Analysis of oxygen transfer performance on sub-surface aeration systems

The efficiency of oxygen transfer depends on many factors including the type, size and shape of diffusers and the tank geometry. In this paper, the effect of the depth of water in the tank and, the extension of coverage area of diffusers on each of oxygen transfer capacity (OC), efficiency (E) and, on a percentage of oxygen absorption (delta) is tested. Experimental procedure is adopted to evaluate the effect of these parameters. The results of the study showed that, both the depth of water and the extent of coverage area of diffuser had a significant effect on the tested parameters. The values of oxygen transfer capacity (OC) and efficiency (E) ranged from 18 to 170 grO2/m3. hr and from 2 to 17 grO2/m3air, respectively; depending on the depth of water in tank and the ratio of diffusers coverage area. The percentage of oxygen absorption ranged from 0.45-5.4% depending on the testing conditions. Specific mathematical models to describe the effect of each parameter were also derived. The exponential form of equation proved to be efficient in describing the effect of a depth water on oxygen transfer capacity (OC) whereas; the linear form of equation was good enough in representing the effect of the other parameters.