WO2012060692A1

WO2012060692A1 - Wireless sound source, device and method for disinfecting a fluid

Info

Publication number: WO2012060692A1
Application number: PCT/NL2011/050689
Authority: WO
Inventors: Simon Bakker; Johannes Kuipers; Doekle Reinder Yntema; Harry Bruning; Huub Rijnaarts
Original assignee: Stichting Wetsus Centre Of Excellence For Sustainable Water Technology
Priority date: 2010-10-08
Filing date: 2011-10-10
Publication date: 2012-05-10
Also published as: NL2005488C2

Abstract

The invention relates to a wireless sound source for disinfecting a fluid, comprising an ultrasonic converter for direct or indirect conversion of an electric, magnetic or electromagnetic field to ultrasonic sound. The invention also relates to a device and method therefor, wherein the device comprises : a container for holding a fluid with at least one inlet and at least one outlet; and at least one sound source placed in the container; and at least one field generator which creates an electric, magnetic or electromagnetic field during use.

Description

WIRELESS SOUND SOURCE, DEVICE AND METHOD FOR DISINFECTING A FLUID

The invention relates to a sound source for disinfecting a fluid. This relates for instance to the purification of a waste water flow using a sound source.

Known in practice are sound sources comprising an ultrasonic converter (transducer) for converting an electrical voltage to ultrasonic sound. Using such a sound source an ultrasonic sound can be produced with which a fluid, for instance water, can be disinfected. Use is for instance made of a piezoelectric ultrasonic converter. With the known sound sources a great deal of energy is required for good disinfection.

An object of the invention is to obviate the above problem and to provide an effective and efficient sound source for disinfecting a fluid.

This object is achieved with the wireless sound source according to the invention, the wireless sound source comprising an ultrasonic converter for direct or indirect conversion of an electric, magnetic or electromagnetic field to ultrasonic sound.

In the context of the invention ultrasonic sound is understood to mean sound with a frequency higher than 1 kHz, in particular higher than 10 kHz, and more particularly higher than 18 kHz. The transition zone of "audible ultrasonic sound", which differs per person, is included in the term ultrasonic. An upper limit of the frequency of ultrasonic sound is generally defined at 800 MHz. Sound with a frequency above 800 MHz is referred to as hypersonic sound. In this text ultrasonic is understood to mean both ultrasonic sound up to 800 MHz and hypersonic sound above 800 MHz.

In the context of the invention disinfection is understood to mean inter alia a reduction in the number of viable micro-organisms, including viruses, phages, protozoa, bacteria such as escherichia coli, fungi and plants. It is noted that the wireless sound source according to the invention can also be applied to clean membranes or for pretreatment during a UV treatment.

The ultrasonic converter can convert an electric, magnetic or electromagnetic field to ultrasonic sound. This conversion is direct or indirect.

For indirect conversion of such a field the field is for instance first converted to an electrical voltage or current, after which it is converted by the converter to ultrasonic sound. This voltage can for instance be realized by capacitive coupling to an electric field, inductive coupling to a magnetic field or by generating an electrical voltage from received radio waves (electromagnetic field) .

An ultrasonic converter for direct conversion of an electric field comprises for instance a coupling to an accumulator or battery, whereby the electric field generated by the accumulator or battery can be directly converted to ultrasonic sound.

Because the sound source according to the invention is wireless, it can be easily placed in a fluid. No cables need be laid. This is particularly advantageous for large-scale applications. A plurality of sound sources according to the invention can be provided movably in a fluid without their freedom of movement being limited by the length of a cable. In addition, the problem of cables becoming entangled does not occur with the sound source according to the invention.

In addition, it is possible to arrange the sound sources according to the invention as a fluidized bed in a disinfecting device .

The intensity of sound decreases quadratically in free field with the distance from the sound source. If sound is applied for the purpose of disinfecting a fluid in which absorbent particles are present, the intensity of the sound decreases even more strongly. In any event, when known sound sources are applied, the sound intensity in the fluid for treatment is not constant over the volume of the fluid. This means that the energy density over volume of the fluid for treatment is not constant, whereby the sound source must produce sound with a higher intensity in order to realize a certain minimum intensity in each volume element of the fluid volume. Energy consumption is therefore relatively high. More energy is for instance required than is available. Because the wireless sound source according to the invention can move through a fluid without the limitations of a cable, it is simple to place a plurality of sound sources according to the invention in a fluid. The sound intensity will hereby not fluctuate, or hardly so, over the volume of the fluid. It is also possible to do without producing sound having an intensity considerably above the minimum intensity. This is energy-efficient .

