JP7545681B2 - Red tide control agent, red tide control agent manufacturing device, red tide control agent manufacturing method and red tide control method - Google Patents

Description

The present invention relates to a red tide control agent, a red tide control agent manufacturing device, a red tide control agent manufacturing method, and a red tide control method.

In aquaculture areas, plankton such as Chattonella, which causes red tides, can grow abnormally. This abnormal growth of plankton not only reduces the dissolved oxygen concentration in seawater, but can also physically suffocate fish by clogging their gills. Abnormal plankton growth has a major impact on seafood, causing major damage to the fishing industry, especially aquaculture sites.

Various red tide control agents have been developed to control red tides. For example, Patent Document 1 discloses a red tide control agent that uses an alkaline earth metal silicate as an active ingredient. In addition, Non-Patent Document 1 discloses that adding burnt alum to montmorillonite clay improves the control effect against Chattonella per unit of clay.

JP 2002-187807 A

Yano, "To prevent red tide damage!", Ushio, Kagoshima Prefectural Fisheries Technology Development Center, March 2017, No. 352, p1-2

As described in Non-Patent Document 1, red tide control agents have been improved, but currently, large amounts of red tide control agents are needed to prevent damage to fisheries. In order to reduce the cost of suppressing red tides, there is a demand for red tide control agents that can efficiently remove plankton.

The present invention was made in consideration of the above circumstances, and aims to provide a red tide control agent that can efficiently remove plankton, a manufacturing device for the red tide control agent, a manufacturing method for the red tide control agent, and a red tide control method.

The inventors focused on the tendency of conventional red tide control agents to aggregate in seawater and conducted extensive research. They discovered that the application of fine bubbles dramatically improves the plankton control ability of plankton removal agents, and thus completed the present invention.

The red tide control agent according to the first aspect of the present invention comprises:
A liquid containing supersaturated carbon dioxide;
A plankton removing agent contained in the liquid;
Fine bubbles in the liquid suppress aggregation of the plankton removal agent and form flocs of the plankton removal agent and plankton;
Includes.

In this case, the fine bubbles are
Including carbon dioxide,
This may also be the case.

In addition, the plankton removing agent is
A montmorillonite clay and anhydrous potassium aluminum sulfate.
This may also be the case.

The concentration ratio of the montmorillonite clay to the anhydrous potassium aluminum sulfate in the liquid is:
The ratio is 10:1.
This may also be the case.

The apparatus for producing a red tide control agent according to the second aspect of the present invention comprises:
The apparatus includes a bubble generating unit that generates fine bubbles containing carbon dioxide in a liquid containing a plankton removing agent , thereby making the liquid contain supersaturated carbon dioxide .

A method for producing a red tide control agent according to a third aspect of the present invention comprises the steps of:
The method includes a bubble generating step of generating fine bubbles containing carbon dioxide in a liquid containing a plankton removing agent , thereby making the liquid contain supersaturated carbon dioxide .

The red tide control method according to the fourth aspect of the present invention comprises:
The method includes a spraying step of spraying the red tide control agent according to the first aspect of the present invention on the sea surface or in the sea.

According to the present invention, plankton can be removed efficiently.

1 is a schematic diagram showing a configuration of a red tide control agent manufacturing apparatus according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing a narrowing portion and the front and rear portions thereof; FIG. 1A and 1B are diagrams showing the configuration of a bubble generating unit and the state of fine bubbles discharged from the bubble generating unit. FIG. 1 is a diagram showing sterilized seawater containing a plankton removing agent. FIG. 1 shows sterilized seawater in which a plankton removal agent has been dissolved and fine bubbles have been generated. FIG. 2 is a diagram showing the appearance of Chattonella observed in Example 1. FIG. 2 is a diagram showing the appearance of Shutnerra observed in a comparative example.

The following describes an embodiment of the present invention with reference to the drawings. Note that the present invention is not limited to the following embodiment and drawings.

(Embodiment)
The red tide control agent according to the present embodiment includes a plankton removing agent contained in a liquid and fine bubbles in the liquid. The liquid is not particularly limited as long as it does not affect the effect of the plankton removing agent. Since the red tide control agent is mainly sprayed in the sea, the liquid is preferably water or seawater in consideration of the impact on the environment.

