Effects of properties on formation of aerobic granular sludge under different organic loadings

With the other operating conditions kept stable, the morphology and pollutant removal performance of aerobic granular sludge (AGS) were tested under different influent organic loadings to analyze its adaptable growth. Results showed that the sludge, with an average particle diameter of 4.0 mm and a good settling ability, was spherical or ellipsoidal and had a smooth and dense surface. The findings also revealed that when the influent organic loading was more than 400 mg/L, this novel form of active sludge removed more than 96, 94, and 90% of ammoniacal nitrogen (NH₃-N), total phosphorus (TP), and chemical oxygen demand (COD) in wastewater, respectively. When the organic loading was reduced from 400 to 100 mg/L, the sludge gradually disintegrated into a rice-like AGS, but the granules maintained their smooth surface and good settling performance. In this case, however, the NH₃-N, TP, and COD removal effects significantly decreased. When the influent organic loading dropped to 100 mg/L, the biomass in the reactor significantly reduced. Correspondingly, the efficiencies of the sludge in removing NH₃-N, TP, and COD were reduced to 60, 55, and 60%, respectively.