Culture drainage treatment system

Abstract

To provide a culture drainage treatment system that can improve water quality of culture drainage.SOLUTION: A culture drainage treatment system 40 for treating culture drainage discharged from a culture aquarium 10 in which fish F is reared comprises an algae cultivation device 44 for making at least one of algae or floating grass absorb ammonia nitrogen contained in the culture drainage. The culture drainage having a higher salt concentration than that of fresh water is supplied to the algae cultivation device 44. The treatment system 40 also comprises a first layer 42 and a second layer 43 which are arranged upstream of the algae cultivation device 44 in a flow direction of the culture drainage, and generate iron capable of being absorbed by at least one of the algae or the floating grass.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technology for aquaculture wastewater treatment system for treating aquaculture wastewater discharged from aquaculture tanks in which fish are raised. [Background technology]

[0002] When cultivating fish in aquaculture tanks (for example, on land), ammonia nitrogen and other substances are produced in the water from fish waste and leftover feed, causing the water quality of the tank to deteriorate. For this reason, it is necessary to drain or purify the water with deteriorated quality from the tanks.

[0003] Patent Document 1 discloses a method for purifying aquaculture wastewater discharged from aquaculture tanks by combining fish farming and plant cultivation. In the method of Patent Document 1, ammonia nitrogen in the aquaculture wastewater is nitrified in a cultivation filter tank and converted to nitrate nitrogen. The nitrate nitrogen is absorbed by vegetables as a nutrient. The aquaculture wastewater thus purified is returned to the aquaculture tanks. This makes it possible to reduce wastewater treatment costs for land-based aquaculture, reduce fertilizer costs for vegetable cultivation, and increase profits from the sale of fish and vegetables.

[0004] If it were possible to cultivate saltwater fish, which are more popular as food than freshwater fish, it would be possible to further increase profits. In order to cultivate saltwater fish, it is necessary to use saltwater such as seawater. However, when cultivating plants in saltwater, the saltwater makes it difficult for the plants to absorb nitrate nitrogen, which is a weakly toxic substance for fish, and there is a possibility that the concentration of nitrate nitrogen will increase.

[0005] As described above, it is anticipated that conventional techniques may not be able to sufficiently improve the water quality of aquaculture wastewater depending on the type of fish being farmed, and therefore there is a demand for techniques that can improve the water quality of aquaculture wastewater. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2-222624 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and the problem to be solved by the present invention is to provide an aquaculture wastewater treatment system capable of improving the water quality of the aquaculture wastewater. [Means for solving the problem]

[0008] The problem to be solved by the present invention has been described above, and the means for solving this problem will now be described.

[0009] That is, claim 1 provides an aquaculture wastewater treatment system for treating aquaculture wastewater discharged from aquaculture tanks in which fish are raised, the system comprising an absorption section for causing at least one of algae or floating plants to absorb ammonia nitrogen contained in the aquaculture wastewater.

[0010] In claim 2, the aquaculture wastewater having a higher salt concentration than fresh water is supplied to the absorption section.

[0011] In claim 3, the aquaculture wastewater further comprises an addition section that is arranged upstream of the absorption section in the flow direction of the aquaculture wastewater and adds iron that can be absorbed by at least one of the algae or floating plants to the aquaculture wastewater.

[0012] In claim 4, the adding section comprises a first section which adds humus components to the aquaculture wastewater, and a second section which is disposed between the first section and the absorbing section in the flow direction and which adds at least iron ions to the aquaculture wastewater.

[0013] In claim 5, the apparatus further comprises a third section that is disposed downstream of the absorption section in the flow direction and nitrifies ammonia nitrogen contained in the aquaculture wastewater.

[0014] In claim 6, the second portion adds iron ions and potassium to the aquaculture wastewater.

[0015] In claim 7, the apparatus further comprises a fourth portion for adding calcium to the aquaculture wastewater.

[0016] In claim 8, the fourth portion is disposed downstream of the third portion in the flow direction.

[0017] In claim 9, at least one of the first portion, the second portion, the third portion, and the fourth portion is detachably provided on a member that forms a circulation path for the aquaculture wastewater.

[0018] In claim 10, the apparatus further comprises a recovery section for recovering the algae cultivated in the absorption section. Effect of the Invention

[0019] The present invention has the following advantages.

[0020] In claim 1, the water quality of aquaculture wastewater can be improved by algae or floating plants.

[0021] In claim 2, the quality of aquaculture wastewater with a high salt concentration can be improved.

[0022] In claim 3, it is possible to suppress adverse effects on the growth of algae and the like caused by iron deficiency, and to facilitate absorption of ammonia nitrogen in the absorption section.

