Sustainable Reuse of Fracking Water

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Hydraulic fracturing - also referred to as “fracking” - is a technique used for the extraction of natural gas that has been widely adopted to exploit natural gas resources in the USA. However, there are growing concerns about the potential impact of fracking activity on the environment and human health, one of which is the question of how to dispose of or recycle the large volume of wastewater generated. Researchers from the University of Colorado have published a study in the journal Science of the Total Environment to characterize flow-back water generated from fracking activities, using a combination of analytical techniques.¹

Fracking describes the process of producing fractures in rock formations by pumping large quantities of hydraulic fracturing fluid at high pressure down a drilled wellbore.² Hydraulic fracturing fluid contains a mixture of water and chemical additives that expand fractures and, once the fracturing process is complete, is returned to the surface. If not disposed of safely or treated effectively, the wastewater can contaminate water sources in the surrounding area.

Corresponding author Karl. G. Linden from the University of Colorado told The Column: “This study is part of a larger effort by our group funded by the National Science Foundation to evaluate sustainable options for water reuse in the oil and gas industry. The first step is to know what is in the flowback and produced waters from hydraulic fracturing, [so] then we can design effective treatment processes to meet goals of reusing the water - either for more fracturing to save other freshwater sources or for safe reuse or distribution into the environment.”

Flowback water was sampled from a well in the Denver-Julesberg basin and assessed for general quality. Volatile fatty acids and inorganic anions were measured using ion chromatography (IC), and gas chromatography coupled to mass spectrometry (GC–MS) was performed to determine volatile and semi-volatile organic compounds.  Linden said: “The specific chemicals and stabilizers that are used in fracturing fluids, mixed with the deep-bed saline formation waters, under pressure and temperature, may form compounds we do not expect to see. To be able to detect unknowns, we need to apply advanced analytical methods such as time-of-flight liquid chromatography–mass spectrometry, with accurate mass analysis.”

According to the paper, the flowback from the Denver-Julesberg basin contained salts, metals, and high levels of organic matter composed of fracturing fluid additives and degradation products. This led the authors to conclude that using biological processing would be the best approach to treating flowback water in this location.

When asked about future work, Linden told The Column: “We are currently studying the evolution of water quality that flows back from the start of a hydraulic fracturing job to the time that the well is fully producing oil and gas.  This study will be a first-of-its-kind time course study to evaluate how water quality evolves during a hydraulic fracturing job and will help inform the treatment strategies that will allow for effective reuse of this water from day 1.  Ideally we want to keep the water safely in the hydraulic cycle and not have to rely on deep well injection for disposal, which has its environmental costs.” - B.D.

References
1. Y. Lester, I. Ferrer, E.M. Thurman, K.A. Sitterley, J.A. Korak, G. Aiken, and K.G. Linden, Science of the Total Environment DOI:10.1016/j.scitotenv.2015.01.043 (2015).
2. United States Environmental Protection Agency [Last accessed 13 April 2015: http://www2.epa.gov/hydraulicfracturing/process-hydraulic-fracturing]

This story was first published in LCGC's digital magazine The Column. Click here to view the full issue>