis of Figure 3(a) in terms of PFOA equivalent concentration using a relative toxicity approach (the same applies to the other decomposition treatment test results below).

[0034] [Table 3]

[0035] The results shown in Table 3 and Figures 3(a) and (b) suggest the following: After 6 hours of treatment, PFOS concentrations decreased from 420 to 60 ng / L (reduction rate of 85.7%) and PFOA concentrations decreased from 300 to 190 ng / L (reduction rate of 36.7%), and the combined PFOS / PFOA concentration decreased from 720 to 250 ng / L (reduction rate of 65.3%). Concentrations of congeners other than PFOS / PFOA (PFOSs (PFSAs): C4-C7, PFOAs (PFCAs): C4-C11) generally decreased, with the exception of PFOSs (PFSAs): C4-C5 and PFOAs (PFCAs): C4-C6. A clear reduction in concentration was confirmed for PFHpS (C7), PFOS (C8), PFOA (C8), PFNA (C9), PFDA (C10), and PFUnDA (C11), which have relatively high RPF (relative potency factor) values ​​(relatively high relative toxicity) proposed by the EC (European Commission). No abnormalities such as discoloration were observed in the treated water.

[0036] [Decomposition treatment test (2)] Using two "Foam Jet" (registered trademark) machines, nitrogen gas was supplied to conduct the decomposition test under the conditions of generating nitrogen UFB. The sample water was heated to a temperature of approximately 45°C. The results are shown in Table 4 and Figures 4(a) and (b).

[0037] [Table 4]

[0038] The results shown in Table 4 and Figures 4(a) and (b) suggest the following: After 6 hours of treatment, PFOS concentrations decreased from 400 to 15 ng / L (96.3% reduction), and PFOA concentrations decreased from 180 to 65 ng / L (63.9% reduction), resulting in a combined PFOS / PFOA concentration of 580 to 80 ng / L (86.2% reduction). PFHxS concentrations decreased from 1400 to 760 ng / L (45.7% reduction). Concentrations of congeners other than PFOS / PFOA (PFOSs (PFSAs): C4-C7, PFOAs (PFCAs): C4-C11) generally decreased, with the exception of PFOAs (PFCAs): C4-C6. PFHpS (C7), PFOS (C8), and PFHpS (C9), which have relatively high RPF (relatively high relative toxicity) values ​​proposed by the European Commission (EC), A clear decrease in concentration was confirmed for OA (C8), PFNA (C9), PFDA (C10), and PFUnDA (C11). Compared to using one "Foam Jet" (registered trademark) unit (Decomposition Treatment Test Results (1)), using two units was more effective in reducing concentrations overall. No abnormalities such as discoloration were observed in the treated water.

[0039] [Decomposition treatment test (3)] Using two "Foam Jet" (registered trademark) machines, nitrogen gas was supplied to conduct the decomposition test under the conditions of generating nitrogen UFB. The sample water was cooled to a temperature of about 25°C. The results are shown in Table 5 and Figures 5(a) and (b).

[0040] [Table 5]

[0041] The results shown in Table 5 and Figures 5(a) and (b) suggest the following. After 6 hours of treatment, PFOS concentrations decreased from 320 to 34 ng / L (reduction rate: 89.4%) and PFOA concentrations decreased from 140 to 45 ng / L (reduction rate: 67.9%), resulting in a combined PFOS / PFOA value of 460 to 79 ng / L (reduction rate: 82.8%). PFHxS concentrations decreased from 730 to 260 ng / L (reduction rate: 64.4%). Concentrations of congeners other than PFOS / PFOA (PFOSs (PFSAs): C4-C7, PFOAs (PFCAs): C4-C11) generally decreased, with the exception of C4 for PFOSs (PFSAs) and C4-C6 for PFOAs (PFCAs). A clear reduction in concentration was confirmed for PFHpS (C7), PFOS (C8), PFOA (C8), PFNA (C9), PFDA (C10), and PFUnDA (C11), which have relatively high RPF (relative potency factor) values ​​(relatively high relative toxicity) proposed by the EC (European Commission). When comparing water temperatures during treatment at approximately 25°C and 45°C (decomposition treatment test results (2)), no significant difference was observed in the concentration reduction effect. No abnormalities such as discoloration were observed in the treated water.

