Water treatment device

Abstract

To provide a water treatment device.SOLUTION: A water treatment device for treating water in a rearing tank and returning it to the rearing tank includes a rotary filter, a motor, a nitrification tank, a backwashing nozzle, a backwashing water reception pan, a water level sensor, and a control part. In the case where the number of times T that a water level detected by the water level sensor in a predetermined detection period reaches a predetermined value or more is less than a first threshold, the control part executes a filter washing operation for rotating the motor in a first operation period when the water level detected by the water level sensor becomes a predetermined value or more, and spraying water from the backwashing nozzle to the filter, and in the case where the number of times T is the first threshold or more, the control part executes the filter washing operation for a second operation period longer than the first operation period.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a water treatment device for treating water to be circulated in a circulating land-based aquaculture facility. [Background technology]

[0002] There is land-based aquaculture, where fish, shellfish or algae are cultivated in farming facilities set up on land rather than in the sea or rivers. Land-based aquaculture is classified into run-of-the-mill (flow-through), closed-circulation, and circulating water injection (semi-circulation) types depending on how the water is used, but closed-circulation land-based aquaculture requires water treatment to remove fish and shellfish waste that is discharged into the breeding water.

[0003] Patent Document 1 discloses a rotating drum-type filtration device as a filtering means in a land-based aquaculture tank, which comprises a hollow drum with a filter membrane on its surface and an air wheel connected to it, with both ends supported horizontally by a cylindrical rotating shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2009 / 116166 Summary of the Invention [Problem to be solved by the invention]

[0005] In land-based aquaculture, the initial costs, including facility costs, and the running costs, including the energy required to create the rearing environment, are higher than in other forms of aquaculture, leading to an increase in production costs overall. In this regard, in closed-circulation land-based aquaculture, the water treatment equipment for removing waste and other materials from the rearing water requires electricity to operate, and there is a demand to reduce this electricity in order to lower the production costs of the fish and shellfish that are the subject of aquaculture. [Means for solving the problem]

[0006] The water treatment device according to one embodiment of the present invention includes: A water treatment device that treats water in a breeding tank and returns it to the breeding tank, a cylindrical rotary filter that can rotate around a rotation axis that intersects the vertical direction and has a filter on a side thereof that captures suspended matter contained in the water obtained from the breeding tank; A motor for rotating the rotary filter; a nitrification tank for nitrifying the nitrogen contained in the water that has passed through the filter and returning the nitrified water to the breeding tank; A backwash nozzle that sprays water onto the filter from the outside; A backwash water receiving pan that captures the suspended solids that have fallen off from inside the filter together with the water sprayed from the backwash nozzle and discharges them to the outside of the rotary filter; A water level sensor that detects a water level in the rotary filter; A control unit that controls the water level sensor, the motor, and the backwash nozzle; The control unit is When the number of times T that the water level detected by the water level sensor becomes equal to or higher than a predetermined level during a predetermined detection period is less than a first threshold value, a filter cleaning operation is performed in which the motor is rotated and water is sprayed from the backwash nozzle toward the filter during a first operation period when the water level detected by the water level sensor becomes equal to or higher than the predetermined level; When the number of times T is equal to or greater than the first threshold value, the filter cleaning operation is performed for a second operation period that is longer than the first operation period. A water treatment device.

[0007] According to such a water treatment device, the amount of suspended solids contained in the water to be treated is estimated according to the water level detected by the water level sensor, and a filter cleaning operation (backwash) is performed, so that the filter cleaning operation can be performed at the necessary timing. Also, the amount of suspended solids contained in the water to be treated can be estimated according to the number of times that the water level in the rotary filter 4 detected by the water level sensor 11 reaches a predetermined level or higher during a detection period, and the frequency and time of performing the filter cleaning operation can be determined. This eliminates the need to perform the filter cleaning operation at unnecessary times, and therefore the power required for the operation of the water treatment device 1 can be reduced. Also, when there is a large amount of suspended solids in the water to be treated, the filter cleaning operation can be performed continuously, so that the water treatment can be performed efficiently.

