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Title: Chromium (VI) reduction in acetate- and molasses-amended natural media: empirical model development

Abstract

Stimulating indigenous microbes to reduce heavy metals from highly toxic oxidized species to more benign reduced species is a promising groundwater remediation technique that has already seen successful field applications. Designing such a bio-remediation scheme requires a model incorporating the kinetics of nonlinear bio-geochemical interactions between multiple species. With this motivation, we performed a set of microcosm experiments in natural sediments and their indigenous pore water and microbes, generating simultaneous time series for concentrations of Cr(VI), an electron donor (both molasses and acetate were considered), and biomass. Molasses was found to undergo a rapid direct abiotic reaction which eliminated all Cr(VI) before any biomass had time to grow. This was not found in the acetate microcosms, and a distinct zero-order bio-reduction process was observed. Existing models were found inappropriate and a new set of three coupled governing equations representing these process dynamics were developed and their parameters calibrated against the time series from the acetate-amended microcosms. Cell suspension batch experiments were also performed to calibrate bio-reduction rates in the absence of electron donor and sediment. The donor used to initially grow the cells (molasses or acetate) was found not to impact the reduction rate constants in suspension, which were ordersmore » of magnitude larger than those explaining the natural media microcosm experiments. This suggests the limited utility of kinetics determined in suspension for remedial design. Scoping studies on the natural media microcosms were also performed, suggesting limited impact of foreign abiotic material and minimal effect of diffusion limitation in the vertical dimension. These analyses may be of independent value to future researchers.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1410609
Report Number(s):
LA-UR-17-30690
DOE Contract Number:  
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 54 ENVIRONMENTAL SCIENCES; Biological Science; Earth Sciences; in-situ bioremediation; bio-reduction; abiotic reduction; bioremediation model; model calibration

Citation Formats

Hansen, Scott, Boukhalfa, Hakim, Karra, Satish, Wang, Dongping, and Vesselinov, Velimir Valentinov. Chromium (VI) reduction in acetate- and molasses-amended natural media: empirical model development. United States: N. p., 2017. Web. doi:10.2172/1410609.
Hansen, Scott, Boukhalfa, Hakim, Karra, Satish, Wang, Dongping, & Vesselinov, Velimir Valentinov. Chromium (VI) reduction in acetate- and molasses-amended natural media: empirical model development. United States. doi:10.2172/1410609.
Hansen, Scott, Boukhalfa, Hakim, Karra, Satish, Wang, Dongping, and Vesselinov, Velimir Valentinov. Tue . "Chromium (VI) reduction in acetate- and molasses-amended natural media: empirical model development". United States. doi:10.2172/1410609. https://www.osti.gov/servlets/purl/1410609.
@article{osti_1410609,
title = {Chromium (VI) reduction in acetate- and molasses-amended natural media: empirical model development},
author = {Hansen, Scott and Boukhalfa, Hakim and Karra, Satish and Wang, Dongping and Vesselinov, Velimir Valentinov},
abstractNote = {Stimulating indigenous microbes to reduce heavy metals from highly toxic oxidized species to more benign reduced species is a promising groundwater remediation technique that has already seen successful field applications. Designing such a bio-remediation scheme requires a model incorporating the kinetics of nonlinear bio-geochemical interactions between multiple species. With this motivation, we performed a set of microcosm experiments in natural sediments and their indigenous pore water and microbes, generating simultaneous time series for concentrations of Cr(VI), an electron donor (both molasses and acetate were considered), and biomass. Molasses was found to undergo a rapid direct abiotic reaction which eliminated all Cr(VI) before any biomass had time to grow. This was not found in the acetate microcosms, and a distinct zero-order bio-reduction process was observed. Existing models were found inappropriate and a new set of three coupled governing equations representing these process dynamics were developed and their parameters calibrated against the time series from the acetate-amended microcosms. Cell suspension batch experiments were also performed to calibrate bio-reduction rates in the absence of electron donor and sediment. The donor used to initially grow the cells (molasses or acetate) was found not to impact the reduction rate constants in suspension, which were orders of magnitude larger than those explaining the natural media microcosm experiments. This suggests the limited utility of kinetics determined in suspension for remedial design. Scoping studies on the natural media microcosms were also performed, suggesting limited impact of foreign abiotic material and minimal effect of diffusion limitation in the vertical dimension. These analyses may be of independent value to future researchers.},
doi = {10.2172/1410609},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Nov 21 00:00:00 EST 2017},
month = {Tue Nov 21 00:00:00 EST 2017}
}

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