Characterization, degradation pathway and microbial community of aerobic granular sludge with ciprofloxacin at environmentally relevant concentrations

Abstract

The removal effect of domesticated aerobic granular sludge on ciprofloxacin (CIP) was studied in SBR system. The morphology and microstructure of cultivated and mature granular sludge were detected by SEM and XRD, and the "crystal nucleus hypothesis" was confirmed as the main reason for the formation of granular sludge. The efficiency of granular sludge to treat conventional pollutant’s COD, NH4+- N, TP and characteristic pollutant CIP is 87%, 97%, 93% and 70% respectively. The degradation path of CIP was clarified by LC/MS analysis. The degradation of CIP was mainly realized by C-N bond easily broken and hydroxylation, oxidative dehydrogenation, defluorination reaction, ring opening cracking, etc. In addition, the abundance of microbial community of aerobic granular sludge was further analyzed by high-throughput sequencing technology. The results showed that Tolumonas was the unique genus of AGS, and Runella, Microbacterium and others were the unique genus of CIP-AGS, Chryseobacterium and Shinella in CIP-AGS were resistant to CIP, with their relative abundance being significantly higher than that of AGS, which indicated that the dominant flora appeared in the domesticated granular sludge under different conditions, and the emergence of these florae may be the key to the degradation of pollutants by granular sludge.