Main factors that can negatively affect the operation of wastewater treatment plant for dairy production were identified. The main negative factors are: low automation of the process, high concentrations of chemical reagents that have a detrimental effect on the biological treatment stage, temporary fluctuations in pH values, insufficient amount of dissolved oxygen at the biological treatment stage. One of the main operation problems of local dairy wastewater treatment plant is a fluctuation of pH value over a wide range, especially at treatment plants of small enterprises. Biological treatment methods were considered as one of the most suitable technologies for the removal of organic substances from dairy wastewater. It was concluded that there are quite stringent conditions for each treatment stage. The pH range is almost neutral and fluctuate within 6-8.5. The average temperature of wastewater should be 20-30ºC for optimal biochemical reactions. The concentration of dissolved oxygen plays an overriding concern for biological treatment stage, since good operation of processes of nitrification, denitrification and biological phosphorus removal are based on this indicator and will not proceed in case of deviations from the normal. © 2022 Institute of Physics Publishing. All rights reserved.