A further advantage is that the wireless sound source according to the invention simplifies upscaling of disinfection devices. Instead of providing a sound source which produces sound with a greater intensity, more sound sources according to the invention can simply be added to the device. This is moreover more energy-efficient.

The sound source preferably comprises a watertight housing comprising the converter. The sound source is hereby wholly or partially protected from the fluid during use, and damage, for instance through short-circuiting, is hereby prevented or reduced.

Sound is preferably produced such that cavitation occurs in the fluid for treatment. The ultrasonic sound waves create vacuum bubbles in the fluid. These bubbles implode and this results in a very high pressure and temperature locally. Micro-organisms can be killed as a result. In addition, it is possible for some organic micro-contaminants, such as dioxane, MBTE,

phenylbenzene, medicine residues and hormones, to be decomposed or otherwise rendered harmless.

In a further preferred embodiment according to the invention the ultrasonic converter converts an external electric, magnetic or electromagnetic field to an ultrasonic sound during use.

The wireless sound source is situated during use in an externally applied field. This field is converted directly or indirectly by the ultrasonic converter to ultrasonic sound. The sound source is thus provided with energy externally and wirelessly. The sound source can hereby be given a relatively small form, since no internal energy source need be provided. Furthermore, a sound source according to the invention can be remotely controlled by regulating the external field. It is for instance possible to activate or deactivate the sound source remotely by activating or deactivating the external field.

In a preferred embodiment according to the invention the converter comprises an electrical conductor for generating an induction voltage in a magnetic field, and an actuator operatively connected to the conductor for generating an ultrasonic sound.

This embodiment comprises an ultrasonic converter for indirect conversion of a field to ultrasonic sound via an induction voltage. Because an induction voltage is generated in the sound source according to the invention, existing actuators which convert a voltage to ultrasonic sound, such as

piezoelectric elements, can be applied.

In a further preferred embodiment the conductor comprises a capacitor operatively connected to the conductor and actuator so that a tuned circuit is formed.

The conductor for generating an induction voltage is operatively connected to a capacitor and optionally a resistor. The resonance frequency of the circuit can be chosen by selecting a correct value of the capacitor and optionally the resistor. The wireless sound source according to the invention can in this way be coupled to a magnetic field by means of resonant inductive coupling. This has the advantage that the resonance circuit determines the frequency for optimum energy transfer. It is hereby possible to provide a wireless sound source which is tuned to a specific frequency of a magnetic field. It is noted that this need not correspond to the frequency of the produced ultrasonic sound.

The resonance frequency is preferably adjustable, for instance by providing a variable capacitor and optionally a variable resistor. The resonance frequency is more preferably automatically adjustable on the basis of values measured in the fluid. The sound source is for instance provided with a measuring system and a control system for modifying the value of a capacitor or a resistor on the basis of the measurements of the measuring system.

An induction voltage is for instance generated in the above described embodiments by moving the electrical conductor in a magnetic field.

The electrical conductor is preferably a coil for generating an induction voltage in a time-varying magnetic field. The generated induction voltage does not hereby depend on movement of the electrical conductor. The time-varying magnetic field is preferably a magnetic field which oscillates at a fixed frequency.

The conductor is preferably embodied as a coil with a core such as a ferrite core. The interaction between the coil and field is hereby enhanced. Experiments have shown that, when a coil with a core is applied, the interaction between the coil and the magnetic field is to large extent insensitive to the medium in which the sound source is immersed. This therefore ensures a sufficient interaction for efficient energy transfer, irrespective of the fluid applied.

In a further preferred embodiment according to the invention the electrical conductor is manufactured by means of

micro-machining.

