JP7744196B2 - Foam separation treatment device and foam separation treatment method - Google Patents

Description

The present invention relates to a foam separation treatment device and a foam separation treatment method.

Environmental pollution problems caused by perfluorooctane sulfonic acid (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 use foam to block the air needed for combustion. Surfactants are used as a component of the foam.

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

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 constant fluctuations in the groundwater level. Furthermore, since the method described in Patent Document 1 vacuum-suctions the foam from the groundwater surface, it is necessary to maintain an appropriate and stable distance between the groundwater surface and the foam suction device. However, Patent Document 1 does not disclose this method.

U.S. Pat. No. 1,075,2521

The present invention was made in consideration of the above circumstances, and aims to provide a foam separation treatment device and foam separation treatment method that can efficiently recover foam.

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] The foam separation treatment device described in [1] or [2] 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] The foam collection section is capable of adjusting the position of the opening in the depth direction of the storage means depending on the water level of the water to be treated. A foam separation treatment device described in any one of [1] to [3].
[5] A foam separation treatment device described in 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, 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.
[7] The foam is liquefied to produce a liquid, which is recovered, and the recovered liquid is separated into a gas contained in the foam and a surfactant concentrate containing the water to be treated. [6] The foam separation treatment method described in [6], wherein the separated gas is circulated to 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.

The present invention provides a foam separation treatment device and a foam separation treatment method that can efficiently recover foam.

1 is a schematic diagram illustrating an example of a foam separation treatment device according to an embodiment of the present invention.

Hereinafter, a foam separation treatment device and a foam separation treatment method according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a schematic diagram showing an example of a foam separation treatment apparatus 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.

[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 located near the water surface of the water to be treated and facing upward relative to the water surface.

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 collection means 30.

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.

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 cross-sectional shape of the storage means 10 perpendicular to the depth direction 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 is preferably 5 cm or more and 20 cm or less, and more preferably 7.5 cm or more and 10 cm or less. If the inner diameter is equal to or greater than the lower limit, the recovery 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 a conventional boring machine.

A top cover 11 that covers the opening 10a of the storage means 10 is preferably provided at the upper end of the storage means 10. By providing the top cover 11, the storage means 10 can be kept airtight. By keeping the storage means 10 airtight, the gas separated in the gas-liquid separation section 61 (described below) can be returned to the water to be treated W via the blower 22 (described below) and recycled to generate foam B.

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

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, for example, composed of 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 tips of the air supply pipes 21 into the water W to be treated. Because the tip positions of air supply pipes 21A, 21B, and 21C are different in the depth direction of storage means 10, the diffusion range of bubbles generated by the gas sent into the water to be treated W in storage means 10 can be expanded over a wide range. This allows bubbles B to be efficiently generated in the water to be treated W in storage means 10.

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 (inner diameter, depth) of the storage means 10 .
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 multiple 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 (inner diameter, depth) of the storage means 10.
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 (inner diameter, depth) of the storage means 10 .

The material of the air supply 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 be deteriorated by these substances.

An example of the blower 22 is a conventional turbo blower (backward-curved blade blower).

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 W to be treated in the storage means 10 .
The recovery means 30 has a foam recovery section 31 for recovering and temporarily storing foam B. The foam recovery 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 arranging the opening 31a of the foam recovery 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 recovered.

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, foam B can be collected in the foam collection section 31 through the strainer 32. In other words, the collection efficiency of foam B can be improved.

The foam collection section 31 is configured as 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 collection 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.

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 according to 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 includes a water level indicator 41 and a water level sensor 42. The water level sensor 42 is placed in a groundwater level observation well 50 constructed in the contaminated soil G separately from the storage means 10, near the storage means 10. Depending on the position (water level) of the water surface W1 of the water W to be treated measured by the water level measurement means 40, the position of the opening 31a of the foam collection section 31 is adjusted so that it is slightly higher than the water surface W1. This allows even trace amounts of foam B floating on the water surface W1 of the water W to be treated to be collected.

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

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 water to be treated W measured by the water level measurement means 40 is a mechanism that adjusts the position of the opening 31a itself using 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.

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.

The foam separation treatment device 1 of this embodiment is equipped with a bubble generating means 20 that generates bubbles by pumping gas into the water to be treated W in the storage means 10, thereby enabling the diffusion range of the bubbles generated by the gas pumped into the water to be treated W in the storage means 10 to be expanded over a wide range. This allows foam B to be efficiently generated in the water to be treated W in the storage means 10.

In addition, the foam separation treatment device 1 of this embodiment is equipped with a recovery means 30 that recovers foam B, which is surfactant-concentrated at the air-water interface of bubbles generated in the water to be treated W in the storage means 10. The recovery means 30 is equipped with a foam recovery section 31 that has an opening 31a positioned near the water surface W1 of the water to be treated W and facing upward relative to the water surface W1, thereby enabling efficient recovery of foam B that has risen to the water surface W1 of the water to be treated W.

