Microalgae harvesting using flocculation and dissolved air flotation: Selecting the right vessel for lab-scale experiments

Flocculation combined with dissolved air flotation (DAF) is a promising technology for harvesting microalgae; therefore, optimisation of flocculant-DAF operating conditions are frequently explored in laboratory experi-ments. DAF systems have jars of differing volumes, height to diameter ratios, shapes and materials used to manufacture the jars; thus, the harvesting efficiency (eta) may differ between these jars. The aim was to sys-tematically compare eta between different types of benchtop DAF jars. Evaluation of 30 different types of DAF jars revealed that eta was not influenced by the volume of the jars, but was impacted by the height to diameter ratio, with optimal eta at a ratio ranging between 1.6 and 2.05. There was no difference in eta between cylindrical and cuboid jars, but jars made of hydrophobic (polypropylene) plastic resulted in a lower eta. Overall, these results are useful to guide the design of lab-scale DAF microalgae harvesting experiments.