Floating ras system, and use and method of operation thereof

Abstract

There is provided a floating recirculating aquaculture system for cultivating aquatic species, the aquaculture system comprising a main body, the main body comprising a tank comprising a central axis and at least one surface drain; a water treatment system comprising a first conduit, at least two filters, at least one bioreactor, and at least one pump, wherein the first conduit comprises a first end and a second end; the tank and the first conduit are in fluid communication via at least one surface drain; and a buoyancy system, wherein at least one filter is arranged at each of the first and second ends of the first conduit. Elements of the tank and / or buoyancy system and / or water treatment system may be arranged symmetrically with respect to first and / or second planes of reflectional symmetry of the main body and / or a central axis of the main body. There is further provided a use of a floating recirculating aquaculture system and a method of operating a floating recirculating aquaculture system.

Description

[0001] FLOATING RAS SYSTEM, AND USE AND METHOD OF OPERATION THEREOF

[0002] Introduction

[0003] The present disclosure relates to a floating Recirculating Aquaculture System (RAS) for cultivating aquatic species.

[0004] RAS overview

[0005] Recirculating aquaculture systems for cultivating aquatic species require the use of water treatment technology to continually remove waste products. Some of these waste products, such as free ammonia, may be toxic to the aquatic species and need to be removed or broken down and processed into non- or less-harmful products.

[0006] During production, i.e. when the aquatic species are being cultivated, water circulates within a main cultivation vessel, also known as a tank, of the RAS. Water flows through various parts of the system before being returned. Water from the tank flows first to a mechanical filter. Here, particulate organic waste products above a certain size threshold are removed. This removal is most commonly performed using a drum filter which captures and then directs the organic material into a sludge container.

[0007] The filtered water exiting the mechanical filter, containing only the finest particles of organic waste alongside dissolved phosphate and nitrogen, then makes its way to a biofilter, also known as a bioreactor. Here, bacteria perform a variety of functions to filter the water and ensure it is suitable for sustaining the aquatic species being cultivated. In the biofilter, for example, some strains of bacteria nitrify the water, removing harmful ammonia by processing it into nitrite and nitrate. Gases such as carbon dioxide, free nitrogen, and hydrogen sulphide may also accumulate in the water during cultivation, and must be removed. This process of removal is known as degassing, aeration, or stripping, and may be performed before and / or after the mechanical filtering and biofiltering stages.

[0008] Further, fine bubble oxygen diffusion can also be used as a means of oxygenation and degassing, and may take place within the main cultivation vessel of the RAS. One way this may be done is to add gaseous oxygen near the bottom of the tank so that it can bubble up through the body of water held there. A tank having a strong, circulating current may also increase the length of the flowpath of the gaseous oxygen through the body of water, increasing the amount of diffusion taking place.

[0009] RAS systems vary in the percentage of water which is recycled. The water recycle ratio of a given system is the percentage of water leaving the tank being treated and returned for reuse per cycle. Traditional flow-through systems, which are not RAS, have a recycle ratio of 0%, and RAS systems considered as fully recirculating typically have a recycle ratio of above 90%. Modern RAS systems typically have a recycle ratio of above 95%.

[0010] Closed RAS systems are those which have a controlled interface between the water and the natural environment, and may utilise a covering for this purpose.

[0011] The present disclosure relates to a floating RAS, and may be compared with a land-based RAS. This is because both concepts rely on the treatment and recirculation of water for the cultivation of aquatic species. The present disclosure, however, has several advantages when compared with a land-based RAS system.

[0012] The present disclosure has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

[0013] The object is achieved through features, which are specified in the description below and in the claims that follow. According to a first aspect of the disclosure, there is provided a floating recirculating aquaculture system for cultivating aquatic species, the aquaculture system comprising a main body, the main body comprising a tank comprising a central axis and at least one surface drain; a buoyancy system; and a water treatment system comprising a first conduit, at least two filters, at least one bioreactor, and at least one pump, wherein the first conduit comprises a first end and a second end; the tank and the first conduit are in fluid communication via at least one surface drain, and wherein at least one filter is arranged at each of the first and second ends of the first conduit.

[0014] Advantageously, having the RAS floating decreases the cost of construction. As the system is floating in a body of water, there is negligible differential pressure between the inside of the tank and the outside when the tank is filled. This means that the tank of the floating RAS system requires less reinforcement to withstand the pressure of the production volume than would otherwise be possible in land-based RAS systems which typically have portions of their filled tank surrounded by air. The lower requirements regarding reinforcement has various benefits, including the increased affordability of larger tanks which lead to the reduction in collisions of aquatic species being cultivated with the tank walls, floating deaths and sinking deaths. Another benefit is that cheaper materials can be used for the construction of the tank walls. A lower volume of material can also be used, leading to a reduction in weight of the unfilled RAS system, potentially increasing its manoeuvrability in and out of the body of water.

[0015] It is estimated that land-based RAS have investment costs of over 1500 EUR per cubic metre of productive water volume. The present disclosure has a comparable investment cost estimated at around 800 EUR per cubic metre of productive water volume.

