Location of Biological Foulants within a Wet Membrane Structure

Microfiltration is an important process in beverage clarification. However, filtration of these streams suffers from permeate flux decline caused by membrane fouling by proteins, polysaccharides, and/or polyphenols. To develop fouling mitigation strategies for microfiltration of biological streams, it is important to understand the mechanisms that lead to fouling.

In this presentation, we will discuss the use of confocal laser scanning microscopy (CLSM) to determine where proteins, polysaccharides, and polyphenols deposit inside polymeric microfiltration membranes when a fluid containing these materials is filtered. By using different fluorescently labeled probes, CLSM permitted evaluation of the location and extent of fouling by individual components (protein: casein, polysaccharide: dextran, polyphenol: catechin) within wet, asymmetric PES microfiltration membranes. We were able to locate each component separately and to visualize co-localization within the membrane. In addition, flux profiles and CLSM images were obtained for membranes that processed single-component solutions and mixtures to better understand the role of each on membrane fouling and to see how component interactions impact the fouling profiles. Analysis of the membrane CLSM images at different levels of fouling for single component solutions and mixtures provided concentration profiles versus depth for each individual component present in the feed solution. Using a new cross-sectional imaging protocol that we developed in a previous investigation, we were able to visualize fouling profiles throughout the entire thickness of the membrane, overcoming limitations of depth of penetration observed in previous CLSM work.