1992 Fiscal Year Final Research Report Summary
A STUDY ON THE METHOD OF REMOVAL OF NITROGEN AND PHOSPHORUS FROM AGRICULTURAL DRAINAGE WATER
| Project/Area Number |
02660233
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
農業土木
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| Research Institution | NIIGATA UNIVERSITY |
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Principal Investigator |
MISAWA Shinichi NIIGATA UNIV., FACULTY OF AGRIC., ASSOCIATE PROF., 農学部, 助教授 (30018791)
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| Co-Investigator(Kenkyū-buntansha) |
OOKUBO Hiroshi YAMAGATA UNIV., FACULTY OF AGRIC., ASSOCIATE PROF., 農学部, 助教授 (80203735)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Water quality / Removal rate / Total nitrogen / Total phosphorus / sedimentation |
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| Research Abstract |
It was found that almost all nitrogen in the drainage water from agricultural land are soluble forms except during the paddling and transplanting season, and phosphorus is always in the insoluble form. Phosphorus combines with iron(Fe) except during the paddling and transplanting season, in that season phosphorus combines with soil particles.
In paddy fields on alluvial planes like the Niigata planes, by deoxidization, iron in the paddy soils becomes soluble, so phosphorus combined with the iron also becomes soluble. Through under-drains, water containing soluble phosphorus flows out into drainage channels.
In the channels, by oxidization phosphorus changes to the insoluble form again and sinks to the channel bed when drainage discharge is small, during floods the sediments rises up and flow down the channels.
If characteristics of sedimentation of phosphorus compounds could be utilized, it would become possible to remove phosphorus from the agricultural drainage water. It was found that the sediments on the channel beds, contains 10 times of phosphorus in paddy soil. Phosphorus volumes contained in sediments from the drainage channel located in front of the Shirone drainage pump station, reached nearly 10% of total effluent phosphorus.
So there is a possibility of removing a lot of phosphorus from agricultural drainage water by artificial settling basins. It is almost impossible to remove nitrogen by sedimentation.
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