Use of biogas produced in upflow anaerobic sludge blanket reactors for the thermal drying of sludge from sewage treatment plants

ABSTRACT

The management of sewage sludge is one of the main responsible for the high operating costs of sewage treatment plants in Brazil. This is mainly due to the need for dewatering and sanitizing steps for this material, being the last one carried out when the agricultural use of the sludge is chosen as a form of destination. To try to reduce costs and improve sludge management at a sewage treatment plant, an option that has been widely discussed is the use of biogas, produced in upflow anaerobic sludge blanket reactors, for the thermal drying of sludge. In this context, the present work reports a study on the thermal drying of different types of sludge, in a pilot system, involving the energy utilization of biogas produced in upflow anaerobic sludge blanket reactors, of a medium-sized sewage treatment plant. The dryer reduced the mass of the different types of sludge subjected to the thermal drying process by approximately 80%, increasing the concentration of total solids in these materials from 20 to 80%. The energy demand values of the dryer to remove 1 kg of water present in the different types of sludge ranged from 1,195 to 1,323 kcal. Additionally, the microbiological characteristics of the different types of sludge, after the drying process, showed the possibility of agricultural use of these materials. These results point to the thermal drying of sludge, using biogas produced in anaerobic treatment systems, as a promising tool for sustainability in the Brazilian sewage sector.

Keywords:
agricultural use of sludge; anaerobic reactors; use of biogas; sewage treatment plant; thermal drying of the sludge