Keywords: wastewater treatment plants, water bodies, the assimilating capacity of a watercourse, the method of normalization sewage discharges, permissible concentrations of pollutants

// Мелиорация.— 2019. – №3(89) – P 76—84

A comparative analysis of the applied methods for calculating the permissible concentrations of pollutants in sewage discharged from urban wastewater treatment plants into natural water bodies is given. It showed that the values of permissible concentrations assigned taking into account the best available technologies and differentiated by the equivalent population significantly exceed the values according to the calculation formulas and an average of 10–20 times higher than MPC. Formulas for determining the length of a section of a watercourse in which the permissible concentrations of pollutants in treated  wastewater are reduced to MPC values are developed. At this length, one should not allow another discharge of wastewater from treatment plants in order to avoid environmental damage to the water body. It is shown that in order to increase the accuracy of determining the coefficient taking into account
the hydraulic conditions for mixing wastewater with water of the watercourse, Shesi’s coefficient and the function of the speed coefficient should be entered into the calculation formula, and not the average value of their product should be taken. If the treated wastewater is discharged into natural watercourse through the water channel, it is recommended to take into account channel assimilative capacity.