WO2025141975A1 - Electrolysis device for aquatic organism farming, circulation type water treatment system for aquatic organism farming, and electrolysis method for aquatic organism farming - Google Patents

Abstract

An electrolysis unit (13) that constitutes at least a portion of an electrolysis device generates a chloric acid compound by electrolyzing rearing water in a region where the rearing water is retained or flows, to decompose ammonia or ammonium ions in the rearing water. The electrolysis unit (13) has: an electrode unit (55) having a first electrode (55A) and a second electrode (55B) that are disposed in the region; and a voltage application unit (51) that applies a voltage between the electrodes. The voltage application unit (51) switches between a first state in which electrolysis is performed in the region by applying a voltage in such a manner that the first electrode (55A) serves as an anode and the second electrode (55B) serves as a cathode, and a second state in which a voltage is applied in such a manner that the second electrode (55B) serves as an anode and the first electrode (55A) serves as a cathode.

Description

Electrolysis device for aquatic organism cultivation, circulating water treatment system for aquatic organism cultivation, and electrolysis method for aquatic organism cultivation

The present disclosure relates to an electrolysis device for aquatic organism cultivation, a circulating water treatment system for aquatic organism cultivation, and an electrolysis method for aquatic organism cultivation.

A closed circulation aquaculture system is known as an example of a system for cultivating aquatic organisms. In a closed circulation aquaculture system, leftover food and excrement discharged by the organisms are decomposed and purified in a filtration tank, and the water is circulated. In general closed circulation aquaculture systems, the mainstream method is to utilize microorganisms to decompose and purify nitrogen compounds in the breeding water. Technologies such as those disclosed in Patent Document 1 have been proposed.

Patent No. 7345037

In the aquaculture management system disclosed in Patent Document 1, ammonia is generated in the tank due to the metabolic activity of aquatic organisms and the decomposition of organic matter such as leftover food, so the water is circulated and passed through a filtration tank for biological filtration, where the ammonia is decomposed and converted into less toxic nitrate. The filtration tank holds nitrifying bacteria (microorganisms) that oxidize ammonia in oxygen-containing water, converting it into nitrite and then nitrate.

However, when a purification method using microorganisms is adopted, as in Patent Document 1, there is a problem in that the purification ability becomes dependent on the microorganisms. In response to this, the inventors of the present application envisaged a method for decomposing ammonia contained in salt-containing breeding water, in which the salt-containing breeding water is electrolyzed to produce sodium hypochlorite, and this sodium hypochlorite is then reacted with the ammonia present in the breeding water to directly decompose it into nitrogen. Using this method, ammonia can be decomposed with less dependency on microorganisms, and the generation of nitrite, nitrate, etc. can be reliably suppressed during the decomposition process.

However, this method has the problem that deposits caused by electrolysis tend to adhere to the surface of the electrode during electrolysis. When deposits adhere to the surface of the electrode in this way, the generation of sodium hypochlorite is suppressed and the rate at which ammonia decomposes tends to decrease.

One of the objectives of this disclosure is to provide a technology that can decompose ammonia in water using electrolysis when cultivating aquatic organisms, and that can easily remove the deposits that form on the surface of the electrodes.

The electrolysis device for aquatic organism cultivation according to the present disclosure includes:
1. An electrolysis device used in a circulating water treatment system, which is a tank for cultivating aquatic organisms and contains salt-containing breeding water from a breeding tank, treats the breeding water while circulating the water, and returns the treated breeding water to the breeding tank,
an electrolysis unit that generates a chlorate compound by electrolyzing the breeding water in a region where the breeding water is stored or flows, 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 first electrode and the second electrode,
The voltage application unit switches between a first state in which a voltage is applied so that the first electrode is an anode and the second electrode is a cathode to perform the electrolysis in the region, and a second state in which a voltage is applied so that the second electrode is an anode and the first electrode is a cathode.

The present disclosure relates to a circulating water treatment system for cultivating aquatic organisms.
A circulating water treatment system for cultivating aquatic organisms comprising the electrolysis apparatus for cultivating aquatic organisms,
a removal unit that removes at least solid matter in a first area where the breeding water sent from the breeding tank is stored or flows;
the electrolysis unit performing the electrolysis of the breeding water in a second area, which is an area in which the breeding water that has passed through the first area is stored or flows;
an activated carbon section that removes at least residual chlorine by activated carbon in a third area in which the rearing water that has passed through the second area is stored or flows;
Includes.

The present disclosure relates to a circulating water treatment system for cultivating aquatic organisms.
A circulating water treatment system for cultivating aquatic organisms comprising the electrolysis apparatus for cultivating aquatic organisms,
An electrolysis tank configured to store or flow the breeding water;
a reaction tank configured to store or flow the breeding water discharged from the electrolysis tank;
Equipped with
The interior of the electrolysis cell is the region,
the electrolytic cell has a first guide path which does not guide water located below a first level in the electrolytic cell to the outside of the electrolytic cell, and guides water located above the first level to the outside of the electrolytic cell,
The reaction tank has a second guide 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.

One embodiment of the electrolysis method for cultivating aquatic organisms disclosed herein includes the steps of:
1. An electrolysis method used in a circulating water treatment system, which is a tank for cultivating aquatic organisms and contains salt-containing breeding water from a breeding tank, treats the breeding water while circulating the water, and returns the treated breeding water to the breeding tank,
An electrolysis unit including an electrode unit having a first electrode and a second electrode, and a voltage application unit that applies a voltage between the first electrode and the second electrode,
With the first electrode and the second electrode disposed in a region in which 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 chlorite compound, and the generated chlorite 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 a voltage is applied so that the first electrode is an anode and the second electrode is a cathode to perform the electrolysis in the region, and a second state in which a voltage is applied so that the second electrode is an anode and the first electrode is a cathode.

The technology disclosed herein can decompose ammonia or ammonium ions in water using electrolysis when cultivating aquatic organisms, and also makes it easy to remove the deposits that form on the surface of the electrodes.

FIG. 1 is an explanatory diagram conceptually illustrating a circulating water treatment system according to the first embodiment. FIG. 2 is a block diagram illustrating a simplified example of the electrical configuration of the circulating water treatment system of FIG. FIG. 3 is an explanatory diagram illustrating a simplified example of the configuration of the removal unit, the electrolysis tank, and the like of the circulating water treatment system of FIG. FIG. 4 is an explanatory diagram showing a more specific example of the configuration of FIG. FIG. 5 is an explanatory diagram illustrating a simplified example of the configuration of the electrolysis tank, reaction tank, etc. of the circulating water treatment system of FIG. FIG. 6 is an explanatory diagram illustrating a simplified example of the configuration of the electrolysis tank of the circulating water treatment system of FIG. 1, viewed from a different direction than that of FIG. FIG. 7 is an explanatory diagram showing a specific example of the residual chlorine removal tank, standby tank, etc. of the circulating water treatment system of FIG. FIG. 8 is an explanatory diagram illustrating a simplified example of the configuration of a removal unit, an electrolysis tank, and the like of a circulating water treatment system according to the second embodiment. FIG. 9 is an explanatory diagram illustrating a simplified example of the configuration of an electrolysis tank, a reaction tank, and the like of a circulating water treatment system according to the third embodiment. FIG. 10 is an explanatory diagram showing specific examples of the residual chlorine removal tank, the switching unit, the standby tank, etc. of the circulating water treatment system of the fourth embodiment.

Each of the following [1] to [13] is an example of a characteristic technology included in this disclosure.

[1] An electrolysis device used in a circulating water treatment system, which is a tank for cultivating aquatic organisms and contains salt-containing breeding water from a breeding tank, treats the breeding water while circulating the water, and returns the treated breeding water to the breeding tank,
an electrolysis unit that generates a chlorate compound by electrolyzing the breeding water in a region where the breeding water is stored or flows, 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 first electrode and the second electrode,
The voltage application unit switches between a first state in which a voltage is applied so that the first electrode is an anode and the second electrode is a cathode to perform the electrolysis in the region, and a second state in which a voltage is applied so that the second electrode is an anode and the first electrode is a cathode.

The electrolysis device of [1] above can generate chloric acid compounds (e.g., sodium hypochlorite) by electrolyzing salt-containing breeding water, and then react this chloric acid compound with ammonia or ammonium ions present in the breeding water to directly decompose it into nitrogen, and can reliably suppress the generation of nitrite, nitric acid, etc. during the decomposition process. However, when this method is adopted, there is a concern that if no measures are taken, deposits will adhere to the surface of the electrodes and hinder electrolysis. However, the electrolysis device can be switched between a first state in which electrolysis is performed by applying a voltage so that the first electrode is the anode and the second electrode is the cathode, and a second state in which a voltage is applied so that the second electrode is the anode and the first electrode is the cathode, so that deposits that have adhered to the surface of the electrodes due to continuous electrolysis can easily detach from the electrodes by switching. Therefore, this electrolysis device makes it easy to remove deposits that have precipitated on the surface of the electrodes.

[2] The electrode unit includes an electrode holder that holds the first electrode and the second electrode, and the first electrode, the second electrode, and the electrode holder are integrally configured,
In the circulating water treatment system, an electrolysis tank configured to store or flow the breeding water is provided, and the inside of the electrolysis tank is the region,
The electrolysis device for cultivating aquatic organisms according to [1], wherein the electrode unit is integrally formed and detachable from the electrolysis tank.

The electrolysis device of [2] above has an electrode unit, which is an integral structure of the first electrode, the second electrode, and the electrode holder, that can be attached and detached from the electrolysis tank, making it easy to remove the electrode unit for cleaning. In particular, the promotion of precipitate removal by switching and the simplification of the work of attaching and detaching the electrode unit have a synergistic effect, making cleaning even easier.

[3] An electrolysis tank configured to store or flow the rearing water,
The interior of the electrolysis cell is the region,
The electrolysis device for cultivating aquatic organisms according to [1] or [2] further comprises a guide unit that guides and collects the precipitate that has sunk from the electrode unit in the electrolysis tank toward a predetermined position in the electrolysis tank.

