title: Effects of CeO2 nanoparticles on biological nitrogen removal in a sequencing batch biofilm reactor and mechanism of toxicity.
abstract: The effects of CeO2 nanoparticles (CeO2 NPs) exposure on biological nitrogen removal in a sequencing batch biofilm reactor (SBBR) were investigated. At low concentration (1 mg/L), no significant effect was observed on total nitrogen (TN) removal. However, at high concentrations (10 and 50 mg/L), the TN removal efficiency reduced from 74.09% to 64.26% and 55.17%, respectively. Scanning electron microscope imaging showed large amounts of CeO2 NPs adsorbed on the biofilm, which increased the production of reactive oxygen species. The exposure at only 50 mg/L CeO2 NPs measurably affected the lactate dehydrogenase release. Confocal laser scanning microscopy showed that high concentrations of CeO2 NPs reduced bacterial viability. Moreover, after a short-term exposure, extracellular polymeric substances (EPS) were observed to increase, forming a compact matrix to protect the bacteria. The activities of nitrate reductase and ammonia monooxygenase were inhibited, but there was no significant impact on the activity of nitrite oxidoreductase.
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Hou
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
authors.forename: Guoxiang
authors.initials: G
authors.lastname: You
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China. Electronic address: pfwang2005@hhu.edu.cn.
authors.forename: Peifang
authors.initials: P
authors.lastname: Wang
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China. Electronic address: mlz1988@126.com.
authors.forename: Lingzhan
authors.initials: L
authors.lastname: Miao
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
authors.forename: Yanhui
authors.initials: Y
authors.lastname: Ao
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.affiliation: Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, People's Republic of China; College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
authors.forename: Bowen
authors.initials: B
authors.lastname: Lv
mesh_terms: D000327:Adsorption / Q000187:drug effects; D001419:Bacteria / Q000378:metabolism; D018441:Biofilms / Q000187:drug effects*; D019149:Bioreactors; D002563:Cerium / Q000008:administration & dosage*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D053758:Nanoparticles / Q000008:administration & dosage*; D050901:Nitrate Reductase / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: D017382:Reactive Oxygen Species; D002563:Cerium; C030583:ceric oxide; D010088:Oxidoreductases; D007770:L-Lactate Dehydrogenase; C045582:ammonia monooxygenase; D050901:Nitrate Reductase; D009584:Nitrogen
keywords: Biofilms; CeO(2) NPs; Nitrogen removal; Sequencing batch biofilm reactor (SBBR); Toxicity mechanism