[0008] In the water treatment device, preferably, a foam separator that generates bubbles in the water obtained from the breeding tank, separates and discharges the generated bubbles, and returns the water from which the bubbles have been separated to the breeding tank; and a blower for supplying oxygen to the water in the breeding tank. The control unit further controls the foam separator and the blower, The control unit is When the number of times T is less than a second threshold value, the foam separator and the blower are operated intermittently; When the number of times T is equal to or greater than the second threshold value, the foam separator and the blower are continuously operated for a third operation period longer than the first operation period, The second threshold is less than the first threshold.

[0009] According to such a water treatment device, the amount of suspended solids contained in the water to be treated can be estimated according to the number of times that the water level in the rotary filter 4 detected by the water level sensor during the detection period reaches or exceeds a predetermined level, and the frequency and time of operation of the foam separator and blower can be determined. This eliminates the need to operate the foam separator and blower at unnecessary times, thereby reducing the power required to operate the water treatment device. In addition, the foam separator and blower are operated continuously as necessary, allowing efficient water treatment.

[0010] In the water treatment device, preferably, the control unit If the number of times T is less than a third threshold value, the execution of the filter cleaning operation is stopped for an operation stop period longer than the first operation period, and the operation of the foam separator and the blower is stopped; The third threshold is less than the second threshold. Effect of the Invention

[0011] According to the water treatment device of one aspect of the present invention, for example, it is possible to reduce the electric power required for the operation of the water treatment device. [Brief description of the drawings]

[0012] [Figure 1] 1 is a front view of a water treatment device according to an embodiment. [Diagram 2] 1 is a side view of a water treatment device according to an embodiment. [Diagram 3] 1 is a side view of a water treatment device according to an embodiment. [Figure 4] 1 is a cross-sectional view of a water treatment device according to an embodiment. [Diagram 5] 1 is a block diagram showing a configuration of a water treatment device according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the embodiment described below is merely a specific example for carrying out the present invention, and is not intended to limit the interpretation of the present invention. In addition, in order to facilitate understanding of the description, the same components in each drawing are given the same reference numerals, and duplicated descriptions may be omitted.

[0014] The water treatment device of this embodiment is mainly used in closed circulation land-based aquaculture, and performs water treatment (filtration) to remove fine suspended matter such as fish and shellfish excrement from breeding water obtained from a breeding tank in which fish and shellfish are raised, and returns the water to the breeding tank. The water treatment device of this embodiment is particularly suitable for closed circulation land-based aquaculture, but can also be applied to circulating water injection-type land-based aquaculture. The fine suspended matter to be removed is also called suspended solids or SS (Suspended Solids), and may be referred to as "SS" in this specification.

[0015] Fig. 1 to Fig. 4 are diagrams showing the water treatment device 1 of this embodiment, Fig. 1 is a front view, Fig. 2 is a side view seen from the arrow B in Fig. 1, Fig. 3 is a side view seen from the arrow C in Fig. 1, and Fig. 4 is a cross-sectional view taken along the line AA in Fig. 1. Fig. 1 to Fig. 4 mainly show the external appearance, but for the sake of convenience, parts that cannot be seen from the outside are also shown, and since they are shown conceptually, each component may be shown in a position different from the actual arrangement. Fig. 5 is a block diagram conceptually showing the functional configuration of the water treatment device 1 of this embodiment, the breeding water, the small water flow which is a small amount of water flow, and the air flow, as well as the connection relationship of the control system.

[0016] [Water treatment device 1] The water treatment device 1 obtains water to be treated (breeding water) from the breeding tank 2, treats it, and returns the treated water to the breeding tank 2. The water treatment device 1 includes a nitrification tank 3, a rotary filter 4, a motor 10, a water level sensor 11, a pump 12, a backwash nozzle 13, a backwash water receiving pan 14, a strainer 15, a foam separator 20, a blower 30, an oxygen mixer 31, a control unit 40, and solenoid valves 41 to 44. The water treatment device 1 may have casters 90 for easy movement. In the following description, explanations of components that can be easily understood by those skilled in the art, such as piping connecting each part, are omitted.

[0017] [Breeding tank 2] The breeding tank 2 is a tank containing fish and shellfish to be cultured in a land-based aquaculture device configured including the water treatment device 1 of this embodiment.

