Data_Sheet_1_Electric Stimulation of Ammonotrophic Methanogenesis.PDF

Reduced nitrogen compounds like ammonium or amines are ubiquitous constituents of wastewater. As a source of electrons, they can be oxidized without producing CO2. This makes them ideal for biogas upgrading in microbial power-to-gas processes in wastewater treatment plants as well as for energy storage. Here, we tested the hypothesis whether ammonium can be oxidized to N2 while producing energy-rich chemicals such as H2 or methane. First, we show that ammonium oxidation can be coupled to H2 production in microbial electrolysis cells. We show that with ammonium and water as the only sources of electrons, N2 gas was produced at potentials between +550 and +150 mV vs. a standard hydrogen electrode. Since H2 can neither be stored, nor transported without major upgrades of our infrastructure, we further tested the hypothesis whether wastewater nitrogen can be oxidized and used to produce methane. At a potential of +500 mV, N2 was produced from domestic wastewater while total nitrogen was removed. We compared two different types of anodes, graphite granule drums and carbon brushes, and found that both were comparable in terms of performance. The drums were slightly better in removing chemical oxygen demand, whereas the brushes produced methane faster. Our research shows that nitrogen contained in wastewater can replace water oxidation in electrolytic biogas upgrading.

诸如铵盐（ammonium）与胺类（amines）这类还原态氮化合物，是废水（wastewater）中广泛存在的组分。作为电子供体，它们可在不产生二氧化碳（CO₂）的前提下被氧化。这使得它们非常适合应用于污水处理厂的微生物电制气（microbial power-to-gas）工艺以实现沼气提质，同时也可用于储能领域。
本研究针对「铵盐可被氧化为氮气（N₂）并同时生成氢气（H₂）、甲烷（methane）这类富能化学品」这一假说开展了验证实验。首先，本研究证实，在微生物电解池（microbial electrolysis cells）中，铵盐氧化可与氢气生成过程相耦合。实验结果表明，当以铵盐与水作为唯一电子供体时，在相对于标准氢电极（standard hydrogen electrode）+550 mV至+150 mV的电位区间内，可生成氮气。
鉴于氢气既无法在现有基础设施无需大规模改造的前提下实现储存与运输，本研究进一步验证了「废水中的氮可被氧化并用于合成甲烷」这一假说。在+500 mV电位下，以生活污水为原料时可生成氮气，同时实现总氮去除。本研究对比了两种不同的阳极：石墨颗粒滚筒（graphite granule drums）与碳刷（carbon brushes），结果显示二者的性能表现相当。石墨颗粒滚筒在化学需氧量（chemical oxygen demand）去除率方面表现略优，而碳刷则可更快地生成甲烷。本研究证实，废水中含有的氮可在电解法沼气提质过程中替代水的氧化反应。