To estimate the manganese source in a dam reservoir and factors affecting manganese release from bottom materials, water and sediment qualities were investigated in the Ryorigawa Dam, which showed a significant increase in manganese concentration in its hypolimnion during the stratified period. In the bottom layer of the water column, the concentration of dissolved manganese correlated with that of dissolved calcium compared with other metals except iron. From the manganese distribution in the water column and manganese content of the sediment, it was estimated that the manganese source in the hypolimnion consisted of not only sediment but also rock or groundwater. Furthermore, the release of metals from bottom materials including rocks and sediment was studied in the laboratory. The releases of Mn from sediment and rock under anoxic condition were found to be promoted by its coexistence with soluble Ca and Fe(II), respectively.

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Pharmaceuticals and personal care products (PPCPs) and their metabolites continually flow into aquatic environments and are detected widely at significant concentrations. However, a comprehensive survey has not been conducted on PPCPs in aquatic environments in Japan. Moreover, the information about removal techniques for PPCPs, such as chlorination and ozonization, is limited. In this study, we investigated the occurrence of fifteen PPCPs in water samples (sewage water and river water) collected in urban areas of Japan and evaluated the PPCPs removal efficiencies of chlorination and powdered activated carbon treatment. PPCPs (except erythromycin, paroxetine, and fluvoxamine) were detected in almost all sewage water and river water samples. The highest value was observed in bezafibrate and detected at μg · l^-1 level. The concentrations of other PPCPs were one order of magnitude lower than that of bezafibrate. The removal efficiency of chlorination varied with the type of PPCPs, and the percentages of relative residuals of fibrates, fluvoxamine, carbamazepine, and ethenzamide were more than 50% at four hours after treatment. On the other hand, although removal rate was relatively low compared with that of chlorination, almost all PPCPs were satisfactory removed by powdered activated carbon treatment. These results suggest that a combination of these treatments could be effective for the removal of PPCPs.

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Pharmaceuticals and personal care products (PPCPs) such as antibiotics are widely used daily in hospitals and in the home, and are mainly excreted in urine. Treatments of PPCPs are not always sufficient and this may result in the occurrence of drag-tolerant microorganisms in the environment. In this study, the concentrations of the antibiotics levofloxacin (LVFX) and clarithromycin (CAM), total coliform count, fecal coliform count, dissolved DNA concentration, and TEM gene load in river water and discharges in Yodo River basin were analyzed and calculated. The concentrations of LVFX and CAM in the river, water samples and discharges were lower than the MICs, and E.coli JM109 grew on the LB agar plate with 100 ng · l^-1 antibiotics. The dissolved DNA in the discharges was found to be approx. 3.4 times higher than that in the river water samples. Although the TEM gene load decreased, the loads of LVFX and CAM remained at least 40% of their cumulative values. Microorganisms were isolated in the presence of 60 μg · ml^-1 ABPC, LVFX, CP, CM and VCM. 90% of the isolates from LVFX formed colonies in 60 μg · ml^-1 of ABPC, CP, CM and VCM.

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The anaerobic fate of six tetraalkylammoniums (TAAs) of the general formula R₄N⁺Br^- (R = C_1∼6) and with different alkyl chain lengths were investigated with laboratory-scale equipment. The results showed that tetramethylammonium, tetraethylammonium, tetra-n-propylammonium and tetra-n-butylammonium were degraded at different levels by anaerobic bacteria, but that tetra-n-pentylammonium and tetra-n-hexylammonium were difficult to degrade and had acute toxicity to biogas production at concentrations of over 50 mgC · l^-1. TAA showed increasing inhibitory activity to the metabolism of glucose with an increase in alkyl chain length under anaerobic condition. A complete bioactivity recovery of anaerobic sludge inhibited by five TAA (C_1∼5) could be achieved in two months. Nevertheless, the toxicity of tetra-n-hexylammonium to anaerobic microorganisms was irreversible, which was considered a substance highly hazardous to anaerobic microorganisms, particularly, methanogens.

