title: Flocculation of Chlorella vulgaris induced by high pH: role of magnesium and calcium and practical implications.
abstract: Microalgae hold great potential as a feedstock for biofuels or bulk protein or treatment of wastewater or flue gas. Realising these applications will require the development of a cost-efficient harvesting technology. Here, we explore the potential of flocculation induced by high pH for harvesting Chlorella vulgaris. Our results demonstrate that flocculation can be induced by increasing medium pH to 11. Although both calcium and magnesium precipitated when pH was increased, only magnesium (≥0.15 mM) proved to be essential to induce flocculation. The costs of four different bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and sodium carbonate) were calculated and evaluated and the use of lime appeared to be the most cost-efficient. Flocculation induced by high pH is therefore a potentially useful method to preconcentrate freshwater microalgal biomass during harvesting.
authors.affiliation: K.U. Leuven Kulak, Laboratory Aquatic Biology, E. Sabbelaan 53, 8500 Kortrijk, Belgium. Dries.Vandamme@kuleuven-kortrijk.be
authors.forename: Dries
authors.initials: D
authors.lastname: Vandamme
authors.forename: Imogen
authors.initials: I
authors.lastname: Foubert
authors.forename: Ilse
authors.initials: I
authors.lastname: Fraeye
authors.forename: Boudewijn
authors.initials: B
authors.lastname: Meesschaert
authors.forename: Koenraad
authors.initials: K
authors.lastname: Muylaert
mesh_terms: D056804:Biofuels; D018533:Biomass; D001709:Biotechnology / Q000191:economics* / Q000379:methods; D002118:Calcium / Q000737:chemistry*; D002126:Calcium Hydroxide / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D048408:Chlorella vulgaris / Q000378:metabolism*; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D007477:Ions; D008274:Magnesium / Q000737:chemistry*; D008276:Magnesium Hydroxide / Q000737:chemistry; D058086:Microalgae / Q000378:metabolism; D017680:Potassium Compounds / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D018508:Water Purification / Q000379:methods
chemical_list: D056804:Biofuels; D002254:Carbonates; D006878:Hydroxides; D007477:Ions; D017680:Potassium Compounds; D014874:Water Pollutants, Chemical; C005686:sodium carbonate; D012972:Sodium Hydroxide; D008274:Magnesium; D008276:Magnesium Hydroxide; D002126:Calcium Hydroxide; D002118:Calcium; C029943:potassium hydroxide