WO2018164586A1

WO2018164586A1 - System for cultivating aquatic organisms by producing feed for the aquatic animals from waste products emanating from said cultivation, particularly carbon dioxide isolated by ultrasound

Info

Publication number: WO2018164586A1
Application number: PCT/NO2018/050069
Authority: WO
Inventors: Terje Ernst MIKALSEN
Original assignee: Tm Holding As
Current assignee: Tm Holding As
Priority date: 2017-03-09
Filing date: 2018-03-09
Publication date: 2018-09-13
Anticipated expiration: 2019-09-09
Also published as: NO20170348A1

Abstract

It is disclosed the use of ultrasound for removing carbon dioxide from water in a closed breeding/cultivation plant for aquatic organisms for improving the water quality as well as a system for breeding/cultivating aquatic organisms (fish) using ultrasound to this end.

Description

System for cultivating aquatic organisms by producing feed for the aquatic animals from waste products emanating from said cultivation, particularly carbon dioxide isolated by ultrasound

Ambit of the Invention The present invention concerns a system for cultivating aquatic organisms by producing feed for the aquatic animals from waste products emanating from said cultivation, particularly carbon dioxide isolated by ultrasound, the system comprising at least one tank for carrying water for cultivating said aquatic animals, said tank being connected to other devices in the system by a number of conduits, wherein at least one of the other devices comprises an ultrasound device for removing carbon dioxide from the water originating from said cultivation tank, and reintroducing said carbon dioxide to a collection of microorganisms for converting said carbon dioxide into carbonaceous feed. The system is particularly related to fish cultivation in land-based or isolated fish cultivation tanks. The invention also includes a process for producing feed for aquatic animals from carbon dioxide emanating from the aquatic animals and being contained in water passed from said aquatic animals and being isolated from said water by ultrasound and reintroduced into a collection of fermenting microorganisms for producing material for said fish feed by fermenting said carbon dioxide. Background for the Invention

When cultivating, breeding or raising fish it is advantageous to use closed cultivation plants because closed plants provide an opportunity to control the conditions for the cultivation such as controlling the pH, regulating the

temperature, regulating and controlling diseases, etc. However, the water in such closed cultivation plants must be monitored for quality. Aquatic organisms eject waste products from their metabolism into the water and it is consequently important to remove such waste products before they influence the water quality negatively in any large extent. One possibility for removing certain waste products is to pass the used water through filters where there may exist microorganisms using the waste products for their own metabolism and thereby removing or transforming such waste products. However, dissolved gases are difficult to remove from the used water, and particularly carbon dioxide is such a gas. Carbon dioxide may be dissolved in water by the gas per se being present in a mechanical solution while also forming carbonic acid (H₂C0₃, HC0₃) through a reaction with the water (C0₂ + H₂0 = > H₂C0₃ = > 2H⁺ + C0₃ ^2"). An excessive amount of dissolved carbon dioxide in the water makes the water unusable to the aquatic organisms because carbon dioxide will replace oxygen in the water having as a consequence that the water will contain too little oxygen to sustain the metabolism of the aquatic animals.

These problems are known from the working of aquariums where it rarely has be taken any steps to remove carbon dioxide but where supplying oxygen to the water often is performed by bubbling air/oxygen into the water. General Disclosure of the Invention

Methods for removing carbon dioxide/gases from water have been known for a long time. One method could be to heat the water for removing dissolved gases, said gases rising to the surface and escaping to the atmosphere above the water. The same will happen if the pressure above the water is reduced. Such methods are, however, time-consuming and do not ensure that all of the dissolved gases are removed. Another method that may be used is to elevate the water and let this water run counter-currently to a stream of air, thereby supplying air to the water while simultaneously removing dissolved carbon dioxide from the used water through gas equilibrium between the supplied air and the dissolved carbon dioxide. Such a method is, however, energy-consuming and does not ensure control of the amount of removed carbon dioxide.

The preferred method for removing carbon dioxide from the used water in the closed fish-cultivation plant according to the present invention is by using ultrasound on all or parts of the used water for removing dissolved gases, inter alia carbon dioxide, from the used water. It is known that using ultrasound in a frequency range above 15000 Hz, e.g. between 15000 and 30000 Hz or more, may force dissolved gases to escape from fluids. Such sound waves will vibrate the fluid/water molecules by creating vibrational apexes and nadirs representing areas of higher and lower pressure. Dissolved gas will collect at the sound wave regions of lower pressure and escape as bubbles. If present, microscopic particles in the fluid/water will work as kernels/foci, easing the formation of gas bubbles. On account of its efficacy and limited cost, the method of removing dissolved gases by ultrasound with a frequency range as stated supra is preferred for removing carbon dioxide from water arriving from closed fish cultivation plants. A different method for reducing/removing carbon dioxide from the used water is to either loop the carbon dioxide-rich water to a vat including micro-organisms using carbon dioxide as a carbon source for their metabolism. Such micro-organisms may be fermenting bacteria, algae or herbal plankton forming organic molecules through photosynthesis or forming organic molecules by using anaerobic reaction paths. The proliferating bacterial mass may be used as a source for a bio-mass for making fish feed.

