Assessment of non-pressurized electro dewatering of waste activated sludge with graphite electrodes

Abstract

Changes of physical and chemical characteristics of sludge were investigated with respect to the pH, process time, and applied voltage by means of the electric field treatments. A model reactor with the desired speed was used to generate an electric field to separate water from the sludge without applying pressure. All electrodes mounted on the reactor were produced from graphite. Two different distances between anode and cathode (2.3 cm and 4.3 cm) were used to examine the effects on dewatering capacity of sludge. Differentiations of dependent variables inferred from the experimental processes were also surveyed by Box-Behnken experimental design. The water in the sludge was separated effectively when the samples were exposed to an electric field. The total solid increased from 1.07% to 6.60% at pH 6.5 when sludge was exposed to 25 V for 60 min. Furthermore, the optimum distance between electrodes was 2.3 cm for dewatering of sludge samples, where the capillary suction time of influent sludge was observed to decrease by approximately 85.5% at raw sludge pH. Similarly, the viscosity parameters decreased by approximately 99%. There was an increase in the soluble chemical oxygen demand, PO4-P, and NH4-N concentrations of water discharged from the model reactor.