Hydraulic fracturing (HF) has grown exponentially, with an estimated 700% increase since 2007. In HF operations a cocktail of chemicals, sand, and water is injected into an underground rock formation to create fractures, which enable release of natural gas. In most HF operations, biocides are added to prevent biofouling of equipment and prevent growth of subsurface microbes during gas extraction and avoid gas souring. During extraction some of the injected water returns to the surface carrying with it many of the injected chemicals including the remaining biocides. It has been reported that flowback water has been accidentally released into the environment, potentially exposing streams to HF chemicals such as biocide. To understand the effect biocides have in HF impacted steams, microcosms were inoculated using stream water impacted by Marcellus shale HF operations (three streams), and as control pristine stream water from the same Marcellus shale area (three streams) was used. Two sets of microcosms were set using the two more commonly used biocides, glutaraldehyde and DBNPA. The microcosms were incubated at ambient temperature over a period of 8 weeks. The microbial community adaptation to biocide was tracked by sampling every two weeks and performing 16s rRNA amplicon sequencing as compared to a biological control (no biocide added). Chemical degradation of the biocide was tracked every week by HPLC (for DBNPA) and GC-FID (for glutaraldehyde), as compared to an autoclaved control to track abiotic degradation of the biocides. Finally, RNA was sampled at time zero and at the end of the experiment to understand what transcripts were upregulated by the presence of biocide, and hence allow the bacteria to adapt and tolerate the biocide. Our aim is that the results of this experiment will help understand the pathways of biocide resistance and the effect they have in the native microbial community.

Environmental microbial community tolerance and adaptation to biocides use in hydraulic fracturing operations

251st National Meeting (2016)

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