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Lohwacharin J.,University of Tokyo | Phetrak A.,University of Tokyo | Takizawa S.,University of Tokyo | Kanisawa Y.,Water Quality Management Center | Okabe S.,Asaka Purification Administration Office
Process Biochemistry | Year: 2015

This study aimed to evaluate the effects of residual ozone and chlorine and the backwash intervals on bacterial activities and density in pilot-scale biological activated carbon (BAC) filters by employing adenosine triphosphate (ATP) measurement and flow cytometry. The BAC filters received water treated by full-scale coagulation-filtration-ozonation processes. The attached bacterial density on the BAC increased rapidly in the first few weeks. The residual chlorine in the influent water caused ca. 1-log reduction of ATP-per-cell in the bacteria attached on the BAC and in the effluent and backwash waters. Extending the backwash interval made the bacteria attached on the BAC more resistant to ozone and chlorine, as suggested by the higher ATP-per-cell of the attached bacteria and the higher percentage of high-nucleic-acid intact bacteria in the backwash water. However, the attached bacterial density was higher for the shorter backwash interval operation than for the longer one during the high-ozone period. Although no significant difference in DOC removal rates was observed between the two BAC filters, fluorescence excitation-emission matrix analysis revealed that high residual ozone decreased the removal of aromatic proteins and soluble microbial product-like compounds. © 2015 Elsevier Ltd.

Kitada S.,Murayama Yamaguchi Reservoir Management Office | Oikawa T.,Water Quality Management Center | Watanabe S.,Water Quality Management Center | Nagai K.,Water Quality Management Center | And 7 more authors.
Desalination and Water Treatment | Year: 2015

Abstract: Radioactive iodine, one of the radionuclides released in the nuclear power plant accident on 11 March 2011, was detected in purified water at water purification plants (WPPs). However, information about removal of radioactive materials in actual water purification process was limited. Therefore, we investigated the removal of radioactive materials (iodine and cesium) immediately after the detection. It is found that non-radioactive iodine in water could be removed by the combined use of pre-chlorination and powdered activated carbon (PAC) treatment. The same result was also obtained in terms of radioactive iodine. Removal of non-radioactive iodine in WPPs was also investigated. Approximately, 60% of iodine was removed by combination of pre-chlorination (0.5–1.0 mg/L) and PAC (15–30 mg/L) in coagulation and sedimentation processes. In water purification process, cesium was mostly removed by coagulation and sedimentation; hence, radioactive cesium was not detected in purified water. It was confirmed that a thorough turbidity control is essential for the prevention of radioactive cesium contamination of purified water. Meanwhile, radioactive iodine in purified water has not been detected since 5 April 2011 and radioactive cesium since 22 March 2011, when the measurement was commenced. Moreover, dehydrated sludge including radioactive cesium has been treated in accordance with Japanese laws and regulations. © 2014 Bureau of Waterworks, Tokyo Metropolitan Government. All rights reserved.

Oikawa T.,Water Quality Management Center | Tsunoda T.,Water Quality Management Center | Nakahigashi H.,Water Quality Management Center | Shimoriku M.,Water Quality Management Center | And 2 more authors.
Journal of Water Supply: Research and Technology - AQUA | Year: 2015

In upstream reaches of the Tama River, musty odor substance (2-methylisoborneol (2-MIB)) began to be detected in 2008 and the concentration has been increasing thereafter. Then, in 2012, 2-MIB in raw water of a water treatment plant reached 210 ng/L. It was suspected that cause of musty odor was benthic cyanobacteria (Phormidium) which attached to stones on the riverbed. However, identification of the benthic Phormidium by microscopic observation had been difficult, thus genetic analysis was carried out. In genetic analysis, almost full-length 16S ribosomal DNA and internal transcribed spacer region gene of benthic Phormidium strains, which include the strain isolated from the Tama River, a strain in the Yoshino River (350 km away from the Tama River) and standard strains, were sequenced and compared. From homology search of these sequences, 2-MIB producing Phormidium in the Tama River was classified into Phormidium autumnale. Furthermore, it was found that P. autumnale in the Tama River was the same species in the Yoshino River. In addition, the result of in vitro cultivation shows that the P. autumnale inhabiting the Tama River thrives and produces more 2-MIB at high temperature, but it can grow and produce 2-MIB even at low temperature. © IWA Publishing Journal of Water Supply: Research and Technology-AQUA 2015.

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