-Line Daumer. Optimization of struvite precipitation in synthetic biologically treated swine wastewater -Determination of the optimal process parameters. Journal of Hazardous Materials, Elsevier, 2013Elsevier, , vol. 244-245, pp. 357-369. <10.1016Elsevier, /j.jhazmat.2012 h i g h l i g h t sStruvite precipitation is mainly influenced by the quantity of MgO added. Optimized parameters favoured struvite formation despite of high [Ca 2+ ] without adding other reagents. 90% of the total dissolved phosphorus is recovered as large crystals of struvite. Raman spectroscopy and solid dissolution show co-precipitation of ACP and presence of CaCO 3 in solid.Keywords: Struvite P-recovery MgO Calcium phosphate Swine wastewater Raman a b s t r a c t A sustainable way to recover phosphorus (P) in swine wastewater involves a preliminary step of P dissolution followed by the separation of particulate organic matter. The next two steps are firstly the precipitation of struvite crystals done by adding a crystallization reagent (magnesia) and secondly the filtration of the crystals. A design of experiments with five process parameters was set up to optimize the size of the struvite crystals in a synthetic swine wastewater. More than 90% of P was recovered as large crystals of struvite in optimal conditions which were: low Mg:Ca ratio (2.25:1), the leading parameter, high N:P ratio (3:1), moderate stirring rate (between 45 and 90 rpm) and low temperature (below 20• C).These results were obtained despite the presence of a large amount of calcium and using a cheap reactant (MgO). The composition of the precipitates was identified by Raman analysis and solid dissolution. Results showed that amorphous calcium phosphate (ACP) co-precipitated with struvite and that carbonates were incorporated with solid fractions.

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