Study on electro-osmotic dewatering of sludge assisted by activated carbon/graphite

Using activated carbon, graphite, and their mixtures in different proportions as additives, the mechanism of influence of different proportions of additives on sludge electro-osmotic dewatering performance and filtrate quality (total organic carbon (TOC) content, heavy metal concentration, organic composition, etc.) was studied. The results indicated that both graphite and activated carbon can increase the dewatering performance and conductivity of sludge. Compared with graphite, activated carbon showed the most obvious impact on lowering the moisture content of sludge cake. The optimal dewatering performance was achieved when the dose of carbon materials was set at 5% of dry sludge mass (DS), and the real moisture content of sludge cake was decreased from 46.0%(mass) to 42.2%(mass), while the apparent moisture content was decreased to 41.0%(mass). The addition of activated carbon or graphite can significantly reduce the TOC and heavy metal concentration of cathodic electrodialysis, the effect of activated carbon is the best, and the effect of graphite is the weakest. The TOC content of the cathodic filtrate decreased from 3740.4 mg/L to 2160.0 mg/L when the dose of activated carbon was increased from 0%DS to 20%DS, whereas the concentrations of heavy metals like Cu, Mn, Cr, Ni, Cd, Zn, Hg, and Pb decreased by 57%—100%. The research findings will provide fundamental data support for enhancing sludge electro-dewatering through carbon-containing materials and establish a theoretical foundation for the promotion and application of sludge electro-osmotic dewatering technology. © 2023 Chemical Industry Press. All rights reserved.