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Researchers at U.K.-based University of Sheffield have developed a microbubble technology that could bring down the cost of algae biofuels by cost-effectively dewatering algae. According to the university, the solution builds on previous research in which microbubbles were used to improve the way algae is cultivated. The research team, led by Will Zimmerman, a professor in the department of chemical and biological engineering, has developed an inexpensive method to produce microbubbles that can float algae cells to the surface of the algae solution, which makes harvesting easier, cheaper and faster. Research on the process has been published in the journal Biotechnology and Bioengineering.
Full citation for the research article: James Hanotu, H.C. Hemaka Bandulasena, William B. Zimmerman (2012). “Microflotation performance for algal separation.” Biotechnology and Bioengineering Online before print. DOI: 10.1002/bit.24449
Abstract: The performance of microflotation, dispersed air flotation with microbubble clouds with bubble size about 50 µm, for algae separation using fluidic oscillation for microbubble generation is investigated. This fluidic oscillator converts continuous air supply into oscillatory flow with a regular frequency to generate bubbles of the scale of the exit pore. Bubble characterization results showed that average bubble size generated under oscillatory air flow state was 86 µm, approximately twice the size of the diffuser pore size of 38 µm. In contrast, continuous air flow at the same rate through the same diffusers yielded an average bubble size of 1,059 µm, 28 times larger than the pore size. Following microbubble generation, the separation of algal cells under fluidic oscillator generated microbubbles was investigated by varying metallic coagulant types, concentration and pH. Best performances were recorded at the highest coagulant dose (150 mg/L) applied under acidic conditions (pH 5). Amongst the three metallic coagulants studied, ferric chloride yielded the overall best result of 99.2% under the optimum conditions followed closely by ferric sulfate (98.1%) and aluminum sulfate with 95.2%. This compares well with conventional dissolved air flotation (DAF) benchmarks, but has a highly turbulent flow, whereas microflotation is laminar with several orders of magnitude lower energy density.