Understanding the microbial ecology and metabolic potential of flowback and produced water from unconventional shale gas extraction

Hydraulic fracturing of deep, unconventional shale produces large volumes of brine  with metals, aqueous and non-aqueous organic matter and naturally- occurring radioactive material known as flowback and produced water. Microbial activity in these wastewaters can increase costs through production of odorous and toxic compounds, bio-corrosion and natural gas souring. Despite the importance of microorganisms in the management of these waters, there is limited information about the microbial populations and their metabolic capabilities. In this study we use molecular ecology methods and bioinformatics tools to characterize the taxonomic and metabolic profile of microbial communities in flowback and produced water during various stages of shale gas extraction. Results showed that flowback and produced waters were enriched in anaerobic halolerant sulfidogenic, fermentative and methanogenic communities as compared to a predominantly aerobic community in fracturing source water. The metabolic profile revealed a relative increase in genes responsible for carbohydrate metabolism, respiration, sporulation and dormancy, iron acquisition and metabolism, stress response and sulfur metabolism in the produced water samples. The overarching goal of this study is to improve the understanding of microbial communities and their metabolic capabilities to enable more efficient water management and disinfection practices for re-use or disposal.