Organizing bioassay data of various chemicals was tried in this work to make use of those data much more effectively and practically for the toxicity control and management of environmental waters. We organized the bioassays' data of single/multi-component chemicals by fitting their dose response relations with formulas. The formulation was generally successful for single/multi-component chemicals except some cases. In addition, interactions among component chemicals were examined by isobole diagram. The toxicity contribution of each chemical in environmental water could be estimated by this method. These trials could be useful for water quality control based on bioassays.

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Performance of BOD removal was investigated using observed data on rural sewerage facilities with submerged biological filter. It was found that probability distribution of BOD in influent and effluent of rural sewerage facilities obeyed logarithmic normal distribution. BOD removal in anaerobic filter tank was assumed to depend primarily on two factors : BOD in influent and SS in effluent. BOD removal in contact aeration tank was also influenced by three factors, that, BOD in influent, SS and ATU - BOD in effluent. Therefore, BOD removal in anaerobic filter tank and contact aeration tank have limitation due to elution of accumulated sludge in biofilm filter. As a result, equations related to BOD removal were derived from the data regarding to BOD in influent, SS and ATU - BOD in effluent. The predicted values of BOD removal were approximately in agreement with observed values. The relation between BOD and SS or ATU - BOD in effluent was approximately linear in the range of BOD in influent of anaerobic filter tank and contact aeration tank. The relationship between BOD, SS and ATU - BOD was nearly in accord with the tendency calculated by equations which was obtained from above data. Deposited sludge thickness on the bottom had a considerable influence on SS in effluent of anaerobic filter tank. Consequently, control of sludge thickness is effective to maintain BOD removal efficiency in anaerobic filter tank.

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Recently, environment-friendly public works are demanded. We evaluated an advantage of the utilization of rainwater and treated domestic wastewater in urban area. The rainwater utilization is the use of rainfall on the roofs, walls and collected runoff storm water in the storm water reservoir for flood controls. In the reuse of treated domestic wastewater, wastewater from the raw sewage is not reused. That is “Domestic Water Recycling System”. We evaluated the amount of conserved drinking water and the amount of decreased final effluent polluted matters by the unused water resources utilization. And we estimated the amount of carbon dioxide emission by the construction and operation of the unused water utilization system. Water self-support system (the use of rainfall on the roofs, walls and the domestic water recycling system) are effective in the decrease of the resources consumption and the environmental loads.

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The grove soil for a better fertilization contains phosphorus in high concentration. In this study, the water quality of leachate through grove soil due to artificial acid rain was investigated, and effects on the growth of aquatic microorganisms were studied. Eluviation of phosphorus and aluminum was caused by artificial acid rain. The maximum concentrations of both the materials were 10mgP · l^-1 and 10mgAl · l^-1 respectively, when the artificial acid rain of pH 3.0 was added. In the case of pH 4.0, they were 1.0 mgP · l^-1 and 0.5mgAl · l^-1 respectively. On the other hand, using microcosm system, it was observed that the growth of Euglena gracilis Z was not inhibited, if pH was more than 3.4 and the concentration of aluminum was less than 1.0 mg · l^-1. So it is suggested that there would be the possibility of the algal growth caused by the nutrients which were eluviated by acid rain of pH 4.0.

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