Model dye wastewater prepared by adding Bordeaux S (BS) dye was treated by a fixed bed of biological activated carbon (BAC) in comparison to granular activated carbon (GAG) treatment of the wastewater. The total removal efficiency of color and COD in the BAC and GAC column, respectively, was studied. It became clear that the biodegradation rate of BS dye was low because of the low growth rate of Y-1 culture, which was isolated from surface of BAG particles. From the study of BS dye adsorption on Y-1 culture, it was found that the adsorption rate was very high, and adsorption capacity increased greatly when the equilibrium concentration became higher. The adsorption capacity of Y-1 culture which exists on SAC surface can be increased greatly, because the concentration of BS dye on the surface of carbon particles becomes higher due to adsorption. It can be considered therefore, that the adsorption of BS dye on Y-1 culture plays an important roles for removal of BS dye by BAC treatment.

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The Salmonella/microsome assay (Ames test) is a useful method for screening mutagens in complex environmental mixtures such as river water and sediment. However, no quantitative and generalized method to evaluate mutagenicity of complex mixtures like sediment has yet been established. In this study, the relationships between coexisting substances and the optimum amounts of S9 were investigated for the Ames mutagenicity tests of complex sediment extract. The strain Salmonella typhimurium TA98 was used.
o-Phenylphenol (o-PP) and di-2-ethylhexyl phthalate (DEHP), which are commonly found in an aquatic environment, and two kinds of sediment extract were used as model coexisting substances. The sediment extract was prepared by extracting with dichloromethane/ethylalchol (4: 1) and refining with reduced-Cu column. The mixtures of these coexisting substances and a fixed amount of the standard mutagens, 3-amino-l-methyl-5H-pyrido [4,3-b] indole (Trp-P -22) or 2-aminofluorenc (2-AF), were tested in changing amounts of S9.
Consequently, it was found that the coexistence of o-PP and the sediment extracts shifted the optimum S9 amounts of the standard mutagens and much influence on the results of the mutagenicity test. On addition of 20μl of S9, o-PP and sediment extracts gave the toxic influence on the TA98 strain, and was more inhibitory in greater amounts. On addition of 50μl, the mutagenicity decreased in the coexistence of over 200μg of the sediment extract, though 2 -AF showed high mutagenicity in the coexistence of c.a. 100μg. It was suggested that the influence was associated with the reactions between S9 and coexisting substance, especialy midium polar substances.

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Photoreactivation of microorganism following UV disinfection is one the research topics for assessing the performance of UV disinfection, because there is little consensus on how the visible light intensity relates to the photoreactivation rate and the maximum survival in wastewater treatment processes.
Obvious photoreactivation by a fluorescent lamp was observed in the case of indicator bacteria (heterotrophic bacteria, coliform bacteria, fecal coliform) in raw sewage, but not E. coli B and E. coli K12 A/λ.(F⁺). Inactivation of fecal coliform was observed simultaneously during photoreactivation process by sunlight.
Dose rate at 360nm wave length as visible light intensity showed it to be an useful good indicator for assessing the photoreactivation rate and the maximum survival by both of the fluorescent lamp and sunlight.

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The effect of resuspension on nutrient release from sediments was studied by field observations and laboratory experiments. Field observations were carried out in two shallow estuaries, Matsushima Bay and Shiogama Port. Three laboratory experiments reflecting the conditions of continuous resuspension, intermittent resuspension and a static state were carried out using estuarine sediment cores. In the estuary, a fluid mud layer was formed just above the sediment and an organic surface layer with an ignition loss of over 20% was found at the top of the sediment in the summer, which increased the concentration of suspended solids during resuspension. The resuspension caused by a tidal current began a little before the low tide and continued until the high tide. It was found that the release rate of dissolved inorganic nitrogen under conditions of continuous resuspension was higher than that under a static state, because the release of ammonium nitrogen from pore water in the sediments occurred simultaneously with that from the sediment in the former case. The nitrification rate under conditions of intermittent resuspension was lower than that in the other two systems. On the other hand, phosphate release was not observed under an aerobic static state. It was also recognized that the concentration of phosphate decreased at the beginning of resuspension, and increased thereafter.

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