A tank and a modular wall element

Abstract

There is provided a tank for farming aquatic organisms comprising: a first tank wall enclosing a tank space arranged to contain water and aquatic organisms to be farmed, optionally, a plurality of elongated support structures fixed onto a lateral surface of the first tank wall, an airlift pump comprising a vertical riser channel (27, 47, 57, 67), the airlift pump comprising a water outlet connected to the tank space, wherein the water outlet is configured to output aerated water into the tank space, wherein the vertical riser channel (27, 47, 57, 67) is integrally connected or integrated to the first tank wall along a height of the vertical riser channel (27, 47, 57, 67).

Description

A TANK AND A MODULAR WALL ELEMENTFIELD

[0001] The present disclosure relates to a tank with an airlift pump for recirculating aquaculture. The present disclosure also relates to a modular wall element for a tank.BACKGROUND

[0002] Aquaculture, generally referred to as farming of aquatic organisms, such as fish and shellfish, under controlled conditions, is a fast-growing agricultural sector that allows for harvesting seafood for human and animal consumption. By means of aquaculture a variety of aquatic species can be produced in a cost-effective manner and with predictable yields regardless of external conditions, such as weather and / or population fluctuations.

[0003] There are three main stages of water treatment in recirculation aquaculture: 1) solids removal, 2) gas exchange (carbon dioxide removal and oxygen addition), and 3) biological water purification (nitrification, and in some cases also denitrification).

[0004] Partial recirculation aquaculture systems have only the first two stages, but no biological water treatment at all.

[0005] All stages of water treatment are usually carried out outside the tank, as individual sub-processes. In the exchange of gases, either trickling towers or separate aeration tanks are used. In the former system, water is supplied into air, and in the latter, air into water. The space requirement of these structures is about 5% of the total area of the farm.

[0006] Gas exchange systems typically account for about 10 to 20% of the investment costs. The cost of centralized gas exchange consists not only of the cost of gas exchange units and the need for a hall building about 5% larger, but also of pipelines and water pumps.

[0007] The exchange of gases is the so-called first production-limiting water treatment process. That is, the removal of carbon dioxide (and the addition of oxygen) determines the need for pumping water in the entire farm. In addition to the aeration units, the pipe andpump sizes of the farm are thus significantly larger compared to a situation in which the pumping could be dimensioned according to the needs of solids removal and biological water treatment. Aeration towers or tanks are dimensioned according to the volume of the fish tanks and the planned growing densities, as well as the use of feed. If the farm is expanded, also the size of the aeration units and the size of the piping between the aeration units and the tanks must be increased, which is very challenging, as the pipelines are placed underground, below the tanks.

[0008] Current technologies for fish tanks with airlift pumps involve locating the airlift pump outside the fish tank or inside the fish tank in the tank water, in both cases as a separate unit.

[0009] Inside the tank, an airlift pump consumes tank space, and additionally it may disturb circulation of tank water and deteriorate tank water quality by re-suspending solid matter from the bottom of the tank.

[0010] It is an aim of the present embodiments to overcome at least some of the disadvantages of known fish tanks and their gas-exchange systems.SUMMARY

[0011] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0012] According to a first aspect, there is provided a tank for farming aquatic organisms comprising: a first tank wall enclosing a tank space arranged to contain water and aquatic organisms to be farmed, optionally, a plurality of elongated support structures fixed onto a lateral surface of the first tank wall, an airlift pump comprising a vertical riser channel, the airlift pump comprising a water outlet connected to the tank space, wherein the water outlet is configured to output aerated water into the tank space, wherein the vertical riser channel is integrally connected or integrated to the first tank wall along a height of the vertical riser channel.

[0013] According to a second aspect, there is provided A modular wall element for a tank for farming aquatic organisms, the modular wall element comprising: a first wall having a first end and a second end, optionally, a plurality of elongated support structures fixed ontoa lateral surface of the first wall, an airlift pump comprising a vertical riser channel, wherein the vertical riser channel is integrally connected or integrated to the first wall along a height of the vertical riser channel, wherein the airlift pump comprises a water outlet configured to output aerated water into the tank space, wherein said ends of the modular wall element are configured to be connected to respective ends of another modular wall element so that the connected modular wall elements encase or confine at least a part of a tank space arranged to contain water and aquatic organisms to be farmed.

