JP7410490B2 - Closed land aquaculture equipment and land aquaculture method using the same - Google Patents

Description

The present invention relates to a closed land aquaculture device and a land aquaculture method using the same.

Various closed land aquaculture methods have been proposed in which aquaculture water is filtered and circulated in a land aquaculture pond to cultivate farmed products such as crustaceans such as shrimp and crabs or fish. On the other hand, proposals have also been made to promote the growth of shrimp and other cultured products by cultivating them while forming microbubbles, nanobubbles, or other microbubbles in the culture water. For example, in Patent Documents 1 and 2, microbubbles are generated using a cavitation nozzle in which a screw member is arranged in the aperture hole. Here, in the case of fish and crustaceans that take in dissolved oxygen through gill respiration, it is recognized that it is advantageous for the oxygen concentration in the culture water to be as high as possible. Additionally, since cavitation nozzles consume dissolved oxygen and turn it into fine bubbles through reduced-pressure boiling, it is thought that the oxygen concentration in the aquaculture water should be high to compensate for the loss of dissolved oxygen due to the surfacing of coarse bubbles. .

In Patent Documents 1 and 2, air (oxygen) or ozone is gas-liquid mixed with culture water using an aspirator, and then subjected to pressurized dissolution treatment to supersaturation in a tank, and then introduced to a cavitation nozzle. Therefore, it is thought that the oxygen concentration of the culture water in the culture pond is maintained at almost the saturated value (8 ppm), and the microbubbles containing a large amount of oxygen generated by cavitation are In this case, re-dissolution is difficult to proceed, so it is thought that the bubbles remain in the bubble state until they are lost due to levitation. These oxygen microbubbles are expected to function as an "oxygen reservoir," so to speak, to supplement the consumption of dissolved oxygen by the cultivated material.

Japanese Patent Application Publication No. 2011-240206 Japanese Patent Application Publication No. 2012-40448

“Analysis of nanobubbles in nanobubbles in water” Nanotech Japan Bulletin Vol. 8, No. 4, 2015

However, the inventor's detailed study revealed that if a large number of microbubbles are suspended in the aquaculture water, the bubbles will adhere to the gills of fish, shrimp, crabs, and other cultured animals, and the uptake of dissolved oxygen will be reduced. It has been found that the growth of the cultured objects is actually hindered, and in severe cases, this can lead to the death of a considerable number of the cultured objects.

The object of the present invention is to provide a closed land-based aquaculture device that can promote the growth of cultivated products without any problems while preventing excessive generation of microbubbles accompanying cavitation treatment of aquaculture water, and a land-based aquaculture device using the same. The objective is to provide a cultivation method.

In order to solve the above problems, the closed land aquaculture device of the present invention accommodates culture water and cultured animals such as crustaceans or fish in an aquaculture pond, and uses a main pump to pump the aquaculture water from the aquaculture pond. In a closed land aquaculture system, the aquaculture water is introduced into a filtration tank to filter out organic residues floating in the aquaculture water, and then circulated back into the aquaculture pond. The oxygen dissolving mechanism supplies and dissolves oxygen-containing gas to the aquaculture water so that the oxygen concentration is maintained at 2.5 ppm or more and 7 ppm or less, and the inlet of the aquaculture water communicates with the aquaculture pond, and the other end is connected to the aquaculture pond. A cavitation treatment pipe is used as a return port for water to the aquaculture pond, and a nozzle flow path is provided in the middle of the cavitation treatment pipe and has an inlet of the aquaculture water at one end and an outlet of the aquaculture water at the other end. and a nozzle body in which a part of the nozzle flow path is defined as a cavitation treatment section, and a plurality of screw members that are assembled to the nozzle body in the cavitation treatment section so that the tip ends of the legs protrude inside the flow path. By making the culture water flow from the culture water inlet to the culture water outlet, and bringing the culture water into contact with the thread valley formed on the outer peripheral surface of the leg of the threaded member in the cavitation treatment part while increasing the speed. , a cavitation nozzle that performs cavitation treatment based on reduced pressure precipitation of dissolved air on the culture water, and a cavitation nozzle installed in the middle of the cavitation treatment piping, and configured to supply the culture water to the cavitation nozzle at an average cross-sectional flow velocity of 8 m/sec or more in the cavitation treatment section. The invention is characterized by comprising a cavitation treatment pump that causes the flow to flow at a specified flow rate.

Furthermore, the terrestrial aquaculture method of the present invention uses the closed type terrestrial aquaculture device of the present invention described above, houses culture water and cultured animals in an aquaculture pond, and uses a main pump to transfer the aquaculture water from the aquaculture pond to a filter tank. The method is characterized in that the organic residues floating in the aquaculture water are filtered and circulated back into the aquaculture pond, and feed is introduced into the aquaculture pond to raise the farmed animals.

The oxygen-containing gas that can be used in the present invention is, for example, air, oxygen gas, or oxygen-enriched air obtained by concentrating oxygen using a well-known oxygen concentrator, etc., and the remainder other than oxygen is composed of an inert gas such as nitrogen. It is better to do so. Note that the oxygen concentration in the oxygen-containing gas is not particularly limited as long as it is, for example, 20% by volume or more, which corresponds to the atmospheric composition.

In the present invention, the oxygen concentration in culture water that decreases due to consumption by the cultivated product is compensated for by an oxygen dissolution mechanism, and the oxygen concentration in culture water is maintained at 2.5 ppm or more and 7 ppm or less, which is less than the saturation value. Then, the culture water is guided by a cavitation treatment pump to a cavitation nozzle through cavitation treatment piping, and is caused to flow at a specified flow rate such that the cross-sectional average flow velocity in the cavitation treatment section is 8 m/sec or more, thereby performing cavitation treatment. By intentionally maintaining the oxygen concentration in the culture water below the saturation value, excessive generation of microbubbles due to cavitation is suppressed, and problems such as bubbles adhering to the gills of the cultured animals inhibiting the uptake of dissolved oxygen. can be effectively prevented.

By ensuring a specified flow rate with a cross-sectional average flow velocity of 8 m/sec or more in the cavitation treatment section, the growth of cultivated products is promoted even though the oxygen concentration of the aquaculture water is set lower than in conventional technology. etc. can be achieved without any problem. If the flow velocity of the cavitation treatment section is maintained within the above range, cavitation accompanied by the generation of microbubbles can be confirmed particularly at the thread root position of the threaded member. However, if the oxygen concentration of the culture water is below the saturation value as mentioned above, the bubbles (especially those with a bubble diameter of 100 nm or more) generated by forced vacuum supersaturated precipitation due to cavitation will not pass through the nozzle. It has been found that re-dissolution occurs rapidly when the particles are returned to the aquaculture pond, and most of them become unobservable after a few minutes using well-known bubble diameter measurement methods (for example, those using a laser scattering particle size meter). ing.

It is clear that if such aquaculture water is used, it is possible to make it difficult for microbubbles to adhere to the gills of the cultivated animals. However, if the absolute value of oxygen concentration in the culture water is lowered, there is a concern that the activity of the cultured animals will be significantly impaired. However, as a result of detailed study by the present inventors, when culture water with oxygen concentration suppressed to the above range is subjected to cavitation treatment, compared to normal culture water with higher oxygen concentration (aquaculture without cavitation treatment), It was found that the activity and growth activity of the cultivated animals were increased to a greater extent than this, and that the fatigue peculiar to oxygen deficiency was hardly observed.

The detailed mechanism is unknown, but ultrafine products of less than 10 nm, which are unique to cavitation processing, are involved, and no effective observation means have been found at this time, and water containing dissolved oxygen penetrates into living tissues. performance may have been significantly improved. For example, the effect of improving permeability obtained by cavitating tap water, etc. does not change significantly even after about one day after the cavitation treatment, so the product can exist continuously in water for a certain period of time. It is also considered to have a form.

Further, even when oxygen bubbles of 100 nm or more are reduced in size due to redissolution, there is a high possibility that the bubbles will not completely dissolve and disappear in the end, but that the above-mentioned products will remain in the water. For example, in Non-Patent Document 1, as a result of freezing nanobubble water, which is a gas-liquid mixture of outside air and water using a swirling flow, and observing it with an ultra-high-pressure electron microscope, it was found that a large amount of bubble-like products with an average diameter of around 7 nm were present. It has been reported that. Although the composition of the observed product and whether or not it is a bubble is unclear, and the causal relationship with the action and effect of the present invention is also unclear, bubbles are precipitated starting from fine nucleation. In the case of cavitation-treated water, it seems likely that similar fine products would be observed at even higher densities. Even if the product is mainly composed of oxygen gas, considering that the surface tension of extremely small bubbles is assumed to be quite high, it is likely that the product is a solid compound of oxygen and water (hydrocarbons). rate, etc.).

In any case, it has been experimentally revealed that there is a significant difference in the activity and growth activity of cultured animals between cavitation-treated culture water and normal culture water. If the permeability of the water itself, which mediates the absorption of dissolved oxygen (for example, the permeability to the capillaries in the dissolved oxygen absorbing organs such as the gills of aquatic organisms), is improved, even water with a somewhat low oxygen concentration can be used. It is also conjectured that the cultured products can efficiently absorb a limited amount of dissolved oxygen, allowing the cultured products to maintain good activity and growth activity.

If the oxygen concentration in the culture water is less than 2.5 ppm, even if the improvement in oxygen absorption efficiency through cavitation treatment is taken into consideration, the amount of oxygen absorbed by the cultured product will be insufficient, resulting in problems such as decreased activity and poor growth. This can lead to an increase in the mortality rate of farmed products as a result of continued aquaculture. On the other hand, if the oxygen concentration of the culture water exceeds 7 ppm, excessive generation of bubbles (especially bubbles with a diameter of 100 nm or more) is likely to occur due to cavitation treatment, and the activity of the cultured product is likely to decrease. When dissolving oxygen-containing gas while supplying it to culture water using an oxygen dissolution mechanism, the oxygen concentration of the culture water is more desirably maintained at 3 ppm or more and 6 ppm or less.

