Study on the effect of type selection for oxygen transfer of weir aerator

IV ABSTRACT PhD Thesis STUDY ON THE EFFECT OF TYPE SELECTION FOR OXYGEN TRANSFER OF WEIR AERATOR Ahmet BAYLAR Fırat University Graduate School of Natural and Applied Sciences Department of Civil Engineering 2002, Page : 85 The amount of dissolved oxygen (DO) in the waters of rivers and streams is very important to 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. Plunging overfall jets from weirs are a particular instance of this, and the aeration properties of such structures have been studied widely in the laboratory and field over a number of years. This paper seeks weirs having different cross-sectional geometry at non-recirculating and recirculating system and how they affect the oxygen transfer efficiency. At non-recirculating system it is demonstrated that the oxygen transfer efficiency of the triangular notch weir generally is better than the other weirs. The results point that the triangular notch weir can be used to effectively increase the oxygen transfer efficiency of rivers and streams. Moreover, it is showed that the oxygen transfer efficiency of the triangular notch weir decreases with increasing weir angle. At recirculating system it is presented that the oxygen transfer efficiency of the rectangular weir, the semi circular weir, and the trapezoidal weir are in general agreement with each other and 90° triangular notch weir generally is better than the other weirs at low drop heights and low discharges. It is demonstrated that the oxygen transfer efficiency of 90° triangular notch weir generally is better than the other weirs. KEY WORDS : Oxygen Transfer, Aeration, Dissolved Oxygen, Oxygen Deficit Ratio, Oxygen Transfer Efficiency, Weir