Southern Research Station

Title: The Revival of a Failed Constructed Wetland Treating of a High Fe Load AMD

Author: Karathanasis, A.D.; Barton, C.D.

Date: 1999

Source: In: Biochemistry of Trace Elements in Coal and Coal Combustion Byproducts, Kennth S. Sajwan, Ashok K. Alva, and Robert F. Keefer (eds.)

Description: Acid mine drainage (AMD) from abandoned mines has significantly impaired water quality in eastern Kentucky. A small surface flow wetland constructed in 1989 to reduce AMD effects and subsequently failed after six months of operation was renovated by incorporating anoxic limestone drains (ALDs) and anaerobic subsurface drains promoting vertical flow through successive alkalinity producing (SAPS)limestone organic compost beds. Two years of post renovation monitoring indicate that mean iron concentrations have decreased from 787 to 39mgL^-1, pH increased from 3.38 to 6.46 and acidity has been reduced from 2,244 to 199mgL^-1, (CaCO₃ equivalent). Mass removal rates averaged 98% for Al, 95% for Fe, 94% for acidity, 55% for sulfate 5 and 49% for Mn during the study period. The combination of ALDs and SAPS technologies used in the renovation and the sequence in which they were implemented within the wetland system appeared to provide sufficient buffering and longer residence time rendering a promising design for treatment of this and other sources of high metal load AMD. Characterization of sediments from abiotic/aerobic zones within the treatment system showed low SO₄/Fe ratios in initial abiotic treatment basins, supporting the formation of jarosite and goethite. As the ratios increased due to treatment and subsequent reductions in iron concentration, jarosite was transformed to other Fe-oxyhydroxysulfates and goethite formation was inhibited. Amorphous iron minerals such as ferrihydrite and Fe(OH)₃ were dominant in biotic wetland cell substrates. However, low Fe³⁺ activity, redox potential, and oxygen diffusion rates in the anaerobic subsurface environment inhibited crystalline iron precipitation. The formation of gypsum, rhodochrosite, and siderite as by products of alkalinity-generating reactions in this system also appeared to have an impact on S, Mn, and Fe solubility controls. Sustaining alkaline conditions within the wetland was necessary for maintaining metal retention consistency and long-term treatment efficiency.

Keywords: 

View and Print this Publication (584 KB)

Pristine Version:  An uncaptured or "pristine" version of this publication is available. It has not been subjected to OCR (Optical Character Recognition) and therefore does not have any errors in the text. However it is a larger file size and some people may experience long download times. The "pristine" version of this publication is available here:

View and Print the PRISTINE copy of this Publication (2.1 MB)

Publication Notes: 

• We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
• This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

 Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

Citation

Karathanasis, A.D.; Barton, C.D.  1999.  The Revival of a Failed Constructed Wetland Treating of a High Fe Load AMD.   In: Biochemistry of Trace Elements in Coal and Coal Combustion Byproducts, Kennth S. Sajwan, Ashok K. Alva, and Robert F. Keefer (eds.)