If the cross-sectional average flow velocity in the cavitation treatment section is less than 8 m/sec, the effect achieved by cavitation treatment will be insufficient, and as mentioned above, even if the culture water is made low in oxygen, the effect of maintaining the activity of the cultured animals will be significant. It disappears. In particular, if the cross-sectional average flow velocity falls below the above-mentioned lower limit when the oxygen concentration of the aquaculture water has decreased to, for example, 3.5 ppm or less due to factors such as the breeding density of the aquaculture target being set high, Cultivated animals are particularly susceptible to weakening and death due to lack of oxygen. More preferably, the cross-sectional average flow velocity in the cavitation treatment section is maintained at 9 m/sec or more.

The cavitation nozzle is formed so that the nozzle flow path has a circular cross section, and each cavitation treatment section has a threaded member with a thread pitch and thread depth of 0.20 mm or more and 0.40 mm or less, and a nominal thread diameter M of 1. A plurality of threaded members with a diameter of .0 mm or more and 2.0 mm or less are arranged, and a screw member within 70% of the radius of the nozzle flow path from the cross-sectional center of the nozzle flow path when projected onto a plane perpendicular to the central axis of the nozzle flow path. When defined as the 70% valley point areal density, which is the total number of valley points located in the area divided by the cross-sectional area of the nozzle flow path, the value of the 70% valley point areal density is 1.6. It is desirable to use a material with a density of at least 2.0 mm/mm ² or more.

If a cavitation nozzle with a 70% valley point area density value of less than 1.6 pieces/ ^mm2 is used, the cavitation treatment effect will be insufficient, and the activity of cultured animals can be maintained even if the culture water is made hypoxic. may become less noticeable. There is no particular upper limit to the value of the 70% valley point areal density of the cavitation nozzle, but it can be set as appropriate within a range that does not cause an increase in pressure loss or insufficient flow rate due to an extreme increase in the number of screws arranged in the cavitation treatment section (for example, , 5 pieces/mm ² ). The value of the 70% valley point area density is more desirably 2.0 pieces/mm ² or more.

When using the cavitation nozzle with the above configuration, the specified flow rate of aquaculture water to the cavitation nozzle is as follows:
K=V2/V1×100 (%)
It is preferable to adjust so that the circulation ratio K expressed by is 2% or less. Even if somewhat coarse air bubbles of 100 nm or more are generated in the cavitation nozzle, the flow rate of culture water per hour (regulated flow rate) can be kept to 2% or less of the total volume of culture water in the culture pond. The re-dissolution of air bubbles can be promoted, and the above-mentioned problems caused by adhesion to the gills, etc. of cultured objects can be further effectively suppressed. Even though the circulation ratio K of the cavitation nozzle to the total volume of aquaculture water is an extremely small value, by adopting the cavitation nozzle with the above configuration, the activity and growth activity of the cultivated product can be maintained extremely well. becomes possible. Note that if the circulation ratio K becomes extremely small, the effect of improving the activity and growth activity of the cultivated product will be insufficient. The lower limit value of the flow circulation ratio K varies depending on the 70% valley point area density of the cavitation nozzle and the set flow rate, but it is preferably set to a value of 0.5% or more, for example, so as not to impair the above effects.

The oxygen dissolution mechanism can be configured to include a multiphase flow supply section that supplies a multiphase flow of oxygen-containing gas and culture water to the cavitation nozzle in order to dissolve the oxygen-containing gas in the cavitation nozzle. In the cavitation nozzle used in the present invention, when the aquaculture water collides with the threaded member and detours downstream, it is squeezed in the thread valley, increasing the speed and causing cavitation, so that the dissolved gas components of the aquaculture water are becomes supersaturated due to negative pressure, and while bubbles are precipitated, the culture water is violently agitated, creating a turbulent region. At this time, by mixing the gas phase (gas) with the aquaculture water supplied to the turbulent area to create a multiphase flow, gas-liquid mixing and agitation progresses due to the above stirring, and the gas phase components (oxygen-containing gas) are absorbed into the aquaculture water. The dissolution can proceed effectively.

In this case, when the multiphase flow collides with the threaded member, if the entire inner space of the thread valley is covered with large bubbles, the contact efficiency between the culture water containing dissolved gas and the thread valley decreases, resulting in cavitation efficiency. (i.e., the thread valley loses its function as an effective thread valley as a cavitation point). As a result, the formation of a turbulent region that generates the driving force for mixing and stirring gas phase components becomes less pronounced, leading to a decrease in gas dissolution efficiency.

Therefore, a hollow outer cylindrical member having an inlet at one end and an outlet at the other end, and a spiral flow path provided inside the outer cylindrical member that connects the inlet and the outlet are used for the spiral flow. a channel forming member formed such that the spiral axis of the channel is along the central axis of the outer cylinder member, and a channel forming member formed on the culture water inlet side of the cavitation nozzle so that the spiral channel communicates with the nozzle channel of the cavitation nozzle. A gas-liquid mixer can be provided, and the multiphase flow supply section can be configured to supply the multiphase flow to the inlet of the gas-liquid mixer. As a result, the multiphase flow is passed through the spiral flow path of the gas-liquid mixer, and the centrifugal force of the forcedly generated spiral flow promotes stirring and mixing of the gas and liquid phases, so the gas phase is made up of fine bubbles. It is supplied to the threaded member of the cavitation nozzle in a crushed state. Thereby, the contact efficiency between the culture water and the screw valley can be increased, and the gas dissolution efficiency can be increased.

The gas-liquid mixer is desirably configured to finely pulverize bubbles to a bubble diameter of 1.5 h or less, with the thread pitch of the screw member being h (mm). If the diameter of the bubbles obtained by pulverization in the gas-liquid mixer exceeds 1.5 hours, the effect of improving gas dissolution efficiency may not be significant. The bubble diameter is more preferably 1.0 h or less. Further, there is no limit to the lower limit of the bubble diameter, but in the case of mixing and stirring using a gas-liquid mixer having a spiral flow path, about 0.2 hours may be the limit for pulverization.

The flow path forming member of the gas-liquid mixer can be configured as a twisted plate member obtained by twisting a band-shaped metal plate so that the central axis in the width direction of the metal plate is the helical axis. By using such a twisted plate member, the spiral flow path of the gas-liquid mixer can be easily and inexpensively formed. Further, by using the twisted plate member, the spiral flow path is formed by a first spiral flow path formed by a space between the first main surface of the twisted plate member and the cylindrical inner peripheral surface of the outer cylinder member, It can be configured to include a second spiral flow path formed by a space between the second main surface of the torsion plate member and the cylindrical inner circumferential surface of the outer cylinder member. Thereby, two systems of spiral flows having different rotational phases can be formed on both sides of the torsion plate member, and the gas phase crushing efficiency can be further improved with a simple structure.

It is preferable that the total length of the outer cylinder member is determined so that the spiral flow path includes a spiral section of one period or more. If the spiral section included in the spiral flow path is less than one cycle, the gas phase pulverization efficiency of the gas-liquid mixer may decrease, and the gas dissolution efficiency in the cavitation nozzle on the downstream side may become insufficient. More preferably, the total length of the outer cylindrical member is determined such that the helical flow path includes a helical section of 1.5 cycles or more, more preferably 2 cycles or more.

Further, the value of λ/Dx is set to 1.5 or more and 4 or less, where the inner diameter of the cylindrical inner peripheral surface of the outer cylinder member is Dx (mm), and the helical period length of the torsion plate member is λ (mm). It's good to be there. If the value of λ/Dx exceeds 4, the total length of the outer cylindrical member becomes too large, causing a problem when securing the number of cycles of the spiral flow path necessary to ensure the gas phase pulverization efficiency of the gas-liquid mixer. There are cases. In addition, if the value of λ/Dx is less than 1.5, the flow resistance of the spiral flow path formed by the twisted plate member becomes too large, the gas-phase pulverization efficiency of the gas-liquid mixer decreases, and cavitation occurs on the downstream side. Gas dissolution efficiency in the nozzle may be insufficient.

The effect of increasing the activity and growth activity of the cultured animals in the culture water can be achieved independently of the oxygen dissolution process by passing the oxygen-containing culture water through a cavitation nozzle. Therefore, the oxygen dissolution mechanism is provided separately from the cavitation nozzle, and includes a well-known air diffuser that injects oxygen-containing gas supplied from the outside into the aquaculture water filling the aquaculture pond so that the average bubble diameter is 0.5 mm or more. It can also be configured as having the following. Here, it is the fine air bubbles of about 100 nm to 30 μm that may have an adverse effect due to adhesion to the gills of the cultivated product, and the well-known air diffuser is advantageous in that such air bubbles are less likely to occur. . However, since the oxygen dissolution efficiency is inferior to that of a cavitation nozzle, it can be said that it is desirable to use it in combination with oxygen dissolution using a cavitation nozzle. When the flow/circulation ratio K of the cavitation nozzle to the total volume of the culture water is small as described above, the desired oxygen concentration may not be maintained by the oxygen dissolving ability of the cavitation nozzle alone. From this point of view as well, it is desirable to use the oxygen dissolution by the aeration section and the oxygen dissolution by the cavitation nozzle in combination.

In this case, it is more preferable to set the flow rate of the oxygen-containing gas supplied to the culture water by the aeration section to be larger than the flow rate of the oxygen-containing gas supplied to the cavitation nozzle. By keeping the flow rate of the oxygen-containing gas supplied to the cavitation nozzle low, it is possible to reduce the density of the above-mentioned microbubbles in the aquaculture pond, and it is possible to more effectively suppress the adverse effects caused by adhesion to the gills, etc. of the aquaculture products.

Next, cavitation nozzles generate fine bubbles by utilizing the reduced pressure boiling effect that occurs when water passes through the narrow aperture of the nozzle, so the flow rate of the water to be treated through the aperture is approximately 10 m/sec or more. It is necessary to secure a higher speed than that. However, when this cavitation nozzle is placed in the circulation path with the filtration tank as described above, if the flow resistance of the aquaculture water to the circulation path increases due to the accumulation of organic residue in the filtration tank, the aquaculture water passing through the cavitation nozzle may There is a problem that the flow rate is insufficient and the amount of microbubbles generated by cavitation is insufficient. In this case, even if a separate circulation path for cavitation treatment is provided, if the culture water is directly sucked into the nozzle, floating organic residues will clog the orifice and the generation of microbubbles will be similarly inhibited. Therefore, in order to prevent this, a new filtration part has to be installed at the entrance of the circulation path on the aquaculture pond side, so this does not solve the problem at all.

