Flux modulation: A novel approach for ultrafiltration fouling control

Abstract

Control of membrane fouling is critical for the long term production of water in a membrane system. Backwashing with or without relaxation is the most common method to control fouling in-situ with ultrafiltration (UF) hollow fiber membrane systems. The inclusion of relaxation is intended to assist with decompression of the membrane cake layers and assist with backwashing. However, it also results in a loss of membrane productivity. This study aimed to investigate the effect of flux modulation with single and dual mode cycles, as well as relaxation, on the performance of an UF membrane with respect to fouling control. Results demonstrated that modulating the flux in place of relaxation results in a substantial improvement in control of membrane fouling while still maintaining membrane productivity. By modulating the flux at different levels compared to a control of flux of 36 LMH, the fouling index values decreased by over 80% while specific water production only dropped 8% (2489 vs 2702 L/m2). Incorporating a relaxation step had minimal impact (<8%) on the performance of a given flux cycle with regards to fouling control. Therefore, high membrane performance can be achieved without the need for a relaxation step, as long as an appropriate flux modulation cycle is selected. This research demonstrates the potential for significant fouling control on an UF membrane by alternating the stress on the membrane surface through flux modulation.