Recycle and Disposal of Contaminated Dredged Sediments Using the Pilot-Scale Hybrid Process in Dredger

Abstract

A pilot-scale plant was installed on a dredger to remove contaminants in dredged sediment and to discharge the treated water for recovering the water storage capacity. The hybrid treatment system comprised a screen, a two-stage hydrocyclone for liquid–solid separation, and a membrane filtration or chemical coagulation step to remove the remaining contaminants. To recycle the treated water after removing greater than 90% of particles 18 μm or larger, the inflow velocities of the hydrocyclone in the first and second stages were fixed at 6.5 and 10 m/s, respectively. In addition, a ratio of the depth of the vortex finder to the cylinder section of 1.5 was shown the highest separation rates. Most water quality items met the standards for lakes after sequential treatment by membrane filtration or chemical coagulation, and the treated water was discharged outside of the ship. However, considering the cost of operation, the sequential treatment should be accompanied by membrane filtration instead of chemical coagulation.