[0018] [Nitrification tank 3] The nitrification tank 3 is an aquarium tank located below the rotary filter 4 as shown in the figure, and is supplied with water that has passed through the rotary filter 4, and nitrifies the nitrogen contained in the water. The nitrification tank 3 contains a carrier having nitrifying bacteria attached thereto, and denitrification is performed by removing nitrogen from the water through the nitrification action of the nitrifying bacteria. As shown in the figure, an aeration pipe 60 connected by piping to the blower 30 is located near the bottom of the nitrification tank 3. The aeration pipe 60 diffuses air supplied from the blower 30 into the nitrification tank 3, thereby assisting in the activation of the nitrifying bacteria in the nitrification tank 3. The water that has been treated in the nitrification tank 3 is returned to the breeding tank 2 via a pump and piping 50 (not shown).

[0019] [Rotary Filter 4] As shown in the figure, the rotary filter 4 is cylindrical (drum-shaped) with its bottom surface oriented perpendicular to the vertical direction, and has a cylindrical filter on its side. The filter performs filtration by capturing suspended solids contained in the water passing through it. Rearing water is supplied from the rearing tank 2 through piping 4a into the interior of the rotary filter 4. The shaft 10a of the motor 10 is connected to the extension of the center line connecting the centers of the circular bottom surfaces of the rotary filter 4, and this allows the rotary filter 4 to rotate around the center line as the rotation axis in accordance with the rotation of the motor 10. The water that has passed through the rotary filter 4 is discharged into the nitrification tank 3.

[0020] Since it is sufficient for rotary filter 4 to perform the function of filtering water and discharging it into nitrification tank 3, it may be disposed so that its center line extends in a direction intersecting the vertical direction. In other words, rotary filter 4 may be disposed so that it is inclined with respect to a direction perpendicular to the vertical direction. However, in consideration of the arrangement space and filtration efficiency, rotary filter 4 is preferably disposed so that its center line is perpendicular to the vertical direction as in the configuration of the embodiment.

[0021] [Motor 10] The motor 10 is disposed to the side of the rotary filter 4, and a shaft 10a extending from the rotation axis of the motor 10 is connected to the rotary filter 4. The motor 10 rotates with the supplied power to rotate the rotary filter 4. A reducer constituted by gears may be provided between the motor 10 and the rotary filter 4. The operation of the motor 10 is controlled by a control unit 40.

[0022] [Water level sensor 11] The water level sensor 11 detects the water level in the rotary filter 4. That is, when suspended matter adheres to the filter mesh of the rotary filter 4, the amount of water passing through the rotary filter 4 per unit time decreases and the water level in the rotary filter 4 rises, and this water level is detected by the water level sensor 11. The water level sensor 11 may be an optical sensor, but may be replaced with another sensor capable of achieving a similar function, and therefore may be configured to indirectly detect the water level by measuring the weight of the water in the rotary filter 4.

[0023] [Pump 12] The pump 12 is disposed in the nitrification tank 3 or connected to the nitrification tank 3, and supplies water from the nitrification tank 3 to the backwash nozzle 13, the foam separator 20, and the oxygen mixer 31 through piping. The water is supplied from the pump 12 to the foam separator 20, specifically to the foam generator 21 and the foam breaker 22. Solenoid valves 41, 42, and 43 are disposed between the pump 12 and the backwash nozzle 13, the foam generator 21, and the foam breaker 22, respectively, and the flow of water is controlled by opening and closing the solenoid valves 41, 42, and 43 by the control unit 40. The flow of water can also be controlled by controlling the drive and stop of the pump 12 by the control unit 40.

[0024] [Backwash nozzle 13] The backwash nozzle 13 sprays water supplied from the nitrification tank 3 via the pump 12 in the form of a shower onto the outside of the filter of the rotary filter 4. As a result, suspended solids adhering to the inside of the filter are dropped into the backwash water receiving pan 14 together with the water sprayed from the backwash nozzle 13. In this specification, the operation of cleaning the filter by spraying water from the opposite side to the direction in which the water to be treated passes through the rotary filter 4 is referred to as "backwash" or "filter cleaning operation."

