Effect of hydroxyapatite, octacalcium phosphate and calcium phosphate on the auto-flocculation of the microalgae in a high-rate algal pond

Recovering microalgae is one of the main technological and economic concerns in a high-rate algal pond (HRAP) because of their small size and their low density. This paper emphasizes the characterization (identification and assessment of potential flocculation) of chemical compounds involved in micr...

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Bibliographic Details
Published in:	Environmental technology Vol. 34; no. 16; pp. 2407 - 2414
Main Authors:	Baya, D.T, Effebi, K.R, Tangou, T.T, Keffala, C, Vasel, J.L
Format:	Journal Article Web Resource
Language:	English
Published:	Abingdon Taylor & Francis 01-08-2013 Taylor & Francis Ltd
Subjects:	Algae Applied sciences auto-flocculation biomass Bioreactors calcium Calcium phosphate calcium phosphates Calcium Phosphates - chemistry Chemical compounds Chlamydomonas - chemistry Chlorella - chemistry Density Durapatite - chemistry Environmental sciences & ecology environmental technology Exact sciences and technology Flocculating Flocculation harvesting high-rate algal pond (HRAP) Hydrogen-Ion Concentration Hydroxyapatite Life sciences microalgae Microalgae - chemistry Microalgae - metabolism neutralization Phosphates Pollution Ponds saturation index Scenedesmus - chemistry Sciences de l’environnement & écologie Sciences du vivant thermodynamics Water Purification - methods yields British Isles Phosphates Flocculation Saturation high-rate algal pond (HRAP) microalgae saturation index Hydroxyapatite Physicochemical purification calcium phosphates auto-flocculation
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Summary:	Recovering microalgae is one of the main technological and economic concerns in a high-rate algal pond (HRAP) because of their small size and their low density. This paper emphasizes the characterization (identification and assessment of potential flocculation) of chemical compounds involved in microalgae auto-flocculation in a HRAP. First, thermodynamic simulations were performed, using two models (i.e. Visual Minteq and a simplified thermodynamic model) in order to determine the chemical compounds of interest. Experimental tests were then carried out with these compounds for assessing their flocculation ability. Both models revealed that precipitates of calcium phosphates and their substituted forms were the compounds involved in the auto-flocculation. Moreover, experimental tests showed that the stoichiometric neutralization of algal charges by calcium phosphates (i.e. hydroxyapatite (Ca ₅(PO ₄) ₃OH), octacalcium phosphate (Ca ₄H(PO ₄) ₃) and amorphous calcium phosphate (Ca ₃(PO ₄) ₂)), at a pH within the range 7–10 yields 70–82% recovered algal biomass. The optimum ratio required for algae auto-flocculation was 0.33 Ca ₅(PO ₄) ₃OH/g DM ₐₗgₐₑ at pH 10, 0.11 Ca ₄H(PO ₄) ₃/g DM ₐₗgₐₑ at pH 7 and 0.23 g Ca ₃(PO ₄) ₂/g DM ₐₗgₐₑ at pH 9. Auto-flocculation appears as a simple, sustainable and promising method for efficient harvesting of microalgae in a HRAP.
Bibliography:	http://dx.doi.org/10.1080/09593330.2013.770563 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 scopus-id:2-s2.0-84886084968
ISSN:	1479-487X 0959-3330 1479-487X
DOI:	10.1080/09593330.2013.770563