Oxygen Transfer through Air Entrainment over Stepped Weir

Oxygen transfer through the air entrainment over the stepped weir by the flow types was presented through the laboratory experiments. In the nappe flow, dominant flow features included an enclosed air pocket, a free-falling nappe impact and subsequent hydraulic jump on the downstream step. Most air was entrained through a free-falling nappe impact and a hydraulic jump. In the skimming flow, air entrainment occurs from the step edges. Downstream of the inception point, the flow is highly aerated at each and every step with very significant splashing. The average values of the oxygen transfer efficiency in the region of the nappe flow and of the skimming flow are about 0.40 and 0.28, respectively. The stepped type of the weir was found to be efficient for water treatment associated with substantial air entrainment.