As the plankton removing agent, a known agent having the effect of inhibiting growth, inhibiting proliferation, and killing plankton that causes red tides can be used. For example, the plankton removing agent includes clay containing aluminum (Al). When the clay is sprayed into seawater, the pH of the seawater decreases, and Al ions are eluted from the clay. The Al ions destroy the cells of the plankton. Examples of the clay include montmorillonite clay, activated clay, acid clay, bentonite A, and bentonite B. As the clay, montmorillonite clay is particularly preferable. The montmorillonite clay is mainly composed of aluminum silicate. More specifically, the montmorillonite clay is montmorillonite produced in Iriki-cho, Satsumasendai City, Kagoshima Prefecture. The montmorillonite includes SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO, MgO, K ₂ O, and Na ₂ O.

The plankton remover may contain a substance that promotes the elution of Al ions from clay. Such substances include potassium aluminum sulfate, particularly its anhydride. Preferably, the plankton remover contains montmorillonite clay and potassium aluminum sulfate anhydride. Potassium aluminum sulfate is a double salt containing potassium ions, hydrated aluminum ions, and sulfate ions. Potassium aluminum sulfate is also called potassium alum. Potassium aluminum sulfate anhydride is strongly acidic and is also called burnt alum.

The concentration of the plankton remover in the red tide control agent according to this embodiment is not particularly limited. For example, the concentration of the plankton remover in the liquid is 10 to 10,000 mg/L, 100 to 5,000 mg/L, 150 to 3,000 mg/L, 200 to 2,000 mg/L, or 250 to 1,500 mg/L. When the plankton remover contains montmorillonite clay and anhydrous potassium aluminum sulfate, the concentration of the montmorillonite clay in the liquid is, for example, 100 to 2,000 mg/L, 150 to 1,500 mg/L, 200 to 1,200 mg/L, or 250 to 1,000 mg/L. On the other hand, the concentration of the anhydrous potassium aluminum sulfate in the liquid is, for example, 10 to 200 mg/L, 15 to 150 mg/L, 20 to 120 mg/L, or 25 to 100 mg/L.

When the red tide control agent according to this embodiment contains montmorillonite clay and anhydrous potassium aluminum sulfate as a plankton removing agent, the concentration ratio of the montmorillonite clay to the anhydrous potassium aluminum sulfate in the liquid is adjusted as appropriate, and is, for example, 1 to 100:1, 2 to 80:1, 3 to 60:1, 4 to 40:1, or 5 to 20:1. The concentration ratio of the montmorillonite clay to the anhydrous potassium aluminum sulfate is preferably 8 to 12:1, and particularly preferably 10:1.

The amount of the red tide control agent used in this embodiment is not particularly limited. When the red tide control agent is sprayed on the sea surface or underwater, it is set appropriately depending on the area of the sea surface over which the red tide control agent is sprayed, etc.

Fine bubbles suppress the aggregation of the plankton removal agent described above. Fine bubbles are minute bubbles with a diameter of 100 μm or less. Fine bubbles may include ultrafine bubbles, which are bubbles with a diameter of less than 1 μm. There are no limitations on the method of generating fine bubbles, and any generation method can be used. Methods of generating fine bubbles include a method of generating fine bubbles by passing a gas through a porous membrane and a method of generating fine bubbles through ultrasound, as well as a method using a shear flow and a method using pressurized dissolution.

A red tide control agent manufacturing apparatus (hereinafter, simply referred to as "manufacturing apparatus") 1 suitable for manufacturing the red tide control agent according to this embodiment will be described. FIG. 1 shows the configuration of the manufacturing apparatus 1. The manufacturing apparatus 1 is an apparatus that generates fine bubbles 5 in an aquarium 4 that contains seawater 3 containing a plankton removing agent 2. The manufacturing apparatus 1 includes piping 6, a pump 7, and a bubble generating unit 8.

