1998 Fiscal Year Final Research Report Summary
An in-situ denitrification treatment of nitrate contaminated water permeated through soil layer by applying a bio-electro method
| Project/Area Number |
09480131
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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 | 一般 |
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| Research Field |
環境保全
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| Research Institution | GUNMA UNIVERSITY |
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Principal Investigator |
KURODA Masao Gunma Univ.Dept of Civil Eng., Professor, 工学部, 教授 (40008446)
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| Co-Investigator(Kenkyū-buntansha) |
WATANABE Tomohide Gunma Univ.Dept of Civil Eng., Research associate, 工学部, 助手 (60251120)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Bio-electro-method / denitrification / nitrate ion / electrolysis / soil permeation / in-situ treatment |
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| Research Abstract |
A novel in-situ denitrification treatment by applying biological and electrochemical method was proposed for nitrate contaminated water permeated through agricultural land soil such as orchards from the view point of prevention of nitrate contamination of groundwater. In the proposed method, biological activated carbon or charcoal layer with relatively high density of denitrifying bacteria was set up in the soil and electrodes were set up under the layer of abundant denitrifying bacteria. Hydrogen gas was produced and was utilized for nitrate reduction in the soil when electric current was applied. in this study, feasibility of the proposed method was demonstrated experimentally by using a simulated soil column. A mathematical model including biological denitrification, electrolysis of water and mass transfer was established and the factors influencing for the nitrate removal was investigated theoretically by the numerical calculation. Compared with the control experiment without electric current, denitrification rate was increased by applying electric current to the electrodes. The denitrification proceeded with simultaneous utilization of hydrogen gas produced by electrolysis of water and organic matter existing in the simulated soil. The simulated soil layer was unsaturated condition and had about 0.3 of volumetric moisture content, about 0.15 cm^3/g-soil of partition coefficient and about 0.5 of voidage. So, the denitrification was proceeded under unsaturated soil condition. Results of numerical calculation based on the established model for the simulated soil column was in good agreement with the experimental data. The numerical results suggested that denitrification rate of the proposed process in this study was influenced by thickness of abundant denitrifying bacteria layer in the soil and electric current. Further investigation is needed for enhancement of current efficiency, treatment stability for long term and arrangement of electrode in the soil.
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