FACILITY FOR BREEDING AQUATIC CREATURES, SALT COMPOSITION, SALT OR BAKED WATER FOR SUCH A FACILITY

Description

[0001] The invention relates to a system for raising aquatic organisms, in particular fish or crustaceans, comprising a rearing tank containing salt or brackish water, wherein the salt or brackish water is produced by a salt composition containing between 70 mol% and 99.9 mol% sodium chloride (NaCl) and between 0.1 mol% and 30 mol% magnesium chloride (MgCl₂), respectively, based on the total amount of the salt composition. The invention further relates to a salt composition for producing brackish or salt water for such a system, brackish or salt water, and a method for producing the brackish or salt water.

[0002] CN 1321913 C describes a salt composition as an artificial seawater additive, for example for fish farming, as well as a method for its production. A low-sulfate salt composition is known from CN 1321913 C. However, a sulfate-free composition is not described.

[0003] JP 2006006150 A describes salt compositions that can be used for shrimp farming. From paragraph

[0017] , a composition is known that contains 85 mol% NaCl, 6.5 mol% MgCl₂, 3.2 mol% MgSO₄, and 1.9 mol% CaSO₄. Thus, a low-sulfate salt composition is described, but not a sulfate-free one.

[0004] From Sowers et al. "Hemolymph osmolality and cation concentrations in Litopenaeus vannamei during exposure to artificial sea salt or a mixed-ion solution: Relationship to potassium flux"; Comparative Biochemistry and Physiology, Part A: Molecular and Integrative Physiology, Elsevier, Vol. 145, No. 2, 20 September 2006, pp. 176-180, a sulfate-free salt composition for the rearing of crustaceans in an aquarium is known.

[0005] Aquaculture is a known technique for raising aquatic organisms such as fish, mussels, or crustaceans. This typically involves using enclosed ponds, channels, basins, or net pens in existing bodies of water, where the organisms grow until harvest. Particularly in coastal regions, net pens are most commonly used, as they allow access to existing salt or brackish water.

[0006] As a form of aquaculture, inland aquafarming is known to take place in so-called recirculating aquaculture systems with rearing tanks. To produce the saline water used for this purpose, which can be artificial seawater, for example, in which the aquatic organisms are raised in the rearing tanks until harvest, sea salt is typically dissolved in pipes, groundwater, or surface water to create a habitat typical for the animals being farmed. This artificial seawater usually has a high sulfate content.

[0007] While aquaculture systems in flowing waters or fjords typically do not remove excrement and leftover feed from the breeding water, and water exchange occurs through circulation within the rearing baskets, recirculating aquaculture systems require multiple filter stages to purify the water in the rearing tanks. Despite continuous filtration and water circulation, a 1 to 4 mm thick layer, known as sediment, can form on the bottom of the rearing tanks, particularly in areas like corners or within water filtration units. This sediment consists of leftover feed and excrement from the aquatic organisms and provides a habitat for microorganisms. Oxygen can only penetrate the sediment to a depth of a few micrometers, as it is immediately consumed by microbial decomposition processes. Typical penetration depths range from 20 to 100 micrometers, depending on various parameters.

[0008] The inventor recognized that microorganisms living in the sediment use sulfate instead of oxygen as an electron acceptor for their metabolism, thereby producing hydrogen sulfide (H₂S) which is released into the water of the rearing tank. This can lead to a locally high H₂S concentration in the sediment area, which is lethal to aquatic life and can result in crop failure, meaning the death of aquatic organisms that are even briefly present in this area. All fish farmed in aquaculture are particularly sensitive to hydrogen sulfide, especially Atlantic salmon ( Salmo salar ), the Yellowtail Kingfish ( Seriola lalandi ) as well as the rainbow trout ( Onchorrynchis mykiss ) . Among crustaceans, the White Tiger prawns are particularly noteworthy ( Litopenaeus vannamei ) as well as the Black Tiger prawns ( Panaeus monodon ) affected.

[0009] The inventor also recognized that this problem is solved by using sulfate-free brackish or salt water, and that up to a certain sulfate concentration there is no danger to aquatic life, meaning that only a harmless amount of H2S is formed in the sediment.

[0010] Simultaneously, a salt composition is created that allows for the production of brackish or saltwater, in which aquatic organisms thrive and are supplied with all the necessary ions in sufficient quantities. This ensures that the growth rates required for commercial aquaculture are achieved.

[0011] The invention is based on the objective of creating a brackish or saltwater facility for the rearing of aquatic organisms of the aforementioned type, in which no hydrogen sulfide is released into a rearing tank of the facility, or only in a quantity that is harmless to the aquatic organisms.