[0023] In claim 4, it is possible to suppress iron ions from becoming trivalent iron under oxidizing conditions, and to facilitate the production of iron that can be absorbed by algae and the like.

[0024] In claim 5, since the ammonia nitrogen whose amount is reduced in the absorption section can be nitrified in the third section, the amount of nitrate nitrogen can be reduced.

[0025] In claim 6, potassium can be supplemented with the second portion.

[0026] In claim 7, calcium can be supplemented by the fourth portion.

[0027] In claim 8, calcium can be efficiently supplemented by the fourth portion.

[0028] According to claim 9, the ease of maintenance can be improved.

[0029] According to claim 10, the occurrence of problems caused by algae can be suppressed. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is an explanatory diagram showing an aquaponics system equipped with an aquaculture wastewater treatment system according to one embodiment of the present invention. [Diagram 2] FIG. 1 is an explanatory diagram showing a processing system. [Diagram 3] FIG. 1 is an explanatory diagram showing an example of a treatment system for using algae as fish feed in aquaculture tanks. [Figure 4] 1A is an explanatory diagram showing a land-based aquaculture system including a treatment system for aquaculture wastewater according to a modified example, and FIG. 1B is an explanatory diagram showing a treatment system according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] An aquaponics system 1 equipped with an aquaculture wastewater treatment system 40 according to one embodiment of the present invention will be described below. The aquaponics system 1 is for simultaneously cultivating fish F and plants P. First, an overview of the aquaponics system 1 will be described.

[0032] When cultivating fish F, the water quality deteriorates due to ammonia nitrogen and the like generated from the excrement and leftover feed of fish F. For this reason, when cultivating fish F, it is necessary to purify the water used in cultivating fish F (hereinafter referred to as "cultivation wastewater"). Specifically, it is necessary to nitrify the ammonia nitrogen in the aquaculture wastewater and convert it to nitrate nitrogen, and then denitrify this nitrate nitrogen.

[0033] Nitrate nitrogen is a weakly toxic substance to fish F, but is a nutrient component for plants P. The aquaponics system 1 focuses on this point and replaces the above-mentioned denitrification with the cultivation of plants P, thereby cultivating fish F and cultivating plants P at the same time while purifying the polluted aquaculture wastewater from the cultivation of fish F. The configuration of the aquaponics system 1 will be described below.

[0034] As shown in FIG. 1, the aquaponics system 1 includes an aquaculture tank 10, a cultivation tank 20, a circulation pump 30, and a treatment system 40.

[0035] The aquaculture tank 10 is for raising fish F. In this embodiment, saltwater fish are raised in the aquaculture tank 10. In this case, water suitable for raising saltwater fish is stored in the aquaculture tank 10. For example, the aquaculture tank 10 stores water with a higher salt concentration than freshwater (natural seawater, artificial seawater, etc.). The type of fish F cultured in the aquaculture tank 10 is not particularly limited. For example, instead of saltwater fish, freshwater fish can also be cultured in the aquaculture tank 10.

[0036] The aquaculture tank 10 is connected to a treatment system 40 (described later) via a first pipe K1. Water discharged from the aquaculture tank 10 (aquaculture wastewater) is supplied to the treatment system 40.

[0037] The cultivation tank 20 is for cultivating the plants P. The cultivation tank 20 is connected to the treatment system 40 via the second piping K2. The cultivation tank 20 is supplied with aquaculture wastewater (water containing nitrate nitrogen, etc.) discharged from the treatment system 40. In the cultivation tank 20, the plants P can be cultivated by hydroponic cultivation using the aquaculture wastewater. In the cultivation tank 20, the nitrate nitrogen contained in the aquaculture wastewater is absorbed by the plants P. This reduces the concentration of nitrate nitrogen, which is weakly toxic to the fish F, and the aquaculture wastewater is purified.

[0038] The plants P cultivated in the cultivation tank 20 are not particularly limited, but are preferably plants P that are suitable for hydroponic cultivation and have relatively high consumer demand. For example, the plants P cultivated in the cultivation tank 20 are preferably leafy vegetables, herbs, tomatoes, etc. By cultivating such plants P, the profitability of cultivating the plants P can be improved.

[0039] The circulation pump 30 is for circulating the aquaculture wastewater in the aquaponics system 1. The circulation pump 30 is connected to the cultivation tank 20 via the third pipe K3. The circulation pump 30 is also connected to the aquaculture tank 10 via the fourth pipe K4. When the circulation pump 30 operates, the aquaculture wastewater can be circulated in the aquaponics system 1 via the first pipe K1, the second pipe K2, the third pipe K3, and the fourth pipe K4. More specifically, the aquaculture wastewater can be repeatedly circulated through the aquaculture tank 10, the treatment system 40, and the cultivation tank 20. In this way, the aquaponics system 1 can cultivate the plant P using the aquaculture wastewater, and return the aquaculture wastewater purified by the cultivation of the plant P to the aquaculture tank 10.

