Effect of step geometry and water quality on effciency of cascade aeration

In this paper, the eect of step geometry with ve dierent tread values from 0.40 m to 0.60 m with an increment by 0.05 m, and three dierent types of water, namely potable, non-potable, and recycled water, on aeration eciency of stepped cascade aeration was studied. Detailed experimental investigations were carried out for dierent hydraulic loading rates of 0.005 m2/s to 0.035 m2/s. All the experiments were conducted for nappe ow condition. Results revealed that the overall aeration eciency at standard conditions (E20) approaches the maximum for t=h = 4, number of steps were 12 with a hydraulic loading rate of 0.02 to 0.025 m2/s for potable and non-potable water. In the case of recycled water, maximum eciency was achieved for t=h = 3:67. Results also revealed that stepped cascade aeration was a very suitable option for enhancing DO content in treatment of waste water before discharging it to water bodies to save aquatic life.