Abstract
Unconventional oil and gas exploration generates an enormous quantity of wastewater, commonly referred to as flowback and produced water (FPW). Limited freshwater resources and stringent disposal regulations have provided impetus for FPW reuse. Organic and inorganic compounds released from the shale/brine formation, microbial activity, and residual chemicals added during hydraulic fracturing bestow a unique as well as temporally varying chemical composition to this wastewater. Studies indicate that many of the compounds found in FPW are amenable to biological degradation, indicating biological treatment may be a viable option for FPW processing and reuse. This review discusses commonly characterized contaminants and current knowledge on their biodegradability, including the enzymes and organisms involved. Further, a perspective on recent novel hybrid biological treatments and application of knowledge gained from omics studies in improving these treatments is explored.
Highlights
Technological advances have led to unprecedented growth in unconventional oil and gas extraction in the US over the last few decades (U.S Energy Information Administration [EIA], 2020)
This review aims to summarize recent trends in biological treatment of Flowback and Produced water (FPW) with an emphasis on organic contaminants and microbial groups involved in their degradation (Figure 1)
We briefly describe compounds found in FPW, including what is known about their degradation and how they may affect biological treatment and reuse of FPW, types of hybrid treatment modules developed, and microbial communities involved in remediation
Summary
Technological advances have led to unprecedented growth in unconventional oil and gas extraction in the US over the last few decades (U.S Energy Information Administration [EIA], 2020). This encompasses extraction of oil and/or natural gas from a wide variety of formations (e.g., shale, tight sands, and coal deposits/seams) through hydraulic fracturing (HF, called “fracking”). During the early production phase, this wastewater mainly consists of injected fluid mixed with formation brine, often called fracturing flowback (FFB). The proportion of formation brine increases and the wastewater is referred to as Produced water (PW). Wastewaters generated during various stages are hereafter collectively referred to as Flowback and Produced water (FPW)
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