The effects of variations of fluid velocity and sea water concentration due to tidal motion on adsorption of anionic surfactants to suspended solids (SS) were examined. The laboratory experiments gave the following results.
1) There were no significant effects of fluid velocity and pH on the adsorption of linear alkylbenzenesulfonates (LAS) to SS.
2) LAS adsorption was affected by electric conductivity due to the high concentration of coexistent substances. As the electric conductivity increased, the LAS adsorption capacity of SS increased.
On the basis of the above results, field observations of the tidal river in Tokushima city were carried out. The following results were obtained concerning the adsorption of MBAS to SS.
3) The COD of SS increased and the SS concentration in water decreased the MBAS adsorption, respectively. These results were similar to those found in former studies.
4) As the electric conductivity of water increased, the MBAS adsorption capacity of SS was likewise increasd. The result see 2) obtained by the laboratory experiments was confirmed by the field observations.
5) The Freundlich isotherms were applied. k was formulated by the parameters which describe the above characteristics under the assumption that n=1.
In the tidal river, where the coexistent substance concentration has large variations due to sea water intrusion, the coexistent substance has a significant effect on the anionic surfactants adsorption to SS.

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Phosphorus concentrations (DIP, DOP, PP) were measured about 12 Km downstream from Namitakidera in the Kurose River basin in three periods under different discharge of river water. Their concentrations were simulated by using a tank model from the view point of unsteady state. The simulated values of the concentrations reasonably agreed with the observed ones.
From the analysis of phosphorus concentrations in dry weather (10th December 1986), it was found that the ratio for direct effluence of phosphorus load into river (L₀) was 0.50-0.60. It was suggested that 0.35 g P·d^-1·capita^-1 was relevant to the unit for phosphorus load of gray water. The mass balance of phosphorus in river was estimated on the basis of this simulation results.

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The photolysis of 2-chlorophenol in natural waters was investigated at pH 11.0 using monochromatic light (500 W xenon-lamp + monochrometer). Water samples were concentrated from 5 to 20-fold. The concentration of 2-chlorophenol was 1.6×10^-6 mol·l^-1 (0.20 ppm). The following results were obtained.
(1) The indirect photolysis rate constants in an infinitesimally thin layer increased linearly with increasing DOC of water samples as predicted theoretically.
(2) The percentage contribution of indirect photolysis to overall one at 300 nm was about 50% and increased with increasing wavelength. The overall photolysis rates calculated with solar illumination intensity showed a maximum at 325 nm.
(3) The quantum yields of direct photolysis were 0.34-0.43 at all wavelengths and those of indirect photolysis decreased from about 10^-3 (300 nm) to 10^-5 (350 nm).

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The activated sludge was entrapped in acrylamide gel, and elastic pellets containing activated sludge were obtained. The pellets were dried and preserved at a room temperature. After 14 days, the volume of the pellets had shrank by 38%, and after 30 days, by 12%. After restoration in wastewater, the pellets swelled to their original size. During preservation periods of up to 30 days, 51% of respiratory activity remained. With the pellet preserved for 30 days, synthetic wastewater of 300 mg-BOD·l^-1 was treated at a high loading rate of 1 kg-BOD·m^-3·d-1. BOD concentration of the effluent could be reduced to 20 mg·l^-1 or less, and the removal was 95%.

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