[0042] [Decomposition treatment test (4)] Two "Foam Jet" (registered trademark) units are used to supply air and generate air UFB. The decomposition test was carried out under the conditions that the sample water was heated to a temperature of about 45°C. The results are shown in Table 6 and Figures 6(a) and (b).

[0043] [Table 6]

[0044] The results shown in Table 6 and Figures 6(a) and (b) suggest the following: After 6 hours of treatment, PFOS concentrations decreased from 500 to 39 ng / L (92.2% reduction), and PFOA concentrations decreased from 230 to 78 ng / L (66.1% reduction), resulting in a combined PFOS / PFOA concentration of 730 to 117 ng / L (84.0% reduction). PFHxS concentrations decreased from 810 to 370 ng / L (54.3% reduction). Concentrations of congeners other than PFOS / PFOA (PFOSs (PFSAs): C4-C7, PFOAs (PFCAs): C4-C11) generally decreased, with the exception of C4 for PFOSs (PFSAs) and C4-C6 for PFOAs (PFCAs). A clear reduction in concentration was confirmed for PFHpS (C7), PFOS (C8), PFOA (C8), PFNA (C9), PFDA (C10), and PFUnDA (C11), which have relatively high RPF (relative potency factor) values ​​(relatively high relative toxicity) proposed by the EC (European Commission). - Discoloration of treated water due to oxidation of iron and manganese was observed. No significant difference was observed in the effectiveness of reducing PFAS concentrations when nitrogen or air was used as the supply gas. However, when air was used, discoloration of the treated water due to oxidation of iron and manganese (the generation of suspended solids) was observed. Therefore, taking into account the subsequent treatment stage, it is preferable to supply nitrogen (decomposition treatment test results (3)).

[0045] [Decomposition Treatment Test (5) (Comparative Example (High Pressure Treatment))] In accordance with the disclosure of Patent Document 4, a decomposition treatment test (comparative example (high-pressure treatment)) was conducted using a high-pressure plunger pump (7.5 kW, manufactured by Super Kogyo Co., Ltd.) and two "Foam Jet" (registered trademark) pumps to supply air and generate air UFB. The sample water was heated to a temperature of approximately 45°C. The results are shown in Table 7 and Figures 7(a) and (b).

[0046] [Table 7]

[0047] The results shown in Table 7 and Figures 7(a) and (b) suggest the following: After 6 hours of treatment, PFOS concentrations decreased from 400 to 14 ng / L (96.5% reduction), and PFOA concentrations decreased from 180 to 30 ng / L (83.3% reduction), resulting in a combined PFOS / PFOA concentration of 580 to 44 ng / L (93.4% reduction). PFHxS concentrations decreased from 1400 to 620 ng / L (55.7% reduction). Concentrations of congeners other than PFOS / PFOA (PFOSs (PFSAs): C4-C8, PFOAs (PFCAs): C4-C11) generally decreased, with the exception of PFOSs (PFSAs): C4-C5 and PFOAs (PFCAs): C4-C7. A clear reduction in concentration was confirmed for PFHpS (C7), PFOS (C8), PFOA (C8), PFNA (C9), PFDA (C10), and PFUnDA (C11), which have relatively high RPF (relative potency factor) values ​​(relatively high relative toxicity) proposed by the EC (European Commission). The comparative example (high-pressure treatment) based on the method for treating water containing organic fluorine compounds disclosed in Patent Document 4 showed a tendency to have a slightly higher concentration reduction effect overall compared to the example (low-pressure treatment, decomposition treatment test result (3)) based on the method for treating water containing organic fluorine compounds of the present invention, but the required treatment energy (1 m of treated water) was 3 It was confirmed that the concentration reduction effect was not commensurate with the significant increase in the concentration (per unit). No abnormalities such as discoloration were observed in the treated water.

[0048] The decomposition treatment test was carried out under the treatment conditions shown in Table 2, with a batch treatment of 30 L of target water volume. Table 8 shows the treatment conditions assumed for an actual machine.

