The objective of this work was to elucidate the impact of different kinds of vegetation in the catchment of a pond on the water quality. The study area covered the irrigation reservoirs distributed over the Hiki hilly areas in Saitama Prefecture. Five reservoirs were chosen for the investigation based on a local survey after pre-selection using the geographic information system （GIS） software. The catchments were composed of different types of vegetation such as deciduous forest （e.g., sawtooth oak “Kunugi”） and coniferous forest （e.g., Japanese cedar “Sugi” or Japanese cypress “Hinoki”）. The concentration ranges （mg・l^－1） of DOC, COD_Mn, total inorganic nitrogen （TIN）, and Chl－a in the surveyed reservoirs were found to be 1.6–3.0, 3.9–6.4, 0.52–2.4, and 0.0024–0.011, respectively. In the reservoirs with deciduous forest-dominated catchments, NH₄－N/TIN and NO₃－N/TIN were ＞30％ and ～60％. However, in the reservoirs with coniferous forest-dominated catchments, NH₄－N/TIN and NO₃－N/TIN were ＜20％ and ～70％. Thus, the water quality of the reservoirs is dependent on the catchment vegetation, with typical abundance ratios of inorganic nitrogen more likely in those with conifer forest or deciduous forest-dominated catchments.

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In order to enhance the photocatalytic activity of AgBr/Ag₃PO₄, Ag nanoparticles (NPs) was employed as dopant in the development of heterojunction Ag/AgBr/Ag₃PO₄. This Ag/AgBr/Ag₃PO₄ (Ag/BrP) heterojunction has been developed by simple photo-deposition method. The results of photocatalytic activity test using methyl orange as targeted pollutant clearly indicated that the activity of Ag/BrP increased up to maxima as a function of Ag NPs loading and tended to decrease upon further loading. The Ag/BrP with the best photocatalytic activity under simulated solar light condition showed much more efficient than AgBr/Ag₃PO₄ in degrading microcystins (MC－LR, －YR and －RR) which are a group of hepatotoxins. Besides, MC－YR was observed to be much more easily removed than MC－LR and MC－RR since it can strongly adsorb onto the surface of the catalyst. These results indicated that an appropriate dosage of Ag NPs on AgBr/Ag₃PO₄ could accelerate the photocatalytic activity of AgBr/Ag₃PO₄ by the combined actions among Ag NPs, AgBr and Ag₃PO₄.

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Geosmin is a nuisance secondary metabolism compound by some actinomycete and filamentous cyanobacteria. In waterworks, geosmin is a contaminant, which is resistant to conventional water treatment such as coagulation and sedimentation. There is some information about geosmin degradation in the presence of various organic matters. This study examined influence of glucose, sodium acetate and acetic acid on geosmin degradation by biofilm. The results revealed that presence of glucose and sodium acetate enhanced geosmin biodegradation. On the other hand, inhibition effect on geosmin biodegradation occurred from second day of acetic acid condition. The 16S rDNA copy number did not change dramatically during the experiment in organic carbon additional condition, but ATP concentration increased in glucose condition at 2^nd day. This result might be showed that geosmin biodegradation was co-metabolism in the presence of glucose or sodium acetate, which played as a role of secondary substrate.

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This study was conducted to develop the formation and collection methods of resting cell of Anabaena macrospora, in order to clarify its physiological characteristics. A. macrospora was cultivated at water temperature of 20℃, illumination of 5,000Lx, and light-dark cycle of 12L－12D. After 4weeks cells entered the stationary phase, and resting cell began to be formed. However, resting cell began to germinate after 6weeks. By putting the medium containing both resting cells and vegetative cells in a separatory funnel, it was possible to separate precipitated resting cells from floated vegetative cells. In addition, an evaluation method of germination of A. macrospora resting cells was established by incubation of resting cells for a certain period in closed cell counting plate. We confirmed the formed resting cell had germination ability.

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