Effect of Step Geometry and Water Quality on Efficiency of Cascade Aeration

Abstract

In this paper, the effect of step geometry with five different tread values from 0.40 m to 0.60 m with an increment of 0.05 m and three different types of water namely potable, non-potable and recycled water on aeration efficiency of stepped cascade aeration was studied. Detailed experimental investigations were carried out for different hydraulic loading rates of 0.005 m2/s to 0.035 m2/s. All the experiments were conducted for nappe flow condition. Results revealed that overall aeration efficiency at standard conditions (E20) approaches maximum for t/h = 4, number of steps = 12, hydraulic loading rate = 0.02 to 0.025 m2/s for potable and non-potable water. In the case of recycled water maximum efficiency was achieved for t/h = 3.67. Results also revealed that stepped cascade aeration was found to be a very suitable option for enhancing DO content in treatment of waste water before discharging it to water bodies to save aquatic life.