Ultrasound and acoustophoresis for water purification

1. A method of separating particulate from a fluid comprising:

flowing the fluid past two or more positions; and

forming three dimensional acoustic standing waves at the two or more positions, wherein each acoustic standing wave is maintained at a different ultrasonic frequency, wherein each ultrasonic frequency is optimized for a specific range of particle sizes, and wherein particulate of the optimized size is trapped in its corresponding acoustic standing wave against the flow of the fluid, thereby concentrating the particulate in its corresponding acoustic standing wave;

wherein the two or more three dimensional acoustic standing waves are pulsed waveforms resulting in high intensity acoustic pressure.

2. The method of claim 1 , wherein at least one of the pulsed waveforms results in the high intensity acoustic pressure having sufficient amplitude to rupture the cell wall and cellular membranes of microorganisms.

3. The method of claim 1 , wherein at least one of the pulsed waveforms results in the high intensity acoustic pressure having sufficient amplitude to cause cavitation.

4. The method of claim 1 , wherein the particulate is selected from the group consisting of microalgae, yeast, fungi, bacteria, spores, gases or oils, metal oxides, metal particles, clays, dirt, plastics, and any particulate with a non-zero contrast factor.

5. The method of claim 1 , further comprising sweeping the frequency of the three dimensional acoustic standing wave at one of the two or more positions, thereby directing the concentrated particulate into a collection pocket.

6. The method of claim 5 , wherein the collection pocket is planar, conical, curved, or spherical in shape; and wherein the collection pocket further comprises a first door sealing the collection pocket away from the fluid.

7. The method of claim 6 , wherein the collection pocket connects to a conduit, and wherein the conduit further comprises a second door which prevents entry of the fluid into the conduit when the first door is open.

8. The method of claim 1 , further comprising electrochemically generating ozone.

9. The method of claim 1 , wherein the three dimensional acoustic standing waves are generated by ultrasonic transducers driven by a voltage amplitude of between 1 and 100 volts (DC).

10. The method of claim 1 , wherein each position includes an ultrasonic transducer and a reflector for forming the three dimensional acoustic standing wave at the position.

11. The method of claim 10 , wherein the ultrasonic transducer at each position is made of a piezo-electric material.

12. The method of claim 1 , wherein the three dimensional acoustic standing waves at the two or more positions are perpendicular to the direction of mean flow.

13. The method of claim 1 , wherein each ultrasonic frequency is from 1 kHz to 100 MHz.

14. The method of claim 1 , wherein the two or more acoustic standing waves are perpendicular to a direction of mean flow in a flow chamber.

15. The method of claim 1 , wherein the three dimensional acoustic standing waves have a horizontal orientation or a vertical orientation.

16. The method of claim 1 , wherein the frequency of excitation of the three dimensional acoustic standing waves is constant.

17. A method of separating particulate from a fluid comprising:

flowing the fluid past two or more positions; and

forming three dimensional acoustic standing waves at the two or more positions, wherein each acoustic standing wave is maintained at a different ultrasonic frequency, wherein each ultrasonic frequency is optimized for a specific range of particle sizes, and wherein particulate of the optimized size is trapped in its corresponding acoustic standing wave against the flow of the fluid, thereby concentrating the particulate in its corresponding acoustic standing wave;

wherein the three dimensional acoustic standing waves are generated by ultrasonic transducers driven by a voltage amplitude of between 1 and 100 volts (DC).

18. The method of claim 17 , wherein the particulate is selected from the group consisting of microalgae, yeast, fungi, bacteria, spores, gases or oils, metal oxides, metal particles, clays, dirt, plastics, and any particulate with a non-zero contrast factor.

19. The method of claim 17 , further comprising sweeping the frequency of the three dimensional acoustic standing wave at one of the two or more positions, thereby directing the concentrated particulate into a collection pocket.

20. The method of claim 19 , wherein the collection pocket is planar, conical, curved, or spherical in shape; and wherein the collection pocket further comprises a first door sealing the collection pocket away from the fluid.

21. The method of claim 20 , wherein the collection pocket connects to a conduit, and wherein the conduit further comprises a second door which prevents entry of the fluid into the conduit when the first door is open.

