Design and experimental evaluation of a Venturi and Venturi-Vortex microbubble aeration system

Abstract

This work presents an experimental evaluation of a Venturi and Venturi-Vortex microbubble aeration system, taking as input variables the water-air flow ratio, water renewal time and area-volume ratio of the water tank. The aeration process response variables are defined in terms of oxygen transfer and aeration efficiency through the standard volumetric mass transfer coefficient (KLa20), standard oxygen transfer rate (SOTR), and standard aeration efficiency (SAE). Two methods of air injection were analyzed: 1. Air injection in the throat chamber of the Venturi generator; 2. air supplying in the suction side of the hydraulic pump of the aeration system. Experimental results indicate that the water renewal time variable (RT) is a statistically significant factor with respect to the KLa20, which can be maximized by decreasing RT. The effects of the variable flow ratio (FR) are greater than the effects of renewal time and area-volume ratio (AVR) concerning SOTR and SAE, indicating a maximum response with a minimum flow ratio, using the Venturi-Vortex microbubble generator. When the flow ratio decreases, the air flow increases, generating and transferring a greater amount of microbubbles (MB) into the water. It was found that increasing the air flow produced an increase in the standard oxygen transfer rate SOTR and standard aeration efficiency SAE. Results allow concluding that the injection of the air flow from the suction side of the pump promotes the generation of microbubbles (MB) for a maximum air flow allowed by the system. SOTR and SAE could be maximized whit the flow ratio factor and the Venturi-Vortex generator, supplying air flow from the suction side of the hydraulic pump.