Apparatus and method of producing nanobubbles

Abstract

The present invention relates to an apparatus for generating nanobubbles in an aqueous medium. Preferably, the aqueous medium may be any media comprising water such as liquid water including any mixture of water together with other media including liquids, gases and / or solids. Advantageously, the apparatus for generating nanobubbles in the aqueous medium does not require provision of any external source of gas. In another aspect, the present invention provides a method for generating nanobubbles comprising oxygen in liquid water comprising dissolved oxygen. In another aspect, the present invention provides a method for generating nanobubbles comprising a significantly higher concentration of oxygen than ambient air in liquid water comprising dissolved oxygen and dissolved nitrogen arising from prior dissolution of ambient air in the water. In another aspect, the present invention provides a method for generating nanobubbles comprising any gas in liquid water comprising that dissolved gas. In another aspect, the present invention provides a method for generating nanobubbles of a particular size distribution and concentration comprising any gas in liquid water comprising that dissolved gas. In another aspect, the present invention provides a method for electronically controlling the size distribution and concentration of nanobubbles generated by the apparatus.

Description

Apparatus and Method of Producing Nanobubbles

[0001] The present invention relates to an apparatus and method for nanobubble generation. In particular, but not exclusively, the present disclosure relates to methods for generating nanobubbles by passing water comprising dissolved gases through an electric field but without electrolysis occurring. More particularly, the present disclosure relates to methods of controlling the type of nanobubbles generated, including controlling the size of the nanobubbles produced so that the nanobubbles generated for particular uses / applications can be optimised.BACKGROUND

[0002] Nanobubbles are bubbles in the nanometre size range, also called ‘ultra-fine’ bubbles, that have a number of properties of value in industries and systems involving treatment, use, storage or handling of aqueous media. They have a high surface-to- volume ratio resulting in a high rate of gas transfer from bubble to water. They are neutrally buoyant and can persist in aqueous media for days to weeks acting as a reservoir for the gas(es) they comprise. Nanobubbles are highly negatively charged with zeta potential below -10 mV which significantly lowers the probability of their coalescing into bigger bubbles. The low zeta potential also has the effect of attracting positively charged suspended particles and ions. Nanobubbles are observed to be more resistant to breakage than larger sized bubbles, possibly due to the complex nature of their surface layers arising from the very high curvature. Due to high internal gas pressure, they generate high concentrations of reactive oxygen species (ROS) when they collapse. They will also penetrate into material adhered to surfaces producing a scouring-type action that can be used for surface cleaning. Typical gases used in nanobubbles include air, oxygen, carbon dioxide, hydrogen and ozone.

[0003] The value of nanobubbles is increasingly being recognised in industries including agriculture, aquaculture, food and beverage production, water purification and wastewater treatment, environmental remediation, industrial cleaning and disinfection, oil & gas production and many others. In irrigated agriculture, nanobubbles comprising oxygen have been shown to boost plant growth by providing a source of oxygen close to root cells thereby enhancing plant root respiration, and by picking up and transporting nutrient particles from solution into plant roots, and as a consequence, shortening time to harvest and reducing the amount of fertiliser required. Their ability to capture positively charged particles, due to their negative surface charge, also has application in separation of suspended solids in water clarification or fine materials in mineral processing. Nanobubbles comprising oxygen, carbon dioxide or ozone are employed to clean biofilm from pipes and tanks and as a disinfecting agent by increasing the oxidation reductionpotential of the cleaning water. Additionally, when they collapse close to the exterior cell walls of plant pathogens, viruses, algae and biofilm, they will damage the cells and destroy the organism. Nanobubbles comprising oxygen are used to oxygenate water with a high oxygen transfer efficiency in nanobubble water oxygenation equipment. They are used to provide an oxygen buffer in aquaculture, to prevent algal growth in water storage tanks and to boost the breakdown of organic matter by aerobic microbes in biological water and wastewater treatment. Nanobubbles comprising ozone increase the efficiency of ozonation processes by extending the lifetime and reach of the treated water. These examples are indicative of the extensive uses of nanobubbles. Due to their particular properties nanobubbles are likely to be of benefit for any industrial process involving the dissolution, transport and storage of gases in water and chemical reaction or physical interaction with water and substances present in the water.

[0004] Significant amounts of research have been carried out to understand the physical properties of nanobubbles and methods of producing nanobubbles.

[0005] Known methods of generating nanobubbles for industrial-scale applications include by ultra-high pressure gas injection through porous media such as ceramics; by cavitation which is the phase change of dissolved gases caused by a sudden pressure drop in the liquid; by electrolysis whereby water is split into hydrogen and oxygen and the resultant gases produced by the electrolysis form nanobubbles; and by adding gas to water and exposing the mixture of gas and water to a static electric field forming nanobubbles in the water. Apart from the method using a static electric field, all other known methods have been found to be costly in terms of energy requirements and the physical apparatus required. Moreover, some methods require additives to be introduced in the process which have the disadvantage that such additives contaminate the liquid, while also producing relatively low gas solubility.

[0006] The known methods that involve electrolysis require direct liquid-electrical contact of water and an electrode or electrical discharge, or the introduction of another ion source. In contrast, the method using a static electric field does not involve direct contact between the electrodes and the water.

[0007] In summary, various methods are known heretofore relating to the preparation of nanobubbles, however, all such known methods require the introduction of a gas from outside i.e. external of the aqueous media, into the aqueous media in which the nanobubbles are to be created. Thus, the known methods disclose and require either a passive or pressurised source of gas and apparatus for delivering the gas to the aqueous media in order to form the nanobubbles.

[0008] W020079020 discloses a system, generator, and method for generating nanobubbles or nanodroplets and treating a multi-component mixture, in particular for treating biogas and wastewater. The method comprises injecting a multicomponent gas into water and using nanobubbles of a gas component, and wastewater, to form hydrates in a treatment vessel; removing residual dirt from the treatment vessel and melting the hydrates to facilitate the release of clean water.

[0009] WO21073780 discloses a method and a generator for producing nanobubbles or nanodroplets at ambient conditions; the method comprises the following steps: providing a volume for accommodating a liquid; distributing a medium within the liquid, wherein the medium is provided to the volume at ambient conditions; generating an electric field using an electrode in the proximity of the volume for facilitating the generation of nanobubbles or nanodroplets; wherein the electrode and the liquid are not in direct electrical contact to prevent electrolysis occurring within the volume. The medium provided to the volume may be a liquid (to produce nanodroplets) or a gas (to produce nanobubbles).

[0010] W020079032 discloses a system and method for treating wastewater, the method comprising the steps of: providing a vessel for receiving wastewater and a gas, wherein the gas comprises one or more constituent gas components; directing the wastewater and a first gas component of the gas to the vessel; reducing the temperature of the contents of the vessel from a first temperature to a second temperature to facilitate the formation of clathrate hydrates comprising the wastewater and the first gas component; increasing the temperature of the contents of the vessel with respect to the second temperature to facilitate melting of the clathrate hydrates; and removing clean water and / or the first gas component from the vessel.

[0011] The present invention seeks to address and alleviate the disadvantages of the known methods for producing nanobubbles.

[0012] In the present application, the term ‘nanobubbles’ is to be understood to mean bubbles with a diameter of 1 - 999 nm.

