Electrolysis device for aquatic life breeding, circulation water treatment system for aquatic life breeding, and electrolysis method for aquatic life breeding

Abstract

To provide an electrolysis device capable of decomposing ammonia or ammonium ions in water using electrolysis, in breeding aquatic lives, and facilitating removal of precipitation precipitated on a surface of an electrode.SOLUTION: An electrolysis part 13 forming at least a part of an electrolysis device performs electrolysis of breeding water for generating a chloric acid compound, in a region where the breeding water is stored or circulated. The electrolysis part 13 has: an electrode part 55 having a first electrode 55A and a second electrode 55B arranged in the region; and a voltage application part 51 for applying a voltage between the electrodes. The voltage application part 51 is switched between a first state where the first electrode 55A is an anode and the second electrode 55B is a cathode and the voltage is applied for performing electrolysis in the region; and a second state where the second electrode 55B is an anode and the first electrode 55A is a cathode and the voltage is applied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an electrolysis device for aquaculture, a circulating water treatment system for aquaculture, and an electrolysis method for aquaculture.

Background Art

[0002] As an example of a system for culturing aquatic organisms, a closed-loop aquaculture system is known. The closed-loop aquaculture system is a system that decomposes and purifies residual feed and manure excreted by organisms in a filtration tank and circulates water. In a general closed-loop aquaculture system, a method that utilizes microorganisms for the decomposition and purification of nitrogen compounds in the breeding water is the mainstream. As this type of technology, something like Patent Document 1 has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the aquaculture management system disclosed in Patent Document 1, ammonia is generated due to the metabolic activities of aquatic organisms in the aquarium and the decomposition of organic substances such as residual feed. Therefore, the breeding water is circulated and passed through a filtration tank for biological filtration to decompose the ammonia and change it into less toxic nitric acid. The filtration tank holds nitrifying bacteria (microorganisms) that oxidize ammonia in water containing oxygen to change it into nitrous acid and then nitric acid.

[0005] However, when adopting a purification method using microorganisms as in Patent Document 1, there is a problem that the purification ability depends on the microorganisms. In this regard, the inventor of the present application assumed a method of decomposing ammonia contained in breeding water containing salt by electrolyzing the breeding water containing salt to generate sodium hypochlorite and then reacting this sodium hypochlorite with the ammonia present in the breeding water to directly decompose it into nitrogen. By using this method, it is possible to decompose ammonia while suppressing dependence on microorganisms, and it is possible to reliably suppress the generation of nitrous acid, nitric acid, etc. during the decomposition process.

[0006] However, when using this method, there is a problem that deposits caused by electrolysis tend to adhere to the surface of the electrodes during electrolysis. When deposits adhere to the surface of the electrodes in this way, the generation of sodium hypochlorite is suppressed and the decomposition rate of ammonia tends to decrease.

[0007] One of the objectives of the present disclosure is to provide a technique that can decompose ammonia in water by a method using electrolysis and is easy to remove deposits deposited on the surface of the electrodes when culturing aquatic organisms.

Means for Solving the Problems

[0008] An electrolysis device for culturing aquatic organisms according to one aspect of the present disclosure is an electrolysis device used in a circulation type water treatment system that circulates and treats the breeding water from a breeding tank that is a tank for culturing aquatic organisms and contains breeding water containing salt, and returns the treated breeding water to the breeding tank, in a region where the breeding water is stored or flows, an electrolysis unit that generates a chlorate compound by electrolyzing the breeding water and decomposes ammonia or ammonium ions in the breeding water by reacting the generated chlorate compound with ammonia or ammonium ions in the breeding water, the electrolysis unit includes an electrode unit having a first electrode and a second electrode disposed in the region, and a voltage application unit that applies a voltage between the electrodes of the first electrode and the second electrode. The voltage application unit switches between a first state in which a voltage is applied with the first electrode as the anode and the second electrode as the cathode to perform the electrolysis within the region, and a second state in which a voltage is applied with the second electrode as the anode and the first electrode as the cathode.

[0009] A circulating water treatment system for aquaculture, which is one of the present disclosures, is a circulating water treatment system for aquaculture provided with the above-described electrolysis device for aquaculture, in a first region where the breeding water sent from the breeding tank is stored or flows, a removal unit that removes at least solids, an electrolysis unit that performs electrolysis of the breeding water in a second region, which is the region where the breeding water that has passed through the first region is stored or flows, and an activated carbon unit that removes at least residual chlorine with activated carbon in a third region where the breeding water that has passed through the second region is stored or flows. It includes.

[0010] A circulating water treatment system for aquaculture, which is one of the present disclosures, is a circulating water treatment system for aquaculture provided with the above-described electrolysis device for aquaculture, an electrolysis tank configured such that the breeding water is stored or flows, a reaction tank configured such that the breeding water discharged from the electrolysis tank is stored or flows, and includes, the inside of the electrolysis tank is the region, the electrolysis tank has a first guiding path that does not guide water located below a first height inside the electrolysis tank to the outside of the electrolysis tank, and guides water located above the first height to the outside of the electrolysis tank, the reaction tank has a second guiding path that does not guide water located below a second height inside the reaction tank to the outside of the reaction tank, and guides water located above the second height to the outside of the reaction tank.

[0011] One of the electrolysis methods for aquaculture disclosed herein is an electrolysis method used in a circulating water treatment system that circulates and treats the breeding water from a breeding tank that is a tank for breeding aquatic organisms and contains saline breeding water, and returns the treated breeding water to the breeding tank, using an electrolysis unit having a first electrode and a second electrode, and a voltage application unit that applies a voltage between the electrodes of the first electrode and the second electrode, with the first electrode and the second electrode arranged in a region where the breeding water is stored or flows, and a voltage is applied between the electrodes by the voltage application unit to electrolyze the breeding water to generate a chloric acid compound, and the generated chloric acid compound is reacted with ammonia or ammonium ions in the breeding water to decompose the ammonia or ammonium ions in the breeding water, the voltage application unit switches between a first state in which the voltage is applied so that the first electrode is the anode and the second electrode is the cathode to perform the electrolysis in the region, and a second state in which the voltage is applied so that the second electrode is the anode and the first electrode is the cathode.

Advantages of the Invention

[0012] The technology according to the present disclosure can decompose ammonia or ammonium ions in water by a method using electrolysis when culturing aquatic organisms, and it is easy to remove deposits deposited on the surface of the electrodes.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

MODE FOR CARRYING OUT THE INVENTION

[0014] Each of the following [1] to

[13] is an example of a characteristic technique included in the present disclosure.

[0015] 〔1〕 An electrolysis device used in a circulating water treatment system that circulates and treats breeding water from a breeding tank that is a tank for breeding aquatic organisms and contains saline breeding water, and returns the treated breeding water to the breeding tank, In a region where the breeding water is stored or flows, an electrolysis unit that generates a chlorate compound by electrolyzing the breeding water and decomposes ammonia or ammonium ions in the breeding water by reacting the generated chlorate compound with ammonia or ammonium ions in the breeding water, The electrolysis unit includes an electrode unit having a first electrode and a second electrode disposed in the region, and a voltage application unit that applies a voltage between the electrodes of the first electrode and the second electrode. The voltage application unit switches between a first state in which a voltage is applied with the first electrode as the anode and the second electrode as the cathode to perform the electrolysis within the region, and a second state in which a voltage is applied with the second electrode as the anode and the first electrode as the cathode. An electrolysis device for aquaculture.

[0016] The electrolysis device of the above [1] generates a chloric acid compound (for example, sodium hypochlorite) by electrolyzing breeding water containing salt, and then reacts this chloric acid compound with ammonia or ammonium ions present in the breeding water to directly decompose it into nitrogen. During the decomposition process, the generation of nitrous acid, nitric acid, etc. can be reliably suppressed. However, when this method is adopted, if no measures are taken, there is a concern that deposits will adhere to the surface of the electrodes, inhibiting electrolysis. However, the above electrolysis device can switch between a first state in which electrolysis is performed by applying a voltage with the first electrode as the anode and the second electrode as the cathode, and a second state in which a voltage is applied with the second electrode as the anode and the first electrode as the cathode. Therefore, the deposits adhering to the surface of the electrodes due to continuous electrolysis are likely to detach from the electrodes by the switching. Thus, this electrolysis device can easily remove the deposits deposited on the surface of the electrodes.

[0017] 〔2〕 The electrode unit includes an electrode holding unit that holds the first electrode and the second electrode, and the first electrode, the second electrode, and the electrode holding unit are integrally formed. In the circulating water treatment system, an electrolysis tank configured such that the breeding water is stored or flows is provided, and the inside of the electrolysis tank is the region. The integrally formed electrode unit is detachable from the electrolysis tank. The electrolysis device for aquaculture according to [1].

[0018] In the electrolysis device of the above [2], since the electrode unit in which the first electrode, the second electrode, and the electrode holding unit are integrally formed is configured to be detachable from the electrolysis cell, the operation of removing the electrode unit for cleaning becomes easy. In particular, the promotion of the detachment of the deposit due to switching and the facilitation of the attachment / detachment operation of the electrode unit exhibit a synergistic effect, and further facilitation of cleaning can be achieved.

[0019] 〔3〕 It includes an electrolysis cell configured such that the breeding water is stored or flows, The inside of the electrolysis cell is the above region, Furthermore, it includes a guiding unit that guides and collects the deposits that have sunk from the electrode unit in the electrolysis cell toward a predetermined position in the electrolysis cell. The electrolysis device for aquaculture described in [1] or [2].

[0020] In the electrolysis device of the above [3], since the deposits that have sunk from the electrode unit can be automatically collected by the guiding unit toward a predetermined position, not only can the deposits be detached from the electrode unit, but also the detached deposits can be easily collected.

[0021] 〔4〕 It includes an electrolysis cell configured such that the breeding water is stored or flows, The inside of the electrolysis cell is the above region, Furthermore, it includes a discharge unit having a pipe for discharging the deposits that have sunk from the electrode unit in the electrolysis cell. The discharge unit takes in the deposits inside the pipe at a position lower than the electrode unit and discharges the deposits from the electrolysis cell through the pipe. The electrolysis device for aquaculture according to any one of [1] to [3].

[0022] In the electrolysis device of the above [4], since the deposits that have sunk from the electrode unit can be taken into the pipe at a position lower than the electrode unit and discharged, it is possible to suppress the deposits from being dispersed during the discharge process and easily flowing into the subsequent process.

[0023] 〔5〕Comprising an electrolysis cell configured such that the breeding water is stored or flows therein, wherein the interior of the electrolysis cell is the region, Furthermore, the electrolysis cell has a guiding path that does not guide water located below a predetermined height within the electrolysis cell to the outside of the electrolysis cell, but guides water located above the predetermined height to the outside of the electrolysis cell. The electrolysis apparatus for aquaculture according to any one of 〔1〕 to 〔4〕.

[0024] The electrolysis apparatus of 〔5〕 above can guide supernatant water located above a predetermined height to the outside, and can make it difficult to guide precipitates that have sunk below the predetermined height to the outside of the electrolysis cell.

[0025] 〔6〕The predetermined height is above the lower end of the electrode part. The electrolysis apparatus for aquaculture according to 〔5〕.

