面向航天生保系统的尿液膜蒸馏过程中N转移、结晶特征与膜污染机制

The development of deep-space exploration in China set higher and urgent demands for urine treatment in CELSS. Membrane distillation (MD) was proven as an effective method for urine treatment, however the knowledge for MD process and its membrane fouling formation mechanism were limited. This project focused on the treatment and reuse of source separated urine in CELSS by MD, the distribution and migration rule of nitrogen was investigated to understand the urine MD process. The dynamic mechanism of bulk phase crystallization and vertical distribution of membrane surface crystallization were illuminated by crystals measurement and crystallization kinetics simulation. And the evolution of bulk phase crystallization and the formation mechanism of surface crystallization were then revealed. The fouling mechanism of hydrophobic membrane under high temperature, salinity, and organic matters was systematically analyzed in terms of XDLVO simulation, measurement of TEP, DOM, EPS, inorganic crystallization, and microbial community structure, pollutants vertical distribution analyzation, and inorganic-organic chelation mechanism investigation. Then the urine MD process can be performance optimized and membrane fouling controlled, and it was evaluated for CELSS application. Theoretically speaking, this project offers new theoretical insights for MD research, especially on hydrophobic membrane fouling investigation. In terms of applications, this work offers new method for source separated urine in CELSS, which would provide theoretical and technical basis for deep space exploration project in China.

深空探测的发展对CELSS中尿液处理提出紧迫的要求，膜蒸馏(MD)是尿液处理与回用的有效手段，但目前对尿液MD过程及其膜污染机制的认识尚有限。本研究从空间站源分离尿液的深度处理和回用入手，考察MD效能，阐明高盐、高有机物、高温条件下N元素分布演变特征及迁移转化规律；通过结晶分析与结晶动力学模拟，阐明体相结晶的动力学机制及膜面结晶的垂直分布特征，解析连续运行过程体相结晶演变特征与膜面结晶形成机制；基于膜污染动力学模拟、TEP-DOM-EPS-无机盐-微生物群落结构综合分析、污染物垂直分布特征、有机无机耦合机制的研究，识别膜污染关键污染物，揭示高温、高盐、高有机物条件下疏水膜复合膜污染机制，实现过程优化、调控与评价。本项目从理论上有望为MD过程分析和膜污染研究提供新思路，丰富MD研究体系；从应用上有望为空间站源分离尿液处理提供新的策略，为我国今后深空探测工程的发展提供坚实的理论依据和技术保障。

针对CELSS中尿液的处理与回收问题，本研究采用膜蒸馏(MD)进行尿液的处理并考察膜污染的形成机制与污染物转化特征。1)明确尿液在存储过程中的性质变化特征与机制；2)将活性炭与铁氧化物用于MD预处理，实现MD的长效稳定运行，并明确了预处理过程污染物去除机制；3)考察了MD过程中温度、流速、pH等操作条件的影响，实现MD工艺优化；4)明确MD处理尿液性能，分析N、P、溶解性有机物等污染物在MD过程中的分布特征与去除机制；5)考察了MD用于尿液处理的长期稳定性能，研究了尿液MD过程中的有效的化学清洗策略； 6)分析了陶瓷膜酸化、吸附等预处理过程对MD过程的影响，明确了有机-无机-微生物污染组成并解析膜污染的形成机制；7)基于项目的支持，考察MD对高盐废水的处理效能与膜污染机制，明确了MD过程中溶解性有机物的转化机制，并初步构建了有机物与微生物代谢的机制；8)以推流式膜组件为对象，采用降维策略，阐明了MD膜污染形成的时空变化过程，揭示了有机-无机-微生物污染的水平与垂直分布特征，阐明了复合膜污染形成的微生物学机制。项目研究成果可为CELSS中废水处理提供科学支撑，同时为高盐废水的脱盐过程中膜污染的研究方法与形成机制提供参考。