After 20 days of operation, the NRR of each anammox reactor became comparable, regardless of their different preservation conditions, namely different SAA. The NRRs increased significantly and ultimately reached 7 kg-Nm_3 d_1 at the end of operation (after 35 days), showing the rapid reactivation of 90-day-stored anammox biomass. Likewise,Magri et al. (2012) revealed that about 70% of SAA was lost during storage, but the SAA was recovered after one month of
reactivation. Based on this experimental result, anammox activity lost during storage at room temperature can be recovered within a short time period, suggesting that the
stored anammox biomass could be directly used for a rapid start-up of anammox process without any additional reactivation steps.