2- Separation Mechanism
UF membranes have a skin layer on the membrane structure surface. This layer contains the pores that effect the rated separation or rejection of substances larger than the membrane pores. This creates a 'concentration polarization' at, or near, the membrane surface. With MF membranes, however, the concentration polarization phenomenon does not occur as the smaller substances (smaller than the MF retained particles or bacteria) permeate the membrane.