Concentration of linear alkylbenzenesulfonates (LAS) in the Lake Teganuma estuary indicated a seasonal variation and a downstream decrease. The downstream decrease in the studied section varied seasonally, and the average was nearly 60 % during 1987-1988. As to explain the decrease, we investigated biodegradation of LAS in water, diffusive exchange of dissolved phase LAS through the sediment/water interface, and settling of adsorbed phase LAS. The biodegradation rate constant (between 0.06 and 3.33d^-1) in water and the diffusive flux rate (between -0.157 and 0.022mg·m^-2·h^-1) from water to sediment were obtained from field observations and experiments. Based on these information, a mathematical model was applied to simulate the downstream decrease of LAS in water. With this model, nearly 10 % of the total LAS from the river was found to be transported to sediment both in summer and winter. The settling flux of LAS in the lake estuary was ten times greater than the diffusive flux. The sessling flux was ten times smaller than the disappearing flux by biodegradation in summer but was the same level in winter.

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Thiocyanate degrading bacteria which were immobilized in photocrosslinked resin polymer were examined in biomass changes and specific activities of thiocyanate degradation under various culture conditions, i.e. aerated, oxygen supplied, shaken and continuous culture systems.
Biomass and specific activities of thiocyanate degradation in aerated culture system were higher than those in reciprocally shaken culture system. Oxidation rates of KSCN-S to SO₄^2--S in the oxygen supplied and shaken culture systems were 81.9-97.9% and 80.7-84.1%, respectively, indicating oxidation of thicyanate and growth of cells in the immobilized beads have been affected by the oxygen concentration. Thiocyanate degrading bacteria formed thick mats on the surface of immobilized beads after long term cultivations under continuous and batch systems. The specific activity of thiocyanate degradation of detached immobilized beads is lower than that of non detached immobilized cells.

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The purpose of thie study is to make clear the decomposition and removal of musty odor producing filamentous blue-green alga Phormidium tenue by ciliata Trithigmostoma cucullulus and musty odor degradable bacteria using monoxenic batch cultivation system and bio-film treatment process. The result obtained from this study are as follows.
1) The predacious velocity of T.cucullulus which have special oral organ called cytopharingeal basket on P.tenue was about 10 to 30 μm·s^-1.2) The growth of T.cucullulus was highly accelarated in the addition of sludge extract. 3) The maximum specific growth rate (μ_max) and the number of the ciliata were 1.61 d^-1 and 1200 N·ml^-1, respectively. 4) It was found that 2-methylisoborneol could be decomposed under the condition of pH value below 4 as was observed in the food vacuole of T.cucullulus. 5) The decomposition of algal cell P.tenue and musty odor substance 2-methylisoborneol were remarkably enhanced in the continuous bio-film treatment system coexisting T.cucullulus and musty odor degradable bacteria.

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