Study On The Stability Of Aerobic Granular Sludge

Aerobic granular sludge with compact structure, good settle ability, high biomass retention is a promising method of wastewater treatment. However, the formation mechanism of aerobic granules has not been discussed thoroughly, and the instability of granules also limits its development and application.In this study, the stability of aerobic granular sludge in different situations such as in toxic industrial wastewater, during storage and reactivation process, in salty wastewater was deeply discussed. MLSS, SVI, SOUR, removal efficiencies of COD and aniline and microbial community structure were determined throughout the whole experiment to describe the change of granules.In the early stages of sequencing batch reactor (SBR) operation, aniline supplement negatively affected the granules (strength decrease, lower growth rate), this effect was thereafter removed because of a change in the microbial community:with aniline present, nitrification and denitrification microbes appeared and gathered in the aerobic granules producing an increased microbial diversity. Aniline (10～500 mg·L-1) could be degraded in 6h, with a removal rate in excess of 90%, while the effluent COD fell below 100 mg·L-1 from the initial about 2000 mg·L-1. The aerobic granules cultured by acetate were compact, stable and resistant to aniline.In the reactivation process, the MLSS and settle ability of aerobic granules could be improved by low COD content of 750mg·L-1 and aeration rate of 200L·h-1. At the same time, the COD and aniline removal rates can also be increased.In addition, the salt in SBR system negatively affected the stability of aerobic granules. The properties of granules were kept in a good condition, when the salt concentration was below 1.0g·L-1; however when it was improved to 2.0g·L-1, MLSS and settle ability decreased due to the dormancy or death of most microorganism.