The electrolysis device of [3] above can automatically collect precipitates that have sunk from the electrode section toward a specified position using the induction section, making it easy not only to detach precipitates from the electrode section, but also to collect the detached precipitates.

[4] An electrolysis tank configured to store or flow the rearing water,
The interior of the electrolysis cell is the region,
The electrolytic cell further includes a discharge section having a pipe for discharging precipitate that has sunk from the electrode section in the electrolytic cell,
The discharge section takes in the precipitate inside the tube at a position below the electrode section and discharges the precipitate from the electrolysis tank through the tube. The electrolysis device for cultivating aquatic organisms according to any one of [1] to [3].

The electrolysis device described in [4] above can take in and discharge the precipitate that has sunk from the electrode section into a tube at a position lower than the electrode section, preventing the precipitate from dispersing during the discharge process and becoming prone to flowing into subsequent processes.

[5] An electrolysis tank configured to store or flow the rearing water,
The interior of the electrolysis cell is the region,
The electrolysis tank further includes a guide path that does not guide water located below a predetermined height in the electrolysis tank to the outside of the electrolysis tank, and guides water located above the predetermined height to the outside of the electrolysis tank.

The electrolysis device of [5] above can guide the supernatant water located above a specified height to the outside, and can make it difficult for the precipitate that has sunk below the specified height to be guided outside the electrolysis tank.

[6] The electrolysis apparatus for cultivating aquatic organisms according to [5], wherein the predetermined height is above a lower end of the electrode portion.

In the electrolysis device of [6] above, the precipitate that detaches from the electrode section and sinks downward from the lower end is less likely to be guided outside the electrolysis cell.

[7] An electrolysis tank configured to store or flow the rearing water,
The interior of the electrolysis cell is the region,
the electrode unit is disposed on the water surface side of the breeding water in the electrolysis tank,
The electrolysis device for cultivating aquatic organisms according to any one of [1] to [6], further comprising a water flow generating unit that causes the breeding water introduced into the electrolysis tank from outside the electrolysis tank to flow upward from below the electrode unit within the electrolysis tank.

The electrolysis device of [7] above can generate a water current in the electrolysis tank that causes the water to rise from the bottom to the top of the electrode, making it easier for new rearing water to be guided to the electrode, further increasing the efficiency of electrolysis.

[8] The electrolysis device for cultivating aquatic organisms described in any one of [1] to [7], wherein the voltage application unit periodically switches between an operation of electrolyzing the rearing water by continuing the first state and an operation of electrolyzing the rearing water by continuing the second state.

The electrolysis device described above in [8] can periodically remove the precipitates and periodically clean the electrodes.

[9] A circulating water treatment system for cultivating aquatic organisms, comprising the electrolysis device for cultivating aquatic organisms according to any one of [1] to [8],
a removal unit that removes at least solid matter in a first area where the breeding water sent from the breeding tank is stored or flows;
the electrolysis unit performing the electrolysis of the breeding water in a second area, which is an area in which the breeding water that has passed through the first area is stored or flows;
an activated carbon section that removes at least residual chlorine by activated carbon in a third area in which the rearing water that has passed through the second area is stored or flows;
A circulating water treatment system for culturing aquatic organisms comprising:

The circulating water treatment system of [9] above can remove solids contained in the breeding water in the first region by the removal section. Furthermore, in the second region after passing through the first region, this circulating water treatment system can decompose ammonia or ammonium ions by the electrolysis section, and since the breeding water is electrolyzed after the removal of solids by the removal section, it is possible to reliably prevent solids from hindering the electrolysis, and it is easy to perform the electrolysis well. Furthermore, in the third region where the breeding water that has passed through the second region is stored or flows, this circulating water treatment system can remove residual chlorine by activated carbon. Therefore, even if chlorate compounds that were not used to decompose ammonia or ammonium ions are contained in the breeding water in the third region, these chlorate compounds can be effectively removed by the activated carbon section. In this way, in the above circulating water treatment system, solids such as feces and leftover food are reliably reduced in the breeding water after passing through the third region, and nitrogen compound components such as ammonia, ammonium ions, nitrite, and nitrate are reliably suppressed, which is extremely advantageous in terms of purifying and detoxifying the breeding water.

[10] A circulating water treatment system for cultivating aquatic organisms, comprising the electrolysis device for cultivating aquatic organisms according to any one of [1] to [8],
An electrolysis tank configured to store or flow the breeding water;
a reaction tank configured to store or flow the breeding water discharged from the electrolysis tank;
Equipped with
The interior of the electrolysis cell is the region,
the electrolytic cell has a first guide path which does not guide water located below a first level in the electrolytic cell to the outside of the electrolytic cell, and guides water located above the first level to the outside of the electrolytic cell,
The reaction tank has a second guide path that does not guide water located below a second level in the reaction tank to the outside of the reaction tank, and guides water located above the second level to the outside of the reaction tank.

The circulating water treatment system of [10] above can guide the supernatant water located above the first height in the electrolysis tank to the outside of the electrolysis tank, so that even if a precipitate detaches from the electrode and sinks, the precipitate is unlikely to be guided to the outside of the electrolysis tank. Even if some precipitate is discharged from the electrolysis tank and enters the reaction tank, the supernatant water located above the second height in the reaction tank can be guided to the outside of the reaction tank, so that the precipitate that enters the reaction tank is likely to settle in the reaction tank and is unlikely to be guided to the outside of the reaction tank.

[11] An electrolysis method used in a circulating water treatment system, which is a tank for cultivating aquatic organisms and contains salt-containing breeding water from a breeding tank, treats the breeding water while circulating the breeding water, and returns the treated breeding water to the breeding tank, comprising:
An electrolysis unit including an electrode unit having a first electrode and a second electrode, and a voltage application unit that applies a voltage between the first electrode and the second electrode,
With the first electrode and the second electrode disposed in a region in which 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 chlorite compound, and the generated chlorite 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 a voltage is applied so that the first electrode is an anode and the second electrode is a cathode to perform the electrolysis in the region, and a second state in which a voltage is applied so that the second electrode is an anode and the first electrode is a cathode.

The electrolysis method of [11] above generates a chlorate compound (e.g., sodium hypochlorite) by electrolyzing the breeding water containing salt, and then this chlorate compound can be reacted with ammonia or ammonium ions present in the breeding water to directly decompose it into nitrogen, and the generation of nitrite, nitric acid, etc. can be reliably suppressed during the decomposition process. However, when this method is adopted, there is a concern that if no measures are taken, deposits will adhere to the surface of the electrodes and hinder electrolysis. However, the above electrolysis method can be switched between a first state in which electrolysis is performed by applying a voltage so that the first electrode is the anode and the second electrode is the cathode, and a second state in which a voltage is applied so that the second electrode is the anode and the first electrode is the cathode, so that deposits that have adhered to the surface of the electrodes due to continuous electrolysis can easily detach from the electrodes by switching. Therefore, this electrolysis method makes it easy to remove deposits that have precipitated on the surface of the electrodes.

[12] Using an electrolysis tank configured so that the rearing water is stored or flows,
The electrode unit is disposed so that the interior of the electrolytic cell is the region;
The electrolysis method for cultivating aquatic organisms described in [11], wherein the breeding water is continuously introduced into the electrolysis tank and discharged from the electrolysis tank, and the breeding water is replaced while the voltage application unit performs operation in the first state, operation in the second state, and switching between the first state and the second state.

The electrolysis method of [12] above allows the breeding water to be continuously introduced into the electrolysis tank and discharged from the electrolysis tank while the breeding water is being replaced, while the first state, second state, and switching between the first and second states can be performed, so that the breeding water can be circulated more efficiently while the electrodes are purified.

[13] The electrolysis method for cultivating aquatic organisms described in [11] or [12], wherein the voltage application unit periodically switches between an operation of electrolyzing the rearing water by continuing the first state and an operation of electrolyzing the rearing water by continuing the second state.

The electrolysis method described above in [13] allows the deposits to be periodically removed and the electrodes to be periodically cleaned.

First Embodiment
1. Overview of a circulating water treatment system 1 used for cultivating aquatic organisms The circulating water treatment system 1 illustrated in FIG. 1 is a system used for cultivating aquatic organisms. The circulating water treatment system 1 is configured as a closed circulating aquaculture system that treats the breeding water in a breeding tank 3 containing salt-containing breeding water outside the breeding tank 3, and then circulates the treated breeding water back to the breeding tank 3, and is a method of circulating water. When cultivating aquatic organisms in the breeding tank 3, the circulating water treatment system 1 operates to continuously breed aquatic organisms in the breeding tank 3, while decomposing and purifying residual food remaining in the breeding water during breeding in the breeding tank 3 and feces and urine discharged by the organisms in the process of circulating the water from the breeding tank 3 and returning it to the breeding tank 3.

As shown in FIG. 1, the circulating water treatment system 1 mainly comprises a breeding tank 3, a removal section 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 section 31, etc. Furthermore, the circulating water treatment system 1 also comprises a temperature regulator 35, a filter 37, etc. The electrical configuration of the circulating water treatment system 1 is, for example, as shown in FIG. 2. There are various types of aquatic organisms that can be bred inside the breeding tank 3, and suitable examples include fish, crustaceans, and shellfish, although other types (for example, squid, octopus, etc.) may also be used.

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. Salty breeding water such as artificial seawater or natural seawater is contained inside the breeding tank 3, and aquatic organisms such as fish and shellfish are raised in this breeding water. The "salty breeding water" contained in the breeding tank 3 is preferably a liquid with a NaCl content of 0.5 mass% or more. In the example of FIG. 1, a plurality of (for example, four) breeding tanks 3 are provided, and the breeding water in these breeding tanks 3 is guided to be collected in a 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 temperature of the breeding water in the breeding tank 3 is adjusted to a desired set temperature by a temperature regulator 35. In the example of FIG. 1, a plurality of breeding tanks 3 are used, but it may be constituted by a single aquarium.

