Foam separation treatment device and foam separation treatment method

Abstract

To provide a foam-separating treatment apparatus and a foam-separating treatment method capable of efficiently collecting foam.SOLUTION: A foam-separating treatment apparatus 1 for separating a surfactant contained in treated water W from the stored treated water W includes: storage means 10 for storing the treated water W; bubble generating means 20 for generating bubbles by feeding gas into the treated water W in the storage means 10; and collection means 30 for collecting foam B in which the surfactant is concentrated on an air-water interface of the bubbles. Recovery means 30 includes a foam recovery part 31 having an opening 31a positioned upwardly with respect to a water surface W1 near the water surface W1 of the treated water W.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a foam separation treatment device and a foam separation treatment method. [Background technology]

[0002] Environmental pollution problems caused by perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), which are classified as fluorinated organic compounds (PFAS), have become apparent. PFOS and PFOA are regulated both domestically and internationally due to their widespread and large-scale use in foam fire extinguishing agents. The principle of foam fire extinguishing is to block the air needed for combustion with foam. Surfactants are used as a component of the foam.

[0003] PFOS and PFOA, the main components of firefighting foam, have a structure that has a "hydrophilic group" that has the property of being compatible with water and a "hydrophobic group" that has the property of being compatible with oil, and behave as surfactants in water. Surfactants have the property of concentrating at the air-water interface. This phenomenon is utilized in the field of water treatment, where air is pumped into the water to generate multiple bubbles (at the air-water interface), and the surfactants concentrated at the interface are collected as foam, a method called "foam fractionation."

[0004] In Patent Document 1, groundwater is purified by injecting nitrogen into the groundwater and collecting PFOS and PFOA concentrated in the bubbles that are generated as foam. However, the amount of foam generated depends on the amount of nitrogen injected, the bubble diameter, and the PFOS and PFOA concentrations in the groundwater. The lower the PFOS and PFOA concentrations in the groundwater, the less foam generated, and the foam on the water surface collapses in a short period of time. The method described in Patent Document 1 vacuum-suctions the foam from the groundwater surface. This method promotes foam collapse, making it difficult to efficiently collect the foam. Furthermore, the method described in Patent Document 1 involves constantly fluctuating groundwater levels. Furthermore, since the method described in Patent Document 1 vacuum-suctions the foam from the groundwater surface, it is necessary to maintain a stable distance between the groundwater surface and the foam suction device. However, Patent Document 1 does not disclose this method. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 10,752,521 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a foam separation treatment device and a foam separation treatment method that can efficiently recover foam. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A foam separation treatment device that separates surfactants contained in stored water to be treated from the water to be treated, a storage means for storing the water to be treated; a bubble generating means for generating bubbles by sending gas into the water to be treated in the storage means; and a recovery means for recovering foam in which the surfactant is concentrated at the air-water interface of the bubbles, The recovery means is provided with a foam recovery section having an opening disposed near the water surface of the water to be treated and facing upward relative to the water surface. [2] The foam separation treatment device described in [1], wherein the foam collection section has a strainer near the opening. [3] A foam separation treatment device as described in [1] or [2], which is provided with a gas-liquid separation means for recovering the liquid produced by liquefaction of the foam in the foam recovery section outside the foam recovery section, separating the recovered liquid into the gas contained in the foam and a surfactant concentrate containing the water to be treated, and circulating the separated gas to the bubble generation means. [4] A foam separation treatment device according to any one of [1] to [3], wherein the position of the opening in the foam collection section in the depth direction of the storage means is adjustable according to the water level of the water to be treated. [5] The foam separation treatment device according to any one of [1] to [4], wherein the foam collection section collects the foam by utilizing the power used in the foam generation means. [6] A foam separation treatment method for separating surfactants contained in stored water to be treated from the water to be treated, A foam separation treatment method in which gas is pumped into stored water to be treated to generate bubbles, surfactant is concentrated at the air-water interface of the bubbles to generate foam, and the foam is collected near the surface of the water to be treated. [7] A foam separation treatment method according to [6], in which the liquid produced by liquefaction of the foam is recovered, and the recovered liquid is separated into the gas contained in the foam and a surfactant concentrate containing the water to be treated, and the separated gas is circulated into the stored water to be treated. [8] The foam separation treatment method according to [6] or [7], wherein the position for collecting the foam is adjusted according to the water level of the water to be treated. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a foam separation treatment device and a foam separation treatment method that can efficiently recover foam. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an example of a foam separation treatment device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] A foam separation treatment device and a foam separation treatment method according to an embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic diagram showing an example of a foam separation treatment device according to an embodiment of the present invention. It should be noted that the present embodiment is specifically described to allow a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[0011] [Foam separation treatment device] The foam separation treatment device of this embodiment is a foam separation treatment device that separates surfactants contained in stored water to be treated from the water to be treated, and is equipped with a storage means for storing the water to be treated, a bubble generating means for generating bubbles by sending gas into the water to be treated in the storage means, and a recovery means for recovering foam in which surfactants are concentrated at the air-water interface of the bubbles, and the recovery means is equipped with a foam recovery section having an opening positioned near the water surface of the water to be treated and facing upward relative to the water surface.

