Co-metabolic removal of ciprofloxacin under condition of interaction between microbes and Fe3O4

Abstract

Potential of effluents from biological hydrogen production process to improve ciprofloxacin (CIP) removal was investigated using ciprofloxacin-degrading enrichments in the presence of Fe3O4 nanoparticles. Effluent addition clearly promoted CIP removal, which was 61%, 38% and 16% higher than those in the enrichments amended with fecal sewage, biogas digestate and water, respectively. Experiments of sterilization and organic components of effluents indicated that the organic substances served as co-metabolic substrate to facilitate CIP removal, where ethanol was the preferred co-metabolic substrate. Although the effluent addition changed the bacterial community composition which corresponded to the changes in the relative abundances of dominant genera in the enrichments, CIP removal performance remained unchanged. The increased Fe (II) concentrations indicated that there might be a positive relationship of CIP removal with the microbial reduction of Fe (III) to Fe (II) in Fe3O4 in the effluents-amended enrichments. It was proposed that the organic substances in the effluents might serve as the co-metabolic substrate to promote CIP removal by CIP-degrading and Fe (III)-reducing bacteria.