Influence of tetracycline contents on the performance of expanded granular sludge bed and its microbial community structure

Antibiotics wastewater is normally treated by anaerobic biological technology, while the perfor-mance is always not satisfied due to the inhibitory effects of high level antibiotics. Here, we inves-tigated the quick start-up process for tetracycline wastewater treatment in expanded granular sludge bed (EGSB) reactor and also the influence of tetracycline content on performance and micro-bial community structure. The results indicated that gradual increase of tetracycline content could keep the stable operation of EGSB system, while cause slight inhibition. With tetracycline content increasing to 210 mg/L, chemical oxygen demand (COD) removal decreased from 96.7% to 73.3%, tetracycline removal slightly decreased from 84.6% to 81.6%, while biogas production decreased from 6.1 to 4.7 L/d with methane production rate of 208 to 175 mL/g COD. Long-term acclimation could eliminate the inhibition by tetracycline and its metabolic products to recover the microbial activity. Bacillus brevis, Cocci and Clostridium became the main bacteria with increase of tetracy-cline contents to form a compact and multi-layer structure of sludge. Tetracycline addition resulted in the increase of Spirochaete and Synergistetes, which might promote the removal of tetracycline. Tetracycline addition decreased the total contents of methanogens and caused less methane produc-tion. It provided an effective start-up method for anaerobic treatment of antibiotics wastewater.