METHOD AND DEVICE FOR PRODUCING A LIQUID CONTAINING A HIGH CONCENTRATION OF TINIEST BUBBLE FILLER

Description

[0001] The invention relates to a method for producing a liquid containing a high concentration of tiny bubbles, in which a liquid is passed from a first reservoir via a nanobubble generator into a second reservoir, and to a device for producing a liquid containing a high concentration of tiny bubbles according to this method.

[0002] Liquids containing tiny bubbles are used in various fields, such as in medicine as ultrasound contrast agents or in the food and beverage industry, particularly for cleaning. For this purpose, it is necessary to generate these bubbles efficiently and in high concentrations.

[0003] To generally generate bubbles in liquids, a gas is introduced into the liquid, using several different methods. These methods include hydrodynamic, acoustic, optical, and particle cavitation. For generating the smallest bubbles—that is, particularly small, fine, or ultrafine bubbles—a hydrodynamic method is frequently employed because it is relatively inexpensive and effective. This method relies on introducing a gas into a moving liquid and simultaneously applying a force to the gas. This force can be based on circulation—gas-water circulation—or on pressure—gas-water decompression. One of these two methods is typically used, especially for generating the smallest bubbles, i.e., tiny gas cavities in the water to further improve the gas content.An increase in the amount of dissolved gas in the liquid is usually achieved through supersaturation.

[0004] Numerous different methods and devices for generating minute bubbles in the nanometer or micrometer range have already been proposed. Existing methods generate such minute bubbles in a tank under high pressure or use a pump to circulate the liquid.

[0005] KR 101894870 B1 discloses a device that produces minute bubbles by adding gas to water in a dissolving tank. A motor is used for the necessary water circulation. Such a motor operates with mechanical, moving parts and can therefore adversely lead to the introduction of foreign particles.

[0006] Tiny bubbles are particularly needed for food products, especially carbonated beverages. Such a process is disclosed in EP 2 213 180 A1. In this process, deionized water is cooled, and then a pump is activated to circulate the water. A nanobubble generator is used to simultaneously add carbon dioxide to this water. However, to ensure a constant temperature, temperature monitoring and adjustments using a cooling jacket or heat exchanger are necessary during the process.

[0007] KR 20200025081 A discloses a process for producing highly concentrated hydrogen water. In this process, water and hydrogen gas are combined using a mixing device and subsequently fed into a tank. Inside the tank, the hydrogen gas is added to the water under high pressure. This high pressure is generated by a pump unit. The water with the added hydrogen gas is then transferred to another container and stored there. During the process, the temperature is between 20 and 25 °C. The use of the pump causes the liquid to heat up, which is a disadvantage. When the liquid cools down again, gas that was already dissolved in the liquid in the form of fine bubbles is released. This reduces the concentration of the bubbles, thus decreasing the efficiency of the process.

[0008] A method for generating a high concentration of fine bubbles with a size of approximately 1 µm is described in EP 3 241 604 A1. In this method, a liquid already containing a certain concentration of fine bubbles is heated and evaporated by further reducing the pressure. A high concentration of fine bubbles is obtained through volume reduction.

[0009] Heating the liquid, however, negatively reduces the amount of gas that can be physically dissolved in it. An alternative method is described in EP 3 231 502 A1. This method uses a filter that is impermeable to some of the bubbles. This also allows for a high concentration to be achieved. It is also possible to combine these two methods, as described in EP 2 946 829 AI. However, filtration is not feasible for all sizes of very small bubbles, and additional energy must be expended to carry out the filtration process.

[0010] Using known methods from the prior art, minute bubbles can be generated in a liquid at concentrations of up to approximately 10⁸ ml⁻¹. However, higher concentrations are required to expand the range of applications, particularly in the fields of medicine, biology, and chemistry, in order to achieve improved efficacy.

[0011] US patent 2015 / 0 343 399 A1 discloses a nanobubble generator with a pressurized gas supply to a container. The gas is also supplied to the headspace of the container, and the liquid is recirculated until a predetermined nanobubble concentration is reached. The use of an ultrasonic vibrator is proposed, and high nanobubble concentrations are achieved.

