Aquaculture system and method for cultivating aquatic organisms

Abstract

An aquaculture system, such as a fish or shrimp farming system, is provided, which is based on recirculating aquaculture, said system comprising at least two aquaculture tanks 105e, at least one tank-specific water treatment unit (106d, 107h) connected to one of the tanks and configured to treat the water of said tank, at least one shared water treatment unit (108, 109) connected to all of the tanks and configured to treat the water recirculating in the system, and means 101a for recirculating water in the system.

Description

[Technical Field]

[0001] This application relates to aquaculture systems, and more particularly to fish farming systems that utilize both individual tank water treatment units and shared water treatment units. [Background technology]

[0002] Aquaculture, which generally refers to the farming of aquatic organisms such as fish and shellfish under controlled conditions, is a fast-growing agricultural sector that enables the harvesting of seafood for human and animal consumption. Aquaculture enables diverse aquatic species to be produced cost-effectively and with predictable yields regardless of external conditions such as weather and / or population fluctuations.

[0003] In recent decades, fish harvesting in aquaculture facilities with full or partial water recirculation has become popular and profitable compared to traditional open pond fish farming. Recirculating aquaculture systems (RAS) vary in design depending on production goals and geographic location. Common practices include the use of raceway systems configured as baffled rectangular tanks or series of tanks, or rearing facilities containing a series of circular ponds or tanks with circular water flow around a central drainpipe. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 240061 [Non-patent literature]

[0005] [Non-Patent Document 1] R. Robertson et al. "Depuration rates and the sensory threshold concentration of geosmin responsible for earthy-musty taint in rainbow trout, Onchorhynchus mykiss," March 2005, Aquaculture 245(l-4):89-99. Summary of the Invention [Problem to be solved by the invention]

[0006] Aquaculture has been the fastest-growing animal production sector in the world for the past few decades. Land-based production of salmonids, in particular, is currently growing extremely rapidly as traditional locations and production methods are unable to meet rapidly increasing demand. Conservative estimates place the land-based sector's growth rate at approximately 60% per year over the next decade. Despite high and growing interest in recirculating aquaculture systems (RAS) technology, the biological challenges and risks of RAS initiatives have not been fully resolved, and mature RAS farms have yet to prove profitable.

[0007] Conventional recirculating aquaculture farms have one or more shared units to centralize the necessary water treatment steps for the entire farm. The units usually include several functions or sub-units dedicated to, for example, aeration and purification of the water. The drawback is that the system does not offer much flexibility in how individual fish tanks can be operated.

[0008] Alternatively, it is known to provide all water treatment functions in association with each individual fish tank. However, equipping each tank with, for example, an aeration unit, a solids separation unit, and a biological purification unit is expensive. Also, while the size of a centralized bioreactor can be based on the average feed load at the farm level, the size of a tank-specific bioreactor should be sized according to the maximum feed load in that tank. Bioreactors adapt slowly to changing feed loads, and after, for example, disinfection, a tank-specific biological purification unit may take weeks or months to mature and function properly. Therefore, this alternative is not widely used.

[0009] Also, in a conventional fish farm, each tank has a single freshwater pipeline and a single wastewater pipeline, and water must be pumped out of the tank through a full water treatment process, regardless of what the primary water quality factor is that limits production.

[0010] Traditional recirculating aquaculture farms that utilize centralized water treatment also suffer from fish health challenges. Because pathogens cannot be isolated from the common water recycle, an infection in one tank inevitably spreads to all tanks in the farm. For the same reason, the use of antibiotics in one tank affects all tanks in the farm, resulting in the suspension of fish sales from the entire farm. Non-negligible antibiotic concentrations spread to all tanks, necessitating a withdrawal period for all tanks.

[0011] A key challenge is the issue of off-flavors caused by compounds such as geosmin and 2-methylisoborneol. Separate purge tanks are expensive to construct, the purging process is labor-intensive, and fish lose weight (up to 15%) during the purging / fasting period before harvest.

[0012] One of the problems is the high energy consumption of current high-head RAS technology (large head differential).

[0013] In modern RAS farms, the priority has been to reduce investment costs, so fish health and welfare issues have been compromised. While building centralized water treatment units is cheaper, it makes all-in, all-out production strategies impossible and medication administration very difficult, often practically impossible.

[0014] SUMMARY OF THE INVENTION Embodiments of the present invention are intended to solve at least some of the above problems. [Means for solving the problem]

[0015] The invention is defined by the features of the independent claims. Some particular embodiments are defined in the dependent claims.

[0016] According to a first aspect of the present invention, there is provided an aquaculture system, such as a fish or shrimp farming system, based on recirculation aquaculture, comprising at least two aquaculture tanks, at least one individual tank water treatment unit connected to one of the tanks and configured to treat the water of said tank, at least one shared water treatment unit connected to all of the tanks and configured to treat the water recirculating in the system, and means for recirculating water in the system.

[0017] Various embodiments of the first aspect may include at least one feature from the following bulleted list. The aquaculture tank is a land-based tank or a floating tank. At least one of the water tanks includes a fresh water inlet connected to a fresh water line. Each water tank includes a water intake connected to said recirculation. Each tank contains a drain connected to a common drain line. The common drain line is connected to an inlet of the at least one shared water treatment unit. The water inlet and the water outlet of the aquarium are configured to be disconnectable from and reconnectable to the system. The at least one aquarium-specific water treatment unit comprises an aquarium-specific unit for aeration of the water in the aquarium and / or for exchange of gases in the water of the aquarium. The aeration or gas exchange includes the addition of air or oxygen to the water in the aquarium, such as oxygenation. The aeration or gas exchange includes the removal of carbon dioxide from the water of the aquarium. The at least one aquarium-specific water treatment unit comprises a aquarium-specific unit for the removal of solids from the water of the aquarium. The solids include sinkable or coarse solids, such as feces and / or leftover food. The separate solids removal unit comprises a gravity-based settler such as a radial flow settler or a swirl separator. The at least one individual water treatment unit comprises an individual unit for the removal of fine suspended solids from the water of the individual water tank by flotation. The at least one shared water treatment unit includes a shared unit for removal of solids from the recirculating water. The solid material includes fine solid material. The shared unit for removing solids comprises a filter such as a drum filter, a drum screen, a belt filter, or a flotation unit. The at least one shared water treatment unit comprises a shared unit for biological treatment of the recirculating water. The shared unit for biological treatment comprises a moving bed bioreactor, a fixed bed bioreactor, a fluidized bed bioreactor, or a trickling filter tower bioreactor. The means for recirculating the water includes an airlift pump, a centrifugal pump, or an axial pump.

