Sam Shead writes in The that the development of a harvesting technique from researchers at Sheffield University builds on previous research in which microbubbles were used to make algae blooms denser and consequently easier to harvest. However, removing the water so the algae could be harvested remained problematic.

Now, a team led by Mark Zimmerman in the Department of Chemical and Process Engineering at Sheffield University has found that they can separate the microalgae from the water using microbubbles created by a fluidic oscillator that switches flows rapidly from one outlet to another, resulting in pulsing flow.

The fluidic oscillating system developed by Zimmerman’s team uses up to 1,000 times less energy to produce the microbubbles than the more traditional dissolved air flotation process. “Our bubbles are made under laminar flow and we use practically no more energy than is required to make the interface of the bubble,” said Zimmerman. “The idea is to create a surface on the algae particles that is hydrophobic so the microbubbles are attracted to it.”

When the bubbles and the particles reach the surface, the added flocculant and the coaggulant keep the algae in a fixed layer. The blanket of algae can then be skimmed off the surface with something such as a belt skimmer, according to Zimmerman.

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