Using high-head and free-surface conduits in water aeration

The amount of dissolved oxygen (DO) in the rivers and water streams is very important for the quality and existence of aquatic life. Hydraulic structures have an impact on the amount of dissolved oxygen in a river system, even though the water is in contact with the structure for only a short time. The same quantity of oxygen transfer that normally would occur over several kilometers in a river can occur at a single hydraulic structure. The primary reason for this accelerated oxygen transfer is that air is entrained into the flow, which produces a large number of bubbles. These air bubbles greatly increase the surface area available for mass transfer. This study seeks the air entrainment of gated conduits and how they affect the oxygen transfer efficiency. Experiments have done for gate opening varying 1.6-4.8 cm, conduit length varying 2-6 m and temprature varying 15-18 °C. It was observed from the results that approximately full transfer up to the saturation value occurred at the high head and free surface gated conduits. The results indicated that and EQsQh/20 increased as Froude number increased in free surface and high head gated conduits. At Froude numbers greater than 15, almost full oxygen transfer, up to the saturation value, occurred. It was observed that gate opening and conduit length did not have an important effect on E20. Also a nonlinear analysis has done by using experimental results and has found equations. There is a close relation between equations and experimental results. KEY WORDS: Oxygen Transfer, Aeration, Dissolved Oxygen, High Head Gated Conduit, Free Surface Gated Conduit