Biological treatment methods are used to remove organic and some inorganic substances from wastewater using the simplest organisms that use these substances for nutrition, breaking them down using cellular processes. The article deals with the aerobic, anaerobic and anoxic stages of biological wastewater treatment. Their differences are explained and the best way to use biological processes is analyzed according to the type of industry/production. At wastewater treatment plants, anaerobic treatment is often used at first to remove a significant part of organic substances from wastewater before sending them for further aerobic treatment. Aerobic treatment is effective for various types of wastewater, especially with lower biochemical oxygen demand (BOD) and chemical oxygen demand (COD). A comparative analysis of wastewater composition from food, oil and gas processing, pharmaceutical and pulp and paper industries was carried out. In the presence of organic compounds, the technology is chosen depending on the total organic matter content or the total COD content, which characterizes the total organic matter in water. A combination of anaerobic and aerobic methods is possible, if a discharge into the sewer system or into water bodies is required. The grounds for the application of biological wastewater treatment of these industries are given.