Water treatment system and water treatment method

Abstract

The purification effect is enhanced during the water treatment process. [Solution] The water treatment system 1 comprises a removal unit 105, an electrolysis unit 113, a residual chlorine removal unit 121, and an induction unit 130. The removal unit 5 removes solid matter contained in the target water W introduced from the supply source 120 in a first region. The electrolysis unit 13 generates chlorate compounds by electrolyzing the target water W in a second region where the target water W is stored or flows. The residual chlorine removal unit 121 removes at least residual chlorine in a third region where the target water W that has passed through the second region is stored or flows. The induction unit 130 returns the target water downstream of the electrolysis unit 111 to a region downstream of the supply source 120 and upstream of the second region, or to the second region.

Description

Technical Field

[0001] The present disclosure relates to a water treatment system and a water treatment method.

Background Art

[0002] Patent Document 1 discloses a recirculating aquaculture system as an example of a water treatment system. This system circulates seawater in a rearing water tank through a circulation path, removes ammonia in the seawater in an electrolysis tank connected to the circulation path, and also uses ammonia removal by biological nitrification in combination.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional water treatment systems, including the system disclosed in Patent Document 1, generally purify water in a purification region and then use the purified treated water as it is. However, this type of system has room for improvement from the perspective of further enhancing the purification effect in the process of treating water.

[0005] One of the objectives of the present disclosure is to provide a technology that makes it easier to further enhance the purification effect in the process of treating water.

Means for Solving the Problems

[0006] A water treatment system that is one aspect of the present disclosure is: A water treatment system that treats water containing chloride ions, which is water introduced from a supply source where water that has come into contact with organic matter is stored or flows, as target water to be treated, a first region portion that constitutes a first region where the target water introduced from the supply source is stored or flows, An electrolysis unit generates chlorate compounds by electrolyzing the target water in a second region where the target water that has passed through the first region is stored or flows, A residual chlorine removal unit is provided downstream of the second region and removes at least residual chlorine in the third region where the target water that has passed through the second region is stored or flows, A main channel having a channel for flowing the target water from the second region to the third region, A guide unit that guides the target water stored or flowing in the second region or downstream of the second region from a first position downstream of the electrolysis unit toward a second position downstream of the supply source and upstream of the electrolysis unit, along a path different from the main flow path, It holds.

[0007] One of the disclosures is a water treatment system, A water treatment system that treats water introduced from a supply source containing or through which water that has come into contact with organic matter is transported as water to be treated, A first region section comprising a first region in which the target water introduced from the supply source is stored or flows, A biological filtration unit in which ammonia is decomposed by microorganisms in a second region where the target water that has passed through the first region is stored or flows, A main channel having a channel for flowing the target water downstream from the second region, A guide unit that guides the target water stored or flowing in the second region or downstream of the second region, from a first position downstream of the biological filtration unit toward a second position upstream of the first position, along a path different from the main flow path, It has, The second position is either a position downstream of the supply source and upstream of the biological filtration unit, or the biological filtration unit itself.

[0008] One of the water treatment methods disclosed herein is A water treatment method for treating water containing chloride ions, which is introduced from a supply source that contains or flows water that has come into contact with organic matter, as the water to be treated. In a water treatment facility configured such that the target water supplied from the supply source is stored or flows in a first region, and the target water that has passed through the first region is stored or flows in a second region, A step of generating chlorate compounds in the target water by electrolyzing the target water in the second region using an electrolysis unit that performs electrolysis, A step of removing at least residual chlorine in a third region where the target water that has passed through the second region is stored or flows, by a residual chlorine removal unit provided downstream of the second region, The process involves flowing the target water from the second region to the third region through the main flow path, The process involves using a guide unit to cause the target water, which is stored or flows in the second region or downstream of the second region, to flow from a first position downstream of the electrolysis unit toward a second position upstream of the first position, along a path different from the main flow path. Perform The second position is set to be downstream of the supply source and upstream of the electrolysis unit.

[0009] One of the water treatment methods disclosed herein is A water treatment method for treating water introduced from a supply source that contains or flows water that has come into contact with organic matter, In a water treatment facility configured such that the target water supplied from the supply source is stored or flows in a first region, and the target water that has passed through the first region is stored or flows in a second region, A step of decomposing ammonia in the second region by microorganisms contained in the biological filtration section, The process involves flowing the target water downstream from the second region through the main channel, The process involves using a guide unit to cause the target water, which is stored or flows in the second region or downstream of the second region, to flow from a first position downstream of the biological filtration unit toward a second position upstream of the first position, along a path different from the main flow path. Perform The second position is set to a position downstream of the supply source and upstream of the biological filtration unit, or the biological filtration unit itself. [Advantageous Effects of Invention]

[0010] The technology according to the present disclosure can easily further enhance the purification effect in the process of treating water. [Brief Description of Drawings]

[0011] [Figure 1] Figure 1 is an explanatory diagram conceptually illustrating the basic configuration of the water treatment system of the first embodiment. [Figure 2] Figure 2 is an explanatory diagram conceptually illustrating Specific Example 1 of the water treatment system of the first embodiment. [Figure 3] Figure 3 is a block diagram schematically illustrating the electrical configuration of the water treatment system of Figure 2. [Figure 4] Figure 4 is an explanatory diagram schematically illustrating the configuration of the solid matter removal unit, the electrolysis tank and the like of the water treatment system of Figure 2. [Figure 5] Figure 5 is an explanatory diagram showing a further embodied example of the configuration of Figure 4. [Figure 6] Figure 6 is an explanatory diagram schematically illustrating the configuration of the electrolysis tank, the reaction tank and the like of the water treatment system of Figure 2. [Figure 7] Figure 7 is an explanatory diagram schematically illustrating the configuration of the electrolysis tank of the water treatment system of Figure 2 as viewed from a direction different from that of Figure 6. [Figure 8] Figure 8 is an explanatory diagram showing specific examples of the activated carbon tank, the standby tank and the like of the water treatment system of Figure 2. [Figure 9] Figure 9 is an explanatory diagram conceptually illustrating the basic configuration of the water treatment system of the second embodiment. [Figure 10] Figure 10 is an explanatory diagram conceptually illustrating the electrolysis unit and the like used in a water treatment system of another embodiment. [Figure 11] Figure 11 is an explanatory diagram conceptually illustrating the reclaimed water generation system for food processing of the third embodiment. [Figure 12]Figure 12 is a simplified explanatory diagram illustrating the configuration of the solid matter removal section of the recycled water generation system shown in Figure 11. [Figure 13] Figure 13 is a simplified explanatory diagram illustrating the configuration of the electrolysis section of the recycled water generation system shown in Figure 11. [Figure 14] Figure 14 is an explanatory diagram showing specific examples of the residual chlorine removal section and water storage section of the recycled water generation system shown in Figure 11. [Figure 15] Figure 15 is an explanatory diagram illustrating a simplified configuration of the electrolysis unit, reaction unit, residual chlorine removal unit, water storage unit, etc., of the recycled water generation system shown in Figure 11. [Figure 16] Figure 16 is a block diagram illustrating a simplified electrical configuration of the recycled water generation system shown in Figure 11. [Modes for carrying out the invention]

[0012] Each of the following [1] to

[13] is an example of a characteristic technology included in this disclosure.

[0013] [1] A water treatment system that treats water containing chloride ions, which is introduced from a supply source where water that has come into contact with organic matter is stored or flows, as the water to be treated. A first region section comprising a first region in which the target water introduced from the supply source is stored or flows, An electrolysis unit generates chlorate compounds by electrolyzing the target water in a second region where the target water that has passed through the first region is stored or flows, A residual chlorine removal unit is provided downstream of the second region and removes at least residual chlorine in the third region where the target water that has passed through the second region is stored or flows, A main channel having a channel for flowing the target water from the second region to the third region, A guide unit that guides the target water stored or flowing in the second region or downstream of the second region from a first position downstream of the electrolysis unit toward a second position downstream of the supply source and upstream of the electrolysis unit, along a path different from the main flow path, has Water treatment system.

[0014] The water treatment system described in [1] above can flow the target water through a different path from the main flow path, from a first position downstream of the electrolysis unit to a second position downstream of the supply source and upstream of the electrolysis unit. In this way, the water treatment system described in [1] above can flow the target water again from the second position upstream of the electrolysis unit after the target water, which has been purified by the generation of chlorate compounds by the electrolysis unit, has flowed downstream, thus making it easier to achieve an even greater purification effect. Therefore, the water treatment system described in [1] above is more likely to enhance the purification effect during the water treatment process.

[0015] [2] A region other than the first region, upstream of the first region or the second region, having an aeration unit that aerates the target water. The water treatment system described in [1].

[0016] The water treatment system described in [2] above can promote the discharge of nitrogen gas from the target water through aeration, and as a result, the reaction between ammonia or ammonium ions and chlorate compounds can be promoted according to Le Chatelier's principle. In particular, by performing aeration in the target water before it enters the second region, the reaction between ammonia or ammonium ions and chlorate compounds can be promoted more effectively in the second region and downstream thereof. Therefore, the water treatment system described in [2] above can more effectively reduce ammonia or ammonium ions from the target water. Furthermore, the effect of aeration can volatilize chloramines in the target water.

[0017] [3] A water treatment system that treats water introduced from a supply source containing or through which water that has come into contact with organic matter is to be treated, A removal unit that removes at least solid matter in the first region where the target water is stored or flows, A biological filtration unit in which ammonia is decomposed by microorganisms in a second region where the target water is stored or flows, A main channel having a channel for flowing the target water downstream from the second region, A guide unit that guides the target water stored or flowing in the second region or downstream of the second region, from a first position downstream of the biological filtration unit toward a second position upstream of the first position, along a path different from the main flow path, It has, The second position is a location downstream of the supply source and upstream of the biological filtration section, or the biological filtration section itself. Water treatment system.

[0018] The water treatment system described in [3] above can flow the target water through a different path from the main flow channel, from a first position downstream of the biological filtration section towards a second position (downstream of the supply source and upstream of the biological filtration section, or the biological filtration section). In this way, after the target water from which ammonia has been decomposed by the biological filtration section flows downstream, the target water can be flowed again from the second position upstream, thus making it easier to achieve a greater ammonia decomposition effect. Therefore, the water treatment system described in [3] above is more likely to enhance the purification effect during the water treatment process.

[0019] [4] Having a removal unit that removes at least solid matter from the target water in the first region. A water treatment system described in any one of the following (1) to (3).

[0020] The water treatment system described in [4] above can remove solid matter in the first region upstream of the second region and supply target water with suppressed solid matter to the second region, thereby enabling better electrolysis by the electrolysis unit. Moreover, the water treatment system described in [4] above can simultaneously suppress solid matter and purify the target water supplied near the electrolysis unit on the upstream side with chlorate compounds.

[0021] [5] The removal unit has a foam separator that generates foam and adsorbs the solid matter contained in the target water onto the foam. The water treatment system described in [4].

[0022] The water treatment system described in [5] above can effectively remove solid matter contained in the target water by causing it to adhere to foam. This system can be even more effective when the target water contains solid matter that easily adheres to foam. Furthermore, by generating foam in the target water, it is possible to produce an effect similar to aeration on the target water upstream of the electrolysis unit.

[0023] [6] Having an ozone generating unit that generates ozone, The foam separator generates foam containing ozone generated in the ozone generating unit. The water treatment system described in [5].

[0024] The water treatment system described in [6] above, in order to purify the target water, can further combine sterilization and disinfection using ozone in addition to the enhanced purification effect based on chlorate compounds.

[0025] [7] The first position is located downstream of the electrolysis unit and upstream of the residual chlorine removal unit. A water treatment system described in any one of [1] through [6].

[0026] The water treatment system described in [7] above can return the target water from a position downstream of the electrolysis unit and upstream of the residual chlorine removal unit, thus allowing the target water with a higher concentration of chlorate compounds to be returned to the upstream side of the electrolysis unit. Therefore, the water treatment system described in [7] above can further enhance the purification effect based on chlorate compounds.

[0027] [8] The second position is in or upstream of the first region. The water treatment system described in [4].

[0028] The water treatment system described in [8] above is configured to remove solid matter from the target water in the first region using a removal unit, and then to return the target water containing chlorate compounds to the first region or to an area upstream of the first region using a guide unit. Since the first region is the region from which solid matter is removed by the removal unit, there is concern about the growth of bacteria caused by solid matter in the first region and the area upstream of it. However, in the water treatment system described in [8] above, the target water containing chlorate compounds is more easily supplied to the first region, so the growth of bacteria can be effectively suppressed, at least in the first region.

[0029] [9] A sensor that detects the numerical value of an element indicating the water quality of the target water at a predetermined position downstream of the second region, or detects whether the element meets the standard. A water treatment system described in any one of [1] through [8].

[0030] The water treatment system described in [9] above can detect numerical values ​​of elements indicating the water quality of the target water or detect whether the elements meet the standards at a predetermined position downstream of the second region, and can make available information indicating the state downstream of the second region.

[0031]

[10] The main channel includes a downstream channel that flows the target water downstream from the second region, The induction section comprises a return channel branching off from the downstream channel and a switching section provided in the downstream channel. The switching unit switches between a first switching state in which the target water is prevented from flowing through the return channel to the second position while allowing the target water to flow through the downstream channel downstream of the switching unit, and a second switching state in which the target water is prevented from flowing through the return channel to the second position while preventing it from flowing through the downstream channel downstream of the switching unit. A water treatment system described in any one of [1] through [9].

[0032] The water treatment system described in

[10] above can switch between a state in which the target water flowing downstream from the electrolysis unit is blocked from flowing into the return channel and flows downstream in the downstream channel, and a state in which the target water flowing downstream in the downstream channel is blocked and flows into the return channel. In other words, the water treatment system described in

[10] above can switch between a use in which the target water that has flowed downstream from the electrolysis unit is returned to the upstream side and a use in which it flows downstream without being returned, allowing for switching according to the situation.

[0033]

[11] A sensor that detects a numerical value of an element indicating the water quality of the target water at a predetermined position downstream of the second region, or detects whether the element meets the standard, A control unit that performs control to switch the switching unit based on the detection result of the sensor, A water treatment system according to

[10] having the following:

[0034] The water treatment system described in

[11] above can detect numerical values ​​of elements indicating the water quality of the target water at a predetermined position downstream of the second region, or detect whether the elements meet the standards, and can switch the switching unit based on the detection results. In other words, the water treatment system described in

[11] above can switch whether to return the water to the upstream side or to discharge it downstream without returning it, depending on the water quality downstream of the second region.

[0035]

[12] A water treatment method for treating water containing chloride ions, which is introduced from a supply source that contains or flows water that has come into contact with organic matter, as the water to be treated, In a water treatment facility configured such that the target water supplied from the supply source is stored or flows in a first region, and the target water that has passed through the first region is stored or flows in a second region, A step of generating chlorate compounds in the target water by electrolyzing the target water in the second region using an electrolysis unit that performs electrolysis, A step of removing at least residual chlorine in a third region where the target water that has passed through the second region is stored or flows, by a residual chlorine removal unit provided downstream of the second region, The process involves flowing the target water from the second region to the third region through the main flow path, The process involves using a guide unit to cause the target water, which is stored or flows in the second region or downstream of the second region, to flow from a first position downstream of the electrolysis unit toward a second position downstream of the supply source and upstream of the electrolysis unit, along a path different from the main flow path. A water treatment method that performs the following actions.

