Cleanup of PCB contaminated soils and sludges by a solvent extraction process: A case study

The feasibility of cleaning PCB contaminated solids via a solvent extraction route was studied using the cleanup of the dried sludge from the Winston-Thomas tertiary lagoon as a test problem. When compared with direct incineration of the sludge, the solvent extraction route has at least 3 shortcomings. First, the solvent extraction route is unable to achieve the same cleanup quality as the direct incineration. Second, the hazardous nature of the material handled requires that the extraction process be carefully designed to be virtually leak-proof and this will be difficult and expensive. Third, it is inevitable that trace levels of solvent will be left behind in the processed sludge and this may be undesirable. On the positive side, when very large amounts of solids contaminated at low (yet unacceptable) levels are to be cleaned, the solvent extraction route may be economically more attractive than direct incineration. On the basis of desorption characteristics determined from bench-scale experiments, the economics of cleanup of Winston-Thomas tertiary lagoon sludge via solvent extraction route and direct incineration are compared. The fractionation unit is the single most important unit in the solvent extraction process. A clever design of this unit will have a significant impact on the economics of the cleanup via solvent extraction route.