[0014] Various embodiments of the first aspect or the second aspect may comprise one or more features from the following bulleted list:• The riser channel comprises a riser channel lateral surface, wherein the riser channel lateral surface either faces a lateral surface of the first tank wall or is part of the first tank wall.• The vertical riser channel is fixed on the lateral surface of the first tank wall.• The airlift pump comprises a plurality of vertical channels, wherein a lateral surface of each vertical channel faces a lateral surface of the first tank wall and is fixed thereon.• A plurality of elongated support structures fixed onto a lateral surface of the first tank wall.• The airlift pump is configured to provide structural integrity to the first tank wall.• The riser channel comprises, in its lower part, an air inlet configured to receive compressed air and a water inlet configured to receive tank water.• The riser channel comprises, in its upper part, a riser channel outlet configured to output aerated water and air.Said plurality of vertical channels comprise a riser channel and, upstream of the riser channel, a water inlet channel.An outlet in a lower part of the water inlet channel is connected to the water inlet of the riser channel.• The water inlet channel comprises, in its upper part, an inlet configured to receive tank water into the water inlet channel, and preferably said inlet is in the form of a grid.• Said plurality of vertical channels comprise a riser channel and, downstream of the riser channel, a water outlet channel.• The outlet of the riser channel is connected to an inlet in an upper part of the water outlet channel.• The water outlet channel comprises one or more water outlets configured to output aerated water into the tank.• The water outlet channel comprises a gas inlet, such as an oxygen gas inlet.• The water outlet channel has a downward widening shape.• The riser channel has an upward widening shape.• At least some of the water outlets are arranged to provide a flow of aerated water in a perpendicular direction with regard to the first tank wall.• At least some of the water outlets are arranged to provide a flow of aerated water in a substantially parallel or tangential direction with regard to the first tank wall.• The water outlets are distributed across a vertical dimension of the water outlet channel.• Said plurality of vertical channels comprise, as a cascade in the direction of water flow: a water inlet channel, a riser channel, and a water outer channel.• Said elongated support structures comprise hollow beams configured to reinforce the first tank wall.• The tank comprises a second tank wall enclosing the first tank wall.• An inner space is defined by the first tank wall and the second tank wall.The elongated support structures are disposed within the inner space.The airlift pump or at least the riser channel thereof is disposed within the inner space.• The plurality of elongated support structures comprises a plurality of planar plates joining the first and the second tank walls to each other.• The planar plates are configured to provide reinforcing connections between the first tank wall and the second tank wall.• The airlift pump comprises a second plurality of planar plates, each being attached to the first tank wall and to the second tank wall.• The second plurality of planar plates are arranged so that at least one vertical channel is formed within the inner space.• Said at least one vertical channel comprises a channel that is configured to function as the riser channel of the airlift pump.• The second plurality of planar plates are arranged so that at least two parallel vertical channels are formed.• The distance between the first tank wall and the second tank wall is in the range 5 to 30 cm.• The first tank wall and the second tank wall and the elongated support structures are provided as an integral entity, such as in the form of a cellular wall panel.• The cross-sectional area of each of the vertical channels is in the range 100 to 10002 cm .• The height of each of the vertical channels is in the range 0.5 to 3 meters.• The tank comprises at least two airlift pumps.• The water outlets of the airlift pumps are arranged to co-operatively produce one or more flows of water, such as circular or oval flows of water, in the tank space.• The tank is made of a plastic material, a composite material, glass fiber, a metal material, such as marine-grade aluminum, or any combination thereof.The overall shape of the tank is circular, rectangular, hexagonal or octagonal.• The modular wall element further comprises a wall adapter located at each of the first end and the second end and configured to connect the modular wall element to said another modular wall element.• The modular wall element and a plurality of other modular wall elements are configured to be connected to each other so that the modular wall elements form an entire wall of the tank, said wall enclosing a tank space.• The modular wall element is configured to be connected to another modular wall element by welding, such as by plastic welding, with fasteners, with mechanical means of attachments, such as bolts or screws, or any combination thereof.• The modular wall element and a plurality of other modular wall elements are configured to be connected to each other so that the connected modular wall elements enclose a tank space.• The wall adapter has a C shape or a U shape or an L shape.• Said modular wall element and said another modular wall element are identical.• Said another modular wall element does not comprise any airlift pump.• The wall adapter comprises a plate extending from one of the ends of the first wall, the plate configured to attach to another modular wall element.• The wall adapter comprises a plate comprising a fastening means configured to attach to another modular wall element.• The modular wall element further comprises a second lateral wall enclosing the first lateral wall, and an inner space defined by the first wall and the second wall.• The elongated support structures are disposed within the inner space.• The airlift pump or at least the riser channel thereof is disposed within the inner space.The modular wall element is configured to attach to another modular wall element by welding, by plastic welding, with fasteners, with mechanical means of attachments, such as bolts or screws, or any combination thereof.• At least a part of the modular wall element is made of a plastic material, a composite material, glass fibre, a metal material, such as stainless steel, marine-grade aluminium, or any combination thereof.• At least a part of the wall adapter is made of a plastic material, a composite material, glass fiber, a metal material, such as stainless steel, marine-grade aluminium, or any combination thereof.

[0015] Advantages

[0016] Locating the airlift pump within the tank wall structure may provide quicker installation and material and energy cost savings. It may also improve quality of tank water as the water intake for the airlift pump takes place in an upper part of the tank, whereby any solid matter that has already settled to the bottom of the tank will not rise and become resuspended to water phase.

[0017] In some embodiments, the gas exchange and flow control functions are tankspecific and are preferably located as an integral part of a tank wall, without increasing the maximum thickness of the tank wall.

[0018] The hall investment costs may be reduced by an estimated 5%.

[0019] The dimensions of water pipelines and the size of water pumps may also be reduced, and therefore the total savings in investment costs may be reduced by up to 10%.

[0020] The savings in operating costs may be even greater than the initial investment costs. The gas exchange may be dimensioned according to the individual needs of the tanks. In addition, vertical water pumping may be substantially reduced as it can be dimensioned according to the ammonium and solids content of water instead of oxygen and carbon dioxide content. The potential for savings in pumping energy is about 50% when compared to the current centralized gas exchange units.

[0021] At least some embodiments may be applicable in container fish farming, such as container recirculation aquaculture systems and container partial recirculation aquaculture systems.

[0022] At least some embodiments may be easily scalable and applicable to tanks with variable volumes and shapes.

[0023] At least some embodiments may be particularly well suited to tanks in which the walls have been reinforced by cellular structures.

[0024] At least some embodiments target a very fast-growing industry that struggles with both high investment and operating costs. The exchange of gases is the most energy- intensive stage of water treatment in recirculation aquaculture. Rising energy costs are currently jeopardising the profitability and sustainability of the entire industry. Therefore, the present embodiments are highly topical and its potential for exploitation may be broad.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIGURE 1 illustrates a fish tank in accordance with an embodiment of the present invention.

[0026] FIGURE 2 shows an inner side of a wall structure of the fish tank shown in FIGURE 1.

[0027] FIGURE 3 shows an outer side of a wall structure of a fish tank in accordance with an embodiment of the present invention.

[0028] FIGURE 4 shows an outer side of a wall structure of a fish tank in accordance with another embodiment of the present invention.

[0029] FIGURE 5 is a schematic view of an airlift pump in accordance with an embodiment of the present invention.

[0030] FIGURE 6 is a schematic view of an airlift pump in accordance with another embodiment of the present invention.

[0031] FIGURES 7 and 8 illustrate wall structures comprising cellular structures in accordance with at least some embodiments of the present invention.

[0032] FIGURES 9 to 11 illustrate three different tank shapes in accordance with at least some embodiments of the present invention.

[0033] FIGURES 12 to 16 illustrate embodiments of the present invention in which modular wall elements have been incorporated to a tank wall structure with various configurations.

[0034] FIGURES 17 and 18 illustrate embodiments of the present invention in which the water outlet channel of the airlift pump comprises a gas inlet.