[0012] As shown in FIG. 1, the foam separation treatment device 1 of this embodiment includes a storage means 10, a bubble generation means 20, and a recovery means 30.

[0013] The storage means 10 is for storing the water to be treated, which contains surfactants and is to be treated by the foam separation treatment device 1. When the foam separation treatment device 1 is installed in situ, the storage means 10 is constructed in contaminated soil G containing the water to be treated W. When the foam separation treatment device 1 is installed in situ, the water to be treated W is groundwater. Here, the contaminated soil G may be, for example, soil containing groundwater (water to be treated W) containing PFAS such as PFOS and PFOA, which are surfactants.

[0014] When the foam separation treatment device 1 is installed in situ, the storage means 10 is an in-situ purification well. The storage means 10 is tubular. The shape of the cross section perpendicular to the depth direction of the storage means 10 is not particularly limited, and examples thereof include a circle, a square, and the like. Furthermore, the inner diameter (diameter of the largest part) of the storage means 10 is not particularly limited. It depends on the number of in-situ purification wells to be installed, taking into account the ease of construction and purification efficiency of the in-situ purification wells, but it is preferably, for example, between 5 cm and 20 cm, and more preferably between 7.5 cm and 10 cm. If the inner diameter is equal to or greater than the lower limit, the collection means 30 can be easily installed in the in-situ purification well. If the inner diameter is equal to or less than the upper limit, drilling and construction of the in-situ purification well can be performed using conventional boring machines.

[0015] It is preferable that an upper lid 11 is provided at the upper end of the storage means 10 to cover the opening 10a of the storage means 10. By providing the upper lid 11, it is possible to maintain airtightness inside the storage means 10. By maintaining airtightness inside the storage means 10, the gas separated in the gas-liquid separation section 61 (described later) can be returned to the water to be treated W via the blower 22 (described later) and recycled for generating foam B.

[0016] The bubble generating means 20 is for sending gas such as nitrogen or air into the water to be treated W in the storage means 10 to generate bubbles. The air bubble generating means 20 has a plurality of air pipes 21 for sending air into the water to be treated W in the storage means 10, and a blower 22 for sending gas into the air pipes 21.

