Bioremediation of chlorate and chromate in cold temperature using Manitoba's native microorganisms
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Groundwater and soil contamination is a growing concern worldwide for public health officials. Chlorate and Chromium (VI) are two chemical contaminants with adverse health effects found separately or together from anthropogenic sources. Several remediation methods were developed to eliminate these compounds from the environment. These ions could be reduced to less toxic and less-mobile forms by physicochemical or biological treatment strategies in ex-situ or in-situ processes. Bioremediation is an approach that employs microorganisms' capability to neutralize pollutants and mostly does not leave any undesirable footprint on the environment. Bioremediation of chlorate and chromium (VI) needs electron donor materials to reduce them to harmless chemicals. The most suitable electron donor is acetate due to its commercial availability and non-fermentable specification. In this study, synthetic groundwater was prepared based on the in-situ mineral groundwater composition and inoculated with native microbiota derived from a site that experienced a high concentration of the ions because of historical activities in the past. Acetate was chosen as an electron donor, and the effect of adding macro-nutrients (phosphorus and nitrogen source), micro-nutrients (ATCC 1191 minerals solution), and temperature drop were investigated. Chlorate and hexavalent chromium, with initial concentrations of 1000 mg/L and 3 mg/L, respectively, were successfully removed from the environment when the electron donor and macro-nutrient additives were present in the media. Adding minerals solution did not change the performance of the reaction. However, the removal rate in samples without added phosphorus and nitrogen sources was insignificant. Complete removal of the chlorate and chromium ions was observed at room temperature (21±1 oC) after 50 days (35 days for chlorate), while at the reduced temperature (10±1 oC), the removal occurred after 80 days. ATP (adenosine triphosphate) analysis revealed that the microbial activity under cold conditions could reach similar higher temperature levels with some delays.
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