In order to solve this problem, a cavitation treatment filtration part is installed at the inlet of the cavitation treatment piping to prevent floating matter in the aquaculture pond from flowing into the cavitation treatment piping, and a The flow rate detection unit detects the flow rate of circulating aquaculture water, and the flow rate of liquid sent to the cavitation nozzle by the cavitation treatment pump is adjusted to the specified flow rate in order to compensate for the flow loss due to the accumulation of suspended matter in the cavitation treatment filtration unit. It is desirable to further add a cavitation flow rate control section to the apparatus of the present invention. A cavitation flow rate control unit is provided that monitors the flow rate of the cavitation treatment piping using a flow rate detection unit and compensates for the flow rate of liquid sent to the cavitation nozzle so that it falls within the above specified range when suspended matter accumulates in the cavitation treatment filtration unit. This makes it possible to stably maintain the advantageous effects on the cultivated product even when organic residue accumulates in the filtration section and flow resistance increases.

Here, the main pump and the cavitation treatment pump may be configured separately, or the main pump may also be used as the cavitation treatment pump. Furthermore, the cavitation treatment filtration section may be provided separately from the filtration tank, or may be configured to serve as both.

For example, it is possible to adopt the following configuration. That is, in this configuration, the inlet of the aquaculture water communicates with the filtration tank, and the main filtration pipe whose other end is the return port of the aquaculture water to the aquaculture pond, and the inlet of the main filtration pipe are provided. , and an auxiliary filtering section that suppresses floating matter in the filtration tank from flowing into the main filtration pipe, and the main pump is provided on the main filtration pipe. Further, the cavitation treatment pipe is provided in such a manner that it branches from the main filtration pipe on the downstream side of the main pump, and opens a return port to the aquaculture pond at a position different from the main filtration pipe. A distribution valve is provided that adjusts the distribution ratio between the main pipe for filtration and the pipe for cavitation treatment according to the valve opening degree. The cavitation flow rate control unit controls the opening degree of the distribution valve to increase the distribution ratio of aquaculture water to the cavitation treatment piping when the water flow rate of the main pump decreases due to accumulation of suspended matter in the auxiliary filtering unit. configured to coordinate control. In the above configuration, the main pump is also used as a cavitation treatment pump, and the auxiliary filtering section is also used as a cavitation treatment filtration section, which greatly simplifies the device configuration and controls the output of the main pump. Even without this, the flow rate of the cavitation treatment piping can be stably maintained within a specified range by adjusting the opening degree of the distribution valve.

The details of the operation and effects of the present invention have already been described in the "Means for Solving the Problems" section, so they will not be repeated here.

FIG. 1 is a conceptual diagram showing an example of a closed land aquaculture apparatus of the present invention. A cross-sectional view and a side view showing an example of a gas-liquid mixer used in the closed land aquaculture device of FIG. 1A. FIG. 1B is a cross-sectional view showing an example of a cavitation nozzle used in the closed land aquaculture apparatus shown in FIG. 1A. FIG. 1C is an axial sectional view showing the screw member layout on each screw arrangement surface of the cavitation nozzle of FIG. 1C. FIG. 3 is an axial sectional view showing an enlarged main part of FIG. 2; FIG. 1C is a cross-sectional view of a main part of the cavitation nozzle in which four sets of plane threads having the layout shown in FIG. 2 are arranged in the central axis direction. FIG. 6 is a cross-sectional view of the main parts of eight cavitation nozzles arranged in the same manner. FIG. 1C is a cross-sectional view of a main part of the cavitation nozzle shown in FIG. 1C, showing a structure in which one surface screw set is rotated by 45 degrees. FIG. 7 is a cross-sectional view of a main part of the cavitation nozzle shown in FIG. 1C, in which one surface screw set has the layout shown in FIG. 6; FIG. 8 is a cross-sectional view of a main part of the cavitation nozzle in which the surface screw set is divided into mutually orthogonal screw member pairs, and the respective positions are shifted in the central axis direction in the structure of FIG. 7 . FIG. 8 is a cross-sectional view of a main part of a cavitation nozzle in which two pairs of plane screw sets similar to the cavitation nozzle of FIG. 7 are arranged in the central axis direction. FIG. 2 is a cross-sectional view showing a state in which a venturi ejector is connected to the gas-liquid mixer of the closed land aquaculture apparatus of FIG. 1A. FIG. 3 is a block diagram showing an example of an electrical configuration of a cavitation flow rate control section. 5 is a flowchart showing the flow of processing of a flow rate control program. 5 is a flowchart showing the flow of processing of an oxygen concentration control program. FIG. 2 is an axial sectional view of the main parts of a two-hole cavitation nozzle. The figure explaining the dimensional relationship of each part of the cavitation nozzle used in the experimental example. FIG. 7 is a schematic diagram showing a modification of the distribution valve. The conceptual diagram which shows the modification of the closed land aquaculture apparatus of FIG. 1A.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1A is a conceptual diagram showing an example of a closed-type land-based aquaculture device, which is an embodiment of the present invention, along with a usage pattern. The closed land aquaculture device 300 accommodates aquaculture water W and a cultured product SP consisting of crustaceans or fish in an aquaculture pond 250, and uses a main pump 175 to transfer the aquaculture water W from the aquaculture pond 250 to a filter tank 252. This is for raising a cultured product SP by introducing feed into the aquaculture pond 250 while filtering the organic residue floating in the aquaculture water W and circulating it back into the aquaculture pond 250.

Although the cultivated product SP is shrimp in this embodiment, it may be other crustaceans such as crabs. Furthermore, other than crustaceans, fish such as red sea bream, tuna, yellowtail, trout, salmon, pufferfish, and carp may be used. In addition, when the cultivated product SP is shrimp, the type of shrimp is, for example, a shrimp belonging to the family Prawnidae, such as black tiger shrimp, vannamei shrimp, black tiger shrimp, black tiger shrimp, and oriole shrimp (common name: Japanese tiger shrimp). It is selected. In addition, the aquaculture water W can be selected from seawater (salt concentration: 3.0 to 4.0 mass%), brackish water (salt concentration: 0.05 to 3.0 mass%), and fresh water depending on the type of the cultivated product. Selected appropriately.

The closed land aquaculture device 300 is provided with an oxygen dissolving mechanism that supplies and dissolves oxygen-containing gas to the culture water W so that the oxygen concentration of the culture water W is maintained at 2.5 ppm or more and 7 ppm or less (described later). . Furthermore, the following components are provided.
- Cavitation treatment pipe 181: An inlet for aquaculture water W communicates with the aquaculture pond 250, and the other end serves as a return port for the aquaculture water W to the aquaculture pond 250.
- Cavitation nozzle 1: The structure will be explained in detail later.
- Pump for cavitation treatment: In this embodiment, the main pump 175 also serves as a pump. It is provided in the middle of the cavitation treatment pipe 181 (a part of the section on the inlet side of the main filtration pipe 180 is also used as the cavitation treatment pipe), and the culture water W is supplied to the cavitation nozzle 1. It is made to flow at a specified flow rate such that the average flow velocity is 8 m/sec or more.
- Cavitation treatment filtration part: The auxiliary filtering part 253f corresponds to this, and is provided at the inlet of the main filtration pipe (cavitation treatment pipe) 180 to prevent floating matter in the aquaculture pond 250 from entering the cavitation treatment pipe 181. Control the influx.
- Flow rate detection unit 182: Comprised of an ultrasonic flow meter or the like, and detects the flow rate of the culture water W flowing through the cavitation treatment pipe 181, for example, on the downstream side of the cavitation nozzle 1. - Control unit 185 (cavitation flow rate control unit): In order to compensate for the flow rate loss due to the accumulation of suspended matter in the cavitation treatment filtration unit 253f, the flow rate of the liquid sent to the cavitation nozzle 1 by the cavitation treatment pump 181p is adjusted to the above specified flow rate. to control.

Specifically, in this embodiment, a main filtration pipe 180 is provided, in which an inlet for aquaculture water W communicates with the filtration tank 252, and the other end serves as a return port for the aquaculture water W to the aquaculture pond 250. Further, an auxiliary filtering section 253f made of a metal net or the like is provided at the inlet of the main filtration pipe 180 to suppress floating substances in the filtration tank 252 from flowing into the main filtration pipe 180. There is. Moreover, the main pump 175 is provided on the main pipe 180 for filtration. On the other hand, the cavitation treatment pipe 181 is branched from the main filtration pipe 180 on the downstream side of the main pump 175, and has a return port for the aquaculture pond 250 opened at a different position from the main filtration pipe 180. provided.

Moreover, the closed land aquaculture apparatus 300 is provided with a distribution valve 183 that adjusts the distribution ratio between the main filtration pipe 180 and the cavitation treatment pipe 181 according to the valve opening degree. In this embodiment, the distribution valve 183 is configured as a proportional control type electromagnetic three-way valve provided at the branch point between the main filtration pipe 180 and the cavitation treatment pipe 181, but as shown in FIG. A pair of proportional control valves 183A and 183B may be provided in the main filtration pipe 180 and the cavitation treatment pipe 181, respectively, on the downstream side of the point. The cavitation flow rate control unit 185 distributes so that the distribution ratio of the culture water W to the cavitation treatment pipe 181 increases when the water flow rate of the main pump 175 decreases due to accumulation of suspended matter in the auxiliary filtering unit 253f. The opening degree of the valve 183 is adjusted and controlled. In the above configuration, the main pump 175 is also used as a cavitation treatment pump, and the auxiliary filtering section 253f is also used as a cavitation treatment filtration section.