[0013] BRIEF SUMMARY OF THE PRESENT INVENTIONFeatures of the present invention are set forth in the appended Claims.In one aspect, the present invention provides an apparatus for generating nanobubbles in an aqueous medium wherein the apparatus comprises: an electrode configured for creating an electric field in the aqueous medium comprising dissolved gas; the electrode configured to be at least partially immersed in the aqueous medium; and a control panel for controlling the electric field; wherein the electrode and the liquid are not in direct electrical contact so as to prevent electrolysis occurring; and wherein a voltage is applied to the aqueous medium to form nanobubbles from the dissolved gas in the aqueous medium without any external gas being supplied for forming the nanobubbles.Preferably, the present invention provides an apparatus for generating nanobubbles in an aqueous medium wherein the apparatus comprises: an electrode configured using an anode and cathode for creating an electric field in the aqueous medium comprising liquid water and dissolved gas; the electrode configured so that the anode and cathode are at least partially immersed in the aqueous medium; and a control panel for controlling the electric field; wherein the electrode and the liquid are not in direct electrical contact; and wherein a voltage is applied between the anode and cathode to the aqueous medium to form nanobubbles from the dissolved gas in the aqueous medium without any external gas being supplied to the device for forming the nanobubbles.Preferably, the aqueous medium may be any media comprising liquid water such as water including any mixture of water together with other media including liquids, gases and / or solids.Gases present in the water may be dissolved in the water or in the form of bubbles of gas.Advantageously, in accordance with the present invention, the apparatus for generating nanobubbles comprising oxygen in the aqueous medium only requires the presence of dissolved gas and does not require any external source of gas such as air or oxygen to result in the formation of nanobubbles comprising the desired gas such as oxygen.Thus, a significant advantage of the present invention is that it does not require the provision of an external gas supply or apparatus for supplying any external gas, thereby greatly simplifying the method for generating nanobubbles relative to known methods for producing nanobubbles.Preferably, the electrode is configured to be at least partially immersed in the water, for creating the electric field in the aqueous medium.In one embodiment, the apparatus for nanobubble generation may be a mesh electrode.Alternatively, in another embodiment, the apparatus for nanobubble generation may be a plate electrode.Alternatively, in another embodiment, the apparatus for nanobubble generation may be a tube electrode.Alternatively, in another embodiment, the apparatus for nanobubble generation may be any configuration of anode and cathode forming an electrode.In one embodiment, the apparatus for generating nanobubbles according to the present invention may be adapted to be inserted into an environment comprising liquid water such that, in use, the apparatus is fully immersed in the water.Alternatively, in another embodiment, the apparatus according to the present invention may be adapted to be inserted into an environment comprising liquid water such that, in use, the apparatus is partially immersed in the water.Preferably, the apparatus for generating nanobubbles is configured to be inserted into any media comprising liquid water such as water including any mixture of water together with other media including liquids, gases and / or solids.Preferably, the control panel is configured to induce a potential difference of 12-1000 Volts in the electrode.Preferably, the control panel is configured to cycle the current in the electrode at a frequency of 0 to 20 GHz; most preferably, the control panel is configured to cycle the current in the electrode at a frequency of 0 to 60 Hertz.In another aspect, the present invention provides a method for generating nanobubbles wherein the method comprises the following steps: generating an electric field using an electrode in the proximity of the volume of water for generating nanobubbles or nanodroplets; wherein the electrode and the liquid are not in direct electrical contact so as to prevent electrolysis occurring.

[0014] The present inventors have surprisingly discovered that applying a voltage to an electrode located in an aqueous medium comprising dissolved gases generates an electric field in the volume of medium comprising the dissolved gases, which results in the formation in nanobubbles. It is understood by the inventors that by applying a voltage to the electrode leads to the generation of nanometre sized cavities referred to as ‘nanocavities’, the sites of nucleation of nanobubbles. These induced nano-cavities are then filled by the dissolved gases in the medium, forming nanobubbles in the medium.In accordance with the present invention, if there is more than one type of dissolved gas in the medium then the ratio of the number of molecules of each gas in the generated nanobubbles will be in proportion to the relative solubility of the component gases in the water. As an example, oxygen is approximately two times more soluble in water than nitrogen so, if the liquid comprises dissolved oxygen and dissolved nitrogen, the nanobubbles generated will comprise a ratio of oxygen: nitrogen of approximately 2:1.The amount of nanobubbles formed is proportional to the intensity of the electric field. The higher the voltage, the greater the intensity of the induced electric field and the higher probability of nanobubble nucleation in the volume of water exposed to the electric field. This in turn, generates a higher number of nanobubbles but due to the finite amount of dissolved gases in the liquid each will comprise smaller volume of gases and therefore have a smaller diameter (Fig 3a and Fig 3b). Additionally, the time that the liquid is exposed to the electric field affects the properties of the nanobubbles. At longer exposure times, the nanobubbles will grow over time, reducing the concentration of nanobubbles but increasing the average diameter of the individual bubbles (Fig 3d). Conversely, short exposure times lead to high concentrations of small nanobubbles (Fig 3c).

[0015] The nucleation and growth of nanobubbles ceases after the electric field is removed.

[0016] The exposure time of the liquid to the electric field is controlled by the relative velocity of the electrode and the aqueous media or by intermittent application of the voltage across the electrode.

[0017] Similarly, the size and configuration of the electrode can affect the volume of liquid exposed to the electric field. This level of control over the size of nanobubbles allows for tailoring of their properties to best suit the intended application.

[0018] Liquid water typically comprises a measure of dissolved gases, including oxygen, nitrogen, carbon dioxide and traces of inert gases. It is well established that encapsulating oxygen in nanobubbles increases its bioavailability, enhancing livestock and plant growth and health. Nanobubbles generated using the apparatus and methods of the presentinvention will preferentially comprise a greater amount of oxygen than the known methods, which generate nanobubbles directly from air supplied to the nanobubble generator. Therefore, the nanobubbles generated by the apparatus and methods of the present invention will have a more beneficial effect in any end use due to the greater amount of oxygen comprised therein.

[0019] Nanobubbles undergo random Brownian motion once generated, which over time leads to an even distribution of nanobubbles in the volume of water. The present invention can therefore be used to efficiently spread useful material such as nutrients or dissolved gases from areas of water where they are present in high concentrations to areas where they are in low concentrations.

[0020] Accordingly, in one embodiment, one use-case for the method of the present invention is in fish farms, where nanobubble generation at different depths of a body of water, such as rivers, lakes and oceans can help transfer nutrients from colder, deeper water that comprises more dissolved oxygen to shallower waters that comprise less dissolved oxygen.

[0021] In an alternative embodiment, a similar use case is to generate nanobubbles from dissolved air (comprising molecules of oxygen and nitrogen) in a flowing body or flow in a pipe of water of high dissolved oxygen content and transport it to regions of low dissolved oxygen content.

[0022] In static or slow-moving shallow waters in the absence of any inflow of water comprising higher levels of dissolved oxygen, there is typically a gradient of dissolved oxygen from high (near saturation) at the surface diminishing descending from the surface. Another application for use of the apparatus and method of the present invention comprises capturing dissolved oxygen from the relatively high dissolved oxygen content near the surface of the water in the form of nanobubbles that will then diffuse downwards to regions where the dissolved oxygen levels are relatively lower. This will particularly benefit cultivation of marine fauna in shallow tanks that mainly dwell on the bottom of such tanks. Accordingly, in one embodiment of the method of the present invention, the method comprises the step of generating nanobubbles near the surface of the water for facilitating diffusion of the oxygen nanobubbles to regions where the dissolved oxygen levels are relatively lower than near the surface of the water.

[0023] In another embodiment, another application of the method of the present invention is to capture in nanobubbles, dissolved oxygen that has been generated in the surface layers of water using some form of electromagnetic or other treatment that accelerates dissolution of oxygen from ambient air into the water surface.

