School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China; State Key Laboratory of Environmental Medicine Engineering, Ministry of Education, Southeast University, Nanjing, Jiangsu 210096, China.
Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
Sci Total Environ. 2020 Dec 1;746:141089. doi: 10.1016/j.scitotenv.2020.141089. Epub 2020 Jul 24.
Methane is a greenhouse gas that can be released from sludge anaerobic fermentation in wastewater treatment plants. Methane is also an alternative additional carbon source for deep nitrate removal of secondary effluent. A sequencing experiment was conducted to study the efficacy of nitrate removal with methane as the sole carbon source. The maximum nitrate removal rate was 17.2 mg-N·L·d. Nitrate removal was confirmed to arise via two pathways: aerobic methane oxidation coupled to denitrification (AME-D) contributed to 55% of the nitrate removal with the rest stemming from assimilation by methanotrophs. Additional study revealed that nitrate assimilated by methanotrophs was used for the synthesis of proteins, resulting in a protein content of 52.2% dry weight. Metagenomic sequencing revealed a high abundance of nitrate assimilation and glutamine synthetase genes, which were primarily provided by methanotrophs (mainly Methylomonas). Assimilatory nitrate removal by methanotrophs has a high potential for advanced nitrogen removal and for alleviating methane emissions. The nitrogen-rich biomass produced by nitrate absorption could also be used as a biofertilizer for nitrogen recycling.
甲烷是一种温室气体，可在污水处理厂的污泥厌氧发酵中释放。甲烷也是深度去除二级出水硝酸盐的替代外加碳源。进行了一项序批实验，以研究甲烷作为唯一碳源的硝酸盐去除效果。最大硝酸盐去除率为 17.2mg-N·L·d。确认硝酸盐去除是通过两种途径实现的：好氧甲烷氧化偶联反硝化（AME-D）贡献了 55%的硝酸盐去除，其余则来自甲烷营养菌的同化。进一步的研究表明，甲烷营养菌同化的硝酸盐用于蛋白质的合成，导致蛋白质含量占干重的 52.2%。宏基因组测序显示，硝酸盐同化和谷氨酰胺合成酶基因的丰度很高，这些基因主要由甲烷营养菌（主要是甲基单胞菌）提供。甲烷营养菌的同化硝酸盐去除对高级脱氮和缓解甲烷排放具有很高的潜力。通过硝酸盐吸收产生的富氮生物质也可用作氮回收的生物肥料。
