Water filter technology takes to sound waves

Acoustic wave technology could be the key to capturing and separating substrates from water without filters or chemicals.

FloDesign Sonics, a small US firm, has developed the patented Acoustic Wave Separation (AWS) technology with funding from the National Science Foundation.

“At the heart of FloDesign Sonics' system is a method called acoustophoresis, in which droplets or particles within a liquid can be manipulated with a special acoustic wave pattern,” the National Science Foundation's Cecile Gonzalez wrote.

“The new system uses a pattern of ultrasonic waves in the megahertz range. The wave pattern exerts acoustic forces that bind substances dispersed in the liquid into clusters.

“Depending on their relative density compared to the liquid, these larger clusters either settle to the bottom or rise to the surface, where they can be separated easily.”

The technology is aimed at cleaning up water produced when oil and gas are extracted from the earth.

Produced water contains naturally occurring hydrocarbons, salt, bacteria, radioactive material and other compounds, as well as any chemical additives used to ease extraction.

Before it can be reused or disposed of it has to be treated, but FloDesign Sonics Co-founder and Senior Engineer Jason Dionne said existing methods were inefficient.

"It's challenging for current technologies to remove particles smaller than 20 microns without the addition of chemicals," Dionne said.

"AWS separates particulates, oil droplets, sand and bacteria as small as one micron."

Dionne said the AWS system would reduce energy and chemical usage by up to 75%, compared to current methods.

The genesis for the design solution came from an unusual source.

“Acoustophoresis has been used primarily in microfluidics and other micro-scale systems," Dionne said.

"When the US Army was looking for a technology for rapid detection of anthrax spores in large bodies of water, we got the idea to develop an acoustic separation technology that works at the macroscale."

And the technology's potential goes far beyond the water world.

“The company can picture the technology being used one day for cleaning and transfusing a patient's own blood during surgery,” Gonzalez wrote.

“In the nearer term, acoustic wave separation may be used to recover biological products from mammalian cells, which requires a purification process with high yield, product consistency and reproducibility.”