The interaction of phases is at the basis of many technologies in different industries. Flotation method is used in wastewater treatment plants to capture and remove contaminants from wastewater. In this case, the interaction of air bubbles with particles of pollution with a hydrophobic surface. These interactions are very difficult to investigate because they are dynamic, subject to a large number of physical and chemical factors, and occur on a small scale. The processes mentioned above have traditionally been studied by laboratory experiments. These tests are tedious and time-consuming and show unsatisfactory accuracy. Analytical studies give idealized results. One of the most powerful alternatives for solving this problem is numerical modeling, which combines dynamics, accuracy and consideration of sophisticated details. This model is based on the discrete elements method. In this paper, a computer model for modeling the kinetics of the interaction of phases in wastewater treatment is considered.

Introduction. In this paper, we consider the operation principle, features, advantages, and disadvantages of compact domestic wastewater treatment plants designed by domestic manufacturers. The compact plants used until 2000 were designed to reduce such two indicators in the waste liquid as BOD and suspended solids. Since 2000, modern compact plants capable of reducing four indicators (BOD, suspended solids, nitrogen, and phosphorus) have been developed and installed in Russia. Methods. Biological methods of removing organic substances and nitrogen from the waste liquid are used at modern compact plants. Phosphorus is removed by using both biological and physical-and-chemical methods. The main issue in the operation of compact domestic wastewater treatment plants is the extremely nonuniform flow of wastewater; the coefficient of hourly nonuniformity can be 3.5 or higher. Another serious issue is the reduction in the waste liquid temperature in the cold period to critical values that hinder the biochemical oxidation of organic substances in aeration tanks. In permafrost areas (Yakutia), the influence of this factor can be observed even in the warm period. Results. Based on theoretical research and many years of experience in commissioning, we identified the consequences of design flaws and violations during operation for the stability and performance efficiency of compact plants of various modifications. Conclusion. The performed study made it possible to develop and recommend the optimal option for wastewater treatment, which allowed us to ensure that the indicators were brought to the maximum permissible concentrations of pollutants (suspended solids — 2–3 mg/l, BODult — 3–5 mg/l, ammonium nitrogen — 0.4 mg/l, nitrate nitrogen — 9 mg/l, phosphorus — 0.2 mg/l), established for discharge into fishing reservoirs.