Arsenic remediation by formation of arsenic sulfide minerals in a continuous anaerobic bioreactor.
Arsenic (As) is a highly toxic metalloid that has been identified at high concentrations in groundwater in certain locations around the world. Concurrent microbial reduction of arsenate (As(V) ) and sulfate (SO4 (2-) ) can result in the formation of poorly soluble arsenic sulfide minerals (ASM). The objective of this research was to study As biomineralization in a minimal iron environment for the bioremediation of As-contaminated groundwater using simultaneous As(V) and SO4 (2-) reduction. A continuous-flow anaerobic bioreactor was maintained at slightly acidic pH (6.25-6.50) and fed with As(V) and SO4 (2-) , utilizing ethanol as an electron donor for over 250 d. A second bioreactor running under the same conditions but lacking SO4 (2-) was operated as a control to study the fate of As (without S). The reactor fed with SO4 (2-) removed an average 91.2% of the total soluble As at volumetric rates up to 2.9 mg As/(L · h), while less than 5% removal was observed in the control bioreactor. Soluble S removal occurred with an S to As molar ratio of 1.2, suggesting the formation of a mixture of orpiment- (As2 S3 ) and realgar-like (AsS) solid phases. Solid phase characterization using K-edge X-ray absorption spectroscopy confirmed the formation of a mixture of As2 S3 and AsS. These results indicate that a bioremediation process relying on the addition of a simple, low-cost electron donor offers potential to promote the removal of As from groundwater with naturally occurring or added SO4 (2-) by precipitation of ASM.
Department of Chemical and Environmental Engineering, The University of Arizona, P.O. Box 210011, Tucson, Arizona. lucia.rodriguez.freire@gmail.com.
Lucia
L
Rodriguez-Freire
Department of Chemical and Environmental Engineering, The University of Arizona, P.O. Box 210011, Tucson, Arizona.
Sarah E
SE
Moore
Department of Chemical and Environmental Engineering, The University of Arizona, P.O. Box 210011, Tucson, Arizona.
Reyes
R
Sierra-Alvarez
Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona.
Robert A
RA
Root
Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona.
Jon
J
Chorover
Department of Chemical and Environmental Engineering, The University of Arizona, P.O. Box 210011, Tucson, Arizona.
James A
JA
Field
D000693:Anaerobiosis; D001151:Arsenic / Q000378:metabolism*; D001152:Arsenicals / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D060587:Groundwater / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008903:Minerals / Q000378:metabolism; D013440:Sulfides / Q000378:metabolism*; D018508:Water Purification; D056928:X-Ray Absorption Spectroscopy
D001152:Arsenicals; D008903:Minerals; D013440:Sulfides; C045816:arsenic trisulfide; D001151:Arsenic
arsenate reduction; biomineralization; bioremediation; orpiment; realgar; sulfate reduction