[0036] The water treatment method described in

[12] above has the same effect as the water treatment system described in [1] above.

[0037]

[13] A water treatment method for treating water introduced from a supply source that contains or flows water that has come into contact with organic matter, In a water treatment facility configured such that the target water supplied from the supply source is stored or flows in a first region, and the target water that has passed through the first region is stored or flows in a second region, A step of decomposing ammonia in the second region by microorganisms contained in the biological filtration section, The process involves flowing the target water downstream from the second region through the main channel, The process involves using a guide unit to cause the target water, which is stored or flows in the second region or downstream of the second region, to flow from a first position downstream of the biological filtration unit toward a second position upstream of the first position, along a path different from the main flow path. Perform The second position is either downstream of the supply source and upstream of the biological filtration unit, or the biological filtration unit itself. Water treatment methods.

[0038] The water treatment method described in

[13] above has the same effect as the water treatment system described in [3] above.

[0039] <First Embodiment> 1-1. Basic Configuration of a Water Treatment System Figure 1 schematically shows the water treatment system of the first embodiment. The water treatment system 100 in Figure 1 is a system that treats water containing chloride ions as the target water for treatment. The target water that the water treatment system 100 treats is water supplied from the supply source 120. The supply source 120 may store water that has come into contact with organic matter, or it may be flowing water that has come into contact with organic matter. The water treatment system 100 is configured to introduce the "water that has come into contact with organic matter" that is stored or flowing in the supply source 120. The water that has come into contact with organic matter may be water that has come into contact with living organisms, or water that has come into contact with food. Alternatively, it may be water that has come into contact with organic matter other than living organisms or food. Examples of water that has come into contact with living organisms include water used in aquaculture of fish, crustaceans, shellfish, etc., or water used in raising living organisms.

[0040] The water treatment system 100 includes a removal unit 105, an electrolysis unit 111, a residual chlorine removal unit 121, a main flow path 140, and an induction unit 130.

[0041] The removal unit 105 removes at least solid matter in the first region where the target water W is stored or flows. In the example of Figure 1, the internal region of the first region unit 101 is the first region, and the target water W may be stored in the internal region of the first region unit 101, or the target water W may flow in the internal region of the first region unit 101. The first region unit 101 may be configured as a tank for storing the target water W, or as a flow path for the target water W to flow along a predetermined path, or it may be a configuration in which the tank and the flow path are mixed.

[0042] The electrolysis unit 111 generates chlorate compounds by electrolyzing the target water W in a second region where the target water W is stored or flows. In the example of Figure 1, the internal region of the second region unit 102 is the second region, and the target water W may be stored in the internal region of the second region unit 102, or the target water W may flow in the internal region of the second region unit 102. The second region unit 102 may be configured as a tank for storing the target water W, or as a flow path for flowing the target water W along a predetermined path, or it may be a configuration in which the tank and the flow path are mixed.

[0043] The residual chlorine removal unit 121 is provided downstream of the second region and removes at least residual chlorine in the third region where the target water that has passed through the second region is stored or flows. In the example of Figure 1, the internal region of the third region section 103 is the third region, and the target water W may be stored in the internal region of the third region section 103, or the target water W may flow in the internal region of the third region section 103. The third region section 103 may be configured as a tank for storing the target water W, or as a flow path for the target water W to flow along a predetermined path, or it may be a configuration in which the tank and the flow path are mixed.

[0044] The main channel 140 is a channel through which the target water flows, and has at least a channel through which the target water flows from the second region to the third region. The main channel 140 may be configured as a channel through which the target water W flows along a predetermined path, as long as it is capable of flowing the target water from the second region to the third region, and it may also be a configuration in which a channel through which the target water W flows along a predetermined path and a tank for storing the target water W are mixed together. In the example in Figure 1, the main channel 140 has a channel 143 through which the target water W flows from the second region section 102 to the switching section 134, a channel 144 through which the target water W flows from the switching section 134 to the third region section 103, and an internal channel within the switching section 134 through which the target water W flows from channel 143 to channel 144. In other words, channel 143, the internal channel, and channel 144 constitute at least a part of the main channel 140.

[0045] In the example shown in Figure 1, the main channel 140 also constitutes a channel for flowing the target water from the first region to the second region. Specifically, the main channel 140 has a channel 142, and the channel 142 is configured to flow the target water W in the first region 101 toward the second region 102.

[0046] The guide unit 130 has the function of directing the target water W, which is stored or flows in the second region or downstream of the second region, from a first position downstream of the electrolysis unit 111 to a second position upstream of the first position, via a path different from the main flow path 140. The second position is located downstream of the supply source 120 and upstream of the electrolysis unit 111.

[0047] In the example in Figure 1, the second region is downstream of the first region. The first position, which is the starting point of the induction unit 130, is downstream of the first region. In the example in Figure 1, the first position is the location where the target water W is stored or flows between the second and third regions. Specifically, it is the location downstream of the electrolysis unit 111 and upstream of the residual chlorine removal unit 121. The third region is downstream of both the first and second regions. The second position, where the induction unit 130 returns the target water, is in the first region or upstream of the first region.

[0048] The water treatment system 1 has an aeration unit that aerates the target water W upstream of the third region. For example, the aeration unit aerates the target water in a region upstream of the second region. Specifically, the aeration unit may aerate the target water in the first region 101, or it may aerate the target water W downstream of the supply source 120 and upstream of the first region 101.

[0049] In the example shown in Figure 1, the flow path 143, the flow path 144, and the internal flow path that carries the target water W from flow path 143 to flow path 144 within the switching section 134 constitute the downstream flow path. This downstream flow path has the function of carrying the target water W downstream from the second region.

[0050] The guide unit 130 includes a return channel 132 that branches off from the downstream channel. The return channel 132 is a channel that returns part or all of the target water W that has entered the downstream channel and flows it to the second position. The guide unit 130 includes a switching unit 134. The switching unit 134 switches between a first switching state and a second switching state. The first switching state is a state in which the flow of target water W through the return channel 132 to the second position is blocked, while the flow of target water W through the downstream channel to a point downstream of the switching unit 134 is blocked. The second switching state is a state in which the flow of target water W through the return channel 132 to the second position is blocked, while the flow of target water W through the downstream channel to a point downstream of the switching unit 134 is blocked.

[0051] Furthermore, the water treatment system 100 includes a sensor 160 and a control unit 152. The sensor 160 detects numerical values ​​of elements indicating the water quality of the target water W at a predetermined position downstream of the electrolysis unit 111, or detects whether the elements meet the criteria. The control unit 152 controls the switching unit 134 based on the detection result of the sensor 160. In the example shown in Figure 1, the sensor 160 detects at a location downstream of the electrolysis unit 111 and upstream of the residual chlorine removal unit 121.

[0052] Sensor 160 may be a residual chlorine concentration sensor that detects the residual chlorine concentration at the detection location of sensor 160. Sensor 160 may be a sensor that detects whether the residual chlorine concentration at the detection location of sensor 160 is above a standard value. Sensor 160 may be a pH sensor that detects the pH at the detection location of sensor 160. Sensor 160 may be a sensor that detects whether the pH at the detection location of sensor 160 is above a standard value. Sensor 160 may be an ammonium ion sensor that detects the ammonium ion concentration at the detection location of sensor 160. Sensor 160 may be a sensor that detects whether the ammonium ion concentration at the detection location of sensor 160 is above a standard value. Sensor 160 may be a sensor that detects the numerical value of other "elements indicating water quality" or whether such elements meet the standards.

[0053] The detection position of the sensor 160 may be at the location of the flow path 144, or it may be at a location where the flow path branches off from the flow path 143 or flow path 144 and takes in the target water from the flow path 143 or flow path 144. Alternatively, the detection position of the sensor 160 may be at a location downstream of the electrolysis unit 111 in the second region. The detection position of the sensor 160 may be at a location downstream of the third region.

[0054] In the example shown in Figure 1, for example, the sensor 160 is configured as a residual chlorine concentration sensor that detects the residual chlorine concentration at a detection position downstream of the electrolysis unit 111 and upstream of the residual chlorine removal unit 121 in the path through which the target water W flows from the second region to the third region. The control unit 152 may control the switching unit 134 to a first switching state when the residual chlorine concentration detected by the sensor 160 is equal to or greater than a reference value, and to a second switching state when the residual chlorine concentration detected by the sensor 160 is less than a reference value.

[0055] 1-2. Specific Example 1 of the First Embodiment 1-2-1. Overview of Water Treatment System 1 in Specific Example 1 The water treatment system 1 illustrated in Figure 2 is a system used, for example, in aquaculture and animal rearing. The water treatment system 1 is configured as a circulating water treatment system. The water treatment system 1 is configured as a closed-loop aquaculture system in which rearing water containing saltwater is treated outside the rearing tank 3, and then the treated rearing water is circulated back to the rearing tank 3, thus utilizing a method of water recycling. When aquatic organisms are reared in the rearing tank 3, the water treatment system 1 operates to continuously rear the aquatic organisms inside the rearing tank 3, and to decompose and purify any leftover feed and waste products discharged by the organisms that remain in the rearing water during rearing in the rearing tank 3, as the water is circulated from the rearing tank 3 back to the rearing tank 3.

[0056] As shown in Figure 2, the water treatment system 1 mainly comprises a rearing tank 3, a solid matter removal unit 5, an electrolysis tank 11, a reaction tank 15, a filtration tank 17, an activated carbon tank 21, a standby tank (water quality adjustment tank) 25, a treatment unit 31, and the like. Furthermore, the water treatment system 1 also includes a temperature controller 35, a filter 37, and the like. The electrical configuration of the water treatment system 1 is, for example, as shown in Figure 3. Various types of aquatic organisms can be reared inside the rearing tank 3, and suitable examples include fish, crustaceans, and shellfish, but other types (for example, squid, octopus, etc.) may also be used.

[0057] 1-2-2. Configuration and operation of each part (Aquarium) The rearing tank 3 shown in Figure 2 constitutes the supply source 120 shown in the basic configuration and is the part where water that has come into contact with organic matter is stored or flows. The rearing tank 3 is a tank for rearing and cultivating aquatic organisms. Inside the rearing tank 3 is rearing water containing saline, such as artificial seawater or natural seawater, and aquatic organisms such as fish and shellfish are reared in this rearing water. It is desirable that the "saline rearing water" contained in the rearing tank 3 is a liquid with an NaCl content of 0.5 mass% or more. In the example in Figure 2, multiple (for example, four) rearing tanks 3 are provided, and the rearing water in these rearing tanks 3 is guided to be collected in a filter 37, filtered by the filter 37, and then circulated internally so that it is distributed from the filter 37 to the multiple rearing tanks 3. The water temperature of the rearing water in the rearing tanks 3 is adjusted to the desired set temperature by a temperature controller 35. Although multiple rearing tanks 3 are used in the example in Figure 2, it may also be composed of a single tank. Rearing water corresponds to an example of target water.

[0058] (Removal section) The solid matter removal unit 5 shown in Figure 2 functions to remove at least solid matter in the first region where rearing water supplied from the rearing tank 3 is stored or flows. The rearing water from the rearing tank 3 is guided to the solid matter removal unit 5 through the flow path 41. As shown in Figure 4, the solid matter removal unit 5 includes an ozone generator 9, a foam separator 7, a storage tank 60, an introduction section 62, an outlet section 64, and a discharge section 66. In Figure 4 and other figures, the symbol W conceptually represents a portion of the circulating rearing water.

[0059] The storage tank 60 is a tank for storing rearing water introduced from the area preceding the solid matter removal unit 5. In the example shown in Figure 2, the area preceding the solid matter removal unit 5 is the area within the rearing tank 3. The method for flowing the rearing water from the rearing tank 3 to the storage tank 60 may be by using a pump, or by utilizing the difference in elevation.

[0060] The ozone generator 9 corresponds to an example of an ozone generating unit, and generates ozone by, for example, a known method, and supplies the generated ozone to the foam separator 7. The method of introducing the ozone from the ozone generator 9 to the foam separator 7 is not particularly limited, but one example is to supply the ozone generated by the ozone generator 9 through an air inlet provided in the foam generating unit of a known foam separator. The foam separator 7 generates foam containing ozone generated by the ozone generator 9 and operates to adsorb solid matter contained in the rearing water in the first region where the rearing water sent from the rearing tank 3 is stored or flows into the foam. In the example in Figure 4, the first region is the internal region of the storage tank 60.

[0061] The introduction section 62 is a flow path that introduces the rearing water stored in the storage tank 60 into the foam separator 7. The discharge section 64 is a flow path that returns the rearing water, which has passed through the foam separator 7, from the foam separator 7 back 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 the area after the solid matter removal section 5. In the examples of Figures 2 and 4, the area after the solid matter removal section 5 is the area inside the electrolysis tank 11.

[0062] In the solid matter removal section 5, solid matter such as feces, leftover feed, and metabolic proteins, bacteria, viruses, and parasites from fish and shellfish contained in the rearing water introduced into the foam separator 7 are removed from the rearing water by attaching to the fine bubbles generated in the foam separator 7. Moreover, since the bubbles generated in the foam separator 7 contain ozone, they have high sterilizing power, and this sterilizing power also acts on the rearing water that passes through the foam separator 7 and returns to the outlet section 64. This operation reliably prevents contaminants from flowing out into the subsequent electrolysis tank 11 and reliably prevents contaminants from interfering with the electrolysis in the electrolysis tank 11.

[0063] In the example shown in Figure 4, the flow path 41 is connected to 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 lower end on the side of the storage tank 60. The flow path 41 corresponds to the flow path 141 in the basic configuration of Figure 1. The inlet (inlet for taking in rearing water) of the introduction section 62 is located near the bottom 60A within the storage tank 60, making it easy to take in rearing water immediately after it is introduced into the storage tank 60 from the flow path 41. On the other hand, the rearing water that has passed through the foam separator 7 is led out by the outlet section 64 to a position closer to the discharge section 66 than to the flow path 41. The outlet (outlet for releasing rearing water) of the outlet section 64 is located closer to the water surface W1 than to the bottom 60A of the storage tank 60. The discharge section 66 is configured as a flow path that directs the rearing water in the storage tank 60 outwards from the storage tank 60. The discharge section 66 is configured to not guide water located below a predetermined first height within the storage tank 60 to the outside of the storage tank 60, but to guide water located above the first height to the outside of the storage tank 60. The first height is the height of the lower end of the boundary between the discharge section 66 and the storage tank 60 on the inner wall surface of the flow path of the discharge section 66. If the water level of the rearing water in the storage tank 60 is higher than this first height, the water in the region above the first height is discharged from the discharge section 66.

