Nitrogen removal using a polyethylene (PE) sponge biomass carrier was evaluated in a fixed-bed reactor for nitrogen removal by the anammox process. The fixed-bed reactor was operated continuously for 240 days. T－N removal efficiencies increased from 38 %, 67 %, 72 %, 74 % to 75 % with stepwise increases in volumetric T－N loading rates. A T－N removal rate of 2.8 kg N/m³/day was obtained after 240 days of operation. After 3 months, anammox biomass fully covered the surface of the PE sponge carrier and the color of the material changed from white to red. Following 5 months of operation, biomass proliferated on the surface of the material and a dark-red color was observed. With the obtained results, PE sponge is auspicious biomass carrier for growth of anammox bacteria.

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Life cycle CO₂ evaluation of kitchen garbage treatment in a house using Johkasou was conducted to compare the impacts of two scenarios. First one is a present case in which kitchen garbage is incinerated with other domestic waste and treats domestic wastewater in Johkasou, and second case is a simultaneous treatment of domestic wastewater and kitchen garbage in household Johkasou. In the second case, disposer was used for kitchen garbage and newly developed Johkasou for this case was used. Potential contributions of these two cases to CO₂ emission in the processes of waste treatment and domestic wastewater treatment were assessed by LCA. A case of a simultaneous treatment of kitchen garbage and domestic wastewater decreased in transportation amount of domestic waste and net CO₂ emission was reduced by 7.8％ (39.9 kg－CO₂ house^－1 year^－1). Because transportation of domestic waste influences CO₂ emission to a greater degree than in Johkasou sludge transportation, a simultaneous treatment process of kitchen garbage and domestic wastewater can reduce more LCCO₂ when the transportation distance of domestic waste is long.

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Relatively high ammonium concentration suggested nitrification inhibition in the pond water of a sea-based solid waste disposal site (SWDS) where incineration ash from municipal wastes is mainly disposed. Depletion of phosphate seemed to affect nitrification in the pond water. Very low concentration of phosphate in the pond water was attributed to the formation of relatively insoluble precipitates with salts contained in the incineration ash such as calcium. To elucidate phosphate deficiency in nitrification, an experiment was carried out in a pilot plant using fibrous contactor as the base of nitrifying biofilm. Addition of phosphate enhanced nitrification even at low temperatures under 10 ℃ while intermission of phosphate addition retarded nitrification even at temperatures above 25 ℃. Phosphate depletion was the primary factor in limitation of nitrification while no such limitation by depletion of inorganic carbon (IC), as an indicator of carbon dioxide or alkalinity, was observed under our experimental conditions. Accumulation of nitrite in the effluent of nitrification tank under low phosphate concentration suggested that nitrite-oxidizing bacteria (NOB) were more sensitive to phosphate depletion than ammonia-oxidizing bacteria (AOB). This implies applicability to partial nitrification by controlling phosphate supplementation.

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Biological treatment of disposer wastewater consists of two biological process; solubilization of kitchen garbage and decomposition of solubilized garbage. Comparative analyses of biological solubilization and decomposition of disposer wastewater in different temperature (13 and 20 ℃) and aeration condition (aeration and non-aeration) were conducted. The solubilization rate of kitchen garbage was affected by both temperature and aeration condition, and highest solubilization rate was obtained in high temperature and aerated condition. Although temperature had an insignificant effect on decomposition of solubilized organic components, the aeration accelerated decrease in SS, BOD and D－BOD. In the non-aeration condition, SS decreased gradually, however, little decrease of BOD and increase of D－BOD were observed. The concentrations of carbohydrate, protein and lipid showed that differences in changes of BOD and D－BOD concentrations in different aeration condition was due to low degradation rate of intermediates such as organic acid and alcohol in non-aeration condition. When the temperature of bench-scale reactor treating disposer wastewater was raised from 13 to 20 ℃, solubilization of the garbage trapped in anaerobic solubilization tank was progressed and temporal deterioration of treatment performance was observed. According to these characteristics of the garbage solubilization and degradation, progress of trapped garbage solubilization by circulation of aerated water from aerobic tank to anaerobic tank could be effective to alleviate deterioration of treatment performance after water temperature increase.

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The application of the enzyme catalase in the textile bleaching process requires the use of catalase under high-temperature, alkaline conditions. We therefore investigated the immobilization of catalase on calcined montmorillonite and pillared interlayer clays (PILCs) as a means of increasing the enzyme’s temperature and pH stabilities. SiO₂－PILCs and Al₂O₃－PILCs were prepared from montmorillonite and were calcined at 400 or 600 ℃. The temperature stability of catalase immobilized on the clays was higher than that of free catalase up to 55 ℃. Additionally, the pH at which the catalase immobilized on the two PILCs was stable was shifted to more alkaline values compared to the pH values for free catalase. In particular, the relative activity (with 100% activity being defined as that observed at pH 7) of catalase immobilized on Al₂O₃－PILCs was higher than that of free catalase at pH 8–12. Furthermore, the relative activity at pH 10–11 of catalase immobilized on Al₂O₃－PILCs calcined at 600 ℃ was only 40–60% of that observed at pH 7 for the same PILC. However, the relative activity of catalase immobilized on calcined montmorillonite was almost the same as that of free catalase at pH ＞7.

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Reduction of activated sludge by using Aqua-ball, which was made from oyster shell powder and harden to 4cm ball type by incineration, was examined. The 4－l scale activated sludge treatment system set up using artificial sewage was used for experiment under completely mixed condition. When 8 pieces of Aqua-ball was added into the aeration vessel, about 25％ reduction of MLSS was observed at steady state of continuous treatment compared with that of control experiments. At this time, respiration quotient of sludge increased and proportion of aerobically grown bacteria increased. Same phenomena were observed when oyster shell powder or and oyster shell extract was added. Therefore, it was suggested that some component(s) of oyster shell promoted the growth of aerobically grown bacteria. As a result, CO₂ exhaust is expected to increase followed by the reduction of activated sludge.

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