The culture water discharged from the outlet pipe 250e of the culture pond 250 undergoes sedimentation and removal of coarse suspended matter in a settling tank 251, and the culture water W overflowing from the settling tank 251 is guided to a filter tank 252. A filter 252f made of nonwoven fabric, porous resin, or the like is arranged in the filtration tank 252, and the culture water W that has passed through the filter 252f flows down from the filtration tank 252 to the buffer layer 253. In the filtration tank 252, the filter 252f can be provided with a propagation medium layer (for example, porous ceramic) for aerobic microorganisms, and can be configured as a biofilter that decomposes organic suspended matter. On the other hand, the entrance side end of the main filtration pipe 180 is immersed in the buffer layer 253, and the opening is covered by an auxiliary filtering part 253f made of a metal net or the like. As the aquaculture pond 250 is used for a long period of time, suspended matter that cannot be removed by the filter 252f flows from the filter tank 252 into the buffer layer 253. The floating substances are separated by the auxiliary filtering section 253f, and are prevented from entering the main filtration pipe 180.

Next, the cavitation treatment piping 181 is provided with a multiphase flow supply section 165, a gas-liquid mixer 150, and a cavitation nozzle 1 in this order from the upstream side. The aquaculture water W is mixed with air as an oxygen-containing gas from the gas supply source 170 via the gas supply pipe 171 in the multiphase flow supply section 165, and the air introduced in the gas-liquid mixer 150 is further pulverized. At least a portion of the gas is dissolved in the cavitation nozzle 1 and returned to the aquaculture pond 250. This gas-liquid mixer 150 cooperates with the cavitation nozzle 1 to constitute a part of the oxygen dissolution mechanism.

FIG. 1B shows an example of the configuration of the gas-liquid mixer 150. The gas-liquid mixer 150 includes an outer cylinder member 151 and a flow path forming member 155. The outer cylinder member 151 is formed into a hollow cylindrical shape with an inlet 159 formed at one end and an outlet 160 formed at the other end. The material is, for example, metal or plastic such as polyvinyl chloride, and in this embodiment stainless steel is used. At both ends of the outer cylindrical member 151, a joint portion for connecting to another piping element, and in this embodiment, a male thread portion 152 is formed.

On the other hand, the flow path forming member 155 is provided inside the outer cylinder member 151, and the spiral flow paths 157, 158 connecting the inlet 159 and the outlet 160 are formed so that the helical axis HC of the helical flow paths 157, 158 It is formed along the central axis of the outer cylinder member 151. In this embodiment, the flow path forming member 155 is a twisted plate member (hereinafter also referred to as the twisted plate member 155) obtained by twisting a band-shaped metal plate so that the central axis O in the width direction is the helical axis HC. It can be configured as The flow path forming member 155 can be made of, for example, stainless steel (SUS316, etc.), but if seawater or brackish water is used, it may be made of a metal that has better corrosion resistance against seawater, such as titanium or a titanium alloy. More desirable.

Inside the outer cylindrical member 151, the torsion plate member 155 has a first spiral flow path 157 between the first main surface of the torsion plate member 155 and the inner peripheral surface of the outer cylindrical member 151; A second spiral flow path 158 is formed between the surface and the inner peripheral surface of the outer cylinder member 151. The total length of the outer cylindrical member 151 is determined so that the helical flow path includes a helical section 156 of one period or more, and in this embodiment, two periods. Further, the value of λ/Dx is set to 1.5 or more and 4 or less, where the inner diameter of the cylindrical inner peripheral surface of the outer cylinder member 151 is Dx (mm), and the helical period length of the torsion plate member 155 is λ (mm). has been done. Dx is, for example, 5 mm or more and 30 mm or less (for example, 15 mm), and the value of λ is, for example, 20 mm or more and 300 mm or less (for example, 50 mm). Further, the thickness of the plate material constituting the torsion plate member 155 is selected within a range not exceeding 1/4 of Dx, for example, in a range of 0.3 mm or more and 4 mm or less (for example, 1 mm).

Further, in this embodiment, an oxygen dissolving mechanism is provided separately from the cavitation nozzle 1, and the oxygen-containing gas supplied from the outside to the culture water W filling the culture pond 250 has an average bubble diameter of 0.5 mm or more. A diffuser 174 is provided in the aquaculture pond 250 to emit air in a manner similar to that shown in FIG. The air diffuser 174 has a well-known structure such as an air diffuser plate with a large number of pores, a ceramic, resin, or metal air diffuser module with a large number of communicating holes, or a swirling gas-liquid mixing type diffuser. Air as an oxygen-containing gas is supplied from the air compressor 170 via the gas supply pipe 173.

The gas supply pipe 171 heading toward the cavitation nozzle 1 (multiphase flow supply section 165) and the gas supply pipe 173 heading toward the aeration section 174 are provided with electromagnetic valves 172 and 184, respectively, and receive control signals from the control section 185. It is driven to open and close. When the electromagnetic valves 172 and 184 open, air is supplied to the cavitation nozzle 1 and the aeration unit 174, that is, oxygen is dissolved in the culture water. When the electromagnetic valves 172 and 184 are closed, air is supplied, that is, oxygen is dissolved in the culture water. Processing stops. An oxygen sensor 186 (of a well-known optical or polarographic configuration) is provided in the aquaculture pond 250, and the control unit 185 reads the oxygen concentration of the aquaculture water measured by the oxygen sensor 186, and also controls the oxygen concentration of the aquaculture water. The electromagnetic valves 172 and 184 are controlled to open and close so that the concentration is 2.5 ppm or more and 7 ppm or less (preferably 3 ppm or more and 6 ppm or less). Note that in this embodiment, the air supply flow rate to the air diffuser 174 is set to be larger than the air supply flow rate to the cavitation nozzle 1.

Next, FIG. 1C is a cross-sectional view showing an example of the cavitation nozzle 1. This cavitation nozzle 1 includes a nozzle body 2 in which a nozzle flow path 3 is formed. The nozzle body 2 is formed into a cylindrical shape, and one nozzle flow path 3 having a circular cross section is formed through the nozzle body 2 in the direction of the central axis O thereof. The nozzle channel 3 has an aquaculture water inlet 4 at one end (on the right side of the drawing) and an aquaculture water outlet 5 at the other end, and an aquaculture water inlet 4 and an aquaculture water outlet 5 at an intermediate position in the flow direction. A throttle hole 9 with a small diameter is also formed to form a part of the nozzle flow path 3. In the nozzle flow path 3, the side closer to the aquaculture water inlet 4 than the throttle hole 9 is an inflow chamber 6, and the side closer to the aquaculture water outlet 5 is an outflow chamber 7. A screw member 10 is attached to the throttle hole 9 so that the tip end of the leg protrudes inside the flow path, thereby forming a cavitation treatment section CV.

The material of the nozzle body 2 is, for example, a resin such as ABS, nylon, polycarbonate, polyacetal, polyvinyl chloride, or PTFE, but it is also composed of a metal such as titanium or a titanium alloy, stainless steel, or even a ceramic such as alumina. Further, the material of the screw member 10 is, for example, stainless steel such as SUS316, but when seawater or brackish water is used, it is more preferable to use a metal such as titanium or a titanium alloy that has better corrosion resistance against seawater. It is also possible to use ceramic materials such as quartz and alumina.

The threaded member 10 used has a thread pitch and thread root depth of 0.20 mm or more and 0.40 mm or less, and a nominal thread diameter M of 1.0 mm or more and 2.0 mm or less. In this embodiment, the screw member 10 is a No. 0 class 1 pan head machine screw defined by JIS. In the cavitation treatment section CV, a plurality of virtual screw arrangement surfaces perpendicular to the central axis O of the nozzle flow path 3 are set along the central axis O, two surfaces LP1 and LP2 in FIG. 1C. The screw member 10 described above is arranged such that the longitudinal direction of the leg portions is along the respective screw arrangement surfaces LP1 and LP2. In the embodiment of FIG. 1C, the total number of screw members 10 is eight (as described later, the number may exceed eight), and there are two or more screw members 10 for each screw placement surface LP1, LP2, and four in FIG. 1C. are distributed one by one. Note that it is also possible to form only one screw arrangement surface (plane screw set).

In FIG. 1C, the screw members 10 are arranged on each screw arrangement surface LP1, LP2 according to the layout shown in FIG. 2. Specifically, the four screw members 10 on each of the screw placement surfaces LP1 and LP2 are arranged in a cross shape orthogonal to each other, and each has a female threaded portion on the inner surface of a screw hole 19 formed in the nozzle body 2. The legs are screwed so that the tips of the legs protrude into the throttle hole 9 from the outer peripheral surface of the wall. The screw hole 19 and the screw member 10 can be set and fixed using an adhesive or the like. FIG. 3 shows a further enlarged view of the inside of the throttle hole 9, and a main flow area 21 is formed between the screw member 10 and the inner peripheral surface of the throttle hole 9. Furthermore, in each throttle hole 9, a circulation gap 15 is formed at the center of the cross formed by the four collision parts 10. The end surfaces of the four collision parts 10 forming the circulation gap 15 (FIG. 3) are formed flat, and the circulation gap 15 is formed in a square shape in the projection described above.

In Fig. 3, the area of the culture water flow area (cross-sectional area of the nozzle flow path in the cavitation treatment section: hereinafter also referred to as the total flow cross-sectional area) a on each screw arrangement surface LP1, LP2 is calculated from the outside of the projected area of the nozzle flow path. The total area inside the periphery (here, the area of the circular axial cross section of the throttle hole 9 in FIG. 1C: πd ² /4 with the inner diameter as d)) is S1, and the projected area area of the collision part 10 (four screw members) is As S2,
a=S1-S2 (unit: mm ² )
Define as . In this embodiment, the total area of the main circulation area 21 and the circulation gap 15 corresponds to the total circulation cross-sectional area a. As shown in FIG. 1C, the opening diameters of the culture water inlet 4 and the culture water outlet 5 are larger than the inner diameter of the throttle hole 9. That is, the opening cross-sectional area of the aquaculture water inlet 4 and the aquaculture water outlet 5 is set larger than the total flow cross-sectional area a. Further, the inner circumferential surfaces of the inflow chamber 6 and the outflow chamber 7 that are connected to the throttle hole 9 are tapered portions 13 and 14, respectively. The tapered portion 14 on the side of the culture water outlet 5 and the taper portion 13 on the side of the culture water inlet 4 have the same drawing ratio, but the section length of the tapered portion 14 is set larger. In each screw arrangement surface LP1, LP2, a total flow cross-sectional area a of 3.8 mm2 ^or more is ensured, and the ratio of the total flow cross-sectional area a to the total cross-sectional area S1 of the nozzle flow path (i.e., a/S1×100 The in-plane distribution area ratio defined as (%)) is ensured at 40% or more.

