Recirculating aquaculture system with improved feed transport and feed transport method in recirculating aquaculture system

Abstract

To provide an aquaculture system for executing improved and gentle feed transport.SOLUTION: An aquaculture system 1 comprises a fish holding unit 2 fluidly connected to a water recirculation conduit 3, a water treatment unit 23, a water inlet and a feed storage unit 31. The system further comprises a feed loading part 30. When feed is loaded into the system at the feed loading part, it is transported to the fish holding unit. Alternatively, a feed transport method in the recirculating aquaculture system is provided.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a system and method for transporting feed, and more particularly to the transport of feed in a recirculating aquaculture system (RAS). [Background technology]

[0002] Farmed fish and shellfish depend on the uptake of all necessary nutrients contained in feed delivered to the aquaculture site, for example in floating cages in the ocean, flow-throughs connected to rivers and ponds, or on-shore facilities such as RAS facilities. Most of the equipment used to transport fish feed to feeding sites today is mainly pneumatic or mechanical. Typically, in pneumatic transport, either a fan or an air compressor is used to blow the feed pellets. As described in WO2015067955, it is well known that pneumatic transport of feed pellets is prone to pellet degradation and the generation of up to 7% dust and fines. Also, the pipes used for feed transport are subject to wear due to friction between the pipe walls and the pellets.

[0003] Steel pipes are heavy, require additional supports and are expensive, whereas plastic pipes are cheaper but require more maintenance and release microplastics into the feed and aquaculture. The generation of fines and dust from feed pellets represents a significant cost and must be minimized as much as possible. This represents a loss of feed and essential / limiting nutrients and pollutes the surrounding environment. In the case of RAS facilities, it additionally puts stress on the mechanical and / or (micro)biological filters used to clean the water in the aquaculture system.

[0004] Another method of transporting fish feed is by hydraulic transport, known from WO2002056676, which relates to a system using hydraulic feeding to supply feed below the water surface, particularly relevant for demersal fish such as catfish, turbot and halibut. Hydraulic transport is also known from WO2011064538 and WO2015067955, which describe a method using hydraulic transport of aquaculture feed to impregnate dried fish feed pellets with water to improve digestibility. Impregnation of the feed will cause mass transfer, not only water entering the feed, but also nutrients and oils leaking out of the feed into the water.

[0005] WO2016160141 discloses a modularized shrimp production system. The system includes a production subunit module, a RAS module, a feed distribution module, and a computer control module. The system is modularized and integrated to form a multi-stage synchronized super-integrated shrimp production system controlled by a custom-designed cyber-physical platform. It is believed that the system can aquaculture shrimp with a significantly reduced total water volume per weight of shrimp produced compared to conventional techniques.

[0006] Nutrient losses are undesirable and incur additional costs as more feed is required to provide the nutrients required by the fish.

[0007] Oil leakage from the feed is not optimal, but is tolerable when fish are kept in open water. However, in RAS facilities, for example, the oil will settle in the filters and reduce their efficiency. This can lead to increased amounts of CO2 in the wash water, which has the effect of slowing down fish growth.

[0008] It is therefore desirable to develop a gentler and more efficient method of transporting feed, particularly in RAS facilities. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2015067955 [Patent Document 2] International Publication No. 2002056676 [Patent Document 3] International Publication No. 2011064538 [Patent Document 4] International Publication No. 2016160141 Summary of the Invention

[0010] It is an object of the present invention to provide an aquaculture system with improved gentle feed transport. Thus, according to a first aspect of the present invention, this and other objects are achieved by an aquaculture system comprising: The system comprises a fish holding unit fluidly connected to a water recirculation conduit, a water treatment unit, a water inlet, and a feed storage unit, and further comprises a feed filling section located upstream of the water inlet or within the water recirculation conduit, where feed is hydraulically transported to the fish holding unit when it is introduced into the system at the feed filling section, the water recirculation conduit comprising the water treatment unit, and the feed filling section located downstream of the water treatment unit.

[0011] The fish holding unit, the water recirculation conduit, the water treatment unit, the water inlet and the feed storage unit may be connected in series, or the fish holding unit, the water recirculation conduit, the water treatment unit, the water inlet and the feed storage unit may be connected in parallel. Similarly, the fish holding unit, the water recirculation conduit, the water treatment unit, the water inlet and the feed storage unit may be connected in a combination of series and parallel. Thus, for example, the water recirculation conduit may comprise the water treatment unit and the feed storage unit connected in series, or the water inlet may be connected to the fish holding unit.

[0012] Hydraulic feed transport has been shown to provide a gentler feed transport and to reduce the amount of dust and fines generated. This system has also been shown to successfully reduce feed losses and the energy required for transport. Furthermore, installation costs can be significantly reduced since plastic pipes can be used without the risk of microplastic generation. Also, the installation of plastic pipes requires much less supports than, for example, steel pipes. Furthermore, when steel pipes are used, especially in RAS facilities designed for marine species such as grown salmon, the steel pipes are usually expensive high-grade stainless steel to avoid corrosion. Hydraulic transport also provides flexibility in installation, since the feed is significantly less damaged by elbows in the present hydraulic system compared to conventional pneumatic transport systems.

