Reaeration in open-channel flow

Bennett, J. P., author
Rathbun, R. E., author
U.S. Department of the Interior, Geological Survey, publisher
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Reaeration, the physical absorption of oxygen from the atmosphere, is the primary process by which a stream replaces oxygen consumed in the biodegradation of organic wastes. The reaeration process in a stream is characterized by its surface reaeration coefficient. Hence, knowledge of the reaeration coefficient permits determination of the quantity of waste that can be discharged into a stream without seriously depleting the dissolved oxygen content of the stream. The three basic methods for measuring the reaeration coefficient are the dissolved oxygen balance, disturbed equilibrium, and tracer procedures. The dissolved oxygen balance method consists of measuring the various sources and sinks of dissolved oxygen and determining by difference the reaeration needed to balance the equation. The disturbed equilibrium method consists of artificially producing dissolved oxygen deficits by the addition of sodium sulfite and subsequent measurement of upstream and downstream concentrations of dissolved oxygen at two different concentration levels. The tracer method consists of using an inert radioactive gas as a tracer for oxygen and correlating the rate of desorption of the tracer gas with the rate of absorption of oxygen. Various theoretical models of the oxygen absorption process exist, however, these models are in general not suited for prediction of the reaeration coefficient in streams because the model parameters have not been adequately related to bulk-flow hydraulic variables. Semi-empirical and empirical equations developed from experimental data adequately predict reaeration coefficients for streams of the type on which the equations were based but large errors may occur when the equations are applied to other types of streams or to conditions outside the range of variables considered in the original correlation.
April, 1971.
Includes bibliographical references (pages 257-274).
Open-file report (Geological Survey (U.S.)).
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