WO2019240588A1

WO2019240588A1 - Improved land-based fish rearing plant

Info

Publication number: WO2019240588A1
Application number: PCT/NO2019/000016
Authority: WO
Inventors: Simen HAALAND; Ketil FJELD; Erik HEIM
Original assignee: Nordic Aquafarms As
Priority date: 2018-06-11
Filing date: 2019-06-07
Publication date: 2019-12-19
Also published as: NO346080B1; NO20180805A1

Abstract

The invention is a land-based fish rearing plant comprising: * * a postsmolt unit (A) with the following features: • - an oval flow tank (1A) for postsmolt, subdivided for postsmolt cohorts of successively increasing sizes, • - at flow generator (9A) for providing a main flow (OAmain), • - water outlets (7A) for a partial flow from the oval flow tank (1A) to a water treatment plant (4A) wherein said water treatment plant (4A) is arranged within the perimeter of an inner wall (lOAi) of said flow tank (1A), * * at least two grow-out units (B, C) for growing salmon in the stages after the postsmolt stages, each grow-out unit (B, C) comprising: • - an oval flow tank (IB, 1C) for said growing salmon, subdivided into tank sections (3B1 to 3Bm, 3C1 to 3Cm) for growing salmon cohorts of successively increasing sizes, • - a main flow generator (9B, 9C) for providing a main flow (OBmain, OCmain), • - water outlets (7B, C) for a partial flow from the oval flow tank (1B, 1C) to a water treatment plant (4B, 4C) comprising and a water return inlet (8B, 8C) to said flow tank (IB, 1C), • - wherein said water treatment plant (4B, 4C) is arranged within the perimeter of an inner wall (lOBi, lOCi) of said flow tank (IB, 1C) • * a purge-unit (12) comprising, arranged between said grow-out units (B, C), wherein the last sections (m) in said grow-out units (B, C) are connected via lock-gates (14B, 14C) to an inlet channel (15) to two or more purge chambers (13a, 13b,... 13z) for temporary holding and purging of the salmon prior to its slaughtering, wherein the purge-unit (12) comprises at least a water treatment plant (16) and an export line (171) to a fish slaughterhouse (17).

Description

IM PROVED LAN D-BASED FISH REARING PLANT

Field of the invention

The present invention relates to the technical field of land-based fish rearing plants. More specifically, in a broad sense, the invention comprises two large units (B, C) comprising oval main flow tanks (B, C) for grow-out fish, each with their own dedicated water treatment plants (4B, 4C) generally entirely arranged within the perimeter of the inner wall of the flow tanks, and a purge plant (12) arranged in between the oval flow tanks (B, C). Even more specifically, the invention comprises a postsmolt tank (A) and grow-out tanks also having their water treatment plants (4A, 4B, 4C) entirely arranged within the perimeter of their inner walls of the flow tanks (1A, I B, 1C) and arranged for feeding postsmolt large enough for transfer to the grow-out tanks.

Background art

WO 2014/183765 depicts a fish farming plant comprising a central tank and one or more surrounding tanks wherein the central tank is used for water treatment, and the one or more surrounding tanks are used for farming of fish, further comprising flow applicators, whereby the flow rate of the water in the surrounding tanks are individually independent of the water exchange rate, wherein the fish farming plant comprises several movable permeable section walls in each of the surrounding tanks dividing said tanks in tanks sections, each surrounding tank is equipped with one or two outlets and one or two inlets a, and a substantially horizontal/laminar flow structure of the water in each one of said one or more surrounding tanks is provided.

Short summary of the invention

The current invention is a land-based fish rearing plant comprising:

* a postsmolt unit (A) comprising:

- an oval flow tank (1A) for postsmolt, subdivided by a number (n) of transverse separation grid (2A1 to 2An) and thus subdivided into the number (n) tank sections (3A1 to 3An) for postsmolt cohorts of successively increasing sizes,

- at least one main flow generator (9A) for providing a main flow (CDAmain) along a main flow path in the oval flow tank (1A),

- at least one water outlet (7A) for a partial flow from the oval flow tank (1A) to a water treatment flow (<DARAS) in a water treatment plant (4A) comprising piping arrangement (5A) and pumps (6A) and at least one water return inlet (8A) to said flow tank (1A),

- wherein said water treatment plant (4A) is arranged within the perimeter of an inner wall (lOAi) of said flow tank (1A), * at least two grow-out units (B, C) for growing salmon in the stages after the postsmolt stages, each grow-out unit (B, C) comprising:

- an oval flow tank (IB, 1C) for said growing salmon, subdivided by a number (m) of transverse separation grids (2B1 to 2Bm, 2C1 to 2Cm) and thus subdivided into the number (m) tank sections (3B1 to 3Bm, 3C1 to 3Cm) for growing salmon cohorts of successively increasing sizes,

- at least one main flow generator (9B, 9C) for providing a main flow (CDBmain, CDCmain) along a main flow path in said oval flow tank (IB, 1C),

- at least one water outlet (7B, C) for a partial flow from the oval flow tank (IB, 1C) to a water treatment flow (<DARAS) in a water treatment plant (4B, 4C) comprising piping arrangment (5B, 5C) and pumps (6B, 6C) and at least one water return inlet (8A) to said flow tank (1A),

- wherein said water treatment plant (4B, 4C) is arranged within the perimeter of an inner wall (lOBi, lOCi) of said flow tank (IB, 1C),

* a purge-unit (12) comprising, arranged between said grow-out units (B, C), wherein the last sections (m) in said grow-out units (B, C) are connected via lock-gates (14B, 14C) to an inlet channel (15) to two or more purge chambers (13a, 13b, ... 13z) for temporary holding and purging of the salmon prior to its slaughtering, wherein the purge-unit (12) comprises at least a water treatment plant (16) and an export line (171) to a fish slaughterhouse (17) .

In an embodiment of the invention is also a method for fish farming in a fish rearing plant according to any of claims 1 - 48,

comprising the following steps:

- running said flow generators (9A, 9B, 9C) and said pumps (6A, 6B, 6C),

- having said sections (3A1 - 3An) occupied with postsmolt and said sections (3B1 - 3Bm) and (3C1 - 3Cm) occupied with grow-out salmon,

- at given time intervals:

- transferring the largest cohort of grow-out salmon alternately from one section (3Bm, 3Cm) to said inlet channel (15) of one of said purge chambers (13a, 13b, ... 13z) for temporary holding and purging of the salmon,

- for each tank section prior to said tank section (3Bm, 3Cm) all the way down to said first section (3B1, 3C1), moving each said grow-out salmon cohort to a next tank section,

- moving / transferring the largest cohort of postsmolt over from the last section (3An) over to at least one of said first sections (3B1, 3C1) in said flow tanks (3B, 3C), - for each tank section prior to section (3An) all the way down to said first section (3A1), moving each postsmolt cohort to a next tank section,

- supplying a new postsmolt cohort to said first tank section (3A1) of said postsmolt tank (1A).

Figure captions

The attached figures illustrate some embodiments of the claimed invention.

Fig 1 illustrates the invention comprising a postsmolt unit (A), two grow-out tanks (B and C) for the fish after the postsmolt stage, and a purge unit (12) for the grown-out fish after the tank (B) or (C).

Fig 2 illustrates an embodiment of the invention and is a perspective view of one of the postsmolt unit A or the grow-out tanks B, or C with a main flow tank (1A, IB, 1C) and a water treatment plant (4A, 4B, 4C) arranged entirely within the perimeter of the inner wall of the main flow tank. Flere, grow-out tank (B) with its annotation is illustrated. The main flow of a tank, here represented by tank (B), (CDBmain) may be generated comprising a flow generator (9B) standing in the main flow itself, please see Fig. 1, or advantageously external flow generators (9B) are arranged in a side flow outside the outer wall of the tank (B), such as shown in Fig. 5 and Fig. 8.

Fig 3 illustrates an embodiment of the invention and is a plan view of one of the postsmolt unit (A) or the grow-out tanks (B or C), with the main flow tank (1A, IB, 1C) and the water treatment plant (4A, 4B, 4C) within the perimeter of the inner wall of the main flow tank, and shows major details such as the filter units (41A), biofilm reactors (42A), degassing units (43A), main flow generators (9A, 9B, 9C) arranged in the main flow tanks (1A, IB, 1C), and water outlets (7A, 7B, 7C) arranged in transverse rows across the main flow at the bottom of the main flow tanks. The return inlets (8A, 8B, 8C) from the water treatment plants are not detailed here.

