Performance, sludge characteristics and microbial community in a salt-tolerant aerobic granular SBR by seeding anaerobic granular sludge

Abstract Salt-tolerant aerobic granular sludge (SAGS) technology is currently a topic of significant interest in research focused on the treatment of saline wastewater. However, the structural stability and nitrogen removal efficiency of SAGS cultured from activated sludge has been found to be insufficient. In this study, an efficient strategy for the cultivation of SAGS, seeding anaerobic granular sludge in a SBR, was explored. Performance results showed that at 3% (w/v) salinity, the chemical oxygen demand (COD), NH4+-N and total nitrogen (TN) removal efficiency was 93.3 ± 1.3%, 92 ± 6.5% and 76 ± 8.4%, respectively. The morphology and settling properties of granules did not change significantly. Bacterial community analysis revealed that the dominant AOB and denitrifiers in SAGS were likely to be Nitrosomonas and Defluviimonas, respectively, while the abundance of NOB of Nitrospira was very low. qPCR results showed that the abundance of nirS and nirK decreased significantly under high salinity conditions, which likely explains the relatively low efficiency of TN removal and NO2−-N accumulation. This study describes a new SAGS culture strategy and promotes the development of salt-containing wastewater biological treatment technology.