Simultaneous removal of ciprofloxacin in PHBV biofilter denitrification process and its influencing factors

Solid carbon source is one of key factors affecting the antibiotics' simultaneous removal during the advanced nitrogen removal process in a denitrifying biofilter. The typical antibiotic ciprofloxacin (CIP) was selected as the research object, and a solid phase carbon source, poly(hydroxybutyrate-co-valerate) (PHBV) supported denitrifying biofilter, was built, focusing on the variation of effluent quality and microbial community structure characteristics of the system under the conditions of different concentrations of CIP. The results showed that the nitrate and CIP removal efficiency were both more than 95% when the influent CIP concentration was lower than 300 μg/L under the suitable temperature (3 to 27 ℃) in autumn. However, under lower temperature (−8 to 12 ℃) in winter, the nitrate and CIP removal efficiency decreased to 60% and 49%, respectively, with influent CIP of 1 000 μg/L. Microbial community structure characteristics analysis revealed that Proteobacteria and Gammaproteobacteria were the most dominant phylum and class, respectively. Gammaproteobacteria was resistant to antibiotics due to their good secretion of extracellular polymeric substances. Meanwhile, the relative abundance of denitrifying bacteria in this system still kept high under a long-term exposure to CIP. The relative abundance of Dechloromonas, the most dominant denitrifying bacteria, was all more than 5% along the longitudinal profile of the system with the highest of 10%. The study confirmed that PHBV supported denitrifying biofilter is an efficient technology to fulfill the simultaneous removal of nitrate and antibiotics. And it also provided data support for denitrifying biological filter under low temperature in practical engineering.