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A New Zealand company that is turning sewage into fuel has also been successful in producing large volumes of clean water from oxidation ponds, attracting the attention of the water-strapped United States.
Aquaflow Bionomic Corporation says it has shown it can turn discharge laden with nutrients and green micro-algae into acceptable drinking water.
Aquaflow chairman Barrie Leay said the system used to produce biodiesel from wild algae grown on human sewage produced clean water as a byproduct.
He said the process in effect could help address the two most significant global issues of energy and water security.
The water side of the Aquaflow system was "just as big" as the fuel side, with huge interest from the United States, which had a major water deficit, he said.
"It looks as though we have a dual-edged opportunity here which is very significant and almost overwhelming in its scale."
Mr Leay said Aquaflow's pilot harvesting plant, based at the Marlborough oxidation ponds, had the potential to release 5.3 billion litres of water back to the region for re-use as irrigation, industrial washing, cooling or other high-value applications.
He said algae were nature's cleaning mechanism, absorbing carbon dioxide from the atmosphere and the breakdown of nutrients in water.
The algae then released dissolved oxygen back to the water, which helped bacteria break down more of the biological material.
Nitrogen and the phosphorous were then absorbed into the algae, which once removed left clean water, at present being diverted for irrigation. Mr Leay said the prototype plant had been running in Blenheim for about four months.
Goldfish were used to test water quality as they were highly sensitive to nitrogen and phosphorous.
"If there are any of those trace elements in the water then it kills them."
Mr Leay said the algae were eventually refined and converted into a green crude biofuel.
"It is a complete closed-loop cycle."
Mr Leay said the company had now reached a point where it could produce water up to a potable standard in a relatively low-cost and patented system not used elsewhere.
"We can start to duplicate from the prototype anywhere in the world."
