Evaluation of diffusion coefficients as surrogate indicators for electrostatic repulsion in ultrafiltration membrane fouling

Abstract

Impacted by the electrostatic repulsion between ultrafiltration (UF) membranes and natural organic matter (NOM), organic fouling precipitates significant operational difficulties in water treatment facilities. This study investigated the applicability of diffusion coefficients as surrogate indicators to evaluate the electrostatic repulsive forces between NOMs and UF membrane surfaces. We utilized three distinct types of NOMs and three different UF membranes, each possessing different charge characteristics. Notably, we found that the reduction in diffusion coefficients was markedly pronounced when membranes rich in ionizable functional groups with strong negative charges were involved, indicating heightened electrostatic repulsion. To confirm the reliability of diffusion coefficient reduction as a surrogate indicator of the electrostatic repulsive force, a comprehensive membrane fouling test was conducted. The results revealed a strong correlation between the two parameters, enhancing our understanding of the intricate dynamics of membrane fouling (R2 = 0.9744-0.9907). Thus, this study proposes the concept of utilizing the reduction in the diffusion coefficient as a surrogate indicator to represent the electrostatic repulsive force between NOMs and the UF membrane surface. This innovative approach contributes to enables proactive and predictive assessments of membrane performance, fostering a shift toward proactive maintenance and enhances the operational efficiency of water treatment facilities.