Formation, Storage and Reactivation of Aerobic Granular Sludge in Real Dyeing Wastewater

This study aimed to evaluate the process of formation, storage and reactivation of aerobic granular sludge (AGS) in real dyeing wastewater. An SBR was employed for the AGS operation, and the results showed that AGS could form in the SBR within 30 days and was reactivated in 20 days after 300 days of storage. The nutrient removal efficiency remained stable after formation and reactivation. Metal ions (Fe and Ca) and inorganic matter from raw wastewater not only improved AGS formation efficiency but also ensured its structural stability during long-term storage. The initially formed AGS was enriched with Fe and Ca. However, during storage, Fe deposited on the AGS surface was lost due to iron-reducing bacteria (Shewanella). In the reactivated AGS, Ca deposited in the core became dominant. This work fully describes the formation, storage, and reactivation of AGS in real dyeing wastewater and reveals the stabilization mechanism of Ca- and Fe-rich AGS during long-term storage.