Filtration method and associated device and system

Abstract

A filtration method using an ultrasonic atomiser having a piezoelectric transducer operatively associated with a membrane having apertures formed therethrough, the method comprising: positioning the atomiser such that: at least a portion of a first face of the membrane is in contact with liquid to be filtered; and at least a portion of an opposite second face of the membrane is exposed to an environment into which liquid filtered via the atomiser can be emitted; and applying an electrical voltage to vibrate the transducer such that the membrane vibrates to move liquid through the apertures so as to emit filtered liquid out the second face of the membrane and into the environment, the apertures being sized to substantially prevent passage of contaminants therethrough.

Description

[0001] Filtration method and associated device and system

[0002] The complete specifications of Australian provisional patent application nos.

[0003] 2025900586 and 2025902197 as originally filed are incorporated herein by reference.

[0004] TECHNICAL FIELD

[0005] The subject matter of the present application relates to a filtration method and associated device and system. In particular, the present specification relates to the filtering of contaminants from a liquid such as water. The filtration method, device and system may be adapted for a variety of applications, including applications in the fields of agriculture, aquaculture, farming, water sanitation and hygiene, and so forth.

[0006] BACKGROUND

[0007] Existing methods, devices and systems for filtering liquids such as water have various inconveniences and disadvantages. For example, existing filtration methods generally separate the filtration and cleaning functions, requiring distinct operational phases that interrupt the continuous processing of liquid. This separation means that filtration efficiency progressively degrades between maintenance cycles, and system downtime is necessary for cleaning procedures. Furthermore, conventional backwashing systems typically require substantial additional water volumes to achieve effective cleaning, resulting in significant waste water production.

[0008] Moreover, known filtration systems and methods often suffer from fouling and clogging issues that can reduce their effectiveness over time. As contaminants accumulate on filter surfaces, filtration capacity diminishes and requires maintenance interventions. Known solutions typically involve backwashing procedures, wherein the filtration process is stopped and the flow direction reversed to flush out accumulated debris. Such backwashing processes are disruptive to continuous operation, consume additional water and energy, and add complexity.

[0009] While the importance of filtering and aerating water in aquarium applications is well-known, the prior art can be relatively noisy, bulky, and unsightly. Moreover, the size of such systems may necessitate larger aquarium tanks, and thus water, than wouldotherwise be necessary. Such systems and devices may be relatively complex, and involve multiple parts or components, one or more of which may be difficult or inconvenient to maintain and / or replace.

[0010] Furthermore, many conventional filtration systems, such as reverse osmosis or traditional pressure-fed mesh filters, rely on the application of significant hydraulic pressure to force liquid through a filter medium. These pressurised systems typically require high-energy pumps and robust structural components to withstand the mechanical stresses of operation, which increases both the cost and the complexity of the system. Moreover, the use of pressure can often exacerbate fouling by compacting contaminants against the filter surface, making them more difficult to remove during cleaning cycles.

[0011] There is a need to address the above, and / or at least provide a useful alternative.

[0012] SUMMARY

[0013] According to a first aspect of the present invention, there is provided a filtration method using an ultrasonic atomiser having a piezoelectric transducer operatively associated with a membrane having apertures formed therethrough, the method comprising: positioning the atomiser such that: at least a portion of a first face of the membrane is in contact with liquid to be filtered; and at least a portion of an opposite second face of the membrane is exposed to an environment into which liquid filtered via the atomiser can be emitted; and applying an electrical voltage to vibrate the transducer such that the membrane vibrates to move liquid through the apertures so as to emit filtered liquid out the second face of the membrane and into the environment, the apertures being sized to substantially prevent passage of contaminants therethrough. In this way, movement of liquid through the apertures is driven by the high-frequency vibration of the membrane (rather than, for example, the application of external hydraulic pressure to the liquid).In some embodiments, the membrane at least partially comprises a curved profile; a curved profile may provide enhanced vibration amplitude as compared with a relatively flat membrane.

[0014] In certain embodiments, at least a portion of the second face of the membrane is exposed to air such that vibration of the membrane directs air through the apertures and into the liquid being filtered. It is envisaged that the piezoelectric transducer may be configured to vibrate in a radial expansion and contraction mode.