[0026] The electrolysis apparatus of 〔6〕 above makes it difficult for precipitates that detach from the electrode part and sink downward from the lower end to be guided to the outside of the electrolysis cell.

[0027] 〔7〕Comprising an electrolysis cell configured such that the breeding water is stored or flows therein, wherein the interior of the electrolysis cell is the region, The electrode part is arranged on the water surface side of the breeding water within the electrolysis cell, Furthermore, it includes a water flow generating part that causes the breeding water introduced into the electrolysis cell from the outside of the electrolysis cell to flow upward from the lower side to the upper side of the electrode part within the electrolysis cell. The electrolysis apparatus for aquaculture according to any one of 〔1〕 to 〔6〕.

[0028] The electrolysis apparatus of 〔7〕 above can generate a water flow so as to flow upward from the lower side to the upper side of the electrode part within the electrolysis cell. Therefore, new breeding water can be easily guided to the electrode part, and the efficiency of electrolysis can be further enhanced.

[0029] 〔8〕The voltage application unit periodically switches between an operation of electrolyzing the breeding water while maintaining the first state and an operation of electrolyzing the breeding water while maintaining the second state. The electrolysis device for aquaculture according to any one of 〔1〕to 〔7〕.

[0030] The electrolysis device of the above 〔8〕can periodically remove deposits and can periodically clean the electrodes.

[0031] 〔9〕A circulating water treatment system for aquaculture comprising the electrolysis device for aquaculture according to any one of 〔1〕to 〔8〕, in a first region where the breeding water sent from the breeding tank is stored or flows, a removing unit that removes at least solids, in a second region which is the region where the breeding water that has passed through the first region is stored or flows, the electrolysis unit that electrolyzes the breeding water, in a third region where the breeding water that has passed through the second region is stored or flows, an activated carbon unit that removes at least residual chlorine with activated carbon, A circulating water treatment system for aquaculture including the above.

[0032] The above-described [[9]] circulating water treatment system can remove solids contained in the breeding water in the first region by a removal unit. Further, in the second region after passing through the first region, this circulating water treatment system can decompose ammonia or ammonium ions by an electrolysis unit, and perform electrolysis of the breeding water after removing solids by the removal unit, so that it is possible to surely suppress solids from inhibiting electrolysis and make it easy to perform electrolysis well. Further, in the third region where the breeding water passing through the second region is stored or flows, residual chlorine can be removed by activated carbon. Therefore, even if a chlorate compound not used for the decomposition of ammonia or ammonium ions is contained in the breeding water in the third region, this chlorate compound can be effectively removed by the activated carbon unit. Thus, in the above circulating water treatment system, solids such as feces and residual feed are surely reduced in the breeding water after passing through the third region, and nitrogen compound components such as ammonia, ammonium ions, nitrous acid, and nitric acid are also surely suppressed, which is extremely advantageous in terms of purification and detoxification of the breeding water.

[0033] 〔10〕 A circulating water treatment system for aquaculture equipped with the electrolysis device for aquaculture according to any one of 〔1〕 to 〔8〕, an electrolysis tank configured such that the breeding water is stored or flows, a reaction tank configured such that the breeding water discharged from the electrolysis tank is stored or flows, comprising the inside of the electrolysis tank being the region, the electrolysis tank having a first guiding path that does not guide water located below a first height in the electrolysis tank to the outside of the electrolysis tank and guides water located above the first height to the outside of the electrolysis tank, the reaction tank having a second guiding path that does not guide water located below a second height in the reaction tank to the outside of the reaction tank and guides water located above the second height to the outside of the reaction tank Circulating water treatment system for aquaculture.

[0034] In the above-mentioned circulating water treatment system of

[10] , since the supernatant water located above the first height in the electrolysis tank can be induced outside the electrolysis tank, when deposits detach from the electrodes and sink, it is difficult for the deposits to be induced outside the electrolysis tank. Even if some deposits are discharged from the electrolysis tank and enter the reaction tank, since the supernatant water located above the second height in the reaction tank can be induced outside the reaction tank, the deposits that enter the reaction tank are likely to precipitate in the reaction tank and are difficult to be induced outside the reaction tank.

[0035] 〔11〕 An electrolysis method used in a circulating water treatment system that circulates and treats the breeding water from a breeding tank that is a tank for culturing aquatic organisms and contains saline breeding water, and returns the treated breeding water to the breeding tank. Using an electrolysis unit provided with an electrode unit having a first electrode and a second electrode, and a voltage application unit that applies a voltage between the electrodes of the first electrode and the second electrode. With the first electrode and the second electrode arranged in the region where the breeding water is stored or flowing, a voltage is applied between the electrodes by the voltage application unit to electrolyze the breeding water to generate a chlorate compound, and the generated chlorate compound is reacted with ammonia or ammonium ions in the breeding water to decompose the ammonia or ammonium ions in the breeding water. The voltage application unit switches between a first state in which the electrolysis is performed in the region by applying a voltage such that the first electrode is the anode and the second electrode is the cathode, and a second state in which a voltage is applied such that the second electrode is the anode and the first electrode is the cathode. Electrolysis method for aquaculture.

[0036] The electrolysis method of

[11] above generates a chloric acid compound (for example, sodium hypochlorite) by electrolyzing breeding water containing salts, and then reacts this chloric acid compound with ammonia or ammonium ions present in the breeding water to directly decompose it into nitrogen. During the decomposition process, the generation of nitrous acid, nitric acid, etc. can be reliably suppressed. However, when this method is adopted, if no measures are taken, there is a concern that deposits will adhere to the surface of the electrodes and inhibit electrolysis. The above electrolysis method can be switched between a first state in which a voltage is applied with the first electrode as the anode and the second electrode as the cathode for electrolysis, and a second state in which a voltage is applied with the second electrode as the anode and the first electrode as the cathode. Therefore, deposits adhering to the surface of the electrodes due to continuous electrolysis are likely to detach from the electrodes by the switching. Thus, this electrolysis method easily removes the deposits deposited on the surface of the electrodes.

[0037]

[12] Using an electrolysis cell configured such that the breeding water is stored or flows, Arranging the electrode part so that the inside of the electrolysis cell is the above region, Continuously guiding the breeding water into the electrolysis cell and draining the breeding water from the electrolysis cell, while replacing the breeding water, the voltage application unit performs the operation in the first state, the operation in the second state, and the switching between the first state and the second state. The electrolysis method for aquaculture described in

[11] .

[0038] The electrolysis method of

[12] above can perform the operation in the first state, the operation in the second state, and the switching between the first state and the second state while continuously guiding the breeding water into the electrolysis cell and draining the breeding water from the electrolysis cell to replace the breeding water. Therefore, while circulating the breeding water more efficiently, the electrodes can be cleaned.

[0039]

[13] The voltage application unit periodically switches between the operation of continuously electrolyzing the breeding water in the first state and the operation of continuously electrolyzing the breeding water in the second state. The electrolysis method for aquaculture described in

[11] or

[12] .

[0040] The electrolysis method of the above

[13] can periodically remove deposits and can periodically clean the electrodes.

[0041] <First Embodiment> 1. Outline of the Circulating Water Treatment System 1 Used for Aquaculture The circulating water treatment system 1 illustrated in FIG. 1 is a system used for aquaculture. The circulating water treatment system 1 is configured as a closed-loop aquaculture system that circulates the breeding water in the breeding tank 3 containing the breeding water containing salt after treating the breeding water outside the breeding tank 3 and then returning the treated breeding water to the breeding tank 3, and is a system that circulates and uses water. When culturing aquatic organisms in the breeding tank 3, the circulating water treatment system 1 continuously breeds the aquatic organisms inside the breeding tank 3, and decomposes and purifies the residual feed and feces discharged by the organisms remaining in the breeding water during the breeding in the breeding tank 3 in the process from circulating the water from the breeding tank 3 and returning it to the breeding tank 3 again.

[0042] As shown in FIG. 1, the circulating water treatment system 1 mainly includes a breeding tank 3, a removal unit 5, an electrolysis tank 11, a reaction tank 15, a filtration tank 17, an activated carbon tank 21, a standby tank (water quality adjustment tank) 25, a treatment unit 31, etc. Further, the circulating water treatment system 1 also includes a temperature controller 35, a filter 37, etc. The electrical configuration of the circulating water treatment system 1 is, for example, as shown in FIG. 2. The types of aquatic organisms that can be bred inside the breeding tank 3 are various. For example, fish, crustaceans, shellfish, etc. are listed as preferred examples, and other types (for example, squid, octopus, etc.) may also be used.

[0043] 2. Configuration and Operation of Each Part (Breeding Tank) The breeding tank 3 shown in Fig. 1 is a tank for breeding and cultivating aquatic organisms. Inside the breeding tank 3, breeding water containing salts such as artificial seawater or natural seawater is stored, and aquatic organisms such as fish and shellfish are bred in this breeding water. In the example of Fig. 1, a plurality (for example, four) of breeding tanks 3 are provided, and the breeding water in these breeding tanks 3 is guided to be collected in the filter 37, filtered by the filter 37, and internally circulated so as to be distributed from the filter 37 to the plurality of breeding tanks 3. The water temperature of the breeding water in the breeding tank 3 is adjusted to a desired set temperature by the temperature controller 35. In the example of Fig. 1, a plurality of breeding tanks 3 are used, but it may also be composed of a single water tank.

[0044] (Removal part) The removal part 5 shown in Fig. 1 functions to remove at least solids in the first region where the breeding water sent from the breeding tank 3 is stored or flows. The breeding water in the breeding tank 3 is guided to the removal part 5 through the flow path 41. As shown in Fig. 3, the removal part 5 includes an ozone generator 9, a foam separator 7, a storage tank 60, an introduction part 62, a derivation part 64, and a discharge part 66. In Fig. 3 and the like, the symbol W conceptually indicates a part of the circulating breeding water.

[0045] The storage tank 60 is a tank for storing the breeding water introduced from the region of the previous process of the removal part 5. In the example of Fig. 1, the region of the previous process of the removal part 5 is the region inside the breeding tank 3. The method of flowing the breeding water from the breeding tank 3 to the storage tank 60 may be a method of flowing it using a pump, or a method of flowing it using a height difference.

[0046] The ozone generator 9 corresponds to an example of an ozone generation unit, generates ozone by a known method, for example, and supplies the generated ozone to the foam separator 7. The method for introducing the ozone from the ozone generator 9 into the foam separator 7 is not particularly limited. For example, a method of supplying the ozone generated by the ozone generator 9 from an inlet provided in the bubble generation section of a known foam separator for introducing air can be mentioned. The foam separator 7 operates to generate foam containing the ozone generated by the ozone generator 9 and adsorb solids contained in the breeding water in the first region where the breeding water sent from the breeding tank 3 is stored or flows onto the foam. In the example of FIG. 3, the first region is the internal region of the storage tank 60.

[0047] The introduction section 62 is a flow path for introducing the breeding water stored in the storage tank 60 into the foam separator 7. The derivation section 64 is a flow path for returning the breeding water that has passed through the foam separator 7 from the foam separator 7 to the storage tank 60. The discharge section 66 has a flow path for discharging the breeding water stored in the storage tank 60 to the region of the subsequent process of the removal section 5. In the examples of FIGS. 1 and 3, the region of the subsequent process of the removal section 5 is the region inside the electrolysis tank 11.