[0016] Further advantageously, having a main body comprising a water treatment system allows the system to be easily maintained and serviced while out of production. When water is pumped out of the tank and water treatment system, the tank will become more buoyant, causing the main body to rise. This has the benefit of facilitating access to the main body and its components both from inside and outside. Having the tank and first conduit in fluid communication via at least one surface drain facilitates the first conduit and water treatment system being fed by gravity.

[0017] Advantageously, arranging at least one filter at each of the first and second ends of the first conduit enables a compact arrangement of the RAS. This reduces the size of the main body in comparison with the tank, enabling more RAS systems to be fit within any given body of water without reducing production capacity. Further, having a more compact arrangement enables the saving of material and construction costs.

[0018] Optionally, the tank comprises at least two surface drains and the water treatment system comprises at least four filters, and further comprises a second conduit, wherein the second conduit comprises a first end and a second end; the tank and the second conduit are in fluid communication via at least one surface drain; and at least one filter is arranged at each end of the first and second ends of the second conduit.

[0019] Advantageously, having at least four filters and a second conduit facilitates redundancy of key components, ensuring production can continue even in cases of component failure or blockage.

[0020] Optionally, the first conduit is a surface open channel.

[0021] Advantageously, open surface channels facilitate degassing of the water during production. Further, open surface channels are easier to clean than closed channels such as pipes, and so maintenance time and thus maintenance costs may be reduced.

[0022] Optionally, the main body further comprises a first plane of reflectional symmetry and a second plane of reflectional symmetry.

[0023] Optionally, the first conduit is arranged symmetrically with respect to the first plane of reflectional symmetry and / or the second plane of reflectional symmetry.

[0024] Advantageously, arranging components rotationally symmetrical and / or reflectionally symmetrically with respect to at least one plane of reflectional symmetry increases floating stability of the RAS. Increasing the floating stability of the RAS also has additional ben- efits when open channels are utilised in the water treatment system, ensuring water remains within these channels and does not tip or spill out.

[0025] Optionally, the first conduit and the second conduit each comprise volumetric centroids and / or centres of mass which are arranged symmetrically with respect to the first plane of reflectional symmetry and / or the second plane of reflectional symmetry.

[0026] Optionally, the first conduit and the second conduit are rotationally symmetrically arranged about the central axis.

[0027] Advantageously, arranging components rotationally symmetrically has the benefits of increasing the stability of the RAS whilst not requiring that components are symmetrical themselves.

[0028] Optionally, at least two filters comprise volumetric centroids and / or centres of mass which are arranged symmetrically with respect to the first plane of reflectional symmetry and / or the second plane of reflectional symmetry.

[0029] Optionally, the water treatment system comprises at least two bioreactors.

[0030] Advantageously, having at least two bioreactors facilitates redundancy of key components, ensuring production can continue even in cases of component failure or blockage.

[0031] Optionally, at least two bioreactors are rotationally symmetrically arranged about the central axis.

[0032] Optionally, at least two bioreactors comprise volumetric centroids and / or centres of mass which are arranged symmetrically with respect to the first plane of reflectional symmetry and / or the second plane of reflectional symmetry.

[0033] Optionally, at least one open channel fluidly connects at least one filter, at least one bioreactor, and at least one pump.

[0034] Optionally, the buoyancy system comprises at least two discrete modules. Advantageously, separation of the buoyancy system into at least two discrete modules may ensure that the RAS remains afloat in the case of failure of one of the modules, for example due to a collision.

[0035] Optionally, at least one of the discrete modules comprises a feeding system and / or a steering system and / or an emergency generator.

[0036] Advantageously, this enables a compact arrangement of the RAS with benefits as described above.

[0037] Optionally, at least two discrete modules are rotationally symmetrically arranged about the central axis.

[0038] Optionally, at least two discrete modules comprise volumetric centroids and / or centres of mass which are arranged symmetrically with respect to the first plane of reflectional symmetry and / or the second plane of reflectional symmetry.

[0039] Optionally, at least two discrete modules are arranged at a periphery of the main body.

[0040] Advantageously, this enables the discrete modules to be arranged as far away as possible from the central axis of the tank, increasing stability of the RAS.

[0041] Optionally, the main body further comprises a covering.

[0042] Advantageously, this reduces the risk of the production volume being contaminated by the external environment during production.

[0043] Optionally, the tank comprises a bottom drain.

[0044] Advantageously, having a bottom drain allows the removal of sunk waste from the tank during production.

[0045] Optionally, the main body has a thermal transmittance U-value of either less than 1.0 W / m2K or less than 0.3 W / m2K.

[0046] Advantageously, this thermally insulates the production volume from the surrounding environment, reducing both heat loss and heat gain, depending on the required tempera- ture of the production volume and that of the surrounding environment, and thus energy consumption of the RAS. Land-based RAS systems are not typically insulated against the surrounding environment, which leads to substantial heat losses.

[0047] According to a second aspect of the disclosure, there is provided a use of the floating recirculating aquaculture system according to the first disclosure.

[0048] According to a third aspect of the disclosure, there is provided a method of operating a floating recirculating aquaculture system comprising the steps of: providing a floating recirculating aquaculture system according to the first disclosure; and providing water in the tank and water treatment system.