[0035] FIGURE 19 illustrates an embodiment of the present invention in which the channels of the airlift pump have tapered shapes.EMBODIMENTS

[0036] DEFINITIONS

[0037] In the present context, the term “recirculation aquaculture” comprises production of aquatic animals, preferably fish, in a system which includes a water recirculation system having water treatment units including a biological water treatment unit, such as a bioreactor or a biofiltration unit.

[0038] In the present context, the term “recirculation principle or conditions” comprises recirculation of water between a fish tank and water treatment units including a biological water treatment unit, such as a bioreactor or a biofiltration unit, and possibly some other water treatment units.

[0039] In the present context, the term “partial recirculation principle or conditions” comprises recirculation or re-use of water in a fish tank or between a fish tank and external water treatment units, typically without any biological water treatment unit.

[0040] In the present context, the term “land-based tank” comprises a tank that has its foundations on land.

[0041] In the present context, the term “floating tank” comprises a tank or a closed container that is floating in a sea or in fresh water such as in a lake.

[0042] In the present context, the term “fresh water line” typically refers to an influent new water line or a line inputting new water.

[0043] In the present context, “gas exchange” is typically synonymous with “aeration” and comprises both removal of carbon dioxide and addition of oxygen. Gas exchange or aeration units may be supplemented also with other gases than air.

[0044] “Oxygenation” refers to feeding of pure oxygen.

[0045] “Supersaturation” occurs with a solution when the concentration of a solute exceeds the concentration specified by the value of solubility at equilibrium.

[0046] In the present context, the term “purging” is typically synonymous with the term “depuration”.

[0047] In the present context, the term “farming” is typically synonymous with the terms “cultivating” and “rearing”.

[0048] In the present context, the term “first tank wall” or “first wall” typically refers to a wall, such as a plate-formed single-layer wall, that is configured to be the innermost wall or surface enclosing a tank space.

[0049] In the present context, the term “wall structure” typically refers to the structure, such as a multi-layer hollow reinforced wall structure, which is configured to enclose a tank space and constitutes a lateral structure that typically endures the pressure of the water in the tank.

[0050] In the present context, the term “vertical channel” also comprises a substantially vertical channel, which has a substantially vertical longitudinal axis.

[0051] In the present context, the term “tank space” typically refers to a space or volume configured to contain water and aquatic organisms that are farmed.

[0052] In the present context, the term “riser channel” typically refers to a vertical or substantially vertical riser channel.

[0053] In the present context, the term “integrally connected” means that a vertical riser channel is fixed on a lateral surface of a first tank wall, preferably along the entireheight of the vertical riser channel, for example by fixing means, such as screws, or by welding.

[0054] In the present context, the term “integrated to” means that a vertical riser channel in manufactured as an integral entity on a lateral surface of a first tank wall, for example, by rotational molding.

[0055] In some embodiments, it is provided a fish tank particularly for recirculating aquaculture or partial recirculation aquaculture with an airlift pump integrated in the tank wall structure. Preferably, a vertical channel, such as a vertical riser channel, of the airlift pump is integrally connected or integrated to the first tank wall along a height of the vertical channel.

[0056] The wall structure of the tank may define or enclose one or more tank spaces or compartments, which may be used for farming fish or aquatic organisms in general. A plurality of such tank spaces may be created by placing internal walls or wall structures in the tank.

[0057] In the following, the airlift pump may be positioned in connection with an external wall structure of the tank and / or an internal wall structure of the tank. By “external wall structure” it is referred to the wall structure separating the tank water from the surrounding environment. By “internal wall structure” it is referred to a wall structure separating the tank volume or tank space to individual sub-volumes or sub-spaces or compartments. The sub-volumes may be only partially separated from each other so that tank water may flow between the compartments. The internal wall structures may have a lighter construction than the external wall structures, which latter ones need to endure the pressure of the water in the tank.

[0058] The present tank, particularly its wall structure, may consist of modular wall elements with an integrated element-specific airlift pump. The airlift pump may act as a gas exchange unit (oxygen or air addition and carbon dioxide removal) and, in addition, airlift pumps may be used to create desired flow conditions in the tank.

[0059] If the tank size, the number of compartments in the tank and / or the number of tanks is increased, also the number of modular wall elements and element-specific airlift pumps can be increased easily. The water treatment capacity may thus be automatically increased.

[0060] At least some embodiments may be applicable in recirculating and partial circulation aquaculture.

[0061] At least some embodiments may be particularly suitable for wall structures reinforced with a cellular or honeycomb structure.

[0062] In an embodiment, the modular wall element has a cellular structure. The modular wall element may comprise elongated hollow cells arranged vertically and joined to each other. Additionally, the modular wall element may comprise for example elongated hollow cells arranged horizontally. The vertical hollow cells may serve as vertical channels of the airlift pump.

[0063] At least some embodiments may be applicable for tanks made of various materials, for example tanks built of stainless steel, acid steel, marine-grade aluminium, plastic materials or various composites materials.

[0064] For example, conventional delta beams which are employed as support structures in fish tanks may serve as channels for airlift pumps, and separate pipelines are not necessarily needed for gas exchange.

[0065] In the following, integration of an airlift pump into a tank wall structure, such as a fish tank wall structure, is described in more detail and according to some embodiments.

[0066] In one aspect, there is provided a tank for farming aquatic organisms, such as fish. The tank, particularly its wall structure, comprises a first tank wall enclosing a tank space arranged to contain water and aquatic organisms to be farmed.

[0067] The tank wall structure may comprise one or more elongated support structures fixed onto a lateral surface of the first tank wall. The purpose of the support structures is to provide support to the wall structure so that it can withstand the pressure exerted by water contained in the tank. Preferably, the support structures are vertically oriented and regularly spaced along the periphery of the tank. The support structures may have a certain thickness and be constructed as beams, such as hollow vertical beams. Such hollow beams may be configured to reinforce the first tank wall.

[0068] Typically, in addition to the vertically oriented support structures, there may be horizontal support structures to provide further support. The vertical support structures, such as hollow beams, may be attached to the bottom of the tank from their lower ends. Theupper ends of the vertically oriented support structures may be attached to a horizontal beam, such as an I beam or an L beam or a U beam.

