Abstract
Testing method called Japan Leaching Test number 13 (JLT 13) was used to evaluate safety of incinerator ash in Japan. This method was focused to evaluate leaching potential of heavy metals in the ash. Therefore, JLT 13 may not be suitable to evaluate leaching potential of organic compounds, such as polycyclic aromatic hydrocarbons (PAHs) or dioxins. Several previous studies reported that leaching behavior of hydrophobic organic compounds, such as PAHs or dioxins was difficult to evaluate short term leaching test. Therefore, objectives of this study are to investigate the leaching behavior of PAHs in incinerator ash and to develop the appropriate method to evaluate long term leaching potential of PAHs in the ash. Result from mini-column test showed that leaching of PAHs in solidified ash was levied into bi-phase, first rapidly leaching phase and second slow leaching phase. Clear correlation between leaching amount of dissolved organic carbon and first leaching potential of PAHs was observed. The leaching behavior estimated by the numerical model presented here was well in agreement with the experimental result in mini-column test. This agreement clearly showed that secondly slow leaching behavior depended on the diffusion rate of PAHs in cement solidified ash. Therefore, diffusion rate of PAHs in cement solidified ash was dominant factor of leaching potential . The long term leaching behavior of large-column test could be estimated from the result of mini-column test using numerical model analysis. However, this estimation method was dificult to estimate the fist rapid leaching behavior, but it was not serious problem to evaluate long term leaching potential of PAHs. Therefore, this estimating method may useful to evaluate long term leaching behavior of PAHs in solidified ash.
