Simulation of fouling and backwash dynamics in dead-end microfiltration: Effect of pore size

Abstract

We carried out numerical simulations of pressure-driven dead-end microfiltration with a backwash operation using a two-way coupling model with consideration of the particle–fluid interactions. This study numerically modeled a membrane with regularly spaced straight pores, which are assumed to be track-etched pores. On the basis of the results obtained by microfiltration under fixed particle concentration (5%), the present paper examines the effect of pore size on particle fouling by comparing snapshots of particle motion, the permeate flux, and the total resistance of the membrane over a period of time. The results of simulations confirm two modes for particle fouling when particle diameter d = 100 nm. The larger pore size membrane ( d m = 3.6 d) shows a fouling mode in which initially particles filled the pores and then form a cake layer on the surface of membrane. The smaller pore size membrane ( d m = 2.5 d) shows a fouling mode in which particles are accumulated on the surface of the membrane without filling the pores and a cake layer forms across the entire filtration. These general behaviors are in agreement with the hypothesis deduced from experiments. In addition, we carried out simulations of a sequence of filtration including a backwash operation and compared the fouling conditions for filtration before and after its inclusion. The particles remaining on the membrane after the backwash operation decrease the effective pore area and cause a change in fouling conditions from pore blockage to cake formation.