[0048] In the removal section 5, solids such as feces and uneaten feed contained in the breeding water introduced into the foam separator 7, removal proteins of metabolites of fish and shellfish, bacteria, viruses, parasites, etc. are attached to the fine bubbles generated in the foam separator 7 and removed from the breeding water. Moreover, since the bubbles generated in the foam separator 7 are air bubbles containing ozone, they have a high sterilizing power, and this sterilizing power also acts on the breeding water that passes through the foam separator 7 and returns to the derivation section 64. By such an operation, it is surely suppressed that dirt flows out to the subsequent electrolysis tank 11, and it is surely suppressed that the dirt obstructs the electrolysis of the electrolysis tank 11.

[0049] In the example of FIG. 3, the flow path 41 communicates near the bottom 60A of the storage tank 60, and the breeding water from the flow path 41 is supplied into the storage tank 60 from a position near the lower end on the side portion of the storage tank 60. The inlet (the inlet for taking in the breeding water) in the introduction part 62 is arranged at a position near the bottom 60A in the storage tank 60, making it easier to take in the breeding water immediately after it is introduced into the storage tank 60 from the flow path 41. On the other hand, the breeding water that has passed through the foam separator 7 is led out by the leading-out part 64 to a position closer to the discharge part 66 than the flow path 41. The outlet (the outlet for discharging the breeding water) of the leading-out part 64 is arranged at a position closer to the water surface W1 than the bottom 60A of the storage tank 60. The discharge part 66 is configured as a flow path for flowing the breeding water in the storage tank 60 toward the outside of the storage tank 60. The discharge part 66 is configured not to guide the water located below a predetermined first height in the storage tank 60 to the outside of the storage tank 60, but to guide the water located above the first height to the outside of the storage tank 60. The above-mentioned first height is the height of the lower end of the boundary with the storage tank 60 on the inner wall surface of the flow path of the discharge part 66. When the water surface of the breeding water in the storage tank 60 is higher than this first height, the water in the region higher than the first height is discharged from the discharge part 66.

[0050] The configuration of the removal part 5 shown in FIG. 3 can be more specifically configured as shown in FIG. 4. In the specific example of FIG. 4, a foam generation part 8 and a foam separation tank 7A are provided in the foam separator 7. Further, the inlet (water intake) of the introduction part 62 configured as a pipe is arranged near the bottom of the storage tank 60 and close to the flow path 45 in the storage tank 60, and a filter 61 is provided so as to cover this inlet. Among the breeding water stored in the storage tank 60, the breeding water that can pass through the filter 61 is introduced from the introduction part 62 into the foam separator 7. The filter 61 is configured to block the passage of objects with a large particle size and allow the passage of objects with a small particle size, and is, for example, configured in a net shape. Although not shown in FIG. 4, a pump for flowing the breeding water so as to flow into the foam separator 7 through the introduction part 62 may be provided.

[0051] In the configuration of FIG. 4, the bubble generating unit 8 injects a gas containing ozone generated by the ozone generator 9 into the breeding water flowing in from the introduction unit 62, and contains bubbles of the gas containing ozone in the breeding water passing through the bubble generating unit 8. The breeding water that has passed through the bubble generating unit 8 flows into the foam separation tank 7A through the introduction unit 63 configured as a pipe as breeding water containing bubbles containing ozone. In the foam separation tank 7A, bubbles to which solids are attached are separated so as to gather near the water surface, and the gathered bubbles are discharged to the outside of the foam separation tank 7A through the discharge path 65. On the other hand, the breeding water on the lower side of the foam separation tank 7A is discharged near the water surface of the storage tank 60 by the lead-out unit 64 configured as a pipe. The outlet (discharge port) of the lead-out unit 64 is arranged so that a vortex is generated in a certain direction in the breeding water stored in the storage tank 60. The discharge unit 66 configured as a flow path for discharge is arranged near the water surface of the storage tank 60, and the supernatant of the breeding water stored in the storage tank 60 is discharged from the discharge unit 66.

[0052] (Electrolysis tank) The electrolysis tank 11 shown in FIG. 5 is a tank for performing electrolysis, and is a tank in which the breeding water that has passed through the removal unit 5 is stored or flows. The internal region of the electrolysis tank 11 is a region in which the breeding water that has passed through the above-described first region (in the example of FIG. 3, the region in the storage tank 60) is stored or flows, and corresponds to an example of the second region. An electrolysis unit 13 is provided in the electrolysis tank 11. The electrolysis unit 13 generates a chloric acid compound (for example, sodium hypochlorite) by electrolyzing the breeding water in the above-described second region, and reacts the generated chloric acid compound with ammonia or ammonium ions in the breeding water to decompose ammonia or ammonium ions. Further, in the electrolysis tank 11, since the electrolysis unit 13 generates a chloric acid compound, sterilization, deodorization, and decolorization of the breeding water can be performed.

[0053] In the electrolysis tank 11, electrolysis shown by the following formula (1) is performed. 2NaCl + 3H2O → NaClO + NaCl + 2H2O + H2↑ ··· (1)

[0054] Then, the decomposition of ammonia or the decomposition of ammonium ions is carried out by the chemical reactions shown in the following formulas (2) and (3). 2NH3 + 3NaClO → N2↑ + 3NaCl + 3H2O ···(2) 2NH4 + + 3NaClO → N2↑ + 3H2O + 3NaCl + 2H + ···(3)

[0055] In the electrolytic cell 11 shown in FIG. 5, the internal region of the electrolytic cell 11 is a "region" where the electrode part 55 is arranged and electrolysis is carried out. The electrolytic cell 11 is provided with an electrolysis part 13. The electrolysis part 13 has an electrode part 55 having a first electrode 55A and a second electrode 55B arranged in the above "region" (second region), and a voltage application part 51 for applying a voltage between the electrodes of the first electrode 55A and the second electrode 55B.

[0056] The voltage application part 51 has a control device 52 and a drive circuit 53. The control device 52 is an information processing device having an information processing part, a storage part, a communication part, etc., and is a device capable of performing various controls and various calculations. The drive circuit 53 is a circuit for applying a voltage between the electrodes of the first electrode 55A and the second electrode 55B according to a command from the control device 52.

[0057] The electrode unit 55 includes an electrode holding unit 55C that holds the first electrode 55A and the second electrode 55B, and the first electrode 55A, the second electrode 55B, and the electrode holding unit 55C are integrally formed. The integrally formed electrode unit 55 is detachably attached to the electrolysis cell 11. The configuration for making the electrode unit 55 detachable from the electrolysis cell 11 is not particularly limited. For example, when mounting, the electrode holding unit 55C is placed on a mounting table provided in the electrolysis cell 11, and when removing, a configuration in which the electrode holding unit 55C is detached from the mounting table can be mentioned. In the example of FIG. 5, a plurality of first electrodes 55A and a plurality of second electrodes 55B are provided, and both the plurality of first electrodes 55A and the plurality of second electrodes 55B are formed in a plate shape from a metal material. In the electrode unit 55, the first electrode 55A and the second electrode 55B are alternately arranged at intervals. The plurality of first electrodes 55A are configured to be short-circuited to each other and are electrically connected to the first terminal of the drive circuit 53 via the conductive path 54A. The plurality of second electrodes 55B are configured to be short-circuited to each other and are electrically connected to the second terminal of the drive circuit 53 via the conductive path 54B. In the example of FIG. 5, the first electrode 55A and the second electrode 55B are alternately arranged at intervals.

[0058] The electrodes used in the electrolysis cell 11 are preferably made of a metal material that is not corroded by seawater and has a high generation efficiency of chloric acid compounds. For example, an electrode formed by coating the surface of titanium with a platinum-iridium alloy can be preferably used. Platinum is excellent in conductivity and corrosion resistance, iridium is excellent in durability and chemical stability, and the platinum-iridium alloy has a characteristic that the surface is uniform and smooth. The electrode formed by coating the surface of titanium with a platinum-iridium alloy can be used for both the anode and the cathode. It should be noted that the examples of the electrodes described here are merely examples, and when the electrode inversion method described later is not used, an electrode obtained by coating titanium with ruthenium or the like may be used as the anode, or other materials may be used.

[0059] Part or all of the electrode part 55 is arranged on the water surface W2 side of the breeding water in the electrolysis tank 11 so that the breeding water is interposed between the first electrode 55A and the second electrode 55B. On the other hand, a water flow generating part 57 is provided in the electrolysis tank 11, and the water flow generating part 57 is adapted to generate a water flow from the lower side to the upper side (electrode part side) of the electrode part 55.

[0060] The water flow generating part 57 has a structure for flowing the breeding water introduced into the electrolysis tank 11 from the outside of the electrolysis tank 11 through the flow path 42 so as to rise from the lower side to the upper side of the electrode part 55 in the electrolysis tank 11. The flow path 42 is a flow path for flowing the breeding water discharged through the discharge part 66 into the electrolysis tank 11, and may be constituted by the discharge part 66 or may be constituted as a flow path following the discharge part 66. The water flow generating part 57 has a first partition wall 57A. The first partition wall 57A is a wall that partitions a predetermined upstream region and a predetermined downstream region in the electrolysis tank 11. The downstream region is a region on the downstream side of the first partition wall 57A and is a region where the electrode part 55 is provided. The upstream region is a region on the upstream side of the first partition wall 57A and on the upstream side of the downstream region.

[0061] In the example of FIG. 5, the upstream region is the internal region of the first breeding water flow chamber 11A constituted by the first partition wall 57A, the outer peripheral wall of the electrolysis tank 11, and the portion on the upstream side of the first partition wall 57A in the bottom wall 11Z, and is a region into which the breeding water flows from the flow path 42. An opening for moving the breeding water in the first breeding water flow chamber 11A to the second breeding water flow chamber is provided on the bottom wall side in the first breeding water flow chamber 11A. In the example of FIG. 5, the opening is constituted by the lower end portion of the first partition wall 57A, the outer peripheral wall of the electrolysis tank 11, and the bottom wall 11Z.

[0062] The downstream region described above is the internal region of the second breeding water flow chamber 11B constituted by the first partition wall 57A, the second partition wall 57B, and the portion between the first partition wall 57A and the second partition wall 57B on the outer peripheral wall and the bottom wall 11Z of the electrolysis cell 11, and is the region where part or all of the electrode portion 55 is arranged. In the second breeding water flow chamber 11B, the height of the upper end portion of the second partition wall 57B is lower than the height of the upper end portion of the outer peripheral wall of the electrolysis cell 11. When water exceeding the upper end portion of the second partition wall 57B enters the second breeding water flow chamber 11B, the water flows to the downstream side of the second breeding water flow chamber 11B beyond the second partition wall 57B. Due to such a configuration, in the second breeding water flow chamber 11B, the breeding water is introduced from the lower opening portion, and the breeding water is led out so as to exceed the upper end portion of the second partition wall 57B. Therefore, a water flow of the breeding water is generated so as to rise from the lower side of the electrode portion 55 toward the electrode portion 55 side.