[0064] The solid matter removal unit 5 shown in Figure 4 can be configured more specifically as shown in Figure 5. In the specific example in Figure 5, the foam separator 7 is provided with a foam generating unit 8 and a foam separation tank 7A. Furthermore, the inlet (water intake) of the introduction unit 62, which is configured as a pipe, is located 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 rearing water stored in the storage tank 60, the rearing water that can pass through the filter 61 is introduced from the introduction unit 62 to the foam separator 7. The filter 61 is configured to block the passage of large particles and allow the passage of small particles, and is configured, for example, in a mesh shape. Although not shown in Figure 5, a pump may be provided to circulate the rearing water so that it flows into the foam separator 7 through the introduction unit 62.

[0065] In the configuration shown in Figure 5, the foam generating unit 8 injects gas containing ozone generated by the ozone generator 9 into the rearing water flowing in from the inlet 62, causing the rearing water passing through the foam generating unit 8 to contain bubbles of ozone-containing gas. The rearing water that has passed through the foam generating unit 8, now containing ozone-containing bubbles, flows into the foam separation tank 7A via the inlet 63, which is configured as a pipe. In the foam separation tank 7A, bubbles with solid matter attached are separated so that they gather near the water surface, and the gathered bubbles are discharged to the outside of the foam separation tank 7A through the discharge passage 65. Meanwhile, the rearing water on the lower side of the foam separation tank 7A is discharged to the water surface of the storage tank 60 via the outlet 64, which is configured as a pipe. The outlet (discharge port) of the outlet 64 is positioned so that a vortex is generated in a certain direction in the rearing water stored in the storage tank 60. The discharge section 66, which is configured as a discharge channel, is positioned 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.

[0066] (Electrolysis tank) The electrolysis tank 11 shown in Figure 6 is a tank that performs electrolysis and is a tank in which the rearing water that has passed through the solid matter removal unit 5 is stored or flows. The electrolysis tank 11 corresponds to the second region 102 of the basic configuration in Figure 1. The internal region of the electrolysis tank 11 is a region in which the rearing water that has passed through the first region (in the example of Figure 4, the region within the storage tank 60) is stored or flows, and corresponds to an example of the second region. The electrolysis tank 11 is provided with an electrolysis unit 13. In the second region, the electrolysis unit 13 generates chlorate compounds (for example, sodium hypochlorite) by electrolyzing the rearing water, and reacts the generated chlorate compounds with ammonia or ammonium ions in the rearing water to decompose the ammonia or ammonium ions. Furthermore, because chlorate compounds are generated by the electrolysis unit 13 in the electrolysis tank 11, sterilization, deodorization, and decolorization of the rearing water can be performed. The electrolysis unit 13 corresponds to the electrolysis unit 111 of the basic configuration in Figure 1.

[0067] In the electrolysis cell 11, electrolysis is performed as shown in equation (1) below. 2NaCl+3H2O→NaClO+NaCl+2H2O+H2↑···(1)

[0068] Then, the decomposition of ammonia or ammonium ions occurs through the chemical reactions shown in equations (2) and (3) below. 2NH3+3NaClO→N2↑+3NaCl+3H2O···(2) 2NH4 + +3NaClO→N2↑+3H2O+3NaCl+2H + ...(3)

[0069] In the electrolysis tank 11 shown in Figure 6, the internal region of the electrolysis tank 11 is the "region" where the electrode section 55 is located and electrolysis is performed. The electrolysis tank 11 is provided with an electrolysis section 13. The electrolysis section 13 has an electrode section 55 having a first electrode 55A and a second electrode 55B located in the "region" (second region), and a voltage application section 51 that applies a voltage between the electrodes of the first electrode 55A and the second electrode 55B.

[0070] The voltage application unit 51 includes a control device 52 and a drive circuit 53. The control device 52 is an information processing device that includes an information processing unit, a storage unit, a communication unit, etc., and is capable of performing various controls and calculations. The drive circuit 53 is a circuit that applies a voltage between the electrodes of the first electrode 55A and the second electrode 55B in response to a command from the control device 52. The control device 52 corresponds to the control unit 152 in the basic configuration of Figure 1.

[0071] The electrode section 55 includes an electrode holding section 55C that holds a first electrode 55A and a second electrode 55B, and the first electrode 55A, the second electrode 55B, and the electrode holding section 55C are integrally configured. The integrally configured electrode section 55 can be attached to and detached from the electrolysis tank 11. The configuration for making the electrode section 55 detachable from the electrolysis tank 11 is not particularly limited, but for example, when attaching, the electrode holding section 55C is placed on a mounting base provided in the electrolysis tank 11, and when removing, the electrode holding section 55C is detached from the mounting base. In the example in Figure 6, 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 made of metal material and are plate-shaped. In the electrode section 55, the first electrodes 55A and the second electrodes 55B are arranged alternately with a gap between them. Multiple first electrodes 55A are short-circuited to each other and electrically connected to the first terminal of the drive circuit 53 via a conductive path 54A. Multiple second electrodes 55B are short-circuited to each other and electrically connected to the second terminal of the drive circuit 53 via a conductive path 54B. In the example shown in Figure 6, the first electrodes 55A and the second electrodes 55B are arranged alternately with a gap between them.

[0072] The electrodes used in the electrolysis cell 11 should preferably be made of a metal material that does not corrode in seawater and has a high efficiency in generating chlorate compounds. For example, electrodes made by coating the surface of titanium with a platinum-iridium alloy can be suitably used. Platinum has excellent conductivity and corrosion resistance, iridium has excellent durability and chemical stability, and platinum-iridium alloy has the characteristic of a uniform and smooth surface. Electrodes made by coating the surface of titanium with a platinum-iridium alloy can be used as both the anode and the cathode. Note that the electrode examples described here are merely examples, and if the electrode inversion method described later is not used, electrodes made of titanium coated with ruthenium may be used as the anode, or other materials may be used.

[0073] Part or all of the electrode section 55 is positioned on the water surface W2 side of the breeding water in the electrolysis tank 11, and is positioned so that breeding water is interposed between the first electrode 55A and the second electrode 55B. On the other hand, the electrolysis tank 11 is provided with a water flow generating unit 57, which generates a water flow from the bottom to the top (electrode side) of the electrode section 55.

[0074] The water flow generating unit 57 has a structure that causes the rearing water introduced into the electrolysis tank 11 from outside the electrolysis tank 11 through the flow path 42 to flow upward from below to above the electrode section 55 within the electrolysis tank 11. The flow path 42 corresponds to the flow path 142 in the basic configuration of Figure 1. The flow path 42 is a flow path that carries the rearing water discharged through the discharge section 66 into the electrolysis tank 11, and may be composed of the discharge section 66, or may be configured as a flow path following the discharge section 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 tank 11. The downstream region is the region downstream of the first partition wall 57A and is the region in which the electrode section 55 is provided. The upstream region is the region upstream of the first partition wall 57A and upstream of the downstream region.

[0075] In the example shown in Figure 6, the upstream region is the internal region of the first rearing water flow chamber 11A, which is composed of the first partition wall 57A and the portion of the outer periphery wall and bottom wall 11Z of the electrolysis tank 11 that is upstream of the first partition wall 57A, and is the region into which rearing water flows from the flow path 42. In the first rearing water flow chamber 11A, an opening is provided on the bottom wall side to move the rearing water in the first rearing water flow chamber 11A to the second rearing water flow chamber. In the example shown in Figure 6, this opening is composed of the lower end of the first partition wall 57A and the outer periphery wall and bottom wall 11Z of the electrolysis tank 11.

[0076] The downstream region described above is the internal region of the second rearing water flow chamber 11B, which is composed of the first partition wall 57A, the second partition wall 57B, and the portion of the outer periphery wall and bottom wall 11Z of the electrolysis tank 11 between the first partition wall 57A and the second partition wall 57B, and is the region in which part or all of the electrode section 55 is located. 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 periphery wall of the electrolysis tank 11, so that if water exceeding the upper end of the second partition wall 57B enters the second rearing water flow chamber 11B, the water will flow beyond the second partition wall 57B to the downstream side of the second rearing water flow chamber 11B. With this configuration, in the second rearing water flow chamber 11B, rearing water is introduced from the lower opening, and the rearing water is led out so as to exceed the upper end of the second partition wall 57B. Consequently, a water flow of rearing water is generated that rises from the lower side of the electrode section 55 toward the electrode section 55.

[0077] In the example shown in Figure 6, a second partition wall 57B is provided, but it is not necessary to provide a second partition wall 57B. In this case, the entire area downstream 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 portions of the outer periphery wall and bottom wall 11Z of the electrolysis tank 11 downstream of the first partition wall 57A.

[0078] As shown in Figure 7, the electrolysis tank 11 is provided with a guide section 58. The guide section 58 functions to guide and collect precipitates that have settled from the electrode section 55 within the electrolysis tank 11 toward a predetermined position within the electrolysis tank 11. In the examples of Figures 6 and 7, the predetermined position is located above a portion of the bottom wall 11Z. In the examples of Figures 6 and 7, downstream of the second rearing water flow chamber 11B, the third rearing water flow chamber 11C is formed by the second partition wall 57B, the outer periphery wall of the electrolysis tank 11, and the portion of the bottom wall 11Z downstream of the second partition wall 57B, and the predetermined position is located above a portion of the bottom wall 11Z within the third rearing water flow chamber 11C. The guide section 58 includes an inclined section 58A having an inclined surface that is inclined in the vertical direction. The inclined surfaces of the inclined sections 58A and 58B constitute the inner wall surface of the third rearing water flow chamber 11C. When a sinking object (e.g., precipitate) in the third rearing water flow chamber 11C reaches the inclined surface of the inclined section 58A, it is guided by the inclined surface as it sinks further, and is led to the vicinity of the predetermined position on the bottom wall 11Z. The inclined surfaces of the inclined sections 58A and 58B guide the sinking object along these inclined surfaces to move in a predetermined first direction perpendicular to the vertical direction (specifically, to move toward the discharge section 59 in the first direction).

[0079] As shown in Figures 6 and 7, the electrolysis tank 11 is provided with discharge sections 59. In the example in Figure 6, there are two discharge sections 59. However, the number of discharge sections 59 is not limited to this example, and there may be one or three or more. The discharge section 59 has a pipe 59A for discharging precipitates that have settled from the electrode section 55 in the electrolysis tank 11, and an opening / closing section 59B for opening and closing this pipe 59A. The discharge section 59 functions to take in precipitates into the pipe 59A at a position below the electrode section 55 and to discharge the precipitates from the electrolysis tank 11 through the pipe 59A.

[0080] In the examples shown in Figures 6 and 7, the opening / closing section 59B is an on / off valve that can be switched between a closed state and an open state of pipe 59A by, for example, manual operation. The opening / closing section 59B may also be a solenoid valve whose opening and closing can be switched by control. In any case, when the opening / closing section 59B is in the open state, the rearing water is discharged through pipe 59A from near the predetermined position in the electrolysis tank 11. If precipitates settle near the predetermined position, the precipitates are discharged through pipe 59A together with the rearing water. In the examples shown in Figures 6 and 7, pipe 59A is a fixed pipe permanently installed in the electrolysis tank 11, but it may also be a pipe that can be attached to and detached from the electrolysis tank 11. Furthermore, when discharging through the pipe from near the predetermined position, the water may be discharged using the water pressure inside the electrolysis tank 11, or it may be discharged by suction or flow using a pump or the like.

[0081] As shown in Figures 6 and 7, the electrolysis tank 11 is provided with a first guide channel 56. The first guide channel 56 is an example of a guide channel. The first guide channel 56 functions as a flow path that guides water located above a first height to the outside of the electrolysis tank 11, while preventing water located below a first height within the electrolysis tank 11 from being guided to the outside of the electrolysis tank 11. The first height is an example of a predetermined height. In the example in Figure 6, the water level W2 of the cultured water in the electrolysis tank 11 is above the lower end of the inner wall surface of the flow path at the inlet of the first guide channel 56 (the boundary with the first guide channel 56, which is the outlet of the electrolysis tank 11), so that water near the water level of the cultured water in the electrolysis tank 11 flows into the first guide channel 56, exceeding the height of the bottom of the first guide channel 56. In the example in Figure 6, the height of the lower end of the inner wall surface of the flow path at the inlet of the first guide channel 56 is the first height (predetermined height), and this first height (predetermined height) is above the lower end of the electrode section 55. The height of the lower end of the electrode section 55 is the height of the lowest position among the multiple first electrodes 55A and multiple second electrodes 55B. The first guideway 56 functions to direct the rearing water in the electrolysis tank 11 toward the reaction tank 15.

[0082] (Reaction vessel) The reaction tank 15 stores the rearing water supplied from the electrolysis tank 11 through the channel 43, and ensures sufficient reaction time between the ammonia or ammonium ions contained in the stored rearing water and the chlorate compound (e.g., sodium hypochlorite) produced in the electrolysis tank 11, thereby promoting these chemical reactions. The channel 43 may be composed of a first guide channel 56, or it may be composed of a channel following the first guide channel 56. If all of the ammonia or ammonium ions present in the rearing water in the electrolysis tank 11 have not reacted with the chlorate compound in the electrolysis tank 11 and remain unresolved before flowing out of the electrolysis tank 11, and if the chlorate compound produced in the electrolysis tank 11 has not reacted completely and flows out of the electrolysis tank 11, then either or both of the chemical reactions described in equation (2) or equation (3) above occur in the reaction tank 15, and the ammonia or ammonium ions are decomposed.

[0083] As shown in Figure 6, a second guide channel 72 is provided in the reaction vessel 15. The second guide channel 72 functions as a flow path that guides water located above the second height to the outside of the reaction vessel 15, while preventing water located below the second height within the reaction vessel 15 from being guided to the outside of the reaction vessel 15. In the example in Figure 6, the water level W3 of the cultured water in the reaction vessel 15 is above the lower end of the inner wall surface of the flow path at the inlet of the second guide channel 72 (the boundary with the second guide channel 72, which is the outlet of the reaction vessel 15), so that water near the water level in the cultured water in the reaction vessel 15 flows into the second guide channel 72, exceeding the height of the bottom of the second guide channel 72. In the example in Figure 6, the height of the lower end of the inner wall surface of the flow path at the inlet of the second guide channel 72 is the second height. The second guide channel 72 functions to direct the cultured water in the reaction vessel 15 toward the downstream process of the reaction vessel 15.

[0084] A filtration tank 17 is provided in the downstream process of the reaction vessel 15, forming a detection area for detecting residual chlorine. The filtration tank 17 is configured to store the rearing water supplied from the reaction vessel 15 through the flow path 44 and to lead it to the flow path 45. The flow path 44 is a flow path that carries the rearing water discharged through the second guideway 72 into the filtration tank 17, and may be composed of the second guideway 72, or may be configured as a flow path following the second guideway 72. In the example in Figure 2, the flow path 44, the filtration tank 17, and the flow path 45 constitute a flow path that guides the rearing water from the reaction vessel 15 to the activated carbon tank 21, but other configurations (for example, a configuration in which a pipe continues from the reaction vessel 15 to the activated carbon tank 21 without the filtration tank 17) may be used as long as the rearing water flows from the reaction vessel 15 to the activated carbon tank 21. Note that the flow path 43, the reaction vessel 15, and the filtration tank 17 correspond to the flow path 143 in the basic configuration of Figure 1. In the flow path 143, an additional flow path may be provided between the filtration tank 17 and the switching section 134. Flow path 45 corresponds to flow path 45 in the basic configuration of Figure 1.