[0049] Optionally, the tank has a tank water level, the first conduit has a first conduit water level, the filters have a filter water level, the bioreactor has a bioreactor water level, and the pump has a pump water level.

[0050] Optionally, the first conduit water level is lower than the tank water level.

[0051] Advantageously, this enables the first conduit to be fed by gravity, reducing pumping requirements of the system and thus energy consumption.

[0052] Optionally, the maximum height difference between the tank water level and each of the first conduit water level, filter water level, bioreactor water level, and pump water level is 1 metre or less.

[0053] Advantageously, this further reduces pumping requirements of the system and thus energy consumption.

[0054] Optionally, the maximum height difference between the tank water level and each of the first conduit water level, filter water level, bioreactor water level, and pump water level is 0.5 metres or less.

[0055] Advantageously, this further reduces pumping requirements of the system and thus energy consumption. The disclosure is defined by the independent patent claims. The dependent claims define advantageous embodiments of the disclosure.

[0056] Brief Summary of the Drawings

[0057] In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein:

[0058] Fig. 1 is a cross-sectional view of an example floating recirculating aquaculture system for cultivating aquatic species;

[0059] Fig. 2 shows a side view of the floating recirculating aquaculture system of Fig. 1;

[0060] Fig. 3 shows a side cross-sectional view of the floating recirculating aquaculture system of Fig. 1;

[0061] Fig. 4 shows a perspective view of the floating recirculating aquaculture system of Fig. 1 further comprising a covering; and

[0062] Fig. 5 shows a schematic flow diagram of the water levels of various sections of the floating recirculating aquaculture system of Fig. 1 when in operation.

[0063] Detailed description

[0064] Main body and symmetry

[0065] Each of the parts referred to in this patent application using reference numerals may be considered as elements.

[0066] Figures 1, 2, 3, and 4 show a floating Recirculating Aquaculture System (RAS) generally at 100. The RAS 100 comprises a main body 200. The main body 200 comprises a tank 300, a buoyancy system 400, and a water treatment system 500.

[0067] The main body 200 may further comprise a covering 202 which may be known as a lid. The covering 202 is for ensuring that the tank 300 and / or water treatment system 500 are insulated from the environment. As such, the covering 202 may cover the tank 300 and / or the water treatment system 500 of the main body 200. The main body 200 may have a first cross-dimension, for example a width, of between 5 and 70 metres, for example 30 metres. The main body 200 may have a second crossdimension, for example a length, of between 5 and 70 metres, for example 47.5 metres. Alternatively, the main body may have a second cross dimension, for example a length, of larger than 70 metres, for example 100 metres.

[0068] The main body 200 may have a rectangular cross-section which may have rounded corners.

[0069] Symmetry

[0070] The main body 200 may also comprise a first plane of reflectional symmetry 204. This means that at least one element of the main body 200 may be arranged in a reflectionally symmetrical manner with respect to this first plane 204. The main body 200 may further comprise a second plane of reflectional symmetry 206. This means that at least one element of the main body 200 may be arranged in a reflectionally symmetrical manner with respect to this second plane 206. In the present example, the first plane of reflectional symmetry 204 extends along the width of the main body 200, and the second plane of reflectional symmetry 206 extends along a length of the main body 200.

[0071] An element may be arranged symmetrically with respect to a plane of reflectional symmetry. This means that an element may be reflectionally symmetrical in that it is bisected by a plane of reflectional symmetry. The reflectionally symmetrical element may have its volumetric centroid and / or centre of mass is located on the plane of reflectional symmetry. Each side of the reflectionally symmetrical element may have a volumetric centroid and / or centre of mass which is arranged reflectionally symmetrically either side of the plane of reflectional symmetry.

[0072] It is important to note that the reflectionally symmetrical arrangement of elements does not necessarily require reflectional symmetry of the individual elements themselves. More specifically, the reflectionally symmetrical arrangement of elements may refer to the reflectionally symmetrical arrangement of components' volumetric centroids and / or centres of masses. Two elements may be arranged symmetrically with respect to one another. In other words, two elements may be arranged reflectionally symmetrically with respect to a plane of reflectional symmetry. This may mean that the two elements have volumetric centroids and / or centres of mass which are arranged symmetrically either side of a plane of reflectional symmetry, i.e. one element on each side of said plane. In other words, the two elements have volumetric centroids and / or centres of mass which are arranged reflectionally symmetrically either side of a plane of reflectional symmetry.

[0073] For example, an element may be bought off-the-shelf and may be asymmetric. However, if two of these elements are arranged reflectionally symmetrically with respect to one another, their volumetric centroids and / or centre of masses are arranged symmetrically with respect to a plane of reflectional symmetry.

[0074] References to one or more planes of reflectional symmetry may be taken to be references to the first plane of reflectional symmetry 204 and / or the second plane of reflectional symmetry 206.

[0075] Elements may also be arranged rotationally symmetrically with respect to a fixed point or axis. In the context of this application, rotationally symmetrical elements may be arranged with respect to the central axis 330 of the tank (discussed below) and / or with respect to a central axis of the main body 200. The central axis 330 of the tank 300 and the central axis of the main body 200 may be coincident. Elements may be arranged rotation- ally symmetrically with respect to any angle. For example, elements may be rotationally symmetric with respect to 60 degrees, 72 degrees, 90 degrees, 120 degrees, or 180 degrees.

