No abstract

The methods of separation of microalgae has a significant impact in the economic aspects of their cultivation. in this study, pine bark was used as a substrate for immobilization of microalgal biomass cultivated in raw municipal sewage. the experiment was conducted in cylindrical photobioreactors (PBRs) with circulation of wastewater. Biomass was cultivated for 42 days. After that time, abundant growth of the biofilm with microalgae on the surface of pine bark as well as improvement of the quality of treated sewage were observed. The efficiency of removal of nutrients from wastewater was 64-81% for total nitrogen and 97-99% for total phosphorus. Moreover, the concentration of suspended solids in sewage was reduced, which resulted in a decrease in turbidity by more than 90%. Colorimetric analysis and Volatile Matter (VM) content in the substrate showed a decrease in the Higher Heating Value (HHV) and concentration of VM due to the proliferation of biofilm.

Water encountering biomass can affect the change in its chemical composition and properties through the leaching process. In the leaching process, leachates are formed, and their composition depends on the type of biomass and the time of exposure to the solvent (water). The aim of the study was to analyze the influence of time of contact of water with biomass on changing the chemical composition of the leachates formed during long-term (counted in days) leaching of pine bark (Pinus sylvestris). Long-term leaching contributes to a loss of organic and inorganic compounds, and in this study, an intensive extraction of biomass components was noted from the first day of leaching. Along with the extension of the leaching time, values for electrical conductivity, concentration of mineral fraction (ashes), concentration of volatile matter, and concentration of total organic carbon significantly increased in the leachates. However, no linear relationship between the extension of the leaching time and the increase in the concentration of chlorides, sulfates, nitrogen, phosphorus, and other elements in the leachates was observed. This study will allow to better understand the impact of vegetation communities on the aquatic and terrestrial ecosystems, as well as help to provide adequate conditions of storage of biomass for technological purposes.

The latest research focused on the analysis of algal growth and the dynamics of their growth use the laser diffraction technique, enabling determination of the volume fraction of suspended particles with specific diameters in aqueous solution as well as their fractal dimensions. This study focuses on the possibility of using a laser granulometer to assess the growth dynamics of algae growing in treated wastewater in a hydroponic system, supported by artificial lighting with the use of light-emitting diodes (LEDs). On the basis of the measurements, the fractal dimension (Df) of algae was determined. An attempt was made to apply the modified Avrami equation describing the crystallization process for the analysis of algae growth dynamics in wastewater. Presented results show that the fractal dimension of suspended matter, largely created by algae, in the case of additional lighting of the hydroponic system at night, takes lower values (Df ~ 1.0) than in sewage without additional light source (Df ~ 2.0). In each measurement series, the fractal dimension of particles in the tank with lighting in the end of the experiment was about 33–43% lower than in the tank without LEDs. The analysis of changes in particle diameters calculated on the basis of Avrami equation largely corresponds with the stages of algae growth. During the measurement series with lower air temperatures, the growth of algae in the tank with additional light was faster than in the tank without LEDs. The obtained information can be the basis for determining the effective method of removing algae from wastewater treated in the hydroponic system, before they are discharged to the receiver in order to prevent the outflow of increased concentrations of total suspended solids.