Studies were carried out for the purpose of establishing a method for evaluating the pollution of river sediment by heavy metals, with easiness and good reproducibility. The result of studies were as follows.
1) Variations in the concentration of heavy metals by particle composition of the bottom sediment were examined. As a result, coefficient of variation was found to become smaller as the particle size become smaller. When particle size is less than 0.075mm, the coefficient of variation was reduced to about 10%, and variation by particle size became smaller.
2) As a result of comparison of metal concentrations in primary and secondary sediments in the bottom sediment, variation in the concentration of heavy metal were found to be influenced largely by metal concentrations of secondary sedimentation. Further, the variation in the metal concentrations in primary sediment are small, and these metal concentrations are supposed to form a back ground concentration at respective positions in a sample collection.
3) By comparing the ratio of heavy metals such as Zn ·Cd-1, etc., it was found that characteristics of respective river is possible to find out.

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Quantitative analytical method is developed to detect the dialkylaminoethylacrylate or polyacrylamide existing in water at low concentration. Photoelectric measurement is utilized to determine the turbidity with co-existence of inorganic salts ; sodium chloride, sodium sulfate and sodium chlorate.
The calibration curves are formed of linear over the concentration range from 0 to 50 mg El^-1 with cation dialkylaminoethylacrylate, from 0 to 20 mg El^-1 with cationic polyacrylamide (mannich), from 0 to 10 mg El^-1 with nonionic polyacrylamide, from 0 to 20 mg El^-1 and from 0 to 30 mg El^-1 with polyacrylamide of 20 mole % and 30 mole % anionic concentration. The detection limits are 1.2, 2.0, 0.02, 0.85 and 2.0mg El^-1 respectively. It has been found that the mechanism of this analytical method for anionic polyelectrolyte is clearly explained with Schulze-Hardy's low and its mechanism is different from that of cationic polyelectrolyte.

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Fluidized-bed granular activated carbon (GAC) anaerobic reactors have been under development to treat wastewaters which contain high concentration of inhibitory and/or refractory compounds as well as easily biodegradable organic compounds. The processes are characterized by the combined physical and biological removal mechanisms ; that is, adsorption by the GAC medium and biodegradation by the attached bacteria on the medium. A simple mathematical model, which incorporates these two mechanisms and was developed for the artificial waste-water containing 3-ethylphenol and acetic acid, was applied to the simulation of the gasification wastewater treatment after a little modification. The values of constants and coefficients included in the model equations were estimated with values obtained for the artificial wastewater and the experimental data for one case of three cases of the experiment simulated. It was demonstrated that the modified simple model is able to simulate the changes with time in effluent soluble COD, COD retained in the GAC medium and daily methane production under different operational conditions. And qualitative and quantitative relationships between each state variables and predominant mechanisms under each operational condition were discussed through the comparison between experimental data and simulated results.

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This study was conducted for the purpose to make clear the effect of hydraulic retention time (HRT) on the removal and decomposition of Microcystis viridis toxic substance cyanoviridin in the bio-film reactor existing small metazoa, and the stability of decomposition of cyanoviridin in the continuous bio-film reactor using high performance liquid chromatography. The results obtained from this study are as follows.
(1) Toxic substance cyanoviridin was removed more than 70% under short HRT such as 1.5h and more than 90% under long HRT such as 12h (2) High removal efficiency of cyanoviridin could be accomplished in the continuous bio-film treatment process for long term. (3) The accumlations of cyanoviridin could not almost be recognized in the bio-film, therefore, it was suggested that cyanoviridin could be decomposed efficiently by biological functions. (4) It was made clear that the bio-film treat-ment process was effective method to remove the both algal cells and toxic substance cyanoviridin in the water purification process from extremely eutrophied lake water.

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