부산대학교 도서관

The objective of this study was to evaluate the performance of a large commercial-scale soil washing plant in a full-scale demonstration for remediation of agent orange/dioxin-contaminated soils (1,200 to 20,000 pg-TEQ/g, 900 tons total) in southern Vietnam. Although there are difficulties in obtaining proper material balances for large commercial-scale plants, dioxin balance analysis was taken into consideration first, before evaluating soil washing performance such as dioxin removal efficiency and volume reduction rate. During this study, observations were made, as follows: 1) dioxin balance of the full-scale demonstration ranged from 88% to 108%, with an average of 93%, values which are sufficient for verifying that the soil washing testing procedure was properly conducted; 2) dioxin removal efficiencies ranged from 67 to 87%, with an average of 79.2%, for the hydrocyclone system alone, and were greatly improved to a range of 91 to 97%, with an average of 94.0%, by the subsequent flotation system; 3) soil washing system clearly demonstrated effective soil cleanup, satisfying the dioxin criteria in Vietnam for residential areas (300) from contaminated soil of up to 6,000 pg-TEQ/g, for recreational areas (600) from contaminated soil of 6,000 to 11,000 pg-TEQ/g, and for commercial/industrial areas (1, 200) from contaminated soils of 11,000 to 16,000 pg-TEQ/g; 4) volume reduction rates of feed soils were also sufficient, ranging from 59 to 74%, with an average of 65%; and 5) dioxin concentration rates of sludge cakes ranged from 1.3 to 3.8 times, with an average of 2.4 times, of feed soils. These results indicate that the soil washing system, combined with flotation, is characterized by both high dioxin removal efficiency and high volume-reduction rate; and that this process can be practically used in southern Vietnam for the effective remediation of dioxin contaminated soils.