(removal part)
The removal unit 5 shown in Fig. 1 functions to remove at least solid matter in a 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 unit 5 through a flow path 41. As shown in Fig. 3, the removal unit 5 includes an ozone generator 9, a foam separator 7, a storage tank 60, an inlet unit 62, an outlet unit 64, and a discharge unit 66. In Fig. 3 and other figures, the symbol W conceptually indicates a portion of the circulating breeding water.

The storage tank 60 is a tank that stores the breeding water introduced from the area before the removal unit 5. In the example of FIG. 1, the area before the removal unit 5 is an area inside the breeding tank 3. The breeding water can be caused to flow from the breeding tank 3 to the storage tank 60 by using a pump or by using a difference in elevation.

The ozone generator 9 corresponds to an example of an ozone generating section, and generates ozone by, for example, a known method, and supplies the generated ozone to the foam separator 7. The method of introducing ozone from the ozone generator 9 to the foam separator 7 is not particularly limited, but an example is a method of supplying the ozone generated by the ozone generator 9 from an inlet for introducing air provided in a foam generating section of a known foam separator. The foam separator 7 generates foam containing the ozone generated by the ozone generator 9, and operates to 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, into the foam. In the example of FIG. 3, the first region is the internal region of the storage tank 60.

The inlet section 62 is a flow path that introduces the rearing water stored in the storage tank 60 into the inside of the foam separator 7. The outlet section 64 is a flow path that returns the rearing 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 that discharges the rearing water stored in the storage tank 60 to an area subsequent to the removal section 5. In the examples of Figures 1 and 3, the area subsequent to the removal section 5 is an area within the electrolysis tank 11.

In the removal section 5, solids such as feces and leftover food contained in the breeding water introduced into the foam separator 7, removal proteins from the metabolism of fish and shellfish, bacteria, viruses, parasites, etc. are attached to fine bubbles generated within the foam separator 7 and removed from the breeding water. Furthermore, the bubbles generated within the foam separator 7 are bubbles containing ozone, and therefore have a high bactericidal power, and this bactericidal power also acts on the breeding water that passes through the foam separator 7 and returns to the outlet section 64. This operation reliably prevents dirt from flowing into the electrolysis tank 11 in the subsequent process, and reliably prevents dirt from interfering with the electrolysis in the electrolysis tank 11.

In the example of FIG. 3, the flow path 41 is connected near the bottom 60A of the storage tank 60, and the rearing water from the flow path 41 is supplied into the storage tank 60 from a position near the bottom end on the side of the storage tank 60. The inlet (the entrance for taking in the rearing water) in the introduction section 62 is located near the bottom 60A in the storage tank 60, making it easy to take in the rearing water immediately after it is introduced into the storage tank 60 from the flow path 41. Meanwhile, the rearing water that has passed through the foam separator 7 is discharged by the discharge section 64 to a position closer to the discharge section 66 than the flow path 41. The discharge outlet (the outlet for discharging the rearing water) of the discharge section 64 is located near the water surface W1 than the bottom 60A of the storage tank 60. The discharge section 66 is configured as a flow path that flows the rearing water in the storage tank 60 toward the outside of the storage tank 60. The discharge section 66 is configured not to guide water located below a predetermined first level in the storage tank 60 to the outside of the storage tank 60, but to guide water located above the first level to the outside of the storage tank 60. The first level is the height of the lower end of the boundary between the storage tank 60 and the inner wall surface of the flow path of the discharge section 66, and when the water level of the rearing water in the storage tank 60 is higher than this first level, the water in the area higher than the first level is discharged from the discharge section 66.

The configuration of the removal section 5 shown in FIG. 3 can be more specifically configured as shown in FIG. 4. In the specific example of FIG. 4, a foam generating section 8 and a foam separation tank 7A are provided in the foam separator 7. Furthermore, an inlet (water intake) of an inlet section 62 configured as a pipe is disposed 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 to cover this inlet. Of the breeding water stored in the storage tank 60, the breeding water that can pass through the filter 61 is introduced from the inlet section 62 to the foam separator 7. The filter 61 is configured to block the passage of objects with large particle sizes and to allow the passage of objects with small particle sizes, and is configured, for example, in a net shape. Although not shown in FIG. 4, a pump may be provided to move the breeding water so that it flows through the inlet section 62 into the foam separator 7.

In the configuration of FIG. 4, the foam generating section 8 injects ozone-containing gas generated by the ozone generator 9 into the breeding water flowing in from the inlet section 62, causing the breeding water passing through the foam generating section 8 to contain bubbles of ozone-containing gas. The breeding water that has passed through the foam generating section 8 flows into the foam separation tank 7A through the inlet section 63 configured as a tube as breeding water containing ozone-containing bubbles. In the foam separation tank 7A, bubbles with solid matter 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. Meanwhile, 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 outlet section 64 configured as a tube. The outlet (discharge port) of the outlet section 64 is positioned so that a vortex is generated in a certain direction in the breeding water stored in the storage tank 60. The discharge section 66, which is configured as a discharge flow path, is disposed near the water surface of the storage tank 60, and the supernatant of the rearing water stored in the storage tank 60 is discharged from the discharge section 66.

(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 first region (the region in the reservoir tank 60 in the example of FIG. 3) is stored or flows, and corresponds to an example of the second region. The electrolysis tank 11 is provided with an electrolysis unit 13. The electrolysis unit 13 generates a chlorine acid compound (e.g., sodium hypochlorite) by electrolyzing the breeding water in the second region, and reacts the generated chlorine acid compound with ammonia or ammonium ions in the breeding water to decompose the ammonia or ammonium ions. Furthermore, since the electrolysis unit 13 generates a chlorine acid compound in the electrolysis tank 11, the breeding water can be sterilized, deodorized, and decolorized.

In the electrolytic cell 11, electrolysis is carried out as shown in the following formula (1).
2NaCl+ _3H2O →NaClO+NaCl+ _2H2O + _H2 ↑...(1)

Then, the decomposition of ammonia or the decomposition of ammonium ions occurs through the chemical reactions shown in the following formulas (2) and (3).
_2NH3 +3NaClO→ _N2 ↑+3NaCl+ _3H2O ...(2)
2NH ₄ ⁺ +3NaClO→N ₂ ↑+3H ₂ O+3NaCl+2H ⁺ ...(3)

In the electrolysis cell 11 shown in FIG. 5, the internal region of the electrolysis cell 11 is the "region" in which the electrode unit 55 is disposed and electrolysis is carried out. The electrolysis cell 11 is provided with an electrolysis unit 13. The electrolysis unit 13 has an electrode unit 55 having a first electrode 55A and a second electrode 55B disposed in the "region" (second region), and a voltage application unit 51 that applies a voltage between the first electrode 55A and the second electrode 55B.

The voltage application unit 51 has a control device 52 and a drive circuit 53. The control device 52 is an information processing device having an information processing unit, a memory unit, a communication unit, etc., and is a device that can perform various controls and various calculations. The drive circuit 53 is a circuit that applies a voltage between the first electrode 55A and the second electrode 55B in response to a command from the control device 52.

The electrode unit 55 includes an electrode holder 55C that holds the first electrode 55A and the second electrode 55B, and the first electrode 55A, the second electrode 55B, and the electrode holder 55C are integrally configured. The integrally configured electrode unit 55 is attached to and detached from the electrolytic cell 11. The configuration that allows the electrode unit 55 to be attached and detached from the electrolytic cell 11 is not particularly limited, but an example of a configuration is that the electrode holder 55C is placed on a mounting base provided on the electrolytic cell 11 when the electrode unit 55 is attached, and the electrode holder 55C is detached from the mounting base when the electrode unit 55 is removed. 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 into a plate shape using a metal material. In the electrode unit 55, the first electrodes 55A and the second electrodes 55B are alternately arranged at intervals. The multiple first electrodes 55A are short-circuited to each other and are electrically connected to a first terminal of the drive circuit 53 via a conductive path 54A. The multiple second electrodes 55B are short-circuited to each other and are electrically connected to a second terminal of the drive circuit 53 via a conductive path 54B. In the example of FIG. 5, the first electrodes 55A and the second electrodes 55B are alternately arranged with a gap between them.

The electrodes used in the electrolysis tank 11 are preferably made of a metal material that is not corroded by seawater and has a high efficiency in generating chloric acid compounds. For example, an electrode made of titanium with a platinum-iridium alloy coated on the surface can be preferably used. Platinum has excellent conductivity and corrosion resistance, iridium has excellent durability and chemical stability, and the platinum-iridium alloy has a uniform and smooth surface. An electrode made of titanium with a platinum-iridium alloy coated on the surface can be used as both an anode and a cathode. Note that the example of the electrode described here is merely one example, and if the electrode inversion method described below is not used, an electrode made of titanium coated with ruthenium or other materials may be used as the anode.

A part or all of the electrode unit 55 is disposed on the water surface W2 side of the rearing water in the electrolysis tank 11, with the rearing water being disposed between the first electrode 55A and the second electrode 55B. Meanwhile, the electrolysis tank 11 is provided with a water flow generating unit 57, which generates a water flow from the lower side of the electrode unit 55 toward the upper side (electrode unit side).

The water flow generating unit 57 has a structure for flowing the rearing water introduced into the electrolysis cell 11 from outside the electrolysis cell 11 through the flow path 42 so that the rearing water rises from below the electrode unit 55 to above it within the electrolysis cell 11. The flow path 42 is a flow path for flowing the rearing water discharged through the discharge unit 66 into the electrolysis cell 11, and may be formed by the discharge unit 66 or may be formed as a flow path continuing to the discharge unit 66. The water flow generating unit 57 has a first partition wall 57A. The first partition wall 57A is a wall that separates a predetermined upstream region and a predetermined downstream region in the electrolysis cell 11. The downstream region is a region downstream of the first partition wall 57A and where the electrode unit 55 is provided. The upstream region is a region upstream of the first partition wall 57A and upstream of the downstream region.

