Biological Remediation of Acid Mine Drainage (AMD)
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Transcript of Biological Remediation of Acid Mine Drainage (AMD)
Biological Remediation of Acid Mine DrainageJarno Laitinen M.Sc. Tech., M.Sc. Econ.
Vice PresidentDoranova Oy
Acid Mine Drainage
Background
Acid Mine Drainage– Refers to outflow of acidic waters from mines and tailings– Mainly caused by pyrite oxidation to sulphuric acid– Often contains concentrations of metals and metalloids– And solids, cyanides, explosives, …
Photo: AMD http://clevergreen.co.za/wp-content/uploads/2010/12/acid-mine-drainage.jpg)
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 3
Properties and Kinetics
Basic Reaction Kinetics
2FeS2 + 2H2O + 7O2 = 2Fe2+ + 4SO42– + 4H+
(aq) Pyrite + water + oxygen = ferrous iron + sulfate + acid
Physico-Chemical properties– Generally, a low pH and above average temperature– At extremes, pH as low as -3.6 and temp. up to 46
deg.C
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 4
Impacts
Effects to Nature– Impacts ecosystems eg. through
acidity, oxygen depletion, metals precipitation and leaching
– Decreases aquatic life and vegetation
– Long term impacts that can spread wide
– Natural bacteria may assist breakdown of sulphide minerals thus accelerating AMD formation
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Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 5
Managing Acid Mine Drainage
Management Approaches
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 7
Remediating the changes caused by
AMD plume dispersion
Preventing or minimizing the formation and
spread of AMD
Combining the prevention and
remediation
Prevention by Source Control
Could be implemented by– Sealing/Flooding and Coating the abandoned deep mines
to prevent the oxidation reactions from happening – Applying anionic surfactants to prevent the microbial
actions assisting in dissolving sulphides in the ground , e.g. sodium dodecyl sulphate
– Blending of acid-generating and acid –consuming materials to react producing benign cover, e.g. adding apatite to pyritic mine waste reducing oxidizing of sulfide minerals
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 8
Abiotic Plume Remediation
Active abiotic treatment systems– Aeration and chemical addition, ion exchange, reverse osmosis– used during production– creates costs in operation / disposal of sludge– needs resources during production
Passive abiotic treatment systems– Based on naturally occurring reactions to decrease metal
concentrations and neutralize acidity– e.g. anoxic limestone drains– requires land area – low maintenance costs, expensive to install– low maintenance need
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 9
Bacteria are the dark matter of the biological world, with 4 million mostly unknown species in a ton of soil- Edward O. Wilson
Sulphate Reducing Bacteria
Sulphate Reducing Bacteria– Comprise several groups of bacteria that reduce sulphate to
sulphide and produce carbonate which increase the pH.– Uses the biogenic production of hydrogen sulfide to form alkalinity
and to remove metals– This chemically stabilizes the toxic metal ions as solid metal
sulphides
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 11
Schematic representation of biolgoical sulfate reduction followed by biological partial sulfide oxidatio http://wiki.biomine.skelleftea.se
Biological Plume Remediation
Active biological treatment systems– Off-line sulfidogenic bioreactors– Uses the biogenic production of hydrogen sulfide to form
alkalinity and to remove metals– Reactors are constructed and operated to optimise production
of hydrogen sulphide
Passive biological treatment systems– Aerobic wetlands – Compost reactors (anaerobic wetlands)– Combination of aerobic and anaerobic wetlands– Permeable reactive barriers– Packed bed iron-oxidation bioreactors
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 12
Aerobic Wetlands
Aerobic Wetlands– are used for treating alkaline mine waters– Effectiveness may be improved by combining with e.g. an anoxic
limestone drain– Removal of arsenic, adsorption onto ferric iron colloids and
possible oxidation from As(III) to As (V) with help of bacteria– is a passive treatment system
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 13
Photo: Laguna de Rocha, the largest wetland in the urban area in Esteban Echeverría Partido, Argentina.
Compost Bioreactor
Compost Bioreactor– May be used for net acidic and metal-rich mine waters– Use organic materials according to local supply and should not
support any macrophytes – Water runs through the compost and strips of dissolved oxygen– Microbially catalysed reactions cause net alkalinity and
biogenic sulfide
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 14
Compost bioreactor schematic redrawn adapted from Johnson and Hallberg, 2005
Permeable Reactive Barrier
Permeable reactive barriers– used for treating polluted groundwater on site– using reactive materials e.g. organic solids and limestone– reductive microbiological processes increase alkalinity and
remove metals as sulfides, hydroxides and carbonates – are passive systems
Metal retention. Geoscienceworld.com
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 15
Permeable Reactive Barrier
Examples of permeable reactive barriers. ITRC 2005
Laitinen, Jarno – Acid Mine Drainage @ EuroMining 2013, Tampere (FIN) Slide 16
Thank you for your interestFor more information:E-mail: [email protected]: +358 44 355 8236Internet: www.doranova.fi