Microbial communities in flowback water impoundments from hydraulic fracturing for recovery of shale gas

Abstract

Hydraulic fracturing for natural gas extraction from shale produces waste brine known as flowback that is impounded at the surface prior to reuse and/or disposal. During impoundment, microbial activity can alter the fate of metals including radionuclides, give rise to odorous compounds, and result in biocorrosion that complicates water and waste management and increases production costs. Here, we describe the microbial ecology at multiple depths of three flowback impoundments from the Marcellus shale that were managed differently. 16S rRNA gene clone libraries revealed that bacterial communities in the untreated and biocide-amended impoundments were depth dependent, diverse, and most similar to species within the taxa γ-proteobacteria, α-proteobacteria, δ-proteobacteria, Clostridia, Synergistetes, Thermotogae, Spirochetes, and Bacteroidetes. The bacterial community in the pretreated and aerated impoundment was uniform with depth, less diverse, and most similar to known iodide-oxidizing bacteria in the α-proteobacteria. Archaea were identified only in the untreated and biocide-amended impoundments and were affiliated to the Methanomicrobia class. This is the first study of microbial communities in flowback water impoundments from hydraulic fracturing. The findings expand our knowledge of microbial diversity of an emergent and unexplored environment and may guide the management of flowback impoundments.

Organic and inorganic composition and microbiology of produced waters from Pennsylvania shale gas wells

“…Halanaerobium-related sequences were also detected in PW from Barnett Shale, TX and Marcellus Shale gas wells (Davis et al, 2012;Struchtemeyer and Elshahed, 2012;Murali Mohan et al, 2013a, 2013bStrong et al, 2013;Cluff et al, 2014). However, the viability of Halanaerobium species in the previous Marcellus Shale studies was not demonstrated.…”

“…Recent work shows that microbial populations change during production, with different community compositions present in pre-fracturing fluids compared to PW recovered over the lifetime of production (Struchtemeyer et al, 2011;Struchtemeyer and Elshahed, 2012;Murali Mohan et al, 2013a, 2013bStrong et al, 2013;Cluff et al, 2014). In the Marcellus Shale, communities shifted during production toward halophilic and hydrocarbon-degrading lineages (Murali Mohan et al, 2013a;Strong et al, 2013;Cluff et al, 2014).…”

Marcellus and mercury: Assessing potential impacts of unconventional natural gas extraction on aquatic ecosystems in northwestern Pennsylvania

“…[18][19][20] Recent research is beginning to define the microbial community structure of injected and flowback waters associated with hydraulic fracturing. [21][22] In Pennsylvania alone, it has been estimated that over six billion liters of wastewater have already been generated, [23] and the mismanagement of produced flowback waters is the significant threat to our water resources. [24] Frackwater has the potential to reach the stream through leaking equipment (waste-water hoses) and impoundments (evaporation pits and holding ponds/ tanks), lateral blowouts and seepage, as well as backflow into the wellhead.…”

Assessing impacts of unconventional natural gas extraction on microbial communities in headwater stream ecosystems in Northwestern Pennsylvania

“…Further, there are no existing studies investigating the potential effects of fracking on aquatic microbial communities. While some limited metagenomic analyses of fracturing fluids and flowback waters have identified potential microbial contaminants of wells and associated infrastructure (Struchtemeyer et al, 2011; Murali Mohan et al, 2013; Wuchter et al, 2013), nothing is currently known about the impacts of fracking on surrounding environmental microbial communities. In this study, we applied microbial community analysis to headwater stream ecosystems with different histories of fracking, specifically focusing on differences between sites with no fracking activity and those with activity.…”