One end of the pipe 6 is placed in the seawater 3 of the tank 4. The pipe 6 has a circulation structure that extends from inside the tank 4 to the outside and returns to the tank 4. Outside the tank 4, a pump 7 is inserted into the pipe 6. The pump 7 is a liquid pump. When the pump 7 is driven, the seawater 3 in the tank 4 is sucked into the pipe 6 and returns to the tank 4 via the pump 7. A commercially available pump can be used as the pump 7. A gas inlet 9 for taking air into the pipe 6 is provided on the primary side of the pump 7 in the pipe 6.

The pump pressure of the pump 7 is not particularly limited, but may be less than 1.0 MPa, for example, 0.2 to 0.8 MPa, 0.3 to 0.6 MPa, or 0.3 to 0.5 MPa. When the seawater 3 containing the plankton remover 2 is sucked into the pump 7, the suction force (negative pressure generated on the primary side of the pump 7) causes gas to enter from the outside through the gas inlet 9 and mix with the seawater 3. Therefore, the seawater 3 flowing from the pump 7 to the piping 6 (seawater 3 on the secondary side of the pump 7) comes to contain gas components.

The bubble generating unit 8 generates fine bubbles 5 in the seawater 3. The bubble generating unit 8 is attached to the other end of the pipe 6, i.e., the discharge part of the seawater 3, and discharges the seawater 3 containing the fine bubbles 5 and the plankton removing agent 2 into the water tank 4. The bubble generating unit 8 has a structure in which a plurality of metal capillaries 10 are bundled in parallel. The spaces between the metal capillaries 10 are sealed with a binder member 11 with both ends of each metal capillary 10 open. The seawater 3 leaving the other end of the pipe 6 passes through the inside of one of the metal capillaries 10 of the bubble generating unit 8 and is discharged into the water tank 4.

The metal capillary 10 has a plurality of narrowed portions 12, which are flattened portions as shown in FIG. 2. In the narrowed portions 12, a cross section of the metal capillary 10 cut along a plane perpendicular to the flow direction of the seawater 3 has a flattened (rectangular) shape. The narrowed portions 12 are formed in the metal capillary 10 by pressing.

Fine bubbles 5 are generated in the constriction section 12 by the following four actions:

(1) Pressurized dissolution by pressure feeding The water pressure flowing upstream of the throttle section 12 due to pressure feeding by the pump pressure of the pump 7 increases due to a decrease in the cross-sectional area (hereinafter also simply referred to as "cross-sectional area") of the metal capillary 10, dissolving the air components contained in the seawater 3 into the seawater 3. At this point, large air bubbles in the seawater 3 disappear. When the seawater 3 from which the air bubbles have disappeared enters the throttle section 12, the flow rate of the seawater 3 increases and its pressure decreases. This decrease in pressure causes small air bubbles to precipitate.

(2) Bubble nucleation by negative pressure In the constriction 12, the flow velocity of the seawater 3 increases, generating a negative pressure lower than atmospheric pressure. As a result, in addition to the phenomenon of the pressure-dissolved gas bubbles precipitating, fine bubble nuclei are generated in the water flow. This phenomenon of bubble nuclei generation is called cavitation.

(3) Crushing of Air Bubbles by Shear Flow In the portion of the metal capillary 10 other than the constricted portion 12, the Reynolds number is, for example, about 3.5×10 ³ , whereas in the constricted portion 12, the Reynolds number is, for example, about 2.9×10 ⁴ , which is very high. As a result, the inside of the constricted portion 12 becomes a fully developed turbulent flow region. The turbulent flow subjects the air bubbles to shear force and destroys them. Furthermore, the plankton-removing agent 2 that has formed aggregates is broken down by this shear force.

(4) Crushing of Air Bubbles by Shock Waves In the metal capillary 10, except for the constricted portion 12, the flow of seawater 3 has a subsonic Mach number of, for example, 0.007. In contrast, in the constricted portion 12, the Mach number is, for example, 0.7 or more, resulting in a transonic flow. In some flow regions of the transonic flow, the flow exceeds the speed of sound, generating shock waves. These shock waves further break down the air bubbles. These shock waves also break down the plankton removing agent 2 that has formed aggregates.

