Structural Health Monitoring of Biofilms for Sustainable Reactive Nitrogen Management

水中的氮污染引起许多环境和公共卫生问题。其中最紧迫的问题包括饮用水源受到硝酸盐污染和有害藻华的刺激。虽然我们已经知道控制氮养分释放的重要性几十年了，但需要新的和更有效的技术来防止氮污染。膜生物反应器是一种很有前途的去除废水中氮污染的技术。膜生物反应器利用生物膜（附着在表面的天然微生物群落）为有效脱氮创造适当的条件。该项目将开发新的科学工具和先进的建模方法，以解决我们对生物膜的机械和结构特性的理解空白。这样做将有助于提高生物反应器的性能，有效地清洁水，防止氮污染。生物膜在自然界中非常普遍，因此这项研究的结果将有益于许多其他科学领域，包括从水中去除其他污染物和防止有害生物膜的生长。该项目的其他好处包括培训代表性不足的学生，从而增加美国STEM劳动力的多样性。对小学生和社区团体的教育推广将增加对控制氮污染重要性的理解，并提高国民的科学素养。生物膜——附着在表面的微生物群落——在工程生物反应器和自然环境中都起着至关重要的作用。尽管生物膜结构作为生物膜生长和活性的重要介质，但人们对生物膜结构与控制生物膜中生物量保留的力学特性之间的关系知之甚少。如果我们要了解如何调节这些特性以提高生物膜反应器的效率，就必须解决这一知识差距。为了解决这一知识差距，pi建议采用一种称为光学相干弹性成像（OCE）的新方法来探索中尺度生物膜粘弹性力学性能、结构和体积氮(N)转化率之间的关系。项目团队将利用OCE对部分硝化和联合硝化-厌氧氨氧化生物膜反应器中的生物膜特性进行基本了解。这两种有前途的节能废水处理技术直接依赖于对生物膜中关键n循环微生物种群的保留和活性的精确控制。工作将围绕两个具体目标展开。目的是研究部分硝化生物膜中常用的工程控制（水动力机制、表面加载速率和投料策略）如何影响中尺度力学性能、中尺度物理结构和微尺度组成之间的耦合。第二个目标是确定中尺度生物膜特性如何控制部分硝化和联合硝化厌氧氨氧化生物膜的关键功能结果（大量N转化和生物量脱离率）。为了将基础科学进步与工程应用相结合，项目团队将把在实验室生物反应器中观察到的微尺度-中尺度-宏观生物膜现象与基于生物膜的全尺寸废水处理系统的预测模型开发联系起来。提高对中尺度生物膜结构、生物力学和紧急系统功能的理解，将为工程生物反应器中生物膜特性的有效监测、建模和控制提供基础，类似于民用基础设施和机械设备的结构健康监测。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nitrogen pollution in water causes numerous environmental and public health problems. Among the most pressing include the contamination of drinking water sources with nitrates and stimulation of harmful algal blooms. Although we have known about the importance of controlling nitrogen nutrient release for decades, new and more efficient technologies are needed to prevent nitrogen pollution. A promising technology to remove nitrogen pollution from wastewater is the use of membrane bioreactors. Membrane bioreactors use biofilms (naturally occurring microbial communities attached to surfaces) to create the appropriate conditions for efficient nitrogen removal. This project will develop new state-of-the-science tools and advanced modeling approaches to address gaps in our understanding of the mechanical and structural properties of biofilms. Doing so will help improve the performance of bioreactors to efficiently clean water and prevent nitrogen pollution. Biofilms are very common in nature, so results of this research will benefit many other scientific areas, including the removal of other pollutants from water and preventing the growth of harmful biofilms. Additional benefits of this project include the training of underrepresented students, thus increasing the diversity of the Nation’s STEM workforce. Educational outreach to grade-school students and community groups will increase understanding of the importance of controlling nitrogen pollution and increase the scientific literacy of the Nation. Biofilms - microbial communities attached to surfaces - play critical roles in both engineered bioreactors and natural environments. Despite the importance of biofilm structure as an essential mediator of biofilm growth and activity, relatively little is known about the relationship between biofilm structure and mechanical properties that control retention of biomass in the biofilm. This knowledge gap must be addressed if we are to understand how these properties can be modulated to increase efficiency in biofilm reactors. To address this knowledge gap, the PIs propose to employ a novel methodology, termed Optical Coherence Elastography (OCE), to probe the relationship between mesoscale biofilm viscoelastic mechanical properties, structure, and bulk nitrogen (N) transformation rates. The project team will employ OCE to develop fundamental understanding of biofilm properties in partial nitritation and combined nitritation-anammox biofilm reactors. These two promising technologies for energy-efficient wastewater treatment depend directly on precise control of the retention and activity of key N-cycling microbial populations in biofilms. Efforts will be organized around two specific objectives. Objective will be to investigate how commonly used engineering controls (hydrodynamic regime, surface loading rate, and feeding strategy) influence coupling between mesoscale mechanical properties, mesoscale physical structure, and microscale composition in partial nitritation biofilms. The second objective is to determine how mesoscale biofilm properties control key functional outcomes (bulk N transformation and biomass detachment rates) in partial nitritation and combined nitritation-anammox biofilms. To integrate fundamental scientific advances with engineering applications, the project team will link microscale-mesoscale-macroscale biofilm phenomena observed in laboratory bioreactors to predictive model development for full-scale biofilm-based wastewater treatment systems. Improved understanding of mesoscale biofilm structure, biomechanics, and emergent system function will provide a basis for effective monitoring, modeling, and control of biofilm properties in engineered bioreactors, analogous to structural health monitoring for civil infrastructure and mechanical devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.