Effect of Impoundment Management Strategies on Microbial Communities and the Fate of Radionuclides

Gregory, Kelvin; Murali Mohan, Arvind; Vidic, Radisav A.

Flowback is commonly impounded at the surface prior to treatment, reuse and/or disposal. During impoundment, microbial activity alters the fate of organic carbon, metals, and gives rise to odor causing compounds that complicate water and waste management, and increase production costs. Here we report on the microbial community that appears in well-head samples of flowback water as well as the microbial community that arises in flowback impoundments under various treatment regimes. We also describe the impacts of various alternate treatment regimes on the fate of uranium in flowback impoundments.

Microbial communities were examined using molecular microbial ecology techniques based on PCR amplification of 16S rRNA genes. A clone library approach in conjunction with Quantitative-PCR was used for the analyses. Results from clone libraries show that the microbial communities present in well-head samples were variable with time and distinct from each other. The majority of the flowback and produced water communities were most closely affiliated with known halotolerant, anaerobic, and sulfidogenic bacteria. Q-PCR enumeration indicated uniform 16S rRNA gene concentrations in fracturing water and flowback samples but were two orders of magnitude lower in the produced water phase.

Microbial community surveys of flowback impoundments reveal that the untreated and biocide-amended impoundment had diverse and depth-dependent bacterial communities of aerobic, fermentative, and anaerobic bacteria. In contrast, the bacterial community in the aerated impoundment was homogeneous with depth and was dominated by sequences most similar to aerobic, iodide oxidizing species. Archaea were only observed in the deeper clines of the untreated and biocide amended impoundments and all were most closely related to known methanogens. Treatment regimes were closely linked with the solubility and hence fate of uranium in flowback impoundments. The findings from these studies reveal the diversity of organisms that are present in flowback water and that environmental management strongly impacts the microbial communities and subsequent biogeochemistry in the impoundments.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013