When using methods removing gases indiscriminately from the used water, oxygen is removed from the water as well as the carbon dioxide. It is thus required either to reintroduce oxygen into the removed water if this water is to be introduced back into the breeding/cultivation tank, or oxygen-rich water may be introduced from a separate source into the breeding/cultivation tank for replacing the amount of removed water. It is in one embodiment of the invention preferred to loop the water into the breeding/cultivation tank after having removed the gases from the water by ultrasound and having introduced oxygen into the water before this water entering into the breeding/cultivation tank.

In a closed breeding/cultivation tank the aquatic animals such as fish, crustaceans, mollusks, etc. are kept in a stationary volume of water in the form of a tank, a container, an excavated or natural chamber etc. The volume containing the stationary amount of water may be of a natural or artificial nature and may be for earning purposes (fish cultivation for subsequent sale of the fish or fish products such as fish oil, fish meal and fish enzymes or corresponding products from different aquatic animals, e.g. crustaceans such as shrimp, crayfish, lobster, crab, or mollusks such as scallops, oysters, etc.). In the context of the present invention "fish breeding and/or cultivation" is meant to include such aquatic animals and organisms. Breeding/cultivation of aquatic animals such as fish may include both fresh and salt water as well as brackish water depending on the preferences of the bred organisms.

The process according to the invention for removing carbon dioxide may be performed on salt as well as fresh water and the treated water may be water for decorative installations such as fresh and salt water aquariums as well. One possible system for breeding/cultivating fish is shown in the enclosed figures, showing an embodiment of a fish breeding/cultivation plant according to the invention.

Fig. 1 shows an embodiment of a possible system/plant for breeding/cultivating aquatic animals (fish) wherein the water is looped and carbon dioxide is removed while oxygen is introduced into the water.

Fig. 2 shows an embodiment of a system for breeding/cultivating aquatic organisms (fish) wherein the system includes electrolysis of water for producing hydrogen and oxygen, the hydrogen being used or discarded, the oxygen being introduced into the breeding/cultivation water and the removed carbon dioxide being transferred to microorganisms for producing fish feed.

In the figures, reference number 1 relates to a breeding/cultivation tank for aquatic organisms (fish) e.g. a fish cultivation plant, an aquarium, etc. containing an amount of water including said aquatic animals (fish). The water from this tank 1 is passed through conduits (pipes, tubes, etc.) 2 to external devices. The water from the tank 1 may in one embodiment be passed to a filter 3 filtering the water for removing waste products such as particles (feed particles, algae, feces, etc.). The direction of the water flow is shown by arrows introduced in the conduits 2 of the figures. From the filter 3 the water may be passed to a holding tank 4, said holding tank optionally being quipped with a generator 5 for ultrasound. Alternatively the water from the breeding/cultivation tank 1 may be passed directly to the ultrasound tank 4 without passing through the filter 3. Yet another alternative may be to introduce the filter 3 after the ultrasound tank 4 (not shown).

After the water has been treated with ultrasound so that the dissolved gases in the water have been removed, the gas-poor water is in one embodiment passed to a gas-introduction tank or chamber 6. In this gas-introducing device or chamber 6 the oxygen-poor water is supplied with oxygen or an oxygen-rich gas such as air or pure oxygen gas. In one embodiment the pressure in the gas-supplying tank or chamber 6 may be larger than atmospheric pressure for increasing the introduction of oxygen into the water. The tank or chamber 6 may have an internal structure for increasing its internal surface to ease the addition of oxygen to the water. Such internal structures may be e.g. glass beads or filaments or both. Oxygen under pressure will provide an adequate admixing into the water. The selection of pressure may be determined by the person skilled in the art by observing tables relating to the air-carrying capacity of water at specific pressures and temperatures combined with the dwelling time of the water in the optionally pressurized tank or chamber 6.

By blowing oxygen into the water instead of large amounts of air, the problem with nitrogen-containing compounds is reduced, but to the extent that nitrogen has to be removed, this is done as in the existing systems, only more simplified.

From the gas-supplying tower/chamber/tank 6 the oxygen-rich water is

reintroduced into the cultivation/breeding tank 1.

The water arriving to the breeding/cultivation tank 1 from the gas-introduction tower/chamber/tank 6 may in an alternative embodiment be added medications or may be filtered for removing possible microorganisms that may be harmful to the organisms in the breeding/cultivation tank 1 (not shown).

In yet another embodiment the water in the gas-removal tank 4 may be treated with ultrasound from more than one ultrasound transducer 5. In such an embodiment the ultrasound waves may be supplied in the form of ultrasound waves that may combine in the form of resonance to amplify the effect of the ultrasound to drive entrained gas from the water. By using more than one ultrasound transducer 5, one or more of the number of transducers may supply ultrasound at different frequencies within the interval of relevant frequencies and optionally at different wavelengths. Also the amplitudes of the ultrasound waves supplied by the ultrasound transducers 5 may be equal or different from each other.

