Drying Kinetics of Sludge from a Wastewater Treatment Plant

Abstract

Drying kinetics of sludge from a municipal sewage treatment plant were determined in a laboratory drying tunnel with parallel airflow at different temperatures and air velocities. The constant drying rate period was identified followed by two falling rate periods. Drying kinetics in these falling rate periods were then satisfactorily modeled using the modified quasi-stationary method and the Fick's second law. The two-period model was used, however, to describe drying kinetics over the entire drying process, and the equation for a generalized drying curve was proposed. The effective diffusivity was also determined from the integrated Fick's equation, and correlated with temperature by an Arrhenius type equation.

Keywords:

• Biological sludge
• Drying kinetics
• Effective diffusivity
• Fick law
• Generalized drying curve
• Quasi-stationary method

Acknowledgments

The authors wish to acknowledge the project FONDECYT # 1010700 for financial support of the research and the “El Trebal” plant for sludge supply.