[0013] In a preferred embodiment, the feed filling section is placed in a conduit made of a plastic material. Preferably, the conduit of the recirculation conduit is also made of a plastic material. Plastics such as, but not limited to, PE, such as high density PE, nylon, PVC, POM, etc. can be used.

[0014] These advantages may be applied to aquaculture system facilities in which water is fully or partially recirculated. Aquaculture systems with recirculated water may be referred to as "recirculating aquaculture systems" (RAS) in the context of the present invention. Thus, in one embodiment, the aquaculture system of the present invention is a RAS. It will be clear to those skilled in the art that these advantages also apply to different types of farmed fish having a water transport pipeline that can be used for feed transport.

[0015] The term hydraulic transport is used to describe a solid-liquid two-phase flow. In this context, the solid-liquid two-phase flow is composed of fish feed, e.g., granules or pellets, and water. Granular or pelleted feed is preferred in this system, but other types of fish feed such as chunk feed, moist or semi-moist feed, or fish fillets may also be used.

[0016] Said fish holding unit may have any desired shape suitable for containing liquids. It may be, for example, a cylindrical shaped unit, or a cuboid shaped unit. It may be a tank, container, aquarium, basin, etc. made of any material. It may also be a pond or a depression in which some filtering and / or cleaning takes place. The top of the fish holding unit may be open or may have a removable or fixed lid. When the system is used as required, i.e. for rearing fish, there is water in the aquaculture system. Most of the water is usually contained within the fish holding unit where the fish are reared. The type of water in the system is adapted to the species of fish being reared. In the case of marine fish, the water is adapted to resemble marine water, whereas in the case of freshwater fish, the water is adapted to resemble fresh water. The quality and properties of the water may also be controlled, such as purity, in the following O2 content, temperature, etc.

[0017] Said recirculation conduit is a series of water conduits or water pipes suitable for transporting water to / from said fish holding unit. The recirculation conduit is fluidly connected to the fish holding unit forming a water circuit. The recirculation conduit is connected to the fish holding unit via at least one opening allowing water intake or discharge. Preferably, the water pipes in the recirculation conduit are used for continuous or intermittent discharge of water from the fish holding unit. The recirculation conduit through which the water passes may include one or more unit operations after which the water is returned to the fish holding unit, i.e. the recirculation conduit recirculates the water. In this context, the unit operations may be, but are not limited to, water treatment, input of solids such as feed, fluid transport means such as pumps. The point at which the water enters the recirculation conduit from the fish holding unit through an opening can be seen as the start of the water cycle. From this starting point, the water flows through the conduit and at some point returns to the fish holding unit. The point at which the water returns to the fish holding unit through an opening can be seen as the end point. It should be understood that the starting point and the ending point are included in the loop made by the recirculation conduit such that the water may flow from the ending point to the starting point. The water undergoes a certain residence time in the fish holding unit before re-entering the recirculation conduit at the starting point. The residence time may be defined from any point in the recirculation conduit to any other point in the recirculation conduit.

[0018] When the terms upstream and downstream are used to describe the location of a unit operation, for example, in a recirculation conduit, they are relative to this starting point unless otherwise specified.

[0019] The recirculation conduit may be coupled to a single fish holding unit, or a recirculation conduit may be used to couple several fish holding units together. In such cases, the fish holding units may be coupled in series or in parallel. When several fish holding units are connected by a recirculation conduit, the water from the fish holding units may be combined and treated in the same water treatment unit. Similarly, feed may be dosed into a single water stream at the feed filling section and then distributed to several individual fish holding units. As mentioned above, one type of unit operation contained within the recirculation conduit may be a water treatment unit. The water treatment unit includes a series of treatment processes to maintain water quality, such as, but not limited to, biological filtration, solids removal, e.g., filtration, oxygenation, pH control, temperature control, CO2 removal, optionally including heating and / or cooling, ultraviolet (UV) treatment and / or ozone treatment.

[0020] The recirculation conduit is not limited to recirculation of water within a single fish-holding unit. It may also flow water from a first fish-holding unit to a second fish-holding unit, preferably with a water treatment unit between the fish-holding units. In this configuration, the fish-holding units would be coupled in series such that the recirculation conduit or another recirculation conduit returns water from the second fish-holding unit to the first fish-holding unit.

[0021] The water inlet may refer to a water inlet that supplies water to the aquaculture system. Typically, fresh water is supplied to the aquaculture system through the water inlet. The water inlet to the aquaculture system may be located anywhere in the aquaculture system, such as in the recirculation conduit or directly in the fish holding unit. If the water inlet is an inlet for adding fresh water to the aquaculture system, it is preferable to locate this inlet upstream of or in the water treatment unit so that the water quality of the inflow water is suitable for the system. The aquaculture system may also comprise a water outlet. The water outlet may be located anywhere in the aquaculture system, such as in the recirculation conduit or in the fish holding unit, or may include a water outlet in both the fish holding unit and the recirculation conduit. The water outlet allows the flow of water out of the system. The aquaculture system may also have a combined conduit for the water inlet and outlet. Typically, in a RAS facility, the fresh water inlet is small because it is expensive to replace the amount of water in the facility.

