Dewatering of Golden Horn sludge with geotextile tube and determination of optimum operating conditions: A novel approach

Abstract

Environmental concerns about Golden Horn's polluted sediments have led to 320,000 m3 of sea dredging, generated annually by bucket dredgers to be stored in landfills without dewatering. This study presents an efficient dewatering methodology and a beneficial alternative to store the sludge. In this scenario, the sludge of a suction-cutter dredger is transported to a pond. The beneficial use of geotextile tubes filled with the sludge at circumferential embankments of pond is evaluated. An anionic polyacrylamide (APAM) is used for conditioning the high plastic silt sludge with 10% solid content. APAM dosage is optimized by Rapid Dewatering Test (RDT) for geotextile material. Microscale SEM-EDS analyzes depicted the flocculated form of the sludge. Laboratory-scale Geotextile Dewatering Test (GDT) shows improvements in the turbidity of filtrate, the quantity of solid particles retained in the tube, and the filtration efficiency, determined to be 92 NTU, 18.5% and 90.5% respectively. In accordance with the ICP-OES analysis, the discharge of the filtrate to the aquatic media is admissible. Undrained shear strength of the dewatered sludge is assessed as low, by Vane and undrained unconsolidated triaxial compression tests. Further improvements of the dewatered sludge with vacuum preloading method were projected by completion of the consolidation tests.