7.Acidic Ph Nucleation and Crystal Growth of Struvite in Aqueous Media: Prospective For Phosphorus Recovery from Wastewater

Accumulation of phosphorus on surface waters is not only a major environmental threat but also the result of the exploitation of one of the important raw materials. The reduction of phosphorus concentration in wastewaters prior to their discharge in aquatic systems by various biological and chemical methods are processes which either do not help with sparing of raw materials or they even contribute to other acute problems including sludge disposal. Reclaiming phosphorus in the form of crystalline magnesium ammonium phosphate hexahydrate (MgNH4PO4⋅6H2O, MAP), known as struvite, is an attractive alternative being at the same time a contribution to the development of sustainable processes much needed for the amelioration of raw materials management. MAP has been encountered in problematic processes like scale formation in wastewater treatment plants and as a component of urinary stones[1,2]. The realization of the possibility of phosphorus recovery from domestic wastewater and agroindustrial waste in the form of crystalline MAP, a valuable fertilizer, has triggered interest in the development of the most suitable processes for the efficient production of crystals which may be applied directly for soil fertilization[3,4]. Despite the great interest however knowledge of the mechanisms involved is rather insufficient and accurate kinetics measurements are sparse in the literature. In the present work we present a kinetics investigation on the crystal growth of MAP from supersaturated synthetic wastewater in batch reactors. The efficiency of nucleation in fluidized beds filled with quartz particles was investigated in order to investigate the possibility in line recovery of phosphorus in the form of MAP.