Immobilization of fly ash from MSW incinerators and ash-melting furnaces

In Japan, residue from the incineration of municipal solid waste — both fly ash and bottom ash — had legally been classified as “municipal waste” and accordingly had been disposed in controlled landfill sites. In a revision implemented in April 1995, however, fly ash was reclassified as a “special-controlled municipal waste” and it became mandatory to dispose of the substance in controlled landfill sites only after it had been stabilized to prevent the leaching of heavy metals. We have conducted comparative fly ash treatment tests with various commercially available stabilizing agents and cement. We have also developed an inexpensive solidifying powder (SFPA, or Sumitomo Fine Powder Agent) and verified its effectiveness. Furthermore, in a series of treatment tests with ash-melting a furnace fly ash having a very high rate of heavy metal leaching such as 480 mg/l of lead, we confirmed that treatments combining SFPA and “special aging” have superior performance controlling lead leaching under 0.05 mg/l.