[0012] US 10 265 266 B2 discloses a method according to the preamble of claim 1 and a device according to the preamble of claim 9.

[0013] However, the use of pumps, due to the use of mechanical, moving components, always carries the risk of unwanted introduction of foreign particles.

[0014] The invention is therefore based on the objective of providing higher concentrations of tiny bubbles in liquids, increasing the efficiency of the process and improving the quality of the liquid containing tiny bubbles.

[0015] The problem is solved by an object with the features according to the independent patent claims. Further developments are specified in the dependent claims.

[0016] The problem is solved in particular by a method according to claim 1 for producing a liquid containing a high concentration of minute bubbles, which comprises the following steps: a) Supplying a liquid in a first sealed reservoir. b) Pressurizing the liquid from the first reservoir into a nanobubble generator and then into a second reservoir, generating tiny bubbles as the liquid flows through the nanobubble generator. The liquid is passed through tubular connections between the first reservoir and the nanobubble generator, as well as between the nanobubble generator and the second reservoir. c) Passing the liquid from the second reservoir back into the first reservoir. Again, the liquid is passed through tubular connections. d) Repeating steps b) and c) as many times as necessary to achieve the specified concentration of tiny bubbles in the liquid.

[0017] According to the invention, the force for moving the liquid is not provided by a pump, but rather the liquid is moved by a thrust force based on another existing fluid or a moving thrust element. This thrust force is based on a gas pressure difference in the reservoirs.

[0018] The pressure in the reservoir from which the liquid is drawn off—that is, the first reservoir in step b and the second reservoir in step c)—must necessarily be higher than the pressure in the reservoir into which the liquid is fed—the second reservoir during step b) and the first reservoir during step c). This pressure difference can be generated in various ways. For example, it can be created by hydrostatic pressure, gas pressure, or by reducing the reservoir volume. Preferably, the pressure difference between the reservoirs is greater than 2 bar.

[0019] An advantage of the method according to the invention is that by dispensing with a pump, adverse heating of the liquid is avoided. This advantageously allows a higher bubble concentration to be achieved.

[0020] In one possible embodiment of the method, a first piston is arranged as a thrust element within the first reservoir, and a second piston is arranged as a thrust element within the second reservoir. The pistons are configured such that the force required to move the liquid is based on a reduction in volume within the reservoirs due to the movement of one of the pistons.

[0021] The thrust element is thus designed as a piston configured to reduce the volume of one of the reservoirs. A first piston is located inside the first reservoir and can reduce its volume. This allows the liquid inside the first reservoir to be pushed towards the second reservoir during step b). A second piston is located inside the second reservoir and can reduce its volume. This pushes the liquid inside the second reservoir towards the first reservoir during step c).

[0022] To achieve a reduction in volume, the piston seals the reservoir so that no liquid can flow past it. This creates a sealed connection between the piston and the reservoir. The volume reduction provides the force that pushes the liquid from the first reservoir to the second reservoir and / or from the second reservoir to the first. The volume reduction within the reservoir is induced by the movement of one of the pistons. Using a single piston to move the liquid is advantageously possible without having to introduce any additional fluid into either reservoir. The process can therefore be carried out in a closed system, making automation easily achievable.

[0023] Preferably, the thrust is provided by a gas as an additional fluid. The gas is arranged in the container, which is designed as a pressurized gas unit. During step b), the gas flows at a certain pressure from a pressurized gas unit connected to the first and second reservoirs via tubular connections into the first reservoir, and during step c), into the second reservoir. The force for moving the liquid is provided by the gas pressure.

[0024] The gas flowing from the pressurized gas unit builds up pressure, which drives the liquid during steps b) and c). The force to move the liquid through the nanobubble generator is thus provided by the gas pressure.

[0025] For the purposes of the invention, a pressurized gas unit is any device which generates gas under increased pressure, in particular a gas compressor or any enclosed container which contains gas under increased pressure, for example a gas cylinder.