[0024] In a further alternative embodiment, another application of the method of the present invention is placement of the nanobubble generator in the outflow of a device generating macrobubbles or microbubbles such as a diffuser aerator or a venturi aerator.

[0025] In a further alternative embodiment, another application, is in irrigated crops where nanobubble generation in water comprising higher levels of nutrient, oxygen or carbon dioxide can help transfer the nutrient, oxygen and / or carbon dioxide to locations closer to plant roots that may have lower levels of one or more of these substances and so boost the growth of plants and the health of the plant-soil microbiome.

[0026] Another application is generation of nanobubbles comprising ozone from ozone already dissolved in the water or ozone bubbles already mixed into the water. This will enable losses due to the short half- life of dissolved ozone and off-gassing of dissolved ozone to be reduced by capturing and storing the ozone in nanobubble form for transport and use elsewhere at a distance from the point of injection and / or generation in water.

[0027] Applications of the method of nanobubble generation according to the invention are numerous and include any scenario in which it is beneficial to capture dissolved gases in nanobubbles for storage and transport to another location where the contents and properties of the nanobubbles will be beneficial.

[0028] In summary, the present invention relates to an apparatus for generating nanobubbles in an aqueous medium. Preferably, the aqueous medium may be any media comprising water such as liquid water including any mixture of water together with other media including liquids, gases and / or solids. Advantageously, the apparatus for generating nanobubbles in the aqueous medium does not require provision of any external source of gas. In another aspect, the present invention provides a method for generating nanobubbles comprising oxygen in liquid water comprising dissolved oxygen.

[0029] In another aspect, the present invention provides a method for generating nanobubbles comprising a significantly higher concentration of oxygen than ambient air in liquid water comprising dissolved oxygen and dissolved nitrogen arising from prior dissolution of ambient air in the water.

[0030] In another aspect, the present invention provides a method for generating nanobubbles comprising any gas in liquid water comprising that dissolved gas.

[0031] In another aspect, the present invention provides a method for generating nanobubbles of a particular size distribution and concentration comprising any gas in liquid water comprising that dissolved gas.

[0032] In another aspect, the present invention provides a method for electronically controlling the size distribution and concentration of nanobubbles generated by the apparatus.

[0033] The present invention will now be described in more detail with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSFigures 1a, 1b and 1c show a side view of one form of deployment of the present invention as an in line nanobubble generator generating nanobubbles from dissolved gases in the inflow water where the electrode is, respectively, (a) a mesh comprising multiple anodes and cathodes intertwined, (b) multiple anodes and cathodes in layers, and (c) anode and cathode as concentric tube and core;

[0034] Figures 2a and 2b are schematic diagrams showing, respectively, the two types of nanobubble formation, namely, heterogenous nucleation and homogenous nucleation;

[0035] Figure 3 shows the setup for the experiments to test the source of gases forming nanobubbles. A volume of distilled water was placed in a container that is at least partially filled with water into which is placed, the nanobubble generator comprising an electrode with positively (anode) and negatively (cathode) charged terminals electrically insulated from the water. The change in dissolved oxygen concentration was measured with and without a lid being placed over the container (not sealed) with and without continuous application of a voltage of 60V across the electrode for a period of time;

[0036] Figure 4 is a schematic diagram showing the results of the experiments carried out using the apparatus illustrated in Figure 3;

[0037] Figures 5a, 5b, 5c and 5d are graphs showing, respectively, (a) change in number of nanobubbles generated as a function of electric field intensity, (b) change in average size of nanobubbles generated as a function of electric field intensity, (c) change in number of nanobubbles with time of exposure to the electric field of intensity 30 kV / m, and (d) change in average size of nanobubbles generated with time of exposure to the electric field of intensity 30 kV / m.

[0038] Figure 6 is a schematic diagram showing the density of water samples comprising nanobubbles and those comprising only dissolved air;

[0039] Figure 7 is a graph showing the average density of nanobubbles over the span of 28 days;

[0040] Figure 8 is a side view of a nanobubble generator adapted for use in hydroponic farming;

[0041] Figure 9 is a side view schematic diagram of a nanobubble generator adapted for use in droplet-sprinklers;

[0042] Figure 10 is a side view schematic diagram of a nanobubble generator adapted for use in open-channel fish farms;

[0043] Figure 11 is a side view schematic diagram of a nanobubble generator adapted for use in marine fish farm pens employing bubble-curtains;

[0044] Figure 12 is a side view schematic diagram of a nanobubble generator adapted for capturing gas before it desorbs from the water and gas that has been absorbed by the water;

[0045] Figure 13 is a side view of a schematic bubble-curtain fish farm utilising the nanobubble generation apparatus and method of the present invention; and

[0046] Figure 14 is a side view of floating nanobubble generator to capture the oxygen molecules before they desorb from the water body and to capture oxygen dissolving from the air into the water in the forming of nanobubbles in the water body.

[0047] Figure 15 is a side view of an embodiment in which a nanobubble generator is immersed in a tank holding water that may be pressurised or unpressurised. Nanobubbles are generated from dissolved air in the water using one or more electrodes suspended in the water. Water containing nanobubbles is then pumped to milking machinery, to drinking water dispensing devices, to milk storage tanks for use in the cleaning cycle and to washing equipment such as power hoses, automatic washing equipment, and other devices for cleaning yards that may then be collected in water and wastewater holding and treatment tanks such as slurry tanks;

[0048] Figure 16 is a side view of a nanobubble generator immersed in a water body generating nanobubbles from air dissolved in the water from ambient air employing a pump to draw water through a closed conduit containing electrodes and discharging the water containing nanobubbles through a closed conduit into the water body;

[0049] Figure 17 is a plan view of an immersed nanobubble generator drawing water through an network of closed conduits using a pump located outside of the water body discharging the water containing nanobubbles back into the water body through a network of closed conduits located in between blocks of plants growing on mats submerged in the water; and

[0050] Figure 18 is a series of photographs over time namely on Day 0, Day 12 and Day 40 and showing the destruction of cyanobacteria (blue-green algae) in a shallow pond by treating the water in the pond with nanobubbles generated from air dissolved in the waterfrom ambient air using an immersed nanobubble generation system of flexible closed conduits containing electrodes by drawing water through the conduits and discharging the water through a network of flexible closed conduits.

[0051] The present invention will now be described more particularly, by way of example only and with reference to the accompany drawings and Examples provided below.

[0052] Comparison Example 1

[0053] Table 1 shows the Comparison data of oxygen transfer from air to water using typical coarse bubble diffuser and nanobubble (nanobubble is abbreviated as “NB”) generator considering dissolved oxygen only, and dissolved oxygen plus oxygen contained in the nanobubbles. Oxygen transfer rate (OTR) is calculated using the following formula:KLaV(Cmax-Csat) where V is the volume of water being aerated and Oxygen Transfer Efficiency (OTE) is OTR / 0.228Qa(m) where Qa(m) is the influent mass air flow rate and the mass fraction of oxygen in air is assumed to be 0.228 kg 02 / kg air.

[0054] Table 1DETAILED DESCRIPTIONReferring initially to Figure 1 , there is shown a side view of a nanobubble generator using the present invention, comprising a closed conduit configured to channel water which houses a mesh electrode connected to a control panel. The electric field generated by the electrode induces nanobubble generation in the flow of water using the existing dissolved gas. Figures 1(a), 1 (b) and 1(c) show a configuration using a mesh, plate or concentric electrode respectively as examples of electrodes that may be of any design that produces a static electric field between the anode and cathode of the electrode.

