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

Exploring the antifouling effect of elastic deformation by DEM–CFD coupling simulation

The influence of elastic deformation and elastic modulus on the release of adhered bacteria was investigated in this paper. Four silicone elastomers (SE) with different elastic moduli and one rigid polystyrene sheet were prepared to verify the antifouling effect of elastic deformation. The SE film has an elastic deformation effect under the stimulus of fluid medium, which makes the surface unstable. That could reduce the adhesion of fouling organisms and provide a foul-release basis. Distinct anti-adhesion properties were observed in our study in that cells more easily adhered to the rigid surface than the elastic surfaces under hydrodynamic conditions. However, the bacterial attachment test showed a similar antifouling performance of SE and the rigid surface under static conditions. To investigate the anti-adhesion ability of the elastic surface and rigid surface, the bacterial adhesive kinetics were studied by Discrete Element Method (DEM)–Computational Fluid Dynamics (CFD) coupling simulation. Results indicated the number of bacteria adhering on the elastic wall was significantly lower than on the rigid wall. And as the elastic modulus increased, the bacterial adhesion increased accordingly within a certain range. This work should not only enhance understanding of elastomer-based antifouling materials, but also facilitate the design and construction of other types non-toxic foul-release materials.

The bacterial adhesive kinetics with different morphology on elastic surface and rigid surface was studied by DEM–CFD coupling simulation.

Spacer geometry and particle deposition in spiral wound membrane feed channels

Deposition of microspheres mimicking bacterial cells was studied experimentally and with a numerical model in feed spacer membrane channels, as used in spiral wound nanofiltration (NF) and reverse osmosis (RO) membrane systems. In-situ microscopic observations in membrane fouling simulators revealed formation of specific particle deposition patterns for different diamond and ladder feed spacer orientations. A three-dimensional numerical model combining fluid flow with a Lagrangian approach for particle trajectory calculations could describe very well the in-situ observations on particle deposition in flow cells. Feed spacer geometry, positioning and cross-flow velocity sensitively influenced the particle transport and deposition patterns. The deposition patterns were not influenced by permeate production. This combined experimental-modeling approach could be used for feed spacer geometry optimization studies for reduced (bio)fouling.