[0026] A nanobubble generator is a device for generating tiny bubbles in a liquid. Gas is supplied to the nanobubble generator through a gas inlet and liquid simultaneously through a liquid inlet. Alternatively, a single inlet can be used for both the liquid and the gas, functioning as a combined gas and liquid inlet. Within the nanobubble generator, tiny bubbles are generated by applying a force to the liquid. The liquid containing these tiny bubbles then exits the nanobubble generator through a liquid outlet. Suitable nanobubble generators utilize a hydrodynamic method in which the gas dissolves in the pressurized liquid.The liquid containing the dissolved gas is then introduced into a region where the pressure is significantly reduced, for example by increasing the volume. This causes a large number of bubbles, particularly tiny bubbles, to form during the process of releasing the gas from the liquid. A nanobubble generator is therefore a component used to produce a liquid containing these tiny bubbles.

[0027] For the purposes of the invention, a bubble is a gaseous body within a liquid. The smallest bubbles are those, according to the standard ISO 20480-1:2017, with a diameter between 10 nm and 100 µm, preferably those with a diameter between 10 nm and 1000 nm. A distinction is made here between fine bubbles, also referred to as microbubbles or fine bubbles, with a diameter of 1 µm to 100 µm, and ultrafine bubbles, also referred to as nanobubbles or ultrafine bubbles, with a diameter of 10 nm to 1000 nm.

[0028] To provide sufficient pressure within the nanobubble generator, it is necessary that the liquid be introduced into the nanobubble generator under pressure. According to the invention, the force required for this is generated by means of a gas flowing under pressure from a pressurized gas unit.

[0029] According to one possible design, the pressure in the second reservoir is lower and the pressure is only increased again when the first reservoir is refilled.

[0030] Advantageously, this method requires no moving parts, thus preventing contamination by foreign particles. In this process, the liquid is presaturated with the gas, so that the gas in the nanobubble generator does not dissolve in the liquid, but is instead used to generate bubbles. Since no additional energy is supplied to the liquid, its temperature remains unchanged; it is not heated. This improves both the efficiency of the process and the achievable bubble concentration. Concentrations of 10⁹ ml⁻¹ and higher can be achieved. The concentration increases with the number of process cycles performed.

[0031] In one possible embodiment of the method, to reduce an elevated gas pressure, gas is released from the first reservoir after step b) via a valve connected to the first reservoir and / or from the second reservoir after step c) via a valve connected to the second reservoir. A reservoir is preferably connected to a valve via tubular connections. This advantageously reduces excessively high gas pressure, thereby preventing hazards caused by excessive gas pressure.

[0032] Preferably, the gas pressure is between 2 bar and 20 bar, particularly preferably between 3 bar and 10 bar. The maximum gas pressure depends on the design of the device for generating the smallest bubbles.

[0033] Another suitable option is to reduce the gas pressure not after each repetition, but only every 2 to 5 repetitions. This advantageously reduces the duration of the procedure.

[0034] One possible variant involves measuring the nanobubble concentration after step b) and / or step c). Here, too, measurements can optionally be taken only every 2 to 5 repetitions. Another suitable approach is to rely on empirical data, i.e., previous measurements of the nanobubble concentration from earlier processes, and thus control the number of repetitions of the procedure, thereby eliminating the need for measurements altogether. The inventive method is advantageously reproducible, so that the level of the nanobubble concentration can be determined by the number of repetitions of the procedure.

[0035] Preferably, in this method, during step c), the liquid from the second reservoir is passed through the nanobubble generator into the first reservoir. As the liquid flows through the nanobubble generator, tiny bubbles are created in it. Thus, the smallest bubbles are generated in the liquid as it flows through the nanobubble generator.

[0036] An advantageous embodiment of the method provides that valves are installed between the pressurized gas unit and the first reservoir, as well as between the pressurized gas unit and the second reservoir, to switch between steps b) and c). For the purposes of the invention, valves are components for controlling the flow of a liquid or gas through a pipe or tubular connection. A valve can completely shut off the flow of the fluid, i.e., the liquid or gas.

[0037] When the valve between the pressurized gas unit and the first reservoir is open and the valve between the pressurized gas unit and the second reservoir is closed, the gas flows into the first reservoir and allows step b) to be carried out. It is then possible to proceed to step c), in which the valve between the pressurized gas unit and the second reservoir is opened and the valve between the pressurized gas unit and the first reservoir is closed.

