Nutrients recovered from residual dewatering liquid from anaerobic digestion

Struvite (MgNHPO4·H2O) and ammonium sulphate [(NH4)2SO4] are compounds used as fertilizers and they can be recovered from residual dewatering liquid of anaerobic digestion. A cascade process obtains the former first, while the latter proceeds from the residual liquid phase. Nutrient recovery technology, a well-established process on wastewater, can be economically profitable on digestate for contents of phosphate (> 240 ppm) and ammonium (> 2500 ppm). The cascade process allows to produce pellet fertilizers that include both compounds.