[0069] The tank comprises at least one airlift pump comprising a vertical riser channel. The main purpose of the airlift pump is to aerate water in the tank. The airlift pump typically comprises an inlet to receive tank water to be aerated, and an outlet connected to the tank space, usually both via the first tank wall, wherein the outlet is configured to output aerated water into the tank.

[0070] Additionally, the airlift pump may provide desired water flows inside the tank by directing the water flow output from the airlift pump to a predetermined direction inside the tank, such as perpendicularly with regard to the tank wall structure, such as with regard to its inner wall or first wall, or tangentially or in parallel with regard to the tank wall structure. Control of the direction of output water flow may be affected for example by means of tubular structures or nozzles constituting water outlets.

[0071] Suitably, water inside the tank may be directed to flow circularly, such as according to one or two circles. In a round tank, one circle is enough whereas in an elongated rectangular tank two or more circles, one of which flows clockwise and the other counterclockwise, is preferred.

[0072] The airlift pump is typically configured to provide structural integrity to the first tank wall, for example by being attached to the first tank wall.

[0073] Other functions of the airlift pump may include removal of carbon dioxide.

[0074] Air, typically pressurized air is usually fed to a lower part of the riser channel. As the air bubbles travel upwards, an upward flow of water is induced in the riser channel and simultaneously the water becomes aerated, i.e., gases present in the air bubbles become dissolved in the water, and simultaneously gases present in the water become released or aerated out of the water, into the air bubbles, depending on the concentration differences. In an upper part of the riser channel, non-dissolved air is allowed to leave the riser channel via an air outlet, such as an air relief valve, while the obtained aerated water is directed into the tank, into tank water, to supplement it with aerated water.

[0075] In some embodiments, the airlift pump provides structural integrity to the tank wall structure at least via the riser channel.

[0076] The riser channel comprises a riser channel lateral surface. The riser channel lateral surface either faces a lateral surface of the first tank wall or is part of the first tank wall. In this way advantageously the riser channel structure may increase strength of the tank wall structure and even function as an elongated support structure that replaces one or more conventional elongated vertical support structures along the periphery of the tank.

[0077] The vertical riser channel is fixed on the lateral surface of the first tank wall, preferably along the entire height of the vertical riser channel, such as by means of screws or by welding. Also manufacturing as an integral entity for example by rotational molding is possible.

[0078] In some embodiments, the airlift pump comprises a plurality of vertical channels, wherein a lateral surface of each vertical channel faces a lateral surface of the first tank wall and is fixed thereon. One of the channels is the vertical riser channel.

[0079] The riser channel comprises, in its lower part, an air inlet configured to receive air, such as compressed air, and a water inlet configured to receive tank water to be aerated. In this way, tank water and air become mixed with each other in a lower part of the riser channel, flow together upwards in the riser channel, and during the rising, gases, typically oxygen, are dissolved into the water and gases, typically carbon dioxide, are released from the water.

[0080] The air inlet is preferably placed at a depth of less than 1.7 meters, so that excessive dissolving of nitrogen into tank water may be avoided. If the air bubbles travel a long distance and in high pressure in the riser channel, in addition to oxygen, a lot of nitrogen becomes dissolved from the air into the water. Nitrogen supersaturation in water is harmful to the fish.

[0081] In some embodiments, the riser channel comprises, in its upper part, a riser channel outlet or outlets configured to output aerated water and air. Separate outlets are typically arranged for the aerated water and for the non-dissolved air. The outlet may be directly connected to the tank space, thus forming the final outlet of the airlift pump.

[0082] Alternatively, the riser channel outlet for water may be connected to a further channel downstream of the riser channel.

[0083] Thus, in some embodiments, the plurality of vertical channels of the airlift pump comprises a riser channel and, downstream of the riser channel, a separate water outlet channel. The (water) outlet of the riser channel is then connected to an inlet in an upper part of the water outlet channel. Aerated water flows from the riser channel to the water output channel which is configured to provide a controlled flow of output water into the tank space.

[0084] Typically, the water outlet channel comprises one or more water outlets, such as 2 to 20, for example 5 to 10 water outlets, configured to output aerated water into the tank.

[0085] The water outlets may be arranged to provide a flow of aerated water in a perpendicular direction with regard to the first tank wall.

[0086] The water outlets may be arranged to provide a flow of aerated water in a substantially parallel or tangential direction with regard to the first tank wall.

[0087] The water outlets may be distributed across a vertical dimension of the water outlet channel, for example with regular spacing, for example in a layout of a column or a matrix consisting of several columns of water outlets.

[0088] The water outlets of the (same) airlift pump may comprise water outlets directed to different directions. For example, lower water outlets may be directed in a perpendicular direction while upper water outlets may be directed in a parallel or tangential direction.

[0089] The water outlets of the (same) airlift pump may comprise water outlets with different sizes, such as with different diameters. An advantage is that it may become possible to control or even out the output water flows into different depths in the tank water. Typically, in an upper part of the water outlet channel, the water flow is higher, whereby in said upper part the water outlets or openings may be smaller than in lower parts of the water outlet channel.

[0090] The water outlet channel may comprise a gas inlet, typically in a lower part of the water outlet channel. Via the gas inlet for example oxygen may be fed to the water flowing in the water outlet channel. Advantageously, the feed of air into the riser channel and the feed of oxygen into the water outlet channel may by mutually adjusted to obtain a desired balance of water flow, aeration, carbon dioxide removal and oxygen addition. In this way for example the pH of the water may be adjusted. In this embodiment, the shape of thewater outlet channel may be tapered, such as widening downward, such as conical or pyramidal, with the apex pointing up.

[0091] In an embodiment, oxygen is fed to the water outlet channel at a volumetric flow rate which is 0.01 to 10%, such as 0.1 to 5%, such as about 1% of the volumetric flow rate at which air is fed to the riser channel.

[0092] In an embodiment, the velocity of water flow in the water outlet channel is 80 to 120% of, such as approximately the same as, the velocity of oxygen bubbles in the water outlet channel.