[0038] A valve is positioned within the tubular connection between the pressurized gas unit and the first reservoir in such a way that the flow of gas from the pressurized gas unit into the first reservoir is either permitted or prevented by the valve. A second valve is positioned within the tubular connection between the pressurized gas unit and the second reservoir. This second valve can either allow or block the flow of gas from the pressurized gas unit into the second reservoir.

[0039] In one embodiment of the invention, the driving gas, which provides the force for moving the liquid, is used to generate minute bubbles in the nanobubble generator. This gas flows under pressure from the pressurized gas unit. Alternatively, a gas is used that is supplied to the nanobubble generator via a separate gas supply. Different gases can be supplied simultaneously or sequentially. In particular, it is also possible to use both the driving gas and a separately supplied gas simultaneously for generating the minute bubbles.

[0040] The problem is also solved by a device according to claim 9 for generating the smallest bubbles according to the inventive method.

[0041] The device has the following features: two enclosed reservoirs, a nanobubble generator with a liquid inlet opening and a liquid outlet opening, wherein the liquid inlet opening of the nanobubble generator is connected to the first reservoir via tubular connections and the liquid outlet opening of the nanobubble generator is connected to the second reservoir via tubular connections and at least one valve arranged between the second reservoir and the nanobubble generator, and a container containing another fluid or a thrust element arranged in one of the reservoirs.

[0042] The additional fluid or the thrust element is arranged and configured in such a way that the liquid can be pushed through the nanobubble generator by means of a thrust force.

[0043] Preferably, the pusher element is designed as a piston within the first reservoir, which is configured to reduce the volume in the first reservoir. The liquid can be pushed from the first reservoir to the second reservoir by the piston.

[0044] Preferably, the container is a pressurized gas unit, and a gas is arranged as a further fluid within the pressurized gas unit. The two sealed reservoirs are connected to the pressurized gas unit via tubular connections and valves. Furthermore, the device includes a nanobubble generator with a liquid inlet and a liquid outlet. The force required to move the liquid through the nanobubble generator is provided by the gas pressure of the gas flowing from the pressurized gas unit into one of the reservoirs.

[0045] Particularly preferred is a first piston arranged as a thrust element in the first reservoir and a second piston arranged as a thrust element in the second reservoir.

[0046] The device according to the invention preferably comprises two sealed reservoirs, which are connected to a pressurized gas unit via tubular connections and valves, and a nanobubble generator with a liquid inlet and a liquid outlet. The liquid inlet of the nanobubble generator is connected to the first reservoir via tubular connections, and the liquid outlet of the nanobubble generator is connected to the second reservoir via tubular connections and at least one valve arranged between the second reservoir and the nanobubble generator. The force for moving the liquid through the nanobubble generator is provided by the gas pressure of the gas flowing from the pressurized gas unit into one of the reservoirs.

[0047] The force for moving the liquid does not result from operating a pump. Therefore, in this arrangement, preferably no pump is located outside the nanobubble generator. The energy for moving the liquid is provided by the gas compressed in the pressurized gas unit. According to the invention, the nanobubble generator is connected to a separate gas reservoir via a gas inlet opening. The gas from the separate gas reservoir is then used within the nanobubble generator to generate minute bubbles in the liquid. The gas used to move the liquid is used to generate these minute bubbles by means of the nanobubble generator. Particularly preferably, both methods are combined; that is, both the gas used to move the liquid and the gas from a separate gas reservoir are utilized.In an advantageous embodiment, the nanobubble generator is connected to two or more separate gas reservoirs, which preferably contain different gases.

[0048] In an advantageous embodiment, tubular connections and a valve are arranged between the nanobubble generator and the two reservoirs in such a way that the liquid from the second reservoir can flow into the first reservoir via the nanobubble generator.

[0049] In an advantageous embodiment, the device comprises a first piston as a thrust element, which is arranged in the first reservoir. Furthermore, the device comprises a second piston, which is arranged in the second reservoir. The thrust force is advantageously provided by the pistons, which can be moved to reduce the volume in the reservoir. Preferably, the device includes a measuring device for determining the nanobubble concentration. This advantageously enables control of the nanobubble concentration, thereby allowing for precise adjustment of the nanobubble concentration.

