The occurrence of perchlorate in water purification plants in the Tone River Basin was investigated. The sampling of raw, processed and treated water at the plants was conducted between September and October 2006. Perchlorate concentrations in raw surface water taken from the upper, middle and lower Tone River Basin were 0.09-0.82, 0.15-15 and 0.15-2.7 μg · l^-1, respectively. Perchlorate concentrations in the upper Tone River Basin were low because the intake points were upstream of the discharge points of perchlorate. Perchlorate concentrations in the lower Tone River Basin were lower than those in the middle Tone River Basin. However, many of the perchlorate concentrations in the lower Tone River Basin were higher than those of the upstream of the discharge points of perchlorate; thus, it was found that perchlorate contamination of the surface water of the Tone River Basin was widespread. Perchlorate concentrations in raw ground water were < 0.05-40 μg · l^-1, and were high at some water purification plants. The shorter the distance between a well and the Tone River, the higher the pechlorate concentration in the well. Perchlorate concentrations in treated surface water of the upper, middle and lower Tone River Basin were 0.12-0.86, 0.22-14 and 0.23-1.8 μg · l^-1, respectively. Perchlorate concentrations in treated ground water were 0.08-24 μg · l^-1. It was shown, in this study, that perchlorate concentrations in treated water were lower than 24.5 μg · l^-1, the Drinking Water Equivalent Level (DWEL) of perchlorate defined by the United States Environmental Protection Agency (USEPA). From the comparison of perchlorate concentrations in raw and treated water at the same water purification plants, it was confirmed that perchlorate was not removed by either conventional or ozone/biological activated carbon (BAC) processes.

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The microbial community structures present in the thermophilic anaerobic digestion (TAD) of waste-activated sludge (WAS) and WAS were analyzed with molecular biological techniques including polymerase chain reaction-denature gradient gel electrophoresis (PCR-DGGE), real-time PCR, and cloning analysis. No significant differences in the microbial community structures present in TAD were observed among three reactors operated with hydraulic retention times of 10, 20 and 30 days. The microbial community present in TAD had less diversity than that present in WAS, and the sequences obtained in WAS were not present in TAD by the cloning analysis. In the TAD bacterial clone library, 97.5% of the total clones belonged to Firmicutes and 73.1% belonged to Coprothermobacter. Real-time PCR and cloning analyses revealed that the number of Methanosarcina thermophila, which is an acetoclastic methanogen, was larger than that of Methanoculleus thermophilus, which is a hydrogenotrophic methanogen, in terms of the numbers of copies of 16S rDNA.

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The bacterial community in a full-scale activated sludge plant for the food industry was investigated for about a year using terminal-restriction fragment length polymorphism (T-RFLP) analysis. The microscopic observation and 16S rDNA-based analysis indicated that the filamentous bacteria that were most frequently observed in this plant were Caldilinea-like bacteria, and that the actynomycetes bacteria that were dominant in the scum were Dermatophilus-like bacteria. The Tetrasphaera sp. of actynomycetes was also detected in the airation tank. According to the T-RFLP analysis, Caldilinea-like bacteria tended to appear frequently when diluted sludge volume index (DSVI) deteriorated unstably and easily. This suggests that these filamentous bacteria had a negative influence on sludge settleability, however, no correlation between the intensity of the T-RF and DSVI was observed. The influence of actinomycetes, on the other hand, was not clear, because these bacteria were detected even when DSVI was low and stable, although they increased when DSVI increased. Therefore, other factors also would have influences on sludge settleability in this plant. We also applied multidimensional scaling analysis on the bases of T-RFs to evaluate the whole bacterial community. The plots obtained were roughly divided into two groups, showing that the community structure changed depending on the sludge settling character.

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The behaviors of haloacetic acids (9 species) and trihalomethanes in the process of two water purification plants at Ogasawara Islands were investigated in August 2003 and January 2004. The total haloacetic acid formation potentials (THAAFPs) in raw water were within the range of 178-356μg · l^-1 with the concentrations in January exceeding those in August. The total trihalomethane formation potentials (TTHFPs) in raw water were within the range of 149-330μg · l^-1 with the concentrations in August exceeding those in January. After coagulating sedimentation treatment, the THAAFPs and TTHMFPs were within the ranges of 33-59μg · l^-1 and 44-86μg · l^-1, respectively. The removal ratios of THAAFP tended to be higher than those of TTHMFP. THAAFP correlated closely with potassium permanganate consumption and ultraviolet absorption (260nm). Following the coagulating sedimentation treatment, the use of chlorination caused a sudden decrease in the bromide ion concentration in water and generated trihalomethanes and haloacetic acids. Almost all of these concentrations gradually increased in tap water, with brominated haloacetic acids and trihalomethanes accounting for nearly all of the total haloacetic acids and total trihalomethanes.

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