[0015] It is considered that the voltage applied and the sizing of the apertures is such that air introduced through the apertures is sufficient to prevent contaminants from obstructing the apertures at the first face of the membrane so that liquid can continue to be drawn therethrough. For example, the voltage applied may be equal to or greater than 50 volts. In certain examples, the voltage may be between 50 and 100 volts, inclusive.

[0016] It is envisaged that each aperture comprises a first diameter associated with the first face of the membrane, and a second diameter associated with the second face of the membrane, wherein: the second diameter is smaller than the first diameter; and the second diameter is greater than 10 microns. In certain examples, the second diameter is between 15 microns and 20 microns, inclusive.

[0017] The atomiser may be mounted to a container containing the liquid to be filtered, wherein the first face of the membrane is in contact with and / or substantially immersed in the liquid, and the second face of the membrane is substantially exposed to the environment such that liquid in the container is filtered through the membrane and emitted out the second face thereof.

[0018] According to a second aspect of the present invention, there is provided a filtration device comprising: a housing having a substantially open upper end; an ultrasonic atomiser associated with the open upper end of the housing, the atomiser having a piezoelectric transducer operatively associated with a membrane having apertures formed therethrough; and an inlet via which liquid to be filtered can enter the housing,wherein in use: at least a portion of a first face of the membrane is in contact with liquid in the housing; at least a portion of an opposite second face of the membrane is exposed to an environment into which liquid filtered via the atomiser can be emitted; and application of an electrical voltage to vibrate the transducer vibrates the membrane so as to move liquid through the apertures so as to emit filtered liquid out the second face of the membrane, wherein the apertures are sized to substantially prevent passage of contaminants therethrough.

[0019] In use, at least a portion of the housing may be immersed in the liquid to be filtered such that the atomiser is positioned proximate the surface of the liquid. In certain embodiments, the membrane is angled from the surface of the liquid to be filtered such that filtered liquid is emitted through the second face in a direction that is generally angled relative to the surface of the liquid.

[0020] It is envisaged that the housing may comprise: an upper portion associated with the ultrasonic atomiser and the inlet; and a lower portion disposed beneath the upper portion, the lower portion being configured to capture contaminants filtered from the liquid. In at least one embodiment, the upper and lower portions of the housing are in fluid communication with one another such that contaminants filtered from the liquid can flow from the upper housing to the lower housing for collection therein.

[0021] Embodiments of the presently disclosed filtration device may further comprise a funnel disposed beneath the atomiser for guiding contaminants filtered from the liquid from the upper portion into the lower portion.

[0022] In certain embodiments, the upper and lower portions are separable from one another. This may facilitate cleaning of contaminants out from the lower portion.

[0023] The filtration device may comprise a float for positioning the device relative to a surface level of the liquid to be filtered such that at least a portion of the membrane is maintained thereabove. In certain embodiments, the filtration device may also comprise a cover for redirecting filtered liquid emitted from the membrane. In at least oneembodiment, the filtration device may also comprise securing means for securing a position of the device relative to a container containing the liquid to be filtered.

[0024] According to a third aspect of the present invention, there is provided an aquarium filtration system comprising a filtration device according to a second aspect of the present invention.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0027] Fig. 1 A is prior art showing an ultrasonic atomiser engaged with a wetted sponge and emitting a liquid mist;

[0028] Fig. 1 B is a schematic top view of an ultrasonic atomiser having a piezoelectric transducer operatively associated with a membrane with apertures formed therethrough;

[0029] Fig. 2 is a front perspective view of a container of water containing contaminants being filtered via an ultrasonic atomiser associated with a container wall;

[0030] Fig. 3A is a front perspective view of a filtration device according to an embodiment of the presently disclosed subject matter;

[0031] Fig. 3B is a rear perspective view of the device of Fig. 3A;

[0032] Fig. 4 is an exploded rear perspective view of the housing and float of the device of Fig.

[0033] 3A; and

[0034] Fig. 5 is a front perspective view of the filtration device of Fig. 3A secured in a tank.