A compact wireless sound source is hereby obtained according to the invention. In addition, it is possible to arrange the conductor by means of micro-machining on the actuator or on an element connected thereto. A wireless sound source is hereby provided which is inexpensive and easy to produce. The electrical conductor is for instance etched directly onto the actuator connected operatively to the conductor.

The electrical conductor as well as electrical components connected thereto, such as capacitors and/or resistors, are preferably arranged by means of micro-machining, such as etching, on the actuator or on another element such as a printed circuit board. An integrated circuit is hereby obtained for the wireless sound source according to the invention, which can be given a relatively small form as a result. The dimensions are then determined mainly by the size of the actuator. These are typically about 5-10 mm in diameter.

In a further preferred embodiment according to the invention the actuator is a piezoelectric element.

Because the actuator is a piezoelectric element, sound can be produced with a frequency in a relatively wide frequency range. Typical piezoelectric elements can produce sound in a range of about 10 kHz to about 1 GHz. Higher or lower frequencies are not precluded.

In a preferred embodiment according to the invention the actuator is a magnetodynamic element.

The actuator is for instance a magnet around which a coil is wound. The coil can be connected to the circuit of the electrical conductor for generating an induction voltage. If an alternating voltage is applied to the coil in which the magnet is located, the magnet will move reciprocally and thereby produce sound.

In a preferred embodiment according to the invention the ultrasonic converter comprises a magnetostrictive or

piezomagnetic element for converting a time-varying magnetic field to ultrasonic sound.

The time-varying magnetic field is for instance a magnetic field with a fixed frequency.

In this embodiment there is a direct conversion of the time-varying magnetic field to ultrasonic sound. Because this is a direct conversion, one signal can be used to control multiple sound sources according to the invention. The frequency of the produced ultrasonic sound is directly related to the frequency of the magnetic field that is converted. This frequency can hereby be directly controlled by means of regulating the frequency of the field. In a preferred embodiment according to the invention the frequency of the ultrasonic sound produced by the sound source lies in a range of 15 kHz-100 MHZ and preferably of 15 kHz-25 kHz, 25 kHz-100 kHz, 100 kHz-1 MHZ or 1 MHz-100 MHZ.

It has been found that the cell walls of micro-organisms become permeable in the frequency range of 15 kHz-40 kHz and that an efficient and effective elimination is achieved at higher frequencies. It is moreover possible at these frequencies to generate cavitation bubbles in the fluid.

The invention further relates to a device for disinfecting a fluid, comprising:

a container for holding a fluid with at least one inlet and at least one outlet; and

at least one sound source as described above placed in the container;

at least one field generator which creates an electric, magnetic or electromagnetic field during use.

Instead of a separate inlet and outlet the device comprises for instance an inlet which also functions as outlet. An inlet also functioning as outlet suffices for instance for batch-wise disinfection of a fluid with the device according to the invention. For a continuous disinfection process with a flowing fluid, at least one inlet and at least one outlet are required.

The device for disinfecting a fluid has the same advantages and effects as the sound source according to the invention.

The device according to the invention moreover has the advantage that it is easy to maintain and clean, since the at least one sound source is easy to remove from the container.

The device preferably comprises a plurality of sound sources as described above placed in the container. It is hereby possible to make as small as possible a distance between the sound source and a volume element of the fluid for treatment. This is moreover energy-efficient. In addition, it is simple to scale up the device by adding more sound sources to such a scaled-up device. The sound sources preferably form a fluidized bed in the container . The sound sources preferably create cavitation bubbles by means of ultrasonic sound. Because the sound sources form a fluidized bed, a uniform distribution of cavitation bubbles is obtained.

The field generator comprises for instance a primary coil for generating a magnetic field, and the container comprises a wireless sound source comprising a coil as specified above. The coil of the wireless sound source then functions as secondary coil .

In an advantageous embodiment the resonance frequency of the field generator is the same as the resonance frequency of the wireless sound sources for the purpose of efficient resonant inductive energy transfer from the field generator to the sound sources .

In a further preferred embodiment the field generator is located in the container. The field generated during use by the field generator is hereby not disrupted, or hardly so, by the container. In the case of for instance a magnetic field generator located inside a container, the magnetic field is hardly affected by the dielectric properties or the magnetic susceptibility of the container. Furthermore, the field generator is in this way situated as close as possible to the fluid for treatment, this being energy-efficient. There is a better interaction when the field generator is located inside the container.

