Long-term storage and subsequent reactivation of Anammox sludge at 35C

The feasibility of a long-term storage and subsequent reactivation of Anammox sludge was investigated. The storage strategy was improved for a long-term storage. The storage at an optimized temperature (35 degrees C) for growth and metabolism of Anammox bacteria was attempted to retain Anammox activity for acceleration of the reactivation process after the storage. During the storage, a little of Anammox nutrient medium containing 50 mg-N l(-1) (NH4)(2)SO4 and NaNO2 was added and periodically (every week) refreshed to keep the survival of Anammox bacteria. After the 6-month storage, there was still an Anammox activity of 0.07 g (NH4+-N + NO2--N) (gVSS x d)(-1), even though most Anammox bacteria were in dormant state. The reactivation of the stored Anammox sludge was achieved in an SBR after a 2-month operation, and the final nitrogen removal rate of 0.32 g (NH4+-N + NO2--N) L-1 d(-1) was gained. Compared with the fresh activated sludge, the stored Anammox sludge could realize a quick start-up of Anammox process. The results demonstrated that the improved storage strategy was suitable for a long-term storage and subsequent reactivation of Anammox sludge.