Struvite

Abstract: The present review provides an understanding of principles of struvite crystallization and examines the techniques and processes experimented to date by researchers at laboratory, pilot, and full-scale to maximize phosphorus removal and reuse as struvite from wastewater effluents. Struvite is mainly known as a scale deposit causing concerns to wastewater companies. Indeed, struvite naturally occurs under the specific condition of pH and mixing energy in specific areas of wastewater treatment plants (e.g., pipes, heat exchangers) when concentrations of magnesium, phosphate, and ammonium approach an equimolar ratio 1:1:1. However, thanks to struvite composition and its fertilizing properties, the control of its precipitation could contribute to the reduction of phosphorus levels in effluents while simultaneously generate a valuable by-product. A number of processes such as stirred tank reactors and air-agitated and -fluidized bed reactors have been investigated as possible configurations for struvite recove...

Abstract: Previous reports have suggested that urease-producing bacteria play a prominent role in the formation of infection-induced urinary stones We have carried out crystalization experiments in vitro which show that bacterial urease alkalinizes urine, thereby causing: (i) supersaturation with respect to struvite and calcium phosphate; and (ii) formation of struvite and apatite crystals Growth of Proteus in urea-free urine or in urine which contained a urease inhibitor did not cause alkalinization, supersaturation, or crystallization of struvite and apatite Growth of Klebsiella, Escherichia coli, or Pseudomonas was not associated with significant alkalinization, supersaturation, or crystallization Struvite and apatite crystals dissolved in Proteus-infected urine in which undersaturation was maintained by urease inhibition Similar results in all experiments were obtained using human urine and a synthetic urine which was devoid of matrix, pyrophosphate, or other undefined solutes Urease-induced supersaturation appears to be the primary cause of infection-induced urinary stones