The depth h of the valley portion 21 appearing in the projected outline of the screw member (collision portion) 10 is ensured to be 0.2 mm or more. In addition, when a circle drawn with a radius corresponding to 70% of the distance to the inner circumferential edge of the nozzle flow path with the projected point of the central axis O as the center is defined as the reference circle _C70 , the bottom position of the valley portion 21 is Among the valley points represented, the number of valley points located inside the reference circle C ₇₀ (indicated by ○), that is, the number of valley points located inside the reference circle C 70, that is, the number of valley points located inside the reference circle C 70, that is, the number of valley points located from the cross-sectional center of the nozzle channel 3 to the nozzle channel 3 when projected onto a plane perpendicular to the central axis O. The number of valley points located in an area within 70% of the radius of 3 is defined as the number of 70% valley points _N70 . Then, the value obtained by dividing the sum of the values of the 70% valley point number _N70 for all screw arrangement surfaces by the cross-sectional area S1 of the nozzle flow path 3 (throttle hole 9) is defined as the 70% valley point areal density. In the cavitation nozzle 1 of FIG. 1C, the value of the 70% valley point area density is ensured to be 1.6 pieces/mm ² or more.

In FIG. 1C, the legs of the screw member 10 are arranged between mutually adjacent screw placement surfaces LP1 and LP2 in a positional relationship in which they overlap each other while making their longitudinal directions coincide when projected onto a plane perpendicular to the central axis O. There is. Specifically, the positional relationship is such that a plane screw assembly consisting of four screw members 10 arranged in a cross shape overlaps each other between the screw arrangement surfaces LP1 and LP2 (i.e., the central axis O of the cross-shaped plane screw assembly). They are arranged in a positional relationship in which the surrounding arrangement angle phases match each other (hereinafter, such an arrangement will be referred to as "in-phase arrangement"). Further, the distance dp between the adjacent screw placement surfaces LP1 and LP2 is set to, for example, 1.05dh or more and 2M or less, where dh is the outer diameter of the screw head 10h in FIG. 2, and M is the nominal thread diameter of the screw leg 10f. has been done.

For the cavitation nozzle 1 in FIG. 1C, for example, the culture water outlet 5 side is opened and the culture water inlet 4 is supplied with water, for example, so that the dynamic pressure is about the normal tap pressure (for example, 0.077 MPa). The effect when distributed will be explained. The water flow is first constricted by the taper portion 13 and the throttle hole 9, and then reaches a liquid flow region formed between the screw member 10 and the inner circumferential surface of the throttle hole 9 and consisting of the main flow region 21 and the flow gap 15 in FIG. It passes through the threaded member 10 while colliding with it.

When passing through the outer circumferential surface of the threaded member 10, a high speed region is formed at the thread root and a low speed region is formed at the thread crest. Then, the high-speed region of the thread root becomes a negative pressure region according to Bernoulli's theorem, and cavitation occurs. Since the thread trough is formed in multiple turns around the outer periphery of the threaded member, and eight or more threaded members 10 are distributed over the plurality of screw placement surfaces LP1 and LP2, cavitation occurs in the trough in the throttle hole 9. This will occur multiple times at the same time. Then, when the water flow collides with the threaded member 10, dissolved air is violently precipitated under reduced pressure at the thread root, causing violent friction between the water flow and the surface of the threaded member 10 and the inner surface of the nozzle channel 3. Stir while stirring.

As mentioned above, the cavitation nozzle 1 in FIG. 1C has an in-plane flow area ratio of 40% or more on each screw arrangement surface LP1, LP2, a total flow cross-sectional area of 3.8 mm ² or more, and The interval dp between adjacent screw arrangement surfaces LP1 and LP2 (plane screw set) is ensured to be larger than the nominal thread diameter of the screw member 10 used. As a result, even if a plurality of surface screw sets are arranged in series in the direction of the flow path center axis O, the increase in pressure loss of the nozzle can be kept extremely small. As a result, even though many screw members are arranged in one nozzle flow path 3, a sufficient flow velocity can be ensured within the cross section. This configuration is particularly advantageous when a high flow rate nozzle with increased cavitation treatment efficiency is desired.

As shown in FIG. 10, the gas-liquid mixer 150 is arranged on the culture water inlet side of the cavitation nozzle 1 so that the spiral channels 157 and 158 communicate with the nozzle channel 3 of the cavitation nozzle 1. Specifically, the male threaded portion 152 on the outlet side of the outer cylinder member 151 is screwed into the female threaded portion 16 of the nozzle body 2 . A separate piping element (not shown) such as a relay pipe may be interposed between the gas-liquid mixer 150 and the cavitation nozzle 1, but secondary bubbles BS may coalesce while flowing through the separate piping element. - There is also a concern that the gas-liquid mixer 150 and the cavitation nozzle 1 may become coarse, so it is desirable that the gas-liquid mixer 150 and the cavitation nozzle 1 be directly connected as shown in FIG.

Further, the multiphase flow supply unit 165 supplies a multiphase flow of gas and culture water to the inlet 159 of the gas-liquid mixer 150. In this embodiment, the multiphase flow supply unit 165 is configured as a venturi ejector, and gas is supplied to the gas supply hole 166 communicating with the throttle hole by the gas supply piping 171 (FIG. 1A) via the gas introduction joint 167. A flow is formed. In this embodiment, the multiphase flow supply section 165 is also directly connected to the inlet 159 side of the gas-liquid mixer 150. The multiphase flow is distributed into a first spiral flow path 157 and a second spiral flow path 158, and crushes the gas phase into secondary bubbles BS while forming a first spiral flow TR1 and a second spiral flow TR2, respectively.

The primary bubbles BP in the multiphase flow are mixed and finely pulverized with the culture water by centrifugal force by flowing through the spiral channels 157 and 158 of the gas-liquid mixer 150, and are mixed with the culture water and pulverized by the threaded member 10 of the cavitation nozzle 1 in FIG. 1C. The secondary cells BS are pulverized into secondary cells BS having a cell diameter of 1.5h or less (preferably 1h or less), with the screw pitch of h (mm). The culture water containing the secondary bubbles BS is supplied to the cavitation nozzle 1, and is dissolved by being caught in the turbulent area generated in the cavitation treatment section CV.

By supplying the gas phase in the multiphase flow to the screw member of the cavitation nozzle 1 in a state of being crushed into finer secondary bubbles BS, the contact efficiency between the gas-containing culture water and the screw valley increases. As a result, the formation of a turbulent region that generates a driving force for mixing and stirring the gas phase components becomes significant, and the gas dissolution efficiency can be improved. Further, in the cavitation treatment section CV, a portion of the dissolved gas is immediately reprecipitated by cavitation, so that the cavitation efficiency within the thread root portion is significantly improved.

Next, FIG. 11 is a block diagram showing an example of the electrical configuration of the control section 185. The control unit 185 includes a CPU 191, a ROM 193 that stores control programs executed by the CPU 191 (nozzle flow rate control program 193a and oxygen concentration control program 193b), a RAM 192 that forms a program execution memory, and an input/output unit 194. It is mainly composed of microcomputer hardware including a connecting bus line 195. The aforementioned distribution valve 183 is connected to the input/output section 194 via a D/A converter section 199 that converts a digital signal indicating an instruction value of the valve opening degree (valve position) into an analog voltage instruction value. Further, the analog sensor outputs of the flow meter 186 and the oxygen sensor 186 are converted into digital signals by A/D converters 196 and 197 and input to the input/output section 194. Furthermore, electromagnetic valves 172 and 184 that open and close the supply of air to the aeration nozzle 174 and the cavitation nozzle 1 are connected to the input/output section 194 via drive circuits 172A and 184A.

The operation of the closed land aquaculture apparatus 300 shown in FIG. 1A will be described below.
First, aquaculture water W is poured into the aquaculture pond 250. For the control unit 185 in FIG. 11, a specified flow rate range (upper limit Q _U , lower limit value _QL ) are set using the input section 198. Further, the specified oxygen concentration range (upper limit value C _U , lower limit value C _L ) of the culture water W is similarly set using the input unit 198 according to the number of the cultured product SP to be input. These setting values are stored in the RAM 192 in FIG.

When the above settings are completed, the operation of the main pump 175 and the control of the flow rate of the cavitation nozzle 1 and the dissolution of oxygen into the culture water W by the control unit 185 are started. Then, the flow rate of the cavitation nozzle 1 indicated by the flow meter 182 and the oxygen concentration indicated by the oxygen sensor 186 are controlled within a specified range, and when these values are stabilized, the cultured material SP is introduced into the culture water W. .

FIG. 12 is a flowchart showing an example of the processing flow of the flow rate control program. In S101, the opening degree S of the distribution valve 183 in FIG. 1A is set to the default value S0. The default value indicates that, for example, when the auxiliary filtering section 253f in FIG. 1A is new and the main pump 175 is rotated at the rated output, the flow rate of the cavitation nozzle 1 indicates the center value of the specified flow rate range. It can be set as follows. In S102, the flow rate value Q2 of the flow meter 182 is read. Next, this flow rate value Q2 is compared with the lower limit value Q _L and the upper limit value Q _U of the specified flow rate range. If Q2< _QL in S103, the flow rate is insufficient, so the process proceeds to S104, and the distribution valve 183 is driven so as to increase the opening degree S toward the cavitation treatment pipe 181 by a predetermined increment ΔS. In other cases, the process proceeds to S105, and if Q _U <Q2, the flow rate is excessive, so in S106, the distribution valve 183 is driven so that the opening degree S is decreased by the increment ΔS toward the cavitation treatment pipe 181 side. If Q _L <Q2 <Q _U , the flow rate is appropriate, and the process advances to S107 to maintain the current value of the opening degree S of the distribution valve 183. Thereafter, if the process does not end in S108, the process returns to S101 and the following process is repeated. The upper limit value _QU of the flow rate is defined as the amount of water stored in the aquaculture pond 250 as V1, and the hourly flow rate of the cavitation nozzle 1 as V2.
K=V2/V1×100 (%)
The distribution/circulation ratio K expressed by is set, for example, so as not to exceed 2%.