[0022] Said feed storage unit is used for storing fish feed. The feed storage unit may be of any shape or size suitable for storing feed in the RAS facility. Typically the feed storage unit is a tank or silo. If the feed is produced on-site at the RAS facility, the feed storage unit may be a container part of a feed production unit in the facility. Such a container part may function to hold at least the freshly produced feed. The feed storage unit is preferably located adjacent to a feed filling section. Said feed filling section is a conduit section in which feed can be dumped into the conduit with water flowing in the conduit. Feed may also be hydraulically transported from the feed storage unit to some of the fish holding units.

[0023] Injection of the feed from the feed storage unit into the water at the feed filling station can be accomplished using mechanical means such as a feed injection means, e.g. a feed screw in a conveyor, or by suction means, e.g. a Venturi injector, which obtains negative pressure to create a flow of feed into the water. Alternatively, the feed may be sucked into the feed loading section by negative pressure provided by a pump.

[0024] The feed filling section is a location in the conduit where the feed is introduced into the water flow. The feed is then hydraulically transported with the flow to the desired location. The feed filling section may be located upstream of the water inlet or may be fluidly connected to the water inlet so that when fresh water is added to the aquaculture system, the feed is hydraulically transported with the fresh water into the fish holding unit. In a RAS facility, it is desirable to minimize the amount of fresh water entering the facility, as this represents an additional cost. Typically, 99.5% of the water in the RAS facility is recirculated. The amount of fresh water added is only about 0.5% of the total water volume. Depending on the amount of fish in the aquaculture system, this water flow may not be sufficient to hydraulically transport a sufficient amount of feed. Therefore, in a preferred embodiment, the feed filling section is located in a water recirculation conduit. By recirculating the water from the fish holding unit, the desired volumetric flow rate for the hydraulic transport of the feed can be obtained without the need for additional fresh water. By controlling the desired volumetric flow rate, generally all parameters related to the water flow can be adapted in a manner suitable for the hydraulic transport of the feed. For example, the flow may be adjusted to be gentle, resulting in less fines and / or liquid losses (such as oil losses). Another example would be the ability to control the flow to distribute the feed more widely. The increased volumetric flow rate provided by recirculation allows for the use of conduits with larger cross-sectional areas at water flow rates suitable for the hydraulic transport of feed. If the feed is hydraulically transported through a conduit with a larger cross-sectional area, the feed is effectively distributed over a larger area / volume when it leaves the conduit and reaches the desired location. Thus, water flow through a conduit with a larger cross-sectional area at a water flow rate suitable for the hydraulic transport of feed results in a more widespread distribution of the feed compared to water flow through a conduit with a smaller cross-sectional area at the same water flow rate suitable for the hydraulic transport of feed. In addition to allowing for a wider distribution area, the higher volumetric flow rate provided by recirculation allows for a higher water velocity in the recirculation conduit, even when a conduit with a larger cross-sectional area is used. Water flowing at a greater velocity through a conduit of a given cross-sectional area will result in a more widespread distribution of feed as the feed-laden water exits the conduit, compared to water flowing at a lower velocity through a conduit of the same cross-sectional area.A broad distribution of feed is advantageous because the feed is more evenly distributed among the fish, resulting in a stock of fish with a smaller average size deviation. This is valuable to the industry because it reduces the number of small, worthless fish. Furthermore, it will take less time to grow fish to the minimum size required for shipping.

[0025] In aquaculture systems with minimal freshwater flow, water treatment is preferred to maintain good water quality. Fish holding units are typically 200m 3 ~50,000m 3 Typically, an industrial aquaculture system comprises several fish holding units. The fish holding units may contain up to 5,000 m 3 of small fish holding units, up to 15,000m 3 of medium-sized fish-holding units, or e.g. 3 , e.g., 25,000~35,000m 3 The fish holding unit may be a large fish holding unit, a small tank, a large fish holding unit, or a combination of these. The recirculation and treatment of the water in the fish holding unit depends heavily on the feed quality as well as the density of the fish in the fish holding unit. Fish density is the number of fish per volume of water in the fish holding unit. The water is recirculated and treated to maintain good water quality for the fish. If the fish density is low, the recirculation of the water may be less, for example, 0.5-5 times / hour, and if the fish density is high, the water in the fish holding unit may be recirculated up to 20 times / hour. Similarly, if the feed quality is high and there is less oil and disintegrated pellet particles present in the water, the recirculation of the water may be less. Thus, for a tank of 400m per 3 / hour~100,000m 3 A recirculating flow of water can be expected per hour. This recirculated water flow is large enough to transport feed. Furthermore, since current RAS facilities already have such conduits, a feed filling section may be retrofitted to the conduits to provide an aquaculture system with hydraulic transport of feed.

[0026] In a preferred embodiment, the water recirculation conduit comprises a water treatment unit located downstream of the starting point and upstream of the ending point, and further comprises a feed filling section located downstream of the water treatment unit and upstream of the ending point. This arrangement ensures that the feed is introduced into the water after the water treatment unit so that the feed is not damaged by differential treatment. Sufficient water treatment also allows exchange of treated water between different fish holding units without increasing the risk of infection between the fish holding units. Thus, water from one fish holding unit can be used to hydraulically transport feed to another fish holding unit.

[0027] In a preferred embodiment, the recirculation conduit from the feed filling section to the feeding point has a substantially constant diameter conduit with minimal height differences. In this way, sudden pressure changes are avoided. Typically, the diameter of the pipe from the feed filling section to the feeding point is between 25mm and 130mm, for example between 30mm and 100mm, preferably between 50mm and 60mm. Typically, a pipe diameter of 50mm to 60mm is sufficient for hydraulic transport of feed to a single fish holding unit, but a pipe diameter of 100mm or more may be required for hydraulic transport of feed to multiple fish holding units.