In a preferred embodiment according to the invention the device comprises a first and a second sound source which produce ultrasonic sound at a different frequency.

The first sound source is for instance a piezoelectric element which is coupled to a coil and a capacitor and a resistor and which is tuned to a first frequency, and a second sound source comprising a circuit tuned to a second frequency. Because the device comprises a plurality of sound sources producing different frequencies of ultrasonic sound, multiple ultrasonic frequencies can be generated in one fluid. It is hereby possible for instance to generate one frequency for a first disinfection purpose and a second frequency for a second disinfection purpose. The first sound source is for instance tuned to a frequency for killing a first bacterium and the second sound source is tuned to a frequency for killing a second bacterium.

In a preferred embodiment according to the invention at least two sound sources occupy a different position in the container during use.

A first of the two sound sources is for instance located during use at the bottom of the container and a second of the at least two sound sources is at the top of the container. This is for instance realized by selecting different mass, shape and/or density of the sound sources. Different treatment zones are hereby created in the container. Treatment zones are for instance created in which different sound frequencies are produced by the sound sources.

In a preferred embodiment according to the invention at least two sound sources are tuned to different field frequencies.

The at least two sound sources can be controlled at a different field frequency. It is hereby possible as desired to control one of the sound sources or both sound sources, so that they produce a sound individually or simultaneously.

The at least two sound sources preferably produce sound at different frequencies and/or are located at a different position in the container, for instance because they have a different density.

In a further preferred embodiment the at least one field generator is set to vary the frequency of the created field during use .

Different sound sources tuned to different frequencies can hereby be successively controlled in time. The container for instance comprises a first sound source tuned to a field frequency of 25 kHz and a second sound source tuned to a field frequency of 100 kHz. It is noted that these field frequencies need not correspond to the frequency of the ultrasonic sound produced. By varying the created field from the first field frequency to the second field frequency the first sound source is controlled first, followed by the second sound source. In addition, it is possible with the field generator to create a pulsating field or a sweep field in which the frequency of the field changes gradually. In the control of the field generator account must be taken of the type of actuator being used in the sound source. If the sound source comprises a magnetostrictive element, this element will substantially follow the field. If a piezoelectric element coupled to a coil is applied, the sound source will substantially follow the time derivative of the applied field.

In an alternative preferred embodiment according to the invention the field generator is set to create a field during use comprising different frequencies which correspond to the frequencies to which the sound sources are tuned.

The field generated by the field generator during use is a superposition of fields with different frequencies. A plurality of sound sources tuned to a different frequency can hereby be controlled using one field.

In an alternative embodiment according to the present invention the device comprises at least two field generators, each set to create a field during use with a frequency corresponding to one of the frequencies to which the sound sources are tuned.

This is realized for instance by a device according to the invention comprising more than one field generator. The field generators can be set to produce a differing field frequency. The field generators are for instance controlled by a control system which activates or deactivates the different field generators subject to measurements of the fluid.

In a preferred embodiment according to the invention the device comprises at least two sound sources which are connected to each other in at least one network.

The at least two sound sources are for instance arranged in a rigid lattice so that they are positioned at fixed locations inside the container. The distance between adjacent sound sources in the network is for instance chosen such that it corresponds to a multiple of the wavelength of the ultrasonic sound produced during use, so that the sound sources produce sound in phase and so co-act to maximum extent so as to obtain the greatest possible sound intensity. In addition, it is possible by alternative arrangement to realize complex patterns by means of amplifying and extinguishing sound produced by the sound sources. Zones with a predetermined sound level and frequency can be created by tuning the phases and/or frequencies of the sound sources .

In a preferred embodiment according to the invention the device comprises at least one UV light source placed in the container. This is preferably at least one UV light source as described in Netherlands patent NL 1035089 of the same applicant.

Providing a UV light source in the container in combination with sound sources for generating ultrasonic sound can achieve a combined action of ultrasonic and ultraviolet. This produces a synergistic effect. Cavitations generated by the ultrasonic sound weaken for instance the cell wall of micro-organisms, whereby the micro-organisms are more sensitive to UV light. This enables an effective and efficient disinfection.