[0017] The multiple air supply pipes 21 are arranged within the storage means 10 along the depth direction of the storage means 10. As shown in Figure 1, the multiple air supply pipes 21 are composed of, for example, three air supply pipes 21A, 21B, and 21C of different lengths. The positions of the tips of the air supply pipes 21A, 21B, and 21C are different in the depth direction of the storage means 10. In Figure 1, the tip of the air supply pipe 21A is at the deepest position relative to the depth of the storage means 10. The tip of the air supply pipe 21B is at the second deepest position relative to the depth of the storage means 10. The tip of the air supply pipe 21C is at the shallowest position relative to the depth of the storage means 10. Gas sent out by the blower 22 is sent out from the tip of the air supply pipe 21 into the water W to be treated. The positions of the tips of the air supply pipes 21A, 21B, and 21C are different in the depth direction of the storage means 10, so that the diffusion range of the bubbles generated by the gas sent into the water W to be treated in the storage means 10 can be expanded over a wide range. This allows the bubbles B to be efficiently generated in the water W to be treated in the storage means 10.

[0018] The number of air pipes 21 is not particularly limited, and is adjusted appropriately depending on the amount of water W to be treated in the storage means 10 and the size of the storage means 10 (inner diameter, depth). The shape of the tip of the air supply pipe 21 is not particularly limited, and the size of the bubbles to be generated can be adjusted appropriately by changing the shape of the outlet and the amount of air to be supplied. The positions of the tips of the plurality of air supply pipes 21 are not particularly limited and are adjusted appropriately depending on the amount of water W to be treated in the storage means 10 and the size of the storage means 10 (inner diameter, depth). The inner diameter of the air supply pipe 21 is not particularly limited, and is adjusted appropriately depending on the amount of water W to be treated in the storage means 10 and the size of the storage means 10 (inner diameter, depth).

[0019] The material of the air pipe 21 is not particularly limited as long as it does not adsorb PFOS or PFOA contained in the water to be treated W or is not deteriorated by these substances.

[0020] The blower 22 may be, for example, a conventional turbo blower (backward-curved blade blower).

[0021] The recovery means 30 is for recovering foam B, in which surfactant is concentrated, by causing it to flow into the air-water interface of the air bubbles generated in the water to be treated W in the storage means 10. The collection means 30 has a foam collection section 31 for collecting and temporarily storing foam B. The foam collection section 31 has an opening 31a that is positioned near the water surface W1 of the water to be treated W and faces upward relative to the water surface W1. By positioning the opening 31a of the foam collection section 31 near the water surface W1 of the water to be treated W in the storage means 10 and facing upward relative to the water surface W1, foam B that has risen to the water surface W1 of the water to be treated W can be efficiently collected.

[0022] The foam collection section 31 has a strainer 32 near the opening 31a, and the opening 31a is preferably installed at a position slightly higher than the water surface W1. By having the strainer 32 near the opening 31a, the foam B can be collected in the foam collection section 31 through the strainer 32. In other words, the collection efficiency of the foam B can be improved.

[0023] The foam collection section 31 is made up of a cylindrical member having a bottom. The foam collection section 31 may be extendable along the depth direction of the storage means 10. The material of the foam collecting section 31 is not particularly limited as long as it does not adsorb PFOS or PFOA contained in the water to be treated W or is not deteriorated by these substances.

[0024] It is preferable that the position of the opening 31a of the foam collection section 31 be adjustable in the depth direction of the storage means 10 in accordance with the water level of the water W to be treated within the storage means 10. To make the position of the opening 31a adjustable, for example, as shown in FIG. 1 , a water level measurement means 40 is used. The water level measurement means 40 has a water level indicator 41 and a water level sensor 42. The water level sensor 42 is disposed in a groundwater level observation well 50 constructed in the contaminated soil G separately from the storage means 10, near the storage means 10. The position of the opening 31a of the foam collection section 31 is adjusted to be slightly higher than the water level W1 in accordance with the position (water level) of the water surface W1 of the water to be treated measured by the water level measurement means 40. This allows even a small amount of foam B floating on the water surface W1 of the water to be treated W to be collected.

[0025] The water level indicator 41 may be, for example, a self-recording water level indicator that displays the electric signal sent from the water level sensor 42 as the water level in real time and can output it to an external device. An example of the water level sensor 42 is a water pressure sensor whose sensor body is submerged in water and has the function of converting changes in water pressure caused by fluctuations in the water level into an electrical signal and outputting it.

