Membrane bioreactor: Distribution of critical flux throughout an immersed HF bundle

If the notion of sustainable critical flux can be analysed in regards to hydrodynamics conditions imposed closed to a defined membrane surface taking into account the suspension characteristics, it is important to integrate the actual heterogeneity of filtration conditions relatively to the individual position of fibres when operating with a hollow fibre immersed system. Taking into account successive works we developed a membrane bioreactor and surface water clarification. The heterogeneous distribution of filtration conditions in hollow fibre systems is discussed to optimise an immersed system configuration.

The radial axis of filtration throughout a HF bundle induces a radial distribution of the suspension characteristics and filtration conditions. According to the bundle diameter and the membrane packing density, dead zones and irreversible sludging may appear in the bundle centre, these phenomena modify drastically the system control facility. Experiments on the lab-scale pilot point out some conditions of sludging control and non sludging control. If hydrodynamics generated by aeration must be in accordance with the filtration intensity, the obligation to minimise energetic costs makes it necessary to minimise the membrane air supply. Then the bundle characteristics appear determining notably its diameter and its membrane packing density (supposing the membrane material and the pore size distribution may be optimised). Of course, the sludge concentration and membrane air distribution remain also important parameters in the choice of the bundle characteristics.