[0076] Elements of the main body 200, for example elements of the tank 300 and / or elements of the buoyancy system 400 and / or elements of the water treatment system 500 may be arranged symmetrically with respect to first and / or second planes of reflectional symmetry of the main body 200 and / or a central axis of the main body 200. Tank

[0077] The tank 300 comprises a watertight tank wall 310, a watertight tank base 320, and may comprise an imaginary central axis 330. In other embodiments, the central axis 330 may be a central axis 330 of the main body 200.

[0078] The dimensions of the tank 300 are dependent upon the application. For example, the tank 300 may have a first cross dimension, for example a diameter, of between 5 and 50 metres, for example 30 metres.

[0079] The tank 300 may also have a second cross dimension, for example a depth, of between 1 and 20 metres, for example 10 metres.

[0080] The tank 300 may further comprise an oxygen inlet (not shown) for fine bubble oxygen diffusion. During production, fine bubble oxygen diffusion can be used as a means of oxygenation and degassing of the water.

[0081] The tank 300 may have a volume of between 2,000 and 10,000 m3, for example 7,000 m3, 5,000 m3or 2,500 m3. The tank 300 may be of any size or shape. In the present embodiment, the tank 300 is a circular tank.

[0082] Symmetry of overall tank

[0083] The tank 300 may be arranged such that its volumetric centroid and / or its centre of mass is located on the first plane of reflectional symmetry 204 and / or the second plane of re- flectional symmetry. In other words, the first and second planes of reflectional symmetry 204, 206 may intersect on the imaginary central axis 330 of the tank 300. The imaginary central axis 330 may extend through the volumetric centroid and / or centre of mass of the tank 300.

[0084] Tank wall and base

[0085] The tank base 320 may be located at one end of the tank wall 310. The tank wall 310, as can be seen in Figures 2 and 3, extends within 15 degrees of parallel with the central axis 330, but in other embodiments may not be within 15 degrees of parallel with the central axis 330 and may, for example, instead take the form of the lateral surface of a frustum. The tank wall 310 may comprise an upper edge 312 which is located away from the tank base 320, and may be located at an opposite end of the tank wall 310 to the tank base 320. The tank wall 310 may further comprise an inner surface 314 and an outer surface 316. The tank wall 310 may be curved. The tank wall 310 may form the lateral surface of a cylinder.

[0086] The tank base 320 may be a substantially flat plate, and may be in the form of a disc. The tank base 320 may include an upper surface 322 and a lower surface 324. The tank base 320 may extend within 15 degrees of perpendicular to the central axis 330. The tank wall 310 and the tank base 320 may form one integral part.

[0087] Together, the inner surface 314 of the tank wall 310 and the upper surface 322 of the tank base 320 form a boundary for enclosing the production volume of water used to cultivate aquatic species.

[0088] Tank drains

[0089] The tank 300 may further comprise a bottom drain 340. In the present embodiment, the bottom drain 340 is located on the tank base 320. The bottom drain 340 is for extracting water at the bottom of the tank 300, where faeces of the aquatic species and uneaten feed particles may accumulate. The bottom drain 340 may also be located coincident with the central axis 330 of the tank 300.

[0090] The tank 300 further comprises a surface drain 350. The surface drain 350 is for extracting water at the surface of the tank 300. The surface drain 350 is located on the tank wall 310, and may be in the form of a cutout in the tank wall 310. The surface drain 350 may have a lower edge. The surface drain 350 may be located at the upper edge 312 of the tank wall 310, and, if so, may be in the form of a notch. The tank 300 may comprise two or more surface drains 350. The surface drains 350 may be arranged reflectionally symmetrically with respect to a plane of reflectional symmetry. As can be seen in Fig. 1, the two surface drains 350 of the shown embodiment are each reflectionally symmetrical with respect to the first plane of reflectional symmetry 204. Further, the two surface drains 350 of the shown embodiment are arranged reflectionally symmetrically with respect to the second plane of reflectional symmetry 206.

[0091] Buoyancy system

[0092] Purpose of buoyancy system

[0093] The buoyancy system 400 provides the RAS 100 with a means for staying afloat. This means that the buoyancy system 400 has an overall volumetric mass density which is less than that of the water in which the RAS 100 is floating, regardless of whether the tank 300 and / or water treatment system 500 is filled with water or not. In practice, the buoyancy system 400 has a density significantly less than the density of the surrounding water in order to offset the weight of the tank and water treatment system components which have a higher density than the density of the surrounding water. The total buoyancy of the RAS 100 must be sufficient to keep itself afloat regardless of whether the tank is filled with water or not.

[0094] Buoyancy modules

[0095] The buoyancy system 400 may comprise one or more buoyancy modules 402, for example two or four. The buoyancy modules 402 may be separate, discrete parts, for example discrete modules. The buoyancy modules 402 may be arranged at a periphery of the main body 200. Two or more of the buoyancy modules 402 may be arranged reflectionally symmetrically with respect to one or more planes of reflectional symmetry. In the present embodiment, four buoyancy modules 402 are arranged reflectionally symmetrically with respect to both the first and second planes of reflectional symmetry 204, 206. Two or more of the buoyancy modules 402 may be arranged rotationally symmetrically. In the present embodiment, a first pair of the buoyancy modules 402 and a second pair of the buoyancy modules may each be considered as being arranged rotationally symmetrically arranged with respect to the central axis 330 and an angle of 180 degrees.