[0055] Referring now to Figures 2(a) and 2(b), there are shown respective schematic diagrams of the two types nanobubble nucleation using an electric field generated by applying a voltage to an electrode comprising an anode (+) and a cathode (-) on either side of a body of water. The two types of nanobubble nucleation are referred to as (a) heterogenous nucleation and (b) homogenous nucleation. In the heterogenous nucleation, shown schematically in Figure 2(a), nanobubbles are formed at the surface of a secondary phase present in the water. The secondary phase may be bubbles of gas introduced to the water at the location of or upstream from the electric field, solid particles or other surfaces separate to the water phase.

[0056] Referring to the present invention, the inventors have discovered that there is a second nanobubble nucleation mechanism, namely, homogenous nucleation, whereby, provided there are dissolved gases in the water, nanobubbles will nucleate homogeneously in the water independent of any contact surfaces of secondary phase materials. This homogenous nucleation is the mechanism of nanobubble formation using the method and process of the present invention and consequently, the apparatus and method of the present invention does not require an external gas supply in order to form nanobubbles.

[0057] Referring now to Figure 4, there is shown a graph showing the rate of nanobubble formation under different experimental conditions that demonstrates homogeneous nanobubble formation in water from dissolved gases, primarily oxygen and nitrogen deriving from air that has previously dissolved in the water. The experiment was carried out under three different experimental conditions: Condition (1) Open Lid: means the container was open to the atmosphere allowing air to enter and dissolve in the water, Condition (2) Open lid with 60V: the container was open to atmosphere allowing air to enter and dissolve in the water in the presence of an electric field of intensity 12 kV / m (60V applied across a distance of 5 mm between the anode and cathode), and Condition (3) Closed lid with 60V: the container was covered with a loosely fitting lid that limited but did not prevent ingress air while of voltage of 60V was applied across the electrode producing an electric field intensity the same as in Condition No. 2. Nanobubbles were generated in Conditions Nos. 2 and 3. Maximum dissolved oxygen concentration was obtained under Condition No.1 due to dissolution of air into the water from the atmosphere. The second highest dissolved oxygen concentration was observed in Condition No. 2 showing that a proportion of the air dissolving into the water was captured in nanobubbles. The lowest dissolved oxygen content in Condition No. 3 demonstrates that nanobubbles have been generated from the oxygen dissolving into the water from the limited amount of air enteringthe container. This Experiment evidences that the homogenous mechanism of nanobubble formation consumes dissolved oxygen in water rather than from bubbles of air.

[0058] The graph shown in Figure 6 demonstrates an alternative method of confirming the presence and measuring the concentration of nanobubbles in a volume of water. Precise measurements of density were made of water free of nanobubbles and water comprising nanobubbles. In both the water samples tested, the water comprised dissolved air but only the sample indicated in the graph in Figure 6, with the dotted lines comprised nanobubbles generated using the apparatus and method of the present invention. The results show that the density of water comprising nanobubbles generated using the apparatus and method of the present invention is approx 0.008% higher than water without nanobubbles. This suggests that: a) the density of gas is the nanobubbles, and so the gas pressure, is much higher than atmospheric pressure, and / or b) the concentration of nanobubbles is much higher.

[0059] Referring now to Figure 7, there is shown a graph displaying the density of a water sample comprising nanobubbles over a period of 28 days. The density of the sample remains constant for the first 5 days, before dropping slightly over the next 14 days and finally dropping more significantly over the final 14 days. This experiment shows that nanobubble residence time in a volume of water remains high for at least two weeks.

[0060] Referring now to Figure 8, there is shown a side view of a schematic sprinkler irrigated crop utilising the nanobubble generation apparatus and method of the present invention. The apparatus comprises a mesh electrode located inside the irrigation tube, which is configured to transport water to the sprinkler devices watering the plants. The mesh electrode is connected to a control box which is configured to control the electric field through the mesh electrode.

[0061] Referring now to Figure 9, there is shown a side view of a schematic hydroponic farm utilising the nanobubble generation apparatus and method of the present invention. The apparatus comprises a mesh electrode submerged in a volume of water, which is watering the roots of plants suspended above the volume of water. The mesh electrode is connected to a control box which is configured to control the electric field through the mesh electrode.

[0062] Referring now to Figure 10, there is shown a side view of a schematic drip irrigated crop utilising the nanobubble generation apparatus and method of the present invention. The apparatus comprises a mesh electrode located inside the irrigation tube, which is configured to transport water to the sprinkler devices watering the plants. The mesh electrode is connected to a control box which is configured to control the electric field through the mesh electrode.

[0063] Referring now to Figure 11 , there is shown a side view of a schematic Recirculating Aquaculture System (RAS) fish farm utilising the nanobubble generation apparatus and method of the present invention. The apparatus comprises a mesh electrode submerged in the water flow in the RAS, where the mesh electrode is connected to a control box configured to control the electric field through the mesh electrode.

[0064] Referring now to Figure 12, there is shown a side view of a schematic openchannel fish farm utilising the nanobubble generation apparatus and method of the present invention. The apparatus comprises a series of mesh electrodes submerged in a plurality of open-channel fish farms, where the mesh electrodes are all connected to a control box configured to control the electric field the mesh electrodes.

[0065] Referring now to Figure 13, there is shown a side view of a schematic bubblecurtain fish farm utilising the nanobubble generation apparatus and method of the present invention. The apparatus comprises a mesh electrode submerged in a volume of water, configured to form an open-topped cuboid shape. The mesh electrode is connected to a control box configured to control the electric field through the mesh electrodes.

[0066] Referring now to Figure 14, there is shown a side view of floating generator to capture the oxygen molecules before they desorb from the water body and to capture oxygen dissolving from the air into the water in the forming of nanobubbles in the water body. This mesh is placed near the surface of the water body where the concentration of dissolved air is highest, and the highest rate of evaporation occurs. The floating mesh electrode is connected to a control box configured to control the electric field through the mesh electrodes. It is noted that any flow of water through the electrode occurs naturally, and no motive power is employed to transport the water through the electrode. The nanobubbles generated from the dissolved air in the water diffuse through the water as a result of water currents in the water and Brownian motion.

[0067] Referring now Figure 15, there is shown a side view of a system for generating nanobubbles in a tank holding water collected from a process such as cooling of milk during milking of animals on a dairy farm or from well water that contains dissolved air. The nanobubble-treated water can be used to sanitise the water used in clusters employed in milking machinery to reduce the amount of sanisting chemicals required. Alternatively, the nanobubble-treated water can be used to santise drinking water or infuse the drining water wigth nanobubbles containing oxygen of benefit to the gut health of the animals. , Alternatively, the nanobubble-treated water can be used as pre-wash for milk storage tanks in the cleaning cycle to reduce the loading of contaminants needed to be treated by subsequent treatment stages such as hot water and chemicals. Alternatively, the nanobubble-treated water can be used to supply washing equipment such as hoses usedto clean teats and udders before milking, power hoses used to clean equipment and yards, automatic washing equipment, and other devices for cleaning. Another benefit of the nanobubble treated water will be increasing the growth rate of aerobic bacteria involved in breakdown of organic material in on-farm treatment of liquid and solid waste.

[0068] Referring now Figure 16, there is shown a side view of an immersed nanobubble generator capturing oxygen molecules that have dissolved from ambient air into water body. Nanobubble generation takes place inside a closed conduit containing the electrode as water is drawn through the conduit by a pump that is immersed in the water. The pump discharges the water containing nanobubbles through a closed conduit back into the water body. The open end of the discharging conduit may be positioned at any location through the water column enabling treatment of water at any depth with nanobubbles containing oxygen.