[0028] The height difference between the feed filling section and the feeding point is preferably not more than 5 meters, more preferably not more than 3 meters, for example in the range of 0-3 meters. The length of the conduit from the feed filling section to the feeding point may vary depending on the design of the aquaculture system. Preferably, the distance is fairly small, such as in the range of 10-50 meters, but it may be greater than 100 meters. Although a certain pressure drop can be expected in the conduit, by avoiding sudden pressure drops due to height differences or changes in pipe diameter, mass transfer of oil and nutrients from the pellets to the water caused by water impregnation of the pellets is unlikely. The total pressure drop is usually between 1 bar and 5 bar, but may be up to 7 bar.

[0029] The feeding point is where the fish in the fish holding unit become able to get food. This feeding point is therefore located within the fish holding unit near the end opening. Usually the maximum pressure drop for the pellets occurs at the feeding point. The pressure in the fish holding unit is around 1 bar, while the pressure in the recirculation conduit can be more / less depending on the water recirculation. When the pellets enter the fish holding unit at the feeding point from the recirculation conduit they can experience a pressure drop of up to 7 bar. Usually this pressure drop is less, such as 2-3 bar.

[0030] The inventors have found that the pressure drop occurs when the pellets enter the stagnant water, which causes the pellets to be saturated with water and to be less likely to release oil and nutrients into the water. Therefore, it is important that the pressure drop in the conduit is small and stable. In a preferred embodiment, the pressure change in the recirculation conduit from the feed filling section to the end point is at most 7 bar, such as at most 5 bar, preferably 3 bar or less, such as 1 bar or less, such as 0.5 bar or less, preferably less than 0.1 bar.

[0031] The small pressure change has the advantage that the water does not impregnate the pellets, thus reducing the bulk migration of nutrients and oils from the pellets. Thus, the amount of oil and / or nutrients in the water when using hydraulic transport of feed according to the invention is similar to when the feed is transported pneumatically or mechanically, so that the water treatment units of existing RAS facilities are sufficient to treat the water.

[0032] Fish feed such as pellets are often composed of dry material with a very low water content. Typically, dry pellets contain 5% to 10% water by weight. When pellets are placed in water, the water begins to permeate the pellet surface and is absorbed into the pellet dry material or is drawn into the pellet's porous structure. The absorption of water into the pellet is called water impregnation. During hydraulic transport of pellets, it is desirable for the degree of water impregnation to be as low as possible. Water-impregnated pellets are softer than dry or partially impregnated pellets. As the pellets absorb water, the outer layer begins to disintegrate.

[0033] Preferably, the flow in the recirculating aquaculture system from the feed filling section to the feeding point has a Reynolds number of less than 500,000, preferably less than 200,000, more preferably less than 100,000, more preferably less than 50,000, most preferably less than 20,000, for example, between 20,000 and 5,000.

[0034] In a preferred embodiment, the residence time from the feed filling section to the feeding point is 3 minutes or less, preferably less than 1 minute, more preferably less than 30 seconds, most preferably less than 15 seconds, most preferably about 5 seconds. The residence time from the feed filling section to the feeding point may also be referred to as the feed residence time. When the feed is introduced into the recirculation conduit at the feed filling section, the feed is transported with the water flow from the feed filling section through the conduit to the fish holding tank. The residence time is the time from the introduction of the pellets into the water at the feed filling section until the feed enters the fish holding unit at the feeding point. Because the residence time of the feed in the water is short, for example in the range of 5 seconds to 2 minutes, only a limited amount of water is absorbed on the surface of the pellets and the pellets are not impregnated with water. These embodiments ensure that leakage of nutrients and / or oils is reduced, since leakage is known to increase with increasing residence time and / or Reynolds number of the flow.

[0035] In another aspect, the present invention relates to a method for transporting feed in a recirculating aquaculture system, the method comprising: - Providing a water flow from a feed filling section of a recirculating aquaculture system to a feeding point; - introducing said feed into said water flow in said feed filling section to obtain a feed flow containing water; - hydraulically transporting said water-containing feed to a feeding point; Including, The water flow is at least partially recirculated from a fish holding unit of the recirculating aquaculture system.

[0036] This method represents an improvement in feed transport as the feed is transported more gently than pneumatic or mechanical transport methods, thereby reducing the amount of dust and fines generated. The recirculating aquaculture system provides a method of rearing fish, e.g., marine fish, away from the sea in locations with limited access to seawater and fresh water. By recirculating water already contained in the system, this water flow can be used to hydraulically transport feed to the feeding point. The water may be recirculated in a recirculation conduit as described above, and the water flow may originate from the same fish holding unit or another fish holding unit.

[0037] In a preferred embodiment, the method further comprises the step of washing said water stream to obtain a stream of washing water, said washing preferably being carried out before introducing feed into said water stream.

[0038] The method can be used in existing facilities, which typically comprise a recirculation conduit in which the water from the fish holding unit is treated and circulated back to the fish holding unit, and a part of the recirculation conduit, preferably the part located downstream of the water treatment unit, may then be made suitable for injecting feed into the water flow. Therefore, existing RAS installations can be adapted for this method at minimal cost since existing conduits can be utilized.