[0040] In this embodiment, since saltwater fish are cultured in the culture tank 10, the culture wastewater with a relatively high salt concentration circulates in the aquaponics system 1. In this case, the salt may make it difficult for the plants P to absorb the nitrate nitrogen. For this reason, if the ammonia nitrogen in the culture wastewater is nitrified as it is, an excessive amount of nitrate nitrogen may be introduced into the cultivation tank 20, and the plants P may not be able to keep up with the absorption of the nitrate nitrogen. In this case, the concentration of nitrate nitrogen in the culture wastewater may increase, which may have a negative effect on the growth of the fish F. For this reason, if the ammonia nitrogen in the culture wastewater is nitrified as it is, it is necessary to take measures to suppress the increase in the concentration of nitrate nitrogen, such as growing a large amount of plants P on a large area of ​​land.

[0041] The treatment system 40 is intended to treat the aquaculture wastewater to suppress the increase in the concentration of nitrate nitrogen described above without growing a large amount of plants P on a vast area of ​​land. The treatment system 40 is configured to absorb the ammonia nitrogen contained in the aquaculture wastewater into at least one of algae and floating plants (algae in this embodiment), and then nitrify the remaining ammonia nitrogen. As a result, the treatment system 40 can supply a relatively small amount of nitrate nitrogen to the cultivation tank 20, so that even if the amount of nitrate nitrogen absorbed by the plants P decreases due to the influence of salinity, the increase in the concentration of nitrate nitrogen can be suppressed. The configuration of the treatment system 40 will be described below.

[0042] As shown in FIGS. 1 and 2, the treatment system 40 includes a strainer 41 , a first layer 42 , a second layer 43 , an algae culture device 44 , a filter 45 , a third layer 46 and a fourth layer 47 .

[0043] The strainer 41 shown in Fig. 1 is for removing solids (such as food left over by fish F and solid feces) contained in the aquaculture wastewater. The strainer 41 is formed to allow water to pass through but not allow solids to pass through. The strainer 41 is provided in, for example, the first pipe K1. Note that the configuration for removing solids is not limited to the strainer 41 and can be changed as desired.

[0044] The first layer 42 shown in Fig. 2 is for adding (supplying) humus components to the aquaculture wastewater. The humus components are components that combine with iron ions (divalent) added in the second layer 43 described below to maintain the iron content in a state that can be absorbed by the algae cultured in the algae culture device 44 and the plants P in the culture tank 20. Examples of humus components include fulvic acid and humic acid. In this embodiment, the iron content that can be absorbed by the algae and the like is in a divalent and dissolved state.

[0045] The first layer 42 is disposed downstream of the strainer 41 (see FIG. 1). The first layer 42 is configured to come into contact with the aquaculture wastewater. In this embodiment, the first layer 42 is formed in a first tubular member T1 through which the aquaculture wastewater can pass (forming part of a circulation path). Specifically, the first layer 42 is formed by filling the first tubular member T1 with fermented leaf mold or wood chips (materials containing humus components). The first layer 42 is not formed over the entire first tubular member T1, but is formed on the upstream side of the first tubular member T1.

[0046] Note that the first layer 42 may have any structure as long as it is capable of contacting the aquaculture wastewater, and the specific structure is not limited to that of this embodiment. For example, the first layer 42 may be provided in a detachable member (cartridge) that is detachable from a member through which the aquaculture wastewater flows. The cartridge is formed to allow the aquaculture wastewater to pass through. The first layer 42 is formed by filling the cartridge with fermented leaf mold or the like. With this structure, maintenance of the first layer 42 can be easily performed by replacing the cartridge.

[0047] The second layer 43 is for adding (supplying) iron ions (divalent) and potassium to the aquaculture wastewater. The second layer 43 is disposed downstream of the first layer 42. The second layer 43 is configured to come into contact with the aquaculture wastewater. In this embodiment, the second layer 43 is formed by filling the first cylindrical member T1 with a material containing potassium and iron. Specifically, the second layer 43 is formed by filling the first cylindrical member T1 with a mixture of powdered or granular activated carbon (bamboo, Mitsumata, etc.) that contains a lot of potassium and iron powder.