[0026] An example of a means for adjusting the position of the opening 31a of the foam collection section 31 in accordance with the position (water level) of the water surface W1 of the treated water W measured by the water level measuring means 40 is a mechanism that adjusts the position of the opening 31a main body by positive or negative power generated by the rotation of a motor or the like in accordance with the amount of fluctuation in the water level output from the water level meter 41.

[0027] The foam separation treatment device 1 of this embodiment preferably includes a gas-liquid separation means 60. The gas-liquid separating means 60 includes a gas-liquid separating section 61 , a conduit 62 , and a circulation path 63 . The gas-liquid separation means 60 recovers the liquid L produced by liquefaction of the foam B in the foam recovery section 31 in the gas-liquid separation section 61 via a conduit 62. The gas-liquid separation section 61 also separates the recovered liquid L into the gas contained in the foam B and a surfactant concentrate containing the water to be treated W. The gas separated in the gas-liquid separation section 61 is then circulated to the bubble generation means 20 via a circulation path 63.

[0028] The foam separation treatment device 1 of this embodiment is provided with the bubble generating means 20 that generates bubbles by sending gas into the water W to be treated in the storage means 10, so that the diffusion range of the bubbles generated by the gas sent into the water W to be treated in the storage means 10 can be expanded over a wide range. This allows foam B to be efficiently generated in the water W to be treated in the storage means 10.

[0029] In addition, according to the foam separation treatment device 1 of this embodiment, a recovery means 30 is provided for recovering foam B, which is a surfactant-concentrated foam at the air-water interface of bubbles generated in the water to be treated W in the storage means 10, and the recovery means 30 is provided with a foam recovery section 31 having an opening 31a positioned upward relative to the water surface W1 near the water surface W1 of the water to be treated W, so that foam B that has risen to the water surface W1 of the water to be treated W can be efficiently recovered.

[0030] [Foam separation treatment method] The foam separation treatment method according to this embodiment is a foam separation treatment method for separating surfactants contained in stored water to be treated from the water to be treated, in which gas is pumped into the stored water to be treated to generate bubbles, surfactants are concentrated at the air-water interface of the bubbles to generate foam, and the foam is collected near the surface of the water to be treated.

[0031] Hereinafter, the foam separation method of this embodiment will be described in detail with reference to FIG. 1, gas is sent from a blower 22 into a plurality of air pipes 21 in water W to be treated in a storage means 10 installed in contaminated soil G, and the gas is sent into the water W to be treated from the plurality of air pipes 21, each with a tip positioned at a different position in the depth direction of the storage means 10, to generate bubbles, and surfactant is concentrated at the air-water interface of the bubbles to generate foam B. The generated foam B rises to the water surface W1 of the water W to be treated in the storage means 10.

[0032] The size (outer diameter) of the bubbles generated in the water to be treated W by the gas sent into the water to be treated is smaller, making it easier for them to flow into the recovery means 30. However, the size of the bubbles generated depends on the amount of surfactant contained in the water to be treated W and the amount of air sent, so it is adjusted appropriately depending on the water quality of the water to be treated W to be treated in the storage means 10. Furthermore, the amount of bubbles generated in the water to be treated W, i.e., the amount of bubbles contained per unit volume of the water to be treated W, is not particularly limited and is adjusted appropriately according to the amount of water to be treated W to be treated in the storage means 10.

[0033] When sending gas into the water W to be treated, it is preferable to send the gas into the water W from air supply pipes 21A, 21B, 21 whose tips are located at different positions in the depth direction of storage means 10. This makes it possible to widely expand the diffusion range of bubbles generated by the gas sent into the water W to be treated in storage means 10. In other words, foam B can be efficiently generated in the water W to be treated in storage means 10.

