title: Size and structure of Chlorella zofingiensis/FeCl(3) flocs in a shear flow.
abstract: Flocculation is a promising method to overcome the economic hurdle to separation of algae from its growth medium in large scale operations. However, understanding of the floc structure and the effects of shear on the floc structure are crucial to the large scale implementation of this technique. The floc structure is important because it determines, in large part, the density and settling behavior of the algae. Freshwater algae floc size distributions and fractal dimensions are presented as a function of applied shear rate in a Couette cell using ferric chloride as a flocculant. Comparisons are made with measurements made for a polystyrene microparticle model system taken here as well as reported literature results. The algae floc size distributions are found to be self-preserving with respect to shear rate, consistent with literature data for polystyrene. Three fractal dimensions are calculated which quantitatively characterize the complexity of the floc structure. Low shear rates result in large, relatively dense packed flocs which elongate and fracture as the shear rate is increased. The results presented here provide crucial information for economically implementing flocculation as a large scale algae harvesting strategy.
authors.affiliation: Engineering Sciences Center, Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico, 87185. nbwyatt@sandia.gov.
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Wyatt
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: O'Hern
authors.forename: Bion
authors.initials: B
authors.lastname: Shelden
authors.forename: Lindsey G
authors.initials: LG
authors.lastname: Hughes
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Mondy
mesh_terms: D002448:Cell Adhesion; D002708:Chlorella / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism*; D005427:Flocculation
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; C024555:ferric chloride
keywords: algae; flocculation; fractal dimension