Application of an enrichment culture of the marine anammox bacterium Ca . Scalindua for nitrogen removal under moderate salinity and in the presence of organic carbon. bioreactor metagenome

Seawater can be directly used for toilet flushing in coastal areas to reduce our dependence on desalination and freshwater resources. The presence of high salt content in the generated wastewater from seawater toilet flushing could limit the performance of conventional biological nitrogen removal processes. Anaerobic ammonium oxidation (anammox) process is regarded as one of the most energy-efficient processes for nitrogen removal from N-rich waste streams. In this study, we demonstrated the application of a novel marine anammox bacterium (Candidatus Scalindua sp. AMX11) in a membrane bioreactor (MBR) to treat moderate-saline (1.2% salinity) and N-rich organic (2 mM acetate) solution, prepared using real seawater. The MBR showed stable performance with nitrogen removal rate of 0.3 kg N m3 d1 at >90% N-removal efficiency. Furthermore, results of 15N stable isotope experiments revealed that anammox bacteria was mainly responsible for respiratory ammonification through NO3 reduction to NH4+ via NO2, and the by-products of respiratory ammonification were used as substrates by anammox bacteria. The dominant role of anammox bacteria in nitrogen removal under saline and organic conditions was further confirmed by genome-centric combined metagenomics and meta-transcriptomic approach. Taken together, these results highlight the potential application of marine anammox bacteria for treating saline wastewater generated from seawater toilet flushing practices.

沿海地区可直接利用海水进行冲厕，以降低对海水淡化与淡水资源的依赖。海水冲厕产生的废水中含盐量较高，这会限制传统生物脱氮工艺的运行效能。厌氧氨氧化（anaerobic ammonium oxidation, anammox）工艺被认为是处理富氮废物流最节能的脱氮工艺之一。本研究中，我们将一株新型海洋厌氧氨氧化菌（Candidatus Scalindua sp. AMX11）应用于膜生物反应器（membrane bioreactor, MBR），以处理采用真实海水配制的中等盐度（盐度1.2%）、富氮有机（含2 mM乙酸盐）溶液。该膜生物反应器运行性能稳定，脱氮速率可达0.3 kg N·m⁻³·d⁻¹，总氮去除率高于90%。此外，15N稳定同位素实验结果表明，厌氧氨氧化菌主要通过经亚硝酸根（NO₂⁻）将硝酸根（NO₃⁻）还原为铵根离子（NH₄⁺）的呼吸型氨化作用发挥功能，而呼吸型氨化作用的副产物可作为厌氧氨氧化菌的底物。通过以基因组为中心的宏基因组学与宏转录组学联合分析方法，进一步证实了厌氧氨氧化菌在盐度与有机负荷共存条件下脱氮过程中的主导作用。综上，上述研究结果凸显了海洋厌氧氨氧化菌在处理海水冲厕产生的含盐废水方面的应用潜力。