The longer the length of the constriction section 12 in the flow direction, the greater the pressure loss of the pump pressure in the constriction section 12, so it is necessary to increase the pump pressure of the pump 7. Therefore, in the metal capillary 10, the length of the seawater 3 in the constriction section 12 in the flow direction is set to the minimum length at which (2) the precipitation of bubbles due to a drop in pressure and (3) the crushing of bubbles due to the shear force of the turbulent flow occur.

As shown in FIG. 3, the metal capillary 10 has multiple throttle sections 12 arranged in series at intervals. In each throttle section 12, the above phenomena (1) to (4) occur, which repeatedly generates fine bubbles. The diameter of the generated bubbles gradually decreases as they pass through each throttle section 12, and ultimately become fine bubbles 5. In each throttle section 12, the plankton remover 2 is broken down into primary particles, and the fine bubbles 5 suppress the aggregation of the plankton remover 2.

In one metal capillary 10, the distance D1 between adjacent constricted sections 12 is long enough for the flow rate of the seawater 3 leaving the constricted section 12 to return to the flow rate of the seawater 3 input into the metal capillary 10. In this way, the above phenomena (1) to (4) can be reliably generated in each constricted section 12.

Also, as shown in FIG. 3, in the bubble generating section 8, multiple metal capillaries 10 may be provided in parallel in the flow path of the seawater 3. In this way, fine bubbles 5 can be generated simultaneously in each metal capillary 10, so that the amount of fine bubbles 5 generated can be easily increased.

In the bubble generating section 8, the binder member 11 is sealed in while maintaining the distance D2 between the metal capillaries 10. In this way, the fine bubbles 5 discharged from each metal capillary 10 do not interfere with each other, and the bubbles can be prevented from adhering to each other and merging.

The gas introduced from the gas inlet 9 may be air, oxygen, or carbon dioxide, or a mixture of these. The gas introduced from the gas inlet 9 is preferably carbon dioxide. When the fine bubbles 5 contain carbon dioxide, carbon dioxide dissolves in the seawater 3 at a level above the saturation solubility. As a result, the seawater 3 contains supersaturated carbon dioxide.

The red tide prevention agent according to this embodiment is obtained by circulating seawater 3 containing plankton removal agent 2 in an aquarium 4 through piping 6 and a bubble generating unit 8.

The plankton that is the target of control by the red tide control agent of this embodiment is one that can occur in the sea or rivers, etc., and is particularly algae. The plankton to be controlled includes Chattonella spp., Chattonella antiqua, Chattonella marina, Heterosigma akashio, Alexandrium spp., Gymnodinium spp., Heterocapsa circularisquama, Karenia spp., Karenia brevis, Karenia mikimotoi, and others. mikimotoi), Prorocentrum spp., Prorocentrum micans, Pseudochattonella verruculosa, Cochlodinium polykrikoides, and Mesodinium rubrum.

The red tide control agent according to this embodiment is sprayed into the sea, a river, or a stream. The method of spraying is not particularly limited. A method of preventing red tides in the sea includes a spraying step of spraying the red tide control agent according to this embodiment onto the sea surface or into the sea.

As shown in the examples below, the fine bubbles 5 form flocs of the plankton removing agent 2 and the plankton. The fine bubbles 5 act as a site for the formation of flocs, allowing the plankton removing agent 2 to be directly adsorbed onto the plankton, resulting in chemical and physical effects of the plankton removing agent 2. This allows the plankton to be removed efficiently.

In addition, in the above red tide control agent, the fine bubbles 5 may contain carbon dioxide, and the seawater 3 may contain supersaturated carbon dioxide. The pH of the seawater 3 containing supersaturated carbon dioxide is lower than the pH of seawater not containing supersaturated carbon dioxide. When the plankton removal agent 2 contains clay, the lowering of the pH further promotes the elution of Al ions from the clay. Furthermore, the increased concentration of dissolved carbon dioxide in the seawater 3 improves the control effect against plankton. As a result, the plankton removal ability of the red tide control agent can be dramatically improved.

The plankton removal agent 2 in the red tide control agent may contain montmorillonite clay and anhydrous potassium aluminum sulfate. By using the plankton removal agent 2 in combination with fine bubbles 5, plankton can be efficiently killed, as shown in Examples 1, 4, and 5 below.

