Long-term effect of temperature on N2O emission from the denitrifying activated sludge.
The long-term effect of various temperature (4°C, 12°C, 20°C, 25°C and 34°C) on nitrous oxide (N2O) emission from lab-scale denitrifying activated sludge was studied in terms of activation energy, abundance of functional gene nosZ and its transcription. Results showed that temperature had a positive effect on N2O emissions as well as the maximum biomass-specific reduction rates of N2O and NO3(-), ranging from 0.006% to 0.681% of (N2O + N2), 17.3-116.2 and 5.2-66.2 mg N g(-1) VSS h(-1), respectively. The activation energies (Ea) for N2O and NO3(-) reduction of 44.1 kJ mol(-1) and 54.9 kJ mol(-1), shed light on differences in denitrifying rate variation. The maximum NO3(-) reduction rates were more sensitive to temperature variation than the corresponding N2O reduction rates under long-term acclimation. As a result, the ratio between N2O and NO3(-) reduction rates declined to 1.87 at 34°C from 3.31 at 4°C, suggesting great potential capacity for N2O losses at high temperature. The copy numbers of denitrifiers as nosZ gene (×10(8) copies mL(-1)) and total bacteria as 16S rRNA gene (×10(10) copies mL(-1)) did not show obvious relationship with temperature, having relative abundance of 0.42% on average. The transcriptional regulation of nosZ gene, in the range of 10(8)-10(5) copies mL(-1), was affected by reductase activity, substrate concentration as well as its duration. The active nosZ gene expression was accompanied with low reductase capacity, high dissolved N2O and the duration of N2O accumulation. These results provide insights into activation energy and gene expression responsible for N2O emission.
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, China. Electronic address: xjwang@iue.ac.cn.
Xiaojun
X
Wang
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, China. Electronic address: xryang@iue.ac.cn.
Xiaoru
X
Yang
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, China. Electronic address: zjzhang@iue.ac.cn.
Zhaoji
Z
Zhang
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, China. Electronic address: xye@iue.ac.cn.
Xin
X
Ye
Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan. Electronic address: jkao@mail.nsysu.edu.tw.
Chih Ming
CM
Kao
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, China. Electronic address: shchen@iue.ac.cn.
Shaohua
S
Chen
D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D058440:Denitrification / Q000502:physiology*; D009609:Nitrous Oxide / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012722:Sewage / Q000382:microbiology*; D013696:Temperature; D013997:Time Factors
D012329:RNA, Bacterial; D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D010088:Oxidoreductases; C022763:nitrous oxide reductase; D009609:Nitrous Oxide
Activation energy; Denitrification; Maximum reduction rate; Nitrous oxide emission; Temperature response; nosZ gene transcription