In a preferred embodiment according to the present invention the device comprises electrodes placed in the container. These are preferably electrodes as described in Netherlands patent NL 1035089 of the same applicant.

Electrodes placed in the container are for instance coupled to an electrical conductor for generating an induction voltage.

A gas discharge preferably occurs in bubbles in the fluid, wherein radicals are created which have a disinfecting action. Some examples of active radicals which can occur in a gas bubble during a gas discharge are oxygen radicals, OH radicals, halogen radicals and hydrocarbon radicals. These radicals have the result that micro-organisms are killed and organic components decomposed. Not only do radicals usually occur during a gas discharge, the plasma resulting during the discharge also results in the release of UV radiation. This can result in a kind of radical bombardment with the above described effects. In addition, the UV radiation also has a direct effect on possible contaminants in the fluid. The UV radiation can cause direct damage to DNA structures.

The application of electrodes in combination with ultrasonic sound has a synergistic effect. Cavitations generated by the ultrasonic sound weaken for instance the cell wall of micro-organisms, whereby the micro-organisms are more sensitive to a gas discharge.

Combinations with actuators other than those stated can also be envisaged, such as a combination of wireless sound sources according to the invention with a microwave generator.

In a preferred embodiment according to the invention the device comprises at least one X-radiation source placed in the container.

Providing at least one X-radiation source placed in the container makes it possible to treat a liquid with a combination of ultrasonic sound and X-radiation. As described above, it is possible to damage or weaken the cell wall of micro-organisms by means of ultrasonic sound. This increases the sensitivity of micro-organisms to X-radiation. X-radiation can for instance serve to damage DNA of micro-organisms. The combination of X-radiation and ultrasonic sound thus achieves a synergistic effect with which a liquid can be effectively disinfected.

In a further preferred embodiment the X-radiation source is an X-ray tube, preferably a micro-X-ray tube, which is electrically connected to a secondary coil. A wireless

X-radiation source is hereby obtained. The wireless X-radiation source has the same advantages and effects as described above for the wireless sound sources.

The combination of X-radiation and ultrasonic sound can also be applied separately in a device for disinfecting a fluid such as water. Such a device comprises a sound source and an X-radiation source. If desired, the device comprises an X-radiation source without sound sources being provided. A method is moreover possible for disinfecting a fluid comprising of exposing the fluid to X-rays and/or ultrasonic sound. The invention further relates to a method for disinfecting a fluid, comprising the following steps of:

- providing a disinfection device as described above;

- guiding a fluid to be disinfected into the container;

- applying a field with the field generator;

- disinfecting the fluid with at least one sound source as described above; and

- guiding the disinfected fluid out of the container.

The method has the same advantages and effects as the device and the wireless sound source.

Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings:

figure 1A shows a wireless sound source comprising a loudspeaker;

figure IB shows a wireless sound source comprising a piezoelectric crystal;

figure 2 shows an alternative embodiment of a sound source with a tuned circuit;

- figure 3 shows a piezoelectric sound source according to the invention;

figure 4 shows a device according to the invention in which magnetostrictive sound sources are placed in the container; figure 5 shows the device of figure 4 in use;

- figure 6 shows a device according to the invention in which sound sources are arranged in a network;

figure 7 shows a graph of the frequency of a magnetic field according to the invention which varies over time;

figure 8 shows a device according to the invention with a conical container in which actuators of differing shape and mass float;

figure 9 is a graph showing the quality factor and phase angle of the transmitter coil in a measurement with air and a measurement with water with a conductivity of 100 mS/m; figure 10 shows the cumulative coupling factor measured between one transmitter coil and a plurality of receiver coils;

figure 11 shows the efficiency of energy transfer between one transmitter coil and one receiver coil at different loads, both calculated and measured;

figure 12 shows the efficiency of energy transfer between one transmitter coil and a plurality of receiver coils, both calculated and measured; and

- figure 13 shows the efficiency of energy transfer as a function of the resistance of the load of the receiving circuit with n=l, 10, 20 and 50 receiver coils.

