[Influence of different recovery methods on the activity of nitrification granular sludge]

Aerobic nitrifying granule sludge cultivated in sequential batch reactor (SBR) was used to investigate the critical activity point of granules and the effect of different ammonia concentration and aeration time on reactivation after storage. The results showed that there was big difference in the activity (SOUR, 02/VSS) of nitrifying bacteria after different storage time. The specific oxygen utilization rate (SOUR) of granules before storage was 13. 15 mg.(g h)-1. After a storage period of 20 days, the SOUR decreased by 1.26 mg.(g.h)-1 , after 5 cycles of reactivation, the ammonia removal efficiency was already increased to 95% while the SOUR was recovered to 13.87 mg.(g.h)-1. But after a storage period of 30 days, the SOUR decreased by 11.63 mg.(g.h)-1, after 51 cycles of reactivation, the ammonia removal efficiecny only eached 92. 64% while the SOUR was recovered to 14.92 mg.(g.h)-1. Meanwhile, this storage method required a longer recovery time. Therefore, we put forward that the critical activity of denitrifying granular sludge should be the activity when activity recovery starts and the nitrifying bacteria SOUR begins to decline. On the basis of the critical activity, we began to restore the activity when the activity of the denitrifying bacteria was reduced to critical activity, and then started a new storage cycle. This storage method was named dynamic storage. Different influent ammonia concentrations of 20, 30 and40 mg.L-1 were applied to reactivate the aerobic granules. Highest SOUR could be achieved when fed with an ammonia concentration of 40 mg.L-1 after reactivation. After three times of dynamic storage, the SOUR remained stable. Different aeration time of 1, 2 and 3 h was applied to reactivate the aerobic granules. Highest SOUR could be obtained when aeration time of 1 h was applied after reactivation and remained stable along with dynamic storage.