Abstract
In ceramic flat-sheet MBRs using a combination of granular scouring and chemically enhanced backwashing (CEB), it is expected that membrane fouling is efficiently controlled, and long-term operation with a high flux may be possible. However, fouling by a transparent gel layer on the membrane became more serious when water temperature was low. Therefore, in this study, we carried out structural and chemical analysis of gel layers formed under different temperatures. The observation using scanning electron microscope (SEM) showed that the gel layer formed under a high temperature had a porous structure, but it was condensed when water temperature was low. Energy dispersive X-ray spectroscopy (EDS) analysis demonstrated that elemental composition of the gel layer changed with water temperature. Fourier transformed infrared spectroscopy analysis showed that proteins and lipids in the gel layer became more significant under a low temperature, and suggested that sub-micron (>0.45μm) particles in mixed liquor supernatants contributed to the formation of the adhesive gel layer when water temperature was low. The ratio of polysaccharides over proteins in the gel layer and that in sludge supernatant decreased when water temperature was low. It was presumed that proteins affected membrane fouling under a low temperature. Inductively coupled plasma (ICP) results indicated that increase of Fe and P in the gel layer was remarkable when water temperature was low.
