The effects of substrate composition on the characteristics of substrate removal and biofilm formation in methanogenic phase of anaerobic two phase digestion were investigated by using laboratory-scale anaerobic fluidized bed reactors with packed media of activated carbon. Three kinds of substrates were used. The first one was composed of acetic acid and the second and third ones were composed of acetic acid, propionic acid and butyric acid. A small amount of yeast extract and glucose were added to the second and third ones, respectively. In the experiments in which yeast extract or glucose was added to the mixed acid substrates, the substrate removal efficiencies were higher than in the experiment using acetic acid substrate. The biofilm formation was accelerated by using the mixed substrate to which yeast extract was added.

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The principal component analysis and cluster analysis were applied to the groundwater quality data in terms of 16 indices. These analyses showed that the wells, which the data were collected from, could be classifyed into four groups. Two of them were supplied water to from the upper one of vertically stratified groundwater reservoirs, and the others from the lower reservoir. Comparing the result with the tetrachloroethylene concetration of the well water, it was revealed that the some limited local spots were contaminated by the chemical in the upper reservoir, whereas the whole was contaminated in the lower reservoir. The classification enabled us to make a contour map of the chemical concentration to visualize the present state of the groundwater pollution in the area.

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The effect of thermal pretreatment on the characteristics of degradation of waste activated sludge in anaerobic digestion was investigated using laboratory-scale batch and continuous experiments at 35±1°C. The pretreatment temperature of waste activated sludge ranged from 62 to 175°C and the holding time were 15, 30, 60 and 90 minutes.
organic solids were solubilizated to soluble proteins and carbohydrates or converted into lower molecular weight compounds such as volatile fatty acid by the thermal pretreatment. The anaerobic biodegradability and methane gas production was increased, and the retention time necessary for anaerobic digestion was possible to be reduced by lower than 10 days. The optimum pretreatment temperature and holding time for the upgrading of anaerobic digestion of waste activated sludge were 170°C and 60 minutes respectively. In this pretreament codition, at the retention time from 5.0 to 10.0 days, COD removal efficencies was about 60% and gas production ranged from 223 to 235 ml·gCOD^-1, which was about 2 times that of the control. The rate of increase in solubilization and anaerobic degradation of major organic compounds in waste activated sludge with thermal pretreatment decreased in the following order : carbohydrate>protein>lipid. The number of total methanogenic bacteria existing at retention time from 1.5 to 10.0 days ranged from 10⁷ to 10⁸ MPN per ml of digester content.

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Nitrogen and phosphorus removal from swine wastewater in three bench-scale activated sludge units with limited and non limited aeration processes (LAP and NLAP) was investigated. The ratio of BOD : T-N : PO₄-P of wastewater charged was 100:33:4. Operational conditions for the units were the same except for aeration periods; in the conventional method (NLAP), aeration began at the charging, while in the limited aeration processes (LAP-13, LAP-8), thirteen and eight hours after the charging, respectively. These units were operated under the loadings of 0.25 and 0.50 kgBOD·m^-3·d^-1. High removal efficiencies for BOD and TOC were achieved with both LAPs and NLAP. However, large difference of nitrogen removal between LAPs and NLAP was found: at a BOD loading rate of 0.50kg·m^-3·d^-1, removal efficiencies for total nitrogen in LAP-13, LAP-8 and NLAP were 52.4%, 53.9% and 19.2%, respectively. The time course analyses during those operations indicated a shortage of aeration for nitrification in LAP-13 at a BOD loading rate of 0.50kg·m^-3·d^-1, and advance of nitrification was needed to attain higher removal efficiency for nitrogen.

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