ABSTRACT
Solid particles in a liquid suspension constitute one of the most complicated two-phase systems encountered in nature. The shape and structure of particles suspended in sewage play an important role in the processes of separating solid particles that occur in sewage treatment plants, such as coagulation, sedimentation and sludge dehydration. Most of the suspensions found in sewage are characterized by irregular and chaotic structures (Figure 1), which excludes the application of classical Euclidian geometry in their description. The theory developed by Mandelbrot in the 1980s enables the characterization of irregular structures by using fractal geometry. The most important numerical parameter in the fractal concept is the fractal dimension, which assumes values from 1 to 3. Once the fractal dimension is known, we can estimate, among others, the “packing degree” of irregular particles in a suspension. A low value of fractal dimension shows
the presence of a large number of open spaces that can absorb many contaminants. In addition, a sludge that is characterized by a large packing degree has better dehydration properties (Smoczyñski & Wardzyñska 2003).
