Potential for bioremediation of a soil heavily contaminated with hexavalent chromium

Janet Lynn Bader, University of Texas at El Paso

Abstract

This dissertation consists of an investigation of the potential for bioremediation of a soil heavily contaminated with hexavalent chromium (Cr(VI)). The purpose of this study was to determine if the indigenous microbial populations in a soil heavily contaminated with Cr(VI) were capable of catalyzing Cr(VI) reduction, thereby decreasing Cr toxicity and bioavailability, and to determine how these populations compared to those in soils with no history of Cr(VI) contamination.^ Chromium-containing industrial effluents are primarily responsible for environmental contamination by toxic and highly mobile, hexavalent chromium. The dilution plate-count method, using media amended with Cr(VI) at concentrations ranging from 0 to 1000 mg L$\sp{-1}$, was used to compare the sizes of Cr(VI)-resistant bacterial populations from a soil contaminated with 25,100 mg kg$\sp{-1}$ total Cr (12,400 mg kg$\sp{-1}$Cr(VI)) to those isolated from a slightly contaminated soil (99.6 mg kg$\sp{-1}$ total Cr) and two other soils without any history of Cr contamination. Bacterial populations resistant to 500 mg L$\sp{-1}$ Cr(VI) were isolated from all soils except the heavily contaminated soil. To determine whether Cr-resistant bacterial populations were indigenous to both the contaminated and the uncontaminated soils, enrichment cultures containing Cr(VI) at concentrations ranging from 0 to 1000 mg L$\sp{-1}$ were employed. Bacterial populations, as high as $10\sp5$ CFU g$\sp{-1}$ soil, tolerant of 500 mg L$\sp{-1}$ Cr(VI) were isolated from all soils within 48 hr of enrichment suggesting that the presence of aerobic Cr(VI)-resistant bacterial populations is unrelated to contamination levels or contamination history.^ Soil containing 25,100 mg kg$\sp{-1}$ total Cr (12,400 mg kg$\sp{-1}$ Cr(VI)) was collected from a Superfund site and used in batch culture studies to evaluate the potential for aerobic reduction of Cr(VI) by the indigenous bacterial population. The concentration of Cr(VI) in the soil microcosms was reduced as much as 33% (from 1,840 to 1,240 mg L$\sp{-1}$) within 21 days under enrichment conditions. Reduction of Cr(VI) in this system was shown to be biologically mediated and dependent on the availability of a usable energy source.^ The final objective of this study was to determine the Cr(VI) tolerance of a fungus isolated from a Cr(VI)-contaminated soil (25,100 mg L$\sp{-1}$ total Cr, and 12,400 mg L$\sp{-1}$ Cr(VI)), and to determine the capacity of this isolate to remove Cr(VI) from solution when grown in a liquid culture. (Abstract shortened by UMI.) ^

Subject Area

Biology, Microbiology|Biogeochemistry|Agriculture, Soil Science|Engineering, Environmental

Recommended Citation

Bader, Janet Lynn, "Potential for bioremediation of a soil heavily contaminated with hexavalent chromium" (1997). ETD Collection for University of Texas, El Paso. AAI9732550.
http://digitalcommons.utep.edu/dissertations/AAI9732550

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