Research of characteristics sewage sludge as the foundation for thermal processing and evaluation of its energy efficiency

Abstract

This paper presents research on the preparation of sewage sludge for thermal treatment. Sampling of sewage sludge was carried out in Doboj (Bosnia and Herzegovina). The sewerage system in Doboj has no sewage sludge treatment plant and no wastewater treatment plant. Wastewater and sewage sludge is extracted from booster stations they directly discharged into the river Bosna. One of the potential solutions for sewage sludge disposal and environmental protection is the preparation of sludge for thermal processing such as pyrolysis, gasification or burning. Technical and elemental analysis of the sewage sludge from Doboj indicates increased mass of coal (C=26.76%) and oxygen (O=67.48%) reduced to the burning mass, which justifies the possibility of applying this sludge for thermal purposes. Sampled sewage sludge mass of 3000 g was dried in a laboratory drier at a temperature of 105ºC and the drying time of 420 min. After the drying process, the mass of an absolutely dry sludge was 2130 g or 71%. The characteristics of the sewage sludge (technical and elemental analysis) and the mass obtained by an absolutely dry sludge indicate the possibility of using energy and matter by thermal processing. During the process of sludge drying in the exhaust gas from the dryer there are no registered values of the volume concentrations CO, CO2 and NOx.