Sound waves deadly to lake algae
Sound waves are being used to kill algae at a water-supply lake in what is believed to be a first in New Zealand.
Algal blooms in summer can render water in the Lower Nihotupu Dam in West Auckland expensive to process or unusable.
But a trial of ultrasonic technology, monitored and constantly adjusted by LG Sonic in the Netherlands, has shown promising results in keeping good water flowing from the dam.
‘‘We are not trying to get rid of the algae, just get it to levels that don’t cause us problems,’’ said Amy Holliday, water quality and environmental analyst for Watercare.
Watercare believed it was the first time the technology had been used in New Zealand, she said.
It was costing $384,100 in capital expenditure and, if adopted, another $20,000 each year in running costs.
The one-year trial started in December and, if it worked, it would save money at the water treatment plant, where less chemicals would be needed.
An American company recouped the cost of deploying the technology in 1.8 years, Holliday said.
So far it appeared to be a great success in New Zealand, with the blue-green algae count during summer 90 per cent less than the year before.
The weather in Auckland had been cooler than most years though and so it was difficult to be sure.
Watercare dam technician Matt Hubrick said the cyanobacteria, also known as blue-green algae, thrived in warm water and formed slimy clumps that could become toxic to mammals.
‘‘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 slowly killed.’’
The ultrasonic vibrations caused the algae cell walls to break – similar to a glass breaking from a high-pitched sound. The vibrations did not harm humans, animals, fish or aquatic plants. crippled and