[0093] Said plurality of vertical channels of the airlift pump may comprise a riser channel and, upstream of the riser channel, a separate water inlet channel. In this embodiment, tank water is not fed directly into the riser channel but into a separate channel preceding the riser channel. In this way a more controlled intake of tank water may be realized.

[0094] For example, the water inlet channel comprises, in its upper part at a predetermined height, a water inlet configured to receive tank water into the water inlet channel, and preferably said water inlet is in the form of a grid. Advantageously, by receiving tank water at a suitable height into the airlift pump, it may be possible to avoid transfer of any settled solid matter from the bottom of the tank space into channels of the airlift pump. Such settled solid matter may include fish faeces, fish feed, and other organic and / or inorganic matter.

[0095] For example, the water inlet, such as the grid, is placed within the uppermost third of the height of the tank water.

[0096] In the water inlet channel, the tank water preferably flows in a downward direction.

[0097] An outlet in a lower part of the water inlet channel is connected to the water inlet in a lower part of the riser channel. Thus, the lower parts of the water inlet channel and the riser channel are connected by a fluid connection.

[0098] As discussed above, the airlift pump may comprise in addition to the riser channel, two optional vertical channels.

[0099] Said plurality of vertical channels may comprise, as a cascade in the direction of water flow: a water inlet channel, a riser channel, and a water outer channel.

[0100] One or more of the channels of the airlift pump may have tapered shapes.

[0101] The riser channel may widen upward, for example at least one lateral surface of the riser channel may be tilted with an angle of 0.5 to 3° with regard to the vertical direction. An advantage of such a riser channel shape is a higher water flow.

[0102] The water outlet channel, particularly when comprising an oxygen inlet in its upper part, may widen downward. Then the water flow in the upper part of the water outlet channel may be higher than the water flow in the lower part of the water outlet channel, which is advantageous in view of oxygen dissolution. The oxygen that is fed to the upper part moves downward and the increasing water pressure may enhance dissolution of oxygen. However, the speed of the bubbles may decrease when going downward in the widening water outlet channel, which may increase the time available for oxygen dissolution.

[0103] In an embodiment, the tank wall structures are constructed as hollow structures which comprise internal support structures.

[0104] For example, the tank may comprise a second, outer tank wall enclosing the first tank wall, whereby an inner, hollow space becomes defined by the first tank wall and the second tank wall. The elongated support structures may be disposed within the inner space.

[0105] The hollow wall structure may be utilized so that it contains the airlift pump and even may form part of the channel structure of the airlift pump. Particularly, if the hollow wall structure comprises vertically oriented hollow channels, these channels may be utilized as one or more of the channels of the airlift pump. In this way, the airlift pump can be integrated into the tank wall structure in a space-saving manner and with minimal addition of further, new structures, since the existing internal structures of the hollow wall structure can be utilized as channels of the airlift pump.

[0106] In an embodiment, the airlift pump or at least the riser channel thereof is disposed within or formed by the inner, hollow space or spaces.

[0107] The internal, preferably elongated, support structures between the inner and outer tank walls (the first and second tank walls) may be constructed in various ways.

[0108] For example, the plurality of elongated support structures may comprise a plurality of planar plates joining the first and the second tank walls to each other. The planar plates may be configured to provide reinforcing connections between the first tank wall and the second tank wall.

[0109] The airlift pump may comprise a second plurality of planar plates, each being attached to the first tank wall and to the second tank wall.

[0110] The second plurality of planar plates may be arranged so that at least one vertical channel is formed within the inner space. Said at least one vertical channel comprises a channel that is configured to function as the riser channel of the airlift pump.

[0111] The second plurality of planar plates may be arranged so that at least two parallel vertical channels are formed.

[0112] In some embodiments, the distance between the first tank wall and the second tank wall is typically in the range 5 to 50 cm, such as 5 to 30 cm.

[0113] In some embodiments, the distance between the first tank wall and the second tank wall is at least 5 cm.

[0114] In some embodiments, the distance between the first tank wall and the second tank wall smaller than 40 cm.

[0115] The first tank wall and the second tank wall and the elongated support structures may be provided in the form of a cellular panel or a honeycomb panel having vertically oriented channels. Preferably, the channels in the cellular panel have a rectangular cross-section, but alternatively the cross-section may be for example hexagonal or octagonal. Thus, the first tank wall, the second tank wall and the elongated support structures can be integrated together to form the cellular panel so that the elongated support structures are placed between the first tank wall and the second tank wall connecting the walls together.

[0116] The cross-sectional area of each of the vertical channels of the airlift pump may be in the range 25 to 1000 cm2.

[0117] The height of each of the vertical channels may be in the range 0.5 to 3 meters, such as 0.5 to 2 meters, for example 0.5 to 1.5 meters.

[0118] The tank may comprise at least two separate airlift pumps, wherein the water outlets of the airlift pump or pumps may be arranged to co-operatively produce one or more circular or oval flows of water in the tank space. Advantageously, optimal flow conditions may be provided for the fish, and self-cleaning of the tank may be improved.

[0119] For example, in an elongated tank, two or more circular water flows may be provided so that the flows interact like gear wheels.

[0120] In an example, when observed from above the tank, the flow of water in the tank space may be circular or oval.

[0121] Particularly, in a tank having a rectangular, elongated shape, the flow of water in the tank space may be oval, conforming to the shape of the tank, when observed from above the tank. In this case it may be sufficient to have water outlets that direct water in a tangential direction, for example in an upper part of the water outlet channel.

[0122] In another example, when observed from the side of the tank, the flow of water in the tank space may be circular or oval.

[0123] Particularly, in a tank having a rectangular, elongated shape, the flow of water in the tank space may be oval when observed from the side of the tank. In an upper part of the tank water volume, the flow is toward one end of the tank, and at the end of the tank the flow changes direction to flow back, toward the other end of the tank, in the bottom part of the tank water volume.

[0124] The tank may be made of a plastic material, such as a thermoplastic material, for example polyethylene, or a composite material, glass fibre, a metal material, such as marine-grade aluminium, or any combination thereof.

