In the modern world with the rapid pace of development of human civilization, the question of negative technogenic impact on the environment in General and on the hydrosphere in particular is increasingly being raised. With the growth of population size and density, the consumption of natural resources increases, and as a result, the load on existing engineering communications increases, and regulatory requirements, including environmental requirements for newly created engineering infrastructure objects, increase. It should be noted that there is a direct relationship between the population and the volume of water consumption, which is constantly growing, which in turn leads to an increase in the amount of wastewater. Taking into account changes in environmental legislation and increasing requirements for the quality of wastewater treatment discharged to water bodies, the issue of finding new calculation methods and creating operational models of sewage treatment plants is urgent.

Keywords: waste water, biological treatment, secondary settling tank, activated sludge, calculation method