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 fl ocs in activated sludge, in the aspect of control of single processes, i.e. sedimentation, dehydration, coagulation or fl occulation. 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 fl ow reactors are more effi cient at capturing suspension particles of a size up to 30 μm and are characterized by an increased removal of particles of a size ranging from 30 μm to 550 μm to the outfl ow. 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 signifi cantly more complex in the spatial aspect.Brought to you by | MIT Libraries Authenticated Download Date | 5/11/18 5:22 PM
Due fast biomass production, high affinity for N and P and possibilities to CO 2 sequestration microalgae are currently in the spotlight, especially in renewable energy technologies sector. The majority of studies focus their attention on microalgae cultivation with respect to biomass production. Fuel produced from algal biomass can contribute to reducing consumption of conventional fossil fuels and be a remedy for a rising energy crisis and global warming induced by air pollution. Some authors opt for possibilities of using sewage as a nutrient medium in algae cultivation. Other scientists go one step further and present concepts to introduce microalgal systems as an integral part of wastewater treatment plants. High costs of different microalgal harvesting methods caused introduction of the idea of algae immobilization in a form of periphyton on artificial substrates. In the present study the attention has focused on possibilities of using waste materials as substrates to proliferation of periphyton in biologically treated sewage that contained certain amounts of nitrogen and phosphorus.
The presented study concerns the efficiency of removing nutrients, organic compounds and metal cations from municipal sewage by a cylindrical photobioreactor (PBR) with the biomass of microalgae growing on pine bark. The study was conducted in two cylindrical PBRs fed with municipal wastewater for 42 days. PBRs were internally illuminated with red and blue light at night. The sewage was additionally enriched in CO 2 and CaCO 3. The concentration of NH 4
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