Nitrogen removal, sludge activity and bacterial community in a sequencing batch reactor at different ciprofloxacin and ibuprofen concentrations

Abstract

Nitrogen removal, sludge activity and bacterial community were examined at different ciprofloxacin and ibuprofen concentrations in a sequencing batch reactor. Ammonia nitrogen (NH 4 + -N) and chemical oxygen demand (COD) elimination rates decreased as the ciprofloxacin (belonged to antibiotics) and/or ibuprofen (belonged to nonsteroidal anti-inflammatory drugs) addition. Ciprofloxacin and ibuprofen had antagonistic inhibitions on the specific rates of nitrate reduction, nitrite oxidation and ammonium oxidation. The levels of protein and polysaccharide and the protein/polysaccharide ratio in extracellular polymeric substances rose as the increment of ibuprofen, ciprofloxacin and mixed ibuprofen/ciprofloxacin concentrations. Mixed ibuprofen/ciprofloxacin did not change the role of protein in extracellular polymeric substances in the bacterial defense to ibuprofen or ciprofloxacin, and tryptophan-like protein was the main protective response of bacteria to ibuprofen, ciprofloxacin and mixed ibuprofen/ciprofloxacin compared with aromatic protein. Both of nitrifiers and denitrifiers relative abundances were lower at the mixed ibuprofen/ciprofloxacin than at the alone ibuprofen stress, while were higher than at the single ciprofloxacin pressure. • Joint IBP and CIP had antagonistic impacts on SAOR, SNOR and SNRR. • Tryptophan-like PN in EPS was more important protective roles than aromatic PN. • Nitrifiers had a better tolerance to IBP, CIP and mixed IBP/CIP than denitrifiers.