| 研究実績の概要 |
This year, I elucidated effects of different conditions (aeration rates and internal recycle flow ratio) on N2O emission by a Modified Ludzak-Ettinger (MLE) process which widely used in the world. (1) Effect of aeration rates (high aeration and low aeration) on N2O emission: N2O emission rate were decreased in high aeration period and increased in low aeration period during the long-term study. Relative gene abundance of nosZ/(nirK+nirS) can indicate ability of N2O consumption step which have negative correlation with N2O emission rate (P<0.05). These indicate high N2O reduction rate result in low N2O emission rate during high aeration period. A potential N2O-reducing bacteria was also identified. (2) Effect of internal recycle flow ratio (IRF) on N2O emission from MLE process: Effects of IRF on N2O emission were conducted at the last month, both N2O gas emission rate and dissolved N2O concentration were decreased when IRF increased, and increased when IRF decreased. The reason is higher IRF ratio increased the N2O-reducing activity, and lower IRF ratio decreased the N2O-reducing activity which reflected by relative nosZ-mRNA transcription levels (related to N2O-reducing step) in anoxic tank.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Our research plan in last year was: elucidation of optimum conditions to accelerate the activity of bacteria capable of nitrous oxide reduction. During last year, I studied effect of aeration rates and internal recycle flow ratio on N2O emission by a Modified Ludzak Ettinger (MLE) process. Higher aeration rate (1.5L/min) and higher IRF (7.2) result in lower N2O emission compared with lower aeration rata and lower IRF, respectively. Higher N2O reducing ability was found in higher aeration rate and higher IRF reflected by relative nosZ-mRNA transcription levels (related to N2O-reducing step). Meanwhile, dynamic of community structure by Next Generation Technology were conducted, potential N2O-reducing bacteria were discussed in our study.
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| 今後の研究の推進方策 |
Next year’s plan is identification of N2O-reducing bacteria and development of a novel activated sludge process to reduce N2O emission. Low pH is regarded as an important stressor leading to N2O accumulation in denitrification (Hanaki et al., 1992; Thorn and Sorensson, 1996). However, the mechanism of this phenomenon still needs to be clarified. On the same time, pH is confirmed as a dominant driver of bacterial community structure (Green et al., 2012 AEM), therefore, different active nitrous oxide reducing bacteria at different pH can be identified by RNA-based stable isotope probing (RNA-SIP) in combination with high-throughput sequencing (HTS). On the other hand, the isolated N2O-reducing bacteria in our lab will be considered to apply to activated sludge process for mitigation of N2O emission.
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