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

The downstream area is an internal area of the second rearing water flow chamber 11B, which is 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 bottom wall 11Z of the electrolysis cell 11, and is an area in which a part or all of the electrode unit 55 is disposed. In the second rearing water flow chamber 11B, the height of the upper end of the second partition wall 57B is lower than the height of the upper end of the outer peripheral wall of the electrolysis cell 11, so that when water that exceeds the upper end of the second partition wall 57B enters the second rearing water flow chamber 11B, the water flows beyond the second partition wall 57B to the downstream side of the second rearing water flow chamber 11B. Because of this configuration, rearing water is introduced into the second rearing water flow chamber 11B from the opening on the lower side, and the rearing water is discharged so as to exceed the upper end of the second partition wall 57B. Therefore, a water flow of rearing water is generated so as to rise from the lower side of the electrode unit 55 toward the electrode unit 55 side.

In the example shown in FIG. 5, the second partition wall 57B is provided, but the second partition wall 57B does not have to be provided. In this case, the entire downstream side of the first partition wall 57A in the electrolysis tank 11 is the downstream region, and the second rearing water flow chamber 11B is formed by the first partition wall 57A and the portion of the outer peripheral wall and bottom wall 11Z of the electrolysis tank 11 downstream of the first partition wall 57A.

As shown in FIG. 6, the electrolytic cell 11 is provided with an induction section 58. The induction section 58 functions to guide and collect the precipitate that has sunk from the electrode section 55 in the electrolytic cell 11 toward a predetermined position in the electrolytic cell 11. In the example of FIG. 5 and FIG. 6, the predetermined position is an upper position of a part of the bottom wall 11Z. In the example of FIG. 5 and FIG. 6, downstream of the second breeding water flow chamber 11B, a third breeding water flow chamber 11C is formed by the second partition wall 57B, the outer peripheral wall of the electrolytic cell 11, and a part of the bottom wall 11Z downstream of the second partition wall 57B, and the predetermined position is an upper position of a part of the bottom wall 11Z in the third breeding water flow chamber 11C. The induction section 58 has an inclined section 58A having an inclined surface that is inclined in the vertical direction. The inclined surfaces of the inclined portions 58A and 58B form the inner wall surface of the third breeding water flow chamber 11C, and when a sinking object (e.g., precipitate) reaches the inclined surface of the inclined portion 58A in the third breeding water flow chamber 11C, the object is guided by the inclined surface as it sinks further, and is guided to the vicinity of the above-mentioned predetermined position on the bottom wall 11Z. The inclined surfaces of the inclined portions 58A and 58B guide the object sinking along these inclined surfaces in a predetermined first direction perpendicular to the up-down direction (specifically, in the first direction, toward the discharge portion 59).

As shown in Figures 5 and 6, the electrolytic cell 11 is provided with a discharge section 59. In the example of Figure 5, the discharge sections 59 are provided in two locations. However, this is not limiting, and the number of discharge sections 59 may be one or three or more. The discharge section 59 has a tube 59A that discharges precipitate that has sunk from the electrode section 55 in the electrolytic cell 11, and an opening/closing section 59B that opens and closes this tube 59A. The discharge section 59 functions to take in the precipitate into the tube 59A at a position below the electrode section 55, and to discharge the precipitate from the electrolytic cell 11 through the tube 59A.

5 and 6, the opening/closing unit 59B is an opening/closing valve that is manually operated to switch between a state in which the tube 59A is blocked and a state in which the tube 59A is open. The opening/closing unit 59B may be an electromagnetic valve that is controlled to switch between open and closed. In either case, when the opening/closing unit 59B is in the open state, the breeding water is discharged through the tube 59A from near the predetermined position in the electrolysis cell 11. If a precipitate settles near the predetermined position, the precipitate is discharged through the tube 59A together with the breeding water. In the example of FIG. 5 and 6, the tube 59A is a fixed tube that is permanently installed in the electrolysis cell 11, but it may be a tube that can be attached and detached from the electrolysis cell 11. When the water is discharged through the tube from near the predetermined position, the water may be discharged by utilizing the water pressure in the electrolysis cell 11, or may be discharged by suction or flow using a pump or the like.

5 and 6, a first induction path 56 is provided in the electrolysis bath 11. The first induction path 56 corresponds to an example of an induction path. The first induction path 56 functions as a flow path so as not to induce water located below the first height in the electrolysis bath 11 to the outside of the electrolysis bath 11, but to induce water located above the first height to the outside of the electrolysis bath 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 electrolysis bath 11 is located above the lower end position of the inner wall surface of the flow path at the entrance of the first induction path 56 (the boundary with the first induction path 56, which is the exit of the electrolysis bath 11), so that the water near the water surface of the breeding water in the electrolysis bath 11 exceeds the height of the bottom of the first induction path 56 and flows into the first induction 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 guide path 56 is a first height (predetermined height), and this first height (predetermined height) is higher than the lower end of the electrode unit 55. The height of the lower end of the electrode unit 55 is the height of the lowest position among the multiple first electrodes 55A and the multiple second electrodes 55B. The first guide path 56 functions to flow the rearing water in the electrolysis tank 11 toward the reaction tank 15.

(Reaction tank)
The reaction tank 15 is a tank that stores rearing water supplied from the electrolysis tank 11 through the flow path 43, ensures a reaction time between ammonia or ammonium ions contained in the stored rearing water and a chloric acid compound (e.g., sodium hypochlorite) generated in the electrolysis tank 11, and promotes the chemical reaction between them. The flow path 43 may be formed by the first induction path 56, or may be formed as a flow path continuing to the first induction path 56. When all of the ammonia or ammonium ions present in the rearing water in the electrolysis tank 11 are not able to completely react with the chloric acid compound in the electrolysis tank 11 and flow out of the electrolysis tank 11, and when the chloric acid compound generated in the electrolysis tank 11 is not able to completely react and flow out of the electrolysis tank 11, either or both of the chemical reactions represented by the above formula (2) and/or the above formula (3) occur in the reaction tank 15, and the ammonia or ammonium ions are decomposed.

As shown in FIG. 5, the reaction tank 15 is provided with a second induction path 72. The second induction path 72 functions as a flow path to guide water located below the second height in the reaction tank 15 to the outside of the reaction tank 15, but not to guide water located above the second height to the outside of the reaction tank 15. In the example of FIG. 5, the water level W3 of the breeding water in the reaction tank 15 is higher than the lower end position of the inner wall surface of the flow path at the entrance of the second induction path 72 (the boundary with the second induction path 72, which is the exit of the reaction tank 15), so that the water near the water level of the breeding water in the reaction tank 15 exceeds the height of the bottom of the second induction path 72 and flows into the second induction 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 entrance of the second induction path 72 is the second height. The second induction path 72 functions to flow the breeding water in the reaction tank 15 toward the subsequent process of the reaction tank 15.

A filtration tank 17 is provided downstream of the reaction tank 15, forming a detection area for detecting residual chlorine. The filtration tank 17 is configured to store the rearing 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 rearing water discharged through the second induction path 72 into the filtration tank 17, and may be formed by the second induction path 72, or may be configured as a flow path continuing to the second induction path 72. In the example of FIG. 1, the flow path that guides the rearing 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 continues from the reaction tank 15 to the activated carbon tank 21) may be used as long as the rearing water flows from the reaction tank 15 to the activated carbon tank 21.

The first residual chlorine sensor 19 is a sensor that detects the concentration of residual chlorine contained in the rearing water after passing through the electrolysis tank 11 and before flowing into the residual chlorine removal tank (specifically, the activated carbon tank 21). For example, it detects the concentration of residual chlorine contained in the rearing water in the area where the rearing water flows from the reaction tank 15 to the activated carbon tank 21. In the representative example shown in FIG. 1, the first residual chlorine sensor 19 detects the residual chlorine contained in the rearing water in the filtration tank 17. In this specification, residual chlorine means the combined chlorine and free chlorine remaining in the rearing 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 rearing water, is the amount of residual chlorine. The first residual chlorine sensor 19 detects the residual chlorine contained in the rearing water in the area between the reaction tank 15 and the activated carbon tank 21, so that 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.

(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 downstream of the detection area (the area in the filtration tank 17 in the example of FIG. 1) in which the first residual chlorine sensor 19 is disposed. The activated carbon tank 21 functions as a tank that removes chlorine acid compounds (e.g., 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 a 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 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, which is a region in which the rearing water that has passed through the second region is stored or flows.

In the activated carbon tank 21, for example, a reaction takes place as shown in the following formula (4), and excess chlorine compounds that have not been used in the decomposition of ammonia or ammonium ions can be removed.
HClO+C→CO+H ⁺ +Cl ^-... (4)

The activated carbon tank 21 illustrated in FIG. 5 can be configured, for example, as shown in FIG. 7. In the example of FIG. 7, the activated carbon tank 21 is configured as a flow path through which the rearing water passes, and the activated carbon section 23 is configured in such a manner that the internal space of the flow path is filled with activated carbon particles. The activated carbon tank 21 is configured so that the rearing water flows through the gaps in the activated carbon section 23 (specifically, the gaps in the internal space filled with activated carbon particles). As the rearing water that flows in from the inlet 21A of the activated carbon tank 21 passes through the gaps between the numerous particles in the activated carbon tank 21, the residual chlorine and residual ozone contained in the rearing water are adsorbed by the activated carbon, and the rearing water discharged from the outlet 21B is rearing water from which some or all of the chlorine and ozone have been removed.

(standby tank)
The rearing water introduced into the activated carbon tank 21 from the flow path 45 passes through the internal region of the activated carbon tank 21, is discharged into the flow path 46, and flows through the flow path 46 into the waiting tank 25. The waiting tank 25 is a tank in which the rearing water that has passed through the activated carbon tank 21 is stored and whose water quality is inspected before it is returned to the rearing tank 3. The internal region of the waiting tank 25 corresponds to an example of the fourth region, and is a region in which the rearing water that has passed through the above-mentioned third region is stored or flows before it is returned to the rearing tank 3.

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 third area is stored or flows before returning to the breeding tank 3, and in the example of FIG. 1, it detects the concentration of residual chlorine contained in the breeding water in the waiting tank 25. When residual chlorine leaks out due to deterioration of the activated carbon provided in the activated carbon section 23, the second residual chlorine sensor 27 can more accurately detect fluctuations in the concentration of residual chlorine caused by such leakage.