[0069] Referring now to Figure 17, there is shown is a plan view of an immersed, distributed nanobubble generation system employed to treat the water in a shallow pond containing blocks of plants growing on mats submerged in the water. The water is drawn in through a network of flexible tubes containing electrodes using a water pump located outside of the water body and discharged back to the water body through a network of flexible tubes. In a variant of this immersed, distributed nanobubble generation system the tubes are perforated with holes. In the tubes drawing water the holes are sized and positioned to maintain an equal volume of water entering the tube along the length of the tube. In the tubes discharging water containing nanobubbles the holes are sized and positioned to maintain an equal discharge of water along the length of the tube. The effect of the nanobubbles is to promote plant growth and to inhibit the growth of cyanobacteria.

[0070] Referring now to Figure 18, there is shown a series of photographs evidencing the destruction of cyanobacteria (blue-green algae) growing in the water in a shallow pond containing blocks of plants cultivated on mats submerged in the water. The images show a reduction and eventual elimination of algae from the water over a period of weeks, resulting from treatment with nanobubbles generated from dissolved air using the immersed, distributed nanobubble generation system shown in Figure 16. It is noted that the majority of algae was eliminated within two weeks.

[0071] In one embodiment, the system and method for generating nanobubbles in accordance with the present invention, is used to increase the bioavailability of oxygen in water delivered via sprinklers to plants growing in soil or a soil substrate. In known, prior art use, the roots of plants watered by sprinklers obtain oxygen by diffusion from air in the interstitial spaces around the roots and dissolved oxygen in the irrigation water that penetrates the roots. According to one example of the method of the present invention, theelectrode (mesh or other type design best suited to the environment) is located inside water supply system to the sprinklers. By applying a voltage to the electrode, nanobubbles comprising oxygen are generated in the water transported to the sprinklers. The nanobubbles will be transported intact through the sprinkler to the soil and through the soil to the plant roots. The nanobubbles will diffuse from the irrigation water into the plant roots leading to increased bioavailability of oxygen for the plants watered by the sprinklers.

[0072] In one embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of nutrients in water delivered to plants that are irrigated by sprinklers. In standard use, nutrients are typically provided to plants by spreading of fertiliser onto the soil, or mixing it in to the soil and then using irrigation and / or rainfall to dissolve the fertiliser and transport it to the plant roots. In the present invention, an electrode can be placed in the water flow used to irrigate the plants. By applying a voltage to the electrode, nanobubbles are generated in the water transported to the sprinklers. The nanobubbles will be transported intact through the sprinkler to the soil and through the soil to the plant roots. Nutrients from the applied fertiliser attach to the nanobubbles and are transported into the plant roots resulting in increased bioavailability of nutrients for the plants. Nutrients produced organically by soil microbes will also attach to the nanobubbles and be transported to the plant roots.

[0073] In a further embodiment of the present invention, the system and method for generating nanobubbles is used to increase the rate of infiltration of water delivered via sprinklers, drip irrigation or gravity-based irrigation to plants growing in soil. In standard use, water delivered to soil by irrigation will have a certain rate of infiltration governed by the soil type, degree of compaction and rate of irrigation. Water usage efficiency for any given soil type and condition and irrigation rate depends on the rate of infiltration to the soil and evaporation from the surface of the soil. Using the present invention, the mesh electrode (or other design best suited to the environment) can be located inside water supply to the irrigation system. By applying a voltage to the electrode, nanobubbles are generated in the water transported to the irrigation system and then to the soil. The nanobubbles reduce the surface tension of the water resulting in an increase in rate of infiltration of water to the soil and an increase in water usage efficiency.

[0074] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of nutrients in water delivered to plants in hydroponic cultivation. In standard use, nutrients are provided to plants by the dissolution of highly soluble nutrients into the water. In the present invention, an electrode can be placed in the water flow used to irrigate and supply nutrients to the plants. By applying a voltage to the electrode, nanobubbles are generated in the water comprising the nutrients transported bythe pipes. Nutrients attach to the nanobubbles and are transported into the plant roots resulting in increased bioavailability of nutrients for the plants.

[0075] In a further embodiment, the system and method for generating nanobubbles is used to reduce the time taken to germinate seeds in agriculture and horticulture. In standard use, dry seeds are wetted by applying water to the soil or soil substrate in which the seeds are planted. In the present invention, by adding electrodes to water applied to the soil or soil substrate and applying a voltage to the electrodes nanobubbles will be generated that capture oxygen and growth stimulants dissolved in the water. The nanobubbles increase the bioavailability of oxygen and growth stimulants to the grains, and stimulate germination resulting in acceleration of the germination process, narrowing of the distribution of seed germination times among the grains leading to faster and more uniform time to germination.

[0076] In a further embodiment, the system and method for generating nanobubbles is used to reduce the time taken to grow sprouted greens such as cress and cereal grasses. In standard use, sprouted greens are grow in in soil, soil substrate or hydroponically. In the present invention, by adding electrodes to water applied to the irrigation water and applying a voltage to the electrodes nanobubbles will be generated that capture oxygen dissolved in the water. The nanobubbles increase the bioavailability of oxygen to the seeds and the young roots, resulting in acceleration of the sprouting process, narrowing of the distribution of seed germination times among the seeds leading to faster sprouting and more uniform sized sprouts.

[0077] In a further embodiment, the system and method for generating nanobubbles is used to increase the rate and uniformity of germination of grains such as barley, wheat, oats, rye, rice, sorghum and millet using in brewing and in production of sprouted grains for food. In standard use, dry grains are wetted by spraying water on the grains or submerging them in water until they absorb sufficient moisture to trigger germination. Further water is applied, usually in the form of a spray, to maintain an optimum moisture content required for germination of the grains. In the present invention, by adding electrodes to water used to wet the grains and applying a voltage to the electrodes nanobubbles will be generated that capture oxygen dissolved in the water. The nanobubbles increase the bioavailability of oxygen to the grains, and stimulate germination resulting in acceleration of the germination process, narrowing of the distribution of germination times among the grains in the bulk leading to a shorter seed germination stage in the malting or sprouted grain production process.

[0078] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of oxygen in water in Recirculating Aquaculture System(RAS) fish, crustacean or mollusc farm. In standard use, a proportion of oxygen added to water in a RAS fish farm is wasted through bubbles that reach the water surface and break, or by desorbing of dissolved oxygen from the water. In the present invention, an electrode can be placed downstream of the oxygen injection system. By applying a voltage to the electrode nanobubbles comprising oxygen are generated in the water. The oxygencomprising nanobubbles provide a reservoir of oxygen and results in increased bioavailability of oxygen for the animals in the RAS farm.

[0079] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of oxygen in water in a flow through fish, crustacean or mollusc farm. In standard use, a proportion of oxygen added to water, or already dissolved in the inflow water in a flow through farm is wasted through bubbles that reach the water surface and break, or by desorbing of dissolved oxygen from the water. In the present invention, an electrode can be placed downstream of the oxygen or air injection system or in the water inflow to the farm. By applying a voltage to the electrode nanobubbles comprising oxygen are generated in the water. The oxygen-comprising nanobubbles provide a reservoir of oxygen and results in increased bioavailability of oxygen for the animals in the flow through fish, crustacean or mollusc farm.

[0080] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of oxygen in water in a fish pen employing forced air to create a curtain of bubbles acting as barrier to entry of phytoplankton, sea lice and other organisms deleterious to the health of the fish. In standard use, most of the oxygen that dissolves from the bubble curtain into the water is not available to the fish. In the present invention, by adding electrodes to the existing bubble-curtain and applying a voltage to the electrodes nanobubbles will be generated that capture the oxygen dissolved in the water acting as a reservoir of oxygen and resulting in an increase in oxygen transferred to the water and in the bioavailability of oxygen for the fish.

