PLANT FOR AQUACULTURE AND OUTLET FOR AQUACULTURE TANKS AND OTHER USES THEREOF

Abstract

A plant for aquaculture, for farming of fish or other aquatic species, comprising a closed or semi-closed tank, at least one inlet for water to the tank and an outlet for water from the tank. The plant is distinguished in that the outlet comprises two pipes, wherein an outer pipe is arranged outside an inner pipe, the outer pipe extends from a bottom of the tank up to an outer pipe upper end, and the outer pipe comprises openings distributed along the immersed part of the outer pipe, the inner pipe extends from the bottom of the tank up to an inner pipe upper end, and the inner pipe comprises an outlet opening at the inner pipe upper end and/or outlet openings at elevation below the inner pipe upper end, and a main outlet from the tank is arranged in the tank bottom in position inside the inner pipe.

Claims

1. Plant for aquaculture, for farming of fish or other aquatic species, comprising a closed or semi-closed tank, at least one inlet for water to the tank and an outlet for water from the tank, wherein the outlet comprises two pipes, an outer pipe and an inner pipe, wherein the outer pipe is arranged outside the inner pipe, wherein the outer pipe extends from a bottom of the tank up to an outer pipe upper end, and the outer pipe comprises openings distributed along the immersed part of the outer pipe, wherein the inner pipe extends from the bottom of the tank up to an inner pipe upper end, and the inner pipe comprises an outlet opening at the inner pipe upper end and/or outlet openings at elevation below the inner pipe upper end, and wherein a main outlet from the tank is arranged in the tank bottom in position inside the inner pipe, further comprising: a primary sludge outlet, arranged in the tank bottom outside the outer pipe, and a secondary sludge outlet, arranged in the tank bottom outside the inner pipe but inside the outer pipe, and wherein water brought into the tank through the at least one inlet preferably flows in substance circular and radial inside the tank, preferably in substance by laminar and/or diverging flow, into and through the openings distributed along the immersed part of the outer pipe, into an annular water column formed between the inner and outer pipe, upwards through the annular water column, into and through the inner pipe outlet, down the inner pipe and out through the main outlet, whilst sludge is separated and brought out from the tank through the primary sludge outlet and the secondary sludge outlet.

2. Plant according to claim 1, wherein the outer pipe extends up to an upper end, at, above or below a tank water level.

3. Plant according to claim 1, wherein the inner pipe comprises outlet at the inner pipe upper end.

4. Plant for aquaculture according to claim 1, wherein the primary sludge and/or the secondary sludge outlet openings are controllable, by comprising replaceable screens, actuators, or other control means, enabling control of the flow rates of sludge/water through said outlets relative to the total flow rate through the tank or main outlet and the contents and size of fish.

5. Plant for aquaculture according to claim 1, wherein the outer pipe and/or the inner pipe comprises openings arranged with filters or screens, and/or the plant comprises level control of the tank water level.

6. Plant for aquaculture according to claim 1, comprising an inlet distributing the water in substance identically as for the outlet openings along the immersed part of the outer pipe with respect to elevation.

7. Outlet for a tank for aquaculture or process liquid, wherein the outlet comprises: two pipes, an outer pipe and an inner pipe, wherein the outer pipe is arranged outside the inner pipe, wherein the outer pipe extends from a bottom of the tank up to an upper end, and the outer pipe comprises openings distributed along the immersed part of the outer pipe, wherein the inner pipe extends from the bottom of the tank up to an inner pipe upper end, wherein a main outlet from the tank is arranged in the tank bottom in position inside the inner pipe, and wherein the outer pipe is arranged inside a primary sludge outlet arranged in the tank bottom outside the outer pipe and a secondary sludge outlet is arranged in the tank bottom outside the inner pipe but inside the outer pipe.

8. Outlet according to claim 7, wherein the outlet is arranged in a tank for aquaculture, in a tank for water treatment, in a tank for process water cleaning, in a tank for drinking water cleaning, and/or as a general header tank outlet.

9. Outlet according to claim 7, wherein the primary sludge and/or the secondary sludge outlet openings are controllable, by comprising replaceable screens, actuators, or other control means, enabling control of the flow rates of sludge/water through said outlets relative to the total flow rate through the tank or main outlet.

10. Use of an outlet according to claim 7, for aquaculture, for water treatment, for process water cleaning, for drinking water cleaning, for water in oil separation, and/or as a general header tank outlet.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0041] FIG. 1 illustrates an embodiment of a plant and an outlet of the invention.

[0042] FIG. 2 illustrates a further embodiment of a plant and an outlet of the invention.

[0043] FIG. 3 illustrates a RAS-embodiment of a plant of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0044] The figures are not to scale with respect to all elements, for clearly illustrating the features essential for the invention and discussed specifically for the respective figure. The embodiments illustrated are typical embodiments, several other embodiments within the scope of the invention are possible. Identical items have identical reference numbers.

[0045] Reference is made to FIG. 1, illustrating a typical embodiment of a plant or tank of the invention, comprising an outlet of the invention. FIG. 1 is a partial cross section of a plant 17 for aquaculture. A common vertical center axis runs through the center of tank 1, the center of the outer pipe 2 and the center of the inner pipe 4, as a common coaxial axis, as briefly indicated in the figure. The components tank wall 1, outer pipe 2, inner pipe 4, primary sludge outlet 5,7 and secondary sludge outlet 8,9 are symmetrical about the center axis, for the illustrated typical embodiment. A partial cross section, that is a cross section not covering the full tank 1 diameter, is illustrated in FIG. 1.