[0035] DETAILED DESCRIPTION

[0036] Fig. 1 A shows the working principle of an off-the-shelf ultrasonic atomiser 2 positioned on a wetted sponge 4. Referring also to Fig. 1 B, the atomiser 2 comprises a

[0037] ring-shaped piezoelectric transducer 6. In one embodiment, the piezoelectric transducer 6 is a ring composed of PZT-4 material, having an outer diameter of approximately 16 mm, an inner diameter of approximately 8 mm, and a thickness of approximately 0.77 mm. The transducer 6 is operatively associated with a membrane 8 having apertures 10 formed therethrough. In the depicted embodiment, the transducer 6 surrounds and is inmechanical communication with the membrane 8 which is in the form of a disc having small apertures 10 formed therethrough. The transducer 6 and membrane 8 may be secured together using a suitable adhesive, such as an epoxy structural adhesive. The membrane 8 is in the form of a disc which may be composed of 304 stainless-steel, having a diameter of approximately 16 mm and a thickness of approximately 0.08 mm.

[0038] When an electrical voltage is applied to the piezoelectric ring 6 (e.g., controlled via a PCB 12 in Fig. 1A), the ring 6 converts the electrical energy into mechanical energy. In particular, when electricity is delivered to the piezoelectric ring 6, the ring 6 responds by vibrating at a high frequency. In turn, the perforated membrane 8 is caused to oscillate back and forth, and this working principle has been utilised in devices such as nebulizers to convert a fluid, such as a medicine, into a fine mist for inhalation.

[0039] The membrane 8 may not be perfectly flat. Rather, it may comprise a slight curvature, particularly in the region where the apertures 10 are located. This curvature, which may be a convex or dome-like shape, is configured to increase the vibration amplitude and displacement of the membrane 8 during operation. In particular, when electricity is delivered to the piezoelectric ring 6, the ring 6 responds by vibrating at a high frequency in a radial expansion and contraction mode. In turn, this radial motion of the ring 6 causes the perforated membrane 8 to oscillate back and forth.

[0040] In Fig. 1 A, a first (lower) face of the membrane 8 of the atomiser 2 is in contact with an upper surface of the wetted sponge 4, whereas an opposite second face of the membrane 8 is exposed to the atmosphere. When an electrical voltage is applied to the transducer 6, oscillation of the membrane 8 against the wetted sponge 4 causes liquid therein to be emitted out the second face of the membrane 8 as a fine mist 14. The inventors have discovered that this mechanism of atomizing liquid can be utilised for filtration thereof. In particular, while liquid can pass through the small apertures 10 in the membrane 8 of the atomiser 2 so as to be emitted as a mist 14, contaminants in the liquid, such as those that are larger than the apertures, cannot pass therethrough. In this way, the oscillating disc 8 acts like an ‘active’ mesh-like filter, the motion of which‘pumps’ water out one face of the membrane 8 (as a filtered mist 14) while contaminants are blocked from passing through the apertures 10 of the membrane 8.

[0041] This filtering functionality is counter-intuitive because it is widely believed that as the contaminated liquid is drawn through the membrane 8, contaminants in the liquid would similarly be drawn toward the membrane 8 and clog the apertures 10, thereby inhibiting further filtration. However, the inventors have discovered that with apertures of sufficient size and / or with the application of sufficient voltage, oscillation of the membrane 8 also provides backwashing, whereby air from the atmosphere is pumped through the membrane 8 and into the contaminated water, the air helping to agitate the side of the membrane that is in contact with the contaminated water. It has been discovered that this introduction of air back into the contaminated water is effective at ‘pushing’ the contaminants away from the immersed face of the membrane, thereby helping to prevent the contaminants from clogging or otherwise blocking the apertures.

[0042] It is thus envisaged that the oscillating membrane functions not only to expel liquid out of the membrane (e.g., as a mist), but also to draw or ‘pump’ air into the contaminated liquid in a direction opposite to that of the liquid expulsion. In this way, the atomiser appears to provide both filtration and backwashing functionality.

[0043] The present specification thus discloses a filtration method using an ultrasonic atomiser having a piezoelectric transducer that is operatively associated with a membrane having apertures formed therethrough. In particular, the method involves

[0044] positioning the atomiser such that at least a portion of a first face of the atomiser membrane is in contact with and / or immersed in a liquid to be filtered, whereas at least a portion of an opposite second face of the membrane is not in contact with said liquid. In particular, the second face is exposed to an environment into which liquid filtered via the atomiser can be emitted. In other words, one side of at least some of the membrane apertures is immersed in the liquid, while the opposite side of those same apertures is not. In this way, the membrane acts to ‘pump’ liquid that is in contact with the first face of the membrane out into the environment via the opposite second face of the membrane. The membrane can also act to ‘pump’ air from the second face of themembrane into the contaminated liquid via the first membrane so as to achieve the aforementioned backwashing functionality. The presently disclosed filtration method thus involves applying an electrical voltage to vibrate the transducer such that the membrane vibrates to move liquid through the apertures so as to emit filtered liquid out the second face of the membrane and into the environment. It is envisaged that the apertures are sized to substantially prevent passage of contaminants therethrough.