[0018] According to a second aspect of the present invention, there is provided a method of cultivating aquatic organisms such as fish or shrimp by using a system according to the first aspect.

[0019] According to a third aspect of the present invention, there is provided a method of cultivating aquatic organisms such as fish or shrimp in a system typically based on recirculating aquaculture, comprising purging the fish or shrimp in culture tanks when they reach a time for slaughter by providing disinfected water or disinfectant, respectively, to the tanks, purging the fish or shrimp of off-flavor substances during a purging period, feeding the fish during at least an initial period of the purging period, and harvesting the fish from the tanks for slaughter after the purging period.

[0020] Various embodiments of the second or third aspect may include at least one feature from the following bulleted list. Each of the tanks is operated independently of the other according to the flow-through, partial recirculation or recirculation principle. At intervals, at least one of the water tanks is operated according to the flow-through principle, the water intake and the water outlet of the water tank being disconnected from the recirculation. At intervals, at least one of the tanks is operated according to the principle of partial recirculation, with either the intake or the outlet of the tank being disconnected from the recirculation. At intervals, at least one of said water tanks, preferably all of said water tanks, is operated according to the principle of recirculation. The method includes operating at least one of the tanks according to a free-flow, partial recirculation, or recirculation principle for a period of time to acclimate the fish or shrimp in the tank to free-flow, partial recirculation, or recirculation conditions, respectively. After said period of time, transferring said acclimatized fish or shrimp from said tanks to said conditions outside said system. The method includes disconnecting the drain of the aquarium from the system, draining the wastewater from the aquarium outside the system, disinfecting the aquarium, introducing new fish or shrimp into the aquarium, and after a period of time, after the health of the fish or shrimp has been confirmed, reconnecting the drain of the aquarium to the system. The method includes disconnecting the aquarium drain from the system, draining the aquarium drain outside the system, treating the fish or shrimp in the aquarium with a drug such as an antibiotic, and reconnecting the aquarium drain to the system after the treatment has been completed and a predetermined withdrawal period has elapsed. the method comprising purging the fish or shrimp in the tank when it is time for them to be slaughtered by providing disinfected water to the tank, purging the fish or shrimp of off-flavor substances during a purging period, and harvesting the fish or shrimp from the tank for slaughter after the purging period. The method includes disconnecting the water intake of the aquarium from the recirculation before providing disinfected water to the aquarium. The purge period consists of a feeding period followed by a fasting period. The method includes supplying fresh disinfecting water to at least one of the water tanks. The disinfected water is obtained by using a disinfectant, which may be hydrogen peroxide, peracetic acid, or ozone, or by UV radiation sterilization, or by a combination thereof. The method includes disinfecting the water in at least one of the aquaria, such as in situ, by supplying hydrogen peroxide to the aquaria for a period of time. The method includes disinfecting the water in at least one of the aquaria, such as in situ, by supplying peracetic acid to the aquaria for a period of time. The method includes disinfecting the water in at least one of the aquaria, such as in situ, by supplying ozone to the aquaria for a period of time. The method includes disinfecting the water in at least one of the aquaria, such as in situ, by advanced oxidation process (AOP) for a period of time. The disinfection is carried out for the purpose of reducing or eliminating the accumulation of off-flavor substances or for the purpose of eliminating pathogens of fish or shrimp. Substantially most of the time, the biological water treatment unit is connected to the system and receives effluent from at least one of the aquaria. The provision of the disinfecting water or disinfectant is preferably continuous during at least a portion of the purge period or is pulsed by supplying one or more pulses of disinfecting water or disinfectant to the water bath. The feeding is stopped for 0.5 to 5 days, such as 2 to 4 days, before the end of the purge period. During the purging period, the aquarium being purged is not connected to any biological water treatment unit in the system, and preferably the aquarium being purged is connected to its own gas exchange unit. The system according to the first aspect is used.

[0021] According to a fourth aspect of the present invention, there is provided the use of both tank-specific water treatment units and such a water treatment unit common to all the tanks in an aquaculture system, such as a fish or shrimp farming system, comprising several culture tanks and configured for recirculating aquaculture. [Effects of the Invention]

[0022] Advantages of the invention

[0023] Some embodiments of the present invention may result in improved water quality. Aquarium-specific settleable / coarse solids removal systems support better water quality than centralized solids removal systems because particles are removed closer to where they are formed before they break down into smaller particles that are more difficult to remove and release nutrients into the water.

[0024] The present invention can result in improved energy efficiency in gas exchange: separate tank gas exchange is more energy efficient than current centralized gas exchange systems, and the greater the concentration difference, the more effective the process.

[0025] Some embodiments of the present invention may result in reduced need for high-head pumping and improved energy efficiency. Oxygen levels and carbon dioxide concentrations in water are two of the main production-limiting factors in aquaculture. When gas exchange is separate from the tank, pumping rates and pump energy consumption for other water treatment processes can be significantly reduced.

[0026] Some embodiments of the present invention may result in reduced piping and equipment costs. Because high exchange rates are not required for gas exchange, the water flow to the centralized (common) water treatment unit can be reduced. Therefore, smaller piping dimensions and smaller device sizes can be used, which reduces investment costs.

[0027] Some embodiments of the present invention may result in improved fish growth and bioreactor or biofilter performance. Higher ammonia concentrations are possible in the fish tank because high pumping rates are not required for gas exchange. Highly ionized ammonia can act as a growth promoter for the fish. Higher ammonia concentrations also directly improve the nitrification capacity of the biofilter. Thus, the fish grow faster and smaller, less expensive biofilters can be used.

[0028] Some embodiments of the present invention may result in reduced aquarium investment costs: any aquarium that has completed growing can be switched from RAS mode to PRAS mode or flow-through mode, eliminating the need for a separate off-flavor treatment aquarium.

