The sorption properties of cadmium on the bottom sediments deposited in the Lake Biwa etc. were investigated and estimated, especially in relation to both physical-chemical characteristics of the sediments and water quality. It was noticed that the particles of the sediments tend to become smaller in size with an increase in the water depth at sampling point. Besides, both moisture and CODcr increase as the particle becomes smaller. The sorption experiments in a batchwise method resulted in the adsorption isotherm expressed by Freundlich type formula. Three kinds of sediments were utilized for this experiment, i.e., wet, dry and heated ones. The parameters estimated from the adsorption isotherms were dependent on the pretreatment process of the sediments. This suggests the significance in both moisture and organic substaces. The effect of several coexisting ions like alkali metal etc. on the Cd sorption of the sediments was observed. Moreover, the effect of both DO and pH was also referred to. It was found that these factors are quite responsible for the change of the Cd sorption capacity.

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A mathematical model simulating the extended aeration activated sludge process was presented.According to the model, the production rate of the sludge and the content of active biomass in the sludge, which depend on operation conditions, are quantitatively analyzed through illustrative calculations.
The concentration of active biomass in the aeration tank decreases abruptly with increase of the apparent mean retention time of liquid in the tank under a constant discharge rate of excess sludge from the system. While the discharge rate of excess sludge does not affect much on the fraction of active biomass in total suspended solids in the tank operating as the standard activated sludge process with of around 0.1 day, the high discharge rate of sludge increases considerably the fraction of active biomass under the extended aeration condition with of around a day.
Although a constant concentration of the active biomass in the tank can be maintained without discharge of the sludge, the mass of total suspended solids increases continuously in such operation.The accumulated suspended solids consist mostly of nonbiodegradable solids in the influent and those produced from the self-oxidation of the active biomass.

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It is generally known that suspended matters or components differ from the dissolved in the relationship between their loadings and flow. We made clear that “n” in the expression of L= a·Qⁿ fairly dispersed with each rain event by the analysis of runoff loadings in an urban stream on twelve rain events for a half year.
The differences of both in the runoff characteristics was mainly depended upon the differences of their runoff behaviours in transit, especially, the temporary storage in river bed and watershed.This influence was comfirmed as the phenomena of high loadings for early stage of runoff and the fluctuation of “n”, that is, (ΔL/L) / (ΔQ/Q) in succession of runoff under one rain event.
The runoff of temporary storage also appeared in the variation of the relationship between cumulative loadings and cumulative flow under a rain event. This phenomena was caused by the differences of initial condition before the rain and runoff pattern, and gave the basis of introductin of temporary storage (S). However, on dissolved matters the sum of runoff loadings (∑L) is able to be estimated by the sum of flow (∑Q), that is, L=a· (∑Q) ⁿ.

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The character of ultraviolet absorbance spectrum of various surface water is statistically investigated.
In all districts, there is high degree of correlation between absorbance at 260mμ and COD, BOD, NH4-N, DO. Absorbande at 240mμ is correlated with electric conductivity.
From the principal components analysis, applicated to the ultraviolet absorbance spectrum, absorbances at 350mμ 260280mμ and 200mμ are usefull to classify the water quality.
Single and or multiple regression curves are examined to estimate some standard water quality index.

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Heavy metals are transported from the upper to the lower of river in three states; solved in water, adshered or adsorbed to floating matters, and together with the bed sediment adhering or adsorbing them. We examined in this report how mercury is transported in river. We confirmed that the membrane filter did not adsorb the mercury compound unspecifically and used the membrane filter to separate river water into soluble and unsoluble solid fractions. As a result it became obvious that most mercury compound was contained in the floating matters, which transported the mercury to the lower stream.

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