a difference in pressure is generated between the two sides of a filter medium so that the liquid charged with biopolymers , for instance xanthan , that is fed through the inlet goes through the filter medium , wherein the biopolymers are retained by the filter medium . as opposed to crossflow filtration , the main direction of movement of the liquid is determined by the difference in transmembrane pressure . a cathode is arranged under the filter membrane . a membrane serving as anode is arranged on the opposite side of the process chamber . an electrical field is built up between the electrodes . due to the fact that the biopolymer components carry a negative surface charge , a force moving in the direction of the anode , and , hence , against the main direction of movement of the liquid , impinges upon said components in the electrical field , whereby the concentration of biopolymers is reduced in the surroundings of the filter medium and filtration speed is increased . a surprising , additional effect is that the electrical field leads to reinforced coagulation tendency of the biopolymers which further favors filtration by the formation of agglomerates .