[0085] The first residual chlorine sensor 19 is a sensor that detects the concentration of residual chlorine in the rearing water from the time it passes through the electrolysis tank 11 until it flows into the residual chlorine removal tank (specifically, the activated carbon tank 21). For example, it detects the concentration of residual chlorine in the rearing water in the region where the rearing water flows between the reaction tank 15 and the activated carbon tank 21. In the representative example shown in Figure 2, 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 refers to the combined and free chlorine remaining in the rearing water. The total amount of chlorine, which is the sum of the combined and free chlorine contained in the rearing water, is the amount of residual chlorine. By detecting the residual chlorine contained in the rearing water in the region between the reaction tank 15 and the activated carbon tank 21, the amount of chlorate compounds remaining after the decomposition of ammonia or ammonium ions in the electrolysis tank 11 and the reaction tank 15 can be measured.

[0086] (Residual chlorine removal tank) In the example shown in Figure 6, an activated carbon tank 21 is provided as an example of a residual chlorine removal tank. The activated carbon tank 21 corresponds to the third region 103 of the basic configuration in Figure 1. The residual chlorine removal tank is a tank that removes at least residual chlorine from the rearing water, and functions to remove residual chlorine from the rearing water by passing the rearing water through the residual chlorine removal section. The activated carbon tank 21 illustrated in Figure 6 is a tank in which the rearing water that has passed through the reaction tank 15 is stored, and specifically, it is a tank provided downstream of the detection region where the first residual chlorine sensor 19 is located (in the example of Figure 2, the region within the filtration tank 17). The activated carbon tank 21 functions as a tank that removes chloric 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 rearing water in the activated carbon tank 21 using activated carbon. In the example shown in Figure 2, the internal region of the activated carbon tank 21 corresponds to an example of the third region, and is the region where the rearing water that has passed through the second region is stored or flows. The activated carbon section 23 corresponds to the residual chlorine removal section 121 in the basic configuration of Figure 1.

[0087] In the activated carbon tank 21, for example, the reaction proceeds as shown in equation (4) below, and excess chlorate compounds that were not used in the decomposition of ammonia and ammonium ions can be removed. HClO + C → CO + H + +Matsu - ...(4)

[0088] The activated carbon tank 21 illustrated in Figure 6 can be configured as shown in Figure 8, for example. In the example in Figure 8, the activated carbon tank 21 is configured as a channel through which rearing water passes, and the activated carbon section 23 is configured such that activated carbon particles are filled into the internal space of the channel. In the activated carbon tank 21, the rearing water is configured to flow 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 flows in from the inlet 21A of the activated carbon tank 21 and passes through the gaps between the many particles in the activated carbon tank 21, residual chlorine and residual ozone contained in the rearing water are adsorbed onto 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.

[0089] (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 and is discharged into the flow path 46, and flows into the waiting tank 25 through the flow path 46. The flow path 46 corresponds to the flow path 145 in the basic configuration of Figure 1. The waiting tank 25 is a tank in which the rearing water that has passed through the activated carbon tank 21 is stored and its water quality is inspected before it returns to the rearing tank 3. The waiting tank 25 corresponds to the fourth region 104 in the basic configuration of Figure 1. 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 third region described above is stored or flows before returning to the rearing tank 3.

[0090] The second residual chlorine sensor 27 is a sensor that detects the concentration of residual chlorine in the rearing water in the fourth region where the rearing water that has passed through the third region is stored or flows before returning to the rearing tank 3. In the example shown in Figure 2, it detects the concentration of residual chlorine in the rearing water in the standby tank 25. The second residual chlorine sensor 27 can more accurately detect fluctuations in residual chlorine concentration due to leakage when residual chlorine leaks out due to deterioration of the activated carbon provided in the activated carbon section 23.

[0091] The ammonium ion sensor 29 is a sensor that detects the concentration of ammonium ions in the rearing water in the fourth region, where the rearing water that has passed through the third region described above is stored or flows before returning to the rearing tank 3. In the example shown in Figure 2, it detects the concentration of ammonium ions in the rearing water in the standby tank 25. The ammonium ion sensor 29 can more accurately detect fluctuations in the concentration of ammonium ions if they remain after the electrolysis tank 11 or reaction tank 15 have not completely reacted.

[0092] The pH sensor 28 is a sensor that measures the pH (hydrogen ion concentration) of the rearing water in the fourth region where the rearing water that has passed through the third region described above is stored or flows before returning to the rearing tank 3. In the example in Figure 2, the pH sensor 28 measures the pH of the rearing water in the standby tank 25 and provides a value to the control device 52 that identifies the pH of the rearing water in the standby tank 25.

[0093] In the standby tank 25, aeration is performed by an aeration device (not shown) to remove CO2 from the rearing water. The rearing water in the standby tank 25 then flows into the rearing tank 3 through the flow path 47. The operation of flowing rearing water from the standby tank 25 to the rearing tank 3 via the flow path 47 can be switched between a state in which rearing water flows continuously from the standby tank 25 to the rearing tank 3 and a state in which the flow of rearing water from the standby tank 25 to the rearing tank 3 is stopped or blocked. Flow path 47 corresponds to flow path 146 in the basic configuration of Figure 1.

[0094] 1-2-3. About the Guidance Section In water treatment system 1, a main flow path 140 is provided as shown in the basic configuration. This main flow path 140 is a flow path that moves the target water from the second region to the third region. In the example in Figure 2, the internal flow paths of flow path 43, reaction tank 15, flow path 44, flow path 45, and switching unit 134 constitute the main flow path 140. Note that the main flow path 140 may also have elements other than these.

[0095] In the water treatment system 1 of specific example 1, the guide unit 130 shown in the basic configuration is also provided. The guide unit 130 is configured to guide the target water stored or flowing in the second region or downstream of the second region from a first position downstream of the electrolysis unit 13 to a second position upstream of the first position, via a path different from the main flow path 140.

[0096] The first position described above is located downstream of the electrolysis unit 13 in the main flow path 140, and in the example shown in Figure 2, it is located within the flow path 45 for guiding rearing water from the filtration tank 17 to the activated carbon tank 21. However, the first position is not limited to this example and may be located within the filtration tank 17, within the flow path 44, within the reaction tank 15, within the flow path 43, or downstream of the electrolysis unit 13 in the electrolysis tank 11.

[0097] The second position described above is located downstream of the rearing tank 3 (supply source) and upstream of the electrolysis unit 13. In specific example 1, the storage tank 60 constitutes part or all of the first region 101, and the storage tank 60 (Figure 5) is the second position. Note that the second position is not limited to this example and may be the flow path 42, the flow path 41, or a location upstream of the electrolysis unit 13 within the electrolysis tank 11.

[0098] In the main flow path 140, the internal flow paths of flow path 43, reaction tank 15, flow path 44, flow path 45, and switching section 134 correspond to an example of a downstream flow path that flows rearing water (target water) from the second region downstream. The guide section 130 includes a return flow path 132 that branches off from the downstream flow path. The return flow path 132 is a flow path that returns some or all of the target water that has entered the downstream flow path and flows it to the second position.

[0099] The guide unit 130 includes a switching unit 134. The switching unit 134 switches between a first switching state and a second switching state. The first switching state is a state in which the flow of the rearing water (target water) through the return channel 132 to the second position is blocked, while the flow of the rearing water (target water) through the downstream channel to a point downstream of the switching unit 134 is blocked. The second switching state is a state in which the flow of the rearing water (target water) through the return channel 132 to the second position is blocked, while the flow of the rearing water through the downstream channel to a point downstream of the switching unit 134 is blocked.

[0100] 1-2-4. Control of Water Treatment System 1 (Configuration for control) In the water treatment system 1, the rearing water in the rearing tank 3 is circulated in the following order: solid matter removal unit 5, electrolysis tank 11, reaction tank 15, filtration tank 17, activated carbon tank 21, and standby tank 25. Along the circulation path that returns the rearing water from the rearing tank 3, there are several pumps (not shown) that circulate the rearing water. The control device 52 shown in Figure 3 controls the operation and stopping of the above pumps. Furthermore, the control device 52 controls the operation and stopping of the temperature controller 35, the ozone generator 9, the foam separator 7, the electrolysis unit 13, and the operation of the treatment unit 31.

[0101] The control device 52 shown in Figure 3 receives input from the detection values ​​of the first residual chlorine sensor 19, the second residual chlorine sensor 27, the pH sensor 28, and the ammonium ion sensor 29. The detection value input from the first residual chlorine sensor 19 indicates the concentration of residual chlorine in the rearing water in the detection area described above (specifically, inside the filtration tank 17). The detection value input from the second residual chlorine sensor 27 indicates the concentration of residual chlorine in the rearing water in the fourth area described above (specifically, inside the standby tank 25). The detection value input from the pH sensor 28 indicates the pH (hydrogen ion concentration) of the rearing water in the fourth area described above (specifically, inside the standby tank 25). The detection value input from the ammonium ion sensor 29 indicates the concentration of ammonium ions in the rearing water in the fourth area described above (specifically, inside the standby tank 25).

[0102] (Control of electrolysis) The control device 52 corresponds to an example of a control unit. The first residual chlorine sensor 19 corresponds to an example of a sensor and detects a numerical value of an element (residual chlorine concentration) indicating the water quality of the rearing water (target water) at a predetermined position downstream of the electrolysis unit 13, or detects whether the element (residual chlorine concentration) meets a standard. The first residual chlorine sensor 19 may be configured to output a numerical value that identifies the residual chlorine concentration at the detection position of the first residual chlorine sensor 19. The first residual chlorine sensor 19 may be configured to output a first signal when the residual chlorine concentration at the detection position of the first residual chlorine sensor 19 is equal to or greater than a standard value, and to output a second signal when the residual chlorine concentration at the detection position of the first residual chlorine sensor 19 is less than a standard value. The control device 52 may operate to control the switching unit 134 based on the detection result of the first residual chlorine sensor 19. For example, the control device 52 may control the system to enter a first switching state when the residual chlorine concentration detected by the first residual chlorine sensor 19 is equal to or greater than a standard value, and to enter a second switching state when the residual chlorine concentration detected by the first residual chlorine sensor 19 is less than a standard value.

[0103] Alternatively, the ammonium ion sensor 29 may function as an example of a "sensor that detects numerical values ​​of elements indicating the water quality of the target water or detects whether or not the elements meet a standard," and the control device 52 may operate to control the switching unit 134 based on the detection result of the ammonium ion sensor 29. For example, the control device 52 may set the system to a second switching state when the ammonium ion concentration value (detected value) detected by the ammonium ion sensor 29 is equal to or greater than the standard value, and to a first switching state when the ammonium ion concentration value (detected value) detected by the ammonium ion sensor 29 is less than the standard value.

[0104] The control device 52 may control the electrolysis of the electrolysis unit 13. The control device 52 may control the electrolysis of the electrolysis unit 13 based on the measurement results of the ammonium ion sensor 29 and the measurement results of the first residual chlorine sensor 19, or it may control the electrolysis of the electrolysis unit 13 based on the measurement results of the ammonium ion sensor 29, or it may control the electrolysis of the electrolysis unit 13 based on the measurement results of the first residual chlorine sensor 19. When the control device 52 controls the electrolysis of the electrolysis unit 13 based on the measurement results of the ammonium ion sensor 29, it may, for example, feedback control the current flowing between the first electrode 55A and the second electrode 55B so that the detected value of the ammonium ion sensor 29 is less than or equal to a predetermined value. When the control device 52 controls the electrolysis of the electrolysis unit 13 based on the measurement results of the first residual chlorine sensor 19, it may, for example, feedback control the current flowing between the first electrode 55A and the second electrode 55B so that the detected value of the first residual chlorine sensor 19 is within a predetermined range.

[0105] In this embodiment, when determining the ammonia concentration and available chlorine concentration in the rearing water (e.g., seawater), these can be determined based on the discontinuous point chlorination method. For example, in the first state, where the concentrations of ammonia and ammonium ions in the rearing water are above a certain concentration relative to the available residual chlorine concentration, the available residual chlorine concentration increases as the amount of chlorate compound added increases. On the other hand, in the second state, where ammonia or ammonium ions are present but their concentrations are below the above-mentioned certain concentration relative to the available residual chlorine concentration, the available residual chlorine concentration decreases even when a chlorate compound is added because it is consumed in reaction with ammonia or ammonium ions. In the third state, where ammonia and ammonium ions are absent, the available residual chlorine concentration increases as the amount of chlorate compound added increases. If the pH, salinity, and temperature of the rearing water are constant, the above-mentioned constant concentration can be considered a fixed value.

[0106] The control device 52 is configured to detect the current flowing between the first electrode 55A and the second electrode 55B in the electrolysis unit 13, and continuously monitors the current flowing between the first electrode 55A and the second electrode 55B. Various configurations can be adopted for the control device 52 to monitor the current flowing between the first electrode 55A and the second electrode 55B. For example, the current may be detected by a current sensor, and the control device 52 may acquire the value detected by the current sensor, or other configurations may be used. 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 the ammonium ion sensor 29 or the first residual chlorine sensor 19, or the detection value of both.

[0107] 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 greater the current flowing between the first electrode 55A and the second electrode 55B, the more electrolysis is promoted and the greater the amount of chlorate compounds generated. Therefore, when the control device 52 performs the first current control, it adjusts the current flowing between the first electrode 55A and the second electrode 55B so that the ammonium ion concentration value (detected value) detected by the ammonium ion sensor 29 is less than or equal to a first threshold. The first threshold may be 0 or a value slightly greater than 0. On the other hand, in the absence of ammonia and ammonium ions, the greater the current flowing between the first electrode 55A and the second electrode 55B, the higher 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 detected value of the ammonium ion sensor 29 is below the first threshold, and the value of the amount of residual chlorine detected by the first residual chlorine sensor 19 (detected value) is below the second threshold.

[0108] The control device 52 may perform a second current control to control the current flowing between the first electrode 55A and the second electrode 55B based on the detection value of the ammonium ion sensor 29, without using the detection value of the first residual chlorine sensor 19. Even when performing the second current control, the control device 52 adjusts the current flowing between the first electrode 55A and the second electrode 55B so that the ammonium ion concentration value (detected value) detected by the ammonium ion sensor 29 is less than or equal to a first threshold value. The first threshold value may be 0 or slightly greater than 0. When performing the second current control, the control device 52 repeats the "current adjustment control in which the current flowing between the first electrode 55A and the second electrode 55B is controlled to a set current value and electrolysis is performed for a certain period of time, and then the ammonium ion concentration value (detected value) detected by the ammonium ion sensor 29 is checked." In this control, if the detected 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 increased by a predetermined percentage (e.g., 10%) from the set current value used in the previous current adjustment control. On the other hand, if the detected value of the ammonium ion sensor 29 is below the first threshold in the previous current adjustment control, the next current adjustment control is performed so that the next set current value is the set current value used in the previous current adjustment control. In this way, electrolysis can be performed while gradually increasing the current until the detected value of the ammonium ion sensor 29 falls below the first threshold, and once the detected value of the ammonium ion sensor 29 falls below the first threshold, electrolysis can be performed while maintaining that current state.

