Vinyl chloride (VC) is known to be the most toxic compound among the dechlorination products from tetrachloroethylene (PCE), and is suspected to be carcinogenic. We investigated contaminations of VC in various soils and groundwaters which were originally contaminated with PCE. The presence of VC was detected in several groundwaters, where a number of orange-pigmented bacteria which dechlorinated PCE to cis-1, 2-dichloroethylene (DCE), were found. The addition of groundwater sediments was necessary to convert PCE to VC and finally to ethylene (ET) . This conversion was stimulated by the addition of glucose and cysteine. The complete dechlorination from PCE to ET and the incomplete dechlorination from PCE to DCE were thus demonstrated in the groundwater. Complete dechlorination required a strict anaerobic condition, and PCE (21 mg/l) was totally converted to ET in 16 days at 25°C. These results suggest that facultative anaerobes are involved in the incomplete dechlorination of PCE to DCE. On the other hand, obligatory anaerobes are involved in the complete dechlorination of PCE to ET.

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The fact that more than 70% of municipal solid waste is being incinerated is creating various problems at landfill sites. One such problem is that of incrustation caused by a calcium coating on water treatment equipment, pumps, mixer blades, rotating plates and the collector sewer. Incinerator ash contains inorganic compounds including calcium and heavy metals, especially air pollution control residues from slaked lime containing many free alkaline calcium compounds, a major cause of calcium scale.
In order to prevent the build-up of calcium scale, carbonation treatment of highly alkaline municipal incinerator fly ash was studied. Moisture content, temperature and reaction time were shown to have an effect on carbonation. Carbonation was checked by the X-ray diffraction method and its effectiveness for insolubilization of calcium was determined by leaching tests (solid liquid ratio= 1 / 10 or 1 / 200) and column elution tests. Test results indicated that carbonated incinerator fly ash did not produce calcium scale and carbonation treatment was effective for the insolubilization of alkaline calcium compounds.

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A new type of municipal waste incinerator was examined through a series of experimental works using hot and cold model furnaces and numerical analyses on the gas flow. The 2-way flow incinerator reduces pollutant gas emissions, such as dioxins, by dividing the combustion gas in the primary stage into CO-rich gas and O₂-rich gas and then impinging each other in the secondary combustion region to promote mixing and complete chemical reactions.
To examine combustion process in the secondary region of the incinerator, combustion gas in the combustion region of the hot model furnace was analyzed, mainly taking notice of carbon monoxide which is connected to dioxins. By using cold models of similar sizes together with the hot model, the mixing processes after impingement of the two jets were also examined, and the relationship between a practical furnace and a hot model furnace was verified.
The experimental and numerical analyses reveal the relationship between the mixing process in the furnace and CO oxidizing, as well as the NOx production reaction processes which are affected by the distribution ratio, reference velocity, furnace temperature and so on.

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The purpose of this study is to make a mathematical model for conversion processes of organic carbon and nitrogens in landfilled layers under semi-aerobic conditions and also to estimate better conditions for landfill. This model is a 1-D three phase model which is composed of several processes including elusion of pollutants from solid waste, microbial decomposition, convection and dispersion in the liquid phase, exchange of liquid in the mobile and stagnant liquid zones, transport between liquid and gas phases, and convection and diffusion in the gas phase. Microbial decompositions consist of aerobic, acid forming and methane producing processes. Microbe growth rates are expressed as a function of both temperature calculated by heat balance and pH in terms of alkalinity.
Numerical simulation results indicate that the elusion of organic matter in the upper layer, aerobic decomposition of organic matter in the middle, and aerobic decomposition, nitrification and denitrification in the lower are predominant. Aerobic zones, especially the bottom layer of the semi-aerobic landfill, play a significant role in the purification of leachate.

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A comparative case study investigated the factors influencing residential waste recycling in North America and Japan. A mail survey sent to household heads in Vancouver, Canada and Sapporo, Japan investigated recycling motivations and recycling activities. These cities were chosen for comparison due to their common status as regional centers in their respective countries, and their similar residential waste generation and recycling rates. Various descriptive and analytic statistics were used to analyze the data. The survey results indicate that citizens in both Sapporo and Vancouver share similar motivational structures for recycling. Altruistic environmental reasons (e. g. conserving natural resources) were the main motivation for recycling, and system limitations (e. g. no pick-up service in the neighborhood) were the main motivation for not recycling. The slight differences which did exist between recycling motivations in Vancouver and Sapporo were attributed to differences in the respective cities recycling systems rather than cultural differences between Canada and Japan. These results indicate that governments in both Japan and North America should strive to develop convenient recycling programs which appeal to altruistic environmental motivations.

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Inoculation of suppressive bacteria into compost raw material was carried out in order to make a functional compost aimed at repressing lawn disease. A spontaneous streptomycin-resistant mutant of suppressive bacterium, B. subtilis N 4- 1 was used to investigate the dynamic change of the inoculated strain during composting. It was concluded that it is important to keep the concentration of the bacteria indigenous in the raw material as low as possible in order to enable the growth of N 4-1. The compost product made from the raw material containing other bacteria less than 4.3 × 10⁵ CFU/g-ds showed a suppressive effect on the pathogen. The feasibility of repeatedly using the compost product as a seed for the next composting was also examined. The concentration of N 4-1, and the ratio of N 4-1 to total bacteria (estimated by summing up the N 4-1 and the other bacteria) in the compost product decreased rapidly as the number of repetitions was increased. The compost product lost the suppressive effect after the 5 th repetition.
It was also ascertained that the ratio of N 4-1 to total bacteria had a strong effect on existence and degree of suppressiveness. The suppressive test experiment using cell suspension mixtures of pure cultured N 4-1 and insuppressible bacterium, Escherichia coli E 2 was performed to ascertain this.

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