An ambitious proposal to diminish the ACT's blue-green algae plague would see five or six shipping containers set up on Lake Burley Griffin's shore at a cost of about $600,000 each.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
Last summer saw the territory's lakes transformed into swirling cesspits of the matted, potentially harmful "cyanobacteria" by what experts have described as some of the worst blooms on record.
Nano Bubble Technologies is just one of the companies hoping to counter the problem, vying for the attention of the ACT government as it considers investing in algae antidotes in the territory's next budget.
Founder Gary Stone says his technology allows for the highest concentration of "nano bubbles", or minuscule, gas-holding cavities, in the world at between 30 and 600 million a millilitre of water.
This essentially means that Nano Bubble's giant patent-pending "injectors" could pump oxygen from air into lakes at record rates, killing off blue-green algae.
Nano bubbles, unlike regular bubbles that come from other aeration methods, are also negatively charged, meaning they keep oxygen contained in the water rather than rising to the top or joining together.
Blue-green algae exposure can cause skin irritation, flu-like symptoms and gastrointestinal illness. At its worst, it can make neurotoxins that destroy nerve tissue and are potentially deadly to animals and humans.
"Strategically placed, five or six [containers] around Lake Burley Griffin for a period of time - and it would not be a hell of a lot of time because the air stays in the water - would change the balance of oxygen in the lakes," Mr Stone said.
"What we can do is manufacture [injectors] in a shipping container, bring that container in, bring power to it, plug in it, and then all we need to do is put a pipe in the water to suck it out of Lake Burley Griffin.
"Then it goes through all the injectors and the water gets put back [into the lake]. It has got the amount of air [in nano bubble form] that you're sucking into the water through a large compressor."
Mr Stone estimates that each container would cost about $600,000 - so six would be about $3.6 million - plus electricity costs. But the injectors would probably only have to run from about November through to February as heat encourages blue-green algae blooms.
He suggests the ACT government could buy one container to trial the technology's performance, although a lot more research would be needed to determine its viability in Lake Burley Griffin.
The technology has had success on a small scale in golf course irrigation systems, fisheries, and hydroponics farms. Nano Bubble is also in talks with a large waste water facility in New South Wales.
"If the [ACT] government would fund it, we would certainly give them a very quick answer not only on how our system would work," Mr Stone said.
Blue-green algae levels in Lake Burley Griffin have dropped significantly in the past few weeks as the weather cools, with the East Basin going from having 686,866 cells a millilitre on February 25 to 701 cells on April 8.
The Captain Cook Memorial has the lake's highest-remaining concentration of blue-green algae cells with 6,090 a millilitre of water. The guideline for safe swimming is 50,000 cells a millilitre.
Lake Tuggeranong, which last recorded blue-green algae levels more than 100 times that recommendation on February 25, remains closed to primary contact activities, although it is expected these levels would have dropped since.
The lake is the subject of tests by the University of Canberra to determine which of four solutions - sampled in separate "mesocosms", or big plastic tubes - would be best to combat the blue-green algae.
The research is being funded as part of the $94 million ACT Healthy Waterways project, the bulk of which is wrapping up on June 30.
"The results from that would be pretty easily extensible to Lake Burley Griffin and Lake Ginninderra. They're fairly similar kinds of lakes," program manager Ralph Ogden said.
Mr Odgen said other technologies such as Nano Bubble could be considered and trialed if those currently being tested by the university showed no promise.
Two of the mesocosms had been treated with Diatomix, a product containing nutrients that promotes the growth of healthy, green algae rather than blue-green algae, lead researcher Dr Fiona Dyer said.
Another two had been covered with shade cloth because light is an important factor in algal growth.
"We've been shading them to see how important light is at limiting algal growth within Lake Tuggeranong," Dr Dyer said.
AlgaEnviro co-founder Dr Simon Tannock, whose company sells Diatomix, likened the product to handing healthy algae a Red Bull or a coffee so it could win resources over blue-green algae.
"Basically, it is 10 different micronutrients that are usually missing in polluted waterways ... they're on what you might call a silica backbone," he said.
"When that goes in the water there's mainly only one type of algae that requires silica and they're called diatoms. So the blue-green algae ... would look at it and go, 'Silica, I don't care'. The diatoms see it and go, 'Hey, I need that.'"
As the new, healthy algae grows, it gets eaten by animals, and so polluting nutrients such as phosphorous and nitrogen, taken on by the diatoms, are moved up the food chain and out of the water.
Dr Tannock estimates a full treatment of Lake Tuggeranong would cost about $9000 a week for four to five months - or $180,000 - and then about half that for the foreseeable future.
"I haven't seen a competitor that can beat us on price, the speed with which we can have a result and sustainability ... there's all sorts of benefits," he said.
Managing director of Phoslock Environmental Technologies Robert Schuitema, which markets the CSIRO-formulated solution Phoslock, says it has been effective in about 350 projects around the world.
Phoslock is a type of clay that draws phosphorus, an enabler of blue-green algae, out of water. Mr Schuitema said the company had pitched the product to the National Capital Authority in the past as a solution to Lake Burley Griffin's blue-green algae problem but was rejected because of a lack of budget.
"For $2 million we would have absorbed all the phosphates in the lake and we would have reset the environmental clock for a number of years," Mr Schuitema said.
"I believe they should be going for a tried and true technology."
A National Capital Authority spokeswoman said it had not considered Phoslock because it was a temporary solution to getting rid of blue-green algae.
"The [authority] would have to weigh up the value and costs associated with treating such a large body of water regularly, particularly for areas within the [lake] that are not always affected by blue-green algae," the spokeswoman said.
Mr Schuitema said an application on the Serpentine lake in London's Hyde Park lasted five years before it had to have another, lesser dose, and the situation would be similar in the ACT's lakes.
The antibacterial hydrogen peroxide was another promising solution being trialed in two mesocosms, Dr Dyer said. It had success in many other parts of the world including south Holland.
It was also being trialed in South Australia's Lake Torrens. More research would have to be done to determine how much it would cost to treat Lake Tuggeranong with it, Dr Dyer said.