[0081] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of oxygen in water in a fish pen employing forced air as an air lift from the bottom of the pen at the centre to create a flow of water from the central region of the pen outwards inhibiting the entry of phytoplankton, sea lice and other organisms deleterious to the health of the fish. In standard use, most of the oxygen that dissolves from the air injected under pressure into the water is not available to the fish. In the present invention, by adding electrodes above and around the forced air delivery system and applying a voltage to the electrodes nanobubbles will be generated that capture the oxygen dissolved in the water acting as a reservoir of oxygen that maintains the dissolved oxygen content of the water in the whole pen.

[0082] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of oxygen in water in a pond, tank or raceway employing forced air diffusion or mechanical mixing of air into the water to oxygenate the water. In standard use, much of the oxygen that dissolves from the air injected or mixed into the water is lost to the atmosphere. In the present invention, by adding electrodes above and around the forced air diffusion or mechanical mixing system and applying a voltage to the electrodes nanobubbles will be generated that capture the oxygen dissolved in the water acting as a reservoir of oxygen that maintains the dissolved oxygen content of the water in the pond, tank or raceway.

[0083] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of oxygen to microbes in biological water and wastewater treatment employing forced air diffusion or mechanical mixing of air into the water to dissolve oxygen in the process water. Aerobic microbes, the primary means of reducing the biological oxygen demand of the water, typically grow in flocs and agglomerations of microbes, in the water. In standard use, the dissolved oxygen levels in water decrease from the surface to the centre of agglomerations of microbes which is the condition of the majority of microbes in the process. In the present invention, by adding electrodes to the process waters and applying a voltage to the electrodes nanobubbles will be generated that capture the oxygen dissolved in the water. The nanobubbles will penetrate inside the agglomerates of microbes increasing the bioavailability of oxygen to the interior microbes resulting in an increase in their metabolic activity and rate of breakdown of organic material and pollutants leading to an intensification of the biological water or wastewater treatment effect.

[0084] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of oxygen to microbes in biological water and wastewater treatment employing synthetic and / or natural media such as sand, charcoal, woodchips, plants and plant roots to clean and purify the water using microbes growing in biofilm on the surfaces of the substrate. In standard use, the dissolved oxygen levels in water decrease from the surface to the centre of the biofilm which reduces the metabolic activity of the microbes resulting in inefficient use of the dissolved oxygen and limitations on the water or wastewater treatment capacity of the process. In the present invention, by adding electrodes to the process waters and applying a voltage to the electrodes nanobubbles will be generated that capture the oxygen dissolved in the water. The nanobubbles will penetrate inside the biofilm increasing the bioavailability of oxygen to the interior microbes resulting in an increase in their metabolic activity and rate of breakdownof organic material and pollutants leading to an intensification of the biological water or wastewater treatment effect.

[0085] In a further embodiment, the system and method for generating nanobubbles is used to increase the bioavailability of gases such as oxygen, hydrogen and carbon dioxide to microbes or fungi in fermentation processes. Microbes typically grow in flocs and agglomerations of microbes in the water while fungi grow as filaments of mycelium. In standard use, the dissolved oxygen levels in water decrease from the surface to the centre of agglomerations of microbes, or filamentous mats of mycelium. In the present invention, by adding electrodes to the process waters and applying a voltage to the electrodes nanobubbles will be generated that capture the gas dissolved in the water. The nanobubbles will penetrate inside the agglomerates of microbes or mats of mycelium increasing the bioavailability of gas to the interior microbes resulting in an increase in their metabolic activity and an intensification of the biological water or wastewater treatment effect.

[0086] In a further embodiment, the system and method for generating nanobubbles is used to increase the effectiveness of carbonation of water using carbon dioxide as a food source for algae. In standard use, carbon dioxide is dissolved in the water but a proportion of the carbon dioxide that is dissolved into the water desorbs to the atmosphere. In the present invention, by adding electrodes to water comprising dissolved carbon dioxide and applying a voltage to the electrodes nanobubbles will be generated that capture carbon dioxide dissolved in the water. The carbon dioxide nanobubbles act as a reservoir of carbon dioxide resulting in increased bioavailability of carbon dioxide for carbon consuming organisms such as algae.

[0087] In a further embodiment, the system and method for generating nanobubbles is used to increase the effectiveness of cleaning, purification and disinfection of water with ozone in a RAS using protein skimmer separators. In known, prior art, use, ozone is dissolved in the water but the dissolved ozone has a short half-life of seconds to minutes after which it degrades to oxygen and much of the ozone that is dissolved into the water is lost to the atmosphere. In the present invention, by adding electrodes downstream of the ozone injection, mixing and dissolution devices and applying a voltage to the electrodes nanobubbles will be generated that capture ozone dissolved in the water extending the lifetime of the ozone. The ozone nanobubbles capture fine particles and chemicals aiding in the cleaning and purification effect of the ozone. The combined effect of the ozone nanobubbles is increased effectiveness of the ozone added to the water in a RAS using protein skimmer separators.

[0088] In a further embodiment, the system and method for generating nanobubbles is used to increase the effectiveness of cleaning, purification and disinfection of water in water handling, reuse and storage systems using ozone. In standard use, ozone is dissolved in the water but the dissolved ozone has a short half-life of seconds to minutes after which it degrades to oxygen and much of the ozone that is dissolved into the water is lost to the atmosphere. In the present invention, by adding electrodes downstream of the ozone injection, mixing and dissolution devices and applying a voltage to the electrodes nanobubbles will be generated that capture ozone dissolved in the water. The ozone nanobubbles act as an ozone reservoir that can be transported longer distances before degrading than the dissolved ozone so extending the lifetime of the ozone resulting in increased volumes of water disinfected and / or disinfection of water a greater distance away from the ozone injection site. The ozone nanobubbles will also penetrate into biofilm and capture suspended organic solids resulting in increased cleaning effect. The combined effect of the ozone nanobubbles is increased effectiveness of the ozone added to the water for the purposes of ozonation in water handling, reuse and storage systems.

[0089] In a further embodiment, the system and method for generating nanobubbles is used to provide a chemical-free method of cleaning biofilm and other adhered material from the internal surfaces of pipes, tanks, towers and the surfaces of discrete objects such as fruit and vegetables, prepared food products and electronics and from textiles. In standard use, chemicals and mechanical methods are used to clean these objects and materials. In the present invention, by adding electrodes to the cleaning water and applying a voltage to the electrodes nanobubbles will be generated from gases dissolved in the water. The nanobubbles act as cleaning agent by mechanically scouring biofilm and other adhered material from surfaces. Nanobubbles comprising oxygen, nitrogen or carbon dioxide are highly oxidative when they collapse, directly damaging microbial and virus cells as well as increasing the oxidation reduction potential of the water. The nanobubbles will also penetrate into biofilm and capture suspended organic solids resulting in increased cleaning effect. The combined effect of the nanobubbles is a chemical-free method of cleaning and disinfection.

[0090] In a further embodiment, the system and method for generating nanobubbles is used to provide a method of eliminating or inhibiting the growth of cyanobacteria (bluegreen algae) in surface water bodies using a floating nanobubble water treatment device. Standard methods employ chemicals or ultrasonic disruption to eliminate cyanobacteria. More recently oxygenation and oxygen nanobubbles injected into the water are being employed. In the present invention, by adding electrodes to the water near the surface of the water body and applying a voltage to the electrodes nanobubbles will be generatedfrom air dissolved in the water. The electrodes are powered by a rechargeable battery that can be solar powered. The nanobubbles penetrate and fatally damage algal cells. They also increase the oxidation reduction potential of the water acting to inhibit the growth of cyanobacteria. The nanobubbles diffuse through the water and provide oxygen for beneficial aerobic bacteria in the water.