22. The method of claim 17 , wherein the two or more three dimensional acoustic standing waves are pulsed waveforms resulting in high intensity acoustic pressure.

23. The method of claim 22 , wherein at least one of the pulsed waveforms results in the high intensity acoustic pressure having sufficient amplitude to rupture the cell wall and cellular membranes of microorganisms.

24. The method of claim 22 , wherein at least one of the pulsed waveforms results in the high intensity acoustic pressure having sufficient amplitude to cause cavitation.

25. The method of claim 17 , further comprising electrochemically generating ozone.

26. The method of claim 17 , wherein each position includes an ultrasonic transducer and a reflector for forming the three dimensional acoustic standing wave at the position.

27. The method of claim 26 , wherein the ultrasonic transducer at each position is made of a piezo-electric material.

28. The method of claim 17 , wherein the three dimensional acoustic standing waves at the two or more positions are perpendicular to the direction of mean flow.

29. The method of claim 17 , wherein each ultrasonic frequency is from 1 kHz to 100 MHz.

30. The method of claim 17 , wherein the two or more acoustic standing waves are perpendicular to a direction of mean flow in a flow chamber.

31. The method of claim 17 , wherein the three dimensional acoustic standing waves have a horizontal orientation or a vertical orientation.

32. The method of claim 17 , wherein the frequency of excitation of the three dimensional acoustic standing waves is constant.

33. A method of separating particulate from a fluid comprising:

flowing the fluid past two or more positions;

forming three dimensional acoustic standing waves at the two or more positions, wherein each acoustic standing wave is maintained at a different ultrasonic frequency, wherein each ultrasonic frequency is optimized for a specific range of particle sizes, and wherein particulate of the optimized size is trapped in its corresponding acoustic standing wave against the flow of the fluid, thereby concentrating the particulate in its corresponding acoustic standing wave; and

sweeping the frequency of the three dimensional acoustic standing wave at one of the two or more positions, thereby directing the concentrated particulate into a collection pocket.

34. The method of claim 33 , wherein the particulate is selected from the group consisting of microalgae, yeast, fungi, bacteria, spores, gases or oils, metal oxides, metal particles, clays, dirt, plastics, and any particulate with a non-zero contrast factor.

35. The method of claim 33 , wherein the two or more three dimensional acoustic standing waves are pulsed waveforms resulting in high intensity acoustic pressure.

36. The method of claim 35 , wherein at least one of the pulsed waveforms results in the high intensity acoustic pressure having sufficient amplitude to rupture the cell wall and cellular membranes of microorganisms.

37. The method of claim 35 , wherein at least one of the pulsed waveforms results in the high intensity acoustic pressure having sufficient amplitude to cause cavitation.

38. The method of claim 33 , further comprising electrochemically generating ozone.

39. The method of claim 33 , wherein the three dimensional acoustic standing waves are generated by ultrasonic transducers driven by a voltage amplitude of between 1 and 100 volts (DC).

40. The method of claim 33 , wherein each position includes an ultrasonic transducer and a reflector for forming the three dimensional acoustic standing wave at the position.

41. The method of claim 40 , wherein the collection pocket is positioned on the transducer or on the wall of the flow chamber opposite the transducer; wherein the collection pocket is planar, conical, curved, or spherical in shape; and wherein the collection pocket further comprises a first door sealing the collection pocket away from the fluid.

42. The method of claim 41 , wherein the collection pocket connects to a conduit, and wherein the conduit further comprises a second door which prevents entry of the fluid into the conduit when the first door is open.

43. The method of claim 40 , wherein the two or more ultrasonic transducers are made of a piezo-electric material.

44. The method of claim 33 , wherein the three dimensional acoustic standing waves at the two or more positions are perpendicular to the direction of mean flow.

45. The method of claim 33 , wherein each ultrasonic frequency is from 1 kHz to 100 MHz.

46. The method of claim 33 , wherein the two or more acoustic standing waves are perpendicular to a direction of mean flow in a flow chamber.

47. The method of claim 33 , wherein the three dimensional acoustic standing waves have a horizontal orientation or a vertical orientation.

48. The method of claim 33 , wherein the frequency of excitation of the three dimensional acoustic standing waves is constant.