Saline storage of aerobic granules and subsequent reactivation

• Saline storage was for the first time revealed its promise for granule storage.
• Saline-stored granules were successfully reactivated and operated for 85 d.
• Reactivated granules were operated in SBR and CFR at varying COD.

Loss of structural stability and bioactivity during long-term storage and operation is primary challenge to field applications of aerobic granular processes. This study for the first time stored aerobic granules in 5% w/w NaCl solution at 4 °C for 187 d. The stored granules were then successfully reactivated and used for 85 d in sequencing batch reactors (SBR) and continuous-flow reactors (CFR) at varying levels of chemical oxygen demand (COD). High-throughput sequencing results reveal that Thauera sp., Paracoccus sp., and Nitrosomonas sp. were the predominant in the stored aerobic granules, and Pseudoxanthomonas sp. accumulated during the reactivation process. Saline storage, in which cells are in an unculturable state by saline stress, is a promising storage process for aerobic granules.