The ammonium ion sensor 29 is a sensor that detects the concentration of ammonium ions contained in the breeding water in the fourth region where the breeding water that has passed through the third region is stored or flows before returning to the breeding tank 3, and in the example of FIG. 1, it detects the concentration of ammonium ions contained in the breeding water in the waiting tank 25. The ammonium ion sensor 29 can more accurately detect fluctuations in the concentration of ammonium ions when ammonium ions are not completely reacted in the electrolysis tank 11 or the reaction tank 15 and remain.

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 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 waiting tank 25 and provides the control device 52 with a value that specifies the pH of the breeding water in the waiting tank 25.

In the waiting tank 25, an aeration device (not shown) is used to aerate the breeding water and remove CO2 from it. The breeding water in the waiting tank 25 then flows into the breeding tank 3 through the flow path 47. The operation of flowing the breeding water from the waiting tank 25 to the breeding tank 3 through the flow path 47 can be switched between a state in which the breeding water flows continuously from the waiting tank 25 to the breeding tank 3, and a state in which the flow of the breeding water from the waiting tank 25 to the breeding tank 3 is stopped or blocked.

3. Control of the circulating water treatment system 1 (Configuration for control)
In the circulating water treatment system 1, the breeding water in the breeding tank 3 is circulated through 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 in this order. Pumps (not shown) for moving the breeding water are provided at multiple locations along the circulation path that circulates the breeding water from the breeding tank 3 and returns it to the breeding tank 3. The control device 52 shown in Fig. 2 controls the driving and stopping of the pumps. Furthermore, 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.

The control device 52 shown in FIG. 2 receives the detection value of the first residual chlorine sensor 19, the detection value of the second residual chlorine sensor 27, the detection value of the pH sensor 28, and the detection value of the ammonium ion sensor 29. 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-mentioned detection area (specifically, in 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-mentioned fourth area (specifically, in the waiting 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-mentioned fourth area (specifically, in the waiting 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-mentioned fourth area (specifically, in the waiting tank 25).

(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 result of the ammonium ion sensor 29 and the measurement result of the first residual chlorine sensor 19, may control the electrolysis of the electrolysis unit 13 based on the measurement result of the ammonium ion sensor 29, or may control the electrolysis of the electrolysis unit 13 based on the measurement result of the first residual chlorine sensor 19. When the control device 52 controls the electrolysis of the electrolysis unit 13 based on the measurement result of the ammonium ion sensor 29, for example, the control device 52 may feedback control the current flowing between the first electrode 55A and the second electrode 55B so that the detection value of the ammonium ion sensor 29 is 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 result of the first residual chlorine sensor 19, for example, the control device 52 may feedback control the current flowing between the first electrode 55A and the second electrode 55B so that the detection value of the first residual chlorine sensor 19 is within a predetermined range.

When determining the ammonia concentration and the effective chlorine concentration in the breeding water (e.g., seawater) used in this embodiment, they can be determined based on the discontinuous chlorination method. For example, in the first state in which the concentrations of ammonia and ammonium ions in the breeding water are equal to or higher than a certain concentration relative to the effective residual chlorine concentration, the effective residual chlorine concentration increases as the amount of chlorate compound added increases. On the other hand, in the second state in which ammonia or ammonium ions are present but the concentrations of ammonia and ammonium ions are equal to or lower than the certain concentration relative to the effective residual chlorine concentration, the effective residual chlorine concentration decreases even if a chlorate compound is added because the chlorate compound is consumed in a reaction with ammonia or ammonium ions. And in the third state in which ammonia and ammonium ions are not present, the effective residual chlorine concentration increases as the amount of chlorate compound added increases. If the pH, salinity, and temperature of the breeding water are constant, the certain concentrations can be considered as fixed values.

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 section 13, and continuously monitors the current flowing between the first electrode 55A and the second electrode 55B. Various configurations can be adopted for the control device 52 to monitor the current flowing between the first electrode 55A and the second electrode 55B, and for example, the current may be detected by a current sensor, and the control device 52 may obtain the value detected by the current sensor, or other configurations may be used. The control device 52 then 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.

The control device 52 may perform a first current control 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 larger the current flowing between the first electrode 55A and the second electrode 55B, the more electrolysis is promoted and the greater the amount of chlorine acid compounds 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 of the ammonium ion concentration detected by the ammonium ion sensor 29 (detection value) 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 in which ammonia and ammonium ions are not present, the greater the current flowing between the first electrode 55A and the second electrode 55B, the greater the effective chlorine concentration. Therefore, the control device 52 adjusts the current flowing between the first electrode 55A and the second electrode 55B so that the current range is such that the detection value of the ammonium ion sensor 29 is equal to or less than the first threshold value, and 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.

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. When performing the second current control, the control device 52 also adjusts the current flowing between the first electrode 55A and the second electrode 55B so that the ammonium ion concentration value (detection value) 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. When performing the second current control, the control device 52 repeats "current adjustment control for controlling the current flowing between the first electrode 55A and the second electrode 55B to a set current value, performing electrolysis for a certain period of time, and then checking the ammonium ion concentration value (detection value) detected by the ammonium ion sensor 29." In this control, if the detection value of the ammonium ion sensor 29 exceeds the first threshold in the previous current adjustment control, the next current adjustment control is performed so that the next set current value is a current value that is increased by a predetermined percentage (for example, 10%) from the set current value used in the previous current adjustment control. On the other hand, if the detection value of the ammonium ion sensor 29 is equal to or less than the first threshold in the previous current adjustment control, the next current adjustment control is performed so that the set current value used in the previous current adjustment control is set to the next set current value. In this way, 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, and when the detection value of the ammonium ion sensor 29 becomes equal to or less than the first threshold, electrolysis can be performed while maintaining that current state.

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 controlling the current flowing between the first electrode 55A and the second electrode 55B to a set current value to perform electrolysis for a certain period of time, and then checking the value (detection value) of the amount of residual chlorine detected by the first residual chlorine sensor 19." 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 current adjustment control before last, 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 current adjustment control before last, it can be estimated that the above-mentioned second state is present, so in this case, in the next current adjustment control (current adjustment control this time), the current adjustment control is performed so that the set current value is the current value increased by a predetermined ratio (for example, 10%) from the set current value used in the previous current adjustment control. In other words, while the value of the detected residual chlorine amount decreases, the current adjustment control is performed each time so that the set current value is increased little by little. On the other hand, when the control is performed to gradually increase the set current value in this manner, if the set current value in the previous current adjustment control is increased by a predetermined percentage (e.g., 10%) compared to the set current value in the current adjustment control before last, and the value of the residual chlorine amount (detection value) detected in the previous current adjustment control is greater than the value of the residual chlorine amount (detection value) detected in the current adjustment control before last, it can be assumed that the above-mentioned third state is occurring.In this case, in the next current adjustment control (current current adjustment control), current adjustment control is performed so that the set current value is the current value reduced by a predetermined percentage (e.g., 10%) from the set current value used in the previous current adjustment control. In addition, when the set current value in the previous current adjustment control is reduced by a predetermined percentage (for example, 10%) from the set current value in the current adjustment control before last, 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 current adjustment control before last, the current adjustment control is performed so that the set current value in the next current adjustment control (current current adjustment control) is the current value reduced by a predetermined percentage (for example, 10%) from the set current value used in the previous current adjustment control, and if the value (detection value) of the residual chlorine amount detected in the previous current adjustment control is greater than the value (detection value) of the residual chlorine amount detected in the current adjustment control before last, the current adjustment control is performed so that the set current value in the next current adjustment control (current current adjustment control) is the current value increased by a predetermined percentage (for example, 10%) from the set current value used in the previous current adjustment control.

(Control based on residual chlorine monitoring)
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.

For example, the treatment unit 31 may supply a neutralizing agent to the breeding water before returning to the breeding tank 3 when the concentration (detection value) of residual chlorine detected by the second residual chlorine sensor 27 exceeds a predetermined value. For example, sodium thiosulfate, catechin, polyphenol, cysteine, etc. can be suitably used as the neutralizing agent. In the example of FIG. 7, a neutralizing agent supplying device 31A that supplies a neutralizing agent to the breeding water in the fourth region is provided as an element that constitutes at least a part of the treatment unit 31. Specifically, for example, the control device 52 and the neutralizing agent supplying device 31A function as the treatment unit 31 and the neutralizing agent supplying unit, and when the concentration (detection value) of residual chlorine detected by the second residual chlorine sensor 27 exceeds a predetermined value, the control device 52 may give a neutralizing agent injection command to the neutralizing agent supplying device 31A, and in response to this neutralizing agent injection command, the neutralizing agent supplying device may operate to inject a "neutralizing agent that causes a neutralizing reaction with residual chlorine" into the waiting tank 25.

The treatment unit 31 may operate to switch the flow path so that the rearing water flows from the waiting tank 25 to another area, instead of returning the rearing water from the waiting tank 25 to the rearing tank 3, when the detection value of the concentration of residual chlorine detected by the second residual chlorine sensor 27 exceeds a predetermined value. 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 rearing water flowing through the flow path 47 may be switched between the rearing tank 3 and another area by the three-way valve. In this example, the control device 52 and the above three-way valve can function as the treatment unit 31. Specifically, the control device 52 may control the supply destination from the three-way valve to the rearing tank 3 when the detection value of the concentration of residual chlorine detected by the second residual chlorine sensor 27 is equal to or lower than a predetermined value, and control the supply destination from the three-way valve to another area when the detection value of the concentration of residual chlorine detected by the second residual chlorine sensor 27 exceeds the predetermined value.

