Water usage of sugar beet factories is characterized by a high level of consumption and a large volume of generated wastewater with a high concentration of mineral and organic pollution. Artificial biological purification facilities are mainly used for purification of sugar production effluents. While a scheme with two-stage aeration tanks is the most widespread in our country,anaerobic-aerobic regimens are frequently used abroad. It is more cost-effective, since the oxidation of large amounts of organic substances exclusively under aerobic conditions is associated with high energy consumption. The use of anaerobic digestion at the first stage allows reducing the concentration of organic substances in effluents by 60-90%, while the post-purification of remaining contaminants is carried out in stage-two aeration tanks with lower energy consumption. To assess the appropriateness of using a digester in the system of purification facilities of a particular enterprise, it is necessary to have information on the effectiveness of digestion and the optimal purification regime of the wastewater of that particular enterprise. This work studies the process of anaerobic digestion of wastewater at one of the beet sugar factories in Ukraine. The experiments were carried out in a bioreactor with an upward flow of activated sludge. The method of mathematical planning of an experiment was used in order to shorten the duration of the research. As a result, data was obtained regarding the influence of determining factors (flow rate, pH, temperature) on biogas yield and substrate fermentation depth. Received data proves the effectiveness and prospects of using anaerobic digestion in the first stage of biological fermentation of wastewater at a sugar beet production.