Assessment of membrane scaling in pilot-scale nanofiltration process

摘要

This study presents membrane fouling due to scale formation in a pilot-scale nanofiltration (NF) process for industrial wastewater reclamation. The scale formation mechanisms were investigated by applying model equations based on the surface crystallization and bulk crystallization. The longitudinal variations of the local flux, flux, permeability loss, and pressure loss in the membrane modules were also analyzed using the model. The pilot plant consisted of two stages NF systems with the total water production capacity of 50 m(3)/d. Since the raw wastewater contains high concentrations of Ca2+ and SO42- ions, gypsum scale formation occurred during the NF processing. As the scaling potential of brine was different, NF membrane elements in the 2nd stage exhibited faster fouling rates than those did in the 1st stage. In the 2nd stage, the fouling mechanism due to scale formation was identified as surface blockage by surface crystallization rather than cake formation by bulk crystallization.