Effect of antibiotics on the performance of moving bed biofilm reactor for simultaneous removal of nitrogen, phosphorus and copper(II) from aquaculture wastewater.

Co-existence of NO-N, antibiotics, phosphorus (P), and Cu in aquaculture wastewater has been frequently detected, but simultaneous removal and relationship between enzyme and pollutants removal are far from satisfactory. In this study, simultaneous removal of NO-N, P, antibiotics, and Cu by moving bed biofilm reactor (MBBR) was established. About 95.51 ± 3.40% of NO-N, 61.24 ± 3.51% of COD, 18.74 ± 1.05% of TP, 88% of Cu were removed synchronously in stage I, and antibiotics removal in stages I-IV was 73.00 ± 1.32%, 79.53 ± 0.88%, 51.07 ± 3.99%, and 33.59 ± 2.73% for tetracycline (TEC), oxytetracycline (OTC), chlortetracycline hydrochloride (CTC), sulfamethoxazole (SMX), respectively. The removal kinetics and toxicity of MBBR effluent were examined, indicating that the first order kinetic model could better reflect the removal of NO-N, TN, and antibiotics. Co-existence of multiple antibiotics and Cu was the most toxicity to E. coli growth. Key enzyme activity, reactive oxygen species (ROS) level, and its relationship with TN removal were investigated. The results showed that enzymes activities were significantly different under the co-existence of antibiotics and Cu. Meanwhile, different components of biofilm were extracted and separated, and enzymatic and non-enzymatic effects of biofilm were evaluated. The results showed that 70.00%- 94.73% of Cu was removed by extracellular enzyme in stages I-V, and Cu removal was mainly due to the action of extracellular enzyme. Additionally, microbial community of biofilm was assessed, showing that Proteobacteria, Bacteroidetes, and Gemmatimonadetes played an important role in the removal of NO-N, Cu, and antibiotics at the phylum level. Finally, chemical bonds of attached and detached biofilm were characterized by X-ray photoelectron spectroscopy (XPS), and effect of nitrogen (N) and P was proposed under the co-existence of antibiotics and Cu. This study provides a theoretical basis for further exploring the bioremediation of NO-N, Cu, and antibiotics in aquaculture wastewater.