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In this paper, we focus on perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in water environment of 21 cities in 10 countries (i.e., Japan, Singapore, Thailand, Malaysia, China, Vietnam, Taiwan, Sweden, Turkey and Canada). 1,160 samples were collected in different water environments (e.g., river, lake, wetland, reservoir, wastewater treatment plant, residence, and sea) from Nov. 2004 to Dec. 2007. The main conclusions obtained in this study are as follows: 1) The average concentration of PFOS in the surface water of rivers was more than 10.0 ng · l^-1 in Osaka. The average concentration of PFOS in residential tap water was more than 10.0 ng · l^-1 in Bangkok and Taipei. 2) The average concentration of PFOA in the surface water of rivers was more than 1,000 ng · l^-1 (median : 48.6 ng · l^-1) in Osaka, and it was more than 15 ng · l^-1 in Kyoto, Shenzhen, Khon Kaen, and Singapore. The average concentration of PFOA in residential tap water was more than 10 ng · l^-1 in Osaka and Okayama in Japan. 3) The number of cities where the difference between river water and tap water was less than 1.0 ng · l^-1 in the median concentrations of dissolved PFOS and PFOA was 16 for PFOS and 11 for PFOA, respectively. 4) The dissolved PFOS and PFOA concentrations in effluent were higher than those in influent of most wastewater treatment plants (16/19 for PFOS, 38/45 for PFOA).

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To protect the aquatic ecosystem, it is important to evaluate the toxicity of contaminated sediments. Moreover, the identification of chemical compounds responsible for the toxicity is needed for effective remediation. In this study, we aimed to identify the principal toxicants of urban river sediments, applying Toxicity Identification Evaluation (TIE) methods to the toxicity test with an ostracod (a benthic crustacean). The toxicity test was conducted using sediments amended with three adsorbents: Zeolite, Chelex-100 and Ambersorb-572. Four of the nine urban river sediment samples showed lethal toxicity to the ostracod, but none of the three adsorbents reduced the mortality of the ostracod. Growth inhibition was observed in all the samples; however, the addition of the carbonaceous adsorbent Ambersorb-572 suppressed the growth inhibition in the 6 samples. This indicates that hydrophobic substances in the sediments inhibit the growth of the ostracod.

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The concentrations and loadings of herbicides were investigated in two paddy fields (C and F) located around Lake Biwa. Herbicide loss was calculated from cumulative loadings from May to June (2003 and 2005), and the amounts of herbicide applied determined using a questionnaire were estimated to be 1.72% for Pretilachlor, 13.0% for Cafenstrol, 11.3% for Daimuron, 0.024% for Esprocarb, 8.0% for Molinate and 44.8% for Simetryn in C in 2003, and 16.9% for Daimuron and 14.3% for Mefenacet in F in 2005. Specific loss was calculated from herbicide loss, and average discharge on nonrainy days was obtained for seven paddy fields including C and F. To estimate herbicide loss, the multiple regression analysis used water solubility, Henry's law constant and soil adsorption constant as independent variables and specific loss as a dependent variable. The analysis of seven paddy fields showed a relatively low multiple correlation coefficient between the observed and calculated values. However, the analysis dividing the seven fields into two soil groups (Brown and Gray lowland soil group, and Gley soil group) improved the multiple correlation coefficient. In both soil groups, the most important contributor to herbicide loss was the adsorption constant of soil.

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To investigate the behavior of heavy metals in infiltration facilities receiving urban road runoff, we performed batch tests, which mimicked the sorption of heavy-metal species in road runoff by soakaway sediments. In soakaway sediment leachates, Ni and Cu were dominantly present as stable complexes, whereas most Zn existed as free ions and labile complexes. Ni and Cu in road runoff were adsorbed by all the soakaway sediments, whereas Zn was released from some soakaway sediments. Instead of the total Zn content in the soakaway sediments, the soluble fraction of Zn (i.e., the concentration of Zn released from sediments by deionized water) was a governing factor for the sorption from soakaways receiving road runoff; however, the behavior of Ni and Cu was not well explained by the total metal content, soluble fraction, and organic content. Desorption tests are useful in identifying soakaway sediments with limited adsorption capacities for Zn. The control and management of sediments based on desorption tests would be effective in minimizing groundwater contamination by heavy metals through infiltration facilities.

