Bioremediation of Hydraulic Fracturing Wastewaters

Lawrence P. Wackett1,,2 and Alptekin Aksan2 ,3biography

1University of Minnesota, Twin Cities
2 Department of Biochemistry and Molecular Biology and Biophysics
BioTechnology Institute
3Department of Mechanical Engineering

Hydraulic fracturing, or fracking, is a controversial process developed for releasing natural gas or petroleum from tight shale formations. The process has opened up large, previously unavailable sources of hydrocarbons for use as fuels and chemical feedstocks. Hydraulic fracturing has been criticized as postponing a shift from non-renewable fossil fuels to renewable biofuels. However, it is questionable that biomass-derived liquid fuels will be sufficient to replace liquid fuels (1). In that context, we feel that hydraulic fracturing to recover abundant oil and gas from shale resources will help meet society’s fuel needs in the short-term. Another criticism of hydraulic fracturing derives from its use of water resources and the contamination of that water with chemicals from the shale and the fracturing process itself. This has brought a focus onto the environmental aspects of hydraulic fracturing.

We have analyzed flowback and produced waters from shale formations in North Dakota and Pennsylvania using methods similar to those employed in the Deepwater Horizon oil spill of 2010 [2] and we have identified similarities in chemical composition as both derive from thermogenic hydrocarbon formations. The oil in the Gulf diminished over time due to weathering, submersion, and biodegradation [3]. The latter was facilitated by the addition of surfactants to break the surface oil layer into micro-droplets that made the oil components more assessable to the indigenous microorganisms in the Gulf waters that are capable of degrading them [4].

Therefore, we believe that biotechnology can play a role in mitigating against the negative impacts of hydraulic fracturing by removing the contaminants in water that derive from fracturing operations. Water discharge into municipal treatment systems is typically not allowed and this has led to the treatment of water using evaporation, filtration, and ozonation processes. The former concentrate wastes, which still require sequestration, typically in hazardous waste landfills. All of these methods are energy intensive. We believe that bioremediation offers unique advantages in not requiring an external energy source to operate and with the potential to degrade organic contaminants completely to carbon dioxide, therefore eliminating the landfilling requirement and expense. In most instances this would clean the waters suitable for re-use in future hydraulic fracturing processes, significantly reducing overall water demand.

Bioremediation can be employed either by utilizing the intrinsic biodegradation capabilities of the bacteria native to the water, or by using engineered systems that contain bacteria selected to degrade the specific contaminants of concern. Flowback and produced waters obtained from fracking operations have been analyzed for microbial populations and are found to be teaming with bacteria [5]. Further analysis is required to determine if those populations might be efficacious in degrading water contaminants. Biodegradation of petroleum hydrocarbons and additives has been an intensive field of study over the last decades and this suggests that engineered systems using characterized bacteria could be effective. The characteristics and biodegradation pathways for many naturally-occurring biodegradative bacteria are freely available from web databases [6]. While there are many publications describing genetically-engineered, biodegrading bacteria, there are regulatory impediments to their use environmentally [7]; thus, most large-scale treatments use naturallyoccurring bacteria. Pure cultures of naturally-occurring bacteria are often used in engineered systems, for example in the biodegradation of trichloroethylene by Burkholderia vietnamiensis G4 [8].

 The question emerges as to what kind of bioremediation would be most useful for hydraulic fracturing water decontamination and where it might be implemented. There is a pressing need currently to recycle water from a hydraulic fracture within one well to be used for other wells. In such an application, the residence time for the water is relatively short and it is more likely that engineered systems would work quickly enough to provide rapid cleaning. In other situations where the water in ponds or storage tanks have long residence times, intrinsic bioremediation by indigenous bacteria might provide a low-cost treatment option. Indigenous populations of bacteria may be stimulated by carbon, nitrogen, or phosphorus-containing nutrients that selectively enhance the biodegrading bacteria present in the medium to be treated [9]. Metagenomic studies [5] can help point the way toward identification and characterization of the bacteria that thrive in the presence of hydrocarbons, high salt concentrations, and high total dissolved solids. Analytical chemistry can reveal what nutrients might be limiting for biodegradation to occur at a maximal rate.

There are several similarities between issues of water re-use following hydraulic fracturing and water contamination due to the extraction of petroleum hydrocarbons from oil sands. The latter process uses large volumes of water and those become contaminated with a complex mixture of high molecular weight hydrocarbons and heterocycles. Treatment of oil sand wastewater by bioremediation has been a very active area of study [10] and research into either area can inform the other.

 In total, we feel that biotechnology offers the potential for cost effective treatment of hydrocarbon remediation stemming from spills and normal operations in hydraulic fracturing and oil sands extraction. Our knowledge of the fundamental biodegradation biochemistry has become extensive; it is necessary to push the envelope on engineered systems to effectively use the biodegradative metabolism that nature has evolved.


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Current Comments contain the personal views of the authors who, as experts, reflect on the direction of future research in their field.

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