Analysis of particle size and fractal dimensions of suspensions contained in raw sewage, treated sewage and activated sludge


M. Kusnierz, P. Wiercik, Analysis of particle size and fractal dimensions of suspensions contained in raw sewage, treated sewage and activated sludge, Archives of Environmental Protection 42 (3), (2016) 67-76. doi:10.1515/aep-2016-0031
Kusnierz M., Wiercik P.,


The analysis of particle size in suspensions carried out with use of the laser diffraction method enables us to obtain not only information about the size of particles, but also about their properties, shape and spatial structure, determined basing on fractal dimension. The fractal dimension permits the evaluation of the interior of aggregates, at the same time showing the degree of complexity of the matter. In literature, much attention is paid to the evaluation of the fractal dimension of flocs in activated sludge, in the aspect of control of single processes, i.e. sedimentation, dehydration, coagulation or flocculation. However, results of research concerning the size of particles and the structure of suspensions existing in raw and treated sewage are still lacking.

The study presents optical fractal dimensions D-3 and particle size distributions measured with use of laser granulometer in raw and treated sewage and activated sludge collected from six mechanical-biological wastewater treatment plants located in the Lower Silesian region.

The obtained test results demonstrate that wastewater treatment plants that use both sequencing batch reactors and continuous flow reactors are more efficient at capturing suspension particles of a size up to 30 mu m and are characterized by an increased removal of particles of a size ranging from 30 mu m to 550 mu m to the outflow. Additionally, in the case of samples of treated sewage and activated sludge collected at the same location, at short intervals, similar particle distributions were observed. As far as the analysis of fractal dimensions is concerned, particles contained in the raw sewage suspension were characterized by the lowest values of the fractal dimension (median equals 1.89),while the highest values occurred in particles of activated sludge (median equals 2.18). This proves that the spatial structure of suspension particles contained in raw sewage was similar to a linear structure, with a large amount of open spaces, while the structure of particles contained in the activated sludge suspension was significantly more complex in the spatial aspect.





The Faculty of Environmental Engineering and Geodesy

Institute of Environmental Engineering

Wrocław University of Environmental and Life Sciences

pl. Grunwaldzki 24,
50-363 Wrocław

Project assumptions

The overall goal of the project is to develop an innovative multifactor mathematical model enabling monitoring of bath contamination used in the electropolishing process of austenitic stainless steels. This model will allow optimization and reduction of process costs and will have an impact on reducing environmental pollution during electrolytic polishing of austenitic stainless steels.

The final outcome of the project will consist in the development of a method of monitoring the gradual contamination of the electropolishing bath.


Zespół zajmuje się badaniami z zakresu elektrochemii, oczyszczania ścieków, monitoringu i optymalizacji procesów w warunkach laboratoryjnych i przemysłowych.

Zróżnicowane doświadczenie poszczególnych członków zespołu IonsMonit jest jego siłą.



Project: “A pioneering model for monitoring pollution of electropolishing process baths (IonsMonit)” financed by the National Center for Research and Development as part of the Lider programme.