Biodegradation in Waters from Hydraulic Fracturing: Chemistry, Microbiology, and Engineering

Abstract

Hydraulic fracturing is a method of oil and gas extraction from shale in which substantial volumes of water return to the surface containing chemicals and microorganisms. This paper begins to address the microbial composition and aqueous chemistry and the potential for intrinsic and enhanced bioremediation of these waters. The waters from a gas and oil shale in the Marcellus and Bakken regions, respectively, were analyzed for inorganic elements, organic chemicals, microbial taxonomic composition, and biodegradative capabilities. The waters were highly saline, reaching NaCl concentrations up to 3.5 N, but no significant levels of radioactive elements were detected. More than 1,000 organic compounds were separated and identified by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry. The major classes of organic compounds, in order of decreasing abundance, were aliphatics, cycloaliphatics, single-ring aromatics, and polycyclic aromatic compounds. The bacterial genera found natively in the waters were identified by sequencing the 16S rRNA genes within the extracted DNA. The major genera identified included strains known to thrive under saline conditions (Halanaerobium, Marinobacter, Oceanimonas, Streptohalobacillus) and degrade petroleum hydrocarbons (Thauera, Pseudomonas, Marinobacterium, Williamsia, Colwellia). Microbial populations were extracted from the Bakken shale waters, encapsulated within silica gels, and then reintroduced into their waters of origin. Both intrinsic biodegradation from the free native microorganisms and enhanced biodegradation with the addition of encapsulated bacteria were observed. In total, this paper begins to better define the properties of waters derived from hydraulic fracturing and suggests a potential for the application of bioremediation to remove organic contaminants.

Use of Silica-Encapsulated Pseudomonas sp. Strain NCIB 9816-4 in Biodegradation of Novel Hydrocarbon Ring Structures Found in Hydraulic Fracturing Waters

“…The presence of ring compounds distinct from the well-studied polycyclic fused-ring substrates in hydraulic fracturing waters gave impetus to the present study (3). It was of particular interest to determine the reactivity of spiro, bridged, and isolated ring compounds with Pseudomonas sp.…”

“…A previous study analyzing flow-back waters and waters produced from shale gas and oil extraction found the presence of compounds containing multiple rings that were spiro, direct-linked, bridge-linked, bridged, fused, and heterocyclic compounds (3). To test the efficacy of Pseudomonas sp.…”

“…Flow-back waters and waters produced from shales represent a problem for biodegradation because the high salinity of the waters could inhibit microbial activities, a problem that has been shown to be at least partly addressed by silica encapsulation to protect the microbes (3). In this context, the present study used silica-encapsulated Pseudomonas sp.…”

“…Recently, flow-back waters and waters produced from hydraulically fractured natural gas and liquid oil shales were analyzed for their chemical composition and shown to contain a significant number of ring hydrocarbons (3). From a human health perspective, the polycyclic aromatic hydrocarbons (PAHs) pose the greatest danger, given that this class includes numerous EPA priority pollutants and known carcinogens (4,5).…”

Aerobic biodegradation of organic compounds in hydraulic fracturing fluids

“…The chemicals aid delivery of proppant into induced fractures to open channels for hydrocarbon flow and to protect well infrastructure against microbial fouling and mineral scaling that may constrict flow paths and decrease well productivity (Arthur et al 2008). A portion of the injected fluid (10-15 %) returns to the surface as flowback (Jiang et al 2013) and may initially contain a signature of injected compounds until wells mature (Abualfaraj et al 2014;Strong et al 2014). Flowback fluids become increasingly enriched in salt with longer residence time in the formation (Cluff et al 2014;Rowan et al 2014) and may be re-used to fracture new wells after treatment and dilution or disposed (Jiang et al 2013;Rahm et al 2013).…”