Alternatively, when the detection 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 rearing water flows from the waiting tank 25 to the rearing tank 3 to stop returning the rearing water to the rearing tank 3, or may stop the circulation of the rearing water in the system 1 to stop returning the rearing water to the rearing tank 3. For example, an opening/closing valve (not shown) may be provided in the middle of the flow path 47, and when the opening/closing valve is in an open state, the flow of the flow path 47 may be permitted, and when the opening/closing valve is in a closed state, the flow of the flow path 47 may be blocked. In this example, the control device 52 and the above-mentioned opening/closing valve can function as the treatment unit 31. Specifically, the control device 52 may control the opening/closing valve to be in an open state when the detection value of the residual chlorine concentration detected by the second residual chlorine sensor 27 is equal to or less than a predetermined value, and to be in a closed state when the detection value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds the predetermined value. In this example, when the on-off valve is shut off, the pump that circulates the rearing water in the system may be stopped to prevent the standby tank 25 from overflowing, and a flow path may be provided so that the rearing water can escape from the standby tank 25 to a separate area when the water level in the standby tank 25 exceeds a certain level.

(Control based on pH monitoring)
In this embodiment, an adjusting material supplying device 32 is provided to supply a pH adjuster to the breeding water in the fourth region. In the example of Fig. 7, the adjusting material supplying device 32 is configured to supply a pH adjuster to the breeding water in the standby tank 25. The control device 52 gives instructions on the supply time and supply rate to the adjusting material supplying device 32, and the adjusting material supplying device 32 supplies the pH adjuster at the supply time and supply rate instructed by the control device 52.

As the pH adjuster supplied from the adjuster supply device 32, for example, any of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate can be suitably used, and it is more preferable to use any of sodium carbonate and sodium bicarbonate, and it is even more preferable to use sodium carbonate. When using sodium carbonate, sodium bicarbonate, calcium carbonate, etc. as the pH adjuster, it is advisable to use an aqueous solution containing any of them. The use of sodium carbonate, which has a high pH, has the advantage that it is a strong alkali and therefore easy to increase the pH of the breeding water and is less likely to disrupt the ion balance. The use of sodium bicarbonate has the advantage that it is less likely to disrupt the ion balance and can exert a pH buffering function. Note that the pH of the pH adjuster is preferably 11.5 or less to prevent the inhibition of the pH adjustment effect due to the precipitation of magnesium contained in seawater.

There are various methods of control by the control device 52, but for example, the control device 52 may operate the adjustment material supply device 32 to supply a pH adjustment material with a pH greater than the first reference value at a predetermined supply rate when the pH of the rearing water detected by the pH sensor 28 falls below a first reference value, and may perform on/off control to stop the supply of pH adjustment material by the adjustment material supply device 32 when the pH of the rearing water detected by the pH sensor 28 exceeds a second reference value while the adjustment material supply device 32 is supplying pH adjustment material. Note that in the above example, the first reference value and the second reference value may be the same or different.

In order to reduce the consumption of the pH adjuster, a calcium carbonate solid (e.g., pellets, etc.) may be provided in the fourth region (e.g., the internal region of the flow paths 46, 47 or the standby tank 25).

In the above example, the timing of adding the pH adjuster is controlled, but instead of this method, the pH adjuster may be continuously supplied at a constant supply rate.

4. Cleaning of electrodes As shown in FIG. 5, in this embodiment, the control device 52 and the drive circuit 53 function as the voltage application unit 51. The voltage application unit 51 operates to switch between a first state in which a voltage is applied so that the first electrode 55A is an anode and the second electrode 55B is a cathode to perform electrolysis in the "area" (specifically, in the electrolysis tank 11) and a second state in which a voltage is applied so that the second electrode 55B is an anode and the first electrode 55A is a cathode. For example, the voltage application unit 51 periodically switches between an operation of electrolyzing the rearing water by continuing the first state and an operation of electrolyzing the rearing water by continuing the second state. The period of switching in the case of periodic switching may be, for example, every tens of minutes, every few hours, every other day, or any other period.

The timing at which the voltage application unit 51 switches between the first state and the second state is not limited to periodic timing, and may be timing at which a predetermined condition is met. For example, the switching may be performed when the operating time of the circulating water treatment system 1 reaches a certain time since the previous switching time, when a detection value from some sensor reaches a predetermined value, when it is determined randomly, or at some other timing.

In this embodiment, while "replacing the rearing water" is performed to continuously guide the rearing water from the flow path 42 to the electrolysis cell 11 and drain the rearing water from the electrolysis cell 11 to the first guide path 56, a first state operation is continuously performed in which a voltage is continuously applied by the voltage application unit 51 to make the first electrode 55A an anode and the second electrode 55B a cathode; if a switching condition is met during operation in the first state, the first state is switched to the second state while the above-mentioned "replacing the rearing water" is performed; after switching, a second state operation is continuously performed in which a voltage is continuously applied while the above-mentioned "replacing the rearing water" is performed to make the second electrode 55B an anode and the first electrode 55A a cathode; if a switching condition is met during operation in the second state, the above-mentioned "replacing the rearing water" is performed while switching from the second state to the first state; in this manner, the first state operation and the second state operation are alternately performed. In addition, while the operation in the first state or the operation in the second state is continuing, the operation may be continued without interruption, or the operation may be temporarily interrupted for some reason.

5. Example 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 can generate a chloric acid compound (e.g., sodium hypochlorite) by electrolyzing breeding water containing salt, and then react this chloric acid compound with ammonia or ammonium ions present in the breeding water to directly decompose it into nitrogen, and can reliably suppress the generation of nitrous acid, nitric acid, etc. during the decomposition process. However, when this method is adopted, there is a concern that if no measures are taken, deposits will adhere to the surfaces of the electrodes and hinder electrolysis. However, the above electrolysis device can be switched between a first state in which electrolysis is performed by applying a voltage so that the first electrode 55A is an anode and the second electrode 55B is a cathode, and a second state in which a voltage is applied so that the second electrode 55B is an anode and the first electrode 55A is a cathode, so that deposits attached to the surfaces of the electrodes due to continuous electrolysis can be easily detached from the electrodes by switching. Therefore, this electrolyzer makes it easy to remove deposits that deposit on the surfaces of the electrodes.

When electrolysis is performed continuously on salty breeding water, for example, there is a problem that a deposit mainly composed of magnesium is generated on the cathode side and covers the electrode. When the deposit covers the electrode in this way, the amount of sodium hypochlorite generated gradually decreases and tends to become unstable. To prevent this from happening, it is possible to periodically clean the deposit on the electrode by applying physical force, but frequent mechanical cleaning can easily damage the electrode, resulting in a problem of shortening its lifespan and performance. In addition, cleaning by scraping off the electrode surface or cleaning with water pressure requires manual work by an operator, making automation, labor saving, and stable operation difficult. However, the above-mentioned electrolysis device can effectively suppress or eliminate this problem.

The above electrolysis device has an electrode unit 55, which is an integral structure of the first electrode 55A, the second electrode 55B, and the electrode holder 55C, that can be attached and detached to the electrolysis tank 11, making it easy to remove the electrode unit 55 for cleaning. In particular, the promotion of precipitate removal by switching and the simplification of the work of attaching and detaching the electrode unit 55 have a synergistic effect, making cleaning even easier.

The electrolysis device described above can automatically collect precipitates that have sunk from the electrode section 55 toward a specified position using the induction section 58, making it easy not only to detach precipitates from the electrode section 55, but also to collect the detached precipitates.

The electrolysis device described above can take in and discharge the precipitate that has sunk from the electrode section 55 into the tube 59A of the discharge section 59 at a position below the electrode section 55, preventing the precipitate from dispersing during the discharge process and becoming prone to flow into subsequent processes.

The electrolysis device described above can guide the supernatant water located above a predetermined height in the electrolysis cell 11 to the outside, and can make it difficult for precipitates that have sunk below the predetermined height to be guided to the outside of the electrolysis cell 11. More specifically, since the predetermined height is above the lower end of the electrode unit 55, precipitates that leave the electrode unit 55 and sink below from the lower end are difficult to guide to the outside of the electrolysis cell 11.

The electrolysis device described above can generate a water current in the electrolysis tank 11 by using the water current generating unit 57 to raise the water from below the electrode unit 55 to above it, making it easier for new rearing water to be guided to the electrode unit 55 and further increasing the efficiency of electrolysis.

The electrolysis device described above periodically switches between an operation of electrolyzing the rearing water by maintaining the first state and an operation of electrolyzing the rearing water by maintaining the second state, so that the precipitates can be periodically removed and the electrodes can be periodically cleaned.

The circulating water treatment system 1 can remove solids contained in the breeding water in the first region by the removal unit 5. Furthermore, in the second region after passing through the first region, the circulating water treatment system 1 can decompose ammonia or ammonium ions by the electrolysis unit 13, and since the breeding water is electrolyzed after the removal of solids by the removal unit 5, it is possible to reliably prevent solids from hindering the electrolysis, and it is easy to perform the electrolysis well. Furthermore, in the third region where the breeding water that has passed through the second region is stored or flows, the circulating water treatment system 1 can remove residual chlorine by the activated carbon unit 23. Therefore, even if chlorate compounds that were not used to decompose ammonia or ammonium ions are contained in the breeding water in the third region, the chlorate compounds can be effectively removed by the activated carbon unit. In this way, in the above-mentioned circulating water treatment system 1, solids such as feces and leftover food are reliably reduced in the breeding water after passing through the third region, and nitrogen compound components such as ammonia, nitrite, and nitrate are also reliably suppressed, which is extremely advantageous in terms of purifying and detoxifying the breeding water.

In the circulating water treatment system 1, the supernatant water located above the first height in the electrolysis tank 11 can be guided to the outside of the electrolysis tank 11, so that even if a precipitate detaches from the electrode and sinks, the precipitate is unlikely to be guided to the outside of the electrolysis tank 11. Even if some precipitate is discharged from the electrolysis tank 11 and enters the reaction tank 15, the supernatant water located above the second height in the reaction tank 15 can be guided to the outside of the reaction tank 15, so that the precipitate that has entered the reaction tank 15 is likely to settle in the reaction tank 15 and is unlikely to be guided to the outside of the reaction tank 15.