[0063] In addition, in the example of FIG. 5, the second partition wall 57B is provided, but the second partition wall 57B may not be provided. In this case, the entire downstream side of the first partition wall 57A in the electrolysis cell 11 is the downstream region described above, and the second breeding water flow chamber 11B is constituted by the first partition wall 57A and the portion on the downstream side of the first partition wall 57A in the outer peripheral wall and the bottom wall 11Z of the electrolysis cell 11.

[0064] As shown in FIG. 6, an induction section 58 is provided in the electrolysis cell 11. The induction section 58 functions to guide and collect the deposits that have settled from the electrode section 55 within the electrolysis cell 11 toward a predetermined position within the electrolysis cell 11. In the examples of FIGS. 5 and 6, the predetermined position is a position above a part of the bottom wall 11Z. In the examples of FIGS. 5 and 6, on the downstream side of the second breeding water flow chamber 11B, a third breeding water flow chamber 11C is formed by the second partition wall 57B and the portion of the outer peripheral wall and the bottom wall 11Z of the electrolysis cell 11 that is downstream of the second partition wall 57B, and the position above a part of the bottom wall 11Z in the third breeding water flow chamber 11C is the predetermined position. The induction section 58 includes an inclined section 58A having an inclined surface inclined with respect to the vertical direction. The inclined surfaces of the inclined sections 58A and 58B form the inner wall surface of the third breeding water flow chamber 11C. When an object (e.g., a deposit) that sinks within the third breeding water flow chamber 11C reaches the inclined surface of the inclined section 58A, it is guided by the inclined surface during the further sinking process and is induced to the vicinity of the predetermined position on the bottom wall 11Z. The inclined surfaces of the inclined sections 58A and 58B guide the object sinking along these inclined surfaces to move in a predetermined first direction orthogonal to the vertical direction (specifically, to move toward the discharge section 59 side in the first direction).

[0065] As shown in FIGS. 5 and 6, a discharge section 59 is provided in the electrolysis cell 11. In the example of FIG. 5, the discharge section 59 is provided at two locations. However, it is not limited to this example, and the number of discharge sections 59 may be 1 or may be 3 or more. The discharge section 59 has a pipe 59A for discharging the deposits that have settled from the electrode section 55 within the electrolysis cell 11 and an opening / closing section 59B for opening and closing this pipe 59A. The discharge section 59 functions to take in the deposits into the interior of the pipe 59A at a position lower than the electrode section 55 and discharge the deposits from the electrolysis cell 11 through the pipe 59A.

[0066] In the examples of FIGS. 5 and 6, the opening / closing part 59B is a stop valve that switches, for example, by manual operation, between a state of blocking the pipe 59A and a state of opening it. Note that the opening / closing part 59B may be an electromagnetic valve or the like whose opening and closing are switched by control. In any case, when the opening / closing part 59B is in the open state, the breeding water is discharged from near the above-mentioned predetermined position in the electrolytic cell 11 through the pipe 59A. When precipitates precipitate near the above-mentioned predetermined position, the precipitates are discharged through the pipe 59A together with the breeding water. Note that in the examples of FIGS. 5 and 6, the pipe 59A is a fixed pipe permanently installed in the electrolytic cell 11, but it may be a pipe that can be attached to and detached from the electrolytic cell 11. Also, when discharging from near the above-mentioned predetermined position through a pipe, it may be discharged by utilizing the water pressure in the electrolytic cell 11, or it may be discharged by suction or flowing by means of a pump or the like.

[0067] As shown in FIGS. 5 and 6, a first guiding path 56 is provided in the electrolytic cell 11. The first guiding path 56 corresponds to an example of a guiding path. The first guiding path 56 functions as a flow path that does not guide the water located below the first height in the electrolytic cell 11 to the outside of the electrolytic cell 11, but guides the water located above the first height to the outside of the electrolytic cell 11. The first height corresponds to an example of a predetermined height. In the example of FIG. 5, the water surface W2 of the breeding water in the electrolytic cell 11 is located above the lower end position of the inner wall surface of the flow path at the inlet of the first guiding path 56 (the boundary part with the first guiding path 56 which is the outlet of the electrolytic cell 11), and the water near the water surface of the breeding water in the electrolytic cell 11 flows into the first guiding path 56 exceeding the height of the bottom of the first guiding path 56. In the example of FIG. 5, the height of the lower end of the inner wall surface of the flow path at the inlet of the first guiding path 56 is the first height (predetermined height), and this first height (predetermined height) is located above the lower end of the electrode part 55. The height of the lower end of the electrode part 55 is the height of the lowest position among the plurality of first electrodes 55A and the plurality of second electrodes 55B. The first guiding path 56 functions to flow the breeding water in the electrolytic cell 11 toward the reaction tank 15.

[0068] (Reaction tank) The reaction tank 15 stores the breeding water supplied from the electrolysis tank 11 through the flow path 43, secures the reaction time between the ammonia or ammonium ions contained in the stored breeding water and the chloric acid compound (for example, sodium hypochlorite) generated in the electrolysis tank 11, and is a tank that promotes these chemical reactions. The flow path 43 may be constituted by the first guiding path 56, or may be configured as a flow path following the first guiding path 56. When all of the ammonia or ammonium ions present in the breeding water in the electrolysis tank 11 do not completely react with the chloric acid compound in the electrolysis tank 11 and remain and flow out of the electrolysis tank 11, and when the chloric acid compound generated in the electrolysis tank 11 does not completely react and flows out of the electrolysis tank 11, either or both of the chemical reactions of the formula (2) or the formula (3) above occur in the reaction tank 15, and the ammonia or ammonium ions are decomposed.

[0069] As shown in FIG. 5, the reaction tank 15 is provided with a second guiding path 72. The second guiding path 72 functions as a flow path that does not guide the water located below the second height in the reaction tank 15 to the outside of the reaction tank 15, but guides the water located above the second height to the outside of the reaction tank 15. In the example of FIG. 5, the water surface W3 of the breeding water in the reaction tank 15 is located above the lower end position of the inner wall surface of the flow path at the inlet of the second guiding path 72 (the boundary portion with the second guiding path 72 which is the outlet of the reaction tank 15), and the water near the water surface of the breeding water in the reaction tank 15 flows into the second guiding path 72 exceeding the height of the bottom of the second guiding path 72. In the example of FIG. 5, the height of the lower end of the inner wall surface of the flow path at the inlet of the second guiding path 72 is the second height. The second guiding path 72 functions to flow the breeding water in the reaction tank 15 toward the subsequent process of the reaction tank 15.

[0070] A filtration tank 17 constituting a detection area for detecting residual chlorine is provided downstream of the reaction tank 15. The filtration tank 17 is configured to store the breeding water supplied from the reaction tank 15 through the flow path 44 and to guide it to the flow path 45. The flow path 44 is a flow path that flows the breeding water discharged through the second guide path 72 into the filtration tank 17, and may be formed by the second guide path 72, or may be configured as a flow path continuing to the second guide path 72. In the example of FIG. 1, the flow path that guides the breeding water from the reaction tank 15 to the activated carbon tank 21 is formed by the flow path 44, the filtration tank 17, and the flow path 45, but other configurations (for example, a configuration in which the filtration tank 17 is not provided and a pipe is continued from the reaction tank 15 to the activated carbon tank 21) may be used as long as the breeding water flows from the reaction tank 15 to the activated carbon tank 21.

[0071] The first residual chlorine sensor 19 is a sensor that detects the concentration of residual chlorine contained in the breeding water after passing through the electrolysis tank 11 and before flowing into the residual chlorine removal tank (specifically, the activated carbon tank 21), and detects the concentration of residual chlorine contained in the breeding water in the area where the breeding water flows from the reaction tank 15 to the activated carbon tank 21, for example. In the representative example shown in FIG. 1, the first residual chlorine sensor 19 detects the residual chlorine contained in the breeding water in the filtration tank 17. In this specification, residual chlorine means the combined chlorine and free chlorine remaining in the breeding water. The total amount of chlorine, which is the sum of the amount of combined chlorine and the amount of free chlorine contained in the breeding water, is the amount of residual chlorine. The first residual chlorine sensor 19 detects the residual chlorine contained in the breeding water in the area between the reaction tank 15 and the activated carbon tank 21, and thereby the amount of chlorine acid compounds remaining after the decomposition of ammonia or ammonium ions in the electrolysis tank 11 and the reaction tank 15 can be measured.

[0072] (Residual chlorine removal tank) In the example of FIG. 5, an activated carbon tank 21 is provided as an example of a residual chlorine removal tank. The residual chlorine removal tank is a tank that removes at least residual chlorine from the breeding water, and functions to remove residual chlorine from the breeding water by passing the breeding water through the residual chlorine removal section. The activated carbon tank 21 illustrated in FIG. 5 is a tank in which the breeding water that has passed through the reaction tank 15 is stored, and specifically, is a tank provided on the downstream side of the detection region (the region in the filtration tank 17 in the example of FIG. 1) where the first residual chlorine sensor 19 is disposed. The activated carbon tank 21 functions as a tank that removes chlorine acid compounds (for example, sodium hypochlorite) generated in the electrolysis tank 11. The activated carbon tank 21 is provided with an activated carbon section 23 equipped with activated carbon, and the activated carbon section 23 corresponds to an example of the residual chlorine removal section. The activated carbon section 23 removes at least residual chlorine and residual ozone from the breeding water in the activated carbon tank 21 by means of the activated carbon. In the example of FIG. 1, the internal region of the activated carbon tank 21 corresponds to an example of the third region, and is a region where the breeding water that has passed through the second region is stored or flows.

[0073] In the activated carbon tank 21, for example, it reacts as shown in the following formula (4), and can remove the surplus chlorine acid compounds that have not been used for the decomposition of ammonia or ammonium ions. HClO + C → CO + H + + Cl - ···(4)

[0074] The activated carbon tank 21 illustrated in FIG. 5 can be configured as shown in FIG. 7, for example. In the example of FIG. 7, the activated carbon tank 21 is configured as a flow path through which the breeding water passes, and the activated carbon section 23 is configured in such a form that the internal space of the flow path is filled with activated carbon particles. In the activated carbon tank 21, the gap in the activated carbon section 23 (specifically, the gap in the internal space filled with activated carbon particles) is configured such that the breeding water flows, and in the process of the breeding water flowing in from the inlet 21A of the activated carbon tank 21 passing through the gaps between a large number of particles in the activated carbon tank 21, the residual chlorine and residual ozone contained in the breeding water are adsorbed by the activated carbon, and the breeding water discharged from the outlet 21B becomes breeding water from which part or all of the chlorine and ozone have been removed.

[0075] (Standby tank) The breeding water introduced from the flow path 45 into the activated carbon tank 21 passes through the internal area of the activated carbon tank 21 and is discharged into the flow path 46, and flows into the standby tank 25 through the flow path 46. The standby tank 25 is a tank in which the breeding water that has passed through the activated carbon tank 21 is stored and the water quality before returning to the breeding tank 3 is inspected. The internal area of the standby tank 25 corresponds to an example of the fourth area, and is an area where the breeding water that has passed through the above-mentioned third area is stored or flows before returning to the breeding tank 3.

