Experiment on drainage reinforcement of landfill sludge by iron salt conditioning combined with vacuum preloading method

Abstract:

The storage capacity of sludge landfills in some places in China is seriously inadequate. To restore the storage capacity and reinforce the pit body, the experiment of vacuum preloading drainage reinforcement of landfill sludge conditioned by FeCl₃ was carried out. The accumulative drainage volume and accumulative settlement of the sludge were recorded, and moisture content test, vane shear test, and mercury intrusion porosimetry were carried out after the experiment. Results show that the effect of deep dewatering of the sludge by vacuum preloading method was limited. After chemical conditioning, the dewatering performance was improved, the drainage rate and drainage volume were increased, and the average moisture content was reduced from 75.8% to 66.6%. After vacuum preloading, the distributions of moisture content and shear strength were uneven, and the closer it was to the drainage board, the greater the change was. The moisture content increased gradually along the radial and depth directions, while the shear strength gradually decreased. The pore diameter of the conditioned sludge was mainly distributed in the range of 200-100 000 nm. The proportion of small holes was the highest, followed by that of the middle holes, and the closer it was to the drainage board, the more the large holes were, the fewer the micropores were. The moisture content and volume of the sludge decreased by 9.2% and 28.8% respectively, and the strength increased by ten times, indicating that the proposed method had better treatment effect. The dewatering and volume reduction effect can be further improved by optimizing agent combination and vacuum preloading process parameters.