Confocal Laser Scanning Microscopy-Compatible Microfluidic Membrane Flow Cell as a Nondestructive Tool for Studying Biofouling Dynamics on Forward Osmosis Membranes

In membrane biofouling studies, quantification of biofouling is often conducted destructively and the results reflect only a snapshot of the biofouling processes. This limitation is mainly due to the lack of tools that allow us to monitor dynamics of biofouling without the need to disassemble the membrane testing systems. In this study, we developed a novel multichannel fluidic membrane biofilm flow cell that allows nondestructive, real-time monitoring of biofouling dynamics on forward osmosis (FO) membranes using confocal laser scanning microscopy. As a proof of concept, we used green fluorescent protein-tagged Shewanella oneidensis as a model organism and examined its biofilm development on membranes in FO mode. The temporal profiles of quantitative biofouling parameters such as surface coverage, biovolume, and biofilm thickness were obtained without disrupting the continuous operation of the membrane testing system. We also demonstrated the applicability of the microfluidic membrane flow cells, revealing biofouling dynamics of natural, untagged bacteria on FO membranes. The microfluidic membrane flow cell developed in this study can be readily applied to evaluate antibiofouling activities of FO membranes and allows direct comparison of biofouling dynamics between FO membranes with different surface modifications.