FRACTAL AGGREGATES EVOLUTION DURING FLOCCULATION

ABSTRACT

A temporal analysis of fractal aggregates during water flocculation is presented. Water was prepared using kaolin solution and a non-intrusive image-based analysis method was used for two-dimensional fractal dimension assessment (d_F). The d_F values were determined for aggregates larger than 270 µm from 100 images taken in each combination of velocity gradients (G_f) and flocculation times (T_f). The G_f values of 20, 30, 40, 50 and 60 s^-1 and T_f values of 2 to 180 minutes were studied, with a ΔT_f of 1 minute for 2 ≤ T_f ≤ 10 minutes and a ΔT_f of 5 minutes for 10 ≤ T_f ≤ 180 minutes. Results showed that d_F tends toward stability from a T_f of 40 minutes, with distinct levels in each G_f. Further, d_F values decrease from 1.80 to 1.35 for G_f from 20 to 60 s^-1.

Key words:
Flocculation; Fractal aggregates; Temporal evolution