[0039] The recirculation conduit may comprise a water inlet for supplying fresh water to the water stream. Thus, in an alternative embodiment, the water stream is at least partially recirculated water from a fish holding unit of an aquaculture system. In an open RAS facility, water may be lost due to evaporation and it is preferable to replenish the fish holding unit with water. In a particular embodiment, the amount of recirculated water is in the range of 90%-99.9%, e.g., fresh water is input in the range of 0.1%-10% of the water. The amount of recirculated water is based on the total amount of water in the RAS. In other embodiments, the amount of recirculated water is in the range of 95%-99.9%, e.g., 98%-99.9%, or 99%-99.9%, or 99.3%-99.7%.

[0040] The water flow may include water from the fish holding unit, processed water from the fish holding unit, water from other or several fish holding units, processed water from other or several fish holding units, fresh water supply, or any mixture of these.

[0041] The circulating water flow can be obtained by using a pump. The use of pumps and how to position them to obtain the appropriate flow are known to those skilled in the art. For example, the pump can provide a positive or negative relative pressure at the appropriate location in the aquaculture system. One or more pumps may be positioned anywhere in the recirculation conduit, for example, to obtain water recirculation. The pump may be positioned upstream of the feed filling section to avoid damaging the feed. Alternatively, a gentle pump, such as a fish pump, that passes the pellets without significant damage may be positioned downstream of the feed filling section. It is preferable to position the pump upstream of the feed filling section to minimize pellet impregnation.

[0042] In a preferred embodiment, water-containing feed is provided to a fish holding unit containing water, such that the fish holding unit has a water surface and there is a feeding point at, above or below the water surface. This allows the feed to be released to suit where the fish species in the fish holding unit will eat the feed. Thus, the location of the feeding point can also be tailored to the type of feeding, for example floating fish pellets can be fed near or above the water surface, while sinking fish pellets can be fed below the water surface or near the bottom of the fish holding unit. If the fish feed near the water surface, the feed may be provided above or just below the water surface. If the fish feed near the bottom, the feed may be provided near the bottom of the fish holding unit.

[0043] In a preferred embodiment, two or more feeding points are located at different positions relative to the water surface. This is beneficial when uniform feeding of fish is desired. Depth is measured vertically from the water surface to the bottom of the fish holding unit, i.e. parallel to the direction of gravity.

[0044] In another preferred embodiment, the method further comprises the step of treating the water with oxygen to obtain an oxygen-enriched water stream. This oxygenation may be combined with the water treatment unit or may be a separate unit, for example located upstream of the feed filling section. In the following description, embodiments of the present invention are explained with reference to schematic diagrams. [Brief description of the drawings]

[0045] [Figure 1] FIG. 1 is a schematic diagram of an aquaculture system including a water recirculation conduit according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of an aquaculture system with two water recirculation conduits according to another embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram of an aquaculture system including a water recirculation conduit according to yet another embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of an aquaculture system including a water recirculation conduit according to yet another embodiment of the present invention. [Diagram 5] FIG. 5 shows six schematic diagrams (5a-5f) of an aquaculture system according to different embodiments of the present invention. [Figure 6] FIG. 6 shows six schematic diagrams (6a-6f) of an aquaculture system according to different embodiments of the present invention. [Figure 7] FIG. 7 shows six schematic diagrams (7a-7f) of an aquaculture system according to different embodiments of the present invention. [Figure 8] FIG. 8 shows five schematic diagrams (8a-8e) of an aquaculture system according to different embodiments of the present invention. [Figure 9] FIG. 9 shows four schematic diagrams (9a-9d) of an aquaculture system according to different embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Referring initially to FIG. 1, a schematic diagram of an aquaculture system 1 of an embodiment of the present invention is shown. The aquaculture system comprises a fish holding unit 2 in the form of a tank with an opening at the top. When the water holding unit 2 is used for its intended use, i.e., raising fish, the water holding unit 2 contains water 99 and fish (not shown). A water recirculation conduit 3 is fluidly connected to the fish holding unit 2. Elements contained in the water recirculation conduit 3 are shown inside the dotted rectangle. As the water is recirculated, it flows from the fish holding unit 2 into the recirculation conduit 3 at a starting point 10 and into the water treatment unit 23. Arrows indicate the conduits in the aquaculture system 1 and the intended direction of water flow. The water flows from the water treatment unit 23 back to the fish holding unit 2 through an ending point 11. In this particular embodiment, the starting point 10 is located underwater below the water surface 100.

[0047] The feed filling section 30 is positioned downstream of the water treatment unit 23 and inputs feed before the treated water returns to the fish holding unit 2 at the termination point 11. A feed storage unit 31 in the form of a silo is positioned adjacent to the feed filling section 30. The feed storage unit 31 supplies feed to the feed filling section 30. The feed filling section 30 comprises feed input means such as a venture injector for directing feed into the conduit. Details not shown or described will be readily apparent to a person skilled in the art. Elements having the same or similar functions have the same reference numbers.

