New insight into effect of antibiotics concentration and process configuration on the removal of antibiotics and relevant antibiotic resistance genes

To compare the performance and antibiotic-resistance character in different process configurations under different levels of antibiotics, anoxic/oxic-membrane bioreactors (MBR) 1#, MBR2# and a sequencing batch reactor (SBR) were operated with identical operating parameters. MBR1# and SBR were operated under high and increasing levels of antibiotics, MBR2# received constant and low concentration of antibiotics. Microbiological community and antibiotic resistance genes (ARGs) were investigated using 16S rDNA gene high-throughput sequencing and qPCR. More than 90% of penicillin and chlortetracycline were removed due to strong hydrolysis, followed by sulfamethoxazole (69.27%-86.25%) through biodegradation and norfloxacin (28.66%-53.86%) through adsorption. Process configuration affected total nitrogen removal more, while antibiotics concentration affected total phosphorus removal more. MBR1# outperformed SBR in reducing sulfamethoxazole, norfloxacin and ARGs due to the retention effect of the membrane module. Retention efficiency of ARGs in MBRs increased along the operation. Compared to the operational taxonomic unit (OTU) number before antibiotics addition, the OTU number in MBR1# and SBR decreased by 23.7% and 28.7%, while that in MBR2# kept relatively stable. Process configuration contributed to higher dissimilarity of microbial community than antibiotics concentration. The research provides an insight into the influence factors of antibiotics-containing wastewater treatment.