1993 Fiscal Year Final Research Report Summary
A Basic Study on the Seawater Purification Function of the Biofilm Process Method and Its Strengthening
| Project/Area Number |
03452215
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hydraulic engineering
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| Research Institution | OSAKA CITY UNIVERSITY |
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Principal Investigator |
OSA Kazuki Osaka City Univ., Faculty of Engrg., Professor, 工学部, 教授 (60047230)
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| Co-Investigator(Kenkyū-buntansha) |
SHIGEMATSU Takaaki Osaka City Univ., Faculty of Engrg., Assoc. researcher, 工学部, 助手 (80206086)
KANJO Yoshinori Osaka City Univ., Faculty of Engrg., Assoc. researcher, 工学部, 助手 (90177759)
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| Project Period (FY) |
1991 – 1993
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| Keywords | rockfilter-type biofilm process / rockfilter-type oxidation process / coefficient of reaction rate / coefficient of removal / coefficient of oxygen consumption rate / coefficient of reoxygen rate / seawater purifiation / removal ratio |
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| Research Abstract |
Laboratory experiments were performed to observe the characteristics of removal of organic matter, plant nutrients and suspended solids from real seawater through the rockfilter-type biofilm process. Based on the results of a series of systematic experiments, it was found that the removal process of COD, SS and so on through the rockfilter-type biofilm process could be expressed by the first-order reaction equiation and the coefficient of removal rate in the equation depended mainly on the mean velocity U of seepage flows through the rockfilter and the specific surface area A of the rockfilter. The coeffecients of removal rate for COD and SS and the coefficient if oxygen consumption rate were formulated empirically by the two physical quantities U and A.
Applying these formulated purification characteristics of the rockfilter-type biofilm process to rubble embankments, the process of seawater purification due to tidal actions in a restricted coastal area enclosed by rubble embankments were predicted by means of the FEM.
As a result, it was seen that the ultimate removal ratios through rubble embankments for COD and SS do not depend so much on the layout of embankments and the size of an enclosed coastal area, but mainly depend on the length of embankment. The ultimate removal ratio for SS increases considerably with the increase of the length of embankment up to about 15m and becomes almost constant when the length is larger than about 25m. As for COD, it increases gradually with the increases of the length. It may be finally proposed that the optimum length of embankment is about 10m to 12.5m.
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