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Microbial Anoxic Oxidation of Arsenite

Microbial Anoxic Oxidation of Arsenite. Lily Milner Chemical and Environmental Engineering, The University of Arizona 4/19/08 Acknowledgements: Dr. Reyes Sierra, Dr. Jim Field, Alex Sun, Estephania Marcos. Health Effects Skin Lesions Lung, Kidney Cancer Diabetes Cardiovascular

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Microbial Anoxic Oxidation of Arsenite

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  1. Microbial Anoxic Oxidation of Arsenite Lily Milner Chemical and Environmental Engineering, The University of Arizona 4/19/08 Acknowledgements: Dr. Reyes Sierra, Dr. Jim Field, Alex Sun, Estephania Marcos

  2. Health Effects Skin Lesions Lung, Kidney Cancer Diabetes Cardiovascular Disease Arsenic Federal standard for Arsenic in drinking water : 10 microgram/L • Inorganic Sources • Wood Treatment • Pesticides • Medicines • Mining • Organic Sources • Volcanic Activity • Sea Organisms • Weathering of Rocks

  3. Arsenic Contamination in the US http://www.usgs.org

  4. Two Common Species of Arsenic Found in The Environment Arsenite [As(III)] OH—As—OH | OH • More Toxic • Absorbs to few minerals • Prevalent in anaerobic environments Arsenate [As(V)] O | | HO-As-OH | OH • Less Toxic • Absorbs to many minerals • Prevalent in aerobic environments

  5. Redox Cycles of Arsenic and Iron & Their Interaction As(III) Oxidation e--acceptor (O2 , NO3-) e—donor (organic matter) As(V) Reduction Fe(II) Oxidation e--acceptor (O2 , NO3 -) e--donor Fe(III) Reduction As(V) As(V) As(III) As(V) Fe(III) Oxides Fe(II) + As(V) As(V) As(V)

  6. Microbial Process of Bioreactors 5 H3AsO3 + 2 NO3-  5 HAsO4-2 + N2 + 8H+ + H2O Influent • Electron Donor • 6.67e-3 mM As(III) • 0.357 mM Fe(II) • Electron Acceptor • 2.5 mM NO3- • Carbon Source • HCO3- Sand Bed Gas Effluent Influent

  7. SF1 Reactor with As(III)/Fe(II) + nitrate SF2 Control reactor with As(III)/Fe(II) – No nitrate

  8. Results For Iron Oxidation

  9. Results for Arsenic Removal

  10. Conclusions • The microbial oxidation of Fe(II) and As(III) to Fe(III) and As(V) by chemolithotrophic denitrifiers can account for the difference in arsenic removal between the columns. • The results show that microbial oxidation of Fe(II) and As(III) linked to denitrification decreases the environmental mobility of arsenic.

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