A proposed separation mechanism of the PTM membranes includes filtrate permeation through the residual cake covering a part of the membrane and filtrate permeation through the membrane free of the residual cake, resulting from the self-cleaning action, with partially blockage of pores effect [2, 3]. The inspection of the photographs of the membrane surface allowed to correlate the fraction of membrane free of residual cake with the shear rate on the separation surface. Hence, an idea of the of the parallel microfiltration resistances seems to be applicable.