[0096] Systems within the buoyancy modules

[0097] The buoyancy system 400 may further comprise a feeding system 410, which may be a blower room, a steering system 420, which may be an electrical steering room controlled by a computer, and / or an emergency generator 430. In the present embodiment, a feeding system 410, steering system 420, and emergency generator 430 are each fully located within a buoyancy module 402.

[0098] Lower surface of buoyancy system

[0099] The buoyancy system 400 further comprises a lower surface 440 which may be offset from the tank base 320. As can be seen in Fig. 3, the lower surface 440 is oriented perpendicular the tank wall 310 and central axis 330 of the tank 300. The tank 300 thus extends beyond the lower surface 440 of the buoyancy system 400.

[0100] Water treatment system

[0101] Overview

[0102] The water treatment system 500 comprises at least one first conduit shown as a surface open channel 510, at least one filter section 520, at least one bioreactor section 530, at least one pump section 540, and at least one inflow section 560. The water treatment system 500 may further comprise at least one skimmer section 550, as it does in the present embodiment.

[0103] The water treatment system 500 may comprise two or more surface open channels 510 and / or two or more filter sections 520 and / or two or more bioreactor sections 530 and / or pump sections 540 and / or skimmer sections 550 and / or inflow sections 560. Having two or more of these critical components present and operational in the RAS 100 ensures that production may continue even in the case of component failure.

[0104] In the present embodiment, there are two surface open channels 510, four filter sections 520, four bioreactor sections 530, two pump sections 540, two skimmer sections 550, and two inflow sections 560.

[0105] The water treatment system 500 may have a lower surface which abuts the outer surface 316 of the tank wall 310 at a location between the upper edge 312 of the tank wall 310 and the tank base 320. Symmetrical arrangement of water treatment system

[0106] The at least one surface open channel 510, at least one filter section 520, at least one bioreactor section 530, at least one pump section 540, at least one skimmer section 550, and at least one inflow section 560 may each be reflectionally symmetric with respect to one or more planes of reflectional symmetry. This means that each of these features may be bisected by one or more planes of reflectional symmetry. In the present embodiment, the surface open channels 510 are bisected by the first plane of reflectional symmetry 204. Further, in the present embodiment, each of the pump sections 540, and inflow sections 560 are bisected by the second plane of reflectional symmetry 206. The surface open channels 510 may be arranged reflectionally symmetrically with respect to one or more planes of reflectional symmetry. Two or more of the surface open channels 510 may be arranged rotationally symmetrically. In the present embodiment, the two surface open channels 510 are arranged reflectionally symmetrically with respect to the first plane of reflectional symmetry 204. In the present embodiment, the two surface open channels 510 may also be considered as being arranged rotationally symmetrically arranged with respect to the central axis 330 and an angle of 180 degrees.

[0107] Two or more of the filter sections 520 may be arranged reflectionally symmetrically with respect to one or more planes of reflectional symmetry. Two or more of the filter sections 520 may be arranged rotationally symmetrically. In the present embodiment, four filter sections 520 are arranged reflectionally symmetrically with respect to both the first and second planes of reflectional symmetry 204, 206. In the present embodiment, a first pair of the filter sections 520 and a second pair of the filter sections 520 may each be considered as being arranged rotationally symmetrically arranged with respect to the central axis 330 and an angle of 180 degrees.

[0108] Two or more of the bioreactor sections 530 may be arranged reflectionally symmetrically with respect to one or more planes of reflectional symmetry. Two or more of the bioreactor sections 530 may be arranged rotationally symmetrically. In the present embodiment, four bioreactor sections 530 are arranged reflectionally symmetrically with respect to both the first and second planes of reflectional symmetry 204, 206. A first pair of the bio- reactor sections 530 and a second pair of the bioreactor sections 530 may each be considered as being arranged rotationally symmetrically arranged with respect to the central axis 330 and an angle of 180 degrees.

[0109] Two or more of the pump sections 540 may be arranged reflectionally symmetrically with respect to one or more planes of reflectional symmetry. Two or more of the pump sections 540 may be arranged rotationally symmetrically. In the present embodiment, two pump sections 540 are arranged reflectionally symmetrically with respect to the first plane of reflectional symmetry 204. In the present embodiment, the two pump sections 540 may be considered as being arranged rotationally symmetrically with respect to the central axis 330 and an angle of 180 degrees.

[0110] Two or more of the skimmer sections 550 may be arranged reflectionally symmetrically with respect to one or more planes of reflectional symmetry. Two or more of the skimmer sections 550 may be arranged rotationally symmetrically. In the present embodiment, two skimmer sections 550 are arranged rotationally symmetrically with respect to the central axis 330 and an angle of 180 degrees.

