## 英文概要

In Japan, the treatment residues such as the incineration ashes and the shredded residues from recycling facility account for 88% or more of the municipal solid waste disposed of into landfill due to MSW treatment which mainly relies on incineration and also the progress of resource recovery. As for the stabilization of the landfilled waste, the principal object is chiefly put on the settling down of degradation of the organic matter, and the methods for achieving it at the early stage were developed and have been introduced so far. However, regarding the treatment residues such as incineration ash, besides the stabilization of the organic matter, the stabilization of the inorganic substances that have the reactivity and high mobility such as salts and immobilization of the toxic substance such as heavy metals etc. are demanded. Therefore, creating new concept of stabilization that differs from conventional one and developing the technology that is able to achieve it early have become significant. Then, in this research, the following three themes were set in order to realize early stabilization of the treatment residue in landfill.

1. To elucidate factor causing stabilization delay in the landfill that mainly accepts treatment residues; the stabilization delay factor is clarified from the site survey and the sample analysis in actual landfill. Moreover, from the comparison on the level of stabilization of wastes that are obtained from both actual site and large-scale test cell where a different landfill method was adopted, a suitable landfill method for the early stabilization is clarified.

2. Examination on the method to promote stabilization of treatment residue; As for the hardening of incineration residue that is thought to be the one factor for stabilization delay, the occurrence is confirmed, the influence of hardening on the wash off of salts and on emission of heavy metals is elucidated, mechanism of hardening is clarified, and how to prevent hardening is provided. Moreover, influence of mixing of different kind of residue before landfilling is examined in terms of the permeability. And how it is effective for early stabilization is evaluated.

3. Investigation of performance of horizontal permeable reactive barrier (HPRB) for capturing hazardous substance; In order to add multiple safeties to landfill, adoption of permeable reactive barrier as cover soil is proposed. It is applied as the backup technology that can correspond to unexpected emission of hazardous substance. And performance on capturing of organic matter, salts, and heavy metals is investigated. Moreover, how to design PRB is examined.

As consequences, the following results were obtained.

1) The landfill method influences significantly the stabilization of the residue in landfill. When conventional landfill method such as dumping without care, high compaction by heavy equipment, and placement of thick and low permeable soil cover, etc. is applied, landfilled waste has high emission potential even after 7 years of its disposal. But at the test cell where another landfill method such as mixing of some kinds of waste before dumping, low compaction, and high permeable soil cover are applied, the wastes were almost stabilized. Landfill method applied to the test cell contributes to the wash-out of salts and immobilization of heavy metals.

2) Solidification of incineration ash in landfill decreases permeability, obstructs the salts wash out, and increase heavy metal emission. Predominant solidification mechanism was the transformation of calcium from oxides/hydroxides to carbonates. Thus, to promote the transformation before disposal by repetition of wetting and drying is effective to avoid solidification. In addition, mixing of incineration ash and shredded residue drastically improves permeability.

3) HPRB comprised of the Fe-rich natural soil has high adsorption capacity on TOC although its performance of capturing on monovalent/bivalent ion wasn't satisfactory. However, it can be improved by addition of zeolite or bentonite. On the other hand, the HPRB has high ability of capturing heavy metals. Especially, its performance can be improved by adding iron powder. Actually, HPRB adopted in test cell captured much heavy metal. Most of heavy metals captured by HPRB were hardly-soluble form. It implies that heavy metals that were originally mobile were ingested to the newly formed compound that is mainly comprised of major soil element such as Al and Si.