A reservoir at Lower Nihotupu Dam in west Auckland has been experiencing severe blue-green algae bloom across its surface during the hot summer months, which makes the water unusable. Some blue-green algae is toxic, which can hurts the animal eco-systems in the water, as well as being a dangerous thing to ingest or swim in. But the most common danger they pose is creating "dead zones" in the water where they absorb all the oxygen as they decompose, imperiling fish and wildlife in the area.
Stuff reports that researchers have discovered an innovative way to beat back the blue-green algae growth on the lake by using experimental technology from the Netherlands called LG Sonic. Five solar-panel powered buoys hold up the machine that emits ultrasonic vibrations that break down the cell walls of the algae. This works sort of like a dog whistle. Only the algae can hear it—it doesn't affect any other living things. Amy Holliday, water quality and environmental analyst for Watercare, who monitor the device's progress, say that the sonic waves have been a real breakthrough.
"We are not trying to get rid of the algae, just get it to levels that don't cause us problems," said Holliday. "It gives that extra assurance that when people turn on the tap the water that they are drinking is safe. This technology is just adding another tool to our toolbox."
The device didn't come cheap. The initial installation cost $384,100 and if the program continues it will be another $20,000 annually. But according to Holliday, an American company using similar technology recouped their losses in less than two years, and the over time the machine saves money. Fewer chemicals are needed for treatment at the water plant, which also means fewer chemicals in drinking water.
Dam technician Matt Hubrick said that the LG Sonic's full potential makes monitoring the algae far easier for technicians, as well.
"The devices we're using not only monitor the water quality, the software program interprets the changing water quality in real time, so that changes can be made almost instantly. This means the onset of algal blooms can be predicted, then crippled and slowly killed," he explained.
The one year trial began last December, so it remains to be seen if Watercare will adopt the use of sonic waves as a permanent weapon against algae blooms. But it sure seems like the way forward is clear.