[0111] Two or more of the inflow sections 560 may be arranged reflectionally symmetrically with respect to one or more planes of reflectional symmetry. Two or more of the inflow sections 560 may be arranged rotationally symmetrical. In the present embodiment, two inflow sections 560 are arranged reflectionally symmetrically with respect to the first plane of reflectional symmetry 204. In the present embodiment, the two inflow sections 540 may be considered as being arranged rotationally symmetrically with respect to the central axis 330 and an angle of 180 degrees.

[0112] Surface open channel

[0113] The surface open channel 510 is an open channel fluidly connecting the tank 300 and the filter section 520. The surface open channel 510 may instead be known as a surface conduit. In the present embodiment, the surface open channel 510 is in fluid communication with the tank 300 via the surface drain 350. The surface open channel 510 may be a linear channel. The surface open channel 510 may further comprise a conduit base. The conduit base may be arranged below the upper edge 312 of the tank wall 310. When the tank wall 310 is curved, the surface open channel 510 may extend tangentially to a curve of the tank wall 310. Further, in the present embodiment there is a first surface open channel 512 and a second surface open channel 514. The first and second surface open channels 512, 514 may optionally be arranged on opposite sides of the upper edge 312 of the tank wall 310 of the tank 300.

[0114] Filter section

[0115] The filter section 520 may comprise a filter 522, a filter open channel 524, and a sludge reservoir 528. The filter 522 may be a mechanical filter, such as a drum filter. Each filter section 520 may comprise two or more filters 522. The filter open channel 524 comprises an inlet portion 525 and an outlet portion 526. At least one filter may be arranged at each end of the surface open channel 510. At least one filter may be in fluid communication with the surface open channel 510. Each of the filters arranged at each end of the surface open channel 510 may be in fluid communication with the surface open channel. The surface open channel 510 may fluidly connect at least two filters 522. More specifically, the inlet portion 525 of the filter open channel 524 is in fluid communication with the surface open channel 510 and the filter 522. The filter 522 is also in fluid communication with the outlet portion 526 of the filter open channel 524 and the sludge reservoir 528. The sludge reservoir 528 collects the waste particles filtered by the filter 522. The sludge reservoir 528 may be fluidly connected to a dry reservoir 570, allowing the waste from the sludge reservoir 528 to be drained into the dry reservoir 570 and pumped outside of the RAS 100 for treatment and / or disposal.

[0116] The bottom drain 340 of the tank 300 further comprises a bottom drain aperture 342 and at least one bottom drain conduit 344. The bottom drain conduit 344 fluidly connects the bottom drain aperture 342 and the inlet portion 525 of the filter open channel 524. The bottom drain conduit 344 may extend along at least portion of the tank wall 310 and / or at least a portion of the tank base 320. The bottom drain conduit 344 further comprises an inlet 346 and an outlet 348. The inlet 346 of the bottom drain conduit 344 is contiguous with the bottom drain aperture 342. The outlet 348 of the bottom drain conduit 344 is contiguous with the inlet portion 525 of the filter open channel 524. The filter open channel 524 may increase in width along its length to maintain a constant flow speed when the water flowing through the outlet 348 of the bottom drain conduit 344 is added to the water flowing through said filter open channel 524 from the surface open channel 510.

[0117] Each surface open channel 510 may fluidly connect two or more filter sections 520. In the present embodiment, there are two filter sections 520 arranged at opposite ends of each surface open channel 510.

[0118] The outlet portion 526 of the filter open channel 524 is in fluid communication with the bioreactor section 530. The outlet portion 526 of the filter open channel 524 may comprise a wall, over which water may flow through to the bioreactor section 530. This wall ensures the outlet portion 526 of the filter open channel 524 remains at least partially submerged during production.

[0119] Bioreactor section

[0120] The bioreactor section 530 comprises a bioreactor 532. The bioreactor 532 comprises an inlet 534, a main body 536, and an outlet 538. The outlet portion 526 of the filter open channel 524 is contiguous with the inlet 534 of the bioreactor 532.

[0121] In the present embodiment, there is one bioreactor section 530 provided for each filter section 520.

[0122] The bioreactor section 530 is in fluid communication with the pump section 540. More specifically, the outlet 538 of the bioreactor 532 is in fluid communication with the pump section 540. The outlet 538 of the bioreactor 532 may comprise a wall, over which water may flow to the pump section 540. This wall ensures that the bioreactor 532 remains at least partially submerged during production.

[0123] Pump section

[0124] The pump section 540 further comprises a pump open basin 542, at least one pump 544, and may comprise at least one UV filter 546. The at least one pump 544 is located at least partially within the pump open basin 542. During production, the pump 544 pumps water from the pump open basin 542 to the inflow section 560. The UV filter 546 may treat water flowing into the pump open basin 542 from the bioreactor section 530.

[0125] In the present embodiment, there is one pump section 540 shared between the two bioreactors 530 fluidly connected to each end of the first and second surface open channels 512, 514.