[0025] [Backwash water receiving pan 14] The backwash water receiving pan 14 captures suspended solids that have fallen off from the inside of the filter of the rotary filter 4 together with the water sprayed from the backwash nozzle 13, and discharges them into a strainer 15 arranged outside the rotary filter 4. The backwash water receiving pan 14 is open on its upper side facing the backwash nozzle 13, and is configured to guide the captured suspended solids and water to a pipe connected to the strainer 15.

[0026] [Strainer 15] The strainer 15 removes suspended solids from the water containing suspended solids discharged from the backwash water receiving pan 14, and separates the water from the suspended solids. The strainer 15 also removes suspended solids from the water containing suspended solids discharged from the foam breaker 22 of the foam separator 20, and separates the water from the suspended solids. The separated suspended solids are discharged outside the water treatment device 1 as waste, and the water is returned to the nitrification tank 3.

[0027] [Foam separator 20] The foam separator 20 generates fine air bubbles inside the water (breeding water) obtained from the breeding tank 2, causes suspended solids contained in the water to attach to the air bubbles, and separates and discharges the suspended solids together with the air bubbles from the water. The water from which the air bubbles containing suspended solids have been removed is returned to the breeding tank 2. Specifically, the foam separator 20 includes a foam generator 21 and a foam breaker 22. The foam separator 20 is a so-called protein skimmer.

[0028] [Bubble Generator 21] The foam generator 21 obtains compressed air from the blower 30 and generates bubbles by supplying the compressed air into the water obtained from the nitrification tank 3. Suspended matter contained in the water adheres to the generated bubbles.

[0029] [Defoaming device 22] The defoamer 22 separates the water containing air bubbles near the water surface from the water in which air bubbles have been generated, and pours water onto the separated water containing air bubbles to eliminate the air bubbles. The water for defoaming supplied from the defoamer 22 is the water from the nitrification tank 3 supplied from the pump 12. The water that has been defoamed and that contained air bubbles becomes water containing suspended solids, and is discharged into the strainer 15.

[0030] [Blower 30] The blower 30 generates compressed air and supplies it to the oxygen mixer 31, the nitrification tank 3, and the foam generator 21. Specifically, the blower 30 supplies compressed air to the air diffuser 60 arranged in the nitrification tank 3 as described above to diffuse the air. The blower 30 also supplies compressed air to the foam generator 21 to generate bubbles. The blower 30 also supplies compressed air to the oxygen mixer 31. The blower 30 operates according to a DO value detected by a DO value sensor that detects a DO value indicating the dissolved oxygen (sometimes abbreviated as "DO"), which represents the oxygen concentration dissolved in the breeding water, or according to a predetermined condition. The blower 30 may operate continuously. The DO value sensor is arranged inside the breeding tank 2 or the nitrification tank 3.

[0031] [Oxygen Mixer 31] The oxygen mixer 31 increases the oxygen concentration by supplying compressed air from the blower 30 to the water supplied from the nitrification tank 3 via the pump 12, and returns the water to the nitrification tank 3. Since the water from the nitrification tank 3 is returned to the breeding tank 2, it can be said that the oxygen mixer 31 indirectly supplies oxygen by mixing it into the water in the breeding tank 2. Similarly, it can be said that the blower 30 supplies oxygen to the water in the breeding tank 2. Oxygen is supplied from the blower 30 to the oxygen mixer 31 via a pipe. A solenoid valve 44 that can be controlled to open and close by the control unit 40 is provided in this pipe.

[0032] [Control unit 40] The control unit 40 directly or indirectly controls the operations of the solenoid valves 41 to 44, the motor 10, the water level sensor 11, the pump 12, the backwash nozzle 13, the rotary filter 4, the blower 30, etc. of the water treatment device 1. The control unit 40 is, for example, a computer.

[0033] [Operation of water treatment device 1] Here, a specific example of the control of the operation of the water treatment device 1 by the control unit 40 will be described. However, only the characteristic control of this embodiment will be described here, and detailed description of the conventionally known control of the operation will be omitted.

