The concentration of dissolved oxygen is very important in wastewater whether before or after treatment. It is a prime indicator in determining how satisfactory a biological wastewater treatment is occurring. In this paper, the aeration performance of stepped cascade was investigated. The natural land formation of one of the mountains in Lebanon is shaped in several cascade structures with different heights. The aeration efficiency, wind speed, step height and flow rate were measured. An empirical correlation predicting the effect of the wind speed, step height and flow rate on the aeration efficiency (E 20 ) was developed. The results indicated that the step height and the flow rate had a significant effect on the aeration efficiency. For low wind speed there is no significant wind effect on the aeration efficiency, while high wind speed improves the aeration efficiency due to higher turbulence. It was noticed that the aeration efficiency is shown to depend on the biochemical oxygen demand.
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