Qualitative effects of morphology of surface on behavior of biofilm were investigated by two-dimensional biofilm model with ideal rough surface which was numerically analyzed by finite element method. This model is presented by diffusion and double Monod-type microbial reactions in the biofilm and the diffusion layer can be included in the model. The biofilm was formed by acidophilic iron-oxidizing bacteria.
Effect of the roughness of surface on the increase rate of flux, which is the rate of substrate removal flux of biofilm with rough surface to that of plane biofilm, is significant when surface roughness is large. This effect is changed by substrate and dissolved oxygen concentration in bulk liquid and the influence of the concentration in bulk liquid is small when the surface roughness is large. The maximum rate of increase of flux approaches to the rate of increase of surface area of biofilm. Morphology and area of biofilm domain (IMFD) which has 99% of substrate removal flux is changed by the surface roughness and the concentration in bulk liquid. The rate of increase of flux becomes large when IMFD changes around the shape of rough surface.

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Oxygen utilization, respiration heat and sludge production in biological nitrification and denitrification of night soil were studied in the pilot and full-scale plants using a U-tube bioreactor with a membrane filter for separation of activated sludge from purified night soil. The U-tube bioreactors were operated under conditions of high MLSS (21kg·m^-3) and high aerobic SRT (29days). Heterotrophic respiration rates and heat in the bioreactor were measured. The experimental equations for prediction of oxygen utilization and heat production rate for nitrification and denitrification of night soil was proposed and verified by using our full-scale plants. It was found that the growth rate of microorganisms was approximately equal to the decay rate of microorganisms under the operating conditions of high aerobic SRT and the amount of excess sludge was approximately equal to the content of non-oxidizable solids in night soil pretreated by a centrifuge.

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Decoloration processes caused by the ozonation of sixteen water-soluble dyes were evaluated by several color measurement methods, and then, the characteristics and relationship between them were investigated. An attempt was made to propose a feasible color control method.
Initial decoloration processes measured by absorbance method were represented as a pseudo-first order reaction. On the other hand, they were not represented by color difference method. The behavior of initial decoloration processes measured by dilution method was relatively similar to that measured by absorbance method. The values measured by both absorbance and dilution methods were correlated by an exponential regression line. Based on this correlation, a feasible color control method corresponding to an aesthetic sense was proposed.

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The development of biological advanced treatment of dioxins in the pulp waste water using immobilized microbes was studied. Microorganisms were immobilized by photo-crosslinked resin with powdered activated carbon (PAC). The effect of adsorption capacity of PAC, adaptation of microorganisms to pulp waste water, and biodegradability of dibenzofuran (DBF), carbon based skeletal structure of dioxins were examined.
The results obtained from this study were as follows.
1) Immobilized microorganisms with PAC removed DBF more effectively due to the adsorption and concentration effect of PAC.
2) Immobilized microorganisms such as Pseudomonas aeruginosa effectively removed organic matter and degraded DBF in the waste water.
3) DBF removal rate and ATP content of immobilized microorganisms were more rapid and higher than those of suspended microorganisms.
4) The adsorption capacity of PAC was reduced due to gel inhibition effect, however, immobilized PAC has worked effectively to DBF treatment.

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The purpose of this study is to clarify the mutual relationships between the Yatoda environmental factors and the Luciola lateralis population. This research was conducted in a hilly land located at Nobi district in the Miura Peninsula. It was found that Yatoda used as paddy field have given close relationships between the human impacts and L. lateralis population density. Multiple regression analysis indicates a significant relationships between the population density of L. lateralis and the environmental factors. The factors that influenced the population density at Yato having narrow and steep geographical features are relative light intensity on the irrigation canal, depth of stream, height of the open space between the stream surface and the river bank line, width of irrigation canal, minimum flow velocity, soil moisture and length of plot. While the factors that influenced the population density at Yato having wide geographical features are relative light intensity on the irrigation canal, depth of stream, height of the open space between the stream surface and the river bank line, width of irrigation canal, ratio of the width of irrigation canal to the width of stream, flow velocity change, width of plot.

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Phosphorus and nitrogen removals from river water were studied at artificial reed-wetland (9.2m×90m) in Koaidame pond (Mizumoto park, Tokyo) from April to December on 1993.
About 30% of total phosphorus (TP, 0.25-0.48mg·l^-1) and 20% of total nitrogen (TN, 1.2-11mg·l^-1) of influent were removed. BOD (5.5-22.2mg·l^-1) and COD (7.8-20.9mg·l^-1) removal rates were low (below 10%) in this wetland.
After pass the wetland, particulate phosphorus and particulate nitrogen of the influent decreased largely, and NO₂-N and NO₃-N appeared in place of NH₄-N depression during the summer (April-September), so that precipitation of particulate in the water and nitrification were considered main causes of TP and TN removal.
The average removed load of TP, TN, BOD and COD during investigation period were calculated at 5.5 mg·m^-2·d^-1, 67.8mg·m^-2·d^-1, 82.8mg·m^-2·d^-1, 79.1 mg·m^-2·d^-1, respectively.

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