Fig 4 illustrates an embodiment of the invention and is a cross sectional view of one of the postsmolt unit (A) or the grow-out tanks (B or C), with the main flow tank (1A, IB, 1C) and the water treatment plant (4A, 4B, 4C) within the perimeter of the inner wall of the main flow tank, and shows major details such as the filter units (41A), biofilm reactors (42A), degassing units with C02 removal (43A), treatment pumps (6A), outlets from tank (7A) with transversal manifold channels (71A) and return inlets to tank (8A) with transversal manifold channels (81A). The different water levels are depicted in the cross-sectional view showing successively the tank level, drum filter level, biofilm reactor level and degassing unit with C02 removal. Fig 5 illustrates an embodiment of the invention similar to Fig 3 but where the main flow generators (9A, 9B, 9C) are placed outside the flow tanks and having continuously incrementally moving grids and sections (3A1 - 3A9, 3B1 - 3B5, and 3C1 - 3C5) while moving each cohort with each section.

The grids may be moved with different speeds in order to adjust section volume with cohort weight.

Fig 6 illustrates the same embodiment as in Fig. 1. the separation grids (2A, 2B, 2C) are provided with motors (18A1, 18B1, 18C1) (see Fig. 10) connected to vertical shafts (19) on grids (2A1 - 2Cm) to pinion (20) to mesh with rack (21B, 21B, 21C).

Fig. 7 illustrates the purge tank with its system to service two grow-out tanks B and C. Fish that are ready to be slaughtered are transferred from the main tanks (B, C) into purge through transfer gates between the tanks. Joint walls with the tanks (B and C) gives construction savings.

Fig. 8 illustrates a simple embodiment of the invention with external flow generators (9A, 9B, 9C) located within a flow channel (92A, 92B, 92C) with a grid (97A, 97B, 97C), main flow outlets (91Ao, 91Bo, 91Co) and return inlets (91Ai, 91Bi, 91Ci).

Fig. 8a is a perspective view of a more detailed embodiment of the invention than Fig. 8, with the external flow generators (see Fig. 8c) arranged in flow channels (92A, 92B, 92C) external to the outer wall of the flow tank, and bottom outlets to the RAS plant and bottom return inlets from the RAS plant.

Fig. 8b: is a plan view of the same as Fig. 8a. Flere is also shown the 18 degs. slant of the separation grids.

Fig. 8c: is a plan detail view corresponding to Fig. 8b, and shows illustrated external flow generators in one end of a tank, (preferably, the opposite end is similarly arranged), the flow generators arranged in the channels external to the outer wall of the flow tank.

Fig. 8d End view and partial section view of outlets to and return inlets from external flow generators (not shown) in one end of a tank, and RAS box outlets and RAS pipe return inlets arranged in transverse rows in the bottom of the flow tank. Fig. 9 illustrates a method of transfer (shown as a matrix) within the flow tank (1A) sections (3A1 to 3A9) and the transferal of the largest cohort of postsmolt over from the last section (3An) in tank (1A) over to at least one of the first sections (3B1, 3C1) in the flow tanks (3B, 3C), and further on to the purge tank (12).

Fig. 10a is a perspective view along the main flow path in a curve, and shows an embodiment of the invention comprising a separation grid (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm), the separation grid arranged running on cog rails along the inner and outer wall of the flow tank (A, B, C). The separation grids (2A, 2B, 2C) are provided with motors (18A, 18B, 18C) are connected to vertical shafts (19) to pinions (20) to mesh with rack / rail (21A, 21B, 21C).

Fig. 10b is a perspective view along a cogged rail (21A, 21B, 21C) along the inner wall (lOi), here an upper cogged rail. A corresponding upper cogged rail is arranged on the outer wall (10o).

Fig. 10c is a perspective view of an embodiment of the invention wherein the separation grids (2A1 - 2A9) have horizontally extending ribs (23). In an embodiment of the invention entire panels (24) may be moved in order to open a gate (22) in the separation grid (2) for allowing fish to wander to a new section.

Fig. lOd is a front view of the panels (24), and the cogged rail and pinion mechanism for opening and closing the lateral panels (24) of the moveable separation grid (2).

Fig. lOe shows in perspective view from above, two separation grids (2) put in near proximity.

Embodiments of the invention

The invention will in the following be described and embodiments of the invention will be explained with reference to the accompanying drawings.

The invention is a land-based fish rearing plant. The invention comprises a post-smolt tank (1A) and two or more grow-out units (B, C) for rearing of the fish cohort's stages after the postsmolt stage, and a purge unit (12) arranged common to the grow-out units (B, C). Grown-out fish at about 4.2 kg is exported from the purge unit (12). The postsmolt is imported from a separate producer of smolt, or smolt is reared locally. The units (B, C) may be arranged transversely in a series of two, with the purge unit (12) placed between units (B) and (C). The materially largest component of each unit is an oval flow tank (1A, IB, 1C). Please see Fig. 1 for the general overview. For forming an overview, the illustrated embodiment's flow tanks (1A, IB, 1C) each have a longside length of 45 metres, an overall length of 80,4 metres, a total width of 35,4 metres, and a height of 6,5 metres and a water depth of 6 metres. The width of each "raceway" is 8,2 metres. Thus, the contained water volume in the raceway alone is about 9200 m3. Additionally, the centrally arranged water treatment plant (4B, 4C) of each unit (B, C) holds considerable amounts of water. Specific measures of main parameters are given in the table below. Please notice that the embodiments described here are dimensioned for salmon post-smolt and grow-out cohorts, but with minor modifications the fish rearing plant could be adapted to other species such as trout, yellowtail kingfish, mahi mahi, grouper fish and others.

In an embodiment of the invention there is arranged a postsmolt unit (A) for rearing of the postsmolt fish cohorts. The postsmolt unit (A) comprises:

Firstly, it has an oval flow tank (1A) for postsmolt, subdivided by a number (n) of generally transverse separation grids (2A1 to 2An) and thus subdivided into the number (n) tank sections (3A1 to 3An) for postsmolt cohorts of successively increasing sizes. In the illustrated embodiment there are nine tank sections. If post-smolt of lOOg is inserted once a month in the first section (3A1), each cohort of postsmolt will reside nine months in the oval flow tank (1A) while growing. Please observe that if the below mentioned flow generators (9A) are placed in the main flow, additional grids (2Ap) must be arranged in order to prevent fish from being damaged or turbulence-affected by the flow generators. If the flow generators are arranged in separate channels (92A) external to the main flow, please see Fig. 8C, then there needs only to be one separation grid (2A1 , 2An) for each section (3A1, 3An).

Secondly, it has one or more of said main flow generators (9A) for providing a main flow (CDAmain) along a main flow path in the oval flow tank (1A), arranged as in Fig. 1 or in Fig. 8c.

Thirdly, it has one or more water outlets (7A) for a partial flow from the oval flow tank (1A) to a water treatment flow (<DARAS) through a water treatment plant (4A) comprising piping arrangement (5A) and pumps (6A) and having one or more water return inlets (8A) to said flow tank (1A).

Fourthly, the water treatment plant (4A) is arranged within the perimeter of an inner wall (lOAi) of said flow tank (1A). Having generally the entire water treatment plant (4A) in the middle oval within the perimeter of the inner wall (lOi) of the postsmolt flow tank (1A) is highly advantageous due to the fact that piping and channels between the oval flow tank (1A) and the water treatment plant (4A) become short, thus requiring significantly less pumping energy and construction and material costs, surface cleaning, disinfection and maintenance costs, compared to if part of the water treatment plant had been arranged also on the outside of the outer wall (lOo); prior art tanks having a water treatment plant subdivided into a internal and an external part relative to the raceway, such as having a particle filter and biofilter plant internal and a degassing plant external, require much transport of water back and forth through passages below or above across the flow tank, thus more pumping energy and more channels crossing the raceway.

In the postsmolt unit (A) flow tank (1A) it is arranged for insertion of smolt cohorts, e.g. at intervals of one month, initially at the size of 100 g, the smolt cohorts for being reared in in the sections (3A1 to 3An) up to a weight of about 1900 g before they are moved to grow-up tanks (A, B).

The largest cohort will preferably be split in two (preferably) fractions and each half of the cohort will be moved over to the two grow-out units (B, C). There may be further grow-out units than two, but we have come to the conclusion that having two such grow-out units per one postsmolt unit is advantageous because the rather large purge unit (12) which shall serve both, is placed immediately between the two grow-out units (B, C), please see Fig. 1..

