Denitrifying woodchip bioreactors (DWBs) are potential low-cost technologies for the removal of nitrate (NO3 - ) in water through denitrification. However, if environmental conditions do not support microbial communities performing complete denitrification, other N transformation processes will occur resulting in the export of nitrite (NO2 - ), nitrous oxide (N2 O), or ammonium (NH4 + ). In order to identify the factors controlling the relative accumulation of NO2 - , N2 O, and/or NH4 + in DWBs, porewater samples were collected over two operational years from a DWB designed for removing NO3 - from mine water. Woodchip samples were collected at the end of the operational period. Changes in the abundances of functional genes involved in denitrification, N2 O reduction, and dissimilatory nitrate reduction to ammonium were correlated with pore water chemistry and temperature. Temporal changes in the abundance of the denitrification gene nirS were significantly correlated with increases in porewater N2 O concentrations, and indicated the preferential selection of incomplete denitrifying pathways ending with N2 O. Temperature and the TOC/NO3 - ratio were strongly correlated with NH4 + concentrations and inversely correlated with the ratio between denitrification genes and the genes indicative of ammonification (∑nir/nrfA), suggesting an environmental control on NO3 - transformations. Overall, our results for a DWB operated at hydraulic residence times of 1.0 - 2.6 days demonstrate the temporal development in the microbial community and indicate an increased potential for N2 O emissions with time from the DWB. This article is protected by copyright. All rights reserved.

中文翻译：

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反硝化木片生物反应器中一氧化二氮净产量的微生物控制

反硝化木片生物反应器 (DWB) 是通过反硝化去除水中硝酸盐 (NO3 - ) 的潜在低成本技术。然而，如果环境条件不支持微生物群落进行完全反硝化，则会发生其他氮转化过程，导致亚硝酸盐 (NO2 - )、一氧化二氮 (N2 O) 或铵 (NH4 + ) 的输出。为了确定控制 DWB 中 NO2 - 、N2 O 和/或 NH4 + 相对积累的因素，从设计用于从矿井水中去除 NO3 - 的 DWB 收集了两年运行时间的孔隙水样本。在运营期结束时收集木片样本。参与反硝化、N2O 还原、和异化硝酸盐还原成铵与孔隙水化学和温度相关。反硝化基因 nirS 丰度的时间变化与孔隙水 N2 O 浓度的增加显着相关，表明优先选择以 N2 O 结束的不完全反硝化途径。温度和 TOC/NO3 - 比与 NH4 + 浓度密切相关并且与反硝化基因和指示氨化的基因之间的比率 (∑nir/nrfA) 呈负相关，表明对 NO3 - 转化的环境控制。总体而言，我们在 1.0 - 2.6 天的水力停留时间下运行的 DWB 的结果证明了微生物群落的时间发展，并表明随着时间的推移，DWB 的 N2 O 排放潜力增加。本文受版权保护。版权所有。