[0045] In embodiments of the presently disclosed filtration method, the atomiser may be positioned at a boundary (e.g., a surface) of the liquid to be filtered. Such a method may provide a versatile approach to filtration that need not be constrained by specific container configurations or orientations. For example, an ultrasonic atomiser can be positioned such that a first face of the membrane thereof is immersed in the liquid to be filtered, whilst the opposite second face of the membrane is exposed to an environment for receiving the filtered liquid.

[0046] It is thought that a relationship exists between the voltage applied to the atomiser and the diameter of the apertures, and in particular, the diameter of the apertures on the side of the membrane that is not in contact with the liquid to be filtered. For example, with sufficiently large aperture diameters on the liquid side, and / or a sufficiently large voltage, it has been discovered that actuation of the atomiser can facilitate the ‘pumping’ of air into the contaminated liquid to achieve the backwashing effect. In certain embodiments, this backwashing effect has been achieved with liquid-side aperture diameter sizes of between approximately 10 microns and approximately 20 microns, and with voltages greater than approximately 50 volts. For example, the voltage applied may be between approximately 50 volts and approximately 100 volts, inclusive. In certain filtration methods, it is observed that the membrane of the atomiser may oscillate or vibrate at approximately 0.1 megahertz.

[0047] Where the apertures of the membrane comprise a first diameter associated with one face and a second diameter associated with the opposite face, it is preferable for the smaller diameter side to be the side that faces into the environment such that at least a portion of that side is not in contact with the liquid to be filtered.Fig. 2 shows an arrangement to illustrate embodiments of the presently disclosed filtration method. Fig. 2 depicts an open container 16 in which liquid to be filtered is contained. In particular, the container 16 is shown containing contaminated water 18. An atomiser 2 is mounted via an opening formed in a wall 20 of the container 16 such that a first face of the atomiser membrane 8 is substantially immersed in the contaminated liquid 18, while a second face of the membrane 8 faces outside of the container 16 and into an environment into which filtered water is to be emitted. In the depicted example, the second face of the membrane 8 is exposed to air outside of the container 16. When the atomiser 2 is actuated, the resulting vibration of the membrane 8 pushes the liquid to be filtered 18, but not contaminants therein, through the apertures of the membrane 8 so that filtered water is emitted out the second face of the membrane 8 and into the environment. The depicted example shows filtered water spraying into the environment as a fine mist 22. Embodiments of the presently disclosed filtration method thus enable generally continuous and simultaneous filtration and backwashing of contaminated liquid.

[0048] As discussed, vibration of the membrane 8 during the presently disclosed filtration method simultaneously introduces air into the contaminated liquid 18. In particular, as the membrane 8 vibrates, air is drawn through the second (‘air-side’) face thereof and ‘pumped’ into the contaminated liquid 18 through the first face of the membrane 8. It is thought that air is introduced as a result of the oscillating motion of the membrane 8. As the membrane 8 vibrates to push liquid through the apertures toward and out the second face of the membrane 8 into the atmosphere, air is simultaneously drawn through the apertures in the opposite direction during the oscillation cycle. This is thought to create air bubbles within the liquid 18 being filtered which continuously agitate the (water-side) first face of the membrane 8, thereby mitigating accumulation of contaminants that might otherwise clog the apertures at the first face of the membrane 8 and potentially reduce filtration efficiency.

