2001 Fiscal Year Final Research Report Summary
Countermeasure for prevention of reservoir eutrophication by controlling thermo-solutal convection
| Project/Area Number |
12555148
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
水工水理学
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| Research Institution | Kobe University |
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Principal Investigator |
MICHIOKU Kohji Dept. Architecture and Civil Engin., Kobe Univ., Professor, 工学部, 教授 (40127303)
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| Co-Investigator(Kenkyū-buntansha) |
OONARI Hirofumi Dept. Civil Engin., Tokuyama Junior College, Professor, 土木建築工学科, 教授 (30045041)
MIYAMOTO Hitoshi Dept. Architecture and Civil Engin., Kobe Univ., Research Associate, 工学部, 助手 (50283867)
KANDA Tohru Dept. Architecture and Civil Engin., Kobe Univ., Professor, 工学部, 教授 (30029144)
MATSUO Katsumi Dept. Civil Engin., Chuden Engineering Consultants co. ltd, Chief Engineer, 環境調査室, 課長(研究職)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Reservoir eutrophication / Akae Bloom / Aeration / Water purification / Micro-bubbles / Thermosolutal Convection / Internal Circulation / Hypolimnion |
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| Research Abstract |
An in-situ experiment on hypolimnic aeration has been carried out in a eutrophic reservoir. Micro air bubbles were discharged into the anaerobic hypolimnion to supply oxygen and improve water quality. The system has been in operation since March in 1999. The aerator unit was so designed that the hypolimnic water is aerated without disturbing thermal stratification. At the beginning of the experiment, however, because of unsuitable design of nozzle structure, the aerator generated unexpectedly large bubbles and promoted vertical mixing. Although the hypolimnic water was aerated due to aerobic water entrained from the epilimnion, this was not the hypolimnic water aeration what we expected. The aerator structure was then modified to prevent macro-bubble generation and the hypolimnic water was successfully aerated without destratification. After all, in the course of the experiment the reservoir has experienced three different dissolved oxygen regimes, i.e. (1) no aeration, (2) aeration with vertical mixing, (3) aeration with little vertical mixing. The present study is to discuss how the dissolved oxygen affects hypolimnic water quality by comparing the field data from the three different DO regimes. The results provide useful information in designing an aeration system as a countermeasure against hypolimnic water eutrophication.
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