Influence of high doses of antibiotics on anoxic-aerobic membrane bioreactor in treating solid waste leachate

This study aims to investigate the influence of high antibiotics doses on the efficiency of an anoxic-aerobic membrane bioreactor (ANX-AMBR) in treating solid waste leachate for one-year operation without sludge withdrawal. Two doses of a mixture of norfloxacin (NOR), trimethoprim (TRM), sulfamethoxazole (SMX) and tetracycline (TC), a total of 4 mg L-1 (1 mg L-1 each) and a total of 20 mg L-1 (5 mg L-1 each), had been fed into the ANX-AMBR operated at HRTs of 12 h and 24 h. A high efficiency of organic matter removal could be achieved > 90% in all conditions. The highest elimination of NOR, 77%; TRM/SMX/TC, 50-57%, was found under a 12 h-HRT with the antibiotic dose of 4 mg L-1. However, high antibiotic doses gave adverse effects on nitrite reduction-oxidation including antibiotic removal efficiency in the ANX-AMBR. Additionally, the extra cellular polymeric substances were produced remarkably in the system after the antibiotic dose of 20 mg L-1. Mass balance analysis suggests that biodegradation was a major role in antibiotics removal in this system. Batch studies showed that the first order kinetics rate constants (k) of antibiotics biodegradation were 0.509-1.573 d(-1) of ANX and 0.128-0.516 d(-1) of AMBR.