[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.

The foam separation method of this embodiment will be described in detail below with reference to FIG.
1, gas is sent from a blower 22 into a plurality of air pipes 21 in water to be treated W in a storage means 10 installed in contaminated soil G, and the gas is sent into the water to be treated W 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 to be treated W in the storage means 10.

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.

When gas is pumped into the water to be treated W, it is preferable to pump the gas into the water to be treated W from air supply pipes 21A, 21B, and 21, each of which has a tip positioned at a different position in the depth direction of the storage means 10. This allows the diffusion range of the bubbles generated by the gas pumped into the water to be treated W in the storage means 10 to be expanded over a wide range. In other words, foam B can be efficiently generated in the water to be treated W in the storage means 10.

When PFAS such as PFOS and PFOA are contained in the water to be treated W, surfactants are concentrated at the air-water interface of the bubbles generated in the water to be treated W, forming foam B. As described above, PFOS and PFOA behave as surfactants, so when gas is pumped into the water to be treated W containing PFOS or PFOA, multiple bubbles (at the air-water interface) are generated. In the foam separation treatment method of this embodiment, bubbles containing surfactants such as PFOS and 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 and collected as foam B.

The gas to be pumped 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, but examples include air and nitrogen.

The method of collecting foam B using the foam collection section 31 of the collection means 30 involves positioning the opening 31a of the foam collection section 31 slightly above the water surface W1 of the water to be treated W in the storage means 10, and allowing foam B to flow into the foam collection section 31 through the opening 31a. By positioning the opening 31a of the foam collection section 31 slightly above the water surface W1 of the water to be treated W in the storage means 10, foam B that has risen to the water surface W1 of the water to be treated W can be selectively and efficiently collected.

By generating bubbles in the water to be treated W 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 quickly liquefies into liquid L. Therefore, the amount of liquid L generated by the liquefaction of foam B gradually increases in the foam collection section 31. Furthermore, when 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, which is equipped with the upper cover 11, increases due to the gas being pumped into the water to be treated W. Therefore, the liquid L generated by the liquefaction of foam B is automatically pushed through the conduit 62 to the gas-liquid separation section 61 along with the gas pumped into the water to be treated W. 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 the circulation path 63. An upper lid 11 is provided to cover the opening 10a of the storage means 10, maintaining airtightness within the storage means 10. This allows the power of the blower 22 used in the bubble generation means to be used to recover foam B, and furthermore, the gas separated in the gas-liquid separation section 61 can be returned to the water to be treated W via the blower 22 and recycled to generate foam B. This reduces the amount of gas used.

Because the water level of the water W to be treated within 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, as shown in FIG. 1, for example, 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. The position of the opening 31a of the foam collection unit 31 is adjusted in accordance with the amount of water level fluctuation measured by the water level measurement means 40 so that the position is slightly higher (height) than 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 slightly floating on the water surface W1 of the water W to be treated.

According to the foam separation treatment method of this embodiment, bubbles are generated by injecting gas into the water to be treated W in the storage means 10, so the diffusion range of the bubbles generated by the gas injected into the water to be treated W in the storage means 10 can be expanded over a wide range. This allows foam B to be efficiently generated in the water to be treated W in the storage means 10.

Furthermore, according to the foam separation treatment method of this embodiment, surfactant is concentrated at the air-water interface of the 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, thereby enabling efficient collection of foam B that has risen to the water surface W1 of the water to be treated W.

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 that do not deviate from the gist of the present invention are naturally included within the scope of the present invention. Furthermore, for example, if each embodiment includes multiple configurations, it naturally includes all possible combinations of these configurations even if not specifically stated. Furthermore, if multiple examples or variants are disclosed in an embodiment as part of the present invention, it naturally includes all possible combinations of configurations across these, even if not specifically stated. Furthermore, it naturally includes configurations depicted in the drawings even if not specifically stated. Furthermore, when the term "etc." is used, it is used to mean including equivalents.

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 can also be suitably used when separating various surfactants contained in stored treated water from the water at a location other than the in-situ.

1 Foam separation treatment device 10 Storage means 11 Upper cover 20 Air bubble generating means 21 Air supply pipe 22 Blower 30 Recovery means 31 Foam recovery 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 path

Claims (6)

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 . 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,
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. The foam separation treatment device according to claim 1 or 2 , wherein the foam collection section has a strainer near the opening. The foam separation treatment device according to claim 1 , wherein the foam collection section collects the foam by utilizing power used in the foam generation means. 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. 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, 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 .