title: Effect of self-alkalization on nitrite accumulation in a high-rate denitrification system: Performance, microflora and enzymatic activities.
abstract: The self-alkalization of denitrifying automatic circulation (DAC) reactor resulted in a large increase of pH up to 9.20 and caused a tremendous accumulation of nitrite up to 451.1 ± 49.0 mgN L(-1) at nitrate loading rate (NLR) from 35 kgN m(-3) d(-1) to 55 kgN m(-3) d(-1). The nitrite accumulation was greatly relieved even at the same NLR once the pH was maintained at 7.6 ± 0.2 in the system. Enzymatic assays indicated that the long-term bacterial exposure to high pH significantly inhibited the activity of copper type nitrite reductase (NirK) rather than the cytochrome cd1 type nitrite reductase (NirS). The terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that the dominant denitrifying bacteria shifted from the NirS-containing Thauear sp. 27 to the NirK-containing Hyphomicrobium nitrativorans strain NL23 during the self-alkalization. The significant nitrite accumulation in the high-rate denitrification system could be therefore, due to the inhibition of Cu-containing NirK by high pH from the self-alkalization. The results suggest that the NirK-containing H. nitrativorans strain NL23 could be an ideal functional bacterium for the conversion of nitrate to nitrite, i.e. denitritation, which could be combined with anaerobic ammonium oxidation (Anammox) to develop a new process for nitrogen removal from wastewater.
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Shan
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Zhi-Yao
authors.initials: ZY
authors.lastname: Wang
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Lin
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Chen-Xu
authors.initials: CX
authors.lastname: Li
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Chao-Yang
authors.initials: CY
authors.lastname: Cai
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Ghulam
authors.initials: G
authors.lastname: Abbas
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Department of Agricultural Resource and Environment, College of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing, China.
authors.forename: Li-Dong
authors.initials: LD
authors.lastname: Shen
authors.affiliation: Department of Civil and Environmental Engineering, University of Missouri, Columbia, USA.
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Hu
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China; MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China. Electronic address: zhaohp@zju.edu.cn.
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Zhao
authors.affiliation: Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China. Electronic address: pzheng@zju.edu.cn.
authors.forename: Ping
authors.initials: P
authors.lastname: Zheng
mesh_terms: D001419:Bacteria / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D058440:Denitrification; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D050901:Nitrate Reductase / Q000378:metabolism*; D009572:Nitrite Reductases / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D004269:DNA, Bacterial; D009573:Nitrites; D012336:RNA, Ribosomal, 16S; D009572:Nitrite Reductases; D050901:Nitrate Reductase; D009609:Nitrous Oxide
keywords: Denitrification; High-load; Microbial mechanism; Nitrite accumulation; Self-alkalization