Controlled Biofouling of Escherichia coli on Perfluoroalkoxy Alkane in a Water Purification System for Testing Separation Performance

An emerging membraneless water purification technology is diffusiophoresis-based separations. Diffusiophoresis is a phenomenon that induces directed separation of colloidal particulate via chemical ion gradients. Diffusiophoresis can be used to separate bacteria from water, but biofouling may occur within the system. Thus, assessing the impact of biofouling on system performance is a critical step for evaluating diffusiophoresis-based water purification. Here, we establish the parameters for intentionally fouling perfluoroalkoxy alkane (PFA) with Escherichia coli to consistently yield biofilms with a height of ~10 µm. Shear stress and growth times were varied to modulate biofilm growth. Biofilm height and structure were quantified using image analysis of confocal laser scanning microscopy images. We found that growing E. coli in tryptic soy broth for 12-hours at a shear stress of 0.02 Pa resulted in the formation of 10 µm tall E. coli biofilms on PFA. Additionally, we report how the fluidic environment of a diffusiophoresis water purification system affects the structure of pre-formed E. coli biofilms. This work establishes the parameters for the controlled biofouling of a diffusiophoresis-based separator to evaluate the extent that biofouling influences the water purification system performance.