[0125] The overall shape of the tank may be circular, rectangular, hexagonal or octagonal.

[0126] In an aspect, there is provided a modular wall element for a tank for farming aquatic organisms.

[0127] The modular wall element comprises a first wall, typically elongated in a horizontal direction, the first wall having a first end and a second end, and optionally, a plurality of elongated support structures fixed onto a lateral surface of the first wall.

[0128] The modular wall element comprises an airlift pump comprising a vertical riser channel, wherein typically at least a part of the airlift pump is either attached to the first wall or is part of the first wall. Preferably the vertical riser channel is integrally connected or integrated to the first wall along a height of the vertical riser channel.

[0129] Said ends of the modular wall element may be configured to be connected to respective ends of another modular wall element so that the connected modular wall elements encase or confine at least a part of a tank space arranged to contain water and aquatic organisms to be farmed.

[0130] The modular wall element may be configured to become attached to further wall elements, preferably in an abutting manner, so that the modular wall element and the further wall elements together form a complete wall of a fish tank.

[0131] In an embodiment, the complete external wall structure of a fish tank may be constructed by connecting several modular wall elements to each other, in an abutting manner, to enclose a tank space with a desired volume and in a desired overall shape.

[0132] The modular wall element may be configured to be attached to a further (modular) wall element by welding, plastic welding, fasteners, adapters or by any combination thereof.

[0133] The modular wall element typically comprises an adapter located at each of the first end and the second end configured to attach the modular wall element to the further wall element.

[0134] Thus, several modular wall elements may be connected to each other via the adapters to define and enclose a tank space of the tank.

[0135] The further wall elements may be otherwise similar to the modular wall element but lacking an airlift pump.

[0136] In an embodiment, the further wall elements may have a conventional structure but equipped with adapters in order to be attachable to the modular wall element in a watertight manner.

[0137] The adapter may comprise a plate extending from one of the ends of the first wall, the plate being configured to attach to another wall element.

[0138] The adapter may comprise a plate comprising a fastening means configured to attach to another wall element.

[0139] The modular wall element may further comprise a second wall enclosing the first wall, and an inner space defined by the first wall and the second wall, wherein the elongated support structures are disposed within the inner space. The airlift pump or at least the riser channel thereof is disposed within the inner space.

[0140] At least part of the modular wall element may be made of a plastic material, a composite material, glass fibre, a metal material, such as marine-grade aluminium, or any combination thereof.

[0141] At least part of the adapter may be made of a plastic material, a composite material, glass fibre, a metal material, such as marine-grade aluminium, or any combination thereof.

[0142] At least some embodiments may be applicable in land-based tanks and in floating tanks.

[0143] In an embodiment, the tank is a land-based tank, which is a tank that has its foundations on land.

[0144] In an embodiment, the tank is a floating tank, which is tank or a closed container that is floating in a sea or in fresh water such as in a lake.

[0145] Turning next to the drawings:

[0146] FIGURE 1 illustrates a fish tank 10.

[0147] FIGURE 2 shows an inner side of a wall structure of the fish tank shown inFIGURE 1. There is a water inlet channel 26 comprising a grid 21, a riser channel 27, and a water outlet channel 28 comprising water outlet nozzles, such as the water outlet nozzle 25a.

[0148] FIGURE 3 shows an outer side of a wall structure of a fish tank in accordance with an embodiment. There are delta beams 39a, 39b to provide structural support to the wall structure (to its first wall).

[0149] FIGURE 4 shows an outer side of a wall structure of a fish tank in accordance with another embodiment. There are delta beams 49 to provide structural support to the wallstructure (to its first wall). The delta beams are connected to each other by tubular fluid connections and employed as the water inlet channel 46, the riser channel 47, and the water outlet channel 48 respectively.

[0150] FIGURE 5 is a schematic view of an airlift pump in accordance with an embodiment. The airlift pump comprises the water inlet channel 56, the riser channel 57, and the water outlet channel 58. The water inlet channel 56 comprises a grid 51. The water outlet channel 58 comprises water outlet nozzles 55a. Air is fed via the aeration pipe 52 and the air inlet 53 into the lower part of the riser channel 57. There is an air release valve or opening 59 in the upper part of the riser channel, through which valve any non-dissolved air can escape.

[0151] FIGURE 6 is a schematic view of an airlift pump in accordance with another embodiment. The airlift pump comprises the water inlet channel 66, the riser channel 67, and the water outlet channel 68. The water inlet channel 66 comprises a grid 61. The water outlet channel 68 comprises water outlet nozzles 65a.

[0152] FIGURES 7 and 8 illustrate wall structures comprising cellular panels in accordance with at least some embodiments.

[0153] FIGURES 9 to 11 illustrate three different tank shapes in accordance with at least some embodiments.

[0154] FIG. 9 shows a rectangular tank. The arrows depict water output flows from water outlet channels 98a-g of individual airlift pumps. There are seven airlift pumps integrated to the wall structures of the tank. Five of the pumps output water in an orthogonal or perpendicular direction with regard to the tank inner wall while two of the pumps output water in a parallel or tangential direction with regard to the tank inner wall.

[0155] FIG. 10 shows a circular tank. The arrows depict water output flows from water outlet channels 108a-f of individual airlift pumps. In this case a single airlift pump, such as the airlift pump comprising the water outlet channel 108a, may be sufficient to provide a desired circular flow of water in the tank. The pumps output water in an approximately parallel or tangential direction with regard to the curved tank inner wall.

[0156] FIG. 11 shows an octagonal tank. The arrows depict water output flows from water outlet channels 118a-h of individual airlift pumps. There are eight airlift pumpsintegrated to the wall structures of the tank. The pumps output water in an approximately parallel or tangential direction with regard to the tank inner wall.

[0157] FIGURES 12 to 16 illustrate embodiments in which modular wall elements, each incorporating one or more airlift pumps, have been incorporated to a tank wall structure with various configurations. FIGURES 12 to 16 show schematic views from above the tank. In these embodiments, each modular wall element has a cellular structure with three, six or nine parallel channels, corresponding to one, two or three airlift pumps, respectively. The tank shown in FIGURES 13 to 16 has been divided by four internal wall structures to five compartments or five inner tank spaces.

