Effects of chloramphenicol on the bacterial community structure and simultaneous nitrification and denitrification performance in a sequencing biofilm batch reactor

Abstract The effects of chloramphenicol (CAP) on the performance of simultaneous nitrification and denitrification (SND), as well as on the bacterial community, were evaluated in a sequencing biofilm batch reactor (SBBR). The chemical oxygen demand (COD) removal decreased as the CAP concentration increased from 0 to 20 mg/l. But CAP had different effects on nitrification and denitrification: in contrast to continuously inhibiting nitrification, 15 mg/l CAP slightly promoted denitrification. Besides, the specific oxygen utilization rate declined with increasing CAP concentration, and the nitrifying and denitrifying rates initially displayed a trend of decreasing, and then increasing and finally decreasing, with increases in CAP concentration. In addition, the SBBR process exhibited an excellent ability to degrade CAP, especially when its concentration was 20 mg/l. The high-throughput sequencing results indicated that some obvious variations in the bacterial community at different CAP concentrations—in particular relative abundance changes in the dominant bacterial species at the phylum, class and genus levels. Overall, this study reveals that the effects of CAP on the nitrogen (N) removal performance in SBBR, provides a theoretical guide for SBBR treatment of practical wastewater.