Collaborative Research: Prechlorination, aging, and backwashing effects on spatiotemporal ultrafiltration fouling:  Optimizing productivity by combining experiments and theory

全世界约有40亿人每年至少有一个月严重缺水，超过5亿人全年缺水。在美国和世界各地，越来越多的自来水公司利用废水回收来增加他们的饮用水供应。在许多废水回收厂中，中空纤维（HF）超滤（UF）膜系统与消毒预处理步骤（如氯化）相结合，以去除二级处理废水中的悬浮物，包括细菌、病毒和其他病原体。然而，在运行过程中，过滤效率和产水量下降，因为膜HFs的孔被去除的悬浮物堵塞。因此，废水回收系统的HF UF膜组件在运行过程中需要频繁清洗（每天多次）。该项目的总体目标是开发和验证新一代的数学和计算模型，这些模型可以指导高频超滤膜系统的操作和优化，以最大限度地提高其产水量，同时降低废水回收过程中的能耗。为了实现这一目标，首席研究员（pi）建议开展一项综合实验和建模研究计划，以建立和验证膜操作的数学/计算模型，该模型考虑了膜模块几何形状、纤维填充密度和氯预处理对HF UF膜系统过滤效率和产水量的影响。通过开发新的基础知识和建模工具，本研究的成功完成将有益于社会，这些知识和工具可以指导废水回收厂超滤HF膜系统的运行，以提高和最大化水产量，同时减少运行此类系统所需的能量。通过对学生的教育和培训，包括对佛罗里达州立大学、伍斯特理工学院和德克萨斯农工大学的三名研究生的指导，将为社会带来额外的好处。中空纤维（HF）超滤（UF）膜组件/系统越来越多地用于废水回收厂，以去除二次处理废水中的悬浮物、细菌、病毒和其他病原体。然而，能够准确模拟UF HF膜组件/系统的操作和性能的经过验证的数学和计算模型的发展仍然难以捉摸。该项目的目标是在多个时间和空间尺度上对高频UF膜模块/系统性能的时空变化进行机械理解。为了实现这一目标，首席研究员（pi）建议利用流体流动方程的解析解，从单个纤维开始，移动到以不同模式排列的“少数”纤维，以重现商用HF UF膜模块的几何形状和水力特性。此外，pi建议开发并验证一个计算模型，该模型可用于模拟HF UF膜模块的性能，目标是确定最佳操作参数，包括氯预处理浓度、正向过滤期间的通量/压力状态、清洗期间的膜反冲洗压力和运行时间。这项研究的成功完成有可能产生变革性的影响，通过产生新的基础知识和经过验证的数学/计算模型来指导废水回收厂HF UF膜模块/系统的设计、操作和优化。为了实现该项目的教育和培训目标，项目负责人建议与lifeology合作开发一门在线课程，以提高公众对水过滤和水再利用的认识。lifeology是一个汇集科学家、传播者和作家设计和制作教育材料以吸引更广泛受众的平台。此外，pi计划利用各自机构现有的外展项目，设计和实施K-12教师培训项目，重点是制定与水质和处理相关的课程计划。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。

Worldwide, approximately 4 billion people experience severe water shortages at least one month per year and over 500 million people experience shortages throughout the year. Wastewater reclamation is increasingly being utilized by water utilities in the United States and worldwide to increase their supply of drinking water. In many wastewater-reclamation plants, a hollow fiber (HF) ultrafiltration (UF) membrane system is combined with a disinfection pretreatment step (e.g., chlorination) to remove suspended solids in secondary treated wastewater including bacteria, viruses, and other pathogens. However, the filtration efficiency and water production decrease during operation as the pores of the membrane HFs become clogged by the removed suspended solids. Thus, the HF UF membrane modules of wastewater reclamation systems needed frequent cleaning (multiple times per day) during their operation. The overarching goal of this project is to develop and validate a new generation of mathematical and computational models that could guide the operation and optimization of an HF UF membrane system with the aim of maximizing its water production while reducing its energy consumption during wastewater reclamation. To advance this goal, the Principal Investigators (PIs) propose to carry out an integrated experimental and modeling research program to build and validate mathematical/computational models of membrane operation that take into account the effects of membrane module geometry, fiber packing density, and chlorine pretreatment on the filtration efficiency and water production of an HF UF membrane system. The successful completion of this research will benefit society though the development of new fundamental knowledge and modeling tools that could guide the operation of UF HF membrane systems in wastewater reclamation plants to improve and maximize water production while reducing the energy required to operate such systems. Additional benefits to society will be achieved through student education and training including the mentoring of three graduate students at Florida State University, Worcester Polytechnic Institute, and Texas A&M University.Hollow fiber (HF) ultrafiltration (UF) membrane modules/systems are increasingly being used in wastewater reclamation plants to remove suspended solids, bacteria, viruses, and other pathogens from secondary treated wastewater. However, the development of validated mathematical and computational models that could accurately simulate the operation and performance of an UF HF membrane module/system has remained elusive. The goal of this project is to derive a mechanistic understanding of spatiotemporal variations in the performance of HF UF membrane module/system over multiple time and spatial scales. To advance this goal, the Principal Investigators (PIs) propose to leverage analytical solutions of fluid flow equations starting with a single fiber, moving to a “few” fibers arranged in different patterns to reproduce the geometry and hydraulic properties of a commercial HF UF membrane module. In addition, the PIs propose to develop and validate a computational model that could be used to simulate the performance of an HF UF membrane module with the goal of identifying optimal operational parameters including chlorine pretreatment concentration, the flux/pressure regimes during forward filtration, and the membrane backwash pressure and run time during cleaning. The successful completion of this research has the potential for transformative impact through the generation of new fundamental knowledge and validated mathematical/computational models to guide the design, operation, and optimization of HF UF membrane modules/systems in wastewater reclamation plants. To implement the educational and training goals of this project, the PIs propose to develop an online course to increase public literacy in water filtration and water reuse in collaboration with Lifeology—a platform that brings together scientists, communicators, and writers to design and produce educational materials to engage broader audiences. In addition, the PIs plan to leverage existing outreach programs at their respective institutions to design and implement K-12 teacher training programs with a focus on the development of lesson plans related to water quality and treatment.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.