Each of the two grow-out units (B, C) for growing salmon in the stages after the postsmolt stages comprises:

Firstly, an oval flow tank (IB, 1C) for said growing salmon. Each oval flow tank is subdivided by a number (m) of transverse separation grids (2B1 to 2Bm, 2C1 to 2Cm) and thus subdivided into the number (m) tank sections (3B1 to 3Bm, 3C1 to 3Cm) for growing salmon cohorts of successively increasing sizes.

Secondly, each grow-out unit (B, C) has one or more main flow generators (9B, 9C) for providing a main flow (CDBmain, CDCmain) along a main flow path in said oval flow tank (IB, 1C). As for the post-smolt tank (A), if the flow generators are arranged in separate channels (92B, 92C) external to the main flow, please see Fig. 8C, then there needs only to be one separation grid (2B1 - 2Bn, 2C1 - 2Cm) for each section (3B1, 3Cm, 3C1 - 3Cm).

Thirdly, each grow-out unit has one or more water outlets (7B, 7C) for a partial flow from the oval flow tank (IB, 1C) to form water treatment flow (<DBRAS, <DCRAS) a in a water treatment plant (4B, 4C). The water treatment plant comprises piping arrangement (5B, 5C) and pumps (6B, 6C) and at least one water return inlet (8B, 8C) to the flow tank (IB, 1C).

Fourthly, the water treatment plant (4B, 4C) is arranged within the perimeter of an inner wall (lOBi, lOCi) of said flow tank (IB, 1C), just as for the water treatment plant (4A) in the postsmolt unit (A). Flaving generally the entire water treatment plant (4A, 4B) in the middle oval within the perimeter of the inner wall of the grow-out flow tank (IB, 1C) is highly advantageous as mentioned for the post-smolt unit (1A).

A purge-unit (12) is arranged between said grow-out units (B, C), wherein the last sections (m) in said grow-out units (B, C) are connected via lock-gates (14B, 14C) to an inlet channel (15) to two or more purge chambers (13a, 13b, ... 13z) for temporary holding and purging of the grown-out salmon cohorts prior to its slaughtering, wherein the purge-unit (12) comprises at least a water treatment plant (16) and an export line to a fish slaughterhouse (17) . In a preferred embodiment of the invention the number of purge chambers is eight.

The invention is a land-based fish rearing plant. The more specifically defined invention comprises a postsmolt unit (A) for rearing of the postsmolt fish cohorts, two or more grow-out units (B, C) for rearing of the fish cohort's stages after the postsmolt stages, and a purge unit (12) arranged common to the grow-out units (B, C).

Grown-out fish at about 4.2 kg is exported from the purge unit (12). The postsmolt is imported from a separate producer of smolt, or smolt is reared locally. The units (A, B, C) may be arranged transversely in a series of three, as in Fig. 1, with the purge unit (12) placed between units (B) and (C). The materially largest component of each unit is an oval flow tank (1A, IB, 1C). Please see Fig. 1 for the general overview. For forming an overview, the illustrated embodiment's flow tanks (1A, IB, 1C) each have a longside length of 45 metres, an overall length of 80,4 metres, a total width of 35,4 metres, and a height of 6,5 metres and a water depth of 6 metres. The width of each flow tank "raceway" is 8,2 metres. Thus, the contained water volume in the raceway alone is about 9200 m3. Additionally, the centrally arranged water treatment plant (4A, 4B, 4C) of each unit (A, B, C) holds considerable amounts of water. Specific measures are given in the table below. Please notice that the embodiments described here are dimensioned for salmon post-smolt and grow-out cohorts, but with dimensional modifications could be adapted to other species such as trout, yellowtail kingfish, mahi mahi, grouper fish and others.

The postsmolt unit (A) comprises:

Firstly, it has an oval flow tank (1A) for postsmolt, subdivided by a number (n) of transverse separation grids (2A1 to 2An) and thus subdivided into the number (n) tank sections (3A1 to 3An) for postsmolt cohorts of successively increasing sizes. In the illustrated embodiment there are nine tank sections. If inserted once a month, each cohort of postsmolt will reside nine months in the oval flow tank (1A) while growing. Please observe that if the below mentioned flow generators (9A) are placed in the main flow, additional grids (2Ap) must be arranged in order to prevent fish from being damaged or turbulence-affected by the flow generators.

Secondly, it has one or more main flow generators (9A) for providing a main flow (CDAmain) along a main flow path in the oval flow tank (1A).

Fourthly, the water treatment plant (4A) is arranged within the perimeter of an inner wall (lOAi) of said flow tank (1A). Having the entire water treatment plant (4A) in the middle oval within the perimeter of the inner wall of the postsmolt flow tank (1A) is highly advantageous due to the fact that piping and channels between the oval flow tank (1A) and the water treatment plant (4A) become short, thus requiring significantly less pumping energy and construction and material costs, surface cleaning, disinfection and maintenance costs. Prior art tanks having a water treatment plant subdivided into a internal and an external part relative to the raceway, such as having a particle filter and biofilter plant internal and a degassing plant external, require much transport of water back and forth through passages below or above across the flow tank.

In the postsmolt unit (A) flow tank (1A) we will insert smolt cohorts, e.g. at intervals of one month, initially at the size of 100 g, and rear in in the sections (3A1 to 3An) up to a weight of about 1900 g.

The largest cohort will be split in two (preferably) fractions and each fraction of the cohort will be moved over to the two grow-out units (B, C). There may be further grow-out units than two, but we have come to the conclusion that having two such grow-out units per one postsmolt unit is advantageous because the rather large purge unit (12) which shall serve both, is placed immediately between them.

Firstly, an oval flow tank (IB, 1C) for said growing salmon. Each oval flow tank is subdivided by a number (m) of transverse separation grids (2B1 to 2Bm, 2C1 to 2Cm) and thus subdivided into the number (m) tank sections (3B1 to 3Bm, 3C1 to 3Cm) for growing salmon cohorts of successively increasing sizes. Secondly, each grow-out unit (B, C) has one or more main flow generators (9B, 9C) for providing a main flow (CDBmain, CDCmain) along a main flow path in said oval flow tank (IB, 1C), the flow generators being arranged directly in the main flow as in Fig. 1, or externally of the main flow as in Fig. 8c.

Thirdly, each grow-out unit has one or more water outlets (7B, C) for a partial flow from the oval flow tank (IB, 1C) to form water treatment flow (<DBRAS, <DCRAS) a in a water treatment plant (4B, 4C). The water treatment plant comprises piping arrangement (5B, 5C) and pumps (6B, 6C) and at least one water return inlet (8B, 8C) to the flow tank (IB, 1C).

A purge-unit (12) is arranged between said grow-out units (B, C), wherein the last sections (m) in said grow-out units (B, C) are connected via lock-gates (14B, 14C) to an inlet channel (15), please see Fig. 1, to two or more purge chambers (13a, 13b, ... 13z) for temporary holding and purging of the grown-out salmon cohorts prior to its slaughtering, wherein the purge-unit (12) comprises at least a water treatment plant (16) and an export line to a fish slaughterhouse (17) . In a preferred embodiment of the invention the number of purge chambers is 8.

In an embodiment of the invention the number of tank sections (3A1 - 3An) of the main are between 6 and 10. As noted above, the number of separation grids (2A1 - 2An) purely for separating the sections is the same number. If flow generators (9A) are arranged in the main flow, one additional grid (2Ap) is required for each flow generator in order to prevent damage to the fish. In an embodiment of the invention, please see Fig. 1, the number of tank sections (3A1 - 3An) in the postsmolt flow tank is 9.

In the embodiment shown in Fig. 1 the final grow-out tank sections (3B5, 3C5) are facing the gate (14) to the purge unit (12) in order for being adjacent to the channel (15) so as for making the transfer of fish feasible. In this embodiment one may say that tank C is a copy of tank B but rotated 180 degrees in the horizontal plane. Please also notice that in the illustrated embodiment shown in Fig. 1 the overall shape and design of tanks B and C is the same as the overall shape of tank A.

All water outlets (7A, 7B, 7C) from the main flow to the water treatment plant (4A, 4B, 4C) must be provided with a grid (77A, 77B, 77C) in order to prevent fish from entering the water treatment plant. If the grid is flush with the tank bottom a separation grid may move unhindered across the outlet (7A, 7B, 7C). Also the water treatment return inlets should be flush with the bottom.