[0034] The water treatment device 1 of this embodiment is intended to mainly remove and filter excrement from the rearing water in land-based aquaculture, so there is a need to extend the operating time after feeding the farmed fish and shellfish, while shortening the operating time until the next feeding time after a certain time has passed since feeding. However, suspended matter floats in the rearing water as solid matter, and it is not easy to quantitatively observe the amount of suspended matter in the rearing water. Therefore, in the water treatment device 1 of this embodiment, the amount of suspended matter in the rearing water is indirectly observed, and backwashing using the backwash nozzle 13, foam separation by the foam separator 20, and oxygen supply by the blower 30 are controlled.

[0035] In the water treatment device 1, when suspended solids adhere to the filter of the rotary filter 4, drainage deteriorates and the water level in the rotary filter 4 rises. Therefore, the water treatment device 1 is provided with a water level sensor 11 that detects the water level of the rotary filter 4, and backwashing is performed when the detected water level becomes equal to or higher than a predetermined level. This backwashing is performed, specifically, by spraying water from the backwash nozzle 13 toward the filter of the rotary filter 4 from the outside and driving the motor 10 to rotate the rotary filter 4. Backwashing is performed for, for example, 20 seconds per session, and when 20 seconds have elapsed from the start, the spraying of water from the backwash nozzle 13 and the operation of the motor 10 are stopped. In this embodiment, the motor 10 operates only during backwashing, but it may be operated continuously or intermittently during other than backwashing. In addition, the length of time for performing backwashing may be changed arbitrarily. Backwashing may be performed continuously until the water level detected by the water level sensor 11 becomes equal to or lower than a certain level. The time for performing backwashing is an example of the "first operation period" of the present invention.

[0036] Furthermore, in the water treatment device 1, the amount of suspended solids in the breeding water is indirectly observed based on the frequency of backwashing performed under the above conditions, and the operation is changed according to the estimated amount of suspended solids, i.e., the concentration of suspended solids (also called "SS concentration"). The frequency of backwashing is determined based on the number of operations of the motor 10 and / or the backwash nozzle 13 per certain time defined as the detection period. The number of operations of the motor 10 and / or the backwash nozzle 13 may be replaced with the number of times the water level detected by the water level sensor 11 has reached a predetermined level or higher. The number of operations of the motor 10 and / or the backwash nozzle 13 is the same as the number of times the water level detected by the water level sensor 11 has reached a predetermined level or higher. Specifically, in this embodiment, the operation of the water treatment device 1 is changed as follows according to the number of operations (start-up number) of the motor 10 per 5 minutes, which is the detection period.

[0037] [Table 1]

[0038] (1) The number of operations per 5 minutes is 10 or more The concentration of suspended solids is estimated to be high. Backwash, the foam separator 20, and the blower 30 are operated continuously. The period of continuous operation is, for example, 10 minutes, but may be set arbitrarily to a time longer than the detection period. The period during which the continuous operation of the backwash is performed may be different from the operation period of the continuous operation of the foam separator 20 and the blower 30. The operation periods of the continuous operation of the foam separator 20 and the blower 30 may also be different. The period during which the continuous operation of the backwash is performed is an example of the "second operation period" of the present invention. The operation period during which the continuous operation of the foam separator 20 and the blower 30 is an example of the "third operation period" of the present invention.

[0039] (2) The number of operations per 5 minutes is 5 to 10 The concentration of suspended solids is estimated to be medium. Backwashing is performed when the water level detected by the water level sensor 11 reaches a predetermined level or higher. The foam separator 20 and the blower 30 are operated continuously. The period of continuous operation is, as above, for example, 10 minutes.

[0040] (3) The number of operations per 5 minutes is between 2 and 5 The concentration of suspended solids is estimated to be low. Backwashing is performed when the water level detected by the water level sensor 11 reaches a predetermined level or higher. The foam separator 20 is operated simultaneously with the backwashing, that is, when the water level detected by the water level sensor 11 reaches a predetermined level or higher. The blower 30 is operated when the DO value detected by the DO value sensor falls below a predetermined level.