FIG. 13 is a flowchart showing an example of the processing flow of the oxygen concentration control program. In S201, as a default setting state, the electromagnetic valve 184 on the side of the air diffuser 174 in FIG. 1A is turned ON (open), and the electromagnetic valve 172 on the side of the cavitation nozzle 1 is also turned ON (open). In S202, the oxygen concentration detection value C of the oxygen sensor 186 is read. Next, this detected oxygen concentration value C is compared with the lower limit value C _L and the upper limit value C _U of the specified oxygen concentration range. If C<C _L in S103, the oxygen concentration is insufficient, so the process proceeds to S204, where the solenoid valve 184 on the diffuser 174 side is turned on (opened), and the solenoid valve 172 on the cavitation nozzle 1 side is also turned on (opened). Maintain the state as follows. In other cases, the process proceeds to S205, and if C _U <C, the oxygen concentration is excessive, so in S206, the solenoid valve 184 on the diffuser 174 side is turned on (opened), and the solenoid valve 172 on the cavitation nozzle 1 side is turned off. (closed) to suppress oxygen dissolution in the cavitation nozzle 1 and reduce the oxygen concentration in the culture water W. Note that if it is desired to further reduce the oxygen concentration, it is also possible to turn off (close) the electromagnetic valve 184 on the side of the air diffuser 174. If C _L < C2 < Q _U , the oxygen concentration is appropriate, and the process proceeds to S207, where the solenoid valve 184 on the diffuser 174 side is turned on (opened), and the solenoid valve 172 on the cavitation nozzle 1 side is intermittently turned on. Turn it ON/OFF to maintain the current oxygen concentration value. Thereafter, if the process does not end in S208, the process returns to S201 and the following process is repeated. For example, the oxygen concentration C in the culture water W is fixedly set within a range of 4 to 6 ppm (for example, 5 ppm) with a central target value C0, and the upper limit C _U is set to, for example, C0 + 0.5 to C0 + 2 ppm based on the central target value C0. (for example, 6 ppm), and the lower limit value C _L can be set, for example, as a value of C0-0.5 to C0-2 ppm (for example, 4 ppm) based on the central target value C0.

Due to the above control, the oxygen concentration in the culture water W, which decreases due to consumption by the cultured product SP, is lower than the saturation value even when fluctuations in oxygen concentration due to sudden factors are taken into account. The content is maintained within a range of 2.5 ppm or more and 7 ppm or less (preferably 3 ppm or more and 8 ppm or less). Then, the culture water W is guided to the cavitation nozzle 1, and cavitation treatment is performed by flowing it at a specified flow rate such that the cross-sectional average flow velocity in the cavitation treatment section is 8 m/sec or more. By intentionally maintaining the oxygen concentration of the culture water W below the saturation value, excessive generation of microbubbles due to cavitation is suppressed, and the bubbles adhere to the gills of the cultured product SP, inhibiting the uptake of dissolved oxygen, etc. problems can be effectively prevented. By ensuring a specified flow rate at which the cross-sectional average flow velocity in the cavitation treatment section is 8 m/sec or more, even though the oxygen concentration of the culture water W is set lower than in the conventional technology, the Growth promotion etc. can be achieved without any problem.

Hereinafter, various modifications of the cavitation nozzle that can be employed in the present invention will be described.
FIG. 4 shows a configuration in which the cavitation treatment section CV of the cavitation nozzle 1 of FIG. 1C has four sets of surface threads arranged in the direction of the central axis O in the layout shown in FIG. Specifically, the four screw arrangement surfaces LP1 to LP4 are arranged in the direction of the central axis O with the same surface spacing dp as in FIG. 1C, so that the cross-shaped surface screw sets in FIG. in phase). In this case, the 16 screw members 10 will be distributed to the four screw placement surfaces LP1 to LP4. Further, FIG. 5 shows an example of a cavitation treatment section CV in which the surface screw set of FIG. 2 is arranged in the same phase with respect to eight screw arrangement surfaces LP1 to LP8. In this case, 32 screw members 10 are distributed over eight screw placement surfaces LP1 to LP8. The 70% valley point areal density of each cavitation treatment section CV can be increased twice in the configuration of FIG. 4 and four times in the configuration of FIG. 5 compared to the configuration in FIG. 2. This improves the efficiency of cavitation treatment and makes it possible to achieve the above-described effects of the present invention more stably.

Next, FIG. 6 shows a state in which a surface screw set similar to the cavitation nozzle 1 of FIG. 1C is rotated by 45 degrees. Of the two screw placement surfaces LP1 and LP2 of the cavitation nozzle 1 in FIG. FIG. 7 shows an example of the cavitation treatment section CV when the cavitation treatment section CV is rotated by 45 degrees around O and brought into the state shown in FIG. The cavitation treatment section CV with this configuration can achieve the same 70% valley point area density as the configuration in FIG. Pressure loss during circulation will be slightly larger. However, by appropriately enlarging the surface spacing dp, this pressure loss is reduced, and cavitation processing capacity approximately equivalent to that of the cavitation processing section CV having the configuration shown in FIG. 2 is exhibited. Further, since the turbulent agitation effect of the culture water is greater than that of the configuration shown in FIG. 1C, this configuration is more advantageous for dissolving gas in the culture water by supplying a multiphase flow.

FIG. 8 shows an example of the cavitation treatment section CV in which the surface screw set is divided into mutually orthogonal screw member pairs, and the respective positions are shifted in the direction of the central axis O in the configuration of FIG. 7. Specifically, the four screw members 10 arranged on the screw arrangement surfaces LP1 and LP2 in FIG. 1C are replaced by two screws separated by the nominal thread diameter M of the thread members 10 in the configuration of FIG. Two mutually orthogonal wires are distributed and arranged on the arrangement planes LP1, LP1' and LP2, LP2'. That is, an example is shown in which eight screw members 10 are distributed to four screw placement surfaces LP1, LP1', LP2, and LP2'. Further, the distance between the screw placement surface LP1' and the screw placement surface LP2 is set to be larger than the nominal thread diameter M (for example, about 1.5M to 2.0M). The 70% valley point area density in this configuration is equivalent to the configuration in FIG.

In addition, FIG. 9 shows cavitation treatment in which two sets of surface screws having the layout of FIG. 2 and two sets of surface screws having the layout of FIG. 6 are arranged alternately on the four screw placement surfaces LP1 to LP4. An example of part CV is shown below. In this example, 16 screw members 10 are distributed and arranged, four each on four screw placement surfaces LP1 to LP4. The 70% valley point areal density in this configuration is twice that of the configuration in FIG.

FIG. 14 shows an example of a cavitation nozzle in which two throttle holes 9 are formed in a partition wall 8 formed in a cavitation treatment section, and four screw members 10 are arranged in a cross shape for each throttle hole 9.

Further, the closed land aquaculture device 300 may have a configuration in which the cavitation treatment pipe 182 and the cavitation treatment pump 181p are provided independently of the filtration main pipe 180 and the main pump 175, as shown in FIG. . The entrance of the cavitation treatment piping 182 opens into the aquaculture pond 250, and is provided with a cavitation treatment filter section 181f having the same configuration as the auxiliary filtering section 253f. The drive input of the cavitation treatment pump 181p is made variable by a power amplifier 181v, and by controlling the output of the power amplifier 181v based on a signal from the control unit 185, the flow rate of liquid sent to the cavitation nozzle 1 is adjusted to the above-mentioned specified flow rate. maintained within range. The rest of the configuration is the same as that in FIG. 1, so detailed explanation will be omitted.

Below, the results of various experiments conducted to confirm the effectiveness of the cavitation nozzle will be explained.
(Example 1)
Cavitation nozzles A and B having the shapes shown in FIG. 1C were created. Note that for the cavitation nozzle A, only one set of surface threads consisting of four screws shown in FIG. 2 is arranged, and for the cavitation nozzle B, two sets of surface threads are arranged in an overlapping positional relationship. FIG. 21 illustrates the dimensional relationship of each part in FIG. 1C. The material of the nozzle body 2 is ABS resin, the inner diameter of the culture water inlet 4 and the culture water outlet 5 is 20 mm, and the lengths of the inlet chamber 6 and the outlet chamber 7 in the flow direction are 15 mm and 45 mm, respectively. The length of the throttle hole 9 in the cavitation treatment section is 12 mm. Further, the inner diameter D of the throttle hole 9 was set to 5.0 mm for cavitation nozzle A, and 14.0 mm for cavitation nozzle B. The screw member used was a No. 0 class 1 pan head machine screw having a metric coarse pitch specified in JIS: B0205 (1997), and was made of titanium. Further, the nominal thread diameter of the leg portion is M1.4 mm.

In addition, the total flow cross-sectional area a (the value obtained by subtracting the area of the area occupied by the screws from the total cross-sectional area of the throttle hole) was calculated on the projected image showing the layout of the screw members in the throttle hole. Furthermore, the value of the 70% valley point area density was calculated for each test nozzle by counting the number of 70% valley points existing inside the reference circle _C70 in FIG. 3 and dividing by the total cross-sectional area S1 of the aperture hole. For each nozzle A and B created, each value of the aperture hole inner diameter, in-plane flow cross-sectional area 70% total number of troughs, 70% trough area density, and flow circulation ratio K when the total water volume of the aquaculture pond is 50 t. are summarized in Table 1. The above cavitation nozzle, in which the 70% valley point density of all nozzles was ensured to be 2.0 pieces/mm ² or more, was incorporated into the closed land aquaculture apparatus 300 of FIG. 1A together with the gas-liquid mixer 150 of FIG. 10.