[0012] According to the invention, the problem is solved by the fact that the salt composition contains between 0.20 mol% and 0.31 mol% sodium bicarbonate (NaHCO3) based on the total amount of substance of the salt composition.

[0013] Sodium bicarbonate is also known as sodium hydrogen carbonate.

[0014] Although sodium bicarbonate is less soluble in water than sodium carbonate, it is significantly easier to store. While sodium carbonate is highly hygroscopic and must be stored either in airtight containers or in a dry atmosphere, sodium bicarbonate can be stored in breathable bags, for example, without any significant change in its properties. This is advantageous for long transport distances to a cultivation facility or for extended storage times within the facility; on-time delivery is not required.

[0015] It is conceivable that sodium bicarbonate is used to produce a salt composition that requires a particularly precise adjustment of the pH value of the salt or brackish water produced therefrom, with which a rearing plant according to the invention is operated.

[0016] A sulfate-free salt composition contains no sulfate at all, while a low-sulfate salt composition contains a maximum of 5 mol% of a sulfate in relation to the total amount of the salt composition, preferably the maximum 5 mol% sulfate consists of magnesium sulfate.

[0017] It is conceivable that the sulfate originates from a solution of sodium and / or potassium sulfate.

[0018] It is also conceivable to use mixtures of different sulfate salts.

[0019] Advantageously, it is ensured that ions required for particularly good growth of aquatic organisms are present in sufficient quantity in brackish or salt water produced with the salt composition according to the invention.

[0020] A sulfate-free or low-sulfate salt composition is achieved in particular by using a chloride salt, for example magnesium chloride, as a substitute for a sulfate salt, for example magnesium sulfate. In the salt composition according to the invention, a sulfate salt is always replaced by a chloride salt. Advantageously, this substitution allows the ion ratios, especially the cation ratios, of the artificial salt or brackish water to be produced, for example magnesium to calcium or magnesium to potassium, to correspond to those of water in the natural habitat of aquatic organisms.

[0021] It goes without saying that sodium chloride can be used as a substitute for sodium sulfate.

[0022] According to the invention, brackish or salt water is sulfate-free or at least low in sulfate, depending on the salt composition used to produce it.

[0023] Advantageously, the salt composition contains potassium chloride (KCl), preferably less than 5 mol% based on the total amount of the salt composition, in particular between 0.5 mol% and 4.0 mol%, most preferably between 1.5 mol% and 2.25 mol%.

[0024] In one embodiment of the invention, the salt composition contains calcium chloride (CaCl₂), preferably less than 5 mol% based on the total amount of the salt composition, particularly between 0.5 mol% and 4 mol%, and most preferably between 1.50 mol% and 2.25 mol%. Calcium and chloride ions are essential for the growth of aquatic organisms. Calcium chloride is particularly soluble in water, so a rearing tank can be used for rearing more quickly than when using another calcium source. This reduces downtime and allows for increased productivity.

[0025] The inventor has recognized that for a sulfate-free or low-sulfate salt composition, a sulfate salt can be replaced by a chloride salt, wherein the ion ratios required for the rearing of aquatic organisms in a rearing facility operated with salt or brackish water according to the invention, for example an ion ratio of magnesium ions to calcium ions or magnesium ions to potassium ions, advantageously correspond to or are at least very similar to those of water in the natural habitat of the aquatic organisms.

[0026] In a further embodiment of the invention, the salt composition contains sodium carbonate (Na₂CO₃), preferably up to 0.5 mol% based on the total amount of the salt composition, particularly between 0.01 mol% and 0.15 mol%, and most preferably 0.065 mol%. Sodium carbonate has a significantly higher solubility in water than sodium bicarbonate, which is known from the prior art as a carbonate source for the production of salt or brackish water for rearing facilities. Due to its higher solubility, the rearing facility is available for further rearing of aquatic organisms more quickly after a change of the salt or brackish water used in the rearing facility. Downtime is reduced.

[0027] A low-sulfate salt composition contains, for example, up to 5 mol% sulfate (SO₄²⁻). A suitable sulfate, for example, is selected from the group consisting of sodium sulfate, magnesium sulfate, potassium sulfate, and calcium sulfate, preferably selected from the group consisting of sodium sulfate and magnesium sulfate.

[0028] In one embodiment, a low-sulfate salt composition contains up to 5 mol% sodium sulfate (Na2SO4), in another embodiment, a low-sulfate salt composition contains up to 5 mol% magnesium sulfate (MgSO4), in each case based on the total amount of substance of the salt composition.