[0049] [Table 8]

[0050] As a bubble generator (UFB generator) that generates bubbles smaller than 1 μm, the "Foam Jet" (registered trademark) manufactured by YBM Corporation (FJP-300-RP; 300 m 3 One or two (parallel) turbines ( / h / unit) are installed to generate UFB, which can become the nucleus for cavitation generation. Here, the ejection pressure of the injection nozzle of "Foam Jet" (registered trademark) (FJP-300-RP) is about 0.01 to 0.1 MPa.

[0051] The following can be said from the above decomposition treatment test conducted under the treatment conditions shown in Table 2 and the treatment conditions assumed for the actual equipment shown in Table 8. The method for treating water containing organic fluorine compounds of the present invention sets the number of times that water containing organic fluorine compounds is circulated through a spray nozzle depending on the content of organic fluorine compounds and the required reduction rate. This eliminates the problems associated with conventional methods for treating water containing organic fluorine compounds (high-pressure treatment), such as the durability of the spray nozzle, the need for expensive high-pressure pumps, and high energy consumption, and makes it possible to treat large amounts of water containing organic fluorine compounds. The number of times that the water containing organic fluorine compounds is circulated through the spray nozzle can be set to 400 to 2000 times (400 to 1000 times in the case of environmental water containing relatively high concentrations of organic fluorine compounds). The energy required to treat water containing organic fluorine compounds per unit volume is 150 kWh / m 3or less (30-130 kWh / m in the case of environmental water containing relatively high concentrations of organic fluorine compounds) 3 .) The decomposition of organic fluorine compounds is particularly effective against perfluoroalkyl sulfonic acids (PFSAs) with C6 or higher and perfluoroalkyl carboxylic acids (PFCAs) with C7 or higher.

[0052] The method for treating water containing organic fluorine compounds of the present invention has been described above based on an embodiment thereof (decomposition treatment test by low-pressure treatment (circulation batch treatment test)). However, the present invention is not limited to the configuration described in the above embodiment, and the configuration can be appropriately changed within the scope of the spirit of the present invention, for example, by performing continuous circulation treatment (supplying a predetermined amount of water containing organic fluorine compounds, circulating the water, and discharging the same amount of treated water). [Industrial Applicability]

[0053] The method for treating water containing organic fluorine compounds of the present invention utilizes cavitation, which is used in the decomposition of organic compounds, to decompose persistent organic fluorine compounds contained in water. In particular, it eliminates problems associated with conventional methods for treating water containing organic fluorine compounds (high-pressure treatment), such as the durability of the spray nozzle, the need for expensive high-pressure pumps, and high energy consumption, and is capable of treating large amounts of water containing organic fluorine compounds. Therefore, the method can be suitably used for low-cost decomposition of PFAS such as PFOS / PFOA contained in environmental water such as river water, lake water, and groundwater. [Explanation of symbols]

[0054] 1 aquarium 2. Air bubble generator (UFB generator) 3 Cooling pipe 4 Cooling water tank

Claims

1. A method for treating water containing organic fluorine compounds, comprising adding a gas to the water containing organic fluorine compounds and injecting the water through an injection nozzle into the water to cause cavitation and generate bubbles of less than 1 μm in size, and decomposing the organic fluorine compounds contained in the water containing organic fluorine compounds by utilizing the cavitation and the bubbles of less than 1 μm, wherein the injection nozzle has a discharge pressure of 0.3 MPa or less, and the number of times the water containing organic fluorine compounds is circulated through the injection nozzle is set according to the content of the organic fluorine compounds and the required reduction rate.

2. 2. The method for treating water containing organic fluorine compounds according to claim 1, wherein the number of times the water containing organic fluorine compounds is circulated through the spray nozzle is 400 to 2,000.

3. The energy required to treat the water containing the organic fluorine compound per unit amount of water is 150 kWh / m ３ 2. The method for treating water containing organic fluorine compounds according to claim 1, wherein the method is as follows:

4. 2. The method for treating water containing organic fluorine compounds according to claim 1, wherein the organic fluorine compounds to be decomposed are perfluoroalkyl sulfonic acids (PFSAs) of C6 or higher and perfluoroalkyl carboxylic acids (PFCAs) of C7 or higher.

5. 5. The method for treating water containing organic fluorine compounds according to claim 1, 2, 3 or 4, wherein the water containing organic fluorine compounds is environmental water.

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