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Kobayashi Y.,Hanshin Water Supply Authority | Itoh M.,Japan National Institute of Public Health | Yamada T.,Gifu University | Akiba M.,Japan National Institute of Public Health | Matsui Y.,Hokkaido University
Water Science and Technology: Water Supply | Year: 2013

One effect of climate change on the water supply systems in Japan may be a sharp increase in the raw-water turbidity following heavy rain. The objective of this study was to evaluate water treatment performance with a sharp increase in raw-water turbidity. This evaluation was carried out from the perspective of turbidity response by a pilot-scale plant using sand filtration and membrane filtration with coagulation-sedimentation pretreatment. Two coagulants were used; namely, polyaluminum chloride with a basicity of either 72% (PACl-72%) or 51% (PACl-51%). Raw-water turbidity was increased from 5 to 300 TU by adding kaolin suspension. In the case of sand filtration, the filteredwater turbidity increased during the filter stabilization period. An increase in the coagulant dosage produced a more rapid decrease in the filtered-water turbidity and shortened the filter stabilizing period. Filtered-water turbidity decreased more rapidly for PACl-72% than for PACl-51%. In the case of membrane filtration, an increase in raw-water turbidity caused no significant increase in filteredwater turbidity or transmembrane pressure. These results demonstrated that, although neither filtration technique completely failed, membrane filtration was more robust than sand filtration against a sharp increase in raw-water turbidity. Copyright © IWA Publishing 2013.

Kosaka K.,Japan National Institute of Public Health | Asami M.,Japan National Institute of Public Health | Ohkubo K.,Japan National Institute of Public Health | Iwamoto T.,Kanagawa Industrial Technology Center | And 4 more authors.
Environmental Science and Technology | Year: 2014

N-Nitrosodimethylamine (NDMA), a potential human carcinogen, is known to be a disinfection byproduct of chloramination and ozonation. NDMA is formed during ozonation at water purification plants in the Yodo River basin, a major drinking water source in western Japan. An NDMA precursor, 1,1,5,5-tetramethylcarbohydrazide (TMCH) was identified in sewage containing industrial effluents via ultrahigh performance liquid chromatography-tandem mass spectrometry, and ultrahigh performance liquid chromatography-time-of-flight mass spectrometry, as well as nuclear magnetic resonance spectroscopy. The mean of the NDMA molar formation yield of TMCH upon ozonation in four water matrices was 140%. TMCH removal was low during biological treatment processes at a sewage treatment plant. The mean TMCH contribution to total NDMA precursors upon ozonation of the primary, secondary, and final effluents of the sewage treatment plant in January and February of 2014 was 43-72%, 51-72%, and 42-60%, respectively, while the contributions of 4,4′-hexamethylenebis(1,1-dimethylsemicarbazide) and 1,1,1′,1′-tetramethyl-4,4′-(methylene-di-p-phenylene)disemicarbazide, two other known NDMA precursors, were limited to 0.6% and 6.9%, respectively. Thus, TMCH was identified as the primary precursor yielding NDMA upon ozonation in the Yodo River basin. © 2014 American Chemical Society.

Nagashio D.,Hanshin Water Supply Authority | Tsuda I.,Hanshin Water Supply Authority | Mayahashi T.,Hanshin Water Supply Authority | Michishita K.,Hanshin Water Supply Authority | Hanamoto T.,Hanshin Water Supply Authority
Journal of Water Supply: Research and Technology - AQUA | Year: 2010

For the continuous and stable supply of safe drinking water, it is essential to not only design suitable water treatment plants that can handle the characteristics of raw water quality but also appropriately operate and control them. Controlling complicated water treatment systems using fewer operators essentially requires hazard identification and the establishment of the operation and control of the systems by a simple method of selecting the relevant data. Therefore, the Hanshin Water Supply Authority has supported operators by adding an advanced operation supporting feature to the renewed information-processing equipment in water treatment plants. Moreover, the Authority has investigated the problem of bromate, examined measures for its reduction, and applied the control measures to the information-processing equipment so that operators can promptly cope with the problem. This supporting system is effective in terms of the Water Safety Plan. The successive development of technologies while considering the aspects of operation and control is important for realizing a continuous stable water supply. © IWA Publishing 2010.

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