[0029] The inventor recognized that, in a low-sulfate salt composition, sodium sulfate can be replaced by magnesium sulfate without negatively impacting the growth of aquatic organisms. Since sodium sulfate is more expensive than magnesium sulfate, a particularly cost-effective salt composition is advantageously created. A rearing system according to the invention is particularly economical to operate.

[0030] A magnesium sulfate content of 4.28 mol%, based on the total amount of the salt, has proven advantageous in a low-sulfate salt composition. This results in optimal harvesting outcomes, i.e., rapid growth with a low loss rate due to aquatic organisms dying before harvesting begins.

[0031] In one embodiment of the invention, a sulfate-free salt composition contains between 7.5 mol% and 12 mol% magnesium chloride (MgCl₂) based on the total amount of the salt composition, preferably between 9.0 and 10.0 mol%. This proportion has proven particularly advantageous for achieving the optimal magnesium-to-calcium and magnesium-to-potassium ion ratios for the metabolism of aquatic organisms in the brackish or salt water of the rearing system. These ion ratios are highly relevant for optimal growth of the aquatic organisms. Advantageously, this results in a particularly efficient rearing system.

[0032] In a further embodiment of the invention, a low-sulfate salt composition contains between 4.0 mol% and 7.0 mol% magnesium chloride (MgCl₂) based on the total amount of the salt composition, preferably between 5.0 and 6.0 mol%. This proportion has proven particularly advantageous for achieving the optimal magnesium-to-calcium and magnesium-to-potassium cation ratios for the metabolism of aquatic organisms in the brackish or salt water of the rearing facility.

[0033] In one embodiment of the invention, the salt composition is magnesium sulfate-free or low in magnesium sulfate. Advantageously, a salt composition is created that, compared to that used for the production of artificial saltwater, contains no sulfate at all, or only a small amount, which is achieved by adding magnesium sulfate. Such a salt composition according to the invention is synthetic and cannot be produced by drying seawater.

[0034] Advantageously, a low-sulfate or sulfate-free salt composition according to the invention for the production of brackish or salt water for a facility for the rearing of aquatic organisms, in particular for the rearing of fish or crustaceans, contains between 70 mol% and 99.9 mol% sodium chloride (NaCl) and between 0.1 mol% and 30 mol% magnesium chloride (MgCl₂), each based on the total amount of substance of the salt composition.

[0035] It goes without saying that the mol% of the salts contained in the salt composition refers to their mol% before the production of brackish or salt water. It is clear to anyone skilled in the art that the mol% can change during the production of the brackish or salt water.

[0036] The salinity of brackish or salt water according to the invention, which is produced with a salt composition according to the invention, is between 0.10% and 5.0%, preferably between 2.5% and 3.5%. A salinity of 2.5% to 3.5% is particularly suitable for raising marine animals.

[0037] When salinity is specified, the percentage refers to the mass fraction of salt in the water. For example, a salinity of 1.0% means that 10 g of salt are added to 1 kg of water to produce the salt water.

[0038] Brackish water has a salinity between 0.1% and 1.0%, while saltwater has a salinity of more than 1.0%. Seawater can have a salinity of 3.0% to 3.5%.

[0039] In a process according to the invention for producing brackish or salt water for a facility for raising aquatic organisms with a salinity required for rearing, a salt composition is introduced into freshwater, in particular into tap water, groundwater or surface water, for example from lakes. The ion content of the freshwater is negligible compared to the ion content that the brackish or salt water according to the invention is intended to have.

[0040] An aquatic organism raised in a rearing facility according to the invention differs from aquatic organisms known from the art in that it is possible to determine, based on the kidney activity of the aquatic organism, whether it was raised in sulfate-free or low-sulfate salt or brackish water. Sulfate detectable in aquatic organisms is formed, for example, through the metabolism of feed containing amino acids or through absorption from the salt or brackish water in which the aquatic organisms are raised. The inventor was thus able to demonstrate that aquatic organisms whose natural habitat is saltwater and which were raised in a rearing facility according to the invention, operated with low-sulfate or sulfate-free salt water, exhibited lower kidney activity than comparable aquatic organisms raised in their natural habitat.

[0041] In dead aquatic organisms, examination of the kidneys can determine whether they were raised in low-sulfate or sulfate-free salt or brackish water.

[0042] It is understood that low-sulfate and sulfate-free water is such salt or brackish water with which the rearing facility is operated, and which has been produced with a low-sulfate or sulfate-free salt composition.

