The influence of physical floc properties on the separation of marine microalgae via alkaline flocculation followed by dissolved air flotation

Flocculation achieved by raising the pH, termed alkaline flocculation is a sustainable way of inducing in marine microalgae. Flocs formed post-alkaline have potential to be harvested via dissolved air flotation (DAF) or sedimentation. While DAF results faster separation and biomass with higher solids content compared sedimentation, it has not been tested saline environments, particularly when combined flocculation. processes, like most techniques, are heavily dependent on physical floc properties. In this study, impact properties performance versus sedimentation was evaluated harvest Nannochloropsis oculata, benchmarking against well-studied ferric chloride This followed use white-water model illustrate how bubble-particle attachment efficiencies. Alkaline flocs were smaller (peakmax < 300 μm; majority 130–470 μm), stronger (~70 % strength factor) more compact (scattering exponent > 2.30) which larger ~ 1700 >65 >1000 relatively weaker (<40 factor), less 1.49–2.30). However, as both hydrophilic, yielded ~15 greater efficiency than DAF. Stoke's Law suggested that benefited due compactness large sizes flocs. Nonetheless, maximum efficiencies ~80–85 still obtained process. From model, bubble-floc (0.01–0.001 %) observed at least an order magnitude (0.001–0.0001 despite methods resulting comparable For flocs, elevated compensated low hydrophilicity; for sizes. Overall, determination post-coagulation-flocculation could used optimise processes.