Influence of module configuration and hydrodynamics in water clarification by immersed membrane systems

Different immersed membrane systems were compared according to the module configuration. Filtering concentrated aqueous suspensions under constant permeate flux, the hydraulic performances of the systems were evaluated and compared through parameters such as critical permeate flux notion and trans-membrane pressure variation rates. Operational variables were membrane size and module fibre density, aeration inside or outside the fibre network, suspension concentration and physico-chemical conditioning. When using hollow fibres including a possible air injection inside the fibre network, results pointed out the positive role of the aeration on the fouling control. But too high a fibre density did not allow an optimal control when the aqueous suspension was very concentrated. On the other hand, when working with capillary membranes showing sufficient space between fibres, the major parameters were the transversal suspension flow circulation through the fibre network and the FeCl₃ conditioning of the suspension. Experimental results show a possible working at a 0.07 m³.m².h¹ permeate flow rate under low TMP evolutions, 0.02 Pa/s, even if the filtration was operated under high concentrated suspension, 5 kgSS/m³.