[0076] The second residual chlorine sensor 27 is a sensor that detects the concentration of residual chlorine contained in the breeding water in the fourth area where the breeding water that has passed through the above-mentioned third area is stored or flows before returning to the breeding tank 3. In the example of FIG. 1, the concentration of residual chlorine contained in the breeding water in the standby tank 25 is detected. The second residual chlorine sensor 27 can more accurately detect the change in the concentration of residual chlorine due to such an outflow when residual chlorine flows out due to deterioration of the activated carbon provided in the activated carbon part 23 or the like.

[0077] The ammonium ion sensor 29 is a sensor that detects the concentration of ammonium ions contained in the breeding water in the fourth area where the breeding water that has passed through the above-mentioned third area is stored or flows before returning to the breeding tank 3. In the example of FIG. 1, the concentration of ammonium ions contained in the breeding water in the standby tank 25 is detected. The ammonium ion sensor 29 can more accurately detect the change in the concentration of ammonium ions when ammonium ions remain without being completely reacted by the electrolysis tank 11 or the reaction tank 15.

[0078] The pH sensor 28 is a sensor that measures the pH (hydrogen ion exponent) of the breeding water in the fourth area where the breeding water that has passed through the above-mentioned third area is stored or flows before returning to the breeding tank 3. In the example of FIG. 1, the pH sensor 28 measures the pH of the breeding water in the standby tank 25 and gives a value specifying the pH of the breeding water in the standby tank 25 to the control device 52.

[0079] In the standby tank 25, aeration is performed by an aeration device (not shown) to remove CO2 from the breeding water. Then, the breeding water in the standby tank 25 flows into the breeding tank 3 through the flow path 47. The operation of flowing the breeding water from the standby tank 25 to the breeding tank 3 through the flow path 47 can be switched between a state where the breeding water continuously flows from the standby tank 25 to the breeding tank 3 and a state where the flow of the breeding water from the standby tank 25 to the breeding tank 3 is stopped or blocked.

[0080] 3. Control of the Recirculating Water Treatment System 1 (Configuration for Control) In the recirculating water treatment system 1, the breeding water in the breeding tank 3 is circulated in the order of the removal unit 5, the electrolysis tank 11, the reaction tank 15, the filtration tank 17, the activated carbon tank 21, and the standby tank 25. A plurality of pumps (not shown) for flowing the breeding water are provided at multiple locations along the circulation path for circulating the breeding water from the breeding tank 3 and returning it to the breeding tank 3. The control device 52 shown in FIG. 2 controls the driving and stopping of the above pumps. Further, the control device 52 controls the driving and stopping of the temperature regulator 35, the driving and stopping of the ozone generator 9, the driving and stopping of the foam separator 7, the driving and stopping of the electrolysis unit 13, the operation of the treatment unit 31, and the like.

[0081] The detection values of the first residual chlorine sensor 19, the second residual chlorine sensor 27, the pH sensor 28, and the ammonium ion sensor 29 are input to the control device 52 shown in FIG. 2. The detection value input from the first residual chlorine sensor 19 is a value indicating the concentration of residual chlorine contained in the breeding water in the above-described detection region (specifically, inside the filtration tank 17). The detection value input from the second residual chlorine sensor 27 is a value indicating the concentration of residual chlorine contained in the breeding water in the above-described fourth region (specifically, inside the standby tank 25). The detection value input from the pH sensor 28 is a value indicating the pH (hydrogen ion exponent) of the breeding water in the above-described fourth region (specifically, inside the standby tank 25). The detection value input from the ammonium ion sensor 29 is a value indicating the concentration of ammonium ions contained in the breeding water in the above-described fourth region (specifically, inside the standby tank 25).

[0082] (Control of Electrolysis) The control device 52 corresponds to an example of a control unit and controls the electrolysis of the electrolysis unit 13. The control device 52 may control the electrolysis of the electrolysis unit 13 based on the measurement results of the ammonium ion sensor 29 and the measurement results of the first residual chlorine sensor 19, may control the electrolysis of the electrolysis unit 13 based on the measurement results of the ammonium ion sensor 29, or may control the electrolysis of the electrolysis unit 13 based on the measurement results of the first residual chlorine sensor 19. When the control device 52 controls the electrolysis of the electrolysis unit 13 based on the measurement results of the ammonium ion sensor 29, for example, the current flowing between the first electrode 55A and the second electrode 55B may be feedback-controlled so that the detected value of the ammonium ion sensor 29 becomes equal to or less than a predetermined value. When the control device 52 controls the electrolysis of the electrolysis unit 13 based on the measurement results of the first residual chlorine sensor 19, for example, the current flowing between the first electrode 55A and the second electrode 55B may be feedback-controlled so that the detected value of the first residual chlorine sensor 19 falls within a predetermined range.

[0083] When grasping the ammonia concentration and the effective chlorine concentration in the breeding water (for example, seawater) used in this embodiment, it can be grasped based on the discontinuous point chlorine treatment method. For example, in the first state where the concentrations of ammonia and ammonium ions in the breeding water are equal to or higher than a certain concentration with respect to the concentration of effective residual chlorine, the higher the addition amount of the chloric acid compound, the higher the effective residual chlorine concentration. On the other hand, in the second state where ammonia or ammonium ions are present but the concentrations of ammonia and ammonium ions are lower than the above-mentioned certain concentration with respect to the concentration of effective residual chlorine, the effective residual chlorine concentration decreases even when a chloric acid compound is added because it is consumed by the reaction with ammonia or ammonium ions. Then, in the third state where ammonia and ammonium ions are not present, the higher the addition amount of the chloric acid compound, the higher the effective residual chlorine concentration. If the pH, salinity concentration, and temperature of the breeding water are constant, the above-mentioned certain concentration can be considered as a fixed value.

[0084] The control device 52 is configured to be able to detect the current flowing between the first electrode 55A and the second electrode 55B in the electrolysis unit 13, and continuously monitors the current flowing between the first electrode 55A and the second electrode 55B. Various configurations can be adopted for the configuration in which the control device 52 monitors the current flowing between the first electrode 55A and the second electrode 55B. For example, the current may be detected by a current sensor, and the control device 52 may acquire the value detected by the current sensor, or other configurations may be used. Then, the control device 52 controls the current flowing between the first electrode 55A and the second electrode 55B based on the detection value of either or both of the ammonium ion sensor 29 and the first residual chlorine sensor 19.

[0085] The control device 52 may perform first current control so as to control the current flowing between the first electrode 55A and the second electrode 55B based on the detection values of both the ammonium ion sensor 29 and the first residual chlorine sensor 19. The greater the current flowing between the first electrode 55A and the second electrode 55B, the more the electrolysis is promoted and the greater the amount of chlorate compound generated. Therefore, when performing the first current control, the control device 52 adjusts the current flowing between the first electrode 55A and the second electrode 55B so that the value (detection value) of the ammonium ion concentration detected by the ammonium ion sensor 29 is equal to or less than the first threshold value. The first threshold value may be 0 or a value slightly greater than 0. On the other hand, in a state where ammonia and ammonium ions are not present, the higher the current flowing between the first electrode 55A and the second electrode 55B, the higher the available chlorine concentration. Therefore, the control device 52 adjusts the current flowing between the first electrode 55A and the second electrode 55B so that it is within the current range where the detection value of the ammonium ion sensor 29 is equal to or less than the first threshold value and within the current range where the value (detection value) of the residual chlorine amount detected by the first residual chlorine sensor 19 is equal to or less than the second threshold value.

[0086] The control device 52 may perform a second current control to control the current flowing between the first electrode 55A and the second electrode 55B based on the detection value of the ammonium ion sensor 29 without using the detection value of the first residual chlorine sensor 19. Even when the control device 52 performs the second current control, it adjusts the current flowing between the first electrode 55A and the second electrode 55B so that the value (detection value) of the ammonium ion concentration detected by the ammonium ion sensor 29 is equal to or less than the first threshold value. The first threshold value may be 0 or a value slightly larger than 0. When the control device 52 performs the second current control, it repeats "current adjustment control in which the current flowing between the first electrode 55A and the second electrode 55B is controlled to a set current value and electrolysis is performed for a certain period of time, and then the value (detection value) of the ammonium ion concentration detected by the ammonium ion sensor 29 is confirmed". In this control, if the detection value of the ammonium ion sensor 29 exceeds the first threshold value in the previous current adjustment control, the next current adjustment control is performed such that the current value increased by a predetermined ratio (for example, 10%) from the set current value used in the previous current adjustment control is used as the next set current value. On the other hand, if the detection value of the ammonium ion sensor 29 is equal to or less than the first threshold value in the previous current adjustment control, the next current adjustment control is performed such that the set current value used in the previous current adjustment control is used as the next set current value. By doing so, electrolysis can be performed while gradually increasing the current until the detection value of the ammonium ion sensor 29 becomes equal to or less than the first threshold value, and when the detection value of the ammonium ion sensor 29 becomes equal to or less than the first threshold value, electrolysis can be performed while maintaining the current state.

[0087] The control device 52 may perform a third current control to control the current flowing between the first electrode 55A and the second electrode 55B based on the detection value of the first residual chlorine sensor 19 without using the detection value of the ammonium ion sensor 29. When performing the third current control, the control device 52 repeats "current adjustment control for confirming the value (detection value) of the residual chlorine amount detected by the first residual chlorine sensor 19 after controlling the current flowing between the first electrode 55A and the second electrode 55B to the set current value and performing electrolysis for a certain period of time". In this control, when the set current value in the previous current adjustment control is increased by a predetermined ratio (for example, 10%) with respect to the set current value in the previous-previous current adjustment control, and the value (detection value) of the residual chlorine amount detected in the previous current adjustment control is smaller than the value (detection value) of the residual chlorine amount detected in the previous-previous current adjustment control, it can be estimated that the above-mentioned second state is present. Therefore, in this case, in the next current adjustment control (the current adjustment control this time), the current adjustment control is performed so that the current value increased by a predetermined ratio (for example, 10%) from the set current value used in the previous current adjustment control is used as the set current value. That is, while the detected value of the residual chlorine amount is decreasing, the current adjustment control for each time is performed so that the set current value is gradually increased. On the other hand, when performing the control of gradually increasing the set current value in this way, when the set current value in the previous current adjustment control is increased by a predetermined ratio (for example, 10%) with respect to the set current value in the previous-previous current adjustment control, and the value (detection value) of the residual chlorine amount detected in the previous current adjustment control is larger than the value (detection value) of the residual chlorine amount detected in the previous-previous current adjustment control, it can be estimated that the above-mentioned third state is present. Therefore, in this case, in the next current adjustment control (the current adjustment control this time), the current adjustment control is performed so that the current value decreased by a predetermined ratio (for example, 10%) from the set current value used in the previous current adjustment control is used as the set current value.In addition, when the set current value in the previous current adjustment control is decreased by a predetermined ratio (e.g., 10%) with respect to the set current value in the previous - previous current adjustment control, if the value (detection value) of the residual chlorine amount detected in the previous current adjustment control is smaller than the value (detection value) of the residual chlorine amount detected in the previous - previous current adjustment control, then in the next current adjustment control (the current adjustment control this time), the current adjustment control is performed such that the set current value is a current value decreased by a predetermined ratio (e.g., 10%) from the set current value used in the previous current adjustment control. If the value (detection value) of the residual chlorine amount detected in the previous current adjustment control is larger than the value (detection value) of the residual chlorine amount detected in the previous - previous current adjustment control, then in the next current adjustment control (the current adjustment control this time), the current adjustment control may be performed such that the set current value is a current value increased by a predetermined ratio (e.g., 10%) from the set current value used in the previous current adjustment control.

