Application of remedy studies to the development of a soil washing pilot plant that uses mineral processing technology: a practical experience

Soil washing employing mineral processing technology to treat radionuclide-contaminated soils has been examined as a remedy alternative to the exclusive excavation, transportation, and disposal of the soil. Successful application depends on a thorough remedy study, employing a systematic tiered approach that is efficient, self-limiting, and cost effective. The study includes: (1) site and soil characterization to determine the basic mineral and physical properties of both the soil and contaminants and to identify their relative associations; (2) treatment studies to evaluate the performance of process units for contaminant separation; (3) conceptual process design to develop a treatment pilot plant; and (4) engineering design to construct, test, and optimize the actual full-scale plant. A pilot plant using soil washing technology for the treatment of radium-contaminated soil was developed, tested, and demonstrated. The plant used particle-size separation to produced a remediated product that represented approximately 50% of the contaminated soil. Subsequently, it was modified for more effective performance and application to soil with alternate characteristics; it awaits further testing. The economic analysis of soil washing using the pilot plant as a model indicates that a remedy plan based on mineral processing technology is very competitive with the traditional alternative employing excavation, transportation, and disposal exclusively, even when disposal costs are modest or when recovery of remediated soil during treatment is low. This paper reviews the tiered approach as it applies to mineral processing technology to treat radionuclide-contaminated soils and a pilot plant developed to test the soil washing process. (C) 1999 Elsevier Science B.V. All rights reserved.