PFAS removal system

Abstract

To provide a PFAS treatment system capable of efficiently removing PFAS, which is suitable for large quantities of treatment targets.SOLUTION: A PFAS treatment system includes ozone dissolution means 1 and PFAS adsorption means 2 arranged in the order from upstream in a flow path L through which liquid A to be treated for PFAS removal flows. The ozone dissolution means 1 dissolves ozone into the liquid A, and the PFAS adsorption means 2 brings the liquid A into contact with activated carbon. Multiple PFAS adsorption means 2 are arranged in parallel, enabling switching between the PFAS adsorption means 2 through which the liquid A flows.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a PFAS removal system suitable for use in removing, for example, PFOS (perfluorooctanesulfonic acid or perfluorooctanesulfonic acid) and PFOA (perfluorooctanoic acid or perfluorooctanoic acid), which are organic fluorine-containing compounds (PFAS), from liquids such as wastewater and spring water. [Background technology]

[0002] PFOS and PFOA are organic fluorine compounds with excellent heat and chemical resistance, and have been used as surfactants, chemicals for semiconductor manufacturing and metal plating, fire extinguishing foams, and auxiliary agents for the production of fluororesins.

[0003] On the other hand, PFOS and PFOA are chemically very stable, water-soluble, and non-volatile substances, so if they are released into the environment, they are likely to migrate into rivers, etc. Furthermore, because they are persistent and bioaccumulating, they tend to remain in the environment, raising concerns about their impact on the ecosystem.

[0004] PFOS and PFOA are chemically very stable and do not decompose in nature, and require high temperatures of approximately 1000°C or higher for thermal decomposition (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-302551 Summary of the Invention [Problem to be solved by the invention]

[0006] Methods for removing PFAS such as PFOS and PFOA from liquids (raw water) containing these compounds include combustion treatment and high-pressure supercritical treatment. However, these treatment methods have the problem that they are not suitable for treating large amounts of material.

[0007] The present invention was made with the above in mind, and its purpose is to provide a PFAS treatment system that can efficiently perform PFAS removal treatment and is suitable even when large amounts of material are to be treated. [Means for solving the problem]

[0008] In order to achieve the above-mentioned objective, the PFAS treatment system of the present invention has an ozone dissolving means and a PFAS adsorption means, in this order from the upstream side, in a flow path through which a liquid to be subjected to PFAS removal treatment flows, and the ozone dissolving means dissolves ozone in the liquid, and the PFAS adsorption means brings the liquid into contact with activated carbon (Claim 1).

[0009] In the above-mentioned PFAS treatment system, a plurality of the PFAS adsorption means may be arranged in parallel, and the PFAS adsorption means through which the liquid flows may be switched (claim 2).

[0010] In the above-described PFAS treatment system, a measuring means for measuring the ozone concentration of the liquid may be provided downstream of the PFAS adsorption means (claim 3). [Effects of the Invention]

[0011] The present invention provides a PFAS treatment system that can efficiently remove PFAS and is suitable for large amounts of material to be treated.

[0012] In other words, the PFAS treatment system of the invention claimed in each claim of this application performs PFAS removal treatment by passing the liquid to be treated for PFAS removal through an ozone dissolution means and a PFAS adsorption means in that order, and since the treatment can be carried out efficiently using ozone and activated carbon, it is suitable even when there is a large amount of liquid to be treated.

[0013] In the PFAS treatment system of the invention of claim 2, multiple PFAS adsorption means are arranged in parallel, and it is possible to switch the PFAS adsorption means through which the liquid to be treated flows.For example, when replacing activated carbon, the replacement work can be easily carried out by not flowing liquid through the PFAS adsorption means containing the activated carbon to be replaced.In addition, if liquid is allowed to flow through other PFAS adsorption means during this work, the PFAS removal process can be continued without interruption.

[0014] In the PFAS treatment system of the invention of claim 3, when activated carbon breaks through, it is thought that the ozone concentration will increase along with the PFAS concentration downstream. By detecting this increase in ozone concentration using a measurement means, it can be determined that activated carbon has broken through. If measures such as replacing the activated carbon are taken at the time such an evaluation is made, it is possible to continue PFAS removal treatment using activated carbon at a high level and also to avoid unnecessarily increasing the number of times the activated carbon is replaced. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of an embodiment of the present invention.

[0023] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the present invention will be described below.

[0017] The PFAS removal system shown in Figure 1 has an ozone dissolving means 1 and a PFAS adsorption means 2 installed in this order from upstream to downstream in a flow path L through which a liquid A (raw water such as spring water in the illustrated example) to be treated for PFAS (e.g., PFOS and / or PFOA) removal flows, with the ozone dissolving means 1 dissolving ozone in the liquid A and the PFAS adsorption means 2 bringing the liquid A into contact with activated carbon. Note that in Figure 1, 80A, 40A, and 20A indicate the sizes (nominal diameters) of the pipes that make up the flow path L.