[0126] Inflow section

[0127] The inflow section 560 comprises a second conduit shown as an open inflow channel 562 and an inflow column (not shown). In other embodiments, the second conduit may take a different form, such as just an open or closed inflow channel without an inflow column, for example a pipe. In this embodiment, the open inflow channel 562 comprises a main section 564, and at least one arm section 566. During production, the pump 544 of the pump section 540 pumps water to the main section 564. The main section 564 is fluidly connected to the arm section 566, which is itself fluidly connected to the inflow column. The inflow column is for distributing the treated water in the open inflow channel 562 throughout the depth of the tank volume. The inflow column may be located at least partially within the tank 300. The inflow column may be hollow and may comprise several outlets 569 along its length. The inflow section 560 may be located at least partially above the tank wall 300.

[0128] The pump open basin 542 is also in fluid communication with the skimmer section 550.

[0129] Skimmer section

[0130] The skimmer section 550 further comprises at least one protein skimmer 552, also known as a foam fractionator. A pump 554 pumps water from the pump open basin 542 through to the protein skimmer 552. Around one quarter to one third of the water in the pump open basin 542 during production passes through the protein skimmer 552.

[0131] In the present embodiment, there are two skimmer sections 550 arranged at opposite ends of the RAS 100, each having a one protein skimmer 552. The water treatment system 500 may be located at least partially within the buoyancy system 400. This means that at least one of the surface open channel 510 and / or filter 522 and / or bioreactor 532 and / or pump 544 and / or skimmer 552 is at least partially located within the buoyancy system 400.

[0132] At least one of the surface open channel 510 and / or filter 522 and / or bioreactor 532 and / or pump 544 and / or skimmer 552 may be fully located within the buoyancy system 400. In some embodiments, all of the surface open channels 510 and / or all of the filters 522 and / or all of the bioreactors 532 and / or all of the pumps 544 and / or all of the skimmers 552 may be fully located within the buoyancy system 400.

[0133] Lifecycle of water through the water treatment system

[0134] Fig. 5 shows a water level flow diagram 600 illustrating schematically the water levels at various stages of the RAS 100 when in operation. A water level axis 604 is used as a reference for indicating the various water levels.

[0135] When in operation, both the tank 300 and the water treatment system 500 are provided with water. The tank 300 having a tank base level 602 is filled to tank water level 605. The water from the tank 300 flows due to gravity through the surface drain, 350 and the bottom drain, 344 to the surface open channels 510, 512, 514 and on to the filter section 520.

[0136] The surface open channels 510, 512, 514 have a water level 610 which is lower than the water level 605 of the tank 300.

[0137] The filter section 520 has a water level 620 which is lower than the water level 605 of the tank 300. The water level 620 of the filter section 520 is lower than the water level 605 of the tank 300. The water is filtered in the filter section 520 and flows due to gravity through to the bioreactor section 530.

[0138] The bioreactor section 530 has a water level 630 which is lower than the water level 620 of the filter section 520. The water is filtered in the bioreactor section 530 and flows due to gravity through to the pump section 540. The pump section 540 has a water level 640 which is lower than the water level 630 of the bioreactor section 530. The water in the pump section 540 is then pumped by the pumps 544 to the inflow section 560 and the pumps 554 to the skimmer section 550.

[0139] The skimmer section 550 has a water level 650 which is higher than the water level 640 of the pump section 540. The inflow section 560 has a water level 660 which is higher than the water level 640 of the pump section 540. Further, water level 650 of the skimmer section 550 is higher than the water level 660 of the inflow section 560. The water from the skimmer section 550 flows due to gravity through to the inflow section 560.

[0140] The water from the inflow section 560 flows due to gravity back into the tank 300, being distributed throughout by outlets 569 of the inflow column. During operation, the water level 605 of the tank 300 remains consistent.

[0141] The maximum height difference between the water level 605 of the tank 300 and the water levels 620, 630, 640, 650, 660 of the filter section 520, bioreactor section 530, pump section 540, and the inflow section 560 is 1 metre or less. For example, this maximum height difference may be 0.5 metres or less, or 0.30 metres or less.

[0142] Any positional indications refer to the position shown in the figures.

[0143] In the figures, same or corresponding elements are indicated by same reference numerals. For clarity reasons, some elements may in some of the figures be with-out reference numerals.

[0144] A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted.

[0145] It should be noted that the above-mentioned embodiments illustrate rather than limit the present disclosure, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0146] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

Claims1. A floating recirculating aquaculture system (100) for cultivating aquatic species, the aquaculture system comprising a main body (200), the main body (200) comprising: a tank (300) comprising a central axis (330) and at least one surface drain (350); a buoyancy system (400); and a water treatment system (500) comprising a first conduit (510, 512), at least two filters (522), at least one bioreactor (532), and at least one pump (554), wherein the first conduit (510, 512) comprises a first end and a second end; the tank (300) and the first conduit (510, 512) are in fluid communication via at least one surface drain (350), c h a r a c t e r i s e d i n t h a t at least one filter (522) is arranged at each of the first and second ends of the first conduit (510, 512).

2. The floating recirculating aquaculture system (100) according to any preceding claim, wherein the tank comprises at least two surface drains (350) and the water treatment system (500) comprises at least four filters (522), and further comprises a second conduit (510, 514), wherein the second conduit (510, 514) comprises a first end and a second end; the tank (300) and the second conduit (510, 514) are in fluid communication via at least one surface drain (530); and at least one filter (522) is arranged at each end of the first and second ends of the second conduit (510, 514).