[0041] (4) Fewer than two operations per five minutes The concentration of suspended solids is estimated to be at a minimum concentration. At this time, the backwash, the foam separator 20, and the blower 30 are stopped. The operation stop period is, for example, 10 minutes, but may be set arbitrarily to a period longer than the detection period.

[0042] In the above example, the description that the blower 30 operates means that the supply of air from the blower 30 to the oxygen mixer 31 is stopped, and the blower 30 may continue to operate. When the blower 30 stops operating, the supply of air by the blower 30 to the nitrification tank 3 and the foam generator 21 is also stopped, so that if the blower 30 is kept operating, the supply of air to the nitrification tank 3 and the foam generator 21 can be continued. The blower 30 may stop operating except when it is necessary to supply air to the oxygen mixer 31, the nitrification tank 3, and the foam generator 21.

[0043] The number of times the water level detected by the water level sensor 11 reaches a predetermined level or higher during the 5-minute detection period, which is the estimation standard for the concentration of suspended solids in the above embodiment, is an example and is not limited to the embodiment. In addition, the detection period, and the backwash, continuous operation period and stop operation period of the foam separator 20 and the blower 30 according to the concentration of suspended solids may be changed arbitrarily.

[0044] The above embodiment can be summarized as follows, with respect to the execution of backwashing, the operation of the foam separator 20, and the operation of the blower 30.

[0045] The water treatment device 1 of this embodiment is a device that treats water in the breeding tank 2 and returns it to the breeding tank 2, and includes a rotary filter 4, a motor 10, a nitrification tank 3, a backwash nozzle 13, a backwash water receiving pan 14, a water level sensor 11, and a control unit 40. The control unit 40 rotates the motor 10 and executes backwashing (filter cleaning operation) by spraying water from the backwash nozzle 13 toward the filter of the rotary filter 4 as follows. In the following explanation, the number of times that the water level in the rotary filter 4 detected by the water level sensor 11 reaches or exceeds a predetermined level within a predetermined detection period (e.g., 5 minutes) is defined as "T".

[0046] (1-1)T<3rd threshold (e.g. 2 times) Stop backwashing during the downtime period (e.g., 10 minutes).

[0047] (1-2) Third threshold (e.g., 2 times) ≦ T < First threshold (e.g., 10 times) When the water level detected by the water level sensor 11 reaches or exceeds a predetermined level, backwashing is performed for a first operation period (for example, 20 seconds).

[0048] (1-3) First threshold (e.g., 10 times)≦T Backwashing is performed continuously during a second operating period (eg, 10 minutes).

[0049] The water treatment device 1 of this embodiment also includes a foam separator 20 and a blower 30, and the control unit 40 controls the operations of the foam separator 20 and the blower 30 as follows.

[0050] (2-1) T<3rd threshold (e.g. 2 times) During the shutdown period (eg, 10 minutes), the foam separator 20 and the blower 30 are shut off.

[0051] (2-2) Third threshold (e.g., 2 times) ≦ T < second threshold (e.g., 5 times) The foam separator 20 is operated simultaneously with the backwashing. The blower 30 is operated when the DO value detected by the DO value sensor falls to a predetermined value or less. That is, the foam separator 20 and the blower 30 are operated intermittently according to predetermined conditions.

[0052] (2-3) Second threshold (e.g., 5 times)≦T The foam separator 20 and blower 30 are operated continuously for a third operating period (eg, 10 minutes).

[0053] According to the water treatment device 1 of this embodiment, the amount of suspended matter contained in the breeding water is estimated and backwashing is performed according to the water level in the rotary filter 4 detected by the water level sensor 11, so that backwashing can be performed at the necessary timing. Also, the amount of suspended matter contained in the breeding water can be estimated and the frequency and time of backwashing can be determined according to the number of times that the water level in the rotary filter 4 detected by the water level sensor 11 reaches a predetermined level or higher during a detection period. This eliminates the need to perform backwashing at unnecessary times, so that the power required for the operation of the water treatment device 1 can be reduced. Also, when there is a large amount of suspended matter in the breeding water, backwashing is performed continuously, so that water treatment can be performed efficiently.