[0048] The second layer 43 may have any structure as long as it can come into contact with the aquaculture wastewater, and the specific configuration is not limited to that of this embodiment. For example, the second layer 43 may be provided in a cartridge, similar to the first layer 42. The second layer 43 may contain charcoal made from oak, beech, or chestnut, or coconut shell charcoal, instead of activated carbon made from bamboo or mitsumata. The second layer 43 may contain converter slag or electric furnace oxidized slag, which contain a relatively large amount of iron, instead of iron powder.

[0049] The algae culture device 44 is mainly for cultivating microalgae. The aquaculture wastewater that has passed through the second layer 43 is supplied to the algae culture device 44. The aquaculture wastewater is used to cultivate algae that can survive in a relatively high salinity and absorb ammonia nitrogen in the algae culture device 44. Furthermore, in the algae culture device 44, the algae are cultured in an environment where photosynthesis is possible (an environment with light and carbon dioxide).

[0050] The specific configuration of the algae culture device 44 is not particularly limited. For example, the algae culture device 44 may be an open-type culture device that cultures algae in an open pond or raceway installed outdoors, or a closed-type culture device that cultures algae in tubes or flat panels installed indoors. Furthermore, the algae culture device 44 is not particularly limited as long as it cultures algae capable of absorbing ammonia nitrogen.

[0051] The algae culture apparatus 44 of this embodiment is connected to a carbon dioxide supply source in order to increase the carbon dioxide concentration in the aquaculture wastewater. For example, the algae culture apparatus 44 is connected to a device that discharges exhaust gas containing carbon dioxide gas during operation. The aquaculture wastewater used for cultivating algae in the algae culture apparatus 44 flows downstream (to the filter 45).

[0052] The filter 45 is for collecting algae. The filter 45 is formed so that the aquaculture wastewater can pass through it, but the algae cannot pass through it. In cases where the resistance of the filter 45 is relatively large, a pump may be provided to pass the aquaculture wastewater through the filter. The use of the algae collected by the filter 45 is not particularly limited. For example, the algae can be used as feed for fish F cultured in the aquaculture tank 10, as shown in FIG. 3. They can also be sold as feed to businesses that culture the fish F. In addition, when the algae produce useful substances (oils and fats, antioxidant components, etc.), the algae can be squeezed to extract the useful substances, and the squeezed residue can be used as feed for the fish F in the aquaculture tank 10. This can reduce the cost of cultivating the fish F and increase the profits from algae cultivation.

[0053] The configuration for collecting algae is not limited to the filter 45, but may be changed as desired. For example, algae may be collected using a strainer and a centrifugal separator.

[0054] The third layer 46 shown in FIG. 2 is for nitrifying ammonia nitrogen and converting it into nitrate nitrogen. The third layer 46 is disposed downstream of the filter 45. The third layer 46 is configured to come into contact with the aquaculture wastewater. In this embodiment, the third layer 46 is formed in the second tubular member T2 through which the aquaculture wastewater can pass (forming a part of the flow path). Specifically, the third layer 46 is formed by filling the second tubular member T2 with a porous material carrying microorganisms (nitrifying bacteria) that nitrify ammonia nitrogen. The third layer 46 is not formed in the entire second tubular member T2, but is formed on the upstream side of the second tubular member T2.

[0055] The fourth layer 47 is for adding (supplying) calcium to the aquaculture wastewater. The fourth layer 47 is disposed downstream of the third layer 46. The fourth layer 47 is configured to come into contact with the aquaculture wastewater. In this embodiment, the fourth layer 47 is formed by, for example, filling oyster shells or the like (materials containing calcium) into the second cylindrical member T2.

[0056] The third layer 46 and the fourth layer 47 may have any structure as long as they are capable of contacting the aquaculture wastewater, and the specific configuration is not limited to that of this embodiment. For example, the third layer 46 and the fourth layer 47 may be provided in a cartridge, similar to the first layer 42. Furthermore, the fourth layer 47 may contain coral or egg shells instead of oyster shells.

[0057] In addition, it is desirable that the materials for forming the first layer 42, the second layer 43, the third layer 46, and the fourth layer 47 utilize domestic materials and waste materials, etc. This will improve self-sufficiency and recycle waste materials.

[0058] The treatment contents of the treatment system 40 will be described below with reference to Figures 1 and 2. In the treatment system 40, the aquaculture wastewater passes through a strainer 41, a first layer 42, a second layer 43, an algae culture device 44, a filter 45, a third layer 46, and a fourth layer 47 in this order, so that the aquaculture wastewater can be treated so that the absorption of nitrate nitrogen in the cultivation tank 20 (plants P) can keep up. A specific description will be given below.

