In-Situ Turbulent Flocculation and Reactor Mixing Characterization for a Square Tank Reactor using Image Analysis and Particle Image Velocimetry Methodologies

Abstract

Coagulation and flocculation are common processes in conventional water treatment and the resulting floc size distributions, mean size, and fractal dimension are impacted by operational parameters, including mixing and coagulant dosing method. In this investigation, a novel, non-intrusive methodology combining image analysis and particle image velocimetry was employed to characterize flocculation and reactor mixing from the same data. Image processing techniques were used to characterize flocculation following conventional FeCl3 chemical coagulation and iron electrocoagulation while particle image velocimetry was used to characterize reactor mixing using flocs as tracking particles. Local velocity gradients were compared with the global velocity gradient, G. Results suggest electrocoagulation produced larger and more compact flocs than flocs formed by conventional coagulation. Use of flocs as tracking particles was more reliable prior to steady-state conditions, when flocs were smaller and more numerous. Compared to local velocity gradients, G underestimated actual mixing near the mixing impeller by 40%.