Stability of Hazardous Heavy Metals in Landfilled Fly Ash Immobilized by Chemicals

Abstract

In an attempt to check the stability of insolubility of hazardous heavy metal elution characteristics from the landfilled fly ash immobilized by chemicals, the authors of this paper have studied the stability of immobilized fly ash for a period of about two years, using large-sized landfill lysimeters of the anaerobic landfill type, filled with fly ash immobilized by chemicals as well as bottom ash and non-combustible shredded solid waste.
The results of the study have revealed that the mass of the Pb and Cd stemming from leachate is smaller by far than the total mass of Pb and Cd contained in the solid waste. Furthermore, the elution tests of the fly ash immobilized by chemicals have demonstrated that the immobilized fly ash trapped hazardous heavy metals in a stable manner. Elution of hazardous heavy metal from solid waste greatly depends on the pH value of the seepage leachate in the solid waste layer. The change of the leachate quality over time is greatly affected by rainfall. A conspicuous change in water quality was observed particularly at the time of strong rainfall and in the event of much precipitation. The pH value of the leachate remaining at the bottom of the lysimeter was observed to decrease and the concentration of hazardous heavy metals in leachate from the lysimeter tended to be higher than that of seepage leachate.