生物电化学耦合厌氧氨氧化强化脱氮及其微生物群落特征

Enhanced nitrogen removal by bioelectrochemical coupling anammox and characteristics of microbial communities

摘要:

为探究生物电化学强化厌氧氨氧化（anaerobic ammonia oxidation，anammox）脱氮作用过程，采用双室微生物电解池（microbial electrolysis cell，MEC）富集电活性微生物，构建耦合厌氧氨氧化阴极的生物电化学系统。具体地，在外加0.2 V电压条件下改变不同总氮进水浓度于30℃进行暗培养批次实验研究，结合循环伏安法、电化学阻抗谱、高通量测序方法等多种表征手段研究了强化脱氮机理。结果表明，在初始总氮浓度分别为200、300和400 mg/L时对应获得了96.9%±0.3%、97.3%±0.4%和99.0%±0.3%的总氮去除率，且阴极电极生物膜表现出良好的电化学活性。高通量测序结果表明外加电压富集了除厌氧氨氧化菌以外的其他脱氮功能菌群：反硝化菌（Denitratisoma）、Limnobacter和氨氧化菌SM1A02和Anaerolineaceae、亚硝化菌（Nitrosomonas europaea）和硝化螺菌属（Nitrospira）等，这些具有电化学活性的微生物构成了体系的氨氧化胞外产电菌（ammonium oxidizing exoelectrogens，AOE）和反硝化电养菌（denitrifying electrotrophs，DNE），它们连同厌氧氨氧化菌Candidatus Brocadia构成了系统的脱氮微生物群落结构。AOE和DNE的种间直接电子传递作用协同厌氧氨氧化是强化系统总氮去除的关键原因。

Abstract:

To investigate the bioelectrochemical enhanced anaerobic ammonia oxidation (anammox) nitrogen removal process, a bioelectrochemical system with coupled anammox cathode was constructed using a dual-chamber microbial electrolysis cell (MEC). Specifically, a dark incubation batch experiment was conducted at 30℃ with different influent total nitrogen concentrations under an applied voltage of 0.2 V, and the enhanced denitrification mechanism was investigated by combining various characterization methods such as cyclic voltammetry, electrochemical impedance spectroscopy and high-throughput sequencing methods. The results showed that the total nitrogen removal rates of 96.9%±0.3%, 97.3%±0.4% and 99.0%±0.3% were obtained when the initial total nitrogen concentration was 200, 300 and 400 mg/L, respectively. In addition, the cathode electrode biofilm showed good electrochemical activity. High-throughput sequencing results showed that the applied voltage enriched other denitrifying functional groups, including Denitratisoma, Limnobacter, and ammonia oxidizing bacteria SM1A02 and Anaerolineaceae, Nitrosomonas europaea and Nitrospira, besides the anammox bacteria. These electrochemically active microorganisms comprised of ammonium oxidizing exoelectrogens (AOE) and denitrifying electrotrophs (DNE). Together with anammox bacteria Candidatus Brocadia, they constituted the microbial community structure of denitrification system. Enhanced direct interspecies electron transfer between AOE and DNE was the fundamental reason for the further improvement of the total nitrogen removal rate of the system.