It is well known that various pollutants are accumulated in estuaries of the urban areas under the strong influences of urban run-off and wastewater discharge, and also by tidal flows and flood. Fluctuations of flow rate and water quality during high and normal water levels were analyzed by using both of a one-dimentional unsteady flow model and a diffusion model. Numerical simulations were carried out for water quality, flow rate and pollution loads under various flooding conditions. Resuspension was dominant only in the upper stream and sedimentation was a major factor for water quality variation in the lower stream. The summary of the results is shown as follows ; Cumulative loads of SS were in proportion to flood flows ; Sedimentation of SS was obtained about 100 ton between Dengaku bridge in the upper stream and Gotanda bridge 3.0 Km downstream ; The maximum cumulative BOD load obtained at the same interval was about twice as much as the value in the upper stream under the flooding conditions.

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A structured model introduced by considering algal mass to be composed of two components which were an intracellular phosphate and a structural substance, was proposed for algal phosphate uptake and growth dynamics. Further, the kinetics for phosphate uptake and growth of Microcystis aeruginosa were investigated at steady state or transient state, using continuous and batch culture experiments.
Continuous culture experiments indicated that specific growth rate, μ was expressed as a hyperbolic function of intracellular phosphorus content, f_P. While, specific rate of phosphate uptake, σ was inversely as f_P. The f_P values ranged from a maximum of about 5.0% to a minimum of about 0.15% phosphate per cell dry weight.
At balanced growth, σ was related to μ and f_P in the form of σ=f_P·μ which was derived from the model presented here. So, parabolic relationship was found between σ and μ, because f_P increased with increasing μ.
The kinetic equation of transient phosphate uptake was given by df_p/dt=σ-μ·f_P. This kinetic model was able to simulate overplus phenomena that when M. aeruginosa grown in a phosphate deficient continuous culture was suddenly brought into contact with a phosphate rich medium, phosphate was accumulated into the cell above the intracellular content required to sustain maximum growth rate.

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Rotifera Philodina erythrophthalma is well known as the valuable microorganism in a biological wastewater treatment process. The aim of this study is to make clear the method of mass culture of P. erythrophthalma for sedentary appearance in mixed culture bio-reactors by inoculation. The flask scale experiments gave the following results.
1) The variety and quantity of bacterial strain as prey were not important for mass culture of P. erythrophthalma.
2) The effects of accumulated metabolic products caused by microorganisms' respiration was important facter for growth of P. erythrophthalma on continuous mass culture.
3) Growth factor like substances contained in rice and potato were extremely effective to mass culture of P. erythrophthalma.
4) Maximum number of P. erythrophthalma in cultivation was to 12,000ml^-1 by using rice extract as the growth factor like substances.
5) P. erythrophthalma get through continuous high density of mass culture by replacement of cultivating solution as prevention of accumulated metabolic products.
6) Inoculation of P. erythrophthalma into accomplished biota was available to be sedentary.

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Attainment conditions of the water quality standard (COD) in Japanese 113 lakes (197 designated sites) were investigated by using observed COD concentration between 1978 and 1988. Observed concentration in about a half of all designated sites have exceeded the standard value of each site every year. Only 20% of the sites have attained the water quality standard every year. Objective 113 lakes could be classified according to two indices of ‘the ratio of exceeding year in 1978-1988’ and ‘the ratio of observed mean in 1978-1988 to the standard’. Though the attainment conditions throughout Japanese lakes have become better, the decreasing ratio of the autochthonous COD to the allochthonous indicated the emphasis of watershed management.

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