[0091] In a further embodiment, the system and method for generating nanobubbles is used to provide a chemical-free means of eliminating or inhibiting the growth of cyanobacteria (blue-green algae) in surface water bodies. Standard methods employ chemicals or ultrasonic disruption to eliminate cyanobacteria. More recently, oxygenation and oxygen nanobubbles injected into the water are being employed. In the present invention, by adding electrodes to the water near the surface of the water body and applying a voltage to the electrodes nanobubbles will be generated from ambient air dissolved in the water. The nanobubbles will diffuse through the water or can be pumped from the surface water layers to any other location in the water column in the region of the device. The electrodes are powered by a rechargeable battery that can be solar powered. The nanobubbles penetrate and fatally damage algal cells and also increase the oxidation reduction potential of the water acting to inhibit the growth of cyanobacteria. The nanobubbles also provide oxygen for beneficial aerobic bacteria in the water.

[0092] In a further embodiment, the system and method for generating nanobubbles is used to provide a means of transferring oxygen from ambient air to water body. Standard methods employ a gas pump or mechanical mixing to entrain air in the water and dissolve the air into the water. In the present invention, by adding electrodes to the water near the surface of the water body and applying a voltage to the electrodes nanobubbles will be generated from ambient air dissolved in the water. The nanobubbles will contain approximately 66% oxygen at high internal pressure. They can diffuse through the water or can be pumped from the surface water layers to any other location in the water column in the region of the device. The electrodes and pump, if used, are powered by a rechargeable battery that can be solar powered. The nanobubbles increase the dissolved oxygen content of lower layers of the water body that are at lower levels of dissolved oxygen than the upper layers. The nanobubbles will penetrate into the sediment at the bottom of ponds, lakes and reservoirs boosting the activity of nitrifying bacteria breaking and increasing the bioavailability of oxygen to aquatic flora and fauna.

[0093] In a further embodiment, the system and method for generating nanobubbles is used to provide a means of exploiting the water used in cooling of milk while milking of animals prior to transfer of the milk to a holding tank for further cooling to enhance other processes involved in animal husbandry. The nanobubbles can be used to increase theoxidation reduction potential of water used in cleaning and sanitising milking equipment. The nanobubbles can also be used to increase the oxidation reduction potential of drinking water for animals and / or to boost the gut health of animals by increasing the bioavailability of oxygen to aerobic gut bacteria. The nanobubbles can also be used to clean surface contaminants in milk storage and cooling tanks and to increase the oxidation reduction potential of the wash water. The nanobubbles can also be used to enhance the cleaning of equipment and yards while at the same time increase the bioavailability of oxygen to aerobic bacteria acting to breakdown ammonia and organic solids in treatment of washwater and solid animal and feed waste.

[0094] It will be understood by those skilled in the art that the foregoing description of the invention is provided by way of illustration only. Various modifications and changes to the embodiments described herein will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Accordingly, the scope of the invention is to be determined by the appended claims and their equivalents, rather than by the embodiments described herein.

Claims

CLAIMS1. An apparatus for generating nanobubbles in an aqueous medium wherein the apparatus comprises: an electrode configured for creating an electric field in the aqueous medium comprising liquid water and dissolved gas; the electrode configured to be at least partially immersed in the aqueous medium; and a control panel for controlling the electric field; wherein the electrode and the liquid are not in direct electrical contact; and wherein a voltage is applied to the aqueous medium to form nanobubbles from the dissolved gas in the aqueous medium without any external gas being supplied to the device for forming the nanobubbles.

2. Apparatus as claimed in claim 1 wherein the aqueous medium comprises any media comprising liquid water such as water including any mixture of water together with other media including liquids, gases and / or solids.

3. Apparatus as claimed in claim 1 wherein the gases present in the aqueous media are in the form of dissolved oxygen, dissolved nitrogen, dissolved ozone, dissolved carbon dioxide, dissolved hydrogen or any other dissolved gas.

4. Apparatus as claimed in claim 1 wherein the gases present in the aqueous media are in the form of bubbles of gas.

5. Apparatus as claimed in any preceding claim wherein the apparatus for generating nanobubbles is adapted so that the electrode comprising an anode and a cathode is fully immersed in the aqueous medium.

6. Apparatus as claimed in any preceding claim wherein the control panel is configured to induce a potential difference of 12-1000 Volts in the electrode.

7. Apparatus as claimed in any preceding claim wherein the control panel is configured to cycle the current in the electrode at a frequency of 0 to 20 GHz.

8. Apparatus as claimed in claim 5 wherein the control panel is configured to cycle the current in the electrode at a frequency of 0 to 60 Hertz.

9. A method for generating nanobubbles wherein the method comprises the following steps: generating an electric field using an electrode comprising an anode and cathode for creating an electric field in aqueous medium comprising liquid water such as water including any mixture of water together with other media including liquids, gases and / or solids in which any of dissolved oxygen, dissolved nitrogen, dissolved ozone, dissolved carbon dioxide, dissolved hydrogen or any other dissolved gas is present;Configuring the electrode so that the anode and cathode are at least partially immersed in the aqueous medium; andControlling the electric field using a control panel; wherein the electrode and the liquid are not in direct electrical contact so as to prevent electrolysis occurring; and wherein a voltage is applied between the anode and cathode to the aqueous medium to form nanobubbles from the dissolved gas in the aqueous medium without any external gas being supplied for forming the nanobubbles.

10. A method for generating nanobubbles wherein the method comprises the following steps: generating an electric field using an electrode comprising an anode and cathode for creating an electric field in the aqueous medium comprising dissolved air (dissolved oxygen and dissolved nitrogen); or comprising dissolved oxygen;Configuring the electrode so that the anode and cathode are at least partially immersed in the aqueous medium; andControlling the electric field using a control panel; wherein the electrode and the liquid are not in direct electrical contact so as to prevent electrolysis occurring; and wherein a voltage is applied between the anode and cathode to the aqueous medium to form nanobubbles from the dissolved oxygen in the aqueous medium without any external gas being supplied for forming the nanobubbles.

11. A method for generating nanobubbles wherein the method comprises the following steps: generating an electric field using an electrode comprising an anode and cathode for creating an electric field in the aqueous medium comprising dissolved ozone;Configuring the electrode so that the anode and cathode are at least partially immersed in the aqueous medium; andControlling the electric field using a control panel; wherein the electrode and the liquid are not in direct electrical contact so as to prevent electrolysis occurring; and wherein a voltage is applied between the anode and cathode to the aqueous medium to form nanobubbles from the dissolved ozone in the aqueous medium without any external gas being supplied for forming the nanobubbles.

12. A method as claimed in claim 9 wherein if there is more than one type of dissolved gas in the medium then the ratio of the number of molecules of each gas in the generated nanobubbles will be in proportion to the relative solubility of the component gases in the water.

13. A method as claimed in claim 9 wherein the amount of nanobubbles formed is proportional to the intensity of the electric field whereby the higher the voltage, the greater the intensity of the induced electric field and the higher probability of nanobubble nucleation in the volume of water exposed to the electric field.

14. A method as claimed in claim 13 wherein intensity of the electric field is controlled by controlling the voltage applied to the electrode.

15. A method as claimed in claim 14 wherein the size of nanobubbles generated is varied by varying the voltage applied to the electrode.