[0109] 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 the control device 52 performs the third current control, it repeats the "current adjustment control" which involves 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 value of the amount of residual chlorine detected by the first residual chlorine sensor 19 (detection value). In this control, if the set current value from the previous current adjustment control is increased by a predetermined percentage (e.g., 10%) compared to the set current value from the current adjustment control before last, and the value of residual chlorine detected in the previous current adjustment control (detected value) is smaller than the value of residual chlorine detected in the current adjustment control before last (detected value), then it can be estimated that the second state described above is occurring. In this case, the next current adjustment control (the current current adjustment control) is performed to set the current value to a current value that is increased by a predetermined percentage (e.g., 10%) from the set current value used in the previous current adjustment control. In other words, as long as the detected residual chlorine value is decreasing, each current adjustment control is performed to gradually increase the set current value. On the other hand, when controlling the current by gradually increasing the set current value in this way, 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 residual chlorine detected in the previous current adjustment control (detected value) is greater than the value of residual chlorine detected in the current adjustment control before last (detected value), then it can be estimated that the above-mentioned third state is occurring. In this case, in the next current adjustment control (the current current adjustment control), the current adjustment control is performed so that the set current value is a current value that is reduced by a predetermined percentage (e.g., 10%) from the set current value used in the previous current adjustment control.Furthermore, if the set current value in the previous current adjustment control is reduced by a predetermined percentage (e.g., 10%) compared to the set current value in the current adjustment control two steps prior, and the amount of residual chlorine detected in the previous current adjustment control is smaller than the amount of residual chlorine detected in the current adjustment control two steps prior, then in the next current adjustment control (the current current adjustment control), the current adjustment control should be performed so that the set current value is a current value reduced by a predetermined percentage (e.g., 10%) from the set current value used in the previous current adjustment control. If the amount of residual chlorine detected in the previous current adjustment control is larger than the amount of residual chlorine detected in the current adjustment control two steps prior, then in the next current adjustment control (the current current adjustment control), the current adjustment control should be performed so that the set current value is a current value increased by a predetermined percentage (e.g., 10%) from the set current value used in the previous current adjustment control.

[0110] (Control based on monitoring of residual chlorine) The treatment unit 31 may operate to remove residual chlorine from the rearing water in the fourth region when a predetermined measurement result is obtained by the second residual chlorine sensor 27, or it may operate to stop returning the rearing water in the fourth region to the rearing tank 3.

[0111] For example, the treatment unit 31 may supply a neutralizing agent to the rearing water before it is returned to the rearing tank 3 when the concentration of residual chlorine (detected value) detected by the second residual chlorine sensor 27 exceeds a predetermined value. Suitable neutralizing agents include, for example, sodium thiosulfate, catechin, polyphenols, cysteine, etc. In the example shown in Figure 8, a neutralizing agent supply device 31A is provided as an element constituting at least a part of the treatment unit 31 to supply a neutralizing agent to the rearing water in the fourth region. Specifically, for example, the control device 52 and the neutralizing agent supply device 31A may function as the treatment unit 31 and the neutralizing agent supply unit, and when the concentration of residual chlorine (detected value) detected by the second residual chlorine sensor 27 exceeds a predetermined value, the control device 52 may issue a neutralizing agent input command to the neutralizing agent supply device 31A, and in response to this neutralizing agent input command, the neutralizing agent supply device may operate to input a "neutralizing agent that causes a neutralization reaction with residual chlorine" into the standby tank 25.

[0112] The treatment unit 31 may operate to switch the flow path so that when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds a predetermined value, the rearing water is not returned from the standby tank 25 to the rearing tank 3, but instead flows from the standby tank 25 to another area. For example, a three-way valve (not shown) may be provided in the middle of the flow path 47, so that the destination of the rearing water flowing through the flow path 47 can be switched by the three-way valve between the rearing tank 3 and another area. In this example, the control device 52 and the three-way valve can function as the treatment unit 31. Specifically, the control device 52 may control the supply from the three-way valve to the rearing tank 3 when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 is below a predetermined value, and to another area when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds a predetermined value.

[0113] Alternatively, the treatment unit 31 may, when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds a predetermined value, block the flow path that carries the rearing water from the standby tank 25 to the rearing tank 3, thereby stopping the return of the rearing water to the rearing tank 3, or it may stop the circulation of the rearing water in system 1, thereby stopping the return of the rearing water to the rearing tank 3. For example, an on-off valve (not shown) may be provided in the middle of the flow path 47, such that when the on-off valve is in the open state, flow in the flow path 47 is permitted, and when the on-off valve is in the closed state, flow in the flow path 47 is blocked. In this example, the control device 52 and the on-off valve can function as the treatment unit 31. Specifically, the control device 52 may control the on-off valve to be in the open state when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 is below a predetermined value, and to be in the closed state when the detected value of the residual chlorine concentration detected by the second residual chlorine sensor 27 exceeds a predetermined value. In this example, when the shut-off valve is closed, the pump that circulates the rearing water in the system may be stopped to prevent the standby tank 25 from overflowing. Alternatively, a flow path may be provided so that the rearing water escapes from the standby tank 25 to another area if the water level in the standby tank 25 exceeds a certain level.

[0114] (Control based on pH monitoring) In this embodiment, a pH adjusting agent supply device 32 is provided to supply a pH adjusting agent to the rearing water in the fourth region. In the example shown in Figure 8, the pH adjusting agent supply device 32 is configured to supply a pH adjusting agent to the rearing water in the waiting tank 25. The control device 52 gives instructions to the pH adjusting agent supply device 32 regarding the timing and rate of supply, and the pH adjusting agent supply device 32 supplies the pH adjusting agent at the timing and rate instructed by the control device 52.

[0115] As the pH adjusting agent supplied from the pH adjusting agent supply device 32, for example, any of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, or sodium bicarbonate can be suitably used, with the use of either sodium carbonate or sodium bicarbonate being more preferable, and sodium carbonate being even more preferable. When using sodium carbonate, sodium bicarbonate, calcium carbonate, etc. as the pH adjusting agent, it is preferable to use an aqueous solution containing any of them. Using sodium carbonate, which has a high pH, ​​has the advantage that it is strongly alkaline, making it easy to raise the pH of the aquarium water and less likely to disrupt the ion balance. Sodium bicarbonate has the advantage that it is less likely to disrupt the ion balance and can exhibit a pH buffering function. Furthermore, in order to prevent the inhibition of the pH adjusting effect due to the precipitation of magnesium contained in seawater, the pH of the pH adjusting agent is preferably 11.5 or lower.

[0116] There are various methods of control by the control device 52. For example, the control device 52 may operate the pH adjusting agent supply device 32 to supply a pH adjusting agent with a pH higher 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 the first reference value, and may perform on / off control to stop the supply of pH adjusting agent by the pH adjusting agent supply device 32 when the pH of the rearing water detected by the pH sensor 28 exceeds the second reference value while the pH adjusting agent supply device 32 is supplying the pH adjusting agent. In the above example, the first reference value and the second reference value may be the same or different.

[0117] Furthermore, in order to reduce the consumption of pH adjusting agents, solid calcium carbonate (e.g., pellets, etc.) may be provided in the fourth region (e.g., the internal region of the flow channels 46 and 47 or the standby tank 25).

[0118] In the example above, the timing of adding the pH adjusting agent is controlled, but instead of this method, the pH adjusting agent may be supplied continuously at a constant rate.

[0119] 1-2-5. Cleaning of electrodes As shown in Figure 6, 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 the anode and the second electrode 55B is the cathode to perform electrolysis within the "region" (specifically, within the electrolysis tank 11), and a second state in which a voltage is applied so that the second electrode 55B is the anode and the first electrode 55A is the cathode. For example, the voltage application unit 51 periodically switches between continuing the first state to electrolyze the aquarium water and continuing the second state to electrolyze the aquarium water. The switching cycle when switching periodically may be, for example, every few tens of minutes, every few hours, every day, or any other cycle.

[0120] The timing at which the voltage application unit 51 switches between the first and second states is not limited to periodic timings, but may be at a timing when predetermined conditions are met. For example, the switch may occur when the operating time of the water treatment system 1 has reached a certain period since the last switch, when a value detected by some sensor reaches a predetermined value, at a randomly determined timing, or at any other timing.

[0121] In this embodiment, the operation of the first state is continuously performed, in which a voltage is continuously applied by the voltage application unit 51 to make the first electrode 55A the anode and the second electrode 55B the cathode, while "exchanging the rearing water" is continuously performed, such as continuously supplying rearing water from the flow path 42 to the electrolysis tank 11 and draining rearing water from the electrolysis tank 11 to the first guideway 56. If the switching condition is met during the operation of the first state, the system switches from the first state to the second state while performing the aforementioned "exchanging the rearing water". After the switch, the system continues to operate in the second state, in which a voltage is continuously applied to make the second electrode 55B the anode and the first electrode 55A the cathode, while "exchanging the rearing water" is continuously performed. If the switching condition is met during the operation of the second state, the system switches from the second state to the first state while performing the aforementioned "exchanging the rearing water". In this manner, the operation of the first state and the operation of the second state are performed alternately. Furthermore, during the continuation of the operation in the first state or the continuation of the operation in the second state, the operation may be continued without interruption, or it may be temporarily interrupted for any reason.

[0122] 1-3. Specific Example 2 of the First Embodiment The configuration of Specific Example 2 is a configuration in which further configurations and functions are added to the configuration of Specific Example 1 of the First Embodiment. In this water treatment system 1 of Specific Example 2, a biological tank is provided in the region from where the rearing water sent from the rearing tank flows into the second region, in which ammonia or ammonium ions in the rearing water are reduced by organisms. In this case, for example, in the water treatment system 1 of Specific Example 1 (Figure 4), a biological tank may be provided between the storage tank 60 and the electrolysis tank 11, and the rearing water flowing out from the storage tank 60 may flow into the biological tank, and the rearing water flowing out from the biological tank may flow into the electrolysis tank 11. Alternatively, the rearing water flowing out from the foam separator 7 may flow into the biological tank, and the rearing water flowing out from the biological tank may flow into the electrolysis tank 11.

[0123] In the example described above, where a biological tank is located upstream of the electrolysis tank 11, it is desirable that the biological tank be configured to receive the rearing water flowing out of the rearing tank 3 via a channel or the like, and to be able to store the incoming rearing water. On the other hand, it is desirable that the biological tank contains, for example, nitrifying bacteria (microorganisms) that oxidize ammonia into nitrite and then nitrate. In this configuration, the ammonia or ammonium ions contained in the rearing water flowing into the biological tank are reduced by the microorganisms, and the rearing water, with the ammonia or ammonium ions thus reduced, flows into the electrolysis tank 11 directly from the biological tank or via another area.

[0124] In the example described above, where the biological tank is located upstream of the electrolysis tank 11, the order of the removal unit and the biological tank may be such that the rearing water flows into the biological tank after passing through the removal unit, or it may be such that the rearing water flows into the removal unit after passing through the biological tank. Alternatively, part or all of the biological tank may also serve as the removal unit. In any case, it is sufficient that part or all of the rearing water flowing out of the rearing tank 3 and into the electrolysis tank 11 flows into the electrolysis tank 11 after passing through the biological tank.

[0125] In the example described above, the biological tank is configured to hold rearing water and microorganisms inside, but instead of this configuration, or in addition to this configuration, the ammonia or ammonium ions contained in the rearing water may be reduced by the action of other organisms. Also, the number of biological tanks is not limited to one, and there may be multiple tanks.

[0126] For example, instead of the "biological tank for holding microorganisms" described above, the biological tank may be configured to cultivate vegetables or other plants as "living organisms." In this case, the cultivation water flowing in directly from the cultivation tank 3 or via another area may be temporarily stored or circulated within the biological tank, and the cultivation water in the biological tank may be continuously or intermittently supplied to the plants to grow, thereby purifying the water by allowing the plants to absorb ammonia or ammonium ions in the cultivation water. In this type of "circulating water treatment system that uses both a biological tank and an electrolysis tank," the biological tank can reduce ammonia or ammonium ions before the electrolysis unit 13 decomposes them. Therefore, compared to a configuration in which the reduction of ammonia or ammonium ions in the rearing water is performed solely by the electrolysis unit 13, the burden on the electrolysis unit 13 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 in the rearing water is not performed solely by the biological tank, ammonia or ammonium ions in the water can be decomposed more effectively in a way that is less dependent on organisms. Furthermore, in the second region (the region within the electrolysis tank 11) into which the rearing water that has passed through the biological tank flows, the above-mentioned circulating water treatment system generates chlorate compounds (e.g., sodium hypochlorite), so in addition to removing ammonia or ammonium ions, it can also sterilize or inactivate viruses if the rearing water that has passed through the biological tank contains bacteria or viruses.

[0127] When such a biological tank is provided, the second position where the induction unit 130 releases the rearing water (target water) should be, for example, located downstream of the biological tank and upstream of the electrolysis unit 13.

[0128] 1-4. Specific Example 3 of the First Embodiment 1-4-1. Overview of the recycled water generation system for food processing in Specific Example 3 In specific example 3, the water treatment system 100 illustrated in Figure 1 is a system used to regenerate water used in a food processing plant. The water treatment system 100 in specific example 3 is a system in which water containing chloride ions, after being treated by bringing it into contact with food (target water) in a food processing plant, is passed through a removal unit 105, an electrolysis unit 111, and a residual chlorine removal unit 121 for treatment, and the resulting regenerated water is guided by a guide unit (flow channel 145) toward a predetermined region (internal region of the fourth region 104).

[0129] 1-4-2. Food Processing Section In the water treatment system 100 of specific example 3, the supply source 120 is designated as a food processing unit. This food processing unit is a place in a food processing plant where water containing chloride ions is brought into contact with food. Examples of water containing chloride ions include water containing sodium chloride, magnesium chloride, bittern, and mixtures thereof. Examples of processes in which water containing chloride ions is brought into contact with food include immersing fish roe (herring roe, cod roe, etc.), seafood (salmon, trout, cod, mackerel, Atka mackerel, shellfish, etc.) in water in which sodium chloride has been dissolved to allow the salt to penetrate. Alternatively, it may be a process in which water in which magnesium chloride has been dissolved is brought into contact with food (for example, a process in the production of tofu). Furthermore, it is not limited to these examples, and may also be a process in which water containing chloride ions is flowed or sprayed onto food.

[0130] In Specific Example 3, the flow path 146 may be omitted. Specific Example 3 is, for example, the configuration of Specific Example 1 shown in Figure 2, but with the supply source (breeding tank 3) changed to a food processing unit. Except for the supply source, the same configuration and control as the water treatment system 1 in Specific Example 2 may be used, and some parts of that configuration (for example, the filtration tank 17, the flow path 47, etc.) may be omitted.

[0131] <Second Embodiment> 2-1. Overview of the Water Treatment System Figure 9 schematically shows the water treatment system of the second embodiment. The water treatment system 200 shown in Figure 9 is a water treatment system that treats water introduced from a supply source 120, which contains or flows water that has come into contact with organic matter, as the water to be treated.

