## 英文概要

From the viewpoint of sustainable development, appropriate waste management is crucial for conserving the local and global environments. Improvement of waste management in developing countries must directly relate to preventing environmental pollution and expanding public health services. Appropriate waste management contributes to reducing not only the emission of water/atmospheric pollutants and odors, but also the GHGs emission. Solid waste disposal sites (SWDSs) that include both managed landfills and unmanaged dump sites were recognized as major GHG emission sources in developing countries. GHGs emission as LFG, that strictly means the direct emission from the waste landfill body, would be reduced by the introduction of new landfill management technology. While the boundary for project evaluation was limited on direct LFG emission and projected duration, the project seems to be successfully implemented. But in order to evaluate the net effect of the social development by project implementation, it must be requisite to assess the long-term influence on global and regional environment by the introduction of the new landfill technology and management.

Behavior of leachate production from landfill body is highly depending on the landfilled waste, landfill operation and management, and climate situation. Tropical Asian city would face the similar problem on the quality and quantity of landfill leachate. Advanced water treatment technologies are neither fundamental nor concrete solution on the huge amount of fluctuated quality of landfill leachate in this region. Sustainable leachate management which objects less impact of leachate to natural environment for whole landfill lifetime must require following conditions; easy operation, low maintenance, low cost and labor, effective reduction of leachate impact, etc. One possible candidate suggested in this study was the constructed wetlands. Application of pilot-scale constructed wetlands for real leachate at a landfill in Thailand exhibited the reduction of leachate amount by evapotranspiration. The combination of indigenous cattail and media was effectively works for stable treatment of the landfill leachate. It also contributed to remove the organics, nitrogen and heavy metals from the leachate. The low-cost and low-energy operation of constricted wetlands indicated the feasibility of this technology for leachate treatment of tropical Asian landfill.

Leachate recirculation into landfill was also considered as possible candidate for the applicable technology for landfills in Asia. It is possible to apply this technology for Asian landfills except the rainy season. Since the raw leachate or leachate from pond would be unsuitable for recirculation, several pre-treatment technologies were examined. Coagulation, ammonia stripping, and reverse osmosis treatments had shown to control the recirculates quality. Removal of ammonium from recirculates was strong benefit for reducing the ecotoxicity. The control of ammonium and salinity must be critical to prevent the inhibition for the microorganisms in landfills.

While we have only focused on the leachate management, it may have leachate drainage, enough capacity of lagoon, and leachate treatment plant (LTP). These differences of management will directly relate to the determination of appropriate boundary. For instance, the pollution of aquatic environment caused by landfill leachate must be accounted for a major source of several environmental problems. Direct and indirect emission of GHGs and long-term cost for operation of the prevention/recovery act of environmental pollution should be included. Landfill gas to energy system, which is normally coupled with capped anaerobic bioreactor type management, possesses a large potential of benefit by the energy production. It might reduce the indirect GHGs emission and may improve the cost balance on the landfill management. The drawback of this system must be a long-term pollution of landfill leachate especially in pluvial Asian nations,