Abstract. In compliance with the requirements of the EU climate and energy package (3 x 20 %), the biomass consumption in energetic industry is systematically growing. As a consequence, a large amount of ashes is produced which requires the management in line with law and ecology. Stringent requirements concerning the chemical composition of ashes prevent the biomass ash from being used in building construction. Specific physicochemical properties of ashes allow for their application in sewage sludge treatment. This paper presents the results of conditioning using ashes from willow combustion in sewage sludge dewatering. The findings could provide a new approach on sewage sludge and biomass ashes utilization.

Możliwość kondycjonowania i odwadniania osadów ściekowych z zastosowaniem popiołów ze spalania biomasyThe wastewater treatment produces a huge amount of excess sludge which has to be removed in line with ecological and legal requirements. Raw sewage sludge is characterized by the high moisture content, over 90 % and the microbiological activity. The high content of water in sewage sludge results in its big volume and generates significant problems with transport and further utilization. As the high moisture content in raw sewage sludge generates significant costs in treatment plants, it is essential to provide effective dewatering. In order to improve the sewage sludge dewatering, conditioning by means of different materials is applied. Chemical conditioning with the application of organic polymers is used in treatment plants more often than any other methods. The drawback of the aforementioned process is the high cost of chemical reagents and for this reason, it is necessary to find inexpensive and effective conditioners. The aim of this paper is the possibility of sewage sludge dewatering after conditioning with the use of biomass ash derived from the biomassfired power plant. The effectiveness of the aforementioned process was based on the capillary suction time (CST) measurement. After conditioning with the use of biomass ash, the article goes on to describe dewater-ability of sewage sludge by vacuum filtration. The results showed that the sewage sludge moisture content decreased as a dosage of biomass ash increased. Mechanical conditioning with the use of biomass ash influenced the increase of filtrate volume after dewatering. Additionally, the application of biomass ash in sewage sludge management confers the earthen structure of sludge which is suitable to the transport and application in the environment. The mixture of ash and sewage sludge might be used as a valuable fertilizer in perennial plants plantations. Owing to agricultural utilization of sewage sludge, fertilizing properties of sludge are used without a minimal risk to human health.

Abstract. This paper presents the results of analyses of the monitoring selected energetic willow plantations (30 ha) located in Podkarpackie Province (Poland), which have been fertilised using a prototype trailer for land-applying municipal sludge. The fertilisation of the willow plantation is undertaken using this prototype for the subsurface application of municipal sewage sludge into soil. The presented prototype is a component of technology of energetic plant production that has been developed at the Rzeszow University of Technology. The results of soil investigations allow to us conclude that the deposition of sewage sludge using the presented prototype of the agricultural trailer is conducted in accordance with legal regulations and does not cause significant perturbation of the natural trophic chain.

A very good knowledge of material properties is required in the analysis of severe plastic deformation problems in which the classical material processing methods are accelerated by the application of the additional cyclic load. A general fuzzy logic-based approach is proposed for the analysis of experimental and numerical data in this paper. As an application of the fuzzy analysis, the calibration of Chaboche–Lemaitre model hardening parameters of PA6 aluminum is considered here. The experimental data obtained in a symmetrical strain-controlled cyclic tension–compression test were used to estimate the material’s hardening parameters. The numerically generated curves were compared to the experimental ones. For better fitting of numerical and experimental results, the optimization approach using the least-square method was applied. Unfortunately, commonly accepted calibration methods can provide various sets of hardening parameters. In order to choose the most reliable set, the fuzzy analysis was used. Primarily selected values of hardening parameters were assumed to be fuzzy input parameters. The error of the hysteresis loop approximation for each set was used to compute its membership function. The discrete value of this error was obtained in the defuzzification step. The correct selections of hardening parameters were verified in ratcheting and mean stress relaxation tests. The application of the fuzzy analysis has improved the convergence between experimental and numerical stress–strain curves. The fuzzy logic allows analyzing the variation of elastic–plastic material response when some imprecisions or uncertainties of input parameters are taken into consideration.

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Due to inappropriate agricultural treatments, soils often turn into wastelands. After years, the return to cultivation is very difficult or even impossible. It is a serious problem for agriculture, also in Poland. In order to improve soil quality and to restore its value in use, different fertilizers are commonly used. As an alternative for artificial fertilizers, sewage sludge and biomass ashes might be applied. High cost of sewage sludge conditioning with the use of polyelectrolytes has resulted in the development of research dedicated to finding new and inexpensive conditioners. The article discusses the possibility of sludge conditioning by means of wood biomass ash. In the paper, the findings of sewage sludge dewatering with the use of wood ash on a laboratory and on a technical scale are presented. The analysis of results has shown that the addition of wood biomass ash improved sludge dewatering by 10-23% in a laboratory scale and by 15-27% on a technical scale. The application of wood ash also reduced the total bacteria number by 83-89% in a laboratory scale and by 40-53% on a technical scale. Additionally, the obtained mixture of sewage sludge and wood biomass ash might be applied in agricultural practices, especially in fertilizing perennial plants plantations. Thanks to that it is possible to obtain inexpensive and valuable natural fertilizer while reducing costs of sludge dewatering. Keywords Sewage sludge • Wood biomass ashes • Dewatering • Conditioning • Higienization • Fertilizer Additionally, the final product of sludge dewatering, namely the mixture of sewage sludge and wood ash, can be used as a natural fertilizer improving the plant growth. The sewage sludge conditioning by means of wood biomass ashes and the possibility of the application of mixture is a new solution in sewage sludge management.

This paper presents the determination of material hardening parameters with the use of the fuzzy set theory. The hardening parameters were initially predicted from measurements taken in the cyclic tensioncompression test. The experimental hysteresis loop was compared to numerical one obtained by the integration of the plastic flow rule. The nonlinear combined hardening model-Voce isotropic hardening and Frederick-Armstrong kinematic hardening-was considered here. After the initial selection, the hardening parameters were adjusted in the optimization problem using the least-squares method. An approximation error of the hysteresis loop was minimized. Finally, nonlinear isotropic and kinematic hardening parameters were assumed to be fuzzy variables. Hardening parameters obtained in the optimization problem were randomly scattered up to 20%, and the membership functions associated with them were computed. The approximation error of the hysteresis loop was found for each selection of the hardening parameters providing the output membership function associated with this error. The α-level optimization method was used as the main numerical tool, while the extension principle was tested only as the reference solution. In the defuzzification process, the most reliable hardening parameters were found.