title: Co-metabolic degradation of steroid estrogens by heterotrophic bacteria and nitrifying bacteria in MBRs.
abstract: Three membrane bioreactors (MBRs) with different carbon/nitrogen ratios were operated in parallel to investigate the effects of heterotrophic bacteria and nitrifying bacteria on the co-metabolic degradation of the steroid estrogens (SEs) estrone (E1) and 17α-ethinylestradiol (EE2). The functional community structures of the MBRs were analyzed using fluorescence in situ hybridization, and correlations between the functional community structures and SE removal efficiencies were established. The results showed that α-Proteobacteria, β-Proteobacteria, and γ-proteobacteria were responsible for the removal of E1, whereas ammonia-oxidizing bacteria, Nitrosomonas sp., Nitrosospira sp., Nitrospira sp., and Nitrobacter sp. were responsible for EE2 removal. Nitrifying activated sludge degraded E1 and EE2 alone, with degradation efficiencies of 71.04 and 65.51%, respectively. Moreover, biodegradation of E1 and EE2 was reduced significantly (by 30.30 and 34.03%, respectively) when nitrification was inhibited. Heterotrophic and nitrifying bacteria were responsible for E1 and EE2 degradation, but nitrification was considered to be the key process in the enhancement of SE degradation. Organic co-metabolism by heterotrophic bacteria had a significant effect on E1 removal, and nitrification co-metabolism by nitrifying bacteria had a significant effect on EE2 removal. These results improve our understanding of the co-metabolic degradation of SEs, which is useful for improving SE removal and guaranteeing the health of aqueous environments.
authors.affiliation: a School of Energy and Environment , Southeast University , Nanjing , China.|b Key Laboratory of Environmental Medicine Engineering of Ministry of Education , Southeast University , Nanjing , China.
authors.forename: Hai L
authors.initials: HL
authors.lastname: Song
authors.affiliation: c School of Civil Engineering , Southeast University , Nanjing , China.
authors.forename: Xiao L
authors.initials: XL
authors.lastname: Yang
authors.affiliation: c School of Civil Engineering , Southeast University , Nanjing , China.
authors.forename: Ming Q
authors.initials: MQ
authors.lastname: Xia
authors.affiliation: c School of Civil Engineering , Southeast University , Nanjing , China.
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D052244:Endocrine Disruptors / Q000032:analysis / Q000378:metabolism*; D004967:Estrogens / Q000032:analysis / Q000378:metabolism*; D004970:Estrone / Q000032:analysis / Q000378:metabolism*; D004997:Ethinyl Estradiol / Q000032:analysis / Q000378:metabolism*; D052836:Heterotrophic Processes; D017404:In Situ Hybridization, Fluorescence; D058465:Nitrification; D009584:Nitrogen / Q000378:metabolism; D020560:Proteobacteria / Q000378:metabolism*; D012722:Sewage / Q000737:chemistry
chemical_list: D052244:Endocrine Disruptors; D004967:Estrogens; D012722:Sewage; D004970:Estrone; D004997:Ethinyl Estradiol; D000641:Ammonia; D009584:Nitrogen
keywords: Co-metabolic degradation; fluorescence in situ hybridization (FISH); functional community structure; organic loading rate; steroid estrogens (SEs)