[0048] Referring now to FIG. 2, an aquaculture system 1 according to another embodiment of the present invention is shown. The aquaculture system 1 comprises a fish holding unit 2 having two water recirculation conduits 3. In the first water recirculation conduit 3, water flows from the fish holding unit 2 at a starting point 10 to a feed filling section 30 which dumps feed into the water flow. The water with feed is then returned to the fish holding unit 2 at an end point 11. A feed storage unit 31 in the form of a silo is arranged adjacent to the feed filling section 30 from which the feed is dumped into the water flow. An adjustable opening in the silo (not shown) can be used to adjust the amount of feed dumped into the water. Alternatively, the opening time of the opening may adjust the amount of feed. Alternatively, the feed may be volumetrically or gravimetrically measured before dumping it into the water. The feed filling section 30 may comprise an opening in the conduit through which the feed can enter the water, or a conduit may be connected from the feed storage unit 31 to the feed filling section.

[0049] In the second water recirculation unit 3, water flows from the fish holding unit 2 to the water treatment unit 23 via the starting point 10. The treated water is then returned to the fish holding unit 2 via the ending point 11. The illustrated aquaculture system 1 may be particularly beneficial when the water treatment unit 23 and the feed storage unit 31 are located away from each other. For example, in an aquaculture system 1, fish are often cultured using multiple fish holding units 2. Each fish holding unit 2 may have an independent water treatment unit 23 fluidly connected thereto, while the feed may be stored centrally at the facility. In this case, it may be more beneficial to have two recirculation conduits as illustrated. Water pumps 24 are arranged in both recirculation conduits 3. In the recirculation conduit 3 with the feed filling section 30, the water pump 24 is arranged upstream of the feed filling section 30. With this design, the feed does not have to pass through the water pump 24 and is therefore not damaged by the water pump 24. If a gentle pump such as a fish pump is used as the water pump 24, it can be located downstream of the feed filling section 30, since there is a possibility that the feed can pass through the fish pump without being damaged. In the recirculation conduit 3 which comprises the water treatment unit 23, the water pump 24 is located downstream of the water treatment unit 23. Alternatively, the water pump 24 may be integrated in the water treatment unit 23 or located upstream of the water treatment unit 23.

[0050] 3, an aquaculture system 1 according to another embodiment of the present invention is shown. A water inlet 22 supplies water into the system 1. This water may be a fresh supply of water that is added to the aquaculture system 1. Alternatively, the water may be from another aquaculture system 1.

[0051] Upstream of the water inlet 22 a feed filling section 30 is arranged. Thus, by supplying the system 1 with, for example, freshly supplied water, feed can be hydraulically transported from the feed filling section 30 to the fish holding unit 2.

[0052] The water recirculation conduit 3 is located adjacent to the fish holding unit 2. Water flows from the fish holding unit 2 via a starting point 10 to the water treatment unit 23. Water from the water treatment unit 23 may flow back to the fish holding unit 2 via an ending point 11. The water recirculation conduit is further coupled to a water outlet 21 for removing water from the aquaculture system 1. A constant water flow may be removed through the water outlet 21 or the outlet may be equipped with a valve (not shown) so that the water outlet can be opened and closed. In this particular embodiment, the outlet 21 is located within the water treatment unit 23. The location of this outlet 21 allows for the removal of treated or partially treated water. However, the location of the outlet 21 may be anywhere within the recirculation conduit 3 or adjacent to the fish holding unit 2. The location of the outlet is primarily determined by the desired water quality to be removed from the aquaculture system 1. Thus, outlet 21 may be located upstream or downstream of, for example, a biofiltration unit, a mechanical filter unit, an oxygenation unit, a pH control unit, a temperature control unit, an ultraviolet (UV) treatment unit, a CO2 stripping unit, and / or an ozonation unit. Alternatively, the system outlet may be located upstream or downstream of a water treatment unit 23. A water pump 24 is located in the recirculation conduit upstream of the water treatment unit, but may be located anywhere in the recirculation conduit 3 downstream of the starting point 10.

[0053] Now referring to FIG. 4, an aquaculture system 1 according to another embodiment of the present invention is shown. The aquaculture system 1 has a fish holding unit 2 with a water recirculation conduit 3. When the system 1 is used for its intended use, i.e., for raising fish, the system contains a desired amount of water located from the water surface 100 to the bottom of the fish holding unit 2. The water can flow from the fish holding unit 2 to a water treatment unit 23 in the water recirculation conduit 3 via a starting point 10. The water is treated in the water treatment unit 23 to provide treated water of a desired purity and quality. The treated water is then returned to the fish holding unit 2 via multiple ending points 11. Feed is input to the treated water in a feed filling section 30. The multiple ending points 11 allow the water and feed from the feed filling section 30 to be distributed to different locations in the fish holding unit 2. In this particular embodiment, one ending point 11 is located above the water surface 100 and two ending points 11 are located at different depths in the water of the fish holding unit 2. This design is beneficial when the fish holding unit 2 contains many fish to be fed at the same time. Different fish species may also prefer to find / eat feed at different depths. In the illustrated embodiment, recirculating water is used to enable hydraulic transport of feed to several depths / locations within the fish holding unit 2.

