Characterizing the Spatial Variation in Particle Aggregation due to Heterogeneous Turbulence in a Flocculation Reactor

Abstract

A study was performed to investigate the impact of turbulent heterogeneity on aggregation and breakup in a flocculation reactor. The influence of the average characteristic velocity gradient (G), particle concentration, and coagulation mechanism on the flocculation performance was also investigated. Experiments were performed in a bench-scale reactor with a low-shear axial-flow impeller using a photometric dispersion analyzer (PDA) to examine the state of aggregation. Results indicated that floc growth increased while the floc size and variance in the floc size distribution decreased as G increased. In addition, floc growth, size, and floc size variance increased when the particle concentration of the water was increased and when moving from a charge neutralization mechanism to a sweep floc mechanism. Lastly, floc growth, size, and variance were found to vary spatially at low G values in the reactor with floc size and growth larger in the bulk region and the variance larger in the impeller discharge region.