[ASC-media] Sound solution for soil pollution

Niall Byrne niall at scienceinpublic.com.au
Sun Aug 20 16:13:12 CEST 2006

The cleaning power of sound waves on the back of a truck 

Embargo 10am Monday 21 August

A young researcher in Sydney is cleaning up contaminated soil by
blasting it with ultrasound.

Andrea Sosa Pintos from CSIRO Industrial Physics has shown that toxic
and carcinogenic pollutants, such as polycyclic aromatic hydrocarbons
(PAHs) and polychlorinated biphenyls (PCBs), can be decomposed quickly,
easily and cheaply using a portable treatment unit.

"Chemical analysis of the soil and water after we've treated it confirms
that more than 90 per cent of pollutants have been destroyed," she says.

Present soil remediation techniques such as landfill disposal,
incineration and bioremediation, have many limitations. "None of these
provides a complete or cost-effective solution. And some of them can be
time-consuming." says Sosa Pintos. 

"Our process is very simple. We generate high-power ultrasound waves in
a slurry of the contaminated soil in water," Sosa Pintos explains. 

The soil and water are mixed and the slurry is pumped through a
treatment unit where it is exposed to the ultrasonic waves. The whole
process only takes a matter of minutes, as opposed to hours and days, or
even months using other techniques.

"Ultrasonic waves travelling through the mixture create micro-bubbles.
When these bubbles burst on the surface of the soil particles, they
release intense shock waves which can generate temperatures of up to
5000 degrees Celsius. Any chemical contaminants on the surface of the
soil particles bear the brunt of these bursts of energy and are blown
apart," she says.

Importantly, the surrounding liquid stays cool, eliminating the
possibility that the remnants of the toxic compounds can recombine to
form dangerous by-products, as sometimes happens using other
technologies. Dioxins are formed during incineration, for instance.

The pilot plant Sosa Pintos and her colleagues have developed can
already process about a tonne of soil a day. For a commercial scale
system a more efficient feeder unit including a higher capacity pump
would be required. 

Sosa Pintos says. "If the right engineering company were interested,
within a couple of years we could develop a commercial treatment unit
able to be hauled to contaminated sites on the back of a truck."
The combination of high destruction rates, very low energy costs, and
the convenience of on-site treatment, makes high-power ultrasound a
promising option for soil remediation.  

For further information or an interview contact: Andrea Sosa Pintos on
(02) 9413 7397 or 0415 073 307 or andrea.sosapintos at csiro.au

Media contact for Fresh Science: Niall Byrne on (03) 5253 1391 or
niall at freshscience.org or Sarah Brooker on (03) 9397 3980 or
sarah at freshscience.org

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