In the electrolysis method using the circulating water treatment system 1 or the electrolysis device described above, the rearing water can be continuously introduced into the electrolysis tank 11 and discharged from the electrolysis tank 11, and the rearing water can be replaced while operating in the first state, operating in the second state, and switching between the first state and the second state. This allows the rearing water to be circulated more efficiently while purifying the electrodes.

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 the removal unit 5 shown in Fig. 1 has a configuration as shown in Fig. 8 instead of the configuration as shown in Fig. 3 and Fig. 4, and are the same as the first embodiment except for the configuration of the removal unit 5. Therefore, in the following description, for the configurations other than that shown in Fig. 3, the configurations shown in Fig. 1, 2, 5, 6, and 7 are used, and the symbols and names attached to these figures are used as appropriate.

In the example of Figure 8, the removal unit 5 is configured to introduce the breeding water introduced from a region upstream of the removal unit 5 into the foam separator 7, and then pass it through the foam separator 7 to discharge it to a region downstream of the removal unit 5 that is different from the region upstream of the removal unit 5. The region upstream of the removal unit 5 is a region within the breeding tank 3. The region downstream of the removal unit 5 is a region within the electrolysis tank 11. In the removal unit 5, the breeding water supplied from the region upstream of the removal unit 5 is introduced into the foam separator 7 via a flow path 41 (flow path 41 corresponds to an example of an inlet path), and then the water is passed through the foam separator 7 and discharged to a "region downstream of the removal unit 5" (e.g., a region within the electrolysis tank 11) that is different from the source region (e.g., a region within the breeding tank 3) where the inlet of the flow path 41 (inlet path) is located. In the removal section 5, the entire amount of rearing water flowing in from the rearing tank 3 through the flow path 41 is sent into the foam separator 7, and there is no flow path from the rearing tank 3 to the electrolysis tank 11 without passing through the foam separator 7. Of the rearing water sent to the foam separator 7, the only thing removed together with the bubbles in the foam separator 7 is sent from the foam separator 7 to the electrolysis tank 11 through the flow path 43. The operation of the foam separator 7 is the same as in the first embodiment, and in this example, bubbles containing ozone are generated in the foam separator 7.

In this way, in the second embodiment of the circulating water treatment system 1, when solids are removed by the removal section 5, the rearing water introduced from the previous process area is introduced into the foam separator 7, and then passed through the foam separator 7 and discharged to a subsequent process area different from the previous process area. This allows the circulating rearing water to pass through the foam separator 7 more reliably, further enhancing the effect of removing solids and the effect of sterilization and disinfection by ozone.

Third Embodiment
The following description relates to the third embodiment.
The circulating 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, and specifically, the third embodiment is the same as the first embodiment except that in addition to the configuration shown in Fig. 5, inclined portions 58C, 58D, 58E, and 58F and discharge portions 110 and 112 are provided. Therefore, in the following description, for the configurations other than those shown in Fig. 5, the configurations shown in Figs. 1 to 4, 6, and 7 are used, and the symbols and names given to these figures are used as appropriate.

As shown in FIG. 9, the electrolytic cell 11 is provided with a discharge section 110 in addition to the discharge section 59. The discharge section 110 has a tube 110A for discharging precipitate that has sunk from the electrode section 55 in the electrolytic cell 11, and an opening/closing section 110B for opening and closing the tube 110A. The discharge section 110 functions to take the precipitate into the tube 110A at a position below the electrode section 55 and to discharge the precipitate from the electrolytic cell 11 through the tube 110A. The opening/closing section 110B is, for example, an opening/closing valve that is manually operated to switch between a state in which the tube 110A is blocked and a state in which the tube 110A is open. The opening/closing section 110B may be an electromagnetic valve that is controlled to be open or closed. In any case, when the opening/closing section 110B is in the open state, the breeding water is discharged through the tube 110A from near a predetermined position in the electrolytic cell 11. If a precipitate settles near the specified position, the precipitate will be discharged along with the rearing water through pipe 110A.

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 up-down direction, and the inclined portion 58C guides an object sinking along the inclined surface of the inclined portion 58C to move in the up-down direction and in a second direction perpendicular to the first direction (specifically, to move in the second direction toward the discharge portion 59). Furthermore, 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 up-down direction, and the inclined portion 58D guides an object sinking along the inclined portion 58D to move in the second direction (specifically, to move in the second direction toward the discharge portion 110).

In the example of FIG. 9, the reaction tank 15 is also provided with a discharge section 112. The discharge section 112 has a tube 112A for discharging precipitates that have sunk in the reaction tank 15, and an opening/closing section 112B for opening and closing the tube 112A. The discharge section 112 functions to take the sinking object into the inside of the tube 112A and discharge it through the tube 112A. The opening/closing section 112B is, for example, an opening/closing valve that is switched between a state in which the tube 112A is blocked and a state in which the tube 112A is open by manual operation. The opening/closing section 112B may be an electromagnetic valve that is switched between open and closed by control. In any case, when the opening/closing section 112B is in an open state, the breeding water is discharged through the tube 112A from near a predetermined position in the reaction tank 15. When an object settles near the above-mentioned predetermined position, the object is discharged through the tube 112A together with the breeding water. The reaction tank 15 is also provided with inclined sections 58E and 58F. The inclined surfaces of the inclined portions 58E and 58F are inclined in the vertical direction, and each of the inclined portions 58E and 58F guides the object sinking along the inclined surface of each inclined portion so as to move in the second direction (specifically, so as to move in the second direction toward the discharge portion 112).

In the example of FIG. 9, pipes 59A, 110A, and 112A are permanently installed fixed pipes, but they may be pipes that can be attached and detached. In addition, when discharging any of the pipes, the water may be discharged using the water pressure in the tank, or may be discharged by suction or flow using a pump or the like.

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 differ from the first embodiment in that a configuration as shown in Fig. 10 is used instead of the configuration as shown in Fig. 7, and differs from the first embodiment in that a switching unit 140 is provided in the middle of the flow path 46 in addition to the configuration as shown in Fig. 7, but the other configurations are the same as those of the first embodiment. Therefore, in the following description, for the configurations other than the switching unit 140, the configurations of Figs. 1 to 7 are used, and the symbols and names attached to these figures are used as appropriate.

In the fourth embodiment of the circulating water treatment system 1, a switching valve 142 is provided in the switching unit 140, and the switching valve 142 can switch the path for flowing the rearing water discharged from the residual chlorine removal tank (e.g., the activated carbon tank 21) to the flow path 46 between the flow path 143A, which does not pass through the second removal unit 146, and the flow path 143B, which passes through the second removal unit 146.

The second removal tank 144 is configured as a flow path through which the rearing water passes, and the internal space of the flow path is filled with a component that removes residual chlorine (e.g., calcium sulfite particles), forming the second removal section 146. The second removal tank 144 is configured as a flow path having an inlet and an outlet, and in a representative example, the internal space is filled with calcium sulfite particles. When the switching valve 142 is set so that the destination of the flow from the switching valve 142 is flow path 143B, the rearing water that passes through the switching valve 142 and flows into the inlet of the second removal tank 144 passes through the gaps in the internal space of the second removal tank 144 (the gaps between the many calcium sulfite particles), and the rearing water discharged from the outlet of the second removal tank 144 to the downstream flow path 46 becomes rearing water from which some or all of the chlorine and ozone have been removed.

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

<Other embodiments>
The present invention is not limited to the embodiments described above and in the drawings. For example, the features of the above or later described embodiments can be combined in any combination within a range that does not contradict. Furthermore, any feature of the above or later described embodiments can be omitted unless it is clearly stated as essential. Furthermore, the above described embodiments may be modified as follows.

In the above embodiment, ozone is supplied as a gas to the foam separator 7 to generate bubbles containing ozone, but it may also be configured to supply another gas (e.g., air) instead of ozone to generate bubbles of the other gas.

In the above embodiment, the second region is the internal region of the electrolysis tank 11 configured as a tank having a portion for storing rearing water, but the electrolysis tank 11 may also be configured as a flow path without a portion for storing rearing water, and this internal region may be the second region.

In the above embodiment, the reaction tank 15 is configured as a tank having a portion for storing rearing water, but it may also be configured as a flow path without a portion for storing water.

In the above embodiment, the first residual chlorine sensor 19 is positioned to detect the concentration of residual chlorine in the rearing water in the filtration tank 17, but it may also be configured to detect the concentration of residual chlorine in the flow path between the reaction tank 15 and the activated carbon tank 21.

In the above embodiment, the internal region of the activated carbon tank 21 configured as a tank having a portion for storing rearing water is the third region, but the activated carbon tank 21 may be configured as a flow path without a storage portion, and this internal region may be the third region.

In the above embodiment, the fourth region is the internal region of the waiting tank 25 configured as a tank having a portion for storing rearing water, but the waiting tank 25 may be configured as a flow path without a portion for storing water, and this internal region may be the fourth region.

In the above embodiment, as shown in Figs. 1 and 7, an activated carbon tank 21 having an activated carbon section 23 filled with activated carbon granules is provided as the residual chlorine removal tank, but calcium sulfite granules may be used instead of the activated carbon granules in the activated carbon section 23, and the calcium sulfite granules may be filled in the tank. In this example, the residual chlorine removal tank can also 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 granules. In this example, the rearing water flowing in from the inlet of the residual chlorine removal tank passes through the gaps in the internal space (the gaps between the numerous calcium sulfite), and the residual chlorine and residual ozone contained in the rearing water are removed by the calcium sulfite, and the rearing water discharged from the outlet is rearing water from which some or all of the chlorine and ozone have been removed.

In the configuration of the fourth embodiment shown in FIG. 10, a switching unit 140 is provided in the middle of the flow path 46, but in any of the configurations of the first to third embodiments, a switching unit 140 may be provided in the middle of the flow path 47 in the configuration of FIG. 1 (for example, the position of the two-dot chain line X in FIG. 1). In this case, by performing control similar to that of the fourth embodiment described above, the path for flowing the rearing water discharged from the waiting tank 25 to the flow path 47 may be 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, so that the rearing water that has passed through either the flow path 143A or the second removal unit 146 is supplied to the rearing tank 3.

