Operators in the Marcellus shale have a strong desire to recycle and reuse waters, particularly flowback for continued use. Recycling water provides many benefits, such as; reduced total water consumption, reduced community impact through decreased truck traffic, and energy savings through avoiding advanced water treatment technologies. With all of the benefits water recycling and reuse has presented, the practice also presents a new set of logistical challenges for the industry that demand an even greater understanding of the unique nature of flowback water. Flowback water from the Marcellus shale often contains higher concentrations of total dissolved solids than traditional produced waters from drilling as well as some metals and hydrocarbons. When impounded prior to treatment and reuse, microbial populations arise and their activity changes the composition of the organic fractions, solubility of metals, and may result in aesthetic issues associated with the odors from gaseous sulfur and nitrogen compounds from microbial metabolism. In order to develop the type of sustainable process the industry, regulators and the communities desire, we characterized and enumerated microbial communities in treated and untreated flowback water impoundments from the Marcellus Shale to gain a comprehensive understanding of those microbial communities and how they are impacted by pre-treatment. We examined the communities at several depths in each impoundment using 16S rRNA gene clone libraries to enable description of the populations with species-level specificity. Results show that flowback water impoundments develop microbial populations that are distinctly different with pretreatment. Within each treated and untreated impoundment, the microbial communities also varied with depth. The treated impoundment was predominately enriched with bacteria closely related to known aerobic hydrocarbon degraders in the !-proteobacterial clade. Untreated impoundments were more diverse and featured populations most closely related to fermentative organisms, those associated with anaerobic sulfur cycling, hydrocarbon degradation and biogenic methane production. Quantification of 16S rRNA genes indicated higher biomass in the untreated impoundments as compared to the treated impoundment. This is the first study to characterize microbial communities in flowback water from the Marcellus shale. Specific knowledge of microbial populations that thrive in flowback water will help producers develop effective management strategies.
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