Fractal Growth Characteristics of Flocs in Flocculation Process in Water Treatment

The fractal growth characteristics of flocs in flocculation process in water treatment was discussed based on diffusion-limited aggregation (DLA) mechanism. Modern structure characterization technology was employed to evaluate the impact of coagulant dosage and slow stirring speed, etc. on the evolution of floc configuration and structure. Combining macroscopic flocculation effect with microscopic floc morphology, accurate quantitative description and interpretation of the flocculation process can be achieved to predict flocculation effect. Moreover, a new fractal dimension called fractal dimension of floc growth was proposed. Feasibility study on its competency of demonstrating the flocculation effect showed that the fractal dimension of floc growth could be used to characterize the variation of floc size and strength in flocculation process and that there was a good correlation between fractal dimension and residual turbidity at different turbidity of raw water. Thereby, the index, capable of reflecting the changes of flocculation effect can be used to optimize flocculation conditions, enhance flocculation efficiency, improve the quality of outflow and cut down the cost of water treatment.