Fate and removal of selected antibiotics in an osmotic membrane bioreactor

The fate and removal behavior of 12 antibiotics from 5 classes were investigated in an osmotic membrane bioreactor (OMBR), along with their effects on the system performance. High overall removal of all the antibiotics (77.7-99.8%) was observed, resulting from their rejection by the forward osmosis membrane (> 90%). Biodegradation (ranging from 16.6% to 94.4%) was a significant removal pathway for all the antibiotics except ofloxacin, ciprofloxacin and roxithromycin. Sulfathiazole, enrofloxacin, and chlortetracycline showed the highest removal via biodegradation at 94.4%, 90.2%, and 78.9% respectively, followed by trimethoprim (68.2%), lomefloxacin (57.1%) and norfloxacin (53.2%). Sorption contributed to varying extent to their removal (at 2.0-30.1%); the highest was observed for ofloxacin and roxithromycin. No evident change was observed in the pollutant removal performance of the bioreactor even after 40 days of continuous exposure to these antibiotics (at 500 ng/L), with the overall TOC and NH4+-N removal maintained > 98% and > 97%, respectively.