[0029] Some embodiments of the present invention may result in reduced fish stress and mortality, better growth, and reduced labor costs in fish logistics. Because off-flavor treatment can be performed in the grow-out tanks, less fish transfer is required. Transferring fish usually causes stress and mortality to the fish. Therefore, less fish transfer means better fish welfare and better fish farming economics.

[0030] Some embodiments of the present invention can result in increased production capacity and profitability. Tank-specific solids removal and gas exchange systems continue to function when the tank is removed from the recirculation loop (typically at least from the biofilter), and oxidizers such as H2O2 can be used to remove tank-level off-flavor compounds, allowing feeding to continue during the off-flavor treatment period. Because the fish continue to grow during the off-flavor period, the process can produce 10% to 20% more biomass for sale. Also, because the fish do not lose weight before harvesting and sale, approximately 5% to 10% less feed is required to produce the same amount of fish. This has a significant impact on production costs, as feed costs account for roughly 50% of total production costs.

[0031] In some embodiments, significant improvements in energy efficiency will lead to recirculating aquaculture that is closer to carbon neutral. The new innovative fish farm types will utilize centralized and decentralized water treatment, which will enable intelligent, demand-driven water treatment.

[0032] The present invention may allow the system to be better protected from biological risks in aquaria.

[0033] The present invention may allow for better protection of the aquarium from chemical risks in the system.

[0034] The present invention may allow any of the aquaria to be fully or partially separated from the centralized water treatment at any time. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 illustrates a system in accordance with at least some embodiments of the present invention. [Figure 2] FIG. 2 illustrates results from experiments conducted on a system according to at least some embodiments of the present invention. [Figure 3] FIG. 3 illustrates results from experiments conducted on a system according to at least some embodiments of the present invention. [Figure 4] FIG. 4 illustrates results from experiments conducted on a system according to at least some embodiments of the present invention. [Figure 5] FIG. 5 illustrates results from experiments conducted on a system according to at least some embodiments of the present invention. [Figure 6] FIG. 6 illustrates results from experiments conducted on a system according to at least some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] definition

[0037] In the present context, the term "recirculating aquaculture" includes the production of aquatic animals, preferably fish, in a system comprising a water recirculation system with a water treatment unit comprising a biological water treatment unit such as a bioreactor or a biological filtration unit.

[0038] In the present context, the term "recirculation principles or conditions" includes the recirculation of water between the fish tank and a water treatment unit, including a biological water treatment unit such as a bioreactor or a biological filtration unit, and possibly other water treatment units.

[0039] In the present context, the term "partial recirculation principles or conditions" includes the recirculation or reuse of water within the fish tank or between the fish tank and an external water treatment unit, usually in the absence of any biological water treatment unit.

[0040] In the present context, the term "flow-through principle or conditions" includes a flow of water through the fish tank. There is no recirculation or reuse of water within said fish tank or between said fish tank and an external water treatment unit. The wastewater may be treated by a so-called end-of-pipe water treatment unit.

[0041] In the present context, the term "land-based aquarium" includes aquariums whose base is on land.

[0042] In the present context, the term "floating aquarium" includes a tank or enclosed container that floats in the sea or in fresh water such as a lake.

[0043] In this context, the term "fresh water line" generally refers to the incoming fresh water line or the line that takes in fresh water.

[0044] In the present context, the term "gas exchange" is generally synonymous with "aeration" and includes both the removal of carbon dioxide and the addition of oxygen. The gas exchange or aeration unit may also be supplemented with gases other than air.

[0045] "Oxygen supply" refers to the supply of pure oxygen.

[0046] In this context, the term "purging" is generally synonymous with the term "depuration."

[0047] In the present context, the term "farming" is generally synonymous with the terms "cultivation" and "raising."

[0048] In the present invention, it has surprisingly been observed that the combination of centralized and decentralized water treatment methods in a fish farm can have unexpected benefits and may allow the farm to operate according to various principles such as full recirculation, partial recirculation, and flow-through.

[0049] According to some embodiments, water treatment steps such as aeration, gas exchange, and removal of settleable solids may be performed by decentralized or tank-specific units each associated with a specific individual fish tank.

[0050] An aquarium-specific unit may be physically located within the aquarium, or outside the aquarium but adjacent or in close proximity to the aquarium.

[0051] According to some embodiments, water treatment steps such as flotation-based or filtration-based solids removal and biological water treatment may be performed centrally for the entire fish farm by a common unit.

[0052] The present invention may be applied both in recirculating aquaculture farms and in modular plants for cultivating aquatic species, such as the installations described in WO 2021 / 240061.

[0053] In one embodiment, gas exchange is performed by a separate tank unit. Gas exchange is most effective when the difference in gas concentrations is greatest.

[0054] In one embodiment, aeration is provided by a separate unit for each aquarium, which is advantageous since oxygen demand varies from aquarium to aquarium.

[0055] In one embodiment, oxygenation is provided by a separate aquarium unit.

[0056] In one embodiment, coarse solids removal is performed in a separate water tank unit. It is advantageous to remove large settleable solid particles from the recycle before they break down into smaller soluble particles. In this way, the need for additional water treatment steps, particularly solids removal, is reduced.

[0057] In one embodiment, fine solids removal is performed by a shared filtration-based unit. Such filtration units are typically expensive and therefore it is advantageous to include only one unit per farm.

[0058] In one embodiment, biological water treatment is performed by a shared unit, such as a shared bioreactor. Biological water treatment units are typically expensive, and therefore it is advantageous to include only one unit per farm. Biological water treatment units also typically require a continuous and even load, which can be better ensured by feeding effluent from several tanks into the same biological water treatment unit. While the amount of fish and feed used in any individual tank, and the resulting biological load entering the bioreactor from any individual tank, can vary significantly, at the farm level the biological load becomes more consistent.

[0059] In one embodiment, the water treatment unit may operate and supply water based on water quality measurements. Water may be routed to the water treatment unit and functions at any time based on actual demand. The amount of pipelines required to achieve such intelligent water treatment may be reduced when some of the water treatment functions are tank-specific and installed in association with individual tanks.