3. The floating recirculating aquaculture system (100) according to any preceding claim, wherein the first conduit (510, 512) is a surface open channel.

4. The floating recirculating aquaculture system (100) according to any preceding claim, wherein the main body (200) further comprises a first plane of reflectional symmetry (204) and a second plane of reflectional symmetry (206).

5. The floating recirculating aquaculture system (100) according to claim 4, wherein the first conduit (510, 512) is arranged symmetrically with respect to the first plane of reflectional symmetry (204) and / or the second plane of reflectional symmetry (206).

6. The floating recirculating aquaculture system (100) according to claim 4 when dependent upon claim 2, wherein the first conduit (510, 512) and the second conduit (510, 514) each comprise volumetric centroids and / or centres of mass which are arranged symmetrically with respect to the first plane of reflectional symmetry (204) and / or the second plane of reflectional symmetry (206).

7. The floating recirculating aquaculture system (100) according to claim 2 or any of claims 3 to 6 when dependent upon claim 2, wherein the first conduit (510, 512) and the second conduit (510, 514) are rotationally symmetrically arranged about the central axis (330).

8. The floating recirculating aquaculture system (100) according to claim 4 or any of claims 5 to 8 when dependent upon claim 4, wherein at least two filters (522) comprise volumetric centroids and / or centres of mass which are arranged symmetrically with respect to the first plane of reflectional symmetry (204) and / or the second plane of reflectional symmetry (206).

9. The floating recirculating aquaculture system (100) according to any preceding claim wherein at least two filters (522) are rotationally symmetrically arranged about the central axis (330).

10. The floating recirculating aquaculture system (100) according to any preceding claim, wherein the water treatment system (500) comprises at least two bioreactors (532).

11. The floating recirculating aquaculture system (100) according to claim 10 wherein at least two bioreactors (532) are rotationally symmetrically arranged about the central axis (330).

12. The floating recirculating aquaculture system (100) according to claim 10 when dependent upon claim 4 or claim 11 when dependent upon claim 4, wherein at least two bioreactors (532) comprise volumetric centroids and / or centres of mass which are arranged symmetrically with respect to the first plane of reflec- tional symmetry (204) and / or the second plane of reflectional symmetry (206).

13. The floating recirculating aquaculture system (100) according to any preceding claim, wherein at least one open channel (524, 542) fluidly connects at least one filter (522), at least one bioreactor (532), and at least one pump (544).

14. The floating recirculating aquaculture system (100) according to any preceding claim, wherein the buoyancy system (400) comprises at least two discrete modules (402).

15. The floating recirculating aquaculture system (100) according to any preceding claim, wherein at least one of the discrete modules (402) comprises a feeding system (410) and / or a steering system (420) and / or an emergency generator (430).

16. The floating recirculating aquaculture system (100) according to claim 14 or claim 15, wherein at least two of the discrete modules (402) are rotationally symmetrically arranged about the central axis (330).

17. The floating recirculating aquaculture system (100) according to any of claims 14 to 16 when dependent upon claim 4 wherein at least two of the discrete modules (602) comprise volumetric centroids and / or centres of mass which are ar-ranged symmetrically with respect to the first plane of reflectional symmetry (204) and / or the second plane of reflectional symmetry (206).

18. The floating recirculating aquaculture system (100) according to any of claims 14 to 17, wherein at least two of the discrete modules (402) are arranged at a periphery of the main body (200).

19. The floating recirculating aquaculture system (100) according to any preceding claim, wherein the main body (200) further comprises a covering (202).

20. The floating recirculating aquaculture system (100) according to any preceding claim wherein the tank (300) further comprises a bottom drain (340).

21. The floating recirculating aquaculture system (100) according to any preceding claim wherein the main body (200) has a thermal transmittance U-value of either less than 1.0 W / m2K or less than 0.3 W / m2K.

22. Use of the floating recirculating aquaculture system (100) according to any of claims 1 to 21.

23. A method of operating a floating recirculating aquaculture system (100) comprising the steps of: providing a floating recirculating aquaculture system (100) according to any of claims 1 to 21; and providing water in the tank (300) and water treatment system (500).

24. The method of operating a floating recirculating aquaculture system (100) according to claim 23, wherein the tank (300) has a tank water level (605), the first conduit (510, 512) has a first conduit water level (610), the filters (522) have a filter water level (620), the bioreactor (532) has a bioreactor water level (630), and the pump (544) has a pump water level (640).

25. The method of operating a floating recirculating aquaculture system (100) according to claim 24, wherein the first conduit water level (610) is lower than the tank water level (605).

26. The method of operating a floating recirculating aquaculture system (100) ac- cording to claim 24 or 25 wherein the maximum height difference between the tank water level (605) and each of the first conduit water level (610), filter water level (620), bioreactor water level (630), and pump water level (640) is 1 metre or less.

27. The method of operating a floating recirculating aquaculture system (100) ac- cording to claim 26, wherein the maximum height difference between the tank water level (605) and each of the first conduit water level (610), filter water level (620), bioreactor water level (630), and pump water level (640) is 0.5 metres or less.

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