基于脱水污泥氧传质特征和增强生物硝化作用的保氮-快速堆肥过程调控机理与技术研究

The treatment and disposal of the sewage sludge has been of great concern in recent years in China. Aerobic composting is a major technology for sludge treatement based on its many advantages, such as low investment and operational cost. However, long production cycle and serious nitrogen loss are the main urgent problems in practical composting production. Recently, our study found that there was longstanding incredible amounts of anaerobic area inside of the dewatered sludge particles during the composting process, which significantly impacted the aerobic biodegradaion rate and increased ammonia release. Furthermore, the widely-used organic bulking agents, such as sawdust and straw, have the lower biodegradation rate than that of the sewage sludge. In this project, the organic bulking agents are replaced with inorganic bulking agent and the matured compost. Many modern detection methods such as microelectrodes, high throughput sequencing and FISH are used to study oxygen transfer process, organics biodegradation and microbial population in the dewatered sludge. The influences of combined bulking agents and anaerobic microenvironment on the sludge composting process and microbial nitrification are evaluated. The micro-ecological characteristics and nitrogen transfromation process are investigated inside of the dewatered sludge particles and the matured compost particles. The spatial differences of the material porosity and the ammonia releasing rate are detected in the composting pile. According to the above research results, we improve oxygen transfer efficienct, enhance the biological nitrification, optimize the spatical material ratio in composting pile and the operation parameters. This project would provide an important theoretical basis and technical support for developping the nitrogen-conservation and fast sludge composting technology.

近年来我国城镇污水厂污泥处理处置问题得到各方面极大关注。好氧堆肥建设投资少、运行费用低，是国内外污泥处理的主流技术。而生产周期长、氮素损失严重是该项技术在实际应用中急需解决的两个主要问题。我们近期发现，目前普遍使用的有机堆肥调理剂的降解速率均明显低于污泥，而且堆肥过程中脱水污泥颗粒内部长期存在大量厌氧区域，影响好氧发酵效率、加速氨气释放。本项目采用无机调理剂和堆肥熟料代替传统有机调理剂，利用微电极、高通量测序、FISH等多种检测技术，研究堆肥过程中脱水污泥颗粒内部氧传质特征、微生物种群分布和有机质降解过程，探讨组合调理剂和厌氧微环境对发酵工况和生物硝化过程的影响，揭示污泥和熟料颗粒内部微生态特征和氮素转化过程，明确堆体中孔隙率和氨气释放速率的空间分布特征。在此基础上，提高氧传质效率、增强生物硝化作用、优化物料空间投配比和工艺条件，为建立新型保氮—快速污泥堆肥控制技术提供理论依据和技术支撑。

我国污水厂污泥处理处置问题亟待解决。好氧堆肥是污水厂污泥处理与资源化的主流技术，但是污泥堆肥生产过程中氨气大量逸出，氮素损失通常到达40%以上，不仅降低了堆肥产品的肥效，并且臭气污染问题也限制了该项技术在人口密集地区的推广应用。本项目已脱水颗粒污泥为研究对象，系统的解析了颗粒内部溶解氧、氧化还原电位、各氮素形态和微生物种群的空间分布特征，首次发现好氧堆肥过程中脱水污泥颗粒内部厌氧环境长期占据主导地位，从而改变了对好氧堆肥过程的原有认识，并揭示了堆肥过的中生物硝化作用收到抑制的主要原因。另外，本研究揭示了堆肥过程中有机质降解转化过程，解析了污泥颗粒表层和内部区域中细菌、真菌种群结构的演替规律，从而在很大程度上提高了对污泥好氧堆肥过程及其微观生态特征的认识水平。在此基础上，研究了多种调理剂和物料空间结构对污泥堆肥氮素转化过程的影响，发现采用熟料回流能提高物料孔隙率和氧传质效率，而调理剂的持水能力对氨气挥发影响显著，并采用堆肥数学模型对污泥堆肥工艺过程进行优化，从而建立了基于增强氧传质的污泥堆肥氮素损失控制技术，为减少污泥堆肥过程中的氮素损失提供新的解决途径。