基于甲烷氧化耦合反硝化的生物法协同净化氨和甲烷机理研究

Animal farming is an important source of atmospheric ammonia and methane emissions. These exhaust gases are very suitable for biological treatment because of the characteristics such as low concentration and large gas volume. However, the removal efficiency of biological method is very low while treating ammonia and methane mixed exhaust gases, which limits the industrial application of this technology. Aerobic methane oxidation coupled to denitrification (AME-D), a process which can utilize the intermediate metabolites of methanotrophs as carbon source for denitrification, provides a potential and effective way for the co-treatment of ammonia and methane. Aerobic denitrifying bacteria can still possess high denitrification ability in aerobic environment, thus combining the aerobic denitrifying bacteria with methanotrophs, can make the co-treatment of ammonia and methane in aerobic conditions more beneficial. This research will first study the impact of methane oxidative metabolites on the aerobic denitrifying bacteria and the release rule of methane oxidative metabolites. Meanwhile, the effect of nitrification products accumulation on methanotrophs will also be clarified. Based on this, the methane oxidation and denitrification characteristics of the AME-D mixed functional microorganisms will be studied. Finally, the experiment of co-purification mechanism of ammonia and methane is carried out in the biotricking filter by using the carbon and nitrogen mass conservation analysis and q-PCR technology. This study can provide scientific basis for methane oxidation coupled to denitrification in theory and technical support for ammonia and methane gas purification in practice.

畜禽养殖是大气氨和甲烷的重要排放源，排放的废气具有浓度低、气量大等特点，适合采用生物法处理。目前生物法高效去除氨和甲烷混合废气难度较大，极大限制了其工业应用。好氧甲烷氧化耦合反硝化（AME-D）能利用甲烷氧化中间产物作为反硝化碳源，为氨和甲烷协同净化提供了潜在有效途径。好氧反硝化菌在有氧环境仍能进行硝酸盐还原，将其与甲烷氧化菌耦合更利于有氧环境中氨和甲烷的协同净化。本项目首先明确甲烷氧化代谢产物对好氧反硝化菌的影响以及甲烷氧化代谢产物释放规律，并探索硝化产物累积对甲烷氧化菌的影响；然后构建AME-D功能菌群并研究其甲烷氧化和脱氮特性；最后开展基于AME-D的生物滴滤塔协同净化氨和甲烷试验研究，通过碳氮守恒分析和q-PCR技术解析生物法协同净化氨和甲烷过程机理，以期在理论上为甲烷氧化耦合反硝化提供科学依据，在实践上为氨和甲烷废气净化提供技术支撑。

甲烷氧化耦合反硝化（AME-D）能利用甲烷氧化中间产物作为反硝化碳源，为畜禽养殖业氨和甲烷混合废气协同净化提供了潜在有效途径。然而，如何基于代谢产物交换和微生物相互作用，构建能够在有氧环境中兼具甲烷氧化和脱氮的AME-D功能菌群尚缺乏系统研究。本项目针对此科学问题，开展了基于异养硝化-好氧反硝化菌和甲烷氧化菌的AME-D功能菌群构建机制研究。首先，探明了生物除氨与生物除甲烷过程的相互影响机制：①对于同步硝化反硝化（SND）除氨而言，在碳源充足和碳源不足的情况下，供试异养硝化-好氧反硝化菌均可以利用甲烷氧化关键产物甲醇作为碳源。而且，柠檬酸钠和甲醇作为碳源均不会影响SND生物滴滤塔的除氨能力；②对于生物除甲烷而言，10mg/L的铵态氮供应不会影响甲烷氧化混合菌的甲烷氧化能力，而且，以铵态氮为氮源的生物过滤塔不仅具有较高的硝化能力，还具有较高的甲烷氧化能力，原因是铵态氮使生物过滤塔中与硝化相关的amoA和hao基因，以及与甲烷氧化相关的fae、mtdA和fmdA基因丰度均显著提高。其次，构建了能在有氧条件下兼具甲烷氧化和脱氮能力的AME-D功能菌群：优选出的异养硝化-好氧反硝化菌Paracoccus pantotrophus ATCC35512与甲烷氧化菌Methylosinus trichosporium OB3b在接种比例为1:0.3时构建的AME-D功能菌群的甲烷氧化能力和反硝化能力最优。构建的AME-D的最佳培养条件为：甲烷浓度为100000ppm，甲烷氧气比为1:1.25，硝态氮浓度为100mg/L，铜离子浓度为15μmol/L，pH为4-9，温度为20-35℃。最后，验证了AME-D生物滴滤塔协同净化氨和甲烷混合废气的效果，在无外加碳源和氮源的情况下，AME-D生物滴滤塔除氨效率接近100%，甲烷去除效率可维持在80%以上。本研究构建的AME-D功能菌群适合于协同净化氨和甲烷混合废气，在畜禽养殖业氨与甲烷协同减排领域具有广阔的应用前景。