[0043] A salt composition known from the prior art for the production of artificial seawater for the operation of an aquaculture plant exhibits the following mole fractions of substances, based on the total amount of substance in the salt composition, as shown in Table 1 below: Table 1: Salt compositions known from the state of the art for the production of artificial salt water Chemical compound Molar fraction (mol-%) Sodium chloride 88,06 Magnesium chloride 1,50 Magnesium sulfate 7,00 Calcium chloride 1,63 Potassium chloride 1,52 Sodium bicarbonate 0,25 Sodium carbonate 0,04

[0044] In the case of brackish or salt water in a rearing facility produced with this composition (7 mol% magnesium sulfate), there is a high risk of crop failure - up to 2% - due to the formation of hydrogen sulfide in the sediment area.

[0045] The invention is explained in more detail below using exemplary embodiments. Example 1:

[0046] A low-sulfate salt composition according to the invention has a composition according to the following Table 2.1: Table 2.1: Low-sulfate salt composition according to the invention Chemical compound Molar fraction (mol-%) Sodium chloride 86,09 Magnesium chloride 5,51 Magnesium sulfate 4,28 Calcium chloride 1,90 Potassium chloride 1,87 Sodium bicarbonate 0,30 Sodium carbonate 0,06

[0047] Salt water with a salinity of 3.0%, prepared with a salt composition according to Table 2.1, has an ion concentration according to Table 2.2 below: Table 2.2: Low-sulfate salt water with a salinity of 3.0% ion Concentration (mol / l) Molar fraction (mol-%) Sodium (Na+<) 0,41 42,83 Chloride (Cl -< ) 0,47 48,17 Magnesium (Mg 2+< ) 0,05 4,84 Sulfate (SO42-<) 0,02 2,12 Calcium (Ca 2+< ) 0,01 0,94 Potassium (K+) 0,01 0,92 Bicarbonate (HCO3-< ) 0,0014 0,15 Carbonate (CO 3 2-< ) 0,00025 0,03 Example 2:

[0048] A sulfate-free salt composition according to the invention has a composition according to the following Table 3.1: Table 3.1: Sulfate-free salt composition according to the invention, page 9 / 12 Chemical compound Molar fraction (mol-%) Sodium chloride 86,46 Magnesium chloride 9,52 Magnesium sulfate 0,0 Calcium chloride 1,85 Potassium chloride 1,82 Sodium bicarbonate 0,29 Sodium carbonate 0,06

[0049] Because a certain amount of magnesium is required for the rearing of aquatic organisms, the omission of magnesium sulfate is compensated for by an increase in the amount of magnesium chloride, i.e., magnesium sulfate is replaced by magnesium chloride.

[0050] By the composition according to Example 2, brackish or salt water can be produced for a rearing facility whose aquatic organisms exhibit a growth curve like those that are reared in brackish or salt water produced by a composition according to Example 1, and in which there is virtually no harvest loss - less than 0.5% - due to hydrogen sulfide leaching from the so-called sediment.

[0051] Salt water with a salinity of 3.0%, prepared with a salt composition according to Table 3.1, has an ion concentration according to the following Table 3.2: Table 3.2: Sulfate-free salt water according to the invention with a salinity of 3.0% ion Concentration (mol / L) Molar fraction (mol-%) Sodium (Na+<) 0,43 43,01 Chloride (Cl -< ) 0,51 50,29 Magnesium (Mg 2+< ) 0,05 4,72 Sulfate (SO42-<) 0 0 Calcium (Ca 2+< ) 0,01 0,92 Potassium (K+) 0,01 0,91 Bicarbonate (HCO3-< ) 0,00136 0,13 Carbonate (CO 3 2-< ) 0,00024 0,02 Example 3:

[0052] Another sulfate-free salt composition according to the invention has a composition according to the following Table 4.1: Table 4.1: A sulfate-free salt composition without sodium bicarbonate Chemical compound Molar fraction (mol-%) Sodium chloride 86,51 Magnesium chloride 9,53 Magnesium sulfate 0,00 Calcium chloride 1,86 Potassium chloride 1,84 Sodium bicarbonate 0,00 Sodium carbonate 0,26

[0053] By the composition according to Example 3, brackish or salt water can be produced for a rearing facility whose aquatic organisms exhibit a growth curve like those that are reared in brackish or salt water that can be produced by a composition according to Example 1 of 2, and in which there is virtually no harvest loss - less than 0.5% - due to hydrogen sulfide leaching from the so-called sediment.

[0054] The composition according to example 3 has the advantage that, due to the high solubility of sodium carbonate and the omission of sodium bicarbonate, a standstill time of the rearing system was possible for several hours less during a water change.

