Alkaline flocculation of Microcystis aeruginosa induced by calcium and magnesium precipitates
The biotechnological potential of Microcystis aeruginosa brings requirements for efficient cultivation and harvesting of biomass. Flocculation of M. aeruginosa at alkaline pH induced by calcium or magnesium precipitates was studied under model conditions, in culture medium with/without cellular organic matter (COM). The effect of independent variables (Ca2+, Mg2+, PO43−, and pH) on the zeta potential and turbidity of cells and inorganic precipitates was quantified by response surface methodology. The experimentally obtained flocculation efficiencies (FEs) were compared with predictions of physicochemical interaction (DLVO) models. The results presented here delimited the concentration ranges of Ca2+, Mg2+, PO43−, and pH, resulting in FE > 85%. The DLVO prediction model suggested that for high FE, positively charged precipitates and sufficient precipitate turbidity were required. At pH 10, alkaline flocculation was more advantageous using magnesium precipitates, since it required less phosphate. High FE with COM was achieved at pH 12 when precipitate formation was induced at a low phosphate concentration by the addition of magnesium hydroxide.
KeywordsCyanobacteria Inorganic precipitates Surface interactions DLVO theory
This research was supported by the Grant Agency of the Czech Republic (project 18-05007S).
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Conflict of interest
The authors declare that they have no conflict of interest.
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