[0050] Furthermore, in an advantageous embodiment, the device includes a control unit that automates the process. Optionally, the process can also be carried out by manually actuating the valves.

[0051] Preferably, the device includes means adapted to perform the steps of the method according to the invention. Advantageously, the method can then be implemented automatically.

[0052] Another aspect of the invention relates to a computer program product according to claim 14, which comprises instructions that cause this device to execute the process steps according to the invention. A further aspect of the invention relates to a computer-readable medium on which the computer program product according to the invention is stored.

[0053] The present method, by design, can generate a high concentration of tiny bubbles. It eliminates the need for a pump to generate the force required to move the liquid, thus preventing any increase in the liquid's temperature. Instead, only gas pressure is used to move the liquid between the reservoirs, ensuring a constant temperature. In essence, a liquid is placed in a reservoir, and a high-pressure gas is used to move the liquid, thus driving the liquid flow.

[0054] According to the invention, the device for generating minute bubbles according to the inventive method comprises at least two sealed reservoirs and a nanobubble generator with a liquid inlet and a liquid outlet. The two reservoirs are each connected to the nanobubble generator via tubular connections, with the first reservoir connected to the liquid inlet of the nanobubble generator and the second reservoir to the liquid outlet of the nanobubble generator.A pressurized gas unit is connected to the first and second reservoirs via tubular connections and valves, so that the force for moving the liquid through the nanobubble generator is provided by a pressure difference in the containers, i.e., in particular by a gas under high pressure, preferably by the gas pressure of the gas flowing from a pressurized gas unit connected to one of the reservoirs into the corresponding reservoir, or by a reduced volume of one of the reservoirs. To increase the concentration of the smallest bubbles, the liquid can be returned to the first reservoir, and the steps described above can be repeated as often as desired.

[0055] Conceptually, a further aspect of the invention relates to a device for carrying out the described method, wherein the device comprises two reservoirs, a nanobubble generator and a pressurized gas unit containing a gas under high pressure, or a device which is arranged and configured in such a way that a volume reduction in the reservoirs is possible by means of this.

[0056] Further details, features, and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1: an arrangement for generating tiny bubbles, in which a liquid flows from a first reservoir into a second reservoir and Fig. 2: the arrangement made of Fig. 1 , in which the liquid flows from the second reservoir into the first reservoir.

[0057] In Fig. 1Figure 1 shows an arrangement for the improved generation of minute bubbles in a liquid. A central element is the gas in the pressurized gas unit 2. The energy generated by the overpressure of the gas in the pressurized gas unit 2 is used to move both the gas and the liquid through lines 3, i.e., tubular connections. Nine valves 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, and 4.9 are arranged to control the flow of the gas and liquid.

[0058] To generate the smallest bubbles, liquid is first introduced into a first reservoir 5. Gas from the pressurized gas unit 2 is then introduced into the first reservoir 5. To generate the smallest bubbles, the liquid-gas mixture present in the first reservoir 5 is introduced into the second reservoir 6, passing through the nanobubble generator 7. This induces tiny bubbles in the liquid. Once a sufficient quantity of the liquid-gas mixture has been introduced into the second reservoir 6, the valves 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, and 4.9 are adjusted as described in Fig. 2 The mixture of liquid and gas is shown to be directed back into the first reservoir 5, passing through the nanobubble generator 7 again.

[0059] To allow the liquid to flow into the first reservoir 5, valve 4.1 is opened, enabling the liquid to enter through this valve. Meanwhile, valves 4.2 and 4.3 are set to position A, and valves 4.5 and 4.7 are closed. Preferably, up to 5 liters or up to 20 liters of liquid are filled through valve 4.1. Optionally, higher volumes can also be filled in a modified configuration. Valve 4.1 can then be closed.

[0060] To supply gas to the first reservoir 5, a pressurized gas unit 2, such as a gas cylinder, is connected to the port adjacent to valve 4.9, and a pressurized gas unit valve, such as a gas cylinder tap, is opened. The desired pressure, for example 3 bar, is set at valve 4.9.

