Fouling monitoring during microfiltration of humic acid by streaming potential measurement

Fouling by natural organic matter like humic substances is one of the major factors limiting the application of microporous membranes for water production. The charge of the pore surface of membrane, which can be characterized by the streaming potential(SP) measurement as the apparent zeta potential ζ obs, has a large effect on its fouling performance. However the relationship between the fouling condition and the apparent zeta potential is not always clear. The objective of this study was to develop a fouling monitoring technique during the microfiltration of humic acid by streaming potential measurement. The apparent zeta potential was measured continuously during the filtration. The apparent zeta potential increased with the increase in filtration resistance during filtration. The apparent zeta potential of fouled membrane was depended on the degree of the fouling however the absolute value of the apparent zeta potential was not same with the zeta potential of Humic acid, which was obtained by electrophoresis method. And it was demonstrated that the apparent zeta potential is useful for the confirmation of the effect of the cleaning of the fouled membrane by the cleaning experiments using pure water and alkali detergent.