Abstract:The drying of sludge presently became an important procedure for sewage disposal. The thin layer drying behavior of sewage sludge was investigated in an indirect drying process and the mathematical modeling was performed by using thin layer drying models. The logarithmic model was found to show better predictions. At the same time, moisture transfer from sewage sludge was described by applying the Fick’s diffusion model. The effective diffusivity coefficient of moisture transfer varied from 8.486′10-10m2/s to 4.386′10-9m2/s over the temperature 80℃ to 150℃. In addition, the temperature dependence of the effective diffusivity coefficient was expressed by Arrhenius type relationship. The activation energy for the moisture diffusion of sludge drying was found to be 29.56 kJ/mol.