[0018] In more detail, a pressure switch 3 (which is turned ON, for example, during PFAS removal processing and turned OFF at other times) is provided in the first flow path L1 (nominal diameter, for example, 80A) at the most upstream part of the flow path L, and downstream of this pressure switch 3, the flow path L branches into two second flow paths L2, and each second flow path L2 is provided with a pump device (for example, a magnetic pump) 4 for flowing liquid A.

[0019] Furthermore, downstream of the two second flow paths L2, each flow path L further branches into two third flow paths L3, which then merge to form a fourth flow path L4, and the two fourth flow paths L4 further merge to form a single fifth flow path L5.

[0020] Here, each third flow path L3 is provided with an ozone dissolving means 1, and in this example, ozone gas is formed in an ozonizer 6 to which oxygen is supplied from an oxygen generator 5, and the ozone dissolving means 1 is a mixing device that dissolves the ozone gas supplied from the ozonizer 6 into liquid A. This mixing device can be configured, for example, to move the liquid up and down in a mixing tank, causing diffusion, collision, and convection to dissolve ozone gas into liquid A, thereby achieving a dissolution rate of ozone concentration of 2.5 ppm or more.

[0021] Two sixth flow paths L6 are connected to the downstream side of the fifth flow path L5 via a three-way selector valve 7. Downstream of each sixth flow path L6, the flow path L further branches into two seventh flow paths L7 and then merges to form an eighth flow path L8, and the two eighth flow paths L8 further merge to form a ninth flow path L9. In other words, by switching the three-way selector valve 7, the state in which liquid A flows through one of the two sixth flow paths L6 can be switched to a state in which liquid A flows through the other.

[0022] Here, each seventh flow path L7 is provided with a PFAS adsorption means 2, which preferably adsorbs at least PFAS (at least PFOS and / or PFOA) and ozone in liquid A, and more preferably also adsorbs other impurities; in this example, a forced adsorption device employing a cartridge filter that can be used by inserting activated carbon (for example, formed by compressing coconut shell powder), ion exchange resin, zeolite, or other granular filtering material inside is used as the PFAS adsorption means 2. The cartridge filter is preferably a cassette type that can be replaced with a single touch, for example, to enable rapid replacement.

[0023] Furthermore, a bypass flow path 8 is provided downstream of the PFAS adsorption means 2 in each of the seventh flow paths L7, and this bypass flow path 8 is provided with an on-off valve 9 and a measuring means (e.g., an ozone concentration meter) 10 that measures the ozone concentration of the liquid A. That is, when the on-off valve 9 is opened and the liquid A is allowed to flow through the bypass flow path 8, the ozone concentration of the liquid A can be measured by the measuring means 10.

[0024] In Figure 1, reference numeral 11 denotes a control unit (e.g., a control panel), which is configured to control the objects that need to be controlled in the PFAS removal system (e.g., a pressure switch 3, a pump device 4, an oxygen generator 5, an ozonizer 5, a three-way switching valve 7, an on-off valve 9, and a measuring means 10).

[0025] The PFAS removal system configured as described above performs PFAS removal treatment by passing the liquid A to be treated for PFAS removal through the ozone dissolution means 1 and the PFAS adsorption means 2 in that order. Since the treatment can be carried out efficiently using the decomposition power of ozone and the adsorption power of activated carbon, etc., it is suitable even when there is a large amount of liquid A to be treated.

[0026] Furthermore, in the PFAS treatment system of this example, multiple PFAS adsorption means 2 are arranged in parallel, and the PFAS adsorption means 2 through which the liquid A to be treated flows can be switched using a three-way switching valve 7. Therefore, for example, when replacing activated carbon (cartridge filter), the replacement work can be easily carried out by preventing liquid A from flowing through the PFAS adsorption means 2 containing the activated carbon (cartridge filter) to be replaced. Furthermore, if liquid A is allowed to flow through other PFAS adsorption means 2 during this work, the PFAS removal process can be continued without interruption.

[0027] Furthermore, in the PFAS treatment system of this example, when the activated carbon breaks through, it is thought that the ozone concentration will increase along with the PFAS concentration in liquid A downstream. By detecting this increase in ozone concentration using measurement means 10, it can be determined that the activated carbon has broken through. If measures such as replacing the activated carbon (cartridge filter) are taken at the time this determination is made, it will be possible to continue performing PFAS removal treatment using activated carbon at a high level and also avoid unnecessarily increasing the number of times the activated carbon (cartridge filter) is replaced.

