1. General principle of membrane filtration

Membrane filtration is a physical separation process in the liquid phase. It is based on the principle of permeation through a permselective membrane. Depending on its intrinsic characteristics and the way it is used, this permselective membrane acts as a barrier, enabling (or promoting) certain material transfers and limiting others (figure 1 ). The driving forces for permeation through the membrane may be diffusion of one of the two phases (active transport), or pressure, concentration or electrical potential differentials (passive transport).