[0060] In some embodiments, the fish farming system includes fewer and / or smaller diameter pipelines than conventional farms for recirculating aquaculture. That is, each tank must have its own freshwater line, but the drain line may be common to all tanks. Also, because the gas exchange is tank-specific, the large hydraulic loads of conventional farms for recirculating aquaculture are not required. The drain line may be implemented as a trough, which may be used as a waterway for transferring fish.

[0061] In a recirculating aquaculture system, the fish tanks must be provided with sufficient oxygen and secretions harmful to the fish, namely carbon dioxide, ammonium, and feces (solids), must be removed.

[0062] Carbon dioxide concentrations are usually the first to rise to levels that are harmful to the fish. Therefore, in conventional RAS farms, carbon dioxide removal determines the pumping demand, i.e., both the amount of water pumped and the height of the pumping. The pumping demand determines the energy consumption of the farm.

[0063] Gas exchange, such as the addition of oxygen and removal of carbon dioxide, is most effective in the fish tank because it occurs when carbon dioxide concentrations are highest and oxygen concentrations are lowest. A large concentration differential accelerates the gas exchange, thereby reducing the need for pumping water throughout the farm and increasing resource efficiency throughout the water treatment process. At the same time, the ammonium concentration of the incoming wastewater can be maintained at a higher level, improving the operation of the bioreactor.

[0064] Separate tank gas exchange can reduce the farm's energy consumption by over 50% due to reduced water pumping requirements (lower water head).

[0065] Solids removal is more effective when it occurs close to where the solids are generated. For example, treating the effluent from an aquarium with a radial flow settler or swirl separator associated with the aquarium can remove any settleable feces and food debris before it breaks down into smaller, non-settling particles that are more difficult to remove.

[0066] Rapid removal of solids can reduce the amount of dissolved nutrients and carbon in the water and the number of bacteria in the water, which correlate well with the number of particles and the concentration of available carbon and nutrients in the water, and also reduce the biological oxygen demand caused by the decomposition of organic matter, thus resulting in lower oxygen / energy consumption throughout the farm.

[0067] Rapid removal of solids can reduce the amount of soluble nutrients and carbon in the wastewater.

[0068] If a significant portion of most of the solids are removed by settling near the source, it may be possible to have a smaller capacity fine solids removal unit, such as a smaller capacity drum filter, as the centralized solids removal unit, which may be better adapted for fine solids removal since the coarse solids are already removed by the separate tank unit.

[0069] The present invention may provide cost benefits during construction of a fish farm and also during operation of said fish farm.

[0070] The present invention may introduce flexibility by allowing the individual fish tanks to be operated according to full recirculation, partial recirculation, or flow-through principles.

[0071] This system can be advantageous for use in research, where the present invention can offer many advantages due to its flexibility: a single system provides three options for research: flow-through, partial recirculation, and full recirculation water treatment principles.

[0072] The system may allow for a low head, for example less than 1 meter, for example less than 0.5 meters, for example less than 0.3 meters, or for example as low as about 0.3 meters, which directly translates into low energy consumption and a small carbon footprint for the farm.

[0073] The present invention eliminates the trickling filter bed required for carbon dioxide removal, which can significantly reduce the need to pump water.

[0074] In the present invention, since the gas exchange can be performed by feeding air to water instead of feeding water to air, and since the various water treatment processes do not have to rely on the same water flow, the aeration effectiveness and therefore energy consumption can also be better controlled and regulated.

[0075] The present invention provides an improved recirculating aquaculture system that is similar to the so-called "all-in, all-out" aquaculture principle, which is a recognized biosafety production strategy in all animal production.

[0076] The fish can be introduced into an aquarium operating according to the partial recirculation principle, with the effluent from the aquarium flowing out of the system. The aquarium is preferably disinfected. Once the fish have grown a little and their health has been confirmed, the aquarium can be connected to the centralized water treatment loop, including a biological water treatment unit. When the fish are nearing the time of slaughter, the aquarium can be disconnected again from the biological water treatment unit. This is possible because aeration and solids removal are performed in conjunction with the aquarium. Inlet fresh water (i.e., inlet fresh water) is introduced into the aquarium after disinfecting the water, for example with hydrogen peroxide. The aquarium operates according to the partial recirculation principle. The effluent from the aquarium can be used as inlet water in the part of the system connected to the biological water treatment.

[0077] The system of the present invention can be particularly advantageous in the production of food or edible fish, typically for human consumption, because it provides improved off-flavor control and reduction capabilities. In some embodiments, the fish is one or more of the following: Atlantic salmon, tilapia, rainbow trout, European whitefish, brown trout, Arctic char, sturgeon, pikeperch, and eel.

[0078] The system according to the present invention can be advantageous for shrimp production.

[0079] Before slaughtering and selling the fish, the fish must be purged to remove off-flavor substances from the fish flesh.

[0080] In traditional purging, the fish are placed in a separate purging tank and are not fed during the purging period, which can last up to two weeks. Due to the fasting, the fish may lose 5% to 15% of their body weight during the traditional purging period.

[0081] Some embodiments of the present invention may provide benefits related to purging fish. It may be possible to continue feeding the fish during the initial period of the purging period. The purging involves disconnecting the purged tank from the recirculation and supplying the tank with fresh water. By continuing to feed the fish in this manner, the fish's metabolism remains more active than if they were starved. In this way, the removal of accumulated off-flavor substances may be more effective. It may also increase the profitability of the fish production, as the fish lose less weight during purging. Fasting may be necessary only for the last few days of the purging period, e.g., 2 to 3 days, to allow the fish's intestinal tracts to empty. The total length of the purging period may be 8 to 12 days.

[0082] In some embodiments, weight loss in the fish may be reduced or avoided during the purging.

[0083] In one embodiment, there is no need to transfer fish from rearing tanks to a separate purge tank, thereby reducing stress and mortality experienced by the fish and the manpower required at the farm.

[0084] The present invention can be advantageous in the production of fingerlings and juveniles.

[0085] The present invention may be advantageous in situations where acclimatization of the fish is required.

[0086] The present invention can facilitate the combination of traditional (non-recirculating) and recirculating aquaculture.

[0087] In this system, the fish can be acclimated to either free-flowing, partially recirculating or fully recirculating conditions, after which they can be safely transferred to a corresponding production environment at any time of year or season.

