Quantitative Evaluation of Optimal Stirring Conditions for Flocculation of Red Soil Particles

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K06295
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 41030:Rural environmental engineering and planning-related
• Research Institution: University of the Ryukyus
• Principal Investigator: Nakandakari Tamotsu 琉球大学, 農学部, 准教授 (70537555)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 赤土 / フロック / 沈砂池

Outline of Final Research Achievements

In order to develop the technology necessary to improve the function of a settling basin as a countermeasure against red soil runoff, we worked on research about red soil particles flocculation. The relationship between stirring conditions and red soil particles flocculation was investigated by an application experiment of the jar test. As a result, the turbidity became transparent more quickly by stirring, and the formation effect of red soil particles flocculation by stirring was able to be confirmed. It was found that the newly devised stirring index has a correlation with the stirring energy, which is useful for grasping the formation effect of red soil particles flocculation. From the results of flow velocity measurements using PIV, it was found that complex velocity distributions and vortices created by stirring are necessary for red soil particles flocculation.

Free Research Field

水利環境

Academic Significance and Societal Importance of the Research Achievements

沖縄地方では、降雨時における畑の土壌侵食に伴う赤土の流出がサンゴ礁海域を代表とする水環境を汚濁している。とくに農地において、沈砂池をはじめとする種々の対策が実施されてはいるが、赤土微粒子を除去することは難しく、対策の改良が求められている。農地に設置された沈砂池には付帯していないフロック形成装置を導入すれば赤土微粒子の流出を防止することができると考えられるが、その装置の設計に必要な技術は開発されていない。本研究は、農地の沈砂池の機能改善に必要な赤土フロック形成技術を開発することによって赤土の流出を防止し、水環境を保全することを目標としている。