[0046] More specifically, FIG. 1 illustrates a plant 17 for aquaculture, for farming of fish or other aquatic species, comprising a semi-closed tank 1, an inlet 16 for water to the tank and an outlet 18 for water from the tank. The tank outlet 18 comprises two pipes, an outer pipe 2 and an inner pipe 4, wherein the outer pipe 2 is arranged outside the inner pipe 4. The outer pipe 2 extends from a bottom 19 of the tank up to below but near a tank water level 20. The outer pipe has closed upper end but comprises openings 3 distributed along the immersed part of the outer pipe. The inner pipe 4 extends from the bottom 19 of the tank at least up to an outlet elevation 21 where an outlet is arranged as an open inner pipe end and/or as openings of sufficient size through the inner pipe wall. The outlet elevation 21 is below the tank water level 20, and a main outlet 11 from the tank is arranged in the tank bottom in position within the inner pipe. The open upper end of the inner pipe, as illustrated, is at elevation of the outlet elevation 21 of a recirculation tank 12 or slightly above, to allow flow by gravity from the tank 1 to the recirculation tank 12. The tank further comprises a primary sludge outlet 5, 7, arranged in the tank bottom around the outer pipe, and a secondary sludge outlet 8, 9, arranged in the tank bottom around the inner pipe but inside the outer pipe. At reference number 24, an outlet for water is indicated. Lost water is replaced, preferably through the inlet or inlets.

[0047] As evident, the illustrated outlets for sludge are circular ducts under a respective screen. The screens are preferably replaceable. Respective outlets below the screens, are coupled to respective ducts. In many preferable embodiments, the primary sludge and/or the secondary sludge outlet openings are controllable, by comprising replaceable screens, actuators, or other control means. Thereby, the flow rates of sludge/water through said outlets can be controlled relative to the total flow rate through the tank or outlet and the contents and size of fish, enabling to control the ratio of water/sludge so as to enable only water through the main outlet feasible for recirculating without further sludge removal.

[0048] As evident from the figure, and as briefly illustrated by arrows, water flowing out from the main outlet 11 is recirculated, via pipe 12, pump 13 and CO.sub.2 filter-aerator 14, recirculating about 50-60% of the water to the tank via pipe 15. Sludge is transported to filter 10 and can be used as fertilizer or as a component for a fertilizer. With the illustrated embodiment up to at least 70% recirculated water, via the main outlet, is feasible. The remaining 30% of outlet flow is shared between the primary sludge outlet and the secondary sludge outlet, typically with a majority of said flow through the primary sludge outlet.

[0049] Notice that water from the main outlet, containing water that has be separated twice, by separating out sludge through both primary and secondary sludge outlets, is bought to the recirculation tank 12, from where most of the water is recirculated back to the tank inlet, via aeration as required in filter 14. Some water from the recirculation tank is or can be brought to filter 10, whereto primary sludge and secondary sludge are brought, and where further separation of sludge takes place.

[0050] FIG. 2 illustrate a further embodiment of a plant of the invention, quite like the embodiment of FIG. 1, but with an outer pipe 2 with open upper end in the outlet, extending up above the tank water level 20. The inner pipe 4 of the outlet has outlet through an open upper end at the outlet elevation 21, or slightly above, depending on the flow situation.

[0051] FIG. 3 illustrates a further plant embodiment of the invention, more specifically a typical RAS aquaculture plant. Again, the embodiment is quite like the embodiments of FIGS. 1 and 2, but with RAS almost all water is recirculated, and further water treatment is required. A biofilter stage 22 and an UV treatment stage 23 are added to the water treatment process. At reference number 25, an outlet for water is indicated.

[0052] The advantage of the invention compared to state-of-the-art plants increases with the requirement for recirculating water, since the recirculated water must be cleaned and conditioned to be fully feasible for aquaculture. The outlet of the plant of the invention separates out particles-sludge at the earliest stage possible, more tenderly and at the same time more effectively than usual, due to minimization of fragmentation and two stage separation, as described above. With RAS, for which recirculation of water is near 100%, the advantage of the invention is at maximum. If operating a RAS plant of the invention as designed, for example as illustrated in FIG. 3, only 10-30% of the water must be further cleaned and conditioned in terms of filtering out solids and particles as comparted to state of the art that filters the total recycling water flow, here excluding the aeration step 14 since all water recycled to the tank is aerated. For some embodiments also the biofiltering is excluded, since all recycled water for some embodiments is biofiltered. Considering the process facilities for water cleaning and conditioning downstream to the sludge outlets of the plant of the invention, the saving in process facilities downstream to the sludge outlets typically is 90-70%, compared to full cleaning and conditioning of all the water entering all of the outlets. The further advantage of the invention in RAS can result into a down scaling of biofilters as the biofilters become more efficient when organic matter is gently filtered out in two upstream stages. This is achieved by the invention as solids are not being crushed into smaller particles that would increase the dissolved organic load of the water that would reduce capacity of the biofilters.

[0053] With the present invention, surprisingly simple and effective water treatment is provided, due to the effective two stage sludge removal of the invention, enabling reduced investments and reduced operation cost.