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Assessing the Potential Consequences of Subsurface Bioremediation: Fe-oxide Bioreductive Processes and the Propensity for Contaminant-colloid Co-transport and Media Structural Breakdown

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Technical Report,07 Jul 2015,31 Dec 2016

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University of Tennessee Knoxville United States

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Bioremediation is an attractive approach for decontamination andor immobilization of organic and inorganic groundwater contaminants based on low cost and effectiveness. The approach typically involves manipulation of the physical and chemical environment to achieve conditions that will stimulate the desired biotic andor abiotic processes necessary to degrade or immobilize the contaminants in situ. However, even though contaminant biotransformation may be achieved, altering the chemical environment may be altered and promote unintended processes that may accelerate or retard subsequent fate and transport of residual contaminants or degrade groundwater quality. For example, many subsurface bioremediation approaches involve the introduction of carbon substrates such as acetate or lactate i.e. electron donors that stimulate anaerobic respiration whereby solid phase mineral oxides of Fe and Mn serve as electron acceptors. During this process oxidized forms of iron are reduced to FeII solubilizing the iron oxide. Secondary precipitation of iron can then result in the formation of colloidal iron minerals. Adsorption of residual contaminants to these colloids may enhance contaminant transport via colloid-facilitated transport. Additionally, if microbial biomass production and colloid generation are significant enough pore clogging may occur reducing the hydraulic conductivity of the porous media. Thus altering the indigenous properties of the subsurface media can significantly impact coupled processes controlling contaminant bioremediation e.g. secondary mineral precipitates, permeability, and changes in microbial activity.

Subject Categories:

  • Hydrology, Limnology and Potamology
  • Inorganic Chemistry
  • Water Pollution and Control

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