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

国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项支持乔治·F·威尔斯博士与Eberhard Morgenroth博士和Eberhard Morgenroth博士及其在Ewag：瑞士联邦水产科学与技术研究所的同事们进行为期24个月的研究。单一反应器中的组合亚硝化和厌氧氨氧化(Anammox)是一种很有前途的低能耗策略，可以去除废水中的氮，从而防止与营养污染相关的对自然系统的负面环境和公共健康影响。组合亚硝化/厌氧氨氧化工艺依赖于几组微生物的协调活动，这些微生物在聚集体中紧密结合生长，包括好氧氨氧化菌和厌氧氨氧化菌(厌氧氨氧化菌)。尽管前景看好，但这些工艺的广泛应用受到工艺不稳定性和关于强有力的温室气体一氧化二氮排放的不确定性的阻碍。该项目的主要假设是，传质限制会影响亚硝化/厌氧氨氧化组合工艺的稳定性和一氧化二氮的排放。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)一氧化二氮生产，以及3)亚硝化/厌氧氨氧化组合工艺变化对工艺不稳定性的敏感性。复制实验室规模的生物反应器采用两种不同的工艺，使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，使用尖端显微镜结合微传感器测量来表征质量传输限制，并通过高通量DNA测序技术来研究微生物群落结构的差异。同时，量化了一氧化二氮的产生率和微生物来源。然后，在模拟工艺颠覆的情况下，表征工艺性能和弹性，工艺稳定性、一氧化二氮产量和微生物多样性与微尺度聚集特征和质量传输限制相关。研究结果将被整合到一个简单的数学模型和监测方法中，以指导用于可持续废水处理和环境保护的亚硝化/厌氧氨氧化组合系统的实际设计和操作，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。这项研究通过在微生物生态学和过程工程小组之间建立跨学科合作，直接促进我们对厌氧氨氧化细菌的了解。厌氨氧化细菌是一组鲜为人知的微生物，对全球生物地球化学氮循环具有深远的重要性。从实践的角度来看，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市政和工业废水处理，以及垃圾渗滤液中的氮管理、生物燃料的生物质生产，以及与营养污染和一氧化二氮生产相关的农业活动。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、硝化菌和反硝化菌之间的相互作用。结果还有助于我们理解微生物温室气体产生的来源和控制，并阐明微生物多样性和生态系统功能之间的关系--这是微生物生态学领域的一个关键研究领域。

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.