[0055] Salt water with a salinity of 3.0%, prepared with a salt composition according to Table 4.1, has an ion concentration according to the following Table 4.2: Table 4.2: Sulfate-free and bicarbonate-free salt water according to the invention with a salinity of 3.0% ion Concentration (mol / L) Molar fraction (mol-%) Sodium (Na+<) 0,44 43,06 Chloride (Cl -< ) 0,51 50,26 Magnesium (Mg 2+< ) 0,05 4,72 Sulfate (SO42-<) 0,00 0,00 Calcium (Ca 2+< ) 0,01 0,92 Potassium (K+) 0,01 0,91 Bicarbonate (HCO3-< ) 0,00 0,00 Carbonate (CO 3 2-< ) 0,00132 0,13

[0056] It is understood that the invention is not limited to these examples. In particular, it is conceivable that brackish or salt water according to the invention has a salinity other than that mentioned, for example 0.75% or 3.5%.

[0057] Furthermore, it is conceivable that a sulfate salt other than magnesium sulfate is used to produce low-sulfate salt or brackish water, for example sodium or potassium sulfate.

Claims

1. Installation for farming aquatic organisms, in particular fish or crustaceans, which has a rearing tank containing saltwater or brackish water, wherein the saltwater or brackish water is produced using a salt composition that contains between 70 mol% and 99,9 mol% sodium chloride (NaCl) and between 0,1 mol% and 30 mol% magnesium chloride (MgCl2), in each case in relation to the total amount of substance in the salt composition, wherein the salt composition is sulphate-free or has at least a low sulphate content, characterized in that the salt composition contains between 0,20 mol% and 0,31 mol% sodium bicarbonate (NaHCO3) in relation to the total amount of substance in the salt composition.

2. Farming installation according to claim 1, characterized in that the salt composition contains potassium chloride (KCl), preferably less than 5 mol% in relation to the total amount of substance in the salt composition, in particular between 0,5 mol% and 4,0 mol%, particularly preferably between 1,5 mol% and 2,25 mol%.

3. Farming installation according to claim 1 or 2, characterized in that the salt composition contains calcium chloride (CaCl2), preferably less than 5 mol% in relation to the total amount of substance in the salt composition, in particular between 0,5 mol% and 4 mol%, particularly preferably between 1,50 mol% and 2,25 mol%.

4. Farming installation according to any one of claims 1 to 3, characterized in that the salt composition contains sodium carbonate (Na2CO3), preferably up to 0,5 mol% in relation to the total amount of substance in the salt composition, in particular between 0,01 mol% and 0,15 mol%, particularly preferably 0,065 mol%.

5. Farming installation according to any one of claims 1 to 4, characterized in that a salt composition that has a low sulphate content contains magnesium sulphate (MgSO4), preferably less than 5,0 mol% in relation to the total amount of substance in the salt composition, particularly preferably between 4,15 mol% and 4,35 mol%.

6. Farming installation according to any one of claims 1 to 4, characterized in that a sulphate-free salt composition contains between 7,5 mol% and 12 mol% magnesium chloride (MgCl2) in relation to the total amount of substance in the salt composition, preferably between 9,0 and 10,0 mol%.

7. Farming installation according to any one of claims 1 to 5, characterized in that a salt composition that has a low sulphate content contains between 4,0 mol% and 7,0 mol% magnesium chloride (MgCl2) in relation to the total amount of substance in the salt composition, preferably between 5,0 and 6,0 mol%.

8. Salt composition for producing brackish water or saltwater for an installation for farming aquatic organisms, in particular for farming fish or crustaceans, which contains between 70 mol% and 99,9 mol% sodium chloride (NaCl) and between 0,1 mol% and 30 mol% magnesium chloride (MgCl2), in each case in relation to the total amount of substance in the salt composition, wherein the salt composition is sulphate-free or has at least a low sulphate content, characterized in that the salt composition contains between 0,20 mol% and 0,31 mol% sodium bicarbonate (NaHCO3) in relation to the total amount of substance in the salt composition.

9. Brackish water or saltwater for an installation for farming aquatic organisms, in particular fish or crustaceans, which is produced by a salt composition according to claim 8.

10. Brackish water or saltwater according to claim 9, characterized in that the salinity of the brackish water or saltwater is between 0,10 % and 5 %, preferably between 2,5 % and 3,5 %.

11. Method for producing brackish water or saltwater for an installation for farming aquatic organisms according to any one of claims 1 to 7, characterized in that a salt composition according to claim 8 is added to fresh water, in particular tap water, groundwater or surface water, wherein a salinity of between 1,0 % and 5,0 % is set.