Wireless sound source 2 (figure 1A) comprises a watertight housing 4 in which is located an ultrasonic converter 6 which is connected to a coil 8 with core 9. In the shown embodiment the ultrasonic converter 6 is a loudspeaker.

Wireless sound source 2 can also comprise a piezoelectric crystal 7 as ultrasonic converter instead of a loudspeaker 6 (figure IB ) .

Wireless sound source 10 (figure 2) comprises a housing 12 in which are located an ultrasonic converter 14, a coil with core 16 and electrical element 18. Electrical element 18 can be a resistor or a capacitor, or a combination of a resistor and a capacitor can be applied. Ultrasonic converter 14 is situated partially outside housing 12 so that during use the ultrasonic sound-producing part of converter 14 is in contact with a fluid.

Wireless sound source 20 (figure 3) does not comprise a housing. The piezo-crystal constructed from layers 22, 24 is coupled to coil 26.

Device 28 (figure 4) for disinfecting a fluid comprises a water feed pipe 30 which runs gradually to a widened portion 34 which is closed on both sides with a grid 32. Situated inside grid 32 are magnetostrictive sound sources 36 according to the invention which form a fluidized bed. Outlet 37 is situated on the upper side of device 28. The sound sources 36 move through the water when it begins to flow as according to arrows 38, 39 (figure 5) . The water flows here along sound sources 36. The device is equipped with an additional housing 40, inside which a magnetic field is generated by means of coils (not shown) . Housing 40 is embodied in metal, so creating a Faraday cage.

Alternatively, a device 44 (figure 6) is provided in which sound sources are arranged in a lattice 48.

It is possible to vary the frequency of the applied electric, magnetic or electromagnetic field through time. Figure 7 shows an example hereof. Time is shown as a random unit on the horizontal axis. The frequency range in kilohertz is shown on the vertical axis. In a first period A the field generator generates a field with a frequency of 15-25 kHz in a device according to the invention. In a second period P a field generates a field with a frequency of 100 kHz-1 MHZ in a device according to the invention. In a third time period C the field generator generates a field with a frequency of 1 MHZ-100 MHZ in a device according to the invention. In the shown graph there is a stepwise transition between the different frequency ranges A, B, C. This transition can also take place gradually, for instance as a so-called sweep function.

Different treatment zones are created in device 54 (figure 8) . The container has a cone-like form 56 with inlet 58 and outlet 59. Tuned sound sources 64, 66 are placed in container 56. Sound sources 64 have a square form and, by selecting suitable values of a coil, capacitor and a resistor, are tuned to a first magnetic field frequency. This frequency corresponds to the field frequency of coil 60. Sound sources 66 have a triangular form and are lighter than sound sources 64, whereby they are located during use in the vicinity of coil 62. Sound sources 66 comprise a coil and a capacitor and a resistor, the values of which are selected so that they are tuned to a second magnetic field frequency corresponding to the field frequency generated by coil 62. Two treatments zones 61, 63 are in this way created at respectively coil 60 and coil 62. It is for instance possible for sound sources 64 to produce an ultrasonic sound with a frequency other than that of sound sources 66. Two treatments zones 61, 63 are hereby created in container 56 in which the fluid is treated with a different frequency of ultrasonic sound.

Container 56 also comprises UV light sources 68 which have a density such that they are present in both treatment zone 61 of coil 60 and in treatment zone 63 of coil 62. A simultaneous or successive treatment is hereby realized with ultrasonic sound from sound sources 64, 66 and ultraviolet light from wireless light sources 68.

Container 56 moreover comprises optional X-radiation sources 72, which are in this case positioned in treatment zone 63 of coil 62. A simultaneous or successive treatment is hereby realized with ultrasonic sound from sound sources 66 and X-radiation coming from sources 72.

For the purpose of disinfecting a fluid a device 28 is provided in which sound sources 36 are located (figure 4) . Water is supplied and discharged by device 28 via inlet/outlet 30. Wireless sound sources 36 are hereby displaced through the water, wherein the movement is bounded by grating 32. An electric, magnetic or electromagnetic field is then applied by means of a field generator. The applied field provides the wireless sound sources with energy, whereby ultrasonic sound is produced in container 34. Cavitation occurs in the fluid as a result of the ultrasonic sound. The applied field can be varied through time in accordance with the desired application.