[0088] (Control based on monitoring of residual chlorine) When a predetermined measurement result is obtained by the second residual chlorine sensor 27, the treatment unit 31 may operate to remove residual chlorine from the breeding water in the fourth area, or may operate to stop returning the breeding water in the fourth area to the breeding tank 3.

[0089] For example, when the concentration (detection value) of the residual chlorine detected by the second residual chlorine sensor 27 exceeds a predetermined value, the treatment unit 31 may supply a neutralizing agent to the breeding water before it returns to the breeding tank 3. As the neutralizing agent, for example, sodium thiosulfate, catechin, polyphenol, cysteine, etc. can be preferably used. In the example of FIG. 7, as an element constituting at least a part of the treatment unit 31, a neutralizing agent supply device 31A for supplying a neutralizing agent to the breeding water in the fourth area is provided. Specifically, for example, the control device 52 and the neutralizing agent supply device 31A function as the treatment unit 31 and the neutralizing agent supply unit. When the concentration (detection value) of the residual chlorine detected by the second residual chlorine sensor 27 exceeds a predetermined value, the control device 52 gives a neutralizing agent input command to the neutralizing agent supply device 31A, and in response to this neutralizing agent input command, the neutralizing agent supply device may operate to input a "neutralizing agent that causes a neutralization reaction with residual chlorine" into the standby tank 25.

[0090] When the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds a predetermined value, the treatment unit 31 may operate to switch the flow path so that the breeding water is not returned from the standby tank 25 to the breeding tank 3 but is made to flow from the standby tank 25 to another area. For example, a three-way valve (not shown) may be provided in the middle of the flow path 47, and the supply destination of the breeding water flowing through the flow path 47 may be switched between the breeding tank 3 and another area by the three-way valve. In this example, the control device 52 and the three-way valve can function as the treatment unit 31. Specifically, when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 is equal to or less than the predetermined value, the control device 52 sets the supply destination from the three-way valve to the breeding tank 3, and when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds the predetermined value, the control device 52 may perform control so that the supply destination from the three-way valve is another area.

[0091] Alternatively, when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds a predetermined value, the treatment unit 31 may block the flow path through which the breeding water flows from the standby tank 25 to the breeding tank 3 and stop returning the breeding water to the breeding tank 3, and may also stop the circulation of the breeding water in the system 1 and stop returning the breeding water to the breeding tank 3. For example, an on-off valve (not shown) may be provided in the middle of the flow path 47, and the flow of the flow path 47 may be allowed when the on-off valve is in the open state, and the flow of the flow path 47 may be blocked when the on-off valve is in the blocked state. In this example, the control device 52 and the on-off valve can function as the treatment unit 31. Specifically, when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 is equal to or less than the predetermined value, the control device 52 sets the on-off valve to the open state, and when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds the predetermined value, the control device 52 may perform control so that the on-off valve is in the blocked state. In this example, when the on-off valve is in the blocked state, the driving of the pump that circulates the breeding water in the system may be stopped so that the standby tank 25 does not overflow, and a flow path may be provided so that the breeding water escapes from the standby tank 25 to another area when the water level in the standby tank 25 exceeds a certain level.

[0092] (Control Based on pH Monitoring) In this embodiment, an adjustment material supply device 32 is provided to supply a pH adjustment material to the breeding water in the fourth region. In the example of FIG. 7, the adjustment material supply device 32 is configured to supply a pH adjustment material to the breeding water in the standby tank 25. The control device 52 gives an instruction on the supply timing and supply rate to the adjustment material supply device 32, and the adjustment material supply device 32 supplies the pH adjustment material at the supply rate instructed by the control device 52 at the supply timing instructed by the control device 52.

[0093] As the pH adjustment material supplied from the adjustment material supply device 32, for example, any one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium hydrogen carbonate can be preferably used, and it is more preferable to use either sodium carbonate or sodium hydrogen carbonate, and it is even more preferable to use sodium carbonate. When using sodium carbonate, sodium hydrogen carbonate, calcium carbonate, etc. as the pH adjustment material, an aqueous solution containing any of them may be used. When using sodium carbonate with a high pH, since it is a strong alkali, it has the merit of easily increasing the pH of the breeding water and being less likely to disrupt the ion balance. Sodium hydrogen carbonate has the merit of being less likely to disrupt the ion balance and being able to exhibit a pH buffering function. In addition, in order to prevent the inhibition of the pH adjustment effect due to the precipitation of magnesium contained in seawater, the pH of the pH adjustment material is preferably 11.5 or less.

[0094] The method of control by the control device 52 is various. For example, when the pH of the breeding water detected by the pH sensor 28 becomes equal to or less than the first reference value, the control device 52 operates the adjustment material supply device 32 to supply a pH adjustment material with a pH higher than the first reference value at a predetermined supply rate. When the pH of the breeding water detected by the pH sensor 28 exceeds the second reference value while the adjustment material supply device 32 is supplying the pH adjustment material, on-off control may be performed to stop the supply of the pH adjustment material by the adjustment material supply device 32. In the above example, the first reference value and the second reference value may be the same or different.

[0095] In addition, in order to reduce the consumption of the pH adjuster, solid calcium carbonate (for example, pellets, etc.) may be provided in the fourth region (for example, the inside of the flow paths 46 and 47 and the standby tank 25).

[0096] In the above example, the timing of inputting the pH adjuster is controlled. Instead of such a method, the pH adjuster may be continuously supplied at a constant supply rate.

[0097] 4. Cleaning of Electrodes As shown in FIG. 5, in the present embodiment, the control device 52 and the drive circuit 53 function as a voltage application unit 51. The voltage application unit 51 applies a voltage so that the first electrode 55A is the anode and the second electrode 55B is the cathode, and performs electrolysis in the above-mentioned "region" (specifically, inside the electrolysis tank 11). It operates to switch to a second state in which a voltage is applied so that the second electrode 55B is the anode and the first electrode 55A is the cathode. For example, the voltage application unit 51 periodically switches between an operation of continuously electrolyzing the breeding water in the first state and an operation of continuously electrolyzing the breeding water in the second state. The switching period in the case of periodic switching may be, for example, every several tens of minutes, every several hours, every day, or other periods.

[0098] The timing at which the voltage application unit 51 switches between the first state and the second state is not limited to a regular timing, and may be a timing when a predetermined condition is satisfied. For example, it may be switched at a timing when the operating time of the circulation type water treatment system 1 has reached a certain time since the previous switching time, or at a timing when a detection value by some sensor has reached a predetermined value, or at a randomly determined timing, or other timings.

[0099] In this embodiment, while continuously performing "replacement of the breeding water" so as to continuously conduct the introduction of the breeding water from the flow path 42 to the electrolysis cell 11 and the drainage of the breeding water from the electrolysis cell 11 to the first induction path 56, the operation in the first state is continuously performed in which the voltage is continuously applied such that the first electrode 55A is the anode and the second electrode 55B is the cathode by the voltage application unit 51. When the switching condition is satisfied during the operation in the first state, the switching from the first state to the second state is performed while performing the above-mentioned "replacement of the breeding water". After the switching, the operation in the second state is continuously performed in which the voltage is continuously applied such that the second electrode 55B is the anode and the first electrode 55A is the cathode while performing the above-mentioned "replacement of the breeding water". When the switching condition is satisfied during the operation in the second state, the switching from the second state to the first state is performed while performing the above-mentioned "replacement of the breeding water", and the operation in the first state and the operation in the second state are alternately performed. During the continuation of the operation in the first state or the continuation of the operation in the second state, the operation may be continuous without interruption, or the operation may be temporarily interrupted for some reason.

[0100] 5. Examples of effects In the above example, the circulating water treatment system 1 may correspond to an example of an electrolysis device, and the electrolysis unit 13 may correspond to an example of an electrolysis device. This electrolysis device or the electrolysis method using the electrolysis device generates a chloric acid compound (for example, sodium hypochlorite) by electrolyzing breeding water containing salts, and then reacts this chloric acid compound with ammonia or ammonium ions present in the breeding water to directly decompose it into nitrogen. During the decomposition process, the generation of nitrous acid, nitric acid, etc. can be reliably suppressed. However, when this method is adopted, if no measures are taken, there is a concern that deposits will adhere to the surface of the electrodes and inhibit electrolysis. The above electrolysis device can switch between a first state in which voltage is applied to perform electrolysis with the first electrode 55A as the anode and the second electrode 55B as the cathode, and a second state in which voltage is applied with the second electrode 55B as the anode and the first electrode 55A as the cathode. Therefore, deposits adhering to the surface of the electrodes due to continuous electrolysis are likely to detach from the electrodes due to the switching. Thus, this electrolysis device can easily remove the deposits deposited on the surface of the electrodes.

[0101] When continuously performing electrolysis on breeding water containing salts, for example, there is a problem that deposits mainly composed of magnesium are generated on the cathode side and cover the electrodes. When the deposits cover the electrodes in this way, the generation amount of sodium hypochlorite gradually decreases or becomes unstable. To prevent such a situation, it is conceivable to apply a physical force to the deposits on the electrodes and clean them regularly. However, if mechanical cleaning, etc. is performed frequently, there is a problem that the electrodes are easily damaged and the lifespan and performance are impaired. Also, cleaning such as scraping from the electrode surface or cleaning by water pressure requires manual work by an operator, so automation, labor saving, and stable operation are difficult. However, the above electrolysis device can effectively suppress or eliminate this problem.

[0102] In the above electrolysis device, since the electrode unit 55, in which the first electrode 55A, the second electrode 55B, and the electrode holding unit 55C are integrally formed, is configured to be detachable from the electrolysis cell 11, the operation of removing the electrode unit 55 for cleaning becomes easier. In particular, the promotion of the detachment of deposits due to switching and the facilitation of the attachment / detachment operation of the electrode unit 55 exhibit a synergistic effect, further facilitating cleaning.

[0103] In the above electrolysis device, since the deposits that have sunk from the electrode unit 55 can be automatically collected by the guiding unit 58 toward a predetermined position, not only can the deposits be detached from the electrode unit 55, but the detached deposits can also be easily collected.

[0104] In the above electrolysis device, since the deposits that have sunk from the electrode unit 55 can be taken into the pipe 59A of the discharge unit 59 and discharged at a position lower than the electrode unit 55, it is possible to suppress "the deposits being dispersed during the process of discharging the deposits and easily flowing into the subsequent process".

[0105] The above electrolysis device can guide the supernatant water located above a predetermined height in the electrolysis cell 11 to the outside, and can make it difficult to guide the deposits that have sunk below the predetermined height to the outside of the electrolysis cell 11. More specifically, since the above predetermined height is above the lower end of the electrode unit 55, it becomes difficult for the deposits that have detached from the electrode unit 55 and sunk downward from the lower end to be guided to the outside of the electrolysis cell 11.

