DEM simulations of initial deposition of colloidal particles around non-woven membrane spacers

The modelling of the initial deposition on membrane spacers of colloidal size particles immersed in a liquid is investigated using the Discrete Element Method (DEM) coupled to Computational Fluid Dynamics (CFD). The ability of this method to model surface interactions allows the modelling of aggregation and deposition at the particle scale. The numerical model adopts a mechanistic approach to represent the forces involved in colloidal suspension by including near wall drag retardation, surface interaction and Brownian forces. The model is implemented using commercially available software, so that results can be replicated in a standard and user-friendly framework. The effect of different spacer orientation with respect to feed direction is examined and results show that deposition of particles is increased around the spacer joints when feed orientation bisects the spacers' angle; when one of the spacer filaments is aligned with the feed inflow deposition occurs exclusively and uniformly on it. Simulation results demonstrate the validity of the method to describe the small-scale behaviour of micro-particles around spacers. The incipient fouling of particles in this size range is analogous to incipient bio-fouling of membrane spacers.