Microbial community response to addition of polylactate compounds to stimulate hexavalent chromium reduction in groundwater |
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Authors: | Brodie Eoin L Joyner Dominique C Faybishenko Boris Conrad Mark E Rios-Velazquez Carlos Malave Josue Martinez Ramon Mork Benjamin Willett Anna Koenigsberg Steven Herman Donald J Firestone Mary K Hazen Terry C |
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Institution: | a Ecology Department, Earth Sciences Division, Lawrence Berkeley National Laboratory, CA, United States b Department of Environmental Science Policy and Management, Division of Ecosystem Sciences, University of California at Berkeley, CA, United States c Department of Biology, University of Puerto Rico, Mayagüez, PR, United States d Regenesis Inc., San Clemente, CA, United States e Interstate Technology & Regulatory Council (ITRC) Washington, DC, United States f Adventus Americas Inc., Irvine, CA, United States |
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Abstract: | To evaluate the efficacy of bioimmobilization of Cr(VI) in groundwater at the Department of Energy Hanford site, we conducted a series of microcosm experiments using a range of commercial electron donors with varying degrees of lactate polymerization (polylactate). These experiments were conducted using Hanford Formation sediments (coarse sand and gravel) immersed in Hanford groundwater, which were amended with Cr(VI) and several types of lactate-based electron donors (Hydrogen Release Compound, HRC; primer-HRC, pHRC; extended release HRC) and the polylactate-cysteine form (Metal Remediation Compound, MRC). The results showed that polylactate compounds stimulated an increase in bacterial biomass and activity to a greater extent than sodium lactate when applied at equivalent carbon concentrations. At the same time, concentrations of headspace hydrogen and methane increased and correlated with changes in the microbial community structure. Enrichment of Pseudomonas spp. occurred with all lactate additions, and enrichment of sulfate-reducing Desulfosporosinus spp. occurred with almost complete sulfate reduction. The results of these experiments demonstrate that amendment with the pHRC and MRC forms result in effective removal of Cr(VI) from solution most likely by both direct (enzymatic) and indirect (microbially generated reductant) mechanisms. |
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Keywords: | Hexavalent chromium Bioremediation Bacteria Polylactate Metal reduction |
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