A Study on Improvement of Dehydration Performance of Sewage Sludge by the Hydrothermal Treatment

Abstract

In order to develop a technology which can efficiently convert sewage sludge into solid fuel, the effect of the hydrothermal treatment on the dehydration performance and the carbon balance in this treatment were investigated. The raw sewage sludge cake with water content of about 80% could not be dehydrated by increasing the pressure of the mechanical press. On the other hand, after the hydrothermal treatment, the sewage sludge became easy to be dehydrated by the mechanical press. Carbon content in the residual solid after the mechanical press decreased with the rise of the reaction temperature of the hydrothermal treatment due to solubilization of part of volatile and fixed carbons in the sludge. By employing the hydrothermal treatment combined with the mechanical dehydration and solid material yielded from the dehydrated water, we can reduce the required energy for drying sewage sludge down to about two-thirds of that of conventional drying processes.