The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged. It is thus possible for instance to treat fluids other than water with the wireless sound sources or the device according to the invention, such as a sugar solution, beer, blood or urine. It is further possible to usefully apply heat released from a component of the invention, for instance the heat released when a piezoelectric crystal is applied. This heat can be used to heat the fluid and/or hold it at temperature. This can result in an improved disinfection; killing can be more effective at a higher temperature. This is particularly advantageous in the case of batchwise disinfection.

Claims

1. Wireless sound source for disinfecting a fluid, comprising an ultrasonic converter for direct or indirect conversion of an electric, magnetic or electromagnetic field to ultrasonic sound.

2. Wireless sound source as claimed in claim 1, wherein the ultrasonic converter converts an external electric, magnetic or electromagnetic field to an ultrasonic sound during use.

3. Wireless sound source as claimed in claim 1 or 2, wherein the converter comprises an electrical conductor for generating an induction voltage in a magnetic field, and an actuator operatively connected to the conductor for generating ultrasonic sound.

4. Wireless sound source as claimed in claim 3, comprising a capacitor operatively connected to the conductor and actuator so that a tuned circuit is formed.

5. Wireless sound source as claimed in claim 3 or 4, wherein the electrical conductor is a coil for generating an induction voltage in a time-varying magnetic field.

6. Wireless sound source as claimed in at least one of the claims 3, 4 or 5, wherein the electrical conductor is manufactured by means of micro-machining.

7. Wireless sound source as claimed in at least one of the claims 3-6, wherein the actuator is a piezoelectric element and/or a magnetodynamic element.

8. Wireless sound source as claimed in claim 1 or 2, wherein the converter comprises a magnetostrictive or piezomagnetic element for converting a time-varying magnetic field to ultrasonic sound.

9. Wireless sound source as claimed in at least one of the claims 1-8, wherein the frequency of the ultrasonic sound produced by the sound source lies in a range of 15 kHz-100 MHZ and preferably of 15 kHz-25 kHz, 25 kHz-100 kHz, 100 kHz-1 MHZ or 1 MHz-100 MHZ.

10. Device for disinfecting a fluid, comprising:

a container for holding a fluid with at least one inlet and at least one outlet;

at least one sound source according to at least one of the claims 1-9 placed in the container; and

- at least one field generator which creates an electric, magnetic or electromagnetic field during use.

11. Device as claimed in claim 10, wherein sound sources placed in the container form a fluidized bed.

12. Device as claimed in claim 10 or 11, wherein the field generator is located in the container.

13. Device as claimed in claim 10, 11 or 12, comprising a first and a second sound source which produce ultrasonic sound at a different frequency.

14. Device as claimed in at least one of the claims 10-13, wherein at least two sound sources occupy a different position in the container during use.

15. Device as claimed in at least one of the claims 10-14, wherein at least two sound sources are tuned to different field frequencies .

16. Device as claimed in claim 15, wherein the field generator is set to vary the frequency of the created field during use .

17. Device as claimed in claim 15 or 16, wherein the field generator is set to create a field during use comprising different frequencies which correspond to the frequencies to which the sound sources are tuned.

18. Device as claimed in claim 15, 16 or 17, comprising at least two field generators, each set to create a field during use with a frequency corresponding to one of the frequencies to which the sound sources are tuned.

19. Device as claimed in at least one of the claims 10-18, comprising at least two sound sources which are connected to each other in at least one network.

20. Device as claimed in at least one of the claims 10-19, comprising at least one UV light source placed in the container.

21. Device as claimed in at least one of the claims 10-20, comprising electrodes placed in the container.

22. Device as claimed in at least one of the claims 10-21, comprising at least one X-radiation source placed in the container .

23. Method for disinfecting a fluid, comprising the following steps of:

providing a disinfection device according to at least one of the claims 10-22;

guiding a fluid to be disinfected into the container; applying a field with the field generator;

- disinfecting the fluid with at least one sound source

according to at least one of the claims 1-9; and guiding the disinfected fluid out of the container.