[0106] In the above electrolysis device, since the water flow generating unit 57 can generate a water flow so as to rise from the lower side to the upper side of the electrode unit 55 in the electrolysis cell 11, new breeding water can be easily guided to the electrode unit 55, and the efficiency of electrolysis can be further enhanced.

[0107] In the above electrolysis device, in order to periodically switch between the operation of electrolyzing the breeding water while maintaining the first state and the operation of electrolyzing the breeding water while maintaining the second state, deposits can be periodically removed, and the electrodes can be periodically cleaned.

[0108] The circulating water treatment system 1 can remove solids contained in the breeding water in the first region by the removal unit 5. Further, in the second region after passing through the first region, the electrolysis unit 13 can decompose ammonia or ammonium ions in the circulating water treatment system 1, and perform electrolysis of the breeding water after removing solids by the removal unit 5, so that it is possible to surely suppress solids from inhibiting electrolysis and it is easy to perform electrolysis well. Further, in the third region where the breeding water passing through the second region is stored or flows, the activated carbon unit 23 can remove residual chlorine. Therefore, even if a chlorate compound not used for the decomposition of ammonia or ammonium ions is contained in the breeding water in the third region, this chlorate compound can be effectively removed by the activated carbon unit. As described above, in the circulating water treatment system 1, solids such as feces and uneaten feed are surely reduced in the breeding water after passing through the third region, and nitrogen compound components such as ammonia, nitrite, and nitrate are also surely suppressed, so it is extremely advantageous in terms of purification and detoxification of the breeding water.

[0109] In the circulating water treatment system 1, since the supernatant water located above the first height in the electrolysis tank 11 can be guided outside the electrolysis tank 11, when deposits detach from the electrodes and sink, the deposits are difficult to be guided outside the electrolysis tank 11. Even if some deposits are discharged from the electrolysis tank 11 and enter the reaction tank 15, since the supernatant water located above the second height in the reaction tank 15 can be guided outside the reaction tank 15, the deposits that have entered the reaction tank 15 are likely to precipitate in the reaction tank 15 and are difficult to be guided outside the reaction tank 15.

[0110] In the circulating water treatment system 1 or the electrolysis method using the above electrolyzer, while continuously replacing the breeding water by conducting the breeding water into the electrolysis tank 11 and discharging the breeding water from the electrolysis tank 11, the operation in the first state, the operation in the second state, and the switching between the first state and the second state can be performed. Therefore, the electrodes can be cleaned while circulating the breeding water more efficiently.

[0111] <Second Embodiment> The following description relates to the second embodiment. The circulating water treatment system 1 according to the second embodiment and the aquaculture method using this system 1 are different from the first embodiment in that, as the removal unit 5 shown in FIG. 1, the configuration shown in FIG. 8 is used instead of the configurations shown in FIGS. 3 and 4. Except for the configuration of the removal unit 5, it is the same as the first embodiment. Therefore, in the following description, regarding the configurations other than those in FIG. 3, it is assumed that the configurations in FIGS. 1, 2, 5, 6, 7, etc. are used, and the reference numerals and names attached to these figures are appropriately used.

[0112] In the example of FIG. 8, the removal unit 5 is configured to introduce the breeding water introduced from the area of the previous process of the removal unit 5 into the foam separator 7, and then pass it through the foam separator 7 and discharge it to an area of a subsequent process different from the area of the previous process. The area of the previous process is the area inside the breeding tank 3. The area of the subsequent process is the area inside the electrolysis tank 11. In the removal unit 5, after introducing the breeding water supplied from the area of the previous process of the removal unit 5 into the foam separator 7 through the flow path 41 (the flow path 41 corresponds to an example of an introduction path), it passes through the foam separator 7 and is discharged to the "area of the subsequent process of the removal unit 5" (for example, the area inside the electrolysis tank 11) different from the area where the inlet of the flow path 41 (introduction path) is arranged (for example, the area inside the breeding tank 3). In the removal unit 5, the total amount of the breeding water flowing in from the breeding tank 3 via the flow path 41 is sent into the foam separator 7, and there is no configuration where the flow path flows from the breeding tank 3 to the electrolysis tank 11 without passing through the foam separator 7. Among the breeding water sent into the foam separator 7, except for the removed substances removed together with the bubbles in the foam separator 7, it is sent into the electrolysis tank 11 via the flow path 43 from the foam separator 7. Note that the operation of the foam separator 7 is the same as that in the first embodiment, and also in this example, bubbles containing ozone are generated in the foam separator 7.

[0113] Thus, when the circulating water treatment system 1 of the second embodiment removes solid matter by the removal unit 5, after introducing the breeding water introduced from the area of the previous process into the foam separator 7, it passes through the foam separator 7 and is discharged to an area of a subsequent process different from the area of the previous process. Therefore, the circulating breeding water can be more surely passed through the foam separator 7, and the effect of removing solid matter and the effects of sterilization and disinfection by ozone can be further enhanced.

[0114] <Third Embodiment> The following description relates to the third embodiment. The circulation type water treatment system 1 according to the third embodiment and the aquaculture method using this system 1 are different from the first embodiment in that the configuration shown in FIG. 9 is used instead of the configuration shown in FIG. 5. Specifically, it is the same as the first embodiment except that the inclined portions 58C, 58D, 58E, 58F and the discharge portions 110, 112 are provided in addition to the configuration shown in FIG. 5. Therefore, in the following description, for the configurations other than those in FIG. 5, it is assumed that the configurations in FIGS. 1 to 4, FIG. 6, FIG. 7, etc. are used, and the reference numerals, names, etc. attached to these figures are appropriately used.

[0115] As shown in FIG. 9, in the electrolysis tank 11, in addition to the discharge portion 59, a discharge portion 110 is provided. The discharge portion 110 has a pipe 110A for discharging the precipitate that has settled from the electrode portion 55 in the electrolysis tank 11 and an opening / closing portion 110B for opening and closing this pipe 110A. The discharge portion 110 functions to take in the precipitate into the inside of the pipe 110A at a position lower than the electrode portion 55 and discharge the precipitate from the electrolysis tank 11 through the pipe 110A. The opening / closing portion 110B is, for example, a valve for switching the pipe 110A between a blocked state and an open state by manual operation. Note that the opening / closing portion 110B may be an electromagnetic valve or the like whose opening and closing are switched by control. In any case, when the opening / closing portion 110B is in the open state, the breeding water is discharged from the vicinity of a predetermined position in the electrolysis tank 11 through the pipe 110A. When the precipitate settles near the predetermined position, the precipitate is discharged through the pipe 110A together with the breeding water.

[0116] In the example of FIG. 9, in addition to the inclined portions 58A and 58B, an inclined portion 58C is provided. The inclined surface of the inclined portion 58C is inclined with respect to the vertical direction, and the inclined portion 58C guides an object that sinks along the inclined surface of the inclined portion 58C to move in the vertical direction and a second direction orthogonal to the first direction (specifically, to move toward the discharge portion 59 side in the second direction). Further, in the example of FIG. 9, an inclined portion 58D is provided. The inclined surface of the inclined portion 58D is inclined with respect to the vertical direction, and the inclined portion 58D guides an object that sinks along the inclined portion 58D to move in the second direction (specifically, to move toward the discharge portion 110 side in the second direction).

[0117] In the example of Fig. 9, a discharge section 112 is also provided in the reaction tank 15. The discharge section 112 has a pipe 112A for discharging the precipitate that has settled in the reaction tank 15 and an opening / closing section 112B for opening and closing this pipe 112A. The discharge section 112 functions to take in the sinking object into the inside of the pipe 112A and discharge it through the pipe 112A. The opening / closing section 112B is, for example, a shut-off valve that switches between a state of blocking the pipe 112A and a state of opening it by manual operation. Note that the opening / closing section 112B may be an electromagnetic valve or the like whose opening and closing are switched by control. In any case, when the opening / closing section 112B is in the open state, the breeding water is discharged from near a predetermined position in the reaction tank 15 through the pipe 112A. When an object precipitates near the above-mentioned predetermined position, the object is discharged through the pipe 112A together with the breeding water. In the reaction tank 15, inclined portions 58E and 58F are also provided. The inclined surfaces of the inclined portions 58E and 58F are inclined with respect to the vertical direction, and each of the inclined portions 58E and 58F guides the object sinking along the inclined surface of each inclined portion to move in the second direction (specifically, to move toward the discharge section 112 side in the second direction).

[0118] Note that in the example of Fig. 9, the pipes 59A, 110A, and 112A are fixed pipes that are permanently installed, but they may be pipes that can be attached and detached. Also, for any of the pipes, when discharging, it may be discharged by utilizing the water pressure in the tank, or it may be discharged by suction or flowing by means of a pump or the like.

[0119] <Fourth Embodiment> The following description relates to the fourth embodiment. The circulating water treatment system 1 according to the fourth embodiment and the aquaculture method using this system 1 are different from the first embodiment in that the configuration shown in Fig. 10 is used instead of the configuration shown in Fig. 7. In addition to the configuration of Fig. 7, it is different from the first embodiment in that a switching section 140 is provided in the middle of the flow path 46, and the other configurations are the same as those of the first embodiment. Therefore, in the following description, for the configurations other than the switching section 140, it is assumed that the configurations shown in Figs. 1 to 7 are used, and the reference numerals, names, etc. attached to these figures are appropriately used.

[0120] In the circulating water treatment system 1 of the fourth embodiment, a switching valve 142 is provided in the switching unit 140. The switching valve 142 can switch the path through which the breeding water discharged from the residual chlorine removal tank (for example, the activated carbon tank 21) to the flow path 46 passes, either to the flow path 143A that does not pass through the second removal unit 146 or to the flow path 143B that passes through the second removal unit 146.

[0121] The second removal tank 144 is configured as a flow path through which the breeding water passes, and the internal space of the flow path is filled with a component for removing residual chlorine (for example, calcium sulfite particles), thereby constituting the second removal unit 146. The second removal tank 144 is configured as a flow path having an inlet and an outlet. In a representative example, the internal space is filled with calcium sulfite particles. When the switching valve 142 is set so that the outflow destination from the switching valve 142 becomes the flow path 143B, the breeding water that has passed through the switching valve 142 and flowed into the inlet of the second removal tank 144 passes through the gaps (gaps between a large number of calcium sulfite particles) in the internal space of the second removal tank 144. In this process, the residual chlorine and residual ozone contained in the breeding water are removed by calcium sulfite, and the breeding water discharged from the outlet of the second removal tank 144 to the downstream flow path 46 becomes breeding water from which part or all of the chlorine and ozone have been removed.

[0122] In such a configuration, when the concentration of residual chlorine detected by the second residual chlorine sensor 27 is equal to or lower than a reference value, the control device 52 switches the switching valve 142 so that the breeding water flows through the flow path 143A from the residual chlorine removal tank (for example, the activated carbon tank 21) and does not flow through the flow path 143B. On the other hand, when the concentration of residual chlorine detected by the second residual chlorine sensor 27 exceeds the reference value, the control device 52 switches the switching valve 142 so that the breeding water flows through the flow path 143B from the residual chlorine removal tank (for example, the activated carbon tank 21) and does not flow through the flow path 143A. By doing so, when the concentration of residual chlorine detected by the second residual chlorine sensor 27 becomes relatively high, the breeding water from the residual chlorine removal tank (for example, the activated carbon tank 21) can be switched to flow through the second removal unit 146, and the second removal unit 146 can also remove the residual chlorine. Note that the control method described here is merely an example, and the timing and period for flowing the breeding water through the second removal tank 144 are not limited to the above example.

