Evaluation of the effectiveness of the stabilization of sewage sludge, thermal and / or chemistry, aiming at the agricultural recycling

Abstract

The final disposal of sewage sludge is a major environmental problem, mainly in urban centers. There are several alternatives for final disposal of sewage sludge, but in all these the sludge needs to be treated fairly, which includes relevant investments. This study is devoted to assess the efficiency of liming as a method of chemical stabilization, drying method and thermal and physical association of both the search for greater efficiency and lower cost. The goals of quality of the final sewage sludge were based on the requirement for agricultural recycling of the sludge for presenting more restrictive parameters in relation to the sanitary and environmental safety. Tests on plant (scale) accompanied by quality control laboratories of the Department of Quality Control of Companhia Estadual de Águas e Esgotos (CEDAE). The results inform the excellent health and environmental quality of sewage sludge produced in sewage treatment plants (ETE’s) of CEDAE, which have low concentration of heavy metals and low density of thermotolerant coliforms. These results together with preliminary assessment of the agronomic potential of the sludge, indicate that the sewage sludge studied have high value for the agricultural recycling. The study of thermal stabilization by drying pointed to the need for the drying temperature in less than 100 ° C for 2 hours. Furthermore, we observed that the use of temperatures below 100 º C can be implemented with the combined use of quicklime.