With the development of technology of purification of toxic oil-containing liquid waste it was shown that the complex compound of the wastewater, its reducing nature (low negative redox-potential) can cause low efficiency of electrolytic coagulation stage and induce coagulation after membrane filtration stage. The possibility of "membrane activation" of the coagulation process was tested with the polystyrene latex model system. In addition, there was shown a lower rate of the electrolytic coagulation with the model system based on phosphate buffer, sodium chloride, an organic dye, gasoline, sodium sulfide than with a similar system adjusted to positive values of redox-potential using hydrogen peroxide. In both cases the analysis of particle size distributions was performed using the analyzer Zetatrac (Microtrac Inc., USA, measured outside dimensions 0.8–6500 nm). Thus, the necessity of control and correction of the redox-potential of the wastewater entering to the coagulation-membrane post-treatment for the effective process of electrolytic coagulation preceding the membrane filtration stage was shown.