[0049] Unlike conventional backwashing systems that require interrupting the filtration process to clean the filter medium, embodiments of the presently disclosed filtration method mayhelp to maintain filtration performance continuously. Air bubbles generated during filtration serve to dislodge contaminants that might otherwise accumulate at the first face of the membrane, ensuring sustained throughput without requiring separate maintenance cycles. This represents a significant advancement over traditional filtration methods where cleaning and filtration must occur as distinct, sequential operations. It is considered that the presently disclosed filtration method can be readily adapted for a wide variety of filtration applications across various industries. The versatility of positioning the ultrasonic atomiser at any boundary of liquid to be filtered enables implementation in contexts where traditional filtration systems may be impractical or inefficient. For example, the presently disclosed filtration method may be utilised by any number of different filtration devices which can exploit the simultaneous filtering and backwashing functionality that the inventors have discovered can be provided by ultrasonic atomisers.

[0050] In general, such a filtration device may comprise a housing having an opening, the atomiser being positioned or otherwise associated with the opening so that filtered liquid can be emitted therethrough (e.g., as a mist). It is considered that the filtration device may comprise a power source for applying an electrical voltage to the atomiser, though of course the power source may be supplied separately and connected to the device.

[0051] The housing may also comprise an inlet via which liquid to be filtered can enter the housing. For example, in use, at least a portion of the housing may be immersed in the liquid to be filtered, wherein liquid enters the housing via the inlet and makes contact with at least a portion of the first face of the membrane of the atomiser. In certain embodiments, the filtration device may comprise a float or other means to provide the device with a level of buoyancy while immersed in liquid. In particular, the float is configured to maintain the filtration device relative to the surface of the liquid such that at least a portion of the second (upper) face of the membrane is exposed to the environment into which liquid filtered via the atomiser can be emitted.

[0052] An example filtration device 24 is shown in Figs. 3 to 5. Referring to Fig. 4, the depicted housing 26 of the filtration device is formed from an upper portion 26a having the openupper end 28 and liquid inlets 30, and a lower portion 26b that is securable to and arranged below the upper portion 26a. In the depicted embodiment, the upper and lower portions 26a, 26b are removably securable to one another via cooperating screw threads 32. In use, the upper portion 26a is at least partially received in the lower portion 26b, and contaminants filtered via the atomiser 2 are arranged to drop down through the upper portion 26a so as to be collected within the lower portion 26b. To this end, both the upper and lower portions 26a, 26b are generally cylindrical, and a base of the upper portion 26a is formed with a funnel 34 which extends down into the open space 36 within the lower portion 26b. When the upper and lower portions 26a, 26b are secured to one another, the funnel 34 is positioned so that it is ‘suspended’ within the space 36 of the lower portion 26b such that the two portions 26a, 26b are in fluid communication with one another via the funnel 34. During filtration, contaminants filtered from the liquid fall through the funnel 34 so as to collect within and at the base of the lower portion 26b. The narrowing funnel 34 facilitates the travel of contaminants from the upper portion 26a into the lower portion 26b, while inhibiting travel of contaminants collected in the lower portion 26b from flowing back into the upper portion 26a.

[0053] The side wall of the upper portion 26a (at a height below the atomiser 2) is formed with inlets 30 through which liquid can enter the upper portion 26a. In use, at least a portion of the lower face of the atomiser membrane 8 contacts and / or is immersed in liquid that has entered the upper portion 26a, whereas at least a portion of the upper face of the membrane 8 is maintained above the surface of the liquid. In this way, when the atomiser 2 is actuated, oscillation of the membrane 8 acts to expel liquid, but not contaminants therein, out the upper face of the membrane 8 as a fine mist or spray. The contaminants, which are too large to fit through the apertures of the membrane 8, are prevented from passing therethrough, and thus may flow (e.g., fall downwardly) towards the lower portion 26b for collection therein.

[0054] The upper portion 26a of the filtration device 24 may comprise positioning means for receiving the atomiser so that it is positioned toward the open upper end of the upper portion. For example, in Fig. 4, the positioning means comprise two pairs of spacedapart projections 38 extending inwardly from an interior wall of the upper portion 26a (only one pair of projections 38 is shown in Fig. 4; the second pair projects from the interior wall opposite the first pair). In use, the ring-shaped transducer 6 of the atomiser 2 slots between the projections 38 of each opposed pair of projections 38 so as to be held within the upper housing portion 26a. In the depicted embodiment, the projections 38 are slightly angled (relative to horizontal) so that, in use, the atomiser 2 is also held at an angle relative to the surface of the liquid (as can be seen in Fig. 3A). In this way, liquid filtered through the atomiser 2 is expelled at an angle rather than being emitted straight up, which would result in the filtered liquid falling back down onto the upper face of the membrane 8.