[0061] The liquid is transferred from the first reservoir 5, via the nanobubble generator 7, to the second reservoir 6. For this, valve 4.2 is set to position B and valve 4.3 to position A. It is also important to set valves 4.4 and 4.6 to position A, shown here pointing upwards. When the pressurized gas unit 2 is opened via the pressurized gas unit valve and the nanobubble generator 7 is simultaneously started, the liquid is drawn into the nanobubble generator 7 by the incoming gas from the first reservoir 5. Bubbles are then generated in the liquid by the incoming gas, after which the liquid is drawn into the second reservoir 6. Once a sufficient quantity of liquid has reached the second reservoir 6, the nanobubble generator 7 can be stopped and the pressurized gas unit 2 closed again.The amount of liquid in the second reservoir 6 can be determined using any level indicator. To complete the process, valve 4.2 is set to position A, taking into account the pressure release. This allows the increased gas pressure to be reduced and some of the gas to escape through valve 4.2.

[0062] To increase the bubble concentration in the fluid, the fluid can be treated as described in Fig. 2The liquid is shown being directed from the second reservoir 6 back into the first reservoir 5. To increase efficiency, the arrangement is preferably designed such that the liquid also passes through the nanobubble generator 7. For this purpose, valve 4.2 is left in position A and valve 4.3 is now set to position B, so that a connection exists between the second reservoir 6 and the pressurized gas unit. Valves 4.4 and 4.6 are then set to position B, shown here pointing downwards. The pressurized gas unit 2 can then be opened and the nanobubble generator 7 started simultaneously. The energy of the high-pressure gas from the pressurized gas unit 2 causes the outgoing gas to flow into the second reservoir 6, thereby directing the liquid towards valve 4.6. The liquid then flows past valve 4.6, which is set to position B, and through valve 4.3, which is also set to position B.The liquid flows through pipes 3 and back into the nanobubble generator 7, then through valve 4.6, which is set to position B. The liquid then flows back into the first reservoir 5. Once a sufficient quantity of liquid has been transferred to the first reservoir 5, the nanobubble generator 7 can be stopped and the pressurized gas unit 2 closed. A level indicator can also be used to determine the quantity of liquid in the first reservoir 5. For example, the pipes 3 adjacent to the respective reservoir 5, 6, or the reservoir 5, 6 itself, could be made at least partially of a transparent material or have a viewing window, allowing the liquid level to be observed through this section or the inserted viewing window.

[0063] Valve 4.3 can be returned to position A, observing the pressure release, so that no further gas flows in. Valve 4.3 can also be used to reduce increased gas pressure. For this purpose, some of the gas from the second reservoir 6 flows out through valve 4.3. The steps described above can be repeated as often as desired: that is, the liquid, for example water, is passed from the first reservoir 5 to the second reservoir 6 via the nanobubble generator 7, and then the liquid is passed from the second reservoir 6 to the first reservoir 5 via the nanobubble generator 7.

[0064] Valves 4.5 and 4.7 are used to remove the liquid from the arrangement 1 and thus empty the arrangement 1. Reference symbol list

[0065] 1. Arrangement 2. Compressed gas unit, gas cylinder, gas compressor 3. Pipe, tubular connection, tubular line 4.1. First valve 4.2. Second valve 4.3. Third valve 4.4. Fourth valve 4.5. Fifth valve 4.6. Sixth valve 4.7. Seventh valve 4.8. Eighth valve 4.9. Ninth valve 5. First container, first reservoir 6. Second container, second reservoir 7. Nanobubble generator

Claims

1. Method for producing a liquid containing a very high concentration of extremely small bubbles, comprising the following steps: a) providing a liquid in a first sealed reservoir (5), b) conducting the liquid under pressure from the first reservoir (5) into a nanobubble generator (7) and onward into a second reservoir (6), wherein extremely small bubbles are generated in the liquid as it flows through the nanobubble generator (7), c) conducting the liquid from the second reservoir (6) into the first reservoir (5), d) repeating steps b) and c) as often as necessary to achieve the specified concentration of extremely small bubbles in the liquid, wherein the force for moving the liquid is not provided by a pump but rather by a thrust force resulting from a further fluid or a thrust element, characterised in that extremely small bubbles are generated in the nanobubble generator (7) using the gas that provides the force for moving the liquid and / or gas supplied via a separate gas supply.

