The aim of the work is a description of the rheological behaviour of thickened sewage sludge. The sample of thickened sludge was collected from the wastewater treatment plant, where pressure flotation unit is used for a process of thickening. The value of dry matter of collected sample was 3.52%. Subsequently the sample was diluted and the rheological properties of individual samples were obtained. Several types of rheological tests were used for the determination of the sample. At first the hysteresis loop test was performed. The next test was focused on the time-dependency, i.e. measurement of dependence of dynamic viscosity on the time at constant shear rate. Further dependence dynamic viscosity on the temperature was performed. Then the activation energy was obtained from measured values. Finally, the hysteresis areas were counted and measured values were evaluated with use of Herschel-Bulkley mathematical model.

Honey is a solution with high viscosity and most types of honey exhibit Newtonian behavior. However, some types show non-Newtonian features (thixotropy or dilatancy), which exerts influence on processing of the honey. The aim of this study was to evaluate the rheological properties of honey from Eucalyptus spp. The investigated samples of eucalypt honey originating from Italy or Australia were analyzed by the following methods: melissopalynological analysis, color on the Pfund scale, optical activity, water content and electrolytic conductivity. Rheological tests were carried out on a highly accurate device. The dependence of apparent viscosity on temperature and time was measured, and hysteresis loop tests were run. The dependence of shear rate on shear stress was described in accordance with the Herschel-Bulkley mathematical model. The rheological tests revealed the following: all samples exhibited non-Newtonian behavior and all were determined as thixotropic fluids. These results are discussed in relation to previous findings on the dilatant behavior of eucalypt honey. Knowledge of rheological properties of foodstuff is important for handling, processing and storing. The description of flow properties can indirectly offer information about the structure of the tested liquid. Most honeys behave as Newtonian fluids. However, there are exceptions such as heather or manuka honey. Eucalypt honey is also among these exceptions. Studies dealing with rheological properties of eucalypt honey are more than 60-years old. This study focused on rheological behavior of this type of honey and revised current knowledge.

Heather honey is a valuable and rheologically special type of honey. Its above-average selling price may motivate its intentional violation with a mixture of honey from another botanical origin, the price of which is lower on the market. This work deals with the rheological properties of such devalued heather honey in order to determine the changes in the individual rheological parameters depending on the degree of dilution of the heather honey. For this purpose, a differently diluted heather honey sample series was created and the following rheological parameters were determined: hysteresis area, n-value, yield stress (τ₀), parameter B (Weltman model), parameter ϕ, or parameter C (model describing the logarithmic dependence of the complex viscosity on the angular frequency). Part of the work was research into whether the set parameters can be used as comparative parameters. It was found that the hysteresis area does not appear to be a suitable relative comparison parameter due to the high variability. The parameters that appear to be suitable are the relative parameters n-value and the parameter ϕ, which showed the greatest stability. The change in the determined rheological parameters is, depending on the degree of dilution, non-linear with a step change between the samples containing 40% (w/w) and 60% (w/w) of a heather honey.

Biogas plants are a specific facility from the QRA (Quantitative Risk Assessment) methodologies' point of view, especially in the case of the determination of the event frequency of accident scenarios for biogas leakage from a gas holder and subsequent initiation. QRA methodologies determine event frequencies for different types of accident events related to vessels made of steel. Gas holders installed at biogas plants are predominantly made of other materials and are often integrated with the fermenter. It is therefore a specific type of gas holder, differing from that which is commonly used in the chemical industry. In addition, long-term experience is not available for the operation of biogas plants, unlike in the chemical industry. The event frequencies listed in the QRA methodologies are not relevant for the risk assessment of biogas plants. This work is focused on setting the prerequisites for QRA of biogas storage, including for example: information on hazardous chemical substances occurring at biogas plants, their classification, and information on the construction of integrated gas holders. For the purpose of the work, a scenario was applied where the greatest damage (to life or property) is expected. This scenario is the leakage of the total volume of hazardous gas substance from the gas holder and subsequent initiation. Based on this information, a "tree" was processed for "Fault Tree Analysis" (FTA), and frequencies were estimated for each event. Thereafter, an "Event Tree Analysis" was carried out. This work follows up on a discussion by experts on the determination of scenario frequencies for biogas plants that was conducted in the past.