WITHDRAWN: Experimental Evaluation of Waste Activated Sludge Treatment Performance in a Rotational Hydrodynamic Cavitation Generator.

In the present study, the effect of cavitation on waste-activated sludge (WAS) treatment in a rotational hydrodynamic cavitation generator (RHCG) was analyzed experimentally. The RHCG employs a variation of the dimple cross-sectional area of the flow at the surface of the rotor to generate cavitation. However, the rotor, which is in liquid, also generates shear stress. To determine the effect of cavitation on the WAS treatment, the performance of the RHCG in the presence and absence of dimples was analyzed. Moreover, because the RHCG produces significant thermal energy (unlike other methods of generating cavitation), determining the effect of thermal energy on WAS treatment requires a study of the RHCG performance based on temperature control. Finally, to determine the effects of inlet pressure and rotational speed, both of which affect the cavitation intensity of an RHCG, WAS treatment performance was evaluated in 12 experimental cases using a full factorial design of inlet pressure and rotational speed. As the assessment factors of WAS treatment performance, particle decomposition and solubilization performances were analyzed using particle-size distribution and soluble chemical oxygen demand. For both of these evaluation factors, differences in performance according to the presence of dimples and temperature control were evident. The WAS treatment performance increased as the rotational speed increased and was minimized at the highest inlet pressure.