Furthermore, according to the manufacturing device 1, a constriction section 12 is provided inside the metal capillary 10, where the water passage is narrower than in the front and rear of the water flow direction. Therefore, when seawater 3 containing gas components is flowed into the metal capillary 10 by the pump 7, fine bubbles 5 including ultrafine bubbles can be generated by the combined effects of (1) pressurized dissolution by pressure feeding, (2) bubble nucleation by negative pressure, (3) bubble crushing by shear flow, and (4) bubble crushing by shock waves.

In other words, fine bubbles 5 can be generated by the combined action of the various principles described above simply by passing seawater 3 through a metal capillary 10 with a simple structure and a throttle section 12. Therefore, fine bubbles 5 with smaller diameters can be generated in large quantities in a short time and at high density at, for example, about 0.3 MPa without requiring a high pump discharge pressure (1.0 MPa).

The cross-sectional shape of the constriction portion 12 may be a polygonal shape such as a circle, an ellipse, a star, or a triangle. The intervals between the constriction portions 12 may or may not be uniform. The number of constriction portions 12 in each metal capillary 10 is optional.

The seawater 3 may be sterilized seawater obtained by sterilizing or disinfecting seawater using a known method. The liquid in the water tank 4 is not limited to seawater 3, and may be water or a highly viscous liquid.

The constriction portion 12 may be formed at only one location on the metal capillary 10. The size, length, number, and spacing of the constriction portions 12 in one metal capillary 10 are determined by the pump pressure of the pump 7, and the design information for the constriction portions 12 can be easily determined by fluid analysis simulation software.

In addition, in the above embodiment, the drawn portion 12 is formed by pressing, but the drawn portion 12 may be formed by other methods.

Another embodiment of the red tide control agent manufacturing device includes a tubular member through which a liquid containing a plankton removing agent passes, and a pump that pumps the liquid containing a gas component into the tubular member. A throttle section is provided inside the tubular member, where the passage of the liquid is narrower than the front and rear of the liquid in the flow direction. In the red tide control agent manufacturing device, the gas components contained in the liquid are dissolved in the liquid by pumping the liquid to the throttle section, and then bubbles are precipitated by reducing the pressure in the throttle section, a negative pressure lower than atmospheric pressure is generated in the throttle section to generate bubble nuclei, turbulence is generated in the liquid in the throttle section, the bubbles in the liquid are crushed by the shear force, and the plankton removing agent is disintegrated, and the bubbles are crushed by shock waves caused by transonic flow generated in the liquid exiting the throttle section, and the plankton removing agent is disintegrated. The liquid containing the plankton removing agent, in which bubbles are generated by passing through the throttle section, is discharged from the tubular member. Preferably, the cross-sectional shape of the constriction section perpendicular to the flow direction is flat, particularly rectangular.

The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited to these examples.

A plankton remover containing montmorillonite (Iriki Montmori, manufactured by Iriki Kaolin Co., Ltd.) produced in Iriki-cho, Satsumasendai City, and burnt alum was dissolved at 33% or 10% by weight in sterilized seawater containing 5,000 to 10,000 cells/mL of Chattonella antica collected from the Yatsushiro Sea and subcultured. The sterilized seawater was circulated for 10 minutes in a manufacturing device with the same configuration as the above-mentioned manufacturing device 1, which was self-suctioned with gas, to generate fine bubbles in the sterilized seawater and obtain a preparation liquid.

In the manufacturing apparatus used in this embodiment, the number of metal capillaries 10 in the bubble generating section 8 was one, and the diameter of the cross-sectional area of the metal capillary 10 other than the constricted section 12 was 24 mm. The number of constricted sections 12 in one metal capillary 10 was one. The cross-sectional shape and size of the constricted section 12 was a rectangle of 32 mm x 2 mm, and the length of the constricted section 12 was 1 mm. The pump pressure of the pump 4 was 0.3 MPa, the liquid flow rate was 20 L/min, and the temperature of the sterilized seawater was controlled to be 25°C or lower.

A given amount of the preparation was added to the sterilized seawater containing Chattonella and left to stand for 10 minutes. Using a plankton counting plate and a microscope, the reduction rate of Chattonella before and after treatment was determined. The effect of the plankton remover on Chattonella was also observed.