In an embodiment the insert postsmolt cohort is 100 grams, and each cohort is fed until it has grown to about 1900 grams in section 3An, i.e. section 3A9 after about 9 months. In an embodiment of the invention, an Oxygen supply outlet (45A) to the water may be installed in the water treatment plant (4A). In another embodiment of the invention, the Oxygen supply outlet (45A) may be installed directly in the flow tank (1A) because it advantageously could be operated by manual valves during undesired intermittent absence of electrical power. The same goes for Oxygen supply outlet (45B, 45C) to the grow-out flow tanks (IB, 1C).

In an embodiment of the invention the water treatment plant (4A) comprises a number of filter units (41A), a biofilm reactor (42A), a degassing unit with C02 treatment (43A), and an Ozone treatment unit (44A). In this way, the entire water treatment flow (<DARAS) may occur within the perimeter of the inner, oval wall of the flow tank (1A), which advantageously thus may have a short flow path.

In an embodiment of the invention, there is a number of separation grids (2Bm and 3Bm) and sections (2Cm and 3Cm) in said grow-out unit's (B, C) oval flow tank (IB, 1C) between 3 and 7. In a further embodiment the number is 5. This makes the retention time for each cohort in the grow-out units to be five months if the interval between the insert cohorts is one month as above described. The cohort from the post-smolt stage is split into one half distributed to each first grow-out tank (3B, 3C) first section (3B1, 3C1) when moved. At this stage each half of the cohort are of the same size and weight unless sorted. One may sort them, but in an embodiment of the invention the temperature in the grow-out tanks is kept different in order for the two parallel cohorts to grow differently so as for the two initially parallelly introduced cohorts to be harvested with the half interval, i.e. harvested with two weeks interval to the purge unit (12).

In an embodiment of the invention the grow-out unit's (B, C) flow tank (IB, 1C) is arranged for holding grow-out salmon in the size range 1900 - 4300 g. In the grow-out tank the rib (23) separation of the grid may be kept at the same common value, but in the post-smolt tank the rib (23) separation should be kept as large as possible without allowing fish though; the rib panels (24) may have to be changed under way as the cohort grows in case the separation grids are moved with the cohort.

In an embodiment of the invention the grow-out unit's (IB, 1C) water treatment plant (4B and 4C) comprise filter units (41B, 41C), a biofilm reactor (42B, 42C), a degassing unit with C02-removal (43B, 43C), and an Ozone treatment unit (44B, 44C).

In an embodiment of the invention the postsmolt tank's (1A) flow generator (9A) providing the main flow (FAiti) is arranged in the main flow path of the oval postsmolt tank (1A). In this embodiment it may have the form of a propeller axially aligned with the main flow path along the oval tank. In another embodiment of the invention the postsmolt tank's (1A) flow generator (9A) providing said main flow (FAiti) is arranged outside the flow tank (1A) as such, i.e. inside the perimeter of the inner wall (lOAi), outside the perimeter of an outer wall (lOAo) please see Figs. 8, 8a - 8d, , or below the bottom (lOAb) in relation to the main flow path in said oval flowtank (1A). Clearly, The external position as shown in Fig. 8 advantageously takes no space from the RAS plant (4) in the middle.

Please see Fig. 8 for this embodiment. In this case the water may be taken out through main flow outlets (91Ao) to a flow generator (9A) such as a propeller or impeller arranged in a tunnel (92A) and a return inlet (91Ai) back to the main flow path in the flow tank (1A). In such embodiments the main flow outlets (91Ao) must be provided with a grid (97A) in order to prevent fish from entering the tunnel (92A) and being killed in the flow generator (9A). The number of flow generators and flow tunnels needs to be adjusted and calculated for each specific application.

Advantageously said outlets and inlets (91Ao, 91Ai) are designed with low-angled inlet and outlet passages in order to minimize energy loss, please see Fig. 8 for illustration. In an embodiment of the invention the flow generators (9A) shall maintain an overall water flow velocity of 0.4 m/s for the main flow (FAiti) for the postsmolt cohorts. We consider the embodiment as shown in Fig. 8 and explained above in this paragraph, with a flow tank (1A, IB, 1C) with the described and illustrated flow generator (9A, 9 B, 9C) arranged outside the flow tank, as an independent invention in itself.

In an embodiment of the invention, the flow generators (9B, 9C) of the oval grow-out flow tanks which provide the main flow (®Bmain, ®C main) are arranged in the main flow path of the oval flow tanks (IB, 1C).

By placing the flow generators (9B, 9C) in the main flow path of the oval flow tanks (IB, 1C) one can provide and optimize the flow path which in turn ensures reduced pumping and pressure loss in the system, thus reducing the total power consumption. In this embodiment it may have the form of a propeller axially aligned with the main flow path along the oval tank.

In an embodiment of the invention, the flow generators (9B, 9C) which provide the main flow (®Bmain, ®C main) in the grow-out flow tanks are arranged within the circumference of the inner wall (lOBi, lOCi), or outside the circumference of the outer wall (lOBo, lOCo), please see Figs. 8, 8a, 8d, or below the bottom (lOBb, lOCb) in relation to the main flow path of the the oval flow tank (IB, 1C). Having the flow generators placed outside of and external to the oval flow tanks (IB, 1C) will reduce the potential of fish getting damaged or killed by the flow generator propellers. Also, by placing the flow generators outside of the oval flow tanks (IB, 1C) it is much simpler to produce a laminar main flow geometrically through piping and/or ducting. A laminar and uniform flow is beneficial for the fish's wellbeing and growth. In such case the water may be taken out through main flow outlets (91Bo, 91Co) to a flow generator (9B, 9C) such as a propeller or impeller arranged in at least one tunnel (92B, 92C) and at least one return inlet (9 IBi, 92Ci) back to the main flow path in the flow tank (IB, 1C), as in Fig. 8, 8a - 8d.

The number of flow generators and flow tunnels needs to be adjusted and calculated for each specific application. In such embodiments the main flow outlets (91Bo, 91Co) must be provided with a grid (97B, 97C) in order to prevent fish from entering the tunnel (92B, 92C) and being killed in the flow generator (9B, 9C). We have arrived at having four such tunnels or pipes in either last half of each bend of the main tanks.

In an embodiment of the invention, the number of the purge chambers (13a, 13b, ...13z) is between four and ten. In another embodiment of the invention, the number of the purge chambers (13a, 13b, ..., 13z) is eight. A preferred configuration will be to use six of the eight purge chambers and have two as spare, whereas the spare chambers will function as a buffer reservoir. This buffer can be beneficial if e.g. there is a price drop in the marked that requires the fish farming plant to hold back a certain amount of grow-out salmon for awaiting the spot market price to rise. Another benefit to having spare capacity in the purge chamber is if there are problems related to the delivery to the fish slaughtering plant. The additional chambers will in this instance act as a buffer until the fault has been rectified with respect to the fish slaughtering plant.

In an embodiment of the invention, the water level in said postsmolt unit (A) decreases successively from the oval flow tank (1A) to said filter unit (41A), to said biofilm reactor (42A) and further to said degassing unit with C02 treatment (43A). In another embodiment of the invention, the water level in the oval flow tanks (B, C) decreases successively from the oval flow tanks (IB, 1C) to said filter units (41B, 41C), to said biofilm reactor (42B, 42C) and further to said degassing unit with C02 treatment (43B, 43C). By utilizing a gravity flow in the water treatment section, i.e. the height differences between the oval flow tanks, the filter units, the biofilm reactor and degassing unit with C02 treatment there is only a need for one step to pump the last portion of the treated water from the degassing unit with C02 treatment back to the oval flow tank (lb, 1C). Thus, reducing the overall pump power consumption. In an embodiment of the invention, wherein a water inlet (7A) for the water treatment flow (<DARAS) to the water treatment plant (4A) is arranged in the bottom (lOAb) of the oval flow tank (1A).

Having the water inlet (7A) for the water treatment flow arranged in the bottom of the oval flow tank (1A) is advantageous since it will be more efficient to extract debris, feces, from the main flow as these elements tend to accumulate at the bottom of the tank.

In an embodiment of the invention, the water treatment flow (<DARAS) from the water treatment plant (4A) is pumped back to the oval flow tank (1A) via a water return inlet (8A) that is arranged through at least one or more of the inner walls (lOAi), the outer wall (lOAo) or the bottom (lOAb) of the oval flow tank (1A). Please see also Fig. 8a, 8b, and 8d. By having the option of different configurations for the water return (8A) one can tune and adjust the return flow in such a manner to reduce the back pressure and power consumption of the pump (6A).