[0132] The supply source 120 is the same as the supply source 120 of the first embodiment, for example, the rearing tank 3 of Specific Example 1 is used. The first region section 101 and the removal section 105 are the same as the first region section 101 and the removal section 105 of the first embodiment, for example, the solid matter removal section 5 as shown in Figure 8 is used. The removal section 105 functions to remove at least solid matter in the first region where the target water is stored or flows.

[0133] In the water treatment system 200 shown in Figure 9, a biological filtration unit 202 is provided in place of the electrolysis unit 111 and the second region unit 102. The biological filtration unit 202 is configured as a biological filtration tank containing microorganisms capable of decomposing ammonia, and the region within the biological filtration tank is designated as the second region where the target water is stored or flows. In this second region, the biological filtration unit 202 decomposes ammonia using microorganisms.

[0134] The water treatment system 200 in Figure 9 is provided with a main channel 140. The main channel 140 has a channel 143 that flows the target water W from the second region in the biological filtration section 202 to the switching section 134, a channel 144 that flows the target water W downstream from the switching section 134, and an internal channel within the switching section 134 that flows the target water W from channel 143 to channel 144. In other words, channel 143, the internal channel, and channel 144 constitute at least a part of the main channel 140.

[0135] 2-2. Guidance part The guide unit 130 directs the target water, which is stored or flows in the second region or downstream of the second region, from a first position downstream of the biological filtration unit 202 to a second position upstream of the first position, via a path different from the main flow path 140. The second position may be downstream of the supply source 120 and upstream of the biological filtration unit 202, or it may be the biological filtration unit 202 itself.

[0136] In the main flow channel 140, the flow channel 143, the internal flow channel, and the flow channel 144 function as downstream flow channels that carry the target water downstream from the second region. The guide section 130 includes a return flow channel 132 that branches off from the downstream flow channel. The return flow channel 132 is a flow channel that returns some or all of the target water that has entered the downstream flow channel and carries it to the second position.

[0137] The guide unit 130 includes a switching unit 134. The switching unit 134 switches between a first switching state and a second switching state. The first switching state is a state in which the flow of target water through the return channel 132 to the second position is blocked, while allowing the target water to flow through the downstream channel downstream of the switching unit 134. The second switching state is a state in which the flow of target water through the return channel 132 to the second position is blocked, while blocking the flow through the downstream channel downstream of the switching unit 134.

[0138] In this embodiment as well, a sensor 160 is provided that detects a numerical value of an element indicating the water quality of the target water at a predetermined position downstream of the second region, or detects whether or not the element meets a standard. The control unit 252 may perform control to switch the switching unit 134 based on the detection result of the sensor 160. The sensor 160 may be configured as, for example, an ammonium ion sensor. In this case, the control device 52 may perform control to set the system to a second switching state when the value of the ammonium ion concentration detected by the sensor 160 (ammonium ion sensor) (detected value) is equal to or greater than the standard value, and to a first switching state when the value of the ammonium ion concentration detected by the sensor 160 (ammonium ion sensor) (detected value) is less than the standard value.

[0139] <Third Embodiment> 3-1. Overview of a recycled water generation system for food processing The recycled water generation system 301 illustrated in Figure 11 is a system used to recycle water used in food processing plants.

[0140] The recycled water generation system 301 of this embodiment is a system in which, after processing water (treated water) that has been brought into contact with food in a food processing plant, is passed through a solid matter removal unit 305, an electrolysis unit 313, a reaction unit 315, and a residual chlorine removal unit 321 for treatment, and the resulting recycled water is guided from a guide unit (flow channel 346) toward a predetermined area.

[0141] As shown in Figure 11, the recycled water generation system 301 mainly comprises a food processing unit 303, a solid matter removal unit 305, an electrolysis unit 313, a residual chlorine removal unit 321, a flow path 346 (an example of an induction unit), and a water storage unit 325. Furthermore, the recycled water generation system 301 also includes an ozone generation unit 309 and a reaction unit 315 (an example of a sterilization tank). The electrical configuration of the recycled water generation system 301 is as shown in Figure 16, for example.

[0142] 3-2. Configuration and operation of each part (Food processing volume 303) The food processing unit 303 shown in Figure 11 is a food processing plant where water containing chloride ions is brought into contact with food. Examples of water containing chloride ions include water containing sodium chloride, magnesium chloride, bittern, and mixtures thereof. Examples of processes in which water containing chloride ions is brought into contact with food include immersing fish roe (herring roe, cod roe, etc.), seafood (salmon, trout, cod, mackerel, Atka mackerel, shellfish, etc.) in water in which sodium chloride has been dissolved to allow the salt to penetrate. Alternatively, it may be a process in which water in which magnesium chloride has been dissolved is brought into contact with food (for example, a process in the production of tofu). Furthermore, it is not limited to these examples, and may also be a process in which water containing chloride ions is flowed or sprayed onto food.

[0143] (Solid removal section 305) The solid matter removal unit 305 shown in Figure 11 has the function of removing at least solid matter from the treated water sent from the food processing unit 303. The treated water sent from the food processing unit 303 is guided to the solid matter removal unit 305 through the flow path 341. The method for flowing the treated water from the food processing unit 303 to the solid matter removal unit 305 may be by using a pump, or by using a difference in elevation.

[0144] As shown in Figure 12, the solid matter removal unit 305 includes an ozone generation unit 309, a supply unit 307, an introduction unit 362, an outlet unit 364, etc. In this embodiment, the supply unit 307 has the function of supplying ozone generated in the ozone generation unit 309 to the treated water. The recycled water generation system 301 of this embodiment has an ozone removal unit that removes ozone from the treated water supplied with ozone by the supply unit 307. In this embodiment, the residual chlorine removal unit 321 is the ozone removal unit (details will be described later).

[0145] The ozone generating unit 309 generates ozone, for example, by a known method, and supplies the generated ozone to the supply unit 307. The method of introducing ozone from the ozone generating unit 309 to the supply unit 307 is not particularly limited, but one example is to supply the ozone generated in the ozone generating unit 309 through an air inlet provided in the foam generating unit 308 of a known foam separator. The supply unit 307 has a foam separator 307A that generates foam containing ozone generated in the ozone generating unit 309 and operates to adsorb solid matter contained in the treated water sent from the food processing unit 303 onto the foam.

[0146] The introduction section 362 is a flow path that introduces treated water sent from the food processing section 303 into the supply section 307. The discharge section 364 has a flow path that discharges the water to an area where a process following the process performed in the solid matter removal section 305 (solid matter removal process) is carried out. In this embodiment, the area where the process following the solid matter removal section 305 is carried out is the electrolysis area section 311.

[0147] In the solid matter removal section 305, solid matter such as garbage, removal proteins from fish and shellfish metabolites, bacteria, viruses, and parasites contained in the treated water introduced into the supply section 307 are removed from the treated water by adhering to fine bubbles generated in the foam separator 307A. Moreover, since the bubbles generated in the foam separator 307A contain ozone, they have high sterilizing power, and this sterilizing power also acts on the treated water that passes through the foam separator 307A and is discharged to the outlet section 364. Through this operation, it is possible to reliably suppress the outflow of contaminants into the subsequent electrolysis section 311 and reliably suppress the interference of contaminants with electrolysis in the electrolysis section 311.

[0148] As shown in Figure 12, the supply unit 307 includes a foam generating unit 308 and a foam separator 307A. Furthermore, a filter (not shown) is provided to cover the inlet (water intake) of the introduction unit 362, which is configured as a pipe. Treated water that can pass through the filter is introduced from the introduction unit 362 to the supply unit 307. The filter is configured to block the passage of large particles and allow the passage of small particles, and is, for example, configured in a mesh shape. Although not shown in Figure 12, a pump may be provided to circulate the treated water so that it flows into the supply unit 307 through the introduction unit 362.

[0149] The foam generating unit 308 injects gas containing ozone generated in the ozone generating unit 309 into the treated water flowing in from the inlet 362, causing the treated water passing through the foam generating unit 308 to contain bubbles of ozone-containing gas. The treated water that has passed through the foam generating unit 308, containing ozone-containing bubbles, flows into the foam separator 307A via the inlet 363, which is configured as a pipe. In the foam separator 307A, bubbles with solid matter attached are separated so that they gather near the water surface, and the gathered bubbles are discharged to the outside of the foam separator 307A through the discharge passage 365. Meanwhile, the treated water on the lower side of the foam separator 307A is discharged through the outlet 364, which is configured as a pipe. The treated water discharged from the outlet 364 is supplied to the electrolysis unit 313 through the flow path 342.

[0150] (Electrolysis section) In the electrolysis unit 313 shown in Figure 13, electrolysis is performed. In the electrolysis unit 313, treated water that has passed through the flow path 342 from the solids removal unit 305 is stored or flows. In the electrolysis unit 313, chlorate compounds (for example, sodium hypochlorite) are generated by electrolyzing the treated water. Furthermore, because chlorate compounds are generated by the electrolysis unit 313, the treated water can be sterilized, deodorized, and decolorized.

[0151] If the water containing chloride ions used in the process carried out in the food processing unit 303 is water containing sodium chloride, then in the electrolysis unit 313, electrolysis is performed as shown in formula (1) below, for example. 2NaCl+3H2O→NaClO+NaCl+2H2O+H2↑···(1)

[0152] In the electrolysis unit 313 shown in Figure 13, an electrode unit 355 is arranged inside the electrolysis unit 313 and electrolysis is performed. The electrolysis unit 313 has an electrode unit 355 having a first electrode 355A and a second electrode 355B, and a voltage application unit 351 that applies a voltage between the first electrode 355A and the second electrode 355B.

[0153] The voltage application unit 351 includes a control device 352 and a drive circuit 353. The control device 352 is an information processing device that includes an information processing unit, a storage unit, a communication unit, etc., and is capable of performing various controls and calculations. The drive circuit 353 is a circuit that applies a voltage between the electrodes of the first electrode 355A and the second electrode 355B in response to a command from the control device 352.

[0154] The electrode section 355 includes an electrode holding section 355C that holds a first electrode 355A and a second electrode 355B, and the first electrode 355A, the second electrode 355B, and the electrode holding section 355C are integrally configured. The integrally configured electrode section 355 can be attached to and detached from the electrolysis area section 311 (electrolysis chamber). The configuration for making the electrode section 355 detachable from the electrolysis area section 311 is not particularly limited, but for example, when attaching, the electrode holding section 355C is placed on a mounting base provided in the electrolysis area section 311, and when removing, the electrode holding section 355C is detached from the mounting base. In the example in Figure 13, a plurality of first electrodes 355A and a plurality of second electrodes 355B are provided, and both the plurality of first electrodes 355A and the plurality of second electrodes 355B are made of metal material and are plate-shaped. In the electrode section 355, the first electrode 355A and the second electrode 355B are arranged alternately with a gap between them. Multiple first electrodes 355A are short-circuited with each other and are electrically connected to the first terminal of the drive circuit 353 via a conductive path 354A. Multiple second electrodes 355B are short-circuited with each other and are electrically connected to the second terminal of the drive circuit 353 via a conductive path 354B. In the example shown in Figure 13, the first electrodes 355A and the second electrodes 355B are arranged alternately with a gap between them.

[0155] As the electrode material, a metallic material that is not corroded by water containing chloride ions and has a high efficiency in generating chlorate compounds is desirable. For example, an electrode made by coating the surface of titanium with a platinum-iridium alloy can be suitably used. Platinum has excellent conductivity and corrosion resistance, iridium has excellent durability and chemical stability, and platinum-iridium alloy has the characteristic of a uniform and smooth surface. An electrode made by coating the surface of titanium with a platinum-iridium alloy can be used as both an anode and a cathode. Note that the electrode example described here is merely an example, and if the electrode inversion method described later is not used, an electrode made of titanium coated with ruthenium may be used as the anode, or other materials may be used.

[0156] In the electrolysis chamber 311 (electrolysis tank), treated water is introduced from the inlet 311A ​​located at the lower end of the electrode section 355. The electrolysis chamber 311 is equipped with a water flow generator, which generates a water flow from the lower side to the upper side (electrode side) of the electrode section 355 in Figure 13. The treated water that enters the electrode section 355 in this manner is electrolyzed to generate chlorate compounds, which are used to sterilize, deodorize, and decolorize the treated water. The sterilized, deodorized, and decolorized treated water is discharged from the outlet 311B located at the upper end of the electrolysis chamber 311 (electrolysis tank) and supplied to the reaction section 315 through the flow path 343.

[0157] (Reaction section) In this embodiment, the reaction unit 315 has the function of storing treated water that has flowed through a channel 343 (an example of a first channel) that carries treated water that has passed through the electrolysis unit 313, and storing treated water containing chlorate compounds for a predetermined time. In the reaction unit 315, treated water containing chlorate compounds supplied from the electrolysis unit 313 through the channel 343 is stored, and the treated water is subjected to treatments such as sterilization, deodorization, and decolorization. The reaction unit 315 is an example of a sterilization tank. The time for storing the treated water (predetermined time) can be appropriately set considering the degree of treatment such as sterilization, deodorization, and decolorization of the treated water in the preceding process (electrolysis process). Furthermore, the time for storing the treated water in the reaction unit 315 can be set considering the numerical value of the residual chlorine concentration detected by the residual chlorine concentration detection unit 319 described later.

[0158] As shown in Figure 15, the treated water stored in the reaction section 315 and treated with sterilization and other processes is led to the flow path 345 (an example of a second flow path). The flow path 345 is a flow path that carries the treated water from the reaction section 315 towards the residual chlorine removal section 321. The flow path 345 is equipped with a residual chlorine concentration detection unit 319 (an example of a second residual chlorine concentration detection unit) and a second switching unit 345Z (an example of a switching unit). In other words, the residual chlorine concentration detection unit 319 is located downstream of the reaction section 315 (i.e., downstream of the electrolysis section 313) and upstream of the residual chlorine removal section 321.

[0159] The residual chlorine concentration detection unit 319 is a sensor that detects the concentration of residual chlorine in the treated water from the time it passes through the reaction unit 315 until it flows into the residual chlorine removal unit 321. For example, it detects the concentration of residual chlorine in the treated water flowing through the channel between the reaction unit 315 and the residual chlorine removal unit 321. In the representative example shown in Figure 15, the residual chlorine concentration detection unit 319 detects the residual chlorine contained in the treated water flowing through the channel 345A led out from the reaction unit 315. This makes it possible to confirm whether sterilization with an appropriate concentration of residual chlorine is being performed. In this specification, residual chlorine refers to the combined chlorine and free chlorine remaining in the treated 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 treated water, is the amount of residual chlorine. By detecting residual chlorine contained in the treated water in the region between the reaction unit 315 and the residual chlorine removal unit 321, the residual chlorine concentration detection unit 319 can measure the amount of chlorate compounds remaining after sterilization of the treated water in the electrolysis region 311 and the reaction unit 315.

