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...

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 D₃ 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 μm and are characterized by an increased removal of particles of a size ranging from 30 μm to 550 μm 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.

Process baths used for electropolishing and pickling of stainless steel have become increasingly contaminated with heavy metal ions over time. There is still lack of research on the neutralization of this type of technological wastewater with high concentrations of metal ions and containing complexing compounds, which significantly hinders their effective treatment. The aim of this paper is to study how the selected methods of heavy metals removal will affect the quality of the treated, industrial post-galvanic sewage from pickling and electropolishing of chromium-nickel steel on a laboratory and technical scale. The research used sodium sulphide or a decomplexing agent based on organic sulphur to neutralize wastewater containing triethanolamine or glycerol. Treatment of electropolishing wastewater poses a challenge. Nevertheless, wastewater with glycerol is easier to neutralize than those containing triethanolamine. In the industrial scale the use of a decomplexing agent is necessary to achieve the required nickel values in the wastewater after treatment below 1 ppm. Even in the case of high concentrations of nickel ions in raw wastewater, the neutralization process of the wastewater originating only from pickling alone was effective. The search for effective methods of neutralization of mixed wastewater is especially important in industrial conditions, where it is not always possible to completely separate these two types of sewage. The paper also presents the results of the composition of post-neutralization sludge, which may be useful in planning further management and disposal of this type of waste.