Collaborative Research: Shape Effects on Microorganism Removal by Microfiltration and Ultrafiltration Membranes

这项由化学和生物分离计划颁发的NSF奖支持从实验和理论两个角度研究微生物大小和形状对膜排斥的影响的工作。微滤和超滤膜越来越多地应用于食品加工、生物技术、制药工业和环境分离。在1993年威斯康星州密尔沃基爆发隐孢子虫后，这些先进的过滤技术在城市水和废水处理中得到了普及。这是美国历史上最大的一次水媒疾病爆发，导致40多万人患病，50人死亡。尽管薄膜对这种寄生虫构成了几乎完全的屏障(传统过滤技术不能)，但病毒和细菌可以通过它们，可能会对人类健康构成风险。微滤和超滤系统也被用于药品、果汁、牛奶和其他产品的净化和制造，在这些产品中，无菌是一个重要的考虑因素。矛盾的是，尽管微滤和超滤系统通常不能实现完全去除病毒和细菌，但控制微生物通过它们的因素并不是很好，特别是对于非球形生物。这就需要保守的膜设计和实现。此外，以往胶体跨膜的实验和理论研究主要集中在球形颗粒上，尽管在供水中经常遇到杆状细菌和非球形病毒。在这项工作中，将进行全面的理论和实验研究，以描绘阻碍微滤和超滤膜去除病毒和细菌的传输现象。重点将集中在系统和严格地确定微生物长宽比的影响以及轴向和旋转的Peclet数对传输的重要性。许多杆状病毒和细菌在一系列孔径和跨膜压力范围内的过滤将使用具有理想孔几何结构的径迹蚀刻膜以及具有复杂孔结构的商业相关的相转化膜来研究。这项工作的更广泛的影响在于：(I)在克拉克森和休斯顿培训一名高中科学/数学教师，(Ii)与米利波尔公司的工业科学家交流，(Iii)培训学生应用交通现象、生物技术和环境工程的原理进行跨学科和协作研究，(Iv)支持本科生通过课程项目和暑期研究进行研究，以及(V)在同行评议的出版物和会议演讲中传播研究成果。我们希望吸引来自休斯敦和波茨坦的各种K-12机构的参与者，特别是那些历史上有少数族裔学生团体的机构参加其中几项活动。

This NSF award by the Chemical and Biological Separations program supports work to examine from both experimental and theoretical viewpoints the effect of microorganism size and shape on membrane rejection. Microfiltration and ultrafiltration membranes are increasingly employed in the food processing, biotechnology, pharmaceutical industries and for environmental separations. These advanced filtration techniques have gained popularity in municipal water and wastewater treatment particularly following the 1993 Cryptosporidium outbreak in Milwaukee, WI. This is the single largest waterborne disease outbreak in the history of the United States resulting in over 400,000 becoming ill and 50 deaths. Even though membranes present a virtually complete barrier to this parasite (conventional filtration techniques do not), viruses and bacteria can pass through them potentially posing human health risks. MF and UF systems are also employed during purification and manufacturing of drugs, juices, milk and other products where sterility is an important consideration.Paradoxically, even though microfiltration and ultrafiltration systems do not generally achieve complete virus and bacteria removal, the factors governing microorganism transport across them are not well understood, particularly for non-spherical organisms. This necessitates conservative membrane design and implementation. Further, previous experimental and theoretical studies of colloid passage across membranes have focused predominantly on spherical particles even though rod-shaped bacteria and non-spherical viruses are frequently encountered in water supplies.In this work comprehensive theoretical and experimental investigations will be performed to delineate hindered transport phenomena contributing to the removal of viruses and bacteria by microfiltration and ultrafiltration membranes. The focus will be on systematically and rigorously determining the influence of microorganism aspect ratio and the importance of axial and rotational Peclet numbers on transport. The filtration of numerous rod-shaped viruses and bacteria across a range of pore sizes and transmembrane pressures will be examined using both track-etched membranes with an idealized pore geometry as well as commercially relevant phase inversion membranes which have a complex porous structure. A rigorous model that incorporates Brownian diffusion and particle alignment with the flow will be developed.Broader impacts of the work lie in (i) training a high school science/math teacher in Clarkson and another at Houston, (ii) communications with industrial scientists at Millipore Corporation, (iii) training students to perform interdisciplinary and collaborative research applying principles from transport phenomena, biotechnology, and environmental engineering, (iv) supporting undergraduates to conduct research through course projects and summer research, and (v) disseminating research results in peer-reviewed publications and conference presentations. We hope to draw participants from a variety of K-12 institutions across Houston and Potsdam, particularly those with historically minority student bodies in several of these activities.