FOULING PHENOMENA IN MICROPOROUS MEMBRANES - FLUX DECLINE KINETICS AND STRUCTURAL MODIFICATIONS

The fouling mechanisms in microfiltration are analyzed with two symmet ric and one asymmetric membranes. Fouling kinetics when microfiltering bovine serum albumin solutions (BSA) are studied for both the consecu tive processes of surface blocking and cake formation. Influence of sh ear stresses and aggregates is analyzed. Permeate flux is recovered by cleaning with different agents and temperatures, thus with different removal and cake coagulation performances. Finally, modifications of t he structure of the porous matrix due to the appearance of a cake on t he retentate layer of the membrane are studied by air permeation porom etry. The flux decay and recovery characteristics as well as the struc tural modifications obtained agree with the two consecutive steps in t he fouling mechanism leading to a solute accumulation on the pore entr ances whose consequences are analyzed here. This model predicts asymme tries in the recovered water flux after cleaning which are effectively found.