Next, 50 tons (water depth: approximately 1.5 m) of artificial seawater adjusted to have brackish water with a salinity of 2.0% is injected into the aquaculture pond 250, and the main pump 175 circulates the water at an initial flow rate of 100 L/min. It started at. Then, the opening degree of the distribution valve 183 was controlled by the method already described in detail so that the flow rate settings for each nozzle A and B were as shown in Table 1. In addition, the oxygen concentration that is the control target of the aquaculture water is determined under each of the conditions numbered 1 to 6 shown in Table 2 below (2.0 ppm to 7.5 ppm, number 1 (2.0 ppm) and number 6 (7.5 ppm)). Comparative Example), and the electromagnetic valves 184 and 174 in FIG. 1A were driven and controlled to maintain the oxygen concentration of the culture water at each set value. Note that the air ejection flow rate of the air diffuser 174 was 50 NL/min (average bubble diameter: 0.3 mm). The air supply flow rate to the cavitation nozzle 1 was adjusted to be 10% of the water flow rate in terms of volumetric flow rate (NL/min) converted to atmospheric pressure. Furthermore, the value of the dynamic hydraulic pressure of the cavitation nozzle at the above flow rate setting measured with a pressure gauge (not shown), and the value of the average flow velocity in the throttle hole (cavitation processing section) calculated from the flow rate value and the total flow cross-sectional area are also displayed. It is shown according to 1. Under any conditions, the average flow velocity in the cavitation treatment section was maintained at a value of 9 m/sec.

In this state, young vannamei shrimp were introduced to the population density of 200 shrimp/ton, and feed containing fishmeal, krill meal, squid meal, and wheat flour was fed to the young shrimp in the pond according to the growth level of the shrimp. The animals were given appropriate doses and reared. As breeding continues, shrimp excrement and uneaten feed become suspended in the culture water as organic residue in the pond. Due to the above-mentioned circulation of the culture water, the floating matter is removed to some extent in the filter tank 252 in FIG. 1A, but if breeding continues for a long period of time, the floating matter that could not be completely removed will flow into the downstream buffer tank. , gradually accumulates on the auxiliary filtering section 253f (filtering section for cavitation treatment). As a result, the suction load on the main filtration pipe 180 by the main pump 175 increases, and the circulation flow rate of the main filtration pipe 180 gradually decreases on the upstream side of the branch point with the cavitation treatment pipe 1. However, because the configuration of the closed land aquaculture device shown in FIG. 1A is adopted, under any conditions, the flow rate distributed to the cavitation treatment piping 181 (i.e., cavitation nozzle 1) is within the specified flow rate range. I was able to keep it within. Regarding the filter 252f in the filtration tank 252, when the total flow rate of the main filtration pipe 180 drops to 30 L/min or less, the circulation is temporarily stopped and the filter 252f is replaced with a new one as appropriate. Note that the interior of the filter tank 252 is aerated with air by an aeration mechanism (not shown), and aerobic microorganisms such as Bacillus that are involved in humus formation are propagated, thereby simultaneously converting the filtered organic residue into humus. ing.

The following items were confirmed and evaluated after 30 days, 90 days, and 120 days had elapsed after starting the above culture test.
(1) COD value Aquaculture water was sampled and measured according to the method specified in JIS K 0102 (2013) 17.
(2) Average body length Thirty shrimp under cultivation were randomly selected, and the body length of each shrimp was measured and the average value was determined.
(3) Mortality rate The number of shrimp carcasses that died and surfaced on the aquaculture pond was checked every 3 hours, and the mortality rate was calculated from the total number of dead shrimp for each day. For comparison, a similar experiment was also conducted in a case where the cavitation nozzle 1 in FIG. 1 was not used and only the gas-liquid mixer 150 was attached to the cavitation treatment piping 181 (no cavitation treatment). The above results are shown in Table 2.

＊は比較例。

* is a comparative example.

Regarding the oxygen concentration of numbers 2 to 5, where the oxygen concentration of the culture water is within the range of the present invention, by using culture water that has been subjected to cavitation treatment, compared to the case where culture water that has not been subjected to cavitation treatment is used. It is clear that shrimp grow much faster even when the culture water has the same oxygen concentration. Furthermore, by performing the cavitation treatment, the COD value of the cultured water was significantly lowered, indicating that the pollution of the cultured water was less likely to progress. Particularly in the low oxygen concentration region of 3 to 4 ppm, the mortality rate of shrimp without cavitation treatment is extremely high, whereas the mortality rate with cavitation treatment is significantly reduced. Recognize.

In addition, in the case of condition No. 1 (2 ppm) in which the oxygen concentration of the culture water is lower than the lower limit of the range of the present invention, the mortality rate increases after 120 days even if cavitation treatment is performed, and the COD value worsens. is being watched. On the other hand, it can be seen that in the case of condition No. 6 (7.5 ppm) in which the oxygen concentration of the culture water exceeds the upper limit of the range of the present invention, the mortality rate is higher than when cavitation treatment is not performed. Condition No. 6 not only has a high oxygen concentration, but also has a large circulation ratio K of the cavitation nozzle 1 to the total volume of the culture water W, so the amount of bubbles that have grown to about 100 nm to 30 μm in the cavitation nozzle 1 is excessive. The cause was thought to be that these air bubbles adhered to the gills of the shrimp, making it difficult for them to take in dissolved oxygen.

(Example 2)
A cavitation nozzle was created with the same dimensional relationship as that shown in FIG. 1C, except that the structure of the cavitation treatment section was changed to the form shown in FIG. 14 (two aperture holes 9 were formed). Two types of inner diameter D of each throttle hole were prepared: φ3.9 mm (referred to as cavitation nozzle C) and φ4.9 mm (referred to as cavitation nozzle D). In addition, for large flow applications, cavitation nozzles with a set of throttle holes 9 similar to those shown in FIG. Two types were prepared. For the former, there are two sets of surface screw sets consisting of four screws shown in FIG. 2, and for the latter, the set of surface screws are arranged at each value of 1 to 3 sets in a mutually overlapping positional relationship. The 70% valley point density of all nozzles is ensured at 2.0 pieces/mm2 ^or higher.

These nozzles were incorporated into the closed land aquaculture apparatus shown in FIG. 1A, and experiments and evaluations similar to those in Example 1 were conducted under the following test conditions. Under all conditions, the set oxygen concentration for the culture water was 4 ppm, and the population density of the cultured product (vannamei shrimp) was 200 shrimp/ton. For cavitation nozzle C, the flow velocity in the cavitation treatment section was adjusted to each value of 7.5 to 9.9 m/sec by setting the control flow rate value to 4.6 to 6.1 L/min. For cavitation nozzle D, the flow velocity in the cavitation treatment section was adjusted to each value of 5.2 to 9.9 m/sec by setting the control flow rate value to 6.0 to 11.7 L/min. For cavitation nozzles E and F, the flow velocity in the cavitation treatment section was adjusted to 9.9 m/sec by setting the control flow values to 33.1 L/min and 86.7 L/min. In addition, the amount of water in the aquaculture pond is variously set in the range of 50t to 500t, but depending on the type of cavitation nozzle and the combination with the flow rate, the value of the distribution circulation ratio K can be kept within 0.5% or more and 2% or less. is set to . The above results are shown in Table 3 (results on the 90th and 120th day are shown for those subjected to cavitation treatment).

Conditions where a cavitation nozzle with a 70% valley point area density of 1.6 pieces/mm2 or ^more is used and the average flow velocity in the cavitation treatment section is 8 m/sec (numbers 51, 53, 54, 56) , 56 to 58), shrimp growth is promoted and the COD value indicating water quality is maintained well, as is clear from comparison with the case of Example 1 with an oxygen concentration of 4 ppm (number 3) without cavitation. It can be seen that the mortality rate is also low. On the other hand, it can be seen that in the comparative examples (numbers 52 and 55) in which the average flow velocity in the cavitation treatment section is less than 8 m/sec, the mortality rate is high and the COD value is also deteriorated. In addition, under the condition No. 59 in which a cavitation nozzle with a 70% valley point area density of less than 1.6 pieces/ ^mm2 was used, a cavitation nozzle with a 70% valley point area density of 1.6 pieces/mm2 or ^more was used. It can be seen that the growth of shrimp is slightly slower and the mortality rate is increased compared to the case.

(Example 3)
Cavitation nozzles A and B, which are exactly the same as in Example 1, are incorporated into the closed land aquaculture device 300 of FIG. 1A together with the gas-liquid mixer 150 of FIG. : approximately 2 m), and circulation by the main pump 175 was started at an initial flow rate of 100 L/min. Then, while controlling the opening degree of the distribution valve 183 so that the flow rate setting is the same as in Example 1 for each nozzle A and B, the oxygen concentration, which is the control target of the aquaculture water, is set to 4.0 ppm to 7.5 ppm ( 7.5 ppm) in the comparative example), and the electromagnetic valves 184 and 174 in FIG. 1A were driven and controlled to maintain the oxygen concentration of the culture water at each set value. The air ejection flow rate of the air diffuser 174 was set to 50 NL/min (average bubble diameter: 0.3 mm). The air supply flow rate to the cavitation nozzle 1 was adjusted to be 10% of the water flow rate in terms of volumetric flow rate (NL/min) converted to atmospheric pressure. In addition, the value of the dynamic hydraulic pressure of the cavitation nozzle at the above flow rate setting measured with a pressure gauge (not shown), and the value of the average flow velocity in the throttle hole (cavitation processing section) calculated from the flow rate value and the total flow cross-sectional area are also displayed. It is shown according to 1. Under any conditions, the average flow velocity in the cavitation treatment section was maintained at a value of 9 m/sec or more.

In this state, young red sea bream were introduced to achieve an individual density of 40 fish/ton, and sardine-based moist pellets were administered to the red sea bream in the pond as appropriate depending on the growth level of the red sea bream. . Also in this embodiment, when the total flow rate of the main filtration pipe 180 drops to 30 L/min or less, the filter 252f in the filtration tank 252 is temporarily stopped circulating and replaced with a new one as appropriate. Furthermore, the inside of the filtration tank 252 is aerated with air by an aeration mechanism (not shown), thereby propagating aerobic microorganisms, thereby simultaneously converting the filtered organic residue into humus.

After 240 days and 510 days had elapsed after starting the above culture test, the average weight and mortality rate of the red sea bream were measured. For comparison, a similar experiment was also conducted in a case where the cavitation nozzle 1 in FIG. 1 was not used and only the gas-liquid mixer 150 was attached to the cavitation treatment piping 181 (no cavitation treatment). The above results are shown in Table 4.

