Understanding the role of activated sludge in oxygen transfer to improve wastewater treatment sustainability

污水处理厂在环境保护中起着至关重要的作用。在美国，城市污水处理厂（WWTPs）每天处理数十亿加仑的废水，以去除悬浮固体、有机物和过量的营养物质，包括氮和磷。曝气是城市污水处理厂的一个关键单元操作，因为它为好氧生物废水处理中使用的活性污泥过程提供所需的氧气，以去除有机物和营养物质。然而，曝气需要大量的能量，占活性污泥废水处理过程中总能量的70- 80%。该项目的总体目标是推动创新解决方案的发展，以减少操作活性污泥废水处理过程所需的曝气能量。为了实现这一目标，首席研究员建议开展一项综合实验和建模计划，以表征和揭示控制活性污泥生物反应器混合液中氧转移的物理化学和生物过程和参数。该项目的成功完成将通过产生新的基础知识和创新的解决方案来造福社会，这些解决方案可以减少城市污水处理厂的能源消耗和温室气体排放。通过拓展和教育活动，包括指导密苏里科技大学的两名研究生，将为社会带来额外的好处。在好氧生物废水处理中，曝气约占整个过程能耗的50%。该项目的首席研究员（PI）的初步研究已经确定，活性污泥的生物和物理化学性质对曝气过程中的氧气传递有重大影响。基于这项初步工作的结果，PI及其研究小组建议对活性污泥生物反应器混合液中的氧气传递过程进行深入研究，包括气-液、液-固和气-液-固界面。本研究的具体目标是：1)评估污泥物理性质（如形态、沉降性、粘度和疏水性）对气液界面氧传递的影响；2)评估污泥物理性质（如上所述）和污泥生物参数（如微生物种群和胞外聚合物质浓度）对液-微生物界面氧传递的影响；3)评价微生物在气液界面增强氧传递的机理；4)开发并验证可用于表征活性污泥生物反应器混合液固有氧传递特性的无量纲工艺参数。该项目的成功完成可能会产生变革性的影响，通过产生基础知识和工艺设计工具，可以利用这些知识和工具来减少曝气和操作活性污泥废水处理所需的能源。为了实施该项目的教育和推广活动，PI计划利用密苏里科技大学的本科生研究经验机会项目，为两名本科生提供研究培训机会。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。

Wastewater treatment plants play a critical role in environmental protection. In the United States, municipal wastewater treatment plants (WWTPs) process billions of gallons of wastewater every day to remove suspended solids, organic matter, and excess nutrients including nitrogen and phosphorus. Aeration is a critical unit operation in municipal WWTPs as it provides the required oxygen for the activated sludge process used in aerobic biological wastewater treatment to remove organic matter and nutrients. However, aeration requires a significant amount of energy and accounts for 70-80 % of the total energy used in an activated sludge wastewater treatment process. The overarching goal of this project is to advance the development of innovative solutions to reduce the aeration energy required to operate an activated sludge wastewater treatment process. To advance this goal, the Principal Investigator proposes to carry out an integrated experimental and modeling program to characterize and unravel the physicochemical and biological processes and parameters that control oxygen transfer in the mixed liquor of an activated sludge bioreactor. The successful completion of this project will benefit society through the generation of new fundamental knowledge and innovative solutions that could reduce the energy consumption and greenhouse gas (GHG) emissions of municipal WWTs. Additional benefits to society will be achieved through outreach and educational activities including the mentoring of two graduate students at the Missouri University of Science and Technology.In aerobic biological wastewater treatment, aeration accounts for approximately 50% of the total process energy consumption. Preliminary research by the Principal Investigator (PI) of this project has established that the biological and physicochemical properties of activated sludge have a significant impact on oxygen transfer during aeration. Building upon the results of this preliminary work, the PI and his research team propose to carry out an in-depth investigation of the oxygen transfer process in the mixed liquor of an activated sludge bioreactor including at the gas-liquid, liquid-solid, and gas-liquid-solid interfaces. The specific objectives of the research are to: 1) Evaluate the effects of sludge physical properties (e.g., morphology, settleability, viscosity, and hydrophobicity) on oxygen transfer at the gas-liquid interface; 2) Assess the effects of the sludge physical properties (listed above) and sludge biological parameters (e.g., microorganism population and concentration of extracellular polymeric substances) on oxygen transfer at the liquid-microorganism interface; 3) Evaluate the mechanisms of enhancement of oxygen transfer by microorganisms at the air-liquid interface; and 4) Develop and validate dimensionless process parameters that could be used to characterize the intrinsic oxygen transfer property of the mixed liquor of an activated sludge bioreactor. The successful completion of this project has the potential for transformative impact through the generation of fundamental knowledge and process design tools that could be leveraged to reduce the energy required to aerate and operate an activated sludge wastewater process. To implement the education and outreach activities of the project, the PI plans to leverage the Opportunities for Undergraduate Research Experiences program at the Missouri University of Science and Technology to provide research training opportunities to two undergraduate students.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.