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Continuous foam flotation harvesting with enhanced drainage: overcoming the recovery-enrichment paradox

Lookup NU author(s): Muayad Al-Karawi, Dr Gary Caldwell, Dr Jonathan LeeORCiD



This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


Microalgae are promising sources of sustainable biofuels, however high harvesting and enriching costs hamper economic competitiveness. Foam flotation––a low-cost, low-energy adsorptive bubble separation technique––may bridge this gap, yet its efficiency and adoption is compromised by a perceived trade-off (based on batch operation) between two key performance indicators: recovery percentage (R%) and concentration factor (biomass enrichment ratio; CF). Previously, we challenged this ‘recovery-enrichment paradox’ under continuous operation (R% 95, CF 173), but performance fell short of expectation. Here, we present a redesign based on the concepts of process intensification, by incorporating a drainage riser, delivering concomitantly high R% (91) and CF (722), retaining low power consumption (0.052 KWh m-3of algae culture) with high total suspended solids yield (14.6%). This compares very favorably with other dewatering/harvesting techniques, overcoming the ‘recovery-enrichment paradox’. Our significant intensification of the foam flotation process will accelerate the advent of economically sustainable microalgae derived biofuels.

Publication metadata

Author(s): Alkarawi MAS, Caldwell GS, Lee JGM

Publication type: Article

Publication status: Published

Journal: Algal Research

Year: 2021

Volume: 54

Print publication date: 01/04/2021

Online publication date: 15/02/2021

Acceptance date: 14/01/2021

Date deposited: 15/01/2021

ISSN (print): 2211-9264

Publisher: Elsevier BV


DOI: 10.1016/j.algal.2021.102203


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