Regarding the oxygen concentration of numbers 101 and 102, where the oxygen concentration of the culture water is within the range of the present invention, by using culture water that has been subjected to cavitation treatment, compared to the case where culture water that has not been subjected to cavitation treatment is used. It is clear that red sea bream grow much faster even if the culture water has the same oxygen concentration. In particular, it can be seen that in the low oxygen concentration region of 4 ppm, the mortality rate of red sea bream is significantly high when cavitation treatment is not performed, whereas the mortality rate when cavitation treatment is performed is significantly reduced. On the other hand, it can be seen that in the case of condition No. 103 (7.5 ppm) in which the oxygen concentration of the culture water exceeds the upper limit of the range of the present invention, the mortality rate is higher than when no cavitation treatment is performed.

1 Cavitation nozzle 2 Nozzle body 3 Nozzle channel 5 Culture water outlet 4 Culture water inlet 9 Throttle hole 10 Screw member 150 Gas-liquid mixer 151 Outer cylinder member 155 Channel forming member 156 Spiral section 157 First spiral channel 158 Second Spiral flow path 159 Inlet 160 Outlet 165 Multiphase flow supply section 174 Diffusion section 175 Main pump 180 Main filtration piping 181 Cavitation treatment piping 181p Cavitation treatment pump 182 Flow rate detection section 183 Distribution valve 185 Cavitation flow control section 250 Aquaculture pond 252 Filtration tank 253f Auxiliary filtering section (filtration section for cavitation treatment)
300 Closed land aquaculture equipment W Aquaculture water SP Cultured product LP1 to LP4 Screw arrangement surface CV Cavitation treatment section

Claims (9)

Culture water and cultured animals consisting of crustaceans or fish are housed in an aquaculture pond, and a main pump is used to guide the aquaculture water from the aquaculture pond to a filter tank, while filtering organic residues floating in the aquaculture water. In a closed land aquaculture device for raising the cultured animals by feeding feed into the aquaculture pond while circulating it back into the aquaculture pond,
an oxygen dissolving mechanism that dissolves while supplying an oxygen-containing gas to the culture water so that the oxygen concentration of the culture water is maintained at 2.5 ppm or more and 7 ppm or less;
a cavitation treatment pipe whose inlet of the aquaculture water communicates with the aquaculture pond, and whose other end serves as a return port for the aquaculture water to the aquaculture pond;
A nozzle flow path is provided in the middle of the cavitation treatment piping and has an inlet of the culture water at one end and an outlet of the culture water at the other end, and a part of the nozzle flow path is subjected to the cavitation treatment. A nozzle body defined as a part is assembled in the cavitation treatment part in a virtual screw arrangement plane perpendicular to the central axis of the nozzle flow path so that the tip end side of the leg protrudes inside the flow path. a plurality of screw members to be attached, the total flow cross-sectional area on the screw arrangement surface is ensured to be 3.8 mm ² or more, and the culture water is made to flow from the culture water inlet to the culture water outlet, Cavitation treatment in which cavitation treatment is performed on the culture water based on reduced pressure precipitation of dissolved air by bringing the culture water into contact with the thread valley formed on the outer circumferential surface of the leg of the threaded member at a cavitation treatment section while increasing the speed. a nozzle and
In the middle of the cavitation treatment piping, it is also used as the main pump or is provided independently from the main pump, and the culture water is supplied to the cavitation nozzle at an average cross-sectional flow velocity of 8 m/sec or more in the cavitation treatment section. a cavitation treatment pump that causes the flow to flow at a prescribed flow rate determined according to the total flow cross-sectional area of the cavitation nozzle;
Equipped with
The oxygen dissolving mechanism is provided separately from the cavitation nozzle and is configured to supply the oxygen-containing gas from the outside to the aquaculture water filling the aquaculture pond so that the average bubble diameter is 0.1 mm or more and 0.5 mm or less. A closed land aquaculture device characterized by including a diffuser that sprays air. Culture water and cultured animals consisting of crustaceans or fish are housed in an aquaculture pond, and a main pump is used to guide the aquaculture water from the aquaculture pond to a filter tank, while filtering organic residues floating in the aquaculture water. In a closed land aquaculture device for raising the cultured animals by feeding feed into the aquaculture pond while circulating it back into the aquaculture pond,
an oxygen dissolving mechanism that dissolves while supplying an oxygen-containing gas to the culture water so that the oxygen concentration of the culture water is maintained at 2.5 ppm or more and 7 ppm or less;
a cavitation treatment pipe whose inlet of the aquaculture water communicates with the aquaculture pond, and whose other end serves as a return port for the aquaculture water to the aquaculture pond;
A nozzle flow path is provided in the middle of the cavitation treatment piping and has an inlet of the culture water at one end and an outlet of the culture water at the other end, and a part of the nozzle flow path is subjected to the cavitation treatment. A nozzle body defined as a part is assembled in the cavitation treatment part in a virtual screw arrangement plane perpendicular to the central axis of the nozzle flow path so that the tip end side of the leg protrudes inside the flow path. a plurality of screw members to be attached, the total flow cross-sectional area on the screw arrangement surface is ensured to be 3.8 mm ² or more, and the culture water is made to flow from the culture water inlet to the culture water outlet, Cavitation treatment in which cavitation treatment is performed on the culture water based on reduced pressure precipitation of dissolved air by bringing the culture water into contact with the thread valley formed on the outer circumferential surface of the leg of the threaded member at a cavitation treatment section while increasing the speed. a nozzle and
In the middle of the cavitation treatment piping, it is also used as the main pump or is provided independently from the main pump, and the culture water is supplied to the cavitation nozzle at an average cross-sectional flow velocity of 8 m/sec or more in the cavitation treatment section. a cavitation treatment pump that causes the flow to flow at a prescribed flow rate determined according to the total flow cross-sectional area of the cavitation nozzle;
Equipped with
The oxygen dissolving mechanism includes a multiphase flow supply unit that supplies a multiphase flow of the oxygen-containing gas and the culture water to the cavitation nozzle in order to dissolve the oxygen-containing gas in the cavitation nozzle, and the cavitation nozzle A closed terrestrial aquaculture device characterized in that functions as a part of the oxygen dissolution mechanism . A hollow outer cylindrical member having an inlet at one end and an outlet at the other end, and a spiral flow path provided inside the outer cylindrical member and connecting the inlet and the outlet. a flow path forming member formed such that a helical axis of the flow path is along a central axis of the outer cylindrical member, and the cavitation nozzle is configured such that the helical flow path communicates with the nozzle flow path of the cavitation nozzle. a gas-liquid mixer provided on the inlet side of the aquaculture water,
The closed land aquaculture apparatus according to claim 2, wherein the multiphase flow supply section supplies the multiphase flow to the inlet of the gas-liquid mixer.. 4. The oxygen dissolving mechanism is configured to dissolve the oxygen-containing gas while supplying the oxygen-containing gas to the culture water so that the oxygen concentration of the culture water is maintained at 3 ppm or more and 6 ppm or less. The closed land aquaculture device described. The cavitation nozzle is formed such that the nozzle flow path has a circular cross section, and each of the cavitation treatment parts has a threaded member having a thread pitch and a thread depth of 0.20 mm or more and 0.40 mm or less, and a nominal thread. A plurality of screw members having a diameter M of 1.0 mm or more and 2.0 mm or less are arranged, and the nozzle flow path is connected from the cross-sectional center of the nozzle flow path when projected onto a plane perpendicular to the central axis of the nozzle flow path. The 70% valley point is defined as the 70% valley point area density, which is defined as the total number of valley points located within 70% of the radius between all screw placement surfaces divided by the cross-sectional area of the nozzle flow path. The closed land aquaculture device according to any one of claims 1 to 4, wherein an area density value of 1.6 pieces/mm2 or more is used. The flow rate of the cavitation nozzle per hour is V1, the water storage amount of the aquaculture pond is V2, and the flow rate of the cavitation nozzle per hour is V2.
K=V2/V1×100 (%)
The closed land aquaculture device according to claim 5 , wherein the distribution/circulation ratio K expressed by is adjusted to be 2% or less. a cavitation treatment filtration section that is provided at the inlet of the cavitation treatment piping and suppresses floating matter in the aquaculture pond from flowing into the cavitation treatment piping;
a flow rate detection unit that detects the flow rate of the aquaculture water flowing through the cavitation treatment piping;
and a cavitation flow rate control unit that controls the flow rate of liquid sent to the cavitation nozzle by the cavitation treatment pump to the specified flow rate in order to compensate for the flow rate loss due to the accumulation of suspended matter in the cavitation treatment filtration unit. The closed land aquaculture device according to any one of claims 1 to 6 . a main pipe for filtration, the inlet of the aquaculture water communicating with the filtration tank, and the other end serving as a return port of the aquaculture water to the aquaculture pond;
an auxiliary filtering section that is provided at the inlet of the main filtration pipe and suppresses floating substances in the filtration tank from flowing into the main filtration pipe, and the main pump is connected to the main filtration pipe. Along with being provided on top,
The cavitation treatment pipe is provided in such a manner that it branches from the main filtration pipe on the downstream side of the main pump, and opens the return port to the aquaculture pond at a position different from the main filtration pipe. is,
Further, a distribution valve is provided that adjusts a distribution ratio between the main piping and the cavitation treatment piping of the aquaculture water according to a valve opening degree,
The main pump is also used as the cavitation treatment pump, and the auxiliary filtering section is also used as the cavitation treatment filtration section, and
The cavitation flow rate control unit is configured to increase a distribution ratio of the aquaculture water to the cavitation treatment piping when the flow rate of the main pump decreases due to the accumulation of suspended matter in the auxiliary filtering unit. The closed land aquaculture apparatus according to claim 7 , wherein the opening degree of the distribution valve is adjusted and controlled. Using the closed land aquaculture apparatus according to any one of claims 1 to 8 , the aquaculture water and the cultured animals are accommodated in the aquaculture pond, and the main pump is used to remove the aquaculture water from the aquaculture pond. The aquaculture water is introduced into the filtration tank, and while organic residues floating in the aquaculture water are filtered and circulated back into the aquaculture pond, feed is introduced into the aquaculture pond to raise the aquaculture animals. Characteristic land-based aquaculture method.

Images