[Analysis of the fractal structure of activated sludge flocs]

The small-angle light scattering (SALS) experiment was executed to calculate the fractal region, and the data of particle size distribution was fitted by Gamma equation. Besides, the atomic force microscope (AFM) and confocal laser scanning microscopy (CLSM) were used to observe the morphology of the microstructure of the sludge flocs under different scales. The results showed that the sluge floc was constituted by a series of clusters with different sizes. The surface of the floc was unsmooth with various "holes" and "gaps" and there were a range of pore structures within the sludge floc. For sludge flocs at large scales, a variety of pore texture coexisted, forming a transport channel for the nutrients and water in the sludge. The results also showed that the fractal structure was present in sludge flocs in the size range of 0.5-50 microm and the particle size distribution was fitted to the Gamma equation distribution model, indicating that the sludge floc formation process is a process dominated by Cluster-Cluster flocculation.