基于碳源强化氨同化作用的污泥好氧堆肥中氧化亚氮释放生物学机制研究

Sewage sludge composting is one of the mainstream technologies for sludge stabilization, but the discharge of a large amount of nitrogen-containing gas (ammonia, nitrous oxide, etc.) during composting seriously affects the ambient air quality and fertilizer efficiency of composting products. Studies had shown that the addition of carbon sources could strengthen microbial ammonia assimilation, inhibit ammonia emission to reduce nitrogen loss, but the relationship of carbon sources and nitrous oxide emission is not clear. Nitrous oxide emission not only cause nitrogen loss, but also bring significant greenhouse effect, so controlling of its emission is one of the key issues in sewage sludge composting process. In this project, the effects of carbon sources on the process of nitrogen conversion and the emission of nitrous oxide will be studied by biochemical methods. The evolutions of key enzyme activities about nitrification and denitrification will be investigated by enzymatic analysis methods. The influence mechanism of carbon sources on the microbial population structure and related functional genes of nitrifying and denitrifying will be analysed by bioseparation and molecular biological techniques. The purpose of this project is to investigate the relationship of carbon sources and nitrification, denitrification, to reveal the biological mechanism of nitrous oxide emission in carbon sources strengthened system, to provides theoretical basis for the improvement of carbon sources strengthened sewage sludge composting process. The feasibility of alternative materials for carbon sources and reduction measures of nitrous oxide emission will be evaluated in the sewage sludge composting process, and then provides technical support for the application of this technology.

污泥堆肥是污泥稳定化处理的主流技术之一，但堆肥过程中大量含氮气体（氨、氧化亚氮等）的排放严重影响环境空气质量及堆肥产品肥效。已有研究表明，外加碳源可以增强微生物氨同化作用，抑制氨挥发减少氮素损失，但外加碳源与氧化亚氮释放的相互关系尚不清楚。氧化亚氮的排放不仅会造成氮素损失，还会带来显著的温室效应，所以控制其排放也是污泥堆肥亟待解决的关键问题之一。本项目通过生化方法和生物分离技术，结合分子生物学及酶学分析手段，研究碳源强化对氮素转化过程及氧化亚氮释放规律的影响，考察硝化反硝化过程中关键酶活性的变化规律，探讨碳源强化对硝化反硝化微生物种群结构及相关功能基因的影响机制，揭示碳源强化与硝化反硝化过程之间的响应关系，探明碳源强化污泥堆肥系统中氧化亚氮的释放生物学机制，为碳源强化污泥堆肥工艺的完善提供理论依据；同时开展碳源强化替代材料和氧化亚氮减排措施的可行性研究，进而为该工艺的应用提供技术支撑。

污泥堆肥由于其操作简单且相对经济，目前是污泥稳定化处理的主流技术之一，但堆肥过程中大量含氮气体的大量排放严重影响环境空气质量及堆肥产品肥效。已有研究证实，外加碳源可以增强微生物氨同化作用，抑制氨挥发减少氮素损失，但外加碳源与氧化亚氮释放的相互关系尚不清楚。本研究通过分析外加碳源强化污泥堆肥与氮素生物转化的相关关系，考察碳源强化对堆肥过程中硝化、反硝化过程的影响机制，分析碳源强化与堆肥系统中硝化、反硝化功能基因之间的相互作用关系。同时分析了菌糠和糖蜜作为外加碳源对污泥堆肥过程中温度、pH值、含水率、有机质、二氧化氮挥发量及氮素损失的影响，还重点考察了菌糠和糖蜜对含氮气体挥发及堆肥腐熟度的影响情况。结果显示，蔗糖组的N2O挥发量减少了33.0%，在整个堆肥过程中蔗糖组的硝化细菌数量均高于空白组1个数量级以上。同时蔗糖的添加提高了amoA基因的丰度，降低了hao基因丰度从而限制了NH2OH-N向NO2--N的转化速度，同时提高了nxrA基因的丰度，可以提高亚硝酸盐氧化还原酶活性，促进了NO2--N向NO3--N 的转化。蔗糖组的反硝化基因丰度都不同程度的低于空白对照组，通过spearman相关性分析发现，硝化细菌数量与NO3--N和nxrA呈显著正相关同时硝化作用的产物NO3--N及亚硝酸盐氧化还原酶基因nxrA丰度也体现出了一致的规律，而NO2--N浓度与N2O挥发量、narG、nirS和norB呈正相关关系，说明堆体中反硝化作用是N2O产生的主要路径。此外，菌糠和糖蜜的添加可以明显延长高温期时间，同时提高了有机质的降解速度，并且明显加快了堆肥的进程，提高了堆肥产品的腐熟度。菌糠和糖蜜联合添加处理组，氨气挥发量减少了33.1%~37.3%，并且对N2O的控制效果较为明显，N2O累积挥发量仅为空白对照组的17.8%~25.4%，最终其氮素损失降低了42.6%~47.6%，说明菌糠和糖蜜的联合添加有效的控制了污泥堆肥中含氮气体的释放和氮素损失。本项目的研究成果对污泥堆肥技术的应用基础研究、新技术开发和工程化应用都具有重要的理论意义和实用价值。