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A factor that controls maximum cell-specific nitrite oxidation rate was examined using the enrichment culture of Nitrobacter. Increasing or decreasing nitrite loading changed the content of Q-10, which served as a hydrogen carrier in the electron transport chain of Nitrobacter, which varied the maximum cell-specific nitrite oxidation rate. That is, the amount of oxidized nitrite, which is the sole electron donor, changed in the maximum cell-specific nitrite oxidation rate. Then, a dynamic change in maximum cell-specific nitrite oxidation rate was examined at short time intervals with increasing nitrite loading. Consequently, it was found that the maximum cell-specific nitrite oxidation rate began to increase after reaching a certain amount of oxidized nitrite. It was additionally indicated that the maximum cell-specific nitrite oxidation rate presumably had an upper limit and increased gradually near the limit. From the results, the response time and variation in maximum cell-specific nitrite oxidation rate are likely to be determined on the basis of the hysteresis of nitrite oxidation by nitrite-oxidizing bacteria.

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The water quality of city park ponds must be kept at certain levels because such ponds are important facilities for the comfortable life of citizens, and hence must be improved if heavy algal blooms occur frequently. Nitrogen, phosphorus, and chlorophyll concentrations were measured from 1999 to 2003 for four park ponds in Osaka city to investigate eutrophication and its causes. The means TN, TP and Chl.a concentrations ranges were 0.89-5.4 mg-N · l^-1, 0.12-0.67 mg-P · l^-1, and 24-310 μg · l^-1 respectively. In the comparison of water quality with those of irrigation ponds and other park ponds, three of the four ponds showed intermediate levels, and the remaining one showed much progressed levels. Treated sewage water, effluent water from a landfill site, and water from a pumping well accelerated the trophic state of ponds easily. A pond where a low Chl.a concentration but with high TN and TP concentrations existed. Thus, it was surmised that treated sewage water flowing into a pond indirectly influences pond water quality. Also, there was a park pond that decreases its TN concentration markedly in summer, and denitrification in the emergent plant zone was suspected. Since such characteristics may also contribute to water quality improvement, further studies are required.

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The Ogochi reservoir is one of the biggest dams for waterworks in Japan. We have been monitoring its water quality since its establishment. We introduced vertical curtains and some types of equipment in order to suppress algal blooms in the reservoir. The equipment showed suppressive effects against algal bloom expansion by suppressing the increase in surface temperature in the reservoir. An extensive flood in September 2007 induced a marked change in water quality. Because there was no turbidity before the flood, turbid water influx was observed in the depth range of 0-40 m near the dam. In the case of an extensive flood, it is necessary to operate the gates of the dam to form the secondary thermocline at an appropriate depth for discharging turbid water speedily.

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Changes of water temperature in Lake Biwa and the atmospheric factors that can affect the water temperature were analyzed. The water temperatures of effluent from sewage plants were found to increase, but it did not affect the annual mean temperatures of the lake surface water. The change pattern of surface water temperatures in summer resembles the change pattern of the number of hot days with temperatures exceeding 25°C. On the other hand, the change pattern of the water temperatures in winter resembles the change pattern of the number of cold days with temperatures dropping below 0°C. These results show that the water temperatures of Lake Biwa conspicuously increased in the past 30 years, and it was caused mainly by increasing atmospheric temperatures. It is suggested that the increase in the annual mean temperature of the deep water is affected by the absence of a decrease in the water temperatures in winter, and the increase in the annual mean temperature of surface water is affected by the increase in the water temperatures in summer.

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