Kinetics of Phosphorus Removal and Recovery as Struvite from Wastewaters with Medium-low Phosphorous Concentration

摘要

The kinetics of phosphorus(P) removal as struvite(magnesium ammonium phosphate, MAP) crystallization under various conditions, including pH, initial phosphorus concentration, molar ratio of Mg/N and N/P, were investigated.Batch experiments with simulated low-phosphorous-containing wastewater were carried out to observe the effects of environmental conditions on MAP nucleation and crystallization kinetics. Results showed that higher pH and lower temperature enhanced the process of the MAP crystallization. The nucleation of MAP followed a first-order reaction in wastewaters with the initial P<80mg/L, compared with those of second-order reactions in wastewater with P>100mg/L. The crystallization rate of MAP increased with the improving of ammonium and magnesium dosage, and the ammonium amendment has a more significant effect on MAP crystallization kinetics than the magnesium. When the phosphorous concentration of the wastewater is low, the super-saturation level has an exponential order effect on MAP nucleation induction time.