[0160] The second switching unit 345Z has the function of switching between an permitted state, which allows treated water to flow from the electrolysis unit 313 to the residual chlorine removal unit 321 (in a typical example, the activated carbon tank 317), and a blocked state, which blocks the flow of treated water from the electrolysis unit 313 to the residual chlorine removal unit 321. When the second switching unit 345Z is in the permitted state, the treated water flowing through the flow path 345A downstream of the electrolysis unit 313 and upstream of the residual chlorine removal unit 321 (for example, between the reaction unit 315 and the second switching unit 345Z) flows through the flow path 345B and is introduced into the residual chlorine removal unit 321. On the other hand, when the second switching unit 345Z is in the shut-off state, the treated water flowing through the flow path 345A, which is downstream of the electrolysis unit 313 and upstream of the residual chlorine removal unit 321 (activated carbon tank 317) (for example, between the reaction unit 315 and the second switching unit 345Z), does not flow in the direction of flow path 345B, but instead flows through flow path 348, is returned upstream of the electrolysis unit 313, and is introduced back into the electrolysis unit 313.

[0161] (Residual chlorine removal section) In the example shown in Figure 14, the activated carbon tank 317 constitutes the residual chlorine removal section 321. The activated carbon tank 317 has the function of removing at least residual chlorine from the treated water, and functions to remove residual chlorine from the treated water by passing the treated water through the activated carbon tank 317. The activated carbon tank 317 is a tank in which the treated water that has passed through the reaction section 315 is stored, and specifically, it is a tank located downstream of the area in which the residual chlorine concentration detection section 319 is located (see Figure 15). The activated carbon tank 317 functions as a tank for removing chloric acid compounds (e.g., sodium hypochlorite) generated in the electrolysis section 311. The activated carbon tank 317 is provided with an activated carbon section 323 containing activated carbon. In this embodiment, the activated carbon tank 317 removes at least residual chlorine and residual ozone from the treated water in the activated carbon tank 317 using activated carbon. In other words, in this embodiment, the residual chlorine removal unit 321 (specifically the activated carbon tank 317) is the ozone removal unit, which removes residual chlorine and ozone from the treated water.

[0162] In the activated carbon tank 317, for example, a reaction like the one shown in equation (2) below occurs, which can remove excess chlorate compounds that were not used for sterilization or other treatments. HClO + C → CO + H + +Matsu - ...(2)

[0163] The activated carbon tank 317 can be configured as shown in Figure 14, for example. In the example in Figure 14, the activated carbon tank 317 is configured as a flow path for treated water, and the activated carbon section 323 is configured such that activated carbon particles fill the internal space of the flow path. In the activated carbon tank 317, treated water is configured to flow through the gaps in the activated carbon section 323 (specifically, the gaps in the internal space filled with activated carbon particles). As the treated water flows in from the inlet 321A of the activated carbon tank 317 and passes through the gaps between the many particles inside the activated carbon tank 317, residual chlorine and residual ozone contained in the treated water are adsorbed onto the activated carbon, and the water discharged from the outlet 321B becomes regenerated water from which some or all of the chlorine and ozone have been removed.

[0164] In a typical example, the residual chlorine removal unit 321 is composed of an activated carbon tank 317, but it may also include elements other than the activated carbon tank 317, and other elements may be used as long as they have the function of removing residual chlorine.

[0165] The reclaimed water discharged from outlet 321B can be introduced into the water storage section 325 (an example of a predetermined area) through a channel 346 (an example of an induction section). As shown in Figure 15, the channel 346 between the residual chlorine removal section 321 (activated carbon tank 317) and the water storage section 325 is provided with a residual chlorine concentration detection section 327 (an example of a first residual chlorine concentration detection section) and a first switching section 346Z (an example of a switching section). In other words, the system 301 of this embodiment includes a residual chlorine concentration detection section 327 that detects the concentration of residual chlorine downstream of the residual chlorine removal section 321.

[0166] The first switching unit 346Z has the function of switching between a first state (permission state) that allows reclaimed water to flow toward the water storage unit 325 in the flow path 346, and a second state (blocking state) that blocks the flow of reclaimed water toward the water storage unit 325. When the first switching unit 346Z is in the first state, the reclaimed water flowing in the flow path 346A (the flow path between the residual chlorine removal unit 321 and the first switching unit 346Z) flows through the flow path 346B and is supplied to the water storage unit 325. On the other hand, when the first switching unit 346Z is in the second state, the reclaimed water flowing in the flow path 346A (the flow path between the residual chlorine removal unit 321 and the first switching unit 346Z) flows through the flow path 349 and is returned to the downstream side of the electrolysis unit 313 and upstream of the residual chlorine removal unit 321, and then flows again through the flow path 345B and is introduced to the residual chlorine removal unit 321. The recycled water, once again introduced into the residual chlorine removal unit 321, has the residual chlorine removed.

[0167] The residual chlorine concentration detection unit 327 is a sensor that detects the concentration of residual chlorine in the reclaimed water in the flow path 346, where the reclaimed water that has passed through the residual chlorine removal unit 321 is stored or flows before it flows toward the water storage unit 325. In the example shown in Figure 15, it detects the concentration of residual chlorine in the reclaimed water within the flow path 346. The residual chlorine concentration detection unit 327 can more accurately detect fluctuations in residual chlorine concentration caused by leakage, such as when residual chlorine leaks out due to deterioration of the activated carbon provided in the activated carbon unit 323.

[0168] Here, if the residual chlorine concentration detected by the residual chlorine concentration detection unit 327 is below a predetermined value, it is highly likely that the residual chlorine contained in the treated water has been sufficiently removed by the residual chlorine removal unit 321. However, if the residual chlorine concentration is higher than the predetermined value, it is possible that the residual chlorine removal unit 321 has not adequately removed the residual chlorine in the treated water. Therefore, the switching between the first state and the second state in the first switching unit 346Z may be performed based on whether or not the residual chlorine concentration detected by the residual chlorine concentration detection unit 327 is below a predetermined value.

[0169] 3-3. Control of the recycled water generation system 301 (Configuration for control) In the recycled water generation system 301 of this embodiment, the treated water in the food processing unit 303 flows in the following order: solid matter removal unit 305, electrolysis unit 313, reaction unit 315 (sterilization tank), residual chlorine removal unit 321 (activated carbon tank 317), and water storage unit 325. Along the path from the food processing unit 303 to the water storage unit 325, there are multiple pumps (not shown) that circulate the treated water. The control device 352 shown in Figure 16 controls the driving and stopping of the above pumps. Furthermore, the control device 352 controls the driving and stopping of the ozone generation unit 309, the foam separator 307A, and the electrolysis unit 313.

[0170] The control device 352 shown in Figure 12 receives the detected values ​​from the residual chlorine concentration detection unit 319 (second residual chlorine concentration detection unit) and the residual chlorine concentration detection unit 327 (first residual chlorine concentration detection unit). The detected value input from the residual chlorine concentration detection unit 319 indicates the concentration of residual chlorine contained in the treated water of the aforementioned flow path 345A. The detected value input from the residual chlorine concentration detection unit 327 indicates the concentration of residual chlorine contained in the water of the aforementioned flow path 346A.

[0171] (Control of electrolysis) The control device 352 is an example of a control unit and controls the electrolysis of the electrolysis unit 313. The control device 352 may also control the electrolysis of the electrolysis unit 313 based on the measurement results of the residual chlorine concentration detection unit 319. When the control device 352 controls the electrolysis of the electrolysis unit 313 based on the measurement results of the residual chlorine concentration detection unit 319, for example, it may control the current flowing between the first electrode 355A and the second electrode 355B so that the detected value of the residual chlorine concentration detection unit 319 is equal to or greater than a predetermined value.

[0172] The control device 352 is configured to detect the current flowing between the first electrode 355A and the second electrode 355B in the electrolysis unit 313, and continuously monitors the current flowing between the first electrode 355A and the second electrode 355B. Various configurations can be adopted for the control device 352 to monitor the current flowing between the first electrode 355A and the second electrode 355B. For example, the current may be detected by a current sensor, and the control device 352 may acquire the value detected by the current sensor, or other configurations may be used. The control device 352 can then control the current flowing between the first electrode 355A and the second electrode 355B based on the value detected by the residual chlorine concentration detection unit 319.

[0173] (Control based on monitoring of residual chlorine in treated water) When a predetermined measurement result is obtained by the residual chlorine concentration detection unit 319, the state of the second switching unit 345Z may be switched to stop or allow the treated water flowing through the flow path 345A to flow to the residual chlorine removal unit 321.

[0174] In a typical example, the second switching unit 345Z is configured as an electrically controllable three-way valve, and when the control device 352 performs a first control on the second switching unit 345Z (for example, when the control device 352 gives a first instruction to the second switching unit 345Z by an electrical signal), the second switching unit 345Z enters a permit state that allows treated water to flow from the electrolysis unit 313 to the residual chlorine removal unit 321. When the control device 352 performs a first control on the second switching unit 345Z, the second switching unit 345Z blocks the flow from the flow path 345A to the flow path 348. However, it is not limited to this blocking operation, and when the control device 352 performs a first control on the second switching unit 345Z, the second switching unit 345Z may allow the flow from the flow path 345A to the flow path 348.

[0175] On the other hand, when the control device 352 performs a second control on the second switching unit 345Z (for example, when the control device 352 gives a second instruction to the second switching unit 345Z by an electrical signal), the second switching unit 345Z enters a shut-off state that blocks the flow of treated water from the electrolysis unit 313 to the residual chlorine removal unit 321. When the control device 352 performs a second control on the second switching unit 345Z, the second switching unit 345Z allows water to flow from the flow path 345A to the flow path 348, and water flows from the flow path 345A to the flow path 348 and is returned to the electrolysis region 311. The water returned from the flow path 345A through the flow path 348 may be returned to the region of the electrolysis unit 313, or it may be returned to a region upstream of the electrolysis unit 313.

[0176] More specifically, for example, the switching between the permitted state and the shut-off state in the second switching unit 345Z can be set based on whether the residual chlorine concentration detected by the residual chlorine concentration detection unit 319 is above a predetermined value. For example, the control device 352 may set the second switching unit 345Z to the permitted state when the residual chlorine concentration detected by the residual chlorine concentration detection unit 319 is above a predetermined value, and control the control device 352 to the shut-off state when the residual chlorine concentration detected by the residual chlorine concentration detection unit 319 is below a predetermined value. In this configuration, when the residual chlorine concentration detected by the residual chlorine concentration detection unit 319 is below a predetermined value, that is, when the residual chlorine is relatively low and the sterilization effect is relatively small, the shut-off state is reached, and the treated water does not flow to the flow path 345B or the residual chlorine removal unit 321, but flows through the flow path 348 and is returned to the upstream side (for example, the electrolysis unit 313 or upstream of the electrolysis unit 313). Then, this treated water is introduced again into the electrolysis unit 313, where electrolysis is performed to increase the residual chlorine concentration, and it then flows through the reaction unit 315. On the other hand, if the residual chlorine concentration detected by the residual chlorine concentration detection unit 319 is above a predetermined value, that is, if the residual chlorine is relatively high and the sterilization effect is relatively likely to be relatively greater, the above-mentioned permitted state is reached, and the treated water flowing through the flow path 345A flows through the flow path 345B and is supplied to the residual chlorine removal unit 321. In other words, only treated water with a relatively high residual chlorine concentration and a higher probability of sufficient sterilization can be sent to the residual chlorine removal unit 321 downstream.

[0177] In the example described above, the second switching unit 345Z is a valve (for example, a three-way valve) that is switched by electrical control, but the second switching unit 345Z may also be configured to be switched manually between the permitted state and the shut-off state.

[0178] (Control based on monitoring of residual chlorine in recycled water) When a predetermined measurement result is obtained by the residual chlorine concentration detection unit 327, the state of the first switching unit 346Z may be switched to stop or allow the reclaimed water flowing through the flow path 346A to flow into the water storage unit 325.

[0179] In a typical example, the first switching unit 346Z is composed of an electrically controllable three-way valve, and when the control device 352 performs first switching control on the first switching unit 346Z (for example, when the control device 352 gives a first switching instruction to the first switching unit 346Z by an electrical signal), the first switching unit 346Z enters a permit state that allows treated water to flow from the residual chlorine removal unit 321 to the water storage unit 325. When the control device 352 performs first switching control on the first switching unit 346Z, the first switching unit 346Z blocks the flow from the flow path 346A to the flow path 349. However, it is not limited to this blocking operation, and when the control device 352 performs first switching control on the first switching unit 346Z, the first switching unit 346Z may allow the flow from the flow path 346A to the flow path 349.

[0180] On the other hand, when the control device 352 performs a second switching control on the first switching unit 346Z (for example, when the control device 352 gives a second switching instruction to the first switching unit 346Z by an electrical signal), the first switching unit 346Z enters a shut-off state that blocks the flow of treated water from the residual chlorine removal unit 321 to the water storage unit 325. When the control device 352 performs a second switching control on the first switching unit 346Z, the first switching unit 346Z allows water to flow from the flow path 346A to the flow path 349, and the water flows from the flow path 346A to the flow path 349 and is returned to the upstream side. The water returned from the flow path 346A through the flow path 349 may be returned to the area upstream of the residual chlorine removal unit 321 (flow path 345B in the example of Figure 15), as shown in Figure 15, or it may be returned to the area of ​​the residual chlorine removal unit 321.

[0181] For example, the control device 352 controls the first switching unit 346Z to the first state (the above-mentioned permission state) if the residual chlorine concentration detected by the residual chlorine concentration detection unit 327 is below a predetermined value, and to the second state (the above-mentioned shut-off state) if the residual chlorine concentration detected by the residual chlorine concentration detection unit 327 is higher than the predetermined value. When this control is performed, if the residual chlorine concentration downstream of the residual chlorine removal unit 321 is higher than the predetermined value, that is, if the residual chlorine removal unit 321 has not been able to remove residual chlorine to below the standard, the first switching unit 346Z will be in the second state (the above-mentioned shut-off state), and the regenerated water will not flow into the flow path 346B but will flow into the flow path 349 and be returned upstream of the residual chlorine removal unit 321. As a result, the regenerated water is introduced back into the residual chlorine removal unit 321, and the residual chlorine is removed again by the activated carbon unit 323. On the other hand, if the residual chlorine concentration is below a predetermined value, and the residual chlorine has been removed to below the standard level by the residual chlorine removal unit 321, the first switching unit 346Z enters the first state (the permitted state described above), and the reclaimed water flowing through the flow path 346A flows through the flow path 346B and is supplied to the water storage unit 325. In other words, reclaimed water from which residual chlorine has been removed to below the standard level is stored in the water storage unit 325. The predetermined value of the residual chlorine concentration can be appropriately determined considering the water quality required for the reclaimed water.

[0182] When the first switching unit 346Z enters the first state, the reclaimed water that flows through the channel 346B and is supplied to the water storage unit 325 is stored in the water storage unit 325 and supplied from the water storage unit 325 to a place where food processing is carried out (for example, the food processing unit 303) as needed. In the example shown in Figure 11, the water (reclaimed water) that flows through the channel 346B is introduced into the water storage unit 325, and the water storage unit 325 is configured as a tank for storing water (reclaimed water). However, the example is not limited to this, and the water that flows through the channel 346B may be supplied to other areas (for example, the food processing unit 303).

