With increasing importance of global-scale environmental issues in addition to regional environmental issues, an analysis of life-cycle environmental impacts becomes essential to the management of basin-scale artificial water use systems. In this study, we evaluate the life-cycle environmental impacts, i.e., global warming potential, acidification potential, eutrophication potential, mineral and fossil resource consumption and induced water resource consumption, of the water and sewage systems in Saitama prefecture and Tokyo's special city wards including advanced treatment and reclaimed water use, in consideration of their construction, operation, and dismantling of such systems. The results indicate that the induced impacts increase with the introduction of advanced water and sewage treatment, and that such impacts are mitigated by substituting reclaimed water for conventional tap water dedicated to flush water and general service water. The net induced impacts except mineral and water resource consumption increase in those scenarios where advanced treatment and reclaimed water use are introduced, while direct water intake and water pollutant emissions are reduced.

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Elucidating the function of the microbial community in activated sludge is the key to understanding its treatment mechanism. Although the removal of organic matter is one of the major functions of a microbial community, the substrate utilization of each microorganism remains to be fully elucidated. In this study, DNA stable isotope probing (DNA-SIP) was applied to the analysis of activated sludge collected from a full-scale wastewater treatment plant to identify glucose- and acetate-assimilating bacteria. Activated sludge was fed with ¹³C-labelled glucose and ¹³C-labelled acetate individually and incubated for 60 hours. Two different substrate concentrations (100 mgC·L^-1, 1000 mgC·L^-1) with the same loading (300 mgC) were tested for glucose, while only one substrate concentration (100 mgC·L^-1, 300 mgC of loading) was tested for acetate. The DNA-SIP experiment clearly revealed that glucose was assimilated by bacteria closely related to Aeromonas, Enterobacteriaceae, and Tolumonas regardless of substrate concentration or activated sludge collected on a different day. On the other hand, a different group of bacteria closely related to Acidovorax, Acinetobacter, and Dechloromonas was identified as acetate-assimilating bacteria. Although specific glucose- and acetate-assimilating bacteria responded to glucose and acetate, most of them were not predominant in the original sludge.

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In the present study, we investigated the feasibility of preventing cyanobacterial dominance using the anti-cyanobacterial allelopathic effect of the submerged macrophyte Myriophyllum spicatum. When the cyanobacterium Microcystis aeruginosa and the green alga Scenedesmus obliquus were cultivated at 25°C and 30°C in a mixed culture system, M. aeruginosa dominated; however the addition of eight allelochemicals equivalent to 288 g dry wt·m^-3 M. spicatum specifically inhibited the growth of M. aeruginosa and maintained it at less than that of S. obliquus, thereby confirming the prevention of M. aeruginosa dominance. As for the factors affecting the anti-cyanobacterial allelopathic effect, the competition with S. obliquus was the factor magnifying the inhibition of M. aeruginosa growth by the eight allelochemicals. Comparing the inhibitory effects observed at 25°C and 30°C, a lower temperature was preferable for the inhibition of M. aeruginosa growth by the eight allelochemicals.

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Using a biological treatment system with sponge cubes made of polyurethane foam, we succeeded in purifying wastewater with 400 to 1600 mg COD·L^-1, that dealt with a fluorescent-penetrant-inspection (FPI) process. Such wastewater contains slowly -biodegradable organic matter and is usually treated by coagulation processes. Field tests in two factories conducted for two years demonstrated that more than 80% COD was removed using the biological process with hydraulic retention time of 4 days, and that more than 97% COD was removed in the total system using the same biological process including post-treatment with granular activated carbon (GAC). Coagulants were not used. The n-hexane extract, whose concentrations in the wastewater were between 50 and 200 mg·L^-1, did not exceed 30 mg·L^-1 in the effluent from the bioreactor or 3 mg·L^-1 in the effluent from the GAC process. This biological system would be an alternative means of FPI wastewater treatment, which reduces chemical cost, the amount of secondary waste and the space needed for chemical tanks.

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We analyzed the relationship between water quality and freshwater fish in major first-grade river systems in northern Kyushu, Japan. The number of fish species preferring flowing water showed a significant negative correlation with BOD, while that of fish species preferring standing water showed no correlation with BOD. The results of receiver operating characteristic curve analysis indicated statistical relationships between the presence of several fish species and some environmental factors including BOD. The comparison between the periods 2001-2010 and 1991-2000 indicated that the number of fish species increased with improvement in river water quality.

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