Abstract
To quantitatively investigate fouling layer development in the gravity driven-membrane filtration, we conducted microscopic observation of fluorescently labeled live cells, dead cells, polysaccharides, and proteins in the fouling layers by a confocal laser scanning microscope and quantitatively analyzed volume, average thickness, roughness coefficient, and surface-to-volume ratio of them. In fouling layers developed on PES membranes which had relatively higher flux, live cells distributed mainly in the upper part of the fouling layer. On the other hand, most of dead cells distributed in the bottom of fouling layer due to the substrate deficit in the bottom part of the fouling layer. Polysaccharides distributed in the same region with live cells, which indicates the release of polysaccharides from live cells. The fouling layers of PES membranes had rough and thick structure with high surface-to-volume ratio and large cavity, which contributed to the reduction of fouling resistance. In the fouling layers on PAN memranes, all targeted constitients uniformly and densely distributed on the proximity of membrane surface, which lead to the higher fouling resistance of PAN membrane filtration. These results indicated the significant influence of filtration flux of gravity driven membrane-filtration on the structure of the fouling layer.