[0158] In FIG. 12, a single wall element 121 has been incorporated to a tank wall structure. The wall element has three parallel channels and correspondingly one airlift pump. The arrows depict attaching of the modular wall element to other parts 122, 123 of the tank wall structure.

[0159] In FIG. 13, a single wall element 131 has been incorporated to a tank wall structure, in a comer of the tank, which wall structure is in this case an external wall structure. The wall element has three parallel channels and correspondingly one airlift pump.

[0160] In FIG. 14, two wall elements 141, 142 have been incorporated to a tank wall structure: one wall element 141 to form a part of the external wall structure and another wall element 142 to form a part of an internal wall structure. The arrows depict direction of water flow from outlets in the water outlet channels.

[0161] In FIG. 15, a single wall element 151 with six parallel channels and correspondingly two airlift pumps have been incorporated to an external wall structure.

[0162] In FIG. 16, a single wall element 161 with nine parallel channels and correspondingly three airlift pumps have been incorporated to an internal wall structure. The arrows depict direction of water flow from outlets in the water outlet channels 168a-c.

[0163] FIGURES 17 and 18 illustrate embodiments in which the water outlet channel of the airlift pump comprises a gas inlet for feeding oxygen.

[0164] In FIG. 17, the airlift pump comprises a water inlet, such as a grid 171, an aeration pipe 172 for feeding air through the air inlet 173 to the lower part of the riser channel, an oxygen inlet 174 for feeding oxygen to an upper part of the water outlet channel,and a plurality of water outlet nozzles, such as 175a, along the water outlet channel. The water inlet 171 feeds used water from the tank into the airlift pump. The air inlet 173 in the riser channel may be a medium or coarse bubble diffuser or an injection nozzle. In the riser channel, aerated water flows upward and continues to the water outlet channel. There is an air release valve or opening 179 in the upper part of the riser channel, through which valve any non-dissolved air can escape. An oxygen source is connected to the oxygen inlet 174. The oxygen inlet may be fine bubble diffuser or an injection nozzle. Aerated and oxygenated water flows from the water outlet nozzles back to the tank.

[0165] In FIG. 18, the airlift pump comprises a water inlet, such as a grid 181, an aeration pipe 182 for feeding air to the lower part of the riser channel, an oxygen inlet 184 for feeding oxygen to a lower part of the water outlet channel, and a plurality of water outlet nozzles, such as 185a, along the water outlet channel. The water inlet 181 feeds used water from the tank into the airlift pump. The air inlet 183 in the riser channel may be a medium or coarse bubble diffuser or an injection nozzle. In the riser channel, aerated water flows upward and continues to the water outlet channel. An oxygen source is connected to the oxygen inlet 184. The oxygen inlet may be fine bubble diffuser or an injection nozzle. Aerated and oxygenated water flows from the water outlet nozzles back to the tank.

[0166] FIGURE 19 illustrates an embodiment in which the channels of the airlift pump have tapered shapes. The riser channel widens upward, for example with an angle of 0.5 to 3°. An advantage of such a riser channel shape is a higher water flow. The water outlet channel, particularly when comprising an oxygen inlet in its upper part (not shown here), widens downward. Then the water flow in the upper part of the water outlet channel is higher than the water flow in the lower part of the water outlet channel, which is advantageous in view of oxygen dissolution. The small-bubble oxygen that is fed to the upper part moves downward and the increasing water pressure enhances dissolution of oxygen. However, the speed of the bubbles decreases when going downward in the widening water outlet channel, which increases the time available for oxygen dissolution.

[0167] It is to be understood that the embodiments disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0168] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0169] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0170] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0171] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0172] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. Thefeatures recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e., a singular form, throughout this document does not exclude a plurality.INDUSTRIAL APPLICABILITY

[0173] The present invention may be industrially applicable at least in farming of aquatic organisms.REFERENCE SIGNS LIST10 tank21, 31, 51, 61, 171, 181, 191 grid25a, 55a, 65a, 175a, 185a, 195a water outlet nozzle26, 46, 56, 66 water inlet channel27, 47, 57, 67 riser channel28, 48, 58, 68 water outlet channel39a, 39b, 49 delta beam52, 172, 182, 192 aeration pipe53, 173, 183, 193 air inlet59, 179 air release valve or opening98a-g, 108a-f, 118a-h water outlet channel121, 131, 141, 142, 151, 161 modular wall element122, 123 tank wall structures168a-c water outlet channels174, 184 oxygen inlet

Claims

CLAIMS:

1. A tank (10) for farming aquatic organisms comprising:- a first tank wall enclosing a tank space arranged to contain water and aquatic organisms to be farmed,- optionally, a plurality of elongated support structures fixed onto a lateral surface of the first tank wall,- an airlift pump comprising a vertical riser channel (27, 47, 57, 67), the airlift pump comprising a water outlet connected to the tank space, wherein the water outlet is configured to output aerated water into the tank space, wherein the vertical riser channel (27, 47, 57, 67) is integrally connected or integrated to the first tank wall along a height of the vertical riser channel (27, 47, 57, 67).

2. The tank (10) according to claim 1, wherein the vertical riser channel (27, 47, 57, 67) comprises a riser channel lateral surface, wherein the riser channel lateral surface either faces a lateral surface of the first tank wall or is part of the first tank wall.

3. The tank (10) according to any one of the preceding claims, wherein the vertical riser channel (27, 47, 57, 67) is fixed on the lateral surface of the first tank wall along the entire height of the vertical riser channel (27, 47, 57, 67).

4. The tank (10) according to claim any one of the preceding claims, wherein the airlift pump comprises a plurality of vertical channels, wherein a lateral surface of each vertical channel faces a lateral surface of the first tank wall or is part of the first tank wall.

5. The tank (10) according to any one of the preceding claims, wherein a plurality of elongated support structures is fixed onto a lateral surface of the first tank wall.

6. The tank (10) according to any one of the preceding claims, wherein one or several vertical channel(s) of the airlift pump is / are configured to provide structural integrity to the first tank wall.

