The present work focuses on problems connected with the location and sampling method for pecton (biofilm) in sewage treatment plants. We also discuss the amount and quantity of pecton necessary to compose a representative sample. Comparisons of other selected contamination indicators in place of pecton sampling, are also presented. Research carried out at the WWTP "Hajdow" demonstrated that everything (starting from grid chambers), coming into contact with sewage surfaces is covered with biofilm This biological formation does not cause any significant changes in sewage quality due to its relatively small surface compared to the sewage flux. As presented in the following analysis, pecton can be used for bioindication of sewage quality. This is possible because the organisms forming these communities use substances contained in flowing sewage as nutritional substrates. In such cases the wastewater purification level in biological sewage treatment plants can, in a way similar to rivers, be determined based on bioindication methods using existing similarities between the prevailing processes and organisms.

Easy-to-handle and effective methods of juice clarification and concentration by membrane technologies are still under exploration. The current article presents results of research on the technological development of an alternative natural sweetener of high biological value and improved organoleptic properties. Sorghum saccharatum stem juice is used in research. It is pre-clarified enzymatically with α-amylase and glucoamylase, clarified by ultrafiltration, and concentrated by the direct contact membrane distillation in various temperature ranges. The study shows the efficacy of membrane methods for improving juice purity, total soluble solids ( TSS), and total sugar (TS) content in the syrup obtained. Clarification depends on membrane characteristics at the beginning of the process, as there are no differences at the end of it. Juice concentration at high-temperature differences allows to accelerate the process by approx. 60% comparing to low-temperature differences. A lower temperature difference ( ΔТ = 20–30°С) in the concentration process results in a longer process and syrup acidisation, whereas a higher temperature difference ( ΔТ = 70°С) affects physicochemical properties of syrup due to local overheating and formation of Maillard reaction products. The juice concentration at ΔТ = 50–60°С allows to obtain high values of total soluble solids without significant degradation of physicochemical and organoleptic properties.