Processing contaminated soils and sediments by high power ultrasound

Following the successful application of high power ultrasound to some areas of mineral processing, attention was directed towards the remediation of contaminated soils and sediments. Laboratory experiments have produced high contaminant destruction rates with surprisingly low energy costs and work at pilot plant scale is under way. The process relies on the phenomenon of cavitation to destroy contaminants such as PCBs, polycyclic aromatic hydrocarbons and organochlorides which adsorb to the surface of soil particles because of their inherent hydrophobicity. Such chemicals persist in the environment because of their chemical stability and they bioaccumulate, posing a serious health threat to animals and humans. High power ultrasound allows low-cost, on-site remediation and circumvents many of the shortcomings posed by conventional remediation technologies. Results are presented for a range of contaminants and the underlying physics of the technology is explained.