Magnesium Ammonium Phosphate Crystallization in Recovering Nitrogen and Phosphorus from Cow Manure Anaerobic Digestate
MgCl2 · 6H2O and Na2HPO4 · 12H2O were chosen as precipitants to conduct magnesium ammonium phosphate (MAP) crystallization experiments for cow manure anaerobic digestate.The effects of N/P ratios,Mg/P ratios,pH,temperature and stirring speed on the MAP crystallization were investigated.The properties of crystallized products were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD).The results showed that the recovery rates of nitrogen and phosphorus were over 75.0％ and 99.0％ respectively when the N/P ratio,Mg/P ratio and the pH value were 1.2,1.0 and 8.5 to 10.5 respectively,with residual pO34--P concentration of below 8.0 mg/L.MAP crystallization could also remove suspended matters from the digestate.The recovery rates of nitrogen and phosphorus could not be improved significantly by increasing temperature and stirring speed.
cow manureanaerobic digestatemagnesium ammonium phosphate (MAP)nitrogen and phosphorus recovery
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