Behavior of Dioxins in Treatment Processes for Landfill Leachates

Abstract
Dioxin removal efficiencies were examined in different kinds of leachate treatment systems at four landfill sites, and the relationship between dioxins and other parameters such as BOD, COD, DOC, SS were discussed.
Dioxin concentrations ranged from 190pg/L (2.1 pg-TEQ/L) to 8,500pg/L (130 pg-TEQ/L) in raw leachates, while ranging from 5pg/L (0.0067pg-TEQ/L) to 120pg/L (1.1 pg-TEQ/L) in final effluents. Removal rates after the total treatment process were 97~99%. High removal efficiency of coagulating sedimentation process showed that dioxins contained in or adsorbed to suspended solids were removed through the coagulating sedimentation process.
We estimated the amount of dioxins removed by the leachate treatment processes and accumulated in the sludge generated from the process. As the estimated amounts were almost similar, it can be concluded that dioxins removed from raw leachates concentrated mainly into the sludge formed in the treatment process.
Dioxin concentrations showed a similar behavior tendency for SS in the treatment processes, while a positive correlation between SS and dioxins were observed in each facility. These results indicate that the parameter SS might be used as a substituting indicator for checking dioxin concentration.
Further studies are necessary in order to clarify the detailed mass balance of dioxins in leachate treatment facility.

Key words: polichlorinated dioxins, waste landfill site, leachate teatment, suspended solids, coagulating sedimentation