In order to critically evaluate a landfull, it is very important to understand the mechanisms for organic decomposition and inorganic stabilization in the dumped layers. In this review, we focus on the distribution and structure of sulfate-reducers and methanogens, which are considered to be the major microorganisms for decomposition and stabilization of wastes, in a landfill site using molecular biological methods. Conventional methods for counting and measuring of bacterium have always required a long cultivation time and the value obtained after cultivation depends on the composition of nutrients, but from 1990 many useful methods based on molecular biology have been developed. This include quantitative PCR method, cloning analysis, DGGE, FRLP, TRFLP, slot-blot DNA (RNA) hybridization, and FISH. We have briefly reviewed these methods and examined the quantitative PCR method and cloning analysis on landfill leachates. Result showed that the distribution ratio of sulfate-reducers and methanogens was 15-30% and 2-3 %, respectively. The genus of Desulfomo-nile, which includes many species of higher dehalogenation activity to halo-compounds, was dominant. The the decomposition of halochemicals in the landfill sites due to wide distribution of the genus is a possible explaration for this.

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Characteristics of leaching of heavy metals from fly and bottom ash were investigated experimentally. Leaching activity was found to depend on pH, L/S ratio and ion concentration in the leaching solution. Low pH increased the elution of lead and cadmium. In order to evaluate the short-and long-term elution of landfill sites, various leaching tests are required. These include the serial batch test and/or the availability test for pH and L/S ratio. The impact analysis of heavy metals on the environment was tested using a the method which combines the results from several leaching tests and hazardous scoring techniques. As a result, it is obvious that short-term landfill cadmium and long-term lead have a more hazardous impact.

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This study deals with quantitative analyses of environmental loads resulting from utilization or disposal of the incineration ash from MSW (Municipal Solid Waste) . Recycling of waste plastics collected separately from households is also evaluated. The study proves that ash utilization, as a raw material of cement production after chlorine removal with the“ash-rinsing technology”, is a highly effective for preventing means to global warming and prolonging the lifetime of landfill sites. The latest cement production process also enables effective utilization of waste plastics as an alternative fuel, thereby effectively preventing global warming and also preserving natural energy sources.

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Polychlorinated biphenyls (PCBs) are reduced to biphenyls in alkaline 2-propanol when irradiated with UV rays. This process brings down the PCBs concentration to below 0.5 ppm and produces sodium chloride (NaCl) as a by-product. In order to develop suitable technology for removing PCBs using this principle it is important to study factors that influence this reaction. In this paper, we investigated the effects of UV irradiation density, reaction temperature, UV wavelength, concentrations of NaOH, H₂O and trichlorobenzenes (TCBz) . It was particularly important to study the effects of TCBz. This study established PCBs decomposition to be independent of TCBz concentration, with TCBz concentration less than PCBs. The decomposition efficiency was also found to be independent of UV irradiation density and solution temperature, between 50°C and 70°C. The effective UV wavelength for reductive dechlorination of PCBs was between 254 and 270 mm. The moisture surrounding the solution was saturated with NaOH to suppress the effect of water in preventing the reaction.

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Dioxin removal efficiencies were examined in different kinds of leachate treatment systems at four landfill sites, and the relationship between dioxins and other parameters such as BOD, COD, DOC, SS were discussed.
Dioxin concentrations ranged from 190 pg/L (2.1 pg-TEQ/L) to 8, 500 pg/L (130 pg-TEQ/L) in raw leachates, while ranging from 5 pg/L (0.0067 pg-TEQ/L) to 120 pg/L (1.1 pg-TEQ/L) in final effluents. Removal rates after the total treatment process were 97-99%. High removal efficiency of coagulating sedimentation process showed that dioxins contained in or adsorbed to suspended solids were removed through the coagulating sedimentation process.
We estimated the amount of dioxins removed by the leachate treatment processea and accumulated in the sludge generated from the process. As the estimated amounts were almost similar, it can be concluded that dioxins removed from raw leachates concentrated mainly into the sludge formed in the treatment process.
Dioxin concentrations showed a similar behavior tendency for SS in the treatment processes, while a positive correlation between SS and dioxins were observed in each facility. These results indicate that the parameter SS might be used as a substituting indicator for checking dioxin concentration.
Further studies are necessary in order to clarify the detailed mass balance of dioxins in leachat treatment facility.

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The degree of pyrolysis of municipal solid waste (MSW) is very important in a gasification melting system for optimal control. The purpose of this study is to decide on the pyrolysis temperature and reaction time of MSW for suitable control in a gasification melting system.
In this study, we used a Refuse Derived Fuel (RDF) for the pyrolysis experiment. We measured the mass balance of char, tar and pyrolysis gases to determine their influence on different pyrolysis conditions. Furthermore, the thermogravimetric curves and the ignition temperature with the use of improved micro heating method of chars were measured to estimate the combustion characteristics of the chars. The four following items 1) lower calorific value of char, 2) lower calorific value of pyrolysis gas, 3) the generation rate of char, 4) the fuel ratio of char, were selected to determine the most suitable pyrolysis condition.
Comprehensive evaluation of each condition was carried out with these items. It was found out that a pyrolysis temperature at 450-500°C and a reaction time of 60 minutes was the optinum.

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