[0034] When PFAS such as PFOS or PFOA is contained in the water to be treated W, surfactants are concentrated at the air-water interface of bubbles generated in the water to be treated W, forming foam B. As described above, PFOS and PFOA behave as surface-active substances, and therefore, when gas is pumped into the water to be treated W containing PFOS or PFOA, multiple bubbles (air-water interface) are generated. In the foam separation treatment method according to this embodiment, bubbles containing surface-active substances such as PFOS or PFOA concentrated at the air-water interface are raised to the water surface W1 of the water to be treated W in the storage means 10 as foam B and collected.

[0035] The gas to be fed into the water to be treated W is not particularly limited as long as it does not chemically react with or dissolve in the water to be treated W, and examples thereof include air and nitrogen.

[0036] The method of collecting the foam B by the foam collection section 31 of the collection means 30 involves arranging the opening 31a of the foam collection section 31 at a position slightly higher than the water surface W1 of the water to be treated W in the storage means 10, and allowing the foam B to flow from the opening 31a into the foam collection section 31. By arranging the opening 31a of the foam collection section 31 at a position slightly higher than the water surface W1 of the water to be treated W in the storage means 10, the foam B that has risen to the water surface W1 of the water to be treated W can be selectively and efficiently collected.

[0037] By generating bubbles in the water W to be treated and continuing to concentrate PFOS and PFOA at the air-water interface of the bubbles, the foam B temporarily stored in the foam collection section 31 liquefies in a short period of time to become liquid L. Therefore, the amount of liquid L generated by the liquefaction of the foam B gradually increases in the foam collection section 31. Note that when the foam B flows into the foam collection section 31 until the amount of stored liquid L exceeds the height of the tip of the conduit 62, the internal pressure of the storage means 10, in which the upper cover 11 is installed, increases due to the gas being pumped into the water W to be treated. Therefore, the liquid L generated by the liquefaction of the foam B is automatically pushed through the conduit 62 to the gas-liquid separation section 61 together with the gas pumped into the water W to be treated. The gas-liquid separation section 61 separates the collected liquid L into a surfactant concentrate containing the gas contained in the foam B and the water to be treated. Furthermore, the gas separated in the gas-liquid separation section 61 is circulated to the bubble generation means 20 via a circulation path 63. An upper lid 11 is provided to cover the opening 10a of the storage means 10, thereby maintaining airtightness within the storage means 10. This makes it possible to use the power of the blower 22 used in the bubble generation means to collect the foam B, and furthermore, the gas separated in the gas-liquid separation section 61 can be returned to the water W to be treated via the blower 22 and recycled to generate foam B. This makes it possible to reduce the amount of gas used.

[0038] Because the water level of the water W to be treated in the contaminated soil G fluctuates from moment to moment, it is preferable to adjust the position at which foam B is collected by the foam collection unit 31 in accordance with the water level of the water W to be treated. Specifically, for example, as shown in FIG. 1 , it is preferable to use a water level measurement means 40 to adjust the position at which foam B is collected by the foam collection unit 31 in accordance with the water level of the water W to be treated. In accordance with the amount of water level fluctuation measured by the water level measurement means 40, the position of the opening 31a of the foam collection unit 31 is adjusted so that it is at a position (height) slightly higher than the position (water level) of the water surface W1 of the water W to be treated, taking into account the positional relationship between the water level measurement value and the storage means 10. This makes it possible to collect even foam B that is slightly floating on the water surface W1 of the water W to be treated.

[0039] According to the foam separation treatment method of the present embodiment, bubbles are generated by sending gas into the water W to be treated in the storage means 10, so that the diffusion range of the bubbles generated by the gas sent into the water W to be treated in the storage means 10 can be expanded over a wide range. This allows bubbles B to be efficiently generated in the water W to be treated in the storage means 10.

[0040] Furthermore, according to the foam separation treatment method of this embodiment, surfactants are concentrated at the air-water interface of bubbles generated in the water to be treated W in the storage means 10 to generate foam B, and foam B is collected near the water surface W1 of the water to be treated W, so that foam B that has risen to the water surface W1 of the water to be treated W can be efficiently collected.

