Advanced sludge treatment processes (AST) reduce the amount of sludge produced and improve the dewaterability, thus probably also affecting the heat transfer properties and the drying characteristics of the sludge. This paper studies the influence of the Fenton peroxidation on the thermal conductivity of the sludge.

Results demonstrate that the Fenton's peroxidation positively influences the sludge cake consistency and hence enhances the mechanical dewaterability and the drying characteristics of the dewatered sludge. For the two sludges used in this study, i.e. obtained from the wastewater treatment plants (WWTP) of Tienen and Sint-Niklaas ? the dry solids content of the mechanically dewatered sludge increased from 22.5% to 40.3% and from 18.7% to 35.2%, respectively. The effective thermal conductivity ke of the untreated and the peroxidized sludges is measured and used to determine the heat transfer coefficient hs. An average improvement for ke of 16.7% (Tienen) and 5.8% (Sint-Niklaas) was observed. Consequently the value of hs increased with 15.6% (Tienen) and 5.0% (Sint-Niklaas). This increased heat transfer coefficient in combination with the increased dewaterability has direct implications on the design of sludge dryers. A plate-to-plate calculation of a multiple hearth dryer illustrates that the number of plates required to dry the peroxidized sludge to 90% DS is less than half the number of plates needed to dry untreated sludge. This results in reduced dryer dimensions or a higher capacity for an existing dryer of given dimensions.

Copyright Elsevier


Auteur: Dewil, Raf; Baeyens Jan & Neyens, Elisabeth
Herkomst: Journal of Hazardous Materials, Volume 117, Issues 2-3, 31 January 2005, Pages 161-170. On line: 8 Dec. 2004
Referentie: Referentie