Abstract:
To study flexible aeration diffuser due to obtaining the optimal diffuser. The physical properties of the various rubber tubes (tube wall thickness, tensile strength, hardness and elongation) were analyzed. The oxygen transfer performances were compared in the term of volumetric mass transfer coefficient (kLa) and energy efficiency occur in 10 liters of aeration tank. The effect of different contaminants (kaolin, NaCl and MLSS) on aeration mechanism was investigated in terms of bubble hydrodynamic and mass transfer parameters. Moreover, the tube fouling was studied and then the suitable cleaning method was proposed. In this study, the effect of tube layout located in tank with 2500 L was also considered by determining the kLa coefficients and residence time distribution (RTD). In addition, the theoretical prediction model was proposed and applied as a primary data in aeration system design and operation. The result has shown that, from oxygen transfer and energy consumption, the tube No. 6.3 should be chosen as the suitable aeration diffuser. The aeration in NaCl solution affected on small bubble size which increased interfacial area (a). While the MLSS condition affected on the oxygen transfer which decreased liquid-side mass transfer coefficient (kL) significantly. The aeration should not be stopped longer than 3 days for avoiding the tube clogging. Air purging should be chosen as the suitable cleaning method with 3 bars of pressure in 30 min. From the study of tube layout, it can be found that the closed oxygen transfer efficiency (15.08%) and the residence time distribution were obtained. Note that the arrangement was applied with 7.5 m. of tube length per 1.33 m2 of the bottom area of the tank. In addition, the suitable model was proposed for predicting the kLa with errors less than 20%.