Penn State: Recycled concrete aggregate may help treat acid mine drainage
Industrial waste materials are put through a batch reactor test to determine their ability to treat acid mine drainage. Credit: Allison Fenske. All Rights Reserved

UNIVERSITY PARK, Pa. — A study led by Penn State researchers suggests that recycled concrete aggregate and an iron-rich byproduct of steel production could help treat acid mine drainage, the toxic runoff that pollutes thousands of miles of streams in Pennsylvania and other coal-mining regions.
The research, published in Mine Water and the Environment, evaluated whether recycled concrete aggregate (RCA) and an iron-rich material (IRM) could replace or supplement limestone, the standard material used in many systems that treat acid mine drainage. The findings, according to the researchers, suggest RCA could be a viable alternative in some locations, while IRM was less effective.
Acid mine drainage forms when mining exposes sulfur-containing rocks to air and water. The resulting chemical reaction creates sulfuric acid, which dissolves metals such as iron, aluminum, and manganese. When contaminated water enters streams, it lowers the water’s pH, deposits orange-colored iron, and harms aquatic life, vegetation, and drinking water supplies. This is typically treated by implementing a limestone treatment system, which neutralizes acidity and helps remove dissolved metals. Researchers, however, are exploring whether less expensive waste materials could serve a similar purpose, potentially turning materials that would otherwise be discarded into useful commodities for treating acid mine drainage.
More than 5,000 miles of streams in Pennsylvania are affected by acid mine drainage, underscoring the scale of the problem in a state with a long history of coal mining.
Allison Fenske, a Penn State alumna and assistant professor of environmental engineering at Juniata College, and Nathaniel Warner, an associate professor of civil and environmental engineering at Penn State, led the study. The researchers explored whether industrial waste materials already available in large quantities could provide a lower-cost option for treating polluted water.
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