[0088] Individual fish tanks may be operated according to partial recirculation whenever desired, for example to medicate the fish therein, so that the microorganisms in the bioreactor are not disturbed, and rest periods are not applied to the entire farm, but only to the tanks to which the medicant is being administered.

[0089] The system may be operated according to the principle of partial recirculation but without the bioreactor. However, the bioreactor may continue to be utilized to treat the wastewater discharged from the system so that the bioreactor remains operational and ready to be reconnected to the recirculation. The bioreactor converts ammonium nitrogen to nitrate. Thus, nitrogen removal from the wastewater may be achieved by a denitrifying bioreactor, such as a denitrifying wood chip bioreactor.

[0090] In one embodiment, the biological water treatment unit is a moving bed bioreactor and the means for recirculating water is an airlift pump. The advantages are improved gas exchange, reduced need for vertical pumping of water, and reduced energy consumption for the farm.

[0091] In one embodiment, the low pumping head allows for the use of energy efficient air lift pumps, which also improve gas exchange.

[0092] Next, a fish farming system according to some embodiments will be described in detail.

[0093] In a preferred embodiment, the fish farming system is based on recirculation aquaculture and comprises at least two fish farming tanks, at least one individual water treatment unit connected to one of the tanks and configured to treat the water of said tank, and at least one shared water treatment unit connected to all of the tanks and configured to treat the water recirculating through the system, and also comprises means for recirculating water through the system.

[0094] The fish farming tank may be a land-based tank or alternatively a floating tank, with land-based tanks being preferred.

[0095] At least one of the aquaria includes a fresh water inlet connected to a fresh water line (i.e., a fresh water line), through which the system is supplied with fresh water (i.e., fresh water), which enters the recirculation system.

[0096] Each aquarium also typically includes a water intake connected to a recirculation loop.

[0097] In one embodiment, each aquarium includes a drain outlet connected to a common drain line, said common or shared drain line being connected to an inlet of said at least one shared water treatment unit.

[0098] In one embodiment, at least some, and preferably all, of the inlets and outlets of the aquaria are configured to be disconnectable from and reconnectable to the system, with the advantage that different operating modes of the system can be used, such as partial recirculation for one or more of the aquaria.

[0099] The at least one aquarium-specific water treatment unit may include an aquarium-specific unit for aeration of the water in the aquarium.

[0100] The at least one aquarium-specific water treatment unit may include an aquarium-specific unit for exchange of gases in the water of the aquarium.

[0101] The gas exchange or aeration typically involves the supply of air or oxygen to the water of the aquarium and the removal of carbon dioxide from the water of the aquarium.

[0102] The at least one aquarium-specific water treatment unit may include a aquarium-specific unit for removal of solids from the water of the aquarium.

[0103] For example, the solids may include sinkable or coarse solids such as fish waste and / or fish food residues.

[0104] The solids removal tank unit may comprise a vertical clarifier or a gravity-based settler such as a radial flow settler or a swirl separator. Preferably, the gravity-based settler is a radial flow settler.

[0105] In one embodiment, said at least one per-tank water treatment unit comprises a per-tank unit for the removal of fine suspended solids from the water of said tank, for example by flotation.

[0106] The at least one shared water treatment unit may include a shared unit for removal of solids from the recirculating water.

[0107] Typically, the solids include fine solids, such as non-settling solids.

[0108] In one embodiment, the shared unit for removing solids comprises a filter, a drum filter, a drum screen, a belt filter, or a flotation unit.

[0109] The at least one shared water treatment unit may include a shared unit for biological treatment of the recirculating water.

[0110] The shared unit for biological treatment may comprise a bioreactor such as a moving bed bioreactor, a fixed bed bioreactor, a fluidized bed bioreactor, or a trickling filter column bioreactor. Preferably, the bioreactor is a moving bed bioreactor.

[0111] The means for recirculating the water may include an airlift pump, a centrifugal pump, or an axial pump, preferably an airlift pump. Conventional water pumps may also be used.

[0112] Below, methods of farming fish according to some embodiments are described.

[0113] In some embodiments, the fish farming method is carried out by the system described above.

[0114] Each of said tanks may be operated independently of the other according to the full recirculation, partial recirculation or flow-through principle.

[0115] The operating principle of any individual aquarium may be changed when and for as long as desired.

[0116] For example, at intervals or for a period of time, at least one of the aquaria may be operated according to the flow-through principle, with the aquaria being disconnected from the recirculation, which typically means that the inlet(s) and the outlet(s) of the aquaria are disconnected from the recirculation loop.

[0117] As another example, at intervals or for a certain period of time, at least one of the aquaria is operated according to the principle of partial recirculation, which usually means that either the intake or the outlet of the aquaria is disconnected from the recirculation loop.

[0118] As a further example, at intervals or for a certain period of time, at least one of the water baths, preferably all of the water baths, is operated according to the principle of recirculation.

[0119] The above examples may be combined so that there can be any combination of aquaria operating according to full recirculation, partial recirculation, or flow-through principles in the system, and so that the operating principles of individual aquaria can be changed over time as desired.

[0120] In one embodiment, the fish in one of the tanks may need to be acclimated to specific conditions. The tank may then be operated according to a free-flow, partial recirculation, or full recirculation principle for a period of time to acclimate the fish in the tank to free-flow, partial recirculation, or recirculation conditions, respectively. After such an acclimation period, the acclimated fish may be transferred from the tank to corresponding conditions outside the system. The present invention may allow such acclimation to occur without the fish welfare issues and mortality associated with direct transfer to different environmental conditions.

[0121] In one embodiment, a new fish is to be introduced into one of the tanks. In such a situation, the method may include disconnecting the drain of the tank from the system, draining the water from the tank outside the system, disinfecting the tank, and then introducing the new fish into the disinfected tank. After the introduction, the health of the fish is monitored. Once it is determined that the new fish is healthy and therefore will not spread pathogens to the fish in the remaining tanks, the drain of the tank containing the new fish is reconnected to the system.

[0122] In one embodiment, medication, such as the administration of an antibiotic, is administered to the fish in a particular aquarium. In this situation, the method may include disconnecting the aquarium's drain from the system, draining the aquarium's wastewater outside the system, and then treating the fish in the aquarium with a medication, such as an antibiotic. The treatment is followed by a withdrawal period during which the medication is released from the treated fish. After the withdrawal period, the aquarium's drain can be reconnected to the recirculation system without any risk of the medication being introduced into the other aquariums.

