A land-based farming system for aquatic organisms, wherein a cylindrical primary production vessel provided with a first outlet for water and arranged at a distance from a side wall is in fluid communication with a water treatment plant, more particularly in that the water treatment plant is arranged in a first annulus wholly or partly encircling the primary production vessel .

A lack of suitable locations in natural water basins in fjords, lakes etc. and also problems regarding waste

handling, control regarding spreading of diseases, parasite attacks and escaping particularly within salmon farming, from such farms has resulted in an increasing interest in being able to implement farming in land-based plants .

Farming of aquatic organisms in vessels onshore sets up a series of requirements for treatment of water. Principally the water treatment process consists of particle separation, C0 ₂ venting, biological cleaning, alkalisation, oxygenation and UV or ozone treatment. In addition to these processes are needed pumps for moving water between farming vessels and water treatment processes and also miscellaneous equipment for monitoring and process control .

Farming vessels are configured and dimensioned for particle separation where larger particles being deposited at the vessel bottom are preferably transported quickly by a bottom current into the centre of the vessel and caught up in a particle outlet. With a correct relationship between the vessel depth and radius and good configuration of a particle trap/outlet, around 70% of the particles brought into the water as feed particle and faeces may be separated and transported out of the system with a small share of the mass of water.

The recirculation systems currently developed and supplied may be split into 2 groups/types:

1. Water treatment systems on a section or plant level. A central and externally located cleaning system common for several farming vessels.

2. Water treatment systems on a vessel level . A cleaning system for each farming unit .

In addition there exist some systems being combinations of these two main groups, where some of the cleaning processes are on a vessel level and some are common for several vessels (one section or the whole plant) . For the first type mostly in current use, the recirculating water must be transported via a piping network to and from the various water treatment systems and back to the farming vessel . As the volumes of water to be recirculated are often large, the cost of this piping network becomes high and makes up a large part of the investment costs for this type of recirculating plant. By the very fact that large volumes of water are moved over large distances, the operation costs also become high for land- based plants of this type.

For the second type of water treatment systems at vessel level there is developed and for sale various systems. A first example is a system where a bio-filter having

ventilation and mechanical particle separation is located beside every farming vessel, known as the BioFish system developed by SINTEF, Trondheim, Norway. In a second example the bio-filter with particle separation and venting is located in the centre of the farming basin. This type is developed and being sold by EcoFarm AS, Bergen, Norway.

The object of the invention is to remedy or reduce at least one of the disadvantages of the prior art, or at least to provide a useful alternative to the prior art.

The object is achieved by the features disclosed in the below description and in the subsequent claims .

There is provided a system for farming of principally any biological species suited for farming in circular farming vessels. The basic idea and the distinction of the system are to use concentric vessels in vessels comprising at least two vessels in a system. A first, central vessel forms a farming volume for primary production, and an annulus formed outside of the first vessel is used for water treatment. Further annuli are used for secondary production at least partly based on waste products from the primary production. This secondary production thus contributes to the water cleaning. The secondary culture is then located in the second annulus encircling the first annulus, as each of the annuli has a dimension adapted to the space needed for technical equipment and the volume needed for the secondary culture .

The central vessel (the primary production vessel) is used for farming of the primary species (for example salmon) .

Roughly 80-90% of the water volume being circulated passes through the water treatment equipment and is cleaned here before being taken back to the primary production vessel. The water treatment may comprise C0 ₂ venting, particle removal, biologic filtering and cleaning, and oxygenation. Also other water treatment may be carried out when needed and when the system is equipped for it. The lower portion of the first annulus forms a water volume preferably provided with bio- cleaning elements of a per se known sort .

The balance of the circulated water volume, roughly 10-20% carries with it sedimentary particles from particle outlets arranged in the bottom portion of the primary production vessel, possibly from sediment traps connected with the water outlet, for example connected to a first outlet. The particle discharge water is taken to the secondary production annulus where the nutrients from the primary production are utilised for production of one or more secondary species contributing to cleaning of the water such that it may be recirculated back to the primary production. If needed, the particle discharge water may undergo cleaning by means of the water treatment equipment as described above before or after it has been in contact with the secondary production culture.

The first outlet may be combined with one or more other outlets arranged in the sidewall. Thereby, at large flow through rates most of the water can be taken out through the other outlets to thereby dampen the flow rate and the whirl formation at the first outlet. The sizes of conduits

connected to the first outlet may thereby be reduced without the system becoming unsuitable for production having need of a high replacement speed.

