Blooms of blue green algae, also known as cyanobacteria, are not something you want occurring in your water system. When ingested, the microorganisms can cause rather unpopular reactions such as headaches, stomach aches, fever, diarrhea, nausea and vomiting. Oh yes, and they can also kill people, not to mention livestock and wildlife that unsuspectingly drink from affected lakes and rivers. Fortunately, researchers at Australia’s University of Adelaide may be on the way to a green (as opposed to blue-green) method of controlling the problem: low-frequency ultrasound.

Blue-green algae is currently eliminated with chemicals such as copper sulphate, which most of us would prefer not having pumped into our waterways, if at all possible. Laboratory tests, however, have shown that ultrasound is also effective. "We know it works but we don't yet know the best frequencies, amplitudes and duration for the most effective, economic and efficient process,” said chief investigator Dr. Carl Howard.

Whatever those optimum frequencies are, they will apparently be low ones. While high-frequency ultrasound is currently used to treat raw sewage, if used on cyanobacteria it breaks down their cell walls, thus releasing their toxins into the water. "The novel part of our solution is that we will be using ultrasound at low amplitudes where it immobilizes the blue-green algae without releasing its toxins into the water and with lower energy input," Dr Howard explained.

The U of A team have just started their research, which will take the form of a three-year collaboration with various Australian water industry organizations. Ultimately, they envision ultrasound generators mounted inside large underwater columns, which would treat the water as it flows past.