[0059] In the treatment system 40, solids in the aquaculture wastewater are removed by a strainer 41 shown in Fig. 1. The aquaculture wastewater then passes through a first layer 42 shown in Fig. 2. This adds humus components (fulvic acid, etc.) to the aquaculture wastewater.

[0060] The aquaculture wastewater to which the humus components have been added passes through the second layer 43. This adds potassium and iron ions to the aquaculture wastewater. In addition, since the second layer 43 of this embodiment is a mixture of powdered or granular activated carbon and iron powder, a local battery is easily formed. This promotes the ionization of iron, making it easier to add (dissolve) iron ions into the aquaculture wastewater.

[0061] The iron ions added in the second layer 43 combine with the humus components added in the first layer 42 to become iron fulvic acid, iron humate, etc. This keeps the iron in the aquaculture wastewater in a divalent state and in a dissolved state (a state in which the algae and plant P can be absorbed).

[0062] In the treatment system 40 of this embodiment, of the humus components and the iron ions, the humus components are added to the aquaculture wastewater first to increase the concentration of the humus components. This configuration makes it easier for the iron ions to combine with the humus components before they become trivalent iron under oxidizing conditions. This allows the treatment system 40 to prevent the iron ions from becoming trivalent iron (a state that cannot be absorbed by plants P) under oxidizing conditions.

[0063] The aquaculture wastewater that has passed through the second layer 43 is supplied to an algae culture device 44. The algae cultured in the algae culture device 44 absorb the ammonia nitrogen contained in the aquaculture wastewater as a nutrient component. This allows the algae culture device 44 to reduce the ammonia nitrogen in the aquaculture wastewater. The algae also absorb a portion of the iron fulvic acid and other substances generated in the second layer 43. This makes it possible to prevent iron deficiency and to prevent adverse effects on the growth of the algae.

[0064] The aquaculture wastewater used for cultivating algae in the algae culture device 44 is supplied to the third layer 46 via a filter 45. This makes it possible to prevent algae from flowing out downstream of the algae culture device 44 (the third layer 46 and the fourth layer 47), and to prevent clogging of the downstream side with algae.

[0065] In the third layer 46, the ammonia nitrogen in the aquaculture wastewater is nitrified and converted to nitrate nitrogen by the action of microorganisms. In this embodiment, since the ammonia nitrogen is reduced in the algae culture device 44, a relatively small amount of nitrate nitrogen is produced.

[0066] The aquaculture wastewater that has passed through the third layer 46 passes through the fourth layer 47. At this time, calcium contained in oyster shells and the like dissolves and is eluted into the aquaculture wastewater as calcium ions. In this way, calcium is added to the aquaculture wastewater. The aquaculture wastewater that has passed through the fourth layer 47 is supplied to the cultivation tank 20 via the second piping K2 shown in FIG. 1. Note that iron fulvic acid and the like that remain unabsorbed by the algae in the algae culture device 44 are absorbed as a nutrient component by the plant P in the cultivation tank 20. This makes it possible to prevent iron deficiency and to prevent adverse effects on the growth of the plant P.

[0067] In this way, the treatment system 40 supplies aquaculture wastewater containing a relatively small amount of nitrate nitrogen to the cultivation tank 20. With this configuration, even if the plants P have difficulty absorbing nitrate nitrogen due to the influence of salinity, it is possible to balance the amount of nitrate nitrogen absorbed by the plants P with the amount of nitrate nitrogen produced in the third layer 46. Therefore, it is possible to prevent an increase in the concentration of nitrate nitrogen without cultivating the plants P over a large area, and it is possible to prevent the cultivation tank 20 from becoming large.

[0068] Here, potassium and calcium are nutrients for the plant P, so in the cultivation tank 20, not only nitrate nitrogen but also potassium and calcium are absorbed by the plant P. Therefore, the treatment system 40 provides the second layer 43 and the fourth layer 47 to replenish the potassium and calcium lost in the cultivation tank 20. This makes it possible to suppress adverse effects on the growth of the plant P caused by potassium deficiency and calcium deficiency.

[0069] In addition, in this embodiment, since the components (calcium, etc.) are eluted from the materials filled in the first tubular member T1 and the second tubular member T2, the components can be added to the aquaculture wastewater continuously for a relatively long period of time (slow release is expected). This reduces the frequency of replacing the materials filled in the first tubular member T1 and the second tubular member T2.

[0070] The treatment system 40 of this embodiment is configured so that the aquaculture wastewater flows through the first layer 42, the second layer 43, the algae culture device 44, the third layer 46, and the fourth layer 47 in that order, thereby appropriately controlling the oxygen concentration and pH (hydrogen ion exponent) of the aquaculture wastewater and efficiently treating each part. First, the control of the oxygen concentration of the aquaculture wastewater will be described.