[0055] Fig. 4 also shows an example float 40 which is in the form of a collar received beneath a rim 42 of the upper housing portion 26a. Referring also to Fig. 3A, it can be seen that the float 40 is arranged generally at the same level of the atomiser 2 so that, in use, at least a portion of the lower face of the atomiser membrane 8 is immersed in the liquid to be filtered, while at least a portion of the upper face of the atomiser membrane 8 is exposed to the environment.

[0056] Fig. 5 shows the filtration device 24 arranged for use within a tank 44, such as that of an aquarium. Where the tank 44 has a substantially open top, it may be preferable to ensure any mist emitted from the atomiser 2 is not expelled outside of the tank 44. In this regard, the present filtration device 24 may comprise a cover 46 to help redirect mist emitted by the atomiser 2. An example cover 46 is shown in Figs. 3A and 3B, and provides an obstructing ‘ceiling’ spaced above the atomiser 2 for receiving and / or redirecting at least a portion of the mist emitted from the atomiser 2. In the depicted embodiment, a rear side of the cover 46 has an attachment location 48 via which the filtration device 24 can be secured, relative to the tank 44, via elements such as a cord 50 terminating in a connector 52 which clips to the tank 44, as shown in Fig. 5. The cabling 54 via which the atomiser 2 is powered may extend rearwardly through an opening 56 formed in the cover 46, as shown in Figs. 3A and 3B. In the depicted embodiment, a rear of the lower housing portion 26b is depicted with track-like guides58 (see Fig. 4) configured to slidingly engage into corresponding slots (not shown) formed in the cover 46 to hold the cover 46 in place.

[0057] Cleaning and maintenance of the present filtration device 24 is relatively convenient and straightforward. With the power source turned off, the filtration device 24 can be removed from the liquid in which it is at least partially immersed. The upper and lower portions 26a, 26b, can be separated from one another, whereby contaminants collected in the lower chamber 26b can be discarded.

[0058] A key innovation in the presently disclosed filtration method (and associated device and system) thus lies in the dual-action "pumping" effect generated by the high-frequency oscillation of the membrane. Unlike traditional passive filters, the present specification considers using an ultrasonic atomiser to create a dynamic interface that moves fluid and air in opposite directions simultaneously.

[0059] When an electrical voltage (e.g., between 50V and 100V) is applied to the piezoelectric transducer, it can vibrate at approximately 0.1 MHz. This mechanical energy causes the membrane 8 to oscillate, which acts as a high-speed pump. Liquid from the contaminated source enters the first (at least partially immersed) face of the membrane. The vibration "pumps" the liquid through the apertures of the membrane, emitting it as a purified mist or spray from the second face of the membrane into the environment. Because the apertures are sized between 10 and 20 microns, contaminants larger than these openings are physically blocked from passage.

[0060] Embodiments of the presently disclosed filtration method and associated devices and systems may address the issue of membrane fouling through a counter-intuitive backwashing process that occurs during the filtration cycle. As the membrane vibrates to expel liquid, the oscillation cycle simultaneously draws air from the second face (the "air-side") and forces it back through the apertures into the contaminated liquid. This "pumped" air creates a continuous stream of micro-bubbles at the first face of the membrane. These bubbles provide constant agitation, "pushing" accumulated debris and contaminants away from the aperture entries.The efficiency of this dual-action filtration and backwashing mechanism may be dependent on the specific geometry of the apertures. For example, each aperture may feature a tapered design where the first diameter (liquid-side) is larger than the second diameter (air-side). Positioning the smaller diameter toward the environment (air) helps to ensure an adequate pressure differential for both the expulsion of liquid mist and the intake of air for backwashing. This may allow for continuous operation without the need for separate cleaning cycles or system downtime.

[0061] It is to be understood that various alterations, modifications and / or additions may be made without departing from the spirit of the present invention as disclosed herein. For example, while the Figures show an atomiser that is removable from the housing, it is considered that the atomiser can be integrally formed with the housing. Of course, any suitable component or structural element may be provided to hold the atomiser in place. In yet another example, the atomiser may be interconnected to the housing via an adjustment means, such as a tiltable plate or the like, which may enable ready adjustment of the angle of the atomiser relative to the surface of the liquid. It is also envisaged that the characteristics of the atomiser, including the size, shape and number of the apertures in the membrane, can be configured to achieve different filtration and aeration outcomes. The presently disclosed filtration device may be battery-powered though can alternatively or additionally also be powered via mains electricity.