[0123] In one embodiment, the fish in the aquarium are to be harvested and slaughtered for sale. In this situation, the fish need to be purged or cleaned of off-flavor substances. The method typically involves disconnecting the water intake of the aquarium from the recirculation, providing the aquarium with fresh, and optionally disinfected, off-flavor-free water, and allowing the off-flavor substances to be purged from the fish during a defined purging period. After the purging period, the fish can be harvested from the aquarium for slaughter.

[0124] Off-flavor problems usually occur in RAS systems, but can also appear in PRAS systems.

[0125] In some embodiments, the purge period consists of a feeding period followed by a fasting period. During the fasting period, the fish are not fed. The purge period may be at least 5 days, for example, 6 to 10 days. The fasting period may be less than 5 days, for example, 2 to 4 days.

[0126] In some embodiments, disinfection of the aquarium may be performed. Such disinfection may be performed by introducing fresh disinfected water into the aquarium. The disinfected water may be obtained by using a disinfectant, which may be hydrogen peroxide, peracetic acid, and / or ozone, or by UV radiation sterilization, or a combination thereof.

[0127] Alternatively or additionally, the disinfection may be performed in situ by disinfecting the water in the aquarium, typically by supplying a disinfectant to the aquarium for a period of time to obtain a defined disinfectant concentration.

[0128] The disinfection may be carried out to reduce the accumulation of off-flavor substances in the fish or to remove off-flavor substances from the fish. The disinfection may also be carried out to remove fish pathogens from the aquarium.

[0129] In some embodiments, a disinfectant and / or oxidant is provided to the fish tank to be purged or during the purging. The disinfectant and / or oxidant may be selected from the following group: hydrogen peroxide, peracetic acid, ozone, and any combination thereof. An advanced oxidation process (AOP) may be used.

[0130] AOP refers to the use of at least two processes selected from a disinfection process and an oxidation process. For example, a combination of ozone and UV light, or a combination of ozone and hydrogen peroxide, or a combination of hydrogen peroxide and UV light can be applied. Such combinations can produce synergistic effects.

[0131] For example, the disinfectant may be hydrogen peroxide, which may be supplied to the aquarium so as to maintain a concentration of hydrogen peroxide in the aquarium at a level of at least 1 mg / L, such as at least 2 mg / L, for example at least 3 mg / L, for example from 1 mg / L to 10 mg / L, preferably from 3 mg / L to 5 mg / L.

[0132] The supply of the disinfectant or oxidant may be carried out as a continuous supply or as a pulsed supply.

[0133] The disinfectant or oxidant may be fed directly to the water tank, or alternatively upstream from the water tank, i.e., to the new water line, in which case the new water can also be disinfected.

[0134] Preferably, the biological water treatment unit is connected to the system and receives effluent from at least one of the aquaria substantially most of the time, so that the biological load can be maintained at a sufficient and stable level for proper operation of the unit.

[0135] The present invention also relates to the use of both tank-specific water treatment units and such a water treatment unit common to all tanks in a fish farming system, which typically comprises several fish tanks and is configured for at least recirculating aquaculture.

[0136] 1 illustrates a system according to at least some embodiments of the present invention. The system includes a moving bed bioreactor (MBBR) and an airlift pump. In particular, the system includes: New water lines 100a, 100b, a water recirculation line 101a driven by an air lift pump; drain line 102, sludge line 103, common drain pipe 104, Fish tank 105e, Aeration unit 106d for separate tanks; Radial flow settler 107h, Drum filter 108, Moving bed bioreactor 109, an overflow pipe 110h from the aeration unit for each tank; and an overflow pipe 111g from the radial flow settler.

[0137] The system includes eight fish tanks, such as tank 105e. Four tanks are located on either side of the common conduit 104 leading to the shared unit. Each tank has its own aeration unit (triangle), such as 106d, and coarse (settling solids) removal unit, such as 107h. The fines removal unit 108 is shared, as is the biological purification unit (MBBR) 109. Arrows, such as 101a, indicate water recirculation pipes, and arrows 100a and 100b indicate freshwater intake pipes. [Example]

[0138] The following describes data from experiments on a hybrid aquaculture system (HAS), which is a system according to one embodiment of the present invention.

[0139] The HAS had separate aeration devices and radial-flow settlers for gas exchange and solids removal. The drum filter and moving-bed bioreactor were common to all six aquaria. The fish tanks were 500 liters in size. The experiment consisted of three phases. Phase 1 (33 days of restricted feeding) was for health assessment and biofilter acclimation of newly arrived fish. All aquaria were used as partial recirculation systems, with aquaria wastewater diverted to the biofilter. Phase 2 (40 days of ad libitum feeding) was the main production phase. The aquaria were connected to the biofiltration and microsolids removal loops. Phase 3 (restricted feeding or no feeding) was a purification step for off-flavor removal. During the purification, all aquaria were placed in partial recirculation mode by disconnecting them from the biofiltration loop, and hydrogen peroxide administration was initiated. Two feeding regimes were compared during the purification process: feeding (restricted feeding) and starvation (no feeding). During the first phase, the water use was 10,000 l / kg feed, during the second phase (RAS) the water use was 650 l / kg feed, and during the third phase the hydraulic retention time was 3.5 h, which is equivalent to 8,800 l / kg feed for the feeding groups (groups A1, A2, A4, and A5). For the administration of hydrogen peroxide, a concentration of 5 mg / l was used.

[0140] Results: During the 28-day cleanup period, the fed fish groups (A1, A2, A4, and A5) experienced a 6.93% increase in fish biomass, while the unfed fish groups (A3 and A6) experienced a 6.49% decrease in biomass (see Figure 2). The concentrations of the off-flavor chemicals geosmin (GSM) and 2-methylisoborneol (MIB) in the water decreased at the same rate in both treatments, reaching source (incoming) water concentrations by the end of the experiment (see Figures 3 and 4). The concentrations of GSM and MIB in the fish flesh were also below their sensory thresholds in both groups (R. Robertson et al., 2005, suggested a sensory threshold of 0.9 μg / kg for GSM and 0.7 μg / kg for MIB in rainbow trout).

