By Janet Raloff
Blooms of algae that produce life-threatening toxins regularly plague water supplies around the world. In many cases, the algae’s toxins can survive standard treatments for purifying water. Researchers at Florida International University in Miami think they have a sound solution: ultrasound.
Blasting water with 640-kilohertz ultrasound waves briefly creates high-pressure microenvironments as hot as 3,700°C, which breaks some water molecules into reactive fragments that can kill the algae.
Chemist Kevin E. O’Shea and his colleagues in an upcoming Environmental Science & Technology, describe tests with a toxin produced by Microcystis aeruginosa, a blue-green alga found in Florida and elsewhere. People have died from exposure to such toxins.
The researchers prepared solutions of the toxin at concentrations higher than those that build up in water supplies. Six-minute treatments with ultrasound destroyed some 90 percent of the M. aeruginosa toxin in the samples. That brought its concentration to safe levels and produced no identifiable toxicity, notes O’Shea. The data indicate that the technique could destroy “a wide variety of other toxins,” he says, including brevetoxins shed into the sea by infamous red-tide algae (see “Toxic Surfs,” in this week’s issue).