In an embodiment of the invention, the water inlet (7A) of the water treatment flow (<DARAS) is co current with the main flow (CDAmain). By having the water inlet (7A) co-current with the main flow one is able to reduce the energy loss and the pressure loss in the water treatment flow.

In an embodiment of the invention, the water inlet (7A) forms an angle of 30 degrees with the bottom (lOAb). In an embodiment of the invention, wherein the number of water inlets (7A) is to, three or more and the water inlets (7A) are generally arranged in a transversal row. Reference is made to Fig. 4. In an embodiment of the invention, the water outlet (7A) is connected to a transversal channel (71A) where the transversal channel (71A) extends from below the bottom (lOAb) and to within the perimeter of the inner wall (lOAi) and to the filter units (41A). In an embodiment of the invention, the water return inlet (8A) of the water treatment flow (<DARAS) is co current with the main flow (CDAmain). In an embodiment of the invention, the water return inlet (8A) forms an angle of 30 degrees with the bottom (lOAb). In an embodiment of the invention, the number of water return inlets (8A) is two, three or more, and the water return inlets (8A) are generally arranged in a transversal row. In an embodiment of the invention, a transversal channel (81A) extends from the pump (6A) and outwards from the bottom (lOAb) to outwards of the inner wall (lOAi) to the water return inlet (8A). Reference is made to Fig. 4. An advantage of this embodiment is that the transversal channel (81A) may have a low profile which requires less ground and civil work during the construction of the tank unit (A). Se particularly Fig. 8d.

In an embodiment of the invention, the water outlet (7B, 7C) for the water treatment flow (<DBRAS, <DCRAS) for the water treatment plant (4B, 4C) is arranged in the bottom (lOBb, lOCb) of the oval flow tank (IB, 1C). The advantage of having the water outlet (7B, 7C) arranged at the bottom (lOBb, lOCb) of the oval flow tank (IB, 1C) is that it will drain out the water comprising the precipitated particles flowing along the bottom layers of the water. In an embodiment of the invention, the water outlet (7B, 7C) of the water treatment flow (<DBRAS) (<DCRAS) is co-current with the main flow (FBiti, <DCm). In an embodiment of the invention, the water outlet (7B, 7C) forms an angle of 30 degrees with the bottom (lOBb, lOCb). The advantage of the above embodiment is that the flow energy loss at the outlet is reduced, which may also result in a reduced turbulence in and around the water outlet (7B, 7C). In an embodiment of the invention, the water outlet (7B, 7C) leads to a transversal channel (71B, 71C) where the transversal channel (71A) extends from below the bottom (lOBb, lOCb) and to within the perimeter of the inner wall (lOBi, lOCi) and to the filter units (41B, 41C). In an embodiment of the invention, the filter units (41B, 41C) are rotating drum filters with continuous flushing and removal of filtered-out particles which are subject to further treatment and drying.

In an embodiment of the invention, the number of water outlets (7B, 7C) is two, three or more, and the water outlets (7B, 7C) are generally arranged in a transversal row across the entire width of the flow tank (1A, IB, 1C), reference is made to Fig. 2, Fig. 3 and Fig. 4. In the embodiment shown in Fig.

3 there are seven water outlets (7A, 7B, 7C) in the transversal row extending across the entire width of the flow tank (1A, IB, 1C). In an embodiment of the invention, the water treatment flow

(®BRAS,(®CRAS) from the water treatment plant (4B, 4C) is pumped back to the oval flow tank (IB,

1C) via a water return inlet (8B, 8C) arranged through at least one or more of the inner walls (lOBi, lOCi) or the bottom (lOBb, lOCb) of the oval flow tank (IB, 1C), reference is made to Fig. 2, Fig. 3 and Fig. 4. Please also see Fig. 8d. In an embodiment of the invention, the water return inlet (8B, 8C) forms an angle of 30 degrees with the bottom (lOAb). In an embodiment of the invention, the number of the water return inlets (8B, 8C) is two, three or more, and the water inlets (7B, 7C) are generally arranged in a transversal row.

An advantage of the above water return inlets (8B, 8C) is that they effectively contribute to maintaining the main water flow (CDBmain, <DC main). In an embodiment of the invention, a transversal channel (81B, 81C) extends from the pump (6B, 6C) and out below the bottom (lOBb, lOCb) and to outside the perimeter of the inner wall (lOBi. lOCi) and to one or more of the water return inlets (8B, 8C). An advantage of this arrangement is that the transversal channel (81B, 81C) may have a low profile which requires less ground work during the construction of the tank units (B, C). Please also see Fig. 8d. In an embodiment of the invention, the water treatment plant (16) for the purge unit (12) comprises a fresh water intake line (161) and a discharge line (168) to the water treatment plants (4B, 4C).

In a further embodiment of the invention, the water treatment plant (16) includes a freshwater intake line (161) and a discharge line (169) to the water treatment plant (4A) of the grow-out tank (A). The freshwater intake line (161) may be from a river, a lake, a well, a municipal water utility line, or the sea, or a combination of the above. The main advantage of having a separate freshwater intake line is that all of the incoming water supply to the entire plant may be controlled, filtered and UV-treated in order to prevent contamination from the environment.

In an embodiment of the invention, the water treatment plant (16) comprises filter units (162), a degassing unit with C02 treatment (163) and ozone treatment unit (164).

In an embodiment of the invention, there may be an oxygen supply (165) to the circuit of the water treatment plant (16) which is automatically controlled, or the oxygen supply (165) may be directly connected to the purge chambers (13a, 13b, ... 13z) and also manually controlled in order to operate also during an electrical black out.

In an embodiment of the invention, the water level in the purge units (12), the water treatment plant (16) is successively decreasing from the purge chambers (13a, 13b, ... 13z) to the filter unit (162), to the degassing unit with C02 treatment (163), further to the UV-treatment unit (166) and to the pumps (167) wherein the pumps (167) pump water back up to a level corresponding to the water level in the purge chambers (13a, 13b, ... 13z). In an embodiment of the invention, the water level in the purge chambers (13a, 13b, ... 13z) is kept at a higher level than in the water flow tanks (IB, 1C). Keeping the water level in the purge chambers at a higher level than in the water flow tanks has two advantages. One advantage is that it is easier to let the fish swim against the current from the last grow-out section (3Bm, 3Cm) via the inlet channel (15) to the purge chambers (13). The second advantage is that we can hinder contamination from the flow tanks (3B, 3C) to the purge unit (12) in case an outbreak of disease occurs in the considerably larger flow tanks (3B, 3C).

In an embodiment of the invention, transfer lines (11B, 11C) from the postsmolt tank (A), please see Fig. 1, comprise a fish pump (110), a flexible hose (111B, 111C) to a separation grid (112B, 112C) which further leads the fish to the first section (3B1, 3C1) in each of the flow tanks (3B, 3C).

The separation grid (112B, 112C) will act as a dry spacer and as a barrier between the mentioned tanks. It will be flanged between the last portion of the flexible hose and the inlet of the first section. Using a separation grid (112B, 112C) between the flexible hose and the first section (3B1, 3C1) may reduce the potential of transferring diseases with the water from the postsmolt tank (A) to the flow tanks (B, C) as there is no significant fluid transfer between the tanks, just wet fish. The drained water from the separation grid (112B, 112C) may be returned to the postsmolt tank (A) or made subject to water treatment and then returned to the postsmolt tank (A) or released to the environment.

In an embodiment of the invention, a fish counting device (113) is provided in the transfer lines (11B, 11C). The fish counting device will ensure that only the planned amount of fish will be transferred from the postsmolt tank (A) to each of the first sections (3B1, 3C1) in each of the flow tanks (3B, 3C). If the fish cohort shall only be distributed evenly between the two first sections (3B1, 3C1), the fish counting device (113) may be used to check the number of fish transferred to each section. The fish counting device (113) can either be placed upstream or downstream said fish pump (110) all depending upon location and required ease of maintenance for the fish counting device (113) and/or fish pump (110).

In an embodiment of the invention, the transverse separation grids (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm) are motorized and movable along their associated flow tanks (1A, IB, 1C). They are in one embodiment only partly movable along the length of the tank due to the presence of internal flow generators in the runway, or entirely movable around the entire length of the tank because the flow generators are placed in side channels (91A, 91B, 91C).

In another embodiment of the invention, the separation grids (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm) are movable via a motor (18A1, 18B1, 18C1) connected to a vertical shaft (19A1, 19B1, 19C1) down to a pinion or gear (20A1, 20B1, 20C1) that is in mesh with a rack (21A1, 21B1, 21C1) that extends along the bottom (lOAb, lOBb, lOCb) or the side walls (IOί, 10o), please see Fig. 10a - lOe, of the oval flow tank (1A, IB, 1C).

