Effect of hydraulic and geometrical properties on stepped cascade aeration system

Stepped cascade aeration system is commonly used to aerate the water and wastewater to increase the dissolved oxygen during pre and post treatment process. in the present research,experiments were conducted to evaluate the performance of a rectangular cascade aeration system with varying flow rates,risers and tread by maintaining constant width of the channel using water collected from reverse osmosis plant. the experiments were carried out with four different risers such as 0.15 m,0.18 m,0.225 m and 0.30 m. each rise was investigated with five different tread of 0.60 m,0.55 m,0.50 m,0.45 m and 0.40 m. comprehensive experimental investigations were carried out for different hydraulic loading rates of 0.005 to 0.035 m3/s/m2. results obtained from the experiments reveals that increasing dimensionless discharges promotes more aeration,attains a maximum up to dimensionless discharge= 2.22 and beyond this there was a significant decrease in aeration. in addition,the increased in number of steps significantly enhances air entertainment and surface fall rate in the stepped cascade aeration system. a regression equation was derived by keeping aeration efficiency as response with dimensionless discharge and oxygen saturation concentration as influencing parameters. the dimension less discharge is a function of critical depth of the rectangular channel and step height,whereas oxygen saturation concentration represents the ratio of oxygen deficit and oxygen saturation concentration. based on the experimental results,the optimum design and/or results such as number of steps (12 numbers) and hydraulic loading rate (0.025 m3/s/m2) with fixed tread width of 0.6 m were identified to achieve maximum aeration rate (0.5-0.60) in aeration system. © school of engineering,taylor’s university.