Feasibility of treating contaminated dredged sediments using ultrasound with acoustic and flow fields

The US requires long-term alternatives to dispose more than 230 million cubic meters of dredged material per year. The dredged sediments in a slurry form need to be de-watered, remediated and disposed. The contaminants (heavy metals and organics) in the dredged sediments are usually attached to the clay and silt fractions. A comprehensive treatment technology coupling ultrasound with acoustic and flow fields was proposed to remove contaminants and water from dredged residues. A complete treatment technology with three different processes was proposed for commercial implementation. In the first process coarse sediments are decontaminated using ultrasound, and fines and the bulk dredged suspension are removed using a sub-atmospheric pressure. The second process treats the fines and bulk solution from the first process using ultrasound and fine sediments are separated from bulk fluid containing contaminants with water using acoustic and flow fields. The treated sediments can be ocean dumped as clean material or used in construction. The extracted organic and inorganic contaminants can be treated using advanced oxidation or concentrated using membrane technology and disposed in hazardous waste landfills. This technology can be easily added to a dredging vessel to minimize material handling. A conceptual arrangement of onboard treatment of sediments inside a dredging vessel is presented. The result of this research indicated that the proposed technology would provide viable alternatives for remediation of contaminated dredge sediments. Copyright ASCE 2008.