Numerical simulations of the effect on twisted spacer filaments on biofouling and scaling in the feed channel of reverse osmosis membrane modules

Abstract

Overcoming biofouling and scaling in membrane-based separation processes is significant as it affects the permeate quality. In the present study, the effect of biofouling (on membrane only, spacer only, membrane as well as spacer) and scaling on the velocity field, pressure variation, solute residence time distribution and water flux in the reverse osmosis feed channel consisting of twisted spacer filaments is presented using numerical simulations. The twisted spacer filaments caused fluid mixing, which enhanced membrane performance. The biofouling on spacer filaments and/or membrane surfaces and scaling resulted in a narrower effective area for fluid flow, thus causing fluid acceleration and higher pressure drop. The study of solute residence time distribution for biofouling revealed that the breakthrough time decreased with residence time due to fluid acceleration. The observations of solute tracer movement revealed that the solute advection pattern broadened when the feed time for the solute tracer was increased. An irregular and heterogeneous pattern of solute tracer movement was observed in the reverse osmosis feed channel with biofouling which enhanced the flow dispersion and acceleration. The effect of feed temperature on the biofouling pattern was also observed. Biofouling reduced with temperature because the increased feed temperature improved biomass mobility. The water flux in the computational domain containing spacer with scaling was higher compared to the computational domain containing spacer with biofouling because biofouling reduced the membrane porosity, diffusion coefficient and increased flow resistance. The present study concludes that the twisted spacer can effectively reduce biofouling and scaling with improved water flux in reverse osmosis membrane modules.