GRAVITY DEWATERING OF DREDGED, CONTAMINATED SEDIMENT TO FACILITATE LANDFILL DISPOSAL

摘要

A bench-scale study was performed to investigate the amount of dewatering and strength gain that would occur in a volume of sediment within 72 hours after being mechanically dredged. Three sediment samples were allowed to sit over a 24-hour period during which supernatant was removed and quantified, following which the sediment from two of the drums (1 and 3) was transferred to two other drums. Drum 2 served as the control in which sediment remained in an undrained condition during the 72 hours after dredging (i.e., only decanting was performed). Drums 1 and 3 both had underdrain systems and the sediment in Drum 3 was mixed twice during the study. At successive intervals during the study, samples were collected for water content, paint-filter, and shear strength testing. Supernatant volumes also were measured at these intervals. For all three scenarios, approximately one-half of the water entrained during dredging was released within the first four hours due to gravity dewatering. The use of an underdrain system, with or without mixing, resulted in the sediment returning close to its average in situ shear strength of approximately 46 pounds per square foot (psf) or 2.2 kiloPascals (kPa), and its average solids content of approximately 69 percent, after 72 hours.