抄録
Membrane filtration has been gaining popularity in the various field. However, membrane fouling is an obstacle for wider application of this technology. Especially, the control of irreversible membrane fouling, which can be defined as fouling requiring chemical reagents to be mitigated, is of importance. The aims of this study were (i) to investigate the degree of irreversible fouling caused by different organic matters and (ii) to characterize the faulants that caused irreversible fouling. In this study, four different organic matters (commercially available humic acid, organic matters isolated from two drinking water sources and a wastewater treatment effluent) and membranes (two microfiltration (ME) membranes and two ultrafiltration (UF) membranes) were used. It was observed that the permeate flux did not decline in the UF membranes while there was a large flux decline in the MF membranes. Especially, a rapid flux decline was observed with the polyvinylidene fluoride (PVDF) membrane. The extents of fouling in the MF membranes were strongly depended on both the types of organic matters and membrane materials. A series of chemical analyses such as fluorescence excitation-emission matrix (EEM), specific UV adsorbance (SUVA) and ion chromatography (IC) were applied to elucidate which fractions of organic matter caused the irreversible fouling. SUVA of faulants was significantly lower than was determined for the feed water. This implies that the faulants had hydrophilic features. The results with EEM and IC also confirmed that a variety of hydrophilic compounds such as polysaccharide or protein-like compounds contributed to the formation of the irreversible fouling observed in this study.
