Mechanism of Reaeration in Natural Streams

The basic theory of turbulent flow has been applied successfully to explain many phenomena occurring in natural and artificial waterways. In this study, turbulent-flow theory, both isotropic and nonisotropic, has been utilized to formulate the theory of reaeration in natural streams that have been subjected to deaeration by the biological oxidation of organic material. The general differential equation of the oxygen balance in a river is accepted as the basis for the analysis, and a theoretical derivation of the reaeration coefficient is presented. Experimental work concerning reaeration under turbulent conditions was conducted to verify the theoretical development. Field data from sanitary river surveys are presented to show the comparison between the theoretically computed values and the observed values of the reaeration coefficients. This comparison, as well as the experimental work, substantiates the derived formulas.