Małgorzata Wzorek

Production of biosolid fuels from municipal sewage sludge: Technical and economic optimisation

The article presents the technical and economic analysis of the production of fuels from municipal sewage sludge. The analysis involved the production of two types of fuel compositions: sewage sludge with sawdust (PBT fuel) and sewage sludge with meat and bone meal (PBM fuel). The technology of the production line of these sewage fuels was proposed and analysed. The main objective of the study is to find the optimal production capacity. The optimisation analysis was performed for the adopted technical and economic parameters under Polish conditions. The objective function was set as a maximum of the net present value index and the optimisation procedure was carried out for the fuel production line input capacity from 0.5 to 3 t h-1, using the search step 0.5 t h-1. On the basis of technical and economic assumptions, economic efficiency indexes of the investment were determined for the case of optimal line productivity. The results of the optimisation analysis show that under appropriate conditions, such as prices of components and prices of produced fuels, the production of fuels from sewage sludge can be profitable. In the case of PBT fuel, calculated economic indexes show the best profitability for the capacity of a plant over 1.5 t h-1 output, while production of PBM fuel is beneficial for a plant with the maximum of searched capacities: 3.0 t h-1. Sensitivity analyses carried out during the investigation show that influence of both technical and economic assessments on the location of maximum of objective function (net present value) is significant.

Co-pelletization of sewage sludge and agricultural wastes

This paper concerns the process of production and properties of pellets based on biomass wastes. Co-pelletization was performed for sewage sludge from municipal wastewater treatment plant and other biomass material such as animal and olive wastes. The aim of the present study was to identify the key factors affecting on the sewage sludge and agricultural residues co-pelletization processes conditions. The impact of raw material type, pellet length, moisture content and particle size on the physical properties was investigated. The technic and technological aspects of co-pelletization were discussed in detail. The physical parameters of pellets, i.e.: drop strength, absorbability and water resistance were determined. Among others, also energy parameters: low and high heat value, content of ash and volatiles were presented. Results showed the range of raw materials moisture, which is necessary to obtain good quality biofuels and also ratio of sewage sludge in pelletizing materials. The analysis of the energetic properties has indicated that the pellet generated on the basis of the sewage sludge and another biomass materials can be applied in the processes of co-combustion with coal. Those biofuels are characterised with properties making them suitable for use in thermal processes and enabling their transport and storage.

Emission characteristics of granulated fuel produced from sewage sludge and coal slime.

Abstract The neutralization of wastewater treatment residues is an issue for many countries. The European Union (EU) legal regulations have limited the use of the residues in agriculture and implemented a ban for their disposal. Therefore, urgent action should be taken to find solutions for the safe disposal of sewage sludge. The problem refers in particular to the new EU member countries, including Poland, where one can now observe an intensive development of sewage system networks and new sewage treatment plants. At the same time, these countries have few installations for thermal sewage sludge utilization (e.g., there is only one installation of that type in Poland). Simultaneously, there are many coal-fired mechanical stoker-fired boilers in some of these countries. This paper presents suggestions for the production of granulated fuel from sewage sludge and coal slime. Additionally, among others, lime was added to the fuel to decrease the sulfur compounds emission. Results are presented of research on fuel with two average grain diameters (∼15 and 35 mm). The fuel with such diameters is adapted to the requirements of the combustion process taking place in a stokerfired boiler. The research was aimed at identifying the behavior of the burning fuel, with special attention paid to its emission properties (e.g., to the emissions of oxides of nitrogen [NOx], sulfur dioxide [SO2], and carbon mon-oxide [CO], among others). The concentration and emission values were compared with similar results obtained while burning hard coal. The combustion process was carried out in a laboratory stand where realization of the large-scale tests is possible. The laboratory stand used made simulation possible for a wide range of burning processes in mechanical stoker-fired boilers.

Przydomowa oczyszczalnia ścieków czy szambo ekologiczne

Abstract In areas with scattered buildings and a low population density, the sewage management infrastructure is underdeveloped. Until recently, the only practical solution was to make a non-effluent and tight tank: a septic tank, which was one of the means to carry sewage away from detached houses in areas without sewage systems. Currently, domestic sewage treatment plants are highly popular. The paper shows the operating principle of a septic tank and a domestic treatment plant and analyses their advantages and disadvantages. Particular attention was paid to the economical aspect.