Emission of Biogas from Sewage Sludge in Psychrophilic Conditions

The stabilization of sewage sludge in Poland is continued in many sewage treatment plants in the open digestion chambers (ODC), which is a phenomenon on the European scale. The sludge is stored in them much longer, which allows obtaining high mineralization of the material, thanks to which it can be used naturally. Although this way of sludge processing is very beneficial owing to the high quality of the final product, the ODC are a source of gas emissions, because the biogas produced in them is usually not detracted. The research was carried out at the Boguszowice sewage treatment plant in Poland, which is equipped with two ODC with a capacity of 5781 m(3) each. Within the chambers a process of stabilization of sludge is carried out based on psychrophilic digestion (i.e. temperature < 20 degrees C). The tests were carried out in two variants. In the first variant, the measurements of the flow of biogas produced were made directly on the open digestion chamber by means of a floating sampler. In the second variant, simulations of the digestion process under laboratory conditions were carried out. Analyzing the results, the high quality of the obtained biogas for both variants of the conducted research can be noticed. The average methane concentration in biogas for real tests was 68.5% and for laboratory tests 69.7%.