By individually regulating the position of the transverse separation grids (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm) one can control the segment length, i.e. segment volume of each tank, thereby establishing the necessary volume for the actual amount and size range of the fish cohort in question.

In an embodiment of the invention, at least one of the separation grids (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm) comprises a gate (22A1, 22B1, 22C1), where said gate (22A1, 22B1, 22C1) is movable for forced displacement of fish from one section to the other sections (3A1 to 3Am or 3B1 to 3Bm or 3C1 to 3Cm).

In an embodiment of the invention, the flow generator (9A, 9B, 9C) that provides the main flow (FAiti, FBiti, F0 m) is arranged within the perimeter of the inner wall (lOAi, lOBi, lOCi), or outside the perimeter of the outer wall (lOAo, lOBo, lOCo), please see Figs. 10a - lOe, or below the bottom (lOAb, lOBb, lOCb) in relation to the main flow path in the oval flowtank (1A, IB, 1C) wherein the grids (2A1 - 2An), (2B1 - 2Bm), (2C1 - 2Cm) are movable to any position within the flow tank (1A, IB, 1C) so as for moving each cohort gradually towards the outlet for fish from the tank instead of moving the fish across a grid, as each cohort fish size grows.

The advantage with this configuration is that sections (3A1 to 3An or 3B1 to 3Bm or 3C1 to 3Cm) successively change roles, in such a manner this embodiment can be seen as if the section 3A1 takes the role of 3A2; section 3A2 takes the role of section 3A3 etc. until when section 3A9 is emptied (or discharged) with its dedicated grown cohort in section 3A9 continues onward and becomes the section 3A1, where it is filled up with a new smolt cohort and repeats the above mentioned sequence. In this way each cohort will stay in a dedicated section and grow from 100 grams to 1900 grams during the rotational sequence in each tank (A, B, C). During this growth sequence each grid (2A1 - 2An), (2B1 - 2Bm), (2C1 - 2Cm) are movable to any position within the flow tank (1A, IB, 1C) to allow for the cohort growth rate.

The individual size of the sections (3A1- 3A9) may thus be varied with increasing average weight or size of the fish in each contained cohort. The same arrangement may be used for the sizes of the sections (3B1 - 3B5) and (3C1 - 3C5) in order to vary them according to the size of the fish in the contained cohort.

Fig. 8a is a perspective view of a more detailed embodiment of the invention than shown in Fig. 8, with the external flow generators (9A, 9B, 9C), please see Fig. 8c, arranged in flow channels (92A, 92B, 92C) external to the outer wall of the flow tank, and bottom outlets to the RAS plant and bottom return inlets from the RAS plant.

Fig. 8b: is a plane view of the same as Fig. 8a. In this embodiment there are arranged one set of an upper and lower flow channel (92A, 92B, 92C) near the end of each curve of the flow tank, there are nine separation grids (2A, 2B, 2C) and thus nine tank sections (3A, 3B, 3C). In embodiments such as this of the invention the grids may be freely moved along the flow tank according to the desire of the operator, due to several reasons: there are no flow generators within the cross section of the flow tank; and the outlets and inlets for the RAS flow are flush with the bottom plane, and the same relates to the outlets and the inlets for the external flow generators' (9A, 9B, 9C) boost flow. Please see Fig. 10 for details of the separation grids of an embodiment of the invention.

Fig. 8c: is a plan detail view corresponding to Fig. 8b, and shows illustrated external flow generators in one end of a tank, the flow generators arranged in the channels external to the outer wall of the flow tank. Fig. 8c illustrates an embodiment of the invention with an arrangement of the flow channels (92A, 92B, 92C) having a main flow outlet (91Ao, 91Bo, 91Co) arranged in a drain box in the vertical wall in the bending outer wall, and return inlets (91Ai, 91 Bi, 91Ci) directed not parallel with the straight portion of the tank but directed at an angle so as for making the returning boost water flow to mix in near the center of the main flow when starting at the straight portion of the tank. The water has significantly higher flow speed when returning through the return inlets (91Ai, 91Bi, 91Ci) and it is important to obtain a high impulse (m x V) transfer rate to the main flow in the tank. In an embodiment the first, shorter flow channel (92A, 92B, 92C) has return inlets (91Ai, 91Bi, 91Ci) with an angle of 45 degrees with the local wall tangent, and the longer flow channel (92A, 92B, 92C) has return inlets (91Ai, 91Bi, 91Ci) with an angle of 30 degrees with the local wall tangent. Dynamic flow analysis has shown that this angle provides a good balance between the need for injecting the return flow deeply into the main flow in order to avoid the return flow to stick along the outer wall, and the need for avoiding much momentum loss due to a too high angle. Lower angle incurs too little mixing into the main flow and the flow gets stuck along the outer wall, and higher angle incurs less impulse transfer along the desired main flow path, and increased turbulence loss.

Fig. 8d End view and partial section view of outlets to and return inlets from external flow generators (not shown) in one end of a tank, and RAS box outlets and RAS pipe return inlets arranged in transverse rows in the bottom of the flow tank.

Fig. 9 illustrates a method of transfer (shown as a matrix) within the flow tank (1A) sections (3A1 to 3A9) and the transferal of the largest cohort of postsmolt over from the last section (3An) in tank (1A) over to at least one of the first sections (3B1, 3C1) in the flow tanks (3B, 3C), and further on to the purge tank (12).

In one embodiment of the invention, the cohorts are moved from one section (3) through a gate in a separation grid (2) to the subsequent section (3). In another embodiment of the invention the separation grids ahead of and after each section (3) are simply moved with the cohort to a new position, the section (3) number just being increased when its separation grids (2) having travelled to a new position. Please see description of Figs. 10a - lOe below.

Fig. 10a is a perspective view along the main flow path in a curve, and shows an embodiment of the invention comprising a separation grid (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm), the separation grid arranged running on cog rails along the inner and outer wall of the flow tank (A, B, C). In the embodiment shown each separation grid (2) is running with one lateral end 18 degrees ahead of the opposite lateral end, in order to better tolerate wall to wall distance variations, particularly when the separation grid (2) shall enter or leave a curve. The separation grids (2A, 2B, 2C) are provided with motors (18A, 18B, 18C) are connected to vertical shafts (19) to pinions (20) to mesh with rack / rail (21A, 21B, 21C). In this embodiment an upper rack and a lower rack (21A) extend along each inner and outer wall (lOAi, lOAo) (lOCi, lOCo) (lOCi, lOCo). These rails will in a preferred embodiment of the invention contain an equal number of perforations around a complete round in the tank, so as for requiring the same number of turns of each corresponding pinion wheel (20) to wander with the same position particularly through the bends. In the shown embodiment a gear box may transfer the rotation to both the inner wall running shaft (19) and via a transfer rod to the outer wall running shaft (19).

Fig. 10b is a perspective view along a cogged rail (21A, 21B, 21C) along the inner wall (lOi), here an upper cogged rail. A corresponding upper cogged rail is arranged on the outer wall (10o). The pinion (20A, 20B, 20C) meshes with the perforations in the rack (21A, 21B, 21C) and is driven by the running shaft (19A, 19B, 19C). Rollers on the separation grids (2) for running on and holding the grid (2) to the rack (21A, 21B, 21C) are mounted in a bracket. The moving pinion wheel and rollers contribute to removing debris from the perforations and the rail. Florizontal ribs (23) with a vertical grating opening small enough to prevent the fish of the actual cohort fish size from trying to pass.

There are two problems related to the grating opening of the separation grids: cohort fish size and flow resistance. The grating opening of the separation grids (2A1 - 2An) may be varied around the flow tank adapted to the cohort fish size. The flow resistance will usually increase with decreasing grating opening size. It is important to reduce flow resistance to the main flow FAMAIN, FBMAIN, F CMAIN in the oval flow tanks, and particularly the the main flow FAMAIN, in the postsmolt tank A because the grating opening size is the smallest in the postsmolt tank A, thus the flow resistance is the largest. Thus keeping a good balance between using the largest allowable grating size opening for each cohort will save much energy. As the cohort fish size may vary from the very smallest postsmolt inserted into section (3A1) the grating opening must be the smallest in the transverse separation grids (2A1) and (2A2) ahead of and after section (3A1), and the subsequent separation grids (2A3) may have a larger grating opening than separation grid (2A2) because it contains a larger fish size cohort. This arrangement may be continued with increasing grating opening for each separation grid up to the largest separation size used for separation grid (2An), where (2An) may be grid no. (2A8) which is behind the cohort in section (3A9) in the illustrated case. The grating opening between section (3A9) and (3A1) must be adapted to the small fish in section (3A1), of course.