16. A method as claimed in any one of claims 9 to 15 comprising the method comprises controlling the time that the aqueous medium is exposed to the electric field so as to provide pre-determined properties of the nanobubbles formed.

17. A method as claimed in claim 13 comprising the step of exposing the aqueous medium to an electric field for a time of 2 to 120 minutes where at longer exposure times, the nanobubbles will grow over time, reducing the concentration of nanobubbles but increasing the average diameter of the individual nanobubbles.

18. A method as claimed in claim 13 to claim 15 comprising the step of exposing the aqueous medium to an electric field for a time of 1 to 120 seconds whereby therelatively short exposure times lead to high concentrations of nanobubbles having relatively smaller average diameters.

19. A method as claimed in claim 13 comprising the step of removing the electric field so as to cause cessation of the nucleation and growth of nanobubbles.

20. A method as claimed in any of claims 13 to 16 wherein the exposure time of the liquid to the electric field is controlled by the relative velocity of the electrode and the aqueous media or by intermittent application of the voltage across the electrode.21 . A method as claimed in any of claims 13 to 16 wherein the size and configuration of the electrode can be varied so as to control the size of nanobubbles so as to provide properties as best suits the intended use / application.

22. An apparatus as claimed in claim any preceding claim wherein the electrodes are suspended at a position below the surface of the aqueous medium using a flotation device.

23. An apparatus as claimed in any of claims 1- 21 wherein the electrodes are fixed at a position below the surface of the aqueous medium.

24. An apparatus as claimed in claims 22 and 23 wherein the electrodes are located inside an open-ended closed conduit.

25. An apparatus as claimed in claim 24 wherein the closed conduit is a rigid pipe or hose.

26. An apparatus as claimed in claim 24 wherein the closed conduit is a network of interconnected rigid pipes or hoses.

27. An apparatus as claimed in claim 24 wherein the closed conduit is a flexible pipe or hose.

28. An apparatus as claimed in claim 24 wherein the closed conduit is a network of interconnected rigid pipes or hoses.

29. An apparatus as claimed in any of claims 25 to 28 wherein the closed conduits are connected to a water pump that draws aqueous medium through each conduit containing electrodes.

30. An apparatus as claimed in claim 29 wherein the water pump is located above the surface of the aqueous medium.31 . An apparatus as claimed in claim 29 wherein the water pump is immersed in the aqueous medium.

32. An apparatus as claimed in claim 30 and claim 31 wherein the water pump is connected to one or more open ended closed conduits so that the aqueous medium in which nanobubbles generated from dissolved gas are present is pumped through the conduits.

33. An apparatus as claimed in claim 32 whereby the closed conduits are rigid pipes or hoses34. An apparatus as claimed in claim 32 whereby the closed conduits are flexible pipes or hoses.

35. An apparatus as claimed in claim 32 whereby the closed conduits are a network of interconnected rigid pipes or hoses.

36. An apparatus as claimed in claim 32 whereby the closed conduits are a network of interconnected flexible pipes or hoses.

37. An apparatus as claimed in any of claims 33 to 36 in which the conduits are suspended in the aqueous media using a flotation device.

38. An apparatus as claimed in any of claims 33 to 36 in which the conduits are suspended below the surface of the aqueous medium using a flotation device.

39. An apparatus as claimed in any of claims 33 to 36 in which the conduits are fixed below the surface of the aqueous medium.

40. An apparatus as claimed in claims 38 and 39 wherein the outlet of the conduits is located at any position vertically between the surface of the aqueous medium and the bottom of the container in which the aqueous medium is located.41 . An apparatus as claimed in claim 40 wherein the container is a tank, pond, lake, reservoir, stream, river, sea or ocean.

42. An apparatus as claimed in claim 40 wherein aqueous medium in which nanobubbles generated from dissolved gas are present is pumped to the location of the open end of the conduits.

43. An apparatus as claimed in claim 29 wherein the water pump is powered using a DC power supplied by a battery.

44. An apparatus as claimed in claim 29 wherein the water pump is powered using single-phase AC power.

45. An apparatus as claimed in claim 29 wherein the water pump is powered using three-phase AC power.

46. An apparatus as claimed in claim 43 wherein the battery is rechargeable using renewable energy such as electricity generated using solar panels or a wind turbine.

47. An apparatus as claimed in any of claims 25 to 28 wherein the conduits containing the electrodes are perforated allowing aqueous medium to be drawn in through the perforations.

48. An apparatus as claimed in claim 47 wherein the perforations are holes spaced at intervals along the length and around the circumference of the conduit.

49. An apparatus as claimed in claim 48 wherein the spacing and hole size of the perforations are adjusted to ensure an equal amount of aqueous medium is drawn in from the bulk aqueous medium along the length of the conduit.

50. An apparatus as claimed in any of claims 33 to 36 wherein the conduits discharging the aqueous medium in which nanobubbles generated from dissolved gas are present are perforated allowing the aqueous medium to pass out of the conduit through the perforations.51 . An apparatus as claimed in claim 50 wherein the perforations are holes spaced at intervals along the length and around the circumference of the conduit.An apparatus as claimed in claim 51 wherein the spacing and hole size of the perforations are adjusted to ensure an equal amount of aqueous medium in which nanobubbles generated from dissolved gas are present passes out of the conduit along the length of the conduit.

52. A method for treating water with nanobubbles using nanobubbles generated using a method as claimed in claim 9 so that electrodes are preferentially configured to be suspended from a floating platform and positioned immediately below the surface of the bulk aqueous medium exposed to ambient air so as to generate nanobubbles from dissolved oxygen that has dissolved from the ambient air into the aqueous medium; wherein the voltage applied across the electrodes is produced using a battery that is powered using a solar cell located on the platform floating above the electrodes53. A method for treating water with nanobubbles using nanobubbles generated using a method as claimed in claim 9 wherein aqueous medium is drawn through one or more openings in closed conduits containing electrodes from one location in a bulk aqueous medium and discharged through one or more openings in closed conduits back to a separate location in the bulk aqueous medium;Configuring the closed conduits so that they are immersed in the aqueous medium and held in position suspended from floats or otherwise fixed or anchored within the bulk aqueous medium; wherein the conduits containing electrodes are preferentially configured to be positioned immediately below the surface of the bulk aqueous medium exposed to ambient air so as to generate nanobubbles from dissolved oxygen that has dissolved from the ambient air into the aqueous medium; a water pump is employed to draw the aqueous medium from the conduits containing electrodes and pump it into the conduits discharging the aqueous medium containing nanobubbles; and the discharging conduits are preferentially configured to be located so that the aqueous medium containing nanobubbles is discharged to regions of the bulk aqueous medium where the effects of treating the bulk aqueous medium will be most beneficial.

54. A method for destroying or inhibiting the growth of cyano-bacteria (blue-green algae) in water bodies by treating the water with nanobubbles containing oxygen wherein the nanobubbles are generated using the method of claims 53 and 54.

55. A method for increasing the dissolved oxygen content of water in the benthic region of water-bodies such as ponds, lakes, stream and rivers by treating the water with nanobubbles containing oxygen wherein the nanobubbles are generated using the method of claim 54.

56. A method for reducing the Chemical Oxygen Demand of water-bodies such as ponds, lakes, streams and rivers by treating the water with nanobubbles containing oxygen wherein the nanobubbles are generated using the method of claims 53 and 54.

57. A method for increasing the Oxidation Reduction Potential of water-bodies such as ponds, lakes, streams and rivers by treating the water with nanobubbles containing oxygen wherein the nanobubbles are generated using the method of claims 53 and 54.

Images