Incubation experiments were carried out to study the leaching behavior of heavy metals (Cr, Cu, Pb and Zn) from municipal solid waste incineration (MSWI) bottom ash, as well as the effects of dissolved organic matter and pH on their leaching behavior. In order to enhance the effect of the organic matter, a mixture of MSWI bottom ash with crushed incombustibles rich in organic matter was also investigated. Two series of incubation experiments were performed under an aerobic condition for 1 year, and the temperatures were set at 37°C and 50°C, respectively. Leaching concentrations of dissolved organic carbon (DOC), selected heavy metals and major ions (Na, K, Ca, SO4 and Cl) from MSWI bottom ash were investigated using Japanese Leaching Test No. 46 (JLT 46). The experiment results showed that dissolved organic matter from MSWI bottom ash was mainly composed of volatile fatty acids (VFA) and humic substances (HSs). The concentration of acetic acid was relatively steady in the early incubation stage, which contributed about 70 % of the total VFA, and was reduced suddenly when pH approached 9. Variation of HSs concentration in the leachate followed the same pattern with DOC, which at first showed an increasing tendency, subsequently decreased after reaching a maximum at the end of 24 weeks incubation period. The pH values of MSWI bottom ash decreased from its original value 12.2 to approximately pH 7-8 after a 1 year incubation process. Leaching concentrations of Pb and Cu from MSWI bottom ash decreased with the incubation time, especially in the first 4 weeks of the incubation period. However, the early incubation process promoted the leachabilities of Cr and Zn. At the end of the incubation process, the leaching concentrations of Cr, Zn and Cu decreased below 0.01 mg/L, while Pb still exceeded the legal limit of Japanese soil pollution. According to the analysis, leaching behavior of Cr, Cu, Zn and Pb had a strong correlation to pH value. And DOC partially contributed to the leaching of Cr and Cu. However, no relationship could be found between DOC and Pb or Zn.
|Number of pages||16|
|Journal||Memoirs of the Faculty of Engineering, Kyushu University|
|Publication status||Published - Dec 1 2007|
All Science Journal Classification (ASJC) codes
- Atmospheric Science
- Earth and Planetary Sciences(all)
- Management of Technology and Innovation