Electrochemical oxidation of activated sludge by using direct and indirect anodic oxidation

摘要

The electrochemical oxidation of activated sludge (EOAS) was studied by direct anodic oxidation on the surfaces of stainless steel and graphite electrodes as well as by indirect anodic oxidation on Pb/PbO2 surface. The effects of several operating parameters such as current density, charge passed, initial pH, mixing speed, and configuration, and position of electrodes on the removal rate of chemical oxygen demand (COD), total and fecal coliform were investigated. The experimental data indicated that COD removal rates were, respectively, 66.9 and 77.5% in direct and indirect methods. The results also showed that the Pb/PbO2 electrode through indirect electrooxidation mediated based on the electrogeneration of physisorbed hydroxyl radical and other oxidants like active chlorine has higher mineralization rates and consumes the least energy. Over 99% of total and fecal coliform was removed, which is mainly attributed to electrogeneration of hypochlorite and chloride ions in the aqueous solution. Kinetic trend of COD and total and fecal coliform removal for Pb/PbO2 electrode were obtained. In order to better function of EOAS, selection of suitable mixing speed and configuration and position of electrodes are essential.