[0054] Furthermore, according to the water treatment device 1 of this embodiment, the amount of suspended matter contained in the breeding water can be estimated according to the number of times that the water level in the rotary filter 4 detected by the water level sensor 11 during the detection period reaches or exceeds a predetermined level, and the frequency and time of operation of the foam separator 20 and the blower 30 can be determined. This eliminates the need to operate the foam separator 20 and the blower 30 at unnecessary times, thereby reducing the power required for operation of the water treatment device 1. Furthermore, since the foam separator 20 and the blower 30 are operated continuously as necessary, water treatment can be performed efficiently.

[0055] [Variations] The water treatment device 1 of the present embodiment is not limited to the aspects described in the embodiment, and can be modified without departing from the spirit of the invention. Specifically, the following modifications may be applied.

[0056] The water treatment device 1 may include configurations for ultraviolet sterilization and temperature adjustment in addition to the configurations described in the embodiment.

[0057] The solenoid valves 41 to 44 may be replaced with other valves or other configurations that can be electrically controlled to open and close by the control unit 40. Also, instead of providing the solenoid valves 41 to 44, a different configuration that can adjust the water or air passing through these pipes may be used.

[0058] The rotary filter 4 does not necessarily have to be cylindrical, but may have other shapes such as a cone shape or a polygonal prism shape.

[0059] The supply of air from the blower 30 to the oxygen mixer 31 may be performed continuously without being stopped. Also, the supply of air from the blower 30 to the oxygen mixer 31 may be always performed according to the DO value.

[0060] The foam separation by the foam separator 20 may be performed continuously without being stopped. Also, the foam separation by the foam separator 20 may be performed regardless of the water level in the rotary filter 4, for example, at a fixed time interval. [Explanation of symbols]

[0061] 1...Water treatment equipment 2. Breeding tank 3…Nitrification tank 4. Rotary filter 10…Motor 11...Water level sensor 12…Pump 13…Backwash nozzle 14…Backwash water receiving pan 15…Strainer 20…foam separator 21...Bubble generator 22...defoaming device 30…Blower 31...Oxygen mixer 40...Control unit 41~44...Solenoid valve 60...Air diffuser

Claims

1. A water treatment device that treats water in a breeding tank and returns it to the breeding tank, a cylindrical rotary filter that can rotate around a rotation axis that intersects the vertical direction and has a filter on a side thereof that captures suspended matter contained in the water obtained from the breeding tank; A motor for rotating the rotary filter; a nitrification tank for nitrifying the nitrogen contained in the water that has passed through the filter and returning the nitrified water to the breeding tank; A backwash nozzle that sprays water onto the filter from the outside; A backwash water receiving pan that captures the suspended solids that have fallen off from inside the filter together with the water sprayed from the backwash nozzle and discharges them to the outside of the rotary filter; A water level sensor that detects a water level in the rotary filter; A control unit that controls the water level sensor, the motor, and the backwash nozzle; The control unit is When the number of times T that the water level detected by the water level sensor becomes equal to or higher than a predetermined level during a predetermined detection period is less than a first threshold value, a filter cleaning operation is performed in which the motor is rotated and water is sprayed from the backwash nozzle toward the filter during a first operation period when the water level detected by the water level sensor becomes equal to or higher than the predetermined level; When the number of times T is equal to or greater than the first threshold value, the filter cleaning operation is performed for a second operation period that is longer than the first operation period. Water treatment equipment.

2. A foam separator that generates bubbles in the water obtained from the breeding tank, separates and discharges the generated bubbles, and returns the water from which the bubbles have been separated to the breeding tank; and a blower for supplying oxygen to the water in the breeding tank. The control unit further controls the foam separator and the blower, The control unit is When the number of times T is less than a second threshold value, the foam separator and the blower are operated intermittently; When the number of times T is equal to or greater than the second threshold value, the foam separator and the blower are continuously operated for a third operation period longer than the first operation period, The second threshold is smaller than the first threshold. The water treatment device according to claim 1 .

3. The control unit is If the number of times T is less than a third threshold value, the execution of the filter cleaning operation is stopped for an operation stop period longer than the first operation period, and the operation of the foam separator and the blower is stopped; the third threshold is less than the second threshold; The water treatment device according to claim 2 .

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