[0071] When the aquaculture wastewater is discharged from the aquaculture tank 10 shown in Fig. 1, the oxygen concentration is low and the carbon dioxide concentration is high due to respiration by the fish F. In the treatment system 40, the aquaculture wastewater with the low oxygen concentration is supplied to the first layer 42 and the second layer 43. This makes it possible to suppress the influence of oxidation conditions caused by oxygen in the aquaculture wastewater on the iron ions added in the second layer 43, and makes it easier for the humus components to bind to the iron ions.

[0072] The aquaculture wastewater that has passed through the second layer 43 is supplied to an algae culture device 44. The carbon dioxide concentration of the aquaculture wastewater remains high even after passing through the second layer 43. The aquaculture wastewater also contains iron fulvic acid and the like that can be absorbed by the algae produced in the second layer 43. The algae cultured in the aquaculture wastewater absorb the iron fulvic acid and the like as nutrients and can actively carry out photosynthesis.

[0073] In this way, by locating the algae culture device 44 downstream of the second layer 43, it is possible to create an environment in which it is easy to culture algae (an environment in which the carbon dioxide concentration is high and the aquaculture wastewater contains nutrients). This makes it possible to increase the algae culture speed in the algae culture device 44. In addition, since the algae culture device 44 is connected to a carbon dioxide supply source, it is also possible to increase the carbon dioxide concentration by using carbon dioxide from the supply source when the carbon dioxide concentration in the aquaculture wastewater is relatively low. This allows the algae culture device 44 to stimulate photosynthesis of algae.

[0074] The aquaculture wastewater discharged from the algae culture device 44 is supplied to the third layer 46. Here, the third layer 46 is a porous material that supports nitrifying bacteria. Oxygen is required for the nitrification reaction by the nitrifying bacteria. Therefore, in this embodiment, the third layer 46 is arranged downstream of the algae culture device 44, and the aquaculture wastewater with an increased oxygen concentration due to the photosynthesis of the algae is supplied to the third layer 46. This makes it easier to advance the nitrification reaction in the third layer 46. The aquaculture wastewater that has passed through the third layer 46 is supplied to the cultivation tank 20 after passing through the fourth layer 47. In this way, in the cultivation tank 20, the plants P are appropriately cultivated by the aquaculture wastewater with a high oxygen concentration.

[0075] Next, the pH control of the aquaculture wastewater will be described. The pH is controlled between the algae culture device 44 and the fourth layer 47.

[0076] Specifically, the oxygen concentration in the aquaculture wastewater increases and the carbon dioxide concentration decreases due to photosynthesis of the algae cultured in the algae culture device 44. This causes the pH of the aquaculture wastewater to increase (become more alkaline).

[0077] Here, the nitrification reaction in the third layer 46 proceeds more easily when the pH of the aquaculture wastewater is closer to alkaline (for example, about 7.2 to 9). Therefore, in this embodiment, the third layer 46 is disposed downstream of the algae culture device 44, and the aquaculture wastewater, the pH of which has been made closer to alkaline by algae photosynthesis, is supplied to the third layer 46. This allows the treatment system 40 to appropriately adjust the pH so that the nitrification reaction proceeds more easily. Note that, because the nitrate nitrogen concentration in the aquaculture wastewater increases due to the nitrification reaction, the pH of the aquaculture wastewater decreases (becomes acidic).

[0078] As described above, the fourth layer 47 is formed by filling the second cylindrical member T2 with oyster shells and the like. The lower the pH of the aquaculture wastewater, the more easily calcium ions will dissolve from the fourth layer 47 (oyster shells and the like). Therefore, in this embodiment, the fourth layer 47 is disposed downstream of the third layer 46, and the aquaculture wastewater whose pH has been reduced by the nitrification reaction is supplied to the fourth layer 47. This allows the treatment system 40 to appropriately adjust the pH so that calcium is easily dissolved (calcium can be efficiently added).

[0079] In the fourth layer 47, when calcium ions dissolve into the aquaculture wastewater, carbonate ions contained in oyster shells and the like react with hydrogen ions in the aquaculture wastewater to reduce the number of hydrogen ions, and the pH that increased in the third layer 46 is neutralized in the fourth layer 47 (from slightly acidic to neutral). The aquaculture wastewater is supplied to the cultivation tank 20. In this way, in the cultivation tank 20, the plants P are appropriately cultivated using the aquaculture wastewater with a neutralized pH.

