This study investigated Fe(II) oxidation during acid mine drainage (AMD) neutralization using CaCO3 in a pilot-scale Sequencing Batch Reactor (SBR) of hydraulic retention time (HRT) of 90 min and sludge retention time (SRT) of 360 min in the presence of air. The removal kinetics of Fe(II), of initial concentration 1,033 ± 0 mg/L, from AMD through oxidation to Fe(III) was observed to depend on both pH and suspended solids, resulting in Fe(II) levels of 679 ± 32, 242 ± 64, 46 ± 16 and 28 ± 0 mg/L recorded after cycles 1, 2, 3 and 4 respectively, with complete Fe(II) oxidation only achieved after complete neutralization of AMD. Generally, it takes 30 min to completely oxidize Fe(II) during cycle 4, suggesting that further optimization of SBR operation based on both pH and suspended solids manipulation can result in significant reduction of the number of cycles required to achieve acceptable Fe(II) oxidation for removal as ferric hydroxide. Overall, complete removal of Fe(II) during AMD neutralization is attractive as it promotes recovery of better quality waste gypsum, key to downstream gypsum beneficiation for recovery of valuables, thereby enabling some treatment-cost recovery and prevention of environmental pollution from dumping of sludge into landfills.
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Research Article|
September 01 2013
Fe(II) oxidation during acid mine drainage neutralization in a pilot-scale sequencing batch reactor
J. N. Zvimba;
1Nanotechnology Environmental Impacts, Natural Resources and the Environment, CSIR, P.O. Box 395, Pretoria 0001, South Africa
E-mail: JZvimba@csir.co.za
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M. Mathye;
M. Mathye
1Nanotechnology Environmental Impacts, Natural Resources and the Environment, CSIR, P.O. Box 395, Pretoria 0001, South Africa
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V. R. K. Vadapalli;
V. R. K. Vadapalli
2Environmental Geosciences, Council for Geoscience, P Bag X112, Pretoria 0001, South Africa
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H. Swanepoel;
H. Swanepoel
3Consulting and Analytical Services, CSIR, P.O. Box 395, Pretoria 0001, South Africa
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L. Bologo
L. Bologo
3Consulting and Analytical Services, CSIR, P.O. Box 395, Pretoria 0001, South Africa
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Water Sci Technol (2013) 68 (6): 1406–1411.
Article history
Received:
March 19 2013
Accepted:
May 22 2013
Citation
J. N. Zvimba, M. Mathye, V. R. K. Vadapalli, H. Swanepoel, L. Bologo; Fe(II) oxidation during acid mine drainage neutralization in a pilot-scale sequencing batch reactor. Water Sci Technol 1 September 2013; 68 (6): 1406–1411. doi: https://doi.org/10.2166/wst.2013.389
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