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Passive treatment of acid mine drainage with high metal concentrations using dispersed alkaline substrate

Lookup NU author(s): Dr Tobias Roetting

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Abstract

Passive treatment systems based on the dissolution of coarse calcite grains are widely used to remediate acid mine drainage (AMD). Unfortunately, they tolerate only low metal concentrations or acidity loads, because they are prone to passivation (loss of reactivity due to coating) and/or clogging (loss of permeability) by precipitates. To overcome these problems, a dispersed alkaline substrate (DAS) composed of a fine-grained alkaline reagent (calcite sand) mixed with a coarse inert matrix (wood chips) was developed. The small grains provide a large reactive surface and dissolve almost completely before the growing layer of precipitates passivates the substrate, whereas the dispersion of nuclei for precipitation on the inert surfaces retards clogging. Chemical and hydraulic performance of DAS was investigated in two laboratory columns fed at different flow rates with natural AMD of pH 2.3 to 3.5 and inflow net acidity 1350 to 2300 mg/L as CaCO3. The DAS columns removed 900 to 1600 mg/L net acidity, 3 to 4.5 times more than conventional passive treatment systems. Regardless of the flow rate employed, Al, Fe(III), Cu, and Pb were virtually eliminated. Minor Zn, Ni, and Cd were removed at low flow rates. High acidity removal is possible because these metals accumulate intentionally in DAS, and their precipitation promotes further calcite dissolution. During 15 mo, DAS operated without clogging at 120 g acidity/m2·d, four times the loading rate recommended for conventional passive systems; DAS may therefore be capable of treating AMD at sites where influent chemistry precludes the use of other passive systems. Copyright © 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.


Publication metadata

Author(s): Rötting T, Thomas R, Ayora C, Carrera J

Publication type: Article

Publication status: Published

Journal: Journal of Environmental Quality

Year: 2008

Volume: 37

Issue: 5

Pages: 1741-1751

Print publication date: 01/09/2008

ISSN (print): 0047-2425

ISSN (electronic): 1537-2537

URL: http://dx.doi.org/10.2134/jeq2007.0517

DOI: 10.2134/jeq2007.0517


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Funding

Funder referenceFunder name
CTM2006-28151-E/TECNOSpanish Government
CTM2007-66724-C02-01Spanish Government
REN-2003-09590-C04-02Spanish Government

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