Fig. 10c is a perspective view of an embodiment of the invention wherein the separation grids (2A1 - 2A9) have horizontally extending ribs (23) with a vertical separation small enough to prevent the passage of the cohort fish size contained in the actual section (3A). Advantageously, when combined with the embodiment wherein each separation grid (2) is running with one lateral end 18 degrees ahead of the opposite lateral end, dead fish will be forced laterally to the farthest end downstream of the section wherein it lived, and is easily collected using a hob. In an embodiment of the invention entire panels (24) may be moved in order to open a gate (22) in the separation grid (2) for allowing fish to wander to a new section. In order to force the displacement of fish through a gate, two separation grids (2) may be put in near proximity, please see Fig. lOd. In the embodiment shown the middle panel (24) of the three panels (24) is fixed while the lateral panels (24) are laterally moveable between their closed position and an open position wherein a lateral panel is displaced to cover the middle panel. The lateral panel (24) may in an embodiment be provided with a panel gate cogged rail

(26) arranged along the top frame portion of the panel, the cogged rail driven by a panel gate pinion

(27) driven by a panel gate pinion drive axle (28). The drive axle (28) may be manually rotated or rotated using a motor, according to the discretion of the design engineer.

Fig. lOd is a front view of the panels (24), and the cogged rail and pinion mechanism for opening and closing the lateral panels (24) of the moveable separation grid (2) by lateral movement across the middle panel (24).

Fig. lOe shows in perspective view from above, two separation grids (2) put in near proximity in order to force the displacement of fish through a gate opened by one of the lateral panels (24) in one of them.

The invention may be only what is described as the unit (A) for post-smolt as described with all its various embodiments as described above, and having grow-out tanks (B, C) of a different kind. Also, the invention may be what is described as the grow-out tanks (B, C) as described with all its various embodiments as described above. However, a great advantage is having the general combination of units (A, B, C) above due to its high production capacity and small footprint, and low energy consumption compared to prior art fish rearing plants on land.

Claims

1. A land-based fish rearing plant comprising:

* a postsmolt unit (A) comprising:

- at least one water outlet (7A) for a partial flow from the oval flow tank (1A) to a water treatment flow (<DARAS) in a water treatment plant (4A) comprising piping arrangment (5A) and pumps (6A) and at least one water return inlet (8A) to said flow tank (1A),

- wherein said water treatment plant (4A) is arranged within the perimeter of an inner wall (lOAi) of said flow tank (1A),

* at least two grow-out units (B, C) for growing salmon in the stages after the postsmolt stages, each grow-out unit (B, C) comprising:

- at least one water outlet (7B, 7C) for a partial flow from the oval flow tank (IB, 1C) to a water treatment flow (<DARAS) in a water treatment plant (4B, 4C) comprising piping arrangement (5B, 5C) and pumps (6B, 6C) and at least one water return inlet (8B, 8C) to said flow tank (IB, 1C),

2. The land-based fish rearing plant according to claim 1, wherein said transverse separation grids and tank sections (2An and 3An) are between 6 and 10.

3. The fish rearing plant according to claim 1 or 2 wherein said transverse separation grids and tank sections (2An and 3An) in said postsmolt tank (1A) are 9.

4. The fish rearing plant according to any of the preceding claims, wherein the post smolt weighs 100 - 1900 grams.

5. The fish rearing plant of any of the preceding claims, wherein said water treatment plant (4A) comprises filter units (41A), a biofilm reactor (42A), a degassing unit with C02 treatment (43A), and preferably an Ozone treatment unit (44A).

6. The fish rearing plant of any of the preceding claims, wherein the number of separation grids (2Bm and 3Bm and 2Cm and 3Cm) in said grow-out unit (B, C) oval flow tank (IB, 1C) is between 3 and 7.

7. The fish rearing plant according to any of the preceding claims, wherein the number of separation grids and tank sections (2Bm og 3Bm og 2Cm og 3Cm) in said grow-out unit's (B, C) flow tank (IB, 1C) is 5.

8. The fish rearing plant according to any of the preceding claims, wherein said grow-out unit's (B, C) flow tank (IB, 1C) is arranged for holding grow-out salmon in the size range 1900 - 4300 g.

9. The fish rearing plant according to any of the preceding claims, wherein said water treatment plant (4B and 4C) comprise filter units (41B, 41C), a biofilm reactor (42B, 42C), a degassing unit with C02- removal (43B, 43C), and preferably an Ozone treatment unit (44B, 44C).

10. The fish rearing plant according to any of the preceding claims, wherein said flow generator (9A) providing said main flow (FAiti) is arranged in the main flow path of the oval postsmolt tank (1A).

11. The fish rearing plant according to any of the preceding claims, wherein said flow generator (9A) providing said main flow (FAiti) is arranged outside the perimeter of said outer wall (lOAo), relative to the main flow path in said oval flow tank (1A).

12. The fish rearing plant according to any of the preceding claims, wherein said flow generator (9A) providing said main flow (FAiti) is arranged within a tunnel (92A) outside the perimeter of said outer wall (lOAo) in relation to the main flow path in said oval flow tank (1A), wherein said tunnel (92A) comprises a main flow outlet (91Ao) with a grid (97A) and a water return outlet (91Ao) back to the oval flow tank (1A).

13. The fish rearing plant according to any of the preceding claims, wherein said flow generators (9B, 9C) providing said main flow (CDBmain, <DC main) is arranged in the main flow path of the oval flow tank (IB, 1C).

14. The fish rearing plant according to any of the preceding claims, wherein said flow generators (9B, 9C) providing said main flow (CDBmain, <DC main) is arranged outside the circumference of the outer wall (lOBo, lOCo) relative to the main flow path of the the oval flow tank (IB, 1C).

15. The fish rearing plant according to any of the preceding claims, wherein said flow generators (9B, C) providing said main flow (CDBmain, <DC main) is arranged within a channel or pipe (92B, 92C) outside the perimeter of said outer wall (lOBo, lOCo) in relation to the main flow path in said oval flowtank (IB, C), wherein said tunnel (92B, C) comprises a main flow outlet (91Bo, 91Co) with a grid (97B, 97C) and a water return outlet (91Bo, 91Co) back to the oval flow tank (IB, 1C).

16. The fish rearing plant according to any of the preceding claims, wherein the number of said purge chambers (13a, 13b, ...13z) is between four and ten.

17. The fish rearing plant according to any of the preceding claims, wherein the number of said purge chambers (13a, 13b, ...13z) is eight.

18. The fish rearing plant according to any of the preceding claims, wherein the water level in said postsmolt unit (A) decreases successively from the oval flow tank (1A) to said filter unit (41A), to said biofilm reactor (42A) and further to said degassing unit with C02 treatment (43A).

19. The fish rearing plant according to any of the preceding claims, wherein the water level in said oval flow tanks (B, C) decreases successively from the oval flow tanks (IB, 1C) to said filter units (41B, 41C), to said biofilm reactor (42B, 42C) and further to said degassing unit with C02 treatment (43B, 43C).

20. The fish rearing plant according to any of the preceding claims, wherein a water inlet (7A) for said water treatment flow (<DARAS) to said water treatment plant (4A) is arranged in said bottom (lOAb) of said oval flow tank (1A).

21. The fish rearing plant according to any of the preceding claims, wherein said water treatment flow (<DARAS) from said water treatment plant (4A) is pumped back to said oval flow tank (1A) via a water return inlet (8A) that is arranged through at least one or more of said inner walls (lOAi), or said bottom (lOAb) of said oval flow tank (1A).

22. The fish rearing plant according to any of the preceding claims, wherein said water inlet (7A) of said water treatment flow (<DARAS) is co-current with said main flow (CDAmain).

23. The fish rearing plant according to claim 20, wherein said water outlet (7A) forms an angle of 30 degrees with said bottom (lOAb).

24. The fish rearing plant according to claim 20 or 21, wherein the number of said water outlets (7A) is to, three or more and said water outlets (7A) are generally arranged in a transversal row.

25. The fish rearing plant according to claim 21 or 22, wherein said water outlet (7A) is connected to a transversal channel (71A) where said transversal channel (71A) extends from below said bottom (lOAb) and to within the perimeter of said inner wall (lOAi) and to said filter units (41A).

