Aeration at overflow dams with curved surfaces by different flashboard spillways

Abstract

Aeration using overflow dams is an eco-friendly and economical method of improving dissolved oxygen levels in polluted urban streams. Laboratory investigations of aeration performance in smooth spillways, as well as in parallel flashboard and interlaced flashboard spillways with different flashboard intervals, for overflow dams with curved surfaces have been conducted separately. Aeration efficiencies of the different types of spillways, in particular the effects of varying discharge rate, total spillway height, and flashboard interval, have been discussed in detail. The test data illustrate that aeration efficiency in all spillways increases with spillway height and decreases with increasing discharge. Flashboard spillways appear to provide significantly higher aeration efficiency than smooth ones, and aeration efficiency increases with the number of flashboards, but with a continuously declining growth rate. By combining Fd_s with , a new dimensionless parameter Ψ is created to characterize the comprehensive effects of hydraulic conditions on aeration. Empirical formulas for oxygen-transfer efficiency in smooth, parallel flashboard, and interlaced flashboard spillways have been developed with Ψ and the dimensionless number of flashboards per unit area of spillway N* as independent variables, and the properties of these formulas are discussed.

Keywords:

• water cleaning technologies
• aeration
• flashboard spillways
• overflow dam with curved surface
• oxygen-transfer efficiency
• spillway Froude number

Additional information

Notes on contributors

Kejian Chu

Kejian CHU. PhD, College of Environment, Hohai University. He has published about 30 academic papers, 3 monographs, and attended 6 international conferences in recent years. Research interests include water cleaning technologies, contaminant transport modelling and simulation, and environmental impact assessment.

Zulin Hua

Zulin HUA. PhD, College of Environment, Hohai University. He has published more than 60 academic papers, 3 monographs, and attended 10 international conferences in recent years. Research interests include water environment treatment and water environment simulation.

Lijun Ji

Lijun JI. Master, College of Environment, Hohai University. Her research interests include water cleaning technologies and cm environmental processes modelling.