Removal of fluoride ion by lime treatment from waste water is insufficient to meet waste water standard, so the adsorption process using activated alumina was studied. Adsorption capacity, mass-transfer rate, effectiveness of regeneration methods and performance of repeated column adsorption were measured and examined to seek the optimam operating condition.
Results obtained are as follows.
1. Sorption of fluoride ion on activated alumina consists of adsorption on pore surface and absorption into solid phase. The latter proceeds slowly and sorbed ion does not easily desorb. So, absortion into solid cannot be utilized in cyclic adsorption processes.
2. Rate of surface adsorption is pore-diffusion rate controlling. Intra-particle mass-transfer coefficient can be estimated from properties of pore structure of adsorbents and molecular diffusivity.
3. Spent adsorbents of activated alumina are preferably reclaimed using aluminium sulfate solution.Effects of concentration, volume and space velocity of regeneration solution on the degree of desorption are presented.

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The increase in the filtration rate for such high-resistant slurries as microcystis was studied under constant-pressure conditions, using a dynamic filter with a rotating cylinder. The slurry was subjected to an intensive shear in the annular filter chamber between two co-axially arranged cylinders ; the inner cylinder (rotor) with the filter medium being the rotating part. The filter cake was continuously swept from the filter medium by the induced flow, thereby accomplishing filtration at a high rate. A further increase in the thin-cake filtration rate was also experimentally assured by adding Korean kaolin as a filter aid. The increase in the filtration rate was obtained by sweeping the filter cake more completely with the aid of both the kaolin and the induced flow, and was marked when the mass ratio of kaolin to microcystis was about 5. It has become apparent that the dynamic filtration performance was mainly dependent on the angular velocity of the rotor, the filtration pressure and the clearance of the filter chamber, and that an increase in the filtration pressure did not necessarily result in an improvement in the dynamic filtration rate.

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Turbidity is a fundamental parameter for the analysis of water pollution and for the monitoring of the plant performance in water and wastewater treatment. It is, however, very difficult to evaluate turbidity correctly by an instrument, because the parameter is closely related with the human sensation.
In this study, the authors tried to clear the fundamental factors of turbidity for the purpose of measuring it automatically. Turbidity judgement of the various samples was made by 15 panellists, and then the physical quantities of the samples were measuered. By means of multidimensional scaling, two and three dimensional configurations were obtained, and it was concluded that the structure of the factors of turbidity was two dimensional. Furthermore, by means of the multiple regression analysis, the relations between the factors and the physical quantities were obtained as follows : first, it was cleared that the fundamental factors of turbidity were the luminous transmittance and the projected area diameter, and second, the axes of the fundamental physical quantities were drawn on the two dimensional configuration diagram.
The factors clarified by this study are the physical quantities, and if the functional relation between the factors and turbidity is defined, the automatic measurement of turbiditity is possible.

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For the determination of total nitrogen in lake waters, three methods were proposed by the Agency of Environment in 1982. Among these methods, a simplest method was an ultraviolet spectrophotometric method after digestion of sample water mixed with potassium peroxodisulfate and sodium hydroxide in an autoclave at 120°C for 30min.
However, serious interference by bromide ion is observed when this method is applied to the determination of nitrogen in sea water samples.
For overcoming the above drawback of the method, a new spectrophotometric method was proposed in this paper. Dilute sea water sample with equal amount of pure water and digest it according to the procedure proposed by the Agency of Environment. Measure the absorbances at 210nm and 220nm or at 215nm and 220nm. Calculate the total nitrogen concentration in the sample.
The proposed method was applied to the determination of total nitrogen in sea water samples collected in Osaka Bay. The results of the determination agreeded with the values obtained with the conventional spectrophotometric method using the N- (1-naphthyl) ethylenediamine reagent.

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