[0183] In the example described above, the first switching unit 346Z is a valve (for example, a three-way valve) that is switched by electrical control, but the first switching unit 346Z may also be configured to be switched manually between the permitted state and the shut-off state.

[0184] 3-4. Cleaning of electrodes As shown in Figure 13, in this embodiment, the control device 352 and the drive circuit 353 function as a voltage application unit 351. The voltage application unit 351 operates to switch between a state in which a voltage is applied so that the first electrode 355A is the anode and the second electrode 355B is the cathode to perform electrolysis in the electrolysis region 311 (third state), and a state in which a voltage is applied so that the second electrode 355B is the anode and the first electrode 355A is the cathode (fourth state). For example, the voltage application unit 351 periodically switches between continuing the third state to electrolyze the treated water and continuing the fourth state to electrolyze the treated water. The switching cycle when switching periodically may be, for example, every few tens of minutes, every few hours, every day, or any other cycle.

[0185] The timing at which the voltage application unit 351 switches between the third and fourth states is not limited to periodic timings, but may also be when predetermined conditions are met. For example, the switch may occur when the operating time of the recycled water generation system 301 has reached a certain period since the last switch, when a value detected by some sensor reaches a predetermined value, at a randomly determined timing, or at any other timing.

[0186] In this embodiment, the operation of the third state is continuously performed by continuously applying voltage using the voltage application unit 351 to make the first electrode 355A the anode and the second electrode 355B the cathode, while "exchanging treated water" is performed to continuously guide treated water from the flow path 342 to the electrolysis area 311 and to drain treated water from the electrolysis area 311 to the flow path 343. If the switching condition is met during the operation of the third state, the operation is switched from the third state to the fourth state while performing the "exchanging treated water" as described above. After the switch, the operation of the fourth state is continuously performed by continuously applying voltage using the "exchanging treated water" as described above to make the second electrode 355B the anode and the first electrode 355A the cathode. If the switching condition is met during the operation of the fourth state, the operation is switched from the fourth state to the third state while performing the "exchanging treated water" as described above. In this way, the operation of the third state and the operation of the fourth state are performed alternately. Furthermore, during the continuation of the operation in the third state or the continuation of the operation in the fourth state, the operation may be continued without interruption, or it may be temporarily interrupted for any reason.

[0187] <Other Embodiments> The present invention is not limited to the embodiments described above and in the drawings. For example, any combination of the features of the embodiments described above or below is possible as long as it does not contradict each other. Furthermore, any feature of the embodiments described above or below may be omitted unless explicitly stated as essential. In addition, the embodiments described above may be modified as follows.

[0188] In specific examples 1 and 2 of the first embodiment, an electrolysis unit 13 as shown in Figure 6 is used, but the electrolysis unit 13 may be configured as shown in Figure 10. In this example as well, the electrode unit 55 is provided with a plurality of first electrodes 55A and a plurality of second electrodes 55B, and both the plurality of first electrodes 55A and the plurality of second electrodes 55B are made of a metal material and are made in the shape of plates. In the electrode unit 55, the first electrodes 55A and the second electrodes 55B are arranged alternately with a gap between them. In this example as well, the plurality of first electrodes 55A are configured to be short-circuited with each other and are electrically connected to the first terminal of the drive circuit 53 via a conductive path 54A. The plurality of second electrodes 55B are configured to be short-circuited with each other and are electrically connected to the second terminal of the drive circuit 53 via a conductive path 54B. The electrolysis tank 11 (electrolysis region) in Figure 10 is configured as a flow path for the target water. The target water is introduced into the tank through an inlet 11E located at one end of the electrolysis tank 11 (electrolysis region), and discharged through an outlet 11D located at a different end from the inlet 11E. The space between the inlet 11E and the outlet 11D is configured, for example, as a tubular flow path.

[0189] In the above-described embodiment, ozone is supplied to the foam separator 7 as a gas to generate ozone-containing foam. However, a configuration may be used in which another gas (e.g., air) is supplied instead of ozone to generate foam of that other gas.

[0190] The configuration of the electrolysis unit in the system of specific example 3 may also be applied to the systems of specific examples 1 and 2.

[0191] In the first 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 channel without a storage portion.

[0192] In specific examples 1 and 2, 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.

[0193] In the first embodiment, the third region is the internal area of ​​the activated carbon tank 21, which is configured as a tank having a portion for storing rearing water. However, the activated carbon tank 21 may be configured as a flow channel that does not have a storage portion, and this internal area may be the third region.

[0194] In specific example 1, the standby tank 25, which is configured as a tank having a section for storing rearing water, corresponds to the fourth region 104 of the basic configuration in Figure 1, and the internal region of the standby tank 25 is the fourth region. However, the standby tank 25 may also be configured as a flow path that does not have a storage section, and this internal region may be considered the fourth region.

[0195] In the first embodiment, as shown in Figures 2 and 8, an activated carbon tank 21 is provided as a residual chlorine removal tank, which has an activated carbon section 23 filled with activated carbon granules. However, instead of activated carbon granules in the activated carbon section 23, calcium sulfite granules may be used, and the tank may be filled with calcium sulfite granules. In this example as well, the residual chlorine removal tank can be configured as a flow path having an inlet and an outlet, and the internal space of the flow path can be filled with calcium sulfite granules. In this example as well, as the rearing water flowing in from the inlet of the residual chlorine removal tank passes through the gaps in the internal space (gaps between numerous calcium sulfite granules), 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.

[0196] In the above embodiment, the target water is supplied directly from the supply source to the first region, but the target water may be supplied from the supply source to the first region via other regions. Also, in the above embodiment, the water that has passed through the third region is returned to the supply source via the fourth region, but only a portion of the water that has passed through the third region may be returned to the supply source, or the water that has passed through the third region may be returned to the flow path 141 or the first region without being returned to the supply source.

[0197] In the third embodiment, a solid matter removal unit was shown that includes a filter and a foam separator that generates foam containing ozone generated in the ozone generation unit. However, in any of the first and third embodiments, the solid matter removal unit may include only a filter, or it may not include a filter but have a foam separator.

[0198] In the above-described embodiment, a system was shown that included a residual chlorine removal unit that combined an ozone removal unit and a residual chlorine removal unit. However, the system may also include the ozone removal unit and the residual chlorine removal unit separately.

[0199] In the third embodiment, a system is shown that includes a residual chlorine concentration detection unit 327 for detecting the concentration of residual chlorine downstream of the residual chlorine removal unit 321. However, a system without the residual chlorine concentration detection unit 327 is also possible.

[0200] In the third embodiment, a system was shown that includes a residual chlorine concentration detection unit 319 for detecting the concentration of residual chlorine downstream of the reaction unit 315 and upstream of the residual chlorine removal unit 321. However, the system may not include the residual chlorine concentration detection unit 319, or it may include an additional residual chlorine concentration detection unit between the electrolysis unit 313 and the reaction unit 315.

[0201] In the third embodiment, a system is shown that includes a reaction unit 315 downstream of the electrolysis unit 313 for containing the treated water that has passed through the electrolysis unit 313 for a predetermined time. However, a system without the reaction unit 315 is also possible.

[0202] In the third embodiment, a system is shown that includes a first switching unit 346Z that switches between a first state that allows reclaimed water to flow toward the water storage unit 325 in the flow path 346 and a second state that blocks the flow of reclaimed water toward the water storage unit 325. However, the system may not include the first switching unit 346Z.

[0203] In the third embodiment, a system is shown that includes a second switching unit 345Z in the flow path 345 from the reaction unit 315 to the residual chlorine removal unit 321, which switches between an permitted state that allows treated water to flow from the electrolysis unit 313 to the residual chlorine removal unit 321 and a blocked state that blocks the flow of treated water from the electrolysis unit 313 to the residual chlorine removal unit 321. However, the system may not include the second switching unit 345Z, or the second switching unit 345Z may be provided in both the flow path 345 from the reaction unit 315 to the residual chlorine removal unit 321 and the flow path 343 from the electrolysis unit 313 to the reaction unit 315, or it may be provided only in the flow path 343.

[0204] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope set forth in the claims or equivalents thereof. [Explanation of symbols]

[0205] 1: Recirculating water treatment system 3: Breeding tank 5:Solid removal section 7: Foam separator 9: Ozone generator 11: Electrolysis cell 11A: First rearing water flow chamber 11B: Second rearing water flow chamber 11C: Third Rearing Water Flow Chamber 11Z:Bottom wall 13: Electrolysis section 15: Reaction vessel 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:Waiting tank 27: Second residual chlorine sensor 29: Ammonium ion sensor 31: Treatment Department 35: Temperature controller 37: Filter 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 part 55A: 1st electrode 55B: 2nd electrode 55C: Electrode holding part 56:1st taxiway 57: Water flow generation section 57A: First partition wall 57B: Second partition wall 58: Induction part 58A, 58B: Inclined part 59: Discharge section 59A :Pipe 59B: Opening / closing part 60: Storage tank 60A: Bottom 62: Introduction 64: Derivation part 66: Discharge section 72:Second taxiway 105:Removal section 111: Electrolysis section 121: Residual chlorine removal section 130: Induction part 132: Recirculation channel 134: Switching section 140: Main channel 152: Control Unit W1:Water surface W2:Water surface W3: Water surface

Claims

1. A water treatment system that treats water containing chloride ions, which is introduced from a supply source where water that has come into contact with organic matter is stored or flows, as the water to be treated. A first region section comprising a first region in which the target water introduced from the supply source is stored or flows, An electrolysis unit generates chlorate compounds by electrolyzing the target water in a second region where the target water that has passed through the first region is stored or flows, A residual chlorine removal unit is provided downstream of the second region and removes at least residual chlorine in the third region where the target water that has passed through the second region is stored or flows, A main channel having a channel for flowing the target water from the second region to the third region, A guide unit that guides the target water stored or flowing in the second region or downstream of the second region from a first position downstream of the electrolysis unit toward a second position downstream of the supply source and upstream of the electrolysis unit, along a path different from the main flow path, An aeration unit that performs aeration on the target water in a region other than the first region, upstream of the first region or the second region, A water treatment system having

2. Having a removal unit that removes at least solid matter from the target water in the first region The water treatment system according to claim 1.

3. The removal unit has a foam separator that generates foam and adsorbs the solid matter contained in the target water onto the foam. The water treatment system according to claim 2.

4. Having an ozone generating unit that generates ozone, The foam separator generates foam containing ozone generated in the ozone generating unit. The water treatment system according to claim 3.

5. The first position is located downstream of the electrolysis unit and upstream of the residual chlorine removal unit. The water treatment system according to claim 1.

6. The second position is in the first region or upstream of the first region. The water treatment system according to claim 2.

7. A sensor that detects a numerical value of an element indicating the water quality of the target water at a predetermined position downstream of the second region, or detects whether the element meets a standard. The water treatment system according to claim 1.

8. The main flow channel includes a downstream flow channel that flows the target water downstream from the second region, The induction section comprises a return channel branching off from the downstream channel and a switching section provided in the downstream channel. The switching unit switches between a first switching state in which the target water is prevented from flowing through the return channel to the second position while allowing the target water to flow through the downstream channel downstream of the switching unit, and a second switching state in which the target water is prevented from flowing through the downstream channel downstream of the switching unit while allowing the target water to flow through the return channel to the second position. The water treatment system according to claim 1.

9. A water treatment system for treating water containing chloride ions, which is introduced from a supply source where water that has come into contact with organic matter is stored or flows, as water to be treated, A first region section comprising a first region in which the target water introduced from the supply source is stored or flows, An electrolysis unit generates chlorate compounds by electrolyzing the target water in a second region where the target water that has passed through the first region is stored or flows, A residual chlorine removal unit is provided downstream of the second region and removes at least residual chlorine in the third region where the target water that has passed through the second region is stored or flows, A main channel having a channel for flowing the target water from the second region to the third region, A guide unit that guides the target water stored or flowing in the second region or downstream of the second region from a first position downstream of the electrolysis unit toward a second position downstream of the supply source and upstream of the electrolysis unit, along a path different from the main flow path, It has, The main channel includes a downstream channel that flows the target water downstream from the second region, The induction section comprises a return channel branching off from the downstream channel and a switching section provided in the downstream channel. The switching unit switches between a first switching state in which the target water is prevented from flowing through the return channel to the second position while allowing the target water to flow through the downstream channel downstream of the switching unit, and a second switching state in which the target water is prevented from flowing through the downstream channel downstream of the switching unit while allowing the target water to flow through the return channel to the second position. Water treatment system.

10. A sensor that detects a numerical value of an element indicating the water quality of the target water at a predetermined position downstream of the second region, or detects whether the element meets a standard, A control unit that performs control to switch the switching unit based on the detection result of the sensor, A water treatment system according to claim 8 or claim 9, having the following features.

11. A water treatment method for treating water containing chloride ions, which is introduced from a supply source that contains or flows water that has come into contact with organic matter, as water to be treated, In a water treatment facility configured such that the target water supplied from the supply source is stored or flows in a first region, and the target water that has passed through the first region is stored or flows in a second region, A step of generating chlorate compounds in the target water by electrolyzing the target water in the second region using an electrolysis unit that performs electrolysis, A step of removing at least residual chlorine in a third region where the target water that has passed through the second region is stored or flows, by a residual chlorine removal unit provided downstream of the second region, The process involves flowing the target water from the second region to the third region through the main flow path, The process involves using a guide unit to cause the target water, which is stored or flows in the second region or downstream of the second region, to flow from a first position downstream of the electrolysis unit toward a second position downstream of the supply source and upstream of the electrolysis unit, along a path different from the main flow path. Perform Furthermore, the aeration unit performs aeration on the target water in areas other than the first region, upstream of the first or second region. Water treatment methods.

12. A water treatment method for treating water containing chloride ions, which is introduced from a supply source that contains or flows water that has come into contact with organic matter, as water to be treated, In a water treatment facility configured such that the target water supplied from the supply source is stored or flows in a first region, and the target water that has passed through the first region is stored or flows in a second region, A step of generating chlorate compounds in the target water by electrolyzing the target water in the second region using an electrolysis unit that performs electrolysis, A step of removing at least residual chlorine in a third region where the target water that has passed through the second region is stored or flows, by a residual chlorine removal unit provided downstream of the second region, The process involves flowing the target water from the second region to the third region through the main flow path, The process involves using a guide unit to cause the target water, which is stored or flows in the second region or downstream of the second region, to flow from a first position downstream of the electrolysis unit toward a second position downstream of the supply source and upstream of the electrolysis unit, along a path different from the main flow path. Perform In the main channel, a downstream channel is provided for flowing the target water downstream from the second region. In the guide section, a return channel branching off from the downstream channel and a switching section provided in the downstream channel are provided. The switching unit switches between a first switching state in which the target water is prevented from flowing through the return channel to the second position while allowing the target water to flow through the downstream channel downstream of the switching unit, and a second switching state in which the target water is allowed to flow through the return channel to the second position while preventing it from flowing through the downstream channel downstream of the switching unit. Water treatment methods.

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