堆肥系统高干脱水-生物淋滤污泥颗粒微环境中氮素转化和N2O生成机制研究

Treatment and disposal of sewage sludge is an urgent issue to solve in China. Composting is regarded as an effective technology for resourceful utilizations of sludge. However, large doses of bulking agents, the emissions of NH3 and greenhouse gases limit the application of composting technology. The sewage sludge, after bioleaching and deeply dewatering, could accomplish high temperature composting process without adding any bulking agents, and the emissions of NH3 and CH4 were significantly reduced. However, it was found that the emission of N2O increased sharply in this incubation process. In this project, the deeply dewatering and bioleaching sludge(DDBS) particle is studied as main subject, and recent monitoring methods are adopted, such as high-throughput sequencing, real-time quantitative PCR, isotope tracer and microelectrodes, and so on. The influences of physicochemical properties of DDBS and non-bulking agent on the composting process are evaluated. The spatial distribution of microbial community, nitrogen metabolism genes, nitrogen forms and ecological factors are detected in the interior of the DDBS particles. The relationships between nitrogen metabolism genes and environmental parameters are analyzed. The nitrogen transformation process, the metabolic pathway and regulatory mechanism of N2O production are clarified in the interior of the DDBS particles. This study provides theoretical and technical support for developing a low-carbon, nitrogen-conservation and non-bulking-agent composting technique.

我国城镇污水厂污泥处理处置问题亟待解决。好氧堆肥是国内外污泥处理的主流技术之一，但调理剂用量大，NH3和温室气体污染严重是该项技术在实际应用中急需解决的主要问题。我们近期研究发现，经过生物淋滤和高干脱水处理后的污泥（高干淋滤污泥）不需要添加任何堆肥调理剂即可实现高温发酵过程，而且NH3和CH4释放现象基本消失，但N2O释放量却明显增加。本项目以无调理剂堆肥系统中高干淋滤污泥颗粒为主要研究对象，采用高通量测序、荧光定量PCR、微电极、同位素示踪等多种检测技术，考察高干淋滤污泥特性和取消调理剂对堆肥工艺过程的影响，研究高干淋滤污泥颗粒内部微生物种群结构、氮代谢功能基因、氮素形态和环境因子的空间分布特征，解析堆肥过程中氮代谢功能基因的变化规律及其与环境因子的相关性，揭示高干淋滤污泥颗粒中氮素转化过程、N2O生成途径及其调控机制，为建立新型低碳-保氮-无调理剂污泥堆肥技术提供理论依据和技术支撑。

我国城镇污水厂污泥处理处置问题亟待解决。好氧堆肥是国内外污泥处理的主流技术之一，但调理剂用量大，NH3和温室气体污染严重是该项技术在实际应用中急需解决的主要问题。本项目以生物淋滤预处理、淋滤脱水污泥颗粒及其无调理剂堆肥过程为主要研究对象，研究了微生物富集、投药比、接种量、HRT等生物淋滤工艺条件对污泥脱水的影响，发现了生物淋滤系统中TOC、pH、ORP、铁盐形态、微生物种群结构、污泥絮体形态、生成晶体结构之间的关系。 揭示了生物淋滤污泥堆肥过程中氮素形态和氮代谢功能基因变化规律，阐明了堆肥系统中生物淋滤污泥中微生物种群结构及其代谢功能，明确了取消调理剂对该过程氮素转化和氧化亚氮产生的影响。揭示了生物淋滤污泥颗粒内部微环境中氨氮、硝态氮、亚硝氮空间分布特征及其氮素转化过程，建立了生物淋滤污泥颗粒微环境中微生物种群结构、氮代谢功能基因、环境因子和N2O生成之间的相关性。证明了物料回流改变narG和norB基因并增强反硝化作用，导致N2O释放总量增加23倍，是堆肥生产中N2O主要成因，揭示了生物淋滤高干脱水污泥堆肥系统中氧化亚氮的产生代谢途径，建立基于生物淋滤预处理的无调理剂污泥堆肥N2O高效减排技术，大幅度降低污泥堆肥工艺的运行成本，实现N2O减排90%以上，上述研究成果揭示了生物淋滤污泥堆肥系统N2O产生代谢途径和消减机制。本项目完成了预期目标，在研期间发表SCI论文10篇（其中中科院一区SCI论文9篇），为建立新型低碳-保氮-无调理剂污泥堆肥技术提供理论依据和技术支撑，具有重要的科学意义和工程应用价值。