ELECTRO-DEWATERING OF WASTEWATER SLUDGE: FACTORS AFFECTING KINETICS AND ENERGY CONSUMPTION

Jean-Baptiste Conrardy (1) , Jérémy Olivier (1) , Jean Vaxelaire (1)

1 LATEP - Laboratoire de Génie Thermique Énergétique et Procédés (EA1932)

The treatment of wastewater produces huge quantities of residue (sludge) which contains a large amount of water. A dewatering step is usually carried out prior to further treatment in order to diminish sludge volume and consequently reduce handling and disposal cost. It is commonly conducted thanks to mechanical processes (plate or belt filter presses, centrifuges) which offer a relatively poor efficiency. The water content at the end of the dewatering usually ranges between 65% and 85%. A way to improve the dewatering efficiency is the implementation of an electric field during the mechanical dewatering (electro-dewatering). It has been shown that applying an electric current through the filter cake could reduce significantly the water content of sludge, down to 40%. A lab-scale device of electro-dewatering has been used to study the phenomena involved in this hybrid process. The experimental setup consists in a cylindrical chamber where a piston presses the sludge cake on a filter cloth. Two electrodes, one anode and one cathode, are placed at the piston head and under the filter cloth, respectively. Dewatering kinetics and electrical behavior of the sludge cake can be studied with this setup. The results of experiments carried out with a constant voltage (or a constant current) show significant correlations between the filtrate flow-rate, the electric current, the electrical resistance of the filter-cake and the water content of sludge. The electric current and the water content of the sludge are found to be key factors that govern electro-dewatering kinetics. Moreover, the electrical resistance through a given cake of sludge is highly correlated to its water content (which decreases during the process). The relationship seems to be valid for a wide range of water content. These results enable a better understanding of how dewatering efficiency and energy consumption are related in the electro-dewatering process.

Mots clés: Dewatering; Electroosmosis; Energy Consumption; Activated Sludge; Sewage Sludge

Domaines: Génie des procédés

Jean-Baptiste Conrardy, Jérémy Olivier, Jean Vaxelaire. ELECTRO-DEWATERING OF WASTEWATER SLUDGE: FACTORS AFFECTING KINETICS AND ENERGY CONSUMPTION. FILTECH 2013, Oct 2013, Wiesbaden, Germany. ⟨hal-01294404⟩