Nitrogen and phosphorus removal and recovery from anaerobic digestion supernatant of sewage sludge using dolomitic lime

The method for nitrogen and phosphorus removal and recovery from anaerobic digestion supernatant of sewage sludge was constructed by using dolomitic lime. And the effects of different solid/liquid (S/L) of dolomitic lime, initial reaction pH values, temperature and reaction time on anaerobic digestion supernatant were investigated. The experimental results showed that nitrogen and phosphorus removal rates were 37.26% and 89.60%, respectively, under the optimal conditions of 300 mg/L dolomitic lime, pH 8.5~9.5, 25.0°C, 150 r/min stirring and 24 h. Based on the analyses and characterization by using X-ray diffraction (XRD) and scanning electron microscope (SEM), it showed that the recovered product consisted of ammonium magnesium phosphate (MAP). This research indicated that nitrogen and phosphorus could be economically and efficiently recovered from anaerobic digestion supernatant of sewage sludge by using dolomitic lime.