The main objective of presented research work was the assessment of the impact of reduced straw content, as organic carbon source, on the course of sewage sludge composting process. During the research work performed in industrial conditions, the composting process going in periodically overturned windrows differing in proportion of dehydrated sludge, straw and structural material being 4:1:1 and 8:1:2 respectively, was observed. The consequence of increase of sludge concentration with relation to straw was decrease of C:N ratio in the input material from 11.5 to 8.5. The following parameters were analyzed as indicators for the assessment of the composting process: contents of fulvic acids (FA), humic acids (HA), lignin, cellulose and hemicellulose as well as absorbance in UV/VIS (λ=280, 465 and 665 nm) range. The results obtained have indicated that the increase of sludge content extends the elevated temperature (T>50°C) period from 42 days to approximately 65 days. Our tests did not confirm that limitation of straw content added to sewage sludge had any adverse effect on the course of composting. PI index (HA/FA), which qualifies the compost as mature in the first case – No 1, exceeds limit value of 3.6 on the 83rd day whereas, in the second case No 2, on the 48th day.

The paper presents the results of studies on the influence of the 2010 Vistula flood on the humification process in the bottom sediments of the Goczałkowice Reservoir in southern Poland. Due to its location in the vicinity of farmlands, forests and urbanized areas, the Goczałkowice Reservoir is characterized by amplified and intense humification processes within its sediments. The studies were focused on the determining the influence of the flood wave containing organic and inorganic suspensions on these processes. Humic acids were analyzed using two spectroscopic methods: Electron Paramagnetic Resonance (EPR) and Fourier Transform Infrared Spectroscopy (FT-IR). Application of these methods allowed to determine the values of free radicals and of the g-factor, which are indicators of oxidation, aromatization and maturation of humic acids during the humification process, as well as the value of the 1650/1720 ratio, reflecting the dissociation of the COOH group to COO− and the formation of complexes of transitional metals with humic acids during the humification process.