IRFP: Towards Sustainable Wastewater Treatment: Mass Transport Limitations, Microbial Diversity, and Nitrous Oxide Production in Anammox Nutrient Removal Processes

国际研究奖学金项目使美国科学家和工程师能够在国外进行9至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项支持George F. Wells博士与Eberhard Morgenroth博士及其同事在eawwag瑞士联邦水产科学技术研究所开展为期24个月的研究。在单一反应器中联合硝化和厌氧氨氧化（anammox）是一种很有前途的低能耗策略，可以从废水中去除氮，从而防止与自然系统的营养污染相关的负面环境和公共卫生影响。联合硝化/厌氧氨氧化过程依赖于聚集在一起生长的几组微生物的协调活动，包括好氧氨氧化剂和厌氧氨氧化剂（厌氧氨氧化）。尽管这些工艺很有前景，但由于工艺的不稳定性和强效温室气体一氧化二氮排放的不确定性，阻碍了这些工艺的广泛应用。该项目的主要假设是，质量传输限制影响联合硝化/厌氧氨氧化过程的稳定性和氧化亚氮的排放。为了解决这一假设，正在进行的实验旨在更好地理解质量传输如何影响1)微生物多样性和功能冗余，2)氧化亚氮生产，以及3)联合硝化/厌氧氨氧化过程变化对过程不稳定性的敏感性。复制实验室规模的生物反应器采用两种工艺变化，采用不同类型的微生物聚集体-悬浮生长生物量和生物膜载体。在每种聚集体类型中，质量传输限制使用尖端显微镜和微传感器测量来表征，并通过高通量DNA测序技术研究微生物群落结构的差异。同时，对氧化亚氮的产率和微生物源进行了量化。然后，在模拟过程中断时表征过程性能和弹性，过程稳定性、氧化亚氮产量和微生物多样性与微尺度聚集体特征和质量传输限制相关。研究结果将整合到一个简单的数学模型和监测方法中，以指导硝化/厌氧氨氧化联合系统的实际设计和运行，以实现可持续的废水处理和环境保护，并将为管理实践提供信息，以最大限度地减少废水处理系统产生的温室气体。本研究通过建立微生物生态学和工艺工程小组之间的跨学科合作，直接有助于我们了解厌氧氨氧化细菌，这是一组对全球生物地球化学氮循环具有深远重要性的鲜为人知的微生物。从实际的角度来看，研究结果为新型生物系统的开发和运行提供了信息，以防止营养物污染和可持续的水再利用。事实上，拟议的工作有可能极大地影响城市和工业废水处理，以及垃圾填埋场渗滤液中的氮管理，生物燃料的生物质生产，以及与营养物污染和氧化亚氮生产相关的相关农业活动。更广泛地说，该项目为全球氮循环的微生物生态提供了新的见解，包括厌氧氨氧化、硝化和反硝化之间的相互作用。研究结果还有助于我们了解微生物温室气体产生的来源和控制，并揭示微生物多样性与生态系统功能之间的关系。微生物生态学研究的一个关键领域。

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award supports a twenty four month research fellowship by Dr. George F. Wells to work with Dr. Eberhard Morgenroth and colleagues at Eawag: Swiss Federal Institute of Aquatic Science and Technology.Combined nitritation and anaerobic ammonium oxidation (anammox) in a single reactor is a promising low-energy strategy for removing nitrogen from wastewater, thereby preventing the rash of negative environmental and public health impacts associated with nutrient pollution to natural systems. Combined nitritation/anammox processes rely on the coordinated activities of several groups of microorganisms that grow in close proximity in aggregates, including aerobic ammonia oxidizers and anaerobic ammonia oxidizers (anammox). Although promising, widespread application of these processes is hampered by process instabilities and uncertainty regarding emissions of the potent greenhouse gas nitrous oxide. The major hypothesis of this project is that mass transport limitations impact combined nitritation/anammox process stability and nitrous oxide emissions. To address this hypothesis, ongoing experiments target an improved understanding of how mass transport affects 1) microbial diversity and functional redundancy, 2) nitrous oxide production, and 3) susceptibility to process instabilities of combined nitritation/anammox process variations. Replicate lab-scale bioreactors are operated with two process variations employing different types of microbial aggregates--suspended growth biomass and biofilm carriers. Within each aggregate type, mass transport limitations are characterized using cutting-edge microscopy coupled to microsensor measurements, and differences in microbial community structure are investigated via high-throughput DNA sequencing techniques. In parallel, the production rate and microbial source of nitrous oxide is quantified. Process performance and resilience is then characterized in the face of a simulated process upset, and process stability, nitrous oxide production, and microbial diversity are correlated to microscale aggregate characteristics and mass transport limitations. Results will be integrated into a simple mathematical model and monitoring approach to guide practical design and operation of combined nitritation/anammox systems for sustainable wastewater treatment and environmental protection, and will inform management practices to minimize greenhouse gas production from wastewater treatment systems.This research directly contributes to our knowledge of anammox bacteria, a group of little-understood microorganisms of profound importance to the global biogeochemical nitrogen cycle, by establishing an interdisciplinary collaboration between microbial ecology and process engineering groups. From a practical standpoint, results inform the development and operation of novel biological systems for prevention of nutrient pollution and for sustainable water reuse. Indeed, the proposed work has the potential to dramatically influence municipal and industrial wastewater treatment, as well as nitrogen management in landfill leachate, biomass production for biofuels, and allied agricultural activities associated with nutrient pollution and nitrous oxide production. More broadly, this project provides new insights into the microbial ecology of the global nitrogen cycle, including interactions between anammox, nitrifiers, and denitrifiers. Results also contribute to our understanding of the sources and controls of microbial greenhouse gas production, and shed light on the relationship between microbial diversity and ecosystem function?a critical area of inquiry to the field of microbial ecology.