[0028] Furthermore, the PFAS removal system in this example can also remove common bacteria in Liquid A using ozone and activated carbon, producing high-quality reclaimed water that can be used as domestic water (sterile water).

[0029] Below are specific examples of the processing capacity and equipment configuration of the PFAS removal system in this example.

[0030] The treatment capacity of the PFAS removal system can be, for example, such that the amount of treated liquid A is 120 L / min, the PFAS concentration of the liquid A to be treated is 1000 ng or less, and the temperature is 10°C to 35°C.

[0031] It is preferable that at least the liquid contacting parts of the ozone dissolving means 1 (mixing device) are made of corrosion-resistant material such as stainless steel.

[0032] Each PFAS adsorption means 2 can accommodate (attach) 12 filter cartridges, for example, and each filter cartridge can have a diameter of 90 mm and a length of 286 mm.

[0033] The pump device 4 may be, for example, a magnetic pump (water pump) with a maximum pumping capacity of 300 L / min.

[0034] The oxygen generator 5 preferably has an oxygen concentration of 90% or more, a discharge pressure of 0.1±0.01 MPa, an oxygen flow rate of 6 L / min, alarm functions (apparatus abnormality, pressure abnormality, power outage alarm) and a check valve function.

[0035] The ozonizer 6 may be of a silent discharge type with a cooling fan.

[0036] The control unit 11 may be an electric control panel that performs sequence control and has an emergency stop function in case of an abnormality.

[0037] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications can be mentioned.

[0038] 1, a total of four third flow paths L3 each having an ozone dissolving means 1 are provided, but the number of third flow paths L3 (ozone dissolving means 1) may be one to three, or five or more. Also, a plurality of ozone dissolving means 1 may be provided in one third flow path L3.

[0039] In the example of Figure 1, the downstream side of the fifth flow path L5 is divided into two systems, a first system S1 and a second system S2, and a three-way switching valve 7 is used to ensure that liquid A flows only through one of systems S1 and S2. However, the number of systems is not limited to two and may be, for example, three or more. In this case, a three-way switching valve or an on-off valve may be provided as appropriate so that it is possible to freely switch which system liquid A flows through.

[0040] In the example of Figure 1, two seventh flow paths L7 each having a PFAS adsorption means 2 are installed in parallel in each of the systems S1 and S2, but one or three or more may be installed in parallel in each system.

[0041] In the example of Figure 1, two sixth flow paths L6 are connected to the fifth flow path L5 via a three-way switching valve 7, but this is not limited to this. For example, instead of providing a three-way switching valve 7, an opening / closing valve may be provided in each of the two sixth flow paths L6.

[0042] In the example of Figure 1, each seventh flow path L7 is provided with a bypass flow path 8, an on-off valve 9, and a measuring means 10, but instead of each seventh flow path L7, each eighth flow path L8 or ninth flow path L9 may be provided with a bypass flow path 8, an on-off valve 9, and a measuring means 10.

[0043] Alternatively, the bypass flow path 8 may not be provided, and the on-off valve 9 and the measuring means 10 may be provided directly in the seventh flow path L7, the eighth flow path L8 or the ninth flow path L9, in which case the on-off valve 9 may not be provided.

[0044] In the event that an increase in ozone concentration is detected by the measuring means 10, for example, a return flow path extending from the ninth flow path L9 to the first flow path L1 may be provided so that liquid A can be returned to the first flow path L1 without being discharged from the ninth flow path L9, and in this case, it is considered that an opening / closing valve or the like may be provided in the return flow path.

[0045] It goes without saying that the above modifications may be combined as appropriate. [Explanation of symbols]

[0046] 1. Ozone dissolution method 2 PFAS adsorption means 3 Pressure Switch 4. Pumping equipment 5. Oxygen generator 6. Ozonizer 7 Three-way valve 8 Bypass flow path 9 On-off valve 10 Measurement means 11 Control section A liquid L flow path L1~L9 1st flow path to 9th flow path

Claims

1. an ozone dissolving means and a PFAS adsorbing means are provided in this order from the upstream side in a flow path through which a liquid to be treated for PFAS removal flows; the ozone dissolving means dissolves ozone in the liquid; The PFAS adsorption means is a PFAS removal system that brings the liquid into contact with activated carbon.

2. 2. The PFAS removal system according to claim 1, wherein a plurality of said PFAS adsorption means are arranged in parallel, and the PFAS adsorption means through which said liquid flows can be switched.

3. 3. The PFAS removal system according to claim 1, further comprising a measuring means for measuring the ozone concentration of the liquid, disposed downstream of the PFAS adsorption means.

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