Simultaneous crystallization of phosphate and potassium as magnesium potassium phosphate using bubble column reactor with draught tube

Livestock water drainage after secondary treatment contains potassium and phosphorus is influenced by the efficiency of the processing method. In this study, we examined the effect of ammonium ion concentration on the simultaneous recovery of coexisting potassium and phosphorus. The ammonium nitrogen, potassium, and phosphorus concentrations were 0.3–8.3 mM, 0.0–25.6 mM, and 7.6 mM, respectively. Magnesium chloride at a concentration of 3 mM was added to a synthetic wastewater bubble column with a draught tube, and the pH was maintained at around 10 using a pH controller. The hydraulic retention time was 2.3 h. When the ammonium nitrogen concentration was less than 1.1 mM, the decreases in the molar ratios of magnesium, potassium, and phosphorus in the liquid almost corresponded to the production of magnesium potassium phosphate (MPP). Also, MPP was confirmed to be the main component of crystals obtained at low ammonia nitrogen concentrations, using various analytical methods.