[0054] In Fig. 5, six different embodiments of the invention (Fig. 5a-5f) are shown to illustrate different configurations of the recirculation conduit 3. The recirculation conduit 3 may comprise several end points 11 at different positions above or below the water surface 100, and / or openings at different depths below the water surface 100 or at different positions above the water surface 100. In Fig. 5e, the water flow is split into two streams after the water treatment unit 23. The first stream is returned directly to the fish holding unit 2, while the second stream is returned to the fish holding unit 2 after feed is added to the water flow in the feed filling section 30. It may be desired not to feed the fish continuously in the fish holding unit 2. In this case, the second stream may comprise a valve arranged upstream of the feed filling section. This valve may be adjusted to an open or closed position, thereby opening or closing the second stream of water. The opening and closing of the conduit by the valve is particularly important when the system is cleaned in place (CIP), to prevent cleaning solutions such as chemicals or hot water from entering the fish holding unit 2.

[0055] Figure 6 shows six embodiments of the invention (Figures 6a to 6f). Figure 6d shows a preferred embodiment where an oxygenation unit 40 is connected to the recirculation conduit 3 near the end point 11. The oxygenation unit 40 may be located either downstream or upstream of the feed filling section 30. This allows the oxygenated water entering the fish holding unit 2 to increase the overall proportion of oxygenated water in the fish holding unit 2. Alternatively, the oxygenation unit 40 may be provided in the water treatment unit 23. Alternatively, the oxygenation unit 40 may be located in the recirculation conduit without the feed filling section or upstream of the water inlet 22.

[0056] Figure 7 shows six further embodiments of the invention (Figures 7a to 7f). In a preferred embodiment shown in Figure 7e, the water recirculation conduit 3 is not present in the fish holding unit 2. The feed is introduced into the water inlet 22 above the feed filling section 30. From the inlet fresh water or water from another aquaculture system 1 may be supplied. Away from the inlet 22 and the feed filling section 30 the water leaves the fish holding unit 2 via the outlet 21.

[0057] Figure 8 shows five alternative embodiments (Figures 8a to 8e). In the preferred embodiment shown in Figure 8b, water flows from the fish holding unit 2 to the water treatment unit 23 and from the water treatment unit 23 to the fish holding unit 2 via the same water conduit. In this case the start point 10 and the end point 11 for recirculating the water to / from the fish holding unit 2 are at the same place. In this embodiment the flow is redirected in two different directions. When the water flow is directed from the water treatment unit 23 to the fish holding unit 2, feed can be added to the water via the feed storage unit and feed filling section 30. When the water flow is directed from the fish holding tank 2 to the water treatment unit 23, no feed is added. This can be controlled by valves that can be opened and closed and pumps that can redirect the water flow.

[0058] In another preferred embodiment shown in Fig. 8c, the two fish holding units 2 are fluidly connected by a water conduit, allowing water flow from the first fish holding unit 2 to the second fish holding unit 2. Another water conduit allows water to flow from the second fish holding unit 2 to the water treatment unit 23. The water flowing from the water treatment unit 23 to the first fish holding unit 2 can be supplied with feed from a feed storage unit 31 in a feed filling section 30. Alternatively, each of the two water conduits may have a feed filling section 30 and a feed storage unit 31. In this embodiment, the recirculation conduit 3 is composed of several water conduits allowing water flow to be recirculated from the first fish holding unit 2 to the second fish holding unit 2 and back to the first fish holding unit 2.

[0059] In another preferred embodiment shown in Fig. 8e, the combined water inlet 22 and water outlet 21 are located adjacent to the water treatment unit 23. The treated water flows back from the water treatment unit 23 to the fish holding unit 2 via the end point 11. A feed storage unit 31 is fluidly connected to the recirculation conduit 3 at the feed filling section 30, allowing for replenishment of the treated water with feed. Furthermore, separate conduits for the water inlet 22 and the water outlet 21 may be connected to the water treatment unit 23. Alternatively, the combined water inlet 22 and water outlet 21 may be located at any other position of the fish holding unit 2.

[0060] Figure 9 shows four alternative embodiments (Figures 9a to 9d). In a preferred embodiment shown in Figure 9a, two fish holding units 2 are connected to the same water treatment unit 23. In such an embodiment, water can be exchanged between the first and second fish holding units 2 by flowing through the water treatment unit 23.

[0061] Feed is introduced into the water stream leaving the water treatment unit 23 at two feed filling stations 30 which are fluidly connected to a single feed storage unit 31 .

[0062] In another preferred embodiment of the present invention shown in Fig. 9b, three fish holding units 2 are provided in the same aquaculture system 1. Additional fish holding units 2 may be included in the same aquaculture system 1 depending on the amount of fish to be reared. Each fish holding unit 2 has an individual water recirculation conduit 3, which has a feed storage unit 31 and a feed filling section 30 allowing the replenishment of feed to each individual fish holding unit 2. Furthermore, each of the three fish holding units 2 is provided in a common water recirculation conduit 3 in which a water treatment unit 23 is arranged. The treated water leaves the water treatment unit 23 and flows back to the three fish holding units 2 via a branched water conduit. The embodiment of Fig. 9b allows the fish in the three fish holding units 2 to be fed different feeds and / or at different feeding rates while treating the water of the fish holding units 2 with a single water treatment unit 23.

[0063] In a further preferred embodiment shown in Figure 9c, two fish holding units 2 are connected by a composite recirculation conduit 3. A pair of start points 10 and end points 11 are arranged in each of the two fish holding units 2.

