Analysis of fluid-dynamical and physico-chemical aspects of capillary membrane backwashing

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The application of membrane filtration with Inside-Out Dead-End driven UF-/ MF- capillary membranes increases in water treatment exponentially. Thereby the required backwash process, which still is a widely unexplored field, has a high potential to enhance the efficiency of the filtration process. In order to optimize the backwash process, which should also minimize irreversible membrane fouling, an improved fundamental comprehension of the mechanisms, which are relevant for the detachment and transport-out of particles and fouling layers from Inside-Out Dead-End driven capillary membranes, is necessary. For a systematic elucidation of these mechanisms as well filtration (target-oriented build-up of fouling layers) and backwash experiments will be performed under defined operation conditions with especially designed laboratory plants. The obtained results (which parts from the fouling layer will detach under what conditions and from which zone of the capillary membrane) will be used as process parameters for a CFD supported numerical simulation of multiphase flow in capillary membranes. The multiphase flow modelling bases on the Euler-Euler method considering the most important forces acting on moving non-Brownian particles. Additionally, hydrodynamic wall effects, particle interactions (collisions and agglomeration) as well was porosity of particle collectives will be regarded. A free open source OpenFOAM and the commercial software CFX 12 will be applied in order to compare both frameworks from the numerical point of view and contribute to the validation of the results. The attained knowledge of backwash mechanisms will be applied to develop optimized backwash conditions with regard to different geometries of the capillary. The optimized backwash modes will be verified using an automated commercial membrane system for long-term experiments.