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The effect of bubble size on the efficiency and economics of harvesting microalgae by foam flotation

Lookup NU author(s): Dr Thea Ekins-Coward, Dr Jonathan LeeORCiD, Dr Gary Caldwell



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


The effect of bubble size and rise velocity on the efficiency of a foam flotation microalgae harvesting unit was determined. Three sparger and input air flow combinations were used: 1. limewood sparger with constant airflow; 2. ceramic flat plate sparger with constant air flow; and, 3. ceramic flat plate sparger with an oscillating air flow. The ceramic sparger with oscillating flow generated the smallest bubbles within the liquid pool and the largest bubbles within the foam phase. This delivered the highest levels of biomass recovery due to enhanced bubble-algae collision and attachment efficiencies. Bubbles generated by the ceramic sparger under constant or oscillating air flow did not conform to the theory that smaller bubbles travel at slower velocities, due to momentum transfer to the liquid phase. Analyses of the harvest economics revealed that the ceramic flat plate sparger with a constant air flow delivered the best overall cost-benefit relationship.

Publication metadata

Author(s): Coward T, Lee JGM, Caldwell GS

Publication type: Article

Publication status: Published

Journal: Journal of Applied Phycology

Year: 2015

Volume: 27

Issue: 2

Pages: 733-742

Print publication date: 01/04/2015

Online publication date: 07/08/2014

Acceptance date: 24/07/2014

Date deposited: 14/04/2015

ISSN (print): 0921-8971

ISSN (electronic): 1573-5176

Publisher: Springer


DOI: 10.1007/s10811-014-0384-5


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Funder referenceFunder name
EP/P502624/1Engineering and Physical Sciences Research Council (EPSRC)