[0080] As described above, the aquaculture wastewater treatment system 40 according to this embodiment is an aquaculture wastewater treatment system 40 for treating the aquaculture wastewater discharged from the aquaculture tank 10 in which fish F are raised, and is equipped with an algae culture device 44 (absorption section) that causes the ammonia nitrogen contained in the aquaculture wastewater to be absorbed by at least one of algae or floating plants.

[0081] By configuring in this way, the water quality of the aquaculture wastewater can be improved.

[0082] The algae culture device 44 is supplied with the aquaculture wastewater, which has a higher salinity than fresh water.

[0083] With this configuration, the quality of the aquaculture wastewater having a high salt concentration can be improved, for example, the quality of the aquaculture wastewater from the aquaculture tank 10 in which saltwater fish are raised can be improved.

[0084] The aquaculture system further includes an additional section (first layer 42 and second layer 43) that is arranged upstream of the algae culture device 44 in the flow direction of the aquaculture wastewater and produces iron that can be absorbed by at least one of the algae or floating plants.

[0085] By configuring in this manner, it is possible to prevent the growth of algae and the like from being adversely affected by iron deficiency, and to make it easier for the algae culture device 44 to absorb ammonia nitrogen.

[0086] The addition section further comprises a first layer 42 (first portion) that adds humus components (fulvic acid, etc.) to the aquaculture wastewater, and a second layer 43 (second portion) that is disposed between the first layer 42 and the algae culture device 44 in the flow direction and adds at least iron ions (divalent) to the aquaculture wastewater.

[0087] By configuring in this manner, it is possible to suppress the iron ions from becoming trivalent iron due to oxidation conditions, and to facilitate the production of iron (such as iron fulvic acid) that can be absorbed by algae and the like.

[0088] The system further includes a third layer 46 (third portion) that is disposed downstream of the algae culture device 44 in the flow direction and nitrifies ammonia nitrogen contained in the aquaculture wastewater.

[0089] With this configuration, the amount of ammonia nitrogen reduced in the algae culture device 44 can be nitrified in the third layer 46, thereby reducing the amount of nitrate nitrogen.

[0090] The second layer 43 adds iron ions and potassium to the aquaculture wastewater.

[0091] With this configuration, potassium can be supplemented in the second layer 43.

[0092] The treatment system 40 further includes a fourth layer 47 (fourth portion) that adds calcium to the aquaculture wastewater.

[0093] With this configuration, calcium can be supplemented by the fourth layer 47.

[0094] The fourth layer 47 is disposed downstream of the third layer 46 in the flow direction.

[0095] By configuring in this manner, calcium can be efficiently supplemented in the fourth portion.

[0096] Furthermore, at least one of the first layer 42, the second layer 43, the third layer 46 and the fourth layer 47 is detachably provided on members (first tubular member T1 and second tubular member T2) that form a circulation path for the aquaculture wastewater.

[0097] Such a configuration can improve maintainability.

[0098] The treatment system 40 further includes a filter 45 (collection section) for collecting the algae cultured in the algae culture device 44.

[0099] With this configuration, it is possible to suppress the occurrence of problems caused by algae (such as clogging due to algae).

[0100] The algae culture apparatus 44 according to this embodiment is one embodiment of an absorption section according to the present invention. Moreover, the first layer 42 and the second layer 43 according to this embodiment are an embodiment of the additional portion according to the present invention. Moreover, the first layer 42 according to this embodiment is one embodiment of the first portion according to the present invention. Moreover, the second layer 43 according to this embodiment is one embodiment of the second portion according to the present invention. Moreover, the third layer 46 according to this embodiment is one embodiment of a third portion according to the present invention. Moreover, the fourth layer 47 according to this embodiment is one embodiment of the fourth portion according to the present invention. The filter 45 according to this embodiment is one embodiment of a collection section according to the present invention.

[0101] Although the embodiment of the present invention has been described above, the present invention is not limited to the above configuration, and various modifications are possible within the scope of the invention described in the claims.

[0102] For example, the treatment system 40 of this embodiment is configured to absorb ammonia nitrogen by algae, but the organisms that absorb ammonia nitrogen may be at least one of algae and floating plants. For example, the treatment system 40 can also absorb ammonia nitrogen by both algae and floating plants. When absorbing ammonia nitrogen by both algae and floating plants in this way, it is also possible to grow floating plants (duckweed, water plantain, etc.) by utilizing the water surface of the algae culture device 44. This can save space.

[0103] The arrangement of the various components of the treatment system 40 is merely an example and can be changed as desired. For example, the fourth layer 47 is disposed downstream of the third layer 46, but it may be disposed upstream of the third layer 46 (such as between the second layer 43 and the algae culture device 44).

