Concentration and/or space-dependent diffusive and convective mass transport, through flat sheet, anisotropic membrane layer or membrane bioreactor through dense or porous membrane, were investigated. A quasi-analytical solution is presented in order to estimate the concentration distribution in the membrane layer and the inlet and outlet mass transfer rates. These properties have been given in closed, explicit, mathematical forms which make the calculation process very simple. The effect of the varying convective permeation velocity and that of the varying diffusion coefficient as well as the effect of the (varying) reaction rate was investigated including these parameters in the Peclet (Pe) number and in the Ha number. The diffusion coefficient can vary with the concentration and/or space coordinate, while the convective velocity can vary with the space-coordinate. Similarly, the biochemical or chemical reaction rate can also change with the space-coordinate. It was shown that the change of the Pe number can have strong effect on the mass transport process; thus its effect must not be neglected. The model developed can be applied by any mathematical function of the variation of the mass transport parameters.