[0062] Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

CLAIMS1. A filtration method using an ultrasonic atomiser having a piezoelectric transducer operatively associated with a membrane having apertures formed therethrough, the method comprising:positioning the atomiser such that:at least a portion of a first face of the membrane is in contact with liquid to be filtered; andat least a portion of an opposite second face of the membrane is exposed to an environment into which liquid filtered via the atomiser can be emitted; and applying an electrical voltage to vibrate the transducer such that the membrane vibrates to move liquid through the apertures so as to emit filtered liquid out the second face of the membrane and into the environment, the apertures being sized to substantially prevent passage of contaminants therethrough.

2. The method of claim 1 , wherein at least a portion of the second face of the membrane is exposed to air such that vibration of the membrane directs air through the apertures and into the liquid being filtered.

3. The method of claim 2, wherein the voltage applied and the sizing of the apertures is such that air introduced through the apertures is sufficient to prevent contaminants from obstructing the apertures at the first face of the membrane so that liquid can continue to be drawn therethrough.

4. The method of any one of the preceding claims, wherein the voltage applied is greater than approximately 50 volts.

5. The method of any one of the preceding claims, wherein each aperture comprises a first diameter associated with the first face of the membrane, and a second diameter associated with the second face of the membrane, wherein:the second diameter is smaller than the first diameter; andthe second diameter is greater than 10 microns.

6. The method of claim 5, wherein the second diameter is between approximately 15 microns and approximately 20 microns.

7. The method of any one of the preceding claims, wherein the atomiser is mounted to a container containing the liquid to be filtered, wherein the first face of the membrane is substantially immersed in the liquid, and the second face of the membrane is substantially exposed to the environment such that liquid in the container is filtered through the membrane and emitted out the second face thereof.

8. A filtration device comprising:a housing having a substantially open upper end;an ultrasonic atomiser associated with the open upper end of the housing, the atomiser having a piezoelectric transducer operatively associated with a membrane having apertures formed therethrough; andan inlet via which liquid to be filtered can enter the housing,wherein in use:at least a portion of a first face of the membrane is in contact with liquid in the housing;at least a portion of an opposite second face of the membrane is exposed to an environment into which liquid filtered via the atomiser can be emitted; and application of an electrical voltage to vibrate the transducer vibrates the membrane so as to move liquid through the apertures so as to emit filtered liquid out the second face of the membrane, wherein the apertures are sized to substantially prevent passage of contaminants therethrough.

9. The device of claim 8, wherein in use, at least a portion of the housing is immersed in the liquid to be filtered such that the atomiser is positioned proximate the surface of the liquid.

10. The device of claim 8 or 9, wherein in use, the membrane is angled from the surface of the liquid to be filtered such that filtered liquid is emitted through the second face in a direction that is generally angled relative to the surface of the liquid.

11. The device of any one of claims 8 to 10, wherein the housing comprises:an upper portion associated with the ultrasonic atomiser and the inlet; and a lower portion disposed beneath the upper portion, the lower portion being configured to capture contaminants filtered from the liquid.

12. The device of claim 11 , wherein the upper and lower portions of the housing are in fluid communication with one another such that contaminants filtered from the liquid can flow from the upper housing to the lower housing for collection therein.

13. The device of claim 11 or 12, further comprising a funnel disposed beneath the atomiser for guiding contaminants filtered from the liquid from the upper portion into the lower portion.

14. The device of any one of claims 11 to 13, wherein the upper and lower portions are separable from one another.

15. The device of any one of claims 8 to 14, further comprising a float for positioning the device relative to a surface level of the liquid to be filtered such that at least a portion of the membrane is maintained thereabove.

16. The device of any one of claims 8 to 15, further comprising a cover for redirecting filtered liquid emitted from the membrane.

17. The device of any one of claims 8 to 16, further comprising securing means for securing a position of the device relative to a container containing the liquid to be filtered.

18. An aquarium filtration system comprising the filtration device of any one of claims

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