2. Method according to claim 1, characterised in that the thrust force is provided as further fluid by a gas, wherein the gas flows, during step b), at a gas pressure out of a compressed gas unit (2) connected to the first reservoir (5) and the second reservoir (6) via tubular connections (3) into the first reservoir (5) and, during step c), into the second reservoir (6), and the force for moving the liquid is provided by the gas pressure.

3. Method according to claim 1, characterised in that a first piston is arranged as first thrust element within the first reservoir (5) and a second piston is arranged as second thrust element within the second reservoir (6), wherein the first piston and the second piston are configured in such a way that the force for moving the liquid is based on a volume reduction within the reservoirs (5, 6) due to a movement of the first or second piston.

4. Method according to claim 3, characterised in that, after step b), gas is discharged out of the first reservoir (5) via a valve (4.2) connected to the first reservoir (5) in order to reduce an elevated gas pressure.

5. Method according to claim 3 or 4, characterised in that, after step c), gas is discharged out of the second reservoir (6) via a valve (4.3) connected to the second reservoir (6) in order to reduce an elevated gas pressure.

6. Method according to one of claims 1 to 5, characterised in that the nanobubble concentration is measured after step b) and / or after step c).

7. Method according to one of claims 1 to 6, characterised in that, during step c), the liquid is conducted from the second reservoir (6) into the first reservoir (5) via the nanobubble generator (7), wherein extremely small bubbles are generated in the liquid as it flows through the nanobubble generator (7).

8. Method according to one of claims 1 to 7, characterised in that valves (4.2, 4.3) arranged between the compressed gas unit (2) and the first reservoir (5) and between the compressed gas unit (2) and the second reservoir (6) are switched in order to alternate between steps b) and c).

9. Device for generating extremely small bubbles according to a method according to claims 1 to 8, having • two sealed reservoirs (5, 6), • a nanobubble generator (7) with a liquid inlet and a liquid outlet, wherein the liquid inlet of the nanobubble generator (7) is connected to the first reservoir (5) via tubular connections (3), and the liquid outlet of the nanobubble generator (7) is connected to the second reservoir (6) via tubular connections (3) and at least one valve (4.6) arranged between the second reservoir (6) and the nanobubble generator (7), and • a container containing a further fluid or a thrust element arranged in one of the reservoirs, wherein the further fluid or the thrust element are arranged and configured in such a way that the liquid can be pushed through the nanobubble generator (7) by means of a thrust force, characterised in that the nanobubble generator (7) is connected to a separate gas reservoir via a gas inlet.

10. Device according to claim 9, characterised: (i) in that the container is a compressed gas unit and a gas is present as further fluid within the compressed gas unit, wherein the two sealed reservoirs (5, 6) are connected to the compressed gas unit (2) via tubular connections (3) and valves (4.2, 4.3), wherein the force for moving the liquid through the nanobubble generator (7) is provided by the gas pressure of the gas flowing out of the compressed gas unit (2) into one of the reservoirs (5, 6), and / or (ii) in that tubular connections (3) and in each case one valve (4.4, 4.6) are arranged between the nanobubble generator (7) and the two reservoirs (5, 6) in such a way that the liquid can flow out of the second reservoir (6) via the nanobubble generator (7) into the first reservoir (5).

11. Device according to claim 9, characterised in that a first piston is arranged as thrust element in the first reservoir (5) and a second piston is arranged as thrust element in the second reservoir (6).

12. Device according to one of claims 9 to 11, characterised in that the device has measuring equipment for determining the nanobubble concentration and / or a control unit.

13. Device according to one of claims 9 to 11, having means which are designed to perform the steps of the method according to one of claims 1 to 8.

14. Computer program product, comprising commands that make the device according to claim 12 perform the method steps according to one of claims 1 to 8.

15. Computer-readable medium, on which the computer program product according to claim 14 is saved.