[0141] It can be concluded that the hybrid aquaculture system / process allows for the separation of the fish tanks at any point in the production cycle. At the end of the production cycle, separate tanks allow for gas exchange and sedimentation, allowing for feeding during the purification process. Experimental results show that the hybrid aquaculture system can produce 13.4% more saleable biomass than the traditional RAS production model. Feed efficiency is also improved because the fish do not lose weight before harvest. Since a feed conversion ratio of 1.0 is common in trout production, the 6.49% weight loss in the fasted group also means that RAS production consumes 6.49% more feed than HAS production to produce the same amount of fish meat. Feed is a major production cost in aquaculture, accounting for approximately 50% of total production costs.

[0142] The results are illustrated in FIGS.

[0143] Figure 2: Changes in rainbow trout body weight during the decontamination process. Tanks A1, A2, A4, and A5 were fed during the decontamination process. Tanks A3 and A6 underwent the decontamination process currently used by the recirculating aquaculture industry, and the fish were fasted during decontamination.

[0144] Figure 3: Concentrations of the off-flavor chemical 2-methylisoborneol (MIB) in tank water and the source (incoming) water in a hybrid aquaculture system experiment. Tanks A1, A2, A4, and A5 were fed during the purification process. Tanks A3 and A6 underwent the purification process currently used by the recirculating aquaculture industry, and the fish were fasted during purification.

[0145] Figure 4: Concentration of the off-flavor chemical geosmin (GSM) in tank water and the source (incoming) water in a hybrid aquaculture system experiment. Tanks A1, A2, A4, and A5 were fed during the purification process. Tanks A3 and A6 underwent the purification process currently used by the recirculating aquaculture industry, and the fish were fasted during purification.

[0146] Figure 5: Concentration of the off-flavor chemical 2-methylisoborneol (MIB) in fish flesh in experimental hybrid aquaculture systems. Tanks A1, A2, A4, and A5 were fed during the depuration process. Tanks A3 and A6 underwent the depuration process currently used by the recirculating aquaculture industry, and the fish were fasted during depuration.

[0147] Figure 6: Concentration of the off-flavor chemical geosmin (GSM) in fish flesh in experimental hybrid aquaculture systems. Tanks A1, A2, A4, and A5 were fed during the depuration process. Tanks A3 and A6 underwent the depuration process currently used by the recirculating aquaculture industry, and the fish were fasted during depuration.

[0148] It is to be understood that the disclosed embodiments of the invention are not limited to the particular structures, process steps, or materials disclosed herein, but extend to equivalents thereof that will be recognized by those skilled in the art. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0149] The reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

[0150] As used herein, a plurality of items, structural elements, components, and / or materials may be presented in common lists for convenience. However, these lists should be construed as though each element of said list were individually identified as a separate and unique element. Accordingly, any individual element of such a list should not be construed as a de facto equivalent of any other element of the same list solely based on being presented in a common group, unless otherwise indicated. Also, various embodiments and examples of the present invention may be referred to herein, along with alternatives for the various components thereof. It should be understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of each other, but rather as separate and independent representations of the present invention.

[0151] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the present invention. However, one skilled in the art will recognize that the present invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the present invention.

[0152] While the foregoing examples illustrate the principles of the present invention in one or more particular applications, it will be apparent to those skilled in the art that numerous variations in embodiment, use, and detail may be made therein without the exercise of the inventive faculty and without departing from the principles and concepts of the present invention. Accordingly, it is not intended that the present invention be limited except as by the claims which follow.

[0153] The verbs "to comprise" and "to include" are used herein as open limitations that do not exclude or require the presence of unrecited features. The features recited in the dependent claims may be freely combined with one another, unless expressly stated otherwise. Furthermore, the use of "a" or "an", i.e., the singular, throughout this document is to be understood as not excluding a plurality.

[0154] (List of acronyms) RAS: Recirculating Aquaculture System PRAS: Partial Recirculating Aquaculture System or Partial Reuse Aquaculture System MBBR: Moving Bed Bioreactor GSM: Geosmin MIB: 2-methylisoborneol AOP: Accelerated oxidation method [Industrial Applicability]

[0155] The present invention is industrially applicable at least in the aquaculture of fish and shrimp. [Explanation of symbols]

[0156] 100a, 100b: New water line 101a: Water recirculation line driven by airlift pump 102: Drain line 103: Sludge line 104: Common drain pipe 105e:Fish tank 106d: Separate aeration unit for tanks 107h: Radial flow settler 108: Drum Filter 109: Moving bed bioreactor 110h: Overflow pipe from aeration unit for each tank 111g: Overflow pipe from radial flow settler

Claims

1. An aquaculture system, such as a fish or shrimp farming system, based on a recirculating aquaculture system, At least two aquaculture tanks, At least one tank-specific water treatment unit connected to one of the aforementioned tanks and configured to treat the water in the aforementioned tank, At least one shared water treatment unit connected to all of the aforementioned tanks and configured to treat the water being recirculated within the system, A system comprising means for recirculating water within the aforementioned system.

2. The system according to claim 1, wherein the aquaculture tank is a land-based tank or a floating tank.

3. At least one of the aforementioned tanks includes a new water inlet connected to a new water line, The system according to claim 1 or 2, wherein each tank includes an intake connected to the recirculation.

4. The system according to claim 1 or 2, wherein each tank includes a drain connected to a common drain line, and the common drain line is connected to the inlet of the at least one shared water treatment unit.

5. The system according to claim 1 or 2, wherein the intake port and the drain port of the water tank are configured to be detachable from the system and reconnectable to the system.

6. The system according to claim 1 or 2, wherein the at least one tank-specific water treatment unit includes a tank-specific unit for aeration of the water in the tank and / or gas exchange in the water in the tank.

7. The system according to claim 6, wherein the aeration or gas exchange includes supplying air or oxygen to the water in the tank, such as oxygen supply.

8. The system according to claim 6, wherein the aeration or gas exchange includes the removal of carbon dioxide from the water in the tank.

9. The system according to claim 1 or 2, wherein the at least one tank-specific water treatment unit includes a tank-specific unit for removing solid matter from the water in the tank.

