The purpose of the work was to study the basic constructional, energetic and technological features of electrochemical reactors (activators) used in processing of whey – a dairy by-product, but also a biologically very valuable liquid. The choice of optimal regimes for processing of various types of whey is specified, aimed at raising the efficiency of isolation of whey protein fractions in the protein-mineral concentrates while reducing energy intensity. It is also demonstrated that it is necessary to reasonably select such constructional features of electro activators as the distance between the electrodes and between the electrodes and the membrane as well as their geometric shape so as to avoid appearance of “dead” areas and to assure a high efficiency of the process. It was also important to find the most appropriate option of electric parameters and processing regimes (periodic or continuous). Besides, the account was taken of the ratio of the whey volume to the main electrode area; of the membrane type; of the initial content of dry matter in each whey type, i.e., its protein compositions; the concentration and composition of the anodic (secondary) liquid. The results of the investigation are of importance in the development of a wasteless technology of by-products processing.