Investigation of the Dewatering Process with Geotextile Tubes by Sedimentation, One- and Two-Dimensional Filtration Test Methods

Dewatering applications are carried out with geotextile tubes for the disposal or reuse of industrial wastes with high water content. Class F Seyitomer thermal power plant fly ash, an industrial waste, was selected in this study. Turbidity, sedimentation and filtration experiments were carried out using anionic and cationic polymers and polypropylene synthetic fiber to investigate the effect of polymers and fibers on the dewatering of fly ash. The use of polymers was determined to significantly accelerate filtration and soil sedimentation speed while leading to a slight increase in the volume of the filter cake. When effective polymer and dosage are used, slurry filtration time can be reduced up to one-eighth of the time and dewatering can be achieved much faster. The addition of synthetic fiber accelerated the sedimentation of the slurry and increased the filtration in the vertical direction, while it did not show a significant effect on the total filtration in two-dimensional filtration. In geotextile tube applications, although one-dimensional filtration experiments might give misleading results in terms of estimating the effectiveness of the polymers used in solid–liquid separation and dewatering times, the jar test, sedimentation and two-dimensional filtration experiments were determined to give compatible and more realistic results. In two-dimensional filtration experiments, approximately 75% of the filtration occurred in the radial direction and the dewatering time was approximately 21–55% of the time estimated by one-dimensional filtration experiment. Geotextile tube dewatering design can be made more predictable and cost-effective in the field by performing small-scale laboratory experiments with the two-dimensional filtration test system designed for this study and various dewatering applications.