The mass flow of dioxins was investigated in a landfill site where municipal solid waste incinerator ashes have been mainly disposed. For this purpose we estimated the amount of dioxins received by the landfill site, discharged from the site, and retained in the site. Input dioxins were estimated from bottom ash, fly ash, cover soil, rain, and dust fall, output dioxins were estimated from the effluent and landfill gas, and retained dioxins were estimated from boring core samples.
The result showed almost all the input of dioxins originated from the fly ash, and almost all the output of dioxins originated from the effluent. The estimated amount of dioxins received into the site was 2, 900 g (45.9 g-TEQ) and those discharged from the site was 0.001 g (0.000001 g-TEQ), The dioxins output was only 0.00005% (0.000002% in TEQ) of the dioxins input. The results indicate that dioxins are not easily decomposed in landfill sites and water soluble dioxin discharge is very low. Therefore the input dioxins will be persistent for a long time.
Further studies are necessary in order to clarify the detailed mass balance of dioxins in landfill sites, because we reasoned from the limited date obtained in this study.

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Removal of dioxins in flue gas from waste incinerators by catalytic oxidative process was investigated. Mono-chlorobenzene (MCB) was used as a model-compound of dioxins in order to study the kinetics of catalytic decomposition. The decomposition of MCB is a first order reaction with respect to the concentration of MCB and the reaction rate was 1.4 times higher at 200°C than at 170°C. The durability test of the catalyst using the real flue gas from a municipal waste incinerator was performed. Dioxins were completely decomposed at the initial stage, and the decomposition efficiency of dioxins after 16, 500 hours was still 95% in TEQ. The influences of reaction temperature and linear velocity on the decomposition of dioxins were clarified. The high decomposition rate of dioxins was maintained in the temperature range of 170-240°C. The decomposition reaction of dioxins was well interpreted by the theoretical calculations based on the mixing diffusion model.

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We investigated and analyzed the material flow of post-consumer containers for food and beverages in order to understand and discuss currently used definitions of the recycling rate of containers because such an analysis has not yet been done. Here we focus on the post-consumer recycling rate, which refers to how much of the total amount of containers emitted by consumers is recycled. Firstly, we investigated amounts of collected or recovered containers, i, e ., steel cans, aluminum cans, and glass bottles (one-way bottles), by interviews and questionnaires in Y City, located in the Tokyo metropolitan area. This study revealed almost the entire (81 to 110%) material flow of post-consumer-stage containers. Secondly, taking into account yield from dealers, we estimated the amount shipped to secondary material producers and then calculated the postconsumer recycling rate. The post-consumer recycling rate that was determined based on the material flow analysis in this paper is defined differently from the generally reported recycling rate. Our values were lower than those generally reported, but the differences between our values and the generally reported values were dependent on the type of containers. Throughout the study, we indicated the importance of material flow consideration in discussing recycling rates and their implications.

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We have developed two methods for identifying used home electric appliances. These identification methods can both improve performance and reduce running costs of a recycling system. We considered methods of identifying appliances according to overall shape, the size of each face of the appliance (face size), mass, design, and information on the name plate. As a result, we found that identification by face size and by face size and mass are the most effective methods. Air conditioners, refrigerators, televisions, and washing machines of four manufacturers were identified by using these two methods. And when identifying by face size, 97.2% of these appliances were identified in a time of 0.5 ms (data recorded on a PC : 486 DX 4 100 Hz CPU), and when identifying by both face size and mass, 99.5% were identified. These results show that the two identification methods (i. e., by face size or by face size and mass) can be applied to recycling systems.

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In order to discuss the treatment efficiency of fly ash in intermediate processing and the risk of dispersion of hazardous substances derived from treated fly ash into the environment, it is necessary to measure not only the specified elements but also multi-elements. Therefore, it is important to determine each element contained in fly ash precisely and simultaneously. In this study, the validity of X-ray fluorescence analysis (XRF) to determination of elements in fly ash was evaluated by comparing measured value from three analysis methods of XRF, inductively coupled plasma atomic emission spectrometry (ICP-AES) and neutron activation analysis (NAA) .
In fly ashes sampled in eighteen municipal solid waste incinerators, analytical results by XRF were in good agreement with those by ICP-AES and NAA for elements contained in large quantities in fly ash. It was found that each element contained in the fly ash except for cobalt, arsenic, selenium and mercury could be determined precisely using both XRF and ICP-AES.

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To predict the volume of waste concrete from demolished highway bridges and evaluate the effect of life-lengthening on reduction in the volume of waste concrete, constructed and demolished bridges in Miyazaki Prefecture were investigated. Normal distribution and Weibull distribution were considered as the life distribution of the bridges and the parameters of the distributions were determined to meet the observed and calculated number of demolished bridges. There were distributions available for estimating the number of demolished bridges. The mean life estimated was 61 years in normal distribution and 69 years in Weibull distribution. Furthermore, distributions were also available for estimating the volume of waste concrete of demolished bridges. These distributions predict that the volume of waste concrete will increase almost linearly by 2100, and if the mean life is extended by 10 years, the accumulated volume of waste concrete will be reduced by 10-20%.

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