[0104] In this embodiment, iron fulvic acid and the like (iron that can be absorbed by plants P) are added to the aquaculture wastewater by the first layer 42 and the second layer 43, but the method of adding iron fulvic acid and the like is not limited to this embodiment. For example, iron fulvic acid and the like can also be added to the aquaculture wastewater by pouring liquid fertilizer containing iron fulvic acid and the like into the aquaculture wastewater.

[0105] Although the treatment system 40 of this embodiment is intended to improve the water quality of the aquaculture wastewater circulating in the aquaponics system 1, the use of the treatment system 40 is not limited to this embodiment. The treatment system 40 can also improve the water quality of the aquaculture wastewater in a system other than the aquaponics system 1. An example of this will be described below with reference to FIG. 4.

[0106] The treatment system 140 according to the modified example shown in Fig. 4 is for improving the water quality of the aquaculture wastewater circulating in the land-based aquaculture system 101. The land-based aquaculture system 101 is for cultivating fish F on land. Since the land-based aquaculture system 101 does not cultivate plants P, the aquaculture tank 10, the circulation pump 30, and the treatment system 140 are connected to each other via piping K. The aquaculture wastewater is repeatedly circulated through the aquaculture tank 10 and the treatment system 140 by operating the circulation pump 30.

[0107] The treatment system 140 is configured to purify the aquaculture wastewater by itself, rather than purifying the aquaculture wastewater in cooperation with the cultivation tank 20 (see FIG. 1). Specifically, as shown in FIG. 4(b), the treatment system 140 includes a first layer 42, a second layer 43, a fourth layer 47, and an algae culture device 144.

[0108] The fourth layer 47 is disposed between the second layer 43 and the algae culture device 144 in the flow direction of the aquaculture wastewater. The algae culture device 144 is configured to be able to absorb all of the ammonia nitrogen in the aquaculture wastewater. For example, the algae culture device 144 is configured to grow floating plants in addition to algae, so that the amount of ammonia nitrogen absorbed is greater than in this embodiment. The algae cultured in the algae culture device 144 is collected using a filter or the like (not shown).

[0109] According to the treatment system 140 of the modified example, even if the plant P is not cultivated, the treatment system 140 alone can improve the water quality of the aquaculture wastewater. Furthermore, by locating the fourth layer 47 upstream of the algae culture device 144, calcium can be efficiently added to the aquaculture wastewater before the pH increases due to photosynthesis of the algae (before calcium becomes difficult to dissolve). [Explanation of symbols]

[0110] 40 Processing System 10 Aquaculture tank 44 Algae cultivation equipment F-fish

Claims

1. An aquaculture wastewater treatment system for treating aquaculture wastewater discharged from an aquaculture tank in which fish are raised, comprising: The ammonia nitrogen contained in the aquaculture wastewater is absorbed by at least one of algae and floating plants. Aquaculture wastewater treatment system.

2. The absorbing portion has The aquaculture wastewater having a higher salinity than freshwater is supplied. The aquaculture wastewater treatment system according to claim 1.

3. The aquaculture wastewater further includes an addition unit that is disposed upstream of the absorption unit in the flow direction of the aquaculture wastewater and adds iron that can be absorbed by at least one of the algae or floating plants to the aquaculture wastewater. The aquaculture wastewater treatment system according to claim 1 or 2.

4. The adding unit is A first part for adding humus components to the aquaculture wastewater; a second portion disposed between the first portion and the absorption portion in the flow direction and configured to add at least iron ions to the aquaculture wastewater; Equipped with The aquaculture wastewater treatment system according to claim 3.

5. The aquaculture wastewater treatment plant further includes a third section that is disposed downstream of the absorption section in the flow direction and nitrifies ammonia nitrogen contained in the aquaculture wastewater. The aquaculture wastewater treatment system according to claim 4.

6. The second portion is Adding iron ions and potassium to the aquaculture wastewater; The aquaculture wastewater treatment system according to claim 5.

7. Further comprising a fourth portion for adding calcium to the aquaculture wastewater. The aquaculture wastewater treatment system according to claim 5.

8. The fourth portion is The third portion is disposed downstream in the flow direction. The aquaculture wastewater treatment system according to claim 7.

9. At least one of the first portion, the second portion, the third portion, and the fourth portion is The member that forms the circulation path of the aquaculture wastewater is detachably provided. The aquaculture wastewater treatment system according to claim 7.

10. Further comprising a recovery section for recovering the algae cultured in the absorption section. The aquaculture wastewater treatment system according to claim 1 or 2.

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