Influence of the amoxicillin concentration on organics removal and microbial community structure in an anaerobic EGSB reactor treating with antibiotic wastewater

In order to investigate the organics removal and microbial community dynamics in accordance with variable amoxicillin (AMX) concentrations, a 1.47 L expanded granular sludge bed (EGSB) reactor was designed and operated for 241 days treating with artificial antibiotic wastewater. Furthermore, microbiological community dynamics with increasing AMX concentrations were also investigated using clone libraries and the terminal restriction fragment length polymorphism (T-RFLP) of PCR-amplified 16S rRNA gene. AMX concentration in the reactor was controlled at 19.2 mg L-1 at first and then gradually increased to around 241.7 mg L-1 from the day 146 to 241. COD and AMX removal efficiencies reached to 85% and 80%, respectively. And T-RFLP results showed that the microbial community structure in the reactor changed with the increased AMX concentrations. Especially for bacteria, T-RFs of 486, 482, 166, 160 and 88 bp were dominant at all stages, whereas abundance of T-RFs 91,163 and 170 bp showed remarkable changes. Besides, clone results combined with T-RFLP showed Firmicutes, Bacteroidetes, Cloacimonetes, Ignavibacteriae and Thermotogae were most dominant bacterial groups in the system and some geneses were also expected to be responsible for the degradation of AMX. For achaea, its community structure (T-RFs of 96, 122 bp) kept stable in all the stages. (C) 2015 Elsevier B.V. All rights reserved.