(result)
Table 1 shows the conditions of the comparative example and Examples 1 to 5 and the reduction rate of Shuttonella. In the comparative example where fine bubbles were not generated, Shuttonella was hardly removed and no effect was obtained. On the other hand, in Example 1 where fine bubbles were generated, no Shuttonella was visible under a microscope and the removal rate was 100%. Although not containing a plankton removing agent, Example 2 where fine bubbles were generated using carbon dioxide as gas showed a reduction rate of 30%, whereas in Example 3 where the gas was air or oxygen, the death behavior of Shuttonella was observed under a microscope but the reduction rate was 0%. Even in Example 4 where the concentration of the plankton removing agent was 1/3 to 1/4 of that in Example 1, the reduction rate was 90% or more. In Example 5 where the amount of plankton removing agent used was 10% by weight, the reduction rate was 30%.

As shown in Figure 4, in the sterilized seawater in which the plankton removal agent was dissolved, the plankton removal agent formed aggregates, whereas in Examples 1, 4, and 5, as shown in Figure 5, the fine bubbles broke the plankton removal agent down to primary particles.

Figure 6 shows Shuttonella observed in Example 1. In Example 1, the Shuttonella was coated with the crushed plankton remover, which stopped the movement of the Shuttonella and accelerated its death. It is believed that the fine bubbles act as a site for the formation of flocs of the plankton remover and Shuttonella, allowing the plankton remover 2 to directly adsorb to the plankton, resulting in the chemical and physical action of the Al ions from the plankton remover 2. Figure 7 shows Shuttonella observed in the comparative example. When fine bubbles were not used, the plankton remover was not adsorbed to the Shuttonella and the plankton swam freely.

When the gas is carbon dioxide, carbon dioxide is dissolved in the preparation liquid at levels above its saturation solubility, and the pH of the preparation liquid also drops. Comparing Example 2, which does not contain a plankton removal agent, with Example 3, there was no reduction in Shuttonella in Example 3, which used air or oxygen as the gas, whereas there was a reduction in Shuttonella in Example 2, which used carbon dioxide as the gas. This shows that the ability to remove Shuttonella can also be improved by adjusting the dissolved gas concentration and pH near the Shuttonella using fine bubbles.

The above shows that the use of fine bubbles dramatically improves the plankton removal agent's plankton control ability. In addition, the use of fine bubbles makes it possible to reduce the amount of plankton removal agent used.

The above-described embodiment is intended to explain the present invention, and does not limit the scope of the present invention. In other words, the scope of the present invention is indicated by the claims, not by the embodiment. Furthermore, various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

The present invention is suitable for use as a red tide control agent in fisheries such as aquaculture.

1 Red tide control agent manufacturing device, 2 Plankton removal agent, 3 Seawater, 4 Water tank, 5 Fine bubbles, 6 Piping, 7 Pump, 8 Bubble generating section, 9 Gas inlet, 10 Metal tube, 11 Binder member, 12 Constriction section

Claims (7)

A liquid containing supersaturated carbon dioxide;
A plankton removing agent contained in the liquid;
Fine bubbles in the liquid suppress aggregation of the plankton removal agent and form flocs of the plankton removal agent and plankton;
A red tide control agent comprising: The fine bubbles are
Including carbon dioxide,
The red tide control agent according to claim 1. The plankton removing agent is
A montmorillonite clay and anhydrous potassium aluminum sulfate.
The red tide control agent according to claim 1 or 2. The concentration ratio of the montmorillonite clay to the anhydrous potassium aluminum sulfate in the liquid is
The ratio is 10:1.
The red tide control agent according to claim 3. A bubble generating unit is provided which generates fine bubbles containing carbon dioxide in a liquid containing a plankton removing agent and causes the liquid to contain supersaturated carbon dioxide .
Red tide control agent manufacturing equipment. The method includes a bubble generating step of generating fine bubbles containing carbon dioxide in a liquid containing a plankton removing agent and causing the liquid to contain supersaturated carbon dioxide .
A method for producing a red tide control agent. The method includes a spraying step of spraying the red tide control agent according to any one of claims 1 to 4 on the sea surface or in the sea.
Red tide control methods.

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