[0041] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the embodiments are merely illustrative of the present invention. Therefore, the present invention is not limited to the configurations of the embodiments, and design changes within the scope of the present invention are also included within the scope of the present invention. Furthermore, for example, when multiple configurations are included in each embodiment, possible combinations of these configurations are also included, even if not specifically stated. Furthermore, when multiple examples or variations are disclosed in an embodiment as the present invention, possible combinations of configurations across these are also included, even if not specifically stated. Furthermore, configurations depicted in the drawings are also included, even if not specifically stated. Furthermore, when the term "etc." is used, it is used to mean that equivalents are included.

[0042] In the above-described embodiment, the storage means 10 is an in-situ purification well installed in situ, the foam separation treatment device 1 is an in-situ treatment device, and the surfactant is a PFAS such as PFOS or PFOA, but the present invention is not limited to this. The foam separation treatment device and foam separation treatment method of the present invention are also suitable for separating various surfactants contained in the treated water from the stored treated water at a location other than the in-situ. [Explanation of symbols]

[0043] 1. Foam separation treatment device 10 Storage means 11 Top lid 20 Bubble generating means 21 Air pipe 22 Blower 30 Recovery Methods 31 Foam collection section 40 Water level measurement means 41 Water level gauge 42 Water level sensor 50 Groundwater level observation well 60 Gas-liquid separation means 61 Gas-liquid separation section 63 Circulation route

Claims

1. A foam separation treatment device that separates surfactants contained in stored water to be treated from the water to be treated, a storage means for storing the water to be treated; a bubble generating means for generating bubbles by sending gas into the water to be treated in the storage means; and a recovery means for recovering foam in which the surfactant is concentrated at the air-water interface of the bubbles, The collection means includes a foam collection unit having an opening disposed in the vicinity of the water surface of the water to be treated and facing upward relative to the water surface, A foam separation treatment device comprising: a gas-liquid separation means for recovering the liquid produced by liquefaction of the foam in the foam recovery section outside the foam recovery section; separating the recovered liquid into the gas contained in the foam and a surfactant concentrate containing the water to be treated; and circulating the separated gas to the bubble generation means.

2. A foam separation treatment device that separates surfactants contained in stored treated water from the treated water, a storage means for storing the water to be treated; a bubble generating means for generating bubbles by sending gas into the water to be treated in the storage means; and a recovery means for recovering foam in which the surfactant is concentrated at the air-water interface of the bubbles, The collection means includes a foam collection unit having an opening disposed in the vicinity of the water surface of the water to be treated and facing upward relative to the water surface, The foam collection section is a foam separation treatment device in which the position of the opening in the depth direction of the storage means can be adjusted according to the water level of the treated water measured by a water level measuring means installed in a groundwater level observation well.

3. The foam separation treatment device according to claim 1 or 2, wherein the foam collection section has a strainer near the opening.

4. The foam separation treatment device according to any one of claims 1 to 3, wherein the foam collection section collects the foam by utilizing power used in the foam generation means.

5. A foam separation treatment method for separating surfactants contained in stored water to be treated from the water to be treated, Gas is pumped into the stored water to be treated to generate bubbles, a surfactant is concentrated at the air-water interface of the bubbles to generate foam, and the foam is collected near the water surface of the water to be treated; A foam separation treatment method in which the liquid produced by liquefaction of the foam is recovered, the recovered liquid is separated into gas contained in the foam and a surfactant concentrate containing the water to be treated, and the separated gas is circulated into the stored water to be treated.

6. A foam separation treatment method for separating surfactants contained in stored treated water from the treated water, comprising: Gas is pumped into the stored water to be treated to generate bubbles, a surfactant is concentrated at the air-water interface of the bubbles to generate foam, and the foam is collected near the water surface of the water to be treated; A foam separation treatment method, wherein the position for recovering the foam is adjusted according to the water level of the water to be treated measured by a water level measuring means provided in a groundwater level observation well.

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