| Project/Area Number |
12792010
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| Research Category |
Grant-in-Aid for University and Society Collaboration
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| Allocation Type | Single-year Grants |
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| Research Field |
水工水理学
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
KOMATSU Toshimitsu KOMATSU,Toshimitsu, 工学研究院, 教授 (50091343)
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| Co-Investigator(Kenkyū-buntansha) |
OSHIKAWA Hideo OSHIKAWA,Hideo, 工学研究院, 助手 (80311851)
INOUE Tetsunori INOUE,Tetsunori, 工学研究院, 助手 (70311850)
ADACHI Takahiro ADACHI,Takahiro, 工学研究院, 助教授 (50325502)
ISERI Yasushi West Japan Engineering Consultants, Inc., Environment Dept., Manager, 環境部, 課長(研究職)
SHIMATANI Yukihiro Ministry of Land, Infrastructure and Transport, Takeo River Office, Director, 武雄河川事務所, 所長(研究職)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥34,100,000 (Direct Cost: ¥34,100,000)
Fiscal Year 2002: ¥16,000,000 (Direct Cost: ¥16,000,000)
Fiscal Year 2001: ¥18,100,000 (Direct Cost: ¥18,100,000)
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| Keywords | water purification / surface water / hypolimnion / DO / dams / reservoirs |
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| Research Abstract |
Dissolved oxygen (DO) depletion, observed in eutrophic lakes and reservoirs, damages natural benthic organisms and induces nutrient release from the sediment. For this problem, a method which injects surface water, including a large amount of DO into the bottom layer in which DO is often depleted, is proposed. In this system, surface water injected into hypolimnion is cooled down to a water temperature of hypolimnion by a heat exchanger, and forms a thin oxic layer immediately above the sediment. As a result, nutrients release from the sediment could be suppressed by operating this system. Effects of surface-water injection into hypolimnion on water quality by this system had been already proved in small-scale area. In this study, therefore, we investigated the degree of water-quality restoration in case of continuous surface-water injection in hypolimnion by field experiments in Lake Tase in Iwate Prefecture, which has 6.0km^2 surface area. Experimental results in 2001 showed that DO concentration in hypolimnion was improved within at least 20m from the experimental equipment. After that, some devices were improved, therefore, expanded effect on the enhancement of DO concentration in hypolimnion was observed within at least 40m from the experimental equipment in 2002. In the period when DO concentration had been improved, PO_4^<3->-P concentration in hypolimnion kept decreasing and it was lowest at the system-installed point. The nitrification was also showed, accompanied by decreasing of NH_4^+-N concentration. These results suggested that injection of surface water into the hypolimnion made water quality in the bottom layer purified, and that appropriate and continuous injection of surface water could expand its water-purification ability, even in a large-scale water area like Lake Tase.
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