Three-dimensional modeling of biofouling and fluid dynamics in feed spacer channels of membrane devices

This study presents a new three-dimensional (3-d) computational model that couples fluid dynamics, solutes transport and biofouling by biofilm formation in NF and RO membrane modules. A computational domain of 3 × 5 feed spacer frames with geometry as applied in practice was used in the model. Comparing the hydrodynamics computed with the realistic spacer geometry and with a spacer made from straight cylindrical filaments, like in previous modeling studies, showed that cylindrical filament feed spacers are too simplified for representative modeling studies. The 3-d numerical simulations showed that biomass accumulation, by attachment and biofilm growth in time, strongly affected the feed channel pressure drop, liquid velocity distribution and residence time distribution. The main pressure drop is encountered by the flow passing over the spacer filaments. Simulations showed the development of a heterogeneous flow pattern and formation of preferential flow channels. This study indicates that the real impact of biofouling is on the flow regime leading to quasi-stagnant zones and an increase in the dispersion of the residence time distribution. The presented 3-d mathematical modeling approach in (bio)fouling of membrane modules may have significant implications for membrane system design and operation to have stable membrane installation performance at minimal costs.