[0123] <Other Embodiments> The present invention is not limited to the embodiments described above with reference to the description and drawings. For example, the features of the above-described or below-described embodiments can be combined in any combination without contradiction. Also, any feature of the above-described or below-described embodiments can be omitted if it is not explicitly specified as essential. Furthermore, the above-described embodiments may be modified as follows.

[0124] In the above-described embodiment, ozone is supplied as a gas to the foam separator 7 to generate bubbles containing ozone, but a configuration may be adopted in which a gas other than ozone (for example, air) is supplied to generate bubbles of the other gas.

[0125] In the above-described embodiment, the internal region of the electrolysis tank 11 configured as a tank having a portion for storing the breeding water is the second region, but the electrolysis tank 11 may be configured as a flow path having no portion for storing, and this internal region may be the second region.

[0126] In the above-described embodiment, the reaction tank 15 is configured as a tank having a portion for storing the breeding water, but it may be configured as a flow path having no portion for storing the water.

[0127] In the above-described embodiment, the first residual chlorine sensor 19 is arranged to detect the concentration of residual chlorine in the breeding water in the filtration tank 17, but it may be configured to detect the concentration of residual chlorine in the flow path between the reaction tank 15 and the activated carbon tank 21.

[0128] In the above-described embodiment, the internal region of the activated carbon tank 21 configured as a tank having a portion for storing the breeding water is the third region, but the activated carbon tank 21 may be configured as a flow path having no portion for storing the water, and this internal region may be the third region.

[0129] In the above-described embodiment, the internal region of the standby tank 25 configured as a tank having a portion for storing the breeding water is the fourth region, but the standby tank 25 may be configured as a flow path having no portion for storing the water, and this internal region may be the fourth region.

[0130] In the above-described embodiment, as shown in FIGS. 1 and 7, as the residual chlorine removal tank, an activated carbon tank 21 having an activated carbon part 23 filled with activated carbon particles is provided. However, instead of the activated carbon particles of the activated carbon part 23, calcium sulfite particles may be used, and a configuration in which the calcium sulfite particles are filled may be adopted. Also in this example, the residual chlorine removal tank can be configured as a flow path having an inlet and an outlet, and the internal space of the flow path can be configured to be filled with calcium sulfite particles. Also in this example, in the process in which the breeding water flowing in from the inlet of the residual chlorine removal tank passes through the gaps in the internal space (gaps between a large number of calcium sulfite particles), the residual chlorine and residual ozone contained in the breeding water are removed by the calcium sulfite, and the breeding water discharged from the outlet is the breeding water from which part or all of the chlorine and ozone have been removed.

[0131] In the configuration of FIG. 10 of the fourth embodiment, the switching unit 140 is provided in the middle of the flow path 46. However, in any of the configurations of the first to third embodiments, the switching unit 140 may be provided in the middle of the flow path 47 (for example, at the position of the two-dot chain line X in FIG. 1) in the configuration of FIG. 1. In this case, by performing the same control as in the above-described fourth embodiment, the path through which the breeding water discharged from the standby tank 25 to the flow path 47 flows is switched to either the flow path 143A that does not pass through the second removal unit 146 or the flow path 143B that passes through the second removal unit 146, and the breeding water that has passed through either the flow path 143A or the second removal unit 146 may be configured to be supplied to the breeding tank 3.

[0132] It should be considered that all the embodiments disclosed this time are illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments disclosed this time, and it is intended that all modifications within the scope indicated by the claims or within the scope equivalent to the claims are included.

Explanation of Signs

[0133] 1: Circulating water treatment system 3: Breeding tank 5: Removal unit 7: Foam separator 9: Ozone generator 11: Electrolysis tank 11A: First breeding water flow chamber 11B: Second breeding water flow chamber 11C: Third breeding water flow chamber 11Z: Bottom wall 13: Electrolysis unit 15: Reaction tank 17: Filtration tank 19: First residual chlorine sensor 21: Activated carbon tank (residual chlorine removal tank) 23: Activated carbon part (residual chlorine removal part) 25: Standby tank 27: Second residual chlorine sensor 29: Ammonium ion sensor 31: Treatment unit 35: Temperature control machine 37: Filter 41, 42, 43, 44, 45, 46, 47: Flow path 51: Voltage application unit 52: Control device 53: Drive circuit 54A: Conductive path 54B: Conductive path 55: Electrode part 55A: First electrode 55B: Second electrode 55C: Electrode holding part 56: First induction path 57: Water flow generation part 57A: First partition wall 57B: Second partition wall 58: Induction part 58A, 58B: Inclined part 59: Discharge part 59A: Pipe 59B: Opening / closing part 60: Storage tank 60A: Bottom 62: Introduction part 64: Derivation part 66: Discharge part 72: Second induction path W1: Water surface W2: Water surface W3: Water surface

Claims

Claim 1 An electrolysis device used in a circulation type water treatment system that treats while circulating the breeding water from a breeding tank that is a tank for breeding aquatic organisms and contains saline breeding water, and returns the treated breeding water to the breeding tank, in a region where the breeding water is stored or flows, an electrolysis unit that generates a chloric acid compound by electrolyzing the breeding water and decomposes ammonia or ammonium ions in the breeding water by reacting the generated chloric acid compound with ammonia or ammonium ions in the breeding water, The electrolysis unit includes an electrode unit having a first electrode and a second electrode disposed in the region, and a voltage application unit that applies a voltage between the electrodes of the first electrode and the second electrode, The voltage application unit switches between a first state in which the voltage is applied so that the first electrode is the anode and the second electrode is the cathode to perform the electrolysis in the region, and a second state in which the voltage is applied so that the second electrode is the anode and the first electrode is the cathode, An electrolysis device for aquaculture. Claim 2 The electrode unit includes an electrode holding unit that holds the first electrode and the second electrode, and the first electrode, the second electrode, and the electrode holding unit are integrally configured, In the circulation type water treatment system, an electrolysis tank configured such that the breeding water is stored or flows is provided, and the inside of the electrolysis tank is the region, The integrally configured electrode unit is detachably attached to the electrolysis tank The electrolysis device for aquaculture according to claim 1. Claim 3 An electrolysis tank configured such that the breeding water is stored or flows is provided, The inside of the electrolysis tank is the region, Furthermore, a guiding unit is provided that guides and collects the precipitate that has settled from the electrode unit in the electrolysis tank toward a predetermined position in the electrolysis tank The electrolysis device for aquaculture according to claim 1 or claim 2. Claim 4 An electrolysis tank configured such that the breeding water is stored or flows is provided, The inside of the electrolysis tank is the region, Furthermore, a discharge unit having a pipe for discharging the precipitate that has settled from the electrode unit in the electrolysis tank is provided, The discharge unit takes in the precipitate inside the pipe at a position lower than the electrode unit, and discharges the precipitate from the electrolysis tank through the pipe The electrolysis device for aquaculture according to claim 1 or claim 2. Claim 5 comprising an electrolysis cell configured to store or flow the breeding water, the interior of the electrolysis cell being the region, furthermore, the electrolysis cell has a guiding path that does not guide the water located below a predetermined height in the electrolysis cell to the outside of the electrolysis cell, and guides the water located above the predetermined height to the outside of the electrolysis cell The electrolysis device for aquaculture according to claim 1 or claim 2.

6. The predetermined height is located above the lower end of the electrode part The electrolysis device for aquaculture according to claim 5.

7. comprising an electrolysis cell configured to store or flow the breeding water, the interior of the electrolysis cell being the region, the electrode part is disposed on the water surface side of the breeding water in the electrolysis cell, furthermore, it comprises a water flow generating part that causes the breeding water introduced into the electrolysis cell from the outside of the electrolysis cell to flow upward from the lower side to the upper side of the electrode part in the electrolysis cell The electrolysis device for aquaculture according to claim 1 or claim 2.

8. The voltage application part periodically switches between an operation of continuously electrolyzing the breeding water in the first state and an operation of continuously electrolyzing the breeding water in the second state The electrolysis device for aquaculture according to claim 1 or claim 2.

9. A circulating water treatment system for aquaculture comprising the electrolysis device for aquaculture according to claim 1 or claim 2, in a first region where the breeding water sent from the breeding tank is stored or flows, a removing part that removes at least solids, an electrolysis part that electrolyzes the breeding water in a second region which is the region where the breeding water that has passed through the first region is stored or flows, in a third region where the breeding water that has passed through the second region is stored or flows, an activated carbon part that removes at least residual chlorine by activated carbon, A circulating water treatment system for aquaculture including the above.

10. A circulating water treatment system for aquaculture comprising the electrolysis device for aquaculture according to claim 1 or claim 2, an electrolysis cell configured to store or flow the breeding water, a reaction tank configured to store or flow the breeding water discharged from the electrolysis cell, comprising, the interior of the electrolysis cell being the region, The electrolysis cell has a first guiding path that does not guide water located below a first height in the electrolysis cell to the outside of the electrolysis cell, but guides water located above the first height to the outside of the electrolysis cell. The reaction tank has a second guiding path that does not guide water located below a second height in the reaction tank to the outside of the reaction tank, but guides water located above the second height to the outside of the reaction tank. A circulating water treatment system for aquaculture.

11. An electrolysis method used in a circulating water treatment system that circulates and treats breeding water from a breeding tank that is a tank for cultivating aquatic organisms and contains salt-containing breeding water, and returns the treated breeding water to the breeding tank. An electrolysis unit having an electrode unit with a first electrode and a second electrode, and a voltage application unit that applies a voltage between the electrodes of the first electrode and the second electrode is used. With the first electrode and the second electrode arranged in a region where the breeding water is stored or flows, a voltage is applied between the electrodes by the voltage application unit to electrolyze the breeding water to generate a chloric acid compound, and the generated chloric acid compound is reacted with ammonia or ammonium ions in the breeding water to decompose the ammonia or ammonium ions in the breeding water. The voltage application unit switches between a first state in which the voltage is applied so that the first electrode is the anode and the second electrode is the cathode to perform the electrolysis in the region, and a second state in which the voltage is applied so that the second electrode is the anode and the first electrode is the cathode. An electrolysis method for aquaculture.

12. An electrolysis cell configured such that the breeding water is stored or flows is used. The electrode unit is arranged such that the inside of the electrolysis cell is the region. Water is continuously introduced into and drained from the electrolysis cell, and the breeding water is replaced while the voltage application unit performs the operation in the first state, the operation in the second state, and the switching between the first state and the second state. The electrolysis method for aquaculture according to claim 11.

13. The voltage application unit periodically switches between an operation of continuously electrolyzing the breeding water in the first state and an operation of continuously electrolyzing the breeding water in the second state. The electrolysis method for aquaculture according to claim 11 or claim 12.

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