The conduits/tubes/pipelines 2 for the transport of water may each or all be equipped with one or more valves 7, optionally of a type that may be regulated, for controlling the water flow in the system. In one particular embodiment shown in Fig. 2, the system according to the invention includes a tank 8 containing a microorganism culture or a microorganism mix culture for fermenting carbon dioxide-rich water into a biomass by culturing said microorganisms and harvesting said biomass for using it as a starting material for making e.g. fish feed. The microorganisms may be of an anaerobic or aerobic type or of a facultative anaerobic type, or may comprise plankton for harvesting the carbon dioxide entrained in the used water arriving from the separating vat 4. In the system according to the present invention the utilization of the introduced energy in the form of initial fish feed and the energy for sustaining the

microorganism culture is optimized by the production of raw material (fish and/or other aquatic animals) as well as fish feed to be re-used for feeding the aquatic animals in the system.

In an alternative embodiment of the system according to the invention, oxygen is generated by electrolysis of water, producing oxygen by the equation 2H₂0 = > 2H₂ + 0₂. Such an embodiment is shown in Figure 2. Here a separate container/tank 9 is included in the system wherein electrolysis of the water is performed. Electric energy is supplied to electrodes located in the container/tank 9 and oxygen and hydrogen is collected at the respective electrodes. The oxygen may be passed to the oxygen-entraining tank 6 or may alternatively be transported directly to the fish-farming/cultivating container/tank 1 to be bubbled into the water at this location. The hydrogen produced by the water electrolysis may be vented to the atmosphere or may be collected for subsequent use as a raw material for different chemical reactions. One such alternative may be to combine the hydrogen with the carbon dioxide separated from the water for producing methane/methanol or other organic compounds. This methane may be further reacted with the oxygen through a known process for producing fish feed also being performed with a

microorganism/bacterial culture. The inventive concept here being that the carbon dioxide originates from aquaculture, e.g. through the breeding/cultivation of fish.

As mentioned supra, an alternative way to utilize carbon dioxide originating from the culture of aquatic organisms (fish) is to pass the carbon dioxide (alternatively as a concentrated water-solution or bubbled directly into the fermenting

microorganism/bacterial culture) directly into a microorganism/bacterial culture together with oxygen without using methane as an intermediate. In this alternative the inventive concept is that the carbon dioxide originates from the aquaculture.

In Fig. 2 the line 11 illustrates the return of the fermented materials from the fermentation chamber 8 to the breeding/cultivation chamber/tank 1 as feed for the aquatic organisms (fish).

Claims

C l a i m s

1. The use of ultrasound for removing carbon dioxide from water originating from a container/tank (1) for breeding/cultivating aquatic organisms.

2. The use according to claim 1, wherein the container/tank for breeding/ cultivating aquatic organisms is part of a stationary fish breeding/cultivating system.

3. The use according to claim 1 or 2, wherein the container/tank (1) for breeding/cultivating aquatic animals is part of a land-based system for breeding/ cultivating fish.

4. A system for breeding/cultivating aquatic animals comprising at least one vessel/container/tank (1) for water to accommodate the aquatic animals, said vessel/container/tank (1) being connected to additional vessels/containers/tanks (4,6) in the system by a number of conduits/pipes/tubes (2), wherein one of the vessels/containers/tanks (4) is equipped with at least one ultrasound transducer (5) for generating ultrasound to separate gases entrained in water from the breeding/cultivation container (1) by subjecting said water to ultrasound waves, and wherein the ultrasound-treated water is passed to a container/tank (6) for introducing oxygen into the treated water before passing said water back to the breeding/cultivation vessel/container/tank (1).

5. System according to claim 4, comprising at least one container/tank (8) including microorganisms, wherein carbon dioxide separated from the water in the ultrasound-treating container/tank (4) is passed to a container/tank (8) including microorganisms using said carbon dioxide as a source for carbon in their metabolism.

6. System according to claim 4 or claim 5, comprising at least one filter (3) for filtering water from the breeding/cultivation tank (1) and/or from the ultrasound treatment container/tank (4).

7. System according to claim 6, wherein the water is treated with ultrasound prior to its entering the filter (3).

8. System according to claim 6, wherein the water is treated with ultrasound subsequently from its exit from the filter (3).

9. System according to any of the claims 4 - 8, wherein there are located more than one ultrasound generator (5) in connection with the treatment tank (4).

10. System according to any of the claims 4 - 9, wherein the ultrasound generator(s) (5) supply ultrasound at frequencies within the range 15000 Hz or more, preferably within the range 15000 to 30000 Hz or more.

11. System according to claim 10, including more than one ultrasound generator and wherein the ultrasound generators provide ultrasound at different frequencies.