In any of the above-mentioned embodiments, a biological tank may be provided in a region before the breeding water discharged from the breeding tank flows into the second region, in which ammonia or ammonium ions in the breeding water are reduced by organisms. In this case, for example, in the circulating water treatment system 1 (FIG. 3) of the first embodiment, a biological tank may be provided between the storage tank 60 and the electrolysis tank 11, and the breeding water flowing out of the storage tank 60 may flow into the biological tank, and the breeding water flowing out of the biological tank may flow into the electrolysis tank 11. Alternatively, in the circulating water treatment system 1 (FIG. 8) of the second embodiment, the breeding water flowing out of the foam separator 7 may flow into the biological tank, and the breeding water flowing out of the biological tank may flow into the electrolysis tank 11.
In this example, the biological tank is preferably configured so that the breeding water flowing out from the breeding tank 3 flows into it via a flow path or the like, and is capable of storing the inflowing breeding water. On the other hand, the biological tank preferably holds, as an example of a living organism, nitrifying bacteria (microorganisms) that oxidize ammonia and convert it to nitrite and then nitrate. In such a configuration, the ammonia or ammonium ions contained in the breeding water that flows into the biological tank are reduced by the microorganisms, and the breeding water in which the ammonia or ammonium ions have been reduced flows from the biological tank directly or via another region into the electrolysis tank 11.
The order of the removal unit and the biotask may be such that the breeding water flows into the biotask after passing through the removal unit, or the breeding water flows into the removal unit after passing through the biotask. Alternatively, part or all of the biotask may double as the removal unit. In any case, it is sufficient that part or all of the breeding water flowing out of the breeding tank 3 and into the electrolysis tank 11 flows into the electrolysis tank 11 via the biotask.
In the above example, the biological tank is configured to hold the breeding water and the microorganisms therein, but instead of or in addition to this configuration, the ammonia or ammonium ions contained in the breeding water may be reduced by the action of other organisms. Also, the number of biological tanks is not limited to one, and multiple biological tanks may be present.
For example, instead of the above-mentioned "biotactic tank for holding microorganisms," the biotactic tank may be configured to raise vegetables or other plants as "organisms." In this case, the breeding water flowing in from the breeding tank 3 directly or via another area may be temporarily stored or flowed in the biotactic tank, and the breeding water in the biotactic tank may be continuously or intermittently supplied to the plants to grow them, thereby causing the plants to absorb ammonia or ammonium ions in the breeding water and purify the plants.
In such a "circulating water treatment system using both a biological tank and an electrolysis tank", ammonia or ammonium ions can be reduced by the biological tank before the electrolysis unit 11 decomposes ammonia or ammonium ions. Therefore, compared with a configuration in which the reduction of ammonia or ammonium ions contained in the breeding water is performed only by the electrolysis unit 11, the burden on the electrolysis unit 11 can be reduced, and the power consumption required for electrolysis can be easily reduced. On the other hand, since the reduction of ammonia or ammonium ions contained in the breeding water is not performed only by the biological tank, ammonia or ammonium ions in the water can be more effectively decomposed by a method that reduces dependency on organisms. Furthermore, the above-mentioned circulating water treatment system generates a chlorine acid compound (e.g., sodium hypochlorite) in the second region (region in the electrolysis tank 11) into which the breeding water that has passed through the biological tank flows, and therefore, in addition to removing ammonia or ammonium ions, when bacteria or viruses are contained in the breeding water that has passed through the biological tank, sterilization or inactivation of viruses can be performed.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments disclosed herein, but is intended to include all modifications within the scope of the claims or within the scope equivalent to the claims.

1: Circulating water treatment system 3: Breeding tank 5: Removal section 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 section 15: Reaction tank 17: Filtration tank 19: First residual chlorine sensor 21: Activated carbon tank (residual chlorine removal tank)
23: Activated carbon section (residual chlorine removal section)
25: standby tank 27: second residual chlorine sensor 29: ammonium ion sensor 31: treatment section 35: temperature regulator 37: filters 41, 42, 43, 44, 45, 46, 47: flow path 51: voltage application section 52: control device 53: drive circuit 54A: conductive path 54B: conductive path 55: electrode section 55A: first electrode 55B: second electrode 55C: electrode holding section 56: first induction path 57: water flow generating section 57A: first partition wall 57B: second partition wall 58: induction sections 58A, 58B: inclined section 59: discharge section 59A: pipe 59B: opening/closing section 60: storage tank 60A: bottom 62: introduction section 64: outlet section 66: discharge section 72: second induction path W1: water surface W2 :Water surface W3 :Water surface

Claims (13)

1. An electrolysis device used in a circulating water treatment system, which is a tank for cultivating aquatic organisms and contains salt-containing breeding water from a breeding tank, treats the breeding water while circulating the water, and returns the treated breeding water to the breeding tank,
an electrolysis unit that generates a chlorate compound by electrolyzing the breeding water in a region where the breeding water is stored or flows, 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 first electrode and the second electrode,
The voltage application unit switches between a first state in which a voltage is applied so that the first electrode is an anode and the second electrode is a cathode to perform the electrolysis in the region, and a second state in which a voltage is applied so that the second electrode is an anode and the first electrode is a cathode. the electrode portion includes an electrode holder that holds the first electrode and the second electrode, the first electrode, the second electrode, and the electrode holder being integrally configured;
In the circulating water treatment system, an electrolysis tank configured to store or flow the breeding water is provided, and the inside of the electrolysis tank is the region,
The electrolysis device for cultivating aquatic organisms according to claim 1 , wherein the electrode unit is integrally formed and is detachable from the electrolysis tank. An electrolysis tank configured to store or flow the rearing water,
The interior of the electrolysis cell is the region,
3. The electrolysis device for cultivating aquatic organisms according to claim 1 or 2, further comprising a guide unit that guides and collects the precipitate that has sunk from the electrode unit in the electrolysis tank toward a predetermined position in the electrolysis tank. An electrolysis tank configured to store or flow the rearing water,
The interior of the electrolysis cell is the region,
The electrolytic cell further includes a discharge section having a pipe for discharging precipitate that has sunk from the electrode section in the electrolytic cell,
3. The electrolysis device for cultivating aquatic organisms according to claim 1, wherein the discharge section takes in the precipitate inside the tube at a position below the electrode section and discharges the precipitate from the electrolysis tank through the tube. An electrolysis tank configured to store or flow the rearing water,
The interior of the electrolysis cell is the region,
3. The electrolysis device for cultivating aquatic organisms according to claim 1, further comprising a guide path which does not guide water located below a predetermined height in the electrolysis tank to the outside of the electrolysis tank, but guides water located above the predetermined height to the outside of the electrolysis tank. The electrolysis apparatus for cultivating aquatic organisms according to claim 5 , wherein the predetermined height is a position above a lower end of the electrode unit. An electrolysis tank configured to store or flow the rearing water,
The interior of the electrolysis cell is the region,
the electrode unit is disposed on the water surface side of the breeding water in the electrolysis tank,
3. The electrolysis device for cultivating aquatic organisms according to claim 1 or 2, further comprising a water flow generating unit that causes the breeding water introduced into the electrolysis tank from outside the electrolysis tank to flow upward from below the electrode unit within the electrolysis tank. 3. The electrolysis device for cultivating aquatic organisms according to claim 1 or claim 2, wherein the voltage application unit periodically switches between an operation of electrolyzing the breeding water by continuing the first state and an operation of electrolyzing the breeding water by continuing the second state. A circulating water treatment system for cultivating aquatic organisms comprising the electrolysis device for cultivating aquatic organisms according to claim 1 or 2,
a removal unit that removes at least solid matter in a first area where the breeding water sent from the breeding tank is stored or flows;
the electrolysis unit performing the electrolysis of the breeding water in a second area, which is an area in which the breeding water that has passed through the first area is stored or flows;
an activated carbon section that removes at least residual chlorine by activated carbon in a third area in which the rearing water that has passed through the second area is stored or flows;
A circulating water treatment system for culturing aquatic organisms comprising: A circulating water treatment system for cultivating aquatic organisms comprising the electrolysis device for cultivating aquatic organisms according to claim 1 or 2,
An electrolysis tank configured to store or flow the breeding water;
a reaction tank configured to store or flow the breeding water discharged from the electrolysis tank;
Equipped with
The interior of the electrolysis cell is the region,
the electrolytic cell has a first guide path which does not guide water located below a first level in the electrolytic cell to the outside of the electrolytic cell, and guides water located above the first level to the outside of the electrolytic cell,
The reaction tank has a second guide path that does not guide water located below a second level in the reaction tank to the outside of the reaction tank, and guides water located above the second level to the outside of the reaction tank. 1. An electrolysis method used in a circulating water treatment system, which is a tank for cultivating aquatic organisms and contains salt-containing breeding water from a breeding tank, treats the breeding water while circulating the water, and returns the treated breeding water to the breeding tank,
An electrolysis unit including an electrode unit having a first electrode and a second electrode, and a voltage application unit that applies a voltage between the first electrode and the second electrode,
With the first electrode and the second electrode disposed in a region in which 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 chlorite compound, and the generated chlorite 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 a voltage is applied so that the first electrode is an anode and the second electrode is a cathode to perform the electrolysis in the region, and a second state in which a voltage is applied so that the second electrode is an anode and the first electrode is a cathode. Using an electrolysis tank configured to store or flow the rearing water,
The electrode unit is disposed so that the interior of the electrolytic cell is the region;
12. The electrolysis method for cultivating aquatic organisms according to claim 11, wherein the breeding water is continuously introduced into the electrolysis tank and discharged from the electrolysis tank, and the breeding water is replaced while the voltage application unit performs operation in the first state, operation in the second state, and switching between the first state and the second state. 13. The electrolysis method for cultivating aquatic organisms according to claim 11 or 12, wherein the voltage application unit periodically switches between an operation of electrolyzing the breeding water by continuing the first state and an operation of electrolyzing the breeding water by continuing the second state.

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