26. The fish rearing plant according to any of the preceding claims, wherein said water return inlet (8A) of said water treatment flow (<DARAS) is co-current with said main flow (CDAmain).

27. The fish rearing plant according to claim 24, wherein said water return inlet (8A) forms an angle of 30 degrees with said bottom (lOAb).

28. The fish rearing plant according to claim 24 or 25, wherein the number of said water return inlets (8A) is two, three or more, and said water return inlets (8A) are generally arranged in a transversal row.

29. The fish rearing plant according to claim 24 -24, wherein a transversal channel (81A) extends from said pump (6A) and outwards from said bottom (lOAb) to outwards of said inner wall (lOAi) to said water return inlets (8A).

30. The fish rearing plant according to any of the preceding claims, wherein said water outlet (7B, 7C) for said water treatment flow (<DBRAS, <DCRAS) for said water treatment plant (4B, 4C) is arranged in said bottom (lOBb, lOCb) of said oval flow tank (IB, 1C).

31. The fish rearing plant according to any of the preceding claims, wherein water outlet (7B, 7C) of said water treatment flow (<DBRAS) (<DCRAS) is co-current with said main flow (FBiti, <DCm).

32. The fish rearing plant according to claim 29, wherein said water outlet (7B, 7C) forms an angle of 30 degrees with said bottom (lOBb, lOCb).

33. The fish rearing plant according to claim 28 - 30, wherein said water outlet (7B, 7C) leads to a transversal channel (71B, 71C) where said transversal channel (71A) extends from below said bottom (lOBb, lOCb) and to within the perimeter of said inner wall (lOBi, lOCi) and to said filter units (41B, 41C).

34. The fish rearing plant according to claim 31, wherein the number of said water outlets (7B, 7C) is two, three or more, and said water outlets (7B, 7C) are generally arranged in a transversal row across the entire width of the flow tank (1A, IB, 1C).

35. The fish rearing plant according to any of the preceding claims, wherein said water treatment flow (<DBRAS, F C RAS) from said water treatment plant (4B, 4C) is pumped back to said oval flow tank (IB, 1C) via a water return inlet (8B, 8C) arranged through at least one or more of said inner walls (lOBi, lOCi), or said bottom (lOBb, lOCb) of said oval flow tank (IB, 1C).

36. The fish rearing plant according to claim 33, wherein said water return inlet (8B, 8C) forms an angle of 30 degrees with said bottom (lOAb).

37. The fish rearing plant according to claim 33 or 34, wherein the number of said water return inlets (8B, 8C) is two, three or more, and said water inlets (7B, 7C) are generally arranged in a transversal row.

38. The fish rearing plant according to claim 33 - 35, wherein a transversal channel (81B, 81C) extends from said pump (6B, 6C) and out below said bottom (lOBb, lOCb) and to outside the perimeter of said inner wall (lOBi. lOCi) and to one or more said water return inlets (8B, 8C).

39. The fish rearing plant according to any of the preceding claims, wherein said water treatment plant (16) for said purge unit (12) comprises a fresh water intake line (161) and a discharge line (168) to said water treatment plants (4B, 4C).

40. The fish rearing plant according to any of the preceding claims, wherein said purge tank water treatment plant (16) includes a freshwater intake line (161) and a discharge line (169) to said water treatment plant (4A) of said grow-out tank (A).

41. The fish rearing plant according to any of the preceding claims, wherein said purge tank water treatment plant (16) comprises filter units (162), a degassing unit with C02 treatment (163) and preferably an ozone treatment unit (164).

42. The fish rearing plant according to any of the preceding claims, wherein the water level in said purge units (12) said water treatment plant (16) is successively decreasing from said purge chambers (13a, 13b, ... 13z) to said filter unit (162), to said degassing unit with C02 treatment (163), further to said UV-treatment unit (166) and to said pumps (167) wherein said pumps (167) pump water corresponding to said water level in said purge chambers (13a, 13b, ... 13z).

43. The fish rearing plant according to any of the preceding claims, wherein the the water level in said purge chambers (13a, 13b, ... 13z) is kept at a higher level than in said water flow tanks (IB, 1C).

44. The fish rearing plant according to any of the preceding claims, wherein transfer lines (11B, 11C) from said postsmolt tank (A) comprise a fish pump (110), a flexible hose (111B, 111C) to a separation grid (112B, 112C) further leading the fish to said first section (3B1, 3C1) in each of said flow tanks (3B, 3C).

45. The fish rearing plant according to any of the preceding claims, wherein said transverse separation grids (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm) are moveable along their associated flow tanks (1A, IB, 1C) by means of motord (18Al-18An, 18Bl-18Bm, 18Cl-18Cm)..

46. The fish rearing plant according to any of the preceding claims, wherein said separation grids (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm) are movable via an above water arranged motor (18Al-18An, 18Bl-18Bm, 18Cl-18Cm) connected to a vertical shaft (19A1, 19B1, 19C1) down to a pinion (20A1, 20B1, 20C1) that meshes with a rack (21A, 21B, 21C) that extends along the wall (IOί, 10o) or near the bottom (lOAb, lOBb, lOCb) of the oval flow tank (1A, IB, 1C).

47. The fish rearing plant according to any of the preceding claims, wherein at least one of said separation grids (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm) comprises a gate (21A1, 21B1, 21C1) with a panel (24) , wherein said panel (24) is movable for crowding of fish from one section to the other sections (3A1 to 3Am or 3B1 to 3Bm or 3C1 to 3Cm).

48. The fish rearing plant according to claim 45 - 46, wherein said flow generator (9A, 9B, 9C) providing said main flow (FAiti, FBiti, ®Cm) is arranged within the perimeter of said inner wall (lOAi, lOBi, lOCi), or outside the perimeter of said outer wall (lOAo, lOBo, lOCo), or below the bottom (lOAb, lOBb, lOCb) in relation to the main flow path in said oval flowtank (1A, IB, 1C) wherein said grids (2A1 - 2An), (2B1 - 2Bm), (2C1 - 2Cm) are movable to any position within the flow tank (1A, IB, 1C) so as for moving each cohort gradually towards the outlet for fish from the tank instead of moving the fish from one section to the next section (3A, 3B, 3C).

49. A method for fish farming in a fish rearing plant according to any of claims 1 - 48,

comprising the following steps:

- running said flow generators (9A, 9B, 9C) and said pumps (6A, 6B, 6C),

- at time intervals :

- moving / transferring the largest cohort of postsmolt over from the last section (3An) over to at least one of said first sections (3B1, 3C1) in said flow tanks (3B, 3C),

- for each tank section prior to section (3An) all the way down to said first section (3A1), moving each postsmolt cohort to a next tank section, - supplying a new postsmolt cohort to said first tank section (3A1) of said postsmolt tank (1A).

50. The method according to claim 49, comprising the following

- transferring of salmon from the purge chamber (11) to an export line (171) to a fish slaughter house (17).

51. The method according to claim 49 - 50, comprising the following

- transferring the largest cohort of postsmolt from the last section (3An) and evenly distributing said largest cohort of postsmolt simultaneously to both first said sections (3B1, 3C1) of said flow tanks (3B, 3C).

52. The method according to claim 49 - 51, comprising the following

- regulating the temperature in the flow tanks (3B, 3C) to different temperatures (TB, TC) in such a way that said cohort in said last sections (3Bm, 3Cm) will achieve their slaughtering weight at different/staggered time intervals, preferably at the interval in-between setting in and transferring of cohorts in the postsmolt tank (3A).

53. The method according to claim 49 - 52, comprising the following

- wherein said transverse separation grids (2A1 - 2An, 2B1 - 2Bm, 2C1 - 2Cm) are movable within said flow tanks (1A, IB, 1C) for adjusting the length of said tank sections (3An, 3Bm, 3Cm) in order to better adjust their volume to the size of the growing cohorts.

54. The method according to claim 49 - 53, wherein said flow generator (9A, 9B, 9C) providing said main flow (FAiti, FBiti, ®Cm) is arranged within the perimeter of said inner wall (lOAi, lOBi, lOCi), or outside the perimeter of said outer wall (lOAo, lOBo, lOCo), or below the bottom (lOAb, lOBb, lOCb) in relation to the main flow path in said oval flowtank (1A, IB, 1C) and wherein said separation grids (2A1 - 2An), (2B1 - 2Bm), (2C1 - 2Cm) are moved to any position within the flow tank (1A, IB, 1C), moving each cohort gradually towards the outlet for fish from the tank instead of moving the fish from one section to the next section (3A, 3B, 3C) across the separation grids (2).