[0064] Water flows from each fish holding unit 2 to a single water treatment unit 23 where the two water streams may be mixed. The treated water then flows from the water treatment units 23 to a single feed filling section 30 where feed is input from a feed storage unit 31. From the feed filling section 30, the water conduit splits into two conduits for carrying water, which feeds back to each of the two fish holding units 2 via the termination point 11. The water inlet branches into said two water inlets downstream of the feed filling section 30, allowing feed supply to both aquaculture systems 1. The present invention is not limited to the embodiments shown and described above, but various modifications and combinations may be made. [Explanation of symbols]

[0065] 1. Aquaculture Systems 2 Fish Holding Units 3 Water recirculation conduit 10 Starting point 11 End point 21 Exit 22 Entrance 23 Water Treatment Unit 24 Pump 30 Feed filling section 31 Feed Storage Unit 40 Oxygenated Water Unit 99 water 100 water surface

[0066] [Example] [Example 1] - Hydraulic transport of feed in RAS Feed (pellets) stored in the feed storage unit was fed into the RAS duct via a lobe pump or ejector. The amount of water relative to the pellets was varied as was the water flow (hereafter referred to as the water to pellet weight ratio). Liquid loss, loss due to fines generation, and retention time were measured. The results are shown in Table 1 below.

[0067] [Table 1]

[0068] Where: Lobe refers to the use of a lobe pump (which pumps pellets from a feed storage unit, where the pellets are stored underwater). Ejector refers to the use of an ejector to introduce pellets into the conduit (by sucking the pellets into the water flow in the conduit). The ejector is placed after the pump in the conduit, thereby eliminating the need for the pellets to pass through the pump in the conduit.

[0069] Loss, liquid refers to weight loss due to, for example, oil coming out of the pellets in the water stream in the conduit. Fines refers to the weight loss of pellets that is lost in the pipe water flow, for example as pellet debris, dust, torn off pieces, etc.

[0070] Velocity refers to the flow rate of the water current carrying the pellets. Retention time refers to the time that the pellets are retained in the water flow of the conduit.

[0071] conclusion Hydraulic transport of pellets generally results in very low fines generation and low liquid loss even at different water to pellet ratios.

Claims

1. 1. An aquaculture system comprising: a fish holding unit fluidly connected to the water recirculation conduit, the water treatment unit, the water inlet, and the feed storage unit; a feed filling section arranged upstream of the water inlet or within the water recirculation conduit, where feed is introduced into the system and hydraulically transported to the fish holding unit, the water recirculation conduit comprising the water treatment unit, the feed filling section arranged downstream of the water treatment unit. Aquaculture systems.

2. The water treatment unit includes a biofilter treatment unit, a solids removal unit, a pH control unit, a temperature control unit, an ultraviolet (UV) treatment unit, an oxygen addition unit, and a CO ２ 10. The aquaculture system of claim 1, comprising one or more of a stripping unit and an ozone treatment unit.

3. 3. An aquaculture system as claimed in claim 1 or claim 2, wherein the fish holding units are fluidly connected to one or more further fish holding units, optionally coupled in series or parallel or a combination thereof.

4. 4. The aquaculture system according to claim 1 , wherein a conduit within the aquaculture system downstream of the feed filling section is made of a plastic material.

5. 1. A method for transporting feed in a recirculating aquaculture system, comprising: - Providing a water flow from a feed filling section of the recirculating aquaculture system to a feeding point; - introducing said feed into said water flow in said feed filling section to obtain a feed flow containing water; - hydraulic transport of said feed containing water to said feeding point; Including, 2. A method of transporting feed, wherein said water flow is at least partially recirculated from a fish holding unit of said recirculating aquaculture system.

6. rinsing said water flow before introducing said feed into said water flow to obtain a rinse water flow; The method of claim 5, further comprising:

7. 7. The method of claim 5 or claim 6, wherein the amount of recirculating water is in the range of 90% to 99.9% based on the total water amount in the recirculating aquaculture system.

8. The step of cleaning the water stream may include biofiltration, solids removal, pH control, temperature control, ultraviolet (UV) treatment, CO ２ 8. A method for transporting feed according to claim 6 or claim 7, comprising one or more of the following steps: stripping; and ozonation.

9. 9. A method for transporting feed according to any one of claims 5 to 8, wherein the change in pressure within the recirculating aquaculture system from the feed filling section to the feeding point is a maximum of 7 bar.

10. A method for transporting feed according to any one of claims 5 to 9, wherein the residence time from the feed filling section to the feeding point is within 3 minutes.

11. A method of transporting feed as claimed in any one of claims 5 to 10, wherein the feed containing water is supplied to the fish holding unit having a water surface, and the feeding point is at the water surface or above or below the water surface.

12. A method for transporting feed according to any one of claims 5 to 11, wherein two or more feeding points are located at different positions relative to the water surface.

13. 13. A method for transporting feed according to any one of claims 5 to 12, wherein the Reynolds number is less than 500,000.

14. 14. A method for transporting feed according to any one of claims 5 to 13, wherein the Reynolds number is in the range of 5,000 to 20,000.

15. 15. The method of transporting feed according to any one of claims 5 to 14, wherein the water in the recirculating aquaculture system is recirculated 0.5 to 20 times per hour.

16. 16. A method for transporting feed according to any one of claims 5 to 15, wherein the feed has a moisture content in the range of 5% w / w to 10% w / w based on the weight of the feed.

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