In the same manner the water inflow is preferably spread among several inlets arranged as spreader pipes provided with several inlet openings distributed over a large part of the vessel water depth and with the spreader pipes distributed in the vessel water volume . The water level in the primary production vessel is higher than in the surrounding annulus, preferably 40-70% higher. For practical purposes this means that for primary production of salmon the water depth in the central vessel may be approx. 5 metres, while the water level in the surrounding secondary production vessel is between 3 and 3.5 metres . The level difference may be utilised for airing of the water.

By letting the water volume in the first annulus be in direct contact with the sidewall of the primary production vessel, this wall may be built for a smaller dimensioning water pressure, the resulting water pressure being reduced to the difference between the water level heights in the primary production vessel and the first annulus. In the same way a water filled second annulus give a lower resulting water pressure on the outside wall of the first annulus.

By using seawater in the primary production the secondary production may typically be sea urchins, mussels and various types of seaweed having a high market value. By using

freshwater the nutrients in the waste may be utilised for secondary production of various types of plants/vegetables. The secondary production annulus may then also function as a greenhouse .

In combination of a primary and a secondary production approximately 100% of the water quantity may be recirculated. There will mainly be a need only for replacing the quantity of water evaporating from the system. This will give a considerable reduction in energy consumption and cost and also investment costs tied to water supply and any heating of the water. In addition the short transfer of water will contribute to reduce the energy consumption and the need for technical auxiliaries is reduced. By utilising the nutrients from the primary production for one or more secondary productions, it is avoided that the nutrients contribute to pollution or an added cost for the farmer. Secondary production will also contribute to an added income. The system according to the invention may be operated with minimal emissions. The system will also provide high safety with regards to spreading of infections, all water treatment being tied to the individual farming unit, and leading used, treated water between the various farming units is avoided.

At the central pipe and the sidewall of the primary

production vessel there may be located grading gates dividing the primary production vessel into sectors. Fish may thereby be graded without having to be moved to an external grading plant . Fastening means for grading gates may be attached to the sidewall of the primary production vessel and to the central pipe.

In a first aspect the invention relates more particularly to an arrangement for a land-based farming plant for aquatic organisms, where a cylindrical primary production vessel provided with a first outlet for water is in fluid

communication with a water treatment plant, characterised in that the water treatment plant is arranged in a first annulus encircling the primary production vessel.

The primary production vessel may be provided with several closable second outlets arranged in the sidewall and in fluid communication with the water treatment plant. Thereby the flow speed around and through the first outlet may be held at a level providing favourable depositing conditions for particles drifting in the water flowing through the first outlet . The first outlet may be arranged as a tubular body projecting upwards from a bottom section and over the water surface and provided with several inlet openings essentially arranged in a lower portion of the tubular body. Alternatively the inlet openings may be distributed over an essential portion of the tubular body vertical extent. The water flow into the first outlet may thus be controlled to promote sedimentation, collection of dead fish etc.

The first outlet may be provided with a central outlet pipe forming a discharge arranged at a vertical distance from a bottom section in the first outlet. The first outlet thus forms a sedimentation basin.

The bottom section may be provided with a sediment trap drainable through several particle outlets. Feed particles, faeces and other waste sedimenting in the first outlet may thereby be removed continuously or in sequences .

The first annulus may form a secondary production vessel comprising organisms arranged to be able to reduce the nutrient content in sediment enriched outlet water from the primary production vessel. Thus means contributing to

cleaning of the water in the primary production vessel is provided, the nutrient content in the waste being utilised in the production of other biologic material .

A water surface in the primary production vessel may in a normal condition be 40-70% higher than a water surface in a secondary production vessel. The primary vessel wall may thereby be dimensioned for a smaller load when the water volume in the secondary production vessel is in direct contact with the primary vessel wall .

The water treatment plant may comprise means picked from the group consisting of devices for C0 ₂ venting, particle removal, biological filtering and cleaning, oxygenation, alkalisation, UV radiation and ozone treatment. Thus the water treatment may be adapted to the needs present at any time .

The water treatment plant may be arranged under walkways encircling an upper portion of the primary production vessel. An improved utilisation of the area occupied by the farming plant is thus achieved.

The primary production vessel may be provided with means arranged for fastening of grading gates extending between a sidewall and a central pipe over the total depth of the primary production vessel. Grading may thus take place in the production vessel without the need for moving of the aquatic organisms to en external grading plant.

