Papers by Keyword: Struvite Precipitation

Abstract: Recovering nitrogen and phosphorus through struvite crystallization from swine wastewater has gained increasing interest. However, effluents of anaerobic digested swine wastewater contains other constituents including complex and hardly definited organic compounds, which may hinder the formation of struvite crystal and affect the purity of the precipitates by forming other insoluble minerals. Struvite precipitation was carried out at laboratory scale by adding magnesium chloride and potassium hydrogen as external sources of magnesium and phosphorus to equal Mg: N: P molar ratio, respectively, and regulating the pH at 9.5 in the absence and presence of organic compounds. Exceeded 70% phosphate and ammonium reduction were obtained. The recovered products were detected and analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and chemical methods, which were proved to be struvite crystals. The soluble organic compounds had less than 6% changes in amount during struvite precipitation and it was proved that the removal of TCOD during the precipitation of struvite may be attributed to the co-precipitation of struvite. The results indicate that struvite precipitation could be a viable method of ammonium removal in the presence of organic compounds from anaerobically digested swine manure.

Abstract: Struvite (MgNH4PO4∙6H2O) is an insoluble double salt. It can precipitate in places such as pipes, aerators and pumps, which could lead to substantial problems influencing the normal operation of wastewater treatment equipments. At present, removal of ammonium nitrogen from various wastewaters by the formation of struvite has been widely investigated. This paper reviewed the research and application efforts concerning the treatment of ammonium nitrogen by struvite precipitation, which were obtained at home and abroad in recent years. The mechanism and influence factors of struvite precipitation for ammonium nitrogen removal were discussed. Additionally, the problems that still should be resolved and the research directions in future were pointed out.