The Performance of Aerobic Granular Sludge Under Different Aeration Strategies at Low Temperature

Aeration strategy is an important factor for the formation and maintenance of aerobic granular sludge (AGS), but aeration is also the most energy-consuming part in the biological wastewater treatment system. In order to optimize the aeration strategy of AGS reactor at low temperature, short- and long-term effects of dissolved oxygen (DO) concentration and aeration intensity (AI) were investigated at 10 ℃ in this study. The results showed that the carbon and phosphorus removal performance of AGS exhibited high resistance to the short-term changes of DO and AI, while the nitrogen removal was greatly influenced. The optimum DO and AI were 4 mg/L and 0.25 cm/s, corresponding to 82.7% and 81.4% of total inorganic nitrogen removal efficiencies, respectively. Long-term operation experiment showed that the properties of AGS kept stable under 4 mg/L DO concentration, but the overgrowth of filamentous bacteria and reduction of extracellular polymeric substance under 0.25 cm/s AI led to a large amount of granule disintegration, which could not be recovered with the prolonged operation. These findings might provide guidance for the operation optimization of AGS system at low temperature.