Effects of Measures to Reduce and Improve the Water Quality of Acid Mine Drainage from a Closed Mine

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  • TOMIYAMA Shingo
    Faculty of Engineering, Hokkaido University
  • HACHIYA Kohei
    Graduate School of System Engineering, Hokkaido University Present: Idemitsu Kosan Co.,Ltd.
  • HAGINO Tsubasa
    Graduate School of System Engineering, Hokkaido University Present: JFE Engineering Corporation
  • IGARASHI Toshifumi
    Faculty of Engineering, Hokkaido University

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Other Title
  • 休廃止鉱山から発生する坑廃水を対象とした水量削減・水質改善対策の効果
  • キュウ ハイシ コウザン カラ ハッセイ スル コウ ハイスイ オ タイショウ ト シタ スイリョウ サクゲン ・ スイシツ カイゼン タイサク ノ コウカ

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Abstract

<p>This study involved a mine in Akita Prefecture, Japan, which was closed in the 1970s and from which acid mine drainage (AMD) flows into a nearby river, after pH adjustment. During rainfall events, surface water was flowing in through the adit mouths and sinkholes of excavated areas. Therefore, countermeasure works to reclaim these were carried out by the project company, between 2017 and 2022. In methodology development, this study aims to evaluate the effectiveness of the countermeasures. AMD flow rate increases with rainfall, and water quality of AMD is acidic (pH 3.0–3.8) with higher concentrations of SO42–, soluble Fe, Cu, and Zn than those of river water. The AMD flow rate, normalized using precipitation, decreased over time, with a 55% decrease in 2022 relative to 2016. With progress in countermeasures, pH of the AMD increases, with a range of change of about 0.2, and concentrations of heavy metals in the AMD decreased. Local inhabitants use river water downstream of the mine, at a point-of-use, for agricultural purposes. Since precipitation phenomena such as heavy metals are not recognized in SO42–, an index indicating the degree of impact of AMD on the water quality of the point-of-use was calculated using SO42– as a contribution ratio; CR. The CR of the AMD to water quality at the point-of-use is in the range of 1.3%–11.8% and decreased over time.</p>

Journal

  • Resources Processing

    Resources Processing 70 (3), 125-133, 2024

    The Resources Processing Society of Japan

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