Modelagem e estimação de parâmetros em um sistema de secagem de lodos produzidos no tratamento de esgotos.

Abstract

The resultant sludge of wastewater treatment process is rich in nutrients, like potassium, phosphorus and nitrogen, which suggest its use in the agriculture as fertilizer. However, many pathogenic organisms are presents in the sludge which forbids its direct disposal in the soil. The increase of the temperature of the sludge may eliminate its pathogenic organisms thus some methods have been used to increase the temperature of the sludge above the environment temperature as the use of biological gas generated in the anaerobic digestion. However, solar energy has not been used as source to heat the sludge. In the typical conditions of the Brazilian northeast, the sun is a powerful source of heat that can be used to rise the temperature well above the environment one. In this work the modeling, identification and parameters estimation in a sludge drying system which uses the sun as heat source, Is performed using a thermal lumped-parameter model. The estimated parameters were thermal resistance, thermal capacity and thermal time constant, R, C and T respectively. The identification of the system was performed with the aid of the algorithms of identification ARX and N4SID, It was necessary to get temperature and radiation information from the sludge drying system to the identification process. Thus a microcontroller based data acquisition system with radio-frequency transmission was developed for the automatic attainment of the necessary information.