7. The tank (10) according to any one of the preceding claims, whereinthe vertical riser channel (27, 47, 57, 67) comprises, in its lower part, an air inlet (53, 173, 183, 193) configured to receive compressed air and a water inlet configured to receive tank water, and the vertical riser channel (27, 47, 57, 67) comprises, in its upper part, a riser channel outlet or outlets configured to output aerated water and air.

8. The tank (10) according to any one of the preceding claims 4 to 6, wherein said plurality of vertical channels comprise a vertical riser channel (27, 47, 57, 67) and, upstream of the vertical riser channel (27, 47, 57, 67), a water inlet channel (26, 46, 56, 66), wherein an outlet in a lower part of the water inlet channel (26, 46, 56, 66) is connected to the water inlet of the vertical riser channel (27, 47, 57, 67), and wherein the water inlet channel (26, 46, 56, 66) comprises, in its upper part, an inlet configured to receive tank water into the water inlet channel (26, 46, 56, 66), and preferably said inlet is in the form of a grid (21, 31, 51, 61, 171, 181, 191).

9. The tank (10) according to any one of the preceding claims 4 to 7, wherein said plurality of vertical channels comprise a vertical riser channel (27, 47, 57, 67) and, downstream of the vertical riser channel (27, 47, 57, 67), a water outlet channel (28, 48, 58, 68), wherein the outlet of the vertical riser channel (27, 47, 57, 67) is connected to an inlet in an upper part of the water outlet channel (28, 48, 58, 68), and wherein the water outlet channel (28, 48, 58, 68) comprises one or more water outlets configured to output aerated water into the tank.

10. The tank (10) according to any one of the preceding claims, wherein the water outlet channel (28, 48, 58, 68) comprises a gas inlet, such as an oxygen gas inlet.

11. The tank (10) according to any one of the preceding claims, wherein the water outlet channel (28, 48, 58, 68) has a downward widening shape.

12. The tank (10) according to any one of the preceding claims, wherein the vertical riser channel (27, 47, 57, 67) has an upward widening shape.

13. The tank (10) according to any one of the preceding claims 8 to 11, wherein at least some of the water outlets are arranged to provide a flow of aerated water in a perpendicular direction with regard to the first tank wall, and / or wherein at least some of the water outlets are arranged to provide a flow of aerated water in a substantially parallel or tangential direction with regard to the first tank wall.

14. The tank (10) according to any one of the preceding claims 8 to 12, wherein the water outlets are distributed across a vertical dimension of the water outlet channel (28, 48, 58, 68).

15. The tank (10) according to any one of the preceding claims 4 to 13, wherein said plurality of vertical channels comprise, as a cascade in the direction of water flow: a water inlet channel (26, 46, 56, 66), a vertical riser channel (27, 47, 57, 67), and a water outer channel (28, 48, 58, 68).

16. The tank (10) according to any one of the preceding claims, wherein said elongated support structures comprise hollow beams configured to reinforce the first tank wall.

17. The tank (10) according to any one of the preceding claims, comprising:- a second tank wall enclosing the first tank wall,- an inner space defined by the first tank wall and the second tank wall, wherein the elongated support structures are disposed within the inner space, wherein the airlift pump or at least the vertical riser channel (27, 47, 57, 67) thereof is disposed within the inner space.

18. The tank (10) according to claim 17, wherein the plurality of elongated support structures comprises a plurality of planar plates joining the first and the second tank walls to each other, and wherein the planar plates are configured to provide reinforcing connections between the first tank wall and the second tank wall.

19. The tank (10) according to claim 18, wherein- the airlift pump comprises a second plurality of planar plates, each being attached to the first tank wall and to the second tank wall,- the second plurality of planar plates are arranged so that at least one vertical channel is formed within the inner space,- said at least one vertical channel comprises a channel that is configured to function as the vertical riser channel (27, 47, 57, 67) of the airlift pump.

20. The tank (10) according to any of claims 17 to 19, wherein the first tank wall and the second tank wall, the elongated support structures, the vertical riser channel (27, 47, 57, 67), and optionally other channels of the airlift pump are provided as an integral entity, such as in the form of a cellular panel.

21. The tank (10) according to any one of the preceding claims, comprising at least two airlift pumps, wherein the water outlets of the airlift pumps are arranged to co-operatively produce one or more circular or oval flows of water in the tank space.

22. A modular wall element (121, 131, 141, 142, 151, 161) for a tank (10) for farming aquatic organisms, the modular wall element (121, 131, 141, 142, 151, 161) comprising:- a first wall having a first end and a second end,- optionally, a plurality of elongated support structures fixed onto a lateral surface of the first wall,- an airlift pump comprising a vertical riser channel (27, 47, 57, 67), wherein the vertical riser channel (27, 47, 57, 67) is integrally connected or integrated to the first wall along a height of the vertical riser channel (27, 47, 57, 67), wherein the airlift pump comprises a water outlet configured to output aerated water into the tank space, wherein said ends of the modular wall element (121, 131, 141, 142, 151, 161) are configured to be connected to respective ends of another modular wall element (121, 131, 141, 142, 151, 161) so that the connected modular wall elements (121, 131, 141, 142, 151, 161) encase or confine at least a part of a tank space arranged to contain water and aquatic organisms to be farmed.

23. The modular wall element (121, 131, 141, 142, 151, 161) according to claim 21, wherein the modular wall element (121, 131, 141, 142, 151, 161) further comprises a wall adapter located at each of the first end and the second end and configured to connect the modular wall element (121, 131, 141, 142, 151, 161) to said another modular wall element (121, 131,141, 142, 151, 161), or wherein the modular wall element (121, 131, 141, 142, 151, 161) is configured to be connected to another modular wall element (121, 131, 141, 142, 151, 161) by welding, such as by plastic welding, with fasteners, with mechanical means of attachments, such as bolts or screws, or any combination thereof.

24. The modular wall element according to any of claims 22 to 23, wherein the modular wall element (121, 131, 141, 142, 151, 161) and a plurality of other modular wall elements (121, 131, 141, 142, 151, 161) are configured to be connected to each other so that the connected modular wall elements (121, 131, 141, 142, 151, 161) enclose a tank space.

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