The gas flow and mixing were experimentally studied by using the reaction between nitrogen monoxide (NO) gas and ozone (O₃) gas in a cold combustion chamber model of a MSW incinerator.
The flow rate distribution of the NO gas tracer was measured and mixing characteristics of flue gas in the chamber were discussed. In addition, reaction characteristics in the chamber were evaluated by measuring reaction rate which was obtained by actual reaction experiments with NO and O₃. A strong correlation between reactiop rate and overlap index, which is calculated from the NO tracer distribution measured and may indicate the degree of mixing, was found. Therefore, it is suggested that the mixing has a dominant role for reaction characteristics in the chamber.
Experimental data of this study as well as the visualization data of previous papers make it possible to evaluate the effectiveness of computational fluid dynamics methods for the combustion chamber.

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The reduction effect on mercury emission by the decrease of mercury content of dry batteries and the removal methods of HCl and SO₂ were investigated at municipal incinerators. Changes of the removed amounts of mercury were estimated in the ward areas of Tokyo from 1986 to 1996 and all over Japan in 1992.
By comparing concentrations of mercury in flue gas from a municipal incinerator in 1986 and 1993 which had adopted the powder CaCO₃ injection method and the electrostatic precipitator (EP), we found that the mean concentration of mercury had gone down from 0.25 mg/m³N to 0.08 mg/m³N and the appearance frequency of high concentration peak of mercury had decreased remarkably.
Mercury was removed by the treatment methods of HCl and SO₂. The mercury removal efficiencies for the CaCO₃ powder injection method, the wet scrubber method, the wet scrubber method added to a chelate compound which was adopted with EP, and the filter method were estimated to be 35, 65, 90, and 75 %, respectively.
In the ward areas of Tokyo, the emitted amount of mercury in 1996 decreased to about one sixth of that in 1986 because of the decrease of mercury content of dry batteries and the adoption of removal methods of HCl and SO₂, though the incinerated amount of waste increased by 1.27 times.
In overall Japan, the emitted amount of mercury was estimated to be 17 t/y and the removed amount of mercury by the flue gas treatment was estimated to be 9 t/y, in 1992.

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To clarify the dissolution of heavy metals from cement solidified waste under landfill layer conditions, we conducted the serial batch extraction from ground materials that were solidified with Portland cement and included cadmium and lead chloride. Distilled water or acetic acid was used as extraction solvent. The ground materials were intermittently exposed to air or 50% of CO₂ between the extraction.
The dissolution of cadmium followed the hydroxide/carbonate solubility equilibrium, although the dissolution of lead did not. When the ground materials were put in contact with a low pH solution, cadmium dissolved rapidly and wholly, and lead for a long period. When the ground materials were exposed to CO₂, both of the metals formed carbonates; cadmium dissolved for a long period, and lead scarcely at all. These results showed that the landfilling of cement solidified wastes over incineration residues and incombustible wastes was effective to avoid heavy metal leaching.

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The reductive dechlorination of tetrachloroethylene (PCE) was studied using glass columns packed with PCE-contaminated soil, to which enriched anaerobic dechlorinating bacteria were added together with wastewater from bean curd to act as electron donors. In batch experiments, ca. 35% of PCE in the soil and more than 88% of PCE in the void water were transformed to cis-1, 2-dichloro-ethylene (DCE) after 29 months. No complete dechlorination from PCE to ethylene was observed under these conditions. On the other hand, in semi-continuous column experiments using wood chips as electron donors, complete elimination of PCE from the soil was estimated to be achieved after 66 months. DCE was detected in all column effluent, which was further degraded by adding toluene and phenol as substrates for aerobic bacteria. Moreover, a genetically modified Pseudomonas strain was very effective to degrade the DCE derived from PCE.

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Crude soya-sauce mash, which is treated as an industrial waste produced in soya-sauce factories, was desalted and dried at a pilot scale plant which treats 100 kg of soya-sauce mash per process. The finished product was dried and its components were analyzed in order to discuss the application methods of the product. 95% of the salt in the crude soya-sauce mash was extracted by dipping the crude mash in water which outweighed the mash in a 3: 1 ratio. The yield of the finished product was 60.1%. C/N ratios and contents of salt and nitrogen in the product were 9.3, 0.44% and 6 %, respectively. These values indicate that the product can be used as fertilizer or as soil conditioner. The product includes 34.2% crude protein. This suggests that the product also includes nutrients needed by domestic animals. The amount of standard plate counts, thermostable bacteria, lactic-acid bacteria or coliform groups in the product was less than 300 CFU/g. The amount of fungi in the product is less than 100 CFU/g. Water activity in the product was 0.540. These factors support the stability of the product during storage.

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The formation of calcium scales have been found in leachate treatment facilities at landfill sites. This problem has a result of the landfilling of incineration ash which contained a large amount of soluble salts. 15 municipal landfill sites were investigated with regard to scale formation and chemical analysis of leacheates. Contributing factors such as calcium concentration, alkalinity, water temperature and ion strength, in particular the former two contributed to calcium scale formation in landfill leachates and the saturation pH (pHs) levels calculated were important. In using two convention indices of scale formation namely the Langelier Saturation Index and the Ryzner'Stability Index both were unsufficient in explaining real scale formation, the former overestimating the amounts and the latter underestimating the amounts. It is considered that if a leacheate is in a condition with pHs<7, calcium concentration>100 mg/1 and alkalinity>100 mg/1, these levels are liable to form calcium scales. Calcite as the main mineral and aragonite were found in real scale, while geochemical calculations showed the possible precipitation of calcite and dolomite, and the possible existence of aragonite, magnesite and huntite in oversaturated solution.

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