Optimization of struvite crystallization to recover nutrients from raw swine wastewater

摘要

For the nitrogen and phosphorus resource recovery from raw swine wastewater, laboratory-scale batch experiments were carried out to investigate the effects of pH value, magnesium dosage, and phosphate dosage on struvite crystallization. The crystallization process of the struvite was observed under inverted microscope, and the composition and morphology of the precipitates were characterized by X-ray diffraction and scanning electron microscope. It has been found that the optimal parameters were a Mg2+/NH4+ molar ratio of 1.6, a PO43-/NH4+ molar ratio of 1.3, and a pH of 10.0. The results showed that a large number of crystals had been formed in 5 min under optimal conditions, the precipitates were orthorhombic crystal systems with 10-20 mu m in length, and they were proved to be struvite. When pH value reached 11.5, there were few crystals in the precipitates, and Mg(OH)(2) was formed instead of struvite.

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