硝化反應是生物除氮過程中重要的一環，在好氧環境下，硝化反應藉由氨氧化菌( Ammonia Oxidizing Bacteria, AOB)及亞硝酸氧化菌( Nitrite Oxidizing Bacteria, NOB)將氨氮轉化成硝酸。AOB與NOB均為自營菌，使用無機碳作為其碳源。幾十年來，已有許多文獻研究影響硝化反應效率的環境與操作因子，但無機碳對硝化反應的限制往往被忽略，近年來廢水中氨氮濃度的提升，使得硝化系統的無機碳源需求增加，研究無機碳濃度對硝化反應的影響及與其限制也顯得重要。先前的研究已證實了不同無機碳濃度可以馴養出不同AOB族群，而本研究將探討無機碳對NOB生態族群的影響。
為了探討無機碳濃度對硝化效率及對NOB族群的影響，此研究設置兩個CSTR生物反應槽，分別加入不同濃度之無機碳，一個加入充足且過量的無機碳 (100 mg-C/L, 高無機碳)，另一個給予有限的無機碳 (15 mg-C/L, 低無機碳)。兩個反應槽有相同的植種源，並維持進流基質氨氮濃度皆為250 mg-N/L，操作約700天。在操作期間中，此兩個反應槽皆可維持約95%的良好硝化效率，硝酸鹽是主要的最終產物且並沒有明顯的亞硝酸鹽累積
此研究應用了分生技術，如: 選殖(cloning)與定序(sequencing)，real-time PCR來偵測與定量常見的兩個亞硝酸氧化菌屬，Nitrospira與Nitrobacter，以研究無機碳濃度對NOB生態結構的影響。從分生技術的結果發現，兩個生物反應槽內皆有這兩屬NOB，且經一年馴養後，高無機碳反應槽中以Nitrospira為優勢種，而低無機碳反應槽中以Nitrobacter為優勢種。此研究並以三個批次試驗進行硝化動力探討，在批次試驗中發現兩個生物反應槽有不同的動力表現，兩者相較起來，高無機碳反應槽有較高的最大亞硝酸氧化速率與較低的亞硝酸親和力，但是在這三個批次試驗中，無機碳濃度並沒有顯著的影響兩者亞硝酸氧化的速率表現。

Nitrification, a key step in biological nitrogen removal processes, is the oxidation of ammonia into nitrate performed by ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) under aerobic conditions. Researchers have focused on factors affecting the performance of nitrification for decades, but the inorganic carbon limitation on nitrification had been neglected. However, the increase in nitrogen in wastewater has increased the need to evaluate and improve our understanding of this limitation. In a previous research, the hypothesis that different inorganic carbon concentrations would enrich different AOB populations has been examined. In this study, the focus was on the effect of inorganic carbon concentration on NOB, which has a close relationship with AOB.
Two 5L lab-scale continuous-flow stirred tank reactors (CSTR) were operated to evaluate the nitrification performance and microbial ecology of nitrifier populations acclimated under inorganic carbon sufficient (high-IC) and limited (low-IC) conditions for approximately 700 days. During the operation period, both bioreactors were able to maintain satisfactory nitrification efficiency higher than 95% at an influent ammonium concentration of 250 mg-N/L. Nitrate was the major end product and no significant nitrite accumulation was observed. To evaluate the effects of inorganic carbon on NOB community structures, cloning/sequencing and real-time PCR were applied to target and quantify the two common NOB genera, Nitrospira and Nitrobacter, as no molecular probe targeting all known NOB is available presently. The results showed that these two genera were both found in the two reactors. Nitrospira was the dominant NOB population in the high-IC bioreactor, while Nitrobacter was dominant in the low-IC one after one year of acclimation. Kinetic analysis revealed that NOB enriched in the two reactors have different kinetic performances. However, IC concentration did not show a significant impact on the nitrite oxidizing kinetics of NOB in the batch tests.

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