Abstract: Study of the permeability of aged sludge is important for the drainage reduction of sludge in landfills. Eight kinds of sludge under different aging conditions were taken as samples in the present work. Compression drainage tests were carried out, and the content and type of soluble organic matter in the supernatant were determined. The aggregate size distribution and Zeta potential were also measured. The interactions between the physicochemical properties of aged sludge were analyzed by conducting a Pearson correlation. The results show that the permeability of aged sludge increases with the decrease of soluble organic matter content in the supernatant, the increase of the relative degree of humification and the absolute value of filtrate Zeta potential. Simultaneously, when the aggregate tends to be stable and the particle size increases, the organic matter wrapped in the aggregate is not easy to release into the supernatant, and the permeability of aged sludge increases. In addition, due to the aging environment variations, the change in total organic content of aged sludge lacks of consistency with the change in organic matter content in the supernatant. Judging permeability based on the organic matter content of aged sludge would cause errors. Finally, the influence models of specific resistance of aged sludge were established, which were the reference for improving the permeability of aged sludge in the pre-treatment process.

Key words: aged sludge, aging condition, physicochemical property, dewatering, permeability