Improving the Reliability of Anaerobic Ammonium Oxidation (ANAMMOX) as an N-Removal Technology through a Mechanistic Understanding of Irreversible Nitrite Inhibition

最近发现的厌氧氨氧化（anammox）的微生物过程提供了一个更经济和环境可持续的选择，在废水处理过程中的营养氮去除相比，传统的硝化-反硝化。厌氧氨氧化细菌催化亚硝酸盐与铵的反应，在没有元素氧的情况下形成二氮气体。该过程最重要的限制因素是所涉及的细菌的缓慢生长速率以及它们对底物亚硝酸盐的敏感性。初步研究表明，亚硝酸盐的抑制是相当严重的能量供体底物的存在下相比，在不存在，导致生物质变得不可逆地失活。饥饿条件下的抑制的依赖性可能与不寻常的厌氧氨氧化细菌的细胞器结构。厌氧氨氧化细菌的中心代谢反应发生在一个专门的细胞器隔室中，即厌氧氨氧化体，它保护细胞的其余部分免受反应性化合物的影响，并为产生能量的质子梯度提供细胞内膜屏障。项目目标的首要目标是证明假设的有效性，并将其作为指导，以制定战略，以防止亚硝酸盐抑制在厌氧氨氧化作为脱氮技术的应用。该项目将描述两种厌氧氨氧化细菌富集培养物的特征，并使用它们来描述和量化亚硝酸盐抑制的范围。通过饥饿或质子梯度耗散影响厌氧氨氧化细菌的代谢能，阐明亚硝酸盐抑制的机制。所获得的机理见解将用于设计和测试在生物反应器的操作过程中防止抑制的策略，包括提供改进的细胞保留的膜生物反应器。营养氮化合物是重要的环境污染物，在地表沃茨中引起氧气耗尽、富营养化和鱼类毒性，以及通过地下水资源构成公共健康威胁。为了减轻这些影响，营养氮的环境法规变得越来越严格。因此，脱氮成为污水处理的一个必要组成部分.目前的做法是基于硝化-反硝化过程，这需要昂贵的曝气和电子供体底物添加。厌氧氨氧化是一种替代脱氮技术，可显著节省曝气成本（62.5%），更紧凑的生物反应器，并消除了对基质补充剂的需求。这些好处转化为氮去除所消耗的能量更少，从而为废水处理提供了更低的碳足迹。厌氧氨氧化特别适用于高氨和低有机碳的废物流，如污泥液和垃圾渗滤液。厌氧氨氧化工艺应用的一个重要缺点是由于对厌氧氨氧化微生物灭活的情况知之甚少而不可靠。该项目的具体目的是了解问题，以便设计策略，提供一个解决方案，使厌氧氨氧化技术更可靠，从而吸引公用事业和技术供应商。该项目将通过支持研究生和本科生的研究以及提供科学成果来开发环境工程课程的模块，从而在教育方面产生效益。在制度上，该项目将加强工业伙伴关系，以扩大厌氧氨氧化技术。

1234211FieldThe recently discovered microbial process of anaerobic ammonium oxidation (anammox) offers a more economical and environmentally sustainable option to nutrient nitrogen removal during wastewater treatment compared to conventional nitrification-denitrification. Anammox bacteria catalyze the reaction of nitrite with ammonium to form dinitrogen gas in the absence of elemental oxygen. The most important limiting factors of the process are the slow growth rates of the bacteria involved combined with their sensitivity to the substrate, nitrite. Preliminary research has demonstrated that nitrite inhibition is considerably more severe in the absence compared to the presence of the energy donating substrate, causing the biomass to become irreversibly inactivated. The dependency of the inhibition on starvation conditions may be related to the unusual organelle structures in anammox bacteria. The central metabolic reactions of anammox bacteria take place in a specialized organelle compartment, the anammoxosome, which protects the rest of the cell from reactive compounds and provides an intracellular membrane barrier for energy yielding proton gradients. The overarching goal of the project goal is to demonstrate the validity of the hypothesis and use it as a guide to develop strategies to prevent nitrite-inhibition during the application of anammox as an N-removal technology. The project will characterize two enrichment cultures of anammox bacteria and use them to describe and quantify the scope of the nitrite-inhibition. Experiments will be conducted to elucidate the mechanisms of nitrite inhibition by influencing the metabolic energy in anammox bacteria via starvation or dissipating proton gradients. The mechanistic insights gained will be used to design and test strategies of preventing inhibition during the operation of bioreactors including membrane bioreactors that provide improved cell retention.Nutrient nitrogen compounds are important environmental contaminants causing depletion of oxygen, eutrophication, and fish toxicity in surface waters as well as a posing a public health threat via ground water resources. To mitigate these impacts, environmental regulations for nutrient nitrogen are becoming stricter. As a result, N- removal is becoming a necessary component of wastewater treatment. The current practice is based upon the nitrification-denitrification process, which requires costly aeration and electron-donating substrate additions. Anammox is an alternative N-removal technology that provides important savings in aeration costs (62.5%), more compact bioreactors and eliminates the need for substrate supplements. These benefits translate to less energy consumed for N removal and thus provide a lowered Carbon-footprint for wastewater treatment. Anammox is particularly suited for waste streams high in ammonia and low in organic carbon such as sludge liquor and landfill leachate. An important drawback for the application of the anammox process has been its unreliability due to the poorly understood cases of anammox organism inactivation. This project specifically aims to understand the problem so as to design strategies to provide a solution to make anammox technology more reliable and thus attractive to utilities and technology suppliers. The project will have benefits in education by supporting graduate and undergraduate student research as well as providing scientific results to develop modules in environmental engineering courses. Institutionally, the project will reinforce industrial partnerships to scale up the anammox technology.