Calculation of the dilution rate in regulating effluent discharge
to water bodies

Summary

Effluent dilution is one of the methods of reducing the concentration of pollutants in water courses and water bodies. Dilution is quantitatively characterized by the dilution ratio of the discharged effluents. The current technique of developing the standards of permissible effluent discharges allows the use of different methods of calculating the dilution rate for water bodies; however their number is substantially less that the number of the methods developed for water courses. The hydraulic mode of water bodies differs significantly from the hydraulic mode of water courses and has a number of specific features that should be taken into account in the process of calculating the dilution rate. In water reservoirs and lakes both discharge and wind currents can occur that emerge under the wind impact that sets the upper water layers in motion that is transferred to the lower layers. This motion creates water setdown from one place to another causing water surface decline and inflow from the depth or from the adjacent water body zones; and also forming the compensating (gradient) current oppositely directed to the surface one. The methods of calculating the dilution ratio of the effluents discharged into water bodies and lakes are presented. The results of calculations for several options of the reference conditions are quoted. The limitations of using different methods are described. The necessary adjustments and recommendations for calculations of the general effluent dilution with account of the initial one are given. The conclusions are made related to the necessity of further developing and improving the methods of calculating the dilution ratio that take into account the specific conditions and size of water bodies.

Key words

wastewater , reservoir , discharge regulation , dilution ratio , water body , outfall