10. The system according to claim 9, wherein the solid matter includes settling solid matter or coarse solid matter, such as feces and / or leftover feed.

11. The system according to claim 9, wherein the separate water tank unit for removing solid matter includes a gravity-based setter such as a radial flow setter or a swirl separator.

12. The system according to claim 1 or 2, wherein the at least one tank-separated water treatment unit includes: i) a tank-separated unit for gas exchange, which includes supplying air and / or oxygen to the water in the tank, wherein the gas exchange includes removing carbon dioxide from the water in the tank; and ii) a tank-separated unit for removing settling solids from the water in the tank.

13. The system according to claim 1 or 2, wherein the at least one shared water treatment unit includes a shared unit for removing solids from the recirculating water.

14. The system according to claim 13, wherein the solid material includes microsolids.

15. The system according to claim 13, wherein the shared unit for removing solid matter includes a filter such as a drum filter, drum screen, belt filter, or flotation unit.

16. The system according to claim 1 or 2, wherein the at least one shared water treatment unit includes a shared unit for the biological treatment of the recirculating water.

17. The system according to claim 16, wherein the shared unit for biological processing includes a moving bed bioreactor, a fixed bed bioreactor, a fluidized bed bioreactor, or a drip filter tower bioreactor.

18. The system according to claim 1 or 2, wherein the means for recirculating the water includes an airlift pump, a centrifugal pump, or an axial flow pump.

19. A method for cultivating aquatic organisms such as fish or shrimp by using the system described in claim 1 or 2.

20. The method according to claim 19, wherein each of the tanks is operated independently of the others according to the principles of flow-through, partial recirculation, or recirculation.

21. The method according to claim 19, wherein at least one of the tanks is operated on a flow-through basis at intervals, and the intake and outlet of the tanks are disconnected from the recirculation.

22. The method according to claim 19, wherein at least one of the tanks is operated at intervals according to the principle of partial recirculation, and either the intake or the outlet of the tank is disconnected from the recirculation.

23. The method according to claim 19, wherein at least one, preferably all, of the tanks are operated at intervals in accordance with the principle of recirculation.

24. At least one of the aforementioned tanks is operated by continuously flowing the fish or shrimp inside it for a certain period of time in order to allow it to adapt to the conditions of partial recirculation or recirculation, and is operated according to the principle of partial recirculation or recirculation. After the aforementioned period, the adapted fish or shrimp are moved from the tank to the conditions outside the system. The method according to claim 19, including the method described in claim 19.

25. Disconnecting the drain port of the aquarium from the system, The drainage from the aforementioned tank is discharged to the outside of the system, Disinfecting the aforementioned tank, Introducing new fish or shrimp into the aforementioned tank, The method according to claim 19, further comprising reconnecting the drain outlet of the aquarium to the system after a certain period of time has passed and the health status of the fish or shrimp has been confirmed.

26. Disconnecting the drain port of the aquarium from the system, The drainage from the aforementioned tank is discharged to the outside of the system, Treating the fish or shrimp in the aquarium with antibiotics or other medications, The method according to claim 19, further comprising reconnecting the drain outlet of the water tank to the system after the completion of the treatment and after a predetermined drug-free period has elapsed.

27. When the time comes for the fish or shrimp in the tank to be slaughtered, To provide disinfectant water to the aforementioned tank, During the purging period, off-flavor substances are purged from the fish or shrimp, After the purging period, the fish or shrimp are harvested from the tank for slaughter. The method according to claim 19, further comprising purging the fish or shrimp by means of.

28. The method according to claim 27, further comprising disconnecting the water intake of the water tank from the recirculation before supplying disinfectant water to the water tank.

29. The method according to claim 27, wherein the purging period comprises a feeding period and a subsequent fasting period.

30. The method according to claim 19, comprising supplying new disinfectant water to at least one of the tanks, wherein the disinfectant water is obtained by using a disinfectant which may be hydrogen peroxide, peracetic acid, or ozone, or by UV radiation sterilization, or a combination thereof.

31. The method according to claim 19, further comprising disinfecting the water in at least one of the aforementioned tanks in situ by supplying hydrogen peroxide to the tank for a certain period of time.

32. The method according to claim 19, further comprising disinfecting the water in at least one of the tanks in situ by supplying peracetic acid to the tank for a certain period of time.

33. The method according to claim 19, further comprising disinfecting the water in at least one of the tanks in situ or the like by supplying ozone to the tank for a certain period of time.

34. The method according to claim 19, further comprising disinfecting the water in at least one of the aforementioned tanks for a certain period of time by accelerated oxidation (AOP) in situ or the like.

35. The method according to claim 30, wherein the disinfection is performed for the purpose of reducing or removing the accumulation of off-flavor substances, or for the purpose of removing pathogens from fish or shrimp.

36. The method according to claim 19, wherein for substantially most of the time the biological water treatment unit is connected to the system and receives wastewater from at least one of the tanks.

37. The use of both individual tank water treatment units and a common water treatment unit for all tanks in an aquaculture system, such as a fish or shrimp farming system, which includes several aquaculture tanks and is configured for recirculating aquaculture.

38. A method of cultivating aquatic organisms such as fish or shrimp in a system based on a recirculating aquaculture system, When the time for slaughtering the fish or shrimp in the aquaculture tank is reached, To provide disinfectant water or disinfectant to the aforementioned tank, During the purging period, off-flavor substances are purged from the fish, Feeding the fish during at least the initial part of the purging period, After the purging period, the fish are harvested from the tank for slaughter. A method comprising purging the fish or shrimp by means of.

39. The method according to claim 38, wherein the provision of the disinfectant water or disinfectant is preferably carried out continuously or in a pulsed manner by supplying one or more pulses of the disinfectant water or disinfectant to the water tank during at least a portion of the purging period.

40. The method according to claim 38 or 39, wherein the feeding is suspended for 0.5 to 5 days, such as 2 to 4 days, before the end of the purging period.

41. The method according to claim 38 or 39, wherein during the purging period, the purged tank is not connected to any biological water treatment unit in the system, and the purged tank is connected to a gas exchange unit specific to the tank.

42. The method according to claim 38, wherein the system described in claim 1 or 2 is used.

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