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

Fig. 1 shows in perspective a system according to the

invention where a centrally arranged primary production vessel is encircled by an annular room containing water treatment equipment and forming a walkway around the primary production vessel;

Fig. 2 shows in perspective and partly sectioned a system provided with a roof and where a secondary production volume is arranged in the same annulus as the water treatment equipment;

Fig. 3 shows in perspective and partly sectioned the main structures of a system comprising two concentric annuli ; Fig. 4 shows in perspective the water treatment system, the surrounding wall structures being removed for clarity;

Fig. 5 shows to a larger scale and in part and partly

sectioned how the water treatment equipment is integrated in the annulus enclosing the primary production vessel ; and

Fig. 6 shows in greater detail a first outlet provided

with a mud trap, where a central pipe is removed for clarity.

In the figures the reference numeral 1 indicates a centrally located, circular primary production vessel defined by a sidewall 11 arranged on a central vessel bottom 12. The primary production vessel 1 is provided with an outlet 13 arranged centrally, as a central pipe 131 projects vertically upward from a bottom section 133 (see particularly fig. 6) integrated in the vessel bottom 12 , and to above the level of a primary water surface 161 in a production volume 16 formed by the primary production vessel 1. From the bottom section 133 abutting sealingly against the central pipe 131, a central discharge pipe 136 with an open outlet portion 136a in the central discharge pipe 136 upper end projects upwardly toward the upper portion of the central pipe 131. Through the central discharge pipe 136 the central pipe 131 is in fluid communication with a distribution chamber 137 arranged under a sediment trap 134 defined by the central pipe 131, the bottom section 133 and the central discharge pipe 136.

Immediately above the sediment trap 134 in the central pipe 131 is arranged several drain openings 132 arranged to lead water out from the primary production vessel 1. From the sediment trap 134 several particle outlets 134 extend to a first portion of the water treatment plant 23. From the distribution chamber 137 several outlet pipes 138 extend to a second portion of the water treatment plant 23.

In the primary production vessel 1 sidewall 11 is arranged several closable second outlets 14 provided with a closing device 141.

The drain openings 132 and the second outlets 14 are provided with means (not shown) arranged to prevent aquatic organisms being farmed to be carried out of the primary production vessel 1 with the discharge water.

Several vertical spreader pipes 15 having a series of outlet openings 151 distributed in an essential part of the depth of the primary production volume 16, are arranged evenly

distributed at a distance from the sidewall 11. The spreader pipes 15 are connected to the water treatment plant 23.

In an upper portion of a first annulus 2 encircling the primary production vessel 1 and defined by a first annulus wall 21 and a first annulus bottom 22, is arranged the water treatment plant 23. The water treatment plant 23 comprises several sections, each section being provided with several modules for airing, particle removal etc., exemplified here by a bio- filter module 231 receiving the water from the outlets 13, 14, a particle removal module 232 treating the discharge from the sediment trap 134 and subsequently

treating all the discharge water by means of per se known means, for example foam stripper, and a further airing module 233 for finishing treatment of cleaned water.

The treated water is pumped back to the primary production vessel 1 through the respective spreader pipes 15.

The transport of water takes place partly by free flow, and partly by means of pumps 24. A lower portion of the first annulus 2 forms a basin for the water treatment plant 23. Here the water depth is typically 3 metres for a plant having a water depth of 5 metres in the primary production vessel 1. The water volume in the first annulus forms a secondary water surface 27.

Above the first annulus 2 is arranged a walkway 4 which also extends in over the primary water surface 161 to the top of the central pipe 131.

In an embodiment shown in figure 2 a roof 6 covers the farming unit .

In yet another embodiment shown in figure 3 is a second annulus 3 arranged encircling the first annulus 2 and being defined by a second annulus wall 31 and a second annulus bottom 32. The height of the second annulus wall 31 is adapted to the water depth in the first annulus 2 as the water in the first annulus 2 is in direct communication with the water volume in the second annulus 3. The water volume in the second annulus 3 is utilised for a secondary production of one or more organisms utilising remaining nutrients in the discharge water from the primary production vessel 1.

In an alternative not shown embodiment the water to the second annulus 3 is supplied from the first annulus 2 via lines provided with spreader nozzles and closable valves, as the second annulus 3 is formed as a greenhouse for plants getting water supplied as irrigation, underground irrigation or the like, and unused water is collected via a drainage system (not shown) and returned to the primary production vessel 1.